Asthma, genes, and air pollution

Lifetime Risk Factors for Pre- and Post-Bronchodilator Lung Function Decline. A Population-based Study

Rationale: Interactions between early life and adult insults on lung function decline are not well understood, with most studies investigating prebronchodilator (pre-BD) FEV₁ decline.Objectives: To investigate relationships between adult risk factors and pre- and post-BD lung function decline and their potential effect modification by early life and genetic factors.Methods: Multiple regression was used to examine associations between adult exposures (asthma, smoking, occupational exposures, traffic pollution, and obesity) and decline in both pre- and post-BD spirometry (forced expiratory volume in 1 s [FEV₁], forced vital capacity [FVC], and FEV₁/FVC) between ages 45 and 53 years in the Tasmanian Longitudinal Health Study (n = 857). Effect modification of these relationships by childhood respiratory risk factors, including low childhood lung function and GST (glutathione S-transferase) gene polymorphisms, was investigated.Results: Baseline asthma, smoking, occupational exposure to vapors/gases/dusts/fumes, and living close to traffic were associated with accelerated decline in both pre- and post-BD FEV₁. These factors were also associated with FEV₁/FVC decline. Occupational exposure to aromatic solvents was associated with pre-BD but not post-BD FEV₁ decline. Maternal smoking accentuated the effect of personal smoking on pre- and post-BD FEV₁ decline. Lower childhood lung function and having the GSTM1 null allele accentuated the effect of occupational exposure to vapors/gases/dusts/fumes and personal smoking on post-BD FEV₁ decline. Incident obesity was associated with accelerated decline in FEV₁ and more pronounced in FVC.Conclusions: This study provides new evidence for accentuation of individual susceptibility to adult risk factors by low childhood lung function, GSTM1 genotype, and maternal smoking.

Development of Telintra as an Inhibitor of Glutathione S-Transferase P

Glutathione S-transferase P (GSTP) is a component of a complex series of pathways that provide cellular redox homeostasis. It is an abundant protein in certain tumors and is over-expressed in cancer drug resistance. It has diverse cellular functions that include, thiolase activities with small electrophilic agents or susceptible cysteine residues on the protein to mediate S-glutathionylation, and chaperone binding with select protein kinases. Preclinical and clinical testing of a nanomolar inhibitor of GSTP, TLK199 (Telintra; Ezatiostat) has indicated a role for the enzyme in hematopoiesis and utility for the drug in the treatment of patients with myelodysplastic syndrome.

Prenatal fine particulate exposure associated with reduced childhood lung function and nasal epithelia GSTP1 hypermethylation: Sex-specific effects

Background

In utero exposure to particulate matter with an aerodynamic diameter of less than 2.5 μm (PM_2.5) has been linked to child lung function. Overlapping evidence suggests that child sex and exposure timing may modify effects and associations may be mediated through glutathione S-transferase P1 (GSTP1) methylation.

Methods

We prospectively examined associations among prenatal PM_2.5 exposure and child lung function and GSTP1 methylation in an urban pregnancy cohort study. We employed a validated satellite-based spatiotemporally resolved prediction model to estimate daily prenatal PM_2.5 exposure over gestation. We used Baysian distributed lag interaction models (BDLIMs) to identify sensitive windows for prenatal PM_2.5 exposure on child lung function and nasal epithelia GSTP1 methylation at age 7 years, and to examine effect modification by child sex.

Results

BDLIMs identified a sensitive window for prenatal PM_2.5 exposure at 35–40 weeks gestation [cumulative effect estimate (CEE) = − 0.10, 95%CI = − 0.19 to − 0.01, per μg/m³ increase in PM_2.5] and at 36–40 weeks (CEE = − 0.12, 95%CI = − 0.20 to − 0.01) on FEV₁ and FVC, respectively, in boys. BDLIMs also identified a sensitive window of exposure at 37–40 weeks gestation between higher prenatal PM_2.5 exposure and increased GSTP1 percent methylation. The association between higher GSTP1 percent methylation and decreased FEV1 was borderline significant in the sample as a whole (β = − 0.37, SE = 0.20, p = 0.06) and in boys in stratified analyses (β = − 0.56, SE = 0.29, p = 0.05).

Conclusions

Prenatal PM_2.5 exposure in late pregnancy was associated with impaired early childhood lung function and hypermethylation of GSTPI in DNA isolated from nasal epithelial cells. There was a trend towards higher GSTP1 percent methylation being associated with reduced FEV1. All findings were most evident among boys.

Traffic-related air pollution exposure over a 5-year period is associated with increased risk of asthma and poor lung function in middle age

Current evidence concerning the impact of exposure to traffic-related air pollution (TRAP) on adult respiratory morbidity mainly comes from cross-sectional studies. We sought to establish more robust measures of this association and potential gene-environment interactions using longitudinal data from an established cohort study.Associations between measures of TRAP (nitrogen dioxide (NO₂) and distance to major roads) and wheeze, asthma prevalence and lung function were investigated in participants of the Tasmanian Longitudinal Health Study at 45- and 50-year follow-ups. Generalised estimating equations were used to quantify associations and the potential modifying effect of glutathione S-transferase gene variants.Living <200 m from a major road was associated with increased prevalence of current asthma and wheeze, and lower lung function. The association between living <200 m from a major road and current asthma and wheeze was more marked for carriers of the GSTT1 null and GSTP1 val/val or ile/val genotypes. Over the 5-year period, higher NO₂ exposures were associated with increased current asthma prevalence. Higher NO₂ exposure was associated with lower forced vital capacity for carriers of the GSTT1 null genotype.TRAP exposures were associated with increased risk of asthma, wheeze and lower lung function in middle-aged adults. The interaction with the GSTT1 genotype suggests that deficient antioxidant mechanisms may play a role in these adverse health effects.

