Cytokine manipulation by methotrexate treatment in murine experimental systemic lupus erythematosus

We reported beneficial effects of methotrexate (MTX) treatment on clinical variables in the murine model of experimental systemic lupus erythematosus (SLE). We now follow the kinetics of several cytokines that are involved in experimental SLE, to find out whether MTX treatment has an effect on cytokine production.

SLE was induced in naive BALB/c female mice by injection of the human monoclonal anti-DNA antibody bearing the common idiotype, 16/6 Id. Six weeks after booster injection, when high levels of autoantibodies were observed, MTX treatment was started (2 mg/kg once a week) for 7 months. Cytokine production by macrophages or splenocytes from these mice was determined monthly by either ELISA or bioassays.

A significant increase in the production of tumor necrosis factor-alpha was determined as early as 2 weeks after injection. Interleukin 1 (IL-1) production increased gradually, starting one month after disease induction. These proinflammatory cytokines reached very high levels that were maintained through disease course. MTX treatment reduced production of these cytokines to normal levels throughout the experimental period. Increased levels of IL-2 and interferon-gamma (IFN-gamma), the Th1 type cytokines, were detected 2-4 months after disease induction. The secretion of the latter then dropped to levels lower than those observed in control mice. Treatment with MTX reversed levels of the cytokines to levels observed in healthy mice, IL-4 and IL-10, the Th2 type cytokines, predominated later in disease course, 5 months after immunization. Two to 3 months later production of IL-4 dropped to levels lower than those of control mice. IL-10 secretion remained higher than in controls throughout the experiment. The production of both IL-4 and IL-10 in MTX treated mice was also similar to that of control mice.

The restoration of the cytokine profile to normal levels observed in the MTX treated mice from the initial steps of disease induction suggests its beneficial effects in SLE might be mediated through modulation of cytokine production.