Investigations into the role of ST2 in acute asthma in children

IL-33/ST2 pathway as upper-hand of inflammation in allergic asthma contributes as predictive biomarker in heart failure

Allergic asthma is an inflammatory disorder of the bronchi, and as a major health problem, more than 350 million people suffer from asthma in the world. Many cardiovascular disorders resulted in the impairment of the heart's power to pump blood that leads to the HF. More than 25 million people worldwide live with HF. Accordingly, identifying the biomarkers to predict the onset of future asthma and HF is necessary. IL-33 is an inflammatory cytokine that has the main role in pathophysiology of asthma and HF. Also, in IL-33 receptor, the ST2 is involved in cardiac fibrosis and remodelling in HF and pathogenesis of allergic asthma. Increased sST2 in allergic asthma helps to control inflammation during asthma, but increased sST2 in HF is a predictable biomarker to present risk factor of HF during the time of the patients.

Evaluation of Serum IL-33, IL-5 and Trace Elements Levels among Asthmatic Patients

The precise relationship between interleukins-33 and IL-5, as well as some trace elements and asthma, is unknown. The target of research was to compare and link the above-mentioned serological parameters in asthmatic patients and healthy controls. In 69 asthmatic patients and 35 healthy controls, serum levels of IL-33, IL-5, zinc, copper, iron, total IgE, Forced expiratory volume (FEV) and Forced expiratory volume (FEV) were compared. Spirometry was used to assess the (FEV) and (FVC) in asthmatic patients, as well as their age and body mass index (BMI). When asthmatic patients were matched to controls, mean levels of IL-33, IL-5, and total IgE appeared highly significant difference (p < 0.001). There was a substantial decline in zinc levels in the asthmatic group, but no significant drop in Copper levels. There was also a statistically significant difference in high Iron mean levels among asthmatic patients. In addition, the findings revealed a significant positive correlation between Iron and IgE levels in patients and the levels of (IL-33 and IL-5), plus a significant negative correlation with Zinc levels. Only Copper had no relationship with the interleukins studied. IL-33, also known as IL-5, is a novel inflammatory marker implicated in asthma progression by interacting with IgE, Zinc, Iron, but not Copper levels. As a result, it could be a one-of-a-kind therapeutic target in these patients.

Viral Induced Effects on a Vulnerable Epithelium; Lessons Learned From Paediatric Asthma and Eosinophilic Oesophagitis

The epithelium is integral to the protection of many different biological systems and for the maintenance of biochemical homeostasis. Emerging evidence suggests that particular children have epithelial vulnerabilities leading to dysregulated barrier function and integrity, that resultantly contributes to disease pathogenesis. These epithelial vulnerabilities likely develop in utero or in early life due to various genetic, epigenetic and environmental factors. Although various epithelia are uniquely structured with specific function, prevalent allergic-type epithelial diseases in children potentially have common or parallel disease processes. These include inflammation and immune response dysregulation stemming from atypical epithelial barrier function and integrity. Two diseases where aetiology and pathogenesis are potentially linked to epithelial vulnerabilities include Paediatric Asthma and Eosinophilic Oesophagitis (EoE). For example, rhinovirus C (RV-C) is a known risk factor for paediatric asthma development and is known to disrupt respiratory epithelial barrier function causing acute inflammation. In addition, EoE, a prevalent atopic condition of the oesophageal epithelium, is characterised by similar innate immune and epithelial responses to viral injury. This review examines the current literature and identifies the gaps in the field defining viral-induced effects on a vulnerable respiratory epithelium and resulting chronic inflammation, drawing from knowledge generated in acute wheezing illness, paediatric asthma and EoE. Besides highlighting the importance of epithelial structure and barrier function in allergic disease pathogenesis regardless of specific epithelial sub-types, this review focuses on the importance of examining other parallel allergic-type disease processes that may uncover commonalities driving disease pathogenesis. This in turn may be beneficial in the development of common therapeutics for current clinical management and disease prevention in the future.

Soluble ST2 links inflammation to outcome after subarachnoid hemorrhage

OBJECTIVE

To investigate whether soluble growth stimulation expressed gene 2 (sST2), a prognostic marker in cardiovascular and inflammatory disorders, is associated with neurological injury after aneurysmal subarachnoid hemorrhage (SAH).

METHODS

We studied SAH patients from 2 independent cohorts. Outcome assessments included functional status at 90 days using the modified Rankin Scale (mRS), mortality, and delayed cerebral ischemia (DCI). The relationships between sST2 plasma level and outcome measures were assessed in both cross-sectional and longitudinal analysis. Primary blood mononuclear cells from SAH patients and elective aneurysm controls were analyzed by multiparameter flow cytometry.

RESULTS

In the discovery cohort, sST2 predicted 90-day mRS 3-6 (C index = 0.724, p < 0.001) and mortality in Kaplan-Meier analysis (p < 0.001). The association with functional status was independent of age, sex, World Federation of Neurosurgical Societies score, modified Fisher score, treatment modality, and cardiac comorbidities (adjusted odds ratio = 2.28, 95% confidence interval = 1.04-5.00, p = 0.039). Higher sST2 concentration was observed in those patients with DCI (90.8 vs 53.7ng/ml, p = 0.003). These associations were confirmed in a replication cohort. In patients with high sST2, flow cytometry identified decreased expression of CD14 (4.27 × 10⁵ ± 2,950 arbitrary unit (AU) vs 5.64 × 10⁵ ± 1,290 AU, p < 0.001), and increased expression of CD16 (39,960 ± 272 AU vs 34,869 ± 183 AU, p < 0.001).

INTERPRETATION

Plasma sST2 predicts DCI, functional outcome, and mortality after SAH, independent of clinical and radiographic markers. Elevated sST2 is also associated with changes in CD14⁺ CD16⁺ monocytes. ANN NEUROL 2019;86:384-394.

Elevated expression of serum soluble ST2 in clinical relapse after stopping long-term Nucleos(t)ide analogue therapy for chronic hepatitis B

Background

The virological or clinical relapse is common in chronic hepatitis B (CHB) patients after stopping long-term nucleos(t)ide analogue (NA) therapy. Soluble growth stimulation expressed gene 2 (sST2), one of the Toll-like/interleukin-1 receptor members, is involved in a variety of inflammatory processes and immune responses. However, the expression and function of serum sST2 in CHB patients after stopping NA treatment remains unknown.

Methods

A total of 91 non-cirrhotic Asian patients with CHB who discontinued NA therapy according to international guidelines were prospectively followed up to 240 weeks. All patients were divided into clinical relapse group and non-clinical relapse (including sustained virological response and only virological relapse) group according HBV DNA and ALT levels. The serum levels of sST2 of all participants were determined by ELISA and compared between each two groups.

Results

Clinical relapse occurred in 26 patients and virological relapse occurred in 57 patients. We found that there was a positive correlation between sST2 expression and HBsAg, ALT, HBV DNA, and anti-HBc levels in CHB patients after discontinuation of NA treatment. Levels of serum sST2 in clinical relapse patients showed a rising trend and most patients showed peak sST2 levels at the point of clinical relapse. Moreover, the sST2 levels of clinical relapse group at week 12, week 24 and week 48 were relatively higher than non-clinical relapse group. However, the level of sST2 at the end of treatment was not an effective biological marker for the early prediction of clinical relapse after discontinuation of long-term NA therapy.

