Prostaglandin E₂Derived from Cyclooxygenases 1 and 2 Mediates Intestinal Epithelial Ion Transport Stimulated by the Activation of Protease-Activated Receptor 2

Abstract

Proteinase-activated receptor (PAR) 2 is activated by trypsinlike serine proteinases and has been implicated in intestinal inflammation. However, its role in the regulation of intestinal mucosal function remains unclear. Using the intestinal epithelial cell line, SCBN, we have studied the stimulus-secretion coupling mechanisms of PAR 2 -induced epithelial chloride transport, focusing on cyclooxygenase (COX)-1 and COX-2 activities and prostaglandin (PG) E 2 secretion. SCBN monolayers were grown on Snapwell supports, mounted in modified Ussing chambers, and exposed to the activating peptide, SLIGRL-NH 2 (50 M), to activate PAR 2 . Pretreatment with inhibitors of cytosolic PLA 2 (cPLA 2 ) (AACOCF3, arachidonyltrifluoromethyl ketone), COX-1 [SC560, 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1H-pyrazole], and COX-2 (celecoxib) resulted in a significant concentration-dependent attenuation of PAR 2 -induced changes in short-circuit current. Immunoblot analysis showed a PAR 2 -induced increase in cPLA 2 phosphorylation that was blocked by the mitogen-activated protein kinase kinase inhibitor, PD98059 [2-(2-amino-3methoxyphenyl)-4H-1benzopyran-4-one, C 16 H 13 NO 3 ], and the pan-protein kinase C inhibitor, GFX (bisindolylmaleimide). PAR 2 stimulation also resulted in a large increase in the production of PGE 2 as determined by enzyme-linked immunosorbent assay and was also blocked by PD98059 and GFX. Immunofluorescence and immunoblot analysis determined that EP2 and EP4 are expressed at the basolateral membrane of SCBN cells. Through the use of selective inhibitors (EP2, AH6809 [6-isopropoxy-9-oxoxanthene-2-carboxylic acid]; EP4, GW627368X [N-{2[4,9-diethoxy-1-oxo-1,3-dihydro-2H-benzo[f]isoindol-2-yl)phenyl] acetyl}benzene sulphonamide]), it was found that both EP2 and EP4 were involved in mediating the PAR 2 -induced chloride secretory response. We conclude that basolateral PAR 2 activation induces epithelial chloride secretion that is mediated by cPLA 2 , COX-1, COX-2, and the subsequent release of PGE 2 . The production of PGE 2 results in an autocrine secretory response that is dependent on basolateral EP2 and EP4 receptors.

Tamoxifen and Its Metabolites Cause Acute Vasorelaxation of Aortic Rings by Inducing Vasodilator Prostanoid Synthesis

“…21 Therefore, we evaluated the effects of AH6809, an antagonist of DP 1 , EP 1 , and EP 2 receptors. [22][23][24] Interestingly, we found that the responses to Tam or its metabolites in the presence of AH6809 were very similar to those found in the presence of the COX inhibitor indomethacin. Taken together, these results provide strong evidence supporting the idea that Tam and its metabolites induce vasorelaxation by promoting the synthesis of vasodilator prostanoids.…”

Ion channels in inflammation

“…More recently, experiments in an intestinal epithelial cell line mounted in Ussing chambers revealed that basolateral protease-activated receptor-2 (PAR-2) activation induces CFTR-mediated chloride secretion by PGE 2 confirming the general applicability of this mechanism, which has previously been noted to be the likely explanation for PGE 2 -and PGF 1 -mediated stimulation of chloride secretion by PAR-2 activation [152].…”

Soluble dipeptidyl peptidase-4 induces microvascular endothelial dysfunction through proteinase-activated receptor-2 and thromboxane A2 release

“…The activation of PAR2 has further been associated with a rapid cellular release of a series of agonists triggering the immediate autocrine or paracrine transactivation of other non-PAR G protein-coupled receptors, including prostanoid receptors [23]. Further supporting a PAR2-dependent release of prostanoids, a few reports have linked PAR2 activation with enhanced COX2 activity and expression not only in endothelial cells but also in other cell types, including mesangial or mast cells [27][28][29]. TXA 2 is a powerful vasoconstrictor and aggregating factor with proinflammatory properties in the cardiovascular system, whose overproduction is associated with disturbed vascular function in different conditions including aging and diabetes [13,15].…”