Cytokine secretion by pathogen recognition receptor-stimulated dendritic cells in rheumatoid arthritis and ankylosing spondylitis

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

Background

Rheumatoid arthritis (RA) is a systemic immune-related disease characterized by synovial inflammation and destruction of joint cartilage. The pathogenesis of RA remains unclear, and diagnostic markers with high sensitivity and specificity are needed urgently. This study aims to identify potential biomarkers in the synovium for diagnosing RA and to investigate their association with immune infiltration.

Methods

We downloaded four datasets containing 51 RA and 36 healthy synovium samples from the Gene Expression Omnibus database. Differentially expressed genes were identified using R. Then, various enrichment analyses were conducted. Subsequently, weighted gene co-expression network analysis (WGCNA), random forest (RF), support vector machine-recursive feature elimination (SVM-RFE), and least absolute shrinkage and selection operator (LASSO) were used to identify the hub genes for RA diagnosis. Receiver operating characteristic curves and nomogram models were used to validate the specificity and sensitivity of hub genes. Additionally, we analyzed the infiltration levels of 28 immune cells in the expression profile and their relationship with the hub genes using single-sample gene set enrichment analysis.

Results

Three hub genes, namely, ribonucleotide reductase regulatory subunit M2 (RRM2), DLG-associated protein 5 (DLGAP5), and kinesin family member 11 (KIF11), were identified through WGCNA, LASSO, SVM-RFE, and RF algorithms. These hub genes correlated strongly with T cells, natural killer cells, and macrophage cells as indicated by immune cell infiltration analysis.

Conclusion

RRM2, DLGAP5, and KIF11 could serve as potential diagnostic indicators and treatment targets for RA. The infiltration of immune cells offers additional insights into the underlying mechanisms involved in the progression of RA.

A Peripheral Blood Signature of Increased Th1 and Myeloid Cells Combined with Serum Inflammatory Mediators Is Associated with Response to Abatacept in Rheumatoid Arthritis Patients

Abatacept (CTLA4-Ig)-a monoclonal antibody which restricts T cell activation-is an effective treatment for rheumatoid arthritis (RA). Nevertheless, only 50% of RA patients attain clinical responses, while predictors of response are rather limited. Herein, we aimed to investigate for early biomarkers of response to abatacept, based on a detailed immunological profiling of peripheral blood (PB) cells and serum proteins. We applied flow cytometry and proteomics analysis on PB immune cells and serum respectively, of RA patients starting abatacept as the first biologic agent. After 6 months of treatment, 34.5% of patients attained response. At baseline, Th1 and FoxP3+ T cell populations were positively correlated with tender joint counts (p-value = 0.047 and p-value = 0.022, respectively). Upon treatment, CTLA4-Ig effectively reduced the percentages of Th1 and Th17 only in responders (p-value = 0.0277 and p-value = 0.0042, respectively). Notably, baseline levels of Th1 and myeloid cell populations were significantly increased in PB of responders compared to non-responders (p-value = 0.009 and p-value = 0.03, respectively). Proteomics analysis revealed that several inflammatory mediators were present in serum of responders before therapy initiation and strikingly 10 amongst 303 serum proteins were associated with clinical responses. Finally, a composite index based on selected baseline cellular and proteomics' analysis could predict response to abatacept with a high sensitivity (90%) and specificity (88.24%).

The role of TRPV1 in RA pathogenesis: worthy of attention

Transient receptor potential cation channel subfamily V member 1 (TRPV1) is a Ca2+permeable, non-selective cation channel that is found primarily in sensory nerve fibres. Previous studies focused on pain transmission. However, recent studies have found that the TRPV1 channel, in addition to being associated with pain, also plays a role in immune regulation and their dysregulation frequently affects the development of rheumatoid arthritis (RA). A thorough understanding of the mechanism will facilitate the design of new TRPV1-targeted drugs and improve the clinical efficacy of RA. Here, we provide an updated and comprehensive overview of how the TRPV1 channel intrinsically regulates neuronal and immune cells, and how alterations in the TRPV1 channel in synoviocytes or chondrocytes extrinsically affect angiogenesis and bone destruction. Rapid progress has been made in research targeting TRPV1 for the treatment of inflammatory arthritis, but there is still much-uncharted territory regarding the therapeutic role of RA. We present a strategy for targeting the TRPV1 channel in RA therapy, summarising the difficulties and promising advances in current research, with the aim of better understanding the role of the TRPV1 channel in RA pathology, which could accelerate the development of TRPV1-targeted modulators for the design and development of more effective RA therapies.

