Air pollutants increase gene expression of the vasoconstrictor endothelin-1 in the lungs

Inhalation of particulate matter containing environmentally persistent free radicals induces endothelial dysfunction mediated via AhR activation at the air-blood interface

Particulate matter (PM) containing environmentally persistent free radicals (EPFR) is formed by the incomplete combustion of organic wastes, resulting in the chemisorption of pollutants to the surface of PM containing redox-active transition metals. In prior studies in mice, EPFR inhalation impaired endothelium-dependent vasodilation. These findings were associated with aryl hydrocarbon receptor (AhR) activation in the alveolar type-II (AT-II) cells that form the air-blood interface in the lung. We thus hypothesized that AhR activation in AT-II cells promotes the systemic release of mediators that promote endothelium dysfunction peripheral to the lung. To test our hypothesis, we knocked down AhR in AT-II cells of male and female mice and exposed them to 280 µg/m3 EPFR lo (2.7e + 16 radicals/g) or EPFR (5.5e + 17 radicals/g) compared with filtered air for 4 h/day for 1 day or 5 days. AT-II-AhR activation-induced EPFR-mediated endothelial dysfunction, reducing endothelium-dependent vasorelaxation by 59%, and eNOS expression by 50%. It also increased endothelin-1 mRNA levels in the lungs and peptide levels in the plasma in a paracrine fashion, along with soluble vascular cell adhesion molecule-1 and iNOS mRNA expression, possibly via NF-kB activation. Finally, AhR-dependent increases in antioxidant response signaling, coupled to increased levels of 3-nitrotyrosine in the lungs of EPFR-exposed littermate control but not AT-II AhR KO mice suggested that ATII-specific AhR activation promotes oxidative and nitrative stress. Thus, AhR activation at the air-blood interface mediates endothelial dysfunction observed peripheral to the lung, potentially via release of systemic mediators.

Indirect mediators of systemic health outcomes following nanoparticle inhalation exposure

The growing field of nanoscience has shed light on the wide diversity of natural and anthropogenic sources of nano-scale particulates, raising concern as to their impacts on human health. Inhalation is the most robust route of entry, with nanoparticles (NPs) evading mucociliary clearance and depositing deep into the alveolar region. Yet, impacts from inhaled NPs are evident far outside the lung, particularly on the cardiovascular system and highly vascularized organs like the brain. Peripheral effects are partly explained by the translocation of some NPs from the lung into the circulation; however, other NPs largely confined to the lung are still accompanied by systemic outcomes. Omic research has only just begun to inform on the complex myriad of molecules released from the lung to the blood as byproducts of pulmonary pathology. These indirect mediators are diverse in their molecular make-up and activity in the periphery. The present review examines systemic outcomes attributed to pulmonary NP exposure and what is known about indirect pathological mediators released from the lung into the circulation. Further focus was directed to outcomes in the brain, a highly vascularized region susceptible to acute and longer-term outcomes. Findings here support the need for big-data toxicological studies to understand what drives these health outcomes and better predict, circumvent, and treat the potential health impacts arising from NP exposure scenarios.

Acute cardiovascular effects of inhaled ambient particulate matter: Chemical composition-related oxidative stress, endothelin-1, blood pressure, and ST-segment changes in Wistar rats

Short-term increases in particulate matter (PM) are associated with heightened morbidity and mortality from cardiovascular causes. Inhalation of PM is known to increase endothelin (ET)-1 levels. Yet, less is known about particle composition-related changes at the molecular level including the endothelinergic system and relationship with cardiovascular function changes. In this work, adult Wistar male rats were exposed for 4 h by nose-only inhalation to clean air, Ottawa urban particles (EHC-93, 48 mg/m³) and water-leached (EHC-93L, 49 mg/m³) particles, to examine the effect of particle compositional changes on oxidative stress, circulating ETs, blood pressure, and heart electrophysiology. Particle deposition in the respiratory compartment was estimated at 85 μg (25 ng/cm²). Lung cell proliferation was low in both treatment groups, indicating absence of acute injury. Inhalation of EHC-93 caused statistically significant elevations (p < 0.05) of oxidative stress markers, ET-1, ET-3, blood pressure, and a decrease of ST-segment duration in the ECG at 1.5 days post-exposure. Leached particles (EHC-93L) caused rapid but transient elevation (p < 0.05) of oxidative stress, ET-1, ET-2, and ET-3 at earlier time points, with no changes in blood pressure or ST-segment. These results demonstrate that inhalation of urban particles at an internal dose inadequate to cause acute lung injury can induce oxidative stress, enhance vasoactive endothelins, leading to vasopressor response, affecting cardiac electrophysiology in Wistar rats, consistent with the cardiovascular impacts of ambient particles in human populations. Change in particle potency after removal of soluble species, notably cadmium, zinc and polar organics suggests that the toxicodynamics of cardiovascular effects can be modified by physicochemical properties of particles.

