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The role of liver X receptors (LXR) in rheumatoid arthritis (RA) remains controversial. We studied the effect of LXR agonists on fibroblast‐like synoviocytes (FLS) from RA patients and the K/BxN arthritis model in LXRα and β double‐deficient (Nr1h2/3−/−) mice. Two synthetic LXR agonists, GW3965 and T0901317, were used to activate LXRs and investigate their effects on cell growth, proliferation and matrix metalloproteinases, and chemokine production in cultured FLS from RA patients. The murine model K/BxN serum transfer of inflammatory arthritis in Nr1h2/3−/− animals was used to investigate the role of LXRs on joint inflammation in vivo. LXR agonists inhibited the FLS proliferative capacity in response to TNF, the chemokine‐induced migration, the collagenase activity in FLS supernatant and FLS CXCL12 production. In the K/BxN mouse model, Nr1h2/3−/− animals showed aggravated arthritis, histological inflammation, and joint destruction, as well as an increase in synovial metalloproteases and expression of proinflammatory mediators such as IL‐1β and CCL2 in joints compared with wild type animals. Taken together, these data underscore the importance of LXRs in modulating the joint inflammatory response and highlight them as potential therapeutic targets in RA. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease characterized by synovial hyperplasia, and fibroblast‐like synoviocytes (FLSs) constitute the majority of cells in the synovial tissue, playing a crucial role in the onset of RA. Dysregulation of FLSs function is a critical strategy in treating joint damage associated with RA. Non‐coding RNAs, a class of RNA molecules that do not encode proteins, participate in the development of various diseases. This article aims to review the progress in the study of long non‐coding RNAs, microRNAs, and circular RNAs in FLSs. Non‐coding RNAs are involved in the pathogenesis of RA, directly or indirectly regulating FLSs' proliferation, migration, invasion, apoptosis, and inflammatory responses. Furthermore, non‐coding RNAs also influence DNA methylation and osteogenic differentiation in FLSs. Therefore, non‐coding RNAs hold promise as biomarkers for diagnosing RA. Targeting non‐coding RNAs in FLSs locally represents a potential strategy for future therapies in RA. [ABSTRACT FROM AUTHOR]

Background: Rheumatoid arthritis (RA) is a chronic immune system disease with a high disability rate threatening the living quality of patients. Identifying potential biomarkers for RA is of necessity to improve the prevention and management of RA. Objectives: This study focused on miR-146b-3p evaluating its clinical significance and revealing the underlying regulatory mechanisms. Materials and methods: A total of 107 RA patients were enrolled, and both serum and synovial tissues were collected. Another 78 osteoarthritis patients (OA, providing synovial tissues), and 72 healthy individuals (providing serum samples) were enrolled as the control group. The expression of miR-146b-3p was analyzed by PCR and analyzed with ROC and Pearson correlation analyses evaluating its significance in diagnosis and development prediction of RA patients. In vitro, MH7A cells were treated with TNF-α. The regulation of cell proliferation, motility, and inflammation by miR-146b-3p was assessed by CCK8, Transwell, and ELISA assays. Results: Significant upregulation of miR-146b-3p was observed in serum and synovial tissues of RA patients, which distinguished RA patients and were positively correlated with the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), anti-cyclic citrullinated peptide antibodies (anti-CCP), and rheumatoid factor (RF) of RA patients. TNF-α promoted the proliferation and motility of MH7A cells and induced significant inflammation in cells. Silencing miR-146b-3p alleviated the effect of TNF-α and negatively regulated the expression of HMGCR. The knockdown of HMGCR reversed the protective effect of miR-146b-3p silencing on TNF-α-stimulated MH7A cells. Conclusions: Increased miR-146b-3p served as a biomarker for the diagnosis and severity of RA. Silencing miR-146b-3p could suppress TNF-α-induced excessive proliferation, motility, and inflammation via regulating HMGCR in MH7A cells. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease characterised by the formation of a hyperplastic pannus, as well as cartilage and bone damage. The pathogenesis of RA is complex and involves broad interactions between various cells present in the inflamed synovium, including fibroblast-like synoviocytes (FLSs), macrophages, and T cells, among others. Under inflammatory conditions, these cells are activated, further enhancing inflammatory responses and angiogenesis and promoting bone and cartilage degradation. Novel treatment methods for RA are greatly needed, and mesenchymal stromal cells (MSCs) have been suggested as a promising new regenerative and immunomodulatory treatment. In this paper, we present the interactions between MSCs and RA-FLSs, and macrophages and T cells, and summarise studies examining the use of MSCs in preclinical and clinical RA studies. [ABSTRACT FROM AUTHOR]

Introduction: Apurinic/apyrimidinic endonuclease 1 (APEX1) is a protein with elevated expression in synovial fluids from rheumatoid arthritis (RA) patients. However, its role in RA pathogenesis remains unexplored. This study investigated the influence of APEX1 on inflammatory pathways in fibroblast-like synoviocytes (FLS) isolated from RA patients. Material and methods: FLS from RA patients (n = 5) were stimulated with recombinant tumor necrosis factor a (TNF-a) and interleukin (IL)-17. Subsequently, cells were treated with recombinant APEX1, and assessments were made on reactive oxygen species (ROS) production and mitochondrial membrane potential. Additionally, mRNA levels of IL-1 family members were quantified. Cell migration was evaluated through Transwell chamber assays, and levels of key secreted inflammatory cytokines were measured via enzyme-linked immunosorbent assay (ELISA). Results: The results demonstrated that APEX1 significantly reduced mitochondrial-specific ROS expression and restored mitochondrial membrane potential in TNF-a/IL-17-stimulated RA FLS. Furthermore, APEX1 treatments attenuated TNF-a/IL-17-induced activation of p38 MAPK, NF-κB, and PI3K 110d signaling pathways. Similarly, APEX1 significantly diminished TNF-a/IL-17-induced expression of inflammatory cytokines, including IL-1 family members, IL-6, IL-8, and vascular endothelial growth factor (VEGF). Notably, APEX1 downregulated cell migration of TNF-a/IL-17-treated RA FLS via inhibition of matrix metalloproteinase 3 (MMP3). Conclusions: These findings collectively underscore the role of APEX1 as a key mediator of cytokine-amplified migration, modulating ROS and MMP3 in RA FLS, thus supporting its potential as a therapeutic target in RA treatment. [ABSTRACT FROM AUTHOR]

Gouty arthritis (GA) is a characteristically inflammatory disease often associated with lipid metabolism disorder. Huangqin Qingrechubi capsule (HQC) has been used for the treatment of GA. To explore the mechanism of HQC in the treatment of GA. A total of 30 GA patients (GA group) and 30 healthy subjects [normal control (NC) group] were recruited. The GA group was treated with HQC (3.6 g/d) for 10 days. Lipid metabolism and inflammation indexes were detected. Five herbal names of HQC, or 'gouty arthritis', 'hyperlipidemia' and 'inflammation' were used as key words to search related databases for network pharmacological analysis. Subsequently, GA-fibroblast-like synoviocytes (FLSs) were stimulated with GA-peripheral blood mononuclear cells (PBMCs) (3:1) and treated with HQC drug-containing serum (20%). RT-qPCR, Western blot, and ELISA were conducted to further explore the mechanism of HQC in improving GA. In clinical observation, HQC decreased the expression of lncRNA H19 and IL-1β, and increased the expression of adiponectin (APN) and IL-4 in the GA group (about half). Through network pharmacology, the PI3K/AKT signaling pathway was identified. Cell experiments showed that HQC treatment reduced the viability of GA-FLSs (49.61%), up-regulated the expression of IL-4 (155.18%), IL-10 (165.13%), and APN (31.24%), and down-regulated the expression of lncRNA H19 (33.70%), IL-1β (64.70%), TNF-α (78.32%), p-PI3K (48.80%), and p-AKT (53.48%). HQC improved lipid metabolism disorder and inflammatory response of GA by regulating the lncRNA H19/APN/PI3K/AKT. Maintaining the stability of lipid metabolism may be an effective way to alleviate GA. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage injury, hyperplasia of bone and inflammatory lesions of synovium. Monoacylglycerol lipase (MAGL), a member of the α/β hydrolase superfamily, is involved in regulation of injury protection and immune-inflammation response. Autoinflammatory response of the synovium and the release of inflammatory mediators play critical roles in occurrence of early-stage OA. Fibroblast-like synoviocytes (FLSs) are resident mesenchymal cells of the synovial tissue. Considering that MAGL inhibition regulates the inflammatory signaling cascade, it is crucial to ascertain the biological effects and specific mechanisms of MAGL in alleviating inflammatory infiltration of OA FLSs. The aim of this study was to investigate the effect of MAGL on biological function in OA FLSs. Results from in vitro experiments showed that MAGL blockade not only effectively inhibited proliferation, invasion and migration of FLSs, but also downregulated expression of inflammatory-associated proteins. Sequencing results indicated that MAGL inhibition significantly suppressed NOX4-mediated oxidative stress, thus promoting Nrf2 nuclear accumulation and inhibiting generation of intracellular reactive oxygen species (ROS). Attenuation of NOX4 further alleviated redox dysplasia and ultimately improved tumor-like phenotypes, such as abnormal proliferation, migration and migration of FLSs. In vivo results corroborated this finding, with MAGL inhibition found to modulate pain and disease progression in an OA rat model. Collectively, these results indicate that MAGL administration is an ideal therapy treating OA. [Display omitted] • MAGL exerted a crucial influence on synovial inflammation and osteoarthritis. • MAGL blockade inhibited the secretion of inflammatory factors in synovial cells. • MAGL blockade regulated Nrf2 nuclear accumulation and the NOX4-Nrf2 redox balance. • MJN110 administration led to a reduction in synovial inflammation in osteoarthritis rats. [ABSTRACT FROM AUTHOR]

