Exposure to inhaled particulate matter impairs cardiac function in senescent mice

Screening Organic Components and Toxicogenic Structures from Regional Fine Particulate Matters Responsible for Myocardial Fibrosis in Male Mice

Numerous studies indicate that fine particulate matters (PM2.5) and its organic components are urgent risk factors for cardiovascular diseases (CVDs). Combining toxicological experiments, effect-directed analyses, and nontarget identification, this study aims to explore whether PM2.5 exposure in coal-combustion areas induces myocardial fibrosis and how to identify the effective organic components and their toxic structures to support regional risk control. First, we constructed an animal model of real-world PM2.5 exposure during the heating season and found that the exposure impaired cardiac systolic function and caused myocardial fibrosis, with chemokine Ccl2-mediated inflammatory response being the key cause of collagen deposition. Then, using the molecular event as target coupled with two-stage chromatographic isolation and mass spectrometry analyses, we identified a total of 171 suspect organic compounds in the PM2.5 samples. Finally, using hierarchical characteristic fragment analysis, we predicted that 40 of them belonged to active compounds with 6 alert structures, including neopentane, butyldimethylamine, 4-ethylphenol, hexanal, decane, and dimethylaniline. These findings provide evidence for risk management and prevention of CVDs in polluted areas.

Particulate matter induces arrhythmia-like cardiotoxicity in zebrafish embryos by altering the expression levels of cardiac development- and ion channel-related genes

Air pollution is a risk factor that increases cardiovascular morbidity and mortality. In this study, we investigated the cardiotoxicity of particulate matter (PM) exposure using a zebrafish embryo model. We found that PM exposure induced cardiotoxicity, such as arrhythmia, during cardiac development. PM exposure caused cardiotoxicity by altering the expression levels of cardiac development (T-box transcription factor 20, natriuretic peptide A, and GATA-binding protein 4)- and ion-channel (scn5lab, kcnq1, kcnh2a/b, and kcnh6a/b)-related genes. In conclusion, this study showed that PM induces the aberrant expression of cardiac development- and ion channel-related genes, leading to arrhythmia-like cardiotoxicity in zebrafish embryos. Our study provides a foundation for further research on the molecular and genetic mechanisms of cardiotoxicity induced by PM exposure.

Impact of Intratracheal Administration of Polyethylene Glycol-Coated Silver Nanoparticles on the Heart of Normotensive and Hypertensive Mice

Silver nanoparticles are widely used in various industrial and biomedical applications; however, little is known about their potential cardiotoxicity after pulmonary exposure, particularly in hypertensive subjects. We assessed the cardiotoxicity of polyethylene glycol (PEG)-coated AgNPs in hypertensive (HT) mice. Saline (control) or PEG-AgNPs (0.5 mg/kg) were intratracheally (i.t.) instilled four times (on days 7, 14, 21, and 28 post-angiotensin II or vehicle [saline] infusion). On day 29, various cardiovascular parameters were evaluated. Systolic blood pressure and heart rate were higher in PEG-AgNPs-treated HT mice than in saline-treated HT or PEG-AgNPs-treated normotensive mice. The heart histology of PEG-AgNPs-treated HT mice had comparatively larger cardiomyocyte damage with fibrosis and inflammatory cells when compared with saline-treated HT mice. Similarly, the relative heart weight and the activities of lactate dehydrogenase and creatine kinase-MB and the concentration of brain natriuretic peptide concentration were significantly augmented in heart homogenates of HT mice treated with PEG-AgNPs compared with HT mice treated with saline or normotensive animals exposed to PEG-AgNPs. Similarly, the concentrations of endothelin-1, P-selectin, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1 in heart homogenates were significantly higher than in the other two groups when HT mice were exposed to PEG-AgNPs. Markers of inflammation and oxidative and nitrosative stress were significantly elevated in heart homogenates of HT mice given PEG-AgNPs compared with HT mice treated with saline or normotensive animals exposed to PEG-AgNPs. The hearts of HT mice exposed to PEG-AgNPs had significantly increased DNA damage than those of HT mice treated with saline or normotensive mice treated with AgNPs. In conclusion, the cardiac injury caused by PEG-AgNPs was aggravated in hypertensive mice. The cardiotoxicity of PEG-AgNPs in HT mice highlights the importance of an in-depth assessment of their toxicity before using them in clinical settings, particularly in patients with pre-existing cardiovascular diseases.

