Altered immunoregulation in rheumatoid arthritis: the role of regulatory T cells and proinflammatory Th17 cells and therapeutic implications

Conventional DMARDs therapy decreases disease activity and inflammation in newly diagnosed patients with rheumatoid arthritis by increasing FoxP3, Sema-3A, and Nrp-1 gene expression

BACKGROUND

Semaphorins are axonal guidance molecules involved in neural development and contribute to the regulation of various phases of the immune response. This study aimed to investigate the plasma levels of the pro-inflammatory cytokine interleukin-6 (IL-6) and the regulatory T (Treg) cell-related cytokine interleukin-10 (IL-10), as well as the gene expression levels of forkhead box P3 (FoxP3), Semaphorin-3A (Sema-3A), Neuropilin-1 (Nrp-1), Semaphorin-4A (Sema-4A), and Plexin-D1 (Plxn-D1), in the peripheral blood of newly diagnosed rheumatoid arthritis (RA) patients treated with conventional disease-modifying antirheumatic drugs (DMARDs) for 6 months compared with healthy controls.

METHODS

Peripheral blood samples were obtained from 40 newly diagnosed RA patients (before and after treatment) and 40 age- and sex-matched healthy subjects. The plasma concentrations of IL-6 and IL-10 were quantified via enzyme-linked immunosorbent assay (ELISA), and the mRNA expression levels of FoxP3, Sema-3A, Nrp-1, Sema-4A, and Plxn-D1 were assessed via quantitative real-time PCR.

RESULTS

Compared with those in the controls, the plasma IL-6 levels in the RA patients (both pre- and post-treatment) were significantly greater (P < 0.001). Compared with the pre-treatment levels, the plasma IL-6 levels decreased significantly after DMARD therapy (P < 0.05). Moreover, plasma IL-10 levels were significantly greater in post-treatment RA patients than in controls (P < 0.05). The gene expression of FoxP3, Sema-3A, and Nrp-1 was significantly lower in pre-treated RA patients than in controls (P < 0.001). Compared with that in pre-treatment RA patients, the gene expression of FoxP3, Sema-3A, and Nrp-1 in DMARDs-treated RA patients was strongly increased (P < 0.05, P < 0.01, and P < 0.01, respectively). There was a positive correlation between Sema-3A gene expression and the gene expression of FoxP3 (r = 0.292, P < 0.01) and Nrp-1 (r = 0.569, P < 0.0001).

CONCLUSION

Conventional DMARDs therapy effectively reduces disease activity and inflammation in newly diagnosed RA patients by increasing FoxP3, Sema-3A, and Nrp-1 gene expression.

Long non-coding RNA ENSMUST00000197208 promotes a shift in the Th17/Treg ratio via the P2X7R-NLRP3 inflammasome axis in collagen-induced arthritis

Recently, long non‑coding RNAs (lncRNAs) have been implicated in several human diseases, including arthritis. However, the role of lncRNAs in regulating the Th17/Treg ratio during the progression of collagen-induced arthritis (CIA) is poorly understood. Therefore, the aim of this study was to determine the role of the lncRNA ENSMUST00000197208 and the P2X7R-NLRP3 inflammasome axis in changes in the Th17/Treg ratio in CIA. To achieve this, the distribution of T cell subgroups in the spleen cells of a CIA mouse model and control mice was examined. Additionally, we examined the expression profile of ENSMUST00000197208 in a CIA mouse model and healthy mice. The results showed that ENSMUST00000197208 expression was significantly upregulated in the CIA models compared with the control group. Additionally, the P2X7R-NLRP3 inflammasome axis participated in the pathogenesis of CIA and knockdown of ENSMUST00000197208 inhibited CD4+ T cell differentiation into Th17 cells. Compared with the control group, joint inflammation was less visible in NLRP3 knockout mice. Additionally, the P2X7R-NLRP3 inflammasome axis, which is downstream of ENSMUST00000197208, can be positively targeted and regulated by ENSMUST00000197208 through miR-107. Overall, the findings of this study showed that the "lncRNA ENSMUST00000197208-miR 107-P2X7R/NLRP3" axis plays an important role in CIA and knocking down ENSMUST00000197208 can efficiently inhibit Th17 differentiation by suppressing the P2X7R-NLRP3 inflammasome axis. Therefore, targeting this axis may represent a novel strategy for arthritis treatment.

An Overview of Therapeutic Targeting of Nrf2 Signaling Pathway in Rheumatoid Arthritis

Rheumatoid arthritis (RA), an autoimmune condition that has a significant inflammatory component and is exacerbated by dysregulated redox-dependent signaling pathways. In RA, the corelationship between oxidative stress and inflammation appears to be regulated by the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway. Furthermore, it has been shown that transcriptional pathways involving Nrf2 and NFκB significantly interact under conditions of oxidative stress and inflammation. Because pathologic cells in RA have a higher chance of surviving, Nrf2's influence on concomitant pathologic mechanisms in the disease is explained by its interaction with key redox-sensitive inflammatory pathways. The current review not only updates knowledge about Nrf2's function in RA but also highlights the complex interactions between Nrf2 and other redox-sensitive transcription factors, which are essential to the self-sustaining inflammatory processes that define RA. This paper also reviews the candidates for treating RA through Nrf2 activation. Finally, future directions for pharmacologic Nrf2 activation in RA are suggested.

Augmenting regulatory T cells: new therapeutic strategy for rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune condition marked by inflammation of the joints, degradation of the articular cartilage, and bone resorption. Recent studies found the absolute and relative decreases in circulating regulatory T cells (Tregs) in RA patients. Tregs are a unique type of cells exhibiting immunosuppressive functions, known for expressing the Foxp3 gene. They are instrumental in maintaining immunological tolerance and preventing autoimmunity. Increasing the absolute number and/or enhancing the function of Tregs are effective strategies for treating RA. This article reviews the studies on the mechanisms and targeted therapies related to Tregs in RA, with a view to provide better ideas for the treatment of RA.

TAGAP activates Th17 cell differentiation by promoting RhoA and NLRP3 to accelerate rheumatoid arthritis development

Rheumatoid arthritis (RA) is a chronic autoimmune disorder that can give rise to joint swelling and inflammation, potentially affecting the entire body, closely linked to the state of T cells. The T-cell activation Rho GTPase activating protein (TAGAP) is associated with many autoimmune diseases including RA and is directly linked to the differentiation of Th17 cells. The present study intends to investigate the influence of TAGAP on the RA progression and its mechanism to empower new treatments for RA. A collagen-induced-arthritis (CIA) rat model was constructed, as well as the extraction of CD4+ T cells. RT-qPCR, H&E staining and safranin O/fast green staining revealed that TAGAP interference reduced TAGAP production in the ankle joint of CIA rats, and joint inflammation and swelling were alleviated, which reveals that TAGAP interference reduces synovial inflammation and cartilage erosion in the rat ankle joint. Expression of inflammatory factors (TNF-α, IL-1β, and IL-17) revealed that TAGAP interference suppressed the inflammatory response. Expression of pro-inflammatory cytokines, matrix-degrading enzymes, and anti-inflammatory cytokines at the mRNA level was detected by RT-qPCR and revealed that TAGAP interference contributed to the remission of RA. Mechanistically, TAGAP interference caused a significant decrease in the levels of RhoA and NLRP3. Assessment of Th17/Treg levels by flow cytometry revealed that TAGAP promotes Th17 cells differentiation and inhibits Treg cells differentiation in vitro and in vivo. In conclusion, TAGAP interference may decrease the differentiation of Th17 cells by suppressing the expression of RhoA and NLRP3 to slow down the RA progression.

Nrf2: A promising therapeutic target in bone-related diseases

Nuclear factor erythroid-2-related factor 2 (Nrf2) plays an important role in maintaining cellular homeostasis, as it suppresses cell damage caused by external stimuli by regulating the transcription of intracellular defense-related genes. Accumulating evidence has highlighted the crucial role of reduction-oxidation (REDOX) imbalance in the development of bone-related diseases. Nrf2, a transcription factor linked to nuclear factor-erythrocyte 2, plays a pivotal role in the regulation of oxidative stress and induction of antioxidant defenses. Therefore, further investigation of the mechanism and function of Nrf2 in bone-related diseases is essential. Considerable evidence suggests that increased nuclear transcription of Nrf2 in response to external stimuli promotes the expression of intracellular antioxidant-related genes, which in turn leads to the inhibition of bone remodeling imbalance, improved fracture recovery, reduced occurrence of osteoarthritis, and greater tumor resistance. Certain natural extracts can selectively target Nrf2, potentially offering therapeutic benefits for osteogenic arthropathy. In this article, the biological characteristics of Nrf2 are reviewed, the intricate interplay between Nrf2-regulated REDOX imbalance and bone-related diseases is explored, and the potential preventive and protective effects of natural products targeting Nrf2 in these diseases are elucidated. A comprehensive understanding of the role of Nrf2 in the development of bone-related diseases provides valuable insights into clinical interventions and can facilitate the discovery of novel Nrf2-targeting drugs.

