Epigenetics in asthma and allergy

Perimenstrual Asthma and Premenstrual Disorders in Adolescents with Asthma

BACKGROUND

Asthma is a common chronic disease in pediatric patients, and perimenstrual asthma (PMA), refers to the worsening of asthma symptoms during the perimenstrual period, mainly reported in adult women. However, there is limited information regarding the exacerbation of symptoms in the presence of premenstrual disorders (PMDs) in adolescents. The aim of this pilot observational study was to investigate the frequency and potential association of PMA and PMDs in a clinical sample of adolescents with asthma.

PATIENTS AND METHODS

The study included 50 adolescents (aged 12-18 years, mean 16.08 ± 2.35) with asthma and at least 2 years of gynecological age. The participants completed the Asthma Control Test (ACT) to assess asthma control (considered pathological if ACT score < 20) and the modified Premenstrual Symptoms Screening Tool for Adolescents (PSST-A) to evaluate PMDs.

RESULTS

A total of 75.5% of adolescents reported PMA. The prevalence of premenstrual symptoms did not significantly differ between the PMA and no-PMA group. Among the study sample, 38.7% experienced symptoms indicative of moderate/severe premenstrual syndrome, and 8.1% exhibited symptoms of premenstrual dysphoric disorder. Compared with the no-PMA group, patients with PMA showed a significant impairment in daily and home activities (P = .03 and P = .02, respectively) and exhibited a difference in the frequency of asthma symptoms (P < .001) and medication use (P ≤ .01).

CONCLUSION

Perimenstrual worsening of asthma symptoms may be common in adolescents with a severe form of asthma. Prospective data collection through menstrual diaries is necessary to further explore the association between PMA and PMDs. Identifying early risk factors for PMA could facilitate the development of preventive strategies and early interventions for adolescents with asthma.

Air pollutants contribute to epithelial barrier dysfunction and allergic diseases

Air pollution is a global problem associated with various health conditions, causing elevated rates of morbidity and mortality. Major sources of air pollutants include industrial emissions, traffic-related pollutants, and household biomass combustion, in addition to indoor pollutants from chemicals and tobacco. Various types of air pollutants originate from both human activities and natural sources. These include particulate matter, pollen, greenhouse gases, and other harmful gases. Air pollution is linked to allergic diseases, including atopic dermatitis, allergic rhinitis, allergic conjunctivitis, food allergy, and bronchial asthma. These pollutants lead to epithelial barrier dysfunction, dysbiosis, and immune dysregulation. In addition, climate change and global warming may contribute to the exacerbation and the development of allergic diseases related to air pollutants. Epigenetic changes associated with air pollutants have also been connected to the onset of allergic diseases. Furthermore, these changes can be passed down through subsequent generations, causing a higher prevalence of allergic diseases in offspring. Modulation of the aryl hydrocarbon receptor could be a valuable strategy for alleviating air pollutant-induced epidermal barrier dysfunction and atopic dermatitis. A more effective approach to preventing allergic diseases triggered by air pollutants is to reduce exposure to them. Implementing public policies aimed at safeguarding individuals from air pollutant exposure may prove to be the most efficient solution. A pressing need exists for global policy initiatives that prioritize efforts to reduce the production of air pollutants.

Issues affecting young people with asthma through the transition period to adult care

Asthma is among the most common medical conditions affecting children and young people, with adolescence a recognised period of increased risk, overrepresented in analyses examining recent increasing asthma mortality rates. Asthma may change significantly during this period and management also occurs in the context of patients seeking increased autonomy and self-governance whilst navigating increasing academic and social demands. A number of disease factors can destabilise asthma during adolescence including: increased rates of anaphylaxis, anxiety, depression, obesity, and, in females, an emerging resistance to corticosteroids and the pro-inflammatory effects of oestrogen. Patient factors such as smoking, vaping, poor symptom recognition, treatment non-adherence and variable engagement with health services contribute to difficult to treat asthma. Significant deficiencies in the current approach to transition have been identified by a recent EAACI task force, and subsequent asthma-specific recommendations, published in 2020 provide an important framework moving forward. As with other chronic conditions, effective transition programmes plan ahead, engage with adolescents and their families to identify the patients' management priorities and the current challenges they are experiencing with treatment. Transition needs may vary significantly across asthma patients and for more complex asthma may include dedicated transition clinics involving multidisciplinary care requiring input including, amongst others, allergy and immunology, psychological medicine, respiratory physicians and scientists and nurse specialists. Across different global regions, barriers to treatment may vary but need to be elicited and an individualised approach taken to optimising asthma care which is sustainable within the local adult healthcare system.

