Acute inflammatory responses in the airways and peripheral blood after short-term exposure to diesel exhaust in healthy human volunteers

Diesel exhaust particles in lung acutely enhance experimental peripheral thrombosis

BACKGROUND

Pollution by particulates has consistently been associated with increased cardiovascular morbidity and mortality, but a plausible biological basis for this association is lacking.

METHODS AND RESULTS

Diesel exhaust particles (DEPs) were instilled into the trachea of hamsters, and blood platelet activation, experimental thrombosis, and lung inflammation were studied. Doses of 5 to 500 micro g of DEPs per animal induced neutrophil influx into the bronchoalveolar lavage fluid with elevation of protein and histamine but without lactate dehydrogenase release. The same doses enhanced experimental arterial and venous platelet rich-thrombus formation in vivo. Blood samples taken from hamsters 30 and 60 minutes after instillation of 50 micro g of DEPs yielded accelerated aperture closure (ie, platelet activation) ex vivo, when analyzed in the Platelet Function Analyser (PFA-100). The direct addition of as little as 0.5 micro g/mL DEPs to untreated hamster blood significantly shortened closure time in vitro.

CONCLUSIONS

The intratracheal instillation of DEPs leads to lung inflammation as well as a rapid activation of circulating blood platelets. The kinetics of platelet activation are consistent with the reported clinical occurrence of thrombotic complications after exposure to pollutants. Our findings, therefore, provide a plausible explanation for the increase in cardiovascular morbidity and mortality accompanying urban air pollution.

Diesel fumes and the rising prevalence of atopy: an urban legend?

Recently, the incidence of allergic diseases has increased in most industrialized countries of the world. Persistent exposure to particulate air pollution from motor vehicles has been implicated as one of the factors that is responsible for the observed increased prevalence of atopy. Epidemiologic studies conducted in different parts of the world have demonstrated an important association between ambient levels of motor vehicle traffic emissions and increased symptoms of asthma and rhinitis. Additionally, recent human and animal laboratory-based studies have shown that particulate toxic pollutants, and in particular diesel exhaust particles (DEP), can enhance allergic inflammation and induce the development of allergic immune responses. In this article, our current understanding of the mechanisms by which pollutants such as DEPs enhance the underlying allergic inflammatory response is reviewed, and the evidence that supports the causative link between particulate air pollution from motor vehicles and increasing allergic diseases is discussed.

Personal PM2.5 exposure and markers of oxidative stress in blood

Ambient particulate air pollution assessed as outdoor concentrations of particulate matter less than or equal to 2.5 micro m in diameter (PM(2.5)) in urban background has been associated with cardiovascular diseases at the population level. However, the significance of individual exposure and the involved mechanisms remain uncertain. We measured personal PM(2.5) and carbon black exposure in 50 students four times in 1 year and analyzed blood samples for markers of protein and lipid oxidation, for red blood cell (RBC) and platelet counts, and for concentrations of hemoglobin and fibrinogen. We analyzed protein oxidation in terms of gamma-glutamyl semialdehyde in hemoglobin (HBGGS) and 2-aminoadipic semialdehyde in hemoglobin (HBAAS) and plasma proteins (PLAAS), and lipid peroxidation was measured as malondialdehyde (MDA) in plasma. Median exposures were 16.1 micro g/m(3) for personal PM(2.5) exposure, 9.2 micro g/m(3) for background PM(2.5) concentration, and 8.1 X 10(-6)/m for personal carbon black exposure. Personal carbon black exposure and PLAAS concentration were positively associated (p < 0.01), whereas an association between personal PM(2.5) exposure and PLAAS was only of borderline significance (p = 0.061). A 3.7% increase in MDA concentrations per 10 micro g/m(3) increase in personal PM(2.5) exposure was found for women (p < 0.05), whereas there was no significant relationship for the men. Similarly, positive associations between personal PM(2.5)exposure and both RBC and hemoglobin concentrations were found only in women (p < 0.01). There were no significant relationships between background PM(2.5) concentration and any of the biomarkers. This suggests that exposure to particles in moderate concentrations can induce oxidative stress and increase RBCs in peripheral blood. Personal exposure appears more closely related to these biomarkers potentially related to cardiovascular disease than is ambient PM(2.5) background concentrations.

Prolonged airway and systemic inflammatory reactions after smoke inhalation

STUDY OBJECTIVES

Smoke inhalation has a prolonged, negative effect on pulmonary function. The immediate change in the airway after smoke inhalation is an intense inflammatory reaction. Obstructive airway disease commonly occurs several years after smoke inhalation, but few studies have focused on long-term reactions in the airway. This study investigated the long-term effects of smoke inhalation, by examining airway responsiveness, airway inflammation, and systemic effects.

DESIGN

Cross-sectional study.

PATIENTS

We assessed victims (n = 9) of smoke inhalation 6 months after they were exposed.

INTERVENTIONS

We studied the clinical symptoms, laboratory data, and pulmonary functions of the patients. We also performed the nonspecific bronchial challenge test with methacholine on these patients. In some patients, we reviewed pathologic specimens of bronchi and measured cytokines (tumor necrosis factor [TNF]-alpha, interferon [INF]-gamma, and interleukin [IL]-2) in serum and BAL fluid.

RESULTS

All the subjects complained of a productive cough, and three subjects had a mild degree of dyspnea on exertion. All but one subject had airway hyperresponsiveness to methacholine. The pulmonary function test results, however, were within normal limits, except for one subject who had a mild obstructive pattern of pulmonary function. Bronchial mucosal biopsy (n = 2) showed inflammatory changes with lymphocyte infiltration. Significantly greater concentrations of TNF-alpha (mean, 1,346.4 pg/mL vs 61.2 pg/mL; p < 0.05) and IFN-gamma (mean, 540.9 pg/mL vs 26.7 pg/mL; p < 0.05) were seen in the serum (n = 4) compared with control subjects. The serum IL-2 level was also increased (mean, 136.8 pg/mL vs undetectable); however, the increase was not significant compared with the control subjects.

CONCLUSIONS

These data suggest that inflammatory reactions in the airways and peripheral blood continue for at least 6 months after smoke inhalation.

Air pollution: the "Heart" of the problem

Air pollution exposure is associated with an increased risk of acute and chronic cardiovascular mortality. Recent observations have implicated fine particulate matter (PM(2.5)) as one of the most important pollutants. Inhalation of PM(2.5) causes acute pulmonary inflammation and oxidative stress. The subsequent generation of a systemic inflammatory response could link air pollution exposure with the development of cardiovascular disease. Human experiments have demonstrated pro-arrhythmic alterations in cardiac autonomic tone, increased blood pressure, higher serum C-reactive protein levels, and alterations in blood rheology favoring coagulation following controlled pollution exposures or in relation to elevated ambient PM(2.5) levels. Recent studies have also uncovered several harmful impacts on the systemic vasculature, including the triggering of acute vasoconstriction and the enhanced development of atherosclerosis. Many questions, however, remain unanswered and future studies will be required to clarify the relevant biologic mechanisms and to identify the specific constituents responsible for mediating the adverse health impacts.

