Abstract 151: Angiotensin II-Mediated Mitochondrial Oxidative Damage Reduces Nitric Oxide Bioavailability: Possible Role in 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 reduce endothelial nitric oxide production and promote vascular oxidative stress. Mitochondria isolated from bovine aortic endothelial cells subjected to Ang II (4-hour, 200 nM) were investigated. Electron Spin Resonance was used to study the effect of Ang II on mito H2O2 production, respiratory activity, glutathione content and endothelial nitric oxide bioavailability. Mitochondrial membrane electrical potential was examined using fluorescence microscopy. Endothelial superoxide formation was quantified using dihydroethidium and an HPLC-based assay. Mitochondrial H2O2 and endothelial superoxide production were significantly increased in Ang II treated cells (Table⇓). This increase was blocked by pre-incubation with apocynin (NADPH oxidase inhibitor), uric acid (scavenger of peroxynitrite), chelerythrine (PKC inhibitor) and post-incubation with 5-hydroxydecanoate (mito ATP-sensitive potassium channels inhibitor). Angiotensin II decreased mito glutathione content, and mito respiratory control ratio. These responses were attenuated by apocynin. In addition, 5-hydroxydecanoate inhibited the Ang II-induced decrease in endothelial nitric oxide production (73% in Ang II treated cells and 94% in Ang II plus 5-hydroxydecanoate vs. 100% in control; P < 0.05) and mito membrane potential. Angiotensin II induces mitochondrial dysfunction via PKC-dependent pathways. Furthermore, mitochondrial dysfunction in response to Ang II modulates endothelial nitric oxide and superoxide generation, which may in turn have ramifications for the development of endothelial dysfunction.