LTB4 and BLT1 in inflammatory arthritis

Inflammatory arthritis, including rheumatoid arthritis (RA), is characterized by infiltration of inflammatory cells into the joints. Biological agents targeting TNF-α and IL-6 dramatically improve RA. However, some RA patients do not respond to current treatments and these broadly active upstream biological agents increase the risk of severe infection. Therefore, there remains a need for other effective and safe treatments for RA. Many studies have implicated that blockade of leukotriene B4 (LTB₄) and its high affinity receptor BLT1 dramatically suppress arthritis in animal models. In addition, levels of LTB₄ in serum, synovial fluid and synovial tissue are increased in RA patients compared to healthy donors or osteoarthritis patients. These data suggest that LTB₄ and BLT1 likely contribute to the pathogenesis of human RA. However, several clinical trials inhibiting BLT1 in RA were not successful. Our recent data revealed that LTB₄ is a key mediator in a complement, lipid, cytokine and chemokine cascade that first initiates and then sustains neutrophilic inflammation in inflammatory arthritis. These new mechanistic studies suggest novel ways to target the LTB₄-BLT1 pathway for the treatment of RA and other inflammatory diseases.     

Eicosanoid production in rheumatoid synovitis

Leukotriene B₄ (LTB₄) synthesis in rheumatoid synovitis was studied using peripheral and synovial fluid polymorphonuclear leukocytes (PMNs) and rheumatic synovial lining cells. No differences were found in LTB₄ synthesis between peripheral PMNs from healthy volunteers and rheumatoid arthritis patients. When peripheral and synovial PMNs from the same RA patient were compared, arachidonic acidinduced LTB₄ synthesis in synovial fluid PMNs was increased 1.7–7.2 fold, whereas the response to Ca ionophore A23187 stimulation was similar. This suggests 5-lipoxygenase stimulating factor(s) in inflamed joints. Rheumatic synovial lining cells in a primary cell culture produced small amounts of LTB₄, the concentrations being less than 0.1 per cent of those of prostaglandin E₂ (PGE₂). PGE₂ synthesis in synovial cells was increased when arachidonic acid or interleukin-1 was added to the culture, whereas LTB₄ production remained unaltered. The present results suggest that in inflamed joints LTB₄ originates mainly from PMNs whereas synovial lining cells are the source for PGE₂.     

Neuropeptides and interleukin-6 in human joint inflammation. Relationship between intraarticular substance P and interleukin-6 concentrations

Plasma and synovial fluid concentrations of interleukin-6 (IL-6), using an enzyme-linked immunosorbent assay, as well as immunoreactive levels of calcitonin gene-related peptide (CGRP), substance P and vasoactive intestinal peptide (VIP) were measured in 18 patients with rheumatoid arthritis and 20 with osteoarthritis of the knee. The concentrations of IL-6 were elevated in both plasma and synovial fluids from patients with rheumatoid arthritis whereas higher levels of substance P-, CGRP- and VIP-like immunoreactivities were found in the synovial fluid, but not in plasma, from patients with rheumatoid arthritis when compared with those in osteoarthritis. Furthermore, IL-6 and substance P levels in synovial fluid were significantly correlated both in rheumatoid arthritis and osteoarthritis patients. Our data seem to support the idea of an important role shared by neuropeptides and IL-6 in the pathogenesis of human inflammatory joint disease.     

Caspase-1 Level in Synovial Fluid Is High in Patients with Spondyloarthropathy but Not in Patients with Gout

