Grape seed proanthocyanidin extract (GSPE) is a natural flavonoid that exerts anti-inflammatory properties. Obesity is an inflammatory condition and inflammatory cells and their secretion of pro-inflammatory molecules contribute to the pathogenesis of obesity. Rheumatoid arthritis (RA) is a chronic autoimmune disease that is characterized by inflammation of joints lined by synovium. Previously, we demonstrated that obesity augmented arthritis severity in collagen induced arthritis (CIA), a murine model of human RA. Here, we investigated whether oral administration of GSPE showed antiobesity and anti-arthritic effects in high-fat diet-induced obese (DIO) mice and in obese CIA mice, respectively. The pathophysiologic mechanisms by which GSPE attenuates weight gain and arthritis severity in vivo were also investigated. In DIO mice, GSPE administration significantly inhibited weight gain, reduced fat infiltration in liver and improved serum lipid profiles. The antiobesity effect of GSPE was associated with increased populations of regulatory T (Treg) cells and those of decreased Th17 cells. Decrease of Th17 cells was associated with significant inhibition of their key transcriptional factors, pSTAT3Tyr705 and pSTAT3Ser727. On the contrary, GSPE-induced Treg induction was associated with enhanced pSTAT5 expression. To identify the anti-arthritis effects of GSPE, GSPE was given orally for 7 weeks after type II collagen immunization. GSPE treatment significantly attenuated the development of autoimmune arthritis in obese CIA model. In line with DIO mice, GSPE administration decreased Th17 cells and reciprocally increased Treg cells by regulating STAT proteins in autoimmune arthritis model. The expressions of pro-inflammatory cytokines and nitrotyrosine in synovium were significantly inhibited by GSPE treatment. Taken together, GSPE functions as a reciprocal regulator of T cell differentiation – suppression of Th17 cells and induction of Tregs in both DIO and obese CIA mice. GSPE may act as a therapeutic agent to treat immunologic diseases related with enhanced STAT3 activity such as metabolic disorders and autoimmune diseases.
Interleukin (IL)-27 is a novel cytokine of the IL-6/IL-12 family that has been reported to be involved in the pathogenesis of autoimmune diseases and has a pivotal role as both a pro- and anti-inflammatory cytokine. We investigated the in vivo effects of IL-27 on arthritis severity in a murine collagen-induced arthritis (CIA) model and its mechanism of action regarding control of regulatory T (Tregs) and IL-17-producing T helper 17 (Th17) cells. IL-27-Fc-treated CIA mice showed a lower severity of arthritis. IL-17 expression in the spleens was significantly decreased in IL-27-Fc-treated CIA mice compared with that in the CIA model. The Th17 population was decreased in the spleens of IL-27-Fc-treated CIA mice, whereas the CD4+CD25+Foxp3+ Treg population increased. In vitro studies revealed that IL-27 inhibited IL-17 production in murine CD4+ T cells, and the effect was associated with retinoic acid-related orphan receptor γT and signal transducer and activator of transcription 3 inhibition. In contrast, fluorescein isothiocyanate-labeled forkhead box P3 (Foxp3) and IL-10 were profoundly augmented by IL-27 treatment. Regarding the suppressive capacity of Treg cells, the proportions of CTLA-4+ (cytotoxic T-lymphocyte antigen 4), PD-1+ (programmed cell death protein 1) and GITR+ (glucocorticoid-induced tumor necrosis factor receptor) Tregs increased in the spleens of IL-27-Fc-treated CIA mice. Furthermore, in vitro differentiated Treg cells with IL-27 exerted a more suppressive capacity on T-cell proliferation. We found that IL-27 acts as a reciprocal regulator of the Th17 and Treg populations in CD4+ cells isolated from healthy human peripheral blood mononuclear cells (PBMCs), as well as from humans with rheumatoid arthritis (RA) PBMCs. Our study suggests that IL-27 has the potential to ameliorate overwhelming inflammation in patients with RA through a reciprocal regulation of Th17 and Treg cells.
collagen-induced arthritis; interleukin-27; interleukin-17-producing T cells; regulatory T cells; rheumatoid arthritis
To investigate the effect of CoenzymeQ10 (CoQ10) on pain severity and cartilage degeneration in an experimental model of rat osteoarthritis (OA).
