Anti-inflammatory effects of leflunomide on cultured synovial macrophages from patients with rheumatoid arthritis

BACKGROUND: Leflunomide and its active metabolite A77 1726 reversibly inhibits the enzyme dihydro-orotate dehydrogenase, the rate limiting step in de novo synthesis of pyrimidines and progression of the cell cycle in different cell lines, mainly activated T lymphocytes. OBJECTIVE: To analyse in vitro the possible anti-inflammatory effects exerted by A77 1726, on cultured macrophages, obtained from the synovial tissues of patients with rheumatoid arthritis (RA). METHODS: The effects of different doses of A77 1726 on intracytoplasmic expression and extracellular concentration of inflammatory cytokines (tumour necrosis factor alpha (TNFalpha), interleukin (IL) 1beta, IL6), as well as the influence on production and expression of intercellular adhesion molecule-1 (ICAM-1) and cyclo-oxygenase 2 (COX-2) by primary cultures of synovial macrophages from patients with RA, were evaluated by immunocytochemistry and western blot analysis. The observations were made at four and 24 hours. RESULTS: A progressive and significant time and dose dependent decrease of the number of positive macrophages for intracellular TNFalpha and IL1beta, treated with different doses of A77 1726, was found in comparison with untreated cells. The extracellular concentration of TNFalpha was found to be significantly decreased in media containing cultured macrophages at 24 hours for all tested doses of A77 1726. At 24 hours, a significant time and dose dependent decrease of ICAM-1 and COX-2 expression by cultured macrophages after A77 1726 treatment was found. CONCLUSIONS: In conclusion, the mechanism of antiproliferative activity exerted by leflunomide on activated T lymphocytes seems to be the same mechanism (alteration of the cell cycle progression) which interferes with the functions of other activated cells-namely, the monocytes/macrophages, which are strongly involved in the inflammatory reaction in RA synovial tissue. The positive clinical results seem to confirm that leflunomide exerts an anti-inflammatory action on phagocytic cells in short and long term treatment of RA.     

类风湿关节炎患者血清滑液和滑膜组织白细胞介素-18的水平及意义

目的 研究类风湿关节炎（RA）患者血清、滑液中白细胞介素－18（IL－18）蛋白及滑膜组织IL－18mRNA表达水平，探讨其在RA致病中的作用。方法 应用双抗夹心酶免疫吸附（ELISA）法和细胞生物法分别测定RA患者血清、滑液中IL－28蛋白水平和生物活性，同时还检测NO、前列腺素E2的含量；有用半定量RT－PCR法检测膜组织IL－18m RNAG表达水平。以骨关节炎（OA）病人及因外伤截肢的正常人作对照。结果 RA患者血清、滑液中IL－18蛋白水平和生物活性均显著高于对照组，滑液中量及活化性比血清高；RA滑膜组织IL－18mRNA表达水平也明显高于对照组。结论 过度表达的IL－18参与了RA的致病过程,；选择性地抑制IL－18生物活性，将是RA治疗的新途径。     

Plasminogen activator in synovial fluid from patients with rheumatoid arthritis

The plasminogen activator in synovial fluid from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) was analyzed on a molecular basis. The level of plasminogen activator in RA was found to be higher than in OA. The plaminogen activators of both RA and OA revealed 3 different molecular weights: 90,000, 55,000 and 33,000. RA demonstrated the 3 plasminogen activators in broadly comparable ratios, but OA had the 55,000 form dominantly. The 90,000 plasminogen activator was a tissue-type plasminogen activator, while the 55,000 and 33,000 plasminogen activators were of the urokinase-type. beta-Methasone suppressed the tissue-type plasminogen activator, and urinary trypsin inhibitor suppressed the urokinase-type plasminogen activators. When urinary trypsin inhibitor was injected clinically into the joint space of a patient with RA, the urokinase-type plasminogen inhibitor was suppressed as in the in vitro study, and the clinical signs and symptoms were markedly improved. Open trials of intraarticular injections of urinary trypsin inhibitor demonstrated improvement of the clinical signs and symptoms.     