Size effect of intratracheally instilled particles on pulmonary inflammation and vascular thrombosis

Particulate air pollution is associated with cardiorespiratory effects and ultrafine particles (UFPs, diameter < 100 nm) are believed to play an important role. We studied the acute (1 h) effect of intratracheally instilled unmodified (60 nm), negatively charged carboxylate-modified (60 nm), or positively charged amine-modified (60 or 400 nm) polystyrene particles on bronchoalveolar lavage (BAL) indices and on peripheral thrombosis in hamster. The latter was assessed by measuring the extent of photochemically induced thrombosis in a femoral vein via transillumination. Unmodified and negative UFPs did not modify thrombosis and BAL indices. Positive UFPs increased thrombosis at 500 microg per animal (+ 341 +/- 96%) and at 50 microg per animal (+ 533 +/- 122%), but not at 5 microg per animal. Neutrophils, lactate dehydrogenase, and histamine were increased in BAL at all these doses but protein concentration was increased only at 500 microg per animal. Positive 400-nm particles (500 microg per animal) did not affect thrombosis, although they led to a neutrophil influx and an increase in BAL proteins and histamine. Using the Platelet Function Analyser (PFA-100), the platelets of hamsters were activated by the in vitro addition of positive UFPs and 400-nm particles to blood. We conclude that intratracheally administered positive ultrafine and 400-nm particles induce pulmonary inflammation within 1 h. Positive UFPs, but not the 400-nm particles enhance thrombosis. Hence, particle-induced lung inflammation and thrombogenesis can be partially uncoupled.

Ultrafine carbon black particles inhibit human lung fibroblast-mediated collagen gel contraction

Both acute and chronic exposure to particulates have been associated with increased mortality and morbidity from a number of causes, including chronic obstructive pulmonary disease and other chronic lung diseases. The current study evaluated the hypothesis that ultrafine carbon particles, a component of ambient particulates, could affect tissue repair. To assess this, the three-dimensional collagen gel contraction model was used. Ultrafine carbon black particles, but not fine carbon black, inhibited fibroblast-mediated collagen gel contraction. Although previous research has indicated that inflammatory effects of ultrafine carbon black particles are mediated by oxidant mechanisms, the current study suggests that ultrafine carbon black's inhibition of fibroblast gel contraction is mediated by the binding of both fibronectin and transforming growth factor (TGF)-beta to the ultrafine particles. Binding of TGF-beta was associated with a reduction in nuclear localization of Smads, indicative of inhibition of TGF-beta signal transduction. There was also a decrease in fibronectin mRNA, consistent with a decrease in TGF-beta-mediated response. Taken together, these results demonstrate the ability of ultrafine particles to contribute to altered tissue repair and extend the known mechanisms by which these biologically active particles exert their effects.

Update on the health effects of outdoor air pollution

The number of studies conducted on the health effects of air pollution has increased exponentially. Important methodological advances include the application of novel observational study designs, in particular the multi-city design, and the development and application of airborne particle concentrators for use in experimental human exposure studies and toxicological studies. Experimental data are validating and providing insight into some surprising observational findings.

[Particulate air pollution and health in Valencia [Spain] 1994-1996]

OBJECTIVE

To estimate the short-term association between levels of air pollution due to suspended particulates and several indicators of morbidity and mortality in the city of Valencia, Spain.

METHODS

We performed an ecological time-series study. Daily levels of air pollution from black smoke were related to indicators of mortality, hospital admissions, and visits to emergency departments in the city of Valencia between 1994 and 1996. The magnitude of the association was estimated through Poisson autoregression using generalized additive models. The form of the relationship, the delayed effect of pollution, and the possible modification of this effect by other pollutants or periods of the year were assessed.

RESULTS

A significant association was found between levels of suspended particulates and several of the indicators analyzed in Valencia. The form of this relationship was linear. An increment of 10 microg/m3 in the daily levels of black smoke was associated with an increase of 1.8% (95% confidence interval: 0.9-2.7%) in the number of deaths on the following day. The same increment in pollutant levels was associated with an increase of 1.5% (0.1-2.8%) in deaths from all cardiovascular causes, an increase of 1.3% (0.0-2.6%) in admissions for all cardiovascular diseases and in an increase of 5.4% (0.6-10.4%) in the number of emergency visits for asthma. This association was not confounded by levels of other pollutants. Black smoke was not associated with mortality from respiratory diseases, with hospital admissions for cerebrovascular diseases, or with emergency visits for chronic obstructive pulmonary disease.

CONCLUSIONS

This study provides evidence that levels of suspended particles in Valencia are associated with emergency visits for asthma, hospital admissions for cardiovascular diseases, and daily deaths. The association found is consistent with the results of previous studies and fits with recent knowledge of psychopathological mechanisms.

Temporal association between pulmonary and systemic effects of particulate matter in healthy and cardiovascular compromised rats

Exposure to particulate matter (PM) has been associated with increased morbidity and mortality among individuals with cardiovascular disease. It is hypothesized that systemic alterations occur concurrent to pulmonary injury/inflammation, and contribute to cardiac events in compromised hosts. We explored this hypothesis using a rat model for human hypertension and cardiovascular disease (spontaneously hypertensive, SH), and normotensive Wistar Kyoto (WKY) rats. SH and WKY rats (12-13 wk old) were exposed either intratracheally (IT; 0.0, 1.0, or 5.0 mg/kg in saline) or nose-only (15 mg/m(3) x 6 h/d x 3 d/wk x 1, 2 or 4 wk) to combustion source residual oil fly ash (ROFA) with low metal content, and examined 1, 2 or 4 d later. Bronchoalveolar lavage fluid (BALF) albumin and neutrophils increased (SH approximately equal WKY) at d 1 following ROFA IT. With inhalation exposure, both strains experienced progressive histological lung damage and increases in BALF albumin and neutrophils during 1 to 4 wk (SH > WKY). Acute lung injury from ROFA IT was temporally associated with increases in plasma fibrinogen in both strains, but only the SH rats responded to the acute 1-wk ROFA inhalation. Longer term (2 or 4 wk) ROFA caused progressive lung injury (SH > WKY), but did not sustain the increase in fibrinogen. BALF glutathione increased in a temporal fashion similar to fibrinogen; however, only WKY rats demonstrated this response. There was a small but consistent decrease in blood lymphocytes and an increase in blood neutrophils in SH rats exposed to ROFA acutely. In conclusion, acute PM exposure can provoke an acute systemic thrombogenic response associated with pulmonary injury/inflammation and oxidative stress in cardiovascular compromised rats. This evidence is consistent with greater cardiovascular events during acute PM episodes in compromised humans.

Air pollution and health

The health effects of air pollution have been subject to intense study in recent years. Exposure to pollutants such as airborne particulate matter and ozone has been associated with increases in mortality and hospital admissions due to respiratory and cardiovascular disease. These effects have been found in short-term studies, which relate day-to-day variations in air pollution and health, and long-term studies, which have followed cohorts of exposed individuals over time. Effects have been seen at very low levels of exposure, and it is unclear whether a threshold concentration exists for particulate matter and ozone below which no effects on health are likely. In this review, we discuss the evidence for adverse effects on health of selected air pollutants.

Ultrafine particles affect experimental thrombosis in an in vivo hamster model

Particulate air pollution is associated with cardiovascular morbidity and mortality. To investigate this association, we studied the effect of ultrafine (60 nm) polystyrene particles on thrombus formation in a hamster model after intravenous and intratracheal administration of unmodified, carboxylate-polystyrene, or amine-polystyrene particles. Unmodified particles had no effect on thrombosis up to 5 mg/kg. Carboxylate-polystyrene particles significantly inhibited thrombus formation at 500 and 100 microg/kg body weight but not at 50 microg/kg body weight. In contrast, amine-polystyrene particles significantly enhanced thrombosis at 500 and 50 microg/kg body weight but not at 5 microg/kg body weight. Similarly, the intratracheal instillation of 5,000 microg of amine-polystyrene particles significantly increased thrombus formation. The unmodified particles and carboxylate-polystyrene particles had no effect. During platelet aggregation in human platelet-rich plasma, induced with 1.25 microM ADP, unmodified particles had no effect up to 100 microg/ml, and carboxylate-polystyrene particles weakly enhanced platelet aggregation at 25 to 100 microg/ml. However, amine-polystyrene particles (50 and 100 microg/ml) induced platelet aggregation themselves and strongly increased the ADP-induced aggregation. We conclude that the presence of (ultrafine) particles in the circulation may affect hemostasis. The observed in vivo prothrombotic tendency results, at least in part, from platelet activation by positively charged amine-polystyrene particles.

