Bacterial peptidoglycans but not CpG oligodeoxynucleotides activate synovial fibroblasts by toll‐like receptor signaling

Objective

To test the hypothesis that bacterial products acting as adjuvants, such as CpG oligodeoxynucleotides (ODNs) and peptidoglycans (PGs), are able to activate synoviocytes, and to determine the involvement of Toll‐like receptors (TLRs) in this activation process.

Methods

Cultured synovial fibroblasts obtained from patients with rheumatoid arthritis (RA) or osteoarthritis (OA) were stimulated with CpG ODNs or PGs. The expression of various integrins was determined by fluorescence‐activated cell sorting. TLR and matrix metalloproteinase (MMP) messenger RNA (mRNA) was measured by real‐time polymerase chain reaction. Additionally, levels of interleukin‐6 (IL‐6) and IL‐8 in the culture supernatants were assessed by enzyme‐linked immunosorbent assay. Blocking experiments were performed by adding anti–TLR‐2 and anti–TLR‐4 monoclonal antibodies to cultures stimulated with bacterial PGs.

Results

Incubation of synovial fibroblasts with CpG ODNs resulted in neither up‐regulation of the expression of integrins on the cell surface, up‐regulation of MMP mRNA expression, nor IL‐6 and IL‐8 production. However, incubation of RA synovial fibroblasts as well as OA synovial fibroblasts with staphylococcal PGs led to an up‐regulation of CD54 (ICAM‐1) surface expression and to increased expression of MMP‐1, MMP‐3, and MMP‐13 mRNA. Furthermore, production of the proinflammatory cytokines IL‐6 and IL‐8 was increased by treatment with PGs. We demonstrated that cultured synovial fibroblasts express low levels of TLR‐2 and TLR‐9 mRNA. TLR‐2 was up‐regulated after stimulation with PGs, whereas TLR‐9 mRNA remained at baseline levels after stimulation with CpG ODNs. Anti–TLR‐2 monoclonal antibodies significantly inhibited production of IL‐6 and IL‐8 induced by stimulation with PGs.

Conclusion

We demonstrate that bacterial PGs activate synovial fibroblasts, at least partially via TLR‐2, to express integrins, MMPs, and proinflammatory cytokines. Inhibition of TLR signaling pathways might therefore have a beneficial effect on both joint inflammation and joint destruction.

     

Expression of Toll-like receptor 2 on CD16+ blood monocytes and synovial tissue macrophages in rheumatoid arthritis

OBJECTIVE: CD16 (IgG Fcgamma receptor type IIIA [FcgammaRIIIA])-expressing CD14+ monocytes express high levels of Toll-like receptor 2 (TLR-2) and are able to efficiently produce proinflammatory cytokines such as tumor necrosis factor alpha (TNFalpha). To understand the role of CD16 and TLR-2 in monocyte and macrophage activation in rheumatoid arthritis (RA), we investigated the expression of TLR-2 on CD16+ blood monocytes and synovial tissue macrophages and the effect of CD16 and TLR-2 activation on cytokine production. METHODS: The expression of CD14, CD16, TLR-2, and TLR-4 on blood monocytes was measured by flow cytometric analysis. CD16 and TLR-2 expression in RA synovial tissue was detected by 2-color immunofluorescence labeling. CD16+ mature monocytes were prepared by incubating blood monocytes in plastic plates for 24 hours. These adhered monocytes were stimulated with lipoteichoic acid (LTA), anti-FcgammaRIII antibody, and Hsp60 for 5 hours, and culture supernatants were measured for various cytokines by immunoassay. The activation of NF-kappaB was detected by electrophoretic mobility shift assay. RESULTS: The frequency of CD16+ cells in all blood monocytes was significantly increased in patients with RA compared with healthy controls. TLR-2 was expressed at higher levels on CD16+ monocytes than on CD16- monocytes, while TLR-4 was expressed similarly on both monocytes. In RA synovial tissue, CD16+/TLR-2+ cells were distributed mainly in the lining layer. TLR-2 expression on monocytes was enhanced by macrophage colony-stimulating factor (M-CSF) and interleukin-10 (IL-10), but was reduced by transforming growth factor beta1, while CD16 expression was inducible by these cytokines. Adhered monocytes ( approximately 50% CD16+) produced TNFalpha, IL-1beta, IL-6, IL-8, IL-12 p40, IL-1 receptor antagonist, and IL-10 after LTA stimulation. This cytokine response was inhibited significantly by anti-TLR-2 antibody and partly by anti-TLR-4 antibody. Anti-FcgammaRIII antibody stimulation markedly enhanced the LTA-induced TNFalpha response. Hsp60 could stimulate TNFalpha production by adhered monocytes, which was inhibited similarly by anti-TLR-2 antibody and anti-TLR-4 antibody. NF-kappaB activation in adhered monocytes was induced by LTA, but this NF-kappaB activity was not augmented by anti-FcgammaRIII antibody stimulation. CONCLUSION: These results suggest that CD16+ monocytes and synovial tissue macrophages with high TLR-2 expression may be induced by M-CSF and IL-10, and their production of TNFalpha could be simulated by endogenous TLR ligands such as Hsp60 and FcgammaRIIIA ligation by small immune complexes in RA joints.     

