Glucose-6-Phosphate Dehydrogenase Overexpression Decreases Endothelial Cell Oxidant Stress and Increases Bioavailable Nitric Oxide

Abstract

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 · ). Therefore, we examined whether overexpression of G6PD would decrease reactive oxygen species accumulation and increase bioavailable NO · 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-α 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 of G6PD in vascular endothelial cells decreases reactive oxygen species accumulation in response to exogenous and endogenous oxidant stress and improves levels of bioavailable NO · .