title: Lithocholic acid attenuates cAMP-dependent Cl- secretion in human colonic epithelial T84 cells.
abstract: Bile acids (BAs) play a complex role in colonic fluid secretion. We showed that dihydroxy BAs, but not the monohydroxy BA lithocholic acid (LCA), stimulate Cl(-) secretion in human colonic T84 cells (Ao M, Sarathy J, Domingue J, Alrefai WA, Rao MC. Am J Physiol Cell Physiol 305: C447-C456, 2013). In this study, we explored the effect of LCA on the action of other secretagogues in T84 cells. While LCA (50 μM, 15 min) drastically (>90%) inhibited FSK-stimulated short-circuit current (Isc), it did not alter carbachol-stimulated Isc LCA did not alter basal Isc, transepithelial resistance, cell viability, or cytotoxicity. LCA's inhibitory effect was dose dependent, acted faster from the apical membrane, rapid, and not immediately reversible. LCA also prevented the Isc stimulated by the cAMP-dependent secretagogues 8-bromo-cAMP, lubiprostone, or chenodeoxycholic acid (CDCA). The LCA inhibitory effect was BA specific, since CDCA, cholic acid, or taurodeoxycholic acid did not alter FSK or carbachol action. While LCA alone had no effect on intracellular cAMP concentration ([cAMP]i), it decreased FSK-stimulated [cAMP]i by 90%. Although LCA caused a small increase in intracellular Ca(2+) concentration ([Ca(2+)]i), chelation by BAPTA-AM did not reverse LCA's effect on Isc LCA action does not appear to involve known BA receptors, farnesoid X receptor, vitamin D receptor, muscarinic acetylcholine receptor M3, or bile acid-specific transmembrane G protein-coupled receptor 5. LCA significantly increased ERK1/2 phosphorylation, which was completely abolished by the MEK inhibitor PD-98059. Surprisingly PD-98059 did not reverse LCA's effect on Isc Finally, although LCA had no effect on basal Isc, nystatin permeabilization studies showed that LCA both stimulates an apical cystic fibrosis transmembrane conductance regulator Cl(-) current and inhibits a basolateral K(+) current. In summary, 50 μM LCA greatly inhibits cAMP-stimulated Cl(-) secretion, making low doses of LCA of potential therapeutic interest for diarrheal diseases.
authors.affiliation: Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois;
authors.forename: Mei
authors.initials: M
authors.lastname: Ao
authors.affiliation: Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois;
authors.forename: Jada C
authors.initials: JC
authors.lastname: Domingue
authors.affiliation: Department of Biology, Benedictine University, Lisle, Illinois.
authors.forename: Nabihah
authors.initials: N
authors.lastname: Khan
authors.affiliation: Department of Biology, Benedictine University, Lisle, Illinois.
authors.forename: Fatima
authors.initials: F
authors.lastname: Javed
authors.affiliation: Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois;
authors.forename: Kashif
authors.initials: K
authors.lastname: Osmani
authors.affiliation: Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois; Department of Biology, Benedictine University, Lisle, Illinois.
authors.forename: Jayashree
authors.initials: J
authors.lastname: Sarathy
authors.affiliation: Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois; Department of Medicine, University of Illinois at Chicago, Chicago, Illinois; and meenarao@uic.edu.
authors.forename: Mrinalini C
authors.initials: MC
authors.lastname: Rao
mesh_terms: D000930:Antidiarrheals / Q000494:pharmacology*; D002460:Cell Line; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000187:drug effects* / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000819:agonists* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism; D007419:Intestinal Secretions / Q000187:drug effects* / Q000378:metabolism; D008095:Lithocholic Acid / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors
chemical_list: D000930:Antidiarrheals; C505032:CFTR protein, human; D002712:Chlorides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D008095:Lithocholic Acid; D000242:Cyclic AMP; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3
keywords: adenosine 3′,5′-cyclic monophosphate signaling; cystic fibrosis transmembrane conductance regulator; potassium ion conductances