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Type: Thesis
Title: The neuroimmunopharmacology of alcohol.
Author: Wu, Yue
Issue Date: 2011
School/Discipline: School of Medical Sciences
Abstract: Background and purpose Alcohol exposure induces glial toll-like receptor 4 (TLR4) signalling, while morphine administration leads to both TLR2 and TLR4 signalling in the central nervous system. However, the acute behavioural consequences of such immune activation remain unknown. This thesis aimed to examine: (a) the role of microglia, TLR2, TLR4, MyD88, and IL-1 receptor signalling in sedation and motor impairment following acute alcohol administration in mice; (b) the relationship between these observed behavioural effects and the changes in central and peripheral alcohol pharmacokinetic profiles; (c) the effect of alcohol on MAPK (ERK, JNK, and p38) and NFκB (IκBα) pathways and the alteration of such effects by attenuating microglial, TLR4, MyD88, and IL-1 receptor signalling ex vivo and in vitro; (d) the role of TLR2, TLR4, MyD88, IL-1 receptor, and μ opioid receptor (MOR) in the interaction between alcohol and morphine as assessed by sedation in mice; and (e) the association between the TLR4 Asp299Gly SNP and opioid or alcohol dependence in humans. Experimental approach In mouse studies and mouse cellular studies, pharmacological blockade of microglial signalling, TLR4, IL-1 receptor, or both MOR and TLR4 by minocycline, (+)-naloxone (the MOR-inactive isomer), IL-1 receptor antagonist, or (-)-naloxone (the MOR-active isomer), respectively, was utilised. Mice deficient in TLR2, TLR4, both TLR2 and TLR4, or MyD88 were used. The sedative effect of alcohol and the interaction between alcohol and morphine were assessed by the sleep time (loss of righting reflex) test, and alcohol dose-induced motor impairment was determined by the rotarod test. The activation of MAPK cascade was determined by ERK, JNK, and p38 phosphorylation using a cytometric bead array assay, and the alteration in NFκB cascades was characterised via cellular IκBα protein levels utilising western blotting experiments. In the human pharmacogenetic study, TLR4 Asp299Gly SNP genotypes were determined by a polymerase chain reaction (PCR)-restriction fragment length polymerase (RFLP) assay in 99 opioid dependent subjects, 100 alcohol dependent subjects, and 56 non-dependent healthy controls. Key results Pharmacological or genetic inhibition of microglial activation, TLR2, TLR4, both TLR2 and TLR4, MyD88, or IL-1 receptor signalling attenuated alcohol dose-induced sedation and motor impairment in mice. The modification of IκBα protein levels by alcohol exposure in vitro was time-dependent, and the increase in such protein levels was attenuated by inhibiting proinflammatory microglial activation, TLR4, MyD88, or IL-1 receptor signalling. In contrast, blocking the activities of TLR2, both TLR2 and TLR4, and MyD88, but not TLR4 or IL-1 receptor, inhibited the enhancement of alcohol’s sedative effect by morphine. The human genetic data showed a lack of association between alcohol or opioid dependence and TLR4 Asp299Gly polymorphisms. Conclusions and implications. Collectively, these data suggest that in mice, alcohol activates microglial and TLR2- and TLR4-MyD88-NFκB-IL-1 receptor signalling rapidly, and this activation subsequently contributes to sedation and motor impairment induced by alcohol administration. However, TLR2-MyD88, but not TLR4 and IL-1 receptor, cascade is involved in the interaction between alcohol and morphine. Such behavioural preclinical data provide novel insights into the immune mechanisms of the effects of alcohol and opioids.
Advisor: Somogyi, Andrew Alexander
Coller, Janet Kristie
Hutchinson, Mark Rowland
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Medical Sciences, 2011
Keywords: alcohol; glia; toll-like receptors; MyD88; interleukin-1; alcohol-morphine interactions; animal study; pharmacogenetics
Provenance: Copyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.
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