Introduction Gastric ulceration is a limiting complication of therapy with cyclooxygenase (COX) antagonists, widely used anti-inflammatory/analgesic drugs in both humans and dogs. COX-derived prostaglandin E (PGE) has an important role in gastric defense and cytoprotection via promotion of blood flow and mucus secretion and inhibition of gastric acid secretion. Given the importance of gastric epithelial cell migration in reestablishing epithelial integrity following gastric damage, we have investigated whether paracrine PGE signalling has a role in the modulation of gastric epithelial cell migration.
Methods In order to retain paracrine signalling between different cell types, we isolated intact gastric glands via collagenase digestion of canine gastric mucosal tissue. Isolated glands spread in vitro to form islands of cells. The rate of gland spreading over 48h was measured as a surrogate for cell migration speed. Lamellipodia protrusion was analysed as an index of spreading activity. A value for lamellopodia area was calculated by measuring spread area minus area bounded by nuclei of cells at the edge of spread glands. Spread glands, when serum-starved, exhibit a reduction in area. We added both a selective and a non-selective COX antagonist and PGE2 to serum-starved glands to assess their effects on migration. All treatments were added blindly to eliminate bias. Statistical significance was assessed using univariate analysis of variance. Expression of COX-2 and PGE receptors (EP-3 and EP-4) was assessed by RT-PCR and immunohistochemistry.
Results RT-PCR confirmed COX-2, EP-3 and EP-4 expression in our samples. COX-2 immunoreactivity was present in the majority of gland cells. The COX 1/2 antagonist indomethacin (50 μM) decreased spreading (0.85-fold, p<0.05, n=5–9 for all experiments) and lamellipodia area (0.3-fold, p<0.05). The COX-2 selective antagonist NS-398 (10μM) caused similar decreases to indomethacin (0.8-fold and 0.65-fold respectively, p<0.05). PGE (1μM) prevented a 0.7-fold reduction in island area elicited by incubation in serum free medium (p<0.05).
Conclusion This data shows a role for COX-2 derived PGE in the promotion of gastric cell migration and cellular lamellipodia formation. A reduction of mucosal PGE via COX-2 antagonism may therefore inhibit gastric epithelial cell migration contributing to COX-antagonist elicited gastric ulceration in both humans and dogs.
Competing interests None declared.
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