Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease that currently has no cure. Fibroblast-like synoviocytes (FLS), present in the RA synovium, play a pivotal role in RA pathogenesis. Notably, FLS in the RA patients (RA-FLS) exhibit characteristics similar to cancer cells, like enhanced migration, invasiveness, uncontrolled proliferation, resistance to apoptosis, and metabolic reprogramming. RA-FLS invasiveness is linked to radiographic joint damage in the patients, whereas inhibiting the FLS migration mitigates disease pathology. However, the molecular mechanisms underlying the migration and invasion capabilities of RA-FLS are not entirely understood. In this work, we have explored the function of mitochondrial calcium uniporter (MCU) and calcium signaling in FLS invasion. Our findings demonstrate a positive correlation between MCU expression and RA disease score. Interestingly, mitochondrial size was reduced, and peripheral localization was more pronounced in the RA-FLS when compared to the control FLS. Mitochondrial calcium import inhibition in the FLS by specific MCU inhibitor, Ruthenium-360 restored these altered mitochondrial dynamics and reduced the invasive phenotype. Through unbiased transcriptome analysis, we identified that MCU-mediated calcium signaling in RA-FLS leads to the enriched actin cytoskeleton and focal adhesion pathways responsible for the invasion phenotype, which can be effectively suppressed by inhibiting MCU. Additionally, we found that mitochondrial transport facilitator Miro1 binds to MCU in a calcium-dependent manner and regulates MCU-mediated mitochondrial dynamics and RA-FLS invasion. Experiments utilizing mice xenograft model demonstrated that MCU silencing diminishes the migration of RA-FLS toward the sites of inflammation in the immunocompromised SCID mice. Altogether, our findings highlight MCU as a promising therapeutic target to inhibit RA-FLS migration and RA progression.

Rheumatoid arthritis (RA) is an autoimmune chronic inflammatory disease that imposes a heavy economic burden on patients and society. Bone and cartilage destruction is considered an important factor leading to RA, and inflammation, oxidative stress, and mitochondrial dysfunction are closely related to bone erosion and cartilage destruction in RA. Currently, there are limitations in the clinical treatment methods for RA, which urgently necessitates finding new effective treatments for patients. Nuclear transcription factor-κB (NF-κB) is a signaling transcription factor that is widely present in various cells. It plays an important role as a stress source in the cellular environment and regulates gene expression in processes such as immunity, inflammation, cell proliferation, and apoptosis. NF-κB has long been recognized as a pathogenic factor of RA, and its activation can exacerbate RA by promoting inflammation, oxidative stress, mitochondrial dysfunction, and bone destruction. Conversely, inhibiting the activity of the NF-κB pathway effectively inhibits these pathological processes, thereby alleviating RA. Therefore, NF-κB may be a potential therapeutic target for RA. This article describes the physiological structure of NF-κB and its important role in RA through the regulation of oxidative stress, inflammatory response, mitochondrial function, and bone destruction. Meanwhile, we also summarized the impact of NF-κB crosstalk with other signaling pathways on RA and the effect of related drugs or inhibitors targeting NF-κB on RA. The purpose of this article is to provide evidence for the role of NF-κB in RA and to emphasize its significant role in RA by elucidating the mechanisms, so as to provide a theoretical basis for targeting the NF-κB pathway as a treatment for RA.

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease with complex pathogenesis. Ubiquitin-specific protease 13 (USP13), a member of the deubiquitinating enzyme (DUB) superfamily, plays diverse roles in cellular events. This study investigates the role of USP13 in RA, revealing its significant downregulation in peripheral blood mononuclear cells (PBMCs) from RA patients compared to healthy individuals. USP13 expression negatively correlates with RA characteristics, including erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and rheumatoid factor (RF). Consistent with these findings, USP13 levels were reduced in knee joint synovial tissues of collagen-induced arthritis (CIA) mice and lipopolysaccharide (LPS)-stimulated bone marrow-derived macrophages (BMDMs). Mechanistically, USP13 directly interacts with tumor necrosis factor receptor-associated factor 6 (TRAF6), reducing its K63-linked polyubiquitination and thereby inhibiting TRAF6 expression. This interaction restrains nuclear factor κB (NF-κB) signaling, leading to a marked attenuation of LPS-induced inflammatory responses in BMDMs. Importantly, the anti-inflammatory effects of USP13 over-expression are largely dependent on TRAF6 suppression. In vitro, USP13 over-expression in BMDMs inhibits the proliferation of fibroblast-like synoviocytes (FLS) and osteoclastogenesis. In addition, USP13-overexpressing BMDMs in CIA mice significantly alleviates RA development, as evidenced by reduced synovial hyperplasia, inflammatory cell infiltration, cartilage destruction, and bone loss. These findings highlight the essential role of USP13 in macrophages during RA progression and reveal its therapeutic potential by targeting TRAF6 signaling.

Fucoxanthin, an abundant carotenoid in marine algae, has garnered attention for its diverse health benefits, including anti-inflammatory and anticancer properties. Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by joint inflammation and damage. This study investigated the therapeutic potential of fucoxanthin extracted from Phaeodactylum tricornutum in collagen-induced RA. Our results demonstrated that fucoxanthin significantly alleviated RA symptoms, including weight loss, joint swelling, and decreased appetite. Histological analysis revealed that fucoxanthin mitigated synovial inflammation, cartilage damage, and bone erosion. Mechanistically, transcriptomic analysis and cell experiments indicated that fucoxanthin suppressed the JAK-STAT signaling pathway by downregulating the expression of inflammatory cytokines, such as IL-6 and IL-1β. Furthermore, metagenomic analysis suggested that fucoxanthin restored the altered gut microbiota composition associated with RA. These findings highlight the therapeutic potential of fucoxanthin from P. tricornutum in the management of RA by targeting multiple pathways, including inflammation and gut microbiota.

Rheumatoid arthritis (RA) is an autoimmune disease characterised by aggressive fibroblast-like synoviocytes (FLSs). Very few RA patients-derived FLSs (RA-FLSs)-specific surface signatures have been identified, and there is currently no approved targeted therapy for RA-FLSs. This study aimed to screen therapeutic aptamers with cell-targeting and cytotoxic properties against RA-FLSs and to uncover the molecular targets and mechanism of action of the screened aptamers.

We developed a cell-specific and cytotoxic systematic evolution of ligands by exponential enrichment (CSCT-SELEX) method to screen the therapeutic aptamers without prior knowledge of the surface signatures of RA-FLSs. The molecular targets and mechanisms of action of the screened aptamers were determined by pull-down assays and RNA sequencing. The therapeutic efficacy of the screened aptamers was examined in arthritic mouse models.

