90 - High Circulatory Leptin Mediated NOX-2 Promotes Kidney Inflammation in Nonalcoholic Fatty Liver Disease Via MiR21-Dependent Mesangial Cell Activation

Abstract

High insulin and leptin resistance followed by underlying inflammation is often ascribed to the ectopic manifestations in non-alcoholic fatty liver disease (NAFLD) but the exact molecular pathways remain unclear. We have shown previously that CYP2E1-mediated oxidative stress and circulating leptin in NAFLD is associated with renal disease severity. Extending the studies, we hypothesized that high circulatory leptin in NAFLD causes renal mesangial cell activation and tubular inflammation via a NOX2 dependent pathway that upregulates proinflammatory miR21. High fat diet (60%kcal) was used to induce fatty liver phenotype with parallel insulin and leptin resistance in WT, Leptin knockout (ob/ob) and p47 phox knockout mice. Kidneys were collected after pathology showed NASH-like phenotype and accelerated oxidative stress in the liver. The kidneys were probed for mesangial cell activation and tubular inflammation. Results showed that NAFLD kidneys had significant increases in α-SMA, a marker of mesangial cell activation, miR21 levels, tyrosine nitration and renal inflammation while they were significantly decreased in leptin and p47 phox knockout mice. Micro RNA21 knockout mice showed decreased tubular immunotoxicity and proinflammatory mediator release. Mechanistically, use of apocynin or phenyl boronic acid (FBA) or DMPO or miR21 antagomir inhibited leptin primed-miR21-mediated mesangial cell activation in vitro suggesting a direct role of leptin-mediated NOX-2 in miR21-mediated mesangial cell activation. Finally JAK-STAT inhibitor completely abrogated the mesangial cell activation in leptin-primed cells suggesting that leptin signaling in the mesangial cells depended on the JAK-STAT pathway. Taken together the study reports a novel mechanistic pathway of leptin-mediated renal inflammation in NAFLD. Grant support R00ES019875 to SC