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.     

Quantitative absorption of interleukin-2 by peripheral blood and synovial fluid lymphocytes from patients with rheumatoid arthritis

Summary Peripheral blood (PBL) and synovial fluid lymphocytes (SFL) from 18 patients with definite rheumatoid arthritis (RA) and from one patient with Reiter's disease (RD) were examined for their capacity to absorb quantitatively interleukin-2 (IL-2) from a standardized, lectin-free IL-2 source. For comparison normal ConA blasts and PBL from various inflammatory and noninflammatory diseases as well as from healthy control persons were studied. IL-2 activity was quantitated by measuring ³H-thymidine-2-deoxyriboside uptake in the IL-2 dependent murine T cell line CTL6. ConA blasts exhibited a high IL-2 absorption capacity and served as a positive control for calibrating the absorption assay. In a population of normal PBL at least 5–10% of ConA blasts were required to detect IL-2 absorption. Significant absorption was assumed if more than 50% of IL-2 activity was removed from 200 l of a lectin-free IL-2 standard following incubation with 5 × 10₆ lymphoid cells for 2 h at 4°C; this criterion was fulfilled with 8 out of 20 SFL and 4 out of 14 PBL preparations from RA patients. As a rule SFL absorbed more IL-2 than PBL. Control PBL did not absorb significant quantities of IL-2. PBL from the RD patient apparently produced an IL-2 inhibitor during incubation with the IL-2 standard. IL-2 absorption by ConA blasts and SFL was fully inhibited by preincubation of the absorbing cells with monoclonal anti-TAC antibody, a reagent known to react with the human IL-2 receptor. The results are discussed in view of current concepts of antigen/mitogen induced T cell activation.     

Detection of oncostatin M in synovial fluid from patients with rheumatoid arthritis

OBJECTIVE—To measure oncostatin M (OSM) in synovial fluid from patients with rheumatoid arthritis (RA) and osteoarthritis (OA).
METHODS—20 samples of synovial fluid from patients with RA and 10 samples from patients with OA were examined using an OSM specific sandwich ELISA.
RESULTS—OSM was detected at concentrations ranging from 2.36 to 901.82 pg/ml in 18 (90%) of 20 samples of synovial fluid from RA patients. There was no detectable OSM in synovial fluid from OA patients. In the RA patients, the OSM concentration in synovial fluid correlated significantly with the synovial fluid white blood cell count (r=0.67, p<0.01), but not with other laboratory parameters of disease activity.
CONCLUSION—These findings suggest that OSM may contribute to joint inflammation in RA.

     

Inactivation of antithrombin III in synovial fluid from patients with rheumatoid arthritis

OBJECTIVE—To investigate the thrombin inhibitory capacity of antithrombin III in the inflamed human joint.
METHODS—Thrombin inhibitory capacity was measured, using a kinetic spectophotometric method, in matched plasma and synovial fluid samples of patients with rheumatoid arthritis (n=22) and osteoarthritis (n=16), together with normal control plasma samples (n=13). In the same samples, the concentration of antithrombin III was also determined by the method of radial immunodiffusion. The combination of these measurements allowed the calculation of the specific thrombin inhibitory capacity of these samples.
RESULTS—An increased concentration of antithrombin III in rheumatoid compared with osteoarthritic synovial fluid was noted (p<0.05). However, there was a significant depression in the specific activity of antithrombin III in rheumatoid synovial fluid when compared with matched plasma samples (p<0.001) or with osteoarthritic synovial fluid (p<0.05).
CONCLUSION—In rheumatoid synovial fluid the thrombin inhibitory capacity of antithrombin III is disproportionately depressed relative to the concentration of antithrombin III, indicating the inactivation of antithrombin III in the rheumatoid joint.