Activation of caspase-1 by NALP3 inflammasomes has been shown to be important in initiating acute gouty arthritis. The objectives of this study were to measure the levels of caspase-1 in synovial fluid in gout and various arthritides, and to elucidate the clinical significance of caspase-1 levels in synovial fluid. Caspase-1, IL-1β, IL-18, and uric acid were measured in synovial fluid from 112 patients with gout and other arthritides, such as rheumatoid arthritis, osteoarthritis, and spondyloarthropathy. Caspase-1 in synovial fluid from patients with crystal-induced arthritis, inflammatory arthritis, osteoarthritis, and spondyloarthropathy was 35.9 ± 86.7, 49.7 ± 107.7, 2.1 ± 7.0, and 152.6 ± 155.7 pg/mL, respectively. The mean level and the frequency of high levels (≥125 pg/mL) of caspase-1 in spondyloarthropathy were significantly higher than those in the other arthritides including gout. Caspase-1 was detectible in the synovial fluid of patients with the various arthritides. Contrary to our hypothesis, the caspase-1 level in the synovial fluid of patients with gout was not higher than in that of other arthritides. High levels of caspase-1 may be helpful in differentiating spondyloarthropathy from other arthritides.     

Correlation of anti-cytoskeleton antibody activities in synovial fluid with interleukin-6 in patients with osteoarthritis and inflammatory joint disease

Summary Synovial fluids and sera from patients with rheumatoid arthritis, psoriatic arthritis, yersinia arthritis, Behçet's syndrome, Crohn's disease, and osteoarthritis were tested for antinuclear antibodies and antibodies to five cytoskeletal components in sensitive enzyme-linked immunosorbent assay (ELISA) systems and for IL-6 concentrations in a proliferation assay (IL-6 dependent hybridoma cell line B13.29, subclone B9). Statistically significant correlations between antibody activities and IL-6 levels were found for vimentin antibodies (r= 0.56; p<0.05) and actin antibodies (r= 0.44;p<0.05). In patients with chronic and active disease like rheumatoid arthritis and psoriatic arthritis, optical densities measured by vimentin- and actin-ELISA were significantly different from those measured in patients with osteoarthritis. To date only a few reports exist concerning the incidence of antibodies in synovial fluids. We have shown to our knowledge for the first time that IL-6 seems to induce synovial fluid antibody activities restricted to cytoskeletal components of synoviocytes (i.e., vimentin and actin). Synovial fluid antibody activities against vimentin and actin appear to be markers of activity in patients with inflammatory joint disease.Abbreviations ELISA enzyme-linked immunosorbent assay - ANA antinuclear antibodies - ACA antibodies against cytoplasmic components - RA rheumatoid arthritis - OA osteoarthritis - SF synovial fluid - RF rheumatoid factors - FCS fetal calf serum - IFT immunofluorescence microscopy - PBS phosphate buffered saline - BSA bovine serum albumin - OD optical density - SLE systemic lupus erythematosus - IL-6 interleukin-6 - HGF hybridoma growth factor - BSF-2 B-cell-stimulatory factor - DMEM Dulbecco's modified Eagles Medium     

Peripheral blood neutrophil leukotriene B4 release and migration in rheumatoid arthritis

The present study was designed to compare peripheral blood neutrophil migration and leukotriene (LT) release between patients with rheumatoid arthritis (RA) and healthy controls and to correlate the neutrophil functions with clinical disease activity. Nineteen patients with moderately active RA and 19 age and sex matched healthy volunteers participated in this study. Isolated peripheral blood neutrophils from RA patients released equal amounts of LTB₄ but their random migration was enhanced as compared with neutrophils from healthy controls. LTB₄ release in whole blood was significantly lower in samples from RA patients than in those from the healthy volunteers (13.5±1.4 and 19.1±1.4 ng/10⁶ neutrophils respectively; P<0.001). LTB₄ release from isolated RA neutrophils correlated with the levels of C-reactive protein, duration of morning stiffness and Ritchie articular swelling index. Concentrations of hyaluronate, cyclic AMP and 13,14-dihydro-15-keto-prostaglandin were not different between patients with RA and healthy volunteers. Neither was there any difference in TXB₂ production by platelets during blood clotting. In conclusion, peripheral blood neutrophils of RA patients seem to be primed and/or activated as their random migration is enhanced as compared with those of healthy volunteers. In RA, LTB₄ release from peripheral blood neutrophils seems to reflect the clinical activity of the disease. However, RA neutrophils released smaller (in whole blood) or equal (isolated cells) amounts of LTB₄ as compared with the respective controls. These contradictory findings suggest that LTB₄ release from peripheral blood neutrophils has no major role in the regulation of disease activity in rheumatoid arthritis.     

