Allergic susceptibility associated with diesel exhaust particle exposure: clear as mud

Short-term transcriptome and microRNAs responses to exposure to different air pollutants in two population studies

Diesel vehicle emissions are the major source of genotoxic compounds in ambient air from urban areas. These pollutants are linked to risks of cardiovascular diseases, lung cancer, respiratory infections and adverse neurological effects. Biological events associated with exposure to some air pollutants are widely unknown but applying omics techniques may help to identify the molecular processes that link exposure to disease risk. Most data on health risks are related to long-term exposure, so the aim of this study is to investigate the impact of short-term exposure (two hours) to air pollutants on the blood transcriptome and microRNA expression levels. We analyzed transcriptomics and microRNA expression using microarray technology on blood samples from volunteers participating in studies in London, the Oxford Street cohort, and, in Barcelona, the TAPAS cohort. Personal exposure levels measurements of particulate matter (PM₁₀, PM_2.5), ultrafine particles (UFPC), nitrogen oxides (NO₂, NO and NOx), black carbon (BC) and carbon oxides (CO and CO₂) were registered for each volunteer. Associations between air pollutant levels and gene/microRNA expression were evaluated using multivariate normal models (MVN). MVN-models identified compound-specific expression of blood cell genes and microRNAs associated with air pollution despite the low exposure levels, the short exposure periods and the relatively small-sized cohorts. Hsa-miR-197-3p, hsa-miR-29a-3p, hsa-miR-15a-5p, hsa-miR-16-5p and hsa-miR-92a-3p are found significantly expressed in association with exposures. These microRNAs target also relevant transcripts, indicating their potential relevance in the research of omics-biomarkers responding to air pollution. Furthermore, these microRNAs are also known to be associated with diseases previously linked to air pollution exposure including several cancers such lung cancer and Alzheimer's disease. In conclusion, we identified in this study promising compound-specific mRNA and microRNA biomarkers after two hours of exposure to low levels of air pollutants during two hours that suggest increased cancer risks.

Identification of Potential Novel Biomarkers and Signaling Pathways Related to Otitis Media Induced by Diesel Exhaust Particles Using Transcriptomic Analysis in an In Vivo System

INTRODUCTION

Air pollutants are associated with inflammatory diseases such as otitis media (OM). Significantly higher incidence rates of OM are reported in regions with air pollution. Diesel exhaust particles (DEPs) comprise a major class of contaminants among numerous air pollutants, and they are characterized by a carbonic mixture of polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs, and small amounts of sulfate, nitrate, metals and other trace elements. DEP exposure is a risk factor for inflammatory diseases. Our previous study identified potential biomarkers using gene expression microarray and pathway analyses in an in vitro system. Although in vitro investigations have been conducted to elucidate plausible biomarkers and molecular mechanisms related to DEP exposure, in vivo studies are necessary to identify the exact biological relevance regarding the incidence of OM caused by DEP exposure. In this study, we identified potential molecular biomarkers and pathways triggered by DEP exposure in a rodent model.

METHODS

Transcriptomic analysis was employed to identify novel potential biomarkers in the middle ear of DEP-exposed mice.

RESULTS

A total of 697 genes were differentially expressed in the DEP-exposed mice; 424 genes were upregulated and 273 downregulated. In addition, signaling pathways among the differentially expressed genes mediated by DEP exposure were predicted. Several key molecular biomarkers were identified including cholinergic receptor muscarinic 1 (CHRM1), erythropoietin (EPO), son of sevenless homolog 1 (SOS1), estrogen receptor 1 (ESR1), cluster of differentiation 4 (CD4) and interferon alpha-1 (IFNA1).

CONCLUSIONS

Our results shed light on the related cell processes and gene signaling pathways affected by DEP exposure. The identified biomarkers might be potential candidates for determining early diagnoses and effective treatment strategies for DEP-mediated disorders.

Prevalence and severity of asthma among Indian school children aged between 6 and 14 years: associations with parental smoking and traffic pollution

OBJECTIVE

Phase three of the International Study of Asthma and Allergy in Children (ISAAC) was carried out at various sites in India. The prevalence of asthma symptoms in school children and the effect of environmental tobacco smoke and traffic pollution on the occurrence of asthma were analysed.

METHODS

Two groups of school children, aged 6-7 yr and 13-14 yr, participated according to the ISAAC protocol. Schools were randomly selected and responses to the ISAAC questionnaire were recorded.

