GSTM1 and GSTP1 and respiratory health in asthmatic children exposed to ozone

Outdoor Air Pollution and Pediatric Respiratory Disease

Outdoor air pollution is ubiquitous, and no safe level of exposure has been identified for the most common air pollutants such as ozone and particle pollution. Children are uniquely more susceptible to the harms of outdoor air pollution, which can cause and exacerbate respiratory disease. Although challenging to identify the effects of outdoor air pollution on individual patients, understanding the basics of outdoor air pollution is essential for pediatric respiratory health care providers. This review covers basic information regarding outdoor air pollution, unique considerations for children, mechanisms for increased susceptibility, and association with incident and exacerbation of respiratory disease in children.

Ozone and childhood respiratory health: A primer for US pediatric providers and a call for a more protective standard

Ground level ozone is a potent respiratory toxicant with decades of accumulated data demonstrating respiratory harms to children. Despite the ubiquity of ozone in the United States, impacting both urban and rural communities, the associated harms of exposure to this important air pollutant are often infrequently or inadequately covered during medical training including pulmonary specialization. Thus, many providers caring for children's respiratory health may have limited knowledge of the harms which may result in reduced discussion of ozone pollution during clinical encounters. Further, the current US air quality standard for ozone does not adequately protect children. In this nonsystematic review, we present basic background information for healthcare providers caring for children's respiratory health, review the US process for setting air quality standards, discuss the respiratory harms of ozone for healthy children and those with underlying respiratory disease, highlight the urgent need for a more protective ozone standard to adequately protect children's respiratory health, review impacts of climate change on ozone levels, and provide information for discussion in clinical encounters.

A Review of the GSTM1 Null Genotype Modifies the Association between Air Pollutant Exposure and Health Problems

Air pollution is one of the significant environmental risks known as the cause of premature deaths. It has deleterious effects on human health, including deteriorating respiratory, cardiovascular, nervous, and endocrine functions. Exposure to air pollution stimulates reactive oxygen species (ROS) production in the body, which can further cause oxidative stress. Antioxidant enzymes, such as glutathione S-transferase mu 1 (GSTM1), are essential to prevent oxidative stress development by neutralizing excess oxidants. When the antioxidant enzyme function is lacking, ROS can accumulate and, thus, cause oxidative stress. Genetic variation studies from different countries show that GSTM1 null genotype dominates the GSTM1 genotype in the population. However, the impact of the GSTM1 null genotype in modifying the association between air pollution and health problem is not yet clear. This study will elaborate on GSTM1's null genotype role in modifying the relationship between air pollution and health problems.

Analysis of the GSTP1 rs1695 polymorphism association with the development of asthma and phenotypic manifestations

OBJECTIVE

The development of asthma and its related phenotypes is most likely due to the polymorphism of the so-called modifier genes. The goal of this study was to evaluate the polymorphic locus rs1695 of the GSTP1 gene association with risk factors for developing asthma and its phenotypic manifestations.

METHODS

This case-control study involved 164 patients with confirmed asthma diagnosis and 147 age- and sex-matched controls. Patients were divided into two groups: with (n = 121) and without complications (n = 43). Among asthmatic patients, 34 manifested hypersensitivity to household allergens. The GSTP1 rs1695 polymorphism was genotyped using the technique of polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

There were no differences between patients and controls in allelic or genotype frequencies of polymorphic locus rs1695 of the GSTP1 gene. However, the frequency of the A/A genotype in the patient group with complications was significantly lower than that in complication-free patients (p = 0.040), while the frequency of the G allele was higher in patients with complications (p = 0.030). The frequency of the A/A genotype was decreased in the patient group with an allergic reaction to household allergens in comparison with controls (p = 0.037).

CONCLUSION

These results suggest that the carriage of the A/A genotype of polymorphic locus rs1695 of the GSTP1 gene is a protective factor in the development of complications and an allergic reaction to house allergens among asthmatics, while the carriage of the G allele is associated with an increased risk for asthma complications.

Antioxidant genes and susceptibility to air pollution for respiratory and cardiovascular health

Oxidative stress occurs when antioxidant defences, which are regulated by a complex network of genes, are insufficient to maintain the level of reactive oxygen species below a toxic threshold. Outdoor air pollution has long been known to adversely affect health and one prominent mechanism of action common to all pollutants is the induction of oxidative stress. An individual's susceptibility to the effects of air pollution partly depends on variation in their antioxidant genes. Thus, understanding antioxidant gene-pollution interactions has significant potential clinical and public health impacts, including the development of targeted and cost-effective preventive measures, such as setting appropriate standards which protect all members of the population. In this review, we aimed to summarize the latest epidemiological evidence on interactions between antioxidant genes and outdoor air pollution, in the context of respiratory and cardiovascular health. The evidence supporting the existence of interactions between antioxidant genes and outdoor air pollution is strongest for childhood asthma and wheeze, especially for interactions with GSTT1, GSTM1 and GSTP1, for lung function in both children and adults for several antioxidant genes (GSTT1, GSTM1, GSTP1, HMOX1, NQO1, and SOD2) and, to a more limited extent, for heart rate variability in adults for GSTM1 and HMOX1. Methodological challenges hampering a clear interpretation of these findings and understanding of true potential heterogeneity are discussed.

Prenatal exposure to particulate matter and ozone: Bulky DNA adducts, plasma isoprostanes, allele risk variants, and neonate susceptibility in the Mexico City Metropolitan Area

Mexico City's Metropolitan Area (MCMA) includes Mexico City and 60 municipalities of the neighbor states. Inhabitants are exposed to emissions from over five million vehicles and stationary sources of air pollutants such as particulate matter (PM) and ozone. MCMA PM contains elemental carbon and organic carbon (OC). OCs include polycyclic aromatic hydrocarbons (PAHs), many of which induce mutagenic and carcinogenic DNA adducts. Gestational exposure to air pollution has been associated with increased risk of intrauterine growth restriction, preterm birth or low birth weight risk, and PAH-DNA adducts. These effects also depend on the presence of risk alleles. We investigated the presence of bulky PAH-DNA adducts, plasma 8-iso-PGF_2α (8-iso-prostaglandin F_2α ) and risk allele variants in neonates cord blood and their non-smoking mothers' leucocytes from families that were living in a highly polluted area during 2014-2015. The presence of adducts was significantly associated with both PM_2.5 and PM₁₀ levels, mainly during the last trimester of gestation in both neonates and mothers, while the last month of pregnancy was significant for the association between ozone levels and maternal plasma 8-iso-PGF_2α . Fetal CYP1B1*3 risk allele was associated with increased adduct levels in neonates while the presence of the maternal allele significantly reduced the levels of fetal adducts. Maternal NQO1*2 was associated with lower maternal levels of adducts. Our findings suggest the need to reduce actual PM limits in MCMA. We did not observe a clear association between PM and/or adduct levels and neonate weight, length, body mass index, Apgar or Capurro score. Environ. Mol. Mutagen. 60:428-442, 2019. © 2019 Wiley Periodicals, Inc.

Variants in genes coding for glutathione S-transferases and asthma outcomes in children

Our hypothesis was that children with mutations in genes coding for glutathione S-transferases (GST) have worse asthma outcomes compared with children with active type genotype. Data were collected in five populations. The rs1695 single nucleotide polymorphism (GSTP1) was determined in all cohorts (3692 children) and GSTM1 and GSTT1 null genotype were determined in three cohorts (2362 children). GSTT1 null (but not other genotypes) was associated with a minor increased risk for asthma attack and there were no significant associations between GST genotypes and asthma severity. Interactions between GST genotypes and SHS exposure or asthma severity with the study outcomes were nonsignificant. We find no convincing evidence that the GST genotypes studied are related to asthma outcomes.

