Synovial fibroblasts: key players in rheumatoid arthritis

Berberine, a natural alkaloid: Advances in its pharmacological effects and mechanisms in the treatment of autoimmune diseases

The rising prevalence of autoimmune diseases poses a significant challenge to global public health. Continual exploration of natural compounds for effective treatments for autoimmune diseases is crucial. Berberine, a benzylisoquinoline alkaloid, is a bioactive component found in various medicinal plants, exhibiting diverse pharmacological properties. This review aims to consolidate the current understanding of berberine's pharmacological effects and mechanisms in addressing four autoimmune diseases: rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, and psoriasis. Overall, as a traditional Chinese medicinal preparation, berberine shows promise as an effective and safe treatment for autoimmune diseases. However, further comprehensive studies, particularly clinical trials, are essential to elucidate additional mechanisms and molecular targets, as well as to assess the efficacy and safety of berberine in treating these autoimmune diseases.

Discovery of CYP2E1 as a novel target in rheumatoid arthritis and validation by a new specific CYP2E1 inhibitor

Considerable evidence indicates that CYP2E1 is associated with a variety of inflammatory diseases. Here we evaluated CYP2E1 as a potential therapeutic target for rheumatoid arthritis (RA) and established the protective effect of a new CYP2E1 inhibitor. Gene-expression datasets were used to analyze the change in expression of CYP2E1 in RA patients; CYP2E1 activity in collagen-induced arthritis (CIA) rats was determined by HPLC. We further evaluated the protective effects of Cyp2e1 knockout and a CYP2E1-specific inhibitor, Q11, synthesized by our group, in CIA and adjuvant-induced arthritis (AIA) rats. The expression of CYP2E1 in synovial tissue was elevated in RA patients and in CIA rats and the activity of CYP2E1 in vivo and in vitro in CIA rats was greater than that of controls. Cyp2e1 knockout significantly reduced the incidence of CIA and alleviated the severity of symptoms. Treatment with different doses of Q11 decreased paw thickness, volume and arthritis scores and reduced the serum levels of IL-6, TNF-α, IL-1β and MDA, and increased the level of GSH in CIA rats. A similar inhibitory effect was exhibited for Q11 in the AIA rats. Moreover, Q11 significantly impeded proliferation, migration, and invasion of human rheumatoid arthritis synovial fibroblasts cells. Q11 decreased the release of ROS and enhanced Nrf2 nuclear translocation and HO-1 expression in the cell nucleus. Overall, our results indicated that CYP2E1 may be a new target for RA and Q11 has potential protective effects against RA by reducing oxidative stress and opposing the inflammatory response via the ROS/Nrf2/HO-1 signaling pathway.

Autoimmunity to stromal-derived autoantigens in rheumatoid ectopic germinal centers exacerbates arthritis and affects clinical response

Ectopic lymphoid structures (ELSs) in the rheumatoid synovial joints sustain autoreactivity against locally expressed autoantigens. We recently identified recombinant monoclonal antibodies (RA-rmAbs) derived from single, locally differentiated rheumatoid arthritis (RA) synovial B cells, which specifically recognize fibroblast-like synoviocytes (FLSs). Here, we aimed to identify the specificity of FLS-derived autoantigens fueling local autoimmunity and the functional role of anti-FLS antibodies in promoting chronic inflammation. A subset of anti-FLS RA-rmAbs reacting with a 60 kDa band from FLS extracts demonstrated specificity for HSP60 and partial cross-reactivity to other stromal autoantigens (i.e., calreticulin/vimentin) but not to citrullinated fibrinogen. Anti-FLS RA-rmAbs, but not anti-neutrophil extracellular traps rmAbs, exhibited pathogenic properties in a mouse model of collagen-induced arthritis. In patients, anti-HSP60 antibodies were preferentially detected in RA versus osteoarthritis (OA) synovial fluid. Synovial HSPD1 and CALR gene expression analyzed using bulk RNA-Seq and GeoMx-DSP closely correlated with the lympho-myeloid RA pathotype, and HSP60 protein expression was predominantly observed around ELS. Moreover, we observed a significant reduction in synovial HSP60 gene expression followed B cell depletion with rituximab that was strongly associated with the treatment response. Overall, we report that synovial stromal-derived autoantigens are targeted by pathogenic autoantibodies and are associated with specific RA pathotypes, with potential value for patient stratification and as predictors of the response to B cell-depleting therapies.

Brucine alleviates fibroblast-like synoviocytes dysfunction and inflammation by regulating YY1 during rheumatoid arthritis

Brucine is a weak alkaline indole alkaloid with wide pharmacological activities and has been identified to protect against rheumatoid arthritis (RA) process. Circular RNAs (circRNAs) are also reported to be involved in the pathogenesis of RA. Here, we aimed to probe the role and mechanism of Brucine and circ_0139658 in RA progression. The fibroblast-like synoviocytes of RA (RA-FLSs) were isolated for functional analysis. Cell proliferation, apoptosis, invasion, migration, as well as inflammatory response were evaluated by CCK-8 assay, EdU assay, flow cytometry, transwell assay, and ELISA analysis, respectively. qRT-PCR and western blotting analyses were utilized to measure the levels of genes and proteins. The binding between miR-653-5p and circ_0139658 or Yin Yang 1 (YY1), was verified using dual-luciferase reporter and RNA pull-down assays. Brucine suppressed the proliferation, migration, and invasion of RA-FLSs, and alleviated inflammation by reducing the release of pro-inflammatory factors and macrophage M1 polarization. RA-FLSs showed increased circ_0139658 and YY1 levels and decreased miR-653-5p levels. Circ_0139658 is directly bound to miR-653-5p to regulate YY1 expression. Brucine treatment suppressed circ_0139658 and YY1 expression but increased YY1 expression in RA-FLSs. Functionally, circ_0139658 overexpression reversed the suppressing effects of Brucine on RA-FLS dysfunction and inflammation. Moreover, circ_0139658 silencing alleviated the dysfunction and inflammation in RA-FLSs, which were reverted by YY1 overexpression. Brucine suppressed the proliferation, migration, invasion, and inflammation in RA-FLSs by decreasing YY1 via circ_0139658/miR-653-5p axis.

Psoriatic Arthritis Involving TMJ: A Review on Pathogenesis and Consideration on Eventual Gender Differences

Psoriatic arthritis is defined as chronic inflammatory arthritis associated with psoriasis. The current data regarding gender differences in clinical manifestation and therapeutic outcomes of psoriatic arthritis are limited. Generally, men show a peripheral disease manifestation, while women have an axial distribution of the lesions. If we look at temporomandibular joint (TMJ) involvement, epidemiological data on the involvement of the TMJ are hard to find. Few studies on therapeutic management and the related impact on the quality of life are reported in the literature. Given the morpho-functional peculiarities of the TMJ and the different pain burdens between male and female genders, when manifestation of psoriatic arthritis occurs, clinicians should face it using a multidisciplinary approach for a correct diagnosis and successful treatment. This review aims to examine the diagnostic signs of psoriatic arthritis in the TMJ, the eventual variations of this disease in male and female patients, and the therapeutical strategies. The coordination of different specialties is fundamental to the remission of clinical symptoms and lesion regression.

An ADAM10 Exosite Inhibitor Is Efficacious in an In Vivo Collagen-Induced Arthritis Model

Rheumatoid arthritis is a systemic autoimmune inflammatory disease that affects millions of people worldwide. There are multiple disease-modifying anti-rheumatic drugs available; however, many patients do not respond to any treatment. A disintegrin and metalloproteinase 10 has been suggested as a potential new target for RA due to its role in the release of multiple pro- and anti-inflammatory factors from cell surfaces. In the present study, we determined the pharmacokinetic parameters and in vivo efficacy of a compound CID3117694 from a novel class of non-zinc-binding inhibitors. Oral bioavailability was demonstrated in the blood and synovial fluid after a 10 mg/kg dose. To test efficacy, we established the collagen-induced arthritis model in mice. CID3117694 was administered orally at 10, 30, and 50 mg/kg/day for 28 days. CID3117694 was able to dose-dependently improve the disease score, decrease RA markers in the blood, and decrease signs of inflammation, hyperplasia, pannus formation, and cartilage erosion in the affected joints compared to the untreated control. Additionally, mice treated with CID 3117694 did not exhibit any clinical signs of distress, suggesting low toxicity. The results of this study suggest that the inhibition of ADAM10 exosite can be a viable therapeutic approach to RA.

Danggui Buxue Decoction exerts its therapeutic effect on rheumatoid arthritis through the inhibition of Wnt/β-catenin signaling pathway

BACKGROUND

Danggui Buxue Decoction (DBD) is a traditional Chinese medicine prescription, which has the functions of benefiting Qi, generating blood and regulating the immune system. At present, various clinical reports suggest that DBD has some efficacy in Rheumatoid arthritis (RA), but its mechanism of action is still unclear. Thus, the present study explored mechanism of this preparation on RA.

METHODS

The effect of DBD was evaluated by tumor necrosis factor (TNF)-α-induced Human fibroblast-like synoviocyte of rheumatoid arthritis (HFLS-RA) cell model and collagen-induced arthritis (CIA) rat model, respectively. Inflammatory factors including TNF-ɑ, IL-1β, IL-6 and IL-10 in the culture supernatants or rat serum were measured using ELISA. The related indexes including fur luster, mental state and activity of rat and the symptoms including swelling and deformation of toes and ankles were also measured.

