Pathogenesis Of Rheumatoid Arthritis Research Articles

Protein Citrullination by Peptidyl Arginine Deiminase/Arginine Deiminase Homologs in Members of the Human Microbiota and Its Recognition by Anti-Citrullinated Protein Antibodies

The human microbiome exists throughout the body, and it is essential for maintaining various physiological processes, including immunity, and dysbiotic events, which are associated with autoimmunity. Peptidylarginine deiminase (PAD) enzymes can citrullinate self-proteins related to rheumatoid arthritis (RA) that induce the production of anti-citrullinated protein antibodies (ACPAs) and lead to inflammation and joint damage. The present investigation was carried out to demonstrate the expression of homologs of PADs or arginine deiminases (ADs) and citrullinated proteins in members of the human microbiota. To achieve the objective, we used 17 microbial strains and specific polyclonal antibodies (pAbs) of the synthetic peptide derived from residues 100–200 of human PAD2 (anti-PAD2 pAb), and the recombinant fragment of amino acids 326 and 611 of human PAD4 (anti-PAD4 pAb), a human anti-citrulline pAb, and affinity ACPAs of an RA patient. Western blot (WB), enzyme-linked immunosorbent assay (ELISA), elution, and a test with Griess reagent were used. This is a cross-sectional case–control study on patients diagnosed with RA and control subjects. Inferential statistics were applied using the non-parametric Kruskal–Wallis test and Mann–Whitney U test generated in the SPSS program. Some members of phyla Firmicutes and Proteobacteria harbor homologs of PADs/ADs and citrullinated antigens that are reactive to the ACPAs of RA patients. Microbial citrullinome and homolog enzymes of PADs/ADs are extensive in the human microbiome and are involved in the production of ACPAs. Our findings suggest a molecular link between microorganisms of a dysbiotic microbiota and RA pathogenesis.

Macrophage polarization in rheumatoid arthritis: signaling pathways, metabolic reprogramming, and crosstalk with synovial fibroblasts

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by persistent synovial inflammation and progressive joint destruction. Macrophages are key effector cells that play a central role in RA pathogenesis through their ability to polarize into distinct functional phenotypes. An imbalance favoring pro-inflammatory M1 macrophages over anti-inflammatory M2 macrophages disrupts immune homeostasis and exacerbates joint inflammation. Multiple signaling pathways, including Notch, JAK/STAT, NF-κb, and MAPK, regulate macrophage polarization towards the M1 phenotype in RA. Metabolic reprogramming also contributes to this process, with M1 macrophages prioritizing glycolysis while M2 macrophages utilize oxidative phosphorylation. Redressing this imbalance by modulating macrophage polarization and metabolic state represents a promising therapeutic strategy. Furthermore, complex bidirectional interactions exist between synovial macrophages and fibroblast-like synoviocytes (FLS), forming a self-perpetuating inflammatory loop. Macrophage-derived factors promote aggressive phenotypes in FLS, while FLS-secreted mediators contribute to aberrant macrophage activation. Elucidating the signaling networks governing macrophage polarization, metabolic adaptations, and crosstalk with FLS is crucial to developing targeted therapies that can restore immune homeostasis and mitigate joint pathology in RA.

Exploring the therapeutic opportunities of potassium channels for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that affects the synovial joint, which leads to inflammation, loss of function, joint destruction, and disability. The disease biology of RA involves complex interactions between genetic and environmental factors and is strongly associated with various immune cells, and each of the cell types contributes differently to disease pathogenesis. Several immunomodulatory molecules, such as cytokines, are secreted from the immune cells and intervene in the pathogenesis of RA. In immune cells, membrane proteins such as ion channels and transporters mediate the transport of charged ions to regulate intracellular signaling pathways. Ion channels control the membrane potential and effector functions such as cytotoxic activity. Moreover, clinical studies investigating patients with mutations and alterations in ion channels and transporters revealed their importance in effective immune responses. Recent studies have shown that voltage-gated potassium channels and calcium-activated potassium channels and their subtypes are involved in the regulation of immune cells and RA. Due to the role of these channels in the pathogenesis of RA and from multiple pieces of clinical evidence, they can be considered therapeutic targets for the treatment of RA. Here, we describe the role of voltage-gated and calcium-activated potassium channels and their subtypes in RA and their pharmacological application as drug targets.

