Epigenetic alterations in rheumatoid arthritis fibroblast-like synoviocytes

Silencing of transient receptor potential canonical channel 4 inhibits endothelial progenitor cell angiogenesis by suppressing VEGF and SDF-1

OBJECTIVES

Endothelial progenitor cells (EPCs) play a crucial role in acquired angiogenesis and endothelial injury repair. Transient receptor potential canonical channel 4 (TRPC4), a key component of store-operated calcium channels, is essential for EPC function. While the role of TRPCs has been clarified in vascular diseases, the relationship between TRPC4 and EPC function, along with the underlying molecular mechanisms, remains unclear and requires further elucidation.

METHODS

EPCs were isolated from canine bone marrow and identified by morphology and flow cytometry. TRPC4 was transfected into EPCs using lentivirus or negative control, and its expression was assessed using real-time polymerase chain reaction (RT-PCR). Proliferation, migration, and tube formation were evaluated using Cell Counting Kit-8 (CCK-8), Transwell, and Matrigel assays, respectively. Levels of vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1 (SDF-1) were measured using enzyme-linked immunosorbent assay (ELISA).

RESULTS

TRPC4 mRNA expression was significantly reduced in TRPC4-short hairpin RNA (shRNA) transfected EPCs compared to the normal control (NC)-shRNA groups. Migration and tube formation were significantly decreased after TRPC4 silencing, while proliferation showed no difference. Additionally, levels of SDF-1 and VEGF in EPCs were markedly reduced following TRPC4 silencing.

CONCLUSION

TRPC4 plays a crucial role in regulating angiogenesis in EPCs. Silencing of TRPC4 can lead to decreased angiogenesis by inhibiting VEGF and SDF-1 expression, suggesting that TRPC4 knockdown might be a novel therapeutic strategy for vascular diseases.

Joint-specific rheumatoid arthritis fibroblast-like synoviocyte regulation identified by integration of chromatin access and transcriptional activity

The mechanisms responsible for the distribution and severity of joint involvement in rheumatoid arthritis (RA) are not known. To explore whether site-specific fibroblast-like synoviocyte (FLS) biology might be associated with location-specific synovitis and explain the predilection for hand (wrist/metacarpal phalangeal joints) involvement in RA, we generated transcriptomic and chromatin accessibility data from FLS to identify the transcription factors and pathways. Networks were constructed by integration of chromatin accessibility and gene expression data. Analysis revealed joint-specific patterns of FLS phenotype, with proliferative, migratory, proinflammatory, and matrix-degrading characteristics observed in resting FLS derived from the hand joints compared with hip or knee. TNF stimulation amplified these differences, with greater enrichment of proinflammatory and proliferative genes in hand FLS compared with hip and knee FLS. Hand FLS also had the greatest expression of markers associated with an "activated" state relative to the "resting" state, with the greatest cytokine and MMP expression in TNF-stimulated hand FLS. Predicted differences in proliferation and migration were biologically validated with hand FLS exhibiting greater migration and cell growth than hip or knee FLS. Distinctive joint-specific FLS biology associated with a more aggressive inflammatory response might contribute to the distribution and severity of joint involvement in RA.

Joint-specific rheumatoid arthritis fibroblast-like synoviocyte regulation identified by integration of chromatin access and transcriptional activity

The mechanisms responsible for the distribution and severity of joint involvement in rheumatoid arthritis (RA) are not known. To explore whether site-specific FLS biology might be associated with location-specific synovitis and explain the predilection for hand (wrist/metacarpal phalangeal joints) involvement in RA, we generated transcriptomic and chromatin accessibility data from FLS to identify the transcription factors (TFs) and pathways. Networks were constructed by integration of chromatin accessibility and gene expression data. Analysis revealed joint-specific patterns of FLS phenotype, with proliferative, migratory, proinflammatory, and matrix-degrading characteristics observed in resting FLS derived from the hand joints compared with hip or knee. TNF-stimulation amplified these differences, with greater enrichment of proinflammatory and proliferative genes in hand FLS compared with hip and knee FLS. Hand FLS also had the greatest expression of markers associated with an 'activated' state relative to the 'resting' state, with the greatest cytokine and MMP expression in TNF-stimulated hand FLS. Predicted differences in proliferation and migration were biologically validated with hand FLS exhibiting greater migration and cell growth than hip or knee FLS. Distinctive joint-specific FLS biology associated with a more aggressive inflammatory response might contribute to the distribution and severity of joint involvement in RA.

Long noncoding RNA/circular RNA regulates competitive endogenous RNA networks in rheumatoid arthritis: molecular mechanisms and traditional Chinese medicine therapeutic significances

Rheumatoid arthritis (RA) is a systemic and autoimmune disease that is mainly featured abnormal fibroblast-like synoviocyte (FLS) proliferation and inflammatory cell infiltration. Abnormal expression or function of long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) are closely related to human diseases, including RA. There has been increasing evidence showing that in the competitive endogenous RNA (ceRNA) networks, both lncRNA and circRNA are vital in the biological functions of cells. Nevertheless, the exact mechanism of ceRNA in RA remains to be investigated. Herein, we summarized the molecular potencies of lncRNA/circRNA-mediated ceRNA networks in RA, with emphasis on the phenotypic regulation of ceRNA in the progression of RA, including regulation of proliferation, invasion, inflammation and apoptosis, as well as the role of ceRNA in traditional Chinese medicine (TCM) in the treatment of RA. In addition, we also discussed the future direction and potential clinical value of ceRNA in the treatment of RA, which may provide potential reference value for clinical trials of TCM therapy for the treatment of RA.Key messagesLong noncoding RNA/circular RNA can work as the competitive endogenous RNA sponge and participate in the pathogenesis of rheumatoid arthritis.Traditional Chinese medicine and its agents have shown potential roles in the prevention and treatment of rheumatoid arthritis via competitive endogenous RNA.

A study of the association between Galectin-9 gene (LGALS9) polymorphisms and rheumatoid arthritis in Egyptian patients

Background

Rheumatoid arthritis (RA) is an incessant synovial inflammation of an autoimmune origin, destroying articular cartilages and bones. Galectins are an evolutionarily conserved family of immune-modulatory animal lectins detected in a number of immune cells like T cells, fibroblasts and macrophages. Galectin 9 (Gal-9) has been the subject of many studies for being linked to regulation of both innate and adaptive immune reactions. The objective of the study was to evaluate the link between the Galectin-9 gene (LGALS9) polymorphisms and the susceptibility of RA in Egyptian patients, as well as, detection of the serum level of Gal-9 in RA and its association with LGALS9 polymorphisms, the activity of RA and radiological damage.

Methods

A study of 85 participants; group (I): 60 RA cases and group (II): 25 apparently healthy subjects. RA Disease activity index (DAS-28) and Larsen index score were assessed. LGALS9 gene and serum Gal-9 were investigated.

Results

rs4239242 TT genotype and T allele occurred more frequently in RA cases than controls with a significant difference (P = 0.006; P < 0.001 respectively). Gal-9 level was significantly higher among RA cases than control group (P = 0.017). The Gal-9 level showed negative significant correlations with DAS-28 and Larsen score (P < 0.001).

Conclusion

RA is strongly linked to genetic alterations in the LGALS9 gene and the single nucleotide polymorphism (SNP) rs4239242 TT genotype in the Egyptian population. RA cases in remission or those with low disease activity had higher levels of serum Gal-9 in comparison to cases with moderate and high disease activity and this would be promising in the future of RA treatment.

HDAC2 exacerbates rheumatoid arthritis progression via the IL-17-CCL7 signaling pathway

Histone deacetylases (HDACs) have been reported to regulate the immune response in rheumatoid arthritis (RA). The current study aimed to explore key HDACs and their molecular mechanism in RA. First, the expression of HDAC1, HDAC2, HDAC3 and HDAC8 in RA synovial tissue was determined by qRT-PCR. The effects of HDAC2 on the proliferation, migration, invasion, and apoptosis of fibroblast-like synoviocytes (FLS) in vitro were studied. Furthermore, collagen-induced arthritis (CIA) rat models were established to evaluate the severity of arthritis in joints, and the levels of inflammatory factors were examined by immunohistochemistry staining, ELISA, and qRT-PCR. Transcriptome sequencing was used to screen differentially expressed genes (DEGs) with HDAC2 silencing in the synovial tissue of CIA rat, and downstream signaling pathways were predicted by enrichment analysis. The results showed that HDAC2 was highly expressed in the synovial tissue of RA patients and CIA rats. Overexpressed HDAC2 promoted FLS proliferation, migration, and invasion and inhibited FLS apoptosis in vitro, resulting in secretion of inflammatory factors and RA exacerbation in vivo. There were 176 DEGs, including 57 downregulated and 119 upregulated genes, after silencing HDAC2 in CIA rats. DEGs were primarily enriched in Platinum drug resistance, IL-17 as well as the PI3K-Akt signaling pathways. CCL7, which was implicated in the IL-17 signaling pathway, was downregulated after HDAC2 silencing. Furthermore, CCL7 overexpression aggravated the development of RA, which was demonstrated to be effectively attenuated by HDAC2 suppression. In conclusion, this study demonstrated that HDAC2 exacerbated the progression of RA by regulating the IL-17-CCL7 signaling pathway, suggesting that HDAC2 may be a promising therapeutic target for RA treatment.

