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Fibroblast growth factor (FGF)-1 and PDGF-B-like factors have been implicated in the pathobiology of RA and animal models of this disease. Since the receptors for FGF-1 and PDGF are tyrosine kinases, we examined the expression of tyrosine phosphorylated proteins (phosphotyrosine, P-Tyr) in synovial tissues from patients with RA and osteoarthritis (OA), and rats with streptococcal cell wall (SCW) and adjuvant arthritis (AA). Synovia from patients with RA and LEW/N rats with SCW and AA arthritis, in contrast to controls, stained intensely with anti-P-Tyr antibody. The staining colocalized with PDGF-B and FGF-1 staining. Comparative immunoblot analysis showed markedly enhanced expression of a 45-kD P-Tyr protein in the inflamed synovia. Treatment with physiological concentrations of dexamethasone suppressed both arthritis and P-Tyr expression in AA. P-Tyr was only transiently expressed in athymic nude Lewis rats and was not detected in relatively arthritis-resistant F344/N rats. These data suggest that (a) FGF-1 and PDGF-B-like factors are upregulated and may induce tyrosine phosphorylation of proteins in vivo in inflammatory joint diseases, (b) persistent high level P-Tyr expression is T lymphocyte dependent, correlates with disease severity, and is strain dependent in rats, (c) corticosteroids, in physiological concentrations, downregulate P-Tyr expression in these lesions.

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The aim of this study was to investigate the expression and localization of cyclooxygenase-1 and -2 (COX-1 and COX-2) in synovial tissues from patients with rheumatoid arthritis (RA). Synovial tissues from 9 patients with RA and 5 patients with osteoarthritis (OA) were examined for COX-1 and COX-2 expressions by immunohistochemical staining using 2 polydonal COX-1 and COX-2 antibodies. In RA synovia, synovial lining cells showed intense immunostaining for COX-1, whereas slight to moderate staining was observed in inflammatory cells, stromal fibroblast-like cells and vascular endothelial cells. There was no significant difference in COX-1 expression between RA and OA synovia. The localization of COX-2 expression dearly differed from that of COX-1 expression, being most intense in inflammatory cells. However, there was no difference in COX-1 and COX-2 expressions between RA and OA synovial tissues. Our observations support that inflammatory mechanisms modulated by COX-1 and COX-2 in chronic RA synovium might be similar to those in chronic OA synovium.

Transin is a neutral metalloproteinase initially isolated from malignantly transformed rat fibroblasts and subsequently shown to be homologous to human stromelysin. We performed Northern blot analysis on synovial tissue specimens from Lewis rats with proliferative and invasive streptococcal cell wall (SCW) arthritis. Transin mRNA was present in abundance, as was the mRNA of the c-myc oncogene, which is associated with cellular proliferation. Immunohistochemical staining of synovia from rats with chronic SCW arthritis showed high-level transin expression in the cells of the lining layer and underlying stroma, as well as in chondrocytes and osteoclasts in subchondral bone. Intense nuclear staining for the Myc oncoprotein was also detected with a cross-reactive antibody to v-Myc. Transin stained similarly in the early, rapid-onset, thymus-independent, acute phase of SCW arthritis. In the T cell-dependent adjuvant arthritis, transin expression was noted by day 4, 6 d before the influx of mononuclear cells and the onset of clinical disease. Athymic rats did not express transin. We concluded that transin is a marker of proliferative, invasive arthritis in rats and appears early in the course of disease development, but requires a competent immune system to sustain its expression in these model arthropathies.

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The synovium from patients with rheumatoid arthritis (RA) and LEW/N rats with streptococcal cell wall (SCW) arthritis, an experimental model resembling RA, is characterized by massive proliferation of synovial connective tissues and invasive destruction of periarticular bone and cartilage. Since heparin binding growth factor (HBGF)-1, the precursor of acidic fibroblast growth factor (FGF), is a potent angiogenic polypeptide and mitogen for mesenchymal cells, we sought evidence that it was involved in the synovial pathology of RA and SCW arthritis. HBGF-1 mRNA was detected in RA synovium using the polymerase chain reaction technique, and its product was immunolocalized intracellularly in both RA and osteoarthritis (OA) synovium. HBGF-1 staining was more extensive and intense in synovium of RA patients than OA and correlated with the extent and intensity of synovial mononuclear cell infiltration. HBGF-1 staining also correlated with c-Fos protein staining. In SCW arthritis, HBGF-1 immunostaining was noted in bone marrow, bone, cartilage, synovium, ligamentous and tendinous structures, as well as various dermal structures and developed early in both T-cell competent and incompetent rats. Persistent high level immunostaining of HBGF-1 was only noted in T-cell competent rats like the disease process in general. These observations implicate HBGF-1 in a multitude of biological functions in inflammatory joint diseases.