Functional implications of rs9373441 with FOXP3+Treg and Tr1 for the clinical effectiveness of csDMARDs in rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by a deficiency in regulatory T cells (Treg), which play a crucial role in immune regulation. While conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) are widely used, there remains a challenge as efficacy varies among patients. In this genome-wide association study (GWAS) involving 410 RA patients, rs9373441 emerged as the most significantly linked single-nucleotide polymorphism (SNP) to csDMARDs response. This non-coding variant functions as a cis-acting regulatory element within the UTRN gene, which is associated with cortical erosion and osteoporosis. Particularly, individuals with the TT allele at rs9373441 exhibited a more favorable response, characterized by a significant increase in FOXP3 + Treg and Type 1 regulatory T cells (Tr1) (p = 0.04, 0.02) and a decrease in Effector T helper cells (Effector Th) (p = 0.03). The GATA3-GCM2-PTH and GATA3-FOXO1-FOXP3 pathways were implicated. RNA-sequencing (RNA-seq) analysis revealed increased expression levels of UTRN, PTH2R, FOXO1, and FOXO3 in good and moderate responders (p = 0.01, 0.03, 0.0005, and 0.02). Notably, the change in FOXP3 + Treg and Tr1 was positively correlated with UTRN expression (both p = 0.03). These findings underscore the critical link between rs9373441 and the response to csDMARDs, empowering clinicians to tailor treatments for enhanced outcomes in patients with RA.

The association between neutrophil-to-lymphocyte ratio and disease activity in rheumatoid arthritis

The inflammatory response is responsible for the promotion of pannus development over the joint, which is the primary factor in joint injury in rheumatoid arthritis (RA). More in-depth investigations have been conducted in recent years leading to a greater understanding of RA. Yet, it's difficult to gauge inflammation levels in RA patients. Some people who have RA do not exhibit normal symptoms, which makes it more challenging to make a diagnosis. Typical RA evaluations are subject to a few restrictions. Earlier research demonstrated that some patients continued to experience the progression of bone and joint degeneration even while in clinical remission. This progression was attributed to ongoing synovial inflammation. As a result, performing a precise evaluation of the level of inflammation is of the utmost importance. The neutrophil-to-lymphocyte ratio (NLR) has consistently been one of the most interesting novel non-specific inflammatory indicators. It is a reflection of the equilibrium between lymphocytes and neutrophils, which are inflammatory regulators and inflammatory activators, respectively. A higher NLR is linked to more severe levels of imbalance and inflammation. The aim of this study was to depict the role of NLR in RA progression and to show if NLR could predict the response to disease-modifying antirheumatic drugs (DMARDs) therapy in RA.

Induced regulatory T cells remain suppressive capability on effector T cells and synovial fibroblasts in collagen-induced arthritis

Rheumatoid arthritis (RA) is a common autoimmune disorder initiated by inflammatory synovitis. Hyperproliferation of destructive synovial fibroblasts (SFs) is one of the pathogenic mechanisms of RA. Abnormalities in regulatory T cells (Tregs) may also play a critical role in this progression. To date, it is unclear whether both natural Tregs (nTregs) and induced Tregs (iTregs) share similar characteristics in RA progression and whether Tregs directly suppress the autoaggressive activities of SFs. In this study, we compared suppressive effects on effector T cells (Teffs) and inflamed SFs between nTregs and iTregs in a collagen-induced arthritis (CIA) model. Our results demonstrated that iTregs but not nTregs maintained a suppressive effect on Teffs after adoptive transfer into CIA mice. Additionally, we discovered that iTregs directly inhibited the destructive activities of CIA-SFs. Thus, this study suggests that administration of the iTreg subset has great potential for treatment of RA in the clinic in the future.

Bioinformatic assay reveal the potential mechanism of Guizhi-Shaoyao-Zhimu decoction against rheumatoid arthritis and mild-to-moderate COVID-19

BACKGROUND AND OBJECTIVE

Patients with rheumatoid arthritis (RA) are more susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) than healthy population, but there is still no therapeutic strategy available for RA patients with corona virus disease 2019 (COVID-19). Guizhi-Shaoyao-Zhimu decoction (GSZD), Chinese ancient experience decoction, has a significant effect on the treatment of Rheumatism and gout. To prevent RA patients with mild-to-moderate COVID-19 from developing into severe COVID-19, this study explored the potential possibility and mechanism of GSZD in the treatment of this population.

METHODS

In this study, we used bioinformatic approaches to explore common pharmacological targets and signaling pathways between RA and mild-to-moderate COVID-19, and to assess the potential mechanisms of in the treatment of patients with both diseases. Beside, molecular docking was used to explore the molecular interactions between GSZD and SARS-CoV-2 related proteins.

RESULTS

Results showed that 1183 common targets were found in mild-to-moderate COVID-19 and RA, of which TNF was the most critical target. The crosstalk signaling pathways of the two diseases focused on innate immunity and T cells pathways. In addition, GSZD intervened in RA and mild-to-moderate COVID-19 mainly by regulating inflammation-related signaling pathways and oxidative stress. Twenty hub compounds in GSZD exhibited good binding potential to SARS-CoV-2 spike (S) protein, 3C-like protease (3CLpro), RNA-dependent RNA polymerase (RdRp), papain-like protease (PLpro) and human angiotensin-converting enzyme 2 (ACE2), thereby intervening in viral infection, replication and transcription.

CONCLUSIONS

This finding provides a therapeutic option for RA patients against mild-to-moderate COVID-19, but further clinical validation is still needed.

Stratified distribution of Th17 and Treg cells in patients with multi-stage rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is a typical, progressive autoimmune disease. Its occurrence and development are associated with dysregulation of T and B cell numbers. However, the specific immune characteristics of different RA courses remain incompletely defined. Here, we describe the peripheral blood lymphocyte subsets, particularly CD4 + T subsets, of different RA courses with a focus on early RA (Ea-RA).

METHODS

In all, 131 patients with Ea-RA, 117 with advanced RA (Ad-RA), and 109 with treated RA (Tr-RA) were enrolled. We collected general clinical data. Whole blood samples obtained from the patients and 97 healthy controls (HCs) were analysed via flow cytometry.

RESULTS

Decreased absolute NK cell numbers and increased CD4/CD8 T cell ratios were observed in different RA groups, including Ea-RA, compared to healthy controls. In Ea-RA patients, the Th17 and Treg cell numbers were similar to those in HCs. We performed k-means clustering based on the profiles of Th17 and Treg cells for patients with multi-stage of RA. We identified three patient types: type A characterised by relatively low Treg and Th17 cell numbers, type B with moderate levels of Treg cells and levels of Th17 cells similar to that of type C patients, and type C with high levels of Treg cells and levels of Th17 cells similar to that of type B patients.

CONCLUSION

The immune characteristics of Ea-RA patients differ from those of HCs; an immune system disorder is apparent although no differences in Th17 and Treg levels were evident between Ea-RA patients and HCs. We found distributional heterogeneities of Th17 and Treg cells in patients with multi-stage of RA. Stratified management based on such heterogeneity may serve as a useful novel immunotherapy allowing of early intervention.

Hypermethylation of Smad7 in CD4+ T cells is associated with the disease activity of rheumatoid arthritis

Background

Smad7 is protective in a mouse model of rheumatoid arthritis. Here we investigated whether Smad7-expressing CD4⁺ T cells and the methylation of Smad7 gene in CD4⁺ T cells contribute to the disease activity of RA in patients.

Methods

Peripheral CD4⁺ T cells were collected from 35 healthy controls and 57 RA patients. Smad7 expression by CD4⁺ T cells were determined and correlated with the clinical parameters of RA including RA score and serum levels of IL-6, CRP, ESR, DAS28-CRP, DAS28-ESR, Swollen joints and Tender joints. Bisulfite sequencing (BSP-seq) was used to determine the DNA methylation in Smad7 promoter (-1000 to +2000) region in CD4⁺ T cells. In addition, a DNA methylation inhibitor, 5-Azacytidine (5-AzaC), was added to CD4⁺ T cells to examine the possible role of Smad7 methylation in CD4⁺ T cell differentiation and functional activity.

Results

Compared to the heath controls, Smad7 expression was significantly decreased in CD4⁺ T cells from RA patients and inversely correlated with the RA activity score and serum levels of IL-6 and CRP. Importantly, loss of Smad7 in CD4⁺ T cell was associated with the alteration of Th17/Treg balance by increasing Th17 over the Treg population. BSP-seq detected that DNA hypermethylation occurred in the Smad7 promoter region of CD4⁺ T cells obtained from RA patients. Mechanistically, we found that the DNA hypermethylation in the Smad7 promoter of CD4⁺ T cells was associated with decreased Smad7 expression in RA patients. This was associated with overreactive DNA methyltransferase (DMNT1) and downregulation of the methyl-CpG binding domain proteins (MBD4). Inhibition of DNA methylation by treating CD4⁺ T cells from RA patients with 5-AzaC significantly increased Smad7 mRNA expression along with the increased MBD4 but reduced DNMT1 expression, which was associated with the rebalance in the Th17/Treg response.

Conclusion

DNA hypermethylation at the Smad7 promoter regions may cause a loss of Smad7 in CD4⁺ T cells of RA patients, which may contribute to the RA activity by disrupting the Th17/Treg balance.

Investigating the correlation of the NF-κB and FoxP3 gene expression with the plasma levels of pro- and anti-inflammatory cytokines in rheumatoid arthritis patients

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic inflammatory systemic autoimmune disease. Cytokines regulate a wide range of inflammatory processes involved in RA pathogenesis. Anti-inflammatory cytokines (i.e., TGF-β and lL-10) and pro-inflammatory cytokines, like IL-6, were found to be potentially implicated in RA pathogenesis. Besides, NF-κB and FoxP3 are critical transcription factors regulating the inflammatory events occurring in RA patients. This study intends to assess the plasma levels of IL-6, IL-10, and TGF-β1 cytokines, as well as the expression of NF-κB and FoxP3 genes in RA patients, compared to the healthy controls.