Regulation of cytokine and chemokine expression by histone lysine methyltransferase MLL1 in rheumatoid arthritis synovial fibroblasts

Histone lysine methylation is thought to play a role in the pathogenesis of rheumatoid arthritis (RA). We previously reported aberrant expression of the gene encoding mixed-lineage leukemia 1 (MLL1), which catalyzes methylation of histone H3 lysine 4 (H3K4), in RA synovial fibroblasts (SFs). The aim of this study was to elucidate the involvement of MLL1 in the activated phenotype of RASFs. SFs were isolated from synovial tissues obtained from patients with RA or osteoarthritis (OA) during total knee joint replacement. MLL1 mRNA and protein levels were determined after stimulation with tumor necrosis factor α (TNFα). We also examined changes in trimethylation of H3K4 (H3K4me3) levels in the promoters of RA-associated genes (matrix-degrading enzymes, cytokines, and chemokines) and the mRNA levels upon small interfering RNA-mediated depletion of MLL1 in RASFs. We then determined the levels of H3K4me3 and mRNAs following treatment with the WD repeat domain 5 (WDR5)/MLL1 inhibitor MM-102. H3K4me3 levels in the gene promoters were also compared between RASFs and OASFs. After TNFα stimulation, MLL1 mRNA and protein levels were higher in RASFs than OASFs. Silencing of MLL1 significantly reduced H3K4me3 levels in the promoters of several cytokine (interleukin-6 [IL-6], IL-15) and chemokine (C–C motif chemokine ligand 2 [CCL2], CCL5, C-X-C motif chemokine ligand 9 [CXCL9], CXCL10, CXCL11, and C-X3-C motif chemokine ligand 1 [CX3CL1]) genes in RASFs. Correspondingly, the mRNA levels of these genes were significantly decreased. MM-102 significantly reduced the promoter H3K4me3 and mRNA levels of the CCL5, CXCL9, CXCL10, and CXCL11 genes in RASFs. In addition, H3K4me3 levels in the promoters of the IL-6, IL-15, CCL2, CCL5, CXCL9, CXCL10, CXCL11, and CX3CL1 genes were significantly higher in RASFs than OASFs. Our findings suggest that MLL1 regulates the expression of particular cytokines and chemokines in RASFs and is associated with the pathogenesis of RA. These results could lead to new therapies for RA.

Inhibition of LSD1 via SP2509 attenuated the progression of rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial hyperplasia, pannus formation, and cartilage and bone destruction. Lysine-specific demethylase 1 (LSD1), an enzyme involved in transcriptional regulation, has an unclear role in synovial inflammation, fibroblast-like synoviocytes migration, and invasion during RA pathogenesis. In this study, we observed increased LSD1 expression in RA synovial tissues and in TNF-α-stimulated MH7A cells. SP2509, an LSD1 antagonist, directly reduced LSD1 expression and reversed the elevated levels of proteins associated with inflammation, apoptosis, proliferation, and autophagy induced by TNF-α. Furthermore, SP2509 inhibited the migratory capacity of MH7A cells, which was enhanced by TNF-α. In CIA models, SP2509 treatment ameliorated RA development, reducing the expression of pro-inflammatory cytokines and alleviating joint pathological symptoms. These findings underscore the significance of LSD1 in RA and propose the therapeutic potential of SP2509.

Triptolide regulates neutrophil function through the Hippo signaling pathway to alleviate rheumatoid arthritis disease progression