Epigenetic Mechanisms in Parenchymal Lung Diseases: Bystanders or Therapeutic Targets?

Epigenetic responses due to environmental changes alter chromatin structure, which in turn modifies the phenotype, gene expression profile, and activity of each cell type that has a role in the pathophysiology of a disease. Pulmonary diseases are one of the major causes of death in the world, including lung cancer, idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), pulmonary hypertension (PH), lung tuberculosis, pulmonary embolism, and asthma. Several lines of evidence indicate that epigenetic modifications may be one of the main factors to explain the increasing incidence and prevalence of lung diseases including IPF and COPD. Interestingly, isolated fibroblasts and smooth muscle cells from patients with pulmonary diseases such as IPF and PH that were cultured ex vivo maintained the disease phenotype. The cells often show a hyper-proliferative, apoptosis-resistant phenotype with increased expression of extracellular matrix (ECM) and activated focal adhesions suggesting the presence of an epigenetically imprinted phenotype. Moreover, many abnormalities observed in molecular processes in IPF patients are shown to be epigenetically regulated, such as innate immunity, cellular senescence, and apoptotic cell death. DNA methylation, histone modification, and microRNA regulation constitute the most common epigenetic modification mechanisms.

The Loss of H3K27 Histone Demethylase Utx in T Cells Aggravates Allergic Contact Dermatitis

The pathogenesis of allergic contact dermatitis (ACD) requires the activation of Ag-specific T cells, including effector and regulatory T cells. The differentiation and function of these T cells is epigenetically regulated through DNA methylation and histone modifications. However, the roles of altered histone H3K27 methylation in T cells in the development of ACD remain unknown. Two types of histone H3K27 demethylases, Utx and Jmjd3, have been reported in mammals. To determine the role of the histone H3K27 demethylase expression of T cells in the development of ACD, we generated T cell-specific, Utx-deficient (Utx KO) mice or Jmjd3-deficient (Jmjd3 KO) mice. Unlike control mice, Utx KO mice had severer symptoms of ACD, whereas Jmjd3 KO mice showed symptoms identical to those in control mice. In Utx KO mice with ACD, the massive infiltration of myeloid cells, including neutrophils and dendritic cells, has been observed. In addition, the expression of proinflammatory cytokines in CD4⁺ T cells of the draining lymph nodes (LNs) and in CD8⁺ T cells of the skin was increased in Utx KO mice, whereas the ratio of Foxp3⁺ regulatory CD4⁺ T cells to Foxp3^- conventional CD4⁺ T cells was decreased in both the draining LNs and the skin of Utx KO mice with ACD. Furthermore, Foxp3⁺ regulatory CD4⁺ T cells of Utx KO mice with ACD expressed a decreased level of CCR4 (a skin-tropic chemokine receptor) in comparison with control. Thus, in CD4⁺ T cells, Utx could potentially be involved in the regulation of the pathogenesis of ACD.

Does parental farm upbringing influence the risk of asthma in offspring? A three-generation study

BACKGROUND

A farm upbringing has been associated with lower risk of asthma and methylation of asthma-related genes. As such, a farm upbringing has the potential to transfer asthma risk across generations, but this has never been investigated. We aimed to study the generational effects from a parental farm upbringing on offspring asthma.

