P300-Targeted Acetylome Reveals a Role for HMGB1 Translocation in Central Cardiac Sympathetic Activation Post Myocardial Infarction

Background: Microglia/macrophage-dominated neuroinflammation in the hypothalamic paraventricular nucleus (PVN) critically mediates sympathetic overactivation, with the underlying mechanism remained elusive. Given that protein acetylation serves as a pivotal epigenetic modifier of inflammatory responses to immune-microenvironmental changes, we aimed to explore the role of acetyltransferase p300 in the pathophysiological process of sympathetic activation post-myocardial infarction (MI). Methods and Results: Rats MI model was established by ligating LAD artery. During early stage, p300 was increased in the PVN and mainly localized on microglia. Microinjection of short-hairpin RNA (shRNA) targeting p300 into the PVN effectively knocked down p300 expression, resulting in reduced peripheral sympathetic nerve activity and decreased cardiac norepinephrine levels. Programmed electrical stimulation post-MI revealed that p300 knockdown decreased ventricular arrhythmia (VA) susceptibility. p300-regulated acetylome was analyzed using shotgun proteomics in human HCM3 cells, and 135 target acetylated proteins were identified. Bioinformatic analysis and coimmunoprecipitation assays revealed that p300 interacted with and acetylated high-mobility group protein B1 (HMGB1). P300 facilitated the cytoplasmic translocation of HMGB in microglia in vivo, thereby contributing to cardiac sympathetic activation. Protein docking analysis and brain slice patch-clamp recordings revealed the potential interaction between HMGB1 and excitatory glutamate receptor N-methyl-D-aspartate receptor (NMDAR) levels. Rescue experiments employing patch-clamp electrophysiology with a recepor-specific inhibitor confirmed direct mediation of HMGB1 in neuronal activation through NMDAR-dependent mechanisms. Conclusion: Microglial p300-mediated translocation of HMGB1 in the PVN may be a fundamental epigenetic mechanism in NMDAR-mediated central sympathetic activation post-MI, suggesting targeting p300 signaling modulation in the PVN as a potential antiarrhythmic therapy.