Synovial fluid (SF) from human knee joints with osteoarthritis (OA) has elevated levels of lysophosphatidylcholine (LPC) species, but their functional role is not well understood. This in vitro study was designed to test the hypothesis that various LPCs found elevated in OA SF and their metabolites, lysophosphatidic acids (LPAs), modulate the abundance of proteins and phospholipids (PLs) in human fibroblast-like synoviocytes (FLSs), with even minute chemical variations in lysophospholipids determining the extent of regulation. Cultured FLSs (n = 5–7) were treated with one of the LPC species, LPA species, IL-1β, or a vehicle. Tandem mass tag peptide labeling coupled with LC-MS/MS/MS was performed to quantify proteins. The expression of mRNA from regulated proteins was analyzed using RT-PCR. PL synthesis was determined via ESI-MS/MS, and the release of radiolabeled PLs was determined by means of liquid scintillation counting. In total, 3960 proteins were quantified using multiplexed MS, of which 119, 8, and 3 were significantly and reproducibly regulated by IL-1β, LPC 16:0, and LPC 18:0, respectively. LPC 16:0 significantly inhibited the release of PLs and the synthesis of phosphatidylcholine, LPC, and sphingomyelin. Neither LPC metabolite—LPA 16:0 nor LPA 18:0—had any reproducible effect on the levels of each protein. In conclusion, small chemical variations in LPC species can result in the significantly altered expression and secretion of proteins and PLs from FLSs. IL-1β influenced all proteins that were reproducibly regulated by LPC 16:0. LPC species are likely to modulate FLS protein expression only in more advanced OA stages with low IL-1β levels. None of the eight proteins being significantly regulated by LPC 16:0 have been previously reported in OA. However, our in vitro findings show that the CD81 antigen, calumenin, and B4E2C1 are promising candidates for further study, focusing in particular on their potential ability to modulate inflammatory and catabolic mechanisms. [ABSTRACT FROM AUTHOR]

Background: Juvenile Idiopathic Arthritis (JIA) is the most prevalent chronic pediatric rheumatic disorder. In joints of JIA patients, aggressive phenotypic changes in fibroblast-like synoviocytes (FLS) of the synovial lining play a key role in inflammation. MicroRNAs are dysregulated in rheumatoid arthritis and JIA, including miR-27a-3p. However, it is not understood if miR-27a-3p, enriched in JIA synovial fluid (SF) and leukocytes, alters FLS function. Methods: Primary JIA FLS cells were transfected with a miR-27a-3p mimic or a negative control microRNA (miR-NC) and stimulated with pooled JIA SF or inflammatory cytokines. Viability and apoptosis were analyzed by flow cytometry. Proliferation was evaluated using a 3H-thymidine incorporation assay. Cytokine production was assessed by qPCR and ELISA. Expression of TGF-β pathway genes was determined using a qPCR array. Results: MiR-27a-3p was constitutively expressed in FLS. Overexpression of miR-27a-3p caused increased interleukin-8 secretion in resting FLS, and interleukin-6 was elevated in SF-activated FLS compared to miR-NC. Furthermore, stimulation with pro-inflammatory cytokines augmented FLS proliferation in miR-27a-3p-transfected FLS relative to miR-NC. Expression of multiple TGF-β pathway genes was modulated by overexpression of miR-27a-3p. Conclusions: MiR-27a-3p significantly contributes to FLS proliferation and cytokine production, making it a potential candidate for epigenetic therapy that targets FLS in arthritis. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is characterized by systemic immune and chronic inflammatory features, leading to the destruction of the joints. Presently, there are no effective drugs able to control synovitis and catabolism in the process of RA. 2-Styrylchromones (2-SC) are a small group of compounds characterized by the attachment of a styryl group to the chromone core that have already been associated to a wide range of biological activities, including antioxidant and anti-inflammatory activities. The present study investigated the effect of a set of six 2-SC on the interleukin-1β (IL-1β)-induced increase of nitric oxide (•NO), inducible form of nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and matrix metalloproteinase-3 (MMP-3) expression levels in human fibroblast-like synoviocytes (HFLS), pointing to the role of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation in the process. From a set of six 2-SC, presenting hydroxy and methoxy substituents, the one presenting two methoxy substituents at C-5 and C-7 of A ring and a catechol group on B ring, significantly reduced •NO production and the expression of its inducible synthase (iNOS). It also significantly reduced the catabolic MMP-3 protein expression. This 2-SC inhibited the NF-κB pathway by reversing the IL-1β - induced levels of cytoplasmatic NF-kB inhibitor alpha (IκBα), and decreasing the p65 nuclear levels, suggesting the involvement of these pathways in the observed effects. The same 2-SC significantly increased the COX-2 expression, which may indicate a negative feedback loop mechanism of action. The properties of 2-SC may be of great value in the development of new therapies with improved efficacy and selectivity towards RA, and thus deserve further exploitation and evaluation to disclose the full potential of 2-SC. [ABSTRACT FROM AUTHOR]

Objectives: This study aims to investigate the inflammatory effect of the microRNA (miRNA) miR-30e-5p on rheumatoid arthritis (RA) development in RA mice and fibroblast-like synoviocytes (FLS). Materials and methods: MiR-30e-5p and atlastin GTPase 2 (Atl2) expression in RA tissues and RA-FLS was evaluated using real-time quantitative polymerase chain reaction. The function of miR-30e-5p in inflammation of RA mice and RA-FLS was analyzed by enzyme-linked immunosorbent assay (ELISA) and Western blotting. 5-ethynyl-2'-deoxyuridine (EdU) assay was used to detect RA-FLS proliferation. Luciferase reporter assay was to confirm the interaction between miR-30e-5p and Atl2. Results: MiR-30e-5p expression was upregulated in the tissues from RA mice. Silencing miR-30e-5p alleviated inflammation in RA mice and RA-FLS. MiR-30e-5p negatively modulated Atl2 expression. Atl2 knockdown exerted a proinflammatory effect on RA-FLS. Atl2 knockdown rescued the inhibitory effect of miR-30e-5p knockdown on proliferation and inflammatory response of RA-FLS. Conclusion: MiR-30e-5p knockdown inhibited the inflammatory response in RA mice and RA-FLS through Atl2. [ABSTRACT FROM AUTHOR]

This study explored the role of the long non-coding RNA (lncRNA) XIST (X-inactive specific transcript) as a driver of RA pathogenesis, with a particular focus on the ability of this lncRNA to interact with GATA1 and CCN6. The GSE83147and GSE181614 datasets were downloaded for analysis. XIST and CCN6 expression were assessed in synovial fibroblasts (SFs) and in both normal cartilage samples and those from RA patients, with the relationship between XIST and CCN6 additionally being examined. XIST and CCN6 were respectively knocked down or overexpressed in SFs to establish their regulatory roles in these cells in the context of RA. Further studies of the regulatory interplay between XIST, GATA1, and CCN6 were then performed through RNA immunoprecipitation, RNA pull-down, gain-of-function, loss-of-function, and luciferase reporter assays. In addition, RA model rats were established and used to measure the production of TNF-α, IL-6, and IL-8 and to subject tissues from these animals to histopathological examination. RA patient synovial tissues and SFs exhibited XIST and CCN6 upregulation. The knockdown of XIST suppressed SF migratory, proliferative, invasive, and angiogenic activity, while CCN6 knockdown partially reversed the ability of XIST to influence these phenotypic outcomes in vitro and in vivo. XIST bound to GATA1 within SFs, thus promoting enhanced CCN6 transcription. Knocking down XIST alleviated RA-related pathological damage, synovial injury, and inflammatory response induction in rats. The binding of XIST to GATA1 leads to CCN6 upregulation, driving RA pathogenesis by altering SF proliferation and angiogenic activity, suggesting that this pathway may represent a viable target for therapeutic intervention. • Long non-coding RNA XIST and CCN6 significantly upregulated in rheumatoid arthritis (RA) patients. • Silencing XIST inhibits proliferation, migration, invasion and angiogenic function of synovial fibroblasts. • The effect of silencing XIST on synovial fibroblasts can be partially reversed by overexpressing CCN6. • XIST increases the transcription of CCN6 by binding GATA1 in synovial fibroblasts. • The downregulation of XIST ameliorates pathological state, the inflammatory response, and synovial injury in RA mice. [ABSTRACT FROM AUTHOR]

