Serum levels of IL-33 and its receptor ST2 are elevated in patients with ankylosing spondylitis

ST2 levels and neurodegenerative diseases: is this a significant relation?

Interleukin-33 (IL-33), belonging to the interleukin-1 cytokine family, has a decoy receptor soluble ST2 (sST2). IL-33 is found in oligodendrocytes and astrocytes and is involved in central nervous system healing and repair, whereas ST2 is found in microglia and astrocytes. Some studies have found a link between changes in the IL-33/ST2 pathway and neurodegenerative disorders. This review article investigates the relationship between the interleukin-33 (IL-33)/ST2 pathway and neurodegenerative disorders. It was discovered that soluble st2 levels were increased. Furthermore, IL-33 levels were found to be lower in many neurodegenerative diseases such as Alzheimer's and amyotrophic lateral sclerosis (ALS). The association with other disorders, such as ankylosing spondylitis, multiple sclerosis, and systemic lupus erythematosus (SLE), was also observed. Various studies suggest that ST2/IL-33 signalling may be pivotal in the disease modulation of neurodegenerative disorders. The serum sST2 level test can be useful in determining the inflammatory status and severity of illness in many neurodegenerative disorders. In this review, we will discuss recent findings concerning the interleukin-33 (IL-33)/ST2 pathway and its role in the diagnosis and treatment of diseases with neurodegeneration.

The Involvement of Alarmins in the Pathogenesis of Sjögren's Syndrome

Sjögren’s syndrome (SS) is a chronic autoimmune disease that affects exocrine glands, primarily the salivary and lachrymal glands. It is characterized by lymphoplasmacytic infiltration of the glandular tissues, ultimately leading to their dysfunction and destruction. Besides classic dry eyes and dry mouth defined as sicca syndrome, patients affected by the disease also typically display symptoms such as fatigue, pain and in more than 50% of cases, systemic manifestations such as arthritis, interstitial lung involvement, neurological involvement and an increased risk of lymphoma. The pathophysiological mechanisms underlying SS still remain elusive. The crucial role of innate immunity has been advocated in recent years regarding the pathogenesis of pSS, especially in the initiation and progression toward autoimmunity. Alarmins are endogenous molecules that belong to the large family of damage associated molecular pattern (DAMP). Alarmins are rapidly released, ensuing cell injury and interacting with pattern recognition receptors (PRR) such as toll-like receptors (TLR) to recruit and activate cells of the innate immune system and to promote adaptive immunity responses. This review highlights the current knowledge of various alarmins and their role in the pathogenesis of pSS.

IL-33 in Rheumatic Diseases

Interleukin-33 (IL-33) is a nuclear factor mainly expressed in barrier epithelium, endothelial cells, and fibroblast reticular cells. Some inflammatory cells also express IL-33 under certain conditions. The important role of IL-33 in allergic reactions, helminth infection, cancer, tissue fibrosis, chronic inflammation, organ transplantation, and rheumatic immune diseases has been extensively studied in recent years. IL-33 primarily activates various circulating and tissue-resident immune cells, including mast cell, group 2 innate lymphoid cell (ILC2), regulatory T cell (Treg), T helper 2 cell (Th2), natural killer cell (NK cell), and macrophage. Therefore, IL-33 plays an immunomodulatory role and shows pleiotropic activity in different immune microenvironments. The IL-33/serum stimulation-2 (ST2) axis has been shown to have a detrimental effect on rheumatoid arthritis, systemic lupus erythematosus, and other rheumatic diseases. Interestingly, IL-33 also plays a protective role in the repair of barrier epithelium and the activation of Tregs. Therefore, the role of IL-33/ST2 depends on the underlying pathological conditions in rheumatic diseases. This review focuses on the dual role of the IL-33/ST2 axis in rheumatic diseases.

IL-33 promotes anemia during chronic inflammation by inhibiting differentiation of erythroid progenitors

An important comorbidity of chronic inflammation is anemia, which may be related to dysregulated activity of hematopoietic stem and progenitor cells (HSPCs) in the bone marrow (BM). Among HSPCs, we found that the receptor for IL-33, ST2, is expressed preferentially and highly on erythroid progenitors. Induction of inflammatory spondyloarthritis in mice increased IL-33 in BM plasma, and IL-33 was required for inflammation-dependent suppression of erythropoiesis in BM. Conversely, administration of IL-33 in healthy mice suppressed erythropoiesis, decreased hemoglobin expression, and caused anemia. Using purified erythroid progenitors in vitro, we show that IL-33 directly inhibited terminal maturation. This effect was dependent on NF-κB activation and associated with altered signaling events downstream of the erythropoietin receptor. Accordingly, IL-33 also suppressed erythropoietin-accelerated erythropoiesis in vivo. These results reveal a role for IL-33 in pathogenesis of anemia during inflammatory disease and define a new target for its treatment.