IL-15 promotes osteoclastogenesis via the PLD pathway in rheumatoid arthritis

Osteoclastogenesis plays an important role in joint destruction in rheumatoid arthritis (RA). IL-15 is a pleiotropic proinflammatory cytokine that appears to help mediate the pathological bone loss. This study was undertaken to explore the signaling molecules essential for osteoclastogenesis mediated by IL-15 in rheumatoid synovial fibroblasts. Expression of phospholipase D1 (PLD1) and osteoclast-related gene expression in synovial tissues and their modulation by treatment with IL-15 and different inhibitors in synovial fibroblasts of RA patients were evaluated using immunohistochemistry and quantitative polymerase chain reaction. The levels of IL-15 in serum and synovial fluid were measured by ELISA. The effects of IL-15 and phosphatidic acid (PA) on osteoclast formation were evaluated in cocultures of rheumatoid synovial fibroblasts and peripheral blood monocytes or monocytes alone in the presence of M-CSF and RANKL. The levels of RANKL and PLD1 but not PLD2 were upregulated significantly by IL-15, and the RANKL level was significantly upregulated by PA in rheumatoid synovial fibroblasts. Blocking PA production with 1-butanol and siRNA against PLD1 significantly inhibited the IL-15-stimulated expression of RANKL and PLD1. IL-15 levels were significantly higher in serum and synovial fluid from patients with RA than in osteoarthritis patients and healthy controls. IL-15 and PA induced osteoclast formation through the mitogen-activated protein kinases (MAPKs) and NF-κB signaling pathways. Activation of PLD1 contributes to IL-15-mediated osteoclastogenesis via the MAPKs and NF-κB signaling pathways in rheumatoid synovial fibroblasts. Our data suggest that PLD1 might be an efficient therapeutic strategy for preventing bone destruction in rheumatoid arthritis.     

Different synovial fluid fibronectin levels in rheumatoid variants

Summary A circulating high-molecular-weight glycoprotein called fibronectin plays a part in cell adhesion and migration before phagocytosis and in morphology, differentiation, and metabolism in inflammatory synovial effusions of patients with rheumatic diseases. A technique of nephelometric immunoassay, based on the measurement of an antigen-antibody reaction, was applied to the analysis of fibronectin concentrations in synovial fluids from 20 patients with rheumatoid arthritis (RA) and other diseases (non-RA). RA synovial fluids have a significantly higher concentration than the specimens obtained from Yersinia arthritis patients (n=12). The mean concentration of other synovial fluids, from 12 patients with osteoarthritis of the knees, did not significantly differ from the synovial fluids of control values obtained from patients who underwent meniscectomy. There was a considerably negative correlation between fibronectin levels and overall indices of inflammatory activity, such as Ritchie articular indices or a whole number of painful rheumatoid arthritis joints. However, a particularly distinct correlation was obtained when raised fibronectin levels were compared with the inflammatory activity of the knee joint, from which the specimen was aspirated. Thus, these findings suggest that the measurements of fibronectin in synovial fluid may be of some differential-diagnostic value in rheumatoid variants, but may only serve as an indicator of inflammatory activity if the joint, from which the specimen is obtained, is taken into account.Dedicated to Prof. Dr. N. Zöllner on his 60th birthdaySupported in part by the Deutsche Forschungsgemeinschaft, Go 236/8–9     

Leukotriene B4 metabolism in human leukocytes: Fact or artefact?