To move or not to move: the paradoxical effect of physical exercise in axial spondyloarthritis

In the last years, new researches focused on the role of biomechanical stress and microdamage in the pathogenesis of inflammatory arthritis and, in particular, in axial spondyloarthritis (axSpA). Animal models showed how entheseal stress and physical exercise could contribute to the development of inflammation and new bone formation at entheseal and articular sites, by activating innate immune system and the release of cytokines. Furthermore, clues of the involvement of biomechanical stress in the development of axSpA are present in clinical experiences. However, rehabilitation and exercise programmes are the cornerstone of treatment for axSpA, reducing disease activity and improving spinal function and quality of life. The concept of mechanical stress as a contributor to disease development and progression represents, potentially, a conceptual challenge for this approach. The aim of this review is to discuss the current evidence on the intriguing contribution of the biomechanical stress to the pathogenesis of inflammation and new bone formation and to evaluate and reflect on the role of exercise in the treatment and in the management of the disease, considering both the beneficial effects and its possible paradoxical action.

Aberrant distribution and function of plasmacytoid dendritic cells in patients with ankylosing spondylitis are associated with unfolded protein response

Although human leucocyte antigen (HLA)-B27 is strongly associated with ankylosing spondylitis (AS), the association of unfolded protein response (UPR) induced by HLA-B27 misfolding in AS remains controversial. Since dendritic cells (DCs) are crucial in induction of AS in HLA-B27-transgenic rats, and plasmacytoid DCs (pDCs) belong to one type of DCs, we here aim to study the relevance of pDCs and UPR in AS. Peripheral pDCs were isolated from 27 HLA-B27(+) AS patients and 37 controls. The bone marrow (BM) and synovium of inflamed hips from AS patients and controls were obtained. We found a significantly higher frequency of pDCs in the peripheral blood, BM, or inflamed synovium of hips, which is associated with the enhanced expression of pDC trafficking molecules, CCR6 and CCL20 in the synovium of AS patients. Functional analysis further revealed that several inflammatory cytokines, including TNFα, IL-6, and IL-23, secreted by pDCs were significantly increased in AS patients as compared with those in controls. Remarkably, protein kinase RNA-like endoplasmic reticulum kinase (PERK) pathway in UPR was up-regulated in pDCs of AS patients. Notably, PERK inhibitor treatment significantly inhibited the enhanced cytokine production by pDCs of AS patients. Further, the extent of PERK activation was significantly associated with the increased disease severity of AS patients. Our data uncover the aberrant distribution and function of pDCs in AS patients. The up-regulated PERK pathway in UPR of pDCs not only contributes to enhanced cytokine production of pDCs, but also is associated with increased disease activity of AS patients.

Dendritic cells, T cells and their interaction in rheumatoid arthritis

Dendritic cells (DCs) are the key professional antigen-presenting cells which bridge innate and adaptive immune responses, inducing the priming and differentiation of naive to effector CD4+ T cells, the cross-priming of CD8+ T cells and the promotion of B cell antibody responses. DCs also play a critical role in the maintenance of immune homeostasis and tolerance. DC-T cell interactions underpin the generation of an autoimmune response in rheumatoid arthritis (RA). Here we describe the function of DCs and review evidence for DC and T cell involvement in RA pathogenesis, in particular through the presentation of self-peptide by DCs that triggers differentiation and activation of autoreactive T cells. Finally, we discuss the emerging field of targeting the DC-T cell interaction for antigen-specific immunotherapy of RA.