Conclusions

In conclusion, we found that an increase in sST2 in clinical relapse patients might be associated with an inflammation-related immune response after discontinuation of NA treatment.

Trial registration

The trial was retrospectively registered at Chinese Clinical Trial Registry: ChiCTR-OOC-17013970. Registration date: December 15, 2017.

Interleukin 1 Receptor-Like 1 (IL1RL1) Promotes Airway Bacterial and Viral Infection and Inflammation

Interleukin 1 receptor-like 1 (IL1RL1), also known as suppression of tumorigenicity 2 (ST2), is the receptor for interleukin 33 (IL-33) and has been increasingly studied in type 2 inflammation. An increase in airway IL-33/ST2 signaling in asthma has been associated with eosinophilic inflammation, but little is known about the role of ST2 in neutrophilic inflammation. Airway Mycoplasma pneumoniae and human rhinovirus (HRV) infections are linked to neutrophilic inflammation during acute exacerbations of asthma. However, whether ST2 contributes to M. pneumoniae- and HRV-mediated airway inflammation is poorly understood. The current study sought to determine the functions of ST2 during airway M. pneumoniae or HRV infection. In cultured normal human primary airway epithelial cells, ST2 overexpression (OE) increased the production of neutrophilic chemoattractant IL-8 in the absence or presence of M. pneumoniae or HRV1B infection. ST2 OE also enhanced HRV1B-induced IP-10, a chemokine involved in asthma exacerbations. In the M. pneumoniae-infected mouse model, ST2 deficiency, in contrast to sufficiency, significantly reduced the levels of neutrophils following acute (≤24 h) infection, while in the HRV1B-infected mouse model, ST2 deficiency significantly reduced the levels of proinflammatory cytokines KC, IP-10, and IL-33 in bronchoalveolar lavage (BAL) fluid. Overall, ST2 overexpression in human epithelial cells and ST2 sufficiency in mice increased the M. pneumoniae and HRV loads in cell supernatants and BAL fluid. After pathogen infection, ST2-deficient mice showed a higher level of the host defense protein lactotransferrin in BAL fluid. Our data suggest that ST2 promotes proinflammatory responses (e.g., neutrophils) to airway bacterial and viral infection and that blocking ST2 signaling may broadly attenuate airway infection and inflammation.

ST2 and the ST2/IL-33 signalling pathway-biochemistry and pathophysiology in animal models and humans

ST2 is an interleukin (IL)-1 receptor family member with transmembrane (ST2L) and soluble (sST2) isoforms. Structurally, the ST2 gene products are very similar in mice and humans. In humans and in mice, alternative promoter activation and splicing produce ST2L and sST2. ST2L represents the longest transcript, whereas sST2 is the truncated, soluble isoform. ST2L is the biological receptor for IL-33, a member of the IL-1 family. IL-33 is the functional ligand of ST2L and signals the presence of tissue damage to local immune cells. IL-33/ST2L signalling leads to the production of inflammatory cytokines/chemokines and to the induction of the immune response. Conversely, sST2 functions as a decoy receptor for IL-33, inhibiting the effects of IL-33/ST2L signalling. Animal studies have allowed the investigation of ST2 and the IL-33/ST2L signalling pathway at multiple levels. However, clinical studies have mainly focused on the determination of sST2 in the circulation. In humans, plasma concentrations of sST2 increase in several diseases, such as heart disease, pulmonary disease, burn injury and graft-versus-host disease. Consequently, increased plasma concentrations of sST2 are not specific for a single disorder in humans and are thus of limited value for diagnostic purposes. However, increased plasma concentrations of sST2 have been linked to a worse prognosis in numerous diseases. Nevertheless, the major source of circulating sST2 in healthy and diseased humans is currently not fully established. In addition, whether the downregulation of sST2 can improve the outcome of patients in the clinical setting has not been elucidated. The aim of the present review was to provide an update on the findings regarding the biochemistry and pathophysiology of ST2 and the sST2 signalling pathway in humans and experimental models.

Elevated ST2 levels are associated with antibody-mediated rejection in heart transplant recipients

Soluble ST2 (sST2) is a novel biomarker of inflammation and fibrosis. Elevated sST2 levels (≥35 ng/mL) are associated with worse outcomes in patients with heart failure (HF). There are sparse data regarding the significance of sST2 levels after heart transplantation (HTx). The study aims were to evaluate trends in soluble ST2 levels after the resolution of HF status with HTx and association between post-HTx sST2 levels and outcomes. Plasma sST2 levels were measured at baseline (median [IQR] of 118 days pre-HTx) and 12 months post-HTx in 62 subjects who were stratified into two groups by post-HTx sST2 levels < or ≥35 ng/mL: "Group 1" or "Group 2," respectively. Plasma sST2 levels were elevated in 58% of patients pre-HTx and in 50% of patients post-HTx. There was no association between elevated sST2 levels before and after HTx, and no significant differences in baseline characteristics between Group 1 and Group 2 patients. Group 2 as compared to Group 1 HTx recipients had significantly higher incidence of antibody-mediated rejection (AMR) for the entire post-transplant follow-up period (32% vs 4%, P = 0.006). There was no association between post-HTx sST2 level status and other post-HTx outcomes including survival. In conclusion, elevated plasma sST2 levels after HTx are associated with increased risk for AMR.

Genetic regulation of IL1RL1 methylation and IL1RL1-a protein levels in asthma

Interleukin-1 receptor-like 1 (IL1RL1) is an important asthma gene. (Epi)genetic regulation of IL1RL1 protein expression has not been established. We assessed the association between IL1RL1 single nucleotide polymorphisms (SNPs), IL1RL1 methylation and serum IL1RL1-a protein levels, and aimed to identify causal pathways in asthma.Associations of IL1RL1 SNPs with asthma were determined in the Dutch Asthma Genome-wide Association Study cohort and three European birth cohorts, BAMSE (Children/Barn, Allergy, Milieu, Stockholm, an Epidemiological survey), INMA (Infancia y Medio Ambiente) and PIAMA (Prevention and Incidence of Asthma and Mite Allergy), participating in the Mechanisms of the Development of Allergy study. We performed blood DNA IL1RL1 methylation quantitative trait locus (QTL) analysis (n=496) and (epi)genome-wide protein QTL analysis on serum IL1RL1-a levels (n=1462). We investigated the association of IL1RL1 CpG methylation with asthma (n=632) and IL1RL1-a levels (n=548), with subsequent causal inference testing. Finally, we determined the association of IL1RL1-a levels with asthma and its clinical characteristics (n=1101).IL1RL1 asthma-risk SNPs strongly associated with IL1RL1 methylation (rs1420101; p=3.7×10^-16) and serum IL1RL1-a levels (p=2.8×10^-56). IL1RL1 methylation was not associated with asthma or IL1RL1-a levels. IL1RL1-a levels negatively correlated with blood eosinophil counts, whereas there was no association between IL1RL1-a levels and asthma.In conclusion, asthma-associated IL1RL1 SNPs strongly regulate IL1RL1 methylation and serum IL1RL1-a levels, yet neither these IL1RL1-methylation CpG sites nor IL1RL1-a levels are associated with asthma.

