Effects of subchronic exposures to concentrated ambient particles (CAPs) in mice. I. Introduction, objectives, and experimental plan

Seventy-five years of impactful environmental and occupational health research at the Nelson Institute of Environmental Medicine at New York University

Founded in 1947 as the Institute of Industrial Medicine, the Nelson Institute and Department of Environmental Medicine at New York University (NYU) Grossman School of Medicine (NYUGSOM) was supported by a National Institute of Environmental Health Science (NIEHS) Center Grant for over 56 years. Nelson Institute researchers generated 75 years of impactful research in environmental and occupational health, radiation effects, toxicology, and cancer. Environmental health research is continuing at NYUGSOM in its departments of medicine and population health. The objective of this historical commentary is to highlight the major achievements of the Nelson Institute and the department in the context of its history at facilities in Sterling Forest, Tuxedo, NY and Manhattan, NY. Aspects of our discussion include leadership, physical facilities, and research in many areas, including air pollution, health effects of environmental radiation exposures, inhalation toxicology methodology, carcinogenesis by chemicals, metals, and hormones, cancer chemoprevention, human microbiome, ecotoxicology, epidemiology, biostatistics, and community health concerns. The research of the institute and department benefited from unique facilities, strong leadership focused on team-based science, and outstanding investigators, students, and staff. A major lasting contribution has been the training of hundreds of graduate students and postdoctoral fellows, many of whom have been and are training the next generation of environmental and occupational health researchers at various institutions.

Gestational exposure to titanium dioxide, diesel exhaust, and concentrated urban air particles affects levels of specialized pro-resolving mediators in response to allergen in asthma-susceptible neonate lungs

Maternal gestational exposures to traffic and urban air pollutant particulates have been linked to increased risk and/or worsening asthma in children; however, mechanisms underlying this vertical transmission are not entirely understood. It was postulated that gestational particle exposure might affect the ability to elicit specialized proresolving mediator (SPM) responses upon allergen encounter in neonates. Lipidomic profiling of 50 SPMs was performed in lungs of neonates born to mice exposed to concentrated urban air particles (CAP), diesel exhaust particles (DEP), or less immunotoxic titanium dioxide particles (TiO2). While asthma-like phenotypes were induced with identical eosinophilia intensity across neonates of all particle-exposed mothers, levels of LXA4, HEPE and HETE isoforms, and HDoHe were only decreased by CAP and DEP only but not by TiO2. However, RvE2 and RvD1 were inhibited by all particles. In contrast, isomers of Maresin1 and Protectin D1 were variably elevated by CAP and DEP, whereas Protectin DX, PGE2, and TxB2 were increased in all groups. Only Protectin D1/DX, MaR1(n-3,DPA), 5(S),15(S)-DiHETE, PGE2, and RvE3 correlated with eosinophilia but the majority of other analytes, elevated or inhibited, showed no marked correlation with inflammation intensity. Evidence indicates that gestational particle exposure leads to both particle-specific and nonspecific effects on the SPM network.

The Role of Fossil Fuel Combustion Metals in PM2.5 Air Pollution Health Associations

In this review, we elucidate the central role played by fossil fuel combustion in the health-related effects that have been associated with inhalation of ambient fine particulate matter (PM2.5). We especially focus on individual properties and concentrations of metals commonly found in PM air pollution, as well as their sources and their adverse health effects, based on both epidemiologic and toxicological evidence. It is known that transition metals, such as Ni, V, Fe, and Cu, are highly capable of participating in redox reactions that produce oxidative stress. Therefore, particles that are enriched, per unit mass, in these metals, such as those from fossil fuel combustion, can have greater potential to produce health effects than other ambient particulate matter. Moreover, fossil fuel combustion particles also contain varying amounts of sulfur, and the acidic nature of the resulting sulfur compounds in particulate matter (e.g., as ammonium sulfate, ammonium bisulfate, or sulfuric acid) makes transition metals in particles more bioavailable, greatly enhancing the potential of fossil fuel combustion PM2.5 to cause oxidative stress and systemic health effects in the human body. In general, there is a need to further recognize particulate matter air pollution mass as a complex source-driven mixture, in order to more effectively quantify and regulate particle air pollution exposure health risks.

