Abstract

Sepsis-associated acute kidney injury (SA-AKI) is a life-threatening complication with limited therapeutic options. While both human umbilical cord mesenchymal stem cell-derived exosomes (HUCMSC-exo) and peroxisome proliferator-activated receptor α (PPARα) activation have shown potential in mitigating kidney injury, their functional interplay and underlying mechanisms, particularly concerning ferroptosis, remain unexplored. Exosomes from HUCMSCs were characterized using flow cytometry, transmission electron microscopy (TEM) and western blot. An in vitro SA-AKI model was established using lipopolysaccharide (LPS)-treated HK-2 cells. CCK-8 assay and flow cytometry were utilized to analyze cell viability and apoptosis. Inflammatory cytokine levels were measured by ELISA, and ferroptosis-related indicators were detected by corresponding kits. Bioinformatics analysis, co-immunoprecipitation, and chromatin immunoprecipitation (ChIP) assays were employed to identify and validate the interaction between PPARA and thioredoxin reductase 1 (TXNRD1). A murine model of SA-AKI was used for in vivo validation, with kidney injury evaluated histologically. Typical characteristics of HUCMSCs exo and the positive markers of HUCMSC-ex were identified. Then, it was found that HUCMSCs exo inhibited LPS-induced cell injury and ferroptosis, while PPARA-overexpressing HUCMSCs secreted exosomes that exhibited the same effect. Mechanistically, PPARA was found to directly bind to the promoter of and transcriptionally upregulate TXNRD1. Silencing TXNRD1 abolished the protective effects of PPARA-modified HUCMSC-exo and concurrently suppressed the activation of the downstream Nuclear Factor Erythroid 2-Related Factor 2 (NRF2)/Heme Oxygenase-1 (HO-1) pathway. In vivo, PPARA-exo treatment most effectively ameliorated renal histopathological damage and dysfunction in SA-AKI mice. PPARA fortifies the therapeutic potential of HUCMSC-exo against SA-AKI, at least in part, by direct transcriptional acti