Reperfusion, not simulated ischemia, initiates intrinsic apoptosis injury in chick cardiomyocytes

Abstract

Although ischemia-reperfusion (I/R) can initiate apoptosis, the timing and contribution of the mitochondrial/cytochrome c apoptosis death pathway to I/R injury is unclear. We studied the timing of cytochrome c release during I/R and whether subsequent caspase activation contributes to reperfusion injury in confluent chick cardiomyocytes. One-hour simulated ischemia followed by 3-h reperfusion resulted in significant cell death, with most cell death evident during the reperfusion phase and demonstrating mitochondrial cytochrome c release within 5 min after reperfusion. By contrast, cells exposed to prolonged ischemia for 4 h had only marginally increased cell death and no detectable cytochrome c release into the cytosol. Caspase activation could not be detected after ischemia only, but it significantly increased after reperfusion. Caspase inhibitors benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, Ac-Asp-Gln-Thr-Asp-H, or benzyloxycarbonyl-Leu-Glu (Ome)-His-Asp-(Ome)-fluoromethyl ketone given only at reperfusion significantly attenuated cell death and resulted in return of contraction. Antixoxidants decreased cytochrome c release, nuclear condensation, and cell death. These results suggest that reperfusion oxidants initiate cytochrome c release within minutes, and apoptosis within hours, significant enough to increase cell death and contractile dysfunction.

Ischemia/reperfusion-induced death of cardiac myocytes: possible involvement of nitric oxide in the coordination of ATP supply and demand during ischemia

“…2), suggesting that almost all the myocytes survived during a prolonged ischemia of at least 3 h and reperfusion is necessary for the induction of myocyte death. This finding is in agreement with the report that chick embryonic cardiomyocytes exposed to a prolonged SI for 4 h exhibited only a marginal increase in cell death [25]. These findings have raised the question as to what mechanisms were responsible for the increase in cell death when cultured myocytes were treated with L-NMMA or carboxy-PTIO during SI.…”

Intra-arrest cooling with delayed reperfusion yields higher survival than earlier normothermic resuscitation in a mouse model of cardiac arrest

“…9,10 Cellular ischemiareperfusion experiments have observed deleterious oxidant generation as well as apoptotic activation immediately after reperfusion, and intra-ischemia cooling blunts these damaging processes. [11][12][13] It is unknown to what degree initial cooling should be given priority over reperfusion and ROSC, if at all. This is particularly controversial if the induction of TH requires a delay in circulatory resuscitation and restoration of perfusion.…”

Hypothermia-induced cardioprotection using extended ischemia and early reperfusion cooling

“…Our own work studying the timing of cell death during simulated ischemia-reperfusion (I/R) in chick cardiomyocytes suggests that, after normothermic ischemia, significant acceleration of death occurs within the first 1 h of reperfusion, preceded by a burst of oxidants and cytochrome c release that occurs within minutes of reperfusion (3,32,35,36). In contrast, cardiomyocytes remain remarkably intact without caspase activation or membrane damage if allowed to remain ischemic for a longer duration without reperfusion (35,36).…”

“…In contrast, cardiomyocytes remain remarkably intact without caspase activation or membrane damage if allowed to remain ischemic for a longer duration without reperfusion (35,36). Cells, of course, cannot survive indefinitely under such pro-longed ischemia.…”