Blood Eosinophil Count and Metabolic, Cardiac and Pulmonary Outcomes: A Mendelian Randomization Study

Blood eosinophil count is associated with a variety of common complex outcomes in epidemiological observation. The aim of this study was to explore the causal association between determined blood eosinophil count and 20 common complex outcomes (10 metabolic, 6 cardiac, and 4 pulmonary). Through Mendelian randomization, we investigated genetic evidence for the genetically determined eosinophil in association with each outcomes using individual-level LifeLines cohort data (n = 13,301), where a weighted eosinophil genetic risk score comprising five eosinophil associated variants was created. We further examined the associations of the genetically determined eosinophil with those outcomes using summary statistics obtained from genome-wide association study consortia (6 consortia and 14 outcomes). Blood eosinophil count, by a 1-SD genetically increased, was not statistically associated with common complex outcomes in the LifeLines. Using the summary statistics, we showed that a higher genetically determined eosinophil count had a significant association with lower odds of obesity (odds ratio (OR) 0.81, 95% confidence interval (CI) [0.74, 0.89]) but not with the other traits and diseases. To conclude, an elevated eosinophil count is unlikely to be causally associated to higher risk of metabolic, cardiac, and pulmonary outcomes. Further studies with a stronger genetic risk score for eosinophil count may support these results.

Predictive value of serum sST2 in preschool wheezers for development of asthma with high FeNO

Wheezing is common in childhood. However, current prediction models of pediatric asthma have only modest accuracy. Novel biomarkers and definition of subphenotypes may improve asthma prediction. Interleukin-1-receptor-like-1 (IL1RL1 or ST2) is a well-replicated asthma gene and associates with eosinophilia. We investigated whether serum sST2 predicts asthma and asthma with elevated exhaled NO (FeNO), compared to the commonly used Asthma Prediction Index (API). Using logistic regression modeling, we found that serum sST2 levels in 2-3 years-old wheezers do not predict doctors' diagnosed asthma at age 6 years. Instead, sST2 predicts a subphenotype of asthma characterized by increased levels of FeNO, a marker for eosinophilic airway inflammation. Herein, sST2 improved the predictive value of the API (AUC=0.70, 95% CI 0.56-0.84), but had also significant predictive value on its own (AUC=0.65, 95% CI 0.52-0.79). Our study indicates that sST2 in preschool wheezers has predictive value for the development of eosinophilic airway inflammation in asthmatic children at school age.

Association of interleukin 1 receptor-like 1 gene polymorphisms with eosinophilic phenotype in Japanese adults with asthma

BACKGROUND

IL1RL1 (ST2) is involved in Th2 inflammation including eosinophil activation. Single nucleotide polymorphisms (SNPs) of the IL1RL1 gene are associated with asthma development and increased peripheral blood eosinophil counts. However, the association between IL1RL1 SNPs and eosinophilic phenotype among adults with asthma remains unexplored.

METHODS

In a primary cohort of 110 adult Japanese patients with stable asthma, we examined the associations between IL1RL1 SNPs and clinical measurements including forced expiratory volume (FEV₁), airway reversibility of FEV₁, exhaled nitric oxide (FeNO), serum soluble-ST2 (sST2) levels, peripheral blood eosinophil differentials and serum total IgE level. The findings in the primary cohort were confirmed in a validation cohort of 126 adult Japanese patients with stable asthma.

RESULTS

Patients with minor alleles in 3 SNPs (rs17026974, rs1420101, and rs1921622) had high FeNO, blood eosinophil differentials, and reversibility of FEV₁, but low levels of serum sST2 and FEV₁. Minor alleles of rs1041973 were associated with low serum sST2 levels alone. In the validation cohort, minor alleles of rs1420101 were associated with high FeNO and blood eosinophil differentials, whereas minor alleles of rs17026974 and rs1921622 were associated with high blood eosinophil differentials and FeNO, respectively. Multivariate analyses revealed that the minor allele of rs1420101 additively contributed to the FeNO, blood eosinophil differentials, and reversibility of FEV₁.

CONCLUSIONS

The minor alleles of IL1RL1 SNPs were associated with high FeNO and peripheral blood eosinophilia among adult Japanese patients with stable asthma. IL1RL1 SNPs may characterize the eosinophilic phenotype with greater eosinophilic inflammation in the Japanese asthma cohort.

A functional IL1RL1 variant regulates corticosteroid-induced sST2 expression in ulcerative colitis

The ST2/IL33 signalling pathway has been associated with ulcerative colitis (UC). ST2, encoded by the IL1RL1 gene, is expressed as both a membrane-anchored receptor (ST2L) activated by IL33 and as a soluble receptor (sST2) with anti-inflammatory properties. In UC patients, sST2 is further increased by corticosteroid treatment; however, the glucocorticoid-mediated molecular regulation remains unknown. We therefore tested whether genetic variants in the IL1RL1 distal promoter are involved in UC and affect glucocorticoid-mediated ST2 expression. Serum ST2 levels and genetic variants in the IL1RL1 distal promoter were examined by ELISA and PCR sequencing in UC patients receiving corticosteroids. Glucocorticoid-mediated ST2 production was evaluated in intestinal mucosa cultures. Molecular regulation of glucocorticoid-mediated ST2 was assessed by RT-qPCR, ChIP assay and luciferase reporter assay. Dexamethasone effect on ST2 transcript expression was analyzed in leukocytes and related to IL1RL1 variants. Sequencing of a distal IL1RL1 promoter region demonstrated that SNPs rs6543115(C) and rs6543116(A) are associated with increased sST2 in UC patients on corticosteroids. Dexamethasone up-regulated sST2 transcription through interaction with the glucocorticoid-response element (GRE) carrying rs6543115(C) variant. Our data indicate that IL1RL1 SNPs rs6543115(C) confer susceptibility to UC and is contained in the GRE, which may modulate glucocorticoid-induced sST2 expression.

The role of ST2 and ST2 genetic variants in schistosomiasis

BACKGROUND

Chronic schistosomiasis and its severe complication, periportal fibrosis, are characterized by a predominant T_h2 response. To date, specific single nucleotide polymorphisms in ST2 have been some of the most consistently associated genetic variants for asthma.

OBJECTIVE

We investigated the role of ST2 (a receptor for the T_h2 cytokine IL-33) in chronic and late-stage schistosomiasis caused by Schistosoma japonicum and the potential effect of ST2 genetic variants on stage of disease and ST2 expression.

METHODS

We recruited 947 adult participants (339 with end-stage schistosomiasis and liver cirrhosis, 307 with chronic infections without liver fibrosis, and 301 health controls) from a S japonicum-endemic area (Hubei, China). Six ST2 single nucleotide polymorphisms were genotyped. Serum soluble ST2 (sST2) was measured by ELISA, and ST2 expression in normal liver tissues, Hepatitis B virus-induced fibrotic liver tissues, and S japonicum-induced fibrotic liver tissues was measured by immunohistochemistry.

