Abstract 5414: Macrophage Migration Inhibitory Factor Inhibits C-jun N Terminal Kinase And Prevents Cardiac Injury During Acute Ischemia Reperfusion
Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine, which is expressed in multiple organs including the heart. Plasma MIF is elevated after myocardial infarction. MIF is released from the heart during ischemia and has an autocrine/paracrine effect to positively modulate AMP-activated protein kinase (AMPK). Genetic deficiency in MIF (MIF−/−) attenuates AMPK activation, leading to cardiac dysfunction and injury during ischemia/reperfusion (IR). MIF also inhibits c-Jun N-terminal kinase (JNK) activation in HeLa cells, but its action in the heart is not known. In Langendorff perfused WT hearts, MIF content was reduced after global ischemia (15 min) and reperfusion (30 min). JNK activation and downstream c-Jun phosphorylation were greater (p<0.05) following IR in MIF−/− (n=6) compared to WT hearts (n=6), suggesting that MIF inhibits JNK activation. Phosphorylation of MAP kinase kinase 4 (MKK4), an upstream enzyme of JNK was also greater in MIF −/− hearts (p<0.05). JNK is known to promote Bad dephosphorylation, disrupting its interaction with anti-apoptotic factors, and MIF−/− hearts following IR showed less Bad phosphorylation (70% decrease, p<0.05). MIF−/−hearts also had worse recovery of LV contractile function after ischemia compared to WT hearts (50% vs. 80% recovery, p<0.05). Perfusion with the JNK inhibitor, SP600125 (10μM) prevented excess JNK activation during IR and improved post-ischemic cardiac function in MIF−/− hearts (n=6, p<0.05). Similarly, regional IR in vivo augmented MKK4, JNK and c-Jun phosphorylation in MIF−/− vs. WT mice. MIF−/− hearts showed more necrosis on TTC staining after LAD occlusion and reperfusion than WT. Increased cardiac injury following IR was associated with less BAD phosphorylation and more cellular apoptosis in MIF−/− hearts. Administration of SP600125 (1mg/kg, IP) prior to ischemia also limited injury in MIF−/− mice. In vitro studies showed that the JNK activator, anisomycin, stimulated the JNK pathway in H9C2 cells in a dose-dependent manner and MIF (50 ng/ml) inhibited anisomycin-activation of MKK4, JNK, and c-Jun. Thus, cardiac-derived MIF inhibits activation of the JNK pathway, which may protect the heart from injury following IR.
This research has received full or partial funding support from the American Heart Association, AHA Founders Affiliate (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, Vermont).