Nicotine blocks TNF-alpha-mediated neuroprotection to NMDA by an alpha-bungarotoxin-sensitive pathway

Excitotoxic neuronal death mediated by N-methyl-D-aspartate (NMDA) glutamate receptors can contribute to the extended brain damage that often accompanies trauma or disease. Both the inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) and nicotine have been identified as possible neuroprotective agents to NMDA assault. We find that TNF-alpha protection of a subpopulation of cultured cortical neurons to chronic NMDA-mediated excitotoxic death requires both the activation of the p55/TNFRI, but not p75/TNFRII, and the release of endogenous TNF-alpha. Nicotine protection to NMDA was mediated through an alpha-bungarotoxin-sensitive receptor. When coapplied, neuroprotection to NMDA by either TNF-alpha or nicotine was abolished but could be recovered with alpha-bungarotoxin. These results suggest that the cytokine TNF-alpha and alpha-bungarotoxin-sensitive nicotinic neurotransmitter receptors confer neuroprotection through potentially antagonistic pathways.