Keywords: antithrombin III; thrombin; rheumatoid arthritis; synovial fluid     

Antiproliferative and antiinflammatory effects of methotrexate on cultured differentiating myeloid monocytic cells (THP-1) but not on synovial macrophages from patients with rheumatoid arthritis

OBJECTIVE: We investigated the antiproliferative and antiinflammatory effects of methotrexate (MTX) on differentiating/differentiated cells, namely cultured human monocytic myeloid cells (THP-1), and primary cultures of synovial macrophages from patients with rheumatoid arthritis (RA). METHODS: We evaluated early and late apoptosis as well as natural cytokine inhibitor production, such as the interleukin 1 (IL-1) receptor antagonist (IL-1ra) and the soluble tumor necrosis factor receptor (sTNFr). RESULTS: Within THP-1 cells we observed a significant (p < 0.001) dose-dependent inhibition of proliferation (at 24-48 and 72-96 h) and a significant presence of apoptosis (at 24-48 h) with MTX concentrations of 500, 100, and 75 microg/ml compared with untreated controls. No significant changes were observed with 5 microg/ml or 500 to 50, and 5 ng/ml. A significant increase of IL-1ra (p < 0.001) was observed with MTX concentrations of 5 microg (51.43 +/- 2.53 vs 16.22 +/- 5.19 pg/ml control) and 500 ng (36.43 +/- 3.3 vs 16.22 +/- 5.19 pg/ml control) at all the tested times. No significant changes were observed for the sTNFr p75. Evaluating the RA synovial macrophages, we obtained no significant effects on cell proliferation and apoptosis with MTX treatment at 24 h and at the concentration of 50 microg/ml (achievable in the serum with low dose MTX treatment in RA). No significant changes were observed for the IL-1ra and no detectable levels for the sTNFr p75 were detected after treatment with MTX. CONCLUSION: This study shows that the antiproliferative and antiinflammatory effects of MTX on human cultured monocytes are dose-dependent. The antiproliferative activity seems to be mediated by cell apoptosis and the antiinflammatory activity seems to be related to cytokine inhibitor release.     

Phospholipase activity in synovial fluid from patients with rheumatoid arthritis, osteoarthritis and crystal-associated arthritis

Phospholipase activity was assayed in cell-free synovial fluid (SF) from patients with rheumatoid arthritis (RA, n = 28), osteoarthritis (OA, n = 10), and crystal-associated arthritis (C, n = 7) by measuring the release of either [14C]oleic acid or [3H]arachidonic acid from radiolabeled E. coli phospholipids. Activity measured by oleic acid release was not significantly different between the three groups of patients (RA = 571 +/- 43.3, OA = 460 +/- 54.7 and C = 718 +/- 162.6 pmol/min/mg). Arachidonic acid release was significantly (p less than 0.005) less in OA (31 +/- 7.3) than RA (61 +/- 4.7) which was similar to C (58 +/- 17.6 pmol/min/mg). Arachidonic acid release correlated significantly with the SF white blood cell count (r = 0.483, p less than 0.01). This study shows the importance of the type of substrate used to measure phospholipase activity and indicates that differences in the capacity to release arachidonic acid may exist between RA and OA disease states.     

Receptor expression in synovial fluid neutrophils from patients with rheumatoid arthritis.

OBJECTIVES--The aim of this study was to determine if neutrophils isolated from the blood and synovial fluid of patients with rheumatoid arthritis had patterns of receptor expression resembling those of blood neutrophils from controls which had been activated and primed in vitro. METHODS--Fluorescence activated cell sorting was used to measure receptor expression in paired blood and synovial fluid neutrophils from patients and in control neutrophils exposed to phorbol myristate acetate and granulocyte-macrophage colony stimulating factor. RESULTS--There was no significant difference in the patterns of receptor expression in blood neutrophils from patients and healthy controls, but neutrophils in the synovial fluid had been primed and activated within the joint. About 50% of rheumatoid synovial fluid neutrophil samples expressed Fc gamma RI, a high affinity receptor for monomeric IgG, which is only expressed in neutrophils exposed to cytokines. CONCLUSIONS--Synovial fluid neutrophils are activated and primed within the inflamed joint and hence their ability to respond to activating factors such as immune complexes will be modulated. As the expression of Fc gamma RI requires active biosynthesis, this work indicates that selective gene activation occurs when neutrophils are recruited into rheumatoid joints.     

