Differential gene expression associated with inflammation and blood pressure regulation induced by concentrated ambient particle exposure

Epidemiological studies have indicated that exposure to particle matter (PM) increased the risk of respiratory and cardiovascular morbidity and mortality. It is suggested that PM smaller than 2.5 μm in aerodynamic diameter (PM(2.5)) may contribute to these responses. However, the molecular mechanism is still unknown. To elucidate the changes in molecular level, we investigated the gene expression profile of concentrated ambient particles (CAPs)-exposed rats. Aged F344 rats were exposed with CAPs (594 μg/m(3)) or clean air 4 h per day for 3 days, and lung and heart tissues were then excised for DNA microarray analysis. Expression profiles related to inflammation and blood pressure regulation revealed differential expression of 7 genes in the lung and that of 3 genes in the heart ventricle. According to the complement activation-associated genes, complement factor B (Bf), complement component 2 and 4a (C4a), and C1 inhibitor genes were up-regulated in CAPs-exposed rat lung. Bf and C4a genes were also up-regulated in the heart. These suggest the treated animal ready for production of these proteins when activation of complement cascade is required. Pro-inflammatory cytokine, interleukin-1β, was also up-regulated in CAPs-exposed rat lung. Gene related with blood pressure regulation (angiotensin I converting enzyme) was also up-regulated in CAPs-exposed rat lung. Negative regulator of blood pressure (neuropeptide Y) was down-regulated in CAPs-exposed rat heart. These results indicate that CAPs may affect respiratory and cardiovascular organs by activation of inflammatory responses and disintegration of blood pressure regulation in early stage of CAPs exposure.     

Seasonal influences on CAPs exposures: differential responses in platelet activation,serum cytokines and xenobiotic gene expression

Increasing evidence suggests a role for a systemic pro-coagulant state in the pathogenesis of cardiac dysfunction subsequent to inhalation of airborne particulate matter (PM). We evaluated platelet activation, systemic cytokines and pulmonary gene expression in mice exposed to concentrated ambient particulate matter (CAPs) in the summer of 2008 (S08) and winter of 2009 (W09) from the San Joaquin Valley of California, a region with severe PM pollution episodes. Additionally, we characterized the PM from both exposures including organic compounds, metals, and polycyclic aromatic hydrocarbons. Mice were exposed to an average of 39.01 μg/m³ of CAPs in the winter and 21.7 μg/m3 CAPs in the summer, in a size range less than 2.5 μm for 6?h/day for 5 days per week for 2 weeks. Platelets were analyzed by flow cytometry for relative size, shape, CD41, P-selectin and lysosomal associated membrane protein-1 (LAMP-1) expression. Platelets from W09 CAPs-exposed animals had a greater response to thrombin stimulation than platelets from S08 CAPs-exposed animals. Serum cytokines were analyzed by bead based immunologic assays. W09 CAPs-exposed mice had elevations in IL-2, MIP-1α, and TNFα. Laser capture microdissection (LCM) of pulmonary vasculature, parenchyma and airways all showed increases in CYP1a1 gene expression. Pulmonary vasculature showed increased expression of ICAM-1 and Nox-2. Our findings demonstrate that W09 CAPs exposure generated a greater systemic pro-inflammatory and pro-coagulant response to inhalation of environmentally derived fine and ultrafine PM. Changes in platelet responsiveness to agonists, seen in both exposures, strongly suggests a role for platelet activation in the cardiovascular and respiratory effects of particulate air pollution.     