RESULTS

The prevalence of asthma was 5.35% in the 6-7 yr age group and 6.05% in the 13-14 yr age group. The odds ratios (ORs) for the risk of asthma in children with exposure to mild, moderate and heavy traffic pollution compared with minimal traffic pollution were 1.63 (95% CI: 1.43, 1.85), 1.71 (95% CI: 1.49, 1.96) and 1.53 (95% CI: 1.31, 1.78), respectively, in the younger group. Similarly, in the older group, they were 1.19 (95% CI: 1.04, 1.36), 1.51 (95% CI: 1.31, 1.75) and 1.51 (95% CI: 1.29, 1.76). Asthma was associated with maternal smoking [6-7 yr group: OR = 2.72 (2.05, 3.6); 13-14 yr group: OR = 2.14 (1.72, 2.66)] and paternal smoking [6-7 yr group: OR = 1.9 (1.70, 2.11); 13-14 yr group: OR = 1.21 (1.09, 1.34)].

CONCLUSIONS

The prevalence of asthma was lower in the 6-7 than the 13-14 yr age group. Environmental tobacco smoke and traffic pollution were the factors most strongly associated with asthma in Indian children.

Impact of air quality on lung health: myth or reality?

The respiratory system is a primary target of the harmful effects of key air pollutants of health concern. Several air pollutants have been implicated including particulate matter (PM), ozone (O3), nitrogen dioxide (NO2) polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). It is well known that episodes of exposure to high concentrations of outdoor air pollutants can cause acute respiratory exacerbations. However, there is now increasing evidence suggesting that significant exposure to outdoor air pollutants may be also associated with development of lung cancer and with incident cases of chronic obstructive pulmonary disease (COPD) and respiratory allergies. Here we provide a critical appraisal of the impact of air pollution on respiratory diseases and discuss strategies for preventing excessive exposure to harmful air pollutants. However, the evidence that significant exposure to air pollutants is causing COPD, lung cancer or respiratory allergies is not conclusive and therefore regulators must be aware that execution of clean air policies may not be that cost-effective and may lead to unintended consequences. Addressing the lung health effects of air pollution must be considered work in progress.

The role of the early-life environment in the development of allergic disease

A consensus has been reached that the development of allergic disorders is strongly influenced by early life exposures. An overview of several prenatal and early life factors that have been investigated for their associations with development of childhood allergy is presented. Delivery mode, the gut microbiome, vitamin D, folate, breastfeeding, pets, antibiotics, environmental tobacco smoke, and airborne traffic pollutants are discussed. Although many studies suggest an effect, overall, no risk factors clearly increase or reduce the risk of allergic outcomes.

Effects of motor vehicle exhaust on male reproductive function and associated proteins

Air pollution is consistently associated with various diseases and subsequent death among children, adult, and elderly people worldwide. Motor vehicle exhaust contributes to a large proportion of the air pollution present. The motor vehicle exhaust systems emit a variety of toxic components, including carbon monoxide, nitrogen oxides, volatile organic compounds, ozone, particulate matter, and polycyclic aromatic hydrocarbons. Several epidemiological studies and laboratory studies have demonstrated that these components are potentially mutagenic, carcinogenic, and endocrine disrupting agents. However, their impact on male reproductive function and associated proteins is not very clear. Therefore, a comprehensive review on the effects of motor vehicle exhaust on male reproductive function and associated proteins is needed to better understand the risks of exhaust exposure for men. We found that motor vehicle exhaust can cause harmful effects on male reproductive functions by altering organ weights, reducing the spermatozoa qualities, and inducing oxidative stress. Remarkably, motor vehicle exhaust exposure causes significant changes in the expression patterns of proteins that are key components involved in spermatogenesis and testosterone synthesis. In conclusion, this review helps to describe the risks of vehicle exhaust exposure and its relationship to potential adverse effects on the male reproduction system.

Sulforaphane-rich broccoli sprout extract attenuates nasal allergic response to diesel exhaust particles

The generation of oxidative stress by ambient air pollution particles contributes to the development of allergic sensitization and asthma, as demonstrated by intranasal challenge with well-characterized diesel exhaust particle (DEP) suspensions in humans. This effect is due to the presence of redox active organic chemicals in DEP, and can be suppressed by antioxidants and inducers of phase II enzymes in animals. In this communication, we determined whether the administration of a standardized broccoli sprout extract (BSE), which contains a reproducible amount of the sulforaphane (SFN) precursor, glucoraphanin, could be used to suppress the nasal inflammatory response in human subjects challenged with 300 μg of an aqueous DEP suspension (equivalent to daily PM exposure levels on a Los Angeles freeway). SFN is capable of inducing an antioxidant and phase II response via activation of the nuclear transcription factor (erythroid-derived 2)-like 2 (Nrf2). Previous studies have shown that 70-90% SFN delivered by BSE is absorbed, metabolized, and excreted in humans. An initial intranasal challenge with DEP in 29 human subjects was used to characterize the magnitude of the inflammatory response. Following a 4 week washout, a BSE that delivers a reproducible and standardized dose of 100 μmol SFN in mango juice was administered daily for four days. The nasal DEP challenge was repeated and lavage fluid collected to perform white blood cell (WBC) counts. The average nasal WBC increased by 66% over the initial screening levels and by 85% over the control levels 24 hours after DEP exposure. However, total cell counts decreased by 54% when DEP challenge was preceded by daily BSE administration for 4 days (p < 0.001). Since the SFN dose in these studies is equivalent to the consumption of 100-200 g broccoli, our study demonstrates the potential preventive and therapeutic potential of broccoli or broccoli sprouts rich in glucoraphanin for reducing the impact of particulate pollution on allergic disease and asthma.

