ROLE OF RECEPTORS IN THE THERAPEUTIC FIELD OF RHEUMATIC DISORDERS

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By:

Amany Abou El Soaud

Assis. Prof. of Rheumatology & Rehabilitation

Faculty of Medicine, Zagazig University

Cytokine Receptors

Before we are going to discuss the role of antirecepotrs in the field of rheumatic disorder, we will give an idea about cytokine receptors.

Cytokine receptors can be grouped into several families depending on structural characteristic (Figure I). The activation pathway triggered after receptor occupancy tend to be similar for receptors of the same family but different for receptors of different families. The fact that several cytokines may share a given receptor explains why some biological properties are common to several interleukins (Virella, 1998).

1) I) The most common type of receptor is the hemopoitein-receptor family, so called because it was initially characterized by an erythropoitein receptor (Virella, 1998):

O 1- The receptors of this family are heterodimers or heterotrimers and include an and a chain, the latter with longer intracytoplasmic segment and signaling functions.

T 2- The receptors for interleukin (IL)-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-9 and IL-15 are included in this family.

Some of them share subunits:

a- a- Receptors for IL-3, IL-5, share a common chain. A different chain is shared by receptors for IL-6 and IL-11.

b- b- Receptors for IL-2, IL-4, IL-7, IL-9 and IL-15 share a third chain () which plays a significant role in signal transduction.

2) II) Other receptor families (Virella, 1998) include the following:

1- The tumor necrosis factor receptor family, which besides receptor for
TNF- and TNF- (Lymphotoxin) include CD40 and fas.

2- The immunoglobulin superfamily receptors, a receptor for colony stimulating factor.

T 3- The chemokine receptor family whose common features are seven transmembrane domains including receptors for IL-8, platelet factor 4, and macrophage chemotactic and activating proteins.

Chemokines comprise a large family of structurally homologous cytokines, that share the ability to stimulate leucocyte motility (chemokinesis) and directed movement (chemotaxis). The name chemokines is a contraction of chemotactic cytokines. Members of this family are IL-8, monocyte chemoattractant protein-1 (MCP-1), MCP-2, MCP-3. They act on neutophil as mediators of acute inflammation (Abbas et al., 1999).

MCP-1 receptor has seven transmembrane spanning receptor which binds to human and murine macrophage inflammatory protein (MIP)-1. This receptor mediates mobilization of intracellular calcium in response to MCP-1 but not to related chemokines (Charo et al., 1994).

The following receptors have a role in rheumatic disorders. Their structures have been illustrated as follow:

I- Interleukin (IL)-1 receptors and signal transduction:

IL-1 and IL-1 bind high affinity receptors which are present on most nucleated cell types. The numbers of receptors range from 50 or fewer on T lymphocytes to several thousands on fibroblast (Ruscetti and Oppenheim, 1997).

Two distinct receptors have been characterized, both of which are transmembrane glycoproteins that bind IL-1and IL- equally. These receptors share only 28% sequence similarity. IL-1 receptor type 1 (IL-1 R₁) is 517 amino acids long, it has a 217 amino acid cytoplasmic tail and transmit signals intra-cellularly when it binds IL-1, it responsible for signaling in all IL-1 responsive cells-IL-1 receptor type II (IL-1 RII) has only 29 amino acids cytoplasmic trail and can not transuduce signals. The extracellular domain of IL1-RII is released in soluble form at sites of local inflammation and into the serum during systemic inflammation (Ruscetti and Oppenheim, 1997).

IL-1 receptor antagonist protein (IL-1Ra) is a substance on T lymphocyte and endothelial cells that inhibits IL-1 activity (Cruse and Lewis, 1999), Figure 3.

IL-1Ra binds to high affinity cell surface IL-1 receptor but has not receptors activation activity (Arned, 1993).

In this way the agonist effects of IL-1 are partially regulated by IL-1Ra. IL-1Ra is released by monocytes and tissue macrophages. IL-1Ra inhibits prostaglandin production by synovial cells and chondrocytes and matrix metalloproteinase production by activated synovial cells and articular chondrocytes (Smith et al., 1991).

