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Acta Physiologica

Impact factor: 4.382 5-Year impact factor: 3.853 Print ISSN: 1748-1708 Online ISSN: 1748-1716 Publisher: Wiley Blackwell (Blackwell Publishing)

Subject: Psychology

Most recent papers:

  • The chromogranin A1‐373 fragment reveals how a single change in the protein sequence exerts strong cardioregulatory effects by engaging neuropilin‐1.
    Carmine Rocca, Fedora Grande, Maria Concetta Granieri, Barbara Colombo, Anna De Bartolo, Francesca Giordano, Vittoria Rago, Nicola Amodio, Bruno Tota, Maria Carmela Cerra, Bruno Rizzuti, Angelo Corti, Tommaso Angelone, Teresa Pasqua.
    Acta Physiologica. 11 days ago
    ["\nAbstract\n\nAim\nChromogranin A (CgA), a 439‐residue long protein, is an important cardiovascular regulator and a precursor of various bio‐active fragments. Under stressful/pathological conditions, CgA cleavage generates the CgA1‐373 proangiogenic fragment. The present work investigated the possibility that human CgA1‐373 influences the mammalian cardiac performance, evaluating the role of its C‐terminal sequence.\n\n\nMethods\nHemodynamic assessment was performed on an ex vivo Langendorff rat heart model, while mechanistic studies were performed using perfused hearts, H9c2 cardiomyocytes, and in silico.\n\n\nResults\nOn the ex vivo heart CgA1‐373 elicited direct dose‐dependent negative inotropism and vasodilation, while CgA1‐372, a fragment lacking the C‐terminal R373 residue, was ineffective. Antibodies against the PGPQLR373 C‐terminal sequence abrogated the CgA1‐373‐dependent cardiac and coronary modulation. Ex vivo studies showed that CgA1‐373‐dependent effects were mediated by endothelium, neuropilin‐1 (NRP1) receptor, Akt/NO/Erk1,2 pathways, nitric oxide (NO) production and S‐nitrosylation. In vitro experiments on H9c2 cardiomyocytes indicated that CgA1‐373 also induced eNOS activation directly on the cardiomyocyte component by NRP1 targeting and NO involvement and provided beneficial action against isoproterenol‐induced hypertrophy, by reducing the increase of cell surface area and brain natriuretic peptide (BNP) release. Molecular docking and all‐atom molecular dynamics simulations strongly supported the hypothesis that the C‐terminal R373 residue of CgA1‐373 directly interacts with NRP1.\n\n\nConclusion\nThese results suggest that CgA1‐373 is a new cardioregulatory hormone and that the removal of R373 represents a critical switch for turning “off” its cardioregulatory activity.\n\n", "Acta Physiologica, Accepted Article. "]
    October 18, 2020   doi: 10.1111/apha.13570   open full text
  • Protein O‐GlcNAcylation levels are regulated independently of dietary intake in a tissue and time‐specific manner during rat postnatal development.
    Thomas Dupas, Manon Denis, Justine Dontaine, Antoine Persello, Laurent Bultot, Angélique Erraud, Didier Vertommen, Bertrand Bouchard, Arnaud Tessier, Matthieu Rivière, Jacques Lebreton, Edith Bigot‐Corbel, Jérôme Montnach, Michel De Waard, Chantal Gauthier, Yan Burelle, Aaron K. Olson, Bertrand Rozec, Christine Des Rosiers, Luc Bertrand, Tarik Issad, Benjamin Lauzier.
    Acta Physiologica. 13 days ago
    ["\nAbstract\n\nAim\nMetabolic sources switch from carbohydrates in utero, to fatty acids after birth and then a mix once adults. O‐GlcNAcylation (O‐GlcNAc) is a post‐translational modification considered as a nutrient sensor. The purpose of this work was to assess changes in protein O‐GlcNAc levels, regulatory enzymes and metabolites during the first periods of life and decipher the impact of O‐GlcNAcylation on cardiac proteins.\n\n\nMethods\nHeart, brain and liver were harvested from rats before and after birth (D‐1 and D0), in suckling animals (D12), after weaning with a standard (D28) or a low‐carbohydrate diet (D28F), and adults (D84). O‐GlcNAc levels and regulatory enzymes were evaluated by western blots. Mass spectrometry (MS) approaches were performed to quantify levels of metabolites regulating O‐GlcNAc and identify putative cardiac O‐GlcNAcylated proteins.\n\n\nResults\nProtein O‐GlcNAc levels decrease drastically and progressively from D‐1 to D84 (13‐fold, P < .05) in the heart, whereas the changes were opposite in liver and brain. O‐GlcNAc levels were unaffected by weaning diet in any tissues. Changes in expression of enzymes and levels of metabolites regulating O‐GlcNAc were tissue‐dependent. MS analyses identified changes in putative cardiac O‐GlcNAcylated proteins, namely those involved in the stress response and energy metabolism, such as ACAT1, which is only O‐GlcNAcylated at D0.\n\n\nConclusion\nOur results demonstrate that protein O‐GlcNAc levels are not linked to dietary intake and regulated in a time and tissue‐specific manner during postnatal development. We have identified by untargeted MS putative proteins with a particular O‐GlcNAc signature across the development process suggesting specific role of these proteins.\n\n", "Acta Physiologica, EarlyView. "]
    October 16, 2020   doi: 10.1111/apha.13566   open full text
  • Mog1 knockout causes cardiac hypertrophy and heart failure by downregulating tbx5‐cryab‐hspb2 signaling in zebrafish.
    Dongzhi Gou, Juan Zhou, Qixue Song, Zhijie Wang, Xuemei Bai, Yidan Zhang, Mengxia Zuo, Fan Wang, Ailan Chen, Muhammad Yousaf, Zhongcheng Yang, Huixing Peng, Ke Li, Wen Xie, Jingluo Tang, Yufeng Yao, Meng Han, Tie Ke, Qiuyun Chen, Chengqi Xu, Qing Wang.
    Acta Physiologica. October 08, 2020
    ["\nAbstract\n\nAims\nMOG1 is a small protein that can bind to small GTPase RAN and regulate transport of RNA and proteins between the cytoplasm and nucleus. However, the in vivo physiological role of mog1 in the heart needs to be fully defined.\n\n\nMethods\nMog1 knockout zebrafish was generated by TALEN. Echocardiography, histological analysis, and electrocardiograms were used to examine cardiac structure and function. RNA sequencing and real‐time RT‐PCR were used to elucidate the molecular mechanism and analyze the gene expression. Isoproterenol was used to induce cardiac hypertrophy. Whole‐mount in situ hybridization was used to observe cardiac morphogenesis.\n\n\nResults\nmog1 knockout zebrafish developed cardiac hypertrophy and heart failure (enlarged pericardium, increased nppa and nppb expression and ventricular wall thickness, and reduced ejection fraction), which was aggravated by isoproterenol. RNAseq and KEGG pathway analyses revealed the effect of mog1 knockout on the pathways of cardiac hypertrophy, dilatation and contraction. Mechanistic studies revealed that mog1 knockout decreased expression of tbx5, which reduced expression of cryab and hspb2, resulting in cardiac hypertrophy and heart failure. Overexpression of cryab, hspb2 and tbx5 rescued the cardiac edema phenotype of mog1 KO zebrafish. Telemetry electrocardiogram monitoring showed QRS and QTc prolongation and a reduced heart rate in mog1 knockout zebrafish, which was associated with reduced scn1b expression. Moreover, mog1 knockout resulted in abnormal cardiac looping during embryogenesis due to the reduced expression of nkx2.5, gata4 and hand2.\n\n\nConclusion\nOur data identified an important molecular determinant for cardiac hypertrophy and heart failure, and rhythm maintenance of the heart.\n\n", "Acta Physiologica, Accepted Article. "]
    October 08, 2020   doi: 10.1111/apha.13567   open full text
  • Proliferation does not contribute to murine models of renin cell recruitment.
    Omar Guessoum, Momna Zainab, Maria Luisa S. Sequeira‐Lopez, R. Ariel Gomez.
    Acta Physiologica. October 05, 2020
    ["\nAbstract\n\nAim\nRenin cells are essential for regulation of blood pressure and fluid‐electrolyte homeostasis. During homeostatic threat, the number of renin cells in the kidney increases, a process termed as recruitment. It has been proposed that recruitment occurs by proliferation, yet no systematic studies have been performed. We sought to determine the extent to which proliferation contributes to the recruitment process.\n\n\nMethods\nMice were subjected to recruitment before analysing the renin cells’ cell cycle. For acute threats, we subjected SV129 and C57Bl6 mice to a low sodium diet plus captopril. Tissue sections from treated mice were co‐stained for proliferation markers (Ki67, PCNA, pH3 and BrdU) and renin. Chronic recruitment was studied in deletion models of aldosterone synthase and angiotensinogen through co‐immunostaining and counting mitotic figures in periodic acid‐Schiff‐stained sections. Finally, RNA‐seq of renin cells isolated from recruited mice was performed to study mitotic signature.\n\n\nResults\nMice subjected to low salt and captopril displayed increases in renin cell number (312 ± 40 in controls to 692 ± 85 in recruited animals, P<.0001), 10‐fold increases in renin mRNA and fourfold increases in circulating renin. Co‐staining these kidney sections for proliferation markers revealed negligible proliferation of renin cells (<2%), indistinguishable from control animals. Similarly, chronic models of recruitment—aldosterone synthase KO and angiotensinogen KO—had negligible proliferation. Additionally, the transcriptome of recruited renin cells revealed overall downregulation of mitotic pathways when compared to proliferative cell lines.\n\n\nConclusion\nAcute and chronic physiological threats to homeostasis produced a distinct increase in renin‐synthesizing cells, but we found no evidence to suggest the involvement of proliferation.\n\n", "Acta Physiologica, Volume 230, Issue 3, November 2020. "]
    October 05, 2020   doi: 10.1111/apha.13532   open full text
  • Th17/Treg imbalance modulates rat myocardial fibrosis and heart failure by regulating LOX expression.
    Min Lu, Xinglei Qin, Jungong Yao, Yuanyuan Yang, Minghu Zhao, Lin Sun.
    Acta Physiologica. October 05, 2020
    ["\n\n\n\n\n\n\n\n\n\n\nAbstract\n\nAim\nThe imbalance of T helper (Th) 17/T regulatory (Treg) is involved in chronic heart failure (HF). The enzyme lysyl oxidase (LOX) contributes to myocardial fibrosis. This study was designed to decipher the regulatory mechanism of Th17/Treg on LOX expression and to validate whether Th17/Treg imbalance regulates myocardial fibrosis by modulating LOX expression.\n\n\nMethods\nHuman cardiac fibroblasts (HCFs) were treated with angiotensin II (Ang II) and co‐cultured with Th17 cells and Tregs which were polarized from control naïve CD4+ T cells. Th17 cells and Tregs were adoptively transferred into abdominal aortic coarctation‐induced chronic HF rats to investigate the efficacy of Th17 and Treg infusions on myocardial fibrosis and HF.\n\n\nResults\nTh17/Treg imbalance (increased Th17 cells and decreased Tregs) was observed in HF patients. Th17 cells/Tregs aggravated/attenuated Ang II‐induced upregulation of LOX and fibrosis‐related indicators (MMP‐2/9 and collagen I/III) in HCFs in vitro and abdominal aortic coarctation‐induced myocardial fibrosis and HF in rats, by promoting/inhibiting LOX expression. Mechanistically, Th17 cells promoted LOX expression by activating the IL‐17/ERK1/2‐AP‐1 pathway, while Tregs inhibited LOX expression by activating the IL‐10/JAK1‐STAT3 pathway.\n\n\nConclusion\nIncreased Th17 cells and decreased Tregs aggravate myocardial fibrosis and HF by inducing LOX expression.\n\n", "Acta Physiologica, Volume 230, Issue 3, November 2020. "]
    October 05, 2020   doi: 10.1111/apha.13537   open full text
  • Subcellular localization‐ and fibre type‐dependent utilization of muscle glycogen during heavy resistance exercise in elite power and Olympic weightlifters.
    Rune Hokken, Simon Laugesen, Per Aagaard, Charlotte Suetta, Ulrik Frandsen, Niels Ørtenblad, Joachim Nielsen.
    Acta Physiologica. October 04, 2020
    ["\nAbstract\n\nAim\nGlycogen particles are found in different subcellular localizations, which are utilized heterogeneously in different fibre types during endurance exercise. Although resistance exercise typically involves only a moderate use of mixed muscle glycogen, the hypothesis of the present study was that high‐volume heavy‐load resistance exercise would mediate a pattern of substantial glycogen depletion in specific subcellular localizations and fibre types.\n\n\nMethods\n10 male elite weightlifters performed resistance exercise consisting of four sets of five (4 × 5) repetitions at 75% of 1RM back squats, 4 × 5 at 75% of 1RM deadlifts and 4 × 12 at 65% of 1RM rear foot elevated split squats. Muscle biopsies (vastus lateralis) were obtained before and after the exercise session. The volumetric content of intermyofibrillar (between myofibrils), intramyofibrillar (within myofibrils) and subsarcolemmal glycogen was assessed by transmission electron microscopy.\n\n\nResults\nAfter exercise, biochemically determined muscle glycogen decreased by 38 (31:45)%. Location‐specific glycogen analyses revealed in type 1 fibres a large decrement in intermyofibrillar glycogen, but no or only minor changes in intramyofibrillar or subsarcolemmal glycogen. In type 2 fibres, large decrements in glycogen were observed in all subcellular localizations. Notably, a substantial fraction of the type 2 fibres demonstrated near‐depleted levels of intramyofibrillar glycogen after the exercise session.\n\n\nConclusion\nHeavy resistance exercise mediates a substantial utilization of glycogen from all three subcellular localization in type 2 fibres, while mostly taxing intermyofibrillar glycogen stores in type 1 fibres. Thus, a better understanding of the impact of resistance training on myocellular metabolism and performance requires a focus on compartmentalized glycogen utilization.\n\n", "Acta Physiologica, EarlyView. "]
    October 04, 2020   doi: 10.1111/apha.13561   open full text
  • Natriuretic peptides relax human intrarenal arteries through natriuretic peptide receptor type‐A recapitulated by soluble guanylyl cyclase agonists.
    Andreas Frees, Kasper B. Assersen, Mia Jensen, Pernille B.L. Hansen, Paul M. Vanhoutte, Kirsten Madsen, Anna Federlein, Lars Lund, Anja Toft, Boye L. Jensen.
    Acta Physiologica. October 03, 2020
    ["\nAbstract\n\nAim\nNatriuretic peptides, BNP and ANP increase renal blood flow in experimental animals. The signaling pathway in human kidney vasculature is unknown. It was hypothesized that BNP and ANP cause endothelium‐independent relaxation of human intrarenal arteries by vascular natriuretic peptide receptor‐A, but not ‐B and ‐C, which is mimicked by agonists of soluble guanylyl cyclase sGC.\n\n\nMethods\nHuman (n=54, diameter: 665 ± 29 µm 95% CI) and control murine intrarenal arteries (n=83, diameter 300 ± 6 µm 95% CI) were dissected and used for force recording by 4‐channel wire myography. Arterial segments were pre‐contracted, then subjected to increasing concentrations of BNP, ANP, phosphodiesterase 5‐inhibitor sildenafil, sGC‐activator BAY 60‐2770 and ‐stimulator BAY 41‐2272. Endothelial nitric oxide synthase (eNOS) dependence was examined by use of L‐NAME and eNOS knockout, respectively. Molecular targets (NPR A‐C, sGC, phosphodiesterase‐5 and neprilysin) were mapped by PCR, immunohistochemistry and RNA‐scope.\n\n\nResults\nBNP, ANP, sildenafil, sGC‐activation and ‐stimulation caused concentration‐dependent relaxation of human and murine intrarenal arteries. BNP responses were independent of eNOS and were not potentiated by low concentration of phosphodiesterase‐5‐inhibitor, sGC‐stimulator or NPR‐C blocker. PCR showed NPR‐A and C, phosphodiesterase‐5, neprilysin and sGC mRNAs in renal arteries. NPR‐A mRNA and protein was observed in vascular smooth muscle and endothelial cells in arteries, podocytes, Bowmans capsule and vasa recta. NPR‐C was observed in tubules, glomeruli and vasculature.\n\n\nConclusion\nActivation of transmembrane NPR‐A and soluble guanylyl cyclase relax human preglomerular arteries similarly to phosphodiestase‐5 inhibition. The human renal arterial bed relaxes in response to cGMP pathway.\n\n", "Acta Physiologica, Accepted Article. "]
    October 03, 2020   doi: 10.1111/apha.13565   open full text
  • Deficiency in insulin‐like growth factors signalling in mouse Leydig cells increase conversion of testosterone to estradiol because of feminization.
    Sava M. Radovic Pletikosic, Isidora M. Starovlah, Dejan Miljkovic, Dragana M. Bajic, Ivan Capo, Serge Nef, Tatjana S. Kostic, Silvana A. Andric.
    Acta Physiologica. October 02, 2020
    ["\nAbstract\n\nAim\nA growing body of evidence pointed correlation between insulin‐resistance, testosterone level and infertility, but there is scarce information about mechanisms. The aim of this study was to identify the possible mechanism linking the insulin‐resistance with testosterone‐producing‐Leydig‐cells functionality.\n\n\nMethods\nWe applied in vivo and in vitro approaches. The in vivo model of functional genomics is represented by INSR/IGF1R‐deficient‐testosterone‐producing Leydig cells obtained from the prepubertal (P21) and adult (P80) male mice with insulin + IGF1‐receptors deletion in steroidogenic cells (Insr/Igf1r‐DKO). The in vitro model of INSR/IGF1R‐deficient‐cell was mimicked by blockade of insulin/IGF1‐receptors on the primary culture of P21 and P80 Leydig cells.\n\n\nResults\nLeydig‐cell‐specific‐insulin‐resistance induce the development of estrogenic characteristics of progenitor Leydig cells in prepubertal mice and mature Leydig cells in adult mice, followed with a dramatic reduction of androgen phenotype. Level of androgens in serum, testes and Leydig cells decrease as a consequence of the dramatic reduction of steroidogenic capacity and activity as well as all functional markers of Leydig cell. Oppositely, the markers for female‐steroidogenic‐cell differentiation and function increase. The physiological significances are the higher level of testosterone‐to‐estradiol‐conversion in double‐knock‐out‐mice of both ages and few spermatozoa in adults. Intriguingly, the transcription of pro‐male sexual differentiation markers Sry/Sox9 increased in P21‐Leydig‐cells, questioning the current view about the antagonistic genetic programs underlying gonadal sex determination.\n\n\nConclusion\nThe results provide new molecular mechanisms leading to the development of the female phenotype in Leydig cells from Insr/Igf1r‐DKO mice and could help to better understand the correlation between insulin resistance, testosterone and male (in)fertility.\n\n", "Acta Physiologica, EarlyView. "]
    October 02, 2020   doi: 10.1111/apha.13563   open full text
  • No impact of sex and age on beta‐adrenoceptor mediated inotropy in human right atrial trabeculae.
    Simon Pecha, Bastiaan Geelhoed, Romy Kempe, Emanuel Berk, Andreas Engel, Evaldas Girdauskas, Hermann Reichenspurner, Ursula Ravens, Alberto Kaumann, Thomas Eschenhagen, Renate B. Schnabel, Torsten Christ.
    Acta Physiologica. October 01, 2020
    ["\nAbstract\n\nAim\nThere is an increasing awareness of the impact of age and sex on cardiovascular diseases. Differences in physiology are suspected. Beta‐adrenoceptors (beta‐AR) are an important drug target in cardiovascular disease and potential differences might have significant impact on the treatment of many patients. To investigate whether age and sex affects beta‐AR function, we analyzed a large data set on beta‐AR‐induced inotropy in human atrial trabeculae.\n\n\nMethods\nWe performed multivariable analysis of individual atrial contractility data from trabeculae obtained during heart surgery of patients in sinus rhythm (535 trabeculae from 165 patients). Norepinephrine or epinephrine were used in the presence of the beta2‐selective antagonist (ICI 118,551, 50nM) or the beta1‐selective antagonist (CGP 20712A, 300 nM) to stimulate beta1‐AR or beta2‐AR, respectively. Agonist concentration required to achieve half maximum inotropic effects (EC50) was taken as a measure of beta‐AR sensitivity.\n\n\nResults\nImpact of clinical variables was modeled using multivariable mixed model regression. As previously reported, chronic treatment with beta‐blockers sensitized beta‐AR. However, there was no significant interaction between basal force, maximum force or beta‐AR sensitivity when age and sex were modelled continuously. In addition, there was no statistically significant effect of body mass index or diabetes on atrial contractility.\n\n\nConclusion\nOur large, multivariable analysis shows that neither age nor sex affects beta‐AR‐mediated inotropy or catecholamine sensitivity in human atrial trabeculae. These findings may have important clinical implications because beta‐adrenoceptors, as a common drug target in cardiovascular disease and heart failure do not behave differently in women and men across age decades.\n\n", "Acta Physiologica, Accepted Article. "]
    October 01, 2020   doi: 10.1111/apha.13564   open full text
  • Keratin 1 attenuates hypoxic pulmonary artery hypertension by suppressing pulmonary artery media smooth muscle expansion.
    Li Zhang, Xi‐Xi Zeng, Yu‐Mei Li, Shao‐Kun Chen, Li‐Yu Tang, Nan Wang, Xi Yang, Mo‐Jun Lin.
    Acta Physiologica. September 24, 2020
    ["\nAbstract\n\nAim\nAbnormally activated vascular smooth muscle cells are key factors in pulmonary artery remodelling (PAR) and pulmonary artery hypertension (PAH). Keratin 1 is involved in inflammatory diseases; however, its role in PAH is unknown. We speculated that keratin 1 could regulate PASMCs and prevent PAH.\n\n\nMethods\nRats were exposed to hypoxia (10% O2) or MCT (50 mg/kg, intraperitoneal injection) or treated with AAV6 virus. PAR was measured through HE and Masson staining. PASMC activities were measured using MTS assay, EdU and Western blot analyses after cell knockdown with siRNAs or overexpression with Krt1 vectors.\n\n\nResults\n1. Hypoxic PAR was associated with a decrease in keratin 1, especially in PASMCs. 2. Keratin 1 knockdown led to cell proliferation, migration and contraction to synthetic transformation, while keratin 1 overexpression attenuated hypoxia‐induced changes in PASMCs. 3. Decreased keratin 1 induced TLR7 upregulation and mediated increases in the inflammatory factors S100a8 and S100a9. 4. Keratin 1 overexpression reduced the inflammatory factor expression induced by TLR7 activation. 5. Further studies demonstrated that keratin 1 expression was negatively correlated with pulmonary vascular pressure following prolonged hypoxia. 6. Pre‐treatment with keratin 1 decreased pulmonary artery pressure and the right heart hypertrophy index and alleviated PAR in two model rats. 7. Keratin 1 exhibited a hypermethylation status in hypoxic pulmonary arteries in the sequencing. Hypoxia‐induced decrease in keratin 1 expression was associated with Dnmt1 upregulation induced by YY1 downregulation in PASMCs.\n\n\nConclusion\nThis study suggests that keratin 1 regulates PASMC expansion and has a preventive effect on PAH.\n\n", "Acta Physiologica, EarlyView. "]
    September 24, 2020   doi: 10.1111/apha.13558   open full text
  • Inactivation of HIF‐prolyl 4‐hydroxylases 1, 2 and 3 in NG2‐expressing cells induces HIF2‐mediated neurovascular expansion independent of erythropoietin.
    Andrés A. Urrutia, Nan Guan, Claudia Mesa‐Ciller, Aqeela Afzal, Olena Davidoff, Volker H. Haase.
    Acta Physiologica. September 22, 2020
    ["\nAbstract\n\nAim\nNG2 cells in the brain are comprised of pericytes and NG2 glia and play an important role in the execution of cerebral hypoxia responses, including the induction of erythropoietin (EPO) in pericytes. Oxygen‐dependent angiogenic responses are regulated by hypoxia‐inducible factor (HIF), the activity of which is controlled by prolyl 4‐hydroxylase domain (PHD) dioxygenases and the von Hippel‐Lindau (VHL) tumour suppressor. However, the role of NG2 cells in HIF‐regulated cerebral vascular homeostasis is incompletely understood.\n\n\nMethods\nTo examine the HIF/PHD/VHL axis in neurovascular homeostasis, we used a Cre‐loxP‐based genetic approach in mice and targeted Vhl, Epo, Phd1, Phd2, Phd3 and Hif2a in NG2 cells. Cerebral vasculature was assessed by immunofluorescence, RNA in situ hybridization, gene and protein expression analysis, gel zymography and in situ zymography.\n\n\nResults\nVhl inactivation led to a significant increase in angiogenic gene and Epo expression. This was associated with EPO‐independent expansion of capillary networks in cortex, striatum and hypothalamus, as well as pericyte proliferation. A comparable phenotype resulted from the combined inactivation of Phd2 and Phd3, but not from Phd2 inactivation alone. Concomitant PHD1 function loss led to further expansion of the neurovasculature. Genetic inactivation of Hif2a in Phd1/Phd2/Phd3 triple mutant mice resulted in normal cerebral vasculature.\n\n\nConclusion\nOur studies establish (a) that HIF2 activation in NG2 cells promotes neurovascular expansion and remodelling independently of EPO, (b) that HIF2 activity in NG2 cells is co‐controlled by PHD2 and PHD3 and (c) that PHD1 modulates HIF2 transcriptional responses when PHD2 and PHD3 are inactive.\n\n", "Acta Physiologica, EarlyView. "]
    September 22, 2020   doi: 10.1111/apha.13547   open full text
  • Nicotinamide adenine dinucleotide: Biosynthesis, consumption and therapeutic role in cardiac diseases.
    Cynthia Tannous, George W. Booz, Raffaele Altara, Dina H. Muhieddine, Mathias Mericskay, Marwan M. Refaat, Fouad A. Zouein.
    Acta Physiologica. September 21, 2020
    ["\nAbstract\nNicotinamide adenine dinucleotide (NAD) is an abundant cofactor that plays crucial roles in several cellular processes. NAD can be synthesized de novo starting with tryptophan, or from salvage pathways starting with NAD precursors like nicotinic acid (NA), nicotinamide (NAM) or nicotinamide riboside (NR), referred to as niacin/B3 vitamins, arising from dietary supply or from cellular NAD catabolism. Given the interconversion between its oxidized (NAD+) and reduced form (NADH), NAD participates in a wide range of reactions: regulation of cellular redox status, energy metabolism and mitochondrial biogenesis. Plus, NAD acts as a signalling molecule, being a cosubstrate for several enzymes such as sirtuins, poly‐ADP‐ribose‐polymerases (PARPs) and some ectoenzymes like CD38, regulating critical biological processes like gene expression, DNA repair, calcium signalling and circadian rhythms. Given the large number of mitochondria present in cardiac tissue, the heart has the highest NAD levels and is one of the most metabolically demanding organs. In several models of heart failure, myocardial NAD levels are depressed and this depression is caused by mitochondrial dysfunction, metabolic remodelling and inflammation. Emerging evidence suggests that regulating NAD homeostasis by NAD precursor supplementation has therapeutic efficiency in improving myocardial bioenergetics and function. This review provides an overview of the latest understanding of the different NAD biosynthesis pathways, as well as its role as a signalling molecule particularly in cardiac tissue. We highlight the significance of preserving NAD equilibrium in various models of heart diseases and shed light on the potential pharmacological interventions aiming to use NAD boosters as therapeutic agents.\n", "Acta Physiologica, EarlyView. "]
    September 21, 2020   doi: 10.1111/apha.13551   open full text
  • Prostacyclin facilitates vascular smooth muscle cell phenotypic transformation via activating TP receptors when IP receptors are deficient.
    Ziqing Li, Wenwei Luo, Shi Fang, Xinyi Chen, Tong Lin, Sihang Zhou, Lili Zhang, Wanqi Yang, Zhenzhen Li, Jiantao Ye, Junjian Wang, Peiqing Liu, Zhuoming Li.
    Acta Physiologica. September 20, 2020
    ["\nAbstract\n\nAim\nBy activating prostacyclin receptors (IP receptors), prostacyclin (PGI2) exerts cardiovascular protective effects such as vasodilation and inhibition of vascular smooth muscle cell (VSMC) proliferation. However, IP receptors are dysfunctional under pathological conditions, and PGI2 produces detrimental effects that are opposite to its physiological protective effects via thromboxane‐prostanoid (TP) receptors. This attempted to investigate whether or not IP receptor dysfunction facilitates the shift of PGI2 action. Methods: The effects of PGI2 and its stable analog iloprost on VSMC phenotypic transformation and proliferation were examined in A10 cells silencing IP receptors, in human aortic VSMCs (HAVSMCs) knocked down IP receptor by CRISPR‐Cas9, or in HAVSMCs transfected with a dysfunctional mutation of IP receptor IPR212C. Results: PGI2/iloprost treatment stimulated cell proliferation, upregulated synthetic proteins and downregulated contractile proteins, suggesting that PGI2/iloprost promotes VSMC phenotypic transformation in IP‐deficient cells. The effect of PGI2/iloprost was prevented by TP antagonist S18886 or TP knockdown, indicating that the VSMC detrimental effect of PGI2 is dependent on TP receptor. RNA sequencing and Western blotting results showed that RhoA/ROCKs, MEK1/2 and JNK signalling cascades were involved. Moreover, IP deficiency increased the distribution of TP receptors at the cell membrane. Conclusion: PGI2 induces VSMC phenotypic transformation when IP receptors are impaired. This is attributed to the activation of TP receptor and its downstream signaling cascades, and to the increased membrane distribution of TP receptors. The VSMC detrimental effect of PGI2 medicated by IP dysfunction and TP activation might probably exacerbate vascular remodelling, accelerating cardiovascular diseases.\n\n", "Acta Physiologica, EarlyView. "]
    September 20, 2020   doi: 10.1111/apha.13555   open full text
  • Are muscle fibres of body builders intrinsically weaker? A comparison with single fibres of aged‐matched controls.
    Elena Monti, Luana Toniolo, Lorenzo Marcucci, Michela Bondì, Ivan Martellato, Bostjan Šimunič, Paolo Toninello, Martino V. Franchi, Marco V. Narici, Carlo Reggiani.
    Acta Physiologica. September 20, 2020
    ["\nAbstract\n\nAim\nSkeletal muscles of Body Builders (BB) represent an interesting model to study muscle mass gains in response to high volume resistance training. It is debated whether muscle contractile performance improves in proportion to mass. Here, we aim to assess whether muscle hypertrophy does not occur at the expense of performance.\n\n\nMethods\nSix BB and Six untrained controls (CTRL) were recruited. Cross‐sectional area (CSA) and maximum voluntary contraction (MVC) of quadriceps femoris muscle (QF) and CSA and architecture of vastus lateralis (VL) were determined. Moreover, a biopsy was taken from VL mid‐portion and single fibres were analysed.\n\n\nResults\nQF CSA and MVC were 32% (n.s., P = .052) and 58% (P = .009) higher in BB than in CTRL, respectively. VL CSA was 37% higher in BB (P = .030). Fast 2A fibres CSA was 24% (P = .048) greater in BB than in CTRL, when determined in immunostained sections of biopsy samples. Single permeabilized fast fibres CSA was 37% (n.s., P = .052) higher in BB than in CTRL, and their force was slightly higher in BB (n.s.), while specific tension (P0) was 19% (P = .024) lower. The lower P0 was not explained either by lower myosin content or by impaired calcium diffusion. Conversely, the swelling caused by skinning‐induced permeabilization was different and, when used to correct P0, differences between populations disappeared.\n\n\nConclusions\nThe results show that high degree of muscle hypertrophy is not detrimental for force generation capacity, as increases in fibre size and force are strictly proportional once the differential swelling response is accounted for.\n\n", "Acta Physiologica, EarlyView. "]
    September 20, 2020   doi: 10.1111/apha.13557   open full text
  • The body region specificity in murine models of muscle regeneration and atrophy.
    Kiyoshi Yoshioka, Yasuo Kitajima, Daiki Seko, Yoshifumi Tsuchiya, Yusuke Ono.
    Acta Physiologica. September 17, 2020
    ["\nAbstract\n\nAim\nSkeletal muscles are distributed throughout the body, presenting a variety of sizes, shapes and functions. Here, we examined whether muscle regeneration and atrophy occurred homogeneously throughout the body in mouse models.\n\n\nMethods\nAcute muscle regeneration was induced by a single intramuscular injection of cardiotoxin in adult mice. Chronic muscle regeneration was assessed in mdx mice. Muscle atrophy in different muscles was evaluated by cancer cachexia, ageing and castration mouse models.\n\n\nResults\nWe found that, in the cardiotoxin‐injected acute muscle injury model, head muscles slowly regenerated, while limb muscles exhibited a rapid regeneration and even overgrowth. This overgrowth was also observed in limb muscles alone (but not in head muscles) in mdx mice as chronic injury models. We described the body region–specific decline in the muscle mass in muscle atrophy models: cancer cachexia‐induced, aged and castrated mice. The positional identities, including gene expression profiles and hormone sensitivity, were robustly preserved in the ectopically engrafted satellite cell‐derived muscles in the castrated model.\n\n\nConclusion\nOur results indicate that positional identities in muscles should be considered for the development of efficient regenerative therapies for muscle weakness, such as muscular dystrophy and age‐related sarcopenia.\n\n", "Acta Physiologica, EarlyView. "]
    September 17, 2020   doi: 10.1111/apha.13553   open full text
  • Characterization of tryptophan‐containing dipeptides for anti‐angiogenic effects.
    Sherif Khedr, Anne Klotzsche‐von Ameln, Maha Khedr, Mohamed H. Elsayed, Thangirala Sudha, Shaker A. Mousa, Andreas Deussen, Melanie Martin.
    Acta Physiologica. September 15, 2020
    ["\nAbstract\n\nAims\nIn the pathogenesis of several diseases, neo‐angiogenesis is increased (e.g. tumour growth). The peptide L‐glutamyl‐L‐tryptophan (EW/IM862) has been claimed to exhibit inhibitory effects on tumour growth in vivo. However, the potential role of natural peptides with respect to anti‐angiogenic properties is unsettled. The current study explores anti‐angiogenic effects of the dipeptides WL, EW, IW and WE.\n\n\nMethods and Results\nUsing a bottom‐up strategy, we first evaluated the effects of the peptides on VEGFR‐2 signalling and quantified their effects in different angiogenesis assays. WL consistently had the strongest effects on phosphorylation of VEGFR‐2 and downstream signalling. Therefore, this peptide was chosen in comparison with EW to further assess anti‐angiogenic properties. However, sprout formation in three‐dimensional (3D) fibrin gel bead assay was significantly inhibited by EW only. Furthermore, vessel sprouting in the mouse aortic ring assay was decreased by the presence of WL and EW compared to control. Results from a chorioallantoic membrane assay showed that under vascular endothelial growth factor (VEGF) stimulation WL and EW decreased the number of blood vessels versus control. These results were in line with those obtained in a matrigel plug assay. The VEGF‐induced increase in the haemoglobin content was nearly abolished when treatment was combined with either WL or EW application. In the murine model of oxygen‐induced retinopathy, WL exhibited a small albeit significant anti‐angiogenic effect.\n\n\nConclusion\nComprehensive screening of WL suggests an anti‐angiogenic effect, demonstrated in in vitro, ex vivo and in vivo models. Thus, WL is a dipeptide with potential anti‐angiogenic effects and is worthy for further exploration.\n\n", "Acta Physiologica, EarlyView. "]
    September 15, 2020   doi: 10.1111/apha.13556   open full text
  • Implication of TRPC3 channel in gustatory perception of dietary lipids.
    Babar Murtaza, Aziz Hichami, Amira S. Khan, Jiri Plesnik, Omar Sery, Alexander Dietrich, Lutz Birnbaumer, Naim A. Khan.
    Acta Physiologica. September 13, 2020
    ["\nAbstract\n\nAim\nThe pathogenesis of obesity has been associated with high intake of dietary fat, and some recent studies have explored the cellular mechanisms of oro‐sensory detection of dietary fatty acids. We further assessed the role of transient receptor potential canonical (TRPC) channels in oro‐sensory perception of dietary lipids.\n\n\nMethods\nWe determined by RT‐qPCR and western blotting the expression of TRPC3/6/7 channels in mouse fungiform taste bud cells (mTBC). Immunocytochemistry was used to explore whether TRPC3 channels were co‐expressed with fatty acid receptors. We employed wild‐type (WT) mTBC, and those transfected with small interfering RNAs (siRNAs) against TRPC3 or STIM1. Ca2+ signalling was studied in TBC from TRPC3−/− mice and their WT littermates.\n\n\nResults\nWe demonstrate that mouse fungiform taste bud cells (mTBC) express TRPC3, but not TRPC6 or TRPC7 channels, and their inactivation by siRNA or experiments on TBC from TRPC3−/− mice brought about a decrease in fatty acid‐induced gustatory Ca2+ signalling, coupled with taste bud CD36 lipid sensor. TRPC3 channel activation was found to be under the control of STIM1 in lingual mTBC. Behavioural studies showed that spontaneous preference for a dietary long‐chain fatty acid was abolished in TRPC3−/− mice, and in mice wherein lingual TRPC3 expression was silenced by employing siRNA.\n\n\nConclusion\nWe report that lingual TRPC3 channels are critically involved in fat taste perception.\n\n", "Acta Physiologica, EarlyView. "]
    September 13, 2020   doi: 10.1111/apha.13554   open full text
  • Hydrophobic interactions between the HA helix and S4‐S5 linker modulate apparent Ca2+ sensitivity of SK2 channels.
    Young‐Woo Nam, Meng Cui, Razan Orfali, Adam Viegas, Misa Nguyen, Eman H. M. Mohammed, Khalid A. Zoghebi, Simin Rahighi, Keykavous Parang, Miao Zhang.
    Acta Physiologica. September 10, 2020
    ["\nAbstract\n\nAim\nSmall‐conductance Ca2+‐activated potassium (SK) channels are activated exclusively by increases in intracellular Ca2+ that binds to calmodulin constitutively associated with the channel. Wild‐type SK2 channels are activated by Ca2+ with an EC50 value of ~0.3 μmol/L. Here, we investigate hydrophobic interactions between the HA helix and the S4‐S5 linker as a major determinant of channel apparent Ca2+ sensitivity.\n\n\nMethods\nSite‐directed mutagenesis, electrophysiological recordings and molecular dynamic (MD) simulations were utilized.\n\n\nResults\nMutations that decrease hydrophobicity at the HA‐S4‐S5 interface lead to Ca2+ hyposensitivity of SK2 channels. Mutations that increase hydrophobicity result in hypersensitivity to Ca2+. The Ca2+ hypersensitivity of the V407F mutant relies on the interaction of the cognate phenylalanine with the S4‐S5 linker in the SK2 channel. Replacing the S4‐S5 linker of the SK2 channel with the S4‐S5 linker of the SK4 channel results in loss of the hypersensitivity caused by V407F. This difference between the S4‐S5 linkers of SK2 and SK4 channels can be partially attributed to I295 equivalent to a valine in the SK4 channel. A N293A mutation in the S4‐S5 linker also increases hydrophobicity at the HA‐S4‐S5 interface and elevates the channel apparent Ca2+ sensitivity. The double N293A/V407F mutations generate a highly Ca2+ sensitive channel, with an EC50 of 0.02 μmol/L. The MD simulations of this double‐mutant channel revealed a larger channel cytoplasmic gate.\n\n\nConclusion\nThe electrophysiological data and MD simulations collectively suggest a crucial role of the interactions between the HA helix and S4‐S5 linker in the apparent Ca2+ sensitivity of SK2 channels.\n\n", "Acta Physiologica, EarlyView. "]
    September 10, 2020   doi: 10.1111/apha.13552   open full text
  • The sodium channel NaV1.5 impacts on early murine embryonic cardiac development, structure and function in a non‐electrogenic manner.
    Gerard A. Marchal, Arie O. Verkerk, Rajiv A. Mohan, Rianne Wolswinkel, Bastiaan J. D. Boukens, Carol Ann Remme.
    Acta Physiologica. September 09, 2020
    ["\nAbstract\n\nAim\nThe voltage‐gated sodium channel NaV1.5, encoded by SCN5A, is essential for cardiac excitability and ensures proper electrical conduction. Early embryonic death has been observed in several murine models carrying homozygous Scn5amutations. We investigated when sodium current (INa) becomes functionally relevant in the murine embryonic heart and how Scn5a/NaV1.5 dysfunction impacts on cardiac development.\n\n\nMethods\nInvolvement of NaV1.5‐generated INa in murine cardiac electrical function was assessed by optical mapping in wild type (WT) embryos (embryonic day (E)9.5 and E10.5) in the absence and presence of the sodium channel blocker tetrodotoxin (30 µmol/L). INa was assessed by patch‐clamp analysis in cardiomyocytes isolated from WT embryos (E9.5‐17.5). In addition, cardiac morphology and electrical function was assessed in Scn5a‐1798insD−/− embryos (E9.5‐10.5) and their WT littermates.\n\n\nResults\nIn WT embryos, tetrodotoxin did not affect cardiac activation at E9.5, but slowed activation at E10.5. Accordingly, patch‐clamp measurements revealed that INa was virtually absent at E9.5 but robustly present at E10.5. Scn5a‐1798insD−/− embryos died in utero around E10.5, displaying severely affected cardiac activation and morphology. Strikingly, altered ventricular activation was observed in Scn5a‐1798insD−/− E9.5 embryos before the onset of INa, in addition to reduced cardiac tissue volume compared to WT littermates.\n\n\nConclusion\nWe here demonstrate that NaV1.5 is involved in cardiac electrical function from E10.5 onwards. Scn5a‐1798insD−/− embryos displayed cardiac structural abnormalities at E9.5, indicating that NaV1.5 dysfunction impacts on embryonic cardiac development in a non‐electrogenic manner. These findings are potentially relevant for understanding structural defects observed in relation to NaV1.5 dysfunction.\n\n", "Acta Physiologica, Volume 230, Issue 2, October 2020. "]
    September 09, 2020   doi: 10.1111/apha.13493   open full text
  • Contribution of oxygen extraction fraction to maximal oxygen uptake in healthy young men.
    Øyvind Skattebo, Jose A. L. Calbet, Bjarne Rud, Carlo Capelli, Jostein Hallén.
    Acta Physiologica. September 09, 2020
    ["\nAbstract\nWe analysed the importance of systemic and peripheral arteriovenous O2 difference (\n\n difference and a‐vfO2 difference, respectively) and O2 extraction fraction for maximal oxygen uptake (\n\n). Fick law of diffusion and the Piiper and Scheid model were applied to investigate whether diffusion versus perfusion limitations vary with \n\n. Articles (n = 17) publishing individual data (n = 154) on \n\n, maximal cardiac output (\n\n; indicator‐dilution or the Fick method), \n\n difference (catheters or the Fick equation) and systemic O2 extraction fraction were identified. For the peripheral responses, group‐mean data (articles: n = 27; subjects: n = 234) on leg blood flow (LBF; thermodilution), a‐vfO2 difference and O2 extraction fraction (arterial and femoral venous catheters) were obtained. \n\n and two‐LBF increased linearly by 4.9‐6.0 L · min–1 per 1 L · min–1 increase in \n\n (R2 = .73 and R2 = .67, respectively; both P < .001). The \n\n difference increased from 118‐168 mL · L–1 from a \n\n of 2‐4.5 L · min–1 followed by a reduction (second‐order polynomial: R2 = .27). After accounting for a hypoxemia‐induced decrease in arterial O2 content with increasing \n\n (R2 = .17; P < .001), systemic O2 extraction fraction increased up to ~90% (\n\n: 4.5 L · min–1) with no further change (exponential decay model: R2 = .42). Likewise, leg O2 extraction fraction increased with \n\n to approach a maximal value of ~90‐95% (R2 = .83). Muscle O2 diffusing capacity and the equilibration index Y increased linearly with \n\n (R2 = .77 and R2 = .31, respectively; both P < .01), reflecting decreasing O2 diffusional limitations and accentuating O2 delivery limitations. In conclusion, although O2 delivery is the main limiting factor to \n\n, enhanced O2 extraction fraction (≥90%) contributes to the remarkably high \n\n in endurance‐trained individuals.\n", "Acta Physiologica, Volume 230, Issue 2, October 2020. "]
    September 09, 2020   doi: 10.1111/apha.13486   open full text
  • Activated FMS‐like tyrosine kinase 3 ameliorates angiotensin II‐induced cardiac remodelling.
    Wenzhuo Ma, Fanfan Liang, Heqin Zhan, Xixi Jiang, Chenying Gao, Xin Zhang, Kaina Zhang, Qiang Sun, Hao Hu, Zhenghang Zhao.
    Acta Physiologica. September 09, 2020
    ["\nAbstract\n\nAim\nFMS‐like receptor tyrosine kinase 3 (Flt3) has been reported to be increased in cardiomyocytes responding to ischaemic stress. This study was to determine whether Flt3 activation could ameliorate pressure overload‐induced heart hypertrophy and fibrosis, and to elucidate the mechanisms of action.\n\n\nMethods\nIn vivo cardiac hypertrophy and remodelling experiments were conducted by infusing angiotensin II (Ang II) chronically in male C57BL/6 mice. Flt3‐specific ligand (FL) was administered intraperitoneally every two days (5 µg/mouse). In vitro experiments on hypertrophy, apoptosis and autophagy mechanism were performed in neonatal rat cardiomyocytes (NRCMs) and H9c2 cells with adenovirus vector‐mediated overexpression of Flt3.\n\n\nResults\nOur results demonstrated that following chronic Ang II infusion for 4 weeks, the mice exhibited heart hypertrophy, fibrosis, apoptosis and contractile dysfunction. Meanwhile, Ang II induced autophagic responses in mouse hearts, as evidenced by increased LC3 II and decreased P62 expression. These pathological alterations in Ang II‐treated mice were significantly ameliorated by Flt3 activation with FL administration. In NRCMs and Flt3‐overexpressed H9c2 cells, FL attenuated Ang II‐induced pathological autophagy and inactivated AMPK/mTORC1/FoxO3a signalling, thereby efficiently mitigating cell hypertrophy and apoptosis. Conversely, the AMPK activator metformin or the mTORC1 inhibitor rapamycin reversed the effects of FL on the alterations of autophagy, hypertrophy and apoptosis in cardiomyocytes induced by Ang II.\n\n\nConclusion\nFlt3 activation ameliorates cardiac hypertrophy, fibrosis and contractile dysfunction in the mouse model of chronic pressure overload, most likely via suppressing AMPK/mTORC1/FoxO3a‐mediated autophagy. These results provide new evidence supporting Flt3 as a novel therapeutic target in maladaptive cardiac remodelling.\n\n", "Acta Physiologica, Volume 230, Issue 2, October 2020. "]
    September 09, 2020   doi: 10.1111/apha.13519   open full text
  • Slc26a3 deletion alters pH‐microclimate, mucin biosynthesis, microbiome composition and increases the TNFα expression in murine colon.
    Archana Kini, Anurag K. Singh, Brigitte Riederer, Ines Yang, Xinjie Tan, Gabriella Stefano, Qinghai Tan, Fang Xiao, Weiliang Xia, Sebastian Suerbaum, Ursula Seidler.
    Acta Physiologica. September 09, 2020
    ["\nAbstract\n\nAim\nSLC26A3 (DRA) mediates the absorption of luminal Cl− in exchange for HCO3− in the distal intestine. Its expression is lost in congenital chloride diarrhoea (CLD) and strongly decreased in the presence of intestinal inflammation. To characterize the consequences of a loss of Slc26a3 beyond disturbed electrolyte transport, colonic mucus synthesis, surface accumulation and composition, pH microclimate, microbiome composition and development of inflammation was studied in slc26a3−/− mice.\n\n\nMethods\nThe epithelial surface pH microclimate and the surface mucus accumulation in vivo was assessed by two photon microscopy in exteriorized mid colon of anaesthetized slc26a3−/− and wt littermates. Mucus synthesis, composition and inflammatory markers were studied by qPCR and immunohistochemistry and microbiome composition by 16S rRNA sequencing.\n\n\nResults\nColonic pH microclimate was significantly more acidic in slc26a3−/− and to a lesser extent in cftr−/− than in wt mice. Goblet cell thecae per crypt were decreased in slc26a3−/− and increased in cftr−/− colon. Mucus accumulation in vivo was reduced, but much less so than in cftr−/− colon, which is possibly related to the different colonic fluid balance. Slc26a3−/− colonic luminal microbiome displayed strong decrease in diversity. These alterations preceded and maybe causally related to increased mucosal TNFα mRNA expression levels and leucocyte infiltration in the mid‐distal colon of slc26a3−/− but not of cftr−/− mice.\n\n\nConclusions\nThese findings may explain the strong increase in the susceptibility of slc26a3−/− mice to DSS damage, and offer insight into the mechanisms leading to an increased incidence of intestinal inflammation in CLD patients.\n\n", "Acta Physiologica, Volume 230, Issue 2, October 2020. "]
    September 09, 2020   doi: 10.1111/apha.13498   open full text
  • Intestinal epithelial ablation of Pit‐2/Slc20a2 in mice leads to sustained elevation of vitamin D3 upon dietary restriction of phosphate.
    Eva M. Pastor‐Arroyo, Thomas Knöpfel, Pedro H. Imenez Silva, Udo Schnitzbauer, Nadège Poncet, Jürg Biber, Carsten A. Wagner, Nati Hernando.
    Acta Physiologica. September 09, 2020
    ["\nAbstract\n\nAim\nSeveral Na+‐dependent phosphate cotransporters, namely NaPi‐IIb/SLC34A2, Pit‐1/SLC20A1 and Pit‐2/SLC20A2, are expressed at the apical membrane of enterocytes but their contribution to active absorption of phosphate is unclear. The aim of this study was to compare their pattern of mRNA expression along the small and large intestine and to analyse the effect of intestinal depletion of Pit‐2 on phosphate homeostasis.\n\n\nMethods\nIntestinal epithelial Pit‐2‐deficient mice were generated by crossing floxed Pit‐2 with villin‐Cre mice. Mice were fed 2 weeks standard or low phosphate diets. Stool, urine, plasma and intestinal and renal tissue were collected. Concentration of electrolytes and hormones, expression of mRNAs and proteins and intestinal transport of tracers were analysed.\n\n\nResults\nIntestinal mRNA expression of NaPi‐IIb and Pit‐1 is segment‐specific, whereas the abundance of Pit‐2 mRNA is more homogeneous. In ileum, NaPi‐IIb mRNA expression is restricted to enterocytes, whereas Pit‐2 mRNA is found in epithelial and non‐epithelial cells. Overall, their mRNA expression is not regulated by dietary phosphate. The absence of Pit‐2 from intestinal epithelial cells does not affect systemic phosphate homeostasis under normal dietary conditions. However, in response to dietary phosphate restriction, Pit‐2‐deficient mice showed exacerbated hypercalciuria and sustained elevation of 1,25(OH)2 vitamin D3.\n\n\nConclusions\nIn mice, the intestinal Na+/phosphate cotransporters are not coexpressed in all segments. NaPi‐IIb but not Pit‐2 mRNA is restricted to epithelial cells. Intestinal epithelial Pit‐2 does not contribute significantly to absorption of phosphate under normal dietary conditions. However, it may play a more significant role upon dietary phosphate restriction.\n\n", "Acta Physiologica, Volume 230, Issue 2, October 2020. "]
    September 09, 2020   doi: 10.1111/apha.13526   open full text
  • Mammalian circadian systems: Organization and modern life challenges.
    Anna‐Marie Finger, Achim Kramer.
    Acta Physiologica. September 09, 2020
    ["\nAbstract\nHumans and other mammalian species possess an endogenous circadian clock system that has evolved in adaptation to periodically reoccurring environmental changes and drives rhythmic biological functions, as well as behavioural outputs with an approximately 24‐hour period. In mammals, body clocks are hierarchically organized, encompassing a so‐called pacemaker clock in the hypothalamic suprachiasmatic nucleus (SCN), non‐SCN brain and peripheral clocks, as well as cell‐autonomous oscillators within virtually every cell type. A functional clock machinery on the molecular level, alignment among body clocks, as well as synchronization between endogenous circadian and exogenous environmental cycles has been shown to be crucial for our health and well‐being. Yet, modern life constantly poses widespread challenges to our internal clocks, for example artificial lighting, shift work and trans‐meridian travel, potentially leading to circadian disruption or misalignment and the emergence of associated diseases. For instance many of us experience a mismatch between sleep timing on work and free days (social jetlag) in our everyday lives without being aware of health consequences that may arise from such chronic circadian misalignment, Hence, this review provides an overview of the organization and molecular built‐up of the mammalian circadian system, its interactions with the outside world, as well as pathologies arising from circadian disruption and misalignment.\n", "Acta Physiologica, EarlyView. "]
    September 09, 2020   doi: 10.1111/apha.13548   open full text
  • Concomitant excitation and tension development are required for myocellular gene expression and protein synthesis in rat skeletal muscle.
    Emil Rindom, Jon Herskind, Bert Blaauw, Kristian Overgaard, Kristian Vissing, Frank V. Paoli.
    Acta Physiologica. August 31, 2020
    ["\nAbstract\n\nAim\nLoading‐induced tension development is often assumed to constitute an independent cue to initiate muscle protein synthesis following resistance exercise. However, with traditional physiological models of resistance exercise, changes in loading‐induced tension development also reflect changes in neural activation patterns, and direct evidence for a mechanosensitive mechanism is therefore limited. Here, we sought to examine the importance of excitation and tension development per se on initiation of signalling, gene transcription and protein synthesis in rat skeletal muscle.\n\n\nMethods\nIsolated rat extensor digitorum longus muscles were allocated to the following interventions: (a) Excitation‐induced eccentric contractions (ECC); (b) Passive stretching without excitation (PAS); (c) Excitation with inhibition of contractions (STIM + IMA) and; (d) Excitation in combination with both inhibition of contractions and PAS (STIM + IMA + PAS). Assessment of transcriptional and translational signalling, gene transcription and acute muscle protein synthesis was compared in stimulated vs contra‐lateral non‐stimulated control muscle.\n\n\nResults\nProtein synthesis increased solely in muscles subjected to a combination of excitation and tension development (ECC and STIM + IMA + PAS). The same pattern was true for p38 mitogen‐activated protein kinase signalling for gene transcription as well as for gene transcription of immediate early genes FOS and JUN. In contrast, mechanistic target of rapamycin Complex 1 signalling for translation initiation increased in all muscles subjected to increased tension development (ECC and STIM + IMA + PAS as well as PAS).\n\n\nConclusions\nThe current study suggests that exercise‐induced increases in protein synthesis as well as transcriptional signalling is dependent on the concomitant effect of excitation and tension development, whereas signalling for translation initiation is only dependent of tension development per se.\n\n", "Acta Physiologica, EarlyView. "]
    August 31, 2020   doi: 10.1111/apha.13540   open full text
  • Myosin heavy chains in extraocular muscle fibres: Distribution, regulation and function.
    Joseph F. Y. Hoh.
    Acta Physiologica. August 26, 2020
    ["\nAbstract\nThis review examines kinetic properties and distribution of the 11 isoforms of myosin heavy chain (MyHC) expressed in extraocular muscle (EOM) fibre types and the regulation and function of these MyHCs. Although recruitment and discharge characteristics of ocular motoneurons during fixation and eye movements are well documented, work directly linking these properties with motor unit contractile speed and MyHC composition is lacking. Recruitment of motor units according to Henneman's size principle has some support in EOMs but needs consolidation. Both neurogenic and myogenic mechanisms regulate MyHC expression as in other muscle allotypes. Developmentally, multiply‐innervated (MIFs) and singly‐innervated fibres (SIFs) are derived presumably from distinct myoblast lineages, ending up expressing MyHCs in the slow and fast ends of the kinetic spectrum respectively. They modulate the synaptic inputs of their motoneurons through different retrogradely transported neurotrophins, thereby specifying their tonic and phasic impulse patterns. Immunohistochemical analyses of EOMs regenerating in situ and in limb muscle beds suggest that the very impulse patterns driving various ocular movements equip effectors with appropriate MyHC compositions and speeds to accomplish their tasks. These experiments also suggest that satellite cells of SIFs and MIFs are distinct lineages expressing different MyHCs during regeneration. MyHC compositions and functional characteristics of orbital fibres show longitudinal variations that facilitate linear ocular rotation during saccades. Palisade endings on global MIFs are postulated to respond to active and passive tensions by triggering axon reflexes that play important roles during fixation, saccades and vergence. How EOMs implement Listings law during ocular rotation is discussed.\n", "Acta Physiologica, EarlyView. "]
    August 26, 2020   doi: 10.1111/apha.13535   open full text
  • Disruption of transverse‐tubular network reduces energy efficiency in cardiac muscle contraction.
    Nicholas G. Mellor, Toan Pham, Kenneth Tran, Denis S. Loiselle, Marie‐Louise Ward, Andrew J. Taberner, David J. Crossman, June‐Chiew Han.
    Acta Physiologica. August 16, 2020
    ["\nAbstract\n\nAim\nAltered organization of the transverse‐tubular network is an early pathological event occurring even prior to the onset of heart failure. Such t‐tubular remodelling disturbs the synchrony and signalling between membranous and intracellular ion channels, exchangers, receptors and ATPases essential in the dynamics of excitation‐contraction coupling, leading to ionic abnormality and mechanical dysfunction in heart disease progression. In this study, we investigated whether a disrupted t‐tubular network has a direct effect on cardiac mechano‐energetics. Our aim was to understand the fundamental link between t‐tubular remodelling and impaired energy metabolism, both of which are characteristics of heart failure. We thus studied healthy tissue preparations in which cellular processes are not altered by any disease event.\n\n\nMethods\nWe exploited the “formamide‐detubulation” technique to acutely disrupt the t‐tubular network in rat left‐ventricular trabeculae. We assessed the energy utilization by cellular Ca2+ cycling and by crossbridge cycling, and quantified the change of energy efficiency following detubulation. For these measurements, trabeculae were mounted in a microcalorimeter where force and heat output were simultaneously measured.\n\n\nResults\nFollowing structural disorganization from detubulation, muscle heat output associated with Ca2+ cycling was reduced, indicating impaired intracellular Ca2+ homeostasis. This led to reduced force production and heat output by crossbridge cycling. The reduction in force‐length work was not paralleled by proportionate reduction in the heat output and, as such, energy efficiency was reduced.\n\n\nConclusions\nThese results reveal the direct energetic consequences of disrupted t‐tubular network, linking the energy disturbance and the t‐tubular remodelling typically observed in heart failure.\n\n", "Acta Physiologica, EarlyView. "]
    August 16, 2020   doi: 10.1111/apha.13545   open full text
  • The zebrafish histamine H3 receptor modulates aggression, neural activity and forebrain functional connectivity.
    Florian Reichmann, Neal Rimmer, Ceinwen A. Tilley, Elisa Dalla Vecchia, Joseph Pinion, Amir Al Oustah, Hector Carreño Gutiérrez, Andrew M. J. Young, Jonathan R. McDearmid, Matthew J. Winter, William H. J. Norton.
    Acta Physiologica. August 12, 2020
    ["\nAbstract\n\nAim\nAggression is a behavioural trait characterized by the intention to harm others for offensive or defensive purposes. Neurotransmitters such as serotonin and dopamine are important mediators of aggression. However, the physiological role of the histaminergic system during this behaviour is currently unclear. Here, we aimed to better understand histaminergic signalling during aggression by characterizing the involvement of the histamine H3 receptor (Hrh3).\n\n\nMethods\nWe have generated a novel zebrafish Hrh3 null mutant line using CRISPR‐Cas9 genome engineering and investigated behavioural changes and alterations to neural activity using whole brain Ca2+ imaging in zebrafish larvae and ribosomal protein S6 (rpS6) immunohistochemistry in adults.\n\n\nResults\nWe show that genetic inactivation of the histamine H3 receptor (Hrh3) reduces aggression in zebrafish, an effect that can be reproduced by pharmacological inhibition. In addition, hrh3−/− zebrafish show behavioural impairments consistent with heightened anxiety. Larval in vivo whole brain Ca2+ imaging reveals higher neuronal activity in the forebrain of mutants, but lower activity in specific hindbrain areas and changes in measures of functional connectivity between subregions. Adult hrh3−/− zebrafish display brain region‐specific neural activity changes in response to aggression of both key regions of the social decision‐making network, and the areas containing histaminergic neurons in the zebrafish brain.\n\n\nConclusion\nThese results highlight the importance of zebrafish Hrh3 signalling for aggression and anxiety and uncover the brain areas involved. Targeting this receptor might be a potential novel therapeutic route for human conditions characterized by heightened aggression.\n\n", "Acta Physiologica, EarlyView. "]
    August 12, 2020   doi: 10.1111/apha.13543   open full text
  • Nitrergic perivascular innervation in health and diseases: Focus on vascular tone regulation.
    Fabiano E. Xavier.
    Acta Physiologica. August 10, 2020
    ["\nAbstract\nFor a long time, the vascular tone was considered to be regulated exclusively by tonic innervation of vasoconstrictor adrenergic nerves. However, accumulating experimental evidence has revealed the existence of nerves mediating vasodilatation, including perivascular nitrergic nerves (PNN), in a wide variety of mammalian species. Functioning of nitrergic vasodilator nerves is evidenced in several territories, including cerebral, mesenteric, pulmonary, renal, penile, uterine and cutaneous arteries. Nitric oxide (NO) is the main neurogenic vasodilator in cerebral arteries and acts as a counter‐regulatory mechanism for adrenergic vasoconstriction in other vascular territories. In the penis, NO relaxes the vascular and cavernous smooth muscles leading to penile erection. Furthermore, when interacting with other perivascular nerves, NO can act as a neuromodulator. PNN dysfunction is involved in the genesis and maintenance of vascular disorders associated with arterial and portal hypertension, diabetes, ageing, obesity, cirrhosis and hormonal changes. For example defective nitrergic function contributes to enhanced sympathetic neurotransmission, vasoconstriction and blood pressure in some animal models of hypertension. In diabetic animals and humans, dysfunctional nitrergic neurotransmission in the corpus cavernosum is associated with erectile dysfunction. However, in some vascular beds of hypertensive and diabetic animals, an increased PNN function has been described as a compensatory mechanism to the increased vascular resistance. The present review summarizes current understanding on the role of PNN in control of vascular tone, its alterations under different conditions and the associated mechanisms. The knowledge of these changes can serve to better understand the mechanisms involved in these disorders and help in planning new treatments.\n", "Acta Physiologica, Volume 230, Issue 1, September 2020. "]
    August 10, 2020   doi: 10.1111/apha.13484   open full text
  • Exercise‐dependent increases in protein synthesis are accompanied by chromatin modifications and increased MRTF‐SRF signalling.
    Francesca Solagna, Leonardo Nogara, Kenneth A. Dyar, Franziska Greulich, Ashfaq A. Mir, Clara Türk, Theresa Bock, Alessia Geremia, Martina Baraldo, Roberta Sartori, Jean Farup, Henriette Uhlenhaut, Kristian Vissing, Marcus Krüger, Bert Blaauw.
    Acta Physiologica. August 10, 2020
    ["\nAbstract\n\nAim\nResistance exercise increases muscle mass over time. However, the early signalling events leading to muscle growth are not yet well‐defined. Here, we aim to identify new signalling pathways important for muscle remodelling after exercise.\n\n\nMethods\nWe performed a phosphoproteomics screen after a single bout of exercise in mice. As an exercise model we used unilateral electrical stimulation in vivo and treadmill running. We analysed muscle biopsies from human subjects to verify if our findings in murine muscle also translate to exercise in humans.\n\n\nResults\nWe identified a new phosphorylation site on Myocardin‐Related Transcription Factor B (MRTF‐B), a co‐activator of serum response factor (SRF). Phosphorylation of MRTF‐B is required for its nuclear translocation after exercise and is accompanied by the transcription of the SRF target gene Fos. In addition, high‐intensity exercise also remodels chromatin at specific SRF target gene loci through the phosphorylation of histone 3 on serine 10 in myonuclei of both mice and humans. Ablation of the MAP kinase member MSK1/2 is sufficient to prevent this histone phosphorylation, reduce induction of SRF‐target genes, and prevent increases in protein synthesis after exercise.\n\n\nConclusion\nOur results identify a new exercise signalling fingerprint in vivo, instrumental for exercise‐induced protein synthesis and potentially muscle growth.\n\n", "Acta Physiologica, Volume 230, Issue 1, September 2020. "]
    August 10, 2020   doi: 10.1111/apha.13496   open full text
  • Co‐cultures of renal progenitors and endothelial cells on kidney decellularized matrices replicate the renal tubular environment in vitro.
    Rita Sobreiro‐Almeida, Maria Elena Melica, Laura Lasagni, Paola Romagnani, Nuno M. Neves.
    Acta Physiologica. August 10, 2020
    ["\nAbstract\n\nAim\nHerein we propose creating a bilayer tubular kidney in‐vitro model. It is hypothesized that membranes composed of decellularized porcine kidney extracellular matrix are valid substitutes of the tubular basement membrane by mimicking the physiological relevance of the in vivo environment and disease phenotypes.\n\n\nMethods\nExtracellular matrix was obtained from decellularized porcine kidneys. After processing by lyophilization and milling, it was dissolved in an organic solvent and blended with poly(caprolactone). Porous membranes were obtained by electrospinning and seeded with human primary renal progenitor cells to evaluate phenotypic alterations. To create a bilayer model of the in vivo tubule, the same cells were differentiated into epithelial tubular cells and co‐cultured with endothelial cells in opposite sites.\n\n\nResults\nOur results demonstrate increasing metabolic activity, proliferation and total protein content of renal progenitors over time. We confirmed the expression of several genes encoding epithelial transport proteins and we could also detect tubular‐specific proteins by immunofluorescence stainings. Functional and transport assays were performed trough the bilayer by quantifying both human serum albumin uptake and inulin leakage. Furthermore, we validated the chemical modulation of nephrotoxicity on this epithelium‐endothelium model by cisplatin exposure.\n\n\nConclusion\nThe use of decellularized matrices in combination with primary renal cells was shown to be a valuable tool for modelling renal function and disease in vitro. We successfully validated our hypothesis by replicating the physiological conditions of an in vitro tubular bilayer model. The developed system may contribute significantly for the future investigation of advanced therapies for kidney diseases.\n\n", "Acta Physiologica, Volume 230, Issue 1, September 2020. "]
    August 10, 2020   doi: 10.1111/apha.13491   open full text
  • Prolonged therapeutic effects of photoactivated adipose‐derived stem cells following ischaemic injury.
    Xin Fan, Kai Li, Luochen Zhu, Xin Deng, Ziqian Feng, Chunrong Xu, Sijing Liu, Jianbo Wu.
    Acta Physiologica. August 10, 2020
    ["\nAbstract\n\nAim\nAdipose‐derived stem cells (ASCs) therapies are emerging as a promising approach to therapeutic angiogenesis. Therapeutic persistence and reduced primitive stem cell function following cell delivery remains a critical hurdle for the clinical translation of stem cells in current approaches.\n\n\nMethods\nCultured ASCs were derived from subcutaneous white adipose tissue isolated from mice fed a normal diet (ND). Unilateral hindlimb ischaemia model was induced in high‐fat diet (HFD)‐fed mice by femoral artery interruption, after which photoactivated and non‐light‐treated ASCs were injected into the tail vein of mice. Laser Doppler imaging was conducted to measure the blood flow reperfusion. Capillary density was measured in the ischaemic gastrocnemius muscle. mRNA levels of angiogenic factors were determined by reverse‐transcription polymerase chain reaction. Flow cytometry was used to determine the characterization of ASCs and endothelial progenitor cell (EPC). Human ASCs secretomes were analysed by liquid chromatography tandem mass spectrometry.\n\n\nResults\nOur study demonstrated that photoactivated ND‐ASCs prolonged functional blood flow perfusion and increased ASCs‐derived EPC and neovascularization 38 days after ligation, when compared with saline‐treated controls. Profiling analysis in ischaemic muscles showed upregulation of genes associated with pro‐angiogenic factors after injection of photoactivated ND‐ASCs when compared with the non‐light‐treated ASCs or saline treated HFD mice. Mass spectrometry revealed that light‐treated ASCs conditioned medium retained a more complete pro‐angiogenic activity with significant upregulation of angiogenesis related proteins.\n\n\nConclusion\nOur data demonstrates that photoactivated ND‐ASCs improve blood flow recovery and their injection may prove to be a useful strategy for the prevention and treatment of diabetic peripheral arterial disease.\n\n", "Acta Physiologica, Volume 230, Issue 1, September 2020. "]
    August 10, 2020   doi: 10.1111/apha.13475   open full text
  • Cytochrome P450 epoxygenase‐derived 5,6‐epoxyeicosatrienoic acid relaxes pulmonary arteries in normoxia but promotes sustained pulmonary vasoconstriction in hypoxia.
    Ievgen Strielkov, Nicole C. Krause, Fenja Knoepp, Nasim Alebrahimdehkordi, Oleg Pak, Claudia Garcia, Hossein A. Ghofrani, Ralph T. Schermuly, Werner Seeger, Friedrich Grimminger, Natascha Sommer, Norbert Weissmann.
    Acta Physiologica. August 10, 2020
    ["\nAbstract\n\nAims\nThe aim of the study was to investigate the role of cytochrome P450 (CYP) epoxygenase‐derived epoxyeicosatrienoic acids (EETs) in sustained hypoxic pulmonary vasoconstriction (HPV).\n\n\nMethods\nVasomotor responses of isolated mouse intrapulmonary arteries (IPAs) were assessed using wire myography. Key findings were verified by haemodynamic measurements in isolated perfused and ventilated mouse lungs.\n\n\nResults\nPharmacological inhibition of EET synthesis with MS‐PPOH, application of the EET antagonist 14,15‐EEZE or deficiency of CYP2J isoforms suppressed sustained HPV. In contrast, knockdown of EET‐degrading soluble epoxide hydrolase or its inhibition with TPPU augmented sustained HPV almost twofold. All EET regioisomers elicited relaxation in IPAs pre‐contracted with thromboxane mimetic U46619. However, in the presence of KCl‐induced depolarization, 5,6‐EET caused biphasic contraction in IPAs and elevation of pulmonary vascular tone in isolated lungs, whereas other regioisomers had no effect. In patch‐clamp experiments, hypoxia elicited depolarization in pulmonary artery smooth muscle cells (PASMCs), and 5,6‐EET evoked inward whole cell currents in PASMCs depolarized to the hypoxic level, but not at their resting membrane potential.\n\n\nConclusions\nThe EET pathway substantially contributes to sustained HPV in mouse pulmonary arteries. 5,6‐EET specifically appears to be involved in HPV, as it is the only EET regioisomer able to elicit not only relaxation, but also sustained contraction in these vessels. 5,6‐EET‐induced pulmonary vasoconstriction is enabled by PASMC depolarization, which occurs in hypoxia. The discovery of the dual role of 5,6‐EET in the regulation of pulmonary vascular tone may provide a basis for the development of novel therapeutic strategies for treatment of HPV‐related diseases.\n\n", "Acta Physiologica, Volume 230, Issue 1, September 2020. "]
    August 10, 2020   doi: 10.1111/apha.13521   open full text
  • Cystic fibrosis transmembrane conductance regulator‐dependent bicarbonate entry controls rat cardiomyocyte ATP release via pannexin1 through mitochondrial signalling and caspase activation.
    Yongshun Wang, Junjun Zhao, Yin Cai, Heather J. Ballard.
    Acta Physiologica. August 10, 2020
    ["\nAbstract\n\nAim\nCystic fibrosis transmembrane conductance regulator (CFTR) is expressed in the heart, but its function there is unclear. CFTR regulates an ATP release pore in many tissues, but the identity and regulatory mechanism of the pore are unknown. We investigated the role of CFTR in ATP release from primary cardiomyocytes and ventricular wall in vivo.\n\n\nMethods\nProteins involved in the signalling pathway for ATP release during simulated ischaemia (lactic acid treatment) were investigated using inhibitors and siRNA; colocalization was identified by coimmunofluorescence and proximity ligation assays; changes in near‐membrane pH and calcium were identified with total internal reflection microscopy; in vivo ATP release was investigated using interstitial microdialysis of rat heart.\n\n\nResults\nLactic acid‐induced CFTR‐dependent ATP release from cultured cardiomyocytes and left ventricle in vivo. Lactic acid entry elevated near‐membrane calcium, which involved Na/H‐ and Na/Ca‐exchangers colocalized with CFTR. Calcium entry‐induced CFTR activation, which involved cAMP, protein kinase A, FAK, Pyk2 and Src. Removal of extracellular bicarbonate abolished cardiomyocyte ATP release induced by lactic acid or CFTR activators. Bicarbonate stimulated cytochrome c expression, cytochrome c release and ATP release from isolated cardiomyocyte mitochondria. Pannexin 1 (Panx1) colocalized with CFTR. Lactic acid increased cardiomyocyte caspase activity: caspase inhibitors or Panx1 siRNA abolished cardiomyocyte ATP release, while pannexin inhibition abolished cardiac ATP release in vivo.\n\n\nConclusion\nDuring simulated ischaemia, CFTR‐dependent bicarbonate entry stimulated ATP and cytochrome c release from mitochondria; in the cytoplasm, cytochrome c‐activated caspase 3, which in turn activated Panx1, and ATP was released through the opened Panx1 channel.\n\n", "Acta Physiologica, Volume 230, Issue 1, September 2020. "]
    August 10, 2020   doi: 10.1111/apha.13495   open full text
  • The role of RIPK3‐regulated cell death pathways and necroptosis in the pathogenesis of cardiac ischaemia‐reperfusion injury.
    Luo Ying, Juthipong Benjanuwattra, Siriporn C. Chattipakorn, Nipon Chattipakorn.
    Acta Physiologica. August 07, 2020
    ["\nAbstract\nDespite advancements in management of acute myocardial infarction, this disease remains one of the leading causes of death. Timely reestablishment of epicardial coronary blood flow is the cornerstone of therapy; however, substantial amount of damage can occur as a consequence of cardiac ischaemia/reperfusion (I/R) injury. It has been previously proposed that the pathway leading to major cell death, apoptosis, is responsible for cardiac I/R injury. Nevertheless, there is compelling evidence to suggest that necroptosis, a programmed necrosis, contributes remarkably to both myocardial injury and microcirculatory dysfunction following cardiac I/R injury. Receptor‐interacting protein kinase 1 (RIPK1), RIPK3, and mixed‐lineage kinase domain‐like pseudokinase (MLKL) are shown as the major mediators of necroptosis. In addition to the traditional perception that RIPK1/RIPK3/MLKL‐dependent plasma membrane rupture is fundamental to this process, several RIPK3‐related pathways such as endoplasmic reticulum stress and mitochondrial fragmentation have also been implicated in cardiac I/R injury. In this review, reports from both in vitro and in vivo studies regarding the roles of necroptosis and RIPK3‐regulated necrosis in cardiac I/R injury have been collectively summarized and discussed. Furthermore, reports on potential interventions targeting these processes to attenuate cardiac I/R insults to the heart have been presented in this review. Future investigations adding to the knowledge obtained from these previous studies are needed in the pursuit of discovering the most effective pharmacological agent to improve cardiac I/R outcomes.\n", "Acta Physiologica, EarlyView. "]
    August 07, 2020   doi: 10.1111/apha.13541   open full text
  • The Drosophila septate junctions beyond barrier function: Review of the literature, prediction of human orthologs of the SJ‐related proteins and identification of protein domain families.
    Erasmia Rouka, Natalia Gourgoulianni, Stefan Lüpold, Chrissi Hatzoglou, Konstantinos Gourgoulianis, Wolf U. Blanckenhorn, Sotirios G. Zarogiannis.
    Acta Physiologica. August 05, 2020
    ["\nAbstract\nThe involvement of Septate Junctions (SJs) in critical cellular functions that extend beyond their role as diffusion barriers in the epithelia and the nervous system has made the fruit fly an ideal model for the study of human diseases associated with impaired Tight Junction (TJ) function. In this study, we summarized current knowledge of the Drosophila melanogaster SJ‐related proteins, focusing on their unconventional functions. Additionally, we sought to identify human orthologs of the corresponding genes as well as protein domain families. The systematic literature search was performed in PubMed and Scopus databases using relevant key terms. Orthologs were predicted using the DIOPT tool and aligned protein regions were determined from the Pfam database. 3‐D models of the smooth SJ proteins were built on the Phyre2 and DMPFold protein structure prediction servers. A total of 30 proteins were identified as relatives to the SJ cellular structure. Key roles of these proteins, mainly in the regulation of morphogenetic events and cellular signalling, were highlighted. The investigation of protein domain families revealed that the SJ‐related proteins contain conserved domains that are required not only for cell‐cell interactions and cell polarity but also for cellular signalling and immunity. DIOPT analysis of orthologs identified novel human genes as putative functional homologs of the fruit fly SJ genes. A gap in our knowledge was identified regarding the domains that occur in the proteins encoded by eight SJ‐associated genes. Future investigation of these domains is needed to provide functional information.\n", "Acta Physiologica, EarlyView. "]
    August 05, 2020   doi: 10.1111/apha.13527   open full text
  • Mechanisms coupling sodium and magnesium reabsorption in the distal convoluted tubule of the kidney.
    Gijs A. C. Franken, Anastasia Adella, René J. M. Bindels, Jeroen H. F. Baaij.
    Acta Physiologica. July 26, 2020
    ["\nAbstract\nHypomagnesaemia is a common feature of renal Na+ wasting disorders such as Gitelman and EAST/SeSAME syndrome. These genetic defects specifically affect Na+ reabsorption in the distal convoluted tubule, where Mg2+ reabsorption is tightly regulated. Apical uptake via TRPM6 Mg2+ channels and basolateral Mg2+ extrusion via a putative Na+‐Mg2+ exchanger determines Mg2+ reabsorption in the distal convoluted tubule. However, the mechanisms that explain the high incidence of hypomagnesaemia in patients with Na+ wasting disorders of the distal convoluted tubule are largely unknown. In this review, we describe three potential mechanisms by which Mg2+ reabsorption in the distal convoluted tubule is linked to Na+ reabsorption. First, decreased activity of the thiazide‐sensitive Na+/Cl− cotransporter (NCC) results in shortening of the segment, reducing the Mg2+ reabsorption capacity. Second, the activity of TRPM6 and NCC are determined by common regulatory pathways. Secondary effects of NCC dysregulation such as hormonal imbalance, therefore, might disturb TRPM6 expression. Third, the basolateral membrane potential, maintained by the K+ permeability and Na+‐K+‐ATPase activity, provides the driving force for Na+ and Mg2+ extrusion. Depolarisation of the basolateral membrane potential in Na+ wasting disorders of the distal convoluted tubule may therefore lead to reduced activity of the putative Na+‐Mg2+ exchanger SLC41A1. Elucidating the interconnections between Mg2+ and Na+ transport in the distal convoluted tubule is hampered by the currently available models. Our analysis indicates that the coupling of Na+ and Mg2+ reabsorption may be multifactorial and that advanced experimental models are required to study the molecular mechanisms.\n", "Acta Physiologica, EarlyView. "]
    July 26, 2020   doi: 10.1111/apha.13528   open full text
  • Pathophysiological mechanisms explaining poor clinical outcome of older cancer patients with low skeletal muscle mass.
    Stéphanie M. L. M. Looijaard, Miriam L. Lintel Hekkert, Rob C. I. Wüst, René H. J. Otten, Carel G. M. Meskers, Andrea B. Maier.
    Acta Physiologica. July 24, 2020
    ["\nAbstract\nLow skeletal muscle mass is highly prevalent in older cancer patients and affects 5% to 89% depending on the type and stage of cancer. Low skeletal muscle mass is associated with poor clinical outcomes such as post‐operative complications, chemotherapy toxicity and mortality in older cancer patients. Little is known about the mediating pathophysiological mechanisms. In this review, we summarize proposed pathophysiological mechanisms underlying the association between low skeletal muscle mass and poor clinical outcomes in older cancer patients including a) systemic inflammation; b) insulin‐dependent glucose handling; c) mitochondrial function; d) protein status and; e) pharmacokinetics of anticancer drugs. The mechanisms of altered myokine balance negatively affecting the innate and adaptive immune system, and altered pharmacokinetics of anticancer drugs leading to a relative overdosage of anticancer drugs are best‐substantiated. The effects of glucose intolerance and circulating mitochondrial DNA as a consequence of low skeletal muscle mass are topics of interest for future research. Restoring myokine balance through physical exercise, exercise mimetics, neuro‐muscular activation and adapting anticancer drug dosing on skeletal muscle mass could be targeted approaches to improve clinical outcomes in older cancer patients with low skeletal muscle mass.\n", "Acta Physiologica, EarlyView. "]
    July 24, 2020   doi: 10.1111/apha.13516   open full text
  • Intact vagal gut‐brain signalling prevents hyperphagia and excessive weight gain in response to high‐fat high‐sugar diet.
    Molly McDougle, Danielle Quinn, Charlene Diepenbroek, Arashdeep Singh, Claire de la Serre, Guillaume de Lartigue.
    Acta Physiologica. July 22, 2020
    ["\nAbstract\n\nAim\nThe tools that have been used to assess the function of the vagus nerve lack specificity. This could explain discrepancies about the role of vagal gut‐brain signalling in long‐term control of energy balance. Here we use a validated approach to selectively ablate sensory vagal neurones that innervate the gut to determine the role of vagal gut‐brain signalling in the control of food intake, energy expenditure and glucose homoeostasis in response to different diets.\n\n\nMethods\nRat nodose ganglia were injected bilaterally with either the neurotoxin saporin conjugated to the gastrointestinal hormone cholecystokinin (CCK), or unconjugated saporin as a control. Food intake, body weight, glucose tolerance and energy expenditure were measured in both groups in response to chow or high‐fat high‐sugar (HFHS) diet. Willingness to work for fat or sugar was assessed by progressive ratio for orally administered solutions, while post‐ingestive feedback was tested by measuring food intake after an isocaloric lipid or sucrose pre‐load.\n\n\nResults\nVagal deafferentation of the gut increases meal number in lean chow‐fed rats. Switching to a HFHS diet exacerbates overeating and body weight gain. The breakpoint for sugar or fat solution did not differ between groups, suggesting that increased palatability may not drive HFHS‐induced hyperphagia. Instead, decreased satiation in response to intra‐gastric infusion of fat, but not sugar, promotes hyperphagia in CCK‐Saporin‐treated rats fed with HFHS diet.\n\n\nConclusions\nWe conclude that intact sensory vagal neurones prevent hyperphagia and exacerbation of weight gain in response to a HFHS diet by promoting lipid‐mediated satiation.\n\n", "Acta Physiologica, EarlyView. "]
    July 22, 2020   doi: 10.1111/apha.13530   open full text
  • Sodium‐glucose cotransporter 1 as a sugar taste sensor in mouse tongue.
    Keiko Yasumatsu, Tadahiro Ohkuri, Ryusuke Yoshida, Shusuke Iwata, Robert F. Margolskee, Yuzo Ninomiya.
    Acta Physiologica. July 22, 2020
    ["\nAbstract\n\nAim\nWe investigated potential neuron types that code sugar information and how sodium‐glucose cotransporters (SGLTs) and T1Rs are involved.\n\n\nMethods\nWhole‐nerve recordings in the chorda tympani (CT) and the glossopharyngeal (GL) nerves and single‐fibre recordings in the CT were performed in T1R3‐KO and wild‐type (WT) mice. Behavioural response measurements were conducted in T1R3‐KO mice using phlorizin (Phl), a competitive inhibitor of SGLTs.\n\n\nResults\nResults indicated that significant enhancement occurred in responses to sucrose and glucose (Glc) by adding 10 mmol/L NaCl but not in responses to KCl, monopotassium glutamate, citric acid, quinine sulphate, SC45647(SC) or polycose in both CT and GL nerves. These enhancements were abolished by lingual application of Phl. In single‐fibre recording, fibres showing maximal response to sucrose could be classified according to responses to SC and Glc with or without 10 mmol/L NaCl in the CT of WT mice, namely, Phl‐insensitive type, Phl‐sensitive Glc‐type and Mixed (Glc and SC responding)‐type fibres. In T1R3‐KO mice, Phl‐insensitive‐type fibres disappeared. Results from behavioural experiments showed that the number of licks and amount of intake for Glc with or without 10 mmol/L NaCl were significantly suppressed by Phl.\n\n\nConclusion\nWe found evidence for the contribution of SGLTs in sugar sensing in taste cells of mouse tongue. Moreover, we found T1R‐dependent (Phl‐insensitive) type, Glc‐type and Mixed (SGLTs and T1Rs)‐type fibres. SGLT1 may be involved in the latter two types and may play important roles in the glucose‐specific cephalic phase of digestion and palatable food intake.\n\n", "Acta Physiologica, EarlyView. "]
    July 22, 2020   doi: 10.1111/apha.13529   open full text
  • Neuromuscular responses to fatiguing locomotor exercise.
    Callum G. Brownstein, Guillaume Y. Millet, Kevin Thomas.
    Acta Physiologica. July 17, 2020
    ["\nAbstract\nOver the last two decades, an abundance of research has explored the impact of fatiguing locomotor exercise on the neuromuscular system. Neurostimulation techniques have been implemented prior to and following locomotor exercise tasks of a wide variety of intensities, durations, and modes. These techniques have allowed for the assessment of alterations occurring within the central nervous system and the muscle, while techniques such as transcranial magnetic stimulation and spinal electrical stimulation have permitted further segmentalization of locomotor exercise‐induced changes along the motor pathway. To this end, the present review provides a comprehensive synopsis of the literature pertaining to neuromuscular responses to locomotor exercise. Sections of the review were divided to discuss neuromuscular responses to maximal, severe, heavy and moderate intensity, high‐intensity intermittent exercise, and differences in neuromuscular responses between exercise modalities. During maximal and severe intensity exercise, alterations in neuromuscular function reside primarily within the muscle. Although post‐exercise reductions in voluntary activation following maximal and severe intensity exercise are generally modest, several studies have observed alterations occurring at the cortical and/or spinal level. During prolonged heavy and moderate intensity exercise, impairments in contractile function are attenuated with respect to severe intensity exercise, but are still widely observed. While reductions in voluntary activation are greater during heavy and moderate intensity exercise, the specific alterations occurring within the central nervous system remain unclear. Further work utilizing stimulation techniques during exercise and integrating new and emerging techniques such as high‐density electromyography is warranted to provide further insight into neuromuscular responses to locomotor exercise.\n", "Acta Physiologica, EarlyView. "]
    July 17, 2020   doi: 10.1111/apha.13533   open full text
  • Adrenal stress hormone action in skeletal muscle during exercise training: An old dog with new tricks?
    Jennifer L. Steiner, Bonde R. Johnson, Robert C. Hickner, Michael J. Ormsbee, David L. Williamson, Bradley S. Gordon.
    Acta Physiologica. June 29, 2020
    ["\nAbstract\nExercise is a key component of a healthy lifestyle as it helps maintain a healthy body weight and reduces the risk of various morbidities and co‐morbidities. Exercise is an acute physiological stress that initiates a multitude of processes that attempt to restore physiological homeostasis and promote adaptation. A component of the stress response to exercise is the rapid release of hormones from the adrenal gland including glucocorticoids, the catecholamines and aldosterone. While each hormone targets several tissues throughout the body, skeletal muscle is of interest as it is central to physical function and various metabolic processes. Indeed, adrenal stress hormones have been shown to elicit specific performance benefits on the muscle. However, how the acute, short‐lived release of these stress hormones during exercise influences adaptations of skeletal muscle to long‐term training remains largely unknown. Thus, the objective of this review was to briefly highlight the known impact of adrenal stress hormones on skeletal muscle metabolism and function (Old Dog), and critically examine the current evidence supporting a role for these endogenous hormones in mediating long‐term training adaptations in skeletal muscle (New Tricks).\n", "Acta Physiologica, EarlyView. "]
    June 29, 2020   doi: 10.1111/apha.13522   open full text
  • Immunity and Hypertension.
    Rong M. Zhang, Kyle P. McNerney, Amy E. Riek, Carlos Bernal‐Mizrachi.
    Acta Physiologica. June 25, 2020
    ["\nAbstract\nHypertension is the primary cause of cardiovascular mortality. Despite multiple existing treatments, only half of those with the disease achieve adequate control. Therefore, understanding the mechanisms causing hypertension is essential for the development of novel therapies. Many studies demonstrate that immune cell infiltration of the vessel wall, kidney and central nervous system, as well as their counterparts of oxidative stress, the renal renin‐angiotensin system (RAS) and sympathetic tone play a critical role in the development of hypertension. Genetically modified mice lacking components of innate and/or adaptive immunity confirm the importance of chronic inflammation in hypertension and its complications. Depletion of immune cells improves endothelial function, decreases oxidative stress, reduces vascular tone and prevents renal interstitial infiltrates, sodium retention and kidney damage. Moreover, the ablation of microglia or central nervous system perivascular macrophages reduces RAS‐induced inflammation and prevents sympathetic nervous system activation and hypertension. Therefore, understanding immune cell functioning and their interactions with tissues that regulate hypertensive responses may be the future of novel antihypertensive therapies.\n", "Acta Physiologica, EarlyView. "]
    June 25, 2020   doi: 10.1111/apha.13487   open full text
  • An update on ACE2 amplification and its therapeutic potential.
    Alonso Marquez, Jan Wysocki, Jay Pandit, Daniel Batlle.
    Acta Physiologica. June 17, 2020
    ["\nAbstract\nThe renin angiotensin system (RAS) plays an important role in the pathogenesis of variety of diseases. Targeting the formation and action of angiotensin II (Ang II), the main RAS peptide, has been the key therapeutic target for last three decades. ACE‐related carboxypeptidase (ACE2), a monocarboxypeptidase that had been discovered 20 years ago, is one of the catalytically most potent enzymes known to degrade Ang II to Ang‐(1‐7), a peptide that is increasingly accepted to have organ‐protective properties that oppose and counterbalance those of Ang II. In addition to its role as a RAS enzyme ACE2 is the main receptor for SARS‐CoV‐2. In this review, we discuss various strategies that have been used to achieve amplification of ACE2 activity including the potential therapeutic potential of soluble recombinant ACE2 protein and novel shorter ACE2 variants.\n", "Acta Physiologica, EarlyView. "]
    June 17, 2020   doi: 10.1111/apha.13513   open full text
  • Intraluminal nutrients acutely strengthen rat intestinal MRP2 barrier function by a glucagon‐like peptide‐2‐mediated mechanism.
    Guillermo N. Tocchetti, Camila J. Domínguez, Felipe Zecchinati, Maite R. Arana, Juan P. Rigalli, María L. Ruiz, Silvina S. M. Villanueva, Aldo D. Mottino.
    Acta Physiologica. June 17, 2020
    ["\nAbstract\n\nAim\nMRP2 is an intestinal ABC transporter that prevents the absorption of dietary xenobiotics. The aims of this work were: (1) to evaluate whether a short‐term regulation of intestinal MRP2 barrier function takes place in vivo after luminal incorporation of nutrients and (2) to explore the underlying mechanism.\n\n\nMethods\nMRP2 activity and localization were assessed in an in vivo rat model with preserved irrigation and innervation. Nutrients were administered into distal jejunum. After 30‐minutes treatments, MRP2 activity was assessed in proximal jejunum by quantifying the transport of the model substrate 2,4‐dinitrophenyl‐S‐glutathione. MRP2 localization was determined by quantitative confocal microscopy. Participation of extracellular mediators was evaluated using selective inhibitors and by immunoneutralization. Intracellular pathways were explored in differentiated Caco‐2 cells.\n\n\nResults\nOleic acid, administered intraluminally at dietary levels, acutely stimulated MRP2 insertion into brush border membrane. This was associated with increased efflux activity and, consequently, enhanced barrier function. Immunoneutralization of the gut hormone glucagon‐like peptide‐2 (GLP‐2) prevented oleic acid effect on MRP2, demonstrating the participation of this trophic factor as a main mediator. Further experiments using selective inhibitors demonstrated that extracellular adenosine synthesis and its subsequent binding to enterocytic A2B adenosine receptor (A2BAR) take place downstream GLP‐2. Finally, studies in intestinal Caco‐2 cells revealed the participation of A2BAR/cAMP/PKA intracellular pathway, ultimately leading to increased MRP2 localization in apical domains.\n\n\nConclusion\nThese findings reveal an on‐demand, acute regulation of MRP2‐associated barrier function, constituting a novel physiological mechanism of protection against the absorption of dietary xenobiotics in response to food intake.\n\n", "Acta Physiologica, EarlyView. "]
    June 17, 2020   doi: 10.1111/apha.13514   open full text
  • Plasminogen deficiency does not prevent sodium retention in a genetic mouse model of experimental nephrotic syndrome.
