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OBJECTIVE: To investigate the immune-modulated effects of decoy receptor 3 (DCR3) in an experimental model of rheumatoid arthritis (RA). METHODS: We delivered DCR3 plasmid into collagen-induced arthritis (CIA) mice using the hydrodynamic method and evaluated the serum level of DCR3 protein by ELISA. After immunization, we assessed disease severity of arthritis incidence, arthritis scores, paw thickness, and means of arthritic limbs, and used hematoxylin and eosin staining to observe synovial hyperplasia. We analyzed numbers of murine splenocytes and inguinal lymphocyte cells, cell populations, and serum proinflammatory cytokines by flow cytometry. We investigated B cell proliferation by carboxyfluorescein succinimidyl ester assay. We evaluated serum levels of total IgG2a and type II collagen-specific IgG and IgG2a using ELISA. RESULTS: DCR3 expression in sera significantly attenuated disease severity in CIA mice. We found that DCR3 inhibited the volume of inguinal lymph nodes, numbers of CD19+ B cells, and populations of interferon-γ, interleukin 4 (IL-4), IL-17A, and Foxp3-producing CD4+ T cell in vivo. We found that DCR3 inhibited Pam3CSK4 (Toll-like receptor 1/2 ligand)-induced B220+ B cell proliferation in vitro. DCR3 treatment reduced the serum level of IL-6, total IgG2a, and CII-specific IgG2a antibody. CONCLUSION: We postulated that the protective effects of DCR3 in CIA resulted from modulation of the immune system by maintaining the B/T cell balance and decreasing lymphocyte expansion. We suggest DCR3 as a prophylactic and potential therapeutic agent in the treatment of RA.

OBJECTIVE: Plectranthus amboinicus has been known to treat inflammatory diseases or swelling symptoms. We investigated whether P. amboinicus exhibited an inhibitory effect on osteoclastogenesis in vitro and inflammatory bone erosion in collagen-induced arthritis (CIA) mice, an animal model of rheumatoid arthritis. We attempted to identify the active component of P. amboinicus involved in regulation of osteoclastogenesis. METHODS: We treated M-CSF- and RANKL-stimulated murine bone marrow-derived macrophages (BMM) and RANKL-induced RAW264.7 cells with different concentrations of P. amboinicus or rosmarinic acid, a phytopolyphenol purified from P. amboinicus, to monitor osteoclast formation by TRAP staining. The mechanism of the inhibition was studied by biochemical analysis such as RT-PCR and immunoblotting. CIA mice were administered gavages of P. amboinicus (375 mg/kg) or placebo. Then clinical, histological, and biochemical measures were assessed to determine the effects of P. amboinicus on synovial inflammation and bone erosion by H&E staining of the inflamed joints and ELISA. RESULTS: Rosmarinic acid strongly inhibited RANKL-induced NF-κB activation and nuclear factor of activated T cells c1 (NFATc1) nuclear translocation in BMM, and also inhibited RANKL-induced formation of TRAP-positive multinucleated cells. A pit formation assay and the CIA animal model showed that P. amboinicus significantly inhibited the bone-resorbing activity of mature osteoclasts. CONCLUSION: We postulated that rosmarinic acid conferred the inhibitory activity on P. amboinicus for inhibition of osteoclastogenesis via downregulation of RANKL-induced NFATc1 expression. Our results indicated the possibility of P. amboinicus as a new remedy against inflammatory bone destruction.

OBJECTIVE: Imbalance of inflammatory and antiinflammatory cytokines plays a critical role in the pathogenesis of rheumatoid arthritis (RA). Precise determination of these cytokines would lead to better understanding of the progression of RA. METHODS: We developed an in vivo microdialysis technique to directly monitor cytokine profiles in knee joints of rats with adjuvant-induced arthritis (AIA). Microdialysates drained from knee joints of rats with AIA and controls were collected and cytokine concentrations were measured by ELISA. Pathological changes of the knee joints and the source of monocyte chemoattractant factor–1 (MCP-1) secretion were also determined by histology and immunohistochemistry. RESULTS: MCP-1 expression in knee joints was significantly higher in AIA rats with erosive changes in their ankles than in normal rats, while interleukin 6 (IL-6) levels were similar in both cases. IL-1β and interferon-g were not detectable in the microdialysates. Increased synovial proliferation and mononuclear inflammatory infiltrates were observed. Synovial cells and mononuclear inflammatory cells expressed both MCP-1 and its receptor, CCR2. CONCLUSION: Our results indicate that the in vivo microdialysis technique is capable of detecting cytokines in the knee joints of rats. Increased expression of MCP-1 and CCR2 in knee joints of AIA rats suggests a role for this cytokine in triggering the mechanisms involved in the pathogenesis of knee joint after ankle erosion.