Effects of NOX-1 Inhibition on Real-Time Blood Nitric Oxide and Hydrogen Peroxide in Acute Hyperglycemia

Philadelphia

Hyperglycemia has been associated with vascular endothelial dysfunction in part by a reduction in nitric oxide (NO) production and increased oxidative stress (e.g., increased superoxide (SO) and hydrogen peroxide (H2O2). Endothelial-derived NO can be significantly reduced by increased SO/H2O2 in part by the activation of NADPH oxidase during hyperglycemia. Of the 7 NADPH oxidase isoforms, NOX1 is mainly expressed in the vasculature and may play a major role in hyperglycemia induced oxidative stress and vascular endothelial dysfunction. To test the hypothesis, we measured blood NO and H2O2 levels in real time via NO and H2O2 microsensors inserted into femoral veins of rats. Hyperglycemia (e.g., 200 mg/dl) was maintained by infusion i.v. of 30% glucose solution for 3 hours with or without a selective NOX1 inhibitor, ML171. We found that hyperglycemia for 3 hours significantly maintained higher blood H2O2 levels (3.06±0.4 μM, n=9) compared to the saline infused control (P<0.01, n=9). By contrast, ML171 (1 and 5 μM) reduced hyperglycemia-induced H2O2 levels by 1.86±0.61 μM (P<0.05, n=8) and 4.85±1.02 μM (P<0.01, n=5), respectively, at the end of experiment compared to glucose control. Meanwhile, hyperglycemia significantly reduced blood NO levels (101.41±10.91 nM, n=8) compared to the saline control (P<0.01, n=8). By contrast, ML171 (1 and 5 μM) attenuated the hyperglycemia induced decrease in blood NO levels and increased blood NO levels by 68.48±12.67 nM (P<0.01, n=5) and 85.95±12.67 nM (P<0.01, n=5) respectively, at the end of experiment. Our results indicate that NOX1 activation may contribute to hyperglycemia-induced oxidative stress and NO reduction. Furthermore, inhibition of NOX1 may mitigate the deleterious effects of hyperglycemia.