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Background: Autoreactive B cells are crucial players in the pathogenesis of rheumatoid arthritis (RA). Autoantibodies specific for citrullinated proteins (ACPA), present in the serum of approximately 60-70 % of patients, have a pathogenic role in the disease. B cell depleting therapies may result in a transient immunosuppression, increasing the risk of infections. Our aim was to develop a new therapeutic approach to selectively deplete the ACPA producing autoreactive B cells. Methods: To target B cells synthetic citrullinated peptide derived from the beta chain of fibrin, beta 60-74Cit(60,72,74) (beta 60-74Cit), the predominant epitope recognized by ACPA was used. Complement dependent cytotoxicity (CDC) was induced by a modified peptide derived from gp120 of HIV-1. To trigger CDC both the targeting peptide and the complement activating peptide were covalently coupled in multiple copies to the surface of poly (DL-lactic-co-glycolic acid) nanoparticles (NPs). Ex vivo antibody synthesis was examined by ELISA and ELISpot. CDC was tested after dead cell staining by flow cytometry. Results: The beta 60-74Cit peptide was selectively recognized by a small subset of B cells from RA patients having high level of peptide specific serum antibody, suggesting that the peptide can target diseased B cells. The modified gp120 peptide covalently coupled to NPs induced the formation of the complement membrane attack complex, C5b-9 in human serum. We show here for the first time that bifunctional NPs coupled to multiple copies of both the targeting peptide and the complement activating effector peptide on their surface significantly reduce beta 60-74Cit peptide specific ex vivo ACPA production, by inducing complement dependent lysis of the citrullinated peptide specific B cells of seropositive RA patients. Conclusions: Bifunctional NPs covalently coupled to autoantigen epitope peptide and to a lytic peptide activating complement may specifically target and deplete the peptide specific autoreactive B-cells.

Besides atherosclerosis and lung cancer, smoking is considered to play a major role in the pathogenesis of autoimmune diseases. It has long been known that there is a connection between rheumatoid factor-positive rheumatoid arthritis and cigarette smoking. Recently, an important gene–environment interaction has been revealed; that is, carrying specific HLA-DRB1 alleles encoding the shared epitope and smoking establish a significant risk for anti-citrullinated protein antibody-positive rheumatoid arthritis. We summarize how smoking-related alteration of the cytokine balance, the increased risk of infections (the possibility of cross-reactivity) and modifications of autoantigens by citrullination may contribute to the development of rheumatoid arthritis.

Introduction Although natural autoantibodies make up the majority of circulating immunoglobulins and are also present in high numbers in therapeutically used intravenous immunoglobulin preparations, they have received little attention and their precise role remains largely unknown. An increasing awareness of the importance of posttranslational autoantigen modifications and glycobiology led us to explore carbohydrate-reactive natural autoantibodies in patients with rheumatoid arthritis. This study examined systematic antibodies reactive to glycosaminoglycans (GAGs), the carbohydrate components of proteoglycans that are released in large amounts from degrading cartilage. Methods To measure antibodies reactive to six different types of GAGs, a specialised ELISA was used in which the carbohydrates were covalently linked to the plastic surface through a 2 nm spacer. Sera from rheumatoid arthritis patients (n = 66), umbilical cord serum samples (n = 11) and adult controls (n = 54) were studied. In order to explore cross-reactivity with microbial antigens, bacterial peptidoglycans and fungal polysaccharides were used. Sera and synovial fluid samples were also tested using a GlycoChip carbohydrate array to characterise individual carbohydrate recognition patterns. We followed a multistep statistical screening strategy for screening GAG-reactive antibodies as predictive disease markers. Results While anti-GAG antibodies were absent in the umbilical cord sera, they were readily detectable in adult controls and were significantly elevated in patients with rheumatoid arthritis (p < 0.001). Anti-GAG antibodies showed significant cross-reactivity among different types of GAGs. They also reacted with bacterial peptidoglycans and fungal polysaccharides. Interestingly, anti-chondroitin sulphate C IgM antibody levels showed inverse correlation both with the Disease Activity Score (DAS) 28 scores and C-reactive protein (CRP) levels in rheumatoid arthritis. Conclusion The highly abundant and cross-reactive, GAG-specific natural autoantibodies in serum may serve as novel disease-state markers in patients with rheumatoid arthritis.