Evidence suggests that IL-1 is an important mediator of inflammation and joint damage through cartilage resorption in experimental arthritis (Firestein et al., 1994). IL-1 B induces prostaglanden (PGE2) release by synovial cells and regulate the production of numerous cytokines, involved in synovitis, such as IL-1, IL-4, IL-10, IL-5 and TNE IL-1 amplifies the T cell activation by inducing IL2 and IL-2 receptor gene expression, but is not required for T cell proliferation (Sany et al., 1999).

In IL-1 receptor type I deficient mice, splenocytes and lymph node cells produce increased amount of IL-4 and IL-10 after antigenic stimulation (Paleolog et al., 1996). These data demonstrate that IL-1 negatively regulate IL-4 and IL-10 expression and favours the Th-1 response. Although IL-1 is a known activator of collagenase and stromelysin, an important step in cartilage breakdown, the effects of IL-1 are counterbalanced by the neutral antagonist IL-1ra and soluble IL-1 receptors I and II (Sany et al., 1999).

When recombinant human soluble IL-1 R1 was administrated to patients with rheumatoid arthritis (RA), it failed to produce significant clinical improvement although there was reduction in monocyte surface
IL-1 (Drevlow et al., 1996), in many cases the disease worsened. This may be due to recombinant soluble IL-1R1 binding to IL-1ra. If this binding occurs, less IL-1ra will bind to cell surface IL-1R1. These free IL-1R1 molecules will therefore engage with IL-1 itself, augmenting IL-1 induced cell activation and inflammation. As soluble IL-1 RII does not bind to
IL-1ra it may be better therapeutic choice (Choy, 1998). Recambinant human IL-1ra administered as subcutaneous (s.c.) injections, has been tested in a double-blind placebo controlled multicenter trial (Bresnihan et al., 1996). A dose 150 mg/day administered s.c. produced significant clinical improvement and slowed the progression of erosion (Choy et al., 1998).

II- Interleukin-6 receptor:

It consists of a 60 KD chain cytokine binding protein and 130 KD signal transducing subunit chain. The binding subunit consists of both an Ig domain and two cysteine motif characteristic of type-1 cytokine receptors. The signal transducing subunit also contains both an Ig domain and two cysteine motif, but it does not bind IL-6 and appear to serve as signaling subunit for several other cytokines. Soluble IL-6 receptors shed from cell surfaces can bind IL-6 and these soluble complexes can also signal through the 130 KD subunit (chain) (Abbas et al., 1999).

Over the past decade, the IL-6R-B chain has been found to form part of receptors for five additional structurally unrelated cytokines: interleukin-11, leucocyte inhibitory factor, oncostatin M and cardiotrophin-1. Each of these cytokines has its own specific receptor containing one or more unique chains that mediate ligand binding. IL-6R chain functions as a common signal-transducing subunit in each of these receptors, which may account for the reported overlap in biologic activities of these structurally dissimilar cytokines (Ruscetti and Oppenheim, 1997).

III- Tumor necrosis factor- receptor:

Tumor necrosis factor- has two transmembrane receptors of 55 KD (TNF-R 55) and 75 KD (TNF-R 75) (Feldemann, 1996). Both receptors have been isolated in soluble form from sera, urine and other biologic fluids of febrile patients and from synovial fluids of RA patients. Soluble TNF receptors may be used to block TNF- activities however soluble receptors are required in 10 to 100-fold larger amounts to overcome total TNF activity (Dayer and Arend, 1997).

The activity of soluble TNF- receptors could be increased by generation of fusion proteins with soluble TNF-R link to Fc region of immunoglobulin G (Szehanecz et al., 1998).

Type I (P55) and type II (75) TNF receptors belong to a large family of structurally related membrane proteins called TNF receptors superfamily (TNFR-SF) which also include Fas, nerve growth factor (NGF) receptor, a TNFR- related protein [TNFR-RP, the receptors for lymphotoxins (LT/LTB complex, CD27, CD30 and CD40)]. The receptors of this super family each contain three or four copies of a cyteine rich repeat of 40 amino acids in their extracellular domains. These repeats contain four or six cysteine residues in characteristic pattern that is distinct from cysteine-rich repeat in other molecules. Some of these receptors bind more than one ligand and unlike most other cytokines (Ruscetti and Oppenheim 1997).