Erosive destruction of joint structures is an important event in the rheumatoid arthritis (RA) development where fibroblast-like synoviocytes (FLS) represent the main effectors. The implication of long noncoding RNAs (lncRNAs) in RA has not been clearly established. Here, we sought to assess the function of lncRNA H19 in RA by assessing its contribution to the phenotype of FLS. H19 was overexpressed in RA-FLS, and H19 promoted RA-FLS proliferation, invasion as well as angiogenesis and reduced RA-FLS apoptosis. Moreover, H19 loss significantly alleviated joint redness and swelling and reduced inflammatory response, synovial hyperplasia and cartilage damage in arthritic mice induced by collagen. Mechanistically, H19 significantly increased the transcription of sorting nexin (SNX) 10 in RA-FLS by promoting STAT1 translocation into the nucleus. Overexpression of SNX10 or STAT1 mitigated the repressing effects of H19 loss on RA in mice. Our findings highlight that H19 upregulation may result in the development of FLS-mediated RA via the STAT1/SNX10 axis. H19 might serve as a possible therapeutic target for RA treatment. [Display omitted] • H19 is highly expressed in RA synovium and promotes the activity of FLS. • Inhibition of H19 improves joint damage in mice with CIA. • STAT1 is recruited by H19 to the nucleus to enhance the transcription of SNX10. • Inhibition of SNX10 significantly reverses the promotion of RA-FLS activity by H19. • H19 cooperates with STAT1 to regulate the expression of SNX10 in RA progression. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is characterized by chronic inflammation of the synovium of joints. Fibroblast-like synoviocytes (FLS) play an important role in RA pathogenesis. We aimed to investigate the effect of N-(4-methoxyphenyl) quinoline-8-sulfonamide (QS-3g) on the inflammatory response of FLS and explore the potential underlying mechanisms. We screened and found that QS-3g exhibits the best anti-inflammatory response against FLS using the CCK8 assay. To investigate the therapeutic effects of QS-3g on K/BxN STA mice, we used H&E staining, immunofluorescence, immunohistochemistry, micro-CT, and other techniques. Additional investigations, including RNA-seq, molecular docking, and CETSA, revealed that QS-3g binds to RAMP1. Among a series of 8-quinoline sulfonyl amide derivatives, QS-3g reduced the inflammatory response in TNF-α stimulated FLS, such as the release of interleukin (IL)-1β and IL-6. H&E staining and micro-CT showed that QS-3g inhibited synovial hypertrophy, inflammatory cell infiltration, and bone destruction. RNA-seq and CETSA analyses revealed the targeted inhibition of RAMP1 by QS-3g. Inhibition of RAMP1 expression could reduce IL-6 and IL-1β levels. Compared with RAMP1-si, combined administration of QS-3g and RAMP1-si reduced the TNF-α-induced inflammation in TNF-α stimulated FLS without statistically significant differences. Finally, the results of in vitro experiments showed that QS-3g could restore the balance of Gαi/Gαs by inhibiting Gαi and activating Gαs and up-regulate the expression of cAMP protein, thus inhibiting the RAMP1-mediated inflammatory response in FLS. QS-3g could inhibit RAMP1 activity and mediate the Gαs/Gαi–cAMP pathway to reduce FLS inflammatory response. Therefore, QS-3g may serve as a novel anti-inflammatory compound for treating RA. [ABSTRACT FROM AUTHOR]

Fibroblast-like synoviocytes (FLS) plays an important role in synovial inflammation and joint damage in rheumatoid arthritis (RA). As the most abundant mRNA modification, N6-methyladenosine (m6A) is involved in the development of various diseases; however, its role in RA remains to be defined. In this study, we reported the elevated expression of the m6A demethylase fat mass and obesity-associated protein (FTO) in FLS and synovium from RA patients. Functionally, FTO knockdown or treatment with FB23–2, an inhibitor of the mRNA m6A demethylase FTO , inhibited the migration, invasion and inflammatory response of RA FLS, however, FTO -overexpressed RA FLS exhibited increased migration, invasion and inflammatory response. We further demonstrated that FTO promoted ADAMTS15 mRNA stability in an m6A- IGF2BP1 dependent manner. Notably, the severity of arthritis was significantly reduced in CIA mice with FB23–2 administration or CIA rats with intra-articular injection of FTO shRNA. Our results illustrate the contribution of FTO -mediated m6A modification to joint damage and inflammation in RA and suggest that FTO might be a potential therapeutic target in RA. [Display omitted] • Increased FTO promotes the migration, invasion and inflammatory response of RA FLS. • FTO controls RA FLS functions by enhancing ADAMTS15 mRNA stability in an m6A-IGF2BP1dependent manner. • The FTO-mediated m6A modification plays an important role in regulating synovial inflammation and joint damage in RA. [ABSTRACT FROM AUTHOR]

Umbelliferone (UMB), a natural coumarin compound, has been reported to possess anti-rheumatic effects on rheumatoid arthritis (RA) experimental models, but its potential role of UMB in regulating migration, invasion and inflammation of RA fibroblast-like synoviocytes (FLS) remain unclear. Herein, MTT assay was performed to confirm the non-cytotoxic concentrations (10, 20, and 40 μ M) and the treatment time (24 h) of UMB on TNF- α -stimulated RA FLS (MH7A cells) in vitro. Results of wound-healing, transwell and phalloidin staining assays revealed that UMB inhibited TNF- α -induced migration, invasion and F-actin cytoskeletal reorganization in MH7A. Results of ELISA, western blot and gelatin zymography indicated that UMB decreased the productions of pro-inflammatory factors, including IL-1 β , IL-6, IL-8, MMP-2 and MMP-9, and inhibited MMP-2 activity in TNF- α -stimulated MH7A cells. In vivo, UMB (25 mg/kg and 50 mg/kg) relieved the joint damage and synovial inflammation in rats with adjuvant-induced arthritis (AIA). Mechanistically, UMB could suppress Wnt/ β -catenin signaling both in TNF- α -induced MH7A cells and in AIA rat synovium, evidenced by decreasing Wnt1 protein level, activating GSK-3 β kinase by blocking GSK-3 β (Ser9) phosphorylation, and reducing the protein level and nuclear translocation of β -catenin. Importantly, combined use of lithium chloride (a Wnt/ β -catenin signaling agonist) eliminated the inhibitory effects of UMB on migration, invasion and inflammation in vitro and the anti-arthritic effects of UMB in vivo. We concluded that UMB inhibited TNF- α -induced migration, invasion and inflammation of RA FLS and attenuated the severity of rat AIA through its ability to block Wnt/ β -catenin signaling pathway. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a chronic, debilitating systemic disease characterized by chronic inflammation and progressive joint destruction. Fibroblast-like synoviocytes (FLSs) are one of the most important players in the pathophysiology of RA, acting like tumor cells and secreting inflammatory cytokines. Previous research has shown that cold atmospheric plasma (CAP) inhibits cancer cells and may have anti-inflammatory properties. This study examined the effects of argon plasma jet-produced CAP on the suppression of invasion and inflammation caused by cultured RA-FLS. The findings revealed that CAP reduced cell viability and elevated the percentage of apoptotic RA-FLS by producing reactive oxygen species. Carboxyfluorescein diacetate succinimidyl ester (CFSE) staining confirmed that CAP could decrease the proliferation of RA-FLS. Furthermore, CAP effectively reduced the production of inflammatory factors (e.g., NF-κB and IL-6) as well as destructive factors like receptor activator of nuclear factor kappa-B ligand (RANKL) and matrix metalloproteinases-3 (MMP-3). These data suggest that CAP could be a promising treatment for slowing the progression of RA by reducing tumor-like features and inflammation in RA-FLS. [ABSTRACT FROM AUTHOR]

Background: Inflammatory cytokine secretion from fibroblast-like synoviocytes (FLS) plays a vital role in the pathological process of rheumatoid arthritis (RA). Photobiomodulation (PBM) has been widely used in the treatment of RA. However, the mechanism of PBM in RA has not been clarified. Objective: In this study, we investigated the underlying mechanism of 630 nm light-emitting diode (LED) irradiation on anti-inflammation using mRNA sequencing analysis. Methods and results: Reverse transcription (RT)-quantitative polymerase chain reaction (RT-qPCR) results showed that 630nm LED irradiation significantly inhibited interleukin (IL)-1β, IL-6, and IL-8 mRNA expression in rheumatoid arthritis fibroblast synovial cells (RA-FLS) and MH7A cells. A total of 1730 differentially expressed genes (DEGs) were identified between tumor necrosis factor α (TNF-α)+LED and TNF-αtreated RA-FLS and 1219 DEGs in MH7A cells by mRNA sequencing analysis. A total of 646 intersecting DEGs from the 2 cell models were used for gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses. Protein-protein interaction (PPI) network of DEGs was used, and 502 nodes and 1452 edges were found. A total of 14 clusters were generated in MCODE, and the top 3 clusters were selected as hub modules. PPI network showed that most of the nodes were DEGs of the heat shock protein (HSP) family. RT-qPCR verified that 630 nm LED irradiation significantly increased HSP70 mRNA expression in FLS. Conclusions: Taken together, our results revealed the correlation between HSP70 and the inhibition of inflammation caused by 630 nm LED irradiation. These findings suggested that HSP may be a novel target of 630 nm LED irradiation to alleviate inflammation in the treatment of RA. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) is one of the most common joint pathologies and a major cause of disability among the population of developed countries. It manifests as a gradual degeneration of the cartilage and subchondral part of the bone, leading to joint damage. Recent studies indicate that not only the cells that make up the articular cartilage but also the synoviocytes, which build the membrane surrounding the joint, contribute to the development of OA. Therefore, the aim of the study was to determine the response to inflammatory factors of osteoarthritic synoviocytes and to identify proteins secreted by them that may influence the progression of OA. This study demonstrated that fibroblast-like synoviocytes of OA patients (FLS-OA) respond more strongly to pro-inflammatory stimulation than cells obtained from control patients (FLS). These changes were observed at the transcriptome level and subsequently confirmed by protein analysis. FLS-OA stimulated by pro-inflammatory factors [such as lipopolysaccharide (LPS) and tumor necrosis factor alpha (TNFα) were shown to secrete significantly more chemokines (CXCL6, CXCL10, and CXCL16) and growth factors [angiopoietin-like protein 1 (ANGPTL1), fibroblast growth factor 5 (FGF5), and insulin-like growth factor 2 (IGF2)] than control cells. Moreover, the translation of proteolytic enzymes [matrix metalloprotease 3 (MMP3), cathepsin K (CTSK), and cathepsin S (CTSS)] by FLS-OA is increased under inflammatory conditions. Our data indicate that the FLS of OA patients are functionally altered, resulting in an enhanced response to the presence of pro-inflammatory factors in the environment, manifested by the increased production of the previously mentioned proteins, which may promote further disease progression. [ABSTRACT FROM AUTHOR]

