Abstract 10814: A Key Role for Caveolin-1 in the Regulation of Oxidative Stress
Reactive oxygen species (ROS) modulate both physiological and pathophysiological responses in the cardiovascular system. Increased ROS production has been implicated in the pathogenesis of cardiovascular diseases. Caveolin-1 is a scaffolding/regulatory protein that interacts with diverse signaling molecules in many cell types. Caveolin-1null mice are viable but have marked cardiovascular phenotypes, including pulmonary arterial hypertension and cardiac hypertrophy. However, the molecular mechanisms whereby loss of caveolin-1 leads to these abnormalities are incompletely understood. We hypothesized that caveolin-1 regulates cellular and organismal redox state in these cardiovascular tissues. We found that plasma 8-isoprostanes levels were strikingly higher in caveolin-1null mice than wild-type mice (0.2 ± 0.1 vs. 9.0 ± 0.5 pg/ml), indicating that caveolin-1null mice have markedly increased oxidative stress. To explore the underlying mechanisms, we exploited small interfering RNA (siRNA) approaches to selectively knock down caveolin-1 and related signaling proteins in cultured endothelial cells. We found that siRNA-mediated caveolin-1 knockdown resulted in a significant 42±3 % increase (n=6, P<0.01) in extracellular hydrogen peroxide (H2O2) levels, quantitated using the Amplex Red assay. Simultaneous siRNA-mediated knockdown of AMP-activated kinase, Rac1 or eNOS did not affect the increase in H2O2 levels seen following caveolin-1 knockdown in these cells. Pharmacological inhibitors of mitochondrial respiration (rotenone) or NADPH oxidases (VAS2870) failed to attenuate the increase in H2O2 levels seen following caveolin-1 knockdown. We next transfected endothelial cells with the H2O2 biosensor HyPer2, and found no change in intracellular H2O2 concentrations following caveolin-1 knockdown. These results taken together indicate that caveolin-1 may regulate membrane transport of H2O2 in endothelial cells. These findings establish that caveolin-1 plays a key role in the regulation of cellular and organismal oxidative stress, and suggest that caveolin-1-modulated pathways may represent novel targets for the amelioration of oxidative stress in cardiovascular diseases.
- © 2011 by American Heart Association, Inc.