The molecular mechanism of osteoclastogenesis in rheumatoid arthritis

Bone-resorbing osteoclasts are formed from hemopoietic cells of the monocyte–macrophage lineage under the control of bone-forming osteoblasts. We have cloned an osteoblast-derived factor essential for osteoclastogenesis, the receptor activator of NF-κB ligand (RANKL). Synovial fibroblasts and activated T lymphocytes from patients with rheumatoid arthritis also express RANKL, which appears to trigger bone destruction in rheumatoid arthritis as well. Recent studies have shown that T lymphocytes produce cytokines other than RANKL such as IL-17, granulocyte–macrophage colony-stimulating factor and IFN-γ, which have powerful regulatory effects on osteoclastogenesis. The possible roles of RANKL and other cytokines produced by T lymphocytes in bone destruction are described.     

The influence of synovial fluid on lymphocyte functions in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic recurrent and systemic inflammatory disease affecting around 1% of the population, that primarily involves the joints. In this study, we determined the Th1/Th2 lymphocytes ratio at the site of rheumatoid inflammation and the influence of the synovial fluid (SF) on the secretory and proliferative function in synovial fluid mononuclear cells (SFMC) and peripheral blood mononuclear cells (PBMC), obtained from patients with RA. Our results showed significant differences concerning the mononuclear cells and the CD4/CD8 ratio in synovial fluid and peripheral blood of patients. In SF prevailed Th1 cells, while in peripheral blood we found another cytokine profile of T lymphocytes. Also synovial fluid lymphocytes had a low PHA-stimulated blastogenic response. Patients plasma and synovial fluid showed an inhibitory effect on prolipheration indexes.     

A comparison of lymphocyte subpopulations simultaneously on local and systemic levels in acute rheumatoid arthritis patients

Rheumatoid arthritis (RA) is one of the most destructive inflammatory and autoimmune joint diseases, most frequently accompanied by extraarticular complications. The pathophysiologic mechanism and the importance of cell subpopulations in the initiation and perpetuation of synovitis are not sufficiently understood. In this study the frequency of lymphocyte subpopulations simultaneously in the synovial fluid (SF), the synovial membrane (SM) and peripheral blood (PB) of acute RA patients is determined, using flow cytometry procedures. The changes in the distribution of T lymphocyte subpopulations were significant on local levels in acute RA patients, resulting in a decreased CD4/CD8 ratio in SF, but an increased CD4/CD8 ratio in SM, compared to the ratio found in PB. The differences observed in the frequency of cells positive on natural killer (NK) cell markers suggest the role of CD16-CD56+ NK cell population in SF of RA patients. Significant differences in the observed frequency of lymphatic subpopulations suggest certain specificities of local immunological events in SM and SF in acute RA. These results confirm the T-lymphocyte hypothesis in initial pathogenic events in RA.     

A novel mechanism for the regulation of IFN-gamma inducible protein-10 expression in rheumatoid arthritis

Chemokines play an essential role in the progression of rheumatoid arthritis (RA). In the present study we examined the expression and regulatory mechanisms of IFN-gamma inducible protein (IP)-10 in RA synovitis. RA synovial fluid contained greater amounts of IP-10 than did synovial fluid from patients with osteoarthritis. Immunolocalization analysis indicated that IP-10 was associated mainly with infiltrating macrophage-like cells, and fibroblast-like cells in the RA synovium. The interaction of activated leukocytes with fibroblast-like synoviocytes resulted in marked increases in IP-10 expression and secretion. Moreover, induction of IP-10 was mediated via specific adhesion molecules, as indicated by the finding that both anti-integrin (CD11b and CD18) and intercellular adhesion molecule-1 antibodies significantly inhibited IP-10 induction. These results suggest that IP-10 expression within inflamed joints appears to be regulated not only by inflammatory cytokines but also by the physical interaction of activated leukocytes with fibroblast-like synoviocytes, and that IP-10 may contribute to the recruitment of specific subpopulations of T cells (Th1 type) from the bloodstream into the synovial joints.     

Significance of cathepsin B accumulation in synovial fluid of rheumatoid arthritis

We measured and compared the activities of various kinds of proteinases, such as cysteine, serine, aspartic, and metalloproteinases, in synovial fluids of 16 patients with rheumatoid arthritis (RA) and 18 patients with osteoarthritis (OA). More than 19-fold higher activity of cathepsin B and about 6-fold higher activity of prolylendopeptidase, compared to those of OA, were accumulated in RA fluid. Moreover, levels of cathepsins B and S using the corresponding sandwich enzyme immunoassays were statistically higher in RA fluid than those in OA. Significant amounts of 41-kDa and 35-kDa procathepsin L were detected in RA fluid using gelatin zymography, while 41-kDa enzyme alone was detected in OA. Cathepsin B in RA fluid could degrade collagen, and this degradation was suppressed by the addition of CA-074, a specific inhibitor of cathepsin B. Therefore, cathepsin B may participate in joint destruction of RA, and its inhibitor may be effective for RA care.     

