Combined inhaled diesel exhaust particles and allergen exposure alter methylation of T helper genes and IgE production in vivo

Childbirth and consequent atopic disease: emerging evidence on epigenetic effects based on the hygiene and EPIIC hypotheses

BACKGROUND

In most high and middle income countries across the world, at least 1:4 women give birth by cesarean section. Rates of labour induction and augmentation are rising steeply; and in some countries up to 50% of laboring women and newborns are given antibiotics. Governments and international agencies are increasingly concerned about the clinical, economic and psychosocial effects of these interventions.

DISCUSSION

There is emerging evidence that certain intrapartum and early neonatal interventions might affect the neonatal immune response in the longer term, and perhaps trans-generationally. Two theories lead the debate in this area. Those aligned with the hygiene (or 'Old Friends') hypothesis have examined the effect of gut microbiome colonization secondary to mode of birth and intrapartum/neonatal pharmacological interventions on immune response and epigenetic phenomena. Those working with the EPIIC (Epigenetic Impact of Childbirth) hypothesis are concerned with the effects of eustress and dys-stress on the epigenome, secondary to mode of birth and labour interventions. This paper examines the current and emerging findings relating to childbirth and atopic/autoimmune disease from the perspective of both theories, and proposes an alliance of research effort. This is likely to accelerate the discovery of important findings arising from both approaches, and to maximize the timely understanding of the longer-term consequences of childbirth practices.

A Longitudinal Study of Association between Heavy Metals and Itchy Eyes, Coughing in Chronic Cough Patients: Related with Non-Immunoglobulin E Mediated Mechanism

The association between heavy metals exposure and respiratory diseases or allergic sensitization showing high serum immunoglobulin E (IgE) has been suggested. However, previous findings have been inconsistent and the mechanisms responsible remain unclear. We evaluated heavy metal exposure and its association with coughing, itchy eyes in chronic cough patients with different IgE levels. Ninety outpatients in Kanazawa University Hospital were recruited between January-June 2011. Subjects whose total IgE measured by radioimmunosorbent test were asked to record their daily symptoms. We collected daily total suspended particles (TSP) from which concentrations of calcium (Ca), cadmium (Cd), chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), and lead (Pb) were determined then divided into high and low level groups. Generalized estimating equations were applied to compute the relationship between concentrations of these metals and symptoms. All metals at high levels were significantly associated with itchy eyes compared with low levels, with exception of Ca, the six others were significant in patients with IgE < 250 IU/mL. Cd, Fe, Mn had association with coughing (odds ratio-OR (95% confidence interval-CI): 1.13 (1.03, 1.24), 1.22 (1.05, 1.42), and 1.13 (1.01, 1.27), respectively), this relationship remained significant for Cd (OR (95% CI): 1.14 (1.03, 1.27)) and Mn (OR (95% CI): 1.15 (1.00, 1.31)) in patients with lower IgE. Our findings demonstrate the relationship between aerial heavy metals and itchy eyes, coughing in chronic cough patients, suggesting these symptoms may be due to a non-IgE mediated mechanism.

I feel you-monitoring environmental variables related to asthma in an integrated real-time frame

The study of asthma and other complex diseases has proven to be a "moving target" for researchers due to its complex aetiology, difficulty in definition, and immeasurable environmental effects. A large number of studies regarding the contribution of both genetic and environmental factors often result in contradictory results, in part due to the highly heterogeneous nature of asthma. Recent literature has focused on the epigenetic signatures of asthma caused by environmental factors, highlighting the importance of environment. However, unlike the genetic techniques, environmental assessment still lacks accuracy. A plausible solution for this problem would be an individual-based environmental exposure assessment, relying on new technologies such as personal real-time environmental sensors. This could prove to enable the assessment of the whole environmental exposure-or exposome-matching in terms of precision the genome that is emphasized in most studies so far. In addition, the measurement of the whole array of biological molecules, in response to the environment action, could help understand the context of the disease. The current perspective comprises a beyond-genetics integrated vision of omics technology coupled with real-time environmental measures targeting to enhance our comprehension of the disease genesis.

Dietary Elimination of Soybean Components Enhances Allergic Immune Response to Peanuts in BALB/c Mice

BACKGROUND

Food allergy research is hampered by a lack of animal models that consistently mimic human food allergic responses. Laboratory mice are generally fed grain-based chow made with large amounts of soybeans rich in immunomodulatory isoflavones. We tested the role of dietary soy components in the induction of food allergic responses in the BALB/c mouse strain, which is known to be resistant to anaphylaxis when orally challenged by food allergens.

METHODS

Mice were fed a soy-free diet for 2 generations. After weaning, mice were maintained on the same diet or fed a diet containing soy isoflavones, i.e. genistein and daidzein, followed by weekly oral sensitizations with crude peanut extract plus cholera toxin and finally challenged at week 7. The anaphylactic symptoms, body temperature, peanut-specific antibodies and mast cell degranulation were assessed.

RESULTS

Soy-free diet mice showed significantly higher anaphylactic symptom scores and mast cell degranulation after challenge and higher peanut-specific antibody levels than mice fed regular chow. Introduction of a regular soy diet or an isoflavone diet to soy-free diet mice significantly suppressed the allergic reactions compared to the soy-free diet.

CONCLUSION

Rodent diet is an important variable and needs to be taken into consideration when designing experiments involving animal models. Our results indicate that elimination of soy components from the diet enhances peanut sensitization in BALB/c mice. In addition to serving as a valuable tool to mimic human food allergy, the dietary influence on the immune response could have far-reaching consequences in research involving animal models.

Epigenetic mechanisms in nanomaterial-induced toxicity

With the growing advent of nanotechnology in medicine (therapeutic, diagnostic and imaging applications), cosmetics, electronics, clothing and food industries, exposure to nanomaterials (NMs) is on the rise and therefore exploring their toxic biological effects have gained great significance. In vitro and in vivo studies over the last decade have revealed that NMs have the potential to cause cytotoxicity and genotoxicity although some contradictory reports exist. However, there are only few studies which have explored the epigenetic mechanisms (changes to DNA methylation, histone modification and miRNA expression) of NM-induced toxicity, and there is a scarcity of information and many questions in this area remain unexplored and unaddressed. This review comprehensively describes the epigenetic mechanisms involved in the induction of toxicity of engineered NMs, and provides comparisons between similar effects observed upon exposure to small or nanometer-sized particles. Lastly, gaps in existing literature and scope for future studies that improve our understanding of NM-induced epigenetic toxicity are discussed.

Effect of Traffic-Related Air Pollution on Allergic Disease: Results of the Children's Health and Environmental Research

Purpose

This study evaluated the relationship of living near to main roads to allergic diseases, airway hyperresponsiveness (AHR), allergic sensitization, and lung function in Korean children.

Methods

A total of 5,443 children aged 6-14 years from 33 elementary schools in 10 cities during 2005-2006 were included in a baseline survey of the Children's Health and Environmental Research. We assessed association of traffic-related air pollution (TAP) exposure with the distance to the nearest main road, total road length of main roads and the proportion of the main road area within the 200-m home area.

