NAD(P)H: Quinone oxidoreductase 1, glutathione S-transferase M1, environmental tobacco smoke exposure, and childhood asthma

Glutathione S-Transferase Gene Associations and Gene-Environment Interactions for Asthma

PURPOSE OF REVIEW

Asthma is one of the most common chronic inflammatory airway diseases. Airway oxidative stress is defined as an imbalance between oxidative and antioxidative processes in the airways. There is evidence that chronic damage caused by oxidative stress may be involved in asthmatic inflammation and reduced lung function. Given their biological antioxidant function, the antioxidant genes in the glutathione S-transferase (GST) family are believed to be associated with development and progression of asthma. This review aims to summarize evidence on the relationship between GST gene polymorphisms and asthma and interactions with environmental exposures.

RECENT FINDINGS

The current evidence on the association between GST genes and asthma is still weak or inconsistent. Failure to account for environmental exposures may explain the lack of consistency. It is highly likely that environmental exposures interact with GST genes involved in the antioxidant pathway. According to current knowledge, carriers of GSTM1(rs366631)/T1(rs17856199) null genotypes and GSTP1 Val105 (rs1695) genotypes are more susceptible to environmental oxidative exposures and have a higher risk of asthma. Some doubt remains regarding the presence or absence of interactions with different environmental exposures in different study scenarios. The GST-environment interaction may depend on exposure type, asthma phenotype or endotype, ethnics, and other complex gene-gene interaction. Future studies could be improved by defining precise asthma endotypes, involving multiple gene-gene interactions, and increasing sample size and power. Although there is evidence for an interaction between GST genes, and environmental exposures in relation to asthma, results are not concordant. Further investigations are needed to explore the reasons behind the inconsistency.

PM2.5 aggravates NQO1-induced mucus hyper-secretion through release of neutrophil extracellular traps in an asthma model

BACKGROUND

Particulate matter of 2.5 µm or less in diameter (PM2.5) is one of the most complex pollutants in the atmospheric environment and harmful to human health. Epidemiologic evidence suggests that asthma exacerbation is associated with PM2.5 exposure. However, the molecular mechanism of PM2.5 in the development of asthma is not fully addressed.

METHODS

PM2.5 was collected from Chengdu, China, and the components were analyzed. The relationship between PM2.5 exposure and asthma severity was investigated in an Ovalbumin (OVA)-induced murine model of asthma. U-BIOPRED data from public database and our own RNA-seq data were analyzed to identify the hub genes. Real-time qPCR, immunofluorescence, immunohistochemistry and pathological staining were applied for mechanism dissection in both in vitro and in vivo studies.

RESULTS

In PM2.5 samples, a total of 11 elements including major elements and trace elements were identified, 14 of the 16 Polycyclic aromatic hydrocarbons (PAHs) were detected except Acenaphthene and Fluorene. PM2.5 exposure aggravated pulmonary inflammation, mucus secretion, and neutrophils infiltration in asthma model. Based on transcriptome analysis of mild-to-severe asthma dataset, it showed that mucus secretion and neutrophil degranulation correlated with asthma severity. Moreover, NAD(P)H:quinone oxidoreductase 1 (NQO1) was screened out as a hub gene whose expression positively correlated with MUC5AC expression in patient with asthma by performing joint analysis. Furthermore, in OVA-induced asthma model and in vitro assay, it also revealed that PM2.5-induced MU5AC expression was regulated by NQO1 through neutrophil extracellular traps (NETs) caused by oxidative stress.

CONCLUSION

Taken together, we discovered a potential relationship between asthma severity and PM2.5 exposure. In addition, neutrophil depletion, NETs inhibition or anti-NQO1 might be novel potential therapeutic options for treatment of PM2.5-induced mucus hyper-secretion.

Do Glutathione S-Transferase Genes Modify the Link between Indoor Air Pollution and Asthma, Allergies, and Lung Function? A Systematic Review

PURPOSE OF REVIEW

Glutathione S-transferase (GST) genes are involved in oxidative stress management and may modify the impact of indoor air pollution. We aimed to assess the influence of GST genes on the relationship between indoor air pollution and allergy/lung function.

RECENT FINDINGS

Our systematic review identified 22 eligible studies, with 15 supporting a gene-environment interaction. Carriers of GSTM1/T1 null and GSTP1 val genotypes were more susceptible to indoor air pollution exposures, having a higher risk of asthma and lung function deficits. However, findings differed in terms of risk alleles and specific exposures. High-exposure heterogeneity precluded meta-analysis. We found evidence that respiratory effects of indoor air pollution depend on the individual's GST profile. This may help explain the inconsistent associations found when gene-environment interactions are not considered. Future studies should aim to improve the accuracy of pollution assessment and investigate this finding in different populations.