Materials and Methods
OA was induced in rats by intra-articular injection of monosodium iodoacetate (MIA) to the knee. Oral administration of CoQ10 was initiated on day 4 after MIA injection. Pain severity was assessed by measuring secondary tactile allodynia using the von Frey assessment test. The degree of cartilage degradation was determined by measuring cartilage thickness and the amount of proteoglycan. The mankin scoring system was also used. Expressions of matrix metalloproteinase-13 (MMP-13), interleukin-1β (IL-1β), IL-6, IL-15, inducible nitric oxide synthase (iNOS), nitrotyrosine and receptor for advanced glycation end products (RAGE) were analyzed using immunohistochemistry.
Treatment with CoQ10 demonstrated an antinociceptive effect in the OA animal model. The reduction in secondary tactile allodynia was shown by an increased pain withdrawal latency and pain withdrawal threshold. CoQ10 also attenuated cartilage degeneration in the osteoarthritic joints. MMP-13, IL-1β, IL-6, IL-15, iNOS, nitrotyrosine and RAGE expressions were upregulated in OA joints and significantly reduced with CoQ10 treatment.
CoQ10 exerts a therapeutic effect on OA via pain suppression and cartilage degeneration by inhibiting inflammatory mediators, which play a vital role in OA pathogenesis.
In this study we examined the in vivo and in vitro effects and mechanisms of action of curcumin on the development of acute graft-versus-host disease (GVHD) using a murine model.
Mixed lymphocyte reactions were used to determine the in vitro effects of curcumin. Treatment with curcumin attenuated alloreactive T cell proliferation and inhibited the production of interferon (IFN)-γ and interleukin (IL)-17. In a murine acute GVHD model, transplantation of curcumin-treated allogeneic splenocytes into irradiated recipient mice significantly reduced the clinical severity scores of acute GVHD manifested in the liver, skin, colon and lung as compared with animals receiving vehicle-treated splenocytes. c-Fos and c-Jun expression levels in the skin and intestine, which are major target organs, were analyzed using immunohistochemical staining. Expression of both proteins was reduced in epithelial tissues of skin and intestine from curcumin-treated GVHD animals. The IFN-γ-expressing CD4+ splenocytes and IFN-γ-expressing lymph node cells were dramatically decreased in curcumin-treated mice. In contrast, CD4+Foxp3+ splenocytes were increased in the curcumin-treated acute GVHD animals. Flow cytometric analysis revealed that animals transplanted with curcumin-treated allogeneic splenocytes showed increased populations of CD4+ regulatory T cells (Tregs) as well as CD8+ Treg cells, compared to animals administered vehicle-treated splenocytes. Curcumin-treated acute GVHD animals could have a change in B cell subpopulations.
In the present study, we investigated the efficacy and mechanism of action of curcumin treatment against acute GVHD. The acute GVHD mice administered with curcumin-treated splenocytes showed significantly reduced severity of acute GVHD. Curcumin exerted in vivo preventive effects on acute GVHD by reciprocal regulation of T helper 1 (Th1) and Treg (both CD4+ and CD8+ Treg) cell lineages as well as B cell homeostasis.
