Destructive Rheumatoid Arthritis Research Articles

Increased expression of omentin-1 is associated with synovitis and bone destruction in rheumatoid arthritis.

The aberrant expression of omentin-1 had been reported in type 2 diabetes and cardiovascular disease. Here, we investigated the expression and role of omentin-1 in rheumatoid arthritis (RA). The expression of omentin-1 in RA and in the normal population was detected by ELISA and immunohistochemistry, and collagen-induced arthritis (CIA) mice were used to detect the role of omentin-1 in RA. We found that the expression of omentin-1 was elevated in serum of RA patients compared with healthy controls (p=0.004), and in the RA disease activity group compared with the disease remission group (p<0.001). In addition, the level of omentin-1 in RA patients was positively correlated with CRP (r=0.427, p=0.002), ESR (r=0.454, p<0.001) and DAS28 (r=0.496, p<0.001; r=0.661, p<0.001, respectively). Multivariable analysis showed that omentin-1 alone was associated with disease activity state (OR=1.018, p=0.004). Immunohistochemical results showed that omentin-1 was increased in the synovium of RA and CIA mice. Omentin-1 injection resulted in an earlier onset of arthritis, an aggravated arthritic progression, more severe synovial hyperplasia and bone erosion in CIA mice. Moreover, omentin-1 treatment markedly enhanced IL-6, TNF-α, MMP-3, MMP-13 and RANKL in the joint tissue of CIA mice. Our results suggested that omentin-1 was up-regulated in RA and can exacerbate synovitis and joint destruction which may provide new insight into the pathogenesis of RA.

GRK2 mediated degradation of SAV1 initiates hyperplasia of fibroblast-like synoviocytes in rheumatoid arthritis

Hyperplasia and migration of fibroblast-like synoviocytes (FLSs) are the key drivers in the pathogenesis of rheumatoid arthritis (RA) and joint destruction. Abundant Yes-associated protein (YAP), which is a powerful transcription co-activator for proliferative genes, was observed in the nucleus of inflammatory FLSs with unknown upstream mechanisms. Using Gene Expression Omnibus database analysis, it was found that Salvador homolog-1 (SAV1), the pivotal negative regulator of the Hippo-YAP pathway, was slightly downregulated in RA synovium. However, SAV1 protein expression is extremely reduced. Subsequently, it was revealed that SAV1 is phosphorylated, ubiquitinated, and degraded by interacting with an important serine-threonine kinase, G protein-coupled receptor (GPCR) kinase 2 (GRK2), which was predominately upregulated by GPCR activation induced by ligands such as prostaglandin E2 (PGE2) in RA. This process further contributes to the decreased phosphorylation, nuclear translocation, and transcriptional potency of YAP, and leads to aberrant FLSs proliferation. Genetic depletion of GRK2 or inhibition of GRK2 by paroxetine rescued SAV1 expression and restored YAP phosphorylation and finally inhibited RA FLSs proliferation and migration. Similarly, paroxetine treatment effectively reduced the abnormal proliferation of FLSs in a rat model of collagen-induced arthritis which was accompanied by a significant improvement in clinical manifestations. Collectively, these results elucidate the significance of GRK2 regulation of Hippo-YAP signaling in FLSs proliferation and migration and the potential application of GRK2 inhibition in the treatment of FLSs-driven joint destruction in RA.

BMP4 up-regulated by 630 nm LED irradiation is associated with the amelioration of rheumatoid arthritis

