POSSIBLE PARTICIPATION OF CYCLOOXYGENASE-2 IN THE RECURRENCE OF ALLERGIC INFLAMMATION IN RATS

In the recurrence of allergic inflammation in a rat air pouch model, p ouch fluid volume, prostaglandin E(2) concentration in the pouch fluid , leukocyte infiltration into the pouch fluid, and granulation tissue weight were markedly increased by the antigen challenge. To clarify th e role of cyclooxygenase-2 in the recurrence of allergic inflammation, the time-course of changes in protein levels of cyclooxygenase-1 and cyclooxygenase-2 in the granulation tissue and in the infiltrated leuk ocytes was examined by Western blot analysis. It was shown that cycloo xygenase-1 levels in the granulation tissue and in the infiltrated leu kocytes were not changed by the antigen challenge, but cycoloxygenase- 2 levels were increased. Furthermore, treatment with the selective cyc looxygenase-2 inhibitor, NS-398 (cyclohexyloxy-4-nitrophenyl]-methanes ulfonamide), suppressed the recurrence of allergic inflammation as did the non-selective cyclooxygenase-1/cyclooxygenase-2 inhibitor, indome thacin. The steroidal anti-inflammatory drug, dexamethasone, inhibited the induction of cyclooxygenase-2, and suppressed the allergic inflam mation. These findings strongly suggested that cyclooxygenase-2 induce d by the antigen challenge plays a role in the recurrence of inflammat ion induced by the allergic mechanism.