Christine Plater-Zyberk

Effect of a CC chemokine receptor antagonist on collagen induced arthritis in DBA/1 mice

Chemokines are small proteins that selectively activate and recruit leukocytes to sites of inflammation. Several of them, including the CC chemokines RANTES, MIP-1 alpha, MIP-1 beta, MCP-1, and the CXC chemokines IL-8, GRO-alpha, ENA-78 have been identified in rheumatoid synovium, implicating a potential role for these molecules in rheumatoid arthritis. We have investigated the expression patterns of CC chemokine receptors in the joints of mice with collagen-induced arthritis, a model for human rheumatoid arthritis. In addition, we have investigated the incidence and severity of arthritis in mice receiving administration of MetRANTES, a modified chemokine which is a nanomolar antagonist of certain CC chemokine receptors. The mRNA expression pattern of the chemokines and their receptors in the joints of arthritic mice was investigated using reverse transcriptase-PCR and in situ hybridization. An upregulation of the CC chemokine receptors mCCR1, mCCR2; mCCR3 and mCCR5 was found in the joints from arthritic mice, compared to control animals. In addition, injections of MetRANTES reduced the incidence of disease in a dose dependent manner. Furthermore, in MetRANTES-treated mice that did develop arthritis a significantly lower severity of disease was observed compared with control animals. Our data clearly demonstrate a role for CC chemokines and their receptors in inflammatory joint destruction and support the use of chemokine receptor antagonists as potential tools to control inflammatory diseases such as rheumatoid arthritis.

Therapeutic effect of neutralizing endogenous IL-18 activity in the collagen-induced model of arthritis.

Two distinct IL-18 neutralizing strategies, i.e. a rabbit polyclonal anti-mouse IL-18 IgG and a recombinant human IL-18 binding protein (rhIL-18BP), were used to treat collagen-induced-arthritic DBA/1 mice after clinical onset of disease. The therapeutic efficacy of neutralizing endogenous IL-18 was assessed using different pathological parameters of disease progression. The clinical severity in mice undergoing collagen-induced arthritis was significantly reduced after treatment with both IL-18 neutralizing agents compared to placebo treated mice. Attenuation of the disease was associated with reduced cartilage erosion evident on histology. The decreased cartilage degradation was further documented by a significant reduction in the levels of circulating cartilage oligomeric matrix protein (an indicator of cartilage turnover). Both strategies efficiently slowed disease progression, but only anti-IL-18 IgG treatment significantly decreased an established synovitis. Serum levels of IL-6 were significantly reduced with both neutralizing strategies. In vitro, neutralizing IL-18 resulted in a significant inhibition of TNF-alpha, IL-6, and IFN-gamma secretion by macrophages. These results demonstrate that neutralizing endogenous IL-18 is therapeutically efficacious in the murine model of collagen-induced arthritis. IL-18 neutralizing antibody or rhIL-18BP could therefore represent new disease-modifying anti-rheumatic drugs that warrant testing in clinical trials in patients with rheumatoid arthritis.

CD23 Regulates monocyte activation through a novel interaction with the adhesion molecules CD11b-CD18 and CD11c-CD18

CD23 is expressed on a variety of haemopoietic cells and displays pleiotropic activities in vitro. We report that in addition to CD21 and IgE, CD23 interacts specifically with the CD11b and CD11c, the alpha chains of the beta 2 integrin adhesion molecule complexes CD11b-CD18 and CD11c-CD18, on monocytes. Full-length recombinant CD23 incorporated into fluorescent liposomes was shown to bind to COS cells transfected with cDNA encoding either CD11b-CD18 or CD11c-CD18 but not with CD11a-CD18. The interaction was specifically inhibited by anti-CD11b or anti-CD11c, respectively, and by anti-CD23 MAbs. The functional significance of this ligand pairing was demonstrated by triggering CD11b and CD11c on monocytes with either recombinant CD23 or anti-CD11b and anti-CD11c MAbs to cause a marked increase in nitrite-oxidative products and pro-inflammatory cytokines (IL-1 beta, IL-6, and TNF alpha). These CD23-mediated activities were decreased by Fab fragments of MAbs to CD11b, CD11c, and CD23. These results demonstrate that CD11b and CD11c are receptors for CD23 and that this novel ligand pairing regulates important activities of monocytes.