Cardiovascular damage by airborne particles: are diabetics more susceptible?

BACKGROUND

Convincing evidence now exists that particulate air pollution exacerbates heart and lung disease, leading to increased morbidity and mortality. The populations particularly susceptible to these exposures are still unclear. Recent work on potential mechanisms of action of particulate air pollution point to pathways also influenced by diabetes.

METHODS

We examined effect modification by concurrent diagnosis of diabetes overall and by age group in a hierarchical model for four U.S. cities. In the first stage, separate Poisson regressions were fit in each city and within each stratum of age and diabetes. In the second stage, the estimated effect size for PM (particulate air matter with aerodynamic diameter less than 10 microns) within city and strata was regressed against the stratification variables, allowing for a random effect. We used Medicare data for Chicago, IL, Detroit, MI, Pittsburgh, PA, and Seattle, WA, for the years 1988-1994.

RESULTS

We found that diabetics have double the risk of a PM10 -associated cardiovascular admission compared with nondiabetics. We also found that persons 75 years of age and older had higher risk, and that the interaction between the two categories (diabetes and age) was less than additive. If the latter is confirmed, it may represent a survivor effect among diabetes, enhanced susceptibility among nondiabetics, or both.

CONCLUSIONS

We conclude that diabetics are a population that is particularly susceptible to cardiovascular damage by airborne particles.

Non-eosinophilic asthma: importance and possible mechanisms

There is increasing evidence that inflammatory mechanisms other than eosinophilic inflammation may be involved in producing the final common pathway of enhanced bronchial reactivity and reversible airflow obstruction that characterises asthma. A review of the literature has shown that, at most, only 50% of asthma cases are attributable to eosinophilic airway inflammation. It is hypothesised that a major proportion of asthma is based on neutrophilic airway inflammation, possibly triggered by environmental exposure to bacterial endotoxin, particulate air pollution, and ozone, as well as viral infections. If there are indeed two (or more) subtypes of asthma, and if non-eosinophilic (neutrophil mediated) asthma is relatively common, this would have major consequences for the treatment and prevention of asthma since most treatment and prevention strategies are now almost entirely focused on allergic/eosinophilic asthma and allergen avoidance measures, respectively. It is therefore important to study the aetiology of asthma further, including the underlying inflammatory profiles.

Photometrically measured continuous personal PM(2.5) exposure: levels and correlation to a gravimetric method

There is evidence that hourly variations in exposure to airborne particulate matter (PM) may be associated with adverse health effects. Still there are only few published data on short-term levels of personal exposure to PM in community settings. The objectives of the study were to assess hourly and shorter-term variations in personal PM(2.5) exposure in Helsinki, Finland, and to compare results from portable photometers to simultaneously measured gravimetric concentrations. The effect of relative humidity on the photometric results was also evaluated. Personal PM(2.5) exposures of elderly persons were assessed for 24 h every second week, resulting in 308 successful measurements from 47 different subjects. Large changes in concentrations in minutes after cooking or changing microenvironment were seen. The median of daily 1-h maxima was over twice the median of 24-h averages. There was a strong significant association between the two means, which was not linear. Median (95th percentile) of the photometric 24-h concentrations was 12.1 (37.7) and of the 24-h gravimetric concentrations 9.2 (21.3) microg/m3. The correlation between the photometric and the gravimetric method was quite good (R2=0.86). Participants spent 94.1% of their time indoors or in a vehicle, where relative humidity is usually low and thus not likely to cause significant effects on photometric results. Even outdoors, the relative humidity had only modest effect on concentrations. Photometers are a promising method to explore the health effects of short-term variation in personal PM(2.5) exposure.

Effect of ozone on bronchial mucosal inflammation in asthmatic and healthy subjects

Epidemiological studies suggestthat asthmatics are more affected by ozone than healthy people. This study tested three hypotheses (1) that short-term exposure to ozone induces inflammatory cell increases and up-regulation of vascular adhesion molecules in airway lavages and bronchial tissue 6 h after ozone exposure in healthy subjects; (2) these responses are exaggerated in subjects with mild allergic asthma; (3) ozone exacerbates pre-existent allergic airways inflammation. We exposed 15 mild asthmatic and 15 healthy subjects to 0.2 ppm of ozone or filtered air for 2 h on two separate occasions. Airway lavages and bronchial biopsies were obtained 6 h post-challenge. We found that ozone induced similar increases in bronchial wash neutrophils in both groups, although the neutrophil increase in the asthmatic group was on top of an elevated baseline. In healthy subjects, ozone exposure increased the expression of the vascular endothelial adhesion molecules P-selectin and ICAM- 1, as well as increasing tissue neutrophil and mast cell numbers. The asthmatics showed allergic airways inflammation at baseline but ozone did not aggravate this at the investigated time point. At 6 h post-ozone-exposure, we found no evidence that mild asthmatics were more responsive than healthy to ozone in terms of exaggerated neutrophil recruitment or exacerbation of pre-existing allergic inflammation. Further work is needed to assess the possibility of a difference in time kinetics between healthy and asthmatic subjects in their response to ozone.

Chemical constituents of diesel exhaust particles induce IL-4 production and histamine release by human basophils

BACKGROUND

An epidemiologic relationship between airway allergic diseases and exposure to atmospheric pollutants has been demonstrated and suggested to be one factor in the increasing prevalence of asthma. Diesel exhaust particles (DEPs) have been shown to participate in the development of allergic airway inflammation, in which the targets include macrophages, B and T cells, epithelial cells, and mast cells. In addition to the adjuvant effect of DEPs on total and allergen-specific IgE production, DEPs also act to induce chemokines and cytokines and may play a key role in primary sensitization.

OBJECTIVE

DEPs have been shown to increase local IL-4-containing Kit(+) cells soon after in vivo nasal challenge. The aim of this study was to examine the effects of DEPs on human basophils, a key source of IL-4.

METHODS

Peripheral blood leukocytes from allergic and control subjects were cultured in the presence of organic extracts of DEP (DEPex) with or without allergen. The cultures were analyzed for IL-4-containing cells by using multiparameter flow cytometry, IL-4 secretion with ELISA, and histamine release.

RESULTS

Basophils, when exposed in vitro to DEPex, expressed IL-4 and released histamine significantly (P <.01) more than with antigen activation. DEPex did not synergize with allergen in cytokine production and histamine release. DEPex-induced basophil IL-4 expression peaked at 2 hours and persisted through 20 hours, in contrast to allergen-induced IL-4, which was transient. The effect of DEPex on basophil cytokine expression and histamine release was dose dependent and occurred with cells from both allergic and nonallergic subjects. DEPex induced IL-4 expression and histamine release in highly enriched basophil populations, suggesting it acts directly on basophils. Other peripheral blood leukocytes, including T cells, did not contribute to this cytokine expression. Preincubation with N-acetylcysteine completely abrogated DEPex-driven basophil IL-4 expression.

CONCLUSIONS

Basophils are a direct target for DEPex, inducing IL-4 expression and histamine release in an IgE-allergen independent fashion. N-acetylcysteine inhibition of DEPex-driven IL-4 expression provides evidence that generation of reactive oxygen species is required for the effects observed. The capability of DEPex to activate basophils in both allergic and nonallergic subjects suggests a potential role of this pollutant in the increasing prevalence of allergic diseases.

Inhalation of fine particulate air pollution and ozone causes acute arterial vasoconstriction in healthy adults

BACKGROUND

Fine particulate air pollution and ozone are associated with increased cardiovascular events. To help explain the mechanism behind these observations, we investigated the effect of air pollution exposure on vascular function.