Circ_0000479 promotes proliferation, invasion, migration and inflammation and inhibits apoptosis of rheumatoid arthritis fibroblast-like synoviocytes via miR-766/FKBP5 axis

Circular RNAs have been demonstrated to play a critical role in the progression of autoimmune diseases. This study aimed to investigate the function of circ_0000479 in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLSs). Circ_0000479 was found to be upregulated in RA-FLSs. Flow cytometry analysis, cell counting Kit-8, transwell, wound-healing and enzyme-linked immunosorbent assays were conducted to evaluate RA-FLS apoptosis, proliferation, invasion, migration and inflammation. The results confirmed that circ_0000479 knockdown suppressed pathogenic properties of RA-FLSs. Through bioinformatics analysis and screening, we obtained 18 miRNAs that can bind to circ_0000479, of which miR-766 was most significantly up-regulated after circ_0000479 knockdown. MiR-766 was confirmed to be down-regulated in RA-FLSs and the combination between circ_0000479 and miR-766 was verified by dual-luciferase reporter assays. Moreover, the inhibitory effect of circ_0000479 knockdown in RA-FLS progression was attenuated by miR-766 inhibitor. By intersecting the target genes of miR-766 with the up-regulated genes in RA, we obtained 8 genes, of which FKBP5 was most significantly down-regulated after miR-766 overexpression. The results of dual-luciferase reporter assays also verified that FKBP5 was the target gene of miR-766. In addition, FKBP5 overexpression abated the inhibition of RA-FLS progression caused by circ_0000479 silencing. In summary, circ_0000479 binds to miR-766 to promote RA progression via FKBP5.

Isochlorogenic Acid C Restrains Erk/JNK/NF-κB Signaling to Alleviate Inflammatory Response and Promote Cell Apoptosis

Isochlorogenic acid C (ICAC) is found in a variety of natural foods and medicinal plant materials. This study aims to validate the biological activity of isochlorogenic acid C in limiting inflammation by the Erk/JNK/NF-κB pathway. In this study, TNF-α-induced human fibroblast-like synoviocytes and collagen-induced arthritis animal models were used to perceive the potential anti-inflammation mechanism of ICAC. The role of isochlorogenic acid C was evaluated by observing the migration, invasion ability, and apoptotic activity of TNF-α-induced fibroblast-like synoviocytes cells in humans and analysing foot swelling, joint index, and histopathological changes in a collagen-induced RA animal model. The results reveal that ICAC inhibited the proliferation of human fibroblast-like synoviocytes and promoted their apoptosis. ICAC also blocked the nuclear transfer of NF-κB, Erk, and JNK. It was observed that ICAC significantly inhibited the degree of posterior foot swelling in CIA, reducing arthritis scores, bone tissue injury, and articular synovitis. ICAC may promote cell apoptosis and inhibit the hyperactivation of inflammatory cells to alleviate inflammation-induced synovial proliferation through the Erk/JNK/NF-κB pathway.

Signaling pathways in rheumatoid arthritis: implications for targeted therapy

Rheumatoid arthritis (RA) is an incurable systemic autoimmune disease. Disease progression leads to joint deformity and associated loss of function, which significantly impacts the quality of life for sufferers and adds to losses in the labor force. In the past few decades, RA has attracted increased attention from researchers, the abnormal signaling pathways in RA are a very important research field in the diagnosis and treatment of RA, which provides important evidence for understanding this complex disease and developing novel RA-linked intervention targets. The current review intends to provide a comprehensive overview of RA, including a general introduction to the disease, historical events, epidemiology, risk factors, and pathological process, highlight the primary research progress of the disease and various signaling pathways and molecular mechanisms, including genetic factors, epigenetic factors, summarize the most recent developments in identifying novel signaling pathways in RA and new inhibitors for treating RA. therapeutic interventions including approved drugs, clinical drugs, pre-clinical drugs, and cutting-edge therapeutic technologies. These developments will hopefully drive progress in new strategically targeted therapies and hope to provide novel ideas for RA treatment options in the future.

Long Noncoding RNA HAFML Promotes Migration and Invasion of Rheumatoid Fibroblast-like Synoviocytes

The aggressive phenotype exhibited by fibroblast-like synoviocytes (FLSs) is critical for the progression of joint destruction in rheumatoid arthritis (RA). Long noncoding RNAs (lncRNAs) have crucial roles in the pathogenesis of diverse disorders; however, few have been identified that might be able to control the joint damage in RA. In this study, we identified an lncRNA, ENST00000509194, which was expressed at abnormally high levels in FLSs and synovial tissues from patients with RA. ENST00000509194 positively modulates the migration and invasion of FLSs by interacting with human Ag R (HuR, also called ELAVL1), an RNA-binding protein that mainly stabilizes mRNAs. ENST00000509194 binds directly to HuR in the cytoplasm to form a complex that promotes the expression of the endocytic adaptor protein APPL2 by stabilizing APPL2 mRNA. Knockdown of HuR or APPL2 impaired the migration and invasion of RA FLSs. Given its close association with HuR and FLS migration, we named ENST00000509194 as HAFML (HuR-associated fibroblast migratory lncRNA). Our findings suggest that an increase in synovial HAFML might contribute to FLS-mediated rheumatoid synovial aggression and joint destruction, and that the lncRNA HAFML might be a potential therapeutic target for dysregulated fibroblasts in a wide range of diseases.

Protein arginine methyltransferase 1 upregulates matrix metalloproteinase-2/9 expression via Zeste Homolog 2 to promote human rheumatoid arthritis fibroblast-like synovial cell survival and metastasis

OBJECTIVE

To explore the role of protein arginine methyltransferase 1 (PRMT1) in the development of rheumatoid arthritis (RA).

METHODS

Fibroblast-like synoviocytes (FLS) were isolated from synovial tissues, cultured and transfected with plasmid vector or short hairpin RNA (shRNA). The morphology and surface markers of FLS were investigated by light microscopy and flow cytometry. The expression levels of PRMT1, Zeste Homolog 2 (EZH2), matrix metalloproteinase-2 (MMP-2) and MMP-9 were detected by real-time polymerase chain reaction and Western blotting. Cell viability was tested by MTT assay, cell proliferation was assessed by EdU assay, cell invasion was evaluated by Transwell invasion test, cell migration was detected by wound healing assay, and cell apoptosis was detected by flow cytometry.

RESULTS

The expression of PRMT1 was elevated in RA synovial tissues compared with control tissues. FLS from control tissues showed a lower level of PRMT1 than FLS from RA tissues, and FLS from RA tissues had a stronger ability of cell survival and metastasis than those from control tissues. When silencing PRMT1 expression, FLS from RA tissues showed a decreased ability of cell survival and metastasis. Additionally, FLS from RA tissues expressed a higher level of MMP-2 and MMP-9. When silencing PRMT1 expression, the expression of MMP-2 and MMP-9 of FLS was suppressed. Furthermore, the effect of PRMT1 on FLS was mediated by EZH2.

CONCLUSION

We found that PRMT1 had an overall effect on FLS via EZH2, which contributed to the development of RA. Hence, PRMT1 and EZH2 provide potential targets for RA treatment.

Pathogenesis of chronic chikungunya arthritis: Resemblances and links with rheumatoid arthritis

Chikungunya virus (CHIKV) infection results from transmission by the mosquito vector. Following an incubation period of 5-7 days, patients develop an acute febrile illness, chikungunya fever (CHIKF), characterized by high fevers, maculopapular rash, headaches, polyarthritis/arthralgias, myalgias, nausea, vomiting, and diarrhea. Joint pain is often severe, and most often involves the hands, the wrists, the ankles, and the metatarsal-phalangeal joints of the feet. Many patients recover within several weeks, but up to 50% develop chronic joint pain and swelling for more than 12 weeks, then we refer to these symptoms as chronic chikungunya arthritis (CCA). The pathogenesis of CCA is not well understood. In this article, we suggest that mesenchymal stem cells (MSCs) may play an important role in this pathogenesis. This heterogeneous group of multipotent cells, morphologically similar to fibroblasts, may undergo epigenetic changes capable of generating aberrant progenies. However, we believe that there is no need for a latent infection. In our pathogenic hypothesis, CHIKV infection of MSCs would cause epigenetic changes both in MSCs themselves and in their progenies, without the need for reactivation of dormant viruses.

Predictive value of drug efficacy by M6A modification patterns in rheumatoid arthritis patients

Background

Rheumatoid arthritis is a highly heterogeneous autoimmune disease characterized by unpredictable disease flares and significant differences in therapeutic response to available treatments. One possible reason for poor efficacy is that it cannot be treated accurately due to no optimal stratification for RA patients.

Objective

This study aims to construct an RA classification model by m6A characters and further predict response to medication.

Methods

Twenty m6A regulators were used to construct a random forest diagnosis model, and RNA-seq analysis was employed for external validation. The RNA modification patterns mediated by 20 m6A regulators were systematically evaluated in 1191 RA samples and explored different molecular clusters associated with other immune microenvironment characteristics and biological pathways. Then, we established an m6A score model to quantify the m6A modification patterns. The model was applied to patients at baseline to test the association between m6Ascore and infliximab responsiveness.

Results

The m6A diagnosis model showed good discriminatory ability in distinguishing RA. Patients with RA were classified into three clusters with distinct molecular and cellular signatures. Cluster A displayed strongly activated inflammatory cells and pathways. Specific innate lymphocytes occupied cluster B. Cluster C was mainly enriched in prominent adaptive lymphocytes and NK-mediated cytotoxicity signatures with the highest m6A score. Patients with a low m6Ascore exhibited significantly infliximab therapeutic benefits compared with those with a high m6Ascore (p< 0.05).