Rheumatoid arthritis (RA) is caused by inflammatory response of joints with cartilage and damage of synovium and bone erosion. In our previous studies, it has showed that irradiation of 630 nm LED reduce inflammation of synovial fibroblasts and cartilage and bone destruction in RA. However, the key genes and mechanism in ameliorating RA by irradiation of 630 nm LED remains unknown. In this study, human fibroblast-like synoviocytes (FLS) cell line MH7A and primary human RA-FLSs were treated with TNF-α and 630 nm LED irradiation with the different energy density. The mRNA sequencing was performed to screen the differentially expressed genes (DEGs). In all datasets, 10 DEGs were identified through screening. The protein interaction network analysis showed that 8 out of the 10 DEGs interacted with each other including IL-6, CXCL2, CXCL3, MAF, PGF, IL-1RL1, RRAD and BMP4. This study focused on BMP4, which is identified as important morphogens in regulating the development and homeostasis. CCK-8 assay results showed that 630 nm LED irradiation did not affect the cell viability. The qPCR and ELISA results showed that TNF-α stimulation inhibited BMP4 mRNA and protein level and irradiation of 630 nm LED increased the BMP4 mRNA and protein level in MH7A cells. In CIA and transgenic hTNF-α mice models, H&E staining showed that irradiation of 630 nm LED decreased the histological scores assessed from inflammation and bone erosion, while BMP4 expression level was up-regulated after 630 nm LED irradiation. Pearson correlation analysis shown that BMP4 protein expression was negatively correlated with the histological score of CIA mice and transgenic hTNF-α mice. These results indicated that BMP4 increased by irradiation of 630 nm LED was associated with the amelioration of RA, which suggested that BMP4 may be a potential targeting gene for photobiomodulation.

Mechanisms of action underlying Shentong Zhuyu decoction based treatment of rheumatoid arthritis using systems biology and computer-aided drug design.

Rheumatoid arthritis is an autoimmune disease characterized by chronic polyarticular pain, for which no cure currently exists. In Chinese medicine, rheumatoid arthritis (RA) is believed to be caused by phlegm and blood stagnation. Shentong Zhuyu decoction can be used to treat RA, as it promotes blood circulation, resolves blood stasis, and relieves pain. In our study, we used network pharmacology and computer-aided drug design to evaluate the components, active compounds, and targets of Shentong Zhuyu decoction (STZY). Our results suggest that STZY contains active compounds such as quercetin, luteolin, and formononetin that regulate immune network targets. RA associated genes are enriched in pathways including those associated with nuclear factor kappa B, phosphatidylinositol-3-kinase/AKT, and hypoxia inducible factor 1 signaling. The main active compounds in STZY (quercetin and luteolin) were derived from Achyranthis Bidentatae Radix, Carthami Flos, licorice, Cyperi Rhizoma, and Myrrha and targeted the pro-inflammatory cytokines interleukin 2, interleukin 1 alpha, interleukin 1 beta, and interleukin 6. In addition, the compounds quercetin, luteolin, and formononetin in these herbs can target the anti-inflammatory cytokines interleukin 4 and interleukin 10. Our results suggest that STZY can balance the immune network, promote an anti-inflammatory environment, and reduce the clinical symptoms of RA. Based on the close relationship between inflammatory response and osteoclast formation, we hypothesized that STZY may inhibit inflammation and alleviate bone destruction in RA. Our findings indicate that STZY can treat RA through multiple components, targets, and pathways. This study may provide a reference for the clinical application of STZY in RA treatment.

JAK inhibitors improve ATP production and mitochondrial function in rheumatoid arthritis: a pilot study

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease associated by inflammation of the synovial tissue and autoantibody production. Oxidative stress and free radicals are known to be indirectly implicated in joint damage and cartilage destruction in RA. Several studies describe the presence of mitochondrial dysfunction in RA, but few of them follow the dynamics in energy parameters after therapy. The aim of our investigation is to evaluate the direct effect of JAK inhibitors on cellular metabolism (and under induced oxidative stress) in RA patients. Ten newly diagnosed RA patients were included in the study. Peripheral blood mononuclear cells (PBMCs) and plasma were isolated before and 6 months after therapy with JAK inhibitors. A real-time metabolic analysis was performed to assess mitochondrial function and cell metabolism in PBMCs. Sonographic examination, DAS28 and conventional clinical laboratory parameters were determined also prior and post therapy. A significant decrease in proton leak after therapy with JAK inhibitors was found. The increased production of ATP indicates improvement of cellular bioenergetics status. These findings could be related to the catalytic action of JAK inhibitors on oxidative phosphorylation which corresponds to the amelioration of clinical and ultra-sonographic parameters after treatment. Our study is the first to establish the dynamics of mitochondrial parameters in PBMCs from RA patients before and after in vivo therapy with JAK inhibitors.