The object of this study was to investigate the importance of omega oxidation in regulating leukotriene B₄ (LTB₄) levels in man. In human polymorphonuclear leukocytes metabolism of LTB₄ was rapid but was critically dependent on PMN number: greater than 1.5×10⁶ PMN/ml were required. Metabolism of LTB₄ was blocked in the presence of plasma. In whole blood and in PMN-rich rheumatoid synovial fluids no significant metabolism of LTB₄ was detected within 30 min at 37°C. We conclude that LTB₄ metabolism at inflamed sites will be regulated both by cellular content and the degree of plasma exudation. In most pathological conditions rapid exchange with the micro-vasculature will be more important than metabolism in limiting LTB₄ levels.     

Terminal complement complexes and C1/C1 inhibitor complexes in rheumatoid arthritis and other arthritic conditions.

Terminal complement complex (TCC) and C1r-C1s-C1 inhibitor complex (C1/C1 INH) concentrations were measured in plasma and synovial fluid from patients with arthritis and related to other measures of disease activity. Both TCC and C1/C1 INH concentrations were significantly increased in patients with rheumatoid arthritis (RA) compared with patients with osteoarthritis (plasma and synovial fluid, P less than 0.05) and normal subjects (plasma only, P less than 0.001). In the patients with RA, there was no correlation between plasma or synovial fluid TCC concentrations and IgM rheumatoid factor, immune complex or C1/C1 INH levels. However, in 10 patients with seronegative RA, C1/C1 INH and immune complex levels correlated significantly in synovial fluid (r = 0.69, P less than 0.05) although not in plasma (r = 0.52). Plasma and synovial fluid TCC and C1/C1 INH concentrations did not differ in rheumatoid patients with severe compared with mild joint disease (categorized by the Ritchie score). These results confirm a role for complement activation in RA but suggest that several mechanisms are involved in its pathogenesis.     

Studies of the third component of complement in synovial fluid from arthritic patients. I. Immunochemical quantitation and relation to total complement

In a study of forty-one patients, most of whom had longstanding rheumatoid arthritis, a comparison was made in serum and synovial fluid between total complement activity (CH₅₀) and C3, measured immunochemically. Nineteen out of twenty-seven patients with rheumatoid arthritis and four out of four cases of systemic lupus erythematosus (SLE) or SLE-like syndromes had a depressed CH₅₀ value in the synovial fluid, while ten cases with a non-rheumatoid form of arthritis all had normal activity.

The total C activity in serum was normal or increased in most cases. While no correlation was found between CH₅₀ and C3 in serum, there was a statistically highly significant correlation in synovial fluid, indicating that C3 determinations can be used to reveal alterations in C activity of synovial fluid.

     

膝骨关节炎滑液中可溶性晚期糖基化终末产物受体水平与其病变程度的相关性

背景：研究表明骨关节炎患者关节滑液内可溶性晚期糖基化终末产物受体水平可能与关节炎病变的严重程度存在负相关,但在中国报道较少。 目的：观察膝关节骨关节炎患者关节滑液内可溶性晚期糖基化终末产物受体水平与其病变严重程度的关系。 方法：共纳入46名膝关节骨关节炎患者及14名健康对照者,纳入的骨关节炎患者符合美国风湿病学会骨关节炎的临床诊断标准。采用Kellgren-Lawrence的标准对膝关节骨关节炎病变严重程度进行分级,使用人可溶性晚期糖基化终末产物受体水平酶联免疫吸附试剂盒在酶标仪下检测测关节滑液的可溶性晚期糖基化终末产物受体水平。 结果与结论：膝关节骨关节炎患者关节滑液可溶性晚期糖基化终末产物受体水平较健康对照组显著降低(P < 0.01),且与膝关节骨关节炎病变严重程度呈显著独立负相关(r =-0.587,P < 0.01)。结果表明关节滑液可溶性晚期糖基化终末产物受体水平可能与膝关节骨关节炎病变的严重性和进展程度相关。     

Role of tumor necrosis factor-α and platelet-activating factor in neoangiogenesis induced by synovial fluids of patients with rheumatoid arthritis

