Interaction(s) between essential fatty acids, eicosanoids, cytokines, growth factors and free radicals: Relevance to new therapeutic strategies in rheumatoid arthritis and other collagen vascular diseases

Abstract

Eicosanoids, lymphokines, and free radicals are known to participate in the pathogenesis of inflammation. Tumour necrosis factor (TNF), interluekin-1 and 6 (IL-1 and IL-6) and colony stimulating factor-1 (CSF-1) are secreted mainly by activated macrophages, whereas T-cells secrete IL-2, IL-3, IL-4 and interferon-γ (IFN-γ). In addition, activated macrophages and lymphocytes can also produce eicosanoids and free radicals which have potent pro-inflammatory actions. Eicosanoids, lymphokines, and free radicals can modulate the immune response, cell proliferation, stimulate collagenase and proteases secretion and induce bone resorption; events which are known to be associated with various collagen vascular diseases. On the other hand transforming growth factor-β (TGF-β) produced by synovial tissue, platelets and lymphocytes can inhibit collagenase production, suppress T-cell and NK-cell proliferation and activation and block free radical generation and seems to be of benefit in rheumatoid arthritis. Drugs such as cyclosporine, 1,25,dihydroxycholecalciferol and pentoxyfylline can block lymphokine and TNF production and thus, may inhibit the inflammatory process. Essential fatty acids, the precursors of eicosanoids, are suppressors of T-cell proliferation, IL-1, IL-2 and TNF production and have been shown to be of benefit in rheumatoid arthritis, systemic lupus erythematosus and glomerulonephritis. Thus, the interactions between essential fatty acids, eicosanoids, lymphokines, TGF-β and free radicals suggest that new therapeutic strategies can be devised to modify the course of collagen vascular diseases.