Genes Interacting with Occupational Exposures to Low Molecular Weight Agents and Irritants on Adult-Onset Asthma in Three European Studies

Update on irritant-induced occupational asthma

PURPOSE OF REVIEW

In this narrative review, we aim to highlight novel research findings on both acute/subacute irritant-induced asthma (IIA) and chronic exposure IIA (also called 'low dose' IIA).

RECENT FINDINGS

Novel case series showed that acute and subacute IIA cases had similar causal agents (e.g., acid or base aerosols/fumes, dusts, mixtures) but had occurred in different circumstances (accidents vs. regular work). Acute and subacute IIA cases had similar clinical characteristics but poorer short-term outcomes than sensitizer-induced occupational asthma patients. Novel large epidemiological studies reported associations between chronic occupational exposure to irritants and current adult-onset asthma and poor asthma control, and with a specific asthma endotype characterized by neutrophilic inflammation and oxidative stress. Recent studies reconfirmed the association of the use of disinfectants and cleaning products (especially sprays) with IIA. A role for genetic susceptibility has been suggested.

SUMMARY

Recent literature provided further understanding of both acute/subacute and chronic exposure IIA, in terms of causes, possible mechanisms, and consequences such as poor asthma control. Research is needed to clarify several aspects of IIA, including its frequency (still likely underestimated), modulating factors, and mechanisms. Research aiming at improving irritant exposure assessment, including intensity/duration, and determining relevant exposure windows would be welcome.

Pharmacogenomics of Leukotriene Modifiers: A Systematic Review and Meta-Analysis

Pharmacogenetics research on leukotriene modifiers (LTMs) for asthma has been developing rapidly, although pharmacogenetic testing for LTMs is not yet used in clinical practice. We performed a systematic review and meta-analysis on the impact of pharmacogenomics on LTMs response. Studies published until May 2022 were searched using PubMed, EMBASE, and Cochrane databases. Pharmacogenomics/genetics studies of patients with asthma using LTMs with or without other anti-asthmatic drugs were included. Statistical tests of the meta-analysis were performed with Review Manager (Revman, version 5.4, The Cochrane Collaboration, Copenhagen, Denmark) and R language and environment for statistical computing (version 4.1.0 for Windows, R Core Team, Vienna, Austria) software. In total, 31 studies with 8084 participants were included in the systematic review and five studies were also used to perform the meta-analysis. Two included studies were genome-wide association studies (GWAS), which showed different results. Furthermore, none of the SNPs investigated in candidate gene studies were identified in GWAS. In candidate gene studies, the most widely studied SNPs were ALOX5 (tandem repeats of the Sp1-binding domain and rs2115819), LTC4S-444A/C (rs730012), and SLCO2B1 (rs12422149), with relatively inconsistent conclusions. LTC4S-444A/C polymorphism did not show a significant effect in our meta-analysis (AA vs. AC (or AC + CC): −0.06, 95%CI: −0.16 to 0.05, p = 0.31). AA homozygotes had smaller improvements in parameters pertaining to lung functions (−0.14, 95%CI: −0.23 to −0.05, p = 0.002) in a subgroup of patients with non-selective CysLT receptor antagonists and patients without inhaled corticosteroids (ICS) (−0.11, 95%CI: −0.14 to −0.08, p < 0.00001), but not in other subgroups. Variability exists in the pharmacogenomics of LTMs treatment response. Our meta-analysis and systematic review found that LTC4S-444A/C may influence the treatment response of patients taking non-selective CysLT receptor antagonists for asthma, and patients taking LTMs not in combination with ICS for asthma. Future studies are needed to validate the pharmacogenomic influence on LTMs response.

The Impact of Ambient Environmental and Occupational Pollution on Respiratory Diseases

Ambient pollutants and occupational pollutants may cause and exacerbate various lung and respiratory diseases. This review describes lung and respiratory diseases in relation to ambient pollutants, particularly particulate matter (PM2.5), and occupational air pollutants, excluding communicable diseases and indoor pollutants, including tobacco smoke exposure. PM2.5 produced by combustion is an important ambient pollutant. PM2.5 can cause asthma attacks and exacerbations of chronic obstructive pulmonary disease in the short term. Further, it not only carries a risk of lung cancer and death, but also hinders the development of lung function in children in the long term. It has recently been suggested that air pollution, such as PM2.5, is a risk factor for severe coronavirus disease (COVID-19). Asbestos, which causes asbestosis, lung cancer, and malignant mesothelioma, and crystalline silica, which cause silicosis, are well-known traditional occupational pollutants leading to pneumoconiosis. While work-related asthma (WRA) is the most common occupational lung disease in recent years, many different agents cause WRA, including natural and synthetic chemicals and irritant gases. Primary preventive interventions that increase awareness of pollutants and reduce the development and exacerbation of diseases caused by air pollutants are paramount to addressing ambient and occupational pollution.