Use of micro-CT to determine tracheobronchial airway geometries in three strains of mice used in inhalation toxicology as disease models

Aerosol dosimetry estimates for mouse strains used as models for human disease are not available, primarily because of the lack of tracheobronchial airway morphometry data. By using micro-CT scans of in-situ prepared lung casts, tracheobronchial airway morphometry for four strains of mice were obtained: Balb/c, AJ, C57BL/6, and Apoe^-/- . The automated tracheobronchial airway morphometry algorithms for airway length and diameter were successfully verified against previously published manual and automated tracheobronchial airway morphometry data derived from two identical in-situ Balb/c mouse lung casts. There was also excellent agreement in tracheobronchial airway length and diameter between the automated and manual airway data for the AJ, C57BL/6, and Apoe^-/- mice. Differences in branch angle measurements were partially due to the differences in definition between the automated algorithms and manual morphometry techniques. Unlike the manual airway morphometry techniques, the automated algorithms were able to provide a value for inclination to gravity for each airway. Inclusion of an inclination to gravity angle for each airway along with airway length, diameter, and branch angle make the current automated tracheobronchial airway data suitable for use in dosimetry programs that can provide dosimetry estimates for inhaled material. The significant differences in upper tracheobronchial airways between Balb/c mice and between C57BL/6 and Apoe^-/- mice highlight the need for mouse strain-specific aerosol dosimetry estimates.

Particulate air pollution: major research methods and applications in animal models

Ambient air pollution is composed of a heterogeneous mixture of gaseous and solid particle compounds in which primary particles are emitted directly into the atmosphere, such as diesel soot, while secondary particles are created through physicochemical transformation. Particulate matter (PM), especially fine and ultrafine particles, can be inhaled and deposited in the alveolar cavities and penetrate into circulation. An association between high levels of air pollutants and human disease has been known for more than half a century and increasing evidences demonstrate a strong link between exposure on PM and the development of systemic diseases, such as cardiovascular and neurological disorders. Experimental animal models have been extensively used to study the underlying mechanism caused by environmental exposure to ambient PM. Due to their availability, quality, cost, and genetically modified strains, rodent models have been widely used. Some common exposure approaches include intranasal instillation, intratracheal instillation, nose-only inhalation, whole-body inhalation, and intravenous injection have been reviewed with brief summary of its performance, merit, limitation, and application. We hope this would provide useful reference in advancing experimental researches about air pollution human health and disease development.

Long-term particulate matter exposure: Attributing health effects to individual PM components

While most in the scientific community are of the opinion that the composition of fine particulate matter (PM2.5) is an important driver of resultant health effects, there is still some degree of uncertainty regarding those components considered to be most harmful. Reviews of the subject from several perspectives have been published, but to our knowledge a comprehensive review of the epidemiological and toxicological literature related to long-term exposure to PM2.5 components does not exist. We reviewed published epidemiological studies that were of a cohort design, included at least one PM component as well as PM2.5 mass, and included quantitative analysis to relate health outcomes to individual components. Toxicological studies were included if they were ≥5 months in duration and either included at least one PM component as well as PM mass or focused on a specific PM or emissions type. Overall, we find that epidemiological and toxicological evidence for long-term effects of PM components is limited, in contrast to the short-term literature, which is more plentiful. Epidemiological literature suggests that a number of components are associated with health effects, and that no component is unequivocally not so associated. Toxicological studies that can more easily identify potentially causal components are generally limited to long-term studies using concentrated ambient particles (CAPs), of which few long-term studies exist. Epidemiological study designs that utilize existing monitoring data routinely collected by the U.S. Environmental Protection Agency would be valuable additions to the literature, as would novel toxicological studies that incorporate innovative designs to separate components or groups of components, such as denuders, filtration, or other approaches. From a policy perspective, it is important to more comprehensively investigate this issue so that if particular constituents are determined to be more potent in inducing health effects, their sources can be controlled.

IMPLICATIONS

Understanding the components of PM2.5 that are most harmful to human health is a critical policy issue. This review examined the epidemiological and toxicological literature related to long-term exposure to PM components and found that, unlike the literature on short-term health effects, there is insufficient information to make clear inferences about causal components. There is a need for further research in this area to exploit existing PM monitoring data in epidemiological studies and to design experimental studies that are able to tease out the effects of multiple constituents.