C57BL/6 mice are known to be resistant to the development of collagen-induced arthritis (CIA). However, they show a severe arthritic phenotype when the Ifng gene is deleted. Although it has been proposed that IFN-γ suppresses inflammation in CIA via suppressing Th17 which is involved in the pathogenesis of CIA, the exact molecular mechanism of the Th17 regulation by IFN-γ is poorly understood. This study was conducted to 1) clarify that arthritogenic condition of IFN-γ knockout (KO) mice is dependent on the disinhibition of Th17 and 2) demonstrate that IFN-γ-induced indoleamine2,3dioxgenase (IDO) is engaged in the regulation of Th17. The results showed that the IFN-γ KO mice displayed increased levels of IL-17 producing T cells and the exacerbation of arthritis. Also, production of IL-17 by the splenocytes of the IFN-γ KO mice was increased when cultured with type II collagen. When Il17 was deleted from the IFN-γ KO mice, only mild arthritis developed without any progression of the arthritis score. The proportion of CD44highCD62Llow memory-like T cells were elevated in the spleen, draining lymph node and mesenteric lymph node of IFN-γ KO CIA mice. Meanwhile, CD44lowCD62Lhigh naïve T cells were increased in IFN-γ and IL-17 double KO CIA mice. When Th17 polarized CD4+ T cells of IFN-γ KO mice were co-cultured with their own antigen presenting cells (APCs), a greater increase in IL-17 production was observed than in co-culture of the cells from wild type mice. In contrast, when APCs from IFN-γ KO mice were pretreated with IFN-γ, there was a significant reduction in IL-17 in the co-culture system. Of note, pretreatment of 1-methyl-DL- tryptophan, a specific inhibitor of IDO, abolished the inhibitory effects of IFN-γ. Given that IFN-γ is a potent inducer of IDO in APCs, these results suggest that IDO is involved in the regulation of IL-17 by IFN-γ.
Fibroblast-like synoviocytes (FLSs) are a major cell population of the pannus that invades adjacent cartilage and bone in rheumatoid arthritis (RA). The study was undertaken to determine the effect of interleukin-17 (IL-17) on the survival and/or proliferation of FLSs from RA patients and to investigate whether signal tranducer and activator of transcription 3 (STAT3) is implicated in this process.
Bcl-2 and Bax expression in FLSs was determined using the real-time PCR and western blot analysis. The expression of Bcl-2 and phosphoSTAT3 in synovial tissues was investigated by confocal microscope. Apoptosis of FLSs was detected by Annexin V/propidium iodide staining and/or phase contrast microscopy. The proliferation of FLSs was determined by CCK-8 ELISA assay.
The pro-apoptotic Bax is decreased and anti-apoptotic Bcl-2 is increased in FLSs from RA patients compared with those from patients with osteoarthritis (OA). IL-17 upregulated the expression of Bcl-2 in FLSs from RA patients, but not in FLSs from OA patients. STAT3 was found to mediate IL-17-induced Bcl-2 upregulation in FLSs from RA patients. Additionally, IL-17 promoted the survival and proliferation of FLSs from RA patients. Most importantly, treatment with STAT3 inhibitor reversed the protective effect of IL-17 on FLSs apoptosis induced by sodium nitroprusside (SNP).
Our data demonstrate that STAT3 is critical in IL-17-induced survival of FLS from RA patients. Therefore, therapeutic strategies that target the IL-17/STAT3 pathway might be strong candidates for RA treatment modalities.
Chronic autoimmune inflammation, which is commonly observed in rheumatoid arthritis (RA), disrupts the delicate balance between bone resorption and formation causing thedestruction of the bone and joints. We undertook this study to verify the effects of natural grape-seed proanthocyanidin extract (GSPE), an antioxidant, on chronic inflammation and bone destruction. GSPE administration ameliorated the arthritic symptoms of collagen-induced arthritis (CIA), which are representative of cartilage and bone destruction. GSPE treatment reduced the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and osteoclast activity and increased differentiation of mature osteoblasts. Receptor activator of NFκB ligand expression in fibroblasts from RA patients was abrogated with GSPE treatment. GSPE blocked human peripheral blood mononuclear cell-derived osteoclastogenesis and acted as an antioxidant. GSPE improved the arthritic manifestations of CIA mice by simultaneously suppressing osteoclast differentiation and promoting osteoblast differentiation. Our results suggest that GSPE may be beneficial for the treatment of inflammation-associated bone destruction.
