Autophagy attenuates renal fibrosis in obstructive nephropathy through inhibiting epithelial-to-mesenchymal transition.

Abstract

To explore the relationship between autophagy and epithelial-to-mesenchymal transition (EMT), and to evaluate whether autophagy can affect the progression of renal fibrosis in obstructive nephropathy by regulating the EMT process. Unilateral ureteral obstruction (UUO) renal fibrosis model of rat was constructed, and the animals were divided into a sham group, an UUO group, an UUO+low-dose rapamycin group, and an UUO+high-dose rapamycin group. HE staining was used to observe the structure of the kidney, and Masson staining was used to observe renal interstitial collagen deposition. The expressions of E-cadherin, alpha-smooth muscle actin (α-SMA), Snail 1, and microtubule-associated protein-1 light chain 3II (LC3II) were detected by Western blotting, reflecting cellular EMT and autophagy. Transforming growth factor β1 (TGF-β1) induced-NRK52E cells model was constructed, and the cells were divided into a control group, a TGF-β1 group, and a TGF-β1+ Snail 1 siRNA group. To explore the effect of autophagy on EMT, the cells were also divided into a control group, a rapamycin group, and a Beclin 1 siRNA group. Western blotting was used to detect the expressions of E-cadherin, α-SMA, Snail 1, LC3II, collagen I, and fibronectin. Compared with the sham group, the kidney damage in the UUO group was significantly worse; compared with the sham group, the collagen deposition in the kidney tissues in the UUO group was significantly increased, which were significantly reduced in the UUO+high-dose rapamycin group and the UUO+low-dose rapamycin group compared with the UUO group; compared with the sham group, the E-cadherin level in the kidney of the UUO group was significantly reduced, and the expression levels of α-SMA and LC3II were significantly increased (all P<0.05). Compared with the UUO group, the expression levels of E-cadherin and LC3II in the UUO+high-dose rapamycin group and the UUO+low-dose rapamycin group were significantly increased (P<0.01 and P<0.05, respectively), and the expression level of α-SMA was significantly decreased (P<0.01 and P<0.05, respectively). The expression levels of Snail 1, α-SMA, collagen I and fibronectin were significantly higher, and the E-cadherin level was significantly lower in the TGF-β1 group than those in the control group (all P<0.05). Compared with the TGF-β1 group, the expression of E-cadherin was increased significantly, and the expressions of α-SMA, collagen I and fibronectin were decreased significantly in the TGF-β1+Snail 1 siRNA group (all P<0.05). Compared with the control group, the expression levels of LC3II and E-cadherin were significantly elevated, and the expression levels of α-SMA and Snail 1 in the rapamycin group were significantly reduced (all P<0.05); the expression levels of LC3II and E-cadherin were significantly reduced, and the expression levels of α-SMA and Snail 1 were significantly increased in the Beclin 1 siRNA group (all P<0.05). Autophagy plays an essential role in the regulation of EMT in obstructive nephropathy fibrosis. Autophagy can alleviate renal fibrosis by inhibiting EMT.