EP4 receptors mediate prostaglandin E2, tumour necrosis factor alpha and interleukin 1beta-induced ion secretion in human and mouse colon mucosa.

Prostaglandin E(2) (PGE(2)) is an inflammatory mediator implicated in several gastrointestinal pathologies that cause diarrhoea. The aim of this study was to establish the contributions of the four different EP receptors (EP(1-4)) to PGE(2)-induced anion secretion in human and mouse colon mucosa. Electrogenic anion secretion (short-circuit current; I(sc)) was measured across colonic mucosae or T84 monolayers placed in Ussing chambers in response to EP receptor agonists and antagonists. PGE(2) and PGE(1)-alcohol increased I(sc) in human colon mucosa, T84 epithelia and mouse colon mucosa, and these responses were inhibited by the EP(4) receptor antagonist, GW627368X alone. In addition, the EP(2) agonist, butaprost increased I(sc) in all three preparations and these responses were inhibited by the non-selective EP(1,2,3) receptor antagonist, AH6809 but not by GW627368X. Conversely, responses mediated by EP(1) and EP(3) receptors were not observed in human colon or T84 monolayers. However, in mouse colon mucosa the EP(3)-preferring agonist, sulprostone reduced I(sc), indicative of G(iα)-signalling. Taken together these results indicate that PGE(2)-induced ion secretion is mediated predominantly by G(s)-coupled EP(4) receptors and also by EP(2) receptors in human mucosa. Furthermore, tumour necrosis factor alpha (TNFα) and interleukin 1beta (IL1ß) increased I(sc) and these responses were also inhibited by the EP(4) receptor antagonist in human colon mucosa. This study establishes the EP receptor pharmacology present in human epithelial preparations, and suggests that EP(4) receptors may be a therapeutic target for the treatment of secretory diarrhoea where PGE(2) is implicated in the aetiology.