Increased serum IL-33 levels may indicate vascular involvement in systemic sclerosis

Endothelial Dysfunction in Systemic Sclerosis

Systemic sclerosis, commonly known as scleroderma, is an autoimmune disorder characterized by vascular abnormalities, autoimmunity, and multiorgan fibrosis. The exact etiology is not known but believed to be triggered by environmental agents in a genetically susceptible host. Vascular symptoms such as the Raynaud phenomenon often precede other fibrotic manifestations such as skin thickening indicating that vascular dysfunction is the primary event. Endothelial damage and activation occur early, possibly triggered by various infectious agents and autoantibodies. Endothelial dysfunction, along with defects in endothelial progenitor cells, leads to defective angiogenesis and vasculogenesis. Endothelial to mesenchymal cell transformation is another seminal event during pathogenesis that progresses to tissue fibrosis. The goal of the review is to discuss the molecular aspect of the endothelial dysfunction that leads to the development of systemic sclerosis.

IL-33 induces histidine decarboxylase, especially in c-kit+ cells and mast cells, and roles of histamine include negative regulation of IL-33-induced eosinophilia

OBJECTIVE AND METHODS

IL-33 is present in endothelial, epithelial, and fibroblast-like cells and released upon cell injury. IL-33 reportedly induces mast-cell degranulation and is involved in various diseases, including allergic diseases. So, IL-33-related diseases seem to overlap with histamine-related diseases. In addition to the release from mast cells, histamine is newly formed by the induction of histidine decarboxylase (HDC). Some inflammatory and/or hematopoietic cytokines (IL-1, IL-3, etc.) are known to induce HDC, and the histamine produced by HDC induction is released without storage. We examined the involvement of HDC and histamine in the effects of IL-33.

RESULTS

A single intraperitoneal injection of IL-33 into mice induced HDC directly and/or via other cytokines (including IL-5) within a few hours in various tissues, particularly strongly in hematopoietic organs. The major cells exhibiting HDC-induction were mast cells and c-kit⁺ cells in the bone marrow. HDC was also induced in non-mast cells in non-hematopoietic organs. HDC, histamine, and histamine H4 receptors (H4Rs) contributed to the suppression of IL-33-induced eosinophilia.

CONCLUSION

IL-33 directly and indirectly (via IL-5) induces HDC in various cells, particularly potently in c-kit⁺ cells and mature mast cells, and the newly formed histamine contributes to the negative regulation of IL-33-induced eosinophilia via H4Rs.

Current Trends in Vascular Biomarkers for Systemic Sclerosis: A Narrative Review

Systemic sclerosis (SSc, scleroderma) is a multifaceted rare connective tissue disease whose pathogenesis is dominated by immune dysregulation, small vessel vasculopathy, impaired angiogenesis, and both cutaneous and visceral fibrosis. Microvascular impairment represents the initial event of the disease, preceding fibrosis by months or years and accounting for the main disabling and/or life-threatening clinical manifestations, including telangiectasias, pitting scars, periungual microvascular abnormalities (e.g., giant capillaries, hemorrhages, avascular areas, ramified/bushy capillaries) clinically detectable by nailfold videocapillaroscopy, ischemic digital ulcers, pulmonary arterial hypertension, and scleroderma renal crisis. Despite a variety of available treatment options, treatment of SSc-related vascular disease remains problematic, even considering SSc etherogenity and the quite narrow therapeutic window. In this context, plenty of studies have highlighted the great usefulness in clinical practice of vascular biomarkers allowing clinicians to assess the evolution of the pathological process affecting the vessels, as well as to predict the prognosis and the response to therapy. The current narrative review provides an up-to-date overview of the main candidate vascular biomarkers that have been proposed for SSc, focusing on their main reported associations with characteristic clinical vascular features of the disease.

