Genetic variants of TSLP and asthma in an admixed urban population

Association between 17q21 variants and asthma predisposition in Pashtun population from Pakistan

OBJECTIVE

Asthma is a heterogeneous and genetically complex respiratory disease, and more than 300 million people are affected worldwide. In this study, frequencies of four SNPs (rs3816470, rs7216389, rs8067378, rs12603332) in chromosome 17q21 region were analyzed and their relationship with the asthma susceptibility, in the Pashtun population of Khyber Pakhtunkhwa province (KPK) of Pakistan were investigated.

METHODS

DNA samples from 500 subjects (asthma cases/controls) were genotyped by Sanger sequencing. Chi-square tests, logistic regression analysis, linkage disequilibrium, and haplotype analysis techniques were applied to study the association of the SNPs with asthma.

RESULTS

Genetic models, including recessive, dominant, co-dominant, over-dominant, and additive, were tested. The frequencies of alleles T/T at rs3816470 (OR = 1.91; 95%CI = 1.15-3.18; p = .011*) and rs7216389 (OR = 2.14; 95%CI = 1.21-3.79; p = .0076*), A/A at rs 8067378 (OR = 1.89; 95%CI = 1.17-3.06; p = .0081*), C/C at rs12603332 (OR = 1.97; 95%CI = 1.18-3.27; p = .008*), under recessive models, respectively, were significantly (p-values < .0125) associated with asthma susceptibility. The frequencies of T/T genotype in rs3816470 (OR = 6.01; 95%CI = 2.48-14.60; p = .000147*), and rs7216389 (OR = 5.05; 95%CI = 1.79-14.21; p = .003296*), and C/C at rs12603332 (OR = 2.64; 95%CI = 1.11-6.32; p = .019063*), were significantly (p-values < .0125) associated with asthma susceptibility in Pashtun women by stratified analysis based on age and gender. Similarly, three unique haplotypes were found associated with disease development and protective effect in female and male subjects. Linkage disequilibrium analysis presented a strong linkage (≥80%) between SNP variants and predicted their co-inheritance in the studied population.

CONCLUSION

The 17q21 variants (rs3816470, rs7216389, rs12603332) were found significantly (p-values < .0125) associated with asthma predisposition in the Pashtun population of KPK exclusively in the female asthmatic cases.

Supplemental data for this article can be accessed.

Gene-Environment Interaction between the IL1RN Variants and Childhood Environmental Tobacco Smoke Exposure in Asthma Risk

(1) Background: Variants of the interleukin-1 receptor antagonist (IL1RN) gene, encoding an anti-inflammatory cytokine, are associated with asthma. Asthma is a chronic inflammatory disease of the airway influenced by interactions between genetic variants and environmental factors. We discovered a gene-environment interaction (GEI) of IL1RN polymorphisms with childhood environmental tobacco smoke (ETS) exposure on asthma susceptibility in an urban adult population. (2) Methods: DNA samples from the NYU/Bellevue Asthma Registry were genotyped for tag SNPs in IL1RN in asthma cases and unrelated healthy controls. Logistic regressions were used to study the GEI between IL1RN variants and childhood ETS exposures on asthma and early onset asthma, respectively, adjusting for population admixture and other covariates. (3) Results: Whereas the rare genotypes of IL1RN SNPs (e.g., GG in SNP rs2234678) were associated with decreased risk for asthma among those without ETS exposure (odds ratio OR = 0.215, p = 0.021), they are associated with increased risk for early onset asthma among those with childhood ETS (OR = 4.467, p = 0.021). (4) Conclusions: We identified a GEI between polymorphisms of IL1RN and childhood ETS exposure in asthma. Analysis of GEI indicated that childhood ETS exposure disrupted the protective effect of some haplotypes/genotypes of IL1RN for asthma and turned them into high-risk polymorphisms for early onset asthma.

TSLP and TSLP receptors variants are associated with smoking

Background

To search for new prevention markers for early detection of the diseases caused by tobacco, we aimed to investigate the polymorphisms in TSLP and TSLPRs associated with cigarette smoking in the Saudi population.

Materials and methods

Samples were collected from 177 smokers and 126 healthy controls. Three TSLP SNPs [rs3806933, rs2289276, and rs10043985], three TSLPR SNPs [rs36133495, rs36177645, and rs36139698], and two IL7R SNPs rs1053496 and rs12516866 were analyzed by genotyping.

Results

Two TSLP SNPs (rs10043985 and rs3806933) and one TSLPR SNP (rs36139698) showed significant correlations with smoking behavior, but not IL7R rs12516866 and rs1053496. rs10043985 showed a clear association with long‐term smoking regardless of daily cigarette consumption. rs2289276 was associated with short‐term smoking but not with daily cigarette consumption. rs3806933 was highly associated with different smoker subgroups. Rs36139698 was highly associated with long‐term smokers who consumed ≥20 cigarettes/day, and the “T” allele was associated only with individuals who smoked ≤20 cigarettes/day. Rs36139698 corresponds to a P195L substitution and produces a TSLPR mutant with a predicted ΔΔG increase of 2.15 kcal/mol and has a more stable structure than the wild‐type variant.

Conclusions

Investigating TSLP and TSLPR polymorphisms is crucial for elucidating the mechanisms underlying tobacco‐induced diseases.

