MiR-29b Regulates Renal Fibrosis Via Targeting PI3K/AKT Signaling Pathway

Aim The purpose of this study is to investigate the effects of miR-29 b to prevent the pathogenesis of interstitial fibrosis in the obstructed kidney of mouse with unilateral ureteral obstruction(UUO)via repressing phosphatidylinositol 3-kinase/protein kinase B(PI3K/AKT)signaling pathway.Methods Adult male CD-1 mice were intraperitoneally injected with vehicle or PI3 K inhibitor LY294002(3 mg/kg,30 mg/kg)daily for one or two weeks after performing UUO or sham operation.The mice were sacrificed on days 7 and 14 after surgery.The rat proximal tubular epithelial cell(TEC)line NRK-52 E was cultured in DMEM and treated with various concentrations angiotensin II(Ang II).Obstructed and sham mouse kidneys were analyzed via HE,Masson and immunohistochemistry to assess the degree of renal fibrosis.Real-time quantitative polymerase chain reaction assays(RT-PCR)was performed to investigate changes in the levels of expression of miR-29 b and Western blotting was used to analyze the activation of PI3K/AKT signaling and expression of E-cadherin,α-smooth muscle actin(α-SMA).Results Histologic analyses of obstructed kidney show that LY294002 attenuated the degree of renal fibrosis.In this study,loss of miR-29 b accompanied with increased epithelial-mesenchymal transition(EMT)was observed in renal tubules of mice after UUO and cultured NRK-52 E cells exposed to Ang II.LY294002 also decreased the gene expression of PI3K/AKT signaling pathway in vivo and vitro.By RT-PCR and Western blotting analysis,LY294002 blocked the PI3K/AKT-induced loss of E-cadherin expression and de novo increase of the expression of α-SMA in a time/dose-dependent manner.The overexpression of miR-29 b markedly reversed the phenotype induced by Ang II in NRK-52 E cells and the downregulation miR-29 b expression with an miR-29 b inhibitor resulted in enhanced EMT.Additionally,the PI3K/AKT signaling pathway was found to be suppressed in the presence of enhanced expression of miR-29 b by direct binding to 3’-untranslated region(3’-UTR)of PIK3R2.Conclusion Our findings suggest that LY294002 significantly attenuated tubulointerstitial damage in a UUO-induced mouse model of renal fibrosis.miR-29 b plays an important role in the negative regulation of Ang II-induced EMT via PI3K/AKT signaling pathway.These results provide novel mechanistic insights thatenhancing miR-29 b level or blocking PI3K/AKT signaling pathway may be a novel anti-fibrotic effect in renal interstitial fibrosis.