Conclusion

Our study is the first to provide a comprehensive analysis of m6A modifications in RA, which provides an innovative patient stratification framework and potentially enables improved therapeutic decisions.

Epigenetic Regulation of Nutrient Transporters in Rheumatoid Arthritis Fibroblast-like Synoviocytes

OBJECTIVE

Since previous studies indicate that metabolism is altered in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS), we undertook this study to determine if changes in the genome-wide chromatin and DNA states in genes associated with nutrient transporters could help to identify activated metabolic pathways in RA FLS.

METHODS

Data from a previous comprehensive epigenomic study in FLS were analyzed to identify differences in genome-wide states and gene transcription between RA and osteoarthritis. We utilized the single nearest genes to regions of interest for pathway analyses. Homer promoter analysis was used to identify enriched motifs for transcription factors. The role of solute carrier transporters and glutamine metabolism dependence in RA FLS was determined by small interfacing RNA knockdown, functional assays, and incubation with CB-839, a glutaminase inhibitor. We performed 1 H nuclear magnetic resonance to quantify metabolites.

RESULTS

The unbiased pathway analysis demonstrated that solute carrier-mediated transmembrane transport was one pathway associated with differences in at least 4 genome-wide states or gene transcription. Thirty-four transporters of amino acids and other nutrients were associated with a change in at least 4 epigenetic marks. Functional assays revealed that solute carrier family 4 member 4 (SLC4A4) was critical for invasion, and glutamine was sufficient as an alternate source of energy to glucose. Experiments with CB-839 demonstrated decreased RA FLS invasion and proliferation. Finally, we found enrichment of motifs for c-Myc in several nutrient transporters.

CONCLUSION

Our findings demonstrate that changes in the epigenetic landscape of genes are related to nutrient transporters, and metabolic pathways can be used to identify RA-specific targets, including critical solute carrier transporters, enzymes, and transcription factors, to develop novel therapeutic agents.

Creating an Optimal In Vivo Environment to Enhance Outcomes Using Cell Therapy to Repair/Regenerate Injured Tissues of the Musculoskeletal System

Following most injuries to a musculoskeletal tissue which function in unique mechanical environments, an inflammatory response occurs to facilitate endogenous repair. This is a process that usually yields functionally inferior scar tissue. In the case of such injuries occurring in adults, the injury environment no longer expresses the anabolic processes that contributed to growth and maturation. An injury can also contribute to the development of a degenerative process, such as osteoarthritis. Over the past several years, researchers have attempted to use cellular therapies to enhance the repair and regeneration of injured tissues, including Platelet-rich Plasma and mesenchymal stem/medicinal signaling cells (MSC) from a variety of tissue sources, either as free MSC or incorporated into tissue engineered constructs, to facilitate regeneration of such damaged tissues. The use of free MSC can sometimes affect pain symptoms associated with conditions such as OA, but regeneration of damaged tissues has been challenging, particularly as some of these tissues have very complex structures. Therefore, implanting MSC or engineered constructs into an inflammatory environment in an adult may compromise the potential of the cells to facilitate regeneration, and neutralizing the inflammatory environment and enhancing the anabolic environment may be required for MSC-based interventions to fulfill their potential. Thus, success may depend on first eliminating negative influences (e.g., inflammation) in an environment, and secondly, implanting optimally cultured MSC or tissue engineered constructs into an anabolic environment to achieve the best outcomes. Furthermore, such interventions should be considered early rather than later on in a disease process, at a time when sufficient endogenous cells remain to serve as a template for repair and regeneration. This review discusses how the interface between inflammation and cell-based regeneration of damaged tissues may be at odds, and outlines approaches to improve outcomes. In addition, other variables that could contribute to the success of cell therapies are discussed. Thus, there may be a need to adopt a Precision Medicine approach to optimize tissue repair and regeneration following injury to these important tissues.

Potential Target Analysis of Triptolide Based on Transcriptome-Wide m6A Methylome in Rheumatoid Arthritis

Triptolide (TP), a major active component of the herb Tripterygium wilfordii Hook F (TwHF), has been shown to exert therapeutic potential against rheumatoid arthritis (RA). However, its molecular mechanism of action has not been fully elucidated. This study aimed to analyze the potential target of TP based on the discovery of differentially methylated and expressed genes (DMEGs) in RA using methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq). Five RA samples and ten control samples were obtained from China-Japan Friendship Hospital. The various levels of m⁶A methylation and genes expressed in the RA and control groups were compared by MeRIP-seq and RNA-seq. Bioinformatics explorations were also performed to explore the enriched biological roles and paths of the differentially expressed m⁶A methylation and genes. Molecular networks between TP target proteins and DMEGs were performed using Ingenuity Pathway Analysis (IPA) software. Potential target of TP was determined with Gene Expression Omnibus (GEO) database mining, molecular docking, and in vitro experiment validation. In total, 583 dysregulated m⁶A peaks, of which 295 were greatly upregulated and 288 were greatly downregulated, were identified. Similarly, 1,570 differentially expressed genes were identified by RNA-seq, including 539 upregulated and 1,031 downregulated genes. According to the deeper joint exploration, the m⁶A methylation and mRNA expression degrees of 35 genes varied greatly. Molecular networks between TP target proteins and DMEGs were constructed, and the results revealed that tubulin beta-2A chain (TUBB2A), insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3), cytoplasmic dynein 1 intermediate chain 1 (DYNC1I1), and FOS-like 1 (FOSL1) were the most relevant genes that correlated with the target proteins of TP. The results of the GEO database showed that the gene expression of IGF2BP3 was increased in RA synovial tissue and consistent with the trend of our sequencing results of RA PBMCs. Molecular docking and in vitro experiment suggested that TP and IGF2BP3 had a high binding affinity and TP could decrease the mRNA expression of IGF2BP3 in PBMCs and MH7A.This research established a transcriptional map of m⁶A in RA PBMCs and displayed the hidden association between RNA methylation alterations and associated genes in RA. IGF2BP3 might be a potential therapeutic target of TP during RA treatment.

Pro Nerve Growth Factor and Its Receptor p75NTR Activate Inflammatory Responses in Synovial Fibroblasts: A Novel Targetable Mechanism in Arthritis

We have recently provided new evidence for a role of p75NTR receptor and its preferential ligand proNGF in amplifying inflammatory responses in synovial mononuclear cells of chronic arthritis patients. In the present study, to better investigate how activation of the p75NTR/proNGF axis impacts synovial inflammation, we have studied the effects of proNGF on fibroblast-like synoviocytes (FLS), which play a central role in modulating local immune responses and in activating pro-inflammatory pathways. Using single cell RNA sequencing in synovial tissues from active and treatment-naïve rheumatoid arthritis (RA) patients, we demonstrated that p75NTR and sortilin, which form a high affinity receptor complex for proNGF, are highly expressed in PRG4pos lining and THY1posCOL1A1pos sublining fibroblast clusters in RA synovia but decreased in RA patients in sustained clinical remission. In ex vivo experiments we found that FLS from rheumatoid arthritis patients (RA-FLS) retained in vitro a markedly higher expression of p75NTR and sortilin than FLS from osteoarthritis patients (OA-FLS). Inflammatory stimuli further up-regulated p75NTR expression and induced endogenous production of proNGF in RA-FLS, leading to an autocrine activation of the proNGF/p75NTR pathway that results in an increased release of pro-inflammatory cytokines. Our data on the inhibition of p75NTR receptor, which reduced the release of IL-1β, IL-6 and TNF-α, further confirmed the key role of p75NTR activation in regulating inflammatory cytokine production. In a set of ex vivo experiments, we used RA-FLS and cultured them in the presence of synovial fluids obtained from arthritis patients that, as we demonstrated, are characterized by a high concentration of proNGF. Our data show that the high levels of proNGF present in inflamed synovial fluids induced pro-inflammatory cytokine production by RA-FLS. The blocking of NGF binding to p75NTR using specific inhibitors led instead to the disruption of this pro-inflammatory loop, reducing activation of the p38 and JNK intracellular pathways and decreasing inflammatory cytokine production. Overall, our data demonstrate that an active proNGF/p75NTR axis promotes pro-inflammatory responses in synovial fibroblasts, thereby contributing to chronic synovial inflammation, and point to the possible use of p75NTR inhibitors as a novel therapeutic approach in chronic arthritis.

14-3-3η Promotes Invadosome Formation via the FOXO3-Snail Axis in Rheumatoid Arthritis Fibroblast-like Synoviocytes

Erosive destruction of joint structures is a critical event in the progression of rheumatoid arthritis (RA), in which fibroblast-like synoviocytes (FLS) are the primary effectors. We previously reported that the ability of RA FLS to degrade extracellular matrix (ECM) components depends on the formation of actin-rich membrane protrusions, called invadosomes, through processes that remain elusive. 14-3-3η belongs to a family of scaffolding proteins involved in a wide range of cellular functions, and its expression is closely related to joint damage and disease activity in RA patients. In this study, we sought to assess the role of 14-3-3η in joint damage by examining its contribution to the invadosome formation phenotype of FLS. Using human primary FLS, we show that 14-3-3η expression is closely associated with their ability to form invadosomes. Furthermore, knockdown of 14-3-3η using shRNAs decreases the level of invadosome formation in RA FLS, whereas addition of the recombinant protein to FLS from healthy individuals promotes their formation. Mechanistic studies suggest that 14-3-3η regulates invadosome formation by increasing Snail expression, a mechanism that involves nuclear exclusion of the transcription repressor FOXO3. Our results implicate the 14-3-3η–FOXO3–Snail axis in promoting the aggressive ECM-degrading phenotype of RA FLS, and suggest a role for this scaffolding protein in cartilage degradation.

