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Intermittent Hypoxia Training Blunts Cerebrocortical Presenilin 1 Overexpression and Amyloid {beta} Accumulation in Ethanol-Withdrawn Rats

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AJP Regulatory Integrative and Comparative Physiology

Published online on

Abstract

Abrupt cessation of chronic alcohol consumption triggers signaling cascades that harm vulnerable brain regions and produce neurobehavioral deficits. We have demonstrated that a program of intermittent, normobaric hypoxia training (IHT) in rats prevents neurobehavioral impairment resulting from abrupt ethanol withdrawal (EW). Moreover, EW induced expression of stress-activated protein kinase p38 and presenilin 1 (PS1), the -secretase component that produces the neurotoxic amyloid-β (Aβ) peptides, Aβ40 and Aβ42. We tested the hypotheses that (1) IHT limits EW-induced activation of the p38-PS1 axis, thereby attenuating -secretase activation and Aβ accumulation, and (2) EW disables heat shock protein 25 (HSP25), a p38 substrate, molecular chaperone and antioxidant, and provokes protein carbonylation in a manner suppressed by IHT. Adult male rats completed two cycles of 4 wk ethanol diet (0 or 6.5% w/v) and 3 wk EW. A 20 d IHT program of cyclic, 5-8 min exposures to 9.5-10% FIO2 was administered during the first EW phase. PS1, phosphorylated p38 (P-p38) and HSP25 were analyzed by immunoblot, PS1 messenger RNA by quantitative polymerase chain reaction, protein carbonyl content by spectrometry, and Aβ40 and Aβ42 contents by enzyme-linked immunosorbent assay, in prefrontal cortical extracts. IHT attenuated the EW-associated increases in PS1, P-p38, Aβ40, Aβ42 and protein carbonyl contents, but not that of PS1 messenger RNA, while preserving functionally competent HSP25 dimers in EW rats. Collectively, these findings demonstrate that IHT attenuates EW-activation of the p38-PS1--secretase axis, thereby dampening Aβ accumulation, and prevents EW-induced oxidative protein damage.