Traffic-related air pollution exposure is associated with allergic sensitization, asthma, and poor lung function in middle age

BACKGROUND

Traffic-related air pollution (TRAP) exposure is associated with allergic airway diseases and reduced lung function in children, but evidence concerning adults, especially in low-pollution settings, is scarce and inconsistent.

OBJECTIVES

We sought to determine whether exposure to TRAP in middle age is associated with allergic sensitization, current asthma, and reduced lung function in adults, and whether these associations are modified by variants in Glutathione S-Transferase genes.

METHODS

The study sample comprised the proband 2002 laboratory study of the Tasmanian Longitudinal Health Study. Mean annual residential nitrogen dioxide (NO₂) exposure was estimated for current residential addresses using a validated land-use regression model. Associations between TRAP exposure and allergic sensitization, lung function, current wheeze, and asthma (n = 1405) were investigated using regression models.

RESULTS

Increased mean annual NO₂ exposure was associated with increased risk of atopy (adjusted odds ratio [aOR], 1.14; 95% CI, 1.02-1.28 per 1 interquartile range increase in NO₂ [2.2 ppb]) and current wheeze (aOR, 1.14; 1.02-1.28). Similarly, living less than 200 m from a major road was associated with current wheeze (aOR, 1.38; 95% CI, 1.06-1.80) and atopy (aOR, 1.26; 95% CI, 0.99-1.62), and was also associated with having significantly lower prebronchodilator and postbronchodilator FEV₁ and prebronchodilator forced expiratory flow at 25% to 75% of forced vital capacity. We found evidence of interactions between living less than 200 m from a major road and GSTT1 polymorphism for atopy, asthma, and atopic asthma. Overall, carriers of the GSTT1 null genotype had an increased risk of asthma and allergic outcomes if exposed to TRAP.

CONCLUSIONS

Even relatively low TRAP exposures confer an increased risk of adverse respiratory and allergic outcomes in genetically susceptible individuals.

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.

Glutathione S-transferase pi modulates NF-κB activation and pro-inflammatory responses in lung epithelial cells

Nuclear Factor kappa B (NF-κB) is a transcription factor family critical in the activation of pro- inflammatory responses. The NF-κB pathway is regulated by oxidant-induced post-translational modifications. Protein S-glutathionylation, or the conjugation of the antioxidant molecule, glutathione to reactive cysteines inhibits the activity of inhibitory kappa B kinase beta (IKKβ), among other NF-κB proteins. Glutathione S-transferase Pi (GSTP) is an enzyme that has been shown to catalyze protein S-glutathionylation (PSSG) under conditions of oxidative stress. The objective of the present study was to determine whether GSTP regulates NF-κB signaling, S-glutathionylation of IKK, and subsequent pro-inflammatory signaling. We demonstrated that, in unstimulated cells, GSTP associated with the inhibitor of NF-κB, IκBα. However, exposure to LPS resulted in a rapid loss of association between IκBα and GSTP, and instead led to a protracted association between IKKβ and GSTP. LPS exposure also led to increases in the S-glutathionylation of IKKβ. SiRNA-mediated knockdown of GSTP decreased IKKβ-SSG, and enhanced NF-κB nuclear translocation, transcriptional activity, and pro-inflammatory cytokine production in response to lipopolysaccharide (LPS). TLK117, an isotype-selective inhibitor of GSTP, also enhanced LPS-induced NF-κB transcriptional activity and pro-inflammatory cytokine production, suggesting that the catalytic activity of GSTP is important in repressing NF-κB activation. Expression of both wild-type and catalytically-inactive Y7F mutant GSTP significantly attenuated LPS- or IKKβ-induced production of GM-CSF. These studies indicate a complex role for GSTP in modulating NF-κB, which may involve S-glutathionylation of IKK proteins, and interaction with NF-κB family members. Our findings suggest that targeting GSTP is a potential avenue for regulating the activity of this prominent pro-inflammatory and immunomodulatory transcription factor.

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.

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.

