title: Effect of colonic bacterial metabolites on Caco-2 cell paracellular permeability in vitro.
abstract: One common effect of tumor promoters is increased tight junction (TJ) permeability. TJs are responsible for paracellular permeability and integrity of the barrier function. Occludin is one of the main proteins responsible for TJ structure. This study tested the effects of physiological levels of phenol, ammonia, primary bile acids (cholic acid, CA, and chenodeoxycholic acid, CDCA), and secondary bile acids (lithocholic acid, LCA, and deoxycholic acid, DCA) on paracellular permeability using a Caco-2 cell model. Paracellular permeability of Caco-2 monolayers was assessed by transepithelial electrical resistance (TER) and the apical to basolateral flux of [14C]-mannitol. Secondary, but not primary, bile acids increased permeability as reflected by significantly decreased TER and increased mannitol flux. Both phenol and ammonia also increased permeability. The primary bile acid CA significantly increased occludin expression (P < 0.05), whereas CDCA had no significant effect on occludin expression as compared to the negative control. The secondary bile acids DCA and LCA significantly increased occludin expression (P < 0.05), whereas phenol had no significant effect on the protein expression as compared to the negative control. This suggests that the increased permeability observed with LCA, DCA, phenol, and ammonia was not related to an effect on occludin expression. In conclusion, phenol, ammonia, and secondary bile acids were shown to increase paracellular permeability and reduce epithelial barrier function at doses typical of levels found in fecal samples. The results contribute to the evidence these gut microflora-generated products have tumor-promoting activity.
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, UK.
authors.forename: Roisin
authors.initials: R
authors.lastname: Hughes
authors.forename: Mary Jo
authors.initials: MJ
authors.lastname: Kurth
authors.forename: Victoria
authors.initials: V
authors.lastname: McGilligan
authors.forename: Hugh
authors.initials: H
authors.lastname: McGlynn
authors.forename: Ian
authors.initials: I
authors.lastname: Rowland
mesh_terms: D000641:Ammonia / Q000378:metabolism / Q000494:pharmacology; D001647:Bile Acids and Salts / Q000378:metabolism / Q000494:pharmacology; D018938:Caco-2 Cells; D002250:Carbon Radioisotopes; D002635:Chenodeoxycholic Acid / Q000378:metabolism / Q000494:pharmacology; D019826:Cholic Acid / Q000378:metabolism / Q000494:pharmacology; D003106:Colon / Q000382:microbiology; D003840:Deoxycholic Acid / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D017097:Electric Impedance; D006801:Humans; D008353:Mannitol / Q000378:metabolism* / Q000494:pharmacology; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism*; D062793:Occludin; D010539:Permeability / Q000187:drug effects*; D019800:Phenol / Q000378:metabolism / Q000494:pharmacology; D019108:Tight Junctions / Q000187:drug effects* / Q000378:metabolism
chemical_list: D001647:Bile Acids and Salts; D002250:Carbon Radioisotopes; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D003840:Deoxycholic Acid; D002635:Chenodeoxycholic Acid; D019800:Phenol; D008353:Mannitol; D000641:Ammonia; D019826:Cholic Acid