ROS-mediated PARP activity undermines mitochondrial function after permeability transition pore opening during myocardial ischemia-reperfusion.

Ischemia-reperfusion (i/r) studies have implicated oxidant stress,the mitochondrial permeability transition pore (mptp),and poly(adp-ribose) polymerase (parp) as contributing factors in myocardial cell death. however,the interdependence of these factors in the intact,blood-perfused heart is not known. we therefore wanted to determine whether oxidant stress,mptp opening,and parp activity contribute to the same death pathway after myocardial i/r. a murine left anterior descending coronary artery (lad) occlusion (30 minutes) and release (1 to 4 hours) model was employed. experimental groups included controls and antioxidant-treated,mptp-inhibited,or parp-inhibited hearts. antioxidant treatment prevented oxidative damage,mptp opening,atp depletion,and parp activity,placing oxidant stress as the proximal death trigger. genetic deletion of cyclophilin d (cypd(-/-)) prevented loss of total nad(+) and parp activity,and mptp-mediated loss of mitochondrial function. control hearts showed progressive mitochondrial depolarization and loss of atp from 1.5 to 4 hours of reperfusion,but not outer mitochondrial membrane rupture. neither genetic deletion of parp-1 nor its pharmacological inhibition prevented the initial mptp-mediated depolarization or loss of atp,but parp ablation did allow mitochondrial recovery by 4 hours of reperfusion. these results indicate that oxidant stress,the mptp,and parp activity contribute to a single death pathway after i/r in the heart. parp activation undermines cell survival by preventing mitochondrial recovery after mptp opening early in reperfusion. this suggests that parp-mediated prolongation of mitochondrial depolarization contributes significantly to cell death via an energetic crisis rather than by mitochondrial outer membrane rupture.