METHODS

Our study involved three generations: 5759 participants from the European Community Respiratory Health Survey (ECRHS) study (born 1945-1971, denoted G1), their 9991 parents (G0) and their 8260 offspring (G2) participating in RHINESSA (Respiratory Health In Northern Europe, Spain and Australia). Questionnaire data were collected on G0 and G1 from G1 in 2010 and on G2 from themselves in 2013. The parental/grandparental place of upbringing was categorized: (i) both parents from farm; (ii) mother from farm, father from village/city; (iii) father from farm, mother from village/city; (iv) both parents from village or one parent from village and one from city; (v) both parents from city (reference group). Grandparental upbringing was equivalently categorized. Offspring asthma was self-reported and data were analysed using Cox-regression models with G2 age as the time scale.

RESULTS

A parental farm upbringing was not associated with offspring asthma when compared with city upbringing [hazard ratio (HR) 1.12, 95% confidence interval (CI) 0.74-1.69]. Findings remained similar when stratified by offspring upbringing and asthma phenotypes. Quantitative bias analyses showed similar estimates for alternative data sources. A grandparental farm upbringing was not associated with offspring asthma in either the maternal (HR 1.05, 95% CI 0.67-1.65) or paternal line (HR 1.02, 95% CI 0.62-1.68).

CONCLUSIONS

This multigenerational analysis suggests no evidence of an association between parental/grandparental farm upbringing and offspring asthma.

Identification of histone acetylation in a murine model of allergic asthma by proteomic analysis

The pathogenesis of asthma is closely related to histone acetylation modification, but the specific acetylation sites related to this process remain indistinct. Herein, our study sought to identify differentially modified acetylation sites and their expression distribution in cells involved in asthma in lung tissues. The airway hyper-responsiveness, inflammation, and remodeling were assessed by non-invasive whole-body plethysmography, ELISA, and hematoxylin-eosin staining to confirm the successful establishment of the allergic asthma model. Afterward, the differentially modified acetylation sites in asthmatic lung tissues were identified and validated by using proteomics and western blotting, respectively. The immunohistochemistry analysis was applied to reveal the distribution of identified acetylation sites in asthmatic lung tissues. A total of 15 differentially modified acetylation sites, including 13 upregulated (H3K9ac, H3K14ac, H3K18ac, H3K23ac,H3K27ac, H3K36ac, H2B1KK120ac, H2B2BK20ac, H2BK16ac, H2BK20ac, H2BK108ac, H2BK116ac, and H2BK120ac) and 2 downregulated (H2BK5ac and H2BK11ac) sites were identified and validated. Furthermore, immunohistochemical staining of lung tissues showed that nine of the identified histone acetylation sites (H2BK5, H2BK11, H3K18, H2BK116, H2BK20, H2BK120, H3K9, H3K36, and H3K27) were differentially expressed in airway epithelial cells, and the acetylation of identified H3 histones were observed in both eosinophil and perivascular inflammatory cells. Additionally, differential expression of histone acetylation sites was also observed in nucleus of airway epithelial cells, vascular smooth muscle cells, perivascular inflammatory cells, and airway smooth muscle cells. In conclusion, we identified potential acetylation sites associated with asthma pathogenesis. These findings may contribute greatly in the search for therapeutic approaches for allergic asthma.

More than a Genetic Code: Epigenetics of Lung Fibrosis

At the end of the last century, genetic studies reported that genetic information is not transmitted solely by DNA, but is also transmitted by other mechanisms, named as epigenetics. The well-described epigenetic mechanisms include DNA methylation, biochemical modifications of histones, and microRNAs. The role of altered epigenetics in the biology of various fibrotic diseases is well-established, and recent advances demonstrate its importance in the pathogenesis of pulmonary fibrosis-predominantly referring to idiopathic pulmonary fibrosis, the most lethal of the interstitial lung diseases. The deficiency in effective medications suggests an urgent need to better understand the underlying pathobiology. This review summarizes the current knowledge concerning epigenetic changes in pulmonary fibrosis and associations of these changes with several cellular pathways of known significance in its pathogenesis. It also designates the most promising substances for further research that may bring us closer to new therapeutic options.

