Acceleration of onset of collagen-induced arthritis by intra-articular injection of tumour necrosis factor or transforming growth factor-beta

Iguratimod inhibits osteoclastogenesis by modulating the RANKL and TNF-α signaling pathways

BACKGROUND

Iguratimod, a small molecular drug, has been proven to have effective bone protection for treatment of patients with bone loss-related diseases, such as rheumatoid arthritis (RA). However, the exact bone protective mechanism of iguratimod remains to be determined. The purpose of this study was to better explore the underlying mechanism of bone protection of iguratimod.

METHODS

Bone marrow monocytes from C57/BL6 mice were stimulated with either RANKL or TNF-α plus M-CSF. The effects of iguratimod on morphology and function of osteoclasts were confirmed by TRAP staining and bone resorption assay, respectively. The expression of osteoclast related genes was detected by RT-PCR and the activation of signal pathway was detected by Western blotting. We used rodent models of osteoporosis (ovariectomy) and of arthritis (modified TNF-α-induced osteoclastogenesis) to evaluate the osteoprotective effect of iguratimod in vivo.

RESULTS

Iguratimod potently inhibited osteoclast formation in a dose-dependent manner at the early stage of RANKL-induced osteoclastogenesis, whereas iguratimod had no effect on M-CSF-induced proliferation and RANK expression in bone marrow monocytes. Bone resorption was significantly reduced by both early and late addition of iguratimod. Administration of iguratimod prevented bone loss in ovariectomized mice. The blockage of osteoclastogenesis elicited by iguratimod results from abrogation of the p38、ERK and NF-κB pathways induced by RANKL. Importantly, Iguratimod also dampened TNF-α-induced osteoclastogenesis in vitro and attenuated osteoclasts generation in vivo through disrupting NF-κB late nuclear translocation without interfering with IκBα degradation.

CONCLUSIONS

Iguratimod not only suppresses osteoclastogenesis by interfering with RANKL and TNF-α signals, but also inhibits the bone resorption of mature osteoclasts. These results provided promising evidence for the therapeutic application of iguratimod as a unique treatment option against RA and especially in prevention of bone loss.

Selective inhibition of tropomyosin-receptor-kinase A (TrkA) reduces pain and joint damage in two rat models of inflammatory arthritis

BACKGROUND

Inflammation is an essential component of arthritis pain. Nerve growth factor (NGF) plays a key role in acute and chronic pain states especially those associated with inflammation. NGF acts through tropomyosin-receptor-kinase A (TrkA). NGF blockade has reduced arthritis pain in clinical trials. We explored the mechanisms within the joint which may contribute to the analgesic effects of NGF by selectively inhibiting TrkA in carrageenan-induced or collagen-induced joint pain behaviour. The goal of the current study was to elucidate whether inflammation is central to the efficacy for NGF blockade.

METHODS

Rats were injected in their left knees with 2 % carrageenan or saline. Collagen-induced arthritis (CIA) was induced by intradermal injections of a mixture of bovine type II collagen (0.2 mg) and incomplete Freund's adjuvant (0.2 mg). Oral doses (30 mg/kg) of AR786 or vehicle control were given twice daily after arthritis induction. Ibuprofen-treated (35 mg/kg, orally, once daily) rats with CIA were used as positive analgesic controls. Pain behaviour was measured as hind-limb weight-bearing asymmetry and hind-paw withdrawal thresholds to von Frey hair stimulation (carrageenan synovitis), or withdrawal to joint compression using a Randall Selitto device (CIA). Inflammation was measured as increased knee joint diameter and by histopathological analysis.

RESULTS

Intra-articular injections of carrageenan or induction of CIA was each associated with pain behaviour and synovial inflammation. Systemic administration of the TrkA inhibitor AR786 reduced carrageenan-induced or CIA-induced pain behaviour to control values, and inhibited joint swelling and histological evidence of synovial inflammation and joint damage.

CONCLUSIONS

By using two models of varying inflammation we demonstrate for the first time that selective inhibition of TrkA may reduce carrageenan-induced or CIA-induced pain behaviour in rats, in part through potentially inhibiting synovial inflammation, although direct effects on sensory nerves are also likely. Our observations suggest that inflammatory arthritis causes pain and the presence of inflammation is fundamental to the beneficial effects (reduction in pain and pathology) of NGF blockade. Further research should determine whether TrkA inhibition may ameliorate human inflammatory arthritis.

Preventive Effect of a Novel Recombinant sTNFRII on Collagen-Induced Arthritis

We developed a novel trimeric sTNFRII fusion protein, named sTNFRII-gAD, which exhibited a higher in vitro antagonistic efficacy for TNFα in comparison with sTNFRII-Fc. This study aimed to investigate the arthritic protection of sTNFRII-gAD in a rat collagen-induced arthritis (CIA). The rats were injected intradermally with collagen type II at days 0 and 7. Three days after the second injection (day 10), the rats were intraperitoneally given sTNFRII-gAD or sTNFRII-Fc, or PBS. Effects of treatments were examined with respect of CIA incidence, severity and pathological changes. Serum TNFα, IL-17A and regulatory T cell (Treg) in periphery were determined at days 10 and 16, respectively. Our results showed that sTNFRIIgAD significantly reduced CIA incidence and severity (p < 0.05); meanwhile it led to a dramatic improvement in cartilage and bone damage. Moreover, the increase in serum anti-CII and IL-17A, and the reduction in Treg population were inhibited (p < 0.05) by sTNFRII-gAD or sTNFRII-Fc. Serum TNFα was found to be accumulated in the groups treated with sTNFRII-gAD or sTNFRII-Fc compared with the group treated with PBS (p < 0.05). It is noteworthy that sTNFRII-gAD displayed a better efficacy than sTNFRII-Fc in CIA incidence, pathological changes in cartilage and the elevation of anti-CII antibody, indicating that sTNFRII-gAD is potentially a more efficacious anti-TNFα agent for rheumatoid arthritis.

Interplay among cytokines and T cell subsets in the progression and control of immune-mediated diseases

Cytokines serve as key mediators of inflammation and tissue damage in a variety of immune-mediated disorders. The induction, progression, and resolution of inflammation in such disorders are characterized by a dynamic balance between both the pro-inflammatory and anti-inflammatory cytokines as well as the pathogenic and protective T cell subsets. Over the past two decades, the roles of the interleukin-17 (IL-17) /IL-23 axis and the T helper 17 (Th17)/ T regulatory (Treg) cell balance in the pathogenesis of autoimmunity and other inflammatory diseases have extensively been analyzed, and their significance validated. However, these studies, coupled with others devoted to well-established Th1/Th2 cytokines, have unraveled some challenging issues including the dual action of cytokines and the plasticity of T cell subsets. Nevertheless, major positive advances have also been made regarding cytokines and T cell subsets as therapeutic targets/agents. In this special issue, "Cytokines in Immune Pathology and Therapy," leading experts have shared their research work and perspectives on the roles of cytokines in the development and control of immune-mediated diseases. An outline of 14 articles in the first volume is presented here. The second volume will follow soon.

Lipopolysaccharide accelerates collagen-induced arthritis in association with rapid and continuous production of inflammatory mediators and anti-type II collagen antibody

Collagen-induced arthritis (CIA) is an animal model for rheumatoid arthritis (RA). Lipopolysaccharide (LPS) is known to accelerate CIA; however, the pathogenetic mechanisms are not yet fully understood. In this study, type II collagen (CII)-immunized mice were found to have marked increases in degree of expression of mRNA of inflammatory mediators such as tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and macrophage inflammatory protein-2 (MIP-2) in their arthritic paws and of serum anti-CII antibody concentration before the onset of arthritis induced by LPS injection. The gene expression was rapid and continuous after direct activation of nuclear factor κB. The amounts of mRNA of TNF-α, IL-1β, and MIP-2, as well as of matrix metalloproteinases and the receptor activator of nuclear factor κB ligand, increased with the development of arthritis, correlated positively with clinical severity and corresponded with histopathological changes. Moreover, anti-TNF-α neutralizing antibody inhibited the development of LPS-accelerated CIA and a single injection of recombinant mouse TNF-α induced increases in anti-CII antibody concentrations, suggesting TNF-α may contribute to the development of arthritis by both initiation of inflammation and production of autoantibodies. These data suggest that exacerbation of RA by LPS is associated with rapid and continuous production of inflammatory mediators and autoantibodies.