    Mengyun Xiao, Bernhard N. Bohnert, Hande Aypek, Oliver Kretz, Florian Grahammer, Ute Aukschun, Matthias Wörn, Andrea Janessa, Daniel Essigke, Christoph Daniel, Kerstin Amann, Tobias B. Huber, Edward F. Plow, Andreas L. Birkenfeld, Ferruh Artunc.
    Acta Physiologica. June 10, 2020
    ["\nAbstract\n\nAim\nSodium retention is the hallmark of nephrotic syndrome (NS) and mediated by the proteolytic activation of the epithelial sodium channel (ENaC) by aberrantly filtered serine proteases. Plasmin is highly abundant in nephrotic urine and has been proposed to be the principal serine protease responsible for ENaC activation in NS. However, a proof of the essential role of plasmin in experimental NS is lacking.\n\n\nMethods\nWe used a genetic mouse model of NS based on an inducible podocin knockout (Bl6‐Nphs2tm3.1Antc*Tg(Nphs1‐rtTA*3G)8Jhm*Tg(tetO‐cre)1Jaw or nphs2Δipod). These mice were crossed with plasminogen deficient mice (Bl6‐Plgtm1Jld or plg−/−) to generate double knockout mice (nphs2Δipod*plg−/−). NS was induced after oral doxycycline treatment for 14 days and mice were followed for subsequent 14 days.\n\n\nResults\nUninduced nphs2Δipod*plg−/− mice had normal kidney function and sodium handling. After induction, proteinuria increased similarly in both nphs2Δipod*plg+/+ and nphs2Δipod*plg−/− mice. Western blot revealed the urinary excretion of plasminogen and plasmin in nphs2Δipod*plg+/+ mice which were absent in nphs2Δipod*plg−/− mice. After the onset of proteinuria, amiloride‐sensitive natriuresis was increased compared to the uninduced state in both genotypes. Subsequently, urinary sodium excretion dropped in both genotypes leading to an increase in body weight and development of ascites. Treatment with the serine protease inhibitor aprotinin prevented sodium retention in both genotypes.\n\n\nConclusions\nThis study shows that mice lacking urinary plasminogen are not protected from ENaC‐mediated sodium retention in experimental NS. This points to an essential role of other urinary serine proteases in the absence of plasminogen.\n\n", "Acta Physiologica, EarlyView. "]
    June 10, 2020   doi: 10.1111/apha.13512   open full text
  • Targeting desmosomal adhesion and signalling for intestinal barrier stabilization in inflammatory bowel diseases—Lessons from experimental models and patients.
    Nicolas Schlegel, Kevin Boerner, Jens Waschke.
    Acta Physiologica. May 22, 2020
    ["\nAbstract\nInflammatory bowel diseases (IBD) such as Crohn’s disease (CD) and Ulcerative colitis (UC) have a complex and multifactorial pathogenesis which is incompletely understood. A typical feature closely associated with clinical symptoms is impaired intestinal epithelial barrier function. Mounting evidence suggests that desmosomes, which together with tight junctions (TJ) and adherens junctions (AJ) form the intestinal epithelial barrier, play a distinct role in IBD pathogenesis. This is based on the finding that desmoglein (Dsg) 2, a cadherin‐type adhesion molecule of desmosomes, is required for maintenance of intestinal barrier properties both in vitro and in vivo, presumably via Dsg2‐mediated regulation of TJ. Mice deficient for intestinal Dsg2 show increased basal permeability and are highly susceptible to experimental colitis. In several cohorts of IBD patients, intestinal protein levels of Dsg2 are reduced and desmosome ultrastructure is altered suggesting that Dsg2 is involved in IBD pathogenesis. In addition to its adhesive function, Dsg2 contributes to enterocyte cohesion and intestinal barrier function. Dsg2 is also involved in enterocyte proliferation, barrier differentiation and induction of apoptosis, in part by regulation of p38MAPK and EGFR signalling. In IBD, the function of Dsg2 appears to be compromised via p38MAPK activation, which is a critical pathway for regulation of desmosomes and is associated with keratin phosphorylation in IBD patients. In this review, the current findings on the role of Dsg2 as a novel promising target to prevent loss of intestinal barrier function in IBD patients are discussed.\n", "Acta Physiologica, EarlyView. "]
    May 22, 2020   doi: 10.1111/apha.13492   open full text
  • Biomarkers and predicting acute kidney injury.
    Friedrich C. Luft.
    Acta Physiologica. May 09, 2020
    ["\nAbstract\n\nAim\nHow can we convert biomarkers into reliable, validated laboratory tests? Glomerular filtration rate (GFR) estimators exist for more than a century. The first utilitarian biomarkers were endogenously produced urea and creatinine. Clinicians then developed simple tests to determine whether or not renal tubular function was maintained. Are there faster and better tests that reflect decreased renal function and increased acute kidney injury (AKI) risk?\n\n\nMethods\nWe inspect earlier, and recently propagated biomarkers. Cystatin C reflects GFR and is not confounded by muscle mass. Direct GFR and plasma volume can now be measured acutely within 3 hours. Better yet would be tests that give information before GFR decreases and prior to urea, creatinine, and cystatin C increases. Prospective tests identifying those persons likely to develop AKI would be helpful. Even more utilitarian would be a test that also suggests a therapeutic avenue.\n\n\nResults\nA number of highly provocative biomarkers have recently been proposed. Moreover the application of big data from huge electronic medical records promise new directions in identifying and dealing with AKI.\n\n\nConclusions\nPipedreams are in the pipeline; the novel findings require immediate testing, verification, and perhaps application. Future research promises to make such dreams come true.\n\n", "Acta Physiologica, EarlyView. "]
    May 09, 2020   doi: 10.1111/apha.13479   open full text
  • Pannexin‐1 mediated ATP release in adipocytes is sensitive to glucose and insulin and modulates lipolysis and macrophage migration.
    Marco Tozzi, Jacob B. Hansen, Ivana Novak.
    Acta Physiologica. October 14, 2019
    --- - |2+ Abstract Aim Extracellular ATP signalling is involved in many physiological and pathophysiological processes in several tissues, including adipose tissue. Adipocytes have crucial functions in lipid and glucose metabolism and they express purinergic receptors. However, the sources of extracellular ATP in adipose tissue are not well characterized. In the present study, we investigated the mechanism and regulation of ATP release in white adipocytes, and evaluated the role of extracellular ATP as potential autocrine and paracrine signal. Methods Online ATP release was monitored in C3H10T1/2 cells and freshly isolated murine adipocytes. The ATP release mechanism and its regulation were tested in cells exposed to adrenergic agonists, insulin, glucose load and pharmacological inhibitors. Cell metabolism was monitored using Seahorse respirometry and expression analysis of pannexin‐1 was performed on pre‐ and mature adipocytes. The ATP signalling was evaluated in live cell imaging (Ca2+, pore formation), glycerol release and its effect on macrophages was tested in co‐culture and migration assays. Results Here, we show that upon adrenergic stimulation white murine adipocytes release ATP through the pannexin‐1 pore that is regulated by a cAMP‐PKA–dependent pathway. The ATP release correlates with increased cell metabolism and is sensitive to glucose. Extracellular ATP induces Ca2+ signalling and lipolysis in adipocytes and promotes macrophage migration. Importantly, ATP release is markedly inhibited by insulin, which operates via the activation of phosphodiesterase 3. Conclusions Our findings reveal an insulin‐pannexin‐1‐purinergic signalling crosstalk in adipose tissue and we propose that deregulation of this signalling may contribute to adipose tissue inflammation and type 2 diabetes. - 'Acta Physiologica, EarlyView. '
    October 14, 2019   doi: 10.1111/apha.13360   open full text
  • The sympathetic nervous system in acute kidney injury.
    Olaf Grisk.
    Acta Physiologica. October 14, 2019
    --- - |2 Abstract Acute kidney injury (AKI) is frequently accompanied by activation of the sympathetic nervous system. This can be due to the presence of chronic diseases associated with sympathetic activation prior to AKI or induced by stressors that ultimately lead to AKI such as endotoxins and arterial hypotension in circulatory shock. Conversely, sympathetic activation may also result from acute renal injury. Focusing on studies in experimental renal ischemia and reperfusion (IR), this review summarizes the current knowledge on how the sympathetic nervous system is activated in IR‐induced AKI and on the consequences of sympathetic activation for the development of acute renal damage. Experimental studies show beneficial effects of sympathoinhibitory interventions on renal structure and function in response to IR. However, few clinical trials obtained in scenarios that correspond to experimental IR, namely major elective surgery, showed that perioperative treatment with centrally acting sympatholytics reduced the incidence of AKI. Apparently discrepant findings on how sympathetic activation influences renal responses to acute IR‐induced injury are discussed and future areas of research in this field identified. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    October 14, 2019   doi: 10.1111/apha.13404   open full text
  • PGC‐1α plays a pivotal role in simvastatin‐induced exercise impairment in mice.
    Miljenko Valentin Panajatovic, François Singh, Noëmi Johanna Roos, Urs Duthaler, Christoph Handschin, Stephan Krähenbühl, Jamal Bouitbir.
    Acta Physiologica. October 12, 2019
    --- - |2+ Abstract Aim Statins decrease cardiovascular complications, but can induce myopathy. Here, we explored the implication of PGC‐1α in statin‐associated myotoxicity. Methods We treated PGC‐1α knockout (KO), PGC‐1α over‐expression (OE) and wild‐type mice (WT) mice orally with 5 mg simvastatin kg‐1 day‐1 for 3 weeks and assessed muscle function and metabolism. Results In WT and KO mice, but not in OE mice, simvastatin decreased grip strength, maximal running distance and vertical power assessed by ergometry. Post exercise plasma lactate concentrations were higher in WT and KO compared to OE mice. In glycolytic gastrocnemius, simvastatin decreased mitochondrial respiration, increased mitochondrial ROS production and free radical leak in WT and KO, but not in OE mice. Simvastatin increased mRNA expression of Sod1 and Sod2 in glycolytic and oxidative gastrocnemius of WT, but decreased it in KO mice. OE mice had a higher mitochondrial DNA content in both gastrocnemius than WT or KO mice and simvastatin exhibited a trend to decrease the citrate synthase activity in white and red gastrocnemius in all treatment groups. Simvastatin showed a trend to decrease the mitochondrial volume fraction in both muscle types of all treatment groups. Mitochondria were smaller in WT and KO compared to OE mice and simvastatin further reduced the mitochondrial size in WT and KO mice, but not in OE mice. Conclusions Simvastatin impairs skeletal muscle function, muscle oxidative metabolism and mitochondrial morphology preferentially in WT and KO mice, whereas OE mice appear to be protected, suggesting a role of PGC‐1α in preventing simvastatin‐associated myotoxicity. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    October 12, 2019   doi: 10.1111/apha.13402   open full text
  • Loss of CD36 protects against diet‐induced obesity but results in impaired muscle stem cell function, delayed muscle regeneration and hepatic steatosis.
    Sandrine Verpoorten, Peggy Sfyri, David Scully, Robert Mitchell, Anastasia Tzimou, Vassilis Mougios, Ketan Patel, Antonios Matsakas.
    Acta Physiologica. October 10, 2019
    --- - |2+ Abstract Aim The prevalence of obesity is a major risk factor for cardiovascular and metabolic diseases including impaired skeletal muscle regeneration. Since skeletal muscle regenerative capacity is regulated by satellite cells, we aimed to investigate whether a high‐fat diet impairs satellite cell function and whether this is linked to fatty acid uptake via CD36. We also aimed to determine whether loss of CD36 impacts on muscle redox homeostasis and skeletal muscle regenerative capacity. Methods We studied the impact of a high‐fat diet and CD36 deficiency on murine skeletal muscle morphology, redox homeostasis, satellite cell function, bioenergetics and lipid accumulation in the liver. We also determined the effect of CD36 deficiency on skeletal muscle regeneration. Results High‐fat diet increased body weight, intramuscular lipid accumulation and oxidative stress in wild‐type mice that were significantly mitigated in CD36‐deficient mice. High‐fat diet and CD36 deficiency independently attenuated satellite cell function on single fibres and myogenic capacity on primary satellite cells. CD36‐deficiency resulted in delayed skeletal muscle regeneration following acute injury with cardiotoxin. CD36‐deficient and wild‐type primary satellite cells had distinct bioenergetic profiles in response to palmitate. High‐fat diet induced hepatic steatosis in both genotypes that was more pronounced in the CD36 deficient mice. Conclusion This study demonstrates that CD36 deficiency protects against diet‐induced obesity, intramuscular lipid deposition and oxidative stress but results in impaired muscle satellite cell function, delayed muscle regeneration and hepatic steatosis. CD36 is a key mediator of fatty acid uptake in skeletal muscle, linking obesity with satellite cell function and muscle regeneration. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    October 10, 2019   doi: 10.1111/apha.13395   open full text
  • Systemic serotonin inhibits brown adipose tissue sympathetic nerve activity via a GABA input to the dorsomedial hypothalamus, not via 5HT1A receptor activation in raphe pallidus.
    Clarissa M.D. Mota, Luiz G.S. Branco, Shaun F. Morrison, Christopher J. Madden.
    Acta Physiologica. October 10, 2019
    --- - |2+ Abstract Aim Serotonin (5‐hydroxytryptamine, 5‐HT), an important neurotransmitter and hormone, modulates many physiological functions including body temperature. We investigated neural mechanisms involved in the inhibition of brown adipose tissue (BAT) sympathetic nerve activity (SNA) and BAT thermogenesis evoked by 5‐HT. Methods Electrophysiological recordings, intravenous (iv) injections and nanoinjections in the brains of anesthetized rats. Results Cooling‐evoked increases in BAT SNA were inhibited by the intra‐rostral raphé pallidus (rRPa) and the iv administration of the 5‐HT1A receptor agonist, 8‐OH‐DPAT, or 5‐HT. The intra‐rRPa 5‐HT, the intra‐rRPa and the iv 8‐OH‐DPAT, but not the iv 5‐HT‐induced inhibition of BAT SNA were prevented by nanoinjection of a 5‐HT1A receptor antagonist in the rRPa. The increase in BAT SNA evoked by nanoinjection of NMDA in the rRPa was not inhibited by iv 5‐HT, indicating that iv 5‐HT does not inhibit BAT SNA by acting in the rRPa or in the sympathetic pathway distal to the rRPa. In contrast, under a warm condition, blockade of 5HT1A receptors in the rRPa increased BAT SNA and BAT thermogenesis, suggesting that endogenous 5‐HT in the rRPa contributes to the suppression of BAT SNA and BAT thermogenesis. The increases in BAT SNA and BAT thermogenesis evoked by nanoinjection of NMDA in the dorsomedial hypothalamus (DMH) were inhibited by iv 5‐HT, but those following bicuculline nanoinjection in the DMH were not inhibited. Conclusions The systemic 5‐HT‐induced inhibition of BAT SNA requires a GABAergic inhibition of BAT sympathoexcitatory neurons in the DMH. In addition, during warming 5‐HT released endogenously in rRPa inhibits BAT SNA. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    October 10, 2019   doi: 10.1111/apha.13401   open full text
  • Doxorubicin‐induced skeletal muscle atrophy: elucidating the underlying molecular pathways.
    Anouk E. Hiensch, Kate A. Bolam, Sara Mijwel, Jeroen A.L. Jeneson, Alwin D.R. Huitema, Onno Kranenburg, Elsken van der Wall, Helene Rundqvist, Yvonne Wengstrom, Anne M. May.
    Acta Physiologica. October 10, 2019
    --- - |2+ Abstract Aim Loss of skeletal muscle mass is a common clinical finding in cancer patients. The purpose of this meta‐analysis and systematic review was to quantify the effect of doxorubicin on skeletal muscle and report on the proposed molecular pathways possibly leading to doxorubicin‐induced muscle atrophy in both human and animal models. Methods A systematic search of the literature was conducted in PubMed, EMBASE, Web of Science and CENTRAL databases. The internal validity of included studies was assessed using SYRCLE's risk of bias tool. Results Twenty eligible articles were identified. No human studies were identified as being eligible for inclusion. Doxorubicin significantly reduced skeletal muscle weight (i.e. EDL, TA, gastrocnemius and soleus) by 14% (95% CI: 9.9; 19.3) and muscle fiber cross‐sectional area by 17% (95% CI: 9.0; 26.0) when compared to vehicle controls. Parallel to negative changes in muscle mass, muscle strength was even more decreased in response to doxorubicin administration. This review suggests that mitochondrial dysfunction plays a central role in doxorubicin‐induced skeletal muscle atrophy. The increased production of ROS plays a key role within this process. Furthermore, doxorubicin activated all major proteolytic systems (i.e. calpains, the ubiquitin‐proteasome pathway and autophagy) in the skeletal muscle. Although each of these proteolytic pathways contribute to doxorubicin‐induced muscle atrophy, the activation of the ubiquitin‐proteasome pathway is hypothesized to play a key role. Finally, a limited number of studies found that doxorubicin decreases protein synthesis by a disruption in the insulin signaling pathway. Conclusion The results of the meta‐analysis show that doxorubicin induces skeletal muscle atrophy in preclinical models. This effect may be explained by various interacting molecular pathways. Results from preclinical studies provide a robust setting to investigate a possible dose‐response, separate the effects of doxorubicin from tumor‐induced atrophy and to examine underlying molecular pathways. More research is needed to confirm the proposed signaling pathways in humans, paving the way for potential therapeutic approaches. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    October 10, 2019   doi: 10.1111/apha.13400   open full text
  • Disturbed cardiac mitochondrial and cytosolic calcium handling in a metabolic risk‐related rat model of heart failure with preserved ejection fraction.
    Daniela Miranda‐Silva, Rob C. I. Wüst, Glória Conceição, Patrícia Gonçalves‐Rodrigues, Nádia Gonçalves, Alexandre Gonçalves, Diederik W. D. Kuster, Adelino F. Leite‐Moreira, Jolanda Velden, Jorge M. Sousa Beleza, José Magalhães, Ger J. M. Stienen, Inês Falcão‐Pires.
    Acta Physiologica. October 10, 2019
    --- - |2+ Abstract Aim Calcium ions play a pivotal role in matching energy supply and demand in cardiac muscle. Mitochondrial calcium concentration is lower in animal models of heart failure with reduced ejection fraction (HFrEF), but limited information is available about mitochondrial calcium handling in heart failure with preserved ejection fraction (HFpEF). Methods We assessed mitochondrial Ca2+ handling in intact cardiomyocytes from Zucker/fatty Spontaneously hypertensive F1 hybrid (ZSF1)‐lean (control) and ZSF1‐obese rats, a metabolic risk‐related model of HFpEF. A mitochondrially targeted Ca2+ indicator (MitoCam) was expressed in cultured adult rat cardiomyocytes. Cytosolic and mitochondrial Ca2+ transients were measured at different stimulation frequencies. Mitochondrial respiration and swelling, and expression of key proteins were determined ex vivo. Results At rest, mitochondrial Ca2+ concentration in ZSF1‐obese was larger than in ZSF1‐lean. The diastolic and systolic mitochondrial Ca2+ concentrations increased with stimulation frequency, but the steady‐state levels were larger in ZSF1‐obese. The half‐widths of the contractile responses, the resting cytosolic Ca2+ concentration and the decay half‐times of the cytosolic Ca2+ transients were higher in ZSF1‐obese, likely because of a lower SERCA2a/phospholamban ratio. Mitochondrial respiration was lower, particularly with nicotinamide adenine dinucleotide (NADH) (complex I) substrates, and mitochondrial swelling was larger in ZSF1‐obese. Conclusion The free mitochondrial calcium concentration is higher in HFpEF owing to alterations in mitochondrial and cytosolic Ca2+ handling. This coupling between cytosolic and mitochondrial Ca2+ levels may compensate for myocardial ATP supply in vivo under conditions of mild mitochondrial dysfunction. However, if mitochondrial Ca2+ concentration is sustainedly increased, it might trigger mitochondrial permeability transition pore opening. - 'Acta Physiologica, EarlyView. '
    October 10, 2019   doi: 10.1111/apha.13378   open full text
  • Nestin affects fusion pore dynamics in mouse astrocytes.
    Eva Lasič, Saša Trkov Bobnar, Ulrika Wilhelmsson, Yolanda de Pablo, Milos Pekny, Robert Zorec, Matjaž Stenovec.
    Acta Physiologica. October 09, 2019
    --- - |2+ Abstract Aim Astrocytes play a homeostatic role in the central nervous system and influence numerous aspects of neurophysiology via intracellular trafficking of vesicles. Intermediate filaments (IFs), also known as nanofilaments, regulate a number of cellular processes including organelle trafficking and adult hippocampal neurogenesis. We have recently demonstrated that the IF protein nestin, a marker of neural stem cells and immature and reactive astrocytes, is also expressed in some astrocytes in the unchallenged hippocampus and regulates neurogenesis through Notch signaling from astrocytes to neural stem cells, possibly via altered trafficking of vesicles containing the Notch ligand Jagged‐1. Methods We thus investigated whether nestin affects vesicle dynamics in astrocytes by examining single vesicle interactions with the plasmalemma and vesicle trafficking with high‐resolution cell‐attached membrane capacitance measurements and confocal microscopy. We used cell cultures of astrocytes from nestin‐deficient (Nes‐/‐) and wild‐type (wt) mice, and fluorescent dextran and Fluo‐2 to examine vesicle mobility and intracellular Ca2+ concentration, respectively. Results Nes‐/‐ astrocytes exhibited altered sizes of vesicles undergoing full fission and transient fusion, altered vesicle fusion pore geometry and kinetics, decreased spontaneous vesicle mobility, and altered ATP‐evoked mobility. Purinergic stimulation evoked Ca2+ signaling that was slightly attenuated in Nes‐/‐ astrocytes, which exhibited more oscillatory Ca2+ responses than wt astrocytes. Conclusion These results demonstrate at the single vesicle level that nestin regulates vesicle interactions with the plasmalemma and vesicle trafficking, indicating its potential role in astrocyte vesicle‐based communication. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    October 09, 2019   doi: 10.1111/apha.13399   open full text
  • The Effects of Acetylcholinesterase Inhibitors on the Heart in Acute Myocardial Infarction and Heart Failure: From Cells to Patient Reports.
    Thawatchai Khuanjing, Siripong Palee, Siriporn C Chattipakorn, Nipon Chattipakorn.
    Acta Physiologica. October 08, 2019
    --- - |2 Abstract Cardiovascular diseases remain a major cause of morbidity and mortality worldwide. Cardiovascular diseases such as acute myocardial infarction, ischemia/reperfusion injury and heart failure are associated with cardiac autonomic imbalance characterized by sympathetic overactivity and parasympathetic withdrawal from the heart. Increased parasympathetic activity by electrical vagal nerve stimulation has been shown to provide beneficial effects in the case of cardiovascular diseases in both animals and patients by improving autonomic function, cardiac remodeling and mitochondrial function. However, clinical limitations for electrical vagal nerve stimulation exist due to its invasive nature, costly equipment and limited clinical validation. Therefore, novel therapeutic approaches which moderate parasympathetic activities could be beneficial for in the case of cardiovascular disease. Acetylcholinesterase inhibitors inhibit acetylcholinesterase and hence increase cholinergic transmission. Recent studies have reported that acetylcholinesterase inhibitors improve autonomic function and cardiac function in cardiovascular disease models. Despite its potential clinical benefits for cardiovascular disease patients, the role of acetylcholinesterase inhibitors in acute myocardial infarction and heart failure remediation remains unclear. This article comprehensively reviews the effects of acetylcholinesterase inhibitors on the heart in acute myocardial infarction and heart failure scenarios from in vitro and in vivo studies to clinical reports. The mechanisms involved are also discussed in this review. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    October 08, 2019   doi: 10.1111/apha.13396   open full text
  • Adult vascular dysfunction in foetal growth‐restricted guinea‐pigs is associated with a neonate‐adult switching in Nos3 DNA methylation.
    Bernardo J. Krause, Estefanía Peñaloza, Alejandro Candia, Daniel Cañas, Cherie Hernández, German A. Arenas, María José Peralta‐Scholz, Rodrigo Valenzuela, Claudio García‐Herrera, Emilio A. Herrera.
    Acta Physiologica. October 07, 2019
    --- - |2+ Abstract Aim Foetal growth restriction (FGR) is associated with endothelial dysfunction and cardiovascular diseases in adult subjects. Early vascular remodelling and epigenetic changes occurring on key endothelial genes might precede this altered vascular function. Further, it has been proposed that oxidative stress during development may determine some of these epigenetic modifications. To address this issue, we studied the in vivo and ex vivo vascular function and Nos3 promoter DNA methylation in arteries from eight‐month‐old guinea‐pig born from control, FGR‐treated and FGR‐NAC‐treated pregnancies. Methods Femoral and carotid arteries in vivo vascular function were determined by Doppler, whilst ex vivo vascular function and biomechanical properties were assessed by wire myography. Levels of eNOS mRNA and site‐specific DNA methylation in Nos3 promoter in aorta endothelial cells (AEC) were determined by qPCR and pyrosequencing respectively. Results FGR adult showed an increased femoral vascular resistance (P < .05), stiffness (P < .05) and arterial remodelling (P < .01), along with an impaired NO‐mediated relaxation (P < .001). These effects were prevented by maternal treatment with NAC. Endothelial‐NOS mRNA levels were decreased in FGR adult compared with control and FGR‐NAC (P < .05), associated with increased DNA methylation levels (P < .01). Comparison of Nos3 DNA methylation in AEC showed a differential methylation pattern between foetal and adult guinea‐pigs (P < .05). Conclusion Altogether, these data suggest that adult vascular dysfunction in the FGR does not result from early changes in Nos3 promoter DNA methylation, but from an altered vessel structure established during foetal development. - 'Acta Physiologica, Volume 227, Issue 3, November 2019. '
    October 07, 2019   doi: 10.1111/apha.13328   open full text
  • Activation of mTORC1 signalling in rat skeletal muscle is independent of the EC‐coupling sequence but dependent on tension per se in a dose‐response relationship.
    Emil Rindom, Anders M. Kristensen, Kristian Overgaard, Kristian Vissing, Frank Vincenzo Paoli.
    Acta Physiologica. October 07, 2019
    --- - |2+ Abstract Aim mTORC1 is regarded as an important key regulator of protein synthesis and hypertrophy following mechanical stimuli in skeletal muscle. However, as excitation and tension development is tightly coupled in most experimental models, very little and largely indirect evidence exist for such a mechanosensitive pathway. Here, we sought to examine whether activation of mTORC1 signalling is dependent on tension per se in rat skeletal muscle. Methods To examine the mechanosensitivity of mTORC1, rat EDL muscles were exposed to either excitation‐induced eccentric contractions (ECC), passive stretching (PAS) with identical peak tension (Tpeak) and Tension‐Time‐Integral (TTI), or ECC with addition of inhibitors of the myosin ATPases (IMA). To further explore the relationship between tension and mTORC1 signalling, rat EDL muscles were subjected to PAS of different magnitudes of Tpeak while standardizing TTI and vice versa. Results PAS and ECC with equal Tpeak and TTI produced similar responses in mTORC1 signalling despite different modes of tension development. When active tension during ECC was nearly abolished by addition of IMA, mTORC1 signalling was reduced to a level comparable to non‐stimulated controls. In addition, when muscles were exposed to PAS of varying levels of Tpeak with standardized TTI, activation of mTORC1 signalling displayed a positive relationship with peak tension. Conclusions The current study directly links tension per se to activation of mTORC1 signalling, which is independent of an active EC‐coupling sequence. Moreover, activation of mTORC1 signalling displays a positive dose‐response relationship with peak tension. - 'Acta Physiologica, Volume 227, Issue 3, November 2019. '
    October 07, 2019   doi: 10.1111/apha.13336   open full text
  • Muscle atrophy and regeneration associated with behavioural loss and recovery of function after sciatic nerve crush.
    Max Grönholdt‐Klein, Mikael Altun, Meneca Becklén, Emelie Dickman Kahm, Andreas Fahlström, Eric Rullman, Brun Ulfhake.
    Acta Physiologica. October 07, 2019
    --- - |2+ Abstract Aim To resolve timing and coordination of denervation atrophy and the re‐innervation recovery process to discern correlations indicative of common programs governing these processes. Methods Female Sprague‐Dawley (SD) rats had a unilateral sciatic nerve crush. Based on longitudinal behavioural observations, the triceps surae muscle was analysed at different time points post‐lesion. Results Crush results in a loss of muscle function and mass (−30%) followed by a recovery to almost pre‐lesion status at 30 days post‐crush (dpc). There was no loss of fibres nor any significant change in the number of nuclei per fibre but a shift in fibres expressing myosins I and II that reverted back to control levels at 30 dpc. A residual was the persistence of hybrid fibres. Early on a CHNR ‐ε to ‐γ switch and a re‐expression of embryonic MyHC showed as signs of denervation. Foxo1, Smad3, Fbxo32 and Trim63 transcripts were upregulated but not Myostatin, InhibinA and ActivinR2B. Combined this suggests that the mechanism instigating atrophy provides a selectivity of pathway(s) activated. The myogenic differentiation factors (MDFs: Myog, Myod1 and Myf6) were upregulated early on suggesting a role also in the initial atrophy. The regulation of these transcripts returned towards baseline at 30 dpc. The examined genes showed a strong baseline covariance in transcript levels which dissolved in the response to crush driven mainly by the MDFs. At 30 dpc the naïve expression pattern was re‐established. Conclusion Peripheral nerve crush offers an excellent model to assess and interfere with muscle adaptions to denervation and re‐innervation. - 'Acta Physiologica, Volume 227, Issue 3, November 2019. '
    October 07, 2019   doi: 10.1111/apha.13335   open full text
  • MicroRNA‐133 suppresses ZFHX3‐dependent atrial remodelling and arrhythmia.
    Wan‐Li Cheng, Yu‐Hsun Kao, Tze‐Fan Chao, Yung‐Kuo Lin, Shih‐Ann Chen, Yi‐Jen Chen.
    Acta Physiologica. October 07, 2019
    --- - |2+ Abstract Aim Atrial fibrillation (AF) is an important cause of morbidity and mortality in the modern world. Loss‐of‐function mutation in the zinc finger homeobox 3 gene (ZFHX3) is associated with increased risk of AF. MicroRNAs (miRNAs) participate in arrhythmogenesis, and thus miRNA modulators may be applicable as therapeutic modalities for AF. However, the altered miRNA profiles after ZFHX3 knockdown (KD) remain unclear. This study aimed to analyse the changes of miRNA expression in loss‐of‐function of ZFHX3 and the effect of miRNA modulation on atrial arrhythmias in this model. Methods We performed small RNA deep sequencing on ZFHX3‐KD and control HL‐1 mouse atrial myocytes. The effect of miRNAs on ZFHX3‐dependent atrial arrhythmia was evaluated through in vitro and in vivo assays in mice. Results Among the differentially expressed miRNAs, 11 were down‐regulated and 6 were up‐regulated after ZFHX3 KD. Quantitative real‐time PCR analysis confirmed that after ZFHX3 KD, miR‐133a and miR‐133b were significantly down‐regulated, whereas miR‐184 was the most significantly up‐regulated. DIANA‐miRPath analysis suggested that miR‐133a/b down‐regulation increases the targeted signalling of miR‐133 (ie, adrenergic, Wnt/calcium and fibroblast growth factor receptor 1 signalling), which could contribute to pathological remodelling of cardiomyocytes. These results were confirmed through Western blotting. After transfection of miR‐133a/b mimics in ZFHX3‐KD cells, miR‐133a/b levels increased, accompanied by the inhibition of their target signalling. Treatment with miR‐133a/b mimics diminished ZFHX3 KD–induced atrial ectopy in mice. Conclusion ZFHX3‐KD promotes distinct miRNA expressional changes in atrial myocytes. MiR‐133a/b mimics may reverse signalling of ZFHX3 KD‐mediated cardiac remodelling and atrial arrhythmia. - 'Acta Physiologica, Volume 227, Issue 3, November 2019. '
    October 07, 2019   doi: 10.1111/apha.13322   open full text
  • Myokines in skeletal muscle physiology and metabolism: Recent advances and future perspectives.
    Dibash K. Das, Zachary A. Graham, Christopher P. Cardozo.
    Acta Physiologica. October 06, 2019
    --- - |2 Abstract Myokines are molecules produced and secreted by skeletal muscle to act in an auto‐, para‐ and endocrine manner to alter physiological function of target tissues. The growing number of effects of myokines on metabolism of distant tissues provides a compelling case for crosstalk between skeletal muscle and other tissues and organs to regulate metabolic homoeostasis. In this review, we summarize and discuss the current knowledge regarding the impact on metabolism of several canonical and recently identified myokines. We focus specifically on myostatin, β‐aminoisobutyric acid, interleukin‐15, meteorin‐like and myonectin, and discuss how these myokines are induced and regulated as well as their overall function. We also review how these myokines may serve as potential prognostic biomarkers that reflect whole‐body metabolism and how they may be attractive therapeutic targets for treating muscle and metabolic diseases. - 'Acta Physiologica, EarlyView. '
    October 06, 2019   doi: 10.1111/apha.13367   open full text
  • Vascular and inflammatory mineralocorticoid receptors in kidney disease.
    Jonatan Barrera‐Chimal, Frederic Jaisser.
    Acta Physiologica. October 03, 2019
    --- - |2 Abstract Mineralocorticoid receptor (MR) activation in the kidney can occur outside the aldosterone‐sensitive distal nephron in sites including the endothelium, smooth muscle and inflammatory cells. MR activation in these cells has deleterious effects on kidney structure and function by promoting oxidative injury, endothelial dysfunction and stiffness, vascular remodelling and calcification, decreased relaxation and activation of T cells and pro‐inflammatory macrophages. Here, we review the data showing the cellular consequences of MR activation in endothelial, smooth muscle and inflammatory cells and how this affects the kidney in pathological situations. The evidence demonstrating a benefit of pharmacological or genetic MR inhibition in various models of kidney disease is also discussed. - 'Acta Physiologica, EarlyView. '
    October 03, 2019   doi: 10.1111/apha.13390   open full text
  • The tRNA‐associated dysregulation in immune responses and immune diseases.
    Chunsheng Zhu, Bao Sun, Anzheng Nie, Zheng Zhou.
    Acta Physiologica. October 03, 2019
    --- - |2 Abstract Transfer RNA (tRNA), often considered as a housekeeping molecule, mainly participates in protein translation by transporting amino acids to the ribosome. Nevertheless, accumulating evidence has shown that tRNAs are closely related to various physiological and pathological processes. The proper functioning of the immune system is the key to human health. The aim of this review is to investigate the relationships between tRNAs and the immune system. We detail the biogenesis and structure of tRNAs and summarize the pathogen tRNA‐mediated infection and host responses. In addition, we address recent advances in different aspects of tRNA‐associated dysregulation in immune responses and immune diseases, such as tRNA molecules, tRNA modifications, tRNA derivatives and tRNA aminoacylation. Therefore, tRNAs play an important role in immune regulation. Although our knowledge of tRNAs in the context of immunity remains, for the most part, unknown, this field deserves in‐depth research to provide new ideas for the treatment of immune diseases. - 'Acta Physiologica, EarlyView. '
    October 03, 2019   doi: 10.1111/apha.13391   open full text
  • Principal mode of Syndecan‐4 mechanotransduction for the endothelial glycocalyx is a scissor‐like dimer motion.
    Xi Zhuo Jiang, Kai H. Luo, Yiannis Ventikos.
    Acta Physiologica. October 03, 2019
    --- - |2+ Abstract Aim Endothelial glycocalyx (EG) plays a pivotal role in a plethora of diseases, like cardiovascular and renal diseases. One hallmark function of the EG as a mechanotransducer which transmits mechanical signals into cytoplasm has been documented for decades. However, the basic question ‐ how the glycocalyx transmits the flow shear stress— is unanswered so far. Our aim is to shed light on the fundamental mode of signal transmission from flow to the endothelial cytoskeleton. Methods We conduct a series of large‐scale molecular dynamics computational experiments to investigate the dynamics of glycocalyx under varying conditions (changing blood flow velocities and shedding of glycocalyx sugar chains). Results We have identified that the main pathway of signal transmission in this system manifests as a scissors‐like motion of the Syndecan‐4 core protein. Results have suggested that the force transmitted into the cytoskeleton with an order of 10 ~ 100 pN, and the main function of sugar chains of a glycocalyx element is to protect the core proteins from severe conformational changes thereby maintaining the functionality of the EG. Conclusion This research provides a reconciling explanation for a longstanding debate about the force transmission threshold based on our findings. A new explanation has also been provided to relate the role of the EG as a mechanotransducer to its function as a microvascular barrier: the EG regulates the mechanotransduction by altering the median value and variation range of the scissor angle, and the EG governs the microvascular barrier via controlling the scissor angle which will affect the intercellular cleft. - 'Acta Physiologica, EarlyView. '
    October 03, 2019   doi: 10.1111/apha.13376   open full text
  • Novel Role of Tieg1 in Muscle Metabolism and Mitochondrial Oxidative Capacities.
    Malek Kammoun, Jerome Piquereau, Lydie Nadal‐Desbarats, Sandra Même, Maud Beuvin, Gisèle Bonne, Vladimir Veksler, Yann Le Fur, Philippe Pouletaut, William Même, Frederic Szeremeta, Jean‐Marc Constans, Elizabeth S. Bruinsma, Molly H. Nelson Holte, Zeynab Najafova, Steven A. Johnsen, Malayannan Subramaniam, John R. Hawse, Sabine F. Bensamoun.
    Acta Physiologica. September 27, 2019
    --- - |2+ Abstract Aim Tieg1 is involved in multiple signaling pathways, human diseases, and is highly expressed in muscle where its functions are poorly understood. Methods We have utilized Tieg1 KO mice to identify novel and important roles for this transcription factor in regulating muscle ultrastructure, metabolism and mitochondrial functions in the soleus and EDL muscles. RNA sequencing, immunoblotting, TEM, MRI, NMR, histochemical and mitochondrial function assays were performed. Results Loss of Tieg1 expression resulted in altered sarcomere organization and a significant decrease in mitochondrial number. Histochemical analyses demonstrated an absence of SDH staining and a decrease in COX enzyme activity in KO soleus with similar, but diminished, effects in the EDL. Decreased complex I, COX and citrate synthase activities were detected in the soleus muscle of KO mice indicating altered mitochondrial function. Complex I activity was also diminished in KO EDL. Significant decreases in citrate synthase and respiratory chain complex activities were identified in KO soleus. 1H‐NMR spectra revealed no significant metabolic difference between WT and KO muscles. However, 31P spectra revealed a significant decrease in phosphocreatine and ATPg. Altered expression of 279 genes, many of which play roles in mitochondrial and muscle function, were identified in KO soleus muscle. Ultimately, all of these changes resulted in an exercise intolerance phenotype in Tieg1 KO mice. Conclusion Our findings have implicated novel roles for Tieg1 in muscle including regulation of gene expression, metabolic activity and organization of tissue ultrastructure. This muscle phenotype resembles diseases associated with exercise intolerance and myopathies of unknown consequence. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    September 27, 2019   doi: 10.1111/apha.13394   open full text
  • Lamin A/C negatively regulated by miR‐124‐3p modulates apoptosis of vascular smooth muscle cells during cyclic stretch application in rats.
    Han Bao, Hai‐Peng Li, Qian Shi, Kai Huang, Xiao‐Hu Chen, Yuan‐Xiu Chen, Yue Han, Qian Xiao, Qing‐Ping Yao, Ying‐Xin Qi.
    Acta Physiologica. September 27, 2019
    --- - |2+ Abstract Aim Apoptosis of vascular smooth muscle cells (VSMCs) influenced by abnormal cyclic stretch is crucial for vascular remodelling during hypertension. Lamin A/C, a nuclear envelope protein, is mechano‐responsive, but the role of lamin A/C in VSMC apoptosis is still unclear. Methods FX‐5000T Strain Unit provided cyclic stretch (CS) in vitro. AnnexinV/PI and cleaved Caspase 3 ELISA detected apoptosis. qPCR was used to investigate the expression of miR‐124‐3p and a luciferase reporter assay was used to evaluate the ability of miR‐124‐3p binding to the Lmna 3’UTR. Protein changes of lamin A/C and relevant molecules were detected using western blot. Ingenuity Pathway Analysis and Protein/DNA array detected the potential transcription factors. Renal hypertensive rats verified these changes. Results High cyclic stretch (15%‐CS) induced VSMC apoptosis and repressed lamin A/C expressions compared with normal (5%‐CS) control. Downregulation of lamin A/C enhanced VSMC apoptosis. In addition, 15%‐CS had no significant effect on mRNA expression of Lmna, and lamin A/C degradation was not induced by autophagy. 15%‐CS elevated miR‐124‐3p bound to the 3’UTR of Lmna and negatively regulated protein expression of lamin A/C. Similar changes occurred in renal hypertensive rats compared with sham controls. Lamin A/C repression affected activity of TP53, CREB1, MYC, STAT1/5/6 and JUN, which may in turn affect apoptosis. Conclusion Our data suggested that the decreased expression of lamin A/C upon abnormal cyclic stretch and hypertension may induce VSMC apoptosis. These mechano‐responsive factors play important roles in VSMC apoptosis and might be novel therapeutic targets for vascular remodelling in hypertension. - 'Acta Physiologica, EarlyView. '
    September 27, 2019   doi: 10.1111/apha.13374   open full text
  • Extended hypoxia‐mediated H2S production provides for long‐term oxygen sensing.
    Kenneth R. Olson, Yan Gao, Eric R. DeLeon, Troy A. Markel, Natalie Drucker, David Boone, Matt Whiteman, Andrea K. Steiger, Michael D. Pluth, Charles R. Tessier, Robert V. Stahelin.
    Acta Physiologica. September 18, 2019
    --- - |2+ Abstract Aim Numerous studies have shown that H2S serves as an acute oxygen sensor in a variety of cells. We hypothesize that H2S also serves in extended oxygen sensing. Methods Here, we compare the effects of extended exposure (24‐48 hours) to varying O2 tensions on H2S and polysulphide metabolism in human embryonic kidney (HEK 293), human adenocarcinomic alveolar basal epithelial (A549), human colon cancer (HTC116), bovine pulmonary artery smooth muscle, human umbilical‐derived mesenchymal stromal (stem) cells and porcine tracheal epithelium (PTE) using sulphur‐specific fluorophores and fluorometry or confocal microscopy. Results All cells continuously produced H2S in 21% O2 and H2S production was increased at lower O2 tensions. Decreasing O2 from 21% to 10%, 5% and 1% O2 progressively increased H2S production in HEK293 cells and this was partially inhibited by a combination of inhibitors of H2S biosynthesis, aminooxyacetate, propargyl glycine and compound 3. Mitochondria appeared to be the source of much of this increase in HEK 293 cells. H2S production in all other cells and PTE increased when O2 was lowered from 21% to 5% except for HTC116 cells where 1% O2 was necessary to increase H2S, presumably reflecting the hypoxic environment in vivo. Polysulphides (H2Sn, where n = 2‐7), the key signalling metabolite of H2S also appeared to increase in many cells although this was often masked by high endogenous polysulphide concentrations. Conclusion These results show that cellular H2S is increased during extended hypoxia and they suggest this is a continuously active O2‐sensing mechanism in a variety of cells. - 'Acta Physiologica, EarlyView. '
    September 18, 2019   doi: 10.1111/apha.13368   open full text
  • Effects of the ventilatory stimulant, doxapram on human TASK‐3 (KCNK9, K2P9.1) channels and TASK‐1 (KCNK3, K2P3.1) channels.
    Kevin P. Cunningham, D. Euan MacIntyre, Alistair Mathie, Emma L. Veale.
    Acta Physiologica. September 18, 2019
    --- - |2+ Abstract Aims The mode of action by which doxapram acts as a respiratory stimulant in humans is controversial. Studies in rodent models, have shown that doxapram is a more potent and selective inhibitor of TASK‐1 and TASK‐1/TASK‐3 heterodimer channels, than TASK‐3. Here we investigate the direct effect of doxapram and chirally separated, individual positive and negative enantiomers of the compound, on both human and mouse, homodimeric and heterodimeric variants of TASK‐1 and TASK‐3. Methods Whole‐cell patch clamp electrophysiology on tsA201 cells was used to assess the potency of doxapram on cloned human or mouse TASK‐1, TASK‐3 and TASK‐2 channels. Mutations of amino acids in the pore‐lining region of TASK‐3 channels were introduced using site‐directed mutagenesis. Results Doxapram was an equipotent inhibitor of human TASK‐1 and TASK‐3 channels, compared with mouse channel variants, where it was more selective for TASK‐1 and heterodimers of TASK‐1 and TASK‐3. The effect of doxapram could be attenuated by either the removal of the C‐terminus of human TASK‐3 channels or mutations of particular hydrophobic residues in the pore‐lining region. These mutations, however, did not alter the effect of a known extracellular inhibitor of TASK‐3, zinc. The positive enantiomer of doxapram, GAL‐054, was a more potent antagonist of TASK channels, than doxapram, whereas the negative enantiomer, GAL‐053, had little inhibitory effect. Conclusion These data show that in contrast to rodent channels, doxapram is a potent inhibitor of both TASK‐1 and TASK‐3 human channels, providing further understanding of the pharmacological profile of doxapram in humans and informing the development of new therapeutic agents. - 'Acta Physiologica, EarlyView. '
    September 18, 2019   doi: 10.1111/apha.13361   open full text
  • Urokinase‐type plasminogen activator contributes to amiloride‐sensitive sodium retention in nephrotic range glomerular proteinuria in mice.
    Gitte R. Hinrichs, Kathrin Weyer, Ulla G. Friis, Per Svenningsen, Ida K. Lund, Rikke Nielsen, Géraldine Mollet, Corinne Antignac, Claus Bistrup, Boye L. Jensen, Henrik Birn.
    Acta Physiologica. September 17, 2019
    --- - |2+ Abstract Aim Activation of sodium reabsorption by urinary proteases has been implicated in sodium retention associated with nephrotic syndrome. The study was designed to test the hypothesis that nephrotic proteinuria in mice after conditional deletion of podocin leads to urokinase‐dependent, amiloride‐sensitive plasmin‐mediated sodium and water retention. Methods Ten days after podocin knockout, urine and faeces were collected for 10 days in metabolic cages and analysed for electrolytes, plasminogen, protease activity and ability to activate γENaC by patch clamp and western blot. Mice were treated with amiloride (2.5 mg kg−1 for 2 days and 10 mg kg−1 for 2 days) or an anti‐urokinase‐type plasminogen activator (uPA) targeting antibody (120 mg kg−1/24 h) and compared to controls. Results Twelve days after deletion, podocin‐deficient mice developed significant protein and albuminuria associated with increased body wt, ascites, sodium accumulation and suppressed plasma renin. This was associated with increased urinary excretion of plasmin and plasminogen that correlated with albumin excretion, urine protease activity co‐migrating with active plasmin, and the ability of urine to induce an amiloride‐sensitive inward current in M1 cells in vitro. Amiloride treatment in podocin‐deficient mice resulted in weight loss, increased sodium excretion, normalization of sodium balance and prevention of the activation of plasminogen to plasmin in urine in a reversible way. Administration of uPA targeting antibody abolished urine activation of plasminogen, attenuated sodium accumulation and prevented cleavage of γENaC. Conclusions Nephrotic range glomerular proteinuria leads to urokinase‐dependent intratubular plasminogen activation and γENaC cleavage which contribute to sodium accumulation. - 'Acta Physiologica, EarlyView. '
    September 17, 2019   doi: 10.1111/apha.13362   open full text
  • Increased hypothalamic hydrogen sulphide contributes to endotoxin tolerance by down‐modulating PGE2 production.
    Bruna M. Santos, Heloísa D. C. Francescato, Flávia C. Turcato, José Antunes‐Rodrigues, Terezila M. Coimbra, Luiz G. S. Branco.
    Acta Physiologica. September 15, 2019
    --- - |2+ Abstract Aim Whereas some patients have important changes in body core temperature (Tb) during systemic inflammation, others maintain a normal Tb, which is intrinsically associated to immune paralysis. One classical model to study immune paralysis is the use of repeated administration of lipopolysaccharide (LPS), the so‐called endotoxin tolerance. However, the neuroimmune mechanisms of endotoxin tolerance remain poorly understood. Hydrogen sulphide (H2S) is a gaseous neuromodulator produced in the brain by the enzyme cystathionine β‐synthase (CBS). The present study assessed whether endotoxin tolerance is modulated by hypothalamic H2S. Methods Rats with central cannulas (drug microinjection) and intraperitoneal datalogger (temperature record) received a low‐dose of lipopolysaccharide (LPS; 100 µg kg−1) daily for four consecutive days. Hypothalamic CBS expression and H2S production rate were assessed, together with febrigenic signalling. Tolerant rats received an inhibitor of H2S synthesis (AOA, 100 pmol 1 µL−1 icv) or its vehicle in the last day. Results Antero‐ventral preoptic area of the hypothalamus (AVPO) H2S production rate and CBS expression were increased in endotoxin‐tolerant rats. Additionally, hypothalamic H2S inhibition reversed endotoxin tolerance reestablishing fever, AVPO and plasma PGE2 levels without altering the absent plasma cytokines surges. Conclusion Endotoxin tolerance is not simply a reflection of peripheral reduced cytokines release but actually results from a complex set of mechanisms acting at multiple levels. Hypothalamic H2S production modulates most of these mechanisms. - 'Acta Physiologica, EarlyView. '
    September 15, 2019   doi: 10.1111/apha.13373   open full text
  • LTBP2 knockdown by siRNA reverses myocardial oxidative stress injury, fibrosis, and remodeling during dilated cardiomyopathy.
    Xue‐Feng Pang, Xue Lin, Jian‐Jun Du, Ding‐Yin Zeng.
    Acta Physiologica. September 11, 2019
    --- - |2+ Abstract Aim Dilated cardiomyopathy (DCM) is is characterised by left ventricular dilation and associated with systolic dysfunction. Recent evidence has reported the high expression of latent transforming growth factor beta‐binding protein 2 (LTBP2) in heart diseases, which may play a role in regulating multiple biological functions of myocardial cells. Thus, this study set out to investigate the molecular mechanism and effects of LTBP2 in myocardial oxidative stress injury, fibrosis and remodeling in a rat model of DCM, with the involvement of NF‐κB signaling pathway. Methods The rat model of DCM was treated with si‐LTBP2 and/or activator of NF‐κB signaling pathway to examine the hemodynamic indexes, cardiac functions, oxidative stress injury, fibrosis and remodeling. Moreover, in vitro experiments were conducted to verify the regulatory role of LTBP2 and NF‐κB signaling pathway in DCM. Results LTBP2 was upregulated in DCM rats. After LTBP2 was knocked down, hemodynamic indexes, HW/BW ratio, collagen volume fraction (CVF) level, positive expression of LTBP2, levels of reactive oxygen species (ROS), malondialdehyde (MDA), interleukin‐6 (IL‐6), tumor necrosis factor‐alpha (TNF‐α), tumor necrosis factor‐beta 1 (TGF‐β1) and brain natriuretic peptide (BNP) were all decreased. Meanwhile, levels of LTBP2, Col‐I, Col‐III, p65 and p52 were also reduced, while HW, BW and levels of SOD and TAOC were increased. In contrast, activation of NF‐κB signaling pathway reversed effects of LTBP2 gene silencing. These findings were confirmed by in vivo experiments. Conclusions LTBP2 silencing can attenuate myocardial oxidative stress injury, myocardial fibrosis and myocardial remodeling in DCM rats by down‐regulating NF‐κB signaling pathway. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    September 11, 2019   doi: 10.1111/apha.13377   open full text
  • Regulation of erythrocyte function: Multiple evolutionary solutions for respiratory gas transport and its regulation in fish.
    Mikko Nikinmaa, Michael Berenbrink, Colin J. Brauner.
    Acta Physiologica. September 08, 2019
    --- - |2 Abstract Gas transport concepts in vertebrates have naturally been formulated based on human blood. However, the first vertebrates were aquatic, and fish and tetrapods diverged hundreds of millions years ago. Water‐breathing vertebrates live in an environment with low and variable O2 levels, making environmental O2 an important evolutionary selection pressure in fishes, and various features of their gas transport differ from humans. Erythrocyte function in fish is of current interest, because current environmental changes affect gas transport, and because especially zebrafish is used as a model in biomedical studies, making it important to understand the differences in gas transport between fish and mammals to be able to carry out meaningful studies. Of the close to thirty thousand fish species, teleosts are the most species‐numerous group. However, two additional radiations are discussed: agnathans and elasmobranchs. The gas transport by elasmobranchs may be closest to the ancestors of tetrapods. The major difference in their haemoglobin (Hb) function to humans is their high urea tolerance. Agnathans differ from other vertebrates by having Hbs, where cooperativity is achieved by monomer‐oligomer equilibria. Their erythrocytes also lack the anion exchange pathway with profound effects on CO2 transport. Teleosts are characterized by highly pH sensitive Hbs, which can fail to become fully O2‐saturated at low pH. An adrenergically stimulated Na+/H+ exchanger has evolved in their erythrocyte membrane, and plasma‐accessible carbonic anhydrase can be differentially distributed among their tissues. Together, and differing from other vertebrates, these features can maximize O2 unloading in muscle while ensuring O2 loading in gills. - 'Acta Physiologica, Volume 227, Issue 2, October 2019. '
    September 08, 2019   doi: 10.1111/apha.13299   open full text
  • MMP‐9‐positive neutrophils are essential for establishing profibrotic microenvironment in the obstructed kidney of UUO mice.
    Haidong Wang, Min Gao, Jiangbo Li, Jian Sun, Ran Wu, Deping Han, Jianmei Tan, Juan Wang, Bin Wang, Liping Zhang, Yanjun Dong.
    Acta Physiologica. September 08, 2019
    --- - |2+ Abstract Aim Matrix metalloproteinase‐9 (MMP9) plays a profibrotic role in renal fibrosis. Neutrophils produce MMP9 in many pathologic models. However, the effect of neutrophil on the progression of renal fibrosis and the relationship of MMP9 to the infiltration of neutrophils into the kidney remain unknown. Methods The surgery of unilateral ureter obstruction (UUO) was performed in male C57BL/6 mice. Kidneys were collected for analyses on days 0, 1, 3, 5 or 7 following surgery. The inflammatory cells were analysed by flow cytometry. The mRNA and protein levels of renal fibrosis factor and inflammatory factor were measured by qRT‐PCR, immumofluorescence and western blot analysis. Results In a mouse kidney model of UUO, neutrophil infiltration significantly increased and neutrophil accumulation reached the highest level at 5 days after the injury. In the obstructed kidney, depleting neutrophils decreased the expression of inflammatory factors, inhibited the accumulation of macrophages including type 2 macrophages and suppressed renal fibrosis. Almost all neutrophils produced MMP9 at the early stage of kidney obstruction. MMP9 attracted neutrophils and inflammatory cells because inhibiting MMP9 suppressed the infiltration of neutrophils and other inflammatory cells and reduced renal fibrosis, regardless of using MMP9 neutralizing antibody or MMP9 inhibitor or different intervening periods of days (0‐6, 0‐3 or 3‐6 were applied after kidney obstruction). Conclusion MMP9 promotes neutrophil infiltration by increasing the inflammatory level, macrophage accumulation and renal fibrosis in the obstructed kidney. Inhibiting MMP9 or depleting neutrophils in the early stage of acute kidney injury can relieve the progression of kidney fibrosis. - 'Acta Physiologica, Volume 227, Issue 2, October 2019. '
    September 08, 2019   doi: 10.1111/apha.13317   open full text
  • A novel sympathetic neuronal GABAergic signalling system regulates NE release to prevent ventricular arrhythmias after acute myocardial infarction.
    Yugen Shi, Yan Li, Jie Yin, Hesheng Hu, Mei Xue, Xiaolu Li, Wenjuan Cheng, Ye Wang, Xinran Li, Yu Wang, Jiayu Tan, Suhua Yan.
    Acta Physiologica. September 08, 2019
    --- - |2+ Abstract Aim Overactivation of the sympathetic nerve may lead to severe ventricular arrhythmias (VAs) after myocardial infarction (MI). Thus, targeting sympathetic nerve activity is an effective strategy to prevent VAs clinically. The superior cervical ganglion (SCG), the extracardiac sympathetic ganglion innervating cardiac muscles, has been found to have a GABAergic signalling system, the physiological significance of which is obscure. We aimed to explore the functional significance of SCG post MI and whether the GABAergic signal system is involved in the process. Methods Adult male Sprague‐Dawley rats were divided into seven different groups. Rats in the MI groups underwent ligation of the left anterior descending coronary artery. All animals were used for electrophysiological testing, renal sympathetic nerve activity (RSNA) testing, and ELISA. Primary SCG sympathetic neurons were used for the in vitro study. Results The GABAA receptor agonist muscimol significantly decreased the ATP‐induced increase in intracellular Ca2+ (P < 0.05). GABA treatment in MI rats significantly attenuated the level of serum and cardiac norepinephrine (NE; P < 0.05). Sympathetic activity and inducible VAs were also lower in MI + GABA rats than in MI rats (P < 0.05). Knockdown of the GABAARs β2 subunit (GABAARβ2) in the SCG of MI rats increased the NE levels in serum and cardiac tissue, RSNA and inducible VAs compared with vehicle shRNA (P < 0.05). Conclusion The GABAergic signalling system is functionally expressed in SCG sympathetic neurons, and activation of this system suppresses sympathetic activity, thereby facilitating cardiac protection and making it a potential target to alleviate VAs. - 'Acta Physiologica, Volume 227, Issue 2, October 2019. '
    September 08, 2019   doi: 10.1111/apha.13315   open full text
  • miR‐29a promotes pathological cardiac hypertrophy by targeting the PTEN/AKT/mTOR signalling pathway and suppressing autophagy.
    Jia‐yu Shi, Chu Chen, Xuan Xu, Qi Lu.
    Acta Physiologica. September 08, 2019
    --- - |2+ Abstract Aim Although miR‐29 has emerged as a crucial non‐coding RNA in the regulation of pathological cardiac hypertrophy, further exploration of its specific mechanisms is necessary to resolve controversy about its major role in this condition. This study therefore evaluated the role of miR‐29a and whether it acts through the PTEN/AKT/mTOR pathway. Methods In this study, a rat model of pressure‐induced cardiac hypertrophy was established by transverse aortic constriction and verified by echocardiography, histological analysis and quantitative RT‐PCR. At the cellular level, we explored the role of miR‐29a in angiotensin II‐stimulated hypertrophic H9c2 cardiomyoblasts by transfecting the cells with miR‐29a inhibitor and mimic. The relationship between miR‐29a and the signalling pathway was investigated with dual luciferase reporter assays, immunofluorescence analysis and Western blotting. We also examined whether autophagy is involved in the regulatory mechanism of miR‐29a through transmission electron microscopy and detection of autophagy‐associated proteins. Results The results showed that miR‐29a was upregulated both in rats 4 weeks after surgery and in 10−6 M angiotensin II‐stimulated cells. In contrast, inhibition of miR‐29a partially attenuated angiotensin II‐induced hypertrophy. Additionally, bioinformatics analysis revealed that PTEN was one of the target genes of miR‐29a, which was also verified by luciferase assay. The results of immunofluorescence and Western blotting indicated that overexpression of miR‐29a inhibited the expression of PTEN, activated the AKT/mTOR pathway and suppressed autophagy, which ultimately led to cardiac hypertrophy. Conclusion In pathological cardiac hypertrophy, miR‐29a was overexpressed and promoted cardiac hypertrophy by regulating the PTEN/AKT/mTOR pathway and suppressing autophagy. - 'Acta Physiologica, Volume 227, Issue 2, October 2019. '
    September 08, 2019   doi: 10.1111/apha.13323   open full text
  • A synthetic epoxyeicosatrienoic acid analogue prevents the initiation of ischemic acute kidney injury.
    Uwe Hoff, Gordana Bubalo, Mandy Fechner, Maximilian Blum, Ye Zhu, Andreas Pohlmann, Jan Hentschel, Karen Arakelyan, Erdmann Seeliger, Bert Flemming, Dennis Gürgen, Michael Rothe, Thoralf Niendorf, Vijaya L. Manthati, John R. Falck, Michael Haase, Wolf‐Hagen Schunck, Duska Dragun.
    Acta Physiologica. September 08, 2019
    --- - |2+ Abstract Aim Imbalances in cytochrome P450 (CYP)‐dependent eicosanoid formation may play a central role in ischemic acute kidney injury (AKI). We reported previously that inhibition of 20‐hydroxyeicosatetraenoic acid (20‐HETE) action ameliorated ischemia/reperfusion (I/R)‐induced AKI in rats. Now we tested the hypothesis that enhancement of epoxyeicosatrienoic acid (EET) actions may counteract the detrimental effects of 20‐HETE and prevent the initiation of AKI. Methods Male Lewis rats underwent right nephrectomy and ischemia was induced by 45 min clamping of the left renal pedicle followed by up to 48 h of reperfusion. Circulating CYP‐eicosanoid profiles were compared in patients who underwent cardiac surgery with (n = 21) and without (n = 38) developing postoperative AKI. Results Ischemia induced an about eightfold increase of renal 20‐HETE levels, whereas free EETs were not accumulated. To compensate for this imbalance, a synthetic 14,15‐EET analogue was administered by intrarenal infusion before ischemia. The EET analogue improved renal reoxygenation as monitored by in vivo parametric MRI during the initial 2 h reperfusion phase. The EET analogue improved PI3K‐ as well as mTORC2‐dependent rephosphorylation of Akt, induced inactivation of GSK‐3β, reduced the development of tubular apoptosis and attenuated inflammatory cell infiltration. The EET analogue also significantly alleviated the I/R‐induced drop in creatinine clearance. Patients developing postoperative AKI featured increased preoperative 20‐HETE and 8,9‐EET levels. Conclusions Pharmacological interventions targeting the CYP‐eicosanoid pathway could offer promising new options for AKI prevention. Individual differences in CYP‐eicosanoid formation may contribute to the risk of developing AKI in clinical settings. - 'Acta Physiologica, Volume 227, Issue 2, October 2019. '
    September 08, 2019   doi: 10.1111/apha.13297   open full text
  • Leptin modulates olfactory discrimination and neural activity in the olfactory bulb.
    Changcheng Sun, Keke Tang, Jing Wu, Han Xu, Wenfeng Zhang, Tiantian Cao, Yang Zhou, Tian Yu, Anan Li.
    Acta Physiologica. September 08, 2019
    --- - |2+ Abstract Aim Leptin is an important peptide hormone that regulates food intake and plays a crucial role in modulating olfactory function. Although a few previous studies have investigated the effect of leptin on odor perception and discrimination in rodents, research on the neural basis underlying the behavioral changes is lacking. Here we study how leptin affects behavioral performance during a go/no‐go task and how it modulates neural activity of mitral/tufted cells in the olfactory bulb, which plays an important role in odor information processing and representation. Methods A go/no‐go odor discrimination task was used in the behavioral test. For in vivo studies, single unit recordings, local field potential recordings and fiber photometry recordings were used. For in vitro studies, we performed patch clamp recordings in the slice of the olfactory bulb. Results Behaviorally, leptin affects performance and reaction time in a difficult odor‐discrimination task. Leptin decreases the spontaneous firing of single mitral/tufted cells, decreases the odor‐evoked beta and high gamma local field potential response, and has bidirectional effects on the odor‐evoked responses of single mitral/tufted cells. Leptin also inhibits the population calcium activity in genetically identified mitral/tufted cells and granule cells. Furthermore, in vitro slice recordings reveal that leptin inhibits mitral cell activity through direct modulation of the voltage‐sensitive potassium channel. Conclusions The behavioral reduction in odor discrimination observed after leptin administration is likely due to decreased neural activity in mitral/tufted cells, caused by modulation of potassium channels in these cells. - 'Acta Physiologica, Volume 227, Issue 2, October 2019. '
    September 08, 2019   doi: 10.1111/apha.13319   open full text
  • Distant organ dysfunction in acute kidney injury.
    Faeq Husain‐Syed, Mitchell H. Rosner, Claudio Ronco.
    Acta Physiologica. September 03, 2019
    --- - |2 Abstract Acute kidney injury (AKI) is a common complication in critically ill patients and it is associated with increased morbidity and mortality. Epidemiological and clinical data show that AKI is linked to a wide range of distant organ injuries, with the lungs, heart, liver, and intestines representing the most clinically relevant affected organs. This distant organ injury during AKI predisposes patients to progression to multiple organ dysfunction syndrome and ultimately, death. The strongest direct evidence of distant organ injury occurring in AKI has been obtained from animal models. The identified mechanisms include systemic inflammatory changes, oxidative stress, increases in leucocyte trafficking and the activation of proapoptotic pathways. Understanding the pathways driving AKI‐induced distal organ injury are critical for the development and refinement of therapies for the prevention and attenuation of AKI‐related morbidity and mortality. The purpose of this review is to summarize both clinical and preclinical studies of AKI and its role in distant organ injury. - 'Acta Physiologica, EarlyView. '
    September 03, 2019   doi: 10.1111/apha.13357   open full text
  • Chemical chaperones improve the functional recovery of stunned myocardium by attenuating the endoplasmic reticulum stress.
    Juan Ignacio Elio Mariángelo, Bárbara Román, María Agustina Silvestri, Margarita Salas, Leticia Vittone, Matilde Said, Cecilia Mundiña‐Weilenmann.
    Acta Physiologica. August 25, 2019
    --- - |2+ Abstract Aim Myocardial ischaemia/reperfusion (I/R) produces structural and functional alterations depending on the duration of ischaemia. Brief ischaemia followed by reperfusion causes reversible contractile dysfunction (stunned heart) but long‐lasting ischaemia followed by reperfusion can result in irreversible injury with cell death. Events during I/R can alter endoplasmic reticulum (ER) function leading to the accumulation of unfolded/misfolded proteins. The resulting ER stress induces activation of several signal transduction pathways, known as unfolded protein response (UPR). Experimental evidence shows that UPR contributes to cell death in irreversible I/R injury; however, there is still uncertainty for its occurrence in the stunned myocardium. This study investigated the ER stress response and its functional impact on the post‐ischaemic cardiac performance of the stunned heart. Methods Perfused rat hearts were subjected to 20 minutes of ischaemia followed by 30 minutes of reperfusion. UPR markers were evaluated by qRT‐PCR and western blot. Post‐ischaemic mechanical recovery was measured in absence and presence of two chemical chaperones: tauroursodeoxycholic acid (TUDCA) and 4‐phenylbutyric acid (4‐PBA). Results Analysis of mRNA and protein levels of various ER stress effectors demonstrated that different UPR signalling cascades, involving both pro‐survival and pro‐apoptotic pathways, are activated. Inhibition of the UPR with chemical chaperones improved the post‐ischaemic recovery of cardiac mechanical function without affecting the I/R‐induced increase in oxidative stress. Conclusion Our results suggest that prevention of ER stress by chemical chaperones could be a therapeutic tool to limit deterioration of the contractile function in clinical settings in which the phenomenon of myocardial stunning is present. - 'Acta Physiologica, EarlyView. '
    August 25, 2019   doi: 10.1111/apha.13358   open full text
  • Roles of lncRNAs and circRNAs in regulating skeletal muscle development.
    Rui Chen, Si Lei, Ting Jiang, Jie Zeng, Shanyao Zhou, Yanling She.
    Acta Physiologica. August 19, 2019
    --- - |2 Abstract The multistep biological process of myogenesis is regulated by a variety of myoblast regulators, such as myogenic differentiation antigen, myogenin, myogenic regulatory factor, myocyte enhancer factor2A‐D and myosin heavy chain. Proliferation and differentiation during skeletal muscle myogenesis contribute to the physiological function of muscles. Certain non‐coding RNAs, including long non‐coding RNAs (lncRNAs) and circular RNAs (circRNAs), are involved in the regulation of muscle development, and the aberrant expressions of lncRNAs and circRNAs are associated with muscular diseases. In this review, we summarize the recent advances concerning the roles of lncRNAs and circRNAs in regulating the developmental aspects of myogenesis. These findings have remarkably broadened our understanding of the gene regulation mechanisms governing muscle proliferation and differentiation, which makes it more feasible to design novel preventive, diagnostic and therapeutic strategies for muscle disorders. - 'Acta Physiologica, EarlyView. '
    August 19, 2019   doi: 10.1111/apha.13356   open full text
  • SHIPping out diabetes—Metformin, an old friend among new SHIP2 inhibitors.
    Sanna Lehtonen.
    Acta Physiologica. August 12, 2019
    --- - |2 Abstract SHIP2 (Src homology 2 domain‐containing inositol 5′‐phosphatase 2) belongs to the family of 5′‐phosphatases. It regulates the phosphoinositide 3‐kinase (PI3K)‐mediated insulin signalling cascade by dephosphorylating the 5′‐position of PtdIns(3,4,5)P3 to generate PtdIns(3,4)P2, suppressing the activity of the pathway. SHIP2 mouse models and genetic studies in human propose that increased expression or activity of SHIP2 contributes to the pathogenesis of the metabolic syndrome, hypertension and type 2 diabetes. This has raised great interest to identify SHIP2 inhibitors that could be used to design new treatments for metabolic diseases. This review summarizes the central mechanisms associated with the development of diabetic kidney disease, including the role of insulin resistance, and then moves on to describe the function of SHIP2 as a regulator of metabolism in mouse models. Finally, the identification of SHIP2 inhibitors and their effects on metabolic processes in vitro and in vivo are outlined. One of the newly identified SHIP2 inhibitors is metformin, the first‐line medication prescribed to patients with type 2 diabetes, further boosting the attraction of SHIP2 as a treatment target to ameliorate metabolic disorders. - 'Acta Physiologica, EarlyView. '
    August 12, 2019   doi: 10.1111/apha.13349   open full text
  • Diagnostic and theranostic microRNAs in the pathogenesis of atherosclerosis.
    Sara Shoeibi.
    Acta Physiologica. August 10, 2019
    --- - |2 Abstract MicroRNAs (miRNAs) are a group of small single strand and noncoding RNAs that regulate several physiological and molecular signalling pathways. Alterations of miRNA expression profiles may be involved with pathophysiological processes underlying the development of atherosclerosis and cardiovascular diseases, including changes in the functions of the endothelial cells and vascular smooth muscle cells, such as cell proliferation, migration and inflammation, which are involved in angiogenesis, macrophage function and foam cell formation. Thus, miRNAs can be considered to have a crucial role in the progression, modulation and regulation of every stage of atherosclerosis. Such potential biomarkers will enable us to predict therapeutic response and prognosis of cardiovascular diseases and adopt effective preclinical and clinical treatment strategies. In the present review article, the current data regarding the role of miRNAs in atherosclerosis were summarized and the potential miRNAs as prognostic, diagnostic and theranostic biomarkers in preclinical and clinical studies were further discussed. The highlights of this review are expected to present opportunities for future research of clinical therapeutic approaches in vascular diseases resulting from atherosclerosis with an emphasis on miRNAs. - 'Acta Physiologica, EarlyView. '
    August 10, 2019   doi: 10.1111/apha.13353   open full text
  • Body temperature control in rats by muscle tone during rest or sleep.
    Terje Lømo, Torsten Eken, Erling Bekkestad Rein, Arild Njå.
    Acta Physiologica. August 09, 2019
    --- - |2+ Abstract Aim To explore the role of tonic motor unit activity in body temperature control. Methods Motor unit activity in soleus and several other skeletal muscles was recorded electromyographically from adult rats placed in a climate chamber on a load sensitive floor, which, together with video monitoring, allowed detection of every successive period of movement and no movement. Results In the absence of movements during rest or sleep, motor unit activity was exclusively tonic and therefore equivalent to muscle tone as defined here. The amount of tonic activity increased linearly in the soleus as the ambient temperature decreased from 32°C to below 7°C, owing to progressive recruitment and increased firing rate of individual units. Brief movements occurred randomly and frequently during rest or sleep in association with brief facilitation or inhibition of motor neurons that turned tonic motor unit activity on or off, partitioning the tonic activity among the available motor units. Shivering first appeared when a falling ambient temperature reached ≤7°C in several muscles except soleus, which was as active between shivering bursts as during them. Conclusion Muscle tone and overt shivering are strikingly different phenomena. Tonic motor unit activity in the absence of movements evokes isometric contractions and, therefore, generates heat. Accordingly, when the amount of tonic activity increases with falling ambient temperature, so must heat production. Consequently, graded muscle tone appears as an important and independent mechanism for thermogenesis during rest or sleep at ambient temperatures ranging from <7°C to at least 32°C. - 'Acta Physiologica, EarlyView. '
    August 09, 2019   doi: 10.1111/apha.13348   open full text
  • Physiological regulation of reactive oxygen species in organisms based on their physicochemical properties.
    Mei‐Zhou Huang, Jian‐Yong Li.
    Acta Physiologica. August 08, 2019
    --- - |2 Abstract Oxidative stress is recognized as free radical dyshomeostasis, which has damaging effects on proteins, lipids and DNA. However, during cell differentiation and proliferation and other normal physiological processes, free radicals play a pivotal role in message transmission and are considered important messengers. Organisms maintain free radical homeostasis through a sophisticated regulatory system in which these “2‐faced” molecules play appropriate roles under physiological and pathological conditions. Reactive oxygen species (ROS), including a large number of free radicals, act as redox signalling molecules in essential cellular signalling pathways, including cell differentiation and proliferation. However, excessive ROS levels can induce oxidative stress, which is an important risk factor for diabetes, cancer and cardiovascular disease. An overall comprehensive understanding of ROS is beneficial for understanding the pathogenesis of certain diseases and finding new therapeutic treatments. This review primarily focuses on ROS cellular localization, sources, chemistry and molecular targets to determine how to distinguish between the roles of ROS as messengers and in oxidative stress. - 'Acta Physiologica, EarlyView. '
    August 08, 2019   doi: 10.1111/apha.13351   open full text
  • Human myometrial artery function and endothelial cell calcium signalling are reduced by obesity: Can this contribute to poor labour outcomes?
    Clodagh Prendergast, Susan Wray.
    Acta Physiologica. August 01, 2019
    --- - |2+ Abstract Aims Determining how obesity affects function in human myometrial arteries, to help understand why childbirth has poor outcomes in obese women. Methods Myometrial arteries were studied from 84 biopsies. Contraction (vasopressin and U‐46619) and relaxation (carbachol, bradykinin, SNAP) was assessed using wire myography. eNOS activity was assessed using L‐NAME. Cholesterol was reduced using methyl‐β‐cyclodextrin to determine whether it altered responses. Differences in endothelial cell intracellular Ca2+ signalling were assessed using confocal microscopy. Results The effects of BMI on relaxation were agonist specific and very marked; all vessels, irrespective of BMI, relaxed to bradykinin but 0% of vessels (0/13) from obese women relaxed to carbachol, compared to 59% (10/17) from normal weight women. Cholesterol‐lowering drugs did not restore carbachol responses (n = 6). All vessels, irrespective of BMI, relaxed when NO was directly released by SNAP (n = 19). Inhibition of eNOS with L‐NAME had a significant effect in normal but not overweight/obese vessels. Compared to bradykinin, a lower proportion of endothelial cells responded to carbachol and the amplitude of the calcium response was significantly less, in all vessels. Furthermore, a significantly lower proportion of endothelial cells responded to carbachol in the overweight/obese group compared to control. In contrast to relaxation, the effect of contractile agonists was unchanged with increasing BMI. Conclusions The ability of human myometrial arteries to relax is significantly impaired with obesity, and our data suggest this is due to a deficit in endothelial calcium signalling. This inability to recover following compression during contractions, might contribute to poor labours in obese women. - 'Acta Physiologica, EarlyView. '
    August 01, 2019   doi: 10.1111/apha.13341   open full text
  • Urinary extracellular vesicles: Origin, role as intercellular messengers and biomarkers; efficient sorting and potential treatment options.
    Per Svenningsen, Rugivan Sabaratnam, Boye L. Jensen.
    Acta Physiologica. August 01, 2019
    --- - |2 Abstract Urinary extracellular vesicles (uEVs) are a heterogenous group of vesicles consisting mainly of microvesicles and exosomes that originate predominantly (99.96%) from kidney, the urinary tract epithelium and the male reproductive tract. Secreted EVs contain molecular cargo from parental cells and provide an attractive source for biomarkers, a potential readout of physiological and pathophysiological mechanisms, and events associated with the urinary system. uEVs are readily enriched and isolated from urine samples and we review 6 standard methods that allow for downstream analysis of the uEV cargo. Although the use of uEVs as a surrogate readout for physiological changes in tissue protein levels is widespread, the protein abundance in uEVs is affected significantly by mechanisms that regulate protein sorting and secretion in uEVs. Data suggest that baseline kidney tissue and uEV levels of apical membrane‐associated electrolyte transport proteins are not directly related in human patients. Recent evidence indicates that EVs may contribute to physiological and pathophysiological intercellular signalling and EVs confer protection against renal ischemia‐reperfusion injury. The therapeutic use of EVs as information carriers has mainly been explored in vitro and a major hurdle lies in the translation of the in vitro findings into an in vivo setting. Thus, the EV research field is moving from a technical focus to a more physiological focus, allowing for a deeper understanding of human physiology, development of diagnostic tools and potential treatment strategies for precision medicine. - 'Acta Physiologica, EarlyView. '
    August 01, 2019   doi: 10.1111/apha.13346   open full text
  • Blunted leptin sensitivity during hedonic overeating can be reinstated by activating galanin 2 receptors (Gal2R) in the lateral hypothalamus.
    Este Leidmaa, Mary Gazea, Alexandre V. Patchev, Anna Pissioti, Nils Christian Gassen, Mayumi Kimura, Zsolt Liposits, Imre Kallo, Osborne F. X. Almeida.
    Acta Physiologica. July 31, 2019
    --- - |2+ Abstract Aim Since foods with high hedonic value are often consumed in excess of energetic needs, this study was designed to identify the mechanisms that may counter anorexigenic signalling in the presence of hedonic foods in lean animals. Methods Mice, in different states of satiety (fed/fasted, or fed/fasted and treated with ghrelin or leptin, respectively), were allowed to choose between high‐fat/high‐sucrose and standard foods. Intake of each food type and the activity of hypothalamic neuropetidergic neurons that regulate appetite were monitored. In some cases, food choice was monitored in leptin‐injected fasted mice that received microinjections of galanin receptor agonists into the lateral hypothalamus. Results Appetite‐stimulating orexin neurons in the lateral hypothalamus are rapidly activated when lean, satiated mice consume a highly palatable food (PF); such activation (upregulated c‐Fos expression) occurred even after administration of the anorexigenic hormone leptin and despite intact leptin signalling in the hypothalamus. The ability of leptin to restrain PF eating is restored when a galanin receptor 2 (Gal2R) agonist is injected into the lateral hypothalamus. Conclusion Hedonically‐loaded foods interrupt the inhibitory actions of leptin on orexin neurons and interfere with the homeostatic control of feeding. Overeating of palatable foods can be curtailed in lean animals by activating Gal2R in the lateral hypothalamus. - 'Acta Physiologica, EarlyView. '
    July 31, 2019   doi: 10.1111/apha.13345   open full text
  • Adipocyte‐derived extracellular vesicles modulate appetite and weight through mTOR signalling in the hypothalamus.
    Jie Gao, Xinyu Li, You Wang, Yan Cao, Dengju Yao, Lijie Sun, Lv Qin, Hui Qiu, Xiaorong Zhan.
    Acta Physiologica. July 27, 2019
    --- - |2+ Abstract Aim Type 2 diabetes and obesity are diseases related to surplus energy in the body. Abnormal interaction between the hypothalamus and adipose tissues is a key trigger of energy metabolism dysfunction. Extracellular vesicles (EVs) regulate intercellular communication by transporting intracellular cargo to recipient cells thereby altering the function of recipient cells. This study aimed to evaluate whether adipocyte‐derived EVs can act on hypothalamic neurons to modulate energy intake and to identify the EV‐associated non‐coding RNAs. Methods Confocal imaging was used to trace the uptake of labelled adipocyte‐derived exosomes by hypothalamic anorexigenic POMC neurons. The effects of adipocyte‐derived EVs on the mammalian target of rapamycin (mTOR) signalling pathway in POMC neurons were evaluated based on mRNA and protein expression in vitro using quantitative real‐time PCR and western blotting. In addition, adipocyte‐derived EVs were injected into recipient mice, and changes in mice body weight and daily food intake were monitored. The biological effects of the EV‐associated MALAT1 on POMC neurons were explored. Results Adipocyte‐derived EVs were successfully transferred into POMC neurons in vitro. Results showed that adipocytes of obese mice secreted MALAT1‐containing EVs, which increased appetite and weight when administered to lean mice. Conversely, adipocyte‐derived EVs from lean mice decreased food intake and weight when administered to obese mice. Conclusion Adipocyte‐derived EVs play important roles in mediating the interaction between adipocytes and hypothalamic neurons. Adipocyte‐derived EVs can regulate POMC expression through the hypothalamic mTOR signalling in vivo and in vitro, thereby affecting body energy intake. - 'Acta Physiologica, EarlyView. '
    July 27, 2019   doi: 10.1111/apha.13339   open full text
  • Loss of nuclear ARC contributes to the development of cardiac hypertrophy in rats.
    Fang Xie, Zhu‐Song Mei, Xue Wang, Tao Zhang, Yun Zhao, Shi‐Da Wang, Ling‐Jia Qian.
    Acta Physiologica. July 27, 2019
    --- - |2+ Abstract Aim Cardiac hypertrophy and myocardial apoptosis are two major factors in heart failure. As a classical regulator of apoptosis, apoptosis repressor with caspase recruitment domain (ARC) has recently also been found to have a protective effect against hypertrophy. However, the mechanism underlying this effect is still not fully understood. Methods In the present study, we established animal and cellular models to monitor the changes in total and nuclear ARC during cardiac hypertrophic processes. The preventive effects of nuclear ARC in cellular hypertrophy were verified by ARC regulation and nuclear export inhibition. To further explore the mechanism for nuclear ARC superficially, we analysed proteins that interact with ARC in the nucleus via Co‐IP and mass spectrometry. Results The expression of total ARC in hypertrophic myocardial tissue and H9C2 cells remained invariant, while the level of nuclear ARC decreased dramatically. By altering the content of ARC in H9C2 cells, we found that both nuclear ARC transfection and nuclear ARC export blockade attenuated norepinephrine or angiotensin II‐induced hypertrophy, while ARC knockdown had an inverse effect. Co‐IP data showed that ARC interacted with prohibitin (PHB) in the nucleus and might participate in maintaining the level of PHB in cells. Conclusions These findings suggest a novel mechanism for ARC in cardiac hypertrophy prevention and also indicate that the anti‐hypertrophic roles of ARC are probably associated with its localization in nucleus, which imply the nuclear ARC as a potential therapeutic target for cardiac hypertrophy. - 'Acta Physiologica, EarlyView. '
    July 27, 2019   doi: 10.1111/apha.13337   open full text
  • Claudin‐15 forms a water channel through the tight junction with distinct function compared to claudin‐2.
    Rita Rosenthal, Dorothee Günzel, Jörg Piontek, Susanne M. Krug, Carlos Ayala‐Torres, Caroline Hempel, Dian Theune, Michael Fromm.
    Acta Physiologica. July 08, 2019
    --- - |2+ Abstract Aim Claudin‐15 is mainly expressed in the small intestine and indirectly involved in glucose absorption. Similar to claudin‐2 and ‐10b, claudin‐15 is known to form a paracellular channel for small cations. Claudin‐2, but not claudin‐10b, also forms water channels. Here we experimentally tested whether claudin‐15 also mediates water transport and if yes, whether water transport is Na+‐coupled, as seen for claudin‐2. Methods MDCK C7 cells were stably transfected with claudin‐15. Ion and water permeability were investigated in confluent monolayers of control and claudin‐15‐expressing cells. Water flux was induced by an osmotic or ionic gradient. Results Expression of claudin‐15 in MDCK cells strongly increased cation permeability. The permeability ratios for monovalent cations indicated a passage of partially hydrated ions through the claudin‐15 pore. Accordingly, its pore diameter was determined to be larger than that of claudin‐2 and claudin‐10b. Mannitol‐induced water flux was elevated in claudin‐15‐expressing cells compared to control cells. In contrast to the Na+‐coupled water flux of claudin‐2 channels, claudin‐15‐mediated water flux was inhibited by Na+ flux. Consequently, water flux was increased in Na+‐free solution. Likewise, Na+ flux was decreased after induction of water flux through claudin‐15. Conclusion Claudin‐15, similar to claudin‐2, forms a paracellular cation and water channel. In functional contrast to claudin‐2, water and Na+ fluxes through claudin‐15 inhibit each other. Claudin‐15 allows Na+ to retain part of its hydration shell within the pore. This then reduces the simultaneous passage of additional water through the pore. - 'Acta Physiologica, EarlyView. '
    July 08, 2019   doi: 10.1111/apha.13334   open full text
  • Complex neural representation of odour information in the olfactory bulb.
    Anan Li, Xiaoping Rao, Yang Zhou, Diego Restrepo.
    Acta Physiologica. July 02, 2019
    --- - |2 Abstract The most important task of the olfactory system is to generate a precise representation of odour information under different brain and behavioural states. As the first processing stage in the olfactory system and a crucial hub, the olfactory bulb plays a key role in the neural representation of odours, encoding odour identity, intensity and timing. Although the neural circuits and coding strategies used by the olfactory bulb for odour representation were initially identified in anaesthetized animals, a large number of recent studies focused on neural representation of odorants in the olfactory bulb in awake behaving animals. In this review, we discuss these recent findings, covering (a) the neural circuits for odour representation both within the olfactory bulb and the functional connections between the olfactory bulb and the higher order processing centres; (b) how related factors such as sniffing affect and shape the representation; (c) how the representation changes under different states; and (d) recent progress on the processing of temporal aspects of odour presentation in awake, behaving rodents. We highlight discussion of the current views and emerging proposals on the neural representation of odorants in the olfactory bulb. - 'Acta Physiologica, EarlyView. '
    July 02, 2019   doi: 10.1111/apha.13333   open full text
  • Angiotensin II inhibits P‐glycoprotein in intestinal epithelial cells.
    Anoop Kumar, Shubha Priyamvada, Vikas Soni, Arivarasu N. Anbazhagan, Tarunmeet Gujral, Ravinder K. Gill, Waddah A. Alrefai, Pradeep K. Dudeja, Seema Saksena.
    Acta Physiologica. July 01, 2019
    --- - |2+ Abstract Aim P‐glycoprotein (Pgp/MDR1) plays a major role in intestinal homeostasis. Decrease in Pgp function and expression has been implicated in the pathogenesis of IBD. However, inhibitory mechanisms involved in the decrease of Pgp in inflammation are not fully understood. Angiotensin II (Ang II), a peptide hormone predominantly expressed in the epithelial cells of the crypt‐villus junction of the intestine, has been shown to exert pro‐inflammatory effects in the gut. It is increased in IBD patients and animals with experimental colitis. Whether Ang II directly influences Pgp is not known. Methods Pgp activity was measured as verapamil‐sensitive 3H‐digoxin flux. Pgp surface expression and exocytosis were measured by cell surface biotinylation studies. Signalling pathways were elucidated by Western blot analysis and pharmacological approaches. Results Ang II (10 nM) significantly inhibited Pgp activity at 60 minutes. Ang II‐mediated effects on Pgp function were receptor‐mediated as the Ang II receptor 1 (ATR1) antagonist, losartan, blocked Pgp inhibition. Ang II effects on Pgp activity appeared to be mediated via PI3 kinase, p38 MAPK and Akt signalling. Ang II‐mediated inhibition of Pgp activity was associated with a decrease in the surface membrane expression of Pgp protein via decreased exocytosis and was found to be dependent on the Akt pathway. Short‐term treatment of Ang II (2 mg/kg b.wt., 2 hours) to mice also decreased the membrane expression of Pgp protein levels in ileum and colon. Conclusion Our findings provide novel insights into the role of Ang II and ATR1 in decreasing Pgp expression in intestinal inflammation. - 'Acta Physiologica, EarlyView. '
    July 01, 2019   doi: 10.1111/apha.13332   open full text
  • AKAP12 deficiency impairs VEGF‐induced endothelial cell migration and sprouting.
    Peter M. Benz, Yindi Ding, Heike Stingl, Annemarieke E. Loot, Joana Zink, Ilka Wittig, Rüdiger Popp, Ingrid Fleming.
    Acta Physiologica. June 21, 2019
    --- - |2+ Abstract Aim Protein kinase (PK) A anchoring protein (AKAP) 12 is a scaffolding protein that anchors PKA to compartmentalize cyclic AMP signalling. This study assessed the consequences of the downregulation or deletion of AKAP12 on endothelial cell migration and angiogenesis. Methods The consequences of siRNA‐mediated downregulation AKAP12 were studied in primary cultures of human endothelial cells as well as in endothelial cells and retinas from wild‐type versus AKAP12−/− mice. Molecular interactions were investigated using a combination of immunoprecipitation and mass spectrometry. Results AKAP12 was expressed at low levels in confluent endothelial cells but its expression was increased in actively migrating cells, where it localized to lamellipodia. In the postnatal retina, AKAP12 was expressed by actively migrating tip cells at the angiogenic front, and its deletion resulted in defective extension of the vascular plexus. In migrating endothelial cells, AKAP12 was co‐localized with the PKA type II‐α regulatory subunit as well as multiple key regulators of actin dynamics and actin filament‐based movement; including components of the Arp2/3 complex and the vasodilator‐stimulated phosphoprotein (VASP). Fitting with the evidence of a physical VASP/AKAP12/PKA complex, it was possible to demonstrate that the VEGF‐stimulated and PKA‐dependent phosphorylation of VASP was dependent on AKAP12. Indeed, AKAP12 colocalized with phospho‐Ser157 VASP at the leading edge of migrating endothelial cells. Conclusion The results suggest that compartmentalized AKAP12/PKA signalling mediates VASP phosphorylation at the leading edge of migrating endothelial cells to translate angiogenic stimuli into altered actin dynamics and cell movement. - 'Acta Physiologica, EarlyView. '
    June 21, 2019   doi: 10.1111/apha.13325   open full text
  • Keeping heart homeostasis in check through the balance of iron metabolism.
    Driton Vela.
    Acta Physiologica. June 19, 2019
    --- - |2 Abstract Highly active cardiomyocytes need iron for their metabolic activity. In physiological conditions, iron turnover is a delicate process which is dependent on global iron supply and local autonomous regulatory mechanisms. Though less is known about the autonomous regulatory mechanisms, data suggest that these mechanisms can preserve cellular iron turnover even in the presence of systemic iron disturbance. Therefore, activity of local iron protein machinery and its relationship with global iron metabolism is important to understand cardiac iron metabolism in physiological conditions and in cardiac disease. Our knowledge in this respect has helped in designing therapeutic strategies for different cardiac diseases. This review is a synthesis of our current knowledge concerning the regulation of cardiac iron metabolism. In addition, different models of cardiac iron dysmetabolism will be discussed through the examples of heart failure (cardiomyocyte iron deficiency), myocardial infarction (acute changes in cardiac iron turnover), doxorubicin‐induced cardiotoxicity (cardiomyocyte iron overload in mitochondria), thalassaemia (cardiomyocyte cytosolic and mitochondrial iron overload) and Friedreich ataxia (asymmetric cytosolic/mitochondrial cardiac iron dysmetabolism). Finally, future perspectives will be discussed in order to resolve actual gaps in knowledge, which should be helpful in finding new treatment possibilities in different cardiac diseases. - 'Acta Physiologica, EarlyView. '
    June 19, 2019   doi: 10.1111/apha.13324   open full text
  • Muscle fibre activation and fatigue with low‐load blood flow restricted resistance exercise—An integrative physiology review.
    Mathias Wernbom, Per Aagaard.