RESULTS

In vitro results showed that DBD cannot only inhibit the proliferation of HFLS-RA cells but also reduce the levels of pro-inflammatory factors while increasing the level of anti-inflammatory factors. Similar results were obtained from in vivo experiments. Rats receiving DBD showed a decrease in the severity of rheumatoid arthritis in rat models. Moreover, the protein levels of c-myc and β-catenin decreased significantly, while the protein level of SFRP4 increased, which indicated that DBD might inhibit the inflammatory reaction by regulating Wnt/β-catenin signaling pathway, thus alleviating the symptoms of RA.

CONCLUSION

Our findings not only provide insights for understanding the molecular mechanism of DBD in treating RA, but also provide the theoretical basis for further clinical prevention and treatment.

Expanding the therapeutic potential of Salvia miltiorrhiza: a review of its pharmacological applications in musculoskeletal diseases

Salvia miltiorrhiz, commonly known as "Danshen" in Chinese medicine, has longstanding history of application in cardiovascular and cerebrovascular diseases. Renowned for its diverse therapeutic properties, including promoting blood circulation, removing blood stasis, calming the mind, tonifying the blood, and benefiting the "Qi", recent studies have revealed its significant positive effects on bone metabolism. This potential has garnered attention for its promising role in treating musculoskeletal disorders. Consequently, there is a high anticipation for a comprehensive review of the potential of Salvia miltiorrhiza in the treatment of various musculoskeletal diseases, effectively introducing an established traditional Chinese medicine into a burgeoning field.

AIM OF THE REVIEW

Musculoskeletal diseases (MSDs) present significant challenges to healthcare systems worldwide. Previous studies have demonstrated the high efficacy and prospects of Salvia miltiorrhiza and its active ingredients for treatment of MSDs. This review aims to illuminate the newfound applications of Salvia miltiorrhiza and its active ingredients in the treatment of various MSDs, effectively bridging the gap between an established medicine and an emerging field.

METHODS

In this review, previous studies related to Salvia miltiorrhiza and its active ingredients on the treatment of MSD were collected, the specific active ingredients of Salvia miltiorrhiza were summarized, the effects of Salvia miltiorrhiza and its active ingredients for the treatment of MSDs, as well as their potential molecular mechanisms were reviewed and discussed.

RESULTS

Based on previous publications, Salvianolic acid A, salvianolic acid B, tanshinone IIA are the representative active ingredients of Salvia miltiorrhiza. Their application has shown significant beneficial outcomes in osteoporosis, fractures, and arthritis. Salvia miltiorrhiza and its active ingredients protect against MSDs by regulating different signaling pathways, including ROS, Wnt, MAPK, and NF-κB signaling.

CONCLUSION

Salvia miltiorrhiza and its active ingredients demonstrate promising potential for bone diseases and have been explored across a wide variety of MSDs. Further exploration of Salvia miltiorrhiza's pharmacological applications in MSDs holds great promise for advancing therapeutic interventions and improving the lives of patients suffering from these diseases.

The effect of tranexamic acid on synovium of patients undergoing arthroplasty and anterior cruciate ligament reconstruction surgery

Preoperative hemorrhage can be reduced using anti-fibrinolytic medicine tranexamic acid (TXA). During surgical procedures, local administration is being used more and more frequently, either as an intra-articular infusion or as a perioperative rinse. Serious harm to adult soft tissues can be detrimental to the individual since they possess a weak ability for regeneration. Synovial tissues and primary fibroblast-like synoviocytes (FLS) isolated from patients were examined using TXA treatment in this investigation. FLS is obtained from rheumatoid arthritis (RA), osteoarthritis (OA), and anterior cruciate ligament (ACL)-ruptured patients. The in vitro effect of TXA on primary FLS was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assays for cell death, annexin V/propidium iodide (PI) staining for apoptotic rate, real-time PCR for p65 and MMP-3 expression, and enzyme-linked immunosorbent assay (ELISA) for IL-6 measurement. MTT assays revealed a significant decrease in cell viability in FLS of all groups of patients following treatment with 0.8-60 mg/ml of TXA within 24 h. There was a significant increase in cell apoptosis after 24 h of exposure to TXA (15 mg/ml) in all groups, especially in RA-FLS. TXA increases the expression of MMP-3 and p65 expression. There was no significant change in IL-6 production after TXA treatment. An increase in receptor activator of nuclear factor kappa-Β ligand (RANK-L) production was seen only in RA-FLS. This study demonstrates that TXA caused significant synovial tissue toxicity via the increase in cell death and elevation of inflammatory and invasive gene expression in FLS cells.

Applications of cold atmospheric plasma in immune-mediated inflammatory diseases via redox homeostasis: evidence and prospects

As a representative technology in plasma medicine, cold atmospheric plasma (CAP) has beneficial outcomes in surface disinfection, wound repair, tissue regeneration, solid tumor therapy. Impact on immune response and inflammatory conditions was also observed in the process of CAP treatment. Relevant literatures were collected to assess efficacy and summarize possible mechanisms of the innovation. CAP mediates alteration in local immune microenvironment mainly through two ways. One is to down-regulate the expression level of several cytokines, impeding further conduction of immune or inflammatory signals. Intervening the functional phenotype of cells through different degree of oxidative stress is the other approach to manage the immune-mediated inflammatory disorders. A series of preclinical and clinical studies confirmed the therapeutic effect and side effects free of CAP. Moreover, several suggestions proposed in this manuscript might help to find directions for future investigation.

Role of soluble epoxide hydrolase in the abnormal activation of fibroblast-like synoviocytes from patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by enigmatic pathogenesis. Polyunsaturated fatty acids (PUFAs) are implicated in RA's development and progression, yet their exact mechanisms of influence are not fully understood. Soluble epoxide hydrolase (sEH) is an enzyme that metabolizes anti-inflammatory epoxy fatty acids (EpFAs), derivatives of PUFAs. In this study, we report elevated sEH expression in the joints of CIA (collagen-induced arthritis) rats, concomitant with diminished levels of two significant EpFAs. Additionally, increased sEH expression was detected in both the synovium of CIA rats and in the synovium and fibroblast-like synoviocytes (FLS) of RA patients. The sEH inhibitor TPPU attenuated the migration and invasion capabilities of FLS derived from RA patients and to reduce the secretion of inflammatory factors by these cells. Our findings indicate a pivotal role for sEH in RA pathogenesis and suggest that sEH inhibitors offer a promising new therapeutic strategy for managing RA.

The protective effects of Phoenixin-20 in tumor necrosis factor α (TNF-α)-induced cell senescence of rheumatoid arthritis fibroblast-like synoviocytes (FLS)

Rheumatoid arthritis (RA) is an age-related joint destruction disease that markedly impacts the normal life of patients. Currently, the clinical treatment strategies are far from satisfactory with severe side effects. Cellular senescence of fibroblast-like synoviocytes (FLS) has been reported to be involved in the pathological process of arthritis, which may provide an important research direction for RA treatment. Phoenixin-20 (PNX-20) is a peptide targeting G-protein-coupled receptor 173 (GPR173) with promising anti-inflammatory properties. Our study will probe into the function of PNX-20 on tumor necrosis factor α (TNF-α)- induced rheumatoid arthritis (RA) FLS cell senescence to provide a theoretical basis for treating RA with PNX-20. RA-FLSs were handled with 10 ng/mL TNF-α, followed by introducing Phoenixin-20 (10, 20 nM) or not for 7 days. Enhanced release of inflammatory cytokines, increased proportion of senescence-associated β-galactosidase (SA-β-gal) positive cells, and declined telomerase activity were all observed in TNF-α-treated RA-FLSs, accompanied by a noticeable decline in the p21 and p53 level, which were notably reversed by 10 and 20 nM PNX-20. Furthermore, the increased signal transducer and activator of transcription 6 (STAT6) level observed in TNF-α-treated RA-FLSs were signally repressed by PNX-20. Moreover, the impact of PNX-20 on TNF-α-induced cellular senescence in RA-FLSs was abrogated by the overexpression of STAT6. Collectively, PNX-20 protected the TNF-α-induced cell senescence in RA-FLSs by downregulating STAT6. Based on these findings, we speculate that PNX-20 might be a promising agent for the treatment of RA.

Extracellular nicotinamide phosphoribosyltransferase: role in disease pathophysiology and as a biomarker

Nicotinamide phosphoribosyltransferase (NAMPT) plays a central role in mammalian cell metabolism by contributing to nicotinamide adenine dinucleotide biosynthesis. However, NAMPT activity is not limited to the intracellular compartment, as once secreted, the protein accomplishes diverse functions in the extracellular space. Extracellular NAMPT (eNAMPT, also called visfatin or pre-B-cell colony enhancing factor) has been shown to possess adipocytokine, pro-inflammatory, and pro-angiogenic activities. Numerous studies have reported the association between elevated levels of circulating eNAMPT and various inflammatory and metabolic disorders such as obesity, diabetes, atherosclerosis, arthritis, inflammatory bowel disease, lung injury and cancer. In this review, we summarize the current state of knowledge on eNAMPT biology, proposed roles in disease pathogenesis, and its potential as a disease biomarker. We also briefly discuss the emerging therapeutic approaches for eNAMPT inhibition.

