Abstract 18316: Knockout of Cyclophilin D Inhibits Oxidant Stress-Induced PARP Activation in Murine Myocardial Ischemia-Reperfusion Injury
Myocardial ischemia-reperfusion (I/R) injury can cause heart failure and death, but the mechanisms underlying cell death are not fully understood. Genetic deletion of Cyclophilin D (CyD), a modulator of the mitochondrial permeability transition pore (MPTP), or Poly-ADP Ribose Polymerase-1 (PARP-1), an NAD-dependent DNA repair enzyme, or inhibition of reactive oxygen species production, can lessen infarct severity in I/R, but the relationships among these systems are not established. We tested whether I/R-induced oxidant stress occurs upstream of MPTP opening and PARP activation, and whether MPTP opening and PARP act in parallel or in a single cell death pathway. I/R injury was measured in mice subjected to LAD occlusion (30 min) followed by reperfusion (4 hr), and infarct size was assessed by differential staining. Compared with wild-type controls, mice with a knockout of CyD showed attenuation of infarct size/area at risk (46+/−2% vs 33+/−3%, n=6). In wild-type mice, the antioxidant compound EUK134, and the PARP inhibitor 3-aminobenzamide (3AB) decreased infarct size to a similar extent (29+/−4% and 29+/−5%, n=6). Treatment of CyD knockouts with EUK134 or 3AB further attenuated cell death (19+/−4% and 19+/−6%, n=6). Protein oxidation (carbonylation) at 1 hr into reperfusion was assessed in the area at risk, while PARP activity was assessed by blotting for protein ADP-ribosylation. CyD knockouts and those treated with EUK134 or with 3AB all show attenuated PARP activation during reperfusion, whereas only treatment with EUK134 lessened protein oxidation. These results suggest that I/R causes oxidant stress that triggers PARP activation, but that PARP is inhibited unless MPTP opening releases NAD+ from the mitochondria, thus implicating MPTP and PARP activation in a single cell death pathway. Supported by AHA, HL35440, HL079750, and RR025355.
- Reperfusion injury
- Ischemia reperfusion
- Oxidative stress
- Myocardial infarction
- Reactive oxygen intermediates
- © 2010 by American Heart Association, Inc.