The Role of the IL-33/ST2 Immune Pathway in Autoimmunity: New Insights and Perspectives

Interleukin (IL)-33, a member of IL-1 cytokine family, is produced by various immune cells and acts as an alarm to alert the immune system after epithelial or endothelial cell damage during cell necrosis, infection, stress, and trauma. The biological functions of IL-33 largely depend on its ligation to the corresponding receptor, suppression of tumorigenicity 2 (ST2). The pathogenic roles of this cytokine have been implicated in several disorders, including allergic disease, cardiovascular disease, autoimmune disease, infectious disease, and cancers. However, alerted levels of IL-33 may result in either disease amelioration or progression. Genetic variations of IL33 gene may confer protective or susceptibility risk in the onset of autoimmune diseases. The purpose of this review is to discuss the involvement of IL-33 and ST2 in the pathogenesis of a variety of autoimmune disorders, such as autoimmune rheumatic, neurodegenerative, and endocrine diseases.

Biomarker development for axial spondyloarthritis

The term axial spondyloarthritis (axSpA) encompasses a heterogeneous group of diseases that have variable presentations, extra-articular manifestations and clinical outcomes, and that will respond differently to treatments. The prototypical type of axSpA, ankylosing spondylitis, is thought to be caused by interaction between the genetically primed host immune system and gut microbiota. Currently used biomarkers such as HLA-B27 status, C-reactive protein and erythrocyte sedimentation rate have, at best, moderate diagnostic and predictive value. Improved biomarkers are needed for axSpA to assist with early diagnosis and to better predict treatment responses and long-term outcomes. Advances in a range of 'omics' technologies and statistical approaches, including genomics approaches (such as polygenic risk scores), microbiome profiling and, potentially, transcriptomic, proteomic and metabolomic profiling, are making it possible for more informative biomarker sets to be developed for use in such clinical applications. Future developments in this field will probably involve combinations of biomarkers that require novel statistical approaches to analyse and to produce easy to interpret metrics for clinical application. Large publicly available datasets from well-characterized case-cohort studies that use extensive biological sampling, particularly focusing on early disease and responses to medications, are required to establish successful biomarker discovery and validation programmes.

An update on serum biomarkers to assess axial spondyloarthritis and to guide treatment decision

Axial spondyloarthritis (axSpA) is a group of debilitating, chronic, rheumatic conditions characterized by inflammation and new bone formation, mainly involving the spine and the sacroiliac joints. The lack of biomarkers in axSpA is well known. Despite significant treatment advances in recent years thanks to the introduction of drugs with a new mode of action, such as new biologic and targeted synthetic disease-modifying antirheumatic drugs, no relevant improvement in the identification of disease biomarkers has been achieved. Common parameters, such as erythrocyte sedimentation rate and C-reactive protein, which are routinely used to measure systemic inflammation, are the sole markers available to date and are not adequate to assess disease activity in all patients. The aim of this study is to review the most promising serum biomarkers that may help treatment decision in axSpA via a proper assessment of disease activity and identification of negative prognostic factors.

Role of TNFRSF1A and TNFRSF1B polymorphisms in susceptibility, severity, and therapeutic efficacy of etanercept in human leukocyte antigen-B27-positive Chinese Han patients with ankylosing spondylitis

