Rhein Inhibits Autophagy in Rat Renal Tubular Cells by Regulation of AMPK/mTOR Signaling

Rhubarb and its bioactive component rhein are frequently used for the treatment of chronic kidney diseases (CKD) in eastern Asia countries. However, the potential therapeutic mechanism remains unclear. Autophagy plays an important role in CKD. However, there were some important related issues that remained unresolved in the role of autophagy in CKD and treatment by rhubarb and rhein. We designed a number of experiments to examine whether rhubarb may reduce renal fibrosis and autophagy in rats with adenine (Ade)-induced renal tubular injury, and whether rhein could affect autophagic pathways in rat renal tubular cells. We found that, autophagic activation accompanied with renal fibrosis in rats with Ade-induced renal tubular injury, and both autophagy and renal fibrosis were attenuated by rhubarb. In addition, we observed that rhein could inhibit autophagy through regulating the key molecules in the AMPK-dependent mTOR signaling pathways, as well as the Erk and p38 MAPKs signaling pathways. These findings may partly explain the therapeutic mechanisms of rhubarb and rhein in treating CKD patients in clinic, and further suggest that targeting autophagy and related signaling pathways may provide new strategies for the treatment of renal fibrosis in CKD.