Gap junction-mediated intercellular communication in ischemic preconditioning.

Gap junction-mediated communication can modulate cell death in different tissues. In myocardium, gap junction communication is altered during ischemia, which contributes to the development of arrhythmias, but still allows synchronization of the onset of rigor contracture in the progression of injury. During reperfusion, gap junction communication allows cell-to-cell spread of hypercontracture and cell death. Since the intracellular signal transduction systems involved in modulation of gap junction-mediated communication are activated during ischemic preconditioning, the hypothesis can be raised that gap junctions are end-effectors of preconditioning contributing to its protective effect on cell death. This paper reviews the available information supporting this hypothesis. It has been shown that ischemic preconditioning may influence gap junction-mediated intercellular communication by activation of different kinases, including PKC and MAPK cascades, and by preservation of cGMP among other mechanisms. Connexin phosphorylation by PKC, p38/MAPK, and PKG, tends to reduce intercellular communication. This effect of ischemic preconditioning seems to have no relevant consequences during prolonged ischemia, and does not significantly modify the time course of either electrical uncoupling or the frequency or temporal distribution of ventricular arrhythmias during this period. However, any modification of gap junction communication during initial reperfusion could contribute to the reduced extent of hypercontracture and cell death observed in preconditioned hearts. The potential role of gap junctions as effectors of ischemic preconditioning against lethal injury secondary to ischemia-reperfusion deserves to be investigated in depth.