Regulatory T cells (Tregs) fulfill a central role in immune regulation. We reported previously that the integrin αEβ7 discriminates distinct subsets of murine CD4+ regulatory T cells. Use of this marker has now helped to unravel a fundamental dichotomy among regulatory T cells. αE−CD25+ cells expressed L-selectin and CCR7, enabling recirculation through lymphoid tissues. In contrast, αE-positive subsets (CD25+ and CD25−) displayed an effector/memory phenotype expressing high levels of E/P-selectin–binding ligands, multiple adhesion molecules as well as receptors for inflammatory chemokines, allowing efficient migration into inflamed sites. Accordingly, αE-expressing cells were found to be the most potent suppressors of inflammatory processes in disease models such as antigen-induced arthritis.

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Developmental stage, phenotype, and migration distinguish naive- and effector/memory-like CD4+ regulatory T cells

This review examines the pharmacokinetics, modes of action and therapeutic properties of the anti-malarial drugs, hydroxychloroquine (HCQ) and chloroquine (CQ), in the treatment of systemic lupus erythematosus
 (SLE), rheumatoid arthritis (RA) and related conditions, as well as osteoarthritis (OA). Both HCQ and CQ have historically been employed successfully for the treatment of SLE and RA for over 70 years. HCQ has been used extensively for SLE where it has a good reputation for controlling the dermatological complications in SLE. It has also been reported to effectively control the symptoms of Sjogren’s syndrome, as well as preventing thrombosis in phospholipid antibody (aPL) syndrome. In RA and SLE, HCQ is preferred because of the lower incidence of gastrointestinal adverse reactions compared with CQ and it might have a lower risk of ocular adverse reactions. There is increasing evidence that HCQ may reduce atherosclerosis and risks of cardiovascular disease in rheumatic patients. Both HCQ and CQ have been shown to improve glycaemia and reduce the risks of type II diabetes mellitus. Although both HCQ and CQ are effective in low-moderate RA, HCQ is now preferred as part of combination therapy for more severe disease. The advantages of combination therapy are that the doses of the individual drugs may be lowered so reducing adverse reactions. Both HCQ and CQ are diastereoisomers, have basic properties and are given as the sulphate and phosphate salts. While being relatively well absorbed orally and with good bioavailability, they have long and variable plasma terminal elimination half-lives (approximately 40–60 days). This reflects their high volume of distribution, V
 D (HCQ 44,000L; CQ 65,000L) which extends into aqueous compartments, long mean residence time (HCQ 1300 h; CQ 900 h) and with about half the drugs (metabolites) undergoing renal clearance. The strong binding to melanin reflects the ocular injury and dermatological properties of these drugs. The consensus is that the occurrence of ocular adverse reactions can be minimised by close attention to the dose (which should be set on a body weight basis) with regular (e.g. quarterly) retinal examination. Although HCQ and CQ can pass through the placenta, the use of these drugs during pregnancy does not appear to risk harm to the baby and might be beneficial to the mother with SLE and her child by controlling the SLE disease activity, which is known to be an important factor affecting pregnancy outcome. The modes of action of HCQ and CQ in these arthritides represent somewhat of an enigma. Undoubtedly, these drugs have multiple actions related, in part, their ability to accumulate in lysosomes and autophagosomes of phagocytic cells as well as affecting MHC Class II expression and antigen presentation; actions of the production of pro-inflammatory cytokines [e.g. interleukin-1 (IL-1) tumour necrosis factor-α (TNFα)]; control of toll-like receptor-9 activation; and leucocyte generation of reactive oxygen species (ROS); i.e. antioxidant activity. The actions of these drugs on T and B cells are less clear but may depend on these leucocyte-mediated actions. Anti-malarials also protect against cytokine-mediated cartilage resorption. This and other actions may underlie the potential benefits in treating OA. The exact relationships of these various actions, mostly determined in vitro, have not been specifically defined in vivo or ex vivo in relation to clinical efficacy. HCQ and CQ have a good reputation for being effective and relatively safe treatments in SLE, mild-moderate RA and Sjogren’s syndrome. There is need for (a) more information on their mode of action in relation to the control of these diseases, (b) scope for developing formulations that have improved pharmacokinetic and therapeutic properties and safety, and (c) further exploring their use in drug combinations not only with other disease-modifying agents but also with biologics.

