Airway inflammation after controlled exposure to diesel exhaust particulates

Link between environmental air pollution and allergic asthma: East meets West

With the levels of outdoor air pollution from industrial and motor vehicle emissions rising rapidly in the fastly-industrializing countries of South East Asia, the prevalence of asthma and allergic diseases has also been increasing to match those in the West. Epidemiological and experimental exposure studies indicate a harmful impact of outdoor air pollution from vehicles and factories both on the development of allergic diseases and asthma and the increase in asthma symptoms and exacerbations. The level of outdoor pollution in Asia is much higher and more diverse than those encountered in Western countries. This may increase the impact of outdoor pollution on health, particularly lung health in Asia. This review discusses the constituents of air pollution in Asia with a special focus on studies in mainland China and Taiwan where the levels of pollution have reached high levels and where such high levels particularly in winter can cause a thick haze that reduces visibility. The onus remains on regulatory and public health authorities to curb the sources of pollution so that the health effects on the population particularly those with lung and cardiovascular diseases and with increased susceptibility can be mitigated.

[Health effects of diesel exhaust: a state of the art]

INTRODUCTION

This review presents the state of knowledge regarding the acute and chronic toxicity of diesel engine exhaust in humans.

STATE OF ART

The health effects of diesel engine exhaust, which is a complex mixture of gas and particulate matter (ultrafine and fine particles), are mainly irritation of the respiratory tract and carcinogenicity. They may also facilitate the development of respiratory allergies. A recent reassessment by the International Agency for Research on Cancer concluded that there is sufficient evidence of a causal association between exposure to diesel engine exhaust and lung cancer.

PERSPECTIVES

The epidemiologic data collected during the last two decades also show limited evidence of increased risks of bladder cancer, as well as of chronic obstructive pulmonary disease in diesel engine exhaust exposed workers. Both experimental and epidemiological studies have involved the effect of emissions from traditional diesel engine technology. Major developments in this technology have occurred recently and the toxicity of emissions from these new engines is still to be characterized.

CONCLUSION

Further studies are needed to explore the link between diesel engine exhaust exposure and the risks of bladder cancer, as well as of chronic obstructive pulmonary disease and respiratory allergies. Research is also needed to get more information about the toxicity of the new diesel technology emissions.

Respiratory effects of fine and ultrafine particles from indoor sources--a randomized sham-controlled exposure study of healthy volunteers

Particulate air pollution is linked to impaired respiratory health. We analyzed particle emissions from common indoor sources (candles burning (CB), toasting bread (TB), frying sausages (FS)) and lung function in 55 healthy volunteers (mean age 33.0 years) in a randomized cross-over controlled exposure study. Lung-deposited particle surface area concentration (PSC), size-specific particle number concentration (PNC) up to 10 µm, and particle mass concentration (PMC) of PM₁, PM_2.5 and PM₁₀ were determined during exposure (2 h). FEV₁, FVC and MEF_25%–75% was measured before, 4 h and 24 h after exposure. Wilcoxon-rank sum tests (comparing exposure scenarios) and mixed linear regression using particle concentrations and adjusting for personal characteristics, travel time and transportation means before exposure sessions were performed. While no effect was seen comparing the exposure scenarios and in the unadjusted model, inverse associations were found for PMC from CB and FS in relation to FEV₁ and MEF_25%–75%. with a change in 10 µg/m³ in PM_2.5 from CB being associated with a change in FEV₁ of −19 mL (95%-confidence interval:−43; 5) after 4 h. PMC from TB and PNC of UFP were not associated with lung function changes, but PSC from CB was. Elevated indoor fine particles from certain sources may be associated with small decreases in lung function in healthy adults.

A mouse model links asthma susceptibility to prenatal exposure to diesel exhaust

BACKGROUND

Most asthma begins in the first years of life. This early onset cannot be attributed merely to genetic factors because the prevalence of asthma is increasing. Epidemiologic studies have indicated roles for prenatal and early childhood exposures, including exposure to diesel exhaust. However, little is known about the mechanisms. This is largely due to a paucity of animal models.

OBJECTIVE

We aimed to develop a mouse model of asthma susceptibility through prenatal exposure to diesel exhaust.

METHODS

Pregnant C57BL/6 female mice were given repeated intranasal applications of diesel exhaust particles (DEPs) or PBS. Offspring underwent suboptimal immunization and challenge with ovalbumin (OVA) or received PBS. Pups were examined for features of asthma; lung and liver tissues were analyzed for transcription of DEP-regulated genes.

RESULTS

Offspring of mice exposed to DEPs were hypersensitive to OVA, as indicated by airway inflammation and hyperresponsiveness, increased serum OVA-specific IgE levels, and increased pulmonary and systemic TH2 and TH17 cytokine levels. These cytokines were primarily produced by natural killer (NK) cells. Antibody-mediated depletion of NK cells prevented airway inflammation. Asthma susceptibility was associated with increased transcription of genes known to be specifically regulated by the aryl hydrocarbon receptor and oxidative stress. Features of asthma were either marginal or absent in OVA-treated pups of PBS-exposed mice.

CONCLUSION

We created a mouse model that linked maternal exposure to DEPs with asthma susceptibility in offspring. Development of asthma was dependent on NK cells and associated with increased transcription from aryl hydrocarbon receptor- and oxidative stress-regulated genes.

Cardiovascular effects caused by increasing concentrations of diesel exhaust in middle-aged healthy GSTM1 null human volunteers

CONTEXT

Epidemiological studies have shown an association between the incidence of adverse cardiovascular effects and exposure to ambient particulate matter (PM). Diesel exhaust (DE) is a major contributor to ambient PM and gaseous emissions in urban areas.

OBJECTIVE

This was a pilot study designed to evaluate concentration-dependent effects of short-term exposure to whole DE on the cardiovascular system in order to identify a threshold concentration that can elicit biological responses in healthy human volunteers.

MATERIALS AND METHODS

Six healthy middle-aged participants with glutathione-S-transferase-Mu 1 (GSTM1) null genotype underwent sequential exposures to 100 µg/m(3), 200 µg/m(3), and 300 µg/m(3) whole DE generated in real time using an idling diesel truck engine. Exposures were separated by 14 d and each was 2 h in duration.

RESULTS

We report concentration-dependent effects of exposure to DE, with 100 µg/m(3) concentration causing minimal cardiovascular effects, while exposure to 300 µg/m(3) DE for 2 h resulted in a borderline significant reduction of baseline brachial artery diameter (3.34 ± 0.27 mm pre- versus 3.23 ± 0.25 mm post-exposure; p = 0.08). Exposure to the highest concentration of DE also resulted in increases of 5 mmHg in diastolic blood pressure as well as a decrease in indices of the frequency domain of heart rate variability (HRV).

DISCUSSION AND CONCLUSIONS

These findings demonstrate that acute exposure to relatively high concentrations of DE produces cardiovascular changes in middle-aged GSTM1 null individuals. This study therefore suggests that arterial vasoconstriction and changes in HRV are responses through which traffic-related air pollution increases the risk of adverse cardiovascular outcomes.

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.

