Suppressive effect of anti-rheumatic drugs on interleukin-1 beta release from human peripheral blood monocytes

The mechanisms of action of disease-modifying antirheumatic drugs: a review with emphasis on macrophage signal transduction and the induction of proinflammatory cytokines

1. Rheumatoid arthritis (RA) is probably the most common source of treatable disability. A major problem in modern rheumatology is that the mechanism(s) of action of the currently used disease-modifying antirheumatic drugs (DMARDs) remain unclear. Many of these drugs entered rheumatology mainly through clinical intuition and have been used for decades. 2. The former T-cell-centered paradigm of rheumatoid inflammation has given way to a model of inflammation highlighting the macrophage and its proinflammatory cytokines. In particular, tumor necrosis factor alpha (TNF-alpha) has gained prominence as a central proinflammatory mediator in RA, and antibodies against TNF-alpha have been successfully used in patients with RA. 3. This review will summarize the recent advances in determining the mechanisms of action of the currently used DMARDs, with particular emphasis on their effects on the induction of TNF-alpha and interleukin 1 (IL-1) in mononuclear phagocytes. Although some DMARDs, such as auranofin, antimalarials and tenidap, act as inhibitors of the induction of these cytokines in monocytes or macrophages or both, other drugs, such as methotrexate, D-penicillamine and aurothiomalate, do not seem to affect either TNF-alpha or IL-1. 4. The drugs' effects on proinflammatory cytokine induction are correlated to those on other macrophage responses.

Complete prevention of the clinical expression of adjuvant-induced arthritis in rats by cyclosporin-A and lobenzarit: the regulation of lymph node cell populations and cytokine production

A single dose of either cyclosporin-A (CsA) or lobenzarit (CCA) given with an arthrogenic adjuvant completely prevented expression of experimental adjuvant arthritis in rats. The aim of this study was to understand how these drugs prevented the arthritis expression by studying the popliteal lymph nodes draining the arthritic joints at various times after adjuvant injection. Neither drug affected the proliferation in popliteal lymph nodes at the time arthritis was normally expressed, however, there was a marked change in the types of cells present. Immunofluorescence assays showed a reduction in the proportion of CD4+ cells, while the proportion of B-lymphocytes was almost doubled. This coincided with a marked elevation in the ability of these cells to produce interleukin (IL)-6. At the same time production of other cytokines (IL-2, tumour necrosis factor (TNF) and interferon (IFN)-gamma) was not greatly affected. However, one day after adjuvant injection IL-2 and IFN-gamma production was reduced. In vitro experiments showed that IL-6 production by lymphoid cells was relatively unaffected by CsA and CCA but IL-2, TNF and IFN-gamma were suppressed by CsA. The results indicate that CsA and CCA may modify the response to the arthritic adjuvant by specifically inhibiting IL-2, TNF and IFN-gamma production at the time of adjuvant injection. The lack of inhibition of IL-6 by these drugs reveals it may not play a key role in the initiation of this model of chronic inflammation.

Effects of antirheumatic agents on cytokines

A review of the literature concerning the effects of traditional antirheumatic drugs on cytokines and the cytokine and anticytokine approaches already used in the therapy of rheumatoid arthritis (RA) is presented. Many antirheumatic drugs are capable of cytokine modulation in vitro. Corticosteroids inhibit the transcription of a broad spectrum of genes including those encoding monocyte, T cell-derived cytokines and several hemopoietic growth factors, whereas drugs such as cyclosporin A and D-penicillamine interfere with T cell activation more specifically by suppressing interleukin 2 (IL-2) production. The in vivo effects of drug therapy on cytokines in RA patients are less well established. Gold compounds reduce circulating IL-6 levels and the expression of monocyte-derived cytokines, such as IL-1, tumor necrosis factor (TNF), and IL-6, in the rheumatoid synovium. Decreases in circulating IL-6, soluble IL-2 (sIL-2R), and TNF receptors and in synovial fluid IL-1 levels have been reported with methotrexate. Reductions in circulating IL-6 and sIL-2R concentrations have also been observed with cyclosporin and corticosteroids, whereas azathioprine reduces IL-6 but not sIL-2R. Studies on sulfasalazine are conflicting and the in vivo effects of D-penicillamine and antimalarials have not been studied yet. Interferon gamma therapy is not effective in RA but may prove a useful antifibrotic for systemic sclerosis. Colony stimulating factors improve the granulocytopenia associated with Felty's syndrome or drug toxicities but can induce arthritis flares and should be reserved to treat infectious complications. Promising results are being obtained with selective antagonism of TNF and IL-1 in RA, and combinations of anticytokine strategies with traditional antirheumatic drugs have been already envisaged. These should preferably be based in a broader knowledge of the effects of antirheumatic agents on the cytokine network.