PHA-T cells in systemic lupus erythematosus and in rheumatoid arthritis: abnormalities in HLA class II antigen induction and in autologous mixed lymphocyte reactions

Analysis of T cells from patients with systemic lupus erythematosus (SLE) and with rheumatoid arthritis (RA) identified a deficit in the induction of HLA Class II antigens by PHA although the proliferative response was normal and in the [3H]thymidine incorporation in autologous mixed lymphocyte reactions (MLR) with PHA-T cells as stimulators. In RA these abnormalities were more marked in patients with active disease than in those in clinical remission. The deficit of autologous MLR with PHA-T cells was more marked than that of autologous MLR with non-T cells and of allogeneic MLR. Serum from patients with SLE and with RA did not display any detectable inhibitory activity on the induction of HLA Class II antigens by PHA, on the proliferative response of lymphocytes to PHA, on autologous MLR with PHA-T cells and with non-T cells as stimulators and on allogeneic MLR. These results suggest that the abnormalities we have identified reflect an intrinsic defect of T cells.     

A new model for rheumatoid arthritis?

A chance observation has led to the development of a new murine model for inflammatory arthritis. Arthritis is induced, and transferred, by T-cell-dependent antibodies to glucose-6-phosphate isomerase. This enzyme is expressed in all cells, and is detectable in serum. There are several similarities to rheumatoid arthritis (RA) in the murine disease. This elegant model raises several questions as to how and why a systemic response focuses inflammation so strongly on synovial joints. The model also re-introduces the possibility that antibodies to widely expressed self-proteins may play a role in the pathogenesis of RA.     

B lymphocyte galactosyltransferase protein levels in normal individuals and in patients with rheumatoid arthritis

We have quantified the level of 4-galactosyltransferase protein in human B lymphocytes using an ELISA-based assay. Between 1-10ng of 4-galactosyltransferase was detected per mg total cellular protein, indicating that this enzyme constitutes <0.001% of B lymphocyte cellular protein. Akin to previous studies, individuals with rheumatoid arthritis exhibited reduced lymphocytic galactosyltransferase enzyme activity compared with normal controls when using ovalbumin as the acceptor substrate. The levels of enzyme protein present in B lymphocytes from patients with rheumatoid arthritis was, however, not reduced suggesting that the B lymphocyte galactosyltransferase catalytic activity may be regulated post-translationally.     

黄酮类化合物抗类风湿关节炎作用及机制研究进展

类风湿性关节炎(rheumatoid arthritis,RA)是以滑膜病变为主要表现,此类不仅疾病影响关节及周围小关节,还容易引发各种并发症。目前还未发现能完全根治此类疾病的药物,发病机制也尚未清楚。近年来黄酮类成分因其高效、安全的特点受到国内外广泛关注。本文对近年来国内外有关抗RA黄酮类成分来源、发病机理及作用机制研究方面进行综述,旨在为更好研究RA及所引发的并发症提供更好的研究思路,并为脂质组学和代谢组学研究提供科学参考。     

Enhancement of lymphocyte migration and cytokine production by ephrinB1 system in rheumatoid arthritis

Although the etiology of early events in rheumatoid arthritis (RA) remains undefined, an anomaly in T cell homeostasis and hyperproliferation of synovial-lining cells are involved in the disease process. Since it has been reported that the ephrin/Eph receptor system plays important signaling roles in inflammation processes, we attempted to examine ephrinB molecules in T cells and synovial cells derived from RA in this study. The expression level of ephrinB1 was significantly high in synovial fibroblasts and CD3-positive exudate lymphocytes in synovial tissues derived from patients with RA compared with those in osteoarthritis (OA). Protein and mRNA levels of ephrinB1 were also higher in peripheral blood lymphocytes (PBLs) prepared from patients with RA than those from normal controls. Similar results were obtained from an animal model of human RA, collagen antibody-induced arthritis mice. Moreover, a recombinant ephrinB1/Fc fusion protein stimulated normal PBLs to exhibit enhanced migration and production of TNF-alpha. EphrinB1/Fc also activated synovial cells established from patients with RA to produce IL-6. Tyrosine phosphorylation of EphB1 was induced in these cells by ephrinB1/Fc. The CpG islands in the 5' upstream regulatory region of the ephrinB1 gene were hypomethylated in RA patients compared with those of normal donors. These results suggest that ephrinB1 and EphB1 receptors play an important role in the inflammatory states of RA, especially by affecting the population and function of T cells. Inhibition of the ephrinB/EphB system might be a novel target for the treatment of RA.     