The pharmacology study of a new recombinant TNF receptor-hyFc fusion protein

TNF-α-blocking agents such as infliximab, adalimumab and etanercept are widely used for the treatment of severe inflammatory diseases including rheumatoid arthritis and psoriasis. The currently used TNF-α blockers have Fc regions of the human IgG1 subtype, which is advantageous in terms of in vivo half-life but also raise the potential for unwanted effector-mediated effects, such as antibody dependent cellular cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC). To address this issue, we constructed a novel hybrid protein by fusing the TNF receptor (TNFR) with a hybrid Fc (hyFc) consisting of the CH2 and CH3 regions of IgG4 and the highly flexible hinge regions of IgD which would not have ADCC and CDC activity. The resulting fusion protein, TNFR-hyFc, was over-expressed in CHO and pharmacological characteristics were evaluated in comparison with the structurally similar etanercept. TNFR-hyFc effectively neutralized TNF-α in L929 bioassay and showed a 1.5-fold higher neutralizing activity compared to etanercept. In a pharmacokinetic study in cynomolgus monkeys, TNFR-hyFc showed plasma half-life and AUC comparable to etanercept. In a mouse collagen induced arthritis model, TNFR-hyFc showed significant amelioration of arthritis compared to etanercept or vehicle control. In an LPS-induced septic shock model, TNFR-hyFc showed a similar level of protection against mortality as etanercept. These results confirm the feasibility of the TNFR-hyFc as an effective TNF-α blocker for the treatment of inflammatory diseases.

Apoptosis as a mechanism of action of tumor necrosis factor antagonists in rheumatoid arthritis

Tumor necrosis factor (TNF) antagonists are drugs developed to block endogenous TNF, an essential proinflammatory molecule with a central role in the pathogenesis of rheumatoid arthritis (RA). Although extensive studies have been performed concerning the mode of action of TNF-blocking agents, there are still many unresolved questions and potential differences between different TNF-blocking drugs. One unresolved issue is to what extent apoptosis is affected by TNF blockade in RA. We provide an overview of studies that have investigated the proapoptotic effect of different anti-TNF drugs in RA, searching for a unified interpretation of somewhat contradictory data.

Cytokines in autoimmunity: role in induction, regulation, and treatment

Cytokines play a pivotal role in the pathogenesis of autoimmune diseases. The precise triggers for the breakdown of self-tolerance and the subsequent events leading to the induction of pathogenic autoimmune responses remain to be defined for most of the naturally occurring autoimmune diseases. Studies conducted in experimental models of human autoimmune diseases and observations in patients have revealed a general scheme in which proinflammatory cytokines contribute to the initiation and propagation of autoimmune inflammation, whereas anti-inflammatory cytokines facilitate the regression of inflammation and recovery from acute phase of the disease. This idea is embodied in the T helper (Th) 1/Th2 paradigm, which over the past two decades has had a major influence on our thinking about the role of cytokines in autoimmunity. Interestingly, over the past decade, the interleukin (IL)-17/IL-23 axis has rapidly emerged as the new paradigm that has compelled us to critically re-examine the cytokine-driven immune events in the pathogenesis and treatment of autoimmunity. In this 2-volume special issue of the journal, leading experts have presented their research findings and viewpoints on the role of cytokines in the context of specific autoimmune diseases.

The role of T helper type 17 cells in inflammatory arthritis

While T cells have been implicated in the pathogenesis of inflammatory arthritis for more than three decades, the focus on the T helper type 17 (Th17) subset of CD4 T cells and their secreted cytokines, such as interleukin (IL)-17, is much more recent. Proinflammatory actions of IL-17 were first identified in the 1990s, but the delineation of a distinct Th17 subset in late 2005 has sparked great interest in the role of these cells in a broad range of immune-mediated diseases. This review summarizes current understanding of the role of Th17 cells and their products in both animal models of inflammatory arthritis and human immune-driven arthritides.

Treatment of adjuvant arthritis using microencapsulated antisense NF-κB oligonucleotides

Antisense oligonucleotides are promising new therapeutic agents used to selectively inhibit target genes such as Nuclear Factor Kappa B (NF-κB), an important transcription factor in the pathogenesis of inflammatory disease. The purpose of the present study was to evaluate microencapsulated antisense oligonucleotides specific to NF-κB for in vitro efficacy and treatment of adjuvant-induced arthritis in rats. Oligonucleotide-loaded albumin microspheres were prepared and characterized in terms of size, zeta potential, morphology and release pattern. This study reports significant NF-κB inhibition in vitro after treatment with microencapsulated antisense oligonucleotides. Furthermore, microencapsulated antisense NF-κB oligonucleotides were found to inhibit paw inflammation associated with rat adjuvant-induced arthritis in a dose-dependent manner. Taken together, the results presented in this work described albumin microspheres to be effective delivery vehicles for antisense NF-κB oligonucleotides and a potential treatment for inflammatory diseases.

Immunomodulation of murine collagen-induced arthritis by N, N-dimethylglycine and a preparation of Perna canaliculus

Background

Rheumatoid arthritis (RA) and its accepted animal model, murine collagen-induced arthritis (CIA), are classic autoimmune inflammatory diseases which require proinflammatory cytokine production for pathogenesis. We and others have previously used N, N-dimethylglycine (DMG) and extracts from the New Zealand green-lipped mussel Perna canaliculus (Perna) as potent immunomodulators to modify ongoing immune and/or inflammatory responses.

Methods

In our initial studies, we treated lipopolysaccahride (LPS) stimulated THP-1 monocytes in vitro with increasing concentrations of Perna extract or DMG. Additionally, we treated rat peripheral blood neutrophils with increasing concentrations of Perna extract and measured superoxide burst. In subsequent in vivo experiments, CIA was induced by administration of type II collagen; rats were prophylactically treated with either Perna or DMG, and then followed for disease severity. Finally, to test whether Perna and/or DMG could block or inhibit an ongoing pathologic disease process, we induced CIA in mice and treated them therapeutically with either of the two immunomodulators.

Results

Following LPS stimulation of THP-1 monocytes, we observed dose-dependent reductions in TNF-α and IL-12p40 production in Perna treated cultures. DMG treatment, however, showed significant increases in both of these cytokines in the range of 0.001–1 μM. We also demonstrate that in vitro neutrophil superoxide burst activity is dose-dependently reduced in the presence of Perna. Significant reductions in disease incidence, onset, and severity of CIA in rats were noted following prophylactic treatment with either of the two immunomodulators. More importantly, amelioration of mouse CIA was observed following therapeutic administration of Perna. In contrast, DMG appeared to have little effect in mice and may act in a species-specific manner.

Conclusion

These data suggest that Perna, and perhaps DMG, may be useful supplements to the treatment of RA in humans.

Prevention of collagen-induced arthritis in mice by Cervus korean TEMMINCK var. mantchuricus Swinhoe

The effect of water extract of deer antler (DAA) prepared from the pilose antler of Cervus korean TEMMINCK var. mantchuricus Swinhoe (Nokyong) on collagen-induced mouse rheumatoid arthritis (RA) model was studied. Identification of common DAA capable of affording protection or modulating the onset and severity of arthritis may have important human health implications. DAA has been shown to possess anti-inflammatory and anti-carcinogenic properties in experimental animals. In this study, we determined the effect of DAA-injection on collagen-induced arthritis in mice. In three independent experiments, mice given DAA in water exhibited significantly reduced incidence of arthritis (30-45%) as compared with mice not given DAA in water (86-98%). The arthritis index also was significantly lower in DAA-injected animals. Western blot analysis showed a marked reduction in the expression of inflammatory mediators such as cyclooxygenase 2, IFN-γ, and tumor necrosis factor α in arthritic joints of DAA-injected mice. The neutral endopeptidase activity was approximately six-fold higher in arthritic joints of non-DAA-injected mice in comparison to non-arthritic joints of unimmunized mice, whereas it was only two-fold higher in the arthritic joints of DAA-injected mice. Additionally, total IgG and type II collagen-specific IgG levels were lower in serum and arthritic joints of DAA-injected mice. Taken together our studies suggest that DAA may be useful in the prevention of onset and severity of arthritis.

