Development and Evaluation of a Prototype Ambient Particle Concentrator for Inhalation Exposure Studies

Serum-borne factors alter cerebrovascular endothelial microRNA expression following particulate matter exposure near an abandoned uranium mine on the Navajo Nation

Background

Commercial uranium mining on the Navajo Nation has subjected communities on tribal lands in the Southwestern United States to exposures from residual environmental contamination. Vascular health effects from these ongoing exposures are an active area of study. There is an association between residential mine-site proximity and circulating biomarkers in residents, however, the contribution of mine-site derived wind-blown dusts on vascular and other health outcomes is unknown. To assess neurovascular effects of mine-site derived dusts, we exposed mice using a novel exposure paradigm, the AirCARE1 mobile inhalation laboratory, located 2 km from an abandoned uranium mine, Claim 28 in Blue Gap Tachee, AZ. Mice were exposed to filtered air (FA) (n = 6) or concentrated ambient particulate matter (CAPs) (n = 5) for 2 wks for 4 h per day.

Results

To assess miRNA differential expression in cultured mouse cerebrovascular cells following particulate matter (PM) exposure (average: 96.6 ± 60.4 μg/m³ for all 4 h exposures), the serum cumulative inflammatory potential (SCIP) assay was employed. MiRNA sequencing was then performed in cultured mouse cerebrovascular endothelial cells (mCECs) to evaluate transcriptional changes. Results indicated 27 highly differentially expressed (p < 0.01) murine miRNAs, as measured in the SCIP assay. Gene ontology (GO) pathway analysis revealed notable alterations in GO enrichment related to the cytoplasm, protein binding and the cytosol, while significant KEGG pathways involved pathways in cancer, axon guidance and Wnt signaling. Expression of these 27 identified, differentially expressed murine miRNAs were then evaluated in the serum. Nine of these miRNAs (~ 30%) were significantly altered in the serum and 8 of those miRNAs demonstrated the same directional change (either upregulation or downregulation) as cellular miRNAs, as measured in the SCIP assay. Significantly upregulated miRNAs in the CAPs exposure group included miRNAs in the let-7a family. Overexpression of mmu-let-7a via transfection experiments, suggested that this miRNA may mediate mCEC barrier integrity following dust exposure.

Conclusions

Our data suggest that mCEC miRNAs as measured in the SCIP assay show similarity to serum-borne miRNAs, as approximately 30% of highly differentially expressed cellular miRNAs in the SCIP assay were also found in the serum. While translocation of miRNAs via exosomes or an alternative mechanism is certainly possible, other yet-to-be-identified factors in the serum may be responsible for significant miRNA differential expression in endothelium following inhaled exposures. Additionally, the most highly upregulated murine miRNAs in the CAPs exposure group were in the let-7a family. These miRNAs play a prominent role in cell growth and differentiation and based on our transfection experiments, mmu-let-7a may contribute to cerebrovascular mCEC alterations following inhaled dust exposure.

Development of a novel aerosol generation system for conducting inhalation exposures to ambient particulate matter (PM)