Variability of blood eosinophils in patients in a clinic for severe asthma

BACKGROUND

Blood eosinophils are used to determine eligibility for agents targeting IL-5 in patients with uncontrolled asthma. However, little is known about the variability of blood eosinophil measures in these patients before treatment initiation.

OBJECTIVE

To characterize variability and patterns of variability of blood eosinophil levels in a real-world clinic for severe asthmatics.

METHODS

Retrospective review of blood eosinophils measured over a 5-year period in patients enrolled in an urban clinic. Repeated measures of blood eosinophil levels in individuals were evaluated, and cluster analysis was performed to characterize patients by eosinophil patterns. Clinical characteristics associated with eosinophil levels and patterns of variability were analysed.

RESULTS

Patients treated in the Bellevue Hospital Asthma Clinic within a 3-month period were identified (n = 219). Blood eosinophil measures were obtained over the previous 5 years. Only 6% (n = 13) of patients had levels that were consistently above 300 cells/μL. Nearly 50% (n = 104) had eosinophil levels that traversed the threshold of 300 cells/μL. In contrast, 102 (46%) had levels that never reached the threshold of 300 cells/μL. Cluster analyses revealed three clusters with differing patterns of levels and variability. There was a suggestion of decreased clinical control and increased atopy in the cluster with the greatest variability in blood eosinophil measures.

CONCLUSION

In an urban clinic for patients referred for uncontrolled asthma, blood measures of eosinophils were variable and showed differing patterns of variability. These data reinforce the need to perform repeated eosinophil blood measures for appropriate designation for therapeutic intervention.

Eosinophilic esophagitis (EoE) genetic susceptibility is mediated by synergistic interactions between EoE-specific and general atopic disease loci

BACKGROUND

Eosinophilic esophagitis (EoE) is an esophageal inflammatory disease associated with atopic diseases. Thymic stromal lymphopoietin (TSLP) and calpain 14 (CAPN14) genetic variations contribute to EoE, but how this relates to atopy is unclear.

OBJECTIVE

The purpose of this study was to explore the relationship between EoE, atopy, and genetic risk.

METHODS

EoE-atopy enrichment was tested by using 700 patients with EoE and 801 community control subjects. Probing 372 single nucleotide polymorphisms (SNPs) in 63 atopy genes, we evaluated EoE associations using 412 nonatopic and 868 atopic disease control subjects. Interaction and stratified analyses of EoE-specific and atopy-related SNPs were performed.

RESULTS

Atopic disease was enriched in patients with EoE (P < .0001). Comparing patients with EoE and nonatopic control subjects, EoE associated strongly with IL-4/kinesin family member 3A (IL4/KIF3A) (P = 2.8 × 10^-6; odds ratio [OR], 1.87), moderately with TSLP (P = 1.5 × 10^-4; OR, 1.43), and nominally with CAPN14 (P = .029; OR, 1.35). Comparing patients with EoE with atopic disease control subjects, EoE associated strongly with ST2 (P = 3.5 × 10^-6; OR, 1.77) and nominally with IL4/KIF3A (P = .019; OR, 1.25); TSLP's association persisted (P = 4.7 × 10^-5; OR, 1.37), and CAPN14's association strengthened (P = .0001; OR, 1.71). Notably, there was gene-gene interaction between TSLP and IL4 SNPs (P = .0074). Children with risk alleles for both genes were at higher risk for EoE (P = 2.0 × 10^-10; OR, 3.67).

CONCLUSIONS

EoE genetic susceptibility is mediated by EoE-specific and general atopic disease loci, which can have synergistic effects. These results might aid in identifying potential therapeutics and predicting EoE susceptibility.

Characterisation of asthma subgroups associated with circulating YKL-40 levels

The chitinase-like protein YKL-40 mediates airway inflammation and serum levels are associated with asthma severity. However, asthma phenotypes associated with YKL-40 levels have not been precisely defined.We conducted an unsupervised cluster analysis of asthma patients treated at the Yale Center for Asthma and Airways Disease (n=156) to identify subgroups according to YKL-40 level. The resulting YKL-40 clusters were cross-validated in cohorts from the Severe Asthma Research Programme (n=167) and the New York University/Bellevue Asthma Repository (n=341). A sputum transcriptome analysis revealed molecular pathways associated with YKL-40 subgroups.Four YKL-40 clusters (C1-C4) were identified. C3 and C4 had high serum YKL-40 levels compared with C1 and C2. C3 was associated with earlier onset and longer duration of disease, severe airflow obstruction, and near-fatal asthma exacerbations. C4 had the highest serum YKL-40 levels, adult onset and less airflow obstruction, but frequent exacerbations. An airway transcriptome analysis in C3 and C4 showed activation of non-type 2 inflammatory pathways.Elevated serum YKL-40 levels were associated with two distinct clinical asthma phenotypes: one with irreversible airway obstruction and another with severe exacerbations. The YKL-40 clusters are potentially useful for identification of individuals with severe or exacerbation-prone asthma.