Platelets in the synovial fluid of patients with rheumatoid arthritis

In a study of synovial fluid from 110 patients with various forms of arthritis, platelets were identified in the synovial fluid of all the 50 rheumatoids, in 18 out of the 25 (72%) with osteoarthritis and in all 35 of those with other forms of inflammatory osteoarthrosis. Identification of platelets by light microscopy was confirmed by electron microscopy. Platelet counts were significantly higher in rheumatoid fluid (mean 14 988/mm3; range 1000-65 000/mm3) compared with fluid from patients with osteoarthrosis (mean 1 592/Mm3; 0-10 000/mm3). In addition, significantly higher platelet counts were found in the synovial fluid (SF) of inflamed joints. There was a positive correlation between the SF platelet count and the total white cell count, polymorph count, hydrogen ion concentration, knee score, acid phosphatase and 5-nucleotidase activity and a negative correlation with the glucose level. All these factors indicate joint activity. Finally, platelet numbers correlated with SF levels of immunoglobulin M, and seropositive patients had significantly higher platelet counts in the SF compared with seronegative patients. Rheumatoid patients with thrombocytosis also had higher SF platelet counts. The close relationship of the SF platelet count to other indices of inflammation supports the concept that platelets may directly contribute to synovial inflammation by a variety of pathways.     

Hormone concentrations in synovial fluid of patients with rheumatoid arthritis

OBJECTIVE: Alterations in local concentrations of hormones, affecting directly synovial cells, could be involved in the modulation of the rheumatic inflammatory processes. The aim of present study was to investigate the levels of selected hormones (steroids, peptide and thyroid hormones) in synovial fluid of knee joint of patients with rheumatoid arthritis (RA) and control individuals with non-rheumatic exudate (with osteoarthrosis, OA). METHODS: Thirty-eight patients, 22 female and 16 males, with rheumatoid arthritis (RA) and 12 subjects with osteoarthrosis (OA, control group, 6 females and 6 males) participated in the study. Concentrations of cortisol (CS), 17-beta-estradiol (ES), dehydroepiandrosterone (DHEA), progesterone (PRG), aldosterone ALD), prolactin (PRL), insulin (INS), and C-peptide were determined by radioimmunoassay in synovial fluid. Insulin binding to isolated cell membrane of cells from synovial sediment was estimated by using radioiodine labeled insulin. In a group of patients (10 with RA and 4 with OS), the levels of free threeiodothyronine (FT3), TSH and growth hormone (GH) were also determined in synovial fluid. RESULTS: Increased levels of ES in synovial fluid of RA patients were observed, and higher differences were noted in men. TE concentrations were moderately elevated in synovial fluid of RA patients, however the ratio of ES/TE was significantly higher in male RA compared to OA patients. Higher levels of PRG, ALD and growth hormone were noted in synovial fluid of RA patients. Besides the steroid hormones the presence of insulin and C-peptide was noted in synovial fluid and the correlation between the levels of these two peptides was highly significant. The concentrations of INS and C-peptide in synovial fluid of patients from RA and OA group were not significantly different, however, highly significant increase of insulin binding to isolated membrane of synovial cells was found. Concentrations of cortisol, dehydroepiandosterone, prolactin, TSH and FT3 in synovial fluid were not significantly different in RA and OA groups. CONCLUSIONS: Besides the steroids also insulin, c-peptide, GH and FT3 were found in synovial fluid. The elevated ALD and GH levels in synovial fluid of RA patients and the presence of INS in synovial fluid with increase of INS binding to plasma membranes of cells from synovial fluid of RA patients suggest that besides the gonadal steroids also these hormones may affect the local inflammatory processes.     

