Mechanisms of cell death in primary cortical neurons and PC12 cells

Increasing evidence suggests that the regulation of neuronal cell death is complex. In this study we compared the neurotoxic effects of tumor necrosis factor-alpha (TNFalpha), nitric oxide, and thrombin on primary rat cortical cell cultures and the neuronal PC12 cell line. Release of lactate dehydrogenase (LDH) and the intracellular accumulation of nucleosomes were used as indicators of necrosis and apoptosis, respectively. There was significant LDH release in both neuronal cell types, however, the pattern of LDH release was variable and agonist-dependent. In response to the nitric oxide generator, sodium nitroprusside (SNP), cortical cells exhibited pronounced LDH release and dramatic morphologic changes, whereas in differentiated PC12 cells, TNFalpha evoked release of LDH with no associated morphologic changes. Both neuronal cell types, but not undifferentiated PC12 cells, responded to TNFalpha and thrombin with increased apoptosis. Caspase inhibition, but not antioxidant treatment, reduced nucleosome accumulation in primary cortical cells, but not in differentiated PC12 cells. In the differentiated PC12 cells, caspase inhibition reduced TNFalpha-mediated LDH release, but not nucleosome accumulation. These data suggest mechanisms involved in neuronal cell death utilize multiple pathways that vary depending on the neurotoxic insult and are also influenced by subtle differences among neuronal cell phenotypes.