Children's Environmental Health: A Systems Approach for Anticipating Impacts from Chemicals

Increasing numbers of chemicals are on the market and present in consumer products. Emerging evidence on the relationship between environmental contributions and prevalent diseases suggests associations between early-life exposure to manufactured chemicals and a wide range of children’s health outcomes. Using current assessment methodologies, public health and chemical management decisionmakers face challenges in evaluating and anticipating the potential impacts of exposure to chemicals on children’s health in the broader context of their physical (built and natural) and social environments. Here, we consider a systems approach to address the complexity of children’s environmental health and the role of exposure to chemicals during early life, in the context of nonchemical stressors, on health outcomes. By advancing the tools for integrating this more complex information, the scope of considerations that support chemical management decisions can be extended to include holistic impacts on children’s health.

BSACI guideline for the diagnosis and management of allergic and non-allergic rhinitis (Revised Edition 2017; First edition 2007)

This is an updated guideline for the diagnosis and management of allergic and non-allergic rhinitis, first published in 2007. It was produced by the Standards of Care Committee of the British Society of Allergy and Clinical Immunology, using accredited methods. Allergic rhinitis is common and affects 10-15% of children and 26% of adults in the UK, it affects quality of life, school and work attendance, and is a risk factor for development of asthma. Allergic rhinitis is diagnosed by history and examination, supported by specific allergy tests. Topical nasal corticosteroids are the treatment of choice for moderate to severe disease. Combination therapy with intranasal corticosteroid plus intranasal antihistamine is more effective than either alone and provides second line treatment for those with rhinitis poorly controlled on monotherapy. Immunotherapy is highly effective when the specific allergen is the responsible driver for the symptoms. Treatment of rhinitis is associated with benefits for asthma. Non-allergic rhinitis also is a risk factor for the development of asthma and may be eosinophilic and steroid-responsive or neurogenic and non- inflammatory. Non-allergic rhinitis may be a presenting complaint for systemic disorders such as granulomatous or eosinophilic polyangiitis, and sarcoidoisis. Infective rhinitis can be caused by viruses, and less commonly by bacteria, fungi and protozoa.

Novel cutaneous mediators of chemical allergy

Chemical allergy can manifest into allergic contact dermatitis and asthma and the importance of skin sensitization in both of these diseases is increasingly being recognized. Given the unique characteristics of chemical allergy, coupled with the distinct immunological microenvironment of the skin research is still unraveling the mechanisms through which sensitization and elicitation occur. This review first describes the features of chemical sensitization and the known steps that must occur to develop a chemical allergy. Next, the unique immunological properties of the skin - which may influence chemical sensitization - are highlighted. Additionally, mediators involved with the development of allergy are reviewed, starting with early ones - including the properties of haptens, skin integrity, the microbiome, the inflammasome, and toll-like receptors (TLR). Novel cellular mediators of chemical sensitization are highlighted, including innate lymphoid cells, mast cells, T-helper (T_H) cell subsets, and skin intrinsic populations including γδ T-cells and resident memory T-cells. Finally, this review discusses two epigenetic mechanisms that can influence chemical sensitization, microRNAs and DNA methylation. Overall, this review highlights recent research investigating novel mediators of chemical allergy that are present in the skin. It also emphasizes the need to further explore these mediators to gain a better understanding of what makes a chemical an allergen, and how best to prevent the development of chemical-induced allergic diseases.

Role of epigenetics and DNA-damage in asthma

PURPOSE OF REVIEW

Although asthma is a common disease worldwide, its pathogenesis remains to be fully elucidated. There is increasing evidence of the interaction between epigenetics, DNA-damage, and environmental allergens in the development of asthma. In this review, we will focus on the role of epigenetics and DNA-damage in asthma.

RECENT FINDINGS

There is growing evidence of environmental allergens, particularly house dust mite, stimulating oxidative DNA damage in airway epithelial cells. The repair of this DNA damage has been implicated in the secretion of Th2 cytokines and the induction of allergic inflammation.