Exhaled breath condensate: a comprehensive update

Since the late 1990s, a surge in interest in the analysis of exhaled breath condensate (EBC) resulted in the American Thoracic Society and European Respiratory Society (ATS/ERS) organising a Task Force in 2001 to develop guidelines on EBC collection and measurement of biomarkers. This Task Force published their guidelines in 2005 based on literature and expert opinions at that time, and multiple shortcomings and knowledge deficits were also identified. The clinical application of EBC collection and its biomarkers are currently still limited by several of these knowledge gaps, hence further guidelines for standardisation are required to ensure external validity. Using related articles produced since the publication of the ATS/ERS Task Force report, this paper attempts to provide a comprehensive update to the original guideline and review the methodological shortcomings identified. This review can hopefully serve as a yardstick for future studies involving this emerging clinical tool.

Effects of diesel exposure on lung function and inflammation biomarkers from airway and peripheral blood of healthy volunteers in a chamber study

Background

Exposure to diesel exhaust causes inflammatory responses. Previous controlled exposure studies at a concentration of 300 μg/m³ of diesel exhaust particles mainly lasted for 1 h. We prolonged the exposure period and investigated how quickly diesel exhaust can induce respiratory and systemic effects.

Methods

Eighteen healthy volunteers were exposed twice to diluted diesel exhaust (PM₁ ~300 μg/m³) and twice to filtered air (PM₁ ~2 μg/m³) for 3 h, seated, in a chamber with a double-blind set-up. Immediately before and after exposure, we performed a medical examination, spirometry, rhinometry, nasal lavage and blood sampling. Nasal lavage and blood samples were collected again 20 h post-exposure. Symptom scores and peak expiratory flow (PEF) were assessed before exposure, and at 15, 75, and 135 min of exposure.

Results

Self-rated throat irritation was higher during diesel exhaust than filtered air exposure. Clinical signs of irritation in the upper airways were also significantly more common after diesel exhaust exposure (odds ratio=3.2, p<0.01). PEF increased during filtered air, but decreased during diesel exhaust exposure, with a statistically significant difference at 75 min (+4 L/min vs. -10 L/min, p=0.005). Monocyte and total leukocyte counts in peripheral blood were higher after exposure to diesel exhaust than filtered air 20 h post-exposure, and a trend (p=0.07) towards increased serum IL-6 concentrations was also observed 20 h post-exposure.

Conclusions

Diesel exhaust induced acute adverse effects such as symptoms and signs of irritation, decreased PEF, inflammatory markers in healthy volunteers. The effects were first seen at 75 min of exposure.

Utility of an alternative bicycle commute route of lower proximity to motorised traffic in decreasing exposure to ultra-fine particles, respiratory symptoms and airway inflammation--a structured exposure experiment

BACKGROUND

Bicycle commuting in an urban environment of high air pollution is known to be a potential health risk, especially for susceptible individuals. While risk management strategies aimed to reduce exposure to motorised traffic emissions have been suggested, only limited studies have assessed the utility of such strategies in real-world circumstances.

OBJECTIVES

The potential to lower exposure to ultrafine particles (UFP; < 0.1 μm) during bicycle commuting by reducing proximity to motorised traffic was investigated with real-time air pollution and intermittent acute inflammatory measurements in healthy individuals using their typical higher proximity, and an alternative lower proximity, bicycle commute route.

METHODS

Thirty-five healthy adults (mean ± SD: age = 39 ± 11 yr; 29% female) completed two return trips, one each in the condition of their typical route (HIGH) and a pre-determined alternative route of lower proximity to motorised traffic (LOW); proximity being determined by the proportion of on-road cycle paths. Particle number concentration (PNC) and diameter (PD) were monitored in-commute in real-time. Acute inflammatory indices of respiratory symptoms (as a scalar of frequency from very low to very high / 1 to 5), lung function and spontaneous sputum (for inflammatory cell analyses) were collected immediately pre-commute, and immediately and three hours post-commute.

RESULTS

In the condition of LOW, compared to in the condition of HIGH, there was a significant decrease in mean PNC (1.91 x e4 ± 0.93 × e4 ppcc vs. 2.95 × e4 ± 1.50 × e4 ppcc; p ≤ 0.001), and the mean frequency of in-commute offensive odour detection (2.1 vs. 2.8; p = 0.019), dust and soot observation (1.7 vs. 2.3; p = 0.038) and nasopharyngeal irritation (1.5 vs. 1.9; p = 0.007). There were no significant differences between LOW and HIGH in the commute distance and duration (12.8 ± 7.1 vs. 12.0 ± 6.9 km and 44 ± 17 vs. 42 ± 17 min, respectively), or other indices of acute airway inflammation.

CONCLUSIONS

Exposure to PNC and offensive odour, and nasopharyngeal irritation, can be significantly lowered when utilising a route of lower proximity to motorised traffic whilst bicycle commuting, without significantly affecting commute distance or duration. This may bring health benefits for both healthy and susceptible individuals.

Associations of ambient air pollution with chronic obstructive pulmonary disease hospitalization and mortality

RATIONALE

Ambient air pollution has been suggested as a risk factor for chronic obstructive pulmonary disease (COPD). However, there is a lack of longitudinal studies to support this assertion.

OBJECTIVES

To investigate the associations of long-term exposure to elevated traffic-related air pollution and woodsmoke pollution with the risk of COPD hospitalization and mortality.

METHODS

This population-based cohort study included a 5-year exposure period and a 4-year follow-up period. All residents aged 45-85 years who resided in Metropolitan Vancouver, Canada, during the exposure period and did not have known COPD at baseline were included in this study (n = 467,994). Residential exposures to traffic-related air pollutants (black carbon, particulate matter <2.5 μm in aerodynamic diameter, nitrogen dioxide, and nitric oxide) and woodsmoke were estimated using land-use regression models and integrating changes in residences during the exposure period. COPD hospitalizations and deaths during the follow-up period were identified from provincial hospitalization and death registration databases.

MEASUREMENTS AND MAIN RESULTS

An interquartile range elevation in black carbon concentrations (0.97 × 10(-5)/m, equivalent to 0.78 μg/m(3) elemental carbon) was associated with a 6% (95% confidence interval, 2-10%) increase in COPD hospitalizations and a 7% (0-13%) increase in COPD mortality after adjustment for covariates. Exposure to higher levels of woodsmoke pollution (tertile 3 vs. tertile 1) was associated with a 15% (2-29%) increase in COPD hospitalizations. There were positive exposure-response trends for these observed associations.

CONCLUSIONS

Ambient air pollution, including traffic-related fine particulate pollution and woodsmoke pollution, is associated with an increased risk of COPD.

Air quality and exercise-induced bronchoconstriction in elite athletes

A higher prevalence of airway hyperresponsiveness, airway remodeling, and asthma has been identified among athletes who compete and train in environmental conditions of cold dry air and/or high air pollution. Repeated long-duration exposure to cold/dry air at high minute ventilation rates can cause airway damage. Competition or training at venues close to busy roadways, or in indoor ice arenas or chlorinated swimming pools, harbors a risk for acute and chronic airway disorders from high pollutant exposure. This article discusses the effects of these harsh environments on the airways, and summarizes potential mechanisms and prevalence of airway disorders in elite athletes.

