Acute effects of inhaled urban particles and ozone: lung morphology, macrophage activity, and plasma endothelin-1

Vascular effects of ambient particulate matter instillation in spontaneous hypertensive rats

Exposure to ambient particulate matter (PM) is associated with increased mortality and morbidity among those people with cardiovascular impairment. We have studied the effects of exposure to PM or lypopolysaccharide (LPS) on ex vivo vascular function of spontaneous hypertensive rats (SHR) at 4 and 24 h post-instillation. Receptor-dependent and -independent relaxation was studied by using acetylcholine (ACh) and sodium nitroprusside (SNP), respectively. We have used phenylephrine (Phe) and KCl for receptor-dependent and -independent contraction. The role of the endothelium was investigated using denuded aorta rings. Exposure to PM (EHC-93, 10 mg/kg) or LPS (350 EU/animal) caused maximal pulmonary inflammation at 24 h post-instillation. PM and LPS elicited a significant increase in receptor-dependent vasorelaxation of aorta compared to saline-instilled rats. The largest effect was seen with PM at 4 h post-instillation (EC50 ACh = 2.3 vs. 5 nM control), while at 24 h effects were much smaller (EC50 ACh = 5.6 vs. 5 nM control). SNP-induced vasorelaxation was increased only in EHC-93-treated rats (EC50 = 71.9 vs. 95.7 nM) at 4 h, and this response was higher than that observed at 24 h. Phe induced a dose-dependent vasoconstriction, but no difference was seen between treatments in the presence or absence of endothelium at 4 h. However, at 24 h after instillation of LPS, a right shift of contraction curve was seen (EC50 = 65.3 vs. 43.3 nM). No change was seen in receptor-independent vasoconstriction induced by KCl, except in the LPS group at 24 h. A direct relaxation was also observed upon in vitro exposure of aorta rings to PM, and model particles coated with metals. Blood metal analysis showed an increase of zinc and vanadium concentration at 1 and 4 h post-instillation. In conclusion, our data show that PM and LPS instillation has a transient effect on the vasorelaxation of rat aorta that is maximal at 4 h. On the other hand, pulmonary inflammation reaches a maximum at 24 h and coincides with impairment of vasorelaxation. Current data do not allow discriminating among the potential mechanisms, but suggest that both a direct effect of metals and inflammation play a role.

Associations between Short-Term Changes in Nitrogen Dioxide and Mortality in Canadian Cities

The association between daily variations in ambient concentrations of nitrogen dioxide (NO2) and mortality was examined in 12 of Canada's largest cities, using a 19-yr time-series analysis (from 1981-1999). The authors employed parametric statistical methods that are not subject to the recently discovered convergence and error estimation problems of generalized additive models. An increase in the 3-d moving average of NO2 concentrations equivalent to the population-weighted study mean of 22.4 ppb was associated with a 2.25% (t = 4.45) increase in the daily nonaccidental mortality rate and was insensitive to adjustment for ozone, sulfur dioxide, carbon monoxide, coefficient of haze, size-fractionated particulate mass, and the sulfate ion measured on an every-6th-day sampling schedule. The 3-d moving average of NO2 was sensitive to adjustment for fine particulate matter measured daily during the 1998-2000 time period.

Air Pollution and Myocardial Infarction in Rome

BACKGROUND

Daily air pollution is associated with increased hospital admissions for cardiovascular diseases, but there are few observations on the link with acute myocardial infarction. To evaluate the relation between various urban air pollutants (total suspended particulate, SO2, CO, NO2) and hospital admissions for acute myocardial infarction in Rome, Italy, we performed a case-crossover analysis and studied whether individual characteristics act as effect modifiers.

METHODS

We studied 6531 subjects residing in Rome and hospitalized for a first episode of acute myocardial infarction (International Classification of Diseases, 9th edition: 410) from January 1995 to June 1997. The following individual information was available: sex, age, date of hospitalization, coexisting illnesses (hypertension, 25%; diabetes, 15%), and cardiac severity (conduction disorders, 6%; cardiac dysrhythmias, 20%; heart failure, 11%). Daily air pollution data were taken from 5 city monitors. We used a time-stratified case-crossover design; control days were the same day of the week as the myocardial infarction occurred, in other weeks of the month.

RESULTS

Positive associations were found for total suspended particulate, NO2 and CO. The strongest and most consistent effect was found for total suspended particulate. The odds ratio (OR) associated with 10 micro g/m3 of total suspended particulate over the 0- to 2-day lag was 1.028 (95% confidence interval [CI] = 1.005-1.052). The association with total suspended particulate tended to be stronger among people older than 74 years of age (OR = 1.046; CI = 1.005-1.089), in the warm period of the year (OR = 1.046; CI = 1.008-1.087), and among subjects who had heart conduction disorders (OR = 1.080; CI = 0.987-1.181).

CONCLUSIONS

The results suggest that air pollution increases the risk of myocardial infarction, especially during the warm season. There was a tendency for a stronger effect among the elderly and people with heart conduction disturbances.