Toxicological and epidemiological studies of cardiovascular effects of ambient air fine particulate matter (PM2.5) and its chemical components: coherence and public health implications

Recent investigations on PM2.5 constituents' effects in community residents have substantially enhanced our knowledge on the impacts of specific components, especially the HEI-sponsored National Particle Toxicity Component (NPACT) studies at NYU and UW-LRRI that addressed the impact of long-term PM2.5 exposure on cardiovascular disease (CVD) effects. NYU's mouse inhalation studies at five sites showed substantial variations in aortic plaque progression by geographic region that was coherent with the regional variation in annual IHD mortality in the ACS-II cohort, with both the human and mouse responses being primarily attributable to the coal combustion source category. The UW regressions of associations of CVD events and mortality in the WHI cohort, and of CIMT and CAC progression in the MESA cohort, indicated that [Formula: see text] had stronger associations with CVD-related human responses than OC, EC, or Si. The LRRI's mice had CVD-related biomarker responses to [Formula: see text]. NYU also identified components most closely associated with daily hospital admissions (OC, EC, Cu from traffic and Ni and V from residual oil). For daily mortality, they were from coal combustion ([Formula: see text], Se, and As). While the recent NPACT research on PM2.5 components that affect CVD has clearly filled some major knowledge gaps, and helped to define remaining uncertainties, much more knowledge is needed on the effects in other organ systems if we are to identify and characterize the most effective and efficient means for reducing the still considerable adverse health impacts of ambient air PM. More comprehensive speciation data are needed for better definition of human responses.

Alteration of cardiac function in ApoE-/- mice by subchronic urban and regional inhalation exposure to concentrated ambient PM2.5

Ambient PM(2.5) (particulate matter with an aerodynamic diameters of less than 2.5 mum) is associated with alterations in the autonomic nervous system and cardiac function, but there are significant response variations. The authors simultaneously studied the effects of concentrated PM(2.5) (CAPs) in Sterling Forest (SF; dominated by long-range transported PM) and at the Mount Sinai School of Medicine (MS; rich in Ni and elemental/organic carbon [EC/OC]) in Manhattan, NY. ApoE(-/-) mice (n = 8/group) were exposed to filtered air or CAPs (average 133 and 123 microg/m(3) in SF and MS, respectively) for 6 h/day, 5 days/week for 6 months. Electrocardiogram (ECG) tracings were monitored using telemetry. At MS, current day CAPs mass was negatively associated with short-term changes in heart rate (HR), and positively with HR variability (HRV). At SF, CAPs mass was positively associated with HR, and negatively with HRV. At MS, HR and HRV changes were associated with PM(2.5) components associated with residual oil combustion > long-range transport > traffic > FeMn > incineration > soil, and fireworks had no associations. At SF, HR and HRV were associated with long-range transport > Ni refinery > soil > residual oil combustion/traffic. At both sites, there were cardiac function associations with PM(2.5), but not EC. At MS, there were associations with Ni and P, whereas at SF, they were with a mixture of long-range transported PM, crustal material, and combustion products. Thus subchronic CAPs exposures at locations with different particle compositions produced different effects on cardiac function in ApoE(-/-) mice.

Oxidant generation capacity of source-apportioned PM2.5

While many studies found associations between ambient particulate matter (PM) and morbidity or mortality outcomes, it is unclear whether these associations were dependent on the composition of PM, which varies with the source of that PM. We address this knowledge gap by conducting a time-series PM-health effects assessment that specifically investigates the role of source-apportioned fine PM (PM2.5) on the oxidant generation capacity that might be responsible for respiratory and cardiovascular health outcomes. Daily PM2.5 composition speciation and black carbon (BC) measurements, conducted in rural New York for 303 days between March 2003 and January 2005, were analyzed using factor analysis source-apportionment model, and five source categories (transported aerosol/secondary sulfate, resuspended soil, metals, residual oil combustion, and industrial/incineration) were identified. After the exposure of human epithelial cells (BEAS-2B) to these PM2.5 samples, cellular nuclear factor-κB (NF-κB) activation showed a relatively significant association Ni (concentration averaging 38 ng/m(3)), and weaker but still significant correlations with Ba (13 ng/m(3)), Mn (9 ng/m(3)), and Fe (500 ng/m(3)). The single-source regression analysis of NF-κB signal showed significant association with metal source only. Our results showed that metals in PM2.5 were the important source for cellular oxidant generation and may be responsible for subsequent health effects associate with particle air pollution.