Ellagic Acid Alleviates Rheumatoid Arthritis in Rats through Inhibiting MTA1/HDAC1-Mediated Nur77 Deacetylation

Ellagic acid (EA) was reported to play protective roles in rheumatoid arthritis (RA). It was found that the level of metastasis-associated gene 1 (MTA1)/histone deacetylase 1 (HDAC1) protein complex was downregulated by polyphenols in several human disorders. Notably, inhibition of MTA1 or HDAC1 has anti-inflammatory effects on RA. Therefore, our study is aimed at investigating whether EA prevents RA progression through regulating the MTA1/HDAC1 complex. Herein, the human fibroblast-like synoviocyte (FLS) cell line MH7A was treated with TNF-α to induce an inflammation model in vitro and then incubated with different concentrations of EA. Western blot analysis showed that EA reduced MTA1 expression in a dose-dependent manner in MH7A cells. Then, TNF-α-treated MH7A cells were incubated with EA alone or together with MTA1 overexpression plasmid (pcDNA-MTA1), and we found that EA inhibited proliferation, inflammation cytokine levels, and oxidative stress marker protein levels and promoted apoptosis in MH7A cells, while MTA1 overexpression abolished these effects. Moreover, coimmunoprecipitation assay verified the interaction between MTA1 and HDAC1. EA downregulated the MTA1/HDAC1 complex in MH7A cells. MTA1 knockdown inhibited proliferation, inflammation, and oxidative stress and promoted apoptosis in MH7A cells, while HDAC1 overexpression reversed these effects. Moreover, chromatin immunoprecipitation assay indicated that EA inhibited HDAC1-mediated Nur77 deacetylation. Rescue experiments demonstrated that Nur77 knockdown reversed the effects of EA on MH7A cell biological behaviors. Additionally, EA treatment attenuated arthritis index, paw swelling, synovial hyperplasia, and inflammation in collagen-induced arthritis (CIA) rats. In conclusion, EA inhibited proliferation, inflammation, and oxidative stress and promoted apoptosis in MH7A cells and alleviated the severity of RA in CIA rats though downregulating MTA1/HDAC1 complex and promoting HDAC1 deacetylation-mediated Nur77 expression.

Epigenetic Regulation (Including Micro-RNAs, DNA Methylation and Histone Modifications) of Rheumatoid Arthritis: A Systematic Review

The inflammatory reaction in rheumatoid arthritis (RA) is controlled by major epigenetic modifications that modulate the phenotype of synovial and immune cells. The aim of this work was to perform a systematic review focusing on miR expression, DNA methylation and histone modifications in RA. We demonstrated that, in human samples, the expressions of miR-155, miR-146a and miR-150 were significantly decreased while the expression of miR-410-3p was significantly increased in the RA group. Moreover, miR-146a significantly decreased pro-autoimmune IL-17 cytokine expression in RA. In a murine model, miR-34a inhibition can ameliorate the arthritis score. However, this evidence remain critically insufficient to support current therapeutic applications in RA patients.

Therapeutic effect of neohesperidin on TNF-α-stimulated human rheumatoid arthritis fibroblast-like synoviocytes

During the pathogensis of rheumatoid arthritis (RA), activated RA fibroblast-like synoviocytes (RA-FLSs) combines similar proliferative features as tumor and inflammatory features as osteoarthritis, which eventually leads to joint erosion. Therefore, it is imperative to research and develop new compounds, which can effectively inhibit abnormal activation of RA-FLSs and retard RA progression. Neohesperidin (Neo) is a major active component of flavonoid compounds with anti-inflammation and anti-oxidant properties. In this study, the anti-inflammation, anti-migration, anti-invasion, anti-oxidant and apoptosis-induced effects of Neo on RA-FLSs were explored to investigate the underlying mechanism. The results suggested that Neo decreased the levels of interleukin IL-1β, IL-6, IL-8, TNF-α, MMP-3, MMP-9 and MMP-13 in FLSs. Moreover, Neo blocked the activation of the MAPK signaling pathway. Furthermore, treatment with Neo induced the apoptosis of FLSs, and inhibited the migration of FLSs. It was also found that Neo reduced the accumulation of reactive oxygen species (ROS) induced by TNF-α. Taken together, our results highlighted that Neo may act as a potential and promising therapeutic drug for the management of RA.

[Effects of Sidaxue, a Miao ethnomedicine recipe, on apoptosis and pyrolysis of human fibroblast-like synovial cells in rheumatoid arthritis]

OBJECTIVE

To investigate the effects of Sidaxue (SX), a recipe in Miao ethnomedicine, on apoptosis and pyrolysis of human fibroblast-like synovial cells in rheumatoid arthritis (RA-FLS).

METHODS

The target proteins related with RA and those involved in cell apoptosis and pyroptosis were searched in different online databases, and Venny software was used to obtain apoptosis- and pyroptosis-related proteins in RA. RA-apoptosis-pyroptosis protein interaction (PPI) network was constructed to identity the key target proteins related with apoptosis and pyroptosis in RA. Autodock vina software was used to perform molecular docking to verify the binding ability of the main active ingredients in SX with the apoptosis- and pyroptosis-related proteins. In the cell experiment, MH7A cells were treated with 5 mg/L TGT (positive control) or 5, 10, 20, and 40 mg/L SX, and the changes in cell migration and invasion abilities and expressions of apoptosis- and pyroptosis-related proteins were examined using wound healing assay, Transwell assay, ELISA and Western blotting.

RESULTS

We identified 9 RA-related apoptotic target proteins, 15 RA-related pyroptosis target proteins, and 4 overlapping target proteins related with RA, apoptosis and pyroptosis. The main active ingredients in SX had a high affinity with the target proteins including TNF-α, Fas, and Bax. In MH7A cells, SX treatment concentration-dependently increased the cell inhibition rate at 24, 48 and 72 h (P < 0.05), and significantly lowered the cell migration ability at 6, 12 and 24 h (P < 0.05); treatment with 20 and 40 mg/L SX for 24 h obviously suppressed MH7A cell invasion (P < 0.05). SX treatment (20 and 40 mg/L) and TGT treatment both significantly lowered the expression levels of TNF-α, IL-1β, and IL-18 in the cells (P < 0.05). The Bax/Bcl-2 ratio and Fas and FasL expressions were increased significantly in cells treated with 20 and 40 mg/L SX (P < 0.05), and caspase-1 expression was decreased significantly in cells treated with 5 and 40 mg/L SX (P < 0.05).

CONCLUSION

SX can induce apoptosis and pyroptosison in RA-FLSs possibly by down-regulating the expressions of TNF-α, IL-1β and IL-18, up-regulating the expressions of Bax, Fas, and FasL, and inhibiting Bcl-2 and caspase-1 protein expressions.

Circ-Sirt1 inhibits proliferation, induces apoptosis, and ameliorates inflammation in human rheumatoid arthritis fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a chronic inflammatory disease related to abnormal activation of fibroblast-like synovium cells (FLS) with apoptosis, inflammation, and oxidative damage. Circular RNA Sirt1 (circ-Sirt1) is an abundant circRNA, exerts the function in inhibiting inflammation. However, little is known about the roles of circ-Sirt1, if any, in RA. The present study aimed to investigate the biological roles and mechanism of circ-Sirt1 on cell inflammation in RA-FLS MH7A cell line. This study showed circ-Sirt1 inhibited the proliferation and induced apoptosis of MH7A cells. Overexpression of circ-Sirt1 decreased of the levels of interleukin (IL)-1β and IL-6, tumour necrosis factor (TNF)-α, and matrix matalloproteinases (MMP)-1 and MMP-3 in MH7A cells. In addition, overexpression of circ-Sirt1 increased the expression of Sirt1, Nrf2, HO-1, IκBα, GCLC and GCLM, and decreased the ratio of acetylated NF-κB to normal NF-κB, and the expression of AP-1, COX-2 and HMGB1. Moreover, the expression of Keap1 and the ratio of acetylated NF-κB to normal NF-κB were partially increased and the Nrf2 and Sirt1 were partially reduced by siSirt1. Additionally, circ-Sirt1 overexpression promoted the activation of Sirt1 signal pathways by upregulating miR-132. In conclusion, the protective effect of Circ-Sirt1 on MH7A depends on inhibiting cell proliferation, promoting apoptosis and miR-132-mediated Sirt1 pathway to reduce inflammation.

The Interleukin-1 Receptor-Associated Kinase 4 Inhibitor PF-06650833 Blocks Inflammation in Preclinical Models of Rheumatic Disease and in Humans Enrolled in a Randomized Clinical Trial

OBJECTIVE

To investigate the role of PF-06650833, a highly potent and selective small-molecule inhibitor of interleukin-1-associated kinase 4 (IRAK4), in autoimmune pathophysiology in vitro, in vivo, and in the clinical setting.