Air pollution particles produce airway wall remodeling in rat tracheal explants

There is evidence that chronic exposure to high levels of ambient particulate pollutants (PM) is associated with chronic airflow obstruction, but how this occurs is not known. We exposed rat tracheal explants to Ottawa urban air particles (ECH93) or diesel exhaust particles. After 7 d in air organ culture, both types of PM increased explant procollagen and transforming growth factor (TGF)-beta 1 gene expression, and markedly increased tissue hydroxyproline. For both types of particle, nuclear factor-kappa B inhibitor SN50 completely blocked increased gene expression. With EHC93, procollagen expression was inhibited by the oxidant scavenger, tetramethylthiourea, and by the iron chelator, deferoxamine, but TGF-beta1 expression was not inhibited by deferoxamine. Inhibitors of extracellular signal regulated kinase and p38 kinase did not affect EHC93-induced gene expression. With diesel exhaust particles, tetramethylthiourea and deferoxamine had no effect, but extracellular signal regulated kinase and p38 inhibitors completely blocked effects on procollagen and TGF-beta 1. Fetuin, an inhibitor of TGF-beta receptor binding, prevented increases in procollagen gene expression. We conclude that two common types of PM can directly induce expression of genes involved in fibrogenesis and actual airway wall fibrosis through nuclear factor-kappa B- and TGF-beta-mediated mechanisms. PM-induced airway wall remodeling may play an important role in producing airflow obstruction in individuals living in high PM regions.

Adjuvant activity of various diesel exhaust and ambient particles in two allergic models

In the framework of an EU study entitled "Respiratory Allergy and Inflammation Due to Ambient Particles" (RAIAP), various collected particulate matter samples were to be tested for their adjuvant potency in two animal models of allergy. A pollen allergy model in the Brown Norway (BN) rat and an ovalbumin model in the BALB/c mouse were used in this study to compare the discriminatory value of these two models and to evaluate them for later studies of collected RAIAP-samples. Two different sources of diesel exhaust particles (DEP I and DEP II ), a residual oil fly ash source (ROFA), and two sources of ambient particles (Ottawa dust, EHC-93, and road tunnel dust, RTD) were tested. Rats were sensitized intratracheally with Timothy grass pollen (Phleum pratense, 200 microl, 10 mg/ml) on d 0, challenged on d 21, and examined on d 25. Mice were sensitized intranasally at d 0 and 14, challenged intranasally at d 35, 38, and 41 (50 microl, 0.4 mg ovalbumin/ml), and examined at d 42. Particulate matter (PM) was administered either during the sensitization phase only or during the sensitization and challenge phases (for mice only) or during the challenge phase only. In the pollen model, only DEP I, but not DEP II, ROFA, EHC-93, and RTD, stimulated the immunoglobulin (Ig) E and IgG1 response in serum to pollen allergens. In addition to this adjuvant effect noted, no other biomarkers in lung or bronchoalveolar lavage (BAL) revealed adjuvant activity in the pollen model. In the BAL of BN rats exposed to a combination of pollen and PM, the percentages of eosinophilic granulocytes were decreased compared to the BAL of BN rats immunized with pollen only. In the ovalbumin model, the IgE levels in serum were increased in mice after coexposure to ovalbumin and PM (including DEPI, DEPII, ROFA, EHC-93, and RTD) in the sensitization phase but not after coexposure during the challenge phase only. The inflammatory response was greater in the lung, predominantly the influx of eosinophilic granulocytes, as was observed by both histopathological examination and BAL analysis. In addition, BAL levels of inflammatory interleukin (IL)-4 were increased. Based on the IgE antibody response to ovalbumin, the ovalbumin model ranked the adjuvant capacity of the particles in the following order: RTD > ROFA > EHC-93 > DEPI > DEPII. In conclusion, the ovalbumin model is a sensitive system to detect adjuvant activity of airborne particles, whereas the pollen-induced allergy model in rat was less sensitive.

Ozone exposure enhances endotoxin-induced mucous cell metaplasia in rat pulmonary airways

Coexposure to different airborne pollutants can be more toxic to airway epithelium than an inhalation exposure to a single pollutant. We have previously reported that coexposure to ozone, the primary oxidant gas in photochemical smog, and unique inflammatory biogenic substances such as allergens or bacterial endotoxin, results in augmented epithelial and inflammatory responses in rat nasal airways (M. V. Fanucchi et al., 1998, Toxicol. Appl. Pharmacol. 152, 1-9; J. G. Wagner et al., 2002a, Toxicol. Sci.67, 284-294). In the present study, we investigated the toxic interaction of ozone and endotoxin on the respiratory epithelium in the pulmonary airways of laboratory rodents. F344 rats were intranasally instilled with 0, 2, or 20 microg endotoxin dissolved in sterile saline (150 microl/nasal passage). Six h after instillation rats were exposed to air or 1 ppm ozone for 8 h. One day later, endotoxin and ozone exposures were repeated. Three days after the last exposure, rats were sacrificed, the lungs were lavaged with saline, and the collected bronchoalveolar lavage fluid (BALF) was analyzed for inflammatory cells and secreted mucosubstances (mucin 5AC). Lung tissues were processed for light microscopic examination and morphometric analysis of numeric density of epithelial cell populations and volume densities of intraepithelial mucosubstances (IM). Conducting airways were microdissected and analyzed by quantitative RT-PCR to determine steady-state mucin gene (rMuc5AC) mRNA levels in respiratory epithelium. Endotoxin instillation caused a dose-dependent increase in BALF neutrophils that was further increased twofold in ozone-exposed rats given 20 microg endotoxin. Mucin glycoprotein 5AC was elevated in BALF from rats exposed to 20 microg, but not 2 microg endotoxin. Exposure to ozone alone did not cause mucus hypersecretion, but ozone potentiated mucus secretion in rats given 2 or 20 microg endotoxin. Airways of rats exposed to air or ozone alone had scant amounts of IM. Endotoxin instillation induced a dose-dependent increase in IM in airway epithelium that was significantly increased (twofold) in rats that were also exposed to ozone. Expression of rMuc5AC was induced in axial pulmonary airways by 2 and 20 microg endotoxin, and was increased further by ozone-exposure in rats instilled with 20 microg endotoxin. These data demonstrate that ozone exposure potentiates neutrophilic inflammation and mucus production and secretion elicited by a biogenic substance in rat pulmonary airways.

