Obesity aggravates the joint inflammation in a collagen-induced arthritis model through deviation to Th17 differentiation

White fat cells secrete adipokines that induce inflammation and obesity has been reported to be characterized by high serum levels of inflammatory cytokines such as IL-6 and TNF-alpha. Rheumatoid arthritis (RA) is a prototype of inflammatory arthritis, but the relationship between RA and obesity is controversial. We made an obese inflammatory arthritis model: obese collagen-induced arthritis (CIA). C57BL/6 mice were fed a 60-kcal high fat diet (HFD) from the age of 4 weeks and they were immunized twice with type II collagen (CII). After immunization, the obese CIA mice showed higher arthritis index scores and histology scores and a more increased incidence of developing arthritis than did the lean CIA mice. After treatment with CII, mixed lymphocyte reaction also showed CII-specific response more intensely in the obese CIA mice than lean CIA. The anti-CII IgG and anti-CII IgG2a levels in the sera of the obese CIA mice were higher than those of the lean CIA mice. The number of Th17 cells was higher and the IL-17 mRNA expression of the splenocytes in the obese CIA mice was higher than that of the lean CIA mice. Obese CIA mice also showed high IL-17 expression on synovium in immunohistochemistry. Although obesity may not play a pathogenic role in initiating arthritis, it could play an important role in amplifying the inflammation of arthritis through the Th1/Th17 response. The obese CIA murine model will be an important tool when we investigate the effect of several therapeutic target molecules to treat RA.

IL-17-deficient allogeneic bone marrow transplantation prevents the induction of collagen-induced arthritis in DBA/1J mice

IL-17-producing CD4+ T cells (Th17) play important functions in autoimmune diseases and allograft rejection of solid organs. We examined the effects of IL 17 and its mechanism of action on arthritis in a murine collagen-induced arthritis (CIA) model using bone marrow transplantation (BMT) system. DBA/1J mice were administered a lethal radiation dose and then rescued with bone marrow derived from either wild-type (WT) or IL-17-/- mice on C57BL/6 background mice. CIA was induced after the bone marrow transplant, and disease progression was characterized. DBA/1J mice with CIA that received IL-17-/- donor bone marrow showed potently inhibited development and severity of clinical arthritis as compared with CIA mice that received WT bone marrow. Reduced secretion of the pro-inflammatory cytokines tumor necrosis factor-alpha, IL-1beta, and IL-6, and collagen-specific T cell responses were observed in mice that received IL-17-/- bone marrow. IL-17 blockade also inhibited effector T cell proliferation by reciprocally regulating the Treg/Th17 ratio. IL-17 blockade prevented joint destruction in mice with CIA. These findings suggest that CIA with BMT is a viable method of immunological manipulation and that IL-17 deficiency suppresses severe joint destruction and inflammation in CIA mice. There may be clinical benefits in blocking IL-17 and BMT in the treatment of rheumatoid arthritis.

Deficiency of Foxp3+ Regulatory T Cells Exacerbates Autoimmune Arthritis by Altering the Synovial Proportions of CD4+ T Cells and Dendritic Cells

BACKGROUND: CD4+Fop3+ regulatory T cells (Tregs) are needed to maintain peripheral tolerance, but their role in the development of autoimmune arthritis is still debated. The present study was undertaken to investigate the mechanism by which Tregs influence autoimmune arthritis, using a mouse model entitled K/BxN. METHODS: We generated Treg-deficient K/BxNsf mice by congenically crossing K/BxN mice with Foxp3 mutant scurfy mice. The arthritic symptoms of the mice were clinically and histopathologically examined. The proportions and activation of CD4+ T cells and/or dendritic cells were assessed in the spleens, draining lymph nodes and synovial tissue of these mice. RESULTS: K/BxNsf mice exhibited earlier onset and more aggressive progression of arthritis than their K/BxN littermates. In particular, bone destruction associated with the influx of numerous RANKL+ cells into synovia was very prominent. They also contained more memory phenotype CD4+ T cells, more Th1 and Th2 cells, and fewer Th17 cells than their control counterparts. Plasmacytoid dendritic cells expressing high levels of CD86 and CD40 were elevated in the K/BxNsf synovia. CONCLUSION: We conclude that Tregs oppose the progression of arthritis by inhibiting the development of RANKL+ cells, homeostatically proliferating CD4+ T cells, Th1, Th2 and mature plasmacytoid dendritic cells, and by inhibiting their influx into joints.

Deficiency of Foxp3+ Regulatory T Cells Exacerbates Autoimmune Arthritis by Altering the Synovial Proportions of CD4+ T Cells and Dendritic Cells

BACKGROUND: CD4+Fop3+ regulatory T cells (Tregs) are needed to maintain peripheral tolerance, but their role in the development of autoimmune arthritis is still debated. The present study was undertaken to investigate the mechanism by which Tregs influence autoimmune arthritis, using a mouse model entitled K/BxN. METHODS: We generated Treg-deficient K/BxNsf mice by congenically crossing K/BxN mice with Foxp3 mutant scurfy mice. The arthritic symptoms of the mice were clinically and histopathologically examined. The proportions and activation of CD4+ T cells and/or dendritic cells were assessed in the spleens, draining lymph nodes and synovial tissue of these mice. RESULTS: K/BxNsf mice exhibited earlier onset and more aggressive progression of arthritis than their K/BxN littermates. In particular, bone destruction associated with the influx of numerous RANKL+ cells into synovia was very prominent. They also contained more memory phenotype CD4+ T cells, more Th1 and Th2 cells, and fewer Th17 cells than their control counterparts. Plasmacytoid dendritic cells expressing high levels of CD86 and CD40 were elevated in the K/BxNsf synovia. CONCLUSION: We conclude that Tregs oppose the progression of arthritis by inhibiting the development of RANKL+ cells, homeostatically proliferating CD4+ T cells, Th1, Th2 and mature plasmacytoid dendritic cells, and by inhibiting their influx into joints.