METHODS

Rheumatoid arthritis (RA) inflammatory pathophysiology was modeled in vitro through 1) stimulation of primary human macrophages with anti-citrullinated protein antibody immune complexes (ICs), 2) RA fibroblast-like synoviocyte (FLS) cultures stimulated with Toll-like receptor (TLR) ligands, as well as 3) additional human primary cell cocultures exposed to inflammatory stimuli. Systemic lupus erythematosus (SLE) pathophysiology was simulated in human neutrophils, dendritic cells, B cells, and peripheral blood mononuclear cells stimulated with TLR ligands and SLE patient ICs. PF-06650833 was evaluated in vivo in the rat collagen-induced arthritis (CIA) model and the mouse pristane-induced and MRL/lpr models of lupus. Finally, RNA sequencing data generated with whole blood samples from a phase I multiple-ascending-dose clinical trial of PF-06650833 were used to test in vivo human pharmacology.

RESULTS

In vitro, PF-06650833 inhibited human primary cell inflammatory responses to physiologically relevant stimuli generated with RA and SLE patient plasma. In vivo, PF-06650833 reduced circulating autoantibody levels in the pristane-induced and MRL/lpr murine models of lupus and protected against CIA in rats. In a phase I clinical trial (NCT02485769), PF-06650833 demonstrated in vivo pharmacologic action pertinent to SLE by reducing whole blood interferon gene signature expression in healthy volunteers.

CONCLUSION

These data demonstrate that inhibition of IRAK4 kinase activity can reduce levels of inflammation markers in humans and provide confidence in the rationale for clinical development of IRAK4 inhibitors for rheumatologic indications.

Cinnamaldehyde Attenuates the Progression of Rheumatoid Arthritis through Down-Regulation of PI3K/AKT Signaling Pathway

Cinnamaldehyde (CA), as an active compound isolated from the bark of Cinnamomum cassia, has been reported to possess the anti-fungal, anti-bacterial, anti-inflammatory, anti-mutagenic, and anti-oxidant properties. However, the possible effects and underlying mechanisms of CA on rheumatoid arthritis (RA) have not been revealed yet. In the present study, we found that CA obviously improved the type II collagen-induced RA in rats, accompanied with decreasing pro-inflammatory factors, proliferation and metastasis. In addition, CA decreased the expression levels of TNF-α, IL-1β, and IL-6 in RA-FLSs. Besides, CA remarkably inhibited the proliferation, downregulated the EdU-positive cells, and promoted apoptosis of RA-FLSs by CCK-8, EdU and flow cytometry analysis. Moreover, the results of wound healing, transwell migration and invasion assays showed that CA inhibited the migration and invasion of RA-FLSs. Further, western blot experiment showed CA inhibited the activation of PI3K/AKT signaling pathway in RA-FLSs. Finally, 740Y-P, the PI3K/AKT signaling pathway activator, could reverse the effects of CA on the proliferation and metastasis in RA-FLSs. In conclusion, we confirmed that CA exhibited potential therapeutic properties against RA via suppressing proliferation and metastasis of RA-FLSs by blockage of PI3K/AKT signaling pathway. Therefore, our study provides evidence that CA may emerge as a therapeutic option for RA treatment.

LncRNA NEAT1_1 suppresses tumor-like biologic behaviors of fibroblast-like synoviocytes by targeting the miR-221-3p/uPAR axis in rheumatoid arthritis

Fibroblast-like synoviocytes (FLSs) are the predominant effector cells in the pathological progression of rheumatoid arthritis (RA). Therefore, elucidating the underlying molecular mechanism of the biologic behaviors in RA-FLSs will be helpful in developing the potent targets for the treatment of RA. We have previously documented that the tumor-like biologic behaviors of RA-FLSs are exacerbated by urokinase-type plasminogen activator receptor (uPAR), a specifically up-regulated receptor in RA-FLSs. Here, we investigate the further mechanism of uPAR and clarify its function in RA-FLSs. We demonstrate that miR-221-3p positively correlates to uPAR and regulates uPAR level in RA-FLSs. Simultaneously, one long noncoding RNA, nuclear paraspeckle assembly transcript 1_1 (NEAT1_1) is identified, which can predictively target miR-221-3p at three sites, indicating a strong possibility of being a competing endogenous RNA in RA-FLSs. Interestingly, NEAT1_1 and miR-221-3p can colocate in the nucleus and cytoplasm in RA-FLSs. Importantly, NEAT1_1 can act as a rheostat for the miR-221-3p/uPAR axis and the downstream JAK signaling. In line with the biologic function, NEAT1_1 negatively regulates the tumor-like characters, and cytokine secretions of RA-FLSs. Collectively, our data provide new insight into the mechanisms of NEAT1_1 in modulating RA-FLSs tumor-like behaviors. The targeting of NEAT1_1 and miR-221-3p/uPAR axis may have a promising therapeutic role in patients with RA.

Loss of microRNA-147 function alleviates synovial inflammation through ZNF148 in rheumatoid and experimental arthritis

MicroRNA-147 (miR-147) had been previously found induced in synoviocytes by inflammatory stimuli derived from T cells in experimental arthritis. This study was designed to verify whether loss of its function might alleviate inflammatory events in joints of experimental and rheumatoid arthritis (RA). Dark Agouti (DA) rats were injected intradermally with pristane to induce arthritis, and rno-miR-147 antagomir was locally administrated into individual ankle compared with negative control or rno-miR-155-5p antagomir (potential positive control). Arthritis onset, macroscopic severity, and pathological changes were monitored. While in vitro, gain or loss function of hsa-miR-147b-3p/hsa-miR-155-5p and ZNF148 was achieved in human synovial fibroblast cell line SW982 and RA synovial fibroblasts (RASF). The expression of miRNAs and mRNAs was detected by using RT-quantitative PCR, and protein expression was detected by using Western blotting. Anti-miR-147 therapy could alleviate the severity, especially for the synovitis and joint destruction in experimental arthritis. Gain of hsa-miR-147b-3p/hsa-miR-155-5p function in TNF-α stimulated SW982 and RASF cells could upregulate, in contrast, loss of hsa-miR-147b-3p/hsa-miR-155-5p function could downregulate the gene expression of TNF-α, IL-6, MMP3, and MMP13. Hence, such alteration could participate in synovial inflammation and joint destruction. RNAi of ZNF148, a miR-147's target, increased gene expression of TNF-α, IL-6, MMP3, and MMP13 in SW982 and RASF cells. Also, mRNA sequencing data showed that hsa-miR-147b-3p mimic and ZNF148 siRNA commonly regulated the gene expression of CCL3 and DEPTOR as well as some arthritis and inflammation-related pathways. Taken together, miR-147b-3p contributes to synovial inflammation through repressing ZNF148 in RA and experimental arthritis.

KDM4B Overexpression Promotes the Growth, Migration, and Invasion of Rheumatoid Arthritis Fibroblast-Like Synoviocytes by Activating STAT3 Pathway

In rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLS) present a unique aggressive phenotype and have a passive response to the inflammatory microenvironment, which are critical for the disease’s progression. KDM4B, as a histone demethylase, functions as an oncogenic factor in many cancers and is implicated in osteoclastogenesis as well as pro-inflammatory cytokine release in inflammatory diseases. However, the effects of KDM4B on RA FLS have not been reported. To investigate this issue, our study determined the expression of KDM4B in RA FLS using RT-qPCR and western blot. The effects of KDM4B on RA FLS viability, apoptosis, migration, and invasion were detected by MTT, flow cytometry, transwell migration, and invasion assays. Furthermore, the interaction of KDM4B with STAT3 signaling was studied by western blot, MTT, flow cytometry, transwell migration, and invasion assays. The experimental results showed that KDM4B expression was upregulated in RA synovial tissues and FLS as compared to healthy control tissues and normal FLS. Knockdown of KDM4B obviously suppressed RA FLS viability, migration and invasion, and induced apoptosis. In addition, knockdown of KDM4B in RA FLS decreased the expression of p-STAT3 and MMP-9 but increased cleaved caspase-3 expression compared with the control group. Moreover, KDM4B overexpression could promote cell growth, migration and invasion, and suppress apoptosis in RA FLS by activating STAT3 signaling. Therefore, these findings provide new insight for understanding the pathogenesis of RA and indicate that KDM4B may have a potential to be an effective therapeutic target for RA.

Nutri-epigenetics: the effect of maternal diet and early nutrition on the pathogenesis of autoimmune diseases

Autoimmune diseases comprise a wide group of diseases involving a self-response of the immune system against the host. The etiopathogenesis is very complex involving disease-specific factors but also environmental factors, among which the diet. Maternal diet during pregnancy as well as early nutrition recently attracted the interest of the scientists as contributing to the immune programming. In this paper, we reviewed the most recent literature on the effect of maternal diet and early nutrition in modulating the immune system in a selected subset of autoimmune diseases: type 1 diabetes, celiac disease, inflammatory bowel disease, juvenile idiopathic arthritis and rheumatoid arthritis. Particularly, we focused our narrative on the role of maternal and perinatal nutrition in the epigenetic mechanisms underlying the auto-immune response. Maternal diet during pregnancy as well as breastfeeding and early nutrition play a big role in many epigenetic mechanisms. Most of the nutrients consumed by the mother and the infant are known exerting epigenetic functions, such as folate, methionine, zinc, vitamins B12 and D, fibers, casein and gliadin, and they were linked to gene expression changes in the immune pathways. Despite the common role of maternal diet, breastfeeding and early nutrition in almost all the autoimmune diseases, each disease seems to have specific diet-driver epigenetic mechanisms that require further investigations. The research in this field is opening new routes to establishing a precision nutrition approach to the auto-immune diseases.

m6A RNA Methylation in Systemic Autoimmune Diseases-A New Target for Epigenetic-Based Therapy?

