EXCEED THE SPACE PROVIDED, We are examining mechanisms of neuronal-glial interactions within the context of how a pro- inflammatory cytokines and the nicotinic cholinergic neurotransmitter systems interact to determine neuronal susceptibility to excitotoxins in a neuroinflammatory environment, as is often present in neurological disease. The Overall Hypothesis is: Pre-exposure of CNS cells to the cholinergic agonist, nicotine, modifies signaling initiated by TNF_ and alters neuronal vulnerability to excitotoxins and the CNS response during neuro-inflammatory processes. This hypothesis stems from several key results that include: 1. Cultured cortical neurons are protected against an NMDA-toxic challenge by TNFo_ or nicotine, however, TNFc_ and nicotine induced neuroprotection is abolished when the agents are present together cultures of mixed neurons and glia, 2. These agents are not antagonistic in enriched neuronal cultures suggesting that other non-neuronal cell types are required, 3. The addition of mononuclear phagocytes/microglial cells (MP/MG) to enriched neuronal cultures restores antagonism between nicotine and TNFot. 4. MP/MG in culture express nAChRs, and they respond functionally to the presence of nicotine, and 5. Nicotine administration alters the kinetics of TNFc_-initiated caspase 8 activation, an important intracellular mediator of TNFa-signaling. We will determine in Specific Aim 1 if nicotine/TNFoc antagonism of neuroprotection to NMDA requires specific cell-cell interactions between cells of the CNS including neurons and MP/MG, In Specific Aim 2 if neuronal nicotinic receptors, in addition to nAChRo_7, and expressed by cell types other than neurons, participate in mechanism(s) related to nicotine/TNFa antagonism of neuroprotection and in Specific Aim 3 if nicotine preconditioning of CNS cells alters their response to TNFa through modifying caspase/protease activation and/or function. These studies have direct and novel implications toward understanding sustained nicotine presence on the normal regulation of neuro-inflammation determine susceptibility to many toxins and influence normal and pathological PERFORMANCE SITE ========================================Section End===========================================
