Relaxin-3 attenuates sepsis-induced myocardial injury by modulating the ACSS2/ACLY-acetyl-CoA-H3K18ac axis in macrophages.

Sepsis-induced myocardial injury (SIMI) is a severe complication of sepsis with limited mechanism-based therapies. We investigated whether Relaxin-3 attenuates SIMI and modulates macrophage inflammatory responses. A caecal ligation and puncture (CLP)-induced sepsis model was established in male C57BL/6J mice, and RAW264.7 macrophages were stimulated with lipopolysaccharide (LPS) to establish an in vitro inflammatory model. Relaxin-3 was administered to evaluate its effects on myocardial injury and M1/M2 macrophage markers. Immunofluorescence staining and immunoblotting were used to assess inflammatory, apoptotic, and macrophage polarization markers in myocardial tissues and RAW264.7 cells. Integrated transcriptomic and CUT&Tag analyses were performed to characterize H3K18ac-associated chromatin changes in LPS-stimulated RAW264.7 cells. Relaxin-3 attenuated myocardial histopathological injury and altered myocardial macrophage polarization marker expression in septic mice, with reduced iNOS/CD86 and increased CD206. In LPS-stimulated RAW264.7 cells, Relaxin-3 inhibited early NF-κB activation, reduced iNOS, and increased CD206. Multi-omics analysis showed increased promoter-proximal H3K18ac enrichment at inflammatory genes, including Hck, Cxcl10, and Ccl5, and Relaxin-3 reduced H3K18ac. Mechanistically, Relaxin-3 reduced ACSS2, ACLY, phospho-ACLY (S455), and acetyl-CoA levels, while pharmacological inhibition of ACSS2/ACLY showed similar effects on H3K18ac, inflammatory genes, and macrophage polarization markers. Relaxin-3 attenuates sepsis-induced myocardial injury by modulating macrophage polarization through the ACSS2/ACLY-acetyl-CoA-H3K18ac axis.