The Innate Cytokines IL-25, IL-33, and TSLP Cooperate in the Induction of Type 2 Innate Lymphoid Cell Expansion and Mucous Metaplasia in Rhinovirus-Infected Immature Mice

Early-life respiratory viral infection is a risk factor for asthma development. Rhinovirus (RV) infection of 6-d-old mice, but not mature mice, causes mucous metaplasia and airway hyperresponsiveness that are associated with the expansion of lung type 2 innate lymphoid cells (ILC2s) and are dependent on IL-13 and the innate cytokine IL-25. However, contributions of the other innate cytokines, IL-33 and thymic stromal lymphopoietin (TSLP), to the observed asthma-like phenotype have not been examined. We reasoned that IL-33 and TSLP expression are also induced by RV infection in immature mice and are required for maximum ILC2 expansion and mucous metaplasia. We inoculated 6-d-old BALB/c (wild-type) and TSLP receptor-knockout mice with sham HeLa cell lysate or RV. Selected mice were treated with neutralizing Abs to IL-33 or recombinant IL-33, IL-25, or TSLP. ILC2s were isolated from RV-infected immature mice and treated with innate cytokines ex vivo. RV infection of 6-d-old mice increased IL-33 and TSLP protein abundance. TSLP expression was localized to the airway epithelium, whereas IL-33 was expressed in epithelial and subepithelial cells. RV-induced mucous metaplasia, ILC2 expansion, airway hyperresponsiveness, and epithelial cell IL-25 expression were attenuated by anti-IL-33 treatment and in TSLP receptor-knockout mice. Administration of intranasal IL-33 and TSLP was sufficient for mucous metaplasia. Finally, TSLP was required for maximal ILC2 gene expression in response to IL-25 and IL-33. The generation of mucous metaplasia in immature RV-infected mice involves a complex interplay among the innate cytokines IL-25, IL-33, and TSLP.

Adult onset asthma and interaction between genes and active tobacco smoking: The GABRIEL consortium

Background

Genome-wide association studies have identified novel genetic associations for asthma, but without taking into account the role of active tobacco smoking. This study aimed to identify novel genes that interact with ever active tobacco smoking in adult onset asthma.

Methods

We performed a genome-wide interaction analysis in six studies participating in the GABRIEL consortium following two meta-analyses approaches based on 1) the overall interaction effect and 2) the genetic effect in subjects with and without smoking exposure. We performed a discovery meta-analysis including 4,057 subjects of European descent and replicated our findings in an independent cohort (LifeLines Cohort Study), including 12,475 subjects.

Results

First approach: 50 SNPs were selected based on an overall interaction effect at p<10⁻⁴. The most pronounced interaction effect was observed for rs9969775 on chromosome 9 (discovery meta-analysis: OR_int = 0.50, p = 7.63*10⁻⁵, replication: OR_int = 0.65, p = 0.02). Second approach: 35 SNPs were selected based on the overall genetic effect in exposed subjects (p <10⁻⁴). The most pronounced genetic effect was observed for rs5011804 on chromosome 12 (discovery meta-analysis OR_int = 1.50, p = 1.21*10^−4; replication: OR_int = 1.40, p = 0.03).

Conclusions

Using two genome-wide interaction approaches, we identified novel polymorphisms in non-annotated intergenic regions on chromosomes 9 and 12, that showed suggestive evidence for interaction with active tobacco smoking in the onset of adult asthma.

The History of the Bellevue Hospital Chest Service (1903-2015)

For more than 100 years, the Bellevue Hospital Chest Service in New York City has contributed major advances in our understanding of pulmonary disease. Research from the cardiopulmonary laboratory of the Chest Service by Drs. Cournand and Richards resulted in the shared Nobel Prize in Physiology or Medicine in 1956 for the development of human cardiac catheterization. In more recent years, continuing its mission to serve the underserved and respond to health crises, the Bellevue Chest Service has served as a leader in the management of HIV infections, multiple drug-resistant tuberculosis epidemics, early detection of lung cancer, and management of urban asthma. Members of the Chest Service founded the World Trade Center Environmental Health Center shortly after collapse of the towers in 2001. The Chest Service became New York's infectious isolation unit caring for the first patient in New York infected with Ebola virus. Recent research has focused on disease management, with the first in-house Directly Observed Therapy Clinic for treatment of tuberculosis, clinical trials of aerosolized IFN-γ, and translational research on host defense against tuberculosis infection. Studies of the airway mucosa have revealed mechanisms by which ambient pollutants promote asthma. Studies on the World Trade Center firefighters and community populations have promoted understanding of systemic inflammation and small airways function. Today, the partnership between a public hospital and an academic institution promotes the synergy that leads to cost-effective and state-of-the art care for an underserved population as well as cutting-edge training and research.

Quantile Regression in the Secondary Analysis of Case-Control Data

Case-control design is widely used in epidemiology and other fields to identify factors associated with a disease. Data collected from existing case-control studies can also provide a cost-effective way to investigate the association of risk factors with secondary outcomes. When the secondary outcome is a continuous random variable, most of the existing methods focus on the statistical inference on the mean of the secondary outcome. In this paper, we propose a quantile-based approach to facilitating a comprehensive investigation of covariates' effects on multiple quantiles of the secondary outcome. We construct a new family of estimating equations combining observed and pseudo outcomes, which lead to consistent estimation of conditional quantiles using case-control data. Simulations are conducted to evaluate the performance of our proposed approach, and a case-control study on genetic association with asthma is used to demonstrate the method.

GLCCI1 Variation Is Associated with Asthma Susceptibility and Inhaled Corticosteroid Response in a Chinese Han Population

BACKGROUND AND AIMS

GLCCI1 variations are found to be associated with response to glucocorticoid therapy in non-Hispanic white subjects with asthma. However, there are also other relevant studies that were not consistent with this finding. In this study we aimed to evaluate the association of GLCCI1 variations with asthma susceptibility and inhaled corticosteroid (ICS) response in a Chinese adult Han population.