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-α, IL-1β, 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.
arthritis, experimental; bone marrow transplantation; interleukin-17; Th17 cells; T-lymphocytes, regulatory; transplantation, homologous
Interleukin (IL)-32 and IL-17 play critical roles in pro-inflammatory responses and are highly expressed in the synovium of patients with rheumatoid arthritis (RA). We investigated the relations between these two cytokines (IL-17 and IL-32) for their ability to induce each other and to stimulate osteoclasts in RA fibroblast-like synoviocytes (FLSs) and T cells.
FLSs were isolated through surgical synovectomy obtained from patients with RA or osteoarthritis (OA). Real-time PCR were performed to evaluate the expression of IL-32, IL-17 and osteoclast-related genes. Immunohistochemical staining and tartrate-resistant acid phosphatase (TRAP) staining were performed to determine the distribution of inflammatory cytokines and the presence of osteoclastogenesis.
IL-17 induced the expression of IL-32 in the FLSs from RA patients, as assessed by microarray. IL-32 production was increased by IL-17. IL-32 in the FLSs from RA patients induced the production of IL-17 in CD4+ T cells. IL-32 and IL-17 were colocalized near TRAP-positive areas in joint specimens. IL-17 and IL-32 synergistically induced the differentiation of osteoclasts, as demonstrated by the expression of osteoclast-related genes. IL-32 and IL-17 also could induce resorption by osteoclasts in a RANKL-dependent manner.
IL-17 affected the expression of IL-32 in FLSs of RA patients and IL-32 induced the production of IL-17 in CD4+ T cells. Both IL-17 and IL-32 cytokines can reciprocally influence each other's production and amplify the function of osteoclastogenesis in the in RA synovium. Separately, IL-17 and IL-32 each stimulated osteoclastogenesis without RANKL. Together, the two cytokines synergistically amplified the differentiation of osteoclasts, independent of RANKL stimulation.
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-α. 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.
arthritis, experimental; inflammation; mice; obesity; Th17 cells
The study was undertaken to investigate the interrelation of toll-like receptor (TLR) and interleukin (IL)-17 in the salivary glands of patients with primary Sjogren's syndrome (pSS) and to determine the role of TLR and IL-17 in the pathophysiology of pSS.
The expressions of various TLRs, IL-17 and the cytokines involved in Th17 cell differentiation including IL-6, IL-23, tumor necrosis factor-alpha (TNF-α) and IL-1β were examined by immunohistochemistry in salivary glands of pSS patients. The IL-17 producing CD4+ T cells (Th17 cells) were examined by flow cytometry and confocal staining in peripheral mononuclear blood cells (PMBCs) and salivary glands of pSS patients. After PBMCs were treated with TLR specific ligands, the induction of IL-17 and IL-23 was determined using real-time PCR and ELISA. The signaling pathway that mediates the TLR2 stimulated production of IL-17 and IL-23 was investigated by using treatment with specific signaling inhibitors.
We showed that TLR2, TLR4, TLR6, IL-17 and the cytokines associated with Th17 cells were highly expressed in salivary glands of pSS patients but not in controls. The expressions of TLR2, TLR4 and TLR6 were observed in the infiltrating mononuclear cells and ductal epithelial cells, whereas IL-17 was mainly observed in infiltrating CD4+ T cells. The number of IL-17 producing CD4+ T cells was significantly higher in pSS patients both in PBMCs and minor salivary glands. The stimulation of TLR2, TLR4 and TLR6 additively induced the production of IL-17 and IL-23 from the PBMCs of pSS patients especially in the presence of TLR2 stimulation. IL-6, signal transducer and activator of transcription 3 (STAT3) and nuclear factor-kappaB (NF-kB) pathways were implicated in the TLR2 stimulated IL-17 and IL-23.