High levels of immunoreactive cyclooxygenase (Cox; prostaglandin H synthase) are present in synovia from patients with rheumatoid arthritis (RA). We now show that the recently identified inducible isoform of Cox, Cox-2, is expressed in synovia from patients with RA. To further explore modulation of the Cox isoforms in RA synovial tissues, we examined the expression and modulation of Cox-1 and -2 in rheumatoid synovial explant cultures and cultured rheumatoid synovial fibroblast-like cells (synoviocytes). Immunoprecipitation of in vitro labeled proteins and Western blot analysis demonstrated the presence of both Cox-1 and -2 under basal conditions in freshly explanted rheumatoid synovial tissues. De novo synthesis of Cox-2 polypeptide was enhanced by IL-1 beta or PMA, and dramatically suppressed by dexamethasone (dex). Cox-1 expression, under the same conditions, showed only minor variation. Since mRNA for Cox-2 is highly unstable, we examined the regulation of Cox-2 transcripts in cultured rheumatoid synoviocytes. Under basal conditions both Cox-1 and -2 mRNAs were present at low levels, but Cox-2 mRNA was markedly increased by treatment with IL-1 beta or PMA. dex markedly suppressed the induction of Cox-2 mRNA. In sharp contrast, Cox-1 transcripts were not modulated by IL-1 beta or dex. These data suggest that modulation of Cox-2 expression by IL-1 beta and corticosteroids may be an important component of the inflammatory process in synovial tissues from patients with RA.

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Experimental arthritis models are considered valuable tools for delineating mechanisms of inflammation and autoimmune phenomena. Use of microarray-based methods represents a new and challenging approach that allows molecular dissection of complex autoimmune diseases such as arthritis. In order to characterize the temporal gene expression profile in joints from the reactivation model of streptococcal cell wall (SCW)-induced arthritis in Lewis (LEW/N) rats, total RNA was extracted from ankle joints from naïve, SCW injected, or phosphate buffered saline injected animals (time course study) and gene expression was analyzed using Affymetrix oligonucleotide microarray technology (RAE230A). After normalization and statistical analysis of data, 631 differentially expressed genes were sorted into clusters based on their levels and kinetics of expression using Spotfire® profile search and K-mean cluster analysis. Microarray-based data for a subset of genes were validated using real-time PCR TaqMan® analysis. Analysis of the microarray data identified 631 genes (441 upregulated and 190 downregulated) that were differentially expressed (Delta > 1.8, P < 0.01), showing specific levels and patterns of gene expression. The genes exhibiting the highest fold increase in expression on days -13.8, -13, or 3 were involved in chemotaxis, inflammatory response, cell adhesion and extracellular matrix remodelling. Transcriptome analysis identified 10 upregulated genes (Delta > 5), which have not previously been associated with arthritis pathology and are located in genomic regions associated with autoimmune disease. The majority of the downregulated genes were associated with metabolism, transport and regulation of muscle development. In conclusion, the present study describes the temporal expression of multiple disease-associated genes with potential pathophysiological roles in the reactivation model of SCW-induced arthritis in Lewis (LEW/N) rat. These findings improve our understanding of the molecular events that underlie the pathology in this animal model, which is potentially a valuable comparator to human rheumatoid arthritis (RA).