Dose-dependent relationship between prenatal exposure to fine particulates and exhaled carbon monoxide in non-asthmatic children. A population-based birth cohort study

OBJECTIVES

The main goal of the study was to assess possible association between fetal exposure to fine particulate matter (PM2.5) and exhaled carbon monoxide (eCO) measured in non-asthmatic children.

MATERIAL AND METHODS

The subjects include 118 children taking part in an ongoing population-based birth cohort study in Kraków. Personal samplers of PM2.5 were used to measure fine particle mass in the fetal period and carbon monoxide (CO) in exhaled breath from a single exhalation effort at the age of 7. In the statistical analysis of the effect of prenatal PM2.5 exposure on eCO, a set of potential confounders, such as environmental tobacco smoke (ETS), city residence area, sensitization to house dust allergens and the occurrence of respiratory symptoms monitored over the seven-year follow-up was considered.

RESULTS

The level of eCO did not correlate with the self-reported ETS exposure recorded over the follow-up, however, there was a positive significant relationship with the prenatal PM2.5 exposure (non-parametric trend p = 0.042). The eCO mean level was higher in atopic children (geometric mean = 2.06 ppm, 95% CI: 1.58-2.66 ppm) than in non-atopic ones (geometric mean = 1.57 ppm, 95% CI: 1.47-1.73 ppm) and the difference was statistically significant (p = 0.036). As for the respiratory symptoms, eCO values were associated positively only with the cough severity score recorded in the follow-up (nonparametric trend p = 0.057). In the nested multivariable linear regression model, only the effects of prenatal PM2.5 and cough severity recorded in the follow-up were related to eCO level. The prenatal PM2.5 exposure represented 5.1%, while children's cough represented only 2.6% of the eCO variability.

CONCLUSION

Our study suggests that elevated eCO in non-asthmatic children may result from oxidative stress experienced in the fetal period and that heme oxygenase (HO) activity in body tissues may be programmed in the fetal period by the exposure to fine particulate matter.

Anacardic acids from cashew nuts ameliorate lung damage induced by exposure to diesel exhaust particles in mice

Anacardic acids from cashew nut shell liquid, a Brazilian natural substance, have antimicrobial and antioxidant activities and modulate immune responses and angiogenesis. As inflammatory lung diseases have been correlated to environmental pollutants exposure and no reports addressing the effects of dietary supplementation with anacardic acids on lung inflammation in vivo have been evidenced, we investigated the effects of supplementation with anacardic acids in a model of diesel exhaust particle- (DEP-) induced lung inflammation. BALB/c mice received an intranasal instillation of 50 μg of DEP for 20 days. Ten days prior to DEP instillation, animals were pretreated orally with 50, 150, or 250 mg/kg of anacardic acids or vehicle (100 μL of cashew nut oil) for 30 days. The biomarkers of inflammatory and antioxidant responses in the alveolar parenchyma, bronchoalveolar lavage fluid (BALF), and pulmonary vessels were investigated. All doses of anacardic acids ameliorated antioxidant enzyme activities and decreased vascular adhesion molecule in vessels. Animals that received 50 mg/kg of anacardic acids showed decreased levels of neutrophils and tumor necrosis factor in the lungs and BALF, respectively. In summary, we demonstrated that AAs supplementation has a potential protective role on oxidative and inflammatory mechanisms in the lungs.

Altered nitric oxide bioavailability contributes to diesel exhaust inhalation-induced cardiovascular dysfunction in man

Background

Diesel exhaust inhalation causes cardiovascular dysfunction including impaired vascular reactivity, increased blood pressure, and arterial stiffness. We investigated the role of nitric oxide (NO) bioavailability in mediating these effects.

Methods and Results

In 2 randomized double‐blind crossover studies, healthy nonsmokers were exposed to diesel exhaust or filtered air. Study 1: Bilateral forearm blood flow was measured during intrabrachial infusions of acetylcholine (ACh; 5 to 20 μg/min) and sodium nitroprusside (SNP; 2 to 8 μg/min) in the presence of the NO clamp (NO synthase inhibitor N^G‐monomethyl‐l‐arginine (l‐NMMA) 8 μg/min coinfused with the NO donor SNP at 90 to 540 ng/min to restore basal blood flow). Study 2: Blood pressure, arterial stiffness, and cardiac output were measured during systemic NO synthase inhibition with intravenous l‐NMMA (3 mg/kg). Following diesel exhaust inhalation, plasma nitrite concentrations were increased (68±48 versus 41±32 nmol/L; P=0.006) despite similar l‐NMMA–induced reductions in basal blood flow (−20.6±14.7% versus −21.1±14.6%; P=0.559) compared to air. In the presence of the NO clamp, ACh and SNP caused dose‐dependent vasodilatation that was not affected by diesel exhaust inhalation (P>0.05 for both). Following exposure to diesel exhaust, l‐NMMA caused a greater increase in blood pressure (P=0.048) and central arterial stiffness (P=0.007), but reductions in cardiac output and increases in systemic vascular resistance (P>0.05 for both) were similar to those seen with filtered air.

Conclusions

Diesel exhaust inhalation disturbs normal vascular homeostasis with enhanced NO generation unable to compensate for excess consumption. We suggest the adverse cardiovascular effects of air pollution are, in part, mediated through reduced NO bioavailability.

Clinical Trial Registration

URL: http://www.ClinicalTrials.gov. Unique identifiers: NCT00845767 and NCT01060930.

[Environmental pollution and allergy: immunological mechanisms]

Airborne pollutants, both particulate and gaseous, represent a major environmental factor promoting allergic sensitization and disease expression. These adverse effects of particulate matter are highly dependent upon the nature and size of the particles, their content of chemicals and metals, and the subject's genetic makeup. Diesel exhaust and gases, in particular ozone, have been shown to exacerbate cellular inflammation and to act as mucosal adjuvants to skew the immune response to inhaled antigens toward a Th2-like phenotype. Growing evidence suggests that mechanisms of pollutant-induced amplification of the allergic reaction depend on oxidative stress that is under the control of susceptibility genes, as well as epigenetic mechanisms.

Feasibility of using biomarkers in blood serum as markers of effect following exposure of the lungs to particulate matter air pollution

Particulate matter (PM) air pollution has significant cardiopulmonary health effects. Serum biomarkers may elucidate the disease mechanisms involved and provide a means for biomonitoring exposed populations, thereby enabling accurate policy decisions on air quality standards to be made. For this review, research investigating association of blood serum biomarkers and exposure to PM was identified, finding 26 different biomarkers that were significantly associated with exposure. Recent evidence links different effects to different components of PM. Future research on biomarkers of effect will need to address exposure by all PM size fractions.