METHODS

We genotyped 24 single nucleotide polymorphisms of GLCCI1 in 182 asthmatic patients and 180 healthy controls. Furthermore, we analyzed the association of GLCCI1 variations with ICS response in 30 mild-to-moderate asthmatics.

RESULTS

rs11976862 homozygote mutant genotype GG was nominally associated with increased asthma risk (OR = 2.435, 95% CI: 1.221-4.854, p = 0.01148, p(corr) = 0.0127). Recessive model of rs37972, rs37973 and rs11976862 showed that the rare alleles were correlated with less improvement in FEV1 after fluticasone treatment for 12 weeks (p = 0.004, p = 0.009 and p = 0.039, respectively). The GLCCI1 mRNA expression level decreased obviously in asthmatics than in healthy controls (0.037663 ± 0.0216833 vs. 0.046352 ± 0.0235812, p = 0.000). For asthmatics, GLCCI1 mRNA expression level significantly increased after fluticasone treatment for 12 weeks (0.067641 ± 0.031547 vs. 0.030048 ± 0.014613, p = 0.000). Moreover, changes of GLCCI1 mRNA expression were significantly related with rs37973 and rs11976862 in a recessive model (p = 0.014 and p = 0.033, respectively).

CONCLUSIONS

GLCCI1 variations are associated with asthma susceptibility and ICS response in a Chinese Han adult population. GLCCI1 variations may affect ICS response by modulating GLCCI1 expression.

A General and Robust Framework for Secondary Traits Analysis

Case-control designs are commonly employed in genetic association studies. In addition to the case-control status, data on secondary traits are often collected. Directly regressing secondary traits on genetic variants from a case-control sample often leads to biased estimation. Several statistical methods have been proposed to address this issue. The inverse probability weighting (IPW) approach and the semiparametric maximum-likelihood (SPML) approach are the most commonly used. A new weighted estimating equation (WEE) approach is proposed to provide unbiased estimation of genetic associations with secondary traits, by combining observed and counterfactual outcomes. Compared to the existing approaches, WEE is more robust against biased sampling and disease model misspecification. We conducted simulations to evaluate the performance of the WEE under various models and sampling schemes. The WEE demonstrated robustness in all scenarios investigated, had appropriate type I error, and was as powerful or more powerful than the IPW and SPML approaches. We applied the WEE to an asthma case-control study to estimate the associations between the thymic stromal lymphopoietin gene and two secondary traits: overweight status and serum IgE level. The WEE identified two SNPs associated with overweight in logistic regression, three SNPs associated with serum IgE levels in linear regression, and an additional four SNPs that were missed in linear regression to be associated with the 75th quantile of IgE in quantile regression. The WEE approach provides a general and robust secondary analysis framework, which complements the existing approaches and should serve as a valuable tool for identifying new associations with secondary traits.

TSLP polymorphisms, allergen exposures, and the risk of atopic disorders in children

BACKGROUND

Thymic stromal lymphopoietin (TSLP) polymorphisms influence atopy risk. TSLP might constitute a key interface between the environment and the allergic immune response. However, whether the effects of TSLP polymorphisms on atopic dermatitis (AD) are modified by allergic sensitization is not clear.

OBJECTIVE

To evaluate the joint effect of allergic sensitization and TSLP polymorphisms on AD and to test whether TSLP polymorphisms increase the risk of asthma in children with AD.

METHODS

A total of 1,520 kindergarten children (375 with AD and 1,145 controls) selected from the Childhood Environment and Allergic Diseases Study cohort in 2010 were enrolled. Information about allergic diseases and environmental exposures was collected by questionnaire. Skin prick tests were performed to measure allergic sensitization. TSLP polymorphisms were genotyped by TaqMan assay. Logistic regressions were conducted to estimate the association among TSLP polymorphisms, allergic sensitization, and AD. For replication, a subsample of the British Isle of Wight birth cohort was used.

RESULTS

The TSLP rs2289278 CC genotype increased the risk of AD (odds ratio 1.90, 95% confidence interval 1.12-3.22). In children sensitized to certain allergens, a genetic predisposition (rs2289278 genotype CC) significantly increased the risk of AD. These findings were replicated in the British subsample using rs2289276 genotypes TT and TC, which are in linkage disequilibrium with rs2289278. In subjects with AD, the rs2289278 C allele also significantly increased the risk of developing asthma (odds ratio 8.31, 95% confidence interval 1.08-64.13).

CONCLUSION

The association of rs2289278 with AD was stronger in children with allergic sensitization than in children without atopy. TSLP polymorphisms also increased the risk of asthma in children with AD.

Genomewide association study identifies HAS2 as a novel susceptibility gene for adult asthma in a Japanese population

BACKGROUND

It is increasingly clear that asthma is not a single disease, but a disorder with vast heterogeneity in pathogenesis, severity, and treatment response. To date, 30 genomewide association studies (GWASs) of asthma have been performed, including by our group. However, most gene variants identified so far confer relatively small increments in risk and explain only a small proportion of familial clustering.

OBJECTIVE

To identify additional genetic determinants of susceptibility to asthma using a selected Japanese population with reduced tobacco smoking exposure.

