Effects of non-steroidal anti-inflammatory drugs on prostaglandin h synthase isoenzyme 2 (cyclo-oxygenase 2) production by porcine gastric mucosa in organ culture

Considerable interest has been shown recently in the relative roles of the prostaglandin H synthase (PGHS) isoenzymes in the control of inflammation and the development of side-effects, especially those in the gastrointestinal (GI) tract, by non-steroidal anti-inflammatory drugs (NSAIDs). To examine the role of the PGHS isoenzymes in the development of prostaglandin-dependent gastric mucosal injury induced by NSAIDs, the distribution of immuno-reactive PGHS isoforms was first established in pig tissue and compared with that in human gastric mucosa of patients undergoing GI investigation. To establish the effects of NSAIDs on the predominant isoform, PGHS-2, and relate this to prostaglandin production, an organ culture system was developed using porcine gastric (fundic) mucosa. This system was used to establish whether the NSAIDs, aspirin and indomethacin, inhibit the expression of this enzyme in the presence or absence of interleukin-1 (IL-1), an inducer of PGHS-2.In fresh expiants as well as in organ culture, no PGHS-1 was evident but pronounced immuno-reactivity for PGHS-2 was observed in the endothelial cells of blood most blood vessels, the inner circular muscle layer, submucosa and muscularis mucosa, with some weak reaction in mucous cells of the fundus and antrum of both humans and pigs.Organ culture of pig fundic mucosa was accomplished successfully in Dulbeco’s Modified Eagles Medium (DMEM) with 5% fetal calf serum added with viability (assessed microscopically) evident for up to 10 days; the morphology of the mucosal cells in cultured mucosa was generally comparable with that in fresh expiants. Tissues treated with aspirin (0.1-2.0 mmol/L) for 1 day showed virtually no PGHS-2 immunoreactivity in the submucosa, muscularis mucosae and endothelial vessels of capillaries compared with controls concomitant with almost total inhibition of prostaglandin E2 (PGE2) production into the culture medium. Indomethacin (100 or 10 μmol/L) failed to alter the intensity of the COX-2 immunoreactivity compared with controls but inhibited PGE2 production into the culture medium.These results show that (a) there is selective distribution of PGHS-2 in the gastric mucosa of pigs and humans, (b) pig fundic mucosa can be successfully maintained in organ culture and employed to study effects of NSAIDs on expression of PGHS-2 isoenzyme, and (c) NSAIDs may vary in their effects on production of PGHS-2 compared with their effects on PGE2 production.