ABSTRACT
BACKGROUND: PolyADPribose polymerase (PARP) is activated by DNA strand breaks to catalyze the addition of ADPribose groups to nuclear proteins, especially PARP-1. Excessive polyADPribosylation leads to cell death through depletion of NAD+ and ATP. MATERIALS AND METHODS: In vivo PARP activation in heart tissue slices was assayed through conversion of [33P]NAD+ into polyADPribose (PAR) following ischemia-reperfusion (I/R) and also monitored by immunohistochemical staining for PAR. Cardiac contractility, nitric oxide (NO), reactive oxygen species (ROS), NAD+ and ATP levels were examined in wild type (WT) and in PARP-1 gene-deleted (PARP-1(-/-)) isolated, perfused mouse hearts. Myocardial infarct size was assessed following coronary artery occlusion in rats treated with PARP inhibitors. RESULTS: Ischemia-reperfusion (I/R) augmented formation of nitric oxide, oxygen free radicals and PARP activity. I/R induced decreases in cardiac contractility and NAD+ levels were attenuated in PARP-1(-/-) mouse hearts. PARP inhibitors reduced myocardial infarct size in rats. Residual polyADPribosylation in PARP-1(-/-) hearts may reflect alternative forms of PARP. CONCLUSIONS: PolyADPribosylation from PARP-1 and other sources of enzymatic PAR synthesis is associated with cardiac damage following myocardial ischemia. PARP inhibitors may have therapeutic utility in myocardial disease.
Subject(s)
Myocardial Ischemia/enzymology , Myocardium/enzymology , Myocardium/pathology , Poly(ADP-ribose) Polymerases/metabolism , Reperfusion Injury/enzymology , Adenosine Triphosphate/metabolism , Animals , Electron Spin Resonance Spectroscopy , Enzyme Activation , Female , Heart/physiopathology , Isoenzymes/antagonists & inhibitors , Isoenzymes/deficiency , Isoenzymes/genetics , Isoenzymes/metabolism , Magnetic Resonance Spectroscopy , Mice , Mice, Knockout , Myocardial Contraction , Myocardial Infarction/enzymology , Myocardial Infarction/genetics , Myocardial Infarction/metabolism , Myocardial Infarction/pathology , Myocardial Ischemia/genetics , Myocardial Ischemia/metabolism , Myocardial Ischemia/pathology , Myocardium/metabolism , NAD/metabolism , Nitric Oxide/metabolism , Poly(ADP-ribose) Polymerase Inhibitors , Poly(ADP-ribose) Polymerases/deficiency , Poly(ADP-ribose) Polymerases/genetics , Rats , Rats, Sprague-Dawley , Reactive Oxygen Species/metabolism , Reperfusion Injury/genetics , Reperfusion Injury/metabolism , Reperfusion Injury/pathologyABSTRACT
Poly(ADP-ribose) polymerase (PARP) transfers ADP ribose groups from NAD(+) to nuclear proteins after activation by DNA strand breaks. PARP overactivation by massive DNA damage causes cell death via NAD(+) and ATP depletion. Heretofore, PARP has been thought to be inactive under basal physiologic conditions. We now report high basal levels of PARP activity and DNA strand breaks in discrete neuronal populations of the brain, in ventricular ependymal and subependymal cells and in peripheral tissues. In some peripheral tissues, such as skeletal muscle, spleen, heart, and kidney, PARP activity is reduced only partially in mice with PARP-1 gene deletion (PARP-1(-/-)), implicating activity of alternative forms of PARP. Glutamate neurotransmission involving N-methyl-d-aspartate (NMDA) receptors and neuronal nitric oxide synthase (nNOS) activity in part mediates neuronal DNA strand breaks and PARP activity, which are diminished by NMDA antagonists and NOS inhibitors and also diminished in mice with targeted deletion of nNOS gene (nNOS(-/-)). An increase in NAD(+) levels after treatment with NMDA antagonists or NOS inhibitors, as well as in nNOS(-/-) mice, indicates that basal glutamate-PARP activity regulates neuronal energy dynamics.
