Trimethylamine N-oxide exacerbates myocardial ischemia-reperfusion injury by sustaining PERK/eIF2α activation and impairing ferredoxin reductase-dependent mitochondrial function

Previous studies demonstrate that individuals with elevated plasma trimethylamine N-oxide (TMAO) suffer worse myocardial injury following acute myocardial infarction. However, whether TMAO promotes myocardial ischemia-reperfusion injury (MIRI) remained undefined. The purpose of this study was to determine if TMAO exacerbated MIRI. In this study, we found that TMAO exacerbated MIRI in both in vivo mouse models of ischemia-reperfusion and in vitro primary cardiomyocyte models of hypoxia/reoxygenation. Mechanistically, RNA Sequencing and gene set enrichment analysis indicated that TMAO suppressed mitochondrial function-related pathways. Further, we confirmed that TMAO aggravated mitochondrial dysfunction during ischemia-reperfusion, manifested as ultrastructural damage, reduced mitochondrial membrane potential, elevated Reactive Oxygen Species overproduction, impaired mitochondrial respiration and inhibited energy metabolism. TMAO-induced mitochondrial dysfunction was mediated through ferredoxin reductase suppression, as ferredoxin reductase overexpression reversed TMAO-exacerbated injury. TMAO bound to eukaryotic translation initiation factor 2-alpha kinase 3 (PERK) and sustained PERK/eukaryotic initiation factor-2α (eIF2α) pathway activation during IR. Pharmacological inhibition of PERK/eIF2α signaling (using GSK2606414 and ISRIB) reversed TMAO-induced ferredoxin reductase suppression, mitochondrial dysfunction, and MIRI exacerbation, indicating the key role of PERK/eIF2α signaling in this process. These findings provide novel insight that TMAO is a risk factor in MIRI. Through maintaining PERK/eIF2α activation, TMAO inhibits ferredoxin reductase expression thereby impairing ferredoxin reductase-dependent mitochondrial function. Pharmacological inhibition of the PERK/eIF2α pathway may represent a therapeutic strategy for alleviating MIRI with elevated TMAO.