Role of gap junction in ischemic preconditioning

Objective To investigate the role of gap junction in ischemic preconditioning (IPC). Methods Sprague-Dawley rats were subjected to a 30 min coronary artery occlusion followed by 4 h of reperfusion (I/R). Rats were divided into seven groups:I/R,IPC/R,IPC/R+5-hydroxydecanoic acid (mitochondrial ATP sensitive potassium channel antagonist),I/R+diazoxide(mitochondrial ATP sensitive potassium channel agonist),I/R+5-hydroxydecanoic acid+diazoxide,I/R+18β-glycyrrhetinic acid (gap junction blocker) and I/R+18β-glycyrrhetinic acid+5-hydroxydecanoic acid. Hemodynamics and myocardial infarct size were measured and connexin43 phosphorylation and subcellular distribution were determined by quantitative immunoblotting and confocal immunofluorescence. Results Infarct size was reduced in IPC/R,I/R+diazoxide and I/R+18β-glycyrrhetinic acid group(13.34%±7.87%,11.02%±2.24%,and 15.03%±11.35%, respectively; P0.001 vs. I/R group: 45.81%±7.91%). 5-hydroxydecanoic acid abolished the cardioprotective effects of IPC and diazoxide (46.57%±5.36% and 47.36%±3.17%;P0.05 vs. I/R) but not the effects of glycyrrhetinic acid (14.60%±7.36%;P 0.001 vs. I/R). Phosphorylation of connexin43 was significantly increased, dephosphorylation and connexin43 intracellular redistribution significantly decreased (Cx43 size in the cellular membrane 1.00%±0.35% and 0. 83%±0.31%,P0.001 vs. I/R:0. 19%±0.06%) by IPC and diazoxide and these effects could be abolished by 5-hydroxydecanoic acid. Conclusion Ischemic preconditioning could reduce myocardial infarction size by activating mitochondrial ATP sensitive potassium channel and modulating connexin43 phosphorylation and internalization.