Renal cortical hydrogen peroxide (H2O2) stimulates renin release from juxtaglomerular (JG) cells and increases blood pressure: Role of JG cell NOX4

Abstract

Renin plays an essential role in blood pressure control and the development of hypertension. Enhanced hydrogen peroxide (H2O2) levels in the kidney are associated with hypertension. This is thought to be due to direct stimulation of tubular salt transport and enhanced vascular reactivity. However, we previously found that H2O2 can directly stimulate renin release from renal juxtaglomerular (JG) cells suggesting that this pathway may also be responsible for the hypertension. However, it is not clear whether enhanced H2O2 in the renal cortex stimulates renin release and increases blood pressure. We hypothesized that enhancing renal cortical H2O2 stimulates renin release and increases blood pressure. To enhance renal cortical H2O2 in mice, we placed a subcapsular renal catheter connected to an osmotic minipump to reach a concentration of 1 μM, and measured blood pressure by radio telemetry and plasma renin concentration (PRC). Two days after infusion of H2O2, systolic blood pressure increased by 22±2 mmHg (p<0.05) and PRC doubled (from 110± 7 to 214±39 ngAngI/hr/ml, p<0.05). In control mice, with renal cortical infusion of saline, blood pressure and PRC were not different from baseline, indicating that renal cortical H2O2 increased renin release and blood pressure. In vivo, H2O2 produced by surrounding cells or endogenously produced, could enhance renin release. We found that in freshly isolated mouse JG cells, decreasing endogenous H2O2 with catalase (100U/ml) decreased baseline renin release by 45±9% (n = 6; p < 0.05) indicating that endogenously produced H2O2 tonically stimulates renin release. To start dissecting the enzymatic sources of H2O2 production, we studied the NADPH oxidase isoforms present in JG cells. By Western blot, we found that NOX1, NOX2 and NOX4 are expressed in JG cell lysates (n=3). By immunofluorescence and confocal imaging, we observed that NOX4 isoform is highly expressed in JG cell renin granules (n=3). Treating JG cells with apocynin (120 μM), a general inhibitor of NADPH oxidases, decreased renin release by 28±7% (p<0.04). To identify whether NOX4 mediates the endogenous H2O2 production, we used adenovirus mediated gene silencing of NOX4. Silencing NOX4 in JG cells decreased renin release by 34 ±4% (p < 0.05). We concluded that renal cortical H2O2 is a potent stimuli for renin release in vivo. Endogenously produced H2O2 from NOX4 expressed in mouse JG cells stimulates renin release. Our data suggest that enhanced renal cortical reactive oxygen species may induce hypertension by enhancing renin release. NOX4 inhibition in JG cells might be a candidate for renin release and blood pressure control.Support or Funding InformationSDG12070304; RO3DK105300‐01