METHODS AND RESULTS

Twenty-five healthy adults underwent a randomized, double-blind, crossover study comparing the vascular response to the 2-hour inhalation of approximately 150 microg/m(3) of concentrated ambient fine particles (CAP) plus ozone (120 ppb) versus the response to the inhalation of filtered air. High-resolution vascular ultrasonography was used to measure alterations in brachial artery diameter, endothelial-dependent flow-mediated dilatation (FMD) and endothelial-independent nitroglycerin-mediated dilatation (NMD). Exposure to CAP plus ozone caused a significant brachial artery vasoconstriction compared with filtered air inhalation (-0.09+/-0.15 mm versus +0.01+/-0.18 mm, P=0.03). There were no significant differences in FMD (+0.29+/-4.11% versus -0.03+/-6.63%, P=0.88), NMD (+3.87+/-5.43% versus +3.46+/-7.92%, P=0.83), or blood pressure responses between exposures.

CONCLUSIONS

Short-term inhalation of fine particulate air pollution and ozone at concentrations that occur in the urban environment causes acute conduit artery vasoconstriction.

Exposure of human lung cells to native diesel motor exhaust--development of an optimized in vitro test strategy

To investigate the effects of native diesel motor exhaust on human lung cells in vitro, a new experimental concept was developed using an exposure device on the base of the cell cultivation system CULTEX (Patent No. DE19801763.PCT/EP99/00295) to handle the cells during a 1-h exposure period independent of an incubator and next to an engine test rig. The final experimental set-up allows the investigation of native (chemically and physically unmodified) diesel exhaust using short distances for the transportation of the gas to the target cells. The analysis of several atmospheric compounds as well as the particle concentration of the exhaust was performed by online monitoring in parallel. To validate the complete system we concentrated on the measurement of two distinct viability parameters after exposure to air and undiluted, diluted and filtered diesel motor exhaust generated under different engine operating conditions. Cell viability was not influenced by the exposure to clean air, whereas dose-dependent cytotoxicity was found contingent on the dosage of exhaust. Additionally, the quality of exhaust, represented by two engine operating conditions (idling, higher load), also showed well-distinguishable cytotoxicity. In summary, the experimental set-up allows research on biological effects of native engine emissions using short exposure times.

PM(10)-exposed macrophages stimulate a proinflammatory response in lung epithelial cells via TNF-alpha

There is now considerable evidence for an association between the levels of particulate air pollution [particulate matter <10 microm in aerodynamic diameter (PM(10))] and various adverse health endpoints. The release of proinflammatory mediators from PM(10)-exposed macrophages may be important in stimulating cytokine release from lung epithelial cells, thus amplifying the inflammatory response. A549 cells were treated with conditioned media from monocyte-derived macrophages stimulated with PM(10), titanium dioxide (TiO(2)), or ultrafine TiO(2). We demonstrate that only conditioned media from PM(10)-stimulated macrophages significantly increased nuclear factor-kappaB and activator protein-1 DNA binding, enhanced interleukin-8 (IL-8) mRNA levels as assessed by RT-PCR, and augmented IL-8 protein levels, over untreated controls. Furthermore, PM(10)-conditioned media also caused transactivation of IL-8 as determined by an IL-8-chloramphenicol acetyl transferase reporter. Analysis of these conditioned media revealed marked increases in tumor necrosis factor-alpha (TNF-alpha) and protein levels and enhanced chemotactic activity for neutrophils. Preincubation of conditioned media with TNF-alpha-neutralizing antibodies significantly reduced IL-8 production. These data suggest that PM(10)-activated macrophages may amplify the inflammatory response by enhancing IL-8 release from lung epithelial cells, in part, via elaboration of TNF-alpha.

Diesel exhaust and asthma: hypotheses and molecular mechanisms of action

Several components of air pollution have been linked to asthma. In addition to the well-studied critera air pollutants, such as nitrogen dioxide, sulfur dioxide, and ozone, diesel exhaust and diesel exhaust particles (DEPs) also appear to play a role in respiratory and allergic diseases. Diesel exhaust is composed of vapors, gases, and fine particles emitted by diesel-fueled compression-ignition engines. DEPs can act as nonspecific airway irritants at relatively high levels. At lower levels, DEPs promote release of specific cytokines, chemokines, immunoglobulins, and oxidants in the upper and lower airway. Release of these mediators of the allergic and inflammatory response initiates a cascade that can culminate in airway inflammation, mucus secretion, serum leakage into the airways, and bronchial smooth muscle contraction. DEPs also may promote expression of the T(subscript)H(/subscript)2 immunologic response phenotype that has been associated with asthma and allergic disease. DEPs appear to have greater immunologic effects in the presence of environmental allergens than they do alone. This immunologic evidence may help explain the epidemiologic studies indicating that children living along major trucking thoroughfares are at increased risk for asthmatic and allergic symptoms and are more likely to have objective evidence of respiratory dysfunction.

Coadministration of antigen and particles optimally stimulates the immune response in an intranasal administration model in mice

Some particulate matter is known to affect human health, yet the mechanism(s) by which it acts is largely unknown. One of the factors that may play a role in the immune- stimulating activity of particles is binding of allergen to particles. This may turn the particles into allergen carriers, resulting in antigen deposition within the altered inflammatory microenvironment created by the particles. We compared the efficacy of simultaneous versus separate administration of antigen and particles during sensitization in an intranasal exposure model in BALB/c mice. Sensitization consisted of three separate doses (10 microg) of TNP-OVA at Days 1, 2, and 3. Two hundred micrograms of carbon black particles (CBP) were administered either 1 day before sensitization (Day 0), 1 day after sensitization (Day 4), or during sensitization. The latter was performed either at Day 1 (200 microg) or at Days 1, 2, and 3 (67 microg/day). At Day 10 a challenge with 10 microg of TNP-OVA was performed, and at Day 15 the immune response was assessed. The total number of cells as well as antibody-forming cells (AFC) in lymph nodes draining the lung (peribronchial lymph nodes [PBLN]) were determined, and immunoglobulin levels in blood were assessed. Cell numbers of PBLN increased significantly in all particle-treated groups compared to controls. The number of TNP-specific IgG1-forming cells in the groups receiving particles during sensitization was significantly higher than control level. Only groups receiving particles during or before sensitization displayed significantly higher IgG1 levels than controls, in contrast to the group receiving particles after sensitization. Only in animals receiving three doses of 67 microg during sensitization did TNP-specific IgE increase significantly compared to controls. IgG2a did not show significant differences compared to controls, indicating that the response is predominantly Th2 mediated. These data indicate that coadministration of particles at all time points of antigen dosing is the most effective way to stimulate an immune response in our model compared to separate particle and antigen dosing. Also, administration shortly before antigen administration was effective in stimulating an immune response, suggesting that time-dependent processes are involved in immune-stimulating activity of particles, supporting the important role of the altered inflammatory microenvironment created by the particles.

Is diesel the cause for the increase in allergic disease?

LEARNING OBJECTIVES

The purpose of this review is to objectively critique available data regarding the role of diesel exhaust particles (DEPs) in allergic disease. Readers of this review should understand the ways in which diesel particulates can affect human airways and the extent of the scientific data which are currently available.

DATA SOURCES

Data were obtained from published studies and reviews.

STUDY SELECTION

The specific reviewed studies selected for this review met the following criteria: human and animal in vivo, in vitro, and pulmonary dosimetry studies, as well as epidemiologic studies to examine the role of DEPs and particulates on the airways.

RESULTS

The results of the published studies show that although DEPs may play a role in the increased levels of allergic disorders through a number of immunologic mechanisms, it remains to be proven whether it is responsible for the recent rise in the prevalence of asthma and other allergic disorders.

