Renal fibrosis progresses to end stage of diabetes kidney disease, which causes irreversible progressive proximal tubular injury. In a previous study, 20-hydroxyecdysterone (20-HE), a phytoecdysteroid, attenuated renal injury in diabetes models. However, the fibrosis regulatory role remains to be investigated.
Methods: The proximal tubular epithelial cells (designated as HK-2) were treated for 48 h with TGF-β1 (5 ng/ml) in different concentrations of 20-HE (0 to 500 nM/ml) in the last 24 h of culture. The extracellular fibronectin was measured by ELISA assay. Western blot and immunofluorescence were used to evaluate the expression of TGF-β1/Smads transducer (including Smad2/3, 4, and 7), epithelial and mesenchymal markers (e.g. E-cadherin and α-smooth muscle actin) and Snail (transcriptional regulators for EMT).
Results: 20-HE reverses TGF-β1-induced increase in fibronectin (both intracellular and extracellular fibronectin). Simultaneously, 20-HE reverses TGF-β1-induced down-regulation of Smad7. In addition, 20-HE significantly attenuates TGF-β1-induced upregulation of Smad2/3 and pSmad2/3, and downregulation of E-Cadherin. Moreover, 20-HE dramatically suppresses TGF-β1-induced increases in the expression of Snail.
Conclusion: We propose that 20-HE is a potential fibrosis antagonist for renal proximal tubule cells. 20-HE might act through suppressing post-receptor signaling of TGF-β1 and restoring tubule epithelial character by blocking the expression of Snail.
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