Celastrol attenuates renal injury in 5/6 nephrectomized rats via inhibiting epithelial-mesenchymal transition and transforming growth factor-ß1/Smad3 pathway.

Renal injury is an important factor in the development of chronic kidney diseases that pathologically manifested as renal fibrosis and podocyte damage. In the disease state, renal fibroblasts lead to high expression levels of α-smooth muscle actin (α-SMA), while podocytes undergo epithelial-mesenchymal transition, leading to proteinuria. Celastrol, a bioactive compound in the medicinal plant Tripterygium wilfordii, was found to delay the progression of early diabetic nephropathy and attenuate renal fibrosis in mice with unilateral ureteral obstruction. However, its effect on the renal system in 5/6 nephrectomized (Nx) rats remains unknown. The aim of this study was to explore the protective effects of celastrol and its underlying mechanisms in 5/6 Nx rats. We found that 24 h proteinuria and levels of blood urea nitrogen, serum creatinine, triglycerides, serum P, renal index and cholesterol significantly increased (P < 0.05), while that of serum albumin decreased significantly in 5/6 Nx rats. After intervention with celastrol, 24 h proteinuria and levels of blood urea nitrogen, serum creatinine, triglycerides, serum P, renal index, and cholesterol significantly decreased, while that of serum albumin significantly increased. Renal tissue pathological staining and transmission electron microscopy showed that celastrol ameliorated kidney injury and glomerular podocyte foot injury and induced significant anti-inflammatory effects. Quantitative polymerase chain reaction (PCR) and western blotting results revealed that nephrin and NEPH1 expression levels were upregulated, whereas α-SMA and Col4a1 expression levels were downregulated in the celastrol group. Celastrol inhibited the expression of transforming growth factor (TGF)-ß1/Smad3 signaling pathway-related molecules such as TGF-ß1 and P-Smad3. In summary, celastrol contributes to renal protection by inhibiting the epithelial-mesenchymal transdifferentiation and TGF-ß1/Smad3 pathways.

[Study of resveratrol suppressing TGF-beta1 induced transdifferentiation of podocytes].

OBJECTIVE: To explore the effect of resveratrol on transforming growth factor-beta1 (TGF-beta1) induced transdifferentiation of podocytes. METHODS: Mouse podocytes in vitro cultured under differentiating conditions for 10 days were divided into the normal group, the model group, the high dose resveratrol group, and the low dose resveratrol group. The podocytes in the high and low dose resveratrol groups were intervened with 5 micromol/L and 2 micromol/L resveratrol respectively for 30 min. Those in the model group and the two resveratrol treated groups were continually incubated with 5 ng/mL TGF-beta1 for 72 h. Those in the normal group were routinely cultured. The protein expression of podocyte phenotypic protein molecules such as E-cadherin, P-cadherin, zonula occludens-1 (ZO-1), NEPH1, and alpha-smooth muscle-actin (alpha-SMA) were detected by immunocytochemistry, flow cytometry (FCM), and Western blot. A simple albumin influx assay was used to evaluate the filtration barrier function of podocyte monolayer. RESULTS: Compared with the normal control group, E-cadherin (+) percentage rate, the protein expression of P-cadherin, ZO-1, and NEPH1 significantly decreased in the model group (P < 0.05), but the expression of alpha-SMA and albumin permeability across podocyte monolayers increased significantly (P < 0.05). Compared with the model group, E-cadherin (+) percentage rate significantly increased (P < 0.05) and albumin permeability across podocyte monolayers decreased significantly (P < 0.05) in the high and low dose resveratrol groups. In the low dose resveratrol group, the expression of P-cadherin and NEPH1 significantly increased (P < 0.05). In the high dose resveratrol group, the expression of P-cadherin, ZO-1, and NEPH1 increased significantly, and the expression of alpha-SMA decreased significantly (P < 0.05). The correlations between resveratrol concentrations and the expression of E-cadherin (+), P-cadherin, and NEPH1 were significantly positive (r(E-cadherin (+)) = 0.772, r(P-cadherin) = 0.756, r(NEPH1) = 0.809, P < 0.05). CONCLUSION: The role of resveratrol in inhibiting TGF-beta1 induced phenotype abnormality might be an important mechanism for preserving the integrality of glomerular filtration barrier and decreasing proteinuria.