TNFR-P55 mediates most of cytotoxic effects fibroblast proliferation and prostaglandin synthesis. TNFR-P75 mediated effects are more restricted, potentiates the cytotoxic effects on TNF-R-P55 and stimulates T-cell proliferation synergistically with IL-1, IL-2 and IL-6 (Koski, 2001).

The two receptors for TNF are designated type I and type II receptor belong to TNF- and TNF-. These two receptors belong to TNF receptor superfamily. The extracellular domains four cyst rich repeat. The two TNF receptors have essentially no homology in their intracellular domains. Soluable form of receptors have been described in urine and serum with exception of erythrocytes and resting T cells. Type IP55 receptor is widely distributed on various cell types, the type II P75 receptor appears confined to hematopoietic cells (Cruse and Lewis, 1999).

IV- T cell receptor (TcR):

It is similar to immunoglobulin in terms of general structure and genetic control of expression. The alpha and beta chains are divided into variable and constant regions, with the former interacting with antigen and the later with CD3 molecules and events leading to T-lymphocyte activation. As with immunoglobulins, the V, D, J and C regions represent gene families and not single genes. Combinational diversity among these regions accounts for the recognition of antigenic differences (Cassidy and Petty, 1995).

The molecular interactions in triggering of antigen-specific immune responsed. Illustrated are components of trimolecular complex essential for T-cell activation HLA class II molecule, peptide antigen and T cell antigen specific receptor -as well as the CD4-coreceptor molecule. The HLA molecule is achored in the membrane of an antigen- presenting cell, with the antigen-recognition domain and its bound peptide accessible to the T-cell receptor. The T-cell receptor recognize the antigen in the context of its HLA class II molecule, while CD4 molecule enhances binding and assists with signal transduction into the T-cell compartment (Nepom and Nepom, 1993).

Anti-TNF Theapy In Rheumatic Diseases

1 I)Rheumatoid arthritis (RA):

RA is a systemic disease of unknow aetiology, characterised by chronic synovial inflammation with frequent progression to articular and bone destruction. Pathologic hallmarks of disease include synovial cell proliferation, abundant secretion of pro inflammatory cytokines such as tumor necrosis factor (TNF-) and interleukin-1 (IL-1) and infiltration of mononuclear cells into synovial tissue, (Perkins et al., 1998).

Two naturally occurring inhibitors of TNF have been identified, soluble TNF receptors (STNF-R) P55 (TNF-R1) and P75 (TNF-RII). Elevated plasma level of these receptors presumed to modulate the immune response (Moreland et al., 1997), they have postulated that major defect in RA relates to a pathological defect in TNF receptor “shedding” from polymorphnuclear neutrophils (Robine et al., 1999).

Most disease modifying antirheumatic drugs (DMARD) are discontinued within 5 years because of loss of clinical efficacy or toxicity. As a result, there has been a concerted effort to develop new immuno-modulatory agents, particularly biological agents, that block pro-inflammatory cytokines (Kalden, 2001) as TNF-blocking agents.

Clinical trails of therapy for RA directed at TNF- including the use of antibodies or a soluble receptor fusion proteins that bind TNF-and block its biologic activity, demonstrate marked dose dependent improvement in both clinical and laboratory measures of inflammation (Moreland et al., 1997 and Maini et al., 1999). Multiple pathophysio-logical activities interrupted by TNF-blockage are important in ameliorating RA (Taylor et al., 1999).

Davis et al., (2000) study showed that recombinant STNF-R1 is an E. coli derived recombinant, turnicated mononmeric form of the 4-domains soluble TNF-type I receptor, can be given s.c. for treatment of R.A. Their study include 82 patients with active, moderate to severe RA, they were radomised to TNF-RI or placebo within one or two dose schedules. In schedule one patients received a single dose of STNF-RI (100 ug/kg, 300 ug/kg) followed 6 weeks later by weekly dosage for 3 weeks. In schedule II, patients received (100 ug/kg, 300 ug/kg) every other week for 6 weeks. No difference were observed in the incidence or severity of adverse events between two dosing schedules and no apparent close response relation was noted between the incidence and severity of adverse events and dose of STNF-RI. Headache, infection site reaction and infection were common adverse side effects.

