Pathogenesis of Joint Destruction in Rheumatoid Arthritis

FGF23 facilitates IL-1β synthesis in rheumatoid arthritis through activating PI3K, Akt, and NF-κB pathways

Rheumatoid arthritis (RA) is a well-known autoimmune disorder related with joint pain, joint swelling, cartilage and bone degradation as well as deformity. Fibroblast growth factor 23 (FGF23) is an endocrine factor of the FGF family primarily produced by osteocytes and osteoblasts, involves an essential effect in pathogenesis of RA. IL-1β is a vital proinflammatory factor in the development of RA. However, the role of FGF23 on IL-1β synthesis in RA has not been fully explored. Our analysis of database revealed higher levels of FGF23 and IL-1β in RA samples compared with healthy controls. High-throughput screening demonstrated that IL-1β is a potential candidate factor after FGF23 treatment in RA synovial fibroblasts (RASFs). FGF23 concentration dependently promotes IL-1β synthesis in RASFs. FGF23 enhances IL-1β expression by activating the PI3K, Akt, and NF-κB pathways. Our findings support the notion that FGF23 is a promising target in the remedy of RA.

The chromatin landscape of pathogenic transcriptional cell states in rheumatoid arthritis

Synovial tissue inflammation is a hallmark of rheumatoid arthritis (RA). Recent work has identified prominent pathogenic cell states in inflamed RA synovial tissue, such as T peripheral helper cells; however, the epigenetic regulation of these states has yet to be defined. Here, we examine genome-wide open chromatin at single-cell resolution in 30 synovial tissue samples, including 12 samples with transcriptional data in multimodal experiments. We identify 24 chromatin classes and predict their associated transcription factors, including a CD8 + GZMK+ class associated with EOMES and a lining fibroblast class associated with AP-1. By integrating with an RA tissue transcriptional atlas, we propose that these chromatin classes represent 'superstates' corresponding to multiple transcriptional cell states. Finally, we demonstrate the utility of this RA tissue chromatin atlas through the associations between disease phenotypes and chromatin class abundance, as well as the nomination of classes mediating the effects of putatively causal RA genetic variants.

CXCL13 promotes TNF-α synthesis in rheumatoid arthritis through activating ERK/p38 pathway and inhibiting miR-330-3p generation

Rheumatoid arthritis (RA) is a well-known autoimmune disorder associated with joint pain, joint swelling, cartilage and bone degradation as well as deformity. The chemokine (C-X-C motif) ligand 13 (CXCL13) plays a crucial role in multiple cellular pathogenesis processes, including RA. TNF-α is a vital proinflammatory factor in the progression of RA. However, the role of CXCL13 in TNF-α production in RA has not been fully explored. Our analysis of both database and clinical samples revealed higher levels of CXCL13 and TNF-α in RA samples compared to healthy controls. CXCL13 concentration-dependently induces TNF-α synthesis in RA synovial fibroblasts. CXCL13 enhances TNF-α expression by interacting with the CXCR5 receptor, activating the ERK/p38 pathways, and inhibiting miR-330-3p generation. Importantly, treatment with CXCL13 shRNA counteracted the upregulation of TNF-α production induced by collagen-induced arthritis. Our findings support the notion that CXCL13 is a promising target in the treatment of RA.

Albumin-binding RNAi Conjugate for Carrier Free Treatment of Arthritis

Osteoarthritis (OA) and rheumatoid arthritis (RA) are joint diseases that are associated with pain and lost quality of life. No disease modifying OA drugs are currently available. RA treatments are better established but are not always effective and can cause immune suppression. Here, an MMP13-selective siRNA conjugate was developed that, when delivered intravenously, docks onto endogenous albumin and promotes preferential accumulation in articular cartilage and synovia of OA and RA joints. MMP13 expression was diminished upon intravenous delivery of MMP13 siRNA conjugates, consequently decreasing multiple histological and molecular markers of disease severity, while also reducing clinical manifestations such as swelling (RA) and joint pressure sensitivity (RA and OA). Importantly, MMP13 silencing provided more comprehensive OA treatment efficacy than standard of care (steroids) or experimental MMP inhibitors. These data demonstrate the utility of albumin 'hitchhiking' for drug delivery to arthritic joints, and establish the therapeutic utility of systemically delivered anti-MMP13 siRNA conjugates in OA and RA.

Editorial summary

Lipophilic siRNA conjugates optimized for albumin binding and "hitchhiking" can be leveraged to achieve preferential delivery to and gene silencing activity within arthritic joints. Chemical stabilization of the lipophilic siRNA enables intravenous siRNA delivery without lipid or polymer encapsulation. Using siRNA sequences targeting MMP13, a key driver of arthritis-related inflammation, albumin hitchhiking siRNA diminished MMP13, inflammation, and manifestations of osteoarthritis and rheumatoid arthritis at molecular, histological, and clinical levels, consistently outperforming clinical standards of care and small molecule MMP antagonists.

NAMPT/SIRT1 Expression Levels in White Blood Cells Differentiate the Different Rheumatoid Arthritis Subsets: An Inspiration from Traditional Chinese Medicine

Background

Rheumatoid arthritis (RA) patients are prone to developing different metabolic complications. Traditional Chinese Medicine attributes this uncertainty to varied syndrome types.

Methods and Results

We retrospectively analyzed some serological indicators of active RA patients and healthy individuals. Randomly selected RA patients were divided into three groups according to NAMPT and SIRT1 expression levels in white blood cells (WBCs). Their disease severity and metabolic status were compared. Representative blood samples were subjected to a UPLC-MS/MS-based metabolomics analysis. Different human WBCs were treated with oleic acid and palmitic acid in vitro. The results indicated that blood glucose and lipid levels were decreased in RA patients, but their decrease was not in accordance with disease severity. Nutrients in the patients highly expressing SIRT1 were well preserved, with the lowest levels of RF and β-CTX and the highest levels of adiponectin and resistin. Most of them exhibited cold symptoms. When SIRT1 deficiency was obvious, lipid depletion became evident, irrespective of expression levels of NAMPT. Simultaneous high-expression of SIRT1 and NAMPT coincided with the increase in production of lactic acid and the prevalence of hot symptoms. Despite the low levels of IL-6, joint injuries were severe. The corresponding WBCs were especially sensitive to fatty acids anti-inflammatory treatments. The levels of CCL27, CCL11, CCL5, AKP, CRP and ESR were similar among all the groups.

Conclusion

NAMPT overexpression is a risk factor for joint injuries and nutrient depletion in RA. Supplementation with lipids would exert beneficial effects on these RA patients. Its aftermath would cause even severe inflammation. Contrarily, SIRT1 up-regulation restrains inflammation and lipid depletion.

A comprehensive analysis of biomarkers associated with synovitis and chondrocyte apoptosis in osteoarthritis

Introduction

Osteoarthritis (OA) is a chronic disease with high morbidity and disability rates whose molecular mechanism remains unclear. This study sought to identify OA markers associated with synovitis and cartilage apoptosis by bioinformatics analysis.

Methods

A total of five gene-expression profiles were selected from the Gene Expression Omnibus database. We combined the GEO with the GeneCards database and performed Gene Ontology and Kyoto Encyclopedia of Genes and Genome analyses; then, the least absolute shrinkage and selection operator (LASSO) algorithm was used to identify the characteristic genes, and a predictive risk score was established. We used the uniform manifold approximation and projection (UMAP) method to identify subtypes of OA patients, while the CytoHubba algorithm and GOSemSim R package were used to screen out hub genes. Next, an immunological assessment was performed using single-sample gene set enrichment analysis and CIBERSORTx.

Results

A total of 56OA-related differential genes were selected, and 10 characteristic genes were identified by the LASSO algorithm. OA samples were classified into cluster 1 and cluster 2 subtypes byUMAP, and the clustering results showed that the characteristic genes were significantly different between these groups. MYOC, CYP4B1, P2RY14, ADIPOQ, PLIN1, MFAP5, and LYVE1 were highly expressed in cluster 2, and ANKHLRC15, CEMIP, GPR88, CSN1S1, TAC1, and SPP1 were highly expressed in cluster 1. Protein-protein interaction network analysis showed that MMP9, COL1A, and IGF1 were high nodes, and the differential genes affected the IL-17 pathway and tumor necrosis factor pathway. The GOSemSim R package showed that ADIPOQ, COL1A, and SPP1 are closely related to the function of 31 hub genes. In addition, it was determined that mmp9 and Fos interact with multiple transcription factors, and the ssGSEA and CIBERSORTx algorithms revealed significant differences in immune infiltration between the two OA subtypes. Finally, a qPCR experiment was performed to explore the important genes in rat cartilage and synovium tissues; the qPCR results showed that COL1A and IL-17A were both highly expressed in synovitis tissues and cartilage tissues of OA rats, which is consistent with the predicted results.