Air pollution and health: emerging information on susceptible populations

Outdoor air pollution poses risks to human health in communities around the world, and research on populations who are most susceptible continues to reveal new insights. Human susceptibility to adverse health effects from exposure to air pollution can be related to underlying disease; demographic or anthropometric characteristics; genetic profile; race and ethnicity; lifestyle, behaviors, and socioeconomic position; and location of residence or daily activities. In health research, an individual or group may have an enhanced responsiveness to a given, identical level of pollution exposure compared to those who are less susceptible. Or, people in these different groups may experience varying levels of exposure (for example, a theoretically homogeneous population whose members differ only by proximity to a road). Often the information available for health research may relate to both exposure and enhanced response to a given dose of pollution. This paper discusses the general direction of research on susceptibility to air pollution, with a general though not an exclusive focus on particulate matter, with specific examples of research on susceptibility related to cardiovascular disease, diabetes, asthma, and genetic and epigenetic features. We conclude by commenting how emerging knowledge of susceptibility can inform policy for controlling pollution sources and exposures to yield maximal health benefit and discuss two areas of emerging interest: studying air pollution and its connection to perinatal health, as well as land use and urban infrastructure design.

The relationship of glutathione-S-transferases copy number variation and indoor air pollution to symptoms and markers of respiratory disease

INTRODUCTION

Exposure to particulate matter (PM) may induce inflammation and oxidative stress in the airways. Carriers of null polymorphisms of glutathione S-transferases (GSTs), which detoxify reactive oxygen species, may be particularly susceptible to the effects of PM.

OBJECTIVES

To investigate whether deletions of GSTM1 and GSTT1 modify the potential effects of exposure to indoor sources of PM on symptoms and objective markers of respiratory disease.

METHODS

We conducted a population-based, cross-sectional study of 3471 persons aged 18-69 years. Information about exposure to indoor sources of PM and respiratory symptoms was obtained by a self-administered questionnaire. In addition, measurements of lung function (spirometry) and fractional exhaled nitric oxide were performed. Copy number variation of GSTM1 and GSTT1 was determined by polymerase chain reaction-based assays.

RESULTS

We found that none of the symptoms and objective markers of respiratory disease were significantly associated with the GST null polymorphisms. An increasing number of positive alleles of the GSTM1 polymorphism tended to be associated lower prevalence of wheeze, cough, and high forced expiratory volume in 1 s (FEV(1) ), but these trends were not statistically significant. Furthermore, we did not observe any statistically significant interactions between GST copy number variation and exposure to indoor sources of PM in relation to respiratory symptoms and markers.

CONCLUSIONS

In this adult population, GST copy number variations were not significantly associated with respiratory outcomes and did not modify the effects of self-reported exposure to indoor sources of PM on respiratory outcomes.

Pulmonary function, bronchial reactivity, and epithelial permeability are response phenotypes to ozone and develop differentially in healthy humans

Effect of laboratory exposure to O₃ (220 ppb) and filtered air (FA) on respiratory physiology were evaluated at two time points (acute and 1 day postexposure) in healthy cohort (n = 138, 18-35 yr, 40% women) comprised mainly of Caucasian (60%) and African American (33.3%) subjects. Randomized exposures had a crossover design and durations of 2.25 h that included rest and treadmill walking. Airway responsiveness (AHR) to methacholine (Mch) and permeability of respiratory epithelium (EI) to hydrophilic radiomarker ((99m)Tc-DTPA, MW = 492), were measured at 1-day postexposure. O₃ significantly affected FEV₁ and FVC indices acutely with mean decrements from pre-exposure values on the order of 7.7 to 8.8% and 1.8 to 2.3% at 1-day post. Acute FEV₁ and FVC decreases were most robust in African American male subjects. At 1-day post, O₃ induced significant changes in AHR (slope of Mch dose response curve) and EI (Tc(99m)-DTPA clearance half-time). Based on conventional thresholds of response and dichotomous classification of subjects as responders and nonresponders, sensitivity to O₃ was shown to be nonuniform. Acute decrements ≥ 15% in FEV₁, a doubling of Mch slope, or ≥ 15% increase in EI developed in 20.3%, 23.1%, and 25.9%, respectively, of subjects evaluated. Results demonstrate a diffuse sensitivity to O₃ and physiological responses, either acutely (decreases in FEV₁) or 1 day post (development of AHR or change in EI) occur differentially in healthy young adults. Random overlap among subjects classified as responsive for respective FEV₁, AHR, and EI endpoints suggests these are separate and independent phenotypes of O₃ exposure.

Current priorities for public health practice in addressing the role of human genomics in improving population health

In spite of accelerating human genome discoveries in a wide variety of diseases of public health significance, the promise of personalized health care and disease prevention based on genomics has lagged behind. In a time of limited resources, public health agencies must continue to focus on implementing programs that can improve health and prevent disease now. Nevertheless, public health has an important and assertive leadership role in addressing the promise and pitfalls of human genomics for population health. Such efforts are needed not only to implement what is known in genomics to improve health but also to reduce potential harm and create the infrastructure needed to derive health benefits in the future.

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.

The role of GSTP1 polymorphisms and tobacco smoke exposure in children with acute asthma

BACKGROUND

The glutathione S-transferase enzymes (GSTs) play an important role in the detoxification of environmental tobacco smoke (ETS), which contributes to airway inflammation, a key component of asthma. Genetic variation in GST genes may influence individuals' ability to detoxify environmental pollutants.

OBJECTIVE

To examine the role of polymorphisms in GSTP1 (Ile105Val and Ala114Val), alone and in combination with ETS exposure, on atopy and asthma severity.