Therapy and pharmacological properties of hydroxychloroquine and chloroquine in treatment of systemic lupus erythematosus, rheumatoid arthritis and related diseases

Immune and inflammatory systems are controlled by multiple cytokines, including ILs and INFs. These cytokines exert their biological functions through Janus tyrosine kinases and STAT transcription factors. One such cytokine, IL-6, has been proposed to contribute to the development of rheumatoid arthritis (RA). We found that STAT3 was strongly tyrosine phosphorylated in synovial tissue of RA patients, but not those with osteoarthritis. Blockade of the IL-6-gp130-JAK-STAT3-signaling pathway might therefore be beneficial in the treatment of RA. We show here that the mRNA for the endogenous cytokine signaling repressor CIS3/SOCS3 is abundantly expressed in RA patients. To determine whether CIS3 is effective in treating experimental arthritis, a recombinant adenovirus carrying the CIS3 cDNA was injected periarticularly into the ankle joints of mice with antigen-induced arthritis or collagen-induced arthritis (CIA). Periarticular injection of CIS3 adenovirus drastically reduced the severity of arthritis and joint swelling compared with control groups. CIS3 was more effective than a dominant-negative form of STAT3 in the CIA model. Thus, induction of CIS3 could represent a new approach for effective treatment of RA.

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Induction of the cytokine signal regulator SOCS3/CIS3 as a therapeutic strategy for treating inflammatory arthritis

Animal models of arthritis are used to study pathogenesis of disease and to evaluate potential anti-arthritic drugs for clinical use. Therefore morphological similarities to human disease and capacity of the model to predict efficacy in humans are important criteria in model selection. Animal models of rheumatoid arthritis (RA) with a proven track record of predictability for efficacy in humans include: rat adjuvant arthritis, rat type II collagen arthritis, mouse type II collagen arthritis and antigen-induced arthritis in several species. Agents currently in clinical use (or trials) that are active in these models include: corticosteroids, methotrexate, nonsteroidal anti-inflammatory drugs, cyclosporin A, leflunomide interleukin-1 receptor antagonist (IL-1ra) and soluble TNF receptors. For some of these agents, the models also predict that toxicities seen at higher doses for prolonged dosing periods would preclude dosing in humans at levels that might provide disease modifying effects. Data, conduct and features of the various models of these commonly utilized models of RA as well as some transgenic mouse models and less commonly utilized rodent models will be discussed with emphasis on their similarities to human disease.

Animal models of rheumatoid arthritis.

Animal models of arthritis are used to evaluate potential antiarthritis drugs for clinical use. Therefore capacity of the model to predict efficacy in human disease is one of the most important criteria in model selection. Animal models of rheumatoid arthritis (RA) with a proven track record of predictability include rat adjuvant arthritis, rat type II collagen arthritis, mouse type II collagen arthritis, and antigen-induced arthritis in several species. Agents currently in clinical use (or trials) that are active in these models include corticosteroids, methotrexate, nonsteroidal anti-inflammatory drugs, cyclosporin A, leflunomide, interleukin-1 receptor antagonist, and soluble tumor necrosis factor receptors. For some of these agents, the models also predict that toxicities seen at higher doses for prolonged periods would preclude dosing in humans at levels that might provide disease-modifying effects. Animal models of osteoarthritis (OA) include mouse and guinea pig spontaneous OA, meniscectomy and ligament transection in guinea pigs, meniscectomy in rabbits, and meniscectomy and cruciate transection in dogs. None of these models have a proven track record of predictability in human disease because there are no agents that have been proven to provide anything other than symptomatic relief in human OA. Efficacy data and features of the various models of RA and OA are discussed with emphasis on their proven relevance to human disease.

