Simvastatin improves endothelial function in spontaneously hypertensive rats through a superoxide dismutase mediated antioxidant effect

Background Hydroxymethylglutaryl coenzyme A (HMGCoA) reductase inhibitors have beneficial effects beyond their cholesterol-lowering properties. The antioxidant mechanism of HMGCoA reductase inhibitors is not completely understood. Objectives To elucidate the antioxidant effect of simvastatin. Methods We studied the influence of simvastatin treatment on the development of hypertension, modification of antioxidant systems, and reactivity of aortic rings in Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Results Simvastatin had no effect on blood pressure (BP). Simvastatin treatment (either 1 or 2 mg/kg body weight for 12 or 20 weeks) increased superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in SHR rats compared with untreated control SHR rats. Carbachol-induced relaxation of aortic rings was impaired in control SHR rats and was restored by simvastatin treatment. Addition of SOD improved the response in control SHR rats and did not have any effect in treated SHR rats. Addition of diethyldithiocarbamic acid, a selective inhibitor of SOD, produced a mild non-significant impairment in carbachol-incluced relaxation in control SHR rats, suggesting a deficient antioxiclant system in these animals. However, in treated SHR and in WKY rats, impairment of the relaxation was marked, implying that SOD activity in these animals was important to maintain endothelial function. In aortic rings without endothelium from SHR rats, contraction induced by free radicals was substantially higher than in WKY rats. This effect was attenuated in 1- mg-treated rats and abolished in 2-mg-treated rats. Conclusions Simvastatin promotes intracellular antioxidant systems, fundamentally SOD, restoring endothelial function but not having any effect on blood pressure. (C) 2002 Lippincott Williams Wilkins.