Ambient ozone modifies the effect of tumor necrosis factor G-308A on bronchitic symptoms among children with asthma

Transcriptomic and metabolomic associations with exposures to air pollutants among young adults with childhood asthma history

Ambient air pollutants are well-known risk factors for childhood asthma and asthma exacerbation. It is unknown whether different air pollutants individually or jointly affect pathophysiological mechanisms of asthma. In this study, we aim to integrate transcriptome and untargeted metabolome to identify dysregulated genetic and metabolic pathways that are associated with exposures to a mixture of ambient and traffic-related air pollutants among adults with asthma history. In this cross-sectional study, 102 young adults with childhood asthma history were enrolled from southern California in 2012. Whole blood transcriptome was measured with 20,869 expression signatures, and serum untargeted metabolomics including 937 metabolites were analyzed by Metabolon, Inc. Participants' exposures to regional air pollutants (NO₂, O₃, PM₁₀, PM_2.5) and near-roadway air pollutants averaged at one month and one year before study visit were estimated based on residential addresses. xMWAS network analysis and joint-pathway analysis were performed to identify subnetworks and genetic and metabolic pathways that were associated with exposure to air pollutants adjusted for socio-characteristic covariates. Network analysis found that exposures to air pollutants mixture were connected to 357 gene markers and 92 metabolites. One-year and one-month averaged PM_2.5 and NO₂ were associated with several amino acids related to serine, glycine, and beta-alanine metabolism. Lower serum levels of carnosine and aspartate, which are involved in the beta-alanine metabolic pathway, as well as choline were also associated with worse asthma control (p < 0.05). One-year and one-month averaged PM₁₀ and one-month averaged O₃ were associated with higher gene expression levels of HSPA5, LGMN, CTSL and HLA-DPB1, which are involved in antigen processing and presentation. These results indicate that exposures to various air pollutants are associated with altered genetic and metabolic pathways that affect anti-oxidative capacity and immune response and can potentially contribute to asthma-related pathophysiology.

Ozone Exposure and Asthma Attack in Children

Background

Increasing evidence indicated that ozone (O3) exposure could trigger asthma attacks in children. However, the effect of O3 at low concentrations is uncertain.

Purpose

This study aimed to explore the effects of O3 exposure at low concentrations on asthma attacks in children.

Methods

A total of 3,475 children with asthma attacks from the First Affiliated Hospital of Xiamen University were available for the analyses. Air pollution data and meteorological data in Xiamen during 2016-2019 were also collected. A case-crossover design and conditional logistic regression models were conducted to evaluate the association between asthma attacks and outdoor air pollution with lag structures (from lag 0 to lag 6) in both single and multi-pollutant models. Furthermore, we estimated the influence of various levels of O3 exposure on an asthma attack in three groups categorized by maximum daily 8-h sliding average ozone (O3-8 h) (O3-8 h ≥ 100 μg/m3, O3-8 h: 80-99 μg/m3, O3-8 h < 80 μg/m3).

Results

For both single-pollutant models and multi-pollutant models, when O3-8 h was higher than 80 μg/m3, O3 exposure was increased the risk of acute asthma attacks on each day of lag. The effect of O3 on children with asthma was significant when O3 concentration was higher than 100 μg/m3.

Conclusion

O3 concentration above 80 μg/m3 contributed to an increased risk of asthma attacks in children.

Association of Air Pollution Exposure and Interleukin-13 Haplotype with the Risk of Aggregate Bronchitic Symptoms in Children

Interleukin-13(IL-13) might play an important role in driving aggregate bronchitic symptoms pathogenesis. However, none of the studies assessed the interaction between air pollutants exposure and IL-13 gene on the risk of aggregate bronchitic symptoms in non-asthma children. To assess the independent and joint effects of the exposure to air pollution and IL-13 haplotypes on the risk of aggregate bronchitic symptoms, we conducted a cross-sectional study and focused on non-asthma children. The study population consisted of 2944 children. The effect of each air pollutant on the risk of aggregate bronchitic symptoms was estimated as odds ratios per interquartile range (IQR) change. In the multiple logistic regressions, adjusted for confounding factors, the risk of chronic phlegm was associated with PM_2.5 exposure (aOR, 1.59; 95% CI, 1.07–2.37 per 12.51 μg/m3 change), O₃ exposure (aOR, 1.54 95% CI, 1.05–2.27 per 8.28 ppb change) and SO₂ exposure (aOR, 1.19; 95% CI, 1.02–1.39 per 0.98 ppb change). Our study further provides the evidence that gene-environment interactions between IL-13 haplotype and O₃ exposure on chronic phlegm (95% CI for interaction, 1.01–1.38). Identifying children who are more sensitive to air pollution helps us to provide them an efficient prevention to avoid aggregate bronchitic symptoms.