SUMMARY

Studies of the role of epigenetics, DNA-damage, and environmental allergens have begun to reveal the their complex interactions and their roles in the development of asthma. Further study in these areas may lead to novel prevention and treatment approaches.

The Implications of DNA Methylation on Food Allergy

Food allergy is a major clinical and public health concern worldwide. The risk factors are well defined, however, the mechanisms by which they affect immune development remain largely unknown, and unfortunately the effective treatment or prevention of food allergy is still being researched. Recent studies show that the genes that are critical for the development of food allergy are regulated through DNA methylation. Environmental factors can affect host DNA methylation status and subsequently predispose people to food allergy. DNA methylation is therefore an important mediator of gene-environment interactions in food allergy and key to understanding the mechanisms underlying the allergic development. Indeed, the modification and identification of the methylation levels of specific genetic loci have gained increasing attention for therapeutic and diagnostic application in combating food allergy. In this review, we summarize and discuss the recent developments of DNA methylation in food allergy, including the pathogenesis, therapy, and diagnosis. This review will also summarize and discuss the environmental factors that affect DNA methylation levels in food allergy.

Maternal phthalate exposure promotes allergic airway inflammation over 2 generations through epigenetic modifications

BACKGROUND

Prenatal and early postnatal exposures to environmental factors are considered responsible for the increasing prevalence of allergic diseases. Although there is some evidence for allergy-promoting effects in children because of exposure to plasticizers, such as phthalates, findings of previous studies are inconsistent and lack mechanistic information.

OBJECTIVE

We investigated the effect of maternal phthalate exposure on asthma development in subsequent generations and their underlying mechanisms, including epigenetic alterations.

METHODS

Phthalate metabolites were measured within the prospective mother-child cohort Lifestyle and Environmental Factors and Their Influence on Newborns Allergy Risk (LINA) and correlated with asthma development in the children. A murine transgenerational asthma model was used to identify involved pathways.

RESULTS

In LINA maternal urinary concentrations of mono-n-butyl phthalate, a metabolite of butyl benzyl phthalate (BBP), were associated with an increased asthma risk in the children. Using a murine transgenerational asthma model, we demonstrate a direct effect of BBP on asthma severity in the offspring with a persistently increased airway inflammation up to the F2 generation. This disease-promoting effect was mediated by BBP-induced global DNA hypermethylation in CD4⁺ T cells of the offspring because treatment with a DNA-demethylating agent alleviated exacerbation of allergic airway inflammation. Thirteen transcriptionally downregulated genes linked to promoter or enhancer hypermethylation were identified. Among these, the GATA-3 repressor zinc finger protein 1 (Zfpm1) emerged as a potential mediator of the enhanced susceptibility for T_H2-driven allergic asthma.

CONCLUSION

These data provide strong evidence that maternal BBP exposure increases the risk for allergic airway inflammation in the offspring by modulating the expression of genes involved in T_H2 differentiation through epigenetic alterations.

An overview of epigenetics in Chinese medicine researches

Chinese medicine (CM) has contributed to human health care for several thousand years and is still popular in Asian countries. But the mechanisms underlying CM remain obscure, and need to be clarifified by modern biological subjects and methods. Recently, CM researches on epigenetics have gained obvious improvement following rapidly developed molecular technologies. In this review, we revealed mutual characteristics of epigenetics and CM, such as holism, yin-yang dynamic nature, reversibility and balance, and visceral manifestation. Moreover, epigenetic modifications, including DNA methylation, histone post-transcriptional modifications, micro RNA interference, etc. may help explore the molecular basis of CM syndrome classifification, and mechanisms of Chinese herbal medicine (CHM), CHM compounds and Chinese herbal formulae activities. Meanwhile, CM and epigenetics might promote each other and jointly develop following the continuous progress of epigenetics in CM researches.

Recent developments in epigenetics of pediatric asthma

PURPOSE OF REVIEW

The goal of this review was to systematically analyze recent studies updating our knowledge on the role of epigenetic mechanisms in childhood asthma.