RESULTS

We found sST2 levels were significantly higher in the end-stage group (36.04 [95% CI, 33.85-38.37]) compared with chronic cases and controls (22.7 [95% CI, 22.0-23.4], P < 1E-10). In addition, S japonicum-induced fibrotic liver tissues showed increased ST2 staining compared with normal liver tissues (P = .0001). Markers rs12712135, rs1420101, and rs6543119 were strongly associated with sST2 levels (P = 2E-10, 5E-05, and 6E-05, respectively), and these results were replicated in an independent cohort from Brazil living in a S mansoni endemic region.

CONCLUSIONS

We demonstrate for the first time that end-stage schistosomiasis is associated with elevated sST2 levels and show that ST2 genetic variants are associated with sST2 levels in patients with schistosomiasis.

Increased Levels of Interleukin-33 and Thymic Stromal Lymphopoietin in Exhaled Breath Condensate in Chronic Bronchial Asthma

BACKGROUND

Epithelium-derived cytokines such as thymic stromal lymphopoietin (TSLP), interleukin (IL)-25, and IL-33 are important contributors to inflammation in asthma. Exhaled breath condensate (EBC) is a noninvasive method used to assess the inflammation of airways. Our aim was to assess the levels of TSLP, IL-25, IL-33, and its receptor ST2l/IL-1 R4 in EBC in patients with asthma and to correlate these with serum levels and asthma control.

METHODS

EBC and serum levels of TSLP, IL-25, IL-33, and ST2l/IL-1 R4 were measured in 44 patients with chronic bronchial asthma (14 in the uncontrolled phase) and 19 healthy control participants.

RESULTS

EBC levels of IL-33 and TSLP and serum levels of IL-33 were statistically higher in patients with asthma than in controls. IL-25 and ST2l/IL-1 R4 were present in EBC at barely detectable levels and were not analyzed. The EBC and serum levels of all studied mediators did not differ between controlled and uncontrolled asthma patients, except for the serum level of ST2l/IL-1 R4, which was higher in uncontrolled asthma. There were no correlations between serum and EBC levels of TSLP and IL-33 or between either serum and EBC levels and the forced expiratory volume in 1 s or the total IgE level.

CONCLUSIONS

Higher levels of IL-33 and TSLP in EBC provide evidence supporting a role for these mediators in asthma. Their levels do not discriminate between controlled and uncontrolled asthma. The local reaction within the epithelium is independent of the systemic reaction.

Activated mast cells synthesize and release soluble ST2-a decoy receptor for IL-33

IL-33 released from damaged cells plays a central role in allergic inflammation by acting through its membrane-bound receptor, ST2 receptor (ST2L). IL-33 activity can be neutralized by the soluble spliced variant of ST2 (sST2) that has been associated with allergic inflammation but its source is not well defined. We investigated whether mast cells (MCs) are a significant source of sST2 following activation through FcεRI or ST2. We find that antigen and IL-33 induce substantial production and release of sST2 from human and mouse MCs in culture and do so synergistically when added together or in combination with stem cell factor. Moreover, increases in circulating sST2 during anaphylaxis in mice were dependent on the presence of MCs. Human MCs activated via FcεRI failed to generate IL-33 and IL-33 produced by mouse bone marrow-derived MCs was retained within the cells. Therefore, FcεRI-mediated sST2 production is independent of MC-derived IL-33 acting in an autocrine manner. These results are consistent with the conclusion that both mouse and human MCs when activated are a significant inducible source of sST2 but not IL-33 and thus have the ability to modulate the biologic impact of IL-33 produced locally by other cell types during allergic inflammation.

ST2 in Pulmonary Disease

In recent years, numerous studies have focused on the use of soluble ST2 (sST2) as a clinical biomarker for cardiovascular disease. However, much preclinical data points to involvement of the ST2 pathway in inflammation, and specifically in pulmonary inflammation. This report summarizes the current body of clinical data suggesting the potential role of the ST2 pathway in clinical disease, including evidence that sST2 could be a useful biomarker in both allergic and nonallergic pulmonary disease.

Soluble ST2--analytical considerations

Suppression of tumorigenicity 2 (ST2, also known as interleukin [IL]-1 receptor-like-1) is an IL-1 receptor family member with transmembrane (ST2L) and soluble isoforms (sST2). ST2L is a membrane-bound receptor, and IL-33 is the functional ligand for ST2L. sST2, a soluble truncated form of ST2L, is secreted into the circulation and functions as a "decoy" receptor for IL-33, inhibiting IL-33/ST2L signaling. Blood concentrations of sST2 are increased in inflammatory diseases and heart disease and are considered a valuable prognostic marker in both conditions. In multiple clinical trials, sST2 has emerged as a clinically useful prognostic biomarker in patients with cardiac diseases. Interestingly, sST2 even provides prognostic information in low-risk community-based populations. In this review, we will discuss analytical considerations of measuring circulating sST2 including pre-analytical issues, such as in vitro stability of sST2, biological variation of sST2, and postanalytical issues, such as reference ranges and comparisons to diseased cohorts.

Associations between variants in IL-33/ST2 signaling pathway genes and coronary heart disease risk

The IL-33/ST2 signaling pathway plays an important role in coronary artery disease (CHD); however, few studies have explored how variants in IL-33/ST2 genes influence CHD risk. Here, we examined the association between genetic variants in IL-33, ST2, and IL-1RAcP of the IL-33/ST2 axis and the risk of CHD. We conducted a case-controlled study with 1146 CHD cases and 1146 age- and sex-frequency-matched controls. Twenty-eight single nucleotide polymorphisms (SNPs) in IL-33, ST2, and IL-1RAcP were genotyped by Sequenom MassArray and TaqMan assay. Logistic regression was used to analyze these associations. The SNP rs4624606 in IL-1RAcP was nominally associated with CHD risk. The AA genotype was associated with a 1.85-fold increased risk of CHD (95% confidence interval (CI) = 1.01-3.36; p = 0.045) compared to the TT genotype. Further analysis showed that AA carriers also had a higher risk of CHD than TT + TA carriers (odds ratio (OR) = 1.85; 95% CI = 1.85-3.35; p = 0.043). However, no significant association was observed between variants in IL-33/ST2 genes and CHD risk. Further studies are needed to replicate our results in other ethnic groups with larger sample size.

