Cardioprotection of Insulin-Like Growth Factor-1 During Reperfusion Therapy

In the setting of acute myocardial infarction, reperfusion of ischemic myocardium carried out early after coronary occlusion can salvage reversibly injured, viable myocardium. Although still controversial, however, reperfusion itself may cause a population of reversibly injured cells to die, a phenomenon termed lethal reperfusion injury .1 A variety of pharmacological agents have been studied to limit ischemia/reperfusion injury as an adjunct to current reperfusion, and some beneficial effects have been demonstrated in experimental animal research, but their clinical applications have not been achieved.2–4Article see p 327Among the various agents claimed to have cardioprotective effects is insulin-like growth factor-1 (IGF-1), which is a hormone produced primarily by the liver. Its molecular structure is similar to that of insulin. IGF-1 plays an important role in cellular survival and growth by binding to its specific receptor (IGF1R), which is present on many cell types, including cardiac cells. Activation of IGF1R, a receptor tyrosine kinase, has been demonstrated to attenuate both apoptotic and necrotic cell death induced by ischemia/reperfusion injury through stimulating both the intracellular phosphoinositide 3-kinase/protein kinase B signaling pathway and extracellular signal-regulated kinase 1/2 signaling cascades.5 Buerke at al6 administered IGF-I 1 hour before ischemia in a murine model of 20 minutes of myocardial ischemia followed by 24 hours of reperfusion. IGF-I preserved ischemic/reperfused myocardium through inhibition of polymorphonuclear leukocyte-induced cardiac necrosis and inhibition of reperfusion-induced apoptosis of cardiac myocytes. Davani et al7 subjected isolated murine hearts to 20 minutes of global ischemia followed by 2 hours of reperfusion with either modified Kreb's solution alone or …