Exposure of mice to concentrated ambient particulate matter results in platelet and systemic cytokine activation

Increasingly, evidence suggests a role for a systemic procoagulant state in the pathogenesis of cardiac dysfunction subsequent to inhalation of airborne particulate matter. The authors evaluated blood cell parameters and markers of platelet activation in mice exposed to concentrated ambient particulate matter (CAPs) from the San Joaquin Valley of California, a region with severe particulate matter (PM) pollution episodes. The authors exposed mice to an average of 88.5 μg/m³ of CAPs in a size range less than 2.5 μm for 6?h/day for 5 days per week for 2 weeks. Platelets were analyzed by flow cytometry for relative size, shape, aggregation, fibrinogen binding, P-selectin, and lysosomal-associated membrane protein-1 (LAMP-1) expression. Serum cytokines were analyzed by bead-based immunologic assays. CAPs-exposed mice had elevations in macrophage inflammatory protein (MIP)-1α, MIP-1β, interleukin (IL)-6, IL-10, tumor necrosis factor alpha (TNFα), macrophage colony-stimulating factor (M-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), platelet-derived growth factor (PDGF)-bb, and RANTES (regulated upon activation, normally T-expressed, and presumably secreted). Platelets were the only peripheral blood cells that were significantly elevated in number in CAPs-exposed mice. Flow cytometric analysis of unstimulated platelets from CAPs-exposed mice indicated size and shape changes, and platelets from CAPs-exposed animals had a 54% increase in fibrinogen binding indicative of platelet priming. Stimulation of platelets by thrombin resulted in up-regulation of LAMP-1 expression in CAPs-exposed animals and an increased microparticle population relative to control animals. These findings demonstrate a systemic proinflammatory and procoagulant response to inhalation of environmentally derived fine and ultrafine PM and suggests a role for platelet activation in the cardiovascular and respiratory effects of particulate air pollution.     

Seasonal influences on CAPs exposures: differential responses in platelet activation, serum cytokines and xenobiotic gene expression

Increasing evidence suggests a role for a systemic pro-coagulant state in the pathogenesis of cardiac dysfunction subsequent to inhalation of airborne particulate matter (PM). We evaluated platelet activation, systemic cytokines and pulmonary gene expression in mice exposed to concentrated ambient particulate matter (CAPs) in the summer of 2008 (S08) and winter of 2009 (W09) from the San Joaquin Valley of California, a region with severe PM pollution episodes. Additionally, we characterized the PM from both exposures including organic compounds, metals, and polycyclic aromatic hydrocarbons. Mice were exposed to an average of 39.01 μg/m(3) of CAPs in the winter and 21.7 μg/m3 CAPs in the summer, in a size range less than 2.5 μm for 6 h/day for 5 days per week for 2 weeks. Platelets were analyzed by flow cytometry for relative size, shape, CD41, P-selectin and lysosomal associated membrane protein-1 (LAMP-1) expression. Platelets from W09 CAPs-exposed animals had a greater response to thrombin stimulation than platelets from S08 CAPs-exposed animals. Serum cytokines were analyzed by bead based immunologic assays. W09 CAPs-exposed mice had elevations in IL-2, MIP-1α, and TNFα. Laser capture microdissection (LCM) of pulmonary vasculature, parenchyma and airways all showed increases in CYP1a1 gene expression. Pulmonary vasculature showed increased expression of ICAM-1 and Nox-2. Our findings demonstrate that W09 CAPs exposure generated a greater systemic pro-inflammatory and pro-coagulant response to inhalation of environmentally derived fine and ultrafine PM. Changes in platelet responsiveness to agonists, seen in both exposures, strongly suggests a role for platelet activation in the cardiovascular and respiratory effects of particulate air pollution.     

Examination of mRNA expression in rat hearts and lungs for analysis of effects of exposure to concentrated ambient particles on cardiovascular function