METHODS

GSTP1 Ile105Val and Ala114Val were genotyped and ETS exposure was assessed by parental questionnaire, which was validated by urinary cotinine measurements. Associations between ETS exposure, GSTP1 polymorphisms, and their interaction on atopy and asthma severity were investigated.

RESULTS

For the functional GSTP1 105 SNP, those with the Ile/Ile genotype had odds for atopy of 2.77 (p = .054) when assessed by genotype alone, which increased to 9.02 (p = .050) when ETS was included, relative to individuals with other genotypes. Likewise, compared to children with other GSTP1 114 genotypes, those with Ala/Ala genotype had a 5.47-fold (p = .002) increased risk of atopy (p = .020) when assessed by genotype alone, increasing to 9.17-fold when ETS was included. The 105 Ile/Ile individuals all had the AA (105 Ile/Ile and 114 Ala/Ala) haplotype group; therefore, the odds for atopy were the same. Individuals without any *C haplotype (105 Val and 114 Val allele) who were exposed to ETS had a 9.17-fold increased risk of atopy when compared with individuals with at least one *C haplotype and not exposed to ETS (p = .020).

CONCLUSION

There were significant interactions between GSTP1 SNPs, atopy, and ETS exposure in this cohort.

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.

Airway mast cells in a rhesus model of childhood allergic airways disease

Asthma is a leading cause of morbidity in children. Risk factors include chronic exposure to allergens and air pollution. While chronically activated mast cells contribute to the pathophysiology of asthma in part through their proteases such as chymase and tryptase, previous studies of airway mast cell abundance and distribution in asthmatics have been inconsistent. To determine whether repeated episodic exposures to environmental pollutants during postnatal lung development alter airway mast cell abundance and distribution, we exposed infant rhesus monkeys to a known human allergen, house dust mite antigen (HDMA), and/or a known environmental pollutant, ozone (O(3)), and quantitatively compared the abundance of tryptase- or chymase-positive mast cells in three airway levels. Mast cells are resident in multiple compartments of the airway wall in infant rhesus monkeys raised from birth in filtered air. Tryptase- and chymase-positive cells were most abundant in trachea and least in terminal bronchioles. The majority of tryptase-positive and almost all chymase-positive cells were in extracellular matrix and smooth muscle bundles. Chronic exposure to HDMA elevated the abundance of both tryptase- and chymase-positive cells in the trachea and intrapulmonary bronchi. Neither exposure to O(3) nor HDMA + O(3) increased mast cell accumulations in the airway wall. We conclude that during postnatal airway development (1) mast cells are a resident airway cell population even in the absence of toxic air contaminants; (2) aeroallergen exposure alters large airway mast cell distribution and abundance, increasing chymase-positive mast cells; and (3) this response is attenuated by exposure to oxidant air pollutants.

Antioxidant effects of mycophenolate mofetil in a murine pleurisy model

Generation of oxidative stress induced by reactive oxygen species (ROS) and nitrogen (RNS) is believed to be a primary factor in the etiology of various inflammatory diseases. Although, the process of generation of oxygen species is a physiological event, in the inflammatory process this event is increased and produces large amounts of reactive species that leads to lipid peroxidation and to cell death. Mycophenolate mofetil (MMF) is a drug effective in protecting against chronic allograft failure and recently was introduced as an alternative for the treatment of various inflammatory diseases such as glomerulopathies, systemic lupus erythematosus and systemic vasculitis. Based on studies of the anti-inflammatory effect of MMF the aim of this study was to evaluate the effects of MMF on the inhibition of leukocytes and exudation, as well as myeloperoxidase and some antioxidant enzyme activities using carrageenan-induced pleurisy in mice. Our results showed that MMF significantly decreased leukocyte influx (P<0.01), exudation (P<0.01), superoxide dismutase (P<0.05), catalase (P<0.05), glutathione peroxidase (P<0.01), glutathione S-transferase (P<0.01) activities, levels of lipid peroxidation (P<0.05), as well as myeloperoxidase activity (P<0.05) on both phases (4h and 48h) of the inflammatory response induced by carrageenan into the mice pleural cavity. In conclusion, the anti-inflammatory effect of MMF may be, at least in part, via inhibition of ROS and/or NRS overgeneration, and consequently, attenuating the related oxidative stress.

The relationship between household income and childhood respiratory health in the United Kingdom

Growing empirical evidence on the association between household income and adverse child health outcomes has generated mixed results with some North-American studies showing a significant inverse relationship and some British studies identifying a much weaker association. We use data from the rich UK Millennium Cohort Study (MCS) dataset and check the robustness of these recent findings by focusing on the impact of household income on adverse childhood respiratory outcomes (i.e. asthma and wheezing). We also identify pathways, such as mother's child-health-related behaviours, parental health and grandparental socioeconomic status, through which income might influence child health. Our econometric strategy is to use, both in a cross-sectional and in a panel data context, detailed information in the MCS dataset to directly account for as many potential confounding factors as possible that might bias the income-child health nexus. Overall our results show that household income has a weak direct effect on child health after we control for potential mechanisms that mediate the income-child health association. We argue that our evidence should inform government health and broader fiscal policies aimed at reducing health inequalities in childhood.