METHODS

Peripheral blood was collected from 50 RA patients (25 new case and 25 under-treatment) and 25 age- and gender-matched healthy subjects. The disease activity was determined using the DAS-28 and ESR criteria. Also, plasma levels of TGF-β1, lL-10, and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA) technique, and the gene expression of NF-κB and FoxP3 was evaluated using the real-time PCR method.

RESULTS

Our results showed a significant up-regulation of Rel-A and NF-κB1, and also a down-regulation of FoxP3 gene expression in under-treatment RA patients compared to the controls (P=0.031, P=0.014, and P=0.011, respectively). Moreover, there was a significant reduction of Rel-A and FoxP3 in the under-treatment RA patients compared to new case RA patients (P=0.005 and P=0.015, respectively). Also, plasma levels of TGF-β1 were significantly increased in both the new case and under-treatment RA patients relative to controls (P<0.001).

CONCLUSION

In conclusion, classical NF-κB (P65/P50) and FoxP3 may have significant pro- and anti-inflammatory roles in RA pathogenesis, respectively. Key Point • NF-κB (P65/P50) has a contribution to the early phase of RA.

Role of T Cells in the Pathogenesis of Rheumatoid Arthritis: Focus on Immunometabolism Dysfunctions

Evidence demonstrated that metabolic-associated T cell abnormalities could be detected in the early stage of RA development. In this context, molecular evaluations have revealed changes in metabolic pathways, leading to the aggressive phenotype of RA T cells. A growing list of genes is downregulated or upregulated in RA T cells, and most of these genes with abnormal expression fall into the category of metabolic pathways. It has been shown that RA T cells shunt glucose towards the pentose phosphate pathway (PPP), which is associated with a high level of nicotinamide adenine dinucleotide phosphate (NADPH) and intermediate molecules. An increased level of NADPH inhibits ATM activation and thereby increases the proliferation capabilities of the RA T cells. Defects in the DNA repair nuclease MRE11A cause failures in repairing mitochondrial DNA, resulting in inhibiting the fatty acid oxidation pathway and further elevated cytoplasmic lipid droplets. Accumulated lipid droplets employ to generate lipid membranes for the cell building program and are also used to form the front-end membrane ruffles that are accomplices with invasive phenotypes of RA T cells. Metabolic pathway involvement in RA pathogenesis expands the pathogenic concept of the disease beyond the common view of autoimmunity triggered by autoantigen recognition. Increased knowledge about metabolic pathways' implications in RA pathogenesis paves the way to understand better the environment/gene interactions and host/microbiota interactions and introduce potential therapeutic approaches. This review summarized emerging data about the roles of T cells in RA pathogenesis with a focus on immunometabolism dysfunctions and how these metabolic alterations can affect the disease process.

Echinocystic Acid Ameliorates Arthritis in SKG Mice by Suppressing Th17 Cell Differentiation and Human Rheumatoid Arthritis Fibroblast-Like Synoviocytes Inflammation

Echinocystic acid (EA), a pentacyclic triterpene, exhibits anti-inflammatory, antioxidant, and analgesic activities to counteract pathological effects in various diseases. Here, we aimed to determine the immunomodulatory effect of EA on zymosan-induced arthritis in SKG mice and how it would influence Th17 differentiation and human rheumatoid arthritis fibroblast-like synoviocytes inflammation. Our results showed that EA (10 and 25 mg/kg) attenuated arthritis symptoms, including high arthritis scores, infiltrating inflammatory cells, synovial hyperplasia, bone erosion, and the high levels of proinflammatory cytokines, such as TNF-α, interleukin (IL)-6, and IL-1β in paw tissues, and reduced the number of splenic Th17 cells. Mechanistically, we found that in vitro treatment of EA inhibited both IL-6- and transforming growth factor-β (TGF-β)-induced Th17 cell differentiation by suppressing the phosphorylation of signal transducers and transcriptional activators, especially STAT3. In line with the in vivo result, EA significantly reduced the protein and mRNA expression of IL-6 and IL-1β in human RA-FLA cells, MH7A cells. Furthermore, the production of both cytokines was confirmed with the downregulation of mitogen-activated protein kinases (MAPK) and nuclear factor-κB (NF-κB) signaling pathways under the stimulation of TNF-α. In conclusion, these findings revealed that EA was capable of amelioration of arthritic disorders in SKG mice through inhibiting Th17 cell differentiation and synovial fibroblast inflammation, supporting that EA is a promising therapeutic candidate for treating RA patients.

Low-dose IL-2 improved clinical symptoms by restoring reduced regulatory T cells in patients with refractory rheumatoid arthritis: A randomized controlled trial

Background

Regulatory T cells (Tregs) have been found to play crucial roles in immune tolerance. However, the status of Tregs in refractory rheumatoid arthritis (RA) is still unclear. Moreover, low-dose interleukin-2 (IL-2) has been reported to selectively promote the expansion of Tregs. This study investigated the status of CD4+ Tregs and low-dose IL-2 therapy in patients with refractory RA.

Methods

The absolute number of CD4+CD25+FOXP3+ Treg (CD4 Treg), CD4+IL17+ T (Th17), and other subsets in peripheral blood (PB) from 41 patients with refractory RA and 40 healthy donors was characterized by flow cytometry combined with an internal microsphere counting standard. Twenty-six patients with refractory RA were treated with daily subcutaneous injections of 0.5 million IU of human IL-2 for five consecutive days. Then, its effects on CD4 Treg and Th17 cells in PB were analyzed.

Results

A decrease in the absolute number of PB CD4 Tregs rather than the increase in the number of Th17 was found to contribute to an imbalance between Th17 and CD4 Tregs in these patients, suggesting an essential role of CD4 Tregs in sustained high disease activity. Low-dose IL-2 selectively increased the number of CD4 Tregs and rebalanced the ratio of Th17 and CD4 Tregs, leading to increased clinical symptom remission without the observed side effects.

Conclusions

An absolute decrease of PB CD4 Tregs in patients with refractory RA was associated with continuing disease activation but not the increase of Th17 cells. Low-dose IL-2, a potential therapeutic candidate, restored decreased CD4 Tregs and promoted the rapid remission of patients with refractory RA without overtreatment and the observed side effects.

Clinical trial registration

http://www.chictr.org.cn/showproj.aspx?proj=13909, identifier ChiCTR-INR-16009546.

Pros and cons of NRF2 activation as adjunctive therapy in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease with an important inflammatory component accompanied by deregulated redox-dependent signaling pathways that are feeding back into inflammation. In this context, we bring into focus the transcription factor NRF2, a master redox regulator that exerts exquisite antioxidant and anti-inflammatory effects. The review does not intend to be exhaustive, but to point out arguments sustaining the rationale for applying an NRF2-directed co-treatment in RA as well as its potential limitations. The involvement of NRF2 in RA is emphasized through an analysis of publicly available transcriptomic data on NRF2 target genes and the findings from NRF2-knockout mice. The impact of NRF2 on concurrent pathologic mechanisms in RA is explained by its crosstalk with major redox-sensitive inflammatory and cell death-related pathways, in the context of the increased survival of pathologic cells in RA. The proposed adjunctive therapy targeted to NRF2 is further sustained by the existence of promising NRF2 activators that are in various stages of drug development. The interference of NRF2 with conventional anti-rheumatic therapies is discussed, including the cytoprotective effects of NRF2 for alleviating drug toxicity. From another perspective, the review presents how NRF2 activation would be decreasing the efficacy of synthetic anti-rheumatic drugs by increasing drug efflux. Future perspectives regarding pharmacologic NRF2 activation in RA are finally proposed.

Immune hallmarks of rheumatoid arthritis management: A brief review

The purpose of this review was to examine current evidence on immunomodulation mediated by conventional drugs and the use of novel biological agents for the treatment of rheumatoid arthritis (RA). Currently, treatment is focused on maximizing quality of life through sustained clinical remission and/or attenuating disease activity. To do so, disease-modifying antirheumatic drugs, especially methotrexate, are used alone or in combination with other drugs, including leflunomide, biological disease-modifying antirheumatic drugs (bDMARDs) and targeted synthetic disease-modifying antirheumatic drugs (tsDMARDs). The most recent strategies modulate the immune response of the individual RA patient using tsDMARDs such as JAK inhibitors and bDMARDs such as ig-CTLA-4, anti- IL6R, anti-TNF-α and anti-CD20. To better understand current immunopharmacological interventions, we also looked at documented mechanisms of RA-mediated immunomodulation, highlighting perspectives potentially boosting RA treatment.

Role of Intestinal Dysbiosis and Nutrition in Rheumatoid Arthritis

Rheumatoid arthritis is a chronic systemic immune-mediated disease caused by genetic and environmental factors. It is often characterized by the generation of autoantibodies that lead to synovial inflammation and eventual multi-joint destruction. A growing number of studies have shown significant differences in the gut microbiota composition of rheumatoid arthritis (RA) patients compared to healthy controls. Environmental factors, and changes in diet and nutrition are thought to play a role in developing this dysbiosis. This review aims to summarize the current knowledge of intestinal dysbiosis, the role of nutritional factors, and its implications in the pathogenesis of rheumatoid arthritis and autoimmunity. The future direction focuses on developing microbiome manipulation therapeutics for RA disease management.