PTEN-mediated FOXO signaling affects autophagy, migration and invasion of rheumatoid arthritis fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a chronic, progressive, systemic autoimmune disease. Among them, abnormal proliferation, migration and vascularization of fibroblast-like synoviocytes (FLS) are the main pathological basis of persistent synovitis and bone destruction in RA. In the current study, we attempted to find effective molecular mechanisms for the treatment of RA by investigating RA-FLS. Firstly, the study was conducted to identify the potential target gene PTEN and its related signaling pathway through bioinformatics analysis. Subsequently, the target gene PTEN overexpression was regulated by cell transfection. The expression of FOXO signaling factors and autophagy-related proteins were detected by western blotting assay. Cell proliferation was measured by CCK-8 and EdU assays. Inflammation level was detected by ELISA. Cell migration and invasion were detected using wound healing assay and transwell chamber assay, respectively. Cell apoptosis was detected using flow cytometry. The results showed that overexpression of PTEN activated FOXO1 signaling in RA-FLS, and regulated autophagy, proliferation, invasion, migration, and the levels of pro-inflammatory factors in the disease. In conclusion, PTEN might provide an effective therapeutic strategy for rheumatoid arthritis by mediating the FOXO1 signaling pathway.

Thinner femoral cortical thickness in patients with destructive rheumatoid arthritis of the knee

BackgroundThe examination of femoral cortical bone thickness in patients with rheumatoid arthritis (RA) has been notably limited in prior research. We aimed to compare femoral cortical thickness in patients with rheumatoid arthritis (RA) and healthy controls and to investigate the association between femoral cortical thickness and clinical parameters within the RA group.MethodsForty-four patients (58 limbs) with RA who underwent total knee arthroplasty were enrolled. Preoperative computed tomography images of the lower limbs were analyzed. The femoral cortex was divided into the proximal, central, and distal diaphysis regions and further into the anterior, posterior, medial, and lateral regions. The divisions were measured using Stradwin® software and standardized by femoral length. Femoral cortical thickness was compared between RA and healthy control (n = 25) groups. Correlation analyses between standardized cortical thickness and disease parameters were performed in the RA group.ResultsThe RA group had significantly lower standardized femoral cortical thickness at the anterior and medial distal diaphysis than healthy controls. Standardized proximal lateral and central lateral in the RA group were significantly larger than those in the healthy control groups. Standardized femoral cortical thickness was significantly correlated with bone mineral density (BMD) in 11 areas, except the posterior central diaphysis, and with body mass index in 8 areas, except the central posterior, distal lateral, distal anterior, and distal medial diaphysis.ConclusionsFemoral cortical thinning was noted in patients with RA complicated with destructive knee, particularly at the anterior and medial distal diaphysis. Femoral cortical thickness was significantly correlated with BMD and body mass index (BMI); thus, patients with RA and low BMD and BMI should be cared for to prevent fragility fractures.

Unraveling the Therapeutic Mechanism of Saussurea involucrata against Rheumatoid Arthritis: A Network Pharmacology and Molecular Modeling-Based Investigation.

Rheumatoid arthritis (RA) is a chronic autoimmune disease with a global prevalence of approximately 0.46%, causing significant impairments in patients' quality of life and an economic burden. Saussurea involucrata (SI) has long been used in traditional medicine to treat RA, but its underlying mechanism remains unclear. This study utilized network pharmacology and molecular docking to explore the potential pharmacological effects of bioactive compounds in SI on RA. A total of 27 active compounds were identified, along with 665 corresponding targets. Additionally, 593 disease-related targets were obtained from multiple databases, with 119 common targets shared with SI. The high-ranking targets mainly belong to the MAPK family and NF-κB pathway, including MAPK14, MAPK1, RELA, TNF, and MAPK8, all of which are associated with inflammation and joint destruction in RA. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed significant pathways related to IL-17 signaling, Th17 cell differentiation, and osteoclast differentiation. Molecular docking and dynamic simulations demonstrated strong interactions between several flavonoids and RA-related targets. Xuelianlactone, Involucratin, and Flazin exhibit outstanding binding efficacy with targets such as MAPK1, MAPK8, and TNF. These findings provide valuable insights into the therapeutic potential of SI for RA and offer directions for further drug development.