Epidemiological studies have suggested that fine particulate matter (f-PM) is associated with adverse effects on cardiovascular health. However, these effects on the cardiovascular system have not yet been fully elucidated. Using mRNA expression and correlation analyses, we designed the present study to elucidate (1) translocation of chemicals in inhaled f-PM to the heart, (2) induction of oxidative stress, one of the causes of cardiovascular diseases (CVDs), (3) mRNA expression related to CVDs, and (4) correlations among mRNA expression of various molecules and cardiovascular function. Wistar Kyoto male rats were exposed to concentrated ambient particles (CAPs, 0.6-1.5mg/m3) in Yokohama for 4 days (4.5h/day) or to filtered air for 3 days and CAPs for 1 day or to filtered air for 4 days. Messenger RNA expression and cardiovascular function were measured after the 4-day exposure. In samples of heart tissue, the mRNAs of cytochrome P450 (CYP) 1B1, a biomarker of exposure to chemicals; heme oxygenase-1 (HO-1), a marker of oxidative stress; and endothelin A (ET A) receptor, a receptor of vasoconstrictors, were up-regulated by CAPs; their levels were significantly correlated with the cumulative weight of CAPs in the exposure chamber. The up-regulation of ET A receptor mRNA was significantly correlated with the increase in HO-1 mRNA and weakly with the increase in mean blood pressure (Delta MBP). These results suggest the possibility that chemicals in CAPs might be translocated to the heart, where they induce oxidative stress and activate endothelin signaling, resulting in an increase in the blood pressure. The exposure to f-PM might thus affect cardiovascular function through activation of endothelin signaling.     

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?μm) 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?μg/m³ (mean?=?502?μg/m³). 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.     

Variable pulmonary responses from exposure to concentrated ambient air particles in a rat model of bronchitis.

Chronic bronchitis may be considered a risk factor in particulate matter (PM)-induced morbidity. We hypothesized that a rat model of human bronchitis would be more susceptible to the pulmonary effects of concentrated ambient particles (CAPs) from Research Triangle Park, NC. Bronchitis was induced in male Sprague-Dawley rats (90-100 days of age) by exposure to 200 ppm sulfur dioxide (SO2), 6 h/day x 5 days/week x 6 weeks. One day following the last SO2 exposure, both healthy (air-exposed) and bronchitic (SO2-exposed) rats were exposed to filtered air (three healthy; four bronchitic) or CAPs (five healthy; four bronchitic) by whole-body inhalation, 6 h/day x 2 or 3 days. Pulmonary injury was determined either immediately (0h) or 18 h following final CAPs exposure. The study protocol involving 0 h time point was repeated four times (study #A, November, 1997; #B, February, 1998; #C and #D, May, 1998), whereas the study protocol involving 18 h time point was done only once (#F). In an additional study (#E), rats were exposed to residual oil fly ash (ROFA), approximately 1 mg/ m(3)x6 h/day x 3 days to mimic the CAPs protocol (February, 1998). The rats allowed 18 h recovery following CAPs exposure (#F) did not depict any CAPs-related differences in bronchoalveolar lavage fluid (BALF) injury markers. Of the four CAPs studies conducted (0 h time point), the first (#A) study (approximately 650 microg/m3 CAPs) revealed significant changes in the lungs of CAPs-exposed bronchitic rats compared to the clean air controls. These rats had increased BALF protein, albumin, N-acetyl glutaminidase (NAG) activity and neutrophils. The second (#B) study (approximately 475 microg/m3 CAPs) did not reveal any significant effects of CAPs on BALF parameters. Study protocols #C (approximately 869 microg/m3 CAPs) and #D (approximately 907 microg/m3 CAPs) revealed only moderate increases in the above mentioned BALF parameters in bronchitic rats exposed to CAPs. Pulmonary histologic evaluation of studies #A, #C, #D, and #F revealed marginally higher congestion and perivascular cellularity in CAPs-exposed bronchitic rats. Healthy and bronchitic rats exposed to ROFA (approximately 1 mg/m3) did not show significant pulmonary injury (#E). Analysis of leachable elemental components of CAPs revealed the presence of sulfur, zinc, manganese, and iron. There was an apparent lack of association between pulmonary injury and CAPs concentration, or its leachable sulfate or elemental content. In summary, real-time atmospheric PM may result in pulmonary injury, particularly in susceptible models. However, the variability observed in pulmonary responses to CAPs emphasizes the need to conduct repeated studies, perhaps in relation to the season, as composition of CAPs may vary. Additionally, potential variability in pathology of induced bronchitis or other lung disease may decrease the ability to distinguish toxic injury due to PM.     

