Astragalus membranaceus ameliorates renal interstitial fibrosis by inhibiting tubular epithelial-mesenchymal transition in vivo and in vitro.

Epithelial-mesenchymal transition (EMT) induces the progression of renal tubulointerstitial fibrosis. Astragalus membranaceus (AM) is a traditional Chinese herbal medicine that has been demonstrated to exert anti-inflammatory and anti-cancer effects, in addition to protecting and supporting the immune system. The present study investigated the effects of AM on renal fibrosis. A mouse model of unilateral ureteral obstruction (UUO) was established and treated with various concentrations of AM (100, 200 or 400 mg/kg/day). Interstitial fibrosis markedly increased in the UUO mice. AM significantly reduced the obstruction-induced upregulation of α-smooth muscle actin (α-SMA) and downregulation of E-cadherin in the kidneys of the UUO mice (P<0.05). Furthermore, AM treatment significantly inhibited the induction of EMT and the deposition of extracellular matrix. In addition, a transforming growth factor (TGF)-β1-stimulated murine renal proximal tubule cell line (NRK-52E) was treated with various concentrations of AM (10, 20, and 40 µg/ml). E-cadherin expression levels significantly decreased and those of α-SMA significantly increased in NRK-52E cells stimulated with TGF-β1 in vitro (P<0.05). Co-treatment with AM reversed these effects (P<0.05), and AM treatment reduced TGF-β1-induced expression and Smad2/3 phosphorylation (P<0.05). These results suggested that AM antagonizes tubular EMT by inhibiting the Smad signaling pathway.