Abstract 006: A Dual Role of 12/15-lipoxygenase in Lipopolysaccharide-Induced Acute Renal Inflammation and Injury

Abstract

Recent studies suggest a potential role of bioactive lipids in lipopolysaccharide (LPS) induced acute kidney injury. The current study was designed to determine the profiling activities of various polyunsaturated fatty acid (PUFA) metabolizing enzymes, including lipoxygenases (LO), cyclooxygenase and cytochrome P450 in the plasma of LPS-injected C57BL/6 mice (4 mg/kg i.p) using LC-MS. Heat map analysis revealed that out of 126 bioactive lipids screened, only the 12/15-LO metabolite, 12-HETE, had a significant (2.24 ± 0.4) fold increase relative to control (P= 0.0001). We then determined the role of the 12/15-LO in LPS-induced acute kidney injury using genetic and pharmacological approaches. Treatment of LPS injected mice with the 12/15-LO inhibitor, baicalein significantly improved creatinine clearance (0.05±0.01 ml/min in baicalein treated vs. 0.02±0.004 ml/min in untreated LPS injected mice) and reduced albumin to creatinine ratio (54±18 μg/mg in baicalein treated vs. 143±31 μg/mg in untreated LPS injected mice) in LPS injected mice. Baicalein treatment significantly reduced markers of renal inflammation {urinary thiobarbituric acid reactive substance (TBARs), urinary monocyte chemoattractant protein-1 (MCP-1), renal intercellular adhesion molecule 1 (ICAM-1), and tumor necrosis factor-α (TNF-α) levels}. Knocking-out of 12/15-LO also reduced markers of renal inflammation and injury elicited by LPS injection. Next, we sought to divert the role of 12/15-LO from being pro-inflammatory to anti-inflammatory via dietary supplementation with docosahexaenoic acid (DHA) and generation of anti-inflammatory metabolite, resolvin D2 (RvD2). DHA-treatment significantly reduced marker of renal injury and inflammation in LPS-injected mice whereas DHA treatment failed to provide any synergistic effects in reducing renal inflammation and injury in LPS injected 12/15-LO knock-out mice by increasing plasma RvD2 levels. This was further confirmed by exogenous RvD2 administration which significantly reduced the elevation in renal injury and inflammation in LPS injected mice. In conclusion, our data suggest a double-edged sword role of 12/15-LO in LPS-induced acute renal injury, depending on the type of substrate available for its activity.