Expression of proteinase-activated receptor 2 on human primary gastrointestinal myofibroblasts and stimulation of prostaglandin synthesis

It is known that subepithelial myofibroblast-derived prostaglandin (PG)E-2 can regulate intestinal epithelial cell functions, and that proteinase-activated receptor-2 (PAR(2)) is abundantly expressed in the gastrointestinal tract. Since PAR(2) activation has previously been associated with stimulation of PGE(2) synthesis, we hypothesized that PAR(2) expressed on primary human gastrointestinal myofibroblasts regulates PGE(2) synthesis via cyclooxygenase (COX)-1 and (or) COX-2, and associated PGE synthases. Primary human myofibroblasts were isolated from the resection tissue of the esophagus, small intestine, and colon. Expression of functional PAR(2) was determined by RT-PCR and by calcium mobilization in Fura-2/AM-loaded cells. Trypsin and the selective PAR(2)-activating peptide (PAR(2)-AP) SLIGRL-NH2 stimulated PGE(2) synthesis in a concentration-dependent manner, as measured by enzyme immunoassay. Selective COX inhibition showed PAR(2)-induced PGE(2) synthesis to be COX-1 dependent in esophageal myofibroblasts and both COX-1 and COX-2 dependent in colonic cells, consistent with the distribution of COX-1 and COX-2 expression. Although both cytosolic and microsomal PGE synthases were expressed in cells from all tissues, microsomal PGE synthases were expressed at highest levels in the colonic myofibroblasts. Activation of PAR(2) on gastrointestinal myofibroblasts stimulates PGE(2) synthesis via different pathways in the colon than in the esophagus and small intestine.