title: Poly (ADP-ribose) polymerase inhibitor 3-aminobenzamide rescues N-methyl-N-nitrosourea-induced photoreceptor cell apoptosis in Sprague-Dawley rats through preservation of nuclear factor-kappaB activity.
abstract: The activation of poly (ADP-ribose) polymerase (PARP) plays a pivotal role in mediating N-methyl-N-nitrosourea (MNU)-induced photoreceptor cell apoptosis. We examined the retinoprotective effects of the PARP inhibitor 3-aminobenzamide (3-AB) against MNU-induced retinal damage in relation to dose and timing of prescription, and the involvement of the transcription factor nuclear factor (NF)-kappaB. Female Sprague-Dawley rats were intraperitoneally injected with 60 mg/kg MNU at 50 days of age, and were then immediately given a subcutaneous injection of 0, 1, 5, 10, 30 or 50 mg/kg of 3-AB, or were injected with 50 mg/kg 3-AB 12h before, concurrently, or 4, 6 or 12h after MNU. Rats were killed 3 and 7 days after MNU, and MNU-treated and 3-AB-injected retinas were compared with MNU-untreated control retinas or MNU-treated/3-AB-uninjected retinas. Apoptosis in photoreceptor cells was detected by performing formamide-induced DNA denaturation and staining with anti-single-stranded DNA antibody. Retinal morphologies were compared and evaluated morphometrically using the photoreceptor cell ratio and retinal damage ratio as indices to evaluate the efficacy of 3-AB. We examined expression of the phosphorylated form of NF-kappaB and IkappaBalpha (p-NF-kappaB and p-IkappaBalpha, respectively) in retinas of MNU-treated rats concurrently treated with or without 50mg/kg 3-AB, compared with MNU-untreated control retinas. 3-AB dose-dependently suppressed photoreceptor cell apoptosis: 50mg/kg 3-AB injected concurrently with MNU completely rescued photoreceptor cell damage; 30 mg/kg 3-AB significantly reduced photoreceptor cell damage; 10 mg/kg 3-AB tended to suppress photoreceptor cell damage; <or=5mg/kg 3-AB was ineffective. When 50mg/kg 3-AB was injected 12h before or >or=4h after MNU, it did not exert a retinoprotective effect. p-NF-kappaB levels of MNU-treated rat retinas were significantly lower than those of MNU-untreated control retinas, while 50 mg/kg 3-AB injected concurrently with MNU preserved the p-NF-kappaB levels; p-IkappaBalpha levels tended to decrease after MNU injection, compared with untreated control retinas, but the difference was not significant. Thus, 3-AB dose-dependently suppressed MNU-induced retinal damage, and 50mg/kg 3-AB injected concurrently with MNU completely rescued photoreceptor cell apoptosis via preservation of NF-kappaB activity.
authors.affiliation: Second Department of Pathology, Kansai Medical University, Moriguchi, Osaka 570-8506, Japan. mikik@takii.kmu.ac.jp
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Miki
authors.forename: Norihisa
authors.initials: N
authors.lastname: Uehara
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Shikata
authors.forename: Miyo
authors.initials: M
authors.lastname: Matsumura
authors.forename: Airo
authors.initials: A
authors.lastname: Tsubura
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001549:Benzamides / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D005260:Female; D008770:Methylnitrosourea; D016328:NF-kappa B / Q000378:metabolism / Q000502:physiology; D018696:Neuroprotective Agents / Q000627:therapeutic use; D020419:Photoreceptor Cells, Vertebrate / Q000187:drug effects* / Q000648:ultrastructure; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D012162:Retinal Degeneration / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*
chemical_list: D001549:Benzamides; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D018696:Neuroprotective Agents; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D008770:Methylnitrosourea; C025160:3-aminobenzamide