We examined the involvement of cyclooxygenase (COX)-1 as well as COX-2 in the healing of gastric ulcers and investigated which prostaglandin (PG) EP receptor subtype is responsible for the healing-promoting action of PGE 2. Male SD rats and C57BL/6 mice, including wild-type, COX-1(Ϫ/Ϫ), and COX-2(Ϫ/Ϫ), were used. Gastric ulcers were produced by thermocauterization under ether anesthesia. Gastric ulcer healing was significantly delayed in both rats and mice by indomethacin and rofecoxib but not

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... C-560 given for 14 days after ulceration. The impaired healing was also observed in COX-2(Ϫ/Ϫ) but not COX-1(Ϫ/Ϫ) mice. Mucosal PGE 2 content increased after ulceration, and this response was significantly suppressed by indomethacin and rofecoxib but not SC-560. The delayed healing in mice caused by indomethacin was significantly reversed by the coadministration of 11-deoxy-PGE 1 (EP3/EP4 agonist) but not other prostanoids, including the EP 1, EP2, and EP3 agonists. By contrast, CJ-42794 (selective EP4 antagonist) significantly delayed the ulcer healing in rats and mice. VEGF expression and angiogenesis were both upregulated in the ulcerated mucosa, and these responses were suppressed by indomethacin, rofocoxib, and CJ-42794. The expression of VEGF in primary rat gastric fibroblasts was increased by PGE 2 or AE1-329 (EP 4 agonist), and these responses were both attenuated by coadministration of CJ-42794. These results confirmed the importance of COX-2/PGE 2 in the healing mechanism of gastric ulcers and further suggested that the healing-promoting action of PGE 2 is mediated by the activation of EP 4 receptors and is associated with VEGF expression. gastric ulcer; healing; prostaglandin E2; cyclooxygenase-1 and -2; selective cyclooxygenase-1 and -2 inhibitors; EP 4 antagonist; rat; cyclooxygenase-1 and -2 knockout mice