A National Multicity Analysis of the Causal Effect of Local Pollution, [Formula: see text], and [Formula: see text] on Mortality

BACKGROUND

Studies have long associated [Formula: see text] with daily mortality, but few applied causal-modeling methods, or at low exposures. Short-term exposure to [Formula: see text], a marker of local traffic, has also been associated with mortality but is less studied. We previously found a causal effect between local air pollution and mortality in Boston.

OBJECTIVES

We aimed to estimate the causal effects of local pollution, [Formula: see text], and [Formula: see text] on mortality in 135 U.S. cities.

METHODS

We used three methods which, under different assumptions, provide causal marginal estimates of effect: a marginal structural model, an instrumental variable analysis, and a negative exposure control. The instrumental approach used planetary boundary layer, wind speed, and air pressure as instruments for concentrations of local pollutants; the marginal structural model separated the effects of [Formula: see text] from the effects of [Formula: see text], and the negative exposure control provided protection against unmeasured confounders.

RESULTS

In 7.3 million deaths, the instrumental approach estimated that mortality increased 1.5% [95% confidence interval (CI): 1.1%, 2.0%] per [Formula: see text] increase in local pollution indexed as [Formula: see text]. The negative control exposure was not associated with mortality. Restricting our analysis to days with [Formula: see text] below [Formula: see text], we found a 1.70% (95% CI 1.11%, 2.29%) increase. With marginal structural models, we found positive significant increases in deaths with both [Formula: see text] and [Formula: see text]. On days with [Formula: see text] below [Formula: see text], we found a 0.83% (95% CI 0.39%, 1.27%) increase. Including negative exposure controls changed estimates minimally.

CONCLUSIONS

Causal-modeling techniques, each subject to different assumptions, demonstrated causal effects of locally generated pollutants on daily deaths with effects at concentrations below the current EPA daily [Formula: see text] standard. https://doi.org/10.1289/EHP2732.

The perpetuation of the misconception that rats receive a 3-5 times lower lung tissue dose than humans at the same ozone concentration

This paper highlights the pervasive misconception concerning 1994 findings from Hatch et al. about ozone (O₃) tissue dose in humans versus rats. That study exposed humans to 0.4 ppm and rats to 2 ppm ¹⁸O-labeled O₃ and found comparable incorporation of ¹⁸O into bronchoalveolar lavage constituents. However, during O₃ exposure humans were exercising, which increased their ventilation rate five-fold, while rats were at rest. This resulted in similar O₃ tissue doses between the two species, and predominantly explained the comparable ¹⁸O incorporation at five-fold different concentrations. The five-times higher exercising human inhalation rate offset the five-times lower concentration, producing the same human dose expected at rest at 2 ppm (i.e. 0.4 ppm × 4686 L/2 hour ≈ 2 ppm × 998 L/2 hour). In 2013, Hatch et al. showed that resting humans and resting rats experienced fairly comparable ¹⁸O incorporation at the same O₃ exposure concentration and activity state into BALF cells. Despite these findings, we show here that in the peer-reviewed literature a substantial proportion of researchers continue to perpetuate the misunderstanding that human lung tissue doses of O₃ are simply 3-5 times greater than rat doses at the same O₃ concentration, due to interspecies differences, and not considering activity state. It is important to correct this misconception to ensure an appropriate understanding of the implications of O₃ studies by the scientific community and policy experts making regulatory decisions (e.g. the US Environmental Protection Agency's National Ambient Air Quality Standards for O₃).

Pediatric Respiratory and Systemic Effects of Chronic Air Pollution Exposure: Nose, Lung, Heart, and Brain Pathology

Exposures to particulate matter and gaseous air pollutants have been associated with respiratory tract inflammation, disruption of the nasal respiratory and olfactory barriers, systemic inflammation, production of mediators of inflammation capable of reaching the brain and systemic circulation of particulate matter. Mexico City (MC) residents are exposed to significant amounts of ozone, particulate matter and associated lipopolysaccharides. MC dogs exhibit brain inflammation and an acceleration of Alzheimer’s-like pathology, suggesting that the brain is adversely affected by air pollutants. MC children, adolescents and adults have a significant upregulation of cyclooxygenase-2 (COX2) and interleukin-1β (IL-1β) in olfactory bulb and frontal cortex, as well as neuronal and astrocytic accumulation of the 42 amino acid form of β-amyloid peptide (Aβ42), including diffuse amyloid plaques in frontal cortex. The pathogenesis of Alzheimer’s disease (AD) is characterized by brain inflammation and the accumulation of Aβ42, which precede the appearance of neuritic plaques and neurofibrillary tangles, the pathological hallmarks of AD. Our findings of nasal barrier disruption, systemic inflammation, and the upregulation of COX2 and IL-1β expression and Aβ42 accumulation in brain suggests that sustained exposures to significant concentrations of air pollutants such as particulate matter could be a risk factor for AD and other neurodegenerative diseases.