Angiotensin AT2 Receptor Stimulation Alleviates Collagen-Induced Arthritis by Upregulation of Regulatory T Cell Numbers

The angiotensin AT₂ receptor (AT₂R) is a main receptor of the protective arm of the renin-angiotensin system and exerts for instance anti-inflammatory effects. The impact of AT₂R stimulation on autoimmune diseases such as rheumatoid arthritis (RA) is not yet known. We investigated the therapeutic potential of AT₂R-stimulation with the selective non-peptide AT₂R agonist Compound 21 (C21) in collagen-induced arthritis (CIA), an animal model for inflammatory arthritis. Arthritis was induced by immunization of DBA/1J mice with collagen type II (CII). Prophylactic and therapeutic C21 treatment alleviates arthritis severity and incidence in CIA. Joint histology revealed significantly less infiltrates of IL-1 beta and IL-17A expressing cells and a well-preserved articular cartilage in C21- treated mice. In CIA, the number of CD4⁺CD25⁺FoxP3⁺ regulatory T (Treg) cells significantly increased upon C21 treatment compared to vehicle. T cell differentiation experiments demonstrated increased expression of FoxP3 mRNA, whereas IL-17A, STAT3 and IFN-gamma mRNA expression were reduced upon C21 treatment. In accordance with the mRNA data, C21 upregulated the percentage of CD4⁺FoxP3⁺ cells in Treg polarizing cultures compared to medium-treated controls, whereas the percentage of CD4⁺IL-17A⁺ and CD4⁺IFN-gamma⁺ T cells was suppressed. To conclude, C21 exerts beneficial effects on T cell-mediated experimental arthritis. We found that C21-induced AT₂R-stimulation promotes the expansion of CD4⁺ regulatory T cells and suppresses IL-17A production. Thus, AT₂R-stimulation may represent an attractive treatment strategy for arthritis.

Peripheral blood CD4posCD25posFoxP3pos cells and inflammatory cytokines as biomarkers of response in rheumatoid arthritis patients treated with CTLA4-Ig

BACKGROUND

Prognostic biomarkers of treatment response to distinct biologic disease-modifying anti-rheumatic drugs (b-DMARDs) are still lacking within the management of rheumatoid arthritis (RA).

METHODS

Thirty-four b-DMARDs naive RA patients, divided by disease duration into early (cohort 1) and long standing (cohort 2), received CTLA4-Ig. At study entry, and every 3 months for 1 year, each patient underwent peripheral blood (PB)-derived CD4^pos cell subpopulation assessment by flow cytometry, STAT3 and STAT5 expression by RT-PCR and IL-6, IL-12p70, TGFβ, and IL-10 serum levels by ELISA. The DAS and CDAI remission was assessed at 6 and 12 months.

RESULTS

DAS- and CDAI-defined remission within 12 months was achieved by 16 (47.1%) and 8 (23.5%) RA patients, respectively. Considering the whole RA cohort, CTLA4-Ig induced a significant decrease of IL-6 serum levels from baseline to 6 and 12 months, as well as of PB CD4^posCD25^posFoxP3^pos cells at 6 and 12 months, and of CD4^posIL17^pos cells after 12 months. PB CD4^pos cells of RA patients showed higher STAT3 and STAT5 expression than healthy controls, which remained unchanged within 12 months of treatment. At study entry, RA patients achieving DAS remission had significantly lower IL-6 serum levels than RA patients not achieving this outcome. In particular, having baseline IL-6 serum levels ≤ 8.4 pg/ml, significantly identified naïve to b-DMARDs RA patients more likely to achieve DAS-remission under CTLA4-Ig at 6 months (66.7%) compared to RA patients with baseline IL-6 serum levels > 8.4 pg/ml [15.4%, OR (95%Cis) 11.00 (1.75-55.82)]. Moreover, having CD4^posCD25^posFoxP3^pos cells rate ≥ 6.0% significantly identifies naïve to b-DMARDs early RA patients more likely to achieve DAS remission at 6 months (83.3%) compared to RA patients with baseline CD4^posCD25^posFoxP3^pos cells < 6.0% [16.7%, OR (95% Cis) 25.00 (1.00-336.81)].

CONCLUSIONS

Baseline IL-6 serum levels and peripheral blood-derived CD4^pos subpopulations are putative novel prognostic biomarkers of CTLA4-Ig response in RA patients.

Yunnan Baiyao Ameliorates Rheumatoid Arthritis in Rats by Shifting the Th17/Treg Cell Balance and Preventing Osteoclast Differentiation

Yunnan Baiyao (YNB) is a traditional Chinese medicine that possesses anti-inflammatory effects. Previously, we have demonstrated the effects of YNB in rheumatoid arthritis (RA) animal models; however, the underlying mechanisms are unclear. In the present study, we aimed to investigate the effects of YNB on the T-helper (Th)17/T-regulatory (Treg) cell balance in a collagen-induced arthritis rat model orally administrated YNB or methotrexate, a widely used therapeutic agent for treating RA. Our results showed that YNB treatment significantly decreased the voix pedis thickness and joint functionality scores and alleviated joint histopathology in these rats. These YNB-induced effects were achieved by decreasing the number of Th17 cells and increasing that of Treg cells in the spleen. Moreover, the interleukin- (IL-) 17 level considerably decreased in the serum of YNB-treated rats, whereas the IL-10 level significantly increased. Furthermore, YNB could inhibit RANKL-induced osteoclast formation by regulating the tumor necrosis factor receptor-associated factor 6/NF-κB/nuclear factor of the activated T-cell pathway. In summary, our study shows that YNB exhibits antiarthritic activity by decreasing the ratio of Th17/Treg cells, regulating the cytokine balance, and inhibiting osteoclast activation, providing an experimental basis that supports the use of this traditional Chinese medicine for the clinical treatment of RA.

Interleukin-17 contributes to Ross River virus-induced arthritis and myositis

Arthritogenic alphaviruses are mosquito-borne viruses that are a major cause of infectious arthropathies worldwide, and recent outbreaks of chikungunya virus and Ross River virus (RRV) infections highlight the need for robust intervention strategies. Alphaviral arthritis can persist for months after the initial acute disease, and is mediated by cellular immune responses. A common strategy to limit inflammation and pathology is to dampen the overwhelming inflammatory responses by modulating proinflammatory cytokine pathways. Here, we investigate the contribution of interleukin-17 (IL-17), a cytokine involved in arthropathies such as rheumatoid arthritis, in the development RRV-induced arthritis and myositis. IL-17 was quantified in serum from RRV-infected patients, and mice were infected with RRV and joints and muscle tissues collected to analyse cellular infiltrates, tissue mRNA, cytokine expression, and joint and muscle histopathology. IL-17 expression was increased in musculoskeletal tissues and serum of RRV-infected mice and humans, respectively. IL-17–producing T cells and neutrophils contributed to the cellular infiltrate in the joint and muscle tissue during acute RRV disease in mice. Blockade of IL-17A/F using a monoclonal antibody (mAb) reduced disease severity in RRV-infected mice and led to decreased proinflammatory proteins, cellular infiltration in synovial tissues and cartilage damage, without affecting viral titers in inflamed tissues. IL-17A/F blockade triggered a shift in transcriptional profile of both leukocyte infiltrates and musculoskeletal stromal cells by downregulating proinflammatory genes. This study highlights a previously uncharacterized role for an effector cytokine in alphaviral pathology and points towards potential therapeutic benefit in targeting IL-17 to treat patients presenting with RRV-induced arthropathy.

Some viruses transmitted by mosquitoes cause painful and debilitating arthritis, which manifests both as an acute form shortly following infection, and a chronic form long after the initial symptoms have subsided. These viruses, termed arboviruses, are difficult to control and there are currently no specific treatments to alleviate the pain and loss of mobility. Arthritis caused by arboviruses shares similarities with a non-infectious, autoimmune form of arthritis called rheumatoid arthritis (RA). In RA, an immune molecule termed interleukin-17, or IL-17, has been shown to drive arthritis and treatments that target or block IL-17 are being developed to treat RA. Here, we asked whether arthritis caused by an arbovirus, Ross River virus (RRV), was also associated with elevated IL-17 in humans and mice. Disease severity in mice was associated with high IL-17 expression in the feet and muscle, and blocking IL-17 using an anti-IL-17 monoclonal antibody ameliorated disease in mice infected with RRV. Our study provides new information on a molecule that is implicated in arthritic inflammation, and could be targeted to treat disease caused by arthritogenic arboviruses.

miRNAs as Biomarkers and Possible Therapeutic Strategies in Rheumatoid Arthritis

Within the past years, more and more attention has been devoted to the epigenetic dysregulation that provides an additional window for understanding the possible mechanisms involved in the pathogenesis of autoimmune rheumatic diseases. Rheumatoid arthritis (RA) is a heterogeneous disease where a specific immunologic and genetic/epigenetic background is responsible for disease manifestations and course. In this field, microRNAs (miRNA; miR) are being identified as key regulators of immune cell development and function. The identification of disease-associated miRNAs will introduce us to the post-genomic era, providing the real probability of manipulating the genetic impact of autoimmune diseases. Thereby, different miRNAs may be good candidates for biomarkers in disease diagnosis, prognosis, treatment and other clinical applications. Here, we outline not only the role of miRNAs in immune and inflammatory responses in RA, but also present miRNAs as diagnostic/prognostic biomarkers. Research into miRNAs is still in its infancy; however, investigation into these novel biomarkers could progress the use of personalized medicine in RA treatment. Finally, we discussed the possibility of miRNA-based therapy in RA patients, which holds promise, given major advances in the therapy of patients with inflammatory arthritis.

