P14: Time dependent regulation of MIF by S-nitros(yl)ation reduces apoptosis in myocardial I/R-injury

Abstract

Background Macrophage migration inhibitory factor (MIF) is cardioprotective in myocardial ischemia/reperfusion (I/R) injury. MIF reduces apoptosis by its extracellular chemokine-like functions and the inhibition of the JNK pathway via intracellular JAB 1 binding. Unbound intracellular MIF reduces oxidative stress via its oxidoreductase activity. S -Nitros(yl)ation of MIF after nitrite application in I/R injury is a phenomenon of the early phase of reperfusion. S -Nitros(yl)ation enhances MIF’s cardioprotective properties: increase of the enzyme-like activity, reduction of infarct sizes and apoptosis. S -Nitros(yl)ation of MIF and MIF/JAB 1 interaction both depend on MIF’s cysteine 81. Whether S -nitros(yl)ation of MIF influences MIF/JAB 1 interaction during different phases of reperfusion and whether this affects MIF’s intra-and extracellular properties, is unclear. Hypothesis S -Nitros(yl)ation of MIF regulates its binding to JAB 1, its localization and its consecutive signaling pathways differentially in the various phases of reperfusion. Methods/Results TUNEL staining of murine hearts after in vivo I/R injury showed reduced apoptosis after S -nitros(yl)ation of MIF (14.5 ± 1.0% vs. 8.0 ± 3.5%, p In early phase of reperfusion, MIF/JAB 1 interaction was reduced upon S -nitros(yl)ation (0.3 ± 0.06% vs. 0.11 ± 0.04%, n = 4, p n = 5). Intracellular MIF protects from ROS induced damage: aconitase acitivity was higher after S -nitros(yl)ation than in control (2.1 ± 0.5 mU/mg protein vs. 1.25 ± 0.5 mU/mg protein, n = 3, p After 4 h of reperfusion, S -nitros(yl)ation and its effect on MIF/JAB 1 interaction was vanished: MIF/JAB 1 interaction was not different in both groups (0.34 ± 0.09% vs. 0.32 ± 0,05%, n = 5, p = ns). MIF concentrations in coronary effluent were higher after S -nitros(yl)ation than in control (4.9 ± 2 ng/min/g heart vs. 0.7 ± 0.3 ng/min/g heart, n = 5) showing time-delayed MIF release. Conclusion S -Nitros(yl)ation of MIF in I/R-injury reduces the MIF/JAB 1 interaction and MIF’s secretion. This detains MIF in the cell during early phase of reperfusion, where MIF reduces oxidative stress. In late phase-when S -nitros(yl)ation of MIF has vanished-MIF is released to the extracellular space, where other signaling pathways can be activated. Disclosure Nothing to disclose.