The successful therapeutic use of anti-TNF biological agents in patients with ankylosing spondylitis (AS) indicates that tumor necrosis factor-α (TNF-α) and tumor necrosis factor receptor (TNFR) genes are involved in the pathogenesis of AS. TNF-α exerts its biological activity by binding to its cell surface receptors (p55 TNF-α receptor [TNFRI, encoded by the Tumor Necrosis Factor Receptor Superfamily Member 1A (TNFRSF1A)] and p75 receptor [TNFRII, encoded by the Tumor Necrosis Factor Receptor Superfamily Member 1B (TNFRSF1B)]. TNFRSF1A and TNFRSF1B may be related to AS, but the relevant studies are still limited. Therefore, we aim to explore the association between TNFRSF1A and TNFRSF1B polymorphisms and susceptibility and short- and long-term response to anti-TNF treatment in human leukocyte antigen-B27 (HLA-B27)-positive Chinese Han patients with AS.A total of 215 HLA-B27-positive patients with AS and 216 HLA-B27-positive matched controls were enrolled and genotyped for rs767455, rs2234649, and rs1061622. A subset of 50 AS patients was also studied for the association of these polymorphisms with the short- and long-term response to etanercept assessed by Assessment in Ankylosing Spondylitis 20 (ASAS20) and Assessment in Ankylosing Spondylitis 40 (ASAS40).Our data showed that rs767455 was associated with the susceptibility of AS, G allele of rs767455 exhibited an association with the risk of developing AS (OR = 1.63 (1.04-2.55), P = .032). Rs1061622 polymorphism was associated with total back pain and chest expansion. Only rs1061622 was significantly associated with long-term efficacy of etanercept: the TG genotype of rs1061622 worsened ASAS20 and ASAS40 responses at 12 months (P = .021 and .041, respectively).The results suggest that TNFRSF1A and TNFRSF1B polymorphisms were associated with susceptibility, severity, and the long-term therapeutic efficacy of etanercept of patients with AS.

Dichotomous function of IL-33 in health and disease: From biology to clinical implications

Interleukin (IL)-33 is a cytokine that is released from epithelial and endothelial cells at barrier surfaces upon tissue stress or damage to operate as an alarmin. IL-33 has been primarily implicated in the induction of T helper (Th) 2 type immune responses. Therefore, IL-33 has attracted a lot of interest as a potential therapeutic target in asthma and other allergic diseases. Over the years, it has become clear that IL-33 has a much broader activity and also contributes to Th1 immunity, expanding the possibilities for therapeutic modulation of IL-33 activity to multiple inflammatory diseases. However, more recently IL-33 has also been shown to mediate immunosuppression and tissue repair by activating regulatory T cells (Treg) and promoting M2 macrophage polarization. These pleiotropic activities of IL-33 illustrate the need for a tight molecular regulation of IL-33 activity, and have to be taken into account when IL-33 or its receptor is targeted for therapeutic modulation. Here we review the multiple molecular mechanisms that regulate IL-33 activity and describe how IL-33 can shape innate and adaptive immune responses by promoting Th1, Th2 and Treg function. Finally, we will discuss the possibilities for therapeutic modulation of IL-33 signaling as well as possible safety issues.

IL33 in rheumatoid arthritis: potential contribution to pathogenesis

A better understanding of the inflammatory mechanisms of rheumatoid arthritis and the development of biological therapy revolutionized its treatment, enabling an interference in the synovitis - structural damage - functional disability cycle. Interleukin 33 was recently described as a new member of the interleukin-1 family, whose common feature is its pro-inflammatory activity. Its involvement in the pathogenesis of a variety of diseases, including autoimmune diseases, raises the interest in the possible relationship with rheumatoid arthritis. Its action has been evaluated in experimental models of arthritis as well as in serum, synovial fluid and membrane of patients with rheumatoid arthritis. It has been shown that the administration of interleukin-33 exacerbates collagen-induced arthritis in experimental models, and a positive correlation between cytokine concentrations in serum and synovial fluid of patients with rheumatoid arthritis and disease activity was found. This review discusses evidence for the role of interleukin-33 with a focus on rheumatoid arthritis.

Biomarkers for diagnosis, monitoring of progression, and treatment responses in ankylosing spondylitis and axial spondyloarthritis

With the growing awareness of the impact of chronic back pain and axial spondyloarthritis and recent breakthroughs in genetics and the development of novel treatments which may impact best on early disease, the need for markers that can facilitate early diagnosis and profiling those individuals at the highest risk for a bad outcome has never been greater. The genetic basis of ankylosing spondylitis has been considerably advanced, and HLA-B27 testing has a role in the diagnosis. Knowledge is still incomplete of the rest of the genetic contribution to disease susceptibility, and it is likely premature to use extensive genetic testing (other than HLA-B27) for diagnosis. Serum and plasma biomarkers have been examined extensively in assessing disease activity, treatment response, and as predictors or radiographic severity. For assessing disease activity, other than C-reactive protein and erythrocyte sedimentation rate, the most work has been in examining cytokines (particularly interleukin 17 and 23), matrix metalloproteinase (MMP) markers (particularly MMP3). For assessing those at the highest risk for radiographic progression, biomarkers of bony metabolism, cartilage and connective tissue degradation products, and adipokines have been most extensively assessed. The problem is that no individual biomarkers has been reproducibly shown to assess disease activity or predict outcome, and this area still remains an unmet need, of relevance to industry stakeholders, to regulatory bodies, to the healthcare system, to academic investigators, and finally to patients and providers.