Surface proteins of Propionibacterium freudenreichii MJ2 inhibit RANKL-induced osteoclast differentiation by lipocalin-2 upregulation and lipocalin-2-mediated NFATc1 inhibition

Osteoclasts degrade bone and osteoclast differentiation has been implicated in bone destruction in rheumatoid arthritis. The dairy bacterium Propionibacterium freudenreichii MJ2 (MJ2) isolated from raw milk inhibits osteoclast differentiation and ameliorates collagen-induced arthritis. This study aimed to investigate the inhibitory effect of the surface proteins of MJ2 on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation and explain the underlying mechanism. The murine macrophage cell line RAW 264.7 was used to study the inhibition of osteoclast differentiation. The surface proteins significantly inhibited RANKL-induced osteoclast differentiation in a protein concentration-dependent manner by inhibiting the expression of genes and proteins related to osteoclast differentiation. RNA microarray analysis showed that the surface proteins significantly upregulated lipocalin-2 (lcn2) expression. In addition, they downregulated c-fos and NFATc1 and inhibited the expression of NFATc1-downstream genes Atp6v0d2, Calcr, and Ctsk. siRNA silencing of lcn2 decreased the extent of surface protein inhibition on osteoclast differentiation, suggesting that lcn2 plays an important role in the inhibition of RANKL-induced osteoclast differentiation. In conclusion, surface proteins of MJ2 show inhibitory effects on RANKL-induced osteoclast differentiation by upregulating lcn2 expression, in turn downregulating NFATc1, leading to the inhibition of NFATc1-downstream osteoclastogenesis-related gene expression.

DKK-1 and Its Influences on Bone Destruction: A Comparative Study in Collagen-Induced Arthritis Mice and Rheumatoid Arthritis Patients.

Dickkopf-1 (DKK-1) has been considered a master regulator of bone remodeling. As precursors of osteoclasts (OCs), myeloid-derived suppressor cells (MDSCs) were previously shown to participate in the process of bone destruction in rheumatoid arthritis (RA). However, the role of DKK-1 and MDSCs in RA is not yet fully understood. We investigated the relevance between the level of DKK-1 and the expression of MDSCs in different tissues and joint destruction in RA patients and collagen-induced arthritis (CIA) mouse models. Furthermore, the CIA mice were administered recombinant DKK-1 protein. The arthritis scores, bone destruction, and the percentage of MDSCs in the peripheral blood and spleen were monitored. In vitro, the differentiation of MDSCs into OCs was intervened with recombinant protein and inhibitor of DKK-1. The number of OCs differentiated and the protein expression of the Wnt/β-catenin signaling pathway were explored. The level of DKK-1 positively correlates with the frequency of MDSCs and bone erosion in RA patients and CIA mice. Strikingly, recombinant DKK-1 intervention significantly exacerbated arthritis scores and bone destruction, increasing the percentage of MDSCs in the peripheral blood and spleen in CIA mice. In vitro experiments showed that recombinant DKK-1 promoted the differentiation of MDSCs into OCs, reducing the expression of β-catenin and TCF4 and increasing the expression of CyclinD1. In contrast, the DKK-1 inhibitor had the opposite effect. Our findings highlight that DKK-1 promoted MDSCs expansion in RA and enhanced the differentiation of MDSCs into OCs via targeting the Wnt/β-catenin pathway, aggravating the bone destruction in RA.

Guizhi Shaoyao Zhimu granules attenuate bone destruction in mice with collagen-induced arthritis by promoting mitophagy of osteoclast precursors to inhibit osteoclastogenesis

