TLR7激动剂imiquimod的研究进展

Imiquimod--aTLR7agonistXiaochenYu20131021IntroductionImiquimodwasthefirstsmallmoleculeapprovedfortopicaluseinhumansthatwasshowntoactthroughtheToll-likereceptor(TLR)pathway.ImiquimodactivatesinnateimmunecellsthatexpressTLR7includingplasmacytoiddendriticcells(pDC),Bcellsandlikelysomemonocytes.Dependingonthecelltype,thisactivationresultsinsecretionofcytokinesincludinginterferon-α(IFN-α)andothers,upregulationofcostimulatorymoleculeexpressionandmaturationand/orproliferation.Itwasfirstidentifiedasacompoundthathasanti-viralactivityinpigsinfectedwithherpessimplexvirus,andhasbeensuccessfullyusedforthetreatmentofgenitalwartscausedbyhumanpapillomavirusintheclinical.Recentstudyrevealeditalsohasdirectproapoptoticactivityagainstvarioustumorcellpopulationsinvitroandinvivo.theantiviralactivityofimiquimodImiquimodanditsanalogueshavenodirectinvitroantiviralactivityandarenotvirucidal,rathertheantiviralisindirectthroughcytokineinductionandimmuneactivation.resiquimod(S-28463),imiquimod(S-26308).Humanperipheralbloodmononuclearcells(PBMC)Mo-DC,dendriticcells(DC)derivedfrommonocytes,plasmacytoiddendriticcells(pDC)Imiquimod'sproapoptoticeffectinvitroImiquimodinhibitscellproliferationinprostatecancercelllines.（detectedbyMTT）Imiquimodinducesapoptosisbyimiquimoddose-dependentandbypassofmitochondria-dependentinprostatecancercellsATLR7inhibitorchloroquinedoesnotrestorethegrowthinhibitionbyimiquimodResults:ImiquimodinducedapoptosiswasindependentlyofTLR7andMyD88ImiquimodinhibitsinvivogrowthofprostatecancerinmicetheroleofimiquimodinmacrophageNumerousmacrophagesarepresentintheshoulderregionsofrupture-pronelifethreateningatheroscleroticplaques.Removalofmacrophagesfromplaquesbymacrophage-specificinductionofcelldeathcouldrepresentanattractiveapproachtostabilizethestructureoftheplaque.Toinitiateselectivemacrophagedeath,weexaminedToll-likereceptor7(TLR7)asapotentialtarget,sinceitisexpressedinmacrophagesbutnotinSMCs.TLR7expressedinmacrophagesbutnotinSMCsmacrophages(Mψ),bonemarrow-derivedmacrophages(BMMψ)fromWT,TLR7+andTLR7-mice,andmouseaorticSMCsfromWTmice.imiquimodinducedcellapoptosisisdependentonTLR7b,eMacrophagesandSMCswereincubatedfor24hwithimiquimod(0.1–30lg/ml).Cellviabilitywasexaminedbyneutralredassays.imiquimodinducedmacrophageautophagybyTLR7Imiquimod-inducedmacrophageinflammationisTLR7dependenttheroleofimiquimodinatheroscleroticplaqueLocaladministrationofimiquimodtorabbitatheroma-likelesionsinducedautophagyinmacrophageswithoutaffectingSMCs,asdemonstratedbyTEM,andinducedanincreaseinplaquearea.Invivotreatmentofatheroma-likelesionswithimiquimoddidnotdepletemacrophages,butratherstimulatedmacrophageinfiltrationduetocytokinerelease.aTransmissionelectron-microscopicimagesofmacrophagesshowautophagosomeformationafterimiquimodtreatmentfor7days.bImagesofSMCsshownautophagosomeformationafterimiquimodtreatmentI,intima;M,media;a,VCAM-1;b,Tcells;c,macrophagesTheseinvivoresultsseemtobeincontrastwithourinvitrofindings(imiquimodinducedautophagicdeath).Thecontradictoryeffectsofimiquimodinvivoversusinvitromightbemisleadingbecausethelevelofautophagyinducedbybothconditionscouldbeentirelydifferent.TLR7/8agonistsasvaccineadjuvantsImiquimodandsimilaranalogshavevaccineadjuvantactivitycamefromstudiesdemonstratingtheabilityofthesemoleculestoactivateAPCs,induceimmunemodulatorycytokinesandactivateB-andT-cellresponses.MicevaccinatedintradermallywithmicroneedlescoatedwithimiquimodandH1N1HAinducedIFN-γ-producingT-cellresponse,highlevelsofIgG2andprotectiveimmunityfollowingalethalchallengewithamouse-adaptedinfuenzastrain.什么是Toll样受体？Toll样受体（Toll-likereceptors,TLR）是参与非特异性免疫（天然免疫）的一类重要蛋白质分子，也是连接非特异性免疫和特异性免疫的桥梁。TLR是单个的跨膜非催化性蛋白质，可以识别来源于微生物的具有保守结构的分子。当微生物突破机体的物理屏障，如皮肤、粘膜等时，TLR可以识别它们并激活机体产生免疫细胞应答。