The Effect of Nitric Oxide Pollution on Oxidative Stress in Pregnant Women Living in Durban, South Africa

The purpose of the study was to evaluate the effect nitric oxide (NO _x ) pollution had on maternal serum 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OHdG) levels and neonatal outcomes in pregnant women living in Durban, South Africa (SA). Women, in their third trimester with singleton pregnancies, were recruited from the heavily industrialised south (n = 225) and less industrialised north (n = 152). Biomarker levels of serum 8-OHdG concentrations were analysed, and the women were genotyped for glutathione-S-transferases pi 1 (GSTP1) and glutathione-S-transferases mu 1 (GSTM1) polymorphisms. The level of NO _x pollution in the two regions was determined by using land use regression modelling. The serum 8-OHdG was shown to correlate significantly with NO _x levels; this relationship was strengthened in the south (p < 0.05). This relationship was still observed after adjusting for maternal characteristics. GSTP1 was significantly associated with the south region, where the variant (AG+GG) genotype was associated with increased 8-OHdG levels as a result of NO _x exposure (p < 0.05). GSTM1 null genotype was associated with a positive correlation between NO _x and 8-OHdG levels (p < 0.05). NO _x levels were found marginally to reduce gestational age (p < 0.05) with mothers carrying male neonates. Variant GSTP1 and living in the north were factors that contributed to gestational age reduction (p < 0.05). Our study demonstrated that NO _x exposure resulted in increased 8-OHdG levels in pregnant women living in Durban, SA, which led to gestational age reduction. The GSTP1 variant increased susceptibility of individuals to harmful effects of NO _x .

Interactions Between Bisphenol A Exposure and GSTP1 Polymorphisms in Childhood Asthma

Purpose

Bisphenol A (BPA) exposure may increase the risk of asthma. Genetic polymorphisms of oxidative stress-related genes, glutathione S-transferases (GSTM1, GSTP1), manganese superoxide dismutase, catalase, myeloperoxidase, and microsomal epoxide hydrolase may be related to BPA exposure. The aim is to evaluate whether oxidative stress genes modulates associations of BPA exposure with asthma.

Methods

We conducted a case-control study comprised of 126 asthmatic children and 327 controls. Urine Bisphenol A glucuronide (BPAG) levels were measured by ultra-performance liquid chromatography/tandem mass spectrometry, and genetic variants were analyzed by a TaqMan assay. Information on asthma and environmental exposure was collected. Analyses of variance and logistic regressions were performed to determine the association of genotypes and urine BPAG levels with asthma.

Results

BPAG levels were significantly associated with asthma (adjusted odds ratio [aOR], 1.29 per log unit increase in concentration; 95% confidence interval [CI], 1.081.55). Compared to the GG genotype, children with a GSTP1 AA genotype had higher urine BPAG concentrations (geometric mean [standard error], 12.72 [4.16] vs 11.42 [2.82]; P=0.036). In children with high BPAG, the GSTP1 AA genotype was related to a higher odds of asthma than the GG genotype (aOR, 4.84; 95% CI, 1.0223.06).

Conclusions

GSTP1 variants are associated with urine BPA metabolite levels. Oxidative stress genes may modulate the effect of BPA exposure on asthma.

Energy landscape of a GSTP1 polymorph linked with cytological function decay in response to chemical stressors

Gene polymorphisms lead to varied structure and functional properties. A single nucleotide polymorphism (SNP) i.e. Ile105Val (rs1695) in glutathione S-transferase P1 (GSTP1) gene influences cytological toxicity and modulates the risk to occupational diseases. Apart from this, cancer, neuropathy, NOx, SOx and ozone mediated respiratory function decline including lung inflammation, asthma, allergy etc., have been reported in people with this missense mutation. Here, the functional properties of rs1695 polymorph are revisited through a computational approach. Changes incurred by GSTP1 antioxidant protein as a result of alteration in its sequence, have been studied through docking followed by Poisson-Boltzmann electrostatic equation interpretation, grid and coulombic energy profile mapping for protein polymorphs with DelPhi. Molecular docking simulation of variant and wild type (WT) protein was carried out with eight FDA approved compounds that target GSTP1 for treatment of various diseases. This was to observe binding pattern variation upon mutation induction. Grid, reaction field and coulombic energy calculation of WT and mutated polymorph, complexed with and without these moieties was then attempted. Alteration in conformation and energy was observed in apo- and holo- form of GSTP1 and their ligand-bound complexes as a result of this mutation. This study is a demo of appraising gene-environment interaction based deleteriousness through molecular docking and dynamics simulation approach.

Do Variants in GSTs Modify the Association between Traffic Air Pollution and Asthma in Adolescence?

Polymorphisms in genes involved in the oxidative stress response may partially explain the documented heterogeneous associations between traffic-related air pollution (TRAP) exposure and asthma and allergies in children. We investigated whether the GSTT1, GSTM1 and GSTP1 gene polymorphisms modified the associations between TRAP exposure during the first year of life and asthma, wheeze and hay fever in adolescence. We used a birth cohort of 620 high risk infants from the Melbourne Atopy Cohort Study. TRAP exposure during the first year of life was defined as the cumulative length of major roads within 150 m of each participant’s residence during the first year of life. Wheeze, asthma and hay fever were measured at ages 12 (n = 370) and 18 (n = 434) years. The associations and interactions with glutathione S-transferases (GST s) were investigated using regression models. Overall, there was no relationship between TRAP exposure during the first year of life and current asthma, wheeze and hay fever at ages 12 or 18 years. However, in GSTT1 null carriers, every 100 m increase in cumulative lengths of major road exposure during the first year of life was associated with a 2.31-fold increased risk of wheeze and a 2.15-fold increased risk of asthma at 12 years. TRAP is associated with some respiratory outcomes in carriers of genetic polymorphisms in oxidative stress metabolism genes.

Interactions between traffic air pollution and glutathione S-transferase genes on childhood asthma

AIM: To evaluate the role of glutathione S-transferase P1 (GSTP1) genetic polymorphisms potentially modifying the association between NO₂ and asthma/wheeze in Taiwanese children.

METHODS: We investigated 3714 schoolchildren in Taiwan Children Health Study from 14 communities. Children’s information was measured from questionnaire by parents. The traffic air pollutant was available from Environmental Protection Administration monitoring stations.

RESULTS: A two-stage hierarchical model and a multiple logistic regression model were fitted to estimate the effects of NO₂ exposures and GSTs polymorphisms on the prevalence of asthma and wheeze. Among children with GSTP1 Ile/Val or Val/Val genotypes, those residing in high-NO₂ communities had significantly increased risks of asthma (OR = 1.76, 95%CI: 1.15-2.70), late-onset asthma (OR = 2.59, 95%CI: 1.24-5.41), active asthma (OR = 1.93, 95%CI: 1.05-3.57), asthma under medication (OR = 2.95, 95%CI: 1.37-6.32) and wheeze (OR = 1.54, 95%CI: 1.09-2.18) when compared with children in low-NO₂ communities. Significant interactions were noted between ambient NO₂ and GSTP1 on asthma, late-onset asthma, asthma under medication and wheeze (P for interaction < 0.05). However, we did not find any association with polymorphisms in GSTM1 and GSTT1.

CONCLUSION: Children under high traffic air pollution exposure are more susceptible to asthma, especially among those with GSTP1 Val allele.

Translational Genomics in Low- and Middle-Income Countries: Opportunities and Challenges

Translation of genomic discoveries into patient care is slowly becoming a reality in developed economies around the world. In contrast, low- and middle-income countries (LMIC) have participated minimally in genomic research for several reasons including the lack of coherent national policies, the limited number of well-trained genomic scientists, poor research infrastructure, and local economic and cultural challenges. Recent initiatives such as the Human Heredity and Health in Africa (H3Africa), the Qatar Genome Project, and the Mexico National Institute of Genomic Medicine (INMEGEN) that aim to address these problems through capacity building and empowerment of local researchers have sparked a paradigm shift. In this short communication, we describe experiences of small-scale medical genetics and translational genomic research programs in LMIC. The lessons drawn from these programs drive home the importance of addressing resource, policy, and sociocultural dynamics to realize the promise of precision medicine driven by genomic science globally. By echoing lessons from a bench-to-community translational genomic research, we advocate that large-scale genomic research projects can be successfully linked with health care programs. To harness the benefits of genomics-led health care, LMIC governments should begin to develop national genomics policies that will address human and technology capacity development within the context of their national economic and sociocultural uniqueness. These policies should encourage international collaboration and promote the link between the public health program and genomics researchers. Finally, we highlight the potential catalytic roles of the global community to foster translational genomics in LMIC.