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by inflammatory changes in the joints, the etiology of which is unclear. It is now well established that regulated cell death (RCD) and migration of neutrophils play an important role in the pathogenesis of RA. Tripterygium wilfordii Hook.f (TwHF) is a total saponin extracted from the root of Tripterygium wilfordii Hook.f, a plant of the family Wesleyanaceae, which has strong anti-inflammatory and immunomodulatory effects and has been used as a basic drug in the clinical treatment of RA. Despite the good efficacy of TwHF treatment, the mechanism of action of TwHF remains unclear. Several studies have demonstrated that the drug tripterygium glycosides, in which TwHF is the main ingredient, has achieved excellent efficacy in the clinical treatment of RA. Investigations have also found that TwHF can affect cellular RCD, cell migration, cell proliferation, and the apoptosis-related Hippo signaling pathway. In this study, we first analyzed the RCD and migration differences of neutrophils in patients with RA through network pharmacology and transcriptome analysis. Subsequently, we used electron microscopy, immunofluorescence, and other methods to identify the RCD phenotype of neutrophils. In collagen-induced arthritis (CIA) model, we demonstrated that Triptolide (the main active ingredient in TwHF) could alleviate the progression of arthritis by reducing the bone destruction and the infiltration of neutrophils. Furthermore, in vitro experiments showed that Triptolide induced neutrophil apoptosis, inhibited the formation of neutrophil extracellular traps (NETs), and impeded the neutrophil migration process in a Hippo pathway-dependent manner. Taken together, these findings indicate that Triptolide has potential for treating RA and provide theoretical support for the clinical application of TwHF, as a traditional Chinese medicine, in RA.

CGAS-STING pathway in pathogenesis and treatment of osteoarthritis and rheumatoid arthritis

Osteoarthritis (OA) and Rheumatoid Arthritis (RA) are significant health concerns with notable prevalence and economic impact. RA, affecting 0.5% to 1.0% of the global population, leads to chronic joint damage and comorbidities. OA, primarily afflicting the elderly, results in joint degradation and severe pain. Both conditions incur substantial healthcare expenses and productivity losses. The cGAS-STING pathway, consisting of cyclic GMP–AMP synthase (cGAS) and stimulator of interferon genes (STING), is a crucial component of mammalian immunity. This pathway is responsible for detecting foreign DNA, particularly double-stranded DNA (dsDNA), triggering innate immune defense responses. When cGAS recognizes dsDNA, it catalyzes the synthesis of cyclic GMP–AMP (cGAMP), which then binds to and activates STING. Activated STING, in turn, initiates downstream signaling events leading to the production of interferons and other immune mediators. The cGAS-STING pathway is essential for defending against viral infections and maintaining cellular balance. Dysregulation of this pathway has been implicated in various inflammatory diseases, including arthritis, making it a target for potential therapeutic interventions. Understanding the intricate molecular signaling network of cGAS-STING in these arthritis forms offers potential avenues for targeted therapies. Addressing these challenges through improved early detection, comprehensive management, and interventions targeting the cGAS-STING pathway is crucial for alleviating the impact of OA and RA on individuals and healthcare systems. This review offers an up-to-date comprehension of the cGAS-STING pathway’s role in the development and therapeutic approaches for these arthritis types.

LC-MS-based rheumatoid arthritis serum metabolomics reveals the role of deoxyinosine in attenuating collagen-induced arthritis in mice

Rheumatoid arthritis (RA) is a persistent autoimmune condition with no identified cure currently. Recently, scientists have applied metabolomics to investigate altered metabolic profiles and unique diseases-associated metabolic signatures. Herein, we applied metabolomics approach to analyze serum samples of 41 RA patients and 42 healthy controls (HC) with the aim to characterize RA patients’ metabolic profile, investigate related underlying pathological processes, and identify target metabolites. By utilizing ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry, we found 168 proposed metabolites and 45 vital metabolic pathways. Our analysis revealed that deoxyinosine (DI), a metabolite of the purine metabolic pathway, was the most significant reduced metabolite in RA patients. Furthermore, through targeted detection, we confirmed lower concentration of DI in RA patients’ peripheral blood. Moreover, DI inhibited lipopolysaccharide-induced inflammation both in vitro and in vivo. We further assessed DI’s therapeutic potential in a collagen-induced arthritis (CIA) murine model. The results revealed that DI attenuated CIA, as evidenced by significantly lowered clinical scores of arthritis, alleviated joint swelling, and mitigated bone destruction. Moreover, we elucidated the underlying mechanism by which DI increased the population of myeloid-derived suppressor cells (MDSCs) and suppressed the proliferation of induced T cells. Collectively, these findings suggested that DI potentially ameliorated RA by inducing immunosuppressive MDSCs. The study provides key observations on RA pathogenesis and may contribute to developing novel therapeutic strategies for this debilitating condition.