Recombinant human soluble TNF receptor (etanercept) is a dimeric fusion protein consisting of extracellular portion of human p75 (TNF-R linked to the FC portion type I immunoglobulin (IgG-1). The drug competitively inhibits the binding of TNF to cell surface receptor and thus renders TNF biological inactive, so etanercept inhibits the proinflammatory effects of TNF and results in reduction of joint inflammation in RA patients (Alldred, 2001).

Kalden (2001) study included 234 patients with severe RA who had not demonstrated adequate response to one or more DMARD. Patients were received 2 dosing regimens of etanercept (10 or 25 mg s.c) twice per week for 6 months. The results showed that etanercept had rapid onset of action and produced significant improvement of diseases activity at 3 and 6 months.

Mathians et al., (2000) reported significantly better functional status based on various rating scales including Health Assessment Questionnaire and the medical outcome study in RA patients received etanercept.

Fink et al., (1999) study included 632 patients with active early stage RA who were on methotraxate. On group was randomised to receive etanercept 10 mg or 25 mg s.c. twice per week and placebo pills once a week for 12 months (group I), the second group received placebo injections in the same dosage as group I and methotraxate pills up to 20 mg weekly. At 12 months the percentage of improvement was 72% and 49% respectively. This study differ from other etanercept trials in that structural joint damage was assessed radiographically and was reported as change in total sharp score (TSS) and its components: erosion score and joint space narrowing (JSN) score. Etanercept 25 mg produced significantly greater improvement than methotraxate at 6 months in both TSS and erosion scores. These findings provided the basis for the expanded indication for etanercept as first line treatment of patients with moderately to severely active RA (Kalden et al., 2001).

Den Broeder et al., (2002) concluded that dose titration of anti-TNF treatment in RA patients using disease activity score is feasible and leads to overall dose reduction while maintaining clinical efficacy. This approach will safe costs and possibly prevent long term side effects.

Effects of etanercept on ovulation induction, conception and delivery after chronic therapy with etanercep in rheumatoid arthritis (Sills et al., 2001):

No human data exist regarding the impact of anti-TNF-potentiates collagenolysis via matrix metalloproteinase gene expression (therapy facilitating ovulation, there exists a theoretical risk that TNF- inhibition could exert an undesirable effect on ovulation and pregnancy. In this report we describe the first case of ovulation induction, intrauterine insemination, normal pregnancy and delivery of a healthy infant following chronic (> 1 year) pre-ovulatory TNF- inhibitor therapy for rheumatoid arthritis. Reproductive endocrinologists, and obstetrician-gynecologists should be familiar with etanercept therapy in context of severe rheumatic disease, and offer appropriate reassurance regarding its safe use for infertility patients planning ovulation induction.

II- Rheumatoid arthritis with digital vasculitis (Broeder et al., 2001):

No data exist about the effect of anti-TNF blocking agents including lenercept (anti-TNF- receptor-I fusion protein) on extra-articular manifestations of rheumatoid arthritis.

Case report of 46 years old women was diagnosed with rheumatoid factor positive erosive RA in 1982, antinuclear antibodies was detected from the beginning of the diseases. Testing for disease specific antibodies was negative on several occasions. In the following years she was treated unsuccessful with hydroxychloroquine, intramuscular gold salts, D-penicillamine, azathioprine, methotraxate and combination of sulphasalazine and methotraxate. Because of progressive joint destruction she received shoulder prosthesis on both sides, total knee joint replacement on both sides. No extra-articular symptoms except for sicca complains. Owing to uncontrollable disease including in 1994 in the study with a fusion protein combining two P55 TNF receptors with FC component of an IgG human antibody (lenercept) (Richter et al., 1999). She received 50 mg lenercept I.V. every 4 weeks, clinical response was noted as regards number of swollen joint, decrease CRP after first injection. Low disease activity was sustained for the following years. Beside lenercept, her drug consisted of 5 mg prednisilone / day and occasionally pracetamol 500 mg.

In spring 1999 she first noted nail fold lesion on the fingers of both hands. These lesions disappear after every injection of lenercept and repeated three weeks thereafter when the effect of lenercept was decreasing (Broeder et al., 2001).

III- Rheumatoid lymphedema:

Etanercept dramatically reduce lymphedema after less than 4 months of therapy in RA patients (Ostrov, 2001).