Our data demonstrate that TLR2 ligation induces the production of IL-23/IL-17 via IL-6, STAT3 and NF-kB pathway in pSS. Therefore, therapeutic strategies that target TLR/IL-17 pathway might be strong candidates for treatment modalities of pSS.
The interleukin-33 (IL-33)/ST2 pathway has emerged as an intercellular signaling system that participates in antigen-allergen response, autoimmunity and fibrosis. It has been suggested that IL-33/ST2 signaling has been involved in the pathogenesis of rheumatoid arthritis (RA), because IL-33 and its receptor have been specifically mapped to RA synovium. The aim of this study was to determine the levels of IL-33 and sST2 in sera and synovial fluids in patients with RA. The serum level of IL-33 was significantly higher in patients with RA (294.9 ± 464.0 pg/mL) than in healthy controls (96.0 ± 236.9 pg/mL, P = 0.002). The synovial fluid level of IL-33 was significantly higher in RA patients than in osteoarthritis patients. The level of serum sST2 was higher in RA patients than in healthy controls (P = 0.042). A significant relationship was found between the levels of IL-33 and IL-1β (r = 0.311, P = 0.005), and IL-33 and IL-6 (r = 0.264, P = 0.017) in 81 RA patients. The levels of IL-33, sST2 and C-reactive protein decreased after conventional disease-modifying antirheumatic drugs treatment in 10 patients with treatment-naïve RA. Conclusively, IL-33 is involved in the pathogenesis of RA and may reflect the degree of inflammation in patients with RA.
Interleukin-33; sST2, ST2L; Arthritis, Rheumatoid
Indoleamine 2,3-dioxygenase (IDO) is a key negative regulator of immune responses and has been implicated in tumor tolerance, autoimmune disease and asthma. IDO was detected in the joint synovial tissue in the inflammatory microenvironment of rheumatoid arthritis (RA), but IDO expression in joint synovial tissue is not sufficient to overcome the inflamed synovial environment. This study aimed to unravel the mechanisms involving the failure to activate tolerogenic IDO in the inflamed joint. We demonstrate that both poly (I:C) and lipopolysaccharide (LPS) induce expression of IDO in synovial fibroblasts. However, inflammatory cytokines such as IL-17, TNF-α, IL-12, IL-23 and IL-16 did not induce IDO expression. Poly (I:C) appeared to induce higher IDO expression than did LPS. Surprisingly, toll-like receptor (TLR)4-mediated IDO expression was upregulated after depletion of myeloid differentiation primary response protein 88 (MyD88) in synovial fibroblasts using small interfering RNA (siRNA). IDO, TLR3 and TLR4 were highly expressed in synovial tissue of RA patients compared with that of osteoarthritis patients. In addition, RA patients with severe disease activity had higher levels of expression of IDO, TLR3 and TLR4 in the synovium than patients with mild disease activity. These data suggest that upregulation of IDO expression in synovial fibroblasts involves TLR3 and TLR4 activation by microbial constituents. We showed that the mechanisms responsible for IDO regulation primarily involve MyD88 signaling in synovial fibroblasts, as demonstrated by siRNA-mediated knockdown of MyD88.
indoleamine-pyrrole 2,3,-dioxygenase; myeloid differentiation factor 88; rheumatoid arthritis; TICAM1 protein, human; toll-like receptors
The receptor for advanced glycation end-products (RAGE) has been implicated in the pathogenesis of arthritis. We conducted this study to determine the effect of interleukin (IL)-17 on the expression and production of RAGE in fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA). The role of nuclear factor-κB (NF-κB) activator 1 (Act1) in IL-17-induced RAGE expression in RA-FLS was also evaluated.
RAGE expression in synovial tissues was assessed by immunohistochemical staining. RAGE mRNA production was determined by real-time polymerase chain reaction. Act-1 short hairpin RNA (shRNA) was produced and treated to evaluate the role of Act-1 on RAGE production.