The association of IL-33 and systemic sclerosis: a systematic review and meta-analysis

A meta-analysis of the association between IL-33 and these diseases is lacking, and we aimed to perform a meta-analysis of the association between IL-33 and systemic sclerosis (SSc). We searched relevant papers through PubMed (via Medline), Embase (via Ovid), and the Cochrane Library through May 18th, 2022. Odds ratios (ORs) and weighted mean differences (WMDs) were estimated using a random effect model. A total of 8 papers were included in our meta-analysis. The pooled results showed that SSc patients had significantly higher serum IL-33 levels than healthy controls (HCs) (SMD = 0.64; 95% CI = 0.34, 0.93; P < 0.001); early SSc patients had significantly higher serum IL-33 levels than late SSc patients (SMD = 1.04; 95% CI = 0.28, 1.80; P = 0.007). However, no significant difference was observed between limited cutaneous SSc and diffuse cutaneous SSc (SMD =  - 0.35; 95% CI =  - 0.76, 0.06; P = 0.094). Our meta-analysis provided important evidence for the use of IL-33 in therapeutic strategies for fibrotic disorders.

The Microbiome in Systemic Sclerosis: Pathophysiology and Therapeutic Potential

Systemic sclerosis (SSc), also known as scleroderma, is an autoimmune disease with unknown etiology characterized by multi-organ fibrosis. Despite substantial investigation on SSc-related cellular and molecular mechanisms, effective therapies are still lacking. The skin, lungs, and gut are the most affected organs in SSc, which act as physical barriers and constantly communicate with colonized microbiota. Recent reports have documented a unique microbiome signature, which may be the pathogenic trigger or driver of SSc. Since gut microbiota influences the efficacy and toxicity of oral drugs, evaluating drug-microbiota interactions has become an area of interest in disease treatment. The existing evidence highlights the potential of the microbial challenge as a novel therapeutic option in SSc. In this review, we have summarized the current knowledge about molecular mechanisms of SSc and highlighted the underlying role of the microbiome in SSc pathogenesis. We have also discussed the latest therapeutic interventions using microbiomes in SSc, including drug-microbiota interactions and animal disease models. This review aims to elucidate the pathophysiological connection and therapeutic potential of the microbiome in SSc. Insights into the microbiome will significantly improve our understanding of etiopathogenesis and developing therapeutics for SSc.

The Role of T Cells in Systemic Sclerosis: An Update

Systemic sclerosis (SSc) is a chronic disease characterized by microvasculopathy, autoantibodies (autoAbs), and fibrosis. The pathogenesis of the disease is incompletely understood. Microvasculopathy and autoAbs appear very early in the disease process. AutoAbs, such as those directed against DNA topoisomerase I (Topo I), are disease specific and associated with disease manifestations, and indicate activation of the adaptive immune system. B cells are involved in fibrosis in SSc. T cells are also involved in disease pathogenesis. T cells show signs of antigen-induced activation; T cells of TH2 type are increased and produce profibrotic cytokines interleukin (IL)-4, IL-13, and IL-31; CD4+ cytotoxic T lymphocytes are increased in skin lesions, and cause fibrosis and endothelial cell apoptosis; circulating T follicular helper (TFH) cells are increased in SSc produce IL-21 and promote plasmablast antibody production. On the other hand, regulatory T cells are impaired in SSc. These findings provide strong circumstantial evidence for T cell implication in SSc pathogenesis and encourage new T cell-directed therapeutic strategies for the disease.

Dendritic cells drive profibrotic inflammation and aberrant T cell polarization in systemic sclerosis

OBJECTIVES

Systemic sclerosis (SSc) is a devastating autoimmune disease characterized by fibrosis and obliterative vasculopathy affecting the skin and visceral organs. While the processes mediating excessive extracellular matrix (EM) deposition and fibroblast proliferation are clear, the exact link between autoimmunity and fibrosis remains elusive. Th17 cells have been proposed as critical drivers of profibrotic inflammation during SSc, but little is known about the immune components supporting their pathogenic role.

METHODS

Dendritic cells (DCs) activate and shape T cell differentiation by producing polarizing cytokines. Hence, we investigated the cytokine responses of monocyte-derived DCs (Mo-DCs) from patients with limited cutaneous SSc (lcSSc), diffuse cutaneous SSc (dcSSc), and healthy controls (HC) after stimulation with toll-like receptor (TLR) agonists. Also, using co-culture assays, we analyzed T cell subpopulations after contact with autologous TLR-activated Mo-DCs.