[Genetic and biochemical mechanisms of involvement of antioxidant defense enzymes in the development of bronchial asthma]

In the present review we have analyzed and summarized recent literature data on genetic and biochemical mechanisms responsible for involvement of antioxidant defense enzymes in the etiology and pathogenesis of bronchial asthma. It has been shown that the mechanisms of asthma development are linked with genetically determined abnormalities in the functioning of antioxidant defense enzymes. These alterations are accompanied by a systemic imbalance between oxidative and anti-oxidative reactions with the shift of the redox state toward increased free radical production and oxidative stress, a key element in the pathogenesis of bronchial asthma.

Interaction of intercellular adhesion molecule 1 (ICAM1) polymorphisms and environmental tobacco smoke on childhood asthma

Asthma is a chronic disease that is particularly common in children. The association between polymorphisms of the gene encoding intercellular adhesion molecule 1 (ICAM1) and gene-environment interactions with childhood asthma has not been fully investigated. A cross-sectional study was undertaken to investigate these associations among children in Taiwan. The effects of two functional single-nucleotide polymorphisms (SNPs) of ICAM1, rs5491 (K56M) and rs5498 (K469E), and exposure to environmental tobacco smoke (ETS) were studied. Two hundred and eighteen asthmatic and 877 nonasthmatic children were recruited from elementary schools. It was found that the genetic effect of each SNP was modified by the other SNP and by exposure to ETS. The risk of asthma was higher for children carrying the rs5491 AT or TT genotypes and the rs5498 GG genotype (odds ratio = 1.68, 95% confidence interval 1.09–2.59) than for those with the rs5491 AA and rs5498 AA or AG genotypes (the reference group). The risk for the other two combinations of genotypes did not differ significantly from that of the reference group (p of interaction = 0.0063). The two studied ICAM1 SNPs were associated with childhood asthma among children exposed to ETS, but not among those without ETS exposure (p of interaction = 0.05 and 0.01 for rs5491 and rs5498, respectively). Both ICAM1 and ETS, and interactions between these two factors are likely to be involved in the development of asthma in childhood.

Effects of the NQO1 609C>T polymorphism on leukemia susceptibility: evidence from a meta-analysis

A functional polymorphism in the NQO1 gene, featuring a 609C>T substitution,leading to proline to serine amino-acid and enzyme activity changes, has been implicated in cancer risk. However, individually published investigations showed inconclusive results, especially for leukemia. In this study, we therefore performed a meta- analysis of 21 publications with a total of 3,634 cases and 4,827controls, mainly for leukemia. We summarized the data on the association between the NQO1 609C>T polymorphism and risk of leukemia and performed subgroup analyses by ethnicity and leukemia type. We found that the variant TT homozygous genotype o was associated with a modestly increased risk of leukemia (TT versus CT/CC: OR = 1.23, 95%CI = 1.00 - 1.51, heterogeneity = 0.76; I2 = 0%). Following further stratified analyses, increased risk was only observed in subgroups of Caucasians. This meta-analysis suggests that the NQO1 609T allele is a high-penetrance risk factor for leukemia in Caucasians. The effect on leukemia may be modified by ethnicity and leukemia type, and the small sample sizes of the subgroup analyses suggest that further larger studies are needed.

Quantitative assessment of the association between the GSTM1-null genotype and the risk of childhood asthma

BACKGROUND

Many studies investigated the association between the glutathione S-transferase M 1 (GSTM1)-null genotype and childhood asthma risk, but there was obvious inconsistence among those studies. The aim of this meta-analysis was to quantify the strength of association between the GSTM1-null genotype and risk of childhood asthma.

METHODS

We searched the PubMed, Embase, and Wangfang databases for studies relating the association between the GSTM1-null genotype and risk of childhood asthma. We estimated the pooled odds ratio (OR) with its 95% confidence interval (95% CI) to assess the association.

RESULTS

Nineteen case-control studies with 4,543 childhood asthma cases and 19,394 controls were included into this meta-analysis. Meta-analysis of all 19 studies showed that the GSTM1-null genotype was associated with increased risk of childhood asthma (OR=1.17, 95% CI 1.03-1.34, p=0.017). Subgroup analyses by ethnicity suggested that the GSTM1-null genotype was associated with an increased risk of childhood asthma in Caucasians and Africans (for Caucasians, fixed-effects OR=1.16, 95% CI 1.07-1.27, p=0.001; for Africans, fixed-effects OR=1.92, 95% CI 1.35-2.74, p<0.001). The cumulative meta-analyses showed a trend of obvious association between the GSTM1-null genotype and risk of childhood asthma as information accumulated in the analyses of both total studies and Caucasians. No evidence of publication bias was observed.