Activation of the peroxisome proliferator–activated receptor α pathway potentiates interleukin-1 receptor antagonist production in cytokine-treated chondrocytes

OBJECTIVE

To determine whether peroxisome proliferator-activated receptor alpha (PPARalpha) agonists protect chondrocytes against the effects of interleukin-1beta (IL-1beta).

METHODS

PPARalpha expression and function in cultured rabbit articular chondrocytes were studied by Northern blotting, electrophoretic mobility shift assay, and transient expression of a luciferase reporter construct bearing the human IL-1 receptor antagonist (Il-1Ra) gene promoter. Chondrocytes were incubated in vitro with IL-1beta alone or in combination with CloFibrate (CloF) or other PPAR ligands. Proteoglycans were evaluated by 35S-sulfate incorporation, matrix metalloproteinase (MMP) levels were assessed by zymography and enzyme-linked immunosorbent assay (ELISA), and MMP messenger RNA (mRNA) levels were measured by Northern blotting and real-time reverse transcriptase-polymerase chain reaction. IL-1beta and IL-1Ra soluble contents were measured by ELISA.

RESULTS

CloF counteracted IL-1beta-induced 35S-proteoglycan degradation, gelatinolytic activity, and MMP-1, -3, and -13 mRNA expression. CloF also maximized IL-1beta-induced endogenous production of soluble IL-1Ra (sIL-1Ra). This stimulating effect on IL-1Ra gene expression was shown, by transient expression assay, to be transcriptional. Inhibition of sIL-1Ra expression by a specific small interfering RNA suppressed the effect of CloF on IL-1beta-induced MMP expression. The stimulatory effect of CloF was enhanced by cotransfection with wild-type PPARalpha and abolished by a dominant-negative PPARalpha mutant. Fenofibrate and WY-14643 displayed a similar stimulating effect on the IL-1Ra promoter, while rosiglitazone did not. Two PPAR response elements, an NF-kappaB-binding site, and a CCAAT/enhancer binding protein-binding site were identified in the IL-1Ra promoter. All 4 sites were necessary for mediation of the effects of CloF.

CONCLUSION

Our findings support the notion that there is a PPARalpha-dependent mechanism that inhibits IL-1beta function in chondrocytes, which operates via an increase in sIL-1Ra production.

Adalimumab: an anti-TNF agent for the treatment of psoriatic arthritis

Tumour necrosis factor (TNF) has a central role in the pathogenesis of psoriatic arthritis (PsA). Adalimumab (Humira, Abbott Laboratories) is the first fully human, recombinant IgG1 monoclonal antibody that specifically targets human TNF. Adalimumab blocks the interaction of TNF with the p55 and p75 cell surface TNF receptors, thereby neutralising the activity of this cytokine. In clinical trials of patients with PsA, adalimumab significantly reduced both joint and skin symptoms. In addition, structural changes were inhibited, and statistically and clinically significant improvements in measures of disability and quality of life were observed. Adalimumab was generally safe and well tolerated.

Latent TGF-β1-transduced CD4+T cells suppress the progression of allergic encephalomyelitis

Systemic injection of small amounts of transforming growth factor-beta (TGF-beta), a cytokine produced by lymphoid and other cells, has a profound effect in protecting mice from the inflammatory demyelinating lesions of experimental allergic encephalomyelitis (EAE; an animal model for multiple sclerosis). However, TGF-beta has side-effects, which might be avoided if the cells producing TGF-beta can be delivered to the affected site in the nervous system to insure its local release in small amounts. Myelin basic protein (MBP)-specific, cloned CD4+ T cells were engineered by retroviral transduction to produce latent TGF-beta. Studies about the spontaneous form of EAE in T cell receptor (TCR)-transgenic recombination-activating gene (RAG)-1(-/-) mice showed that essentially all of the MBP-specific, TCR-transgenic RAG-1(-/-) (BALB/cxB10.PL)F1 mice develop spontaneous EAE by the age of 11 weeks. By 12 weeks, 25-50% of the mice have died from disease. A single injection of TGF-beta1-transduced T helper cell type 1 (Th1) cells significantly protected the mice from EAE, and untransduced Th1 cells did not protect. MBP-specific BALB/c Th2 clones, transduced with TGF-beta1-internal ribosome entry site-green fluorescent protein (GFP) significantly reduced EAE induction by untransduced Th1 cells in RAG-1(-/-) B10.PL mice. Furthermore, the GFP+ TGF-beta1-producing Th2 cells were detectable in the spinal cords of the injected mice.

Diagnosis and treatment of psoriatic arthritis

Psoriatic arthritis is a chronic, heterogeneous disease whose pathogenesis is unknown, although genetic, environmental, and immunologic factors play major roles. Psoriatic arthritis can follow an aggressive clinical course, and differentiating it from other arthropathies is sometimes difficult. Diagnosis of psoriatic arthritis is based on history, physical examination, the usual absence of rheumatoid factor, and characteristic radiographic features. At least 40% of patients with psoriatic arthritis develop radiographically detectable joint destruction; therefore, proper diagnosis and early treatment can have a significant impact on disease course and outcome. Understanding the pathogenesis of psoriatic disease has led to the use of several biologic agents that work by modulating T-cell signaling or by inhibiting key cytokines involved in inflammation, such as tumor necrosis factor (TNF). TNF inhibitors have demonstrated excellent efficacy in resolving skin and joint disease in patients with psoriatic arthritis and have been shown to be safe agents in various inflammatory disorders. This article reviews the diagnostic and treatment challenges of psoriatic arthritis as they relate to pathogenesis and burden of disease.

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should have acquired a more comprehensive knowledge of our current understanding of the classification, clinical presentation, etiology, pathophysiology, differential diagnosis, and treatment of psoriatic arthritis.

Thrombospondin 1 as an effective gene therapeutic strategy in collagen-induced arthritis

OBJECTIVE

Because thrombospondin 1 (TSP-1) inhibits angiogenesis and activates latent transforming growth factor beta (TGFbeta), a potent immunosuppressive and antiinflammatory cytokine, we investigated the prophylactic and therapeutic effects of TSP-1 gene transfer in the collagen-induced arthritis (CIA) model in rats.

METHODS

Adenoviral vectors encoding mouse TSP-1 (AdTSP-1) or beta-galactosidase (AdLacZ) as the control were administered by intraarticular injection into CIA rats. The treated ankles were assessed clinically, radiographically, and histologically. Furthermore, expression levels of TSP-1, TGFbeta, vascular endothelial growth factor (VEGF), and interleukin-1beta (IL-1beta) were examined in the synovial tissue.

RESULTS

Intraarticular administration of AdTSP-1 reduced the severity of CIA as revealed by examination of the clinical, radiographic, and histologic aspects. Rats treated with AdTSP-1, as compared with AdLacZ-treated controls, were found to have fewer blood vessels (mean +/- SEM 21.0 +/- 0.6 versus 45.3 +/- 2.3/mm(2); P < 0.001) and lower production of VEGF (17 +/- 4 versus 45 +/- 10 pg/mg of total protein; P < 0.05) and IL-1beta (374 +/- 41 versus 526 +/- 39 pg/mg of total protein; P < 0.05), as well as higher levels of TSP-1 and TGFbeta in the synovial tissue.

CONCLUSION

Direct intraarticular administration of adenoviral vectors encoding TSP-1 significantly ameliorated the clinical course of CIA, accompanied by reduction of synovial hypertrophy and fewer blood vessels. These results suggest that TSP-1 gene therapy may have therapeutic potential for the management of rheumatoid arthritis.

