Inhibition of antigen-induced arthritis in guinea pigs by a selective LTB4 receptor antagonist LY293111Na

Objective and design: To investigate the role of leukotriene B-4 (LTB4) and prostaglandin E-2 (PGE(2)) in the development and progression of antigen-induced arthritis (AIA) in guinea pigs and rats. Methods: Arthritis was induced by injecting cationic amidated bovine serum albumin (aBSA) into the knee joint of immunized guinea pigs or rats. The effect of a potent and selective LTB4 receptor antagonist, LY293111Na (2-[2-propyl-3 -[3-[2-ethyl-4-(4-fluorophenyl)-5-hydroxyphenoxy]-propoxy]-phenoxy]benzoic acid sodium salt) was compared with those of indomethacin and dexamethasone. The effect of LY293111Na on adjuvant arthritis in rats was also examined. Results: LY293111Na (5 to 50 mg/kg b. i. d.) significantly inhibited knee joint swelling and histopathological changes of AIA in guinea pigs, but not in rats. Especially its protective effect against bone and cartilage destruction was substantial. In contrast, the cyclooxygenase inhibitor indomethacin significantly inhibited AIA in rats, but slightly inhibited in guinea pigs, while dexamethasone markedly inhibited AIA in both guinea pigs and rats. Increases of LTB4 and myeloperoxidase (MPO) activity were observed in the knee joint tissue of AIA guinea pigs, and LY293111Na dose-dependently inhibited the increase of MPO activity Moreover, in adjuvant arthritic rats, LY293111Na showed slight inhibitory effect, while indomethacin showed marked inhibition. Conclusions: LTB4 but not PGE(2) appeared to play important roles as an effective mediator in joint, particularly in cartilage and bone destruction of AIA in guinea pigs probably by inducing polymorphonuclear leukocytes (PMNs) chemotaxis to the joint tissue. In contrast, PGE(2) but not LTB4 is an important mediator of arthritis in rats.