Animal Models of Arthritis: Relevance to Human Disease

Chronic monoarticular allergic arthritis was induced in BALB/c mice using methylated BSA as antigen and Freund's complete adjuvant, together with Bordetella pertussis as a secondary adjuvant. The optimum conditions for induction of chronic persistent arthritis and the histological characteristics of the arthritic lesion are described. Both the synovitis and erosive progression of the arthritis could be suppressed by daily treatment with prednisolone (1–10 mg/kg) or dexamethasone (0.5–2.5 mg/kg) for 4 weeks commencing 2 weeks after the induction of arthritis. In contrast, daily treatment with the non-steroidal anti-inflammatory agents ibuprofen (50–100 mg/kg), flurbiprofen (1–9 mg/kg) or indomethacin (0.1–3 mg/kg) had no significant effect on either the synovitis or erosions as judged histologically. Synovial fluid differential leukocyte counts were altered by treatment with ibuprofen and indomethacin but not by flurbiprofen or the corticosteroids. The suppressive effect of the corticosteroids was not due to either suppression of antibody synthesis or alteration of the number of leukocytes in the peripheral circulation.

Pharmacological studies of antigen-induced arthritis in BALB/c mice. I. Characterization of the arthritis and the effects of steroidal and non-steroidal anti-inflammatory agents.

The effects of treatment with second-line antirheumatic drugs and cytotoxic agents on the severity of experimental monoarticular arthritis in BALB/c mice have been investigated. The arthritis was assessed histologically in terms of synovitis and erosions of cartilage and bone.

Pharmacological studies of antigen-induced arthritis in BALB/c mice II. The effects of second-line antirheumatic drugs and cytotoxic agents on the histopathological changes

Antigen-induced arthritis in mice.

The model of antigen-induced monoarticular arthritis in BALB/c mice, originally described by Brackertz et al. (1), has been examined with regard to disease pathogenesis and the activities of established antirheumatic agents. The acute phase of the arthritis, up to 7 days after intra-articular (IA) challenge, was characterized by intense polymorphonuclear leukocyte infiltration into the challenged joint, synovial lining cell hypertrophy and hyperplasia, accumulation of mononuclear cells within the subsynovial tissue, and pannus formation. Erosions of articular cartilage and bone commenced 7-14 days after IA challenge and progressed with time. Chronic synovitis was still evident 56 days after IA challenge. Prednisolone at 1 and 5 mg/kg, when administered against an established arthritis (dosing days 14-42), suppressed the histopathological changes. A similar level of suppression was observed when prednisolone was administered from days 0-42, indicating that the drug had no additional effect on the development phase of the arthritis. The non-steroidal anti-inflammatory agents (NSAIAs) indomethacin, ibuprofen and flurbiprofen failed to suppress either the established or developing disease. Daily treatment with D-penicillamine, tiopronin or chloroquine on days 14-42 had no significant effect on the arthritis; treatment with either D-penicillamine or chloroquine on days 0-56 was also ineffective. When administered on days 14-42 or 0-42 neither gold thiomalate nor auranofin were able to suppress the erosive changes. Sulphasalazine (10-30 mg/kg) suppressed the arthritis whereas sulphapyridine was inactive. Azathioprine (20 mg/kg) suppressed the erosive changes when administered over days 14-42 or 0-42; this activity was associated with toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the effects of pharmacological agents on antigen-induced arthritis in BALB/c mice.

Acute phase protein levels have been measured during the induction and progression of antigen-induced mono-articular arthritis in rabbits and mice. In rabbits there was a short lived elevation in serum C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) immediately following intra-articular injection which returned to baseline levels 10-12 days after the injection. In BALB/c mice, serum amyloid P-component (SAP) and the third component of complement (C3) were elevated after intra-articular injection, returning towards baseline levels 6 weeks after the injection. The levels of CRP and SAP correlated with the inflammatory changes in the joints during the acute phase of the arthritic response (7 days after intra-articular injection). During the chronic phase the levels of these acute phase proteins bore no relationship to the degree of connective tissue destruction.

I. M. Hunneyball

Papers

Pharmacological studies of antigen-induced arthritis in BALB/c mice. I. Characterization of the arthritis and the effects of steroidal and non-steroidal anti-inflammatory agents.

Pharmacological studies of antigen-induced arthritis in BALB/c mice II. The effects of second-line antirheumatic drugs and cytotoxic agents on the histopathological changes

Antigen-induced arthritis in mice.

Studies on the effects of pharmacological agents on antigen-induced arthritis in BALB/c mice.

Acute phase protein changes in antigen-induced mono-articular arthritis in rabbits and mice.