Corticotropin-releasing hormone (CRH), the principal regulator of the hypothalamic-pituitary-adrenal axis, is also secreted in peripheral inflammatory sites, where it acts as a local proinflammatory agent. Arthritis-susceptible LEW/N rats have profoundly deficient hypothalamic CRH responses to inflammatory stimuli and other stressors. Arthritis-resistant F344/N rats, on the other hand, have a robust increase in hypothalamic CRH in response to the same stimuli. Contrasting with these hypothalamic CRH responses, we now show that CRH expression is markedly increased in the joints and surrounding tissues of LEW/N rats with streptococcal cell wall- and adjuvant-induced arthritis, whereas it is not increased in similarly treated F344/N rats and is only transiently increased in congenitally athymic nude LEW.rnu/rnu rats. Glucocorticoid treatment suppressed, but did not eliminate, CRH immunoreactivity in the joints of LEW/N rats. CRH mRNA was present in inflamed synovia, as well as in spinal cord, and inflamed synovia also expressed specific CRH-binding sites. We compared CRH expression in inflamed joints with another well-characterized proinflammatory neuropeptide, substance P (SP), and found that SP immunoreactivity paralleled that of CRH. In summary, although LEW/N rats have deficient hypothalamic CRH responses to inflammatory stimuli compared with F344/N rats, they express relatively high levels of CRH at the site of inflammation. Analogous to SP, CRH may be delivered to the inflammatory site by peripheral nerves and/or synthesized at the inflammatory site. These data provide further support for the concept that CRH not only triggers the pituitary-adrenal antiinflammatory cascade, but also functions as an antithetically active local mediator of acute and chronic inflammatory arthritis. These data also illustrate the complex interrelationships of the nervous, endocrine, immune, and inflammatory systems.

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We have previously reported that a single intraperitoneal injection of an aqueous suspension of group A streptococcal cell wall (SCW) fragments induces extensive hepatic granulomas in LEW/N female rats, but not in F344/N female rats. To further understand the mechanisms underlying these differences, we compared granuloma development and class II major histocompatibility complex antigen (Ia) expression in histocompatible LEW/N, F344/N, and CAR/N female rats in response to SCW fragments of four different average molecular sizes. In LEW/N female rats, the smallest fragments (less than 5 megadaltons) induced the most severe hepatic inflammatory disease, with development of widespread granulomas composed of macrophages, lymphocytes, and a peripheral rim of fibroblasts. The largest fragments (greater than 500 megadaltons) induced equivocal disease. Fragments of intermediate size induced granulomas of intermediate severity. The extent of granuloma development, the intensity of Ia antigen expression, and the amount of SCW antigen deposited in the liver qualitatively paralleled each other. In contrast, injection of the most granulomagenic SCW fragments into F344/N and CAR/N rats did not induce granulomas. Although these rat strains are histocompatible with the LEW/N (i.e., RTL.1) strain, hepatic Ia antigen expression in these strains was not increased significantly above basal levels. The amount of SCW antigen in the livers of the resistant rat strains appeared similar to the amount in the susceptible LEW/N strain. These data indicate that granuloma development is dependent on the size of the SCW fragment and host genetic background and that Ia expression directly parallels the severity of the hepatic disease. In addition, the data suggest that non-major histocompatibility complex genetic loci play a major role in regulating the development of the hepatic disease.

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Background:

Membrane-bound heparan sulphate proteoglycans (HSPGs) act as co-receptors and presenters of cytokines and are involved in cell–matrix and cell–cell adhesion.

Aim:

To investigate which HSPGs are expressed in knee joint synovia from patients with different forms of arthritis and normal individuals.

Methods:

Synovial samples were obtained from patients with early rheumatoid arthritis (n = 8), longstanding rheumatoid arthritis (n = 13), psoriatic arthritis (n = 7), osteoarthritis (n = 6) and normal joints (n = 12). Expression of syndecan-1, -2, -3 and -4 and glypican-1, -3 and -4 was analysed by immunohistochemistry and dual label immunofluorescence.

Results:

The expression of HSPGs in chronically inflamed synovium exhibited a differential distribution. Syndecan-1 was present in the mononuclear infiltrates of synovia from patients with rheumatoid and psoriatic arthritis where it was expressed by plasma cells. Syndecan-2 was present mainly in blood vessels where it occurred on endothelial cells, pericytes and smooth muscle cells. Syndecan-3 stained intensely in endothelial cells but also occurred in sublining macrophages and the lining layer. Glypican-4 occurred in the lining layer and blood vessels. Increased expression of these HSPGs was apparent in rheumatoid and psoriatic compared to osteoarthritic and normal synovia. Little or no staining for syndecan-4, glypican-1 and glypican-3 was seen in all samples.

Discussion:

Selected HSPGs, such as syndecan-1, -2 and -3 and glypican-4, could play a part in the pathophysiology of arthritis, such as the migration and retention of leukocytes and angiogenesis in the chronically inflamed synovium.