In this study, we developed a novel method for generating aerosols that are representative of real-world ambient particulate matter (PM) in terms of both physical and chemical characteristics, with the ultimate objective of using them for inhalation exposure studies. The protocol included collection of ambient PM on filters using a high-volume sampler, which were then extracted with ultrapure Milli-Q water using vortexing and sonication. As an alternative approach for collection, ambient particles were directly captured into aqueous slurry samples using the versatile aerosol concentration enrichment system (VACES)/aerosol-into-liquid collector tandem technology. The aqueous samples from both collection protocols were then re-aerosolized using commercially available nebulizers. The physical characteristics (i.e., particle size distribution) of the generated aerosols were examined by the means of a scanning mobility particle sizer (SMPS) connected to a condensation particle counter (CPC) at different compressed air pressures of the nebulizer, and dilution air flow rates. In addition, the collected PM samples (both ambient and re-aerosolized) were chemically analyzed for water-soluble organic carbon (WSOC), elemental and organic carbon (EC/OC), inorganic ions, polycyclic aromatic hydrocarbons (PAHs), and metals and trace elements. Using the aqueous filter extracts, we were able to effectively recover the water-soluble components of ambient PM (e.g., water-soluble organic matter, and water-soluble inorganic ions); however, this method was deficient in recovering some of the important insoluble components such as EC, PAHs, and many of the redox-active trace elements and metals. In contrast, using the VACES/aerosol-into-liquid collector tandem technology for collecting ambient PM directly into water slurry, we were able to preserve the water-soluble and water-insoluble components very effectively. These results illustrate the superiority of the VACES/aerosol-into liquid collector tandem technology to be used in conjunction with the re-aerosolization setup to create aerosols that fully represent ambient PM, making it an attractive choice for application in inhalation exposure studies.

A cross-disciplinary evaluation of evidence for multipollutant effects on cardiovascular disease

BACKGROUND

The current single-pollutant approach to regulating ambient air pollutants is effective at protecting public health, but efficiencies may be gained by addressing issues in a multipollutant context since multiple pollutants often have common sources and individuals are exposed to more than one pollutant at a time.

OBJECTIVE

We performed a cross-disciplinary review of the effects of multipollutant exposures on cardiovascular effects.

METHODS

A broad literature search for references including at least two criteria air pollutants (particulate matter [PM], ozone [O₃], oxides of nitrogen, sulfur oxides, carbon monoxide) was conducted. References were culled based on scientific discipline then searched for terms related to cardiovascular disease. Most multipollutant epidemiologic and experimental (i.e., controlled human exposure, animal toxicology) studies examined PM and O₃ together.

DISCUSSION

Epidemiologic and experimental studies provide some evidence for O₃ concentration modifying the effect of PM, although PM did not modify O₃ risk estimates. Experimental studies of combined exposure to PM and O₃ provided evidence for additivity, synergism, and/or antagonism depending on the specific health endpoint. Evidence for other pollutant pairs was more limited.

CONCLUSIONS

Overall, the evidence for multipollutant effects was often heterogeneous, and the limited number of studies inhibited making a conclusion about the nature of the relationship between pollutant combinations and cardiovascular disease.

Altered heart rate variability in spontaneously hypertensive rats is associated with specific particulate matter components in Detroit, Michigan

BACKGROUND

Exposure to fine particulate matter [aerodynamic diameter ≤ 2.5 μm (PM2.5)] is linked to adverse cardiopulmonary health effects; however, the responsible constituents are not well defined.

OBJECTIVE

We used a rat model to investigate linkages between cardiac effects of concentrated ambient particle (CAP) constituents and source factors using a unique, highly time-resolved data set.

METHODS

Spontaneously hypertensive rats inhaled Detroit Michigan, CAPs during summer or winter (2005-2006) for 13 consecutive days. Electrocardiogram data were recorded continuously, and heart rate (HR) and heart rate variability (HRV) metrics were derived. Extensive CAP characterization, including use of a Semicontinuous Elements in Aerosol Sampler (SEAS), was performed, and positive matrix factorization was applied to investigate source factors.

RESULTS

Mean CAP exposure concentrations were 518 μg/m(3) and 357 μg/m(3) in the summer and winter, respectively. Significant reductions in the standard deviation of the normal-to-normal intervals (SDNN) in the summer were strongly associated with cement/lime, iron/steel, and gasoline/diesel factors, whereas associations with the sludge factor and components were less consistent. In winter, increases in HR were associated with a refinery factor and its components. CAP-associated HR decreases in winter were linked to sludge incineration, cement/lime, and coal/secondary sulfate factors and most of their associated components. Specific relationships for increased root mean square of the standard deviation of successive normal-to-normal intervals (RMSSD) in winter were difficult to determine because of lack of consistency between factors and associated constituents.