We obtained an aptamer SAPT8 that selectively recognised and killed RA-FLSs. The molecular target of SAPT8 was nucleolin (NCL), a shuttling protein overexpressed on the surface and involved in the tumor-like transformation of RA-FLSs. Mechanistically, SAPT8 interacted with the surface NCL and was internalised to achieve lysosomal degradation of NCL, leading to the upregulation of proapoptotic p53 and downregulation of antiapoptotic B-cell lymphoma 2 (Bcl-2) in RA-FLSs. When administrated systemically to arthritic mice, SAPT8 accumulated in the inflamed FLSs of joints. SAPT8 monotherapy or its combination with tumour necrosis factor (TNF)-targeted biologics was shown to relieve arthritis in mouse models.

CSCT-SELEX could be a promising strategy for developing cell-targeting and cytotoxic aptamers. SAPT8 aptamer selectively ablates RA-FLSs via modulating NCL-p53/Bcl-2 signalling, representing a potential alternative or complementary therapy for RA.

Rheumatoid arthritis (RA) is a prevalent autoimmune disease, affecting approximately 1% of the global population. Methotrexate (MTX) is the most widely prescribed drug for RA treatment; however, its efficacy is often limited, with resistance frequently observed. Fibroblast-like synoviocytes (FLS) play a pivotal role in RA progression and are closely linked to drug resistance, although the underlying mechanisms remain poorly understood. In this study, we conducted a comprehensive analysis of public single-cell transcriptomics data from osteoarthritis and rheumatoid arthritis synovial tissues, identifying RNF19A as a gene potentially associated with RA resistance in FLS. Our findings indicate that RNF19A is significantly overexpressed in drug-resistant FLS and is closely associated with the dysregulation of FLS proliferation, migration, invasion, and apoptosis. Furthermore, we demonstrated that RNF19A promotes functional disruption in FLS by ubiquitinating and degrading MKP-1, thereby activating the MAPK signaling pathway. This activation also facilitates the nuclear translocation of ZBTB20, an upstream transcription factor of RNF19A, which further enhances RNF19A transcription. This biological process creates a positive feedback loop in FLS, contributing to RA resistance-a mechanism that was also validated in vivo. In summary, this study is the first to underscore the crucial role of RNF19A in mediating drug resistance in RA FLS, elucidating the underlying biological processes, and providing novel insights into RA pathogenesis, thereby offering a new experimental foundation for RA drug development.

This study investigated the chemical compositions isolated from Cyathula officinalis (CES) and elucidated its anti-RA effects and potential mechanisms. In vitro results revealed that CES suppressed interleukin (IL)-1β-stimulated proliferation, migration, and invasion of MH7A cells in a concentration-dependent manner. In vivo results indicated that CES could reduce the arthritis score, paw swelling, and improve histopathological deterioration. The levels of inflammatory factors, matrix metalloproteinases, and proteins expressed in rat synovial tissue were suppressed after treatment with CES. These findings illustrate that CES is involved in the PI3K/AKT/mTOR/SREBP1/SCD-1/GPX4 axis-mediated ferroptosis and anti-inflammation, exerting its protective effects against the progression of RA.

Rheumatoid arthritis (RA) is a relatively frequent autoimmune disorder with individual and socioeconomic burden, particularly if diagnosed late. Therefore, identifying novel biomarkers for RA that assist in early diagnosis and managing plan is essential. Long noncoding RNA nuclear paraspeckle assembly transcript 1 (NEAT1), micro-RNA 21 (miR-21) and interleukin 17 (IL17) have emerging roles in the pathogenesis of numerous inflammatory conditions. The present research aims to evaluate NEAT1, miR-21 and IL17 roles in RA manifestations and activity and the possibility of utilizing them as biomarkers or therapeutic targets for the disease. Therefore, expression levels of NEAT1, miR-21 and IL17 in sera of 100 RA cases, and 100 age and sex-matched healthy controls were compared. A subsequent analysis was conducted to examine the correlation of their levels to various RA manifestations and disease activity.

Both NEAT1 and IL17 were significantly up regulated, while miR-21 was significantly down regulated in cases compared to controls. NEAT1 demonstrated a significant positive correlation with tender and swollen joint counts and with the overall DAS-28 score. A significant negative correlation was noted between miR-21 and RA disease duration.

NEAT1, miR-21, and IL17 have differential levels in patients with RA where NEAT1 and IL17 have up regulation, while miR-21 has down regulation. NEAT1 has a significant correlation with RA disease activity. We recommend further research to determine if they could be useful as future biomarkers for RA.

Fibroblast-like synoviocytes (FLS) are crucial for maintaining synovial homeostasis. SMYD5, a member of the histone lysine methyltransferase subfamily SMYDs, is involved in many pathological processes. This study aimed to investigate the role of SMYD5 in regulating synovial fibroblast homeostasis and the pathogenesis of rheumatoid arthritis (RA).

Proteomic screening was conducted to assess SMYD5 expression in the synovium of patients with osteoarthritis (OA) and RA. In vitro, interleukin-1 beta (IL-1β) was used to induce proliferation and inflammation in FLS. Further, we performed loss-of-function and gain-of-function experiments to investigate the biological function of SMYD5. In vivo, adeno-associated virus (AAV) vectors carrying SMYD5 short-hairpin RNA (AAV-shSMYD5) were injected into the knee joints to knock down SMYD5 in a collagen-induced arthritis (CIA) mouse model to evaluate its role in joint damage.

We observed a significant elevation of SMYD5 expression in the synovial tissues of patients with RA and IL-1β-induced FLS. SMYD5 facilitated posttranslational modifications and activated downstream signaling pathways, thereby promoting proliferation and inflammation in FLS. Mechanistically, SMYD5 mediated the methylation of Forkhead box protein O1 (FoxO1), which accelerated its degradation through ubiquitination, resulting in substantial FLS proliferation. Additionally, SMYD5 promoted lactate release to activate NF-κB signaling pathways by upregulating hexokinases-2 (HK2) expression, a key glycolytic enzyme, thereby intensifying the inflammatory response in FLS. Supporting these findings, intraarticular delivery of AAV-mediated SMYD5 knockdown in the CIA mice model effectively alleviated joint swelling, bone erosion, and overall arthritis severity.