Discussion

In the future, common therapeutic targets might be found forsimultaneous remissions of both phenotypes of OA.

Targeting transcription factors for therapeutic benefit in rheumatoid arthritis

Rheumatoid arthritis (RA) is a destructive inflammatory autoimmune disease that causes pain and disability. Many of the currently available drugs for treating RA patients are aimed at halting the progression of the disease and alleviating inflammation. Further, some of these treatment options have drawbacks, including disease recurrence and adverse effects due to long-term use. These inefficiencies have created a need for a different approach to treating RA. Recently, the focus has shifted to direct targeting of transcription factors (TFs), as they play a vital role in the pathogenesis of RA, activating key cytokines, chemokines, adhesion molecules, and enzymes. In light of this, synthetic drugs and natural compounds are being explored to target key TFs or their signaling pathways in RA. This review discusses the role of four key TFs in inflammation, namely NF-κB, STATs, AP-1 and IRFs, and their potential for being targeted to treat RA.

Mechanism of action of quercetin in rheumatoid arthritis models: meta-analysis and systematic review of animal studies

Quercetin, a typical flavonoid derived from a common natural plant, has multiple biological activities. Previous research in animal models has demonstrated the effectiveness of quercetin in treating rheumatoid arthritis (RA). The pharmacological effects and probable mechanisms of quercetin were evaluated in this study. Three databases, PubMed, Web of Science, and Embase, were searched for relevant studies from the creation of the databases to November 2022. Methodological quality was assessed using the SYRCLE risk of bias tool. STATA 15.1 was used to perform the statistical analysis. This research included 17 studies involving 251 animals. The results indicated that quercetin was able to reduce arthritis scores, paw swelling, histopathological scores, interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-17 (IL-17), tumor necrosis factor-α (TNF-α), monocyte chemotactic protein-1 (MCP-1), C-reactive protein (CRP), malondialdehyde (MDA), reactive oxygen species (ROS), thiobarbituric acid reactive substances (TBARS), nuclear factor kappa B (NF-kB) and increase interleukin-10 (IL-10), catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), glutathione (GSH), and heme oxygenase-1 (HO-1). These may be related to quercetin's potential anti-inflammatory, anti-oxidative stress, and osteoprotective properties. However, more high-quality animal studies are needed to assess the effect of quercetin on RA. Additionally, the safety of quercetin requires further confirmation. Given the importance of the active ingredient, dose selection and the improvement of quercetin's bioavailability remain to be explored.

The Chromatin Landscape of Pathogenic Transcriptional Cell States in Rheumatoid Arthritis

Synovial tissue inflammation is the hallmark of rheumatoid arthritis (RA). Recent work has identified prominent pathogenic cell states in inflamed RA synovial tissue, such as T peripheral helper cells; however, the epigenetic regulation of these states has yet to be defined. We measured genome-wide open chromatin at single cell resolution from 30 synovial tissue samples, including 12 samples with transcriptional data in multimodal experiments. We identified 24 chromatin classes and predicted their associated transcription factors, including a CD8+ GZMK+ class associated with EOMES and a lining fibroblast class associated with AP-1. By integrating an RA tissue transcriptional atlas, we found that the chromatin classes represented 'superstates' corresponding to multiple transcriptional cell states. Finally, we demonstrated the utility of this RA tissue chromatin atlas through the associations between disease phenotypes and chromatin class abundance as well as the nomination of classes mediating the effects of putatively causal RA genetic variants.

Resveratrol-induced SIRT1 activation inhibits glycolysis-fueled angiogenesis under rheumatoid arthritis conditions independent of HIF-1α

OBJECTIVE

This study investigated the impacts of SIRT1 activation on rheumatoid arthritis (RA)-related angiogenesis.

METHODS

HUVECs were cultured by different human serum. Intracellular metabolites were quantified by UPLC-MS. Next, HUVECs and rat vascular epithelial cells under different inflammatory conditions were treated by a SIRT1 agonist resveratrol (RSV). Cytokines and biochemical indicators were detected by corresponding kits. Protein and mRNA expression levels were assessed by immunoblotting and PCR methods, respectively. Angiogenesis capabilities were evaluated by migration, wound-healing and tube-formation experiments. To down-regulate certain signals, gene-specific siRNA were applied.

RESULTS

Metabolomics study revealed the accelerated glycolysis in RA serum-treated HUVECs. It led to ATP accumulation, but did not affect GTP levels. RSV inhibited pro-angiogenesis cytokines production and glycolysis in both the cells, and impaired the angiogenesis potentials. These effects were mimicked by an energy metabolism interrupter bikini in lipopolysaccharide (LPS)-primed HUVECs, largely independent of HIF-1α. Both RSV and bikinin can inhibit the activation of the GTP-dependent pathway Rho/ROCK and reduce VEGF production. Abrogation of RhoA signaling reinforced HIF-1α silencing-brought changes in LPS-stimulated HUVECs, and overshadowed the anti-angiogenesis potentials of RSV.

CONCLUSION

Glycolysis provides additional energy to sustain Rho/ROCK activation in RA subjects, which promotes VEGF-driven angiogenesis and can be inhibited by SIRT1 activation.

The Expression of Inflammasomes NLRP1 and NLRP3, Toll-Like Receptors, and Vitamin D Receptor in Synovial Fibroblasts From Patients With Different Types of Knee Arthritis

Activated rheumatoid arthritis (RA) synovial fibroblasts (SFs) are among the most important cells promoting RA pathogenesis. They are considered active contributors to the initiation, progression, and perpetuation of the disease; therefore, early detection of RASF activation could advance contemporary diagnosis and adequate treatment of undifferentiated early inflammatory arthritis (EA). In this study, we investigated the expression of nucleotide-binding, oligomerization domain (NOD)-like receptor family, pyrin domain containing (NLRP)1, NLRP3 inflammasomes, Toll-like receptor (TLR)1, TLR2, TLR4, vitamin D receptor (VDR), and secretion of matrix metalloproteinases (MMPs) in SFs isolated from patients with RA, osteoarthritis (OA), EA, and control individuals (CN) after knee surgical intervention. C-reactive protein, general blood test, anticyclic citrullinated peptide (anti-CCP), rheumatoid factor (RF), and vitamin D (vitD) in patients’ sera were performed. Cells were stimulated or not with 100 ng/ml tumor necrosis factor alpha (TNF-α) or/and 1 nM or/and 0.01 nM vitamin D3 for 72 h. The expression levels of NLRP1, NLRP3, TLR1, TLR2, TLR4, and VDR in all examined SFs were analyzed by quantitative real-time PCR (RT-qPCR). Additionally, the secretion of IL-1β by SFs and MMPs were determined by ELISA and Luminex technology. The expression of NLRP3 was correlated with the levels of CRP, RF, and anti-CCP, suggesting its implication in SF inflammatory activation. In the TNF-α-stimulated SFs, a significantly lower expression of NLRP3 and TLR4 was observed in the RA group, compared with the other tested forms of arthritis. Moreover, upregulation of NLRP3 expression by TNF-α alone or in combination with vitD3 was observed, further indicating involvement of NLRP3 in the inflammatory responses of SFs. Secretion of IL-1β was not detected in any sample, while TNF-α upregulated the levels of secreted MMP-1, MMP-7, MMP-8, MMP-12, and MMP-13 in all patient groups. Attenuating effects of vitD on the expression of NLRP3, TLR1, and TLR4 suggest potential protective effects of vitD on the inflammatory responses in SFs. However, longer studies may be needed to confirm or fully rule out the potential implication of vitD in SF activation in inflammatory arthritis. Both VDR and NLRP3 in the TNF-α-stimulated SFs negatively correlated with the age of patients, suggesting potential age-related changes in the local inflammatory responses.