RNA released from necrotic synovial fluid cells activates rheumatoid arthritis synovial fibroblasts via Toll-like receptor 3

OBJECTIVE: To assess the expression of Toll-like receptor 3 (TLR-3) protein in synovial tissues and cultured synovial fibroblasts obtained from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) and to investigate the consequences of stimulation of cultured synovial fibroblasts with TLR-3 ligands. METHODS: TLR-3 expression in synovial tissues was determined by immunohistochemistry and immunofluorescence, and expression in cultured RA synovial fibroblasts (RASFs) was determined by fluorescence-activated cell sorting and real-time polymerase chain reaction techniques. TLR-3 signaling was assessed by incubating RASFs with poly(I-C), lipopolysaccharide, palmitoyl-3-cysteine-serine-lysine-4, or necrotic synovial fluid cells from RA patients in the presence or absence of hydroxychloroquine or Benzonase. Subsequent determination of interferon-beta (IFNbeta), CXCL10, CCL5, and interleukin-6 (IL-6) protein production in the culture supernatants was performed by enzyme-linked immunosorbent assays. RESULTS: TLR-3 protein expression was found to be higher in RA synovial tissues than in OA synovial tissues. TLR-3 expression was localized predominantly in the synovial lining, with a majority of the TLR-3-expressing cells coexpressing fibroblast markers. Stimulation of cultured RASFs with the TLR-3 ligand poly(I-C) resulted in the production of high levels of IFNbeta, CXCL10, CCL5, and IL-6 protein. Similarly, coincubation of RASFs with necrotic synovial fluid cells from patients with RA resulted in up-regulation of these cytokines and chemokines in a TLR-3-dependent manner. CONCLUSION: Our findings demonstrate the expression of TLR-3 in RA synovial tissue and the activation of RASFs in vitro by the TLR-3 ligand poly(I-C) as well as by necrotic RA synovial fluid cells, and indicate that RNA released from necrotic cells might act as an endogenous TLR-3 ligand for the stimulation of proinflammatory gene expression in RASFs.     

Matrix metalloproteinase 10 promotion of collagenolysis via procollagenase activation: implications for cartilage degradation in arthritis