Together, these findings suggest that SMYD5 is a dual target for regulating synovial fibroblast homeostasis and the pathogenesis of RA. Targeting SMYD5 through local treatment strategies may provide a novel therapeutic approach for RA, particularly when combined with immunotherapy.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial inflammation and progressive joint destruction. Existing evidence indicates that hypoxia potentially contributes to the pathology of RA, though the specific mechanism remains unidentified. In this study, we explored the molecular mechanism through which the hypoxia-inducible factor (HIF-1α) contributed to the pathological process of RA. Our preliminary results suggested that hypoxia stimulates the activation of fibroblast-like synoviocytes (FLS) by inducing mitochondrial damage to activate cGAS-STING signaling, which can be effectively inhibited by silencing HIF-1α. In line with this, HIF-1α deficiency significantly alleviated the symptoms of collagen-induced arthritis (CIA) mice. RNA-Seq and CUT-Tag analysis revealed that HIF-1α down-regulated the expression of AlkB homologue 7 (ALKBH7) by acting on the ALKBH7 promoter site on chromosome 19 6372400-6372578. Using dual luciferase reporter analysis, we identified that ACCGTGGC as the motif to which HIF-1α bound directly. Subsequently, we demonstrated that knockdown of ALKBH7 induces mitochondrial damage and activates cGAS-STING signaling by downregulating the expression of UQCRC2. Conversely, overexpression of ALKBH7 could resist hypoxia-induced mitochondrial damage and FLS activation. In conclusion, HIF-1α triggers mitochondrial damage by downregulating the expression of ALKBH7 thereby promoting FLS activation, which may be the molecular mechanism by which hypoxia is involved in the pathological process of RA. Hypoxia promotes the activation of FLS through the induction of mitochondrial damage, which subsequently activates cGAS-STING signaling. Mechanistically, HIF-1α triggers mitochondrial damage by downregulating the expression of ALKBH7 in a target manner. Furthermore, the deletion of ALKBH7 leads to mitochondrial damage under hypoxic conditions, primarily through the downregulation of UQCRC2, as opposed to other complexes.

Dioscin is a natural, bioactive steroid saponin that has the antiarthritic activity. Circular RNAs (circRNAs) are stable noncoding RNAs involving in the pathogenesis of rheumatoid arthritis (RA). Here, this study aimed to probe the role and mechanism of dioscin and circ_0008267 in RA progression. Cell proliferation, apoptosis, invasive, and migratory abilities, as well as inflammatory response were evaluated by CCK-8 assay, EdU assay, flow cytometery, transwell assay, wound healing assay, and ELISA analysis, respectively. Levels of genes and protein were tested by qRT-PCR and western blotting. The interaction between miR-942-5p and circ_0008267 or FK506-binding protein 5 (FKBP5) was confirmed using dual-luciferase reporter and RNA pull-down assays. Dioscin treatment was demonstrated to suppress RA-FLS proliferation, invasion, migration, and inflammatory response, but induced cell apoptosis. Circ_0008267 is a stable circRNA, and was increased in RA samples. Moreover, its expression was reduced by dioscin in RA-FLS, overexpression of circ_0008267 reversed the effects of dioscin on RA-FLS. Mechanistically, circ_0008267 acted as a sponge for miR-942-5p, which targeted FKBP5. Dioscin reduced FKBP5 expression, but elevated miR-942-5p level in RA-FLS. MiR-942-5p inhibition or FKBP5 upregulation abolished the inhibitory effects of dioscin on RA-FLS dysfunction. Moreover, circ_0008267 deficiency impaired RA-FLS proliferation, invasion, migration, and inflammation through regulating FKBP5. Dioscin suppressed the proliferation, invasion, migration, and inflammatory response in RA-FLS via circ_0008267/miR-942-5p/FKBP5 axis, providing new insights for RA prevention.

Rheumatoid arthritis (RA) is a systemic inflammatory and autoimmune disorder in which monocytes/macrophage infiltrate synovial membrane, differentiating into the pro- and anti-inflammatory M1 and M2 macrophage phenotypes. Omentin-1 is one of the adipokines that has anti-inflammatory and immunomodulatory effects; nevertheless, investigators have yet to elucidate the function of omentin-1 in RA development. It is still unclear how omentin-1 affects human autoimmune disease and what its beneficial role is. Thus, we show that omentin-1 exhibits a therapeutic effect on RA.

Utilizing patient or animal tissue, MH7A cell-line, ELISA, and qPCR, we examined the expression of omentin-1 and inflammatory cytokines in the GEO databases. Omentin-1's effects on macrophage polarization were investigated using Immunofluorescence staining (IF) and qPCR. Additionally, the method by which omentin-1 regulates interleukins was discovered by IF labeling for STAT6 translocation, siRNA transfection, IPA software using several and pharmacological inhibitors. Omentin-1's effects were examined in an in vivo investigation using the type II collagen-induced arthritis model, micro-CT, and histological evaluation.

Results from the GSE97779 dataset and patients' tissues discovered that the level of omentin-1 and M2 macrophage markers are downregulated in human RA tissue samples compared to healthy tissue and negatively correlated with the expression of pro-inflammatory interleukins (ILs) and M1 macrophage. Stimulation of RA synovial fibroblasts with omentin-1 augmented IL-4 synthesis and subsequently enhanced anti-inflammatory ability as well as M2 polarization. The STAT6 transactivation through AMPK, PI3K, ERK, and JAK cascades regulates omentin-1-induced promotion of IL-4. Importantly, intra-articular injection of omentin-1 blocked collagen-induced arthritis-augmented pro-inflammatory response, cartilage degradation, and bone loss through upregulating IL-4 and M2 macrophages in vivo.

Our findings support a potential therapy goal for RA and a tenable mechanism to explain the relationship between omentin-1.

Numerous patients with rheumatoid arthritis (RA) manifest severe syndromes, including elevated synovial fluid volumes (SF) with abundant immune cells, which can be controlled by TNF/JAK inhibitors. Here, we apply single-cell RNA sequencing (scRNA-seq) and subsequent validations in SF from RA patients. These analyses of synovial tissue show reduced density of SF-derived pathogenic cells (e.g., SPP1+ macrophages and CXCL13+CD4+ T cells), altered gene expression (e.g., SPP1 and STAT1), molecular pathway changes (e.g., JAK/STAT), and cell-cell communications in drug-specific manners in samples from patients pre-/post-treated with adalimumab/tofacitinib. Particularly, SPP1+ macrophages exhibit pronounced communication with CXCL13+CD4+ T cells, which are abolished after treatment and correlate with treatment efficacy. These pathogenic cell types alone or in combination can augment inflammation of fibroblast-like synoviocytes in vitro, while conditional Spp1 knocking-out reduces RA-related cytokine expression in collagen-induced arthritis mice models. Our study shows the functional role of SF-derived pathogenic cells in progression and drug-specific treatment outcomes in RA.

