Role of Renal DJ-1 in the Pathogenesis of Hypertension Associated With Increased Reactive Oxygen Species Production

Abstract

The D₂ dopamine receptor (D₂R) is important in the pathogenesis of essential hypertension. We have already reported that systemic deletion of the D₂R gene in mice results in reactive oxygen species (ROS)-dependent hypertension, suggesting that the D₂R has antioxidant effects. However, the mechanism of this effect is unknown. DJ-1 is a protein that has antioxidant properties. D₂R and DJ-1 are expressed in the mouse kidney and colocalize and coimunoprecipitate in mouse renal proximal tubule cells. We hypothesized that D₂Rs regulate renal ROS production in the kidney through regulation of DJ-1 expression or function. Heterozygous D₂^+/− mice have increased blood pressure, urinary 8-isoprostanes, and renal Nox 4 expression, but decreased renal DJ-1 expression. Silencing D₂R expression in mouse renal proximal tubule cells increases ROS production and decreases the expression of DJ-1. Conversely, treatment of these cells with a D₂R agonist increases DJ-1 expression and decreases Nox 4 expression and NADPH oxidase activity, effects that are partially blocked by a D₂R antagonist. Silencing DJ-1 expression in mouse renal proximal tubule cells increases ROS production and Nox 4 expression. Selective renal DJ-1 silencing by the subcapsular infusion of DJ-1 siRNA in mice increases blood pressure, renal Nox4 expression, and NADPH oxidase activity. These results suggest that the inhibitory effects of D₂R on renal ROS production are at least, in part, mediated by a positive regulation of DJ-1 expression/function and that DJ-1 may have a role in the prevention of hypertension associated with increased ROS production.