METHODS

We performed a GWAS by genotyping a total of 480 098 single-nucleotide polymorphisms (SNPs) for a Japanese cohort consisting of 734 healthy controls and 240 patients with asthma who had smoked for no more than 10 pack-years. The SNP with the strongest association was genotyped in two other independent Japanese cohorts consisting of a total of 531 healthy controls and 418 patients with asthma who had smoked for no more than 10 pack-years. For the hyaluronan synthase 2 (HAS2) gene, we investigated SNP-gene associations using an expression quantitative trait loci (eQTL) database and also analysed its gene expression profiles in 13 different normal tissues.

RESULTS

In the discovery GWAS, a SNP located upstream of HAS2, rs7846389, showed the strongest statistical significance (P = 1.43 × 10(-7) ). In the two independent replication cohorts, rs7846389 was consistently associated with asthma (nominal P = 0.0152 and 0.0478 in the first and second replication cohorts, respectively). In the meta-analysis, association of rs7846389 with susceptibility to asthma reached the level of genomewide significance (P = 7.92 × 10(-9) ). This variant was strongly correlated with HAS2 mRNA expression. The strongest expression of the gene was detected in the lung.

CONCLUSIONS

Our study identified HAS2 as a novel candidate gene for susceptibility to adult asthma.

Coexpression of type 2 immune targets in sputum-derived epithelial and dendritic cells from asthmatic subjects

BACKGROUND

Noninvasive sputum sampling has enabled the identification of biomarkers in asthmatic patients. Studies of discrete cell populations in sputum can enhance measurements compared with whole sputum in which changes in rare cells and cell-cell interactions can be masked.

OBJECTIVE

We sought to enrich for sputum-derived human bronchial epithelial cells (sHBECs) and sputum-derived myeloid type 1 dendritic cells (sDCs) to describe transcriptional coexpression of targets associated with a type 2 immune response.

METHODS

A case-control study was conducted with patients with mild asthma (asthmatic cases) and healthy control subjects. Induced sputum was obtained for simultaneous enrichment of sHBECs and sDCs by using flow cytometry. Quantitative PCR was used to measure mRNA for sHBEC thymic stromal lymphopoietin (TSLP), IL33, POSTN, and IL25 and downstream targets in sDCs (OX40 ligand [OX40L], CCL17, PPP1R14A, CD1E, CD1b, CD80, and CD86).

RESULTS

Final analyses for the study sample were based on 11 control subjects and 13 asthmatic cases. Expression of TSLP, IL33, and POSTN mRNA was increased in sHBECs in asthmatic cases (P = .001, P = .05, and P = .04, respectively). Expression of sDC OX40L and CCL17 mRNA was increased in asthmatic cases (P = .003 and P = .0001, respectively). sHBEC TSLP mRNA expression was strongly associated with sDC OX40L mRNA expression (R = 0.65, P = .001) and less strongly with sDC CCL17 mRNA expression. sHBEC IL33 mRNA expression was associated with sDC OX40L mRNA expression (R = 0.42, P = .04) but not sDC CCL17 mRNA expression.

CONCLUSIONS

Noninvasive sampling and enrichment of select cell populations from sputum can further our understanding of cell-cell interactions in asthmatic patients with the potential to enhance endotyping of asthmatic patients.

Pediatric asthma and ambient pollutant levels in industrializing nations

Asthma is one of the most common chronic diseases in childhood and its prevalence has been increasing within industrializing nations. The contribution of ambient pollutants to asthma symptomatology has been explored in some countries through epidemiological investigations, molecular analysis and monitoring functional outcomes. The health effects of rising environmental pollution have been of increasing concern in industrializing nations with rising urbanization patterns. This review article provides an overview of the link between pediatric asthma and exposure to rising sources of urban air pollution. It primarily focuses on the asthma-specific effects of sulfur dioxide, nitrogen dioxide, ozone and particulate matter. Worldwide trends of asthma prevalence are also provided which detail the prominent rise in asthma symptoms in many urban areas of Africa, Latin America and Asia. The molecular and functional correlation of ambient pollutants with asthma-specific airway inflammation in the pediatric population are also highlighted. The final aspect of the review considers the correlation of motor vehicle, industrial and cooking energy sources, ascribed as the major emitters among the pollutants in urban settings, with asthma epidemiology in children.

Emissions from commercial-grade charbroiling meat operations induce oxidative stress and inflammatory responses in human bronchial epithelial cells

Commercial charbroiling emissions are a significant source of ambient particulate matter (PM) in urban settings. The objective of this study was to determine whether organic extract of PM emissions from commercial charbroiling meat operations could induce an inflammatory response in human bronchial epithelial cells and whether this effect was mediated by oxidative stress. PM samples were collected during cooking hamburgers on a commercial-grade under-fired charbroiler and sequentially extracted with water and methanol to obtain the aqueous PM suspension (AqPM) and organic extract (OE). The pro-oxidative and pro-inflammatory effects of OE were assessed using human bronchial epithelial cell line BEAS-2B. While AqPM did not have any effect, OE effectively induced the expression of heme oxygennase-1 and cyclooxygenase-2 in BEAS-2B cells. OE also up-regulated the levels of IL-6, IL-8, and prostaglandin E2. OE-induced cellular inflammatory response could be effectively suppressed by the antioxidant N-acetyl cysteine, nuclear factor (erythroid-derived 2)-like 2 activator sulforaphane and p38 MAPK inhibitor SB203580. In conclusion, organic chemicals emitted from commercial charbroiling meat operations could induce an inflammatory response in human bronchial epithelial cells, which was mediated by oxidative stress and p38 MAPK.