Modulation of ovine SBD-1 expression by 17beta-estradiol in ovine oviduct epithelial cells

Background

Mucosal epithelia, including those of the oviduct, secrete antimicrobial innate immune molecules (AIIMS). These have bactericidal/bacteriostatic functions against a variety of pathogens. Among the AIIMs, sheep β-defensin-1 (SBD-1) is one of the most potent. Even though the SBD-1 is an important AIIM and it is regulated closely by estrogenic hormone, the regulation mechanism of 17β-estradiol has not been clearly established. We investigated the effects of E₂ and agonist or inhibitor on ovine oviduct epithelial cells in regard to SBD-1 expression using reverse transcription quantitative PCR (RT-qPCR). In addition, three different pathways were inhibited separately or simultaneously to confirm the effect of different inhibitors in the regulation mechanism.

Results

17beta-estradiol (E₂) induced release of SBD-1 in ovine oviduct epithelial cells. SBD-1 expression was mediated through G-protein-coupled receptor 30 (GPR30) and Estrogen Receptors (ERs) activation in ovine oviduct epithelial cell. Inhibition of gene expression of protein kinase A (PKA), protein kinase C (PKC), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) led to a decreased SBD-1 expression.

Conclusions

Taken together, E₂-induced up-regulation of SBD-1 expressions were GPR30-dependent during prophase and ERs-dependent during later-stage in ovine oviduct epithelial cells, and we assume that the effect was completed by the PKA, PKC, and NF-κB pathways simultaneous.

Suppression of the NF-κB pathway by diesel exhaust particles impairs human antimycobacterial immunity

Epidemiological studies suggest that chronic exposure to air pollution increases susceptibility to respiratory infections, including tuberculosis in humans. A possible link between particulate air pollutant exposure and antimycobacterial immunity has not been explored in human primary immune cells. We hypothesized that exposure to diesel exhaust particles (DEP), a major component of urban fine particulate matter, suppresses antimycobacterial human immune effector cell functions by modulating TLR-signaling pathways and NF-κB activation. We show that DEP and H37Ra, an avirulent laboratory strain of Mycobacterium tuberculosis, were both taken up by the same peripheral human blood monocytes. To examine the effects of DEP on M. tuberculosis-induced production of cytokines, PBMC were stimulated with DEP and M. tuberculosis or purified protein derivative. The production of M. tuberculosis and purified protein derivative-induced IFN-γ, TNF-α, IL-1β, and IL-6 was reduced in a DEP dose-dependent manner. In contrast, the production of anti-inflammatory IL-10 remained unchanged. Furthermore, DEP stimulation prior to M. tuberculosis infection altered the expression of TLR3, -4, -7, and -10 mRNAs and of a subset of M. tuberculosis-induced host genes including inhibition of expression of many NF-κB (e.g., CSF3, IFNG, IFNA, IFNB, IL1A, IL6, and NFKBIA) and IFN regulatory factor (e.g., IFNG, IFNA1, IFNB1, and CXCL10) pathway target genes. We propose that DEP downregulate M. tuberculosis-induced host gene expression via MyD88-dependent (IL6, IL1A, and PTGS2) as well as MyD88-independent (IFNA, IFNB) pathways. Prestimulation of PBMC with DEP suppressed the expression of proinflammatory mediators upon M. tuberculosis infection, inducing a hyporesponsive cellular state. Therefore, DEP alters crucial components of antimycobacterial host immune responses, providing a possible mechanism by which air pollutants alter antimicrobial immunity.

Aldo-keto reductase 1C15 as a quinone reductase in rat endothelial cell: its involvement in redox cycling of 9,10-phenanthrenequinone

9,10-Phenanthrenequinone (9,10-PQ), a redox-active quinone in diesel exhausts, triggers cellular apoptosis via reactive oxygen species (ROS) generation in its redox cycling. This study found that induction of CCAAT/enhancer-binding protein-homologous protein (CHOP), a pro-apoptotic factor derived from endoplasmic reticulum stress, participates in the mechanism of rat endothelial cell damage. The 9,10-PQ-mediated CHOP induction was strengthened by a proteasome inhibitor (MG132) and the MG132-induced cell sensitization to the 9,10-PQ toxicity was abolished by a ROS inhibitor, suggesting that ROS generation and consequent proteasomal dysfunction are responsible for the CHOP up-regulation caused by 9,10-PQ. Aldo-keto reductase (AKR) 1C15 expressed in rat endothelial cells reduced 9,10-PQ into 9,10-dihydroxyphenanthrene concomitantly with superoxide anion formation, implying its participation in evoking the 9,10-PQ-redox cycling. The 9,10-PQ-induced damage was augmented by AKR1C15 over-expression. 9,10-PQ also provoked the AKR1C15 up-regulation, which sensitized against the quinone toxicity. These results suggest the presence of a negative feedback loop exacerbating the quinone toxicity in rat endothelial cells.