RESULTS

In general, we observed an increased production of Th17 related cytokines like IL-1β, IL-17F, IL-21, IL-22 by SSc compared with HC Mo-DCs, with variations between lcSSc vs. dcSSc and early- vs. late-stage subgroups. Noticeably, we found a significant increment in IL-33 production by Mo-DCs in all SSc cases regardless of their clinical phenotype. Strikingly, T cells displayed Th2, Th17, and dual Th2/Th17 phenotypes after exposure to autologous TLR-stimulated Mo-DCs from SSc patients but not HC. These changes were pronounced in individuals with early-stage dcSSc and less significant in the late-stage lcSSc subgroup.

CONCLUSIONS

Our findings suggest that functional alterations of DCs subsidize the immune mechanisms favoring the aberrant T cell polarization and profibrotic inflammation behind the clinical SSc heterogeneity.

Alarmins in autoimmune diseases

Alarmins are endogenous, constitutively expressed, chemotacting and immune activating proteins or peptides released because of non-programmed cell death (i.e. infections, trauma, etc). They are considered endogenous damage-associated molecular patterns (DAMPs), able to induce a sterile inflammation. In the last years, several studies highlighted a possible role of different alarmins in the pathogenesis of various autoimmune and immune-mediated diseases. We reviewed the relevant literature about this topic, for about 160 articles. Particularly, we focused on systemic autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, idiopathic inflammatory myopathies, ANCA-associated vasculitides, Behçet's disease) and cutaneous organ-specific autoimmune diseases (vitiligo, psoriasis, alopecia, pemphigo). Finally, we discussed about future perspectives and potential therapeutic implications of alarmins in autoimmune diseases. In fact, identification of receptors and downstream signal transducers of alarmins may lead to the identification of antagonistic inhibitors and agonists, with the capacity to modulate alarmins-related pathways and potential therapeutic applicability.

IL-13 and IL-33 Serum Levels Are Increased in Systemic Sclerosis Patients With Interstitial Lung Disease

Objective

Systemic sclerosis (SSc) mortality is extremely variable in its internal organ involvement. Pulmonary fibrosis occurs in up to 30% of the cases. Animal models provide evidence that IL-33 is able to induce both cutaneous and pulmonary fibrosis via increased IL-13 and in SSc patients the levels of IL-33 correlate with skin fibrosis. Our aim was to test whether both IL-33 and IL-13 are higher in patients with diffuse SSc and interstitial lung disease (SSc-ILD) compared to SSc patients without ILD and healthy controls.

Methods

Serum levels of IL-13 and IL-33 were measured in 30 SSc patients with diffuse disease and 30 healthy controls by enzyme-linked immunosorbent assay. The extent of pulmonary fibrosis was assessed according to HRCT Warrick score. Pulmonary function tests included lung diffusion capacity for carbon monoxide, forced vital capacity and total lung capacity.

Results

Both IL-13 and IL-33 levels were increased in SSc patients compared to controls and significantly associated each other. DLco, FVC and TLC scores were inversely associated with IL-33 and IL-13 levels. Both IL-33 and IL-13 levels were significantly associated with the Warrick severity score and higher in the group of SSc patients with reduced pulmonary function compared to SSc patients with normal pulmonary function tests.

Conclusion

The IL-13/IL-33 axis needs to be further explored in longitudinal studies of SSc-ILD patients to assess its validity as a biomarker and future treatment target, as does downstream mediator ST2.

IL33 and sST2 serum level in systemic sclerosis microvascular involvement

AIM

Endothelial dysfunction and microvascular damage are hallmarks of systemic sclerosis (SSc). Objective of this study was to evaluate IL33 and ST2 serum levels in SSc patients and healthy controls (HC). Secondary aim was to evaluate the IL33 axis in the SSc microvascular manifestation.

METHODS

IL33 and sST2 have been assessed in 46 SSc patients and 24 HC matched for sex and age. Main clinimetric indexes were assessed. Skin perfusion of hands was evaluated by Laser Speckle Contrast Analysis (LASCA) and echocolordoppler ultrasound of renal arteries was performed to evaluate subclinical renal involvement.

