Abstract 12132: 3′,4′-Dihydroxyflavonol Reduces Superoxide and Improves Nitric Oxide Function in Diabetic Rat Mesenteric Arteries
3′,4′-Dihydroxyflavonol (DiOHF) is an effective antioxidant that acutely preserves nitric oxide (NO) activity in the presence of elevated superoxide. We hypothesized that DiOHF treatment (7 days, 1mg/kg per day sc) would improve relaxation in mesenteric arteries from diabetic rats where oxidant stress causes endothelial dysfunction. Mesenteric arteries were isolated from normal, normal+DiOHF, diabetic and diabetic+DiOHF rats. Superoxide levels, assayed by lucigenin chemiluminescence, were significantly increased in diabetic mesenteric arteries (diabetes, 4892±946 counts/mg versus normal 2486±344 counts/mg, n=7–10, p<0.01) associated with an increase in Nox2 expression but DiOHF (2094±300 counts/mg, n=10, p<0.001) reversed that effect. Acetylcholine (ACh)-induced relaxation of mesenteric arteries was assessed using wire myography (pEC50=7.94±0.13 n=12). Diabetes significantly reduced the sensitivity to ACh and treatment with DiOHF prevented endothelial dysfunction (pEC50, diabetic 6.86±0.12 versus diabetic+DiOHF, 7.49±0.13, n=11, p<0.01). Elimination of the contribution of NO to relaxation by L-NNA (10-4 M) and ODQ (10-5 M), decreased the sensitivity to ACh in diabetic arteries (diabetic, 6.63±0.15 versus normal, 7.14±0.12, n=12, p<0.05), and treatment with DiOHF (6.85±0.12, n=12) had no effect. Thus DiOHF did not affect the contribution of endothelium-derived hyperpolarizing factor (EDHF) to relaxation. When the contribution of EDHF was inhibited using potassium channel blockers, TRAM-34 (10-6 M), apamin (10-6 M) and iberiotoxin (10-7 M), the maximum relaxation to ACh was decreased in diabetic arteries (diabetic 24±7 versus normal, 68±10, n=9–10, p<0.01), suggesting that diabetes impaired NO activity. This was associated with decreased endothelial nitric oxide synthase (eNOS) expression and eNOS uncoupling ie reduced dimerization. DiOHF treatment improved NO-dependent relaxation (69±6, n=11, p<0.01) and increased total and dimeric eNOS expression. In Conclusions, this is the first report that the antioxidant DiOHF improves NO activity in diabetes by reducing Nox2-dependent superoxide production and preventing eNOS uncoupling to preserve endothelial function without affecting the contribution of EDHF.
- Endothelial function
- Free radicals/Free-radical scavengers
- Nitric oxide
- Nitric oxide synthase
- © 2010 by American Heart Association, Inc.