Diesel exhaust (DE) aggravates pathology of delayed-type hypersensitivity (DTH) induced by methyl-bovine serum albumin (mBSA) in mice

Diesel exhaust particles (DEP), a well-known air pollutant, exacerbate type I hypersensitivity conditions, such as asthma and pollen allergy. In this study, we examined the effect of diesel exhaust (DE) exposure on delayed-type hypersensitivity (DTH), a type IV hypersensitivity, induced with methyl-bovine serum albumin (mBSA) in C57BL/6 mice. Mice were exposed to DE containing DEP at a dose of 1.78 mg/m(3) in an inhalation chamber for 14 days. On Day 7, DTH mice and DE-exposed DTH mice were injected s.c. with 200 microl of 1.25 mg/ml mBSA emulsified with CFA in the dorsal region as initial sensitization. On Day 14, mice were injected s.c. into one footpad with 20 microl of 10 mg/ml mBSA dissolved in PBS as challenge. On Day15, footpad thickness and spleen weight were measured. Significant footpad swelling (%) was observed in DTH mice compared with normal control mice, and this swelling was significantly augmented by DE exposure. The levels of pro-inflammatory cytokines, including IFN-gamma, TNF-alpha, and IL-6, in DTH mice were significantly higher than in normal mice, and were also further enhanced by DE exposure. DE exposure increased production of IL-17, which enhances local tissue inflammation through up-regulation of pro-inflammatory cytokines, while production of IL-10, which inhibits local tissue inflammation through suppression of immune cell proliferation, was unchanged. No change was observed in the percentage of CD4(+)CD25(+)Foxp3(+)T regulatory (Treg) cells in splenic lymphocytes following DE exposure. IL-6 production was increased by DE, and this would facilitate the differentiation of naïve T cells to IL-17-producing Th17 cells, while concomitantly suppressing the competing differentiation pathway to IL-10-producing Treg cells. Our results indicate that DE inhalation may, in part, exacerbate the pathological symptoms of DTH and induction of pro-inflammatory cytokines such as IFN-gamma, TNF-alpha, IL-6 and IL-17.

Mouse models to unravel the role of inhaled pollutants on allergic sensitization and airway inflammation

Air pollutant exposure has been linked to a rise in wheezing illnesses. Clinical data highlight that exposure to mainstream tobacco smoke (MS) and environmental tobacco smoke (ETS) as well as exposure to diesel exhaust particles (DEP) could promote allergic sensitization or aggravate symptoms of asthma, suggesting a role for these inhaled pollutants in the pathogenesis of asthma. Mouse models are a valuable tool to study the potential effects of these pollutants in the pathogenesis of asthma, with the opportunity to investigate their impact during processes leading to sensitization, acute inflammation and chronic disease. Mice allow us to perform mechanistic studies and to evaluate the importance of specific cell types in asthma pathogenesis. In this review, the major clinical effects of tobacco smoke and diesel exhaust exposure regarding to asthma development and progression are described. Clinical data are compared with findings from murine models of asthma and inhalable pollutant exposure. Moreover, the potential mechanisms by which both pollutants could aggravate asthma are discussed.

Involvement of an aldo-keto reductase (AKR1C3) in redox cycling of 9,10-phenanthrenequinone leading to apoptosis in human endothelial cells

9,10-Phenanthrenequinone (9,10-PQ), a major quinone found in diesel exhaust particles, is considered to generate reactive oxygen species (ROS) through its redox cycling. Here, we show that 9,10-PQ evokes apoptosis in human aortic endothelial cells (HAECs) and its apoptotic signaling includes ROS generation and caspase activation. The 9,10-PQ-induced cytotoxicity was inhibited by ROS scavengers, indicating that intracellular ROS generation is responsible for the 9,10-PQ-induced apoptosis. Comparison of mRNA expression levels and kinetic constants in the 9,10-PQ reduction among 10 human reductases suggests that aldo-keto reductase 1C3 (AKR1C3) is a 9,10-PQ reductase in HAECs. In in vitro 9,10-PQ reduction by AKR1C3, the reduced product 9,10-dihydroxyphenanthrene and superoxide anions were formed, suggesting the enzymatic two-electron reduction of 9,10-PQ that thereby causes oxidative stress through its redox cycling. In addition, the participation of AKR1C3 in 9,10-PQ-redox cycling was confirmed by the data that AKR1C3 overexpression in endothelial cells augmented the ROS generation and cytotoxicity by 9,10-PQ, and the ROS scavengers inhibited the toxic effects. Pretreatment of the overexpressing cells with AKR1C3 inhibitors, flufenamic acid and indomethacin, suppressed the 9,10-PQ-induced GSH depletion. These results suggest that AKR1C3 is a key enzyme in the initial step of 9,10-PQ-induced cytotoxicity in HAECs.