The burden of pulmonary hypertension in resource-limited settings

Pulmonary vascular disease (PVD) is a significant global health problem and accounts for a substantial portion of cardiovascular disease in the developing world. Although there have been considerable advances in therapeutics for pulmonary arterial hypertension, over 97% of the disease burden lies within the developing world where there is limited access to health care and pharmaceuticals. The causes of pulmonary arterial hypertension differ between industrialized and developing nations. Infectious diseases-including schistosomiasis human immunodeficiency virus, and rheumatic fever-are common causes of PVD, as are hemoglobinopathies, and untreated congenital heart disease. High altitude and exposure to household air pollutants also contribute to a significant portion of PVD cases. Although diagnosis of pulmonary arterial hypertension requires the use of imaging and invasive hemodynamics, access to equipment may be limited. PVD therapies may be prohibitively expensive and limited to a select few. Prevention is therefore important in limiting the global PVD burden.

Factors associated with isolated right heart failure in women: a pilot study from western Kenya

BACKGROUND

Small observational studies have found that isolated right heart failure (IRHF) is prevalent among women of sub-Saharan Africa. Further, several risk factors for the development of IRHF have been identified. However, no similar studies have been conducted in Kenya.

OBJECTIVE

We hypothesized that specific environmental exposures and comorbidities were associated with IRHF in women of western Kenya.

METHODS

We conducted a case-control study at a referral hospital in western Kenya. Cases were defined as women at least 35 years old with IRHF. Control subjects were similarly aged volunteers without IRHF. Exclusion criteria in both groups included history of tobacco use, tuberculosis, or thromboembolic disease. Participants underwent echocardiography, spirometry, 6-min walk test, rest/exercise oximetry, respiratory health interviews, and human immunodeficiency virus (HIV) testing. Home visits were performed to evaluate kitchen ventilation, fuel use, and cook smoke exposure time, all surrogate measures of indoor air pollution (IAP). A total of 31 cases and 65 control subjects were enrolled. Surrogate measures of indoor air pollution were not associated with IRHF. However, lower forced expiratory volume at 1 s percent predicted (adjusted odds ratio [AOR]: 2.02, 95% confidence interval [CI]: 1.27 to 3.20; p = 0.004), HIV positivity (AOR: 40.4, 95% CI: 3.7 to 441; p < 0.01), and self-report of exposure to occupational dust (AOR: 3.9, 95% CI: 1.14 to 14.2; p = 0.04) were associated with IRHF. In an analysis of subgroups of participants with and without these factors, lower kitchen ventilation was significantly associated with IRHF among participants without airflow limitation (AOR: 2.63 per 0.10 unit lower ventilation, 95% CI: 1.06 to 6.49; p = 0.04), without HIV (AOR: 2.55, 95% CI: 1.21 to 5.37; p = 0.02), and without occupational dust exposure (AOR: 2.37, 95% CI: 1.01 to 5.56; p = 0.05).

CONCLUSIONS

In this pilot study among women of western Kenya, lower kitchen ventilation, airflow limitation, HIV, and occupational dust exposure were associated with IRHF, overall or in participant subgroups. Direct or indirect causality requires further study.

Inflammatory response to acute exposure to welding fumes during the working day

OBJECTIVES

To investigate cardiorespiratory and inflammatory responses in male workers following exposure to welding fumes and airborne particles in actual workplace conditions.

MATERIALS AND METHODS

We measured blood leukocytes and their differential counts, platelet count, hemoglobin, sensitive C-reactive protein, fibrinogen, E-selectin, IL-(interleukin)1β, IL-6, IL-8, tumor necrosis factor alpha (TNF-α) and endothelin-1 in blood samples of twenty workers before and after their working day. We also studied peak expiratory flow (PEF), forced expiratory volume in one second (FEV1), and exhaled nitric oxide (NO). We assessed heart rate variability (HRV) by obtaining 24-hour ambulatory electrocardiograms.

RESULTS

The total blood leukocytes and neutrophils increased after the work shift, whereas IL-1β and E-selectin decreased significantly. There were no statistically significant changes in exhaled NO, FEV1, PEF or HRV.

CONCLUSION

Occupational exposure to welding fumes and particles caused a slight, acute inflammatory effect estimated based on the increased values of leukocytes and neutrophils in blood and a decrease in the interleukin 1β and E-selectin values, but no changes in the pulmonary function (exhaled NO, FEV1, PEF) or HRV during the working day were observed.

Waiting to inhale: An exploratory review of conditions that may predispose to pulmonary hypertension and right heart failure in persons exposed to household air pollution in low- and middle-income countries

The health effects of exposure to household air pollution are gaining international attention. While the bulk of the known mortality estimates due to these exposures are derived from respiratory conditions, there is growing evidence of adverse cardiovascular health effects. Pulmonary hypertension and right heart failure are common conditions in low- and middle-income countries whose etiology may be related to common exposures in these regions such as schistosomiasis, human immunodeficiency virus, tuberculosis infections and other causes. While little is known of the interplay between exposure to household air pollution, right heart function and such conditions, the large burden of pulmonary hypertension and right heart failure in regions where there is significant exposure to household air pollution raises the possibility of a linkage. This review is presented in three parts. First, we explore what is known about pulmonary hypertension and right heart failure in low- and middle-income countries by focusing on eight common causes thereof. We then review what is known of the impact of household air pollution on pulmonary hypertension and posit that when individuals with one of these eight common comorbidities are exposed to household air pollution they may be predisposed to develop pulmonary hypertension or right heart failure. Lastly, we posit that there may be a direct link between exposure to household air pollution and right heart failure independent of pre-existing conditions which merits further investigation. Our overall aim is to highlight the multifactorial nature of these complex relationships and offer avenues for research in this expanding field of study.