α-Mangostin Alleviated HIF-1α-Mediated Angiogenesis in Rats With Adjuvant-Induced Arthritis by Suppressing Aerobic Glycolysis

A previously validated anti-rheumatic compound α-mangostin (MAN) shows significant metabolism regulatory effects. The current study aimed to clarify whether this property contributed to its inhibition on synovial angiogenesis. Male wistar rats with adjuvant-induced arthritis (AIA) were orally treated by MAN for 32 days. Afterwards, biochemical parameters and cytokines in plasma were determined by corresponding kits, and glycometabolism-related metabolites were further accurately quantified by LC-MS method. Anti-angiogenic effects of MAN were preliminarily assessed by joints based-immunohistochemical examination and matrigel plug assay. Obtained results were then validated by experiments in vitro. AIA-caused increase in circulating transforming growth factor beta, interleukin 6, hypoxia inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in blood and local HIF-1α/VEGF expression in joints was abrogated by MAN treatment, and pannus formation within matrigel plugs implanted in AIA rats was inhibited too. Scratch and transwell assays revealed the inhibitory effects of MAN on human umbilical vein endothelial cells (HUVECs) migration. Furthermore, MAN inhibited tubule formation capability of HUVECs and growth potential of rat arterial ring-derived endothelial cells in vitro. Meanwhile, MAN eased oxidative stress, and altered glucose metabolism in vivo. Glycolysis-related metabolites including glucose 6-phosphate, fructose 6-phosphate, 3-phosphoglyceric acid and phosphoenolpyruvic acid in AIA rats were decreased by MAN, while the impaired pyruvate-synthesizing capability of lactate dehydrogenase (LDH) was recovered. Consistently, MAN restored lipopolysaccharide-elicited changes on levels of glucose and LDH in HUVECs culture system, and exerted similar effects with LDH inhibitor stiripentol on glycometabolism and VEGF production as well as tubule formation capability of HUVECs. These evidences show that MAN treatment inhibited aerobic glycolysis in AIA rats, which consequently eased inflammation-related hypoxia, and hampered pathological neovascularization.

Anti-nociceptive effect of Portulaca oleracea L. ethanol extracts attenuated zymosan-induced mouse joint inflammation via inhibition of Nrf2 expression

The aim of this study was to explore the effects of ethanol extracts from Portulaca oleracea L. (ePO) on joint inflammation and to explain the underlying mechanisms. A joint inflammation mouse model was constructed by injecting zymosan, and the Von Frey method was employed and the joint thickness measured. The numbers of leukocytes, neutrophils, and monocytes were counted in the joint cavity and the infiltration of inflammatory cells was assessed by joint histopathological analysis. The mRNA levels of inflammatory cytokines were determined by quantitative RT-PCR and their secretion levels were determined by specific ELISAs. Pre-treatment with ePO inhibited articular mechanical hyperalgesia and edema and ameliorated the recruitment of mononuclear neutrophils and leukocytes. In addition, pre-treatment with ePO improved pathological alternations in the joint tissues by reducing the number of inflammatory cells. Pre-treatment with ePO regulated the nuclear factor erythroid 2-related factor 2 (Nrf2)-related proteins and thereby inhibited oxidative stress. In addition, ePO inhibited NLR family pyrin domain containing 3 (NLRP3) inflammasome-related genes (NLRP3, ASC, pro-caspase-1 and pro-IL-1ß), modulated inflammatory cytokines and the activation of NF-κB. ePO attenuated zymosan-induced joint inflammation by regulating oxidative stress, NLRP3 inflammasome, and NF-κB.

Hot spot 19 F magnetic resonance imaging of inflammation

Among the preclinical molecular imaging approaches, lately fluorine (¹⁹ F) magnetic resonance imaging (MRI) has garnered significant scientific interest in the biomedical research community, due to the unique properties of fluorinated materials and the ¹⁹ F nucleus. Fluorine is an intrinsically sensitive nucleus for MRI-there is negligible endogenous ¹⁹ F in the body and, thus, no background signal which allows the detection of fluorinated materials as "hot spots" by combined ¹ H/¹⁹ F MRI and renders fluorine-containing molecules as ideal tracers with high specificity. In addition, perfluorocarbons are a family of compounds that exhibit a very high fluorine payload and are biochemically as well as physiologically inert. Perfluorocarbon nanoemulsions (PFCs) are well known to be readily taken up by immunocompetent cells, which can be exploited for the unequivocal identification of inflammatory foci by tracking the recruitment of PFC-loaded immune cells to affected tissues using ¹ H/¹⁹ F MRI. The required ¹⁹ F labeling of immune cells can be accomplished either ex vivo by PFC incubation of isolated endogenous immune cells followed by their re-injection or by intravenous application of PFCs for in situ uptake by circulating immune cells. With both approaches, inflamed tissues can unambiguously be detected via background-free ¹⁹ F signals due to trafficking of PFC-loaded immune cells to affected organs. To extend ¹⁹ F MRI tracking beyond cells with phagocytic properties, the PFC surface can further be equipped with distinct ligands to generate specificity against epitopes and/or types of immune cells independent of phagocytosis. Recent developments also allow for concurrent detection of different PFCs with distinct spectral signatures allowing the simultaneous visualization of several targets, such as various immune cell subtypes labeled with these PFCs. Since ligands and targets can easily be adapted to a variety of problems, this approach provides a general and versatile platform for inflammation imaging which will strongly extend the frontiers of molecular MRI. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease.

RA-map: building a state-of-the-art interactive knowledge base for rheumatoid arthritis

Rheumatoid arthritis (RA) is a progressive, inflammatory autoimmune disease of unknown aetiology. The complex mechanism of aetiopathogenesis, progress and chronicity of the disease involves genetic, epigenetic and environmental factors. To understand the molecular mechanisms underlying disease phenotypes, one has to place implicated factors in their functional context. However, integration and organization of such data in a systematic manner remains a challenging task. Molecular maps are widely used in biology to provide a useful and intuitive way of depicting a variety of biological processes and disease mechanisms. Recent large-scale collaborative efforts such as the Disease Maps Project demonstrate the utility of such maps as versatile tools to organize and formalize disease-specific knowledge in a comprehensive way, both human and machine-readable. We present a systematic effort to construct a fully annotated, expert validated, state-of-the-art knowledge base for RA in the form of a molecular map. The RA map illustrates molecular and signalling pathways implicated in the disease. Signal transduction is depicted from receptors to the nucleus using the Systems Biology Graphical Notation (SBGN) standard representation. High-quality manual curation, use of only human-specific studies and focus on small-scale experiments aim to limit false positives in the map. The state-of-the-art molecular map for RA, using information from 353 peer-reviewed scientific publications, comprises 506 species, 446 reactions and 8 phenotypes. The species in the map are classified to 303 proteins, 61 complexes, 106 genes, 106 RNA entities, 2 ions and 7 simple molecules. The RA map is available online at ramap.elixir-luxembourg.org as an open-access knowledge base allowing for easy navigation and search of molecular pathways implicated in the disease. Furthermore, the RA map can serve as a template for omics data visualization.

Stromal cell-derived factor-1 (CXCL12) and its role in bone and muscle biology

Musculoskeletal disorders are the leading cause of disability worldwide; two of the most prevalent of which are osteoporosis and sarcopenia. Each affect millions in the aging population across the world and the associated morbidity and mortality contributes to billions of dollars in annual healthcare cost. Thus, it is important to better understand the underlying pathologic mechanisms of the disease process. Regulatory chemokine, CXCL12, and its receptor, CXCR4, are recognized to be essential in the recruitment, localization, maintenance, development and differentiation of progenitor stem cells of the musculoskeletal system. CXCL12 signaling results in the development and functional ability of osteoblasts, osteoclasts, satellite cells and myoblasts critical to maintaining musculoskeletal homeostasis. Interestingly, one suggested pathologic mechanism of osteoporosis and sarcopenia is a decline in the regenerative capacity of musculoskeletal progenitor stem cells. Thus, because CXCL12 is critical to progenitor function, a disruption in the CXCL12 signaling axis might play a distinct role in these pathological processes. Therefore, in this article, we perform a review of CXCL12, its physiologic and pathologic function in bone and muscle, and potential targets for therapeutic development.

