Pathogenic Mechanisms Of Rheumatoid Arthritis Research Articles

Possible Future Avenues for Rheumatoid Arthritis Therapeutics: Hippo Pathway.

Rheumatoid arthritis (RA) is a persistent systemic autoimmune disease with the hallmarks of swelling of the joint, joint tenderness, and progressive joint destruction, which may cause synovial inflammation and pannus as a basic pathological change, resulting in joint malformations and serious disorders. At present, the precise etiology and mechanism of pathogenesis of RA are unknown. The imbalance of immune homeostasis is the origin of RA. Hippo pathway is widely expressed in a range ofcell lineages and plays a fundamental role in maintaining the immune steady state and may be involved in the pathogenic mechanism of RA. This study reviews the progress of Hippo pathway and its main members in the pathogenesis of RA from three aspects: regulating the maintenance of autoimmune homeostasis, promoting the pathogenicity of synovial fibroblasts and regulating the differentiation of osteoclasts. The study also presentsa new way to recognizethe pathogenesis of rheumatoid arthritis, which is favorable for finding a new way for treating the rheumatoid arthritis.

YY1 regulation by miR-124-3p promotes Th17 cell pathogenicity through interaction with T-bet in rheumatoid arthritis.

Th17 cells are involved in rheumatoid arthritis (RA) pathogenesis. Our previous studies have revealed that transcription factor Yin Yang 1 (YY1) plays an important role in the pathogenic mechanisms of RA. However, whether YY1 has any role in Th17 cell pathogenicity and what molecular regulatory mechanism is involved remain poorly understood. Here, we found the proportion of pathogenic Th17 (pTh17) cells was significantly higher in RA than in control individuals and showed a potential relationship with YY1 expression. In addition, we also observed YY1 expression was increased in pTh17, and the pTh17 differentiation was hampered by YY1 knockdown. Consistently, knockdown of YY1 decreased the proportion of pTh17 cells and attenuated joint inflammation in collagen-induced arthritis mice. Mechanistically, YY1 could regulate the pathogenicity of Th17 cells through binding to the promoter region of transcription factor T-bet and interacting with T-bet protein. This function of YY1 for promoting pTh17 differentiation was specific to Th17 cells and not to Th1 cells. Moreover, we found miR-124-3p negatively correlated with YY1 in RA patients, and it could bind to 3′-UTR regions of YY1 to inhibit the posttranscriptional translation of YY1. Altogether, these findings indicate YY1 regulation by miR-124-3p could specifically promote Th17 cell pathogenicity in part through interaction with T-bet, and these findings present promising therapeutic targets in RA.

Overexpression of Aquaporin 1 in Synovium Aggravates Rat Collagen-Induced Arthritis Through Regulating β-Catenin Signaling: An in vivo and in vitro Study.

IntroductionPrevious studies have confirmed that aquaporin 1 (AQP1) is up-regulated in synovium of rheumatoid arthritis (RA), but its exact pathogenic mechanisms in RA are unclear. This study revealed the pathogenic role of AQP1 in rat collagen-induced arthritis (CIA) and the underlying mechanisms related to β-catenin signaling.Materials and MethodsSecondary paw swelling and pathological changes of ankle joints were used to evaluate the severity of rat CIA. Synovial AQP1 and β-catenin expression were measured by immunohistochemistry (IHC) and Western blot assay. AQP1 siRNA was applied to knockdown AQP1 in cultured CIA fibroblast-like synoviocyte (FLS). Assays of MTT, PCNA immunofluorescence and transwell were performed to detect cell proliferation, migration and invasion. The protein levels of β-catenin pathway members and ratio of TOP/FOP luciferase activity were also measured.ResultsIn vivo, we revealed that synovial AQP1 and β-catenin expressions in CIA rats were higher than normal rats, and synovial AQP1 expression of CIA rats increased in parallel with secondary paw swelling and total pathological score on joint damage. Correlation analysis of IHC results indicated that synovial AQP1 expression positively correlated with β-catenin expression in CIA rat. In vitro, AQP1 siRNA apparently reduced the proliferation, migration and invasion of CIA FLS by inhibiting β-catenin signaling pathway. As an activator of β-catenin signaling, lithium chloride (an inhibitor of GSK-3β) reversed the inhibitory effects of AQP1 siRNA on the cultured CIA FLS.ConclusionWe concluded that the overexpression of synovial AQP1 aggravated rat CIA by promoting the activation of FLS through β-catenin signaling pathway.