The aim of the present study was to investigate in vivo in a mouse model the stimulation of neoangiogenesis by synovial fluids of patients with rheumatoid arthritis (RA) and to determine the role of tumor necrosis factor (TNF)-α and platelet-activating factor (PAF) in the formation of new vessels. Angiogenesis was studied in a mouse model in which Matrigel, injected subcutaneously, was used as a vehicle for the delivery of potential angiogenic stimuli. Synovial fluids of patients with RA but not with osteoarthritis (OA) were shown to induce neoangiogenesis. Since synovial fluid of patients with RA contained significantly higher levels of TNF-α-like bioactivity and of PAF than that of patients with OA, the role of these mediators was evaluated by using an anti-TNF-α neutralizing monoclonal antibody (mAb) and a PAF receptor antagonist, WEB 2170. When added to Matrigel, anti-TNF-α mAb and particularly WEB 2170 significantly reduced neoangiogenesis induced by synovial fluids of RA patients. Moreover, PAF extracted and purified from synovial fluid induced angiogenesis. These results suggest that the neoangiogenesis observed in rheumatoid synovitis may be due, at least in part, to the angiogenic effect of locally produced TNF-α and PAF.     

Tryptase is a candidate autoantigen in rheumatoid arthritis

Autoimmune processes have been implicated in the development of rheumatoid arthritis (RA); however, specific autoantigens that play a role in the aetiology of RA have been lacking. In this study, we found that sera from RA patients were particularly immunoreactive against the protein tryptase. Compared with osteoarthritis (OA) patients and healthy controls, RA patients had relatively higher levels of tryptase and concomitant anti‐tryptase antibodies in their synovial tissues and sera. Similarly, synovial fluid from RA patients, but not from OA patients, contained antibodies that recognized tryptase in vitro. In addition, serum tryptase levels in both early and late RA patients significantly correlated with clinical indices usually used to diagnose RA, such as rheumatoid factor, Disease Activity Score using 28 joint counts and autoantibodies against cyclic citrullinated peptide. Our results identify tryptase as a candidate autoantigen involved in the pathogenesis of RA and monitoring its levels may have diagnostic and prognostic value.     

Stimulation of osteoclast formation by inflammatory synovial fluid

Peri-articular bone resorption is a feature of arthritis due to crystal deposition and rheumatoid disease. Under these conditions, the synovial fluid contains numerous inflammatory cells that produce cytokines and growth factors which promote osteoclast formation. The aim of this study was to determine whether inflammatory synovial fluid stimulates the formation of osteoclasts. Synovial fluid from rheumatoid arthritis (RA), pyrophosphate arthropathy (PPA) and osteoarthritis (OA) patients was added to cultures (n=8) of human peripheral blood mononuclear cells (PBMCs) in the presence and absence of macrophage colony-stimulating factor (M-CSF) and the receptor activator of NF-κB ligand (RANKL). Osteoclast formation was assessed by the formation of cells positive for tartrate-resistant acid phosphatase (TRAP) and vitronectin receptor (VNR) and the extent of lacunar resorption. The addition of 10% OA, RA and PPA synovial fluid to PBMC cultures resulted in the formation of numerous multinucleated or mononuclear TRAP⁺ and VNR⁺ cells which were capable of lacunar resorption. In contrast to PBMC cultures incubated with OA synovial fluid, there was marked stimulation of osteoclast formation and resorption in cultures containing inflammatory RA and PPA synovial fluid which contained high levels of tumour necrosis factor alpha, a factor which is known to stimulate RANKL-induced osteoclast formation.     

Soluble Forms of P-Selectin and Intercellular Adhesion Molecule-3 in Synovial Fluids