Circulating levels of inflammatory cytokines and cytokine receptors in patients with ankylosing spondylitis: a cross-sectional comparative study

OBJECTIVES

Insight into the most important inflammatory pathways in ankylosing spondylitis (AS) could be of importance in risk stratification and the development of treatment strategies. Therefore, we aimed to compare circulating levels of inflammatory biomarkers between AS patients and controls, and explore associations between these biomarkers and clinical measures of disease activity.

METHOD

In a cross-sectional study, 143 AS patients were compared with 124 population controls. Blood samples were analysed by immunoassays for interleukin (IL)-6, IL-17a, IL-23, soluble tumour necrosis factor receptor 1 (sTNF-R1) and 2 (sTNF-R2), and osteoprotegerin (OPG). Disease activity was measured by the AS Disease Activity Score (ASDAS) and the Bath AS Disease Activity Index (BASDAI).

RESULTS

Analysis of covariance (ANCOVA) demonstrated elevated plasma levels of sTNF-R1 [geometrical mean 0.94 (95% CI 0.88-1.00) vs. 0.83 (95% CI 0.78-0.89) ng/mL, p < 0.01] and OPG (2.3, 95% CI 2.1-2.4 vs. 2.0, 95% CI 1.9-2.2 ng/mL, p = 0.02) and, although not significant, of IL-23 (122, 95% CI 108-139 vs. 106, 95% CI 93-120 pg/mL, p = 0.07) in AS patients vs.

CONTROLS

More AS patients had a high level of sTNF-R2 than controls (22 vs. 1, p < 0.01). No differences between the groups were seen for IL-6 and IL-17a. In patients, no significant associations were seen between inflammatory markers and disease activity measures after adjusting for personal characteristics.

CONCLUSION

Significantly higher plasma levels of sTNF-R1, sTNF-R2, and OPG and numerically but non-significantly higher levels of IL-23 were found in AS patients compared to controls, indicating that these cytokines and cytokine receptors are important inflammatory pathways. Clinical measures of disease activity were not significantly correlated with circulating inflammatory markers.

Cytokine profiles in axial spondyloarthritis

Objectives

Current studies concentrate on the cytokine network and its role in the pathogenesis of spondyloarthritis (SpA). In this study, we analyzed whether the serum cytokine profile (interleukins: IL-10, IL-11, IL-12, IL-15, IL-17, IL-23 and IL-33) correlates with demographic data, clinical manifestations, disease activity and treatment outcome in a group of patients with axial spondyloarthritis.

Material and methods

Forty-nine patients with an established diagnosis of axial spondyloarthritis (aSpA) and 19 healthy volunteers as controls were enrolled in the study. Clinical evaluation included patient's medical history, 44 joint count, back pain intensity and global disease activity in the preceding week (VAS), the duration of morning stiffness and blood tests. Disease activity was assessed using BASDAI and ASDAS-CRP. Serum concentration of IL-10, IL-11, IL-12, IL-15, IL-17, IL-23 and IL-33 was determined.

Results

In patients with aSpA, elevated serum concentration of IL-10, IL-15, IL-17 and IL-23 was detected. In the aSpA group we detected higher values of serum concentration of IL-23 and IL-33 in the subgroup with anterior uveitis (83.1 ±184.0 pg/ml vs. 14.0 ±17.1 pg/ml, p < 0.0001 and 45.5 ±71.9 pg/ml vs. 18.4 ±14.3 pg/ml, p < 0.0001, respectively). Additionally, in the subgroup with peripheral arthritis, elevation of serum concentration of IL-12 (249.3 ±246.9 pg/ml vs. 99.9 ±105.9 pg/ml, p = 0.0001) was detected. Patients with preradiological SpA had higher serum concentration of IL-17 than patients with established diagnosis of AS (6.37 ±8.50 pg/ml vs. 2.04 ±2.98 pg/ml, p = 0.0295). No differences in serum concentration of analyzed cytokines were found between the subgroup with low to moderate disease activity and the subgroup with high to very high disease activity.

