ATF4–histone 2‐hydroxyisobutyrylation feedback loop drives sepsis‐induced inflammation

Background and Purpose The role and mechanisms of lysine 2‐hydroxyisobutyrylation (Khib) in the acute inflammatory phase of sepsis remain unclear. We investigated the function and underlying mechanisms of histone H4 lysine 5 2‐hydroxyisobutyrylation (H4K5‐hib) in sepsis‐induced inflammation in vivo and in vitro . Experimental Approach Acute sepsis was induced by caecal ligation and puncture (CLP) in mice, and inflammatory responses were modelled in lipopolysaccharide (LPS)‐stimulated macrophages. CUT&Tag‐seq was used to identify genomic targets associated with H4K5‐hib and activating transcription factor 4 (ATF4). Immunofluorescence, Western blotting, qPCR, dual‐luciferase assays, and ELISA were performed to investigate the underlying mechanisms. Key Results H4K5‐hib levels were increased in macrophages during the acute inflammatory phase of sepsis. LPS stimulation enhanced H4K5‐hib enrichment at the ATF4 promoter, thereby promoting ATF4 transcription. Inhibition of EP300‐mediated 2‐hydroxyisobutyrylation or mutation of H4K5 abolished ATF4 activation. Increased H4K5‐hib activated the ATF4/NLRP3 signalling axis, promoting inflammasome assembly and amplifying inflammatory responses. ATF4 directly bound to the EP300 promoter and enhanced its transcription, forming a positive feedback loop that further increased H4K5‐hib levels. In CLP‐induced sepsis, pharmacological inhibition of EP300 or ATF4 reduced H4K5‐hib levels and suppressed NLRP3 inflammasome activation. Conclusion and Implications These findings reveal a previously unrecognized epigenetic mechanism underlying sepsis‐induced inflammation and identify the EP300/ATF4/H4K5‐hib positive feedback loop as a potential therapeutic target for sepsis.