Experimental asthma persists in IL-33 receptor knockout mice because of the emergence of thymic stromal lymphopoietin-driven IL-9+ and IL-13+ type 2 innate lymphoid cell subpopulations.

BACKGROUND: IL-33 plays an important role in the development of experimental asthma. OBJECTIVE: We sought to study the role of the IL-33 receptor suppressor of tumorigenicity 2 (ST2) in the persistence of asthma in a mouse model. METHODS: We studied allergen-induced experimental asthma in ST2 knockout (KO) and wild-type control mice. We measured airway hyperresponsiveness by using flexiVent; inflammatory indices by using ELISA, histology, and real-time PCR; and type 2 innate lymphoid cells (ILC2s) in lung single-cell preparations by using flow cytometry. RESULTS: Airway hyperresponsiveness was increased in allergen-treated ST2 KO mice and comparable with that in allergen-treated wild-type control mice. Peribronchial and perivascular inflammation and mucus production were largely similar in both groups. Persistence of experimental asthma in ST2 KO mice was associated with an increase in levels of thymic stromal lymphopoietin (TSLP), IL-9, and IL-13, but not IL-5, in bronchoalveolar lavage fluid. Expectedly, ST2 deletion caused a reduction in IL-13+ CD4 T cells, forkhead box P3-positive regulatory T cells, and IL-5+ ILC2s. Unexpectedly, ST2 deletion led to an overall increase in innate lymphoid cells (CD45+lin-CD25+ cells) and IL-13+ ILC2s, emergence of a TSLP receptor-positive IL-9+ ILC2 population, and an increase in intraepithelial mast cell numbers in the lung. An anti-TSLP antibody abrogated airway hyperresponsiveness, inflammation, and mucus production in allergen-treated ST2 KO mice. It also caused a reduction in innate lymphoid cell, ILC2, and IL-9+ and IL-13+ ILC2 numbers in the lung. CONCLUSIONS: Genetic deletion of the IL-33 receptor paradoxically increases TSLP production, which stimulates the emergence of IL-9+ and IL-13+ ILC2s and mast cells and leads to development of chronic experimental asthma. An anti-TSLP antibody abrogates all pathologic features of asthma in this model.

Sputum transcriptomics reveal upregulation of IL-1 receptor family members in patients with severe asthma.

BACKGROUND: Sputum analysis in asthmatic patients is used to define airway inflammatory processes and might guide therapy. OBJECTIVE: We sought to determine differential gene and protein expression in sputum samples from patients with severe asthma (SA) compared with nonsmoking patients with mild/moderate asthma. METHODS: Induced sputum was obtained from nonsmoking patients with SA, smokers/ex-smokers with severe asthma, nonsmoking patients with mild/moderate asthma (MMAs), and healthy nonsmoking control subjects. Differential cell counts, microarray analysis of cell pellets, and SOMAscan analysis of sputum analytes were performed. CRID3 was used to inhibit the inflammasome in a mouse model of SA. RESULTS: Eosinophilic and mixed neutrophilic/eosinophilic inflammation were more prevalent in patients with SA compared with MMAs. Forty-two genes probes were upregulated (>2-fold) in nonsmoking patients with severe asthma compared with MMAs, including IL-1 receptor (IL-1R) family and nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing 3 (NRLP3) inflammasome members (false discovery rate < 0.05). The inflammasome proteins nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing 1 (NLRP1), NLRP3, and nucleotide-binding oligomerization domain (NOD)-like receptor C4 (NLRC4) were associated with neutrophilic asthma and with sputum IL-1ß protein levels, whereas eosinophilic asthma was associated with an IL-13-induced TH2 signature and IL-1 receptor-like 1 (IL1RL1) mRNA expression. These differences were sputum specific because no activation of NLRP3 or enrichment of IL-1R family genes in bronchial brushings or biopsy specimens in patients with SA was observed. Expression of NLRP3 and of the IL-1R family genes was validated in the Airway Disease Endotyping for Personalized Therapeutics cohort. Inflammasome inhibition using CRID3 prevented airway hyperresponsiveness and airway inflammation (both neutrophilia and eosinophilia) in a mouse model of severe allergic asthma. CONCLUSION: IL1RL1 gene expression is associated with eosinophilic SA, whereas NLRP3 inflammasome expression is highest in patients with neutrophilic SA. TH2-driven eosinophilic inflammation and neutrophil-associated inflammasome activation might represent interacting pathways in patients with SA.

IL-33/s-ST2 ratio, systemic symptoms, and basophil activation in Pru p 3-sensitized allergic patients.