[A definition of work-related asthma and its social and occupational consequences in adults and teenagers]

Work-related asthma (WRA) accounts for 10-25% of all adult asthma. It therefore seems important to raise questions regarding an asthmatic's approach to occupational or job training activities. WRA takes on two forms: work-exacerbated asthma (WEA) and occupational asthma (OA), which encompasses different subtypes of heterogeneous mechanisms. It currently represents a major challenge for occupational medicine in terms of detailed diagnosis, social care, the economic repercussions for workers and employers and, last but not least, social insurance. This review aims to sensitize health care practitioners to the peculiarities of WRA management in routine practice. More specifically, prognosis depends on early diagnosis, medical care and work adjustment measures. WEA and OA are explained in detail in view of identifying causative agents and at-risk occupations and defining adapted medical strategy. Relevant lines of questioning and complementary exams are presented. In addition, the key role of the occupational physician, especially as regards recognition and identification of occupational disease, is underlined, the objective being to facilitate optimal professional and social management. In future studies, the key role of counseling and orientation mechanisms should be highlighted as means of preventing WRA occurrence.

Course monitoring of membranous nephropathy: Both autoantibodies and podocytes require multidimensional attention

A variety of podocyte antigens have been identified in human membranous nephropathy (MN), which is divided into various antigen-dominated subtypes, confirming the concept that MN is the common pattern of glomerular injury in multiple autoimmune responses. The detection of autoantibodies has been widely used, which promoted the clinical practice of MN toward personalized precision medicine. However, given the potential risks of immunosuppressive therapy, more autoantibodies and biomarkers need to be identified to predict the prognosis and therapeutic response of MN more accurately. In this review, we attempted to summarize the autoantigens/autoantibodies and autoimmune mechanisms that can predict disease states based on the current understanding of MN pathogenesis, especially the podocyte injury manifestations. In conclusion, both the autoimmune response and podocyte injury require multidimensional attention in the disease course of MN.

Asthma Phenotypes and Host Risk Factors Associated With Various Asthma-Related Outcomes in Health Workers

Background: Work-related asthma phenotypes in health workers (HWs) exposed to cleaning agents have not been investigated extensively as other occupational exposures. This study aimed to describe asthma phenotypes and to identify important host risk factors associated with various asthma-related outcomes.

Methods: A cross-sectional study of 699 HWs was conducted in two large tertiary hospitals. A total of 697 HWs completed questionnaire interviews. Sera collected from 682 HWs were analyzed for atopy (Phadiatop) and IgE to occupational allergens (NRL—Hev b5, Hev b6.02; chlorhexidine and ortho-phthalaldehyde—OPA). Methacholine (MCT), bronchodilator challenge (BDR) and fractional exhaled nitric oxide (FeNO) were performed. An asthma symptom score (ASS) used five asthma-related symptoms reported in the past 12 months. Current asthma was based on use of asthma medication or an asthma attack or being woken up by an attack of shortness of breath in the past 12 months. Nonspecific bronchial hyperresponsiveness (NSBH) was defined as having either a positive MCT or a significant bronchodilator response. Two continuous indices of NSBH [continuous index of responsiveness (CIR) and dose-response slope (DRS)] were calculated.

Results: The prevalence of current asthma was 10%, atopic asthma (6%) and non-atopic asthma (4%). Overall, 2% of subjects had work-related asthma. There was a weak positive association between NSBH and FeNO [CIR: Beta coefficient (β) = 0.12; CI: 0.03–0.22 and DRS: β = 0.07; CI: 0.03–0.12]. Combining FeNO ≥ 50 ppb with a BDR [mean ratio (MR) = 5.89; CI: 1.02–34.14] or with NSBH (MR = 4.62; CI: 1.16–18.46) correlated better with ASS than FeNO alone (MR = 2.23; CI: 1.30–3.85). HWs with current asthma were twice as likely to be atopic. FeNO was positively associated with atopy (OR = 3.19; CI: 1.59–6.39) but negatively associated with smoking status (GMR = 0.76; CI: 0.62–0.94). Most HWs sensitized to occupational allergens were atopic.