Increased numbers of mast cells are found in the synovial tissues and fluids of patients with rheumatoid arthritis, and at sites of cartilage erosion. Mast cell activation has been reported for a significant proportion of rheumatoid specimens. Because the mast cell contains potent mediators, including histamine, its potential contributions to the processes of inflammation and matrix degradation have recently become evident; thereafter, we investigated the potential protective effect of histamine deficiency against aggrecan-induced arthritis. To study the role of histamine in rheumatoid arthritis we investigated cartilage proteoglycan (aggrecan)-induced arthritis in histidine decarboxylase knockout (HDC-KO) mice, with complete lack of endogenously produced histamine. Aggrecan-induced arthritis was similar in HDC-KO and wild-type (WT) mice. Arthritis was even more severe in HDC-KO mice than in the WT animals 10 weeks following the immunization with aggrecan (arthritis score 1.2 ± 1.5 and 0 ± 0, respectively; P = 0.01). At later time points, arthritis scores were similar in both HDC-KO and WT mice. Since T-lymphocyte dysfunction has an important role in the pathogenesis of rheumatoid arthritis, next we investigated T-cell signal transduction and cytokine production in HDC-KO and WT mice. In the absence of histamine, elevated INFγ mRNA and protein levels of splenocytes (P < 0.001 and P = 0.001, respectively) were associated with a markedly increased (2.5-fold, P = 0.0009) nitric oxide (NO) production, compared with WT animals. Furthermore, histamine treatment decreased the NO production of splenocytes from both WT and HDC-KO mice (P = 0.001 and P = 0.0004, respectively). NO precursor (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl) amino]diazen-1-ium-1,2-diolate-diethylenetriamine (NOC-18) elicited IFNγ production (P = 0.0002), suggesting the role of NO in regulating IFNγ synthesis. The cytoplasmic Ca2+ concentration of unstimulated T cells and the T-cell activation-induced Ca2+ signal were increased in T cells from the HDC-KO mice (P = 0.02 and P = 0.04, respectively), while the T-cell activation-induced CD3 internalization was similar in both HDC-KO and WT animals. Our present data indicate that histamine deficiency does not protect against aggrecan-induced arthritis. The Th1 cytokine pattern and increased NO production may both contribute to the sensitivity of HDC-KO mice to aggrecan-induced arthritis. Furthermore, our data indicate that histamine, in addition to its direct effects on T-lymphocyte function, regulates cytokine production and T-cell signal transduction through regulating NO production.

Experimental and clinical evidence for T-cell involvement in the pathogenesis of rheumatoid arthritis (RA) is compelling, and points to a local dysregulation of T-cell function in the inflamed joint. Nitric oxide (NO) has been shown to regulate T-cell function under physiological conditions, but overproduction of NO may contribute to lymphocyte dysfunction in RA. NO has recently been recognized as a key signaling intermediate for T-cell activation and mitochondrial biogenesis. NO is synthesized from L-arginine by NO synthetases (NOS). Three distinct isoforms of NOS are known, including neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS) enzymes. We previously detected the expression of eNOS and nNOS and the absence of iNOS in human PBL, while during inflammation macrophages and monocytes express iNOS. Systemic lupus erythematosus (SLE) is a systemic autoimmune disease of unknown origin characterized by the involvement of multiple organs. Several studies carried out on patients with both RA and SLE have documented increased endogenous NO synthesis, but its contribution to T-lymphocyte mitochondrial biogenesis and T-cell dysregulation is not known. We investigated the role of NO in T-cell mitochondrial biogenesis in RA and SLE. The mitochondrial mass, NO production and cytoplasmic Ca2+ levels were measured by flow cytometry. Mitochondria were visualized using transmission electron microscope. T cells from RA patients produce >2.5 times more NO than T cells from healthy donors (P < 0.001). Unexpectedly, the mitochondrial mass was found to be similar in RA and control T cells (P = 0.65), whilst increased NO production was associated with increased cytoplasmic Ca2+ concentrations in RA T cells (P < 0.001). We observed that T-cell NO production decreased in most RA patients following anti-TNF treatment. Although lupus T cells produced comparable amounts of NO to normal T cells, lupus monocytes produced twice as much NO as normal monocytes (P = 0.015). We also observed increased mitochondrial mass (47.7 ± 2.8%; P = 0.00017) and increased cytoplasmic (38 ± 6.4%; P = 0.0023) Ca2+ content in T cells from SLE patients when compared with control donors. Electron microscopy revealed that T cells of lupus patients contained 8.76 ± 1 mitochondria, while control donors contained 3.18 ± 0.28 mitochondria per cell (P = 0.0009). In addition, lupus lymphocytes harbor several-fold enlarged mega-mitochondria. These data suggest that monocytes are the primary source of NO in SLE, while T lymphocytes are the primary source of NO in RA. Although the iNOS pathway is not as rapid as eNOS or nNOS, it is thought to be capable of generating much larger quantities of NO (nanomolar range) than the constitutive NOS isoforms (picomolar range), explaining the differences in T-cell mitochondrial biogenesis in SLE and RA. Since mitochondria can take up, store and release Ca2+, increased mitochondrial mass may account for altered Ca2+ handling in SLE. Furthermore increased NO production may contribute to T-cell dysfunction in both SLE and RA.

