Epigenetic BET protein signaling drives autophagy dysfunction in HFpEF

Background

Cardiometabolic heart failure with preserved ejection fraction (cHFpEF) is a prevalent condition with poorly defined molecular mechanisms. Impaired autophagy has emerged as a key contributor to disease progression, while epigenetic regulators may link environmental stressors to maladaptive gene expression. Bromodomain and extraterminal domain (BET) proteins act as epigenetic readers of acetylated histones and represent promising therapeutic targets; however, their role in cardiac autophagy regulation remains largely unknown. We hypothesized that BET proteins contribute to autophagy dysregulation in cHFpEF and that pharmacological BET inhibition restores autophagic flux and cardiac function.

Methods

An established mouse model of cHFpEF induced by combined metabolic and hemodynamic stress for 15 weeks was used. Autophagy-related transcriptional changes were assessed using single-nucleus RNA sequencing (snRNA-seq; 10x Genomics). Chromatin immunoprecipitation sequencing (ChIP-seq) was performed to evaluate histone modifications at autophagy-associated gene loci, and pathway-level changes were analyzed by gene set enrichment analysis (GSEA) using Reactome gene sets with false discovery rate (FDR) correction.

cHFpEF and control mice were subsequently treated for 21 days with vehicle or the selective BET inhibitor RVX-208 (Apabetalone). Cardiac function was assessed by echocardiography, and autophagy-related gene expression was quantified using a custom real-time PCR array. Cardiomyocytes exposed to palmitic acid were used as an in vitro model of metabolic stress.

Results

snRNA-seq revealed a significant downregulation of autophagy-related genes in cHFpEF hearts compared with controls. Clustering analysis identified a distinct subset of ventricular cardiomyocytes with impaired autophagy, characterized by activation of mTOR and calcineurin signaling, sustained oxidative stress, altered mitochondrial dynamics, and increased apoptotic signaling. Epigenomic profiling demonstrated enrichment of active chromatin marks, particularly H3K27ac, at autophagy- and stress-responsive gene loci, consistent with BET-dependent transcriptional regulation. Importantly, BET inhibition with RVX-208 restored autophagy-related transcriptional programs and significantly improved diastolic function and exercise capacity.

Conclusions

These findings identify a BET-driven epigenetic mechanism regulating autophagy in cHFpEF and demonstrate that pharmacological BET inhibition restores autophagic signaling and improves cardiac function, supporting BET proteins as therapeutic targets in HFpEF.Molecular phenotyping of HFpEF miceFor image description, please refer to the figure legend and surrounding text.Chromatin remodeling in HFpEFFor image description, please refer to the figure legend and surrounding text.