Results

Positive exposure-response relationships were found between the length of the main road within the 200-m home area and lifetime wheeze (adjusted prevalence ratio [PR] for comparison of the longest to the shortest length categories=1.24; 95% CIs, 1.04-1.47; P for trend=0.022) and diagnosed asthma (PR=1.42; 95% CIs, 1.08-1.86; P for trend=0.011). Living less than 75 m from the main road was significantly associated with lifetime allergic rhinitis (AR), past-year AR symptoms, diagnosed AR, and treated AR. The distance to the main road (P for trend=0.001), the length of the main road (P for trend=0.041), and the proportion of the main road area (P for trend=0.006) had an exposure-response relationship with allergic sensitization. A strong inverse association was observed between residential proximity to the main load and lung function, especially FEV1, FEV1/FVC, and FEF_25-75. The length of the main road and the proportion of the main road area were associated with reduced FEV1 in schoolchildren.

Conclusions

The results of this study suggest that exposure to traffic-related air pollution may be associated with increased risk of asthma, AR, and allergic sensitization, and with reduced lung function in schoolchildren.

Cohort Profile: Swedish Twin Study on Prediction and Prevention of Asthma (STOPPA)

Asthma is a common childhood disease and several risk factors have been identified; however, the impact of genes and environment is not fully understood. The aim of the Swedish Twin study On Prediction and Prevention of Asthma (STOPPA) is to identify environmental (birth characteristics and early life) and genetic (including epigenetic) factors as determinants for asthmatic disease. Based on the Child and Adolescent Twin Study in Sweden (CATSS) (parental interview at 9 or 12 years, N ~23,900) and an asthma and/or wheezing algorithm, we identified a sample of monozygotic (MZ) and dizygotic (DZ) same-sexed twin pairs. The twin pairs were classified as asthma concordant (ACC), asthma discordant (ADC) and healthy concordant (HCC). A sample of 9- to 14-year-old twins and their parents were invited to participate in a clinical examination. Background characteristics were collected in questionnaires and obtained from the National Health Registers. A clinical examination was performed to test lung function and capacity (spirometry with reversibility test and exhaled nitric oxide) and collect blood (serology and DNA), urine (metabolites), feces (microbiota), and saliva (cortisol). In total, 376 twin pairs (752 individual twins) completed the study, response rate 52%. All participating twins answered the questionnaire and >90% participated in lung function testing, blood-, and saliva sampling. This article describes the design, recruitment, data collection, measures, and background characteristics, as well as ongoing and planned analyses in STOPPA. Potential gains of the study include the identification of biomarkers, the emergence of candidates for drug development, and new leads for prevention of asthma and allergic disease.

Evaluating the effect of ambient particulate pollution on DNA methylation in Alaskan sled dogs: potential applications for a sentinel model of human health

BACKGROUND

Exposure to ambient particulate matter (PM) is known to be associated with increased morbidity and mortality in human populations. During the winter months in Fairbanks, Alaska, severe temperature inversions lead to elevated concentrations of ambient PM smaller than 2.5 μm (PM2.5). Sled dogs represent an easily accessible environmentally exposed population that may yield findings informative for human health risk assessment.

OBJECTIVES

In this pilot study, we evaluated whether ambient PM was associated with markers of global methylation in sled dogs.

METHODS

Kennels were strategically recruited to provide a wide PM2.5 exposure gradient for the Fairbanks area. Continuous monitoring of ambient PM2.5 was conducted at each kennel during the winter of 2012/13 using a DustTrak 8530. Dogs received a physical examination and assessment of standard hematology and clinical chemistries. Global methylation was determined using the LUminometric Methylation Assay (LUMA) and 5-Methycytosine (5-mC) quantification.

RESULTS

Three sled dog kennels (n~30 dogs/kennel) were evaluated and sampled. The average PM2.5 concentrations measured for kennels A, B, and C were 90 μg/m(3), 48 μg/m(3), 16 μg/m(3) (p<0.0001), respectively. The average (standard deviation) global methylation percentage for each kennel measured by LUMA was 76.22 (1.85), 76.52 (1.82), and 76.72 (2.26), respectively. The average (standard deviation) global methylation percentage for each kennel measured by 5-mC was 0.16 (0.04), 0.15 (0.04), and 0.15 (0.05), respectively. There was no statistically significant difference between the three kennels and their average global methylation percentage either by LUMA or 5-mC.

CONCLUSIONS

In this study we evaluated global methylation using LUMA and 5-mC and found no differences between kennels, though exposure to ambient PM2.5 was significantly different between kennels. As more information becomes available regarding immunologically-related canine genes and functionally active promoter subunits, the utility of this surrogate could increase.

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.

Update on epigenetics in allergic disease

Chronic inflammatory diseases, including allergies and asthma, are the result of complex gene-environment interactions. One of the most challenging questions in this regard relates to the biochemical mechanism of how exogenous environmental trigger factors modulate and modify gene expression, subsequently leading to the development of chronic inflammatory conditions. Epigenetics comprises the umbrella of biochemical reactions and mechanisms, such as DNA methylation and chromatin modifications on histones and other structures. Recently, several lifestyle and environmental factors have been investigated in terms of such biochemical interactions with the gene expression-regulating machinery: allergens; microbes and microbial compounds; dietary factors, including vitamin B12, folic acid, and fish oil; obesity; and stress. This article aims to update recent developments in this context with an emphasis on allergy and asthma research.

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.

Environmental effects on immune responses in patients with atopy and asthma

Despite attempts and some successes to improve air quality over the decades, current US national trends suggest that exposure to outdoor and indoor air pollution remains a significant risk factor for both the development of asthma and the triggering of asthma symptoms. Emerging science also suggests that environmental exposures during the prenatal period and early childhood years increase the risk of asthma. Multiple mechanisms mediate this risk because a wide range of deleterious air pollutants contribute to the pathogenesis of asthma across a variety of complex asthma phenotypes. In this review we will consider the role of altered innate and adaptive immune responses, gene-environment interactions, epigenetic regulation, and possibly gene-environment-epigene interactions. Gaining a greater understanding of the mechanisms that underlie the effect of exposure to air pollution on asthma, allergies, and other airway diseases can identify targets for therapy. Such interventions will include pollutant source reduction among those most exposed and most vulnerable and novel pharmaceutical strategies to reduce asthma morbidity.

Maternal allergy increases susceptibility to offspring allergy in association with TH2-biased epigenetic alterations in a mouse model of peanut allergy

BACKGROUND

Although maternal atopy is a risk factor for the development of peanut allergy, this phenomenon has not been well characterized experimentally, and the mechanisms underlying offspring risk are unclear.

OBJECTIVE

We sought to determine whether offspring of mothers with peanut allergy (O-PAM mice) are more susceptible to peanut allergy than offspring of naive mothers (O-NM mice) in a murine model and, if so, whether the susceptibility is linked to TH2-biased epigenetic alterations.

METHODS

Five-week-old O-PAM and O-NM mice were intragastrically sensitized to and challenged with peanut. Serum peanut-specific IgE levels, plasma histamine levels, anaphylactic reactions, and splenocyte and MLN cell cytokine production were measured. DNA methylation levels of the Il4 gene promoter from splenocytes and MLN cells from sensitized offspring and splenocytes from unsensitized neonatal offspring were determined by means of pyrosequencing.