Soluble ST2 in heart failure

In addition to routine clinical laboratory tests (including natriuretic peptides and cardiac troponins), other biomarkers are gaining attention for their utility in heart failure (HF) management. Among them, soluble ST2 (sST2) a novel biomarker integrating inflammation, fibrosis, and cardiac stress has been included in the 2013 ACCF/AHA guideline for additive risk stratification of patients with acute and chronic HF. sST2 is an interleukin-1 (IL-1) receptor family member, is secreted into the circulation and functions as a "decoy" receptor for IL-33, inhibiting IL-33/ST2 signaling. Blood concentrations of sST2 are increased in various diseases such as inflammatory diseases and heart diseases and are considered a valuable prognostic marker in both conditions. sST2 lacks disease specificity and, therefore, is not a valuable marker for the diagnosis of HF. In acute and chronic HF, however, sST2 is strongly associated with measures of HF severity and poor outcome. Several studies in patients with HF indicate that serial measurement of sST2 has prognostic value and could have a potential role in future biomarker-directed therapy. In this review, the role of sST2 as a HF biomarker will be discussed, specifically addressing analytical considerations of measuring sST2 as well as the clinical applications of measurement of sST2 for the diagnosis, prognosis and monitoring of acute and chronic HF.

Induced sputum levels of IL-33 and soluble ST2 in young asthmatic children

OBJECTIVE

Interleukin-33 is an IL-1 family cytokine which signals via its T1/ST2 receptor, and acts as a key regulator of inflammation, notably the type-2 response implicated in asthma. This study aims to measure the expression of soluble ST2 (sST2) and IL-33 in asthmatic children, depending on disease activity.

METHODS

Thirty-seven children with well-defined asthma (20 moderate and 17 mild asthmatics) were studied. IL-33 and sST2 were measured by ELISA in serum and induced sputum (IS) samples, and compared with 22 age- and sex-matched healthy controls. Real-time quantitative PCR was used to determine IL-33 and TNF-α mRNA expression in IS.

RESULTS

sST2 and IL-33 levels in IS and serum were significantly higher in patients compared with healthy controls (p = 0.0001). The increase in sST2 and IL33 was significantly more important in moderate cases than in mild asthma. A significant correlation was observed between serum and IS IL-33 levels (r = 0.497; p = 0.0018). Higher levels of IL-33 mRNA were detected in IS from asthmatics than those observed in controls. A significant correlation was found between TNF-α and IL-33 mRNA expression in the asthmatic subjects (r = 0.772, p = 0.0001).

CONCLUSIONS

Values of sST2 and IL-33 observed in IS were found to correlate with disease activity. Elevated IL-33 mRNA expression in IS and its correlation with TNF-α reflected the inflammatory process observed in the lung of young asthmatics.

The Presage(®) ST2 Assay: analytical considerations and clinical applications for a high-sensitivity assay for measurement of soluble ST2

The Presage(®) ST2 Assay (Critical Diagnostics, CA, USA) is an in vitro diagnostic device that quantitatively measures soluble suppression of tumorigenicity 2 (sST2) in serum and plasma by ELISA. This assay is US FDA approved and is indicated to be used in conjunction with clinical evaluation as an aid in assessing the prognosis of patients diagnosed with chronic heart failure. sST2 binds to IL-33 and functions as a 'decoy' receptor for IL-33, thereby attenuating the systemic effects of IL-33. Due to the role of IL-33/transmembrane isoform of suppression of tumorigenicity 2 signaling in cardiac remodeling, sST2 has emerged as a novel cardiovascular biomarker. In recent studies, it was shown that sST2 is a valuable predictor of several end points in heart failure, in acute coronary syndromes and in critically ill patients. In this review, analytical considerations and clinical applications of the Presage ST2 Assay will be discussed, as well as probable future concepts for adoption of sST2 measurements into clinical practice.

The role of interleukin-33 in rhinitis

IL-33, a member of the IL-1 cytokine family and a ligand to receptor ST2, has great potential to induce a T helper 2-type inflammatory response. IL-33 is proven to be released by epithelial cells during their injury by different environmental stimuli such as airborne allergens, viruses, and air pollutants. IL-33 acting as an endogenous danger signal is termed an alarmin. As such, this cytokine is considered to play a crucial role in an allergic inflammatory disease such as rhinitis. Recent investigations regarding the IL-33/ST2 axis involvement in Th2 inflammatory response and pathogenesis of rhinitis have been reviewed. The role of IL-33 as a novel promising therapeutic target has also been discussed.

Role of interleukin-33 in innate-type immune cells in allergy

Interleukin-33 (IL-33), a member of the IL-1 cytokine family, is preferentially and constitutively expressed in epithelial cells, and it is especially localized in the cells' nucleus. The nuclear IL-33 is released by necrotic cells after tissue injury and/or trauma, and subsequently provokes local inflammation as an alarmin, like high-mobility group box protein-1 (HMGB-1) and IL-1α. IL-33 mainly activates Th2 cells and such innate-type immune cells as mast cells, basophils, eosinophils and natural helper cells that express IL-33R (a heterodimer of IL-1 receptor-like 1 [IL-1RL1; also called ST2, T1, Der4, fit-1] and IL-1 receptor accessory protein [IL-1RAcP]). That activation causes the cells to produce Th2 cytokines, which contribute to host defense against nematodes. On the other hand, excessive and/or inappropriate production of IL-33 is also considered to be involved in the development of such disorders as allergy. In this review, we summarize current knowledge regarding the pathogenic roles of IL-33 in the development of allergic inflammation by focusing on its effects on innate-type immune cells.

Interleukin-33 in allergy

Interleukin-33 (IL-33) is a member of the IL-1 cytokine family, which includes IL-1 and IL-18, and is considered to be important for host defense against nematodes by inducing Th2 cytokine production via the IL-33 receptor. IL-33 receptor is a heterodimer of IL-1 receptor-like 1 (IL-1RL1; also called ST2, T1, Der4, and fit-1) and IL-1 receptor accessory protein (IL-1RAcP). On the other hand, excessive and/or inappropriate production of IL-33 is considered to be involved in the development of various disorders, such as allergic and autoimmune diseases. Unlike IL-1β and IL-18, IL-33 does not seem to be secreted through the activation of inflammasomes in events such as apoptosis. However, IL-33 is localized in the nucleus of cells and is released during tissue injury associated with necrosis. This suggests that it acts as an alarmin, like IL-1α and high-mobility group box chromosomal protein-1 (HMGB-1). This review summarizes current knowledge regarding the roles of IL-33 in the functions of various cell types and the pathogenesis of allergy.

Serum IL-33 but not ST2 level is elevated in intermittent allergic rhinitis and is a marker of the disease severity

BACKGROUND

Th2 cells play an important role in intermittent allergic rhinitis (IAR). Interleukin (IL)-33 stimulates the production of Th2-associated cytokines. IL-33 binds to ST2 receptor which is highly expressed on mast cells and selectively on Th2 cells. IL-33 and ST2 might be involved in the Th2-mediated immune response.

OBJECTIVE

We analyzed the serum level of IL-33 and its receptor ST2 in patients with IAR sensitive to grass and/or tree pollen to assess if the serum level of IL-33 and/or ST2 may be a marker of the disease severity.

METHODS

IL-33, ST2 and total immunoglobulin (Ig) E were measured in sera of patients with IAR sensitive to birch and/or grass pollen and in patients with controlled bronchial asthma and in non-allergic controls. IAR severity was assessed by total nasal symptom score.