RESULTS

SSc patients had higher serum level of IL33 and sST2 than HC. IL33 and sST2 were significantly higher in SSc patient with digital ulcers (DUs) compared to SSc patients without DUs. SSc patients with late nailfold videocapillaroscopy (NVC) pattern had higher serum levels of sST2 than SSc patients with active NVC pattern. SSc patients without proximal-distal gradient (PDG) at LASCA had significantly higher sST2 serum level compared to SSc patients with PDG. SSc patients with renal resistive index (RRI) ≥ 0.70 had higher serum levels of sST2 than SSc patients with RRI < 0.70. A positive linear correlation was shown between sST2 and RRI, between sST2 and intrarenal S/D and between sST2 and PI. Kaplan-Meier curves show a significantly reduced free survival from DUs in patients with increased sST2 (p = 0.025). In multivariate analysis, sST2 is associated with the development of new DUs.

CONCLUSION

IL33 and sST2 are increased in SSc patients and ST2 might be a marker of microvascular damage.

Increased Serum Levels of soluble ST2 as a Predictor of Disease Progression in Systemic Sclerosis

OBJECTIVE

Interleukin-33 (IL-33) has been investigated as a mediator in the pathogenesis of fibrosis in lung, liver, and heart. There is accumulating evidence for the involvement of the IL-33/IL-33 receptor ST2L signalling pathway in systemic sclerosis (SSc). Little is known about the role of serum sST2 in SSc, which is the subject of the present investigation.

METHOD

Serum levels of sST2 were measured in 49 patients with SSc, recruited prospectively between November 2017 and March 2019. Patients were divided into those with progressive and those with stable disease. Receiver operating characteristics (ROC) curve analysis was applied to study sST2 as a marker for identifying patients with progressive disease. We used multivariate logistic regression analysis to evaluate the predictive value of sST2 for progressive disease after adjustment for potential confounding factors.

RESULTS

Serum sST2 levels in patients with progressive disease were significantly elevated compared with patients with stable disease (mean ± sem: 50.4 ± 4.7 ng/mL vs 29.2 ± 2.97 ng/mL, p < 0.001). ROC curve analysis identified an sST2 cut-off value of 37.8 ng/mL as optimal for discriminating patients with progressive disease from those with stable disease (sensitivity 80.0%, specificity 79.3%, area under the curve 0.80). After controlling for potential confounding factors (age, gender, C-reactive protein, pro-brain natriuretic peptide, and sum of internal medicine comorbidities), sST2 remained predictive of progressive disease (odds ratio 1.070, 95% confidence interval 1.017-1.126, p < 0.009).

CONCLUSION

In the present study, sST2 serum levels were predictive of disease progression in patients with SSc.

Role of Alarmins in the Pathogenesis of Systemic Sclerosis

Systemic sclerosis (SSc) is a rare chronic autoimmune disease associated with significant morbidity and mortality. Two main subsets of SSc are recognized: (i) diffuse cutaneous SSc with rapidly progressive fibrosis of the skin, lungs, and other internal organs; and (ii) limited cutaneous SSc, which is dominated by vascular manifestations, with skin and organ fibrosis generally limited and slowly progressing. In spite of intense investigation, both etiology and pathogenesis of SSc are still unknown. Genetic and environmental factors, as well as abnormalities of immune functions, are strongly suggested for etiology, while microvascular abnormalities, immune system activation, and oxidative stress are suggested for the pathogenesis. Recently, it has been found that a multitude of mediators and cytokines are implicated in the fibrotic processes observed in SSc. Among these, a central role could be exerted by “alarmins”, endogenous and constitutively expressed proteins/peptides that function as an intercellular signal defense. This review describes, in a detailed manner, the role of alarmins in the pathogenesis of scleroderma.

IL-33/IL-31 Axis in Immune-Mediated and Allergic Diseases

Several allergic and immunologic diseases including asthma, food allergy (FA), chronic spontaneous urticaria (CSU), atopic dermatitis (AD), systemic lupus erythematosus (SLE), systemic sclerosis (SSc), rheumatoid arthritis (RA), and Behçet's disease (BD) are characterized by the involvement of Th2 immunity. Several mediators lead to immunoglobulin (Ig)E production, thus including key cytokines such as interleukin (IL)-4, IL-5, and IL-13. Among them, IL-31 and IL-33 have been recently studied as novel biomarkers and future therapeutic targets for allergic and immunological disorders. IL-31 is a proinflammatory cytokine-it regulates cell proliferation and is involved in tissue remodeling. IL-33, acting through its receptor suppression of tumorigenity (ST2L), is an alarmin cytokine from the IL-1 family, whose expression is mediated by tissue damage. The latter has a pleiotropic effect, as it may modulate specific and innate immune cells functions. To date, several researchers have investigated the involvement of IL-31 and IL-33 in several allergic and immune-mediated diseases. Further studies are needed to understand the future applications of these molecules as novel therapeutic agents. This paper aims to give the readers a complete and updated review of IL-31 and IL-33 involvement among the most common autoimmune and allergic disorders.