Lower peripheral helper T cell levels in the synovium are associated with a better response to anti-TNF therapy in rheumatoid arthritis

BackgroundThe mechanisms by which only some rheumatoid arthritis (RA) patients respond favorably to TNF blockade are still poorly characterized. The goal of this study was to identify biological features that explain this differential response using a multilevel transcriptome analysis of the synovial membrane.MethodsSynovial samples from 11 patients on anti-TNF therapy were obtained by arthroscopy at baseline and week 20. Analysis of the synovial transcriptome was performed at the gene, pathway, and cell-type levels. Newly characterized pathogenic cell types in RA, peripheral helper T cells (TPH), and CD34-THY1+ fibroblasts were estimated using a cell-type deconvolution approach. TPH association was validated using immunofluorescence. External validation was performed on an independent dataset.ResultsAfter multiple-test correction, 16 and 4 genes were differentially expressed at baseline and week 20, respectively. At the pathway level, 86 and 17 biological processes were significantly enriched at baseline and week 20, respectively. Longitudinal expression changes were associated with a drastic decrease of innate immune activity (P < 5e−30), and an activation of the bone and cartilage regeneration processes (P < 5e−10). Cell-type deconvolution revealed a significant association between low TPH cells at baseline and a better response (P = 0.026). Lower TPH cells were maintained in good responders up to week 20 (P = 0.032). Immunofluorescent analyses confirmed the accuracy of the cell-type estimation (r2 = 0.58, P = 0.005) and an association with response. TPH association with anti-TNF response was validated in an independent sample of RA patients (P = 0.0040).ConclusionsA lower abundance in the synovial membrane of the pathogenic T cell type newly associated with RA, peripheral helper T lymphocyte, is associated with a good response to anti-TNF therapy. Major changes in the myeloid cell compartment were also observed in response to therapy. The results of this study could help develop more effective therapies aimed at treating the pathogenic mechanisms in RA that are currently not well targeted by anti-TNF agents.

Exercise Exacerbates the Transcriptional Profile of Hypoxia, Oxidative Stress and Inflammation in Rats with Adjuvant-Induced Arthritis.

Physical exercise (PE) is recommended for Rheumatoid Arthritis (RA), but the molecular and biological mechanisms that impact the inflammatory process and joint destruction in RA remain unknown. The objective of this study was to evaluate the effect of PE on the histological and transcriptional changes in the joints of adjuvant-induced arthritis (AIA) rat model. AIA rats were subjected to PE on a treadmill for eight weeks. The joints were subjected to histological and microarray analysis. The differentially expressed genes (DEGs) by PE in the arthritic rats were obtained from the microarray. The bioinformatic analysis allowed the association of these genes in biological processes and signaling pathways. PE induced the differential expression of 719 genes. The DEGs were significantly associated with pathogenic mechanisms in RA, including HIF-1, VEGF, PI3-Akt, and Jak-STAT signaling pathways, as well as response to oxidative stress and inflammatory response. At a histological level, PE exacerbated joint inflammatory infiltrate and tissue destruction. The PE exacerbated the stressed joint environment aggravating the inflammatory process, the hypoxia, and the oxidative stress, conditions described as detrimental in the RA joints. Research on the effect of PE on the pathogenesis process of RA is still necessary for animal models and human.