    Acta Physiologica. June 18, 2019
    --- - |2 Abstract Blood flow‐restricted resistance exercise (BFRRE) has been shown to induce increases in muscle size and strength, and continues to generate interest from both clinical and basic research points of view. The low loads employed, typically 20%‐50% of the one repetition maximum, make BFRRE an attractive training modality for individuals who may not tolerate high musculoskeletal forces (eg, selected clinical patient groups such as frail old adults and patients recovering from sports injury) and/or for highly trained athletes who have reached a plateau in muscle mass and strength. It has been proposed that achieving a high degree of muscle fibre recruitment is important for inducing muscle hypertrophy with BFRRE, and the available evidence suggest that fatiguing low‐load exercise during ischemic conditions can recruit both slow (type I) and fast (type II) muscle fibres. Nevertheless, closer scrutiny reveals that type II fibre activation in BFRRE has to date largely been inferred using indirect methods such as electromyography and magnetic resonance spectroscopy, while only rarely addressed using more direct methods such as measurements of glycogen stores and phosphocreatine levels in muscle fibres. Hence, considerable uncertainity exists about the specific pattern of muscle fibre activation during BFRRE. Therefore, the purpose of this narrative review was (1) to summarize the evidence on muscle fibre recruitment during BFRRE as revealed by various methods employed for determining muscle fibre usage during exercise, and (2) to discuss reported findings in light of the specific advantages and limitations associated with these methods. - 'Acta Physiologica, EarlyView. '
    June 18, 2019   doi: 10.1111/apha.13302   open full text
  • Thyroid hormone regulation of neural stem cell fate: From development to ageing.
    Jean‐David Gothié, Pieter Vancamp, Barbara Demeneix, Sylvie Remaud.
    Acta Physiologica. June 17, 2019
    --- - |2 Abstract In the vertebrate brain, neural stem cells (NSCs) generate both neuronal and glial cells throughout life. However, their neuro‐ and gliogenic capacity changes as a function of the developmental context. Despite the growing body of evidence on the variety of intrinsic and extrinsic factors regulating NSC physiology, their precise cellular and molecular actions are not fully determined. Our review focuses on thyroid hormone (TH), a vital component for both development and adult brain function that regulates NSC biology at all stages. First, we review comparative data to analyse how TH modulates neuro‐ and gliogenesis during vertebrate brain development. Second, as the mammalian brain is the most studied, we highlight the molecular mechanisms underlying TH action in this context. Lastly, we explore how the interplay between TH signalling and cell metabolism governs both neurodevelopmental and adult neurogenesis. We conclude that, together, TH and cellular metabolism regulate optimal brain formation, maturation and function from early foetal life to adult in vertebrate species. - 'Acta Physiologica, EarlyView. '
    June 17, 2019   doi: 10.1111/apha.13316   open full text
  • O‐GlcNAcylation as a regulator of the functional and structural properties of the sarcomere in skeletal muscle: An update review.
    Matthias Lambert, Charlotte Claeyssen, Bruno Bastide, Caroline Cieniewski‐Bernard.
    Acta Physiologica. June 12, 2019
    --- - |2 Abstract Although the O‐GlcNAcylation process was discovered in 1984, its potential role in the physiology and physiopathology of skeletal muscle only emerged 20 years later. An increasing number of publications strongly support a key role of O‐GlcNAcylation in the modulation of important cellular processes which are essential for skeletal muscle functions. Indeed, over a thousand of O‐GlcNAcylated proteins have been identified within skeletal muscle since 2004, which belong to various classes of proteins, including sarcomeric proteins. In this review, we focused on these myofibrillar proteins, including contractile and structural proteins. Because of the modification of motor and regulatory proteins, the regulatory myosin light chain (MLC2) is related to several reports that support a key role of O‐GlcNAcylation in the fine modulation of calcium activation parameters of skeletal muscle fibres, depending on muscle phenotype and muscle work. In addition, another key function of O‐GlcNAcylation has recently emerged in the regulation of organization and reorganization of the sarcomere. Altogether, this data support a key role of O‐GlcNAcylation in the homeostasis of sarcomeric cytoskeleton, known to be disturbed in many related muscle disorders. - 'Acta Physiologica, EarlyView. '
    June 12, 2019   doi: 10.1111/apha.13301   open full text
  • To learn, to remember, to forget—How smart is the gut?
    Michael Schemann, Thomas Frieling, Paul Enck.
    Acta Physiologica. June 05, 2019
    --- - |2 Abstract The enteric nervous system (ENS) resides within the gut wall and autonomously controls gut functions through coordinated activation of sensory, inter and motor neurons. Its activity is modulated by the enteric immune and endocrine system as well as by afferent and efferent nerves of the parasympathetic and sympathetic nervous system. The ENS is often referred to as the second brain and hence is able to perform sophisticated tasks. We review the evidence that the “smartness” of the ENS may even extend to its ability to learn and to memorize. Examples for habituation, sensitization, conditioned behaviour and long‐term facilitation are evidence for various forms of implicit learning. Moreover, we discuss how this may change not only basic Neurogastroenterology but also our understanding of development of gut diseases and chronic disorders in gut functions. At the same time, we identify open questions and future challenges to confirm learning, memory and memory deficits in the gut. Despite some remaining experimental challenges, we are convinced that the gut is able to learn and are tempted to answer the question with: Yes, the gut is smart. - 'Acta Physiologica, EarlyView. '
    June 05, 2019   doi: 10.1111/apha.13296   open full text
  • Chronic adult‐onset of growth hormone/IGF‐I hypersecretion improves cognitive functions and LTP and promotes neuronal differentiation in adult rats.
    Juan Francisco Martín‐Rodríguez, Víctor Darío Ramos‐Herrero, Gloria G. Parras, Álvaro Flores‐Martínez, Ainara Madrazo‐Atutxa, David A. Cano, Agnès Gruart, José María Delgado‐García, Alfonso Leal‐Cerro, Rocío Leal‐Campanario.
    Acta Physiologica. June 02, 2019
    --- - |2+ Abstract Aim Besides their metabolic and endocrine functions, the growth hormone (GH) and its mediated factor, the insulin‐like growth factor I (IGF‐I), have been implicated in different brain functions, including neurogenesis. Long‐lasting elevated GH and IGF‐I levels result in non‐reversible somatic, endocrine and metabolic morbidities. However, the subcutaneous implantation of the GH‐secreting (GH‐S) GC cell line in rats leads to the controllable over‐secretion of GH and elevated IGF‐I levels, allowing the experimental study of their short‐term effects on brain functions. Methods Adult rats were implanted with GC cells and checked 10 weeks later, when a GH/IGF‐I‐secreting tumour was already formed. Results Tumour‐bearing rats acquired different operant conditioning tasks faster and better than controls and tumour‐resected groups. They also presented better retentions of long‐term memories in the passive avoidance test. Experimentally evoked long‐term potentiation (LTP) in the hippocampus was also larger and longer lasting in the tumour bearing than in the other groups. Chronic adult‐onset of GH/IGF‐I hypersecretion caused an acceleration of early progenitors, facilitating a faster neural differentiation, maturation and integration in the dentate gyrus, and increased the complexity of dendritic arbours and spine density of granule neurons. Conclusion Thus, adult‐onset hypersecretion of GH/IGF‐I improves neurocognitive functions, long‐term memories, experimental LTP and neural differentiation, migration and maturation. - 'Acta Physiologica, EarlyView. '
    June 02, 2019   doi: 10.1111/apha.13293   open full text
  • Oxygenation of adipose tissue: A human perspective.
    Ioannis G. Lempesis, Rens L. J. Meijel, Konstantinos N. Manolopoulos, Gijs H. Goossens.
    Acta Physiologica. June 02, 2019
    --- - |2 Abstract Obesity is a complex disorder of excessive adiposity, and is associated with adverse health effects such as cardiometabolic complications, which are to a large extent attributable to dysfunctional white adipose tissue. Adipose tissue dysfunction is characterized by adipocyte hypertrophy, impaired adipokine secretion, a chronic low‐grade inflammatory status, hormonal resistance and altered metabolic responses, together contributing to insulin resistance and related chronic diseases. Adipose tissue hypoxia, defined as a relative oxygen deficit, in obesity has been proposed as a potential contributor to adipose tissue dysfunction, but studies in humans have yielded conflicting results. Here, we will review the role of adipose tissue oxygenation in the pathophysiology of obesity‐related complications, with a specific focus on human studies. We will provide an overview of the determinants of adipose tissue oxygenation, as well as the role of adipose tissue oxygenation in glucose homeostasis, lipid metabolism and inflammation. Finally, we will discuss the putative effects of physiological and experimental hypoxia on adipose tissue biology and whole‐body metabolism in humans. We conclude that several lines of evidence suggest that alteration of adipose tissue oxygenation may impact metabolic homeostasis, thereby providing a novel strategy to combat chronic metabolic diseases in obese humans. - 'Acta Physiologica, EarlyView. '
    June 02, 2019   doi: 10.1111/apha.13298   open full text
  • Urokinase‐type plasminogen activator (uPA) is not essential for epithelial sodium channel (ENaC)‐mediated sodium retention in experimental nephrotic syndrome.
    Bernhard N. Bohnert, Sophie Daiminger, Matthias Wörn, Florian Sure, Tobias Staudner, Alexandr V. Ilyaskin, Firas Batbouta, Andrea Janessa, Jonas C. Schneider, Daniel Essigke, Sandip Kanse, Silke Haerteis, Christoph Korbmacher, Ferruh Artunc.
    Acta Physiologica. May 20, 2019
    --- - |2+ Abstract Aim In nephrotic syndrome, aberrantly filtered plasminogen (plg) is converted to active plasmin by tubular urokinase‐type plasminogen activator (uPA) and thought to lead to sodium retention by proteolytic activation of the epithelial sodium channel (ENaC). This concept predicts that uPA is an important factor for sodium retention and that inhibition of uPA might be protective in nephrotic syndrome. Methods Activation of amiloride‐sensitive currents by uPA and plg were studied in Xenopus laevis oocytes expressing murine ENaC. In doxorubicin‐induced nephrotic mice, uPA was inhibited pharmacologically by amiloride and genetically by the use of uPA‐deficient mice (uPA−/−). Results Experiments in Xenopus laevis oocytes expressing murine ENaC confirmed proteolytic ENaC activation by a combination of plg and uPA which stimulated amiloride‐sensitive currents with concomitant cleavage of the ENaC γ‐subunit at the cell surface. Treatment of nephrotic wild‐type mice with amiloride inhibited urinary uPA activity, prevented urinary plasmin formation and sodium retention. In nephrotic mice lacking uPA (uPA−/−), urinary plasmin formation from plg was suppressed and urinary uPA activity absent. However, in nephrotic uPA−/− mice, sodium retention was not reduced compared to nephrotic uPA+/+ mice. Amiloride prevented sodium retention in nephrotic uPA−/− mice which confirmed the critical role of ENaC in sodium retention. Conclusion uPA is responsible for the conversion of aberrantly filtered plasminogen to plasmin in the tubular lumen in vivo. However, uPA‐dependent plasmin generation is not essential for ENaC‐mediated sodium retention in experimental nephrotic syndrome. - 'Acta Physiologica, EarlyView. '
    May 20, 2019   doi: 10.1111/apha.13286   open full text
  • The importance of being rhythmic: Living in harmony with your body clocks.
    Charna Dibner.
    Acta Physiologica. May 03, 2019
    --- - |2 Abstract Circadian rhythms have developed in all light‐sensitive organisms, including humans, as a fundamental anticipatory mechanism that enables proactive adaptation to environmental changes. The circadian system is organized in a highly hierarchical manner, with clocks operative in most cells of the body ensuring the temporal coordination of physiological processes. Circadian misalignment, stemming from modern life style, draws increasing attention due to its tight association with the development of metabolic, cardiovascular, inflammatory and mental diseases as well as cancer. This review highlights recent findings emphasizing the role of the circadian system in the temporal orchestration of physiology, with a particular focus on implications of circadian misalignment in human pathologies. - 'Acta Physiologica, EarlyView. '
    May 03, 2019   doi: 10.1111/apha.13281   open full text
  • Exercise training remodels human skeletal muscle mitochondrial fission and fusion machinery towards a pro‐elongation phenotype.
    Christopher L. Axelrod, Ciarán E. Fealy, Anny Mulya, John P. Kirwan.
    Acta Physiologica. December 01, 2018
    --- - |2+ Abstract Aims Mitochondria exist as a morphologically plastic network driven by cellular bioenergetic demand. Induction of fusion and fission machinery allows the organelle to regulate quality control and substrate flux. Physiological stressors promote fragmentation of the mitochondrial network, a process implicated in the onset of metabolic disease, including type 2 diabetes and obesity. It is well‐known that exercise training improves skeletal muscle mitochondrial volume, number, and density. However, the effect of exercise training on muscle mitochondrial dynamics remains unclear. Methods Ten sedentary adults (65.8 ± 4.6 years; 34.3 ± 2.4 kg/m2) underwent 12 weeks of supervised aerobic exercise training (5 day/wk, 85% of HRMAX). Body composition, cardio‐metabolic testing, hyperinsulinaemic‐euglycaemic clamps, and skeletal muscle biopsies were performed before and after training. MFN1, MFN2, OPA1, OMA1, FIS1, Parkin, PGC‐1α, and HSC70 protein expression was assessed via Western blot. Results Exercise training led to improvements in insulin sensitivity, aerobic capacity, and fat oxidation (all P < 0.01), as well as reductions in body weight, BMI, fat mass and fasting glucose (all P < 0.001). When normalized for changes in mitochondrial content, exercise reduced skeletal muscle FIS1 and Parkin (P < 0.05), while having no significant effect on MFN1, MFN2, OPA1, and OMA1 expression. Exercise also improved the ratio of fusion to fission proteins (P < 0.05), which positively correlated with improvements in glucose disposal (r2 = 0.59, P < 0.05). Conclusions Exercise training alters the expression of mitochondrial fusion and fission proteins, promoting a more fused, tubular network. These changes may contribute to the improvements in insulin sensitivity and substrate utilization that are observed after exercise training. - 'Acta Physiologica, EarlyView. '
    December 01, 2018   doi: 10.1111/apha.13216   open full text
  • Tauroursodeoxycholic acid (TUDCA) abolishes chronic high salt‐induced renal injury and inflammation.
    C. De Miguel, R. Sedaka, M. Kasztan, J. M. Lever, M. Sonnenberger, A. Abad, C. Jin, P. K. Carmines, D. M. Pollock, J. S. Pollock.
    Acta Physiologica. November 30, 2018
    --- - |2+ Abstract Aim Chronic high salt intake exaggerates renal injury and inflammation, especially with the loss of functional ETB receptors. Tauroursodeoxycholic acid (TUDCA) is a chemical chaperone and bile salt that is approved for the treatment of hepatic diseases. Our aim was to determine whether TUDCA is reno‐protective in a model of ETB receptor deficiency with chronic high salt‐induced renal injury and inflammation. Methods ETB‐deficient and transgenic control rats were placed on normal (0.8% NaCl) or high salt (8% NaCl) diet for 3 weeks, receiving TUDCA (400 mg/kg/day; i.p.) or vehicle. Histological and biochemical markers of kidney injury, renal cell death and renal inflammation were assessed. Results In ETB‐deficient rats, high salt diet significantly increased glomerular and proximal tubular histological injury, proteinuria, albuminuria, excretion of tubular injury markers KIM‐1 and NGAL, renal cortical cell death and renal CD4+ T cell numbers. TUDCA treatment increased proximal tubule megalin expression as well as prevented high salt diet‐induced glomerular and tubular damage in ETB‐deficient rats, as indicated by reduced kidney injury markers, decreased glomerular permeability and proximal tubule brush border restoration, as well as reduced renal inflammation. However, TUDCA had no significant effect on blood pressure. Conclusions TUDCA protects against the development of glomerular and proximal tubular damage, decreases renal cell death, and inflammation in the renal cortex in rats with ETB receptor dysfunction on a chronic high salt diet. These results highlight the potential use of TUDCA as a preventive tool against chronic high salt induced renal damage. This article is protected by copyright. All rights reserved. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    November 30, 2018   doi: 10.1111/apha.13227   open full text
  • Interactive effects of age and hydration state on human thermoregulatory function during exercise in hot‐dry conditions.
    Robert D. Meade, Sean R. Notley, Andrew W. D'Souza, Sheila Dervis, Pierre Boulay, Ronald J. Sigal, Glen P. Kenny.
    Acta Physiologica. November 27, 2018
    --- - |2+ Abstract Aim Aging and hypohydration independently attenuate heat dissipation during exercise; however, the interactive effects of these factors remain unclear. We assessed the hypothesis that aging suppresses hypohydration‐induced reductions in whole‐body heat loss during exercise in the heat. Methods On two occasions, eight young (mean [SD]: 24 [4] years) and eight middle‐aged (59 [5] years) men performed 30‐min bouts of light (heat production of 175 W·m−2) and moderate (275 W·m−2) cycling (separated by 15‐min rest) in the heat (40°C, 15% relative humidity) when euhydrated and hypohydrated (~4% reduction in body mass). Heat production and whole‐body net heat exchange (evaporative heat loss + dry heat gain) were measured via indirect and direct calorimetry (respectively) and heat storage was calculated via their temporal summation. Results Net heat exchange was reduced, while heat storage was elevated, in the middle‐aged men during moderate exercise when euhydrated (both P≤0.01). In the young, evaporative heat loss was attenuated in the hypohydrated vs euhydrated condition during light (199±6 vs 211±10 W·m−2; P≤0.01) and moderate (287±15 vs 307±13 W·m−2; P≤0.01) exercise, but was similar in the middle‐aged men, averaging 223±6 and 299±15 W·m−2, respectively, across conditions (both P≥0.32). Heat storage was thereby exacerbated by hypohydration in the young (both P<0.01) but not the middle‐aged (both P≥0.32) during both exercise bouts and, as a result, was similar between groups when hypohydrated (both P≥0.50). Conclusion Hypohydration attenuates heat loss via sweating in young but not middle‐aged men, indicating that aging impairs one's ability to mitigate further sweat‐induced fluid loss during hypohydration. This article is protected by copyright. All rights reserved. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    November 27, 2018   doi: 10.1111/apha.13226   open full text
  • Work of breathing influences muscle sympathetic nerve activity during semi‐recumbent cycle exercise.
    Paolo B. Dominelli, Keisho Katayama, Tyler D. Vermeulen, Troy J.R. Stuckless, Courtney V. Brown, Glen E. Foster, A. William Sheel.
    Acta Physiologica. November 25, 2018
    --- - |2+ Abstract Reducing the work of breathing during exercise improves locomotor muscle blood flow and reduces diaphragm and locomotor muscle fatigue and is thought to be the result of a sympathetically mediated reflex. Aim The aim of this study was to assess muscle sympathetic nerve activity (MSNA) when the work of breathing is experimentally lowered during dynamic exercise. Methods Healthy subjects (n = 12; age = 29 ± 9 years) performed semi‐recumbent cycling trials at 40%, 60%, and 80% of peak workload. Exercise trials consisted of spontaneous breathing, reduced work of breathing (proportional assist ventilator), followed by further spontaneous breathing (post‐ventilator). MSNA was recorded from the median nerve. Results There was no difference in work of breathing between PAV and post‐PAV at 40% peak work. At 60% peak work, the ventilator significantly (P < 0.05) reduced work of breathing (103 ± 39 vs 144 ± 47 J min−1), sympathetic nerve activity (35 ± 5 vs 42 ± 8 burst min−1), and (2.4 ± 0.5 vs 2.6 ± 0.5 L min−1) without influencing ventilation (86 ± 9 vs 82 ± 10 L min−1; P > 0.05), for PAV and post‐PAV respectively. During 80% peak work (n = 8), the ventilator significantly (P < 0.05) reduced work of breathing (235 ± 110 vs. 361 ± 150 J min−1), MSNA (48 ± 7 vs 54 ± 11 burst min−1), and (2.9 ± 0.6 vs 3.2 ± 0.7 L min−1) but not ventilation (121 ± 20 vs 123 ± 20 L min−1; P > 0.05), for PAV and post‐PAV respectively. There was a significant relationship between MSNA and (P < 0.0001) with a significant interaction due to the ventilator (P < 0.05). Conclusion Lowering the normally occurring work of breathing during exercise results in commensurate reductions in MSNA. Our findings provide evidence of a sympathetically mediated vasoconstrictor effect emanating from respiratory muscles during exercise. - 'Acta Physiologica, EarlyView. '
    November 25, 2018   doi: 10.1111/apha.13212   open full text
  • The novel antidepressant ketamine enhances dentate gyrus proliferation with no effects on synaptic plasticity or hippocampal function in depressive‐like rats.
    Henrik Michaëlsson, Mats Andersson, Johan Svensson, Lars Karlsson, Johan Ehn, Georgia Culley, Anders Engström, Nicklas Bergström, Parthenia Savvidi, Hans‐Georg Kuhn, Eric Hanse, Henrik Seth.
    Acta Physiologica. November 25, 2018
    --- - |2+ Abstract Aim Major depressive disorder is a common and debilitating condition with substantial economic impact. Treatment options, although effective, are aimed at relieving the symptoms with limited disease modification. Ketamine, a commonly used anaesthetic, has received substantial attention as it shows rapid antidepressant effects clinically. We studied the effects of ketamine on hippocampal function and dentate gyrus proliferation in rats showing a depressive‐like phenotype. Methods Adolescent and adult animals were pre‐natally exposed to the glucocorticoid analog dexamethasone, and we verified a depressive‐like phenotype using behavioural tests, such as the sucrose preference. We subsequently studied the effects of ketamine on hippocampal synaptic transmission, plasticity and dentate gyrus proliferation. In addition, we measured hippocampal glutamate receptor expression. We also tested the ketamine metabolite hydroxynorketamine for NMDA‐receptor independent effects. Results Surprisingly, our extensive experimental survey revealed limited effects of ketamine or its metabolite on hippocampal function in control as well as depressive‐like animals. We found no effects on synaptic efficacy or induction of long‐term potentiation in adolescent and adult animals. Also there was no difference when comparing the dorsal and ventral hippocampus. Importantly, however, ketamine 24 hours prior to experimentation significantly increased the dentate gyrus proliferation, as revealed by Ki‐67 immunostaining, in the depressive‐like phenotype. Conclusion We find limited effects of ketamine on hippocampal glutamatergic transmission. Instead, alterations in dentate gyrus proliferation could explain the antidepressant effects of ketamine. - 'Acta Physiologica, EarlyView. '
    November 25, 2018   doi: 10.1111/apha.13211   open full text
  • Na+/Ca2+ Exchanger 1 is a Key Mechanosensitive Molecule of the Esophageal Myenteric Neurons.
    Hui Dong, Bo Tang, Yanfen Jiang, Ravinder K. Mittal.
    Acta Physiologica. November 22, 2018
    --- - |2+ Abstract Aim Our earlier studies showed that mechanical stretch activates inhibitory motor neurons of the esophagus; however, the underlying molecular mechanisms are unclear. Here, we sought to examine if Na+/Ca2+ exchanger 1 (NCX1) is responsible for the mechanosensitivity in the esophageal myenteric neurons (EMN) of rats and humans. Methods The function of NCX1 in primary culture of neurons was determined using calcium imaging, and mechanosensitivity was tested using osmotic stretch and direct mechanical stretch. Axial stretch‐induced relaxation of the lower esophageal sphincter (LES) was also studied in vivo in rats. Results The expression and co‐localization of NCX1 with nNOS were identified in the EMN from both rats and humans. The extracellular Ca2+ entry caused by ATP through purinergic signaling in the rat EMN was significantly inhibited by selective NCX blockers. Removal of extracellular Na+ to activate the Ca2+ entry mode of NCX1 induced an increase in the cytoplasmic calcium ([Ca2+]cyt), which was attenuated by NCX blockers. Osmotic stretch and mechanical stretch‐induced [Ca2+]cyt signaling in the rat and human EMN were attenuated by NCX blockers as well as specific NCX1 knockdown. Osmotic stretch and mechanical stretch also induced [Ca2+]cyt signaling in the Chinese hamster ovary (CHO) cells with NCX1 over‐expression, which was attenuated by NCX blockers. Finally, NCX blockade inhibited axial stretch‐activated LES relaxation in‐vivo experiments in the rats. Conclusions We demonstrate a novel NCX1/Ca2+ pathway in the mechanosensitive neurons of rat and human esophagus, which may provide a potential therapeutic target for the treatment of esophageal motility disorders. This article is protected by copyright. All rights reserved. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    November 22, 2018   doi: 10.1111/apha.13223   open full text
  • Role of melanocortin 4 receptor in hypertension induced by chronic intermittent hypoxia.
    Jussara M. do Carmo, Alexandre A. da Silva, Sydney P. Moak, Fernanda S. da Silva, Frank T. Spradley, John E. Hall.
    Acta Physiologica. November 22, 2018
    --- - |2+ Abstract Aim We previously demonstrated that central nervous system (CNS) melanocortin 4 receptors (MC4R) play a key role in regulating blood pressure (BP) in some conditions associated with increased SNS activity, including obesity. In this study we examined if activation of CNS MC4R contributes to chronic intermittent hypoxia (CIH)‐induced hypertension and ventilatory responses to hypercapnia. Methods Rats were instrumented with an intracerebroventricular (ICV) cannula in the lateral cerebral ventricle for continuous infusion of MC4R antagonist (SHU‐9119) and telemetry probes for measuring mean arterial pressure (MAP) and heart rate (HR). Untreated and SHU‐9119 treated rats as well as obese and lean MC4R deficient rats were exposed to CIH for 7 to 18 consecutive days. Results CIH reduced cumulative food intake by 18±5 g while MAP and HR increased by 10±3 mmHg and 9±5 bpm in untreated rats. SHU‐9119 increased food intake (from 15±1 to 46±3 g) and prevented CIH‐induced reduction in food intake. CIH‐induced hypertension was not attenuated by MC4R antagonism (average increase of 10±1 vs. 9±1 mmHg for untreated and SHU‐9119 treated rats). In obese MC4R deficient rats CIH for 7 days raised BP by 11±4 mmHg. However, when MC4R deficient rats were food restricted to prevent obesity, CIH‐induced hypertension was attenuated by 32%. We also found that MC4R deficiency was associated with impaired ventilatory responses to hypercapnia independently of obesity. Conclusion These results show that obesity and the CNS melanocortin system interact in complex ways to elevate BP during CIH and that MC4R may be important in the ventilatory responses to hypercapnia. This article is protected by copyright. All rights reserved. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    November 22, 2018   doi: 10.1111/apha.13222   open full text
  • Mitochondrial complex IV mutation increases reactive oxygen species production and reduces lifespan in aged mice.
    Gesine Reichart, Johannes Mayer, Cindy Zehm, Timo Kirschstein, Tursonjan Tokay, Falko Lange, Simone Baltrusch, Markus Tiedge, Georg Fuellen, Saleh Ibrahim, Rüdiger Köhling.
    Acta Physiologica. November 20, 2018
    --- - |2+ Abstract Aim Mitochondrial DNA (mtDNA) mutations can negatively influence lifespan and organ function. More than 250 pathogenic mtDNA mutations are known, often involving neurological symptoms. Major neurodegenerative diseases share key etiopathogenetic components ie mtDNA mutations, mitochondrial dysfunction and oxidative stress. Methods Here, we characterized a conplastic mouse strain (C57BL/6 J‐mtNOD) carrying an electron transport chain complex IV mutation that leads to an altered cytochrome c oxidase subunit III. Since this mouse also harbours adenine insertions in the mitochondrial tRNA for arginine, we chose the C57BL/6 J‐mtMRL as control strain which also carries a heteroplasmic stretch of adenine repetitions in this tRNA isoform. Results Using MitoSOX fluorescence, we observed an elevated mitochondrial superoxide production and a reduced gene expression of superoxide dismutase 2 in the 24‐month‐old mtNOD mouse as compared to control. Together with the decreased expression of the fission‐relevant gene Fis1, these data confirmed that the ageing mtNOD mouse had a mitochondrial dysfunctional phenotype. On the functional level, we could not detect significant differences in synaptic long‐term potentiation, but found a markedly poor physical constitution to perform the Morris water maze task at the age of 24 months. Moreover, the median lifespan of mtNOD mice was significantly shorter than of control animals. Conclusion Our findings demonstrate that a complex IV mutation leads to mitochondrial dysfunction that translates into survival. - 'Acta Physiologica, EarlyView. '
    November 20, 2018   doi: 10.1111/apha.13214   open full text
  • CCN family member 1 deregulates cholesterol metabolism and aggravates atherosclerosis.
    Jin‐Feng Zhao, Hsiang‐Ying Chen, Jeng Wei, Shr‐Jeng Jim Leu, Tzong‐Shyuan Lee.
    Acta Physiologica. November 19, 2018
    --- - |2+ Abstract Aim CCN family member 1 (CCN1) is an extracellular matrix cytokine and appears in atherosclerotic lesions. However, we have no evidence to support the role of CCN1 in regulating cholesterol metabolism and atherosclerosis. Methods Apolipoprotein E‐deficient (apoE−/−) mice were used as in vivo model. Oxidized low‐density lipoprotein (oxLDL)‐induced macrophage‐foam cells were used as in vitro model. RT‐PCR and western blot analysis were used for evaluating gene and protein expression, respectively. Conventional assay kits were used for assessing the levels of cholesterol, triglycerides, and cytokines. Results We show predominant expression of CCN1 in foamy macrophages in atherosclerotic aortas of apoE−/−mice. In apoE−/− mice, CCN1 treatment worsened hyperlipidaemia, systemic inflammation, and the progression of atherosclerosis. In addition, CCN1 decreased the capacity of reverse cholesterol transport and downregulated the protein expression of ATP‐binding cassette transporter A1 (ABCA1) and ABCG1 in atherosclerotic aortas. Notably, CCN1 decreased the protein expression of cholesterol clearance‐related proteins, including ABCG5, ABCG8, liver X receptor α (LXRα), cholesterol 7α‐hydrolase and LDL receptor in liver, and exacerbated hepatic lipid accumulation. In macrophages, treatment with oxLDL increased CCN1 expression. Inhibition of CCN1 activity by neutralizing antibody or small interfering RNA attenuated the oxLDL‐induced lipid accumulation. In contrast, cotreatment with CCN1 or overexpression of CCN1 augmented oxLDL‐induced lipid accumulation by impairing apolipoprotein AI‐ and high‐density lipoprotein‐dependent cholesterol efflux, which was attributed to downregulation of LXRα‐dependent expression of ABCA1 and ABCG1. Conclusion Our findings suggest that CCN1 plays a pivotal role in regulating cholesterol metabolism and the development of atherosclerosis. - 'Acta Physiologica, EarlyView. '
    November 19, 2018   doi: 10.1111/apha.13209   open full text
  • Fatty acid taste quality information via GPR120 in the anterior tongue of mice.
    Keiko Yasumatsu, Shusuke Iwata, Mayuko Inoue, Yuzo Ninomiya.
    Acta Physiologica. November 19, 2018
    --- - |2+ Abstract Aim To elucidate whether fatty acid taste has a quality that does not overlap with other primary qualities, we investigated potential neuron types coding fatty acid information and how GPR120 is involved. Methods Single fibre recordings in the chorda tympani (CT) nerve and behavioural response measurements using a conditioned taste aversion paradigm were performed in GPR120‐knockout (KO) and wild‐type (WT) mice. Results Single fibres can be classified into fatty acid (F)‐, S‐, M‐, electrolyte (E)‐, Q‐, and N‐type groups according to the maximal response among oleic acid, sucrose, monopotassium glutamate (MPG), HCl, quinine hydrochloride, and NaCl respectively. Among fibres, 4.0% in GPR120‐KO and 17.9% in WT mice showed a maximal response to oleic acid (F‐type). Furthermore, half or more of S‐ and M‐type fibres showed responses to fatty acids in both mouse strains, although the thresholds in KO mice were significantly higher and impulse frequencies lower than those in WT mice. GPR120‐KO mice conditioned to avoid linoleic acid showed generalized stimulus avoidances for MPG, indicating qualitative similarity between linoleic acid and MPG. The KO mice showed a higher generalization threshold for linoleic acid than that of WT mice. Conclusion Fatty acid taste is suggested to have a unique quality owing to the discovery of F‐type fibres, with GPR120 involved in neural information pathways for a unique quality and palatable taste qualities in the mouse CT nerve. GPR120 plays roles in distinguishing fatty acid taste from other primary tastes and the detection of low linoleic acid concentrations. - 'Acta Physiologica, EarlyView. '
    November 19, 2018   doi: 10.1111/apha.13215   open full text
  • Cachexia does not induce loss of myonuclei or muscle fibres during xenografted prostate cancer in mice.
    Ivan Myhre Winje, Xia Sheng, Kenth‐Arne Hansson, Andreas Solbrå, Simen Tennøe, Fahri Saatcioglu, Jo Christiansen Bruusgaard, Kristian Gundersen.
    Acta Physiologica. November 16, 2018
    --- - |2+ Abstract Aim Cachexia is a severe wasting disorder involving loss of body‐ and muscle mass reducing survival and quality of life in cancer patients. We aim at determining if cachexia is a mere perturbation of the protein balance or if the condition also involves a degenerative loss of myonuclei within the fibre syncytia or loss of whole muscle fibres. Methods We induced cachexia by xenografting PC3 prostate cancer cells in nu/nu mice. Six weeks later, we counted myonuclei by in vivo microscopic imaging of single live fibres in the extensor digitorum longus muscle (EDL), and the EDL, soleus and tibialis anterior muscles were also harvested for ex vivo histology. Results The mice lost on average 15% of the whole‐body wt. The muscle wet weight of the glycolytic, fast EDL was reduced by 14%, the tibialis anterior by 17%, and the slow, oxidative soleus by 6%. The fibre cross‐sectional area in the EDL was reduced by 21% with no loss of myonuclei or any significant reduction in the number of muscle fibres. TUNEL‐positive nuclei or fibres with embryonic myosin were rare both in cachectic and control muscles, and haematoxylin‐eosin staining revealed no clear signs of muscle pathology. Conclusion The data suggest that the cachexia induced by xenografted prostate tumours induces a pronounced atrophy not accompanied by a loss of myonuclei or a loss of muscle fibres. Thus, stem cell related treatment might be redundant, and the quest for treatment options should rather focus on intervening with intracellular pathways regulating muscle fibre size. - 'Acta Physiologica, EarlyView. '
    November 16, 2018   doi: 10.1111/apha.13204   open full text
  • Regression of left ventricular hypertrophy provides an additive physiological benefit following treatment of aortic stenosis: Insights from serial coronary wave intensity analysis.
    Christopher J. Broyd, Fausto Rigo, Sukhjinder Nijjer, Sayan Sen, Ricardo Petraco, Rasha Al‐Lamee, Nicolas Foin, Andrew Chukwuemeka, Jon Anderson, Jessica Parker, Iqbal S. Malik, Ghada W. Mikhail, Darrel P. Francis, Kim Parker, Alun D. Hughes, Jamil Mayet, Justin E. Davies.
    Acta Physiologica. November 15, 2018
    --- - |2+ Abstract Aim Severe aortic stenosis frequently involves the development of left ventricular hypertrophy (LVH) creating a dichotomous haemodynamic state within the coronary circulation. Whilst the increased force of ventricular contraction enhances its resultant relaxation and thus increases the distal diastolic coronary “suction” force, the presence of LVH has a potentially opposing effect on ventricular‐coronary interplay. The aim of this study was to use non‐invasive coronary wave intensity analysis (WIA) to separate and measure the sequential effects of outflow tract obstruction relief and then LVH regression following intervention for aortic stenosis. Methods Fifteen patients with unobstructed coronary arteries undergoing aortic valve intervention (11 surgical aortic valve replacement [SAVR], 4 TAVI) were successfully assessed before and after intervention, and at 6 and 12 months post‐procedure. Coronary WIA was constructed from simultaneously acquired coronary flow from transthoracic echo and pressure from an oscillometric brachial cuff system. Results Immediately following intervention, a decline in the backward decompression wave (BDW) was noted (9.7 ± 5.7 vs 5.1 ± 3.6 × 103 W/m2/s, P < 0.01). Over 12 months, LV mass index fell from 114 ± 19 to 82 ± 17 kg/m2. Accompanying this, the BDW fraction increased to 32.8 ± 7.2% at 6 months (P = 0.01 vs post‐procedure) and 34.7 ± 6.7% at 12 months (P < 0.001 vs post‐procedure). Conclusion In aortic stenosis, both the outflow tract gradient and the presence of LVH impact significantly on coronary haemodynamics that cannot be appreciated by examining resting coronary flow rates alone. An immediate change in coronary wave intensity occurs following intervention with further effects appreciable with hypertrophy regression. The improvement in prognosis with treatment is likely to be attributable to both features. - 'Acta Physiologica, Volume 224, Issue 4, December 2018. '
    November 15, 2018   doi: 10.1111/apha.13109   open full text
  • Obesity leads to impairments in the morphology and organization of human skeletal muscle lipid droplets and mitochondrial networks, which are resolved with gastric bypass surgery‐induced improvements in insulin sensitivity.
    M. D. Kristensen, S. M. Petersen, K. E. Møller, M. T. Lund, M. Hansen, C. N Hansen, J. Courraud, J. W. Helge, F. Dela, C. Prats.
    Acta Physiologica. November 15, 2018
    --- - |2+ Abstract Aims Skeletal muscle lipid stores and mitochondrial function have been appointed as key players in obesity‐induced insulin resistance. However, there are conflicting reports in the literature based on in vitro quantitative measurements. Here, we test the hypothesis that it is not the quantity but the quality that matters. Methods This study combines quantitative and qualitative structural measurements of lipid stores and mitochondrial dynamics in skeletal muscle from lean subjects, and subjects with morbid obesity, with and without type 2 diabetes, before and after gastric bypass surgery. Results The structural organization of muscle mitochondrial networks in type II muscle fibres from subjects with morbid obesity is impaired. In addition, the amount of skeletal muscle perilipin 2 protein per intramyocellular lipid is reduced in subjects with morbid obesity, resulting in qualitative alterations in perilipin 2 coat around some lipid droplets. Gastric bypass surgery‐induced weight loss and insulin resistance remission were associated with decreases in intramyocellular lipid stores and, qualitative improvements in lipid droplets’ morphology, perilipin 2 coat and mitochondrial dynamics. Conclusion Morbid obesity leads to severe qualitative alterations of both skeletal muscle lipid stores and mitochondrial networks. The degree of structural improvements after gastric bypass surgery was proportional to the improvements in whole body insulin sensitivity, suggesting an association between these events. - 'Acta Physiologica, Volume 224, Issue 4, December 2018. '
    November 15, 2018   doi: 10.1111/apha.13100   open full text
  • Muscle PGC‐1α in exercise and fasting‐induced regulation of hepatic UPR in mice.
    Caroline Maag Kristensen, Henrik Jessen, Stine Ringholm, Henriette Pilegaard.
    Acta Physiologica. November 15, 2018
    --- - |2+ Abstract Aim To provide a detailed time course of hepatic autophagy and all UPR branches in response to an acute bout of exercise and 24 hours of fasting and test the hypothesis that muscle‐specific PGC‐1α overexpression dampens the UPR and autophagy responses to these metabolic challenges. Methods Muscle‐specific PGC‐1α overexpression (TG) and wild‐type (WT) mice (a) performed a single bout of exercise, where the liver was obtained immediately after exercise, 2, 6 or 10 hours into recovery as well as from resting mice or (b) fasted for 24 hours or remained fed and the liver was obtained. Results In both genotypes, hepatic PERK and eIF2α phosphorylation increased immediately after exercise, with no change in IRE1α phosphorylation and cleaved ATF6 protein. Fasting decreased PERK, eIF2α and IRE1α phosphorylation as well as increased cleaved ATF6 protein in both genotypes. Hepatic p62 was unchanged, while LC3II/LC3I ratio increased immediately after exercise and LC3II protein increased in response to fasting in both genotypes. TG mice had lower eIF2α phosphorylation after exercise, a blunted fasting‐induced CHOP and HSP72 mRNA response and in fasted mice lower GADD34 and BiP mRNA as well as FAS protein in the liver than WT mice. Conclusion This study provides for the first time evidence for transient pathway‐specific activation of hepatic UPR and increase in markers of autophagy in the liver with acute exercise. On the other hand, fasting both increased and decreased UPR branches and seemed to increase autophagy. In addition, muscle PGC‐1α seemed to dampen some of these responses. - 'Acta Physiologica, Volume 224, Issue 4, December 2018. '
    November 15, 2018   doi: 10.1111/apha.13158   open full text
  • Coronary artery hypoxic vasorelaxation is augmented by perivascular adipose tissue through a mechanism involving hydrogen sulphide and cystathionine‐β‐synthase.
    J. Donovan, P. S. Wong, M. J. Garle, S. P. H. Alexander, W. R. Dunn, V. Ralevic.
    Acta Physiologica. November 15, 2018
    --- - |2+ Abstract Aim Hypoxia causes vasodilatation of coronary arteries which protects the heart from ischaemic damage through mechanisms including the generation of hydrogen sulphide (H2S), but the influence of the perivascular adipose tissue (PVAT) and myocardium is incompletely understood. This study aimed to determine whether PVAT and the myocardium modulate the coronary artery hypoxic response and whether this involves hydrogen sulphide. Methods Porcine left circumflex coronary arteries were prepared as cleaned segments and with PVAT intact, myocardium intact or both PVAT and myocardium intact, and contractility investigated using isometric tension recording. Immunoblotting was used to measure levels of H2S‐synthesizing enzymes: cystathionine‐β‐synthase (CBS), cystathionine γ‐lyase (CSE) and 3‐mercaptopyruvate sulphurtransferase (MPST). Results All three H2S‐synthesizing enzymes were detected in the artery and myocardium, but only CBS and MPST were detected in PVAT. Hypoxia elicited a biphasic response in cleaned artery segments consisting of transient contraction followed by prolonged relaxation. In arteries with PVAT intact, hypoxic contraction was attenuated and relaxation augmented. In arteries with myocardium intact, hypoxic contraction was attenuated, but relaxation was unaffected. In replacement experiments, replacement of dissected PVAT and myocardium attenuated artery contraction and augmented relaxation to hypoxia, mimicking the effect of in situ PVAT and indicating involvement of a diffusible factor(s). In arteries with intact PVAT, augmentation of hypoxic relaxation was reversed by amino‐oxyacetate (CBS inhibitor), but not DL‐propargylglycine (CSE inhibitor) or aspartate (inhibits MPST pathway). Conclusion PVAT augments hypoxic relaxation of coronary arteries through a mechanism involving H2S and CBS, pointing to an important role in regulation of coronary blood flow during hypoxia. - 'Acta Physiologica, Volume 224, Issue 4, December 2018. '
    November 15, 2018   doi: 10.1111/apha.13126   open full text
  • Platelet releasate promotes skeletal myogenesis by increasing muscle stem cell commitment to differentiation and accelerates muscle regeneration following acute injury.
    David Scully, Peggy Sfyri, Sandrine Verpoorten, Petros Papadopoulos, María Carmen Muñoz‐Turrillas, Robert Mitchell, Ahmed Aburima, Ketan Patel, Laura Gutiérrez, Khalid M. Naseem, Antonios Matsakas.
    Acta Physiologica. November 14, 2018
    --- - |2+ Abstract Aim The use of platelets as biomaterials has gained intense research interest. However, the mechanisms regarding platelet‐mediated skeletal myogenesis remain to be established. The aim of this study was to determine the role of platelet releasate in skeletal myogenesis and muscle stem cell fate in vitro and ex vivo respectively. Methods We analysed the effect of platelet releasate on proliferation and differentiation of C2C12 myoblasts by means of cell proliferation assays, immunohistochemistry, gene expression and cell bioenergetics. We expanded in vitro findings on single muscle fibres by determining the effect of platelet releasate on murine skeletal muscle stem cells using protein expression profiles for key myogenic regulatory factors. Results TRAP6 and collagen used for releasate preparation had a more pronounced effect on myoblast proliferation vs thrombin and sonicated platelets (P < 0.05). In addition, platelet concentration positively correlated with myoblast proliferation. Platelet releasate increased myoblast and muscle stem cell proliferation in a dose‐dependent manner, which was mitigated by VEGFR and PDGFR inhibition. Inhibition of VEGFR and PDGFR ablated MyoD expression on proliferating muscle stem cells, compromising their commitment to differentiation in muscle fibres (P < 0.001). Platelet releasate was detrimental to myoblast fusion and affected differentiation of myoblasts in a temporal manner. Most importantly, we show that platelet releasate promotes skeletal myogenesis through the PDGF/VEGF‐Cyclin D1‐MyoD‐Scrib‐Myogenin axis and accelerates skeletal muscle regeneration after acute injury. Conclusion This study provides novel mechanistic insights on the role of platelet releasate in skeletal myogenesis and set the physiological basis for exploiting platelets as biomaterials in regenerative medicine. - 'Acta Physiologica, EarlyView. '
    November 14, 2018   doi: 10.1111/apha.13207   open full text
  • Energy efficient physiologic coupling of gait and respiration is altered in chronic obstructive pulmonary disease.
    Jennifer M. Yentes, William Denton, Kaeli Samson, Kendra K. Schmid, Casey Wiens, Stephen I. Rennard.
    Acta Physiologica. November 10, 2018
    --- - |2+ Abstract Aims Coupling between walking and breathing in humans is well established. In healthy systems, the ability to couple and uncouple leads to energy economization. It is unknown if physiologic efficiency is susceptible to alteration particularly in individuals with airflow obstruction. The aim of this research to determine if coupling was compromised in a disease characterized by abnormal airflow and dyspnea, and if this was associated with reduced energy efficiency. Methods As a model of airflow obstruction, 17 chronic obstructive pulmonary disease (COPD) patients and 23 control subjects were included and walked on a treadmill for six‐minutes at three speeds (preferred speed and ±20% preferred speed) while energy expenditure, breathing, and walking were recorded. Rating of perceived exertion was recorded at the end of each walking trial. The most commonly used frequency ratio (i.e. strides:breath) and cross recurrence quantification analysis were used to quantify coupling. Linear regression models were used to determine associations. Results Less complex frequency ratios, simpler ratios, (i.e. 1:1 and 3:2) accompanied with stronger coupling were moderately associated with increased energy expenditure in COPD subjects. This was found for all three speeds. Conclusion The novel finding was that increased energy expenditure was associated with stronger and less complex coupling. Increased effort is needed when utilizing a frequency ratio of 1:1 or 3:2. The more stable the coupling, the more effort it takes to walk. In contrast to the complex energy efficient coupling of controls, those with airflow obstruction manifested simpler and stronger coupling associated with reduced energy efficiency. This article is protected by copyright. All rights reserved. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    November 10, 2018   doi: 10.1111/apha.13217   open full text
  • Molecular stressors underlying exercise training‐induced improvements in K+ regulation during exercise and Na+,K+‐ATPase adaptation in human skeletal muscle.
    Danny Christiansen.
    Acta Physiologica. November 04, 2018
    --- - |2 Abstract Despite substantial progress made towards a better understanding of the importance of skeletal muscle K+ regulation for human physical function and its association with several disease states (eg type‐II diabetes and hypertension), the molecular basis underpinning adaptations in K+ regulation to various stimuli, including exercise training, remains inadequately explored in humans. In this review, the molecular mechanisms essential for enhancing skeletal muscle K+ regulation and its key determinants, including Na+,K+‐ATPase function and expression, by exercise training are examined. Special attention is paid to the following molecular stressors and signaling proteins: oxygenation, redox balance, hypoxia, reactive oxygen species, antioxidant function, Na+,K+, and Ca2+ concentrations, anaerobic ATP turnover, AMPK, lactate, and mRNA expression. On this basis, an update on the effects of different types of exercise training on K+ regulation in humans is provided, focusing on recent discoveries about the muscle fibre‐type‐dependent regulation of Na+,K+‐ATPase‐isoform expression. Furthermore, with special emphasis on blood‐flow‐restricted exercise as an exemplary model to modulate the key molecular mechanisms identified, it is discussed how training interventions may be designed to maximize improvements in K+ regulation in humans. The novel insights gained from this review may help us to better understand how exercise training and other strategies, such as pharmacological interventions, may be best designed to enhance K+ regulation and thus the physical function in humans. - 'Acta Physiologica, EarlyView. '
    November 04, 2018   doi: 10.1111/apha.13196   open full text
  • Epac1−/− mice have elevated baseline permeability and do not respond to histamine as measured with dynamic contrast‐enhanced magnetic resonance imaging with contrast agents of different molecular weights.
    Fitz‐Roy E. Curry, Torfinn Taxt, Cecilie Brekke Rygh, Tina Pavlin, Ronja Bjønrstad, Stein Ove Døskeland, Rolf K. Reed.
    Acta Physiologica. November 02, 2018
    --- - |2+ Abstract Aim Epac1−/− mice, but not Epac2−/− mice have elevated baseline permeability to albumin. This study extends the investigations of how Epac‐dependent pathways modulate transvascular exchange in response to the classical inflammatory agent histamine. It also evaluates the limitations of models of blood‐to‐tissue exchange in transgenic mice in DCE‐MRI measurements. Methods We measured DCE‐MRI signal intensity in masseter muscle of wt and Epac1−/− mice with established approaches from capillary physiology to determine how changes in blood flow and vascular permeability contribute to overall changes of microvascular flux. We used two tracers, the high molecular weight tracer (Gadomer‐17, MW 17 kDa, apparent MW 30‐35 kDa) is expected to be primarily limited by diffusion and therefore less dependent on changes in blood flow and the low molecular weight tracer (Dotarem (MW 0.56 kDa) whose transvascular exchange is determined by both blood flow and permeability. Paired experiments in each animal combined with analytical methods provided an internally consistent description of microvascular transport. Results Epac1−/− mice had elevated baseline permeability relative to wt control mice for Dotarem and Gadomer‐17. In contrast to wt mice, Epac1−/− mice failed to increase transvascular permeability in response to histamine. Dotarem underestimated blood flow and vascular volume and Gadomer‐17 has limited sensitivity in extravascular accumulation. Conclusion The study suggests that the normal barrier loosening effect of histamine in venular microvessels do not function when the normal barrier tightening effect of Epac1 is already compromised. The study also demonstrated that the numerical analysis of DCE‐MRI data with tracers of different molecular weight has significant limitations. - 'Acta Physiologica, EarlyView. '
    November 02, 2018   doi: 10.1111/apha.13199   open full text
  • Genetic deletion of ADP‐activated P2Y12 receptor ameliorates lithium‐induced nephrogenic diabetes insipidus in mice.
    Yue Zhang, Kenny M. Hansson, Tao Liu, Kerstin Magnell, Yufeng Huang, Noel G. Carlson, Bellamkonda K. Kishore.
    Acta Physiologica. October 31, 2018
    --- - |2+ Abstract Aim Therapeutic use of lithium in bipolar disorder is limited by the development of nephrogenic diabetes insipidus (NDI). We reported that pharmacological blockade of P2Y12 receptor (R) with clopidogrel or prasugrel significantly ameliorated lithium‐induced NDI in rodents. Using mice genetically lacking P2Y12‐R we evaluated whether the observed amelioration is mediated through P2Y12‐R Methods P2ry12−/− mouse line (C57/BL6) was rederived from cryopreserved embryos of the knockout (KO) mice generated by Deltagen Inc. Syngeneic wild type (WT) mice obtained by heterozygous crossing were inbred. Groups of adult WT and KO mice were fed lithium‐added (40 mmol LiCl/kg food) or regular diet, and euthanized after 2 or 4 weeks. Twenty‐four hour urine samples and terminal blood and kidney samples were analyzed. Results At both time points, lithium‐induced polyuria and decrease in aquaporin‐2 (AQP2) protein abundance in the kidney medulla were less marked in KO vs WT mice. Immunofluorescence microscopy revealed that lithium‐induced alterations in the cellular disposition of AQP2 protein in the medullary collecting ducts of WT mice were blunted in KO mice. Serum lithium, sodium and osmolality were similar in both genotypes after lithium treatment. After 2 weeks, lithium induced marked increases in urinary excretion of Na, K, and arginine vasopressin in WT mice but not in KO mice. Conclusion Taken together, our data show that similar to pharmacological blockade, deletion of P2Y12‐R significantly ameliorates lithium‐induced NDI, without reducing serum lithium levels. Hence, targeting P2Y12‐R with currently available drugs in the market offers a novel and safer method for treating NDI. - 'Acta Physiologica, EarlyView. '
    October 31, 2018   doi: 10.1111/apha.13191   open full text
  • A reduction in compliance or activation level reduces residual force depression in human tibialis anterior.
    Brent J. Raiteri, Daniel Hahn.
    Acta Physiologica. October 29, 2018
    --- - |2+ Abstract Aim We investigated if residual force depression (rFD) is present during voluntary fixed‐end contractions of human tibialis anterior (TA) and whether reducing TA's activation level after active shortening could reduce rFD. Methods Ten participants performed fixed‐end dorsiflexion contractions to a low, moderate or high level while electromyography (EMG), dorsiflexion force and TA ultrasound images were recorded. Contractions were force‐ or EMG‐matched and after the low or high contraction level was attained, participants respectively increased or decreased their force/EMG to a moderate level. Participants also performed moderate level contractions while the TA muscle‐tendon unit (MTU) was lengthened during the force/EMG rise to the reference MTU length. Results Equivalent fascicle shortening over moderate and low to moderate level contractions did not alter EMG (P = 0.45) or dorsiflexion force (P = 0.47) at the moderate level. Greater initial fascicle shortening magnitudes (1.7 mm; P ≤ 0.01) to the high contraction level did not alter EMG (P = 0.45) or dorsiflexion force (P = 0.30) at the subsequent moderate level compared with moderate level contractions. TA MTU lengthening during the initial force/EMG rise reduced TA fascicle shortening (−2.5 mm; P ≤ 0.01), which reduced EMG (−3.9% MVC; P < 0.01) and increased dorsiflexion force (3.7% MVC; P < 0.01) at the moderate level compared with fixed‐end moderate level contractions. Conclusion rFD is present during fixed‐end dorsiflexion contractions because fascicles actively shorten as force/EMG increases and rFD can be reduced by reducing the effective MTU compliance. A reduction in muscle activation level also reduces rFD by potentially triggering residual force enhancement‐related mechanisms as force drops and some fascicles actively lengthen. - 'Acta Physiologica, EarlyView. '
    October 29, 2018   doi: 10.1111/apha.13198   open full text
  • Phosphorylation of cardiac voltage‐gated sodium channel: potential players with multiple dimensions.
    Shahid Muhammad Iqbal, Rosa Lemmens‐Gruber.
    Acta Physiologica. October 26, 2018
    --- - |2 Abstract Cardiomyocytes are highly coordinated cells with multiple proteins organized in micro domains. Minor changes or interference in subcellular proteins can cause major disturbances in physiology. The cardiac sodium channel (NaV1.5) is an important determinant of correct electrical activity in cardiomyocytes which are localized at intercalated discs, T‐tubules and lateral membranes in the form of a macromolecular complex with multiple interacting protein partners. The channel is tightly regulated by post‐translational modifications for smooth conduction and propagation of action potentials. Among regulatory mechanisms, phosphorylation is an enzymatic and reversible process which modulates NaV1.5 channel function by attaching phosphate groups to serine, threonine or tyrosine residues. Phosphorylation of NaV1.5 is implicated in both normal physiological and pathological processes and is carried out by multiple kinases. In this review we discuss and summarize recent literature about the 1) structure of NaV1.5 channel, 2) formation and subcellular localization of NaV1.5 channel macromolecular complex, 3) post‐translational phosphorylation and regulation of NaV1.5 channel and 4) how these phosphorylation events of NaV1.5 channel alter the biophysical properties and affect the channel during disease status. We expect, by reviewing these aspects will greatly improve our understanding of NaV1.5 channel biology, physiology and pathology, which will also provide an insight into the mechanism of arrythmogenesis at molecular level. This article is protected by copyright. All rights reserved. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    October 26, 2018   doi: 10.1111/apha.13210   open full text
  • Neurons in the rat ventral lateral preoptic area are essential for the warm‐evoked inhibition of brown adipose tissue and shivering thermogenesis.
    Ellen P. S. Conceição, Christopher J. Madden, Shaun F. Morrison.
    Acta Physiologica. October 26, 2018
    --- - |2+ Abstract Aim To determine the role of neurons in the ventral part of the lateral preoptic area (vLPO) in CNS thermoregulation. Methods In vivo electrophysiological and neuropharmacological were used to evaluate the contribution of neurons in the vLPO to the regulation of brown adipose tissue (BAT) thermogenesis and muscle shivering in urethane/chloralose‐anesthetized rats. Results Nanoinjections of NMDA targeting the medial preoptic area (MPA), and the vLPO suppressed the cold‐evoked BAT sympathetic activity (SNA), and reduced BAT temperature (TBAT), expired CO2, mean arterial pressure (MAP), and heart rate. Inhibition of vLPO neurons with muscimol or AP5/CNQX elicited increases in BAT SNA, TBAT, tachycardia, and small elevations in MAP. The BAT thermogenesis evoked by AP5/CNQX in vLPO was inhibited by activation of MPA neurons. The inhibition of BAT SNA by vLPO neurons does not require a GABAergic input to dorsomedial hypothalamus (DMH), but MPA provides a GABAergic input to DMH. Activation of vLPO neurons inhibits the BAT thermogenesis evoked by NMDA in the rostral raphe pallidus (rRPa), but not that after bicuculline in rRPa. The BAT thermogenesis elicited by vLPO inhibition is dependent on glutamatergic inputs to DMH and rRPa, but these excitatory inputs do not arise from MnPO neurons. Activation of neurons in the vLPO also inhibits cold‐ and prostaglandin‐evoked muscle shivering, and vLPO inhibition is sufficient to evoke shivering. Conclusion The vLPO contains neurons that are required for the warm ambient‐evoked inhibition of muscle shivering and of BAT thermogenesis, mediated through a direct or indirect GABAergic input to rRPa from vLPO. This article is protected by copyright. All rights reserved. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    October 26, 2018   doi: 10.1111/apha.13213   open full text
  • cOAlition S troubles top journals.
    Pontus B. Persson.
    Acta Physiologica. October 22, 2018
    --- - - Acta Physiologica, EarlyView.
    October 22, 2018   doi: 10.1111/apha.13197   open full text
  • The emerging role of stimulator of interferons genes signaling in sepsis: Inflammation, autophagy, and cell death.
    Qiongyuan Hu, Patrick H. Knight, Yanhan Ren, Huajian Ren, Jiashuo Zheng, Xiuwen Wu, Jianan Ren, Robert G. Sawyer.
    Acta Physiologica. October 22, 2018
    --- - |2 Abstract Stimulator of interferons genes (STING) is an adaptor protein that plays a critical role in the secretion of type I interferons and pro‐inflammatory cytokines in response to cytosolic nucleic acid. Recent research indicates the involvement of the STING pathway in uncontrolled inflammation, sepsis, and shock. STING signaling is significantly up‐regulated in human sepsis, and STING agonists are suggested to contribute to the pathogenesis of sepsis and shock. Nevertheless, little is known about the consequences of activated STING‐mediated signaling during sepsis. It has been shown that aberrant activation of the STING‐dependent way can result in increased inflammation, type I interferons responses, and cell death (including apoptosis, necroptosis, and pyroptosis). In addition, autophagy modulation has been demonstrated to protect against multiple organs injuries in animal sepsis model. However, impaired autophagy may contribute to the aberrant activation of STING signaling, leading to uncontrolled inflammation and cell death. Here we present a comprehensive review of recent advances in the understanding of STING signaling, focusing on the regulatory mechanisms and the roles of this pathway in sepsis. - Acta Physiologica, EarlyView.
    October 22, 2018   doi: 10.1111/apha.13194   open full text
  • New insights into the astonishing diversity of hormone functions.
    Anika Westphal, Ralf Mrowka.
    Acta Physiologica. October 22, 2018
    --- - - Acta Physiologica, EarlyView.
    October 22, 2018   doi: 10.1111/apha.13188   open full text
  • The sympathetic nervous system regulates skeletal muscle motor innervation and acetylcholine receptor stability.
    Anna C. Z. Rodrigues, Maria L. Messi, Zhong‐Min Wang, Martin C. Abba, Andrea Pereyra, Alexander Birbrair, Tan Zhang, Meaghan O’Meara, Ping Kwan, Elsa I. S. Lopez, Monte S. Willis, Akiva Mintz, D. Clark Files, Cristina Furdui, Ronald W. Oppenheim, Osvaldo Delbono.
    Acta Physiologica. October 22, 2018
    --- - |2+ Abstract Aim Symptoms of autonomic failure are frequently the presentation of advanced age and neurodegenerative diseases that impair adaptation to common physiologic stressors. The aim of this work was to examine the interaction between the sympathetic and motor nervous system, the involvement of the sympathetic nervous system (SNS) in neuromuscular junction (NMJ) presynaptic motor function, the stability of postsynaptic molecular organization, and the skeletal muscle composition and function. Methods Since muscle weakness is a symptom of diseases characterized by autonomic dysfunction, we studied the impact of regional sympathetic ablation on muscle motor innervation by using transcriptome analysis, retrograde tracing of the sympathetic outflow to the skeletal muscle, confocal and electron microscopy, NMJ transmission by electrophysiological methods, protein analysis, and state of the art microsurgical techniques, in C57BL6, MuRF1KO and Thy‐1 mice. Results We found that the SNS regulates motor nerve synaptic vesicle release, skeletal muscle transcriptome, muscle force generated by motor nerve activity, axonal neurofilament phosphorylation, myelin thickness, and myofibre subtype composition and CSA. The SNS also modulates the levels of postsynaptic membrane acetylcholine receptor by regulating the Gαi2‐Hdac4‐Myogenin‐MuRF1pathway, which is prevented by the overexpression of the guanine nucleotide‐binding protein Gαi2 (Q205L), a constitutively active mutant G protein subunit. Conclusion The SNS regulates NMJ transmission, maintains optimal Gαi2 expression, and prevents any increase in Hdac4, myogenin, MuRF1, and miR‐206. SNS ablation leads to upregulation of MuRF1, muscle atrophy, and downregulation of postsynaptic AChR. Our findings are relevant to clinical conditions characterized by progressive decline of sympathetic innervation, such as neurodegenerative diseases and aging. - 'Acta Physiologica, EarlyView. '
    October 22, 2018   doi: 10.1111/apha.13195   open full text
  • The circadian clock regulates the diurnal levels of microbial short‐chain fatty acids and their rhythmic effects on colon contractility in mice.
    Anneleen Segers, Louis Desmet, Theo Thijs, Kristin Verbeke, Jan Tack, Inge Depoortere.
    Acta Physiologica. October 22, 2018
    --- - |2+ Abstract Aim The microbiota shows diurnal oscillations that are synchronized by the host's circadian clock and feeding rhythms. Short‐chain fatty acids (SCFAs) produced by the microbiota are possible synchronizers of peripheral circadian clocks. We aimed to investigate whether faecal SCFAs show a diurnal rhythm that regulates the rhythm of SCFA receptor expression (FFAR2/3, OLFR78, HCAR2) and SCFA‐induced colonic contractility. The role of the circadian clock was studied in mice lacking the core clock gene Bmal1. Methods Mice were sacrificed at 4‐hour intervals. Faecal SCFA concentrations and SCFA receptor expression were determined. The effect of increasing concentrations of a SCFA mix on electrical field‐induced neural responses in colon strips was measured isometrically. Results Diurnal fluctuations in faecal SCFA concentrations (peak 4 hours after lights on) were observed that were in phase with the rhythm of Ffar2/3 expression in the colonic muscle layer. Olfr78 expression was not diurnal and Hcar2 was not detectable. The inhibitory effect of a SCFA mix on neural contractions in colonic smooth muscle strips showed a diurnal rhythm and oscillated in phase with faecal SCFA concentrations and Ffar2/3 expression. In contrast, neither excitatory neural responses nor acetylcholine‐induced smooth muscle contractions showed a diurnal rhythm. In Bmal1−/− mice, no fluctuations in faecal SCFA levels, Ffar3 expression and neural responses to SCFAs were observed. Conclusion Diurnal microbial SCFA levels regulate the rhythm of Ffar3 expression in the colonic myenteric plexus, which causes rhythmicity in SCFA‐induced colonic motility. Deletion of Bmal1 abolishes rhythmicity of SCFA levels and their downstream effects. - 'Acta Physiologica, EarlyView. '
    October 22, 2018   doi: 10.1111/apha.13193   open full text
  • Normalization of force to muscle cross‐sectional area: A helpful attempt to reduce data scattering in contractility studies?
    Simon Pecha, Jussi Koivumäki, Bastiaan Geelhoed, Romy Kempe, Emanuel Berk, Andreas Engel, Hermann Reichenspurner, Thomas Eschenhagen, Ursula Ravens, Alberto Kaumann, Torsten Christ.
    Acta Physiologica. October 19, 2018
    --- - |2 Abstract There have been several attempts to reduce data scattering in contractility studies. When using superfused muscle preparations for contractility experiments, there is always the question how to compensate for variabilities in muscle thickness. A simple but rather imperfect approach is the normalization of force to cross‐sectional area. However, this attempt does not consider the possibility of hypoxic cores in thick muscles, which probably do not really contribute to force development. Han et al. recently published a new computer model to investigate the relevance of oxygen distribution for force generation when intact muscles are superfused, as frequently used in physiological experiments. This article is protected by copyright. All rights reserved. - Acta Physiologica, Volume 0, Issue ja, -Not available-.
    October 19, 2018   doi: 10.1111/apha.13202   open full text
  • Editorial: Critical Illness Myopathy: Glucocorticoids revisited?
    Werner J. Z'Graggen, Joerg C. Schefold.
    Acta Physiologica. October 19, 2018
    --- - |2 Abstract Over the past decades, survival rates of critical illness have constantly increased. As a consequence, the incidences of important complications of intensive care unit (ICU) treatment become more and more prevalent. Critical illness myopathy (CIM) belongs to one of the most frequent neuromuscular complications and its presence is associated with prolonged need for mechanical ventilation and ICU stay, increased morbidity and mortality 1,2. High‐dose glucocorticoid (GC) treatment was early after the initial description of CIM postulated to be a major triggering factor for the development of the disease. In the current issue of Acta Physiologica, Akkad et al. investigate the effects of two GC drugs (prednisolone and a new dissociative GC termed vamorolone) on CIM development3. This article is protected by copyright. All rights reserved. - Acta Physiologica, Volume 0, Issue ja, -Not available-.
    October 19, 2018   doi: 10.1111/apha.13205   open full text
  • Did you know How the cardiovascular system achieves its high efficiency as a compound irrigation device and why this is relevant to future cardiovascular studies.
    Yuh‐Ying Lin Wang, Wei‐Kung Wang.
    Acta Physiologica. October 19, 2018
    --- - |2 Abstract Historically, some important concepts that help explain the power saving character of the circulatory system have been raised. About 2000 years ago, Greek physician Galen surmised that the arterial pulse propagates directly through the tunics of the arteries. Otto Frank first proposed arterial resonance in 1899. In the introduction of the second edition of McDonald's book1, it was stated: “The main developments since 1950 have been in terms of treating the whole arterial system as being in a steady‐state oscillation produced by the regularly repeated beat of the heart.” However, these three important findings are neglected in the prevailing hemodynamic models. This article is protected by copyright. All rights reserved. - Acta Physiologica, Volume 0, Issue ja, -Not available-.
    October 19, 2018   doi: 10.1111/apha.13206   open full text
  • High‐intensity exercise training ameliorates aberrant expression of markers of mitochondrial turnover but not oxidative damage in skeletal muscle of men with essential hypertension.
    Matteo Fiorenza, Thomas P. Gunnarsson, Thomas S. Ehlers, Jens Bangsbo.
    Acta Physiologica. October 19, 2018
    --- - |2+ Abstract Aim To examine whether hypertensive individuals exhibit altered muscle mitochondrial turnover and redox homeostasis compared with healthy normotensive counterparts, and whether the antihypertensive effect of high‐intensity exercise training is associated with improved mitochondrial quality and enhanced anti‐oxidant defence. Methods In a cross‐sectional and longitudinal parallel design, 24 essential hypertensive (HYP) and 13 healthy normotensive (NORM) men completed six weeks of high‐intensity interval training (HIIT). 24‐h ambulatory blood pressure, body composition, cardiorespiratory fitness, exercise capacity and skeletal muscle characteristics were examined before and after HIIT. Protein levels of markers of mitochondrial turnover, anti‐oxidant protection and oxidative damage were determined in vastus lateralis muscle biopsies. Muscle protein levels of eNOS and VEGF, and muscle capillarity were also evaluated. Results At baseline, HYP exhibited lower expression of markers of mitochondrial volume/biogenesis, mitochondrial fusion/fission and autophagy along with depressed eNOS expression compared with NORM. Content of markers of anti‐oxidant protection was similar in HYP and NORM, whereas oxidative damage was higher in HYP than NORM. In HYP, HIIT lowered blood pressure, improved body composition, cardiorespiratory fitness and exercise capacity, up‐regulated markers of mitochondrial volume/biogenesis and autophagy and increased eNOS and VEGF expression. Furthermore, in HYP, HIIT induced divergent responses in markers of mitochondrial fusion and anti‐oxidant protection, did not affect markers of mitochondrial fission, and increased apoptotic susceptibility and oxidative damage. Conclusion The present results indicate aberrant muscle mitochondrial turnover and augmented oxidative damage in hypertensive individuals. High‐intensity exercise training can partly reverse hypertension‐related impairments in muscle mitochondrial turnover, but not redox imbalance. This article is protected by copyright. All rights reserved. - 'Acta Physiologica, Volume 0, Issue ja, -Not available-. '
    October 19, 2018   doi: 10.1111/apha.13208   open full text
  • ω‐6 and ω‐9 polyunsaturated fatty acids with double bonds near the carboxyl head have the highest affinity and largest effects on the cardiac IKs potassium channel.
    Briana M. Bohannon, Marta E. Perez, Sara I. Liin, Hans Peter Larsson.
    Acta Physiologica. October 17, 2018
    --- - |2+ Abstract Aim The IKs channel is important for termination of the cardiac action potential. Hundreds of loss‐of‐function mutations in the IKs channel reduce the K+ current and, thereby, delay the repolarization of the action potential, causing Long QT Syndrome. Long QT predisposes individuals to Torsades de Pointes which can lead to ventricular fibrillation and sudden death. Polyunsaturated fatty acids (PUFAs) are potential therapeutics for Long QT Syndrome, as they affect IKs channels. However, it is unclear which properties of PUFAs are essential for their effects on IKs channels. Methods To understand how PUFAs influence IKs channel activity, we measured effects on IKs current by two‐electrode voltage clamp while changing different properties of the hydrocarbon tail. Results There was no, or weak, correlation between the tail length or number of double bonds in the tail and the effects on or apparent binding affinity for IKs channels. However, we found a strong correlation between the positions of the double bonds relative to the head group and effects on IKs channels. Conclusion Polyunsaturated fatty acids with double bonds closer to the head group had higher apparent affinity for IKs channels and increased IKs current more; shifting the bonds further away from the head group reduced apparent binding affinity for and effects on the IKs current. Interestingly, we found that ω‐6 and ω‐9 PUFAs, with the first double bond closer to the head group, left‐shifted the voltage dependence of activation the most. These results allow for informed design of new therapeutics targeting IKs channels in Long QT Syndrome. - 'Acta Physiologica, EarlyView. '
    October 17, 2018   doi: 10.1111/apha.13186   open full text
  • Klotho protein supplementation reduces blood pressure and renal hypertrophy in db/db mice, a model of type 2 diabetes.
    Tsuneo Takenaka, Hiroyuki Kobori, Takashi Miyazaki, Hiromichi Suzuki, Akira Nishiyama, Naohito Ishii, Maho Yamashita, Matsuhiko Hayashi.
    Acta Physiologica. October 16, 2018
    --- - |2+ Abstract Aims Klotho interacts with various membrane proteins, such as receptors for transforming growth factor (TGF)‐β and insulin‐like growth factor (IGF), to alter their function. Renal expression of klotho is diminished in diabetes. The present study examined whether exogenous klotho protein supplementation ameliorates kidney injury and renin–angiotensin system (RAS) in db/db mice. Methods We investigated the effects of klotho supplementation on diabetic kidney injury and RAS. Recombinant human klotho protein (10 μg/kg/d) was administered to db/db mice daily. Results Klotho protein supplementation reduced kidney weight, systolic blood pressure (SBP), albuminuria, glomerular filtration rate, and 8‐epi‐prostaglandin F2α excretion without affecting body weight. Although klotho supplementation did not alter glycated albumin, it reduced renal angiotensin II levels associated with reduced renal expression of angiotensinogen. Klotho supplementation improved renal expression of superoxide dismutase (SOD), and endogenous renal expression of klotho. Klotho supplementation reduced the levels of hypoxia‐inducible factor, phosphorylated Akt, and phosphorylated mTOR and decreased the renal expression of TGF‐β, tumour necrosis factor (TNF), and fibronectin. Conclusions These data indicate that klotho supplementation reduces blood pressure and albuminuria along with ameliorating renal RAS activation in db/db mice. Furthermore, these results suggest that klotho inhibits IGF signalling, induces SOD expression to reduce oxidative stress, and suppresses Akt‐mTOR signalling to inhibit abnormal kidney growth. Collectively, the results suggest that klotho inhibits TGF‐β and TNF signalling, resulting in a decline in renal fibrosis. - 'Acta Physiologica, EarlyView. '
    October 16, 2018   doi: 10.1111/apha.13190   open full text
  • Issue Information.

    Acta Physiologica. October 12, 2018
    --- - - Acta Physiologica, Volume 224, Issue 3, November 2018.
    October 12, 2018   doi: 10.1111/apha.12960   open full text
  • The acute blood pressure‐lowering effect of amiloride is independent of endothelial ENaC and eNOS in humans and mice.
    Rikke Ydegaard, Henrik Andersen, Christina S. Oxlund, Ib A. Jacobsen, Pernille B. L. Hansen, Jonathan F. Jürgensen, Antonio Augusto Peluso, Paul M. Vanhoutte, Mette Stæhr, Per Svenningsen, Boye L. Jensen.
    Acta Physiologica. October 11, 2018
    --- - |2+ Abstract Aims The epithelial sodium channel (ENaC) is expressed in cultured endothelial cells and inhibitory coupling to eNOS activity has been proposed. The present study tested the hypothesis that ENaC blockers increase systemic NO‐products and lower blood pressure in patients and mice, depending on eNOS. Methods NO‐products and cGMP were measured in diabetes patient urine and plasma samples before and after amiloride treatment (20‐40 mg for two days, plasma n = 22, urine n = 12 and 5‐10 mg for eight weeks, plasma n = 52, urine n = 55). Indwelling catheters were implanted in the femoral artery and vein in mice for continuous arterial blood pressure and heart rate recordings and infusion. Results Treatment with amiloride for two days increased plasma and urine NO‐products, while plasma cGMP decreased and urinary cGMP was unchanged in patient samples. Eight weeks of treatment with amiloride did not alter NO‐products and cGMP. In mice, amiloride boli of 5, 50, and 500 µg/kg lowered heart rate and arterial blood pressure significantly and acutely. Benzamil had no effect on pressure and raised heart rate. In hypertensive eNOS−/− and L‐NAME‐treated mice, amiloride lowered blood pressure significantly. L‐NAME infusion significantly decreased NO‐products in plasma; amiloride and eNOS‐deletion had no effect. An acetylcholine bolus resulted in acute blood pressure drop that was attenuated in eNOS−/− and L‐NAME mice. ENaC subunit expressions were not detected consistently in human and mouse arteries and endothelial cells. Conclusion Amiloride has an acute hypotensive action not dependent on ENaC and eNOS and likely related to the heart. - 'Acta Physiologica, EarlyView. '
    October 11, 2018   doi: 10.1111/apha.13189   open full text
  • Epigenetic Soluble Epoxide Hydrolase Regulation Causes Endothelial Dysfunction.
    John D. Imig.
    Acta Physiologica. October 11, 2018
    --- - |2 Abstract A novel epigenetic regulator, Jarid1b (KDM5B), that contributes to increasing vascular soluble epoxide hydrolase (sEH) protein expression and impairing endothelial function was identified by Vasconez et al. in this edition of Acta Physiologica. Elevated angiotensin II levels contribute to several cardiovascular diseases and endothelial dysfunction in hypertension. Endothelial dysfunction in angiotensin II dependent hypertension is partly due to increased sEH activity. This article is protected by copyright. All rights reserved. - Acta Physiologica, Volume 0, Issue ja, -Not available-.
    October 11, 2018   doi: 10.1111/apha.13203   open full text
  • Dorsal hypothalamic dopaminergic neurons play an inhibitory role in the hypothalamic‐pituitary‐adrenal axis via activation of D2R in mice.
    Tingting Di, Peipei Chen, Zihao Yuan, Ya Wang, Sha Sha, Ling Chen.
    Acta Physiologica. September 27, 2018
    --- - |2+ Abstract Aim The present study investigated the effects of dorsal hypothalamic dopamine (dh‐DA) neurons on activation of hypothalamic‐pituitary‐adrenal (HPA) axis in adult male mice. Methods Tyrosine hydroxylase‐labelled DA neurons, DA content, c‐Fos immune‐positive (c‐Fos+) cells and CRH expression in paraventricular nuclei (PVN), serum CORT and ACTH were examined at 4‐, 8‐, and 12‐hour after a signal injection of MPTP (20 mg kg−1) respectively. Results The dh‐DA neurons and DA content in PVN at 4‐hour post‐MPTP were reduced with recovery at 12‐hour post‐MPTP, while decline of nigrostriatal DA neurons and DA content in striatum started from 12‐hour post‐MPTP. Number of c‐Fos+ cells, and CORT/ACTH levels increased at 4‐hour post‐MPTP, followed by recovery at 12‐hour post‐MPTP. The CRH mRNA was elevated at 4‐hour post‐MPTP, and sustained for over 12 hours. At 2‐hour post‐MPTP, PVN‐injection of D2R agonist quinpirole corrected the increases in c‐Fos+ cells, CORT/ACTH and CRH mRNA, but D1R agonist SKF38393 did not. PVN‐injection of D2R antagonist L‐sulpiride alone caused increases in c‐Fos+ cells, CORT/ACTH and CRH mRNA. Similarly, PVN‐injection of CB1R agonist WIN552,12 prevented the increases in c‐Fos+ cells and CORT/ACTH rather than CRH mRNA, which were blocked by CB1R antagonist AM251. Levels of PKA and CREB phosphorylation in PVN were increased at 4‐hour post‐MPTP, which were blocked by quinpirole, but not WIN552,12. PKA inhibitor H89 corrected the increase of CRH mRNA at 8‐hour post‐MPTP. Conclusion The activation of dh‐DA neurons regulates negatively HPA axis through targeting D2Rs of CRH neurons to enhance endocannabinoid release and inhibit PKA‐CREB pathway. - 'Acta Physiologica, EarlyView. '
    September 27, 2018   doi: 10.1111/apha.13187   open full text
  • Issue Information.

    Acta Physiologica. September 27, 2018
    --- - - Acta Physiologica, Volume 224, Issue 2, October 2018.
    September 27, 2018   doi: 10.1111/apha.12959   open full text
  • Modifiers of hypertension.
    Ralf Mrowka.
    Acta Physiologica. September 25, 2018
    --- - - Acta Physiologica, Volume 224, Issue 3, November 2018.
    September 25, 2018   doi: 10.1111/apha.13184   open full text
  • Exercise training ameliorates bleomycin‐induced epithelial mesenchymal transition and lung fibrosis through restoration of H2S synthesis.
    Shu‐Fang Du, Xiu‐Li Wang, Chang‐Lin Ye, Ze‐Jia He, Dong‐Xia Li, Bai‐Ren Du, Yu‐Jian Liu, Xiao‐Yan Zhu.
    Acta Physiologica. September 21, 2018
    --- - |2+ Abstract Aims Clinical trials have shown the beneficial effects of exercise training against pulmonary fibrosis. This study aimed to investigate whether prophylactic intervention with exercise training attenuates lung fibrosis via modulating endogenous hydrogen sulphde (H2S) generation. Methods First, ICR mice were allocated to Control, Bleomycin, Exercise, and Bleomycin + Exercise groups. Treadmill exercise began on day 1 and continued for 4 weeks. A single intratracheal dose of bleomycin (3 mg/kg) was administered on day 15. Second, ICR mice were allocated to Control, Bleomycin, H2S, and Bleomycin + H2S groups. H2S donor NaHS (28 μmol/kg) was intraperitoneally injected once daily for 2 weeks. Results Bleomycin‐treated mice exhibited increased levels of collagen deposition, hydroxyproline, collagen I, transforming growth factor (TGF)‐β1, Smad2/Smad3/low‐density lipoprotein receptor‐related proteins (LRP‐6)/glycogen synthase kinase‐3β (GSK‐3β) phosphorylation, and Smad4/β‐catenin expression in lung tissues (P < 0.01), which was alleviated by exercise training (P < 0.01 except for Smad4 and phosphorylated GSK‐3β: P < 0.05). Bleomycin‐induced lung fibrosis was associated with increased α smooth muscle actin (α‐SMA) and decreased E‐cadherin expression (P < 0.01). Double immunofluorescence staining showed the co‐localization of E‐cadherin/α‐SMA, indicating epithelial‐mesenchymal transition (EMT) formation, which was ameliorated by exercise training. Moreover, exercise training restored bleomycin‐induced downregulation of cystathionine‐β‐synthase (CBS) and cystathionine‐γ‐lyase (CSE) expression, as well as H2S generation in lung tissue (P < 0.01). NaHS treatment attenuated bleomycin‐induced TGF‐β1 production, activation of LRP‐6/β‐catenin signalling, EMT and lung fibrosis (P < 0.01 except for β‐catenin: P < 0.05). Conclusion Exercise training restores bleomycin‐induced downregulation of pulmonary CBS/CSE expression, thus contributing to the increased H2S generation and suppression of TGF‐β1/Smad and LRP‐6/β‐catenin signalling pathways, EMT and lung fibrosis. - 'Acta Physiologica, EarlyView. '
    September 21, 2018   doi: 10.1111/apha.13177   open full text
  • Combined hydroxyurea and ETA receptor blockade reduces renal injury in the humanized sickle cell mouse.
    Crystal Taylor, Malgorzata Kasztan, Binli Tao, Jennifer S. Pollock, David M. Pollock.
    Acta Physiologica. September 20, 2018
    --- - |2+ Abstract Aim The objective of this study is to determine if ambrisentan (ETA selective antagonist) and hydroxyurea (HU) treatment has a synergistic effect on renal injury in sickle cell nephropathy when compared to HU treatment alone. The premise of the study is based on recent studies showing that endothelin‐1 (ET‐1) contributes to the pathophysiology of nephropathy in sickle cell disease (SCD) and that ETA receptor blockade improves renal function and protects against renal injury. Hydroxyurea (HU) is commonly prescribed for the treatment of SCD and has been shown to reduce renal injury in patients with SCD. Methods Male 12‐week‐old humanized sickle mice (HbSS) and their genetic controls (HbAA) were treated with vehicle, HU, ambrisentan, or HU with ambrisentan for 2 weeks and renal structure and function were assessed. Results Vehicle treated HbSS mice exhibited significant proteinuria compared to vehicle treated HbAA mice. HbSS mice also displayed significantly elevated plasma ET‐1 concentrations and decreased urine osmolality compared to HbAA controls. Proteinuria was significantly lower in both HU and ambrisentan treated animals compared to vehicle treated HbSS mice; however, there was no additional improvement in HbSS mice treated with combined ambrisentan and HU. The combination of HU and ambrisentan resulted in significantly lower KIM‐1 excretion, glomerular injury, and interstitial inflammation than HU alone. Conclusion These findings indicate that HU and ETA receptor blockade produce similar reductions in renal injury in the humanized sickle mouse suggesting that both treatments may converge on the same mechanistic pathway. - 'Acta Physiologica, EarlyView. '
    September 20, 2018   doi: 10.1111/apha.13178   open full text
  • Isolation of mitochondrial subpopulations from skeletal muscle: Optimizing recovery and preserving integrity.
    Nicola Lai, China M. Kummitha, Mariana G. Rosca, Hisashi Fujioka, Bernard Tandler, Charles L. Hoppel.
    Acta Physiologica. September 17, 2018
    --- - |2+ Abstract Aim The subsarcolemmal (SSM) and interfibrillar (IFM) mitochondria in skeletal muscle appear to have distinct biochemical properties affecting metabolism in health and disease. The isolation of mitochondrial subpopulations has been a long‐time challenge while the presence of a continuous mitochondrial reticulum challenges the view of distinctive SSM and IFM bioenergetics. Here, a comprehensive approach is developed to identify the best conditions to separate mitochondrial fractions. Methods The main modifications to the protocol to isolate SSM and IFM from rat skeletal muscle were: (a) decreased dispase content and homogenization speed; (b) trypsin treatment of SSM fractions; (c) recentrifugation of mitochondrial fractions at low speed to remove subcellular components. To identify the conditions preserving mitochondrial function, integrity, and maximizing their recovery, microscopy (light and electron) were used to monitor effectiveness and efficiency in separating mitochondrial subpopulations while respiratory and enzyme activities were employed to evaluate function, recovery, and integrity. Results With the modifications described, the total mitochondrial yield increased with a recovery of 80% of mitochondria contained in the original skeletal muscle sample. The difference between SSM and IFM oxidative capacity (10%) with complex‐I substrate was significant only with a saturated ADP concentration. The inner and outer membrane damage for both subpopulations was <1% and 8%, respectively, while the respiratory control ratio was 16. Conclusion Using a multidisciplinary approach, conditions were identified to maximize SSM and IFM recovery while preserving mitochondrial integrity, biochemistry, and morphology. High quality and recovery of mitochondrial subpopulations allow to study the relationship between these organelles and disease. - 'Acta Physiologica, EarlyView. '
    September 17, 2018   doi: 10.1111/apha.13182   open full text
  • Transient receptor potential vanilloid‐4 channels are involved in diminished myogenic tone in brain parenchymal arterioles in response to chronic hypoperfusion in mice.
    Siu‐Lung Chan, Mark T. Nelson, Marilyn J. Cipolla.
    Acta Physiologica. September 16, 2018
    --- - |2+ Abstract Aim Adaptive responses of brain parenchymal arterioles (PAs), a target for cerebral small vessel disease, to chronic cerebral hypoperfusion are largely unknown. Previous evidence suggested that transient receptor potential vanilloid 4 channels may be involved in the regulation of cerebrovascular tone. Therefore, we investigated the role of TRPV4 in adaptations of PAs in a mouse model of chronic hypoperfusion. Methods TRPV4 knockout (−/−) and wild‐type (WT) mice were subjected to unilateral common carotid artery occlusion (UCCAo) for 28 days. Function and structure of PAs ipsilateral to UCCAo were studied isolated and pressurized in an arteriograph. Results Basal tone of PAs was similar between WT and TRPV4−/− mice (22 ± 3 vs 23 ± 5%). After UCCAo, active inner diameters of PAs from WT mice were larger than control (41 ± 2 vs 26 ± 5 μm, P < 0.05) that was due to decreased tone (8 ± 2 vs 23 ± 5%, P < 0.05), increased passive inner diameters (46 ± 3 vs 34 ± 2 μm, P < 0.05), and decreased wall‐to‐lumen ratio (0.104 ± 0.01 vs 0.137 ± 0.01, P < 0.05). However, UCCAo did not affect vasodilation to a small‐ and intermediate‐conductance calcium‐activated potassium channel agonist NS309, the nitric oxide (NO) donor sodium nitroprusside, or constriction to a NO synthase inhibitor L‐NNA. Wall thickness and distensibility in PAs from WT mice were unaffected. In TRPV4−/− mice, UCCAo had no effect on active inner diameters or tone and only increased passive inner diameters (53 ± 2 vs 43 ± 3 μm, P < 0.05). Conclusion Adaptive response of PAs to chronic cerebral hypoperfusion includes myogenic tone reduction and outward remodelling. TRPV4 channels were involved in tone reduction but not outward remodelling in response to UCCAo. - 'Acta Physiologica, EarlyView. '
    September 16, 2018   doi: 10.1111/apha.13181   open full text
  • Distinct patterns of skeletal muscle mitochondria fusion, fission and mitophagy upon duration of exercise training.
    Yoan Arribat, Nicholas T. Broskey, Chiara Greggio, Marie Boutant, Sonia Conde Alonso, Sameer S. Kulkarni, Sylviane Lagarrigue, Elvis A. Carnero, Cyril Besson, Carles Cantó, Francesca Amati.
    Acta Physiologica. September 14, 2018
    --- - |2+ Abstract Aim Healthy ageing interventions encompass regular exercise to prevent mitochondrial dysfunction, key player in sarcopenia pathogenesis. Mitochondrial biogenesis has been well documented, but mitochondrial remodelling in response to exercise training is poorly understood. Here we investigated fusion, fission and mitophagy before and after an exercise intervention in older adults. Methods Skeletal muscle biopsies were collected from 22 healthy sedentary men and women before and after 4 months of supervised training. Eight lifelong trained age‐ and gender‐matched volunteers served as positive controls. Transmission electron microscopy was used to estimate mitochondrial content. Western blotting and qRT‐PCR were used to detect changes in specific proteins and transcripts. Results After intervention, mitochondrial content increased to levels of controls. While enhancement of fusion was prevalent after intervention, inhibition of fission and increased mitophagy were dominant in controls. Similarly to PARKIN, BCL2L13 content was higher in controls. The observed molecular adaptations paralleled long‐term effects of training on physical fitness, exercise efficiency and oxidative capacity. Conclusions This study describes distinct patterns of molecular adaptations in human skeletal muscle under chronic exercise training. After 16 weeks of exercise, the pattern was dominated by fusion to increase mitochondrial content to the metabolic demands of exercise. In lifelong exercise, the pattern was dominated by mitophagy synchronized with increased fusion and decreased fission, indicating an increased mitochondrial turnover. In addition to these temporally distinct adaptive mechanisms, this study suggests for the first time a specific role of BCL2L13 in chronic exercise that requires constant maintenance of mitochondrial quality. - 'Acta Physiologica, EarlyView. '
    September 14, 2018   doi: 10.1111/apha.13179   open full text
  • Smelling through calcium‐sensing receptor affects sympathetic control of blood pressure and regional blood flow.
    Boye L. Jensen.
    Acta Physiologica. September 11, 2018
    --- - - Acta Physiologica, EarlyView.
    September 11, 2018   doi: 10.1111/apha.13180   open full text
  • Negative feedback regulation of vasocontraction by potassium channels in 10‐ to 15‐day‐old rats: Dominating role of Kv7 channels.
    Anastasia A. Shvetsova, Dina K. Gaynullina, Olga S. Tarasova, Rudolf Schubert.
    Acta Physiologica. September 10, 2018
    --- - |2+ Abstract Aim Potassium channels are key regulators of smooth muscle membrane potential and arterial tone. However, the roles of potassium channels in vascular tone regulation in the systemic circulation during early postnatal development are poorly understood. Therefore, this study tested the hypothesis that the negative feedback regulation of vasocontraction by potassium channels changes during maturation. Methods Experiments were performed on endothelium‐denuded saphenous arteries from 10‐ to 15‐day‐old and 2‐ to 3‐month‐old male rats. Isometric force and membrane potential were recorded using wire myography and the sharp microelectrode technique respectively; mRNA and protein contents were determined by qPCR and Western blotting. Results The effects of Kv1, Kir and Kv7 channel blockers (DPO‐1, BaCl2, XE991) on methoxamine‐induced contraction were larger in arteries of 10‐ to 15‐day‐old compared to 2‐ to 3‐month‐old animals. In contrast, the BKCa channel blocker iberiotoxin had a stronger influence in 2‐ to 3‐ month‐old rats. The effects of KATP and Kv2 channel blockers (glibenclamide, stromatoxin) were not pronounced at both ages. The larger influence of Kv7 and Kir channel blockade on arterial contraction in 10‐ to 15‐day‐old rats was associated with more prominent smooth muscle depolarization. The developmental alterations in potassium channel functioning were generally consistent with their mRNA and protein expression levels in arterial smooth muscle. Conclusion The negative feedback regulation of vasocontraction by potassium channels varies during maturation depending on the channel type. A dominating contribution of Kv7 channels to the regulation of basal tone and agonist‐induced contraction was observed in arteries of 10‐ to 15‐day‐old animals. - 'Acta Physiologica, EarlyView. '
    September 10, 2018   doi: 10.1111/apha.13176   open full text
  • Vamorolone treatment improves skeletal muscle outcome in a critical illness myopathy rat model.