CONCLUSIONS

Further studies in humans are needed to elucidate the mechanisms by which DEPs may be responsible for the increased prevalence of allergic disorders.

Induction of inflammatory response of mice exposed to diesel exhaust is modulated by CD4(+) and CD8(+) T cells

Exposure to diesel exhaust (DE) increased airway inflammatory responses and airway responsiveness to allergen challenge. To clarify the roles of T cells in DE exposure-induced early inflammation, we studied the effect of CD4 and CD8 cells on the effect DE might have on allergic inflammation by using monoclonal antibody-mediated cellular depletion assays. In the bronchoalveolar lavage (BAL) fluid, the numbers of inflammatory cells from 3 mg/m(3) DE-exposed and ovalbumin (OVA)-immunized mice markedly increased. Depletion of CD4(+) cells resulted in reduced accumulation of inflammatory cells. DE exposure to OVA-immunized mice significantly increased interleukin (IL)-1 beta production but decreased IL-12 production. DE exposure significantly enhanced production of the macrophage inflammatory proteins (MIP)-1 alpha and MIP-2, but not monocyte chemoattractant protein (MCP)-1 and regulated upon activation normal T cells expressed and secreted (RANTES). Treatment with anti-CD4 and anti-CD8 mAbs abrogated the adverse effect of DE exposure. In CLN cells from OVA + DE-exposed mice, CD45R/B220-, CD3-, CD4-, and CD8-positive cells were significantly increased, but the OVA-stimulated cytokine production remained at the same levels with OVA-immunized mice. These findings suggest that the induction of early inflammatory responses by DE exposure may initially be related to the modulated function of lymphocyte subpopulations.

Is air pollution a risk factor for low birth weight in Seoul?

Environmental factors contributing to reduced birth weight are of great concern because of the well-known relation of birth weight to infant mortality and adverse effects in later life. We examined the associations between air pollution exposures during pregnancy and low birth weight among all full-term births (gestational age 37-44 weeks) for a 2-year period (January 1996 through December 1997) in Seoul, South Korea. We evaluated these associations with a generalized additive logistic regression adjusting for gestational age, maternal age, parental educational level, parity, and infant sex. We used smoothing plots with generalized additive models to analyze the exposure-response relation for each air pollutant. The adjusted relative risk of low birth weight was 1.08 [95% confidence interval (CI) = 1.04-1.12] for each interquartile increase for carbon monoxide concentrations during the first trimester of pregnancy. The relative risks were 1.07 (95% CI = 1.03-1.11) for nitrogen dioxide, 1.06 (95% CI = 1.02-1.10) for sulfur dioxide, and 1.04 (95% CI = 1.00-1.08) for total suspended particles also for interquartile increase in exposure. Carbon monoxide, nitrogen dioxide, sulfur dioxide, and total suspended particle concentrations in the first trimester of pregnancy period are risk factors for low birth weight.

Diffuse alveolar damage after exposure to an oil fly ash

Epidemiological investigation has established an association between exposure to particulate matter (PM) and both human mortality and diverse indices of human morbidity. However, attributing adverse health effects of specific individuals to PM exposure in these studies is not possible. Consequently, their clinical presentation remains ill-defined. We describe a 42-yr-old male with both respiratory damage, abnormal blood end points, and cardiac effects following an exposure to an emission source air pollution particle aerosolized during the cleaning of his domestic oil-burning stove. Early symptoms of shortness of breath and wheezing progressed over 2 wk to hypoxic respiratory failure necessitating mechanical ventilation. Blood indices were abnormal. Thoracoscopic biopsy demonstrated particle-laden macrophages and diffuse alveolar damage. Symptomatic and objective improvement rapidly followed initiation of corticosteroids. He developed typical anginal symptoms within 2 wk of discharge; however, coronary angiography did not identify any significant narrowing of the epicardial coronary arteries. This patient presents with the aggregate of potential injuries described by epidemiological methods to be associated with air pollution particle exposure.

Organic compounds from diesel exhaust particles elicit a proinflammatory response in human airway epithelial cells and induce cytochrome p450 1A1 expression

Diesel exhaust particles (DEP) are known to enhance inflammatory responses in human volunteers. In cultured human bronchial epithelial (16HBE) cells, they induce the release of proinflammatory cytokines after triggering transduction pathways, including nuclear factor (NF)-kappaB activation and mitogen-activated protein kinase (MAPK) phosphorylation. This study compares the effects of native DEP (nDEP), organic extracts of DEP (OE-DEP), and carbonaceous particles, represented by stripped DEP (sDEP) and carbon black particles (CB), in order to clarify their respective roles. OE-DEP and nDEP induce granulocyte macrophage colony-stimulating factor (GM-CSF) release, NF-kappaB activation, and MAPK phosphorylation. The carbonaceous core generally induces less intense effects. Reactive oxygen species are produced in 16HBE cells and are involved in GM-CSF release and in the stimulation of NF-kappaB DNA binding by nDEP and OE-DEP. We demonstrate, for the first time, in airway epithelial cells in vitro that nDEP induce the expression of the CYP1A1, a cytochrome P450 specifically involved in polycyclic aromatic hydrocarbons metabolism, thereby demonstrating the critical role of organic compounds in the DEP-induced proinflammatory response. Understanding the respective contributions of DEP components in these effects is important for vehicle manufacturers in order to improve their exhaust gas post-treatment technologies. In conclusion, the DEP-induced inflammatory response in airway epithelial cells mainly involves organic compounds such as PAH, which induce CYP1A1 gene expression.

Are diabetics more susceptible to the health effects of airborne particles?

Convincing evidence now exists that particulate air pollution exacerbates heart and lung disease, leading to increased morbidity and mortality. The populations particularly susceptible to these exposures are still unclear. Recent work on potential mechanisms of action of particulate air pollution point to pathways also influenced by diabetes. We examined whether diabetes modified the effect of airborne particles by looking at the association of PM(10) with hospital admissions for heart and lung disease in persons with or without diabetes as a comorbidity. In addition we stratified by age within persons with and without diabetes. We used Medicare data for Cook County, Illinois for the years 1988-1994, and found that a 10 microg/m(3) increase in PM(10) was associated with a 2.01% (95% CI 1.40-2.62%) increase in admissions for heart disease with diabetes, but only a 0.94% (95% CI 0.61-1.28%) increase in persons without diabetes. Similar effect modification was not seen for lung diseases. When analyzing by age we found twice the PM(10)-associated risk for heart disease in diabetics than nondiabetics in both age groups. We found for pneumonia admissions that diabetes is an effect modifier in the younger age group, and for COPD in the older age group. We conclude that persons with diabetes are a susceptible population.

Respiratory symptoms and lung function in workers in heavy and highway construction: a cross-sectional study

BACKGROUND

Occupational exposures for workers in heavy and highway (HH) construction include cement-containing dusts and diesel exhaust (DE). To investigate possible health effects, respiratory symptoms and lung function were examined in laborers, tunnel workers (TW), and operating engineers (OE) in HH and tunnel construction. The principal outcome of interest was airways disease.

METHODS

Subjects were recruited through their unions. Medical and occupational histories and flow-volume loops were obtained. Based on self-report, asthma and chronic bronchitis were categorized as (1) physician-diagnosed or (2) for asthma, undiagnosed likely, and (3) for chronic bronchitis, symptomatic. Trade and time in the union were used as surrogates of exposure. Prevalence of asthma and chronic bronchitis, lung function outcome, and relationships with exposure variables were examined.