RECENT FINDINGS

A systematic literature search was conducted that identified 23 fresh articles published within the last 5 years reporting the results of human studies on the relationships between epigenetic modifications and childhood asthma or its/related phenotypes. In almost all these studies, meaningful associations between levels of epigenetic marks (DNA methylation and/or histone modifications) and pediatric asthma or its/related phenotypes have been observed. In addition, many studies identified by our screening analyzed those associations in the context of environmental factors, such as pollution, tobacco smoke, farming, or diet, showing in a huge majority a modifying effect of those exposures.

SUMMARY

The results of our systematic literature search provide a strong support for the role of epigenetic mechanisms in (mediating the effects of environmental exposure on) pediatric asthma. This knowledge may possibly be translated into diagnostic and/or therapeutic approaches.

A review on emerging frontiers of house dust mite and cockroach allergy research

Currently, mankind is afflicted with diversified health issues, allergies being a common, yet little understood malady. Allergies, the outcome of a baffled immune system encompasses myriad allergens and causes an array of health consequences, ranging from transient to recurrent and mild to fatal. Indoor allergy is a serious hypersensitivity in genetically-predisposed people, triggered by ingestion, inhalation or mere contact of allergens, of which mite and cockroaches are one of the most-represented constituents. Arduous to eliminate, these aeroallergens pose constant health challenges, mostly manifested as respiratory and dermatological inflammations, leading to further aggravations if unrestrained. Recent times have seen an unprecedented endeavour to understand the conformation of these allergens, their immune manipulative ploys and other underlying causes of pathogenesis, most importantly therapies. Yet a large section of vulnerable people is ignorant of these innocuous-looking immune irritants, prevailing around them, and continues to suffer. This review aims to expedite this field by a concise, informative account of seminal findings in the past few years, with particular emphasis on leading frontiers like genome-wide association studies (GWAS), epitope mapping, metabolomics etc. Drawbacks linked to current approaches and solutions to overcome them have been proposed.

Asthma transition from childhood into adulthood

Asthma is the most prevalent chronic respiratory disease both in children and adults and resembles a complex syndrome rather than a single disease. Different methods have been developed to better characterise distinct asthma phenotypes in childhood and adulthood. In studies of adults, most phenotyping relies on biomaterials from the lower airways; however, this information is missing in paediatric studies because of restricted accessibility. Few patients show symptoms throughout childhood, adolescence, and adulthood. Risk factors for this might be genetics, family history of asthma and atopy, infections early in life, allergic diseases, and lung function deficits. In turn, a large proportion of children with asthma lose their symptoms during school age and adolescence. This improved prognosis, which might also reflect a better treatment response, is associated with being male and with milder and less allergic disease. Importantly, whether clinical remission of symptoms equals the disappearance of underlying pathology is unknown. In fact, airway hyper-responsiveness and airway inflammation might remain despite the absence of overt symptoms. Additionally, a new-onset of asthma symptoms is apparent in adulthood, especially in women and in the case of impaired lung function. However, many patients do not remember childhood symptoms, which might reflect relapse rather than true initiation. Both relapse and adult-onset of asthma symptoms have been associated with allergic disease and sensitisation in addition to airway hyper-responsiveness. Thus, asthma symptoms beginning in adults might have originated in childhood. Equivocally, persistence into, relapse, and new-onset of symptoms in adulthood have all been related to active smoking. However, underlying mechanisms for the associations remain unclear, and future asthma research should therefore integrate standardised molecular approaches in identical ways in both paediatric and adult populations and in longitudinal studies.