Protein kinase C-ζ mediates lung injury induced by diesel exhaust particles

Recently, we reported that diesel exhaust particles (DEPs) disrupt tight junctions (TJs) in alveolar epithelial cells (AECs) via an increase in reactive oxygen species (ROS). In this study, we investigated the role of protein kinase C (PKC)-ζ activation in DEP-induced lung injury. C57/bl6 mice were instilled intratracheally with 50 μl of saline containing 100 μg of DEPs or titanium dioxide (TiO2). Twenty-four hours later, bronchoalveolar lavage was performed to assess neutrophil counts and protein concentrations. In addition, in vitro experiments were performed in primary rat and human AECs exposed to DEPs (50 μg/cm(2)) for 3 hours. Transepithelial electrical conductance was measured, and TJ protein association was analyzed by immunoprecipitation. To determine whether the overexpression of antioxidants prevented DEP-induced lung injury, AECs and mice were infected with adenoviruses containing catalase and manganese superoxide dismutase (MnSOD) plasmids. In vivo, the overexpression of catalase and MnSOD prevented DEP-induced neutrophil recruitment. The inhibition of PKC-ζ activation also prevented DEP-induced neutrophil recruitment in vivo. In vitro, DEPs activated PKC-ζ in AECs, but not in alveolar macrophages. Using a specific myristolated PKC-ζ pseudosubstrate pepetide (PKC-ζ ps), we showed that PKC-ζ mediated the DEP-induced dissociation of occludin and zonula occludin-1 (ZO1) in rat and human AECs. In addition, the overexpression of constitutively active PKC-ζ induced the dissociation of occludin and ZO1 in AECs. DEP-induced TJ disruption occurs via PKC-ζ. TJ disruption seems to be in part responsible for DEP-induced lung injury.

Short-term effects of air pollution on pulse pressure among nonsmoking adults

BACKGROUND

Previous studies on the effects of acute air pollution have focused primarily on blood pressure (BP).

METHODS

Our study enrolled 9238 nonsmoking adults over 30 years of age from 6 townships in Taiwan: 1 seaport, 1 urban, 1 industrial, and 3 rural. Using generalized additive models, we evaluated the associations between brachial BP and short-term exposure to 5 air pollutants: particulate matter with diameter <10 μm (PM(10)), sulfur dioxide (SO(2)), nitrogen dioxide (NO(2)), carbon monoxide (CO), and ozone (O(3)).

RESULTS

After adjusting for individual and meteorologic factors, the systolic BP was decreased by all 5 pollutants, whereas the diastolic BP was increased by SO(2), NO(2), and O(3). The pulse pressure was consistently decreased by all 5 pollutants, with changes of -1.5 (95% confidence interval = -2.0 to -1.1), -0.6 (-0.9 to -0.4), -2.4 (-3.0 to -1.8), -1.2 (-1.6 to -0.9), and -1.4 (-1.8 to -0.9) mm Hg for interquartile range increases in 3-day lagged PM(10), SO(2), NO(2), carbon monoxide, and O(3), respectively. PM(10) exposure was more strongly associated with reduction of pulse pressure among men, persons >60 years of age, those with hypertension, and those living in the industrial township.

CONCLUSIONS

Short-term exposure to air pollution reduces pulse pressure. PM(10) in industrial emissions may contribute to pulse pressure changes. Age, sex, and hypertensive status may modify the effects of PM(10) on pulse pressure.

Diesel exhaust particles and airway inflammation

PURPOSE OF REVIEW

Epidemiologic investigation has associated traffic-related air pollution with adverse human health outcomes. The capacity of diesel exhaust particles (DEPs), a major emission source air pollution particle, to initiate an airway inflammation has subsequently been investigated. We review the recent controlled human exposures to diesel exhaust and DEPs, and summarize the investigations into the associations between this emission source air pollution particle and airway inflammation.

RECENT FINDINGS

Using bronchoalveolar lavage, bronchial biopsies, and sputum collection, studies have demonstrated inflammation in the airways of healthy individuals after exposure to diesel exhaust and DEPs. This inflammation has included neutrophils, eosinophils, mast cells, and lymphocytes. Elevated expression and concentrations of inflammatory mediators have similarly been observed in the respiratory tract after diesel exhaust and DEP exposure. An increased sensitivity of asthmatic individuals to the proinflammatory effects of DEPs has not been confirmed.

SUMMARY

Inflammation after diesel exhaust and DEP exposure is evident at higher concentrations only; there appears to be a threshold dose for DEPs approximating 300 μg/m. The lack of a biological response to DEPs at lower concentrations may reflect a contribution of gaseous constituents or interactions between DEPs and gaseous air pollutants to the human inflammatory response and function loss.

Physiological and inflammatory responses in an anthropomorphically relevant model of acute diesel exhaust particle exposure are sex and dose-dependent

CONTEXT

Diesel exhaust particles (DEP) are an important contributor to suspended particulate matter (PM) in urban areas. While epidemiological evidence exists for a sex-influenced dose-response relationship between acute PM exposure and respiratory health, similar data are lacking for DEP. Further, experimental evidence showing deleterious effects on respiratory health due to acute DEP exposure is sparse.

OBJECTIVE

To establish and characterize a mouse model of acute DEP exposure, comparing male and female mice and assessing the kinetics of the elemental carbon content of alveolar macrophages (AMs) to relate our model to human exposure.

MATERIALS AND METHODS

Adult BALB/c mice were intranasally inoculated with 0 (control), 10, 30 or 100 µg DEP in saline. Bronchoalveolar lavage cellular inflammation and cytokine levels were assessed 3, 6, 12, 24, 48 and 168 hours post exposure. Elemental carbon uptake by AMs was additionally assessed at 336 and 672 hours post DEP exposure. Thoracic gas volume and lung mechanics were measured 6 and 24 hours post exposure.

RESULTS

DEP resulted in dose-dependent cellular inflammation and cytokine production in both sexes. Males and females responded differently with females having more severe and prolonged neutrophilia, monocyte chemoattractant protein-1 and developing greater abnormalities in lung function. The sexual dimorphism in response was not related to the capacity of AMs to phagocytise DEP.

CONCLUSIONS

Our mouse model of acute diesel exhaust particle exposure shows a dose dependency and sexual dimorphism in response. Quantification of elemental carbon in AMs allows for comparison of the results of our study with human studies.

A randomised cross-over cohort study of exposure to emissions from a road tunnel ventilation stack

BACKGROUND AND OBJECTIVE

Road tunnels are increasingly important components of urban infrastructure. However, knowledge of their health impact on surrounding communities is limited. Our objective was to estimate the short-term respiratory health effects of exposure to emissions from a road tunnel ventilation stack.

METHODS

We conducted a randomised cross-over cohort study in 36 volunteers who underwent three exposure scenarios in 2006 before the road tunnel opened, and in 2007 (n=27) and 2008 (n=20) after the tunnel opened. Exposure downwind of the stack was compared to upwind of the stack and to a distant heavily trafficked location adjacent to a main road. Spirometry, exhaled nitric oxide (eNO) and symptom scores were measured repeatedly during each 2 h exposure session.

RESULTS

Downwind locations were associated with increased reports of 'dry nose' (score difference 0.36; 95% CI 0.09 to 0.63) compared with the control location (2006 vs 2007/2008), but not with impaired lung function, increased airway inflammation or other symptoms. The heavily trafficked location was associated with significantly increased eNO (ratio=1.09; 95% CI 1.04 to 1.14), eye (score difference 0.05; 95% CI 0.01 to 0.10) and chest (score difference 0.21; 95% CI 0.09 to 0.33) symptoms compared to the stack locations.

CONCLUSIONS

There was no consistent evidence of adverse respiratory effects from short-term exposures downwind of the tunnel ventilation stack, except for dry nose symptoms. However, the findings of increased airway inflammation and symptoms in subjects after only 2 h exposure at the heavily trafficked location, are suggestive of detrimental effects of short-term exposures to traffic-related air pollution.

