INDUCTION OF NITRIC-OXIDE SYNTHASE AND NITRIC OXIDE-MEDIATED APOPTOSIS IN NEURONAL PC12 CELLS AFTER STIMULATION WITH TUMOR-NECROSIS-FACTOR-ALPHA LIPOPOLYSACCHARIDE

Exposure of neuronal PC12 cells, differentiated by nerve growth factor , to tumor necrosis factor-alpha (TNF-alpha) and bacterial lipopolysac charide (LPS) resulted in de novo synthesis of inducible nitric oxide synthase (iNOS) mRNA and protein with an increase up to 24 h., Brain N OS expression was unaffected. The induction of iNOS in differentiated PC12 cells was associated with cell death characterized by features of apoptosis. The NOS inhibitors N-monomethylarginine, aminoguanidine, a nd 2-amino-5,6-dihydro-6-methyl-4H-1 ,3-thiazine . HCl prevented TNF-a lpha/LPS-induced cell death and DNA fragmentation, suggesting that the TNF-alpha/LPS-induced cell death is mediated by iNOS-derived NO. This hypothesis is supported by the finding that addition of L-arginine, w hich serves as a precursor and limiting factor of enzyme-derived NO pr oduction, potentiated TNF-alpha/LPS-induced loss of viability.