Imaging in inflammatory arthritis: progress towards precision medicine

Imaging techniques such as ultrasonography and MRI have gained ground in the diagnosis and management of inflammatory arthritis, as these imaging modalities allow a sensitive assessment of musculoskeletal inflammation and damage. However, these techniques cannot discriminate between disease subsets and are currently unable to deliver an accurate prediction of disease progression and therapeutic response in individual patients. This major shortcoming of today's technology hinders a targeted and personalized patient management approach. Technological advances in the areas of high-resolution imaging (for example, high-resolution peripheral quantitative computed tomography and ultra-high field MRI), functional and molecular-based imaging (such as chemical exchange saturation transfer MRI, positron emission tomography, fluorescence optical imaging, optoacoustic imaging and contrast-enhanced ultrasonography) and artificial intelligence-based data analysis could help to tackle these challenges. These new imaging approaches offer detailed anatomical delineation and an in vivo and non-invasive evaluation of the immunometabolic status of inflammatory reactions, thereby facilitating an in-depth characterization of inflammation. By means of these developments, the aim of earlier diagnosis, enhanced monitoring and, ultimately, a personalized treatment strategy looms closer.

1,25(OH)2D3 and its analogue calcipotriol inhibit the migration of human synovial and mesenchymal stromal cells in a wound healing model - A comparison with glucocorticoids

Vitamin D analogue calcipotriol is currently used in the local treatment of psoriasis. However, it also has antiproliferative and anti-inflammatory effects in the cells of the joint - suggesting a possible benefit in local treatment of arthritis. In this study, calcipotriol was studied in different in vitro methods to find out its effect on synovial and mesenchymal stromal cells. Primary human cell lines of osteoarthritis or rheumatoid arthritis patients (five mesenchymal stromal cells, MSC, and four synovial stromal cells, SSC) were cultured to study migration and proliferation of the cells in a wound healing model. The media was supplemented with calcipotriol, 1,25(OH)2D3, dexamethasone, betamethasone, methylprednisolone or control solution in 1-100 nM concentrations. To see possible toxic effects of calcipotriol, concentrations up to 10 µM in SSCs and MSCs were studied in apoptosis and necrosis assays in four cell lines. Calcipotriol and 1,25(OH)2D3, as well as the three glucocorticoids, reduced the migration of both SSCs and MSCs. In SSCs, the effect of calcipotriol and 1,25(OH)2D3 was at least as effective as with glucocorticoids, while with MSCs, the glucocorticoids were stronger inhibitors of migration. The antimigratory of calcipotriol and 1,25(OH)2D3 was consistently maintained in 10 µM and 1 µM. Calcipotriol was not toxic to MSCs and SSCs up to concentrations of 10 µM. Calcipotriol, as well as 1,25(OH)2D3, exerts antimigratory and antiproliferative effects on human SSCs and MSCs of the joint. These effects are not caused by apoptosis or necrosis. Both calcipotriol and 1,25(OH)2D3 have similar effects as glucocorticoids without apparent toxicity, suggesting that calcipotriol might be an eligible candidate to the local treatment of arthritis with a broad therapeutic window.

Involvement of Epithelial-Mesenchymal Transition (EMT) in Autoimmune Diseases

Epithelial-mesenchymal transition (EMT) is a complex reversible biological process characterized by the loss of epithelial features and the acquisition of mesenchymal features. EMT was initially described in developmental processes and was further associated with pathological conditions including metastatic cascade arising in neoplastic progression and organ fibrosis. Fibrosis is delineated by an excessive number of myofibroblasts, resulting in exuberant production of extracellular matrix (ECM) proteins, thereby compromising organ function and ultimately leading to its failure. It is now well acknowledged that a significant number of myofibroblasts result from the conversion of epithelial cells via EMT. Over the past two decades, evidence has accrued linking fibrosis to many chronic autoimmune and inflammatory diseases, including systemic sclerosis (SSc), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjögren's syndrome (SS), and inflammatory bowel diseases (IBD). In addition, chronic inflammatory states observed in most autoimmune and inflammatory diseases can act as a potent trigger of EMT, leading to the development of a pathological fibrotic state. In the present review, we aim to describe the current state of knowledge regarding the contribution of EMT to the pathophysiological processes of various rheumatic conditions.

Circ_0000396 suppresses the proliferation and inflammation of rheumatoid arthritis synovial fibroblasts by targeting miR-574-5p/RSPO1 axis

BACKGROUND

Circular RNAs (circRNAs) are important regulators on the onset and progression of rheumatoid arthritis (RA). Our purpose is to explore the role and underpin mechanism of circ_0000396 in RA progression.

METHODS

RA patients (n = 39) and healthy volunteers (n = 33) were recruited from the Affiliated Hospital of Shaanxi University of Chinese Medicine for the present work. Circ_0000396, microRNA-574-5p (miR-574-5p) and R-spondin 1 (RSPO1) RNA levels were analyzed by reverse transcription-quantitative polymerase chain reaction. Cell proliferation was analyzed by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, colony formation assay, and 5-ethynyl-2'-deoxyuridine (EDU) assay. Cell apoptosis was assessed by flow cytometry. Protein expression levels of proliferating cell nuclear antigen (PCNA), Cyclin D1, Cyclin E1, BCL2-associated × protein (Bax), B-cell lymphoma-2 (Bcl2), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and RSPO1 were detected by western blot assay. Enzyme-linked immunosorbent assay (ELISA) was conducted to analyze the secretion of pro-inflammatory cytokines including IL-1β and TNF-α. The interaction between miR-574-5p and circ_0000396 or RSPO1 was confirmed by dual-luciferase reporter assay and RNA-pull down assay.

RESULTS

Circ_0000396 expression was notably down-regulated in RA patients compared with healthy controls. Circ_0000396 overexpression suppressed the proliferation and inflammatory response and triggered the apoptosis of RA synovial fibroblasts (RASFs), accompanied by decreases in PCNA, Cyclin D1, Cyclin E1, Bcl2, IL-1β and TNF-α protein expression and an increase in Bax protein expression. Circ_0000396 acted as a molecular sponge for miR-574-5p, and circ_0000396 overexpression-mediated protective effects on RASFs dysfunction were largely reversed by the introduction of miR-574-5p mimics. miR-574-5p interacted with the 3' untranslated region (3'UTR) of RSPO1, and miR-574-5p negatively regulated RSPO1 expression in RASFs. Circ_0000396 could up-regulate the expression of RSPO1 by sponging miR-574-5p in RASFs. RSPO1 interference largely overturned circ_0000396 overexpression-mediated effects in RASFs.

CONCLUSION

Circ_0000396 restrained the proliferation and inflammation and induced the apoptosis of RASFs by mediating miR-574-5p/RSPO1 axis, which provided novel potential targets for RA treatment.

Global, but not chondrocyte-specific, MT1-MMP deficiency in adult mice causes inflammatory arthritis

Membrane-type I metalloproteinase (MT1-MMP/MMP14) plays a key role in various pathophysiological processes, indicating an unaddressed need for a targeted therapeutic approach. However, mice genetically deficient in Mmp14 show severe defects in development and growth. To investigate the possibility of MT1-MMP inhibition as a safe treatment in adults, we generated global Mmp14 tamoxifen-induced conditional knockout (Mmp14kd) mice and found that MT1-MMP deficiency in adult mice resulted in severe inflammatory arthritis. Mmp14kd mice started to show noticeably swollen joints two weeks after tamoxifen administration, which progressed rapidly. Mmp14kd mice reached a humane endpoint 6 to 8 weeks after tamoxifen administration due to severe arthritis. Plasma TNF-α levels were also significantly increased in Mmp14kd mice. Detailed analysis revealed chondrocyte hypertrophy, synovial fibrosis, and subchondral bone remodeling in the joints of Mmp14kd mice. However, global conditional knockout of MT1-MMP in adult mice did not affect body weight, blood glucose, or plasma cholesterol and triglyceride levels. Furthermore, we observed substantial expression of MT1-MMP in the articular cartilage of patients with osteoarthritis. We then developed chondrocyte-specific Mmp14 tamoxifen-induced conditional knockout (Mmp14chkd) mice. Chondrocyte MT1-MMP deficiency in adult mice also caused apparent chondrocyte hypertrophy. However, Mmp14chkd mice did not exhibit synovial hyperplasia or noticeable arthritis, suggesting that chondrocyte MT1-MMP is not solely responsible for the onset of severe arthritis observed in Mmp14kd mice. Our findings also suggest that highly cell-type specific inhibition of MT1-MMP is required for its potential therapeutic use.

Lycium ruthenicum Murr. anthocyanins inhibit hyperproliferation of synovial fibroblasts from rheumatoid patients and the mechanism study powered by network pharmacology

BACKGROUND

Rheumatoid arthritis (RA), is a typical autoimmune disease affecting nearly 1% of the world's population. The dysfunctional hyperproliferation of synovial fibroblast (SF) in articular cartilage of RA patients is considered as the essential etiology. Traditional chemotherapeutic agents for RA treatment are imperfect for their high cost and unpredictable side-effects. L. ruthenicum anthocyanins (LRAC) is a natural product that of potential for therapeutic application against RA.

METHODS

LRAC was characterized by UPLC-MS/MS. Bioinformatics analyses based on network pharmacology were applied to predict the potential targets of LRAC, and to select DEGs (differentially expressed genes) caused by RA pathogenesis from GSE77298. Interactions between LRAC and the predicted targets were evaluated by molecular docking. Effects of LRAC on SFs from RA patients were examined by in vitro assays, which were analyzed by flow cytometry and western blotting (WB).