CONCLUSIONS

Our results indicate that specific modulation of cardiac function in Detroit was most strongly linked to local industrial sources. Findings also highlight the need to consider both factor analytical results and component-specific results when interpreting findings.

Cardiopulmonary responses in spontaneously hypertensive and Wistar-Kyoto rats exposed to concentrated ambient particles from Detroit, Michigan

Toxicological effects have been observed in rats exposed to concentrated ambient particles (CAPs) from different regions of the United States. The objective of this study was to evaluate the cardiopulmonary and systemic effects of CAPs in Detroit. The authors stationed a mobile concentrator at a location near major traffic and industrial sources. Spontaneously hypertensive (SH) and Wistar-Kyoto (WKY) rats were exposed to fine CAPs (diameter < 0.1-2.5 microm) 8 h/day for 13 consecutive days. Animals were implanted with telemeters, and electrocardiogram data were recorded continuously. Bronchoalveolar lavage (BAL) fluid and plasma were analyzed. Comprehensive exposure monitoring was conducted, including CAPs components. CAPs exposure concentrations were 103-918 microg/m(3) (mean = 502 microg/m(3)). The authors found no statistically significant differences in heart rate or SDNN (standard deviation of the normal-to-normal intervals), a measure of heart rate variability, between CAPs-exposed and control rats. The authors found significantly higher levels of C-reactive protein in the serum of CAPs-exposed SH rats compared with air-exposed animals. Protein in BAL fluid was elevated in WKY rats exposed to CAPs. Measurement of trace metals in lung tissue showed elevated concentrations of V, Sb, La, and Ce in CAPs-exposed SH animals versus controls. These elements are generally associated with oil combustion, oil refining, waste incineration, and traffic. Examination of wind rose data from the exposure period confirmed that the predominant wind direction was SSW, the direction of many of the aforementioned sources. These results indicate that ambient particles in Detroit can cause mild pulmonary and systemic changes in rats, and suggest the importance of local PM(2.5) sources in these effects.

Chronic social stress and susceptibility to concentrated ambient fine particles in rats

BACKGROUND

Epidemiologic evidence suggests that chronic stress may alter susceptibility to air pollution. However, persistent spatial confounding between these exposures may limit the utility of epidemiologic methods to disentangle these effects and cannot identify physiologic mechanisms for potential differential susceptibilities.

OBJECTIVES

Using a rat model of social stress, we compared respiratory responses to fine concentrated ambient particles (CAPs) and examined biological markers of inflammation.

METHODS

Twenty-four 12-week-old male Sprague-Dawley rats were randomly assigned to four groups [stress/CAPs, stress/filtered air (FA), nonstress/CAPs, nonstress/FA]. Stress-group animals were individually introduced into the home cage of a dominant male twice weekly. Blood drawn at sacrifice was analyzed for immune and inflammatory markers. CAPs were generated using the Harvard ambient particle concentrator, which draws real-time urban ambient fine particles, enriching concentrations approximately 30 times. CAPs/FA exposures were delivered in single-animal plethysmographs, 5 hr/day for 10 days, and respiratory function was continuously monitored using a Buxco system.

RESULTS

Stressed animals displayed higher average C-reactive protein, tumor necrosis factor-alpha, and white blood cell counts than did nonstressed animals. Only among stressed animals were CAPs exposures associated with increased respiratory frequency, lower flows, and lower volumes, suggesting a rapid, shallow breathing pattern. Conversely, in animals with elevated CAPs exposures alone, we observed increased inspiratory flows and greater minute volumes (volume of air inhaled or exhaled per minute).

CONCLUSIONS

CAPs effects on respiratory measures differed significantly, and substantively, by stress group. Higher CAPs exposures were associated with a rapid, shallow breathing pattern only under chronic stress. Blood measures provided evidence of inflammatory responses. Results support epidemiologic findings that chronic stress may alter respiratory response to air pollution and may help elucidate pathways for differential susceptibility.