The Roles of IL-1 Family Cytokines in the Pathogenesis of Systemic Sclerosis

The IL-1 family consists of 11 cytokines, 7 ligands with agonist activity (IL-1α, IL-1β, IL-18, IL-33, IL-36α, IL-36β, IL-36γ) and four members with antagonistic activities [IL-1 receptor antagonist (IL-1Ra), IL-36Ra, IL-37, IL-38]. Recent articles have described that most members of IL-1 family cytokines are involved in the process of innate and adaptive immunity as well as fibrosis in systemic sclerosis (SSc). IL-1 family gene polymorphisms, abnormal expression of IL-1 and its potential role in the fibrosis process have been explored in SSc. IL-33 and IL-18 have also been discussed in the recent years. IL-33 may contribute to the fibrosis of SSc, while IL-18 remains to be researched to confirm its role in fibrosis process. There is a lack of study on the pathophysiological roles of IL-36, IL-37, and IL-38 in SSc, which might provide us new study area. Here, we aim to give a brief overview of IL-1 family cytokines and discuss their pivotal roles in the pathogenesis of SSc.

Elevated serum levels of interleukin-1β and interleukin-33 in patients with systemic sclerosis in Chinese population

PURPOSE OF THE STUDY

Systemic sclerosis (SSc) is a multisystem autoimmune disease. Although the pathogenesis of the disease remains incompletely understood, some cytokines or growth factors which regulate SSc induction may be involved in the injury of endothelial cells and the modulation of leukocyte function. We aimed to perform this case-control study to determine serum levels of interleukin (IL)-1α, IL-1β, IL-18 and IL-33 and their associations with clinical manifestations in SSc patients.

MATERIALS AND METHODS

There were 56 patients with SSc and 56 healthy individuals who were recruited from local hospital between 2012 and 2014. Serum IL-1α, IL-1β, IL-18 and IL-33 levels were measured with specific enzyme-linked immunosorbent assay kits.

RESULTS

Univariate analysis revealed that serum IL-1β, IL-18 and IL-33 levels in SSc patients were significantly higher than that in healthy controls. After adjusting possible confounding factors (sex, age, smoking and drinking) by multivariable analyses, serum IL-1β levels (OR = 1.082; 95 % CI: 1.013-1.155) and serum IL-33 levels (OR = 1.100; 95 %CI: 1.022-1.185) were still related factors. There were interrelationships among the serum levels of IL-1α, IL-1β, IL-18 and IL-33 and these associations were not consistent in SSc patients and controls. No associations of serum IL-1α, IL-1β, IL-18 and IL-33 levels with clinical parameters were found.

CONCLUSION

IL-1β and IL-33 may contribute to the development of SSc. While there were no direct associations between these cytokines and disease manifestations, they still could be considered as serum markers of development of SSc. Further studies are required to validate this incipient data.

Interleukin-33 in Systemic Sclerosis: Expression and Pathogenesis

Interleukin-33 (IL-33), a member of the IL-1 superfamily, functions as a traditional cytokine and nuclear factor. It is proposed to have an “alarmin” role. IL-33 mediates biological effects by interacting with the ST2 receptor and IL-1 receptor accessory protein, particularly in innate immune cells and T helper 2 cells. Recent articles have described IL-33 as an emerging pro-fibrotic cytokine in the immune system as well as a novel potential target for systemic sclerosis. Here, we review the available information and focus on the pleiotropic expression and pathogenesis of IL-33 in systemic sclerosis, as well as the feasibility of using IL-33 in clinical applications.