Inhibition of Tubulin β-chain May Play a Regulatory Role in the Development of Rheumatoid Arthritis

AbstractPathological characteristics of Rheumatoid arthritis (RA), a systemic autoimmune disease, includes abnormal proliferation of synovial fibroblasts and increased angiogenesis.The study assessed the effect of tubulin β-chain gene (TBB) gene knockdown on the behaviour of rheumatoid arthritis (RA) fibroblast-like synoviocytes (SFs), which is significantly affected by the synthesis of tubulin. Cultured SFs were isolated from the mixed knee-joint synovial tissue of five RA patients and treated with siRNA targeting TBB. Knockdown efficiency and expression of relevant genes were detected by RT-PCR following 24 h and 36 h of transfection. MTT, Transwell, and wound scratch assays and flow cytometric analysis were used to assess cell proliferation and invasive and migratory capacity following TBB knockdown. The expression of TBB was detected after inhibition of the ERK, STAT3 and NF-kB pathways. The expression of IL-17, TNF-α, IL-1α, IL1-β, and IL-6 was quantified following TBB knockdown. The proliferation, invasion, and migration of RASFs were significantly decreased following TBB knockdown. ELISA showed a significant decrease in interleukin 1β (IL-1β) secretion and insignificantly reduced secretion of TNF-α, IL-17, and IL-1α after TBB knockdown. The expression of TBB in RASFs decreased with the increasing concentration of a STAT3 pathway inhibitor while TBB expression increased after down regulation of the ERK pathway. These results support a protective role for TBB knockdown in suppressing RASFs, laying a foundation for further studies on the pathogenic mechanisms of RA.

Paroxetine alleviates T lymphocyte activation and infiltration to joints of collagen-induced arthritis

T cell infiltration to synovial tissue is an early pathogenic mechanism of rheumatoid arthritis (RA). In the present work, we reveal that G protein coupled receptor kinase 2 (GRK2) is abundantly expressed in T cells of collagen-induced arthritis (CIA). A GRK2 inhibitor, paroxetine protects the joints from inflammation and destruction, primarily through inhibition of both CD4+ helper T (Th) cell and CD8+ cytotoxic T (Tc) cell migration to synovial tissue. Meanwhile, paroxetine restores the balance of Th/Tc, effector Th (Theff)/ naïve Th (Thnaive) and effector Tc (Tceff)/ naïve Tc (Tcnaive) to equilibrium by elevating the frequency of Thnaive, Tcnaive and regulatory Th cells; reducing the increased Theff, activated Th and Tceff, having a similar effect as methotrexate (MTX). In addition, both serum and synovial IL-1β, TNF-α and CX3CL1 expression was effectively inhibited in treated rats. In vitro assay confirmed that paroxetine inhibits CX3CL1-induced T cell migration through blocking the activity of GRK2. Among three MAPK families, paroxetine was found to be able to decrease the phosphorylation of ERK. This study elucidates that paroxetine attenuates the symptoms of CIA rats due to its inhibitory effect on T cell activation and infiltration to synovial tissue via suppression of ERK pathway.

SAT0105 Circulating MIR-223 is downregulated in SERA of patients with early RA after treatment with methotrexate

BackgroundMiRs are involved as fine tuning regulators of gene expression in crucial cellular processes and their dysregulation has been described in many diseases. Incorporated in microvesicles, in complexes with Ago2...

Dendritic cells provide a potential link between smoking and inflammation in rheumatoid arthritis

