Abstract 1229: Molecular Mechanisms of Angiotensin II-Mediated Mitochondrial Dysfunction: Linking Mitochondrial Oxidative Damage and Vascular Endothelial Dysfunction
Mitochondrial (mito) dysfunction is a prominent feature of most cardiovascular diseases including hypertension, diabetes, and heart failure. Angiotensin II (Ang II) is an important stimulus for atherogenesis and hypertension; however, its effects on mito function remain unknown. We hypothesized that Ang II may induce mito oxidative damage that in turn may decrease endothelial nitric oxide (NO•) and promote vascular oxidative stress. Mitochondria isolated from control and Ang II (200 nM, 4 hours) treated bovine aortic endothelial cells II were investigated. Electron Spin Resonance was used to study the effect of Ang II on mito ROS production, mito respiration, glutathione content and endothelial NO•. Mitochondrial membrane potential was examined using fluorescence microscopy. Endothelial O2−• formation was quantified using an HPLC-based dihydroethidium assay. Mitochondrial H2O2 and endothelial O2−• production increased significantly after treatment of endothelial cells with Ang II. This increase was blocked by preincubation of intact cells with apocynin (NADPH oxidase inhibitor), uric acid (scavenger of peroxynitrite), chelerythrine (PKC inhibitor), N (G)-nitro-L-arginine methyl ester (L-NAME) (nitric oxide synthase inhibitor), 5-hydroxydecanoate (5-HD, mitochondrial ATP-sensitive potassium channels inhibitor) or glibenclamide. Depletion of p22phox subunit of NADPH oxidase with siRNA led to significant (P<0.001) reduction in Ang II-mediated mito ROS production. Angiotensin II decreased mito glutathione content, and mito respiratory control ratio. These responses were attenuated by apocynin, 5-HD and glibenclamide. In addition, 5-HD prevented the Ang II-induced decrease in endothelial NO• (73% in Ang II-treated cells and 94% in Ang II plus 5-HD vs. 100% in control; P < 0.05) and mito membrane potential. These events were not associated with activation of caspase-3. Angiotensin II induces mito dysfunction via a pathway that depends on PKC, the NADPH oxidase and formation of peroxynitrite. Furthermore, mito dysfunction in response to Ang II modulates endothelial NO•and O2−• generation, which may in turn have ramifications for the development of endothelial dysfunction.