Tyrosine kinases play a central role in the activation of signal transduction pathways and cellular responses that mediate the pathogenesis of rheumatoid arthritis. Imatinib mesylate (imatinib) is a tyrosine kinase inhibitor developed to treat Bcr/Abl-expressing leukemias and subsequently found to treat c-Kit-expressing gastrointestinal stromal tumors. We demonstrate that imatinib potently prevents and treats murine collageninduced arthritis (CIA). We further show that micromolar concentrations of imatinib abrogate multiple signal transduction pathways implicated in RA pathogenesis, including mast cell c-Kit signaling and TNF-α release, macrophage c-Fms activation and cytokine production, and fibroblast PDGFR signaling and proliferation. In our studies, imatinib attenuated PDGFR signaling in fibroblast-like synoviocytes (FLSs) and TNF-α production in synovial fluid mononuclear cells (SFMCs) derived from human RA patients. Imatinib-mediated inhibition of a spectrum of signal transduction pathways and the downstream pathogenic cellular responses may provide a powerful approach to treat RA and other inflammatory diseases.
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