NADPH Oxidase 2 Mediates Intermittent Hypoxia-Induced Mitochondrial Complex I Inhibition: Relevance to Blood Pressure Changes in Rats

Department of Medicine, Center for Systems Biology of O2 Sensing, University of Chicago, Chicago, Illinois 60637, USA.
Antioxidants & Redox Signaling (Impact Factor: 7.41). 01/2010; 14(4). DOI: 10.1089/ars.2010.3213


Previous studies identified NADPH oxidases (Nox) and mitochondrial electron transport chain at complex I as major cellular sources of reactive oxygen species (ROS) mediating systemic and cellular responses to intermittent hypoxia (IH). In the present study, we investigated potential interactions between Nox and the mitochondrial complex I and assessed the contribution of mitochondrial ROS in IH-evoked elevation in blood pressure. IH treatment led to stimulus-dependent activation of Nox and inhibition of complex I activity in rat pheochromocytoma (PC)12 cells. After re-oxygenation, Nox activity returned to baseline values within 3 h, whereas the complex I activity remained downregulated even after 24 h. IH-induced complex I inhibition was prevented by Nox inhibitors, Nox2 but not Nox 4 siRNA, in cell cultures and was absent in gp91(phox-/Y) (Nox2 knock-out; KO) mice. Using pharmacological inhibitors, we show that ROS generated by Nox activation mobilizes Ca(2+) flux from the cytosol to mitochondria, leading to S-glutathionylation of 75- and 50-kDa proteins of the complex I and inhibition of complex I activity, which results in elevated mitochondrial ROS. Systemic administration of mito-tempol prevented the sustained but not the acute elevations of blood pressure in IH-treated rats, suggesting that mitochondrial-derived ROS contribute to sustained elevation of blood pressure.

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    • "growth. To determine the importance of NOX2 for dendritic growth, sympathetic neurons were transfected with siRNAs previously shown to inhibit either NOX2 or NOX4 in PC12 cells (Khan et al., 2011). Cultured sympathetic neurons transfected with NOX2 siRNA, followed by treatment with BMP-7 (50 ng/ml) showed reduced dendritic growth compared to BMP-7 treated neurons transfected with either control siRNA or no siRNA (Fig. 8A). "
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    • "Thus, it is plausible to suggest that CIH-induced NOXdependent elevated ROS might impair muscle force-generating capacity without concomitant widespread oxidative stress/injury. CIH-induced oxidative damage has been observed in skeletal muscle (Dutta et al., 2008) and other tissues (Veasey et al., 2004; Raghuraman et al., 2009; Khan et al., 2011). It appears that the detrimental effects of CIH manifest in a " dose " -dependent manner and the effects of oxidative stress may be organ-specific (Shan et al., 2007; Jun et al., 2008). "
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    • "Mitochondrial and cytosol fractions were isolated from cells or adrenal medullary extracts by differential centrifugation as described [22]. Aconitase activity was measured in both the fractions using aconitase assay kit (Cayman chemical company; # 705502) as described. "
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