Conclusions

We report that in aSpA patients, compared to controls, elevated serum concentrations of IL-10, IL-15, IL-17 and IL-23 were observed. Some cytokines may predispose to a more severe course of aSpA.

The Interleukin 33/ST2 Axis in Patients with Primary Sjögren Syndrome: Expression in Serum and Salivary Glands, and the Clinical Association

Objective.

To evaluate the expression of interleukin 33 (IL-33) and its receptor in sera and salivary tissues of patients with primary Sjögren syndrome (pSS), and to investigate the association with clinical profiles.

Methods.

Serum IL-33 and soluble ST2 (sST2) of 55 patients with pSS and 48 controls were determined by ELISA and assessed for clinical correlation. The expression of IL-33/ST2 in salivary tissues was investigated by immunohistochemical staining and was further characterized by confocal microscopy. We also measured IL-33 production in salivary glandular epithelial cells by proinflammatory stimuli.

Results.

Serum levels of IL-33 and sST2 were higher in patients with pSS compared to those in controls (p = 0.018 and p < 0.0001, respectively). Among patients with pSS, sST2 concentration was associated with thrombocytopenia (p = 0.029) and correlated with disease duration (p = 0.013) and the European League Against Rheumatism Sjögren Syndrome Disease Activity Index (p = 0.042). The expression of IL-33 and ST2 was elevated in salivary glands of patients with pSS with grade 2 inflammation, and diminished in advanced inflammation. In patients with pSS, IL-33 was mainly observed in epithelial and endothelial cells of glandular tissue. The production of IL-33 mRNA by salivary gland epithelial cell line increased under stimulation with interferon-γ.

Conclusion.

The expression of IL-33 and its receptor was elevated in sera and salivary tissues of patients with pSS. These results suggest that the IL-33/ST2 axis might have a role in the pathogenesis of pSS.

Circulating periostin levels in patients with AS: association with clinical and radiographic variables, inflammatory markers and molecules involved in bone formation

OBJECTIVE

The aim of this study was to evaluate serum periostin levels in patients with AS in comparison with healthy controls as well as their association with clinical, inflammatory and radiographic parameters and molecules involved in bone formation.

METHODS

Serum samples for periostin, total Dickkopf-1 (Dkk-1), sclerostin, VEGF and inflammatory markers were obtained from 65 TNF inhibitor-naive patients with AS. The BASDAI, BASFI, modified Stoke AS Spine Score and BASRI for the spine (BASRI-s) were assessed for each patient. Serum periostin levels were also measured in 36 sex-, age- and BMI-matched controls.

RESULTS

Serum periostin levels were significantly lower in AS patients compared with controls [234.4 pg/ml (s.e.m. 7.5) vs 291.4 (s.e.m. 8.3), respectively; P < 0.001]. Periostin levels were higher in AS patients with elevated CRP (P = 0.005), high BASDAI (P = 0.014) and low BASRI-s (P = 0.033) and were correlated with BMI (r = -0.304, P = 0.014), ESR (r = 0.395, P = 0.001), CRP (r = 0.413, P = 0.001), BASRI-s (r = -0.242, P = 0.047) and sclerostin (r = -0.280, P = 0.024). In multiple regression analysis, periostin levels were an independent variable of CRP (β = 0.160, P = 0.009) and sclerostin levels (β = -0.311, P = 0.012).

CONCLUSION

Our data suggest that periostin levels are low in patients with AS. Among AS patients, periostin levels are higher in those with higher disease activity, higher systemic inflammation and less extensive radiographic damage. Periostin is independently associated with CRP and sclerostin levels.

The role of IL-33 in rheumatic diseases

Interleukin-33 (IL-33), a novel member of IL-1 family, has been recently implicated in several inflammatory and autoimmune diseases. IL-33 can be produced by various types of tissues and cells and induce gene expression of Th2-associated cytokines via binding to the orphan receptor ST2. By promoting Th2 type immune response, IL-33 plays important roles in the allergy, whereas its function in autoimmune diseases attracts more attention. Recent studies reported the correlation of IL-33 with rheumatic diseases, and most of them found that the IL-33 expression levels were consistent with disease activity and development. Furthermore, evidence has indicated that IL-33-related treatment may ameliorate the pathogenic conditions and attenuate disease progression of those rheumatic diseases. Therefore, elucidation of the roles of IL-33 in rheumatic diseases would be beneficial to understand the pathogenesis and therapy of these diseases. In this paper, we will summarize the roles of IL-33 in the rheumatic diseases.