BackgroundGuizhi Shaoyao Zhimu decoction, a traditional Chinese medicine formula used empirically for the treatment of rheumatoid arthritis (RA), has been shown to alleviate bone destruction in rats with collagen-induced arthritis (CIA). PurposeThe aim of this study is to characterize the effects of Guizhi Shaoyao Zhimu granules (GSZGs) on bone destruction in RA and the underlying mechanism. Study designA CIA arthritis model using DBA/1 mice. The animals were divided into a normal group; CIA model group; low, medium, and high-dose GSZG groups (3, 6, and 9 g/kg/day); and a methotrexate group (1.14 mg/kg/w). In vitro, a cytokine induced osteoclastogenesis model was established. MethodsAfter 28 days of treatment, the paw volume was measured, bone destruction was examined by micro-CT, and the generation of osteoclasts in bone tissue was evaluated via tartrate-resistant acid phosphatase (TRAP) staining. Furthermore, the inhibitory effect and underlying mechanism of action of GSZG on RANKL-induced osteoclastogenesis were investigated in vitro. ResultsThe in vivo analyses demonstrated that the paw volume and degree of bone erosion of mice in the medium- and high-dose GSZG groups were significantly decreased compared to the CIA model group. In addition, GSZG treatment suppressed the excessive generation of osteoclasts in the bone tissue of CIA mice. In vitro, GSZG inhibited RANKL-induced osteoclastogenesis and osteoclast-mediated bone resorption. Specifically, it only inhibited the generation of osteoclast precursors (OCPs); it had no significant effect on the fusion of OCPs or maturation of osteoclasts. Finally, we showed that the inhibitory effect of GSZG on osteoclastogenesis was related to the promotion of PTEN-induced kinase protein 1 (PINK1)/Parkin pathway-mediated mitophagy of osteoclast precursors, which was verified using a PINK1 knockdown small interfering RNA in OCPs. ConclusionThese findings indicate that GSZG is a candidate for the treatment of bone destruction in RA and provide a more detailed elucidation of the mechanism of GSZG anti-RA bone erosion, i.e., inhibition of the ROS/NF-κB axis through the PINK1/Parkin-mediated mitochondrial autophagic pathway to inhibit osteoclast precursor production, compared to the published literature.

Unraveling the mechanisms behind joint damage

A subtype of myeloid monocyte mediates the transition from autoimmunity to joint destruction in rheumatoid arthritis.

Identification of novel TACE inhibitors using DNN based- virtual screening, molecular dynamics and biological evaluation

Rheumatoid Arthritis (RA) is a well-known autoimmune inflammatory disease, distressing roughly 1% of the adult population throughout the globe. Many studies have suggested that overexpression of TNF-α, a pro-inflammatory cytokine, is responsible for the progression of RA. Furthermore, inhibition of the shedding rate of TNF-α is regulated by the TACE (TNF-α converting enzyme) protein and, hence is considered as an important therapeutic target for the prevention of progressive synovial joint destruction in rheumatoid arthritis. In the present study, we have proposed a deep neural network (DNN)-based workflow for the virtual screening of compounds towards the identification of potential inhibitors against the TACE proteins. Subsequently, a set of compounds were shortlisted, based on the molecular docking and subjected to the biological evaluation to validate the inhibitory activities of the screened compounds, determine the practical applicability of the DNN-based model, and strengthen the hypothesis. Out of seven, three compounds (BTB10246, BTB10247, and BTB10245) showed significant inhibition at 10 µM and 0.1 µM concentration. These three compounds also showed a stable and significant interaction potential against the TACE protein as compared with the re-docked complex system and can serve as a novel scaffold for further design of new molecules with improved inhibitory activities against TACE. Communicated by Ramaswamy H. Sarma

Decipher the pharmacological mechanisms of raw and wine-processed Curculigo orchioides Gaertn. on bone destruction in rheumatoid arthritis rats using metabolomics.

