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Inflammatory cytokines tumour necrosis factor‐α and interleukin‐8 enhance airway smooth muscle contraction by increasing L‐type Ca2+ channel expression

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Clinical and Experimental Pharmacology and Physiology

Published online on


--- - |2 Summary Inflammation elevates intracellular calcium concentrations ([Ca2+]i) in airway smooth muscle (ASM). The L‐type Ca2+ channel (L‐VDCC) plays an important role in regulating Ca2+ influx in ASM. However, the role of L‐VDCC in the inflammatory cytokine‐induced pathology of ASM remains unclear. In the present study, we used calcium imaging and isometric tension measurements to assess the role of L‐VDCC in agonist‐induced [Ca2+]i rise and the associated contractions in mouse ASM, and we used immunoblotting to identify L‐VDCC protein expression levels in mouse ASM after exposure to tumour necrosis factor alpha (TNF‐α) or interleukin‐8 (IL‐8). Our results showed that high‐K+‐ or carbachol‐induced contractions of mouse ASM were significantly greater after pretreatment with TNF‐α or IL‐8 for 24 hours. Both verapamil and nifedipine, L‐VDCC inhibitors, abolished this increased contraction induced by TNF‐α or IL‐8 pretreatment. Moreover, TNF‐α treatment enhanced carbachol‐induced Ca2+ influx in ASM cells, and this effect was abrogated by verapamil. Additionally, immunoblotting results showed that preincubation of mouse ASM with TNF‐α or IL‐8 also enhanced L‐VDCC protein expression. On the basis of these findings, we concluded that proinflammatory cytokines, such as TNF‐α and IL‐8, increase the expression level of L‐VDCC, which in turn contributes to augmented agonist‐induced ASM contractions. This effect of inflammation on L‐VDCC expression in ASM may be associated with airway hyper‐responsiveness and involved in the development of asthma. - 'Clinical and Experimental Pharmacology and Physiology, EarlyView. '