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Limited studies explored the interactions between IL-13 gene and air pollutants exposure on the risk of bronchitic symptoms.

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Genetic susceptibility of IL-13 may interact with O₃ exposure causing the pathogenesis of bronchitic symptoms.

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Identifying children susceptible to air pollutants helps us to provide them an efficient prevention of bronchitic symptoms.

Genetic susceptibility may interact with specific environmental factors causing the pathogenesis of aggregate bronchitic symptoms. Limited studies have explored the interactions between Interleukin-13 (IL-13) gene and air pollutants exposure on the risk of aggregate bronchitic symptoms. Our study further provides the evidence that gene-environment interactions between IL-13 gene and O₃ exposure may play an important role in aggregate bronchitic symptoms. Identifying children who are more sensitive to air pollutants helps us to provide them an efficient prevention to avoid aggregate bronchitic symptoms.

Associations of TNFα -308G>A, TNFα -238G>A, IL-1α -889C>T and IL-10 -1082G>A Genetic Polymorphisms with Atopic Diseases: Asthma, Rhinitis and Dermatitis

BACKGROUND

Polymorphisms of cytokine genes are an interesting focus for association studies involving atopic diseases due to their role in immune cell communications during inflammation. The aim of this study was to investigate associations of TNFα -308G>A, TNFα -238G>A, IL-1α -889C>T and IL-10 -1082G>A polymorphisms with atopic diseases with adjustment for confounding lifestyle and environmental factors.

METHODS

This study was performed on 356 Croatian students. The diagnosis of atopic asthma, atopic rhinitis and atopic dermatitis was based on symptoms reported by the modified International Study of Asthma and Allergies in Childhood questionnaire and a positive skin prick test (SPT) to at least one common inhalatory allergen. Genetic polymorphisms were genotyped using the polymerase chain reaction-based technique. The influence of personal (gender, body mass index, parental history of atopic disease), lifestyle (cigarette smoking, pet ownership) and environmental (urban/rural residency, residency in continental/Mediterranean region) factors reported in the questionnaire was investigated by univariate and multivariate analysis.

RESULTS

Compared to the control subjects, univariate analysis showed a significant negative association of the TNFα -308G>A polymorphism with atopic asthma, atopic dermatitis, asthma and skin symptoms and positive SPT. These observations were confirmed in a multivariate model only for atopic dermatitis and skin symptoms (atopic dermatitis: OR = 0.27; 95% CI 0.07-1.00; p = 0.050; skin symptoms: OR = 0.29; 95% CI 0.10-0.83; p = 0.021).

CONCLUSIONS

The results indicate a protective role of TNFα -308G>A genetic polymorphisms regarding atopic dermatitis and skin symptoms even after controlling for personal, lifestyle and environmental factors. Further studies are needed to elucidate the molecular patterns of this association in atopic dermatitis and other chronic inflammatory skin disorders.

Novel Roles for Notch3 and Notch4 Receptors in Gene Expression and Susceptibility to Ozone-Induced Lung Inflammation in Mice

BACKGROUND

Ozone is a highly toxic air pollutant and global health concern. Mechanisms of genetic susceptibility to ozone-induced lung inflammation are not completely understood. We hypothesized that Notch3 and Notch4 are important determinants of susceptibility to ozone-induced lung inflammation.

METHODS

Wild-type (WT), Notch3 (Notch3-/-), and Notch4 (Notch4-/-) knockout mice were exposed to ozone (0.3 ppm) or filtered air for 6-72 hr.

RESULTS

Relative to air-exposed controls, ozone increased bronchoalveolar lavage fluid (BALF) protein, a marker of lung permeability, in all genotypes, but significantly greater concentrations were found in Notch4-/- compared with WT and Notch3-/- mice. Significantly greater mean numbers of BALF neutrophils were found in Notch3-/- and Notch4-/- mice compared with WT mice after ozone exposure. Expression of whole lung Tnf was significantly increased after ozone in Notch3-/- and Notch4-/- mice, and was significantly greater in Notch3-/- compared with WT mice. Statistical analyses of the transcriptome identified differentially expressed gene networks between WT and knockout mice basally and after ozone, and included Trim30, a member of the inflammasome pathway, and Traf6, an inflammatory signaling member.