Composition of air pollution particles and oxidative stress in cells, tissues, and living systems

Epidemiological studies demonstrated an association between increased levels of ambient air pollution particles and human morbidity and mortality. Production of oxidants, either directly by the air pollution particles or by the host response to the particles, appears to be fundamental in the biological effects seen after exposure to particulate matter (PM). However, the precise components and mechanisms responsible for oxidative stress following PM exposure are yet to be defined. Direct oxidant generation by air pollution particles is attributed to organic and metal components. Organic compounds generate an oxidative stress through redox cycling of quinone-based radicals, by complexing of metal resulting in electron transport, and by depletion of antioxidants by reactions between quinones and thiol-containing compounds. Metals directly support electron transport to generate oxidants and also diminish levels of antioxidants. In addition to direct generation of oxidants by organic and metal components, cellular responses contribute to oxidative stress after PM exposure. Reactive oxygen species (ROS) production occurs in the mitochondria, cell membranes, phagosomes, and the endoplasmic reticulum. Oxidative stress following PM exposure initiates a series of cellular reactions that includes activation of kinase cascades and transcription factors and release of inflammatory mediators, which ultimately lead to cell injury or apoptosis. Consequently, oxidative stress in cells and tissues is a central mechanism by which PM exposure leads to injury, disease, and mortality.

Sensitization and irritant-induced occupational asthma with latency are clinically indistinguishable

BACKGROUND

Acute irritant exposures at work are well-recognized causes of asthma. In the occupational setting, low-dose exposure to the same agent does not provoke asthma. Occupational asthma (OA) with latency due to irritants is not widely accepted.

AIMS

To compare workers with OA with latency likely to be due to irritant exposures with workers with the more usual sensitization-induced OA.

METHODS

Following identification of a worker who fulfils all the criteria for irritant-induced OA with latency whose investigation documented lime dust as a cause for his OA, we searched the Shield reporting scheme database between 1989 and 2010 for entries where the OA was more likely to be due to irritant than allergic mechanisms and compared these with the remainder where allergic mechanisms were likely. Outcome measures were latent interval from first exposure to first work-related symptom, non-specific bronchial reactivity, smoking, atopy and the presence of pre-existing asthma.

RESULTS

A previously fit lecturer teaching bricklaying had irritant-induced OA with latency without unusual exposures with an immediate asthmatic reaction following exposure to a sand/lime mixture (pH 8). The Shield database identified 127 workers with likely irritant-induced asthma with latency and 1646 with hypersensitivity-induced OA. The two groups were indistinguishable in terms of pre-existing asthma, atopy, age, latent interval, non-specific reactivity and smoking.

CONCLUSIONS

Irritant exposure is a cause of OA with latency currently clinically indistinguishable from OA due to sensitization.

In-traffic air pollution exposure and CC16, blood coagulation, and inflammation markers in healthy adults

BACKGROUND

Exposure to traffic-related air pollution is a risk factor for cardiovascular events, probably involving mechanisms of inflammation and coagulation. Little is known about effects of the short exposures encountered while participating in traffic.

OBJECTIVES

The objective of the study was to examine effects of exposure of commuters to air pollution on cardiovascular biomarkers.

METHODS

Thirty-four healthy adult volunteers commuted for 2 hr by bus, car, or bicycle during the morning rush hour. During the commute, exposure to particle number, particulate matter (PM) ≤ 2.5 µm in aerodynamic diameter (PM2.5), PM ≤ 10 µm in diameter (PM10), and soot was measured. We estimated inhaled doses based on heart rate monitoring. Shortly before exposure and 6 hr after exposure, blood samples were taken and analyzed for CC16 (Clara cell protein 16), blood cell count, coagulation markers, and inflammation markers. Between June 2007 and June 2008, 352 pre- and postexposure blood samples were collected on 47 test days. We used mixed models to analyze the associations between exposure and changes in health parameters.

RESULTS

We observed no consistent associations between the air pollution exposures and doses and the various biomarkers that we investigated.

CONCLUSIONS

Air pollution exposure during commuting was not consistently associated with acute changes in inflammation markers, blood cell counts, or blood coagulation markers.

Diesel exhaust causing low-dose irritant asthma with latency?

BACKGROUND

Diesel exhaust exposure may cause acute irritant-induced asthma and potentiate allergen-induced asthma. There are no previous reports of occupational asthma due to diesel exhaust.

AIMS

To describe occupational asthma with latency in workers exposed to diesel exhaust in bus garages.

METHODS

The Shield database of occupational asthma notifications in the West Midlands, UK, was searched between 1990 and 2006 for workers where diesel exhaust exposure was thought to be the cause of the occupational asthma. Those without other confounding exposures whose occupational asthma was validated by serial peak expiratory flow (PEF) analysis using Oasys software were included.

RESULTS

Fifteen workers were identified with occupational asthma attributed to diesel exhaust. Three had validated new-onset asthma with latency. All worked in bus garages where diesel exhaust exposure was the only likely cause of their occupational asthma. Occupational asthma was confirmed by measures of non-specific reactivity and serial measurements of PEF with Oasys scores of 2.9, 3.73 and 4 (positive score > 2.5).

CONCLUSIONS

The known non-specific irritant effects of diesel exhaust suggest that this is an example of low-dose irritant-induced asthma and that exposures to diesel exhaust in at least some bus garages are at a sufficient level to cause this.

Respiratory effects of commuters' exposure to air pollution in traffic

BACKGROUND

Much time is spent in traffic, especially during rush hours, when air pollution concentrations on roads are relatively high. Controlled exposure studies have shown acute respiratory effects of short, high exposures to air pollution from motor vehicles. Acute health effects of lower real-life exposures in traffic are unclear.

METHODS

Exposures of 34 healthy, nonsmoking adult volunteers were repeatedly measured while commuting for 2 hours by bus, car, or bicycle. Particle number (PN), particulate matter (PM2.5 and PM10), and soot exposures were measured. Lung function and airway resistance were measured directly before, directly following, and 6 hours after exposure. Exhaled nitric oxide (NO) was measured directly before and 6 hours after exposure. Inhaled doses were estimated based on monitored heart rates. Mixed models were used to analyze effects of exposure on changes in health parameters after exposure compared with before.

RESULTS

PN, PM10, and soot were associated with decreased peak expiratory flow directly following but not 6 hours after exposure. PN doses were associated with decreases in maximum midexpiratory flow and forced expiratory flow (FEV1) 6 hours after exposure, whereas PN and soot exposures were associated with increased maximum midexpiratory flow and FEV1 directly after exposure. PN and soot were associated with increased exhaled NO after car and bus but not bicycle trips. PN was also associated with an increase in airway resistance directly following exposure but not 6 hours later.

CONCLUSIONS

We found modest effects of 2-hour in-traffic exposure to air pollutants on peak flow, exhaled NO, and airway resistance.

Long-term exposure to traffic-related air pollution and the risk of coronary heart disease hospitalization and mortality

BACKGROUND

Epidemiologic studies have demonstrated that exposure to road traffic is associated with adverse cardiovascular outcomes.