Peroxisome Proliferator-activated Receptor-γ Down-regulates Chondrocyte Matrix Metalloproteinase-1 via a Novel Composite Element

Interleukin-1beta (IL-1beta) induces degradation via hyperexpression of an array of genes, including metalloproteinases (MMP), in cartilage cells during articular degenerative diseases. In contrast, natural ligands for peroxisome proliferator-activated receptors (PPARs) display protective anti-cytokine effects in these cells. We used the PPAR agonist rosiglitazone (Rtz) to investigate PPAR-gamma isotype on IL-1beta-target genes. Immunocytochemistry, electrophoretic mobility shift, and transient transfection assays revealed a functional PPAR-gamma in chondrocytes in vitro. Rtz displayed significant inhibition of IL-1beta effects in chondrocytes. Low Rtz concentrations (close to K(d) values for PPAR-gamma, 0.1 to 1 microm) inhibited the effects of IL-1beta on (35)S-sulfated proteoglycan production and gelatinolytic activities and downregulated MMP1 expression at mRNA and protein levels. We have investigated the mechanism of action of Rtz against IL-1beta-mediated MMP1 gene hyperexpression. Rtz effect occurs at the transcriptional level of the MMP1 promoter, as observed in transiently transfected cells with pMMP1-luciferase vector. Transient expression of wild type PPAR-gamma enhanced Rtz inhibitory effect in chondrocytes, whereas a mutated dominant negative PPAR-gamma abolished it, supporting the role of PPAR-gamma in this effect. MMP1 gene promoter analysis revealed the involvement of a cis-acting element located at -83 to -77, shown to be a composite PPRE/AP1 site. Gel mobility and supershift assays demonstrated that PPAR-gamma and c-Fos/c-Jun proteins bind this cis-acting element in a mutually exclusive way. Our data highlight a new PPAR-gamma-dependent inhibitory mechanism on IL-1beta-mediated cartilage degradation occurring through DNA binding competition on the composite PPRE/AP1 site in the MMP1 promoter.

The usefulness and the limitations of animal models in identifying targets for therapy in arthritis

Animal models have played a critical role in the history of modern drug development for rheumatoid arthritis (RA). In this chapter I examine the contributions of animal models in arthritis therapy from adjuvant arthritis and COX-1 inhibitors to transgenic mice and biological response modifiers. Advances in knowledge of the mechanisms of connective tissue disease are frequently derived from the study of animal models, and these findings frequently identify therapeutic targets that are subsequently evaluated in animal models. Hence a critical relationship between insights into the pathology of arthritis and the development of novel therapeutic approaches exists around the study of animal models of arthritis. In particular, we examine how the study of collagen-induced arthritis in rodents led to pioneering work in cytokine inhibitors for the successful therapy of RA.

Immunotherapy in Collagen-Induced Arthritis: Past, Present, and Future

Type II collagen-induced arthritis has played a critical role in the development of novel approaches to the treatment of rheumatoid arthritis. The model has provided insights into autoimmune mechanisms relevant to the pathogenesis of joint disease and permitted the identification of potential targets for arthritis therapy. Notably, the model excelled in the development of cytokine inhibition for rheumatoid arthritis, with investigations demonstrating that a complex network of cytokine interactions regulate the autoimmune response to collagen. Recent studies of collagen-induced arthritis provide indications of novel approaches to disease intervention. New directions include modulation of the recognition and presentation of autoantigens, inhibition of specific T cell subsets responding to autoantigens, blocking of stimulatory cosignals at the cell surface, decoys for cytoplasmic and nuclear activation signals, interference with lymphocyte migration to the synovial joint, and reduction of the mediators of joint destruction. These approaches can be implemented through gene therapy, biological response mediators, or classic pharmacological intervention.

Molecular targets in immune-mediated diseases: the case of tumour necrosis factor and rheumatoid arthritis

Rheumatoid arthritis is a common autoimmune condition in which, for unknown reasons, synovial joints become the target of a sustained immune response. For many years, rheumatoid arthritis was in the 'too hard basket' in terms of understanding disease mechanisms and providing rational therapy. This has changed dramatically over the last 10 years and rheumatoid arthritis is now at the forefront of biotechnology. In this review, we outline one of the most exciting recent developments, namely antagonists of the cytokine TNF. The preclinical evaluation of TNF in animal models of rheumatoid arthritis, and subsequent clinical trials of TNF inhibitors in patients, provides insight into the 'bench to bedside' paradigm. We therefore briefly review rheumatoid arthritis, animal models of rheumatoid arthritis, the biology of TNF, the pivotal clinical trials of TNF antagonists and the emerging data on side-effects. Tumour necrosis factor inhibitors in rheumatoid arthritis represent the first attempt to achieve sustained blockade of a single cytokine in a human disease. Whilst this approach has been even more successful than might have been predicted, we suggest it is only the beginning of what has become a new therapeutic era.

Mediators of inflammation are down-regulated while apoptosis is up-regulated in rheumatoid arthritis synovial tissue by polymerized collagen

The aim of the study was to determine whether collagen-polyvinylpyrrolidone (collagen-PVP) modifies some proinflammatory responses in synovium cultures from rheumatoid arthritis (RA) patients. Synovium from 10 RA patients were cultured with or without 1% collagen-PVP. Tissues on the 3rd, 5th and 7th culture day were sectioned and stained by the Herovici technique. Total collagen and type I/III collagen ratios were evaluated by the Woessner micromethod and by interrupted gel electrophoresis, respectively. Collagenolytic activity was assessed by degradation of [3H]-collagen in supernatants. TIMP-1, IL-1beta and TNF-alpha were determined in supernatants by ELISA, and the results were normalized by DNA concentration. IL-1beta, TNF-alpha, IL-6, IL-8, MMP-1, TIMP-1, Cox-1, VCAM-1, ICAM-1 and Fas/APO95 expression was evaluated by immunohistochemistry. Apoptosis was detected by TUNEL technique. The histological analysis and electrophoresis revealed a 1.7-fold increase of type III collagen in a time-dependent fashion in collagen-PVP-treated cultures. Proinflammatory cytokines (IL-1beta: 58 +/- 9 versus 22 +/- 10; TNF-alpha: 41 +/- 6 versus 11 +/- 3; IL-8: 59 +/- 12 versus 29 +/- 9; treated versus untreated), adhesion molecule (ICAM-1: 57 +/- 11 versus 29 +/- 15; VCAM-1: 49 +/- 7 versus 21 +/- 13; treated versus untreated) as well as Cox-1 (59 +/- 10 versus 20 +/- 3) expression was down-regulated in RA synovium treated. Meanwhile, TIMP-1 (36 +/- 7 versus 57 +/- 11) and Fas expression (20 +/- 10 versus 55 +/- 13) and apoptosis (14 +/- 3 versus 55 +/- 5) were up-regulated in treated cultures compared with controls. In supernatants, the collagenolytic activity, as well as IL-1beta and TNF-alpha, levels were all down-regulated in treated cultures (two, three, fourfold, respectively). The addition of collagen-PVP to synovium-induced down-modulation of some inflammatory parameters and an increase in apoptosis of synovial cells. Perhaps this mechanism could contribute to inhibit outgrowth of pannus formation and to down-regulate inflammation of joints in patients with RA.

The kappa-opioid agonist, asimadoline, alters cytokine gene expression in adjuvant arthritis

OBJECTIVE

We have previously found that the kappa-opioid agonist, asimadoline, attenuates adjuvant arthritis in a dose-dependent, antagonist-reversible manner. To elucidate possible mechanisms, we investigated the effects of asimadoline (5 mg/kg/day i.p.) or vehicle on in vivo cytokine expression and T-cell recruitment in adjuvant arthritis.

METHODS

Arthritis severity was assessed every 3-4 days for 21 days. Rats were killed on days 0, 13 and 21 post-induction and synovial membrane and inguinal lymph nodes were removed for mRNA extraction. Changes in cytokine mRNA expression were measured using reverse transcription-polymerase chain reaction (RT-PCR) and densitometry. T cells in joints were quantified by immunohistochemistry.

RESULTS

Asimadoline significantly decreased arthritis severity at day 13, with a concomitant decrease in synovial membrane expression of cytokines interleukin-17 and transforming growth factor-beta (TGF-beta) mRNA at day 13, and no change in T cell numbers in the joints of arthritic rats. By contrast, in the inguinal lymph nodes, expression of tumour necrosis factor was increased at day 13 and TGF-beta mRNA was increased throughout.