Residual oil combustion: 2. Distributions of airborne nickel and vanadium within New York City

In an earlier paper based on PM(2.5) speciation network data, we showed that nickel (Ni) concentrations were much higher in New York City (NYC) than in New Jersey (NJ) and Connecticut (CT), and that the NYC levels, but not those in NJ and CT, were much higher in the winter than in summer. However, all of the speciation sites in NYC were in the northern half of the city. To determine the distributions of Ni and other PM(2.5) components within NYC, we collected 8-weeklong filter samples at 10 sites throughout NYC in both winter and summer, and measured the concentrations of the elements by X-ray fluorescence (XRF). The resulting data, together with speciation network site data, were used to construct seasonal average concentration isopleth maps for Ni and vanadium (V). As expected, Ni was much higher in Bronx than in Brooklyn, and much higher in winter than in summer. By contrast, V was higher in Brooklyn than in Bronx, and the winter and summer levels were similar. It appears that space-heating boilers are the major source category for Ni in NYC, whereas the Port of New York is the major source of V.

Particulate matter (PM) research centers (1999-2005) and the role of interdisciplinary center-based research

OBJECTIVE

The U.S. Environmental Protection Agency funded five academic centers in 1999 to address the uncertainties in exposure, toxicity, and health effects of airborne particulate matter (PM) identified in the "Research Priorities for Airborne Particulate Matter" of the National Research Council (NRC). The centers were structured to promote interdisciplinary approaches to address research priorities of the NRC. In this report, we present selected accomplishments from the first 6 years of the PM Centers, with a focus on the advantages afforded by the interdisciplinary, center-based research approach. The review highlights advances in the area of ultrafine particles and traffic-related health effects as well as cardiovascular and respiratory effects, mechanisms, susceptibility, and PM exposure and characterization issues.

DATA SOURCES AND SYNTHESIS

The collective publications of the centers served as the data source. To provide a concise synthesis of overall findings, authors representing each of the five centers identified a limited number of topic areas that serve to illustrate the key accomplishments of the PM Centers program, and a consensus statement was developed.

CONCLUSIONS

The PM Centers program has effectively applied interdisciplinary research approaches to advance PM science.

Effects of Subchronic Exposures to Concentrated Ambient Particles in Mice: IX. Integral Assessment and Human Health Implications of Subchronic Exposures of Mice to CAPs

In order to examine the biologic plausibility of adverse chronic cardiopulmonary effects in humans associated with ambient particulate matter (PM) exposure, we exposed groups of normal mice (C57) and knockout mice that develop atherosclerotic plaque (ApoE-/- and ApoE-/- LDLr-/-) for 6 h/day, 5 days/wk for 5 or 6 mo during the spring/summer of 2003 to either filtered air or 10-fold concentrated ambient particles (CAPs) in Tuxedo, NY (average PM2.5 concentration during exposure = 110 microg/m3). Some of the mice had implanted electrocardiographic monitors. We demonstrated that: (1) this complex interdisciplinary study was technically feasible in terms of daily exposure, collection of air quality monitoring data, the collection, analysis, and interpretation of continuous data on cardiac function, and the collection and analyses of tissues of the animals sacrificed at the end of the study; (2) the daily variations in CAPs were significantly associated, in ApoE-/- mice, with daily variations in cardiac functions; (3) there were significant differences between CAPs and sham-exposed ApoE-/- mice in terms of cardiac function after the end of exposure period, as well as small differences in atherosclerotic plaque density, coronary artery disease, and cell density in the substantia nigra in the brain in the ApoE-/- mice; (4) there are suggestive indications of gene expression changes for genes associated with the control of circadian rhythm in the ApoE-/- LDLr-/- double knockout (DK) mice. These various CAPs-related effects on cardiac function and the development of histological evidence of increased risk of clinically significant disease at the end of exposures in animal models of atherosclerosis provide biological plausibility for the premature mortality associated with PM2.5 exposure in human subjects and provide suggestive evidence for neurogenic disease as well.

