Important roles of endothelial caveolin-1 in endothelium-dependent hyperpolarization and ischemic angiogenesis in mice.

Although increased levels of reactive oxygen species (ROS) are involved in the pathogenesis of cardiovascular diseases, the importance of physiological ROS has also been emerging. We have previously demonstrated that endothelium-derived hydrogen peroxide (H2 O2 ) is one of endothelium-dependent hyperpolarization (EDH) factors and that loss of endothelial caveolin-1 reduces EDH/H2 O2 in microcirculation. Caveolin-1 (Cav-1) is a scaffolding/ regulatory protein that interacts with diverse signaling pathways including angiogenesis. However, it remains unclear whether endothelial Cav-1 plays a role in ischemic angiogenesis by modulating EDH/H2 O2 . In this study, we thus addressed this issue in a mouse model of hindlimb ischemia by using male endothelium-specific Cav-1-knockout (eCav-1-KO) mice. In isometric tension experiments with femoral arteries from eCav-1-KO mice, reduced EDH-mediated relaxations to acetylcholine and desensitization of SNP-mediated endothelial-independent relaxations were noted (n=4~6). Aortic ring assay ex vivo also showed that the extent of microvessel sprouting was significantly reduced in eCav-1-KO mice compared with WT littermate (n=12 each). Blood flow recovery at 4 weeks assessed with a laser speckle flowmeter after femoral artery ligation was significantly impaired in eCav-1-KO mice as compared with WT littermates (n=10 each), associated with reduced capillary density and muscle fibrosis in the legs (n=6 each). Importantly, post-translational protein modifications by reactive nitrogen and oxygen species, as evaluated by thiol glutathione adducts and nitrotyrosine, respectively, were both increased in eCav-1-KO mice (n=6~7 each). These results indicate that endothelial Cav-1 plays an important role in EDH-mediated vasodilatation and ischemic angiogenesis through post-translational protein modifications by nitro-oxidative stress in mice in vivo.