Altered cytokine expression by macrophages from HLA-B27-positive spondyloarthritis patients without evidence of endoplasmic reticulum stress

Objectives

We investigated endoplasmic reticulum (ER) stress and cytokine expression in peripheral blood-derived macrophages and synovial tissue from HLA-B27⁺ SpA patients.

Methods

Macrophages from healthy donors, SpA and RA patients were polarized with IFN-γ or IL-10 and activated with lipopolysaccharide. Expression of ER stress markers (BiP, CHOP, ERdj4) and cytokines (IL-23, IL-12, TNF, IL-10) was measured by qRT-PCR. Expression of ER stress markers and cytokines in synovial tissue from SpA patients was evaluated by microarray analysis.

Results

Macrophages from HLA-B27⁺ SpA patients did not show elevated ER stress markers. However, the expression of IL-23 and IL-12 by peripheral blood-derived macrophages was higher in HLA-B27⁺ SpA in comparison with healthy donors. Synovial tissue from HLA-B27⁺ SpA patients showed higher expression of TNF compared with HLA-B27⁻ SpA patients.

Conclusion

HLA-B27⁺ SpA patients showed increased expression of IL-23, IL-12 and TNF without evidence of ER stress.

The interaction between host genetics and the microbiome in the pathogenesis of spondyloarthropathies

PURPOSE OF REVIEW

The intestinal microbiome is increasingly implicated in the pathogenesis of ankylosing spondylitis, reactive arthritis, and other diseases collectively known as the spondyloarthropathies (SpAs). In common with other complex inflammatory diseases, SpAs have both a strong genetic and environmental component. Recent genetic studies have highlighted host pathways that may intersect the host-microbiota interaction and offer novel paradigms to understand the pathophysiology of these diseases.

RECENT FINDINGS

Genetic association studies have identified genes such as RUNX3, PTPEN2, and IL-33 as susceptibility loci for SpAs. Functional studies in humans have extended knowledge of established genetic risk factors for ankylosing spondylitis that include ERAP1, ERAP2, and interleukin-23R. Recent basic research has identified new mechanisms that regulate host immune responses to the microbiota that conceivably may be dysregulated in SpA.

SUMMARY

Intestinal barrier function, deletional tolerance, Th17 signature response, and endoplasmic reticulum stress pathways have been recently linked to SpA. Dysregulated immune responses to the gut microbiota and an altered microbial community structure are shared features of SpA. Although the cause-effect dynamic of this relationship remains equivocal, it nonetheless has major implications for both intestinal and extra-intestinal pathology observed in SpA.

The function of myeloid dendritic cells in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease that causes joint pain, inflammation, and loss of function. Disease pathogenesis involves activation and proliferation of autoreactive pro-inflammatory effector T cells. While the details of RA onset and progression remain controversial, dendritic cell (DC) numbers dramatically increase in the synovial joint tissues of RA patients. Based on their key functions as antigen-presenting cells and inducers of T cell differentiation, DCs may play an important role in the initiation of joint inflammation. Myeloid DC contributions are likely central to the development of RA, as they are more efficient at antigen presentation in comparison with their closely related cousins, plasmacytoid DCs. Synovial fluid in the joints of RA patients is enriched with pro-inflammatory cytokines and chemokines, which may stimulate or result from DC activation. Epidemiological evidence indicates that smoking and periodontal infection are major environmental risk factors for RA development. In this review, factors in the synovial environment that contribute to altered myeloid DC functions in RA and the effects of environmental risk factors on myeloid DCs are described.

