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A NOX4/TRPC6 Pathway in Podocyte Calcium Regulation and Renal Damage in Diabetic Kidney Disease.

ABSTRACT: Background Loss of glomerular podocytes is an indicator of diabetic kidney disease (DKD). The damage to these cells has been attributed in part to elevated intrarenal oxidative stress. The primary source of the renal reactive oxygen species, particularly H2O2, is NADPH oxidase 4 (NOX4). We hypothesized that NOX4-derived H2O2 contributes to podocyte damage in DKD via elevation of podocyte calcium.Methods We used Dahl salt-sensitive (SS) rats with a null mutation for the Nox4 gene (SSNox4-/-) and mice with knockout of the nonselective calcium channel TRPC6 or double knockout of TRPC5 and TRPC6. We performed whole animal studies and used biosensor measurements, electron microscopy, electrophysiology, and live calcium imaging experiments to evaluate the contribution of this pathway to the physiology of the podocytes in freshly isolated glomeruli.Results Upon induction of type 1 diabetes with streptozotocin, SSNox4-/- rats exhibited significantly lower basal intracellular Ca2+ levels in podocytes and less DKD-associated damage than SS rats did. Furthermore, the angiotensin II-elicited calcium flux was blunted in glomeruli isolated from diabetic SSNox4-/- rats compared with that in glomeruli from diabetic SS rats. H2O2 stimulated TRPC-dependent calcium influx in podocytes from wild-type mice, but this influx was blunted in podocytes from Trpc6-knockout mice and, in a similar manner, in podocytes from Trpc5/6 double-knockout mice. Finally, electron microscopy revealed that podocytes of glomeruli isolated from Trpc6-knockout or Trpc5/6 double-knockout mice were protected from damage induced by H2O2 to the same extent.Conclusions These data reveal a novel signaling mechanism involving NOX4 and TRPC6 in podocytes that could be pharmacologically targeted to abate the development of DKD.

SUBMITTER: Ilatovskaya DV

PROVIDER: S-EPMC6050934 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Diabetic glomerular injury is a major complication of diabetes mellitus and is the leading cause of end stage renal disease (ESRD). Healthy podocytes are essential for glomerular function and health. Injury or loss of these cells results in increased proteinuria and kidney dysfunction and is a common finding in various glomerulopathies. Thus, mechanistic understanding of pathways that protect podocytes from damage are essential for development of future therapeutics. MicroRNA-146a (miR-146a) is a negative regulator of inflammation and is highly expressed in myeloid cells and podocytes. We previously reported that miR-146a levels are significantly reduced in the glomeruli of patients with diabetic nephropathy (DN). Here we report generation of mice with selective deletion of miR-146a in podocytes and use of these mice in models of glomerular injury. Induction of glomerular injury in C57BL/6 wildtype mice (WT) and podocyte-specific miR-146a knockout (Pod-miR146a-/-) animals via administration of low-dose lipopolysaccharide (LPS) or nephrotoxic serum (NTS) resulted in increased proteinuria in the knockout mice, suggesting that podocyte-expressed miR-146a protects these cells, and thus glomeruli, from damage. Furthermore, induction of hyperglycemia using streptozotocin (STZ) also resulted in an accelerated development of glomerulopathy and a rapid increase in proteinuria in the knockout animals, as compared to the WT animals, further confirming the protective role of podocyte-expressed miR-146a. We also confirmed that the direct miR-146a target, ErbB4, was significantly upregulated in the diseased glomeruli and erlotinib, an ErbB4 and EGFR inhibitor, reducedits upregulation and the proteinuria in treated animals. Primary miR146-/- podocytes from these animals also showed a basally upregulated TGFβ-Smad3 signaling in vitro. Taken together, this study shows that podocyte-specific miR-146a is imperative for protecting podocytes from glomerular damage, via modulation of ErbB4/EGFR, TGFβ, and linked downstream signaling.

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A NOX4/TRPC6 Pathway in Podocyte Calcium Regulation and Renal Damage in Diabetic Kidney Disease.

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