Project description:Erosive destruction of joint structures is a critical event in the progression of rheumatoid arthritis (RA), in which fibroblast-like synoviocytes (FLS) are the primary effectors. We previously reported that the ability of RA FLS to degrade extracellular matrix (ECM) components depends on the formation of actin-rich membrane protrusions, called invadosomes, through processes that remain elusive. 14-3-3η belongs to a family of scaffolding proteins involved in a wide range of cellular functions, and its expression is closely related to joint damage and disease activity in RA patients. In this study, we sought to assess the role of 14-3-3η in joint damage by examining its contribution to the invadosome formation phenotype of FLS. Using human primary FLS, we show that 14-3-3η expression is closely associated with their ability to form invadosomes. Furthermore, knockdown of 14-3-3η using shRNAs decreases the level of invadosome formation in RA FLS, whereas addition of the recombinant protein to FLS from healthy individuals promotes their formation. Mechanistic studies suggest that 14-3-3η regulates invadosome formation by increasing Snail expression, a mechanism that involves nuclear exclusion of the transcription repressor FOXO3. Our results implicate the 14-3-3η-FOXO3-Snail axis in promoting the aggressive ECM-degrading phenotype of RA FLS, and suggest a role for this scaffolding protein in cartilage degradation.
Project description:LncRNA NEAT1 functions as an oncogene in multiple human cancers. However, its expression and role in fibroblast-like synoviocytes (FLSs) from patients with rheumatoid arthritis (RA) remain unclear. Thus, we investigated the expression of NEAT1 in synovial tissues and FLSs in RA, to determine its role in the development of RA. Quantitative real-time polymerase chain reaction was used to measure the expression of NEAT1. FLS proliferation was evaluated using cell proliferation assays. Flow cytometry was used to analyze cell cycle progression and apoptosis in FLSs. Binding between NEAT1 and miR-410-3p was demonstrated by dual-luciferase assays. We found that NEAT1 was upregulated in synovial tissues and FLSs in RA. Upregulation of NEAT1 promoted cell proliferation, induced S-to G2/M phase transition, and suppressed apoptosis in RA FLSs. NEAT1 directly bound to and negatively modulated miR-410-3p expression, while positively regulating YinYang 1(YY1; a miR-410-3p target). Inhibiting miR-410-3p and upregulating YY1 partially restored the inhibitory role in cell viability induced by the depletion of NEAT1 in RA FLSs. Besides pro-proliferative and anti-apoptotic roles, upregulation of NEAT1 promoted migration, invasion, and inflammatory cytokines secretion in RA FLSs. Taken together, our results suggest that the NEAT1 may serve as a novel diagnostic and therapeutic target for patients with RA.
Project description:Dysregulation of circular RNAs (circRNAs) is involved in various human diseases. Fibroblast-like synoviocytes (FLSs), which form the lining of the joint, are epigenetically imprinted with an aggressive phenotype and contribute to joint destruction in rheumatoid arthritis (RA). In the present study, we identified a novel circRNA, Circ_0088194, which was upregulated in RA fibroblast-like synoviocytes (RA-FLSs) and correlated with the disease activity score in 28 joints. Overexpression of Circ_0088194 promoted RA-FLS migration and invasion, while inhibition of Circ_0088194 had the opposite effect. Mechanistically, Circ_0088194 acted as a miR-766-3p sponge to relieve the repressive effect of miR-766-3p on its target, MMP2 (encoding matrix metalloproteinase 2), thereby promoting migration and invasion. The expression level of Circ_0088194 was inversely correlated with that of miR-766-3p in RA-FLSs. Importantly, overexpression of miR-766-3p partially blocked the migration and invasion induced by Circ_0088194 overexpression. Collectively, this study identified a novel circRNA Circ_0088194 that promotes RA-FLS invasion and migration via the miR-766-3p/MMP2 axis. Circ_0088194 might represent a novel therapeutic target to prevent and treat RA.
Project description:Fibroblast-like synoviocytes (FLSs) are key effector cells in the pathogenesis of rheumatoid arthritis (RA) and display a unique aggressive tumor-like phenotype with remarkable hyperplasia, increased cell migration and invasion. How FLSs undergo these changes in RA remains unknown. We previously reported a novel function of transcription factor SOX5 in RA-FLSs that promote cell migration and invasion. In this study, we found that miR-15a/16 directly targets the SOX5 3'UTR and suppresses SOX5 expression. Moreover, miR-15a/16 is significantly down-regulated in RA-FLSs, which negatively correlates with SOX5 expression. Transfection with miR-15a/16 mimics in RA-FLSs inhibits cell migration, invasion, IL-1β and TNFα expression. Overexpression SOX5 in RA-FLSs decreases miR-15a/16 expression and rescues miR-15a/16-mediated inhibitory effect. Furthermore, RA patients with the lower baseline serum miR-15a/16 level present poor response of 3 months disease-modifying antirheumatic drugs (DMARDs) therapy. Collectively, this study reveals that miR-15a/16/SOX5 axis functions as a key driver of RA-FLSs invasion, migration and inflammatory response in a mutual negative feedback loop and correlates with DMARDs treatment response in RA.