RESULTS

LRAC was able to inhibit the abnormal proliferation and aggressive invasion of SFs from RA patients. LRAC was mainly constituted by petunidin (82.7%), with small amount of delphinidin (12.9%) and malvidin (4.4%) in terms of anthocyanidin. Bioinformatics analyses showed that in 3738 RA-related DEGs, 58 of them were collectively targeted by delphinidin, malvidin and delphinidin. AR, CDK2, CHEK1, HIF1A, CXCR4, MMP2 and MMP9, the seven hub genes constructed a central network mediating the signal transduction. Molecular docking confirmed the high affinities between the LRAC ligands and the protein receptors encoded by the hub genes. The in vitro assays validated that LRAC repressed the growth of RASF by cell cycle arresting and cell invasion paralyzing (c-Myc/p21/CDK2), initiating cell apoptosis (HIF-1α/CXCR4/Bax/Bcl-2), and inducing pyroptosis via ROS-dependent pathway (NOX4/ROS/NLRP3/IL-1β/Caspase-1).

CONCLUSION

LRAC can selectively inhibit the proliferation of RASFs, without side-effecting immunosuppression that usually occurred for RA treatment using MTX (methotrexate). These findings demonstrate the potential application of LRAC as a phytomedicine for RA treatment, and provide a valid approach for exploring natural remedies against autoimmune diseases.

NIH/3T3 Fibroblasts Selectively Activate T Cells Specific for Posttranslationally Modified Collagen Type II

It has been shown that synovial fibroblasts (SF) play a key role in the initiation of inflammation and joint destruction, leading to arthritis progression. Fibroblasts may express major histocompatibility complex class II region (MHCII) molecules, and thus, they could be able to process and present antigens to immunocompetent cells. Here we examine whether different types of fibroblasts (synovial, dermal, and thymic murine fibroblasts, destructive LS48 fibroblasts, and noninvasive NIH/3T3 fibroblasts) may be involved in the initiation of rheumatoid arthritis (RA) pathogenesis and can process and present type II collagen (COL2)-an autoantigen associated with RA. Using a panel of MHCII/Aq-restricted T-cell hybridoma lines that specifically recognize an immunodominant COL2 epitope (COL2_259-273), we found that NIH/3T3 fibroblasts activate several T-cell clones that recognize the posttranslationally glycosylated or hydroxylated COL2_259-273 epitope. The HCQ.3 hybridoma, which is specific for the glycosylated immunodominant COL2 epitope 259-273 (Gal264), showed the strongest response. Interestingly, NIH/3T3 cells, but not destructive LS48 fibroblasts, synovial, dermal, or thymic fibroblasts, were able to stimulate the HCQ.3 hybridoma and other COL2-specific T-cell hybridomas. Our experiments revealed that NIH/3T3 fibroblasts are able to activate COL2-specific T-cell hybridomas even in the absence of COL2 or a posttranslationally modified COL2 peptide. The mechanism of this unusual activation is contact-dependent and involves the T-cell receptor (TCR) complex.

Enhancer variants on chromosome 2p14 regulating SPRED2 and ACTR2 act as a signal amplifier to protect against rheumatoid arthritis

Genome-wide association studies (GWASs) have repeatedly reported multiple non-coding single-nucleotide polymorphisms (SNPs) at 2p14 associated with rheumatoid arthritis (RA), but their functional roles in the pathological mechanisms of RA remain to be explored. In this study, we integrated a series of bioinformatics and functional experiments and identified three intronic RA SNPs (rs1876518, rs268131, and rs2576923) within active enhancers that can regulate the expression of SPRED2 directly. At the same time, SPRED2 and ACTR2 influence each other as a positive feedback signal amplifier to strengthen the protective role in RA by inhibiting the migration and invasion of rheumatoid fibroblast-like synoviocytes (FLSs). In particular, the transcription factor CEBPB preferentially binds to the rs1876518-T allele to increase the expression of SPRED2 in FLSs. Our findings decipher the molecular mechanisms behind the GWAS signals at 2p14 for RA and emphasize SPRED2 as a potential candidate gene for RA, providing a potential target and direction for precise treatment of RA.

Obesity defined molecular endotypes in the synovium of patients with osteoarthritis provides a rationale for therapeutic targeting of fibroblast subsets

BACKGROUND

Osteoarthritis (OA), a multifaceted condition, poses a significant challenge for the successful clinical development of therapeutics due to heterogeneity. However, classifying molecular endotypes of OA pathogenesis could provide invaluable phenotype-directed routes for stratifying subgroups of patients for targeted therapeutics, leading to greater chances of success in trials. This study establishes endotypes in OA soft joint tissue driven by obesity in both load-bearing and non-load bearing joints.

METHODS

Hand, hip, knee and foot joint synovial tissue was obtained from OA patients (n = 32) classified as obese (BMI > 30) or normal weight (BMI 18.5-24.9). Isolated fibroblasts (OA SF) were assayed by Olink proteomic panel, seahorse metabolic flux assay, Illumina's NextSeq 500 bulk and Chromium 10X single cell RNA-sequencing, validated by Luminex and immunofluorescence.

RESULTS

Targeted proteomic, metabolic and transcriptomic analysis found the inflammatory landscape of OA SFs are independently impacted by obesity, joint loading and anatomical site with significant heterogeneity between obese and normal weight patients, confirmed by bulk RNAseq. Further investigation by single cell RNAseq identified four functional molecular endotypes including obesity specific subsets defined by an inflammatory endotype related to immune cell regulation, fibroblast activation and inflammatory signaling, with up-regulated CXCL12, CFD and CHI3L1 expression. Luminex confirmed elevated chitase3-like-1(229.5 vs. 49.5 ng/ml, p < .05) and inhibin (20.6 vs. 63.8 pg/ml, p < .05) in obese and normal weight OA SFs, respectively. Lastly, we find SF subsets in obese patients spatially localise in sublining and lining layers of OA synovium and can be distinguished by differential expression of the transcriptional regulators MYC and FOS.

CONCLUSION

These findings demonstrate the significance of obesity in changing the inflammatory landscape of synovial fibroblasts in both load bearing and non-load bearing joints. Describing multiple heterogeneous OA SF populations characterised by specific molecular endotypes, which drive heterogeneity in OA disease pathogenesis. These molecular endotypes may provide a route for the stratification of patients in clinical trials, providing a rational for the therapeutic targeting of specific SF subsets in specific patient populations with arthritic conditions.

Autophagy pathways in autoimmune diseases

Autophagy comprises a growing range of cellular pathways, which occupy central roles in response to energy deprivation, organelle turnover and proteostasis. Over the years, autophagy has been increasingly linked to governing several aspects of immunity, including host defence against various pathogens, unconventional secretion of cytokines and antigen presentation. While canonical autophagy-mediated antigen processing in thymic epithelial cells supports the generation of a self-tolerant CD4+ T cell repertoire, mounting evidence suggests that deregulated autophagy pathways contribute to or sustain autoimmune responses. In animal models of multiple sclerosis (MS), non-canonical autophagy pathways such as microtubule-associated protein 1 A/1 B-light chain 3 (LC3)-associated phagocytosis can contribute to major histocompatibility complex (MHC) class II presentation of autoantigen, thereby amplifying autoreactive CD4+ T cell responses. In systemic lupus erythematosus (SLE), increased type 1 interferon production is linked to excessive autophagy in plasmacytoid dendritic cells (DCs). In rheumatoid arthritis (RA), autophagy proteins contribute to pathological citrullination of autoantigen. Immunotherapies effective in autoimmune diseases modulate autophagy functions, and strategies harnessing autophagy pathways to restrain autoimmune responses have been developed. This review illustrates recent insights in how autophagy, distinct autophagy pathways and autophagy protein functions intersect with the evolution and progression of autoimmune diseases, focusing on MS, SLE and RA.

Inhibition of Cdc37 Ameliorates Arthritis in Collagen-Induced Arthritis Rats by Inhibiting Synoviocyte Proliferation and Migration Through the ERK Pathway

Rheumatoid arthritis (RA) is a chronic autoimmune disease that can lead to synovial inflammation, pannus formation, cartilage damage, bone destruction, and ultimate disability. Fibroblast-like synoviocytes (FLS) are involved in the pathogenetic mechanism of RA. Cdc37 (cell division cycle protein 37) is regarded as a molecular chaperone involved in various physiological processes such as cell cycle progression, cell proliferation, cell signal transduction, tumorigenesis, and progression. However, the precise role of Cdc37 in the pathogenesis of rheumatoid arthritis (RA) remains uncertain. In our study, we found that Cdc37 expression was upregulated in human rheumatoid synovia in contrast with the normal group. Interestingly, Cdc37 activated the ERK pathway to promote RA-FLS proliferation and migration in vitro. Ultimately, in vivo experiments revealed that silencing of Cdc37 alleviated ankle swelling and cartilage destruction and validated the ERK signaling pathways in vitro findings. Collectively, we demonstrate that Cdc37 promotes the proliferation and migration of RA-FLS by activation of ERK signaling pathways and finally aggravates the progression of RA. These data indicated that Cdc37 may be a novel target for the treatment of RA.