The General Synovitis Score (GSS) is a well-established method for scoring synovial inflammation. Despite its widespread use, the GSS does not fully capture the inflammatory manifestations characteristic of the synovium in rheumatoid arthritis (RA). To address this limitation, the modified GSS (mGSS) was developed. The present study compared the correlation of the mGSS and the GSS with clinical disease activity. The aim was to provide a more precise histopathological scoring system based on hematoxylin and eosin (H&E) staining for assessing synovial inflammation in patients with active RA. In this cross-sectional study, synovial tissues were obtained from 60 patients with RA using a novel synovial biopsy device. Sections from synovial tissues were stained with H&E, and were assessed using the GSS and the mGSS. Neovascularization was observed in 56 patients (93.3%) and was significantly correlated with disease activity score in 28 joints-C-reactive protein (DAS28-CRP) (ρ=0.49; P<0.001), erythrocyte sedimentation rate (ESR) (ρ=0.44; P<0.001) and CRP (ρ=0.51; P<0.001). In addition, patients with severe neovascularization had significantly higher DAS28-CRP, ESR and CRP levels than those with mild-to-moderate neovascularization (P<0.05). Synoviocyte detachment, which occurred in nine patients (15.0%), was associated with higher DAS28-CRP, ESR and CRP levels than in the patients with synoviocyte proliferation (P<0.05). Furthermore, the mGSS was more strongly correlated with DAS28-CRP (ρ=0.62; P<0.001) than the GSS (ρ=0.37; P=0.003). These findings indicated that neovascularization and synoviocyte detachment, which are critical yet often overlooked aspects in the traditional GSS, are important in RA. Incorporating these elements into the mGSS may enhance the assessment of disease activity, providing a more precise and accurate evaluation of the synovial histopathology in patients with RA.

Circular RNAs (circRNAs) play a crucial role in the development of various diseases. However, few studies have investigated the role of circRNAs in rheumatoid arthritis (RA). Herein, we aimed to identified the novel circRNAs involved in the migration and invasion of RA fibroblast-like synoviocytes (RA-FLS).

The RA-FLS were isolated from the synovial membrane of patients with RA. The CircRNA profile was screened by CircRNA microarray analysis. Circ_0088200 and miR-127-5p expression levels were detected using quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). The protein level of matrix metalloproteinase 1 (MMP1) was evaluated by western blotting. Wound healing and Transwell assays were performed to analyze the migration and invasion of RA-FLS. RNA immunoprecipitation (RIP) and dual-luciferase reporter assays were used to validate the interaction between Circ_0088200 and miR-127-5p. Collagen-induced arthritis (CIA) mouse models were established to evaluate the role of Circ_0088200 in the development of arthritis in vivo.

Circ_0088200 was highly expressed in RA-FLS compared with osteoarthritis fibroblast-like synoviocytes (OAFLS) and correlated positively with the disease activity score in 28 joints. Inhibition of Circ_0088200 suppressed the migration and invasion of RA-FLS. Conversely, overexpression of Circ_0088200 significant promoted the migration and invasion of RA-FLS. Mechanistically, Circ_0088200 functions as a sponge for miR-127-5p and relieve its repressive effect on MMP1, thereby promoting the migration and invasion of RA-FLS. Importantly, intra-articular injection of Adenoassociated virus expressing Circ_0088200 significantly increased the severity of arthritis in mice with CIA.

Circ_0088200 promotes the migration and invasion of RA-FLS by sponging miR-127-5p. Thus Circ_0088200 is a potential therapeutic target for RA.

Rheumatoid arthritis (RA) is a systemic autoimmune disease that is prevalent worldwide and seriously threatens human health. RA-fibroblast-like synoviocytes (FLS) play important roles in almost all aspects of RA progression. This study aimed to study the effect of Amentoflavone (AMF), a polyphenol compound derived from extracts of Selaginella tamariscina, on the abnormal biological behaviors of RA-FLS. The immortalized human RA-FLS cell line (MH7A) was treated with AMF or transfected with small interfering RNAs (siRNAs) targeting peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1). Then, cell viability was detected by CCK-8 assay. EDU staining, wound healing and transwell assays were employed to measure the capacities of MH7A cell proliferation, migration and invasion. The levels of inflammatory factors were assessed using ELISA kits. Additionally, ferroptosis was analyzed by detecting Fe2+ content, lipid reactive oxygen species (ROS) level and expression of ferroptosis-related proteins. Pull-down assay was employed to verify the targeted binding of AMF to PIN1. Further, PIN1 overexpression or ferroptosis inhibitor Ferrostatin-1 (Fer-1) addition was conducted to elucidate the regulatory mechanism of AMF on PIN1 and ferroptosis. Results revealed that AMF intervention or PIN1 knockdown inhibited the proliferation, migration, invasion and inflammation in MH7A cells. AMF facilitated lipid peroxidation and ferroptosis in MH7A cells. Moreover, AMF targeted inhibition of PIN1 expression, and PIN1 overexpression restored the promoting effect of AMF on lipid peroxidation and ferroptosis in MH7A cells. Besides, Fer-1 reversed the impacts of AMF on the abnormal biological behaviors of MH7A cells. In summary, AMF induced ferroptosis to inhibit the proliferation, migration, invasion and inflammation in RA-FLS by inhibiting PIN1, providing a promising candidate for RA treatment.

Ferroptosis is involved in the occurrence and development of inflammatory arthritis. RND1 has been reported to possess pro-ferroptosis activity.

This study was designed to explore the role and the molecular mechanism of RND1 in rheumatoid arthritis (RA).

DBA/1 mice were exposed to type II collagen immunization. The pathological damage of the knee joints of mice was observed with H&E staining and RND1 expression in synovial tissues was detected using Western blot. In vitro, Western blot was used to measure RND1, ferroptosis-, migration- and inflammation-related proteins. The cell proliferation, migration and invasion were detected using CCK-8 method, EdU staining, wound healing and transwell assays. The levels of inflammatory factors were detected with ELISA and RT-qPCR. Relative iron level, GSH and MDA concentrations were detected with corresponding assay kits. BODIPY 581/591 C11 kit measured lipid ROS. 4-HNE and GPX4 expression were detected using immunofluorescence assay.

This study found that RND1 expression was reduced in the synovial tissues of RA mice and human fibroblast-like MH7A synoviocytes. It was also found that the upregulation of RND1 inhibited the proliferation, migration, invasion and inflammatory response in rheumatoid synovial cells via ferroptosis.

Collectively, RND1 exerted protective impacts on RA, which might be mediated by ferroptosis.

Inflammation is a complex response to harmful stimuli, crucial for immunity, and linked to chronic diseases and cancer, with TGF-β and NF-κB pathways as key regulators. CD109 is a glycosylphosphatidylinositol (GPI)-anchored protein, that our group has originally identified as a TGF-β co-receptor and inhibitor of TGF-β signaling. CD109 modulates TGF-β and NF-κB pathways, to influence immune responses and inflammation. CD109's multifaceted role in inflammation spans various tissue types, including the skin, lung, bone and bone-related tissues, and various types of cancers. CD109 exerts its effects by modulating processes such as cytokine secretion, immune cell recruitment, macrophage polarization, T helper cell function and cancer cell phenotype and function. Here, we review CD109's regulatory functions in inflammatory responses in these various tissues and cell types. Exploration of CD109's mechanisms of action will enhance our understanding of its contributions to disease pathology and its potential for therapeutic applications.