Conclusion: Atopic asthma was more prevalent than non-atopic asthma in HWs. Most asthma-related outcomes were positively associated with allergic predictors suggesting a dominant role for IgE mechanisms for work-related symptoms and asthma associated with sensitization to OPA or chlorhexidine.

Maternal preconception occupational exposure to cleaning products and disinfectants and offspring asthma

BACKGROUND

Emerging research suggests health effects in offspring after parental chemical exposures before conception. Many future mothers are exposed to potent chemicals at work, but potential offspring health effects are hardly investigated.

OBJECTIVE

We sought to investigate childhood asthma in relation to mother's occupational exposure to cleaning products and disinfectants before conception.

METHODS

The multicenter Respiratory Health In Northern Europe/Respiratory Health In Northern Europe, Spain and Australia generation study investigated asthma and wheeze starting at age less than 10 years in 3318 mother-offspring pairs. From an asthma-specific Job-Exposure Matrix and mothers' occupational history, we defined maternal occupational exposure to indoor cleaning agents (cleaning products/detergents and disinfectants) starting before conception, in the 2-year period around conception and pregnancy, or after birth. Never-employed mothers were excluded. Exposed groups include cleaners, health care workers, cooks, and so forth. Associations were analyzed using mixed-effects logistic regression and ordinary logistic regression with clustered robust SEs and adjustment for maternal education.

RESULTS

Maternal occupational exposure to indoor cleaning starting preconception and continuing (n = 610) was associated with offspring's childhood asthma: odds ratio 1.56 (95% CI, 1.05-2.31), childhood asthma with nasal allergies: 1.77 (1.13-2.77), and childhood wheeze and/or asthma: 1.71 (95% CI, 1.19-2.44). Exposure starting around conception and pregnancy (n = 77) was associated with increased childhood wheeze and/or asthma: 2.25 (95% CI, 1.03-4.91). Exposure starting after birth was not associated with asthma outcomes (1.13 [95% CI, 0.71-1.80], 1.15 [95% CI, 0.67-1.97], 1.08 [95% CI, 0.69-1.67]).

CONCLUSIONS

Mother's occupational exposure to indoor cleaning agents starting before conception, or around conception and pregnancy, was associated with more childhood asthma and wheeze in offspring. Considering potential implications for vast numbers of women in childbearing age using cleaning agents, and their children, further research is imperative.

PID1 is associated to a respiratory endotype related to occupational exposures to irritants

BACKGROUND

Studying associations between genes and asthma endotypes and interactions with environment could help to identify new susceptibility genes. We used a previously identified asthma endotype characterized by adult-onset asthma, poor lung function, and high level of Fluorescent oxidation products, a marker of damages due to oxidative stress. This endotype was associated with high occupational exposure to irritants. We aimed to investigate the associations between genes related to oxidative stress and this endotype, and if the associations differed according to irritants exposure.

METHODS

We conducted association analyses between the asthma endotype and genetic variants (4715 SNPs) located in 422 genes involved in the "response to oxidative stress" in adults from the Epidemiological study on the Genetic and Environment of Asthma. Analyses using logistic regression were conducted first in all participants, and then separately among high vs. non-exposed participants to assess whether association differs according to irritants exposure.

RESULTS

An association was found between the SNP rs1419958 located in PID1 gene and the endotype (P = 2.2E-05), reaching significance level after correction for multiple testing. This association was even more significant in non-exposed participants (P = 1.06E-06) while there was no association in participants with high exposure to occupational irritants.

CONCLUSION

This study showed a significant association between an asthma endotype and PID1, a promising candidate gene, the association being different according to the exposure to irritants. These results highlight the interest of studying asthma endotypes in association with genes from candidate pathways and their link with occupational irritants to decipher asthma etiology.

Occupation, socioeconomic status and chronic obstructive respiratory diseases - The EpiLung study in Finland, Estonia and Sweden

OBJECTIVE

To study occupational groups and occupational exposure in association with chronic obstructive respiratory diseases.