RESULTS

O-PAM mice exhibited 3-fold higher peanut-specific IgE levels after peanut sensitization, as well as 5-fold higher histamine levels and significantly higher anaphylactic symptom scores after challenge than O-NM mice (P < .05-.01). Cultured splenocytes and MLNs from O-PAM mice produced significantly more TH2 cytokines than cells from O-NM mice (P < .05-.01). Cells from O-PAM mice exhibited significantly reduced DNA methylation at CpG sites of the Il4 gene promoter than cells from O-NM mice. DNA methylation levels were inversely correlated with IL-4 and IgE production. O-PAM neonatal splenocyte hypomethylation of the Il4 gene promoter was also present.

CONCLUSION

This study is the first to demonstrate that increased susceptibility to peanut allergy in O-PAM mice is associated with epigenetic alteration of the Il4 gene promoter. This finding might provide insight into preventing the development of early-life allergy.

Asthma in inner-city children at 5-11 years of age and prenatal exposure to phthalates: the Columbia Center for Children's Environmental Health Cohort

BACKGROUND

Studies suggest that phthalate exposures may adversely affect child respiratory health.

OBJECTIVES

We evaluated associations between asthma diagnosed in children between 5 and 11 years of age and prenatal exposures to butylbenzyl phthalate (BBzP), di-n-butyl phthalate (DnBP), di(2-ethylhexyl) phthalate (DEHP), and diethyl phthalate (DEP).

METHODS

Phthalate metabolites were measured in spot urine collected from 300 pregnant inner-city women. Children were examined by an allergist or pulmonologist based on the first parental report of wheeze, other respiratory symptoms, and/or use of asthma rescue/controller medication in the preceding 12 months on repeat follow-up questionnaires. Standardized diagnostic criteria were used to classify these children as either having or not having current asthma at the time of the physician examination. Children without any report of wheeze or the other asthma-like symptoms were classified as nonasthmatics at the time of the last negative questionnaire. Modified Poisson regression analyses were used to estimate relative risks (RR) controlling for specific gravity and potential confounders.

RESULTS

Of 300 children, 154 (51%) were examined by a physician because of reports of wheeze, other asthma-like symptoms, and/or medication use; 94 were diagnosed with current asthma and 60 without current asthma. The remaining 146 children were classified as nonasthmatic. Compared with levels in nonasthmatics, prenatal metabolites of BBzP and DnBP were associated with a history of asthma-like symptoms (p < 0.05) and with the diagnosis of current asthma: RR = 1.17 (95% CI: 1.01, 1.35) and RR = 1.25 (95% CI: 1.04, 1.51) per natural log-unit increase, respectively. Risk of current asthma was > 70% higher among children with maternal prenatal BBzP and DnBP metabolite concentrations in the third versus the first tertile.

CONCLUSION

Prenatal exposure to BBzP and DnBP may increase the risk of asthma among inner-city children. However, because this is the first such finding, results require replication.

Molecular biology of atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with specific genetic and immunological mechanisms. The rapid development of new techniques in molecular biology had ushered in new discoveries on the role of cytokines, chemokines, and immune cells in the pathogenesis of AD. New polymorphisms of AD are continually being reported in different populations. The physical and immunological barrier of normal intact skin is an important part of the innate immune system that protects the host against microbials and allergens that are associated with AD. Defects in the filaggrin gene FLG may play a role in facilitating exposure to allergens and microbial pathogens, which may induce Th2 polarization. Meanwhile, Th22 cells also play roles in skin barrier impairment through IL-22, and AD is often considered to be a Th2/Th22-dominant allergic disease. Mast cells and eosinophils are also involved in the inflammation via Th2 cytokines. Release of pruritogenic substances by mast cells induces scratching that further disrupts the skin barrier. Th1 and Th17 cells are mainly involved in chronic phase of AD. Keratinocytes also produce proinflammatory cytokines such as thymic stromal lymphopoietin (TSLP), which can further affect Th cells balance. The immunological characteristics of AD may differ for various endotypes and phenotypes. Due to the heterogeneity of the disease, and the redundancies of these mechanisms, our knowledge of the pathophysiology of the disease is still incomplete, which is reflected by the absence of a cure for the disease.

Promoter demethylation contributes to TSLP overexpression in skin lesions of patients with atopic dermatitis

BACKGROUND

Thymic stromal lymphopoietin (TSLP) plays an important role in promoting T-cell homeostasis, and appears to be a central player in the development of allergic symptoms, especially in asthma and atopic dermatitis (AD). Human TSLP is overexpressed in keratinocytes of patients with acute and chronic AD. However, the mechanism of TSLP overexpression remains unclear.

AIM

To investigate whether TSLP expression is regulated by aberrant DNA methylation modification of the TSLP promoter in keratinocytes of patients with AD.

METHODS

mRNA and protein levels of TSLP in lesional skin samples from 10 children with AD and 10 healthy controls were measured by real-time quantitative reverse transcriptase-PCR and immunohistochemistry. Bisulfite sequencing was performed to determine the methylation status of the TSLP promoter, and 5-azacytidine (5-aza), a DNA methyltransferase inhibitor, was used to determine the influence of DNA methylation on TSLP expression.

RESULTS

TSLP mRNA and protein expression levels were increased in skin lesions from patients with AD compared with healthy controls. Moreover, promoter hypomethylation of the TSLP gene was identified in skin lesions from patients with AD, and treating keratinocytes with 5-aza reduced the methylation level of the TSLP promoter and increased TSLP transcription.

CONCLUSIONS

DNA demethylation of a specific regulatory region of the TSLP gene may contribute to TSLP overexpression in skin lesions in patients with AD.

Perspective: ambient air pollution: inflammatory response and effects on the lung's vasculature

Particulates from air pollution are implicated in causing or exacerbating respiratory and systemic cardiovascular diseases and are thought to be among the leading causes of morbidity and mortality. However, the contribution of ambient particulate matter to diseases affecting the pulmonary circulation, the right heart, and especially pulmonary hypertension is much less documented. Our own work and that of other groups has demonstrated that prolonged exposure to antigens via the airways can cause severe pulmonary arterial remodeling. In addition, vascular changes have been well documented in a typical disease of the airways, asthma. These experimental and clinical findings link responses in the airways with responses in the lung's vasculature. It follows that particulate air pollution could cause, or exacerbate, diseases in the pulmonary circulation and associated pulmonary hypertension. This perspective details the literature for support of this concept. Data regarding the health effects of particulate matter from air pollution on the lung's vasculature, with emphasis on the lung's inflammatory responses to particulate matter deposition and pulmonary hypertension, are discussed. A deeper understanding of the health implications of exposure to ambient particulate matter will improve our knowledge of how to improve the management of lung diseases, including diseases of the pulmonary circulation. As man-made ambient particulate air pollution is typically linked to economic growth, a better understanding of the health effects of exposure to particulate air pollution is expected to integrate the global goal of achieving healthy living for all.

Environmental changes, microbiota, and allergic diseases

During the last few decades, the prevalence of allergic disease has increased dramatically. The development of allergic diseases has been attributed to complex interactions between environmental factors and genetic factors. Of the many possible environmental factors, most research has focused on the most commonly encountered environmental factors, such as air pollution and environmental microbiota in combination with climate change. There is increasing evidence that such environmental factors play a critical role in the regulation of the immune response that is associated with allergic diseases, especially in genetically susceptible individuals. This review deals with not only these environmental factors and genetic factors but also their interactions in the development of allergic diseases. It will also emphasize the need for early interventions that can prevent the development of allergic diseases in susceptible populations and how these interventions can be identified.