OBJECTIVE: We have previously reported the up-regulation of matrix metalloproteinase 10 (MMP-10) following treatment with the procatabolic stimulus of interleukin-1 (IL-1) and oncostatin M (OSM) in chondrocytes. Although MMP-10 is closely related to MMP-3, little is known about the role of MMP-10 in cartilage catabolism. The purpose of this study was to determine whether MMP-10 is expressed in connective tissue cells and to assess how it may contribute to cartilage collagenolysis. METHODS: MMP gene expression was assessed by real-time polymerase chain reaction using RNA from human articular chondrocytes and synovial fibroblasts stimulated with IL-1 plus OSM or tumor necrosis factor alpha (TNFalpha) plus OSM. Synovial fluid levels of MMP-10 were determined by specific immunoassay. Recombinant procollagenases were used in activation studies. Immunohistochemistry assessed MMP-10 expression in diseased joint tissues. RESULTS: MMP-10 expression was confirmed in both chondrocytes and synovial fibroblasts following stimulation with either IL-1 plus OSM or TNFalpha plus OSM, and MMP-10 was detected in synovial fluid samples from patients with various arthropathies. Exogenous MMP-10 significantly enhanced collagenolysis from IL-1 plus OSM-stimulated cartilage, and MMP-10 activated proMMP-1, proMMP-8, and proMMP-13. Immunohistochemistry revealed the presence of MMP-10 in the synovium and cartilage of an IL-1 plus OSM-induced model of arthritis as well as in samples of diseased human tissues. CONCLUSION: We confirm that both synovial fibroblasts and articular chondrocytes express MMP-10 following treatment with procatabolic stimuli. Furthermore, the detectable levels of synovial fluid MMP-10 and the histologic detection of this proteinase in diseased joint tissues strongly implicate MMP-10 in the cartilage degradome during arthritis. The ability of MMP-10 to superactivate procollagenases that are relevant to cartilage degradation suggests that this activation represents an important mechanism by which this MMP contributes to tissue destruction in arthritis.     

Effects of RWJ 67657, a p38 mitogen activated protein kinase (MAPK) inhibitor, on the production of inflammatory mediators by rheumatoid synovial fibroblasts

OBJECTIVE: To investigate the effect of the p38 mitogen activated protein kinase (MAPK) inhibitor RWJ 67657 on inflammatory mediator production by rheumatoid synovial fibroblasts (RSF). METHODS: RSF were pretreated with RWJ 67657 and stimulated with TNF alpha and/or IL-1 beta. Protein levels and mRNA expression of MMP-1, MMP-3, TIMP-1, IL-6, and IL-8 were determined, as was mRNA expression of COX-2 and ADAMTS-4. RESULTS: MMP-3 production was significantly inhibited at 1 microM RWJ 67657 and MMP-1 production at 10 microM, while TIMP-1 production was not inhibited. Inhibition of IL-6 and IL-8 protein production was seen at 0.1 microM RWJ 67657. Expression profiles of mRNA were in accordance with protein production. Inhibition of COX-2 mRNA expression occurred at 0.01 microM RWJ 67657. CONCLUSIONS: RWJ 67657 inhibits major proinflammatory mediator production in stimulated RSF at pharmacologically relevant concentrations. These findings could have important relevance for the treatment of rheumatoid arthritis.     

The expression of toll-like receptors 3 and 7 in rheumatoid arthritis synovium is increased and costimulation of toll-like receptors 3, 4, and 7/8 results in synergistic cytokine production by dendritic cells