RAGE, IL-17, and Act-1 expression increased in RA synovium compared to osteoarthritis synovium. RAGE expression and production increased by IL-17 and IL-1β (*P <0.05 vs. untreated cells) treatment but not by tumor necrosis factor (TNF)-α in RA-FLS. The combined stimuli of both IL-17 and IL-1β significantly increased RAGE production compared to a single stimulus with IL-17 or IL-1β alone (P <0.05 vs. 10 ng/ml IL-17). Act-1 shRNA added to the RA-FLS culture supernatant completely suppressed the enhanced production of RAGE induced by IL-17.
RAGE was overexpressed in RA synovial tissues, and RAGE production was stimulated by IL-17 and IL-1β. Act-1 contributed to the stimulatory effect of IL-17 on RAGE production, suggesting a possible inhibitory target for RA treatment.
B cells play an important role in the pathogenesis of rheumatoid arthritis (RA). High levels of B cell activating factor (BAFF) are detected in autoimmune diseases. BAFF and BAFF receptor (BAFF-R) are expressed in B and T cells of RA synovium. The study was undertaken to identify the NF-κB signal pathway involved in the induction of BAFF-R in human B cells. Immunohistochemical staining of NF-κB p65, NF-κB p50, BAFF, and BAFF-R was performed on sections of synovium from severe and mild RA and osteoarthritis (OA) patients. Peripheral blood mononuclear cells (PBMCs) were isolated from control and RA patients and B cells were isolated from controls. BAFF-R was analyzed by flow cytometry, realtime PCR and confocal staining after treatment with NF-κB inhibitors. NF-κB p65, NF-κB p50, BAFF, and BAFF-R were highly expressed in severe RA synovium relative to mild RA synovium or OA synovium. BAFF-R expression was reduced by NF-κB inhibitors in PBMCs and B cells from normal controls. We also showed reduction in expression of BAFF-R via inhibition of the NF-κB pathway in PBMCs of RA patients. BAFF/BAFF-R signaling is an important mechanism of pathogenesis in RA and that BAFF-R reduction by NF-κB blocking therapy is another choice for controlling B cells in autoimmune diseases such as RA.
B-cell activation factor receptor; B-cell activating factor; B-lymphocytes; NF-κB; rheumatoid arthritis
Angiogenesis, which is a critical step in the initiation and progression of rheumatoid arthritis (RA), involves pro-angiogenic factors, including interleukin (IL)-8 and vascular endothelial growth factor (VEGF). We investigated the role of Toll-like receptor 3 (TLR3) in the regulation of pro-angiogenic factors in RA fibroblast-like synoviocytes (FLS).
FLS were isolated from RA synovial tissues and stimulated with the TLR3 ligand, poly (I:C). The levels of VEGF and IL-8 in the culture supernatants were measured using enzyme-linked immunosorbent assays, and the mRNA levels were assessed by semiquantitative reverse transcription-polymerase chain reaction. The expression patterns of VEGF and IL-8 in the RA synovium and osteoarthritis (OA) synovium were compared using immunohistochemistry.
The expression levels of TLR3, VEGF, and IL-8 were significantly higher in the RA synovium than in the OA synovium. VEGF and IL-8 production were increased in the culture supernatants of RA FLS stimulated with poly (I:C), and the genes for these proteins were up-regulated at the transcriptional level after poly (I:C) treatment. Treatment with inhibitors of nuclear factor-kappaB (NF-κB), i.e., pyrrolidine dithiocarbamate and parthenolide, abrogated the stimulatory effect of poly (I:C) on the production of VEGF and IL-8 in RA FLS.
Our results suggest that the activation of TLR3 in RA FLS promotes the production of proangiogenic factors, in a process that is mediated by the NF-κB signaling pathway. Therefore, targeting the TLR3 pathway may be a promising approach to preventing pathologic angiogenesis in RA.
Toll-like receptor 3; Arthritis, rheumatoid; Vascular endothelial growth factor; Interleukin-8; Synovial fibroblast
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.