Effects of Subchronic Exposures to Concentrated Ambient Particles (CAPs) in Mice: II. The Design of a CAPs Exposure System for Biometric Telemetry Monitoring

We modified, assembled, tested, and validated the versatile aerosol concentration enrichment system (VACES) developed by Sioutas et al. (1999) for use in a subchronic experiment that involved exposure of mice in vivo and of respiratory epithelial cells in vitro to concentrated ambient particles (CAPs). Since the labor-intensive nose-only exposure regimen is not an option in a long-term experiment, a whole-body exposure mouse chamber was designed specifically for use with the VACES. The exposure system concsists of a stainless-steel (SS) tub with 32 cubicles (1 mouse per cubicle) separated by perforated SS sheets. The tops of these cubicles are covered with perforated plastic sheets to allow telemetry monitoring during the exposure. In each exposure chamber, perforated aluminum tubes are used to distribute CAPs evenly (within 2% difference) throughout the exposure chamber. The exhaust consists of perforated aluminum tubes covered with a urine shield. The modification to the original design of the VACES facilitated the operation of the system in a subchronic study. Mass flow controllers maintain a constant flow rate into the exposure chambers. For a sham control exposure, the identical system is used, except that a HEPA filter at the inlet to the VACES removes 98% of ambient particles. The entire system allow for simultaneous exposure of 64 mice to CAPs, with an equal number of sham-expose mice as controls. Telemetry receives have been modified so that 16 mice per group with electrocardiograph (EKG) transmitters can be monitored during exposure. Furthermore, a BioSampler is used to collect CAPs (one sample per day) for the in vitro exposures. In this article, the assessments of flow and particle distribution of the exposure chamber as well as the performance of the system during the subchronic exposure experiment are described.

Cardiovascular effects of nickel in ambient air

BACKGROUND

Fine particulate matter (FPM) in ambient air causes premature mortality due to cardiac disease in susceptible populations.

OBJECTIVE

Our objective in this study was to determine the most influential FPM components.

METHODS

A mouse model of atherosclerosis (ApoE-/-) was exposed to either filtered air or concentrated FPM (CAPs) in Tuxedo, New York (85 microg/m3 average, 6 hr/day, 5 days/week, for 6 months), and the FPM elemental composition was determined for each day. We also examined associations between PM components and mortality for two population studies: National Mortality and Morbidity Air Pollution Study (NMMAPS) and Hong Kong.

RESULTS

For the CAPs-exposed mice, the average of nickel was 43 ng/m3, but on 14 days, there were Ni peaks at approximately 175 ng/m3 and unusually low FPM and vanadium. For those days, back-trajectory analyses identified a remote Ni point source. Electrocardiographic measurements on CAPs-exposed and sham-exposed mice showed Ni to be significantly associated with acute changes in heart rate and its variability. In NMMAPS, daily mortality rates in the 60 cities with recent speciation data were significantly associated with average Ni and V, but not with other measured species. Also, the Hong Kong sulfur intervention produced sharp drops in sulfur dioxide, Ni, and V, but not other components, corresponding to the intervention-related reduction in cardiovascular and pulmonary mortality.

CONCLUSIONS

Known biological mechanisms cannot account for the significant associations between Ni with the acute cardiac function changes in the mice or with cardiovascular mortality in people at low ambient air concentrations; therefore, further research is needed.

Translocation and potential neurological effects of fine and ultrafine particles a critical update

Particulate air pollution has been associated with respiratory and cardiovascular disease. Evidence for cardiovascular and neurodegenerative effects of ambient particles was reviewed as part of a workshop. The purpose of this critical update is to summarize the evidence presented for the mechanisms involved in the translocation of particles from the lung to other organs and to highlight the potential of particles to cause neurodegenerative effects.

Fine and ultrafine particles, after deposition on the surfactant film at the air-liquid interface, are displaced by surface forces exerted on them by surfactant film and may then interact with primary target cells upon this displacement. Ultrafine and fine particles can then penetrate through the different tissue compartments of the lungs and eventually reach the capillaries and circulating cells or constituents, e.g. erythrocytes. These particles are then translocated by the circulation to other organs including the liver, the spleen, the kidneys, the heart and the brain, where they may be deposited. It remains to be shown by which mechanisms ultrafine particles penetrate through pulmonary tissue and enter capillaries. In addition to translocation of ultrafine particles through the tissue, fine and coarse particles may be phagocytized by macrophages and dendritic cells which may carry the particles to lymph nodes in the lung or to those closely associated with the lungs. There is the potential for neurodegenerative consequence of particle entry to the brain. Histological evidence of neurodegeneration has been reported in both canine and human brains exposed to high ambient PM levels, suggesting the potential for neurotoxic consequences of PM-CNS entry. PM mediated damage may be caused by the oxidative stress pathway. Thus, oxidative stress due to nutrition, age, genetics among others may increase the susceptibility for neurodegenerative diseases. The relationship between PM exposure and CNS degeneration can also be detected under controlled experimental conditions. Transgenic mice (Apo E -/-), known to have high base line levels of oxidative stress, were exposed by inhalation to well characterized, concentrated ambient air pollution. Morphometric analysis of the CNS indicated unequivocally that the brain is a critical target for PM exposure and implicated oxidative stress as a predisposing factor that links PM exposure and susceptibility to neurodegeneration.