The importance of biological samples in longitudinal birth cohort studies

Here we describe how measurements in biological samples can be used to provide direct measures of exposures to environmental pollutants, nutrients, infectious organisms and drugs of abuse, and to validate other less direct measures of exposure such as questionnaire responses. They can also be used as measures of outcome traits or intermediate phenotypes which may lie on the pathways to disease.

Regulatory T cells in bronchial asthma

The main focus of this review was the role of a specific subset of T cells with immunomodulatory or immunosuppressive activities, termed regulatory T cells (Tregs), in the pathogenesis and treatment of bronchial asthma. Evidence that these cells are important in maintaining immune homeostasis in health and exhibit impaired activity in active disease will be discussed. Their therapeutic potential is perhaps best highlighted by evidence that therapies with demonstrated efficacy in allergic and asthmatic disease are associated with the induction or restoration of regulatory T-cell function, e.g. glucocorticoids, allergen immunotherapy. Strategies to improve the safety and efficacy of these treatments and that induce or boost Tregs in bronchial asthma are discussed.

Air pollution exposure assessment methods utilized in epidemiological studies

The assessment of personal exposure to air pollution is a critical component of epidemiological studies associating air pollution and health effects. This paper critically reviewed 157 studies over 29 years that utilized one of five categories of exposure methods (proximity, air dispersion, hybrid, human inhalation, and biomarkers). Proximity models were found to be a questionable technique as they assume that closer proximity equates to greater exposure. Inhalation models and biomarker estimates were the most effective in assessing personal exposure, but are often cost prohibitive for large study populations. This review suggests that: (i) factors such as uncertainty, validity, data availability, and transferability related to exposure assessment methods should be considered when selecting a model; and (ii) although an entirely discreet new class of approach is not necessary, significant progress could be made through the development of a 'hybrid' model utilizing the strengths of several existing methods. Future work should systematically evaluate the performance of hybrid models compared to other individual exposure assessment methods utilizing geospatial information technologies (e.g. geographic information systems (GIS) and remote sensing (RS)) to more robustly refine estimates of ambient exposure and quantify the linkages and differences between outdoor, indoor and personal exposure estimates.

Comparative microarray analysis and pulmonary changes in Brown Norway rats exposed to ovalbumin and concentrated air particulates

The interaction between air particulates and genetic susceptibility has been implicated in the pathogenesis of asthma. The overall objective of this study was to determine the effects of inhalation exposure to environmentally relevant concentrated air particulates (CAPs) on the lungs of ovalbumin (ova) sensitized and challenged Brown Norway rats. Changes in gene expression were compared with lung tissue histopathology, morphometry, and biochemical and cellular parameters in bronchoalveolar lavage fluid (BALF). Ova challenge was responsible for the preponderance of gene expression changes, related largely to inflammation. CAPs exposure alone resulted in no significant gene expression changes, but CAPs and ova-exposed rodents exhibited an enhanced effect relative to ova alone with differentially expressed genes primarily related to inflammation and airway remodeling. Gene expression data was consistent with the biochemical and cellular analyses of the BALF, the pulmonary pathology, and morphometric changes when comparing the CAPs-ova group to the air-saline or CAPs-saline group. However, the gene expression data were more sensitive than the BALF cell type and number for assessing the effects of CAPs and ova versus the ova challenge alone. In addition, the gene expression results provided some additional insight into the TGF-beta-mediated molecular processes underlying these changes. The broad-based histopathology and functional genomic analyses demonstrate that exposure to CAPs exacerbates rodents with allergic inflammation induced by an allergen and suggests that asthmatics may be at increased risk for air pollution effects.

Systemic first-line phenotyping

With the completion of the mouse genome sequence an essential task for biomedical sciences in the twenty-first century will be the generation and functional analysis of mouse models for every gene in the mammalian genome. More than 30,000 mutations in ES cells will be engineered and thousands of mouse disease models will become available over the coming years by the collaborative effort of the International Mouse Knockout Consortium. In order to realize the full value of the mouse models proper characterization, archiving and dissemination of mouse disease models to the research community have to be performed. Phenotyping centers (mouse clinics) provide the necessary capacity, broad expertise, equipment, and infrastructure to carry out large-scale systemic first-line phenotyping. Using the example of the German Mouse Clinic (GMC) we will introduce the reader to the different aspects of the organization of a mouse clinic and present selected methods used in first-line phenotyping.

Air pollutants, oxidative stress and human health

Air pollutants have, and continue to be, major contributing factors to chronic diseases and mortality, subsequently impacting public health. Chronic diseases include: chronic obstructive pulmonary diseases (COPD), cardiovascular diseases (CVD), asthma, and cancer. Byproducts of oxidative stress found in air pollutants are common initiators or promoters of the damage produced in such chronic diseases. Such air pollutants include: ozone, sulfur oxides, carbon monoxide, nitrogen oxides, and particulate matter. Interaction between oxidative stress byproducts and certain genes within our population may modulate the expression of specific chronic diseases. In this brief review we attempt to provide some insight into what we currently know about the health problems associated with various air pollutants and their relationship in promoting chronic diseases through changes in oxidative stress and modulation of gene expression. Such insight eventually may direct the means for effective public health prevention and treatment of diseases associated with air pollution and treatment of diseases associated with air pollution.