Exposures of Elderly Volunteers with and without Chronic Obstructive Pulmonary Disease (COPD) to Concentrated Ambient Fine Particulate Pollution

The elderly and individuals who have chronic obstructive pulmonary disease (COPD) may be sensitive to particulate matter (PM) air pollution. We evaluated short-term health responses of 13 elderly volunteers with COPD and 6 age-matched healthy adults to controlled exposures of ambient PM pollution in suburban Los Angeles. Using a Harvard particle concentrator and a whole-body chamber, we exposed each person on separate occasions to approximately 200 microg/m(3) concentrated ambient particles (CAP) less than 2.5 mum in diameter and to filtered air (FA). Each exposure lasted 2 h with intermittent mild exercise. We found no significant effects of CAP on symptoms, spirometry, or induced sputum. A significant negative effect of CAP on arterial oxygenation (measured by pulse oximetry) immediately postexposure was more pronounced in healthy subjects. Peripheral blood basophils increased after CAP in healthy but not in COPD subjects. In both groups, red cell counts increased slightly 1 day after exposure to FA but not to CAP. Preexposure ectopic heartbeats were infrequent in healthy subjects, but increased modestly during/after CAP exposure relative to FA. Ectopic beats were more frequent in COPD subjects, but decreased modestly during/after CAP relative to FA. Heart-rate variability over multi-hour intervals was lower after CAP than after FA in healthy elderly subjects but not in COPD subjects. Thus, in this initial small-scale study of older volunteers experimentally exposed to ambient PM, some acute cardiopulmonary responses were consistent with effects reported from epidemiologic studies. Unexpectedly, individuals with COPD appeared less susceptible than healthy elderly individuals. Further investigation of older adults is warranted to understand the pathophysiology and public health significance of these findings.

Exposure to Concentrated Ambient Particles (CAPs): A Review

Epidemiologic studies support a participation of fine particulate matter (PM) with a diameter of 0.1 to 2.5 microm in the effects of air pollution particles on human health. The ambient fine particle concentrator is a recently developed technology that can enrich the mass of ambient fine particles in real time with little modification. The advantages of concentrators are that the particles produced are "real world" and they allow exposure at pertinent masses. Limitations include variability in both particle mass and composition and some uncertainty over the best statistical approach to analyze the data. Cumulative evidence provided by the body of initial investigation shows that exposures to concentrated ambient particles (CAPs) can be accomplished safely in both humans and animals. Human investigation using the CAPs has shown acute lung inflammation and changes in both blood indices and heart rate variability. Animal studies support a potential pulmonary inflammation, blood changes, alterations of specific cardiac endpoints, and an increased susceptibility of specific models. These studies have helped establish the causal relationship between find particle exposure and adverse health effects in the lung and cardiovascular system. In addition, it appears that specific components in CAPS may differentially affect these tissues.

A single-particle characterization of a mobile Versatile Aerosol Concentration Enrichment System for exposure studies

BACKGROUND

An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to investigate the size and chemical composition of fine concentrated ambient particles (CAPs) in the size range 0.2-2.6 microm produced by a Versatile Aerosol Concentration Enrichment System (VACES) contained within the Mobile Ambient Particle Concentrator Exposure Laboratory (MAPCEL). The data were collected during a study of human exposure to CAPs, in Edinburgh (UK), in February-March 2004. The air flow prior to, and post, concentration in the VACES was sampled in turn into the ATOFMS, which provides simultaneous size and positive and negative mass spectral data on individual fine particles.

RESULTS

The particle size distribution was unaltered by the concentrator over the size range 0.2-2.6 microm, with an average enrichment factor during this study of approximately 5 (after dilution of the final air stream). The mass spectra from single particles were objectively grouped into 20 clusters using the multivariate K-means algorithm and then further grouped manually, according to similarity in composition and time sequence, into 8 main clusters. The particle ensemble was dominated by pure and reacted sea salt and other coarse inorganic dusts (as a consequence of the prevailing maritime-source climatology during the study), with relatively minor contributions from carbonaceous and secondary material. Very minor variations in particle composition were noted pre- and post-particle concentration, but overall there was no evidence of any significant change in particle composition.

