抄録
Nitric oxide (NO) produced by the inducible NO synthase (iNOS) in the some tissue is associated with acute and chronic inflammatory process. This study is to examine that the effect of methotrexate (MTX) on the NO production from rat peritoneal macrophages by the iNOS. Macrophages from normal rats were cultured in the presence of drug followed by activation with lipopolysaccharide (LPS) . After 24 hrs, NO-2 as a metabolite of NO was measured by Griess reaction. MTX, bucillamine (BU), and indomethacin (IM) did not influence on the NO-2 accumulation with LPS. Aminoguanidine (AG), a preferential inhibitor of iNOS, and dexamethasone (DEXA) abolished NO-2 accumulation with LPS in concentration dependent manner.
On the other hand, adjuvant-induced arthritis (AA) was induced in rats by the injection of Mycobacterium tuberculosis into the right hind foot pad. Drugs were administered daily by the oral route from day 1 to day 21. On day 22, macrophages from AA rats had an enhanced capacity to produce NO in vitro. MTX (0.1 mg/kg), DEXA (0.5 mg/kg) and IM (1 mg/kg) reduced the paw swelling and inhibited the increased NO production by macrophages. AG (100 mg/kg) only partly inhibited the increased NO production, while BU (10 mg/kg) did not influence the paw swelling and the increased NO production.
Our data revealed that oral administration of MTX to AA rats significantly inhibited ex vivo LPS-induced NO production from peritoneal macrophages in accordance with its in vivo prophylactic effect of arthritis, suggesting that NO blockade might be one of the important mode of action for MTX in animal models of arthritis.