Objective: To explore the effect and underlying mechanism of Myricitrin (Myr) in regulating fibroblast-like synoviocyte (FLS)-mediated synovitis and joint destruction in RA. Methods: FLSs were isolated from synovial tissues from patients with RA. Gene expression was measured using quantitative RT-qPCR. Protein expression was detected by immunohistochemistry or Western blot. Cell apoptosis was performed by an Annexin-PI staining assay. EdU incorporation was used to assess the proliferation of RA FLS. Transwell assay was used to characterize the cell migration and invasion ability of RA FLS. The potential target of Myr was identified by RNA sequencing analysis. The in vivo effect of Myr was assessed in a collagen-induced arthritis (CIA) model. Results: Myr treatment inhibited the lamellipodia formation, migration, and invasion, but not the apoptosis and proliferation, of RA FLSs. Myr also reduced the expression of CCL2, IL-6, IL-8, MMP-1, MMP-3, and MMP-13 induced by TNF-a. The RNA-seq results indicated that AIM2 may be a target gene of Myr in RA FLSs. Furthermore, compared to healthy controls, AIM2 expression showed higher levels in synovial tissues and FLSs from RA patients. AIM2 knockdown also inhibited RA FLS migration, invasion, cytokine, and MMP expression. In addition, either Myr treatment or AIM2 knockdown reduced the phosphorylation of AKT induced by TNF-a stimulation. Importantly, Myr administration relieved arthritis symptoms and inhibited AIM2 expression in the synovium of CIA mice. Conclusion: Our results indicate that Myr exerts an anti-inflammatory and antiinvasion effect in RA FLSs and provide evidence of the therapeutic potential of Myr for RA. [ABSTRACT FROM AUTHOR]

Inflammatory and invasive fibroblast‐like synoviocytes (FLS) contribute to the pathology of rheumatoid arthritis (RA). Isoginkgetin (IGKG) has been identified as having anti‐inflammatory properties. This study investigated whether IGKG could be utilized to treat RA. Primary FLS were isolated from synovial tissues derived from six RA patients, which were over‐expressed with matrix metallopeptidase 9 and cultured with or without tumor necrosis factor (TNF)‐α and then further treated with IGKG. IGKG down‐regulated the content of various interleukins (ILs), namely, IL‐1β, IL‐6, and IL‐8, in RA‐FLS supernatant with or without TNF‐α stimulation, with diminished migration and invasion properties as assayed by the transwell system. Furthermore, down‐regulated inflammatory cytokine secretion and down‐regulated migration and invasion properties could be reversed through matrix metallopeptidase 9 overexpression. Dual‐luciferase reporter gene assay indicated that IGKG could inhibit nuclear factor kappa B transcription activity. Western blot analysis also demonstrated that IGKG down‐regulated the expression of p‐IκBα, p‐p65, and MMP9. IGKG displayed the ability to inhibit the inflammatory response of RA‐FLS through the NF‐κB/MMP9 pathway with diminished migration and invasion. [ABSTRACT FROM AUTHOR]

Introduction: Overexpressed inflammatory cytokines are the main factors causing rheumatoid arthritis (RA) tissue damage and pathological deterioration, and lncRNAs has found to beinvolved in some autoinflammatory diseases. Methods: We designed this study to investigate the effect of lncRNA linc00152 on rheumatoid arthritis inflammation and explore its molecular mechanism.Result: We found that linc00152 was not only up‐regulated in rheumatoid arthritis fibroblast‐like synoviocytes (RAFLS), but also stimulated by TNF‐α/IL‐1β in adose‐ and time‐dependent manner in RAFLS and this expression depends on the NF‐κB signaling pathway. Conversely, linc00152 promoted TNF‐α/IL‐1β expression in RAFLS induced by TNF‐α/IL‐1β. In addition, we found that linc00152 promoted TAK1 expression by targeting inhibition of miR‐103a and activated TAK1‐mediated NF‐κB pathway. NF‐kB indirectly promotes linc00152 expression by promoting the transcription activity of YY1, and YY1 directly promotes linc00152 expression by binding the promoter of linc00152. Conclusion: Our data suggested that the linc00152/NF‐κB feedback loop promotes RAFLS inflammation via regulating miR‐103a/TAK1 axis and YY1 expression. Thus, linc00152 acts as a switch to control this regulatory circuit and may serve as a diagnostic and therapeutic target for RA treatment. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is characterized by a tumor-like expansion of the synovium and subsequent destruction of adjacent articular cartilage and bone. In our previous work we showed that phosphatase and tension homolog deleted on chromosome 10 (PTEN) contributes to the activation of fibroblast-like synoviocytes (FLS) in adjuvant-induced arthritis (AIA), but the underlying mechanism is not unknown. In this study, we show that PTEN is downregulated while DNA methyltransferase (DNMT)1 is upregulated in FLS from RA patients and a rat model of AIA. DNA methylation of PTEN was increased by administration of tumor necrosis factor (TNF)-α in FLS of RA patients, as determined by chromatin immunoprecipitation and methylation-specific PCR. Treatment with the methylation inhibitor 5-azacytidine suppressed cytokine and chemokine release and FLS activation in vitro and alleviated paw swelling in vivo. PTEN overexpression reduced inflammation and activation of FLS via protein kinase B (AKT) signaling in RA, and intra-articular injection of PTEN-expressing adenovirus into the knee of AIA rats markedly reduced inflammation and paw swelling. Thus, PTEN methylation promotes the inflammation and activation of FLS in the pathogenesis of RA. These findings provide insight into the molecular basis of articular cartilage destruction in RA, and indicate that therapeutic strategies that prevent PTEN methylation may an effective treatment. [ABSTRACT FROM AUTHOR]

• Dual drug nanoparticle hydrogel of MTX and PEITC (DD NP HG) was biocompatible to healthy FLS. • DD NP HG exerts a synergistic anti-inflammatory effect in LPS-stimulated RA-FLS. • The combination approach of PEITC and MTX (DD NP HG) effectively promoted bone remodeling in LPS-stimulated RA-FLS. • DD NP HG-induced apoptosis protected RA-FLS from undergoing autophagy. Rheumatoid arthritis (RA) is a chronic immune-mediated joint inflammatory disorder associated with aberrant activation of fibroblast-like synoviocytes (FLS). Recently, FLS gained importance due to its crucial role in RA pathogenesis, and thus, targeting FLS is suggested as an attractive treatment strategy for RA. FLS-targeted approaches may be combined with disease-modifying antirheumatic drugs (DMARDs) and natural phytochemicals to improve efficacy in RA control and negate immunosuppression. In this study, we assessed the therapeutic effectiveness of DD NP HG in primary RA-FLS cells isolated from the synovial tissue of FCA-induced RA rats. We observed that DD NP HG had good biosafety for healthy FLS cells and, at higher concentrations, a mild inhibitory effect on RA-FLS. The combination therapy (DD NP HG) of MTX NP and PEITC NE in RA-FLS showed a higher rate of apoptosis with significantly reduced LPS-induced expression of pro-inflammatory cytokines (TNF-α, IL-17A, and IL-6) in arthritic FLS. Further, the gene expression studies showed that DD NP HG significantly down-regulated the mRNA expression of IL-1β, RANKL, NFATc1, DKK1, Bcl-xl, Mcl-1, Atg12, and ULK1, and up-regulated the mRNA expression of OPG, PUMA, NOXA and SQSTM1 in LPS-stimulated RA-FLS cells. Collectively, our results demonstrated that DD NP HG significantly inhibited the RA-FLS proliferation via inducing apoptosis, down-regulating pro-inflammatory cytokines, and further enhancing the expression of genes associated with bone destruction in RA pathogenesis. A nanotechnology approach is a promising strategy for the co-delivery of dual drugs to regulate the RA-FLS function and achieve synergistic treatment of RA. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Previous study showed that circular RNA Absent-Small-Homeotic-2--Like protein (circASH2L) was higher in rheumatoid arthritis (RA) patients. However, the roles and mechanisms of circASH2L in RA progression remain unclear. Methods: Levels analysis was conducted using western blot and qRT-PCR. The proliferation, apoptosis, cell cycle progression, migration, invasiveness, and inflammation of RA fibroblast-like synoviocytes (RA-FLSs) were determined via MTT, flow cytometry, western blot, transwell, and ELISA assays. Results: CircASH2L knockdown in RA-FLSs suppressed cell proliferative, migratory, and invasive capacities, triggered cell cycle arrest, promoted apoptosis, and inhibited inflammation. Mechanistically, circASH2L targeted miR-129-5p, and repression of miR-129-5p abolished the functions of circASH2L silencing on the growth, motility, and inflammation of RA-FLSs. Besides, miR-129-5p was found to directly target HIPK2, and suppressed the tumor-like biologic behaviors and inflammation of RA-FLSs via regulating HIPK2. Importantly, we proved that circASH2L could modulate HIPK2 expression via miR-129-5p. Conclusion: CircASH2L promoted RA-FLS growth, motility, and inflammation through miR-129-5p/HIPK2 axis. [ABSTRACT FROM AUTHOR]