Secukinumab for ankylosing spondylitis and psoriatic arthritis

The treatment of ankylosing spondylitis (AS) and psoriatic arthritis (PsA) positively changed since the introduction of anti-TNFα drugs. These treatments were shown to reduce the symptoms and signs of the diseases and improve the quality of life. However, a variable percentage of patients do not respond to anti-TNFα or can exhibit a loss of response and, furthermore, despite anti-TNFα drugs' proven efficacy in reducing peripheral radiographic progression in PsA, the impact in reducing radiographic damage in AS is still debated. Recently, the discovery of new pathogenic mechanisms paved the way to the development of new drugs that target other pro-inflammatory cytokines. In particular, the inhibition of interleukin (IL)-17, which is the principal cytokine produced by Th17 lymphocytes, a pro-inflammatory subset involved in both inflammation and new bone formation in AS and PsA, demonstrated promising results. The new molecule secukinumab, an IL-17A inhibitor, showed its efficacy and safety in phase III randomized clinical trials in AS and PsA and is the first non-anti-TNFα biologic approved for the treatment of AS, providing a useful alternative treatment strategy in both diseases. The aim of this article was to review the pathophysiological basis, the efficacy and the safety of secukinumab treatment in AS and PsA patients.

Maturation and cytokine production potential of dendritic cells isolated from rheumatoid arthritis patients peripheral blood and induced in vitro

BACKGROUND

Since dendritic cells (DC) are involved in the development of autoimmune inflammation, researchers consider DC both as target cells for specific therapy of rheumatoid arthritis (RA) and as candidate cells for the development of cell-based methods to treat autoimmune diseases. The development of treatment strategies requires comprehensive research into the quantitative and qualitative characteristics of DC subtypes both ex vivo from RA patients and in vitro, to determine the possibility of inducing functionally mature DC in RA.

OBJECTIVE

To study the phenotypic and functional properties of myeloid (mDC) and plasmacytoid (pDC) DC isolated from the peripheral blood of patients with RA and induced in vitro.

MATERIALS AND METHODS

Blood samples were obtained from RA patients and healthy donors. Immature DC in the whole blood and in vitro induced DC were characterized by the positive expression of CD80, CD83, CCR7, IL-10, IL-4, IL-12 and IFN-α. R848 and lipopolysaccharide were used to determine DC maturation ability. From PBMCs of RA patients and health donors DCs with myeloid (imDC) and plasmacytoid (ipDC) phenotype were induced.

RESULTS

The relative count of mDC in the peripheral blood between studied groups did not differ. pDC count was significantly lower for RA patients. DC from RA patients were characterized by low expression levels of CD80 and CD83 on both populations cells and high expression of CCR7 only on pDC. An increase in pDC producing IL-12 and IFN-α and a decrease in mDC and pDC producing IL-4 and IL-10 were shown in RA. imDC and ipDC obtained from RA patients according to their phenotype and cytokine profile did not differ from those obtained from healthy donors.

CONCLUSIONS

There is an imbalance between subpopulations of DC in the peripheral blood of RA patients. DC of RA patients are less mature. The data suggest the involvement of DC in RA pathogenesis and confirm DC participation in balance shift towards Th1-type immune responses. At the same time, in vitro induced RA DC are phenotypically and functionally competent.

Allele-Independent Turnover of Human Leukocyte Antigen (HLA) Class Ia Molecules

Major histocompatibility complex class I (MHCI) glycoproteins present cytosolic peptides to CD8+ T cells and regulate NK cell activity. Their heavy chains (HC) are expressed from up to three MHC gene loci (human leukocyte antigen [HLA]-A, -B, and -C in humans), whose extensive polymorphism maps predominantly to the antigen-binding groove, diversifying the bound peptide repertoire. Codominant expression of MHCI alleles is thus functionally critical, but how it is regulated is not fully understood. Here, we have examined the effect of polymorphism on the turnover rates of MHCI molecules in cell lines with functional MHCI peptide loading pathways and in monocyte-derived dendritic cells (MoDCs). Proteins were labeled biosynthetically with heavy water (2H2O), folded MHCI molecules immunoprecipitated, and tryptic digests analysed by mass spectrometry. MHCI-derived peptides were assigned to specific alleles and isotypes, and turnover rates quantified by 2H incorporation, after correcting for cell growth. MHCI turnover half-lives ranged from undetectable to a few hours, depending on cell type, activation state, donor, and MHCI isotype. However, in all settings, the turnover half-lives of alleles of the same isotype were similar. Thus, MHCI protein turnover rates appear to be allele-independent in normal human cells. We propose that this is an important feature enabling the normal function and codominant expression of MHCI alleles.