IV- Wegener’s Granulomatosis (W.G):

Evidence suggests that abnormal regulation of TNF may play a role in WG (Stone et al 2001). In animal models, granulation formation is markedly impaired by antibodies directed against TNF. Serum levels of soluble TNF- receptors are elevated in patients with active WG and normalize with the induction of remission (Nossonvo et al, 1997). In vitro priming of activated neutrophils with TNF markedly enhances the ability of anti-neutrophil cytoplasmic antibodies (ANCA) to stimulate neutrophil degranulation, potentially fueling the vasculitis associated with this disorder (Falk et al 1990).

In an open trials by Stone et al (2001) etanercept used in a dose
25 mg s.c. twice weekly in combination with standard treatments was well-tolerated in patients with active W.G. Adverse events were few. Improvement was noticed at 6 months.

V- Spondyloarthropathy:

a- Ankylosing spondylitis:

Few data exist about the expression of TNF- in joint biopsy specimens from patients with ankylosing spondylitis, an abundant TNF- message could be found by in situ hybridisation (Braun et al, 1995). Hohler et al (1998) have described an association of different TNF promoter allele frequencies in patients with ankylosing spondylitis and in HLA- B27 positive individuals.

Theoretically up regulation of the TNF- receptors might be expected upon constant blockage of agonist. This has been noted in studies of infliximab (anti- TNF) and etanercept in RA during long term treatment even when constant therapeutic plasma levels are maintained (Kremer et al 2000 and Schatten- Kirchner et al 2000). This suggests this is true also for patients with ankylosing spondylitis.

b- Psoriatic arthritis (PSA):

TNF is an important inflammatory disease mediator in a wide spectrum of articular diseases including RA, JRA and PSA (Green, 2000).

Etanercept has been shown to provide rapid and sustained improvement in these diseases and it is an important new treatment option for patients with these conditions (Green, 2000).

The efficacy of etanercept was also studied in placebo controlled double blind study of 60 patients with severe PSA who were treated with either etanercept 25 mg or placebo s.c. twice weekly for 12 weeks (Mease et al., 2000). The end points of the trial were improvement in PSA response criteria as well as the ACR 20 response. The effect of etanercept on dermatological response was analysed in a subset of patients who had 3% of the total body improvement in their psoriasis by assessing target lesions and by using the psoriasis Area and severity index (PASI) and a composite measure based on scale, erythema and induration of psoriasis lesions (Green 2000). Patients treated with etanercept had significant improvement in disease activity compared with those of placeb. At 12 weeks 87% of patients treated with etanercept met the psoriatic arthritis response criteria (PSARC) compared with 23% patients treated with placeb. 46% of patients showed improvement using psoriasis area and severity index compared with 9% in placebo group. No deaths, serious adverse events or serious infections occurred in either treatment arm.

Also, etanercep and infiximab have been approved for treatment of psoriatic arthritis by Braun et al., (2001).

VI- Sjogren’s Syndrome (SS):

Modulation of TNF- by neutralizing antibodies, soluble receptors and TNF-R: FC Fusion proteins are being developed for therapeutic modulation of immune inflammation.

It is becoming increasingly important to understand the state and involvement of TNF-/TNF-R system in various rheumatic diseases. TNF- affects its target cells through binding to two different receptors, TNF-R-P55 and TNF-R-P75. Cytotoxic effects of TNF- on various cells have bean reported. In SS focal sialoadenitis leads to salivary gland destruction and loss of function. Although TNF- is one possible mediator in these processes, nothing is known about the spatial distribution of TNF- in relation to its receptors/ target cells in salivary gland tissue (Koski et al., 2001).

Koski et al., (2001) concluded that there were localisation of TNF receptors and their ligand TNF- in SS. The expression of TNF-and its receptor in fibroblast and ductal cells may contribute to ductal hyperplasia and glandular fibrosis. This may suggest the role of neutralizing TNF agents for therapeutic modulation of immune inflammation is such disease, SS may be one of auto-immune diseases for future indication for new biologic agents but till now no studies have been done on such agents and clinical response of this disease.

