Abstract 10387: Macrophage Migration Inhibitory Factor Maintains Mitochondrial Integrity in Aging During Ischemic Insults

Abstract

Introduction: The expression and secretion of cardiac MIF (macrophage migration inhibitory factor) are downregulated in aging. A small molecule MIF agonist, MIF20 can increase the binding affinity of MIF with CD74 receptor to modulate AMPK signaling. However, the pharmacological mechanisms by which MIF20 triggers MIF-AMPK signaling cascade to benefit heart in response to ischemia and reperfusion (I/R) stress remain unknown. Hypothesis: MIF20 rescues an impaired MIF-AMPK signaling in aging through augmenting the interaction between MIF and CD74 receptor to maintain mitochondrial integrity of aged heart under ischemic stress. Methods: Young (3-5 months) and aged (21-24 months) C57BL/6J mice were subjected to 45 min of ligation of LAD (left anterior descending coronary artery) and injection of MIF20 (0.15 μg/kg, i.v.) 5 min before 24 hr of reperfusion with release of LAD. Echocardiography measures cardiac functions, and TTC/Evans blue staining for determination of myocardial infarction size. Seahorse XF Analyzer for mitochondrial respiration functions of isolated cardiomyocytes. Results: The echocardiography data showed that I/R caused cardiac systolic dysfunctions but not effect on cardiac diastolic functions of both young and aged C57BL/6J mice. There were no differences between male and female groups. Administration of MIF20 significantly ameliorated I/R-induced cardiac dysfunctions in both young and aged mice, while more improvement observed in aged versus young mice. MIF20 treatment reduced myocardial infarct size caused by I/R in both young and aged mice, but the reduction extent of aged hearts was higher than that of young hearts (p<0.05). Mitochondrial respiration rates of isolated cardiomyocytes as indicted by ATP production were impaired by I/R versus sham operations in both young and aged hearts. Intriguingly, MIF20 treatment significantly rescued the impaired mitochondrial functions caused by I/R in both young and aged cardiomyocytes. Moreover, the mitochondrial functions of young and aged cardiomyocytes were improved to a similar level under I/R with MIF20. Conclusions: MIF agonist MIF20 rescues the impaired energy metabolism in aged heart. The mitochondrial integrity under I/R by MIF20 could limit ischemic insults in aging.