Rheumatoid arthritis (RA) is an autoimmune condition that predominantly affects synovial joints, manifesting with joint swelling, pain, and stiffness. In advanced stages, unchecked inflammation can inflict damage on bone and cartilage, resulting in disabilities and deformities of the joints. Additionally, systemic and extra-articular complications may arise due to the consequences of uncontrolled inflammation. Helicobacter pylori (H. pylori) is one of the most prevalent chronic bacterial infections in humans. This microorganism is a spiral-shaped, flagellated, microaerophilic gram-negative bacterium. Prolonged exposure leads to the activation of the immune system, with infected gastric mucosa epithelial cells continuously producing cytokines. This production, in turn, triggers the generation of antibodies as well as T Helper 1 and T Helper 2 effector T cells. The persistent antigenic stimulation resulting from H. pylori infection could lead to the progression of autoimmune diseases. Numerous clinical and pharmacological trials have illustrated the efficacy of traditional Chinese medicine against H. pylori. This review aims to delve into the connection between H. pylori and rheumatoid arthritis so as understand the pathogenesis. The concluding section of this review explores the interplay of Chinese medicine and Helicobacter pylori concerning rheumatoid arthritis.

Rheumatoid arthritis (RA) is a systemic disease that primarily manifests as chronic synovitis of the symmetric small joints. Despite the availability of various targeted drugs for RA, these treatments are limited by adverse reactions, warranting new treatment approaches. Suberosin (SBR), isolated from Plumbago zeylanica-a medicinal plant traditionally used to treat RA in Asia-possesses notable biological activities. This study aimed to investigate the effects and potential underlying pathways of SBR on RA.

Tumor necrosis factor-alpha (TNF-α) induced inflammation in RA-derived fibroblast-like synoviocytes (RA-FLS), and the expression of proinflammatory mediators was assessed using q-RT PCR and ELISA after treatment with various SBR concentrations. Bone marrow-derived macrophages (BMDMs) were induced to differentiate into M1 and M2 macrophages, followed by treatment with various SBR concentrations and macrophage polarization assessment. Low-dose (0.5 mg/kg/d) and high-dose (2 mg/kg/d) SBR regimens were administered to a collagen-induced arthritis (CIA) mouse model for 21 days, and the anti-arthritic effects of SBR were evaluated. Network pharmacology and molecular docking analyses were used to predict the anti-arthritic targets of SBR. The effect of SBR on the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway was evaluated.

SBR suppressed macrophage polarization toward the M1 phenotype while enhancing their polarization toward the M2 phenotype. SBR reduced the levels of proinflammatory mediators in TNF-α-induced RA-FLS. Mechanistically, SBR inhibited the phosphorylation of the JAK1/STAT3 signaling pathway in RA-FLS and M1 macrophages and promoted the phosphorylation of the JAK1/STAT6 pathway in M2 macrophages, enhancing M2 polarization. In vivo, prophylactic treatment of low-dose SBR reduced M1 macrophage infiltration into synovial tissue, increased the proportion of M2 macrophages, and decreased the expression of inflammatory mediators in the serum and synovial tissue, alleviating synovial inflammation. SBR significantly alleviated arthritis in CIA mice through macrophage repolarization and inhibition of inflammation.

SBR significantly reduced clinical symptoms, joint pathological damage, and expression inflammatory cytokine expression in CIA mice. SBR exhibited anti-arthritic effects via the JAK1/STAT3 and JAK1/STAT6 signaling pathways, inhibiting synovial tissue inflammation and M1 macrophage polarization while promoting M2 macrophage polarization. Therefore, SBR may be an effective candidate for RA treatment.

Fibroblast-like synoviocytes (FLS) are key players in rheumatoid arthritis (RA) by resisting apoptosis via increased autophagy. Elevated synovial aquaporin 1 (AQP1) affects RA FLS behaviors, but its relationship with FLS autophagy is unclear. We aim to clarify that silencing AQP1 inhibits autophagy to exert its anti-RA effects.

We studied the effects and mechanisms of AQP1 silencing on autophagy in TNF-α-induced RA FLS and examined the crucial role of autophagy inhibition in its impacts on RA FLS pathogenic behaviors. We explored whether silencing synovial AQP1 relieved rat adjuvant-induced arthritis (AIA) by reducing synovial autophagy.

TNF-α stimulation increased AQP1 expression and autophagy levels in RA FLS, with a positive correlation between them. AQP1 silencing inhibited autophagy in TNF-α-stimulated RA FLS, along with suppressing proliferation, promoting apoptosis, and mitigating inflammation. Notably, the inhibitory effects of AQP1 silencing on RA FLS pathogenic behaviors were cancelled by autophagy activation with rapamycin (Rapa) but enhanced by autophagy inhibition using 3-Methyladenine. Mechanistically, silencing AQP1 enhanced the binding of Bcl-2 to Beclin1 by decreasing Beclin1-K63 ubiquitination, thus inhibiting RA FLS autophagy. In vivo, silencing synovial AQP1 relieved the severity and development of rat AIA, alongside reducing Ki67 expression, promoting apoptosis, and decreasing autophagy within AIA rat synovium. Expectedly, the Rapa co-administration nullified the anti-AIA effects of silencing synovial AQP1.

These findings reveal that silencing AQP1 inhibits RA FLS pathogenic behaviors and attenuates rat AIA through autophagy inhibition. This study may help clarify the pathogenic role of AQP1 in enhancing autophagy during RA development.

Rheumatoid arthritis (RA) is a systemic immune disease with severe implications for joint health. The issue of non-specific drug distribution potentially limits the therapeutic efficacy and increases the risk associated with RA treatment. Researchers employed cytomembrane-coated biomimetic nanoparticles (NPs) to enhance the targeting delivery efficacy to meet the demand for drug accumulation within the affected joints. Furthermore, distinct cytomembranes offer unique functionalities, such as immune cell activation and augmented NP biocompatibility. In this review, the current strategies of RA treatments were summarized in detail, and then an overview of RA's pathogenesis and the methodologies for producing cytomembrane-coated biomimetic NPs was provided. The application of cytomembrane biomimetic NPs derived from various cell sources in RA therapy is explored, highlighting the distinctive attributes of individual cytomembranes as well as hybrid membrane configurations. Through this comprehensive assessment of cytomembrane biomimetic NPs, we elucidate the prospective applications and challenges in the realm of RA therapy, and the strategy of combined therapy is proposed. In the future, cytomembrane biomimetic NPs have a broad therapeutic prospect for RA.

