The Role of Macrophages in the Rheumatic Diseases

Activated monocytes induce arthritis-associated changes in mitochondria of cultured synovial fibroblasts

We have recently shown that synovial fibroblasts cultured from patients with reactive or rheumatoid arthritis exhibit increased autofluorescence when compared with controls. Morphological studies suggested that this increase was related to the anomalous structure of mitochondria in cells cultured from rheumatoid or non-rheumatoid inflammatory synovial tissue. The present study describes attempts to find an explanation for these observations. The effects of conditioned media of cultured mononuclear cells were tested on normal synovial fibroblasts. Conditioned media of monocytes stimulated with lipopolysaccharide or poly-IC induced an increase in the cellular autofluorescence and changes in the morphology of mitochondria in normal fibroblasts. These changes were indistinguishable from those seen in synovial fibroblasts cultured from various arthritides. Indomethacin or gold salts did not abolish the effects of monocyte-conditioned media. Abnormal mitochondria could not be induced in the presence of cycloheximide. This study describes a new aspect of monocyte-fibroblast interactions during rheumatoid and non-rheumatoid inflammation of synovial tissue.

The effects of synovial fluid macrophages and interleukin-1 on hyaluronic acid synthesis by normal synovial fibroblasts

The effects of peripheral blood monocyte and rheumatoid synovial fluid macrophage conditioned media were studied on hyaluronic acid (HA) metabolism of normal synovial fibroblasts. Both media stimulated HA synthesis about two-fold compared to controls (1% fetal calf serum). The activated mononuclear phagocyte conditioned media did not contain HA-degrading activity in these experiments. The effects of various concentrations of interleukin-1 (IL-1) on HA synthesis and proliferation of synovial fibroblasts were studied. Even at very low concentrations (0.1 IU IL-1/ml) HA synthesis was stimulated. With increasing concentrations HA synthesis did not increase but proliferation was stimulated. Stimulated fibroblasts synthesized mainly high molecular weight HA. Thus with IL-1-activation, normal synovial fibroblasts could not produce increased amounts of abnormal HA with decreased molecular weight.

Effects of gold salts on experimental periodontitis. II. Cell population characteristics

A previous study showed that the systemic administration of soluble gold salts (gold sodium thiomalate) resulted in significantly less periodontal destruction after 2 weeks of experimentally induced periodontitis. In order to provide information on the possible mechanisms of action of gold salts in the experimental periodontitis situation, the present study analyzed and compared the characteristics of the inflammatory cell populations in animals receiving gold salts with those present in animals which had not received gold salts. Maxillary gingival biopsy specimens were obtained from the buccal aspect of ligatured teeth after 2 weeks of experimental periodontitis. Cell populations were characterized and enumerated, on 1-micron sections, in an epithelial and superficial connective tissue zone, and a deep connective tissue zone. Significantly fewer inflammatory cells were present in experimental (gold receiving) specimens, and this reduction was due primarily to fewer polymorphonuclear leucocytes (PMNs). No significant reduction occurred in any other inflammatory cell-type. The reduction in number of PMNs in experimental specimens was associated with a decreased number of morphologically altered, degenerating fibroblasts in the connective tissue compared to the PMN-dominated lesion of control specimens. Mechanisms whereby gold salts can reduce chemotaxis and functional capabilities of inflammatory cells are discussed.

Investigations on vitamin E and lipid peroxide status in rheumatic diseases

Patients of both sexes suffering from two types of rheumatic diseases-- rheumatoid arthritis and osteoarthrosis--were examined. Healthy volunteers of similar age served as controls. No significant difference was found in the plasma vitamin E content of the patients. Plasma malondialdehyde content was significantly higher /P less than 0.001/ in both sexes in the RA and OA groups as compared to the controls. Plasma catalase activity in both sexes was significantly higher (P less than 0.01) in RA and OA groups while RBC glutathione-peroxidase showed significantly (P less than 0.001) higher activity only in the female RA group, as compared to the control subjects. A difference was found between RA and OA groups in malondialdehyde content and in glutathione-peroxidase activity in subjects of both sexes.

The effect of rheumatoid synovial fluid macrophages on DNA, glycosaminoglycan and collagen synthesis by synovial fibroblasts

The effects of soluble factors secreted by peripheral blood monocytes and rheumatoid synovial fluid macrophages were tested on human synovial fibroblast cultures. Both monocytes and macrophages liberated factors which reduced DNA synthesis (3H-thymidine incorporation) by synovial fibroblasts. Monocyte and macrophage factors stimulated hyaluronic acid synthesis. The activation obtained with rheumatoid synovial macrophages was considerably greater than that with monocytes. Foetal bovine serum was found to have a clear stimulatory effect on the synthesis of collagen and other proteins by fibroblasts. The effects of monocyte and macrophage factors on protein synthesis in synovial fibroblasts were small: collagen synthesis was slightly increased relative to other extracellular proteins.

Gold inhibition of the production of the second complement component by lymphokine-stimulated human monocytes

The ability of gold sodium thiomalate to inhibit production of the second complement component (C2) by monocytes stimulated by a lymphokine (monocyte complement stimulator is demonstrated. This gold salt inhibits C2 production irreversibly if monocytes are incubated with it before or during lymphokine stimulation. Thiomalic acid is not inhibitory. Monocytes already stimulated by lymphokine are resistant to inhibition of C2 production by gold sodium thiomalate. Gold salts do not reduce monocyte viability, phagocytic ability (latex heads) accessory cell function (as measured by the ability to present antigen to autologous lymphocytes), or capacity to act as stimulating cells in mixed leukocyte culture. Gold sodium thiomalate's inhibition of monocyte responsiveness to lymphokine may be significant in explaining the therapeutic benefit of gold salts in rheumatoid arthritis.