Structure and functions of CD23.

This review summarizes recent data on CD23, a low affinity receptor for IgE (Fc epsilon RII). CD23 is the only FcR which does not belong to the immunoglobulin gene superfamily. The CD23 molecule was discovered independently as an IgE receptor on human lymphoblastoid B cells [1], as a cell surface marker expressed on Epstein-Barr-Virus-transformed B cells (EBVCS) [2] and as a B-cell activation antigen (Blast 2) [3]. CD23 was shown to be a low affinity receptor for IgE [4,5]. Similar to most FcR, soluble forms of CD23 (sCD23) are released into extracellular fluids. The soluble fragments formed by proteolytic cleavage of surface CD23 are not only capable of binding IgE (IgE binding factors) but also exhibit multiple functions that are not IgE related. These observations together with the finding that CD23 displays significant homology with Ca(2+)-dependent (C-type) animal lectins, suggested the existence of natural ligands other than IgE. The recent finding that CD23 interacts with CD21, CD11b and CD11c indicates that CD23 should be viewed not only as a low affinity IgE receptor but also as an adhesion molecule involved in cell-cell interaction. After a brief overview of the molecular structure, there follows a discussion of the biological activities ascribed to human CD23.

Marked amelioration of established collagen-induced arthritis by treatment with antibodies to CD23 in vivo.

CD23 is a low-affinity receptor for immunoglobulin E (IgE) expressed by a variety of haematopoietic cells. Proteolytic cleavage of the transmembrane receptor generates soluble forms, which can be detected in biological fluids. CD23 regulates many functional aspects of immune cells, both in its cell-associated and soluble forms. In view of the increased levels of CD23 in rheumatoid arthritis, we have studied the effect of neutralizing CD23 in type II collagen-induced arthritis in mice, a model for human rheumatoid arthritis. Successful disease modulation is achieved by treatment of arthritic DBA/1 mice with either polyclonal or monoclonal antibodies to mouse CD23. Treated mice show a dose-related amelioration of arthritis with significantly reduced clinical scores and number of affected paws. This improvement in clinical severity is confirmed by histological examination of the arthritic paws. A marked decrease in cellular infiltration of the synovial sublining layer and limited destruction of cartilage and bone is evident in animals treated with therapeutic doses of anti-CD23 antibody. These findings demonstrate the involvement of CD23 in a mouse model of human rheumatoid arthritis.

A new role for CD23 in inflammation

Abstract CD23, is expressed on a variety of haematopoietic cell types and displays pleiotropic activities in vitro . Here Jean-Yves Bonnefoy and collegues discuss a novel interaction between CD23 and the α chains of the β 2 integrins, CD11b and CD11c, that leads to a proinflammatory pattern of macrophage activation. They describe how neutralizing antibodies to CD23 can decrease the severity of murine arthritis.

Combined blockade of granulocyte-macrophage colony stimulating factor and interleukin 17 pathways potently suppresses chronic destructive arthritis in a tumour necrosis factor alpha-independent mouse model.

Objective: A pathogenic role for granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin (IL)17 in rheumatoid arthritis (RA) has been suggested. In previously published work, the therapeutic potentials of GM-CSF and IL17 blockade in arthritis have been described. In the present study, the simultaneous blockade of both pathways in a mouse model for chronic arthritis was investigated to identify whether this double blockade provides a superior therapeutic efficacy. Methods: A chronic relapsing arthritis was induced in C57Bl/6 wild type (WT) and C57Bl/6 genetically deficient for IL17 receptor (IL17R knockout (KO)) mice by intra-articular injection of Streptococcal cell wall (SCW) fragments into knees on days 0, 7, 14 and 21. Treatments (intraperitoneal) were given weekly starting on day 14. Animals were analysed for inflammation, joint damage and a range of inflammatory mediators. Results: Joint swelling and cartilage damage were significantly reduced in the IL17R KO mice and in WT mice receiving anti-GM-CSF neutralising mAb 22E9 compared to isotype control antibodies. The therapeutic effect was significantly more pronounced in mice where IL17 and GM-CSF pathways were inhibited (eg, IL17R KO mice treated with 22E9 mAb). Tumour necrosis factor (TNF)α blockade had essentially no effect. Conclusion: Our data further support the therapeutic potentials of GM-CSF and IL17 blockade in a RA model that is no longer responsive to an established TNFα antagonist, moreover, our results suggest that concomitant inhibition of both pathways may provide the basis for a highly effective treatment of chronic RA in patients that are resistant to treatment by TNFα inhibitors.