CONCLUSIONS

These novel findings are consistent with Notch3 and Notch4 as susceptibility genes for ozone-induced lung injury, and suggest that Notch receptors protect against innate immune inflammation.

Chronic effects of air pollution on respiratory health in Southern California children: findings from the Southern California Children's Health Study

Outdoor air pollution is one of the leading contributors to adverse respiratory health outcomes in urban areas around the world. Children are highly sensitive to the adverse effects of air pollution due to their rapidly growing lungs, incomplete immune and metabolic functions, patterns of ventilation and high levels of outdoor activity. The Children's Health Study (CHS) is a continuing series of longitudinal studies that first began in 1993 and has focused on demonstrating the chronic impacts of air pollution on respiratory illnesses from early childhood through adolescence. A large body of evidence from the CHS has documented that exposures to both regional ambient air and traffic-related pollutants are associated with increased asthma prevalence, new-onset asthma, risk of bronchitis and wheezing, deficits of lung function growth, and airway inflammation. These associations may be modulated by key genes involved in oxidative-nitrosative stress pathways via gene-environment interactions. Despite successful efforts to reduce pollution over the past 40 years, air pollution at the current levels still brings many challenges to public health. To further ameliorate adverse health effects attributable to air pollution, many more toxic pollutants may require regulation and control of motor vehicle emissions and other combustion sources may need to be strengthened. Individual interventions based on personal susceptibility may be needed to protect children's health while control measures are being implemented.

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

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

Impact of single nucleotide polymorphism in tumor necrosis factor-α gene 308G/A in Egyptian asthmatic children and wheezing infants

Bronchial asthma is a common disease with multiple determinants that include genetic variation. Although tumor necrosis factor alpha (TNF-α) is a major pro-inflammatory cytokine, the functions of genetic polymorphisms in this cytokine has not been thoroughly examined in the context of asthma pathology. Therefore, we aimed to investigate whether single nucleotide polymorphism (SNP) in TNF-α is associated with asthma and wheezing and whether the association is related to the severity of the disease and other epidemiological factors. Frequencies of TNF-α-308G/A polymorphism were compared in 100 asthmatic children, 100 wheezy infants and 100 age and gender matched controls. Genotype frequencies for TNF-α-308G/A were significantly higher in asthmatic children (60%) and wheezy infants (68%) than the control group (30%). Higher serum levels of TNF-α were observed in genotypes G/A and G/G of asthmatic children and wheezy infants than in controls. No association was found between the G/A polymorphism and the severity of the disease, the total eosinophil count and IgE levels in both groups. We can conclude that genetic variation in TNF-α-308G/A may contribute to childhood asthma and wheezing. These findings could be helpful for future early intervention studies which may have a potential impact on family counseling and management.

Joint analysis for integrating two related studies of different data types and different study designs using hierarchical modeling approaches

BACKGROUND

A chronic disease such as asthma is the result of a complex sequence of biological interactions involving multiple genes and pathways in response to a multitude of environmental exposures. However, methods to model jointly all factors are still evolving. Some of the current challenges include how to integrate knowledge from different data types and different disciplines, as well as how to utilize relevant external information such as gene annotation to identify novel disease genes and gene-environment inter-actions.

METHODS

Using a Bayesian hierarchical modeling framework, we developed two alternative methods for joint analysis of an epidemiologic study of a disease endpoint and an experimental study of intermediate phenotypes, while incorporating external information.

RESULTS

Our simulation studies demonstrated superior performance of the proposed hierarchical models compared to separate analysis with the standard single-level regression modeling approach. The combined analyses of the Southern California Children's Health Study and challenge study data suggest that these joint analytical methods detected more significant genetic main and gene-environment interaction effects than the conventional analysis.

CONCLUSION

The proposed prior framework is very flexible and can be generalized for an integrative analysis of diverse sources of relevant biological data.

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.