"Osteomicrobiology": The Nexus Between Bone and Bugs

A growing body of scientific evidence supports the notion that gut microbiota plays a key role in the regulation of various physiological and pathological processes related to human health. Recent findings have now established that gut microbiota also contributes to the regulation of bone homeostasis. Studies on animal models have unraveled various underlying mechanisms responsible for gut microbiota-mediated bone regulation. Normal gut microbiota is thus required for the maintenance of bone homeostasis. However, dysbiosis of gut microbiota communities is reported to be associated with several bone-related ailments such as osteoporosis, rheumatoid arthritis, osteoarthritis, and periodontitis. Dietary interventions in the form of probiotics, prebiotics, synbiotics, and postbiotics have been reported in restoring the dysbiotic gut microbiota composition and thus could provide various health benefits to the host including bone health. These dietary interventions prevent bone loss through several mechanisms and thus could act as potential therapies for the treatment of bone pathologies. In the present review, we summarize the current knowledge of how gut microbiota and its derived microbial compounds are associated with bone metabolism and their roles in ameliorating bone health. In addition to this, we also highlight the role of various dietary supplements like probiotics, prebiotics, synbiotics, and postbiotics as promising microbiota targeted interventions with the clinical application for leveraging treatment modalities in various inflammatory bone pathologies.

Dose-dependent effects of oleuropein administration on regulatory T-cells in patients with rheumatoid arthritis: An in vitro approach

Introduction:

Rheumatoid arthritis (RA) is an autoimmune disease that is identified with chronic inflammation and progressive destruction of the joints. The defective activity of regulatory T cells (Tregs) plays a crucial role in RA development. Oleuropein (OLEU) is the most common polyphenolic compound in olive leaf extracts with numerous pharmacological activities. In this study, the potential effects of OLEU in shifting CD4⁺ T cells toward Tregs are evaluated in patients with RA.

Methods

32 healthy controls (HC) and 45 RA patients were included in two groups. The immunoturbidometric technique was used to measure serum levels of c-reactive protein (CRP) and rheumatoid factor (RF). Isolated CD4⁺ T cells from peripheral blood mononuclear cells (PBMCs) of HC and RA patients were cultured with appropriate concentrations of OLEU. The cytotoxicity effects of OLEU were determined using the MTT assay at 24, 48, and 72 h. The percentage of CD4⁺CD25 + FoxP3 regulatory T lymphocytes (Tregs) and the expressions of IL-10 and TGF-β were evaluated by flow cytometry and immunoassay techniques after treatment of cells with different concentrations of OLEU for 24 h. The serum levels of RF and CRP in patients with RA were 11.8 ± 5.32 IU/ml and 6.36 ± 5.82 mg/l, respectively.

Results

OLEU had a dose-dependent effect on the CD4⁺ T cells via increasing the frequency of CD4⁺CD25 + FoxP3 Tregs (p = 0.0001). Moreover, it induced the production of IL-10 (p = 0.0001) and TGF-β (p < 0.01) in both HC and RA patients.

Conclusion

The findings of this study suggest that OLEU may have immunomodulatory effects by inducing Tregs, and it might help in developing a novel nutrition strategy for management of autoimmune diseases such as RA.

Role of interleukin-6 in bone destruction and bone repair in rheumatoid arthritis

Rheumatoid arthritis (RA) is a common inflammatory form of arthritis leading to the progressive bone and joint destruction. Many factors are closely involved in the pathology of RA, in particular bone-related cells and inflammatory cytokines such as TNF-α and interleukin-6 (IL-6). Because RA patients with progressive bone destruction experience accelerated deterioration of their quality of life, inhibition of disease progression and joint destruction has become an important clinical goal. Recent studies have also found that drug intervention targeting proinflammatory cytokines such as IL-6 results in bone repair in addition to suppression of bone and joint destruction, and these results suggest the potential for new therapeutic goals. Regarding the relationship between IL-6 and bone destruction, essential roles of osteoclasts have been reported over many years; however, more recent studies have explored the relationship of IL-6 with osteoblasts and osteocytes. In this review, we highlight the perspectives of basic and clinical research, adding new findings on the relationships between IL-6 and bone-related cells associated with inflammation, and the possibility of bone repair by blocking IL-6.

Cedrol from Ginger Ameliorates Rheumatoid Arthritis via Reducing Inflammation and Selectively Inhibiting JAK3 Phosphorylation

Ginger, as a food spice, is widely applied due to its extensive effects. Cedrol (CE) found in ginger is a sesquiterpene with anti-inflammatory activity. The objective of this research is to discuss the efficacy of CE on ameliorating rheumatoid arthritis (RA). CE inhibited chronic inflammation and pain in a dose-dependent manner accompanied by rapid onset and long duration. Besides, CE treatment effectively ameliorated the paw edema volume and arthritis score with no significant effect on body weight. Organ index, T-cell and B-cell proliferation, histopathology, and immunohistochemistry demonstrated that CE had immunological enhancement and attenuated RA effects. Remarkably, inhibition of phosphorylated-JAK3 protein, thereby abating the secretion of pro-inflammatory cytokines and inflammation-related mediators, was involved in the potential mechanism of CE efficiency through forming a hydrogen bond with ARG953 and ILE955 in the JAK3 active pocket. At the same time, the pharmacokinetic results showed that the absolute bioavailability of CE at 20, 40, and 80 mg/kg was 30.30, 23.68, and 16.11%, respectively. The current results offered clues for mastering the ameliorated RA of CE and further perfected the effective substance basis on the anti-inflammatory effect of ginger, which was beneficial for further applications.

Low-dose IL-2 therapy limits the reduction in absolute numbers of circulating regulatory T cells in rheumatoid arthritis

Background:

Circulating regulatory T cells (Tregs) are responsible for mediating immune tolerance and maintaining immunological homeostasis. Decreases in Tregs may be involved in the onset of rheumatoid arthritis (RA). Low-dose interleukin-2 (IL-2) has been considered for the treatment of inflammatory diseases mediated by T cells. This study focused on the status of circulating CD4⁺T subsets and the clinical feasibility of IL-2 therapies in patients with RA.

Methods:

The subjects included 888 patients with RA and 100 healthy controls (HCs); 233 RA patients received IL-2 treatment with 0.5 million international units (MIU)/day from days 1 through 5. The demographic features, disease activity, and levels of CD4+T cells measured by modified flow cytometry were collected in all RA patients before and after treatment.

Results:

RA patients had lower absolute Treg counts (but not Th17) compared with HCs, which was associated with disease activity; previously treated RA patients had the fewest circulating Tregs (p < 0.05). Patients treated with low-dose IL-2 had a three-fold increase in absolute anti-inflammatory Treg counts, as well as a two-fold increase in the other CD4⁺T subsets. Moreover, post-treatment levels of markers of disease activity in RA patients treated with IL-2 were significantly lower than the baseline values (p < 0.001), with no apparent side effects.

Conclusion:

Decreased absolute counts of circulating CD4⁺T lymphocyte subsets were observed in patients with RA. Circulating Tregs, which mediate immune tolerance, may be involved in the pathogenesis and progression of RA; however, this was ameliorated by low-dose IL-2, without obvious side effects.

Plain language summary

Low-dose IL-2 treatment for rheumatoid arthritis

• Circulating Tregs may be involved in the pathogenesis and progression of RA.

• The absolute count of Tregs was significantly correlated with disease activity measures.

• Low-dose IL-2 was able to effectively expade Tregs and help for RA patients’ symptoms remission without evaluated side effects.

The gut-joint axis in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disorder that primarily affects the joints. One hypothesis for the pathogenesis of RA is that disease begins at mucosal sites as a consequence of interactions between the mucosal immune system and an aberrant local microbiota, and then transitions to involve the synovial joints. Alterations in the composition of the microbial flora in the lungs, mouth and gut in individuals with preclinical and established RA suggest a role for mucosal dysbiosis in the development and perpetuation of RA, although establishing whether these alterations are the specific consequence of intestinal involvement in the setting of a systemic inflammatory process, or whether they represent a specific localization of disease, is an ongoing challenge. Data from mouse models of RA and investigations into the preclinical stages of disease also support the hypothesis that these alterations to the microbiota predate the onset of disease. In addition, several therapeutic options widely used for the treatment of RA are associated with alterations in intestinal microbiota, suggesting that modulation of intestinal microbiota and/or intestinal barrier function might be useful in preventing or treating RA.

Decreased numbers and sex-based differences of circulating regulatory T cells in patients with seropositive undifferentiated arthritis

Aims:

CD4⁺ T cells play crucial roles as both mediators and regulators of the pathogenesis of rheumatoid arthritis (RA). However, the characteristics of CD4⁺ T cell subpopulations in the earliest stage of RA development remain unclear. Hence, we determined the proportions and absolute counts of circulating CD4⁺ T cell subsets in patients with seropositive undifferentiated arthritis (SUA), the early and preclinical stage of RA.

Methods:

Peripheral blood samples and clinical information were collected from 177 patients with SUA, 104 patients with RA, and 120 healthy controls. All patients were newly diagnosed and untreated. Proportions and absolute counts of CD4⁺ T cell subpopulations were determined by flow cytometric analysis.

Results:

In patients with SUA, percentages and absolute counts of circulating regulatory T (Treg) cells were decreased significantly and Th17/Treg cell ratios were abnormally increased, whereas Th17 cell numbers were similar to those in healthy controls. In addition, sex-based differences in circulating Treg cells were observed, with female SUA patients having lower proportions and absolute counts of Treg cells than those in males. Moreover, female patients with SUA had higher erythrocyte sedimentation rates and 28-joint Disease Activity Scores than those in males.

Conclusion:

Immune tolerance deficiency resulting from an abnormal reduction in circulating Treg cells might be the most crucial immunological event in the earliest stage of RA. The sex-specific disparity in Treg cells should also be considered for immunoregulatory and preventive strategies targeting early RA.