GM-CSF neutralisation suppresses inflammation and protects cartilage in acute streptococcal cell wall arthritis of mice.

Objective: The pathogenic involvement of granulocyte-macrophage colony-stimulating factor (GM-CSF) in arthritis has been put forward. We have investigated the therapeutic effect of GM-CSF neutralisation in the streptococcal cell wall (SCW) arthritis model in mice. In this model, the pathogenic contribution of tumour necrosis factor (TNF)α is minor and is expressed only on joint swelling, whereas cartilage proteoglycan depletion is independent of this cytokine. Methods: Acute monarthritis was induced by injection of SCW bacterial extracts to mouse knees. Treatments (mAb 22E9 at 300, 100, 30 μg; or Enbrel 300 μg) were given twice intraperitoneally 2 h before and 3 days after disease induction. Swelling was assessed by 99mTc uptake into knees on days 1 and 2. Local cytokine levels were determined in patellae washouts on day one. Proteoglycan loss from cartilage was scored on histological sections at termination on day four. Results: Treatment with anti-GM-CSF mAb 22E9 showed a dose-related efficacy by decreasing swelling that was significant at the 300 and 100 μg doses in comparison to isotype control, and comparable to dexamethasone (5 mg/ml). Proteoglycan loss from cartilage was also significantly reduced by mAb 22E9 300 μg (p = 0.001). This reduced proteoglycan loss observed after GM-CSF neutralisation was not seen after TNFα-blockade with Enbrel. Similarly, levels of interleukin 1β in joints were reduced after treatment with 22E9 mAb (p = 0.003) but not in mice receiving Enbrel. Conclusions: Our findings show a pathogenic role for GM-CSF in this arthritis model, support the therapeutic potential of neutralising this cytokine, and may indicate therapeutic activity of an anti-GM-CSF mAb in TNFα-independent disease situations.

IL-18 blockade is a potential disease-modifying therapy for rheumatoid arthritis

Interleukin-18 (IL-18) has been demonstrated as promoting the development of a TH1 response in vivo in synergy with IL-12. Significant levels of IL-18 and IL-12 have been detected in the joints of patients with rheumatoid arthritis (RA).

Chemokines in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an inflammatory disease in which the precise etiology is still unknown (1,2). Hormonal and genetic factors are involved with a threefold predominance of RA in women, and an HLA class II epitope shared between diseasesusceptible haplotype carriers (3). However, the discordant disease development between identical twins suggests that nongenetic factors such as infectious agents also play a role in the etiology of RA (4). The prime site of disease activity is the synovial joint, but in severe cases other organs can also be affected. Many mononuclear leukocytes infiltrate the synovium of RA patients and the joint fluid becomes highly enriched in polymorphonuclear leukocytes (PMNs) (5,6). This cellular infiltrate initiates a cascade of humoral and cell -mediated inflammatory events, ultimately resulting in the failure of the diseased joint. During the development of RA, the normally two- to three-cell thick layer lining the synovium proliferates, and the whole synovial membrane becomes hypertrophied and inflamed under the influence of the inflammatory leukocytes. This results in the formation of a pannus, an area rich in aggressively growing cells, particularly fibroblastlike and macrophage-like cells. The junction between the synovium, cartilage, and bone is the site where the irreversible damage originates. During disease development, the pannus grows over the cartilage and into the subchondral bone. The cells in the pannnus release a variety of cytokines and destructive enzymes, including matrix metalloproteinases (MMIPs), which cause cartilage and bone erosions that ultimately lead to the destruction of the joint (7–12).