title: Epithelial barrier dysfunction in lymphocytic colitis through cytokine-dependent internalization of claudin-5 and -8.
abstract: Watery diarrhea is the cardinal symptom of lymphocytic colitis (LC). We have previously shown that colonic Na malabsorption is one of the major pathologic alterations of LC and found evidence for an epithelial barrier defect. On these grounds, this study aimed to identify the inherent mechanisms of this epithelial barrier dysfunction and its regulatory features.
  
  
  
  Epithelial resistance (Repi) was determined by one-path impedance spectroscopy and3H-mannitol fluxes were performed on biopsies from sigmoid colon in miniaturized Ussing chambers. Tight junction proteins were analyzed by Western blot and confocal microscopy. Inflammatory signaling was characterized in HT-29/B6 cells. Apoptosis and mucosal surface parameters were quantified morphologically.
  
  
  
  Repiwas reduced to 53% and3H-mannitol fluxes increased 1.7-fold in LC due to lower expression of claudin-4, -5, and -8 and altered subcellular claudin-5 and -8 distributions off the tight junction. TNFα and IFNγ could mimic subcellular redistribution in HT-29/B6 cells, a process which was independent on MLCK activation. Epithelial apoptosis did not contribute to barrier dysfunction in LC and mucosal surface area was unchanged.
  
  
  
  Epithelial barrier dysfunction in LC occurs through downregulation of claudin-4, -5, and -8, and redistribution of claudin-5 and -8 off the tight junction, which contributes to diarrhea by a leak-flux mechanism. The key effector cytokines TNFα and IFNγ turned out to be the trigger for redistribution of claudin-5 and -8. Thus, alongside sodium malabsorption, leak-flux is yet another important diarrheal mechanism in LC.
authors.affiliation: Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité, Campus Benjamin Franklin, Berlin, Germany.|Institute of Clinical Physiology, Charité, Campus Benjamin Franklin, Hindenburgdamm 30, 12203, Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Barmeyer
authors.affiliation: Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Irene
authors.initials: I
authors.lastname: Erko
authors.affiliation: Institute of Clinical Physiology, Charité, Campus Benjamin Franklin, Hindenburgdamm 30, 12203, Berlin, Germany.
authors.forename: Karem
authors.initials: K
authors.lastname: Awad
authors.affiliation: Institute of Clinical Physiology, Charité, Campus Benjamin Franklin, Hindenburgdamm 30, 12203, Berlin, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Fromm
authors.affiliation: Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Bojarski
authors.affiliation: Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Svenja
authors.initials: S
authors.lastname: Meissner
authors.affiliation: Institute of Pathology, Charité, Campus Benjamin Franklin, Berlin, Germany.|Institute of Pathology PathoTres, Berlin, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Loddenkemper
authors.affiliation: Max Planck Institute for Molecular Genetics, Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Kerick
authors.affiliation: Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Siegmund
authors.affiliation: Institute of Clinical Physiology, Charité, Campus Benjamin Franklin, Hindenburgdamm 30, 12203, Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Fromm
authors.affiliation: Max Planck Institute for Molecular Genetics, Berlin, Germany.|Cologne Center for Genomics, University of Cologne, Cologne, Germany.
authors.forename: Michal R
authors.initials: MR
authors.lastname: Schweiger
authors.affiliation: Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité, Campus Benjamin Franklin, Berlin, Germany. joerg.schulzke@charite.de.|Institute of Clinical Physiology, Charité, Campus Benjamin Franklin, Hindenburgdamm 30, 12203, Berlin, Germany. joerg.schulzke@charite.de.
authors.forename: Jörg-Dieter
authors.initials: JD
authors.lastname: Schulzke
mesh_terms: D000328:Adult; D000368:Aged; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D016022:Case-Control Studies; D062506:Claudin-4 / Q000378:metabolism; D062507:Claudin-5 / Q000378:metabolism*; D057167:Claudins / Q000378:metabolism*; D046730:Colitis, Lymphocytic / Q000503:physiopathology*; D016207:Cytokines / Q000378:metabolism; D003967:Diarrhea / Q000209:etiology; D058266:Dielectric Spectroscopy / Q000379:methods; D015536:Down-Regulation; D005260:Female; D019073:HT29 Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000473:pathology*; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D012964:Sodium / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism
chemical_list: C107466:CLDN5 protein, human; D062506:Claudin-4; D062507:Claudin-5; D057167:Claudins; D016207:Cytokines; D012964:Sodium; C502011:claudin 8
keywords: Claudin; Cytokines; Lymphocytic colitis; Tight junction