Mesenchymal stromal cell therapy for patients with rheumatoid arthritis

Management of relapses and refractory rheumatoid arthritis (RA) patients is complex and difficult. Even after the administration of new biological disease-modifying anti-rheumatic drugs (DMARDs), only a few patients achieve the complete remission phase. DMARDs help only in modifying the disease activity, which sooner or later fails. They do not manage the disease at the patho-etiological level. There are some serious side effects as well as drug interaction with DMARDs. There are few subsets of RA patients who do not respond to DMARDs, reasons unknown. Mesenchymal stem cells (MSCs) provide a promising alternative, especially in such cases. This review elaborates on the studies pertaining to the application of MSCs in rheumatoid arthritis over the last two decades. A total of 14 studies (one review article) including 447 patients were included in the study. Most of the studies administered MSCs in refractory RA patients through the intravenous route with varied dosages and frequency of administration. MSCs help in RA treatment via various mechanisms including paracrine effects. All the studies depicted a better clinical outcome with minimal adverse events. The functional scores including the VAS scores improved significantly in all studies irrespective of dosage and source of MSCs. The majority of the studies depicted no complications. Although the use of MSCs in RA is still in the early stages requiring further refinement in the source of MSCs, dosage, and frequency. The role of MSCs in the management of RA has a promising prospect. MSCs target the RA at the molecular level and has the potential to manage refractory RA cases not responding to conventional treatment. Multicentric, large sample populations, and long-term studies are required to ascertain efficacy and safety.

Network pharmacology and experimental validation to identify the potential mechanism of Hedyotis diffusa Willd against rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, systemic, autoimmune disease that may lead to joint damage, deformity, and disability, if not treated effectively. Hedyotis diffusa Willd (HDW) and its main components have been widely used to treat a variety of tumors and inflammatory diseases. The present study utilized a network pharmacology approach, microarray data analysis and molecular docking to predict the key active ingredients and mechanisms of HDW against RA. Eleven active ingredients in HDW and 180 potential anti-RA targets were identified. The ingredients-targets-RA network showed that stigmasterol, beta-sitosterol, quercetin, kaempferol, and 2-methoxy-3-methyl-9,10-anthraquinone were key components for RA treatment. KEGG pathway results revealed that the 180 potential targets were inflammatory-related pathways with predominant enrichment of the AGE-RAGE, TNF, IL17, and PI3K-Akt signaling pathways. Screened through the PPI network and with Cytoscape software, RELA, TNF, IL6, TP53, MAPK1, AKT1, IL10, and ESR1 were identified as the hub targets in the HDW for RA treatment. Molecular docking was used to identify the binding of 5 key components and the 8 related-RA hub targets. Moreover, the results of network pharmacology were verified by vitro experiments. HDW inhibits cell proliferation in MH7A cells in a dose and time-dependent manner. RT-qPCR and WB results suggest that HDW may affect hub targets through PI3K/AKT signaling pathway, thereby exerting anti-RA effect. This study provides evidence for a clinical effect of HDW on RA and a research basis for further investigation into the active ingredients and mechanisms of HDW against RA.

Hypoxia and TNF-α Synergistically Induce Expression of IL-6 and IL-8 in Human Fibroblast-like Synoviocytes via Enhancing TAK1/NF-κB/HIF-1α Signaling

Hypoxia and increased levels of inflammatory cytokines in the joints are characteristics of rheumatoid arthritis (RA). However, the effects of hypoxia and tumor necrosis factor-α (TNF-α) on interleukin (IL)-6 and IL-8 production on fibroblast-like synoviocytes (FLSs) remain to be clarified. This study aimed to explore how hypoxia and TNF-α affect the expression of IL-6 and IL-8 in human FLSs isolated from RA patients. Hypoxia or TNF-α treatment alone significantly increased the expression and promoter activity of IL-6, IL-8, and hypoxia-inducible factor-1α (HIF-1α). Treatment of hypoxic FLSs with TNF-α further significantly elevated the expression of these cytokines and enhanced promoter activity of HIF-1α, which was abrogated by treatment with the HIF-1α inhibitor YC-1. Similarly, TNF-α alone elevated the phosphorylation and promoter activity of nuclear factor-κBp65 (NF-κBp65) in the FLSs. These effects were further enhanced by the combined treatment of hypoxia and TNFα but were attenuated by the NF-κB inhibitor BAY11-7082. NF-κB-p65 inhibition decreased the effect of TNF-α on HIF-1α upregulation in the FLSs in response to hypoxia. The combination of hypoxia and TNF-α also significantly upregulated transforming growth factor-β-activated kinase 1 (TAK1) expression, and silencing TAK1 dramatically decreased NF-κB-p65, HIF-1α, IL-6, and IL-8 expression under the same conditions. Our results indicate that hypoxia and TNF-α synergistically increase IL-6 and IL-8 expression in human FLSs via enhancing TAK1/NF-κB/HIF-1α signaling.

Inhibition of NUCB2 suppresses the proliferation, migration, and invasion of rheumatoid arthritis synovial fibroblasts from patients with rheumatoid arthritis in vitro

Rheumatoid arthritis (RA) is an autoimmune polyarthritis in which synovial fibroblasts (SF) play a major role in cartilage and bone destruction through tumorlike proliferation, migration, and invasion. Nesfatin-1, an 82-amino-acid-long peptide discovered by Oh-I in 2006, is derived from the precursor protein nucleobindin-2 (NUCB2). NUCB2/nesfatin-1 promotes cell proliferation, migration, and invasion in various tumors. We have previously shown that increased nesfatin-1 levels in the synovium may be associated with disease severity in patients with RA. However, the effect of NUCB2 on the tumorlike transformation of RASF has not yet been reported. The expression of NUCB2 mRNA in the synovium of RA and non-RA patients was further confirmed using three individual datasets from the NCBI GEO database. Gene set enrichment analysis (GSEA) was employed to explore the association between NUCB2 mRNA and RA-related gene signatures or signaling pathways in the GSE77298 dataset. Cell proliferation, migration, and invasion abilities were determined using Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), wound healing, and transwell assays, respectively. The results showed that the levels of NUCB2 mRNA in the synovium were significantly elevated in patients with RA. Moreover, GSEA showed that high expression of NUCB2 mRNA was related to gene signatures, including those involved in the cell cycle, DNA replication, extracellular matrix-receptor interaction, and focal adhesion. Furthermore, the results of CCK-8 and EdU assays indicated that inhibition of NUCB2 markedly repressed RASF proliferation. Additionally, the results of wound healing and transwell assays demonstrated that inhibition of NUCB2 significantly suppressed the migratory and invasive abilities of RASFs. Our findings are the first to demonstrate that the inhibition of NUCB2 suppresses the proliferation, migration, and invasion of RASFs in vitro.

Complement Regulation in Immortalized Fibroblast-like Synoviocytes and Primary Human Endothelial Cells in Response to SARS-CoV-2 Nucleocapsid Protein and Pro-Inflammatory Cytokine TNFα

Background: Case reports are available showing that patients develop symptoms of acute arthritis during or after recovery from SARS-CoV-2 infection. Since the interrelation is still unknown, our aim was to study the impact of the SARS-CoV-2 nucleocapsid protein (NP) on human fibroblast-like synoviocytes and human endothelial cells (hEC) in terms of complement and cytokine regulation. Methods: Non-arthritic (K4IM) synoviocyte, arthritic (HSE) synoviocyte cell lines and primary hEC were stimulated with recombinant NP and/or TNFα. Analyses of cell viability, proliferation, gene and protein expression of cytokines and complement factors were performed. Results: NP suppressed significantly the vitality of hEC and proliferation of HSE. NP alone did not induce any significant changes in the examined gene expressions. However, NP combined with TNFα induced significantly higher TNFα in HSE and K4IM as well as higher IL-6 and CD55 gene expression in HSE and suppressed C3aR1 gene expression in hEC. HSE proliferated twice as fast as K4IM, but showed significantly lesser gene expressions of CD46, CD55, CD59 and TNFα with significantly higher IL-6 gene expression. CD35 gene expression was undetectable in K4IM, HSE and hEC. Conclusions: NP might contribute in combination with other inflammatory factors to complement regulation in arthritis.

Baicalein Induces Apoptosis of Rheumatoid Arthritis Synovial Fibroblasts through Inactivation of the PI3K/Akt/mTOR Pathway

Purpose

Rheumatoid arthritis (RA) shows abnormal proliferation, apoptosis, and invasion in fibroblast-like synoviocytes (FLSs). Baicalein (BAI), extracted from Scutellaria baicalensis, is used as an anticancer drug through inducing cancer cells apoptosis. However, the mechanism of BAI in RA progression still remains unknown. Here, we demonstrated that BAI inhibited FLS proliferation and migration, whereas it enhanced apoptosis via the PI3K/Akt/mTOR pathway in vitro.

Methods

Cell viability and colony formation were analyzed by MTT and plate colony formation assays in SW982 cells, respectively. Apoptosis was detected by flow cytometry and western blotting. Epithelial-mesenchymal transition (EMT), MMP family proteins (MMP2/9), and the PI3K/Akt/mTOR pathway were detected by western blot. Cell migration was detected by scratch healing assay under BAI treatment in SW982 cells.

Results

BAI dose-dependently inhibited cell viability and colony forming in SW982 cells. BAI upregulated apoptotic proteins and downregulated EMT-related proteins, resulting in enhanced cell apoptosis and inhibited cell migration in SW982 cells. BAI also dose-dependently inhibited the phosphorylation of PI3K, Akt, and mTOR.