The role of endothelial cells in the vasculopathy of systemic sclerosis: A systematic review

INTRODUCTION

Systemic sclerosis (SSc) is an autoimmune connective tissue disorder characterized by fibroproliferative vasculopathy, immunological abnormalities and progressive fibrosis of multiple organs including the skin. In this study, all English speaking articles concerning the role of endothelial cells (ECs) in SSc vasculopathy and representing biomarkers are systematically reviewed and categorized according to endothelial cell (EC) (dys)function in SSc.

METHODS

A sensitive search on behalf of the EULAR study group on microcirculation in Rheumatic Diseases was developed in Pubmed, The Cochrane Library and Web of Science to identify articles on SSc vasculopathy and the role of ECs using the following Mesh terms: (systemic sclerosis OR scleroderma) AND pathogenesis AND (endothelial cells OR marker). All selected papers were read and discussed by two independent reviewers. The selection process was based on title, abstract and full text level. Additionally, both reviewers further searched the reference lists of the articles selected for reading on full text level for supplementary papers. These additional articles went through the same selection process.

RESULTS

In total 193 resulting articles were selected and the identified biomarkers were categorized according to description of EC (dys)function in SSc. The most representing and reliable biomarkers described by the selected articles were adhesion molecules for EC activation, anti-endothelial cell antibodies for EC apoptosis, vascular endothelial growth factor (VEGF), its receptor VEGFR-2 and endostatin for disturbed angiogenesis, endothelial progenitors cells for defective vasculogenesis, endothelin-1 for disturbed vascular tone control, Von Willebrand factor for coagulopathy and interleukin (IL)-33 for EC-immune system communication. Emerging, relatively new discovered biomarkers described in the selected articles, are VEGF₁₆₅b, IL-17A and the adipocytokines. Finally, myofibroblasts involved in tissue fibrosis in SSc can derive from ECs or epithelial cells through a process known as endothelial-to-mesenchymal transition.

CONCLUSION

This systematic review emphasizes the growing evidence that SSc is primarily a vascular disease where EC dysfunction is present and prominent in different aspects of cell survival (activation and apoptosis), angiogenesis and vasculogenesis and where disturbed interactions between ECs and various other cells contribute to SSc vasculopathy.

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.

Red Blood Cells Store and Release Interleukin-33

Interleukin-33 (IL-33) is a member of the IL-1 cytokine superfamily that potently drives production of a variety of cytokines and contributes to the pathogenesis of inflammatory diseases. The IL-33 is a nuclear protein and is released from apoptotic or necrotic cells. Serum IL-33 levels are increased in various diseases, such as atopic dermatitis, chronic hepatitis C infection, and asthma. Here, we show that red blood cells (RBCs) are one of the major sources of plasma IL-33. The IL-33 levels are significantly increased in supernatants from lysed RBCs. Plasma IL-33 levels are increased in patients during hemolysis, and plasma IL-33 levels show a positive correlation with degree of hemolysis. The IL-33 protein and messenger RNA levels were detected in the late stages of differentiation in ex vivo primary human erythroid progenitor cell cultures, suggesting that IL-33 is expressed during maturation of RBCs. Furthermore, hemoglobin depleted red cell lysates induced IL-8 expression in human epithelial cells. This effect was attenuated in IL-33 decoy receptor expressing cells and was enhanced in IL-33 receptor expressing cells. These results suggest that erythroid progenitor cells produce IL-33 and circulating RBCs represent a major source of IL-33 that is released upon hemolysis.

The IL-33 gene is related to increased susceptibility to systemic sclerosis

Systemic sclerosis (SSc) is a chronic inflammatory disease characterized by widespread fibrosis of the skin and several visceral organs. The pro-fibrotic potential of interleukin (IL)-33 has been demonstrated by in both in vitro and in vivo settings; moreover, increased level of IL-33 has also been reported in patients with SSc. Therefore, the aim of the present study was to detect the potential association of IL-33 gene polymorphisms on the susceptibility of SSc. A total of 300 SSc patients and 280 healthy controls (HC) were enrolled in this multicentric preliminary candidate gene study. DNA samples were harvested using an appropriate commercial DNA isolation kit. Four single nucleotide polymorphisms (SNPs) of IL-33 gene (rs7044343, rs1157505, rs11792633 and rs1929992) were genotyped using the appropriate commercial primer/probe sets on real-time PCR. There was no significant difference in terms of the allelic distributions and minor allele frequencies of evaluated four IL-33 polymorphisms between the SSc and HC groups (P > 0.05 for all). Moreover, the genotypic distributions of rs1157505, rs11792633 and rs1929992 polymorphisms were not significantly different (P > 0.05 for all). However, CC genotype of rs7044343 SNP was significantly higher in the SSc group compared to the HC group (P = 0.013, OR 1.75, 95 % CI 1.12-2.72). This preliminary candidate gene study demonstrates that rs7044343 polymorphism of IL-33 gene is associated with the susceptibility to the SSc in Turkish population. It may be suggested that IL-33 gene may be a candidate gene to research in SSc.