Pro-inflammatory mediators and neutrophils are increased in synovial fluid from heifers with acute ruminal acidosis

BACKGROUND

Acute ruminal acidosis (ARA) is a metabolic disease of cattle characterized by an aseptic synovitis. ARA is the result of an increased intake of highly fermentable carbohydrates that frequently occurs in dairy cattle subjected to high production requirements. In human joint diseases such as rheumatoid arthritis and gout, several pro-inflammatory molecules are increased in the synovial fluid, including cytokines, prostaglandin E₂ (PGE₂), metalloproteinases, and neutrophil extracellular traps (NETs). The aim of this study was to identify the presence of proinflammatory mediators and neutrophils in the synovial fluid of heifers with ARA, induced by an oligofructose overload. Five heifers were challenged with an oligofructose overload (13 g/kg BW) dissolved in water. As a control, a similar vehicle volume was used in four heifers. Synovial fluid samples were collected from the tarso-crural joint and PGE₂, IL-6, IL-1β, ATP, lactate dehydrogenase (LDH), albumin, glucose, matrix metalloproteinase-9 (MMP-9), cellular free DNA, NETs, and serpin B1 were analyzed at 0, 9, and 24 h post treatment.

RESULTS

At 9 h post oligofructose overload, an increase of IL-1β, IL-6, PGE₂, serpin B1 and LDH was detected in the joints when compared to the control group. At 24 h, the synovial fluid was yellowish, viscous, turbid, and contained abundant neutrophils. An increase of DNA-backbone-like traps, histone 3 (H₃cit), aggregated neutrophil extracellular traps (aggNETs), and serpin B1 were observed 24 h post treatment. Furthermore, albumins, LDH, ATP, MMP-9, IL-6, and IL-1β were increased after 24 h.

CONCLUSIONS

The overall results indicate that IL-1β, IL-6 and PGE₂, were the earliest proinflammatory parameters that increased in the synovial fluid of animals with ARA. Furthermore, the most sever inflammatory response in the joint was observed after 24 h and could be associated with a massive presence of neutrophils and release of aggNETs.

Comparative Studies of Different Extracts from Eucommia ulmoides Oliv. against Rheumatoid Arthritis in CIA Rats

To compare efficacy of different extracts from Eucommia ulmoides Oliv. with both immune inflammation and joint destruction in collagen induced arthritis (CIA) rat model. Rats were divided into normal group (Nor), control group (CIA), TG group (treated with tripterygium glycoside), E70 group (treated with 70% ethanol extract from Eucommia ulmoides Oliv.), EA group (treated with ethyl acetate fraction from E70), and EN group (treated with n-butyl alcohol fraction from E70). All extracts from Eucommia ulmoides Oliv. could significantly inhibit ankle swelling, pathological manifestations, and cytokine levels in serum and spleen, by using foot volume measurement, H&E staining, ELISA, and RT-QPCR methods, respectively. All extracts could significantly inhibit rough joint surface and marginal osteophytes, improve RANKL/OPG ratio, and decrease MMP-9 expression, by using micro-CT and immunohistochemical staining. The activation of IKK/NF-κB signaling pathway was also inhibited by all extracts. In addition, ethyl acetate fraction from E70 presented better effect on RANKL/OPG system. This study identified effective extracts from Eucommia ulmoides Oliv. relieving immune inflammation and maintaining structural integrity of joints in CIA rats.

The overexpression of Fra1 disorders the inflammatory cytokine secretion by mTEC of myasthenia gravis thymus

The thymus of a myasthenia gravis (MG) patient is often accompanied by and effected with follicular hyperplasia. Inflammatory cytokines in thymus induce the formation of germinal centres (GC). MG thymic inflammatory cytokines are predominantly secreted by stromal cells. Our previous studies revealed that the expression level of the Fra1 protein, which is a Fos member of the activator protein 1 transcription factors (AP-1), was higher in the MG thymus compared with that of the normal thymus. Based on that, we demonstrated that Fra1 was mainly expressed in medulla thymic epithelial cells (mTECs) and that the rate of Fra1 positive mTECs in the MG thymus was higher than normal. In vitro, we found that the expression of CCL-5, CCL-19 and CCL-21 could be regulated by Fra1 in mTEC and that IL-1β, IL-6, IL-8 and ICAM1 were downregulated in the Fra1 overexpression group and upregulated in the Fra1 knock-down group. Meanwhile, we detected that the expression levels of suppressor of cytokine signalling 3 (SOCS3) were significantly upregulated along with the overexpression of Fra1. Hence, we considered that the overexpression of Fra1 disrupted inflammatory cytokine secretion by mTEC in the MG thymus and that STAT3 and SOCS3 were strongly involved in this process.

Identification of prolargin expression in articular cartilage and its significance in rheumatoid arthritis pathology

Qualitative 2D gel-electrophoresis (2DE) protein profiling for osteoarthritis (OA) and rheumatoid arthritis (RA) is challenging because of selective protein loss due to discrepancies in protein precipitation methodologies. Thus, we aimed at developing qualitative protein representation from OA/RA articular cartilage without protein precipitation towards identification of clinically relevant proteins. Chondroitinase digested human articular cartilages from RA patients were subjected to protein extraction using guanidinium hydrochloride (GuHCl) or 8 M urea with 10 or 2% ASB-14-4 or 0.45 M urea with 2% ASB-14-4 with cetylpyridinium chloride (CPC). The GuHCl extract is further protein precipitated with acetone or ammonium acetate-methanol or centricon-fractionated using 100 kDa cut filters and protein precipitated using ethanol. Processed extracts were subjected to 2DE to identify protein profiles. Poor proteins representations were observed in 2D gels with protein precipitated samples compared to qualitative protein representations seen in 2D gels of 0.45 M urea and 2%ASB-14-4 extraction procedure reproducibly. The strategy circumventing protein precipitation generated qualitative 2D gels. RA vs OA gel comparison showed elevated prolargin levels in RA with biglycan levels remaining unaltered. Up regulation of prolargin in RA suggests the likelihood of an adaptive mechanism to control the increased osteoclastogenesis in RA and may have therapeutic value in controlling the disease.

Flavonoid quercetin-methotrexate combination inhibits inflammatory mediators and matrix metalloproteinase expression, providing protection to joints in collagen-induced arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation of synovial tissues in joints, leading to progressive destruction of cartilage and joints. The disease-modifying anti-rheumatic drugs currently in use have side-effects. Thus, there is an urgent need for safe anti-inflammatory therapies for RA. This study aimed to evaluate the therapeutic effect of the flavonoid quercetin on arthritis in mice immunized with type II collagen (CII). An arthritis model was established in C57/BL6 mice by intradermal administration of chicken CII mixed with Freund's complete adjuvant. Quercetin (30 mg/kg orally) and methotrexate (0.75 mg intraperitoneally twice a week) were administered to investigate their protective effects against collagen-induced arthritis (CIA). Levels of tumour necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and the matrix metalloproteinases (MMP), 3, and 9 were detected to assess the anti-inflammatory effect of quercetin. The mRNA expression of MMP3, MMP9, CCL2, and TNF-α was also measured by quantitative real-time PCR. Quercetin significantly alleviated joint inflammation by reducing the levels of circulating cytokines and MMPs. There was a significant decrease in the expression of TNFα and MMP genes in the ankle joints of arthritic mice. A significant reduction in the levels of knee-joint inflammatory mediators were observed with combined quercetin and methotrexate treatment. Thus, quercetin has the potential to prevent joint inflammation and could be used as an adjunct therapy for RA patients who have an inadequate response to anti-rheumatic monotherapy.

Clitoria ternatea flower petals: Effect on TNFR1 neutralization via downregulation of synovial matrix metalloproteases

ETHNOPHARMACOLOGICAL RELEVANCE

Clitoria ternatea Linn. (C. ternatea) is a traditionally used herb in arthritis, and its anti-arthritic activity has been attributed to polyphenols (e.g. quercetins) from its flower petal.

AIM OF THE STUDY

The present study was designed to investigate whether C. ternatea or quercetin-3ß-D-glucoside (QG) support the antibody mediated TNFα-receptor 1 (TNFR1) neutralization to ameliorate arthritis in mice.

MATERIALS AND METHODS

Development of collagen-induced arthritis (CIA) in male Swiss mice (20-22g, 3-4 weeks of age) was followed by estimation of synovial polymorphonuclear cell (PMN) accumulation (in terms of myeloperoxidase activity), synovial and systemic release of cytokines, chemokines and C-reactive protein (CRP) by enzyme-linked immunosorbent assay (ELISA), biochemical estimation of synovial free radical generation and antioxidant status, as well as immunoblot assessment of synovial TNFR1, toll-like receptor 2(TLR2), cyclooxygenase-2(COX-2) and inducible nitric oxide synthase (iNOS) expression; and zymographic analysis of synovial matrix-metalloprotease-2 (MMP-2) activity.