The role of toll like receptors in giant cell arteritis

GCA is a common primary systemic vasculitis that results in granulomatous inflammation of medium to large arteries. Both innate and adaptive immune mechanisms combine to drive intimal hyperplasia, luminal stenosis and ultimately occlusion. While the pathogenesis of GCA is incompletely understood, the activation of resident adventitial dendritic cells via toll like receptors (TLRs) appears to be a crucial inciting event. Here we explore the role of TLRs in the pathogenesis of GCA, including their effects on dendritic cell and T cell activation and recruitment, putative infectious triggers for GCA and the potential of TLR inhibition as a novel therapeutic strategy in GCA.

Ankylosing spondylitis patients display altered dendritic cell and T cell populations that implicate pathogenic roles for the IL-23 cytokine axis and intestinal inflammation

Objective. AS is a systemic inflammatory disease of the SpA family. Polymorphisms at loci including HLA-B27, IL-23R and ERAP-1 directly implicate immune mechanisms in AS pathogenesis. Previously, in an SpA model, we identified HLA-B27–mediated effects on dendritic cells that promoted disease-associated Th17 cells. Here we extend these studies to AS patients using deep immunophenotyping of candidate pathogenic cell populations. The aim of our study was to functionally characterize the immune populations mediating AS pathology.

Methods. Using 11-parameter flow cytometry, we characterized the phenotype and functions of lymphocyte and myeloid cells from peripheral blood, and the synovial phenotype of AS patients and age-matched healthy controls.

Results. Significantly fewer circulating CD1c-expressing dendritic cells were observed in AS patients, offset by an increase in CD14⁻ CD16⁺ mononuclear cells. Ex vivo functional analysis revealed that this latter population induced CCR6 expression and promoted secretion of IL-1β and IL-6 when co-cultured with naive CD4⁺ T cells. Additionally, systemic inflammation in AS patients significantly correlated with increased proportions of activated CCR9⁺ CD4⁺ T cells.

Conclusion. CD14⁻ CD16⁺ mononuclear cells may contribute to AS by promoting Th17 responses, and antigen-presenting cells of mucosal origin are likely to contribute to systemic inflammation in AS.

Role of genetics in infection-associated arthritis

Genetic discoveries in arthritis and their associated biological pathways spanning the innate and adaptive immune system demonstrate the strong association between susceptibility to arthritis and control of exogenous organisms. The canonical theory of the aetiology of immune-mediated arthritis and other immune-mediated diseases is that the introduction of exogenous antigenic stimuli to a genetically susceptible host sets up the environment for an abnormal immune response manifesting as disease. A disruption in host-microbe homeostasis driven by disease-associated genetic variants could ultimately provide the source of exogenous antigen triggering disease development. We discuss genetic variants impacting the innate and adaptive arms of the immune system and their relationship to microbial control and arthritic disease. We go on to consider the evidence for a relationship between HLA-B27, infection and arthritis, and then emerging evidence for an interaction between microbiota and rheumatoid arthritis.

Interleukin-23 mediates the intestinal response to microbial β-1,3-glucan and the development of spondyloarthritis pathology in SKG mice

OBJECTIVE

Spondyloarthritides (SpA) occur in 1% of the population and include ankylosing spondylitis (AS) and arthropathy of inflammatory bowel disease (IBD), with characteristic spondylitis, arthritis, enthesitis, and IBD. Genetic studies implicate interleukin-23 (IL-23) receptor signaling in the development of SpA and IBD, and IL-23 overexpression in mice is sufficient for enthesitis, driven by entheseal-resident T cells. However, in genetically prone individuals, it is not clear where IL-23 is produced and how it drives the SpA syndrome, including IBD or subclinical gut inflammation of AS. Moreover, it is unclear why specific tissue involvement varies between patients with SpA. We undertook this study to determine the location of IL-23 production and its role in SpA pathogenesis in BALB/c ZAP-70(W163C)-mutant (SKG) mice injected intraperitoneally with β-1,3-glucan (curdlan).

