title: Effects of inhibition of poly(adenosine diphosphate-ribose) synthase on acute cardiac allograft rejection.
abstract: BACKGROUND
  Nitric oxide synthase (NOS)-2 is expressed during acute cardiac allograft rejection in association with death of heart muscle cells. The nuclear enzyme poly(adenosine diphosphate [ADP]-ribose) synthase (PARS) is activated by agonists such as NO and peroxynitrite, which cause single-strand DNA breaks; PARS, in turn can promote both necrosis and apoptosis. To investigate the hypothesis that NO produced by NOS-2 in cardiomyocytes activates PARS and contributes to heart muscle cell death by apoptosis, experiments were performed using a heterotopic rat abdominal heart transplant model and cytokine-stimulated heart muscle cells in tissue culture.
  
  
  METHODS
  Cardiac allografts were treated after transplantation with either the PARS inhibitor 5-aminoisoquinolinone at 3 mg/kg subcutaneously daily or with vehicle. Isolated purified adult rat cardiomyocytes incubated with cytokines to induce NOS-2 were treated in vitro with another PARS inhibitor, 3-aminobenzamide (3AB).
  
  
  RESULTS
  PARS inhibition increased cardiac-allograft survival from 6 +/- 2 to 10 +/- 3 days (n=6, n=6, P<0.05). The inflammatory infiltrate, NOS-2-positive macrophages, myocyte apoptosis, and myocyte content of nitrotyrosine and poly(ADP-ribose) were significantly decreased in PARS inhibited allografts at day 5 posttransplantation. Similarly, apoptosis and PARS activity were diminished in cytokine-stimulated adult rat cardiomyocytes when either 3AB or L-NMMA were applied.
  
  
  CONCLUSIONS
  The data indicate that PARS activation occurs during acute cardiac-allograft rejection and contributes significantly to the inflammatory response and to the death of cardiac muscle cells by apoptosis. They suggest that PARS inhibition combined with immunosuppression might enhance salvage of heart-muscle cells during acute cardiac-allograft rejection.
authors.affiliation: Department of Medicine, Division of Cardiology, College of Physicians and Surgeons, Columbia University, 630W 168th Street, New York, NY 10032, USA.
authors.forename: Yulin
authors.initials: Y
authors.lastname: Liu
authors.forename: Ni Huiping
authors.initials: NH
authors.lastname: Son
authors.forename: Matthias J
authors.initials: MJ
authors.lastname: Szabolcs
authors.forename: Ninsheng
authors.initials: N
authors.lastname: Ma
authors.forename: Robert R
authors.initials: RR
authors.lastname: Sciacca
authors.forename: Arline
authors.initials: A
authors.lastname: Albala
authors.forename: Niloo
authors.initials: N
authors.lastname: Edwards
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Cannon
mesh_terms: D000208:Acute Disease; D000818:Animals; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D006084:Graft Rejection / Q000473:pathology / Q000517:prevention & control*; D006085:Graft Survival / Q000187:drug effects / Q000276:immunology*; D016027:Heart Transplantation / Q000276:immunology* / Q000473:pathology; D007546:Isoquinolines / Q000627:therapeutic use*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D051381:Rats; D011917:Rats, Inbred Lew; D011920:Rats, Inbred WF; D014184:Transplantation, Homologous
chemical_list: C411425:5-aminoisoquinolinone; D029742:Caenorhabditis elegans Proteins; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; C400703:nos-2 protein, C elegans