PEROXYNITRITE AND HYDROGEN-PEROXIDE INDUCED CELL-DEATH IN THE NSC34 NEUROBLASTOMA X SPINAL-CORD CELL-LINE - ROLE OF POLY(ADP-RIBOSE) POLYMERASE

The reaction of superoxide and nitric oxide results in the formation o f peroxynitrite, a long lived and highly reactive oxidant species. It has been suggested that the formation of peroxynitrite in vivo may con tribute to cell death in some neurological conditions. We have examine d the effect of peroxynitrite on cell death in the NSC34 spinal cord c ell line. A brief (30 min) exposure to either peroxynitrite or hydroge n peroxide caused delayed cell death with an EC50 for both Of similar to 1 mM. Cell death was prevented by the RNA synthesis inhibitor actin omycin D and included DNA damage as an early event. We sought to clari fy the potential role of the DNA binding enzyme poly(ADP-ribose) polym erase (PARP) in cell death in these cells. Several PARP inhibitors [be nzamide, 3-aminobenzamide, nicotinamide, and 6(5H)-phenanthridinone] p revented cell death, but the inactive analogue benzoic acid did not. H owever, there was no evidence of cleavage of PARP, which occurs in apo ptosis via the activation of the caspase CPP32. Therefore, we suggest that PARP contributes to neuronal injury as an early event, probably b y lethal NAD depletion, without any requirement for proteolytic cleava ge.