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.
The production of MIF by RA synovial fibroblasts increased in a dose-dependent manner after ConA stimulation. MIF was also induced by interferon-γ, CD40 ligand, interleukin-15, interleukin-1β, tumor necrosis factor-α, and transforming growth factor-β. 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.
These results suggest that MIF production was induced through a p38 MAP-kinase-dependent pathway in RA synovial fibroblasts.
Macrophage, migration-inhibitory factors; Arthritis rheumatoid; Synovial fibroblast; p38 mitogen-activated protein kinases
The aim of this study was to investigate the expressions of Toll-like receptor (TLR) 2, TLR4, TLR9, and their correlations with the expression of cytokines that are associated with activation of CD4+ T cells and inflammation including interferon γ (IFNγ), interleukin 4 (IL4), interleukin 17 (IL17), and tumor necrosis factor α (TNFα) in muscle tissues of patients with dermatomyositis (DM) and polymyositis (PM). The expressions of TLR2, TLR4, TLR9, IFNγ, IL4, IL17, and TNFα were measured by real-time reverse transcription–polymerase chain reaction in muscle tissues from 14 patients with DM and PM (nine patients with DM, five patients with PM) and three controls. The expressions of TLR2, TLR4, and TLR9 were also localized with immunohistochemistry. The expression levels of TLR2, TLR4, TLR9, IFNγ, IL4, IL17, and TNFα were significantly high in patients with DM and PM compared with those in the controls, and the expression levels of TLR4 and TLR9 had significant positive correlations with the expressions of IFNγ, IL4, IL17, and TNFα. Immunohistochemistry showed that TLR2, TLR4, and TLR9 were expressed by infiltrating cells of perimysium in DM, whereas they were expressed by infiltrating cells of endomysium in PM. These results suggest that the involvement of TLR4 and TLR9 in immunopathogenesis of DM and PM might be connected with activation of CD4+ T cells.
Dermatomyositis; Polymyositis; Toll-like receptors
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 fibroblastlike 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-1β, IFN-γ, 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-1β, and IFN-γ. 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 dosedependently, 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.
interleukin-16; interleukin-17; rheumatoid arthritis; synovial membrane; Toll-like receptors
It is well known that interferon (IFN)-α is important to the pathogenesis of systemic lupus erythematosus (SLE). However, several reports have indicated that the number of IFN-α producing cells are decreased or that their function is defective in patients with SLE. We studied the function of plasmacytoid dendritic cells (pDCs) under persistent stimulation of Toll-like receptor (TLR)9 via a TLR9 ligand (CpG ODN2216) or SLE serum.
The concentrations of IFN-α were determined in serum and culture supernatant of peripheral blood mononuclear cells (PBMCs) from SLE patients and healthy controls after stimulation with CpG ODN2216 or SLE serum. The numbers of circulating pDCs were analyzed by fluoresence-activated cell sorting analysis. pDCs were treated with CpG ODN2216 and SLE serum repeatedly, and levels of produced IFN-α were measured. The expression of IFN-α signature genes and inhibitory molecules of TLR signaling were examined in PBMCs from SLE patients and healthy control individuals.
Although there was no significant difference in serum concentration of IFN-α and number of circulating pDCs between SLE patients and healthy control individuals, the IFN-α producing capacity of PBMCs was significantly reduced in SLE patients. Interestingly, the degree which TLR9 ligand-induced IFN-α production in SLE PBMCs was inversely correlated with the SLE serum-induced production of IFN-α in healthy PMBCs. Because repeated stimulation pDCs with TLR9 ligands showed decreased level of IFN-α production, continuous TLR9 stimulation may lead to decreased production of IFN-α in SLE PBMCs. In addition, PBMCs isolated from SLE patients exhibited higher expression of IFN-α signature genes and inhibitory molecules of TLR signaling, indicating that these cells had already undergone IFN-α stimulation and had become desensitized to TLR signaling.