OBJECTIVE: To evaluate the expression of Toll-like receptors (TLRs) 3 and 7 in synovium and to study potential differences in the maturation and cytokine production mediated by TLR-2, TLR-3, TLR-4, and TLR-7/8 by dendritic cells (DCs) from rheumatoid arthritis (RA) patients and DCs from healthy controls. METHODS: Synovial expression of TLR-3 and TLR-7 in RA was studied using immunohistochemistry. Monocyte-derived DCs from RA patients and healthy controls were cultured for 6 days and subsequently stimulated for 48 hours via TLR-mediated pathways (lipoteichoic acid, Pam(3)Cys, and fibroblast-stimulating lipopeptide 1 for TLR-2, poly[I-C] for TLR-3, lipopolysaccharide and extra domain A for TLR-4, and R848 for TLR-7/8). Phenotypic DC maturation was measured using flow cytometry. The secretion of tumor necrosis factor alpha (TNFalpha), interleukin-6 (IL-6), IL-10, and IL-12 was measured using the Bio-Plex system. Cell lines expressing TLR-2 and TLR-4 were used for the detection of TLR-2 and TLR-4 ligands in serum and synovial fluid from RA patients. RESULTS: TLR-3 and TLR-7 were highly expressed in RA synovium. All TLR ligands elicited phenotypic DC maturation equally between DCs from RA patients and those from healthy controls. TLR-2- and TLR-4-mediated stimulation of DCs from RA patients resulted in markedly higher production of inflammatory mediators (TNFalpha and IL-6) compared with DCs from healthy controls. In contrast, upon stimulation of TLR-3 and TLR-7/8, the level of cytokine production was equal between DCs from RA patients and those from healthy controls. Remarkably, both TLR-3 and TLR-7/8 stimulation resulted in a skewed balance toward IL-12. Intriguingly, the combined stimulation of TLR-4 and TLR-3-7/8 resulted in a marked synergy with respect to the production of inflammatory mediators. As a proof of concept, TLR-4 ligands were increased in the serum and synovial fluid of RA patients. CONCLUSION: TLRs are involved in the regulation of DC activation and cytokine production. We hypothesize that various TLR ligands in the joint trigger multiple TLRs simultaneously, favoring the breakthrough of tolerance in RA.     

类风湿关节炎炎性关节中高水平脂联素促进白细胞介素-6单核细胞趋化因子-1和核因子-κB受体活化因子配体表达

目的 研究类风湿关节炎(RA)炎性关节中高水平脂联素(AD)表达的意义.方法 酶联免疫吸附试验(ELISA)测定关节液中AD及白细胞介素(IL)-1β、IL-6、IL-8、肿瘤坏死因子(TNF)-α、单核细胞趋化因子(MCP)-1和基质金属蛋白酶(MMP)-9等促炎因子/趋化因子的含量,并分析AD与其相关性.双重免疫标记分析RA滑膜中AD在滑膜成纤维细胞(SFLs)、T淋巴细胞、单核细胞、中性粒细胞和肥大细胞的表达.ELISA测定重组AD因子刺激SFLs后培养上清液中细胞因子含量变化.实时荧光定量反转录-聚合酶链反应(real-time PCR)分析AD和IL-6共刺激对人滑膜细胞系MH7A中核因子-κB受体活化因子配体(RANKL)mRNA表达影响.3组间采用多变量方差分析,2组比较采用Student's t检验.Mann-Whitney U检验,相关性分析采用Spearman检验.结果 RA关节液中AD与IL-6含量呈正相关(r=0.27,P=0.03).AD与成纤维细胞双重免疫标记呈阳性反应.以重组AD因子30g/ml刺激SFLs 24 h后,培养上清液中IL-6和MCP-1分泌量与刺激前相比分别增加了11.4倍和8倍(P<0.05).AD和IL-6共刺激后,MH7A中RANKL mRNA表达显著增加(82±26).结论 炎性关节中高水平AD可促进IL-6、MCP-1和RANKL表达,其可能在RA慢性炎症和骨侵蚀过程中发挥重要作用.     

S100A4 is expressed at site of invasion in rheumatoid arthritis synovium and modulates production of matrix metalloproteinases

The metastasis-associated protein S100A4 promotes the progression of cancer by regulating the remodelling of the extracellular matrix. The expression of S100A4 in vivo is shown and the functional role of S100A4 in the pathogenesis of osteoarthritis and rheumatoid arthritisis is explored. The expression of S100A4 in rheumatoid arthritis, osteoarthritis and normal synovial tissues was determined by immunohistochemistry. The expression of matrix metalloproteinase (MMP) mRNA was measured in rheumatoid arthritis and osteoarthritis synovial fibroblasts treated and untreated with S100A4 oligomer by real-time polymerase chain reaction. Levels of released MMPs were confirmed by ELISA in cell culture supernatants. S100A4 protein was expressed in rheumatoid arthritis and osteoarthritis synovial tissues, in contrast with normal synovium. S100A4 up regulated MMP-3 mRNA in rheumatoid arthritis synovial fluid, with a peak after 6 h. This resulted in release of MMP-3 protein. MMP-1, MMP-9 and MMP-13 mRNA were also up regulated in synovial fluid, but with different kinetics. MMP-14 mRNA showed no change. Thus, S100A4 protein is expressed in synovial tissues of patients with rheumatoid arthritis and osteoarthritis in contrast with healthy people. It induces the expression and release of MMP-3 and other MMPs from synovial fluid. The data suggest that S100A4-producing cells could be involved in the pathogenesis of osteoarthritis and rheumatoid arthritis, including pannus formation and joint destruction.     