IL-17 and Toll-like Receptor 2 or Toll-like Receptor 4 Combined Engagement Upregulates RANKL and IL-6 in Human Rheumatoid Synovial Fibroblasts / 대한류마티스학회지

OBJECTIVE: The aim of this study was to clarify whether stimulation of recombinant IL-17, TLR2 and TLR4 by their specific ligands induces the production of RANKL and IL-6 in the fibroblast-like synoviocytes (FLSs) from RA patients. METHODS: FLSs were isolated from RA synovial tissues and they were stimulated with the IL-17, TLR2 ligand bacterial peptidoglycan (PGN) and TLR4 ligand lipopolysaccharide (LPS). The RANKL levels were assessed by RT-PCR and western blotting. The expressions of IL-17, TLR2, TLR4, RANKL and IL-6 in the RA synovium were quantified by immunohistochemistry and these values were compared with the values obtained in the osteoarthritis synovium. The increased IL-6 production in the culture supernatants of the RA FLSs was quantified by sandwich ELISA. RESULTS: The mRNA and protein levels of RANKL and IL-6 increased in the RA FLSs stimulated with PGN, LPS and IL-17, or PGN plus IL-17 or LPS plus IL-17. The expressions of IL-17, TLR2, TLR4, RANKL and IL-6 were much higher in the RA synovium than those in the osteoarthritis (OA) synovium. CONCLUSION: We observed synergistic effects of TLR-2, TLR-4 and IL-17 upon the induction of RANKL. In conclusion, our data supports the previous evidence of an important role of TLR-2, TLR-4 and IL-17 in the pathogenesis of RA.

Induction of Macrophage Migration Inhibitory Factor in ConA-Stimulated Rheumatoid Arthritis Synovial Fibroblasts through the P38 MAP Kinase-Dependent Signaling Pathway

BACKGROUND/AIMS: This study was undertaken to identify the intracellular signaling pathway involved in induction of macrophage migration inhibitory factor (MIF) in human rheumatoid arthritis (RA) synovial fibroblasts. METHODS: Human RA synovial fibroblasts were treated with concanavalin A (ConA), various cytokines, and inhibitors of signal transduction molecules. The production of MIF by synovial fibroblasts was measured in culture supernatants by ELISA. The expression of MIF mRNA was determined using reverse transcriptase polymerase chain reaction (RT-PCR) and real-time PCR. Phosphorylation of p38 mitogen-activated protein (MAP) kinase in synovial fibroblasts was confirmed using Western blotting. The expression of MIF and p38 MAP kinase in RA synovium was determined using dual immunohistochemistry. RESULTS: The production of MIF by RA synovial fibroblasts increased in a dose-dependent manner after ConA stimulation. MIF was also induced by interferon-gamma, CD40 ligand, interleukin-15, interleukin-1beta, tumor necrosis factor-alpha, and transforming growth factor-beta. The production of MIF by RA synovial fibroblasts was significantly reduced after inhibition of p38 MAP kinase. The expression of MIF and p38 MAP kinase was upregulated in the RA synovium compared with the osteoarthritis synovium. CONCLUSIONS: These results suggest that MIF production was induced through a p38 MAP-kinase-dependent pathway in RA synovial fibroblasts.

IL-17 induces the production of IL-16 in rheumatoid arthritis

The purpose of this study was to investigate the expression of IL-16 in the rheumatoid synovium and the role of inflammatory cytokines and Toll-like receptor (TLR) ligands in IL-16 production by fibroblast- like synoviocytes (FLS) of rheumatoid arthritis (RA) patients. Immunohistochemical staining was performed with a monoclonal antibody to IL-16 in synovial tissues from patients with RA and likewise in patients with osteoarthritis (OA). FLS were isolated from RA synovial tissues and stimulated with IL-15, IL-1beta, IFN-gamma, and IL-17. The IL-16 mRNA level was assessed by semiquantitative RT-PCR and real time (RT) PCR and a comparison was made between IL-16 mRNA levels produced by RA-FLS and OA-FLS. Production of IL-16 was identified by a western blot assay, and IL-16 production after stimulation by specific ligands of TLR2 and TLR4 was assessed by RT-PCR. While immunohistochemical staining demonstrated strong expression of IL-16 mRNA in synovial tissues from patients with RA, similar findings were not present in the OA group. Moreover, mRNA expression of IL-16 by RA-FLS increased after treatment with IL-17 but not with IL-15, IL-1beta, and IFN-gamma. Specifically, IL-17 increased IL-16 mRNA level by RA-FLS and peripheral blood mononuclear cells in a dose-dependent manner. However, IL-17 did not stimulate IL-16 production in OA-FLS. Peptidoglycan, a selective TLR2 ligand, also increased production of IL-16 by RA-FLS dose- dependently, whereas LPS, a selective TLR4 ligand, had no such stimulatory effect. The results from our data demonstrate that IL-17 and TLR2 ligands stimulate the production of IL-16 by RA-FLS.