Rheumatoid arthritis cytotoxicity

Human tumor necrosis factor (TNF) (Fig. 1) is a hormone-like proinflammatory peptide belonging to the group of cytokines. It is mainly produced by cells of the immune system in response to infection, inflammation, or cell damage. Disregulated TNF is an important factor in many pathological situations, like sqDsis, rheumatoid arthritis, inflammatory bowel disease (Crohn s disease), and Cachexia. The cytotoxic activity of TNF is of interest in development of new antitumoral strategies. 

Selley et al. (1992) have recently employed gas chromatography combined with mass spectrometric detection to determine levels of the cytotoxic monounsaturated aldehyde 4-hydroxy-/7 t-2-nonenal in the blood plasma of healthy human subjects, and patients with rheumatoid and osteoarthritis. Intriguingly, this lipid peroxidation end-product is present at a concentration ofc. lx 10 mol/dm in healthy and osteoarthritic human plasma samples (but significantly elevated in those collected from rheumatoid arthritis patients). Although at least some of this could originate from the oxidative degradation of PUFAs invm, there may be a relationship existing between these levels and the frequency of thermally/... 

Human chronic inflammatory diseases are characterized by populations of cells with altered regulation and function. A large body of evidence suggests that many of these cellular abnormalities may be linked to an increase in the production of free radicals and/or deficiencies of antioxidant defence systems. Oxygen free radicals attack cell structures, altering their function, and are cytotoxic. They have therefore been implicated in the pathogenesis of rheumatoid arthritis as well as many other human diseases (HaUiwell, 1991). 

Nanki T, Imai T, Nagasaka K, et al. Migration of CX3CR1-positive T cells producing type 1 cytokines and cytotoxic molecules into the synovium of patients with rheumatoid arthritis. Arthritis Rheum 2002 46(ll) 2878-2883. 

Caryophyllidae are an interesting source of oligosaccharides and peptides with potential anti-inflammatory and/or immunomodulating effect. These polar compounds might for instance explain the fact that the fresh juice expressed from Aerva lanata (L.) Juss. (Amaranthaceae) inhibits carrageenan-induced edema in rodent. Note that the seeds of Gomphrena species inhibit the formation of IL-6 by osteoblastic cells (MC3T3-E10) without cytotoxicity in vitro. Such property could be useful for the treatment of chronic rheumatoid arthritis, infection, and cancer. In the Lauraceae, trans-cinnamal-dehyde from Cinnamomum cassia (Lauraceae, order Laurales) inhibits in vitro the... 

However, it is now recognised that neutrophils can contribute to host-tissue damage if they are activated to secrete reactive oxidants and granule enzymes, and if the local concentrations of anti-oxidants and protease inhibitors within the tissue are low or defective. Thus, inappropriate neutrophil activation leading to host-tissue damage has been implicated in reperfusion injury, Crohn s disease, adult respiratory distress syndrome (ARDS) and rheumatoid arthritis. In these conditions, it is envisaged that neutrophils accumulate in tissues and become inappropriately activated to secrete their cytotoxic products, which then initiate or contribute to host-tissue damage. 

Tumor Necrosis Factor There are two types of tumor necrosis factor TNF-a and TNF- 8. Of the two, TNF-a has been studied in more detail. TNF-a is a 157 amino acid polypeptide. It is a mediator of immune regulation, including the activation of macrophages and induction of the proliferation of T cells. Another TNF-a function is its cytotoxic effects on a number of tumor cells. Recent research, however, concentrates on its property in the stimulation of inflammation, particularly in the case of rheumatoid arthritis. Clinical trials are being conducted with drugs to block TNF-a with anti-TNF-a monoclonal antibodies. These antibodies target the excessive levels of TNF-a in the synovial fluid of joints and provide relief to sufferers of rheumatoid arthritis (Exhibit 4.10). 

Presumably, any cytotoxic substance that destroys bone marrow and lymphoid tissue may be used as an immunosuppressant. Among these drugs, the most widely used primarily for autoimmune diseases are vincristine, methotrexate, and cytarabine. However, their use should be considered experimental. Only methotrexate is seriously and sufficiently recognized as an initial drug for treating rheumatoid arthritis. 