[Exposure to fine air particles and occurrence of allergic diseases: results of ISAAC-France phase 2]

To evaluate whether fine air particles could be involved in the occurrence of atopy and allergic diseases, we performed a cross-sectional epidemiological survey involving primary schoolchildren living in six French towns with contrasted air pollution levels. Air pollution was measured during a week in the school yards and by standard air monitoring networks. Children get an examination in school looking for atopic dermatitis and bronchial hyperresponsiveness assessed by a standardized run test. Besides, parents or guardians provided past medical history and environmental data, especially on passive smoking. Overall, 5,338 children, aged 10.4 (+/-0.7) years, coming from 108 different schools and 401 different classes were included in the survey. Taking into account potential confounders, high exposure to proximity PM(2.5) was linked to a higher point prevalence of atopic dermatitis and hyperresponsiveness, to a higher cumulative prevalence of allergic asthma and a higher sensitization rate to common indoor allergens. Thus, these data suggest that chronic exposure to urban fine particles could be a risk factor for atopy, hyperresponsiveness and asthma.

Can fine particulate matter explain the paradoxical ozone associations?

Our previous paper entitled "Paradoxical ozone associations could be due to methyl nitrite from combustion of methyl ethers or esters in engine fuels" (Env. Int.. 2007;33;1090) reviewed 11 studies of the impact of ozone on human health that, paradoxically, found a negative coefficient for ozone-morbidity associations. We argued that the most likely explanation for this effect would be methyl nitrite (MN) as an unsuspected exhaust component of engines with methyl ether in the fuel. The basis of the argument was the fact that MN is rapidly destroyed by sunlight, so that MN would be negatively correlated with ozone. All (but one) of the reviewed studies concluded that criterion pollutants could not explain the negative slope. The argument was strengthened by the observation that such paradoxical ozone associations have not been found in regions without significant methyl ether in gasoline. Left unaddressed in the previous paper was the possibility that fine particulate matter (FPM) might explain the POA. If this were true, then it would be necessary that the FPM be negatively correlated with ozone in those regions that found a POA. The current paper reviews data on FPM-ozone correlations in those regions where a POA was identified. The results show that FPM was, in most cases, positively correlated with ozone and so could not explain the POA.

Traffic, outdoor air pollution, and asthma

The epidemiology of asthma and outdoor air pollution has shown that respiratory health effects can vary in relation to different emission sources, types of pollutants, underlying nutritional status, medication use, and genetic polymorphisms. Using sophisticated exposure assessment methods in conjunction with clinical tests and biomarkers that provide mechanistic information, the study of outdoor epidemiology and asthma has evolved into a complex multidisciplinary field. This article presents an overview of the mechanisms by which outdoor air pollution and traffic-related emissions lead to changes in respiratory health and lung function in subjects with asthma.

Cigarette smoking is associated with a greater risk of incident asthma in allergic rhinitis

BACKGROUND

Asthma and rhinitis are often comorbid conditions, and several studies have suggested that rhinitis often precedes asthma. Sensitization to allergen has been shown to be one of the strongest determinants of incident asthma, but little is known about the effects of cigarette smoking among individuals with allergic rhinitis.

OBJECTIVE

We sought to evaluate the importance of cigarette smoking as an additional risk factor for incident asthma in a cohort of hospital-referred nonasthmatic adult subjects with allergic rhinitis.

METHODS

The study population selected at baseline was invited for a follow-up visit 10 years later to check for possible asthma features. Categories of smokers, exsmokers, and never smokers were used in the analyses together with pack-years to calculate the level of cumulative exposure.

RESULTS

Complete data were available from 325 patients. Smoking was significantly related to the risk of incident asthma, with the odds ratio (OR) being 2.67 (95% CI, 1.70-4.19) for univariate and 2.98 (95% CI, 1.81-4.92) for multivariate analyses. A clear dose-response association for exposure to tobacco and risk of new-onset asthma was observed in the multivariate analyses: those with 1 to 10 pack-years had an OR of 2.05 (95% CI, 0.99-4.27), those with 11 to 20 pack years had an OR of 3.71 (95% CI, 1.77-7.78), and those with 21 or more pack-years had an OR of 5.05 (95% CI, 1.93-13.20) compared with never smokers.

CONCLUSIONS

The current findings support the hypothesis that cigarette smoking is an important independent risk factor for the development of new asthma cases in adults with allergic rhinitis.