RESULTS

CIA was induced from day 2 post-secondary immunizations as evidenced from arthritic scores and joint swelling in parallel to increased inflammatory and oxidative stress parameters in synovial joints. Long term supplementation with extract from Clitoria ternatea flower petals CTE (50mg/kg) and QG (2.5mg/kg) upto 24 days post booster immunization augmented anti-arthritic potential of TNFR1 neutralization with anti-TNFR1 antibody (10μg per mice) in terms of reduced MPO activity, decrease in release of pro-inflammatory cytokines, chemokines, reactive oxygen species (ROS)/ reactive nitrogen species (RNS) production in parallel to significant (p<0.05) reduction in TNFR1, TLR2, iNOS, COX-2 and MMP-2 expression.

CONCLUSION

CTE and QG possess potential anti-arthritic activity which targets synovial MMP-2 in arthritic joints and TNFR1 targeting followed by CTE or QG treatment might become a combinatorial approach in future therapeutic research in treatment of arthritis.

Mucosa-associated lymphoid tissue lymphoma translocation 1 as a novel therapeutic target for rheumatoid arthritis

Emerging evidence suggests that mucosa-associated lymphoid tissue lymphoma translocation 1 (MALT1) is a key regulator of inflammatory diseases; however, the pathological role of MALT1 in rheumatoid arthritis (RA) is not well understood. Consequently, this protein has not been therapeutically targeted for the treatment of RA. MALT1 plays a role in the paracaspase pathway, has proteolytic activity and is involved in the regulation of inflammatory responses. In this study, we found that the MALT1-targeting inhibitory small molecule, MALT1 selective inhibitor 2-chloro-N-[4-[5-(3,4-dichlorophenyl)-3-(2-methoxyethoxy)-1H-1,2,4-triazol-1-yl]phenylacetamide (MI-2) strongly suppresses the differentiation of monocytes into osteoclasts in the absence or presence of the inflammatory cytokine tumour necrosis factor α. Furthermore, MI-2 ameliorates pathologic bone erosion and synovitis in an in vivo mouse model of collagen-induced arthritis. Mechanistically, MI-2 blocked expression of the master osteoclast regulator - nuclear factor of activated T cells 1 (NFATc1) - by inhibiting nuclear factor κB (NF-κB), which is a critical regulator of NFATc1. These findings highlight the important regulatory role of MALT1 in the NF-κB-NFATc1-signalling axis during osteoclastogenesis and suggest that targeting MALT1 is a promising treatment option for rheumatoid arthritis.

Anti-rheumatic effects of Aconitum leucostomum Worosch. on human fibroblast-like synoviocyte rheumatoid arthritis cells

The aim of the present study was to investigate the effects of Aconitum leucostomum Worosch. crude drug, processed products and monomer components on human fibroblast-like synoviocyte rheumatoid arthritis (HFLS-RA) cells, and its associated mechanisms. Following drug treatment, cell proliferation was assessed using a Cell Counting Kit-8 assay. Cellular apoptosis and cell cycle were evaluated using flow cytometry. Levels of hypoxia-inducible factor 1α (HIF-1α), vascular endothelial growth factor (VEGF) and toll-like receptor 4 (TLR4) mRNA and protein were evaluated using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis, respectively. Levels of pro-inflammatory cytokines were evaluated using ELISA. Analysis of cell proliferation indicated that crude drug and processed products markedly inhibited the cell proliferation. Compared with the control group, the apoptosis rates were significantly elevated in all treatment groups (all P<0.05). Furthermore, the proportion of cells in G0/G1 phase was significantly decreased in all treatment groups compared with the control group (all P<0.05). RT-qPCR and western blotting indicated that, compared with the control group, mRNA and protein expression levels of HIF-1α, and TLR4 were significantly downregulated in all treatment groups (P<0.05). The mRNA and protein expression levels of VEGF in all treatment groups were decreased compared with those in the control group, but the difference was not significant. Results from ELISA demonstrated that the levels of interleukin (IL)-6, IL-1β and tumor necrosis factor-α in the cell culture supernatant were all significantly decreased following drug treatment in HFLS-RA cells (all P<0.05). Therefore, A. leucostomum Worosch. crude drug, processed products and monomer components may exert anti-rheumatic effects on HFLS-RA cells, inhibiting cell proliferation and enhancing cellular apoptosis. These effects may be attributable to the downregulated expression of HIF-1α and TLR4, as well as decreased levels of pro-inflammatory cytokines.

Mandibular movements in older people with rheumatoid arthritis

OBJECTIVE

The aim of this study was to compare the mandibular movements in older people with and without temporomandibular disorder (TMD) associated with rheumatoid arthritis (RA).

STUDY DESIGN

Thirty partially or completely edentulous older adults (65.33 ± 4.7 years) were assigned to 2 groups: (1) with RA and TMD and (2) without RA and TMD. Chewing movements of the jaws during mastication of the test material (Optocal) and the range of mandibular movements were evaluated by using the JT-3-D kinesiographic device before and after new removable prosthesis insertion. Multiple comparisons were made with analysis of variance (ANOVA) and the Tukey-Kramer test.

RESULTS

Comparisons between the 2 groups before and after new prosthesis insertion revealed that the RA and TMD group had reduced opening angles (P < .05) during chewing. After insertion of new prostheses, both groups showed increased opening and closing angles during chewing (P < .05). The mandibular range of motion results showed that patients with RA and TMD exhibited lower aperture and laterality movements (P < .05) compared with controls before and after new prosthesis insertion. However, there was an increase in aperture, lefty laterality, and protrusion values after new prosthesis insertion in both groups.

CONCLUSIONS

TMD associated with RA may impair mandibular movements. Well-fitted prostheses may improve mandibular movements in older adults, especially those with RA.

Excavatolide B Attenuates Rheumatoid Arthritis through the Inhibition of Osteoclastogenesis

Osteoclasts are multinucleated giant cells of macrophage/monocyte lineage, and cell differentiation with the upregulation of osteoclast-related proteins is believed to play a major role in the destruction of the joints in the course of rheumatoid arthritis (RA). Pro-inflammatory cytokines, such as interleukin-17A (IL-17A) and macrophage colony-stimulating factor (M-CSF), can be overexpressed in RA and lead to osteoclastogenesis. In a previous study, we found that cultured-type soft coral-derived excavatolide B (Exc-B) exhibited anti-inflammatory properties. In the present study, we thus aimed to evaluate the anti-arthritic activity of Exc-B in in vitro and in vivo models. The results demonstrated that Exc-B inhibits LPS-induced multinucleated cell and actin ring formation, as well as TRAP, MMP-9, and cathepsin K expression. Additionally, Exc-B significantly attenuated the characteristics of RA in adjuvant (AIA) and type II collagen-induced arthritis (CIA) in rats. Moreover, Exc-B improved histopathological features, and reduced the number of TRAP-positive multinucleated cells in the in vivo AIA and CIA models. Immunohistochemical analysis showed that Exc-B attenuated the protein expression of cathepsin K, MMP-2, MMP-9, CD11b, and NFATc1 in ankle tissues of AIA and CIA rats. Level of interleukin-17A and macrophage colony-stimulating factor were also decreased by Exc-B. These findings strongly suggest that Exc-B could be of potential use as a therapeutic agent by inhibiting osteoclast differentiation in arthritis. Moreover, this study also illustrates the use of the anti-inflammatory marine compound, Exc-B, as a potential therapeutic strategy for RA.

Serum Levels of IL-6 and TNF-α May Correlate with Activity and Severity of Rheumatoid Arthritis

Background

We aimed to investigate the association of rheumatoid arthritis (RA) with interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α) through a meta-analysis.

Material/Methods

The case-control studies that investigated the association between RA and serum levels of IL-6 and TNF-α were retrieved strictly according to the inclusion and exclusion criteria. The statistical analysis was performed using STATA statistical software (Version 12.0, Stata Corporation, College Station, TX, USA).