Background: The aggressive phenotype of fibroblast-like synoviocytes (FLSs) is essential in the synovitis and bone destruction in rheumatoid arthritis (RA). Punicalagin is a natural polyphenol extracted in pomegranate juice, which possesses antioxidant, anti-inflammatory and anti-tumor properties suggesting it may be a potent drug for RA therapy. However, there is paucity of information on its effect in RA. Objective: To investigate the effects of punicalagin on synovial inflammation and bone destruction in RA. Methods: FLSs were isolated from synovial tissue of RA patients. The mRNA levels were evaluated by quantitative real-time PCR. Western blot was used for protein level measurements. The secretion of pro-inflammatory cytokines and metalloproteinases (MMPs) was detected by ELISA assays. Edu staining assays were carried out to investigate the proliferation of FLSs. Cell migration was assessed by Boyden chambers, wound scratch assays and F-actin staining in vitro. The intracellular translocation of nuclear factor kappa B (NF-κB) was investigated using immunofluorescence. The effects of punicalagin in vivo were measured by using collagen-induced arthritis (CIA) mice. Results: Punicalagin treatments significantly reduced the TNF-α induced expressions of pro-inflammatory cytokines (IL-1β, IL-6, IL-8 and IL-17A) and MMPs (MMP-1 and MMP-13) of RA FLSs. Punicalagin also suppressed the proliferation and migration of RA FLSs. Moreover, punicalagin (50mg/kg/d) alleviated arthritis severity and bone destruction, and decreased serum IL-6 and TNF-α in CIA mice. Further mechanism studies indicated that punicalagin blocked NF-κB activation via suppressing phosphorylation of IKK and IkBα, and preventing the translocation of 65. Conclusion: Our findings suggested that punicalagin might be one of natural therapeutic compounds for relieving RA progress via suppressing FLSs inflammation and migration through modulating NF-κB pathways. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is an autoimmune disease. Fibroblast-like synoviocytes (FLS) serve a major role in synovial hyperplasia and inflammation in RA. (5R)-5-hydroxytriptolide (LLDT-8), a novel triptolide derivative, shows promising therapeutic effects for RA and is now in phase II clinical trials in China. However, the underlying mechanism of LLDT-8 is still not fully understood. Here, we found that LLDT-8 inhibited proliferation and invasion of RA FLS, as well as the production of cytokines. Microarray data demonstrated that LLDT-8 upregulated the expression of long non-coding RNA (lncRNA) WAKMAR2, which was negatively associated with proliferation and invasion of RA FLS, as well as the production of pro-inflammatory cytokines. Knockdown of WAKMAR2 abolished the inhibitory effects of LLDT-8 on RA FLS. Mechanistically, WAKMAR2 sponged miR-4478, which targeted E2F1 and downstreamed p53 signaling. Rescue experiments indicated that the inhibitory effects of LLDT-8 on RA FLS were dependent on WAKMAR2/miR-4478/E2F1/p53 axis. [ABSTRACT FROM AUTHOR]

Activating transcription factor 2(ATF2), a transcription factor belonging to the AP-1 family, plays an important role in inflammation. However, its biological functions and underlying molecular mechanisms in rheumatoid arthritis (RA) remain unclear. Western blot and immunohistochemistry were used to identify the expression of ATF2 and Sprouty2(SPRY2) in RA synovial tissues. SW982 cells were stimulated by TNF-α to establish an in vitro RA fibroblast-like synoviocyte (RA-FLS) model. Transwell and monolayer wound-healing were used to detect cell migration and invasion. RNA interference (si-ATF2) and adenovirus vector (Ad-SPRY2) methods were employed to manipulate ATF2 or SPRY2 expression in SW982 cells. The protein expression and phosphorylation levels in SW982 cells were evaluated by western blot. ATF2 expression and phosphorylation were upregulated in the RA synovial tissues. In RA-FLS model, ATF2 expression and phosphorylation were increased in a time-dependent manner. ATF2 knockdown inhibited the migration and invasion of RA-FLS model, reducing the inflammatory factors, which was consistent with the influence on cell behaviors caused by SPRY2 overexpression. Moreover, SPRY2 overexpression inhibited the TNF-α-induced phosphorylation of ERK and ATF2 in SW982 cells. The high expression and phosphorylation of ATF2 promoted migration and invasion of RA-FLSs. SPRY2 might inhibited the inflammatory responses of RA-FLSs via suppressing ERK-ATF2 pathway. [ABSTRACT FROM AUTHOR]

Adiponectin is an adipokine with a modulatory role in metabolism and exerting both anti- and pro-inflammatory effects. Levels of adiponectin are increased in serum and synovial fluid from patients with rheumatoid arthritis (RA). Adiponectin is able to stimulate the production of different pro-inflammatory factors from peripheral blood mononuclear cells (PBMCs) and fibroblast-like synoviocytes (FLS) from subjects with established RA. As increased circulating adiponectin levels are a risk factor for future development of RA in subjects with obesity, we hypothesize that adiponectin is implicated in the development of RA at an early stage by initiating the pro-inflammatory processes associated with the disease pathogenesis. Therefore, we aimed to determine if adiponectin is able to induce pro-inflammatory responses in cells involved in the pathogenesis of RA, but collected from subjects without any known inflammatory disease. PBMCs and FLS were obtained from non-inflamed subjects and stimulated with 5 μg/ml human recombinant adiponectin. Supernatants collected after 48 h were analyzed for the production of 13 chemokines and 12 cytokines using multiplex assay and ELISA. Adiponectin significantly stimulated the production of CXCL1, CXCL5, and interleukin (IL)-6 in both PBMCs and FLS, whereas it induced CCL20, CCL4, CCL3, CCL17, tumor necrosis factor (TNF), granulocyte-macrophage colony-stimulating factor and IL-10 only in PBMCs, and CXCL8, CXCL10, CCL5, CCL11, and CCL2 only in FLS. Pre-stimulation with TNF of FLS from non-inflamed subjects did not significantly enhance the release of most pro-inflammatory factors compared to adiponectin alone. Our findings indicate that PBMCs and FLS from non-inflamed subjects react to adiponectin stimulation with the secretion of several pro-inflammatory chemokines and cytokines. These results suggest that adiponectin is able to initiate pro-inflammatory responses in cells from non-inflamed subjects and support the hypothesis that adiponectin is implicated in the early phases of RA pathogenesis. [ABSTRACT FROM AUTHOR]

In contrast to the significant advances in our understanding of the mesenchymal stem cell (MSC) populations in bone marrow (BM), little is known about the MSCs that are resident in the synovial joint and their possible roles in the tissue homeostasis, chronic inflammation as well as in repair. Neural crest is a transient embryonic structure, generating multipotential MSC capable of migrating along peripheral nerves and blood vessels to colonize most tissue types. In adult, these MSC can provide functional stromal support as a stem cell niche for lymphocyte progenitors for instance in the BM and the thymus. Critically, MSC have major immunoregulatory activities to control adverse inflammation and infection. These MSC will remain associated to vessels (perivascular (p) MSC) and their unique expression of markers such as myelin P0 and transcription factors (e.g. Gli1 and FoxD1) has been instrumental to develop transgenic mice to trace the fate of these cells in health and disease conditions. Intriguingly, recent investigations of chronic inflammatory diseases argue for an emerging role of pMSC in several pathological processes. In response to tissue injuries and with the release of host cell debris (e.g. alarmins), pMSC can detach from vessels and proliferate to give rise to either lipofibroblasts, osteoblasts involved in the ossification of arteries and myofibroblasts contributing to fibrosis. This review will discuss currently available data that suggest a role of pMSC in tissue homeostasis and pathogenesis of the synovial tissue and joints. [ABSTRACT FROM AUTHOR]

Purpose: Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease with synovitis as pathological changes. The immune microenvironment of RA promotes metabolic reprogramming of immune cells and stromal cells, which leads to dysfunction and imbalance of immune homeostasis. Cell metabolism undergoes the switch from a static regulatory state to a highly metabolic active state, which changes the redox-sensitive signaling pathway and also leads to the accumulation of metabolic intermediates, which in turn can act as signaling molecules and further aggravate the inflammatory response. The reprogramming of immunometabolism affects the function of immune cells and is crucial to the pathogenesis of RA. In addition, mitochondrial dysfunction plays a key role in glycolytic reprogramming in RA. These metabolic changes may be potential therapeutic targets for RA. Therefore, we reviewed the metabolic reprogramming of RA immune cells and fibroblast-like synovium cells (FLS) and its relationship with mitochondrial dysfunction. Methods: A computer-based online search was performed using the PubMed database and Web of Science database for published articles concerning immunometabolic reprogramming, mitochondrial dysfunction, and rheumatoid arthritis. Results: This article reviews the metabolic reprogramming of immune cells and fibroblast-like synoviocytes in RA and their relationship to mitochondrial disfunction, as well as the key pro-inflammatory pathways associated with metabolic reprogramming and chemotherapy as a potential future therapeutic strategy for RA. [ABSTRACT FROM AUTHOR]

