Involvement of NOX in the Regulation of Renal Tubular Expression of Na/K-ATPase in Acute Unilateral Ureteral Obstruction Rats

Abstract

Background/Aims: Renal tubular expression of Na/K-ATPase has been reported to be rapidly reduced in kidneys after unilateral ureteral obstruction (UUO), contributing to compromised sodium regulation. In this study, apocynin was utilized to test the hypothesis that the renal nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) system is involved in the regulation of Na/K-ATPase expression in early UUO. Methods: Eighty Wistar rats underwent UUO or sham surgery, and half of each group was administered 100 mg/kg apocynin by oral gavage after surgery. Renal tissue samples were collected on day 1 and day 3 after surgery and the distribution of NOX2, NOX4 and Na/K-ATPase was assessed by immunofluorescence and immunohistochemical staining. The Heme oxygenase-1 (HO-1), NOX2, NOX4, osteopontin, Na/K-ATPase and aquaporin-1 (AQP-1) content of renal homogenates was assessed by immunoblotting, and malondialdehyde (MDA), nitric oxide (NO) content was assessed by biochemical analyses. Activity of inducible NO synthase (iNOS) and antioxidant enzymes was assessed by enzymatic assay. Results: Kidney Na/K-ATPase and AQP-1 content was decreased, and MDA and NOX4, NOX2 and HO-1 content were increased in the obstructed kidneys of UUO rats. Apocynin attenuated these changes and partially, but significantly, reversed the downregulation of Na/K-ATPase and AQP-1 in UUO rats. However, apocynin did not alter iNOS activity and NO production, osteopontin expression or the activity of antioxidant enzymes. Conclusion: Activation of the NOX system and subsequent production of ROS are likely responsible for the downregulation of renal tubular Na/K-ATPase expression in early UUO.