Rescue of interleukin‐1 activity by leucovorin following inhibition by methotrexate in a murine in vitro system

Abstract
We have recently shown that methotrexate (MTX) inhibits interleukin-1 (IL-1) activity in vitro. This effect may play an important role in the rapid antiinflammatory action of MTX in rheumatoid arthritis. In the present study, we showed that the inhibition of IL-1 activity in vitro by MTX is dependent on folate pathways since, after the addition of leucovorin, the inhibitory effect of MTX was abolished. These findings may shed more light on the mechanism of action of MTX in rheumatoid arthritis. They also point to the fact that some IL-1 activities may be dependent on intracellular folate pathways.