Human synovial fibroblasts coexpress IL-1 receptor type I and type II mRNA. The increased level of the IL-1 receptor in osteoarthritic cells is related to an increased level of the type I receptor.

BACKGROUND: Cytokines, in particular IL-1, are believed to be responsible for mediating cartilage degradation in osteoarthritis (OA). To investigate the role of the IL-1 system in this disease, we studied in normal and OA human synovial fibroblasts the nature, the number, and the level of expression of the IL-1 receptor (IL-1R) and through which receptor the biologic stimulation of these cells by IL-1 is mediated. EXPERIMENTAL DESIGN: We determined the IL-1R level by radioligand assay, the type of IL-1R with the use of specific antibodies and by the reverse transcriptase-PCR (RT-PCR), and the mRNA level of the type I IL-1R by slot blot analysis. Biologic activity was measured on the synovial fibroblasts via IL-1 binding and prostaglandin E2 production. RESULTS: Binding data revealed the presence of a single class of high affinity IL-1R in both normal (kD, 21 +/- 4.5 pM) and OA (kD, 23 +/- 5.0 pM) human synovial fibroblasts. The number of receptors was significantly higher (p < 0.004) in OA synovial fibroblasts (2534 +/- 187 sites/cell) than in normal cells (1310 +/- 96 sites/cell). This increase was transient; OA synovial fibroblasts in second and third passages had a normal level of IL-1R. Analysis of the mRNA species by RT-PCR revealed that both type I and type II IL-1R are coexpressed in normal and OA synovial fibroblasts; the type I mRNA was the most predominant in all samples. No difference in the relative amount of type I IL-1R mRNA level was found between normal and OA cells. A blocking Ab against the type I IL-1R completely inhibited, in both normal and OA cells, the receptor binding and IL-1 beta stimulated PGE2 production, whereas the treatment with anti-type II IL-1R was ineffective. CONCLUSIONS: These results indicate that the type I IL-1R is up-regulated in OA synovial fibroblasts and is responsible for mediating the biologic activation of these cells by IL-1. This phenomenon is probably secondary to an abnormality in the post-transcriptional regulation of the type I IL-1R. Although type II IL-1R is also expressed, its translation seems to be inoperative, or this receptor is already shed.

The defective in vitro expression of interferon-gamma messenger RNA in rheumatoid arthritis is recovered by cycloheximide.

Circulating T lymphocytes from patients with rheumatoid arthritis (RA) were found to produce low concentrations of interferon-gamma (IFN-gamma) and express low amounts of this messenger RNA (mRNA) in response to stimulation with phytohemagglutinin (PHA). In this study, we have examined the superinduction effect of cycloheximide (CHX) on the IFN-gamma mRNA expression in PHA-stimulated T lymphocytes from nine patients with active RA compared to three healthy individuals. When CHX was added 6 hr postactivation, the expression of IFN-gamma mRNA in RA patients increased significantly at 24 and 48 hr (P less than 0.01) and reached levels similar to those observed in controls. We suggest that posttranscriptional events could play a role in the defective production of IFN-gamma observed in RA.

Interferon-gamma mRNA expression upon in vitro T lymphocyte activation is decreased in rheumatoid arthritis patients.

A decreased production of interferon-gamma (IFN-gamma) and interleukin-2 (IL-2) upon in vitro stimulation by phytohemagglutinin (PHA) peripheral blood leucocyte in active rheumatoid arthritis (RA) patients has been described as an important immunological abnormality in this disease. However, the molecular level at which this defect might occur has not been fully documented. We have investigated the kinetics of IFN-gamma, interleukin-2 receptor (IL-2 R), and interleukin-1 beta (IL-1 beta) messenger RNA (mRNA) expression in RA patients (n = 9) and normal controls (n = 5) after PHA leucocyte activation. We demonstrate here a significantly decreased expression of IFN-gamma mRNA in RA patients without modification of its kinetics associated with a similar IL-1 beta mRNA expression.

In vivo beneficial effects of cyclosporin A and 1,25-dihydroxyvitamin D3 on the induction of experimental autoimmune thyroiditis.

In a recent work, we provided evidence that the in vitro inhibitory effect of cyclosporin A (CsA) was potentiated by the addition of another immunosuppressive molecule, the 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). In the present study, we investigated the in vivo influence of the association of both drugs administered at infratherapeutic doses, using an experimental model of autoimmune thyroiditis in CBA mice. Treatment regimen of the animals was initiated at priming with thyroglobulin (Tg) and consisted of daily administration of CsA (10 and 20 mg/kg/day, intragastrically) and/or 1,25(OH)2D3 (0.1 and 0.2 microgram/kg/day, ip) for 21 days. Control mice that were given a placebo preparation orally and the vehicle of vitamin D3 metabolite ip developed a severe disease as assessed by histological examination on Day 28 postimmunization and detection of circulating anti-Tg antibodies. Treatment with either drug administered alone at the doses mentioned above did not affect the incidence of thyroiditis and only reduced by up to 26% the severity of histological lesions. In contrast, the mice treated simultaneously with both drugs exhibited a lower incidence of thyroid pathology and developed a significantly milder disease (P less than 0.001) as compared to controls. However, there was no alteration in the levels of anti-Tg antibodies. This in vivo beneficial effect of low doses of CsA and 1,25(OH)2D3 was not due to an accumulation of CsA in the blood of treated mice since the levels of CsA were similar, regardless of the administration of 1,25(OH)2D3. Our data suggest that these two immunomodulatory agents used together at low doses may be an effective therapy of autoimmune disorders with fewer side effects.