Project description:IntroductionFibroblast-like synoviocytes (FLS) play an important role in the pathogenesis of rheumatoid arthritis (RA). This study aimed to investigate the role of glucose 6-phosphate isomerase (GPI) in the proliferation of RA-FLS.MethodsThe distribution of GPI in synovial tissues from RA and osteoarthritis (OA) patients was examined by immunohistochemical analysis. FLS were isolated and cultured, cellular GPI level was detected by real-time polymerase chain reaction (PCR) and Western blot analysis, and secreted GPI was detected by Western blot and enzyme-linked immunosorbent assay (ELISA). Doxorubicin (Adriamycin, ADR) was used to induce apoptosis. Cell proliferation was determined by MTS assay. Flow cytometry was used to detect cell cycle and apoptosis. Secreted pro-inflammatory cytokines were measured by ELISA.ResultsGPI was abundant in RA-FLS and was an autocrine factor of FLS. The proliferation of both RA and OA FLS was increased after GPI overexpression, but was decreased after GPI knockdown. Meanwhile, exogenous GPI stimulated, while GPI antibody inhibited, FLS proliferation. GPI positively regulated its receptor glycoprotein 78 and promoted G1/S phase transition via extracellular regulated protein kinases activation and Cyclin D1 upregulation. GPI inhibited ADR-induced apoptosis accompanied by decreased Fas and increased Survivin in RA FLS. Furthermore, GPI increased the secretion of tumor necrosis factor-α and interleukin-1β by FLS.ConclusionsGPI plays a pathophysiologic role in RA by stimulating the proliferation, inhibiting the apoptosis, and increasing pro-inflammatory cytokine secretion of FLS.
Project description:Background/objectivesFerroptosis is a type of regulated cell death that involves iron-dependent accumulation of lipid peroxides. Because fibroblast-like synoviocytes (FLSs) in patients with rheumatoid arthritis (RA) have a hyperplastic and inflammatory phenotype, selective induction of FLS cell death is considered a potential treatment strategy for RA. Liver kinase B1 (LKB1)-activated AMP-activated protein kinase (AMPK) signaling regulates the inflammation and migration of RA FLSs, contributing to RA pathogenesis. Here, we aimed to determine the effect of LKB1 knockdown on the ferroptosis pathway in RA FLSs.MethodsSynovial tissues from patients with RA (n = 5) were transfected with siRNA targeting LKB1. Cell viability was evaluated via 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay and Annexin V/7-aminoactinomycin D (7-AAD) staining. Ferroptosis was assessed using boron-dipyrromethene (BODIPY) lipid probes, a ferrous ion detection kit, and a glutathione detection assay. Expression of hallmarks of various cell death pathways was analyzed using western blot.ResultsRA FLS cell death significantly increased after transfection with LKB1 siRNA (p < 0.01). Lipid peroxidation was upregulated and the expression levels of glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11) were suppressed in LKB1-deficient cells. Additionally, LKB1 inhibition made RA FLSs highly sensitive to ferroptosis. When RA FLSs were incubated with an activator of AMPK, LKB1 knockdown-mediated inhibition was restored through upregulated expression of GPX4 and SLC7A11.Conclusionsthese findings suggest that LKB1-AMPK signaling is essential to protect RA FLSs against ferroptosis.
Project description:BackgroundLong non-coding RNAs (lncRNAs) have drawn increasing attention because they play a pivotal role in various types of autoimmune diseases, including rheumatoid arthritis (RA). Fibroblast-like synoviocytes (FLSs), a prominent component of hyperplastic synovial pannus tissue, are the primary effector cells in RA synovial hyperplasia and invasion which can lead to joint destruction. In this study, we investigated whether lncRNAs could act as competing endogenous RNAs to regulate the pathological behaviors of RA-FLSs.MethodsLncRNA microarray was conducted to establish lncRNA expression profiles in FLSs isolated from RA patients and healthy controls (HCs). Differentially expressed lncRNAs were verified by quantitative real-time PCR (qRT-PCR) on RA-FLSs and synovial fluid. The functional role of lncRNA PICSAR downregulation was evaluated in RA-FLSs. We conducted molecular biological analysis to predict miRNAs which have a potential binding site for PICSAR and further refined the results by qRT-PCR. Luciferase reporter assay was adopted to validate the interaction of lncRNA PICSAR and miR-4701-5p. Western Blot and qPCR were used to identify the target gene and protein. The functional role of miR-4701-5p upregulation was examined in RA-FLSs.FindingsWe identified a long intergenic non-protein-coding RNA162 (LINC00162), also known as lncRNA PICSAR (p38 inhibited cutaneous squamous cell carcinoma associated lincRNA), has significantly higher expression in RA-FLSs and RA synovial fluid. The cell proliferation, migration, invasion and proinflammatory cytokines production of RA-FLSs showed significant alterations after the lncRNA PICSAR suppression. Mechanistically, lncRNA PICSAR functioned through sponging miR-4701-5p in RA-FLSs.InterpretationOur results reveal PICSAR may exert an essential role in promoting synovial invasion and joint destruction by sponging miR-4701-5p in RA and that lncRNA PICSAR may act as a biomarker of RA.
