| Summary: | Accumulating evidence indicates that angiotensin (1-7) [Ang-(1-7)] protects against idiopathic pulmonary fibrosis (IPF) in animal experiments. However, whether Ang-(1-7) effectively inhibits epithelial-mesenchymal transition (EMT) induced by transforming growth factor-β1 (TGF-β1) remains unclear. The aim of this study is to examine the eff ;ects of Ang-(1-7) on TGF-β1-induced EMT in human alveolar epithelial cells. We found that angiotensin-converting enzyme 2 (ACE2) /Ang-(1-7)/MasR were decreased in the lungs of mice with IPF induced by bleomycin, and were negatively correlated with Tgfb1 mRNA expression. In vitro, our data showed that exogenous Ang-(1-7) restored the expression of E-cadherin and decreased the expressions of α-SMA and Vimentin induced by TGF-β1 in A549 cells. Ang-(1-7) also reduced TGF-β1-induced migration and synthesis of the extracellular matrix, such as collagen Ⅰ and collagen Ⅲ. Mechanistically, we observed that Ang-(1-7) directly inhibited TGF-β1-induced phosphorylation of Smad2 and Smad3, and suppressed the expression of the downstream target gene of TGF-β1-Smad signaling, including ZEB1, ZEB2, TWIST, and SNAIL1. Additionally, phosphorylation of mTOR induced by TGF-β1 also been suppressed by Ang-(1-7) treatment in A549 cells. Interestingly, we found that TGF-β1 strongly suppressed the expression of ACE2 in A549 cells through inhibiting SIRT1. In conclusion, our findings indicate that Ang-(1-7) directly inhibits TGF-β1-induced EMT in alveolar epithelial cells via disruption of TGF-β1-Smad signaling pathway, contributing to the protective effect against IPF.
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