Laminin-dependent inflammatory response in synovial fibroblasts of rheumatoid arthritis patients

Elevated expression of matrix-metalloproteinases (MMP) contributes to cartilage destruction in rheumatoid arthritis. We report on a novel pathway of inflammatory activation of synovial fibroblasts that is induced by TGF-beta and laminin (extracellular matrix) and leads to increased expression of the proteases MMP-3 and MMP-10. Neither costimulation by the central inflammatory cytokines TNF-alpha and IL-1beta nor NFkB signalling is needed for this pathway.     

Expression of interleukin-21 receptor, but not interleukin-21, in synovial fibroblasts and synovial macrophages of patients with rheumatoid arthritis

OBJECTIVE: To determine the role and expression of the cytokine/receptor pair interleukin-21 (IL-21)/IL-21 receptor (IL-21R) in rheumatoid arthritis (RA). METHODS: The expression of IL-21R and IL-21 was analyzed by TaqMan real-time polymerase chain reaction (PCR) and in situ hybridization of synovial biopsy samples from patients with RA and osteoarthritis (OA). Double labeling by immunohistochemistry after in situ hybridization was performed with anti-CD68 antibodies. The expression of IL-21R at the protein level was confirmed by Western blotting. Stimulation experiments were performed with recombinant IL-1beta, tumor necrosis factor alpha (TNFalpha), platelet-derived growth factor (PDGF), and transforming growth factor beta (TGFbeta). The role of IL-21R in cartilage destruction was analyzed in the SCID mouse coimplantation model of RA. RESULTS: IL-21R was found in total RNA extracts and in synovial biopsy samples from RA patients, whereas no expression or only minimal expression was seen in samples from OA patients. Double labeling indicated that both synovial macrophages and synovial fibroblasts expressed IL-21R. Western blotting with anti-IL-21R antibodies confirmed the expression of IL-21R protein in RA synovial fibroblasts (RASFs). Of note, IL-21 was not detectable by real-time PCR and in situ hybridization in the same samples in vivo as in vitro. The level of expression of IL-21R messenger RNA (mRNA) was not altered by stimulation with IL-1beta, TNFalpha, PDGF, or TGFbeta. Interestingly, in the SCID mouse coimplantation model, RASFs did not maintain their expression of IL-21R at sites of invasion into the cartilage. Similarly, IL-21R mRNA was not expressed at sites of invasion into cartilage and bone in RA synovium. CONCLUSION: Our data demonstrate that IL-21R is expressed in RA synovium by RASFs and synovial macrophages. IL-21R is associated with the activated phenotype of RASFs independently of the major proinflammatory cytokines IL-1beta and TNFalpha, but correlates negatively with the destruction of articular cartilage and bone.     

Neurotransmitter modulation of interleukin 6 (IL-6) and IL-8 secretion of synovial fibroblasts in patients with rheumatoid arthritis compared to osteoarthritis