Together, these data present evidence for potential translocation of ambient particles on organs distant from the lung and the neurodegenerative consequences of exposure to air pollutants.

Activation of the stress axis and neurochemical alterations in specific brain areas by concentrated ambient particle exposure with concomitant allergic airway disease

OBJECTIVE

Exposure to ambient particulate matter (PM) has been linked to respiratory diseases in people living in urban communities. The mechanism by which PM produces these diseases is not clear. We hypothesized that PM could act on the brain directly to stimulate the stress axis and predispose individuals to these diseases. The purpose of this study was to test if exposure to PM can affect brain areas involved in the regulation of neuroendocrine functions, especially the stress axis, and to study whether the presence of preexisting allergic airway disease aggravates the stress response.

DESIGN

Adult male rats (n = 8/group) with or without ovalbumin (OVA)-induced allergic airway disease were exposed to concentrated air particles containing PM with an aerodynamic diameter pound 2.5 microm (PM(2.5)) for 8 hr, generated from ambient air in an urban Grand Rapids, Michigan, community using a mobile air research laboratory (AirCARE 1). Control animals were exposed to normal air and were treated with saline.

MEASUREMENTS

A day after PM(2.5) exposure, animals were sacrificed and the brains were removed, frozen, and sectioned. The paraventricular nucleus (PVN) and other brain nuclei were microdissected, and the concentrations of aminergic neurotransmitters and their metabolites were measured using high-performance liquid chromatography with electrochemical detection. Serum corticosterone levels were measured using radioimmunoassay.

RESULTS

A significant increase in the concentration (mean +/- SE, pg/microg protein) of norepinephrine in the PVN was produced by exposure to concentrated ambient particles (CAPs) or OVA alone (12.45 +/- 2.7 and 15.84 +/- 2.8, respectively) or after sensitization with OVA (19.06 +/- 3.8) compared with controls (7.98 +/- 1.3 ; p < 0.05). Serum corticosterone (mean +/- SE, ng/mL) was significantly elevated in the OVA + CAPs group (242.786 +/- 33.315) and in the OVA-presensitized group (242.786 +/- 33.315) compared with CAP exposure alone (114.55 +/- 20.9). Exposure to CAPs (alone or in combination with OVA pretreatment) can activate the stress axis, and this could probably play a role in aggravating allergic airway disease.

Response of spontaneously hypertensive rats to inhalation of fine and ultrafine particles from traffic: experimental controlled study

BACKGROUND

Many epidemiological studies have shown that mass concentrations of ambient particulate matter (PM) are associated with adverse health effects in the human population. Since PM is still a very crude measure, this experimental study has explored the role of two distinct size fractions: ultrafine (<0.15 microm) and fine (0.15- 2.5 microm) PM. In a series of 2-day inhalation studies, spontaneously hypersensitive (SH) rats were exposed to fine, concentrated, ambient PM (fCAP) at a city background location or a combination of ultrafine and fine (u+fCAP) PM at a location dominated by traffic. We examined the effect on inflammation and both pathological and haematological indicators as markers of pulmonary and cardiovascular injury. Exposure concentrations ranged from 399 microg/m3 to 3613 microg/m3 for fCAP and from 269 microg/m3 to 556 microg/m3 for u+fCAP.

RESULTS

Ammonium, nitrate, and sulphate ions accounted for 56 +/- 16% of the total fCAP mass concentrations, but only 17 +/- 6% of the u+fCAP mass concentrations. Unambiguous particle uptake in alveolar macrophages was only seen after u+fCAP exposures. Neither fCAP nor u+fCAP induced significant changes of cytotoxicity or inflammation in the lung. However, markers of oxidative stress (heme oxygenase-1 and malondialdehyde) were affected by both fCAP and u+fCAP exposure, although not always significantly. Additional analysis revealed heme oxygenase-1 (HO-1) levels that followed a nonmonotonic function with an optimum at around 600 microg/m3 for fCAP. As a systemic response, exposure to u+fCAP and fCAP resulted in significant decreases of the white blood cell concentrations.

