BackgroundSome of cannabinoids, which are chemical compounds contained in marijuana, are immunosuppressive. One of the receptors, CB receptor 1 (CB1), is expressed predominantly by the cells in the central nervous system, whereas CB receptor 2 (CB2) is expressed primarily by immune cells. Theoretically, selective CB2 agonists should be devoid of psychoactive effects. In this study, we investigated therapeutic effects of a selective CB2 agonist on arthritis.MethodsThe expression of CB2 was analyzed with immunohistochemistry and Western blotting. Interleukin (IL)-6, matrix metalloproteinase-3 (MMP-3), and chemokine (C-C motif) ligand 2 (CCL2) were quantified with enzyme-linked immunosorbent assays (ELISA). Osteoclastogenesis was assessed with tartrate-resistant acid phosphatase staining and the resorption of coated-calcium phosphate. Effect of JWH133, a selective CB2 agonist, on murine collagen type II (CII)-induced arthritis (CIA) was evaluated with arthritis score, and histological and radiographic changes. IFN-γ and IL-17 production by CII-stimulated splenocytes and serum anti-CII Ab were analyzed by ELISA.ResultsImmunohistochemistry showed that CB2 was expressed more in the synovial tissues from the rheumatoid joints than in those from the osteoarthritis joints. CB2 expression on RA FLS was confirmed with Western blot analysis. JWH133 inhibited IL-6, MMP-3, and CCL2 production from tumor necrosis factor-α-stimulated fibroblast-like synoviocytes (FLS) derived from the rheumatoid joints, and osteoclastogenesis of peripheral blood monocytes. Administration of JWH133 to CIA mice reduced the arthritis score, inflammatory cell infiltration, bone destruction, and anti-CII IgG1 production.ConclusionThe present study suggests that a selective CB2 agonist could be a new therapy for RA that inhibits production of inflammatory mediators from FLS, and osteoclastogenesis.

IntroductionChemerin is a chemotactic agonist identified as a ligand for ChemR23 that is expressed on macrophages and dendritic cells (DCs). In this study, we analyzed the expression of chemerin and ChemR23 in the synovium of rheumatoid arthritis (RA) patients and the stimulatory effects of chemerin on fibroblast-like synoviocytes (FLSs) from RA patients.MethodsChemerin and ChemR23 expression in the RA synovium was ascertained by immunohistochemistry and Western blot analysis. Chemerin expression on cultured FLSs was analyzed by ELISA. ChemR23 expression on FLSs was determined by immunocytochemistry and Western blot analysis. Cytokine production from FLSs was measured by ELISA. FLS cell motility was evaluated by utilizing a scrape motility assay. We also examined the stimulating effect of chemerin on the phosphorylation of mitogen-activated protein kinase (MAPK), p44/42 mitogen-activated protein kinase (ERK1/2), p38MAPK, c-Jun N-terminal kinase (JNK)1/2 and Akt, as well as on the degradation of regulator of NF-κB (IκBα) in FLSs, by Western blot analysis.ResultsChemerin was expressed on endothelial cells and synovial lining and sublining cells. ChemR23 was expressed on macrophages, immature DCs and FLSs and a few mature DCs in the RA synovium. Chemerin and ChemR23 were highly expressed in the RA synovium compared with osteoarthritis. Chemerin and ChemR23 were expressed on unstimulated FLSs. TNF-α and IFN-γ upregulated chemerin production. Chemerin enhanced the production of IL-6, chemokine (C-C motif) ligand 2 and matrix metalloproteinase 3 by FLSs, as well as increasing FLS motility. The stimulatory effects of chemerin on FLSs were mediated by activation of ERK1/2, p38MAPK and Akt, but not by JNK1/2. Degradation of IκB in FLSs was not promoted by chemerin stimulation. Inhibition of the ERK1/2, p38MAPK and Akt signaling pathways significantly suppressed chemerin-induced IL-6 production. Moreover, blockade of the p38MAPK and Akt pathways, but not the ERK1/2 pathway, inhibited chemerin-enhanced cell motility.ConclusionsThe interaction of chemerin and ChemR23 may play an important role in the pathogenesis of RA through the activation of FLSs.

