Therapeutic effect of farnesylthiosalicylic acid on adjuvant-induced arthritis through suppressed release of inflammatory cytokines.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by pronounced inflammation and leucocyte infiltration in affected joints. Despite significant therapeutic advances, a new targeted approach is needed. Our objective in this work was to investigate the anti-inflammatory effects of the Ras inhibitor farnesylthiosalicylic acid (FTS) on adjuvant-induced arthritis (AIA) in rats, an experimental model for RA. Following AIA induction in Lewis rats by intradermal injection of heat-killed Mycobacterium tuberculosis, rats were treated with either FTS or dexamethasone and assessed daily for paw swelling. Joints were imaged by magnetic resonance imaging and computerized tomography and analysed histologically. The anti-inflammatory effect of FTS was assessed by serum assay of multiple cytokines. After adjuvant injection rats demonstrated paw swelling, leucocyte infiltration, cytokine secretion and activation of Ras-effector pathways. Upon FTS treatment these changes reverted almost to normal. Histopathological analysis revealed that the synovial hyperplasia and leucocyte infiltration observed in the arthritic rats were alleviated by FTS. Periarticular bony erosions were averted. Efficacy of FTS treatment was also demonstrated by inhibition of CD4(+) and CD8(+) T cell proliferation and of interferon (IFN)-γ, tumour necrosis factor (TNF)-α, interleukin (IL)-6 and IL-17 release. The Ras effectors PI3K, protein kinase B (AKT), p38, and extracellular-regulated kinase (ERK) were significantly attenuated and forkhead box protein 3 (FoxP3) transcription factor, a marker of regulatory T cells, was significantly increased. Thus, FTS possesses significant anti-inflammatory and anti-arthritic properties and accordingly shows promise as a potential therapeutic agent for RA. Its effects are apparently mediated, at least in part, by a decrease in proinflammatory cytokines.