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 microg/m(3)). 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.

The time course of vasoconstriction and endothelin receptor A expression in pulmonary arterioles of mice continuously exposed to ambient urban levels of air pollution

The present study aimed to verify the time course of the effects of environmental levels of urban air pollution toxicity on lung arterioles. BALB/c mice (n=56) were continuously exposed to selective chambers equipped with (filtered, F) or without (non-filtered, NF) filter devices for particles and toxic gases for 24h/day, over 14, 21, 30 or 45 days. After exposure, we evaluated the lumen-wall relationship (an estimator of arteriolar narrowing), endothelial nitric oxide synthase (eNOS) and endothelin type A receptor (ETAr) expression in the vascular wall and inflammatory influx of the peribronchiolar area. Concentrations of fine particulate matter (PM<or=2.5 microg/m(3)), nitrogen dioxide (NO(2)), black smoke (BS), humidity and temperature in both the environment and inside the chambers were measured daily. Filters cleared 100% of BS and 97% of PM inside the F chamber. The arteriole wall of the lungs of mice from NF chamber had an increased ETAr expression (p<or=0.042) concomitant to a decrease in the lumen/wall ratio (p=0.02) on the early days of exposure, compared to controls. They also presented a progressive increment of inflammatory influx in the peribronchiolar area during the study (p=0.04) and decrement of the eNOS expression on the 45th day of exposure in both vascular layers (p<or=0.03). We found that after 14 days of exposure, the ambient levels of air pollutants in Sao Paulo induced vasoconstriction that was associated with an increase in ETAr expression. These vascular results do not appear to be coupled to the progressive inflammatory influx in lung tissue, suggesting a down-regulation of vasoconstrictive mechanisms through an imbalance in the cytokines network. It is likely that these responses are protective measures that decrease tissue damage brought about by continuous exposure to air pollutants.

Toxicogenomic analysis of susceptibility to inhaled urban particulate matter in mice with chronic lung inflammation

Background

Individuals with chronic lung disease are at increased risk of adverse health effects from airborne particulate matter. Characterization of underlying pollutant-phenotype interactions may require comprehensive strategies. Here, a toxicogenomic approach was used to investigate how inflammation modifies the pulmonary response to urban particulate matter.

Results

Transgenic mice with constitutive pulmonary overexpression of tumour necrosis factor (TNF)-α under the control of the surfactant protein C promoter and wildtype littermates (C57BL/6 background) were exposed by inhalation for 4 h to particulate matter (0 or 42 mg/m³ EHC-6802) and euthanized 0 or 24 h post-exposure. The low alveolar dose of particles (16 μg) did not provoke an inflammatory response in the lungs of wildtype mice, nor exacerbate the chronic inflammation in TNF animals. Real-time PCR confirmed particle-dependent increases of CYP1A1 (30–100%), endothelin-1 (20–40%), and metallothionein-II (20–40%) mRNA in wildtype and TNF mice (p < 0.05), validating delivery of a biologically-effective dose. Despite detection of striking genotype-related differences, including activation of immune and inflammatory pathways consistent with the TNF-induced pathology, and time-related effects attributable to stress from nose-only exposure, microarray analysis failed to identify effects of the inhaled particles. Remarkably, the presence of chronic inflammation did not measurably amplify the transcriptional response to particulate matter.

Conclusion

Our data support the hypothesis that health effects of acute exposure to urban particles are dominated by activation of specific physiological response cascades rather than widespread changes in gene expression.

Cardiovascular effects of air pollution

Air pollution is a heterogeneous mixture of gases, liquids and PM (particulate matter). In the modern urban world, PM is principally derived from fossil fuel combustion with individual constituents varying in size from a few nanometres to 10 μm in diameter. In addition to the ambient concentration, the pollution source and chemical composition may play roles in determining the biological toxicity and subsequent health effects. Nevertheless, studies from across the world have consistently shown that both short- and long-term exposures to PM are associated with a host of cardiovascular diseases, including myocardial ischaemia and infarctions, heart failure, arrhythmias, strokes and increased cardiovascular mortality. Evidence from cellular/toxicological experiments, controlled animal and human exposures and human panel studies have demonstrated several mechanisms by which particle exposure may both trigger acute events as well as prompt the chronic development of cardiovascular diseases. PM inhaled into the pulmonary tree may instigate remote cardiovascular health effects via three general pathways: instigation of systemic inflammation and/or oxidative stress, alterations in autonomic balance, and potentially by direct actions upon the vasculature of particle constituents capable of reaching the systemic circulation. In turn, these responses have been shown to trigger acute arterial vasoconstriction, endothelial dysfunction, arrhythmias and pro-coagulant/thrombotic actions. Finally, long-term exposure has been shown to enhance the chronic genesis of atherosclerosis. Although the risk to one individual at any single time point is small, given the prodigious number of people continuously exposed, PM air pollution imparts a tremendous burden to the global public health, ranking it as the 13th leading cause of morality (approx. 800000 annual deaths).

