Hederagenin improves renal fibrosis in diabetic nephropathy by regulating Smad3/NOX4/SLC7A11 signaling-mediated tubular cell ferroptosis

Diabetic nephropathy (DN) is a common complication of diabetes, characterized by renal fibrosis and poor patient prognosis. Hederagenin (HDG) has shown promising improvement in chronic kidney disease (CKD) kidney fibrosis, but its mechanism in DN-induced kidney fibrosis remains unclear. In this study, a model of diabetic nephropathy (DN) in mice was induced by intraperitoneal injection of streptozocin (50 mg/kg), while in vitro, high glucose (25 mM) was used to induce HK2 cell damage, simulating tubular injury in DN kidneys. The improvement of HDG treatment intervention was evaluated by observing changes in renal function, pathological structural damage, and the expression of fibrosis-related proteins in renal tubular cells. The results demonstrate that HDG intervention alleviates renal dysfunction and pathological damage in DN mice, accompanied by reduced expression of fibrotic markers α-smooth muscle actin (α-SMA), fibronectin (FN) and Collagen-I. Mechanistically, this study found that HDG can inhibit ferroptosis and fibrosis induced by the ferroptosis inducer Erastin (1 μM) in renal tubular cells. Phosphorylation of Smad3 promotes ferroptosis in renal tubular cells. After using its specific inhibitor SIS3 (4 μM), the expression of downstream target protein NADPH oxidase 4 (NOX4) significantly decreases, while the level of glutathione peroxidase 4 (GPX4) is notably restored, mitigating ferroptosis. Smad3 overexpression attenuates the therapeutic effect of HDG on tubular cell fibrosis induced by high glucose. These results demonstrate HDG inhibits Smad3 phosphorylation, thereby reducing the expression of NOX4 and enhancing the expression of GPX4, ultimately attenuating ferroptosis induced renal fibrosis. These findings suggest that HDG offer therapeutic potential for DN renal fibrosis by targeting Smad3-mediated ferroptosis in renal tubular cells.