Knockdown of Angiopoietin-Like Protein 2 Ameliorates Diabetic Nephropathy by Inhibiting TLR4

Abstract

Background/Aims: Angiopoietin-like protein 2 (ANGPTL2) was reported to be implicated in the pathogenesis of inflammatory disease. Its role in diabetic nephropathy (DN) remained illdefined. Methods: qRT-PCR and western blot analysis were performed to detect the expressions of ANGPTL2 or TLR4 in streptozotocin (STZ)-induced DN rats and HG-stimulated podocytes. The renal injury index including 24-h proteinuria, blood glucose level, serum creatinine and blood urea nitrogen were measured in DN rats using corresponding commercial kits. The effect of ANGPTL2 knockdown on the secretion or expression of inflammatory cytokines was detected by ELISA or qRT-PCR analysis. The effect of ANGPTL2 knockdown on extracellular matrix (ECM) accumulation was determined by testing TGF-β1, Collagen-IV, fibronectin (FN) and PTEN expression via western blot. Results: ANGPTL2 and TLR4 were both highly expressed in DN rats compared with control group. ANGPTL2 knockdown alleviated renal injury in STZ-induced DN rat model. ANGPTL2 knockdown also suppressed inflammatory cytokines (IL-6, TNF-α, MCP-1, IL-1β) expression and ECM accumulation (TGF-β1, Collagen-IV, FN, PTEN) in HG-induced podocytes. Moreover, ANGPTL2 knockdown led to a significant decrease of TLR4 expression in both DN rat and cell model. Furthermore, TAK-242 treatment exacerbated the inhibitory effect of ANGPTL2 knockdown on inflammatory cytokines expression and ECM accumulation in HG-induced podocytes. Conclusion: ANGPTL2 knockdown ameliorates DN by inhibiting TLR4 expression, an observation contributing to a better understanding of DN pathogenesis.