Direct renin inhibition is not enough to prevent reactive oxygen species generation and vascular dysfunction in renovascular hypertension.

Renin-angiotensin system activation promotes oxidative stress and endothelial dysfunction. However, no previous study has examined the effects of the renin inhibitor aliskiren, either alone or combined with angiotensin II type 1 antagonists on alterations induced by two-kidney, one-clip (2K1C) hypertension. We compared the vascular effects of aliskiren (50mg/kg/day), losartan (10mg/kg/day), or both by gavage for 4 weeks in 2K1C and control rats. Treatment with losartan, aliskiren, or both exerted similar antihypertensive effects. Aliskiren lowered plasma Ang I concentrations in sham rats and in hypertensive rats treated with aliskiren or with both drugs. Aliskiren alone or combined with losartan decreased plasma angiotensin II concentrations measured by high performance liquid chromatography, whereas losartan alone had no effects. In contrast, losartan alone or combined with aliskiren abolished hypertension-induced increases in aortic angiotensin II concentrations, whereas aliskiren alone exerted no such effects. While hypertension enhanced aortic oxidative stress assessed by dihydroethidium fluorescence and by lucigenin chemiluminescence, losartan alone or combined with aliskiren, but not aliskiren alone, abolished this alteration. Hypertension impaired aortic relaxation induced by acetylcholine, and losartan alone or combined with aliskiren, but not aliskiren alone, reversed this alteration. Losartan alone or combined with aliskiren, but not aliskiren alone, increased plasma nitrite concentrations in 2K1C rats. These findings show that antihypertensive effects of aliskiren do not prevent hypertension-induced vascular oxidative stress and endothelial dysfunction. These findings contrast those found with losartan and suggest that renin inhibition is not enough to prevent hypertension-induced impaired redox biology and vascular dysfunction.

Quercetin restores plasma nitrite and nitroso species levels in renovascular hypertension.

Quercetin has antioxidants properties which may increase nitric oxide (NO) bioavailability. However, the effects of quercetin on NO status have been poorly studied. We evaluated whether quercetin improves the plasma levels of NO metabolites in two-kidney one-clip (2K1C) hypertensive rats and assessed its effect on endothelial function. Sham-operated and 2K1C rats were treated with quercetin (10 mg(-1) kg(-1) day(-1) by gavage) or vehicle for 3 weeks. Systolic blood pressure (SBP) was monitored weekly. Vascular responses to acetylcholine (Ach) and sodium nitroprusside (SNP) were assessed in hindquarter vascular bed. Plasma nitrate levels were assessed by Griess reagent and plasma nitrite and nitroso species (S, N-nitroso species) were assessed by ozone- based chemiluminescence. Aortic NADPH oxidase activity and superoxide production were evaluated. While quercetin had no effects in control normotensive rats (P > 0.05), it significantly reduced SBP in 2K1C rats (P < 0.05). At the end of treatment, plasma nitrate levels were similar in all experimental groups (P > 0.05). However, plasma nitrite and the nitroso species levels were significantly lower in 2K1C rats when compared with controls (P < 0.05). Quercetin treatment restored plasma nitrite and nitroso species levels to those found in the sham-vehicle group (P < 0.05). While quercetin treatment induced no significant changes in responses to SNP (P > 0.05), it restored the vascular responses to Ach. Quercetin significantly attenuated 2K1C-hypertension-induced increases in NADPH oxidase activity and vascular superoxide production (P < 0.05). These results suggest that the antihypertensive effects of quercetin were associated with increased NO formation and improved endothelial function, which probably result from its antioxidant effects.