IntroductionSmoking increases the risk of developing rheumatoid arthritis (RA) and affects the severity of established RA. Smoking can impact on Th17 lymphocyte differentiation and function through activation of the aryl hydrocarbon receptor (AHR), a process with implications for the pathogenic mechanisms in RA that involve the cytokine, interleukin (IL)-17A. The objective of this study was to establish any effect of smoking on the inflammatory tissue lesions of rheumatoid arthritis via the AHR and IL-17A.MethodsTwenty synovial and eighteen subcutaneous nodule tissue samples from 31 patients with RA were studied. Patient smoking status at the time of tissue collection was established. Expression of AHR, CYP1A1, AHRR, IL6, IL17A, IL17F, IL22, IL23, IL23R, IFNG, TBX21, IDO1 and FOXP3 genes were assessed in tissues and cultured cells using real-time PCR. Two-colour immunofluorescence was used to co-localise AHR and CYP1A1 protein in synovial tissues. The response of monocytes and monocyte-derived dendritic cells (mo-DCs) to the AHR agonist, benzo(a)pyrene (BaP) was compared in vitro.ResultsAHR gene expression was demonstrated in rheumatoid synovial tissues and nodules with significantly greater expression in synovia. Expression was not influenced by smoking in either tissue. Evidence of AHR activation, indicated by CYP1A1 and AHRR gene expression, was found only in synovia from patients who smoked. However, IL17A gene expression was lower in synovia from smokers. TBX21 and FOXP3 expression was not affected by smoking. Within the synovial tissues of smokers the principal cell type with evidence of AHR activation was a subset of synovial DCs. This observation was consistent with the sensitivity of human mo-DCs to BaP stimulation demonstrated in vitro. Exposure to BaP affected mo-DC function as demonstrated by decreased IL6 expression induced by PolyI:C, without affecting indoleamine 2,3 dioxygenase (IDO)1 expression.ConclusionOur findings show that one effect of smoking on inflamed rheumatoid synovial tissue involves activation of the AHR pathway. A subset of synovial DCs is important in the response to cigarette smoke. The potential for smoking to affect DC behaviour in joint tissues has relevance to both early and late phases of RA pathogenesis and warrants further investigation.

Tissue-Specific Expression of Human Calcineurin-Binding Protein 1 in Mouse Synovial Tissue Can Suppress Inflammatory Arthritis

Calcineurin (CN) is a calcium- and calmodulin-dependent serine/threonine phosphatase. In immune cells, CN controls the activity of a wide range of transcription factors, including nuclear factor of activated T, nuclear factor-kappa B, c-fos, and Elk-1. CN plays an important role in synoviocyte activation and arthritis progression in vivo and this function is tightly linked to dysregulated intracellular Ca(2+) store and Ca(2+) response triggered by proinflammatory cytokines. In the present study, transgenic mice expressing human calcineurin-binding protein 1 (hCabin1) were generated, driven by type II collagen promoter, and the efficiency of these mice was investigated by experimental arthritis. These transgenic mice successfully expressed hCabin1 in joint tissue as well as other organs such as liver, heart, and brain. The overexpression of hCabin1 reduced the disease severity during collagen-induced arthritis. In fibroblast-like synoviocytes (FLSs) from hCabin1 transgenic mice, the productions of these cytokines, including interleukin (IL)-2, IL-4, and IFN-γ, were decreased and matrix metalloproteinases were also depressed in transgenic mice FLS. In addition, these effects were only found in the joint tissue, which is a major inflammation site. These findings will provide a better knowledge of the pathogenic mechanisms of rheumatoid arthritis and a potential animal model of the chronic inflammatory conditions, including atherosclerosis and transplantation.

Collagen-Induced Arthritis as an Animal Model for Rheumatoid Arthritis: Focus on Interferon-γ

Rheumatoid arthritis (RA), an autoimmune disease causing inflammation, destruction, and deformity of the joints, affects around 1% of the world population. It is a systemic disease as patients exhibit extra-articular manifestations as well. Collagen-induced arthritis (CIA) in DBA/1 mice is one of the many animal models used to study possible pathogenic mechanisms of RA. It involves immunizing mice with collagen type II in complete Freund's adjuvant. Here we briefly review the general characteristics of RA and CIA and present an overview of data obtained by studying CIA in several gene knockout mice. In particular, detailed analysis of CIA in interferon-gamma (IFN-γ) receptor-deficient mice has pin-pointed IFN-γ as an important cytokine in the pathogenesis and has exposed new functions of IFN-γ in immunological processes. Pilot trials with exogenous IFN-γ in RA have been indicative of a beneficial effect. That improvement of the disease symptoms by IFN-γ treatment was not spectacular may be explained by the fact that RA is a heterogeneous disease in which the severity of the autoimmune disease is strongly determined by environmental factors.