METHODS

In early 2000s, structured interviews on chronic respiratory diseases and measurements of lung function as well as fractional expiratory nitric oxide (F_ENO) were performed in adult random population samples of Finland, Sweden and Estonia. Occupations were categorized according to three classification systems. Occupational exposure to vapours, gases, dusts and fumes (VGDF) was assessed by a Job-Exposure Matrix (JEM). The data from the countries were combined.

RESULTS

COPD, smoking and occupational exposure were most common in Estonia, while asthma and occupations requiring higher educational levels in Sweden and Finland. In an adjusted regression model, non-manual workers had a three-fold risk for physician-diagnosed asthma (OR 3.18, 95%CI 1.07-9.47) compared to professionals and executives, and the risk was two-fold for healthcare & social workers (OR 2.28, 95%CI 1.14-4.59) compared to administration and sales. An increased risk for physician-diagnosed COPD was seen in manual workers, regardless of classification system, but in contrast to asthma, the risk was mostly explained by smoking and less by occupational exposure to VGDF. For F_ENO, no associations with occupation were observed.

CONCLUSIONS

In this multicenter study from Finland, Sweden and Estonia, COPD was consistently associated with manual occupations with high smoking prevalence, highlighting the need to control for tobacco smoking in studies on occupational associations. In contrast, asthma tended to associate with non-manual occupations requiring higher educational levels. The occupational associations with asthma were not driven by eosinophilic inflammation presented by increased F_ENO.

Mining GWAS and eQTL data for CF lung disease modifiers by gene expression imputation

Genome wide association studies (GWAS) have identified several genomic loci with candidate modifiers of cystic fibrosis (CF) lung disease, but only a small proportion of the expected genetic contribution is accounted for at these loci. We leveraged expression data from CF cohorts, and Genotype-Tissue Expression (GTEx) reference data sets from multiple human tissues to generate predictive models, which were used to impute transcriptional regulation from genetic variance in our GWAS population. The imputed gene expression was tested for association with CF lung disease severity. By comparing and combining results from alternative approaches, we identified 379 candidate modifier genes. We delved into 52 modifier candidates that showed consensus between approaches, and 28 of them were near known GWAS loci. A number of these genes are implicated in the pathophysiology of CF lung disease (e.g., immunity, infection, inflammation, HLA pathways, glycosylation, and mucociliary clearance) and the CFTR protein biology (e.g., cytoskeleton, microtubule, mitochondrial function, lipid metabolism, endoplasmic reticulum/Golgi, and ubiquitination). Gene set enrichment results are consistent with current knowledge of CF lung disease pathogenesis. HLA Class II genes on chr6, and CEP72, EXOC3, and TPPP near the GWAS peak on chr5 are most consistently associated with CF lung disease severity across the tissues tested. The results help to prioritize genes in the GWAS regions, predict direction of gene expression regulation, and identify new candidate modifiers throughout the genome for potential therapeutic development.

Idiopathic Membranous Nephropathy: Glomerular Pathological Pattern Caused by Extrarenal Immunity Activity

Idiopathic membranous nephropathy (IMN) is a pathological pattern of glomerular damage caused by an autoimmune response. Immune complex deposition, thickness of glomerular basement membrane, and changes in the podocyte morphology are responsible for the development of proteinuria, which is caused by the targeted binding of auto-antibodies to podocytes. Several auto-antigens have recently been identified in IMN, including M-type receptor for secretory phospholipase A2 (PLA2R1), thrombospondin type-1 domain-containing 7A (THSD7A), and neural epidermal growth factor-like 1 protein (NELL-1). The measurement of peripheral circulating antibodies has become an important clinical reference index. However, some clinical features of IMN remain elusive and need to be further investigated, such as the autoimmunity initiation, IgG4 predominance, spontaneous remission, and the unique glomerular lesion. As these unresolved issues are closely related to clinical practice, we have proposed a hypothetical pathogenesis model of IMN. Induced by environmental stimuli or other causes, the PLA2R1 antigen and/or THSD7A antigen exposed to extrarenal tissues, such as lungs, then produce the auto-antibodies that target and cause damage to the podocytes in circulation. In this review, we highlighted the potential association between environmental stimuli, immune activity, and glomerular lesions, the underlying basis for spontaneous immune and proteinuria remission.

