Methotrexate inhibits LPS-induced tumor necrosis factor production in vivo

We investigated the effects of methotrexate (MTX) on the production of tumo r necrosis factor (TNF), nitric oxide (NO) and interleukin-10 (IL-10) in vi vo. Administration of low doses of MTX (450 mu g/kg once a week for 4 weeks ) in Balb/c mice resulted in a significant inhibition of the systemic relea se of TNF and NO upon LPS challenge, whereas the production of IL-10 remain ed unchanged. These anti-inflammatory effects of MTX were exerted at the ma crophage level since peritoneal macrophages from mice, injected for 4 weeks with MTX produced lower levels of TNF than cells from control mice upon LP S stimulation ex vivo. In parallel, nle found that MTX-treated mice mere le ss susceptible to a lethal challenge with LPS and D-galactosamine. MTX did not inhibit TNF release after injection of Concanavalin A (ConA) or anti-CD 3 monoclonal antibody (mAb), indicating that MTX does not inhibit TNF produ ction at the T cell level. We conclude that repeated administration of a lo w dose of MTX in mice is associated with a decreased production of TNF by m acrophages upon LPS activation.