The major histocompatibility complex and multiple sclerosis: a smoking gun?

There are many theories on the aetiology of multiple sclerosis but most lack much in the way of direct experimental support. Despite overwhelming evidence that the pathogenesis involves an interplay between genetic and environmental effects, progress in identifying the relevant risk factors has been painfully slow and there is practically no understanding about how these might interact and result in disease. In this issue, Hedstrom et al . (2011) present an integration of a specific genetic and environmental effect. In a case ( n = 843) control ( n = 1209) study carefully designed to reduce potential confounding, they consider established genetic factors (DRB1 and HLA-A) in the context of smoking; and find evidence that the effects on susceptibility attributable to these genetic loci are amplified by this lifestyle exposure. On the basis of this observation, and by analogy with established pathogenic mechanisms in rheumatoid arthritis (Karlson et al ., 2010), they argue that the post-translational modification of lung proteins caused by smoking might lead to multiple sclerosis in genetically susceptible individuals by priming circulating lymphocytes against cross-reacting CNS antigens. This is an intriguing hypothesis, which if confirmed would represent a major step forward in our understanding. Attempting to unravel the pathogenesis of any complex trait through association analysis is a perilous exercise, littered with traps for the unwary. Past experience has shown that researchers using this approach need to pay obsessional attention to detail if they are to avoid adding to the enormous literature confidently describing what turn out to be false positive associations (Ioannidis, 2005). At face value nothing could be simpler than establishing the relevance of an exposure by identifying a difference in its frequency between cases and controls. In this deceptively straightforward paradigm, establishing statistical significance appears to be the most challenging issue; and simultaneously avoiding confounding due to systematic …

Study of the Gene Expressions in Rheumatoid Arthritis Synovial Macrophages Using Network Analysis

Objective We wanted to investigate the mechanisms that could account for the pathogenesis of rheumatoid arthritis, so we examined the different expressions of the genes in rheumatoid arthritis (RA) synovial fluid macrophages as compared with that of normal peripheral blood (PB) mon-ocyte-derived macrophages using microarray and bioinformatic analysis. Methods We examined the expression of genes by using a gene expression oligonucleotide microarray. The differences of the gene expressions between the RA synovial macrophages and the normal PB monocytes-derived macrophages were analyzed using bioinformatic tools, including cytoscape and its plugin. Results In this study, we found that 899 genes (464 genes upregulated and 435 genes down-regulated) were differentially expressed between the two groups. Among the 899 genes, 552 genes were included for gene ontology analysis and network analysis. Based on biological process ontology, they were categorised mainly into immune response processes, responses to stimulus and signaling and regulation of biological processes. In addition to the genes related with STAT1 and AP-1 signaling, we found that the genes involved in the antigen processing and the cell cycle are abundantly expressed in RA synovial macrophages, sug-gesting that these genes may play an important role in the pathogenesis of RA. Conclusion Our study suggest that this approach using integration of the gene expression profile with the protein interaction data may help to find several important pathogenic mechanisms in RA.

Overexpression of CXC Chemokine Ligand 14 Exacerbates Collagen-Induced Arthritis

CXCL14 is a relatively new chemokine with unidentified receptor and undefined function. Recently, we found that CXCL14 is upregulated in arthritic joints in a mouse model of autoimmune arthritis, collagen-induced arthritis. To examine the role of CXCL14 in the development and pathogenesis of autoimmune arthritis, we have generated transgenic (Tg) mice that overexpress CXCL14 under control of phosphoglycerate kinase promoter. The results showed that CXCL14-Tg mice developed more severe arthritis compared with wild-type controls. The draining lymph nodes of CXCL14-Tg mice were significantly enlarged and contained an increased number of activated T cells, particularly the CD44(+)CD62L(low) effector memory cells. In addition, T cells from CXCL14-Tg mice exhibited an enhanced proliferative response against collagen II and produced higher levels of IFN-gamma but not IL-4 or IL-17. CXCL14-Tg mice also had elevated levels of IgG2a autoantibodies. These findings indicated that CXCL14 plays an important role in the autoimmune arthritis, which may have an implication in understanding the pathogenic mechanisms of rheumatoid arthritis in humans and, ultimately, therapeutic interference.