OBJECTIVE: The sensory nervous system with the 2 neurotransmitters substance P (SP) and calcitonin gene related peptide (CGRP) is proinflammatory in experimental models of arthritis. The role of the sympathetic nervous system with norepinephrine (NE), adenosine, beta-endorphin, and methionine enkephalin (MENK) is not clearly understood. We studied the influence of these neurotransmitters on secretion of interleukin 6 (IL-6) and IL-8 in primary cultures of synovial fibroblasts of patients with rheumatoid arthritis (RA) compared to osteoarthritis (OA). METHODS: Fibroblasts were isolated using fresh synovial tissue of 5 patients with RA and 5 with OA who underwent knee joint replacement surgery. Modulation of spontaneous secretion of IL-6 and IL-8 was investigated in vitro using the neurotransmitters noted above. RESULTS: In RA fibroblasts, CGRP increased IL-6 and IL-8 secretion at 10(-10) to 10(-8) M (p at least < 0.01), which was not observed in OA fibroblasts. SP had no effect on either cytokine in RA fibroblasts but stimulated IL-8 secretion at 10(-8) M in OA fibroblasts (p < 0.01). In RA fibroblasts, adenosine and NE inhibited secretion of both cytokines at low concentrations (10(-8) M; p < 0.01). However, in OA fibroblasts there was a NE induced increase of IL-8 and IL-6 secretion at 10(-7) and 10(-6) M (p < 0.01), but no inhibition at lower concentrations (10(-8) M; p = NS). In RA fibroblasts, beta-endorphin and MENK inhibited IL-8 secretion at 10(-9) to 10(-7) M (p < 0.01), whereas in OA fibroblasts the dose response curve was shifted to lower concentrations (10(-12) M, 10(-11) M; p < 0.01). CONCLUSION: In OA fibroblasts, the sympathetic neurotransmitters were stimulatory at higher concentrations. CGRP was the most potent stimulatory neurotransmitter in RA fibroblasts whereas the sympathetic adenosine, NE, beta-endorphin, and MENK were inhibitory. This indicates a dualism of action of sympathetic and sensory neurotransmitters, with inhibitory and stimulatory effects on cytokine secretion of RA fibroblasts.     

Expression of toll-like receptors 2 and 4 in rheumatoid synovial tissue and regulation by proinflammatory cytokines interleukin-12 and interleukin-18 via interferon-gamma

OBJECTIVE: To study the expression of Toll-like receptor 2 (TLR-2) and TLR-4 and its association with proinflammatory cytokines in synovial tissue from patients with rheumatoid arthritis (RA), osteoarthritis (OA), and healthy individuals. METHODS: Synovial tissue specimens from 29 RA patients were stained for TLR-2, TLR-4, and proinflammatory cytokines (interleukin-1beta [IL-1beta], IL-12, IL-17, IL-18, and tumor necrosis factor alpha [TNFalpha]). The expression of TLR-2, TLR-4, and cytokines as well as the degree of inflammation in synovial tissue were compared between patients with RA, patients with OA (n = 5), and healthy individuals (n = 3). Peripheral blood mononuclear cells (PBMCs) were incubated with IL-12 and IL-18, and TLR expression was assessed using fluorescence-activated cell sorter analysis. Production of TNFalpha and IL-6 was measured using Luminex bead array technology. RESULTS: In RA synovial tissue, the expression of TLR-2 was slightly higher than that of TLR-4. Interestingly, both TLR-2 and TLR-4 were expressed at higher levels in moderately inflamed synovium, as compared with synovial tissue with no or severe inflammation. TLR expression in both the lining and the sublining was associated with the presence of IL-12 and IL-18, but no other cytokines, in the lining. The expression of both TLRs was low in synovial tissue from OA patients and healthy donors. Stimulation of PBMCs with IL-12 and IL-18 resulted in increased expression of both TLR-2 and TLR-4; this could be blocked with anti-interferon-gamma (anti-IFNgamma) antibodies, suggesting a role for IFNgamma. Lipopolysaccharide- or lipoteichoic acid-mediated triggering of PBMCs incubated with IL-12/IL-18 or IFNgamma led to an increased production of both TNFalpha and IL-6, indicating the functionality of TLR-2 and TLR-4. CONCLUSION: TLR-2 and TLR-4 are expressed in synovial tissue of patients with clinically active disease and are associated with the levels of both IL-12 and IL-18. The synergistic effect of IL-12 and IL-18 on T cell IFNgamma production seems to regulate expression of TLR-2 and TLR-4 in the synovial tissue of RA patients.