    Hazem Akkad, Nicola Cacciani, Monica Llano‐Diez, Rebeca Corpeno Kalamgi, Tamara Tchkonia, James L. Kirkland, Lars Larsson.
    Acta Physiologica. September 06, 2018
    --- - |2+ Abstract Aim Critical illness myopathy (CIM) is a consequence of modern critical care, leading to skeletal muscle atrophy/paralysis with negative consequences for mortality/morbidity and health care costs. Glucocorticoids (GCs) have been proposed to trigger CIM. Here, we compare outcomes of two GCs, the commonly used prednisolone and the newly developed dissociative vamorolone in response to the intensive care unit (ICU) condition for 5 days, ie, sedation, immobilization, and mechanical ventilation. Methods Rats were divided into a 0‐day sham‐operated control group, and three groups exposed to 5 days ICU condition during treatment with prednisolone (PRED) or vamorolone (VAM) or none of these GCs (ICU‐group). Survival, body and muscle weights, cytokine concentrations, regulation of muscle contraction in single fast‐ and slow‐twitch muscle fibres, myofibrillar protein expression and protein degradation pathways were studied. Results Critical illness myopathy geno‐ and pheno‐types were confirmed in the ICU group. However, VAM and PRED groups showed reduced atrophy/weakness than the ICU group, and muscle specific differences with more severe negative effects on fast‐twitch muscle fibres in the PRED than the other groups. Conclusion These results show that vamorolone provides a GC intervention superior to typical GCs in improving CIM outcomes. Further, the findings do not support the notion that moderate‐dose GC treatment represents a factor triggering CIM. - 'Acta Physiologica, EarlyView. '
    September 06, 2018   doi: 10.1111/apha.13172   open full text
  • Foetal circadian rhythms, interpretation of foetal heart rate recordings and clues about foetal preparedness for stressful situations.
    João Bernardes.
    Acta Physiologica. September 06, 2018
    --- - - Acta Physiologica, Volume 224, Issue 2, October 2018.
    September 06, 2018   doi: 10.1111/apha.13174   open full text
  • Water is life.
    Pontus B. Persson, Anja Bondke Persson.
    Acta Physiologica. September 06, 2018
    --- - - Acta Physiologica, Volume 224, Issue 2, October 2018.
    September 06, 2018   doi: 10.1111/apha.13173   open full text
  • Endotoxaemia differentially regulates the expression of renal Ca2+ transport proteins in mice.
    Manuel Meurer, Klaus Höcherl.
    Acta Physiologica. September 03, 2018
    --- - |2+ Abstract Aim Alterations in parathyroid hormone (PTH) and/or vitamin D signalling are frequently reported in patients with sepsis. The consequences on renal and intestinal Ca2+ and Pi regulatory mechanisms are still unclear. We hypothesized that endotoxaemia alters the expression of important renal and intestinal Ca2+ and Pi transport proteins. Methods Male C57BL/6 mice were treated with lipopolysaccharide (LPS; 3 mg/kg; i.p.). The mRNA and protein levels of renal and intestinal Ca2+ and Pi transport proteins were measured by RT‐qPCR, immunohistochemistry and western blot analysis. Results Lipopolysaccharide‐induced hypocalcaemia and hyperphosphataemia was paralleled by a decrease in glomerular filtration rate and urinary excretion of Ca2+ and Pi. Endotoxaemia augmented plasma levels of PTH and affected the fibroblast growth factor 23 (FGF23)‐klotho‐vitamin D axis by increasing plasma levels of FGF23 and downregulation of renal klotho expression. Renal expression of CYP27b1 and plasma levels of 1,25‐dihydroxyvitamin D3 were increased in response to LPS. Endotoxaemia augmented the renal expression of TRPV5, TRPV6 and PiT1, whereas the renal expression of calbindin‐D28K, NCX1, NaPi‐2a and NaPi‐2c were decreased. Incubation of primary distal tubule cells with LPS increased TRPV6 mRNA levels. Furthermore, LPS decreased the intestinal expression of TRPV6, calbindin‐D9K and of NaPi‐2b. Conclusion Our findings indicate that endotoxaemia is associated with hypocalcaemia and hyperphosphataemia and a disturbed FGF23‐klotho‐vitamin D signaling. Further, LPS‐induced acute kidney injury was accompanied by an increased or decreased expression of specific renal and intestinal Ca2+ and Pi transporters respectively. It seems unlikely that LPS‐induced hypocalcaemia is due to renal loss of Ca2+. - 'Acta Physiologica, EarlyView. '
    September 03, 2018   doi: 10.1111/apha.13175   open full text
  • Cardiovascular sequelae of the sleep apnoea syndrome: Sex, stress and therapeutic strategies.
    Ken D. O'Halloran.
    Acta Physiologica. August 30, 2018
    --- - - Acta Physiologica, EarlyView.
    August 30, 2018   doi: 10.1111/apha.13170   open full text
  • DUOX1‐mediated hydrogen peroxide release regulates sodium transport in H441 bronchiolar epithelial cells.
    Frédérique Mies, Myrna Virreira, Arnaud Goolaerts, Sami Djerbib, Renaud Beauwens, Vadim Shlyonsky, Alain Boom.
    Acta Physiologica. August 29, 2018
    --- - |2+ Abstract Aim Dexamethasone has been shown to induce the formation of epithelial domes by bronchiolar H441 cells. It stimulates the expression of both amiloride inhibitable epithelial sodium channels (ENaC) and dual oxidase‐1 (DUOX1). We therefore ask the question whether DUOX1 expression and production of submillimolar amounts of H2O2 is instrumental for the sodium channel upregulation observed in H441 cells. Methods In vitro cell culture, nystatin‐perforated whole‐cell patch‐clamp technique, immunocytochemistry and RT‐PCR methods have been used. Results Cells forming epithelial domes induced by dexamethasone (0.1 μmol L−1, 24 hours) and by 5‐aza‐2′‐deoxytidine (1 μmol L−1, 48 hours) expressed more DUOX1 protein compared with other cells in the monolayer. Dome formation could be inhibited by exogenous catalase in a concentration‐dependent manner and by the NADPH oxidase inhibitor diphenyliodonium, which suggested the involvement of H2O2. While single application of 0.2 mmol L−1 H2O2 induced transient dome formation, lower doses were ineffective and higher doses disrupted the cell monolayer. Hydrogen peroxide (0.1 mmol L−1) activated acutely amiloride‐sensitive whole‐cell currents from 3.91 ± 0.79 pA pF−1 to 4.76 ± 0.98 pA pF−1 in dome‐forming cells and had no effect in cells outside of domes. ENaC but not DUOX1 transcription was potentiated by catalase in the presence of dexamethasone, which suggested negative feedback of H2O2 on ENaC gene expression. Conclusion Our observations suggest that tonic production of H2O2 by DUOX1 participates in maintaining the level of vectorial sodium transport by lung epithelial cells. Moreover, the system appears to be well tuned as it would allow H2O2‐dependent innate immunity without inducing airway/alveolar sodium and fluid hyperabsorption. - 'Acta Physiologica, EarlyView. '
    August 29, 2018   doi: 10.1111/apha.13166   open full text
  • Perivascular adipose tissue: A new possible tissue augmenting coronary vasodilatation in response to acute hypoxia.
    Ulf Simonsen, Asbjørn G. Petersen.
    Acta Physiologica. August 25, 2018
    --- - - Acta Physiologica, EarlyView.
    August 25, 2018   doi: 10.1111/apha.13171   open full text
  • The histone demethylase Jarid1b mediates angiotensin II‐induced endothelial dysfunction by controlling the 3′UTR of soluble epoxide hydrolase.
    Andrea E. Vasconez, Patrick Janetzko, James A. Oo, Beatrice Pflüger‐Müller, Corina Ratiu, Lunda Gu, Kristian Helin, Gerd Geisslinger, Ingrid Fleming, Katrin Schröder, Christian Fork, Ralf P. Brandes, Matthias S. Leisegang.
    Acta Physiologica. August 25, 2018
    --- - |2+ Abstract Aim The histone demethylase Jarid1b limits gene expression by removing the active methyl mark from histone3 lysine4 at gene promoter regions. A vascular function of Jarid1b is unknown, but a vasoprotective function to inflammatory and hypertrophic stimuli, like angiotensin II (AngII) could be inferred. This hypothesis was tested using Jarid1b knockout mice and the inhibitor PBIT. Methods Mice or aortic segments were treated with AngII to induce endothelial dysfunction. Aortae from WT and Jarid1b knockout were studied in organ chambers and endothelium‐dependent dilator responses to acetylcholine and endothelium‐independent responses to DetaNONOate were recorded after pre‐constriction with phenylephrine in the presence or absence of the NO‐synthase inhibitor nitro‐L‐arginine. Molecular mechanisms were investigated with chromatin immunoprecipitation, RNA‐Seq, RNA‐3′‐adaptor‐ligation, actinomycin D and RNA‐immunoprecipitation. Results Knockout or inhibition of Jarid1b prevented the development of endothelial dysfunction in response to AngII. This effect was not a consequence of altered nitrite oxide availability but accompanied by a loss of the inflammatory response to AngII. As Jarid1b mainly inhibits gene expression, an indirect effect should account for this observation. AngII induced the soluble epoxide hydrolase (sEH), which degrades anti‐inflammatory lipids, and thus promotes inflammation. Knockout or inhibition of Jarid1b prevented the AngII‐mediated sEH induction. Mechanistically, Jarid1b maintained the length of the 3′untranslated region of the sEH mRNA, thereby increasing its stability and thus sEH protein expression. Loss of Jarid1b activity therefore resulted in sEH mRNA destabilization. Conclusion Jarid1b contributes to the pro‐inflammatory effects of AngII by stabilizing sEH expression. Jarid1b inhibition might be an option for future therapeutics against cardiovascular dysfunction. - 'Acta Physiologica, EarlyView. '
    August 25, 2018   doi: 10.1111/apha.13168   open full text
  • Starfish larvae lose substantial energy to maintain digestion under ocean acidification conditions.
    Narimane Dorey.
    Acta Physiologica. August 21, 2018
    --- - - Acta Physiologica, Volume 224, Issue 2, October 2018.
    August 21, 2018   doi: 10.1111/apha.13169   open full text
  • The double‐hyperbolic force‐velocity relationship in humans.
    Julian Alcazar, Roberto Navarro‐Cruz, Carlos Rodriguez‐Lopez, Sara Vila‐Maldonado, Ignacio Ara, Luis M. Alegre.
    Acta Physiologica. August 14, 2018
    --- - - Acta Physiologica, EarlyView.
    August 14, 2018   doi: 10.1111/apha.13165   open full text
  • Intestinal macrophages and their interaction with the enteric nervous system in health and inflammatory bowel disease.
    Elisa Meroni, Nathalie Stakenborg, Maria Francesca Viola, Guy E. Boeckxstaens.
    Acta Physiologica. August 13, 2018
    --- - |2 Abstract Over the past decades, there has been an increasing understanding of cellular and molecular mechanisms that mediate modulation of the immune system by the autonomic nervous system. The discovery that vagal nerve stimulation (VNS) attenuates endotoxin‐induced experimental sepsis paved the way for further studies investigating neuro‐immune interaction. In particular, great attention is now given to intestinal macrophages: several studies report the existence of both intrinsic and extrinsic neural mechanisms by which intestinal immune homoeostasis can be regulated in different layers of the intestine, mainly by affecting macrophage activation through neurotransmitter release. Given the important role of inflammation in numerous disease processes, such as inflammatory bowel disease (IBD), cholinergic anti‐inflammatory mechanisms are under intense investigation both from a basic and clinical science perspective in immune‐mediated diseases such as IBD. This review discusses recent insights on the cross‐talk between enteric neurons and the immune system, especially focusing on macrophages, and provides an overview of basic and translational aspects of the cholinergic anti‐inflammatory response as therapeutic alternative to reinstall immune homoeostasis in intestinal chronic inflammation. - Acta Physiologica, EarlyView.
    August 13, 2018   doi: 10.1111/apha.13163   open full text
  • Akt3 deletion in mice impairs spatial cognition and hippocampal CA1 long long‐term potentiation through downregulation of mTOR.
    Tingting Zhang, Zhaochun Shi, Ya Wang, Ling Wang, Baofeng Zhang, Guiquan Chen, Qi Wan, Ling Chen.
    Acta Physiologica. August 13, 2018
    --- - |2+ Abstract Aim Loss‐of‐function mutation of Akt3 in humans has been associated with microcephaly and cognitive defects. Two Akt isoforms, Akt1 and Akt3, are highly expressed in hippocampal pyramidal cells. We explored the roles of Akt1 and Akt3, respectively, in spatial cognition and underlying mechanisms. Methods We used Akt1 knockout (Akt1‐KO) and Akt3 knockout (Akt3‐KO) mice to examine the influence of Akt1 and Akt3 deficiency on spatial memory, as well as induction and maintenance of hippocampal CA1 NMDA receptor‐dependent and protein synthesis‐dependent long‐term potentiation (LTP). Results Long‐term spatial memory was impaired in Akt3‐KO mice, but not in Akt1‐KO mice, as assessed by the Morris water maze task. Akt3‐KO and Akt1‐KO mice displayed reductions in brain size without concurrent changes in the number of pyramidal cells or basal properties of synaptic transmission. One‐train high‐frequency stimulation (HFS × 1) induced NMDA receptor‐dependent LTP in Akt3‐KO mice and Akt1‐KO mice. Four‐train HFS (HFS × 4) induced rapamycin‐sensitive long‐LTP in Akt1‐KO mice, but not Akt3‐KO mice. Basal level of mTOR phosphorylation was reduced in Akt3‐KO mice rather than Akt1‐KO mice. HFS × 4 induced an elevation of mTOR and p70S6K phosphorylation in Akt1‐KO mice, which led to enhanced 4EBP2 and eIF4E phosphorylation along with an increase in AMPA receptor protein. However, the same protocol of HFS × 4 failed to trigger the mTOR‐p70S6K signalling cascade or increase 4EBP2 and eIF4E phosphorylation in Akt3‐KO mice. Conclusion The Akt3 deficiency via inactivation of mTOR suppresses HFS × 4‐induced mTOR‐p70S6K signalling to reduce phosphorylation of 4EBP and eIF4E, which impairs protein synthesis‐dependent long‐LTP and long‐term spatial cognitive function. - 'Acta Physiologica, EarlyView. '
    August 13, 2018   doi: 10.1111/apha.13167   open full text
  • Is IGF‐1 a useful inhibitor of Na+/H+‐exchanger activity?
    Antonius Baartscheer, Marieke W. Veldkamp.
    Acta Physiologica. August 13, 2018
    --- - - Acta Physiologica, Volume 224, Issue 2, October 2018.
    August 13, 2018   doi: 10.1111/apha.13164   open full text
  • Emerging relevance of circadian rhythms in headaches and neuropathic pain.
    Mark J. Burish, Zheng Chen, Seung‐Hee Yoo.
    Acta Physiologica. July 25, 2018
    --- - |2 Abstract Circadian rhythms of physiology are the keys to health and fitness, as dysregulation, by genetic mutations or environmental factors, increases disease risk and aggravates progression. Molecular and physiological studies have shed important light on an intrinsic clock that drives circadian rhythms and serves essential roles in metabolic homoeostasis, organ physiology and brain functions. One exciting new area in circadian research is pain, including headache and neuropathic pain for which new mechanistic insights have recently emerged. For example, cluster headache is an intermittent pain disorder with an exceedingly precise circadian timing, and preliminary evidence is emerging linking several circadian components (eg, Clock and Nr1d1) with the disease. In this review, we first discuss the broad metabolic and physiological relevance of the circadian timing system. We then provide a detailed review of the circadian relevance in pain disease and physiology, including cluster headache, migraine, hypnic headache and neuropathic pain. Finally, we describe potential therapeutic implications, including existing pain medicines and novel clock‐modulating compounds. The physiological basis for the circadian rhythms in pain is an exciting new area of research with profound basic and translational impact. - 'Acta Physiologica, EarlyView. '
    July 25, 2018   doi: 10.1111/apha.13161   open full text
  • Connexins in the control of vasomotor function.
    K. Pogoda, P. Kameritsch, H. Mannell, U. Pohl.
    Acta Physiologica. July 23, 2018
    --- - |2 Abstract Vascular endothelial cells, as well as smooth muscle cells, show heterogeneity with regard to their receptor expression and reactivity. For the vascular wall to act as a functional unit, the various cells’ responses require integration. Such an integration is not only required for a homogeneous response of the vascular wall, but also for the vasomotor behaviour of consecutive segments of the microvascular arteriolar tree. As flow resistances of individual sections are connected in series, sections require synchronization and coordination to allow effective changes of conductivity and blood flow. A prerequisite for the local coordination of individual vascular cells and different sections of an arteriolar tree is intercellular communication. Connexins are involved in a dual manner in this coordination. (i) By forming gap junctions between cells, they allow an intercellular exchange of signalling molecules and electrical currents. In particular, the spread of electrical currents allows for coordination of cell responses over longer distances. (ii) Connexins are able to interact with other proteins to form signalling complexes. In this way, they can modulate and integrate individual cells' responses also in a channel‐independent manner. This review outlines mechanisms allowing the vascular connexins to exert their coordinating function and to regulate the vasomotor reactions of blood vessels both locally, and in vascular networks. Wherever possible, we focus on the vasomotor behaviour of small vessels and arterioles which are the main vessels determining vascular resistance, blood pressure and local blood flow. - Acta Physiologica, EarlyView.
    July 23, 2018   doi: 10.1111/apha.13108   open full text
  • Aromatherapy: Activating olfactory calcium‐sensing receptors impairs renal hemodynamics via sympathetic nerve‐mediated vasoconstriction.
    Shih‐Pin Lee, Wei‐Yi Wu, Jong‐Kai Hsiao, Jia‐Hao Zhou, Hao‐Hsiang Chang, Chiang‐Ting Chien.
    Acta Physiologica. July 22, 2018
    --- - |2+ Abstract Aim This study determines whether the activation of olfactory calcium‐sensing receptor initiates a sympathetic activation‐dependent neurovascular reflex subsequently contributing to renal hemodynamic depression. Methods Immunohistochemistry and nose‐loading calcium‐sensitive dye were used to explore the location and function of calcium‐sensing receptor on the olfactory sensory neuron. The renal sympathetic nervous activity, renal hemodynamics and the microcirculation of kidney, liver and intestine were evaluated after liquid‐phase intranasal administrations of saline, lidocaine, calcium‐sensing receptor agonists and antagonist in sham and bilateral renal denervated rats. Real‐time renal glomerular filtration rate was measured by a magnetic resonance renography. Results Calcium‐sensing receptors were expressed on the cilia the olfactory sensory neuron and their activation depolarized olfactory sensory neuron and induced the calcium influx in the terminal side on olfactory glomeruli. Activating olfactory calcium‐sensing receptors significantly increased arterial blood pressure and renal sympathetic nervous activities and subsequently decreased renal blood flow, renal, hepatic and enteral microcirculation. Cotreatments with calcium‐sensing receptor antagonist or lidocaine inhibited these physiological alterations. The renal hemodynamic depressions by olfactory calcium‐sensing receptor activation were significantly blocked by bilateral renal denervation. The intranasal manganese administration decreased the glomerular filtration rate. Conclusion Calcium‐sensing receptor acts as a functional chemosensory receptor on olfactory sensory neuron, and its activation causes the global sympathetic enhancement contributing to systematic vasoconstriction and subsequently depresses renal blood flow and glomerular filtration rate. These data implicate a possibly clinical aspect that several environmental stimuli may activate olfactory calcium‐sensing receptors to evoke a sympathetic nervous system‐mediated neurovascular reflex to depress renal hemodynamics. - 'Acta Physiologica, EarlyView. '
    July 22, 2018   doi: 10.1111/apha.13157   open full text
  • Protective roles of estradiol against vascular oxidative stress in ovariectomized female rats exposed to normoxia or intermittent hypoxia.
    Alexandra Ribon‐Demars, Vincent Pialoux, Anaëlle Boreau, François Marcouiller, Richard Larivière, Aida Bairam, Vincent Joseph.
    Acta Physiologica. July 17, 2018
    --- - |2+ Abstract Aim We tested the hypothesis that estradiol (E2) reduces aortic oxidative stress and endothelial dysfunction in ovariectomized (OVX) female rats exposed to room air (RA) or chronic intermittent hypoxia (CIH). Methods We used intact or OVX female rats treated with vehicle or E2 (0.5 mg/kg/d) and exposed to RA or CIH (21%‐10% O2, 10 cycles/h, 8 h/d) for 7 or 35 days, and measured the arterial pressure, heart rate and plasma endothelin‐1 levels. We also measured in thoracic aortic samples, the activities of the pro‐oxidant enzymes NADPH (NOX) and xanthine oxidase (XO), the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase and the advanced oxidation protein products (AOPP—oxidative stress marker). Finally, we used aortic rings to assess the contractile response to phenylephrine and the vasodilatory response to acetylcholine. Results After 7 or 35 days of CIH, E2 supplementation reduced arterial pressure. E2 reduced plasma endothelin‐1 levels after 7 days of CIH, but not after 35 days. Ovariectomy, but not CIH for 7 days, increased aortic oxidative stress and E2 treatment prevented this effect. Remarkably, in animals exposed to RA, this was achieved by a reduction in NOX and XO activities, but in animals exposed to CIH this was achieved by increased catalase activity. In OVX female rats exposed to CIH for 7 days, E2 supplementation improved the NO‐mediated vasodilation. After 35 days of CIH, enzymatic activities, AOPP and aortic reactivity were similar in all groups. Conclusion E2‐based therapy could help prevent the vascular consequences of CIH in apneic women. - 'Acta Physiologica, EarlyView. '
    July 17, 2018   doi: 10.1111/apha.13159   open full text
  • IGF‐1 in exercise‐induced enhancement of episodic memory.
    P. D. Loprinzi.
    Acta Physiologica. July 13, 2018
    --- - - Acta Physiologica, EarlyView.
    July 13, 2018   doi: 10.1111/apha.13154   open full text
  • Endothelium‐dependent responses in the microcirculation observed in vivo.
    W. I. Rosenblum.
    Acta Physiologica. July 10, 2018
    --- - |2 Abstract Endothelium‐dependent responses were first demonstrated 40 years ago in the aorta. Since then, extensive research has been conducted in vitro using conductance vessels and materials derived from them. However, the microcirculation controls blood flow to vital organs and has been the focus of in vivo studies of endothelium‐dependent dilation beginning immediately after the first in vitro report. Initial in vivo studies employed a light/dye technique for selectively damaging the endothelium to unequivocally prove, in vivo, the existence of endothelium‐dependent dilation and in the microvasculature. Endothelium‐dependent constriction was similarly proven. Endothelium‐dependent agonists include acetylcholine (ACh), bradykinin, arachidonic acid, calcium ionophore A‐23187, calcitonin gene‐related peptide (CGRP), serotonin, histamine and endothelin‐1. Normal and disease states have been studied. Endothelial nitric oxide synthase, cyclooxygenase and cytochrome P450 have been shown to generate the mediators of the responses. Some of the key enzyme systems generate reactive oxygen species (ROS) like superoxide which may prevent EDR. However, one ROS, namely H2O2, is one of a number of hyperpolarizing factors that cause dilation initiated by endothelium. Depending upon microvascular bed, a single agonist may use different pathways to elicit an endothelium‐dependent response. Interpretation of studies using inhibitors of eNOS is complicated by the fact that these inhibitors may also inhibit ATP‐sensitive potassium channels. Other in vivo observations of brain arterioles failed to establish nitric oxide as the mediator of responses elicited by CGRP or by ACh and suggest that a nitrosothiol may be a better fit for the latter. - Acta Physiologica, Volume 224, Issue 2, October 2018.
    July 10, 2018   doi: 10.1111/apha.13111   open full text
  • Dorsal striatum dopamine oscillations: Setting the pace of food anticipatory activity.
    Guillaume Lartigue, Molly McDougle.
    Acta Physiologica. June 27, 2018
    --- - |2 Abstract Predicting the uncertainties of the ever‐changing environment provides a competitive advantage for animals. The need to anticipate food sources has provided a strong evolutionary drive for synchronizing behavioural and internal processes with daily circadian cycles. When food is restricted to a few hours per day, rodents exhibit increased wakefulness and foraging behaviour preceding the arrival of food. Interestingly, while the master clock located in the suprachiasmatic nucleus entrains daily rhythms to the light cycle, it is not necessary for this food anticipatory activity. This suggests the existence of a food‐entrained oscillator located elsewhere. Based on the role of nigrostriatal dopamine in reward processing, motor function, working memory and internal timekeeping, we propose a working model by which food‐entrained dopamine oscillations in the dorsal striatum can enable animals maintained on a restricted feeding schedule to anticipate food arrival. Finally, we summarize how metabolic signals in the gut are conveyed to the nigrostriatal pathway to suggest possible insight into potential input mechanisms for food anticipatory activity. - 'Acta Physiologica, EarlyView. '
    June 27, 2018   doi: 10.1111/apha.13152   open full text
  • Sex‐related differences in muscle size explained by amplitudes of higher‐threshold motor unit action potentials and muscle fibre typing.
    M. A. Trevino, A. J. Sterczala, J. D. Miller, M. E. Wray, H. L. Dimmick, A. B. Ciccone, J. P. Weir, P. M. Gallagher, A. C. Fry, T. J. Herda.
    Acta Physiologica. June 27, 2018
    --- - |2+ Abstract Aim To investigate the relationships between motor unit action potential amplitudes (MUAPAMP), muscle cross‐sectional area (mCSA) and composition (mEI), per cent myosin heavy chain (%MHC) areas and sex in the vastus lateralis (VL). Methods Ten males and 10 females performed a submaximal isometric trapezoid muscle action that included a linearly increasing, steady torque at 40% maximal voluntary contraction, and linearly decreasing segments. Surface electromyographic decomposition techniques were utilized to determine MUAPAMPS in relation to recruitment thresholds (RT). Ultrasound images were taken to quantify muscle mCSA and mEI. Muscle biopsies were collected to calculate %MHC areas. Y‐intercepts and slopes were calculated for the MUAPAMP vs RT relationships for each subject. Independent‐samples t tests and ANOVA models examined sex‐related differences in mCSA, mEI, slopes and y‐intercepts for the MUAPAMP vs RT relationships and %MHC areas. Correlations were performed among type IIA and total type II %MHC area, mCSA and the slopes and y‐intercepts for the MUAPAMP vs RT relationships. Results Males exhibited greater slopes for the MUAPAMP vs RT relationships (P = .003), mCSA (P < .001) and type IIA %MHC (P = .011), whereas females had greater type I %MHC area (P = .010) and mEI (P = .024). The mCSA, type IIA and total II %MHC area variables were correlated (P < .001‐.015, r = .596‐.836) with the slopes from the MUAPAMP vs RT relationships. Conclusion Sex‐related differences in mCSA and MUAPAMPS of the higher‐threshold MUs were likely the result of larger muscle fibres expressing type II characteristics for males. - 'Acta Physiologica, EarlyView. '
    June 27, 2018   doi: 10.1111/apha.13151   open full text
  • The case against personalized impact factors.
    N. Strugala, P. B. Persson.
    Acta Physiologica. June 22, 2018
    --- - - Acta Physiologica, Volume 224, Issue 3, November 2018.
    June 22, 2018   doi: 10.1111/apha.13112   open full text
  • Serotonergic regulation of insulin secretion.
    L. R. Cataldo Bascuñan, C. Lyons, H. Bennet, I. Artner, M. Fex.
    Acta Physiologica. June 20, 2018
    --- - |2 Abstract The exact physiological role for the monoamine serotonin (5‐HT) in modulation of insulin secretion is yet to be fully understood. Although the presence of this monoamine in islets of Langerhans is well established, it is only with recent advances that the complex signalling network in islets involving 5‐HT is being unravelled. With more than fourteen different 5‐HT receptors expressed in human islets and receptor‐independent mechanisms in insulin‐producing β‐cells, our understanding of 5‐HT's regulation of insulin secretion is increasing. It is now widely accepted that failure of the pancreatic β‐cell to release sufficient amounts of insulin is the main cause of type 2 diabetes (T2D), an ongoing global epidemic. In this context, 5‐HT signalling may be of importance. In fact, 5‐HT may serve an essential role in regulating the release of insulin and glucagon, the two main hormones that control glucose and lipid homoeostasis. In this review, we will discuss past and current understanding of 5‐HT's role in the endocrine pancreas. - 'Acta Physiologica, EarlyView. '
    June 20, 2018   doi: 10.1111/apha.13101   open full text
  • Muscle mass and inspired oxygen influence oxygen extraction at maximal exercise: Role of mitochondrial oxygen affinity.
    D. A. Cardinale, F. J. Larsen, M. Jensen‐Urstad, E. Rullman, H. Søndergaard, D. Morales‐Alamo, B. Ekblom, J. A. L. Calbet, R. Boushel.
    Acta Physiologica. June 20, 2018
    --- - |2+ Abstract Aim We examined the Fick components together with mitochondrial O2 affinity (p50mito) in defining O2 extraction and O2 uptake during exercise with large and small muscle mass during normoxia (NORM) and hyperoxia (HYPER). Methods Seven individuals performed 2 incremental exercise tests to exhaustion on a bicycle ergometer (BIKE) and 2 on a 1‐legged knee extension ergometer (KE) in NORM or HYPER. Leg blood flow and VO2 were determined by thermodilution and the Fick method. Maximal ADP‐stimulated mitochondrial respiration (OXPHOS) and p50mito were measured ex vivo in isolated mitochondria. Mitochondrial excess capacity in the leg was determined from OXPHOS in permeabilized fibres and muscle mass measured with magnetic resonance imaging in relation to peak leg O2 delivery. Results The ex vivo p50mito increased from 0.06 ± 0.02 to 0.17 ± 0.04 kPa with varying substrate supply and O2 flux rates from 9.84 ± 2.91 to 16.34 ± 4.07 pmol O2·s−1·μg−1 respectively. O2 extraction decreased from 83% in BIKE to 67% in KE as a function of a higher O2 delivery and lower mitochondrial excess capacity. There was a significant relationship between O2 extraction and mitochondrial excess capacity and p50mito that was unrelated to blood flow and mean transit time. Conclusion O2 extraction varies with mitochondrial respiration rate, p50mito and O2 delivery. Mitochondrial excess capacity maintains a low p50mito which enhances O2 diffusion from microvessels to mitochondria during exercise. - 'Acta Physiologica, EarlyView. '
    June 20, 2018   doi: 10.1111/apha.13110   open full text
  • Cutaneous pH landscape as a facilitator of melanoma initiation and progression.
    A. Koch, A. Schwab.
    Acta Physiologica. June 18, 2018
    --- - |2 Abstract Melanoma incidence is on the rise and currently causes the majority of skin cancer‐related deaths. Yet, therapies for metastatic melanoma are still insufficient so that new concepts are essential. Malignant transformation of melanocytes and melanoma progression are intimately linked to the cutaneous pH landscape and its dysregulation in tumour lesions. The pH landscape of normal skin is characterized by a large pH gradient of up to 3 pH units between surface and dermis. The Na+/H+ exchanger NHE1 is one of the major contributors of acidity in superficial skin layers. It is also activated by the most frequent mutation in melanoma, BRAFV600E, thereby causing pH dysregulation during melanoma initiation. Melanoma progression is supported by an extracellular acidification and/or NHE1 activity which promote the escape of single melanoma cells from the primary tumour, migration and metastatic spreading. We propose that viewing melanoma against the background of the acid‐base physiology of the skin provides a better understanding of the pathophysiology of this disease and allows the development of novel therapeutic concepts. - Acta Physiologica, EarlyView.
    June 18, 2018   doi: 10.1111/apha.13105   open full text
  • Sustained conduction of vasomotor responses in rat mesenteric arteries in a two‐compartment in vitro set‐up.
    T. Palao, A. Weert, A. Leeuw, J. Vos, E. N. T. P. Bakker, E. Bavel.
    Acta Physiologica. June 17, 2018
    --- - |2+ Abstract Aim Conduction of vasomotor responses may contribute to long‐term regulation of resistance artery function and structure. Most previous studies have addressed conduction of vasoactivity only during very brief stimulations. We developed a novel set‐up that allows the local pharmacological stimulation of arteries in vitro for extended periods of time and studied the conduction of vasomotor responses in rat mesenteric arteries under those conditions. Methods The new in vitro set‐up was based on the pressure myograph. The superfusion chamber was divided halfway along the vessel into two compartments, allowing an independent superfusion of the arterial segment in each compartment. Local and remote cumulative concentration‐response curves were obtained for a range of vasoactive agents. Additional experiments were performed with the gap junction inhibitor 18β‐glycyrrhetinic acid and in absence of the endothelium. Results Phenylephrine‐induced constriction and acetylcholine‐induced dilation were conducted over a measured distance up to 2.84 mm, and this conduction was maintained for 5 minutes. Conduction of acetylcholine‐induced dilation was inhibited by 18β‐glycyrrhetinic acid, and conduction of phenylephrine‐induced constriction was abolished in absence of the endothelium. Constriction in response to high K+ was not conducted. Absence of remote stimulation dampened the local response to phenylephrine. Conclusion This study demonstrates maintained conduction of vasoactive responses to physiological agonists in rat mesenteric small arteries likely via gap junctions and endothelial cells, providing a possible mechanism for the sustained functional and structural control of arterial networks. - Acta Physiologica, Volume 224, Issue 3, November 2018.
    June 17, 2018   doi: 10.1111/apha.13099   open full text
  • A dual role of miR‐22 in rhabdomyolysis‐induced acute kidney injury.
    S. Mathia, L. J. Rudigier, M. Kasim, K. M. Kirschner, P. B. Persson, K.‐U. Eckardt, C. Rosenberger, M. Fähling.
    Acta Physiologica. June 14, 2018
    --- - |2+ Abstract Aim In acute kidney injury (AKI), regions of the kidney are hypoxic. However, for reasons yet unknown, adaptation to hypoxia through hypoxia‐inducible factor (HIF) is limited. Here, we studied miR‐22, a potential HIF repressor, in normal kidneys, as well as in rhabdomyolysis‐induced AKI, a condition where miR‐22 is up‐regulated. Methods AKI in mice was provoked by IM injection of glycerol. Tissue homogenates were processed to determine the levels of candidate RNAs and proteins, as well as global gene expression profiles. Reporter assays quantified in vitro miR‐22 activity and its modulation by mimic or inhibitor molecules, under normoxia or hypoxia (1% O2) respectively. In vivo, anti–miR‐22 molecules were applied to normal mice or prior to induction of AKI. Renal outcome was assessed by measuring plasma creatinine, plasma urea and the levels of the injury markers Kim‐1 and Ngal. Results Renal miR‐22 is inducible by hypoxia and represses hypoxia‐inducible factor (HIF). Specific inhibition of miR‐22 regulates 1913 gene transcripts in kidneys controls and 3386 in AKI, many of which are involved in development or carcinogenesis. Specific inhibition of miR‐22 up‐regulates tissue protective HIF target genes, yet renal function and injury markers are unchanged or worsened. Conclusions miR‐22 is a HIF repressor constitutively expressed in the adult kidney and up‐regulated in AKI. Specific inhibition of miR‐22 is efficient in vivo and profoundly affects renal gene expression in health and disease, including up‐regulation of HIF. However, the net effect on rhabdomyolysis‐induced AKI outcome is neutral or even negative. - Acta Physiologica, Volume 224, Issue 3, November 2018.
    June 14, 2018   doi: 10.1111/apha.13102   open full text
  • Less than recommended training of aerobic fitness and muscle strength: What to expect?
    H. B. Benestad, K. L. Sand, J. C. Bruusgaard.
    Acta Physiologica. June 11, 2018
    --- - - Acta Physiologica, EarlyView.
    June 11, 2018   doi: 10.1111/apha.13104   open full text
  • Physiological role of Kvβ2 (AKR6) in murine skeletal muscle growth and regulation.
    K. C. Chapalamadugu, J. Tur, S. L. Badole, R. C. Kukreja, M. Brotto, S. M. Tipparaju.
    Acta Physiologica. June 06, 2018
    --- - |2+ Abstract Aim Potassium channel accessory subunits (Kvβ) play a key role in cardiac electrical activity through ion channel modulation. In this study, we hypothesize that Kvβ2 regulates skeletal muscle growth and fibre phenotype via protein‐protein interactions. Methods Kvβ2 knockout mouse model was used for morphometric, immunohistochemical and biochemical analysis to evaluate the role of Kvβ2 in skeletal muscle physiology. Results Deletion of Kvβ2 gene in mice (Kvβ2 knockout, KO) leads to significant decrease in body weight along with skeletal muscle size. Key hindlimb muscles such as biceps, soleus and gastrocnemius were significantly smaller in size in KO mice compared to that of wild type. Morphometric measurements and histological analysis clearly point that the fibre size is decreased in each of the muscle type in KO compared with wild‐type mice. In addition, Kvβ2 deletion contributes to fibre‐type switching from fast to slow fibre as indicated by more abundant MHCI‐expressing fibres in gastrocnemius and soleus muscles, which may underscore the smaller muscle size alongside increase in U3 ubiquitin ligase; NEDD4 expression. Using targeted siRNA knockdown approach, we identified that Kvβ2 knockdown does not affect the myoblasts proliferation. However, Pax7 expression was significantly decreased in 4‐week‐old gastrocnemius muscle, suggesting that cellular reserve for growth may be deficient in KO mice. This is further supported by decreased migratory capacity of C2C12 cells upon siRNA‐targeted Kvβ2 knockdown. Conclusion Overall, this is the first report identifying that genetic deletion of Kvβ2 leads to decreased skeletal muscle size along with isotype switching. - Acta Physiologica, Volume 224, Issue 2, October 2018.
    June 06, 2018   doi: 10.1111/apha.13083   open full text
  • Remembrances of Ulf Svante von Euler.
    Rajko Igić.
    Acta Physiologica. June 05, 2018
    --- - - Acta Physiologica, Volume 224, Issue 3, November 2018.
    June 05, 2018   doi: 10.1111/apha.13098   open full text
  • Altered exocytosis in chromaffin cells from mouse models of neurodegenerative diseases.
    A. M. García Diego, A. García García.
    Acta Physiologica. June 04, 2018
    --- - |2 Abstract Chromaffin cells from the adrenal gland (CCs) have extensively been used to explore the molecular structure and function of the exocytotic machinery, neurotransmitter release and synaptic transmission. The CC is integrated in the sympathoadrenal axis that helps the body maintain homoeostasis during both routine life and in acute stress conditions. This function is exquisitely controlled by the cerebral cortex and the hypothalamus. We propose the hypothesis that damage undergone by the brain during neurodegenerative diseases is also affecting the neurosecretory function of adrenal medullary CCs. In this context, we review here the following themes: (i) How the discharge of catecholamines is centrally and peripherally regulated at the sympathoadrenal axis; (ii) which are the intricacies of the amperometric techniques used to study the quantal release of single‐vesicle exocytotic events; (iii) which are the alterations of the exocytotic fusion pore so far reported, in CCs of mouse models of neurodegenerative diseases; (iv) how some proteins linked to neurodegenerative pathologies affect the kinetics of exocytotic events; (v) finally, we try to integrate available data into a hypothesis to explain how the centrally originated neurodegenerative diseases may alter the kinetics of single‐vesicle exocytotic events in peripheral adrenal medullary CCs. - Acta Physiologica, Volume 224, Issue 2, October 2018.
    June 04, 2018   doi: 10.1111/apha.13090   open full text
  • Maternal exercise, season and sex modify the daily fetal heart rate rhythm.
    J. Sletten, G. Cornelissen, J. Assmus, T. Kiserud, S. Albrechtsen, J. Kessler.
    Acta Physiologica. June 01, 2018
    --- - |2+ Abstract Aim The knowledge on biological rhythms is rapidly expanding. We aimed to define the longitudinal development of the daily (24‐hour) fetal heart rate rhythm in an unrestricted, out‐of‐hospital setting and to examine the effects of maternal physical activity, season and fetal sex. Methods We recruited 48 women with low‐risk singleton pregnancies. Using a portable monitor for continuous fetal electrocardiography, fetal heart rate recordings were obtained around gestational weeks 24, 28, 32 and 36. Daily rhythms in fetal heart rate and fetal heart rate variation were detected by cosinor analysis; developmental trends were calculated by population‐mean cosinor and multilevel analysis. Results For the fetal heart rate and fetal heart rate variation, a significant daily rhythm was present in 122/123 (99.2%) and 116/121 (95.9%) of the individual recordings respectively. The rhythms were best described by combining cosine waves with periods of 24 and 8 hours. With increasing gestational age, the magnitude of the fetal heart rate rhythm increased, and the peak of the fetal heart rate variation rhythm shifted from a mean of 14:25 (24 weeks) to 20:52 (36 weeks). With advancing gestation, the rhythm‐adjusted mean value of the fetal heart rate decreased linearly in females (P < .001) and nonlinearly in males (quadratic function, P = .001). At 32 and 36 weeks, interindividual rhythm diversity was found in male fetuses during higher maternal physical activity and during the summer season. Conclusion The dynamic development of the daily fetal heart rate rhythm during the second half of pregnancy is modified by fetal sex, maternal physical activity and season. - Acta Physiologica, Volume 224, Issue 2, October 2018.
    June 01, 2018   doi: 10.1111/apha.13093   open full text
  • Targeting transcriptional control of soluble guanylyl cyclase via NOTCH for prevention of cardiovascular disease.
    C. Rippe, S. Albinsson, G. Guron, H. Nilsson, K. Swärd.
    Acta Physiologica. May 30, 2018
    --- - |2 Abstract Soluble guanylyl cyclase (sGC) is an effector enzyme of nitric oxide (NO). Recent work has unravelled how levels of this enzyme are controlled, and highlighted a role in vascular disease. We provide a timely summary of available knowledge on transcriptional regulation of sGC, including influences from the NOTCH signalling pathway and genetic variants. It is speculated that hypertension‐induced repression of sGC starts a vicious circle that can be initiated by periods of stress, diet or genetic factors, and a key tenet is that reduction in sGC further raises blood pressure. The idea that dysregulation of sGC contributes to syndromes caused by defective NOTCH signalling is advanced, and we discuss drug repositioning for vascular disease prevention. The advantage of targeting sGC expression rather than activity is also considered. It is argued that transcriptional inputs on sGC arise from interactions with other cells, the extracellular matrix and microRNAs (miRNAs), and concluded that the promise of sGC as a target for prevention of cardiovascular disease has increased in recent time. - Acta Physiologica, EarlyView.
    May 30, 2018   doi: 10.1111/apha.13094   open full text
  • Reduced fibre size, capillary supply and mitochondrial activity in constitutional thinness' skeletal muscle.
    B. Galusca, J. Verney, E. Meugnier, Y. Ling, P. Edouard, L. Feasson, M. Ravelojaona, H. Vidal, B. Estour, N. Germain.
    Acta Physiologica. May 30, 2018
    --- - |2+ Abstract Aim Constitutional thinness (CT) is a rare condition of natural low body weight, with no psychological issues, no marker of undernutrition and a resistance to weight gain. This study evaluated the skeletal muscle phenotype of CT women by comparison with a normal BMI control group. Methods Ten CT women (BMI < 17.5 kg/m2) and 10 female controls (BMI: 18.5‐25 kg/m2) underwent metabolic and hormonal assessment along with muscle biopsies to analyse the skeletal muscular fibres pattern, capillarity, enzymes activities and transcriptomics. Results Constitutional thinness displayed similar energy balance metabolic and hormonal profile to controls. Constitutional thinness presented with lower mean area of all the skeletal muscular fibres (−24%, P = .01) and percentage of slow‐twitch type I fibres (−25%, P = .02, respectively). Significant downregulation of the mRNA expression of several mitochondrial‐related genes and triglycerides metabolism was found along with low cytochrome c oxidase (COX) activity and capillary network in type I fibres. Pre‐ and post‐mitochondrial respiratory chain enzymes levels were found similar to controls. Transcriptomics also revealed downregulation of cytoskeletal‐related genes. Conclusion Diminished type I fibres, decreased mitochondrial and metabolic activity suggested by these results are discordant with normal resting metabolic rate of CT subjects. Downregulated genes related to cytoskeletal proteins and myocyte differentiation could account for CT's resistance to weight gain. - Acta Physiologica, Volume 224, Issue 3, November 2018.
    May 30, 2018   doi: 10.1111/apha.13097   open full text
  • Skin temperature may not yield human brown adipose tissue activity in diverse populations.
    J. T. Sarasniemi, K. Koskensalo, J. Raiko, P. Nuutila, J. Saunavaara, R. Parkkola, K. A. Virtanen.
    Acta Physiologica. May 28, 2018
    --- - - Acta Physiologica, Volume 224, Issue 3, November 2018.
    May 28, 2018   doi: 10.1111/apha.13095   open full text
  • Cardioprotective role of IGF‐1 in the hypertrophied myocardium of the spontaneously hypertensive rats: A key effect on NHE‐1 activity.
    A. M. Yeves, J. I. Burgos, A. J. Medina, M. C. Villa‐Abrille, I. L. Ennis.
    Acta Physiologica. May 28, 2018
    --- - |2+ Abstract Aim Myocardial Na+/H+ exchanger‐1 (NHE‐1) hyperactivity and oxidative stress are interrelated phenomena playing pivotal roles in the development of pathological cardiac hypertrophy and heart failure. Exercise training is effective to convert pathological into physiological hypertrophy in the spontaneously hypertensive rats (SHR), and IGF‐1—key humoral mediator of exercise training—inhibits myocardial NHE‐1, at least in normotensive rats. Therefore, we hypothesize that IGF‐1 by hampering NHE‐1 hyperactivity and oxidative stress should exert a cardioprotective effect in the SHR. Methods NHE‐1 activity [proton efflux () mmol L−1 min−1], expression and phosphorylation; H2O2 production; superoxide dismutase (SOD) activity; contractility and calcium transients were measured in SHR hearts in the presence/absence of IGF‐1. Results IGF‐1 significantly decreased NHE‐1 activity ( at pHi 6.95: 1.39 ± 0.32, n = 9 vs C 3.27 ± 0.3, n = 20, P < .05); effect prevented by AG1024, an antagonist of IGF‐1 receptor (2.7 ± 0.4, n = 7); by the PI3K inhibitor wortmannin (3.14 ± 0.41, n = 7); and the AKT inhibitor MK2206 (3.37 ± 0.43, n = 14). Moreover, IGF‐1 exerted an antioxidant effect revealed by a significant reduction in H2O2 production accompanied by an increase in SOD activity. In addition, IGF‐1 improved cardiomyocyte contractility as evidenced by an increase in sarcomere shortening and a decrease in the relaxation constant, underlined by an increase in the amplitude and rate of decay of the calcium transients. Conclusion IGF‐1 exerts a cardioprotective role on the hypertrophied hearts of the SHR, in which the inhibition of NHE‐1 hyperactivity, as well as the positive inotropic and antioxidant effects, emerges as key players. - Acta Physiologica, Volume 224, Issue 2, October 2018.
    May 28, 2018   doi: 10.1111/apha.13092   open full text
  • Decreased levels of keratin 8 sensitize mice to streptozotocin‐induced diabetes.
    C. M. Alam, J. S. G. Silvander, T. O. Helenius, D. M. Toivola.
    Acta Physiologica. May 22, 2018
    --- - |2+ Abstract Aim Diabetes is a result of an interplay between genetic, environmental and lifestyle factors. Keratin intermediate filaments are stress proteins in epithelial cells, and keratin mutations predispose to several human diseases. However, the involvement of keratins in diabetes is not well known. K8 and its partner K18 are the main β‐cell keratins, and knockout of K8 (K8−/−) in mice causes mislocalization of glucose transporter 2, mitochondrial defects, reduced insulin content and altered systemic glucose/insulin control. We hypothesize that K8/K18 offer protection during β‐cell stress and that decreased K8 levels contribute to diabetes susceptibility. Methods K8‐heterozygous knockout (K8+/−) and wild‐type (K8+/+) mice were used to evaluate the influence of keratin levels on endocrine pancreatic function and diabetes development under basal conditions and after T1D streptozotocin (STZ)‐induced β‐cell stress and T2D high‐fat diet (HFD). Results Murine K8+/− endocrine islets express ~50% less K8/K18 compared with K8+/+. The decreased keratin levels have little impact on basal systemic glucose/insulin regulation, β‐cell health or insulin levels. Diabetes incidence and blood glucose levels are significantly higher in K8+/− mice after low‐dose/chronic STZ treatment, and STZ causes more β‐cell damage and polyuria in K8+/− compared with K8+/+. K8 appears upregulated 5 weeks after STZ treatment in K8+/+ islets but not in K8+/−. K8+/− mice showed no major susceptibility risk to HFD compared to K8+/+. Conclusion Partial K8 deficiency reduces β‐cell stress tolerance and aggravates diabetes development in response to STZ, while there is no major susceptibility to HFD. - Acta Physiologica, Volume 224, Issue 2, October 2018.
    May 22, 2018   doi: 10.1111/apha.13085   open full text
  • Thermoregulatory profile of neurodegeneration‐induced dementia of the Alzheimer's type using intracerebroventricular streptozotocin in rats.
    A. C. P. Motzko‐Soares, R. C. L. Vizin, T. M. S. Martins, A. R. O. Hungaro, J. R. Sato, M. C. Almeida, D. C. Carrettiero.
    Acta Physiologica. May 22, 2018
    --- - |2+ Abstract Aim Here, we have extensively investigated the relationship between thermoregulation and neurodegeneration‐induced dementia of the Alzheimer's type using intracerebroventricular injections of streptozotocin (icv‐STZ). Methods Male Wistar rats were treated with bilateral injections of icv‐STZ, and their thermoregulatory profiles (core body temperature, tail‐skin temperature, cold and heat defence responses and thermal place preference) were evaluated. Spatial memory, locomotor activity, social interaction, brain ventricular volume, and Aβ1‐42 and tau protein levels in the brain were analysed to characterize the effects of STZ on the brain and behaviour. Results In addition to deficits in spatial memory, reduced social interaction and an increased brain ventricular volume, icv‐STZ rats presented a pattern of hyperthermia, as demonstrated by an increased core body temperature. Hyperthermia was due to the activation of both autonomic heat conservation and behavioural cold avoidance, as STZ‐treated rats presented tail‐cutaneous vasoconstriction and an altered thermal preference. They also showed a distinct cold defence response when exposed to cold. Conclusion Our data bring evidence that icv‐STZ in rats causes hyperthermia, with activation of both autonomic and behavioural thermoregulatory defence responses when challenged at colder temperatures, leading us to hypothesize that they are more efficient in preventing hypothermia. These data are relevant for a better understanding of neurodegenerative disease mechanisms. - Acta Physiologica, Volume 224, Issue 2, October 2018.
    May 22, 2018   doi: 10.1111/apha.13084   open full text
  • Trans‐life cycle acclimation to experimental ocean acidification affects gastric pH homeostasis and larval recruitment in the sea star Asterias rubens.
    M. Y. Hu, E. Lein, M. Bleich, F. Melzner, M. Stumpp.
    Acta Physiologica. May 09, 2018
    --- - |2+ Abstract Aim Experimental simulation of near‐future ocean acidification (OA) has been demonstrated to affect growth and development of echinoderm larval stages through energy allocation towards ion and pH compensatory processes. To date, it remains largely unknown how major pH regulatory systems and their energetics are affected by trans‐generational exposure to near‐future acidification levels. Methods Here, we used the common sea star Asterias rubens in a reciprocal transplant experiment comprising different combinations of OA scenarios, to study trans‐generational plasticity using morphological and physiological endpoints. Results Acclimation of adults to pHT 7.2 (pCO2 3500 μatm) led to reductions in feeding rates, gonad weight and fecundity. No effects were evident at moderate acidification levels (pHT 7.4; pCO2 2000 μatm). Parental pre‐acclimation to pHT 7.2 for 85 days reduced developmental rates even when larvae were raised under moderate and high pH conditions, whereas pre‐acclimation to pHT 7.4 did not alter offspring performance. Microelectrode measurements and pharmacological inhibitor studies carried out on larval stages demonstrated that maintenance of alkaline gastric pH represents a substantial energy sink under acidified conditions that may contribute up to 30% to the total energy budget. Conclusion Parental pre‐acclimation to acidification levels that are beyond the pH that is encountered by this population in its natural habitat (eg, pHT 7.2) negatively affected larval size and development, potentially through reduced energy transfer. Maintenance of alkaline gastric pH and reductions in maternal energy reserves probably constitute the main factors for a reduced juvenile recruitment of this marine keystone species under simulated OA. - Acta Physiologica, Volume 224, Issue 2, October 2018.
    May 09, 2018   doi: 10.1111/apha.13075   open full text
  • Acute mitogen activated protein kinase 1/2 inhibition improves functional recovery and vascular changes after ischemic stroke in rat‐ monitored by 9.4 T Magnetic Resonance Imaging.
    Maryam Mostajeran, Friedrich Wetterling, Frank W Blixt, Lars Edvinsson, Saema Ansar.
    Acta Physiologica. October 21, 2017
    Aim The aim was to evaluate the beneficial effect of early mitogen activated protein kinase (MEK)1/2 inhibition administered at a clinical relevant time‐point using the transient middle cerebral artery occlusion model and a dedicated rodent magnetic resonance imaging system (9.4T) to monitor cerebrovascular changes non‐invasively for two weeks. Method Transient middle cerebral artery occlusion was induced in male rats for two hours followed by reperfusion. The specific MEK1/2 inhibitor U0126 was administered i.p at 6 and 24 hours post‐reperfusion. Neurological functions were evaluated by 6‐ and 28‐point tests. 9.4 T magnetic resonance imaging was used to monitor morphological infarct changes at day 2, 8 and 14 after stroke and to evaluate cerebral perfusion at day 14.Immunohistochemistry evaluation of Ki67 was performed 14 days post‐stroke. Results U0126 improved long‐term behavioral outcome and significantly reduced infarct size. In addition, cerebral perfusion in U0126‐treated animals was improved compared to the vehicle group. Immunohistochemistry showed a significant increase of Ki67+ cells in U0126 treated animals compared to the vehicle group. Conclusion Early MEK1/2 inhibition improves long‐term functional outcome, promotes recovery processes after stroke and most importantly provides a realistic time window for therapy. This article is protected by copyright. All rights reserved.
    October 21, 2017   doi: 10.1111/apha.12985   open full text
  • Functional interaction of Junctophilin 2 with small conductance Ca2+‐activated potassium channel subtype 2(SK2) in mouse cardiac myocytes.
    Hong K. Fan, Tian X. Luo, Wei D. Zhao, Yong H. Mu, Yang Yang, Wen J. Guo, Hui Y. Tu, Qian Zhang.
    Acta Physiologica. October 21, 2017
    Aim Junctophilins (JPs), a protein family of the junctional membrane complex, maintain the close conjunction between cell surface and intracellular membranes in striate muscle cells mediating the cross talk between extracellular Ca2+ entry and intracellular Ca2+ release. The small conductance Ca2+‐activated K+ channels are activated by the intracellular calcium and play an essential role in the cardiac action potential profile. Molecular mechanisms of regulation of the SK channels are still uncertain. Here we sought to determine whether there is a functional interaction of junctophilin type 2(JP2) with the SK channels and whether JP2 gene silencing might modulate the SK channels function in cardiac myocytes. Methods Association of JP2 with SK2 channel in mouse heart tissue as well as HEK 293 cells was studied using in vivo and in vitro approaches. siRNA knockdown of JP2 gene was assessed by Real time PCR. The expression of proteins was analyzed by Western blotting. Ca2+‐activated K+ current (IK,Ca) in infected adult mouse cardiac myocytes was recorded using whole‐cell voltage‐clamp technique. The intracellular Ca2+ transient was measured using an IonOptix photometry system. Results We showed for the first time that JP2 associates with the SK2 channel in native cardiac tissue. JP2, via the Membrane Occupation and Recognition Nexus (MORN motifs) in its N terminus, directly interacted with SK2 channels. A co‐localization of the SK2 channel with its interaction protein of JP2 was found in the cardiac myocytes. Moreover, we demonstrated that JP2 is necessary for the proper cell‐surface expression of the SK2 channel in HEK293. Functional experiments indicated that knockdown of JP2 caused a significant decrease in the density of IK,Ca and reduced the amplitude of the Ca2+ transient in infected cardiomyocytes. Conclusions The present data provide evidence that the functional interaction between JP2 and SK2 channels is present in the native mouse heart tissue. Junctophilin 2, as junctional membrane complex (JMC)protein, is an important regulator of the cardiac SK channels. This article is protected by copyright. All rights reserved.
    October 21, 2017   doi: 10.1111/apha.12986   open full text
  • Chemokine (C‐X‐C motif) ligand 1 is a myokine induced by palmitate and is required for myogenesis in mouse satellite cells.
    S. Masuda, M. Tanaka, T. Inoue, R. Ohue‐Kitano, H. Yamakage, K. Muranaka, T. Kusakabe, A. Shimatsu, K. Hasegawa, N. Satoh‐Asahara.
    Acta Physiologica. October 19, 2017
    Aim The functional significance of the myokines, cytokines and peptides produced and released by muscle cells has not been fully elucidated. The purpose of this study was to identify a myokine with increased secretion levels in muscle cells due to saturated fatty acids and to examine the role of the identified myokine in the regulation of myogenesis. Methods Human primary myotubes and mouse C2C12 myotubes were used to identify the myokine; its secretion was stimulated by palmitate loading. The role of the identified myokine in the regulation of the activation, proliferation, differentiation and self‐renewal was examined in mouse satellite cells (skeletal muscle stem cells). Results Palmitate loading promoted the secretion of chemokine (C‐X‐C motif) ligand 1 (CXCL1) in human primary myotubes, and it also increased CXCL1 gene expression level in C2C12 myotubes in a dose‐ and time‐dependent manner. Palmitate loading increased the production of reactive oxygen species along with the activation of nuclear factor‐kappa B (NF‐κB) signalling. Pharmacological inhibition of NF‐κB signalling attenuated the increase in CXCL1 gene expression induced by palmitate and hydrogen peroxide. Palmitate loading significantly increased CXC receptor 2 gene expression in undifferentiated cells. CXCL1 knockdown attenuated proliferation and myotube formation by satellite cells, with reduced self‐renewal. CXCL1 knockdown also significantly decreased the Notch intracellular domain protein level. Conclusion These results suggest that secretion of the myokine CXCL1 is stimulated by saturated fatty acids and that CXCL1 promotes myogenesis from satellite cells to maintain skeletal muscle homeostasis.
    October 19, 2017   doi: 10.1111/apha.12975   open full text
  • Effects of manipulating tetanic calcium on the curvature of the force‐velocity relationship in isolated rat soleus muscles.
    A. M. Kristensen, O. B. Nielsen, K. Overgaard.
    Acta Physiologica. October 19, 2017
    Aim In dynamically contracting muscles, increased curvature of the force‐velocity relationship contributes to the loss of power during fatigue. It has been proposed that fatigue‐induced reduction in [Ca++]i causes this increased curvature. However, earlier studies on single fibres have been conducted at low temperatures. Here, we investigated the hypothesis that curvature is increased by reductions in tetanic [Ca++]i in isolated skeletal muscle at near‐physiological temperatures. Methods Rat soleus muscles were stimulated at 60 Hz in standard Krebs‐Ringer buffer, and contraction force and velocity were measured. Tetanic [Ca++]i was in some experiments either lowered by addition of 10 μmol/L dantrolene or use of submaximal stimulation (30 Hz) or increased by addition of 2 mmol/L caffeine. Force‐velocity curves were constructed by fitting shortening velocity at different loading forces to the Hill equation. Curvature was determined as the ratio a/F0 with increased curvature reflecting decreased a/F0. Results Compared to control levels, lowering tetanic [Ca++]i with dantrolene or reduced stimulation frequency decreased the curvature slightly as judged from increase in a/F0 of 13 ± 1% (P = < .001) and 20 ± 2% (P = < .001) respectively. In contrast, increasing tetanic [Ca++]i with caffeine increased the curvature (a/F0 decreased by 17 ± 1%; P = < .001). Conclusion Contrary to our hypothesis, interventions that reduced tetanic [Ca++]i caused a decrease in curvature, while increasing tetanic [Ca++]i increased the curvature. These results reject a simple causal relation between [Ca++]i and curvature of the force‐velocity relation during fatigue.
    October 19, 2017   doi: 10.1111/apha.12977   open full text
  • Uteroplacental insufficiency in rats induces renal apoptosis and delays nephrogenesis completion.
    James SM Cuffe, Jessica F. Briffa, Shannyn Rosser, Andrew L Siebel, Tania Romano, Deanne H. Hryciw, Mary E Wlodek, Karen M Moritz.
    Acta Physiologica. October 19, 2017
    Aim Uteroplacental insufficiency in rats reduces nephron endowment, leptin concentrations and programs cardiorenal disease in offspring. Cross‐fostering growth restricted (Restricted) offspring onto a mother with normal lactation restores leptin concentrations and nephron endowment. This study aimed to determine if the reduced nephron endowment in Restricted offspring is due to delayed glomerular formation and dysregulation of renal genes regulating branching morphogenesis, apoptosis or leptin signalling. Furthermore, we aimed to investigate if cross‐fostering Restricted offspring onto Control mothers could improve glomerular maturation and restore renal gene abundance. Methods Uteroplacental insufficiency was induced by bilateral uterine vessel ligation (Restricted) or sham (Control) surgery on gestation day 18 (E18). Kidneys were collected at E20, postnatal day 1 (PN1) and PN7. An additional cohort was cross‐fostered onto separate mothers at birth and kidneys collected at PN7. Results Kidneys were lighter in the Restricted group, but weight was restored with cross‐fostering. At E20, Bax, Flt1 and Vegfa abundance were increased in Restricted offspring, while Ret and Bcl2 transcripts were increased only in Restricted females. At PN7, Gdnf and Ret abundance were higher in Restricted offspring, as was Casp3. Restricted offspring had a wider nephrogenic zone with more immature glomeruli suggesting a delayed or extended nephrogenic period. Cross‐fostering had subtle effects on gene abundance and glomerular maturity. Conclusion Uteroplacental insufficiency induced apoptosis in the developing kidney and delayed and extended nephrogenesis. Cross‐fostering Restricted offspring onto Control mothers had beneficial effects on kidney growth and renal maturity, which may contribute to the restoration of nephron endowment. This article is protected by copyright. All rights reserved.
    October 19, 2017   doi: 10.1111/apha.12982   open full text
  • Genetic ablation of carbonic anhydrase IX disrupts gastric barrier function via claudin‐18 downregulation and acid backflux.
    T. Li, X. Liu, B. Riederer, K. Nikolovska, A. K. Singh, K. A. Mäkelä, A. Seidler, Y. Liu, G. Gros, H. Bartels, K. H. Herzig, U. Seidler.
    Acta Physiologica. October 19, 2017
    Aim This study aimed to explore the molecular mechanisms for the parietal cell loss and fundic hyperplasia observed in gastric mucosa of mice lacking the carbonic anhydrase 9 (CAIX). Methods We assessed the ability of CAIX‐knockout and WT gastric surface epithelial cells to withstand a luminal acid load by measuring the pHi of exteriorized gastric mucosa in vivo using two‐photon confocal laser scanning microscopy. Cytokines and claudin‐18A2 expression was analysed by RT‐PCR. Results CAIX‐knockout gastric surface epithelial cells showed significantly faster pHi decline after luminal acid load compared to WT. Increased gastric mucosal IL‐1β and iNOS, but decreased claudin‐18A2 expression (which confer acid resistance) was observed shortly after weaning, prior to the loss of parietal and chief cells. At birth, neither inflammatory cytokines nor claudin‐18 expression were altered between CAIX and WT gastric mucosa. The gradual loss of acid secretory capacity was paralleled by an increase in serum gastrin, IL‐11 and foveolar hyperplasia. Mild chronic proton pump inhibition from the time of weaning did not prevent the claudin‐18 decrease nor the increase in inflammatory markers at 1 month of age, except for IL‐1β. However, the treatment reduced the parietal cell loss in CAIX‐KO mice in the subsequent months. Conclusions We propose that CAIX converts protons that either backflux or are extruded from the cells rapidly to CO2 and H2O, contributing to tight junction protection and gastric epithelial pHi regulation. Lack of CAIX results in persistent acid backflux via claudin‐18 downregulation, causing loss of parietal cells, hypergastrinaemia and foveolar hyperplasia.
    October 19, 2017   doi: 10.1111/apha.12923   open full text
  • Knock‐out of histamine receptor H3 alters adaptation to sudden darkness and monoamine levels in the zebrafish.
    Henri A. J. Puttonen, Maria Sundvik, Svetlana Semenova, Yukako Shirai, Yu‐Chia Chen, Pertti Panula.
    Acta Physiologica. October 16, 2017
    Aim Histamine receptor H3 has substantial neuropharmacological potential. Currently, knock‐out models of this receptor have been investigated only in mice. We characterized the expression of this receptor in the zebrafish and generated a zebrafish histamine receptor H3 knock‐out line. Using this model, we studied the role of histamine receptor H3 in important behaviours. We also analyzed the effect of histamine receptor H3 knock‐out on monoaminergic systems, which has not been thoroughly studied in any animal model. Methods Generation of a mutant zebrafish line using the CRISPR/Cas9 system. Analysis of locomotor and social behaviour. Expression of histamine receptor H3 was characterized using in situ hybridization. Analysis of monoamine networks using HPLC, immunohistochemistry and quantitative PCR. Results We found that histamine receptor H3 knock‐out zebrafish larvae showed a shorter period of increased locomotion after a sudden onset of darkness, while the knock‐out larvae had a wild type like acute response to sudden darkness. Adult knock‐out fish showed decreased swimming velocity, although locomotor activity of knock‐out larvae was unaltered. Additionally, levels of dopamine and serotonin were significantly decreased in the knock‐out fish, while monoamine‐related gene expression and immunohistochemistry patterns were unchanged. Conclusions Our results show that histamine receptor H3 knock‐out larvae adapt faster to sudden darkness, suggesting a role for this receptor in regulating responses to changes in the environment. The decreased levels of dopamine and serotonin provides the first direct evidence that knock‐out of histamine receptor H3 alters these systems. This article is protected by copyright. All rights reserved.
    October 16, 2017   doi: 10.1111/apha.12981   open full text
  • Muscle specific differences in expression and phosphorylation of the Janus kinase 2/ Signal Transducer and Activator of Transcription 3 following long‐term mechanical ventilation and immobilization in rats.
    Heba Salah, Wen Fury, Jesper Gromada, Yu Bai, Tamar Tchkonia, James L. Kirkland, Lars Larsson.
    Acta Physiologica. October 15, 2017
    Aim Muscle wasting is one of the factors most strongly predicting mortality and morbidity in critically ill intensive care unit (ICU). This muscle wasting affects both limb and respiratory muscles but the understanding of underlying mechanisms and muscle‐specific differences remains incomplete. This study aims at investigating the temporal expression and phosphorylation of the Janus kinase / signal transducer and activator of transcription (JAK/STAT) pathway in muscle wasting associated with the ICU condition in order to characterize the JAK/STAT proteins and the related changes leading or responding to their activation during exposure to the ICU condition. Methods A novel experimental ICU model allowing long‐term exposure to the ICU condition, immobilization and mechanical ventilation, was used in this study. Rats were pharmacologically paralyzed by post‐synaptic neuromuscular blockade and mechanically ventilated for durations varying between 6 hours and 14 days to study muscle‐specific differences in the temporal activation of the JAK/STAT pathway in plantaris, intercostal and diaphragm muscles. Results The JAK2/STAT3 pathway was significantly activated irrespective of muscle, but muscle‐specific differences were observed in the temporal activation pattern between plantaris, intercostal, and diaphragm muscles. Conclusion The JAK2/STAT3 pathway was differentially activated in plantaris, intercostal, and diaphragm muscles in response to the ICU condition. Thus, JAK2/STAT3 inhibitors may provide an attractive pharmacological intervention strategy in immobilized ICU patients, but further experimental studies are required in the study of muscle‐specific effects on muscle mass and function in response to both short‐ and long‐term exposure to the ICU condition prior to the translation into clinical research and practice. This article is protected by copyright. All rights reserved.
    October 15, 2017   doi: 10.1111/apha.12980   open full text
  • MicroRNA‐214‐3p: A link between autophagy and endothelial cell dysfunction in atherosclerosis.
    J. Wang, W.‐N. Wang, S.‐B. Xu, H. Wu, B. Dai, D.‐D. Jian, M. Yang, Y.‐T. Wu, Q. Feng, J.‐H. Zhu, L. Zhang, L. Zhang.
    Acta Physiologica. October 14, 2017
    Aim Endothelial cell injury assumes a fundamental part in the pathogenesis of atherosclerosis, and endothelial cell autophagy has protective effects on the development of atherosclerosis, although the underlying molecular regulation mechanism is indistinct. This study aimed to investigate whether microRNA‐214‐3p (miR‐214‐3p) is involved in the endothelial cell autophagy regulation of atherosclerosis. Methods We utilized ApoE−/− mice provided with a high‐fat diet (HFD) as atherosclerosis model. We analysed the level of miR‐214‐3p and the levels of autophagy‐related protein 5 (ATG5) and autophagy‐related protein 12 (ATG12) in the purified CD31+ endothelial cells from mouse aorta. Bioinformatics analysis and a dual‐luciferase reporter assay were performed to confirm the binding target of miR‐214‐3p. In vitro study, human umbilical vein endothelial cells (HUVECs) were transfected with miR‐214‐3p mimics/inhibitor and stimulated with 100 μg/mL oxidized low‐density lipoprotein (ox‐LDL) for 12 hours to initiate a stress‐repairing autophagic process. Results In mouse models, we identified an inverse correlation between miR‐214‐3p, ATG5 and ATG12. We observed that in young HUVECs, ox‐LDL‐initiated autophagy was repressed by miR‐214‐3p overexpression, as evaluated by autophagic protein analysis, microtubule‐associated protein 1 light chain 3B‐II (LC3B‐II) immunofluorescence assay and transmission electron microscopy (TEM). Also, miR‐214‐3p promoted ox‐LDL accumulation in HUVECs and THP‐1 monocyte adhesion. Conversely, in old HUVECs, suppression of miR‐214‐3p preserved the ability to initiate a protective autophagy reaction to the ox‐LDL stimulation. Conclusion miR‐214‐3p regulates ox‐LDL‐initiated autophagy in HUVECs by directly targeting the 3′UTR of ATG5 and may have a suitable role in the pathogenesis of atherosclerosis.
    October 14, 2017   doi: 10.1111/apha.12973   open full text
  • Molecular pathways of Estrogen receptors and β‐adrenergic receptors in cardiac cells: Recognition of their similarities, interactions and therapeutic value.
    Machuki Ong'achwa Jeremiah, Hong‐Yuan Zhang, Sian Harding, Hong Sun.
    Acta Physiologica. October 09, 2017
    Estrogen receptors (ERs) and β‐adrenergic receptors (βARs) play important roles in the cardiovascular system. Moreover, these receptors are expressed in cardiac myocytes and vascular tissues. Numerous experimental observations support the hypothesis that similarities and interactions exist between the signaling pathways of ERs (ERα, ERβ, GPR30) and βARs (β1, β2, and β3AR). The recently discovered estrogen receptor GPR30 shares structural features with the βARs, and this forms the basis for the interactions and functional overlap. GPR30 possess protein kinase A (PKA) phosphorylation sites, PDZ binding motifs, and interacts with A‐kinase anchoring protein 5 (AKAP5), all of which enable its interaction with the βARs pathways. The interactions between ERs and βARs occur downstream of the G protein‐coupled receptor, through the Gαs and Gαi proteins. This review presents an up‐to‐date description of ERs and βARs and demonstrates functional synergism and interactions between these receptors in cardiac cells. We explore their signaling cascades and the mechanisms that orchestrate their interactions and propose new perspectives on the signaling patterns for the GPR30 based on its structural resemblance to the βARs. In addition, we explore the relevance of these interactions to cell physiology, drugs (especially β‐blockers and calcium channels blockers), and cardioprotection. Furthermore, a receptor‐independent mechanism for estrogen and its influence on the expression of βARs and calcium‐handling proteins are discussed. Finally, we highlight promising therapeutic avenues that can be derived from the shared pathways, especially the phosphatidylinositol‐3‐OH kinase (PI3K/Akt) pathway. This article is protected by copyright. All rights reserved.
    October 09, 2017   doi: 10.1111/apha.12978   open full text
  • A method for assessment of the dynamic response of the arterial baroreflex.
    M. T. Lund, M. Salomonsson, T. E. N. Jonassen, N.‐H. Holstein‐Rathlou.
    Acta Physiologica. September 26, 2017
    Aim The baroreflex is a key mechanism in cardiovascular regulation, and alterations in baroreceptor function are seen in many diseases, including heart failure, obesity and hypertension. We propose a new method for analysing baroreceptor function from continuous blood pressure (BP) and heart rate (HR) in both health and disease. Methods Forty‐eight‐hour data series of BP and HR were collected with telemetry. Sprague Dawley rats on standard chow (n = 11) served as controls, while rats on a high‐fat, high‐fructose (HFHC) diet (n = 6) constituted the obese‐hypertensive model. A third group of rats underwent autonomic blockade (n = 6). An autoregressive–moving‐average with exogenous inputs (ARMAX) model was applied to the data and compared with the α‐coefficient. Results Autonomic blockade caused a significant reduction in the strength of the baroreflex as estimated by ARMAX [ARMAX‐ baroreflex sensitivity (BRS)] −0.03 ± 0.01 vs. −0.19 ± 0.04 bpm heartbeat−1). Both methods showed a ~50% reduction in BRS in the obese‐hypertensive group compared with control (body weight 531 ± 27 vs. 458 ± 19 g, P < 0.05; mean arterial pressure 119 ± 3 vs. 102 ± 1 mmHg, P < 0.05; ARMAX‐BRS −0.08 ± 0.01 vs. −0.15 ± 0.01 bpm heartbeat−1, P < 0.05; α‐coefficient BRS 0.51 ± 0.07 vs. 0.89 ± 0.07 ms mmHg−1, P < 0.05). The ARMAX method additionally showed the open‐loop gain of the baroreflex to be reduced by ~50% in the obese‐hypertensive group (−2.3 ± 0.3 vs. −4.1 ± 0.3 bpm, P < 0.05), while the rate constant was similar between groups. Conclusion The ARMAX model represents an efficient method for estimating several aspects of the baroreflex. The open‐loop gain of the baroreflex was attenuated in obese‐hypertensive rats compared with control, while the time response was similar. The algorithm can be applied to other species including humans.
    September 26, 2017   doi: 10.1111/apha.12962   open full text
  • SUMO co‐expression modifies KV11.1 channel activity.
    A. B. Steffensen, M. N. Andersen, N. Mutsaers, A. Mujezinovic, N. Schmitt.
    Acta Physiologica. September 26, 2017
    Aim The voltage‐gated potassium channel KV11.1 is the molecular basis for the IKr current, which plays an important role in cardiac physiology. Its malfunction is associated with both inherited and acquired cardiac arrhythmias. Native currents differ from those in experimental models, suggesting additional regulatory mechanisms. We hypothesized that the post‐translational modification sumoylation fine‐tunes channel activity. Methods The functional effects of sumoylation on KV11.1 were addressed by employing two‐electrode voltage‐clamp (TEVC) experiments in Xenopus laevis oocytes. Site‐directed mutagenesis enabled a further analysis of the SUMO‐target amino acids. We assessed protein expression levels and used confocal imaging for localization studies. Results Co‐expression with Ubc9 and SUMO alters the electrophysiological properties of KV11.1 leading to a decrease in steady‐state current amplitude largely due to faster inactivation and alteration of deactivation kinetics. We identified three lysines (K21, K93 and K116) in the PAS domain as the putative SUMO‐targets. Conclusion This study indicates KV11.1 as a sumoylation target and offers three main targets: K21, K93, and K116. Furthermore, it proposes an underlying mechanism for the observed kinetic impact of the PAS domain.
    September 26, 2017   doi: 10.1111/apha.12974   open full text
  • Autophagic dysfunction and autophagosome escape in the mdx mus musculus model of Duchenne muscular dystrophy.
    H. R. Spaulding, E. M. Kelly, J. C. Quindry, J. B. Sheffield, M. B. Hudson, J. T. Selsby.
    Acta Physiologica. September 20, 2017
    Aim Duchenne muscular dystrophy is caused by the absence of functional dystrophin protein and results in a host of secondary effects. Emerging evidence suggests that dystrophic pathology includes decreased pro‐autophagic signalling and suppressed autophagic flux in skeletal muscle, but the relationship between autophagy and disease progression is unknown. The purpose of this investigation was to determine the extent to which basal autophagy changes with disease progression. We hypothesized that autophagy impairment would increase with advanced disease. Methods To test this hypothesis, 7‐week‐old and 17‐month‐old dystrophic diaphragms were compared to each other and age‐matched controls. Results Changes in protein markers of autophagy indicate impaired autophagic stimulation through AMPK, however, robust pathway activation in dystrophic muscle, independent of disease severity. Relative protein abundance of p62, an inverse correlate of autophagic degradation, was dramatically elevated with disease regardless of age. Likewise, relative protein abundance of Lamp2, a lysosome marker, was decreased twofold at 17 months of age in dystrophic muscle and was confirmed, along with mislocalization, in histological samples, implicating lysosomal dysregulation in this process. In dystrophic muscle, autophagosome‐sized p62‐positive foci were observed in the extracellular space. Moreover, we found that autophagosomes were released from both healthy and dystrophic diaphragms into the extracellular environment, and the occurrence of autophagosome escape was more frequent in dystrophic muscle. Conclusion These findings suggest autophagic dysfunction proceeds independent of disease progression and blunted degradation of autophagosomes is due in part to decreased lysosome abundance, and contributes to autophagosomal escape to the extracellular space.
    September 20, 2017   doi: 10.1111/apha.12944   open full text
  • High doses of anti‐inflammatory drugs compromise muscle strength and hypertrophic adaptations to resistance training in young adults.
    M. Lilja, M. Mandić, W. Apró, M. Melin, K. Olsson, S. Rosenborg, T. Gustafsson, T. R. Lundberg.
    Acta Physiologica. September 16, 2017
    Aims This study tested the hypothesis that high doses of anti‐inflammatory drugs would attenuate the adaptive response to resistance training compared with low doses. Methods Healthy men and women (aged 18–35 years) were randomly assigned to daily consumption of ibuprofen (IBU; 1200 mg; n = 15) or acetylsalicylic acid (ASA; 75 mg; n = 16) for 8 weeks. During this period, subjects completed supervised knee‐extensor resistance training where one leg was subjected to training with maximal volitional effort in each repetition using a flywheel ergometer (FW), while the other leg performed conventional (work‐matched across groups) weight‐stack training (WS). Before and after training, muscle volume (MRI) and strength were assessed, and muscle biopsies were analysed for gene and protein expression of muscle growth regulators. Results The increase in m. quadriceps volume was similar between FW and WS, yet was (averaged across legs) greater in ASA (7.5%) compared with IBU (3.7%, group difference 34 cm3; P = 0.029). In the WS leg, muscle strength improved similarly (11–20%) across groups. In the FW leg, increases (10–23%) in muscle strength were evident in both groups yet they were generally greater (interaction effects P < 0.05) for ASA compared with IBU. While our molecular analysis revealed several training effects, the only group interaction (P < 0.0001) arose from a downregulated mRNA expression of IL‐6 in IBU. Conclusion Maximal over‐the‐counter doses of ibuprofen attenuate strength and muscle hypertrophic adaptations to 8 weeks of resistance training in young adults. Thus, young individuals using resistance training to maximize muscle growth or strength should avoid excessive intake of anti‐inflammatory drugs.
    September 16, 2017   doi: 10.1111/apha.12948   open full text
  • Study of termination of postprandial gastric contractions in humans, dogs and Suncus murinus: role of motilin‐ and ghrelin‐induced strong contraction.
    T. Mikami, K. Ito, H. O. Diaz‐Tartera, P. M. Hellström, E. Mochiki, S. Takemi, T. Tanaka, S. Tsuda, T. Jogahara, I. Sakata, T. Sakai.
    Acta Physiologica. September 16, 2017
    Aim Stomach contractions show two types of specific patterns in many species, that is migrating motor contraction (MMC) and postprandial contractions (PPCs), in the fasting and fed states respectively. We found gastric PPCs terminated with migrating strong contractions in humans, dogs and suncus. In this study, we reveal the detailed characteristics and physiological implications of these strong contractions of PPC. Methods Human, suncus and canine gastric contractions were recorded with a motility‐monitoring ingestible capsule and a strain‐gauge force transducer. The response of motilin and ghrelin and its receptor antagonist on the contractions were studied by using free‐moving suncus. Results Strong gastric contractions were observed at the end of a PPC in human, dog and suncus models, and we tentatively designated this contraction to be a postprandial giant contraction (PPGC). In the suncus, the PPGC showed the same property as those of a phase III contraction of MMC (PIII‐MMC) in the duration, motility index and response to motilin or ghrelin antagonist administration. Ghrelin antagonist administration in the latter half of the PPC (LH‐PPC) attenuated gastric contraction prolonged the duration of occurrence of PPGC, as found in PII‐MMC. Conclusion It is thought that the first half of the PPC changed to PII‐MMC and then terminated with PIII‐MMC, suggesting that PPC consists of a digestive phase (the first half of the PPC) and a discharge phase (LH‐PPC) and that LH‐PPC is coincident with MMC. In this study, we propose a new approach for the understanding of postprandial contractions.
    September 16, 2017   doi: 10.1111/apha.12933   open full text
  • Orexin A increases sympathetic nerve activity through promoting expression of proinflammatory cytokines in Sprague‐Dawley rats.
    Yuanyuan Fan, Enshe Jiang, Taija Hahka, Qinghui Chen, Jianqun Yan, Zhiying Shan.
    Acta Physiologica. September 05, 2017
    Aim Accumulating evidence suggests that orexin signaling is involved in the regulation of blood pressure and cardiovascular function. However, the underlying mechanisms are not clear. Here we test the hypothesis that upregulated orexin A signaling in the paraventricular nucleus (PVN) increases sympathetic nerve activity (SNA) through stimulating expression of proinflammatory cytokines (PICs). Methods In vivo sympathetic nerve recordings were performed to test the impact of PVN orexin signaling on sympathetic outflow in Sprague‐Dawley (SD) rats. Real‐time PCR was carried out to assess effects of central administration of orexin A on PVN PICs expression in SD rats. To test whether orexin A induced increases in PICs were exclusively mediated by orexin receptor 1 (OX1R), OX1R expressing PC12 (PC12‐OX1R) cells were incubated with different dose of orexin A, then PICs mRNA and immunoreactivity were measured. Results Orexin A microinjection (25 pmol) into the PVN significantly increased splanchnic SNA (93.5%) and renal SNA (83.3%) in SD rats, and these increases were attenuated by OX1R antagonist SB408124. Intracerebroventricular injection of orexin A (0.2 nmol) into SD rats increased mRNA levels of PICs including IL1‐β (2.7‐fold), IL6 (1.7‐fold) and TNF‐α (1.5‐fold), as well as Fra1 (1.6‐fold) in the PVN. Orexin A treatment in PC12‐OX1R cells resulted in a dose‐ and time‐dependent increase in the expression of PICs and Fra1, a subunit of AP1 transcriptional factor. The increase in the PICs was blocked by AP1 blocker curcumin. Conclusion PVN orexin system activation is involved in SNA regulation maybe through triggering AP1‐PICs pathway. This article is protected by copyright. All rights reserved.
    September 05, 2017   doi: 10.1111/apha.12963   open full text
  • Apelin‐induced cardioprotection against ischaemia/reperfusion injury: roles of epidermal growth factor and Src.
    A. Folino, L. Accomasso, C. Giachino, P. G. Montarolo, G. Losano, P. Pagliaro, R. Rastaldo.
    Acta Physiologica. August 30, 2017
    Aim Apelin, the ligand of the G‐protein‐coupled receptor (GPCR) APJ, exerts a post‐conditioning‐like protection against ischaemia/reperfusion injury through activation of PI3K‐Akt‐NO signalling. The pathway connecting APJ to PI3K is still unknown. As other GPCR ligands act through transactivation of epidermal growth factor receptor (EGFR) via a matrix metalloproteinase (MMP) or Src kinase, we investigated whether EGFR transactivation is involved in the following three features of apelin‐induced cardioprotection: limitation of infarct size, suppression of contracture and improvement of post‐ischaemic contractile recovery. Method Isolated rat hearts underwent 30 min of global ischaemia and 2 h of reperfusion. Apelin (0.5 μm) was infused during the first 20 min of reperfusion. EGFR, MMP or Src was inhibited to study the pathway connecting APJ to PI3K. Key components of RISK pathway, namely PI3K, guanylyl cyclase or mitochondrial K+‐ATP channels, were also inhibited. Apelin‐induced EGFR and phosphatase and tensing homolog (PTEN) phosphorylation were assessed. Left ventricular pressure and infarct size were measured. Results Apelin‐induced reductions in infarct size and myocardial contracture were prevented by the inhibition of EGFR, Src, MMP or RISK pathway. The involvement of EGFR was confirmed by its phosphorylation. However, neither direct EGFR nor MMP inhibition affected apelin‐induced improvement of early post‐ischaemic contractile recovery, which was suppressed by Src and RISK inhibitors only. Apelin also increased PTEN phosphorylation, which was removed by Src inhibition. Conclusion While EGFR and MMP limit infarct size and contracture, Src or RISK pathway inhibition suppresses the three features of cardioprotection. Src does not only transactivate EGFR, but also inhibits PTEN by phosphorylation thus playing a crucial role in apelin‐induced cardioprotection.
    August 30, 2017   doi: 10.1111/apha.12924   open full text
  • Overexpression of integrin α11 induces cardiac fibrosis in mice.
    A. Romaine, I. W. Sørensen, C. Zeltz, N. Lu, P. M. Erusappan, A. O. Melleby, L. Zhang, B. Bendiksen, E. L. Robinson, J. M. Aronsen, K. M. Herum, H. E. Danielsen, I. Sjaastad, G. Christensen, D. Gullberg.
    Acta Physiologica. August 30, 2017
    Aim To understand the role of the collagen‐binding integrin α11 in vivo, we have used a classical approach of creating a mouse strain overexpressing integrin α11. A transgenic mouse strain overexpressing α11 in muscle tissues was analysed in the current study with special reference to the heart tissue. Methods We generated and phenotyped integrin α11 transgenic (TG) mice by echocardiography, magnetic resonance imaging and histology. Wild‐type (WT) mice were subjected to aortic banding (AB) and the expression of integrin α11 was measured in flow cytometry‐sorted cardiomyocytes and non‐myocytes. Results TG mice developed left ventricular concentric hypertrophy by 6 months, with increased collagen deposition and reactivation of mRNA encoding foetal genes associated with cardiovascular pathological remodelling compared to WT mice. Masson's trichrome staining revealed interstitial fibrosis, confirmed additionally by magnetic resonance imaging and was found to be most prominent in the cardiac septum of TG but not WT mice. TG hearts expressed increased levels of transforming growth factor‐β2 and transforming growth factor‐β3 and upregulated smooth muscle actin. Macrophage infiltration coincided with increased NF‐κB signalling in TG but not WT hearts. Integrin α11 expression was increased in both cardiomyocytes and non‐myocyte cells from WT AB hearts compared to sham‐operated animals. Conclusion We report for the first time that overexpression of integrin α11 induces cardiac fibrosis and left ventricular hypertrophy. This is a result of changes in intracellular hypertrophic signalling and secretion of soluble factors that increase collagen production in the heart.
    August 30, 2017   doi: 10.1111/apha.12932   open full text
  • TRPM5 in the battle against diabetes and obesity.
    Rudi Vennekens, Margot Mesuere, Koenraad Philippaert.
    Acta Physiologica. August 21, 2017
    TRPM5 is a nonselective monovalent cation channel activated by increases of intracellular Ca2+. It has a distinct expression pattern: expression is detected in chemosensitive tissues from solitary chemosensory cells to the taste receptor cells and in pancreatic β‐cells. The role of TRPM5 has been investigated with the use of knockout mouse models. Trpm5‐/‐ mice have a lack of type II taste perception and show reduced glucose‐induced insulin secretion. Expression levels of TRPM5 are reduced in obese, leptin signaling deficient mice and mutations in TRPM5 have been associated with type II diabetes and metabolic syndrome. In this review we aim to give an overview of the activation, selectivity, modulation and physiological roles of TRPM5. This article is protected by copyright. All rights reserved.
    August 21, 2017   doi: 10.1111/apha.12949   open full text
  • Extravasal albumin concentration modulates contractile responses of renal afferent arterioles.
    X. Gao, Z. Z. Liu, H. Mohammed, D. Braun, Z. Zhuge, M. Liu, E. Y. Lai, L. Jansson, M. Carlström, A. Patzak, A. E. G. Persson.
    Acta Physiologica. August 19, 2017
    Aim Afferent arterioles (AA) hold a key position in the regulation of renal blood flow and glomerular filtration rate. Being the effector site of tubuloglomerular feedback, the afferent arteriole contributes to the renal handling of sodium and fluid. Dehydration goes along with increased renal interstitial protein concentration. Here, the hypothesis was tested that extravasal protein concentration directly modulates afferent arteriolar tone, a mechanism which may contribute to body fluid volume control. Method The effect of increased extravasal albumin concentration on the vascular reactivity was investigated in renal AA and interlobar arteries of mice, in rat renal AA and in pancreatic islet arterioles. Results Albumin (2 and 4% in the bath solution) significantly potentiated the contractile response of renal afferent arterioles induced by angiotensin II and adenosine, as well as their combination, compared to the control situation (0.1% albumin). Albumin did not influence the contractility of larger renal vessels or pancreatic islet arterioles. Mimicking the increase in the osmolality induced by 4% albumin by applying mannitol to the bath solution also increased the response of renal arterioles to Ang II. However, the effect was smaller compared to that of albumin. The nitric oxide bioavailability, measured by DAF‐FM fluorescence, was reduced in afferent arterioles exposed to 4% albumin. Conclusion The protein‐induced modulation of AA tone is mediated by the increased osmolality as well as by NO scavenging. The results suggest a possible contribution of these mechanisms to the control of extracellular fluid volume via adjustment of renal blood flow and glomerular filtration rate.
    August 19, 2017   doi: 10.1111/apha.12925   open full text
  • MICAL2 promotes breast cancer cell migration by maintaining epidermal growth factor receptor (EGFR) stability and EGFR/P38 signalling activation.
    Y. Wang, W. Deng, Y. Zhang, S. Sun, S. Zhao, Y. Chen, X. Zhao, L. Liu, J. Du.
    Acta Physiologica. August 19, 2017
    Aim MICAL2, a cytoskeleton dynamics regulator, is identified associated with survival and metastasis of several types of cancers recently. This study was designed to investigate the role of MICAL2 in breast cancer cell migration as well as its underlying mechanisms. Methods The relationship between MICAL2 and EGF/EGFR signalling was analysed by gene overexpression and knock‐down techniques. Cell migration was measured by wound‐healing assays. Activation of EGF/EGFR signalling pathways were evaluated by immunofluorescence, qPCR, Western blotting and zymography techniques. Rac1 activity was assessed by pull‐down assay. Correlation of MICAL2 and EGFR in breast cancer specimens was examined by immunohistochemical analysis. Results Ectopic expression of MICAL2 in MCF‐7 cells augmented EGFR protein level, accompanied by the promotion of cell migration. Silencing MICAL2 in MDA‐MB‐231 cells destabilized EGFR and inhibited cell migration. In mechanism, the maintaining effect of MICAL2 on EGFR protein content was due to a delay in EGFR degradation. Expression of MICAL2 was also shown positively correlated with the activation of P38/HSP27 and P38/MMP9 signallings, which are the main downstream signalling cascades of EGF/EGFR involved in cell migration. Further analysis indicated that Rac1 activation contributed to the maintaining effect of MICAL2 on EGFR stability. In addition, analysis of breast cancer specimens revealed a positive correlation between MICAL2 and EGFR levels and an association between MICAL2 expression and worse prognosis. Conclusion MICAL2 is a major regulator of breast cancer cell migration, maintaining EGFR stability and subsequent EGFR/P38 signalling activation through inhibiting EGFR degradation in a Rac1‐dependent manner.