Gene-environment interaction from international cohorts: impact on development and evolution of occupational and environmental lung and airway disease

Environmental and occupational pulmonary diseases impose a substantial burden of morbidity and mortality on the global population. However, it has been long observed that only some of those who are exposed to pulmonary toxicants go on to develop disease; increasingly, it is being recognized that genetic differences may underlie some of this person-to-person variability. Studies performed throughout the globe are demonstrating important gene-environment interactions for diseases as diverse as chronic beryllium disease, coal workers' pneumoconiosis, silicosis, asbestosis, byssinosis, occupational asthma, and pollution-associated asthma. These findings have, in many instances, elucidated the pathogenesis of these highly complex diseases. At the same time, however, translation of this research into clinical practice has, for good reasons, proceeded slowly. No genetic test has yet emerged with sufficiently robust operating characteristics to be clearly useful or practicable in an occupational or environmental setting. In addition, occupational genetic testing raises serious ethical and policy concerns. Therefore, the primary objective must remain ensuring that the workplace and the environment are safe for all.

Modification of the association between PM10 and lung function decline by cadherin 13 polymorphisms in the SAPALDIA cohort: a genome-wide interaction analysis

BACKGROUND

Both air pollution and genetic variation have been shown to affect lung function. Their interaction has not been studied on a genome-wide scale to date.

OBJECTIVES

We aimed to identify, in an agnostic fashion, genes that modify the association between long-term air pollution exposure and annual lung function decline in an adult population-based sample.

METHODS

A two-stage genome-wide interaction study was performed. The discovery (n = 763) and replication (n = 3,896) samples were derived from the multi-center SAPALDIA cohort (Swiss Cohort Study on Air Pollution and Lung Disease in Adults). Annual rate of decline in the forced mid-expiratory flow (FEF25-75%) was the main end point. Multivariate linear regression analyses were used to identify potential multiplicative interactions between genotypes and 11-year cumulative PM10 exposure.

RESULTS

We identified a cluster of variants intronic to the CDH13 gene as the only locus with genome-wide significant interactions. The strongest interaction was observed for rs2325934 (p = 8.8 × 10(-10)). Replication of the interaction between this CDH13 variant and cumulative PM10 exposure on annual decline in FEF25-75% was successful (p = 0.008). The interaction was not sensitive to adjustment for smoking or body weight.

CONCLUSIONS

CDH13 is functionally linked to the adipokine adiponectin, an inflammatory regulator. Future studies need to confirm the interaction and assess how the result relates to previously observed interactions between air pollution and obesity on respiratory function.

Short-term diesel exhaust inhalation in a controlled human crossover study is associated with changes in DNA methylation of circulating mononuclear cells in asthmatics

Background

Changes in DNA methylation have been associated with traffic-related air pollution in observational studies, but the specific mechanisms and temporal dynamics therein have not been explored in a controlled study of asthmatics. In this study, we investigate short-term effects of diesel exhaust inhalation on DNA methylation levels at CpG sites across the genome in circulating blood in asthmatics.

Methods

A double-blind crossover study of filtered air and diesel exhaust exposures was performed on sixteen non-smoking asthmatic subjects. Blood samples were collected pre-exposure, and then 6 and 30 hours post-exposure. Peripheral blood mononuclear cell DNA methylation was interrogated using the Illumina Infinium HumanMethylation450 Array. Exposure-related changes in DNA methylation were identified. In addition, CpG sites overlapping with Alu or LINE1 repetitive elements and candidate microRNA loci were also analyzed.

Results

DNA methylation at 2827 CpG sites were affected by exposure to diesel exhaust but not filtered air; these sites enriched for genes involved in protein kinase and NFkB pathways. CpG sites with significant changes in response to diesel exhaust exposure primarily became less methylated, with a site residing within GSTP1 being among the significant hits. Diesel exhaust-associated change was also found for CpG sites overlapping with Alu and LINE1 elements as well as for a site within miR-21.

Conclusion

Short-term exposure to diesel exhaust resulted in DNA methylation changes at CpG sites residing in genes involved in inflammation and oxidative stress response, repetitive elements, and microRNA. This provides plausibility for the role of DNA methylation in pathways by which airborne particulate matter impacts gene expression and offers support for including DNA methylation analysis in future efforts to understand the interactions between environmental exposures and biological systems.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-014-0071-3) contains supplementary material, which is available to authorized users.

Evaluating potential response-modifying factors for associations between ozone and health outcomes: a weight-of-evidence approach

BACKGROUND

Epidemiologic and experimental studies have reported a variety of health effects in response to ozone (O3) exposure, and some have indicated that certain populations may be at increased or decreased risk of O3-related health effects.

OBJECTIVES

We sought to identify potential response-modifying factors to determine whether specific groups of the population or life stages are at increased or decreased risk of O3-related health effects using a weight-of-evidence approach.

METHODS

Epidemiologic, experimental, and exposure science studies of potential factors that may modify the relationship between O3 and health effects were identified in U.S. Environmental Protection Agency's 2013 Integrated Science Assessment for Ozone and Related Photochemical Oxidants. Scientific evidence from studies that examined factors that may influence risk were integrated across disciplines to evaluate consistency, coherence, and biological plausibility of effects. The factors identified were then classified using a weight-of-evidence approach to conclude whether a specific factor modified the response of a population or life stage, resulting in an increased or decreased risk of O3-related health effects.

DISCUSSION

We found "adequate" evidence that populations with certain genotypes, preexisting asthma, or reduced intake of certain nutrients, as well as different life stages or outdoor workers, are at increased risk of O3-related health effects. In addition, we identified other factors (i.e., sex, socioeconomic status, and obesity) for which there was "suggestive" evidence that they may increase the risk of O3-related health effects.

CONCLUSIONS

Using a weight-of-evidence approach, we identified a diverse group of factors that should be considered when characterizing the overall risk of health effects associated with exposures to ambient O3.

Gender-dependent effect of GSTM1 genotype on childhood asthma associated with prenatal tobacco smoke exposure

It remains unclear whether the GSTM1 genotype interacts with tobacco smoke exposure (TSE) in asthma development. This study aimed to investigate the interactions among GSTM1 genotype, gender, and prenatal TSE with regard to childhood asthma development. In a longitudinal birth cohort in Taiwan, 756 newborns completed a 6-year follow-up, and 591 children with DNA samples available for GSTM1 genotyping were included in the study, and the interactive influences of gender-GSTM1 genotyping-prenatal TSE on childhood asthma development were analyzed. Among these 591 children, 138 (23.4%) had physician-diagnosed asthma at 6 years of age, and 347 (58.7%) were null-GSTM1. Prenatal TSE significantly increased the prevalence of childhood asthma in null-GSTM1 children relative to those with positive GSTM1. Further analysis showed that prenatal TSE significantly increased the risk of childhood asthma in girls with null-GSTM1. Furthermore, among the children without prenatal TSE, girls with null-GSTM1 had a significantly lower risk of developing childhood asthma and a lower total IgE level at 6 years of age than those with positive GSTM1. This study demonstrates that the GSTM1 null genotype presents a protective effect against asthma development in girls, but the risk of asthma development increases significantly under prenatal TSE.

Oxidative stress in airway diseases

Airway oxidative stress is broadly defined as an imbalance between prooxidative and antioxidative processes in the airway. Given its direct exposure to the environment, the lung has several mechanisms to prevent an excessive degree of oxidative stress. Both enzymatic and nonenzymatic systems can buffer a wide range of reactive oxidative species and other compounds with oxidative potential. In diseases like asthma and chronic obstructive lung disease, airway oxidative stress can occur from a number of sources, including greater exposure to environmental prooxidants, airway infiltration of inflammatory cells, metabolic deregulation, and reduced levels of antioxidants. Airway oxidative stress has been associated with worse disease severity, reduced lung function, and epigenetic changes that can diminish response to steroids. Although oxidative stress has been linked to a wide range of adverse biological effects, it has also been associated with adaptive responses and with resolution of inflammation. Therefore, more than being an imbalance with a predictable threshold after which disease or injury ensues, oxidative stress is a dynamic and continuous process. This might explain why supplementing antioxidants has largely failed to improve diseases such as asthma and chronic obstructive pulmonary disease. However, the therapeutic potential of antioxidants could be greatly improved by taking an approach that considers individual and environmental risk factors, instead of treating oxidative airway stress broadly.

GSTP1 and TNF Gene variants and associations between air pollution and incident childhood asthma: the traffic, asthma and genetics (TAG) study

BACKGROUND

Genetics may partially explain observed heterogeneity in associations between traffic-related air pollution and incident asthma.