Interactions between glutathione S-transferase P1, tumor necrosis factor, and traffic-related air pollution for development of childhood allergic disease

BACKGROUND

Air pollutants may induce airway inflammation and sensitization due to generation of reactive oxygen species. The genetic background to these mechanisms could be important effect modifiers.

OBJECTIVE

Our goal was to assess interactions between exposure to air pollution and single nucleotide polymorphisms (SNPs) in the beta2-adrenergic receptor (ADRB2), glutathione S-transferase P1 (GSTP1), and tumor necrosis factor (TNF) genes for development of childhood allergic disease.

METHODS

In a birth cohort originally of 4,089 children, we assessed air pollution from local traffic using nitrogen oxides (traffic NO(x)) as an indicator based on emission databases and dispersion modeling and estimated individual exposure through geocoding of home addresses. We measured peak expiratory flow rates and specific IgE for inhalant and food allergens at 4 years of age, and selected children with asthma symptoms up to 4 years of age (n = 542) and controls (n = 542) for genotyping.

RESULTS

Interaction effects on allergic sensitization were indicated between several GSTP1 SNPs and traffic NO(x) exposure during the first year of life (p(nominal) < 0.001-0.06). Children with Ile105Val/Val105Val genotypes were at increased risk of sensitization to any allergen when exposed to elevated levels of traffic NO(x) (for a difference between the 5th and 95th percentile of exposure: odds ratio = 2.4; 95% confidence interval, 1.0-5.3). In children with TNF-308 GA/AA genotypes, the GSTP1-NO(x) interaction effect was even more pronounced. We observed no conclusive interaction effects for ADRB2.

CONCLUSION

The effect of air pollution from traffic on childhood allergy appears to be modified by GSTP1 and TNF variants, supporting a role of genes controlling the antioxidative system and inflammatory response in allergy.

Background, approaches and recent trends for setting health-based occupational exposure limits: a minireview

The setting of occupational exposure limits (OELs) are founded in occupational medicine and the predictive toxicological testing, resulting in exposure-response relationships. For compounds where a No-Observed-Adverse-Effect-Level (NOAEL) can be established, health-based OELs are set by dividing the NOAEL of the critical effect by an overall uncertainty factor. Possibly, the approach may also be used for carcinogens if the mechanism is epigenetic or the genetic effect is secondary to effect from reactions with proteins such as topoisomerase inhibitors, and mitotic and meiotic spindle poisons. Additionally, the NOAEL approach may also be used for compounds with weak genotoxic effect, playing no or only a minor role in the development of tumours. No health-based OEL can be set for direct-acting genotoxic compounds where the life-time risks may be estimated from the low-dose linear non-threshold extrapolation, allowing a politically based exposure level to be set. OELs are set by several agencies in the US and Europe, but also in-house in major chemical and pharmaceutical companies. The benchmark dose approach may in the future be used where it has advantage over the NOAEL approach. Also, more attention should be devoted to sensitive groups, toxicological mechanisms and interactions as most workplace exposures are mixtures.

Oxygen, the lead actor in the pathophysiologic drama: enactment of the trinity of normoxia, hypoxia, and hyperoxia in disease and therapy

Aerobic life has evolved a dependence on molecular oxygen for its mere survival. Mitochondrial oxidative phosphorylation absolutely requires oxygen to generate the currency of energy in aerobes. The physiologic homeostasis of these organisms is strictly maintained by optimal cellular and tissue-oxygenation status through complex oxygen-sensing mechanisms, signaling cascades, and transport processes. In the event of fluctuating oxygen levels leading to either an increase (hyperoxia) or decrease (hypoxia) in cellular oxygen, the organism faces a crisis involving depletion of energy reserves, altered cell-signaling cascades, oxidative reactions/events, and cell death or tissue damage. Molecular oxygen is activated by both nonenzymatic and enzymatic mechanisms into highly reactive oxygen species (ROS). Aerobes have evolved effective antioxidant defenses to counteract the reactivity of ROS. Although the ROS are also required for many normal physiologic functions of the aerobes, overwhelming production of ROS coupled with their insufficient scavenging by endogenous antioxidants will lead to detrimental oxidative stress. Needless to say, molecular oxygen is at the center of oxygenation, oxidative phosphorylation, and oxidative stress. This review focuses on the biology and pathophysiology of oxygen, with an emphasis on transport, sensing, and activation of oxygen, oxidative phosphorylation, oxygenation, oxidative stress, and oxygen therapy.