Interactions of exogenous or evoked agents and particles: the role of reactive oxygen species

Humans are commonly exposed to combinations of particles (occupational or environmental) and exogenous agents such as ozone and cigarette smoke that generate reactive oxygen species (ROS). Particles also evoke production of ROS from inflammatory cells and of mediators such as TNF-alpha that operate through ROS-related mechanisms. The interactions of particles and ROS-generating agents have been little explored. Adhesion of particles to the surface of pulmonary epithelial cells is increased by exposure to cigarette smoke, ozone, and TNF-alpha. Cigarette smoke and ozone increase the uptake of particles by epithelial cells, and both adhesion and uptake can be decreased by scavengers of ROS. Increased adhesion and uptake probably lead to increased levels of inflammatory and fibrogenic mediator production, and cigarette smoke definitely increases whole lung particle retention and enhances the fibrogenic effects of asbestos. In experimental models, the combination of particles plus ozone, cigarette smoke, or reagent hydrogen peroxide augments the inflammatory response to particles, increases cell proliferation, and leads to liberation of increased levels of chemoattractant mediators as well as vascular mediators such as endothelin. The small airways appear to be particular targets of coexposure to smoke or ozone and particles, a phenomenon that may produce chronic airflow obstruction.

Inhalation of concentrated ambient air particles exacerbates myocardial ischemia in conscious dogs

Short-term increases in ambient air pollution have been associated with an increased incidence of acute cardiac events. We assessed the effect of inhalation exposure to concentrated ambient particles (CAPs) on myocardial ischemia in a canine model of coronary artery occlusion. Six mongrel dogs underwent thoracotomy for implantation of a vascular occluder around the left anterior descending coronary artery and tracheostomy to facilitate particulate exposure. After recovery (5-13 weeks), pairs of subjects were exposed for 6 hr/day on 3 or 4 consecutive days. Within each pair, one subject was randomly assigned to breathe CAPs on the second exposure day and filtered air at other times. The second subject breathed CAPs on the third exposure day and filtered air at other times. Immediately after each exposure, subjects underwent 5-min coronary artery occlusion. We determined ST-segment elevation, a measure of myocardial ischemia heart rate, and arrhythmia incidence during occlusion from continuous electrocardiograms. Exposure to CAPs (median, 285.7; range, 161.3-957.3 microg/m3) significantly (p = 0.007) enhanced occlusion-induced peak ST-segment elevation in precordial leads V4 (9.4 +/- 1.7 vs. 6.2 +/- 0.9 mm, CAPs vs. filtered air, respectively) and V5 (9.2 +/- 1.3 vs. 7.5 +/- 0.9 mm). ST-segment elevation was significantly correlated with the silicon concentration of the particles and other crustal elements possibly associated with urban street dust (p = 0.003 for Si). No associations were found with CAPs mass or number concentrations. Heart rate was not affected by CAPs exposure. These results suggest that exacerbation of myocardial ischemia during coronary artery occlusion may be an important mechanism of environmentally related acute cardiac events.

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.

Associations between ambient air pollution and daily mortality among persons with congestive heart failure

We conducted a mortality time series study to investigate the association between daily mortality for congestive heart failure (CHF), and daily concentrations of particles and gaseous pollutants in the ambient air of Montreal, Quebec, during the period 1984-1993. In addition, using data from the universal Quebec Health Insurance Plan, we identified individuals >/=65 years of age who, one year before death, had a diagnosis of CHF. Fixed-site air pollution monitors in Montreal provided daily mean levels of pollutants. We regressed the logarithm of daily counts of mortality on the daily mean levels of each pollutant, after accounting for seasonal and subseasonal fluctuations in the mortality time series, non-Poisson dispersion, weather variables, and other gaseous and particle pollutants. Using cause of death information, we did not find any associations between daily mortality for CHF and any air pollutants. The analyses of CHF defined from the medical record showed positive associations with coefficient of haze, the extinction coefficient, SO(2), and NO(2). For example, the mean percent increase in daily mortality for an increase in the coefficient of haze across the interquartile range was 4.32% (95% CI: 0.95-7.80%) and for NO(2) it was 4.08% (95% CI: 0.59-7.68%). These effects were generally higher in the warm season.