CONCLUSION

Meta-analyses of available data suggest a significant association between the GSTM1-null genotype and the risk of childhood asthma, and the GSTM1-null genotype contributes to increased risk of childhood asthma, especially in Caucasians and Africans.

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.

Genetic association between obstructive bronchitis and enzymes of oxidative stress

OBJECTIVE

Obstructive respiratory diseases, mainly the chronic obstructive pulmonary disease (COPD) and asthma, are associated with functional polymorphisms of xenobiotic-metabolizing enzymes (XMEs). To date, association for obstructive bronchitis has not been described.

MATERIAL/METHODS

In this study, we investigated the genotypes from 26 functional polymorphisms of 20 XMEs in children (n, 1028) at the age of 6 years from the German prospective birth cohort study (LISAplus) and analyzed the associations between genotypes and obstructive bronchitis.

RESULTS

For the first time, we found noteworthy gene-disease associations for the functional PON1 M55L and EPHX1 H139R polymorphisms and gene-environment associations for the functional COMT V158M and NQO1 P187S polymorphisms after stratification for maternal active smoking behaviour during pregnancy. The noteworthy associations were substantiated by the biological findings that all the risk genotypes belong to genes involved in oxidative stress and code for proteins with a fast enzymatic activity or concomitantly appear in common estrogene-metabolizing pathway (COMT, NQO1).

CONCLUSION

The oxidative stress has to be taken into account in mechanism of the obstructive bronchitis in early childhood. The risk genotypes may serve as risk factors for respiratory obstruction rather than for signs of COPD or asthma.

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.

Expression analysis of asthma candidate genes during human and murine lung development

BACKGROUND

Little is known about the role of most asthma susceptibility genes during human lung development. Genetic determinants for normal lung development are not only important early in life, but also for later lung function.

OBJECTIVE

To investigate the role of expression patterns of well-defined asthma susceptibility genes during human and murine lung development. We hypothesized that genes influencing normal airways development would be over-represented by genes associated with asthma.

METHODS

Asthma genes were first identified via comprehensive search of the current literature. Next, we analyzed their expression patterns in the developing human lung during the pseudoglandular (gestational age, 7-16 weeks) and canalicular (17-26 weeks) stages of development, and in the complete developing lung time series of 3 mouse strains: A/J, SW, C57BL6.

RESULTS

In total, 96 genes with association to asthma in at least two human populations were identified in the literature. Overall, there was no significant over-representation of the asthma genes among genes differentially expressed during lung development, although trends were seen in the human (Odds ratio, OR 1.22, confidence interval, CI 0.90-1.62) and C57BL6 mouse (OR 1.41, CI 0.92-2.11) data. However, differential expression of some asthma genes was consistent in both developing human and murine lung, e.g. NOD1, EDN1, CCL5, RORA and HLA-G. Among the asthma genes identified in genome wide association studies, ROBO1, RORA, HLA-DQB1, IL2RB and PDE10A were differentially expressed during human lung development.

CONCLUSIONS

Our data provide insight about the role of asthma susceptibility genes during lung development and suggest common mechanisms underlying lung morphogenesis and pathogenesis of respiratory diseases.

Impact of environmental tobacco smoke on children admitted with status asthmaticus in the pediatric intensive care unit

INTRODUCTION

Environmental tobacco smoke (ETS) and allergens are risk factors in children with critical status asthmaticus. Genetic studies support that ETS-associated asthma is a special inflammatory entity, causing significant number of hospital admissions and relapses. Accordingly, the course and outcome of patients with ETS-induced status asthmaticus might also be different.

HYPOTHESIS

We hypothesized that the progression, course, and outcome of patients with ETS-induced status asthmaticus would be worse than those of patients without ETS exposure.

METHODS

Medical records of children who were admitted to the Pediatric Intensive Care Unit (PICU) with the diagnosis of asthma at the Children's Hospital of Winnipeg, Manitoba, over 10 years were audited after Institutional Review Board (IRB) approval. Two hundred thirty records were reviewed. We extracted data including demographics and analyzed the patient's deterioration defined as clinical asthma score (CAS) drift between the ED and PICU. We computed the treatment response, expressed as length of stay (LOS) in the PICU and in hospital. The risk factors were stratified as none, ETS exposure, allergies, and ETS with allergies.

RESULTS

There were 55 (25%) patients with no risk factors, 66 (30%) with ETS exposure only, 46 (21%) with allergies only, and 53 (24%) with both. There was a 25% decrease in CAS deterioration when patients were exposed to ETS (P < 0.05). For patients with or without allergies but with exposure to ETS, both the PICU and overall hospital LOS were ∼15% longer (P < 0.05) than for those not exposed to ETS. Stratifying for gender and race in multivariate analysis did not alter the results.

CONCLUSIONS

Patients with ETS-associated critical status asthmaticus deteriorate and recover slower than non-ETS-exposed patients.