Euthymic LEW rats, when injected with streptococcal cell walls, exhibited rapid onset development of acute exudative arthritis coincident with enhanced synovial expression of Ia antigen. By 21 d after injection, the expression of Ia was markedly increased compared with basal conditions and paralleled the severity of the later developing proliferative and erosive disease. Immunodeficient athymic and cyclosporin A-treated LEW rats developed only the early phase arthritis, which was again paralleled by synovial Ia expression. Chronic expression of high levels of Ia antigen was not observed. Histocompatible F344 rats, both athymic and euthymic, developed minimal, if any, clinically significant arthritis and did not exhibit the enhanced Ia expression demonstrated in the LEW rats. Our results indicate that enhanced synovial Ia expression parallels clinical disease severity and varies by rat strain, and that the rapid onset enhanced synovial Ia expression is thymus independent, whereas the markedly enhanced chronic phase Ia expression is thymus dependent.

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Lewis rats are susceptible to several forms of experimental arthritis- induced using heat-killed Mycobacterium tuberculosis (adjuvant arthritis, or AA), streptococcal cell walls, collagen type II, and the lipoidal amine CP20961. Prior immunization with the mycobacterial 65-kD heat shock protein (hsp65) was reported to protect against AA, and other athritis models not using M. tuberculosis, via a T cell-mediated mechanism. Hsp65 shares 48% amino acid identity with mammalian hsp60, which is expressed at elevated levels in inflamed synovia. Several studies have reported cross-reactive T cell recognition of mycobacterial hsp65 and self hsp60 in arthritic and normal individuals. We previously described nine major histocompatibility complex class II- restricted epitopes in mycobacterial hsp65 recognized by Lewis rat T cells. Of these only one, covering the 256-270 sequence, primed for cross-reactive T cell responses to the corresponding region of rat hsp60. Here we have tested each hsp65 epitope for protective activity by immunizing rats with synthetic peptides. A peptide containing the 256-270 epitope, which induced cross-reactive T cells, was the only one able to confer protection against AA. Similarly, administration of a T cell line specific for this epitope protected against AA. Preimmunization with the 256-270 epitope induced T cells that responded to heat-shocked syngeneic antigen-presenting cells, and also protected against CP20961-induced arthritis, indicating that activation of T cells, recognizing an epitope in self hsp60 can protect against arthritis induced without mycobacteria. Therefore, in contrast to the accepted concept that cross-reactive T cell recognition of foreign and self antigens might induce aggressive autoimmune disease, we propose that cross-reactivity between bacterial and self hsp60 might also be used to maintain a protective self-reactive T cell population. This discovery might have important implications for understanding T cell- mediated regulation of inflammation.

Background

The use of TNF inhibitors has been a major progress in the treatment of chronic inflammation. However, not all patients respond. In addition, response will be often lost when treatment is stopped. These clinical aspects indicate that other cytokines might be involved and we focus here on the role of IL-17. In addition, the chronic nature of joint inflammation may contribute to reduced response and enhanced chronicity. Therefore we studied the capacity of IL-17 to regulate synoviolin, an E3 ubiquitin ligase implicated in synovial hyperplasia in human rheumatoid arthritis (RA) FLS and in chronic reactivated streptococcal cell wall (SCW)-induced arthritis.

Methodology/Principal Findings

Chronic reactivated SCW-induced arthritis was examined in IL-17R deficient and wild-type mice. Synoviolin expression was analysed by real-time RT-PCR, Western Blot or immunostaining in RA FLS and tissue, and p53 assessed by Western Blot. Apoptosis was detected by annexin V/propidium iodide staining, SS DNA apoptosis ELISA kit or TUNEL staining and proliferation by PCNA staining. IL-17 receptor A (IL-17RA), IL-17 receptor C (IL-17-RC) or synoviolin inhibition were achieved by small interfering RNA (siRNA) or neutralizing antibodies. IL-17 induced sustained synoviolin expression in RA FLS. Sodium nitroprusside (SNP)-induced RA FLS apoptosis was associated with reduced synoviolin expression and was rescued by IL-17 treatment with a corresponding increase in synoviolin expression. IL-17RC or IL-17RA RNA interference increased SNP-induced apoptosis, and decreased IL-17-induced synoviolin. IL-17 rescued RA FLS from apoptosis induced by synoviolin knockdown. IL-17 and TNF had additive effects on synoviolin expression and protection against apoptosis induced by synoviolin knowndown. In IL-17R deficient mice, a decrease in arthritis severity was characterized by increased synovial apoptosis, reduced proliferation and a marked reduction in synoviolin expression. A distinct absence of synoviolin expressing germinal centres in IL-17R deficient mice contrasted with synoviolin positive B cells and Th17 cells in synovial germinal centre-like structures.

