3,4-dihydroxyflavonol reduces superoxide and improves nitric oxide function in diabetic rat mesenteric arteries

Background: 3’,4’-Dihydroxyflavonol (DiOHF) is an effective antioxidant that acutely preserves nitric oxide (NO) activity in the presence of elevated reactive oxygen species (ROS). We hypothesized that DiOHF treatment (7 days, 1 mg/kg per day s.c.) would improve relaxation in mesenteric arteries from diabetic rats where endothelial dysfunction is associated with elevated oxidant stress. Methodology/Principal Findings: In mesenteric arteries from diabetic rats there was an increase in ROS, measured by L-012 and 2’,7’-dichlorodihydrofluorescein diacetate fluorescence. NADPH oxidase-derived superoxide levels, assayed by lucigenin chemiluminescence, were also significantly increased in diabetic mesenteric arteries (diabetes, 48926946 counts/mg versus normal 24866344 counts/mg, n = 7–10, p,0.01) associated with an increase in Nox2 expression but DiOHF (20946300 counts/mg, n = 10, p,0.001) reversed that effect. Acetylcholine (ACh)-induced relaxation of mesenteric arteries was assessed using wire myography (pEC50 = 7.9460.13 n = 12). Diabetes significantly reduced the sensitivity to ACh and treatment with DiOHF prevented endothelial dysfunction (pEC50, diabetic 6.8660.12 versus diabetic+DiOHF, 7.4960.13, n = 11, p,0.01). The contribution of NO versus endothelium-derived hyperpolarizing factor (EDHF) to ACh-induced relaxation was assessed by evaluating responses in the presence of TRAM-34+apamin+iberiotoxin or N-nitro-L-arginine+ODQ respectively. Diabetes impaired the contribution of both NO (maximum relaxation, Rmax diabetic 246