Project description:We aimed to investigate the possible effects of thioredoxin 1 (Trx1) on the proliferation and apoptosis of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLSs) and elucidate the possible mechanisms involved. We investigated the distribution and expression of Trx1 in synovial tissues from RA and osteoarthritis (OA) patients by immunohistochemistry and real-time polymerase chain reaction (RT-PCR) analyses. RA-FLSs were isolated and cultured under normoxic (21% oxygen) or hypoxic (3% oxygen) concentrations. Transfection of Trx1-siRNAs and a Trx1 overexpression construct was conducted to manipulate the expression of Trx1. Protein expression was detected by Western blot. Doxorubicin (Adriamycin, ADR) was used to induce apoptosis. LY-294002 was used for the inhibition of PI3K-Akt. Cell proliferation and apoptosis were determined by MTS (3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium, inner salt) assay and flow cytometry, respectively. The mRNA and protein expression of Trx1 in RA tissues was higher than that in OA tissues. The expression levels of Trx1 and cell proliferation in RA-FLSs were increased under hypoxia in comparison to those under normoxia. In hypoxia, downregulation of Trx1 significantly suppressed FLS proliferation, and the expression of PI3Kp85, phospho-Akt, and Bcl-2, while notably increased FLS apoptosis and the expression of active Caspase3 and Bax. In normoxia, Trx1 overexpression promoted the FLS proliferation and the expression of PI3Kp85, phospho-Akt, and Bcl-2, but inhibited FLS apoptosis and the expression of active Caspase3 and Bax in FLSs. Such effects were partially repressed by LY-294002 treatment. Trx1 may play an important role in regulating the proliferation and apoptosis of RA-FLSs by modulating PI3K-Akt activation.
Project description:Epigenetics contributes to the pathogenesis of immune-mediated diseases like rheumatoid arthritis (RA). Here we show the first comprehensive epigenomic characterization of RA fibroblast-like synoviocytes (FLS), including histone modifications (H3K27ac, H3K4me1, H3K4me3, H3K36me3, H3K27me3, and H3K9me3), open chromatin, RNA expression and whole-genome DNA methylation. To address complex multidimensional relationship and reveal epigenetic regulation of RA, we perform integrative analyses using a novel unbiased method to identify genomic regions with similar profiles. Epigenomically similar regions exist in RA cells and are associated with active enhancers and promoters and specific transcription factor binding motifs. Differentially marked genes are enriched for immunological and unexpected pathways, with "Huntington's Disease Signaling" identified as particularly prominent. We validate the relevance of this pathway to RA by showing that Huntingtin-interacting protein-1 regulates FLS invasion into matrix. This work establishes a high-resolution epigenomic landscape of RA and demonstrates the potential for integrative analyses to identify unanticipated therapeutic targets.
Project description:Hypoxia is associated with the pathogenesis of rheumatoid arthritis (RA). RA fibroblast-like synoviocytes (FLSs) are able to differentiate into osteoblasts and adipocytes. In this study, we aimed to investigate the role of hypoxia in the osteogenesis or adipogenesis of RA-FLSs. Bioinformatics analysis was performed to profile gene expression in the datasets of GSE21959, GSE32006, and GSE55875, and flow cytometry was performed for FLS characterization, while Alizarin Redand Oil Red O staining for osteogenic or adipogenic differentiation of FLSs, respectively. RNA interference leptin knockdown was used to determine the role of leptin in the osteogenesis and adipogenesis of RA-FLSs, and the expression of osteogenic and adipogenic markers was quantified by RT-qPCR and Western blotting. FLSs exhibited a mesenchymal stem cell (MSC)-like phenotype and we observed a limited self-renewal capacity in RA-FLSs compared to that in MSCs, but it was still greater than osteoarthritis (OA)-FLSs. Hypoxia did not change the RA-FLS MSC-like phenotype but inhibited the osteogenic differentiation and promoted the adipogenic differentiation of RA-FLSs. From the bioinformatics analysis ofGSE21959, GSE32006, and GSE55875 datasets, we found leptin, the only perturbed hypoxia-mediated upregulated gene across the three profiled datasets. Leptin knockdown in RA-FLSs reversed the hypoxia-mediated reduction of osteogenesis and hypoxia-mediated enhancement of adipogenesis by elevated expression of osteogenic markers and reduced expression of adipogenic markers, respectively. Therefore, hypoxia-leptin regulation of the osteogenic and adipogenic differentiation of RA-FLSs advances our understanding of RA pathogenesis, meanwhile also provides opportunities for future therapeutic intervention of RA.