Curculigo orchioides Gaertn. (CO), a traditional Chinese herb recorded in Chinese Pharmacopoeia, can nourish kidney yang, strengthen bones, and dispell cold-dampness. Raw CO (rCO) and wine-processed CO (pCO), the main processed products of CO for clinical application, show differences in nourishing kidney yang and ameliorate osteoporosis. However, the difference in efficacy and mechanism of rCO and pCO on bone destruction in rheumatoid arthritis (RA) remain unclear. To compare the pharmacodynamics of rCO and pCO in the treatment of bone destruction in RA and to reveal the potential mechanism by which rCO and pCO exert effects by metabolomics approach. Ultra-high performance liquid chromatography Q exactive mass spectrometry (UHPLC-Q-Exactive-MS) combined with multivariate data analysis was applied to identify the differential chemical components in rCO and pCO. Collagen-induced arthritis (CIA) rats were orally administrated with different doses of rCO and pCO for 4 weeks. The body weight, paw swelling, arthritis scores, serum inflammatory cytokines concentration, knee tumor necrosis factor (TNF)-α, interleukin (IL)-6 protein levels, and inflammatory cell infiltration were determined to investigate the effects of rCO and pCO on arthritic symptoms and inflammatory responses in CIA rats. The effects of rCO and pCO on bone destruction were assessed using safranin O-fast green and tartrate-resistant acid phosphatase (TRAP) staining, immunohistochemical analysis of osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) proteins, and micro-computed tomography (micro-CT) in rats. In addition, metabolomics was performed to explore the mechanism of rCO and pCO against bone destruction in RA. A total of 41 chemical constituents were identified in both rCO and pCO, 9 of which were screened out as discriminatory compounds. According to the pharmacodynamic assays, pCO exhibited a stronger effect than rCO in attenuating the severity of arthritis, reducing inflammation, and inhibiting bone destruction. The metabolomics results showed that pentose phosphate pathway was the key metabolic pathways regulated by rCO, while pCO regulated multiple metabolic pathways including phenylalanine metabolism pathways, phenylalanine, tyrosine and tryptophan biosynthesis, taurine and hypotaurine metabolism, and glycerophospholipid metabolism pathways. pCO displayed a better effect on alleviating bone destruction in RA was than rCO. This might be associated with that pCO can decrease inflammation in RA through regulating more metabolism pathways.

Recent advances of osteoimmunology research in rheumatoid arthritis: From single-cell omics approach.

Cellular immune responses as well as generalized and periarticular bone loss are the key pathogenic features of rheumatoid arthritis (RA). Under the pathological conditions of RA, dysregulated inflammation and immune processes tightly interact with skeletal system, resulting in pathological bone damage via inhibition of bone formation or induction of bone resorption. Single-cell omics technologies are revolutionary tools in the field of modern biological research.They enable the display of the state and function of cells in various environments from a single-cell resolution, thus making it conducive to identify the dysregulated molecular mechanisms of bone destruction in RA as well as the discovery of potential therapeutic targets and biomarkers. Here, we summarize the latest findings of single-cell omics technologies in osteoimmunology research in RA. These results suggest that single-cell omics have made significant contributions to transcriptomics and dynamics of specific cells involved in bone remodeling, providing a new direction for our understanding of cellular heterogeneity in the study of osteoimmunology in RA.

Clonally Expanded Cytotoxic CD8 +T cells Target Citrullinated Antigens In ACPA+ Rheumatoid Arthritis

Abstract The immune mechanisms that mediate synovitis and joint destruction in rheumatoid arthritis (RA) remain poorly defined. Although increased levels of CD8 +T cells have been described in RA, their role in pathogenesis remains unclear. Here we perform single cell transcriptome and T cell receptor (TCR) sequencing of CD8 +T cells derived from anti-citrullinated protein antibodies (ACPA)+ RA blood. We identify GZMB +CD8 +subpopulations containing large clonal lineage expansions that express cytotoxic and tissue homing transcriptional programs, while a GZMK +CD8 +memory subpopulation comprises of smaller clonal expansions that express effector T cell transcriptional programs. We demonstrate RA citrullinated autoantigens presented by MHC class I activate RA blood-derived GZMB +CD8 +T cells to expand, express cytotoxic mediators, and mediate killing of target cells. We also demonstrate that these clonally expanded GZMB +CD8 +cells are present in RA synovium. These findings suggest that cytotoxic CD8 +T cells targeting citrullinated antigens have a role in contributing to synovitis and joint tissue destruction in ACPA+ RA. The study was supported by following grants: National Institutes of Health grant R01 AR063676, U19 AI110491, R01 AR078268, and Janssen Biotech, Inc.

Components of the sympathetic nervous system as targets to modulate inflammation – rheumatoid arthritis synovial fibroblasts as neuron-like cells?