Replication and fine mapping of asthma-associated loci in individuals of African ancestry

Asthma originates from genetic and environmental factors with about half the risk of disease attributable to heritable causes. Genome-wide association studies, mostly in populations of European ancestry, have identified numerous asthma-associated single nucleotide polymorphisms (SNPs). Studies in populations with diverse ancestries allow both for identification of robust associations that replicate across ethnic groups and for improved resolution of associated loci due to different patterns of linkage disequilibrium between ethnic groups. Here we report on an analysis of 745 African-American subjects with asthma and 3,238 African-American control subjects from the Candidate Gene Association Resource (CARe) Consortium, including analysis of SNPs imputed using 1,000 Genomes reference panels and adjustment for local ancestry. We show strong evidence that variation near RAD50/IL13, implicated in studies of European ancestry individuals, replicates in individuals largely of African ancestry. Fine mapping in African ancestry populations also refined the variants of interest for this association. We also provide strong or nominal evidence of replication at loci near ORMDL3/GSDMB, IL1RL1/IL18R1, and 10p14, all previously associated with asthma in European or Japanese populations, but not at the PYHIN1 locus previously reported in studies of African-American samples. These results improve the understanding of asthma genetics and further demonstrate the utility of genetic studies in populations other than those of largely European ancestry.

Thymic stromal lymphopoietin-elicited basophil responses promote eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a food allergy-associated inflammatory disease characterized by esophageal eosinophilia. Current management strategies for EoE are nonspecific, and thus there is a need to identify specific immunological pathways that could be targeted to treat this disease. EoE is associated with polymorphisms in the gene that encodes thymic stromal lymphopoietin (TSLP), a cytokine that promotes allergic inflammation, but how TSLP might contribute to EoE disease pathogenesis has been unclear. Here, we describe a new mouse model of EoE-like disease that developed independently of IgE, but was dependent on TSLP and basophils, as targeting TSLP or basophils during the sensitization phase limited disease. Notably, therapeutic TSLP neutralization or basophil depletion also ameliorated established EoE-like disease. In human subjects with EoE, we observed elevated TSLP expression and exaggerated basophil responses in esophageal biopsies, and a gain-of-function TSLP polymorphism was associated with increased basophil responses in patients with EoE. Together, these data suggest that the TSLP-basophil axis contributes to the pathogenesis of EoE and could be therapeutically targeted to treat this disease.

A distinct sensitization pattern associated with asthma and the thymic stromal lymphopoietin (TSLP) genotype

BACKGROUND

Atopy is a phenotypically heterogeneous condition, and the extent to which atopy accounts for asthma is controversial. In this study, we aimed to identify the presence of distinct sensitization patterns to common inhaled allergens and their association with asthma, allergic rhinitis and TSLP genotypes.

METHODS

We studied 1683 adults from Tsukuba, a city in central Japan and 297 adults from Kamishihoro, a cedar-free, birch-dominant town in northern Japan. Levels of total serum IgE and specific IgE antibodies towards 14 major inhaled allergens were measured. With the use of these measures, cluster analysis was applied to classify the subjects' sensitization patterns. We also examined the genetic effects of 2 TSLP functional SNPs on the development of each sensitization pattern.

RESULTS

In the Tsukuba study, cluster analysis identified four clusters, including "Dust mite dominant", "Multiple pollen", "Cedar dominant", and "Low reactivity". In the Kamishihoro study, "Dust mite dominant", "Multiple pollen" and "Low reactivity" clusters were also identified, but a "Cedar dominant" cluster was not formed. The association with asthma was strongest for the "Dust mite dominant" cluster in both the Tsukuba and the Kamishihoro studies. In never smokers, both SNPs were associated with the "Dust mite dominant" cluster (OR > 1.2). In contrast, in current or past smokers, these alleles were inversely associated with the "Multiple pollen" cluster (OR < 0.5).

CONCLUSIONS

Cluster analysis identified the presence of distinct sensitization patterns to common inhaled allergens. TSLP may cause asthma by promoting innate allergic responses to indoor allergens and this contribution is significantly modified by smoking.

MicroRNA-375 regulation of thymic stromal lymphopoietin by diesel exhaust particles and ambient particulate matter in human bronchial epithelial cells

Air pollution contributes to acute exacerbations of asthma and the development of asthma in children and adults. Airway epithelial cells interface innate and adaptive immune responses, and have been proposed to regulate much of the response to pollutants. Thymic stromal lymphopoietin (TSLP) is a pivotal cytokine linking innate and Th2 adaptive immune disorders, and is upregulated by environmental pollutants, including ambient particulate matter (PM) and diesel exhaust particles (DEP). We show that DEP and ambient fine PM upregulate TSLP mRNA and human microRNA (hsa-miR)-375 in primary human bronchial epithelial cells (pHBEC). Moreover, transfection of pHBEC with anti-hsa-miR-375 reduced TSLP mRNA in DEP but not TNF-α-treated cells. In silico pathway evaluation suggested the aryl hydrocarbon receptor (AhR) as one possible target of miR-375. DEP and ambient fine PM (3 μg/cm(2)) downregulated AhR mRNA. Transfection of mimic-hsa-miR-375 resulted in a small downregulation of AhR mRNA compared with resting AhR mRNA. AhR mRNA was increased in pHBEC treated with DEP after transfection with anti-hsa-miR-375. Our data show that two pollutants, DEP and ambient PM, upregulate TSLP in human bronchial epithelial cells by a mechanism that includes hsa-miR-375 with complex regulatory effects on AhR mRNA. The absence of this pathway in TNF-α-treated cells suggests multiple regulatory pathways for TSLP expression in these cells.

