Rhein Inhibited Ferroptosis and EMT to Attenuate Diabetic Nephropathy by Regulating the Rac1/NOX1/β-Catenin Axis

BACKGROUND: Diabetic nephropathy (DN) is one of the most serious complications of diabetes. Rhein has been reported to be effective in treating DN. This study aimed to investigate the role and mechanism of rhein in the treatment of DN. METHODS: High glucose-induced (HG) podocyte injury model and streptozocin-induced (STZ) DN mouse model were constructed and intervened with rhein. Cell viability was detected by Cell Counting Kit-8 (CCK-8) assay. The reactive oxygen species (ROS) level was measured by flow cytometry. The expression of Ras-related C3 botulinum toxin substrate 1 (Rac1), NADPH Oxidase 1 (NOX1), and β-catenin were measured by quantitative real-time PCR (RT-qPCR). The contents of glutathione peroxidase 4 (GPX4), α-smooth muscle actin (α-SMA), Nephrin, and Podocin were characterized by immunofluorescence (IF) staining. Hematoxylin-eosin (HE) staining and Masson staining were employed to observe the renal morphological changes and tubulointerstitial fibrosis. The contents of α-SMA and Nephrin were detected by immunohistochemistry (IHC) staining. The kits were utilized to analyze various biochemical indicators. RESULTS: Rhein inhibited the HG-induced accumulation of ROS, malondialdehyde (MDA), and Fe2+, and the expression of α-SMA, Transferrin Receptor 1 (TFR1), acyl-CoA synthetase long-chain family member 4 (ACSL4), Vimentin, Snail, and Desmin. Rhein inhibited the expression of Rac1 and its downstream targets NOX1 and β-catenin. Rac1 silencing (si-Rac1) inhibited the accumulation of MDA and Fe2+ and the expression of Rac1, NOX1, β-catenin, α-SMA, TFR1, and ACSL4. Rac1 overexpression (oe-Rac1) resulted in the inhibition of superoxide dismutase (SOD), glutathione (GSH), GPX4 synthesis, and down-regulation of Recombinant Solute Carrier Family 7, Member 11 (SLC7A11) and Nephrin expression in HG-treated podocytes. Rac1 Lentivirus (LV-Rac1) injection significantly promoted the accumulation of MDA and Fe2+ and increased the expression of RAC1, NOX1, β-catenin, TFR1, ACSL4, and α-SMA in DN mice. CONCLUSIONS: Rhein inhibited ferroptosis and epithelial-mesenchymal transition (EMT) to attenuate DN by regulating the Rac1/NOX1/β-catenin axis.