Increased Serum Levels of the IL-33 Neutralizing sST2 in Limited Cutaneous Systemic Sclerosis

The pathophysiology of both limited cutaneous systemic sclerosis (lcSSc) and diffuse cutaneous SSc (dcSSc), representing two subtypes of an autoimmune disease of the connective tissue, is still enigmatic. Life-limiting, progressive fibrotic changes as a consequence of vasculopathy and autoimmunity are characteristic in varying extent for lcSSc and dcSSc. Previously, an increased IL-33 serum concentration in early phase SSc patients and an elevated tissue expression of its receptor, ST2L, on endothelial cells (EC) were described. While suggested as a biomarker for fibrotic diseases, for example liver fibrosis, the role of soluble ST2 (sST2) in the pathological processes and its contribution to vascular fibrosis in SSc has not been investigated. Here, we showed that sST2 is elevated in late phase limited cutaneous SSc (lcSSc) as compared to patients with shorter disease duration or with the diffuse subtype of SSc. We demonstrated that sST2, not IL-33, is significantly increased in serum of lcSSc patients with disease duration over 9 years. Soluble ST2 was not elevated in healthy controls or in SSc patients with early skin involvement or disease duration shorter than 9 years. Furthermore, we observed that sST2 serum levels were lowered by iloprost (prostacyclin) treatment. After 5 days of iloprost infusion, sST2 serum levels fell in 6 of 7 patients. Therefore, we not only like to propose sST2 as a biomarker for progressive vascular fibrosis, but moreover, suggest that the involvement of sST2 in the pathogenesis of lcSSc may be exploited therapeutically.

Regulatory T cells produce profibrotic cytokines in the skin of patients with systemic sclerosis

BACKGROUND

Systemic sclerosis (SSc) is an autoimmune disorder characterized by fibrosis of the skin and internal organs. Pathologic conversion of regulatory T (Treg) cells into inflammatory cytokine-producing cells is thought to be an important step in the progression of autoimmunity, but whether loss of normal Treg cell function contributes to SSc is unknown.

OBJECTIVE

We sought to determine whether Treg cells in the blood and skin of patients with SSc acquired abnormal production of effector cytokines.

METHODS

Peripheral blood and skin biopsy specimens were collected from control subjects and patients with limited or diffuse SSc. Flow cytometry was used to evaluate expression of cell-surface proteins and the cytokine production profile of forkhead box protein 3-positive Treg cells compared with forkhead box protein 3-negative conventional T cells.

RESULTS

Treg cells in the blood of patients with SSc had a normal phenotype and did not produce T-effector cytokines. In contrast, Treg cells from skin affected by SSc produced significant amounts of IL-4 and IL-13. Although Treg cells in the blood of patients with SSc did not make TH2 cytokines, they contained a significantly higher proportion of skin-homing cells expressing TH2 cell-associated chemokine receptors. Evidence that IL-33 caused the differentiation of skin Treg cells into TH2-like cells, combined with high tissue-localized expression of this cytokine in patients with SSc and expression of the ST2 chain of the IL-33 receptor on skin-localized Treg cells, suggests that IL-33 might be an important stimulator of tissue-localized loss of normal Treg cell function.

CONCLUSION

These data are the first evidence for the presence of TH2-like Treg cells in human autoimmunity and show that Treg cell plasticity can be tissue specific. Localized dysfunction of Treg cells is a previously unknown factor that might contribute to fibrosis in patients with SSc.