Resolving the etiology of atopic disorders by using genetic analysis of racial ancestry

Atopic dermatitis (AD), food allergy, allergic rhinitis, and asthma are common atopic disorders of complex etiology. The frequently observed atopic march from early AD to asthma, allergic rhinitis, or both later in life and the extensive comorbidity of atopic disorders suggest common causal mechanisms in addition to distinct ones. Indeed, both disease-specific and shared genomic regions exist for atopic disorders. Their prevalence also varies among races; for example, AD and asthma have a higher prevalence in African Americans when compared with European Americans. Whether this disparity stems from true genetic or race-specific environmental risk factors or both is unknown. Thus far, the majority of the genetic studies on atopic diseases have used populations of European ancestry, limiting their generalizability. Large-cohort initiatives and new analytic methods, such as admixture mapping, are currently being used to address this knowledge gap. Here we discuss the unique and shared genetic risk factors for atopic disorders in the context of ancestry variations and the promise of high-throughput "-omics"-based systems biology approach in providing greater insight to deconstruct their genetic and nongenetic etiologies. Future research will also focus on deep phenotyping and genotyping of diverse racial ancestry, gene-environment, and gene-gene interactions.

Establishing a birth cohort to investigate the course and aetiology of asthma and allergies across three generations - rationale, design, and methods of the ACROSSOLAR study

Background

Atopic diseases are a major burden of disease on a global scale. Regarding their aetiology, the early years of life are assumed to play a crucial role. In addition, there is growing evidence that elucidating the impact of cross-generational effects and epigenetic mechanisms such as DNA methylation can substantially widen the scientific knowledge of the occurrence and progression of these diseases. We are thus aiming at following the course of asthma, allergies, and potential risk factors for their occurrence across three generations by establishing a birth cohort in the offspring of an existing population-based cohort.

Methods/Design

2051 young adults who have been recruited in 1995 for Phase II of the International Study of Asthma and Allergies in Childhood (ISAAC) and who have subsequently been followed-up by the Study on Occupational Allergy Risks (SOLAR) are asked bi-annually since 2009 if they conceived a child in the meantime. If parenthood is reported, parents are invited to enrol along with their children in the ACROSSOLAR cohort. Participation involves completing a questionnaire assessing general and health-related information about the course of the pregnancy and the first year of life of their children. Subsequently, the children are followed up until primary school age when asthma and allergies can be diagnosed reliably. In addition, DNA for epigenetic analysis will be collected and analysed. Longitudinal data analysis techniques will then be used to assess potential associations between early-life exposures and onset of childhood asthma and allergies taking into account epigenetics.

Discussion

Birth cohorts are especially suited to elucidate the impact of genetic predisposition, epigenetics, exposures during the first years of life, and gene-environment interactions on the occurrence and progression of asthma and allergies. By building upon an existing cohort, ACROSSOLAR offers a unique and cost-effective opportunity to investigate the aetiology of atopic disease in a prospective and cross-generational way.

Gene-environment interactions in the study of asthma in the postgenomewide association studies era

PURPOSE OF REVIEW

Asthma is a complex disease characterized by an intricate interplay of both heritable and environmental factors. Understanding the mechanisms through which genes and environment interact represents one of the major challenges for pulmonary researchers. This review provides an overview of the recently published literature on gene-environment (G × E) interactions in asthma, with a special focus on the new methodological developments in the postgenomewide association studies (GWAS) era.

RECENT FINDINGS

Most recent studies on G × E interaction in asthma used a candidate-gene approach. Candidate-gene studies considering exposure to outdoor air pollutants showed significant interactions mainly with variants in the GSTP1 gene on asthma in children. G × E studies on passive and active smoking, including one genomewide interaction study, identified novel genes of susceptibility to asthma and a time-dependent effect of maternal smoking. Other recent studies on asthma found interactions between candidate genes and occupational allergen exposure and several domestic exposures such as endotoxin and gas cooking. New methods were developed to efficiently estimate G × E interaction in GWAS, and a pathway-based strategy to select an enriched gene-set for G × E studies has recently been proposed.

SUMMARY

The G × E studies presented in this review offer a good example on how candidate-gene approaches can complement and help in validating GWAS findings.

