Amelioration of rat antigen-induced arthritis by liposomally conjugated methotrexate is accompanied by down-regulation of cytokine mRNA expression

Objectives. We examined the temporal changes in the expression of interleukin 1 beta (IL-1 beta). tumour necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) in the rat antigen-induced arthritis (AIA) model and investigated how their expression was modulated following disease amelioration by liposomally conjugated methotrexate (G-MLV). Methods. On the day of arthritis induction (day 0), rats were treated with a single intraarticular injection of G-MLV, methotrexate (MTX). a dose of lipid equivalent to G-MLV (E-LIPO) or saline. On days 3 and 7 after disease induction, animals from each experimental group were killed. Joint tissue was examined histologically and for mRNA expression (IL-6, IL-1 beta and TNF-alpha) using semiquantitative reverse transcription-polymerase chain reaction. Results. There was no significant difference (ANOVA) in knee swelling between MTX-, E-MLV- or saline-treated animals from day 0 to day 7. By day 1, G-MLV significantly reduced knee swelling (1.94 +/- 0.12 mm; P < 0.0001) compared with rats treated with MTX (3.17 +/- 0.18 mm). G-MLV treatment also significantly inhibited the histological progression of AIA. This reduction in disease severity was accompanied by a reduction in IL-1 beta mRNA expression in synovial tissue extracts on day 3 and IL-6 mRNA expression on both day 3 and day 7. Conclusions. Liposomally conjugated MTX may exert its beneficial effects in experimental arthritis through IL-1 beta and IL-6 inhibition.