Objectives We investigated the reciprocal relationship linking fibroblast-like synoviocytes (FLS) and T lymphocytes in the inflamed RA synovium and subsequently targeted cellular metabolic pathways in FLS to identify key molecular players in joint inflammation. Methods RA FLS were cultured with CD4 T cells or T cell conditioned medium (CD4CM); proliferation, expression of adhesion molecules and intracellular cytokines were examined by flow cytometry. FLS invasiveness and secreted cytokines were measured by transwell matrigel invasion chambers and ELISA, while metabolic profiles were determined by extracellular Seahorse flux analysis. Gene expression was quantified by real-time quantitative RT-PCR. Results Our results showed mutual activation between CD4 T cells and FLS, which resulted in increased proliferation and expression of intercellular adhesion molecule 1 and vascular cell adhesion molecule 1 by both CD4 T cells and FLS. Furthermore, interaction between CD4 T cells and FLS resulted in an increased frequency of TNF-α+, IFN-γ+ and IL-17A+ CD4 T cells and augmented TNF-α, IFN-γ, IL-17A, IL-6, IL-8 and VEGF secretion. Moreover, CD4CM promoted invasiveness and boosted glycolysis in FLS while downregulating oxidative phosphorylation, effects paralleled by increased glucose transporters GLUT1 and GLUT3 ; key glycolytic enzymes GSK3A , HK2 , LDHA and PFKFB3 ; angiogenic factor VEGF and MMP-3 and MMP-9. Importantly, these effects were reversed by the glycolytic inhibitor 2-DG and AMP analogue 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR). Conclusion This study demonstrates that CD4 T cells elicit an aggressive phenotype in FLS, which subsequently upregulate glycolysis to meet the increased metabolic demand. Accordingly, 2-DG and AICAR prevent this activation, suggesting that glycolytic manipulation could have clinical implications for RA treatment. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA), the most ubiquitous degenerative disease affecting the entire joint, is characterized by cartilage degradation and synovial inflammation. Although the pathogenesis of OA remains poorly understood, synovial inflammation is known to play an important role in OA development. However, studies on OA pathophysiology have focused more on cartilage degeneration and osteophytes, rather than on the inflamed and thickened synovium. Fibroblast‐like synoviocytes (FLS) produce a series of pro‐inflammatory regulators, such as inflammatory cytokines, nitric oxide (NO) and prostaglandin E2 (PGE2). These regulators are positively associated with the clinical symptoms of OA, such as inflammatory pain, joint swelling and disease development. A better understanding of the inflammatory immune response in OA‐FLS could provide a novel approach to comprehensive treatment strategies for OA. Here, we have summarized recently published literatures referring to epigenetic modifications, activated signalling pathways and inflammation‐associated factors that are involved in OA‐FLS‐mediated inflammation. In addition, the current related clinical trials and future perspectives were also summarized. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is the major autoimmune destructive disease of joints with a complicated pathogenesis. The contribution of tumor necrosis factor‐like ligand 1A (TL1A) in RA pathogenesis, especially on fibroblast‐like synoviocytes (FLS), has been suggested clinically. The present study investigated the role of TL1A in mitochondrial dysfunction, induced oxidative stress in mitochondria, apoptosis resistance and the inflammatory response in FLS obtained from RA patients (RA‐FLS). RA‐FLS were incubated with TL1A and tumor necrosis factor receptor 2 (TNFR2) antagonist. Respiratory function, mitochondrial membrane potential and respiration associated genes of mitochondria were measured in both TL1A stimulated and non‐stimulated RA‐FLS. Additionally, the effects of TL1A on reactive oxygen species (ROS) production in mitochondria, apoptosis and the inflammatory response in RA‐FLS were also assessed. The role of TL1A in association between ROS generation, especially mitochondrial type and the inflammatory response, was evaluated by measuring inflammation‐related cytokines and signaling pathways using ROS inhibitors, diphenyleneiodonium chloride and Mito‐TEMPO (Sigma‐Aldrich, Miamisburg, OH, USA). We found that TL1A induced mitochondrial dysfunction by weakening mitochondrial respiration and membrane potential, which was blocked by a TNFR2 antagonist. Increased ROS synthesis in impaired mitochondria was observed with MitoSOX (Invitrogen, CA, USA) immunofluorescence staining in TL1A‐stimulated RA‐FLS but inhibited by a TNFR2 antagonist. TL1A influenced apoptosis resistance and inflammatory mediators via TNFR2. Inhibition of mitochondria‐derived ROS compromised the production of inflammatory factors in TL1A‐stimulated RA‐FLS, suggesting that mitochondrial dysfunction mediated by the TL1A/TNFR2 axis might amplify the inflammatory response via regulation of mitochondria‐derived ROS generation. Collectively, our results reveal that TL1A might be involved in making FLS more aggressive in RA pathogenesis via cell respiration interruption. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) is considered the most frequent degenerative disease and is characterized by cartilage degradation and synovial inflammation. Fibroblast-like synoviocytes (FLSs) are vital to synovial inflammation in OA. Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance and hyperinsulinemia (HINS) and has been demonstrated to be an independent risk factor for OA. Autophagy is involved in the processes of various inflammatory diseases, and autophagy inhibition can stimulate OA development. Thus, we aimed to investigate the role of insulin in the inflammatory phenotype and autophagy of FLSs in OA. The data showed that cell viability and proinflammatory cytokine production in FLSs were both increased after insulin stimulation. We also found that high insulin could promote macrophage infiltration and chemokine production but inhibited autophagy in FLSs. To further explore the potential mechanisms, the effects of insulin on PI3K/Akt/mTOR and NF-ĸB signaling activation were evaluated. The results indicated that insulin activated PI3K/Akt/mTOR/NF-ĸB signaling, and the above-mentioned inflammatory responses, including autophagy inhibition, were notably attenuated by specific signaling inhibitors in the presence of high insulin. Moreover, the data showed that a positive feedback loop existed between proinflammatory cytokines (e.g., IL-1β, IL-6, and TNF-α) and PI3K/mTOR/Akt/NF-ĸB signaling in FLSs, and insulin enhanced this feedback loop to accelerate OA progression. Our study suggests that insulin may be a novel therapeutic strategy for OA prevention and treatment in the future. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease, and the pathogenesis of RA is still unknown. Rheumatoid arthritis fibroblast‐like synoviocytes (RA‐FLSs) are of significance in the pathogenesis of RA. In this study, three microarray profiles (GSE55457, GSE55584, and GSE55235) of human joint FLSs from 33 RA patients and 20 normal controls were extracted from the Gene Expression Omnibus Dataset and analyzed to investigate the underlying pathogenesis of RA. As analyzed by the differently expressed genes, gene ontology, Kyoto Encyclopedia of Genes and Genomes pathway enrichment, and protein‐protein interaction network analysis, syndecan‐4 (SDC4), a receptor of multiple cytokines and chemokines, which played a key role in the regulation of inflammatory response, was found to be an essential regulator in RA. To further validate these results, the levels of SDC4, reactive oxygen species (ROS), nitric oxide (NO), inflammation, and apoptosis in RA‐FLSs were examined. SDC4‐silenced RA‐FLSs were also used. The results demonstrated that SDC4 and the level of ROS, NO, and inflammation were highly expressed while the apoptosis was decreased in RA‐FLSs compared with normal FLSs. SDC4 silencing significantly suppressed the levels of ROS, NO, and inflammation; elevated the expression of nuclear factor erythroid 2‐related factor 2; and promoted the apoptosis of RA‐FLSs. Collectively, our results demonstrated a new mechanism of SDC4 in initiating the inflammation and inhibiting the apoptosis of RA‐FLSs and that a potential target for the diagnosis and treatment of RA in the clinic might be developed. [ABSTRACT FROM AUTHOR]

