Endotoxin Pretreatment Mitigates Myocardial Ischemia-Reperfusion Injury Through Preservation of Mitochondrial Respiration: A Combined Assessment of In Vivo, Ex Vivo, and In Vitro Data

Acute myocardial infarction is the most common form of coronary artery disease, and myocardial ischemia-reperfusion injury remains a major challenge despite advances in reperfusion therapy. Endotoxin preconditioning has been linked to reduced ischemia-reperfusion injury, but mechanisms remain unclear, and prior studies have used varied assessment methods with inconsistent results. In this study, we confirmed the protective effect of endotoxin preconditioning and assessed its role in preserving mitochondrial respiration using a multi-model approach of in vivo ischemia-reperfusion rat model, ex vivo normothermic rat heart perfusion, and in vitro hypoxia-reoxygenation in neonatal rat cardiomyocytes. Hemodynamic and cell-based analyses were performed in control (<i>n</i> = 5), ischemia-reperfusion/hypoxia-reoxygenation (<i>n</i> = 4/3), and endotoxin-pretreated (<i>n</i> = 5/3) groups. Low-dose endotoxin pretreatment significantly preserved left ventricular function, myocardial oxygen consumption, and mitochondrial respiration (<i>p</i> < 0.001). Preservation of function was associated with reduced hypoxia-inducible factor 1-alpha (HIF-1α) expression and decreased mitochondrial superoxide production, indicating reduced oxidative stress. Nonlethal endotoxin pretreatment protects the myocardium from ischemia-reperfusion injury by sustaining mitochondrial respiration and limiting oxidative damage. These findings support further investigation in large animal models to better replicate human myocardial infarction and evaluate translational potential.