Multi-omics analysis identifies NFIL3 as a hypoxia-associated immune regulator in septic cardiomyopathy

Background Sepsis is a life-threatening syndrome caused by a dysregulated host response to infection and is associated with high mortality in intensive care units. Septic cardiomyopathy (SCM) is a frequent and severe complication of sepsis; however, its underlying molecular mechanisms and immune regulatory networks remain incompletely understood. Methods Transcriptomic profiling of septic mouse myocardium was performed to characterize hypoxia-associated immune remodeling at both bulk and single-cell levels. Hypoxia-related genes were identified through integrative differential expression and network analyses. These candidate genes were mapped to human peripheral blood transcriptomic datasets for machine learning–based biomarker selection, followed by two-sample Mendelian randomization analysis to assess their causal relevance to sepsis. In vivo and in vitro experiments were conducted to validate the mechanistic involvement of key genes in septic cardiomyopathy. Results Septic myocardium exhibited prominent activation of hypoxia-related signaling accompanied by immune landscape remodeling, characterized by increased macrophage infiltration. NFIL3, TGM2, and SDC4 were identified as key hypoxia-associated hub genes and showed robust diagnostic performance in independent human peripheral blood cohorts. Two-sample Mendelian randomization analysis demonstrated that genetically predicted higher NFIL3 expression was significantly associated with increased sepsis risk. Single-cell analysis revealed predominant enrichment of Nfil3 in macrophages. Consistently, in vivo and in vitro experiments confirmed time-dependent upregulation of NFIL3 and HIF-1α in myocardial macrophages during sepsis, with evident spatial colocalization. Functional experiments further demonstrated that NFIL3 negatively regulates macrophage inflammatory responses, at least in part through inhibition of NF-κB signaling. Conclusion This study systematically delineates the molecular basis of septic cardiomyopathy, highlighting hypoxia-driven immune dysregulation as a central pathogenic mechanism. As a key hypoxia-responsive immune regulator, NFIL3 may play a critical role in the development of septic cardiac injury. These findings identify novel molecular targets for the early diagnosis and therapeutic intervention of sepsis and its associated myocardial damage.