An Overview of the NF-kB mechanism of pathophysiology in rheumatoid arthritis, investigation of the NF-kB ligand RANKL and related nutritional interventions

Nuclear Factor Kappa-Β (NF-kB) is recognized as one of the main inflammatory pathways in the Autoimmune Disease (AD) Rheumatoid Arthritis (RA), which exhibits high levels of inflammatory cytokines such as IL-1, TNFa and IL-6 linked to bone erosion and disease progression. NF-kB is also the most studied pathophysiological mechanism in RA, however, over the last few decades, a more recently discovered Receptor Activator of Nuclear Factor Kappa-Β Ligand (RANKL), also linked to NF-kB activation and bone erosion, has been the topic of interest for research in the area of AD management. As the non-discriminative long term suppression of the NF-kB pathway by pharmacological agents in the management of RA has been linked with a number of side effects and with the discovery of the RANKL mechanism, which may present a more targeted approach to the management of the AD, there has been renewed interest in research on the potential impact of nutritional interventions influencing the NF-kB pathway, RANKL as well as RA disease outcomes. Existing research highlights the potential utility of nutrients such as Omega 3 and Vitamin D, which may lower NF-kB activation in RA. There is, however, a gap in the knowledge of the effects of nutritional interventions on pathophysiological mechanisms contributing to RA and a more robust systematic analysis of whether nutrients or specific vitamins can have an effect on the NF-kB and RANKL main drivers of pathology in RA. Findings from this study suggest the potential of Vitamin D supplementation in lowering the levels of RANKL and related markers/cytokines such as Th17 cell levels, OPG/RANKL ratio and CXCL10 pathway, which may present as a viable nutrition intervention for the management of RA. The methodology of this review involved a Systematic Search of the Literature with a Critical Appraisal of papers. It incorporated three tranche searches of 1. review, 2. animal/in vitro and 3. intervention peer reviewed research published in the last 10 years, resulting in a total of 119 papers. Results provide an overview of the NF-kB pathway, a detailed mechanistic examination of the Receptor Activator of Nuclear Factor Kappa-Β Ligand (RANKL) which is linked to bone erosion, and finally a review of nutritional interventions relating to this mechanism of pathophysiology. The accepted papers were critically appraised using SIGN50 for human studies and the ARRIVE guidelines for animal studies; the narrative was and the extracted information coded into key themes.

Anti-inflammatory and immune-modulatory impacts of berberine on activation of autoreactive T cells in autoimmune inflammation

Autoreactive inflammatory CD4+ T cells, such as T helper (Th)1 and Th17 subtypes, have been found to associate with the pathogenesis of autoimmune disorders. On the other hand, CD4+ Foxp3+ T regulatory (Treg) cells are crucial for the immune tolerance and have a critical role in the suppression of the excessive immune and inflammatory response promoted by these Th cells. In contrast, dendritic cells (DCs) and macrophages are immune cells that through their inflammatory functions promote autoreactive T-cell responses in autoimmune conditions. In recent years, there has been increasing attention to exploring effective immunomodulatory or anti-inflammatory agents from the herbal collection of traditional medicine. Berberine, an isoquinoline alkaloid, is one of the main active ingredients extracted from medicinal herbs and has been shown to exert various biological and pharmacological effects that are suggested to be mainly attributed to its anti-inflammatory and immunomodulatory properties. Several lines of experimental study have recently investigated the therapeutic potential of berberine for treating autoimmune conditions in animal models of human autoimmune diseases. Here, we aimed to seek mechanisms underlying immunomodulatory and anti-inflammatory effects of berberine on autoreactive inflammatory responses in autoimmune conditions. Reported data reveal that berberine can directly suppress functions and differentiation of pro-inflammatory Th1 and Th17 cells, and indirectly decrease Th cell-mediated inflammation through modulating or suppressing other cells assisting autoreactive inflammation, such as Tregs, DCs and macrophages.

Er Miao San, a traditional Chinese herbal formula, attenuates complete Freund's adjuvant-induced arthritis in rats by regulating Th17/Treg cells

Context: Er Miao San (EMS) is a traditional Chinese medicine composed of Atractylodis Rhizoma and Phellodendri Cortex in a 1:1 weight ratio. EMS has been used to treat rheumatism in China for many years.Objective: To evaluate the anti-arthritic activity of EMS extract on adjuvant-induced arthritis (AA) in Sprague-Dawley rats and to clarify its mechanisms of action.Materials and methods: EMS (0.75, 1.5 and 3 g/kg, once daily) was orally administered from day 18 after immunization to day 31. The effects of EMS on AA rats were evaluated by histopathological examination, paw swelling and polyarthritis index. The proliferation of fibroblast-like synoviocyte (FLS) and T cells was detected by CCK-8. The percentages of Th17 cells and Treg cells in splenocytes were determined by flow cytometry. Levels of cytokines in serum were detected by ELISA.Results: EMS treatment significantly decreased the paw volume (from 1.20 to 0.81), polyarthritis index (from 9.56 to 4.46) and alleviated ankle joint histopathology in AA rats. EMS inhibited the proliferation of FLS and T cells. Furthermore, EMS treatment decreased Th17 cells (from 4.62 to 2.08%) and increased Treg cells (from 2.77 to 4.75%) in splenocytes. The levels of IL-17A, TNF-α and IL-6 were remarkably decreased in the serum of EMS-treated rats, whereas the levels of IL-10 and TGF-β1 were significantly increased.Conclusions: EMS exhibits anti-arthritic activity in the AA model by regulating the balance of cytokines and the ratio of Th17 and Treg cells. These insights may provide an experimental basis for the clinical treatment of RA.

Aberrant expression of USF2 in refractory rheumatoid arthritis and its regulation of proinflammatory cytokines in Th17 cells

IL-17-producing Th17 cells are implicated in the pathogenesis of rheumatoid arthritis (RA) and TNF-α, a proinflammatory cytokine in the rheumatoid joint, facilitates Th17 differentiation. Anti-TNF therapy ameliorates disease in many patients with rheumatoid arthritis (RA). However, a significant proportion of patients do not respond to this therapy. The impact of anti-TNF therapy on Th17 responses in RA is not well understood. We conducted high-throughput gene expression analysis of Th17-enriched CCR6+CXCR3-CD45RA- CD4+ T (CCR6+ T) cells isolated from anti-TNF-treated RA patients classified as responders or nonresponders to therapy. CCR6+ T cells from responders and nonresponders had distinct gene expression profiles. Proinflammatory signaling was elevated in the CCR6+ T cells of nonresponders, and pathogenic Th17 signature genes were up-regulated in these cells. Gene set enrichment analysis on these signature genes identified transcription factor USF2 as their upstream regulator, which was also increased in nonresponders. Importantly, short hairpin RNA targeting USF2 in pathogenic Th17 cells led to reduced expression of proinflammatory cytokines IL-17A, IFN-γ, IL-22, and granulocyte-macrophage colony-stimulating factor (GM-CSF) as well as transcription factor T-bet. Together, our results revealed inadequate suppression of Th17 responses by anti-TNF in nonresponders, and direct targeting of the USF2-signaling pathway may be a potential therapeutic approach in the anti-TNF refractory RA.

Immunomodulatory effects of berberine on the inflamed joint reveal new therapeutic targets for rheumatoid arthritis management

Rheumatoid arthritis (RA) is a chronic inflammatory syndrome designated by synovial joint inflammation leading to cartilage degradation and bone damage as well as progressive disability. Synovial inflammation is promoted through the infiltration of mononuclear immune cells, dominated by CD4+ T cells, macrophages and dendritic cells (DCs), together with fibroblast-like synoviocytes (FLS), into the synovial compartment. Berberine is a bioactive isoquinoline alkaloid compound showing various pharmacological properties that are mainly attributed to immunomodulatory and anti-inflammatory effects. Several lines of experimental study have recently investigated the therapeutic potential of berberine and its underlying mechanisms in treating RA condition. The present review aimed to clarify determinant cellular and molecular targets of berberine in RA and found that berberine through modulating several signalling pathways involved in the joint inflammation, including PI3K/Akt, Wnt1/β-catenin, AMPK/lipogenesis and LPA/LPA1 /ERK/p38 MAPK can inhibit inflammatory proliferation of FLS cells, suppress DC activation and modulate Th17/Treg balance and thus prevent cartilage and bone destruction. Importantly, these molecular targets may explore new therapeutic targets for RA treatment.

Regulatory T Cell Plasticity and Stability and Autoimmune Diseases

CD4⁺CD25⁺ regulatory T cells (Tregs) are a class of CD4⁺ T cells with immunosuppressive functions that play a critical role in maintaining immune homeostasis. However, in certain disease settings, Tregs demonstrate plastic differentiation, and the stability of these Tregs, which is characterized by the stable expression or protective epigenetic modifications of the transcription factor Foxp3, becomes abnormal. Plastic Tregs have some features of helper T (Th) cells, such as the secretion of Th-related cytokines and the expression of specific transcription factors in Th cells, but also still retain the expression of Foxp3, a feature of Tregs. Although such Th-like Tregs can secrete pro-inflammatory cytokines, they still possess a strong ability to inhibit specific Th cell responses. Therefore, the plastic differentiation of Tregs not only increases the complexity of the immune circumstances under pathological conditions, especially autoimmune diseases, but also shows an association with changes in the stability of Tregs. The plastic differentiation and stability change of Tregs play vital roles in the progression of diseases. This review focuses on the phenotypic characteristics, functions, and formation conditions of several plastic Tregs and also summarizes the changes of Treg stability and their effects on inhibitory function. Additionally, the effects of Treg plasticity and stability on disease prognosis for several autoimmune diseases were also investigated in order to better understand the relationship between Tregs and autoimmune diseases.