Diesel exhaust inhalation elicits acute vasoconstriction in vivo

BACKGROUND

Traffic-related air pollution is consistently associated with cardiovascular morbidity and mortality. Recent human and animal studies suggest that exposure to air pollutants affects vascular function. Diesel exhaust (DE) is a major source of traffic-related air pollution.

OBJECTIVES

Our goal was to study the effects of short-term exposure to DE on vascular reactivity and on mediators of vascular tone.

METHODS

In a double-blind, crossover, controlled exposure study, 27 adult volunteers (10 healthy and 17 with metabolic syndrome) were exposed in randomized order to filtered air (FA) and each of two levels of diluted DE (100 or 200 microg/m(3) of fine particulate matter) in 2-hr sessions. Before and after each exposure, we assessed the brachial artery diameter (BAd) by B-mode ultrasound and collected blood samples for endothelin-1 (ET-1) and catecholamines. Postexposure we also assessed endothelium-dependent flow-mediated dilation (FMD).

RESULTS

Compared with FA, DE at 200 microg/m(3) elicited a decrease in BAd (0.11 mm; 95% confidence interval, 0.02-0.18), and the effect appeared linearly dose related with a smaller effect at 100 microg/m(3). Plasma levels of ET-1 increased after 200 microg/m(3) DE but not after FA (p = 0.01). There was no consistent impact of DE on plasma catecholamines or FMD.

CONCLUSIONS

These results demonstrate that short-term exposure to DE is associated with acute endothelial response and vasoconstriction of a conductance artery. Elucidation of the signaling pathways controlling vascular tone that underlie this observation requires further study.

Air pollution alters brain and pituitary endothelin-1 and inducible nitric oxide synthase gene expression

Recent work suggests that air pollution is a risk factor for cerebrovascular and neurodegenerative disease. Effects of inhaled pollutants on the production of vasoactive factors such as endothelin (ET) and nitric oxide (NO) in the brain may be relevant to disease pathogenesis. Inhaled pollutants increase circulating levels of ET-1 and ET-3, and the pituitary is a potential source of plasma ET, but the effects of pollutants on the expression of ET and NO synthase genes in the brain and pituitary are not known. In the present study, Fischer-344 rats were exposed by nose-only inhalation to particles (0, 5, 50mg/m3 EHC-93), ozone (0, 0.4, 0.8 ppm), or combinations of particles and ozone for 4 h. Real-time reverse transcription polymerase chain reaction was used to measure mRNA levels in the cerebral hemisphere and pituitary 0 and 24 h post-exposure. Ozone inhalation significantly increased preproET-1 but decreased preproET-3 mRNAs in the cerebral hemisphere, while increasing mRNA levels of preproET-1, preproET-3, and the ET-converting enzyme (ECE)-1 in the pituitary. Inducible NO synthase (iNOS) was initially decreased in the cerebral hemisphere after ozone inhalation, but increased 24 h post-exposure. Particles decreased tumour necrosis factor (TNF)-alpha mRNA in the cerebral hemisphere, and both particles and ozone decreased TNF-alpha mRNA in the pituitary. Our results show that ozone and particulate matter rapidly modulate the expression of genes involved in key vasoregulatory pathways in the brain and pituitary, substantiating the notion that inhaled pollutants induce cerebrovascular effects.

Elevated plasma endothelin-1 and pulmonary arterial pressure in children exposed to air pollution

BACKGROUND

Controlled exposures of animals and humans to particulate matter (PM) or ozone air pollution cause an increase in plasma levels of endothelin-1, a potent vasoconstrictor that regulates pulmonary arterial pressure.

OBJECTIVES

The primary objective of this field study was to determine whether Mexico City children, who are chronically exposed to levels of PM and O(3) that exceed the United States air quality standards, have elevated plasma endothelin-1 levels and pulmonary arterial pressures.

METHODS

We conducted a study of 81 children, 7.9 +/- 1.3 years of age, lifelong residents of either northeast (n = 19) or southwest (n = 40) Mexico City or Polotitlán (n = 22), a control city with PM and O(3) levels below the U.S. air quality standards. Clinical histories, physical examinations, and complete blood counts were done. Plasma endothelin-1 concentrations were determined by immunoassay, and pulmonary arterial pressures were measured by Doppler echocardiography.