BackgroundCatecholamines are major neurotransmitters of the sympathetic nervous system (SNS) and they are of pivotal importance in regulating numerous physiological and pathological processes. Rheumatoid arthritis (RA) is influenced by the activity of the SNS and its neurotransmitters norepinephrine (NE) and dopamine (DA) and early sympathectomy alleviates experimental arthritis in mice. In contrast, late sympathectomy aggravates RA, since this procedure eliminates anti-inflammatory, tyrosine hydroxylase (TH) positive cells that appear in the course of RA. While it has been shown that B cells can take up, degrade and synthesize catecholamines it is still unclear whether this also applies to synovial fibroblasts, a mesenchymal cell that is actively engaged in propagating inflammation and cartilage destruction in RA. Therefore, this study aims to present a detailed description of the catecholamine pathway and its influence on human RA synovial fibroblasts (RASFs).ResultsRASFs express all catecholamine-related targets including the synthesizing enzymes TH, DOPA decarboxylase, dopamine beta-hydroxylase, and phenylethanolamine N-methyltransferase. Furthermore, vesicular monoamine transporters 1/2 (VMAT1/2), dopamine transporter (DAT) and norepinephrine transporter (NET) were detected. RASFs are also able to degrade catecholamines as they express monoaminoxidase A and B (MAO-A/MAO-B) and catechol-O-methyltransferase (COMT). TNF upregulated VMAT2, MAO-B and NET levels in RASFs. DA, NE and epinephrine (EPI) were produced by RASFs and extracellular levels were augmented by either MAO, COMT, VMAT or DAT/NET inhibition but also by tumor necrosis factor (TNF) stimulation. While exogenous DA decreased interleukin-6 (IL-6) production and cell viability at the highest concentration (100 μM), NE above 1 μM increased IL-6 levels with a concomitant decrease in cell viability. MAO-A and MAO-B inhibition had differential effects on unstimulated and TNF treated RASFs. The MAO-A inhibitor clorgyline fostered IL-6 production in unstimulated but not TNF stimulated RASFs (10 nM-1 μM) while reducing IL-6 at 100 μM with a dose-dependent decrease in cell viability in both groups. The MAO-B inhibitor lazabemide hydrochloride did only modestly decrease cell viability at 100 μM while enhancing IL-6 production in unstimulated RASFs and decreasing IL-6 in TNF stimulated cells.ConclusionsRASFs possess a complete and functional catecholamine machinery whose function is altered under inflammatory conditions. Results from this study shed further light on the involvement of sympathetic neurotransmitters in RA pathology and might open therapeutic avenues to counteract inflammation with the MAO enzymes being key candidates.

New Insights into the Role of Synovial Fibroblasts Leading to Joint Destruction in Rheumatoid Arthritis

Rheumatoid arthritis (RA), one of the most common autoimmune diseases, is characterized by multiple-joint synovitis with subsequent destruction of bone and cartilage. The excessive autoimmune responses cause an imbalance in bone metabolism, promoting bone resorption and inhibiting bone formation. Preliminary studies have revealed that receptor activator of NF-κB ligand (RANKL)-mediated osteoclast induction is an important component of bone destruction in RA. Synovial fibroblasts are the crucial producers of RANKL in the RA synovium; novel analytical techniques, primarily, single-cell RNA sequencing, have confirmed that synovial fibroblasts include heterogeneous subsets of both pro-inflammatory and tissue-destructive cell types. The heterogeneity of immune cells in the RA synovium and the interaction of synovial fibroblasts with immune cells have recently received considerable attention. The current review focused on the latest findings regarding the crosstalk between synovial fibroblasts and immune cells, and the pivotal role played by synovial fibroblasts in joint destruction in RA.

Mechanism of artesunate on bone destruction in experimental rheumatoid arthritis based on transcriptomics and network pharmacology

