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 Ϫ 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 M, 15 min) drastically (Ͼ90%) 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 I sc stimulated by the cAMP-dependent secretagogues 8-bromocAMP, 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 2ϩ concentration ([Ca 2ϩ ]i), chelation by BAPTA-AM did not reverse LCA's effect on I sc. 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 I sc. Finally, although LCA had no effect on basal I sc, nystatin permeabilization studies showed that LCA both stimulates an apical cystic fibrosis transmembrane conductance regulator Cl Ϫ current and inhibits a basolateral K ϩ current. In summary, 50 M LCA greatly inhibits cAMP-stimulated Cl Ϫ secretion, making low doses of LCA of potential therapeutic interest for diarrheal diseases.

The Yin and Yang of bile acid action on tight junctions in a model colonic epithelium

“…We and others have shown that LCA does not activate Cl − secretion, but attenuates the prosecretory effects of cAMP‐dependent agents in T84 cells (Ao et al. ).…”

“…We have reported that these cells were female as determined by RT‐PCR amplification of the amelogenin gene (Ao et al. ). Cells, between passages 39 and 50, were incubated in a humidified atmosphere of 5% CO 2 at 37°C and grown in Transwells until transepithelial resistance (TER) reached 1000 Ω cm 2 (generally 2–3 weeks).…”

“…), whereas LCA is antisecretory at the concentrations (0.005–0.05 mmol/L) found in the colon (Ao et al. ). Of the two prosecretory bile acids, CDCA is more potent and present in larger amounts in normal physiology (Dawson ).…”

“…In short‐term (≈30 min) Ussing chamber studies, neither CDCA nor LCA altered TER (Ao et al. ). However, Kelly et al.…”

The Effect of Deoxycholic Acid on Secretion and Motility in the Rat and Guinea Pig Large Intestine

“…16 This discrepancy may be due to differences in agonist action on GpBAR1. Ursodeoxycholic acid and lithocholic acid attenuate colonic epithelial secretory function 22,23 In contrast, DCA activates ion channels in colonocytes and acts on non-epithelial cells to activate chloride secretion indirectly. 17 Furthermore, pretreatment with TTX changed the secretory responses to DCA, confirming that the nervous system is associated with secretion induced by DCA.…”