#CXCR5/CXCL13 pathway, a key driver for migration of regulatory B10 cells, is defective in patients with rheumatoid arthritis

Circulating DNA methylation level of CXCR5 correlates with inflammation in patients with rheumatoid arthritis

OBJECTIVES

To assess the differences in circulating DNA methylation levels of CXCR5 between rheumatoid arthritis (RA) and osteoarthritis (OA) and healthy controls (HC), and the correlation of methylation changes with clinical characteristics of RA patients.

METHODS

Peripheral blood samples were collected from 239 RA patients, 30 patients with OA, and 29 HC. Target region methylation sequencing to the promoter region of CXCR5 was achieved using MethylTarget. The methylation level of cg04537602 and methylation haplotype were compared among the three groups, and the correlation between methylation levels and clinical characteristics of RA patients was performed by Spearman's rank correlation analysis.

RESULTS

The methylation level of cg04537602 was significantly higher in the peripheral blood of RA patients compared with OA patients (p = 1.3 × 10^-3 ) and in the HC group (p = 5.5 × 10^{- 4} ). The sensitivity was enhanced when CXCR5 methylation level combined with rheumatoid factor and anti-cyclic citrullinated peptide with area under curve (AUC) of 0.982 (95% confidence interval 0.970-0.995). The methylation level of cg04537602 in RA was positively correlated with C-reactive protein (CRP) (r = .16, p = .01), and in RA patients aged 60 years and above, cg04537602 methylation levels were positively correlated with CRP (r = .31, p = 4.7 × 10^{- 4} ), tender joint count (r = .21, p = .02), visual analog scales score (r = .21, p = .02), Disease Activity Score in 28 joints (DAS28) using the CRP level DAS28-CRP (r = .27, p = 2.1 × 10^{- 3} ), and DAS28-ESR (r = .22, p = .01). We also observed significant differences of DNA methylation haplotypes in RA patients compared with OA patients and HC, which was consistent with single-loci-based CpG methylation measurement.

CONCLUSION

The methylation level of CXCR5 was significantly higher in RA patients than in OA and HC, and correlated with the level of inflammation in RA patients, our study establishes a link between CXCR5 DNA methylation and clinical features that may help in the diagnosis and disease management of RA patients.

Regulatory B cells protect against chronic hypoxia-induced pulmonary hypertension by modulating the Tfh/Tfr immune balance

Hypoxia-induced pulmonary hypertension (HPH) is a progressive and lethal disease characterized by the uncontrolled proliferation of pulmonary artery smooth muscle cells (PASMCs) and obstructive vascular remodelling. Previous research demonstrated that Breg cells were involved in the pathogenesis of pulmonary hypertension. This work aimed to evaluate the regulatory function of Breg cells in HPH. HPH mice model were established and induced by exposing to chronic hypoxia for 21 days. Mice with HPH were treated with anti-CD22 or adoptive transferred of Breg cells. The coculture systems of Breg cells with CD4⁺ T cells and Breg cells with PASMCs in vitro were constructed. Lung pathology was evaluated by HE staining and immunofluorescence staining. The frequencies of Breg cells, Tfh cells and Tfr cells were analysed by flow cytometry. Serum IL-21 and IL-10 levels were determined by ELISA. Protein levels of Blimp-1, Bcl-6 and CTLA-4 were determined by western blot and RT-PCR. Proliferation rate of PASMCs was measured by EdU. Compared to the control group, mean PAP, RV/(LV + S) ratio, WA% and WT% were significantly increased in the model group. Anti-CD22 exacerbated abnormal hemodynamics, pulmonary vascular remodelling and right ventricle hypertrophy in HPH, which ameliorated by adoptive transfer of Breg cells into HPH mice. The proportion of Breg cells on day 7 induced by chronic hypoxia was significantly higher than control group, which significantly decreased on day 14 and day 21. The percentage of Tfh cells was significantly increased, while percentage of Tfr cells was significantly decreased in HPH than those of control group. Anti-CD22 treatment increased the percentage of Tfh cells and decreased the percentage of Tfr cells in HPH mice. However, Breg cells restrained the Tfh cells differentiation and expanded Tfr cells differentiation in vivo and in vitro. Additionally, Breg cells inhibited the proliferation of PASMCs under hypoxic condition in vitro. Collectively, these findings suggested that Breg cells may be a new therapeutic target for modulating the Tfh/Tfr immune balance in HPH.

Risk-associated single nucleotide polymorphisms of mitochondrial D-loop mediate imbalance of cytokines and redox in rheumatoid arthritis

BACKGROUND

We have identified rheumatoid arthritis (RA) risk-associated single nucleotide polymorphisms (SNPs) in the mitochondrial displacement loop (D-loop) including the major alleles of nucleotides 195T/C, 16260C/T, and 16519C/T as well as the minor alleles of nucleotides 146T/C and 150C/T previously.

