TRIM24 preserves cardiomyocyte immune quiescence by repressing interferon/STAT signaling

Innate immune activation in cardiomyocytes is a key driver of inflammatory heart disease and heart failure progression, yet the mechanisms by which cardiomyocytes maintain transcriptional immune quiescence remain poorly understood. TRIM24, a multidomain chromatin reader implicated in cancer and inflammation, has not been previously studied in the heart. Here, we investigated whether TRIM24 regulates interferon/STAT-driven inflammatory programs and paracrine signaling in cardiomyocytes. Single-nucleus RNA sequencing revealed a pronounced downregulation of TRIM24 specifically in cardiomyocytes from human ischemic cardiomyopathy, a change not detected by bulk RNA-sequencing in either human or mouse myocardial infarction samples, likely due to masking by non-cardiomyocyte cell populations. Fractionated protein analysis further demonstrated that TRIM24 is enriched in cardiomyocyte nuclei. Functional studies in neonatal rat ventricular cardiomyocytes showed that TRIM24 represses interferon-stimulated and STAT-dependent genes, including Mx1, Irf7, and Ifit3. ChIP-Seq revealed TRIM24 occupancy at STAT-bound regulatory regions, suggesting cooperative suppression of inflammatory gene networks. Mechanistically, TRIM24 decreased Stat1a/b and Stat3 transcription, reduced protein abundance, and inhibited phosphorylation independently of proteasomal degradation; these effects were partially reversible by bromodomain inhibition. Functionally, TRIM24 overexpression dampened paracrine macrophage recruitment, whereas TRIM24 depletion amplified it. Collectively, these findings identify TRIM24 as a cardiomyocyte-enriched chromatin regulator that restrains STAT1/3 signaling and suppresses paracrine inflammatory activation. TRIM24 acts as a transcriptional safeguard of immune quiescence in the heart and represents a potential therapeutic target for limiting cardiac inflammation.