Concentrated ambient air particles induce vasoconstriction of small pulmonary arteries in rats

The objective of this study was to determine whether short-term exposures to concentrated ambient particles (CAPs) alter the morphology of small pulmonary arteries in normal rats and rats with chronic bronchitis (CB). Sprague-Dawley male rats were exposed to CAPs, using the Harvard Ambient Particle Concentrator, or to particle-free air (sham) under identical conditions during 3 consecutive days (5 hr/day) in six experimental sets. CB was induced by exposure to 276 +/- 9 ppm of sulfur dioxide (5 hr/day, 5 days/week, 6 weeks). Physicochemical characterization of CAPs included measurements of particle mass, size distribution, and composition. Rats were sacrificed 24 hr after the last CAPs exposure. Histologic slides were prepared from random sections of lung lobes and coded for blinded analysis. The lumen/wall area (L/W) ratio was determined morphometrically on transverse sections of small pulmonary arteries. When all animal data (normal and CB) were analyzed together, the L/W ratios decreased as concentrations of fine particle mass, silicon, lead, sulfate, elemental carbon, and organic carbon increased. In separate univariate analyses of animal data, the association for sulfate was significant only in normal rats, whereas silicon was significantly associated in both CB and normal rats. In multivariate analyses including all particle factors, the association with silicon remained significant. Our results indicate that short-term CAPs exposures (median, 182.75 micro g/m3; range, 73.50-733.00 micro g/m3) can induce vasoconstriction of small pulmonary arteries in normal and CB rats. This effect was correlated with specific particle components and suggests that the pulmonary vasculature might be an important target for ambient air particle toxicity.

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.

Effects of air pollution on adults with chronic obstructive pulmonary disease

Few studies have been conducted on the effects of air pollution on patients with chronic obstructive pulmonary disease (COPD). During a 14-mo period, 39 Parisian adults with severe COPD were monitored by their physicians. Daily levels of 4 air pollutants were provided by an urban air-quality network. Exacerbation of COPD was associated only with ozone (O3) (odds ratio [OR] = 1.44 for a 10-microg/m3 increase in O3; 95% confidence interval [CI] = 1.14, 1.82), with a lag of 2-3 days. The effect of O3 was greater in patients whose carbon dioxide pressure (PaCO2) was higher than 43 mm Hg (OR = 1.83; 95% CI = 1.36, 2.47) vs. those with a lower PaCO2 (OR = 1.26; 95% CI = 0.90, 1.77). The effect of O3 was unchanged, regardless of the maintenance medications used. The only air pollutant to which patients with severe COPD were particularly sensitive was O3.

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.

Systemic inflammatory response induced by particulate matter air pollution: the importance of bone-marrow stimulation

The relationship between the level of particulate air pollution (PM(10)) and the mortality and morbidity rates from respiratory and cardiovascular diseases is well established, but the biological mechanisms responsible for these associations are still unclear. The injurious effects of particulate air pollution may be either local (in the lung) or systemic. Bone-marrow release of leukocytes and platelets is an important component of the systemic inflammatory response. We have developed methods to quantify bone-marrow stimulation and showed in animals that acute exposure to ambient particles accelerates the transit of polymorphonuclear leukocytes (PMN) through the marrow whereas chronic exposure expands the size of the bone marrow pool of PMN. Human studies showed that an episode of severe air pollution stimulates the bone marrow in a manner similar to that observed in animals. In vitro and in vivo studies suggest that alveolar macrophage produce the mediators implicated in the bone marrow response to ambient particles. Cytokines produced in the lung due to deposition of ambient particles also appear in the circulation. In vitro and in vivo studies have shown that PMN recently released from the bone marrow preferentially sequester in pulmonary capillaries, are less chemotactic, and contain more damaging granular enzymes, all factors that potentate their ability to damage alveolar tissue. In animals that naturally develop atherosclerosis, deposition of ambient particles in the lung causes progression of atherosclerotic plaques with phenotypic changes in atherosclerotic plaques characteristic of lesions vulnerable to rupture. We conclude that exposure to ambient particulate matter air pollution induces a systemic inflammatory response that includes the release of inflammatory mediators into the circulation that stimulate the bone marrow to release leukocytes and platelets. We postulate that this systemic response to particulate air pollution augments lung inflammation and changes the phenotype of atherosclerotic plaques to make them more vulnerable to rupture.

Health effects and time course of particulate matter on the cardiopulmonary system in rats with lung inflammation

Recent epidemiological studies associate health effects and particulate matter in ambient air. Exacerbation of the particle-induced inflammation can be a mechanism responsible for increased hospitalization and death due to cardiopulmonary events in high-risk groups of the population. Systems regulating blood pressure that depend on lung integrity can be involved in progression of cardiovascular diseases. This study focused on the expression levels of various genes involved in cardiovascular and pulmonary diseases to assess their role in the onset of cardiovascular problems due to ambient particulate matter and compared these with the corresponding products. Rats with ozone-induced (1600 microg/m(3); 8 h) pulmonary inflammation were exposed to 0.5 mg, 1.5 mg, or 5 mg of particulate matter (PM) from Ottawa Canada (EHC-93) by intratracheal instillation. mRNA levels of various genes and their products were measured 2, 4, and 7 d after instillation. At 2 d after exposures to PM, tumor necrosis factor (TNF)-alpha levels in bronchoalveolar lavage fluid (BALF) were elevated approximately 4 times for the highest EHC-93 dose. MIP-2 protein levels in BALF were elevated approximately three times during the entire time period studied, whereas IL-6 levels were not affected compared to control groups. The MIP-2 mRNA levels revealed a similar pattern of induction. A twofold increase in endothelin (ET)-1 levels at d 2 and a 20% decrease in angiotensin-converting enzyme (ACE) activity at d 7 were measured in plasma. A 60% decrease of ACE and ET-1 mRNA levels suggested a possible endothelial damage in the lung blood vessels. Inducible nitric oxide synthase (iNOS) mRNA was found to be increased 3.5 times 2 d after instillation of the particles. Therefore, the endothelial damage could have been caused by large amounts of the free radical NO. Also, plasma levels of fibrinogen were elevated (20%), which could presumably increase blood viscosity, leading to decreased tissue blood flow. These changes in hematological and hemodynamic parameters observed in our study are in line with heart failure in high-risk groups of the population after high air pollution episodes.