Exhaled Nitric Oxide Reflects the Immune Reactions of the Airways in Early Rheumatoid Arthritis

Patients with rheumatoid arthritis (RA) have altered levels of exhaled nitric oxide (NO) compared with healthy controls. Here, we investigated whether the clinical features of and immunological factors in RA pathogenesis could be linked to the NO lung dynamics in early disease. A total of 44 patients with early RA and anti-citrullinated peptide antibodies (ACPAs), specified as cyclic citrullinated peptide 2 (CCP2), were included. Their exhaled NO levels were measured, and the alveolar concentration, the airway compartment diffusing capacity and the airway wall concentration of NO were estimated using the Högman–Meriläinen algorithm. The disease activity was measured using the Disease Activity Score for 28 joints. Serum samples were analysed for anti-CCP2, rheumatoid factor, free secretory component, secretory component containing ACPAs, antibodies against Porphyromonas gingivalis (Rgp) and total levels of IgA, IgA1 and IgA2. Significant negative correlations were found between the airway wall concentration of NO and the number of swollen joints (Rho −0.48, p = 0.004), between the airway wall concentration of NO and IgA rheumatoid factor (Rho −0.41, p = 0.017), between the alveolar concentration and free secretory component (Rho −0.35, p = 0.023) and between the alveolar concentration and C-reactive protein (Rho −0.36, p = 0.016), but none were found for anti-CCP2, IgM rheumatoid factor or the anti-Rgp levels. In conclusion, altered NO levels, particularly its production in the airway walls, may have a role in the pathogenesis of ACPA-positive RA.

Fibroblast expression of neurotransmitter receptor HTR2A associates with inflammation in rheumatoid arthritis joint

The study of neuroimmune crosstalk and the involvement of neurotransmitters in inflammation and bone health has illustrated their significance in joint-related conditions. One important mode of cell-to-cell communication in the synovial fluid (SF) is through extracellular vesicles (EVs) carrying microRNAs (miRNAs). The role of neurotransmitter receptors in the pathogenesis of inflammatory joint diseases, and whether there are specific miRNAs regulating differentially expressed HTR2A, contributing to the inflammatory processes and bone metabolism is unclear. Expression of neurotransmitter receptors and their correlated inflammatory molecules were identified in rheumatoid arthritis (RA) and osteoarthritis (OA) synovium from a scRNA-seq dataset. Immunohistochemistry staining of synovial tissue (ST) from RA and OA patients was performed for validation. Expression of miRNAs targeting HTR2A carried by SF EVs was screened in low- and high-grade inflammation RA from a public dataset and validated by qPCR. HTR2A reduction by target miRNAs was verified by miRNAs mimics transfection into RA fibroblasts. HTR2A was found to be highly expressed in fibroblasts derived from RA synovial tissue. Its expression showed a positive correlation with the degree of inflammation observed. 5 miRNAs targeting HTR2A were decreased in RA SF EVs compared to OA, three of which, miR-214-3p, miR-3120-5p and miR-615-3p, mainly derived from monocytes in the SF, were validated as regulators of HTR2A expression. The findings suggest that fibroblast HTR2A may play a contributory role in inflammation and the pathogenesis of RA. Additionally, targeting miRNAs that act upon HTR2A could present novel therapeutic strategies for alleviating inflammation in RA.

