Triptolide ameliorates renal tubulointerstitial fibrosis through EZH2

Renal fibrosis is the final pathological pathway of various kidney disease in progression to the end stage of renal failure. Recent studies showed that the histone methyltransferase enhancer of zeste homolog 2 (EZH2) is an important epigenetic regulator of renal fibrosis by promoting epithelial-mesenchymal transition (EMT) and activation of TGF-{beta}/Smad3 signaling pathway in fibrotic kidneys. Triptolide is component extracted from radix tripterygium wilfordii, which provides renal benefits to patients with renal diseases in China. Recently, triptolide was identified as an inhibitor of EZH2. Thus, we hypothesized that triptolide inhibits renal fibrosis through EZH2. In this study, we found that triptolide reduced the deposition of extracellular matrix in the kidney of unilateral ureteral obstruction (UUO) mice. The anti-fibrotic effect of triptolide was further confirmed in TGF-{beta} stimulated HK2 cells, a human renal epithelial cell line. Moreover, treatment of triptolide blocked the up-regulation of EZH2 in UUO kidneys and reduced the expression of EZH2 in TGF-{beta} stimulated HK2 cells. Down-regulation of EZH2 by triptolide was correlated with reduced expression of EMT markers and phosphorylation of Smad3 in UUO kidneys and TGF-{beta} stimulated HK2 cells. Finally, we showed that inhibition of EZH2 by 3-DZNep attenuated the inhibitory effect of triptolide on the expression of extracellular matrix protein, EMT markers and activation of Smad3 in TGF-{beta} stimulated HK2 cells. In conclusion, triptolide inhibits renal tubulointerstitial fibrosis through EZH2 in obstructive kidneys.