Causes and Phenotypes of Work-Related Asthma

Work-related asthma (WRA) includes heterogeneous conditions, which have in common (i) symptoms and signs compatible with asthma and (ii) a relationship with exposures in the workplace. The types of WRA described in this review are distinguished by their etiology, comprising of work-exacerbated asthma (WEA), irritant-induced asthma (IIA), and immunologic occupational asthma (OA). There have been significant advances in the definition and characterization of the different forms of WRA by international panels of experts. The present review provides a comprehensive and updated view of the current knowledge on causes and phenotypes of WRA. Health care practitioners should consider WRA in any case of adult asthma, given that one fifth of workers with asthma report symptoms of WEA and it has been estimated that OA represents 10% to 25% of asthma in adulthood. The information provided in this review will facilitate the physician in the recognition of the different forms of WRA, since it has been established that five categories of agents are responsible for at least 60% of WEA cases and seven groups of agents are the cause of 70% of immunologic OA. In addition, there is agreement that IIA can be elicited not only by a single massive irritant exposure, but also by low/moderate repeated irritant exposures.

Occupational exposure to disinfectants and asthma incidence in U.S. nurses: A prospective cohort study

BACKGROUND

Exposure to disinfectants among healthcare workers has been associated with respiratory health effects, in particular, asthma. However, most studies are cross-sectional and the role of disinfectant exposures in asthma development requires longitudinal studies. We investigated the association between occupational exposure to disinfectants and incident asthma in a large cohort of U.S. female nurses.

METHODS

The Nurses' Health Study II is a prospective cohort of 116 429 female nurses enrolled in 1989. Analyses included 61 539 participants who were still in a nursing job and with no history of asthma in 2009 (baseline; mean age: 55 years). During 277 744 person-years of follow-up (2009-2015), 370 nurses reported incident physician-diagnosed asthma. Occupational exposure was evaluated by questionnaire and a Job-Task-Exposure Matrix (JTEM). We examined the association between disinfectant exposure and subsequent asthma development, adjusted for age, race, ethnicity, smoking status, and body mass index.

RESULTS

Weekly use of disinfectants to clean surfaces only (23% exposed) or to clean medical instruments (19% exposed) was not associated with incident asthma (adjusted hazard ratio [95% confidence interval] for surfaces, 1.12 [0.87-1.43]; for instruments, 1.13 [0.87-1.48]). No association was observed between high-level exposure to specific disinfectants/cleaning products evaluated by the JTEM (formaldehyde, glutaraldehyde, bleach, hydrogen peroxide, alcohol quats, or enzymatic cleaners) and asthma incidence.

CONCLUSIONS

In a population of late career nurses, we observed no significant association between exposure to disinfectants and asthma incidence. A potential role of disinfectant exposures in asthma development warrants further study among healthcare workers at earlier career stage to limit the healthy worker effect.

[Association of cytoplasmic phospholipase A2 gene polymorphism with bronchial asthma and response to montelukast in children]

OBJECTIVE

To study the association of cytoplasmic phospholipase A2 (PLA2G4) rs932476 polymorphism with the development of bronchial asthma and the response to montelukast, a leukotriene receptor antagonist, in children.

METHODS

A total of 128 children with bronchial asthma were enrolled as case group, and 100 healthy children were enrolled as control group. The genotype and allele frequencies of PLA2G4 rs932476 were compared between the two groups. The children in the case group were administered with montelukast except routine treatment for 2 months, and the changes in serum levels of leukotriene B4 (LTB4), interleukin-4 (IL-4), immunoglobulin E (IgE), and interferon gamma (IFN-γ), pulmonary function and fractional exhaled nitric oxide (FeNO) after treatment were observed.

RESULTS

There were no significant differences in the genotype and allele frequencies of PLA2G4 rs932476 between the case and control groups, as well as between the groups with different severities of asthma (P>0.05). After treatment, the children with AA genotype had a significantly higher overall response rate than those with GG genotype. After treatment, the case group had significant reductions in the serum levels of IgE and IL-4 and a significant increase in the level of IFN-γ (P<0.05). After treatment, the children with GG genotype had a higher serum level of IL-4 and a lower level of IFN-γ than those with AA genotype. After treatment, the case group had significant increases in pulmonary function parameters, and the children with AA genotype had significantly higher parameters than those with GG genotype. The case group had a significant reduction in the level of FeNO, and the children with AA genotype had a significantly lower level than those with GG genotype after treatment. The case group had a significantly higher serum level of LTB4 than the control group before treatment (P<0.05). After treatment the case group had a significant reduction in the serum level of LTB4 (P<0.05). The children with GG genotype had a significantly higher level of LTB4 than those with AA genotype after treatment (P<0.05).

