title: Caspase-1 and poly (ADP-ribose) polymerase inhibitors may protect against peroxynitrite-induced neurotoxicity independent of their enzyme inhibitor activity.
abstract: We investigated the mechanism of 3-morpholinosyndnomine (SIN-1) neurotoxicity in nearly pure neuronal cultures. In a simple saline solution, SIN-1 neurotoxicity was found to be mediated by peroxynitrite and independent of glutamate receptor activation [Y. Zhang & P.A. Rosenberg (2002) Eur. J. Neurosci, 16, 1015-1024]. To further study the mechanism of peroxynitrite toxicity to neurons we investigated the role of caspases and poly (ADP-ribose) polymerase (PARP) in this model system. Ac-Tyr-Val-Ala-Asp-chloromethyl ketone (Ac-YVAD-cmk), a specific caspase-1 inhibitor, completely blocked neurotoxicity as well as ATP depletion induced by SIN-1. However, a caspase-3 inhibitor and a pan-caspase inhibitor were both without effect. These results suggested that the protection of Ac-YVAD-cmk might not be due to its inhibition of caspase-1. Indeed, Western blot analysis and assay of caspase activity indicated that caspase activation was not involved in SIN-1 toxicity. Ac-YVAD-cmk also completely blocked in vitro protein nitration induced by SIN-1 or peroxynitrite, suggesting that Ac-YVAD-cmk may interact with peroxynitrite directly. Similarly, although activation of PARP is thought to be a major cause of peroxynitrite-induced ATP depletion, and two PARP inhibitors, 1,5-dihydroxyisoquinoline (DHQ) and 3-aminobenzamide (3-AB), completely prevented ATP depletion and neurotoxicity induced by SIN-1, SIN-1 did not increase poly (ADP-ribosyl)ation and PARP activity. Furthermore, DHQ and 3-AB completely prevented in vitro protein nitration induced by peroxynitrite, indicating that DHQ and 3-AB directly interact with peroxynitrite. Taken together, these results suggest that in the model system used here peroxynitrite neurotoxicity is independent of caspase and PARP activation, and therefore implicate a novel mechanism.
authors.affiliation: Department of Neurology, Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, Massachusetts 02115, USA.
authors.forename: Yumin
authors.initials: Y
authors.lastname: Zhang
authors.forename: Paul A
authors.initials: PA
authors.lastname: Rosenberg
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D061945:Caspase Inhibitors; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007700:Kinetics; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000633:toxicity*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D030421:Peroxynitrous Acid / Q000037:antagonists & inhibitors / Q000633:toxicity*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; C098738:N-acetyl-tyrosyl-valyl-alanyl-aspartyl chloromethyl ketone; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D030421:Peroxynitrous Acid; C002385:linsidomine; D000255:Adenosine Triphosphate; D008981:Molsidomine; D011065:Poly(ADP-ribose) Polymerases