title: Poly(adenosine diphosphate ribose) polymerase inhibition prevents necrosis induced by H2O2 but not apoptosis.
abstract: OBJECTIVE
  H2O2 causes DNA damage, which activates poly(adenosine diphosphate ribose) polymerase (PARP), a nuclear enzyme that uses nicotinamide adenine dinucleotide (NAD) as a substrate. When DNA strand breaks are extensive, consumption of NAD by PARP can cause adenosine triphosphate depletion. The aim was to study the effect of PARP inhibition on H2O2-induced cell injury in the intestinal epithelial cell line HT-29-18-C1.
  
  
  METHODS
  Cell injury was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide test and flow cytometric analysis.
  
  
  RESULTS
  The PARP inhibitors 3-aminobenzamide and nicotinamide both prevented cell death immediately after exposure to 1 mmol/L H2O2 and loss of cellular NAD and adenosine triphosphate. The inactive structural analogues 3-aminobenzoic acid and nicotinic acid had no such protective effect. H2O2 also caused HT-29 cells to detach from the monolayer up to 24 hours after exposure and die by apoptosis in the incubating medium. Flow cytometric analysis showed that 3-aminobenzamide had no effect on this delayed detachment process.
  
  
  CONCLUSIONS
  H2O2 induces two distinct death pathways in HT-29 cells: one that is immediate and may represent necrosis and another that is delayed, causing cell detachment leading to apoptosis. PARP inhibition prevents necrosis but has no effect on delayed cell detachment leading to apoptosis.
authors.affiliation: Department of Medicine, Hope Hospital, University of Manchester, Salford, England.
authors.forename: A J
authors.initials: AJ
authors.lastname: Watson
authors.forename: J N
authors.initials: JN
authors.lastname: Askew
authors.forename: R S
authors.initials: RS
authors.lastname: Benson
mesh_terms: D062365:Aminobenzoates / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001549:Benzamides / Q000494:pharmacology*; D002452:Cell Count / Q000187:drug effects; D002460:Cell Line; D004260:DNA Repair / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide; D007413:Intestinal Mucosa / Q000473:pathology*; D009336:Necrosis / Q000139:chemically induced / Q000517:prevention & control*; D009525:Niacin / Q000494:pharmacology; D009536:Niacinamide / Q000494:pharmacology*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D013997:Time Factors; D062368:meta-Aminobenzoates
chemical_list: D062365:Aminobenzoates; D001549:Benzamides; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D062368:meta-Aminobenzoates; D009536:Niacinamide; D009525:Niacin; C025160:3-aminobenzamide; D006861:Hydrogen Peroxide; C044855:3-aminobenzoic acid