Etiology of rheumatoid arthritis

Effects of Leflunomide on Hyaluronan Synthases (HAS): NF-κB-Independent Suppression of IL-1-Induced HAS1 Transcription by Leflunomide

Despite evidence that points to unfettered hyaluronic acid (HA) production as a culprit in the progression of rheumatic disorders, little is known about differences in regulation and biological functions of the three hyaluronan synthase (HAS) genes. Testing the effects of drugs with proven anti-inflammatory effects could help to clarify biological functions of these genes. In this study, we demonstrate that leflunomide suppresses HA release in fibroblast-like synoviocytes (FLS) in a dose-dependent manner. We further demonstrate that leflunomide suppresses HA synthase activity, as determined by (14)C-glucuronic acid incorporation assays. Additional experiments revealed that in FLS, leflunomide specifically blocked the induction of HAS1. HAS2 and HAS3, genes that are, in contrast to HAS1, constitutively expressed in FLS, are not significantly affected. Leflunomide can function as a NF-kappaB inhibitor. However, EMSA experiments demonstrate that at the concentrations used, leflunomide neither interferes with IL-1beta- nor with PMA-induced NF-kappaB translocation. Furthermore, reconstituting the pyrimidine synthase pathway did not lead to the restoration of IL-1beta-induced HAS1 activation. More importantly, two tyrosine kinase inhibitors mimicked the effect of leflunomide in that both blocked IL-1beta-induced HAS1 activation without affecting HAS2 or HAS3. These data point at HAS1 activation as the possible cause for unfettered HA production in rheumatoid arthritis and might explain, at least in part, the beneficial effects of leflunomide treatment. These findings also support the concept that IL-1beta-induced HAS1 activation depends on the activation of tyrosine kinases, and indicate that leflunomide blocks HA release by suppressing tyrosine kinases rather than through inhibition of NF-kappaB translocation.

Change in cellular localization of a rheumatoid arthritis-related antigen (RA-A47) with downregulation upon stimulation by inflammatory cytokines in chondrocytes

We previously isolated a rheumatoid arthritis-related antigen (RA-A47) protein that had reactivity with RA sera from a human chondrosarcoma-derived chondrocytic cell line, HCS-2/8. Sequencing analysis of ra-a47 cDNA revealed RA-A47 as a product of the colligin-2 gene, which is also known as the human heat shock protein (HSP) 47 gene. Expression of hsp47 has been shown to be cooperatively altered with that of collagen genes upon stimulation. In this study, it was confirmed that the mRNA expression of ra-a47 and COL2A1, a type II collagen gene, was upregulated on stimulation with transforming growth factor (TGF) beta in chondrocytes. However, in contrast, inflammatory cytokines such as tumor necrosis factor (TNF) alpha, interferon (IFN) beta, and interleukin (IL)-6 downregulated the expression of ra-a47 mRNA, whereas the expression of COL2A1 mRNA was not repressed, or even upregulated, in HCS-2/8 cells. Of note, inducible NO synthase (iNOS) and matrix metalloproteinase (MMP)-9 mRNAs were strongly stimulated by TNFalpha. We also found that cell-surface type II collagen disappeared upon such a stimulation, suggesting that decrement of RA-A47 may inhibit the secretion of type II collagen and lead to its accumulation inside the cells. RA-A47 was detected in the cultured medium of TNFalpha-treated HCS-2/8 cells and of IL-1-treated rabbit chondrocytes by Western blot analysis. Under the same conditions, RA-A47 was detected on the cell surface by immunofluorescence staining. These findings demonstrate that the RA-A47 chaperone protein is specifically downregulated, causing the intracellular accumulation of unsecretable type II collagen, while the extracellular matrix (ECM) is degraded by MMPs and iNOS through the stimulation of chondrocytes by TNFalpha. The altered localization of RA-A47 to the surface or outside of cells may represent the mechanism for the recognition of RA-A47 as an autoantigen during rheumatoid arthritis.

