Bufalin post-transcriptionally suppresses STAT3 to alleviate renal ferroptosis and tubulointerstitial fibrosis in diabetic kidney disease.

The pathological hallmark of diabetic kidney disease (DKD) is tubulointerstitial fibrosis (TIF), which arises from extracellular matrix (ECM) synthesis in renal tubular epithelial cells (RTECs). Bufalin has the potential in delaying the progression of kidney disease, and ferroptosis plays a critical role in this regulatory process. In this study, we investigated the effects of bufalin on DKD models by analyzing the expression of TIF and ferroptosis-related markers and evaluating the impact of ferrostatin-1 (Fer-1) on TIF. Our findings revealed that the treatment of bufalin in db/db mice and high glucose (HG)-induced RTECs altered the expression of TIF-related indicators. Ferroptosis was activated during the progression of TIF. Characteristic changes in ferroptosis, including iron overload, increased production of lipid peroxidation products, and decreased mitochondrial cristae, are induced by HG, and the treatment of Fer-1 reversed ferroptosis and further mitigated TIF. Notably, the intervention of bufalin in DKD models exhibited an inhibitory effect on ferroptosis. Network pharmacology analysis identified signal transducer and activator of transcription 3 (STAT3) as a target of bufalin, and knockdown of STAT3 altered the expression of ferroptosis and TIF-related indicators. Molecular docking studies, dual-luciferase reporter assay, and mRNA stability analysis further elucidated the regulation of STAT3 by bufalin and regulatory mechanism. Overall, these results demonstrate that bufalin promotes the degradation of STAT3 mRNA via a post-transcriptional mechanism. This downregulation inhibits STAT3-mediated ferroptosis, ultimately alleviating TIF in DKD.