Air pollution as a determinant of asthma among schoolchildren in Mohammedia, Morocco

The objective of the study was to investigate whether air quality in western Morocco is truly a significant risk factor in the development and exacerbation of respiratory diseases and, in particular, asthma. The continuous measurement of the mean concentrations of sulfur dioxide (SO(2)) in the air and the density of Total Suspended Particulates (TSP) for a period of four years was determined. Information on individual characteristics and indoor environments from 1318 children with an average age of 12 years was evaluated by questionnaire, completed by parents (assisted by professional investigators) and symptoms/diseases were medically diagnosed and reported. We have used the Student's t-test, Chi-square tests & odds ratios (ORs) with 95% confidence intervals (CI 95%) for estimates of the risk of asthma. The prevalence of asthma varies in a significant way according to the zone (chi(2) = 14.61, p < 0.05). Respiratory diseases (OR 6.27, 95% confidence interval [CI] 4.09-9.64, p < 0.0001), strongly polluted zone (OR 3.62, 95% CI 1.71-7.81, p < or = 0.0001) and infectious diseases (OR 3.29, 95% CI 1.99-5.47, p < 0.0001) are high risk factors for asthma. Air pollution is a determinant factor but is not the only factor increasing the risk of asthma in children; other factors such as respiratory diseases, infectious diseases, genetic and passive smoking present a high-risk threat.

Interactive effect of family history and environmental factors on respiratory tract-related morbidity in infancy

BACKGROUND

Family and environmental factors affect the development of respiratory morbidity. How these factors interact is unclear.

OBJECTIVE

We sought to clarify the interactive effect of family history of asthma and environmental factors on the occurrence of respiratory morbidity.

METHODS

Two hundred twenty-one infants with a positive family history of asthma (PFH) and 308 with a negative family history of asthma (NFH) were prenatally selected and followed until the age of 2 years. Exposure to environmental factors and the occurrence of respiratory morbidity were recorded. By using multiple logistic regression analysis, increased risk was expressed in odds ratios (ORs) adjusted for relevant covariables.

RESULTS

Infants with a PFH had more respiratory morbidity than infants with an NFH. Adjusted ORs ranged from 1.7 (95% CI, 1.0-2.8) for expiratory wheezing to 4.9 (95% CI, 1.7-13.6) for croup. Parental smoking increased the OR of a PFH for wheezing ever (OR, 5.8 [95% CI, 2.5-13.8]) and attacks of wheezing (OR, 6.8 [95% CI, 2.7-16.9]), as did Der p 1 (OR, 10.2 [95% CI, 2.8-36.3] and OR, 7.1 [95% CI, 7.1-21.0], respectively). Exposure to both parental smoking and Der p 1 further increased this OR (OR, 30.8 [95%, CI, 6.9-137.2] and OR, 26.2 [95% CI, 5.9-115.6], respectively). Breast-feeding decreased the ORs of PFH for tonsillitis and acute otitis media: the increased ORs for these diagnoses in formula-fed infants with PFHs versus those with NFHs (OR, 9.2 [95% CI, 2.1-39.7] and OR, 2.9 [95% CI, 1.1-7.2], respectively) was attenuated in breast-fed infants (OR, 1.8 [95% CI, 0.8-3.8] and OR, 0.7 [95% CI, 0.4-1.3]).

CONCLUSION

Parental smoking and Der p 1 increase the effect of a PFH on respiratory morbidity. Breast-feeding reduces this effect.

CLINICAL IMPLICATIONS

Extra attention should be given to stimulate mothers to breast-feed their children in case they cannot stop smoking or taking sanitation measures.

Vitamin E deficiency enhances pulmonary inflammatory response and oxidative stress induced by single-walled carbon nanotubes in C57BL/6 mice

Exposure of mice to single-walled carbon nanotubes (SWCNTs) induces an unusually robust pulmonary inflammatory response with an early onset of fibrosis, which is accompanied by oxidative stress and antioxidant depletion. The role of specific components of the antioxidant protective system, specifically vitamin E, the major lipid-soluble antioxidant, in the SWCNT-induced reactions has not been characterized. We used C57BL/6 mice, maintained on vitamin E-sufficient or vitamin E-deficient diets, to explore and compare the pulmonary inflammatory reactions to aspired SWCNTs. The vitamin E-deficient diet caused a 90-fold depletion of alpha-tocopherol in the lung tissue and resulted in a significant decline of other antioxidants (GSH, ascorbate) as well as accumulation of lipid peroxidation products. A greater decrease of pulmonary antioxidants was detected in SWCNT-treated vitamin E-deficient mice as compared to controls. Lowered levels of antioxidants in vitamin E-deficient mice were associated with a higher sensitivity to SWCNT-induced acute inflammation (total number of inflammatory cells, number of polymorphonuclear leukocytes, released LDH, total protein content and levels of pro-inflammatory cytokines, TNF-alpha and IL-6) and enhanced profibrotic responses (elevation of TGF-beta and collagen deposition). Exposure to SWCNTs markedly shifted the ratio of cleaved to full-length extracellular superoxide dismutase (EC-SOD). Given that pulmonary levels of vitamin E can be manipulated through diet, its effects on SWCNT-induced inflammation may be of practical importance in optimizing protective strategies.

Correlations of asthma mortality with traffic-related factors: use of catalytic converters and radial tires

OBJECTIVE

: The objective of this study was to test the hypotheses that the post-1970 rise in asthma mortality in industrialized nations was related to introduction of catalytic converters and/or radial tires.

METHODS

: Annual asthma mortality data were plotted on linear coordinates for fraction of automobile fleet with converters or radial tires in Canada, Germany, Japan, and the United States.