Among the numerous treatment options for rheumatoid arthritis (RA), the promotion of synoviocyte apoptosis and inhibition of inflammation are considered the most effective. However, the potential pro-apoptotic effects of gross saponins of Tribulus terrestris (GSTT), which are natural saponins derived from the herb Tribulus terrestris L., on rheumatoid arthritis fibroblast-like synoviocytes (RA-FLSs) and their essential molecular mechanisms remain unclear. The aim of the present study was to investigate the influence of different concentrations of GSTT on RA-FLSs using various assays, including cell counting kit-8 (CCK-8), reverse transcription polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), flow cytometry, terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) and western blot analysis. These assessments were conducted to evaluate the cell viability, changes in the levels of inflammatory cytokines, apoptosis rates and alterations in protein expression related to this process. In vivo, arthritis clinical score, haematoxylin and eosin (HE) staining and ELISA were used to assess paw inflammation, histopathology and serum inflammatory cytokine changes. Our findings demonstrated that GSTT substantially promotes the apoptosis of RA-FLSs and reduces pro-inflammatory cytokine levels. GSTT also reduced the Bcl-2/Bax ratio and inhibited JNK and p38 phosphorylation. Furthermore, GSTT exhibits positive effects on RA by improving clinical scores, reducing synovial inflammatory infiltration and lowering serum pro-inflammatory cytokine levels. Therefore, by promoting the apoptosis of RA-FLSs and suppressing inflammation through the inhibition of the MAPK signalling pathway, GSTT is a promising therapeutic intervention for RA.

Rheumatoid arthritis (RA) is an enduring autoimmune inflammatory condition distinguished by continual joint inflammation, hyperplasia of the synovium, erosion of bone, and deterioration of cartilage.Fibroblast-like synoviocytes (FLSs) exhibiting "tumor-like" traits are central to this mechanism.ADP-ribosylation factor-like 4c (ARL4C) functions as a Ras-like small GTP-binding protein, significantly impacting tumor migration, invasion, and proliferation.However, it remains uncertain if ARL4C participates in the stimulation of RA FLSs exhibiting "tumor-like" features, thereby fostering the advancement of RA. In our investigation, we unveiled, for the inaugural instance, via the amalgamated scrutiny of single-cell RNA sequencing (scRNA-seq) and Bulk RNA sequencing (Bulk-seq) datasets, that activated fibroblast-like synoviocytes (FLSs) showcase high expression of ARL4C, and the ARL4C protein expression in FLSs derived from RA patients significantly surpasses that observed in individuals with osteoarthritis (OA) and traumatic injury (trauma).Silencing of the ARL4C gene markedly impeded the proliferation of RA FLSs by hindered the transition of cells from the G0/G1 phase to the S phase, and intensified cell apoptosis and diminished the migratory and invasive capabilities. Co-culture of ARL4C gene-silenced RA FLSs with monocytes/macrophages significantly inhibited the polarization of monocytes/macrophages toward M1 and the repolarization of M2 to M1.Furthermore, intra-articular injection of shARL4C significantly alleviated synovial inflammation and cartilage erosion in collagen-induced arthritis (CIA) rats. In conclusion, our discoveries propose that ARL4C assumes a central role in the synovial inflammation, cartilage degradation, and bone erosion associated with RA by triggering the PI3K/AKT and MAPK signaling pathways within RA FLSs.ARL4C holds promise as a prospective target for the development of pharmaceutical agents targeting FLSs, with the aim of addressing RA.

Interleukin-22 (IL-22) is a vital cytokine that is dysregulated in various autoimmune conditions including rheumatoid arthritis (RA), multiple sclerosis (MS), and Alzheimer's disease (AD). As the starting point for the activation of numerous signaling pathways, IL-22 plays an important role in the initiation and development of autoimmune diseases. Specifically, imbalances in IL-22 signaling can interfere with other signaling pathways, causing cross-regulation of target genes which ultimately leads to the development of immune disorders. This review delineates the various connections between the IL-22 signaling pathway and autoimmune disease, focusing on the latest understanding of the cellular sources of IL-22 and its effects on various cell types. We further explore progress with pharmacological interventions related to targeting IL-22, describing how such therapeutic strategies promise to usher in a new era in the treatment of autoimmune disease.

Rheumatoid arthritis (RA) is a systemic inflammatory disease characterized by active polyarthritis, which leads to functional loss and joint deformities. Natural compounds derived from marine organisms are considered valuable immune-modulating agents. This study aimed to assess the anti-inflammatory effect of sinulariolide, a soft coral-derived compound, on RA fibroblast-like synoviocytes and its therapeutic efficacy against collagen-induced arthritis (CIA).

To determine the effects of sinulariolide on tumor necrosis factor-alpha (TNF-α)-induced inflammation, MH7A cells pre-treated with 10 ng/mL TNF-α for 24 h were treated with sinulariolide. The effect of sinulariolide on proinflammatory cytokine expressions at both the mRNA and protein levels in the MH7A cells was assessed using real-time-polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA). Further, we analyzed the effect of sinulariolide on the activation of mitogen-activated protein kinase (MAPK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways using Western blotting and the TransAM NF-κB p65 kit. To comprehensively evaluate the potential application of sinulariolide in the treatment of inflammatory diseases, we used a well-established collagen-induced arthritis (CIA) mouse model. We examined the tissue sections of the ankle joints of the mice, assessed synovial hyperplasia, inflammatory cell infiltration, and cartilage damage, and used ELISA to analyze changes in cytokine expression in the hind paw tissues.

MH7A cells treated with sinulariolide showed a notable reduction in the expression of proinflammatory cytokines, which could be due to decreased activation of the MAPK and NF-kB pathways. Additionally, sinulariolide-treated mice showed significantly reduced joint swelling and lower clinical arthritis scores than those in the normal and control groups. Significant reductions in synovial hyperplasia, inflammatory cell infiltration, and cartilage damage were observed in the tissue sections of the ankle joints of the mice treated with sinulariolide. Furthermore, the expression of inflammatory cytokines in the hind paw tissue of the mice treated with sinulariolide was significantly decreased.

Sinulariolide inhibited the progression of inflammation in MH7A cells. Sinulariolide treatment significantly reduced clinical arthritis symptoms and histological inflammatory responses in mice with CIA. Sinulariolide may serve as a potential therapeutic agent for RA.