CONCLUSION

These results confirm, via single particle analysis, the preservation of the size distribution and chemical composition of fine ambient PM in the size range 0.2-2.6 microm after passage through the VACES concentration instrumentation.

Exposure to concentrated ambient air particles alters hematologic indices in humans

Descriptions of changes in hematological indices have contested the premise that the biological effects of suspended particulate matter (PM) are restricted to the lung. Employing approximately 40 hematologic parameters reflecting blood cells, chemistries, mediators, and coagulation factors, we tested the hypothesis that exposure to concentrated ambient air particles (CAPs) can be associated with changes in hematologic indices in normal humans. Twenty healthy young volunteers were exposed to either filtered air (n = 5) or CAPs (n = 15) with a mean PM mass of 120.5 +/- 14.0 microg/m3 and a range from 15.0-357.6 microg/m3. Hematologic indices were measured. Changes in all parameters are expressed as the absolute value either immediately after or 24 h after exposure. Differences between responses of those individuals exposed to filtered air and CAPs were tested using the T-test of independent means. If significant differences between the two groups were suggested by the T-test (p < .10), the relationship was further evaluated employing linear regression techniques. Regression analysis verified significant linear relationships between particle mass the individual was exposed to and (1) decrements in WBC count 24 h later, (2) decreases in lactate dehydrogenase (LDH) concentration 24 h later, and (3) elevations in fibrinogen levels 24 h later. There were no changes in either inflammatory mediators in the blood or indices of coagulation/fibrinolysis other than fibrinogen. We conclude that exposure of healthy volunteers to CAPs can be associated with decreases of both white blood cell (WBC) count and LDH and increased concentrations of fibrinogen in the blood.

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.

On-line analysis of urban particulate matter focusing on elevated wintertime aerosol concentrations

A 10-day winter sampling campaign was conducted in downtown Toronto for particulate matter (PM) air pollution in the fine (<2.5 microm) size range. An aerosol laser ablation mass spectrometer (LAMS), a tapered-element oscillating microbalance (TEOM), and an aerodynamic particle sizer (APS) were operated in parallel to characterize the PM on-line. In this study, the LAMS observed differences in the chemical composition between three separate episodes with higher PM2.5 mass and APS counts. LAMS results showed that in one instance of elevated PM, organic amines were present in the particulates. Temporal analyses of this episode revealed chemical transformations as the amines, characterized by m/z peaks 58(C3HeN)+, 86(C5H2N)+, and nitrates, increased in number concentration while Ca and hydrocarbon particle classes concurrently decreased. On another day, sulfates were found to have increased significantly. The third event was only 4 h in duration and exhibited an increase in the number of submicron-sized K/hydrocarbons and sulfate-containing particles. In this last event, the hydrocarbons and a K to Fe ratio enrichment indicated there was likely a contribution from a combustion source. This work offers some of the first insights into single particle size and chemistry in a cold winter climate.

Insoluble components of concentrated air particles mediate alveolar macrophage responses in vitro