Increased Serum Interleukin-2 Levels Are Associated with Abnormal Peripheral Blood Natural Killer Cell Levels in Patients with Active Rheumatoid Arthritis

Objective

To investigate the relationship between serum interleukin-2 (IL-2) levels and disease activity, absolute numbers of peripheral lymphocyte subsets, autoantibodies, and associated cytokines in patients with rheumatoid arthritis (RA).

Methods

This study included 106 patients with RA, evaluated their disease activity (DAS28 score), and divided them into disease remission (DAS28 ≤ 2.6), low disease activity (DAS28 ≤ 3.2), and moderate-high disease activity (DAS28 > 3.2) groups. Flow cytometry was used to detect the absolute numbers of peripheral lymphocyte subpopulations and CD4+ T cell subsets in each group, and serum cytokine levels were measured using cytometric bead array.

Results

Serum IL-2 levels in RA patients were positively correlated with disease activity and rheumatoid factor titers (p < 0.001 and p = 0.045, respectively), and multiple regression analysis revealed that serum IL-2 levels were an independent factor affecting disease activity. Serum IL-2 levels were positively correlated with Th17/Treg ratios (p = 0.013). Compared with the remission group, peripheral lymphocyte and CD4+ T lymphocyte subsets in patients with active RA decreased to varying degrees; however, the numbers of peripheral natural killer (NK) cells were significantly higher in the moderate-high disease activity group than in the remission (p = 0.046) and low disease activity (p = 0.020) groups; the percentages of NK cells had the same trend. In addition, the number and percentage of NK cells were positively correlated with serum IL-2 levels (p = 0.018 and p = 0.006, respectively).

Conclusions

In RA patients, serum IL-2 levels were not only correlated with patients' disease activity and autoantibody levels but were also involved in their Th17/Treg immune imbalance. In addition, in patients with active RA, NK cell levels were abnormally elevated, possibly due to high serum levels of IL-2.

Vitamin D: does it help Tregs in active rheumatoid arthritis patients

Background Regulatory T cells (Tregs) play an important role in the maintenance of immunological tolerance. Tregs deficiency or suppressor functions reduction may be associated with autoimmune diseases development. Objectives To estimate the effect of vitamin D supplementation on Tregs level in the peripheral blood of active rheumatoid arthritis (RA) patients. Methods 40 active RA patients were randomly assigned into two groups. Group I received methotrexate (MTX) plus hydroxychloroquine, group II received MTX, hydroxychloroquine plus vitamin D supplementation for 3 months, and 30 healthy volunteers as control group. Peripheral blood Tregs were measured at baseline and after 3 months by Flow Cytometry. Results At baseline, Tregs percentage was significantly decreased (p<0.001) in both RA patient groups (13.52±1.95%, 13.65±2.98% respectively), compared to controls (28.44±7.37%) with no significant difference between the two patient groups (p=0.866). After 3 months, there was a significant elevation in Tregs percentage in group II compared to group I (p<0.001). Tregs elevation was associated with significant DAS-28 score reduction (p<0.001). Conclusion Vitamin D appears to have important immunomodulatory functions. Vitamin D supplementation can be combined safely with traditional DMARDs to regulate the immune system. Clinical trial registration Tanta University Protocol Record 33846, Vitamin D Effect in Rheumatoid Arthritis, http://www.clinicaltrials.gov, NCT04472481.

Regulation of T Cell Activities in Rheumatoid Arthritis by the Novel Fusion Protein IgD-Fc-Ig

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation and T cell hyper-activation. Emerging evidence has shown that the stimulation of immunoglobulin D (IgD) induces T cell activation and may contribute to disease pathogenesis. In this study, the sIgD concentrations were positively associated with disease activity score in 28 joints (DAS28) and anti-cyclic citrullinated peptide (anti-CCP) in RA. We demonstrated that IgD-Fc-Ig (composed of human IgD Fc domain and IgG₁ Fc domain, obtained through prokaryotic protein expression and chromatography purification) effectively inhibited the activation and proliferation of T cells in healthy controls and PBMCs in RA patients stimulated by IgD, recovered the Th17/Treg cell subset balance, and downregulated p-Lck and p-ZAP70 expression. Moreover, in vivo, IgD-Fc-Ig decreased the swollen joint counts and arthritis indices in mice with collagen-induced arthritis (CIA), and ameliorated histopathological changes in joint and spleen tissue. It also downregulated thymocyte proliferation and reduced the percentage of helper T cells (Th) and CD154⁺ T cells, reversed the imbalance of Th1/Th2 and Th17/Treg cell subsets, reduced cytokine and chemokine levels, and inhibited p-Lck and p-ZAP70 expression. Our data suggest that IgD-Fc-Ig fusion protein regulates T cell activity in RA. These findings have potential implications for IgD-targeted strategies to treat IgD-associated RA.

CXCR3 antagonist AMG487 inhibits glucocorticoid-induced tumor necrosis factor-receptor-related protein and inflammatory mediators in CD45 expressing cells in collagen-induced arthritis mouse model

Rheumatoid arthritis (RA) is an autoimmune disease classified by uncontrolled joint inflammation leading to the destruction of both cartilage and joints. Despite progress made in RA treatment in the past decade, new drugs with high efficacy and fewer long-term adverse effects are still needed; thus, safe anti-inflammatory therapies for RA are urgently needed. Previous results demonstrated that the CXCR3 antagonist is an extremely attractive therapeutic target for the treatment of several autoimmune diseases, suggesting that it might have an inhibitory effect on RA. In this study, we investigated the effect of AMG487, a selective CXCR3 antagonist, on collagen-induced arthritis (CIA) in mice and evaluated its potential therapeutic mechanism.Following induction of CIA, mice were treated with AMG487 (5 mg/kg, intraperitoneally), to investigate their protective effects against CIA. CD4, CD25, CCR6, IL-9, NF-κB, IL-6, IL-17A, IL-21, STAT6 and Foxp3 expressing GITR⁺ and CD45⁺ cells were measured in the spleen using flow cytometry to assess anti-inflammatory effects of AMG487. The mRNA and protein expression of GITR, CCR6, IL-9, and IL-21 were measured using quantitative real-time PCR and western blot analysis in knee tissue. AMG487 significantly alleviated joint inflammation by decreasing GITR⁺CD25⁺, GITR⁺CD45⁺, GITR⁺IL-9⁺, GITR⁺NF-κB⁺ CD45⁺CD4⁺, CD45⁺CCR6⁺, CD45⁺IL-6⁺ cells, CD45⁺IL-17A⁺, and CD45⁺IL-21⁺, and increasing GITR⁺Foxp3⁺ and GITR⁺STAT6⁺ cells. There was a significant decrease in mRNA and protein expression of GITR, CD4, CCR6, IL-6, IL-9, and IL-21 in knee tissue of CIA mice. This study demonstrates that AMG487 has a potential therapeutic effect on RA and could explore novel anti-inflammatory therapies for its treatment.

Additive Effects of VDBP and 1,25(OH)2D3 on the Viability and Apoptosis of Rheumatoid Arthritis Synovial Fibroblasts

AIM

This study is to investigate the additive effect of Vitamin D-binding protein (VDBP) and 1,25(OH)2D3 on the viability and apoptosis of synovial cells from patients with rheumatoid arthritis (RA).

METHODS

Synovial tissues and synovial fluid of patients with RA and osteoarthritis (OA) were collected. The expression of VDBP was analyzed with immunohistochemistry and ELISA. CCK-8 assay was applied to detect cell viability. Flow cytometry was used to analyze cell cycle and apoptosis.

RESULTS

Immunohistochemical results showed that the expression of VDBP in the synovium of RA patients was significantly lower than that of OA (P<0.05). Similarly, ELISA results presented a lower expression of VDBP in the synovial fluid of RA patients. The results of CCK-8 assay showed that both 1,25(OH)2D3 and VDBP significantly inhibited the viability of rheumatoid arthritis synovial fibroblasts (RASF) (P<0.05). The treatment with 1,25(OH)2D3+VDBP led to more significantly inhibited viability of RASF, compared with 1,25(OH)2D3 alone (P<0.05). The results of flow cytometry showed that 1,25(OH)2D3 and VDBP both promoted the apoptosis of RASF (P<0.05) and 1,25(OH)2D3+VDBP led to a higher proportion of RASF apoptosis, compared with 1,25(OH)2D3 alone (P<0.05). However, 1,25(OH)2D3 and VDBP had no significant effect on the cell cycle of RASF. Additionally, 1,25(OH)2D3 promoted the expression of VDBP in RASF, but not concentration-dependently.

CONCLUSION

VDBP is reduced in the synovial tissue and synovial fluid of RA patients and can inhibit viability of RASF and promote the apoptosis of RASF. The 1,25(OH)2D3 can upregulate the expression of VDBP in RASF. Additionally, VDBP can enhance the effects of 1,25(OH)2D3 on viability and apoptosis of RASF.

Secreted Frizzled-related proteins (sFRPs) in osteo-articular diseases: much more than simple antagonists of Wnt signaling?