Conclusion/Significance

IL-17 induction of synoviolin may contribute at least in part to RA chronicity by prolonging the survival of RA FLS and immune cells in germinal centre reactions. These results extend the role of IL-17 to synovial hyperplasia.

Exuberant tumor-like synovial cell proliferation with invasion of periarticular bone is a feature of rheumatoid arthritis in humans and of streptococcal cell wall (SCW)-induced arthritis in rats. These histologic observations prompted us to examine synoviocytes from arthritic joints for phenotypic characteristics of transformed cells. The capacity to grow in vitro under anchorage-independent conditions is a characteristic that correlates closely with potential in vivo tumorigenicity. In medium supplemented with 20% serum or in basal media supplemented with platelet-derived growth factor (PDGF), early passage synoviocytes from both SCW-induced and rheumatoid arthritic joints formed colonies in soft agarose. Epidermal growth factor (EGF), interleukin 1 (IL-1), tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), and transforming growth factor-beta (TGF-beta) did not support growth, although EGF enhanced PDGF-dependent growth. On the other hand, TGF-beta, as well as all-trans-retinoic acid, inhibited colony growth. Early passage normal rat and human synoviocytes also grew under the same conditions, but lung, skin, and late-gestation embryonic fibroblast-like cells did not. Considered in the context of other published data our findings provide cogent evidence that synoviocytes, but not other types of fibroblast-like cells, readily acquire phenotypic characteristics commonly associated with transformed cells. Expression of the transformed phenotype in the inflammatory site is likely regulated by paracrine growth factors, such as PDGF and TGF-beta.

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OBJECTIVE: To investigate the possibility that synovial cells might respond to thrombin in the inflamed human joint, using immunohistochemical detection of thrombin receptors. METHODS: Frozen sections of synovial membrane from 20 patients with rheumatoid arthritis, 16 with osteoarthritis, and four normal controls were stained using a monoclonal antibody to the human thrombin receptor. Sections were also double stained for both receptors and non-specific esterase. RESULTS: Receptor positive cells were present in rheumatoid synovia, with some cells also staining positively for non-specific esterase. In contrast, both osteoarthritic and normal synovia contained very few cells expressing receptors. CONCLUSIONS: Thrombin may mediate important pathological changes during chronic inflammatory joint disease.

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Rodent models of immune-mediated arthritis (RMIA) are the conventional approach to evaluating mechanisms of inflammatory joint disease and the comparative efficacy of antiarthritic agents. Rat adjuvant-induced (AIA), collagen-induced (CIA), and streptococcal cell wall-induced (SCW) arthritides are preferred models of the joint pathology that occurs in human rheumatoid arthritis (RA). Lesions of AIA are most severe and consistent; structural and immunological changes of CIA best resemble RA. Lesion extent and severity in RMIA depends on experimental methodology (inciting agent, adjuvant, etc.) and individual physiologic parameters (age, genetics, hormonal status, etc.). The effectiveness of antiarthritic molecules varies with the agent, therapeutic regimen, and choice of RMIA. All RMIA are driven by overactivity of proinflammatory pathways, but the dominant molecules differ among the models. Hence, as with the human clinical experience, the efficacy of various antiarthritic molecules differs among RMIA, especially when the agent is a specific cytokine inhibitor.

Introduction

Experimental streptococcal cell wall (SCW)-induced arthritis is characterized by two successive phases of the disease. The acute phase occurs early and is associated with an inflammatory process and neutrophil infiltration into the synovium. The second chronic phase is related to effector T-cell activation and the dysregulation of macrophage function. Creation of an immunomodulatory environment has been attributed to apoptotic cells themselves, apoptotic cell uptake by phagocytes as well as a less sensibility of phagocytes capturing apoptotic bodies to activation. Therefore we evaluated the potential of apoptotic cell injection to influence the course of inflammation in SCW-induced arthritis in rats.