RESULTS

Data were obtained on 389 workers: 186 laborers, 45 TWs, and 158 OEs. Prevalence of asthma was 13 and 11.4% for laborers (including TW) and OEs, respectively, and of symptomatic chronic bronchitis, 6.5 and 1.9%, respectively. Odds ratios (OR) for undiagnosed asthma likely were significantly elevated in TWs compared to OEs, and marginally elevated for chronic bronchitis. Inverse relationships were observed between time in the union, and risk for asthma and chronic bronchitis. Asthma (physician-diagnosed or undiagnosed likely) predicted lower FEV(1). Current cigarette use was associated with chronic bronchitis but not asthma.

CONCLUSIONS

TWs, laborers, and OEs in HH construction are at increased risk for asthma. TWs also appear to be at increased risk for chronic bronchitis. Our data suggest that symptomatic workers are self-selecting out of their trade. Asthma was associated with lower lung function in those affected.

Diesel exhaust enhances airway responsiveness in asthmatic subjects

Particulate matter (PM) pollution has been associated with negative health effects, including exacerbations of asthma following exposure to PM peaks. The aim of the present study was to investigate the effects of short-term exposure to diesel exhaust (DE) in asthmatics, by specifically addressing the effects on airway hyperresponsiveness, lung function and airway inflammation. Fourteen nonsmoking, atopic asthmatics with stable disease, on continuous treatment with inhaled corticosteroids, were included. All were hyperresponsive to methacholine. Each subject was exposed to DE (particles with a 50% cut-off aerodynamic diameter of 10 microm (PM10) 300 microg x m(-3)) and air during 1 h on two separate occasions. Lung function was measured before and immediately after the exposures. Sputum induction was performed 6 h, and methacholine inhalation test 24 h, after each exposure. Exposure to DE was associated with a significant increase in the degree of hyperresponsiveness, as compared to after air, of 0.97 doubling concentrations at 24 h after exposure (p < 0.001). DE also induced a significant increase in airway resistance (p=0.004) and in sputum levels of interleukin (IL)-6 (p=0.048). No changes were detected in sputum levels of methyl-histamine, eosinophil cationic protein, myeloperoxidase and IL-8. This study indicated that short-term exposure to diesel exhaust, equal to high ambient levels of particulate matter, is associated with adverse effects in asthmatic airways, even in the presence of inhaled corticosteroid therapy. The increase in airway responsiveness may provide an important link to epidemiological findings of exacerbations of asthma following exposure to particulate matter.

Induction of the imbalance of helper T-cell functions in mice exposed to diesel exhaust

Administration of diesel exhaust particles (DEP) increases antigen-specific IgE production and IgE-secreting cells, and induces Th2-type cytokine profiles in the airway in mice and humans. To determine the early effects of diesel exhaust (DE) inhalation on the cytokine production profile, BALB/c mice were exposed to 0 (controls) and 1.0 mg/m3 DE inhalation for 4 weeks. Intraperitoneal sensitization with ovalbumin (OVA) was conducted immediately before DE inhalation. Mice were treated with anti-CD4 or anti-CD8 mAb 1 day before and after the sensitization. On day 21, these mice were boosted with OVA and blood; bronchoalveolar lavage (BAL) fluid, and spleens were collected on day 28. In BAL fluid, both TNFalpha and IL-10 production in DE-exposed and control mice remained basically the same. IL-6 production in the anti-CD4 treatment group of DE-exposed mice, however, significantly increased compared with that of the controls. In vitro antigen-stimulated interleukin-4 (IL-4) and -10 (IL-10) production in spleen cells of exposed mice were not affected by low-dose DE inhalation. In vitro interferon (IFN)-gamma production in the anti-CD4 treated group of exposed mice decreased markedly. Although anti-OVA IgE production in the plasma of sham-treated mice exposed to DE was the same level as for controls, anti-CD4 mAb treatment in DE-exposed mice significantly reduced IgE production compared to controls. In anti-OVA IgG1 production, anti-CD4 or anti-CD8 mAb treatment in DE-exposed groups also significantly reduced. Anti-OVA IgG2a production was reduced by treatment with anti-CD4 mAb, but increased by anti-CD8 mAb treatment in DE-exposed mice. Low dose DE inhalation is thus shown to adversely affect the cytokine and antibody production in mice by altering CD4+ and CD8+ T-cell functions.

Health effects of diesel exhaust emissions

Epidemiological studies have demonstrated an association between different levels of air pollution and various health outcomes including mortality, exacerbation of asthma, chronic bronchitis, respiratory tract infections, ischaemic heart disease and stroke. Of the motor vehicle generated air pollutants, diesel exhaust particles account for a highly significant percentage of the particles emitted in many towns and cities. This review is therefore focused on the health effects of diesel exhaust, and especially the particular matter components. Acute effects of diesel exhaust exposure include irritation of the nose and eyes, lung function changes, respiratory changes, headache, fatigue and nausea. Chronic exposures are associated with cough, sputum production and lung function decrements. In addition to symptoms, exposure studies in healthy humans have documented a number of profound inflammatory changes in the airways, notably, before changes in pulmonary function can be detected. It is likely that such effects may be even more detrimental in asthmatics and other subjects with compromised pulmonary function. There are also observations supporting the hypothesis that diesel exhaust is one important factor contributing to the allergy pandemic. For example, in many experimental systems, diesel exhaust particles can be shown to act as adjuvants to allergen and hence increase the sensitization response. Much of the research on adverse effects of diesel exhaust, both in vivo and in vitro, has however been conducted in animals. Questions remain concerning the relevance of exposure levels and whether findings in such models can be extrapolated into humans. It is therefore imperative to further assess acute and chronic effects of diesel exhaust in mechanistic studies with careful consideration of exposure levels. Whenever possible and ethically justified, studies should be carried out in humans.

Benzene-extracted components are important for the major activity of diesel exhaust particles: effect on interleukin-8 gene expression in human bronchial epithelial cells

Epidemiologic and experimental studies suggest that diesel exhaust particles (DEPs) may be related to increasing respiratory mortality and morbidity. We have shown that DEPs augmented the production of inflammatory cytokines by human airway epithelial cells in vitro. To better understand the mechanisms of their proinflammatory activities, we studied the effects of several components extracted from DEPs on interleukin (IL)-8 expression in human bronchial epithelial cell line BEAS-2B and normal human airway epithelial cells obtained from very peripheral airways by an ultrathin bronchoscope. We used several agents active on signal transduction pathways in cytokine expression, such as the protein kinase C inhibitor staurosporin, antioxidant agents including N-acetyl cysteine (NAC) and pyrrolidine dithiocarbamate (PDTC), and p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580. Benzene-extracted components showed effects mimicking DEPs on IL-8 gene expression, release of several cytokines (IL-8; granulocyte macrophage colony-stimulating factor; and regulated on activation, normal T cells expressed and secreted) and nuclear factor (NF)-kappa B activation. We also found that NAC, PDTC, and SB203580 suppressed the activities of DEPs and their benzene extracts, suggesting the roles of oxidants-mediated NF-kappa B activation and p38MAPK pathways. Finally, benzo[a]pyrene, one of the important compounds included in the benzene component, replicated the activities shown by DEPs.

The bronchial epithelium in chronic and severe asthma

Although patients with severe, steroid-refractory asthma represent a minor proportion of the asthmatic population, they consume a disproportionate amount of healthcare costs and have a greatly impaired quality of life. They respond poorly to conventional anti-inflammatory therapy and frequently exhibit a component of fixed airflow obstruction that has been linked to airway wall remodeling. In addition to its classic barrier function, the bronchial epithelium responds to changes in the external environment by secreting cytoprotective molecules and mediators that signal to cells of the immune system. In asthma, the bronchial epithelium is stressed and damaged, with shedding of the columnar cells into the airway lumen. This damage and ensuing repair responses are proposed to orchestrate airway inflammation and remodeling via activation of myofibroblasts in the underlying lamina reticularis. This allows the two cell types to work as a trophic unit, propagating and amplifying the response at the cell surface into the submucosa. Because wound healing involves inflammation, repair, and remodeling processes, this review considers the evidence that exaggerated inflammation and remodeling of the airways arise as a consequence of abnormal injury and repair responses coordinated by the bronchial epithelium, highlighting, where possible, steroid-insensitive components.