RESULTS

Serum levels of IL-33 in patients with IAR were comparable with patients with bronchial asthma and were significantly higher in patients with IAR (P=0.0035) and in patients with bronchial asthma (P=0.008) than in controls. Serum levels of IL-33 correlated with disease severity.

CONCLUSION

Elevated level of IL-33 in sera of patients with IAR sensitive to tree and/or grass pollen and the correlation of IL-33 with the disease severity suggest that IL-33 is involved in the pathogenesis of intermittent allergic rhinitis.

ST2 requires Th2-, but not Th17-, type airway inflammation in epicutaneously antigen- sensitized mice

BACKGROUND

IL-33 is known to induce Th2-type cytokine production by various types of cells through its receptors, ST2 and IL-1RAcP. Polymorphism in the ST2 and/or IL-33 genes was found in patients with atopic dermatitis and asthma, implying that the IL-33/ST2 pathway is closely associated with susceptibility to these diseases. Exposure to allergens through damaged skin is suspected to be a trigger for allergen sensitization, resulting in development of such allergic disorders as asthma and atopic dermatitis.

METHODS

To elucidate the role(s) of the IL-33/ST2 pathway in asthma in individuals who had been epicutaneously sensitized to an antigen, wild-type and ST2-/- mice were epicutaneously sensitized with ovalbumin (OVA) and then were intranasally challenged with OVA. The degree of airway inflammation, the number of leukocytes and the activities of myeloperoxidase (MPO) and eosinophil peroxidase (EPO) in bronchoalveolar lavage fluids (BALFs), The levels of cytokines and chemokines in lungs and OVA-specific IgE levels in sera were determined by histological analysis, a hemocytometer, colorimetric assay, quantitative PCR or ELISA, respectively.

RESULTS

The number of eosinophils in BALFs, the levels of Th2 cytokines and chemoattractants in the lungs and OVA-specific IgE in sera from ST2-/- mice were significantly reduced compared with wild-type mice. Although the number of neutrophils in BALFs and the pulmonary levels of IL-17 were comparable in both mice, the levels of MPO activity in BALFs and neutrophil chemoattractants in the lung were reduced in ST2-/- mice.

CONCLUSIONS

The IL-33/ST2 pathway is crucial for Th2-cytokine-mediated eosinophilic, rather than Th17-cytokine-mediated neutrophilic, airway inflammation in mice that had been epicutaneously sensitized with antigens and then challenged with antigen.

IL1RL1 gene variants and nasopharyngeal IL1RL-a levels are associated with severe RSV bronchiolitis: a multicenter cohort study

Background

Targets for intervention are required for respiratory syncytial virus (RSV) bronchiolitis, a common disease during infancy for which no effective treatment exists. Clinical and genetic studies indicate that IL1RL1 plays an important role in the development and exacerbations of asthma. Human IL1RL1 encodes three isoforms, including soluble IL1RL1-a, that can influence IL33 signalling by modifying inflammatory responses to epithelial damage. We hypothesized that IL1RL1 gene variants and soluble IL1RL1-a are associated with severe RSV bronchiolitis.

Methodology/Principal Findings

We studied the association between RSV and 3 selected IL1RL1 single-nucleotide polymorphisms rs1921622, rs11685480 or rs1420101 in 81 ventilated and 384 non-ventilated children under 1 year of age hospitalized with primary RSV bronchiolitis in comparison to 930 healthy controls. Severe RSV infection was defined by need for mechanical ventilation. Furthermore, we examined soluble IL1RL1-a concentration in nasopharyngeal aspirates from children hospitalized with primary RSV bronchiolitis. An association between SNP rs1921622 and disease severity was found at the allele and genotype level (p = 0.011 and p = 0.040, respectively). In hospitalized non-ventilated patients, RSV bronchiolitis was not associated with IL1RL1 genotypes. Median concentrations of soluble IL1RL1-a in nasopharyngeal aspirates were >20-fold higher in ventilated infants when compared to non-ventilated infants with RSV (median [and quartiles] 9,357 [936–15,528] pg/ml vs. 405 [112–1,193] pg/ml respectively; p<0.001).

Conclusions

We found a genetic link between rs1921622 IL1RL1 polymorphism and disease severity in RSV bronchiolitis. The potential biological role of IL1RL1 in the pathogenesis of severe RSV bronchiolitis was further supported by high local concentrations of IL1RL1 in children with most severe disease. We speculate that IL1RL1a modifies epithelial damage mediated inflammatory responses during RSV bronchiolitis and thus may serve as a novel target for intervention to control disease severity.

Dynamic role of epithelium-derived cytokines in asthma

Asthma is an inflammatory disorder of the airways, characterized by infiltration of mast cells, eosinophils, and Th2-type CD4+ T cells in the airway wall. Airway epithelium constitutes the first line of interaction with our atmospheric environment. The protective barrier function of the airway epithelium is likely impaired in asthma. Furthermore, recent studies suggest critical immunogenic and immunomodulatory functions of airway epithelium. In particular, a triad of cytokines, including IL-25, IL-33 and TSLP, is produced and released by airway epithelial cells in response to various environmental and microbial stimuli or by cellular damage. These cytokines induce and promote Th2-type airway inflammation and cause remodeling and pathological changes in the airway walls, suggesting their pivotal roles in the pathophysiology of asthma. Thus, the airway epithelium can no longer be regarded as a mere structural barrier, but must be considered an active player in the pathogenesis of asthma and other allergic disorders.

IL-33-responsive lineage- CD25+ CD44(hi) lymphoid cells mediate innate type 2 immunity and allergic inflammation in the lungs

Innate immunity provides the first line of response to invading pathogens and a variety of environmental insults. Recent studies identified novel subsets of innate lymphoid cells that are capable of mediating immune responses in mucosal organs. In this paper, we describe a subset of lymphoid cells that is involved in innate type 2 immunity in the lungs. Airway exposure of naive BALB/c or C57BL/6J mice to IL-33 results in a rapid (<12 h) production of IL-5 and IL-13 and marked airway eosinophilia independently of adaptive immunity. In the lungs of nonsensitized naive mice, IL-33-responsive cells were identified that have a lymphoid morphology, lack lineage markers, highly express CD25, CD44, Thy1.2, ICOS, Sca-1, and IL-7Rα (i.e., Lin(-)CD25(+)CD44(hi) lymphoid cells), and require IL-7Rα for their development. Airway exposure of naive mice to a clinically relevant ubiquitous fungal allergen, Alternaria alternata, increases bronchoalveolar lavage levels of IL-33, followed by IL-5 and IL-13 production and airway eosinophilia without T or B cells. This innate type 2 response to the allergen is nearly abolished in mice deficient in IL-33R (i.e., ST2), and the Lin(-)CD25(+)CD44(hi) lymphoid cells in the lungs are required and sufficient to mediate the response. Thus, a subset of innate immune cells that responds to IL-33 and vigorously produces Th2-type cytokines is present in mouse lungs. These cells may provide a novel mechanism for type 2 immunity in the airways and induction of allergic airway diseases such as asthma.

