#2743 Impact of fatty acid-binding protein 4 on SUMOylation balance and renal tubular epithelial cell senescence in acute kidney injury

Abstract Background and Aims Dysregulated lipid metabolism and cellular senescence intricately interact in the context of acute kidney injury (AKI). Fatty acid-binding protein 4 (FABP4), a critical enzyme regulating lipid metabolism, potentially induces cell senescence through lipotoxicity in AKI. However, the specific mechanisms remain unclear. Method We established an ischemia-reperfusion-induced AKI (IRI-AKI) model in C57 mice and quantified and localized FABP4 expression in renal tissues using Western blotting (WB), qPCR, and immunofluorescence (IF). Oil Red O staining and beta-galactosidase staining were employed to assess lipid deposition and cellular senescence in tubular cells. The same measurements were repeated in IRI-AKI by knocking out Fabp4. Additionally, bulk mRNA sequencing and single-cell sequencing were conducted on renal tissues to analyze key molecules and related mechanisms. Results In vivo, we observed a significant decline in renal function, severe tubular epithelial damage, and abundant inflammation in the IRI-AKI group, which was noticeably alleviated in the Fabp4 knockout group (Fig. 1). Furthermore, we detected upregulation of FABP4 expression in the kidneys of IRI-AKI, primarily localized in the tubular epithelial cells. Fabp4 knockout effectively reduced tubular lipid accumulation and cellular senescence (Fig. 3). Through integrating mRNA and single-cell sequencing data, UBC9, an E2 enzyme involved in protein SUMOylation, emerged as a potential key regulator of cell senescence and AKI. WB and qPCR both confirmed the upregulation of UBC9 expression in IRI-AKI and its downregulation after Fabp4 knockout. Conversely, we observed that downregulated SUMOylation in IRI-AKI was upregulated in the Fabp4 knockout group (Fig. 4). Conclusion In conclusion, FABP4 modulates the expression of UBC9 and SUMOylation, thereby mediating cellular senescence and causing renal tubular cell damage in IRI-AKI. The mechanisms underlying FABP4’s regulation of UBC9 and the opposing trend between UBC9 and SUMOylation require further elucidation.