N-acetylcysteine prevents lung inflammation after short-term inhalation exposure to concentrated ambient particles.

Lung inflammation is a key response to increased levels of particulate air pollution (PM); however, the cellular mechanisms leading to this response are poorly understood. To determine whether oxidants are implicated in PM-dependent lung inflammation, we tested the ability of N-acetylcysteine (NAC) to prevent lung inflammation in a rat model of short-term exposure to concentrated ambient particles (CAPs). Adult Sprague-Dawley rats were exposed to either CAPs aerosols (CAPs mass concentration 1060 +/- 300 microg/m(3)) or filtered air (Sham controls) for 5 h. NAC-treated rats received 50 mg/kg (ip) NAC 1 h prior to exposure to CAPs. Oxidative stress and recruitment of inflammatory cells into bronchoalveolar lavage were evaluated 24 h after removal of the animals from the exposure chamber. Rats breathing CAPs aerosols showed significant oxidative stress, determined by the accumulation of thiobarbituric reactive substances (TBARS, 90 +/- 15 pmol/mg protein; sham control: 50 +/- 5 pmol/mg protein, p < 0.02) and oxidized proteins (1.6 +/- 0.4 nmol/mg protein, sham: 0.70 +/- 0.02 nmol/mg protein, p < 0.01) in their lungs. CAPs-induced oxidative stress was associated with increased numbers of polymorphonuclear leukocytes in bronchoalveolar lavage (BAL) (9 +/- 2%; sham: 1.6 +/- 0.5%, p < 0.001) and slight lung edema (wet/dry ratio: 4.77 +/- 0.03, sham: 4.69 +/- 0.02). No significant change was found in BAL protein concentration, total cell count, or lactate dehydrogenase (LDH) activity. NAC pretreatment effectively prevented CAPs-induced TBARS accumulation (30 +/- 10 pmol/mg protein, p < 0.006), lung edema (4.64 +/- 0.08, p < 0.05), and polymorphonuclear neutrophil (PMN) influx into the lungs (2.1 +/- 0.5%, p < 0.001), but did not alter the protein carbonyl content. Histological evaluation of tissue samples confirmed the BAL findings. CAPs-exposed animals showed slight bronchiolar inflammation and thickened vessels at the bronchiole, whereas NAC treated animals showed no histological alterations. Regression analyses showed strong associations between increased TBARS accumulation and the CAPs content of Al, Si, and Fe, and trends of association between carbonyl content and Cr and Na concentrations, and between BAL PMN count and Cr, Zn, and Na. These data demonstrate that oxidants are critical mediators of the inflammatory response elicited by PM inhalation.     

Inhalation of concentrated particulate matter produces pulmonary inflammation and systemic biological effects in compromised rats

Although significant progress has been made over the past few years, there is still debate on the causal fractions that are responsible for particulate matter (PM)-associated adverse health effects. A series of 1-d inhalation exposures to concentrated ambient particles (CAPs) were performed in compromised rats, focusing on pulmonary inflammation and changes in blood factors as biological outcomes. Studies were carried out in The Netherlands at an urban background location in Bilthoven, an industrialized location in the city of Utrecht, as well as at a location that is heavily dominated by freeway emissions. It was hypothesized that exposure to CAPs resulted in oxidative stress in the lung, producing a release of inflammatory mediators, which in turn can result in cardiovascular effects. Both spontaneously hypertensive rats and rats preexposed to ozone were studied. The effects were studied at 2d postexposure, focusing on pathology and cell proliferation, bronchoalveolar lavage fluid (BALF) analysis (including cytokines, biochemistry, cell differentials, cell viability and proliferation, and Clara-cell 16 protein), and blood analyses (fibrinogen, Clara-cell 16 protein, Von Willebrand factor, and cell differentials). Using CAPs exposures as a binary term, mild inflammation (increased numbers of neutrophils) and increased lung permeability (protein and albumin leakage in BALF) were evident. In addition, CAPs also produced increased fibrinogen concentrations in blood of spontaneously hypertensive rats. In conclusion, inhalation up to 3700 microg/m3 CAPs in the size range of 0.15-2.5 microm did induce statistically significant effects in the lung and blood, but the effects observed may not potentially be very biologically relevant. PM mass concentrations and lung permeability were weakly associated. This suggests that other PM metrics might be more appropriate.     

