Cytokines in chronic inflammatory arthritis. III. Rheumatoid arthritis monocytes are not unusually sensitive to gamma-interferon, but have defective gamma-interferon-mediated HLA-DQ and HLA-DR induction

Effects of the Sri Lankan medicinal plant, Salacia reticulata, in rheumatoid arthritis

Salacia reticulata is a native plant of Sri Lanka. In the traditional medicine of Sri Lanka and India, Salacia reticulata bark is considered orally effective in the treatment of rheumatism, gonorrhea, skin disease and diabetes. We have investigated, both in vivo and in vitro, whether the leaf of Salacia reticulata (SRL) can ameliorate collagen antibody-induced arthritis (CAIA) in mice as the rheumatoid arthritis (RA) model. The mice were fed a lard containing chow diet (AIN-93G) or the same diet containing 1% (w/w) SRL powder. All mice were bred for 23 days. On day 7 or 14 after LPS injection, mice were killed, and tissue and blood samples were collected. Histological analysis was performed, and serum levels of inflammatory mediators and the mRNA levels of inflammation-related genes and osteoclast-related genes were measured. SRL treatment ameliorated the rapid initial paw swelling, inflammatory cells infiltration, skeletal tissues damage, osteoclast activation and the mRNA levels for osteoclast-related genes compared with the CAIA mice. However, the serum and mRNA levels of inflammatory mediators did not differ between the CAIA mice and the SRL-treated mice. SRL might reduce the inflammatory cells induction and skeletal tissue degradation by CAIA by the regulating osteoclastogenesis.

Nitric oxide production and inducible nitric oxide synthase expression in inflammatory arthritides

In this study, we have identified the source of nitric oxide (NO) produced in the human inflammatory joints by analyzing expression of inducible NO synthase. In ex vivo organ cultures, both inflammatory synovium and cartilage from patients with rheumatoid arthritis produced NO. The NO production was suppressed by NG-monomethyl-L-arginine, an inhibitor of NO synthase. The amount of NO produced by the synovium correlated with the proportion of CD14+ cells in the corresponding tissue (r = 0.8, P < 0.05). Immunohistochemical analysis as well as in situ hybridization showed that inducible NO synthase was predominantly expressed in synovial lining cells, endothelial cells, chondrocytes, and to a lesser extent, in infiltrating mononuclear cells and synovial fibroblasts. The synovial lining cells and the infiltrating cells expressing inducible NO synthase were identified where CD14+ cells were located. Together with morphological features, this suggests that they are type A synoviocytes. NO production from freshly isolated synoviocytes and chondrocytes was up-regulated by in vitro stimulation with a combination of IL-TNF-beta, TNF-alpha, and LPS. In summary, the present results suggest that NO is produced primarily by CD14+ synoviocytes, chondrocytes, and endothelial cells in inflammatory joints of arthritides. NO production can be upregulated by cytokines present in inflamed joints. The increased NO production may thus contribute to the pathological features in inflammatory arthritides.

Cytokines in rheumatic diseases

IL-1 and related cytokines have multiple biologic activities relevant to the rheumatic diseases. In addition to mediating inflammatory and immune responses, these proteins regulate many aspects of connective tissue metabolism. The cytokines interact in complex cascades: because of this, and various technical reasons, the exact role of cytokines in the pathogenesis of rheumatic diseases remains uncertain. However, considerable experimental data suggest that the abnormal regulation of cytokines contributes to such siseases as inflammatory arthritis, systemic lupus erythematosus, scleroderma, and dermatomyositis. Animal models of these diseases have contributed to understanding the role of cytokines in pathogenesis. Furthermore, drugs useful in treating these diseases affect cytokine pathways; some cytokines, their antagonists, or related substances have been used therapeutically to treat rheumatic diseases. The therapeutic use of these agents will likely increase as knowledge about the role of cytokines in the pathogenesis of rheumatic diseases expands.

Expression of monocyte chemotactic and activating factor in rheumatoid arthritis. Regulation of its production in synovial cells by interleukin-1 and tumor necrosis factor

OBJECTIVE

To investigate whether monocyte chemotactic and activating factor (MCAF) contributes to the accumulation of macrophages in the joints of patients with rheumatoid arthritis (RA).

METHODS

MCAF was measured by radioimmunoassay. MCAF gene expression was determined by Northern blotting and reverse-transcriptase polymerase chain reaction. Recombinant human MCAF was injected into rabbit joints to evaluate the effect of MCAF on infiltration of macrophages.