L-Xylulose reductase is involved in 9,10-phenanthrenequinone-induced apoptosis in human T lymphoma cells

9,10-Phenanthrenequinone (9,10-PQ), a major component in diesel exhaust particles, is suggested to generate reactive oxygen species (ROS) through its redox cycling, leading to cell toxicity. l-Xylulose reductase (XR), a NADPH-dependent enzyme in the uronate pathway, strongly reduces alpha-dicarbonyl compounds and was thought to act as a detoxification enzyme against reactive carbonyl compounds. Here, we have investigated the role of intracellular ROS generation in apoptotic signaling in human acute T-lymphoblastic leukemia MOLT-4 cells treated with 9,10-PQ and the role of XR in the generation of ROS. Treatment with 9,10-PQ elicited not only apoptotic signaling, including mitochondrial membrane dysfunction and activation of caspases and poly(ADP-ribose) polymerase, but also intracellular ROS generation and consequent glutathione depletion. The apoptotic effects of 9,10-PQ were drastically mitigated by pretreatment with intracellular ROS scavengers, such as N-acetyl-l-cysteine, glutathione monoethyl ester, and polyethylene glycol-conjugated catalase, indicating that intracellular ROS generation is responsible for the 9,10-PQ-evoked apoptosis. Surprisingly, the ROS generation and cytotoxicity by 9,10-PQ were augmented in an XR-transformed cell line. XR indeed reduced 9,10-PQ and produced superoxide anion through redox cycling. In addition, the expression levels of XR and its mRNA in the T lymphoma cells were markedly enhanced after the exposure to 9,10-PQ, and the induction was completely abolished by the ROS scavengers. Moreover, the 9,10-PQ-induced apoptosis was partially inhibited by the pretreatment with XR-specific inhibitors. These results suggest that initially produced ROS induce XR, which accelerates the generation of ROS.

Respiratory effects of exposure to diesel traffic in persons with asthma

BACKGROUND

Air pollution from road traffic is a serious health hazard, and people with preexisting respiratory disease may be at increased risk. We investigated the effects of short-term exposure to diesel traffic in people with asthma in an urban, roadside environment.

METHODS

We recruited 60 adults with either mild or moderate asthma to participate in a randomized, crossover study. Each participant walked for 2 hours along a London street (Oxford Street) and, on a separate occasion, through a nearby park (Hyde Park). We performed detailed real-time exposure, physiological, and immunologic measurements.

RESULTS

Participants had significantly higher exposures to fine particles (<2.5 microm in aerodynamic diameter), ultrafine particles, elemental carbon, and nitrogen dioxide on Oxford Street than in Hyde Park. Walking for 2 hours on Oxford Street induced asymptomatic but consistent reductions in the forced expiratory volume in 1 second (FEV1) (up to 6.1%) and forced vital capacity (FVC) (up to 5.4%) that were significantly larger than the reductions in FEV1 and FVC after exposure in Hyde Park (P=0.04 and P=0.01, respectively, for the overall effect of exposure, and P<0.005 at some time points). The effects were greater in subjects with moderate asthma than in those with mild asthma. These changes were accompanied by increases in biomarkers of neutrophilic inflammation (sputum myeloperoxidase, 4.24 ng per milliliter after exposure in Hyde Park vs. 24.5 ng per milliliter after exposure on Oxford Street; P=0.05) and airway acidification (maximum decrease in pH, 0.04% after exposure in Hyde Park and 1.9% after exposure on Oxford Street; P=0.003). The changes were associated most consistently with exposures to ultrafine particles and elemental carbon.

CONCLUSIONS

Our observations serve as a demonstration and explanation of the epidemiologic evidence that associates the degree of traffic exposure with lung function in asthma.

Particulate matter in the environment: pulmonary and cardiovascular effects

PURPOSE OF REVIEW

The mechanisms related to adverse respiratory and cardiovascular effects in populations exposed to particulate matter are under debate and different models have been used to further our understanding of the various aspects of those effects. In this review we present some studies that may give new insights into the cellular and systemic mechanisms related to particulate matter toxicity.

RECENT FINDINGS

Strong epidemiological evidence is now available regarding exposure markers and health effects. This is evident in the correlation between carbon content in macrophages and decrease in lung function, an increase in the risk of chronic obstructive pulmonary disease, lung cancer and postnatal mortality. The role of outdoor temperature and a missing allele for GSTM1 and the impact of these factors on cardiovascular effects are also reported. At the experimental level, the effects of particulate matter and the interactions between different cell types, the role of toll-like receptor-2 and 4, the translocation of particles through cell monolayers and the activation of endothelial cells by particulate matter are also discussed. The role of composition is under intense debate, and different statistical analyses have been proposed.

SUMMARY

Experimental studies on the effects of particulate matter are giving plausibility to the epidemiological findings, but the possible mechanisms of action are also becoming a hot topic.

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.