Differences in DNA methylation profile of Th1 and Th2 cytokine genes are associated with tolerance acquisition in children with IgE-mediated cow's milk allergy

BACKGROUND

Epigenetic changes in DNA methylation could regulate the expression of several allergy-related genes. We investigated whether tolerance acquisition in children with immunoglobulin E (IgE)-mediated cow's milk allergy (CMA) is characterized by a specific DNA methylation profile of Th2 (IL-4, IL-5) and Th1 (IL-10, IFN-γ)-associated cytokine genes.

RESULTS

DNA methylation of CpGs in the promoting regions of genes from peripheral blood mononuclear cells and serum level of IL-4, IL-5, IL-10 and INF-γ were assessed in children with active IgE-mediated CMA (group 1), in children who acquired tolerance to cow's milk proteins (group 2) and in healthy children (group 3). Forty children (24 boys, aged 3 to 18 months) were enrolled: 10 in group 1, 20 in group 2, and 10 in the control group. The DNA methylation profiles clearly separated active CMA patients from healthy controls. We observed an opposite pattern comparing subjects with active IgE-mediated CMA with healthy controls and group 2 children who outgrew CMA. The IL-4 and IL-5 DNA methylation was significantly lower, and IL-10 and INF-γ DNA methylation was higher in active IgE-mediated CMA patients. Gene promoter DNA methylation rates of all cytokines and respective serum levels were strongly correlated. Formula selection significantly influenced cytokine DNA methylation profiles in group 2.

CONCLUSIONS

Tolerance acquisition in children with IgE-mediated CMA is characterized by a distinct Th1 and Th2 cytokine gene DNA methylation pattern. These results suggest that DNA methylation may be a target for CMA prevention and treatment.

Histone lysine methyltransferase Ezh1 promotes TLR-triggered inflammatory cytokine production by suppressing Tollip

Histone modifications play critical roles in the regulation of gene expression; however, their roles in the regulation of the innate response remain to be fully investigated. Using transcriptome analysis of mouse immature dendritic cells (DCs) and LPS-induced mature DCs, we identified that Ezh1 was the most upregulated histone methyltransferase during DC maturation. In this study, we investigated the role of Ezh1 in regulating the innate immune response. We found that silencing of Ezh1 significantly suppressed TLR-triggered production of cytokines, including IL-6, TNF-α, and IFN-β, in DCs and macrophages. Accordingly, TLR-activated signaling pathways were impaired in Ezh1-silenced macrophages. By transcriptome analysis of Ezh1-silenced macrophages, we found that Toll-interacting protein (Tollip), one well-known negative regulator of TLR signaling, was upregulated. Silencing of Tollip rescued TLR-triggered cytokine production in Ezh1-silenced macrophages. The SET domain of Ezh1 is essential for its enhancing effect on the TLR-triggered innate immune response and downstream signaling, indicating that Ezh1 promotes a TLR-triggered innate response through its lysine methyltransferase activity. Finally, Ezh1 was found to suppress the transcription of Tollip by directly targeting the proximal promoter of tollip and maintaining the high level of trimethylation of histone H3 lysine 27 there. Therefore, Ezh1 promotes TLR-triggered inflammatory cytokine production by suppressing the TLR negative regulator Tollip, contributing to full activation of the innate immune response against invading pathogens.

An update on epigenetics and childhood respiratory diseases

Epigenetic mechanisms, defined as changes in phenotype or gene expression caused by mechanisms other than changes in the underlying DNA sequence, have been proposed to constitute a link between genetic and environmental factors that affect complex diseases. Recent studies show that DNA methylation, one of the key epigenetic mechanisms, is altered in children exposed to air pollutants and environmental tobacco smoke early in life. Several candidate gene studies on epigenetics have been published to date, but it is only recently that global methylation analyses have been performed for respiratory disorders such as asthma and chronic obstructive pulmonary disease. However, large-scale studies with adequate power are yet to be presented in children, and implications for clinical use remain to be evaluated. In this review, we summarize the recent advances in epigenetics and respiratory disorders in children, with a main focus on methodological challenges and analyses related to phenotype and exposure using global methylation approaches.