Increased CCL24/eotaxin-2 with postnatal ozone exposure in allergen-sensitized infant monkeys is not associated with recruitment of eosinophils to airway mucosa

Epidemiology supports a causal link between air pollutant exposure and childhood asthma, but the mechanisms are unknown. We have previously reported that ozone exposure can alter the anatomic distribution of CD25+ lymphocytes in airways of allergen-sensitized infant rhesus monkeys. Here, we hypothesized that ozone may also affect eosinophil trafficking to allergen-sensitized infant airways. To test this hypothesis, we measured blood, lavage, and airway mucosa eosinophils in 3-month old monkeys following cyclical ozone and house dust mite (HDM) aerosol exposures. We also determined if eotaxin family members (CCL11, CCL24, CCL26) are associated with eosinophil location in response to exposures. In lavage, eosinophil numbers increased in animals exposed to ozone and/or HDM. Ozone+HDM animals showed significantly increased CCL24 and CCL26 protein in lavage, but the concentration of CCL11, CCL24, and CCL26 was independent of eosinophil number for all exposure groups. In airway mucosa, eosinophils increased with exposure to HDM alone; comparatively, ozone and ozone+HDM resulted in reduced eosinophils. CCL26 mRNA and immunofluorescence staining increased in airway mucosa of HDM alone animals and correlated with eosinophil volume. In ozone+HDM animal groups, CCL24 mRNA and immunofluorescence increased along with CCR3 mRNA, but did not correlate with airway mucosa eosinophils. Cumulatively, our data indicate that ozone exposure results in a profile of airway eosinophil migration that is distinct from HDM mediated pathways. CCL24 was found to be induced only by combined ozone and HDM exposure, however expression was not associated with the presence of eosinophils within the airway mucosa.

The -308 G/A polymorphism in TNF-α gene is associated with asthma risk: an update by meta-analysis

BACKGROUND

The -308 G/A polymorphism in TNF-α gene has been extensively investigated for association to asthma; however, results of different studies have been inconsistent. The aim of this study is to comprehensively evaluate the genetic risk of -308 G/A polymorphism in TNF-α gene for asthma.

METHODS

A meta-analysis was carried out to analyze the association between the -308 G/A polymorphism TNF-α gene and asthma risk.

RESULTS

A total of 4717 cases and 5012 controls in 29 case-control studies were included in this meta-analysis. The result indicated that the variant A allele carriers had a 38% increased risk of asthma, when compared with the homozygote GG (odds ratio (OR) = 1.40, 95% confidence interval (CI), 1.13-1.68 for AA + AG vs. GG). In the subgroup analysis by ethnicity, significant elevated risks were associated with A allele carriers in Asians (OR = 1.53, 95% CI = 1.17-2.01 and P = 0.002) but not in Caucasians(OR = 1.06, 95% CI = 0.75-1.50 and P = 0.73). In the subgroup analysis by age, significant elevated risks were associated with A allele carriers in adults (OR = 1.44, 95% CI = 1.14-1.81, and P = 0.002) and children (OR = 1.37, 95% CI = 1.03-1.82, and P = 0.003). In the subgroup analysis by atopic status, significant elevated risks of asthma were associated with A allele carriers in atopic population (OR = 1.68, 95% CI = 1.34-2.10, and P < 0.00001) but not in non-atopic population (OR = 0.98, 95% CI = 0.58-1.68, and P = 0.95).

CONCLUSIONS

Our results suggest that the TNF-α -308 G/A polymorphism contributes to susceptibility to asthma.

Identification of novel susceptibility genes in ozone-induced inflammation in mice

Ozone (O(3)) remains a prevalent air pollutant and public health concern. Inf2 is a significant quantitative trait locus on murine chromosome 17 that contributes to susceptibility to O(3)-induced infiltration of polymorphonuclear leukocytes (PMNs) into the lung, but the mechanisms of susceptibility remain unclear. The study objectives were to confirm and restrict Inf2, and to identify and test novel candidate susceptibility gene(s). Congenic strains of mice that contained overlapping regions of Inf2 and their controls, and mice deficient in either major histocompatibility complex (MHC) class II genes or the Tnf cluster, were exposed to air or O(3). Lung inflammation and gene expression were assessed. Inf2 was restricted from 16.42 Mbp to 0.96 Mbp, and bioinformatic analysis identified MHC class II, the Tnf cluster and other genes in this region that contain potentially informative single nucleotide polymorphisms between the susceptible and resistant mice. Furthermore, O(3)-induced inflammation was significantly reduced in mice deficient in MHC class II genes or the Tnf cluster genes, compared with wild-type controls. Gene expression differences were also observed in MHC class II and Tnf cluster genes. This integrative genetic analysis of Inf2 led to identification of novel O(3) susceptibility genes that may provide important, new therapeutic targets in susceptible individuals.