Methods

Rat apoptotic thymocytes were injected intraperitoneally (2 × 108) in addition to an arthritogenic dose of systemic SCW in LEW female rats. Control rats received SCW immunization and PBS. Rats were then followed for arthritis occurrence and circulating cytokine detection. At sacrifice, regulatory T cells (Tregs) and macrophages were analyzed.

Results

Apoptotic cell injection profoundly suppressed joint swelling and destruction typically observed during the acute and chronic phases of SCW-induced arthritis. Synovial inflammatory cell infiltration and bone destruction were also markedly suppressed. Ex vivo experiments revealed reduced levels of TNF in cultures of macrophages from rats challenged with SCW in the presence of apoptotic thymocytes as well as reduced macrophage response to lipopolysaccharide. Moreover, apoptotic cell injection induced higher Foxp3+ Tregs in the lymphoid organs, especially in the draining lymph nodes.

Conclusions

Our data indicate that apoptotic cells modulate macrophage function and result in Treg generation/increase. This may be involved in inhibition of inflammation and amelioration of arthritis. This highlights and confirms previous studies showing that in vivo generation of Tregs using apoptotic cell injection may be a useful tool to prevent and treat inflammatory autoimmune responses.

The quantity of streptococcal cell wall localized in the joints of rats of strains which are either susceptible (Sprague-Dawley, LEW/N, M520/N) or resistant (Buffalo, WKY/N, F344/N) to cell wall-induced chronic erosive arthritis was measured after intraperitoneal injection of group A streptococcal cell wall fragments. Susceptibility or resistance was not associated with a difference in the amount of cell wall localized in limbs or other tissues. It is concluded that although localization of cell wall in joint tissue is essential for development of arthritis, the relative resistance of certain rat strains reflects genetic regulation of inflammatory response rather than a quantitative difference in localization of cell wall in joints.

OBJECTIVE—To investigate in situ the expression of the integrin receptor subunits α6 and β1 and the distribution of the ligand laminin in the synovia from osteoarthritis (OA) and rheumatoid arthritis (RA) patients and to study the effect of cytokines and antirheumatic drugs on the expression of the α6 and β1 integrin subunits on long term cultures of fibroblast-like synoviocytes (FBS) derived from OA and RA.
METHODS—The expression of the α6 and β1 integrin subunits and the distribution of laminin were examined immunohistochemically in normal synovia and in synovia from patients with OA and RA. The effect of proinflammatory cytokines (IL1β and TNFα), and of antirheumatic drugs (salicylic acid, dexamethasone, and methotrexate) on the α6 and β1 expression of cultured normal FBS and FBS from patients with OA and RA was determined by flow cytometry.
RESULTS—In normal synovia and in OA synovia samples with a low grade of inflammation, synovial lining cells (SLC) showed a parallel expression and distribution of α6 and laminin. In synovia samples of OA with a higher grade of inflammation and in the majority of RA synovia samples laminin was pericellularly distributed in a low number of SLC, whereas α6 was expressed on the surface of a high number of SLC. In RA synovia samples with severe inflammatory changes the gradual loss of laminin generally corresponded to a decrease of the α6 integrin subunit. β1 was always strongly expressed in all synovia samples detected. Proinflammatory cytokines up regulated the expression of α6 and β1 on OA-FBS, whereas these effectors decreased α6 and β1 on RA-FBS. In contrast, antirheumatic drugs, in particular methotrexate and dexamethasone, reduced the expression of α6 and β1 on OA-FBS, whereas the same treatment on RA-FBS stimulated the expression of these integrin subunits.
CONCLUSION—The gradual loss of laminin in chronic synovitis may contribute to the altered expression of α6 in SLC. IL1β and TNFα down regulated the expression of the α6 and β1 integrin subunits on long term cultures of FBS derived from RA. Therefore, these cytokines may be among the effectors regulating the expression of the α6 integrin subunit in SLC in vivo. As antirheumatic drugs increase the expression of α6 on RA-FBS, the presence of the laminin receptor may confer a protective effect on the synovia in vivo.

 Keywords: laminin; alpha 6; integrins; rheumatoid arthritis; osteoarthritis

The anti-inflammatory effect of adenosine was previously found to be mediated via activation of the A3 adenosine receptor (A3AR). The aim of the present study was to decipher the molecular mechanism involved with the inhibitory effect of IB-MECA, an A3AR agonist, on adjuvant-induced arthritis.