A number of adhesion molecules have been identified in synovial tissues of patients with rheumatoid arthritis (RA). Some of them are upregulated and may play an important role in the inflammatory processes of the diseased joint. In addition to synovial tissue cell surface expression, synovial fluids contain soluble forms of many adhesion molecules, such as intercellular adhesion molecule-1, E-selectin (sE-selectin), and L-selectin. In this study, we investigated the expression of soluble P-selectin (sP-selectin) and intercellular adhesion molecule-3 (sICAM-3) in synovial fluids from patients with RA, osteoarthritis (OA), and other forms of arthritis. sP-selectin and sICAM-3 levels in RA synovial fluids were significantly increased compared to those in OA. The levels of sP-selectin in synovial fluids correlated with sICAM-3 and sE-selectin in synovial fluids. The levels of sICAM-3 in synovial fluids correlated with synovial fluid leukocyte counts and erythrocyte sedimentation rate.In vitro,synovial fluid mononuclear cells produced sICAM-3 spontaneously. Elevated levels of sP-selectin and sICAM-3 in RA synovial fluids compared to OA may indicate inflammatory interactions between endothelial cells, leukocytes, and other synovial cells in the diseased joint.     

Immunopathological changes in rheumatoid arthritis and other joint diseases.

A comparative study of the distribution of immunoglobulins G, M, and A and C3 in the synovium and inside synovial fluid leucocytes and of the relative levels of IgG, IgM, AND C3 in paired samples of serum and synovial fluid from both seropositive and seronegative patients with rheumatoid arthritis and other types of non-infective synovitis shows that although there is no distinctive immunopathological feature of rheumatoid arthritis, the incidence of immune complexes containing IgG and IgM with and without detectable C3 in the affected synovium or inside synovial fluid granulocytes is higher in rheumatoid arthritis and especially so in seropositive cases. The mean level of C3 in synovial fluid from patients with rheumatoid arthritis is lower than that from the group without rheumatoid arthritis. In contrast to previous reports, extracellular clumps of IgA could be detected in the affected synovium of a number of affected patients. Aggretated human IgG could be bound by some of the synovial biopsies and synovial fluid leucocytes from both seropositive and seronegative rheumatoid arthritis patients. Antinuclear factor and rheumatoid factor could be detected in the synovial fluid but not in the serum of several patients suggesting either selective sequestration or local synthesis of antinuclear and rheumatoid factors in the affected joints.     

Serum from NSAID-treated patients attenuates the capacity of rat leukocytes to synthesize leukotriene B4

The synthesis of leukotriene B₄ by A23187-stimulated rat peritoneal leukocytes was studied in the presence of 0.1% normal human serum, serum from patients treated with NSAIDs for either an inflammatory (rheumatoid arthritis, RA) or a non-inflammatory condition (lumbar disc protrusion, LDP), and serum from RA patients drawn one week after withdrawal from NSAID treatment. The capacity for LTB₄ synthesis was significantly lower in the presence of serum from NSAID treated patients: thirty per cent less than observed in presence of normal serum in the RA group, and fifty per cent in the LDP group. When NSAIDs were withdrawn from RA patients, the LTB₄ production in presence of serum increased, but was not completely normalized after one week. These results indicate that NSAID treatment may down-regulate the capacity for leukotriene synthesis by an indirect effect.accepted by M. J. Parnham     

A study of opioid peptides in synovial fluid and synovial tissue in patients with rheumatoid arthritis]

Authors have often experienced that psychological stress influences rheumatoid arthritis (RA). In addition, recent reports show a modulatory role for neuropeptide such as substance P in arthritis. These findings prompted us to study endogenous opioid peptides in RA, which are found mainly in the brain and have an effect on the central nervous system. We examined methionine-enkephalin (Met-enk), leucine-enkephalin (Leu-enk) and beta-endorphin (beta-end) in opioid peptides. We measured these peptides in plasma and synovial fluid samples obtained from 28 knees of 24 RA patients and the quantity in the synovial tissue of 13 knees. We also measured plasma and synovial fluid samples from patients with osteoarthritis of the knee and plasma samples from healthy candidates. Leu-enk and beta-end levels in synovial fluid were significantly higher than plasma levels only in RA. Larger quantity of Leu-end and beta-end were contained apparently in the synovial tissue than Met-enk. The synovial tissue with proliferative change tends to contain larger quantity of opioid peptides. These results indicate that the synovial tissue produces or secretes Leu-enk and beta-end and that opioid peptides are related to the degree of inflammation in RA.