CONCLUSION

Minor pulmonary and systemic effects are observed after both fine and ultrafine + fine PM exposure. These effects do not linearly correlate with the CAP mass. A greater component of traffic CAP and/or a larger proportion ultrafine PM does not strengthen the absolute effects.

PM source apportionment for short-term cardiac function changes in ApoE-/- mice

Daily rates of cardiovascular mortality and morbidity are have been associated with daily variations in fine particulate matter (aerodynamic diameter < or = 2.5 microm, PM2.5), but little is known about the influences of the individual source-related PM2.5 categories or the temporal lags for the effects. We investigated heart rate (HR) and HR variability (HRV) data collected during a 5-month study involving 6 hr/day, 5 day/week exposures of normal (C57) mice and a murine model for atherosclerotic disease (ApoE-/-) in Sterling Forest (Tuxedo, New York, USA). The mice were exposed to concentrated ambient particles (PM2.5 concentrated 10-fold, producing an average of 113 microg/m3). Daily 6-hr PM2.5 air samples were analyzed by X-ray fluorescence, permitting attribution to major PM source categories [secondary sulfate (SS), resuspended soil (RS), residual oil (RO) combustion, and other, largely due to motor vehicle traffic]. We examined associations between these PM2.5 components and both HR and HRV for three different daily time periods: during exposure, the afternoon after exposure, and late at night. For HR there were significant transient associations for RS during exposure, and for SS in the afternoon after exposure. For HRV, there were comparable associations with RO in the afternoon after exposure and for both SS and RS late at night. The biologic bases for these associations and their temporal lags are not known but may be related to the differential solubility of the biologically active PM components at the respiratory epithelia and their access to cells that release mediators that reach the cardiovascular system. Clearly, further research to elucidate the underlying processes is needed.

Effects of subchronic exposures to concentrated ambient particles (CAPs) in mice. IV. Characterization of acute and chronic effects of ambient air fine particulate matter exposures on heart-rate variability

Long-term exposure to fine particulate air pollution (PM2.5) has been associated increased risk of death from cardiopulmonary diseases. Cardiac function parameters have also been affected by ambient particulate matter (PM) exposure, including heart-rate variability (HRV), a measure of autonomic function that has been recognized as a well-defined, quantitative indicator of autonomic dysfunction. However, the role of HRV in ambient PM-induced cardiovascular effect is not fully understood. In an accompanying article, we report significant decreasing patterns of heart rate (HR), body temperature, and physical activity for mice lacking apoliproprotein (ApoE-/-) over 5 mo of exposure to concentrated ambient PM (CAPs), with smaller and nonsignificant change for C57 mice. In this article, we report the effects of subchronic CAPs exposure on HRV parameters that are sensitive to cardiac sympathetic and parasympathetic nerve activity. The standard deviation of normal to normal beat intervals (SDNN) and the square root of the mean squared differences of successive RR intervals (RMSSD) in the late afternoon and overnight for the ApoE-/- mice showed a gradual increase for the first 6 wk, a decline for about 12 more wk, and a slight turn upward at the end of the study period. For C57 mice, there were no chronic effect changes of SDNN or RMSSD in the late afternoon, an a slight increase after 6 wk for the overnight period. The response patterns of ApoE-/- mice indicated a perturbation of the homeostatic function in the cardiovascular system (initial enhancement and late depression of the HRV parameters). Our results complement the findings in human panel and controlled CAPs exposure studies in demonstrating that increased levels of particle pollution are able to perturb cardiac autonomic function, which may lead to adverse cardiovascular outcomes.

Effects of subchronic exposures to concentrated ambient particles (CAPs) in mice. VI. Gene expression in heart and lung tissue

The purpose of this exploratory study within the integrated subchronic inhalation exposure study (Lippmann et al., 2005) was to identify genes in heart and lung tissue that changed in expression level as a result of subchronic exposure to concentrated ambient particles (CAPs). Identification of CAPs exposure-related changes in gene expression could serve in the formulation of mechanistic hypotheses and/or to suggest possible biomarkers of exposure. In this exploratory study undertaken here, tissues from multiple replicates of ApoE/low-density-lipoprotein double knockout (DK) mice were examined for relative exposure-related changes in gene expression. Due to limited resources, the number of replicates was three for each tissue (lung and heart) of each exposure condition (CAPs or air control). A rigorous comparison of exposure versus control data using the "significance analysis of microarrays" (SAM) method indicated that only one gene was differentially expressed at a significant level. However, when using a less restrictive, nonstatistical analytical treatment of the data, several genes that might be involved in PM-related heart or lung pathology, and/or the circadian rhythm of physiological processes, were identified. A more comprehensive study is required to mre definitively assess differences in gene expression in heart and lung resulting from exposure to CAPs.