OBJECTIVE

Our aim was to investigate the impact of gene variants associated with oxidative stress and inflammation on associations between air pollution and incident childhood asthma.

METHODS

Traffic-related air pollution, asthma, wheeze, gene variant, and potential confounder data were pooled across six birth cohorts. Parents reported physician-diagnosed asthma and wheeze from birth to 7-8 years of age (confirmed by pediatric allergist in two cohorts). Individual estimates of annual average air pollution [nitrogen dioxide (NO2), particulate matter ≤ 2.5 μm (PM2.5), PM2.5 absorbance, ozone] were assigned to each child's birth address using land use regression, atmospheric modeling, and ambient monitoring data. Effect modification by variants in GSTP1 (rs1138272/Ala114Val and rs1695/IIe105Val) and TNF (rs1800629/G-308A) was investigated.

RESULTS

Data on asthma, wheeze, potential confounders, at least one SNP of interest, and NO2 were available for 5,115 children. GSTP1 rs1138272 and TNF rs1800629 SNPs were associated with asthma and wheeze, respectively. In relation to air pollution exposure, children with one or more GSTP1 rs1138272 minor allele were at increased risk of current asthma [odds ratio (OR) = 2.59; 95% CI: 1.43, 4.68 per 10 μg/m3 NO2] and ever asthma (OR = 1.64; 95% CI: 1.06, 2.53) compared with homozygous major allele carriers (OR = 0.95; 95% CI: 0.68, 1.32 for current and OR = 1.20; 95% CI: 0.98, 1.48 for ever asthma; Bonferroni-corrected interaction p = 0.04 and 0.01, respectively). Similarly, for GSTP1 rs1695, associations between NO2 and current and ever asthma had ORs of 1.43 (95% CI: 1.03, 1.98) and 1.36 (95% CI: 1.08, 1.70), respectively, for minor allele carriers compared with ORs of 0.82 (95% CI: 0.52, 1.32) and 1.12 (95% CI: 0.84, 1.49) for homozygous major allele carriers (Bonferroni-corrected interaction p-values 0.48 and 0.09). There were no clear differences by TNF genotype.

CONCLUSIONS

Children carrying GSTP1 rs1138272 or rs1695 minor alleles may constitute a susceptible population at increased risk of asthma associated with air pollution.

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.

Frequency of polymorphism -262 c/t in catalase gene and oxidative damage in Slovak children with bronchial asthma

INTRODUCTION

Bronchial asthma is a complex disease in which genetic factors, environmental factors and oxidative damage are responsible for the initiation and modulation of disease progression. If antioxidant mechanisms fail, reactive oxygen species damage the biomolecules followed by progression of the disease. Catalase is one of the most important endogenous enzymatic antioxidants. In the present study, we examined the hypothesis that increased oxidative damage and polymorphism in the CAT gene (-262 promoter region, C/T) are associated with childhood bronchial asthma.

PATIENTS AND METHODS

Genotyping of the polymorphisms in the CAT gene in healthy (249) and asthmatic children (248) was performed using polymerase chain reaction-restriction fragment length polymorphism. Markers of oxidative damage: content of sulfhydryl groups and thiobarbituric acid-reactive substances were determined by spectrophotometry in children.

RESULTS

The TT genotype of catalase was more frequent among the asthmatic patients (22.6%) than in healthy children (4.8%) (odds ratio=5.63; 95% confidence interval=2.93-10.81, P<.001). The amount of sulfhydryl groups decreased significantly and conversely, the content of thiobarbituric acid-reactive substances increased significantly in bronchial asthma and in catalase TT genotype compared to other catalase genotypes of this gene.

CONCLUSIONS

These results suggest that catalase polymorphism might participate in development of bronchial asthma and in enhanced oxidative damage in asthmatic children. Genetic variation of enzymatic antioxidants may modulate disease risk.

Expression pattern of GSTP1 and GSTA1 in the pathogenesis of asthma

Reactive oxygen species (ROS) are known aggravating factors for airway inflammation in asthma. Glutathione S-transferases (GSTs) detoxify ROS and toxic compounds in environmental exposures. However, little is known about the regulation of GST and expression of GST subtypes in asthma. The aim of this study was to evaluate how GSTs are regulated in asthma. We observed total GST activity and expression of GST subtypes in murine asthma models and GST expressions in induced sputum cells of asthmatics. Total GST activity was increased in BAL fluids of OVA-treated murine asthma model. GSTP and GSTA are highly expressed in peribronchiolar mononuclear inflammatory cells and epithelial cells in OVA-treated mice. GSTM are expressed in epithelial cells in both OVA and PBS-treated groups. GSTP1 mRNA expression was increased in the lung of OVA-treated mice compared with PBS-treated mice. GSTA1, GSTM1, and GSTT1 mRNA expressions were not different between both groups. GSTA1 mRNA expression was increased in induced sputum cells of asthmatics compared with healthy controls. GSTP1, GSTM1, and GSTT1 mRNA expressions were not different between asthmatics and healthy controls. In asthmatics, GSTP1 and GSTA1 mRNA expressions were higher in induced sputum cells of asthmatics with PC20 ≤ 4 mg/ml than those with PC20 > 4 mg/ml. GSTM1 and GSTT1 mRNA expressions were not different between two groups. These findings suggest that GSTs are upregulated in the airways of asthmatics in response to increased oxidative stress. GSTP and GSTA are thought to play an important role in protecting the airways of asthmatics compared with GSTM and GSTT.

Childhood allergic rhinitis, traffic-related air pollution, and variability in the GSTP1, TNF, TLR2, and TLR4 genes: results from the TAG Study

BACKGROUND

Associations between traffic-related air pollution (TRAP) and allergic rhinitis remain inconsistent, possibly because of unexplored gene-environment interactions.

OBJECTIVE

In a pooled analysis of 6 birth cohorts (Ntotal = 15,299), we examined whether TRAP and genetic polymorphisms related to inflammation and oxidative stress predict allergic rhinitis and sensitization.

METHODS

Allergic rhinitis was defined with a doctor diagnosis or reported symptoms at age 7 or 8 years. Associations between nitrogen dioxide, particulate matter 2.5 (PM2.5) mass, PM2.5 absorbance, and ozone, estimated for each child at the year of birth, and single nucleotide polymorphisms within the GSTP1, TNF, TLR2, or TLR4 genes with allergic rhinitis and aeroallergen sensitization were examined with logistic regression. Models were stratified by genotype and interaction terms tested for gene-environment associations.

RESULTS

Point estimates for associations between nitrogen dioxide, PM2.5 mass, and PM2.5 absorbance with allergic rhinitis were elevated, but only that for PM2.5 mass was statistically significant (1.37 [1.01, 1.86] per 5 μg/m(3)). This result was not robust to single-cohort exclusions. Carriers of at least 1 minor rs1800629 (TNF) or rs1927911 (TLR4) allele were consistently at an increased risk of developing allergic rhinitis (1.19 [1.00, 1.41] and 1.24 [1.01, 1.53], respectively), regardless of TRAP exposure. No evidence of gene-environment interactions was observed.

CONCLUSION

The generally null effect of TRAP on allergic rhinitis and aeroallergen sensitization was not modified by the studied variants in the GSTP1, TNF, TLR2, or TLR4 genes. Children carrying a minor rs1800629 (TNF) or rs1927911 (TLR4) allele may be at a higher risk of allergic rhinitis.

Respiratory health effects of ambient air pollution: an update

There is new evidence for ambient air pollution (AAP) leading to an increased incidence of respiratory diseases in adults. Research has demonstrated that co-exposures have the potential to dramatically augment the effects of AAP and lower the threshold of effect of a given pollutant. Interactions between genes related to oxidative stress and AAP seem to significantly alter the effect of AAP on an individual and population basis. A better definition of vulnerable populations may bolster local or regional efforts to remediate AAP. Advances in genetic research tools have the potential to identify candidate genes that can guide further research.

Ozone exposure, vitamin C intake, and genetic susceptibility of asthmatic children in Mexico City: a cohort study

Background

We previously reported that asthmatic children with GSTM1 null genotype may be more susceptible to the acute effect of ozone on the small airways and might benefit from antioxidant supplementation. This study aims to assess the acute effect of ozone on lung function (FEF_25-75) in asthmatic children according to dietary intake of vitamin C and the number of putative risk alleles in three antioxidant genes: GSTM1, GSTP1 (rs1695), and NQO1 (rs1800566).

