Molecular Mechanisms of Angiotensin II–Mediated Mitochondrial Dysfunction

Abstract

Abstract-Mitochondrial dysfunction is a prominent feature of most cardiovascular diseases. Angiotensin (Ang) II is an important stimulus for atherogenesis and hypertension; however, its effects on mitochondrial function remain unknown. We hypothesized that Ang II could induce mitochondrial oxidative damage that in turn might decrease endothelial nitric oxide (NO˙) bioavailability and promote vascular oxidative stress. The effect of Ang II on mitochondrial ROS, mitochondrial respiration, membrane potential, glutathione, and endothelial NO˙was studied in isolated mitochondria and intact bovine aortic endothelial cells using electron spin resonance, dihydroethidium high-performance liquid chromatography -based assay, Amplex Red and cationic dye fluorescence. Ang II significantly increased mitochondrial H 2 O 2 production. This increase was blocked by preincubation of intact cells with apocynin (NADPH oxidase inhibitor), uric acid (scavenger of peroxynitrite), chelerythrine (protein kinase C inhibitor), N G -nitro-L-arginine methyl ester (nitric oxide synthase inhibitor), 5-hydroxydecanoate (mitochondrial ATP-sensitive potassium channels inhibitor), or glibenclamide. Depletion of p22 phox subunit of NADPH oxidase with small interfering RNA also inhibited Ang II-mediated mitochondrial ROS production. Ang II depleted mitochondrial glutathione, increased state 4 and decreased state 3 respirations, and diminished mitochondrial respiratory control ratio. These responses were attenuated by apocynin, 5-hydroxydecanoate, and glibenclamide. In addition, 5-hydroxydecanoate prevented the Ang II-induced decrease in endothelial NO˙and mitochondrial membrane potential. Therefore, Ang II induces mitochondrial dysfunction via a protein kinase C-dependent pathway by activating the endothelial cell NADPH oxidase and formation of peroxynitrite. Furthermore, mitochondrial dysfunction in response to Ang II modulates endothelial NO˙and O 2 . generation, which in turn has ramifications for development of endothelial dysfunction. (Circ Res. 2008;102:488-496.)Key Words: mitochondria Ⅲ angiotensin II Ⅲ endothelial cells Ⅲ oxidative stress A ngiotensin (Ang) II mediates endothelial dysfunction and promotes vascular inflammation and atherogenesis. [1][2][3] Reactive oxygen species (ROS) play key roles in these processes. 4,5 In addition to vascular NADPH oxidase-derived ROS, Ang II has been shown to stimulate mitochondrial dysfunction in cardiac, renal, and vascular smooth muscle cells. 6 -9 Dysfunctional mitochondria, in turn, produce excessive amounts of ROS such as superoxide (O 2 . ), hydrogen peroxide (H 2 O 2 ), and peroxynitrite (ONOO Ϫ ). 10,11 This overproduction of mitochondrial ROS has been implicated in neurodegenerative diseases, ischemia reperfusion injury, atherosclerosis and aging. [12][13][14][15][16] Moreover, recent studies have demonstrated that mitochondrial ROS levels can be decreased by overexpression of either manganese superoxide dismutase or the peroxiredoxins 3 or 5 and that this protects against mitochondrial ...

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