RESULTS

Mexico City children had higher plasma endothelin-1 concentrations compared with controls (p < 0.001). Mean pulmonary arterial pressure was elevated in children from both northeast (p < 0.001) and southwest (p < 0.05) Mexico City compared with controls. Endothelin-1 levels in Mexico City children were positively correlated with daily outdoor hours (p = 0.012), and 7-day cumulative levels of PM air pollution < 2.5 mum in aerodynamic diameter (PM(2.5)) before endothelin-1 measurement (p = 0.03).

CONCLUSIONS

Chronic exposure of children to PM(2.5) is associated with increased levels of circulating endothelin-1 and elevated mean pulmonary arterial pressure.

Is air pollution a cause of cardiovascular disease? Updated review and controversies

Particulate matter (PM) air pollution is associated with an increased risk of cardiovascular morbidity and mortality. The focus of this review will be on the role that both acute and chronic exposure to PM plays in causing cardiovascular disease and on the latest major new findings and controversies in this field of research. Even short-term exposure to PM2.5 over a few hours can trigger myocardial infarctions, cardiac ischemia, arrhythmias, heart failure, stroke, exacerbation of peripheral arterial disease, and sudden death. Chronic exposure to moderately elevated levels also enhances the risk for developing a variety of cardiovascular diseases, possibly including hypertension and systemic atherosclerosis. Recent epidemiologic studies have furthered our understanding of the linkage between air pollutants and human health, with a multitude of plausible mechanistic explanations having been demonstrated experimentally during the past few years. Although a number of finer details relating to both the epidemiology and the mechanisms involved require more investigation, the overall weight of evidence is now sufficient to implicate PM exposure as a cause of cardiovascular disease. Without doubt, exposure to particulate matter can play a causal role in triggering a host of acute cardiovascular events via many mechanisms. Although long-term air pollution exposure has been shown to promote the development of atherosclerosis, the clinical significance of this relation requires more investigation.

The pharmacology of particulate matter air pollution-induced cardiovascular dysfunction

Since the London fog of 1952, in which more than 4000 people were killed in 4 days, the combined efforts of scientists from several disciplines, including those from the environmental health, clinical and biomedical disciplines, have raised serious concerns about the impact of air pollutants on human health. These environmental pollutants are rapidly being recognized as important and independent risk factors for several diseases such as asthma, chronic obstructive pulmonary disease, lung cancer, atherosclerosis, ischemic heart disease and stroke. Although the relative effects of particulate matter air pollution (aerodynamic diameter <10 microm, or PM(10)) are greater for respiratory than for cardiovascular deaths, the number of deaths attributable to PM(10) is much larger for cardiovascular than for respiratory reasons due to the higher prevalence of cardiovascular disease in the general population. This review summarizes current understanding of the mechanisms underlying the associations between PM(10) exposure and cardiovascular morbidity and mortality.

Pollutant particles enhanced H2O2 production from NAD(P)H oxidase and mitochondria in human pulmonary artery endothelial cells

Particulate matter (PM) induces oxidative stress and cardiovascular adverse health effects, but the mechanistic link between the two is unclear. We hypothesized that PM enhanced oxidative stress in vascular endothelial cells and investigated the enzymatic sources of reactive oxygen species and their effects on mitogen-activated protein kinase (MAPK) activation and vasoconstriction. We measured the production of extracellular H2O2, activation of extracellular signal-regulated kinases1/2 (ERK1/2) and p38 MAPKs in human pulmonary artery endothelial cells (HPAEC) treated with urban particles (UP; SRM1648), and assessed the effects of H2O2 on vasoconstriction in pulmonary artery ring and isolated perfused lung. Within minutes after UP treatment, HPAEC increased H2O2 production that could be inhibited by diphenyleneiodonium (DPI), apocynin (APO), and sodium azide (NaN3). The water-soluble fraction of UP as well as its two transition metal components, Cu and V, also stimulated H2O2 production. NaN3 inhibited H2O2 production stimulated by Cu and V, whereas DPI and APO inhibited only Cu-stimulated H2O2 production. Inhibitors of other H2O2-producing enzymes, including Nomega-methyl-L-argnine, indomethacin, allopurinol, cimetidine, rotenone, and antimycin, had no effects. DPI but not NaN3 attenuated UP-induced pulmonary vasoconstriction and phosphorylation of ERK1/2 and p38 MAPKs. Knockdown of p47phox gene expression by small interfering RNA attenuated UP-induced H2O2 production and phosphorylation of ERK1/2 and p38 MAPKs. Intravascular administration of H2O2 generated by glucose oxidase increased pulmonary artery pressure. We conclude that UP induce oxidative stress in vascular endothelial cells by activating NAD(P)H oxidase and the mitochondria. The endothelial oxidative stress may be an important mechanism for PM-induced acute cardiovascular health effects.

Associations between ambient air pollution and daily mortality among persons with diabetes and cardiovascular disease

BACKGROUND

Recent studies suggest that persons with diabetes and with cardiovascular disease may be at higher risk for the short-term effects of air pollution. We carried out this mortality time series study in Montreal, Quebec, Canada to confirm these observations and to determine whether diabetics who had other health conditions were also at higher risk of dying when air pollution increases.

