title: Bile acids modulate tight junction structure and barrier function of Caco-2 monolayers via EGFR activation.
abstract: 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.
authors.affiliation: Division of Neonatology, Department of Pediatrics, "Federico II" University, Naples, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Raimondi
authors.forename: Pasquale
authors.initials: P
authors.lastname: Santoro
authors.forename: Maria Vittoria
authors.initials: MV
authors.lastname: Barone
authors.forename: Serena
authors.initials: S
authors.lastname: Pappacoda
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Barretta
authors.forename: Merlin
authors.initials: M
authors.lastname: Nanayakkara
authors.forename: Carmela
authors.initials: C
authors.lastname: Apicella
authors.forename: Letizia
authors.initials: L
authors.lastname: Capasso
authors.forename: Roberto
authors.initials: R
authors.lastname: Paludetto
mesh_terms: D000911:Antibodies, Monoclonal; D001647:Bile Acids and Salts / Q000378:metabolism*; D018938:Caco-2 Cells; D002635:Chenodeoxycholic Acid / Q000378:metabolism; D019826:Cholic Acid / Q000378:metabolism; D003840:Deoxycholic Acid / Q000378:metabolism; D003911:Dextrans / Q000378:metabolism; D017097:Electric Impedance; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism; D062793:Occludin; D009942:Organometallic Compounds / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D010539:Permeability; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D019108:Tight Junctions / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: C412373:AG 1879; D000911:Antibodies, Monoclonal; D001647:Bile Acids and Salts; D003911:Dextrans; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D009942:Organometallic Compounds; D009943:Organophosphorus Compounds; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D003840:Deoxycholic Acid; D002635:Chenodeoxycholic Acid; C066850:Cascade Blue; D004815:Epidermal Growth Factor; C512478:EGFR protein, human; D066246:ErbB Receptors; D019061:src-Family Kinases; D019826:Cholic Acid