The general background of autoimmune diseases is a combination of genetic, epigenetic and environmental factors, that lead to defective immune reactions. This erroneous immune cell activation results in an excessive production of autoantibodies and prolonged inflammation. During recent years epigenetic mechanisms have been extensively studied as potential culprits of autoreactivity. Alike DNA and proteins, also RNA molecules are subjected to an extensive repertoire of chemical modifications. N6-methyladenosine is the most prevalent form of internal mRNA modification in eukaryotic cells and attracts increasing attention due to its contribution to human health and disease. Even though m6A is confirmed as an essential player in immune response, little is known about its role in autoimmunity. Only few data have been published up to date in the field of RNA methylome. Moreover, only selected autoimmune diseases have been studied in respect of m6A role in their pathogenesis. In this review, I attempt to present all available research data regarding m6A alterations in autoimmune disorders and appraise its role as a potential target for epigenetic-based therapies.

microRNA-23 inhibits inflammation to alleviate rheumatoid arthritis via regulating CXCL12

Rheumatoid arthritis (RA) is a common systemic, inflammatory and autoimmune disorder. MicroRNAs (miRs) are strongly associated with the initiation and progression of RA. However, the functions and mechanisms underlying miR-23 in RA are not completely understood. Therefore, the present study aimed to investigate the molecular mechanisms underlying miR-23 in RA. A bioinformatics tool (StarBase) and a wide range of experimental assays, including reverse transcription-quantitative PCR, western blotting, luciferase reporter assays and ELISAs, were performed to investigate the biological role of miR-23 in RA. The results indicated that miR-23 was downregulated and chemokine C-X-C motif ligand 12 (CXCL12) was upregulated in RA samples compared with healthy samples. Furthermore, miR-23 overexpression suppressed inflammation via reducing TNF-α, IL-1β and IL-8 expression levels compared with the NC mimic group. Regarding the underlying mechanism, compared with NC mimic, miR-23 mimic decreased CXCL12 mRNA expression by binding to its 3'-untranslated region. Additionally, CXCL12 overexpression reversed miR-23 mimic-mediated effects on inflammation. NF-κB signaling is associated with inflammation. Therefore, the present study indicated that CXCL12 promoted inflammation by activating NF-κB signaling. In conclusion, miR-23 inhibited inflammation to alleviate RA by regulating CXCL12 via the NF-κB signaling pathway, which may serve as a potential target for the diagnosis and treatment of RA.

Sexual Dimorphism in the Expression of Pain Phenotype in Preclinical Models of Rheumatoid Arthritis

Rheumatoid arthritis is one of most frequent rheumatic diseases, affecting around 1% of the population worldwide. Pain impacting the quality of life for the patient with rheumatoid arthritis, is often the primary factor leading them to seek medical care. Although sex-related differences in humans and animal models of rheumatoid arthritis are described, the correlation between pain and sex in rheumatoid arthritis has only recently been directly examined. Here we review the literature and explore the mechanisms underlying the expression of the pain phenotype in females and males in preclinical models of rheumatoid arthritis.

Anti-Inflammatory Effect of Geniposide on Regulating the Functions of Rheumatoid Arthritis Synovial Fibroblasts via Inhibiting Sphingosine-1-Phosphate Receptors1/3 Coupling Gαi/Gαs Conversion

The activated Gα protein subunit (Gαs) and the inhibitory Gα protein subunit (Gαi) are involved in the signal transduction of G protein coupled receptors (GPCRs). Moreover, the conversion of Gαi/Gαs can couple with sphingosine-1-phosphate receptors (S1PRs) and have a critical role in rheumatoid arthritis (RA). Through binding to S1PRs, sphingosine-1-phosphate (S1P) leads to activation of the pro-inflammatory signaling in rheumatoid arthritis synovial fibroblasts (RASFs). Geniposide (GE) can alleviate RASFs dysfunctions to against RA. However, its underlying mechanism of action in RA has not been elucidated so far. This study aimed to investigate whether GE could regulate the biological functions of MH7A cells by inhibiting S1PR1/3 coupling Gαi/Gαs conversion. We use RASFs cell line, namely MH7A cells, which were obtained from the patient with RA and considered to be the main effector cells in RA. The cells were stimulated with S1P (5 μmol/L) and then were treated with or without different inhibitors: Gαi inhibitor pertussis toxin (0.1 μg/mL), S1PR1/3 inhibitor VPC 23019 (5 μmol/L), Gαs activator cholera toxin (1 μg/mL) and GE (25, 50, and 100 μmol/L) for 24 h. The results showed that GE may inhibit the abnormal proliferation, migration and invasion by inhibiting the S1P-S1PR1/3 signaling pathway and activating Gαs or inhibiting Gαi protein in MH7A cells. Additionally, GE could inhibit the release of inflammatory factors and suppress the expression of cAMP, which is the key factor of the conversion of Gαi and Gαs. GE could also restore the dynamic balance of Gαi and Gαs by suppressing S1PR1/3 and inhibiting Gαi/Gαs conversion, in a manner, we demonstrated that GE inhibited the activation of Gα downstream ERK protein as well. Taken together, our results indicated that down-regulation of S1PR1/3-Gαi/Gαs conversion may play a critical role in the effects of GE on RA and GE could be an effective therapeutic agent for RA.

miRNA-146a Improves Immunomodulatory Effects of MSC-derived Exosomes in Rheumatoid Arthritis

Background:

Rheumatoid arthritis (RA) is a severe inflammatory joint disorder, and several studies have taken note of the probability that microRNAs (miRNAs) play an important role in RA pathogenesis. MiR-146 and miR-155 arose as primary immune response regulators. Mesenchymal stem cells (MSCs) immunomodulatory function is primarily regulated by paracrine factors, such as exosomes. Exosomes, which serve as carriers of genetic information in cell-to-cell communication, transmit miRNAs between cells and have been studied as vehicles for the delivery of therapeutic molecules.

Aims:

The current research aimed to investigate the therapeutic effect of miR-146a/miR-155 transduced mesenchymal stem cells (MSC)-derived exosomes on the immune response.

Methods:

Here, exosomes were extracted from normal MSCs with over-expressed miR-146a/miR-155; Splenocytes were isolated from collagen-induced arthritis (CIA) and control mice. Expression levels miR-146a and miR-155 were then monitored. Flow cytometry was performed to assess the impact of the exosomes on regulatory T-cell (Treg) levels. Expression of some key autoimmune response genes and their protein products, including retinoic acid-related orphan receptor (ROR)-γt, tumor necrosis factor (TNF)-α, interleukin (IL)-17, -6, -10, and transforming growth factor (TGF)-β in the Splenocytes was determined using both quantitative real-time PCR and ELISA. The results showed that miR-146a was mainly down-regulated in CIA mice. Treatment with MSC-derived exosomes and miR-146a/miR-155-transduced MSC-derived exosomes significantly altered the CIA mice Treg cell levels compared to in control mice.

Results:

Ultimately, such modulation may promote the recovery of appropriate T-cell responses in inflammatory situations such as RA.

Conclusion:

miR-146a-transduced MSC-derived exosomes also increased forkhead box P3 (Fox- P3), TGFβ and IL-10 gene expression in the CIA mice; miR-155 further increased the gene expressions of RORγt, IL-17, and IL-6 in these mice. Based on the findings here, Exosomes appears to promote the direct intracellular transfer of miRNAs between cells and to represent a possible therapeutic strategy for RA. The manipulation of MSC-derived exosomes with anti-inflammatory miRNA may increase Treg cell populations and anti-inflammatory cytokines.

The Contribution of Genetics and Epigenetics to Our Understanding of Health Disparities in Rheumatic Diseases

Socioeconomic determinants of health are associated with worse outcomes in the rheumatic diseases and contribute significantly to health disparities. However, genetic and epigenetic risk factors may affect different populations disproportionally and further exacerbate health disparities. We discuss the role of genetics and epigenetics to the health disparities observed in rheumatic diseases. We review concepts of population genetics and natural selection, current genome-wide genetic and epigenetic studies of several autoimmune diseases, and environmental exposures associated with disease risk in different populations. To understand how genomics influence health disparities in the rheumatic diseases, further studies in different populations worldwide are needed.

Association between gene polymorphisms of TGF-β and Smad3 and susceptibility to arthritis: a meta-analysis

OBJECTIVES

This meta-analysis was performed to investigate the associations between single-nucleotide polymorphisms (SNPs) in the TGF- β and Smad3 genes and arthritis.

METHODS

A meta-analysis was performed in STATA 14.0, with publication bias and meta-regression analysis. All types of arthritis were included, and subgroup analyses were performed to interpret variations among different types of arthritis.

RESULTS

Twenty-two qualified studieswere selected to analyze the pooled accuracy, and 4 SNP sites were involved. The analysis of the TGFB1 SNP rs1800470 showed an association with arthritis in allelic (P = 0.011), homozygous (P = 0.034) and recessive (P = 0.021) genetic models. The analysis of the TGFB1 SNP rs1800471 demonstrated a close association with rheumatoid arthritis (RA) in homozygous (P = 0.000, 95%) and recessive (P = 0.008) models. The analysis of the SMAD3 SNP rs12901499 revealed a close association with osteoarthritis (OA) in the allelic (P = 0.001) model.