Complement activation in synovial fluid and tissue from patients with juvenile rheumatoid arthritis

Synovial fluid (SF) and synovial tissue from 10 patients with juvenile rheumatoid arthritis were examined. The SFs were heterogeneous with respect to the degree of complement activation. Quantification of C3dg and the terminal complement complex revealed a positive correlation between activation of the early and the late parts of the cascade in all patients. The amount of C-reactive protein and the number of white blood cells in the SF correlated significantly with the degree of complement activation. Weak deposits of C3, C3dg, or terminal complement complex were observed in a few vessels in the synovial tissue from 5 of the patients. There was no correlation between complement activity in SF and in the corresponding tissue. Furthermore, there was no correlation between clinical activity in the joints and the degree of complement activation. It is concluded that there is a discrepancy between synovial tissue and synovial fluid with respect to complement activation. C-reactive protein may, to some extent, be responsible for activation in SF, and the accumulation of white blood cells may be due to complement activation products.     

Complement and immunoglobulins in synovial fluid from synovectomized patients with rheumatoid arthritis.

In order to see if the complement (C) consumption and conversion, which are typical of rheumatoid joints, continue after synovectomy, 23 knee joints in which synovectomy had been performed from 4-5 to 6-5 years previously, were studied. The mean ratio of the concentration of C3, C4, and C5 in synovial fluid to that in palsma of the same patient was significantly lower than the corresponding ratio for the total protein content. This was found both in joints with active arthritis and in joints without clinical signs of arthritis, and in both seropositive and seronegative patients. Conversion products of C3 were found in 7 of the synovial fluids. The study thus indicated that the complement alterations in synovectomized joints are very similar to those in nonsynovectomized rheumatoid joints. In one synovial fluid agarose electrophoresis showed multiple sharp bands in the gamma region. By crossed immunoelectrophoresis some bands seemed to contain IgG with one type of light chains only. In plasma of the same patients the bands were much weaker, indicating local production of oligoclonal IgG in the joint.     

Dysregulation of interleukin-10-dependent gene expression in rheumatoid arthritis synovial macrophages

OBJECTIVE: The inflammatory cytokines tumor necrosis factor alpha (TNFalpha) and interleukin-1 (IL-1) are produced by activated macrophages, are key mediators of pathogenesis, and are validated therapeutic targets in rheumatoid arthritis (RA) and seronegative spondylarthritis (SpA). IL-10 is a potent antiinflammatory cytokine that suppresses macrophage TNFalpha and IL-1 production, yet is not effective in suppressing inflammatory arthritis. To gain insight into IL-10 responses in inflammatory arthritis, we used microarray analysis to determine the patterns of IL-10-inducible gene expression in freshly isolated RA and seronegative SpA synovial macrophages. METHODS: Macrophages from the synovial fluid of 5 patients with RA and 3 with seronegative SpA (2 with psoriatic arthritis and 1 with ankylosing spondylitis) were isolated by positive selection and stimulated ex vivo with IL-10 or interferon-gamma (IFNgamma). Gene expression was analyzed using Affymetrix microarrays and protocols. Real-time polymerase chain reaction was used to confirm changes in gene expression. RESULTS: The number of genes induced by IL-10 in arthritic macrophages was markedly smaller than that induced in control macrophages, and the strength of induction was lower in arthritic macrophages for most genes. The residual response of arthritic macrophages to IL-10 stimulation was qualitatively altered, such that IL-10 preferentially increased expression of IFNgamma-inducible genes. In contrast, arthritic macrophages expressed many IFNgamma-inducible genes prior to stimulation, and their response to IFNgamma remained mostly intact. CONCLUSION: These results demonstrate that IL-10 responses are dysregulated in RA synovial macrophages. An altered biologic response to IL-10, with attenuation of its antiinflammatory function and a concomitant retention of IFNgamma-like activating functions, provides a basis for the lack of efficacy of IL-10 in suppressing inflammatory arthritis.     

Increased carbonyl content of proteins in synovial fluid from patients with rheumatoid arthritis

The carbonyl content of proteins in the synovial fluid (SF) of patients with rheumatoid arthritis was significantly (p less than or equal to 0.10) elevated over levels in the SF of patients with osteoarthritis (OA). Other indicators of oxidative damage including catalse, ceruloplasmin, ferritin and superoxide dismutase also showed statistically significant differences (p less than or equal to 0.05) compared to patients with OA.