We sought to characterize the bioactive constituents of concentrated ambient air particles (CAPs) through correlation of alveolar macrophage (AM) biological responses (production of TNF, macrophage inflammatory protein (MIP-2), nitrite; cell viability) to components of particle samples. CAPs samples collected on different days showed a range of bioactivity and a strong correlation was found between AM cytokine release and increased AM light scatter, a flow cytometric measure of relative particle load. Evaluation of soluble and insoluble fractions of CAPs suspensions indicate that 1) most biological effects on AMs are mediated by insoluble components and certain particle adsorbed factors such as endotoxin; 2) the variable bioactivity of CAPs collected on different days arises primarily from differences in the relative proportion of insoluble and soluble mass present in particle suspensions; and 3) the activation state of the AM influences which insoluble components are most bioactive. Use of endotoxin neutralizing agents (e.g., polymyxin-B) showed particle-adsorbed endotoxin in CAPs suspensions causes activation of normal (control) AMs while other (nonendotoxin) components are predominantly responsible for the enhanced cytokine release observed by primed AMs incubated with CAPs. The AM biological response did not correlate with any of a panel of elements quantified within insoluble CAPs samples (Al, Cd, Cr, Cu, Fe, Mg, Mn, Ni, S, Ti, V). These data demonstrate an important role for cell activation and phagocytosis of insoluble particulate matter in the response of AMs to CAPs suspensions.

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.

Effects of environmental aerosols on airway hyperresponsiveness in a murine model of asthma

Increased morbidity in persons suffering from inflammatory lung diseases, such as asthma and bronchitis, has been associated with air pollution particles. One hypothesis is that particles can cause an amplification of the pulmonary inflammation associated with these diseases, thus worsening affected individuals' symptoms. This hypothesis was tested in a murine model of asthma by inhalation exposure to (1) concentrated air particles (CAPs), (2) the leachate of residual oil fly ash (ROFA-S), and (3) lipopolysaccharide (LPS). Allergen-sensitized mice (ip ovalbumin, OVA) were 21 days old when challenged with an aerosol of 3% OVA in phosphate-buffered saline (PBS) for 10 min (controls were challenged with PBS only) for 3 days. On the same days, mice were further exposed to 1 of 3 additional agents: CAPs (or filtered air) for 6 h/day; LPS (5 microg/ml, or PBS) for 10 min/day; or ROFA-S (leachate of 50 mg/ml, or PBS) for 30 min on day 2 only. At 24 h later, mice challenged with OVA aerosol showed airway inflammation and airway hyperresponsiveness (AHR) to methacholine (Mch), features absent in mice challenged with PBS alone. Both OVA- and PBS-challenged mice subsequently exposed to ROFA-S showed increased AHR to Mch when compared to their respective controls (OVA only or PBS only). In contrast, when OVA-challenged mice were further exposed to CAPs or LPS, no changes in AHR were seen in comparison to mice challenged with OVA only. Bronchoalveolar lavage (BAL) analysis and histopathology 48 h postexposure showed OVA-induced allergic inflammation. No significant additional effects were caused by CAPs or ROFA-S. LPS, in contrast, caused significant increases in total cell, macrophage, and polymorphonuclear cell numbers. The data highlight discordance between airway inflammation and hyperresponsiveness.

Air pollution and asthma

Asthma is a disease syndrome that has captured a great deal of attention for several years. One of the perplexing aspects to asthma is that the prevalence is increasing in most industrialized countries. The reasons for this widespread increase are largely unknown. Another aspect of industrialization is the persistence of air pollution in urban areas. Because much air pollution is due to vehicles, no solution appears in sight. The topic of this article is the association between air pollution and various signs and symptoms of asthma. Air pollution is convincingly associated with many signs of asthma aggravation. These include pulmonary function decrements, increased bronchial hyperresponsiveness, visits to emergency departments, hospital admissions, increased medication use and symptom reporting, inflammatory changes, interactions between air pollution and allergen challenges, and immune system changes. With the exception of exposure to environmental tobacco smoke, common air pollutants have not been shown to cause asthma. It seems prudent for clinicians to counsel their patients about the potential risks of asthma aggravation from common outdoor air pollutants.