A Subgroup of Rheumatoid Arthritis (RA) Associated with Selective Binding of Rheumatoid Factors to Antigen Structures of Cytomegalovirus (CMV)

We compared antibodies (Ab) with both, antiviral and anti IgG properties in patients with rheumatoid arthritis with malignant progress, short remissions and no improvement to therapy. The selective binding of Rheumatoid Factor (RF) to antigen structures of CMV were tested in 180 patients by a newly established ELISA with antiidiotypic goat antibodies of CMV neutralizing human monoclonal Ab and against the virus antigen directly. Displacement reactions on the idiotypic bindingsite as well as comparative ELISA gave proof of the special RF activity. 24,2% of the patients suffering from RA, with IgM RF, showed selective binding to antigen structures of CMV and anti IgG activity.

The evidence of the specific binding capacity of RF to the virus antigen in chronic CMV infection as well as their defined binding capacity to the Fc Fragment of IgG suggest CMV specific RF as the pathogenetic factor of malignant forms of inflammatory rheumatism.

Arthritis-associated changes in flow cytometric characteristics of cultured synovial fibroblasts

Synovial fibroblasts cultured from patients with rheumatoid or reactive arthritis and from controls were studied by flow cytometry, spectroscopy, and electron microscopy. Analysis of 29 cell lines revealed consistent differences between arthritic and normal fibroblasts. Cells cultured from inflamed synovial tissue exhibited higher autofluorescence than did control fibroblasts, and displayed exceptional light scatter properties in flow cytometry, indicating changes in cytoplasmic structures. Electron microscopic examination of the fibroblasts from arthritic synovial tissue revealed large numbers of round, swollen, laminated, mitochondrion-like bodies, which were not observed in the control fibroblasts. The changes observed by flow cytometry (light scatter and autofluorescence) coincided with the presence of the mitochondrion-like organelles. The strong autofluorescence observed in the arthritic fibroblasts resembled the fluorescence spectrum of mitochondrial flavoproteins. These data suggest that persistent metabolic and structural changes have occurred in the mitochondria of synovial fibroblasts and inflammatory synovial tissue. The usefulness of flow cytometry in identifying such cells is described.

Future trends in the treatment of rheumatoid arthritis in the light of current etiopathogenetic theories

The current treatment of rheumatoid arthritis is based on the use of synthetic chemical compounds, the mechanism and action of which have been more or less unknown. Usually this therapeutic effectiveness was discovered accidentally. Often the initial use of such compounds was motivated on the basis of generally diffuse ideas about the eventual pathogenesis of rheumatoid arthritis. The main site of action of most of these drugs has recently been elucidated. Depending on their multiple sites of action the polypharmacy frequency relied upon at present seems also to be theoretically motivated. Many new possibilities for treatment which have appeared recently have resulted from the amission of page limitation. These include various thymic (46), steroid and other hormones (67) and various vehicles or new modes of application, e.g. percutaneous, for directing the effects of drugs selectively to the target tissue, organ and cells. The use of specific T cell clones in therapy (68) has been only briefly dealt with in this article, and the development of operative techniques, endoprosthesis technology and orthopedic devices have not been dealth with at all. Chemical synovectomies with 165Dy-FHMA and other agents (69) will be developed further etc. This overview mainly deals with future trends in the treatment of rheumatoid arthritis based on advances made in the evaluation of the etiopathogenesis. Due to advances in basic sciences and medicine, the pathogenetic mechanisms effective in rheumatoid arthritis are better known today than ever before. The same progress in science has for the first time in history provided us with a potential means of producing bioactive mediators and reagents in sufficient amounts to enable their use also for therapeutic trials and treatment. In addition to the need to develop better methods of treatment for the patients crippled by this chronic disease, studies on the pathogenesis will also be of great benefit to our ideas about exactly what is involved in the complex process clinically known as rheumatoid arthritis.