Antiinflammatory and immunoregulatory action of methotrexate in the treatment of rheumatoid arthritis: Evidence of increased interleukin‐4 and interleukin‐10 gene expression demonstrated in vitro by competitive reverse transcriptase‐polymerase chain reaction

Abstract

Objective To look for in vitro modulation of the main immunoregulatory and antiinflammatory cytokines by methotrexate (MTX) during the course of rheumatoid arthritis (RA). Methods We quantified interleukin-2 (IL-2), IL-4, IL-10, and interferon-γ (IFNγ) gene expression by peripheral blood mononuclear cells ex vivo under basal conditions and in vitro after stimulation with phytohemagglutinin (PHA) or PHA plus MTX, by competitive reverse transcriptase-polymerase chain reaction (RT-PCR), in 12 patients with untreated active RA (group 1), 10 patients with MTX-treated disease in partial remission (group 2), and 11 healthy control subjects. Simultaneously, under the same experimental conditions, we quantified cytokine production by specific enzymelinked immunosorbent assays (ELISAs). Results Under basal conditions, we found no differences in IL-2, IL-10, and IFNγ gene expression in the 3 groups, while IL-4 gene expression was significantly decreased in RA patient group 1 compared with the control group. In vitro, under the action of MTX, IL-10 gene expression was significantly increased in the 3 groups, IL-4 gene expression was significantly increased in RA group 1 and in the control group, and IL-2 and IFNγ gene expression was significantly decreased in RA group 1. Cytokine gene expression assessed by RT-PCR and cytokine production assessed by specific ELISAs were highly correlated. Conclusion In vitro modulation of the cytokine network by MTX, increasing Th2 cytokines and decreasing Th1 cytokines, could explain its antiinflammatory and immunoregulatory actions in vivo during the treatment of RA.