METHODS AND RESULTS

In one analysis, we related daily deaths from diabetes (using the underlying cause) to daily concentrations of particles and gaseous pollutants. In another analysis, we created subgroups by identifying subjects diagnosed 1 year before death with diabetes and other major health conditions from billing and prescription data from the universal Quebec Health Insurance Plan. The analysis made use of parametric log-linear Poisson models that were adjusted for long-term temporal trends and daily weather conditions. We found positive associations between most air pollutants and daily mortality from diabetes as well as among subjects diagnosed with diabetes 1 year before death. In the latter group of subjects, greater effects were found generally in the warm season and especially among subjects who had diabetes and who also had any cardiovascular disease, chronic coronary disease, and atherosclerosis. We did not find evidence of associations among persons who only had diabetes (i.e., did not also have cancer, cardiovascular disease, or lower respiratory disease).

CONCLUSIONS

These data indicate that individuals with diabetes who also have cardiovascular disease may be susceptible to the short-term effects of air pollution.

Effects of ambient air particles on the endothelin system in human pulmonary epithelial cells (A549)

Inhalation of urban particles results in higher circulating levels of the vasoconstrictor peptide endothelin-1 (ET-1), which may account for the adverse cardiovascular impacts associated with air pollution. The objective of this study was to examine the direct effects of urban particles on the production of ET-1 by human epithelial cells (A549). A549 cells were exposed to TiO(2), SiO(2), Ottawa urban particulate matter EHC-93, and fractions of the urban particles. The levels of ET-1, interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF) in the culture medium were detected by ELISA. The mRNA levels of preproET-1, endothelin converting enzyme (ECE-1), ETa receptor and ETb receptor, matrix metalloproteinase (MMP-2), tissue inhibitor of MMP (TIMP-2), and heat shock protein (HSP-70) were determined by quantitative real-time RT-PCR. Cluster analysis of the variables identified similarities in the patterns of effects. Cluster I comprised variables that were primarily inhibited by particles: ET-1 and MMP-2 mRNAs, ET-1 and bigET-1 peptides, and cell viability. Clusters II and III comprised variables that were either inhibited or induced, depending on the test material: HSP-70, ETaR and ECE mRNAs, and IL-8 and VEGF proteins. Cluster IV comprised variables that were mainly induced by particle preparations: ETbR and TIMP-2 mRNAs. The decreased expression of preproET-1 in A549 cells suggests that epithelial cells may not be the source of higher pulmonary ET-1 spillover in the circulation measured in vivo in response to inhaled urban particles. However, higher ECE-1 in A549 cells after exposure to particles suggests an increased ability to process bigET-1 into the mature ET-1 peptide, while increased receptor expression implies higher responsiveness. The increased release of IL-8 and VEGF by epithelial cells in response to particles could possibly upregulate ET-1 production in the adjacent pulmonary capillary endothelial cells, with concomitant increased ET-1 spillover in the systemic circulation.

Differential regulation of the lung endothelin system by urban particulate matter and ozone

Periodic elevation of ambient particulate matter and ozone levels is linked to acute cardiac morbidity and mortality. Increased plasma levels of the potent vasoconstrictor endothelin (ET)-1, a prognostic indicator of cardiac mortality, have been detected in both animal models and humans after exposure to air pollutants. The lungs are the primary source of circulating ET-1, but the direct effects of individual air pollutants and their interaction in modulating the pulmonary endothelin system are unknown. Fischer-344 rats were exposed to particles (0, 5, 50 mg/m3 EHC-93), ozone (0, 0.4, 0.8 ppm), or combinations of particles and ozone for 4 h. Changes in gene expression were measured using real-time reverse transcription polymerase chain reaction immediately after exposure and following 24 h recovery in clean air. Both pollutants individually increased preproET-1, endothelin converting enzyme-1, and endothelial nitric oxide synthase mRNA levels in the lungs shortly after exposure, consistent with the concomitant increase in plasma of the 21 amino acid ET-1[1-21] peptide measured by HPLC-fluorescence. PreproET-1 mRNA remained elevated 24 h after exposure to particles but not after ozone, in line with previously documented changes of the peptide in plasma. Both pollutants transiently increased endothelin-B receptor mRNA expression, while ozone decreased endothelin-A receptor mRNA levels. Coexposure to particles plus ozone increased lung preproET-1 mRNA but not plasma ET-1[1-21], suggesting alternative processing or degradation of endothelins. This coincided with an increase in the lungs of matrix metalloproteinase-2 (MMP-2), an enzyme that cleaves bigET-1 to ET-1[1-32]. Taken together, our data indicate that ozone and particulate matter independently regulate the expression of lung endothelin system genes, but show complex toxicological interaction with respect to plasma ET-1.