Pulmonary retention of particulate matter is associated with airway inflammation in allergic rats exposed to air pollution in urban Detroit

A collaborative research study was conducted in order to improve our understanding of the source-to-receptor pathway for ambient fine particulate matter (aerodynamic diameter < or = 2.5 mu m; PM2.5) and subsequently to investigate the identity and sources of toxic components in PM2.5 responsible for adverse health effects in allergic humans. This research used a Harvard fine particle concentrator to expose Brown Norway rats, with and without ovalbumin-induced allergic airway disease, to concentrated air particles (CAPs) generated from ambient air in an urban Detroit community where the pediatric asthma rate was three times higher than the national average. Rats were exposed to CAPs during the exposure periods in July (mean = 676 microg/m3) and September (313 microg/m3) of 2000. Twenty-four hours after exposures lung lobes were either lavaged with saline to determine cellularity and protein in bronchoalveolar lavage fluid (BALF), or removed for analysis by inductively coupled plasma-mass spectrometry (ICP-MS) to detect ambient PM2.5-derived trace element retention. PM2.5 trace elements of anthropogenic origin, lanthanum (La), vanadium (V), manganese (Mn), and sulfur (S), were recovered from the lung tissues of CAPs-exposed rats. Recovery of those pulmonary anthropogenic particles was further increased in rats with allergic airways. In addition, eosinophils and protein in BALF were increased only in allergic animals exposed to CAPs. These results demonstrate preferential retention in allergic airways of air particulates derived from identified local combustion sources after a short-term exposure. Our findings suggest that the enhancement of allergic airway responses by exposure to PM2.5 is mediated in part by increased pulmonary deposition and localization of potentially toxic elements in urban air.     

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: IV. Characterization of Acute and Chronic Effects of Ambient Air Fine Particulate Matter Exposures on Heart-Rate Variability

Abstract

Long-term exposure to fine particulate air pollution (PM_2.5) has been associated with 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 effects 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 changes 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, and 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 later 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.     

Cardiac Oxidative Stress and Electrophysiological Changes in Rats Exposed to Concentrated Ambient Particles are Mediated by TRP-Dependent Pulmonary Reflexes

Previous studies suggest that, through the stimulation of pulmonarynervous endings, ambient particles modulate the autonomic toneon the heart leading to cardiac oxidant stress and dysfunction.In this paper we investigated the effect of blockade of vanilloidreceptor 1 (Transient Receptor Potential Vanilloid Receptor1 [TRPV1]) on concentrated ambient particles (CAPs)–inducedcardiac oxidative stress and dysfunction in a rat model of inhalationexposure. Capsazepine (CPZ), a selective antagonist of TRPV1,was given ip or as an aerosol immediately before exposure toCAPs. Control and CPZ-treated rats were exposed to filteredair or CAPs aerosols for 5 h using the Harvard Ambient ParticleConcentrator (mean PM_2.5 mass concentration: 218 ± 23µg/m³). At the end of the exposure we measured cardiacoxidative stress (in situ chemiluminescence [CL]), lipid peroxidation(thiobarbituric acid reactive substances [TBARS]), and tissueedema. Cardiac function was monitored throughout the exposure.CPZ (ip or aerosol) decreased CAPs-induced CL, lipid TBARS,and edema in the heart, indicating that blocking TRP receptors,systemically or locally, decreases heart CL. CAPs exposure ledto significant decreases in heart rate (CAPs 350 ± 32bpm, control: 370 ± 29), and in the length of the QT,RT, Pdur and Tpe intervals. These changes were observable immediatelyupon exposure and were maintained throughout the 5 h of CAPsinhalation. Changes in cardiac rhythm and electrocardiogrammorphology were prevented by CPZ. These data suggest that currentabnormalities in CAPs-exposed rats alter the action potentialsleading to changes in conduction velocity and ventricular repolarization,and that triggering of TRPV1-mediated autonomic reflexes inthe lung is essential for the observed changes in cardiac rhythms.     