Gene-environment interactions in asthma and allergic diseases: challenges and perspectives

The concept of gene-environment (GxE) interactions has dramatically evolved in the last century and has now become a central theme in studies that assess the causes of human disease. Despite the numerous efforts to discover genes associated in asthma and allergy through various approaches, including the recent genome-wide association studies, investigation of GxE interactions has been mainly limited to candidate genes, candidate environmental exposures, or both. This review discusses the various strategies from hypothesis-driven strategies to the full agnostic search of GxE interactions with an illustration from recently published articles. Challenges raised by each piece of the puzzle (ie, phenotype, environment, gene, and analysis of GxE interaction) are put forward, and tentative solutions are proposed. New perspectives to integrate various types of data generated by new sequencing technologies and to progress toward a systems biology approach of disease are outlined. The future of a molecular network-based approach of disease to which GxE interactions are related requires space for innovative and multidisciplinary research. Assembling the various parts of a puzzle in a complex system could well occur in a way that might not necessarily follow the rules of logic.

TSLP: A Key Regulator of Asthma Pathogenesis

Asthma is a complex disorder of the airways that is characterized by T helper type 2 (Th2) inflammation. The pleiotrophic cytokine TSLP has emerged as an important player involved in orchestrating the inflammation seen in asthma and other atopic diseases. Early research elucidated the role of TSLP on CD4⁺ T cells, and recent work has revealed the impact of TSLP on multiple cell types. Furthermore, TSLP plays an important role in the sequential progression of atopic dermatitis to asthma, clarifying the key role of TSLP in the pathogenesis of asthma, a finding with therapeutic implications.

Polymorphisms in thymic stromal lymphopoietin gene demonstrate a gender and nasal polyposis-dependent association with chronic rhinosinusitis

BACKGROUND

Recent studies have suggested that thymic stromal lymphopoietin (TSLP), a key cytokine involved in the dendritic cell-mediated activation of Th2-mediated inflammatory responses, is significantly increased in nasal polyps from atopic individuals. Our objective was therefore to explore firstly any associations between single nucleotide polymorphisms (SNPs) in and around the TSLP gene and development of chronic rhinosinusitis (CRS; with (CRSwNP) or without (CRSsNP) nasal polyps and, and secondly the influence of nasal polyposis and gender.

METHODS

A population-based case-control association analysis was performed in a Han Chinese cohort. DNA extracted from peripheral blood leukocytes from 638 subjects with CRS (306 CRSwNP and 332 CRSsNP) and 325 healthy controls was assessed for 11 SNPs in and around TSLP gene, selected from the Chinese HapMap genotyping dataset. Genetic association tests were performed using the Haploview and STATA software package.

RESULTS

Single-locus analysis of CRS risk, showed no significant differences in allele or genotype frequencies between CRS subjects and controls. Stratified analyses of association between the selected SNPs and CRS adjusted for gender demonstrated that rs13156068 (CC genotype: P=0.010, OR=0.289) and rs764917 (CC genotype: P=0.040, OR=0.509) were significantly protective against CRS, whereas rs6886755 (GT genotype: P=0.040, OR=0.509) presented a risk among females. In contrast, rs764917 (CA genotype: P=0.033, OR=1.553) presented risk for CRS in males. Furthermore, SNPs rs252706 (AA genotype: P=0.012, OR=0.552) and rs764917 (CA genotype: P=0.001, OR=0.182) displayed protective roles among CRSwNP, but not CRSsNP, subjects.

CONCLUSIONS

This study suggests that SNPs in TSLP gene may exert a gender and/or nasal polyposis-dependent risk for development of CRS in Chinese subjects.

Application of the asthma phenotype algorithm from the Severe Asthma Research Program to an urban population

Rationale

Identification and characterization of asthma phenotypes are challenging due to disease complexity and heterogeneity. The Severe Asthma Research Program (SARP) used unsupervised cluster analysis to define 5 phenotypically distinct asthma clusters that they replicated using 3 variables in a simplified algorithm. We evaluated whether this simplified SARP algorithm could be used in a separate and diverse urban asthma population to recreate these 5 phenotypic clusters.

Methods

The SARP simplified algorithm was applied to adults with asthma recruited to the New York University/Bellevue Asthma Registry (NYUBAR) to classify patients into five groups. The clinical phenotypes were summarized and compared.

Results

Asthma subjects in NYUBAR (n = 471) were predominantly women (70%) and Hispanic (57%), which were demographically different from the SARP population. The clinical phenotypes of the five groups generated by the simplified SARP algorithm were distinct across groups and distributed similarly to those described for the SARP population. Groups 1 and 2 (6 and 63%, respectively) had predominantly childhood onset atopic asthma. Groups 4 and 5 (20%) were older, with the longest duration of asthma, increased symptoms and exacerbations. Group 4 subjects were the most atopic and had the highest peripheral eosinophils. Group 3 (10%) had the least atopy, but included older obese women with adult-onset asthma, and increased exacerbations.

Conclusions

Application of the simplified SARP algorithm to the NYUBAR yielded groups that were phenotypically distinct and useful to characterize disease heterogeneity. Differences across NYUBAR groups support phenotypic variation and support the use of the simplified SARP algorithm for classification of asthma phenotypes in future prospective studies to investigate treatment and outcome differences between these distinct groups.

