IL-6 involvement in alcohol-withdrawal excitability

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Project Summary Recent studies provide convincing evidence that alcohol exposure induces astrocytes of the CNS to produce neuroimmune factors including the proinflammatory cytokine IL-6. The consequences of the in- creased levels of IL-6 relative to the actions of alcohol remain to be elucidated. To address this question, we are using transgenic (tg) mice that express elevated levels of IL-6 in the CNS through astrocyte ex- pression. The CNS of the IL-6 tg mice model some of the changes induced in the CNS by a history of al- cohol drinking, which would lead to persistently elevated levels of astrocyte produced IL-6 in the CNS. Our recent studies showed that neuroadaptive changes are produced in the CNS of the IL-6 tg mice that re- sults in increased levels of CNS activity during alcohol withdrawal compared to non-tg littermate controls, as measured by handling induced convulsions and EEG recordings. Moreover, the characteristics of the EEG activity under baseline conditions and the during the alcohol exposure/withdrawal cycle differed for IL-6 tg and non-tg mice. Consistent with these results, field potential recording of synaptic responses at the Schaffer collateral to CA1 pyramidal neuron synapse of hippocampal slices showed that acute alcohol enhanced excitability of the pyramidal neurons in the IL-6 tg hippocampus but not in the non-tg hippocam- pus. Based on these and other results, we hypothesize that alcohol-induced IL-6 production plays a key role in alcohol-induced withdrawal hyperexcitability and the escalation of withdrawal hyperexcitability with binge alcohol exposure. We also hypothesize that the signal transduction partner, STAT3, that mediates the biological effects of IL-6 plays a key role in the alcohol/IL-6 interactions and that the hyperexcitability produced by alcohol/IL-6 interactions involves reduced inhibitory influences mediated by GABAergic mechanisms and A-type K+ channels. To address these hypotheses, a multidisciplinary and multi- laboratory approach will be used to study alcohol exposure/withdrawal in IL-6 tg and non-tg mice and IL-6 KO mice. The approach involves a correlation of results from behavior studies to be carried out in the la- boratory of Dr. Amanda Roberts, electrophysiological studies to be carried out in the laboratory of Dr. Marisa Roberto and biochemical/immunohistochemical studies to be carried out in the laboratory of Dr. Donna Gruol, PI of the grant. The behavioral studies will involve EEG recordings. The electrophysiological studies will involve current and voltage clamp studies of tonic and phasic GABA mechanisms and re- sponses mediated by A-type K+ channels. The biochemical studies will involve measurements of neuro- immune factors and cellular and synaptic proteins. The immunohistochemical studies will identify cells in which the changes in protein levels occurred. Results have the potential to significantly advance/revise our understanding of the mechanisms underlying CNS actions of alcohol and reveal new target sites for thera- peutic intervention.