NADPH oxidase and ETA receptors mediate glomerular reactive oxygen species production in sickle cell nephropathy

Abstract

Sickle cell nephropathy (SCN) is a form of chronic renal disease characterized in part by extensive glomerular damage; however, the mechanism is unknown. Recent evidence suggests that endothelin (ET) contributes to proteinuria and renal injury. We hypothesized that SCN is associated with increased reactive oxygen species (ROS) production in glomeruli, an effect mediated by ET. We found that sickle mice have increased proteinuria (5.7±1.1 vs. 2.8±0.5 mg/mg creatinine/day n=6) and nephrinuria (2.8±0.6 vs. 0.8±0.3 μg/mg creatinine/day n=3–4) at baseline compared to C57/BL6J controls. In isolated glomeruli, we observed that sickle mice had significantly higher glomerular ROS production compared to controls following stimulation with phorbol myristae acetate (PMA)(26.3±4.8 v. 3.4±0.7 AU*min, respectively, p<0.01). This effect was abrogated in vitro by the NADPH oxidase inhibitor, apocynin (0.8±0.2 AU*min, p<0.001 v. untreated sickle glomeruli). Furthermore, we demonstrated that PMA‐induced ROS was absent following in vivo treatment with the ETA antagonist, ABT‐627 (5mg/kg/day, 7 days) (6.7±3.2 AU*min, p<0.01 v. untreated sickle glomeruli). These data indicate a novel mechanism for glomerular injury in the setting of sickle cell disease and suggests that ETA antagonism could provide a viable treatment strategy to prevent the initiation and progression of SCN.