Synergistic effects induced by a low dose of diesel particulate extract and ultraviolet-A in Caenorhabditis elegans: DNA damage-triggered germ cell apoptosis

Diesel exhaust has been classified as a potential carcinogen and is associated with various health effects. A previous study showed that the doses for manifesting the mutagenetic effects of diesel exhaust could be reduced when coexposed with ultraviolet-A (UVA) in a cellular system. However, the mechanisms underlying synergistic effects remain to be clarified, especially in an in vivo system. In the present study, using Caenorhabditis elegans (C. elegans) as an in vivo system we studied the synergistic effects of diesel particulate extract (DPE) plus UVA, and the underlying mechanisms were dissected genetically using related mutants. Our results demonstrated that though coexposure of wild type worms at young adult stage to low doses of DPE (20 μg/mL) plus UVA (0.2, 0.5, and 1.0 J/cm2) did not affect worm development (mitotic germ cells and brood size), it resulted in a significant induction of germ cell death. Using the strain of hus-1::gfp, distinct foci of HUS-1::GFP was observed in proliferating germ cells, indicating the DNA damage after worms were treated with DPE plus UVA. Moreover, the induction of germ cell death by DPE plus UVA was alleviated in single-gene loss-of-function mutations of core apoptotic, checkpoint HUS-1, CEP-1/p53, and MAPK dependent signaling pathways. Using a reactive oxygen species (ROS) probe, it was found that the production of ROS in worms coexposed to DPE plus UVA increased in a time-dependent manner. In addition, employing a singlet oxygen (1O2) trapping probe, 2,2,6,6-tetramethyl-4-piperidone, coupled with electron spin resonance analysis, we demonstrated the increased 1O2 production in worms coexposed to DPE plus UVA. These results indicated that UVA could enhance the apoptotic induction of DPE at low doses through a DNA damage-triggered pathway and that the production of ROS, especially (1)O2, played a pivotal role in initiating the synergistic process.

cFLIP expression is altered in severe corticosteroid-resistant asthma

Dysregulation of alternative splicing of mRNA precursors is known to contribute to numerous human diseases. In this study we carried out the first systematic search for asthma-associated changes in alternative splicing events, using a model of Aspergillus fumigatus (A. fumigatus)-sensitized mice and an exon junction microarray to detect potential changes in alternative splicing. One of the sensitization-associated changes identified in the search was a shift in alternative splicing of the mRNA encoding cFLIP, a modulator of the caspase-mediated extrinsic apoptosis pathway. Expanding these studies to human asthma patients, we discovered a significant decrease in the expression of both cFLIP isoforms in severe corticosteroid-resistant asthmatics. Although it is unclear whether these changes were due solely to differences in alternative splicing, these findings provide evidence that dysregulation of the extrinsic apoptosis pathway is part of the underlying immunopathogenesis of severe refractory asthma.

DNA methylation of the allergy regulatory gene interferon gamma varies by age, sex, and tissue type in asthmatics

Background

Asthma is associated with allergic sensitization in about half of all cases, and asthma phenotypes can vary by age and sex. DNA methylation in the promoter of the allergy regulatory gene interferon gamma (IFNγ) has been linked to the maintenance of allergic immune function in human cell and mouse models. We hypothesized that IFNγ promoter methylation at two well-studied, key cytosine phosphate guanine (CpG) sites (-186 and -54), may differ by age, sex, and airway versus systemic tissue in a cohort of 74 allergic asthmatics.

Results

After sampling buccal cells, a surrogate for airway epithelial cells, and CD4+ lymphocytes, we found that CD4+ lymphocyte methylation was significantly higher in children compared to adults at both CpG sites (P <0.01). Buccal cell methylation was significantly higher in children at CpG -186 (P = 0.03) but not CpG -54 (P = 0.66). Methylation was higher in males compared to females at both CpG sites in CD4+ lymphocytes (-186: P <0.01, -54: P = 0.02) but not buccal cells (-186: P = 0.14, -54: P = 0.60). In addition, methylation was lower in CD4+ lymphocytes compared to buccal cells (P <0.01) and neighboring CpG sites were strongly correlated in CD4+ lymphocytes (r = 0.84, P <0.01) and weakly correlated in buccal cells (r = 0.24, P = 0.04). At CpG -186, there was significant correlation between CD4+ lymphocytes and buccal cells (r = 0.24, P = 0.04) but not at CpG -54 (r = -0.03, P = 0.78).

Conclusions

These findings highlight significant age, sex, and tissue-related differences in IFNγ promoter methylation that further our understanding of methylation in the allergic asthma pathway and in the application of biomarkers in clinical research.

Air toxics and epigenetic effects: ozone altered microRNAs in the sputum of human subjects

Ozone (O3) is a criteria air pollutant that is associated with numerous adverse health effects, including altered respiratory immune responses. Despite its deleterious health effects, possible epigenetic mechanisms underlying O3-induced health effects remain understudied. MicroRNAs (miRNAs) are epigenetic regulators of genomic response to environmental insults and unstudied in relationship to O3 inhalation exposure. Our objective was to test whether O3 inhalation exposure significantly alters miRNA expression profiles within the human bronchial airways. Twenty healthy adult human volunteers were exposed to 0.4 ppm O3 for 2 h. Induced sputum samples were collected from each subject 48 h preexposure and 6 h postexposure for evaluation of miRNA expression and markers of inflammation in the airways. Genomewide miRNA expression profiles were evaluated by microarray analysis, and in silico predicted mRNA targets of the O3-responsive miRNAs were identified and validated against previously measured O3-induced changes in mRNA targets. Biological network analysis was performed on the O3-associated miRNAs and mRNA targets to reveal potential associated response signaling and functional enrichment. Expression analysis of the sputum samples revealed that O3 exposure significantly increased the expression levels of 10 miRNAs, namely miR-132, miR-143, miR-145, miR-199a*, miR-199b-5p, miR-222, miR-223, miR-25, miR-424, and miR-582-5p. The miRNAs and their predicted targets were associated with a diverse range of biological functions and disease signatures, noted among them inflammation and immune-related disease. The present study shows that O3 inhalation exposure disrupts select miRNA expression profiles that are associated with inflammatory and immune response signaling. These findings provide novel insight into epigenetic regulation of responses to O3 exposure.