OBJECTIVE

We evaluated the potential relationships of these SNPs with status for oxidative stress and inflammation cytokines.

METHODS

The DNA was extracted from blood samples of RA patients, and the SNPs of DNA D-loop were verified by polymerase chain reaction amplification and sequence analysis. Serum levels of inflammatory cytokines including interferon-γ (IFN-γ), interleukin-2 (IL-2), IL-6, IL-10, and tumor necrosis factor-α (TNF-α) were determined by cytometric bead array. Plasma reactive oxygen species (ROS) levels were measured by fluorescent probe technology.

RESULTS

The RA risk-related allele 16519C was significantly associated with high IFN-γ levels (100.576 ± 11.769 vs 64.268 ± 8.199, 95% confidence interval [CI] -66.317 to -6.299, P = 0.018). This allele also associated with ROS at borderline statistics level (619.295 ± 36.687 vs 526.979 ± 25.896, 95% CI -186.145 to -1.513, P = 0.054). The subsequent analysis also showed that the ROS levels were positively correlated with IFN-γ levels (R = 0.291, P = 0.002). Further analysis showed that RA patients with high C-reactive protein levels displayed a higher ROS level (P = 0.001).

CONCLUSION

Our results imply that the 16519C allele of the mtDNA D-loop might promote ROS and IFN-γ levels by altering the replication and transcription of mtDNA, thereby modifying RA development.

REMARK

The potential relationships of RA-associated SNPs in the mitochondrial D-loop with status for oxidative stress and inflammation were evaluated. The 16519C allele of the mtDNA D-loop might promote ROS and IFN-γ levels by altering the replication and transcription of mtDNA to modify RA development.

Chemokines and chemokine receptors as promising targets in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that commonly causes inflammation and bone destruction in multiple joints. Inflammatory cytokines, such as IL-6 and TNF-α, play important roles in RA development and pathogenesis. Biological therapies targeting these cytokines have revolutionized RA therapy. However, approximately 50% of the patients are non-responders to these therapies. Therefore, there is an ongoing need to identify new therapeutic targets and therapies for patients with RA. In this review, we focus on the pathogenic roles of chemokines and their G-protein-coupled receptors (GPCRs) in RA. Inflamed tissues in RA, such as the synovium, highly express various chemokines to promote leukocyte migration, tightly controlled by chemokine ligand-receptor interactions. Because the inhibition of these signaling pathways results in inflammatory response regulation, chemokines and their receptors could be promising targets for RA therapy. The blockade of various chemokines and/or their receptors has yielded prospective results in preclinical trials using animal models of inflammatory arthritis. However, some of these strategies have failed in clinical trials. Nonetheless, some blockades showed promising results in early-phase clinical trials, suggesting that chemokine ligand-receptor interactions remain a promising therapeutic target for RA and other autoimmune diseases.

IRG1/itaconate increases IL-10 release to alleviate mechanical and thermal hypersensitivity in mice after nerve injury

Inflammation plays an important role in the occurrence and development of neuropathic pain. Immune-responsive gene 1 (IRG1) decarboxylates cis-aconitate to produce itaconate in the mitochondria. Itaconate serves as an immunomodulator of macrophages and represses inflammation in infectious diseases. Recently, a study showed that an itaconate derivative inhibits neuroinflammation and reduces chronic pain in mice. However, the function and molecular mechanisms of endogenous itaconate in neuropathic pain have not been fullyelucidated. In this study, the content of itaconate in the ipsilateral spinal cord after nerve-injured mice was detected with mass spectrometry. The Irg1-/- mouse was constructed to determine the role of endogenous itaconate in the chronic constriction nerve injury (CCI) model. The analgesic effect of exogenous itaconate was assessed with intraperitoneal and intrathecal administration in both male and female CCI mice. The spinal application of 4-OI also reduced the evoked responses of wide dynamic range neurons in CCI mice. The potential analgesic mechanism of itaconate was explored through molecular biology experiments and verified in Interleukin (IL)-10-/- mice. We found the levels of itaconate and IRG1 in the spinal cord significantly increased after CCI. Irg1 deficiency aggravated the mechanical and heat hypersensitivity, while the exogenous administration of the itaconate derivative 4-OI alleviated the neuropathic pain in male and female CCI mice. Mechanistically, the treatment of 4-OI increased the level of IL-10 and activates STAT3/β-endorphin pathway in the spinal cord, and the analgesia effect of itaconate was impaired in IL-10-/- mice. Finally, we showed that the upregulation of IL-10 induced by 4-OI was mainly from spinal neurons through Nrf2 pathway. This study demonstrated the analgesic effect of endogenous and exogenous itaconate in the neuropathic pain model, suggesting that the spinal IL-10/STAT3/β-endorphin pathway might mediate the analgesia effect of itaconate.

