LAUSR

Evidence from human epidemiological studies suggests that exertional heat stroke (EHS) results in elevated risk of long-term cardiovascular and systemic disease. Previous results using a preclinical mouse model of EHS demonstrated severe metabolic imbalances in ventricular myocardium developing at 9-14 d of recovery. Whether this resolves over time is unknown. We hypothesized that long-term effects of EHS on the heart reflect retained maladaptive epigenetic responses. In this study, we evaluated genome-wide DNA methylation, RNA-Seq and metabolomic profiles of the left ventricular myocardium in female C57BL/6 mice, 30 d after EHS (exercise in 37.5°C; n = 7-8), compared to exercise controls. EHS mice ran to loss of consciousness, reaching core temperatures of 42.4±0.2°C. All mice recovered quickly. After 30 d, the left ventricles were rapidly frozen for DNA methyl sequencing, RNA-Seq and untargeted metabolomics. Ventricular DNA from EHS mice revealed >13,000 differentially methylated cytosines (DMCs) and >900 differentially methylated regions (DMRs;≥5 DMCs with ≤300 bp between each CpG). Pathway analysis using DMRs revealed alterations in genes regulating basic cell functions, DNA binding, transcription and metabolism. Metabolomics and mRNA expression revealed modest changes that are consistent with a return to homeostasis. Methylation status did not predict RNA expression or metabolomic state at 30 d. We conclude that EHS induces a sustained DNA methylation memory lasting over 30 d of recovery, but ventricular gene expression and metabolism return to a relative homeostasis at rest. Such long-lasting alterations to the DNA methylation landscape could alter responsiveness to environmental or clinical challenges later in life.