Astragaloside IV inhibits glucose-induced epithelial-mesenchymal transition of podocytes through autophagy enhancement via the SIRT-NF-κB p65 axis

Both autophagy and podocyte epithelial-mesenchymal transition (EMT) are critical factors in glomerular diseases that involve proteinuria and fibrosis. Here, we sought to determine whether plant-derived saponin astragaloside IV (AS-IV) was able to reverse renal fibrosis and improve renal function through regulation of autophagy and podocyte EMT. Cultured immortalized mouse podocytes and KK-Ay mice models of diabetes were exposed to AS-IV. Western blotting, real-time PCR, immunofluorescence and histochemistry were used to analyze markers of autophagy and podocyte EMT. We observed that AS-IV inhibited glucose-induced podocyte EMT and enhanced autophagy by decreasing NF-kappa B subunit p65 acetylation as well as increasing Sirtuin1 (SIRT1) expression. Treatment of the cells and animal models with a SIRT1 inhibitor EX527 was able to reverse these effects. The SIRT1 activator SRT1720 was also found to decrease p65 acetylation and enhance autophagy in glucose-induced podocyte EMT. Additionally, further treatment with autophagy inhibitor 3-methyladenine was able to reverse the effects of AS-IV on podocyte EMT, while the autophagy activator rapamycin or the NF-kappa B pathway inhibitor ammonium pyrrolidinedithiocarbamate (PDTC) were able to reverse glucose-induced podocyte EMT. Notably, both renal fibrosis and renal function in diabetic KK-Ay mice were improved after treatment with AS-IV. These findings support AS-IV as a renoprotective agent that likely exerts its effects on podocyte EMT through modulation of the SIRT1-NF-kappa B pathway and autophagy activation. Further studies are required to clarify the role of AS-IV as a potential therapeutic agent in glomerular diseases.