Target Role of Monocytes as Key Cells of Innate Immunity in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, systemic, and inflammatory autoimmune condition characterized by synovitis, pannus formation (with adjacent bone erosion), and joint destruction. In the perpetuation of RA, fibroblast-like synoviocytes (FLSs), macrophages, B cells, and CD4+ T-cells—specifically Th1 and Th17 cells—play crucial roles. Additionally, dendritic cells, neutrophils, mast cells, and monocytes contribute to the disease progression. Monocytes, circulating cells primarily derived from the bone marrow, participate in RA pathogenesis. Notably, CCR2 interacts with CCL2, and CX3CR1 (expressed by monocytes) cooperates with CX3CL1 (produced by FLSs), facilitating the migration involved in RA. Canonical “classical” monocytes predominantly acquire the phenotype of an “intermediate” subset, which differentially expresses proinflammatory cytokines (IL-1β, IL-6, and TNF) and surface markers (CD14, CD16, HLA-DR, TLRs, and β1- and β2-integrins). However, classical monocytes have greater potential to differentiate into osteoclasts, which contribute to bone resorption in the inflammatory milieu; in RA, Th17 cells stimulate FLSs to produce RANKL, triggering osteoclastogenesis. This review aims to explore the monocyte heterogeneity, plasticity, antigenic expression, and their differentiation into macrophages and osteoclasts. Additionally, we investigate the monocyte migration into the synovium and the role of their cytokines in RA.

OA27 Molecular divergences in CD4+ T Cells between early and refractory rheumatoid arthritis

Abstract Background/Aims Up to 21% of rheumatoid arthritis (RA) patients remain refractory to available treatments. This represents a clinical challenge due to the lack of efficacious alternatives for refractory RA (rRA) patients. Although CD4+ T cells are paramount in RA pathogenesis, a comprehensive understanding of their roles in rRA versus non-refractory RA has not been characterised. The aim of this study is to dissect the molecular differences in CD4+ T cells across these patient sub-groups and identify novel mechanisms driving rRA, which may inform tailored therapeutic strategies, using single cell multiomic analysis. Methods Primary CD4+ T-cells were isolated from PBMCs obtained from 3 rRA patients (defined as per EULAR definition of difficult-to-treat RA) and 3 treatment-naïve, early RA (ERA) patients, all seropositive with active disease (DAS28-ESR > 3.2), collected as part of the PRECISE-RA programme. Following nuclei extraction, the 10x Genomics Multiome ATAC + Gene Expression assay was used to simultaneously determine the transcriptional and chromatin landscapes from individual cells. Results Patient characteristics are reported in Table 1. 8,215 T-cells cells were clustered into 11 distinct cell states, which showed a trend towards diminished Tregs and modulated effector memory (TEM)/Th17 phenotype expressions in rRA compared to ERA patients. In ERA, expression of INPP4B, pivotal for cell growth and survival, was upregulated within naïve CD4+ T-cell subsets. ITGA4, crucial in leukocyte migration and adhesion, was elevated within a subset of naïve CD4+ T cells in early RA. ZEB2 exhibited increased expression within CD4 TEM/Th17 phenotype cells, potentially implicating divergent cellular differentiation, and migratory pathways within early RA contexts. Next, we utilised the multiomic nature of the data to functionally annotate GWAS variants, by creating peak-gene maps and overlaying RA risk SNPs. For example, an RA susceptibility SNP mapping to an intron of ANKRD55, rs7731626, was linked to the novel RA causal gene IL6ST. Furthermore, the RA SNP rs71508903, previously assigned to the ARID5B gene, was linked to the RTKN2 promoter, elucidating potential avenues for further exploration into RA pathogenesis. Conclusion These findings, to be validated in a larger cohort, suggest distinct biological mechanisms driving rRA and may help identify novel biomarkers and therapeutic avenues. Disclosure S.L. Smith: None. S. Rossi: None. R. Shukla: None. Y. Tan: None. A. Ariff: None. I. Lazar: None. K. Patel: None. C.F. Yap: None. N. Nair: None. S. Eyre: None. M.H. Buch: None. M.H. Buch: None. P. Martin: None. G. Orozco: None.

P124 Elucidating the role of risk variants in the BIM gene enhancer in T-Cell dysregulation and rheumatoid arthritis pathogenesis