Genetics of interleukin 1 receptor-like 1 in immune and inflammatory diseases

Interleukin 1 receptor-like 1 (IL1RL1) is gaining in recognition due to its involvement in immune/inflammatory disorders. Well-designed animal studies have shown its critical role in experimental allergic inflammation and human in vitro studies have consistently demonstrated its up-regulation in several conditions such as asthma and rheumatoid arthritis. The ligand for IL1RL1 is IL33 which emerged as playing an important role in initiating eosinophilic inflammation and activating other immune cells resulting in an allergic phenotype.An IL1RL1 single nucleotide polymorphism (SNP) was among the most significant results of a genome-wide scan investigating eosinophil counts; in the same study, this SNP associated with asthma in 10 populations.The IL1RL1 gene resides in a region of high linkage disequilibrium containing interleukin 1 receptor genes as well as interleukin 18 receptor and accessory genes. This poses a challenge to researchers interested in deciphering genetic association signals in the region as all of the genes represent interesting candidates for asthma and allergic disease.The IL1RL1 gene and its resulting soluble and receptor proteins have emerged as key regulators of the inflammatory process implicated in a large variety of human pathologies We review the function and expression of the IL1RL1 gene. We also describe the role of IL1RL1 in asthma, allergy, cardiovascular disease, infections, liver disease and kidney disease.

Paracrine IL-33 stimulation enhances lipopolysaccharide-mediated macrophage activation

Background

IL-33, a member of the IL-1 family of cytokines, provokes Th2-type inflammation accompanied by accumulation of eosinophils through IL-33R, which consists of ST2 and IL-1RAcP. We previously demonstrated that macrophages produce IL-33 in response to LPS. Some immune responses were shown to differ between ST2-deficient mice and soluble ST2-Fc fusion protein-treated mice. Even in anti-ST2 antibody (Ab)-treated mice, the phenotypes differed between distinct Ab clones, because the characterization of such Abs (i.e., depletion, agonistic or blocking Abs) was unclear in some cases.

Methodology/Principal Findings

To elucidate the precise role of IL-33, we newly generated neutralizing monoclonal Abs for IL-33. Exogenous IL-33 potentiated LPS-mediated cytokine production by macrophages. That LPS-mediated cytokine production by macrophages was suppressed by inhibition of endogenous IL-33 by the anti-IL-33 neutralizing mAbs.

Conclusions/Significance

Our findings suggest that LPS-mediated macrophage activation is accelerated by macrophage-derived paracrine IL-33 stimulation.

Endogenous IL-33 enhances Th2 cytokine production and T-cell responses during allergic airway inflammation

IL-33 is an IL-1-related cytokine which has been implicated in T(h)2-associated biology and allergic diseases in humans and mice. IL-33 stimulates T(h)2 cells, mast cells, eosinophils, basophils, iNKT cells and circulating CD34(+) stem cells to proliferate and produce pro-allergic cytokines such as IL-5 and IL-13. IL-33 mediates its cytokine effects through a receptor consisting of ST2 and IL-1RAcP. Whereas IL-1RAcP is ubiquitously expressed, ST2 expression is cell-type restricted and determines responsiveness to IL-33. Studies employing ST2-deficient mice have reported variable results on the role of this receptor, and consequently IL-33, with regards to allergic lung inflammation. In this study, we demonstrate that IL-33 is important for allergic lung inflammation. Intra-nasal administration of IL-33 triggered an immediate allergic response in the airways, and more importantly, we show that endogenous IL-33 contributes to airway inflammation and peripheral antigen-specific responses in ovalbumin-induced acute allergic lung inflammation using IL-33-deficient mice. Our results suggest that IL-33 is sufficient and required for severe allergic inflammation in the lung and support the concept of IL-33 as a therapeutic target in allergic lung inflammation.

IL-33 and Airway Inflammation

Interleukin-33 (IL-33) is the 11th member of IL-1 cytokine family which includes IL-1 and IL-18. Unlike IL-1β and IL-18, IL-33 is suggested to function as an alarmin that is released upon endothelial or epithelial cell damage and may not enhance acquired immune responses through activation of inflammasome. ST2, a IL-33 receptor component, is preferentially expressed by T-helper type (Th) 2 cells, mast cells, eosinophils and basophils, compared to Th1 cells, Th17 cells and neutrophils. Thus, IL-33 profoundly enhances allergic inflammation through increased expression of proallergic cytokines and chemokines. Indeed, IL-33 and its receptor genes are recognized as the most susceptible genes for asthma by several recent genomewide association studies. It has also recently been shown that IL-33 plays a crucial role in innate eosinophilic airway inflammation rather than acquired immune responses such as IgE production. As such, IL-33 provides a unique therapeutic way for asthma, i.e., ameliorating innate airway inflammation.

Genetic variability of the distal promoter of the ST2 gene is associated with angiographic severity of coronary artery disease

Genetic polymorphy of the distal promoter region of the ST2 gene influences transcriptional activity and susceptibility to atopic dermatitis and asthma. Based on the inflammatory background of atherosclerosis we hypothesized that ST2 distal promoter genetic polymorphy could also affect susceptibility to coronary artery disease (CAD). To test our hypothesis we performed direct sequencing of a 825 bp locus of the distal promoter -with previously reported significant polymorphy in 63 angiographically diagnosed CAD patients and 63 age and sex matched controls with negative coronary angiography. We identified 13 polymorphisms spanning this region two of which (-27307 T/A and -27614 C/A) had allele frequencies greater than 0.05. We further genotyped 111 subjects by applying allele-specific real-time PCR for the -27307 T/A and 27614 C/A polymorphisms, thereby increasing our sample to 129 CAD patients and 108 age- and sex-matched controls. We identified no phenotype-genotype interactions between cases and controls. However, among case subjects the severity of CAD expressed as a mean number of diseased vessels was greater in -27307 A allele carriers and either allele carriers (-27614 A or -27307 A) than in non-carriers (2.56 ± 0.73 vs. 1.83 ± 0.84, adjusted P = 0.027; 2.47 ± 0.74 vs. 1.8 ± 0.83, adjusted P = 0.023). Additionally, either allele carriers (-27614 A or -27307 A) were significantly more common in the multi-vessel disease group (n = 54) than in the single-vessel disease group (n = 75). In conclusion, we reported two new polymorphisms in the distal promoter region of the ST2 gene that possibly influence susceptibility to severe CAD. The functional impact of these polymorphisms remains to be determined.

Interleukin-1 receptor-like 1 polymorphisms are associated with serum IL1RL1-a, eosinophils, and asthma in childhood

BACKGROUND

IL-1 receptor-like 1 (IL1RL1) is a membrane receptor involved in T(H)2 inflammatory responses and eosinophilia. Single nucleotide polymorphisms (SNPs) in IL1RL1 have been associated with blood eosinophil counts in a genome-wide association study and with asthma in family-based and case-control studies.

OBJECTIVE

We assessed in the prospective birth cohort Prevention and Incidence of Asthma and Mite Allergy (PIAMA) whether IL1RL1 SNPs associate with levels of its soluble transcript IL1RL1 (IL1RL1-a) in serum, blood eosinophil counts, and asthma prevalence from birth to age 8 years, and whether IL1RL1-a serum levels associate with blood eosinophil counts.