RESULTS

High levels of MCAF were detected in synovial fluid from patients with RA. Cells freshly isolated from synovial fluid expressed MCAF messenger RNA (mRNA). Fibroblast-like synoviocytes were found to express MCAF mRNA and to secrete MCAF in response to interleukin-1 (IL-1) and tumor necrosis factor in vitro. IL-1 also promoted MCAF gene expression in rabbit synovial tissue in vivo. MCAF caused marked infiltration of macrophages in rabbit synovial tissue.

CONCLUSION

Our findings suggest that MCAF may contribute to the accumulation of macrophages in inflamed rheumatoid joints.

Defective HLA class II expression in monocytes of type 1 diabetic patients. The Childhood Diabetes in Finland Study Group

Activation of T-helper cells is modulated by the intensity of HLA class II expression on antigen-presenting cells. We evaluated whether any abnormalities could be found in the expression of HLA-DR and -DQ molecules on monocytes in type 1 diabetic subjects. DR and DQ molecules were induced by human recombinant interferon-gamma on cultured peripheral blood monocytes obtained from children with type 1 diabetes (N = 28), their siblings (N = 18) and unrelated healthy controls (N = 21). The response in DQ induction varied considerably between different individuals, but the average responsiveness was significantly lower in patients compared to siblings and unrelated controls. In addition to the diabetic subjects deficient DQ induction was also observed in three siblings. One of them had high levels of islet cell antibodies and presented with diabetes 6 months later, and another had active rheumatoid arthritis. The response in DR induction was also slightly lower in patients than in siblings, but did not differ from that in unrelated controls. The results suggest abnormalities in the regulation of HLA class II expression in type 1 diabetic subjects possibly reflecting the ongoing autoimmune process.

Interleukin-6 can prime THP-1 macrophages for enhanced production of tumor necrosis factor-alpha in response to LPS

Although interferon-gamma has been shown to effectively prime macrophages for enhanced production of tumor necrosis factor-alpha (TNF alpha), it is reasonable to assume that other cytokines present in the extracellular environment may likewise facilitate cytokine biosynthesis. For example, interleukin-6 (IL-6) is synthesized by synovial lining macrophages and fibroblasts, and has been detected (along with TNF alpha) in rheumatoid synovial effusions. Therefore, the purpose of the present study was to determine whether IL-6 influences the production of IL-1 beta and/or TNF alpha by THP-1 macrophages. Although IL-6 treatment alone resulted in only a slight increase in TNF alpha levels, administration of IL-6 followed by Sal. minnesota LPS resulted in a synergistic potentiation of TNF alpha production by THP-1 macrophages. The priming effect of IL-6 could be reversed by boiling, or by the addition of a neutralizing polyclonal antibody against IL-6. Notably, IL-6 only weakly enhanced interleukin-1 beta production. In summary, the ability of IL-6 to potentiate TNF alpha production by THP-1 macrophages may provide insight into the regulation of the cytokine network in inflammatory diseases, such as rheumatoid arthritis.

Class II major histocompatibility complex antigen expression on unstimulated and gamma-interferon stimulated monocytes from patients with multiple sclerosis, rheumatoid arthritis and normal controls

HLA-DR, HLA-DQ, and HLA-DP antigen expression was assessed by immunofluorescent flow cytometry on monocytes from 19 patients with active multiple sclerosis (MS), 19 with inactive MS, 7 patients with early active rheumatoid arthritis (RA), and 19 normal controls. Percentage positivity and median channel fluorescence (MCF) were determined after separation of the monocytes (TO) and following 48 h culture with (T48 + IFN) and without (T48) recombinant gamma interferon (rIFN-gamma). The percentage positivity of the cells was normal at TO for all groups of patients for each of the HLA types but statistically significantly increased above normal, on monocytes from patients with inactive MS, after culture with rIFN-gamma. At TO, the MCF values for HLA-DQ, and HLA-DP were statistically significantly increased above normal on monocytes from patients with active MS indicating some pre-programming of the cells in vivo. After culture, when the carry-over from baseline TO values was eliminated, the increment in MCF for HLA-DR, on monocytes from patients with inactive MS, was statistically significantly lower than normal in the non-gamma-IFN cultures but was normal in the presence of rIFN-gamma. Conversely, the increment in MCF for HLA-DP on monocytes from patients with active MS was significantly lower than normal after culture with rIFN-gamma. Therefore, the stimulation required to increase antigen density on cells already expressing antigen may be different to that required to stimulate de novo expression on negative cells. Both systems appear to be abnormal in MS, possibly reflecting differences in disease activity, while only one system appears abnormal in RA.