Methods

257 asthmatic children from two cohort studies conducted in Mexico City were included. Stratified linear mixed models with random intercepts and random slopes on ozone were used. Potential confounding by ethnicity was assessed. Analyses were conducted under single gene and genotype score approaches.

Results

The change in FEF_25-75 per interquartile range (60 ppb) of ozone in persistent asthmatic children with low vitamin C intake and GSTM1 null was −91.2 ml/s (p = 0.06). Persistent asthmatic children with 4 to 6 risk alleles and low vitamin C intake showed an average decrement in FEF_25-75 of 97.2 ml/s per 60 ppb of ozone (p = 0.03). In contrast in children with 1 to 3 risk alleles, acute effects of ozone on FEF_25-75 did not differ by vitamin C intake.

Conclusions

Our results provide further evidence that asthmatic children predicted to have compromised antioxidant defense by virtue of genetic susceptibility combined with deficient antioxidant intake may be at increased risk of adverse effects of ozone on pulmonary function.

Maternal environmental exposure, infant GSTP1 polymorphism, and risk of isolated congenital heart disease

The GSTP1 gene, highly expressed early in fetal life, is the most abundant phase 2 xenobiotic metabolism enzyme in a human placenta. Fetal inherited GSTP1 Ile105Val polymorphism may modify the metabolism and excretion of xenobiotics from fetal tissue and increase the risk of congenital heart disease (CHD). This study aimed to analyze the joint effects of GSTP1 genetic polymorphism (Ile105Val) and maternal environmental exposure on CHD risk. Within a case-control design, a total of 190 children with CHD (104 boys age 4 ± 5.6 years) and 190 healthy children (114 newborn boys) were genotyped for the GSTP1 Ile105Val polymorphism. Mothers completed a structured questionnaire on the demographics as well as the preconceptional and lifestyle exposures. A higher frequency of mothers of children with CHD (38 %) reported a positive history of exposure to toxicants (occupational and environmental) than mothers of healthy children (23 %) (p = 0.0013). Logistic regression analysis showed that maternal occupational and environmental exposures increased the risk of CHD (odds ratio, 2.6; 95 % confidence interval, 1.6-4.2; p < 0.0001). No significant differences in Ile105Val genotype frequencies were observed between the children with CHD and the healthy children (p = 0.9). Furthermore, case-control analysis showed no evidence of significant interaction between the maternal exposures and GSTP1 polymorphism. Maternal exposure to toxicants increased the risk of children with CHD. However, fetal GSTP1 Ile105Val polymorphism did not increase the risk of CHD.

Fine particle, ozone exposure, and asthma/wheezing: effect modification by glutathione S-transferase P1 polymorphisms

Background

There are limited studies on the role of interaction between exposure to ambient air pollution and glutathione-S-transferase (GST) P1 on the risk of asthma/wheezing among children, which provided suggestive, but inconclusive results.

Methods

To assess the joint effect of air pollutants and GSTP1 on asthma/wheezing, we conducted a nationwide cross-sectional study of 3,825 children in Taiwan Children Health Study. The studied determinants were three GSTP1 Ile105Val (rs 1695) genotypes (Ile-Ile; Ile-Val and Val-Val) and expoure to ambient air pollutants. We used routine air-pollution monitoring data for ozone (O₃) and particles with an aerodynamic diameter of 2.5 µm or less (PM_2.5). The effect estimates were presented as odds ratios (ORs) per interquartile changes for PM_2.5 and O₃.

Findings

In a two-stage hierarchical model adjusting for confounding, the risk of asthma was negatively associated with PM_2.5 (adjusted odds ratio (OR) 0.60; 95% confidence interval (CI) 0.45, 0.82) and O₃ (OR 0.74; 95% CI 0.60, 0.90) among Ile105 homozygotes, but positively associated with PM_2.5 (OR 1.52; 95% CI 1.01, 2.27) and O₃ (OR 1.19; 95% CI 0.91, 1.57) among those with at least one val105 allele (interaction p value = 0.001 and 0.03, respectively). A similar tendency of effect modification between PM_2.5 and O₃ and GSTP1 on wheezing was found.

Conclusion

Children who carried Ile105 variant allele and exposed to PM_2.5 and O₃ may be less likely to occurrence of asthma/wheezing.

Glutathione S-transferase polymorphisms, asthma susceptibility and confounding variables: a meta-analysis

Oxidative stress is one of the main risk factors for asthma development. Glutathione S-transferases play an important role in antioxidant defences and may influence asthma susceptibility. In particular, GSTM1 and GSTT1 positive/null genotypes and the GSTP1 Ile105 Val polymorphism have been analyzed in a number of genetic association studies, with conflicting outcomes. Two previous meta-analyses have attempted to clarify the associations between GST genes and asthma, but these studies have also showed contrasting results. Our aim was to perform a meta-analysis that included independent genetic association studies on GSTM1, GSTP1, and GSTT1, evaluating also the effect of potential confounding variables (i.e. ethnicity, population age, and urbanization). Systematic review and meta-analysis of the effects of GST genes on asthma were conducted. The meta-analyses were performed using a fixed or, where appropriate, random effects model. The meta-analysis of the GSTM1 (n = 35), GSTT1 (n = 31) and GSTP1 (n = 28) studies suggests that no significant associations with asthma susceptibility were observed for GSTM1 and GSTP1 gene polymorphisms, whereas a significant outcome was detected for the GSTT1 positive/null genotype (pooled OR = 1.33, 95 %CI = 1.10-1.60). However, high between-study heterogeneity was identified in all the general analyses (p heterogenetity < 0.05). The stratification analysis seems to explain the heterogeneity only in few cases. This picture is probably due to the interactive process of genetics and environment that characterizes disease pathogenesis. Further studies on interactions of GST genes with the potential oxidative stress sources and with other antioxidant genes are needed to explain the role of GST enzymes in asthma.

GSTM1 and GSTP1 gene variants and the effect of air pollutants on lung function measures in South African children

BACKGROUND

Several genes are associated with an increased susceptibility to asthma, which may be exacerbated by ambient air pollution. These genes include GSTM1 (glutathione-S-transferase M1 gene) and GSTP1 (glutathione-S-transferase P1 gene), which may modulate the response to epithelial oxidative changes caused by air pollutant exposure. This study evaluated fluctuations in the forced expiratory volume in one second (FEV(1)) in relation to lagged daily averages of ambient air pollutants (SO(2), NO(2), NO, and PM(10)) while considering genotype as an effect modifier.

METHODS

A longitudinal cohort of 129 schoolchildren of African descent from Durban, South Africa was assessed. GSTM1 (null vs. present genotype) and GSTP1 (Ile105Val; AA → AG/GG) genotypes were determined using standard techniques. SO(2), NO(2), NO, and PM(10) were measured continuously over a year using validated methods. The outcome was intraday variability in FEV(1) . Data were collected daily over a 3-week period in each of four seasons (2004-2005).

RESULTS

Among the children tested, 27% had the GSTM1 null genotype and 81% carried the GSTP1 G allele. Approximately 26 out 104 children (25%) showed evidence of bronchial hyperreactivity, 13% reported having symptoms in keeping with persistent asthma, and a further 25% reported symptoms of mild intermittent asthma. PM(10) and SO(2) levels were moderately high relative to international guidelines. Neither GSTM1 nor GSTP1 genotypes alone were significantly associated with FEV(1) intraday variability. In models not including genotype, FEV(1) variability was statistically significantly associated only with NO(2) for 5-day lags (% change in intraday variability in FEV1 per interquartile range = 1.59, CI 0.58, 2.61). The GSTP1 genotype modified the effect of 3 days prior 24-hr average PM(10) and increased FEV(1) variability. A similar pattern was observed for lagged 3 day SO(2) exposure (P interaction < 0.05). Adverse effects of these pollutants were limited to individuals carrying the G allele for this polymorphism.

CONCLUSION

Among this indigenous South African children cohort, the GSTP1 genotype modified the effects of ambient exposures to PM(10) and SO(2) and lung function. A plausible mechanism for these observed effects is decreased capacity to mount an effective response to oxidative stress associated with the GSTP1 AG + GG genotype.