Fibroblast-like synoviocytes (FLSs) are among the main disease-driving players in most cases of monoarthritis (MonoA), oligoarthritis, and polyarthritis. In this review, we look at the characteristics and therapeutic challenges at the onset of arthritis and during follow-up management. In some cases, these forms of arthritis develop into autoimmune polyarthritis, such as rheumatoid arthritis (RA), whereas local eradication of the RA synovium could still be combined with systemic treatment using immunosuppressive agents. Currently, the outcomes of local synovectomies are well studied; however, there is still a lack of a comprehensive analysis of current local intra-articular treatments highlighting their advantages and disadvantages. Therefore, the aim of this study is to review local intra-articular therapy strategies. According to publications from the last decade on clinical studies focused on intra-articular treatment with anti-inflammatory molecules, a range of novel slow-acting forms of steroidal drugs for the local treatment of synovitis have been investigated. As pain is an essential symptom, caused by both inflammation and cartilage damage, various molecules acting on pain receptors are being investigated in clinical trials as potential targets for local intra-articular treatment. We also overview the new targets for local treatment, including surface markers and intracellular proteins, non-coding ribonucleic acids (RNAs), etc.

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by the abnormal proliferation of fibroblast-like synoviocytes and changes in the joint synovium, including elevated reactive oxygen species, decreased pH, and reduced oxygen content. In this study, we synthesized a novel nanocomposite material, namely HA-PBA-TiO2 Janus nanocomposite, by in situ etching in prussian blue analogs doped with Co and Ni, followed by the growth of TiO2 nano-flowers and encapsulation in hyaluronic acid. When these janus nanoparticles diffused to the inflammatory sites of RA, they exhibited outstanding photocatalytic water-splitting ability under 660 nm laser irradiation, generating H2 and O2. This capability helps ameliorate the hypoxic microenvironment at RA inflammatory sites by eliminating reactive oxygen species (ROS) and enhancing antioxidation and oxygenation. Furthermore, owing to the doping of Co and Ni, HA-PBA-TiO2 exhibits photothermal conversion capability, which significant damage to FLS upon exposure to 660 nm laser irradiation, thereby controlling their aberrant proliferation. Through a series of in vitro and in vivo experiments, we validated the significant therapeutic efficacy of HA-PBA-TiO2 in treating RA, highlighting its broad prospects for application.

For the non-invasive treatment of rheumatoid arthritis (RA), a chondroitin sulfate C (CSC)-based dissolving microneedles (cMN) was prepared to deliver human adipose stem cell-derived extracellular vesicles (hASC-EV) into inflamed joints. Owing to their anti-inflammatory function, the hASC-EV-bearing cMN (EV@cMN) significantly suppressed activated fibroblast-like synoviocytes (aFLS) and M1 macrophages (M1), which are responsible for the progression of RA. In addition, EV@cMN facilitated the chondrogenic differentiation of bone marrow-derived stem cells. In mice with collagen-induced arthritis, EV@cMN efficiently delivered both hASC-EV and CSC to inflamed joints. Interestingly, pro-inflammatory cytokines in the inflamed joints were remarkably downregulated by the synergistic effect of CSC and hASC-EV. Consequently, as judged from the overall clinical score and joint swelling, EV@cMN showed an outstanding therapeutic effect, even comparable to the wild-type mice, without significant adverse effects. Overall, EV@cMN might have therapeutic potential for RA by efficiently delivering CSC and hASC-EV into the inflamed joints in a non-invasive manner.

Synovial inflammation is vital for the progression of osteoarthritis (OA). The objective of this study was to explore the effects and potential molecular mechanisms of sphingosine kinase 2 (SPHK2) on the proliferation and migration of fibroblast-like synoviocytes (FLS).

A TNF-α-stimulated FLS model and a papain-induced OA rat model were constructed. The functions of SPHK2 knockdown in OA were explored by a series of in vivo and in vitro assays. Downstream target genes of SPHK2 were investigated using transcriptome sequencing and validated by reverse transcription quantitative PCR (RT-qPCR). The effects of the SPHK2/IL-17 signaling pathway on inflammation, proliferation, and migration of OA-FLS were investigated using the IL-17 pathway inhibitor (secukinumab) and the activator (rhIL-17A).

TNF-α stimulation promoted SPHK2 expression at mRNA and protein levels in OA-FLS. SPHK2 knockdown reduced IL-1β, IL-6, MMP-2, MMP-9, cyclinD1, and PCNA levels and suppressed proliferation and migration of OA-FLS. SPHK2 knockdown alleviated cartilage damage and synovial inflammation in the OA rat model. LRRIQ3, H4C8, CXCL1, CABP4, COL23A1, and PROK2 expression levels were regulated by SPHK2. SPHK2 knockdown inhibited the protein levels of IL-17A, IL-17RA, and Act1. The IL-17 pathway inhibitor secukinumab enhanced the inhibitory effect of SPHK2 knockdown on the proliferation and migration of OA-FLS, while the IL-17 pathway activator rhIL-17A exerted the opposite effect.

SPHK2 knockdown inhibits proliferation and migration of OA-FLS by blocking the IL-17 pathway, which provides a novel approach to the OA treatment.

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease. The fruits of Illicium verum, which is a medicinal and edible resource, have been shown to have anti-inflammatory properties.

In this study, we investigated the effects of I. verum extracts (IVEs) on human RA fibroblasts-like synoviocytes (RA-FLS) by using a sensitive and selective ultra-high-performance liquid chromatography with high-definition mass spectrometry (UPLC-HDMS) method. We subsequently analyzed the metabolites produced after the incubation of cultured RA-FLS with IVEs.

IVEs inhibited the proliferation and suppressed the migration of RA-FLS, and reduced the levels of inflammatory factors including TNF-α and IL-6. Twenty differential metabolites responsible for the effects of IVEs were screened and annotated based on the UPLC-HDMS data by using a cell metabolomics approach.

Our findings suggest that treating RA-FLS with IVEs can regulate lipid and amino acid metabolism, indicating that this extract has the potential to modify the metabolic pathways that cause inflammation in RA.

This might lead to novel therapeutic strategies for managing patients with RA.

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic and symmetrical polyarthritis. RA patients often experience inflammatory reaction and hypercoagulable state, which together affect the self-perception of patient (SPP). Currently, inhibiting inflammation and hypercoagulable state are common treatment methods for alleviating RA symptoms. Xinfeng Capsules (XFC) has a long history of treating RA, and can effectively improve the inflammatory response and hypercoagulable state of RA. However, the potential mechanisms have not yet been determined.

This study elucidated the action mechanism of XFC in RA inflammation and hypercoagulability through the lncDSCR9/RPLP2/PI3K/AKT axis.

