Silencing of angiotensin II type-1 receptor inhibits high glucose-induced epithelial-mesenchymal transition in human renal proximal tubular epithelial cells via inactivation of mTOR/p70S6K signaling pathway

The epithelial-mesenchymal transition (EMT) plays a significant role in renal tubulointerstitial fibrosis (TIF), which is one of hallmark pathological feature of diabetic nephropathy (DN). Angiotensin II via its type-1 receptor AT1R is involved in the development of TIF. The purpose of our study was aimed to investigate the effect of silencing of AT1R on EMT and elucidate the possible mechanism underling these effects. EMT was induced by high glucose (HG) in human proximal tubular epithelial cell line HK-2 cells. The mRNA levels of AT1R were determined. The expression of AT1R was silenced by small interfering RNA (siRNA) technology and confirmed by quantitative real time PCR (qRT-PCR). After transfection with siAT1R, cell viability and expression levels of epithelial cell marker (epithelial (E)-cadherin), mesenchymal cell marker (alpha-smooth muscle actin (alpha-SMA)), four transcriptional factors (snail, slug, twist, and ZEB-1) were determined, as well as the roles of mechanistic target of rapamycin (mTOR)/p70S6K signaling pathway. The levels of AT1R were significantly higher after exposure to HG (P < 0.05). Transfection with siAT1R had no effect on cell viability, but reversed HG-induced EMT by up-regulation of E-cadherin expression and decrease of alpha-SMA, snail, and twist levels. MTOR/p70S6K signaling pathway was highly activated in HK-2 cells cultured under HG, but was inhibited by transfection with siAT1R. Our results suggest that silencing of AT1R inhibits EMT induced by HG in HK-2 cells via inactivation of mTOR/p70S6K signaling pathway. Silencing of AT1R might be a new strategy to treat DN. (C) 2015 Elsevier Inc. All rights reserved.