    August 19, 2017   doi: 10.1111/apha.12920   open full text
  • Serotonergic paraneurones in the female mouse urethral epithelium and their potential role in peripheral sensory information processing.
    F. A. Kullmann, H. H. Chang, C. Gauthier, B. M. McDonnell, J.‐C. Yeh, D. R. Clayton, A. J. Kanai, W. C. Groat, G. L. Apodaca, L. A. Birder.
    Acta Physiologica. August 08, 2017
    Aim The mechanisms underlying detection and transmission of sensory signals arising from visceral organs, such as the urethra, are poorly understood. Recently, specialized ACh‐expressing cells embedded in the urethral epithelium have been proposed as chemosensory sentinels for detection of bacterial infection. Here, we examined the morphology and potential role in sensory signalling of a different class of specialized cells that express serotonin (5‐HT), termed paraneurones. Methods Urethrae, dorsal root ganglia neurones and spinal cords were isolated from adult female mice and used for immunohistochemistry and calcium imaging. Visceromotor reflexes (VMRs) were recorded in vivo. Results We identified two morphologically distinct groups of 5‐HT+ cells with distinct regional locations: bipolar‐like cells predominant in the mid‐urethra and multipolar‐like cells predominant in the proximal and distal urethra. Sensory nerve fibres positive for calcitonin gene‐related peptide, substance P, and TRPV1 were found in close proximity to 5‐HT+ paraneurones. In vitro 5‐HT (1 μm) stimulation of urethral primary afferent neurones, mimicking 5‐HT release from paraneurones, elicited changes in the intracellular calcium concentration ([Ca2+]i) mediated by 5‐HT2 and 5‐HT3 receptors. Approximately 50% of 5‐HT responding cells also responded to capsaicin with changes in the [Ca2+]i. In vivo intra‐urethral 5‐HT application increased VMRs induced by urethral distention and activated pERK in lumbosacral spinal cord neurones. Conclusion These morphological and functional findings provide insights into a putative paraneurone‐neural network within the urethra that utilizes 5‐HT signalling, presumably from paraneurones, to modulate primary sensory pathways carrying nociceptive and non‐nociceptive (mechano‐sensitive) information to the central nervous system.
    August 08, 2017   doi: 10.1111/apha.12919   open full text
  • Control of breathing and ventilatory acclimatization to hypoxia in deer mice native to high altitudes.
    C. M. Ivy, G. R. Scott.
    Acta Physiologica. August 08, 2017
    Aim We compared the control of breathing and heart rate by hypoxia between high‐ and low‐altitude populations of Peromyscus mice, to help elucidate the physiological specializations that help high‐altitude natives cope with O2 limitation. Methods Deer mice (Peromyscus maniculatus) native to high altitude and congeneric mice native to low altitude (Peromyscus leucopus) were bred in captivity at sea level. The F1 progeny of each population were raised to adulthood and then acclimated to normoxia or hypobaric hypoxia (12 kPa, simulating hypoxia at ~4300 m) for 5 months. Responses to acute hypoxia were then measured during stepwise reductions in inspired O2 fraction. Results Lowlanders exhibited ventilatory acclimatization to hypoxia (VAH), in which hypoxia acclimation enhanced the hypoxic ventilatory response, made breathing pattern more effective (higher tidal volumes and lower breathing frequencies at a given total ventilation), increased arterial O2 saturation and heart rate during acute hypoxia, augmented respiratory water loss and led to significant growth of the carotid body. In contrast, highlanders did not exhibit VAH – exhibiting a fixed increase in breathing that was similar to hypoxia‐acclimated lowlanders – and they maintained even higher arterial O2 saturations in hypoxia. However, the carotid bodies of highlanders were not enlarged by hypoxia acclimation and were similar in size to those of normoxic lowlanders. Highlanders also maintained consistently higher heart rates than lowlanders during acute hypoxia. Conclusions Our results suggest that highland deer mice have evolved high rates of alveolar ventilation and respiratory O2 uptake without the significant enlargement of the carotid bodies that is typical of VAH in lowlanders, possibly to adjust the hypoxic chemoreflex for life in high‐altitude hypoxia.
    August 08, 2017   doi: 10.1111/apha.12912   open full text
  • Distribution of muscle fiber conduction velocity for representative samples of motor units in the full recruitment range of the tibialis anterior muscle.
    Alessandro Del Vecchio, Francesco Negro, Francesco Felici, Dario Farina.
    Acta Physiologica. August 01, 2017
    Aim Motor units are recruited in an orderly manner according to the size of motor neurons. Moreover, because larger motor neurons innervate fibers with larger diameters than smaller motor neurons, motor units should be recruited orderly according to their conduction velocity (MUCV). Because of technical limitations, these relations have been previously tested either indirectly or in small motor unit samples that revealed weak associations between motor unit recruitment threshold (RT) and MUCV. Here we analyze the relation between MUCV and RT for large samples of motor units. Methods Ten healthy volunteers completed a series of isometric ankle dorsiflexions at forces up to 70% of the maximum. Multi‐channel surface electromyographic signals recorded from the tibialis anterior muscle were decomposed into single motor unit action potentials, from which the corresponding motor unit RT, MUCV, and action potential amplitude were estimated. Established relations between muscle fiber diameter and CV were used to estimate the fiber size. Results Within individual subjects, the distributions of MUCV and fiber diameters were unimodal and did not show distinct populations. MUCV was strongly correlated with RT (mean (SD) R2 = 0.7 (0.09), p<0.001; 406 motor units), which supported the hypothesis that fiber diameter is associated to RT. Conclusion The results provide further evidence for the relations between motor neuron and muscle fiber properties for large samples of motor units. The proposed methodology for motor unit analysis has also the potential to open new perspectives in the study of chronic and acute neuromuscular adaptations to ageing, training, and pathology. This article is protected by copyright. All rights reserved.
    August 01, 2017   doi: 10.1111/apha.12930   open full text
  • Cerebrocortical activity during self‐paced exercise in temperate, hot and hypoxic conditions.
    J. D. Périard, K. De Pauw, F. Zanow, S. Racinais.
    Acta Physiologica. July 25, 2017
    Aim Heat stress and hypoxia independently influence cerebrocortical activity and impair prolonged exercise performance. This study examined the relationship between electroencephalography (EEG) activity and self‐paced exercise performance in control (CON, 18 °C, 40% RH), hot (HOT, 35 °C, 60% RH) and hypoxic (HYP, 18 °C, 40% RH FiO2: 0.145) conditions. Methods Eleven well‐trained cyclists completed a 750 kJ cycling time trial in each condition on separate days in a counterbalanced order. EEG activity was recorded with α‐ and β‐activity evaluated in the frontal (F3 and F4) and central (C3 and C4) areas. Standardized low‐resolution brain electromagnetic tomography (sLORETA) was also utilized to localize changes in cerebrocortical activity. Results Both α‐ and β‐activity decreased in the frontal and central areas during exercise in HOT relative to CON (P < 0.05). α‐activity was also lower in HYP compared with CON (P < 0.05), whereas β‐activity remained similar. β‐activity was higher in HYP than in HOT (P < 0.05). sLORETA revealed that α‐ and β‐activity increased at the onset of exercise in the primary somatosensory and motor cortices in CON and HYP, while only β‐activity increased in HOT. A decrease in α‐ and β‐activity occurred thereafter in all conditions, with α‐activity being lower in the somatosensory and somatosensory association cortices in HOT relative to CON. Conclusion High‐intensity prolonged self‐paced exercise induces cerebrocortical activity alterations in areas of the brain associated with the ability to inhibit conflicting attentional processing under hot and hypoxic conditions, along with the capacity to sustain mental readiness and arousal under heat stress.
    July 25, 2017   doi: 10.1111/apha.12916   open full text
  • Mechanisms of sphingosine‐1‐phosphate‐mediated vasoconstriction of rat afferent arterioles.
    Z. Guan, F. Wang, X. Cui, E. W. Inscho.
    Acta Physiologica. July 13, 2017
    Aim Sphingosine‐1‐phosphate (S1P) influences resistance vessel function and is implicated in renal pathological processes. Previous studies revealed that S1P evoked potent vasoconstriction of the pre‐glomerular microvasculature, but the underlying mechanisms remain incompletely defined. We postulated that S1P‐mediated pre‐glomerular microvascular vasoconstriction involves activation of voltage‐dependent L‐type calcium channels (L‐VDCC) and the rho/rho kinase pathway. Methods Afferent arteriolar reactivity was assessed in vitro using the blood‐perfused rat juxtamedullary nephron preparation, and diameter was measured during exposure to physiological and pharmacological agents. Results Exogenous S1P (10−9–10−5 mol L−1) evoked concentration‐dependent vasoconstriction of afferent arterioles. Superfusion with nifedipine, a L‐VDCC blocker, increased arteriolar diameter by 39 ± 18% of baseline and significantly attenuated the S1P‐induced vasoconstriction. Superfusion with the rho kinase inhibitor, Y‐27632, increased diameter by 60 ± 12% of baseline and also significantly blunted vasoconstriction by S1P. Combined nifedipine and Y‐27632 treatment significantly inhibited S1P‐induced vasoconstriction over the entire concentration range tested. In contrast, depletion of intracellular Ca2+ stores with the Ca2+‐ATPase inhibitors, thapsigargin or cyclopiazonic acid, did not alter the S1P‐mediated vasoconstrictor profile. Scavenging reactive oxygen species (ROS) or inhibition of nicotinamide adenine dinucleotide phosphate oxidase activity significantly attenuated S1P‐mediated vasoconstriction. Conclusion Exogenous S1P elicits potent vasoconstriction of rat afferent arterioles. These data also demonstrate that S1P‐mediated pre‐glomerular vasoconstriction involves activation of L‐VDCC, the rho/rho kinase pathway and ROS. Mobilization of Ca2+ from intracellular stores is not required for S1P‐mediated vasoconstriction. These studies reveal a potential role for S1P in the modulation of renal microvascular tone.
    July 13, 2017   doi: 10.1111/apha.12913   open full text
  • Exercise training increases skeletal muscle mitochondrial volume density by enlargement of existing mitochondria and not de novo biogenesis.
    A.‐K. Meinild Lundby, R. A. Jacobs, S. Gehrig, J. Leur, M. Hauser, T. C. Bonne, D. Flück, S. Dandanell, N. Kirk, A. Kaech, U. Ziegler, S. Larsen, C. Lundby.
    Acta Physiologica. July 06, 2017
    Aims (i) To determine whether exercise‐induced increases in muscle mitochondrial volume density (MitoVD) are related to enlargement of existing mitochondria or de novo biogenesis and (ii) to establish whether measures of mitochondrial‐specific enzymatic activities are valid biomarkers for exercise‐induced increases in MitoVD. Method Skeletal muscle samples were collected from 21 healthy males prior to and following 6 weeks of endurance training. Transmission electron microscopy was used for the estimation of mitochondrial densities and profiles. Biochemical assays, western blotting and high‐resolution respirometry were applied to detect changes in specific mitochondrial functions. Result MitoVD increased with 55 ± 9% (P < 0.001), whereas the number of mitochondrial profiles per area of skeletal muscle remained unchanged following training. Citrate synthase activity (CS) increased (44 ± 12%, P < 0.001); however, there were no functional changes in oxidative phosphorylation capacity (OXPHOS, CI+IIP) or cytochrome c oxidase (COX) activity. Correlations were found between MitoVD and CS (P = 0.01; r = 0.58), OXPHOS, CI+CIIP (P = 0.01; R = 0.58) and COX (P = 0.02; R = 0.52) before training; after training, a correlation was found between MitoVD and CS activity only (P = 0.04; R = 0.49). Intrinsic respiratory capacities decreased (P < 0.05) with training when respiration was normalized to MitoVD. This was not the case when normalized to CS activity although the percentage change was comparable. Conclusions MitoVD was increased by inducing mitochondrial enlargement rather than de novo biogenesis. CS activity may be appropriate to track training‐induced changes in MitoVD.
    July 06, 2017   doi: 10.1111/apha.12905   open full text
  • Myoendothelial coupling through Cx40 contributes to EDH‐induced vasodilation in murine renal arteries: evidence from experiments and modelling.
    J. C. Brasen, C. de Wit, C. M. Sorensen.
    Acta Physiologica. July 02, 2017
    Regulation of renal vascular resistance plays a major role in controlling arterial blood pressure. The endothelium participates in this regulation as endothelial derived hyperpolarization plays a significant role in smaller renal arteries and arterioles, but the exact mechanisms are still unknown. Aim To investigate the role of vascular gap junctions and potassium channels in the renal endothelial derived hyperpolarization. Methods In interlobar arteries from wild‐type and connexin40 knockout mice, we assessed the role of calcium‐activated small (SK) and intermediate (IK) conductance potassium channels. The role of inward rectifier potassium channels (Kir) and Na+/K+‐ATPases was evaluated as was the contribution from gap junctions. Mathematical models estimating diffusion of ions and electrical coupling in myoendothelial gap junctions were used to interpret the results. Results Lack of connexin40 significantly reduces renal endothelial hyperpolarization. Inhibition of SK and IK channels significantly attenuated renal EDH to a similar degree in wild‐type and knockout mice. Inhibition of Kir and Na+/K+‐ATPases affected the response in wild‐type and knockout mice but at different levels of stimulation. The model confirms that activation of endothelial SK and IK channels generates a hyperpolarizing current that enters the vascular smooth muscle cells. Also, extracellular potassium increases sufficiently to activate Kir and Na+/K+‐ATPases. Conclusion Renal endothelial hyperpolarization is mainly initiated by activation of IK and SK channels. The model shows that hyperpolarization can spread through myoendothelial gap junctions but enough potassium is released to activate Kir and Na+/K+‐ATPases. Reduced coupling seems to shift the signalling pathway towards release of potassium. However, an alternative pathway also exists and needs to be investigated.
    July 02, 2017   doi: 10.1111/apha.12906   open full text
  • Astroglial vesicular network: Evolutionary trends, physiology and pathophysiology.
    Robert Zorec, Vladimir Parpura, Alexei Verkhratsky.
    Acta Physiologica. June 30, 2017
    Intracellular organelles, including secretory vesicles, emerged when eukaryotic cells evolved some 3 billion years ago. The primordial organelles that evolved in Archaea were similar to endolysosomes, which developed, arguably, for specific metabolic tasks, including uptake, metabolic processing, storage and disposal of molecules. In comparison to prokaryotes, cell volume of eukaryotes increased by several orders of magnitude and vesicle traffic emerged to allow for communication between distant intracellular locations. Lysosomes, first described in 1955, a prominent intermediate of endo‐ and exocytotic pathways, operate virtually in all eukaryotic cells including astroglia, the most heterogeneous type of homeostatic glia in the central nervous system. Astrocytes support neuronal network activity in particular through elaborated secretion, based on a complex intracellular vesicle network dynamics. Deranged homeostasis underlies disease and astroglial vesicle traffic contributes to the pathophysiology of neurodegenerative (Alzheimer's disease, Huntington's disease), neurodevelopmental diseases (intellectual deficiency, Rett's disease) and neuroinfectious (Zika virus) disorders. This review addresses astroglial cell‐autonomous vesicular traffic network, classified into primary and secondary vesicular network defects in diseases, targets for developing new therapies for neurologic conditions. This article is protected by copyright. All rights reserved.
    June 30, 2017   doi: 10.1111/apha.12915   open full text
  • Isolated pulmonary regurgitation causes decreased right ventricular longitudinal function and compensatory increased septal pumping in a porcine model.
    S. Kopic, S. S. Stephensen, E. Heiberg, H. Arheden, P. Bonhoeffer, M. Ersbøll, N. Vejlstrup, L. Søndergaard, M. Carlsson.
    Acta Physiologica. June 29, 2017
    Aim Longitudinal ventricular contraction is a parameter of cardiac performance with predictive power. Right ventricular (RV) longitudinal function is impaired in patients with free pulmonary regurgitation (PR) following corrective surgery for Tetralogy of Fallot (TOF). It remains unclear whether this is a consequence of the surgical repair, or whether it is inherent to PR. The aim of this study was to assess the relationship between longitudinal, lateral and septal pumping in a porcine model of isolated PR. Methods Piglets were divided into a control (n = 8) group and a treatment (n = 12) group, which received a stent in the pulmonary valve orifice, inducing PR. After 2–3 months, animals were subjected to cardiac magnetic resonance imaging. A subset of animals (n = 6) then underwent percutaneous pulmonary valve replacement (PPVR) with follow‐up 1 month later. Longitudinal, lateral and septal contributions to stroke volume (SV) were quantified by measuring volumetric displacements from end‐diastole to end‐systole in the cardiac short axis and long axis. Results PR resulted in a lower longitudinal contribution to RV stroke volume, compared to controls (60.0 ± 2.6% vs. 73.6 ± 3.8%; P = 0.012). Furthermore, a compensatory increase in septal contribution to RVSV was observed (11.0 ± 1.6% vs. −3.1 ± 1.5%; P < 0.0001). The left ventricle (LV) showed counter‐regulation with an increased longitudinal LVSV. Changes in RV longitudinal function were reversed by PPVR. Conclusion These findings suggest that PR contributes to decreased RV longitudinal function in the absence of scarring from cardiac surgery. Measurement of longitudinal RVSV may aid risk stratification and timing for interventional correction of PR in TOF patients.
    June 29, 2017   doi: 10.1111/apha.12904   open full text
  • Endothelial colony forming cells and proangiogenic cells: clarifying definitions and their potential role in mitigating acute kidney injury.
    David P. Basile, Jason A. Collett, Mervin C. Yoder.
    Acta Physiologica. June 28, 2017
    Acute kidney injury (AKI) represents a significant clinical concern that is associated with high mortality rates and also represents a significant risk factor for the development of chronic kidney disease (CKD). This article will consider alterations in renal endothelial function in the setting of AKI that may underlie impairment in renal perfusion and how inefficient vascular repair may manifest post‐AKI and contribute to the potential transition to CKD. We provide updated terminology for cells previously classified as “endothelial progenitor” that may mediate vascular repair such as pro‐angiogenic cells and endothelial colony forming cells. We consider how endothelial repair may be mediated by these different cell types following vascular injury, particularly in models of AKI. We further summarize the potential ability of these different cells to mitigate the severity of AKI, improve perfusion and maintain vascular structure in pre‐clinical studies. This article is protected by copyright. All rights reserved.
    June 28, 2017   doi: 10.1111/apha.12914   open full text
  • Acute toll‐like receptor 4 activation impairs rat renal microvascular autoregulatory behaviour.
    J. P. Van Beusecum, S. Zhang, A. K. Cook, E. W. Inscho.
    Acta Physiologica. June 27, 2017
    Aim Little is known about how toll‐like receptor 4 (TLR4) influences the renal microvasculature. We hypothesized that acute TLR4 stimulation with lipopolysaccharide (LPS) impairs afferent arteriole autoregulatory behaviour, partially through reactive oxygen species (ROS). Methods We assessed afferent arteriole autoregulatory behaviour after LPS treatment (1 mg kg−1; i.p.) using the in vitro blood‐perfused juxtamedullary nephron preparation. Autoregulatory behaviour was assessed by measuring diameter responses to stepwise changes in renal perfusion pressure. TLR4 expression was assessed by immunofluorescence, immunohistochemistry and Western blot analysis in the renal cortex and vasculature. Results Baseline arteriole diameter at 100 mmHg averaged 15.2 ± 1.2 μm and 12.2 ± 1.0 μm for control and LPS groups (P < 0.05) respectively. When perfusion pressure was increased in 15 mmHg increments from 65 to 170 mmHg, arteriole diameter in control kidneys decreased significantly to 69 ± 6% of baseline diameter. In the LPS‐treated group, arteriole diameter remained essentially unchanged (103 ± 9% of baseline), indicating impaired autoregulatory behaviour. Pre‐treatment with anti‐TLR4 antibody or the TLR4 antagonist, LPS‐RS, preserved autoregulatory behaviour during LPS treatment. P2 receptor reactivity was normal in control and LPS‐treated rats. Pre‐treatment with Losartan (angiotensin type 1 receptor blocker; (AT1) 2 mg kg−1; i.p.) increased baseline afferent arteriole diameter but did not preserve autoregulatory behaviour in LPS‐treated rats. Acute exposure to Tempol (10−3 mol L−1), a superoxide dismutase mimetic, restored pressure‐mediated vasoconstriction in kidneys from LPS‐treated rats. Conclusion These data demonstrate that TLR4 activation impairs afferent arteriole autoregulatory behaviour, partially through ROS, but independently of P2 and AT1 receptor activation.
    June 27, 2017   doi: 10.1111/apha.12899   open full text
  • Adaptations to endurance training depend on exercise‐induced oxidative stress: exploiting redox interindividual variability.
    N. V. Margaritelis, A. A. Theodorou, V. Paschalis, A. S. Veskoukis, K. Dipla, A. Zafeiridis, G. Panayiotou, I. S. Vrabas, A. Kyparos, M. G. Nikolaidis.
    Acta Physiologica. June 21, 2017
    Aim The aim of this study was to reveal the role of reactive oxygen and nitrogen species (RONS) in exercise adaptations under physiological in vivo conditions and without the interference from other exogenous redox agents (e.g. a pro‐oxidant or antioxidant). Methods We invented a novel methodological set‐up that exploited the large redox interindividual variability in exercise responses. More specifically, we used exercise‐induced oxidative stress as the ‘classifier’ measure (i.e. low, moderate and high) and investigated the physiological and redox adaptations after a 6‐week endurance training protocol. Results We demonstrated that the group with the low exercise‐induced oxidative stress exhibited the lowest improvements in a battery of classic adaptations to endurance training (VO2 max, time trial and Wingate test) as well as in a set of redox biomarkers (oxidative stress biomarkers and antioxidants), compared to the high and moderate oxidative stress groups. Conclusion The findings of this study substantiate, for the first time in a human in vivo physiological context, and in the absence of any exogenous redox manipulation, the vital role of RONS produced during exercise in adaptations. The stratification approach, based on a redox phenotype, implemented in this study could be a useful experimental strategy to reveal the role of RONS and antioxidants in other biological manifestations as well.
    June 21, 2017   doi: 10.1111/apha.12898   open full text
  • Temporal overexpression of SIRT1 in skeletal muscle of adult mice does not improve insulin sensitivity or markers of mitochondrial biogenesis.
    K. Svensson, S. A. LaBarge, V. F. Martins, S. Schenk.
    Acta Physiologica. June 13, 2017
    Aims Activation of the NAD+ dependent protein deacetylase SIRT1 has been proposed as a therapeutic strategy to treat mitochondrial dysfunction and insulin resistance in skeletal muscle. However, lifelong overexpression of SIRT1 in skeletal muscle does not improve parameters of mitochondrial function and insulin sensitivity. In this study, we investigated whether temporal overexpression of SIRT1 in muscle of adult mice would affect skeletal muscle mitochondrial function and insulin sensitivity. Methods To circumvent potential effects of germline SIRT1 overexpression, we utilized an inducible model of SIRT1 overexpression in skeletal muscle of adult mice (i‐mOX). Insulin sensitivity was assessed by 2‐deoxyglucose uptake, muscle maximal respiratory function by high‐resolution respirometry and systemic energy expenditure was assessed by whole body calorimetry. Results Although SIRT1 was highly, and specifically, overexpressed in skeletal muscle of i‐mOX compared to WT mice, glucose tolerance and skeletal muscle insulin sensitivity were comparable between genotypes. Additionally, markers of mitochondrial biogenesis, muscle maximal respiratory function and whole‐body oxygen consumption were also unaffected by SIRT1 overexpression. Conclusion These results support previous work demonstrating that induction of SIRT1 in skeletal muscle, either at birth or in adulthood, does not impact muscle insulin action or mitochondrial function.
    June 13, 2017   doi: 10.1111/apha.12897   open full text
  • Isopimaric acid – a multi‐targeting ion channel modulator reducing excitability and arrhythmicity in a spontaneously beating mouse atrial cell line.
    S. Salari, M. Silverå Ejneby, J. Brask, F. Elinder.
    Acta Physiologica. June 09, 2017
    Aim Atrial fibrillation is the most common persistent cardiac arrhythmia, and it is not well controlled by present drugs. Because some resin acids open voltage‐gated potassium channels and reduce neuronal excitability, we explored the effects of the resin acid isopimaric acid (IPA) on action potentials and ion currents in cardiomyocytes. Methods Spontaneously beating mouse atrial HL‐1 cells were investigated with the whole‐cell patch‐clamp technique. Results 1–25 μmol L−1 IPA reduced the action potential frequency by up to 50%. The effect of IPA on six different voltage‐gated ion channels was investigated; most voltage‐dependent parameters of ion channel gating were shifted in the negative direction along the voltage axis, consistent with a hypothesis that a lipophilic and negatively charged compound binds to the lipid membrane close to the positively charged voltage sensor of the ion channels. The major finding was that IPA inactivated sodium channels and L‐ and T‐type calcium channels and activated the rapidly activating potassium channel and the transient outward potassium channel. Computer simulations of IPA effects on all of the ion currents were consistent with a reduced excitability, and they also showed that effects on the Na channel played the largest role to reduce the action potential frequency. Finally, induced arrhythmia in the HL‐1 cells was reversed by IPA. Conclusion Low concentrations of IPA reduced the action potential frequency and restored regular firing by altering the voltage dependencies of several voltage‐gated ion channels. These findings can form the basis for a new pharmacological strategy to treat atrial fibrillation.
    June 09, 2017   doi: 10.1111/apha.12895   open full text
  • Microparticles of healthy origins improve endothelial progenitor cell dysfunction via microRNA transfer in an atherosclerotic hamster model.
    N. Alexandru, E. Andrei, L. Niculescu, E. Dragan, V. Ristoiu, A. Georgescu.
    Acta Physiologica. June 08, 2017
    Aim In this study, we aimed: (i) to obtain and functionally characterize the cultures of late endothelial progenitor cells (EPCs) from the animal blood; (ii) to investigate the potential beneficial effects of circulating microparticles (MPs) of healthy origins on EPC dysfunctionality in atherosclerosis as well as involved mechanisms. Methods Late EPCs were obtained and expanded in culture from peripheral blood isolated from two animal groups: hypertensive–hyperlipidaemic (HH) and control (C) hamsters. In parallel experiments, late EPC cultures from HH were incubated with MPs from C group. Results The results showed that late EPCs display endothelial cell phenotype: (i) have ability to uptake 1,1‐dioctadecyl‐3,3,3,3 tetramethylindocarbocyanine‐labelled acetylated low‐density lipoprotein and Ulex europaeus agglutinin lectin‐1; (ii) express CD34, CD133, KDR, CD144, vWF, Tie‐2. Late EPCs from HH exhibited different morphological and functional characteristics compared to control: (i) are smaller and irregular in shape; (ii) present decreased endothelial surface marker expression; (iii) display reduced proliferation, migration and adhesion; (iv) lose ability to organize themselves into tubular structures and integrate into vascular network; (v) have diminished function of inward rectifier potassium channels. The incubation of late EPCs with MPs improved EPC functionality by miR‐10a, miR‐21, miR‐126, miR‐146a, miR‐223 transfer and IGF‐1 expression activation; the kinetic study of MP incorporation into EPCs demonstrated MP uptake by EPCs followed by the miRNA transfer. Conclusion The data reveal that late EPCs from atherosclerotic model exhibit distinctive features and are dysfunctional, and their function recovery can be supported by MP ability to transfer miRNAs. These findings bring a new light on the vascular repair in atherosclerosis.
    June 08, 2017   doi: 10.1111/apha.12896   open full text
  • Age‐related endothelial dysfunction in human skeletal muscle feed arteries: the role of free radicals derived from mitochondria in the vasculature.
    S.‐Y. Park, O. S. Kwon, R. H. I. Andtbacka, J. R. Hyngstrom, V. Reese, M. P. Murphy, R. S. Richardson.
    Acta Physiologica. June 08, 2017
    Aim This study sought to determine the role of free radicals derived from mitochondria in the vasculature in the recognized age‐related endothelial dysfunction of human skeletal muscle feed arteries (SMFAs). Methods A total of 44 SMFAs were studied with and without acute exposure to the mitochondria‐targeted antioxidant MitoQ and nitric oxide synthase (NOS) blockade. The relative abundance of proteins from the electron transport chain, phosphorylated (p‐) to endothelial (e) NOS ratio, manganese superoxide dismutase (MnSOD) and the mitochondria‐derived superoxide (O2−) levels were assessed in SMFA. Endothelium‐dependent and endothelium‐independent SMFA vasodilation was assessed in response to flow‐induced shear stress, acetylcholine (ACh) and sodium nitroprusside (SNP). Results MitoQ restored endothelium‐dependent vasodilation in the old to that of the young when stimulated by both flow (young: 68 ± 5; old: 25 ± 7; old + MitoQ 65 ± 9%) and ACh (young: 97 ± 4; old: 59 ± 10; old + MitoQ: 98 ± 5%), but did not alter the initially uncompromised, endothelium‐independent vasodilation (SNP). Compared to the young, MitoQ in the old diminished the initially elevated mitochondria‐derived O2− levels and appeared to attenuate the breakdown of MnSOD. Furthermore, MitoQ increased the ratio of p‐eNOS to NOS and the restoration of endothelium‐dependent vasodilation in the old by MitoQ was ablated by NOS blockade. Conclusion This study demonstrated that MitoQ reverses age‐related vascular dysfunction by what appears to be an NO‐dependent mechanism in human SMFAs. These findings suggest that mitochondria‐targeted antioxidants may have utility in terms of counteracting the attenuated blood flow and vascular dysfunction associated with advancing age.
    June 08, 2017   doi: 10.1111/apha.12893   open full text
  • Improvement in baroreflex control of renal sympathetic nerve activity in obese Sprague Dawley rats following immunosuppression.
    S. A. Khan, M. Z. A. Sattar, N. A. Abdullah, H. A. Rathore, A. Ahmad, M. H. Abdulla, E. J. Johns.
    Acta Physiologica. June 07, 2017
    Aim This investigation explored the hypothesis that in obesity an inflammatory response in the kidney contributed to a renal nerve‐dependent blunting of the baroreflex regulation of renal sympathetic nerve activity. Methods Rats received a normal (12% kcal) or high‐fat (45% kcal) diet for 8 weeks plus daily injections of vehicle (0.9% NaCl i.p) or tacrolimus (0.25 mg kg−1 day−1 i.p) from weeks 3–8. Following anaesthesia, left renal sympathetic nerve activity was recorded, baroreflex gain curves were generated, by infusing phenylephrine and sodium nitroprusside, and cardiopulmonary baroreceptors challenged by infusing a saline load. Results The high‐fat diet elevated weight gain and adiposity index by 89 and 129% (both, P < 0.001). Mean blood pressure (132 ± 4 vs 103 ± 5 mmHg), fractional noradrenaline excretion and creatinine clearance (5.64 ± 0.55 vs 3.32 ± 0.35 mL min−1 kg−1) were 28, 77 and 69% higher (all P < 0.05), but urine flow and fractional sodium excretions were 42 and 72% (both P < 0.001) lower compared to normal rats. Plasma and renal TNF‐α and IL‐6 concentrations were fourfold to fivefold (P < 0.001) and 22 and 20% higher (both, P < 0.05), in obese rats but normalized following tacrolimus. In obese rats, baroreflex sensitivity was reduced by 80% (P < 0.05) but restored by renal denervation or tacrolimus. Volume expansion reduced renal sympathetic nerve activity by 54% (P < 0.001) in normal and obese rats subjected to renal denervation and tacrolimus, but not in obese rats with an intact renal innervation. Conclusion Obesity induced a renal inflammation and pointed to this being both the origin of autonomic dysregulation and a potential focus for targeted therapy.
    June 07, 2017   doi: 10.1111/apha.12891   open full text
  • Inhibitory action of oxytocin on spontaneous contraction of rat distal colon by nitrergic mechanism: involvement of cyclic GMP and apamin‐sensitive K+ channels.
    R. Wang, M. T. Han, X. L. Lv, Y. A. Yu, S. Q. Chai, C. M. Qu, C. Y. Liu.
    Acta Physiologica. May 20, 2017
    Aim The mechanisms underlying the inhibitory effects of oxytocin (OT) on colon tone are not totally understood. We explore the mechanisms of OT on spontaneous contractility in rat distal colon and identify the mediators involved in this action. Methods In rat distal colon strips, mechanical activity was analysed and the production of nitric oxide (NO) in tissue loaded with the fluorochrome DAF‐FM was visualized by confocal microscopy. OT receptor (OTR) expression was determined by Western blotting and immunofluorescence. Results In rat distal colon, OT produced a concentration‐dependent reduction in the spontaneous contraction, which was abolished by the OTR antagonist atosiban, the neural blocker tetrodotoxin and the inhibitor of neuronal nitric oxide synthase (nNOS) NPLA. The inhibitory effects of OT were not affected by propranolol, atropine, the nicotinic cholinoceptor blocker hexamethonium, the vasoactive intestinal peptide receptor antagonist VIPHyb, the P2 purinoceptor antagonist PPADS, the adenosine A1 receptors antagonist DPCPX and the prostacyclin receptor antagonist Ro1138452. The soluble guanylyl cyclase (sGC) inhibitor ODQ and the small conductance Ca2+‐activated K+ (CaK+) channels blocker apamin significantly reduced the relaxation induced by OT, nicotine, sodium nitroprusside and the sGC activator BAY 41‐2272. The neural release of NO elicited by OT was prevented by NPLA, tetrodotoxin and atosiban. The presence of the OTR and its co‐localization with nNOS was detected by immunohistochemistry and Western blotting experiments. Conclusion These results demonstrate the NO release from enteric neurones induced by activation of OTR mediates distal colon relaxation. sGC and small conductance CaK+ channels are involved in this relaxation.
    May 20, 2017   doi: 10.1111/apha.12890   open full text
  • Deferoxamine‐activated hypoxia‐inducible factor‐1 restores cardioprotective effects of sevoflurane postconditioning in diabetic rats.
    P. Xie, L. Yang, A. Talaiti, J. J. Wu, J. Yu, T. Yu, H. Y. Wang, B. Huang, Q. Wu, Y. Maimaitili, J. Wang, H. P. Ma, Y. N. Yang, H. Zheng.
    Acta Physiologica. May 15, 2017
    Aim The cardioprotective effects of sevoflurane postconditioning (SpostC) are eliminated under diabetic conditions, and the underlying mechanism for this phenomenon remains unclear. Many studies have demonstrated that the hypoxia‐inducible factor‐1 (HIF‐1) signalling pathway in the myocardium is impaired under diabetic conditions. This study was to investigate whether deferoxamine (DFO)‐induced activation of HIF‐1 signalling pathway can restore the cardioprotective effects of SpostC in diabetic rats. Methods A model of myocardial ischaemia/reperfusion (I/R) injury was induced via ligation of the left anterior descending artery. SpostC was conducted by administering 1.0 MAC sevoflurane. After inducing the I/R injury, the following parameters were measured: myocardial infarct size, cardiac function, myocardial ultrastructure, mitochondrial respiratory function, respiratory chain enzyme activity, rate of reactive oxygen species (ROS) generation, and protein expression of HIF‐1α, vascular endothelial growth factor (VEGF), cleaved caspase‐3, Bcl‐2 and Bax. Results After DFO activated HIF‐1 in the impaired myocardium of diabetic rats, SpostC significantly upregulated the protein expression of HIF‐1α and its downstream mediator VEGF. This improved myocardial mitochondrial respiratory function and respiratory chain enzyme activity and reduced ROS generation as well as the protein expression of cleaved caspase‐3 and Bax. As a result, myocardial infarct size decreased, and cardiac function and mitochondrial ultrastructure improved. Conclusion This study demonstrates for the first time that abolishment of the cardioprotective effects of SpostC in diabetic rats is associated with impairment of the HIF‐1 signalling pathway and that DFO can activate HIF‐1 to restore these cardioprotective effects of SpostC in diabetic rats.
    May 15, 2017   doi: 10.1111/apha.12874   open full text
  • CO2 permeability and carbonic anhydrase activity of rat cardiomyocytes.
    M. Arias‐Hidalgo, S. Al‐Samir, N. Weber, C. Geers‐Knörr, G. Gros, V. Endeward.
    Acta Physiologica. May 15, 2017
    Aim To determine the CO2 permeability (PCO2) of plasma membranes of cardiomyocytes. These cells were chosen because heart possesses the highest rate of O2 consumption/CO2 production in the body. Methods Cardiomyocytes were isolated from rat hearts using the Langendorff technique. Cardiomyocyte suspensions exhibited a vitality of 2–14% and were studied by the previously described mass spectrometric 18O‐exchange technique deriving PCO2. We showed by mass spectrometry and by carbonic anhydrase (CA) staining that non‐vital cardiomyocytes are free of CA and thus do not contribute to the mass spectrometric signal, which is determined exclusively by the fully functional vital cardiomyocytes. Results Lysed cardiomyocytes yielded an intracellular CA activity for vital cells of 5070; that is, the rate of CO2 hydration inside the cell is accelerated 5071‐fold. Using this number, analyses of the mass spectrometric recordings from cardiomyocyte suspensions yield a PCO2 of 0.10 cm s−1 (SD ± 0.06, n = 15) at 37 °C. Conclusion In comparison with the PCO2 of other cells, this value is quite high and about identical to that of the human red cell membrane. As no major protein CO2 channels such as aquaporins 1 and 4 are present in rat cardiac sarcolemma, the high PCO2 of this membrane is likely due to its low cholesterol content of about 0.2 (mol cholesterol)·(mol total membrane lipids)−1. Previous work predicted a PCO2 of ≥0.1 cm s−1 from this level of cholesterol. We conclude that the low cholesterol establishes a PCO2 high enough to render the membrane resistance to CO2 diffusion almost negligible, even under conditions of maximal O2 consumption of the heart.
    May 15, 2017   doi: 10.1111/apha.12887   open full text
  • Neurological and Neuropsychological Effects of Low and Moderate Prenatal Alcohol Exposure.
    Erika Comasco, Jenny Rangmar, Ulf J. Eriksson, Lars Oreland.
    Acta Physiologica. May 04, 2017
    Several explanations for the diverse results in research on Foetal Alcohol Spectrum Disorders (FASD) or Alcohol‐Related Neuro‐developmental Disorder (ARND) might be at hand: timing, amount and patterns of alcohol exposure, as well as complex epigenetic responses. The genetic background of the offspring and its interaction with other prenatal and postnatal environmental cues are likely also of importance. In the present report, key findings about the possible effects of low and moderate doses of maternal alcohol intake on the neuropsychological development of the offspring are reviewed and plausible mechanisms discussed. Special focus is put on the serotonergic system within developmental and gene‐environment frameworks. The review also suggests guidelines for future studies, as well as summarises some of to be‐answered questions of relevance to clinical practice. Contradictory findings and paucity of studies on the effects of exposure to low alcohol levels during foetal life for the offspring's neuropsychological development call for large prospective studies, as well as for studies including neuroimaging and multi‐omics analyses to dissect the neurobiological underpinnings of alcohol exposure‐related phenotypes and to identify biomarkers. Finally, it remains to be investigated whether any safe threshold of alcohol drinking during pregnancy can be identified. This article is protected by copyright. All rights reserved.
    May 04, 2017   doi: 10.1111/apha.12892   open full text
  • Extracellular acidosis and very low [Na+] inhibit NBCn1‐ and NHE1‐mediated net acid extrusion from mouse vascular smooth muscle cells.
    L. Bonde, E. Boedtkjer.
    Acta Physiologica. April 25, 2017
    Aim The electroneutral Na+, HCO3− cotransporter NBCn1 and Na+/H+ exchanger NHE1 regulate acid–base balance in vascular smooth muscle cells (VSMCs) and modify artery function and structure. Pathological conditions – notably ischaemia – can dramatically perturb intracellular (i) and extracellular (o) pH and [Na+]. We examined effects of low [Na+]o and pHo on NBCn1 and NHE1 activity in VSMCs of small arteries. Methods We measured pHi by 2′,7′‐bis‐(2‐carboxyethyl)‐5‐(and‐6)‐carboxyfluorescein‐based fluorescence microscopy of mouse mesenteric arteries and induced intracellular acidification by NH4+ prepulse technique. Results NBCn1 activity – defined as Na+‐dependent, amiloride‐insensitive net base uptake with CO2/HCO3− present – was inhibited equally when pHo decreased from 7.4 (22 mm HCO3−/5% CO2) by metabolic (pHo 7.1/11 mm HCO3−: 22 ± 8%; pHo 6.8/5.5 mm HCO3−: 61 ± 7%) or respiratory (pHo 7.1/10% CO2: 35 ± 11%; pHo 6.8/20% CO2: 56 ± 7%) acidosis. Extracellular acidosis more prominently inhibited NHE1 activity – defined as Na+‐dependent net acid extrusion without CO2/HCO3− present – at both pHo 7.1 (45 ± 9%) and 6.8 (85 ± 5%). Independently of pHo, lowering [Na+]o from 140 to 70 mm reduced NBCn1 and NHE1 activity <20% whereas transport activities declined markedly (25–50%) when [Na+]o was reduced to 35 mm. Steady‐state pHi decreased more during respiratory (ΔpHi/ΔpHo = 71 ± 4%) than metabolic (ΔpHi/ΔpHo = 30 ± 7%) acidosis. Conclusion Extracellular acidification inhibits NBCn1 and NHE1 activity in VSMCs. NBCn1 is equivalently inhibited when pCO2 is raised or [HCO3−]o decreased. Lowering [Na+]o inhibits NBCn1 and NHE1 markedly only below the typical physiological and pathophysiological range. We propose that inhibition of Na+‐dependent net acid extrusion at low pHo protects against cellular Na+ overload at the cost of intracellular acidification.
    April 25, 2017   doi: 10.1111/apha.12877   open full text
  • Alpha adrenergic receptor blockade increases capillarization and fractional O2 extraction and lowers blood flow in contracting human skeletal muscle.
    S. P. Mortensen, S. Egginton, M. Madsen, J. B. Hansen, G. D. W. Munch, U. W. Iepsen, T. Åkerström, B. K. Pedersen, Y. Hellsten.
    Acta Physiologica. April 11, 2017
    Aim To assess the effect of elevated basal shear stress on angiogenesis in humans and the role of enhanced skeletal muscle capillarization on blood flow and O2 extraction. Methods Limb haemodynamics and O2 extraction were measured at rest and during one‐leg knee‐extensor exercise (12 and 24 W) in 10 healthy untrained young men before and after 4‐week treatment with an α1 receptor‐antagonist (Terazosin, 1–2 mg day−1). Corresponding biopsies were taken from the m. vastus lateralis. Results Resting leg blood flow was increased by 57% 6 h following Terazosin treatment (P < 0.05), while basal capillary‐to‐fibre ratio was 1.69 ± 0.08 and increased to 1.90 ± 0.08 after treatment (P < 0.05). Leg O2 extraction during knee‐extensor exercise was higher (4–5%; P < 0.05), leg blood flow and venous lactate levels lower (6–7%; P < 0.05), while leg VO2 was not different after Terazosin treatment. Conclusions These results demonstrate that daily treatment with an α‐adrenergic receptor blocker induces capillary growth in human skeletal muscle, likely due to increased shear stress. The increase in capillarization resulted in an increased fractional O2 extraction, a lower blood flow and venous lactate levels in the exercising leg. The increase in capillarization, and concomitant functional readouts in the exercising leg, may provide a basis for novel angiotherapy.
    April 11, 2017   doi: 10.1111/apha.12857   open full text
  • Release of calcium into the myofibrillar space in response to active shortening of striated muscle.
    K. A. P. Edman, C. Caputo.
    Acta Physiologica. April 11, 2017
    Aim The study was undertaken to explore whether shortening of striated muscle during activity is associated with release of bound Ca2+ into the myofibrillar space as has previously been proposed in order to explain the depressant effect of active shortening. Methods The experiments were carried out on single muscle fibres isolated from the anterior tibialis muscle of Rana temporaria. The fibres were loaded with the calcium sensitive indicator Fluo‐3. The fibres, stimulated to produce a partially fused isometric tetanus, were subjected to a shortening ramp or, alternatively, to a stretch ramp during activity while force, fibre length, sarcomere length and the Fluo‐3 signal were recorded. Results A shortening ramp performed during a partially fused tetanus caused an increase in the myofibrillar free calcium concentration and produced, simultaneously, a decrease in active force. The isometric force recovered gradually after the shortening ramp, while the intracellular Ca2+ concentration stayed above the control level during the remainder of the stimulation period. A stretch ramp applied during a partially fused tetanus caused a considerably smaller change in the myofibrillar Ca2+ concentration. Conclusion The results provide evidence that the myosin cross‐bridges interact with the calcium binding sites on the thin filaments during active shortening, causing sustained release of calcium and reduced contractile strength.
    April 11, 2017   doi: 10.1111/apha.12876   open full text
  • Weak by the Machines: Muscle Motor Protein Dysfunction ‐NDASH‐ a side Effect of Intensive Care Unit Treatment.
    O Friedrich, S Diermeier, L Larsson.
    Acta Physiologica. April 07, 2017
    Intensive care interventions involve periods of mechanical ventilation, sedation and complete mechanical silencing of patients. Critical illness myopathy (CIM) is an ICU‐acquired myopathy that is associated with limb muscle weakness, muscle atrophy, electrical silencing of muscle and motor‐proteinopathy. The hallmark of CIM is a preferential muscle myosin loss due to increased catabolic and reduced anabolic activity. The ubiquitin‐proteasome pathway plays an important role, apart from recently identified novel mechanisms affecting nonlysosomal protein degradation or autophagy. CIM is not reproduced by pure disuse atrophy, denervation atrophy, steroid‐induced atrophy or septic myopathy, although combinations of high‐dose steroids and denervation can mimic CIM. Novel animal models of critical illness and ICU‐treatment (i.e. mechanical ventilation and complete immobilization) provide novel insights regarding the time course of protein synthesis and degradation alterations, and the role of protective chaperone activities in the process of myosin loss. Altered mechano‐signaling seems involved in triggering a major part of myosin loss in experimental CIM models and passive loading of muscle potently ameliorates the CIM phenotype. We provide a systematic overview of similarities and distinct differences in the signaling pathways involved in triggering muscle atrophy in CIM and isolated trigger factors. Since preferential myosin loss is mostly determined from biochemistry analyses providing no spatial resolution of myosin loss processes within myofibres, we also provide first results monitoring myosin signal intensities during experimental ICU‐intervention using multiphoton Second harmonic Generation microscopy. Our results confirm that myosin loss is an evenly distributed process within myofibres rather than being confined to hot spots. This article is protected by copyright. All rights reserved.
    April 07, 2017   doi: 10.1111/apha.12885   open full text
  • Calcium‐dependent Nedd4‐2 upregulation mediates degradation of the cardiac sodium channel Nav1.5: implications for heart failure.
    L. Luo, F. Ning, Y. Du, B. Song, D. Yang, S. C. Salvage, Y. Wang, J. A. Fraser, S. Zhang, A. Ma, T. Wang.
    Acta Physiologica. April 06, 2017
    Aim Reductions in voltage‐gated sodium channel (Nav1.5) function/expression provide a slowed‐conduction substrate for cardiac arrhythmias. Nedd4‐2, which is activated by calcium, post‐translationally modulates Nav1.5. We aim to investigate whether elevated intracellular calcium ([Ca2+]i) reduces Nav1.5 through Nedd4‐2 and its role in heart failure (HF). Methods Using a combination of biochemical, electrophysiological, cellular and in vivo methods, we tested the effect and mechanism of calcium on Nedd4‐2 and in turn Nav1.5. Results Increased [Ca2+]i, following 24‐h ionomycin treatment, decreased sodium current (INa) density and Nav1.5 protein without altering its mRNA in both neonatal rat cardiomyocytes (NRCMs) and HEK 293 cells stably expressing Nav1.5. The calcium chelator BAPTA‐AM restored the reduced Nav1.5 and INa in NRCMs pre‐treated by ionomycin. Nav1.5 was decreased by Nedd4‐2 transfection and further decreased by 6‐h ionomycin treatment. These effects were not observed in cells transfected with the catalytically inactive mutant, Nedd4‐2 C801S, or with Y1977A‐Nav1.5 mutant containing the impaired Nedd4‐2 binding motif. Furthermore, elevated [Ca2+]i increased Nedd4‐2, the interaction between Nedd4‐2 and Nav1.5, and Nav1.5 ubiquitination. Nav1.5 protein is decreased, whereas Nedd4‐2 is increased in volume‐overload HF rat hearts, with increased co‐localization of Nav1.5 with ubiquitin or Nedd4‐2 as indicated by immunofluorescence staining. BAPTA‐AM rescued the reduced Nav1.5 protein, INa and increased Nedd4‐2 in hypertrophied NRCMs induced by isoproterenol or angiotensin II. Conclusion Calcium‐mediated increases in Nedd4‐2 downregulate Nav1.5 by ubiquitination. Nav1.5 is downregulated and co‐localizes with Nedd4‐2 and ubiquitin in failing rat heart. These data suggest a role of Nedd4‐2 in Nav1.5 downregulation in HF.
    April 06, 2017   doi: 10.1111/apha.12872   open full text
  • The role of neuropeptide W in energy homeostasis.
    Hui Li, Stephen J Kentish, Gary A Wittert, Amanda J Page.
    Acta Physiologica. April 04, 2017
    Neuropeptide W is the endogenous ligand for G‐protein‐coupled receptors GPR7 and GPR8. In this review, we summarize findings on the distribution of neuropeptide W and its receptors in the central nervous system and the periphery, and discuss the role of NPW in food intake and energy homeostasis. This article is protected by copyright. All rights reserved.
    April 04, 2017   doi: 10.1111/apha.12884   open full text
  • Transcriptional regulation of voltage‐gated Ca2+ channels.
    Ricardo González‐Ramírez, Ricardo Felix.
    Acta Physiologica. March 31, 2017
    The transcriptional regulation of voltage‐gated Ca2+ (CaV) channels is an emerging research area that promises to improve our understanding of how many relevant physiological events are shaped in the central nervous system, the skeletal muscle, and other tissues. Interestingly, a picture of how transcription of CaV channel subunit genes is controlled is evolving with the identification of the promoter regions required for tissue‐specific expression, and the identification of transcription factors that control their expression. These promoters share several characteristics that include multiple transcriptional start sites, lack of a TATA box, and the presence of elements conferring tissue‐selective expression. Likewise, changes in CaV channel expression occur throughout development, following ischemia, seizures, or chronic drug administration. This review focuses on insights achieved regarding the control of CaV channel gene expression. To further understand the complexities of expression and to increase the possibilities of detecting CaV channel alterations causing human disease, a deeper knowledge on the structure of the 5’ upstream regions of the genes encoding these remarkable proteins will be necessary. This article is protected by copyright. All rights reserved.
    March 31, 2017   doi: 10.1111/apha.12883   open full text
  • Role of renal vascular potassium channels in physiology and pathophysiology.
    Max Salomonsson, Jens Christian Brasen, Charlotte M. Sorensen.
    Acta Physiologica. March 30, 2017
    The control of renal vascular tone is important for the regulation of salt and water balance, blood pressure and the protection against damaging elevated glomerular pressure. The K+ conductance is a major factor in the regulation of the membrane potential (Vm) in vascular smooth muscle (VSMC) and endothelial cells (EC). The vascular tone is controlled by Vm via its effect on the opening probability of voltage operated Ca2+channels (VOCC) in VSMC. When K+ conductance increases Vm becomes more negative and vasodilation follows, while deactivation of K+ channels leads to depolarization and vasoconstriction. K+ channels in EC indirectly participate in the control of vascular tone by endothelium derived vasodilation. Therefore, by regulating the tone of renal resistance vessels, K+ channels have a potential role in the control of fluid homeostasis and blood pressure as well as in the protection of the renal parenchyma. The main classes of K+ channels (calcium activated (KCa), inward rectifier (Kir), voltage activated (Kv) and ATP sensitive (KATP)) have been found in the renal vessels. In this review, we summarize results available in the literature and our own studies in the field. We compare the ambiguous in vitro and in vivo results. We discuss the role of single types of K+ channels and the integrated function of several classes. We also deal with the possible role of renal vascular K+ channels in the pathophysiology of hypertension, diabetes mellitus and sepsis. This article is protected by copyright. All rights reserved.
    March 30, 2017   doi: 10.1111/apha.12882   open full text
  • Exercise and epigenetic inheritance of disease risk.
    Joshua Denham.
    Acta Physiologica. March 30, 2017
    Epigenetics is the study of gene expression changes that occur in the absence of altered genotype. Current evidence indicates a role for environmentally induced alterations to epigenetic modifications leading to health and diseases changes across multiple generations. This phenomenon is called intergenerational or transgenerational epigenetic inheritance of health or disease. Environmental insults, in the form of toxins, plastics and particular dietary interventions, perturb the epigenetic landscape and influence the health of F1 through to F4 generations in rodents. There is, however, the possibility that healthy lifestyles and environmental factors, such as exercise training, could lead to favourable, heritable epigenetic modifications that augment transcriptional programs protective of disease, including metabolic dysfunction, heart disease and cancer. The health benefits conferred by regular physical exercise training are unquestionable, yet many of the molecular changes may have heritable health implications for future generations. Similar to other environmental factors, exercise modulates the epigenome of somatic cells and researchers are beginning to study exercise epigenetics in germ cells. The germ cell epigenetic modifications affected by exercise offer a molecular mechanism for the inheritance of health and disease risk. The aims of this review are to: 1) provide an update on the expanding field of exercise epigenetics; 2) offer an overview of data on intergenerational/transgenerational epigenetic inheritance of disease by environmental insults; 3) to discuss the potential of exercise‐induced intergenerational inheritance of health and disease risk; and finally, outline potential mechanisms and avenues for future work on epigenetic inheritance through exercise. This article is protected by copyright. All rights reserved.
    March 30, 2017   doi: 10.1111/apha.12881   open full text
  • Vagal nerve stimulation reduces infarct size via a mechanism involving the alpha‐7 nicotinic acetylcholine receptor and downregulation of cardiac and vascular arginase.
    A. Kiss, Y. Tratsiakovich, A. Mahdi, J. Yang, A. T. Gonon, B. K. Podesser, J. Pernow.
    Acta Physiologica. March 24, 2017
    Aims Vagal nerve stimulation (VNS) protects from myocardial and vascular injury following myocardial ischaemia and reperfusion (IR) via a mechanism involving activation of alpha‐7 nicotinic acetylcholine receptor (α7 nAChR) and reduced inflammation. Arginase is involved in development of myocardial IR injury driven by inflammatory mediators. The aim of the study was to clarify whether VNS downregulates myocardial and vascular arginase via a mechanism involving activation of α7 nAChR following myocardial IR. Methods Anaesthetized rats were randomized to (i) sham‐operated, (ii) control IR (30‐min ischaemia and 2‐h reperfusion, (iii) VNS throughout IR, (iv) the arginase inhibitor nor‐NOHA+IR, (v) nor‐NOHA+VNS+IR, (vi) selective α7 nAChR blockade by methyllycaconitine (MLA) followed by VNS throughout IR and (vii) MLA+IR. Results Infarct size was reduced by VNS compared to control IR (41 ± 3% vs. 67 ± 2% of the myocardium at risk, P < 0.001). Myocardial IR increased myocardial and aortic arginase activity 1.7‐ and 3.1‐fold respectively (P < 0.05). VNS attenuated the increase in arginase activity compared to control IR both in the myocardium and aorta (P < 0.05). MLA partially abolished the cardioprotective effect of VNS and completely abrogated the effect of VNS on arginase activity. Arginase inhibition combined with VNS did not further reduce infarct size. Conclusion Vagal nerve stimulation reduced infarct size and reversed the upregulation of arginase induced by IR both in the myocardium and aorta via a mechanism depending on α7 nAChR activation. The data suggest that the cardioprotective effect of VNS is mediated via reduction in arginase activity.
    March 24, 2017   doi: 10.1111/apha.12861   open full text
  • Hypoxia‐stimulated membrane trafficking requires T‐plastin.
    M. Wottawa, S. Naas, J. Böttger, G. J. van Belle, W. Möbius, N. H. Revelo, D. Heidenreich, M. von Ahlen, A. Zieseniss, K. Kröhnert, S. Lutz, C. Lenz, H. Urlaub, S. O. Rizzoli, D. M. Katschinski.
    Acta Physiologica. March 23, 2017
    Aim Traffic between the plasma membrane and the endomembrane compartments is an essential feature of eukaryotic cells. The secretory pathway sends cargoes from biosynthetic compartments to the plasma membrane. This is counterbalanced by a retrograde endocytic route and is essential for cell homoeostasis. Cells need to adapt rapidly to environmental challenges such as the reduction of pO2 which, however, has not been analysed in relation to membrane trafficking in detail. Therefore, we determined changes in the plasma membrane trafficking in normoxia, hypoxia, and after reoxygenation. Methods Membrane trafficking was analysed by using the bulk membrane endocytosis marker FM 1‐43, the newly developed membrane probe mCLING, wheat germ agglutinin as well as fluorescently labelled cholera toxin subunit B. Additionally, the uptake of specific membrane proteins was determined. In parallel, a non‐biased SILAC screen was performed to analyse the abundance of membrane proteins in normoxia and hypoxia. Results Membrane trafficking was increased in hypoxia and quickly reversed upon reoxygenation. This effect was independent of the hypoxia‐inducible factor (HIF) system. Using SILAC technology, we identified that the actin‐bundling protein T‐plastin is recruited to the plasma membrane in hypoxia. By the use of T‐plastin knockdown cells, we could show that T‐plastin mediates the hypoxia‐induced membrane trafficking, which was associated with an increased actin density in the cells as determined by electron microscopy. Conclusion Membrane trafficking is highly dynamic upon hypoxia. This phenotype is quickly reversible upon reoxygenation, which suggests that this mechanism participates in the cellular adaptation to hypoxia.
    March 23, 2017   doi: 10.1111/apha.12859   open full text
  • Muscle oxygen saturation increases during head‐up tilt‐induced (pre)syncope.
    A. Lund, H. Sørensen, T. W. Jensen, M. J. Niemann, N. D. Olesen, H. B. Nielsen, N. V. Olsen, N. H. Secher.
    Acta Physiologica. March 22, 2017
    Aim To evaluate whether muscle vasodilatation plays a role for hypotension developed during central hypovolaemia, muscle oxygenation (SmO2) was examined during (pre)syncope induced by head‐up tilt (HUT). Skin blood flow (SkBF) and oxygenation (SskinO2) were determined because evaluation of SmO2 may be affected by superficial tissue oxygenation. Furthermore, we evaluated cerebral oxygenation (ScO2) and middle cerebral artery mean blood flow velocity (MCAvmean). Methods Twenty healthy male volunteers (median age 24 years; range 19–38) were subjected to passive 50° HUT for 1 h or until (pre)syncope. ScO2 and SmO2 (near‐infrared spectroscopy), MCAvmean (transcranial Doppler) along with mean arterial pressure (MAP), heart rate (HR), stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) (Modelflow®) were determined. Results (Pre)syncopal symptoms appeared in 17 subjects after 11 min (median; range 2–34) accompanied by a decrease in MAP, SV, CO and TPR, while HR remained elevated. During (pre)syncope, ScO2 decreased [73% (71–76; mean and 95% CI) to 68% (65–71), P < 0.0001] along with MCAvmean [40 (37–43) to 32 (29–35) cm s−1, P < 0.0001]. In contrast, SmO2 increased [63 (56–69)% to 71% (65–78), P < 0.0001], while SskinO2 [64% (58–69) to 53% (47–58), P < 0.0001] and SkBF [71 (44–98) compared to a baseline of 99 (72–125) units, P = 0.020] were reduced. Conclusion We confirm that the decrease in MAP during HUT is associated with a reduction in indices of cerebral perfusion. (Pre)syncope was associated with an increase in SmO2 despite reduced SskinO2 and SkBF, supporting that muscle vasodilation plays an important role in the circulatory events leading to hypotension during HUT.
    March 22, 2017   doi: 10.1111/apha.12863   open full text
  • Chronically elevated bilirubin protects from cardiac reperfusion injury in the male Gunn rat.
    B. Bakrania, E. F. Du Toit, K. J. Ashton, K‐H. Wagner, J. P. Headrick, A. C. Bulmer.
    Acta Physiologica. March 14, 2017
    Aims Bilirubin is associated with reduced risk of cardiovascular disease, as evidenced in conditions of mild hyperbilirubinaemia (Gilbert's Syndrome). Little is known regarding myocardial stress resistance in hyperbilirubinaemic conditions or whether life‐long exposure modifies cardiac function, which might contribute to protection from cardiovascular disease. Methods Hyperbilirubinaemic rats and littermate controls underwent echocardiography at 3, 6 and 12 months of age, with hearts subsequently assessed for resistance to 30 min of ischaemia. Heart tissue was then collected for assessment of bilirubin content. Results No difference in baseline cardiac function was evident until 6 months onwards, where Gunn rats demonstrated aortic dilatation and reduced peak ejection velocities. Additionally, duration of ventricular ejection increased progressively, indicating a negative inotropic effect of bilirubin in vivo. Ex vivo analysis of baseline function revealed reduced left ventricular pressure development (LVDP) and contractility in hyperbilirubinaemic rats. Furthermore, stress resistance was improved in Gunn hearts: post‐ischaemic recoveries of LVDP (76 ± 22% vs. 29 ± 17% Control, P < 0.01) and coronary flow (96 ± 9% vs. 86 ± 16% Control, P < 0.01) were improved in Gunn hearts, accompanied by reduced infarct area (21 ± 5% vs. 47 ± 15% Control, P < 0.01), and ventricular malondialdehyde and protein carbonyl content. Expression of myocardial nitric oxide‐regulating genes including Nos1 and Noa1 were not significantly different. Conclusions These data reveal life‐long hyperbilirubinaemia induces age‐dependent hypocontractility in male Gunn rats, and improved stress resistance. In addition, bilirubin exerts sex‐independent effects on vascular structure, myocardial function and ischaemic tolerance, the latter likely mediated via bilirubin's antioxidant properties.
    March 14, 2017   doi: 10.1111/apha.12858   open full text
  • Mind the gap: mechanisms regulating the endothelial barrier.
    Mariya Y. Radeva, Jens Waschke.
    Acta Physiologica. February 23, 2017
    The endothelial barrier consists of intercellular contacts localized in the cleft between endothelial cells, which is covered by the glycocalyx in a sieve‐like manner. Both types of barrier‐forming junctions, i.e. the adherens junction (AJ) serving mechanical anchorage and mechanotransduction and the tight junction (TJ) sealing the intercellular space to limit paracelullar permeability, are tethered to the actin cytoskeleton. Under resting conditions, the endothelium thereby builds a selective layer controlling the exchange of fluid and solutes with the surrounding tissue. However, in the situation of an inflammatory response such as in anaphylaxis or sepsis intercellular contacts disintegrate in postcapillary venules leading to intercellular gap formation. The resulting edema can cause shock and multi‐organ failure. Therefore, maintenance as well as coordinated opening and closure of interendothelial junctions is tightly regulated. The two principle underlying mechanisms comprise spatiotemporal activity control of the small GTPases Rac1 and RhoA and the balance of the phosphorylation state of AJ proteins. In the resting state, junctional Rac1 and RhoA activity is enhanced by junctional components, actin‐binding proteins (ABPs), cAMP signaling and extracellular cues such as sphingosine‐1‐phosphate (S1P) and angiopoitin‐1 (Ang‐1). In addition, phosphorylation of AJ components is prevented by junction‐associated phosphatases including vascular endothelial protein tyrosine phosphatase (VE‐PTP). In contrast, inflammatory mediators inhibiting cAMP/Rac1 signaling cause strong activation of RhoA and induce AJ phosphorylation finally leading to endocytosis and cleavage of VE‐cadherin. This results in dissolution of TJs the outcome of which is endothelial barrier breakdown. This article is protected by copyright. All rights reserved.
    February 23, 2017   doi: 10.1111/apha.12860   open full text
  • The water channel AQP1 is expressed in human atherosclerotic vascular lesions and AQP1 deficiency augments angiotensin II‐induced atherosclerosis in mice.
    P. Wintmo, S. H. Johansen, P. B. L. Hansen, J. S. Lindholt, S. Urbonavicius, L. M. Rasmussen, P. Bie, B. L. Jensen, J. Stubbe.
    Acta Physiologica. February 22, 2017
    Aim The water channel aquaporin 1 (AQP1) promotes endothelial cell migration. It was hypothesized that AQP1 promotes neovascularization and growth of atherosclerotic plaques. Methods AQP1 immunoreactivity and protein abundance was examined in human and murine atherosclerotic lesions and aortic aneurysms. Apolipoprotein E (ApoE) knockout (−/−) and AQP1−/−ApoE−/− mice were developed and fed Western diet (WD) for 8 and 16 weeks to accelerate the atherosclerosis process. In ApoE−/− and AQP1−/−ApoE−/− mice abdominal aortic aneurysms (AAA) were induced by angiotensin II (ANGII) infusion by osmotic minipumps for 4 weeks. Results In human atherosclerotic lesions and AAA, AQP1 immunoreactive protein was associated with intralesional small vessels. In ApoE−/− mouse aorta, APQ1 mRNA levels were increased with time on WD (n = 7–9, P < 0.003). Both in murine lesions at the aortic root and in the abdominal aortic aneurysmal wall, AQP1 immunoreactivity was associated with microvascular structures. The atherosclerotic lesion burden was enhanced significantly in ANGII‐infused AQP1−/−ApoE−/− mice compared with ApoE−/− mice, but neither incidence nor progression of AAA was different. The aortic lesion burden increased with time on WD but was not different between ApoE−/− and AQP1−/−ApoE−/− mice at either 8 or 16 weeks (n = 13–15). Baseline blood pressure and ANGII‐induced hypertension were not different between genotypes. Conclusion AQP1 is expressed in atherosclerotic lesion neovasculature in human and mouse arteries and AQP1 deficiency augments lesion development in ANGII‐promoted atherosclerosis in mice. Normal function of AQP1 affords cardiovascular protection.
    February 22, 2017   doi: 10.1111/apha.12853   open full text
  • Maternal–fetal cholesterol transport in the second half of mouse pregnancy does not involve LDL receptor‐related protein 2.
    M. V. Zwier, M. E. Baardman, T. H. Dijk, A. Jurdzinski, L. J. Wisse, V. W. Bloks, R. M. F. Berger, M. C. DeRuiter, A. K. Groen, T. Plösch.
    Acta Physiologica. February 22, 2017
    Aim LDL receptor‐related protein type 2 (LRP2) is highly expressed on both yolk sac and placenta. Mutations in the corresponding gene are associated with severe birth defects in humans, known as Donnai–Barrow syndrome. We here characterized the contribution of LRP2 and maternal plasma cholesterol availability to maternal–fetal cholesterol transport and fetal cholesterol levels in utero in mice. Methods Lrp2+/− mice were mated heterozygously to yield fetuses of all three genotypes. Half of the dams received a 0.5% probucol‐enriched diet during gestation to decrease maternal HDL cholesterol. At E13.5, the dams received an injection of D7‐labelled cholesterol and were provided with 1‐13C acetate‐supplemented drinking water. At E16.5, fetal tissues were collected and maternal cholesterol transport and fetal synthesis quantified by isotope enrichments in fetal tissues by GC‐MS. Results The Lrp2 genotype did not influence maternal–fetal cholesterol transport and fetal cholesterol. However, lowering of maternal plasma cholesterol levels by probucol significantly reduced maternal–fetal cholesterol transport. In the fetal liver, this was associated with increased cholesterol synthesis rates. No indications were found for an interaction between the Lrp2 genotype and maternal probucol treatment. Conclusion Maternal–fetal cholesterol transport and endogenous fetal cholesterol synthesis depend on maternal cholesterol concentrations but do not involve LRP2 in the second half of murine pregnancy. Our results suggest that the mouse fetus can compensate for decreased maternal cholesterol levels. It remains a relevant question how the delicate system of cholesterol transport and synthesis is regulated in the human fetus and placenta.
    February 22, 2017   doi: 10.1111/apha.12845   open full text
  • Repeated maximal‐intensity hypoxic exercise superimposed to hypoxic residence boosts skeletal muscle transcriptional responses in elite team‐sport athletes.
    F. Brocherie, G. P. Millet, G. D'Hulst, R. Van Thienen, L. Deldicque, O. Girard.
    Acta Physiologica. February 22, 2017
    Aim To determine whether repeated maximal‐intensity hypoxic exercise induces larger beneficial adaptations on the hypoxia‐inducible factor‐1α pathway and its target genes than similar normoxic exercise, when combined with chronic hypoxic exposure. Methods Lowland elite male team‐sport athletes underwent 14 days of passive normobaric hypoxic exposure [≥14 h·day−1 at inspired oxygen fraction (FiO2) 14.5–14.2%] with the addition of six maximal‐intensity exercise sessions either in normobaric hypoxia (FiO2 ~14.2%; LHTLH; n = 9) or in normoxia (FiO2 20.9%; LHTL; n = 11). A group living in normoxia with no additional maximal‐intensity exercise (LLTL; n = 10) served as control. Before (Pre), immediately after (Post‐1) and 3 weeks after (Post‐2) the intervention, muscle biopsies were obtained from the vastus lateralis. Results Hypoxia‐inducible factor‐1α subunit, vascular endothelial growth factor, myoglobin, peroxisome proliferator‐activated receptor‐gamma coactivator 1‐α and mitochondrial transcription factor A mRNA levels increased at Post‐1 (all P ≤ 0.05) in LHTLH, but not in LHTL or LLTL, and returned near baseline levels at Post‐2. The protein expression of citrate synthase increased in LHTLH (P < 0.001 and P < 0.01 at Post‐1 and Post‐2, respectively) and LLTL (P < 0.01 and P < 0.05 at Post‐1 and Post‐2, respectively), whereas it decreased in LHTL at Post‐1 and Post‐2 (both P < 0.001). Conclusion Combined with residence in normobaric hypoxia, repeated maximal‐intensity hypoxic exercise induces short‐term post‐intervention beneficial changes in muscle transcriptional factors that are of larger magnitude (or not observed) than with similar normoxic exercise. The decay of molecular adaptations was relatively fast, with most of benefits already absent 3 weeks post‐intervention.
    February 22, 2017   doi: 10.1111/apha.12851   open full text
  • The innervation of the kidney in renal injury and inflammation: A cause and consequence of deranged cardiovascular control.
    Mohammed H Abdulla, Edward J Johns.
    Acta Physiologica. February 09, 2017
    Extensive investigations have revealed that renal sympathetic nerves regulate renin secretion, tubular fluid reabsorption and renal haemodynamics which can impact on cardiovascular homoeostasis normally and in pathophysiological states. The significance of the renal afferent innervation and its role in determining the autonomic control of the cardiovascular system is uncertain. The transduction pathways at the renal afferent nerves have been shown to require pro‐inflammatory mediators and TRPV1 channels. Reno‐renal reflexes have been described, both inhibitory and excitatory, demonstrating that a neural link exists between kidneys and may determine the distribution of excretory and haemodynamic function between the two kidneys. The impact of renal afferent nerve activity on basal and reflex regulation of global sympathetic drive remains opaque. There is clinical and experimental evidence that in states of chronic kidney disease and renal injury there is infiltration of T‐helper cells with a sympatho‐excitation and blunting of the high and low pressure baroreceptor reflexes regulating renal sympathetic nerve activity. The baroreceptor deficits are renal nerve‐dependent as the dysregulation can be relieved by renal denervation. There is also experimental evidence that in obese states there is a sympatho‐excitation and disrupted baroreflex regulation of renal sympathetic nerve activity which is mediated by the renal innervation. This body of information provides an important basis for directing greater attention to the role of renal injury/inflammation causing an inappropriate activation of the renal afferent nerves as an important initiator of aberrant autonomic cardiovascular control. This article is protected by copyright. All rights reserved.
    February 09, 2017   doi: 10.1111/apha.12856   open full text
  • Targeting multiple pathways reduces renal and cardiac fibrosis in rats with subtotal nephrectomy followed by coronary ligation.
    N. R. Oosterhuis, L. G. Bongartz, M. C. Verhaar, C. Cheng, Y. J. Xu, A. Koppen, M. J. Cramer, R. Goldschmeding, C. A. Gaillard, P. A. Doevendans, B. Braam, J. A. Joles.
    Acta Physiologica. February 07, 2017
    Aim Multiple interacting pathways contribute to progression of renal and cardiac damage in chronic kidney disease followed by chronic heart failure (renocardiac syndrome). We hypothesized that simultaneous pharmacological modulation of critical pathways implicated in renocardiac syndrome would effectively reduce fibrosis in and preserve function of heart and kidney. Methods Rats were subjected to subtotal nephrectomy followed 9 weeks later by coronary artery ligation. From week 11 until week 16, rats received vehicle or losartan, or a combination of the NF‐kB inhibitor PDTC, the NO donor molsidomine and superoxide dismutase mimetic tempol, or a combination of all four of these plus metoprolol together. At week 16, renal and cardiac structure, function and gene expression were assessed. Results Individual and combined treatments were similarly effective in limiting cardiac fibrosis and further decline in systolic function. Combined treatment with all five drugs reduced renal fibrosis and CTGF gene expression more effectively than other strategies. Combining all five drugs reduced heart rate, inotropy and mean arterial pressure (MAP). Conclusion Thus, in our model of chronic renocardiac syndrome, combined treatments similarly decreased cardiac fibrosis and stabilized systolic function as losartan alone, perhaps suggesting a dominant role for a single factor such as angiotensin II type 1 (AT1) receptor activation or inflammation in the network of aberrant systems in the heart. However, tubulointerstitial fibrosis was most effectively reduced by a five‐drug regimen, pointing to additive effects of multiple pathophysiological pathways in the kidney.
    February 07, 2017   doi: 10.1111/apha.12829   open full text
  • Enhanced contractility of intraparenchymal arterioles after global cerebral ischaemia in rat – new insights into the development of delayed cerebral hypoperfusion.
    S. Spray, S. E. Johansson, A. Radziwon‐Balicka, K. A. Haanes, K. Warfvinge, G. K. Povlsen, P. A. T. Kelly, L. Edvinsson.
    Acta Physiologica. January 29, 2017
    Aim Delayed cerebral hypoperfusion is a secondary complication found in the days after transient global cerebral ischaemia that worsens the ischaemic damage inflicted by the initial transient episode of global cerebral ischaemia. A recent study demonstrated increased cerebral vasoconstriction in the large arteries on the brain surface (pial arteries) after global cerebral ischaemia. However, smaller arterioles inside the brain (parenchymal arterioles) are equally important in the regulation of cerebral blood flow and yet their pathophysiology after global cerebral ischaemia is largely unknown. Therefore, we investigated whether increased contractility occurs in the intraparenchymal arterioles. Methods Global cerebral ischaemia was induced in male Wistar rats by bilateral common carotid occlusion for 15 min combined with hypovolaemia. Regional cerebral blood flow was determined by quantitative autoradiography. Intraparenchymal arterioles were isolated and pressurized, and concentration–response curves to endothelin‐1 with and without the endothelin B receptor‐selective antagonist BQ788 was generated. Endothelin B receptor expression was investigated by quantitative flow cytometry and immunohistochemistry. Results We observed increased endothelin‐1‐mediated contractility of parenchymal arterioles correlating with reduced cerebral blood flow of the cortex, hippocampus and caudate nucleus 48 h after global cerebral ischaemia. The increased endothelin‐1‐mediated contractility was abolished by BQ788, and the vascular smooth muscle cell‐specific expression of endothelin B receptors was significantly increased after global cerebral ischaemia. Conclusion Increased endothelin‐1‐mediated contractility and expression of endothelin B receptors in the intraparenchymal vasculature contributes to the development of delayed cerebral hypoperfusion after global cerebral ischaemia in combination with vascular changes of the pial vasculature.
    January 29, 2017   doi: 10.1111/apha.12834   open full text
  • The effect of physical fatigue on oscillatory dynamics of the sensorimotor cortex.
    A. Fry, K. J. Mullinger, G. C. O'Neill, M. J. Brookes, J. P. Folland.
    Acta Physiologica. January 29, 2017
    Aim While physical fatigue is known to arise in part from supraspinal mechanisms within the brain, exactly how brain activity is modulated during fatigue is not well understood. Therefore, this study examined how typical neural oscillatory responses to voluntary muscle contractions were affected by fatigue. Methods Eleven healthy adults (age 27 ± 4 years) completed two experimental sessions in a randomized crossover design. Both sessions first assessed baseline maximal voluntary isometric wrist‐flexion force (MVFb). Participants then performed an identical series of fourteen test contractions (2 × 100%MVFb, 10 × 40%MVFb, 2 × 100%MVFb) both before and after one of two interventions: forty 12‐s contractions at 55%MVFb (fatigue intervention) or 5%MVFb (control intervention). Magnetoencephalography (MEG) was used to characterize both the movement‐related mu and beta decrease (MRMD and MRBD) and the post‐movement beta rebound (PMBR) within the contralateral sensorimotor cortex during the 40%MVFb test contractions, while the 100%MVFb test contractions were used to monitor physical fatigue. Results The fatigue intervention induced a substantial physical fatigue that endured throughout the post‐intervention measurements (28.9–29.5% decrease in MVF, P < 0.001). Fatigue had a significant effect on both PMBR (anova, session × time‐point interaction: P = 0.018) and MRBD (P = 0.021): the magnitude of PMBR increased following the fatigue but not the control interventions, whereas MRBD was decreased post‐control but not post‐fatigue. Mu oscillations were unchanged throughout both sessions. Conclusion Physical fatigue resulted in an increased PMBR, and offset attenuations in MRBD associated with task habituation.
    January 29, 2017   doi: 10.1111/apha.12843   open full text
  • Autophagy in Renal Tubular Injury and Repair.
    Fangming Lin.
    Acta Physiologica. January 23, 2017
    Autophagy is a fundamental cellular process that maintains normal function and structure of the cell. It can be induced during stress and serves as an adaptive response for cell survival. Normal kidneys have high metabolic demands yet are relatively hypoxic, especially in the medulla and papilla. Injury or aging aggravates metabolic perturbation and activates autophagy in many types of renal cells. In the kidney, tubular epithelial cells consume the most energy due to active transport mechanisms and therefore are the most susceptible to injuries from hypoxic or low energy states. This brief review will summarize current understandings of the biological function and molecular regulation of epithelial autophagy during tubular injury and repair. This article is protected by copyright. All rights reserved.
    January 23, 2017   doi: 10.1111/apha.12852   open full text
  • A comparison of left and right atrial fibroblasts reveals different collagen production activity and stress‐induced mitogen‐activated protein kinase signalling in rats.
    C.‐C. Chung, Y.‐H. Kao, C.‐J. Yao, Y.‐K. Lin, Y.‐J. Chen.
    Acta Physiologica. January 16, 2017
    Aim Atrial fibrosis plays a pivotal role in the pathophysiology of heart failure (HF). The left atrium (LA) experiences greater fibrosis than the right atrium (RA) during HF. It is not clear whether LA cardiac fibroblasts contain distinctive activities that predispose LA to fibrosis. Methods LA and RA fibrosis were evaluated in healthy and isoproterenol‐induced HF Sprague Dawley rats. Rat LA and RA primary isolated fibroblasts were subjected to proliferation assay, oxidative stress assay, cell migration analysis, collagen measurement, cytokine array and Western blot. Results Healthy rat LA and RA had a similar extent of collagen deposition. HF significantly increased fibrosis to a greater severity in LA than in RA. Compared to isolated RA fibroblasts, the in vitro experiments showed that isolated LA fibroblasts had higher oxidative stress and exhibited higher collagen, transforming growth factor‐β1, connective tissue growth factor production and less vascular endothelial growth factor (VEGF) production, but had similar migration, myofibroblast differentiation and proliferation activities. VEGF significantly increased the collagen production ability of LA fibroblasts, but not RA fibroblasts. LA fibroblasts had more phosphorylated ERK1/2 and P38 expression. ERK inhibitor (PD98059, 50 μmol L−1) significantly attenuated collagen production and increased VEGF production in RA fibroblasts but not in LA fibroblasts. P38 inhibitor (SB203580, 30 μmol L−1) significantly attenuated collagen production in LA fibroblasts but not in RA fibroblasts. P38 inhibitor also significantly increased VEGF production in RA and LA fibroblasts. Conclusions Differences in profibrotic activity between LA and RA fibroblasts may be caused by different responses to mitogen‐activated protein kinase signalling.
    January 16, 2017   doi: 10.1111/apha.12835   open full text
  • Neuromuscular changes and the rapid adaptation following a bout of damaging eccentric exercise.
    S. Goodall, K. Thomas, M. Barwood, K. Keane, J. T. Gonzalez, A. St Clair Gibson, G. Howatson.
    Acta Physiologica. January 05, 2017
    Introduction An initial bout of eccentric exercise is known to protect against muscle damage following a repeated bout of the same exercise; however, the neuromuscular adaptations owing to this phenomenon are unknown. Aim To determine whether neuromuscular disturbances are modulated following a repeated bout of eccentric exercise. Methods Following eccentric exercise performed with the elbow flexors, we measured maximal voluntary force, resting twitch force, muscle soreness, creatine kinase (CK) and voluntary activation (VA) using motor point and motor cortex stimulation at baseline, immediately post‐exercise and at 1, 2, 3, 4 and 7 days post‐exercise on two occasions, separated by 3 weeks. Results Significant muscle damage and fatigue were evident following the first exercise bout; maximal voluntary contraction (MVC) was reduced immediately by 35% and remained depressed at 7 days post‐exercise. Soreness and CK release peaked at 3 and 4 days post‐exercise respectively. Resting twitch force remained significantly reduced at 7 days (−48%), whilst VA measured with motor point and motor cortex stimulation was reduced until 2 and 3 days respectively. A repeated bout effect (RBE) was observed with attenuated soreness and CK release and a quicker recovery of MVC and resting twitch force. A similar decrement in VA was observed following both bouts; however, following the repeated bout there was a significantly smaller reduction in, and a faster recovery of, VA measured using motor cortical stimulation. Conclusion Our data suggest that the RBE may be explained, partly, by a modification in motor corticospinal drive.
    January 05, 2017   doi: 10.1111/apha.12844   open full text
  • Cutaneous exposure to hypoxia does not affect skin perfusion in humans.
    C. Siebenmann, M. E. Keramidas, H. Rundqvist, S. Mijwel, A. S. Cowburn, R. S. Johnson, O. Eiken.
    Acta Physiologica. November 30, 2016
    Aim Experiments have indicated that skin perfusion in mice is sensitive to reductions in environmental O2 availability. Specifically, a reduction in skin‐surface PO2 attenuates transcutaneous O2 diffusion, and hence epidermal O2 supply. In response, epidermal HIF‐1α expression increases and facilitates initial cutaneous vasoconstriction and subsequent nitric oxide‐dependent vasodilation. Here, we investigated whether the same mechanism exists in humans. Methods In a first experiment, eight males rested twice for 8 h in a hypobaric chamber. Once, barometric pressure was reduced by 50%, while systemic oxygenation was preserved by O2‐enriched (42%) breathing gas (HypoxiaSkin), and once barometric pressure and inspired O2 fraction were normal (Control1). In a second experiment, nine males rested for 8 h with both forearms wrapped in plastic bags. O2 was expelled from one bag by nitrogen flushing (AnoxiaSkin), whereas the other bag was flushed with air (Control2). In both experiments, skin blood flux was assessed by laser Doppler on the dorsal forearm, and HIF‐1α expression was determined by immunohistochemical staining in forearm skin biopsies. Results Skin blood flux during HypoxiaSkin and AnoxiaSkin remained similar to the corresponding Control trial (P = 0.67 and P = 0.81). Immunohistochemically stained epidermal HIF‐1α was detected on 8.2 ± 6.1 and 5.3 ± 5.7% of the analysed area during HypoxiaSkin and Control1 (P = 0.30) and on 2.3 ± 1.8 and 2.4 ± 1.8% during AnoxiaSkin and Control2 (P = 0.90) respectively. Conclusion Reductions in skin‐surface PO2 do not affect skin perfusion in humans. The unchanged epidermal HIF‐1α expression suggests that epidermal O2 homoeostasis was not disturbed by HypoxiaSkin/AnoxiaSkin, potentially due to compensatory increases in arterial O2 extraction.
    November 30, 2016   doi: 10.1111/apha.12825   open full text
  • PGC‐1α4 gene expression is suppressed by the IL‐6—MEK—ERK 1/2 MAPK signalling axis and altered by resistance exercise, obesity and muscle injury.
    J. L. Brown, M. E. Rosa‐Caldwell, D. E. Lee, L. A. Brown, R. A. Perry, K. L. Shimkus, T. A. Blackwell, J. D. Fluckey, J. A. Carson, S. Dridi, T. A. Washington, N. P. Greene.
    Acta Physiologica. November 25, 2016
    Aim PGC‐1α4 is a novel regulator of muscle hypertrophy; however, there is limited understanding of the regulation of its expression and role in many (patho)physiological conditions. Therefore, our purpose was to elicit signalling mechanisms regulating gene expression of Pgc1α4 and examine its response to (patho)physiological stimuli associated with altered muscle mass. Methods IL‐6 knockout mice and pharmacological experiments in C2C12 myocytes were used to identify regulation of Pgc1α4 transcription. To examine Pgc1α4 gene expression in (patho)physiological conditions, obese and lean Zucker rats with/without resistance exercise (RE), ageing mice and muscle regeneration from injury were examined. Results In IL‐6 knockout mice, Pgc1α4mRNA was ~sevenfold greater than wild type. In C2C12 cells, Pgc1α4mRNA was suppressed ~70% by IL‐6. Suppression of Pgc1α4 by IL‐6 was prevented by MEK–ERK–MAPK inhibition. RE led to ~260% greater Pgc1α4mRNA content in lean rats. However, obese Zucker rats exhibited ~270% greater Pgc1α4mRNA than lean, sedentary with no further augmentation by RE. No difference was seen in IL‐6mRNA or ERK‐MAPK phosphorylation in Zucker rats. Aged mice demonstrated ~50% lower Pgc1α4mRNA and ~fivefold greater ERK‐MAPK phosphorylation than young despite unchanged Il‐6mRNA. During muscle regeneration, Pgc1α4 content is ~30% and IL‐6mRNA >threefold of uninjured controls 3 days following injury; at 5 days, Pgc1α4 was >twofold greater in injured mice with no difference in IL‐6mRNA. Conclusion Our findings reveal a novel mechanism suppressing Pgc1α4 gene expression via IL‐6–ERK‐MAPK and suggest this signalling axis may inhibit Pgc1α4 in some, but not all, (patho)physiological conditions.
    November 25, 2016   doi: 10.1111/apha.12826   open full text
  • Acute physical exercise and long‐term individual shear rate therapy increase telomerase activity in human peripheral blood mononuclear cells.
    A. Zietzer, E. E. Buschmann, D. Janke, L. Li, M. Brix, H. Meyborg, P. Stawowy, C. Jungk, I. Buschmann, P. Hillmeister.
    Acta Physiologica. November 22, 2016
    Aim Physical activity is a potent way to impede vascular ageing. However, patients who suffer from peripheral artery disease (PAD) are often unable to exercise adequately. For those patients, we have developed individual shear rate therapy (ISRT), which is an adaptation of external counterpulsation and enhances endovascular fluid shear stress to increase collateral growth (arteriogenesis). To evaluate the effects of physical exercise and ISRT on the telomere biology of peripheral blood mononuclear cells (PBMCs), we conducted two clinical trials. Methods In the ISRT‐1 study, we assessed PBMC telomerase activity in 26 young healthy volunteers upon a single (short‐term) ISRT session and a single treadmill running session. In the ISRT‐2 study, we investigated PBMC telomere biology of 14 elderly patients with PAD, who underwent 30 h of (long‐term) ISRT within a 5‐week period. Results We demonstrate that telomerase activity significantly increased from 39.84 Total Product Generated (TPG) Units ± 6.15 to 58.10 TPG ± 10.46 upon a single treadmill running session in healthy volunteers. In the ISRT‐2 trial, PBMC telomerase activity and the mRNA expression of the telomere‐protective factor TRF2 increased from 40.87 TPG ± 4.45 to 60.98 TPG ± 6.83 and 2.10‐fold ± 0.40, respectively, upon long‐term ISRT in elderly patients with PAD. Conclusion In summary, we show that acute exercise and long‐term ISRT positively affect PBMC telomerase activity, which is indicative for an improved regenerative potential of immune cells and vascular tissues. Long‐term ISRT also enhances the gene expression of the telomere‐protective factor TRF2.
    November 22, 2016   doi: 10.1111/apha.12820   open full text
  • Striated muscle activator of Rho signalling (STARS) is reduced in ageing human skeletal muscle and targeted by miR‐628‐5p.
    A. P. Russell, M. A. Wallace, M. Kalanon, E. Zacharewicz, P. A. Della Gatta, A. Garnham, S. Lamon.
    Acta Physiologica. November 18, 2016
    Aim The striated muscle activator of Rho signalling (STARS) is a muscle‐specific actin‐binding protein. The STARS signalling pathway is activated by resistance exercise and is anticipated to play a role in signal mechanotransduction. Animal studies have reported a negative regulation of STARS signalling with age, but such regulation has not been investigated in humans. Methods Ten young (18–30 years) and 10 older (60–75 years) subjects completed an acute bout of resistance exercise. Gene and protein expression of members of the STARS signalling pathway and miRNA expression of a subset of miRNAs, predicted or known to target members of STARS signalling pathway, were measured in muscle biopsies collected pre‐exercise and 2 h post‐exercise. Results For the first time, we report a significant downregulation of the STARS protein in older subjects. However, there was no effect of age on the magnitude of STARS activation in response to an acute bout of exercise. Finally, we established that miR‐628‐5p, a miRNA regulated by age and exercise, binds to the STARS 3’UTR to directly downregulate its transcription. Conclusion This study describes for the first time the resistance exercise‐induced regulation of STARS signalling in skeletal muscle from older humans and identifies a new miRNA involved in the transcriptional control of STARS.
    November 18, 2016   doi: 10.1111/apha.12819   open full text
  • 3,5‐diiodothyronine (3,5‐T2) reduces blood glucose independently of insulin sensitization in obese mice.
    S. Silva Teixeira, C. Filgueira, D. H. Sieglaff, C. Benod, R. Villagomez, L. J. Minze, A. Zhang, P. Webb, M. T. Nunes.
    Acta Physiologica. November 17, 2016
    Aim Thyroid hormones regulate metabolic response. While triiodothyronine (T3) is usually considered to be the active form of thyroid hormone, one form of diiodothyronine (3,5‐T2) exerts T3‐like effects on energy consumption and lipid metabolism. 3,5‐T2 also improves glucose tolerance in rats and 3,5‐T2 levels correlate with fasting glucose in humans. Presently, however, little is known about mechanisms of 3,5‐T2 effects on glucose metabolism. Here, we set out to compare effects of T3, 3,5‐T2 and another form of T2 (3,3‐T2) in a mouse model of diet‐induced obesity and determined effects of T3 and 3,5‐T2 on markers of classical insulin sensitization to understand how diiodothyronines influence blood glucose. Methods Cell‐ and protein‐based assays of thyroid hormone action. Assays of metabolic parameters in mice. Analysis of transcript and protein levels in different tissues by qRT‐PCR and Western blot. Results T3 and 3,5‐T2 both reduce body weight, adiposity and body temperature despite increased food intake. 3,3′‐T2 lacks these effects. T3 and 3,5‐T2 reduce blood glucose levels, whereas 3,3′‐T2 worsens glucose tolerance. Neither T3 nor 3,5‐T2 affects markers of insulin sensitization in skeletal muscle or white adipose tissue (WAT), but both reduce hepatic GLUT2 glucose transporter levels and glucose output. T3 and 3,5‐T2 also induce expression of mitochondrial uncoupling proteins (UCPs) 3 and 1 in skeletal muscle and WAT respectively. Conclusions 3,5‐T2 influences glucose metabolism in a manner that is distinct from insulin sensitization and involves reductions in hepatic glucose output and changes in energy utilization.
