Sodium butyrate improves the cardiac immune microenvironment after myocardial ischemia-reperfusion injury by regulating macrophage polarization

Background Myocardial ischemia-reperfusion injury (MI/RI) remains a major determinant limiting the benefit of reperfusion therapy and is closely associated with dysregulated inflammatory responses[1, 2]. Gut microbiota-derived short-chain fatty acids, particularly butyrate, have emerged as potential modulators of cardiovascular immunity, yet their role in post-ischemic immune remodeling remains unclear[3]. Purpose To investigate whether sodium butyrate improves MI/RI and whether its effects are associated with macrophage polarization and metabolic reprogramming. Methods A rat MI/RI model was established with sodium butyrate intervention alongside Sham and untreated I/R groups. Single-cell RNA sequencing was performed on cardiac tissue at day 3 post-reperfusion to characterize immune composition and metabolic profiles. KEGG enrichment analysis was applied to evaluate macrophage metabolic patterns. Immunofluorescence staining assessed CD86 and CD206 expression, while Western blot quantified iNOS, Arg1, IL-1β, and TNF-α levels. Publicly available transcriptomic data of human macrophages treated with butyrate under lipopolysaccharide stimulation were analyzed using GSEA to evaluate mitochondrial energy metabolism pathways. Results Single-cell transcriptomic analysis demonstrated that MI/RI increased inflammatory macrophage subsets, whereas sodium butyrate promoted their transition toward reparative phenotypes. KEGG analysis indicated a shift in macrophage metabolic programming toward oxidative phosphorylation following butyrate treatment. Immunofluorescence confirmed decreased CD86+ macrophages and increased CD206+ macrophages in the treated group. Consistently, sodium butyrate reduced iNOS expression and increased Arg1 levels, accompanied by decreased IL-1β and TNF-α expression. GSEA of human macrophage datasets further showed enrichment of mitochondrial energy metabolism pathways, including oxidative phosphorylation and fatty acid metabolism, alongside remodeling of inflammation-related signaling pathways. Conclusions Sodium butyrate improves the cardiac immune microenvironment after MI/RI by promoting a metabolic shift toward oxidative phosphorylation, which facilitates macrophage polarization from a pro-inflammatory to a reparative phenotype, suggesting that gut-derived metabolic signals may regulate post-ischemic inflammation through immune cell remodeling.