OBJECTIVES

We aimed to identify specific traffic-related air pollutants that are associated with the risk of coronary heart disease (CHD) morbidity and mortality to support evidence-based environmental policy making.

METHODS

This population-based cohort study included a 5-year exposure period and a 4-year follow-up period. All residents 45-85 years of age who resided in Metropolitan Vancouver during the exposure period and without known CHD at baseline were included in this study (n=452,735). Individual exposures to traffic-related air pollutants including black carbon, fine particles [aerodynamic diameter ≤ 2.5 µm (PM(2.5))], nitrogen dioxide (NO(2)), and nitric oxide were estimated at residences of the subjects using land-use regression models and integrating changes in residences during the exposure period. CHD hospitalizations and deaths during the follow-up period were identified from provincial hospitalization and death registration records.

RESULTS

An interquartile range elevation in the average concentration of black carbon (0.94 × 10(-5)/m filter absorbance, equivalent to approximately 0.8 µg/m(3) elemental carbon) was associated with a 3% increase in CHD hospitalization (95% confidence interval, 1-5%) and a 6% increase in CHD mortality (3-9%) after adjusting for age, sex, preexisting comorbidity, neighborhood socioeconomic status, and copollutants (PM(2.5) and NO(2)). There were clear linear exposure-response relationships between black carbon and coronary events.

CONCLUSIONS

Long-term exposure to traffic-related fine particulate air pollution, indicated by black carbon, may partly explain the observed associations between exposure to road traffic and adverse cardiovascular outcomes.

Subchronic effects of nasally instilled diesel exhaust particulates on the nasal and airway epithelia in mice

Diesel exhaust is the major source of ultrafine particles released during traffic-related pollution. Subjects with chronic respiratory diseases are at greater risk for exacerbations during exposure to air pollution. This study evaluated the effects of subchronic exposure to a low-dose of diesel exhaust particles (DEP). Sixty male BALB/c mice were divided into two groups: (a) Saline: nasal instillation of saline (n = 30); and (b) DEP: nasal instillation of 30 microg of DEP/10 microl of saline (n = 30). Nasal instillations were performed 5 days a week, over 30 and 60 days. Animals were anesthetized with pentobarbital sodium (50 mg/kg intraperitoneal [i.p.]) and sacrificed by exsanguination. Bronchoalveolar lavage (BAL) fluid was performed to evaluate the inflammatory cell count and the concentrations of the interleukin (IL)-4, IL-10, and IL-13 by enzyme-linked immunosorbent assay (ELISA). The gene expression of oligomeric mucus/gel-forming (Muc5ac) was evaluated by real-time polymerase chain reaction (PCR). Histological analysis in the nasal septum and bronchioles was used to evaluate the bronchial and nasal epithelium thickness as well as the acidic and neutral nasal mucus content. The saline group (30 and 60 days) did not show any changes in any of the parameters. However, the instillation of DEP over 60 days increased the expression of Muc5ac in the lungs and the acid mucus content in the nose compared with the 30-day treatment, and it increased the total leukocytes in the BAL and the nasal epithelium thickness compared with saline for 60 days. Cytokines concentrations in the BAL were detectable, with no differences among the groups. Our data suggest that a low-dose of DEP over 60 days induces respiratory tract inflammation.

Role of oxidative stress on diesel-enhanced influenza infection in mice

Numerous studies have shown that air pollutants, including diesel exhaust (DE), reduce host defenses, resulting in decreased resistance to respiratory infections. This study sought to determine if DE exposure could affect the severity of an ongoing influenza infection in mice, and examine if this could be modulated with antioxidants. BALB/c mice were treated by oropharyngeal aspiration with 50 plaque forming units of influenza A/HongKong/8/68 and immediately exposed to air or 0.5 mg/m³ DE (4 hrs/day, 14 days). Mice were necropsied on days 1, 4, 8 and 14 post-infection and lungs were assessed for virus titers, lung inflammation, immune cytokine expression and pulmonary responsiveness (PR) to inhaled methacholine. Exposure to DE during the course of infection caused an increase in viral titers at days 4 and 8 post-infection, which was associated with increased neutrophils and protein in the BAL, and an early increase in PR. Increased virus load was not caused by decreased interferon levels, since IFN-β levels were enhanced in these mice. Expression and production of IL-4 was significantly increased on day 1 and 4 p.i. while expression of the Th1 cytokines, IFN-γ and IL-12p40 was decreased. Treatment with the antioxidant N-acetylcysteine did not affect diesel-enhanced virus titers but blocked the DE-induced changes in cytokine profiles and lung inflammation. We conclude that exposure to DE during an influenza infection polarizes the local immune responses to an IL-4 dominated profile in association with increased viral disease, and some aspects of this effect can be reversed with antioxidants.

Subclinical responses in healthy cyclists briefly exposed to traffic-related air pollution: an intervention study

BACKGROUND

Numerous epidemiological studies have demonstrated adverse health effects of a sedentary life style, on the one hand, and of acute and chronic exposure to traffic-related air pollution, on the other. Because physical exercise augments the amount of inhaled pollutants, it is not clear whether cycling to work in a polluted urban environment should be encouraged or not. To address this conundrum we investigated if a bicycle journey along a busy commuting road would induce changes in biomarkers of pulmonary and systematic inflammation in a group of healthy subjects.

METHODS

38 volunteers (mean age: 43 ± 8.6 years, 26% women) cycled for about 20 minutes in real traffic near a major bypass road (road test; mean UFP exposure: 28,867 particles per cm3) in Antwerp and in a laboratory with filtered air (clean room; mean UFP exposure: 496 particles per cm3). The exercise intensity (heart rate) and duration of cycling were similar for each volunteer in both experiments. Exhaled nitric oxide (NO), plasma interleukin-6 (IL-6), platelet function, Clara cell protein in serum and blood cell counts were measured before and 30 minutes after exercise.

RESULTS

Percentage of blood neutrophils increased significantly more (p = 0.004) after exercise in the road test (3.9%; 95% CI: 1.5 to 6.2%; p = 0.003) than after exercise in the clean room (0.2%; 95% CI: -1.8 to 2.2%, p = 0.83). The pre/post-cycling changes in exhaled NO, plasma IL-6, platelet function, serum levels of Clara cell protein and number of total blood leukocytes did not differ significantly between the two scenarios.

CONCLUSIONS

Traffic-related exposure to particles during exercise caused a small increase in the distribution of inflammatory blood cells in healthy subjects. The health significance of this isolated change is unclear.

Phytoceuticals: the new 'physic garden' for asthma and chronic obstructive pulmonary disease

Phytoceuticals (non-nutritional but beneficial plant chemicals) merit investigation as pharmacotherapy for asthma and chronic obstructive pulmonary disease (COPD). Although asthma is mostly treated adequately, COPD is not. Thus, there is a need for new drugs with improved therapeutic benefit, especially in COPD. Recent interest in herbal remedies has redirected attention towards plants as sources of improved treatments for lung disease. Phytoceuticals from a variety of plants and plant products, including butterbur, English ivy, apples, chocolate, green tea and red wine, demonstrate broad-spectrum pharmacotherapeutic activities that could be exploited in the clinic. Well-designed clinical trials are required to determine whether these beneficial activities are reproduced in patients, with the prospect that phytoceuticals are the new physic garden for asthma and COPD.