    November 17, 2016   doi: 10.1111/apha.12821   open full text
  • Of Channels and Pumps: Different Ways to Boost the Aldosterone?
    Sascha Bandulik.
    Acta Physiologica. November 15, 2016
    The mineralocorticoid aldosterone is a major factor controlling the salt and water balance and thereby also the arterial blood pressure. Accordingly, primary aldosteronism characterized by an inappropiately high aldosterone secretion is the most common form of secondary hypertension. The physiological stimulation of aldosterone synthesis in adrenocortical glomerulosa cells by angiotensin II and an increased plasma K+ concentration depends on a membrane depolarization and an increase of the cytosolic Ca2+ activity. Recurrent gain‐of‐function mutations of ion channels and transporters have been identified in a majority of cases of aldosterone producing adenomas and in familial forms of primary aldosteronism. In this review, the physiological role of these genes in the regulation of aldosterone synthesis and the altered function of the mutant proteins as well are described. The specific changes of the membrane potential and the cellular ion homeostasis in adrenal cells expressing the different mutants are compared and their impact on autonomous aldosterone production and proliferation is discussed. This article is protected by copyright. All rights reserved.
    November 15, 2016   doi: 10.1111/apha.12832   open full text
  • Electrical Pulse Stimulation of Cultured Skeletal Muscle Cells as a Model for in vitro Exercise – Possibilities and Limitations.
    Nataša Nikolić, Sven W. Görgens, G. Hege Thoresen, Vigdis Aas, Jürgen Eckel, Kristin Eckardt.
    Acta Physiologica. November 10, 2016
    The beneficial health‐related effects of exercise are well recognized, and numerous studies have investigated underlying mechanism using various in vivo and in vitro models. Although electrical pulse stimulation (EPS) for the induction of muscle contraction has been used for quite some time, its application on cultured skeletal muscle cells of animal or human origin as a model of in vitro exercise is a more recent development. In this review, we compare in vivo exercise and in vitro EPS with regard to effects on signaling, expression level, and metabolism. We provide a comprehensive overview of different EPS protocols and their applications, discuss technical aspects of this model including critical controls and the importance of a proper maintenance procedure and finally, discuss the limitations of the EPS model. This article is protected by copyright. All rights reserved.
    November 10, 2016   doi: 10.1111/apha.12830   open full text
  • Biology of VO2max: looking under the physiology lamp.
    Carsten Lundby, David Montero, Michael Joyner.
    Acta Physiologica. November 07, 2016
    In this review we argue that several key features of maximal oxygen uptake (VO2max) should underpin discussions about the biological and reductionist determinants of its inter‐individual variability: 1) Training induced increases in VO2max are largely facilitated by expansion of red blood cell volume and an associated improvement in stroke volume, which also adapts independent of changes in red blood cell volume. These general concepts are also informed by cross sectional studies in athletes that have very high values for VO2max. Therefore, 2) variations in VO2max improvements with exercise training are also likely related to variations in these physiological determinants. 3) All previously untrained individuals will respond to endurance exercise training in terms of improvements in VO2max provided the stimulus exceeds a certain volume and/or intensity. Thus genetic analysis and/or reductionist studies performed to understand or predict such variations might focus specifically on DNA variants or other molecular phenomena of relevance to these physiological pathways. This article is protected by copyright. All rights reserved.
    November 07, 2016   doi: 10.1111/apha.12827   open full text
  • Renoprotection: Focus on TRPV1, TRPV4, TRPC6 and TRPM2.
    Lajos Markó, Marwan Mannaa, Timo Nicolas Haschler, Stephanie Krämer VMD, Maik Gollasch.
    Acta Physiologica. November 07, 2016
    Members of the transient receptor potential (TRP) cation channel receptor family have unique sites of regulatory function in the kidney which enables them to promote regional vasodilatation and controlled Ca2+ influx into podocytes and tubular cells. Activated TRP vanilloid 1 receptor channels (TRPV1) have been found to elicit renoprotection in rodent models of acute kidney injury following ischemia/reperfusion. Transient receptor potential cation channel, subfamily C, member 6 (TRPC6) in podocytes is involved in chronic proteinuric kidney disease, particularly in focal segmental glomerulosclerosis (FSGS). TRP vanilloid 4 receptor channels (TRPV4) are highly expressed in the kidney, where they induce Ca2+ influx into endothelial and tubular cells. TRP melastatin (TRPM2) non‐selective cation channels are expressed in the cytoplasm and intracellular organelles, where their inhibition ameliorates ischemic renal pathology. Though some of their basic properties have been recently identified, the renovascular role of TRPV1, TRPV4, TRPC6, and TRPM2 channels in disease states such as obesity, hypertension and diabetes is largely unknown. In this review, we discuss recent evidence for TRPV1, TRPV4, TRPC6 and TRPM2 serving as potential targets for acute and chronic renoprotection in chronic vascular and metabolic disease. This article is protected by copyright. All rights reserved.
    November 07, 2016   doi: 10.1111/apha.12828   open full text
  • Urothelium update. How the bladder mucosa measures bladder filling.
    D.A.W. Janssen, J.A. Schalken, J.P.F.A. Heesakkers.
    Acta Physiologica. November 02, 2016
    Aim This review critically evaluates the evidence on mechanosreceptors and pathways in the bladder urothelium that are involved in normal bladder filling signaling. Methods Evidence from in vitro and in vivo studies on 1) signaling pathways like the adenosine triphosphate pathway, cholinergic pathway and Nitrc Oxide and adrenergic pathway will be evaluated and 2) different urothelial receptors that are involved in bladder filling signaling like purinergic receptors, sodium channels and TRP channels will be evaluated. Other potential pathways and receptors will also be discussed. Results Bladder filling results in continuous changes in bladder wall stretch and exposure to urine. Both barrier and afferent signaling functions in the urothelium are constantly adapting to cope with these dynamics. Current evidence shows that the bladder mucosa host essential pathways and receptors that mediate bladder filling signaling. Intracellular calcium ion increase is a dominant factor in this signaling process. However, there is still no complete understanding how interacting receptors and pathways create a bladder filling signal. Currently, there are still novel receptors investigated that that could also be participating in bladder filling signaling. Conclusions Normal bladder filling sensation is dependent on multiple interacting mechanoreceptors and signaling pathways. Research efforts need to focus on how these pathways and receptors interact in order to fully understand normal bladder filling signaling. This article is protected by copyright. All rights reserved.
    November 02, 2016   doi: 10.1111/apha.12824   open full text
  • High glucose concentration abrogates sevoflurane post‐conditioning cardioprotection by advancing mitochondrial fission but dynamin‐related protein 1 inhibitor restores these effects.
    J. Yu, Y. Maimaitili, P. Xie, J. J. Wu, J. Wang, Y. N. Yang, H. P. Ma, H. Zheng.
    Acta Physiologica. October 26, 2016
    Aim Hyperglycaemia‐induced cell injury is a primary cause of cardiovascular complications in patients with diabetes. In vivo studies demonstrated that sevoflurane post‐conditioning (SpostC) was cardioprotective against ischaemia/reperfusion injury, which was blocked by hyperglycaemia. This study investigated whether high glucose concentration abrogated SpostC cardioprotection in vitro by advancing mitochondrial fission and whether mitochondrial division inhibitor‐1 (Mdivi‐1) restored SpostC cardioprotection in cultured primary neonatal rat cardiomyocytes (NCMs). Methods Primary cultured NCMs in low and high glucose concentrations were subjected to hypoxia/reoxygenation (H/R) injury. SpostC was carried out by adding 2.4% sevoflurane to the cells at the beginning of reoxygenation for 15 min. Cell viability, lactate dehydrogenase (LDH) level, cell death, mitochondrial morphology, mitochondrial membrane potential and mitochondrial permeability transition pore (mPTP) opening level, as well as fission‐ and fusion‐related proteins, were measured after H/R injury. Mdivi‐1 treatment was performed 40 min before hypoxia to inhibit DRP1. Results SpostC protected cultured cardiomyocytes by increasing cell viability and reducing the LDH level and cell death following H/R, but high glucose concentration eliminated the cardioprotective effect. High glucose concentration abrogated SpostC cardioprotection via mitochondrial fragmentation (evidenced by decreased mitochondrial interconnectivity and elongation) and facilitation of mPTP opening. Decreased mitochondrial membrane potential was investigated with increased DRP1, FIS1 and MFN2 and decreased MFN1 and OPA1 expressions. Mdivi‐1 (100 μmol L−1) inhibited excessive mitochondrial fission and restored the cardioprotective effect of SpostC in high glucose conditions. Conclusion SpostC‐induced cardioprotection against H/R injury was impaired under high glucose concentrations, but the inhibition of excess mitochondrial fission restored these effects.
    October 26, 2016   doi: 10.1111/apha.12812   open full text
  • Cyclosporin a induces renal episodic hypoxia.
    M. Fähling, S. Mathia, J. Scheidl, R. Abramovitch, Z. Milman, A. Paliege, H. Peters, P. B. Persson, S. N. Heyman, C. Rosenberger.
    Acta Physiologica. October 18, 2016
    Aim Cyclosporin A (CsA) causes renal toxicity. The underlying mechanisms are incompletely understood, but may involve renal hypoxia and hypoxia‐inducible factors (Hifs). We sought for hypoxia and Hif in mouse kidneys with CsA‐induced toxicity, assessed their time course, Hif‐mediated responses and the impact of interventional Hif upregulation. Methods Mice received CsA or its solvent cremophore for up to 6 weeks. Low salt diet (Na+↓) was given in combination with CsA to enhance toxicity. We assessed fine morphology, renal function, blood oxygen level‐dependent magnetic resonance imaging under room air and following changes in breathing gas composition which correlate with vascular reactivity, pimonidazole adducts (which indicate O2 tensions below 10 mmHg), Hif‐α proteins, as well as expression of Hif target genes. Stable Hif upregulation was achieved by inducible, Pax8‐rtTA‐based knockout of von Hippel–Lindau protein (Vhl‐KO), which is crucial for Hif‐α degradation. Results Cyclosporin A transiently increased renal deoxyhaemoglobin (R2*). Augmented vascular reactivity was observed at 2 h, but decreased at 24 h after CsA treatment. Na+↓/CsA provoked chronic renal failure with tubular degeneration and interstitial fibrosis. Nephron segments at risk for injury accumulated pimonidazole adducts, as well as Hif‐α proteins. Remarkably, Hif target gene expression remained unchanged, while factor‐inhibiting Hif (Fih) was enhanced. Na+↓/CsA/Vhl‐KO aggravated morpho‐functional outcome of chronic renal CsA toxicity. Conclusions Cyclosporin A provokes episodic hypoxia in nephron segments most susceptible to chronic CsA toxicity. Fih is upregulated and likely blocks further Hif activity. Continuous tubular Hif upregulation via Vhl‐KO worsens the outcome of chronic CsA‐induced renal toxicity.
    October 18, 2016   doi: 10.1111/apha.12811   open full text
  • Adopting an external focus of attention alters intracortical inhibition within the primary motor cortex.
    Y.‐A. Kuhn, M. Keller, J. Ruffieux, W. Taube.
    Acta Physiologica. October 17, 2016
    Aim Although it is well established that an external (EF) compared to an internal (IF) or neutral focus of attention enhances motor performance, little is known about the underlying neural mechanisms. This study aimed to clarify whether the focus of attention influences not only motor performance but also activity of the primary motor cortex (M1) when executing identical fatiguing tasks of the right index finger (first dorsal interosseous). Transcranial magnetic stimulation (TMS) at intensities below motor threshold was applied over M1 to assess and compare the excitability of intracortical inhibitory circuits. Methods In session 1, 14 subjects performed an isometric finger abduction at 30% of their maximal force to measure the time to task failure (TTF) with either an IF or EF. In session 2, the same task was performed with the other focus. In sessions 3 and 4, subthreshold TMS (subTMS) and paired‐pulse TMS were applied to the contralateral M1 to compare the activity of cortical inhibitory circuits within M1 during EF and IF. Results With an EF, TTF was significantly prolonged (P = 0.01), subTMS‐induced electromyographical suppression enhanced (P = 0.001) and short‐interval intracortical inhibition (SICI) increased (P = 0.004). Conclusion The level of intracortical inhibition was previously shown to influence motor performance. Our data shed new light on the ability to instantly modulate the activity of inhibitory circuits within M1 by changing the type of attentional focus. The increased inhibition with EF might contribute to the better movement efficiency, which is generally associated with focusing externally.
    October 17, 2016   doi: 10.1111/apha.12807   open full text
  • Peroxynitrite formed during a transient episode of brain ischaemia increases endothelium‐derived hyperpolarization‐type dilations in thromboxane/prostaglandin receptor‐stimulated rat cerebral arteries.
    Y. Onetti, A. P. Dantas, B. Pérez, A. J. McNeish, E. Vila, F. Jiménez‐Altayó.
    Acta Physiologica. October 16, 2016
    Aim Increased thromboxane A2 and peroxynitrite are hallmarks of cerebral ischaemia/reperfusion (I/R). Stimulation of thromboxane/prostaglandin receptors (TP) attenuates endothelium‐derived hyperpolarization (EDH). We investigated whether EDH‐type middle cerebral artery (MCA) relaxations following TP stimulation are altered after I/R and the influence of peroxynitrite. Methods Vascular function was determined by wire myography after TP stimulation with the thromboxane A2 mimetic 9,11‐dideoxy‐9α, 11α ‐methano‐epoxy prostaglandin F2α (U46619) in MCA of Sprague Dawley rats subjected to MCA occlusion (90 min)/reperfusion (24 h) or sham operation, and in non‐operated (control) rats. Some rats were treated with saline or the peroxynitrite decomposition catalyst 5,10,15,20‐tetrakis(4‐sulfonatophenyl)porphyrinato iron (III) (20 mg kg−1). Protein expression was evaluated in MCA and in human microvascular endothelial cells submitted to hypoxia (overnight)/reoxygenation (24 h) (H/R) using immunofluorescence and immunoblotting. Results In U46619‐pre‐constricted MCA, EDH‐type relaxation by the proteinase‐activated receptor 2 agonist serine–leucine–isoleucine–glycine–arginine–leucine–NH2 (SLIGRL) was greater in I/R than sham rats due to an increased contribution of small‐conductance calcium‐activated potassium channels (SKCa), which was confirmed by the enlarged relaxation to the SKCa activator N‐cyclohexyl‐N‐2‐(3,5‐dimethyl‐pyrazol‐1‐yl)‐6‐methyl‐4‐pyrimidinamine. I/R and H/R induced endothelial protein tyrosine nitration and filamentous‐actin disruption. In control MCA, either cytochalasin D or peroxynitrite disrupted endothelial filamentous‐actin and augmented EDH‐type relaxation. Furthermore, peroxynitrite decomposition during I/R prevented the increase in EDH‐type responses. Conclusion Following TP stimulation in MCA, EDH‐type relaxation to SLIGRL is greater after I/R due to endothelial filamentous‐actin disruption by peroxynitrite, which prevents TP‐induced block of SKCa input to EDH. These results reveal a novel mechanism whereby peroxynitrite could promote post‐ischaemic brain injury.
    October 16, 2016   doi: 10.1111/apha.12809   open full text
  • Mode of perfusion influences infarct size, coronary flow and stress kinases in the isolated mouse heart.
    M. Bliksøen, A. Rutkovskiy, J. Vaage, K.‐O. Stensløkken.
    Acta Physiologica. October 14, 2016
    Aim The isolated, retrogradely perfused heart (modified Langendorff model) is a widely used method in experimental heart research. The presence of an intraventricular balloon is necessary to get functional measurements. We have previously shown that the balloon induces phosphorylation of some suggested cardioprotective mitogen‐activated protein kinases (MAPK): P38‐MAPK, ERK 1/2 and JNK. We hypothesized that the balloon could influence cardioprotection, protect against ischaemia reperfusion injury and interfere with coronary flow. Methods and Results Isolated mouse hearts were perfused for 5, 10, 20, 40 and 60 min with a balloon in the left ventricle. We found a wavelike phosphorylation of all MAPK while AKT displayed a gradual dephosphorylation when compared to non‐perfused hearts. Hearts were subjected to 20 min of stabilization with or without the balloon, followed by 35 min of ischaemia and 120 min of reperfusion. Although the MAPK were phosphorylated, the infarcts were larger in the balloon group. When the balloon was present during the entire protocol, compared to removal at the end of ischaemia, the infarct size was also larger, especially in the endocardial layer. The balloon reduced post‐ischaemic endocardial coronary flow, despite a higher average flow, indicating a hyperperfused epicard. Blocking the balloon‐induced ERK 1/2 phosphorylation during stabilization did not affect infarct size. The effect of post‐conditioning was influenced by the balloon, showing reduced infarct size when the balloon was present. Conclusion The balloon used for pressure measurements may contributes to cell death possibly by reducing endocardial coronary flow.
    October 14, 2016   doi: 10.1111/apha.12773   open full text
  • Receptor‐interacting Protein 140 represses Sirtuin 3 to facilitate hypertrophy, mitochondrial dysfunction and energy metabolic dysfunction in cardiomyocytes.
    J. You, Z. Yue, S. Chen, Y. Chen, X. Lu, X. Zhang, P. Shen, J. Li, Q. Han, Z. Li, P. Liu.
    Acta Physiologica. October 12, 2016
    Aim The transcriptional cofactor receptor‐interacting protein 140 (RIP140) is known as a deleterious regulator of cardiac mitochondrial function and energy metabolic homeostasis. This study revealed that RIP140 repressed Sirtuin 3 (SIRT3), a mitochondrial deacetylase that plays an important role in regulating cardiac function. Methods RIP140 was overexpressed by adenovirus infection or was knocked down by RNA interference in neonatal rat cardiomyocytes. Results RIP140 overexpression repressed, while RIP140 silencing elevated the expression and activity of SIRT3. Ad‐RIP140 enhanced the expressions of the cardiac hypertrophic markers and increased cardiomyocyte surface area, whereas SIRT3 overexpression prevented the effect of Ad‐RIP140. Additionally, SIRT3 overexpression reversed Ad‐RIP140‐induced mitochondrial dysfunction and energy metabolic dysfunction, such as increase in oxidative stress, decrease in mitochondrial membrane potential and ATP production, as well as downregulation of mitochondrial DNA‐encoded genes and genes related to mitochondrial genome replication and transcription, mitochondrial oxidative phosphorylation and fatty acid oxidation. In contrast, SIRT3 silencing exacerbated RIP140‐induced cardiomyocyte hypertrophy and mitochondrial dysfunction. Furthermore, the repression of SIRT3 by RIP140 was dependent on estrogen‐related receptor‐α (ERRα). The involvement of peroxisome proliferator‐activated receptor‐γ coactivator‐1α (PGC‐1α) was ruled out of SIRT3 suppression by RIP140. RIP140 and PGC‐1α might act as functional antagonists on the regulation of SIRT3. Conclusion This study indicates that suppression of SIRT3 by RIP140 facilitates the development of cardiomyocyte hypertrophy, mitochondrial dysfunction and energy metabolic dysfunction. Strategies targeting inhibition of RIP140 and upregulation of SIRT3 might improve cardiac energy metabolism and suggest therapeutic potential for heart diseases.
    October 12, 2016   doi: 10.1111/apha.12800   open full text
  • Beneficial effects of renal denervation on cardiac angiogenesis in rats with prolonged pressure overload.
    D. Lu, K. Wang, S. Wang, B. Zhang, Q. Liu, Q. Zhang, J. Geng, Q. Shan.
    Acta Physiologica. October 12, 2016
    Aim Renal denervation (RDN) has beneficial effects on cardiac remodelling and function in resistant hypertension. We aimed to investigate the impact of RDN on cardiac angiogenesis during prolonged pressure overload. Methods Cardiac pressure overload was reproduced by transverse aorta constriction (TAC) procedure in adult Sprague Dawley male rats (n = 35). RDN/sham‐RDN procedure was performed in surviving rats at 5 weeks after TAC. Results Five weeks post‐TAC, transthoracic echocardiography revealed that myocardial hypertrophy occurred in TAC rats, with ejection fraction and fractional shortening not significantly changed. At the end of 10 weeks, cardiac systolic function was preserved in RDN group, but not in sham group. CD31 immunohistochemical staining showed that RDN‐treated rats had higher cardiac capillary density than sham rats. However, no significant between‐group difference was observed in the kidneys. A decreased protein expression of left ventricle vascular endothelial growth factor (VEGF) was observed in sham group, while RDN attenuated this decrease. Compared with sham, RDN resulted in a higher protein expression of VEGF receptor 2 (VEGFR2) and phosphorylated endothelial nitric oxide synthase (p‐eNOS) in the heart. Conclusion Renal denervation benefits cardiac angiogenesis during sustained pressure overload, involving regulation of VEGF and VEGFR2 expression as well as activation of eNOS.
    October 12, 2016   doi: 10.1111/apha.12793   open full text
  • Dopamine enhances duodenal epithelial permeability via the dopamine D5 receptor in rodent.
    X.‐Y. Feng, D.‐N. Zhang, Y.‐A. Wang, R.‐F. Fan, F. Hong, Y. Zhang, Y. Li, J.‐X. Zhu.
    Acta Physiologica. October 06, 2016
    Aim The intestinal barrier is made up of epithelial cells and intercellular junctional complexes to regulate epithelial ion transport and permeability. Dopamine (DA) is able to promote duodenal epithelial ion transport through D1‐like receptors, which includes subtypes of D1 (D1R) and D5 (D5R), but whether D1‐like receptors influence the duodenal permeability is unclear. Methods FITC–dextran permeability, short‐circuit current (ISC), Western blot, immunohistochemistry and ELISA were used in human D5R transgenic mice and hyperendogenous enteric DA (HEnD) rats in this study. Results Dopamine induced a downward deflection in ISC and an increase in FITC–dextran permeability of control rat duodenum, which were inhibited by the D1‐like receptor antagonist, SCH‐23390. However, DA decreased duodenal transepithelial resistance (TER), an effect also reversed by SCH‐23390. A strong immunofluorescence signal for D5R, but not D1R, was observed in the duodenum of control rat. In human D5R knock‐in transgenic mice, duodenal mucosa displayed an increased basal ISC with high FITC–dextran permeability and decreased TER with a lowered expression of tight junction proteins, suggesting attenuated duodenal barrier function in these transgenic mice. D5R knock‐down transgenic mice manifested a decreased basal ISC with lowered FITC–dextran permeability. Moreover, an increased FITC–dextran permeability combined with decreased TER and tight junction protein expression in duodenal mucosa were also observed in HEnD rats. Conclusion This study demonstrates, for the first time, that DA enhances duodenal permeability of control rat via D5R, which provides new experimental and theoretical evidence for the influence of DA on duodenal epithelial barrier function.
    October 06, 2016   doi: 10.1111/apha.12806   open full text
  • Development of somatosensory‐evoked potentials in foetal sheep: effects of betamethasone.
    P. Anegroaie, M. G. Frasch, S. Rupprecht, I. Antonow‐Schlorke, T. Müller, H. Schubert, O. W. Witte, M. Schwab.
    Acta Physiologica. October 04, 2016
    Aim Antenatal glucocorticoids are used to accelerate foetal lung maturation in babies threatened with premature labour. We examined the influence of glucocorticoids on functional and structural maturation of the central somatosensory pathway in foetal sheep. Somatosensory‐evoked potentials (SEP) reflect processing of somatosensory stimuli. SEP latencies are determined by afferent stimuli transmission while SEP amplitudes reveal cerebral processing. Methods After chronic instrumentation of foetal sheep, mothers received saline (n = 9) or three courses of betamethasone (human equivalent dose of 2 × 110 μg kg−1 betamethasone i.m. 24 h apart, n = 12) at 0.7, 0.75 and 0.8 of gestational age. Trigeminal SEP were evoked prior to, 4 and 24 h after each injection and at 0.8 of gestational age before brains were histologically processed. Results Somatosensory‐evoked potentials were already detectable at 0.7 of gestation age. The early and late responses N20 and N200 were the only reproducible peaks over the entire study period. With advancing gestational age, SEP latencies decreased but amplitudes remained unchanged. Acutely, betamethasone did not affect SEP latencies and amplitudes 4 and 24 h following administration. Chronically, betamethasone delayed developmental decrease in the N200 but not N20 latency by 2 weeks without affecting amplitudes. In parallel, betamethasone decreased subcortical white matter myelination but did not affect network formation and synaptic density in the somatosensory cortex. Conclusion Somatosensory stimuli are already processed by the foetal cerebral cortex at the beginning of the third trimester. Subsequent developmental decrease in SEP latencies suggests ongoing maturation of afferent sensory transmission. Antenatal glucocorticoids affect structural and functional development of the somatosensory system with specific effects at subcortical level.
    October 04, 2016   doi: 10.1111/apha.12795   open full text
  • Desoxycorticosterone pivalate‐salt treatment leads to non‐dipping hypertension in Per1 knockout mice.
    K. Solocinski, M. Holzworth, X. Wen, K.‐Y. Cheng, I. J. Lynch, B. D. Cain, C. S. Wingo, M. L. Gumz.
    Acta Physiologica. October 03, 2016
    Aim Increasing evidence demonstrates that circadian clock proteins are important regulators of physiological functions including blood pressure. An established risk factor for developing cardiovascular disease is the absence of a blood pressure dip during the inactive period. The goal of the present study was to determine the effects of a high salt diet plus mineralocorticoid on PER1‐mediated blood pressure regulation in a salt‐resistant, normotensive mouse model, C57BL/6J. Methods Blood pressure was measured using radiotelemetry. After control diet, wild‐type (WT) and Per1 (KO) knockout mice were given a high salt diet (4% NaCl) and the long‐acting mineralocorticoid deoxycorticosterone pivalate. Blood pressure and activity rhythms were analysed to evaluate changes over time. Results Blood pressure in WT mice was not affected by a high salt diet plus mineralocorticoid. In contrast, Per1 KO mice exhibited significantly increased mean arterial pressure (MAP) in response to a high salt diet plus mineralocorticoid. The inactive/active phase ratio of MAP in WT mice was unchanged by high salt plus mineralocorticoid treatment. Importantly, this treatment caused Per1 KO mice to lose the expected decrease or ‘dip’ in blood pressure during the inactive compared to the active phase. Conclusion Loss of PER1 increased sensitivity to the high salt plus mineralocorticoid treatment. It also resulted in a non‐dipper phenotype in this model of salt‐sensitive hypertension and provides a unique model of non‐dipping. Together, these data support an important role for the circadian clock protein PER1 in the modulation of blood pressure in a high salt/mineralocorticoid model of hypertension.
    October 03, 2016   doi: 10.1111/apha.12804   open full text
  • Unsung Renal Receptors: Orphan G‐protein coupled receptors play essential roles in renal development and homeostasis.
    Premraj Rajkumar, Jennifer L. Pluznick.
    Acta Physiologica. October 03, 2016
    Recent studies have shown that orphan GPCRs of the GPR family are utilized as specialized chemosensors in various tissues to detect metabolites, and in turn to activate downstream pathways which regulate systemic homeostasis. These studies often find that such metabolites are generated by well‐known metabolic pathways, implying that known metabolites and chemicals may perform novel functions. In this review, we summarize recent findings highlighting the role of deorphanized GPRs in renal development and function. Understanding the role of these receptors is critical in gaining insights into mechanisms that regulate renal function both in health and in disease. This article is protected by copyright. All rights reserved.
    October 03, 2016   doi: 10.1111/apha.12813   open full text
  • Bradykinin receptor blockade restores the baroreflex control of renal sympathetic nerve activity in cisplatin‐induced renal failure rats.
    M. H. Abdulla, M. Duff, H. Swanton, E. J. Johns.
    Acta Physiologica. September 29, 2016
    Aim This study investigated the effect of renal bradykinin B1 and B2 receptor blockade on the high‐ and low‐pressure baroreceptor reflex regulation of renal sympathetic nerve activity (RSNA) in rats with cisplatin‐induced renal failure. Methods Cisplatin (5 mg/kg) or saline was given intraperitoneally 4 days prior to study. Following chloralose/urethane anaesthesia, rats were prepared for measurement of mean arterial pressure (MAP), heart rate and RSNA and received intrarenal infusions of either Lys‐[des‐Arg9, Leu8]‐bradykinin (LBK), a bradykinin B1 receptor blocker, or bradyzide (BZ), a bradykinin B2 receptor blocker. RSNA baroreflex gain curves and renal sympatho‐inhibitory responses to volume expansion (VE) were obtained. Results In the control and renal failure groups, basal MAP (89 ± 3 vs. 80 ± 8 mmHg) and RSNA (2.0 ± 0.3 vs. 1.7 ± 0.6 μV.s) were similar but HR was lower in the latter group (331 ± 8 vs. 396 ± 9 beats/min). The baroreflex gain for RSNA in the renal failure rats was 39% (P < 0.05) lower than the control but was restored to normal values following intrarenal infusion of BZ, but not LBK. VE had no effect on MAP or HR but reduced RSNA by some 40% (P < 0.05) in control but not renal failure rats. Intrarenal LBK infusion in the renal failure rats normalized the VE induced renal sympatho‐inhibition whereas BZ only partially restored the response. Conclusion These findings suggest that pro‐inflammatory bradykinin acting at different receptors within the kidney generates afferent neural signals which impact differentially within the central nervous system on high‐ and low‐pressure regulation of RSNA.
    September 29, 2016   doi: 10.1111/apha.12801   open full text
  • Non‐linear effects of potassium channel blockers on endothelium‐dependent hyperpolarization.
    Harold A. Coleman, Marianne Tare, Helena C. Parkington.
    Acta Physiologica. September 17, 2016
    In a number of published studies on endothelium‐dependent hyperpolarization and relaxation, the results of the effects of K+ blockers have been difficult to interpret. When the effects of two blockers have been studied, often either blocker by itself had little effect, whereas the two blockers combined tended to abolish the responses. Explanations suggested in the literature include an unusual pharmacology of the K+ channels, and possible blocker binding interactions. In contrast, when we applied the same blockers to segments of small blood vessels under voltage‐clamp, the blockers reduced the endothelium‐dependent K+ current in a linearly additive manner. Resolution of these contrasting results is important since endothelium‐derived hyperpolarization (EDH) makes its greatest contribution to vasorelaxation in arterioles and small resistance arteries, where it can exert a significant role in tissue perfusion and blood pressure regulation. Furthermore, EDH is impaired in various diseases. Here we consider why the voltage‐clamp results differ from earlier free‐running membrane potential and contractility studies. We fitted voltage‐clamp derived current‐voltage relationships with mathematical functions and considered theoretically the effects of partial and total block of endothelium‐derived K+‐currents on the membrane potential of small blood vessels. When the K+‐conductance was partially reduced, equivalent to applying a single blocker, the effect on EDH was small. Total block of the endothelium‐dependent K+ conductance abolished the hyperpolarization, in agreement with various published studies. We conclude that nonlinear summation of the hyperpolarizing response evoked by endothelial stimulation can explain the variable effectiveness of individual K+ channel blockers on endothelium‐dependent hyperpolarization and resulting relaxation. This article is protected by copyright. All rights reserved.
    September 17, 2016   doi: 10.1111/apha.12805   open full text
  • A review of wave mechanics in the pulmonary artery with an emphasis on wave intensity analysis.
    Junjing Su, Ole Hilberg, Luke Howard, Ulf Simonsen, Alun D Hughes.
    Acta Physiologica. September 16, 2016
    Mean pulmonary arterial pressure and pulmonary vascular resistance remain the most common hemodynamic measures to evaluate the severity and prognosis of pulmonary hypertension. However, pulmonary vascular resistance only captures the non‐oscillatory component of the right ventricular hydraulic load and neglects the dynamic compliance of the pulmonary arteries and the contribution of wave transmission. Wave intensity analysis offers an alternative way to assess the pulmonary vasculature in health and disease. Wave speed is a measure of arterial stiffness and the magnitude and timing of wave reflection provide information on the degree of impedance mismatch between the proximal and distal circulation. Studies in the pulmonary artery have demonstrated distinct differences in arterial wave propagation between individuals with and without pulmonary vascular disease. Notably, greater wave speed and greater wave reflection are observed in patients with pulmonary hypertension and in animal models exposed to hypoxia. Studying wave propagation makes a valuable contribution to the assessment of the arterial system in pulmonary hypertension and here, we briefly review the current state of knowledge of the methods used to evaluate arterial waves in the pulmonary artery. This article is protected by copyright. All rights reserved.
    September 16, 2016   doi: 10.1111/apha.12803   open full text
  • Progesterone‐induced miR‐133a inhibits the proliferation of endometrial epithelial cells.
    J.‐l. Pan, D.‐z. Yuan, Y.‐b. Zhao, L. Nie, Y. Lei, M. Liu, Y. Long, J.‐h. Zhang, L. J. Blok, C. W. Burger, L.‐m. Yue.
    Acta Physiologica. September 15, 2016
    Aim This study aimed to understand the role of miR‐133a in progesterone actions, explore the regulative mechanism of the progesterone receptor, and investigate the effects of miR‐133a on the progesterone‐inhibited proliferation of mouse endometrial epithelial cells. Methods The expression of miR‐133a induced by progesterone was detected by quantitative real‐time PCR both in vivo and in vitro. Ishikawa subcell lines stably transfected with progesterone receptor subtypes were used to determine the receptor mechanism of progesterone inducing miR‐133a. Specific miR‐133a mimics or inhibitors were transfected into mouse uteri and primary cultured endometrial epithelial cells to overexpress or downregulate the miR‐133a. The roles of miR‐133a in the cell cycle and proliferation of endometrial epithelial cells were analysed by flow cytometry and Edu incorporation analysis. The protein levels of cyclinD2 in uterine tissue sections and primary cultured endometrial epithelial cells were determined by immunohistochemistry and Western blot analysis. Results Progesterone could induce miR‐133a expression in a PRB‐dependent manner in endometrial epithelial cells. miR‐133a inhibited endometrial epithelial cell proliferation by arresting cell cycle at the G1‐S transition. Moreover, miR‐133a acted as an inhibitor in downregulating cyclinD2 in endometrial epithelial cells. Conclusion We showed for the first time that progesterone‐induced miR‐133a inhibited the proliferation of endometrial epithelial cells by downregulating cyclinD2. Our research indicated an important mechanism for progesterone inhibiting the proliferation of endometrial epithelial cells by inducing special miRNAs to inhibit positive regulatory proteins in the cell cycle.
    September 15, 2016   doi: 10.1111/apha.12762   open full text
  • Physiological aspects of Toll‐like receptor 4 activation in sepsis‐induced acute kidney injury.
    Sara Bülow Anderberg, Tomas Luther, Robert Frithiof.
    Acta Physiologica. September 07, 2016
    Sepsis‐induced acute kidney injury (SI‐AKI) is common and associated with high mortality. Survivors are at increased risk of chronic kidney disease. The precise mechanism underlying SI‐AKI is unknown and no curative treatment exists. Toll‐like receptor 4 (TLR4) activates the innate immune system in response to exogenous microbial products. The result is an inflammatory reaction aimed at clearing a potential infection. However, the consequence may also be organ dysfunction as the immune response can cause collateral damage to host tissue. The purpose of this review is to describe the basis for how ligand binding to TLR4 has the potential to cause renal dysfunction and the mechanisms by which this may take place in gram‐negative sepsis. In addition, we highlight areas for future research that can further our knowledge of the pathogenesis of SI‐AKI in relation to TLR4 activation. TLR4 is expressed in the kidney. Activation of TLR4 causes cytokine and chemokine release as well as renal leukocyte infiltration. It also results in endothelial and tubular dysfunction in addition to altered renal metabolism and circulation. From a physiological standpoint inhibiting TLR4 in large‐animal experimental SI‐AKI significantly improves renal function. Thus, current evidence indicates that TLR4 has the ability to mediate SI‐AKI by a number of mechanisms. The strong experimental evidence supporting a role of TLR4 in the pathogenesis of SI‐AKI in combination with the availability of pharmacological tools to target TLR4 warrants future human studies. This article is protected by copyright. All rights reserved.
    September 07, 2016   doi: 10.1111/apha.12798   open full text
  • Evidence for a functional role of calsequestrin 2 in mouse atrium.
    U. Gergs, C. M. Fahrion, P. Bock, M. Fischer, H. Wache, S. Hauptmann, W. Schmitz, J. Neumann.
    Acta Physiologica. August 31, 2016
    Aim Several genetically modified mice models were studied so far to investigate the role of cardiac calsequestrin (CSQ2) for the contractile function of the ventricle and for the occurrence of ventricular tachycardia. Using a CSQ2 knockout mouse, we wanted to study also the atrial function of CSQ2. Methods The influence of CSQ2 on atrial function and, for comparison, ventricular function was studied in isolated cardiac preparations and by echocardiography as well as electrocardiography in mice with deletion of CSQ2. Results Using deletion of exon 1, we have successfully generated a constitutive knockout mouse of the calsequestrin 2 gene (CSQ2−/−). CSQ2 protein was absent in the heart (atrium, ventricle), but also in oesophagus and skeletal muscle of homozygous knockout mice. In 6‐month‐old CSQ2−/− mice, relative left atrial weight was increased, whereas relative heart weight was unchanged. The staircase phenomena in paced left atrial preparations on force of contraction and the post‐rest potentiation were different between wild type and CSQ2−/− indicative for a decreased sarcoplasmic Ca2+ load and supporting an important role of CSQ2 also in the atrium. The incidence of arrhythmias was increased in CSQ2−/−. In 2‐year‐old CSQ2−/− mice, cardiac hypertrophy and heart failure were noted possibly as a result of chronically increased cytosolic Ca2+ levels. Conclusion These data suggest a functional role of CSQ2 not only in the ventricle but also in the atrium of mammalian hearts. Loss of CSQ2 function can cause not only arrhythmias, but also cardiac hypertrophy and heart failure.
    August 31, 2016   doi: 10.1111/apha.12766   open full text
  • Hypoxia exposure and B‐type natriuretic peptide release from Langendorff heart of rats.
    K. Anttila, T. Streng, J. Pispa, M. Vainio, M. Nikinmaa.
    Acta Physiologica. August 26, 2016
    Aim We studied whether available oxygen without induced mechanical stretch regulates the release of the biologically active B‐type natriuretic peptide (BNP) from Langendorff heart. Methods Rat hearts were isolated and perfused with a physiological Krebs–Henseleit solution at a constant hydrostatic pressure in Langendorff set‐up. The basal O2 level of perfusate (24.4 ± 0.04 mg L−1) was gradually lowered to 3.0 ± 0.01 mg L−1 over 20 min using N2 gas (n = 7). BNP and O2 level were measured from coronary flow. During control perfusions (n = 5), the O2 concentration was kept at 26.6 ± 0.3 mg L−1. Results A low oxygen concentration in the perfusate was associated with a significant increase in BNP release (F = 40.4, P < 0.001). Heart rate decreased when the oxygen concentration in the perfusate reached 9.1 ± 0.02 mg L−1 and continued to fall in lower oxygen concentrations (F = 14.8, P < 0.001). There was also a significant but inverse correlation between BNP and oxygen in the coronary flow (R2 = 0.27, P < 0.001). Conclusion In the spontaneously beating Langendorff rat heart, a decreasing concentration of oxygen in the ingoing perfusion increased the secretion of BNP. The effect of oxygen was independent of mechanical stretch of the heart as it occurred even when the heart rate decreased but the pressure conditions remained constant. The difference in the oxygen capacitance of blood and Krebs–Henseleit solution appears to be a major factor affecting secretion of BNP, which is correlated with the oxygen tension of myocardial cells and affected both by the oxygen concentration and capacitance of solution perfusing the heart and by the coronary flow.
    August 26, 2016   doi: 10.1111/apha.12767   open full text
  • Body ownership and a new proprioceptive role for muscle spindles.
    Annie A. Butler, Martin E. Héroux, Simon C. Gandevia.
    Acta Physiologica. August 26, 2016
    Knowledge of which body parts belong to us is referred to as the sense of body ownership. There is increasing evidence that this important aspect of human proprioception is highly malleable. Research into ownership of individual body parts was stimulated by Botvinick and Cohen's rubber‐hand illusion (1998), which demonstrated that an artificial body part can be incorporated in one's body representation and can cause real body parts to be sensed erroneously. Here, we review key studies that have advanced our understanding of the sense of body ownership, including the important role played by multisensory integration and spatiotemporal congruence of sensory signals. We also discuss our recent discovery that body ownership can be induced in response to movement stimuli by signals from a single class of sensory receptor, namely, muscles spindles. This article is protected by copyright. All rights reserved.
    August 26, 2016   doi: 10.1111/apha.12792   open full text
  • Back‐calculating baseline creatinine overestimates prevalence of acute kidney injury with poor sensitivity.
    F. Kork, F. Balzer, A. Krannich, M. H. Bernardi, H. K. Eltzschig, J. Jankowski, C. Spies.
    Acta Physiologica. August 25, 2016
    Aim Acute kidney injury (AKI) is diagnosed by a 50% increase in creatinine. For patients without a baseline creatinine measurement, guidelines suggest estimating baseline creatinine by back‐calculation. The aim of this study was to evaluate different glomerular filtration rate (GFR) equations and different GFR assumptions for back‐calculating baseline creatinine as well as the effect on the diagnosis of AKI. Methods The Modification of Diet in Renal Disease, the Chronic Kidney Disease Epidemiology (CKD‐EPI) and the Mayo quadratic (MQ) equation were evaluated to estimate baseline creatinine, each under the assumption of either a fixed GFR of 75 mL min−1 1.73 m−2 or an age‐adjusted GFR. Estimated baseline creatinine, diagnoses and severity stages of AKI based on estimated baseline creatinine were compared to measured baseline creatinine and corresponding diagnoses and severity stages of AKI. Results The data of 34 690 surgical patients were analysed. Estimating baseline creatinine overestimated baseline creatinine. Diagnosing AKI based on estimated baseline creatinine had only substantial agreement with AKI diagnoses based on measured baseline creatinine [Cohen's κ ranging from 0.66 (95% CI 0.65–0.68) to 0.77 (95% CI 0.76–0.79)] and overestimated AKI prevalence with fair sensitivity [ranging from 74.3% (95% CI 72.3–76.2) to 90.1% (95% CI 88.6–92.1)]. Staging AKI severity based on estimated baseline creatinine had moderate agreement with AKI severity based on measured baseline creatinine [Cohen's κ ranging from 0.43 (95% CI 0.42–0.44) to 0.53 (95% CI 0.51–0.55)]. Conclusion Diagnosing AKI and staging AKI severity on the basis of estimated baseline creatinine in surgical patients is not feasible. Patients at risk for post‐operative AKI should have a pre‐operative creatinine measurement to adequately assess post‐operative AKI.
    August 25, 2016   doi: 10.1111/apha.12763   open full text
  • Ventricular repolarization time, location of pacing stimulus and current pulse amplitude conspire to determine arrhythmogenicity in mice.
    T. Speerschneider, S. Grubb, S. P. Olesen, K. Calloe, M. B. Thomsen.
    Acta Physiologica. August 24, 2016
    Aim In this study, we investigate the impact of altered action potential durations (APD) on ventricular repolarization time and proarrhythmia in mice with and without genetic deletion of the K+‐channel‐interacting protein 2 (KChIP2−/− and WT respectively). Moreover, we examine the interrelationship between the dispersion of repolarization time and current pulse amplitude in provoking ventricular arrhythmia. Methods Intracardiac pacing in anesthetized mice determined refractory periods and proarrhythmia susceptibility. Regional activation time (AT), APD and repolarization time (=AT + APD) were measured in isolated hearts using floating microelectrodes. Results Proarrhythmia in WT and KChIP2−/− was not sensitive to changes in refractory periods. Action potentials were longer in KChIP2−/− hearts compared to WT hearts. Isolated WT hearts had large apico‐basal dispersion of repolarization time, whereas hearts from KChIP2−/− mice had large left‐to‐right ventricular dispersion of repolarization time. Pacing from the right ventricle in KChIP2−/− mice in vivo revealed significant lower current pulse amplitudes needed to induce arrhythmias in these mice. Conclusion Large heterogeneity of repolarization time is proarrhythmic when pacing is delivered from the location of earlier repolarization time. Ventricular repolarization time, location of the pacing stimulus and the amplitude of the stimulating current pulse are critical parameters underlying arrhythmia vulnerability.
    August 24, 2016   doi: 10.1111/apha.12761   open full text
  • Insight towards the identification of cytosolic Ca2+‐binding sites in ryanodine receptors from skeletal and cardiac muscle.
    Marta Gaburjakova, Jana Gaburjakova.
    Acta Physiologica. August 20, 2016
    Ca2+ plays a critical role in several processes involved in skeletal and cardiac muscle contraction. One key step in cardiac excitation‐contraction (E‐C) coupling is the activation of the cardiac ryanodine receptor (RYR2) by cytosolic Ca2+ elevations. Although this process is not critical for skeletal E‐C coupling, the activation and inhibition of the skeletal ryanodine receptor (RYR1) seems to be important for overall muscle function. The RYR1 and RYR2 channels fall within the large category of Ca2+‐binding proteins that harbour highly selective Ca2+ ‐binding sites to receive and translate the various Ca2+ signals into specific functional responses. However, little is known about the precise localization of these sites within the cytosolic assembly of both RYR isoforms, although several experimental lines of evidence have highlighted their EF‐hand nature. EF‐hand proteins share a common helix‐loop‐helix structural motif with highly conserved residues involved in Ca2+ coordination. The first step in predicting EF‐hand positive regions is to compare the primary protein structure with the EF‐hand motif by employing available bioinformatics tools. Although this simple method narrows down search regions, it does not provide solid evidence regarding which regions bind Ca2+ in both RYR isoforms. In this review, we seek to highlight the key findings and experimental approaches that should strengthen our future efforts to identify the cytosolic Ca2+‐binding sites responsible for activation and inhibition in the RYR1 channel, as much less work has been conducted on the RYR2 channel. This article is protected by copyright. All rights reserved.
    August 20, 2016   doi: 10.1111/apha.12772   open full text
  • The translationally relevant mouse model of the 15q13.3 microdeletion syndrome reveals deficits in neuronal spike firing matching clinical neurophysiological biomarkers seen in schizophrenia.
    J. Thelin, P. Halje, J. Nielsen, M. Didriksen, P. Petersson, J. F. Bastlund.
    Acta Physiologica. August 16, 2016
    Aim To date, the understanding and development of novel treatments for mental illness is hampered by inadequate animal models. For instance, it is unclear to what extent commonly used behavioural tests in animals can inform us on the mental and affective aspects of schizophrenia. Methods To link pathophysiological processes in an animal model to clinical findings, we have here utilized the recently developed Df(h15q13)/+ mouse model for detailed investigations of cortical neuronal engagement during pre‐attentive processing of auditory information from two back‐translational auditory paradigms. We also investigate if compromised putative fast‐spiking interneurone (FSI) function can be restored through pharmacological intervention using the Kv3.1 channel opener RE1. Chronic multi‐array electrodes in primary auditory cortex were used to record single cell firing from putative pyramidal and FSI in awake animals during processing of auditory sensory information. Results We find a decreased amplitude in the response to auditory stimuli and reduced recruitment of neurones to fast steady‐state gamma oscillatory activity. These results resemble encephalography recordings in patients with schizophrenia. Furthermore, the probability of interneurones to fire with low interspike intervals during 80 Hz auditory stimulation was reduced in Df(h15q13)/+ mice, an effect that was partially reversed by the Kv3.1 channel modulator, RE1. Conclusion This study offers insight into the consequences on a neuronal level of carrying the 15q13.3 microdeletion. Furthermore, it points to deficient functioning of interneurones as a potential pathophysiological mechanism in schizophrenia and suggests a therapeutic potential of Kv3.1 channel openers.
    August 16, 2016   doi: 10.1111/apha.12746   open full text
  • High‐salt diet induces outward remodelling of efferent arterioles in mice with reduced renal mass.
    L. Zhao, Y. Gao, X. Cao, D. Gao, S. Zhou, S. Zhang, X. Cai, F. Han, C. S. Wilcox, L. Li, E. Y. Lai.
    Acta Physiologica. August 15, 2016
    Aim The glomerular filtration rate (GFR) falls progressively in chronic kidney disease (CKD) which is caused by a reduction in the number of functional nephrons. The dysfunctional nephron exhibits a lower glomerular capillary pressure that is induced by an unbalance between afferent and efferent arteriole. Therefore, we tested the hypothesis that oxidative stress induced by CKD differentially impairs the structure or function of efferent vs. afferent arterioles. Methods C57BL/6 mice received sham operations (sham) or 5/6 nephrectomy (RRM) and three months of normal‐ or high‐salt diet or tempol. GFR was assessed from the plasma inulin clearance, arteriolar remodelling from media/lumen area ratio, myogenic responses from changes in luminal diameter with increases in perfusion pressure and passive wall compliance from the wall stress/strain relationships. Results Mice with RRM fed a high salt (vs. sham) had a lower GFR (553 ± 25 vs. 758 ± 36 μL min−1 g−1 kidney, P < 0.01) and a larger efferent arteriolar diameter (9.6 ± 0.8 vs. 7.4 ± 0.7 μm, P < 0.05) resulting in a lower media/lumen area ratio (1.4 ± 0.1 vs. 2.4 ± 0.2, P < 0.01). These alterations were corrected by tempol. The myogenic responses of efferent arterioles were about one‐half that of afferent arterioles and were unaffected by RRM or salt. Passive wall compliance was reduced by high salt in both afferent and efferent arterioles. Conclusion A reduction in renal mass with a high‐salt diet induces oxidative stress that leads to an outward eutrophic remodelling in efferent arterioles and reduced wall compliance in both afferent and efferent arterioles. This may contribute to the lower GFR in this model of CKD.
    August 15, 2016   doi: 10.1111/apha.12759   open full text
  • c‐Jun N‐terminal Kinase mediates prostaglandin‐induced sympathoexcitation in rats with chronic heart failure by reducing GAD1 and GABRA1 expression.
    R. Wang, W. Zhang, Z. Dong, Y. Qi, M. Hultström, X. Zhou, E. Y. Lai.
    Acta Physiologica. August 12, 2016
    Aim Prostaglandin E2 mediates sympathoexcitation in chronic heart failure (CHF) through EP3 receptors (PTGER3) in the paraventricular nucleus (PVN). The aim of this study was to investigate the role of c‐Jun N‐terminal kinase (JNK) in expressional regulation of gamma‐aminobutyric acid signalling in PVN in CHF rats. Methods Chronic heart failure was induced by left coronary ligation in Wistar rats. Renal sympathetic nerve discharge (RSND) and mean arterial pressure (MAP) responses to the PVN infusion were determined in anaesthetized rats. Osmotic minipumps were used for chronic PVN infusion. PTGER3 expression was examined with immunofluorescence staining, quantitative real‐time PCR and Western blot. Results Chronic heart failure rats had increased JNK activation and decreased glutamate decarboxylase 1 (GAD1) and GABAA receptor alpha 1 subunit (GABRA1) expression in the PVN. PVN infusion of the PTGER3 agonist SC‐46275 caused sympathoexcitation in sham‐operated control (Sham) rats and increased it further in CHF. The PTGER3 antagonist L798106 reduced sympathoexcitation and cardiac dysfunction in CHF. PVN infusion of EP1 receptor antagonist SC‐19220, EP2 receptor antagonist AH6809 or EP4 receptor antagonist L‐161982 had no effect on sympathoexcitation. The JNK inhibitor SP600125 normalized sympathoexcitation and GAD1 and GABRA1 expression in PVN in CHF rats. Both the p44/42 and p38 mitogen‐activated protein kinase inhibitors PD98059 and SB203580 could not prevent the downregulation of GAD1 and GABRA1 expression in PVN in CHF. PTGER3 agonist activated JNK but downregulated GAD1 and GABRA1 expression in NG108 neuronal cells. Conclusion Prostaglandin signalling through upregulated PTGER3 activates JNK which reduces GAD1 and GABRA1 expression in the PVN, and contributes to sympathoexcitation in CHF.
    August 12, 2016   doi: 10.1111/apha.12758   open full text
  • Expression of sex steroid hormone receptors in human skeletal muscle during the menstrual cycle.
    L. Ekenros, Z. Papoutsi, C. Fridén, K. Dahlman Wright, A. Lindén Hirschberg.
    Acta Physiologica. August 09, 2016
    Aim Variations in sex hormone levels during the menstrual cycle may affect neuromuscular performance and the risk of sustaining musculoskeletal injury in women. The aim of this study was to investigate mRNA and protein levels for sex steroid hormone receptors in skeletal muscle in three distinct phases of the menstrual cycle. Methods Fifteen, healthy women with regular menstrual cycles participated in the study. Muscle biopsies from the vastus lateralis were obtained in three hormonally verified phases of the menstrual cycle for each individual, that is the follicular phase, the ovulatory phase and the luteal phase. mRNA and protein levels of oestrogen (ERα and ERβ), progesterone (PR) and androgen (AR) receptors were analysed. Results There was an overall significant variation in mRNA and protein levels of ERα and PR across the menstrual cycle. mRNA and protein levels of ERα were highest in the follicular phase when oestradiol levels were low, whereas protein levels of PR were highest in the luteal phase when progesterone levels were high. mRNA levels of PR were highest in the ovulatory phase. No significant variation in AR levels was detected across the menstrual cycle. ERβ levels were very low in all three phases of the menstrual cycle. Conclusion Significant variations in mRNA and protein levels of ERα and PR were detected in skeletal muscle during three confirmed phases of the menstrual cycle. These results may have an impact on effects of muscular training and sports injuries in women.
    August 09, 2016   doi: 10.1111/apha.12757   open full text
  • Emerging roles of calcium‐activated K channels and TRPV4 channels in lung oedema and pulmonary circulatory collapse.
    Ulf Simonsen, Christine Wandall‐Frostholm, Aida Oliván‐Viguera, Ralf Köhler.
    Acta Physiologica. August 06, 2016
    It has been suggested that the transient receptor potential cation (TRP) channel subfamily V (vanilloid) type 4 (TRPV4) and intermediate‐conductance calcium‐activated potassium (KCa3.1) channels contribute to endothelium‐dependent vasodilation. Here we summarize very recent evidence for a synergistic interplay of TRPV4 and KCa3.1 channels in lung disease. Among the endothelial Ca2+‐permeable TRPs, TRPV4 is best characterized and produces arterial dilation by stimulating Ca2+‐dependent NO synthesis and endothelium‐dependent hyperpolarization. Besides these roles, some TRP channels control endothelial/epithelial barrier functions and vascular integrity, while KCa3.1 channels provide the driving force required for Cl‐ and water transport in some cells and most secretory epithelia. The three conditions, increased pulmonary venous pressure caused by left heart disease, high inflation pressure, and chemically‐induced lung injury may lead to activation of TRPV4 channels followed by Ca2+ influx leading to activation of KCa3.1 channels in endothelial cells ultimately leading to acute lung injury. We find that a deficiency in KCa3.1channels protects against TRPV4‐induced pulmonary arterial relaxation, fluid extravasation, hemorrhage, pulmonary circulatory collapse, and cardiac arrest in vivo. These data identify KCa3.1 channels as crucial molecular components in downstream TRPV4‐signal transduction and as a potential target for the prevention of undesired fluid extravasation, vasodilatation, and pulmonary circulatory collapse. This article is protected by copyright. All rights reserved.
    August 06, 2016   doi: 10.1111/apha.12768   open full text
  • Salt‐losing nephropathy in mice with a null mutation of the Clcnk2 gene.
    A. Grill, I. M. Schießl, B. Gess, K. Fremter, A. Hammer, H. Castrop.
    Acta Physiologica. August 01, 2016
    Aim The basolateral chloride channel ClC‐Kb facilitates Cl reabsorption in the distal nephron of the human kidney. Functional mutations in CLCNKB are associated with Bartter's syndrome type 3, a hereditary salt‐losing nephropathy. To address the function of ClC‐K2 in vivo, we generated ClC‐K2‐deficient mice. Methods ClC‐K2‐deficient mice were generated using TALEN technology. Results ClC‐K2‐deficient mice were viable and born in a Mendelian ratio. ClC‐K2−/− mice showed no gross anatomical abnormalities, but they were growth retarded. The 24‐h urine volume was increased in ClC‐K2−/− mice (4.4 ± 0.6 compared with 0.9 ± 0.2 mL per 24 h in wild‐type littermates; P = 0.001). Accordingly, ambient urine osmolarity was markedly reduced (590 ± 39 vs. 2216 ± 132 mosmol L−1 in wild types; P < 0.0001). During water restriction (24 h), urinary osmolarity increased to 1633 ± 153 and 3769 ± 129 mosmol L−1 in ClC‐K2−/− and wild‐type mice (n = 12; P < 0.0001), accompanied by a loss of body weight of 12 ± 0.4 and 8 ± 0.2% respectively (P < 0.0001). ClC‐K2−/− mice showed an increased renal sodium excretion and compromised salt conservation during a salt‐restricted diet. The salt‐losing phenotype of ClC‐K2−/− mice was associated with a reduced plasma volume, hypotension, a slightly reduced glomerular filtration rate, an increased renal prostaglandin E2 generation and a massively stimulated renin–angiotensin system. Clckb−/− mice showed a reduced sensitivity to furosemide and were completely resistant to thiazides. Conclusion Loss of ClC‐K2 compromises TAL function and abolishes salt reabsorption in the distal convoluted tubule. Our data suggest that ClC‐K2 is crucial for renal salt reabsorption and concentrating ability. ClC‐K2‐deficient mice in most aspects mimic patients with Bartter's syndrome type 3.
    August 01, 2016   doi: 10.1111/apha.12755   open full text
  • 4D in vivo imaging of glomerular barrier function in a zebrafish podocyte injury model.
    F. Siegerist, W. Zhou, K. Endlich, N. Endlich.
    Acta Physiologica. August 01, 2016
    Aim Zebrafish larvae with their simplified pronephros are an ideal model to study glomerular physiology. Although several groups use zebrafish larvae to assess glomerular barrier function, temporary or slight changes are still difficult to measure. The aim of this study was to investigate the potential of in vivo two‐photon microscopy (2‐PM) for long‐term imaging of glomerular barrier function in zebrafish larvae. Methods As a proof of principle, we adapted the nitroreductase/metronidazole model of targeted podocyte ablation for 2‐PM. Combination with a strain, which expresses eGFP‐vitamin D‐binding protein in the blood plasma, led to a strain that allowed induction of podocyte injury with parallel assessment of glomerular barrier function. We used four‐dimensional (4D) 2‐PM to assess eGFP fluorescence over 26 h in the vasculature and in tubules of multiple zebrafish larvae (5 days post‐fertilization) simultaneously. Results By 4D 2‐PM, we observed that, under physiological conditions, eGFP fluorescence was retained in the vasculature and rarely detected in proximal tubule cells. Application of metronidazole induced podocyte injury and cell death as shown by TUNEL staining. Induction of podocyte injury resulted in a dramatic decrease of eGFP fluorescence in the vasculature over time (about 50% and 90% after 2 and 12 h respectively). Loss of vascular eGFP fluorescence was paralleled by an endocytosis‐mediated accumulation of eGFP fluorescence in proximal tubule cells, indicating proteinuria. Conclusion We established a microscopy‐based method to monitor the dynamics of glomerular barrier function during induction of podocyte injury in multiple zebrafish larvae simultaneously over 26 h.
    August 01, 2016   doi: 10.1111/apha.12754   open full text
  • Biomarkers in acute kidney injury – pathophysiological basis and clinical performance.
    Eva V. Schrezenmeier, Jonathan Barasch, Klemens Budde, Timm Westhoff, Kai M. Schmidt‐Ott.
    Acta Physiologica. July 30, 2016
    Various biomarkers of acute kidney injury (AKI) have been discovered and characterized in the recent past. These molecules can be detected in urine or blood and signify structural damage to the kidney. Clinically, they are proposed as adjunct diagnostics to serum creatinine and urinary output to improve the early detection, differential diagnosis and prognostic assessment of AKI. The most obvious requirements for a biomarker include its reflection of the underlying pathophysiology of the disease. Hence, a biomarker of AKI should derive from the injured kidney and reflect a molecular process intimately connected with tissue injury. Here, we provide an overview of the basic pathophysiology, the cellular sources and the clinical performance of the most important currently proposed biomarkers of acute kidney injury: neutrophil gelatinase‐associated lipocalin (NGAL), kidney injury molecule‐1 (KIM‐1), liver‐type fatty acid–binding protein (L‐FABP), interleukin 18 (IL‐18), insulin‐like growth factor binding protein 7 (IGFBP7), tissue inhibitor of metalloproteinase 2 (TIMP‐2), and calprotectin (S100A8/9). We also acknowledge each biomarker's advantages and disadvantages as well as important knowledge gaps and perspectives for future studies. This article is protected by copyright. All rights reserved
    July 30, 2016   doi: 10.1111/apha.12764   open full text
  • Novel Routes of Albumin Passage Across the Glomerular Filtration Barrier.
    Hayo Castrop, Ina Maria Schießl.
    Acta Physiologica. July 25, 2016
    Albuminuria is a hallmark of kidney diseases of various etiologies and an unambiguous symptom of the compromised integrity of the glomerular filtration barrier. Furthermore, there is increasing evidence that albuminuria per se aggravates the development and progression of chronic kidney disease. This review covers new aspects of the movement of large plasma proteins across the glomerular filtration barrier in health and disease. Specifically, this review focuses on the role of endocytosis and transcytosis of albumin by podocytes, which constitutes a new pathway of plasma proteins across the filtration barrier. Thus, we summarize what is known about the mechanisms of albumin endocytosis by podocytes and address the fate of the endocytosed albumin, which is directed to lysosomal degradation or transcellular movement with subsequent vesicular release into the urinary space. We also address the functional consequences of overt albumin endocytosis by podocytes, such as the formation of pro‐inflammatory cytokines, which might eventually result in a deterioration of podocyte function. Finally, we consider the diagnostic potential of podocyte‐derived albumin‐containing vesicles in the urine as an early marker of a compromised glomerular barrier function. In terms of new technical approaches, the review covers how our knowledge of the movement of albumin across the glomerular filtration barrier has expanded by the use of new intravital imaging techniques. This article is protected by copyright. All rights reserved.
    July 25, 2016   doi: 10.1111/apha.12760   open full text
  • Activation of the hypoxia‐inducible factor pathway induced by prolyl hydroxylase domain 2 deficiency enhances the effect of running training in mice.
    A. Nunomiya, J. Shin, Y. Kitajima, T. Dan, T. Miyata, R. Nagatomi.
    Acta Physiologica. July 25, 2016
    Aims Hypoxic response mediated by hypoxia‐inducible factor (HIF) seems to contribute to the benefit of endurance training. To verify the direct contribution of HIF activation to running training without exposure to atmospheric hypoxia, we used prolyl hydroxylase domain 2 (PHD2) conditional knockout mice (cKO), which exhibit HIF activation independent of oxygen concentration, and we examined their maximal exercise capacity before and after 4 weeks of treadmill exercise training. Methods Phd2f/f mice (n = 26) and Phd2 cKO mice (n = 24) were randomly divided into two groups, trained and untrained, and were subjected to maximal running test before and after a 4‐week treadmill‐training regimen. Results Prolyl hydroxylase domain 2 deficiency resulted in HIF‐α protein accumulation. Phd2 cKO mice exhibited marked increases in haematocrit values and haemoglobin concentrations, as well as an increase in the capillary number in the skeletal muscle. The 4‐week training elicited an increase in the capillary‐to‐fibre (C/F) ratio and succinyl dehydrogenase activity of the skeletal muscle. Importantly, trained Phd2 cKO mice showed a significantly greater improvement in running time than trained control mice (P < 0.05). Collectively, these data suggest that the combination of training and the activation of the HIF pathway are important for maximizing the effect of running training. Conclusion We conclude that the activation of the HIF pathway induced by PHD2 deficiency enhances the effect of running training.
    July 25, 2016   doi: 10.1111/apha.12751   open full text
  • Claudin‐2‐mediated cation and water transport share a common pore.
    R. Rosenthal, D. Günzel, S. M. Krug, J.‐D. Schulzke, M. Fromm, A. S. L. Yu.
    Acta Physiologica. July 20, 2016
    Aim Claudin‐2 is a tight junction protein typically located in ‘leaky’ epithelia exhibiting large paracellular permeabilities like small intestine and proximal kidney tubule. Former studies revealed that claudin‐2 forms paracellular channels for small cations like sodium and potassium and also paracellular channels for water. This study analyses whether the diffusive transport of sodium and water occurs through a common pore of the claudin‐2 channel. Methods Wild‐type claudin‐2 and different claudin‐2 mutants were expressed in MDCK I kidney tubule cells using an inducible system. Ion and water permeability and the effect of blocking reagents on both were investigated on different clones of the mutants. Results Neutralization of a negatively charged cation interaction site in the pore with the mutation, D65N, decreased both sodium permeability and water permeability. Claudin‐2 mutants (I66C and S68C) with substitution of the pore‐lining amino acids with cysteine were used to test the effect of steric blocking of the claudin‐2 pore by thiol‐reactive reagents. Addition of thiol‐reactive reagents to these mutants simultaneously decreased conductance and water permeability. Remarkably, all experimental perturbations caused parallel changes in ion conductance and water permeability, disproving different or independent passage pathways. Conclusion Our results indicate that claudin‐2‐mediated cation and water transport are frictionally coupled and share a common pore. This pore is lined and determined in permeability by amino acid residues of the first extracellular loop of claudin‐2.
    July 20, 2016   doi: 10.1111/apha.12742   open full text
  • Bladder pain induced by prolonged peripheral alpha 1A adrenoceptor stimulation involves the enhancement of transient receptor potential vanilloid 1 activity and an increase of urothelial adenosine triphosphate release.
    R. Matos, J. M. Cordeiro, A. Coelho, S. Ferreira, C. Silva, Y. Igawa, F. Cruz, A. Charrua.
    Acta Physiologica. July 20, 2016
    Aim Pathophysiological mechanisms of chronic visceral pain (CVP) are unknown. This study explores the association between the sympathetic system and bladder nociceptors activity by testing the effect of a prolonged adrenergic stimulation on transient receptor potential vanilloid 1 (TRPV1) activity and on urothelial adenosine triphosphate (ATP) release. Methods Female Wistar rats received saline, phenylephrine (PHE), PHE + silodosin, PHE + naftopidil or PHE + prazosin. TRPV1 knockout and wild‐type mice received saline or PHE. Visceral pain behaviour tests were performed before and after treatment. Cystometry was performed, during saline and capsaicin infusion. Fos immunoreactivity was assessed in L6 spinal cord segment. Human urothelial ATP release induced by mechanical and thermal stimulation was evaluated. Results Subcutaneous, but not intrathecal, PHE administration induced pain, which was reversed by silodosin, a selective alpha 1A adrenoceptor antagonist, but not by naftopidil, a relatively selective antagonist for alpha 1D adrenoceptor. Silodosin also reversed PHE‐induced bladder hyperactivity and L6 spinal cord Fos expression. Thus, in subsequent experiments, only silodosin was used. Wild‐type, but not TRPV1 knockout, mice exhibited phenylephrine‐induced pain. Capsaicin induced a greater increase in voiding contractions in PHE‐treated rats than in control animals, and silodosin reversed this effect. When treated with PHE, ATP release from human urothelial cells was enhanced either by mechanical stimulation or by lowering the thermal threshold of urothelial TRPV1, which becomes abnormally responsive at body temperature. Conclusion This study suggests that the activation of peripheral alpha 1A adrenoceptors induces CVP, probably through its interaction with TRPV1 and ATP release.
    July 20, 2016   doi: 10.1111/apha.12744   open full text
  • Adipocytokine, progranulin, augments acetylcholine‐induced nitric oxide‐mediated relaxation through the increases of cGMP production in rat isolated mesenteric artery.
    K. Kazama, K. Hoshino, T. Kodama, M. Okada, H. Yamawaki.
    Acta Physiologica. July 15, 2016
    Aim Progranulin (PGRN) is a novel adipocytokine with anti‐inflammatory effects in vascular cells. The aim of this study was to clarify the effects of PGRN on reactivity of isolated blood vessel. Methods Isometric contraction of rat isolated superior mesenteric artery was measured. Results Pre‐treatment with PGRN (10–100 ng mL−1, 30 min) had no effect on noradrenaline‐ or 5‐hydroxytriptamine‐induced contraction. On the other hand, pre‐treatment with PGRN (100 ng mL−1) augmented acetylcholine (ACh; 30 nm)‐induced endothelium‐dependent relaxation. Pre‐treatment with PGRN (100 ng mL−1) augmented ACh (10 μm)‐induced nitric oxide (NO)‐mediated relaxation in the presence of indomethacin (10 μm), a cyclooxygenase inhibitor, and tetraethyl ammonium (10 mm), a non‐selective potassium channel blocker. In contrast, pre‐treatment with PGRN (100 ng mL−1) had no effect on ACh‐induced endothelium‐derived hyperpolarizing factor‐mediated relaxation. Pre‐treatment with PGRN (100 ng mL−1) had no effect on ACh (10 μm, 1 min)‐induced endothelial NO synthase phosphorylation (at Ser1177) as determined by Western blotting. Pre‐treatment with PGRN (100 ng mL−1) augmented an NO donor, sodium nitroprusside (SNP; 30 nm–1 μm)‐ but not a membrane‐permeable cGMP analogue, 8‐bromo‐cGMP‐induced relaxation. In the presence of 3‐isobutyl‐1‐methylxanthine (100 μm), a phosphodiesterase inhibitor, pre‐treatment with PGRN (100 ng mL−1) increased SNP (30 nm, 5 min)‐induced cGMP production as determined by enzyme immunoassay. Conclusion We for the first time demonstrate that PGRN augments ACh‐induced NO‐mediated relaxation through the increases of cGMP production in smooth muscle. These results indicate PGRN as a possible pharmacotherapeutic target against cardiovascular diseases including obesity‐related hypertension.
    July 15, 2016   doi: 10.1111/apha.12739   open full text
  • Right ventricle dimensions and function in response to acute hypoxia in healthy human subjects.
    N. C. Netzer, K. P. Strohl, J. Högel, H. Gatterer, R. Schilz.
    Acta Physiologica. July 15, 2016
    Aim Acute hypoxia produces acute vasoconstriction in the pulmonary circulation with consequences on right ventricular (RV) structure and function. Previous investigations in healthy humans have been restricted to measurements after altitude acclimatization or were interrupted by normoxia. We hypothesized that immediate changes in RV dimensions in healthy subjects in response to normobaric hypoxia differ without the aforementioned constraints. Methods Transthoracic echocardiography was performed in 35 young, healthy subjects exposed to 11% oxygen, as well as six controls under sham hypoxia (20.6% oxygen, single blind) first at normoxia and after 30, 60, 100, 150 min of hypoxia or normoxia respectively. A subgroup of 15 subjects continued with 3‐min cycling exercise in hypoxia with subsequent evaluation followed by an assessment 1 min at rest while breathing 4 L min−1 oxygen. Results During hypoxia, there was a significant linear increase of all RV dimensions (RVD1 + 29 mm, RVD2 + 42 mm, RVD3 + 41 mm, RVOT + 13 mm, RVEDA + 18 mm, P < 0.01) in the exposure group vs. the control group. In response to hypoxia, right ventricular systolic pressure (RVSP) showed a modest increase in hypoxia at rest (+7.3 mmHg, P < 0.01) and increased further with physical effort (+11.8 mmHg, P < 0.01). After 1 min of oxygen at rest, it fell by 50% of the maximum increase. Conclusion Acute changes in RV morphology occur quickly after exposure to normobaric hypoxia. The changes were out of proportion to a relatively low‐estimated increase in pulmonary pressure, indicating direct effects on RV structure. The results in healthy subjects are basis for future clinically oriented interventional studies in normobaric hypoxia.
    July 15, 2016   doi: 10.1111/apha.12740   open full text
  • Brain‐derived neurotrophic factor of the cerebral microvasculature: a forgotten and nitric oxide‐dependent contributor of brain‐derived neurotrophic factor in the brain.
    A. Monnier, A. Prigent‐Tessier, A. Quirié, N. Bertrand, S. Savary, C. Gondcaille, P. Garnier, C. Demougeot, C. Marie.
    Acta Physiologica. July 15, 2016
    Aim Evidence that brain‐derived neurotrophic factor (BDNF), a neurotrophin largely involved in cognition, is expressed by cerebral endothelial cells led us to explore in rats the contribution of the cerebral microvasculature to BDNF found in brain tissue and the link between cerebrovascular nitric oxide (NO) and BDNF production. Methods Brain BDNF protein levels were measured before and after in situ removal of the cerebral endothelium that was achieved by brain perfusion with a 0.2% CHAPS (3‐[(3‐cholamidopropyl) dimethylammonio]‐1‐propane sulphonate) solution. BDNF protein and mRNA levels as well as levels of endothelial NO synthase phosphorylated at serine 1177 (P‐eNOSser1177) were measured in cerebral microvessel‐enriched fractions. These fractions were also exposed to glycerol trinitrate. Hypertension (spontaneously hypertensive rats) and physical exercise training were used as experimental approaches to modulate cerebrovascular endothelial NO production. Results CHAPS perfusion resulted in a marked decrease in brain BDNF levels. Hypertension decreased and exercise increased P‐eNOSser1177 and BDNF protein levels. However, BDNF mRNA levels that were increased by exercise did not change after hypertension. Finally, in vitro exposure of cerebral microvessel‐enriched fractions to glycerol trinitrate enhanced BDNF production. Conclusion These data reveal that BDNF levels measured in brain homogenates correspond for a large part to BDNF present in cerebral endothelial cells and that cerebrovascular BDNF production is dependent on cerebrovascular endothelial eNOS activity. They provide a paradigm shift in the cellular source of brain BDNF and suggest a new approach to improve our understanding of the link between endothelial function and cognition.
    July 15, 2016   doi: 10.1111/apha.12743   open full text
  • Increased hydrogen peroxide impairs angiotensin II contractions of afferent arterioles in mice after renal ischaemia–reperfusion injury.
    Q. Huang, Q. Wang, S. Zhang, S. Jiang, L. Zhao, L. Yu, M. Hultström, A. Patzak, L. Li, C. S. Wilcox, E. Y. Lai.
    Acta Physiologica. July 15, 2016
    Aim Renal ischaemia–reperfusion injury (IRI) increases angiotensin II (Ang II) and reactive oxygen species (ROS) that are potent modulators of vascular function. However, the roles of individual ROS and their interaction with Ang II are not clear. Here we tested the hypothesis that IRI modulates renal afferent arteriolar responses to Ang II via increasing superoxide (O2−) or hydrogen peroxide (H2O2). Methods Renal afferent arterioles were isolated and perfused from C57BL/6 mice 24 h after IRI or sham surgery. Responses to Ang II or noradrenaline were assessed by measuring arteriolar diameter. Production of H2O2 and O2− was assessed in afferent arterioles and renal cortex. Activity of SOD and catalase, and mRNA expressions of Ang II receptors were assessed in pre‐glomerular arterioles and renal cortex. Results Afferent arterioles from mice after IRI had a reduced maximal contraction to Ang II (−27±2 vs. −42±1%, P < 0.001), but retained a normal contraction to noradrenaline. Arterioles after IRI had a 38% increase in H2O2 (P < 0.001) and a 45% decrease in catalase activity (P < 0.01). Contractions were reduced in normal arterioles after incubation with H2O2 (−22±2 vs. −42±1%, P < 0.05) similar to the effects of IRI. However, the impaired contractions were normalized by incubation with PEG catalase despite a reduced AT1R expression. Conclusions Renal IRI in mice selectively impairs afferent arteriolar responses to Ang II because of H2O2 accumulation that is caused by a reduced catalase activity. This could serve to buffer the effect of Ang II after IRI and may be a protective mechanism.
    July 15, 2016   doi: 10.1111/apha.12745   open full text
  • The principal pathways involved in the in vivo modulation of hypoxic pulmonary vasoconstriction, pulmonary arterial remodelling and pulmonary hypertension.
    David Kylhammar, Göran Rådegran.
    Acta Physiologica. July 06, 2016
    Hypoxic pulmonary vasoconstriction (HPV) serves to optimize ventilation‐perfusion matching in focal hypoxia and thereby enhances pulmonary gas exchange. During global hypoxia, however, HPV induces general pulmonary vasoconstriction, which may lead to pulmonary hypertension (PH), impaired exercise capacity, right‐heart failure and pulmonary oedema at high altitude. In chronic hypoxia, generalized HPV together with hypoxic pulmonary arterial remodelling, contribute to the development of PH. The present article reviews the principal pathways in the in vivo modulation of HPV, hypoxic pulmonary arterial remodelling and PH with primary focus on the endothelin‐1, nitric oxide, cyclooxygenase and adenine nucleotide pathways. In summary, endothelin‐1 and thromboxane A2 may enhance, whereas nitric oxide and prostacyclin may moderate, HPV as well as hypoxic pulmonary arterial remodelling and PH. The production of prostacyclin seems to be coupled primarily to cyclooxygenase‐1 in acute hypoxia, but to cyclooxygenase‐2 in chronic hypoxia. The potential role of adenine nucleotides in modulating HPV is unclear, but warrants further study. Additional modulators of the pulmonary vascular responses to hypoxia may include angiotensin II, histamine, serotonin/5‐hydroxytryptamine, leukotrienes and epoxyeicosatrienoic acids. Drugs targeting these pathways may reduce acute and/or chronic hypoxic PH. Endothelin receptor antagonists and phosphodiesterase‐5 inhibitors may additionally improve exercise capacity in hypoxia. Importantly, the modulation of the pulmonary vascular responses to hypoxia varies between species and individuals, with hypoxic duration and age. The review also define how drugs targeting the endothelin‐1, nitric oxide, cyclooxygenase and adenine nucleotide pathways may improve pulmonary haemodynamics, but also impair pulmonary gas exchange by interference with HPV in chronic lung diseases. This article is protected by copyright. All rights reserved.
    July 06, 2016   doi: 10.1111/apha.12749   open full text
  • Dexamethasone promotes long‐term functional recovery of neuromuscular junction in a murine model of tourniquet‐induced ischaemia–reperfusion.
    D. Zhang, D. Wang, I. I. Pipinos, R. L. Muelleman, Y.‐L. Li.
    Acta Physiologica. July 05, 2016
    Aim Tourniquet‐induced ischaemia and subsequent reperfusion cause serious ischaemia–reperfusion (IR) injury in the neuromuscular junction (NMJ) and skeletal muscle. Here, we investigated whether dexamethasone (Dex) promotes long‐term functional recovery of the NMJ and skeletal muscle in tourniquet‐induced hindlimb IR. Methods Unilateral hindlimb of C57/BL6 mice was subjected to 3 h of ischaemia following 6 weeks of reperfusion (6‐wk IR). Dex treatment began on the day of IR induction and lasted for different periods. Sciatic nerve‐stimulated gastrocnemius muscle contraction was detected in situ. Function of the NMJ was measured in situ using electrophysiological recording of the miniature endplate potential (mEPP) and endplate potential (EPP). Western blot was used to detect protein expression of nicotinic acetylcholine receptors (nAChRs) in gastrocnemius muscles. Results Gastrocnemius muscle contraction in mice with 6‐wk IR was about 60% of normal skeletal muscle contraction recorded in age‐matched sham mice. The amplitude of the mEPP and EPP was lower in mice with 6‐wk IR, compared to sham mice. Dex treatment for 1 or 3 days did not restore the function of the NMJ and improve gastrocnemius muscle contraction in mice with 6‐wk IR. Dex treatment for 1 week exerted a maximum effect on improving the function of the NMJ and skeletal muscle, with the effect of Dex gradually lessening with prolonged Dex treatment. There are no significant differences in protein expression of nAChR‐α1 and nAChR‐β1 subunits in the gastrocnemius muscle among all groups. Conclusion Dex promotes repair of the NMJ and subsequently restores skeletal muscle contractile function in tourniquet‐induced 6‐wk IR.
    July 05, 2016   doi: 10.1111/apha.12737   open full text
  • Hypometabolism as the ultimate defense in stress response: how the comparative approach helps understanding of medically relevant questions.
    Thomas A. Gorr.
    Acta Physiologica. July 01, 2016
    First conceptualized from breath‐hold diving mammals, later recognized as the ultimate cell‐autonomous survival strategy in anoxia‐tolerant vertebrates and burrowing or hibernating rodents, hypometabolism is typically recruited by resilient organisms to withstand and recover from otherwise life‐threatening hazards. Through the coordinated down‐regulation of biosynthetic, proliferative and electrogenic expenditures at times when little ATP can be generated, a metabolism turned “down to the pilot light” allows the re‐balancing of energy demand with supply at a greatly suppressed level in response to noxious exogenous stimuli or seasonal endogenous cues. A unifying hallmark of stress‐tolerant organisms, the adaptation effectively prevents lethal depletion of ATP, thus delineating a marked contrast with susceptible species. Along with disengaged macromolecular syntheses, attenuated trans‐membrane ion shuttling and pO2‐conforming respiration rates, the metabolic slowdown in tolerant species usually culminates in a non‐cycling, quiescent phenotype. However, such a reprogramming also occurs in leading human pathophysiologies. Ranging from microbial infections through ischaemia‐driven infarcts to solid malignancies, cells involved in these disorders may again invoke hypometabolism to endure conditions nonpermissive for growth. At the same time, their reduced activities underlie the frequent development of a general resistance to therapeutic interventions. On the other hand, a controlled induction of hypometabolic and/or hypothermic states by pharmacological means has recently stimulated intense research aimed at improved organ preservation and patient survival in situations requiring acutely administered critical care. The current review article therefore presents an up‐to‐date survey of concepts and applications of a coordinated and reversibly down‐regulated metabolic rate as the ultimate defense in stress responses. This article is protected by copyright. All rights reserved.
    July 01, 2016   doi: 10.1111/apha.12747   open full text
  • Heat stress‐induced phosphorylation of FoxO3a signalling in rat skeletal muscle.
    T. Yoshihara, H. Kobayashi, R. Kakigi, T. Sugiura, H. Naito.
    Acta Physiologica. July 01, 2016
    Aim A recent study demonstrated that FoxO3a was directly induced by the overexpression of Hsp72 in rat soleus muscle. However, whether heat stress treatment induces FoxO3a phosphorylation in rat skeletal muscle remains unclear. This study examined the effects of heat stress on the regulation of the FoxO3a signalling pathway in rat skeletal muscle. Methods Thirty‐two male Wistar rats (15 weeks old) were randomly assigned into two groups; sedentary control group (Sed, n = 8) and experimental group (n = 24). After an overnight fast, one leg of each rat (HS leg) in the experimental group was immersed in hot water (43 °C) for 30 min, and the soleus and plantaris muscles in both legs were removed immediately (0 min), 30 min, 60 min, or 24 h after the heat stress (n = 6 each group). The contralateral, non‐heated leg in the experimental group served as an internal control (CT leg). Results Heat stress treatment resulted in a significant increase in FoxO3a phosphorylation (Ser253) in the soleus and plantaris muscles of heat‐stressed legs after 24 h. Hsp72 expression in heat‐stressed legs was significantly higher at 60 min and 24 h in these muscles. Activation of the PTEN/Akt and MEK/ERK pathways was also observed in these muscles immediately after stress, but not at 24 h. There were no differences in FoxO1 and AMPKα phosphorylation in either muscle. Conclusion Heat stress in rat skeletal muscle induces phosphorylation of FoxO3a signalling, and it may be related to Hsp72 upregulation, and the activation of the PTEN/Akt and MEK/ERK pathways.
    July 01, 2016   doi: 10.1111/apha.12735   open full text
  • Shear stress‐induced angiogenesis in mouse muscle is independent of the vasodilator mechanism and quickly reversible.
    S. Egginton, A. Hussain, J. Hall‐Jones, B. Chaudhry, F. Syeda, K. E. Glen.
    Acta Physiologica. July 01, 2016
    Aim Is modulation of skeletal muscle capillary supply by altering blood flow due to a presumptive shear stress response per se, or dependent on the vasodilator mechanism? Methods The response to four different vasodilators, and cotreatment with blockers of NO and prostaglandin synthesis, was compared. Femoral artery blood flow was correlated with capillary‐to‐fibre ratio (C:F) and protein levels of putative angiogenic compounds. Results All vasodilators induced a similar increase in blood flow after 14 days, with a similar effect on C:F (1.62 ± 0.05, 1.60 ± 0.01, 1.57 ± 0.06, 1.57 ± 0.07, respectively, all P < 0.05 vs. control 1.20 ± 0.01). Concomitant inhibitors revealed differential effects on blood flow and angiogenesis, demonstrating that a similar response may have different signalling origins. The time course of this response with the most commonly used vasodilator, prazosin, showed that blood flow increased from 0.40 mL min−1 to 0.61 mL min−1 by 28 days (P < 0.05), dropped within 1 week after the cessation of treatment (0.54 mL min−1; P < 0.05) and returned to control levels by 6 weeks. In parallel with FBF, capillary rarefaction began within 1 week (P < 0.05), giving C:F values similar to control by 2 weeks. Of the dominant signalling pathways, prazosin decreased muscle VEGF, but increased its cognate receptor Flk‐1 (both P < 0.01); levels of eNOS varied with blood flow (P < 0.05), and Ang‐1 initially increased, while its receptor Tie‐2 was unchanged, with only modest changes in the antiangiogenic factor TSP‐1. Conclusion Hyperaemia‐induced angiogenesis, likely in response to elevated shear stress, is independent of the vasodilator involved, with a rapid induction and quick regression following the stimulus withdrawal.
    July 01, 2016   doi: 10.1111/apha.12728   open full text
  • Role of transient receptor potential vanilloid 1 in regulating erythropoietin‐induced activation of endothelial nitric oxide synthase.
    Y.‐B. Yu, K.‐H. Su, Y. R. Kou, B.‐C. Guo, K.‐I. Lee, J. Wei, T.‐S. Lee.
    Acta Physiologica. June 29, 2016
    Aims Erythropoietin (EPO), the key hormone involved in erythropoiesis, beneficially affects endothelial cells (ECs), but the detailed mechanisms are yet to be completely understood. In this study, we investigated the role of transient receptor potential vanilloid type 1 (TRPV1), a ligand‐gated non‐selective calcium (Ca2+) channel, in EPO‐mediated endothelial nitric oxide synthase (eNOS) activation and angiogenesis. Methods and results In ECs, EPO time dependently increased intracellular levels of calcium; this increase was abrogated by the Ca2+ chelators and pharmacological inhibitors of TRPV1 in bovine aortic ECs (BAECs) and TRPV1‐transfected HEK293 cells. In addition, EPO‐induced nitrite oxide (NO) production, phosphorylation of eNOS, Akt and AMP‐activated protein kinase (AMPK) and the formation of TRPV1–Akt–AMPK–eNOS complex as well as tube formation were diminished by the pharmacological inhibition of TRPV1 in BAECs. Moreover, EPO time dependently induced the phosphorylation of phospholipase C‐γ1 (PLC‐γ1). Inhibition of PLC‐γ1 activity blunted the EPO‐induced Ca2+ influx, eNOS phosphorylation, TRPV1–eNOS complex formation and NO production. The phosphorylated level of eNOS increased in the aortas of EPO‐treated wild‐type (WT) mice or EPO‐transgenic (Tg) mice but not in those of EPO‐treated TRPV1‐deficient (TRPV1−/−) mice or EPO‐Tg/TRPV1−/− mice. Matrigel plug assay showed that EPO‐induced angiogenesis was abrogated in TRPV1 antagonist capsazepine‐treated WT mice and TRPV1−/− mice. Conclusion These findings indicate the EPO‐induced Ca2+ influx via the activation of the PLC‐γ1 signalling pathway, which leads to TRPV1 activation and consequently increases the association of the TRPV1–Akt–AMPK–eNOS complex, eNOS activation, NO production and angiogenesis.
    June 29, 2016   doi: 10.1111/apha.12723   open full text
  • P/Q‐type and T‐type voltage‐gated calcium channels are involved in the contraction of mammary and brain blood vessels from hypertensive patients.
    A. D. Thuesen, K. S. Lyngsø, L. Rasmussen, J. Stubbe, O. Skøtt, F. R. Poulsen, C. B. Pedersen, L. M. Rasmussen, P. B. L. Hansen.
    Acta Physiologica. June 29, 2016
    Aim Calcium channel blockers are widely used in cardiovascular diseases. Besides L‐type channels, T‐ and P/Q‐type calcium channels are involved in the contraction of human renal blood vessels. It was hypothesized that T‐ and P/Q‐type channels are involved in the contraction of human brain and mammary blood vessels. Methods Internal mammary arteries from bypass surgery patients and cerebral arterioles from patients with brain tumours with and without hypertension were tested in a myograph and perfusion set‐up. PCR and immunohistochemistry were performed on isolated blood vessels. Results The P/Q‐type antagonist ω‐agatoxin IVA (10−8 mol L−1) and the T‐type calcium blocker mibefradil (10−7 mol L−1) inhibited KCl depolarization‐induced contraction in mammary arteries from hypertensive patients with no effect on blood vessels from normotensive patients. ω‐Agatoxin IVA decreased contraction in cerebral arterioles from hypertensive patients. L‐type blocker nifedipine abolished the contraction in mammary arteries. PCR analysis showed expression of P/Q‐type (Cav2.1), T‐type (Cav3.1 and Cav3.2) and L‐type (Cav1.2) calcium channels in mammary and cerebral arteries. Immunohistochemical labelling of mammary and cerebral arteries revealed the presence of Cav2.1 in endothelial and smooth muscle cells. Cav3.1 was also detected in mammary arteries. Conclusion P/Q‐ and T‐type Cav are present in human internal mammary arteries and in cerebral penetrating arterioles. P/Q‐ and T‐type calcium channels are involved in the contraction of mammary arteries from hypertensive patients but not from normotensive patients. Furthermore, in cerebral arterioles P/Q‐type channels importance was restricted to hypertensive patients might lead to that T‐ and P/Q‐type channels could be a new target in hypertensive patients.
    June 29, 2016   doi: 10.1111/apha.12732   open full text
  • Pro‐inflammatory cytokines, IL‐1β and TNF‐α, produce persistent compromise in tonic immobility defensive behaviour in endotoxemia guinea‐pigs.
    A. B. Ribeiro, P. C. G. Barcellos‐Filho, C. R. Franci, L. Menescal‐de‐Oliveira, R. S. Saia.
    Acta Physiologica. June 28, 2016
    Aim Sepsis has been associated with acute behavioural changes in humans and rodents, which consists of a motivational state and an adaptive response that improve survival. However, the involvement of peripheral cytokines synthesized during systemic inflammation as modulators of the tonic immobility (TI) defensive behaviour remains a literature gap. Our purposes were to characterize the TI defensive behaviour in endotoxemia guinea‐pigs at acute phase and after recovery from the initial inflammatory challenge. Furthermore, we investigated whether peri‐aqueductal grey matter (PAG) exists as a brain structure related to this behaviour and also pro‐inflammatory cytokines, tumour necrosis factor (TNF)‐α and interleukin (IL)‐1β, act at this mesencephalic nucleus. Methods Endotoxemia was induced by lipopolysaccharide (LPS) administration in guinea‐pigs. The parameters evaluated included TI defensive behaviour, survival, cytokines production, as well as neuronal activation and apoptosis in the PAG. Results Endotoxemia guinea‐pigs exhibited a reduction in the duration of TI episodes, starting at 2 h after LPS administration and persisting throughout the experimental period evaluated over 7 days. Moreover, endotoxemia increased the c‐FOS immunoreactivity of neurones in the ventrolateral PAG (vlPAG), as well as the caspase‐3 expression. The LPS microinjection into vlPAG reproduces the same compromise, that is a decrease in the duration of TI defensive behaviour, observed after the peripheral administration. The immunoneutralization against IL‐1β and TNF‐α into vlPAG reverts all the effects produced by peripheral LPS administration. Conclusion Our findings confirm that vlPAG is an important brain structure involved in the behavioural alterations induced by endotoxemia, possibly changing the neuronal activity caused by pro‐inflammatory cytokines produced peripherally.
    June 28, 2016   doi: 10.1111/apha.12729   open full text
  • Long‐term exercise training prevents mammary tumorigenesis‐induced muscle wasting in rats through the regulation of TWEAK signalling.
