PEPTIDE GROWTH-FACTORS PROTECT AGAINST ISCHEMIA IN CULTURE BY PREVENTING NITRIC-OXIDE TOXICITY

Reduction or elimination of nitric oxide (NO) production in cortical n eurons by NO synthase (NOS) inhibitors during glutamate toxicity in vi tro or during focal cerebral ischemia in vivo can prevent neuronal cel l death. In contrast, growth factors can prevent neuronal degeneration induced by treatment with glutamate or potassium cyanide. We have det ermined whether NO mediates hippocampal cell death during anoxia in vi tro and whether the peptide growth factors basic fibroblast growth fac tor (bFGF) and epidermal growth factor (EGF) can prevent hippocampal n euronal death during anoxia or NO exposure. Both bFGF and EGF increase d hippocampal neuronal survival from about 35% in anoxic cultures to a bout 65% in treated cultures during an 8 hr period of anoxia. Inhibiti on of NOS by N(G)-monomethyl-L-arginine, a competitive inhibitor of NO S, rescued 65-70% of the neurons that would normally die during an 8 h r anoxic incubation, and this effect was reversed by L-arginine, a pre cursor for NO. Thus, hippocampal neuronal death following anoxia is, a t least in part, mediated by NO. NO, generated by either nitroprusside or 3-morpholino-sydnonimine, was toxic to hippocampal neurons. Pretre atment of cultures with either bFGF (10 ng/ml) or EGF (10 ng/ml) prior to NO exposure increased survival from approximately 40% in untreated cultures to 80% in treated cultures, yet the effect of combining bFGF and EGF was not greater than treatment with either of the growth fact ors alone. Knowledge that the growth factors bFGF and EGF are neuropro tective against NO toxicity provides insights into the mechanisms of i schemic neuronal death that may direct future therapeutic modalities f or cerebrovascular disease and neurodegenerative disorders.