Tamoxifen ameliorates renal tubulointerstitial fibrosis by modulation of estrogen receptor α-mediated transforming growth factor-β1/Smad signaling pathway.

BACKGROUND: After insult to the kidney, a renal fibrotic process is initiated with sustained inflammation, fibroblast activation and accumulation of extracellular matrix (ECM). Tamoxifen has been used as an anti-estrogen for the prevention and treatment of breast cancer. In this study, we investigated the protective effects of tamoxifen on unilateral ureteral obstruction (UUO)-induced renal tubulointerstitial fibrosis and its molecular mechanism.

METHODS: Renal fibrosis was induced by UUO in 7-week-old C57BL/6 mice. Tamoxifen (50 mg/kg) was given by oral gavage for 5 days before induction of renal fibrosis. Tamoxifen treatment was continued for 14 days after UUO operation. Histologic changes were examined by periodic acid-Schiff stain and Masson's trichrome stain. Expression of α-smooth muscle actin, vimentin, type I collagen, fibronectin and cell adhesion molecules were evaluated by immunohistochemistry and western blot analysis. We also evaluated the effect of tamoxifen on estrogen receptor (ER)-α-mediated transforming growth factor (TGF)-β1/Smad signaling pathway in vitro.

RESULTS: Renal tubular injury and fibrosis were increased after UUO. Tamoxifen treatment significantly decreased UUO-induced renal tubular injury and fibrosis. Renal fibroblast activation, ECM deposition and inflammation were significantly increased after ureteral ligation. However, tamoxifen treatment significantly decreased UUO-induced renal fibroblast activation, ECM deposition and inflammation by suppression of TGF-β1/Smad signaling pathway in vivo. Tamoxifen decreased TGF-β1-induced fibroblast proliferation and cell migration by modulating ERα-mediated TGF-β1/Smad signaling pathway in vitro.

CONCLUSION: These findings indicate that tamoxifen has a beneficial effect on UUO-induced tubulointerstitial fibrosis by suppression of renal fibroblast activation via modulation of ERα-mediated renal TGF-β1/Smad signaling pathway.