Results

Fourteen studies were enrolled in our meta-analysis, with a total of 890 patients with RA and 441 healthy people as the controls. The results of this meta-analysis revealed that the serum IL-6 and TNF-α levels of RA patients were significantly higher than in the controls, and this difference was statistically significant (IL-6: SMD=2.40, 95% CI=1.57~3.24, P<0.001; TNF-α: SMD=1.93, 95% CI=1.23~2.64, P<0.001). According to ethnic subgroup analysis, the serum IL-6 and TNF-α levels of RA patients were also significantly higher compared with the controls in Asians and Caucasians (IL-6: Asians: SMD=3.64, 95% CI=2.16~5.12, P<0.001; Caucasians: SMD=0.75, 95% CI=0.47~1.02, P<0.001; TNF-α: Asians: SMD=2.74, 95%CI=1.58~3.91, P<0.001; Caucasians: SMD=0.81, 95% CI=0.50~1.11, P<0.001).

Conclusions

IL-6 and TNF-α may play crucial roles in the activity and severity of RA.

Chaetocin inhibits RANKL-induced osteoclast differentiation through reduction of Blimp1 in Raw264.7 cells

AIMS

Periodontitis is one of the most common bone-destructive diseases. Osteoclast is differentiated from hematopoietic macrophage-like cells through receptor activator of NFκB ligand (RANKL)-RANK signaling system, and the reduction in osteoclast formation may result in prevention of bone-resorptive diseases. Chaetocin is a compound isolated from fungal cultures and has been reported as a potent and selective inhibitor of suppressor of variegation 3-9 homolog 1 (Suv39h1), which catalyzes histone methylation on histone H3 lysine 9 (H3K9) residues. However, the effect of chaetocin on osteoclast differentiation is uncertain. In this study, we examine the effect of chaetocin on RANKL-induced osteoclast differentiation and cell growth.

MAIN METHODS

Mouse macrophage-like Raw264.7 cells were treated with RANKL in the presence or absence of chaetocin, and tartrate-resistant acid phosphatase (TRAP) staining was performed. Cell growth was measured as the amount of DNA stained with SYTOX Green dye. Expression and production of osteoclast differentiation markers, anti-osteoclastogenic genes, B lymphocyte-induced maturation protein-1 (Blimp1), and cell growth suppressors were examined by qRT-PCR or/and Western blot analysis.

KEY FINDINGS

Here we show that chaetocin dose-dependently reduced RANKL-induced osteoclast differentiation and cell growth via Blimp1 downregulation which results in the upregulation of osteoclast differentiation inhibitors and cell growth suppressors. These effects were not derived from the chaetocin's inhibitory effect of Suv39h1.

SIGNIFICANCE

These results suggest that chaetocin suppresses RANKL-induced osteoclastogenesis and cell growth through blimp1 downregulation, followed by induction of anti-osteoclastogenic genes and cell growth suppressors, without inhibition of Suv39h1. Thus, chaetocin might be a drug candidate for the prevention of bone resorption in bone-destructive diseases.

Acacetin inhibits expression of matrix metalloproteinases via a MAPK-dependent mechanism in fibroblast-like synoviocytes

It is well known that rheumatoid arthritis (RA) is an autoimmune joint disease in which fibroblast-like synoviocytes (FLSs) play a pivotal role. In this study, we investigated the anti-arthritic properties of acacetin in FLSs. The expression of matrix metalloproteinase (MMP)-1, MMP-3 and MMP-13 were investigated by quantitative RT-PCR and western blot at gene and protein levels. At the same time, the phosphorylation of mitogen-activated protein kinases (MAPK) was investigated. The DNA-binding activity of NF-κB was investigated by electrophoretic mobility shift assay. We found that acacetin inhibits p38 and JNK phosphorylation and reduces MMP-1, MMP-3 and MMP-13 expression in interleukin-1β-induced FLSs. Our results suggest that acacetin has antiarthritic effects in FLSs. Thus, acacetin should be further studied for the treatment of arthritis.

Uncovering pharmacological mechanisms of Wu-tou decoction acting on rheumatoid arthritis through systems approaches: drug-target prediction, network analysis and experimental validation

Wu-tou decoction (WTD) has been extensively used for the treatment of rheumatoid arthritis (RA). Due to lack of appropriate methods, pharmacological mechanisms of WTD acting on RA have not been fully elucidated. In this study, a list of putative targets for compositive compounds containing in WTD were predicted by drugCIPHER-CS. Then, the interaction network of the putative targets of WTD and known RA-related targets was constructed and hub nodes were identified. After constructing the interaction network of hubs, four topological features of each hub, including degree, node betweenness, closeness and k-coreness, were calculated and 79 major hubs were identified as candidate targets of WTD, which were implicated into the imbalance of the nervous, endocrine and immune (NEI) systems, leading to the main pathological changes during the RA progression. Further experimental validation also demonstrated the preventive effects of WTD on inflammation and joint destruction in collagen-induced arthritis (CIA) rats and its regulatory effects on candidate targets both in vitro and in vivo systems. In conclusion, we performed an integrative analysis to offer the convincing evidence that WTD may attenuate RA partially by restoring the balance of NEI system and subsequently reversing the pathological events during RA progression.

BIX01294 suppresses osteoclast differentiation on mouse macrophage-like Raw264.7 cells

Gene expressionis controlled by epigenetic mechanisms including histone methylation. Osteoclasts are bone-resorptive cells that differentiate from hematopoietic-precursor cells by receptor activator of nuclear factor-κB ligand (RANKL) stimulation. Although BIX01294, a specific inhibitor of G9a, which works as a histone H3 lysine 9 (H3K9) methyltransferase, reportedly changes cellular differentiational stage, its effect on osteoclast differentiation is unclear. In this study, the effects of BIX01294 on osteoclast differentiation were examined. Here, we showed that BIX01294 dose-dependently reduced RANKL-induced tartrate-resistant acid phosphatase positive multinuclear osteoclast-like cell differentiation from murine macrophage-like Raw264.7 cells. During differentiation, growth rates reduced only less than 14% of those of cells stimulated with RANKL alone by BIX01294 treatment. Moreover, western blot analysis showed that BIX01294 reduced RANKL-induced carbonic anhydrase II and cathepsin K production and decreased RANKL-induced nuclear factor of activated T-cell c1, a master regulatory transcription factor, production during osteoclast differentiation. These results suggest that BIX01294 suppresses RANKL-induced osteoclast differentiation. This is the first report about the effect of BIX01294 on osteoclast differentiation.

Reciprocal activation of CD4+ T cells and synovial fibroblasts by stromal cell-derived factor 1 promotes RANKL expression and osteoclastogenesis in rheumatoid arthritis

OBJECTIVE

Stromal cell-derived factor 1 (SDF-1) is a chemokine that is involved in the bone-destructive process in rheumatoid arthritis (RA) and bony metastasis in malignancy. This study was undertaken to determine the role and mechanism of SDF-1 in RA-associated osteoclastogenesis.

METHODS

The expression of SDF-1, tumor necrosis factor α (TNFα), and RANKL in RA synovial tissue was analyzed using confocal microscopy. After synovial fibroblasts and CD4+ T cells were treated with SDF-1, RANKL messenger RNA expression was determined by real-time and reverse transcription polymerase chain reaction. Osteoclastogenesis was assessed by counting tartrate-resistant acid phosphatase-positive multinucleated cells in CD14+ monocytes cultured with SDF-1 in the presence of anticytokine antibodies or signal inhibitors and in monocytes cocultured with SDF-1-pretreated synovial fibroblasts and CD4+ T cells.

RESULTS

RANKL, TNFα, and SDF-1 were coexpressed in the lining and sublining of RA synovium. SDF-1 stimulated RANKL expression in RA synovial fibroblasts and CD4+ T cells, and TNFα inhibition reduced this stimulation. When monocytes isolated from human peripheral blood were cultured with SDF-1, they were differentiated into osteoclasts in the absence of RANKL. Monocytes were also differentiated into osteoclasts when they were cocultured with SDF-1-pretreated synovial fibroblasts or CD4+T cells; however, this osteoclastogenesis was reduced by TNFα inhibition.

CONCLUSION

Our findings indicate that SDF-1 induces osteoclastogenesis directly and indirectly via up-regulating RANKL expression in RA synovial fibroblasts and CD4+ T cells, and that this is mediated by TNFα. The axis of SDF-1 and RANKL is a potential therapeutic target for RA-associated bone destruction.