Vascular biomarkers and correlation with peripheral vasculopathy in systemic sclerosis

Vascular disease is a hallmark of systemic sclerosis (SSc). It is present in every patient, being responsible both for the earliest clinical manifestations and the major life-threatening complications of the disease, and thus determining important morbidity and mortality. In SSc, progressive vascular injury leads to vascular tone dysfunction and reduced capillary blood flow, with consequent tissue ischemia and chronic hypoxia. These phenomena are often accompanied by abnormal levels of vascular factors. Microangiopathy in SSc may be easily assessed by nailfold videocapillaroscopy. The variety of derangements detected in the nailfold capillaries is accompanied by abnormal levels of different vascular mediators and appears to be the best evaluable predictor of the development of peripheral vascular complications, such as digital ulcers. The purpose of this review is to summarize in SSc the most relevant vascular biomarkers and the main associations between vascular biomarkers and capillaroscopic parameters and/or the presence of digital ulcers. Vascular biomarkers could become useful predictive factors of vascular damage in SSc, allowing an earlier management of vascular complications.

Emerging role of interleukin-33 in autoimmune diseases

Interleukin-33 (IL-33) is a member of the IL-1 cytokine family. It predominantly induces type 2 immune responses and thus is protective against atherosclerosis and nematode infections but contributes to allergic airway inflammation. Interleukin-33 also plays a pivotal role in the development of many autoimmune diseases through mechanisms that are still not fully understood. In this review, we focus on the recent advances in understanding of the expression and function of IL-33 in some autoimmune disorders, aiming to provide insight into its potential role in disease development.

Potential involvement of the IL-33-ST2 axis in the pathogenesis of primary Sjogren's syndrome

OBJECTIVES

To investigate the role of the interleukin (IL)-33-ST2 axis in the pathophysiology of primary Sjögren's syndrome (pSS).

METHODS

Serum levels of IL-33 and sST2 were determined by ELISA. The expression of IL-33 and ST2 was investigated in salivary glands (SG) by immunohistochemistry. PBMC were isolated and stimulated with IL-33, IL-12 and IL-23 and the cytokine profile response was examined by flow cytometry. Intracellular cytokine detection of IFNγ and IL-17 was performed by flow cytometry.

RESULTS

Serum IL-33 and sST2 levels were increased in pSS patients compared with controls and patients with systemic lupus erythematosus. Expression of IL-33 was upregulated in SG with Chisholm scores of 2 and 3 of pSS patients but comparable with controls for SG with Chisholm score of 4. ST2 expression in SG was downregulated in pSS patients. IL-33 at different concentrations did not increase the secretion of pro-inflammatory cytokines but acted synergistically with IL-12 and IL-23 to promote IFNγ production. NK and NKT cells were identified as main producers of IFNγ in vitro and were found in SG of pSS patients.

CONCLUSIONS

IL-33 is released in pSS, and acts with IL-12 and IL-23 to favour the secretion of IFNγ by NK and NKT cells.

Macrophage phenotype in the subclinical gut inflammation of patients with ankylosing spondylitis

OBJECTIVE

Long-term evolution of subclinical gut inflammation to overt Crohn's disease (CD) has been described in AS patients. The aim of this study was to evaluate macrophage polarization occurring in the inflamed gut of patients with AS.

METHODS

Twenty-seven HLA-B27(+) AS patients, 20 CD patients and 17 normal controls were consecutively enrolled. Classic M1 (iNOS(+)IL-10(-)), resolution phase (iNOS(+)IL-10(+)), M2 and CD14(+) macrophages were characterized by immunohistochemistry and flow cytometry. Quantitative gene expression analysis of IFN-γ, IL-4, IL-5, IL-33 and STAT6 was performed by real time PCR.

RESULTS

Classic M1 macrophages were expanded in CD and AS, where resolution phase macrophages predominate. A large increase in CD163(+) (M2) macrophages was observed in AS strictly correlated with the expression of IL-33, a Th2 cytokine involved in M2 polarization. Unlike in CD, CD14(+) macrophages were virtually absent in the gut of AS patients and controls.

CONCLUSION

The absence of CD14(+) macrophages together with the expansion of resolution phase and M2 macrophages is the immunological signature of subclinical ileal inflammation in AS.

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.