CONCLUSIONS

PLA2G4 rs932476 polymorphism is not associated with the susceptibility and severity of bronchial asthma in children, but it may has certain influence on children's response to the leukotriene receptor antagonist montelukast, possibly by affecting the level of LTB4.

[Association of cytoplasmic phospholipase A2 gene polymorphism with bronchial asthma and response to montelukast in children]

OBJECTIVE

To study the association of cytoplasmic phospholipase A2 (PLA2G4) rs932476 polymorphism with the development of bronchial asthma and the response to montelukast, a leukotriene receptor antagonist, in children.

METHODS

A total of 128 children with bronchial asthma were enrolled as case group, and 100 healthy children were enrolled as control group. The genotype and allele frequencies of PLA2G4 rs932476 were compared between the two groups. The children in the case group were administered with montelukast except routine treatment for 2 months, and the changes in serum levels of leukotriene B4 (LTB4), interleukin-4 (IL-4), immunoglobulin E (IgE), and interferon gamma (IFN-γ), pulmonary function and fractional exhaled nitric oxide (FeNO) after treatment were observed.

RESULTS

There were no significant differences in the genotype and allele frequencies of PLA2G4 rs932476 between the case and control groups, as well as between the groups with different severities of asthma (P>0.05). After treatment, the children with AA genotype had a significantly higher overall response rate than those with GG genotype. After treatment, the case group had significant reductions in the serum levels of IgE and IL-4 and a significant increase in the level of IFN-γ (P<0.05). After treatment, the children with GG genotype had a higher serum level of IL-4 and a lower level of IFN-γ than those with AA genotype. After treatment, the case group had significant increases in pulmonary function parameters, and the children with AA genotype had significantly higher parameters than those with GG genotype. The case group had a significant reduction in the level of FeNO, and the children with AA genotype had a significantly lower level than those with GG genotype after treatment. The case group had a significantly higher serum level of LTB4 than the control group before treatment (P<0.05). After treatment the case group had a significant reduction in the serum level of LTB4 (P<0.05). The children with GG genotype had a significantly higher level of LTB4 than those with AA genotype after treatment (P<0.05).

CONCLUSIONS

PLA2G4 rs932476 polymorphism is not associated with the susceptibility and severity of bronchial asthma in children, but it may has certain influence on children's response to the leukotriene receptor antagonist montelukast, possibly by affecting the level of LTB4.

DNA methylation in nasal epithelium, atopy, and atopic asthma in children: a genome-wide study

BACKGROUND

Epigenetic mechanisms could alter the airway epithelial barrier and ultimately lead to atopic diseases such as asthma. We aimed to identify DNA methylation profiles that are associated with-and could accurately classify-atopy and atopic asthma in school-aged children.

METHODS

We did a genome-wide study of DNA methylation in nasal epithelium and atopy or atopic asthma in 483 Puerto Rican children aged 9-20 years, recruited using multistage probability sampling. Atopy was defined as at least one positive IgE (≥0·35 IU/mL) to common aeroallergens, and asthma was defined as a physician's diagnosis plus wheeze in the previous year. Significant (false discovery rate p<0·01) methylation signals were correlated with gene expression, and top CpGs were validated by pyrosequencing. We then replicated our top methylation findings in a cohort of 72 predominantly African American children, and in 432 children from a European birth cohort. Next, we tested classification models based on nasal methylation for atopy or atopic asthma in all cohorts.