METHODS

Eight weeks after curdlan injection in wild-type or IL-17A(-/-) SKG or BALB/c mice, pathology was scored in tissue sections. Mice were treated with anti-IL-23 or anti-IL-22. Cytokine production and endoplasmic reticulum (ER) stress were determined in affected organs.

RESULTS

In curdlan-treated SKG mice, arthritis, enthesitis, and ileitis were IL-23 dependent. Enthesitis was specifically dependent on IL-17A and IL-22. IL-23 was induced in the ileum, where it amplified ER stress, goblet cell dysfunction, and proinflammatory cytokine production. IL-17A was pathogenic, while IL-22 was protective against ileitis. IL-22+CD3- innate-like cells were increased in lamina propria mononuclear cells of ileitis-resistant BALB/c mice, which developed ileitis after curdlan injection and anti-IL-22.

CONCLUSION

In response to systemic β-1,3-glucan, intestinal IL-23 provokes local mucosal dysregulation and cytokines driving the SpA syndrome, including IL-17/IL-22-dependent enthesitis. Innate IL-22 production promotes ileal tolerance.

Regulation of innate immune responses by transmembrane interactions: lessons from the TLR family

The mammalian innate immune response is responsible for the early stages of defense against invading pathogens. One of the major receptor families facilitating innate immune activation is the Toll-like receptor (TLR) family. These receptors are type 1 membrane proteins spanning the membrane with a single transmembrane domain (TMD). All TLRs form homo- and hetero-dimers within membranes and new data suggest that the single transmembrane domain of some of these receptors is involved in their dimerization and function. Newly identified TLR dimers are continuously reported but only little is known about the importance of the TMDs for their dimer assembly and signaling regulation. Uncontrolled or untimely activation of TLRs is related to a large number of pathologies ranging from cystic fibrosis to sepsis and cancer. In this review we will focus on the contribution of the TMDs of innate immune receptors - specifically TLR2-to their regulation and function. In addition, we will address the current issues remaining to be solved regarding the mechanistic insights of this regulation. This article is part of a Special Issue entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.

Antihelminthic niclosamide modulates dendritic cells activation and function

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Effect of niclosamide on the activation of LPS-stimulated BMDCs was investigated.

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Niclosamide decreased ability to stimulate antigen specific T cell proliferation.

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Niclosamide attenuated hapten induced contact hypersensitivity (CHS) in vivo.

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Blocking the MAPK and NF-κB contribute to the inhibitory effect of niclosamide.

Dendritic cells (DCs) link the sensing of the environment by the innate immune system to the initiation of adaptive immune responses. Accordingly, DCs are considered to be a major target in the development of immunomodulating compounds. In this study, the effect of niclosamide, a Food and Drug Administration-approved antihelminthic drug, on the activation of lipopolysaccharide (LPS)-stimulated murine bone marrow-derived DCs was examined. Our experimental results show that niclosamide reduced the pro-inflammatory cytokine and chemokine expression of LPS-activated DCs. In addition, niclosamide also affected the expression of MHC and costimulatory molecules and influenced the ability of the cells to take up antigens. Therefore, in mixed cell cultures composed of syngeneic OVA-specific T cells and DCs, niclosamide-treated DCs showed a decreased ability to stimulate T cell proliferation and IFN-γ production. Furthermore, intravenous injection of niclosamide also attenuated contact hypersensitivity (CHS) in mice during sensitization with 2,4-dinitro-1-fluorobenzene. Blocking the LPS-induced activation of MAPK-ERK, JNK and NF-κB may contribute to the inhibitory effect of niclosamide on DC activation. Collectively, our findings suggest that niclosamide can manipulate the function of DCs. These results provide new insight into the immunopharmacological role of niclosamide and suggest that it may be useful for the treatment of chronic inflammatory disorders or DC-mediated autoimmune diseases.