Dietary benzo(a)pyrene and fetal growth: effect modification by vitamin C intake and glutathione S-transferase P1 polymorphism

BACKGROUND

Previous studies have reported maternal exposure to airborne polycyclic aromatic hydrocarbons (PAH), as well as DNA adducts reflecting total PAH exposure, to be associated with reduced fetal growth. The role of diet, the main source of PAH exposure among non-smokers, remains uncertain.

OBJECTIVE

To assess associations between birth weight, length and small size for gestational age (SGA) with maternal intakes of the genotoxic PAH benzo(a)pyrene [B(a)P] during pregnancy, exploring potential effect modification by dietary intakes of vitamin C, vitamin E, alpha- and beta-carotene, as well as glutathione S-transferase P1 (GSTP1) polymorphisms, hypothesized to influence PAH metabolism.

METHODS

657 women in the INMA (Environment and Childhood) Project from Sabadell (Barcelona) were recruited during the first trimester of pregnancy. Dietary B(a)P and nutrient intakes were estimated from food consumption data. Genotyping was conducted for the Ile105Val variant of GSTP1. Multivariable models were used to assess associations between size at birth and dietary B(a)P, evaluating potential interactions with candidate nutrients and GSTP1 variants.

RESULTS

There were significant interactions between elevated intakes of vitamin C (above the mean of 189.41 mg/day) and dietary B(a)P during the first trimester of pregnancy in models for birth weight and length (P<0.05), but no interactions were found with other nutrients. B(a)P intakes were associated with significant reductions in birth weight and length (coefficient±SE for a 1-SD increase in B(a)P: -101.63±34.62 g and -0.38±0.16 cm, respectively) among women with low, but not high, vitamin C intakes. Elevated dietary B(a)P was also associated with increased risk of SGA births among women with low dietary vitamin C. Among these women, associations were strongest in those carrying the GSTP1 Val allele, associated with lower contaminant detoxification activity.

CONCLUSION

Results suggest that dietary B(a)P exposure may impair fetal growth, particularly in genetically susceptible populations, and that increasing maternal intakes of vitamin C may help to reduce any adverse effects.

Air pollution and the respiratory system

Over the past 250 years-since the Industrial Revolution accelerated the process of pollutant emission, which, until then, had been limited to the domestic use of fuels (mineral and vegetal) and intermittent volcanic emissions-air pollution has been present in various scenarios. Today, approximately 50% of the people in the world live in cities and urban areas and are exposed to progressively higher levels of air pollutants. This is a non-systematic review on the different types and sources of air pollutants, as well as on the respiratory effects attributed to exposure to such contaminants. Aggravation of the symptoms of disease, together with increases in the demand for emergency treatment, the number of hospitalizations, and the number of deaths, can be attributed to particulate and gaseous pollutants, emitted by various sources. Chronic exposure to air pollutants not only causes decompensation of pre-existing diseases but also increases the number of new cases of asthma, COPD, and lung cancer, even in rural areas. Air pollutants now rival tobacco smoke as the leading risk factor for these diseases. We hope that we can impress upon pulmonologists and clinicians the relevance of investigating exposure to air pollutants and of recognizing this as a risk factor that should be taken into account in the adoption of best practices for the control of the acute decompensation of respiratory diseases and for maintenance treatment between exacerbations.

Role of GSTM1 in resistance to lung inflammation

Lung inflammation resulting from oxidant/antioxidant imbalance is a common feature of many lung diseases. In particular, the role of enzymes regulated by the NF-E2-related factor 2 transcription factor has recently received increased attention. Among these antioxidant genes, glutathione S-transferase Mu 1 (GSTM1) has been most extensively characterized because it has a null polymorphism that is highly prevalent in the population and associated with increased risk of inflammatory lung diseases. Present evidence suggests that GSTM1 acts through interactions with other genes and environmental factors, especially air pollutants. Here, we review GSTM1 gene expression and regulation and summarize the findings from epidemiological, clinical, animal, and in vitro studies on the role played by GSTM1 in lung inflammation. We discuss limitations in the existing knowledge base and future perspectives and evaluate the potential of pharmacologic and genetic manipulation of the GSTM1 gene to modulate pulmonary inflammatory responses.

Association study of genes associated to asthma in a specific environment, in an asthma familial collection located in a rural area influenced by different industries

Eight candidate genes selected in this study were previously associated with gene-environment interactions in asthma in an urban area. These genes were analyzed in a familial collection from a founder and remote population (Saguenay-Lac-Saint-Jean; SLSJ) located in an area with low air levels of ozone but with localized areas of relatively high air pollutant levels, such as sulphur dioxide, when compared to many urban areas. Polymorphisms (SNPs) were extracted from the genome-wide association study (GWAS) performed on the SLSJ familial collection. A transmission disequilibrium test (TDT) was performed using the entire family sample (1,428 individuals in 254 nuclear families). Stratification according to the proximity of aluminium, pulp and paper industries was also analyzed. Two genes were associated with asthma in the entire sample before correction (CAT and NQO1) and one was associated after correction for multiple analyses (CAT). Two genes were associated when subjects were stratified according to the proximity of aluminium industries (CAT and NQO1) and one according to the proximity of pulp and paper industries (GSTP1). However, none of them resisted correction for multiple analyses. Given that the spatial pattern of environmental exposures can be complex and inadequately represented by a few stationary monitors and that exposures can also come from sources other than the standard outdoor air pollution (e.g., indoor air, occupation, residential wood smoke), a new approach and new tools are required to measure specific and individual pollutant exposures in order to estimate the real impact of gene-environment interactions on respiratory health.

Bivalent enzyme inhibitors discovered using dynamic covalent chemistry

A bivalent dynamic covalent chemistry (DCC) system has been designed to selectively target members of the homodimeric glutathione-S-transferase (GST) enzyme family. The dynamic covalent libraries (DCLs) use aniline-catalysed acylhydrazone exchange between bivalent hydrazides and glutathione-conjugated aldehydes and the bis-hydrazides act as linkers to bridge between each glutathione binding site. The resultant DCLs were found to be compatible and highly responsive to templating with different GST isozymes, with the best results coming from the M and Schistosoma japonicum (Sj) class of GSTs, targets in cancer and tropical disease, respectively. The approach yielded compounds with selective, nanomolar affinity (K(i) =61 nM for mGSTM1-1) and demonstrates that DCC can be used to simultaneously interrogate binding sites on different subunits of a dimeric protein.

Urban air pollutants are significant risk factors for asthma and pneumonia in children: the influence of location on the measurement of pollutants

BACKGROUND

Air pollution is associated with a substantial burden on human health; however, the most important pollutants may vary with location. Proper monitoring is necessary to determine the effect of these pollutants on respiratory health.

OBJECTIVES

This study was designed to evaluate the role of outdoor, indoor and personal exposure to combustion-related pollutants NO(2) and O(3) on respiratory health of children in a non-affluent urban area of São Paulo, Brazil.

METHODS

Levels of NO(2) and O(3) were continuously measured in outdoor and indoor air, as well as personal exposure, for 30 days using passive measurement monitors. Respiratory health was assessed with a Brazilian version of the ISAAC questionnaire.

RESULTS

Complete data were available from 64 children, aged 6-10 years. Respiratory morbidity was high, with 43 (67.2%) reporting having had wheezing at any time, 27 (42.2%) wheezing in the last month, 17 (26.6%) asthma at any time and 21 (32.8%) pneumonia at any time. Correlations between levels of NO(2) and O(3) measured in the three locations evaluated were poor. Levels of NO(2) in indoor air and personal exposure to O(3) were independently associated with asthma (both cases P=.02), pneumonia (O(3), P=.02) and wheezing at any time (both cases P<.01). No associations were seen between outdoor NO(2) and O(3) and respiratory health.

CONCLUSIONS

Exposure to higher levels of NO(2) and O(3) was associated with increased risk for asthma and pneumonia in children. Nonetheless, the place where the pollutants are measured influences the results. The measurements taken in indoor and personal exposure were the most accurate.

Variants in the genes encoding TNF-α, IL-10, and GSTP1 influence the effect of α-tocopherol on inflammatory cell responses in healthy men

BACKGROUND

Despite evidence of antioxidant effects of vitamin E in vitro and in animal studies, large, randomized clinical trials have not substantiated a benefit of vitamin E in reducing inflammation in humans. An individual's genetic background may affect the response to α-tocopherol supplementation, but this has rarely been investigated.

