Hyperaldosteronism is associated with impaired vascular reactivity; however, the mechanisms by which aldosterone promotes endothelial dysfunction remain unknown. Glucose-6-phosphate dehydrogenase (G6PD) modulates vascular function by limiting oxidant stress to preserve bioavailable nitric oxide (NO(*)). Here we show that aldosterone (10(-9)-;10(-7) mol/l) decreased endothelial G6PD expression and activity in vitro, resulting in increased oxidant stress and decreased NO(*) levels-similar to what is observed in G6PD-deficient endothelial cells. Aldosterone decreased G6PD expression by increasing expression of the cyclic AMP-response element modulator (CREM) to inhibit cyclic AMP-response element binding protein (CREB)-mediated G6PD transcription. In vivo, infusion of aldosterone decreased vascular G6PD expression and impaired vascular reactivity. These effects were abrogated by spironolactone or vascular gene transfer of G6pd. These findings demonstrate that aldosterone induces a G6PD-deficient phenotype to impair endothelial function; aldosterone antagonism or gene transfer of G6pd improves vascular reactivity by restoring G6PD activity.
Objective-Glucose-6-phosphate dehydrogenase (G6PD), the principal source of NADPH, serves as an antioxidant enzyme to modulate the redox milieu and nitric oxide synthase activity. Deficient G6PD activity is associated with increased endothelial cell oxidant stress and diminished bioavailable nitric oxide (NO ⅐ ). Therefore, we examined whether overexpression of G6PD would decrease reactive oxygen species accumulation and increase bioavailable NO ⅐ in endothelial cells. Methods and Results-Adenoviral-mediated gene transfer of G6PD increased G6PD expression, activity, and NADPH levels in bovine aortic endothelial cells (BAECs). BAECs overexpressing G6PD demonstrated a significant reduction in reactive oxygen species accumulation when exposed to hydrogen peroxide, xanthine-xanthine oxidase, or tumor necrosis factor-␣ compared with BAECs with basal levels of G6PD. BAECs overexpressing G6PD maintained intracellular glutathione stores when exposed to oxidants because of increased activity of glutathione reductase, an effect that was not observed in endothelial cells with normal G6PD activity. Overexpression of G6PD was also associated with enhanced nitric oxide synthase activity, resulting in elevated levels of cGMP, nitrate, and nitrite, and this response was increased after stimulation with bradykinin.
Conclusions-Overexpression
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