miR-136 improves renal fibrosis in diabetic rats by targeting down-regulation of tyrosine kinase SYK and inhibition of TGF-β1/Smad3 signaling pathway

OBJECTIVE: To investigate the way that miR-136 regulated spleen tyrosine kinase (SYK) and transforming growth factor-β1 (TGF-β1)/Smad3 signaling pathways on renal fibrosis. METHODS: 100 male SD (Sprague-Dawley) rats were randomly divided into diabetic nephropathy (DN) group, normal control (NC) group, miR-136 mimics group, and control group. The renal fibrosis model of diabetic rats was established by streptozotocin (STZ) method. NRK-52E cells were transfected into six groups: HG group, HG + miR-136 group, HG + miR-NC group, miR-136 + SYK group, miR-136 + NC group, and control group. Histopathological examination, the expressions of miR-136 and SYK mRNA, the expression of mTOR, blood glucose, urine protein, body weight, creatinine level, blood urea nitrogen (BUN), and KW/BW were detected in each group. Transfection efficiency, the targeted binding, and regulation between miR-136 and SYK, as well as the expression level of related inflammatory factors, the expression levels of SYK, E-Cad (E-cadherin), Vimentin, Collagen I, α-smooth muscle actin (α-SMA), and vascular endothelial growth factor A (VEGFA) were detected. RESULTS: It was shown that the expression level of miR-136 in DN group significantly decreased. The blood glucose and urine protein concentrations in the DN group and miR-136 mimics group significantly increased and the body weight was decreased, but the blood glucose concentration in the miR-136 mimics group increased with time. The prolongation of the decline significantly decreased, and the growth rate of urinary protein reduced. Creatinine, BUN, and the kidney weight to body weight ratio (KW/BW) in DN group increased significantly. Cell culture results showed that SYK was a target gene of miR-136 and miR-136/SYK-mediated renal fibrosis by activating TGF-β1/Smad3 signal. CONCLUSION: SYK activates TGF-β1/Smad3 signaling, while miR-136 inhibits TGF-β1/Smad3 signaling mediating tubular epithelial cell fibrosis by down-regulating SYK.