OBJECTIVE

The aim of this study was to explore the role of genetic polymorphisms on changes in LPS-stimulated inflammatory cytokine production from peripheral blood mononuclear cells (PBMCs) after α-tocopherol supplementation.

DESIGN

A total of 160 healthy, middle-aged male volunteers (mean age: 52.7 y) were given dietary supplements of either 75 IU (low dose; n = 57) or 600 IU (high dose; n = 103) α-tocopherol/d for 6 wk. The production of TNF-α and IL-1β, -6, and -10 by PBMCs after LPS stimulation was measured at baseline and after 6 wk. Polymorphisms in 15 genes involved in inflammation or responses to oxidative stress were characterized in the subjects.

RESULTS

The ability of α-tocopherol to affect TNF-α production by LPS-stimulated PBMCs was influenced by the TNFA -238 polymorphism (P = 0.016). The ability of α-tocopherol to affect IL-6 production was influenced by the GSTP1 313 polymorphism (P = 0.019). The ability of α-tocopherol to affect IL-1β production was influenced by the IL10 -592 and -1082 polymorphisms (P = 0.025 and P = 0.016, respectively).

CONCLUSIONS

In healthy control subjects, the effect of α-tocopherol supplementation on the production of inflammatory cytokines appears to be dependent on an individual's genotype. These genotype-specific differences may help explain some of the discordant results in studies that used vitamin E.

Genetic variants in antioxidant genes are associated with diisocyanate-induced asthma

Diisocyanates are a common cause of occupational asthma, but risk factors are not well defined. A case-control study was conducted to investigate whether genetic variants of antioxidant defense genes, glutathione S-transferases (GSTM1, GSTT1, GSTM3, GSTP1), manganese superoxide dismutase (SOD2), and microsomal epoxide hydrolase (EPHX1) are associated with increased susceptibility to diisocyanate-induced asthma (DA). The main study population consisted of 353 Caucasian French-Canadians from among a larger sample of 410 diisocyanate-exposed workers in three groups: workers with specific inhalation challenge (SIC) confirmed DA (DA(+), n = 95); symptomatic diisocyanate workers with a negative SIC (DA(-), n = 116); and asymptomatic exposed workers (AW, n = 142). Genotyping was performed on genomic DNA, using a 5'-nuclease PCR assay. The SOD2 rs4880, GSTP1 rs1695, and EPHX1 rs2740171 variants were significantly associated with DA in both univariate and multivariate analyses. In the first logistic regression model comparing DA(+) and DA(-) groups, SOD2 rs4880, GSTM1 (null), GSTP1 rs762803, and EPHX1 rs2854450 variants were associated with DA (p = 0.004, p = 0.047, p = 0.021, p <0.001, respectively). Genotype combinations GSTT1*GSTP1 rs762803, GSTM1*EPHX1 rs2854450, EPHX1 rs2740168*EPHX1 rs1051741, and GSTP1 rs762803*EPHX1 rs2740168 were also associated with DA in this model (p = 0.027, p = 0.002, p = 0.045, p = 0.044, respectively). The GSTP1 rs1695 and EPHX1 rs1051741 and rs2740171 variants showed an association with DA in the second model comparing DA(+) and AW groups (p = 0.040, p = 0.019, p = 0.002, respectively). The GSTM3 rs110913*EPHX1 rs1051741 genotype combination was also associated with DA under this model (p = 0.042). The results suggest that variations in SOD2, GST, and EPHX1 genes and their interactions contribute to DA susceptibility.

Oxidative stress in asthma

Asthma is a chronic inflammatory lung disease that results in airflow limitation, hyperreactivity, and airway remodeling. There is strong evidence that an imbalance between the reducing and oxidizing systems favoring a more oxidative state is present in asthma. Endogenous and exogenous reactive oxygen species, such as superoxide anion, hydroxyl radical, hypohalite radical, and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide, peroxynitrite, and nitrite, play a major role in the airway inflammation and are determinants of asthma severity. Asthma is also associated with decreased antioxidant defenses, such as superoxide dismutase, catalase, and glutathione. In this review, we will summarize the current knowledge and discuss the current and future strategies for the modulation of oxidative stress in asthma.

GSTM1 modulation of IL-8 expression in human bronchial epithelial cells exposed to ozone

Exposure to the major air pollutant ozone can aggravate asthma and other lung diseases. Our recent study in human volunteers has shown that the glutathione S-transferase Mu 1 (GSTM1)-null genotype is associated with increased airway neutrophilic inflammation induced by inhaled ozone. The aim of this study was to examine the effect of GSTM1 modulation on interleukin 8 (IL-8) production in ozone-exposed human bronchial epithelial cells (BEAS-2B) and the underlying mechanisms. Exposure of BEAS-2B cells to 0.4 ppm ozone for 4 h significantly increased IL-8 release, with a modest reduction in intracellular reduced glutathione (GSH). Ozone exposure induced reactive oxygen species (ROS) production and NF-κB activation. Pharmacological inhibition of NF-κB activation or mutation of the IL-8 promoter at the κB-binding site significantly blocked ozone-induced IL-8 production or IL-8 transcriptional activity, respectively. Knockdown of GSTM1 in BEAS-2B cells enhanced ozone-induced NF-κB activation and IL-8 production. Consistently, an ozone-induced overt increase in IL-8 production was detected in GSTM1-null primary human bronchial epithelial cells. In addition, supplementation with reduced GSH inhibited ozone-induced ROS production, NF-κB activation, and IL-8 production. Taken together, GSTM1 deficiency enhances ozone-induced IL-8 production, which is mediated by generated ROS and subsequent NF-κB activation in human bronchial epithelial cells.

Ambient pollutants, polymorphisms associated with microRNA processing and adhesion molecules: the Normative Aging Study

BACKGROUND

Particulate air pollution has been associated with cardiovascular morbidity and mortality, but it remains unclear which time windows and pollutant sources are most critical. MicroRNA (miRNA) is thought to be involved in cardiovascular regulation. However, little is known about whether polymorphisms in genes that process microRNAs influence response to pollutant exposure. We hypothesized that averaging times longer than routinely measured one or two day moving averages are associated with higher soluble intercellular adhesion molecule-1 (sICAM-1) and vascular cell adhesion molecule-1 (sVCAM-1) levels, and that stationary and mobile sources contribute differently to these effects. We also investigated whether single nucleotide polymorphisms (SNPs) in miRNA-processing genes modify these associations.

METHODS

sICAM-1 and sVCAM-1 were measured from 1999-2008 and matched to air pollution monitoring for fine particulate matter (PM2.5) black carbon, and sulfates (SO42-). We selected 17 SNPs in five miRNA-processing genes. Mixed-effects models were used to assess effects of pollutants, SNPs, and interactions under recessive inheritance models using repeated measures.

RESULTS

723 participants with 1652 observations and 1-5 visits were included in our analyses for black carbon and PM2.5. Sulfate data was available for 672 participants with 1390 observations. An interquartile range change in seven day moving average of PM2.5 (4.27 μg/m3) was associated with 3.1% (95%CI: 1.6, 4.6) and 2.5% (95%CI: 0.6, 4.5) higher sICAM-1 and sVCAM-1. Interquartile range changes in sulfates (1.39 μg/m3) were associated with 1.4% higher (95%CI: 0.04, 2.7) and 1.6% (95%CI: -0.4, 3.7) higher sICAM-1 and sVCAM-1 respectively. No significant associations were observed for black carbon. In interaction models with PM2.5, both sICAM-1 and sVCAM-1 levels were lower in rs1062923 homozygous carriers. These interactions remained significant after multiple comparisons adjustment.

CONCLUSIONS

PM2.5 seven day moving averages are associated with higher sICAM-1 and sVCAM-1 levels. SO4-2 seven day moving averages are associated with higher sICAM-1 and a suggestive association was observed with sVCAM-1 in aging men. SNPs in miRNA-processing genes may modify associations between ambient pollution and sICAM-1 and sVCAM-1, which are correlates of atherosclerosis and cardiovascular disease.

