title: Lubiprostone activates CFTR, but not ClC-2, via the prostaglandin receptor (EP(4)).
abstract: The goal of this study was to determine the mechanism of lubiprostone activation of epithelial chloride transport. Lubiprostone is a bicyclic fatty acid approved for the treatment of constipation [1]. There is uncertainty, however, as to how lubiprostone increases epithelial chloride transport. Direct stimulation of ClC-2 and CFTR chloride channels as well as stimulation of these channels via the EP(4) receptor has been described [2-5]. To better define this mechanism, two-electrode voltage clamp was used to assay Xenopus oocytes expressing ClC-2, with or without co-expression of the EP(4) receptor or β adrenergic receptor (βAR), for changes in conductance elicited by lubiprostone. Oocytes co-expressing CFTR and either βAR or the EP(4) receptor were also studied. In oocytes co-expressing ClC-2 and βAR conductance was stimulated by hyperpolarization and acidic pH (pH = 6), but there was no response to the β adrenergic agonist, isoproterenol. Oocytes expressing ClC-2 only or co-expressing ClC-2 and EP(4) did not respond to the presence of 0.1, 1, or 10 μM lubiprostone in the superperfusate. Oocytes co-expressing CFTR and βAR did not respond to hyperpolarization, acidic pH, or 1 μM lubiprostone. However, conductance was elevated by isoproterenol and inhibited by CFTR(inh)172. Co-expression of CFTR and EP(4) resulted in lubiprostone-stimulated conductance, which was also sensitive to CFTR(inh)172. The EC(50) for lubiprostone mediated CFTR activation was ~10 nM. These results demonstrate no direct action of lubiprostone on either ClC-2 or CFTR channels expressed in oocytes. However, the results confirm that CFTR can be activated by lubiprostone via the EP(4) receptor in oocytes.
authors.affiliation: Department of Physiology - Pharmacology, Oregon Health and Science University, OR 97239, USA.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Norimatsu
authors.forename: Aurelia R
authors.initials: AR
authors.lastname: Moran
authors.forename: Kelvin D
authors.initials: KD
authors.lastname: MacDonald
mesh_terms: D000527:Alprostadil / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000819:agonists*; D005260:Female; D000068238:Lubiprostone; D009865:Oocytes; D011943:Receptors, Adrenergic, beta / Q000378:metabolism; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D011943:Receptors, Adrenergic, beta; D058309:Receptors, Prostaglandin E, EP4 Subtype; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000068238:Lubiprostone; D000527:Alprostadil