CONCLUSION

This research showed that genetic variants of the TGF-β pathway impact arthritis. The polymorphisms rs1800470, rs1800471 and rs12901499 were correlated with a higher prevalence of arthritis.

Multifaceted Functions and Novel Insight Into the Regulatory Role of RNA N6-Methyladenosine Modification in Musculoskeletal Disorders

RNA modifications have emerged as key regulators of transcript expression in diverse physiological and pathological processes. As one of the most prevalent types of RNA modifications, N⁶-methyladenosine (m⁶A) has become the highlight in modulation of various diseases through interfering RNA splicing, translation, nuclear export, and decay. In many cases, the detailed functions of m⁶A in cellular processes and diseases remain unclear. Notably, recent studies have determined the relationship between m⁶A modification and musculoskeletal disorders containing osteosarcoma, osteoarthritis, rheumatoid arthritis, osteoporosis, etc. Herein, this review comprehensively summarizes the recent advances of m⁶A modification in pathogenesis and progression of musculoskeletal diseases. Specifically, the underlying molecular mechanisms, detection technologies, regulatory functions, clinical implications, and future perspectives of m⁶A in musculoskeletal disorders are discussed, with the aim to provide a novel insight into their association.

Expression levels of CXCR4 and CXCL12 in patients with rheumatoid arthritis and its correlation with disease activity

The present study aimed to investigate the expression levels of C-X-C motif chemokine receptor 4 (CXCR4) and CXC ligand 12 (CXCL12) in patients with rheumatoid arthritis (RA) and the correlation with disease activity. In total, 60 patients with RA were selected as the study group, comprising of 28 patients in active-stage and 32 patients in remission-stage. In addition, 60 patients with osteoarthritis were selected as the control group. Western blotting and ELISA were used to detect the expression of CXCR4 and CXCL12, respectively. The Spearman's correlation test was used to analyze correlations between CXCR4 and CXCL12, and erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), disease activity score 28 (DAS28) scores and rheumatoid factor (RF). The present results suggested that CXCR4 and CXCL12 expression levels in the serum and joint synovial fluid of the study group were significantly higher compared with the control group (P<0.05). Moreover, CXCR4 and CXCL12 expression levels in the RA-active group were higher compared with the remission (P<0.05) and control groups (P<0.01). The Pearson test results suggested that the expression levels of CXCR4 and CXCL12 in the serum and joint synovial fluid of patients with RA had a positive correlation with the ESR, CRP, RF and DAS28 scores (P<0.05). CXCL12 and CXCR4 were highly expressed in the serum and joint synovial fluid of patients with RA, and these expression levels were positively correlated with ESR, CRP, RF and DAS28 scores. Therefore, these clinical parameters may be used as indicators to evaluate the disease activity of patients with RA.

Urban Particulate Matter Enhances ROS/IL-6/COX-II Production by Inhibiting MicroRNA-137 in Synovial Fibroblast of Rheumatoid Arthritis

BACKGROUND

Rheumatoid arthritis (RA) has been associated with air pollution, possibly due to the augmentation of inflammatory effects. In this study, we aimed to determine the roles of inflammatory pathways and microRNA involved in the pathogenesis of RA fibroblast-like synoviocytes (FLS) inflammation induced by particulate matter.

METHODS

The inflammatory mediators, messenger RNAs, microRNAs and their interrelationships were investigated using western blotting, QPCR, ELISA and immunohistochemistry.

RESULTS

Particulate matter (PMs) induced an increase in the expression of interleukin-6 (IL-6) and cyclooxygenase-II (COX-II) in RA-FLS and microRNA-137 was found definitely to mediate the inflammatory pathways. PMs-induced generation of reactive oxygen species (ROS) in RA-FLS was attenuated by pretreatment with antioxidants. Nox-dependent ROS generation led to phosphorylation of ERK1/2, p38 and JNK, followed by downregulation of microRNA-137. In vivo studies, the joints of rats exposed to PMs revealed synovial fibroblast inflammation under pathologic examination and the expressions of IL-6 and COX-II were obviously increased. PMs exposure results in activated ROS-mediated mitogen-activated protein kinase (MAPK) signaling pathways and cause increased IL-6 and COX-II through downregulation of hsa-miRNA-137, which lead to inflammation and RA exacerbation.

CONCLUSIONS

microRNA-137 plays an important role in PMs-induced RA acute exacerbation through MAPK signaling pathways and IL-6/COX-II activation. Targeting these mechanisms can potentially be used to develop new therapeutic strategies and prevention of RA inflammation in the future.

Restoring synovial homeostasis in rheumatoid arthritis by targeting fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a chronic immune-mediated disease that primarily affects the synovium of diarthrodial joints. During the course of RA, the synovium transforms into a hyperplastic invasive tissue that causes destruction of cartilage and bone. Fibroblast-like synoviocytes (FLS), which form the lining of the joint, are epigenetically imprinted with an aggressive phenotype in RA and have an important role in these pathological processes. In addition to producing the extracellular matrix and joint lubricants, FLS in RA produce pathogenic mediators such as cytokines and proteases that contribute to disease pathogenesis and perpetuation. The development of multi-omics integrative analyses have enabled new ways to dissect the mechanisms that imprint FLS, have helped to identify potential FLS subsets with distinct functions and have identified differences in FLS phenotypes between joints in individual patients. This Review provides an overview of advances in understanding of FLS biology and highlights omics approaches and studies that hold promise for identifying future therapeutic targets.

Detection and Comparative Analysis of Methylomic Biomarkers of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a common autoimmune disorder influenced by both genetic and environmental factors. To investigate possible contributions of DNA methylation to the etiology of RA with minimum confounding genetic heterogeneity, we investigated genome-wide DNA methylation in disease-discordant monozygotic twin pairs. This study hypothesized that methylomic biomarkers might facilitate accurate RA detection. A comprehensive series of biomarker detection algorithms were utilized to find the best methylomic biomarkers for detecting RA patients using the methylomic data of the peripheral blood samples. The best model achieved 100.00% in accuracy (Acc) with 81 methylomic biomarkers and a 10-fold cross-validation (10FCV) strategy. Some of the methylomic biomarkers were experimentally confirmed to be associated with the onset or development of RA. It is also interesting to observe that many of the detected biomarkers were from chromosome Y, supporting the knowledge that RA has a significant gender discrepancy.

Epigenetics in rheumatoid arthritis; fibroblast-like synoviocytes as an emerging paradigm in the pathogenesis of the disease

Rheumatoid arthritis (RA) is characterized by immune dysfunctions and chronic inflammation that mainly affects diarthrodial joints. Genetics has long been surveyed in searching for the etiopathogenesis of the disease and partially clarified the conundrums within this context. Epigenetic alterations, such as DNA methylation, histone modifications, and noncoding RNAs, which have been considered to be involved in RA pathogenesis, likely explain the nongenetic risk factors. Epigenetic modifications may influence RA through fibroblast-like synoviocytes (FLSs). It has been shown that FLSs play an essential role in the onset and exacerbation of RA, and therefore, they may illustrate some aspects of RA pathogenesis. These cells exhibit a unique DNA methylation profile in the early stage of the disease that changes with disease progression. Histone acetylation profile in RA FLSs is disrupted through the imbalance of histone acetyltransferases and histone deacetylase activity. Furthermore, dysregulation of microRNAs (miRNAs) is immense. Most of these miRNAs have shown an aberrant expression in FLSs that are involved in proliferation and cytokine production. Besides, dysregulation of long noncoding RNAs in FLSs has been revealed and attributed to RA pathogenesis. Further investigations are needed to get a better view of epigenetic alterations and their interactions. We also discuss the role of these epigenetic alterations in RA pathogenesis and their therapeutic potential.

The P2X7 receptor (P2X7R)-specific antagonist A804598 inhibits inflammatory reaction in human fibroblast-like synoviocytes

Activation of the P2X7 receptor (P2X7R) has been found to increase expression of tumor necrosis factor-α (TNF-α) in the joints and synovial lining of patients with rheumatoid arthritis (RA). Increased expression of TNF-α promotes joint destruction through deterioration of type II collagen by matrix metalloproteinases (MMPs), expression of proinflammatory cytokines, oxidative stress, and activation of cellular signaling pathways. In the present study, we exposed fibroblast-like synoviocytes (FLSs) to TNF-α in the presence and absence of the P2X7R antagonist A804598. We then employed real time PCR and western blot analysis to analyze the mRNA and protein expression levels of P2X7R in both control and RA-FLSs. We confirmed that P2X7R is expressed on FLSs and is upregulated in RA-FLSs and FLSs exposed to TNF-α. Importantly, we also demonstrate the ability of P2X7R antagonism using A804598 to suppress oxidative stress, expression of interleukin (IL)-1β, IL-6, MMP-1, MMP-3, MMP-13 as well as activation of the Janus family of tyrosine kinase/signal transducer and activator of transcription (JAK1/STAT3) proinflammatory signaling pathway. These findings implicate a novel role of antagonism of P2X7R as a target for the treatment and prevention of RA.

DNA methylation profile of genes related to immune response in generalized periodontitis

BACKGROUND AND OBJECTIVE

Epigenetic events, as the DNA methylation, may be related to development of inflammatory diseases. Due to the important role of host's response in the pathogenesis of periodontitis, the purpose of the present study was to investigate the methylation profile of genes related to immune response in gingival tissues from patients with generalized periodontitis (GP) compared to healthy individuals.