Detection of allergens adsorbed to ambient air particles collected in four European cities

Air pollution has been implicated as one of the factors responsible for the increased incidence of allergic diseases observed in recent years. High concentrations of air pollutants may promote airway sensitization by acting as adjuvants. Ambient particles as carriers of adsorbed allergens are, therefore, of special interest since they may act as mediators of inflammatory as well as allergic responses. Ambient air particles from four cities in Europe were collected, in three different seasons, to examine the variation of allergens and their possible binding to the pollution particles. The particle fraction, PM10, was collected on polycarbonate filters using a low-volume sampling regime. The presence of pollen allergens, latex and beta-glucans was investigated using an immunogold labelling method directly on the collection filters. Scanning electron microscopy revealed mainly the classical carbon particles and aggregates determined to originate from vehicle exhaust. The immunogold labelling visualised in the backscatter electron imaging mode, showed that allergens from pollens, latex and also beta-glucans were bound to and, hence, transported by the combustion particles in ambient air. Thus, combustion particles in ambient air are carriers of allergens and act as depots of allergens inhaled into the airways.

Diesel exhaust particles increase IL-1beta-induced human beta-defensin expression via NF-kappaB-mediated pathway in human lung epithelial cells

Background

Human β-defensin (hBD)-2, antimicrobial peptide primarily induced in epithelial cells, is a key factor in the innate immune response of the respiratory tract. Several studies showed increased defensin levels in both inflammatory lung diseases, such as cystic fibrosis, diffuse panbronchiolitis, idiopathic pulmonary fibrosis and acute respiratory distress syndrome, and infectious diseases. Recently, epidemiologic studies have demonstrated acute and serious adverse effects of particulate air pollution on respiratory health, especially in people with pre-existing inflammatory lung disease. To elucidate the effect of diesel exhaust particles (DEP) on pulmonary innate immune response, we investigated the hBD-2 and interleukin-8 (IL-8) expression to DEP exposure in interleukin-1 beta (IL-1β)-stimulated A549 cells.

Results

IL-1β markedly up-regulated the hBD-2 promoter activity, and the subsequent DEP exposure increased dose-dependently the expression of hBD-2 and inflammatory cytokine IL-8 at the transcriptional level. In addition, DEP further induced the NF-κB activation in IL-1β-stimulated A549 cells more rapidly than in unstimulated control cells, which was showed by nuclear translocation of p65 NF-κB and degradation of IκB-α. The experiment using two NF-κB inhibitors, PDTC and MG132, confirmed that this increase of hBD-2 expression following DEP exposure was regulated through NF-κB-mediated pathway.

Conclusion

These results demonstrated that DEP exposure increases the expression of antimicrobial peptide and inflammatory cytokine at the transcriptional level in IL-1β-primed A549 epithelial cells and suggested that the increase is mediated at least partially through NF-κB activation. Therefore, DEP exposure may contribute to enhance the airway-responsiveness especially on the patients suffering from chronic respiratory disease.

Asthma, genes, and air pollution

OBJECTIVE

The objective of this article is to evaluate genetic risks associated with the pulmonary response to air pollutants, including particulates and ozone.

METHODS

A comprehensive review of articles related to the genetics of asthma with particular attention to air pollution was conducted through a search of the National Library of Medicine's PubMed database.

RESULTS

Asthma, which affects over 15 million people in the United States, is characterized by inflammation leading to reversible airflow obstruction. Triggered by exposure to numerous occupational and environmental agents, asthma has long been considered to occur more frequently in families, with upwards of a 50% higher rate in the offspring of parents with asthma. Asthma genetic studies have used two major methods: mapping techniques that pinpoint gene loci and studies that identify genes and polymorphisms associated with various asthma mechanisms such as inflammatory mediators. The most consistently replicated chromosomal regions associated with asthma have been chromosomes 2q, 5q, 6p, 12 q, and 13q. Because the formation of reactive oxygen species is a major aspect of the inflammatory process of asthma, genetic aberrations associated with antioxidants such as glutathione S-transferase (GST) may shed light on reasons why some people with asthma seem more at risk of exacerbations as a result of air pollution. People with a polymorphism at the GSTP 1 locus, which codes for GST, one of a family of pulmonary antioxidants, have higher rates of asthma. Children in Mexico City with the GSTM1 null genotype demonstrated significant ozone-related decrements in lung function. Animal studies support the key role of antioxidants in reducing the inflammatory response associated with exposure to diesel exhaust particles.

CONCLUSIONS

Oxidative stress is a key mechanism underlying the toxic effects of exposure to some types of air pollution. Asthmatics with the null genotype for the antioxidant, GST, seem more at risk of the pulmonary effects of air pollution.