Chemical constituents of Plectranthus amboinicus and the synthetic analogs possessing anti-inflammatory activity

This study demonstrates that compounds 1-4 from an extract of Plectranthus amboinicus inhibit the binding of AP-1 to its consensus DNA sequence. Thymoquinone (5) was further identified as a nonpolar ingredient from the hexane extract of P. amboinicus to suppress the expression of lipopolysaccharide-induced tumor necrosis factor-alpha (TNF-α). We then synthesized 2-alkylidenyl-4-cyclopentene-1,3-diones as the designed biomimetics of thymoquinone, and found that compounds 8a, 8b and 8d were more potent TNF-α inhibitors.

Adenosine dialdehyde suppresses MMP-9-mediated invasion of cancer cells by blocking the Ras/Raf-1/ERK/AP-1 signaling pathway

Adenosine dialdehyde (AdOx) inhibits transmethylation by the accumulation of S-adenosylhomocysteine (SAH), a negative feedback inhibitor of methylation, through the suppression of SAH hydrolase (SAHH). In this study, we aimed to determine the regulatory effect of AdOx on cancer invasion by using three different cell lines: MDA-MB-231, MCF-7, and U87. The invasive capacity of these cells in the presence (MCF-7) or absence (MDA-MB-231 and U87) of phorbal 12-myristate 13-acetate (PMA) was strongly decreased by AdOx treatment. Furthermore, the expression, secretion, and activation of matrix metalloproteinase (MMP)-9, a critical enzyme regulating cell invasion, in these cells were diminished by AdOx treatment. AdOx strongly suppressed AP-1-mediated luciferase activity and, in parallel, reduced the translocation of c-Fos and c-Jun into the nucleus. AdOx was shown to block a series of upstream AP-1 activation signaling complexes composed of extracellular signal-related kinase (ERK), mitogen-activated protein ERK kinase (MEK)1/2, Raf-1, and Ras, as assessed by measuring the levels of the phosphorylated and membrane-translocated forms. Furthermore, we found that suppression of SAHH by siRNA and 3-deazaadenosine, knock down of isoprenylcysteine carboxyl methyltransferase (ICMT), and treatment with SAH showed inhibitory patterns similar to those of AdOx. Therefore, our data suggest that AdOx is capable of targeting the methylation reaction regulated by SAHH and ICMT and subsequently downregulating MMP-9 expression and decreasing invasion of cancer cells through inhibition of the Ras/Raf-1/ERK/AP-1 pathway.

Prolonged ingestion of ovalbumin diet by Ova sensitized mice suppresses mBSA-induced arthritis

Concomitant chronic diseases are a common finding in clinics and may consist in a major issue in therapeutics. Here, we investigated whether prolonged ingestion of ovalbumin (Ova) by sensitized mice would reduce the severity of an associated concurrent immunomediated condition such as antigen-induced arthritis (AIA). AIA was induced by administration of methylated bovine albumin (mBSA) into the knee joints of previously immunized mice, and evaluated by articular leukocyte trafficking and levels of cytokines (TNF-α, IL-1β) and chemokine (CXCL-1) in the periarticular tissue. Continuous Ova feeding by Ova sensitized mice decreased serum levels of anti-Ova IgE, and led to a significant suppression of leukocyte adhesion and infiltration into synovial tissue and cavity. Also, a marked cytokine reduction was observed, suggesting that prolonged ingestion of ovalbumin by sensitized mice suppresses specific IgE production with concomitant reduction in peripheral T cells, which may impact in the pathogenesis of AIA, a non-related condition.

A soft coral-derived compound, 11-epi-sinulariolide acetate suppresses inflammatory response and bone destruction in adjuvant-induced arthritis

In recent years, a significant number of metabolites with potent anti-inflammatory properties have been discovered from marine organisms, and several of these compounds are now under clinical trials. In the present study, we isolated 11-epi-sinulariolide acetate (Ya-s11), a cembrane-type compound with anti-inflammatory effects, from the Formosa soft coral Sinularia querciformis. Preliminary screening revealed that Ya-s11 significantly inhibited the expression of the proinflammatory proteins induced nitric oxide synthase and cyclooxygenase-2 in lipopolysaccharide-stimulated murine macrophages. We also examined the therapeutic effects of Ya-s11 on adjuvant-induced arthritis (AIA) in female Lewis rats, which demonstrate features similar to human rheumatoid arthritis (RA). Animal experiments revealed that Ya-s11 (subcutaneously 9 mg/kg once every 2 days from day 7 to day 28 postimmunization) significantly inhibited AIA characteristics. Moreover, Ya-s11 also attenuated protein expression of cathepsin K, matrix metalloproteinases-9 (MMP-9), tartrate-resistant acid phosphatase (TRAP), and tumor necrosis factor-α (TNF-α) in ankle tissues of AIA-rats. Based on its attenuation of the expression of proinflammatory proteins and disease progression in AIA rats, the marine-derived compound Ya-s11 may serve as a useful therapeutic agent for the treatment of RA.

Shorter disease duration is important for tocilizumab to achieve Boolean remission

OBJECTIVE

To determine the optimal conditions for inducing rheumatoid arthritis (RA) into disease remission by tocilizumab (TCZ), we analyzed the TCZ therapy carried out in our facility.

METHOD

The study group comprised 116 patients with RA who started TCZ therapy at Kobe University Hospital and Konan-Kakogawa Hospital. The clinical response to TCZ was evaluated by the 2011 Boolean definition and the disease activity score of 28 joints erythrocyte sedimentation rate 4 (DAS28-ESR4).

RESULTS

After 24 weeks of TCZ therapy, 25.9% of the patients achieved a Boolean-defined disease remission (Boolean remission). DAS28-ESR4 was improved from 5.25 ± 1.15 at week 0 to 2.75 ± 1.34 at week 24 (mean ± SD, P < 0.0001), and 57.8% patients achieved DAS28 remission. Analysis of the relationship between disease duration and remission showed that this odds ratio peaked at 3.0 years. Univariate analyses showed that Boolean remission was associated with baseline ESR levels, Steinbrocker's class and stage, and patient global assessment of disease activity (PGA). Accordingly, we categorized and compared the patient groups referring to the 3.0-year peak. We found significant differences in Steinbrocker's class and stage.

CONCLUSION

TCZ therapy leading to Boolean disease remission is optimal when initiated less than 3.0 years after disease onset.

New advances of microRNAs in the pathogenesis of rheumatoid arthritis, with a focus on the crosstalk between DNA methylation and the microRNA machinery

Rheumatoid arthritis (RA) is a symmetrical polyarticular disease of unknown aetiology that affects primarily the articular cartilage and bone. Characteristic features of RA pathogenesis are persistent inflammation, synovium hyperplasia and cartilage erosion accompanied by joint swelling and joint destruction. Several lines of evidence have showed a crucial role of activated fibroblast-like synoviocytes (FLS) in the pathogenesis of RA. MicroRNAs (miRNAs) are endogenous, single-stranded, non-coding RNAs with about 21 nucleotides in length and have been detected in a variety of sources, including tissues, serum, and other body fluids, such as saliva. In light of key roles of miRNAs in the regulation of gene expression, miRNAs influence a wide range of physiological and pathological processes. For example, miRNAs are evident in various malignant and nonmalignant diseases, and accumulating evidence also shows that miRNAs have important roles in the pathogenesis of RA. It has been demonstrated that miRNAs can be aberrantly expressed even in the different stages of RA progression, allowing miRNAs to help understand the pathogenesis of the disease, to act as important biomarkers, and to monitor the disease severity and the effects of drug treatment. In addition, miRNAs are emerging as potential targets for new therapeutic strategies of this kind of autoimmune disorders. The ultimate goal is the identification of miRNA targets that could be manipulated through specific therapies, aiming at activation or inhibition of specific miRNAs responsible for the RA development. In this review, the importance of miRNAs in the pathogenesis of RA is discussed systematically, with particular emphasis on the role of the crosstalk between DNA methylation and the microRNA machinery.

Aryl hydrocarbon receptor antagonism mitigates cytokine-mediated inflammatory signalling in primary human fibroblast-like synoviocytes

OBJECTIVES

Rheumatoid Arthritis (RA) is a chronic inflammatory disease of unclear aetiology, which is associated with inflamed human fibroblast-like synoviocytes (HFLS). Epidemiological studies have identified a positive correlation between tobacco smoking (a rich source of aryl hydrocarbon receptor (AHR) agonists) and aggressive RA phenotype. Thus, we hypothesise that antagonism of AHR activity by a potent AHR antagonist GNF351 can attenuate the inflammatory phenotype of HFLS-RA cells.