Conclusions

These results indicated that BAI inhibited FLSs proliferation and EMT, whereas induced cell apoptosis through blocking the PI3K/Akt/mTOR pathway, supporting clinical application for RA progression.

Imperatorin Inhibits Proliferation, Migration, and Inflammation via Blocking the NF-κB and MAPK Pathways in Rheumatoid Fibroblast-like Synoviocytes

Rheumatoid arthritis (RA) is a chronic joint inflammatory disease associated with the aberrant activation of fibroblast-like synoviocytes (FLSs). Searching for natural compounds that may suppress the activation of FLSs has become a complementary approach for RA treatment. Here, we investigated the effects and mechanisms of imperatorin (IPT) on proliferation, migration, and inflammation in primary cultured arthritic FLSs. We found that IPT significantly suppressed TNFα-induced proliferation and migration of arthritic FLSs, but showed little effect on survival and apoptosis. In addition, IPT treatment significantly reduced the TNFα-induced expression of pro-inflammatory cytokines (IL-1β, TNFα, IL-6, and IL-8) in arthritic FLSs. Further mechanism studies suggested that IPT inhibited the activations of p38 and extracellular signal-regulated kinase (ERK). Also, IPT blocked the nuclear factor of κB (NF-κB) activation by suppressing the phosphorylation and degradation of IκBα, thereby preventing the translocation of p65. Collectively, our results demonstrated that IPT could inhibit the over-activated phenotypes of arthritic FLSs via the mitogen-activated protein kinase (MAPK) (p38 and ERK) and NF-κB pathways leading to the down-regulation of pro-inflammatory cytokines, which might be beneficial to the anti-proliferative and anti-migratory activities of FLS cells. These findings suggest that IPT has the potential to be developed as a novel agent for RA treatment.

Peimine suppresses collagen-induced arthritis, activated fibroblast-like synoviocytes and TNFα-induced MAPK pathways

BACKGROUND AND PURPOSE

Peimine (PM), a main isosterol alkaloid component isolated from the bulbs of traditional Chinese herb Fritillaria cirrhosa D. Don, has been demonstrated to exhibit multiple pharmacological properties, including anti-inflammation, anti-cancer and pain suppression. However, its effect on rheumatoid arthritis (RA) remains unknown. In the present study, we investigated the effect of PM on collagen-induced arthritis (CIA) rats in vivo and its inhibition on destructive behaviors of arthritic fibroblast-like synoviocytes (FLSs) in vitro.

METHODS

Arthritis was induced in rats by chicken type II collagen. Arthritis score, radiological evaluation, and histopathological assessment were used to evaluate the therapeutic effects of PM on CIA rats. EdU assay, wound healing assay and real-time PCR were used to examine the inhibitory effect of PM on proliferation, migration, and over-expression of pro-inflammatory cytokines in TNFα-induced arthritic FLSs. TRAP staining and scanning electron microscopy were used to analyze the effect of PM on osteoclastogensis and bone resorption. Western blot was used to reveal PM's molecular mechanism of action on RA.

RESULTS

PM significantly suppressed synovitis and bone destruction in CIA rats. In vitro experiments showed that PM treatment significantly inhibited TNFα-induced destructive behaviors of arthritic FLSs, including over-proliferation, migration and over-expression of pro-inflammatory cytokines. Additionally, RANKL-induced osteoclast formation and bone-resorpting function were also inhibited by PM. Further molecular mechanism studies revealed that PM treatment significantly suppressed TNFα-induced activations of MAPKs (ERK, JNK and p38) in arthritic FLSs.

CONCLUSION

Our findings provide strong evidence that PM has the potential to be developed as a therapeutic agent for patients with RA.

Circ_0004712 Silencing Suppresses the Aggressive Changes of Rheumatoid Arthritis Fibroblast-Like Synoviocytes by Targeting miR-633/TRAF6 Axis

Circular RNA_0004712 (circ_0004712) is reported to be up-regulated in rheumatoid arthritis (RA) patients. Nevertheless, its role and mechanism in RA pathology remain to be clarified. RNA and protein expression was determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot assay. Cell viability, proliferation, apoptosis, migration, and inflammation were assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, 5-ethynyl-20-deoxyuridine assay, flow cytometry, scratch test, and enzyme-linked immunosorbent assay. The target correlation between microRNA-633 (miR-633) and circ_0004712 or TNF receptor associated factor 6 (TRAF6) was verified by dual-luciferase reporter assay and RNA immunoprecipitation assay. Circ_0004712 was up-regulated in RA synovial tissues and RA fibroblast-like synoviocytes (RA-FLSs). Circ_0004712 silencing suppressed the viability, proliferation, migration and inflammatory response and facilitated the apoptosis of RA-FLSs. miR-633 was confirmed to be a direct target of circ_0004712, and miR-633 knockdown reversed circ_0004712 silencing-mediated protective effects on the dysfunction and inflammation of RA-FLSs. TRAF6 was a direct target of miR-633, and miR-633 overexpression suppressed the aggressive changes of RA-FLSs by down-regulating TRAF6. Circ_0004712 could up-regulate TRAF6 expression by sponging miR-633 in RA-FLSs. Circ_0004712 interference inactivated nuclear factor (NF)-κB signaling by targeting miR-633/TRAF6 axis. Circ_0004712 silencing inhibited the aggressive changes of RA-FLSs by targeting miR-633/TRAF6 axis and NF-κB signaling, which provided new targets for RA therapy.

The Role of Podoplanin in the Immune System and Inflammation

Podoplanin is a small cell-surface mucin-like glycoprotein that participates in multiple physiological and pathological processes. Podoplanin exerts an important function in the immune response and is upregulated in fibroblasts, macrophages, T helper cells, and epithelial cells during inflammation. Herein, we summarize the latest knowledge on the functional expression of podoplanin in the immune system and review the contribution of podoplanin to several inflammatory diseases. Furthermore, we discuss podoplanin as a novel therapeutic target for various inflammatory diseases.

Inhibitory Effects of Cold Atmospheric Plasma on Inflammation and Tumor-Like Feature of Fibroblast-Like Synoviocytes from Patients with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, debilitating systemic disease characterized by chronic inflammation and progressive joint destruction. Fibroblast-like synoviocytes (FLSs) are one of the most important players in the pathophysiology of RA, acting like tumor cells and secreting inflammatory cytokines. Previous research has shown that cold atmospheric plasma (CAP) inhibits cancer cells and may have anti-inflammatory properties. This study examined the effects of argon plasma jet-produced CAP on the suppression of invasion and inflammation caused by cultured RA-FLS. The findings revealed that CAP reduced cell viability and elevated the percentage of apoptotic RA-FLS by producing reactive oxygen species. Carboxyfluorescein diacetate succinimidyl ester (CFSE) staining confirmed that CAP could decrease the proliferation of RA-FLS. Furthermore, CAP effectively reduced the production of inflammatory factors (e.g., NF-κB and IL-6) as well as destructive factors like receptor activator of nuclear factor kappa-B ligand (RANKL) and matrix metalloproteinases-3 (MMP-3). These data suggest that CAP could be a promising treatment for slowing the progression of RA by reducing tumor-like features and inflammation in RA-FLS.

TNF-α Induces Mitophagy in Rheumatoid Arthritis Synovial Fibroblasts, and Mitophagy Inhibition Alleviates Synovitis in Collagen Antibody-Induced Arthritis

Mitophagy is a selective form of autophagy that removes damaged mitochondria. Increasing evidence indicates that dysregulated mitophagy is implicated in numerous autoimmune diseases, but the role of mitophagy in rheumatoid arthritis (RA) has not yet been reported. The aim of the present study was to determine the roles of mitophagy in patient-derived RA synovial fibroblasts (RASFs) and in the collagen antibody-induced arthritis mouse model. We measured the mitophagy marker PTEN-induced putative kinase 1 (PINK1) in RASFs treated with tumor necrosis factor-α (TNF-α) using Western blotting and immunofluorescence. Arthritis was induced in PINK1^−/− mice by intraperitoneal injection of an anti-type II collagen antibody cocktail and lipopolysaccharide. RA severity was assessed by histopathology. PINK1 expression and damaged mitochondria increased in TNF-α treated RASFs via increased intracellular levels of reactive oxygen species. PINK1 knockdown RASFs decreased cellular migration and invasion functions. In addition, PINK1^−/− mice with arthritis exhibited markedly reduced swelling and inflammation relative to wild-type mice with arthritis. Taken together, these findings suggest that regulation of PINK1 expression in RA could represent a potential therapeutic and diagnostic target for RA.

Synovial Macrophage and Fibroblast Heterogeneity in Joint Homeostasis and Inflammation

The synovial tissue is an immunologically challenging environment where, under homeostatic conditions, highly specialized subsets of immune-regulatory macrophages and fibroblasts constantly prevent synovial inflammation in response to cartilage- and synovial fluid-derived danger signals that accumulate in response to mechanical stress. During inflammatory joint diseases, this immune-regulatory environment becomes perturbed and activated synovial fibroblasts and infiltrating immune cells start to contribute to synovial inflammation and joint destruction. This review summarizes our current understanding of the phenotypic and molecular characteristics of resident synovial macrophages and fibroblasts and highlights their crosstalk during joint homeostasis and joint inflammation, which is increasingly appreciated as vital to understand the molecular basis of prevalent inflammatory joint diseases such as rheumatoid arthritis.