METHODS

Fifteen IL1RL1 SNPs were genotyped. Serum IL1RL1-a levels were measured in 2 independent subsets within PIAMA, at 4 and 8 years. Blood eosinophil counts were measured in 4-year-old children.

RESULTS

In 2 independent subsets of children, 13 of 15 SNPs were associated with serum IL1RL1-a levels at ages 4 and 8 years with a consistent direction of effect for each allele. Rs11685480 allele A and rs1420102 allele A were significantly associated with lower numbers of blood eosinophils. In the total cohort, rs1041973 allele A was associated with a decreased risk of developing asthma (odds ratio, 0.70; 95% CI, 0.54-0.90). Rs1420101, recently identified in a genome-wide association study in the Icelandic population, was not associated with asthma in this study. IL1RL1-a levels were not associated with eosinophil counts.

CONCLUSION

We demonstrate that IL1RL1 polymorphisms are associated with serum IL1RL1-a, blood eosinophils, and asthma in childhood.

The role of GSTP1 polymorphisms and tobacco smoke exposure in children with acute asthma

BACKGROUND

The glutathione S-transferase enzymes (GSTs) play an important role in the detoxification of environmental tobacco smoke (ETS), which contributes to airway inflammation, a key component of asthma. Genetic variation in GST genes may influence individuals' ability to detoxify environmental pollutants.

OBJECTIVE

To examine the role of polymorphisms in GSTP1 (Ile105Val and Ala114Val), alone and in combination with ETS exposure, on atopy and asthma severity.

METHODS

GSTP1 Ile105Val and Ala114Val were genotyped and ETS exposure was assessed by parental questionnaire, which was validated by urinary cotinine measurements. Associations between ETS exposure, GSTP1 polymorphisms, and their interaction on atopy and asthma severity were investigated.

RESULTS

For the functional GSTP1 105 SNP, those with the Ile/Ile genotype had odds for atopy of 2.77 (p = .054) when assessed by genotype alone, which increased to 9.02 (p = .050) when ETS was included, relative to individuals with other genotypes. Likewise, compared to children with other GSTP1 114 genotypes, those with Ala/Ala genotype had a 5.47-fold (p = .002) increased risk of atopy (p = .020) when assessed by genotype alone, increasing to 9.17-fold when ETS was included. The 105 Ile/Ile individuals all had the AA (105 Ile/Ile and 114 Ala/Ala) haplotype group; therefore, the odds for atopy were the same. Individuals without any *C haplotype (105 Val and 114 Val allele) who were exposed to ETS had a 9.17-fold increased risk of atopy when compared with individuals with at least one *C haplotype and not exposed to ETS (p = .020).

CONCLUSION

There were significant interactions between GSTP1 SNPs, atopy, and ETS exposure in this cohort.

IL-33 family members and asthma - bridging innate and adaptive immune responses

The discovery of IL-33 as the ligand for the orphan Th2 associated receptor ST2 has uncovered a whole range of different avenues for this pathway. Although the extracellular functions of ST2 as a marker for Th2 cell and mast cell activity were well defined, the complexities of IL-33 regulation, nuclear function and secretion are only just being realised. The well documented expression pattern of ST2 has identified a role for the IL-33/ST2 axis in the classical Th2 cell and mast cell driven pathogenesis of asthma and anaphylaxis. However, the induction of IL-33 expression by environmental or endogenous triggers now suggests a wider role for the pathway during infection, inflammation and tissue damage.

IL-33 and IL-33 receptors in host defense and diseases

Interleukin-33 (IL-33) is a member of the IL-1 cytokine family, which includes IL-1 and IL-18. IL-33 is considered to be crucial for induction of Th2-type cytokine-associated immune responses such as host defense against nematodes and allergic diseases by inducing production of such Th2-type cytokines as IL-5 and IL-13 by Th2 cells, mast cells, basophils and eosinophils. In addition, IL-33 is involved in the induction of non-Th2-type acute and chronic inflammation as a proinflammatory cytokine, similar to IL-1 and IL-18. In this review, we summarize and discuss the current knowledge regarding the roles of IL-33 and IL-33 receptors in host defense and disease development.

IL-33: a tissue derived cytokine pathway involved in allergic inflammation and asthma

Besides classic T cell-derived T-helper type 2 (Th2) cytokines such as IL-4, IL-5 and IL-13, tissue-produced cytokines such as thymic stromal lymphopoietin, IL-25 and IL-33 are now recognized as important contributors to allergic inflammation. IL-33 is produced by various tissue dwelling cells and broadly enhances allergic inflammation through its effects on hematopoietic cell types. The environmental or endogenous triggers that provoke IL-33 cellular release may be associated with infection, inflammation or tissue damage. This review summarizes the wide range of documented IL-33 activities on human cellular mediators of inflammation as well as genetic evidence that IL-33 contributes to disease. Finally, there will be a discussion of still unanswered questions regarding the mechanisms by which cytokine activity is generated and IL-33's relationship with other Th2-associated cytokines.

ST2 protein in heart disease: from discovery to mechanisms and prognostic value

Biomarkers aid in diagnosis by providing important information for the clinical assessment of patients that is not achieved by other means. This article focuses on the use of soluble ST2 as a biomarker in cardiovascular disease. Soluble ST2 is a secreted receptor belonging to the IL-1 receptor family that regulates inflammation and immunity. Recent studies have shown that soluble ST2 is a decoy receptor that disrupts the interaction of IL-33 with the full-length ST2L receptor. The rapidly evolving and expanding literature on ST2 and its ligand reveal emerging roles for this system in the regulation of inflammation in a variety of diseases. Elevated ST2 levels have been detected in cardiovascular diseases and levels provide useful prognostic information in many, but not all, of these diseases, which will be discussed here. Additional studies demonstrating elevated soluble ST2 levels in other human diseases will also be discussed.

IL-33 synergizes with IgE-dependent and IgE-independent agents to promote mast cell and basophil activation

OBJECTIVE

Mast cell and basophil activation contributes to inflammation, bronchoconstriction, and airway hyperresponsiveness in asthma. Because IL-33 expression is inflammation inducible, we investigated IL-33-mediated effects in concert with both IgE-mediated and IgE-independent stimulation.

METHODS

Because the HMC-1 mast cell line can be activated by GPCR and RTK signaling, we studied the effects of IL-33 on these pathways. The IL-33- and SCF-stimulated HMC-1 cells were co-cultured with human lung fibroblasts and airway smooth muscle cells in a collagen gel contraction assay. IL-33 effects on IgE-mediated activation were studied in primary mast cells and basophils.

RESULT

IL-33 synergized with adenosine, C5a, SCF, and NGF receptor activation. IL-33-stimulated and SCF-stimulated HMC-1 cells demonstrated enhanced collagen gel contraction when cultured with fibroblasts or smooth muscle cells. IL-33 also synergized with IgE receptor activation of primary human mast cells and basophils.

CONCLUSION

IL-33 amplifies inflammation in both IgE-independent and IgE-dependent responses.