VII- Juvenile idiopathic arthritis (JIA):

Although the cause of JIA is not well understood, evidence exists that pro-inflammatory cytokines such as interleukin (IL)-1, IL-6, and TNF- play an important role in the pathogenesis of disease (Schmeling et al., 2001). TNF- can be neutralized by monocloncal antibodies or etanercept (extracellular domain of P75TNF receptor molecule and the human immunoglobulin gamma chain FC fragment).

A placebo controlled trail using etanercep in polyarticular JIA has been published recently (Lovell et al., 2000). Six patients continued the treatment for at least 24 weeks. Immediate significant decrease in joint pain, disappearance of morning stiffness and regression of joint swelling was observed. Improvement was apparent after two injections. Also, there was significant decrease in erythocyte sedimentation rate, C reactive protein and IL-6. Side effects consisted of mild reaction at injection site in two children.

Schmeling et al., (2001) concluded that etanercept in combination with methotraxate was well tolerated and highly effective in treating juvenile polyarthritis.

Children with systemic arthritis etanercept was stopped because of persisting spiking fever, joint pain and rash (Lovell et al., 2000 and Schmeling et al., 2001).

Impact of TNF inhibition on the development of erosive disease in JIA has not been confirmed. However, the delay in radiographic progression in patients with RA raises hope that this phenomenanon may occur in JIA. Furthermore, it will be of interest to investigate wheather etanercept is effective for two major problems of paediatric rheumatology, rheumatoid uveitis and systemic arthritis. An attempt to treat with etanercept a boy with systemic arthritis was unsuccessful (Schmeling et al., 2001).

Also, twenty two patients with polyarticular course JIA were treated in other trail by etanercept in a dose 0.4 mg/kg twice a week. All patients showed clinical improvement with decrease in swollen joint count, decrease in tender joint count and morning stiffness. Furthermore, haemoglobin concentration increased on average by 14 g/L. No major side effects were noted (Kietz et al., 2002). They concluded that etanercept continues to be clinically effective and well tolerated in patients with polyarticular course JIA over a two years period.

Smith et al., (2001) showed that etanercept or infliximab are well tolerated immunosuppressive mediacations that may benefit certain subgroups of patients with inflammatory eye disease, but they appear to be more effective in controlling associated inflammatory arthritis (Smith et al., 2001).

Reiff et al., (2001) evaluated safety and efficacy of etanercept in children with treatment resistant uveitis with and without arthritis. Improvement of arthritis as well as well as resistant treatment uveitis occurred in 63% of treated children.

VIII- Others: “Future indication for etanercept”

Etanercept is currently being studied in other disorders in which TNF seems to play an important pathogenic part including sarcoidosis and Cronh’s disease (Green, 2000).

Patients should discontinue anti-TNF therapy if: (Kalden, 2001)

1- They do not demonstrate adequate response (based on predetermined response criteria) within 12 (or 16) weeks after starting treatment at the recommended dosing schedule (or earlier in the event of serious adverse reaction). Many of these serious events including serious infection and sepsis have occurred in patients with underlying diseases (i.e. diabetes, congestive heart failure, history of active or chronic infections) could predispose them to develop infections.

2- Recent infection (i.e. tuberculosis, bone/joint infection) or recent previous malignancy particularly lymphoma should be considered potential contraindications to TNF- blocking therapy.

3- Chronic infections (hepatitis B or C or HIV), mycobacterial disease.

4- During pregnancy and lactation.

5- Rare conditions of lupus like disease have been reported in patients receiving anti- TNF agents and the use of such therapy should be discontinued if there is clinical evidence of such syndrome.

However, the presence of antinuclear or anticardiolipin antibodies, in absence of clinical symptoms does not role out the use of TNF- blocking agents.

Anti-Interleukin-1 agents

Recent research has shown that in the process of RA, interleukin-1 (IL-1) is one of the pivotal cytokines in initiating disease and body’s natural response. It leads to joint destruction (Gabay, 2000). IL-1 and IL-1 are two of members of IL-1 gene super-family. Both are agonists that activate target cells by binding to an IL-1 receptor (Bresnihan et al., 1998). IL-1 also stimulates cartilage and bone resorption through activation of osteoclast and inhibits the synthesis of articular collagen and proteoglycan (Vandeloo et al., 1995).