CONCLUSION

An altered balance, therefore, in the pro- and anti-inflammatory effects of TGF-beta by asimadoline might explain its striking anti-arthritic actions.

The genetic and immunopathological processes underlying collagen-induced arthritis

Animal models of rheumatoid arthritis (RA) have provided substantial insights into basic pathogenic mechanisms of chronic inflammatory arthritis and autoimmune disease in general. Of the variety of models reported, collagen-induced arthritis (CIA) has been the most characterized in terms of both its pathogenesis and its underlying immunological basis. Collagen-induced arthritis has also been the model of choice in terms of testing potential new therapeutic agents for the treatment of human RA. Nevertheless, the complex nature of the balance between T-cell cytokines and the chronic inflammatory processes is only recently becoming clear. This review focuses on these developments, highlighting their implications for our understanding of RA and for the use of CIA as a suitable animal model.

Peroxisome proliferator--activated receptor gamma activators inhibit interleukin-1beta-induced nitric oxide and matrix metalloproteinase 13 production in human chondrocytes

OBJECTIVE

To determine the effects of peroxisome proliferator-activated receptor gamma (PPARgamma) agonists on interleukin-1 (IL-1) induction of nitric oxide (NO) and matrix metalloproteinase 13 (MMP-13) in human chondrocytes.

METHODS

PPARgamma expression and synthesis in human chondrocytes were determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry, respectively. Chondrocytes were cultured with IL-1beta, tumor necrosis factor alpha (TNFalpha), and IL-17 in the presence or absence of PPARgamma agonists, and NO and MMP-13 synthesis and expression levels were measured. Transient transfection experiments were performed with the 7-kb inducible NO synthase (iNOS) and 1.6-kb MMP-13 human promoters, as well as with the PPARgamma expression vector and the activator protein 1 (AP-1) and nuclear factor kappaB (NF-kappaB) reporter constructs.

RESULTS

RT-PCR and immunohistochemical analysis revealed that human chondrocytes expressed and produced PPARgamma. Treatment of chondrocytes with PPARgamma ligands BRL 49653 and 15-deoxy-delta12,14-prostaglandin J2 (15d-PGJ2), but not with PPARalpha ligand Wy 14643, decreased IL-1beta-induced NO and MMP-13 production in a dose-dependent manner. In addition, both iNOS and MMP-13 messenger RNA were inhibited in the presence of 15d-PGJ2. The inhibitory effect of PPARgamma activation was not restricted to IL-1beta, since TNFalpha- and IL-17-induced NO and MMP-13 production were also inhibited by 15d-PGJ2. In transient transfection experiments, we showed that a constitutively active form of mitogen-activated protein kinase kinase kinase 1 (AMEKK-1) induced the MMP-13 and iNOS human promoter activity. This process was reduced by 15d-PGJ2 and further inhibited by cotransfection with a PPARgamma expression vector. Similarly, in a PPARgamma-dependent manner, 15d-PGJ2 inhibited deltaMEKK-1-induced AP-1- and NF-kappaB-luciferase reporter plasmid activation.

CONCLUSION

The findings of this study demonstrate that PPARgamma agonists inhibit IL-1beta induction of both NO and MMP-13 in human chondrocytes. The inhibition occurs at least at the transcriptional level through a PPARgamma-dependent pathway, probably by interfering with the activation of AP-1 and NF-kappaB.

Dynamics of early synovial cytokine expression in rodent collagen-induced arthritis : a therapeutic study using a macrophage-deactivating compound

This study was performed to elucidate pathophysiological events before and during the course of collagen-induced arthritis in Dark Agouti rats, a model for rheumatoid arthritis. Kinetic studies of local cytokine responses were determined using immunohistochemical techniques, quantified by computer-assisted image analysis. We recently reported that the macrophage-pacifying agent CNI-1493 successfully ameliorated collagen-induced arthritis. In the present trial, we investigated the potential of CNI-1493 to down-regulate pro-inflammatory cytokines. Synovial cryosections were analyzed at various time points for the presence of interleukin (IL)-1beta, tumor necrosis factor (TNF), and transforming growth factor (TGF)-beta. Unexpectedly, an early simultaneous TNF and IL-1beta expression was detected in resident cells in the lining layer, preceding disease onset and inflammatory cell infiltration by >1 week. The predominant cytokine synthesis by synovial (ED1+) macrophages coincided with clinical disease. TNF production greatly exceeded that of IL-1beta. CNI-1493 treatment did not affect the early disease-preceding TNF and IL-1beta synthesis in the lining layer. However, after disease onset, CNI-1493 intervention resulted in a pronounced reduced IL-1beta and in particular TNF expression. Furthermore, CNI-1493 significantly up-regulated synthesis of the anti-inflammatory cytokine TGF-beta and thereby shifted the balance of pro-inflammatory and anti-inflammatory cytokines in the arthritic joint in a beneficial way.

Production of murine collagen-induced arthritis using Klebsiella pneumoniae O3 lipopolysaccharide as a potent immunological adjuvant

Collagen-induced arthritis (CIA) was produced in mice with non H-2q and H-2r haplotypes by repeated immunization of porcine type-II collagen (CII) together with Klebsiella O3 lipopolysaccharide (KO3 LPS) as an immunological adjuvant. Histological changes that appeared in joints of repeatedly immunized mice were characterized by destruction of normal joint structure, synovial hyperplasia with proliferation of synovial cells, and infiltration of inflammatory cells. No such lesions were produced in mice receiving repeated injections of CII alone or KO3 LPS alone. Development of the humoral antibody and the delayed-type hypersensitivity to CII was exclusively found in mice immunized with the mixture of CII and KO3 LPS. It was therefore suggested that arthritis lesions induced by repeated immunization with the mixture of CII and KO3 LPS might be caused by an autoimmune mechanism, and that the experimental model might be useful for characterization of human rheumatoid arthritis (RA).

Interleukin-1beta (IL-1beta) inhibition: a possible mechanism for the anti-inflammatory potency of liposomally conjugated methotrexate formulations in arthritis

1. Liposomes with conventional and long-circulation times were employed as carriers for the methotrexate derivative MTX-gamma-DMPE (MTX-EPC and MTX-PEG respectively), their mechanism of action was investigated in vitro and in vivo and their therapeutic efficacy assessed using the rat collagen-induced arthritis (CIA) model. 2. At non-toxic dose, both MTX-EPC and MTX-PEG inhibited the lipopolysaccharide (LPS) induced release of IL-1beta from activated rat peritoneal macrophages (rPMPhi) in a dose and time dependent manner. Free methotrexate (MTX) was not active in this respect. After a single intravenous injection (i.v.), and at equivalent doses, both free MTX (500 microg) and MTX-EPC inhibited the LPS induced rise in plasma IL-1beta levels observed in MTX-PEG and saline treated rats. 3. When used to treat established CIA, MTX-EPC resulted in significantly lower clinical score (CS) (1.0+/-0.42 (P<0.001)) and hind paw diameter (HPD) (6.5+/-0.34 mm (P<0.001)) measurements than controls (3.0+/-0.26; 7.33+/-0.41 mm), after only two i.v. doses, and remained significantly lower for the entire experimental period. By day 24 both CS (2+/-0.61 (P<0.001)) and HPD (6.97+/-0.25 mm (P<0.002)) measurements had also become significantly lower in MTX-PEG treated rats than in saline treated controls (3.62+/-0.17, 7. 92+/-0.38 mm) and remained lower until day 30. Joint inflammation in MTX treated rats was completely ameliorated by day 20 but the health and well being of the animals was compromised and the experiment terminated at this time-point. 4. Our results clearly demonstrate that both MTX-EPC and MTX-PEG liposomes have potential for development into therapeutic modalities for the treatment of inflammatory joint disease in man.

