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J Gastroenterol. 2017 Oct;52(10):1090-1100. doi: 10.1007/s00535-017-1309-2. Epub 2017 Jan 30.

Epithelial barrier dysfunction in lymphocytic colitis through cytokine-dependent internalization of claudin-5 and -8.

Author information

1
Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité, Campus Benjamin Franklin, Berlin, Germany.
2
Institute of Clinical Physiology, Charité, Campus Benjamin Franklin, Hindenburgdamm 30, 12203, Berlin, Germany.
3
Institute of Pathology, Charité, Campus Benjamin Franklin, Berlin, Germany.
4
Institute of Pathology PathoTres, Berlin, Germany.
5
Max Planck Institute for Molecular Genetics, Berlin, Germany.
6
Cologne Center for Genomics, University of Cologne, Cologne, Germany.
7
Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité, Campus Benjamin Franklin, Berlin, Germany. joerg.schulzke@charite.de.
8
Institute of Clinical Physiology, Charité, Campus Benjamin Franklin, Hindenburgdamm 30, 12203, Berlin, Germany. joerg.schulzke@charite.de.

Abstract

BACKGROUND:

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.

METHODS:

Epithelial resistance (R epi) was determined by one-path impedance spectroscopy and 3H-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.

RESULTS:

R epi was reduced to 53% and 3H-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.

CONCLUSIONS:

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.

KEYWORDS:

Claudin; Cytokines; Lymphocytic colitis; Tight junction

PMID:
28138755
DOI:
10.1007/s00535-017-1309-2
[Indexed for MEDLINE]

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