IL-1 receptor antagonist (IL-Ra) is an endogenous molecule that can prevent the binding of IL-1 to its cell surface receptor and improve the inflammatory symptoms of arthritis in experimental animals (Otani et al., 1996). IL-1 Ra could constitute an important new approach to treat patients with RA that significantly reduce signs and symptoms of disease, reduce joint destruction and up to now has proved safe and well tolerated (Dayer et al., 2001).

To evaluate the effects of treatment with IL-1 Ra (anakinra) on synovial tissue in RA, twelve patients with RA were entering a randomized clinical trial of human recombinant IL-1 Ra under went synovial biopsies before and after treatment. Cellular infiltration and adhesion molecule expression were evaluated after immunohistochemical staining. There was notable reduction in intimal layer macrophage and subintimal macrophage and lymphocyte after treatment with IL-1 Ra at 150 mg/day. Increased cellular infiltration was observed in all patients receiving placebo. Variable changes were observed after IL-1 Ra (30 mg/ day).

Down regulation of E selectin and vascular cell adhesion
molecule-1 was observed after treatment with IL-1 Ra 150 mg/ day, but not after 30mg/ day or placebo. So, treatment of RA with IL-1 Ra resulted in reduced mononuclear cell infiltration of synovial membrane, which may represent the in vivo inhibition of biologically relevant IL-1 mediated pathogenic effects (Cunnane et al 2001).

Study by Paget (2002), compared the effects of anakinra
(a recombinant human IL-1 Ra) with those of etanercept and infliximab, two drugs that target TNF- . He concluded that agents that block IL-1, TNF- appear similary effective in slowing radiographic progression in patients with active RA.

Effects of combination of anticytokines in type II collagen arthritic rats:

The ability of combination of STNF-RI and IL- 1 Ra to modify the extent of skeletal damage and inflammation was tested in two studies of animal models of arthritis. In the first study (Bendele et al, 1999) adjuvant arthritis rats with established disease were give PEG STNF- RI (3 mg/ kg intraperotineal), IL- 1 Ra (100 mg/kg s.c. daily on days 8-14). The percent inhibition of disease was measured for ankle swelling, histological bone resorption, body weight.

Bendele et al (1999) and Davis et al (2000) concluded that combination of STNF- RI and IL-1 Ra were synergistic, resulting in inhibition of paw swelling and inhibition of loss of bone mineral density. The results of these studies provide the preclinical rationale for investigating anticytokine combination treatment in clinical trials.

Gene therapy and anti-receptor agents

Interleukin-1 receptor antagonist (IL-1Ra) gene transfer in experimental arthritis:

Somatic gene transfer has been introduced into experimental antirheumatic therapy (Robbins et al 1998). We have found the rat adjuvant induced arthritis model suitable for such studies (Kock et al 1998).

IL-1 Ra gene transfer was evaluated in rabbit and rat experimental arthritis models. IL- 1 Ra gene has a chondroprotective effect in rabbits, in rats it inhibited paw swelling, and partially reduced cartilage and bone erosions (Szehanecz et al, 1998).

Recently adeno-virus mediated gene transfer for soluble IL- 1 B receptor type I and TNF- receptor type I were used together in rabbits with antigen- induced arthritis. When both soluble receptors were used together, there was greater reduction in synovitis and significant inhibition of cartilage breakdown. This therapy may be applied in RA (Strand and Keystone 2002).

IL-1Ra and gene therapy in early experimental osteo-arthritis (OA):

Pelletier et al., (1997) study showed that a local increase of IL-1 Ra production in O.A. joints by intra-articular injection of transduced synovial cells can reduce the progression of experimentally induced lesions.

Gene therapy and antireceptors agents for treatment of systemic lupus erythematosus (SLE):

Autoimmune diseases are associated with excessive production of inflammatory cytokines such as IL-1 and TNF-. Vectors encoding inhibitors of these cytokines such as IL-1 Ra, soluble IL-R, and soluble TNF-r/IgG-FC fusion proteins are protective in models of either arthritis type I diabetes mellitus, SLE. We use intramuscular injection of nacked plasmid DNA for cytokine or anticytokine therapy (Prudhomme, 2000).