Effects of subchronic exposures to concentrated ambient particles (CAPs) in mice. III. Acute and chronic effects of CAPs on heart rate, heart-rate fluctuation, and body temperature

Normal mice (C57) and mice prone to develop atherosclerosis (ApoE-/-) were implanted with electrocardiograph (EKG), core body temperature, and motion transmitters were exposed daily for 6 h to Tuxedo, NY, concentrated ambient particles (CAPs) for 5 day/wk during the spring and summer of 2003. The series of 5-min EKG monitoring and body-temperature measurements were obtained for each animal in the CAPs and filtered air sham exposure groups. Our hypothesis was that chronic exposure could cause cumulative health effects. We used our recently developed nonparametric method to estimate the daily time periods that mean heart rates (HR), body temperature, and physical activity differed significantly between the CAPs and sham exposed group. CAPs exposure most affected heart rate between 1:30 a.m. and 4:30 a.m. With the response variables being the average heart rate, body temperature, and physical activity, we adopted a two-stage modeling approach to obtain the estimates of chronic and acute effects on the changes of these three response variables. In the first stage, a time-varying model estimated daily crude effects. In the second stage, the true means of the estimated crude effects were modeled with a polynominal function of time for chronic effects, a linear term of daily CAPs exposure concentrations for acute effects, and a random component for unknown noise. A Bayesian framework combined these two stages. There were significant decreasing patterns of HR, body temperature, and physical activity for the ApoE-/- mice over the 5 mo of CAPs exposure, with smaller and nonsignificant changes for the C57 mice. The chronic effect changes of the three response variables for ApoE-/- mice were maximal in the last few weeks. There was also a significant relationship between CAPs exposure concentration and short-term changes of heart rate in ApoE-/- mice during exposure. Response variables were also defined for examining fluctuations of 5-min heart rates within long (i.e., 3-6 h) and short time periods (i.e., approximately 15 min). The results for the ApoE-/- mice showed that heart-rate fluctuation within the longer periods increased to 1.35-fold by the end of exposure experiment, while the heart-rate fluctuation within 15 min decreased to 0.7-fold.

Effects of subchronic exposures to concentrated ambient particles (CAPs) in mice. VIII. Source-related daily variations in in vitro responses to CAPs

The NYU PM Center subchronic animal inhalation study addressed the issues of composition and sources of ambient fine particulate matter (PM2.5), as well as the relationship of these PM2.5 characteristics to the cellular response of human bronchial epithelial cells. In this simultaneous study, we used an in vitro exposure technique to compare the daily variations of the responses of cells to fine concentrated ambient particles (CAPs) collected from a rural area upwind of New York City for the period of 9 a.m. to 3 p.m. on weekdays only, March-September, 2003. Chemical composition data for CAPs were modeled using factor analysis with varimax orthogonal rotation to determine four particle source categories contributing significant amount of mass to CAPs at Sterling Forest (Tuxedo, NY). These source categories are: (1) regional secondary sulfate characterized by high S, Si, and organic carbon (OC); (2) resuspended soil characterized by high concentrations of Ca, Fe, Al, and Si; (3) oil-fired power plants emissions of the eastern United States identified by presence of V, Ni, and Se; and (4) unknown other sources. To estimate the mass contributions of each individual source category, the CAPs mass concentration was regressed against the factor scores. Regional sulfate was the largest contributor to mass (65%), followed by soil (20%), residual oil combustion (2%), and the other sources contributing 13%. Based on an evaluation of the cellular responses to CAPs and a detailed chemical characterization of the ambient PM2.5, we investigated the sources and individual components of ambient PM2.5 that are responsible for the induced cellular response. Nuclear Factor kappa B (NF-kappa B) was selected as a monitor of cellular stress response that followed after the exposure to CAPs. The results of the NF-kappa B assay were found to be most highly correlated with Ni and V among the individual components, and with the residual oil combustion source category.