Mitochondrial plasticity in classical ischemic preconditioning-moving beyond the mitochondrial KATP channel.

Ischemic preconditioning is a powerful biologic phenomenon that activates innate cell survival programs to protect the heart from ischemic injury. The preponderance of research into classical ischemic preconditioning has focused on signaling pathways orchestrating cardioprotection. Conceptually classified into triggers, mediators and end effectors of preconditioning multiple distinct signaling pathways appear to 'converge' on the mitochondria possibly via activation of the mitochondrial ATP-sensitive potassium (mK(ATP)) channel. The mechanisms by which mK(ATP) channel activation induces preconditioning are incompletely elucidated but include perturbations of mitochondrial architecture and function. Since evidence invoking the mK(ATP) channel has almost exclusively been based on studies using diazoxide and 5-hydroxydecanote the finding that these two compounds have mitochondrial effects independent of the mK(ATP) channel has initiated a controversy regarding the exclusivity of this particular channel in preconditioning. A concerted effort to characterize the mitochondrial phenotype is important to advance our understanding of the mechanistic events that underlie the robust cardioprotective phenotype unmasked by preconditioning. The purpose of this review is to collate the information available on mitochondrial biology associated with classical preconditioning, to delineate the distinct temporal presentation of these mitochondrial perturbations, to reassess the role of the mitochondrial K(ATP) channel and to propose a working model integrating the mitochondrial adaptations into the biology driving this cyto-protective phenotype.