Abstract 25: Limiting Cardiac Ischemic Injury by Augmenting the MIF-AMPK Signaling Cascade With a Novel Class of MIF Receptor Agonists
Background: Macrophage migration inhibitory factor (MIF) is released by ischemic cardiomyocytes and exerts a protective effect by activating AMP-activated protein kinase (AMPK). While developing small molecule antagonists of the MIF receptor for immunomodulatory applications, we uncovered compounds that increased MIF's affinity for its receptor. We hypothesize that such agonists may be useful in augmenting MIF dependent AMPK activation and limiting ischemic cardiac injury.
Methods and Results: An in vitro competition assay employing MIF and immobilized receptor ectodomain (sCD74) led to the identification of three compounds (MIF020, MIF021, MIF033) that increased MIF interaction with its receptor in a dose-dependent fashion. Treatment of murine cardiomyocytes with MIF together with MIF020 (both at 8 nmol/L), augmented AMPK phosphorylation (2 fold vs. MIF alone, p<0.05). MIF plus MIF020 increased by 50% the surface expression of glucose transporter (GLUT4) and increased cellular glucose uptake by 25% when compared to MIF alone. Murine hearts from WT or MIF-KO mice (n=4 per group) were perfused with MIF020 for 15 min prior to 25 min of no-flow ischemia and 30 min reperfusion. In the WT hearts, post-ischemic left ventricular function was improved by MIF020 when compared to vehicle controls (47 ± 8% vs. 26 ± 5% of baseline, p<0.05). By contrast, a cardioprotective action of MIF020 during ischemia and reperfusion was not observed in MIF-KO hearts (20 ± 5% vs. 17 ± 2% of baseline, p=NS). MIF020 also increased cardiac MIF-AMPK activation (2.9 fold vs. control, p<0.05) and augmented glucose uptake in WT hearts when compared to vehicle controls (1.32 ± 0.02 vs. 1.04 ± 0.09 μmol/min/g, p<0.05). Finally, the cardioprotective effect of MIF020 was verified in an in vivo regional ischemia model: WT or MIF-KO mice were pre-treated with MIF020 for 20 min followed by left coronary artery occlusion (20 min) and then reperfusion (4 hr). MIF020 significantly reduced myocardial infarction in WT hearts (14 ± 3% vs. 24 ± 6%, infarct area/area at risk, n=4, p=0.025) but not in MIF-KO hearts (30 ± 5% vs. 34 ± 3%, n=3, p=NS).
Conclusions: MIF receptor agonism by a small molecule approach offers protection against cardiac ischemic injury by augmenting the MIF-AMPK signaling pathway.
- © 2010 by American Heart Association, Inc.