title: Nox2 as a potential target of mitochondrial superoxide and its role in endothelial oxidative stress.
abstract: Superoxide (O2(·-)) production by the NADPH oxidases is implicated in the pathogenesis of many cardiovascular diseases, including hypertension. We have previously shown that activation of NADPH oxidases increases mitochondrial O2(·-) which is inhibited by the ATP-sensitive K(+) channel (mitoKATP) inhibitor 5-hydroxydecanoic acid and that scavenging of mitochondrial or cytoplasmic O2(·-) inhibits hypertension. We hypothesized that mitoKATP-mediated mitochondrial O2(·-) potentiates cytoplasmic O2(·-) by stimulation of NADPH oxidases. In this work we studied Nox isoforms as a potential target of mitochondrial O2(·-). We tested contribution of reverse electron transfer (RET) from complex II to complex I in mitochondrial O2(·-) production and NADPH oxidase activation in human aortic endothelial cells. Activation of mitoKATP with low dose of diazoxide (100 nM) decreased mitochondrial membrane potential (tetramethylrhodamine methyl ester probe) and increased production of mitochondrial and cytoplasmic O2(·-) measured by site-specific probes and mitoSOX. Inhibition of RET with complex II inhibitor (malonate) or complex I inhibitor (rotenone) attenuated the production of mitochondrial and cytoplasmic O2(·-). Supplementation with a mitochondria-targeted SOD mimetic (mitoTEMPO) or a mitochondria-targeted glutathione peroxidase mimetic (mitoEbselen) inhibited production of mitochondrial and cytoplasmic O2(·-). Inhibition of Nox2 (gp91ds) or Nox2 depletion with small interfering RNA but not Nox1, Nox4, or Nox5 abolished diazoxide-induced O2(·-) production in the cytoplasm. Treatment of angiotensin II-infused mice with RET inhibitor dihydroethidium (malate) significantly reduced blood pressure. Our study suggests that mitoKATP-mediated mitochondrial O2(·-) stimulates cytoplasmic Nox2, contributing to the development of endothelial oxidative stress and hypertension.
authors: Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee.
authors: Rafal R
authors: RR
authors: Nazarewicz
authors: Anna E
authors: AE
authors: Dikalova
authors: Alfiya
authors: A
authors: Bikineyeva
authors: Sergey I
authors: SI
authors: Dikalov
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D019069:Cell Respiration / Q000502:physiology; D002478:Cells, Cultured; D003981:Diazoxide / Q000494:pharmacology; D042967:Electron Transport Complex I / Q000502:physiology; D042963:Electron Transport Complex II / Q000502:physiology; D042783:Endothelial Cells / Q000502:physiology*; D006801:Humans; D008562:Membrane Glycoproteins / Q000502:physiology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000502:physiology*; D018384:Oxidative Stress / Q000502:physiology*; D015221:Potassium Channels / Q000378:metabolism; D013481:Superoxides; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D008562:Membrane Glycoproteins; D015221:Potassium Channels; D014665:Vasodilator Agents; C117780:mitochondrial K(ATP) channel; D013481:Superoxides; D042963:Electron Transport Complex II; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D042967:Electron Transport Complex I; D003981:Diazoxide
keywords: NADPH oxidase; endothelial cells; hypertension; mitochondria; superoxide
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