FINDINGS

DNA methylation profiles were markedly different between children with (n=312) and without (n=171) atopy in the Puerto Rico discovery cohort, recruited from Feb 12, 2014, until May 8, 2017. After adjustment for covariates and multiple testing, we found 8664 differentially methylated CpGs by atopy, with false discovery rate-adjusted p values ranging from 9·58 × 10^-17 to 2·18 × 10^-22 for the top 30 CpGs. These CpGs were in or near genes relevant to epithelial barrier function, including CDHR3 and CDH26, and in other genes related to airway epithelial integrity and immune regulation, such as FBXL7, NTRK1, and SLC9A3. Moreover, 28 of the top 30 CpGs replicated in the same direction in both independent cohorts. Classification models of atopy based on nasal methylation performed well in the Puerto Rico cohort (area under the curve [AUC] 0·93-0·94 and accuracy 85-88%) and in both replication cohorts (AUC 0·74-0·92, accuracy 68-82%). The models also performed well for atopic asthma in the Puerto Rico cohort (AUC 0·95-1·00, accuracy 88%) and the replication cohorts (AUC 0·82-0·88, accuracy 86%).

INTERPRETATION

We identified specific methylation profiles in airway epithelium that are associated with atopy and atopic asthma in children, and a nasal methylation panel that could classify children by atopy or atopic asthma. Our findings support the feasibility of using the nasal methylome for future clinical applications, such as predicting the development of asthma among wheezing infants.

FUNDING

US National Institutes of Health.

Identification of novel susceptibility genes associated with seven autoimmune disorders using whole genome molecular interaction networks

Convergent evidence from multiple and independent genetics studies implicate a small number of genes that predispose individuals to multiple autoimmune disorders (AuD). These intersecting loci reinforced the hypothesis that disorders with overlapping etiology group into a cluster of closely related genes within a whole genome molecular interaction network. We tested the hypothesis that "biological network proximity" within a whole genome molecular interaction network can be used to inform the search for multigene inheritance. Using a set of nine previously published genome wide association studies (GWAS) of AuD genes, we generated AuD-specific molecular interaction networks to identify networks of associated genes. We show that all nine "seed genes" can be connected within a 35-member network via interactions with 26 connecting genes. We show that this network is more connected than expected by chance, and 13 of the connecting genes showed association with multiple AuD upon GWAS reanalysis. Furthermore, we report association of SNPs in five new genes (IL10RA, DGKA, GRB2, STAT5A, and NFATC2) which were not previously considered as AuD candidates, and show significant association in novel disease samples of Crohn's disease and systemic lupus erythematosus. Furthermore, we show that the connecting genes show no association in four non-AuD GWAS. Finally, we test the connecting genes in psoriasis GWAS, and show association to previously identified loci and report new loci. These findings support the hypothesis that molecular interaction networks can be used to inform the search for multigene disease etiology, especially for disorders with overlapping etiology.

Interactive effect between ATPase-related genes and early-life tobacco smoke exposure on bronchial hyper-responsiveness detected in asthma-ascertained families

BACKGROUND

A positional cloning study of bronchial hyper-responsiveness (BHR) at the 17p11 locus in the French Epidemiological study on the Genetics and Environment of Asthma (EGEA) families showed significant interaction between early-life environmental tobacco smoke (ETS) exposure and genetic variants located in DNAH9. This gene encodes the heavy chain subunit of axonemal dynein, which is involved with ATP in the motile cilia function.Our goal was to identify genetic variants at other genes interacting with ETS in BHR by investigating all genes belonging to the 'ATP-binding' and 'ATPase activity' pathways which include DNAH9, are targets of cigarette smoke and play a crucial role in the airway inflammation.

METHODS

Family-based interaction tests between ETS-exposed and unexposed BHR siblings were conducted in 388 EGEA families. Twenty single-nucleotide polymorphisms (SNP) showing interaction signals (p≤5.10^-3) were tested in the 253 Saguenay-Lac-Saint-Jean (SLSJ) families.

RESULTS

One of these SNPs was significantly replicated for interaction with ETS in SLSJ families (p=0.003). Another SNP reached the significance threshold after correction for multiple testing in the combined analysis of the two samples (p=10^-5). Results were confirmed using both a robust log-linear test and a gene-based interaction test.

CONCLUSION

The SNPs showing interaction with ETS belong to the ATP8A1 and ABCA1 genes, which play a role in the maintenance of asymmetry and homeostasis of lung membrane lipids.

Advances in environmental and occupational disorders in 2016

In this review we highlight recent studies that advance the knowledge and understanding of the effects of various environmental factors and associated immune responses in patients with allergic diseases. This review will focus on new literature regarding allergic and immune responses to a variety of environmental factors, including aeroallergens, stinging insects, fungi, pollutants, viral respiratory tract infections, climate change, and microbial exposures.