Lubiprostone activates CFTR, but not ClC-2, via the prostaglandin receptor (EP4)

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 EP4 receptor has been described [2; 3; 4; 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 EP4 receptor or β adrenergic receptor (βAR), for changes in conductance elicited by lubiprostone. Oocytes co-expressing CFTR and either βAR or the EP4 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 EP4 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 1µM lubiprostone. However, conductance was elevated by isoproterenol and inhibited by CFTRinh172. Co-expression of CFTR and EP4 resulted in lubiprostone-stimulated conductance, which was also sensitive to CFTRinh172. The EC50 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 EP4 receptor in oocytes.

Lubiprostone Prevents Nonsteroidal Anti-Inflammatory Drug–Induced Small Intestinal Damage by Suppressing the Expression of Inflammatory Mediators via EP4 Receptors

“…methyl]phenyl}propanoic acid, an EP3 antagonist: 10 mg/kg] , or propionylamino)phenyl)butyric acid, an EP4 antagonist: 3 mg/kg] (Hatazawa et al, 2006), and CFTR(inh)-172 (a CFTR inhibitor; 1 and 10 mg/kg) (Norimatsu et al, 2012) were administered intraperitoneally 30 minutes before the administration of lubiprostone. The doses of these EP and CFTR antagonists were chosen to induce the respective pharmacologic action, according to the findings of previous studies (Takeuchi et al, , 2011Kunikata et al, 2002a;Hatazawa et al, 2006;Aihara et al, 2007;Norimatsu et al, 2012).…”

“…The doses of these EP and CFTR antagonists were chosen to induce the respective pharmacologic action, according to the findings of previous studies (Takeuchi et al, , 2011Kunikata et al, 2002a;Hatazawa et al, 2006;Aihara et al, 2007;Norimatsu et al, 2012).…”

ClC-2 regulation of intestinal barrier function: Translation of basic science to therapeutic target

“…[111][112][113] However, a recent study has shown that CFTR ihn 172 also inhibits ClC-2 Cl ¡ currents. 114 Other laboratories have detected dual activation of CFTR and ClC-2 in a dose-dependent manner.…”

Current and Emerging Treatments for Irritable Bowel Syndrome with Constipation and Chronic Idiopathic Constipation: Focus on Prosecretory Agents

“…Pathway 1: Lubiprostone is thought to bind and directly activate the chloride (Cl − ) channel type 2 (ClC‐2) independent of protein kinase A ( PKA ) activation, resulting in increased chloride secretion that, in turn, leads to passive secretion of sodium and water and the secretion of isotonic fluid into the intestinal lumen . Pathway 2: Lubiprostone may activate the transmembrane prostanoid receptor prostanoid receptor subtype 4 ( EP 4), which has a downstream effect on the cystic fibrosis transmembrane conductance regulator ( CFTR ) chloride channel through a PKA ‐dependent mechanism . EP 4 receptor activation results in elevation of cyclic adenosine monophosphate ( cAMP ) and activation of PKA .…”