Altered gene expression profiles of rat lung in response to an emission particulate and its metal constituents

Comprehensive and systematic approaches are needed to understand the molecular basis for the health effects of particulate matter (PM) reported in epidemiological studies. Due to the complex nature of the pollutant and the altered physiological conditions of predisposed populations, it has been difficult to establish a direct cause and effect relationship. A high-throughput technology such as gene expression profiling may be useful in identifying molecular networks implicated in the health effects of PM and its causative constituents. Differential gene expression profiles derived for rat lungs exposed to PM and its constituent metals using a custom rat cardiopulmonary cDNA array are presented here. This array consists of 84 cardiopulmonary-related genes representing various biological functions such as lung injury/inflammation, repair/remodeling, structural and matrix alterations, and vascular contractility, as well as six expressed sequence tags (ESTs). The cDNA array was hybridized with (32)P-labeled cDNA generated from rat lung RNA. Total lung RNA was isolated from male Sprague-Dawley rats at 3 and 24 h following intratracheal instillation of either saline, residual oil fly ash (ROFA; 3.3 mg/kg), or its most toxic metallic constituents, nickel (NiSO(4); 3.3 mmol/kg) and vanadium (VSO(4); 5.7 mmol/kg). Metal concentrations reflected the levels present in one ROFA instillate. Densitometric scans of the array blots indicated ROFA- and metal-specific increased expression (1.5 to 3-fold) of stress response, inflammatory, and repair-related genes, and also genes involved in vascular contractility and thrombogenic activity. Expression of multiple cytokines in ROFA exposed rat lung compared to Ni and V suggest the role and importance of understanding constituent interactions in PM toxicity. Expression profiling using genomic approaches will aid in our understanding of toxicant-specific altered molecular pathways in lung injury and pathogenesis.

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.

Vascular immunotargeting of glucose oxidase to the endothelial antigens induces distinct forms of oxidant acute lung injury: targeting to thrombomodulin, but not to PECAM-1, causes pulmonary thrombosis and neutrophil transmigration

Oxidative endothelial stress, leukocyte transmigration, and pulmonary thrombosis are important pathological factors in acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Vascular immunotargeting of the H(2)O(2)-generating enzyme glucose oxidase (GOX) to the pulmonary endothelium causes an acute oxidative lung injury in mice.(1) In the present study we compared the pulmonary thrombosis and leukocyte transmigration caused by GOX targeting to the endothelial antigens platelet-endothelial cell adhesion molecule (PECAM) and thrombomodulin (TM). Both anti-PECAM and anti-TM delivered similar amounts of (125)I-GOX to the lungs and caused a dose-dependent, tissue-selective lung injury manifested within 2 to 4 hours by high lethality, vascular congestion, polymorphonuclear neutrophil (PMN) sequestration in the pulmonary vasculature, severe pulmonary edema, and tissue oxidation, yet at an equal dose, anti-TM/GOX inflicted more severe lung injury than anti-PECAM/GOX. Moreover, anti-TM/GOX-induced injury was accompanied by PMN transmigration in the alveolar space, whereas anti-PECAM/GOX-induced injury was accompanied by PMN degranulation within vascular lumen without PMN transmigration, likely because of PECAM blockage. Anti-TM/GOX caused markedly more severe pulmonary thrombosis than anti-PECAM/GOX, likely because of TM inhibition. These results indicate that blocking of specific endothelial antigens by GOX immunotargeting modulates important pathological features of the lung injury initiated by local generation of H(2)O(2) and that this approach provides specific and robust models of diverse variants of human ALI/ARDS in mice. In particular, anti-TM/GOX causes lung injury combining oxidative, prothrombotic, and inflammatory components characteristic of the complex pathological picture seen in human ALI/ARDS.

Effects of air pollutants on acute stroke mortality

The relationship between stroke and air pollution has not been adequately studied. We conducted a time-series study to examine the evidence of an association between air pollutants and stroke over 4 years (January 1995-December 1998) in Seoul, Korea. We used a generalized additive model to regress daily stroke death counts for each pollutant, controlling for seasonal and long-term trends and meteorologic influences, such as temperature, relative humidity, and barometric pressure. We observed an estimated increase of 1.5% [95% confidence interval (CI), 1.3-1.8%] and 2.9% (95% CI, 0.3-5.5%) in stroke mortality for each interquartile range increase in particulate matter < 10 microm aerodynamic diameter (PM(10)) and ozone concentrations in the same day. Stroke mortality also increased 3.1% (95% CI, 1.1-5.1%) for nitrogen dioxide, 2.9% (95% CI, 0.8-5.0%) for sulfur dioxide, and 4.1% (95% CI, 1.1-7.2%) for carbon monoxide in a 2-day lag for each interquartile range increase in single-pollutant models. When we examined the associations among PM(10) levels stratified by the level of gaseous pollutants and vice versa, we found that these pollutants are interactive with respect to their effects on the risk of stroke mortality. We also observed that the effects of PM(10) on stroke mortality differ significantly in subgroups by age and sex. We conclude that PM(10) and gaseous pollutants are significant risk factors for acute stroke death and that the elderly and women are more susceptible to the effect of particulate pollutants.