The present study investigated the mechanism of artesunate in the treatment of bone destruction in experimental rheumatoid arthritis(RA) based on transcriptomics and network pharmacology. The transcriptome sequencing data of artesunate in the inhibition of osteoclast differentiation were analyzed to obtain differentially expressed genes(DEGs). GraphPad Prism 8 software was used to plot volcano maps and heat maps were plotted through the website of bioinformatics. GeneCards and OMIM were used to collect information on key targets of bone destruction in RA. The DEGs of artesunate in inhibiting osteoclast differentiation and key target genes of bone destruction in RA were intersected by the Venny 2.1.0 platform, and the intersection target genes were analyzed by Gene Ontology(GO)/Kyoto Encyclopedia of Genes and Genomes(KEGG) enrichment. Finally, the receptor activator of nuclear factor-κB(RANKL)-induced osteoclast differentiation model and collagen-induced arthritis(CIA) model were established. Quantitative real time polymerase chain reaction(q-PCR), immunofluorescence, and immunohistochemistry were used to verify the pharmacological effect and molecular mechanism of artesunate in the treatment of bone destruction in RA. In this study, the RANKL-induced osteoclast differentiation model in vitro was established and intervened with artesunate, and transcriptome sequencing data were analyzed to obtain 744 DEGs of artesunate in inhibiting osteoclast differentiation. A total of 1 291 major target genes of bone destruction in RA were obtained from GeneCards and OMIM. The target genes of artesunate in inhibiting osteoclast differentiation and the target genes of bone destruction in RA were intersected to obtain 61 target genes of artesunate against bone destruction in RA. The intersected target genes were analyzed by GO/KEGG enrichment. According to the results previously reported, the cytokine-cytokine receptor interaction signaling pathway was selected for experimental verification. Artesunate intervention in the RANKL-induced osteoclast differentiation model showed that artesunate inhibited CC chemokine receptor 3(CCR3), CC chemokine receptor 1(CCR1) and leukemia inhibitory factor(LIF) mRNA expression in osteoclasts in a dose-dependent manner compared with the RANKL-induced group. Meanwhile, the results of immunofluorescence and immunohistochemistry showed that artesunate could dose-dependently reduce the expression of CCR3 in osteoclasts and joint tissues of the CIA rat model in vitro. This study indicated that artesunate regulated the CCR3 in the cytokine-cytokine receptor interaction signaling pathway in the treatment of bone destruction in RA and provided a new target gene for the treatment of bone destruction in RA.

Elevated fatty acid β-oxidation by leptin contributes to the proinflammatory characteristics of fibroblast-like synoviocytes from RA patients via LKB1-AMPK pathway

Fibroblast-like synoviocytes (FLS) maintain chronic inflammation leading to joint destruction in rheumatoid arthritis (RA). Fatty acid β-oxidation (FAO) regulates cell function. Here, we aimed to investigate the effect of FAO enhanced by leptin on the characteristics of RA-FLS and elucidate the potential metabolic mechanism. Key enzymes involved in lipid metabolism were detected with qPCR in HSF, MH7A cell line and isolated RA-FLS treated with RA or healthy control (HC) serum. In some experiments, FAO inhibitor, etomoxir (ETO) or anti-leptin antibody were added into serum-treated RA-FLS. In other experiments, RA-FLS were stimulated with leptin together with ETO or AMP-activated protein kinase (AMPK) inhibitor compound C (CC) or silencing liver kinase B1 (LKB1). Cell proliferation, proinflammatory factor production, pro-angiogenesis, chemoattractive potential, FAO-related key enzymes, AMPK and LKB1 in FLS were analyzed. FAO-related key enzymes were evaluated in serum-treated RA-FLS with or without anti-leptin antibody. Related functions of leptin-stimulated RA-FLS were examined in the presence or absence of ETO. AMP-activated protein kinase (AMPK) and liver kinase B1 (LKB1) in leptin-stimulated RA-FLS were tested with western blot. Activation of AMPK in leptin-stimulated RA-FLS was detected after silencing LKB1. We found that MH7A cell line and RA serum-treated FLS exhibited upregulated FAO, and ETO could inhibit the proinflammatory phenotypes of RA-FLS. The addition of anti-leptin antibody suppressed the elevation of FAO mediated by RA serum. More importantly, leptin promoted the proinflammatory characteristics of RA-FLS, which was reversed by ETO. Leptin activated AMPK by upregulating LKB1. CC impaired leptin-induced CPT-1A expression in RA-FLS. Our study uncovers that elevated FAO mediated by leptin drives abnormal function of RA-FLS and suggests leptin or FAO inhibition may serve as a promising therapeutic strategy for RA.