HNRNPK Lactylation Amplifies Inflammation and Exacerbates Myocardial Ischemia/Reperfusion Injury by Regulating Jag2 Splicing.

BACKGROUND: Myocardial ischemia/reperfusion injury triggers profound metabolic reprogramming and lactate accumulation. However, how this metabolic stress regulates inflammatory gene expression remains poorly understood. We hypothesized that lactylation, a lactate-derived posttranslational modification, links metabolic stress to aberrant RNA splicing and cardiac inflammation through the RNA-binding protein HNRNPK (heterogeneous nuclear ribonucleoprotein K). METHODS: We analyzed atrial tissues from patients undergoing cardiopulmonary bypass and murine ischemia/reperfusion hearts to assess lactylation dynamics. Lactylation-specific proteomics, RNA sequencing, and crosslinking and immunoprecipitation followed by quantitative polymerase chain reaction were used to identify HNRNPK targets. Mechanisms were defined using site-directed mutagenesis (HNRNPK-K405R), isoform-specific overexpression, and a therapeutic splice-switching antisense oligonucleotide in mice and cardiomyocytes. RESULTS: Reperfusion significantly increased global protein lactylation in human and murine myocardium. Proteomics identified HNRNPK as a key target, specifically lactylated at lysine 405 (K405la). Ischemia-induced K405la promoted HNRNPK binding to Jag2 pre-mRNA, suppressing exon 10 skipping and shifting splicing from the Jag2 (Jagged2) short (Jag2-S) to the long (Jag2-L) isoform. Jag2-L, but not Jag2-S, exhibited high affinity for Notch1, hyperactivating Notch-NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) signaling and exacerbating inflammation and infarct size. Mice expressing a lactylation-deficient variant (HNRNPK-K405R) were protected from ischemia/reperfusion injury. Treatment with a specific antisense oligonucleotide (Jag2-i9) that blocks the HNRNPK-Jag2 interaction prevented Jag2-L production and attenuated cardiac dysfunction. CONCLUSIONS: HNRNPK lactylation acts as a metabolic sensor coupling lactate accumulation to pathogenic Jag2 splicing. Targeting this metabolic-splicing axis offers a precise therapeutic strategy to limit inflammation and preserve cardiac function in ischemic heart disease. REGISTRATION: URL: http://www.chictr.org.cn; Unique identifier: ChiCTR2400091959.