An automated high-performance liquid chromatography fluorescence method for the analyses of endothelins in plasma samples

A high-performance liquid chromatographic method with fluorescence detection was developed to simultaneously analyze endothelins, a class of vasoactive peptides, in plasma samples. Sample preparation for HPLC analysis was carried out by initial stabilization of blood and plasma samples against transformation of big endothelins to mature endothelins and breakdown of mature endothelins by serine proteases, as well as oxidative modifications of endothelins. Deproteinization of plasma samples was achieved with acidified acetone, and the samples were further purified on molecular weight cutoff filters. Endothelins were separated on a reversed phase LC-318 column by gradient elution using a mobile phase containing acetonitrile and water (0.1% trifluoroacetic acid) and were analyzed by fluorescence detection (lambda(Ex), 280 nm; lambda(Em), 340). Limit of detection values were in the range of 0.2-0.5 pmol. Linear (R(2), 0.99) calibration curves were established for analyte amounts in the range of 1 to 100 pmols. Recoveries of endothelins from spiked plasma samples analyzed ranged from 60-95%. Under optimized conditions the HPLC-fluorescence method was determined to be sensitive and specific for the analysis of big endothelin-1, endothelin-1, endothelin-2, and endothelin-3 in plasma. Simultaneous measurement of these endothelins by the HPLC method should permit a better understanding of their specific roles and relationships under various pathological conditions.

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.

Identification of persons with cardiorespiratory conditions who are at risk of dying from the acute effects of ambient air particles

This study was undertaken to identify subgroups of the population susceptible to the effects of ambient air particles. Fixed-site air pollution monitors in Montreal, Quebec, Canada, provided daily mean levels of various measures of particulates and gaseous pollutants. Total sulfates were also measured daily (1986-1993) at a monitoring station 150 km southeast of the city (Sutton, Quebec, Canada). We used coefficient of haze (COH), extinction coefficient, and Sutton sulfates to predict fine particles and sulfates from a fine particles model for days that were missing. We used the universal Quebec medicare system to obtain billings and prescriptions for each Montreal resident who died in the city from 1984 to 1993. These data were then used to define cardiovascular and respiratory conditions that subjects had before death. Using standard Poisson regression time-series analyses, we estimated the association between daily nonaccidental mortality and daily concentrations of particles in the ambient air among persons with cardiovascular and respiratory conditions diagnosed before death. We found no persuasive evidence that daily mortality increased when ambient air particles were elevated for subgroups of persons with chronic upper respiratory diseases, airways disease, cerebrovascular diseases, acute coronary artery disease, and hypertension. However, we found that daily mortality increased linearly as concentrations of particles increased for persons who had acute lower respiratory diseases, chronic coronary artery diseases (especially in the elderly), and congestive heart failure. For this latter set of conditions, the mean percent increase in daily mortality (MPC) for an increase in the COH across its interquartile range (18.5 COH units per 327.8 linear meters), averaged over the day of death and the 2 preceding days, was MPC = 5.09% [95% confidence interval (CI) 2.47-7.79%], MPC = 2.62 (95% CI 0.53-4.75%), and MPC = 4.99 (95% CI 2.44-7.60%), respectively. Adjustments for gaseous pollutants generally attenuated these associations, although the general pattern of increased daily mortality remained. In addition, there appeared to be a stronger association in the summer season. The positive associations found for persons who had acute lower respiratory diseases and congestive heart failure are consistent with some prevailing hypotheses and may also be consistent with recent toxicologic data implicating endothelins. Further epidemiologic studies are required to confirm these findings.

The association between daily mortality and ambient air particle pollution in Montreal, Quebec. 2. Cause-specific mortality

This study was undertaken to determine whether variations in concentrations of particulates in the ambient air of Montreal, Quebec, during the period 1984 to 1993, were associated with daily variations in cause-specific daily mortality. Fixed-site air pollution monitors in Montreal provided daily mean levels of various measures of particles and gaseous pollutants. Total sulfate was also measured daily (1986-1993) at a monitoring station 150 km southeast of the city (Sutton, Quebec). We used coefficient of haze (COH), extinction coefficient, and sulfate from the Sutton station to predict fine particles and sulfate from fine particles for days that were missing. We estimated associations between cause-specific mortality and PM(2.5), PM(10), predicted fine particles and fine sulfate particles, total suspended particles, coefficient of haze, extinction coefficient, and total sulfate measured at the Sutton station. We selected a set of underlying causes of death, as recorded on the death certificates, as the endpoint and then regressed the logarithm of daily counts of cause-specific mortality on the daily mean levels for the above measures of particulates, after accounting for seasonal and subseasonal fluctuations in the mortality time series, non-Poisson dispersion, weather variables, and gaseous pollutants. We found positive and statistically significant associations between the daily measures of ambient particle mass and sulfate mass and the deaths from respiratory diseases and diabetes. The mean percentage change in daily mortality (MPC), evaluated at the interquartile range for pollutants averaged over the day of death and the preceding 2 days, for deaths from respiratory diseases was MPC(COH)=6.90% (95% CI: 3.69-10.21%), MPC(Predicted PM2.5)= 9.03% (95% CI: 5.83- 12.33%), and MPC(Sutton sulfate)=4.64% (95% CI: 2.46-6.86%). For diabetes, the corresponding estimates were MPC(COH)=7.50% (95% CI: 1.96-13.34%), MPC(Predicted PM2.5)=7.59% (95% CI: 2.36-13.09%), and MPC(Sutton sulfate)=4.48% (95% CI: 1.08-7.99%). Among individuals older than 65 years at time of death, we found consistent associations across our metrics of particles for neoplasms and coronary artery diseases. Associations with sulfate mass were also found among elderly persons who died of cardiovascular diseases and of lung cancer. These associations were consistent with linear relationships. The associations found for respiratory diseases and for cardiovascular diseases, especially in the elderly, are in line with some of the current hypotheses regarding mechanisms by which ambient particles may increase daily mortality. The positive associations found for cancer and for diabetes may be understood through a general hypothesis proposed by Frank and Tankersley, who suggested that persons in failing health may be at higher risk for external insults through the failure of regulating physiological set points. The association with diabetes may be interpreted in light of recent toxicological findings that inhalation of urban particles in animals increases blood pressure and plasmatic levels of endothelins that enhance vasoconstriction and alter electrophysiology. Further research to confirm these findings and to determine whether they are causal is warranted.

