Page - 74 - in Advances in Neuroimmunology

BrainSci. 2016,6, 16 3.6.DifferentialEffects ofTreatmentonBDNFConcentrations Hippocampal BDNF concentrations were assessed to see the potential impact of microglia activitybecausealternativemicroglia,observedherein,areassociatedwithneurotrophicsupport [62]. A one-way ANOVA on BDNF concentrations indicated a significant effect of treatment in the hippocampus (F(3,28) = 19.00, p < 0.0001). Post-hoc Tukey’s tests indicated a 20% increase in BDNFconcentration in thehippocampus in theEtOH/EtOHcomparedwithall othergroups, but Con/EtOHratshaddecreasedconcentrationsofBDNFcomparedtoboth theCon/Conandad libitum groups (Figure8). Correlationsbetweenbingeanimalmodeldataaswell asmarkersofmicroglial activationwere runversusBDNFconcentrations forboth theCon/EtOHandEtOH/EtOHgroups (Table5). Theestimatedtotalnumberofmicroglia (P(10)=0.835,p=0.003)wascorrelatedtoBDNF concentrationsonly in theCon/EtOHgroup(Figure7). Figure 8. Ethanol Experience-Contingent Effects on BDNF. Concentrations of brain derived neurotrophic factor (BDNF)weredeterminedbyELISAinthehippocampus. BDNFwasdecreasedby approximately15%inCon/EtOHtreatedanimalscomparedwithCon/Conorad libitumgroupsbut increasedby20%intheEtOH/EtOHgroup. *p<0.05vs. ad libitumandCon/Congroups;#p<0.05vs. toCon/EtOH. 4.Discussion Thesedatacollectively indicate thatmicrogliapreviouslyactivatedbyalcoholexposurecanbe further exacerbated by a second alcohol binge. This pointwas demonstrated by: (a) potentiated OX-42 immunoreactivity; (b) increasedmicroglialnumber;and(c) increasedTNF-αconcentration in EtOH/EtOH(doublebinge)ratscomparedwithCon/EtOH(singlebinge)rats. Thealcoholmodelused producesalow-grademicroglialactivationstatethatissimilartoanM2phenotype[22,31].However,as thesubsequentbingeproducedmorepro-inflammatory-likeeffects, thesealcohol-activatedmicroglia may also be primed. This enhanced response to a second binge aligns with the definition of microglial priming, which iswhere a stimulus changesmicroglia to bemore susceptible to and over-respondtoasecondinsult[33,63,64]. Primedmicrogliaand/oranexacerbatedmicroglialresponse could leadtoabnormally increasedcelldeathandisahypothesizedetiologyofneurodegenerative disorders [28]. Furthermore,giventhat themajorityof individualswithanAUDdrink inanepisodic bingepattern [38,65], therepeatedcyclesofbingedrinkingwithperiodsofwithdrawal, andtherefore repeatedmicroglial insult,mayleadtoevenmoredynamicmicroglialactivationover time. Thefirstevidenceof thispotentiatedmicroglia response in thedoublebingegroupwas increased immunoreactivity to the OX-42 antibody. Increased OX-42 immunoreactivity, which labels CR3, is one of the earliest signs ofmicroglial activation [22,46]. CR3 is associatedwith cell adhesion necessaryforremovingpathogensordamaged/dyingneurons [45,66,67]. IncreasedOX-42staining hasbeenreported inanumberofanimalmodelsofethanolexposure [22,68–70]. Thecurrent study confirmsthosefindings;but furthers thatworkbyshowingthatasecondhitofbingeethanolexposure 74