Low dose methotrexate decreases intraarticular prostaglandin and interleukin 1 levels in antigen induced arthritis in rabbits.

OBJECTIVE

To investigate the effects of methotrexate (MTX) on inflammation variables of antigen induced arthritis (AIA) in rabbits, such as protein leakage to the articular cavity, synovial fluid (SF) leukocyte count, synovial membrane polymorphonuclear (PMN) cell infiltrate, and intraarticular production of eicosanoids and interleukin 1 (IL-1). Dexamethasone and indomethacin were used for comparison.

METHODS

NZW rabbits were treated with the following drugs: MTX (0.25 mg/kg), dexamethasone (0.15 mg/kg), indomethacin (4 mg/kg), and sterile saline (control group). All drugs were given by intramuscular route before arthritis was induced and the animals were sacrificed 4 or 24 h later. Leukocyte migration, protein leakage (Evans blue method), synovium PMN cell infiltrate, and intraarticular concentration of prostaglandin E2 (PGE2), thromboxane B2 (TXB2), leukotriene B4 (LTB4) (radioimmunoassay), and IL-1 beta (ELISA) were quantified in SF.

RESULTS

Significant reduction of leukocyte migration and protein leakage was observed in the joint fluid of all treated animals. Decrease in the intensity of synovium PMN cell infiltrate also occurred with all treatments. Intraarticular PGE2, TXB2, and IL-1 beta were significantly reduced after 4 h of arthritis induction in animals treated with MTX and dexamethasone. Treatment with indomethacin reduced only PGE2 and TXB2 in SF. Treatments did not change SF IL-1 beta concentration 24 h after arthritis induction. Treatment with dexamethasone increased inflammatory variables and SF LTB4 concentration 24 h after the synovial cavity was challenged with antigen.

CONCLUSION

Our results show that MTX, like dexamethasone, reduces the intensity of leukocyte afflux, protein leakage, synovial membrane PMN cell infiltrate, as well as the intraarticular production of PGE2, TXB2, and IL-1 beta in the early phase of antigen induced arthritis in rabbits.