Caveolae regulate nitroxidative signaling via localized nitration of Src‐family kinase in endothelial cells

Abstract

Peroxynitrite (ONOO−)‐mediated tyrosine nitration of proteins has been implicated in vascular pathologies. The regulatory mechanism of cross‐reaction between O2− and NO for ONOOgeneration and subsequent nitroxidative signaling is poorly understood. Given our previous findings that endothelial cell caveolae localize NAPDH oxidase enzyme complexes (O2−) and eNOS (NO), we hypothesize that caveolae may act as compartments for radical generation and oxidative/nitrative signaling pathways that lead to endothelial dysfunction. Here, we report that caveolae‐localized Src‐family kinase (SFK's) become nitrated in a superoxide‐ and NO‐dependent manner in response to the proinflammatory cytokine, TNFα. We further tested whether SFK's nitration serves as an early, upstream mediator of endothelial dysfunction. We found a significant reduction in TNFα induced activation of the NFkB pathway and upregulation of adhesion molecule expression (ICAM‐1/VCAM‐1) in cells pretreated with an inhibitor to SFK's (PP2). Moreover, disruption of caveolae domains showed a similar decrease in the activation of these proinflammatory pathways. These findings were confirmed in arteries from Cav1KO mice where both general and SFK‐specific protein tyrosine nitration and adhesion molecule expression were attenuated compared to WT animals infused with TNFα. Our results indicate that caveolae act as reaction centers for nitroxidative signaling that contribute to endothelial dysfunction.