Caveolae are involved in stretch-induced Ca2+ signaling in pulmonary hypertension - 04/04/15
Résumé |
Introduction |
Vascular smooth muscle cells are submitted to stretch forces exerted by the blood pressure. Pulmonary arteries can transduce a mechanical stimulus of stretch into a biological response of contraction, a mechanism called myogenic tone, which involves plasma membrane Ca2+ stretch-activated channels (SAC). As membrane plasticity and shape are important for the SAC activity, we investigate the involvement of caveolae in the Ca2+ and contraction response to stretch of pulmonary arterial smooth muscle cells (PA-SMC).
Methods |
Isometric contractions were performed in pulmonary arterial vessels from normoxic rats (Nx rats) and rats with a pulmonary hypertension induced by a chronic hypoxia of 3weeks (CH rats). Inward currents from SAC were recorded on freshly isolated PA-SMC after a negative pressure applied by a patch-clamp pipette and Ca2+ variations were simultaneously recorded with the fluorescent probe indo-1. Sarcoplasmic reticulum Ca2+ was measured by a confocal microscope with the fluo-5N probe. Finally, a pharmacological approach using methyl-β-cyclodextrin (MβCD, a caveolae disrupter) coupled with different immunolabelings of caveolin-1 and sarcoplasmic Ca2+ stores were used to investigate the role of caveolae.
Results |
We show that caveolae are present and caveolin-1 expressed in PA-SMC from both normal and pulmonary hypertensive rats. Isolated PA-SMC and pulmonary arteries exhibit a higher SAC activity, Ca2+ response and contraction to stretch in CH rats than in Nx rats. These responses are reduced by MβCD only in CH rats. In the absence of extracellular calcium, a stretch induces a Ca2+ and contraction response only in CH rats but not in Nx rats. This phenomenon involves a Ca2+ release from the sarcoplasmic reticulum and is fully inhibited by MβCD.
Conclusion |
Caveolae are important for stretch-induced calcium response in CH rats via a new subcellular organization between caveolae and intracellular calcium stores.
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