Cardiac oxidative stress and dysfunction by fine concentrated ambient particles (CAPs) are mediated by angiotensin-II

Inhalation exposure to fine concentrated ambient particles (CAPs) increases cardiac oxidants by mechanisms involving modulation of the sympathovagal tone on the heart. Angiotensin-II is a potent vasoconstrictor and a sympatho-excitatory peptide involved in the regulation of blood pressure. We hypothesized that increases in angiotensin-II after fine particulate matter (PM) exposure could be involved in the development of cardiac oxidative stress. Adult rats were treated with an angiotensin-converting enzyme (ACE) inhibitor (benazepril^®), or an angiotensin receptor blocker (ARB; valsartan^®) before exposure to fine PM aerosols or filtered air. Exposures were carried out for 5 hours in the chamber of the Harvard fine particle concentrator (fine PM mass concentration: 440 ± 80 μg/m³). At the end of the exposure the animals were tested for in situ chemiluminescence (CL) of the heart, thiobarbituric acid reactive substances (TBARS) and for plasma levels of angiotensin-II. Also, continuous electrocardiogram (ECG) measurements were collected on a subgroup of exposed animals. PM exposure was associated with statistically significant increases in plasma angiotensin concentrations. Pre-treatment with the ACE inhibitor effectively lowered angiotensin concentration, whereas ARB treatment led to increases in angiotensin above the PM-only level. PM exposure also led to significant increases in heart oxidative stress (CL, TBARS), and a shortening of the T-end to T-peak interval on the ECG that were prevented by treatment with both the ACE inhibitor and ARB. These results show that ambient fine particles can increase plasma levels of angiotensin-II and suggest a role of the renin–angiotensin system in the development of particle-related acute cardiac events.     

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.     

Enhanced cerebellar myelination with concomitant iron elevation and ultrastructural irregularities following prenatal exposure to ambient particulate matter in the mouse

Abstract

Accumulating evidence indicates the developing central nervous system (CNS) is a target of air pollution toxicity. Epidemiological reports increasingly demonstrate that exposure to the particulate matter (PM) fraction of air pollution during neurodevelopment is associated with an increased risk of neurodevelopmental disorders (NDDs) such as autism spectrum disorder (ASD). These observations are supported by animal studies demonstrating prenatal exposure to concentrated ambient PM induces neuropathologies characteristic of ASD, including ventriculomegaly and aberrant corpus callosum (CC) myelination. Given the role of the CC and cerebellum in ASD etiology, this study tested whether prenatal exposure to concentrated ambient particles (CAPs) produced pathological features in offspring CC and cerebella consistent with ASD. Analysis of cerebellar myelin density revealed male-specific hypermyelination in CAPs-exposed offspring at postnatal days (PNDs) 11–15 without alteration of cerebellar area. Atomic absorption spectroscopy (AAS) revealed elevated iron (Fe) in the cerebellum of CAPs-exposed female offspring at PNDs 11–15, which connects with previously observed elevated Fe in the female CC. The presence of Fe inclusions, along with aluminum (Al) and silicon (Si) inclusions, were confirmed at nanoscale resolution in the CC along with ultrastructural myelin sheath damage. Furthermore, RNAseq and gene ontology (GO) enrichment analyses revealed cerebellar gene expression was significantly affected by sex and prenatal CAPs exposure with significant enrichment in inflammation and transmembrane transport processes that could underlie observed myelin and metal pathologies. Overall, this study highlights the ability of PM exposure to disrupt myelinogenesis and elucidates novel molecular targets of PM-induced developmental neurotoxicity.     