Acute respiratory diseases and carboxyhemoglobin status in school children of Quito, Ecuador

Outdoor carbon monoxide comes mainly from vehicular emissions, and high concentrations occur in areas with heavy traffic congestion. CO binds to hemoglobin, forming carboxyhemoglobin (COHb), and reduces oxygen delivery. We investigated the link between the adverse effects of CO on the respiratory system using COHb as a marker for chronic CO exposure. We examined the relationship between acute respiratory infections (ARIs) and COHb concentrations in school-age children living in urban and suburban areas of Quito, Ecuador. We selected three schools located in areas with different traffic intensities and enrolled 960 children. To adjust for potential confounders we conducted a detailed survey. In a random subsample of 295 children, we determined that average COHb concentrations were significantly higher in children attending schools in areas with high and moderate traffic, compared with the low-traffic area. The percentage of children with COHb concentrations above the safe level of 2.5% were 1, 43, and 92% in low-, moderate-, and high-traffic areas, respectively. Children with COHb above the safe level are 3.25 [95% confidence interval (CI), 1.65-6.38] times more likely to have ARI than children with COHb < 2.5%. Furthermore, with each percent increase in COHb above the safety level, children are 1.15 (95% CI, 1.03-1.28) times more likely to have an additional case of ARI. Our findings provide strong evidence of the relation between CO exposure and susceptibility to respiratory infections.

Diesel exhaust particles suppress in vivo IFN-gamma production by inhibiting cytokine effects on NK and NKT cells

Diesel exhaust particles (DEP) have strong, selective Th2 adjuvant activity when inhaled with conventional Ags. We used a novel technique for measuring in vivo cytokine production to investigate possible mechanisms by which DEP might promote a Th2 response. Injection of DEP i.p. stimulated IL-6 secretion, but failed to increase IL-4, IL-10, or TNF-alpha secretion, and decreased basal levels of IFN-gamma. When injected with or before LPS, DEP had little effect on the LPS-induced TNF-alpha responses, but partially inhibited the LPS-induced IL-10 response and strongly inhibited the LPS-induced IFN-gamma response. DEP also inhibited the IFN-gamma responses to IL-12, IL-12 plus IL-18, IL-2, and poly(I.C). DEP treatment had little effect on the percentages of NK and NKT cells in the spleen, but inhibited LPS-induced IFN-gamma production by splenic NK and NKT cells. In contrast, DEP failed to inhibit the IFN-gamma response by anti-CD3 mAb-activated NKT cells. Taken together, these observations suggest that DEP inhibit Toll-like receptor ligand-induced IFN-gamma responses by interfering with cytokine signaling pathways that stimulate NK and NKT cells to produce IFN-gamma. Our observations also suggest that DEP may promote a Th2 response by stimulating production of inflammatory cytokines while simultaneously inhibiting production of IFN-gamma, and raise the possibility that the same mechanisms contribute to the association between DEP exposure and asthma.

Effect of diesel exhaust particulate (DEP) on immune responses: contributions of particulate versus organic soluble components

The effect of diesel exhaust particulate (DEP) exposure on innate, cellular and humoral pulmonary immunity was studied using high-dose, acute-exposure rat, mouse, and cell culture models. DEP consists of a complex mixture of petrochemical-derived organics adsorbed onto elemental carbon particles. DEP is a major component of particulate urban air pollution and a health concern in both urban and occupational environments. The alveolar macrophage is considered a key cellular component in pulmonary innate immunity. DEP and DEP organic extracts have been found to suppress alveolar macrophage function as demonstrated by reduced production of cytokines (interleukin-1 [IL-1], tumor necrosis factor- alpha [TNF- alpha]) and reactive oxygen species (ROS) in response to a variety of agents, including lipopolysaccharide (LPS), interferon- gamma (IFN- gamma), and bacteria. Fractionation of DEP organic extract suggests that this activity was predominately in polyaromatic-containing and more polar (resin) fractions. Organic-stripped DEP did not alter these innate pulmonary immune responses. DEP also depressed pulmonary clearance of Listeria monocytogenes and Bacillus Calmette-Guerin (BCG). The contribution of the organic component of DEP is less well defined with respect to acquired and humoral immunity. Indeed, both DEP and carbon black enhanced humoral immune responses (specific immunoglobulin [Ig] E and IgG) in an ovalbumin-sensitized rat model. It is concluded that both the particulate and adsorbed organics may contribute to DEP-mediated immune alterations.

Exposure to road traffic enhances allergic skin wheal responses and increases plasma neuropeptides and neurotrophins in patients with atopic eczema/dermatitis syndrome

The effect of exposure to road traffic was studied by sitting on chairs for 30 min beside a road with heavy wheeled traffic. Exposure to road traffic enhanced allergen-induced, but not histamine-induced, skin wheal responses in 26 patients with atopic eczema/dermatitis syndrome, while it had no effect on skin wheal responses in 26 normal subjects. Exposure to road traffic also increased plasma levels of substance P, vasoactive intestinal peptide, nerve growth factor, and neurotrophin-3 in patients with atopic eczema/dermatitis syndrome, while it had no effect on these plasma parameters in normal subjects. Collectively, exposure to road traffic may aggravate allergic diseases by enhancing allergic responses with concomitant increase in plasma levels of neuropeptides and neurotrophins.