The adjuvant-induced arthritis rats responded to IB-MECA treatment with a decrease in the clinical score and the pathological score of the disease. The response to IB-MECA was neutralized by the antagonist MRS 1220, confirming that the efficacy of the synthetic agonist was A3AR mediated.

The A3AR protein expression level was highly expressed in the synovia, in the peripheral blood mononuclear cells and in the drain lymph node (DLN) tissues of adjuvant-induced arthritis rats in comparison with naïve animals. Downregulation of A3AR expression was noted upon treatment with IB-MECA. Analysis of synovia and DLN protein extracts revealed a decreased expression level of PI3K, PKB/Akt, IKK, NF-κB and tumor necrosis factor alpha, known to affect survival and apoptosis of inflammatory cells, whereas the caspase-3 level was upregulated.

Taken together, high A3AR expression is found in the synovia, in the immune cells in the DLN and in peripheral blood mononuclear cells. IB-MECA, an orally bioavailable molecule, activates the A3AR, inducing receptor downregulation and the initiation of a molecular mechanism that involves de-regulation of the PI3K–NF-κB signaling pathway. As a result, a potent anti-inflammatory effect manifested in the improvement of the disease clinical score and pathological score occurs. The finding that the A3AR expression level in the peripheral blood mononuclear cells and in the DLN reflects the receptor status in the remote inflammatory site suggests use of the A3AR as a follow-up biomarker.

Hyaluronan is a major molecule in joint fluid and plays a crucial role in joint motion and the maintenance of joint homeostasis. The concentration and average molecular weight of hyaluronan in the joint fluids are reduced in osteoarthritis and rheumatoid arthritis. To elucidate the underlying mechanism, we analyzed the message expression of three isoforms of hyaluronan synthase and hyaluronidase from knee synovium, using real-time reverse transcriptase polymerase chain reaction. Synovia were obtained from 17 patients with osteoarthritis, 14 patients with rheumatoid arthritis, and 20 healthy control donors. The message expression of hyaluronan synthase-1 and -2 in the synovium of both types of arthritis was significantly less than in the control synovium, whereas that of hyaluronidase-2 in the synovium of both arthritides was significantly greater than in the control synovium. The decreased expression of the messages for hyaluronan synthase-1 and -2 and/or the increased expression of the message for hyaluronidase-2 may be reflected in the reduced concentration and decreased average molecular weight of hyaluronan in the joint fluids of patients with osteoarthritis and rheumatoid arthritis.

Inhibition of histone deacetylases (HDAC) has been shown to modulate gene expression and cytokine production after stimulation with several stimuli. In the present study, the antiinflammatory effect of a potent HDACi, ITF2357, was explored in different experimental models of arthritis. In addition, the bone protective effect of ITF2357 was investigated in vitro. Treatment of acute arthritis (Streptococcus pyogenes cell wall [SCW] arthritis) with ITF2357 showed that joint swelling and cell influx into the joint cavity were reduced. Furthermore, the chondrocyte metabolic function was improved by treatment of ITF2357. The production of proinflammatory cytokines by synovial tissue was reduced after ITF2357 treatment. To examine the effect of HDAC inhibition on joint destruction, ITF2357 was applied to both rat adjuvant arthritis and mouse collagen type II arthritis. ITF2357 treatment both ameliorates the severity scores in arthritis models and prevents bone destruction. In an in vitro bone destruction assay, ITF2357 was highly effective at a dose of 100 nmol/L. In conclusion, inhibition of HDAC prevents joint inflammation and cartilage and bone destruction in experimental arthritis.

