Effect of barbiturates on hydroxyl radicals, lipid peroxidation, and hypoxic cell death in human NT2-N neurons

Background: Barbiturates have been shown to be neuroprotective in several a nimal models, but the underlying mechanisms are unknown. In this study, the authors investigated the effect of barbiturates on free radical scavenging and attempted to correlate this with their neuroprotective effects in a mo del of hypoxic cell death in human NT2-N neurons. Methods: Hydroxyl radicals were generated by ascorbic acid and iron and wer e measured by conversion of salicylate to 2,3-dihydroxybenzoic acid. The ef fect of barbiturates on lipid peroxidation measured as malondialdehyde and 4-hydroxynon-2-enal was also investigated Hypoxia studies were then perform ed on human NT2-N neurons, The cells were exposed to 10 h of hypoxia or com bined oxygen and glucose deprivation for 3 or 5 h in the presence of thiope ntal (50-600 mu M), methohexital (50-400 mu M), phenobarbital (10-400 mu M) , or pentobarbital (10-400 mu M), and cell death was evaluated after 24 h b y lactate dehydrogenase release. Results: Pentobarbital, phenobarbital, methohexital, and thiopental dose-de pendently inhibited formation of 2,3-dihydroxybenzoic acid and iron-stimula ted lipid peroxidation, There were significant but moderate differences in antioxidant action between the barbiturates. While phenobarbital (10-400 mu M) and pentobarbital (10-50 mu M) increased lactate dehydrogenase release after combined oxygen and glucose deprivation, thiopental and methohexital protected the neurons at all tested concentrations. At a higher concentrati on (400 mu M), pentobarbital also significantly protected the neurons, At b oth 50 and 400 mu M, thiopental and methohexital protected the NT2-N neuron s significantly better than phenobarbital and pentobarbital. Conclusions: Barbiturates differ markedly in their neuroprotective effects against combined oxygen and glucose deprivation in human NT2-N neurons. The variation in neuroprotective effects could only partly be explained by dif ferences in antioxidant action.