Abstract Background/Aims The balance governing T-cell responses is pivotal for immune homeostasis. Disruptions to this balance may lead to aberrant behaviours, potentially resulting in autoimmunity. Rheumatoid Arthritis (RA), an autoimmune disorder primarily manifesting in the joints, is characterised by a defective immune response, resulting in chronic inflammation. Enhanced T-cell apoptosis resistance in this context can contribute to sustained activation and abnormal proliferation in a pro-inflammatory environment. Understanding these disease mechanisms could lead to improvements in clinical care. Genome-wide association studies (GWAS) have identified hundreds of single nucleotide polymorphisms (SNPs) associated with RA, preferentially enriched in non-coding, T-cell-specific putative enhancers. Enhancers are DNA elements that can regulate the transcription of specific genes, often from many kilobases away. Our previous work identified BCL2L11, or BIM, as the probable causal gene within the RA locus rs13396472, despite the GWAS variants' intronic positioning relative to ACOXL. The RA risk variant disrupts a distant enhancer regulating the BIM gene, pivotal for apoptosis. Given the role of apoptosis in immune tolerance, disruption of this pathway driven by RA risk variants could pave the way for autoimmune responses. Our aim was to investigate the effect of this enhancer on T-cell proliferation and function in an in vivo model. Methods We mapped the human RA-locus to the mouse genome and utilised CRISPR-Cas9 to delete this putative RA enhancer in mice. Two sgRNAs, combined with Cas9, were microinjected into C57BL6/J zygote pronuclei, followed by embryo transfer to pseudo-pregnant mice. PCR and Sanger sequencing confirmed enhancer deletion in pups, establishing an RA-enhancer deletion colony. To gauge cell proportion differences, murine splenocytes or thymocytes were stained with specific fluorochrome markers and analysed via a flow cytometer. For the antigen-induced arthritis (AIA) model, wildtype and RA-enhancer deletion mice were subjected to arthritis induction via intra-articular injection of methylated bovine serum albumin, following prior immunisation, and monitored for arthritis signs. Results We observed an increased CD4+CD8+ double positive (DP) T-cell population in aged mice homozygous and heterozygous for the RA-enhancer deletion, but not in younger and wild-type controls. Knockout mice exhibited visibly enlarged spleens in response to the immunisation step prior to AIA induction. Further work will establish the mechanisms underlying this and disease progression after arthritis induction. These observations underscore a potential impact this enhancer might have on immune responses and survival upon immune system alteration. Conclusion Our research indicates that perturbing mouse non-coding sequences syntenic to human GWAS loci can provide a physiological model to elucidate novel mechanisms underlying RA, potentially suggesting therapeutic targets. Future research will explore the mechanism by which the enhancer deletion leads to an increase in DP T-cells and the altered phenotype, and the implications of such a change for T- and B-cell biology and RA. Disclosure S. Rossi: None. E. Richards: None. J. Ding: None. C. Shi: None. M. Menon: None. J. Gibbs: None. R. Grencis: None. A. Adamson: None. G. Orozco: None.

Machine learning and weighted gene co-expression network analysis identify a three-gene signature to diagnose rheumatoid arthritis.

Rheumatoid arthritis (RA) is a systemic immune-related disease characterized by synovial inflammation and destruction of joint cartilage. The pathogenesis of RA remains unclear, and diagnostic markers with high sensitivity and specificity are needed urgently. This study aims to identify potential biomarkers in the synovium for diagnosing RA and to investigate their association with immune infiltration. We downloaded four datasets containing 51 RA and 36 healthy synovium samples from the Gene Expression Omnibus database. Differentially expressed genes were identified using R. Then, various enrichment analyses were conducted. Subsequently, weighted gene co-expression network analysis (WGCNA), random forest (RF), support vector machine-recursive feature elimination (SVM-RFE), and least absolute shrinkage and selection operator (LASSO) were used to identify the hub genes for RA diagnosis. Receiver operating characteristic curves and nomogram models were used to validate the specificity and sensitivity of hub genes. Additionally, we analyzed the infiltration levels of 28 immune cells in the expression profile and their relationship with the hub genes using single-sample gene set enrichment analysis. Three hub genes, namely, ribonucleotide reductase regulatory subunit M2 (RRM2), DLG-associated protein 5 (DLGAP5), and kinesin family member 11 (KIF11), were identified through WGCNA, LASSO, SVM-RFE, and RF algorithms. These hub genes correlated strongly with T cells, natural killer cells, and macrophage cells as indicated by immune cell infiltration analysis. RRM2, DLGAP5, and KIF11 could serve as potential diagnostic indicators and treatment targets for RA. The infiltration of immune cells offers additional insights into the underlying mechanisms involved in the progression of RA.