G-Protein-Coupled Receptors in Rheumatoid Arthritis: Recent Insights into Mechanisms and Functional Roles

Rheumatoid arthritis (RA) is a chronic inflammatory disease that leads to joint damage and even disability. Although there are various clinical therapies for RA, some patients still have poor or no response. Thus, the development of new drug targets remains a high priority. In this review, we discuss the role of G-protein-coupled receptors (GPCRs), including chemokine receptors, melanocortin receptors, lipid metabolism-related receptors, adenosine receptors, and other inflammation-related receptors, on mechanisms of RA, such as inflammation, lipid metabolism, angiogenesis, and bone destruction. Additionally, we summarize the latest clinical trials on GPCR targeting to provide a theoretical basis and guidance for the development of innovative GPCR-based clinical drugs for RA.

CXCL13 as a Novel Immune Checkpoint for Regulatory B Cells and Its Role in Tumor Metastasis

Tumor metastasis is the primary cause of mortality in patients with cancer. Several chemokines are identified as important mediators of tumor growth and/or metastasis. The level of CXCL13 has been reported to be elevated in serum or tumor tissues in patients, which mainly functions to attract B cells and follicular B helper T cells. However, the role of CXCL13 in cancer growth and metastasis is not fully explored. In the current study, we found that CXCL13 is not a strong mediator to directly promote tumor growth; however, the mice deficient in CXCL13 had far fewer pulmonary metastatic foci than did the wild-type mice in experimental pulmonary metastatic models. In addition, Cxcl13 ^-/- mice also had fewer IL-10-producing B cells (CD45⁺CD19⁺IL-10⁺) in the metastatic tumor immune microenvironment than those of wild-type C57BL/6 mice, resulting in an enhanced antitumor immunity. Notably, CXCL13 deficiency further improved the efficacy of a traditional chemotherapeutic drug (cyclophosphamide), as well as that of anti-programmed death receptor-1 immunotherapy. These results suggested that CXCL13 has an important role in regulating IL-10-producing B cells in tumor metastasis and might be a promising target for improving therapeutic efficiency and stimulating tumor immunity in future cancer therapy.

Role of the CXCL13/CXCR5 Axis in Autoimmune Diseases

CXCL13 is a B-cell chemokine produced mainly by mesenchymal lymphoid tissue organizer cells, follicular dendritic cells, and human T follicular helper cells. By binding to its receptor, CXCR5, CXCL13 plays an important role in lymphoid neogenesis, lymphoid organization, and immune responses. Recent studies have found that CXCL13 and its receptor CXCR5 are implicated in the pathogenesis of several autoimmune diseases, such as rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, primary Sjögren’s syndrome, myasthenia gravis, and inflammatory bowel disease. In this review, we discuss the biological features of CXCL13 and CXCR5 and the recent findings on the pathogenic roles of the CXCL13/CXCR5 axis in autoimmune diseases. Furthermore, we discuss the potential role of CXCL13 as a disease biomarker and therapeutic target in autoimmune diseases.

[Innovative strategies for treatment of rheumatoid arthritis]

Besides excellent guidelines and newly developed highly effective drugs, evidence-based strategic use of these new drugs has especially contributed to enormous advances in rheumatoid arthritis treatment, apparent especially since 2000. Currently, the treat-to-target (T2T) strategy has proven to be the most successful in several studies and systematic reviews. The target is to achieve remission, which should be reached and sustained for an optimal outcome (i.e. stable over a long time period). If the initial disease-modifying antirheumatic drug (DMARD) treatment fails, the best strategy for continuing treatment is controversial, with swap or switch being open to debate (change within a class of drugs or change in the mechanism of action). Recent studies seem to indicate that switching to another mechanism of action is the most successful approach. A hotly discussed topic is the question whether DMARD treatment can or should be tapered when sustained remission has been achieved? Many patients wish for a reduction of drugs in cases of stable remission; however, the stable disease control might become destabilized by tapering. The main priority is the reduction or tapering of glucocorticoid treatment. When the decision for reduction of DMARD treatment is made together with the patient, a complete cessation bears a high risk of a flare, therefore, a careful step by step reduction of DMARD treatment should be preferred. In the case of a running combination, the question whether the conventional DMARD (mostly methotrexate), the biological (b)DMARD or targeted synthetic (ts)DMARD should be reduced first, must be decided on an individual basis. Most patients prefer to first reduce methotrexate and transfer to a monotherapy.