Because osteoclasts erode bone in RA joints, we next examined the formation of pits in osteologic disks, an indication of the ability of osteoclasts to resorb bone
Because osteoclasts erode bone in RA joints, we next examined the formation of pits in osteologic disks, an indication of the ability of osteoclasts to resorb bone. M GW2580 or imatinib. After 48 ELX-02 sulfate hours, FLS cultures were pulsed with [3H] thymidine for 18 hours. Values are expressed relative to PDGF-bb treatment. Data shown in a-d are representative of at least 2 independent experiments. ar2940-S1.PDF (218K) GUID:?3938C435-B9F4-4D65-A82A-C949C78A9DB4 Additional file 2 GW2580 does not modulate T-cell function em in vivo /em . Splenocytes were harvested from DBA/1 ELX-02 sulfate mice with CIA and treated with GW2580, imatinib, or vehicle, and stimulated with 20 g/ml heat-denatured, whole CII. [3H]thymidine incorporation was used to measure proliferation of CII-specific T cells. IFN, TNF and IL-10 were measured in culture supernatants by ELISA. Values are the mean SEM. * em P /em 0.05 compared with stimulated cells from vehicle-treated CIA mice. Results are representative of 2 independent experiments. ar2940-S2.PDF (53K) GUID:?888EF077-62E5-4AB2-B667-C067CECFFBA1 Abstract Introduction Tyrosine kinases are key mediators of multiple signaling pathways implicated in rheumatoid arthritis (RA). We previously demonstrated that imatinib mesylate–a Food and Drug Administration (FDA)-approved, antineoplastic drug that potently inhibits the ELX-02 sulfate tyrosine kinases Abl, c-Kit, platelet-derived growth factor receptor (PDGFR), and c-Fms–ameliorates murine autoimmune arthritis. However, which of the imatinib-targeted kinases is the principal culprit in disease pathogenesis remains unknown. Here we examine the role of c-Fms in autoimmune arthritis. Methods We tested the therapeutic efficacy of orally administered imatinib or GW2580, a small molecule that specifically inhibits c-Fms, in three mouse models of RA: collagen-induced arthritis (CIA), anti-collagen antibody-induced arthritis (CAIA), and K/BxN serum transfer-induced arthritis (K/BxN). Efficacy was evaluated by visual scoring of arthritis severity, paw thickness measurements, and histological analysis. We assessed the em in vivo /em effects of imatinib and GW2580 on macrophage infiltration of synovial joints in CIA, and their em in vitro /em effects on macrophage and osteoclast differentiation, and on osteoclast-mediated bone resorption. Further, we determined the effects of imatinib and GW2580 on the ability of macrophage colony-stimulating factor (M-CSF; the ligand for c-Fms) to prime bone marrow-derived macrophages to produce tumor necrosis factor (TNF) upon subsequent Fc receptor ligation. Finally, we measured M-CSF levels in synovial fluid from patients with RA, osteoarthritis (OA), or psoriatic arthritis (PsA), and levels of total and phosphorylated c-Fms in synovial tissue from patients with RA. Results GW2580 was as efficacious as imatinib in reducing arthritis PLAT severity in CIA, CAIA, and K/BxN models of RA. Specific inhibition of c-Fms abrogated (i) infiltration of macrophages into synovial joints of arthritic mice; (ii) differentiation of monocytes into macrophages and osteoclasts; (iii) osteoclast-mediated bone resorption; and (iv) priming of macrophages to produce TNF upon Fc receptor stimulation, an important trigger of synovitis in RA. Expression and activation of c-Fms in RA synovium were high, and levels of M-CSF were higher in RA synovial fluid than in OA or PsA synovial fluid. Conclusions These ELX-02 sulfate results suggest that c-Fms plays a central role in the pathogenesis of RA by mediating the differentiation and priming of monocyte lineage cells. Therapeutic targeting of c-Fms could provide benefit in RA. Introduction Rheumatoid arthritis (RA) is an autoimmune synovitis that affects 0.6% of the world population [1]. RA is characterized by inflammation and pannus formation in the synovial joints and by periarticular erosions, biomechanical dysfunction, and early mortality. Although the advent of biological therapeutics has revolutionized the treatment of RA, a significant number of patients with RA do not respond well to therapy. The current generation of biologic agents either blocks a critical cytokine, such as tumor necrosis factor (TNF) [2], or targets cells of the adaptive immune system, such as B [3] and T [4] cells. However, non-antigen-specific cellular responses may also contribute to the pathogenesis of RA [1]. While adaptive autoimmune responses directed against synovial joint antigens are likely involved in the early stages of RA, widespread dysregulation of non-antigen-specific cellular responses–including aggressive growth of fibroblast-like synoviocytes (FLSs), proinflammatory cytokine production by macrophages, and activation of osteoclasts–likely underlies the chronic inflammatory stage of RA. Elucidation of the cellular responses that are central to the pathogenesis of RA could lead to the development of novel targeted therapies. Imatinib mesylate (imatinib) is a tyrosine kinase inhibitor approved for the ELX-02 sulfate treatment of Bcr-Abl-expressing chronic myelogenous leukemias and c-Kit-expressing gastrointestinal stromal tumors [5,6]. Recent case reports describe the alleviation of RA symptoms in RA patients receiving imatinib for the treatment of these cancers [7-9], suggesting that tyrosine kinases are important in the pathogenesis of RA..