The interaction between particulate air pollution and allergens in enhancing allergic and airway responses

Although the detrimental effects of air pollution on human health have been brought widely to public notice, it appears that less attention has been given to the potential role of toxic air pollutants in the induction of allergic conditions such as asthma, rhinoconjunctivitis, and atopic eczema. A number of large epidemiologic studies have shown that people exposed to intense motor vehicle traffic and its associated emissions are at major risk for allergic symptoms, reduced lung function, and increased sensitization to common airborne allergens. Several laboratory-based studies have demonstrated that particulate air pollutants emitted from motor vehicles can induce allergic inflammation, enhance IgE responses, and increase airway hyperresponsiveness, which could provide an underlying mechanism for the increasing prevalence of allergic diseases. This article reviews the evidence that supports the causative link between particulate air pollution and the sharp increase in the prevalence of type I allergies in developed countries.

Is there harvesting in the association of airborne particles with daily deaths and hospital admissions?

Although many studies have shown that airborne particles are associated with increased daily death and hospitalization rates, some have questioned whether these events are occurring in persons who would die or enter the hospital within a few days in any case. This hypothesis is usually called the harvesting effect. Harvesting is postulated to occur because the size of the pool of susceptibles decreases as a result of air pollution. I have developed a framework for examining this hypothesis. I used a smoothing technique that allowed me to examine the association between daily deaths and daily hospital admissions net of any such rebound that occurred within a fixed time scale. By varying that time scale I could look at effects net of rebounds on successively larger time scales, ranging from 15 to 60 days. I examined daily deaths and hospital admissions in Chicago for the years 1988-1993. In baseline analyses, particulate matter less than 10 microm in aerodynamic diameter (PM10) was associated with increased daily deaths and hospital admissions for heart disease, pneumonia, and chronic obstructive pulmonary disease. A 10 microg/m3 increase in PM10 was associated with a 0.89% increase in daily deaths (95% confidence interval = 0.61-1.16%), for example. Using smoothing to look at effects net of short-term rebounds, the effect-size estimates for daily deaths and for chronic obstructive pulmonary disease admissions more than doubled. They did not change for pneumonia and heart disease admissions. The increased effect size for daily deaths occurred only for deaths outside of the hospital. These results are consistent with air pollution increasing the size of the risk pool and for most of the deaths being advanced by months to years.

Diesel exhaust particles directly induce activated mast cells to degranulate and increase histamine levels and symptom severity

BACKGROUND

The ability of combustion products, such as diesel exhaust particles (DEPs), to modulate the immune system has now been firmly established. DEPs can synergize with allergen at the human upper respiratory mucosa to enhance allergen-specific IgE production, initiate a T(H)2 cytokine environment, and even promote primary allergic sensitization. Experiments suggest that these effects result from the initial activation of mast cells to produce IL-4.

OBJECTIVE

We sought to demonstrate that in vivo mast cell activation by DEPs plus allergen will also affect the release of classic mast cell mediators and consequently enhance the immediate-phase response.

METHODS

Dust mite-sensitive subjects were challenged intranasally with allergen, and symptom scores and histamine levels in nasal wash samples were compared after prechallenge with 0.3 mg of DEPs.

RESULTS

If the subjects were first sprayed with DEPs, mean symptom scores rose from 3.7 to 9.9; additionally, only one fifth of the amount of intranasal dust mite allergen was required to induce clinical symptoms. DEPs alone had no effect. The changes in symptoms correlated with histamine levels measured in nasal lavage specimens from these subjects. Although challenge with DEPs alone did not induce histamine release, challenge with both DEPs and allergen resulted in 3-fold higher histamine concentrations than those seen with allergen alone. In contrast, carbon black particles (elemental carbon devoid of chemicals) had no effect. The role of chemicals was confirmed because degranulation of a murine mast cell line by FcepsilonRI cross-linking was increased significantly (by 72%) by the soluble organic chemicals extracted from DEPs.

CONCLUSIONS

Overall, these results suggest that exposure to DEPs can enhance the severity of clinical symptoms to allergen by enhancing mast cell degranulation.

Vanilloid (capsaicin) receptors influence inflammatory sensitivity in response to particulate matter

The signs of airway inflammation and hyperresponsiveness that occur in animals exposed to air pollutants are often strain- and species-specific. To investigate the underlying causes of this phenomenon, BALB/c and C57bl/6 mice were exposed intratracheally to residual oil fly ash (ROFA, 3 mg/kg) and examined after 24 h for signs of airway inflammation. BALB/c showed significantly higher numbers of neutrophils and increased airway hyperresponsiveness in response to methacholine challenge, whereas B6 mice showed no significant change in either inflammatory endpoint. To determine the underlying cause of this strain specificity, cultures of dorsal root ganglion (DRG) sensory neurons, which innervate the upper airways in situ, were explanted from both BALB/c and B6 fetal mice. After 5-7 days in culture, they were exposed to ROFA, other urban and industrial particulate matter (PM; e.g., oil fly ash, woodstove, Mt. St. Helen, St. Louis, Ottawa, coal fly ash) or to prototype irritants (e.g., capsaicin 3-10 microM, pH 5.0 and 6.5). In all instances (except for woodstove), DRG neurons from BALB/c mice released significantly higher levels of the pro-inflammatory cytokine IL-6 into their nutrient media relative to neurons from B6 mice. This cytokine release could be significantly reduced for all PM treated cultures (except woodstove) by pretreatment of cultures with capsazepine (CPZ), a competitive antagonist of vanilloid receptors. DRG neurons, cultured from BALB/c and B6 neonates, were loaded with Fluo-3 AM and exposed to the prototype irritants, acid pH (5.0, 6.5), or capsaicin (3, 10 microM). Analysis of their increases in intracellular calcium showed that significantly higher numbers of BALB/c neurons responded to these prototype irritants, relative to B6 neurons. Morphometric analysis of BALB/c neurons, histochemically stained with cobalt to label neurons bearing capsaicin-sensitive receptors, showed a significantly higher level of stained neurons relative to B6 neurons. Finally, semiquantitative RT-PCR showed a higher expression of VR1 receptor mRNA in DRG and spinal cord taken from neonatal BALB/c mice relative to B6 mice. Taken together, these data suggest that capsaicin and acid-sensitive irritant receptors, located on somatosensory cell bodies and their nerve fiber terminals, subserve PM-induced airway inflammation and are quantitatively different in responsive and nonresponsive mouse strains.

Concentrated ambient air particles induce mild pulmonary inflammation in healthy human volunteers

We tested the hypothesis that exposure of healthy volunteers to concentrated ambient particles (CAPS) is associated with an influx of inflammatory cells into the lower respiratory tract. Thirty-eight volunteers were exposed to either filtered air or particles concentrated from the immediate environment of the Environmental Protection Agency (EPA) Human Studies Facility in Chapel Hill, North Carolina. Particle concentrations in the chamber during the exposures ranged from 23.1 to 311.1 microgram/m(3). While in the exposure chamber, volunteers alternated between moderate exercise (15 min) and rest (15 min) for a total exposure time of 2 h. There were no symptoms noted by volunteers after the exposure. Similarly, there were no decrements in pulmonary function. Eighteen hours after exposure, analysis of cells and fluid obtained by bronchoalveolar lavage showed a mild increase in neutrophils in both the bronchial and alveolar fractions in those individuals exposed to CAPS (8.44 +/- 1.99 and 4.20 +/- 1.69%, respectively, in those with the greatest exposure) relative to filtered air (2.69 +/- 0.55 and 0.75 +/- 0.28%, respectively). Blood obtained 18 h after exposure to CAPS contained significantly more fibrinogen relative to samples obtained before exposure. We conclude that ambient air particles are capable of inducing a mild inflammation in the lower respiratory tract, as well as an increased concentration of blood fibrinogen.

