title: TNF-alpha-induced increase in intestinal epithelial tight junction permeability requires NF-kappa B activation.
abstract: Crohn's disease (CD) patients have an abnormal increase in intestinal epithelial permeability. The defect in intestinal tight junction (TJ) barrier has been proposed as an important etiologic factor of CD. TNF-alpha increases intestinal TJ permeability. Because TNF-alpha levels are markedly increased in CD, TNF-alpha increase in intestinal TJ permeability could be a contributing factor of intestinal permeability defect in CD. Our purpose was to determine some of the intracellular mechanisms involved in TNF-alpha modulation of intestinal epithelial TJ permeability by using an in vitro intestinal epithelial system consisting of filter-grown Caco-2 monolayers. TNF-alpha produced a concentration- and time-dependent increase in Caco-2 TJ permeability. TNF-alpha-induced increase in Caco-2 TJ permeability correlated with Caco-2 NF-kappa B activation. Inhibition of TNF-alpha-induced NF-kappa B activation by selected NF-kappa B inhibitors, curcumin and triptolide, prevented the increase in Caco-2 TJ permeability, indicating that NF-kappa B activation was required for the TNF-alpha-induced increase in Caco-2 TJ permeability. This increase in Caco-2 TJ permeability was accompanied by down-regulation of zonula occludens (ZO)-1 proteins and alteration in junctional localization of ZO-1 proteins. TNF-alpha modulation of ZO-1 protein expression and junctional localization were also prevented by NF-kappa B inhibitors. TNF-alpha did not induce apoptosis in Caco-2 cells, suggesting that apoptosis was not the mechanism involved in TNF-alpha-induced increase in Caco-2 TJ permeability. These results demonstrate for the first time that TNF-alpha-induced increase in Caco-2 TJ permeability was mediated by NF-kappa B activation. The increase in permeability was associated with NF-kappa B-dependent downregulation of ZO-1 protein expression and alteration in junctional localization.
authors.affiliation: Department of Internal Medicine, University of New Mexico, Albuquerque, NM 87131-0001, USA. tma@salud.unm.edu
authors.forename: Thomas Y
authors.initials: TY
authors.lastname: Ma
authors.forename: Gary K
authors.initials: GK
authors.lastname: Iwamoto
authors.forename: Neil T
authors.initials: NT
authors.lastname: Hoa
authors.forename: Vimesh
authors.initials: V
authors.lastname: Akotia
authors.forename: Ali
authors.initials: A
authors.lastname: Pedram
authors.forename: Michel A
authors.initials: MA
authors.lastname: Boivin
authors.forename: Hamid M
authors.initials: HM
authors.lastname: Said
mesh_terms: D017209:Apoptosis / Q000502:physiology; D001665:Binding Sites / Q000187:drug effects; D001711:Biotransformation / Q000502:physiology; D015153:Blotting, Western; D018938:Caco-2 Cells; D002463:Cell Membrane Permeability / Q000187:drug effects; D003474:Curcumin / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D004224:Diterpenes / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D024202:Electrophoretic Mobility Shift Assay; D004852:Epoxy Compounds; D019793:Fluorescein; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects*; D008565:Membrane Proteins / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000502:physiology*; D010616:Phenanthrenes / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D011233:Precipitin Tests; D019108:Tight Junctions / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D062826:Zonula Occludens-1 Protein
chemical_list: D004224:Diterpenes; D004852:Epoxy Compounds; D008565:Membrane Proteins; D016328:NF-kappa B; D010616:Phenanthrenes; D010750:Phosphoproteins; C569042:TJP1 protein, human; D014409:Tumor Necrosis Factor-alpha; D062826:Zonula Occludens-1 Protein; C001899:triptolide; D004247:DNA; D003474:Curcumin; D019793:Fluorescein