Interactive effects of antioxidant genes and air pollution on respiratory function and airway disease: a HuGE review

Susceptibility to the respiratory effects of air pollution varies between individuals. Although some evidence suggests higher susceptibility for subjects carrying variants of antioxidant genes, findings from gene-pollution interaction studies conflict in terms of the presence and direction of interactions. The authors conducted a systematic review on antioxidant gene-pollution interactions which included 15 studies, with 12 supporting the presence of interactions. For the glutathione S-transferase M1 gene (GSTM1) (n=10 studies), only 1 study found interaction with the null genotype alone, although 5 observed interactions when GSTM1 was evaluated jointly with other genes (mainly NAD(P)H dehydrogenase [quinone] 1 (NQO1)). All studies on the glutathione S-transferase P1 (GSTP1) Ile105Val polymorphism (n=11) provided some evidence of interaction, but findings conflicted in terms of risk allele. Results were negative for glutathione S-transferase T1 (GSTT1) (n=3) and positive for heme oxygenase 1 (HMOX-1) (n=2). Meta-analysis could not be performed because there were insufficient data available for any specific gene-pollutant-outcome combination. Overall the evidence supports the presence of gene-pollution interactions, although which pollutant interacts with which gene is unclear. However, issues regarding multiple testing, selective reporting, and publication bias raise the possibility of false-positive findings. Larger studies with greater accuracy of pollution assessment and improved quality of conduct and reporting are required.

Asthma in swimmers: a review of the current literature

Asthma is common in many types of athletes, but its prevalence appears to be particularly high in swimmers. Long-term and acute exposure to swimming pool disinfectants has been shown to increase asthma risk in swimmers through inducing oxidative stress, which results in inflammation of the pulmonary epithelium and subsequent airway remodeling. Individuals with specific genotypes are more likely to develop asthma when exposed to inhaled irritants. Therefore, it is important for physicians to be knowledgeable about the risks associated with asthma in swimmers, as well as the diagnostic techniques and practices to reduce asthma symptoms.

Short-term effects of air pollution on wheeze in asthmatic children in Fresno, California

BACKGROUND

Although studies have demonstrated that air pollution is associated with exacerbation of asthma symptoms in children with asthma, little is known about the susceptibility of subgroups, particularly those with atopy.

OBJECTIVE

This study was designed to evaluate our a priori hypothesis that identifiable subgroups of asthmatic children are more likely to wheeze with exposure to ambient air pollution.

METHODS

A cohort of 315 children with asthma, 6-11 years of age, was recruited for longitudinal follow-up in Fresno, California (USA). During the baseline visit, children were administered a respiratory symptom questionnaire and allergen skin-prick test. Three times a year, participants completed 14-day panels during which they answered symptom questions twice daily. Ambient air quality data from a central monitoring station were used to assign exposures to the following pollutants: particulate matter ≤ 2.5 μm in aerodynamic diameter, particulate matter between 2.5 and 10 μm in aerodynamic diameter (PM10-2.5), elemental carbon, nitrogen dioxide (NO2), nitrate, and O3.

RESULTS

For the group as a whole, wheeze was significantly associated with short-term exposures to NO2 [odds ratio (OR) = 1.10 for 8.7-ppb increase; 95% confidence interval (CI), 1.02-1.20] and PM10-2.5 (OR = 1.11 for 14.7-μg/m3 increase; 95% CI, 1.01-1.22). The association with wheeze was stronger for these two pollutants in children who were skin-test positive to cat or common fungi and in boys with mild intermittent asthma.

CONCLUSION

A pollutant associated with traffic emissions, NO2, and a pollutant with bioactive constituents, PM10-2.5, were associated with increased risk of wheeze in asthmatic children living in Fresno, California. Children with atopy to cat or common fungi and boys with mild intermittent asthma were the subgroups for which we observed the largest associations.

Genetic mechanisms of susceptibility to ozone-induced lung disease

Environmental oxidants remain a major public health concern in industrialized cities throughout the world. Population and epidemiological studies have associated oxidant air pollutants with morbidity and mortality outcomes, and underscore the important detrimental effects of these pollutants on the lung. Interindividual variation in pulmonary responses to air pollutants suggests that some subpopulations are at increased risk to detrimental effects of pollutant exposure, and it has become clear that genetic background is an important susceptibility factor. A number of genetics and genomics tools have recently emerged to enable identification of genes that contribute to differential responsiveness to oxidants, including ozone (O(3)). Integrative omics approaches have been applied in inbred mice to identify genes that determine differential responsiveness to O(3)-induced injury and inflammation, including Tnf, Tlr4, and MHC Class II genes. Combined investigations across cell models, inbred mice, and humans have provided, and will continue to provide, important insight to understanding genetic factors that contribute to differential susceptibility to oxidants.

Is the air pollution health research community prepared to support a multipollutant air quality management framework?

Ambient air pollution is always encountered as a complex mixture, but past regulatory and research strategies largely focused on single pollutants, pollutant classes, and sources one-at-a-time. There is a trend toward managing air quality in a progressively "multipollutant" manner, with the idealized goal of controlling as many air contaminants as possible in an integrated manner to achieve the greatest total reduction of adverse health and environmental impacts. This commentary considers the current ability of the environmental air pollution exposure and health research communities to provide evidence to inform the development of multipollutant air quality management strategies and assess their effectiveness. The commentary is not a literature review, but a summary of key issues and information gaps, strategies for filling the gaps, and realistic expectations for progress that could be made during the next decade. The greatest need is for researchers and sponsors to address air quality health impacts from a truly multipollutant perspective, and the most limiting current information gap is knowledge of personal exposures of different subpopulations, considering activities and microenvironments. Emphasis is needed on clarifying the roles of a broader range of pollutants and their combinations in a more forward-looking manner; that is not driven by current regulatory structures. Although advances in research tools and outcome data will enhance progress, the greater need is to direct existing capabilities toward strategies aimed at placing into proper context the contributions of multiple pollutants and their combinations to the health burdens, and the relative contributions of pollutants and other factors influencing the same outcomes. The authors conclude that the research community has very limited ability to advise multipollutant air quality management and assess its effectiveness at this time, but that considerable progress can be made in a decade, even at current funding levels, if resources and incentives are shifted appropriately.

Gene by environment interaction and ambient air pollution

Epidemiologic studies have clearly shown that air pollution is associated with a range of respiratory effects. Recent research has identified oxidative stress as a major biologic pathway underlying the toxic effect of air pollutants. Genetic susceptibility is likely to play a role in response to air pollution. Genes involved in oxidative stress and inflammatory pathways are logical candidates for the study of the interaction with air pollutants. In this article we use the example of asthma, a genetically complex disease, to address the issue of gene by environment interaction with air pollution. The majority of studies have focused on the genes GSTM1, GSTP1, NQO1, and TNF, but the inconsistency of the results prevents the drawing of firm conclusions. The limited sample size of most studies to date make them underpowered for the study of gene by gene interactions. Large consortia of studies with repeated measurements of environmental exposures and clear phenotypic assessments may help determine special environmental triggers and the window of susceptibility in the development of atopy and asthma. The role of gene by gene interactions and epigenetic mechanisms needs to be considered along with gene by environment interactions.

Novel antioxidant approaches to the treatment of upper airway inflammation

PURPOSE OF REVIEW

Current understanding of the role of oxidative stress in airway inflammation suggests that antioxidant therapy may be important to optimize the treatment. This review summarizes recent investigations of novel antioxidant agents for upper airway inflammation, with selected studies focused on lower airway disease as additional candidate therapeutics.

RECENT FINDINGS

Recently investigated antioxidant therapies for airway inflammation may be broadly grouped into three categories: endogenous metabolic agents, vitamins/nutrients, and botanical extracts. Studies examining effects in upper airway inflammation are limited and primarily consist of in-vitro human and in-vivo animal models. More extensive studies have investigated the benefits of antioxidants in lower airway conditions such as allergic asthma. Existing evidence identifies antioxidant agents with potential therapeutic value, although human studies suggest that subpopulations affected by specific genetic, environmental, dietary factors, or all are most likely to benefit from antioxidant therapy.

SUMMARY

Oxidative stress plays a causative role in upper airway inflammation, and novel strategies to mitigate cellular injury with antioxidant therapy may ameliorate disease in target populations. Preclinical studies demonstrate evidence of anti-inflammatory effects for a number of promising antioxidant agents. Well designed interventional human studies of the upper airway, which account for complex gene-environment-diet interactions, will be necessary to adequately examine the potential clinical benefit of antioxidant therapies for rhinosinusitis.