Cardioprotective mechanisms of PKC isozyme-selective activators and inhibitors in the treatment of ischemia-reperfusion injury

Current treatment for acute myocardial infarction (AMI) is aimed at limiting the duration of ischemia by either mechanical (balloon catheters) or enzymatic (thrombolytics) means to disrupt the occlusion. While these treatments are effective in limiting the duration of ischemia, no therapeutic treatment is currently available to prevent ischemic injury and to reduce reperfusion injury, which occurs after these interventions. The development of rationally designed PKC isozyme-selective regulator peptides has permitted investigation into the role of specific PKC isozymes in ischemia-reperfusion (IR) injury. Based on these studies, it is now evident that ɛ and δPKC have distinct temporal and opposing roles in regulating myocardial damage induced by IR. Activation of ɛPKC before ischemia protects the heart by mimicking preconditioning, whereas inhibition of δPKC during reperfusion protects the heart from reperfusion-induced damage. These cardioprotective effects have been observed in isolated cardiomyocytes, isolated perfused hearts and in vivo in all species tested including mouse, rat and pig and may provide the basis for future therapeutic agents. Having established the efficacy of PKC isozyme-specific regulators in reducing IR injury, the next challenge is to outline the molecular mechanisms regulated by δ and ɛPKC isozymes that result in enhanced tolerance to IR. In this review, we discuss progress that has been made in establishing cytoprotective mechanisms, which arise as a consequence of ɛPKC activation or δPKC inhibition, and how they may lead to protection in the setting of myocardial ischemia reperfusion.