Alterations of the lung methylome in allergic airway hyper-responsiveness

Asthma is a chronic airway disorder characterized by recurrent attacks of breathlessness and wheezing, affecting 300 million people around the world (available at: www.who.int). To date, genetic factors associated with asthma susceptibility have been unable to explain the full etiology of asthma. Recent studies have demonstrated that the epigenetic disruption of gene expression plays an equally important role in the development of asthma through interaction with our environment. We sensitized 6-week-old C57BL/6J mice with house-dust-mite (HDM) extracts intraperitoneally followed by 5 weeks of exposure to HDM challenges (three times a week) intratracheally. HDM-exposed mice showed an increase in airway hyper-responsiveness (AHR) and inflammation together with structural remodeling of the airways. We applied methylated DNA immunoprecipitation-next generation sequencing (MeDIP-seq) for profiling of DNA methylation changes in the lungs in response to HDM. We observed about 20 million reads by a single-run of massive parallel sequencing. We performed bioinformatics and pathway analysis on the raw sequencing data to identify differentially methylated candidate genes in HDM-exposed mice. Specifically, we have revealed that the transforming growth factor beta signaling pathway is epigenetically modulated by chronic exposure to HDM. Here, we demonstrated that a specific allergen may play a role in AHR through an epigenetic mechanism by disrupting the expression of genes in lungs that might be involved in airway inflammation and remodeling. Our findings provide new insights into the potential mechanisms by which environmental allergens induce allergic asthma and such insights may assist in the development of novel preventive and therapeutic options for this debilitative disease.

Epigenetic regulation: the interface between prenatal and early-life exposure and asthma susceptibility

Asthma is a complex disease with genetic and environmental influences and emerging evidence suggests that epigenetic regulation is also a major contributor. Here, we focus on the developing paradigm that epigenetic dysregulation in asthma and allergy may start as early as in utero following several environmental exposures. We summarize the pathways important to the allergic immune response that are epigenetically regulated, the key environmental exposures associated with epigenetic changes in asthma genes, and newly identified epigenetic biomarkers that have been linked to clinical asthma. We conclude with a brief discussion about the potential to apply newly developing technologies in epigenetics to the diagnosis and treatment of asthma and allergy. The inherent plasticity of epigenetic regulation following environmental exposures offers opportunities for prevention using environmental remediation, measuring novel biomarkers for early identification of those at risk, and applying advances in pharmaco-epigenetics to tailor medical therapies that maximize efficacy of treatment. 'Precision Medicine' in asthma and allergy is arriving. As the field advances this may involve an individually tailored approach to the prevention, early detection, and treatment of disease based on the knowledge of an individual's epigenetic profile.

Epigenetic changes in inflammatory and autoimmune diseases

In higher eukaryotic organisms epigenetic modifications are crucial for proper chromatin folding and thereby proper regulation of gene expression. In the last years the involvement of aberrant epigenetic modifications in inflammatory and autoimmune diseases has been recognized and attracted significant interest. However, the epigenetic mechanisms underlying the different disease phenotypes are still poorly understood. As autoimmune and inflammatory diseases are at least partly T cell mediated, we will provide in this chapter an introduction to the epigenetics of T cell differentiation followed by a summary of the current knowledge on aberrant epigenetic modifications that dysfunctional T cells display in various diseases such as type 1 diabetes, rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, inflammatory bowel disease, and asthma.

Associations between inflammatory and immune response genes and adverse respiratory outcomes following exposure to outdoor air pollution: a HuGE systematic review

Variants of inflammatory and immune response genes have been associated with adverse respiratory outcomes following exposure to air pollution. However, the genes involved and their associations are not well characterized, and there has been no systematic review. Thus, we conducted a review following the guidelines of the Human Genome Epidemiology Network. Six observational studies and 2 intervention studies with 14,903 participants were included (2001-2010). Six studies showed at least 1 significant gene-pollutant interaction. Meta-analysis was not possible due to variations in genes, pollutants, exposure estimates, and reported outcomes. The most commonly studied genes were tumor necrosis factor α (TNFA) (n = 6) and toll-like receptor 4 (TLR4) (n = 3). TNFA -308G>A modified the action of ozone and nitrogen dioxide on lung function, asthma risk, and symptoms; however, the direction of association varied between studies. The TLR4 single-nucleotide polymorphisms rs1927911, rs10759931, and rs6478317 modified the association of particulate matter and nitrogen dioxide with asthma. The transforming growth factor β1 (TGFB1) polymorphism -509C>T also modified the association of pollutants with asthma. This review indicates that genes controlling innate immune recognition of foreign material (TLR4) and the subsequent inflammatory response (TGFB1, TLR4) modify the associations of exposure to air pollution with respiratory function. The associations observed have biological plausibility; however, larger studies with improved reporting are needed to confirm these findings.

Environmental epigenetics and its implication on disease risk and health outcomes

This review focuses on how environmental factors through epigenetics modify disease risk and health outcomes. Major epigenetic events, such as histone modifications, DNA methylation, and microRNA expression, are described. The function of dose, duration, composition, and window of exposure in remodeling the individual's epigenetic terrain and disease susceptibility are addressed. The ideas of lifelong editing of early-life epigenetic memories, transgenerational effects through germline transmission, and the potential role of hydroxylmethylation of cytosine in developmental reprogramming are discussed. Finally, the epigenetic effects of several major classes of environmental factors are reviewed in the context of pathogenesis of disease. These include endocrine disruptors, tobacco smoke, polycyclic aromatic hydrocarbons, infectious pathogens, particulate matter, diesel exhaust particles, dust mites, fungi, heavy metals, and other indoor and outdoor pollutants. We conclude that the summation of epigenetic modifications induced by multiple environmental exposures, accumulated over time, represented as broad or narrow, acute or chronic, developmental or lifelong, may provide a more precise assessment of risk and consequences. Future investigations may focus on their use as readouts or biomarkers of the totality of past exposure for the prediction of future disease risk and the prescription of effective countermeasures.

Epigenetic alterations by DNA methylation in house dust mite-induced airway hyperresponsiveness

Asthma is one of the most prevalent chronic lung diseases, affecting 235 million individuals around the world, with its related morbidity and mortality increasing steadily over the last 20 years. Exposure to the environmental allergen, house dust mite (HDM), results in airway inflammation with a variable degree of airway obstruction. Although there has been much experimental work in the past using HDM challenge models to understand mechanistic details in allergic inflammation and airway hyperresponsiveness (AHR), there has been no study on reprogramming of lung or airways mediated through epigenetic mechanisms in response to an acute HDM exposure. Male mice, 6 weeks of age, were administrated HDM extracts or saline at Days 1, 14, and 21. Exposure of mice to HDM extracts caused significant airway inflammation and increased AHR. These HDM-challenged mice also exhibited a change in global DNA methylation as compared with saline-exposed (control) mice. Next, by employing methylation-sensitive restriction fingerprinting, we identified a set of genes, showing aberrant methylation status, associated with the HDM-induced AHR. These candidate genes are known to be involved in cAMP signaling (pde4 d), Akt-signaling (akt1 s1), ion transport (tm6 sf1, pom121l2, and slc8a3), and fatty acid metabolism (acsl3). Slc8a3 and acsl3 were down-regulated, whereas pde4 d, akt1 s1, tm6 sf1, and pom121l2 were up-regulated in the mice exposed to HDM. Hence, our results suggest that HDM exposure induces a series of aberrant methylated genes that are potentially important for the development of allergic AHR.

Allergic diseases and air pollution

The prevalence of allergic diseases has been increasing rapidly, especially in developing countries. Various adverse health outcomes such as allergic disease can be attributed to rapidly increasing air pollution levels. Rapid urbanization and increased energy consumption worldwide have exposed the human body to not only increased quantities of ambient air pollution, but also a greater variety of pollutants. Many studies clearly demonstrate that air pollutants potently trigger asthma exacerbation. Evidence that transportation-related pollutants contribute to the development of allergies is also emerging. Moreover, exposure to particulate matter, ozone, and nitrogen dioxide contributes to the increased susceptibility to respiratory infections. This article focuses on the current understanding of the detrimental effects of air pollutants on allergic disease including exacerbation to the development of asthma, allergic rhinitis, and eczema as well as epigenetic regulation.