Synergistic effect of diesel organic extracts and allergen Der p 1 on the release of chemokines by peripheral blood mononuclear cells from allergic subjects: involvement of the map kinase pathway

The organic compounds of diesel exhaust particles (DEP-PAHs) have been shown to favor immunoglobulin production and bronchial hyperresponsiveness and to affect cytokine and chemokine productions. To evaluate if diesel exhaust could act in synergy with a house dust mite allergen (Der p 1), peripheral blood mononuclear cells from allergic patients were exposed to DEP-PAHs, with or without purified Der p 1. DEP-PAHs and Der p 1 separately induced an increase in interleukin (IL)-8, regulated on activation, normal T cells expressed and secreted (RANTES), and tumor necrosis factor-alpha concentrations. Interestingly, a synergy between the two stimuli was also observed. In the case of monocyte chemotactic protein (MCP)-1, DEP-PAHs reduced the release, whereas Der p 1 enhanced it. A simultaneous exposure led to reduced production as compared with allergen exposure alone, but still represented an increase as compared with the control exposure. Mitogen-activated protein (MAP) kinase Erk1/2 antagonist mainly inhibited the release of MCP-1, whereas MAP kinase p38 antagonist mainly suppressed the release of IL-8 and RANTES. Messenger RNA expression correlated with protein measurements. Moreover, supernatants from cells exposed to both DEP-PAHs and Der p 1 had a significant chemotactic activity on neutrophils and eosinophils. These findings suggest that simultaneous exposure of allergic patients to DEPs and allergens could result in high local chemokine levels via MAP kinase pathways activation, increasing the likelihood of reaching a critical threshold leading to the initiation of respiratory allergic symptoms.

Airway inflammation after controlled exposure to diesel exhaust particulates

Epidemiologic evidence suggests a link between morbidity and mortality and levels of particulate matter in the atmosphere. We studied the inflammatory response to inhalation of diesel exhaust particulates (DEP) in normal volunteers. DEP were collected from the exhaust of a stationary diesel engine and were resuspended in an exposure chamber. Ten nonsmoking healthy volunteers were exposed for 2 h at rest to a controlled concentration of DEP (monitored at 200 microg/m(3) particulate matter of less than 10 microm aerodynamic diameter [PM(10)]) or air in a double-blind, randomized, crossover study. Exposures were followed by serial spirometry and measurement of pulse, blood pressure, exhaled carbon monoxide (CO), and methacholine reactivity, as well as sputum induction and venesection for up to 4 h after exposure, and a repeat of all these procedures at 24 h after exposure. There were no changes in cardiovascular parameters or lung function following exposure to DEP. Levels of exhaled CO were increased ater exposure to DEP, and were maximal at 1 h (air: 2.9 +/- 0.2 ppm [mean +/- SEM]; DEP: 4.4 +/- 0.3 ppm; p < 0.001). There was an increase in sputum neutrophils and myeloperoxidase (MPO) at 4 h after DEP exposure as compared with 4 h after air exposure (neutrophils: 41 +/- 4% versus 32 +/- 4%; MPO: 151 ng/ml versus 115 ng/ml, p < 0.01), but no change in concentrations of inflammatory markers in peripheral blood. Exposure to DEPs at high ambient concentrations leads to an airway inflammatory response in normal volunteers.

Diesel exhaust particles activate human bronchial epithelial cells to express inflammatory mediators in the airways: a review

OBJECTIVE

Epidemiological as well as experimental studies suggest that particulate air pollutants, including diesel exhaust particles (DEP), may play a role in the recent increase of respiratory morbidity and mortality. We studied the effect of DEP on the production of inflammatory cytokines and mediators including IL-8 and granulocyte macrophage colony stimulating factor (GM-CSF) by human airway epithelial cells in vitro.

METHODOLOGY

Suspended DEP were added to cultured normal human bronchial epithelial cells or transformed BEAS-2B cells. The release of cytokines and mediators was evaluated by enzyme-linked immunosorbent assay. The transcriptional levels of IL-8 mRNA was studied by northern blot analysis and run-on transcription assay. Activation of transcription factors was assessed by electrophoretic mobility shift assay.

RESULTS

Non-toxic doses of suspended DEP showed a significant stimulatory effect on IL-8 and GM-CSF production by airway epithelial cells. Diesel exhaust particles increased the steady-state levels of IL-8 mRNA, which was suggested to be largely due to increased transcriptional rates. Electrophoretic mobility shift assay demonstrated that DEP induced increased binding to the specific motif of nuclear factor (NF)-kappaB, but not of transcription factor AP-1. Both N-acetylcysteine and pyrrolidine dithiocarbamate attenuated the action of DEP on IL-8 mRNA expression, suggesting that oxidant-mediated pathway might be involved in its processes. Transient transfection of airway epithelial cells with wild and NF-kappaB binding motifs indicated that the activation of NF-kappaB was essential for IL-8 gene upregulation by reporter gene assay.

CONCLUSIONS

These results suggested that DEP activate NF-kappaB, which might be an important pathway for the expression of inflammatory cytokines in vitro.

Diesel exhaust particles up-regulate expression of intercellular adhesion molecule-1 (ICAM-1) in human bronchial epithelial cells

Epidemiological and experimental studies suggest that diesel exhaust particles (DEP) may play an active role in the increased respiratory mortality and morbidity. We have shown that DEP augmented the production of inflammatory cytokines by human airway epithelial cells in vitro. ICAM-1 has been shown to play an important role in the local accumulation of inflammatory cells. We studied the effect of DEP on ICAM-1 gene expression and surface expression in human bronchial epithelial cell line BEAS-2B. DEP (5-50 microg/ml) showed a stimulatory effect on ICAM-1 mRNA levels as evaluated by reverse transcription-polymerase chain reaction (RT-PCR). Flow cytometric analysis demonstrated an increased ICAM-1 expression on the epithelial cell surfaces. The soluble form of ICAM-1 molecules was also increased by the stimulation of DEP. In vitro neutrophil attachment onto DEP-stimulated epithelial cells was augmented, which was partially blocked by anti-ICAM-1 neutralizing antibody. Finally, these events were significantly inhibited by pretreatment with anti-oxidants pyrrolidine dithiocarbamate and N-acetyl cysteine, and p38 mitogen activated protein kinase (MAPK) inhibitor SB203580. These findings suggested that DEP induced up-regulation of ICAM-1 gene, and this process might be largely dependent on oxidant-mediated NF-kappaB activation and p38-MAPK pathways.

Race, gender, and social status as modifiers of the effects of PM10 on mortality

Interest has recently been focused on which populations are most at risk of premature mortality induced by air pollution. This coincides with greater concern about environmental justice. We analyzed total mortality in the four largest US cities with daily measurements of particulate matter less than 10 microns (PM10) and combined the results to determine whether race, sex, and education are potential modifiers of the effects of PM10 on mortality. We computed daily counts of deaths stratified by sex, race, and education in each city and investigated their associations with PM10 in a Poisson regression model. We combined the results by using inverse variance weighted averages. We found evidence of effect modification by sex, with the slope in female deaths one third larger than in male deaths, whereas for social factors and race we found only weak evidence of effect modification. In general, the effect modification appeared modest compared with other reports of substantial effect modification by medical conditions.