The advent of new medications and new treatment strategies for rheumatoid arthritis has made it possible to achieve remission in more patients than before. Furthermore, recent clinical trials and register studies suggest that some patients who initially required aggressive therapy may achieve biologic-free remission or even the ultimate goal of therapy, drug-free remission, resembling recovery. Here, we present a discursive review of the most important studies addressing these issues. Based on the overall results, it remains unclear if achieving biologic-free and drug-free remissions are primarily due to the natural course of the disease or to the early therapeutic intervention according to the ‘window of opportunity’ hypothesis. Although medication-free remission is only achievable in a small subset of patients, characterizing this patient cohort may provide important information about beneficial prognostic factors and the underlying mechanisms. In summary, in a subset of patients biologic-free and even drug-free remission can be achieved; pursuing these possibilities in practice may decrease the risk for long-term side effects and attenuate the economic burden of the disease.

Introduction Similar to matrix metalloproteinases, glycosidases also play a major role in cartilage degradation. Carbohydrate cleavage products, generated by these latter enzymes, are released from degrading cartilage during arthritis. Some of the cleavage products (such as hyaluronate oligosaccharides) have been shown to bind to Toll-like receptors and provide endogenous danger signals, while others (like N-acetyl glucosamine) are reported to have chondroprotective functions. In the current study for the first time we systematically investigated the expression of glycosidases within the joints. Methods Expressions of β-D-hexosaminidase, β-D-glucuronidase, hyaluronidase, sperm adhesion molecule 1 and klotho genes were measured in synovial fibroblasts and synovial membrane samples of patients with rheumatoid arthritis and osteoarthritis by real-time PCR. β-D-Glucuronidase, β-D-glucosaminidase and β-D-galactosaminidase activities were characterized using chromogenic or fluorogenic substrates. Synovial fibroblast-derived microvesicles were also tested for glycosidase activity. Results According to our data, β-D-hexosaminidase, β-D-glucuronidase, hyaluronidase, and klotho are expressed in the synovial membrane. Hexosaminidase is the major glycosidase expressed within the joints, and it is primarily produced by synovial fibroblasts. HexA subunit gene, one of the two genes encoding for the alpha or the beta chains of hexosaminidase, was characterized by the strongest gene expression. It was followed by the expression of HexB subunit gene and the β-D-glucuronidase gene, while the expression of hyaluronidase-1 gene and the klotho gene was rather low in both synovial fibroblasts and synovial membrane samples. Tumor growth factor-β1 profoundly downregulated glycosidase expression in both rheumatoid arthritis and osteoarthritis derived synovial fibroblasts. In addition, expression of cartilage-degrading glycosidases was moderately downregulated by proinflammatory cytokines including TNFα, IL-1β and IL-17. Conclusions According to our present data, glycosidases expressed by synovial membranes and synovial fibroblasts are under negative regulation by some locally expressed cytokines both in rheumatoid arthritis and osteoarthritis. This does not exclude the possibility that these enzymes may contribute significantly to cartilage degradation in both joint diseases if acting in collaboration with the differentially upregulated proteases to deplete cartilage in glycosaminoglycans.