OBJECTIVE—The goal of this study was to investigate the role of endogenous interleukin 12 (IL12) in acute murine streptococcal cell wall (SCW) arthritis.
METHODS—C57black/6 mice were injected intraperitoneally with rat anti-murine IL12 (C17.8), shortly before induction of arthritis by intra-articular injection of 25 µg SCW fragments into the right knee joint. Joint swelling and chondrocyte synthetic function was analysed several days after induction of SCW arthritis. Local cytokine profile was determined, protein by using ELISA and mRNA by RT-PCR technology. To confirm the findings at later time points, tissue chamber model of inflammation was used. Histology was performed to examine cell influx and cartilage damage.
RESULTS—Suppression of joint swelling was noted at days 2 and 4, whereas no suppressive effect of anti-IL12 was found at day 1. Severe inhibition of chondrocyte proteoglycan synthesis was seen at day 1 in both arthritic control and anti-IL12 treated mice. However, chondrocyte function was restored at day 4 of arthritis in the anti-IL12 injected animals, but not in the arthritic controls. Moreover, cell influx in synovial tissue and joint cavity was reduced by anti-IL12 treatment. Neutralisation of IL12 reduced the local levels of IL1β, IL12 and interferon γ, when examined shortly after induction of SCW arthritis, whereas tumour necrosis factor α levels were not affected. In contrast, IL10 and IL1Ra protein and mRNA levels were strongly up regulated in synovial tissues after IL12 blockade. Enhancement of IL10 and IL1Ra by anti-IL12 was confirmed in a tissue chamber model with SCW induced inflammation.
CONCLUSIONS—This study indicates that IL12 is a pro-inflammatory cytokine during onset of acute SCW arthritis. Balances of proinflammatory and anti-inflammatory cytokines were strongly improved by anti-IL12 treatment.



Turmeric (Curcuma longa L., Zingiberaceae) rhizomes contain two classes of secondary metabolites, curcuminoids and the less well-studied essential oils. Having previously identified potent anti-arthritic effects of the curcuminoids in turmeric extracts in an animal model of rheumatoid arthritis (RA), studies were undertaken to determine whether the turmeric essential oils (TEO) were also joint protective using the same experimental model. Crude or refined TEO extracts dramatically inhibited joint swelling (90-100% inhibition) in female rats with streptococcal cell wall (SCW)-induced arthritis when extracts were administered via intraperitoneal injection to maximize uniform delivery. However, this anti-arthritic effect was accompanied by significant morbidity and mortality. Oral administration of a 20-fold higher dose TEO was non-toxic, but only mildly joint-protective (20% inhibition). These results do not support the isolated use of TEO for arthritis treatment, but, instead, identify potential safety concerns in vertebrates exposed to TEO.

OBJECTIVE--To assess the likely importance of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) in the arthritic process. METHODS--Synovial samples from seven joints with rheumatoid arthritis and three osteoarthritic joints were analysed by indirect immunofluorescence microscopy. Using specific human antisera, we documented the frequencies and distributions of collagenase, stromelysins 1 and 2, matrilysin, gelatinases A and B, TIMP-1, and TIMP-2. RESULTS--Stromelysin 1 was found in all synovia, bound to extracellular matrix, within cells, or both, indicating stromelysin synthesis. Matrilysin was present in only one active inflammatory synovium, and focal synthesis of collagenase and gelatinase A was seen in four synovia. Stromelysin 2 and TIMP-2 were not observed, but TIMP-1 synthesis was seen in five synovia, and in two active synovia the distribution of TIMP-1 positive cells was more widespread than that of MMPs. CONCLUSIONS--The presence of stromelysin 1 in all synovia clearly implicates this enzyme in joint damage. Collagenase, gelatinase A and matrilysin may also have a role in rheumatoid arthritis, but are not significant in osteoarthritis. However, marked regional variations were found in the synthesis of these MMPs, indicating not only that these diseases are episodic but that control of enzyme synthesis is focal. Only TIMP-1 may be considered an inhibitory factor.

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The influx of cells into the synovial intima in rheumatoid joints may include osteoclasts and their precursors. The distribution of osteoclast markers--namely, tartrate resistant acid phosphatase activity and the expression of vitronectin receptor (shown with monoclonal antibodies 13C2 and 23C6)--was therefore examined in synovium obtained from patients with rheumatoid (RA) or degenerative (OA) arthritis. Tartrate resistant acid phosphatase positive cells were found in frozen sections of 60% (n = 30) of RA and 69% (n = 29) of OA synovial membranes. Whereas all synovia tested (four RA, four OA) showed diffuse staining of the lining cells with 13C2, 55% (n = 11) of RA and 57% (n = 14) of OA synovial membranes contained isolated cells stained with 23C6 scattered throughout the tissue. In cultures of synovial cells, tartrate resistant acid phosphatase positive, multinuclear, and 23C6 positive cells were found; these cells did not, however, form resorption pits on bone slices. The results show that fully differentiated osteoclasts are uncommon in synovium from patients with either degenerative or inflammatory arthropathies.

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