Effect of diesel exhaust inhalation on antioxidant and oxidative stress responses in adults with metabolic syndrome

BACKGROUND

Traffic-related air pollution is associated with cardiovascular morbidity and mortality. Although the biological mechanisms are not well understood, oxidative stress may be a primary pathway. Subpopulations, such as individuals with metabolic syndrome (MeS), may be at increased risk of adverse effects associated with air pollution. Our aim was to assess the relationship between exposure to diesel exhaust (DE) and indicators of systemic antioxidant and oxidative responses in adults with MeS. We hypothesized that DE exposure would result in greater oxidative stress and antioxidant responses compared with filtered air (FA).

METHODS

Ten adult subjects with MeS were exposed on separate days for two hours to FA or DE (at 200microg/m3), in a double blind, crossover experiment. Urinary 8-isoPGF2alpha (F2-isoprostanes), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were assessed as markers of oxidative stress at 3 hrs and 22 hrs, respectively, after exposure initiation. To assess the short-term antioxidant response we analyzed plasma ascorbic acid (AA) 90 minutes after exposure initiation. All outcomes were compared to pre-exposure levels, and mean changes were compared between FA and DE exposures.

RESULTS

Mean changes in urinary F2-isoprostanes (ng/mg creatinine), (-0.05 [95% CI = -0.29, 0.15]), and 8-OHdG (microg/g creatinine) (-0.09 [-0.13, 0.31]), were not statistically significant. Mean changes in plasma AA (mg/dl) were also not significant (-0.02 [-0.78, 0.04]).

CONCLUSIONS

In this carefully controlled experiment, we did not detect significant changes in oxidative stress or systemic antioxidant responses in subjects with MeS exposed to 200microg/m3 DE.

Particulate matter air pollution and cardiovascular disease: An update to the scientific statement from the American Heart Association

In 2004, the first American Heart Association scientific statement on "Air Pollution and Cardiovascular Disease" concluded that exposure to particulate matter (PM) air pollution contributes to cardiovascular morbidity and mortality. In the interim, numerous studies have expanded our understanding of this association and further elucidated the physiological and molecular mechanisms involved. The main objective of this updated American Heart Association scientific statement is to provide a comprehensive review of the new evidence linking PM exposure with cardiovascular disease, with a specific focus on highlighting the clinical implications for researchers and healthcare providers. The writing group also sought to provide expert consensus opinions on many aspects of the current state of science and updated suggestions for areas of future research. On the basis of the findings of this review, several new conclusions were reached, including the following: Exposure to PM <2.5 microm in diameter (PM(2.5)) over a few hours to weeks can trigger cardiovascular disease-related mortality and nonfatal events; longer-term exposure (eg, a few years) increases the risk for cardiovascular mortality to an even greater extent than exposures over a few days and reduces life expectancy within more highly exposed segments of the population by several months to a few years; reductions in PM levels are associated with decreases in cardiovascular mortality within a time frame as short as a few years; and many credible pathological mechanisms have been elucidated that lend biological plausibility to these findings. It is the opinion of the writing group that the overall evidence is consistent with a causal relationship between PM(2.5) exposure and cardiovascular morbidity and mortality. This body of evidence has grown and been strengthened substantially since the first American Heart Association scientific statement was published. Finally, PM(2.5) exposure is deemed a modifiable factor that contributes to cardiovascular morbidity and mortality.

Exposure to nitrogen dioxide is not associated with vascular dysfunction in man

BACKGROUND

Exposure to air pollution is associated with increased cardiorespiratory morbidity and mortality. It is unclear whether these effects are mediated through combustion-derived particulate matter or gaseous components, such as nitrogen dioxide.

OBJECTIVES

To investigate the effect of nitrogen dioxide exposure on vascular vasomotor and six fibrinolytic functions.

METHODS

Ten healthy male volunteers were exposed to nitrogen dioxide at 4 ppm or filtered air for 1 h during intermittent exercise in a randomized double-blind crossover study. Bilateral forearm blood flow and fibrinolytic markers were measured before and during unilateral intrabrachial infusion of bradykinin (100-1000 pmol/min), acetylcholine (5-20 microg/min), sodium nitroprusside (2-8 microg/min), and verapamil (10-100 microg/min) 4 h after the exposure. Lung function was determined before and after the exposure, and exhaled nitric oxide at baseline and 1 and 4 h after the exposure.

RESULTS

There were no differences in resting forearm blood flow after either exposure. There was a dose-dependent increase in forearm blood flow with all vasodilators but this was similar after either exposure for all vasodilators (p > .05 for all). Bradykinin caused a dose-dependent increase in plasma tissue-plasminogen activator, but again there was no difference between the exposures. There were no changes in lung function or exhaled nitric oxide following either exposure.

CONCLUSION

Inhalation of nitrogen dioxide does not impair vascular vasomotor or fibrinolytic function. Nitrogen dioxide does not appear to be a major arbiter of the adverse cardiovascular effects of air pollution.

Acute changes in sputum collected from exposed human subjects in mining conditions

Neprilysin (NEP) is a key cell surface peptidase in the maintenance of airway homeostasis and the development of pulmonary disorders. However, little information is available about the effect of particulate matter (PM) on airway NEP. In this controlled human exposure study, changes in induced sputum were measured in 11 subjects at baseline, overshot (OS) mucking, and diesel exhaust (DE) exposure days. Neither OS condition nor DE exposure was found to induce significant changes in total protein, but DE induced significant increases in cell numbers of macrophages and epithelium. Moreover, significant increases in soluble NEP were observed following OS mining dust particulates (0.43 +/- 0.06 nmol/microg protein/min; p = .023) and DE exposure (0.40 +/- 0.03 nmol/microg protein/min; p = .035) when compared with the baseline control (0.30 +/- 0.04 nmol/microg protein/min), with 42% and 31% average net increase, respectively. Pearson's correlation analyses indicated that sputum NEP activity was significantly associated with personal exposure product (elemental carbon concentration [mg/m(3)] x time [min]; C x T). The data suggest that changes in NEP activity may be an early, accurate endpoint for airway epithelial injury and provide a new insight into the mechanism of airway effects following particulate exposure.

Polycyclic aromatic hydrocarbons from diesel emissions exert proallergic effects in birch pollen allergic individuals through enhanced mediator release from basophils

BACKGROUND

Diesel exhaust particles (DEPs) act as adjuvants in the immune system and contribute to the increased prevalence and morbidity of asthma and allergic rhinitis. Polycyclic aromatic hydrocarbons (PAHs) are major components of DEPs, which may be involved in the induction and enhancement of proallergic processes. In this study we explored adjuvant effects of DEP-PAHs on activation parameters of human basophils, fostering allergic inflammation through the release of preformed or granule-derived mediators.

METHODS

Heparinized blood samples from birch pollen allergic and control donors were stimulated with Bet v 1, the major allergen of birch pollen grains, alone or together with a mixture of 16 environmental prominent PAHs (EPA-PAH standard). Flow cytometric analysis was performed for quantitative determination of PAH-enhanced basophil activation. To assess direct PAH effects on basophils, enriched cultures from both donor groups were exposed to benzo[a]pyrene (B[a]P) or phenanthrene (Phe), two major DEP-PAHs, with and without allergen. Supernatants were assayed for IL-4 and IL-8 secretion and histamine release by means of ELISA.

