Bile acids modulate tight junction structure and barrier function of Caco-2 monolayers via EGFR activation

Intestinal and systemic illnesses have been linked to increased gut permeability. Bile acids, whose luminal profile can be altered in human disease, modulate intestinal paracellular permeability. We investigated the mechanism by which selected bile acids increase gut permeability using a validated i...

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Bibliographic Details
Published in:	American journal of physiology: Gastrointestinal and liver physiology Vol. 294; no. 4; p. G906
Main Authors:	Raimondi, Francesco, Santoro, Pasquale, Barone, Maria Vittoria, Pappacoda, Serena, Barretta, Maria Luisa, Nanayakkara, Merlin, Apicella, Carmela, Capasso, Letizia, Paludetto, Roberto
Format:	Journal Article
Language:	English
Published:	United States 01-04-2008
Subjects:	Antibodies, Monoclonal Bile Acids and Salts - metabolism Caco-2 Cells Chenodeoxycholic Acid - metabolism Cholic Acid - metabolism Deoxycholic Acid - metabolism Dextrans - metabolism Electric Impedance Enzyme Activation Epidermal Growth Factor - metabolism Humans Intestinal Mucosa - drug effects Intestinal Mucosa - enzymology Intestinal Mucosa - metabolism Kinetics Membrane Proteins - metabolism Occludin Organometallic Compounds - metabolism Organophosphorus Compounds - metabolism Permeability Phosphorylation Protein Kinase Inhibitors - pharmacology Pyrimidines - pharmacology Receptor, Epidermal Growth Factor - immunology Receptor, Epidermal Growth Factor - metabolism src-Family Kinases - antagonists & inhibitors src-Family Kinases - metabolism Tight Junctions - drug effects Tight Junctions - enzymology Tight Junctions - metabolism
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Summary:	Intestinal and systemic illnesses have been linked to increased gut permeability. Bile acids, whose luminal profile can be altered in human disease, modulate intestinal paracellular permeability. We investigated the mechanism by which selected bile acids increase gut permeability using a validated in vitro model. Human intestinal Caco-2 cells were grown in monolayers and challenged with a panel of bile acids. Transepithelial electrical resistance and luminal-to-basolateral fluxes of 10-kDa Cascade blue-conjugated dextran were used to monitor paracellular permeability. Immunoprecipitation and immunoblot analyses were employed to investigate the intracellular pathway. Redistribution of tight junction proteins was studied by confocal laser microscopy. Micromolar concentrations of cholic acid, deoxycholic acid (DCA), and chenodeoxycholic acid (CDCA) but not ursodeoxycholic acid decreased transepithelial electrical resistance and increased dextran flux in a reversible fashion. Coincubation of 50 muM CDCA or DCA with EGF, anti-EGF monoclonal antibody, or specific src inhibitor 4-Amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP-2) abolished the effect. A concentration of 50 muM of either CDCA or DCA also induced EGF receptor phosphorylation, occludin dephosphorylation, and occludin redistribution at the tight junction level in the same time frame and in a reversible fashion. We conclude that selected bile acids modulate intestinal permeability via EGF receptor autophosphorylation, occludin dephosphorylation, and rearrangement at the tight junction level. The effect is mediated by the src family kinases and is abolished by EGF treatment. These data also support the role of bile acids in the genesis of necrotizing enterocolitis and the protective effect of EGF treatment.
ISSN:	0193-1857
DOI:	10.1152/ajpgi.00043.2007