Nephroprotective mechanism of Kunkui Baoshen decoction in diabetic kidney disease: Targeting the HERC2/NCOA4-mediated autophagy-dependent ferroptosis pathway.

BACKGROUND: Diabetic kidney disease (DKD) stands as the key contributor to chronic kidney disease worldwide. Clinical studies have shown that Kunkui Baoshen decoction (KKBS) effectively reduces proteinuria and enhances renal function in DKD patients. However, its precise molecular targets and therapeutic mechanisms remain to be thoroughly clarified. AIM: To evaluate the nephroprotective efficacy of KKBS in DKD and explore the underlying mechanisms of action. METHODS: Liquid chromatography-tandem mass spectrometry was utilized to analyze the chemical constituents of KKBS. Metabonomic and transcriptomic analyses were conducted to identify key targets and pathways associated with the therapeutic effects of KKBS on DKD. The nephroprotective effects of KKBS were assessed both in high glucose-induced human kidney-2 cells and in db/db mice. A variety of assays were performed, including Cell Counting Kit-8, Western blot, quantitative reverse transcription-polymerase chain reaction, immunofluorescence, co-immunoprecipitation, periodic acid-Schiff staining, Masson staining, hematoxylin and eosin staining, immunohistochemistry, and mitochondrial morphology analysis. RESULTS: The glutathione metabolic pathway emerged as the most prominent metabolic pathway in the metabonomic analysis of KKBS. Transcriptomic and bioinformatic analyses revealed that nuclear receptor coactivator 4 (NCOA4) was instrumental in regulating ferroptosis within renal tubules of mice with DKD. Both in vitro and in vivo experiments showed that KKBS ameliorated renal dysfunction, mitigated renal tissue damage, and repressed the expression of autophagy-dependent ferroptosis markers and inflammatory fibrosis. Mechanistically, KKBS enhanced the interaction between the homologous to E6-AP C-terminus and RCC1-like domain-containing E3 ubiquitin protein ligase (HERC2) and NCOA4, leading to K48-related ubiquitination and subsequent degradation of NCOA4. This process inhibited autophagy-dependent ferroptosis, reduced the release of pro-fibrotic inflammatory factors, and ultimately exerted an anti-fibrotic effect in DKD. CONCLUSION: KKBS confers nephroprotection in DKD by modulating HERC2/NCOA4-mediated autophagy-dependent ferroptosis, thereby alleviating renal fibrosis.