Page - 111 - in Advances in Neuroimmunology

BrainSci. 2017,7, 14 modulateNLRP12activity,directlyor indirectly, therebyexerting its immunosuppressiveeffectsand opposingtheLPS-induceddecrease inNLRP12 in thepresenceofmorphine tolerance. Birc3,adownstreamregulatorof inflammasomesignaling, isessential forcontrollingthesynthesis of cytokines and chemokines in the inflammatoryMapkandNF-κBpathways. It is also required for inflammasomeactivation, subsequentcaspase1activity,andIL-1β formation[31]. Inourstudy, Birc3expressionwassignificantly increased inboth theplacebo-controlandmorphine-tolerant rats in response toLPS, indicating thatLPS isable to inducean inflammatoryresponse throughBirc3activity, following inhibitionof theanti-inflammatoryNLRP12.However, inresponse toLPS,Birc3expression in themorphine-tolerant ratsdidnotchange incomparisonto theplacebo-control rats. This indicates thatmorphinemaynotbeable tomodulateBirc3expression,andtherefore there isnochange, increase ordecrease, in itsexpression in themorphine tolerantstate. NF-κB is important in the activation of inflammatory mediators such as cytokines and chemokines[16]. PreviousstudieshavereportedthatNLRP12inhibitsbothcanonicalandnon-canonical NF-κBactivation [16,28] and thatNfkbia, a downstream regulator of inflammasomes, inhibits the activity of dimericNF-κB/Rel complexes [32]. In our study,Nfkbiawas significantly increased in response to LPS in both theplacebo-control andmorphine-tolerant rats. During an inflammatory response,onewouldexpect theexpressionandactivityofapositiveregulatorof inflammationtobe increased,whereas thatofanegativeregulatorwouldbedecreased.However, fromaphysiological standpoint, there isaconstanteffort tobalancepro-andanti-inflammatoryactivity[33,34]. Thisquest to balance thepro-andanti-inflammatoryresponsescouldbeoneof thereasons foran increase inNfkbia, which isknownto inhibit theactivityof thepro-inflammatorydimericNF-κB/REL, thusreducingthe productionofpro-inflammatorymediators. Asexpected,wefoundthat theexpressionofpro-inflammatorycytokines (IL-1βandIL-6)and chemokines (Ccl2,Ccl7,Cxcl1, andCxcl3)was increased in response toLPS in theplacebo-control rats [35–37]. In themorphine-tolerant rats, however, the LPS-induced cytokine and chemokine expression levelswere lower, suggestingthatNLRP12 inhibition inresponse toLPSmaybeopposed orsubduedin themorphine tolerantstate. In a previous study, we observed that, in peripheral immune organs such as the spleen, NLRP3 expression, but notNLRP12 expression, is altered in response to LPS,with andwithout morphine tolerance [38], suggesting that themechanism(s)of inflammasomeactivation inresponse to pathogensmaybedifferent inperipheral immuneorgans, comparedto thecentralnervoussystem. Duringmorphinetolerance, theLPS-inducedexpressionofNLRP3,aswellas thatofcytokinesand chemokines, isreducedincomparisontotheplacebo-controlratsgivenLPS[38]. Theseobservationsare consistentwithpreviousstudiesshowingthat immuneactivation, includinganinflammatoryresponse, isdiminishedduringmorphine tolerance [39]. Therefore, thedata fromthepresentstudy,aswellas fromourpreviousreport [38], collectively indicate thatmorphinemayexert itseffects throughboth pro-andanti-inflammatory inflammasomes. LINCSanalysis is able topredict potential target genes basedona certain treatment and the geneprofilesignatures in itsdatabase. Inourstudy,LINCSwasable togenerateareportofpotential targetswith a p value of <0.05 from the list of geneswith altered expression in response to LPS in control rats (placebo-control + salineversusplacebo-control +LPS) butnot from theother two comparisons (placebo-control+salineversusmorphine-tolerant+saline,morphine-tolerant+saline versusmorphine-tolerant+LPS),because therewerenotenoughsignificantgenefeatures in those two groups.Whenenlargingthesetofgenefeatures for thecomparisonofplacebo-control+salineversus placebo-control+LPStoap-valueof<0.1,LINCSgeneratedareportwithsimilarpotential targets. Thus, the gene featureswere then studiedwith a p-value of <0.1 on all three sets of comparisons. VPS28,PROCR,andCHMP2Awere the topthreewith thehighest scores inLINCSreportgenerated basedonplacebo-control+ salineversusplacebo-control+LPSgenealternations, suggesting that Vps28, Procr andChmp2awerepotential targets ofLPS. In the report forplacebo-control+ saline versusmorphine-tolerant+saline,SMARCE1,AHRR,andGPX7werethemost likely targetsalteredin 111