Azathioprine also has applications in certain disorders with autoimmune components, most commonly rheumatoid arthritis. It is as effective as cyclophosphamide in the treatment of Wegener s granulomatosis. It has largely been replaced by cyclosporine in immunosuppressive therapy. Relative to other cytotoxic agents, the better oral absorption of azathioprine is the reason for its more widespread clinical use. 

IL-18 augments T- and NK-cell maturation, cytotoxicity and cytokine production. It stimulates TH differentiation, promotes secretion of TNF-a, IFN-y and GM-CSF and enhances NK cell cytotoxicity by increasing FasL expression. IL-8-mediated neutrophil chemotaxis is promoted by IL-18 via its effects on TNF-a and IFN-y, which are stimulatory in action. It plays an important role in maintaining synovial inflammation and inducing joint destruction in rheumatoid arthritis. In synovium of patients with rheumatoid arthritis, enhanced levels of TNF-a and IL-1 are associated with augmented expression of IL-18. 

Methotrexate, which is used for several disease states such as rheumatoid arthritis (where OTC analgesics are often taken to relieve pain) or malignant disease, as a cytotoxic (where pain relief also becomes important) - increased methotrexate levels may occur, with risk of toxicity. 

Pro-inflammatory cytokines are important mediators of inflammation and tissue destruction. This section describes two cell-based assays that were used to screen for inhibitors of cytokine production and some of the compounds discovered using these screens. The two screens were important elements of a collaboration between Xenova Ltd and the Suntory Institute of Biomedical Research to find microbial metabolites with potential utility for the treatment of rheumatoid arthritis. Both screens were cell stimulatory assays with similar formats, the principle of which is illustrated in Figure 3. Treatment of cells with a particular stimulus activates a signal transduction pathway, one of the end results of which is production of a cytokine, which is secreted into the assay medium. After a separation step, the cytokine of interest is measured quantitatively in the supernatant by dissociation enhanced lanthanide fluorescence immunoassay (DELFIA) using a europium-labeled tertiary antibody. At the same time, cytotoxic properties of test substances are determined by assessing their effect on proliferation of the separated cells. 

Azathioprine is indicated in renal homotransplantation (five-year patient survival rate of 35%) in rheumatoid arthritis (for patients with severe, active, and erosive disease not responding to conventional therapies) and in chronic ulcerative colitis, myasthenia gravis, and Behcet s syndrome (adverse effects may offset its limited value). As with other cytotoxic drugs, azathioprine can affect rapidly growing cells, resulting in leukopenia, thrombocytopenia, and gastrointestinal toxicity. In addition, hepatotoxicity (cholestasis) has been reported. Many of the general problems of immunosuppression, such as increased risk of infections, can also occur. 

Natural killer (NK) cells and cytotoxic T lymphocytes (CTL) are the primary line of defense against viruses and other intracellular pathogens in the immune system. The cytotoxic lymphocytes recognize infected host cells and kill them with the help of the pore-forming protein perforin and by proteolytic events carried out by members of the granzyme family of serine proteases. Although an essential component of immunity under normal conditions, aberrant cytotoxic lymphocyte activity has been associated with autoimmune disorders such as rheumatoid arthritis, diabetes, or allograft rejection [65],... 

At the site of inflammation the stimulated PMNL are capable of producing reactive oxygen species such as the cytotoxic superoxide anion ( 02 ) which can react with other molecules to produce the extremely reactive hydroxyl radical ( OH), considered the main initiator of lipid peroxidation. In addition, inflammatory cells are able to release large quantities of hydrolases, such as elastase and collagenase, that catalyse the hydrolysis of tissue components involved in the extracellular proteolysis of rheumatoid arthritis and other inflammatory states Fig. (3) . If the noxious stimulus persists, the action of all these mediators contributes to the chronic proliferative phase of inflammation. It is in this third and last phase that tissue degeneration and fibrosis occur. Differentiation between the acute and/or chronic inflammation is traditionally based on the kind of inflammatory cells that predominate in the lesions. In fact, in acute injury... 

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