A novel preclinical model for rheumatoid arthritis research

Based on increasing knowledge on the pathogenesis of rheumatoid arthritis (RA), more and more potential therapeutics have been developed. To evaluate their therapeutic efficacy, safety and toxicity, appropriate animal models are required. Although rodent models of RA have been extensively used for preclinical evaluation, the differences between rodents and humans limit their usability for some species-specific therapeutics. Therefore, autoimmune arthritis developed in a non-human primate with essential hallmarks of RA will be an alternative model for preclinical studies.     

The human endoplasmic reticulum molecular chaperone BiP is an autoantigen for rheumatoid arthritis and prevents the induction of experimental arthritis

Rheumatoid arthritis (RA) is the most common, crippling human autoimmune disease. Using Western blotting and tandem mass spectroscopy, we have identified the endoplasmic reticulum chaperone BiP, a 78-kDa glucose-regulated protein, as a possible autoantigen. It preferentially stimulated increased proliferation of synovial T cells from patients with RA but not from patients with other arthritides. Mice with established collagen- or pristane-induced arthritis developed IgG Abs to BiP. Although BiP injected in CFA failed to induce arthritis in several strains of rats and mice, including HLA-DR4(+/-)- and HLA-DR1(+/+)-transgenic animals, it completely inhibited the development of arthritis when given i.v. 1 wk before the injection of type II collagen arthritis. Preimmunization with BiP suppressed the development of adjuvant arthritis in Lewis rats in a similar manner. This is the first report of a mammalian chaperone that is an autoantigen in human RA and in experimental arthritis and that can also prevent the induction of experimental arthritis. These findings may stimulate the development of new immunotherapies for the treatment of RA.     

ICAM-1 expression on chondrocytes in rheumatoid arthritis: induction by synovial cytokines

The intercellular adhesion molecule-1 (ICAM-1) was found by immunostaining chondrocytes in cartilage from three patients with rheumatoid arthritis. Expression of ICAM-1 was restricted to chondrocytes in areas of erodedcartilage adjacent to the invading synovial tissue. Toluidine blue staining of these areas demonstrated severe depletion of the cartilage extracellular matrix. In areas of undamaged cartilage there was no ICAM-1 expression. Since ICAM-1 is not constitutively expressed on normal human articular cartilage, but could be induced in vitro by exogenous IL-1alpha, TNFalpha and IFNgamma or by co-culturing cartilage with inflammatory rheumatoid synovium, we conclude that the induction of ICAM-1 on rheumatoid chondrocytes results from the synergistic action of a variety of cytokines produced by the inflammatory cells of the invading pannus.     

Mesenchymal stromal cells. Nurse-like cells reside in the synovial tissue and bone marrow in rheumatoid arthritis

A major question concerning the immunopathology of rheumatoid arthritis is why the disease is localized to particular joints. A possible explanation could be the presence within the synovium of cells that foster inflammation or easy accessibility of the synovium to migratory disease enhancing cells. Within both the bone marrow and the synovium, fibroblastic stromal cells play an important role in supporting the differentiation and survival of normal cells, and also contribute to the pathologic processes. Among fibroblastic stromal cells in synovial tissue and bone marrow, nurse-like cells are a unique population having the specific capacity to promote pseudoemperipolesis (adhesion and holding beneath) of lymphocytes, and also the ability to promote the growth and function of some populations of lymphocytes and monocytes. Nurse-like cells could therefore contribute to the immunopathogenesis of rheumatoid arthritis, and may contribute to the localization of inflammation within specific joints. The present review considers the evidence that supports these possibilities.     

HLA-DR4 restricted lymphocyte proliferation to a Mycobacterium tuberculosis extract in rheumatoid arthritis and healthy subjects

The ability of an antigenic extract of Mycobacterium tuberculosis to induce proliferation of PMBC from rheumatoid arthritis (RA) patients and normal controls was examined. The subjects were further classified as bearing or not bearing the HLA-DR4 phenotype, since this specificity is regarded as a genetic determinant commonly associated with RA. The mycobacterial extract induced significantly higher proliferative responses in lymphocytes from all HLA-DR4 positive as compared to HLA-DR4 negative subjects regardless of whether they had RA or not. This response was maximal at day 6 of incubation and could be abrogated by anti-DR/DQ mAb added to the culture. SDS-PAGE of this extract revealed three major protein bands located at Mr 14, 47, and 65 kDa. After fractionation, Western blotting, and resuspension of protein-laden nitrocellulose particles, only the 14- and 47-kDa proteins retained the original proliferative capacity of the mycobacterial extract. The band separating with a Mr of 47 kDa was found to be the most strongly associated with the HLA-DR4 restricted lymphocyte proliferation, and represents a newly identified M. tuberculosis Ag of relevance in T cell responses. These data provide insight into the pathogenic potential of certain bacterial Ag which could trigger or perpetuate inflammatory disorders when presented in the appropriate genetical background.