The Role of α-Enolase on the Production of Interleukin (IL)-32 in Con A-Mediated Inflammation and Rheumatoid Arthritis (RA).

Interleukin (IL)-32 is produced by T lymphocytes, natural killer cells, monocytes, and epithelial cells. IL-32 induces the production of pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α, IL-1β, IL-6, and IL-8, and IL-32 expression is highly increased in rheumatoid arthritis (RA) patients. Enolase-1 (ENO1) is a glycolytic enzyme and the stimulation of ENO1 induces high levels of pro-inflammatory cytokines in concanavalin A (Con A)-activated peripheral blood mononuclear cells (PBMCs) and macrophages in RA patients. In addition, there are many reports that anti-ENO1 antibody is correlated with the disease progression of RA. It implies that ENO1 could regulate IL-32 production during inflammation related to the pathogenesis of RA. Therefore, we investigated the role of ENO1 in IL-32 production using Con A-activated PBMCs and RA PBMCs. IL-32 expression is increased by ENO1 stimulation using real-time PCR and ELISA. In addition, we confirmed that IL-32 production was decreased in Con A-activated PBMCs and RA PBMCs pre-treated with NF-κB or p38 MAPK pathway inhibitors. Taken together, these results suggest that ENO1 plays an important role in inflammation through the induction of IL-32 production by the activation of the NF-κB and p38 MAPK pathways.

The Role of Alarmins in the Pathogenesis of Rheumatoid Arthritis, Osteoarthritis, and Psoriasis.

Alarmins are immune-activating factors released after cellular injury or death. By secreting alarmins, cells can interact with immune cells and induce a variety of inflammatory responses. The broad family of alarmins involves several members, such as high-mobility group box 1, S100 proteins, interleukin-33, and heat shock proteins, among others. Studies have found that the concentrations and expression profiles of alarmins are altered in immune-mediated diseases. Furthermore, they are involved in the pathogenesis of inflammatory conditions. The aim of this narrative review is to present the current evidence on the role of alarmins in rheumatoid arthritis, osteoarthritis, and psoriasis. We discuss their potential involvement in mechanisms underlying the progression of these diseases and whether they could become therapeutic targets. Moreover, we summarize the impact of pharmacological agents used in the treatment of these diseases on the expression of alarmins.

CCR9+CD4+ T cells are associated with disease activity in patients with rheumatoid arthritis.

An increase in CD4+ T cells in the synovium is closely linked to the pathogenesis of rheumatoid arthritis (RA). We aimed to identify the possible causes of the elevated CD4+ T cell levels and to explore the factors influencing disease activity in RA. Fifty-five RA patients, including 28 with active RA (ARA), 27 with inactive RA, and 22 healthy controls, were recruited for this study. The proportion of CCR9+CD4+ T cells and the expression of chemokine receptor 9 (CCR9) on CD4+ T cells were analyzed by flow cytometry. Enzyme-linked immunosorbent assay and chemiluminescent immunoassay were used to evaluate interleukin (IL)-17A and IL-6 levels, respectively. The proportion of CCR9+CD4+ T cells and the expression of CCR9 on CD4+ T cells increased significantly in peripheral blood (PB) and synovial fluid (SF) in ARA compared to those in inactive RA. Furthermore, SF contained more CCR9+CD4+ T cells, IL-6, and IL-17A than PB in RA patients. Moreover, CD4+ T cells in the PB of patients with RA, especially ARA, expressed more CCR9 and secreted more IL-6 and IL-17A after activation. Here, we also demonstrated that both the percentage of CCR9+ cells in CD4+ T cells and the expression of CCR9 on circulating CD4+ T cells were positively correlated with erythrocyte sedimentation rate, hypersensitive C-reactive protein, rheumatoid factor, and anti-cyclic citrullinated peptide antibody. CCR9+CD4+ T cells are elevated in PB and SF, and are associated with disease activity in patients with RA.

Unveiling the Nexus: Cellular Metabolomics Unravels the Impact of Estrogen on Nicotinamide Metabolism in Mitigating Rheumatoid Arthritis Pathogenesis.