Osteo-articular diseases are characterized by a dysregulation of joint and/or bone homeostasis. These include diseases affecting the joints originally, such as osteoarthritis and rheumatoid arthritis, or the bone, such as osteoporosis. Inflammation and the involvement of Wingless-related integration site (Wnt) signaling pathways are key pathophysiological features of these diseases resulting in tissue degradation by matrix-degrading enzymes, namely matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinases with thrombospondin motifs (ADAMTs), secreted by the joint resident cells and/or by infiltrating immune cells. Activation of Wnt signaling pathways is modulated by different families of proteins, including Dickkopfs and the secreted Frizzled-related proteins (sFRPs). The sFRP family is composed of five secreted glycoproteins in mammals that regulate Wnt signaling in the extracellular compartment. Indeed, sFRPs are able to bind both to the soluble Wnt ligands and to their cell membrane receptors, the Frizzled proteins. Their expression profile is altered in osteo-articular diseases, suggesting that they could account for the abnormal activation of Wnt pathways. In the present article, we review how sFRPs are more than simple antagonists of the Wnt signaling pathways and discuss their pathophysiological relevance in the context of osteo-articular diseases. We detail their Wnt-dependent and their Wnt-independent roles, with a particular emphasis on their ability to modulate the inflammatory response and extracellular matrix (ECM) remodeling. We also discuss their potential therapeutic use with a focus on bone remodeling, osteo-articular cancers, and tissue engineering.

Quantifying circulating Th17 cells by qPCR: potential as diagnostic biomarker for rheumatoid arthritis

OBJECTIVE

The diagnosis of RA patients remains a challenge, especially in ACPA-negative disease. Novel T-cell subsets, particularly Th17 may be useful, although data on Th17 frequency using flow cytometry in RA are conflicting. We investigated whether a novel epigenetic qPCR assay for the quantification of Th17 could differentiate patients with RA from those with symptoms evolving towards an alternative diagnosis.

METHODS

We used a qPCR assay measuring the extent of the methylation at a key position in the IL-17 and CD4 genes. Assays were performed on whole blood from 49 healthy controls (HC) and 165 early arthritis clinic patients. Flow cytometry was further used to detect the expression of CXCR4 on Th17 cells.

RESULTS

In 75 inflammatory arthritis patients who progressed to RA, the qPCR assays showed significantly fewer Th17 cells compared with 90 patients who did not (P<0.0001). Regression models demonstrated a high predictive value for RA development (75.8% correct prediction), and particularly for the ACPA-negative group (n = 125) where Th17 and swollen joint count (SJC) were the only predictors (73% correct prediction). The chemokine receptor CXCR4 had significantly higher expression on Th17 from early RA patients (n = 11) compared with HC (n = 15).

CONCLUSION

The results of the epigenetic qPCR assay showed that low levels of Th17 cells were predictive of developing RA, particularly in the ACPA-negative patients. This could have value for insights into pathogenesis and management. The results suggest the recruitment of Th17 to the inflammatory disease site, consistent with high CXCR4 expression.

Potential therapeutic effects of cyanidin-3-O-glucoside on rheumatoid arthritis by relieving inhibition of CD38+ NK cells on Treg cell differentiation

Background

CD38+ NK cells are overabundant in rheumatoid arthritis (RA). Cyanidin-3-O-glucoside (C3G) is an inhibitor of CD38. This study investigated the pathogenic role of CD38+ NK cells and the effect of C3G on RA.

Methods

Rats with bovine type II collagen-induced arthritis (CIA) were injected with C3G. RA synovial fibroblasts (RASFs) or mononuclear cells (MNCs) were cultured with C3G. MNCs were also cocultured with CD38+ NK cells following C3G pretreatment.

Results

C3G injection significantly alleviated CIA. C3G also significantly increased the level of interleukin (IL)-10 and the regulatory T (Treg) cell proportion, and it decreased the interleukin (IL)-6 and interferon (IFN)-γ levels and CD38+ NK cell proportion in rat peripheral blood and synovial fluid. Additionally, C3G significantly increased RASF apoptosis and decreased RASF proliferation and IL-6 production in the culture medium. Furthermore, C3G stimulated MNCs to increase IL-2 and IL-10 production and the Treg cell proportion, and it caused MNCs to decrease IL-6 and IFN-γ production and the CD38+ NK cell proportion. Although CD38+ NK cells significantly decreased the Treg cell proportion and IL-10 level in MNCs, CD38+ NK cells that had been pretreated with C3G increased the proportion of Treg cells and IL-10 levels and decreased the IL-6 and IFN-γ levels in the coculture. In CD38+ NK cells, C3G significantly increased Sirtuin 6 (Sirt6) expression and the tumor necrosis factor (TNF)-α level, and it decreased natural killer group 2D (NKG2D) expression and the IFN-γ level. However, when CD38+ NK cells were treated with Sirt6 siRNA, C3G did not change the NKG2D expression, the TNF-α level sharply decreased, and the IFN-γ level increased. When MNCs were cocultured with C3G-pretreated CD38+ NK cells in the presence of TNF-α and an anti-IFN-γ antibody, the IL-10+ Treg cell proportion significantly increased. When MNCs were cocultured with C3G-pretreated CD38+ NK cells in the presence of IFN-γ and an anti-TNF-α antibody, the IL-10+ Treg cell proportion sharply decreased. When CIA rats were injected with both C3G and the Sirt6 inhibitor OSS_128167, the rats exhibited joint inflammation and a low Treg cell proportion, but the CD38+ NK proportion was still low.

Conclusion

C3G has therapeutic effects on CIA and RA. C3G decreased the proportion of CD38+ cells, RASF proliferation, and proinflammatory cytokine secretion, and it increased the Treg cell proportion. C3G also elevated Sirt6 expression to suppress NKG2D expression, increase TNF-α secretion, and decrease IFN-γ secretion in CD38+ NK cells, which stimulates MNCs to differentiate into Treg cells. This study also demonstrates that the inhibition of Treg cell differentiation in MNCs by CD38+ NK cells is a potential cause of the immune imbalance in RA and CIA.

Progress in interleukin-2 therapy for rheumatic immune diseases by regulating the immune balance of T cells

Breaking the balance between effector T cells, including Th17 (T helper cell 17) cells, and regulatory T cells (Tregs) is a key link in the pathogenesis of rheumatic immune diseases, which lead to a new concept of regulating immune balance in the treatment of rheumatic immune diseases. Interleukin (IL)-2 can effectively regulate the differentiation, development and functional activity of regulatory T cells, thus restoring the immune balance between regulatory T cells and effector T cells. Therefore, low-dose IL-2 has been used in the treatment of rheumatic immune diseases, and it has become a promising new choice to achieve therapeutic purpose by regulating the immune balance of T cell. Here, we discuss the role of T cells immune imbalance in the pathogenesis of rheumatic immune diseases and the mechanism of IL-2 in the treatment of rheumatic immune diseases by regulating T cells immune balance and summarize the relevant clinical trials.

Prophylactic effects of probiotic Bifidobacterium spp. in the resolution of inflammation in arthritic rats

In the present study, the modulatory effects of bifidobacterial spp. (Bifidobacterium breve NCIM 5671, Bifidobacterium longum NCIM 5672 and Bifidobacterium bifidum NCIM 5697) on adjuvant induced arthritis in rats were evaluated. Arthritis was induced in male Wistar rats by injecting 250 μg of Freund's adjuvant directly into the paw. Fifteen days before and 15 days after the induction of arthritis, suspended cultures of bifidobacteria (10⁹ cfu/ml) were administered by oral gavage. Paw volume, bone mineral content, oxidative stress markers, antioxidant enzymes, cytokines, eicosanoids and expression of COX2, as well as bone hydrolytic enzymes, were assessed by RT PCR. Although piroxicam-treated groups (drug control) had better effects than bifidobacteria-treated groups, bifidobacteria probiotics administration exhibited significant (P < 0.05) prophylactic effects in terms of downregulating arthritis markers. Parameters including paw volume, bone mineral content, cytokines, and eicosanoids level were significantly (p < 0.05) modulated in bifidobacteria administered groups compared to arthritic control group. Among the three strains tested, B. breve NCIM 5671 exhibited superior prophylactic effects as assessed in the experimental rat model of arthritis. In conclusion, bifidobacteria probiotics administration can downregulate the markers of arthritis and hence can be a potential therapeutic regimen in the treatment of arthritis.

Decreased regulatory T-cell frequency and interleukin-35 levels in patients with rheumatoid arthritis

Interleukin-35 (IL-35) is a newly discovered anti-inflammatory cytokine predominantly released by regulatory T cells (Tregs) and may serve an important role in the pathogenesis of autoimmune diseases. The levels of IL-35 and corresponding Treg frequencies in patients with rheumatoid arthritis (RA) have scarcely been reported. The present study aimed to detect serum IL-35 levels and Treg frequencies in patients with RA, and analyze their association with each other and with indicators of RA. A total of 55 patients with RA, including 37 active-phase (AP) and 18 chronic-phase (CP) cases, as well as 20 healthy controls (HC), were recruited. Clinical parameters, including erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) levels, rheumatoid factor (RF), anti-cyclic citrullinated peptide (CCP) antibody and 28-joint disease activity score (DAS28) were assessed. The Treg frequency in peripheral blood (PB) was determined by flow cytometry. IL-35 mRNA in PB mononuclear cells of the patients with RA was measured by reverse transcription-quantitative polymerase chain reaction analysis, and IL-35 levels in the serum were detected by ELISA. The correlations between IL-35 levels and the abovementioned indexes were analyzed by determining Pearson's correlation coefficient. The results of the present study indicated that the Treg frequency was significantly decreased in patients with RA compared with that in HC. No significant difference in Treg frequency between the AP and CP groups of RA patients was identified. In addition, the serum IL-35 levels and mRNA expression in RA patients were obviously lower than those in the HC. Of note, the serum IL-35 levels were negatively correlated with the ESR and DAS28 of patients with RA, while no correlation with CRP, RF or anti-CCP antibodies was identified. In addition, a significant positive correlation was revealed between serum IL-35 levels and the Treg frequency. These results suggest that IL-35 and Tregs have a protective role regarding the development of RA.