Comparative effects of inhaled diesel exhaust and ambient fine particles on inflammation,atherosclerosis, and vascular dysfunction

Ambient air PM_2.5 (particulate matter less than 2.5 μm in diameter) has been associated with cardiovascular diseases (CVDs), but the underlying mechanisms affecting CVDs are unknown. The authors investigated whether subchronic inhalation of concentrated ambient PM_2.5 (CAPs), whole diesel exhaust (WDE), or diesel exhaust gases (DEGs) led to exacerbation of atherosclerosis, pulmonary and systemic inflammation, and vascular dysfunction; and whether DEG interactions with CAPs alter cardiovascular effects. ApoE^?/? mice were simultaneously exposed via inhalation for 5 hours/day, 4 days/week, for up to 5 months to one of five different exposure atmospheres: (1) filtered air (FA); (2) CAPs (105 μg/m³); (3) WDE (DEP = 436 μg/m³); (4) DEG (equivalent to gas levels in WDE group); and (5) CAPs+DEG (PM_2.5: 113 μg/m³; with DEG equivalent to WDE group). After 3 and 5 months, lung lavage fluid and blood sera were analyzed, and atherosclerotic plaques were quantified by ultrasound imaging, hematoxylin and eosin (H&E stain), and en face Sudan IV stain. Vascular functions were assessed after 5 months of exposure. The authors showed that (1) subchronic CAPs, WDE, and DEG inhalations increased serum vascular cell adhesion molecule (VCAM)-1 levels and enhanced phenylephrine (PE)-induced vasoconstriction; (2) for plaque exacerbation, CAPs > WDE > DEG?=?FA, thus PM components (not present in WDE) were responsible for plaque development; (3) atherosclerosis can exacerbated through mechanistic pathways other than inflammation and vascular dysfunction; and (4) although there were no significant interactions between CAPs and DEG on plaque exacerbation, it is less clear whether the effects of CAPs on vasomotor dysfunction and pulmonary/systemic inflammation were enhanced by the DEG coexposure.     

Effects of Subchronic Exposures to Concentrated Ambient Particles in Mice: VI. Gene Expression in Heart and Lung Tissue

Abstract

The purpose of this exploratory study within the integrated subchronic inhalation exposure study () 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 the 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 more definitively assess differences in gene expression in heart and lung resulting from exposure to CAPs.     

Synergistic effects of exposure to concentrated ambient fine pollution particles and nitrogen dioxide in humans

Context: Exposure to single pollutants e.g. particulate matter (PM) is associated with adverse health effects, but it does not represent a real world scenario that usually involves multiple pollutants.

Objectives: Determine if simultaneous exposure to PM and NO₂ results in synergistic interactions.

Materials and methods: Healthy young volunteers were exposed to clean air, nitrogen dioxide (NO₂, 0.5 ppm), concentrated fine particles from Chapel Hill air (PM_2.5CAPs, 89.5?±?10.7 µg/m³), or NO₂+PM_2.5CAPs for 2?h. Each subject performed intermittent exercise during the exposure. Parameters of heart rate variability (HRV), changes in repolarization, peripheral blood endpoints and lung function were measured before and 1 and 18?h after exposure. Bronchoalveolar lavage (BAL) was performed 18?h after exposure.

Results: NO₂ exposure alone increased cholesterol and HDL 18?h after exposure, decreased high frequency component of HRV one and 18?h after exposure, decreased QT variability index 1?h after exposure, and increased LDH in BAL fluid. The only significant change with PM_2.5CAPs was an increase in HDL 1?h after exposure, likely due to the low concentrations of PM_2.5CAPs in the exposure chamber. Exposure to both NO₂ and PM_2.5CAPs increased BAL α1-antitrypsin, mean t wave amplitude, the low frequency components of HRV and the LF/HF ratio. These changes were not observed following exposure to NO₂ or PM_2.5CAPs alone, suggesting possible interactions between the two pollutants.

Discussion and conclusions: NO₂ exposure may produce and enhance acute cardiovascular effects of PM_2.5CAPs. Assessment of health effects by ambient PM should consider its interactions with gaseous copollutants.