Maternal exposure to combustion generated PM inhibits pulmonary Th1 maturation and concomitantly enhances postnatal asthma development in offspring

BACKGROUND

Epidemiological studies suggest that maternal exposure to environmental hazards, such as particulate matter, is associated with increased incidence of asthma in childhood. We hypothesized that maternal exposure to combustion derived ultrafine particles containing persistent free radicals (MCP230) disrupts the development of the infant immune system and results in aberrant immune responses to allergens and enhances asthma severity.

METHODS

Pregnant C57/BL6 mice received MCP230 or saline by oropharyngeal aspiration on gestational days 10 and 17. Three days after the second administration, blood was collected from MCP230 or saline treated dams and 8-isoprostanes in the serum were measured to assess maternal oxidative stress. Pulmonary T cell populations were assayed in the infant mice at six days, three and six weeks of postnatal age. When the infant mice matured to adults (i.e. six weeks of age), an asthma model was established with ovalbumin (OVA). Airway inflammation, mucus production and airway hyperresponsiveness were then examined.

RESULTS

Maternal exposure to MCP230 induced systemic oxidative stress. The development of pulmonary T helper (Th1/Th2/Th17) and T regulatory (Treg) cells were inhibited in the infant offspring from MCP230-exposed dams. As the offspring matured, the development of Th2 and Treg cells recovered and eventually became equivalent to that of offspring from non-exposed dams. However, Th1 and Th17 cells remained attenuated through 6 weeks of age. Following OVA sensitization and challenge, mice from MCP230-exposed dams exhibited greater airway hyperresponsiveness, eosinophilia and pulmonary Th2 responses compared to offspring from non-exposed dams.

CONCLUSIONS

Our data suggest that maternal exposure to MCP230 enhances postnatal asthma development in mice, which might be related to the inhibition of pulmonary Th1 maturation and systemic oxidative stress in the dams.

A panel study of occupational exposure to fine particulate matter and changes in DNA methylation over a single workday and years worked in boilermaker welders

BACKGROUND

Exposure to pollutants including metals and particulate air pollution can alter DNA methylation. Yet little is known about intra-individual changes in DNA methylation over time in relationship to environmental exposures. Therefore, we evaluated the effects of acute- and chronic metal-rich PM2.5 exposures on DNA methylation.

METHODS

Thirty-eight male boilermaker welders participated in a panel study for a total of 54 person days. Whole blood was collected prior to any welding activities (pre-shift) and immediately after the exposure period (post-shift). The percentage of methylated cytosines (%mC) in LINE-1, Alu, and inducible nitric oxide synthase gene (iNOS) were quantified using pyrosequencing. Personal PM2.5 (particulate matter with an aerodynamic diameter ≤ 2.5 μm) was measured over the work-shift. A questionnaire assessed job history and years worked as a boilermaker. Linear mixed models with repeated measures evaluated associations between DNA methylation, PM2.5 concentration (acute exposure), and years worked as a boilermaker (chronic exposure).

RESULTS

PM2.5 exposure was associated with increased methylation in the promoter region of the iNOS gene (β = 0.25, SE: 0.11, p-value = 0.04). Additionally, the number of years worked as a boilermaker was associated with increased iNOS methylation (β = 0.03, SE: 0.01, p-value = 0.03). No associations were observed for Alu or LINE-1.

CONCLUSIONS

Acute and chronic exposure to PM2.5 generated from welding activities was associated with a modest change in DNA methylation of the iNOS gene. Future studies are needed to confirm this association and determine if the observed small increase in iNOS methylation are associated with changes in NO production or any adverse health effect.

Epigenetic changes associated with disease progression in a mouse model of childhood allergic asthma

Development of asthma in childhood is linked to viral infections of the lower respiratory tract in early life, with subsequent chronic exposure to allergens. Progression to persistent asthma is associated with a Th2-biased immunological response and structural remodelling of the airways. The underlying mechanisms are unclear, but could involve epigenetic changes. To investigate this, we employed a recently developed mouse model in which self-limited neonatal infection with a pneumovirus, followed by sensitisation to ovalbumin via the respiratory tract and low-level chronic challenge with aerosolised antigen, leads to development of an asthmatic phenotype. We assessed expression of microRNA by cells in the proximal airways, comparing changes over the period of disease progression, and used target prediction databases to identify genes likely to be up- or downregulated as a consequence of altered regulation of microRNA. In parallel, we assessed DNA methylation in pulmonary CD4(+) T cells. We found that a limited number of microRNAs exhibited marked up- or downregulation following early-life infection and sensitisation, for many of which the levels of expression were further changed following chronic challenge with the sensitizing antigen. Targets of these microRNAs included genes involved in immune or inflammatory responses (e.g. Gata3, Kitl) and in tissue remodelling (e.g. Igf1, Tgfbr1), as well as genes for various transcription factors and signalling proteins. In pulmonary CD4(+) T cells, there was significant demethylation at promoter sites for interleukin-4 and interferon-γ, the latter increasing following chronic challenge. We conclude that, in this model, progression to an asthmatic phenotype is linked to epigenetic regulation of genes associated with inflammation and structural remodelling, and with T-cell commitment to a Th2 immunological response. Epigenetic changes associated with this pattern of gene activation might play a role in the development of childhood asthma.

Progress in understanding the epigenetic basis for immune development, immune function, and the rising incidence of allergic disease

The profile of allergic disease worldwide continues to change as the number of severe IgE-mediated allergies increases. This phenomenon is thought to reflect the outcome of combined genetic/environmental/developmental/stochastic effects on immune development, but understanding this remains a challenge. Epigenetic disruption at key immune genes during development has been proposed as a potential explanation for how environmental exposures may alter immune cell development and function. This represents an emerging area of research with the potential to yield new understanding of how disease risk is modified. Here, we examine recent developments in this field that are defining new epigenetic paradigms of allergic disease.

Early-life cockroach allergen and polycyclic aromatic hydrocarbon exposures predict cockroach sensitization among inner-city children

BACKGROUND

Sensitization to cockroach is one of the strongest identified risk factors for greater asthma morbidity in low-income urban communities; however, the timing of exposures relevant to the development of sensitization has not been elucidated fully. Furthermore, exposure to combustion byproducts, including polycyclic aromatic hydrocarbons (PAHs), can augment the development of allergic sensitization.

OBJECTIVE

We sought to test the hypotheses that domestic cockroach allergen measured prenatally would predict cockroach sensitization in early childhood and that this association would be greater for children exposed to higher PAH concentrations.

METHODS

Dominican and African American pregnant women living in New York City were enrolled. In the third trimester expectant mothers wore personal air samplers for measurement of 8 nonvolatile PAHs and the semivolatile PAH pyrene, and dust was collected from homes for allergen measurement. Glutathione-S-transferase μ 1 (GSTM1) gene polymorphisms were measured in children. Allergen-specific IgE levels were measured from the children at ages 2, 3, 5, and 7 years.