    A. I. Padrão, A. C. C. Figueira, A. I. Faustino‐Rocha, A. Gama, M. M. Loureiro, M. J. Neuparth, D. Moreira‐Gonçalves, R. Vitorino, F. Amado, L. L. Santos, P. A. Oliveira, J. A. Duarte, R. Ferreira.
    Acta Physiologica. June 27, 2016
    Aim Exercise training has been suggested as a non‐pharmacological approach to prevent skeletal muscle wasting and improve muscle function in cancer cachexia. However, little is known about the molecular mechanisms underlying such beneficial effect. In this study, we aimed to, firstly, examine the contribution of TWEAK signalling to cancer‐induced skeletal muscle wasting and, secondly, evaluate whether long‐term exercise alters TWEAK signalling and prevents muscle wasting. Methods Female Sprague‐Dawley rats were randomly assigned to control and exercise groups. Fifteen animals from each group were exposed to N‐Methyl‐N‐nitrosourea carcinogen. Animals in exercise groups were submitted to moderate treadmill exercise for 35 weeks. After the experimental period, animals were killed and gastrocnemius muscles were harvested for morphological and biochemical analysis. Results We verified that exercise training prevented tumour‐induced TWEAK/NF‐κB signalling in skeletal muscle with a beneficial impact in fibre cross‐sectional area and metabolism. Indeed, 35 weeks of exercise training promoted the upregulation of PGC‐1α and oxidative phosphorylation complexes. This exercise‐induced muscle remodelling in tumour‐bearing animals was associated with less malignant mammary lesions. Conclusion Data support the benefits of an active lifestyle for the prevention of muscle wasting secondary to breast cancer, highlighting TWEAK/NF‐ κB signalling as a potential therapeutic target for the preservation of muscle mass.
    June 27, 2016   doi: 10.1111/apha.12721   open full text
  • Haemodiafiltration at increased plasma ionic strength for improved protein‐bound toxin removal.
    D. H. Krieter, E. Devine, T. Körner, M. Rüth, C. Wanner, M. Raine, J. Jankowski, H.‐D. Lemke.
    Acta Physiologica. June 22, 2016
    Aim Protein‐bound uraemic toxin accumulation causes uraemia‐associated cardiovascular morbidity. Enhancing the plasma ionic strength releases toxins from protein binding and makes them available for removal during dialysis. This concept was implemented through high sodium concentrations ([Na+]) in the substituate of pre‐dilution haemodiafiltration at increased plasma ionic strength (HDF‐IPIS). Methods Ex vivo HDF‐IPIS with blood tested increasing [Na+] to demonstrate efficacy and haemocompatibility. Haemocompatibility was further assessed in sheep using two different HDF‐IPIS set‐ups and [Na+] between 350 and 600 mmol L−1. Safety and efficacy of para‐cresyl sulphate (pCS) and indoxyl sulphate (IS) removal was further investigated in a randomized clinical pilot trial comparing HDF‐IPIS to HD and HDF. Results Compared to [Na+] of 150 mmol L−1, ex vivo HDF‐IPIS at 500 mmol L−1 demonstrated up to 50% higher IS removal. Haemolysis in sheep was low even at [Na+] of 600 mmol L−1 (free Hb 0.016 ± 0.001 g dL−1). In patients, compared to HD, a [Na+] of 240 mmol L−1 in HDF‐IPIS resulted in 40% greater reduction (48.7 ± 23.6 vs. 67.8 ± 7.9%; P = 0.013) in free IS. Compared to HD and HDF (23.0 ± 14.8 and 25.4 ± 10.5 mL min−1), the dialytic clearance of free IS was 31.6 ± 12.8 mL min−1 (P = 0.017) in HDF‐IPIS, but [Na+] in arterial blood increased from 132 ± 2 to 136 ± 3 mmol L−1 (0 vs. 240 min; P < 0.001). Conclusion HDF‐IPIS is technically and clinically feasible. More effective HDF‐IPIS requires higher temporary plasma [Na+], but dialysate [Na+] has to be appropriately adapted to avoid sodium accumulation.
    June 22, 2016   doi: 10.1111/apha.12730   open full text
  • Adenine‐induced chronic renal failure in rats decreases aortic relaxation rate and alters expression of proteins involved in vascular smooth muscle calcium handling.
    L. Nguy, E. Shubbar, M. Jernås, I. Nookaew, J. Lundgren, B. Olsson, H. Nilsson, G. Guron.
    Acta Physiologica. June 19, 2016
    Aim Rats with adenine‐induced chronic renal failure (A‐CRF) develop a reduced rate of relaxation of the thoracic aorta. The aim of this study was to elucidate the mechanisms underlying this abnormality. Methods Male Sprague Dawley rats received either chow containing adenine or were pair‐fed with normal chow (controls). After 8–14 weeks, arterial function was analysed ex vivo using wire myography and the expression of proteins involved in vascular smooth muscle excitation–contraction coupling in the thoracic aorta was analysed. Results The rate of relaxation following washout of KCl was reduced in A‐CRF rats vs. controls in the thoracic aorta (P < 0.01), abdominal aorta (P < 0.05), and common carotid artery (P < 0.05), but not in the common femoral artery. Relaxation rates of thoracic aortas increased (P < 0.01), but were not normalized, in response to washout of KCl with Ca2+‐free buffer. Microarray and qRT‐PCR analyses of genes involved in excitation–contraction coupling identified 10 genes, which showed significantly altered expression in A‐CRF thoracic aortas. At the protein level, the α2 subunit of the Na,K‐ATPase (P < 0.001) and SERCA2 (P < 0.05) was significantly downregulated, whereas stromal interaction molecule 1 and calsequestrin‐1 and calsequestrin‐2 were significantly upregulated (P < 0.05). Conclusions Rats with A‐CRF show a marked alteration in relaxation of larger conduit arteries localized proximal to the common femoral artery. This abnormality may be caused by reduced cytosolic Ca2+ clearance in vascular smooth muscle cells secondary to dysregulation of proteins crucially involved in this process.
    June 19, 2016   doi: 10.1111/apha.12724   open full text
  • Morphometry of skeletal muscle capillaries: the relationship between capillary ultrastructure and ageing in humans.
    M. Bigler, D. Koutsantonis, A. Odriozola, S. Halm, S. A. Tschanz, A. Zakrzewicz, A. Weichert, O. Baum.
    Acta Physiologica. June 16, 2016
    Aim To determine whether the ultrastructure of the capillary system in human skeletal muscle changes during advancing senescence, we evaluated the compartmental and subcompartmental organization of capillaries from vastus lateralis muscle (VL) biopsies of 41 non‐diseased persons aged 23–75 years. Methods From each VL biopsy, 38–40 randomly selected capillaries were assessed by transmission electron microscopy and subsequent morphometry with a newly established tablet‐based image analysis technique. Results Quantification of the compartmental organization revealed most indicators of the capillary ultrastructure to be only non‐significantly altered (P > 0.05) over age. However, the peri‐capillary basement membrane (BM) was thicker in the older participants than in the younger ones (P ≤ 0.05). Regression analysis revealed a bipartite relationship between the two parameters: a homogenous slight increase in BM thickness up to the age of approximately 50 years was followed by a second phase with more scattered BM thickness values. In 44.5% of the capillary profiles, projections/filopodia of the pericytes (PCs) traversed the BM and invaded endothelial cells (ECs) visible as PC pegs in pale cytoplasm holes (EC sockets). Strikingly, PC pegs were often in proximity to the EC nucleus. In PC profiles, sockets were likewise detected in 14.2% of the capillaries. Within these PC sockets, cellular profiles were frequently seen, which could be assigned to EC filopodia, internal PC curling or PC–PC interactions. Quantification of the occurrence of peg–socket junctions revealed the proportions of empty EC sockets and empty PC sockets to increase (P ≤ 0.05) during ageing. Conclusion Our investigation demonstrates advancing senescence to be associated with increase in BM thickness and loss of EC and PC filopodia length in skeletal muscle capillaries.
    June 16, 2016   doi: 10.1111/apha.12709   open full text
  • Na+ dependence of K+‐induced natriuresis, kaliuresis and Na+/Cl− cotransporter dephosphorylation.
    I. S. Jensen, C. K. Larsen, J. Leipziger, M. V. Sørensen.
    Acta Physiologica. June 15, 2016
    Aim High dietary K+ intake is associated with protection against hypertension. In mammals, acute K+ intake induces natriuresis and kaliuresis, associated with a marked dephosphorylation of the renal Na+/Cl− cotransporter (NCC). It has been suggested that reduced activity of NCC increases the driving force for more distal tubular epithelial Na+ channel (ENaC)‐dependent K+ secretion. This study investigated the ENaC dependence of urinary K+ and Na+ excretion following acute K+ loading. Methods Mice were fed low (0.03%), control (0.2%) or high (2%) Na+ diets for 25 days to preserve or promote Na+ loss and thus ENaC activity. Once a week, the mice received either K+‐containing gavage or a control gavage. Following the gavage treatment, the mice were placed in metabolic cages and urine was collected in real time. ENaC dependence of kaliuresis was assessed by benzamil injections prior to gavage. Results We confirmed that dietary Na+ content is inversely related to plasma aldosterone, NCC phosphorylation and ENaC cleavage products. The novel findings were as follows: (i) acute K+ feeding caused NCC dephosphorylation in all dietary groups; (ii) under all dietary conditions, K+ loading induced natriuresis; (iii) high Na+ diet markedly reduced the K+ excretion following K+ gavage; (iv) benzamil injection prior to K+ loading increased natriuresis, decreased kaliuresis and eliminated the differences between the dietary groups. Conclusion These data indicate that acute K+‐induced kaliuresis is ENaC dependent. Maximal K+ excretion rates are attenuated when ENaC is physiologically down‐regulated or pharmacologically blocked. NCC is dephosphorylated following acute K+ loading under all dietary Na+ regimens. This leads to natriuresis, even in severely Na+‐restricted animals.
    June 15, 2016   doi: 10.1111/apha.12707   open full text
  • Coupling of myocardial stress resistance and signalling to voluntary activity and inactivity.
    B. P. Budiono, L. E. See Hoe, A. R. Brunt, J. N. Peart, J. P. Headrick, L. J. Haseler.
    Acta Physiologica. June 15, 2016
    Aims We examined coupling of myocardial ischaemic tolerance to physical activity and inactivity, and whether this involves modulation of survival (AKT, AMPK, ERK1/2, HSP27, EGFR) and injury (GSK3β) proteins implicated in ischaemic preconditioning and calorie restriction. Methods Proteomic modifications were assessed in ventricular myocardium, and tolerance to 25‐min ischaemia in ex vivo perfused hearts from C57Bl/6 mice subjected to 14‐day voluntary activity in running‐naïve animals (Active); 7 days of subsequent inactivity (Inactive); brief (day 3) restoration of running (Re‐Active); or time‐matched inactivity. Results Active mice increased running speed and distance by 75–150% over 14 days (to ~40 m min−1 and 10 km day−1), with Active hearts resistant to post‐ischaemic dysfunction (40–50% improvements in ventricular pressure development, diastolic pressure and dP/dt). Cardioprotection was accompanied by ~twofold elevations in AKT, AMPK, HSP27 and GSK3β phosphorylation and EGFR expression. Ischaemic tolerance was reversed in Inactive hearts, paralleling reduced EGFR expression and GSK3β and ERK1/2 phosphorylation (AKT, AMPK, HSP27 phosphorylation unaltered). Running characteristics, ischaemic tolerance, EGFR expression and GSK3β phosphorylation returned to Active levels within 1–3 days of restored activity (without changes in AKT, AMPK or HSP27 phosphorylation). Transcriptional responses included activity‐dependent Anp induction vs. Hmox1 and Sirt3 suppression, and inactivity‐dependent Adora2b induction. Conclusions Data confirm the sensitive coupling of ischaemic tolerance to activity: voluntary running induces cardioprotection that dissipates within 1 week of inactivity yet recovers rapidly upon subsequent activity. While exercise in naïve animals induces a molecular profile characteristic of preconditioning/calorie restriction, only GSK3β and EGFR modulation consistently parallel activity‐ and inactivity‐dependent ischaemic tolerance.
    June 15, 2016   doi: 10.1111/apha.12710   open full text
  • Elk‐1‐mediated 15‐lipoxygenase expression is required for hypoxia‐induced pulmonary vascular adventitial fibroblast dynamics.
    Y. Li, L. Zhang, X. Wang, M. Chen, Y. Liu, Y. Xing, X. Wang, S. Gao, D. Zhu.
    Acta Physiologica. June 03, 2016
    Aim 15‐Lipoxygenase (15‐LO) is an important factor in the pathogenesis of pulmonary artery hypertension (PAH). However, the role of 15‐LO in the adventitia of the pulmonary arterial wall is unclear. The aim of this study was to explore the role of 15‐LO in the modulation of pulmonary adventitial fibroblast (PAF) dynamics. Methods Rats were exposed to normoxic or hypoxic (fraction of inspired O2 = 0.12) treatments for 7 days. PAF proliferation and cell cycle alterations were measured by MTT assay, cell immunofluorescence, flow cytometry and Western blot analysis. The 15‐LO promoter was analysed by luciferase reporter and ChIP assays. Results Our results showed that hypoxia induced 15‐LO expression in PAFs both in vivo and in vitro. In addition, hypoxia stimulated JNK phosphorylation in PAFs. Blocking 15‐LO or JNK suppressed 15‐LO‐induced PAF proliferation and cell cycle alterations. The inhibition of p27kipl by gene silencing attenuated 15‐LO‐induced PAF proliferation and cell cycle alterations. Furthermore, JNK inhibition or Elk‐1 knockdown suppressed hypoxia‐induced 15‐LO expression in PAFs. Luciferase reporter and ChIP assays revealed that the 15‐LO promoter contains Elk‐1‐binding sites and also that Elk‐1 increased the hypoxia‐induced activity of the 15‐LO promoter. Conclusion These results suggest that hypoxia promotes changes in the cellular dynamics of PAFs by inducing 15‐LO expression, which leads to vascular adventitial remodelling. The modulation of p27kipl expression by 15‐LO enhances PAF proliferation and cell cycle alterations. Furthermore, the JNK‐dependent increase in Elk‐1 signalling is required for hypoxia‐induced 15‐LO expression in PAFs.
    June 03, 2016   doi: 10.1111/apha.12711   open full text
  • Reduction in central venous pressure enhances erythropoietin synthesis: role of volume‐regulating hormones.
    D. Montero, S. Rauber, J. P. Goetze, C. Lundby.
    Acta Physiologica. June 01, 2016
    Aims Erythropoiesis is a tightly controlled biological event, but its regulation under non‐hypoxic conditions, however, remains unresolved. We examined whether acute changes in central venous blood pressure (CVP) elicited by whole‐body tilting affect erythropoietin (EPO) concentration according to volume‐regulating hormones. Methods Plasma EPO, angiotensin II (ANGII), aldosterone, pro‐atrial natriuretic peptide (proANP) and copeptin concentrations were measured at supine rest and up to 3 h during 30° head‐up (HUT) and head‐down tilt (HDT) in ten healthy male volunteers. Plasma albumin concentration was used to correct for changes in plasma volume and CVP was estimated through the internal jugular vein (IJV) aspect ratio with ultrasonography. Results From supine rest, the IJV aspect ratio was decreased and increased throughout HUT and HDT respectively. Plasma EPO concentration increased during HUT (13%; P = 0.001, P for linear component = 0.017), independent of changes in albumin concentration. Moreover, ANGII and copeptin concentrations increased during HUT, while proANP decreased. The increase in EPO concentration during HUT disappeared when adjusted for changes in copeptin. During HDT, EPO, ANGII and copeptin concentrations remained unaffected while proANP increased. In regression analyses, EPO was positively associated with copeptin (β = 0.55; 95% CI = 0.18, 0.93; P = 0.004) irrespective of changes in other hormones and albumin concentration. Conclusion Reduction in CVP prompts an increase in plasma EPO concentration independent of hemoconcentration and hence suggests CVP per se as an acute regulator of EPO synthesis. This effect may be explained by changes in volume‐regulating hormones.
    June 01, 2016   doi: 10.1111/apha.12708   open full text
  • Is Plasminogen Activator Inihibitor‐1 a Physiological Bottleneck Bridging Major Depressive Disorder (MDD) and Cardiovascular Disease (CVD)?
    Calan Savoy, Ryan J. Van Lieshout, Meir Steiner.
    Acta Physiologica. June 01, 2016
    Major Depressive Disorder (MDD) is estimated to affect one in twenty people worldwide. MDD is highly co‐morbid with cardiovascular disease (CVD), itself one of the single largest causes of mortality worldwide. A number of pathological changes observed in MDD are believed to contribute to the development of cardiovascular disease, although no single mechanism has been identified. There are also no biological markers capable of predicting the future risk of developing heart disease in depressed individuals. Plasminogen Activator Inhibitor 1(PAI‐1) is a pro‐thrombotic plasma protein secreted by endothelial tissue and has long been implicated in CVD. An expanding body of literature has recently implicated it in the pathogenesis of Major Depressive Disorder as well. In this paper we review candidate pathways implicating MDD in CVD and consider how PAI‐1 might act as a mediator by which MDD induces CVD development; chiefly through sleep disruption, adiposity, Brain Derived Neurotrophic Factor (BDNF) metabolism, systemic inflammation, and Hypothalamic‐Pituitary‐Adrenal (HPA) axis dysregulation. As both MDD and CVD are more prevalent in women than men, and both incidence of either condition is dramatically increased during reproductive milestones, we also explore hormonal and sex specific associations between MDD, PAI‐1 and CVD. Of special interest is the role PAI‐1 plays in perinatal depression and in cardiovascular complications of pregnancy. Finally, we propose a theoretical model whereby PAI‐1 might serve as a useful biomarker for CVD risk in those with depression, and as a potential target for future treatments. This article is protected by copyright. All rights reserved.
    June 01, 2016   doi: 10.1111/apha.12726   open full text
  • Uraemia: an unrecognised driver of central neurohumoral dysfunction in chronic kidney disease?
    Conor F. Underwood, Cara M. Hildreth, Benjamin F. Wyse, Rochelle Boyd, Ann K. Goodchild, Jacqueline K. Phillips.
    Acta Physiologica. June 01, 2016
    Chronic kidney disease (CKD) carries a large cardiovascular burden in part due to hypertension and neurohumoral dysfunction – manifesting as sympathetic overactivity, baroreflex dysfunction and chronically elevated circulating vasopressin. Alterations within the central nervous system (CNS) are necessary for the expression of neurohumoral dysfunction in CKD however the underlying mechanisms are poorly defined. Uraemic toxins are a diverse group of compounds that accumulate as a direct result of renal disease and drive dysfunction in multiple organs, including the brain. Intensive haemodialysis improves both sympathetic overactivity and cardiac baroreflex sensitivity in renal failure patients, indicating that uraemic toxins participate in the maintenance of autonomic dysfunction in CKD. In rodents exposed to uraemia, immediate early gene expression analysis suggests upregulated activity of not only presympathetic but also vasopressin‐secretory nuclei. We outline several potential mechanisms by which uraemia might drive neurohumoral dysfunction in CKD. These include superoxide‐dependent effects on neural activity, depletion of nitric oxide and induction of low‐grade systemic inflammation. Recent evidence has highlighted superoxide production as an intermediate for the depolarising effect of some uraemic toxins on neuronal cells. We provide preliminary data indicating augmented superoxide production within the hypothalamic paraventricular nucleus in the Lewis Polycystic Kidney rat, which might be important for mediating the neurohumoral dysfunction exhibited in this CKD model. We speculate that the uraemic state might serve to sensitise the central actions of other sympathoexcitatory factors, including renal afferent nerve inputs to the CNS and angiotensin II, by way of recruiting convergent superoxide‐dependent and pro‐inflammatory pathways. This article is protected by copyright. All rights reserved.
    June 01, 2016   doi: 10.1111/apha.12727   open full text
  • Effects of shear stress on endothelial cells: go with the flow.
    Dmitry A. Chistiakov, Alexander N. Orekhov, Yuri V. Bobryshev.
    Acta Physiologica. June 01, 2016
    Hemodynamic forces influence functional properties of vascular endothelium. Endothelial cells have a variety of receptors, which sense flow and transmit mechanical signals through mechanosensitive signaling pathways to recipient molecules, that lead to phenotypic and functional changes. Arterial architecture varies greatly exhibiting bifurcations, branch points, and curved regions, which are exposed to various flow patterns. Clinical studies showed that atherosclerotic plaques develop preferentially at arterial branches and curvatures, i.e. in the regions exposed to disturbed flow and shear stress. In the atheroprone regions, the endothelium has a proinflammatory phenotype associated with low nitric oxide production, reduced barrier function, and increased proadhesive, procoagulant, and proproliferative properties. Atheroresistant regions are exposed to laminar flow and high shear stress that induce prosurvival antioxidant signals and maintain the quiescent phenotype in endothelial cells. Indeed, various flow patterns contribute to phenotypic and functional heterogeneity of arterial endothelium whose response to proatherogenic stimuli is differentiated. This may explain the preferential development of endothelial dysfunction in arterial sites with disturbed flow. This article is protected by copyright. All rights reserved.
    June 01, 2016   doi: 10.1111/apha.12725   open full text
  • TRPV4 channels in the human urogenital tract play a role in cell junction formation and epithelial barrier.
    D. A. W. Janssen, C. J. F. Jansen, T. G. Hafmans, G. W. Verhaegh, J. G. Hoenderop, J. P. F. A. Heesakkers, J. A. Schalken.
    Acta Physiologica. May 25, 2016
    Aim The molecular interactions between transient receptor potential vanilloid subtype 4 channels (TRPV4) and cell junction formation were investigated in the human and mouse urogenital tract. Materials and Methods A qualitative study was performed to investigate TRPV4 channels, adherence junctions (AJs) and tight junctions (TJs) in kidney, ureter and bladder tissues from humans and wild‐type and transgenic TRPV4 knockout (−/−) mice with immunohistochemistry, Western blotting, immunoprecipitation and reverse trasnscription‐PCR. Cell junction formation in the wild‐type and TRPV4 knockout (−/−) mouse was evaluated with immunohistochemistry and transmission electron microscope (TEM) techniques. Results TRPV4 channels are predominantly located in membranes of epithelial cells of the bladder, ureter and the collecting ducts of the kidney. There is a molecular interaction between the TRPV4 channel and the AJ. TEM evaluation showed that AJ formation is disrupted in the TRPV4 −/− mouse resulting in deficient intercellular connections and integrity of the epithelium. Conclusions TRPV4 is believed to be a mechanoreceptor in the bladder. This study demonstrates that TRPV4 is also involved in intercellular connectivity and structural integrity of the epithelium.
    May 25, 2016   doi: 10.1111/apha.12701   open full text
  • Reversing dobutamine‐induced tachycardia using ivabradine increases stroke volume with neutral effect on cardiac energetics in left ventricular post‐ischaemia dysfunction.
    J. P. Bakkehaug, T. Næsheim, E. Torgersen Engstad, A. B. Kildal, T. Myrmel, O.‐J. How.
    Acta Physiologica. May 24, 2016
    Aim Compensatory tachycardia can potentially be deleterious in acute heart failure. In this study, we tested a therapeutic strategy of combined inotropic support (dobutamine) and selective heart rate (HR) reduction through administration of ivabradine. Methods In an open‐chest pig model (n = 12) with left ventricular (LV) post‐ischaemia dysfunction, cardiac function was assessed by LV pressure catheter and sonometric crystals. Coronary flow and blood samples from the coronary sinus were used to measure myocardial oxygen consumption (MVO2). LV energetics was assessed by comparing MVO2 with cardiac work at a wide range of workloads. Results In the post‐ischaemia heart, dobutamine (5 μg kg−1 min−1) increased cardiac output (CO) by increasing HR from 102 ± 21 to 131 ± 16 bpm (beats per min; P < 0.05). Adding ivabradine (0.5 mg kg−1) slowed HR back to 100 ± 9 bpm and increased stroke volume from 30 ± 5 to 36 ± 5 mL (P < 0.05) by prolonging diastolic filling time and increasing end‐diastolic dimensions. Adding ivabradine had no adverse effects on CO, mean arterial pressure and cardiac efficiency. Similar findings on efficiency and LV function were also seen using an ex vivo working mouse heart protocol. Conclusions A combined infusion of dobutamine and ivabradine had a neutral effect on post‐ischaemia LV efficiency and increased left ventricular output without an increase in HR.
    May 24, 2016   doi: 10.1111/apha.12704   open full text
  • Normotension, hypertension and body fluid regulation: Brain and kidney.
    Peter Bie, Roger G. Evans.
    Acta Physiologica. May 23, 2016
    The fraction of hypertensive patients with essential hypertension (EH) is decreasing as the knowledge of mechanisms of secondary hypertension increase, but in most new cases of hypertension the pathophysiology remains unknown. Separate neurocentric and renocentric concepts of etiology have prevailed without much interaction. In this regard, several questions regarding the relationships between body fluid and blood pressure regulation are pertinent. Are all forms of EH associated with sympathetic overdrive or a shift in the pressure natriuresis curve? Is body fluid homeostasis normally driven by the influence of arterial blood pressure directly on the kidney? Does plasma renin activity, driven by renal nerve activity and renal arterial pressure, provide a key to stratification of EH? Our review indicates that (i) a narrow definition of EH is useful, (ii) in EH, indices of cardiovascular sympathetic activity are elevated in about 50% of cases, (iii) in EH as in normal conditions, mediators other than arterial blood pressure are the major determinants of renal sodium excretion, (iv) chronic hypertension is always associated with a shift in the pressure natriuresis curve, but this may be an epiphenomenon, (v) plasma renin levels are useful in the analysis of EH only after metabolic standardization and then determination of the renin function line (plasma renin as a function of sodium intake), and (vi) angiotensin II mediated hypertension is not a model of EH. Recent studies of baroreceptors and renal nerves as well as sodium intake and renin secretion help bridge the gap between the neurocentric and renocentric concepts. This article is protected by copyright. All rights reserved.
    May 23, 2016   doi: 10.1111/apha.12718   open full text
  • Fibroblast growth factor 21 (FGF21) therapy attenuates left ventricular dysfunction and metabolic disturbance by improving FGF21 sensitivity, cardiac mitochondrial redox homoeostasis and structural changes in pre‐diabetic rats.
    P. Tanajak, P. Sa‐nguanmoo, X. Wang, G. Liang, X. Li, C. Jiang, S. C. Chattipakorn, N. Chattipakorn.
    Acta Physiologica. May 20, 2016
    Aims Fibroblast growth factor 21 (FGF21) acts as a metabolic regulator and exerts cardioprotective effects. However, the effects of long‐term FGF21 administration on the heart under the FGF21‐resistant condition in obese, insulin‐resistant rats have not been investigated. We hypothesized that long‐term FGF21 administration reduces FGF21 resistance and insulin resistance and attenuates cardiac dysfunction in obese, insulin‐resistant rats. Methods Eighteen rats were fed on either a normal diet (n = 6) or a high‐fat diet (HFD; n = 12) for 12 weeks. Then, rats in the HFD group were divided into two subgroups (n = 6 per subgroup) and received either the vehicle (HFV) or recombinant human FGF21 (rhFGF21, 0.1 mg kg−1 day−1; HFF) injected intraperitoneally for 28 days. The metabolic parameters, inflammation, malondialdehyde (MDA), heart rate variability (HRV), left ventricular (LV) function, cardiac mitochondrial redox homoeostasis, cardiac mitochondrial fatty acid β‐oxidation (FAO) and anti‐apoptotic signalling pathways were determined. Results HFV rats had increased dyslipidaemia, insulin resistance, plasma FGF21 levels, TNF‐α, adiponectin and MDA, depressed HRV, and impaired LV and mitochondrial function. HFV rats also had decreased cardiac Bcl‐2, cardiac PGC‐1α and CPT‐1 protein expression. However, FGF21 restored metabolic parameters, decreased TNF‐α and MDA, increased serum adiponectin, and improved HRV, cardiac mitochondrial and LV function in HFF rats. Moreover, HFF rats had increased cardiac Bcl‐2, cardiac PGC‐1α and CPT‐1 protein expression. Conclusion Long‐term FGF21 therapy attenuates FGF21 resistance and insulin resistance and exerts cardioprotection by improving cardiometabolic regulation via activating anti‐apoptotic and cardiac mitochondrial FAO signalling pathways in obese, insulin‐resistant rats.
    May 20, 2016   doi: 10.1111/apha.12698   open full text
  • PAFAH1B1 and the lncRNA NONHSAT073641 maintain an angiogenic phenotype in human endothelial cells.
    I. Josipovic, C. Fork, J. Preussner, K‐K. Prior, D. Iloska, A. E. Vasconez, S. Labocha, C. Angioni, D. Thomas, N. Ferreirós, M. Looso, S. S. Pullamsetti, G. Geisslinger, D. Steinhilber, R. P. Brandes, M. S. Leisegang.
    Acta Physiologica. May 20, 2016
    Aim Platelet‐activating factor acetyl hydrolase 1B1 (PAFAH1B1, also known as Lis1) is a protein essentially involved in neurogenesis and mostly studied in the nervous system. As we observed a significant expression of PAFAH1B1 in the vascular system, we hypothesized that PAFAH1B1 is important during angiogenesis of endothelial cells as well as in human vascular diseases. Method The functional relevance of the protein in endothelial cell angiogenic function, its downstream targets and the influence of NONHSAT073641, a long non‐coding RNA (lncRNA) with 92% similarity to PAFAH1B1, were studied by knockdown and overexpression in human umbilical vein endothelial cells (HUVEC). Results Knockdown of PAFAH1B1 led to impaired tube formation of HUVEC and decreased sprouting in the spheroid assay. Accordingly, the overexpression of PAFAH1B1 increased tube number, sprout length and sprout number. LncRNA NONHSAT073641 behaved similarly. Microarray analysis after PAFAH1B1 knockdown and its overexpression indicated that the protein maintains Matrix Gla Protein (MGP) expression. Chromatin immunoprecipitation experiments revealed that PAFAH1B1 is required for active histone marks and proper binding of RNA Polymerase II to the transcriptional start site of MGP. MGP itself was required for endothelial angiogenic capacity and knockdown of both, PAFAH1B1 and MGP, reduced migration. In vascular samples of patients with chronic thromboembolic pulmonary hypertension (CTEPH), PAFAH1B1 and MGP were upregulated. The function of PAFAH1B1 required the presence of the intact protein as overexpression of NONHSAT073641, which was highly upregulated during CTEPH, did not affect PAFAH1B1 target genes. Conclusion PAFAH1B1 and NONHSAT073641 are important for endothelial angiogenic function.
    May 20, 2016   doi: 10.1111/apha.12700   open full text
  • Increased microvascular permeability in mice lacking Epac1 (Rapgef3).
    R. K. Kopperud, C. Brekke Rygh, T. V. Karlsen, C. Krakstad, R. Kleppe, E. A. Hoivik, M. Bakke, O. Tenstad, F. Selheim, Å. Lidén, L. Madsen, T. Pavlin, T. Taxt, K. Kristiansen, F.‐R. E. Curry, R. K. Reed, S. O. Døskeland.
    Acta Physiologica. May 17, 2016
    Aim Maintenance of the blood and extracellular volume requires tight control of endothelial macromolecule permeability, which is regulated by cAMP signalling. This study probes the role of the cAMP mediators rap guanine nucleotide exchange factor 3 and 4 (Epac1 and Epac2) for in vivo control of microvascular macromolecule permeability under basal conditions. Methods Epac1−/− and Epac2−/− C57BL/6J mice were produced and compared with wild‐type mice for transvascular flux of radio‐labelled albumin in skin, adipose tissue, intestine, heart and skeletal muscle. The transvascular leakage was also studied by dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) using the MRI contrast agent Gadomer‐17 as probe. Results Epac1−/− mice had constitutively increased transvascular macromolecule transport, indicating Epac1‐dependent restriction of baseline permeability. In addition, Epac1−/− mice showed little or no enhancement of vascular permeability in response to atrial natriuretic peptide (ANP), whether probed with labelled albumin or Gadomer‐17. Epac2−/− and wild‐type mice had similar basal and ANP‐stimulated clearances. Ultrastructure analysis revealed that Epac1−/− microvascular interendothelial junctions had constitutively less junctional complex. Conclusion Epac1 exerts a tonic inhibition of in vivo basal microvascular permeability. The loss of this tonic action increases baseline permeability, presumably by reducing the interendothelial permeability resistance. Part of the action of ANP to increase permeability in wild‐type microvessels may involve inhibition of the basal Epac1‐dependent activity.
    May 17, 2016   doi: 10.1111/apha.12697   open full text
  • Acute temperature effects on function of the chick embryonic heart.
    F. Vostarek, J. Svatunkova, D. Sedmera.
    Acta Physiologica. May 12, 2016
    Aim We analysed the effects of acute temperature change on the beating rate, conduction properties and calcium transients in the chick embryonic heart in vitro and in ovo. Methods The effects of temperature change (34, 37 and 40 °C) on calcium dynamics in isolated ED4 chick hearts in vitro were investigated by high‐speed calcium optical imaging. For comparison and validation of in vitro measurements, experiments were also performed in ovo using videomicroscopy. Artificial stimulation experiments were performed in vitro and in ovo to uncover conduction limits of heart segments. Results Decrease in temperature from 37 to 34 °C in vitro led to a 22% drop in heart rate and unchanged amplitude of Ca2+ transients, compared to a 25% heart rate decrease in ovo. Increase in temperature from 37 to 40 °C in vitro and in ovo led to 20 and 23% increases in heart rate, respectively, and a significant decrease in amplitude of Ca2+ transients (atrium −35%, ventricle −38%). We observed a wide spectrum of arrhythmias in vitro, of which the most common was atrioventricular (AV) block (57%). There was variability of AV block locations. Pacing experiments in vitro and in ovo suggested that the AV blocks were likely caused by relative tissue hypoxia and not by the tachycardia itself. Conclusion The pacemaker and AV canal are the most temperature‐sensitive segments of the embryonic heart. We suggest that the critical point for conduction is the connection of the ventricular trabecular network to the AV canal.
    May 12, 2016   doi: 10.1111/apha.12691   open full text
  • Intra‐cranial mechanisms for preserving brain blood flow in health and disease.
    Fiona D McBryde, Simon C Malpas, Julian FR Paton.
    Acta Physiologica. May 12, 2016
    The brain is an exceptionally energetically demanding organ with little metabolic reserve, and multiple systems operate to protect and preserve the brain blood supply. But how does the brain sense its own perfusion? In this review, we discuss how the brain may harness the cardiovascular system to counter threats to cerebral perfusion sensed via intracranial pressure (ICP), cerebral oxygenation and ischemia. Since the work of Cushing over 100 years ago, the existence of brain baroreceptors capable of eliciting increases in sympathetic outflow and blood pressure has been hypothesized. In the clinic, this response has generally been thought to occur only in extremis, to perfuse the severely ischemic brain as cerebral autoregulation fails. We review evidence that pressor responses may also occur with smaller, physiologically‐relevant increases in ICP. The incoming brain oxygen supply is closely monitored by the carotid chemoreceptors, however, hypoxia and other markers of ischemia are also sensed intrinsically by astrocytes or other support cells within brain tissue itself, and elicit reactive hyperaemia. Recent studies suggest that astrocytic oxygen signalling within the brainstem may directly affect sympathetic nerve activity and blood pressure. We speculate that local cerebral oxygen tension is a major determinant of the mean level of arterial pressure, and discuss recent evidence that this may be the case. We conclude that intrinsic intra‐ and extra‐cranial mechanisms sense and integrate information about hypoxia/ischemia and intracranial pressure, and play a major role in determining the long‐term level of sympathetic outflow and arterial pressure, in order to optimise cerebral perfusion. This article is protected by copyright. All rights reserved.
    May 12, 2016   doi: 10.1111/apha.12706   open full text
  • Heat shock transcription factor 1‐associated expression of slow myosin heavy chain in mouse soleus muscle in response to unloading with or without reloading.
    S. Yokoyama, Y. Ohno, T. Egawa, K. Yasuhara, A. Nakai, T. Sugiura, Y. Ohira, T. Yoshioka, M. Okita, T. Origuchi, K. Goto.
    Acta Physiologica. May 09, 2016
    Aim The effects of heat shock transcription factor 1 (HSF1) deficiency on the fibre type composition and the expression level of nuclear factor of activated T cells (NFAT) family members (NFATc1, NFATc2, NFATc3 and NFATc4), phosphorylated glycogen synthase kinase 3α (p‐GSK3α) and p‐GSK3β, microRNA‐208b (miR‐208b), miR‐499 and slow myosin heavy chain (MyHC) mRNAs (Myh7 and Myh7b) of antigravitational soleus muscle in response to unloading with or without reloading were investigated. Methods HSF1‐null and wild‐type mice were subjected to continuous 2‐week hindlimb suspension followed by 2‐ or 4‐week ambulation recovery. Results In wild‐type mice, the relative population of slow type I fibres, the expression level of NFATc2, p‐GSK3 (α and β), miR‐208b, miR‐499 and slow MyHC mRNAs (Myh7 and Myh7b) were all decreased with hindlimb suspension, but recovered after it. Significant interactions between train and time (the relative population of slow type I fibres; P = 0.01, the expression level of NFATc2; P = 0.001, p‐GSKβ; P = 0.009, miR‐208b; P = 0.002, miR‐499; P = 0.04) suggested that these responses were suppressed in HSF1‐null mice. Conclusion HSF1 may be a molecule in the regulation of the expression of slow MyHC as well as miR‐208b, miR‐499, NFATc2 and p‐GSK3 (α and β) in mouse soleus muscle.
    May 09, 2016   doi: 10.1111/apha.12692   open full text
  • Muscle immobilization activates mitophagy and disrupts mitochondrial dynamics in mice.
    C. Kang, D. Yeo, L. L. Ji.
    Acta Physiologica. April 30, 2016
    Aim Skeletal muscle atrophy following prolonged immobilization (IM) is a catabolic state characterized by increased proteolysis and functional deterioration. Previous research indicates that discord of mitochondrial homoeostasis plays a critical role in muscle atrophy. We hypothesized that muscle IM would activate the ubiquitin‐proteolysis, autophagy–lysosome (mitophagy) pathway, mitochondrial dynamics remodelling and apoptosis partially controlled by the FoxO signalling pathway. Methods Female FVB/N mice were randomly divided into five groups (n = 8 each): control (CON), IM with banding of one of the hindlimbs for 1, 2 and 3 weeks (1w‐, 2w‐ and 3w‐IM) and 2w‐IM followed by 1 week of remobilization (RM). Results Mitochondrial density and DNA copies in tibialis anterior (TA) muscle were reduced by approx. 80% (P < 0.05 for 2w‐IM; P < 0.01 for 3w‐IM), along with activation of FoxO3a, atrogin‐1 and MuRF1 following 2w‐ and 3w‐IM (P < 0.01). Protein markers of autophagy/mitophagy, such as beclin 1 (approx. 2.7‐fold; P < 0.01), LC3, ubiquitin‐binding adaptor (approx. 1.47‐fold; P < 0.01), Rheb (approx. 1.9‐fold; P < 0.05) and parkin (approx. 70%; P < 0.05), were all increased by IM and remained activated after RM, whereas BNIP3 and PINK1 levels were decreased by IM (P < 0.05), but elevated upon RM (P < 0.01). IM decreased Mfn2 expression (approx. 50%; P < 0.01) and increased Fis‐1 expression (approx. 2.4‐fold; P < 0.05). Muscle apoptosis indicator Bax/Bcl2 ratio was elevated at 2w‐ to 3w‐IM (approx. 3.7‐fold; P < 0.01), whereas caspase‐3 activity was five‐ to sixfold higher (P < 0.01) and remained threefold higher above CON (P < 0.05). Conclusion Our data indicate that IM‐induced mitochondrial deterioration is associated with altered protein expressions in the autophagic/mitophagic pathway, more fragmented mitochondrial network and activation of apoptosis partly under the influence of FoxO3 activation.
    April 30, 2016   doi: 10.1111/apha.12690   open full text
  • Lactobacillus reuteri increases mucus thickness and ameliorates dextran sulphate sodium‐induced colitis in mice.
    D. Ahl, H. Liu, O. Schreiber, S. Roos, M. Phillipson, L. Holm.
    Acta Physiologica. April 30, 2016
    Aim The aim of this study was to investigate whether two Lactobacillus reuteri strains (rat‐derived R2LC and human‐derived ATCC PTA 4659 (4659)) could protect mice against colitis, as well as delineate the mechanisms behind this protection. Methods Mice were given L. reuteri R2LC or 4659 by gavage once daily for 14 days, and colitis was induced by addition of 3% DSS (dextran sulphate sodium) to drinking water for the last 7 days of this period. The severity of disease was assessed through clinical observations, histological evaluation and ELISA measurements of myeloperoxidase (MPO) and pro‐inflammatory cytokines from colonic samples. Mucus thickness was measured in vivo with micropipettes, and tight junction protein expression was assessed using immunohistochemistry. Results Colitis severity was significantly reduced by L. reuteri R2LC or 4659 when evaluated both clinically and histologically. The inflammation markers MPO, IL‐1β, IL‐6 and mKC (mouse keratinocyte chemoattractant) were increased by DSS and significantly reduced by the L. reuteri strains. The firmly adherent mucus thickness was reduced by DSS, but significantly increased by L. reuteri in both control and DSS‐treated mice. Expression of the tight junction proteins occludin and ZO‐1 was significantly increased in the bottom of the colonic crypts by L. reuteri R2LC. Conclusion These results demonstrate that each of the two different L. reuteri strains, one human‐derived and one‐rat‐derived, protects against colitis in mice. Mechanisms behind this protection could at least partly be explained by the increased mucus thickness as well as a tightened epithelium in the stem cell area of the crypts.
    April 30, 2016   doi: 10.1111/apha.12695   open full text
  • Translational machinery of mitochondrial mRNA is promoted by physical activity in Western diet‐induced obese mice.
    D. E. Lee, J. L. Brown, M. E. Rosa, L. A. Brown, R. A. Perry, T. A. Washington, N. P. Greene.
    Acta Physiologica. April 25, 2016
    Aim Mitochondria‐encoded proteins are necessary for oxidative phosphorylation; however, no report has examined how physical activity (PA) and obesity affect mitochondrial mRNA translation machinery. Our purpose was to determine whether Western diet (WD)‐induced obesity and voluntary wheel running (VWR) impact mitochondrial mRNA translation machinery and whether expression of this machinery is dictated by oxidative phenotype. Methods Obesity was induced with 8‐wk WD feeding, and in the final 4 wks, half of mice were allowed VWR. Mitochondrial mRNA translation machinery including initiation factors (mtIF2/3), elongation factor Tu (TUFM) and translational activator (TACO1), and mitochondria‐encoded proteins (CytB and ND4) was assessed by immunoblotting. The relation of mitochondrial mRNA translation to muscle oxidative phenotype was assessed using PGC‐1α transgenic overexpression (MCK‐PGC‐1α vs. wild‐type mice) and comparing across muscle groups in wild‐type mice. Results mtIF3 and TACO1 proteins were ~45% greater in VWR than sedentary (SED), and TACO1 and mtIF2 proteins were ~60% and 125% greater in WD than normal chow (NC). TUFM protein was ~50% lower in WD‐SED than NC‐SED, but ~50% greater in WD‐VWR compared to NC‐SED. CytB and ND4 were ~40% greater in VWR and ND4 was twofold greater with WD. TUFM, TACO1, ND4 and CytB were greater in MCK‐PGC‐1α compared to wild‐type, and mtIF2/3 contents were not different. In oxidative muscle (soleus), mitochondrial translation machinery was elevated compared to mixed (gastrocnemius) or glycolytic (extensor digitorum longus) muscles. Conclusion These data suggest a novel mechanism promoting mitochondrial function by translation of mitochondrial protein following PA. This may act to promote muscle health by PA in obesity.
    April 25, 2016   doi: 10.1111/apha.12687   open full text
  • Characterization of cold‐induced remodelling reveals depot‐specific differences across and within brown and white adipose tissues in mice.
    R. Jia, X.‐Q. Luo, G. Wang, C.‐X. Lin, H. Qiao, N. Wang, T. Yao, J. L. Barclay, J. P. Whitehead, X. Luo, J.‐Q. Yan.
    Acta Physiologica. April 24, 2016
    Aim Brown and beige adipose tissues dissipate energy in the form of heat via mitochondrial uncoupling protein 1, defending against hypothermia and potentially obesity. The latter has prompted renewed interest in understanding the processes involved in browning to realize the potential therapeutic benefits. To characterize the temporal profile of cold‐induced changes and browning of brown and white adipose tissues in mice. Methods Male C57BL/6J mice were singly housed in conventional cages under cold exposure (4 °C) for 1, 2, 3, 4, 5 and 7 days. Food intake and body weight were measured daily. Interscapular brown adipose tissue (iBAT), inguinal subcutaneous (sWAT) and epididymal white adipose tissue (eWAT) were harvested for histological, immunohistochemical, gene and protein expression analysis. Results Upon cold exposure, food intake increased, whilst body weight and adipocyte size were found to be transiently reduced. iBAT mass was found to be increased, whilst sWAT and eWAT were found to be transiently decreased. A combination of morphological, genetic (Ucp‐1, Pgc‐1α and Elov13) and biochemical (UCP‐1, PPARγ and aP2) analyses demonstrated the depot‐specific remodelling in response to cold exposure. Conclusion Our results demonstrate the differential responses to cold‐induced changes across discrete BAT and WAT depots and support the notion that the effects of short‐term cold exposure are achieved by expansion, activation and increasing thermogenic capacity of iBAT, as well as browning of sWAT and, to a lesser extent, eWAT.
    April 24, 2016   doi: 10.1111/apha.12688   open full text
  • Crosstalk between cardiomyocyte‐rich perivascular tissue and coronary arteries is reduced in the Zucker Diabetic Fatty rat model of type 2 diabetes mellitus.
    L. Bonde, P. Shokouh, P. B. Jeppesen, E. Boedtkjer.
    Acta Physiologica. April 21, 2016
    Aim We tested the hypothesis that crosstalk between cardiomyocyte‐rich perivascular tissue (PVT) and coronary arteries is altered in diabetes. Methods We studied the vasoactive effects of PVT in arteries from the Zucker Diabetic Fatty (ZDF) rat model of type 2 diabetes, streptozotocin (STZ)‐treated Wistar rats with type 1 diabetes, and corresponding – heterozygous Zucker Lean (ZL) or vehicle‐treated Wistar – control rats. Vasocontractile and vasorelaxant functions of coronary septal arteries with and without PVT were investigated using wire myography. Results After careful removal of PVT, vasoconstriction in response to serotonin and thromboxane analogue U46619 was similar in arteries from ZDF and ZL rats, whereas depolarization‐induced vasoconstriction – caused by elevating extracellular [K+] – was reduced in arteries from ZDF compared to ZL rats. PVT inhibited serotonin‐, U46619‐ and depolarization‐induced vasoconstriction in arteries from ZL rats, but this anticontractile influence of PVT was attenuated in arteries from ZDF rats. Methacholine‐induced vasorelaxation was smaller in arteries from ZDF than ZL rats both with and without PVT, and the antirelaxant influence of PVT was comparable between arteries from ZDF and ZL rats. We observed no differences in vasoconstriction, vasorelaxation or PVT‐dependent vasoactive effects between arteries from STZ‐ and vehicle‐treated Wistar rats. Conclusion Anticontractile influences of PVT are attenuated in coronary arteries from ZDF rats but unaffected in arteries from STZ‐treated rats. Signs of endothelial dysfunction are evident in coronary septal arteries – with and without PVT – from ZDF rats but not STZ‐treated rats. We propose that altered signalling between cardiomyocyte‐rich PVT and coronary arteries can contribute to cardiovascular complications in type 2 diabetes mellitus.
    April 21, 2016   doi: 10.1111/apha.12685   open full text
  • Day‐restricted feeding during pregnancy and lactation programs glucose intolerance and impaired insulin secretion in male rat offspring.
    J. Almeida Faria, T. M. F. Araújo, R. I. Mancuso, J. Meulman, D. Silva Ferreira, T. M. Batista, J. F. Vettorazzi, P. M. R. Silva, S. C. Rodrigues, A. Kinote, E. M. Carneiro, S. Bordin, G. F. Anhê.
    Acta Physiologica. April 21, 2016
    Aim The maternal environment during pregnancy and lactation plays a determining role in programming energy metabolism in offspring. Among a myriad of maternal factors, disruptions in the light/dark cycle during pregnancy can program glucose intolerance in offspring. Out‐of‐phase feeding has recently been reported to influence metabolism in adult humans and rodents; however, it is not known whether this environmental factor impacts offspring metabolism when applied during pregnancy and lactation. This study aims to determine whether maternal day‐restricted feeding (DF) influences energy metabolism in offspring. Methods Pregnant and lactating Wistar rats were subjected to ad libitum (AL) or DF during pregnancy and lactation. The offspring born to the AL and DF dams were intra‐ and interfostered, which resulted in 4 group types. Results The male offspring born to and breastfed by the DF dams (DF/DF off) were glucose intolerant, but without parallel insulin resistance as adults. Experiments with isolated pancreatic islets demonstrated that the male DF/DF off rats had reduced insulin secretion with no parallel disruption in calcium handling. However, this reduction in insulin secretion was accompanied by increased miRNA‐29a and miRNA34a expression and decreased syntaxin 1a protein levels. Conclusion We conclude that out‐of‐phase feeding during pregnancy and lactation can lead to glucose intolerance in male offspring, which is caused by a disruption in insulin secretion capacity. This metabolic programming is possibly caused by mechanisms dependent on miRNA modulation of syntaxin 1a.
    April 21, 2016   doi: 10.1111/apha.12684   open full text
  • Cardiotrophin‐1 decreases intestinal sugar uptake in mice and in Caco‐2 cells.
    M. López‐Yoldi, R. Castilla‐Madrigal, M. P. Lostao, A. Barber, J. Prieto, J. A. Martínez, M. Bustos, M. J. Moreno‐Aliaga.
    Acta Physiologica. April 07, 2016
    Aim Cardiotrophin‐1 (CT‐1) is a member of the IL‐6 family of cytokines with a key role in glucose and lipid metabolism. In the current investigation, we examined the in vivo and in vitro effects of CT‐1 treatment on intestinal sugar absorption in different experimental models. Methods rCT‐1 effects on α‐Methyl‐D‐glucoside uptake were assessed in everted intestinal rings from wild‐type and CT‐1−/− mice and in Caco‐2 cells. rCT‐1 actions on SGLT‐1 expression in brush border membrane vesicles and the identification of the potential signalling pathways involved were determined by Western blot. Results In vivo administration (0.2 mg kg−1) of rCT‐1 caused a significant decrease on α‐Methyl‐D‐glucoside uptake in everted intestinal rings from wild‐type and CT‐1−/− mice after short‐term and long‐term treatments. Similarly, in vitro treatment (1–50 ng mL−1) with rCT‐1 reduced α‐Methyl‐D‐glucoside uptake in everted intestinal rings. In Caco‐2 cells, rCT‐1 treatment (20 ng mL−1, 1 and 24 h) lowered apical uptake of α‐Methyl‐D‐glucoside in parallel with a decrease on SGLT‐1 protein expression. rCT‐1 promoted the phosphorylation of STAT‐3 after 5 and 15 min treatment, but inhibited the activation by phosphorylation of AMPK after 30 and 60 min. Interestingly, pre‐treatment with the JAK/STAT inhibitor (AG490) and with the AMPK activator (AICAR) reversed the inhibitory effects of rCT‐1 on α‐Methyl‐D‐glucoside uptake. AICAR also prevented the inhibition of SGLT‐1 observed in rCT‐1‐treated cells. Conclusions CT‐1 inhibits intestinal sugar absorption by the reduction of SGLT‐1 levels through the AMPK pathway, which could also contribute to explain the hypoglycaemic and anti‐obesity properties of CT‐1.
    April 07, 2016   doi: 10.1111/apha.12674   open full text
  • Biosensor cell assay for measuring real‐time aldosterone‐induced release of histamine from mesenteric arteries.
    E. G. Dalgaard, K. Andersen, P. Svenningsen, P. B. L. Hansen.
    Acta Physiologica. April 05, 2016
    Aims The aims were to develop a method for real‐time detection of histamine release and to test whether incubation with aldosterone induces histamine release from isolated, perfused mice mesenteric arteries. Methods Fura‐2‐loaded HEK‐293 cells transfected with the histamine H1 receptor was used as a sensitive biosensor assay for histamine release from isolated mouse mesenteric arteries. Activation of the H1 receptor by histamine was measured as an increased number of intracellular Ca2+ transient peaks using fluorescence imaging. Results The developed biosensor was sensitive to histamine in physiological relevant concentrations and responded to substances released by the artery preparation. Aldosterone treatment of mesenteric arteries from wild‐type mice for 50 min resulted in an increased number of intracellular Ca2+ transient peaks in the biosensor cells, which was significantly inhibited by the histamine H1 blocker pyrilamine. Mesenteric arteries from mast cell‐deficient SASH mice induced similar pyrilamine‐sensitive Ca2+ transient response in the biosensor cells. Mesenteric arteries from wild‐type and SASH mice expressed histamine decarboxylase mRNA, indicating that mast cells are not the only source of histamine release. Conclusion The developed biosensor assay can measure release of substances from vascular preparations. Histamine is released from the vessel preparation in response to aldosterone treatment independently of mast cells. The assay enables us to study a new signaling mechanism for vascular responses induced by aldosterone.
    April 05, 2016   doi: 10.1111/apha.12680   open full text
  • Polyunsaturated fatty acids are potent openers of human M‐channels expressed in Xenopus laevis oocytes.
    S. I. Liin, U. Karlsson, B. H. Bentzen, N. Schmitt, F. Elinder.
    Acta Physiologica. March 23, 2016
    Aim Polyunsaturated fatty acids have been reported to reduce neuronal excitability, in part by promoting inactivation of voltage‐gated sodium and calcium channels. Effects on neuronal potassium channels are less explored and experimental data ambiguous. The aim of this study was to investigate anti‐excitable effects of polyunsaturated fatty acids on the neuronal M‐channel, important for setting the resting membrane potential in hippocampal and dorsal root ganglion neurones. Methods Effects of fatty acids and fatty acid analogues on mouse dorsal root ganglion neurones and on the human KV7.2/3 channel expressed in Xenopus laevis oocytes were studied using electrophysiology. Results Extracellular application of physiologically relevant concentrations of the polyunsaturated fatty acid docosahexaenoic acid hyperpolarized the resting membrane potential (−2.4 mV by 30 μm) and increased the threshold current to evoke action potentials in dorsal root ganglion neurones. The polyunsaturated fatty acids docosahexaenoic acid, α‐linolenic acid and eicosapentaenoic acid facilitated opening of the human M‐channel, comprised of the heteromeric human KV7.2/3 channel expressed in Xenopus oocytes, by shifting the conductance‐vs.‐voltage curve towards more negative voltages (by −7.4 to −11.3 mV by 70 μm). Uncharged docosahexaenoic acid methyl ester and monounsaturated oleic acid did not facilitate opening of the human KV7.2/3 channel. Conclusions These findings suggest that circulating polyunsaturated fatty acids, with a minimum requirement of multiple double bonds and a charged carboxyl group, dampen excitability by opening neuronal M‐channels. Collectively, our data bring light to the molecular targets of polyunsaturated fatty acids and thus a possible mechanism by which polyunsaturated fatty acids reduce neuronal excitability.
    March 23, 2016   doi: 10.1111/apha.12663   open full text
  • Peroxisome proliferator‐activated receptor γ activation favours selective subcutaneous lipid deposition by coordinately regulating lipoprotein lipase modulators, fatty acid transporters and lipogenic enzymes.
    P. G. Blanchard, V. Turcotte, M. Côté, Y. Gélinas, S. Nilsson, G. Olivecrona, Y. Deshaies, W. T. Festuccia.
    Acta Physiologica. March 12, 2016
    Aim Peroxisome proliferator‐activated receptor (PPAR) γ activation is associated with preferential lipoprotein lipase (LPL)‐mediated fatty acid storage in peripheral subcutaneous fat depots. How PPARγ agonism acts upon the multi‐level modulation of depot‐specific lipid storage remains incompletely understood. Methods We evaluated herein triglyceride‐derived lipid incorporation into adipose tissue depots, LPL mass and activity, mRNA levels and content of proteins involved in the modulation of LPL activity and fatty acid transport, and the expression/activity of enzymes defining adipose tissue lipogenic potential in rats treated with the PPARγ ligand rosiglitazone (30 mg kg−1 day−1, 23 days) after either a 10‐h fasting period or a 17‐h fast followed by 6 h of ad libitum refeeding. Results Rosiglitazone stimulated lipid accretion in subcutaneous fat (SF) ~twofold and significantly reduced that of visceral fat (VF) to nearly half. PPARγ activation selectively increased LPL mass, activity and the expression of its chaperone LMF1 in SF. In VF, rosiglitazone had no effect on LPL activity and downregulated the mRNA levels of the transendothelial transporter GPIHBP1. Overexpression of lipid uptake and fatty acid transport proteins (FAT/CD36, FATP1 and FABP4) and stimulation of lipogenic enzyme activities (GPAT, AGPAT and DGAT) upon rosiglitazone treatment were of higher magnitude in SF. Conclusions Together these findings demonstrate that the depot‐specific transcriptional control of LPL induced by PPARγ activation extends to its key interacting proteins and post‐translational modulators to favour subcutaneous lipid storage.
    March 12, 2016   doi: 10.1111/apha.12665   open full text
  • Long‐term facilitation of expiratory and sympathetic activities following acute intermittent hypoxia in rats.
    E. V. Lemes, S. Aiko, C. B. Orbem, C. Formentin, M. Bassi, E. Colombari, D. B. Zoccal.
    Acta Physiologica. March 03, 2016
    Aim Acute intermittent hypoxia (AIH) promotes persistent increases in ventilation and sympathetic activity, referred as long‐term facilitation (LTF). Augmented inspiratory activity is suggested as a major component of respiratory LTF. In this study, we hypothesized that AIH also elicits a sustained increase in expiratory motor activity. We also investigated whether the expiratory LTF contributes to the development of sympathetic LTF after AIH. Methods Rats were exposed to AIH (10 × 6–7% O2 for 45 s, every 5 min), and the cardiorespiratory parameters were evaluated during 60 min using in vivo and in situ approaches. Results In unanesthetized conditions (n = 9), AIH elicited a modest but sustained increase in baseline mean arterial pressure (MAP, 104 ± 2 vs. 111 ± 3 mmHg, P < 0.05) associated with enhanced sympathetic and respiratory‐related variabilities. In the in situ preparations (n = 9), AIH evoked LTF in phrenic (33 ± 12%), thoracic sympathetic (75 ± 25%) and abdominal nerve activities (69 ± 14%). The sympathetic overactivity after AIH was phase‐locked with the emergence of bursts in abdominal activity during the late‐expiratory phase. In anesthetized vagus‐intact animals, AIH increased baseline MAP (113 ± 3 vs. 122 ± 2 mmHg, P < 0.05) and abdominal muscle activity (535 ± 94%), which were eliminated after pharmacological inhibition of the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG). Conclusion These findings indicate that increased expiratory activity is also an important component of AIH‐elicited respiratory LTF. Moreover, the development of sympathetic LTF after AIH is linked to the emergence of active expiratory pattern and depends on the integrity of the neurones of the RTN/pFRG.
    March 03, 2016   doi: 10.1111/apha.12661   open full text
  • Conducted dilatation to ATP and K+ in rat skeletal muscle arterioles.
    K. A. Dora.
    Acta Physiologica. February 22, 2016
    Aim During exercise in humans, circulating levels of ATP and K+ increase at a time when blood flow increases to satisfy metabolic demand. Both molecules can activate arteriolar K+ channels to stimulate vasodilatation; here, it is established whether conducted dilatation is observed in a skeletal muscle bed. Methods Isolated and cannulated rat cremaster arterioles were used to assess both local and conducted responses. Agents were either added to the bath, focally pulse‐ejected to the downstream end of arterioles, or in triple‐cannulated arterioles, luminally perfused into the downstream branches to assess both local and conducted responses. Results The endothelium‐dependent agonist ACh and the KATP channel opener levcromakalim each stimulated both local and conducted vasodilatation. Focal, bolus delivery of ATP (10 μm) or KCl (33 mm) to the outside of arterioles stimulated a biphasic vasomotor response: rapid vasoconstriction followed by dilatation as each washed away. At lower concentrations of KCl (19 mm), constriction was avoided, and instead, Ba2+‐sensitive local dilatation and conducted dilatation were both observed. Luminal perfusion of ATP avoided constriction and activated P2Y1 receptors stimulating vasodilatation secondary to opening of KCa channels. In triple‐cannulated arterioles, either ATP (10 μm) or K+ (15 mm) luminally perfused into daughter branches of a bifurcation stimulated local dilatation which conducted into the parent arteriole. Conclusion The recognized physiological autocrine and paracrine mediators ATP and K+ each act to evoke both local and conducted vasodilatation in rat cremaster arterioles. Therefore, in situations when circulating levels are raised, such as during exercise, these agents can act as important regulators of blood flow.
    February 22, 2016   doi: 10.1111/apha.12656   open full text
  • Muscle force loss and soreness subsequent to maximal eccentric contractions depend on the amount of fascicle strain in vivo.
    G. Guilhem, V. Doguet, H. Hauraix, L. Lacourpaille, M. Jubeau, A. Nordez, S. Dorel.
    Acta Physiologica. February 02, 2016
    Aim Defining the origins of muscle injury has important rehabilitation and exercise applications. However, current knowledge of muscle damage mechanics in human remains unclear in vivo. This study aimed to determine the relationships between muscle–tendon unit mechanics during maximal eccentric contractions and the extent of subsequent functional impairments induced by muscle damage. Methods The length of the muscle–tendon unit, fascicles and tendinous tissues was continuously measured on the gastrocnemius medialis using ultrasonography, in time with torque, during 10 sets of 30 maximal eccentric contractions of plantar flexors at 45°s−1, in seventeen participants. Results Muscle–tendon unit, fascicles and tendinous tissues were stretched up to 4.44 ± 0.33 cm, 2.31 ± 0.64 cm and 1.92 ± 0.61 cm respectively. Fascicle stretch length, lengthening amplitude and negative fascicle work beyond slack length were significantly correlated with the force decrease 48 h post‐exercise (r = 0.51, 0.47 and 0.68, respectively; P < 0.05). Conclusions This study demonstrates that the strain applied to human muscle fibres during eccentric contractions strongly influences the magnitude of muscle damage in vivo. Achilles tendon compliance decreases the amount of strain, while architectural gear ratio may moderately contribute to attenuating muscle fascicle lengthening and hence muscle damage. Further studies are necessary to explore the impact of various types of task to fully understand the contribution of muscle–tendon interactions during active lengthening to muscle damage.
    February 02, 2016   doi: 10.1111/apha.12654   open full text
  • Thyroid hormone reduces inflammatory cytokines improving glycaemia control in alloxan‐induced diabetic wistar rats.
    A. C. Panveloski‐Costa, S. Silva Teixeira, I. M. R. Ribeiro, C. Serrano‐Nascimento, R. X. Neves, R. R. Favaro, M. Seelaender, V. R. Antunes, M. T. Nunes.
    Acta Physiologica. January 30, 2016
    Aim This study aimed at evaluating whether thyroid hormone treatment could improve glycaemia and insulin response in alloxan‐induced diabetic rats by altering cytokine expression in the skeletal muscle and epididymal white adipose tissue (eWAT) as well as altering inflammatory cell infiltration in eWAT. Methods Diabetes mellitus (DM) was induced in male Wistar rats by alloxan injection, and a subset of the diabetic rats was treated with T3 (1.5 μg per 100 g body weight) for a 28‐day period (DT3). Cytokines were measured in serum (MILIplex assay kit) as well as in soleus and EDL skeletal muscles and eWAT by Western blotting. Thyroid function was evaluated by morphological, molecular and biochemical parameters. Cardiac function was assessed by measuring heart rate, blood pressure, maximal rate of pressure development (dp/dtmax) and decline (dp/dtmin) as well as the contractility index (CI). Sixty rats were used in the study. Results Diabetic rats exhibited decreased thyroid function and increased inflammatory cytokines in serum, soleus muscle and eWAT. T3 treatment decreased glycaemia and improved insulin sensitivity in diabetic animals. These alterations were accompanied by decreased TNF‐alpha and IL‐6 content in soleus muscle and eWAT, and inflammatory cell infiltration in eWAT. T3 treatment did not affect cardiac function of diabetic rats. Conclusions The present data provide evidence that T3 treatment reduces glycaemia and improves insulin sensitivity in diabetic rats, and that at least part of this effect could result from its negative modulation of inflammatory cytokine expression.
    January 30, 2016   doi: 10.1111/apha.12647   open full text
  • Longitudinal evaluation of functional connectivity variation in the monkey sensorimotor network induced by spinal cord injury.
    J.S. Rao, Z. Liu, C. Zhao, R.H. Wei, W. Zhao, Z.Y. Yang, X.G. Li.
    Acta Physiologica. January 13, 2016
    Aim Given the unclear pattern of cerebral function reorganization induced by spinal cord injury (SCI), this study aimed to longitudinally evaluate the changes in resting‐state functional connectivity (FC) in the sensorimotor network after SCI and explore their relationship with gait performance. Methods Four adult female rhesus monkeys were examined using resting‐state functional magnetic resonance imaging during their healthy stage and after hemitransected SCI (4, 8 and 12 weeks after SCI), and the gait characteristics of their hindlimbs were recorded (except 4 weeks after SCI). Twenty sensorimotor‐related cortical areas were adopted in the FC analysis to evaluate the functional network reorganization. Correlation analyses were then used to explore the relationship between functional network variations and gait characteristic changes. Results Compared with that during the healthy stage, the FC strength during post‐SCI period was significantly increased in multiple areas of the motor control network, including the primary sensorimotor cortex, supplementary motor area (SMA) and putamen (Pu). However, the FC strength was remarkably reduced in the thalamus and parieto‐occipital association cortex of the sensory network 8 weeks after SCI. Most FC intensities gradually approached the normal level 12 weeks after the SCI. Correlation analyses revealed that the enhanced FC strength between Pu and SMA in the left hemisphere, which regulates motor functions of the right side, was negatively correlated with the gait height of the right hindlimb. Conclusion The cerebral functional network presents an adjust–recover pattern after SCI, which may help us further understand the cerebral function reorganization after SCI.
    January 13, 2016   doi: 10.1111/apha.12645   open full text
  • Vascular hepoxilin and trioxilins mediate vasorelaxation through TP receptor inhibition in mouse arteries.
    L. Siangjong, D. H. Goldman, T. Kriska, K. M. Gauthier, E. M. Smyth, N. Puli, G. Kumar, J. R. Falck, W. B. Campbell.
    Acta Physiologica. January 04, 2016
    Aim 12/15‐lipoxygenase (12/15‐LO) metabolizes arachidonic acid (AA) into several vasoactive eicosanoids. In mouse arteries, we previously characterized the enzyme's 15‐LO metabolites 12(S)‐hydroxyeicosatetraenoic acid (HETE), 15‐HETE, hydroxyepoxyeicosatrienoic acids (HEETAs) and 11,12,15‐trihydroxyeicosatrienoic acids (11,12,15‐THETAs) as endothelium‐derived relaxing factors. However, the observed 12‐LO metabolites remained uncharacterized. The purpose of this study was to determine the structure and biological functions of eicosanoids generated by the enzyme's 12‐LO activity. Methods Metabolites extracted from aortas of C57BL/6 male mice were separated using a series of reverse and normal phase chromatographic steps and identified as hepoxilin A3, trioxilin A3 and trioxilin C3 by mass spectrometry. Activities of these natural compounds were tested on isometric tension and intracellular calcium release. The role of thromboxane (TP) receptor was determined in HEK293 cells overexpressing TPα receptor (TPα ‐HEK). Results All identified vascular 12‐LO metabolites were biologically active. In mouse mesenteric arteries, trioxilin A3, C3 and hepoxilin A3 (3 μm) relaxed arteries constricted with the thromboxane mimetic, U46619‐constricted arteries (maximum relaxations of 78.9 ± 3.2, 29.7 ± 4.6, 82.2 ± 5.0 and 88.0 ± 2.4% respectively), but not phenylephrine‐constricted arteries. In TPα‐HEK cells, trioxilin A3, C3 and hepoxilin A3 (10 μm) inhibited U46619 (10 nM)‐induced increases in intracellular calcium by 53.0 ± 7.2%, 32.8 ± 5.0% and 37.9 ± 13.5% respectively. In contrast, trioxilin B3 and hepoxilin B3 were not synthesized in arteries and exhibited little biological activity. Conclusion Trioxilin A3 and C3 and hepoxilin A3 are endogenous vascular relaxing factors. They are not endothelium‐derived hyperpolarizing factors but mediate vascular relaxation by inhibiting TP agonist‐induced increases in intracellular calcium. Thus, they regulate vascular homeostasis by acting as endogenous TP antagonists.
    January 04, 2016   doi: 10.1111/apha.12642   open full text
  • Gastric bypass surgery is protective from high‐fat diet‐induced non‐alcoholic fatty liver disease and hepatic endoplasmic reticulum stress.
    J. D. Mosinski, M. R. Pagadala, A. Mulya, H. Huang, O. Dan, H. Shimizu, E. Batayyah, R. K. Pai, P. R. Schauer, S. A. Brethauer, J. P. Kirwan.
    Acta Physiologica. December 29, 2015
    Aim High‐fat diets are known to contribute to the development of obesity and related co‐morbidities including non‐alcoholic fatty liver disease (NAFLD). The accumulation of hepatic lipid may increase endoplasmic reticulum (ER) stress and contribute to non‐alcoholic steatohepatitis and metabolic disease. We hypothesized that bariatric surgery would counter the effects of a high‐fat diet (HFD) on obesity‐associated NAFLD. Methods Sixteen of 24 male Sprague Dawley rats were randomized to Sham (N = 8) or Roux‐en‐Y gastric bypass (RYGB) surgery (N = 8) and compared to Lean controls (N = 8). Obese rats were maintained on a HFD throughout the study. Insulin resistance (HOMA‐IR), and hepatic steatosis, triglyceride accumulation, ER stress and apoptosis were assessed at 90 days post‐surgery. Results Despite eating a HFD for 90 days post‐surgery, the RYGB group lost weight (−20.7 ± 6%, P < 0.01) and improved insulin sensitivity (P < 0.05) compared to Sham. These results occurred with no change in food intake between groups. Hepatic steatosis and ER stress, specifically glucose‐regulated protein‐78 (Grp78, P < 0.001), X‐box binding protein‐1 (XBP‐1) and spliced XBP‐1 (P < 0.01), and fibroblast growth factor 21 (FGF21) gene expression, were normalized in the RYGB group compared to both Sham and Lean controls. Significant TUNEL staining in liver sections from the Obese Sham group, indicative of accelerated cell death, was absent in the RYGB and Lean control groups. Additionally, fasting plasma glucagon like peptide‐1 was increased in RYGB compared to Sham (P < 0.02). Conclusion These data suggest that in obese rats, RYGB surgery protects the liver against HFD‐induced fatty liver disease by attenuating ER stress and excess apoptosis.
    December 29, 2015   doi: 10.1111/apha.12640   open full text
  • Vaspin prevents elevation of blood pressure through inhibition of peripheral vascular remodelling in spontaneously hypertensive rats.
    S. Kameshima, Y. Sakamoto, M. Okada, H. Yamawaki.
    Acta Physiologica. December 24, 2015
    Aim Visceral adipose tissue‐derived serine protease inhibitor (vaspin) is a relatively novel adipocytokine with protective effects on metabolic diseases including obesity and type II diabetes. We have previously demonstrated that vaspin exerts anti‐inflammatory and antimigratory roles through antioxidative effects in vascular smooth muscle cells. As inflammatory responses and migration of smooth muscle in peripheral vascular wall are key mechanisms for the pathogenesis of hypertension, we hypothesized that vaspin could prevent the development of hypertension in in vivo hypertensive animal model. Methods Vaspin (1 μg kg−1 day−1) was administered intraperitoneally to 5‐week‐old male spontaneously hypertensive rats (SHR) for 4 weeks. Superior mesenteric artery was isolated and used for measurement of isometric contraction and histological analysis. Results Long‐term vaspin treatment significantly prevented an elevation of systolic blood pressure (SBP) at 8 weeks of age. Vaspin had no effect on reactivity of isolated mesenteric artery from SHR. In contrast, vaspin significantly inhibited mesenteric arterial wall hypertrophy in SHR. Moreover, vaspin significantly inhibited an increase of tumour necrosis factor‐α expression and a production of reactive oxygen species in isolated mesenteric artery from SHR. Conclusion This study for the first time demonstrates that vaspin prevents the increase of SBP in SHR through inhibiting peripheral vascular hypertrophy possibly via antioxidative and anti‐inflammatory mechanisms.
    December 24, 2015   doi: 10.1111/apha.12636   open full text
  • Inhibition of mitogen‐activated protein kinase 1/2 in the acute phase of stroke improves long‐term neurological outcome and promotes recovery processes in rats.
    M. Mostajeran, L. Edvinsson, K. Warfvinge, R. Singh, S. Ansar.
    Acta Physiologica. December 17, 2015
    Aim Extracellular signal‐regulated kinase (ERK) 1/2 is activated during acute phase of stroke and contributes to stroke pathology. We have found that acute treatment with MEK1/2 inhibitors decreases infarct size and neurological deficits 2 days after experimental stroke. However, it is not known whether benefits of this inhibition persist long‐term. Therefore, the aim of this study was to assess neurological function, infarct size and recovery processes 14 days after stroke in male rats to determine long‐term outcome following acute treatment with the MEK1/2 inhibitor U0126. Methods Transient middle cerebral artery occlusion was induced in male rats. U0126 or vehicle was given at 0 and 24 h of reperfusion. Neurological function was assessed by staircase, 6‐point and 28‐point neuroscore tests up to 14 days after induction of stroke. At day 14, infarct volumes were determined and recovery processes were evaluated by measuring protein expression of the tyrosine kinase receptor Tie‐2 and nestin. Levels of p‐ERK1/2 protein were determined. Results Acute treatment with U0126 significantly improved long‐term functional recovery, reduced infarct size, and enhanced Tie‐2 and nestin protein expression at 14 days post‐stroke. There was no residual blockade of p‐ERK1/2 at this time point. Conclusion It is demonstrated that benefits of early treatment with U0126 persist beyond subacute phase of ischaemic stroke in male rats. Prevention of ERK1/2 activation in the acute phase results in improved long‐term functional outcome and enhances later‐stage recovery processes. These results expand our understanding of the benefits and promise of using MEK1/2 inhibitors in stroke recovery.
    December 17, 2015   doi: 10.1111/apha.12632   open full text
  • Response to exercise and mechanical efficiency in non‐ischaemic stunning, induced by short‐term rapid pacing in dogs: a role for calcium?
    M. De Pauw, K. Mubagwa, D. Hodeige, M. Borgers, W. Flameng, J. Van de Voorde, G. R. Heyndrickx.
    Acta Physiologica. December 15, 2015
    Aim Rapid pacing (RP) is a regularly used model to induce heart failure in dogs. The aim of the study was to evaluate Ca2+ handling, left ventricular (LV) contractile response during Ca2+ administration compared to exercise, as well as oxygen consumption and mechanical efficiency after 48 h of RP. Methods Fifty‐three mongrel dogs were instrumented to measure LV pressure, LV fractional shortening, regional wall thickening and coronary blood flow. Contractile reserve was measured with isoproterenol and intravenous (IV) Ca2+ administration. To assess the function of the sarcoplasmic reticulum (SR), post‐extrasystolic potentiation (PESP) and SR Ca2+ uptake were measured. A graded treadmill test was performed in baseline and after RP (n = 14). In a separate group of animals (n = 5), myocardial performance and oxygen consumption were measured using a wide range of loading conditions. Results Left ventricular contractility was significantly decreased upon cessation of pacing. The contractile response to isoproterenol was blunted compared to a preserved response to IV Ca2+. Post‐extrasystolic potentiation was slightly increased after RP. Maximal velocity (Vmax) of SR Ca2+ uptake was unchanged. Contractile response during exercise is attenuated after RP. External work is reduced, whereas oxygen consumption is preserved, provoking a reduced mechanical efficiency. Conclusion Forty‐eight‐hours RP provokes a reversible LV dysfunction, while the SR function and response to exogenous Ca2+ are preserved. This is compatible with an intracellular functional remodelling to counteract Ca2+ overload provoked by RP. Left ventricular dysfunction is accompanied by a reduced contractile reserve, but an unchanged oxygen consumption, illustrating an alteration in oxygen utilization.
    December 15, 2015   doi: 10.1111/apha.12629   open full text
  • Nitric oxide and Na,K‐ATPase activity in rat skeletal muscle.
    C. Juel.
    Acta Physiologica. November 03, 2015
    Aim It has been suggested that nitric oxide (NO) stimulates the Na,K‐ATPase in cardiac myocytes. Therefore, the aims of this study were to investigate whether NO increases Na,K‐ATPase activity in skeletal muscle and, if that is the case, to identify the underlying mechanism. Method The study used isolated rat muscle, muscle homogenates and purified membranes as model systems. Na,K‐ATPase activity was quantified from phosphate release due to ATP hydrolysis. Results Exposure to the NO donor spermine NONOate (10 μm) increased the maximal Na,K‐ATPase activity by 27% in isolated glycolytic muscles, but had no effect in oxidative muscles. Spermine NONOate increased the maximal Na,K‐ATPase activity by 58% (P < 0.05) in homogenates from glycolytic muscle, but had no effect in oxidative muscle. The stimulatory effect of NONOate was not related to one specific Na,K‐ATPase α‐isoform. Incubation with cGMP (1 mm) increased the maximal Na,K‐ATPase activity in homogenates from glycolytic muscle by 16% (P < 0.05), but had no effect on homogenates from oxidative muscle. cGMP had no effect on phospholemman phosphorylation at serine 68. Spermine NONOate had no effect in muscle membranes in which the ATPase activity was depressed by oxidized glutathione. Conclusion NO and cGMP stimulate the Na,K‐ATPase in glycolytic skeletal muscle. Direct S‐nitrosylation and interference with S‐glutathionylation seem to be excluded. In addition, phosphorylation of phospholemman at serine 68 is not involved. Most likely, the NO/cGMP/protein kinase G signalling pathway is involved.
    November 03, 2015   doi: 10.1111/apha.12617   open full text
  • The change in motor unit firing rates at derecruitment relative to recruitment is correlated with type I myosin heavy chain isoform content of the vastus lateralis in vivo.
    Trent J. Herda, Jonathan D. Miller, Michael A. Trevino, Eric M. Mosier, Philip M. Gallagher, Andrew C. Fry, John P. Vardiman.
    Acta Physiologica. October 29, 2015
    Aim To investigate the change in motor unit (MU) firing rates (FR) at derecruitment relative to recruitment and the relation to percent type I myosin heavy chain isoform content (type I %MHC) of the vastus lateralis (VL) in vivo. Methods Ten subjects performed a 22 second submaximal isometric trapezoid muscle action that included a linearly increasing, steady force at 50% maximal voluntary contraction, and linearly decreasing segments. Surface electromyographic signals were collected from the VL and were decomposed into constituent MU action potentials trains. A tissue sample from the VL was taken to calculate type I %MHC. Y‐intercepts and slopes were calculated for the changes (Δ) in FR at derecruitment (FRDEREC) relative to FR at recruitment (FRREC) versus FRREC relationship for each subject. Correlations were performed between the y‐intercepts and slopes with type I %MHC. Results The majority of MUs had greater FRDEREC than FRREC. The y‐intercepts (r=‐0.600, P=0.067) were not significantly correlated, but the slopes (r=‐0.793, P=0.006) were significantly correlated with type I %MHC. Conclusion The majority of the motoneuron pool had greater FRDEREC than FRREC, however, individuals with higher type I %MHC had a greater propensity to have MUs with FRREC > FRDEREC as indicated by the slope values. Overall, the contractile properties of the muscle (MHC) could partially explain the differences in MU firing rates at derecruitment relative to recruitment. Thus, suggesting the fatigability of the muscle influences the alterations in MU firing rates from recruitment to derecruitment. This article is protected by copyright. All rights reserved.
    October 29, 2015   doi: 10.1111/apha.12624   open full text
  • The NADPH Oxidase Nox4 mediates tumour angiogenesis.
    V. Helfinger, N. Henke, Sabine Harenkamp, Maria Walter, Jeremy Epah, Cornelia Penski, Michel Mittelbronn, K. Schröder.
    Acta Physiologica. October 29, 2015
    Aim The aim of this work was to identify the role of the NADPH oxidase Nox4 for tumour angiogenesis in a slow growing tumour model in mice. Methods Tumour angiogenesis was studied in tumours induced by the carcinogen 3‐methylcholanthrene (MCA) in wild‐type and Nox knock out mice. Mice were sacrificed when the tumour reached a diameter of 1.5 cm and tumour tissue was used for histological and molecular analysis. Results 3‐methylcholanthrene induced fibro sarcoma in wildtype, Nox1y/‐, Nox2y/‐ and Nox4‐/‐ mice. Histological analysis of vessel density using anti‐CD31 staining showed a significant 38% reduction in tumour vascularization in fibro sarcomas of Nox4‐/‐ mice. In contrast tumour angiogenesis was doubled in Nox1 knock out mice, whereas knock out of Nox2 had no effect on tumour vessel density. As underlying mechanisms we identified a defect in hypoxia signalling in Nox4‐/‐ mice. Hypoxia‐ inducible factor 1‐alpha (Hif‐1α) accumulation in the tumours was attenuated as was the expression of the Hif‐1α‐dependent pro‐angiogenic genes vascular endothelial growth factor‐A, glucose transporter 1 and adrenomedullin. Conclusion By regulating the tumour vessel density through stabilization of Hif‐1α and induction of VEGF expression Nox4 promotes tumour angiogenesis and may represent a novel target for anti‐angiogenic tumour therapy. This article is protected by copyright. All rights reserved.
    October 29, 2015   doi: 10.1111/apha.12625   open full text
  • The bitter truth about bitter taste receptors: Beyond sensing bitter in the oral cavity.
    Bert Avau, Inge Depoortere.
    Acta Physiologica. October 23, 2015
    The bitter taste receptor (TAS2R)‐family of GPCRs has been identified on the tongue as detectors of bitter taste over a decade ago. In the last few years, they have been discovered in an ever growing number of extra‐oral tissues, including the airways, the gut, the brain and even the testis. In tissues that contact the exterior, protective functions for TAS2Rs have been proposed, in analogy to their function in the tongue as toxicity detector. However, TAS2Rs have also been found in internal organs, suggesting other roles for these receptors, perhaps involving as yet unidentified endogenous ligands. The current review gives an overview of the different proposed functions for TAS2Rs in tissues other than the oral cavity; from appetite regulation to the treatment of asthma, regulation of gastrointestinal motility and control of airway innate immunity. This article is protected by copyright. All rights reserved.
    October 23, 2015   doi: 10.1111/apha.12621   open full text
  • Deficiency or inhibition of lysophosphatidic acid receptor 1 protects against hyperoxia‐induced lung injury in neonatal rats.
    Xueyu Chen, Frans J Walther, Ruben Boxtel, El Houari Laghmani, Rozemarijn M A Sengers, Gert Folkerts, Marco C. DeRuiter, Edwin Cuppen, Gerry T M Wagenaar.
    Acta Physiologica. October 23, 2015
    Aim Blocking of lysophosphatidic acid (LPA) receptor (LPAR) 1 may be a novel therapeutic option for bronchopulmonary dysplasia (BPD) by preventing the LPAR1‐mediated adverse effects of its ligand (LPA), consisting of lung inflammation, pulmonary arterial hypertension (PAH) and fibrosis. Methods In Wistar rats with experimental BPD, induced by continuous exposure to 100% oxygen for 10 days, we determined the beneficial effects of LPAR1 deficiency in neonatal rats with a missense mutation in cytoplasmic helix 8 of LPAR1 and of LPAR1 and ‐3 blocking with Ki16425. Parameters investigated included survival, lung and heart histopathology, fibrin and collagen deposition, vascular leakage, and differential mRNA expression in the lungs of key genes involved in LPA signalling and BPD pathogenesis. Results LPAR1 mutant rats were protected against experimental BPD and mortality with reduced alveolar septal thickness, lung inflammation (reduced influx of macrophages and neutrophils, and CINC1 expression), and collagen III deposition. However, LPAR1 mutant rats were not protected against alveolar enlargement, increased medial wall thickness of small arterioles, fibrin deposition, and vascular alveolar leakage. Treatment of experimental BPD with Ki16425 confirmed the data observed in LPAR1 mutant rats, but did not reduce the pulmonary influx of neutrophils, CINC1 expression, and mortality in rats with experimental BPD. In addition, Ki16425 treatment protected against PAH and right ventricular hypertrophy. Conclusion LPAR1 deficiency attenuates pulmonary injury by reducing pulmonary inflammation and fibrosis, thereby reducing mortality, but does not affect alveolar and vascular development and, unlike Ki16425 treatment, does not prevent PAH in neonatal rats with experimental BPD. This article is protected by copyright. All rights reserved.
    October 23, 2015   doi: 10.1111/apha.12622   open full text
  • Effects of renal denervation on renal pelvic contractions and connexin expression in rats.
    A. Koenen, A. Steinbach, K. Schaper, U. Zimmermann, B. Miehe, B. Kurt, R. Rettig, O. Grisk.
    Acta Physiologica. October 22, 2015
    Aims The renal pelvis shows spontaneous rhythmic contractile activity. We assessed to what extent this activity depends on renal innervation and studied the role of connexins in pelvic contractions. Methods Rats underwent unilateral renal denervation or renal transplantation. Renal pelvic pressure and diuresis were measured in vivo. Spontaneous and agonist‐induced contractions of isolated renal pelves were investigated by wire myography. Rat and human renal pelvic connexin mRNA abundances and connexin localization were studied by real‐time PCR and immunofluorescence respectively. Results Renal denervation or transplantation increased renal pelvic pressure in vivo by about 60 and 150%, respectively, but did not significantly affect pelvic contraction frequency. Under in vitro conditions, isolated pelvic preparations from innervated or denervated kidneys showed spontaneous contractions. Pelves from denervated kidneys showed about 50% higher contraction frequencies than pelves from innervated kidneys, whereas contraction force was similar in pelves from denervated and innervated kidneys. There was no denervation‐induced supersensitivity to noradrenaline or endothelin‐1. Renal denervation did not increase pelvic connexin37, 40, 43 or 45 mRNA abundances. Gap junction blockade had no effect on spontaneous pelvic contractile activity. Conclusions The denervation‐induced effect on pelvic pressure may be the consequence of the enhanced diuresis. The mechanisms underlying the denervation‐induced effects on pelvic contraction frequency remain unknown. Our data rule out a major role for two important candidates, by showing that renal denervation neither induced supersensitivity to contractile agonists nor increased connexin mRNA abundance in the pelvic wall.
    October 22, 2015   doi: 10.1111/apha.12612   open full text
  • Altered neurotrophic factors expression profiles in the nucleus of the solitary tract of spontaneously hypertensive rats.
    Sabine S Gouraud, Miwa Takagishi, Akira Kohsaka, Masanobu Maeda, Hidefumi Waki.
    Acta Physiologica. October 20, 2015
    Aim Our previous findings suggest that the nucleus of the solitary tract (NTS), a pivotal region for regulating the set‐point of arterial pressure, exhibits abnormal inflammation in pre‐hypertensive and spontaneously hypertensive rats (SHRs), with elevated anti‐apoptotic and low apoptotic factor levels compared with that of normotensive Wistar‐Kyoto (WKY) rats. Whether this chronic condition affects neuronal growth and plasticity in the NTS remains unknown. To unveil the characteristics of the neurodevelopmental environment in the NTS of SHRs, we investigated the expression of neurotrophic factors transcripts in SHRs. Methods RT2 Profiler PCR Array targeting rat neurotrophins and their receptors was used to screen for differentially expressed transcripts in the NTS of SHRs compared to that of WKY rats. Protein expression and physiological functions of some of the differentially expressed transcripts were also studied. Results Gene and protein expressions of glial cell line‐derived neurotrophic factor family receptor alpha‐3 (Gfrα‐3) factor were both upregulated in the NTS of adult SHRs. Gene expressions of corticotropin releasing hormone binding protein (Crhbp), Interleukin‐10 receptor alpha (Il10ra), and hypocretin (Hcrt) were downregulated in the NTS of adult SHRs. The Gfrα‐3 transcript was increased and the Hcrt transcript was decreased in the NTS of young pre‐hypertensive SHRs, suggesting that these profiles are not secondary to hypertension. Moreover, microinjection in the NTS of hypocretin‐1 decreased blood pressure in adult SHRs. Conclusion These results suggest that altered neurotrophic factors transcript profiles may affect the normal development and function of neuronal circuitry that regulates cardiovascular autonomic activity; thereby resulting in manifestations of neurogenic hypertension in SHRs. This article is protected by copyright. All rights reserved.
    October 20, 2015   doi: 10.1111/apha.12618   open full text
  • Impaired sodium‐evoked paraventricular nucleus neuronal activation and blood pressure regulation in conscious Sprague–Dawley rats lacking central Gαi2 proteins.
    C. Y. Carmichael, A. C. T. Carmichael, J. T. Kuwabara, J. T. Cunningham, R. D. Wainford.
    Acta Physiologica. October 19, 2015
    Aim We determined the role of brain Gαi2 proteins in mediating the neural and humoral responses of conscious male Sprague–Dawley rats to acute peripheral sodium challenge. Methods Rats pre‐treated (24‐h) intracerebroventricularly with a targeted oligodeoxynucleotide (ODN) (25 μg per 5 μL) to downregulate brain Gαi2 protein expression or a scrambled (SCR) control ODN were challenged with an acute sodium load (intravenous bolus 3 m NaCl; 0.14 mL per 100 g), and cardiovascular parameters were monitored for 120 min. In additional groups, hypothalamic paraventricular nucleus (PVN) Fos immunoreactivity was examined at baseline, 40, and 100 min post‐sodium challenge. Results In response to intravenous hypertonic saline (HS), no difference was observed in peak change in mean arterial pressure between groups. In SCR ODN pre‐treated rats, arterial pressure returned to baseline by 100 min, while it remained elevated in Gαi2 ODN pre‐treated rats (P < 0.05). No difference between groups was observed in sodium‐evoked increases in Fos‐positive magnocellular neurons or vasopressin release. V1a receptor antagonism failed to block the prolonged elevation of arterial pressure in Gαi2 ODN pre‐treated rats. A significantly greater number of Fos‐positive ventrolateral parvocellular, lateral parvocellular, and medial parvocellular neurons were observed in SCR vs. Gαi2 ODN pre‐treated rats at 40 and 100 min post‐HS challenge (P < 0.05). In SCR, but not Gαi2 ODN pre‐treated rats, HS evoked suppression of plasma norepinephrine (P < 0.05). Conclusion This highlights Gαi2 protein signal transduction as a novel central mechanism acting to differentially influence PVN parvocellular neuronal activation, sympathetic outflow, and arterial pressure in response to acute HS, independently of actions on magnocellular neurons and vasopressin release.
    October 19, 2015   doi: 10.1111/apha.12610   open full text
  • Training‐induced anti‐atherosclerotic effects are associated with increased vascular PPARgamma expression in apolipoprotein E deficient mice.
    Justyna Szostak, Carole Miguet‐Alfonsi, Alain Berthelot, Pascal Laurant.