Abnormalities in the function of fibroblast-like synoviocytes (FLSs) are crucial factors leading to joint damage of rheumatoid arthritis. In recent years, the role of circular RNA (circRNA) in RA has gradually been revealed. However, the functional regulation of FLSs mediated by circRNA and its potential mechanisms remain unclear. In this study, we elucidated the expression profile of circRNA in FLSs, as well as the role and molecular mechanisms of circTldc1. Through sequencing and validation experiments on primary FLSs derived from collagen-induced arthritis (CIA) rats, we found that circTldc1 can promote FLSs proliferation and exacerbate CIA-induced joint damage. The data revealed that circTldc1's parent gene, Tldc1, is homologous to human Tldc1, and circTldc1 is located in the cytoplasm of FLSs, belonging to the exonic circRNA category. The results from bioinformatics analysis, molecular experiments on FLSs (manipulating circTldc1 expression in vitro), and animal experiments (local regulation of circTldc1 expression in vivo) collectively confirmed that circTldc1 promotes Tldc1 expression by targeting miR-485–5p. High expression of Tldc1 further enhances FLSs proliferation and inflammatory responses, thereby worsening joint damage in CIA rats. High expression of circTldc1 and its parent gene Tldc1 may serve as biomarkers for RA. Local regulation of circTldc1 and Tldc1 gene levels in the joint cavity may represent a potential strategy to improve joint damage and inflammation in RA. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] The role of Galectin-9 (Gal-9) in the pathogenesis of rheumatoid arthritis (RA) remains unclear. This study aimed to investigate the mechanism of action and therapeutic potential of Gal-9 in RA. We detected Gal-9 expression in clinical samples, explored the mechanism of function of Gal-9 by knockdown and overexpression in fibroblast-like synoviocytes (FLSs), and further verified it in collagen-induced arthritis (CIA) model. We found that the levels of Gal-9 were considerably elevated in RA synovium than in osteoarthritis (OA) patients. A substantial decrease of Gal-9 was demonstrated after tumor necrosis factor (TNF-α) inhibitor treatment in the plasma of patients with RA. Additionally, transcriptome sequencing revealed that Gal-9 was involved in the regulation of the TNF-α pathway. Gal-9 was considerably upregulated after TNF-α stimulation in FLSs, and knockdown of Gal-9 substantially inhibited TNF-α activated proliferation, migration and inflammatory response. According to cell transcriptome sequencing results, we further confirmed that Gal-9 could achieve these effects by interacting with MAFB and affecting PI3K/AKT/mTOR pathway. Finally, we knocked down Gal-9 on the CIA model and found that it could alleviate the progression of arthritis. In conclusion, our study revealed that the knockdown of Gal-9 could inhibited TNF-α induced activation in RA through MAFB, PI3K/AKT/mTOR. [ABSTRACT FROM AUTHOR]

The autoimmune regulator AIRE controls the negative selection of self-reactive T-cells as well as the induction of regulatory T-cells in the thymus by mastering the transcription and presentation of tissue restricted antigens (TRAs) in thymic cells. However, extrathymic AIRE expression of hitherto unknown clinical significance has also been reported. Genetic polymorphisms of AIRE have been associated with rheumatoid arthritis (RA), but no specific disease-mediating mechanism has been identified. Rheumatoid arthritis is characterized by a systemic immune activation and arthritis. Activated fibroblast-like synoviocytes (FLS) are key effector cells, mediating persistent inflammation, and destruction of joints. In this study, we identified AIRE as a cytokine-induced RA risk gene in RA FLS and explored its role in these pathogenic stroma cells. Using RNA interference and RNA sequencing we show that AIRE does not induce TRAs in FLS, but augments the pro-inflammatory response induced by tumor necrosis factor and interleukin-1β by promoting the transcription of a set of genes associated with systemic autoimmune disease and annotated as interferon-γ regulated genes. In particular, AIRE promoted the production and secretion of a set of chemokines, amongst them CXCL10, which have been associated with disease activity in RA. Finally, we demonstrate that AIRE is expressed in podoplanin positive FLS in the lining layer of synovial tissue from RA patients. These findings support a novel pro-inflammatory role of AIRE at peripheral inflammatory sites and provide a potential pathological mechanism for its association with RA. [ABSTRACT FROM AUTHOR]

Kirenol is a diterpenoid extracted from the Chinese herbal medicine Siegesbeckiae. Siegesbeckiae has been used to treat Rheumatoid arthritis (RA) in China for several centuries. RA is characterized by the proliferation of synoviocytes in inflamed synovia, as well as by their expression of inflammatory cytokines. In the present study, we found that Kirenol inhibited the migration, invasion, and proinflammatory of IL-6 secretion of RA-associated synovial fibroblasts (FLS) at a concentration of 100–200 μg/ml in vitro. Proinflammatory cytokines production and synovium hyperplasia and cartilage erosion were also inhibited in a collagen-induced arthritis (CIA) mouse model upon Kirenol treatment. Together, our results thus confirm that Kirenol has potent therapeutic efficacy in RA owing to its ability to suppress negative FLS activities. [ABSTRACT FROM AUTHOR]

Astragalin, as a bioactive flavonoid with anti-inflammatory, antioxidant, and protective properties, provides a potential agent for rheumatoid arthritis (RA). In this study, its therapeutic efficacy and the underlying mechanisms were explored using DBA/1J mice with collagen-induced arthritis (CIA). It was demonstrated that astragalin could significantly attenuate inflammation of CIA mice. The effects were associated with decreased severity of arthritis (based on the arthritis index), joint swelling and reduced bone erosion and destruction. Furthermore, astragalin treatment suppressed the production of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-8), and inhibited the expression of matrix metalloproteinases (MMP-1, MMP-3, and MMP-13) in chondrocytes and synovial cells of CIA mice. Fibroblast-like synoviocytes derived from RA patients (MH7A cells) were applied to verify these effects. In vitro , astragalin inhibited the expression of matrix metalloproteinases (MMP-1, MMP-3, and MMP-13) dose-dependently in TNF-α-induced MH7A cells, with no apparent cytotoxicity. Furthermore, astragalin suppressed the phosphorylation of p38, JNK, and the activation of c-Jun/AP-1 in TNF-α-induced MH7A cells. In conclusion, it has proven that astragalin could attenuate synovial inflammation and joint destruction in RA at least partially by restraining the phosphorylation of MAPKs and the activating of c-Jun/AP-1. Therefore, astragalin can be a potential therapeutic agent for RA. [ABSTRACT FROM AUTHOR]

Abstract Rheumatoid arthritis (RA) is featured by erosive cartilage and bone destruction. The enhancing aggressive property of fibroblast-like synoviocytes (FLSs) plays a critical role in this process. Small ubiquitin-like modifier (SUMO) proteins, including SUMO-1, SUMO-2, SUMO-3 and SUMO-4, participate in regulating many cellular events such as survival, migration and signal transduction in some cell lines. However, their roles in the pathogenesis of RA are not well established. Therefore, we evaluated the role of SUMO proteins in RA FLSs migration and invasion. We found that expression of both SUMO-1 and SUMO-2 was elevated in FLSs and synovial tissues (STs) from patients with RA. SUMO-1 suppression by small interference RNA (siRNA) reduced migration and invasion as well as MMP-1 and MMP-3 expression in RA FLSs. We also demonstrated that SUMO-1 regulated lamellipodium formation during cell migration. To explore further into molecular mechanisms, we evaluated the effect of SUMO-1 knockdown on the activation of Rac1/PAK1, a critical signaling pathway that controls cell motility. Our results indicated that SUMO-1-mediated SUMOylation controlled Rac1 activation and modulated downstream PAK1 activity. Inhibition of Rac1 or PAK1 also decreased migration and invasion of RA FLSs. Our findings suggest that SUMO-1 suppression could be protective against joint destruction in RA by inhibiting aggressive behavior of RA FLSs. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is an autoimmune disease characterized by enigmatic pathogenesis. Polyunsaturated fatty acids (PUFAs) are implicated in RA's development and progression, yet their exact mechanisms of influence are not fully understood. Soluble epoxide hydrolase (sEH) is an enzyme that metabolizes anti-inflammatory epoxy fatty acids (EpFAs), derivatives of PUFAs. In this study, we report elevated sEH expression in the joints of CIA (collagen-induced arthritis) rats, concomitant with diminished levels of two significant EpFAs. Additionally, increased sEH expression was detected in both the synovium of CIA rats and in the synovium and fibroblast-like synoviocytes (FLS) of RA patients. The sEH inhibitor TPPU attenuated the migration and invasion capabilities of FLS derived from RA patients and to reduce the secretion of inflammatory factors by these cells. Our findings indicate a pivotal role for sEH in RA pathogenesis and suggest that sEH inhibitors offer a promising new therapeutic strategy for managing RA. [ABSTRACT FROM AUTHOR]

Src-associated substrate during mitosis of 68 KDa (Sam68), also known as KH domain containing, RNA binding, signal transduction associated 1 (KHDRBS1), is the prototypic member of the signal transduction activator of RNA (STAR) family of RNA-binding proteins. Previous studies have indicated that Sam68 regulates nuclear transcription factor kappa B (NF-κB) to mediate inflammation. In this study, we analyzed the effect and possible mechanisms of Sam68 in rheumatoid arthritis (RA). By western blot analysis and immunohistochemistry, we found that the expression of Sam68 in synovial tissue of RA patients was increased compared with the control group. Immunoflourescent staining demonstrated that Sam68 co-localized with fibroblast-like synoviocytes (FLS) of RA patients. Additionally, the expression of Sam68 in FLS was increased by tumor necrosis factor (TNF)-α stimulation, in a time-dependent manner. Upon TNF-α treatment, Sam68 translocated from the cytoplasm to the nucleus where it interacted with the p65 subunit of NF-κB, as examined by immunoprecipitation and immunofluorescent staining assay. Furthermore, inhibiting the expression of Sam68 by siRNA significantly suppressed the TNF-α-induced expression of interleukin (IL)-6, and matrix metalloproteinase (MMP)-1, reduced the proliferation, migration, and invasion, and markedly decreased the phosphorylation of P65 and IκBα in FLS. Collectively, our findings suggested that Sam68 contributed to the production of inflammatory cytokines, proliferation, migration, and invasion of RA FLS through the NF-κB P65 signal transduction pathway and underscored the importance of Sam68 in the inflammation process of RA. [ABSTRACT FROM AUTHOR]