RESULTS

Bla g 2 in prenatal kitchen dust predicted cockroach sensitization at the ages of 5 to 7 years (adjusted relative risk [RR], 1.15; P = .001; n = 349). The association was observed only among children with greater than (RR, 1.22; P = .001) but not less than (RR, 1.07; P = .24) the median sum of 8 nonvolatile PAH levels. The association was most pronounced among children with higher PAH levels and null for the GSTM1 gene (RR, 1.54; P = .001).

CONCLUSIONS

Prenatal exposure to cockroach allergen was associated with a greater risk of allergic sensitization. This risk was increased by exposure to nonvolatile PAHs, with children null for the GSTM1 mutation particularly vulnerable.

[Environmental pollution and allergy: immunological mechanisms]

Airborne pollutants, both particulate and gaseous, represent a major environmental factor promoting allergic sensitization and disease expression. These adverse effects of particulate matter are highly dependent upon the nature and size of the particles, their content of chemicals and metals, and the subject's genetic makeup. Diesel exhaust and gases, in particular ozone, have been shown to exacerbate cellular inflammation and to act as mucosal adjuvants to skew the immune response to inhaled antigens toward a Th2-like phenotype. Growing evidence suggests that mechanisms of pollutant-induced amplification of the allergic reaction depend on oxidative stress that is under the control of susceptibility genes, as well as epigenetic mechanisms.

Ultrafine particles in urban ambient air and their health perspectives

Ultrafine particles (UfPs, PM<0.1) are constituents of urban ambient air aerosol. We have reviewed literature on UfPs in urban ambient air and their health perspectives. Generally traffic-linked and of anthropogenic origin, these are toxicants and a health risk factor for urban subjects. UfPs occur in single and agglomerate forms. Studies on the number concentrations of UfPs show tens of thousand times greater levels in urban aerosol than in nonurban aerosol. These nanosize pollutants seem to have more aggressive implications than other respirable fractions of urban aerosol. In literature, it is hypothesized that a chronic exposure to their high number concentrations and their vast surface area, transporting various toxicants, injure tissues or cells and induce inflammation or, eventually, adverse health effects. UfPs are deposited deep in the tissues, translocate, and skip the innate clearance mechanisms. After retention for a long time, these can infiltrate into the interstitium and permeate cells. Traffic-linked UfPs have been found to be toxic to the respiratory, cardiovascular, and nervous systems. At the molecular level, UfPs influence signaling cascade, actin-cytoskeleton pathway, immunoregulation, reactive oxygen species generation to trigger histaminic response, mast cell activation, and pro-inflammatory changes; their mutagenic and carcinogenic effects are also tacit in view of the carcinogenic potential of diesel exhaust in humans. The molecular changes are proposed to be the subclinical effects that manifest disease exacerbations or the predisposition of subjects to pathologies after exposure to UfP. A legislatively regulated monitoring of UfP-contaminated urban ambient air environment is also endorsed to reduce the disease load or its exacerbation that is growing in diesel exhaust (a human carcinogen)-polluted urban areas.

Hypomethylation of dual specificity phosphatase 22 promoter correlates with duration of service in firefighters and is inducible by low-dose benzo[a]pyrene

OBJECTIVE

Firefighters (FFs) are chronically exposed to smoke and products of incomplete combustion, which frequently contain polycyclic aromatic hydrocarbons (PAHs). This study examined the possibility of an association between PAH-induced epigenetic alterations and occupational firefighting exposure.

METHODS

Promoter methylation was analyzed in four genes in blood DNA from 18 FFs and 20 non-FFs (controls). Jurkat and human normal prostate epithelial cells were treated with benzo[a]pyrene to ascertain the epigenetic effects of this type of agent.

RESULTS

Firefighters had a higher prevalence of dual specificity phosphatase 22-promoter hypomethylation in blood DNA (P = 0.03) and the extent of hypomethylation correlated with duration of firefighting service (P = 0.04) but not with age. Benzo[a]pyrene reduced promoter methylation and increased gene expression of the same gene in Jurkat and normal prostate epithelial cells.

CONCLUSIONS

Cumulative occupational exposure to combustion-derived PAHs during firefighting can cause epigenetic changes in promoters of specific genes.

Air pollution: impact and prevention

Air pollution is becoming a major health problem that affects millions of people worldwide. In support of this observation, the World Health Organization estimates that every year, 2.4 million people die because of the effects of air pollution on health. Mitigation strategies such as changes in diesel engine technology could result in fewer premature mortalities, as suggested by the US Environmental Protection Agency. This review: (i) discusses the impact of air pollution on respiratory disease; (ii) provides evidence that reducing air pollution may have a positive impact on the prevention of disease; and (iii) demonstrates the impact concerted polices may have on population health when governments take actions to reduce air pollution.

Secondhand smoke in combination with ambient air pollution exposure is associated with increasedx CpG methylation and decreased expression of IFN-γ in T effector cells and Foxp3 in T regulatory cells in children

BACKGROUND

Secondhand smoke (SHS) and ambient air pollution (AAP) exposures have been associated with increased prevalence and severity of asthma and DNA modifications of immune cells. In the current study, we examined the association between SHS and AAP with DNA methylation and expression of interferon-gamma (IFN-γ) and forkhead box protein 3 (Foxp3) in T cell populations.

METHODS

Subjects 7-18 years old were recruited from Fresno (high AAP; n = 62) and Stanford, CA (low AAP; n = 40) and divided into SHS-exposed (Fresno: n = 31, Stanford: n = 6) and non-SHS-exposed (nSHS; Fresno: n = 31, Stanford: n = 34) groups. T cells purified from peripheral blood were assessed for levels of DNA methylation and expression of IFN-γ (in effector T cells) or Foxp3 (in regulatory T cells).

RESULTS

Analysis showed a significant increase in mean % CpG methylation of IFN-γ and Foxp3 associated with SHS exposure (IFN-γ: FSHS 62.10%, FnSHS 41.29%, p < 0.05; SSHS 46.67%, SnSHS 24.85%, p < 0.05; Foxp3: FSHS 74.60%, FnSHS 54.44%, p < 0.05; SSHS 62.40%, SnSHS 18.41%, p < 0.05) and a significant decrease in mean transcription levels of both genes (IFN-γ: FSHS 0.75, FnSHS 1.52, p < 0.05; SHS 2.25, nSHS 3.53, p < 0.05; Foxp3: FSHS 0.75, FnSHS 3.29, p < 0.05; SSHS 4.8, SnSHS 7.2, p < 0.05). AAP was also associated with hypermethylation (IFN-γ: FSHS vs. SSHS, p < 0.05; FnSHS vs. SnSHS, p < 0.05; Foxp3: FSHS vs. SSHS, p < 0.05; FnSHS vs. SnSHS, p < 0.05) and decreased transcription of both genes (IFN-γ: FSHS vs. SSHS, p < 0.05; FnSHS vs. SnSHS, p < 0.05; Foxp3: FSHS vs. SSHS, p < 0.05; FnSHS vs. SnSHS, p < 0.05). Average methylation between AAP- and SHS-only exposures was not significantly different (IFN-γ: p = 0.15; Foxp3: p = 0.27), nor was Foxp3 expression (p = 0.08); IFN-γ expression was significantly decreased in AAP-only subjects (p < 0.05).