BACKGROUND: Although IL-33/ST2 axis is involved in the development of allergic diseases, its contribution in food allergy is still unknown. METHODS: In this study, we assessed the serum levels of IL-33 and its s-ST2 receptor in 53 control patients (without allergic diseases), 47 peach (Pru p 3)-sensitized allergic patients (SAP), and in 68 non-Pru p 3-SAP. Basophil activation test (BAT) was used to assess the basophil activation due to allergen exposure before and after the addition of s-ST2 to the blood samples from 5 Pru p 3-SAP. RESULTS: IL-33 levels in Pru p 3-SAP were higher than in non-Pru p 3-SAP and in normal controls. Lower s-ST2 levels were found in Pru p 3-SAP than in non-Pru p 3-SAP. IL-33/s-ST2 ratio was higher in Pru p 3-SAP than in both non-Pru p 3-SAP and controls. Higher IL-33/s-ST2 ratio was observed in Pru p 3-SAP with severe than in those with mild systemic symptoms. BAT analysis in Pru p 3-SAP showed a decrease in basophil activation due to Pru p 3 exposure after the addition of s-ST2 to the blood samples. CONCLUSIONS: An imbalance in the baseline levels of IL-33/ST2 pathway is present in Pru p 3-SAP. The measurement of this pathway might be helpful to detect patients at a higher risk of developing severe systemic symptoms.

Special aspects of interleukin-33 and the IL-33 receptor complex.

Interleukin-33 (IL-33) is an unconventional member of the IL-1 family: it is a dual function cytokine. Many different cell types, tissue cells and leukocytes, produce IL-33 either constitutively or after stimulation and release it by a poorly defined molecular mechanism. Free IL-33 acts as a classical cytokine by binding to target cells expressing receptors for IL-33 minimally consisting of ST2 and IL-1RAcP. Depending on the target cell type IL-33 will stimulate cell-type specific signal transduction mechanisms and thereby change the biosynthetic profile of the respective cell. In addition, it is stored in the nucleus of cells and may be released after cell stress, death by injury or necrosis, acting as an alarmin by orchestrating a sterile inflammation. Furthermore, IL-33 has intracrine functions in the cell producing it, which are independent of IL-33 receptors. Intracellular IL-33 is predominantly found in the nucleus associated to the chromatin and may exert gene regulatory function by yet poorly defined mechanisms. It is the aim of this review to address two basic biological aspects of the IL-33/IL-33 receptor system. First, to summarize the current understanding of the fate and function of intracellular IL-33, and second, to discuss recent advances in the knowledge of the molecular composition, function and regulation of the IL-33 receptor complex, including initial signaling mechanisms.

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.

Evaluation of IL-33R and Galectin-3 as New Biomarkers of Cardiac Damage after Polytrauma-Association with Cardiac Comorbidities and Risk Factors.

Polytrauma is one of the disorders with the greatest economic impact on healthcare in society and one predictor for poor outcome is cardiac damage. Interleukin 33 receptors (IL-33R) and galectin-3 are two new potential cardiac trauma biomarkers that are the subjects of this investigation. Additionally, this study assesses pre-existing cardiac damage or risk factors as predictors of cardiac damage after polytrauma. This retrospective study includes 107 polytraumatized patients with an ISS ≥16 admitted in a Level 1 Trauma Centre. Plasma samples were taken at admission. IL-33R and galectin-3 concentrations were detected in plasma samples by ELISA. Both did not correlate with the cardiac damage measured by troponin. Next to troponin, IL-33R was increased in patients with pre-existing cardiac comorbidities. In the subgroup of patients with cardiac comorbidities, the BMI and the initial blood sugar level were significantly increased compared to patients without cardiac comorbidities. Galectin-3 and IL-33R were shown to not correlate with cardiac damage. However, our data suggests that IL-33R protein should be revised in future studies as a marker of cardiac comorbidities. Further, our data indicate that patients with cardiac comorbidities represent a separate group of polytrauma patients characterized by higher concentrations of troponin, IL-33R, BMI and initial sugar level.

IL-33/ST2-mediated inflammation in macrophages is directly abrogated by IL-10 during rheumatoid arthritis.

IL-10 is an immunosuppressive cytokine produced and sensed by many immune cells and exerts a protective role in autoimmune diseases. However, the underlying mechanism by which IL-10 contributes to prevent the arthritic inflammation in macrophages is poorly understood. Herein we report on a novel anti-arthritic property of IL-10 through the inhibition of IL-33 signaling by macrophages during collagen-induced arthritis (CIA) development. We show that IL-33 expression rather than its receptor (ST2) is positively correlated with IL-10 level in active RA. IL-10 deficiency in mice leads to significant upregulation of IL-33 expression and aggravates the progression of CIA, while exogenous IL-10 treatment effectively diminishes IL-33 production in IL-10 knockout (IL-10-/-) CIA mice. We demonstrate further that the inhibitory effect of IL-10 in suppressing IL-33 production requires STAT3 activation in macrophages. Furthermore, IL-33 stimulated proinflammatory genes are notably increased in IL-10-/- CIA mice, whereas macrophages treated with recombinant IL-10 exhibit decreased IL-33 amplified inflammation and inhibited IL-33 activated NF-κB signaling pathway. Our findings indicate that IL-10 act as a negative regulator of IL-33/ST2 signaling pathways in vivo, suggesting a potential therapeutic role of IL-10 in autoimmune diseases.