Oxidative stress causes imbalance of renal renin angiotensin system (RAS) components and hypertension in obese Zucker rats

Abstract

Background-Oxidative stress plays an important role in the pathogenesis of hypertension, especially in obesity-related hypertension. The natriuretic and antinatriuretic components of the renal renin angiotensin system (RAS) maintain sodium homeostasis and blood pressure. Here, we test the hypothesis that increased oxidative stress leads to the imbalance of RAS components and hypertension in obese Zucker rats. Methods and Results-Lean and obese rats received vehicle or tempol, a superoxide dismutase mimetic in the drinking water for 4 weeks. Compared with vehicle-treated lean rats, vehicle-treated obese rats exhibited higher blood pressure and increased renal oxidative stress, accompanied by increased diuretic and natriuretic responses to AT1R antagonist (Candesartan) and AT2R agonist (CGP-42112A) and reduced diuretic and natriuretic response to MasR agonist (Ang-[1 to 7]). Moreover, obese rats had higher ACE, AT1R and AT2R, lower ACE2 and MasR expressions in the kidney. All of the above-mentioned abnormalities were reversed to some degree by tempol treatment. In primary cultures of renal proximal tubular (RPT) cells from lean and obese rats, tempol treatment also increased AT2R, ACE2, and MasR expressions but decreased AT1R and ACE expressions in obese rats. Conclusions-Taken together, our study indicated that the imbalance of renal RAS components was associated with increased oxidative stress in obese rats. Furthermore, antioxidant treatment with tempol reversed the imbalance of renal RAS components and led to diuresis and natriuresis, which, at least in part, explains the blood pressure-lowering effect of antioxidant supplementation in obesity-related hypertension.