Pollutant particles produce vasoconstriction and enhance MAPK signaling via angiotensin type I receptor

Exposure to particulate matter (PM) is associated with acute cardiovascular mortality and morbidity, but the mechanisms are not entirely clear. In this study, we hypothesized that PM may activate the angiotensin type 1 receptor (AT1R), a G protein-coupled receptor that regulates inflammation and vascular function. We investigated the acute effects of St. Louis, Missouri, urban particles (UPs; Standard Reference Material 1648) on the constriction of isolated rat pulmonary artery rings and the activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 mitogen-activated protein kinases (MAPKs) in human pulmonary artery endothelial cells with or without losartan, an antagonist of AT1R. UPs at 1-100 microg/mL induced acute vasoconstriction in pulmonary artery. UPs also produced a time- and dose-dependent increase in phosphorylation of ERK1/2 and p38 MAPK. Losartan pretreatment inhibited both the vasoconstriction and the activation of ERK1/2 and p38. The water-soluble fraction of UPs was sufficient for inducing ERK1/2 and p38 phosphorylation, which was also losartan inhibitable. Copper and vanadium, two soluble transition metals contained in UPs, induced pulmonary vasoconstriction and phosphorylation of ERK1/2 and p38, but only the phosphorylation of p38 was inhibited by losartan. The UP-induced activation of ERK1/2 and p38 was attenuated by captopril, an angiotensin-converting enzyme inhibitor. These results indicate that activation of the local renin-angiotensin system may play an important role in cardiovascular effects induced by PM.

90-day repeated inhalation exposure of surfactant Protein-C/tumor necrosis factor-alpha, (SP-C/TNF-alpha) transgenic mice to air pollutants

Tumor necrosis factor (TNF)-alpha, a cytokine present in inflammed lungs, is known to mediate some of the adverse effects of ozone and inhaled particles. The authors evaluated transgenic mice with constitutive pulmonary expression of TNF-alpha under transcriptional regulation of the surfactant protein-C promoter as an animal model of biological susceptibility to air pollutants. To simulate a repeated, episodic exposure to air pollutants, wild-type and TNF mice inhaled air or a mixture of ozone (0.4 ppm) and urban particles (EHC-93, 4.8 mg/m3) for 4 h, once per week, for 12 consecutive weeks and were sacrificed 20 h after last exposure. TNF mice exhibited chronic lung inflammation with septal thickening, alveolar enlargement, and elevated protein and cellularity in bronchoalveolar lavage fluid (genotype main effect, p < .001). Repeated exposure to pollutants did not result in measurable inflammatory changes in wild-type mice and did not exacerbate the inflammation in TNF mice. The pollutants decreased recovery of alveolar macrophages in tavage fluid of both wild-type and TNF mice (exposure main effect, p < .001). Exacerbation of the rate of protein nitration reactions specifically in the lungs of TNF mice was revealed by the high ratio of 3-nitrotyrosine to L-DOPA after exposure to the air pollutants (Genotype x Exposure factor interaction, p = .014). Serum creatine kinase-MM isoform increased in TNF mice exposed to pollutants (Genotype X Exposure factor interaction, p = .043). The marked pollutant-related nitration in the lungs of the TNF mice reveals basic differences in free radical generation and scavenging in the inflamed lungs in response to pollutants. Furthermore, elevation of circulating creatine kinase-MM isoform specifically in TNF mice exposed to pollutants suggests systemic adverse impacts from lung inflammatory mediators, possibly on muscles and the cardiovascular system.

Altered gene expression patterns in MCF-7 cells induced by the urban dust particulate complex mixture standard reference material 1649a

Human exposures to polycyclic aromatic hydrocarbon (PAH) occur in complex mixtures. Here, gene expression patterns were investigated using standard reference material (SRM) 1649a (urban dust). MCF-7 cells were exposed to SRM 1649a alone or SRM 1649a with either benzo[a]pyrene (BP) or dibenzo[a,l]pyrene (DBP) for 24 hours. Global analyses of the gene expression data revealed alterations of 41 RNA transcripts with at least 2-fold change (signal log ratio </= -1 or >/= 1) in response to SRM 1649a exposure. Increase in expression of cytochrome P450 (CYP) genes was observed in response to BP exposure (CYP1A1 and CYP1B1; signal log ratio of 4.7 and 2.5, respectively). An additive induction of CYP1A1 and CYP1B1 was observed with cotreatment of SRM 1649a and BP. On the contrary, no change in gene expression of CYP1A1 and CYP1B1 was observed when the cells were exposed to DBP. Furthermore, to study the effect of complex PAH mixtures on the metabolic activation of carcinogenic PAH to DNA-binding derivatives and to relate this with gene expression studies, PAH-DNA adduct formation was determined. SRM 1649a decreased the total level of BP-DNA adducts in comparison with BP alone. No significant difference in adduct levels was observed in response to either DBP alone or in combination with SRM 1649a. These results provide a transcriptional signature for chemical carcinogen exposure; in addition, they suggest a major factor in carcinogenic activity of PAH within complex mixtures is their ability to promote or inhibit the activation of carcinogenic PAH by the induction of CYP enzymes.