What magnetic resonance imaging has told us about the pathogenesis of rheumatoid arthritis – the first 50 years

Modern imaging modalities, including magnetic resonance imaging (MRI), are valuable diagnostic and therapy monitoring tools in rheumatoid arthritis (RA). This article reviewed how these imaging modalities have greatly improved our understanding of pathogenic mechanisms in RA, namely the link between inflammation and damage. For example, traditional paradigms regarding the mechanisms of joint destruction, including the idea that synovitis and damage are uncoupled, have been challenged. As the power of MRI increases, there is a need to define normality since apparently normal joints occasionally exhibit MRI evidence of synovitis in the absence of symptoms.

The use of TNF-α blocking agents in rheumatoid arthritis: an update

TNF-α has been found to play a pivotal role in the pathogenic mechanisms of rheumatoid arthritis (RA). Drugs targeting TNF-α have been developed to neutralise the deleterious effects of this inflammatory cytokine. There are, at present, three drugs available for the treatment of RA patients with active disease who are refractory to conventional treatments including methotrexate: 2 monoclonal antibodies, infliximab and adalimumab, and a fusion protein with p75 receptors, etanercept. These three agents have proved to be effective and safe in large placebo-controlled trials enrolling patients with established or early disease and showed effectiveness in controlling signs and symptoms of the disease, improving quality of life and in slowing and even arresting the progression of radiographic damage. With the long-term surveillance of these drugs were described serious adverse events, particularly infections such as tuberculosis, especially with infliximab. The risk for malignancies under TNF-α antagonists, especially lymphoma, remains controversial. Specific recommendations are given by international experts for selecting and monitoring RA patients with TNF-α antagonists. Other drugs targeting TNF-α such as PEGylated molecules (CDP870 or certolizumab) are in development. These new biological therapies blocking TNF-α undoubtedly constitute a considerable advancement in the management of RA, but careful evaluation at the initiation of the treatment and long-term surveillance of the patients receiving such drugs remains necessary.

The use of TNF-? blocking agents in rheumatoid arthritis: an overview

TNF-α has been found to play a pivotal role in the pathogenic mechanisms of rheumatoid arthritis (RA). The overexpression of TNF-α in RA synovium, the data from in vitro synovial cell cultures with the use of anti-TNF-α antibody and the results from TNF-α blockade in animal models of arthritis argued for the importance of this cytokine in RA. Drugs targeting TNF-α have been developed to neutralise the deleterious effects of this inflammatory cytokine. There are currently three drugs available in the treatment of RA patients with active disease, which was refractory to conventional treatments including methotrexate, infliximab (a chimeric mouse/human monoclonal antibody), etanercept (a fusion protein combining 2 p75 TNF receptors with a Fc fragment of human IgG1) and adalimumab (a fully human monoclonal antibody). These three drugs have proved to be effective and safe in appropriate and well conducted clinical trials and showed effectiveness in slowing and even arresting the progression of radiographic damage. With the long-term surveillance of these drugs serious adverse events were described, particularly intracellular organism infections such as tuberculosis. Other drugs targeting TNF-α are in development and include monoclonal antibody (CDP571), pegylated molecules (CDP870 and PEG-r-Hu-sTNF-RI) or soluble p55 TNF receptor construct (lenercept). These new biological therapies blocking TNF-α undoubtedly constitute a considerable advance in the management of RA, but careful evaluation at the initiation of the treatment and long-term surveillance of the patients receiving such drugs remains necessary.