Trial Registration

Clinicaltrials.gov NCT00212537

Single nucleotide polymorphisms in thymic stromal lymphopoietin gene are not associated with allergic rhinitis susceptibility in Chinese subjects

Background

Thymic stromal lymphopoietin (TSLP) is an epithelial cell-derived cytokine, implicated in the development and progression of allergic diseases. Recent studies have demonstrated significantly increased expression and synthesis of TSLPin nasal mucosa of patients with allergic rhinitis (AR), compared with nonallergic control subjects. Also, there is significant correlation between the level of TSLP mRNA and symptom severity in AR patients. In this study, we investigated whether polymorphisms in the TSLP gene were associated with increased risk of AR in the Chinese population.

Methods

In a candidate gene association study, we tested 11 single nucleotide polymorphisms (SNPs) in the TSLP gene in 368 AR and 325 control adult Han Chinese subjects from Beijing. The 11 SNPs were selected from the Chinese HapMap genotyping dataset to ensure complete genetic coverage. AR was established by questionnaire and clinical examination, and blood was drawn from all subjects for DNA extraction. The PLINK software package was used to perform statistical testing.

Results

In the single-locus analysis of AR risk, no significant differences in allele and genotype frequencies were found between AR and control subjects. Further logistic regression analyses adjusted for age and gender also failed to reveal significant associations between AR and the selected SNPs. Similarly, analysis stratified by gender, and haplotype or diplotype did not reveal any association with AR risk.

Conclusion

Although TSLP presents itself as a good candidate for contributing to allergy, this study failed to find an association between specific SNPs in the TSLP gene and AR susceptibility in the Han Chinese population.

Functions of thymic stromal lymphopoietin in immunity and disease

Thymic stromal lymphopoietin (TSLP) is an interleukin 7-like cytokine expressed mainly by epithelial cells. Current studies provide compelling evidence that TSLP is capable of activating dendritic cells to promote T helper (Th) 2 immune responses. TSLP has also been shown to directly promote Th2 differentiation of naïve CD4(+) T cell and activate natural killer T cells, basophils and other innate immune cells at the initial stage of inflammation. In addition, TSLP affects B cell maturation and activation and can also influence regulatory T (Treg) cell differentiation and development. TSLP-induced Th2 responses are associated with the pathogenesis of allergic inflammatory diseases, including atopic dermatitis, asthma, and rhinitis. Based on recent findings in humans and mouse models, TSLP might also be involved in the pathogenesis of inflammatory bowel disease and progression of cancer. In this review, we will summarize our current understanding of the biology of TSLP and highlight the important issues for future investigations.

Thymic stromal lymphopoietin: a promising therapeutic target for allergic diseases

Thymic stromal lymphopoietin (TSLP), an interleukin 7-like cytokine, can trigger dendritic cell (DC)-mediated T-helper type 2 (Th2) inflammatory responses. Recent evidence demonstrates that cytokines TSLP and OX40 (CD134)/OX40 ligand seem to be important players in the maintenance of Th2 memory pool in the pathogenesis of asthma. Accumulating data reveal that the pathogenic T cells involved in asthma are likely to be inflammatory Th2 cells. TSLP is involved in the development of asthma through crosstalk with nuclear factor NF-ĸB. Progression of skin fibrosis in atopic dermatitis occurs via TSLP/TSLP receptor. TSLP-mediated dermal inflammation aggravates experimental allergic asthma. Also, TSLP polymorphisms are associated with susceptibility to asthma, atopic dermatitis, and eczema herpeticum. These findings suggest a master switch of TSLP in the initiation of allergic and adaptive inflammation through innate pathways at the epithelial cell-DC interface. The TSLP pathway is therefore a promising target for immunotherapy of allergic diseases.

Interleukin 13 and the evolution of asthma therapy

This is a concise review on Interleukin (IL)-13 and the evolution of asthma therapy, from discovery of the molecule, the identification of its pathogenic role in animal models of asthma, to the development of clinically successful neutralizing agents. The translational path from basic research to clinical application was not sequential as expected but random with respect to the tools (molecular & cell biology, animal models, human studies) used and to the application of academic versus industry research. The experiences with the development of neutralizing anti-IL-13 reagents emphasize the need for inclusion of a biomarker assay in the clinical trials that both identifies individuals that actually have aberrant expression of the pathway of interest and allows determining whether the target of interest is neutralized.

The multiple facets of thymic stromal lymphopoietin (TSLP) during allergic inflammation and beyond

Originally shown to promote the growth and activation of B cells, TSLP is now known to have wide-ranging impacts on hematopoietic and nonhematopoietic cell lineages, including DCs, basophils, eosinophils, mast cells, CD4(+), CD8(+), and NK T cells, B cells, and epithelial cells. Whereas the role of TSLP in the promotion of TH2 responses has been studied extensively in the context of lung- and skin-specific allergic disorders, it is becoming increasingly clear that TSLP may impact multiple disease states within multiple organ systems, including the blockade of TH1/TH17 responses and the promotion of cancer and autoimmunity. This review will highlight recent advances in the understanding of TSLP signal transduction, as well as the role of TSLP in allergy, autoimmunity, and cancer. Importantly, these insights into the multifaceted roles of TSLP could potentially allow for novel, therapeutic manipulations of these disorders.