We suggest that the persistent presence of endogenous IFN-α inducing factors induces TLR tolerance in pDCs of SLE patients, leading to impaired production of IFN-α.
The present study was devised to understand the role of systemic indoleamine 2,3-dioxygenase (IDO) in the tolerance induction for orally tolerized mice in collagen-induced arthritis (CIA). We examined whether IDO-expressing dendritic cells (DCs) are involved in the generation of CD4+CD25+ regulatory T cells during the induction of oral tolerance in a murine CIA model.
Type II collagen was fed six times to DBA/1 mice beginning 2 weeks before immunization, and the effect on arthritis was assessed. To examine the IDO expression, the DCs of messenger RNA and protein were analyzed by RT-PCR and Flow cytometry. In addition, a proliferative response assay was also carried out to determine the suppressive effects of DCs through IDO. The ability of DCs expressing IDO to induce CD4+CD25+ T regulatory cells was examined.
CD11c+ DCs in Peyer's patches from orally tolerized mice expressed a higher level of IDO than DCs from nontolerized CIA mice. IDO-expressing CD11c+ DCs were involved in the suppression of type II collagen-specific T-cell proliferation and in the downregulation of proinflammatory T helper 1 cytokine production. The suppressive effect of IDO-expressing CD11c+ DCs was mediated by Foxp3+CD4+CD25+ regulatory T cells.
Our data suggest that tolerogenic CD11c+ DCs are closely linked with the induction of oral tolerance through an IDO-dependent mechanism and that this pathway may provide a new therapeutic modality to treat autoimmune arthritis.
Inflammatory mediators have been recognized as being important in the pathogenesis of rheumatoid arthritis (RA). Interleukin (IL)-17 is an important regulator of immune and inflammatory responses, including the induction of proinflammatory cytokines and osteoclastic bone resorption. Evidence for the expression and proinflammatory activity of IL-17 has been demonstrated in RA synovium and in animal models of RA. Although some cytokines (IL-15 and IL-23) have been reported to regulate IL-17 production, the intracellular signaling pathways that regulate IL-17 production remain unknown. In the present study, we investigated the role of the phosphoinositide 3-kinase (PI3K)/Akt pathway in the regulation of IL-17 production in RA. Peripheral blood mononuclear cells (PBMC) from patients with RA (n = 24) were separated, then stimulated with various agents including anti-CD3, anti-CD28, phytohemagglutinin (PHA) and several inflammatory cytokines and chemokines. IL-17 levels were determined by sandwich enzyme-linked immunosorbent assay and reverse transcription–polymerase chain reaction. The production of IL-17 was significantly increased in cells treated with anti-CD3 antibody with or without anti-CD28 and PHA (P < 0.05). Among tested cytokines and chemokines, IL-15, monocyte chemoattractant protein-1 and IL-6 upregulated IL-17 production (P < 0.05), whereas tumor necrosis factor-α, IL-1β, IL-18 or transforming growth factor-β did not. IL-17 was also detected in the PBMC of patients with osteoarthritis, but their expression levels were much lower than those of RA PBMC. Anti-CD3 antibody activated the PI3K/Akt pathway; activation of this pathway resulted in a pronounced augmentation of nuclear factor κB (NF-κB) DNA-binding activity. IL-17 production by activated RA PBMC is completely or partly blocked in the presence of the NF-κB inhibitor pyrrolidine dithiocarbamate and the PI3K/Akt inhibitor wortmannin and LY294002, respectively. However, inhibition of activator protein-1 and extracellular signal-regulated kinase 1/2 did not affect IL-17 production. These results suggest that signal transduction pathways dependent on PI3K/Akt and NF-κB are involved in the overproduction of the key inflammatory cytokine IL-17 in RA.
interleukin-17; nuclear factor κB; PI3K/Akt pathway; peripheral blood mononuclear cells; rheumatoid arthritis