Rheumatoid arthritis (RA) is a metabolic joint disorder influenced by hormonal regulation, notably estrogen, which plays a cytoprotective role against inflammation. While estrogen's impact on RA pathogenesis has been studied, the altered metabolite expression under estrogen's influence remains unexplored. This study investigated the changes in the metabolome of synovial fibroblasts isolated from RA patients under 17β-estradiol (E2) using the liquid chromatography with tandem mass spectrometry (LC-MS/MS) approach followed by multivariate and biological pathway analysis along with in vitro validation. Results identified 3624 m/z, among which eight metabolites were significant (p < 0.05). Nicotinate and nicotinamide metabolism was found to be highly correlated with the treatment of E2, with metabolites NAD+ and 1-methynicotinamide (1-MNA) upregulated by E2 induction in RA-FLS. PharmMapper analysis identified potential gene targets of 1-MNA, which were further matched with RA gene targets, and thus, STAT1, MAPK14, MMP3, and MMP9 were concluded to be the common targets. E2 treatment affected the expression of these gene targets and ameliorated the development of oxidative stress associated with RA inflammation, which can be attributed to increased concentration of 1-MNA. Thus, an LC-MS/MS-based metabolomics study revealed the prominent role of estrogen in preventing inflammatory progression in RA by altering metabolite concentration, which can support its therapeutic capacity in remitting RA.

Functional Significance of miR-4693-5p in Targeting HIF1α and Its Link to Rheumatoid Arthritis Pathogenesis.

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that causes joint inflammation and destruction with an unknown origin. Our study aims to elucidate the molecular mechanism behind HIF1α overexpression in RA. Dysregulated miRNA expressions are known to influence gene behavior, thereby enhancing cell proliferation, inflammation, and resistance to apoptosis, contributing to RA development. Our earlier finding indicated that exogenous miRNA similar to miR-4693-5p may modulate RA-related targets. However, the specific role of miR-4693-5p and its targets in RA remain unexplored. In this study, we found that miR-4693-5p was significantly reduced in PBMCs of RA patients, with evidence suggesting it targets the 3' UTR of HIF1α, thereby potentially contributing to its overexpression in RA. In vitro overexpression of miR-4693-5p leads to the knockdown of HIF1α, resulting in inhibited expression of Survivin to disrupt apoptosis resistance, inflammation suppression, and a reduction in the total cellular ROS response in SW982 and RAFLS cells. The results were validated using the CIA Rat model. In conclusion, this study provides a crucial foundation for understanding the functional role of miR-4693-5p. These findings improve our understanding and provide novel insights into the molecular mechanisms underlying RA pathogenesis.

TRPM7 facilitates fibroblast-like synoviocyte proliferation, metastasis and inflammation through increasing IL-6 stability via the PKCα-HuR axis in rheumatoid arthritis

Transient receptor potential melastatin 7 (TRPM7) is a cation channel that plays a role in the progression of rheumatoid arthritis (RA), yet its involvement in synovial hyperplasia and inflammation has not been determined. We previously reported that TRPM7 affects the destruction of articular cartilage in RA. Herein, we further confirmed the involvement of TRPM7 in fibroblast-like synoviocyte (FLS) proliferation, metastasis and inflammation. We observed increased TRPM7 expression in FLSs derived from human RA patients. Pharmacological inhibition of TRPM7 protected primary RA-FLSs from proliferation, metastasis and inflammation. Furthermore, we found that TRPM7 contributes to RA-FLS proliferation, metastasis and inflammation by increasing the intracellular Ca2+ concentration. Mechanistically, the PKCα-HuR axis was demonstrated to respond to Ca2+ influx, leading to TRPM7-mediated RA-FLS proliferation, metastasis and inflammation. Moreover, HuR was shown to bind to IL-6 mRNA after nuclear translocation, which could be weakened by TRPM7 channel inhibition. Additionally, adeno-associated virus 9-mediated TRPM7 silencing is highly effective at alleviating synovial hyperplasia and inflammation in adjuvant-induced arthritis rats. In conclusion, our findings unveil a novel regulatory mechanism involved in the pathogenesis of RA and suggest that targeting TRPM7 might be a potential strategy for the prevention and treatment of RA.