Anti-interleukin- 6 agents

Overproduction of IL-6 in RA may lead to persistent synovitis with synovial proliferation and destructive change in bone and cartilage of multiple joints. Also it causes increased platelet counts, globulin, CRP, ESR and serum amyloid A level (Yoshizaki et al., 1998). IL- 6 may be involved in osteoporosis, bone and cartilage destruction in RA. As
IL- 6 can upregulate the expression of intercellular adhesion molecule (ICAM)- 1 (Yamamoto et al 2000) it may recruit immunocompetent cells into the inflammatory tissues.

Interference of IL-6 signal transduction with humanised anti IL- 6 receptor antibody (MRA) is one of new therapeutic approaches in RA. Eleven patients with refractory RA, all had active disease, resist conventional treatment using various disease modifying antirheumatic drugs including methotraxate and corticosteroids. Patients were treated with MRA in a dose 50-100 mg once a week. The treatment was well tolerated and no major side effect was observed except an appearance of anti-idiopathic antibody in one case who withdrawn. Patients received treatment for 8-24 weeks with improvement in both clinical and biological measures. These results indicate that MRA is relatively safe and useful far treatment of RA (Nishimot et al 2000). Combination treatment consisting of some agents may be more effective than that of a single agent.

T- cell receptors vaccination

T- cell receptors VB chains were expanded in lesional sites such as synovium, compared with blood. It was proposed that such expanded T- cells would be pathologically relevant. Vaccination with peptides from T- cell receptors on pathogenic T cells would inhibit disease (Choy et al 1995). Many different VB populations were reported as expanded by various groups of investigator. However, one group looked VB 17 usage by recently activated T- cells defined as T-cells expressing the IL- 2 receptor on the basis that these recently activated cells were more relevant to disease pathogenesis- clinical trial was done in RA, investigators noted that patient joints scores decreased at all follow up visits as did VB 17 + IL- 2 R- T cells in the blood. No toxicity was observed (Klippel and Dieppe 1998). Further studies were needed.

Selective estrogen receptor modulators (SERMs)

SERMs, a new class of drugs with selective activity in various organ systems, act as weak estrogen in some systems and as oestrogen antagonist on others (Iqbal and Ala, 2000). The potential benefits of these drugs include protection against four important hormone-dependant diseases: osteoporosis, coronary heart disease, endometrial cancer and breast cancer (Spencer et al., 1999). One of the first SERMs to be developed was tamoxifen which used to protect recurrent breast cancer because it appears to block the effect of estrogen in breast tissue (antagonist) (Iqbal and Ala, 2000). Tomoxifen used in treatment and prevention of breast cancer, can maintain bone mass in postmenopausal women. However, tomoxifen’s effects on the risk of fracture are unclear (Love et al., 1992).

Raloxifene is a newer SERMs approved by FDA for prevention of postmenopausal osteoporosis. It stimulates bone and cardiovascular tissue the way estrogen does (agonistic effects) while not stimulating breast and uterine tissue (antagonistic effects) (Grese and Dodge, 1998)

Raloxifene’s biologic actions are mediated through binding receptors (Khovidhunkit and Shoback, 1999). This binding results in differential expression of multiple estrogen-regulated genes in various tissues (Iqbal and Ala, 2000). In clinical studies of postmenopausal women, raloxifene at dose 60 mg/day for 2 years increased bone mineral density as compared with placebo. The most commonly reported side effects are hot flushes and leg cramps, flushes reported during the first six months of treatment also deep venous thrombosis may occur (Balfour and Goa, 1998).

Antichemokine receptor (CCR₂) agents

Monocyte chemoattractant protein-1 (MCP-1 (9-76), a truncated form of MCP-1, a potent antagonist of the CCR₂, prevented the onset of adjuvant-induced arthritis in urine model of SLE (Gong et al., 1997).

Lastly, biologic agents for treatment of rheumatic disorders have a number of advantages over conventional small molecules. Administration of these agents typically results in rapid onset of action. All agents tested were compatible with combination therapy with other second line agents such as methotraxate. Many biologic agents appear to modulate specific elements with pathological process, thus avoiding generalised immunosuppression (Strand and Keystone 2002).

Biologic agents have a number of disadvantages over conventional therapy. They may be immunogenic on retreatment, frequently there is substantial cost associated with their manufacture and resulting high market price may limit patient access (Strand and Keystone 2002).

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