RESULTS

At environmental relevant exposure levels EPA-PAH standard synergized with antigen and significantly enhanced basophil activation of all birch pollen allergic individuals up to 95%. Single PAHs significantly drove IL-8 secretion from sensitized basophils of all patients tested, and there was no further enhancement by addition of rBet v 1. B[a]P and Phe also significantly induced IL-4 secretion, a key factor for Th2 development, from purified sensitized basophils in the absence of antigen suggesting an adjuvant role of DEP-PAHs in allergic sensitization. None of the basophil samples from healthy controls showed any PAH effect on mediator release.

CONCLUSION

DEP-PAHs exert proallergic effects on sensitized basophils in an allergen independent fashion, suggesting a potential role of these pollutants for the allergic breakthrough in atopic individuals, who have not developed an allergic disease yet.

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.

Particles from wood smoke and road traffic differently affect the innate immune system of the lung

The effect of particles from road traffic and wood smoke on the innate immune response in the lung was studied in a lung challenge model with the intracellular bacterium Listeria monocytogenes. Female Balb/cA mice were instilled intratracheally with wood smoke particles, particles from road traffic collected during winter (studded tires used; St+), and during autumn (no studded tires; St-), or diesel exhaust particles (DEP). Simultaneously with, and 1 or 7 days after particle instillation, 10(5) bacteria were inoculated intratracheally. Bacterial numbers in the lungs and spleen 1 day after Listeria challenge were determined, as an indicator of cellular activation. In separate experiments, bronchoalveolar lavage (BAL) fluid was collected 4 h and 24 h after particle instillation. All particles tested reduced the numbers of bacteria in the lung 24 h after bacterial inoculation. When particles were given simultaneously with Listeria, the reduction was greatest for DEP, followed by St+ and St-, and least for wood smoke particles. Particle effects were no longer apparent after 7 days. Neutrophil numbers in BAL fluid were increased for all particle exposed groups. St+ and St- induced the highest levels of IL-1beta, MIP-2, MCP-1, and TNF-alpha, followed by DEP, which induced no TNF-alpha. In contrast, wood smoke particles only increased lactate dehydrogenase (LDH) activity, indicating a cytotoxic effect of these particles. In conclusion, all particles tested activated the innate immune system as determined with Listeria. However, differences in kinetics of anti-Listeria activity and levels of proinflammatory mediators point to cellular activation by different mechanisms.

Nano titanium dioxide particles promote allergic sensitization and lung inflammation in mice

The purpose of this study was to investigate whether photocatalytic TiO₂ nanoparticles have adjuvant effect, when administered in combination with ovalbumin (OVA) in mice. Mice were immunized via intraperitoneal injections of OVA, OVA + TiO₂ or OVA + Al(OH)₃ and challenged with aerosols of OVA. At the end of the study, serum was analysed for content of OVA-specific IgE, IgG1 and IgG2a antibodies, and the bronchoalveolar lavage fluid (BALF) was analysed for content of inflammatory cells and levels of interleukin (IL)-4, IL-5, IL-10 and interferon-γ. The TiO₂ particles promoted a Th2 dominant immune response with high levels of OVA-specific IgE and IgG1 in serum and influx of eosinophils, neutrophils and lymphocytes in BALF. The TiO₂ particles induced a significantly higher level of OVA-specific IgE than the standard adjuvant Al(OH)₃. However, the two substances were comparable regarding the level of eosinophilic inflammation and interleukins present in BALF.

Decreased PM10 exposure attenuates age-related lung function decline: genetic variants in p53, p21, and CCND1 modify this effect

BACKGROUND

Decreasing exposure to airborne particulates was previously associated with reduced age-related decline in lung function. However, whether the benefit from improved air quality depends on genetic background is not known. Recent evidence points to the involvement of the genes p53 and p21 and of the cell cycle control gene cyclin D1 (CCND1) in the response of bronchial cells to air pollution.

OBJECTIVE

We determined in 4,326 participants of the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA) whether four single-nucleotide polymorphisms in three genes [CCND1 (rs9344 [P242P], rs667515), p53 (rs1042522 [R72P]), and p21 (rs1801270 [S31R])] modified the previously observed attenuation of the decline in the forced expiratory flow between 25% and 75% of the forced vital capacity (FEF(25-75)) associated with improved air quality.

METHODS

Subjects of the prospective population-based SAPALDIA cohort were assessed in 1991 and 2002 by spirometry, questionnaires, and biological sample collection for genotyping. We assigned spatially resolved concentrations of particulate matter with aerodynamic diameter < or = 10 microm (PM(10)) to each participant's residential history 12 months before the baseline and follow-up assessments.

RESULTS

The effect of diminishing PM(10) exposure on FEF(25-75) decline appeared to be modified by p53 R72P, CCND1 P242P, and CCND1 rs667515. For example, a 10-microg/m(3) decline in average PM(10) exposure over an 11-year period attenuated the average annual decline in FEF(25-75) by 21.33 mL/year (95% confidence interval, 10.57-32.08) among participants homozygous for the CCND1 (P242P) GG genotype, by 13.72 mL/year (5.38-22.06) among GA genotypes, and by 6.00 mL/year (-4.54 to 16.54) among AA genotypes.

CONCLUSIONS

Our results suggest that cell cycle control genes may modify the degree to which improved air quality may benefit respiratory function in adults.

Spatial analysis of air pollution and childhood asthma in Hamilton, Canada: comparing exposure methods in sensitive subgroups

BACKGROUND

Variations in air pollution exposure within a community may be associated with asthma prevalence. However, studies conducted to date have produced inconsistent results, possibly due to errors in measurement of the exposures.

METHODS

A standardized asthma survey was administered to children in grades one and eight in Hamilton, Canada, in 1994-95 (N approximately 1467). Exposure to air pollution was estimated in four ways: (1) distance from roadways; (2) interpolated surfaces for ozone, sulfur dioxide, particulate matter and nitrous oxides from seven to nine governmental monitoring stations; (3) a kriged nitrogen dioxide (NO2) surface based on a network of 100 passive NO2 monitors; and (4) a land use regression (LUR) model derived from the same monitoring network. Logistic regressions were used to test associations between asthma and air pollution, controlling for variables including neighbourhood income, dwelling value, state of housing, a deprivation index and smoking.

RESULTS

There were no significant associations between any of the exposure estimates and asthma in the whole population, but large effects were detected the subgroup of children without hayfever (predominately in girls). The most robust effects were observed for the association of asthma without hayfever and NO2LUR OR = 1.86 (95%CI, 1.59-2.16) in all girls and OR = 2.98 (95%CI, 0.98-9.06) for older girls, over an interquartile range increase and controlling for confounders.

CONCLUSION

Our findings indicate that traffic-related pollutants, such as NO2, are associated with asthma without overt evidence of other atopic disorders among female children living in a medium-sized Canadian city. The effects were sensitive to the method of exposure estimation. More refined exposure models produced the most robust associations.