Total polysaccharides of the Sijunzi decoction attenuate tumor necrosis factor-α-induced damage to the barrier function of a Caco-2 cell monolayer via the nuclear factor-κB-myosin light chain kinase-myosin light chain pathway

AIMToexploretheprotectiveeffectsandunderlyingmechanismsoftotalpolysaccharidesoftheSijunzidecoction(TPSJ)ontheepithelialbarriersinvitro.METHODSCaco-2cellmonolayersweretreatedwithorwithoutTPSJinthepresenceorabsenceofTNF-α,andparacellularpermeabilityandtransepithelialelectricalresistance(TEER)weremeasuredtoevaluatetheepithelialbarrierfunction.Immunofluorescenceandwesternblottingwererespectivelyusedtoevaluatethedistributionandexpressionofthetightjunctionproteinsclaudin1,claudin2,zo3,andoccludininCaco-2cells.Westernblottingwasalsousedtoevaluatethecellularexpressionofmyosinlightchain(MLC),phosphorylatedMLC(pMLC),MLCkinase(MLCK),andnuclearfactor(NF)-κBp65.RESULTSTPSJpromotedtheproliferationofCaco-2cellsandinhibitedTNF-α-inducedsecretionofpro-inflammatorycytokines.Furthermore,TPSJsignificantlyamelioratedboththereductionofTEERandtheincreasedparacellularpermeabilityobservedintumornecrosisfactor(TNF)-α-damagedCaco-2monolayers.Furthermore,TPSJremarkablyattenuatedTNF-α-inducedmorphologicalchanges,downregulatedtheexpressionofclaudin1,claudin2,zo3,andoccludin,andmarkedlysuppressedTNF-α-mediatedupregulationofp-MLCandMLCKexpression.Finally,TPSJinhibitedtheactivationandexpressionofNF-κBp65.CONCLUSIONOurresultsdemonstratethatTPSJalleviatestheTNF-α-inducedimpairmentoftheintestinalepithelialcellbarrierfunctionbysuppressingNF-κBp65-mediatedphosphorylationofMLCKandMLC.