Autophagy in Rheumatic Diseases: Role in the Pathogenesis and Therapeutic Approaches

Autophagy is a lysosomal pathway for the degradation of damaged proteins and intracellular components that promotes cell survival under specific conditions. Apoptosis is, in contrast, a critical programmed cell death mechanism, and the relationship between these two processes influences cell fate. Recent evidence suggests that autophagy and apoptosis are involved in the self-tolerance promotion and in the regulatory mechanisms contributing to disease susceptibility and immune regulation in rheumatic diseases. The aim of this review is to discuss how the balance between autophagy and apoptosis may be dysregulated in multiple rheumatic diseases and to dissect the role of autophagy in the pathogenesis of rheumatoid arthritis, systemic lupus erythematosus, and Sjögren’s syndrome. Furthermore, to discuss the potential capacity of currently used disease-modifying antirheumatic drugs (DMARDs) to target and modulate autophagic processes.

Deletion of activin A in mesenchymal but not myeloid cells ameliorates disease severity in experimental arthritis

Objective

The aim of this study was to assess the extent and the mechanism by which activin A contributes to progressive joint destruction in experimental arthritis and which activin A-expressing cell type is important for disease progression.

Methods

Levels of activin A in synovial tissues were evaluated by immunohistochemistry, cell-specific expression and secretion by PCR and ELISA, respectively. Osteoclast (OC) formation was assessed by tartrat-resistant acid phosphatase (TRAP) staining and activity by resorption assay. Quantitative assessment of joint inflammation and bone destruction was performed by histological and micro-CT analysis. Immunoblotting was applied for evaluation of signalling pathways.

Results

In this study, we demonstrate that fibroblast-like synoviocytes (FLS) are the main producers of activin A in arthritic joints. Most significantly, we show for the first time that deficiency of activin A in arthritic FLS (ActβA^d/d ColVI-Cre) but not in myeloid cells (ActβA^d/d LysM-Cre) reduces OC development in vitro, indicating that activin A promotes osteoclastogenesis in a paracrine manner. Mechanistically, activin A enhanced OC formation and activity by promoting the interaction of activated Smad2 with NFATc1, the key transcription factor of osteoclastogenesis. Consistently, ActβA^d/d LysM-Cre hTNFtg mice did not show reduced disease severity, whereas deficiency of activin A in ColVI-Cre-expressing cells such as FLS highly diminished joint destruction reflected by less inflammation and less bone destruction.

Conclusions

The results highly suggest that FLS-derived activin A plays a crucial paracrine role in inflammatory joint destruction and may be a promising target for treating inflammatory disorders associated with OC formation and bone destruction like rheumatoid arthritis.

Importance of Gedunin in Antagonizing Rheumatoid Arthritis via Activating the Nrf2/ARE Signaling

Objective

This study assessed the anti-arthritic effect and protection of Gedunin (GDN) on joint tissues and revealed the possible mechanism in suppressing rheumatoid arthritis (RA).

Methods

LPS-induced macrophages and TNF-α-stimulated synovial fibroblasts (MH7A) or IL-1β-stimulated primary rheumatoid arthritis synovial fibroblasts (RASFs) were used to evaluate the antiinflammatory effect of GDN. In addition, CIA-induced arthritis was employed here to evaluate the anti-arthritic effect. MTT and BRDU assays were utilized to evaluate the cell viability and proliferation, Q-PCR was conducted to detect the mRNA expression of cytokines, FACS was adopted to monitor ROS production, while western blotting (WB) and siRNA interference were applied in confirming the anti-arthritic effects of GDN via the Nrf2 signaling. Results. In vitro, cell viability was inhibited in macrophages and MH7A cells, but not in RASFs; but the proliferation of RASFs was significantly suppressed in time- and dose-dependent manners. GDN suppressed cytokine levels in LPS-stimulated macrophages and TNF-α-stimulated MH7A cells or RASFs. GDN suppressed ROS expression. Furthermore, GDN treatment notably dose-dependently decreased the mRNA and protein expression of iNOS in LPS-induced macrophages. sip62 interference results showed that GDN cause the less expression of HO-1 and Keap1 and also fail to inhibit cytokines after sip62 interference. In vivo, GDN effectively inhibited paw swelling, arthritis score, and arthritis incidence and cytokines.

Conclusions

Our study suggested that GDN exhibited strong antagonistic effect on arthritis both in vitro and in vivo via activation of Nrf2 signaling. Our work will provide a promising therapeutic strategy for RA.

7-deacetyl-gedunin suppresses proliferation of Human rheumatoid arthritis synovial fibroblast through activation of Nrf2/ARE signaling

BACKGROUND

Rheumatoid arthritis (RA) is an chronic autoimmune disease and characterized by high incidence. However, there is no effective therapies for RA. Therefore, it is urgent to discover new drugs for RA treatment. Nuclear factor erythroid 2 (NF-E2)-related factor (Nrf2) can effectively protect against arthritic inflammatory diseases through diverse stages, such as regulating redox balance, detoxification, metabolism and inflammation. Dimethyl fumarate (DMF), targets the Nrf2 pathway, was approved by FDA for the clinical treatment of multiple sclerosis (MS), which is another autoimmune disease. The latest report shown that DMF ameliorates complete Freund's adjuvant-induced arthritis in rats through activation of the Nrf2/HO-1 signaling pathway. Hence, Nrf2 serves as an important target for inflammation interference and oxidative stress of macrophages and RASFs in RA; therefore, it can be adopted as an effective therapeutic approach in the future. Rheumatoid arthritis synovial fibroblasts (RASFs) play crucial roles in the RA pathogenesis. Our results revealed that 7-deacetyl-gedunin (7-d-GDN), derived from fruits of Toona sinensis (A. Juss.) Roem, significantly inhibited RASFs proliferation in dose- and time- dependent manners and inhibited cell viability in MH7A cells, which is a kind of immortal cell line from joints of patients with RA. Additionally, 7-d-GDN remarkably down-regulated MMP-1/3/9/13 in RASFs, IL-6 and IL-33 in MH7A cells. Besides, 7-d-GDN sharply inhibited reactive oxygen species (ROS) in RASFs. Further mechanistic study demonstrated that 7-d-GDN induced heme oxygenase-1 (HO-1), NAD(P)H dehydrogenase quinone 1(NQO1), which all participated in suppressing of oxidative stress. Additionally, 7-d-GDN increased sequestosome 1 (SQSTM1, p62), causing down-regulating Kelch-like ECH-associated protein 1 (Keap1), which resulting in NF-E2-related factor 2 (Nrf2) cytoplasm accumulation and subsequently translocation into nucleus. Collectively, 7-d-GDN exerts the anti-inflammatory effect through regulating anti-oxidative enzymes via p62/ Nrf2/ARE signaling. All suggest that the potential of 7-d-GDN in suppression of inflammation, especially antagonizing RA severity. Our works support for drugs discovery in RA treatment.

Toxic mechanisms of cigarette smoke and heat-not-burn tobacco vapor inhalation on rheumatoid arthritis

Tobacco combustion exposure worsens rheumatoid arthritis (RA). Non-combustible tobacco devices, as heat-not-burn tobacco (HNBT), are emerging as harm reduction to smokers by releasing nicotine and lower combustible tobacco products. Nevertheless, HNBT toxicity remains unclear. Hence, here we investigated the impacts of the tobacco combustible product (cigarette smoke; CS) or HNBT vapor exposures on antigen-induced arthritis (AIA) in C57BL/6 mice. Animals were exposed to airflow, HNBT vapor, or CS during 1 h/twice a day, under the Health Canada Intense (HCI) smoking regime, between days 14 to 20 after the first immunization. At day 21, 16 h after the last exposures, mice were i.a. challenged and the AIA effects were evaluated 24 h later. CS- or HNBT-exposed mice presented equivalent blood nicotine levels. CS exposure worsened articular symptoms, pulmonary inflammation, and expression of lung metallothioneins. Nevertheless, CS or HNBT exposures reduced lymphoid organs' cellularity, splenocyte proliferation and IL-2 secretion. Additional in vitro CS or HNBT exposures confirmed the harmful effects on splenocytes, which were partially mediated by the activation of nicotine/α7nAchR pathway. Associated, data demonstrate the toxic mechanisms of CS or HNBT inhalation at HCI regime on RA, and highlight that further investigations are fundamental to assure the toxicity of emerging tobacco products on the immune system during specific challenges.