RESULTS

: Catalytic converter association could not account for asthma mortality that rose in Germany before general adoption of the technology there. Radial tire use was, however, linearly correlated with asthma mortality in all four countries.

CONCLUSION

: Rising exposure to materials related to radial tire use may account for a substantial fraction of increased asthma mortality risk since approximately 1970.

HFE Genotype, Particulate Air Pollution, and Heart Rate Variability

Background— Particulate air pollution has been associated with cardiovascular mortality and morbidity. Transition metals such as iron bound to the particles may be responsible for those associations. The protein product of the hemochromatosis ( HFE ) gene modulates uptake of iron and divalent cations from pulmonary sources and reduces their toxicity. Two HFE polymorphisms (C282Y and H63D) associated with increased iron uptake may modify the effect of metal-rich particles on the cardiovascular system.

Methods and Results— We investigated the association between particulate matter ≤2.5 μm in aerodynamic diameter and heart rate variability in 518 older men from the Normative Aging Study who were examined between November 2000 and December 2004. Linear regression models were fit to evaluate interactions between HFE genotype and particulate matter ≤2.5 μm in aerodynamic diameter in relation to heart rate variability, controlling for potential confounders. A 10-μg/m 3 increase in particulate matter ≤2.5 μm in aerodynamic diameter during the 48 hours before heart rate variability measurement was associated with a 31.7% (95% CI, 10.3% to 48.1%) decrease in the high-frequency component of heart rate variability in persons with the wild-type genotype, whereas no relationship in the high-frequency component was observed in persons with either HFE variant. The difference in effect of particulate matter ≤2.5 μm in aerodynamic diameter on the high-frequency component between persons with and without HFE variants was significant ( P for interaction=0.02).

Conclusions— The effect of particles on cardiac autonomic function was shielded in subjects with at least 1 copy of an HFE variant compared with wild-type subjects. Transition metals, including iron, bound to ambient particles and the related oxidative stress may play an important role in cardiac toxicity of particles.

Arylamine N-acetyltransferase gene polymorphisms: markers for atopic asthma, serum IgE and blood eosinophil counts

INTRODUCTION

Polymorphisms in N-acetyltransferase 2 (NAT2), present on chromosome 8p22, are responsible for the N-acetylation variants, which segregate human populations into rapid, intermediate and slow acetylators and influence the susceptibility towards atopic disorders. We have undertaken a study of the North Indian population to screen for various NAT2 polymorphisms and to investigate their association with atopic asthma and related phenotypes.

METHODS

First, to establish linkage of the 8p22 region with asthma, 158 families were recruited from North India. Next, a total of 219 unrelated atopic asthmatics and 210 unrelated healthy controls were recruited for case-control disease association studies.

RESULTS

A suggestive linkage was observed with microsatellite marker D8S549, 2.6 MB upstream of NAT2. By sequencing the DNA of 40 individuals, the T111C, G191A, A434C and C759T single nucleotide polymorphisms (SNPs) in NAT2 were found to be nonpolymorphic in our population and a pattern of strong linkage disequilibrium was observed among the T341C, C481T and A803G polymorphisms. Thus, a total of 429 individuals were genotyped for the C481T and unlinked C282T polymorphisms. The C481T polymorphism was found to be significantly associated with asthma in our case-control studies at the genotype level (Armitage p = 0.00027). C481T also showed a marginal association with serum total IgE (TsIgE) (p = 0.022). Furthermore, percent blood eosinophil counts were found to be significantly higher in patients carrying the 481T allele (p = 0.0037). Significant association was also detected with respect to the C282T polymorphism and TsIgE (p = 0.008). Moreover, C_T was found to be an important risk (p = 0.001), while C_C was a major protective haplotype (p = 0.0005). The associations remained significant after Bonferroni correction for multiple testing.

CONCLUSION

In summary, the genetic variants of the NAT2 gene do not seem to affect asthma alone, but act as modulators of asthma-related traits, such as serum IgE and blood eosinophil counts, and therefore could serve as genetic markers.

Adverse health effects of outdoor air pollutants

Much research on the health effects of outdoor air pollution has been published in the last decade. The goal of this review is to concisely summarize a wide range of the recent research on health effects of many types of outdoor air pollution. A review of the health effects of major outdoor air pollutants including particulates, carbon monoxide, sulfur and nitrogen oxides, acid gases, metals, volatile organics, solvents, pesticides, radiation and bioaerosols is presented. Numerous studies have linked atmospheric pollutants to many types of health problems of many body systems including the respiratory, cardiovascular, immunological, hematological, neurological and reproductive/ developmental systems. Some studies have found increases in respiratory and cardiovascular problems at outdoor pollutant levels well below standards set by such agencies as the US EPA and WHO. Air pollution is associated with large increases in medical expenses, morbidity and is estimated to cause about 800,000 annual premature deaths worldwide [Cohen, A.J., Ross Alexander, H., Ostro, B., Pandey, K.D., Kryzanowski, M., Kunzail, N., et al., 2005. The global burden of disease due to outdoor air pollution. J Toxicol Environ Health A. 68: 1-7.]. Further research on the health effects of air pollution and air pollutant abatement methods should be very helpful to physicians, public health officials, industrialists, politicians and the general public.