Effects of air pollution on blood pressure: a population-based approach

OBJECTIVES

This analysis assessed the association between blood pressure, meteorology, and air pollution in a random population sample.

METHODS

Blood pressure measurements of 2607 men and women aged 25 to 64 years who participated in the Augsburg Monitoring of Trends and Determinants in Cardiovascular Disease survey were analyzed in association with 24-hour mean concentrations of air pollutants.

RESULTS

During the air pollution episode in Europe in January 1985, an association between blood pressure and air pollution was observed, which disappeared after adjustment for meteorology. Continuous concentrations of total suspended particulates and sulfur dioxide were associated with an increase in systolic blood pressure of 1.79 mm Hg (95% confidence interval [CI] = 0.63, 2.95) per 90 micrograms/m3 total suspended particulates and 0.74 mm Hg (95% CI = 0.08, 1.40) per 80 micrograms/m3 sulfur dioxide. In subgroups with high plasma viscosity levels and increased heart rates, systolic blood pressure increased by 6.93 mm Hg (95% CI = 4.31, 9.75) and 7.76 mm Hg (95% CI = 5.70, 9.82) in association with total suspended particulates.

CONCLUSIONS

The observed increase in systolic blood pressure associated with ambient air pollution could be related to a change in cardiovascular autonomic control.

Zinc is the toxic factor in the lung response to an atmospheric particulate sample

The atmospheric dust sample EHC-93 is known to induce lung cell injury and inflammation in which the toxicity has been attributed to a soluble component, possibly metal ions. To determine whether any specific metal is responsible for the pulmonary reactivity, various metal salts, at the concentration of metal present in the soluble fraction of EHC dust, have now been instilled into mouse lung. After 3 days, only a solution containing all metals tested and that of a zinc salt alone induced an increase in inflammatory cells and protein in lung lavage fluid. These two solutions also increased DNA synthesis in lung cells at this time, indicating a reparative response. Other solutions containing metals such as Cu, Fe, Al, Pb, Mg, or Ni induced no changes in the preceding measurements at the EHC dose level of metal. In a more extensive 28-day study, zinc salts induced rapid focal necrosis of Type 1 alveolar epithelial cells followed by inflammation and elevation of protein levels in lavage fluid over a 2-week period. Following the injury, epithelial cell proliferation increased and focal fibrosis was seen at 4 weeks. A solution containing all the other metals tested without the zinc component induced only minimal lung effects. When a zinc salt was administered at a 10x dose, the pulmonary changes were greatly enhanced, and after 4 weeks fibrosis could be measured biochemically. The results indicate that the acute toxicity associated with EHC atmospheric dust is most likely the result of the level of soluble zinc in this particulate sample. This suggests that a high soluble metal content of atmospheric dust, in this case the zinc level, may be a crucial factor in determining pulmonary cell reactivity to inhaled particulates.

The spontaneously hypertensive rat as a model of human cardiovascular disease: evidence of exacerbated cardiopulmonary injury and oxidative stress from inhaled emission particulate matter