Influence of long term silicone implantation on type II collagen induced arthritis in mice

OBJECTIVES

The use of silicone implants in cosmetic and reconstructive surgery has been implicated in the development of autoimmune connective tissue diseases. Previous investigation of the influence of short-term silicone implantation using an experimental model of rheumatoid arthritis revealed no adverse influence upon disease despite the generation of autoantibodies against silicone bound proteins. This study was designed to examine the influence of long term implantation of different forms of silicone in collagen induced arthritis.

METHODS

DBA/1 mice were surgically implanted with silicone elastomers, gel or oil nine months before immunisation with type II collagen emulsified in Freund's incomplete adjuvant. The incidence and severity of arthritis, antibodies to type II collagen, and serum cytokines were assessed and compared with sham implanted mice. Silicone implants were recovered, and autoantibodies to silicone bound proteins evaluated in arthritic and non-arthritic mice.

RESULTS

Immunisation with CII/FIA resulted in a 30% arthritis incidence in sham implanted DBA/1 mice. Long term silicone implantation resulted in an increased incidence of arthritis, with a significant increase of 90% arthritis in animals implanted with silicone elastomers. Animals implanted with silicone elastomer also developed foreign body sarcomas during the study. Serum concentrations of interleukin 10 were increased in mice implanted with elastomers and immunised with CII/FIA, while interleukin 5 concentrations were significantly diminished in these mice. The production of autoantibodies to autologous silicone bound proteins, including anti-type I collagen antibody, was also attributed to the implantation of either silicone gel or silicone elastomer in type II collagen immunised animals.

CONCLUSIONS

These data suggest that long term silicone implantation results in both the production of autoantibodies to connective tissue antigens and increased susceptibility to an experimental model of autoimmune disease.

Anti-inflammatory effects of systemic anti-tumour necrosis factor alpha treatment in human/murine SCID arthritis

OBJECTIVES

To evaluate in vivo the contribution of tumour necrosis factor alpha (TNFalpha) to the chimeric transfer model of human rheumatoid arthritis synovial membrane into SCID mice (hu/mu SCID arthritis), systemic anti-TNFalpha treatment was performed and the clinical, serological, and histopathological effects of this treatment assessed.

METHODS

Animals were treated with the rat-antimouse TNFalpha monoclonal antibody V1q, starting on day 1 after hu/mu engraftment, twice weekly for 12 weeks. Joint swelling, serum concentrations of human and murine interleukin 6 (IL6), and serum amyloid P (SAP) were measured. Histopathological and immunohistochemical analyses of the joints were also performed at the end of treatment.

RESULTS

Neutralisation of murine TNFalpha induced the following effects: (a) reduction of extent and duration of the acute arthritis phase, with significant reduction of joint swelling at two weeks; (b) decrease of murine SAP concentrations after the first antibody administration; and (c) increase of murine IL6 in the serum. At the end of treatment, there was a significant reduction of the inflammatory infiltration in the engrafted joints. Because of the mild degree of joint erosion, no treatment effects could be demonstrated on the destructive process.

CONCLUSION

In the lymphocyte independent hu/mu SCID arthritis, anti-TNFalpha treatment reduces local and systemic signs of inflammation.

Prevention of collagen-induced arthritis in mice by a polyphenolic fraction from green tea

Identification of common dietary substances capable of affording protection or modulating the onset and severity of arthritis may have important human health implications. An antioxidant-rich polyphenolic fraction isolated from green tea (green tea polyphenols, GTPs) has been shown to possess anti-inflammatory and anticarcinogenic properties in experimental animals. In this study we determined the effect of oral consumption of GTP on collagen-induced arthritis in mice. In three independent experiments mice given GTP in water exhibited significantly reduced incidence of arthritis (33% to 50%) as compared with mice not given GTP in water (84% to 100%). The arthritis index also was significantly lower in GTP-fed animals. Western blot analysis showed a marked reduction in the expression of inflammatory mediators such as cyclooxygenase 2, IFN-gamma, and tumor necrosis factor alpha in arthritic joints of GTP-fed mice. Histologic and immunohistochemical analysis of the arthritic joints in GTP-fed mice demonstrated only marginal joint infiltration by IFN-gamma and tumor necrosis factor alpha-producing cells as opposed to massive cellular infiltration and fully developed pannus in arthritic joints of non-GTP-fed mice. The neutral endopeptidase activity was approximately 7-fold higher in arthritic joints of non-GTP-fed mice in comparison to nonarthritic joints of unimmunized mice whereas it was only 2-fold higher in the arthritic joints of GTP-fed mice. Additionally, total IgG and type II collagen-specific IgG levels were lower in serum and arthritic joints of GTP-fed mice. Taken together our studies suggest that a polyphenolic fraction from green tea that is rich in antioxidants may be useful in the prevention of onset and severity of arthritis.

Distribution of TNF-alpha, TNF-R55 and TNF-R75 in the rheumatoid synovial membrane: TNF receptors are localized preferentially in the lining layer; TNF-alpha is distributed mainly in the vicinity of TNF receptors in the deeper layers

The expression of TNF-alpha and its receptors in the rheumatoid synovial membrane was investigated using immunohistochemistry and immunocytofluorescence. TNF-alpha+ cells (< 10% of all cells) were found in all regions, predominantly in sublining and diffuse infiltrates. The highest percentage of TNF-R+ cells was found in the lining layer (50-90%), with a slight predominance of TNF-R55. In the sublining, fewer cells expressed TNF-R (approximately 50%), mostly TNF-R75. TNF-R75+ cells were also detectable in diffuse infiltrates and lymphoid aggregates (10-50%). These contained only individual TNF-R55+ cells. In diffuse infiltrates, there were slightly more TNF-R55+ cells than in lymphoid aggregates (in both cases < 10%). In sequential sections, TNF-alpha+ cells localized mostly in the vicinity of TNF-R+ cells. Macrophage-like cells appeared to be the predominant TNF-R+ cell type. CD3+ T cells in lymphoid aggregates expressed exclusively TNF-R75. Subsequently, the expression of membrane-bound TNF-alpha, TNF-R55 and TNF-R75 was tested by FACS analysis in isolated RA synoviocytes (n = 7 patients). Only four specimens expressed mTNF-alpha, and that on a low percentage of cells (2 +/- 2.4%; mean +/- SD). In contrast, all specimens expressed higher percentages of TNF-R55 and TNF-R75 (21 +/- 1% and 14 +/- 7.1%, respectively). These results demonstrate that: (1) the percentage of cells expressing soluble/transmembrane TNF-alpha is greatly outnumbered by the percentage of cells expressing TNF receptors; and (2) TNF-alpha-expressing cells are localized in regions expressing substantial levels of TNF receptors. Therefore, the known pro-inflammatory and pro-arthritic effects of TNF-alpha are probably mediated by local interactions between the receptors and their soluble and transmembrane ligands.

Collagen-induced arthritis, an animal model of autoimmunity

Collagen induced arthritis (CIA) is an autoimmune model that in many ways resembles rheumatoid arthritis (RA). Immunization of genetically susceptible strains of rodents and primates with type II collagen (CII) leads to the development of a severe polyarticular arthritis that is mediated by an autoimmune response. Like RA, synovitis and erosions of cartilage and bone are hallmarks of CIA, and susceptibility to both RA and CIA is linked to the expression of specific MHC class II molecules. Although not identical to RA, CIA clearly establishes the biological plausibility that an autoimmune reaction to a cartilage component can lead to a chronic, destructive, polyarthritis. Although it is induced in susceptible animals by immunization with heterologous CII, it is the autoreactive component of the immune response that leads to disease. A wealth of evidence indicates that synovitis is initiated by the production of pathogenic autoreactive antibodies capable of fixing and activating complement. The elucidation of the specific amino acid sequences of collagen that are recognized by the MHC molecules has enabled at least two approaches to specific immunotherapy to be considered. Firstly, small synthetic peptides representing dominant epitopes have been used as effectively as the original antigen as a tolerogen. The rather fastidious physicochemical properties of collagen that make it difficult for its routine use in therapy are thereby circumvented by the use of oligopeptides. Secondly, analysis of the specific amino acid side chains that are involved in MHC contact and TCR recognition enables analog peptides to be devised which can specifically and exquisitely inhibit the response to CII, preventing the onset of arthritis. Further investigations involving this model may contribute to the development of specific immunotherapies in the human disorder.

