Ischemic preconditioning attenuates ischemia/reperfusion-induced activation of caspases and subsequent cleavage of poly(ADP-ribose) polymerase in rathearts in vivo

Recently, we have demonstrated that ischemic preconditioning (IP) both limi ts infarct size and decreases internucleosomal DNA fragmentation in rat hea rts in vivo, and that there was a direct correlation between myocardial inf arct size and DNA fragmentation even after TP. In this study, we examined t he ability of TP to attenuate processing and activation of caspase-1 and ca spase-3, and cleavage of poly(ADP-ribose) polymerase (PARP), after prolonge d ischemia and reperfusion using the same in vivo animal model. Rats that u nderwent IP and controls (Ctrl) were subjected to 30 min of left coronary a rtery occlusion followed by 180 min of reperfusion. IP was accomplished by five 5-min cycles of ischemia, each followed by 5 min of reperfusion. The a mount of soluble nucleosomes was measured by enzyme-linked immunosorbent as say. Cleavage of caspases-1 and -3, and of one of their substrates PARP, wa s analyzed by Western blotting. Nucleosomal DNA fragmentation was significa ntly reduced in ischemic left ventricular (LV) tissue obtained from IP comp ared with Ctrl animals. The proforms of caspases-1 and -3, and the active f orm of PARP were not cleaved in the nonischemic LV region of both IP and Ct rl hearts. In contrast, the preform of caspase-3 and the active form of PAR P were cleaved in the ischemic LV region of Ctrl hearts, while processing o f caspase-1 was increased. Cleavages of caspases-1 and -3, and inactivation of PARP were prevented by IF. The results of this study indicate that TP a ttenuates both internucleosomal DNA fragmentation and caspases processing, and suggest that the prevention of caspases activation by TP may be importa nt steps in protecting the heart against ischemia/reperfusion injury in viv o. (C) 1999 Elsevier Science BN. All rights reserved.