Cardiovascular disease is considered a probable risk factor of particulate matter (PM)-related mortality and morbidity. It was hypothesized that rats with hereditary systemic hypertension and underlying cardiac disease would be more susceptible than healthy normotensive rats to pulmonary injury from inhaled residual oil fly ash (ROFA) PM. Eight spontaneously hypertensive (SH) and eight normotensive Wistar-Kyoto (WKY) rats (12-13 weeks old) were implanted with radiotelemetry transmitters on Day -10 for measurement of electrocardiographic (ECG) waveforms. These and other nonimplanted rats were exposed to filtered air or ROFA (containing leachable toxic levels of metals) on Day 0 by nose-only inhalation (ROFA, 15 mg/m(3) x 6 h/day x 3 days). ECGs were monitored during both exposure and nonexposure periods. At 0 or 18 h post-ROFA exposure, rats were assessed for airway hyperreactivity, pulmonary and cardiac histological lesions, bronchoalveolar lavage fluid (BALF) markers of lung injury, oxidative stress, and cytokine gene expression. Comparisons were made in two areas: (1) underlying cardiopulmonary complications of control SH rats in comparison to control WKY rats; and (2) ROFA-induced cardiopulmonary injury/inflammation and oxidative burden. With respect to the first area, control air-exposed SH rats had higher lung and left ventricular weights when compared to age-matched WKY rats. SH rats had hyporeactive airways to acetylcholine challenge. Lung histology revealed the presence of activated macrophages, neutrophils, and hemorrhage in control SHrats. Consistently, levels of BALF protein, macrophages, neutrophils, and red blood cells were also higher in SH rats. Thiobarbituric acid-reactive material in the BALF of air-exposed SH rats was significantly higher than that of WKY rats. Lung inflammation and lesions were mirrored in the higher basal levels of pulmonary cytokine mRNA expression. Cardiomyopathy and monocytic cell infiltration were apparent in the left ventricle of SH rats, along with increased cytokine expression. ECG demonstrated a depressed ST segment area in SH rats. With regard to the second area of comparison (ROFA-exposed rats), pulmonary histology indicated a slightly exacerbated pulmonary lesions including inflammatory response to ROFA in SH rats compared to WKY rats and ROFA-induced increases in BALF protein and albumin were significantly higher in SH rats than in WKY rats. In addition, ROFA caused an increase in BALF red blood cells in SH rats, indicating increased hemorrhage in the alveolar parenchyma. The number of alveolar macrophages increased more dramatically in SH rats following ROFA exposure, whereas neutrophils increased similarly in both strains. Despite greater pulmonary injury in SH rats, ROFA-induced increases in BALF GSH, ascorbate, and uric acid were attenuated when compared to WKY rats. ROFA inhalation exposure was associated with similar increases in pulmonary mRNA expression of IL-6, cellular fibronectin, and glucose-6-phosphate dehydrogenase (relative to that of beta-actin) in both rat strains. The expression of MIP-2 was increased in WKY but attenuated in SH rats. Thus, SH rats have underlying cardiac and pulmonary complications. When exposed to ROFA, SH rats exhibited exacerbated pulmonary injury, an attenuated antioxidant response, and acute depression in ST segment area of ECG, which is consistent with a greater susceptibility to adverse health effects of fugitive combustion PM. This study shows that the SH rat is a potentially useful model of genetically determined susceptibility with pulmonary and cardiovascular complications.

Acute exposure to diesel exhaust increases IL-8 and GRO-alpha production in healthy human airways

We have previously demonstrated that short-term exposure to diesel exhaust (DE) for 1 h induced a marked leukocytic infiltration in the airways of healthy human volunteers involving neutrophils, lymphocytes, and mast cells along with increases in several inflammatory mediators. We hypothesized that the leukocyte infiltration and the various inflammatory responses induced by DE were mediated by enhanced chemokine and cytokine production by resident cells of the airway tissue and lumen. To investigate this, 15 healthy human volunteers were exposed to diluted DE and air on two separate occasions for 1 h each in an exposure chamber. Fiberoptic bronchoscopy was performed 6 h after each exposure to obtain endobronchial biopsies and bronchial wash (BW) cells. Using reverse transcriptase/polymerase chain reaction enzyme-linked immunosorbent assay (RT-PCR ELISA), a novel and sensitive technique to quantify relative amounts of cytokine mRNA gene transcripts, and immunohistochemical staining with computer-assisted image analysis to quantify expression of cytokine protein in the bronchial tissue, we have demonstrated that DE enhanced gene transcription of interleukin-8 (IL-8) in the bronchial tissue and BW cells along with increases in IL-8 and growth-regulated oncogene-alpha (GRO-alpha) protein expression in the bronchial epithelium, and an accompanying trend toward an increase in IL-5 mRNA gene transcripts in the bronchial tissue. There were no significant changes in the gene transcript levels of interleukin-1B (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), interferon gamma (IFN-gamma), and granulocyte macrophage colony-stimulating factor (GM-CSF) either in the bronchial tissue or BW cells after DE exposure at this time point. These observations suggest an underlying mechanism for DE-induced airway leukocyte infiltration and offer a possible explanation for the association observed between ambient levels of particulate matter and various respiratory health outcome indices noted in epidemiological studies.

Cell injury and interstitial inflammation in rat lung after inhalation of ozone and urban particulates

Coexposure of the lung to urban dust along with ozone appears to potentiate ozone-induced injury. This conclusion was derived from whole-lung studies involving tissue and lavaged cells, but we now speculate that the injury and inflammatory response at the main site of reactivity, the bronchoalveolar duct region, is underestimated by such whole-lung studies. We exposed rats to ozone at 0.8 ppm and urban particulates (EHC93) at 50 mg/m3 for 4 h. Animals were killed 33 h later with tritiated thymidine (3HT) injected 1.5 h before death. Lungs were fixed by vascular perfusion to avoid disturbing any epithelial cell changes or local inflammation and edema in the air spaces. Tissue was embedded from central and peripheral areas of the lung, then counts of labeled cells, polymorphonuclear leukocytes (PMN), and macrophages (MAC) were made separately on methacrylate sections. The results showed that epithelial cell injury and regeneration (% of 3HT-labeled cells) was greatest in the ozone plus dust group, and was three times higher in periductal areas than in whole-lung counts. Although some increase in inflammatory cells in the air spaces was found in the coexposure group, much higher numbers of PMN and MAC were counted in the lung tissue compartment, and counts were significantly higher than those found after ozone or dust alone. Values from the latter groups were also higher than those from air controls or samples of distal lung taken from any inhalation group. The results demonstrate that inhalation of an urban dust at a level that causes few lung effects when inhaled alone can potentiate ozone toxicity, particularly in the vicinity of the alveolar duct, where the accumulation of interstitial inflammatory cells may be an important factor in the development of any subsequent pathologic changes.