CONCLUSIONS

Exposures to SHS and AAP are associated with significant hypermethylation and decreased expression of IFN-γ in Teffs and Foxp3 in Tregs. Relative contributions of each exposure to DNA modification and asthma pathogenesis warrant further investigation.

Genomics and the respiratory effects of air pollution exposure

Adverse health effects from air pollutants remain important, despite improvement in air quality in the past few decades. The exact mechanisms of lung injury from exposure to air pollutants are not yet fully understood. Studying the genome (e.g. single-nucleotide polymorphisms (SNP) ), epigenome (e.g. methylation of genes), transcriptome (mRNA expression) and microRNAome (microRNA expression) has the potential to improve our understanding of the adverse effects of air pollutants. Genome-wide association studies of SNP have detected SNP associated with respiratory phenotypes; however, to date, only candidate gene studies of air pollution exposure have been performed. Changes in epigenetic processes, such DNA methylation that leads to gene silencing without altering the DNA sequence, occur with air pollutant exposure, especially global and gene-specific methylation changes. Respiratory cell line and animal models demonstrate distinct gene expression signatures in the transcriptome, arising from exposure to particulate matter or ozone. Particulate matter and other environmental toxins alter expression of microRNA, which are short non-coding RNA that regulate gene expression. While it is clearly important to contain rising levels of air pollution, strategies also need to be developed to minimize the damaging effects of air pollutant exposure on the lung, especially for patients with chronic lung disease and for people at risk of future lung disease. Careful study of genomic responses will improve our understanding of mechanisms of lung injury from air pollution and enable future clinical testing of interventions against the toxic effects of air pollutants.

Enhancing effects of trichloroethylene and tetrachloroethylene on type I allergic responses in mice

Trichloroethylene (TCE) and tetrachloroethylene (perchloroethylene; PCE) are commonly identified as environmental contaminants of groundwater. Previously, we investigated the enhancing effects of TCE and PCE on antigen-induced histamine release and inflammatory mediator production in rat mast cells. In this study, to examine the potential effect of TCE and PCE on antigen-induced histamine release from mouse mast cells, mouse bone marrow-derived mast cells (BMMC) were sensitized with anti-dinitrophenol (DNP) monoclonal IgE antibody and then stimulated with DNP-BSA containing with TCE or PCE. Both TCE and PCE significantly enhanced antigen-induced histamine release from BMMC. Next we investigated the effects of TCE and PCE on the passive cutaneous anaphylaxis (PCA) reaction in vivo using ICR mice. TCE and PCE significantly enhanced the PCA reaction in a dose-dependent manner. In addition, we examined the enhancing effects of ingesting small amount of TCE and PCE in drinking water on antigen-stimulated allergic responses. After the ICR mice had ingested TCE or PCE in their drinking water for 2 or 4 weeks, we performed the PCA reaction. Both TCE and PCE ingestion enhanced the PCA reaction in a dose-dependent manner for 4 weeks. These results suggest that exposure to TCE and PCE leads to the augmentation of type I allergic responses in many species.

Epigenetics and childhood asthma: current evidence and future research directions

Asthma is the most common chronic disease of childhood, affecting one in eight children in the USA and worldwide. It is a complex disease, influenced by both environmental exposures and genetic factors. Although epigenetic modifications (DNA methylation, histone modification and miRNA) can affect transcriptional activity in multiple genetic pathways relevant for asthma development, very limited work has been carried out so far to examine the role of epigenetic variations on asthma development and management. This review provides a brief overview of epigenetic modifications, summarizes recent findings, and discusses some of the major methodological concerns that are relevant for asthma epigenetics.

Motor vehicle air pollution and asthma in children: a meta-analysis

BACKGROUND

Asthma affects more than 17 million people in the United States;1/3 of these are children. Children are particularly vulnerable to airborne pollution because of their narrower airways and because they generally breathe more air per pound of body weight than adults, increasing their exposure to air pollutants. However, the results from previous studies on the association between motor vehicle emissions and the development of childhood wheeze and asthma are conflicting. Therefore, we conducted a meta-analysis to clarify their potential relationship.

METHODS

MEDLINE, Highwire, and The Cochrane Library databases were searched for relevant studies. Adjusted odds ratio (OR) with corresponding 95% confidence interval (CI) for the association between traffic air pollutants and wheeze or asthma were retrieved from individual studies and pooled to generate summary effect estimates (meta-OR) in STATA 11.1.

RESULTS

Nineteen studies were included in the meta-analysis. Exposure to nitrogen dioxide (meta-OR: 1.05, 95% CI: 1.00-1.11), nitrous oxide (meta-OR: 1.02, 95% CI: 1.00-1.04), and carbon monoxide (meta-OR: 1.06, 95% CI: 1.01-1.12) were positively associated with a higher prevalence of childhood asthma. Exposure to sulfur dioxide (meta-OR: 1.04, 95% CI: 1.01-1.07) was positively associated with a higher prevalence of wheeze in children. Exposure to nitrogen dioxide was positively associated with a higher incidence of childhood asthma (meta-OR: 1.14, 95% CI: 1.06-1.24), and exposures to particulate matter was positively associated with a higher incidence of wheeze in children (meta-OR: 1.05, 95% CI: 1.04-1.07).

CONCLUSIONS

Living or attending schools near high traffic density roads exposes children to higher levels of motor vehicle air pollutants, and increases the incidence and prevalence of childhood asthma and wheeze.

Maternal exposure to polycyclic aromatic hydrocarbons and 5'-CpG methylation of interferon-γ in cord white blood cells

BACKGROUND

Maternal factors are implicated in the onset of childhood asthma. Differentiation of naïve CD4+ T lymphocytes into pro-allergic T-helper 2 cells induces interleukin (IL)4 expression and inhibits interferon (IFN)γ expression accompanied by concordant methylation changes in the promoters of these genes. However, it has yet to be established whether maternal exposure to polycyclic aromatic hydrocarbons (PAHs) can alter these gene promoters epigenetically during fetal development.

OBJECTIVES

In this study we sought to elucidate the relationship between maternal PAH exposure and promoter methylation status of IFNγ and IL4.

METHODS

We assessed the effects of benzo[a]pyrene (BaP), a representative airborne PAH, on the methylation status of the IFNγ and IL4 promoters in Jurkat cells and two lung adenocarcinoma cell lines, and on gene expression. In addition, we evaluated methylation status of the IFNγ promoter in cord white blood cells from 53 participants in the Columbia Center for Children's Environmental Health cohort. Maternal PAH exposure was estimated by personal air monitoring during pregnancy.

RESULTS

In vitro exposure of the cell models to low, noncytotoxic doses (0.1 and 1 nM) of BaP elicited increased promoter hypermethylation and reduced expression of IFNγ, but not IL4. IFNγ promoter methylation in cord white blood cells was associated with maternal PAH exposure in the cohort study subsample.

CONCLUSION

Consistent with the results for the cell lines, maternal exposure to PAHs was associated with hypermethylation of IFNγ in cord blood DNA from cohort children. These findings support a potential role of epigenetics in fetal reprogramming by PAH-induced environmental diseases.