Clinical observations indicated that there was a strong link between XFC therapy and improvements in inflammatory and coagulation biomarkers, as well as SPP among RA patients. The subsequent network pharmacology analysis results identified the PI3K/AKT signaling pathway as a potential mediator for XFC treatment of RA. Furthermore, clinical validation and sequencing results revealed that lncRNA DSCR9 expression (a gene implicated in inflammation and coagulation) was negatively correlated with clinical markers of inflammation and coagulation, while positively correlated with SF-36 indicators. Notably, XFC treatment remarkably upregulated lncRNA DSCR9 expression and downregulated PI3K and AKT expressions, showing opposite expression trends to the untreated cases.The regulatory effect of XFC on the lncRNA DSCR9/RPLP2/PI3K/AKT axis in RA was investigated using techniques such as RNA pull-down assay, Western blot analysis, RT-PCR, and EdU assay. Moreover, the administration of the PI3K/AKT agonist RMH can counteract the effects of XFC on p-PI3K, p-AKT, inflammation, and hypercoagulability, reinforcing the role of pathway. Finally, animal studies utilizing HE staining and transmission electron microscopy (TEM) demonstrated that XFC notably decreased PI3K and AKT expressions in adjuvant-induced arthritis (AA) rats, mitigated inflammation and hypercoagulability, and enhanced the ultrastructure of synovial cells. These findings underscored the potential mechanisms of XFC in the treatment of RA.

Regulating the lncRNA DSCR9/RPLP2/PI3K/AKT axis may be an important mechanism by which XFC improved RA inflammatory response and hypercoagulable state.

Recent studies indicate that N-acetyltransferase 10 (NAT10)-mediated ac4C modification plays unique roles in tumour metastasis and immune infiltration. This study aimed to uncover the role of NAT10-mediated ac4C in fibroblast-like synoviocytes (FLSs) functions and synovial immune cell infiltration in rheumatoid arthritis (RA).

FLSs were obtained from active established patients with RA. Protein expression was determined by western blotting or immunohistochemistry or multiplexed immunohistochemistry. Cell migration was measured using a Boyden chamber. ac4C-RIP-seq combined with RNA-seq was performed to identify potential targets of NAT10. RNA immunoprecipitation was used to validate the interaction between protein and mRNA. NAT10 haploinsufficiency, inhibitor remodelin or intra-articular Adv-NAT10 was used to suppress arthritis in mice with delayed-type hypersensitivity arthritis (DYHA) and collagen II-induced arthritis (CIA) and rats with CIA.

We found elevated levels of NAT10 and ac4C in FLSs and synovium from patients with RA. NAT10 knockdown or specific inhibitor treatment reduced the migration and invasion of RA FLSs. Increased NAT10 level in the synovium was positively correlated with synovial infiltration of multiple types of immune cells. NAT10 inhibition in vivo attenuated the severity of arthritis in mice with CIA and DTHA, and rats with CIA. Mechanistically, we explored that NAT10 regulated RA FLS functions by promoting stability and translation efficiency of N4-acetylated PTX3 mRNA. PTX3 also regulated RA FLS aggression and is associated with synovial immune cell infiltration.

Our findings uncover the important roles of NAT10-mediated ac4C modification in promoting rheumatoid synovial aggression and inflammation, indicating that NAT10 may be a potential target for the treatment of RA, even other dysregulated FLSs-associated disorders.

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.

FLS from RA patients (n = 5) were stimulated with recombinant tumor necrosis factor α (TNF-α) 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).

The results demonstrated that APEX1 significantly reduced mitochondrial-specific ROS expression and restored mitochondrial membrane potential in TNF-α/IL-17-stimulated RA FLS. Furthermore, APEX1 treatments attenuated TNF-α/IL-17-induced activation of p38 MAPK, NF-κB, and PI3K 110 δ signaling pathways. Similarly, APEX1 significantly diminished TNF-α/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-α/IL-17-treated RA FLS via inhibition of matrix metalloproteinase 3 (MMP3).

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.

Despite recent advances in the mechanism of oxidized DNA activating NLRP3, the molecular mechanism and consequence of oxidized DNA associating with NLRP3 remains unknown. Cytosolic NLRP3 binds oxidized DNA which has been released from the mitochondria, which subsequently triggers inflammasome activation. Human glycosylase (hOGG1) repairs oxidized DNA damage which inhibits inflammasome activation. The fold of NLRP3 pyrin domain contains amino acids and a protein fold similar to hOGG1. Amino acids that enable hOGG1 to bind and cleave oxidized DNA are conserved in NLRP3. We found NLRP3 could bind and cleave oxidized guanine within mitochondrial DNA. The binding of oxidized DNA to NLRP3 was prevented by small molecule drugs which also inhibit hOGG1. These same drugs also inhibited inflammasome activation. Elucidating this mechanism will enable the design of drug memetics that treat inflammasome pathologies, illustrated herein by NLRP3 pyrin domain inhibitors which suppressed interleukin-1β (IL-1β) production in macrophages.

Fibroblast-like synoviocytes (FLS) contribute to the pathogenesis of rheumatoid arthritis (RA), in part due to activation of the proinflammatory transcription factor NF-κB. Neddylation is modulated by the negative regulator of ubiquitin-like protein (NUB) 1. We determined whether NUB1 and neddylation are aberrant in the models with RA FLS, thereby contributing to their aggressive phenotype.

Models with RA or osteoarthritis (OA) FLS were obtained from arthroplasty synovia. Real-time quantitative polymerase chain reaction and Western blot analysis assessed gene and protein expression, respectively. NUB1 was overexpressed using an expression vector. NF-κB activation was assessed by stimulating FLS with interleukin (IL)-1β. Neddylation inhibitor (MLN4924) and proteasome inhibitor were used in migration and gene expression assays. MLN4924 was used in the model with K/BxN serum-transfer arthritis.

Enhanced H3K27ac and H3K27me3 peaks were observed in the NUB1 promoter in the OA FLS compared with the RA FLS. NUB1 was constitutively expressed by FLS, but induction by IL-1β was significantly greater in the OA FLS. The ratio of neddylated cullin (CUL) 1 to nonneddylated CUL1 was lower in the OA FLS than the RA FLS. NUB1 overexpression decreased NF-κB nuclear translocation and IL-6 messenger RNA (mRNA) in IL-1β-stimulated the RA FLS. MLN4924 decreased CUL1 neddylation, NF-κB nuclear translocation, and IL-6 mRNA in IL-1β-stimulated the RA FLS. MLN4924 significantly decreased arthritis severity in the model with K/BxN serum-transfer arthritis.

CUL1 neddylation and NUB1 induction is dysregulated in the models with RA, which increases FLS activation. Inhibition of neddylation is an effective therapy in an animal model of arthritis. These data suggest that the neddylation system contributes to the pathogenesis of RA and that regulation of neddylation could be a novel therapeutic approach.