Summary: Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by joint tissue inflammation. Cyanidin‐3‐glucoside (C3G) is a major component in the flavonoid family and has shown anti‐inflammatory, anti‐oxidant and anti‐tumour activity. In this study, we investigated the effects of C3G on lipopolysaccharides (LPS)‐induced inflammation on human rheumatoid fibroblast‐like synoviocytes (FLS) and on collagen‐induced arthritis (CIA) mice model. We treated FLS with C3G followed by LPS induction, the expressions of tumour necrosis factor alpha (TNF‐α), interleukin 1 beta (IL‐1β) and IL‐6 and the activation of nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB) and mitogen‐activated protein kinase (MAPK) signalling pathway were analyzed. CIA was induced in mice and the arthritic mice were treated with C3G for 3 weeks. The disease severity was compared between control and C3G treated mice. The serum levels of TNF‐α, IL‐1β and IL‐6 were analyzed by ELISA. C3G inhibited LPS‐induced TNF‐α, IL‐1β and IL‐6 expression in FLS. Moreover, C3G inhibited LPS‐induced p65 production and IκBa, p38, ERK and JNK phosphorylation. Administration of C3G significantly attenuated disease in mice with CIA and decreased the serum level of TNF‐α, IL‐1β and IL‐6. C3G inhibited LPS‐induced inflammation in human FLS by inhibiting activation of NF‐κB and MAPK signalling pathway. C3G exhibited therapeutic effects in mice with CIA. [ABSTRACT FROM AUTHOR]

The discovery of new therapeutic drugs with the ability of preventing inflammation and joint destruction with less adverse effects is urgently needed for rheumatoid arthritis (RA). Carnosic acid (CA), a major phenolic compound isolated from the leaves of Rosemary (Rosmarinus officinalis L.), has been reported to have antioxidative and antimicrobial properties. However, its effects on RA have not been elucidated. Here, we investigated the effects of CA on osteoclasts and fibroblast‐like synoviocytes in vitro and on collagen‐induced arthritis (CIA) in Wistar rats in vivo. Our in vitro and in vivo studies showed that CA suppressed the expression of pro‐inflammatory cytokines including TNFɑ, IL‐1β, IL‐6, IL‐8, IL‐17 and MMP‐3, and downregulated the production of RANKL. More importantly, we observed that CA inhibited osteoclastogenesis and bone resorption in vitro and exerted therapeutic protection against joint destruction in vivo. Further biochemical analysis demonstrated that CA suppressed RANKL‐induced activations of NF‐κB and MAPKs (JNK and p38) leading to the downregulation of NFATc1. Taken together, our findings provide the convincing evidence that rosemary derived CA is a promising natural compound for the treatment of RA. [ABSTRACT FROM AUTHOR]

Summary: This study examined the expression of the inhibitory receptor, leucocyte‐associated immunoglobulin (Ig)‐like receptor‐1 (LAIR‐1) in fibroblast‐like synoviocytes (FLS) in rheumatoid arthritis (RA) patients to investigate its potential role in the modulation of inflammatory cytokines, matrix metalloproteinases (MMPs) and invasiveness of synoviocytes. LAIR‐1 expression in synovial tissues from RA patients, osteoarthritis patients and healthy donors was analysed by immunohistochemistry. The membrane‐bound form (mLAIR‐1) was detected by flow cytometry. Factors involved in inflammation and MMP activity in FLS were analysed by quantitative polymerase chain reaction (qPCR). LAIR‐1 expression was higher in the synovia of the RA patients than those of the osteoarthritis patients. Co‐immunostaining of vimentin/LAIR‐1 demonstrated that LAIR‐1 was localized mainly in FLS in the RA patients. Surprisingly, primary FLS isolated from the RA patients had low levels of mLAIR‐1 expression, with cytoplasmic distribution. The extracellular domain of LAIR‐1 was shed from the cell surface in response to tumour necrosis factor (TNF)‐α, and this process could be blocked by serine protease inhibitors. Additional experiments indicated that LAIR‐1 over‐expression reduced FLS invasion considerably, which reduced simultaneously the mRNA levels of interleukin (IL)‐6, IL‐8 and MMP‐13 in the presence of TNF‐α. Our study demonstrated that LAIR‐1 is an anti‐inflammatory molecule, and was up‐regulated in FLS in the RA patients; however, cell‐surface LAIR‐1 could be shed from cells in the inflammatory microenvironment in RA. This may weaken the interaction of LAIR‐1 with its ligand, thus reducing the anti‐inflammatory effects of LAIR‐1. These findings suggested that LAIR‐1 may be an important factor involved in the mediation of the progressive joint destruction in RA. [ABSTRACT FROM AUTHOR]

Despite improved therapy, rheumatoid arthritis (RA) remains an unmet medical need. Previous efforts to validate therapeutic targets in the mitogen-activated protein kinase (MAPK) family have had minimal success. Therefore, we evaluated the potential for targeting an upstream MAPK, namely apoptosis signal-regulating kinase 1 (ASK1), as an alternative approach. ASK1 protein and gene expression were observed in RA and osteoarthritis (OA) synovium as determined by immunohistochemistry (IHC) and qPCR, respectively, particularly in the synovial intimal lining. For RA, but not OA synovium, ASK1 correlated with IL-1β and TNF gene expression. ASK1 was also expressed by cultured fibroblast-like synoviocytes (FLS), with significantly higher levels in RA compared with OA cells. IL-1β and TNF stimulation significantly increased ASK1 expression in a time-and concentration-dependent manner in cultured FLS. ASK1 promoter activity was significantly increased by IL-1β and TNF and was dependent on an upstream RelA binding motif. A selective small molecule ASK1 inhibitor reduced RA FLS invasion, migration and proliferation in vitro and decreased arthritis severity in the rat collagen-induced arthritis (CIA) model. In summary, our findings demonstrate that ASK1 modulates signaling pathways relevant to RA in vitro and in vivo . It is induced by inflammatory cytokines through the activation of NF-κB, which could provide some site- and event specificity. Thus, inhibitors of the upstream MAPK ASK1 could be a novel approach to treating inflammatory arthritis. [ABSTRACT FROM AUTHOR]

Pyroptosis is triggered by inflammasomes after its activation by various inflammatory stimulations, including lipopolysaccharide (LPS) and improper pH. This may result in programmed death of the affected cell. It is well known that NLRP1 and NLRP3 inflammasomes mediate the production of various cytokines in inflammatory disorders; however, it is still unknown whether NLRP1 and NLRP3 inflammasomes can influence the LPS‑induced pyroptosis in the progression of knee osteoarthritis (KOA). In the present study, the correlation between the NLRP inflammasomes and fibroblast‑like synoviocytes (FLSs) pyroptosis was investigated in vivo and in vitro. Human synovial samples were collected from KOA patients and the expression of NLRP1 and NLRP3 inflammasomes was analyzed. Human FLS were isolated in vitro and stimulated with LPS. To determine whether NLRP1 and NLRP3 inflammasomes are involved in FLS pyroptosis, NLRP1 and NLRP3 small interfering RNAs (siRNAs) were used. The results showed that the expression of NLRPs and inflammasome‑related proteins were upregulated and FLS stimulated with LPS+ATP resulted in cell pyroptosis. However, LPS+ATP‑induced pyroptosis was attenuated by NLRP1 and NLRP3 siRNAs. The results of the present study indicate that LPS‑induced FLS pyroptosis may be mediated by either NLRP1 or NLRP3 inflammsomes. Overall, based on the data obtained from patients and in vitro cells, the present finsings showed that NLRP1 and NLRP3 inflammasomes are highly involved in the FLS inflammation and pyroptosis. Furthermore, inhibition of NLRP1 and NLRP3 led to a remarkable reduction of pyroptosis‑related cytokines. Thus, NLRP1 and NLRP3 inflammasomes may be important in the pathogenesis of OA and may represent a novel therapeutic target. [ABSTRACT FROM AUTHOR]

Transient receptor potential ankyrin 1 (TRPA1) is a membrane-associated cation channel, widely expressed in neuronal and non-neuronal cells. Recently, emerging evidences suggested the crucial role of TRPA1 in the disease progression of osteoarthritis (OA). Therefore, we aimed to investigate whether TRPA1 mediate lipopolysaccharide (LPS)-induced inflammatory responses in primary human OA fibroblast-like synoviocytes (OA-FLS). The expression of TRPA1 in LPS-treated OA-FLS was assessed by polymerase chain reaction (PCR) and western blot (WB), and the functionality of TRPA1 channel by Ca2+ influx measurements. Meanwhile, production of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6, matrix metalloproteinase (MMP)-1, and MMP-3 in LPS-treated cells was measured by immunoassay. Histological observation after inhibition of TRPA1 was also performed in rats with LPS-induced inflammatory arthritis. After being induced by LPS, the gene and protein expression of TRPA1 was increased in the time-dependent or dose-dependent manner. Meanwhile, Ca2+ influx mediated by TRPA1 in human OA-FLS was also enhanced. In addition, pharmacological inhibition and gene silencing of TRPA1 downregulated the production of IL-1β, TNF-α, IL-6, MMP-1, and MMP-3 in LPS-treated FLS. Finally, synovial inflammation and cartilage degeneration were also reduced by the TRPA1 antagonist. We found the LPS caused the increased functional expression of TRPA1, the activation of which involved in LPS-reduced inflammatory responses in primary human OA-FLS, and the inhibition of TRPA1 produces protective effect in LPS-induced arthritis. [ABSTRACT FROM AUTHOR]