Abstract 546: Negative Regulation of Reactive Oxygen Species From Nadph Oxidases by Caveolar Proteins

The importance of caveolar proteins, including caveolin-1 (Cav1) have been widely explored in cardiovascular disease. Cav1 binds to numerous signaling proteins via interactions with its scaffolding domain, and caveolin-2 (Cav2) and Cavin1 depend on Cav1 for stability and expression. The NADPH oxidases (Nox) are a primary source of reactive oxygen species (ROS) and oxidative stress. Loss of cav1 has been shown to increase vascular ROS production and can promote cardiovascular diseases such as pulmonary arterial hypertension. However, the ability of Cav1 to regulate Nox enzymes is not known. Here, we found that increased expression of Cav1 by gene transfer or by administration of its scaffolding domain peptide, potently inhibited ROS production from Nox1, Nox2, Nox4 and Nox5. In contrast, inhibition of endogenous Cav1 with small interfering RNA increased ROS production from human vascular cells. The Cav1 scaffolding domain mutant, Cav1 F16A, failed to inhibit Nox activity. In addition, Cav2 and Cavin-1 can also decreased ROS production from Nox enzymes. To further explore the underlying mechanism, we found Cav1 did not modify intracellular calcium but reduced ROS output in an isolated enzyme assay. Furthermore, we found increased Cav1, Cav2 and Cavin-1 expression robustly decreased the expression level of Nox proteins. Given the similar intracellular location of Cav1 and Nox and the presence of highly conserved Cav1 binding sequence in Nox enzymes, we predict that caveolin proteins may directly bind with Nox and promote their degradation. It is also possible that degradation is mediated by Cav1 regulated Nox protein ubiquitylation. Together, these results suggest that caveolin proteins negatively regulate NADPH oxidases to ameliorate cellular stress and are an important regulatory pathway in the cardiovascular system.