Triptolide inhibits cell growth and inflammatory response of fibroblast-like synoviocytes by modulating hsa-circ-0003353/microRNA-31-5p/CDK1 axis in rheumatoid arthritis

Triptolide (TPL) is an active component derived from Tripterygium wilfordii Hook F (TwHF) with therapeutic potential for rheumatoid arthritis (RA). However, the underlying mechanism of TPL is remains under-studied. Competing endogenous RNA (ceRNA) networks may participate in the response to TPL in RA. Herein, we sought to identify a TPL response-related ceRNA axis. A circular RNA (circRNA)-microRNA (miRNA)-mRNA ceRNA axis associated with the TPL response was constructed according to our previous study. Modulatory mechanisms of the ceRNA axis were ascertained through a series of experimentations. The clinical relevance of the ceRNA axis was also determined using computational models. Here, we found that TPL had excellent clinical effect on RA and promising therapeutic efficacy in experimental animals. The ceRNA axis of hsa-circ-0003353 (circ0003353), miR-31-5p, and CDK1 was identified as a candidate biomarker for the response of RA patients to TPL. TPL inhibited the viability, proliferation, and cell cycle entry of RA-fibroblast-like synoviocytes (FLSs), as well as the production of cytokines. Overexpression of circ0003353 abolished the inhibitory effects of TPL on RA-FLSs. Mechanistically, circ0003353 sponged miR-31-5p that inversely targeted CDK1 and manipulated the p21/Cyclin B axis. Additionally, consecutive rescue experiments indicated that the inhibitory impacts of TPL on RA-FLSs were dependent on the circ0003353/miR-31-5p/CDK1 axis. Molecular docking was also applied to predict the specific binding sites and binding capacity of TPL to related targets. In conclusion, the present study demonstrated that TPL repressed the cell growth and inflammatory response of RA-FLSs by mediating the expression of the circ0003353/miR-31-5p/CDK1 axis. This novel ceRNA axis may serve as a biomarker for screening RA patients who respond to TPL treatment, which holds potential applications in the diagnosis and therapy of RA.

The protective effect of gentisic acid on rheumatoid arthritis via the RAF/ERK signaling pathway

Background

RAF and ERK pathways are known to be activated in human rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS), which play an important role in the pathogenesis and destruction of RA. Gentisic acid (GA) was a natural product derived from plants, which has been reported can attenuate pressure overload‐induced cardiac hypertrophy and fibrosis in mice through inhibition of the ERK1/2 pathway. Whether GA can inhibit the occurrence and development of RA through RAF/ERK signaling pathway has not been reported. The purpose of this study is to determine whether GA may have a certain therapeutic effect on RA-FLS.

Method

Bovine type II collagen was used to establish a rat model of rheumatism. Enzyme-linked immunosorbent assay was used to detect inflammatory factors, anti-inflammatory mediators, and rheumatoid factor. Hematoxylin and eosin and TUNEL staining were used to detect the effect of GA on histochemical with rheumatoid arthritis. RAF, ERK, and p-ERK expressions in synovial tissue were measured by western blot and immunohistochemical. Besides, human rheumatoid arthritis fibroblast-like synoviocytes cell line MH7A was used to investigate the biological behavior influenced by GA. Apoptosis assay was performed to detect apoptosis of GA on MH7A cells. Transwell invasion assay was performed to detect the ability of cell migration.

Result

The result showed that GA could reduce joint swelling and inflammation. At the same time, it can also promote the apoptosis of synovial cells and down-regulate the RAF/ERK pathway.

Conclusion

GA may ameliorate inflammatory factors’ abnormality, synovial hyperplasia, and apoptosis of synovium via inhibiting the RAF/ERK signaling pathway.

Immunomodulatory matrix-bound nanovesicles mitigate acute and chronic pristane-induced rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation and destruction of synovial joints affecting ~7.5 million people worldwide. Disease pathology is driven by an imbalance in the ratio of pro-inflammatory vs. anti-inflammatory immune cells, especially macrophages. Modulation of macrophage phenotype, specifically an M1 to M2, pro- to anti-inflammatory transition, can be induced by biologic scaffold materials composed of extracellular matrix (ECM). The ECM-based immunomodulatory effect is thought to be mediated in part through recently identified matrix-bound nanovesicles (MBV) embedded within ECM. Isolated MBV was delivered via intravenous (i.v.) or peri-articular (p.a.) injection to rats with pristane-induced arthritis (PIA). The results of MBV administration were compared to intraperitoneal (i.p.) administration of methotrexate (MTX), the clinical standard of care. Relative to the diseased animals, i.p. MTX, i.v. MBV, and p.a. MBV reduced arthritis scores in both acute and chronic pristane-induced arthritis, decreased synovial inflammation, decreased adverse joint remodeling, and reduced the ratio of synovial and splenic M1 to M2 macrophages (p < 0.05). Both p.a. and i.v. MBV reduced the serum concentration of RA and PIA biomarkers CXCL10 and MCP-3 in the acute and chronic phases of disease (p < 0.05). Flow-cytometry revealed the presence of a systemic CD43hi/His48lo/CD206+, immunoregulatory monocyte population unique to p.a. and i.v. MBV treatment associated with disease resolution. The results show that the therapeutic efficacy of MBV is equal to that of MTX for the management of acute and chronic pristane-induced arthritis and, further, this effect is associated with modulation of local synovial macrophages and systemic myeloid populations.

Berberine and its derivatives represent as the promising therapeutic agents for inflammatory disorders

Berberine, with the skeleton of quaternary ammonium, has been considered as the well-defined natural product in treating multiple diseases, including inflammation, acute and chronic infection, autoimmune diseases, and diabetes. However, due to the low bioavailability and systemic exposure, broad clinical applications of berberine have been largely impeded. Numerous studies have been conducted to further explore the therapeutic capacities of berberine in preclinical and clinical trials. Over the past, berberine and its derivatives have been shown to possess numerous pharmacological activities, as evidenced in intestinal, pulmonary, skin, and bone inflammatory disorders. In the present review, the pharmacological impact of berberine on inflammatory diseases are fully discussed, with indication that berberine and its potential derivatives represent promising natural therapeutic agents with anti-inflammatory properties.

7-Hydroxycoumarin mitigates the severity of collagen-induced arthritis in rats by inhibiting proliferation and inducing apoptosis of fibroblast-like synoviocytes via suppression of Wnt/β-catenin signaling pathway

BACKGROUND

7-Hydroxycoumarin (7-HC) as a coumarin compound is widely found in Chinese herbs and exhibits diverse biological activities. Promoting cell apoptosis of fibroblast-like synoviocytes (FLS) is a meaningful strategy for rheumatoid arthritis (RA). Though the protective effect of 7-HC on RA experimental models has been reported, the specific mechanisms, especially the possible relationships of this effect to regulating FLS proliferation and apoptosis, still need clarification.

PURPOSE

This study clarified the therapeutic effects of 7-HC on collagen-induced arthritis (CIA) in rats and explored the underlying mechanisms.

METHODS

In vivo, 7-HC (15, 30 or 60 mg/kg) was intraperitoneally given to CIA rats, and its therapeutic effect and anti-inflammatory activity were evaluated. Ki67 immunohistochemistry, TUNEL assay and synovial proteins detection were conducted. In vitro, after treating with 7-HC (20, 40 or 80 μM) in TNF-α-stimulated RA FLS (MH7A cell line), cell proliferation and apoptosis were examined. The involvement of Wnt/β-catenin pathway was checked in vivo and in vitro.

RESULTS

7-HC attenuated the severity of rat CIA, evidenced by the reduction of paw swelling, arthritis index, joint damage, collagen type II antibody serum level, and IL-1β, IL-6, TNF-α production in serum and synovium. Particularly, 7-HC in vivo had anti-proliferative and pro-apoptotic effects on CIA rat synovial cells, indicated by reduced synovial Ki67 expression, raised synovial apoptosis index, decreased Bcl-2 protein level and increased level of Bax and cleaved caspase 3 protein. Further, 7-HC in vitro suppressed proliferation and promoted apoptosis of TNF-α-stimulated MH7A cells by regulating the mitochondrial pathway. Mechanistically, 7-HC treatment inhibited Wnt/β-catenin pathway, suggested by the reduction of pathway-related proteins (e.g. Wnt1, LRP6, p-GSK-3β (Ser9), β-catenin, cyclin D1 and c-Myc), the recovery of GSK-3β activity and the inhibition of β-catenin nuclear translocation. As expected, combined use of lithium chloride, an activator of Wnt/β-catenin signaling, reversed the anti-proliferative and pro-apoptotic effects of 7-HC in vitro.

CONCLUSION

7-HC relieved the severity of rat CIA by inhibiting cell proliferation and inducing apoptosis of rheumatoid FLS via inhibition of Wnt/β-catenin pathway.

Injectable hyaluronic acid hydrogels encapsulating drug nanocrystals for long-term treatment of inflammatory arthritis

Antiproliferative chemotherapeutic agents offer a potential effective treatment for inflammatory arthritis. However, their clinical application is limited by high systemic toxicity, low joint bioavailability as well as formulation challenges. Here, we report an intra-articular drug delivery system combining hyaluronic acid hydrogels and drug nanocrystals to achieve localized and sustained delivery of an antiproliferative chemotherapeutic agent camptothecin for long-term treatment of inflammatory arthritis. We synthesized a biocompatible, in situ-forming injectable hyaluronic acid hydrogel using a naturally occurring click chemistry: cyanobenzothiazole/cysteine reaction, which is the last step reaction in synthesizing D-luciferin in fireflies. This hydrogel was used to encapsulate camptothecin nanocrystals (size of 160-560 nm) which released free camptothecin in a sustained manner for 4 weeks. In vivo studies confirmed that the hydrogel remained in the joint over 4 weeks. By using the collagen-induced arthritis rat model, we demonstrate that the hydrogel-camptothecin formulation could alleviate arthritis severity as indicated by the joint size and interleukin-1β level in the harvested joints, as well as from histological and microcomputed tomography evaluation of joints. The hydrogel-nanocrystal formulation strategy described here offers a potential solution for intra-articular therapy for inflammatory arthritis.