Lipopolysaccharide priming amplifies lung macrophage tumor necrosis factor production in response to air particles

Elevated concentrations of ambient air particles can result in increased mortality and morbidity, especially in people with preexisting pulmonary disease. We postulate that in the inflammatory milieu of diseased lungs, alveolar macrophages (AMs) may be primed for enhanced responses to stimuli such as inhaled air particles. To test this hypothesis in vitro, we first cultured normal AMs with or without lipopolysaccharide (LPS). We then incubated the cells with particle suspensions (urban air particles (UAP, Washington, D.C.), residual oil fly ash (ROFA), concentrated respirable-size (PM2.5) air particles (CAPs), and inert TiO2) and compared rat and human AM production of the critical proinflammatory mediator, tumor necrosis factor (TNF). LPS priming amplified TNF production by both rat and human AMs in response to UAP and CAPs but not inert TiO2. There were also differences observed between rat and human AM responses to particle suspensions. Striking changes seen only in rat were cytotoxic effects of ROFA and diminished particle uptake in response to LPS priming. The potency of CAPs samples (which are collected on separate days) varied when comparing one day's sample with another. When centrifuged, the majority of bioactivity seen in particle suspensions (TNF release) remained within the pelleted fraction while the supernatant showed minimal bioactivity. The data suggest that AMs activated by extant pulmonary inflammation may promote further inflammation by an enhanced cytokine response to inhaled ambient air particles.

Particulate air pollution and asthma: a review of epidemiological and biological studies

The link between exposure to air pollution and exacerbation of asthma symptoms has been investigated by epidemiological study and by direct biological experimentation. In asthmatics, epidemiological studies generally show a positive correlation between the particulate fraction of air pollution and increased morbidity, although roles for other co-pollutants (for example, ozone) are implicated as well. Direct experimentation using air pollutants, especially particles, to investigate their effects on humans or on animal models of asthma provides corroboration of the epidemiology and has begun to identify the pathophysiological mechanisms involved. We begin this review with an overview of air pollution, followed by a survey of the epidemiological and experimental data regarding air pollution particles and asthma. We finish with a discussion of directions for future research.

Lung epithelial cell (A549) interaction with unopsonized environmental particulates: quantitation of particle-specific binding and IL-8 production

The A549 cell line was used to model in vitro the interaction of alveolar epithelium with environmental particulates. Confocal and electron microscopy demonstrated A549 binding and internalization of titanium dioxide (TiO2), iron oxide (Fe2O3), concentrated ambient air particulates (CAPs), and the fibrogenic particle alpha-quartz. Flow cytometry allowed quantitation of particle binding by measuring increased right angle light scatter (RAS) (TiO2) [40 micrograms/mL], Fe2O3 [100 micrograms/mL], alpha-quartz [200 micrograms/mL], or CAPs [40 micrograms/mL] fold increase RAS: 8.1 +/- 0.9, 4.3 +/- 0.4, 2 +/- 0.1, 1.6 +/- 0.1, respectively). With this quantitative assay, binding of particle was found to be calcium-dependent for TiO2 and Fe2O3 (% inhibition, 61.0 +/- 1.9, 40.0 +/- 5.6, respectively), while alpha-quartz binding was calcium-independent. A panel of polyanionic ligands known to inhibit scavenger-type receptors was used to identify binding mechanisms for environmental particulates. Both heparin and polyinosinic acid (polyI), but not the control polyanion chondroitin sulfate, caused marked inhibition of particulate binding by A549 cells (e.g., TiO2 [40 micrograms/mL] binding; polyI, heparin, and chondroitin sulfate: 73.8 +/- 3.5, 75.5 +/- 6.0, 7.5 +/- 6.7% inhibition, respectively; mean +/- SE, n > or = 4), indicating that scavenger receptor(s), albeit those distinct from the heparin-insensitive acetylated-LDL receptor, mediate particulate binding. The particulates ability to stimulate interleukin (IL-8) production in A549 cells was also tested. alpha-quartz, but not TiO2 or CAPs, caused a dose-dependent production of IL-8 (range 1-6 ng/mL), demonstrating a particle-specific spectrum of epithelial cell cytokine (IL-8) response. The results suggest that lung epithelial cell interaction with environmental particles is mediated by distinct receptors and can lead to particle dependent cytokine responses.