Objective. Lysophosphatidic acid (LPA) is a bioactive lipid that binds to a group of cell surface G protein-coupled receptors (LPA receptors 1-6 [LPA 1-6 ]) and has been implicated as an important mediator of angiogenesis, inflammation, and cancer growth. This study was undertaken to analyze the effects of LPA 1 on the development of arthritis.Methods. Expression of LPA receptors on synovial tissue was analyzed by immunohistochemistry and quantitative reverse transcription-polymerase chain reaction. The effects of abrogation of LPA 1 on collageninduced arthritis (CIA) were evaluated using LPA 1 -deficient mice or LPA 1 antagonist. Migrating fluorescence-labeled CD11b؉ splenocytes, which were transferred into the synovium of mice with CIA, were counted. CD4؉ naive T cells were incubated under Th1-, Th2-, or Th17-polarizing conditions, and T helper cell differentiation was assessed. Osteoclast formation from bone marrow cells was examined.Results. LPA 1 was highly expressed in the synovium of patients with rheumatoid arthritis (RA) compared with that of patients with osteoarthritis. LPA 1 -deficient mice did not develop arthritis following immunization with type II collagen (CII). LPA 1 antagonist also ameliorated murine CIA. Abrogation of LPA 1 was associated with reductions in cell infiltration, bone destruction in the joints, and interleukin-17 production from CII-stimulated splenocytes. Infiltration of transferred CD11b؉ macrophages from LPA 1 -deficient mice into the synovium was suppressed compared with infiltration of macrophages from wild-type mice. LPA 1 antagonist inhibited the infiltration of macrophages from wild-type mice. Differentiation into Th17, but not Th1 or Th2, and osteoclast formation were also suppressed under conditions of LPA 1 deficiency or LPA 1 inhibition in vitro.Conclusion. Collectively, these results indicate that LPA/LPA 1 signaling contributes to the development of arthritis via cellular infiltration, Th17 differentiation, and osteoclastogenesis. Thus, LPA 1 may be a promising target molecule for RA therapy.Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by inflammatory cell infiltration and bone destruction at multiple joints. The inflammation process in RA leads to synovial hyperplasia with proliferation of fibroblast-like synoviocytes (FLS), angiogenesis, and infiltration of inflammatory cells, including lymphocytes and macrophages (1,2).

IntroductionBiological drugs are effective in patients with rheumatoid arthritis (RA), but increase severe infections. The CC chemokine receptor (CCR) 9 antagonist was effective for Crohn’s disease without critical adverse effects including infections in clinical trials. The present study was carried out to explore the pathogenic roles of chemokine (C-C motif) ligand (CCL) 25 and its receptor, CCR9, in autoimmune arthritis and to study if the CCR9 antagonist could be a new treatment for RA.MethodsCCL25 and CCR9 expression was examined with immunohistochemistry and Western blotting. Concentration of interleukin (IL)-6, matrix metalloproteinase (MMP)-3 and tumor necrosis factor (TNF)-α was measured with enzyme-linked immunosorbent assays. Effects of abrogating CCR9 on collagen-induced arthritis (CIA) was evaluated using CCR9-deficient mice or the CCR9 antagonist, CCX8037. Fluorescence labeled-CD11b+ splenocytes from CIA mice were transferred to recipient CIA mice and those infiltrating into the synovial tissues of the recipient mice were counted.ResultsCCL25 and CCR9 proteins were found in the RA synovial tissues. CCR9 was expressed on macrophages, fibroblast-like synoviocytes (FLS) and dendritic cells in the synovial tissues. Stimulation with CCL25 increased IL-6 and MMP-3 production from RA FLS, and IL-6 and TNF-α production from peripheral blood monocytes. CIA was suppressed in CCR9-deficient mice. CCX8037 also inhibited CIA and the migration of transferred CD11b+ splenocytes into the synovial tissues.ConclusionsThe interaction between CCL25 and CCR9 may play important roles in cell infiltration into the RA synovial tissues and inflammatory mediator production. Blocking CCL25 or CCR9 may represent a novel safe therapy for RA.

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