Abstract 19823: AMP-Activated Protein Kinase Limits the Activation of C-jun N Terminal Kinase and Prevents Cardiac Injury During Ischemia-Reperfusion
AMP-activated protein kinase (AMPK) limits and c-Jun N terminal kinase (JNK) exacerbates cardiac injury during ischemia-reperfusion. Pharmacological AMPK activators and constitutively-active AMPK attenuate JNK pathway activation in endothelial and cancer cells, but AMPK's effect on heart cell signaling during ischemia-reperfusion is largely unknown. Thus, we investigated the role of AMPK in modulating JNK activation during ischemia (20 min)-reperfusion (0–60 min) in an in vivo mouse model. Ischemia induced by coronary artery occlusion increased AMPK Thr172 phosphorylation three-fold, which persisted for 10 min following reperfusion. JNK was activated following reperfusion and maximal phosphorylation (five-fold) occurred 10 min after reperfusion. The major JNK upstream kinase, MKK4 was fully activated by 5 min of reperfusion. Compared to wild-type (WT), the ischemic-reperfused region from AMPK kinase dead (KD) hearts demonstrated 60% (P<0.05) greater JNK phosphorylation and 100% (P<0.05) increased activation of MKK4 during ischemia. Increased JNK pathway signaling was associated with a two-fold increase in cardiac necrosis (measured by TTC staining) in KD hearts following ischemia-reperfusion compared to WT (P<0.05), Necrosis in the KD hearts was diminished (P<0.05) by the JNK inhibitor, SP600125 (2 mg/kg iv). PKCδ appears to regulate JNK signaling. Thus, we measured PKCδ Thr505 phosphorylation and found that it increased following ischemia-reperfusion to a greater extent (P<0.05) in KD vs. WT hearts. Additionally, in H9C2 cells, the AMPK activator metformin (2 μM) decreased both PKCδ and JNK phosphorylation following treatment with the JNK activator, anisomycin (0.01ug/ml). The PKCδ inhibitor, rottlerin (6 mM) also diminished JNK activation by anisomycin. Thus, AMPK negatively modulates the activation of MKK4-JNK pathway during reperfusion, in part through inhibiting PKCδ activation. The inhibition of JNK by AMPK activation during ischemia-reperfusion reduces cardiac injury.
- © 2010 by American Heart Association, Inc.