Increase in caveolae and caveolin-1 expression modulates agonist-induced contraction and store- and receptor-operated Ca(2+) entry in pulmonary arteries of pulmonary hypertensive rats.

Caveolin-1 (Cav-1) is a major component protein associated with caveolae in the plasma membrane and has been identified as a regulator of store-operated Ca(2+) entry (SOCE) and receptor-operated Ca(2+) entry (ROCE). However, the contributions of caveolae/Cav-1 of pulmonary arterial smooth muscle cells (PASMCs) to the altered Ca(2+) signaling pathways in pulmonary arteries (PAs) during pulmonary hypertension (PH) have not been fully characterized. The present study quantified caveolae number and Cav-1 expression, and determined the effects of caveolae disruption on ET-1, cyclopiazonic acid (CPA) and 1-Oleoyl-2-acetyl-glycerol (OAG)-induced contraction in PAs and Ca(2+) influx in PASMCs of chronic hypoxia (CH)- and monocrotaline (MCT)-induced PH rats. We found that the number of caveolae, and the Cav-1 mRNA and protein levels were increased significantly in PASMCs in both PH models. Disruption of caveolae by cholesterol depletion with methyl-β-cyclodextrin (MβCD) significantly inhibited the contractile response to ET-1, CPA and OAG in PAs of control rats. ET-1, SOCE and ROCE-mediated contractile responses were enhanced, and their susceptibility to MβCD suppression was potentiated in the two PH models. MβCD-induced inhibition was reversed by cholesterol repletion. Introduction of Cav-1 scaffolding domain peptide to mimic Cav-1 upregulation caused significant increase in CPA- and OAG-induced Ca(2+) entry in PASMCs of control, CH and MCT-treated groups. Our results suggest that the increase in caveolae and Cav-1 expression in PH contributes to the enhanced agonist-induced contraction of PA via modulation of SOCE and ROCE; and targeting caveolae/Cav-1 in PASMCs may provide a novel therapeutic strategy for the treatment of PH.