Emodin ameliorates renal fibrosis in rats via TGF-beta 1/Smad signaling pathway and function study of Smurf 2

Emodin is a natural active component extracted from Chinese herbs. In this study, we investigated the therapeutic effect of emodin on surgery-induced renal fibrosis in rat. Moreover, the function of Smad ubiquitination regulatory factor 2 (Smurf 2) was further studied in vitro. The renal fibrosis rat model was established via 5/6 renal mass reduction. The histopathological abnormalities of renal tissues in rats were tested via staining method and microscopic examination. Renal function indicators, the serum creatinine, blood urea nitrogen and total urinary protein were measured via spectrophotometric method. The renal tissues were tested via Western blotting and real-time quantitative PCR. Moreover, Smurf 2 protein expression under different conditions and its regulatory function in vitro was measured via Western blotting. Our results showed that the histopathological abnormalities, the decrease in rat body weight and the abnormal renal function caused by renal fibrosis were improved by emodin. Further, mRNA expression of TGF-beta 1 was decreased by emodin. Furthermore, extracellular matrix (ECM) components as well as TGF-beta 1/Smad signaling-related Smurf 2 were decreased by emodin both in vivo and in vitro. The protein level of mothers against decapentaplegic homolog 7 (Smad7) was up-regulated. In addition, ECM components were increased by Smurf 2 over-expression and these effects were weakened by emodin co-treatment in vitro. Emodin showed an anti-fibrosis effect in surgery-induced renal fibrotic rats. And this effect was potentially achieved via down-regulating expressions of TGF-beta 1 and Smurf 2 and up-regulating Smad7 expression.