METHODS

Quantitative PCR was used to examine IL1B-induced mRNA expression in primary HFLS-RA cells. A structurally diverse AHR antagonist CH223191 and transient AHR repression using AHR small interfering RNA (siRNA) in primary HFLS-RA cells were used to demonstrate that effects observed by GNF351 are AHR-mediated. The levels of PTGS2 were determined by western blot and secretory cytokines such as IL1B and IL6 by ELISA. Chromatin-immunoprecipitation was used to assess occupancy of the AHR on the promoters of IL1B and IL6.

RESULTS

Many of the chemokine and cytokine genes induced by IL1B in HFLS-RA cells are repressed by co-treatment with GNF351 at both the mRNA and protein level. Pretreatment of HLFS-RA cells with CH223191 or transient gene ablation of AHR by siRNA confirmed that the effects of GNF351 are AHR-mediated. GNF351 inhibited the recruitment of AHR to the promoters of IL1B and IL6 confirming occupancy of AHR at these promoters is required for enhanced inflammatory signalling.

CONCLUSIONS

These data suggest that AHR antagonism may represent a viable adjuvant therapeutic strategy for the amelioration of inflammation associated with RA.

Upregulation of tumor necrosis factor receptor-associated factor 6 correlated with synovitis severity in rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic inflammatory disease leading to joint destruction and disability. Focal bone erosion is due to excess bone resorption of osteoclasts. Tumor necrosis factor receptor-associated factor 6 (TRAF6) is one of the critical mediators both in inflammatory signal pathway and differentiation and resorption activity of osteoclasts. Here we aimed to investigate TRAF6 expression in RA synovium and its correlation with histological synovitis severity and radiological joint destruction in RA.

METHODS

Synovitis score was determined in needle biopsied synovium from 44 patients with active RA. Synovium from nine patients with osteoarthritis (OA) and seven with orthopedic arthropathies (Orth.A) were enrolled as "less inflamed" disease controls. Serial sections were stained immunohistochemically for TRAF6 as well as CD68 (macrophage), CD3 (T cell), CD20 (B cell), CD38 (plasmocyte), CD79a (B lineage cells from pre-B cell to plasmocyte stage), and CD34 (endothelial cell). Double immunofluorescence staining of TRAF6 and CD68 were tested. Densities of positive staining cells were determined and correlated with histological disease activity (synovitis score) and radiographic joint destruction (Sharp score).

RESULTS

TRAF6 expression was found in the intimal and subintimal area of RA synovium, with intense staining found in the endochylema and nucleus of intimal synoviocytes and subintimal inflammatory cells. Double immunofluorescence staining showed TRAF6 was expressed in most of the intimal cells and obviously expressed in CD68+ cells and some other CD68- cells in subintimal area. Synovial TRAF6 was significantly over-expressed in the RA group compared with the OA and Orth.A group (2.53 ± 0.94 vs. 0.72 ± 0.44 and 0.71 ± 0.49, P < 0.0001). Synovial TRAF6 expression in RA correlated significantly with synovitis score (r = 0.412, P = 0.006), as well as the inflammatory cell infiltration (r = 0.367, P = 0.014). Significant correlation was detected between synovial TRAF6 expression and intimal CD68+ cells, as well as the cell density of subintimal CD68+ cells, CD3+ cells, CD20+ cells, CD38+ cells, and CD79a+ cells (all P < 0.05).

CONCLUSIONS

Elevated synovial TRAF6 expression correlated with synovitis severity and CD68+ cell density in RA. It is, therefore, hypothesized that synovial TRAF6 is involved in the pathogenesis of synovial inflammation and osteoclast differentiation in RA.

Anticitrullinated Protein Antibody, But Not Its Titer, Is a Predictor of Radiographic Progression and Disease Activity in Rheumatoid Arthritis

Objective.

To study the contribution of anticitrullinated protein antibody (ACPA), and especially of its titer, to radiographic progression and disease activity in rheumatoid arthritis (RA).

Methods.

Patients with RA (n = 396) who attended a Japanese clinic within 2 years after disease onset were divided into the following groups according to second-generation (ACPA-2) ACPA titer on their first visit: negative (0–4.4 U/ml; n = 115), low-positive (4.5–121 U/ml; n = 141), and high-positive (> 121 U/ml; n = 140). The ACPA-2-positive groups were further subdivided into lowest (4.5–32 U/ml), low (33–121 U/ml), high (122–277 U/ml), and highest (> 278 U/ml) quartiles. All patients were treated with disease-modifying antirheumatic drugs (DMARD) including methotrexate, but not biologics. Subsequent radiographic progression and disease activity for 2 years were prospectively evaluated using the van der Heijde-modified Sharp score (SHS) and 28-joint Disease Activity Score (DAS28).

Results.

After treatment with DMARD, the disease activity (including number of swollen joints, number of tender joints, duration of morning stiffness, DAS28-erythrocyte sedimentation rate, and DAS28-C-reactive protein) was significantly decreased in all patient groups. Disease activity and radiographic progression as revealed by the change in SHS remained relatively higher in the ACPA-2 low- and high-positive groups as compared with the ACPA-2-negative group. The relationship between the titer of ACPA-2 at baseline and subsequent radiographic progression was not exactly linear, and the extent of disease activity or radiographic progression was similar between ACPA-2 low- and high-positive groups and also between ACPA-2 lowest- and highest-positive quartile groups. The results were demonstrable in cumulative SHS probability plots, and also repeatable in seronegative patients, which indicated that the titer of ACPA-2 is not a predictor of disease activity or radiographic progression in RA, and ACPA-2-negative patients, especially those with < 3 U/ml, showed minimal radiographic progression.

Conclusion.

Presence of ACPA-2, but not its titer, at baseline is a predictor of radiographic progression or disease activity, where radiographic progression is minimal in ACPA-2-negative patients.

Rheumatic autoimmune diseases: proposed elimination of autoreactive B-cells with magnetic nanoparticle-linked antigens

Although the pathogenesis of rheumatoid arthritis and other rheumatic diseases is still not fully understood, it has become clear that in many cases autoimmune responses with production of autoantibodies against physiological targets play a significant and causal role. Current immunosuppressive and immunomodulatory approaches such as bone marrow transplantation or the therapeutic antibody rituximab are effective, but unspecific and have serious side effects. Here, a method for targeted elimination of specific autoreactive B-cells which are essential for autoantibody production and maintenance of the autoimmune response is proposed. By binding to their receptive antigens linked to magnetic nanoparticles, the autoreactive B-cells can be separated from the rest of the blood in an extracorporeal filtration process, reducing the number of autoimmune cells and autoantibodies in the blood. The method can be adapted for use in different autoimmune diseases provided some key aspects of pathogenesis are known, and can be repeated if necessary. Evidence for feasibility and safety of this method is briefly reviewed, and potential limitations and hurdles to overcome are discussed.

Intrinsic danger: activation of Toll-like receptors in rheumatoid arthritis

RA is a debilitating disorder that manifests as chronic localized synovial and systemic inflammation leading to progressive joint destruction. Recent advances in the molecular basis of RA highlight the role of both the innate and adaptive immune system in disease pathogenesis. Specifically, data obtained from in vivo animal models and ex vivo human tissue explants models has confirmed the central role of Toll-like receptors (TLRs) in RA. TLRs are pattern recognition receptors (PRRs) that constitute one of the primary host defence mechanisms against infectious and non-infectious insult. This receptor family is activated by pathogen-associated molecular patterns (PAMPs) and by damage-associated molecular patterns (DAMPs). DAMPs are host-encoded proteins released during tissue injury and cell death that activate TLRs during sterile inflammation. DAMPs are also proposed to drive aberrant stimulation of TLRs in the RA joint resulting in increased expression of cytokines, chemokines and proteases, perpetuating a vicious inflammatory cycle that constitutes the hallmark chronic inflammation of RA. In this review, we discuss the signalling mechanisms of TLRs, the central function of TLRs in the pathogenesis of RA, the role of endogenous danger signals in driving TLR activation within the context of RA and the current preclinical and clinical strategies available to date in therapeutic targeting of TLRs in RA.