    Acta Physiologica. October 15, 2015
    Aim Physical exercise prevents cardiovascular risk and atherosclerosis lesions. However, the molecular aspects are still unknown. Vascular Peroxisome Proliferator‐Activated Receptors (PPARs) exert anti‐atherogenic effects. The aim of this study was to determine whether exercise‐induced anti‐atherosclerotic effect is associated with change in PPARs vascular expression in apolipoprotein E deficient (ApoE‐/‐) mice. Methods Male ApoE‐/‐ mice were fed with a high fat diet and randomized into two groups: one trained group undergoing swimming training for 3 months, and one sedentary group. Sedentary and trained C57BL/6J mice were used as control. PPAR‐α, ‐β/δ and ‐γ mRNA were measured in aorta by quantitative PCR. Pro‐ (TNF‐α, IL‐1β) and anti‐inflammatory (IL‐10, IL‐1Ra) cytokines mRNA were also measured. Results Atherosclerotic lesion size was significantly reduced in trained ApoE‐/‐ mice compared to sedentary ones. In contrast, reduction of atherosclerotic lesion size was not observed in trained ApoE‐/‐ mice supplied with BADGE, an antagonist of PPAR‐ γ. Exercise training significantly increased PPAR‐γ expression in aorta. PPAR‐γ expression was inversely correlated with the atherosclerotic plaque area. Aortic PPAR‐α and ‐β/δ mRNA expression were not changed in response to exercise training. Atherosclerosis increased the aortic mRNA expression of TNF‐α, IL‐1β, IL‐10, and IL‐1Ra. Exercise training decreased aortic IL‐1β mRNA expression in ApoE‐/‐ mice, but did not change expression of TNF‐α, IL‐10, and IL‐1Ra. IL‐1β mRNA expression was also significantly lower in atherosclerosis lesions from trained ApoE‐/‐ compared with those from sedentary ones. Conclusions Exercise training increases vascular PPAR‐γ expression in ApoE‐/‐ mice that could potentially underlie training‐related beneficial effects on atherosclerosis. This article is protected by copyright. All rights reserved.
    October 15, 2015   doi: 10.1111/apha.12615   open full text
  • The effect of exercise mode on the acute response of satellite cells in old men.
    J. P. Nederveen, S. Joanisse, C. M. L. Séguin, K. E. Bell, S. K. Baker, S. M. Phillips, G. Parise.
    Acta Physiologica. October 14, 2015
    Aim A dysregulation of satellite cells may contribute to the progressive loss of muscle mass that occurs with age; however, older adults retain the ability to activate and expand their satellite cell pool in response to exercise. The modality of exercise capable of inducing the greatest acute response is unknown. We sought to characterize the acute satellite cell response following different modes of exercise in older adults. Methods Sedentary older men (n = 22; 67 ± 4 years; 27 ± 2.6 kg*m−2) were randomly assigned to complete an acute bout of either resistance exercise, high‐intensity interval exercise on a cycle ergometer or moderate‐intensity aerobic exercise. Muscle biopsies were obtained before, 24 and 48 h following each exercise bout. The satellite cell response was analysed using immunofluorescent microscopy of muscle cross sections. Results Satellite cell expansion associated with type I fibres was observed 24 and 48 h following resistance exercise only (P ˂ 0.05), while no expansion of type II‐associated satellite cells was observed in any group. There was a greater number of activated satellite cells 24 h following resistance exercise (pre: 1.3 ± 0.1, 24 h: 4.8 ± 0.5 Pax7 + /MyoD+cells/100 fibres) and high‐intensity interval exercise (pre: 0.7 ± 0.3, 24 h: 3.1 ± 0.3 Pax7 + /MyoD+cells/100 fibres) (P ˂ 0.05). The percentage of type I‐associated SC co‐expressing MSTN was reduced only in the RE group 24 h following exercise (pre: 87 ± 4, 24 h: 57 ± 5%MSTN+ type I SC) (P < 0.001). Conclusion Although resistance exercise is the most potent exercise type to induce satellite cell pool expansion, high‐intensity interval exercise was also more potent than moderate‐intensity aerobic exercise in inducing satellite cell activity.
    October 14, 2015   doi: 10.1111/apha.12601   open full text
  • Changes in myonuclear domain size do not precede muscle hypertrophy during prolonged resistance‐type exercise training.
    T. Snijders, J. S. J. Smeets, J. Kranenburg, A. K. Kies, L. J. C. Loon, L. B. Verdijk.
    Acta Physiologica. October 09, 2015
    Aim Muscle fibre hypertrophy is accompanied by an increase in myonuclear number, an increase in myonuclear domain size or both. It has been suggested that increases in myonuclear domain size precede myonuclear accretion and subsequent muscle fibre hypertrophy during prolonged exercise training. In this study, we assessed the changes in muscle fibre size, myonuclear and satellite cell content throughout 12 weeks of resistance‐type exercise training in young men. Methods Twenty‐two young men (23 ± 1 year) were assigned to a progressive, 12‐weeks resistance‐type exercise training programme (3 sessions per week). Muscle biopsies from the vastus lateralis muscle were taken before and after 2, 4, 8 and 12 weeks of exercise training. Muscle fibre size, myonuclear content, myonuclear domain size and satellite cell content were assessed by immunohistochemistry. Results Type I and type II muscle fibre size increased gradually throughout the 12 weeks of training (type I: 18 ± 5%, type II: 41 ± 6%, P < 0.01). Myonuclear content increased significantly over time in both the type I (P < 0.01) and type II (P < 0.001) muscle fibres. No changes in type I and type II myonuclear domain size were observed at any time point throughout the intervention. Satellite cell content increased significantly over time in both type I and type II muscle fibres (P < 0.001). Conclusion Increases in myonuclear domain size do not appear to drive myonuclear accretion and muscle fibre hypertrophy during prolonged resistance‐type exercise training in vivo in humans.
    October 09, 2015   doi: 10.1111/apha.12609   open full text
  • Insulin‐like growth factor 1 prevents diastolic and systolic dysfunction associated with cardiomyopathy and preserves adrenergic sensitivity.
    S. R. Roof, J. Boslett, D. Russell, C. Rio, J. Alecusan, J. L. Zweier, M. T. Ziolo, R. Hamlin, P. J. Mohler, J. Curran.
    Acta Physiologica. October 08, 2015
    Aims Insulin‐like growth factor 1 (IGF‐1)‐dependent signalling promotes exercise‐induced physiological cardiac hypertrophy. However, the in vivo therapeutic potential of IGF‐1 for heart disease is not well established. Here, we test the potential therapeutic benefits of IGF‐1 on cardiac function using an in vivo model of chronic catecholamine‐induced cardiomyopathy. Methods Rats were perfused with isoproterenol via osmotic pump (1 mg kg−1 per day) and treated with 2 mg kg−1 IGF‐1 (2 mg kg−1 per day, 6 days a week) for 2 or 4 weeks. Echocardiography, ECG, and blood pressure were assessed. In vivo pressure–volume loop studies were conducted at 4 weeks. Heart sections were analysed for fibrosis and apoptosis, and relevant biochemical signalling cascades were assessed. Results After 4 weeks, diastolic function (EDPVR, EDP, tau, E/A ratio), systolic function (PRSW, ESPVR, dP/dtmax) and structural remodelling (LV chamber diameter, wall thickness) were all adversely affected in isoproterenol‐treated rats. All these detrimental effects were attenuated in rats treated with Iso+IGF‐1. Isoproterenol‐dependent effects on BP were attenuated by IGF‐1 treatment. Adrenergic sensitivity was blunted in isoproterenol‐treated rats but was preserved by IGF‐1 treatment. Immunoblots indicate that cardioprotective p110α signalling and activated Akt are selectively upregulated in Iso+IGF‐1‐treated hearts. Expression of iNOS was significantly increased in both the Iso and Iso+IGF‐1 groups; however, tetrahydrobiopterin (BH4) levels were decreased in the Iso group and maintained by IGF‐1 treatment. Conclusion IGF‐1 treatment attenuates diastolic and systolic dysfunction associated with chronic catecholamine‐induced cardiomyopathy while preserving adrenergic sensitivity and promoting BH4 production. These data support the potential use of IGF‐1 therapy for clinical applications for cardiomyopathies.
    October 08, 2015   doi: 10.1111/apha.12607   open full text
  • Deficiency of heat shock transcription factor 1 suppresses heat stress‐associated increase in slow soleus muscle mass of mice.
    Y. Ohno, T. Egawa, S. Yokoyama, A. Nakai, T. Sugiura, Y. Ohira, T. Yoshioka, K. Goto.
    Acta Physiologica. September 28, 2015
    Aim Effects of heat shock transcription factor 1 (HSF1) deficiency on heat stress‐associated increase in slow soleus muscle mass of mice were investigated. Methods Both HSF1‐null and wild‐type mice were randomly assigned to control and heat‐stressed groups. Mice in heat‐stressed group were exposed to heat stress (41 °C for 60 min) in an incubator without anaesthesia. Results Significant increase in wet and dry weights, and protein content of soleus muscle in wild‐type mice was observed seven days after the application of the heat stress. However, heat stress had no impact on soleus muscle mass in HSF1‐null mice. Neither type of mice exhibited much effect of heat stress on HSF mRNA expression (HSF1, HSF2 and HSF4). On the other hand, heat stress upregulated heat shock proteins (HSPs) at the mRNA (HSP72) and protein (HSP72 and HSP110) levels in wild‐type mice, but not in HSF1‐null mice. The population of Pax7‐positive nuclei relative to total myonuclei of soleus muscle in wild‐type mice was significantly increased by heat stress, but not in HSF1‐null mice. Furthermore, the absence of HSF1 gene suppressed heat stress‐associated phosphorylation of Akt and p70 S6 kinase (p‐p70S6K) in soleus muscle. Conclusion Heat stress‐associated increase in skeletal muscle mass may be induced by HSF1 and/or HSF1‐mediated stress response that activates muscle satellite cells and Akt/p70S6K signalling pathway.
    September 28, 2015   doi: 10.1111/apha.12600   open full text
  • Inverse gradient of nitrergic and purinergic inhibitory cotransmission in the mouse colon.
    N. Mañé, R. Viais, M. Martínez‐Cutillas, D. Gallego, P. Correia‐de‐Sá, M. Jiménez.
    Acta Physiologica. September 28, 2015
    Aim Gastrointestinal smooth muscle relaxation is accomplished by the neural corelease of ATP or a related purine and nitric oxide. Contractions are triggered by acetylcholine and tachykinins. The aim of this work was to study whether regional differences in neurotransmission could partially explain the varied physiological roles of each colonic area. Methods We used electrophysiological and myography techniques to evaluate purinergic (L‐NNA 1 mm incubated tissue), nitrergic (MRS2500 0.3 μm incubated tissue) and cholinergic neurotransmission (L‐NNA 1 mm and MRS2500 0.3 μm incubated tissue) in the proximal, mid and distal colon of CD1 mice (n = 42). Results Purinergic electrophysiological responses elicited by single pulses (28 V) were greater in the distal (IJPfMAX = −35.3 ± 2.2 mV), followed by the mid (IJPfMAX = −30.6 ± 1.0 mV) and proximal (IJPfMAX = −11.7 ± 1.1 mV) colon. In contrast, nitrergic responses decreased from the proximal colon (IJPsMAX = −11.4 ± 1.1 mV) to the mid (IJPsMAX = −9.1 ± 0.4 mV), followed by the distal colon (IJPsMAX = −1.8 ± 0.3 mV). A similar rank of order was observed in neural mediated inhibitory mechanical responses including electrical field stimulation‐mediated responses and neural tone. ADPβs concentration–response curve was shifted to the left in the distal colon. In contrast, NaNP responses did not differ between regions. Cholinergic neurotransmission elicited contractions of a similar amplitude throughout the colon. Conclusion An inverse gradient of purinergic and nitrergic neurotransmission exists through the mouse colon. The proximal and mid colon have a predominant nitrergic neurotransmission probably due to the fact that their storage function requires sustained relaxations. The distal colon, in contrast, has mainly purinergic neurotransmission responsible for the phasic relaxations needed to propel dehydrated faeces.
    September 28, 2015   doi: 10.1111/apha.12599   open full text
  • Antihypertensive and cardioprotective effects of the dipeptide isoleucine–tryptophan and whey protein hydrolysate.
    M. Martin, I. Kopaliani, A. Jannasch, C. Mund, V. Todorov, T. Henle, A. Deussen.
    Acta Physiologica. September 22, 2015
    Aims Angiotensin‐converting enzyme inhibitors are treatment of choice in hypertensive patients. Clinically used inhibitors exhibit a structural similarity to naturally occurring peptides. This study evaluated antihypertensive and cardioprotective effects of ACE‐inhibiting peptides derived from food proteins in spontaneously hypertensive rats. Methods and Results Isoleucine–tryptophan (in vitro IC50 for ACE = 0.7 μm), a whey protein hydrolysate containing an augmented fraction of isoleucine–tryptophan, or captopril was given to spontaneously hypertensive rats (n = 60) over 14 weeks. Two further groups, receiving either no supplement (Placebo) or intact whey protein, served as controls. Systolic blood pressure age‐dependently increased in the Placebo group, whereas the blood pressure rise was effectively blunted by isoleucine–tryptophan, whey protein hydrolysate and captopril (−42 ± 3, −38 ± 5, −55 ± 4 mm Hg vs. Placebo). At study end, myocardial mass was lower in isoleucine–tryptophan and captopril groups but only partially in the hydrolysate group. Coronary flow reserve (1 μm adenosine) was improved in isoleucine–tryptophan and captopril groups. Plasma ACE activity was significantly decreased in isoleucine–tryptophan, hydrolysate and captopril groups, but in aortic tissue only after isoleucine–tryptophan or captopril treatment. This was associated with lowered expression and activity of matrix metalloproteinase‐2. Following isoleucine–tryptophan and captopril treatments, gene expression of renin was significantly increased indicating an active feedback within renin–angiotensin system. Conclusion Whey protein hydrolysate and isoleucine–tryptophan powerfully inhibit plasma ACE resulting in antihypertensive effects. Moreover, isoleucine–tryptophan blunts tissue ACE activity, reduces matrix metalloproteinase‐2 activity and improves coronary flow reserve. Thus, whey protein hydrolysate and particularly isoleucine–tryptophan may serve as innovative food additives with the goal of attenuating hypertension.
    September 22, 2015   doi: 10.1111/apha.12578   open full text
  • The exercise‐regulated myokine chitinase‐3‐like protein 1 stimulates human myocyte proliferation.
    S. W. Görgens, M. Hjorth, K. Eckardt, S. Wichert, F. Norheim, T. Holen, S. Lee, T. Langleite, K. I. Birkeland, H. K. Stadheim, K. J. Kolnes, D. S. Tangen, A. J. Kolnes, J. Jensen, C. A. Drevon, J. Eckel.
    Acta Physiologica. September 08, 2015
    Aim Chitinase‐3‐like protein 1 (CHI3L1) is involved in tissue remodelling and inflammatory processes. Plasma levels are elevated in patients with insulin resistance and T2DM. We recently showed that CHI3L1 and its receptor protease‐activated receptor 2 (PAR‐2) are expressed in skeletal muscle. Activation of PAR‐2 by CHI3L1 protects against TNF‐α‐induced inflammation and insulin resistance. However, the effect of exercise on CHI3L1 and PAR‐2 signalling remains unknown. The aim of this work was to study the impact of exercise on CHI3L1 production and the effect of CHI3L1/PAR‐2 signalling on skeletal muscle growth and repair. Methods Three human exercise studies were used to measure CHI3L1 plasma levels (n = 32). In addition, muscle and adipose tissue CHI3L1 mRNA expression was measured in response to acute and long‐term exercise (n = 24). Primary human skeletal muscle cells were differentiated in vitro, and electrical pulse stimulation was applied. In addition, myoblasts were incubated with CHI3L1 protein and activation of MAP kinase signalling as well as proliferation was measured. Results Circulating CHI3L1 levels and muscle CHI3L1 mRNA were increased after acute exercise. In addition, CHI3L1 mRNA expression as well as CHI3L1 secretion was enhanced in electrically stimulated cultured myotubes. Incubation of cultured human myoblasts with CHI3L1 protein leads to a strong activation of p44/42, p38 MAPK and Akt as well as enhanced myoblast proliferation. Conclusion Our findings suggest that CHI3L1 is induced by acute exercise and that CHI3L1/PAR‐2 signalling activates myocyte proliferation, which is important for restructuring of skeletal muscle in the response to exercise training.
    September 08, 2015   doi: 10.1111/apha.12579   open full text
  • Visceral adipose tissue‐derived serine protease inhibitor augments acetylcholine‐induced relaxation via the inhibition of acetylcholine esterase activity in rat isolated mesenteric artery.
    S. Kameshima, K. Yamada, T. Morita, M. Okada, H. Yamawaki.
    Acta Physiologica. August 31, 2015
    Aim Visceral adipose tissue‐derived serine protease inhibitor (vaspin) is an adipocytokine with insulin‐sensitizing activity originally identified in visceral adipose tissues of obesity‐related type II diabetic rats. We previously showed that vaspin inhibits vascular cell migration and apoptosis as well as inflammatory responses, which are crucial for the development of hypertension. However, little is known about the effects of vaspin on vascular reactivity. The aim of this study was thus to explore the effects of vaspin on contraction and relaxation of isolated blood vessel. Methods After mesenteric arteries were isolated from male Wistar rats, the effects of pretreatment with vaspin (3 ng mL−1, 30 min) on concentration–contraction and concentration–relaxation relationships for each agent were examined. The effects of vaspin on acetylcholine (ACh)‐induced phosphorylation of endothelial nitric oxide (NO) synthase (eNOS) and ACh esterase (AChE) activity were also examined using Western blotting and colorimetric method respectively. Results Vaspin did not affect noradrenaline‐ or 5‐hydroxytryptamine‐induced contraction. In contrast, vaspin augmented ACh‐ but not histamine‐, A23187‐ or carbachol‐induced NO‐mediated relaxation. Vaspin significantly increased ACh‐induced eNOS phosphorylation and inhibited AChE activity. Conclusion We for the first time demonstrate that vaspin augments the ACh‐induced NO‐mediated endothelium‐dependent relaxation via the inhibition of AChE activity.
    August 31, 2015   doi: 10.1111/apha.12563   open full text
  • Circulating microparticles from diabetic rats impair endothelial function and regulate endothelial protein expression.
    K. Ishida, K. Taguchi, M. Hida, S. Watanabe, K. Kawano, T. Matsumoto, Y. Hattori, T. Kobayashi.
    Acta Physiologica. August 20, 2015
    Aim Diabetes mellitus increases the risk of cardiovascular disease, which is accompanied by functional and structural changes in the vascular system. Microparticles (MPs) have been described as biological vectors of endothelial dysfunction in other pathologies. However, the molecular mechanisms underlying their formation and signalling are unclear. We investigated the role of MPs derived from streptozotocin (STZ)‐induced diabetic rats in endothelial function. Methods Male Wistar rats were injected with STZ to induce diabetes, and MPs isolated from control or STZ‐induced diabetic rats were characterized by dot blotting (assessed by CD62P detections), flow cytometry (assessed by annexin V detections) and ELISA. Carotid arteries from rats were incubated with MPs, and expressions of enzymes and endothelium‐dependent relaxation were analysed. Results The circulating levels of MPs, particularly the levels of platelet‐derived microparticles, from diabetic rats were higher than those present in controls. Endothelium‐dependent relaxation induced by acetylcholine (ACh) was attenuated in carotid arteries from STZ‐induced diabetic rats. Following the incubation of control carotid arteries with MPs isolated from STZ rats, ACh‐induced endothelium‐dependent relaxation was impaired, but MPs isolated from control rats had no such effect. Furthermore, the effect of MPs was mediated by a decrease in expression of endothelial nitric oxide synthase (eNOS) and the overexpression of caveolin‐1. Conclusion Circulating MPs isolated from STZ‐induced diabetic rats induce endothelial dysfunction in carotid arteries and regulate protein expressions of eNOS and caveolin‐1. These data advance our understanding of the deleterious effects of circulating MPs observed in disorders with diabetic complications.
    August 20, 2015   doi: 10.1111/apha.12561   open full text
  • Claudin expression in follicle‐associated epithelium of rat Peyer's patches defines a major restriction of the paracellular pathway.
    A. G. Markov, E. L. Falchuk, N. M. Kruglova, J. Radloff, S. Amasheh.
    Acta Physiologica. August 18, 2015
    Aim Members of the tight junction protein family of claudins have been demonstrated to specifically determine paracellular permeability of the intestinal epithelium. In small intestinal mucosa, which is generally considered to be a leaky epithelium, Peyer's patches are a primary part of the immune system. The aim of this study was to analyse the tight junctional barrier of follicle‐associated epithelium covering Peyer's patches (lymphoid follicles). Methods Employing small intestinal tissue specimens of male Wistar rats, electrophysiological analyses including the Ussing chamber technique, marker flux measurements and one‐path impedance spectroscopy were performed. Morphometry of HE‐stained tissue sections was taken into account. Claudin expression and localization was analysed by immunoblotting and confocal laser scanning immunofluorescence microscopy. Results Almost twofold higher parameters of epithelial and transepithelial tissue resistance and a markedly lower permeability for the paracellular permeability markers 4 and 20 kDa FITC–dextran were detected in follicle‐associated epithelium compared to neighbouring villous epithelium. Analysis of claudin expression and localization revealed a stronger expression of major sealing proteins in follicle‐associated epithelium, including claudin‐1, claudin‐4, claudin‐5 and claudin‐8. Therefore, the specific expression and localization of claudins is in accordance with barrier properties of follicle‐associated epithelium vs. neighbouring villous epithelium. Conclusion We demonstrate that follicle‐associated epithelium is specialized to ensure maximum restriction of the epithelial paracellular pathway in Peyer's patches by selective sealing of tight junctions. This results in an exclusive transcellular pathway of epithelial cells as the limiting and mandatory route for a controlled presentation of antigens to the underlying lymphocytes under physiological conditions.
    August 18, 2015   doi: 10.1111/apha.12559   open full text
  • The calcium‐activated potassium channel KCa3.1 plays a central role in the chemotactic response of mammalian neutrophils.
    C. Henríquez, T. T. Riquelme, D. Vera, F. Julio‐Kalajzić, P. Ehrenfeld, J. E. Melvin, C. D. Figueroa, J. Sarmiento, C. A. Flores.
    Acta Physiologica. July 19, 2015
    Aim Neutrophils are the first cells to arrive at sites of injury. Nevertheless, many inflammatory diseases are characterized by an uncontrolled infiltration and action of these cells. Cell migration depends on volume changes that are governed by ion channel activity, but potassium channels in neutrophil have not been clearly identified. We aim to test whether KCa3.1 participates in neutrophil migration and other relevant functions of the cell. Methods Cytometer and confocal measurements to determine changes in cell volume were used. Cells isolated from human, mouse and horse were tested for KCa3.1‐dependent chemotaxis. Chemokinetics, calcium handling and release of reactive oxygen species were measured to determine the role of KCa3.1 in those processes. A mouse model was used to test for neutrophil recruitment after acute lung injury in vivo. Results We show for the first time that KCa3.1 is expressed in mammalian neutrophils. When the channel is inhibited by a pharmacological blocker or by genetic silencing, it profoundly affects cell volume regulation, and chemotactic and chemokinetic properties of the cells. We also demonstrated that pharmacological inhibition of KCa3.1 did not affect calcium entry or reactive oxygen species production in neutrophils. Using a mouse model of acute lung injury, we observed that Kca3.1−/− mice are significantly less effective at recruiting neutrophils into the site of inflammation. Conclusions These results demonstrate that KCa3.1 channels are key actors in the migration capacity of neutrophils, and its inhibition did not affect other relevant cellular functions.
    July 19, 2015   doi: 10.1111/apha.12548   open full text
  • Ca2+‐activated K+ current is essential for maintaining excitability and gene transcription in early embryonic cardiomyocytes.
    S. Karppinen, R. Rapila, N. Naumenko, T. Tuomainen, J. T. Koivumäki, S. L. Hänninen, T. Korhonen, P. Tavi.
    Acta Physiologica. June 28, 2015
    Aim Activity of early embryonic cardiomyocytes relies on spontaneous Ca2+ oscillations that are induced by interplay between sarcoplasmic reticulum (SR) – Ca2+ release and ion currents of the plasma membrane. In a variety of cell types, Ca2+‐activated K+ current (IK(Ca)) serves as a link between Ca2+ signals and membrane voltage. This study aimed to determine the role of IK(Ca) in developing cardiomyocytes. Methods Ion currents and membrane voltage of embryonic (E9‐11) mouse cardiomyocytes were measured by patch clamp; [Ca2+]i signals by confocal microscopy. Transcription of specific genes was measured with RT‐qPCR and Ca2+‐dependent transcriptional activity using NFAT‐luciferase assay. Myocyte structure was assessed with antibody labelling and confocal microscopy. Results E9‐11 cardiomyocytes express small conductance (SK) channel subunits SK2 and SK3 and have a functional apamin‐sensitive K+ current, which is also sensitive to changes in cytosolic [Ca2+]i. In spontaneously active cardiomyocytes, inhibition of IK(Ca) changed action and resting potentials, reduced SR Ca2+ load and suppressed the amplitude and the frequency of spontaneously evoked Ca2+ oscillations. Apamin caused dose‐dependent suppression of NFAT‐luciferase reporter activity, induced downregulation of a pattern of genes vital for cardiomyocyte development and triggered changes in the myocyte morphology. Conclusion The results show that apamin‐sensitive IK(Ca) is required for maintaining excitability and activity of the developing cardiomyocytes as well as having a fundamental role in promoting Ca2+‐ dependent gene expression.
    June 28, 2015   doi: 10.1111/apha.12540   open full text
  • In search for better pharmacological prophylaxis for acute mountain sickness: looking in other directions.
    Hui Lu, Rong Wang, Juan Xiong, Hua Xie, Bengt Kayser, Zheng‐ping Jia.
    Acta Physiologica. March 09, 2015
    ["\nAbstract\nDespite decades of research, the exact pathogenic mechanisms underlying acute mountain sickness (AMS) are still poorly understood. This fact frustrates the search for novel pharmacological prophylaxis for AMS. The prevailing view is that AMS results from an insufficient physiological response to hypoxia and that prophylaxis should aim at stimulating the response. Starting off from the opposite hypothesis that AMS may be caused by an initial excessive response to hypoxia we suggest that directly or indirectly blunting specific parts of the response might provide promising research alternatives. This reasoning is based on the observations that 1) humans, once acclimatized, can climb Mt Everest experiencing arterial partial oxygen pressures (PaO2) as low as 25 mmHg without AMS symptoms, 2) paradoxically AMS usually develops at much higher PaO2 levels, and 3) several biomarkers, suggesting initial activation of specific pathways at such PaO2, are correlated with AMS. Apart from looking for substances that stimulate certain hypoxia triggered effects, such as the ventilatory response to hypoxia, we suggest to also investigate pharmacological means aiming at blunting certain other specific hypoxia activated pathways, or stimulating their agonists, in the quest for better pharmacological prophylaxis for AMS.\nThis article is protected by copyright. All rights reserved.\n", "Acta Physiologica, Accepted Article. "]
    March 09, 2015   doi: 10.1111/apha.12486   open full text
  • Actin Sliding Velocity On Pure Myosin Isoforms From Hindlimb Unloaded Mice.
    Manuela Maffei, Emanuela Longa, Rizwan Qaisar, Valentina Agoni, Jean‐François Desaphy, Diana Conte Camerino, Roberto Bottinelli, Monica Canepari.
    Acta Physiologica. May 29, 2014
    Aim Notwithstanding the widely accepted idea that following disuse skeletal muscles become faster, an increase in shortening velocity was previously observed mostly in fibers containing type 1 myosin, whereas a decrease was generally found in fibers containing type 2B myosin. In this study unloaded shortening velocity of pure type 1 and 2B fibers from hindlimb unloaded mice was determined and a decrease in type 2B fibers was found. Methods To clarify whether the decrease in shortening velocity could depend on alterations of myosin motor function, an in vitro motility assay approach was applied to study pure type 1 and pure type 2B myosin from hindlimb unloaded mice. The latter approach, assessing actin sliding velocity on isolated myosin in the absence of other myofibrillar proteins, enabled to directly investigate myosin motor function. Results Actin sliding velocity was significantly lower on type 2B myosin following unloading (2.70±0.32 μms‐1) than in control conditions (4.11±0.35 μms‐1), whereas actin sliding velocity of type 1 myosin was not different following unloading (0.89±0.04 μms‐1) compared to control conditions (0.84±0.17 μms‐1). Myosin light chain isoform composition of type 2B myosin from hindlimb unloaded and control mice was not different. No oxidation of either type 1 or 2B myosin was observed. Higher phosphorylation of regulatory myosin light chain in type 2B myosin after unloading was found. Conclusion Results suggest that the observed lower shortening velocity of type 2B fibers following unloading could be related to slowing of acto‐myosin kinetics in the presence of myosin light chain phosphorylation. This article is protected by copyright. All rights reserved.
    May 29, 2014   doi: 10.1111/apha.12320   open full text
  • The force‐velocity relationship at negative loads (assisted shortening) studied in isolated, intact muscle fibres of the frog.
    K.A.P. Edman.
    Acta Physiologica. May 29, 2014
    Aim The study was undertaken to explore the force‐velocity relationship under conditions where the myofilament system is subjected to an external force that serves as a negative load and assists the shortening movement. Methods The experiments were carried out on single muscle fibres isolated from the anterior tibialis muscle of Rana temporaria. The fibres, being operated under load‐clamp control, were released to shorten during tetanic stimulation at sarcomere lengths where the fibres carried different degrees of passive tension. The shortening thus occurred while the sarcomeres were subjected to a force that may be characterized as a “negative load”, i.e. a force assisting the shortening movement. Results The force‐velocity relationship below zero load was found to be a smooth continuation of the force‐velocity curve recorded at positive loads the shortening velocity increasing steeply at loads below zero. A negative load amounting to merely 10% of the isometric force thus raised the shortening velocity to a level 2‐3 times higher than V0, the velocity recorded at zero load. Conclusion The results provide evidence that, even in the presence of a longitudinal compressive force, the speed of shortening of the muscle fibre is determined by the cycling rate of the interacting cross‐bridges. The force‐velocity relationship at negative loads may play a relevant part during fast movements of striated muscle as pointed out in the discussion. This article is protected by copyright. All rights reserved.
    May 29, 2014   doi: 10.1111/apha.12321   open full text
  • The Effect of Tendon Vibration on Motor Unit Activity, Intermuscular Coherence, and Force Steadiness in the Elbow Flexors of Males and Females.
    B Harwood, KMD Cornett, DL Edwards, RE Brown, JM Jakobi.
    Acta Physiologica. May 28, 2014
    Compartmentalized responses in motor unit (MU) activity of the short (SH) and long (LH) heads of the biceps brachii are observed following forearm position change. Differential muscle spindle afferent distribution has been proposed as a potential mechanism underlying this behavior. Tendon vibration is an effective, non‐invasive method of increasing muscle spindle afferent activity of a target muscle group offering a paradigm in which this hypothesis may be investigated further. Aim To determine the effect of tendon vibration on MU recruitment and discharge rates of the SH and LH, muscle activity of the elbow flexors and triceps brachii, intermuscular coherence among the SH, LH, brachioradialis and triceps brachii, and force steadiness in young male and females during isometric elbow flexion. Methods Intramuscular electromyography (EMG) of the SH and LH, and surface EMG of the elbow flexors were recorded pre‐ and post‐vibration during low force isometric contractions. Motor unit recruitment thresholds, MU discharge rates, and MU discharge variability; surface EMG amplitude, intermuscular coherence, and force steadiness were determined pre‐ and post‐vibration. Results Differential changes in all MU properties, EMG amplitude and intermuscular coherence were observed among elbow flexors. Although MU properties exhibited differential changes, they accounted for little variance in isometric force steadiness. However, intermuscular EMG coherence among all muscles investigated was reduced post‐vibration. Conclusion Uncoupling of common oscillatory input as a result of differential muscle spindle afferent inputs to elbow flexors may be responsible for the reduction in force steadiness following tendon vibration and a forearm position change. This article is protected by copyright. All rights reserved.
    May 28, 2014   doi: 10.1111/apha.12319   open full text
  • Estrogen‐dependent satellite cell activation and proliferation following a running exercise occurs via the PI3K signalling pathway and not IGF‐1.
    Gary Mangan, Eric Bombardier, Andrew Mitchell, Joe Quadrilatero, Peter M. Tiidus.
    Acta Physiologica. May 24, 2014
    Aim The purpose of this study was to determine whether 17β‐Estradiol (E2) enhances the activation, proliferation and differentiation of muscle satellite cells (SC) following eccentric exercise either via Insulin‐like Growth Factor‐1 (IGF‐1) or through phosphatidylinositol 3‐kinase (PI3K) signaling. Methods This study used 64, nine‐week old, ovariectomized Sprague‐Dawley rats that were divided into eight treatments groups based on: estrogen status (0.25 mg estrogen pellet or sham), exercise status (90 min run @ 17 m/min, ‐13.5° or unexercised), PI3K signaling inhibition (0.7 mg Wortmannin·kg−1 Body Weight or DMSO control). Results Significant increases in total SCs were found in both soleus and white gastrocnemius muscles (immunofluorescent co‐localization of Pax7+ nuclei) 72 hr following eccentric exercise (p < 0.05). Estrogen‐supplementation caused a further enhancement in total SCs in exercised rats (p < 0.05). In animals where the PI3K pathway was inhibited, regardless of estrogen or exercise status, there was no significant enhancement of SC number in both the soleus or white gastrocnemius muscles. Interestingly, estrogen‐supplementation lowered muscle levels of IGF‐1 with this effect being most prominent in the soleus muscle. While IGF‐1 was increased following exercise (p < 0.05), estrogen‐supplementation abrogated this increase back to sedentary levels. Conclusion This data suggests that the increase in SC population following exercise in estrogen‐supplemented females may be mediated via PI3K pathway signaling and not IGF‐1. This article is protected by copyright. All rights reserved.
    May 24, 2014   doi: 10.1111/apha.12317   open full text
  • Acute response and subcellular movement of HSP27, αB‐crystallin and HSP70 in human skeletal muscle after blood‐flow‐restricted low‐load resistance exercise.
    K. T. Cumming, G. Paulsen, M. Wernbom, I. Ugelstad, T. Raastad.
    Acta Physiologica. May 23, 2014
    Aim Heat‐shock proteins (HSP) are important chaperones for stressed and damaged proteins. Low‐load blood‐flow‐restricted resistance exercise (BFRE) is generally believed not to induce significant muscle damage, but is hitherto unverified with intracellular markers. Consequently, the aim of this study was to investigate the HSP response after BFRE in human skeletal muscle. Methods Nine healthy volunteers performed five sets to failure of unilateral knee extension at 30% of 1RM with partial blood‐flow restriction. The contralateral leg performed the same work with free blood flow. Muscle biopsies were collected before exercise, 1, 24 and 48 h after exercise and analysed for HSP27, αB‐crystallin, HSP70, desmin, glycogen content and myosin heavy chain by immunohistochemistry, ELISA and western blotting. Results One hour after exercise, HSP27 and αB‐crystallin levels were reduced in the cytosolic and increased in the cytoskeletal fraction in the BFRE leg. HSP70 showed a delayed response and was increased over 48 h in the BFRE leg. Immunohistochemical analyses showed higher staining intensity of HSP70 in type 1 fibres in the BFRE leg at 24 and 48 h post‐exercise. PAS staining showed decreased glycogen levels after BFRE, and interestingly, glycogen was still depleted 48 h after exercise in the same fibres displaying high HSP70 staining (type 1 fibres). Conclusion Translocation of HSP27 and αB‐crystallin from cytosol to cytoskeletal structures indicates that cytoskeletal proteins are stressed during BFRE. However, overt signs of myofibrillar disruptions were not observed. Interestingly, the stress response was more pronounced in type 1 than in type 2 fibres and coincided with low glycogen levels.
    May 23, 2014   doi: 10.1111/apha.12305   open full text
  • Metformin induces lactate production in peripheral blood mononuclear cells and platelets through specific mitochondrial complex I inhibition.
    S. Piel, J. K. Ehinger, E. Elmér, M. J. Hansson.
    Acta Physiologica. May 23, 2014
    Aim Metformin is a widely used antidiabetic drug associated with the rare side effect of lactic acidosis which has been proposed to be linked to drug‐induced mitochondrial dysfunction. Using respirometry, the aim of this study was to evaluate mitochondrial toxicity of metformin to human blood cells in relation to that of phenformin, a biguanide analogue withdrawn in most countries due to a high incidence of lactic acidosis. Methods Peripheral blood mononuclear cells and platelets were isolated from healthy volunteers, and integrated mitochondrial function was studied in permeabilized and intact cells using high‐resolution respirometry. A wide concentration range of metformin (0.1–100 mm) and phenformin (25–500 μm) was investigated for dose‐ and time‐dependent effects on respiratory capacities, lactate production and pH. Results Metformin induced respiratory inhibition at complex I in peripheral blood mononuclear cells and platelets (IC50 0.45 mm and 1.2 mm respectively). Phenformin was about 20‐fold more potent in complex I inhibition of platelets than metformin. Metformin further demonstrated a dose‐ and time‐dependent respiratory inhibition and augmented lactate release at a concentration of 1 mm and higher. Conclusion Respirometry of human peripheral blood cells readily detected respiratory inhibition by metformin and phenformin specific to complex I, providing a suitable model for probing drug toxicity. Lactate production was increased at concentrations relevant for clinical metformin intoxication, indicating mitochondrial inhibition as a direct causative pathophysiological mechanism. Relative to clinical dosing, phenformin displayed a more potent respiratory inhibition than metformin, possibly explaining the higher incidence of lactic acidosis in phenformin‐treated patients.
    May 23, 2014   doi: 10.1111/apha.12311   open full text
  • On the antioxidant properties of erythropoietin and its association with the oxidative–nitrosative stress response to hypoxia in humans.
    D. M. Bailey, C. Lundby, R. M. G. Berg, S. Taudorf, H. Rahmouni, M. Gutowski, C. W. Mulholland, J. L. Sullivan, E. R. Swenson, J. McEneny, I. S. Young, B. K. Pedersen, K. Møller, S. Pietri, M. Culcasi.
    Acta Physiologica. May 23, 2014
    Aim The aim of this study was to examine if erythropoietin (EPO) has the potential to act as a biological antioxidant and determine the underlying mechanisms. Methods The rate at which its recombinant form (rHuEPO) reacts with hydroxyl (HO˙), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH˙) and peroxyl (ROO˙) radicals was evaluated in‐vitro. The relationship between the erythopoietic and oxidative–nitrosative stress response to poikilocapneic hypoxia was determined separately in‐vivo by sampling arterial blood from eleven males in normoxia and following 12 h exposure to 13% oxygen. Electron paramagnetic resonance spectroscopy, ELISA and ozone‐based chemiluminescence were employed for direct detection of ascorbate (A˙−) and N‐tert‐butyl‐α‐phenylnitrone spin‐trapped alkoxyl (PBN‐OR) radicals, 3‐nitrotyrosine (3‐NT) and nitrite (NO2−). Results We found rHuEPO to be a potent scavenger of HO˙ (kr = 1.03–1.66 × 1011 m−1 s−1) with the capacity to inhibit Fenton chemistry through catalytic iron chelation. Its ability to scavenge DPPH˙ and ROO˙ was also superior compared to other more conventional antioxidants. Hypoxia was associated with a rise in arterial EPO and free radical‐mediated reduction in nitric oxide, indicative of oxidative–nitrosative stress. The latter was confirmed by an increased systemic formation of A˙−, PBN‐OR, 3‐NT and corresponding loss of NO2− (P < 0.05 vs. normoxia). The erythropoietic and oxidative–nitrosative stress responses were consistently related (r = −0.52 to 0.68, P < 0.05). Conclusion These findings demonstrate that EPO has the capacity to act as a biological antioxidant and provide a mechanistic basis for its reported cytoprotective benefits within the clinical setting.
    May 23, 2014   doi: 10.1111/apha.12313   open full text
  • Truncated splice variant PGC‐1α4 is not associated with exercise‐induced human muscle hypertrophy.
    T. R. Lundberg, R. Fernandez‐Gonzalo, J. Norrbom, H. Fischer, P. A. Tesch, T. Gustafsson.
    Acta Physiologica. May 21, 2014
    Introduction A truncated PGC‐1α splice variant (PGC‐1α4) has been implicated in the regulation of resistance exercise (RE)‐induced muscle hypertrophy, and basal expression levels said to be augmented in response to concurrent aerobic (AE) and RE training. Aim The current study investigated human muscle truncated and non‐truncated PGC‐1α transcripts in response to both acute and chronic RE, and with or without preceding AE (AE+RE). Methods Ten men performed 5 weeks of unilateral AE+RE and RE training. Before (untrained) and after (trained) this intervention, PGC‐1α transcripts were assessed in vastus lateralis muscle biopsies obtained before and 3 h after acute RE, with or without preceding AE. Additionally, samples were collected 72 h after the last exercise bout of the training programme. Results The truncated splice variant increased (P < 0.05) its expression after acute exercise regardless of mode. However, the expression was greater (P < 0.05) after AE+RE than RE. Other PGC‐1α transcripts showed similar response. Truncated transcripts originated from both the alternative and proximal promoter, and AE+RE increased PGC‐1α expression from both promoter sites. RE induced transcripts from the alternative promoter only. PGC‐1α expressions after acute exercise were comparable across isoforms in both untrained and trained muscle. Steady‐state levels of isoforms were unchanged after 5‐week training (P > 0.05). Exercise‐induced expression of PGC‐1α variants did not correlate with changes in muscle size or strength (P > 0.05). Conclusion Our results do not support the view that truncated PGC‐1α coordinates exercise‐induced hypertrophy in human skeletal muscle. Rather, all PGC‐1α isoforms appear to be regulated transiently in response to acute exercise and regardless of mode.
    May 21, 2014   doi: 10.1111/apha.12310   open full text
  • MicroRNAs: potential therapeutic targets in diabetic complications of the cardiovascular and renal systems.
    Miriam Frankenthal Figueira, Gustavo Monnerat‐Cahli, Emiliano Medei, Adriana Bastos Carvalho, Marcelo Marcos Morales, Marcelo Einicker Lamas, Rodrigo Nunes da Fonseca, Jackson Souza‐Menezes.
    Acta Physiologica. May 19, 2014
    Diabetes mellitus is a serious health problem that can lead to several pathologic complications in numerous organs and tissues. The most important and most prevalent organs affected by this disease are the heart and the kidneys and these complications are the major causes of death in patients with diabetes. MicroRNAs (miRNAs), short non‐coding RNAs, have been found to be functionally important in the regulation of several pathologic processes and they are emerging as an important therapeutic tool to avoid the complications of diabetes mellitus. This review summarizes the knowledge on the effects of miRNAs in diabetes. The use of miRNAs in diabetes from a clinical perspective is also discussed, focusing on their potential role to repair cardiovascular and renal complications. This article is protected by copyright. All rights reserved.
    May 19, 2014   doi: 10.1111/apha.12316   open full text
  • Contraction‐evoked vasodilation and functional hyperaemia are compromised in branching skeletal muscle arterioles of young pre‐diabetic mice.
    N. M. Novielli, D. N. Jackson.
    Acta Physiologica. May 16, 2014
    Aim To investigate the effects of pre‐diabetes on microvascular network function in contracting skeletal muscle. We hypothesized that pre‐diabetes compromises contraction‐evoked vasodilation of branching second‐order (2A), third‐order (3A) and fourth‐order (4A) arterioles, where distal arterioles would be affected the greatest. Methods Intravital video microscopy was used to measure arteriolar diameter (in 2A, 3A and 4A) and blood flow (in 2A and 3A) changes to electrical field stimulation of the gluteus maximus muscle in pre‐diabetic (The Pound Mouse, PD) and control (c57bl6, CTRL) mice. Results Baseline diameter and blood flow were similar between groups (2A: ~20 μm, 3A: ~14 μm and 4A: ~8 μm; 2A: ~1 nL s−1 and 3A: ~0.5 nL s−1). Single tetanic contraction (100 Hz; 200, 400, 800 ms duration) evoked rapid‐onset vasodilation (ROV) and blood flow responses that were blunted by ~50% and up to 81%, respectively, in PD vs. CTRL (P < 0.05). The magnitude of ROV was up to 2‐fold greater at distal arterioles (3A and 4A) vs. proximal arterioles (2A) in CTRL; however, in PD, ROV of only 4A was greater than 2A (P < 0.05). Rhythmic contraction (2 and 8 Hz, 30 s) evoked vasodilatory and blood flow responses that were also attenuated by ~50% and up to 71%, respectively, in PD vs. CTRL (P < 0.05). The magnitude of vasodilatory responses to rhythmic contraction was also up to 2.5‐fold greater at 4A vs. 2A in CTRL; however spatial differences in vasodilation across arteriolar branch orders was disrupted in PD. Conclusions Arteriolar dysregulation in pre‐diabetes causes deficits in contraction‐evoked dilation and blood flow, where greatest deficits occur at distal arterioles.
    May 16, 2014   doi: 10.1111/apha.12297   open full text
  • Bile deficiency induces changes in intestinal Cl− and HCO3− secretions in mice.
    P. Song, Y. Du, W. Song, X. Liu, L. Hong, H. Li, H. Xie, L. Zhou, B. Tuo, S. Zheng.
    Acta Physiologica. May 16, 2014
    Aims Biliary tract obstruction is a common clinical lesion. However, the effect of biliary tract obstruction on intestinal secretion is poorly understood. In this study, we made an investigation on intestinal HCO3− and Cl− secretions in an experimental model of murine biliary duct ligation. Methods Murine intestinal mucosal HCO3− and Cl− secretions were examined in vitro in Ussing chambers by pH‐stat and short‐circuit current (Isc) techniques. The mRNA and protein expressions of the cystic fibrosis transmembrane conductance regulator (CFTR) and the Na+–K+–2Cl− cotransporter (NKCC1) were analysed by real‐time PCR, western blot and immunohistochemistry. Results Basal Cl− secretion and forskolin‐stimulated duodenal and jejunal mucosal HCO3− and Cl− secretions in mice with common biliary duct ligation were markedly elevated, compared with controls (P < 0.05 and P < 0.01). Further experiments showed that basal Cl− secretion and forskolin‐stimulated duodenal and jejunal mucosal HCO3− and Cl− secretions in mice with external bile drainage were also markedly elevated. CFTRinh‐172 inhibited forskolin‐stimulated HCO3− and Cl− secretions. The mRNA and protein expression levels of CFTR and NKCC1 in the intestinal mucosa with both biliary duct ligation and external bile drainage were markedly higher than those in controls (P < 0.001). Bile acid administration restored the changes in function and expression of CFTR and NKCC1 in the intestinal mucosa. Conclusion Bile deficiency in the intestine up‐regulates the expressions of intestinal mucosal CFTR and NKCC1 and enhances intestinal mucosal HCO3− and Cl− secretion capacity, which contributes to the understanding of intestinal physiological function for patients with biliary duct obstruction.
    May 16, 2014   doi: 10.1111/apha.12301   open full text
  • Alterations of calcium homeostasis in cultured rat astrocytes evoked by bioactive sphingolipids.
    Matjaž Stenovec, Saša Trkov, Marko Kreft, Robert Zorec.
    Acta Physiologica. May 13, 2014
    Aim In the brain, alterations in sphingolipid metabolism contribute to several neurologic disorders; however, their effect on astrocytes is largely unknown. Here, we identified bioactive sphingolipids that affect intracellular free calcium concentration ([Ca2+]i), mobility of peptidergic secretory vesicles, signaling pathways involved in alterations of calcium homeostasis and explored the relationship between the stimulus‐evoked increase in [Ca2+]i and attenuation of vesicle mobility. Methods Confocal time‐lapse images were acquired to explore [Ca2+]i signals, the mobility of fluorescently tagged peptidergic vesicles and the structural integrity of the microtubules and actin filaments before and after the addition of exogenous sphingolipids to astrocytes. Results Fingolimod (FTY720), a recently introduced therapeutic for multiple sclerosis, and sphingosine, a releasable constituent of membrane sphingolipids, evoked long‐lasting increases in [Ca2+]i in the presence and absence of extracellular Ca2+; the evoked responses were diminished in the absence of extracellular Ca2+. Activation of phospholipase C and inositol‐1,4,5‐triphosphate receptors was necessary and sufficient to evoke increases in [Ca2+]i as revealed by the pharmacologic inhibitors; Ca2+ flux from the extracellular space intensified these responses several fold. The lipid‐evoked increases in [Ca2+]i coincided with the attenuated vesicle mobility. High and positive correlation between increase in [Ca2+]i and decrease in peptidergic vesicle mobility was confirmed independently in astrocytes exposed to evoked, transient Ca2+ signaling triggered by purinergic and glutamatergic stimulation. Conclusion Exogenously added cell‐permeable sphingosine‐like lipids exert complex, Ca2+‐dependent effects on astrocytes and likely alter their homeostatic function in vivo. This article is protected by copyright. All rights reserved.
    May 13, 2014   doi: 10.1111/apha.12314   open full text
  • L‐type calcium channels in sympathetic α3β2‐nAChR‐mediated cerebral nitrergic neurogenic vasodilation.
    Celeste Yin‐Chieh Wu, Reggie Hui‐Chao Lee, Po‐Yi Chen, Andy Po‐Yi Tsai, Mei‐Fang Chen, Jon‐Son Kuo, Tony Jer‐Fu Lee.
    Acta Physiologica. May 13, 2014
    Aim Nicotine stimulation of α3β2‐nicotinic acetylcholine receptors (α3β2‐nAChRs) located on sympathetic nerves innervating basilar arteries causes calcium‐dependent norepinephrine release, leading to activation of parasympathetic nitrergic nerves and dilation of basilar arteries. This study aimed to investigate the major subtype of calcium channels located on cerebral perivascular sympathetic nerves, which is involved in nicotine‐induced α3β2‐nAChR‐mediated nitrergic vasodilation in basilar arteries. Methods Nicotine‐ and transmural nerve stimulation (TNS)‐induced dilation of isolated porcine basilar arteries was examined using in vitro tissue bath. Nicotine‐induced calcium‐influx, norepinephrine‐release, and inward‐currents were evaluated in rat superior cervical ganglion (SCG) neurons, perivascular sympathetic nerves of porcine basilar arteries, and α3β2‐nAChRs‐expressing oocytes, respectively. mRNA and protein expression of Cav1.2‐ and Cav1.3‐channels were detected by RT‐PCR, Western blotting, and immunohistochemistry. Results Nicotine‐induced vasodilation was not affected by ω‐agatoxin TK (selective P/Q‐type calcium‐channel blocker) or ω‐conotoxin GVIA (N‐type calcium‐channel blocker). The vasodilation, however, was inhibited by nicardipine (L‐type calcium‐channel blocker) in concentrations which did not affect TNS‐induced vasodilation, suggesting the specific blockade. Nicardipine concentration‐dependently inhibited nicotine‐induced calcium‐influx in rat SCG neurons and reduced nicotine‐induced norepinephrine release from perivascular sympathetic nerves of porcine basilar arteries. Nicardipine (10 μM), which significantly blocked nicotine‐induced vasorelaxation by 70 %, did not appreciably affect nicotine‐induced inward currents in α3β2‐nAChRs‐expressing oocytes. Furthermore, the mRNAs and proteins of Cav1.2 and Cav1.3 channels were expressed in porcine SCG and perivascular nerve terminals. Conclusion The sympathetic neuronal calcium‐influx through L‐type calcium‐channels is modulated by α3β2‐nAChRs. This calcium‐influx causes norepinephrine release, initiating sympathetic‐parasympathetic (axo‐axonal) interaction‐induced nitrergic dilation of porcine basilar arteries. This article is protected by copyright. All rights reserved.
    May 13, 2014   doi: 10.1111/apha.12315   open full text
  • Function and evolution of vertebrate globins.
    Thorsten Burmester, Thomas Hankeln.
    Acta Physiologica. May 08, 2014
    Globins are heme‐proteins that bind O2 and thus play an important role in the animal's respiration and oxidative energy production. However, globins may also have other functions such as the decomposition or production of NO, the detoxification of reactive oxygen species, or intracellular signalling. In addition to the well‐investigated haemoglobins and myoglobins, genome sequence analyses have led to the identification of six further globin types in vertebrates: androglobin, cytoglobin, globin E, globin X, globin Y and neuroglobin. Here, we review the present state of knowledge on the functions, the taxonomic distribution and evolution of vertebrate globins, drawing conclusions about the functional changes underlying present‐day globin diversity. This article is protected by copyright. All rights reserved.
    May 08, 2014   doi: 10.1111/apha.12312   open full text
  • Quantification of skeletal muscle mitochondrial function by 31P magnetic resonance spectroscopy techniques: a quantitative review.
    Graham J Kemp, Raja Elina Ahmad, Klaas Nicolay, Jeanine J Prompers.
    Acta Physiologica. April 28, 2014
    Magnetic resonance spectroscopy (MRS) can give information about cellular metabolism in vivo which is difficult to obtain in other ways. In skeletal muscle, noninvasive 31P MRS measurements of the post‐exercise recovery kinetics of pH, [PCr], [Pi] and [ADP] contain valuable information about muscle mitochondrial function and cellular pH homeostasis in vivo, but quantitative interpretation depends on understanding the underlying physiology. Here, by giving examples of the analysis of 31P MRS recovery data, by some simple computational simulation, and by extensively comparing data from published studies using both 31P MRS and invasive direct measurements of muscle O2 consumption in a common analytical framework, we consider what can be learnt quantitatively about mitochondrial metabolism in skeletal muscle using MRS‐based methodology. We explore some technical and conceptual limitations of current methods, and point out some aspects of the physiology which are still incompletely understood. This article is protected by copyright. All rights reserved.
    April 28, 2014   doi: 10.1111/apha.12307   open full text
  • Fatty acids and cardiac disease: Fuel carrying a message.
    Marc Bilsen, Anna Planavila.
    Acta Physiologica. April 28, 2014
    From the viewpoint of the prevention of cardiovascular disease (CVD) burden, there has been a continuous interest in the detrimental effects of the Western‐type high‐fat diet for more than half a century. More recently, this general view has been subject to change as epidemiological studies showed that replacing fat by carbohydrate may even be worse and that various polyunsaturated fatty acids (FA) have beneficial rather than detrimental effects on CVD outcome. At the same time advances in lipid biology have provided insight into the mechanisms by which the different lipid components of the Western diet affect the cardiovascular system. In fact, this still is a rapidly growing field of research and in recent years novel FA derivatives and FA receptors have been discovered. This includes fish‐oil derived FA‐derivatives with anti‐inflammatory properties, the so‐called resolvins, and various G‐protein coupled receptors that recognize FA as ligands. In the present review we will extensively discuss the role of FA and their metabolites on cardiac disease, with special emphasis on the role of the different saturated and polyunsaturated FA and their respective metabolites in cellular signal transduction and the possible implications for the development of cardiac hypertrophy and cardiac failure This article is protected by copyright. All rights reserved.
    April 28, 2014   doi: 10.1111/apha.12308   open full text
  • L‐type Ca2+ channel current characteristics are preserved in rat tail artery myocytes after one‐day storage.
    P. Mugnai, M. Durante, G. Sgaragli, S. Saponara, G. Paliuri, S. Bova, F. Fusi.
    Acta Physiologica. April 23, 2014
    Aim To develop a cheap and simple method of storing for 24‐h vascular tissue and single myocytes while preserving therein the biophysical and pharmacological characteristics of L‐type Ca2+ channels and contractile activity. Methods Rings or vascular smooth muscle cells obtained from the rat tail main artery were used either freshly (R0h and VSMC0h) or stored for 24 h (R24h and VSMC24h) at 4 °C, to record whole‐cell L‐type Ca2+ currents (ICa(L)) or measure contractile responses. Results R0h/VSMC0h and R24h/VSMC24h comparably contracted when stimulated with phenylephrine, high KCl or ATP. In both VSMC0h and VSMC24h, ICa(L) was identified and characterized as a stable inward current for at least 35 min; ICa(L) was comparably inhibited by the Ca2+ antagonists nifedipine, verapamil and diltiazem and increased by the Ca2+ channel agonist (S)‐(‐)‐Bay K 8644; current density and current–voltage relationships were similar; at more hyperpolarized holding potentials, ICa(L) intensity increased comparably; nifedipine shifted the steady‐state inactivation curve towards more negative potentials, while verapamil blocked ICa(L) in a frequency‐dependent manner and slowed down the rate of recovery from inactivation in a comparable way. Conclusion Findings show that smooth muscle contractile activity and the biophysical and pharmacological features of L‐type Ca2+ channels are similar in VSMC24h and VSMC0h. The fact that reproducible results were obtained in vascular myocytes up to 24 h after dissociation may facilitate vascular smooth muscle cell investigation by increasing throughput and reducing the number of animals required.
    April 23, 2014   doi: 10.1111/apha.12282   open full text
  • Changes in the activity and expression of protein phosphatase‐1 accompany the differential regulation of NHE3 before and after the onset of hypertension in spontaneously hypertensive rats.
    R. O. Crajoinas, T. D. Pessoa, M. V. Rodrigues, G. Malnic, A. C. C. Girardi.
    Acta Physiologica. April 23, 2014
    Aim The Na+/H+ exchanger NHE3 activity decreases in the proximal tubule of spontaneously hypertensive rats (SHRs) as blood pressure increases, and this reduction is correlated with higher NHE3 phosphorylation levels at the PKA consensus site serine 552. This study tested the hypothesis that this lowered NHE3 activity is associated with an increase in PKA activity and expression, and/or a decrease in protein phosphatase‐1 (PP1) activity and expression. Methods Proximal tubule NHE3 activity was measured as the rate of bicarbonate reabsorption by stationary microperfusion. NHE3 phosphorylation and protein expression were determined by immunoblotting. PKA and PP1 activities were determined using specific substrates under optimal enzymatic conditions. Results The PKA activator, 6‐MB‐cAMP, increased the phosphorylation levels of NHE3 at serine 552 in the renal cortex; this increase happens to a much greater extent in young pre‐hypertensive SHRs (Y‐SHRs) compared to adult SHRs with established hypertension (A‐SHRs). Likewise, the inhibitory effect of 6‐MB‐cAMP on NHE3 transport activity was much more pronounced in the proximal tubules of Y‐SHRs than in those of A‐SHRs. Renal cortical activity of PKA was not significantly different between Y‐SHRs and A‐SHRs. On the other hand, Y‐SHRs exhibited higher protein phosphatase 1 (PP1) activity, and their expression of the PP1 catalytic subunit PP1α in the renal cortex was also higher than in A‐SHRs. Conclusion Collectively, these results support the idea that the lower NHE3 transport activity and higher phosphorylation occurring after the development of hypertension in SHRs are due, at least in part, to reduced PP1‐mediated dephosphorylation of NHE3 at serine 552.
    April 23, 2014   doi: 10.1111/apha.12288   open full text
  • Associations of subjective vitality with DNA damage, cardiovascular risk factors and physical performance.
    S. Maynard, G. Keijzers, Å.‐M. Hansen, M. Osler, D. Molbo, L. Bendix, P. Møller, S. Loft, M. Moreno‐Villanueva, A. Bürkle, C. P. Hvitby, S. H. Schurman, T. Stevnsner, L. J. Rasmussen, K. Avlund, V. A. Bohr.
    Acta Physiologica. April 23, 2014
    Aim To examine associations of DNA damage, cardiovascular risk factors and physical performance with vitality, in middle‐aged men. We also sought to elucidate underlying factors of physical performance by comparing physical performance parameters to DNA damage parameters and cardiovascular risk factors. Methods We studied 2487 participants from the Metropolit cohort of 11 532 men born in 1953 in the Copenhagen Metropolitan area. The vitality level was estimated using the SF‐36 vitality scale. Cardiovascular risk factors were determined by body mass index (BMI), and haematological biochemistry tests obtained from non‐fasting participants. DNA damage parameters were measured in peripheral blood mononuclear cells (PBMCs) from as many participants as possible from a representative subset of 207 participants. Results Vitality was inversely associated with spontaneous DNA breaks (measured by comet assay) (P = 0.046) and BMI (P = 0.002), and positively associated with all of the physical performance parameters (all P < 0.001). Also, we found several associations between physical performance parameters and cardiovascular risk factors. In addition, the load of short telomeres was inversely associated with maximum jump force (P = 0.018), with lowered significance after exclusion of either arthritis sufferers (P = 0.035) or smokers (P = 0.031). Conclusion Here, we show that self‐reported vitality is associated with DNA breaks, BMI and objective (measured) physical performance in a cohort of middle‐aged men. Several other associations in this study verify clinical observations in medical practice. In addition, the load of short telomeres may be linked to peak performance in certain musculoskeletal activities.
    April 23, 2014   doi: 10.1111/apha.12296   open full text
  • Influence of age on leptin induced skeletal muscle signalling.
    A. Guadalupe‐Grau, S. Larsen, B. Guerra, J. A. L. Calbet, F. Dela, J. W. Helge.
    Acta Physiologica. April 18, 2014
    Aim Age associated fat mass accumulation could be because of dysregulation of leptin signalling in skeletal muscle. Thus, we investigated total protein expression and phosphorylation levels of the long isoform of the leptin receptor (OB‐Rb), and leptin signalling through janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3), insulin receptor substrate 1 (IRS‐1), AMP‐activated protein kinase (AMPK) and acetyl‐coenzyme A carboxylase (ACC), combined with the leptin signalling inhibitors suppressor of cytokine signalling 3 (SOCS3) and protein tyrosine phosphatase 1B (PTP1B) in human skeletal muscle of different age. Methods Vastus lateralis muscle biopsies were obtained from 39 men matched for BMI < 30 kg m−2 and separated into three groups: 13 young (Y, 24 ± 4 years); 14 middle aged (MA, 44 ± 5 years) and 12 aged (A, 58 ± 8 years) subjects. Results Whole body fat percentage and plasma leptin were higher (P < 0.05), whereas lean mass, plasma free testosterone and total testosterone were lower (P < 0.05) in A compared to Y. Skeletal muscle OB‐Rb (170 KDa) protein expression and pTyr1141‐OB‐R170 were comparable between groups, whereas pTyr985‐OB‐R170 was lower in A compared to Y (P < 0.05). pSTAT3 levels tended (P = 0.09) to be lower (50%) in A compared to Y. In A, muscle PTP1B was greater and IRS‐1 lower than Y and MA respectively (P < 0.05). PTyr612‐IRS‐1 tended to be lower in A than in Y (P = 0.09). Suppressor of cytokine signalling 3 (SOCS3) protein expression, pJAK2, pSer1101‐IRS‐1, pAMPKα and pACCβ were similar between groups. Conclusion Age is associated with dysregulation of the leptin signalling and increased PTP1B protein expression in skeletal muscle.
    April 18, 2014   doi: 10.1111/apha.12273   open full text
  • Activation of histamine H1 receptors in the nucleus tractus solitarii attenuates cardiac baroreceptor reflex function in rats.
    M. Takagishi, S. S. Gouraud, M. E. R. Bhuiyan, A. Kohsaka, M. Maeda, H. Waki.
    Acta Physiologica. April 18, 2014
    Aim The nucleus tractus solitarii (NTS) is a central brainstem structure that plays an important role in regulating cardiovascular homeostasis. In this study, we examined whether H1 receptors in the NTS can control the baroreceptor reflex function by modulating synaptic transmission. Methods Cardiac baroreceptor reflex function was assessed before and after the microinjection of 2‐pyridylethylamine (10–25 nmol), a histamine H1 receptor‐specific agonist, into the NTS of urethane‐anaesthetized Wistar rats. The cardiovascular responses induced by l‐glutamate microinjection into the NTS were also examined before and after the NTS administration of 2‐pyridylethylamine. Results Nucleus tractus solitarii microinjections of 2‐pyridylethylamine significantly inhibited the gain of the cardiac baroreceptor reflex and bradycardiac/depressor responses induced by l‐glutamate microinjection into the NTS. These findings suggest that histamine H1 receptors regulate the cardiac baroreceptor reflex in a post‐synaptic manner to inhibit barosensitive NTS neurons. Conclusion Taken together with our previous findings, the present results provide further evidence that histamine may play a role within the NTS in regulating cardiovascular homeostasis.
    April 18, 2014   doi: 10.1111/apha.12278   open full text
  • The role of nitric oxide in the cardiovascular response to chronic and acute hypoxia in White Leghorn chicken (Gallus domesticus).
    N. K. Iversen, T. Wang, E. Baatrup, D. A. Crossley.
    Acta Physiologica. April 18, 2014
    Aim Prenatal hypoxia due to placental insufficiency results in deleterious phenotypes and compensatory mechanisms including increased sympathetic tone. Utilizing the embryonic chicken model, we investigated (i) changes in nitric oxide (NO)‐mediated tone in response to chronic hypoxic development and (ii) the in vivo role of NO‐mediated tone during acute hypoxic exposure, which has not been previously studied. We hypothesized that NO tone on the cardiovascular system would be unaffected by chronic hypoxic incubation in White Leghorn chicken (Gallus domesticus) embryos. Methods We measured arterial pressure, heart rate and femoral blood flow (via a Doppler flow probe) in response to acute hypoxia (10% O2) and pharmacological manipulations in normoxic‐ and hypoxic (15% O2)‐incubated embryos. This was performed at 70 and 90% of total incubation time (21 days). At 70% of incubation (day 15), blood volume and chorioallantoic membrane development are maximal; 90% of incubation (day 19) is 1 day prior to lung ventilation. Results Acute hypoxic exposure decreased femoral flow in both 90% groups, but increased femoral artery resistance in the hypoxic group. NO tone increased during development, but was not affected by hypoxic incubation. Inhibition of NO production by L‐NAME (100 mg kg−1) revealed that NO plays a significant role in the flow response to hypoxia. Conclusion Chronic hypoxic incubation has no effect on cardiovascular NO tone during White Leghorn chicken development. In the intact animal, NO function during acute hypoxic stress is suppressed by hypoxic incubation, indicating that chronic hypoxic stress dampens the NO contribution.
    April 18, 2014   doi: 10.1111/apha.12286   open full text
  • Assessment of human baroreflex function using carotid ultrasonography: what have we learnt?
    Chloe E Taylor, Christopher K Willie, Philip N Ainslie, Yu‐Chieh Tzeng.
    Acta Physiologica. April 17, 2014
    The arterial baroreflex is critical to both short and long‐term regulation of blood pressure. However, human baroreflex research has been largely limited to the association between blood pressure and cardiac period (or heart rate) or indices of vascular sympathetic function. Over the past decade, emerging techniques based on carotid ultrasound imaging have allowed new means of understanding and measuring the baroreflex. In this review, we describe the assessment of the mechanical and neural components of the baroreflex through the use of carotid ultrasound imaging. The mechanical component refers to the change in carotid artery diameter in response to changes in arterial pressure, and the neural component refers to the change in R‐R interval (cardiac baroreflex) or muscle sympathetic nerve activity (sympathetic baroreflex) in response to this barosensory vessel stretch. The key analytical concepts and techniques are discussed, with a focus on the assessment of baroreflex sensitivity via the modified Oxford method. We illustrate how the application of carotid ultrasound imaging has contributed to a greater understanding of baroreflex physiology in humans, covering topics such as ageing and diurnal variation, and physiological challenges including exercise, postural changes and mental stress. This article is protected by copyright. All rights reserved.
    April 17, 2014   doi: 10.1111/apha.12302   open full text
  • Three‐dimensional reconstruction of the human skeletal muscle mitochondrial network as a tool to assess mitochondrial content and structural organization.
    R. Dahl, S. Larsen, T. L. Dohlmann, K. Qvortrup, J. W. Helge, F. Dela, C. Prats.
    Acta Physiologica. April 15, 2014
    Aim Mitochondria undergo continuous changes in shape as result of complex fusion and fission processes. The physiological relevance of mitochondrial dynamics is still unclear. In the field of mitochondria bioenergetics, there is a need of tools to assess cell mitochondrial content. To develop a method to visualize mitochondrial networks in high resolution and assess mitochondrial volume. Methods Confocal fluorescence microscopy imaging of mitochondrial network stains in human vastus lateralis single muscle fibres and focused ion beam/ scanning electron microscopy (FIB/SEM) imaging, combined with 3D reconstruction was used as a tool to analyse mitochondrial morphology and measure mitochondrial fractional volume. Results Most type I and type II muscle fibres have tubular highly interconnected profusion mitochondria, which are thicker and more structured in type I muscle fibres (Fig. 1). In some muscle fibres, profission‐isolated ellipsoid‐shaped mitochondria were observed. Mitochondrial volume was significantly higher in type I muscle fibres and showed no correlation with any of the investigated molecular and biochemical mitochondrial measurements (Fig. 2). Three‐dimensional reconstruction of FIB/SEM data sets shows that some subsarcolemmal mitochondria are physically interconnected with some intermyofibrillar mitochondria (Fig. 3). Conclusion Two microscopy methods to visualize skeletal muscle mitochondrial networks in 3D are described and can be used as tools to investigate mitochondrial dynamics in response to life‐style interventions and/or in certain pathologies. Our results question the classification of mitochondria into subsarcolemmal and intermyofibrillar pools, as they are physically interconnected.
    April 15, 2014   doi: 10.1111/apha.12289   open full text
  • Cardiovascular and metabolic responses to tap water ingestion in young humans: does the water temperature matter?
    M. Girona, E. K. Grasser, A. G. Dulloo, J. P. Montani.
    Acta Physiologica. April 15, 2014
    Aim Drinking water induces short‐term cardiovascular and metabolic changes. These effects are considered to be triggered by gastric distension and osmotic factors, but little is known about the influence of water temperature. Methods We determined, in a randomized crossover study, the acute cardiovascular and metabolic responses to 500 mL of tap water at 3 °C (cold), 22 °C (room) and 37 °C (body) in 12 young humans to ascertain an effect of water temperature. We measured continuous beat‐to‐beat haemodynamics, skin blood flux with laser‐Doppler flowmetry and resting energy expenditure by indirect calorimetry starting with a 30‐min baseline followed by a 4‐min drink period and a subsequent 90‐min post‐drink observation. Results Ingestion of cold‐ and room‐tempered water led to decreased heart rate (P < 0.01) and double product (P < 0.01), and increased stroke volume (P < 0.05); these effects were not observed with body‐tempered water. Drinking cold‐ and room‐, but not body‐tempered water, led to increased high frequency power of heart rate variability (P < 0.05) and baroreflex sensitivity (P < 0.05). Cold‐ and room‐tempered water increased energy expenditure over 90 min by 2.9% (P < 0.05) and 2.3% (ns), respectively, accompanied by a diminished skin blood flux (P < 0.01), thereby suggesting that both small increases in heat production together with decreased heat loss contribute to warming up the ingested water to intra‐abdominal temperature levels. Conclusions Overall, ingestion of cold‐ and room‐, but not body‐tempered water reduced the workload to the heart through a reduction in heart rate and double product which could be mediated by an augmented cardiac vagal tone.
    April 15, 2014   doi: 10.1111/apha.12290   open full text
  • Ca2+ signals, NAADP and Two Pore Channels: Role in Cellular Differentiation.
    John Parrington, Ruth Tunn.
    Acta Physiologica. April 07, 2014
    Ca2+ signals regulate a wide range of physiological processes. Intracellular Ca2+ stores can be mobilized in response to extracellular stimuli via a range of signal transduction mechanisms, often involving recruitment of diffusible second messenger molecules. The Ca2+ mobilizing messengers InsP3 and cADPR release Ca2+ from the endoplasmic reticulum via the InsP3 and ryanodine receptors, respectively, while a third messenger, NAADP, releases Ca2+ from acidic endosomes and lysosomes. Bidirectional communication between the ER and acidic organelles may have functional relevance for endolysosomal function as well as for the generation of Ca2+ signals. The two‐pore channels (TPCs), are currently strong candidates for being key components of NAADP‐regulated Ca2+ channels. Ca2+ signals have been shown to play important roles in differentiation; however, much remains to be established about the exact signalling mechanisms involved. The investigation of the role of NAADP and TPCs in differentiation is still at an early stage but recent studies have suggested that they are important mediators of differentiation of neurons, skeletal muscle cells, and osteoclasts. NAADP signals and TPCs have also been implicated in autophagy, an important process in differentiation. Further studies will be required to identify the precise mechanism of TPC action and their link with NAADP signalling, as well as relating this to their roles in differentiation and other key processes in the cell and organism. This article is protected by copyright. All rights reserved.
    April 07, 2014   doi: 10.1111/apha.12298   open full text
  • Pathophysiology and Potential Treatments of Pulmonary Hypertension due to Systolic Left Heart Failure.
    Jakob Lundgren, Göran Rådegran.
    Acta Physiologica. April 05, 2014
    Pulmonary hypertension (PH) due to left heart failure is becoming increasingly prevalent, and is associated with poor outcome. The precise pathophysiological mechanisms behind PH due to left heart failure are, however, still unclear. In its early course, PH is caused by elevated left ventricular filling pressures, without pulmonary vessel abnormalities. Conventional treatment for heart failure may partly reverse such passive PH by optimizing left ventricular function. However, if elevated pulmonary pressures persists, endothelial damage, excessive vasoconstriction and structural changes in the pulmonary vasculature may occur. There is, at present, no recommended medical treatment for this active component of PH due to left heart failure. However, as the vascular changes in PH due to left heart failure may be similar to those in pulmonary arterial hypertension (PAH), a selected group of these patients may benefit from PAH treatment targeting the endothelin, nitric oxide or prostacyclin pathways. Such potent pulmonary vasodilators could, however, be detrimental in patients with left heart failure without pulmonary vascular pathology, as selective pulmonary vasodilatation may lead to further congestion in the pulmonary circuit, resulting in pulmonary oedema. The use of PAH therapies is therefore, currently not recommended, and would require the selection of suitable patients based on the underlying causes of the disease, and careful monitoring of their progress. The present review focuses on: i. the pathophysiology behind PH resulting from systolic left heart failure and: ii. the current evidence for medical treatment of this condition, especially the role of PAH‐targeted therapies in systolic left heart failure. This article is protected by copyright. All rights reserved.
    April 05, 2014   doi: 10.1111/apha.12295   open full text
  • Acylated and unacylated ghrelin inhibit doxorubicin‐induced apoptosis in skeletal muscle.
    A. P. Yu, X. M. Pei, T. K. Sin, S. P. Yip, B. Y. Yung, L. W. Chan, C. S. Wong, P. M. Siu.
    Acta Physiologica. April 02, 2014
    Aim Doxorubicin, a potent chemotherapeutic drug, has been demonstrated previously as an inducer of apoptosis in muscle cells. Extensive induction of apoptosis may cause excessive loss of muscle cells and subsequent functional decline in skeletal muscle. This study examined the effects of acylated ghrelin, a potential agent for treating cancer cachexia, on inhibiting apoptotic signalling in doxorubicin‐treated skeletal muscle. Unacylated ghrelin, a form of ghrelin that does not bind to GHSR‐1a, is also employed in this study to examine the GHSR‐1a signalling dependency of the effects of ghrelin. Methods Adult C57BL/6 mice were randomly assigned to saline control (CON), doxorubicin (DOX), doxorubicin with treatment of acylated ghrelin (DOX+Acylated Ghrelin) and doxorubicin with treatment of unacylated ghrelin (DOX+Unacylated Ghrelin). Mice in all groups that involved DOX were intraperitoneally injected with 15 mg of doxorubicin per kg body weight, whereas mice in CON group received saline as placebo. Gastrocnemius muscle tissues were harvested after the experimental period for analysis. Results The elevation of apoptotic DNA fragmentation and number of TUNEL‐positive nuclei were accompanied with the upregulation of Bax in muscle after exposure to doxorubicin, but all these changes were neither seen in the muscle treated with acylated ghrelin nor unacylated ghrelin after doxorubicin exposure. Protein abundances of autophagic markers including LC3 II‐to‐LC3 I ratio, Atg12‐5 complex, Atg5 and Beclin‐1 were not altered by doxorubicin but were upregulated by the treatment of either acylated or unacyated ghrelin. Histological analysis revealed that the amount of centronucleated myofibres was elevated in doxorubicin‐treated muscle while muscle of others groups showed normal histology. Conclusions Collectively, our data demonstrated that acylated ghrelin administration suppresses the doxorubicin‐induced activation of apoptosis and enhances the cellular signalling of autophagy. The treatment of unacylated ghrelin has similar effects as acylated ghrelin on apoptotic and autophagic signalling, suggesting that the effects of ghrelin are probably mediated through a signalling pathway that is independent of GHSR‐1a. These findings were consistent with the hypothesis that acylated ghrelin inhibits doxorubicin‐induced upregulation of apoptosis in skeletal muscle while treatment of unacylated ghrelin can achieve similar effects as the treatment of acylated ghrelin. The inhibition of apoptosis and enhancement of autophagy induced by acylated and unacylated ghrelin might exert myoprotective effects on doxorubicin‐induced toxicity in skeletal muscle.
    April 02, 2014   doi: 10.1111/apha.12263   open full text
  • High‐intensity interval training alters ATP pathway flux during maximal muscle contractions in humans.
    R. G. Larsen, L. Maynard, J. A. Kent.
    Acta Physiologica. April 02, 2014
    Aim High‐intensity interval training (HIT) results in potent metabolic adaptations in skeletal muscle; however, little is known about the influence of these adaptations on energetics in vivo. We used magnetic resonance spectroscopy to examine the effects of HIT on ATP synthesis from net PCr breakdown (ATPCK), oxidative phosphorylation (ATPOX) and non‐oxidative glycolysis (ATPGLY) in vivo in vastus lateralis during a 24‐s maximal voluntary contraction (MVC). Methods Eight young men performed 6 sessions of repeated, 30‐s ‘all‐out’ sprints on a cycle ergometer; measures of muscle energetics were obtained at baseline and after the first and sixth sessions. Results Training increased peak oxygen consumption (35.8 ± 1.4 to 39.3 ± 1.6 mL min−1 kg−1, P = 0.01) and exercise capacity (217.0 ± 11.0 to 230.5 ± 11.7 W, P = 0.04) on the ergometer, with no effects on total ATP production or force–time integral during the MVC. While ATP production by each pathway was unchanged after the first session, 6 sessions increased the relative contribution of ATPOX (from 31 ± 2 to 39 ± 2% of total ATP turnover, P < 0.001) and lowered the relative contribution from both ATPCK (49 ± 2 to 44 ± 1%, P = 0.004) and ATPGLY (20 ± 2 to 17 ± 1%, P = 0.03). Conclusion These alterations to muscle ATP production in vivo indicate that brief, maximal contractions are performed with increased support of oxidative ATP synthesis and relatively less contribution from anaerobic ATP production following training. These results extend previous reports of molecular and cellular adaptations to HIT and show that 6 training sessions are sufficient to alter in vivo muscle energetics, which likely contributes to increased exercise capacity after short‐term HIT.
    April 02, 2014   doi: 10.1111/apha.12275   open full text
  • Time‐course effect of exercise‐induced muscle damage on localized muscle mechanical properties assessed using elastography.
    L. Lacourpaille, A. Nordez, F. Hug, A. Couturier, C. Dibie, G. Guilhem.
    Acta Physiologica. April 02, 2014
    Aim Changes in muscle stiffness after exercise‐induced muscle damage have been classically inferred from passive torque–angle curves. Elastographic techniques can be used to estimate the shear modulus of a localized muscular area. This study aimed to quantify the changes in shear elastic modulus in different regions of the elbow flexors after eccentric exercise and their relation to muscle length. Methods Shear elastic modulus and transverse relaxation time (T2) were measured in the biceps brachii and brachialis muscles of sixteen participants, before, 1 h, 48 h and 21 days after three sets of ten maximal isokinetic eccentric contractions performed at 120° s−1. Results The shear elastic modulus of the elbow flexors significantly increased 1 h (+46%; P = 0.005), with no significant change at 48 h and 21D, post‐exercise. In contrast, T2 was not modified at 1 h but significantly increased at 48 h (+15%; P < 0.05). The increase in shear elastic modulus was more pronounced at long muscle lengths and reached a similar extent in the different regions of the elbow flexors. The normalized hysteresis area of shear elastic modulus–length relationship for the biceps brachii increased 1 h post‐exercise (31%) in comparison with the pre‐exercise value (18%), but was not significantly altered after five stretching cycles (P = 0.63). Conclusion Our results show homogeneous changes in muscle shear elastic modulus within and between elbow flexors. The greater increase in shear elastic modulus observed at long muscle lengths suggests the putative involvement of both cross‐bridges number and titin in the modifications of muscle shear elastic modulus after damaging exercise.
    April 02, 2014   doi: 10.1111/apha.12272   open full text
  • Andrographolide inhibits HMGB1‐induced inflammatory responses in human umbilical vein endothelial cells and in murine polymicrobial sepsis.
    W. Lee, S. Ku, H. Yoo, K. Song, J. Bae.
    Acta Physiologica. March 24, 2014
    Aim Nuclear DNA‐binding protein high‐mobility group box 1 (HMGB1) protein acts as a late mediator of severe vascular inflammatory conditions, such as septic shock, upregulating pro‐inflammatory cytokines. Andrographolide (AG) is isolated from the plant of Andrographis paniculata and used as a folk medicine for treatment of viral infection, diarrhoea, dysentery and fever. However, the effect of AG on HMGB1‐induced inflammatory response has not been studied. Methods Firstly, we accessed this question by monitoring the effects of post‐treatment AG on lipopolysaccharide (LPS) and caecal ligation and puncture (CLP)‐mediated release of HMGB1 and HMGB1‐mediated regulation of pro‐inflammatory responses in human umbilical vein endothelial cells (HUVECs) and septic mice. Results Post‐treatment AG was found to suppress LPS‐mediated release of HMGB1 and HMGB1‐mediated cytoskeletal rearrangements. AG also inhibited HMGB1‐mediated hyperpermeability and leucocyte migration in septic mice. In addition, AG inhibited production of tumour necrosis factor‐α (TNF‐α) and activation of AKT, nuclear factor‐κB (NF‐κB) and extracellular‐regulated kinases (ERK) 1/2 by HMGB1 in HUVECs. AG also induced downregulation of CLP‐induced release of HMGB1, production of interleukin (IL) 1β/6/8 and mortality. Conclusion Collectively, these results suggest that AG may be regarded as a candidate therapeutic agent for the treatment of vascular inflammatory diseases via inhibition of the HMGB1 signalling pathway.
    March 24, 2014   doi: 10.1111/apha.12264   open full text
  • Changes in arterial function in a mouse model of human familial hypercholesterolaemia.
    O. Brinkmann, K. Schmerbach, U. J. F. Tietge, T. Dietrich, H. Guski, D. Linz, H. Kühn, A. Patzak, K. Wilfert.
    Acta Physiologica. March 24, 2014
    Aim Atherosclerosis is the most common cause of cardiovascular disease. The ApoB mouse is a model for human familial hypercholesterolaemia and has a lipoprotein profile similar to that of humans with atherosclerosis. Therefore, it is a suitable model to investigate the changes in vasoreactivity during atherogenesis. This study investigates contractile and dilatative properties of arteries in this model in relation to age. Methods Male ApoB mice and B6, wild‐type (WT), mice were examined at age four or 18 months. Isometric measurements of 2‐mm ring preparations of the aorta thoracica were performed using a wire myograph. Histological and biochemical methods served to determine atherosclerosis, lipid status and endothelial markers respectively. Results Morphometric analysis showed that all old ApoB mice had severe atherosclerosis in the aorta. Atherosclerotic alteration of the aorta of the ApoB mice coincided with a diminished vasodilatation to acetylcholine. The phenylephrine response was significantly attenuated already to the same degree in the non‐atherosclerotic aorta of the young ApoB mice as in the atherosclerotic aorta of the older ApoB mice. Serum parameters showed a rise in total cholesterol and triglycerides in the ApoB strain compared to WT mice. Soluble intercellular adhesion molecule (sICAM)‐1 and soluble vascular adhesion molecule (sVCAM)‐1 were increased in old compared to young ApoB mice. Conclusion The study shows that reduced acetylcholine‐induced dilatation is related to the presence of atherosclerosis in old ApoB mice. Remarkably, the impaired vessel reactivity to phenylephrine already in young ApoB mice indicates early changes in vascular function in this model.
    March 24, 2014   doi: 10.1111/apha.12262   open full text
  • Low‐intensity training increases peak arm VO2 by enhancing both convective and diffusive O2 delivery.
    R. Boushel, I. Ara, E. Gnaiger, J. W. Helge, J. González‐Alonso, T. Munck‐Andersen, H. Sondergaard, R. Damsgaard, G. Hall, B. Saltin, J. A. L. Calbet.
    Acta Physiologica. March 17, 2014
    Aim It is an ongoing discussion the extent to which oxygen delivery and oxygen extraction contribute to an increased muscle oxygen uptake during dynamic exercise. It has been proposed that local muscle factors including the capillary bed and mitochondrial oxidative capacity play a large role in prolonged low‐intensity training of a small muscle group when the cardiac output capacity is not directly limiting. The purpose of this study was to investigate the relative roles of circulatory and muscle metabolic mechanisms by which prolonged low‐intensity exercise training alters regional muscle VO2. Methods In nine healthy volunteers (seven males, two females), haemodynamic and metabolic responses to incremental arm cycling were measured by the Fick method and biopsy of the deltoid and triceps muscles before and after 42 days of skiing for 6 h day−1 at 60% max heart rate. Results Peak pulmonary VO2 during arm crank was unchanged after training (2.38 ± 0.19 vs. 2.18 ± 0.2 L min−1 pre‐training) yet arm VO2 (1.04 ± 0.08 vs. 0.83 ± 0.1 L min1, P < 0.05) and power output (137 ± 9 vs. 114 ± 10 Watts) were increased along with a higher arm blood flow (7.9 ± 0.5 vs. 6.8 ± 0.6 L min−1, P < 0.05) and expanded muscle capillary volume (76 ± 7 vs. 62 ± 4 mL, P < 0.05). Muscle O2 diffusion capacity (16.2 ± 1 vs. 12.5 ± 0.9 mL min−1 mHg−1, P < 0.05) and O2 extraction (68 ± 1 vs. 62 ± 1%, P < 0.05) were enhanced at a similar mean capillary transit time (569 ± 43 vs. 564 ± 31 ms) and P50 (35.8 ± 0.7 vs. 35 ± 0.8), whereas mitochondrial O2 flux capacity was unchanged (147 ± 6 mL kg min−1 vs. 146 ± 8 mL kg min−1). Conclusion The mechanisms underlying the increase in peak arm VO2 with prolonged low‐intensity training in previously untrained subjects are an increased convective O2 delivery specifically to the muscles of the arm combined with a larger capillary–muscle surface area that enhance diffusional O2 conductance, with no apparent role of mitochondrial respiratory capacity.
    March 17, 2014   doi: 10.1111/apha.12258   open full text
  • Impaired epicardial activation–repolarization coupling contributes to the proarrhythmic effects of hypokalaemia and dofetilide in guinea pig ventricles.
    O. E. Osadchii.
    Acta Physiologica. March 17, 2014
    Aim Activation–repolarization coupling refers to the inverse relationship between action potential duration and activation time in myocardial regions along the path of ventricular excitation. This study examined whether the activation–repolarization coupling plays a role in coordinating repolarization times between the right ventricular (RV) and left ventricular (LV) chambers, and if impaired coordination contributes to electrical instability produced by hypokalaemia or dofetilide, a blocker of the delayed rectifier K+ current. Methods In Langendorff‐perfused, isolated guinea pig hearts, six monophasic action potential recording electrodes were attached to RV and LV epicardium. Local activation time and action potential duration (APD90) were determined during spontaneous beating, regular pacing and extrasystolic excitation. Results In regularly beating hearts, the RV epicardial sites had longer APD90, but exhibited earlier activation times, as compared to LV sites, which minimized the interventricular difference in repolarization time. Upon extrasystolic stimulation, the APD90 was reduced to a greater extent in RV compared with LV, which translated to a reversed slope of APD90‐to‐activation time relationship, and increased spatial repolarization gradients. Hypokalaemia and dofetilide prolonged APD90, with the effect being greater in LV compared with RV. In hypokalaemic hearts, LV activation was delayed. These changes contributed to increased asynchrony in repolarization times in the LV and RV in both regular and extrasystolic beats, and enhanced susceptibility to tachyarrhythmia. Conclusion Impaired RV‐to‐LV activation–repolarization coupling is an important determinant of electrical instability in the setting of non‐uniformly prolonged epicardial APD90 or slowed interventricular conduction.
    March 17, 2014   doi: 10.1111/apha.12259   open full text
  • Endogenous α‐calcitonin‐gene‐related peptide promotes exercise‐induced, physiological heart hypertrophy in mice.
    B. Schuler, G. Rieger, M. Gubser, M. Arras, M. Gianella, O. Vogel, P. Jirkof, N. Cesarovic, J. Klohs, P. Jakob, M. Brock, T. A. Gorr, O. Baum, H. Hoppeler, V. Samillan‐Soto, M. Gassmann, J. A. Fischer, W. Born, J. Vogel.
    Acta Physiologica. March 13, 2014
    Aim It is unknown how the heart distinguishes various overloads, such as exercise or hypertension, causing either physiological or pathological hypertrophy. We hypothesize that alpha‐calcitonin‐gene‐related peptide (αCGRP), known to be released from contracting skeletal muscles, is key at this remodelling. Methods The hypertrophic effect of αCGRP was measured in vitro (cultured cardiac myocytes) and in vivo (magnetic resonance imaging) in mice. Exercise performance was assessed by determination of maximum oxygen consumption and time to exhaustion. Cardiac phenotype was defined by transcriptional analysis, cardiac histology and morphometry. Finally, we measured spontaneous activity, body fat content, blood volume, haemoglobin mass and skeletal muscle capillarization and fibre composition. Results While αCGRP exposure yielded larger cultured cardiac myocytes, exercise‐induced heart hypertrophy was completely abrogated by treatment with the peptide antagonist CGRP(8‐37). Exercise performance was attenuated in αCGRP−/− mice or CGRP(8‐37) treated wild‐type mice but improved in animals with higher density of cardiac CGRP receptors (CLR‐tg). Spontaneous activity, body fat content, blood volume, haemoglobin mass, muscle capillarization and fibre composition were unaffected, whereas heart index and ventricular myocyte volume were reduced in αCGRP−/− mice and elevated in CLR‐tg. Transcriptional changes seen in αCGRP−/− (but not CLR‐tg) hearts resembled maladaptive cardiac phenotype. Conclusions Alpha‐calcitonin‐gene‐related peptide released by skeletal muscles during exercise is a hitherto unrecognized effector directing the strained heart into physiological instead of pathological adaptation. Thus, αCGRP agonists might be beneficial in heart failure patients.
    March 13, 2014   doi: 10.1111/apha.12244   open full text
  • The effects of equal caloric high fat and western diet on metabolic syndrome, oxidative stress and vascular endothelial function in mice.
    I. Heinonen, P. Rinne, S. T. Ruohonen, S. Ruohonen, M. Ahotupa, E. Savontaus.
    Acta Physiologica. March 13, 2014
    Aim Nutrition contributes to increased adiposity, but it remains to be determined whether high fat rather than Western diet exacerbates the development of obesity and other characteristics of metabolic syndrome and vascular function. Methods We studied the effects of high fat (45% kcal) diet (HFD) and equal caloric Western diet (WD) high in fat, sucrose and cholesterol for 8 weeks in male C57B1/6N mice. Results Mice fed with HFD and WD showed substantially higher body adiposity (body fat %) compared with control mice receiving low fat (10%) diet (LFD). However, total body weight was higher only in HFD mice compared with other groups. The amount of liver triglycerides, cholesterol and oxidative damage was higher in WD mice compared with mice on LFD. There were no significant differences in fasting blood glucose or serum insulin, serum or muscle triglycerides, glucose tolerance or systolic blood pressure between the groups, but serum free fatty acids were increased in HFD mice compared with LFD. Increased levels of tissue and serum diene conjugation as a marker of oxidative stress were evident especially in WD mice. The endothelium‐dependent relaxations were significantly impaired in the small mesenteric arteries of HFD mice, but not in the aorta. Maximal relaxations correlated negatively with body adiposity in WD but not in HFD mice. Conclusions The major finding in the present study is that without changing body weight, Western diet induces marked whole‐body oxidative stress and elevates body adiposity, which associates with the endothelial function of resistance arteries.
    March 13, 2014   doi: 10.1111/apha.12253   open full text
  • Task‐related changes in sensorimotor integration influence the common synaptic input to motor neurones.
    C. M. Laine, Ş. U. Yavuz, D. Farina.
    Acta Physiologica. March 13, 2014
    Aim The purpose of this investigation was to understand how visual information, when used to guide muscle activity, influences the frequency content of the neural drive to muscles and the gain of afferent feedback. Methods Subjects maintained static, isometric contractions of the tibialis anterior muscle by matching a vi