METHODS

Gingival tissues were collected from 20 individuals with GP and 20 healthy individuals. Genomic DNA was extracted and submitted to enzymatic digestions. An initial screening using a panel of genes involved with the response immune was performed in pools containing six samples of each group. Genes that presented different levels of methylation between the groups were selected for individual assays for validation.

RESULTS

The array results showed an unmethylated profile in the majority of genes evaluated in both groups. MALT1, LTB, and STAT5 genes presented a profile of partial methylation in the control compared with GP group. Validation individual assays using a larger number of samples (n = 20, each group) confirmed the hypomethylation of STAT5 in the GP group compared with control group (P < .001).

CONCLUSION

Generalized periodontitis is associated with hypomethylation of the STAT5 gene. Further studies are necessary to evaluate the functional impact these findings.

Synovial biopsies in inflammatory arthritis: precision medicine in rheumatoid arthritis

Introduction: Synovial tissue (ST) is composed of a lining and sublining layer and is the target tissue involved in the inflammatory arthritides (IA), in which there is lining layer hyperplasia, inflammatory cell influx, macrophage recruitment and change in number and behavior of lining fibroblasts. Understanding synovial pathology has been critical in providing insights into pathogenetic mechanisms of disease and therapeutics. Pathobiological insights into ST have been underpinned by progress in molecular analytic methods; research in this area holds promise in individualizing treatment and optimizing response.Areas covered: We explore ST in IA and cover in-depth the utility of synovial biopsy and ST heterogeneity. We review recent advances in ST research and discuss implications with regards to therapeutic response. Finally, we provide perspectives on the identification of new drug targets and new diagnostic and prognostic markers.Expert opinion: ST holds the potential to individualize therapy by detecting biomarkers of diagnosis, therapeutic choice, and treatment modification in IA. Advances in molecular biology including high-throughput omics are likely to provide information that has hitherto remained unknown. ST analyzes pre- and post-treatment needs to be standard of care; only by routinely collecting and analyzing ST will we achieve the precision medicine outcomes described herein.

Interleukin 1β and Prostaglandin E2 affect expression of DNA methylating and demethylating enzymes in human gingival fibroblasts

Periodontitis is a common chronic inflammatory condition that results in increased levels of inflammatory cytokines and inflammatory mediators. In addition to oral disease and tooth loss, it also causes low-grade systemic inflammation that contributes to development of systemic conditions including cardiovascular disease, pre-term birth, diabetes and cancer. Chronic inflammation is associated with epigenetic change, and it has been suggested that such changes can alter cell phenotypes in ways that contribute to both ongoing inflammation and development of associated pathologies. Here we show that exposure of human gingival fibroblasts to IL-1β increases expression of maintenance methyltransferase DNMT1 but decreases expression of de novo methyltransferase DNMT3a and the demethylating enzyme TET1, while exposure to PGE2 decreases expression of all three enzymes. IL-1β and PGE2 both affect global levels of DNA methylation and hydroxymethylation, as well as methylation of some specific CpG in inflammation-associated genes. The effects of IL-1β are independent of its ability to induce production of PGE2, and the effects of PGE2 on DNMT3a expression are mediated by the EP4 receptor. The finding that exposure of fibroblasts to IL-1β and PGE2 can result in altered expression of DNA methylating/demethylating enzymes and in changing patterns of DNA methylation suggests a mechanism through which inflammatory mediators might contribute to the increased risk of carcinogenesis associated with inflammation.

Galectin-9 gene (LGALS9) polymorphisms are associated with rheumatoid arthritis in Brazilian patients

Introduction

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and hyperplasia, as well as cartilage and bone destruction. Several proteins are associated with the pathogenesis of the disease. Galectin-9 belongs to the family of lectins that are involved in various biological processes and have anti-inflammatory activity.

Objective

To investigate associations between the SNPs of the GAL-9 gene (LGALS9) and serum levels in rheumatoid arthritis patients. We extracted DNA from 356 subjects, 156 RA patients and 200 healthy controls from northeastern Brazil. Three polymorphisms (rs4795835, rs3763959, and rs4239242) in the LGALS9 gene were selected and genotyped using TaqMan SNP genotyping assay. Serum concentrations of galectin-9 were analyzed by ELISA.

Results

The rs4239242 TT genotype showed a positive association with RA (p = 0.0032, odds ratio = 0.28), and heterozygous TC were prevalent in the control group compared to RA patients (p = 0.0001, odds ratio = 7.99). Galectin-9 serum levels were significantly increased in RA patients compared to the control group (p<0.0001). Patients in remission had high levels of galectin compared to the moderate activity group (p<0.0001). Regarding the Clinical Disease Activity Index (CDAI), patients in remission or low activity presented high levels of galectin when compared to patients in severity (p<0.0001). Patients performing moderate activity had a significant value compared to patients who were in high disease severity (p = 0.0064). Interestingly, the AG genotype (rs3763959) has been associated with a higher presence of bone erosion in RA patients (p = 0.0436). The SNP rs4239242 TT genotype showed a positive association with RA in comparison to the control group. The AG genotype (rs3763959) has been associated with a higher presence of bone erosion in RA patients.

Fibroblast-Like Synoviocytes Glucose Metabolism as a Therapeutic Target in Rheumatoid Arthritis

Metabolomic studies show that rheumatoid arthritis (RA) is associated with metabolic disruption that may be therapeutically targetable. Among them, glucose metabolism and glycolytic intermediaries seem to have an important role in fibroblast-like synoviocytes (FLS) phenotype and might contribute to early stage disease pathogenesis. RA FLS are transformed from quiescent to aggressive and metabolically active cells and several works have shown that glucose metabolism is increased in activated FLS. Glycolytic inhibitors reduce not only FLS aggressive phenotype in vitro but also decrease bone and cartilage damage in several murine models of arthritis. Essential glycolytic enzymes, including hexokinase 2 (HK2) and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase (PFKFB) enzymes, have important roles in FLS behavior. Of interest, HK2 is an inducible enzyme present only in the inflamed rheumatic tissues compared to osteoarthritis synovium. It is a contributor to glucose metabolism that could be selectively targeted without compromising systemic homeostasis as a novel approach for combination therapy independent of systemic immunosuppression. More information about metabolic targets that do not compromise global glucose metabolism in normal cells is needed.

Aberrant Histone Methylation in Patients with Graves' Disease

BACKGROUND

Graves' disease (GD) is an organ-specific autoimmune disease. Accumulated data have indicated that aberrant epigenetic modifications are associated with many autoimmune disorders. However, it remains unknown whether histone methylation plays a role in the pathogenesis of GD. In the present study, we aimed to assess histone modification patterns in peripheral blood mononuclear cells (PBMCs) from GD patients. The rate (degree) of H3K4 and H3K9 methylation and the expressions of histone-modifying genes were investigated.

METHODS

A total of 68 GD patients and 32 healthy controls were enrolled in this study. Global histone H3K4/H3K9 methylation of PBMCs was evaluated by the EpiQuik™ global histone H3K4/H3K9 methylation assay kit. The expressions of histone methyltransferases (HMTs) and histone demethylases (HDMs) at the mRNA level were determined by real-time quantitative polymerase chain reaction.

RESULTS

Global histone H3K9 methylation in PBMCs of GD patients was significantly decreased compared with that in the healthy controls (P=0.007). The expressions of HMTs (SUV39H1 and SUV39H2) at the mRNA level were significantly decreased in PBMCs from GD patients compared with healthy controls (P<0.001), whereas the SETD1A expression at the mRNA level was significantly increased in GD patients compared with healthy controls (P=0.004). In addition, the expressions of HDMs, including JHDM2A and JMJD2A, at the mRNA level were significantly increased in GD patients compared with healthy controls (P<0.001; P=0.007). Moreover, the mRNA expression levels of JARID1A and LSD1 did not significantly differ in GD patients and healthy controls (P>0.05).

CONCLUSIONS

These findings firstly suggested that the histone methylation was aberrant in PBMCs of GD patients, which could be possibly attributed to the deregulation of epigenetic modifier genes. Abnormal histone methylation modification may be involved in the pathogenesis of GD.

Kaempferitrin inhibits proliferation, induces apoptosis, and ameliorates inflammation in human rheumatoid arthritis fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a complex chronic inflammatory disease that is associated with the aberrant activation of fibroblast-like synoviocytes (FLS). Kaempferitrin is a natural flavonoid glycoside that possesses anti-inflammatory bioactivity. However, the effect of kaempferitrin on RA has not yet been revealed. The aim of the present study was to investigate the effect of kaempferitrin on human RA-FLS MH7A cell line. We found that kaempferitrin inhibited proliferation and induced apoptosis of MH7A cells. Kaempferitrin decreased the levels of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, matrix metalloproteinase (MMP)-1, and MMP-3 in MH7A cells. Moreover, kaempferitrin blocked the activation of nuclear factor-κB (NF-κB) and protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathways. Furthermore, treatment with kaempferitrin decreased paw thickness and arthritis scores, and reduced the serum levels of IL-1β, IL-6, and TNF-α in a collagen-induced arthritis mouse model. In conclusion, kaempferitrin inhibited cell proliferation, induced cell apoptosis, and ameliorated inflammation of RA-FLS by suppressing the NF-κB and Akt/mTOR pathways.