The influence of silicone implantation on type II collagen-induced arthritis in mice

OBJECTIVE

To determine whether silicone implantation exacerbates autoimmune disease in a murine experimental model of arthritis.

METHODS

DBA/1 mice were implanted with silicone in the form of an elastomer, gel, or oil, and immunized with type II collagen. The influence of silicone implantation on collagen-induced arthritis and the immune response to type II collagen were determined by comparison against control mice receiving sham implantation. Adjuvant effects of silicone implantation were examined by measuring cytokine levels in implanted animals and assessing autoantibodies against proteins extracted from recovered silicone implants.

RESULTS

No adverse influence of silicone implantation on the clinical aspects of collagen-induced arthritis was observed. Further, polydimethylsiloxane silicone oil failed to serve as an adjuvant in the immune or arthritogenic response to type II collagen in mice. Cytokine analysis indicated that tumor necrosis factor alpha levels were lower and interleukin-2 levels were higher in silicone-implanted mice. The development of arthritis increased protein binding to implanted elastomers and gel, and autoantibodies against silicone-bound proteins were present in sera from arthritic mice and absent in sera from nonarthritic mice.

CONCLUSION

The data suggest that silicone implantation may result in autoantibodies against silicone-bound proteins, and the presence of arthritis may either provoke or increase the level of such autoantibodies. However, silicone implantation did not increase the incidence or severity of disease compared with sham-operated controls. Thus, it appears that autoantibodies against silicone-bound proteins may not have pathologic significance in this experimental model of arthritis.

New insights into the pathogenesis and treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic multisystemic inflammatory disease with autoimmune features, and of unknown cause, associated with characteristic joint deformities and increased mortality rate. The pathogenesis of this serious disease seems to be multifactorial, where several cytokines, particularly interleukin-1 and tumor necrosis factor-alpha, are strongly involved in the induction and perpetuation of the chronic inflammatory process of the joints in RA and in the systemic manifestations of the disease. Other factors, such as reactive oxygen species and metalloproteinases, may also participate in the destruction of the rheumatoid joint. Current treatments of RA are inadequate in that they only partially control established RA, and despite optimal use of current antirheumatic agents, the outcome of many patients with RA consists of pain, severe functional decline, and premature death. The gloomy recent data regarding the prognosis of RA with the use of the current treatments stress the need for new therapeutic regimens with the ability to effectively control the inflammatory process in the rheumatoid joint and to induce long-term remission or even cure. Controlling the production and the activity of the factors involved in the pathogenesis of the disease represents the major therapeutic goal. Since several factors are involved in the pathogenesis of RA, neutralizing one or some of these factors may be of only limited benefit. In this regard, interleukin-4 may be a very promising agent for an effective treatment of RA, because this cytokine is not limited by its inhibitory effects to a single factor, but rather it inhibits most of the main factors involved in the pathogenesis of the disease. Although recent data strongly support this approach with interleukin-4, controlled long-term clinical trails should be undertaken in order to prove the validity and the effectiveness of this promising approach.

Expression of TNF alpha in arthritis caused by caprine arthritis encephalitis virus

Goats infected with caprine arthritis encephalitis virus (CAEV) develop chronic arthritis sharing many features with human rheumatoid arthritis (RA). TNF is thought to be a key mediator contributing to the formation of the arthritic lesion in RA. We studied this cytokine in goats suffering from chronic arthritis. TNF alpha expressing cells were detected by in situ hybridization in synovial membranes of arthritic carpal joints. Expression of TNF alpha did not correlate with the degree of viral replication as assessed by in situ hybridization for viral RNA. In line with the lack of correlation between the degree of viral replication and TNF expression in vivo, we failed to detect increased cytokine RNA in goat macrophages infected with CAE virus in vitro and no TNF protein was found in culture supernatants. In addition, virus infection failed to prime goat macrophages for enhanced TNF expression in response to lipopolysaccharide. Taken together, these findings argue against a direct role of CAE virus in increasing the expression of TNF alpha in caprine arthritis.

Attenuation of collagen-induced arthritis in mice by treatment with vector cells engineered to secrete interleukin-13

The anti-inflammatory effects of the recently identified cytokine interleukin (IL)-13 on collagen-induced arthritis (CIA) was explored and compared to those of IL-4 using systemic administration of these cytokines via two injections of xenogeneic vector cells transfected with a plasmid construct. CIA was induced in DBA/I mice by immunization with native bovine type II collagen (CII). Chinese hamster ovary (CHO) fibroblasts transfected with the mouse IL-13 or IL-4 genes were inoculated subcutaneously on days 10 and 25 post-priming with CII and mice were monitored for signs of arthritis by observers unaware of the status of the animal. Incidence and severity of CIA were significantly reduced in the groups of mice treated with IL-13 and IL-4 gene-transfected CHO cells compared to control groups receiving nontransfected cells. Expression of various cytokines in spleen cells from individual mice was assessed by quantitative reverse transcriptase-polymerase chain reaction at different times after immunization. Our data show that IL-13-induced suppression of CIA coincided with a decreased TNF-alpha mRNA expression in the spleen of treated animals. This may explain at least partially the anti-inflammatory effects of IL-13 in CIA. Thus, our results may have important implications for the clinical use of T helper (Th)1/TH2 modulatory cytokines as therapeutic agents in the treatment of autoimmune diseases.

Phagocytic lining cells determine local expression of inflammation in type II collagen-induced arthritis

OBJECTIVE

To investigate the in vivo role of phagocytic synovial lining cells in the local expression of inflammation in type II collagen-induced arthritis (CIA) in DBA/1J mice.

METHODS

On various days before arthritis induction (day 7, 5, or 2), phagocytic lining cells were selectively depleted from the synovial layer by injecting multilamellar liposomes containing clodronate (dichloromethylene diphosphonate) directly into the knee joints. As controls, either PBS or PBS-laden liposomes were injected. CIA was induced by immunizing mice with heterologous bovine type II collagen in Freund's complete adjuvant. Arthritis onset was synchronized by a single intraperitoneal injection of lipopolysaccharide; arthritis was evaluated in hematoxylin and eosinstained knee joint sections. Chemotactic activity in synovial washout samples was detected in a Transwell chemotactic assay. Interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) protein levels were measured in NOB-1 and L929 bioassays, respectively. IL-1 messenger RNA (mRNA) in synovial specimens was measured by reverse transcriptase-polymerase chain reaction. IL-1 was also detected immunohistologically in knee joint sections.

RESULTS

In clodronate-laden liposome-treated, lining-depleted knee joints, there was significantly decreased inflammation compared with controls. Cell influx into the synovium was markedly decreased. Expression of IL-1 mRNA in the synovium was significantly reduced. IL-1 was detected only in some cells in the deeper synovial layer, in contrast to controls, in which large numbers of cells in the deeper synovial layer were stained. In synovial washouts from lining-depleted knee joints, biologically active IL-1 levels were reduced by 40% at 6 hours after arthritis induction. Most strikingly, chemotactic activity was highly decreased in these synovial washout samples. When IL-1 or TNF alpha was injected into the knee joints of immunized mice in which arthritis was not yet expressed, arthritis was not induced in the lining-depleted joints, whereas marked cell influx was found in control joints.

CONCLUSION

Our data indicate that phagocytic lining cells play a crucial role in the local expression of inflammation in systemically induced CIA. Phagocytic lining cells probably form an important source of chemotactic factors which are set free upon activation by IL-1 or TNF alpha.

