Ca2+/calmodulin dependent kinase II: A critical mediator in determining reperfusion outcomes in the heart?

Ischaemic heart disease is a major cause of death and disability in the Western world, and a substantial health burden. Cardiomyocyte Ca2+ overload is known to significantly contribute to contractile dysfunction and myocyte death in ischaemia and reperfusion, and significant advancements have been made in identifying the downstream mediators and cellular origins of this Ca2+ mismanagement. Ca2+/calmodulin-dependent kinaseII (CaMKII) is recognized as an important mediator linking pathological changes in subcellular environments to modifications in cardiomyocyte Ca2+ handling. Activated in response to fluctuations in cellular Ca2+ and to various post-translational modifications, CaMKII targets numerous Ca2+ channels/transporters involved in Ca2+ handling and contractile function regulation. CaMKII is activated early in reperfusion, where it exacerbates Ca2+ leak from the sarcoplasmic reticulum and promotes the onset of ventricular arrhythmias. Inhibiting CaMKII can increase functional recovery in reperfusion and reduce apoptotic/necrotic death, at least partly through indirect and direct influences on mitochondrial Ca2+ levels and function. Yet, CaMKII can also have beneficial actions in ischaemia and reperfusion, in part by providing inotropic support for the stunned myocardium and contributing as an intermediate to cardioprotective preconditioning signalling cascades. There is considerable potential in targeting CaMKII as a part of a surgical reperfusion strategy, though further mechanistic understanding of the relationship between CaMKII activation status and the extent of ischaemia/reperfusion injury are required to fully establish an optimal pharmacological approach.