Caveolin and Endothelial NO Signaling.

Pulmonary vascular diseases are associated with several factors including infection, cigarette smoking, abuse of dietary suppressants and drugs, prolonged exposure to high altitude, and other causes which in part induce significant oxidative stress resulting in endothelial cell injury, apoptosis, hyperproliferation, and vaso-occlusive disease. Maintenance of normal endothelial cell function is a critical role of endothelial nitric oxide synthase (eNOS) activity and physiologic nitric oxide (NO) signaling in the vascular wall. eNOS expression and activity is regulated by the membrane-associated scaffolding protein caveolin-1 (Cav-1), the main protein constituent of caveolae. This chapter summarizes the literature and highlights unanswered questions related to how inflammation-associated oxidative stress affects Cav-1 expression and regulatory functions, and how dysregulated eNOS enzymatic activity promotes endothelial dysfunction. Focus is given to how the conversion of eNOS from a NO-producing enzyme to a transient oxidant-generating system is associated twith Cav-1 depletion, endothelial cell injury, and pulmonary vascular diseases. Importantly, the vascular defects observed in absence of Cav-1 that give rise to injured or hyperproliferative endothelial cells and promote remodeled vasculature can be rescued by "re-coupling," inhibiting, or genetically deleting eNOS, supporting the notion that strict control of Cav-1 expression and eNOS activity and signaling is critical for maintaining pulmonary vascular homeostasis.