Relationship between Th1/Th2 cytokine patterns and the arthritogenic response in collagen-induced arthritis

It is hypothesized that the balance of cytokines produced by Th1/Th2 subsets of T helper cells plays an important role in the development of autoimmune diseases. Murine collagen-induced arthritis (CIA) is an example of an autoimmune disease in which immunization with cartilage-derived type II collagen induces, firstly, a T cell response to type II collagen and, secondly, the manifestation of a destructive inflammatory response in affected joints. We have investigated the role of Th1/Th2 responses in the development of CIA by monitoring levels of interferon (IFN)-gamma (a Th1 cytokine) and interleukin (IL)-4 and IL-10 (Th2 cytokines), and IL-1 beta and tumor necrosis factor (TNF) (pro-inflammatory cytokines) produced by cultured draining lymph node cells (LNC) from collagen-immunized DBA/1 mice during the induction phase of arthritis and throughout the time of clinical manifestation and subsequent remission of the disease. Although a transient increase in IL-10 was detected 3 days after immunization, Th2 cytokine production was found to be almost completely suppressed 6 days after immunization. In contrast, IFN-gamma was detected in LNC cultures as early as 6 days after immunization and the addition of type II collagen to the culture medium resulted in an approximately 10-fold increase in IFN-gamma production, indicating that a predominantly Th1 response had become established by this time. IFN-gamma production by LNC was found to be further increased at the time of clinical manifestation of arthritis and could be up-regulated by co-culture with type II collagen. IL-10 was not detected in LNC cultures at the onset of arthritis and IL-4, although present, was found to be markedly suppressed in LNC cultures containing type II collagen. These findings indicate that Th1 responses are predominant at the time of onset of arthritis and that the activation of collagen-specific Th1 cells may result in suppression of Th2 activity. IFN-gamma production declined progressively during the progression and subsequent remission of arthritis whereas levels of IL-10 increased and low, though persistent, levels of IL-4 were detected throughout this period. High levels of IL-1 beta and TNF-alpha production were detected at the onset of the disease. The role of Th1 responses in the development of CIA was further emphasized by the observation that immunization of mice with type II collagen in incomplete Freund's adjuvant, which normally fails to induce arthritis, resulted in a predominantly Th2 cytokine profile.

Anticytokine treatment of established type II collagen-induced arthritis in DBA/1 mice. A comparative study using anti-TNF alpha, anti-IL-1 alpha/beta, and IL-1Ra

OBJECTIVE

To examine the role of tumor necrosis factor alpha (TNF alpha), interleukin-1 alpha (IL-1 alpha), and IL-1 beta in collagen-induced arthritis (CIA), immediately after onset and during the phase of established arthritis.

METHODS

Male DBA/1 mice with collagen-induced arthritis were treated with antibodies against murine TNF alpha and IL-1 alpha/beta at different time points of the disease. IL-1 receptor antagonist (IL-1Ra) was administered using Alzet osmotic minipumps. The effect of anticytokine treatment was monitored by visual scoring. Histology and cytokine reverse transcription polymerase chain reaction (RT-PCR) analyses were performed at the end of the treatment period.

RESULTS

Anti-TNF alpha treatment showed efficacy shortly after onset of the disease, but had little effect on fully established CIA. Histologic analysis after early treatment revealed that anti-TNF alpha significantly reduced joint pathology, as determined by infiltration of inflammatory cells and cartilage damage. Anti-IL-1 alpha/beta treatment ameliorated both early and full-blown CIA. This clear suppression of established arthritis was confirmed by administration of high doses of IL-1Ra. Dose-response experiments showed that a continuous supply of 1 mg/day was needed for optimal suppression. Histologic analysis showed markedly reduced cartilage destruction both in the knee and the ankle joints. Autoradiography demonstrated full recovery of chondrocyte synthetic function of articular cartilage. In addition, we found that the IL-1 beta isoform plays a dominant role in established CIA. Profound suppression of CIA was observed with anti-IL-1 beta, although elimination of both IL-1 alpha and IL-1 beta still gave better protection. Analysis of messenger RNA with RT-PCR revealed that IL-1 beta was highly upregulated in synovium and cartilage at late stages of CIA, whereas anti-IL-1 beta treatment markedly reduced IL-1 beta message in the synovium.

CONCLUSION

The present study identified different TNF alpha/IL-1 dependencies in various stages of CIA and revealed that blocking of TNF alpha does not necessarily eliminate IL-1. Continuous, high doses of IL-1Ra are needed to block CIA.

Role of cytokines in rheumatoid arthritis

Analysis of cytokine mRNA and protein in rheumatoid arthritis tissue revealed that many proinflammatory cytokines such as TNF alpha, IL-1, IL-6, GM-CSF, and chemokines such as IL-8 are abundant in all patients regardless of therapy. This is compensated to some degree by the increased production of anti-inflammatory cytokines such as IL-10 and TGF beta and cytokine inhibitors such as IL-1ra and soluble TNF-R. However, this upregulation in homeostatic regulatory mechanisms is not sufficient as these are unable to neutralize all the TNF alpha and IL-1 produced. In rheumatoid joint cell cultures that spontaneously produce IL-1, TNF alpha was the major dominant regulator of IL-1. Subsequently, other proinflammatory cytokines were also inhibited if TNF alpha was neutralized, leading to the new concept that the proinflammatory cytokines were linked in a network with TNF alpha at its apex. This led to the hypothesis that TNF alpha was of major importance in rheumatoid arthritis and was a therapeutic target. This hypothesis has been successfully tested in animal models, of, for example, collagen-induced arthritis, and these studies have provided the rationale for clinical trials of anti-TNF alpha therapy in patients with long-standing rheumatoid arthritis. Several clinical trials using a chimeric anti-TNF alpha antibody have shown marked clinical benefit, verifying the hypothesis that TNF alpha is of major importance in rheumatoid arthritis. Retreatment studies have also shown benefit in repeated relapses, indicating that the disease remains TNF alpha dependent. Overall these studies demonstrate that analysis of cytokine expression and regulation may yield effective therapeutic targets in inflammatory disease.

Inflammatory cytokine production induced by an analogue of muramyl dipeptide MDP-Lys(L18) in rat macrophage cultures and dog synovial fluid

To examine the involvement of cytokines in the mechanisms of N2-[(N-acetylmuramoyl)-L-alanyl-D-isoglutaminyl]-N6-stearoyl-L-lysine, MDP-Lys(L18)-induced arthritis, we analyzed interleukin-1 (IL-1), tumor necrosis factor (TNF), colony-stimulating factor (CSF), and neutrophil chemotactic factor (NCF) by bioassays in the rat macrophage-conditioned medium (Mluminal diameter-CM) stimulated by MDP-Lys(L18) in vitro and the synovial fluid from dogs treated subcutaneously with MDP-Lys(L18) for 14 days in vivo. The dog showed arthritis characterized by swelling of the knee joint, increased synovial fluid and thickened synovial membrane, and a single subcutaneous injection of MDP-Lys(L18) was previously shown to induced synovitis in rat tarsal joint. IL-1, TNF, CSF, and NCF activities in Mluminal diameter-CM were increased by MDP-Lys(L18), while only NCF activity was detected in the dog synovial fluid. Partial purification procedures revealed that NCF in Mluminal diameter-CM was not leukotriene B4 but a protein having heparin-affinity, and, in addition, immuno-reactive IL-8 was evident to be in Mluminal diameter-CM. The NCF activity in the dog synovial fluid was not inhibited by dialysis, showing that NCF is a protein substance, possibly a chemokine. These results suggest that MDP-Lys(L18) produces a chemokine, such as IL-8, which recruits neutrophils to the synovial membrane for subsequent development of synovitis in rats and dogs.

Anti-cytokine therapy in rheumatoid arthritis

The past few years have seen an explosion of knowledge concerning the role of cytokines and their naturally occurring inhibitors in the promotion and modulation of inflammatory disease. In RA, this knowledge has been translated into the clinic, with ongoing evaluation of specific cytokine inhibitors, including those targeting tumour necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) and interleukin-6 (IL-6). In this review, we outline the scientific data supporting anti-cytokine therapies in RA and describe the results of published and unpublished clinical trials with biological agents. At least for anti-TNF therapy, short-term clinical efficacy and good tolerability have been confirmed in randomized, placebo controlled trials. The results of IL-1 blockade in vivo also appear encouraging, although detailed descriptions of trail outcomes are awaited. Problems associated with long-term administration of biological agents are discussed, including the development of antiglobulin responses to injected monoclonal antibodies and poor pharmacokinetics of low-molecular-weight inhibitors. Ways of facilitating the long-term use of current biological agents and alternative means for inhibiting cytokine function in future studies in RA are presented.