Cytokine autoantibodies in rheumatoid arthritis

Sera from 42 patients with rheumatoid arthritis (RA) and 40 healthy controls (HC) were examined for cytokine autoantibodies (CK-aAb) by accurate and sensitive radioimmunoassays. The prevalences of detectable CK-aAb in RA (HC) were: aAb-IL-1 alpha = 36% (38%); aAb-IL-6 = 29% (13%), p = 0.06; aAb-IL-8 = 0% (0%); aAb-IFN alpha = 12% (3%), p = 0.11. The levels of the individual CK-aAb did not correlate, and there were no correlations between CK-aAb levels and clinical or laboratory variables. CK-aAb levels remained constant in 8 RA patients tested over a period of 6 months. With regard to alterations in aAb-IL-1 alpha levels, 4/11 HC were consistently positive over 18-36 months; 2/11 converted and became highly positive. The levels of aAb-IFN alpha and aAb-IL-6, but not aAb-IL-1 alpha, tended to be increased in RA patients; aAb-IL-8 were undetectable in both RA and HC.

Salicylates for ulcerative colitis--their mode of action

Delivery of 5-aminosalicylic acid to the colon by sulphasalazine, other azo-bonded compounds and controlled-release preparations is introduced in the context of metabolism by epithelial cells and therapeutic efficacy in ulcerative colitis. Potential modes of action are then reviewed, including actions on luminal bacteria, epithelial cell surface receptors, cellular events (such as nitric oxide release or butyrate oxidation), electrolyte transport and epithelial permeability. Evidence for an influence of salicylates on circulating and lamina propria inflammatory cells is presented, as well as actions on adhesion molecules, chemotactic peptides and inflammatory mediators, such as eicosanoids, platelet-activating factor, cytokines or reactive oxygen metabolites. The precise mechanism will remain uncertain as long as the aetiology of ulcerative colitis is unknown, but a pluripotential mode of action of salicylates is an advantage when influencing the network of events that constitute chronic inflammation.

Monocyte chemoattractant protein 1 and interleukin 8 production by rheumatoid synoviocytes. Effects of anti-rheumatic drugs

Activated synoviocytes are major effector cells in the pathogenesis of rheumatoid arthritis (RA) because of their capacity to secrete a variety of inflammatory mediators. Among these mediators, the chemotactic proteins monocyte chemoattractant protein 1 (MCP-1) and interleukin 8 (IL-8) are likely to contribute to the recruitment of inflammatory cells into the arthritic joint. We examined the effects of anti-rheumatic drugs on the MCP-1 and IL-8 production by cultured RA synoviocytes exposed to pro-inflammatory agonists. Both chemotactic cytokines were quantified by specific enzyme-linked immunosorbent assays (ELISA), and found to accumulate in the culture supernatants. Although the time course of formation was similar, the yield of IL-8 was three to 10-fold higher than that of MCP-1. Non-steroidal anti-inflammatory drugs inhibited the synthesis of prostaglandins, but did not influence the production and release of both chemotactic cytokines. Of three disease-modifying drugs tested, dexamethasone and gold sodium thiomalate (GST) inhibited the production of IL-8 and MCP-1, while methotrexate (MTX) was inactive. Dexamethasone reduced the production of MCP-1 and IL-8 by 20-65% and 60-80%, respectively, whilst GST inhibited MCP-1 and IL-8 synthesis in suboptimally, but not in optimally stimulated synoviocytes. Taken together, these results show that the production of MCP-1 and IL-8 is similarly affected by anti-rheumatic drugs and that dexamethasone is the most potent inhibitor suggesting that part of the anti-rheumatic action of glucocorticoids is due to prevention of accumulation of chemotactic cytokines acting on neutrophils and monocytes.

Sulphasalazine inhibition of human granulocyte activation by inhibition of second messenger compounds

The effects of sulphasalazine on the production of second messenger compounds in human granulocytes have been characterised by various stimuli. The increases in cytosolic calcium, inositol trisphosphate, diacylglycerol, and phosphatidic acid (all important mediators of intracellular signal transduction) triggered by stimulation were inhibited by sulphasalazine. The metabolites 5-amino-salicylic acid and sulphapyridine were less potent inhibitors than the mother compound. It is concluded that sulphasalazine inhibits the synthesis of phosphoinositide derived second messenger compounds at the level of phospholipase C or its regulatory guanosine 5'-triphosphate (GTP) binding protein. Inhibition of phosphatidic acid synthesis was either due to the same mechanism, or to interaction with a phospholipase D regulating GTP binding protein.