Caveolin-1 (Cav-1)−/− mice develop mild pulmonary hypertension as they age. In this study, we sought to determine the effect of chronic hypoxia, an established model of pulmonary hypertension, on young Cav-1−/− mice with no measurable signs of pulmonary hypertension. Exposure of Cav-1−/− mice to chronic hypoxia resulted in an initial rise in right ventricular (RV) systolic pressure (RVSP) similar to wild-type (WT) mice. By three weeks RVSP decreased in the Cav-1−/− mice, whereas it was maintained in WT mice. The drop in RVSP in Cav-1−/− mice was accompanied by decreased cardiac output, increased RV hypertrophy, RV interstitial fibrosis, decreased RV sarco(endo)plasmic reticulum Ca2+-ATPase 2a mRNA and decreased RV function compared with WT mice. Importantly, minimal differences were noted in pulmonary vascular remodeling between WT and Cav-1−/− mice, and left ventricular function was normal in hypoxic Cav-1−/− mice. Mechanistically, increased endothelial nitric oxide synthase uncoupling and increased tyrosine nitration of protein kinase G were detected in the RV of Cav-1−/− mice. These hemodynamic, histological, and molecular changes were prevented in Cav-1−/− mice expressing an endothelial-specific Cav-1 transgene or by nitric oxide synthase inhibition. These data suggest that, in Cav-1−/− mice, increased oxidative/nitrosative stress due to endothelial nitric oxide synthase uncoupling modifies the response of the RV to pressure overload, accelerating the deterioration of RV function.
Effects of chronic hypoxia and altered hemodynamics on endothelial nitric oxide synthase expression in the adult rat lung.