NO2 exposure contributes to cardiac hypertrophy in male mice through apoptosis signaling pathways

Nitrogen dioxide (NO₂) is one of the most common indoor and outdoor air pollutants. Inhalation of NO₂ is associated with an increased risk of health problems, especially cardiovascular diseases. However, the underlying pathogenic mechanisms still remain unclear. In this study, we exposed C57BL/6J mice to NO₂ (2.5 ppm, 5 h/d) for 28 days and found that NO₂ inhalation induced cardiac dysfunction in male mice, but not in female mice, including left ventricular dilation and cardiac systolic dysfunction. Pathological staining showed that NO₂ inhalation induced eccentric hypertrophy with enlarged individual cardiomyocytes, dilated left ventricle, and thinning of the left ventricular wall in male mice. The transcriptional analysis suggested that NO₂ exposure could disrupt Ca²⁺ homeostasis, actin cytoskeletal reorganization, myocardial contractility, and vascular dilation in male mice. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that differentially expressed genes (DEGs) were closely associated with the apoptotic signaling pathways. These findings suggested that NO₂ exposure caused cardiac eccentric hypertrophy and cardiac dysfunction through apoptotic signaling pathways, and contributed to cardiotoxicity.

Cardiac tissue remodeling in healthy aging: the road to pathology

This review aims to highlight the normal physiological remodeling that occurs in healthy aging hearts, including changes that occur in contractility, conduction, valve function, large and small coronary vessels, and the extracellular matrix. These "normal" age-related changes serve as the foundation that supports decreased plasticity and limited ability for tissue remodeling during pathophysiological states such as myocardial ischemia and heart failure. This review will identify populations at greater risk for poor tissue remodeling in advanced age along with present and future therapeutic strategies that may ameliorate dysfunctional tissue remodeling in aging hearts.

PM2.5 exposure induces age-dependent hepatic lipid metabolism disorder in female mice

Particulate matter exposure has been described to elevate the risk of lung and cardiovascular diseases. An increasing number of recent studies have indicated positive correlations between PM_2.5 (the fraction of airborne particles with an aerodynamic diameter less than 2.5 μm) exposure and the risk of liver diseases. However, research on the effects of PM_2.5 exposure on liver fat synthesis, secretion, and clearance mechanisms under normal diet conditions is limited, and whether these effects are age-dependent is largely unknown. Female C57BL/6 mice at different ages (4 weeks (4 w), 4 months (4 m), and 10 months (10 m)) were treated with 3 mg/kg body weight of PM_2.5 every other day for 4 weeks. Subsequently, the ultrastructural changes of liver, the expression of genes involved in oxidative damage and lipid metabolism in the liver were examined. Observation of hepatic ultrastructure showed more and larger lipid droplets in the livers of 4-week-old and 10-month-old mice exposed to PM_2.5. Further analysis showed that PM_2.5 exposure increased the expression of genes related to lipid synthesis, but decreased the expression of genes involved in lipid transport and catabolism in the livers of 10-month-old mice. Our findings suggest that exposure to PM_2.5 disrupts the normal metabolism of liver lipids and induces lipid accumulation in the liver of female mice in an age-dependent manner, with older mice being more susceptible to PM_2.5.

World Trade Center-Cardiorespiratory and Vascular Dysfunction: Assessing the Phenotype and Metabolome of a Murine Particulate Matter Exposure Model

Vascular changes occur early in the development of obstructive airways disease. However, the vascular remodeling and dysfunction due to World Trade Center-Particulate Matter (WTC-PM) exposure are not well described and are therefore the focus of this investigation. C57Bl/6 female mice oropharyngeally aspirated 200 µg of WTC-PM₅₃ or phosphate-buffered saline (PBS) (controls). 24-hours (24-hrs) and 1-Month (1-M) after exposure, echocardiography, micro-positron emission tomography(µ-PET), collagen quantification, lung metabolomics, assessment of antioxidant potential and soluble-receptor for advanced glycation end products (sRAGE) in bronchoalveolar lavage(BAL) and plasma were performed. 24-hrs post-exposure, there was a significant reduction in (1) Pulmonary artery(PA) flow-velocity and pulmonary ejection time(PET) (2) Pulmonary acceleration time(PAT) and PAT/PET, while (3) Aortic ejection time(AET) and velocity time integral(VTI) were increased, and (4) Aortic acceleration time (AAT)/AET, cardiac output and stroke volume were decreased compared to controls. 1-M post-exposure, there was also significant reduction of right ventricular diameter as right ventricle free wall thickness was increased and an increase in tricuspid E, A peaks and an elevated E/A. The pulmonary and cardiac standard uptake value and volume 1-M post-exposure was significantly elevated after PM-exposure. Similarly, α-smooth muscle actin(α-SMA) expression, aortic collagen deposition was elevated 1-M after PM exposure. In assessment of the metabolome, prominent subpathways included advanced glycation end products (AGEs), phosphatidylcholines, sphingolipids, saturated/unsaturated fatty acids, eicosanoids, and phospholipids. BAL superoxide dismutase(SOD), plasma total-antioxidant capacity activity, and sRAGE (BAL and plasma) were elevated after 24-hrs. PM exposure and associated vascular disease are a global health burden. Our study shows persistent WTC-Cardiorespiratory and Vascular Dysfunction (WTC-CaRVD), inflammatory changes and attenuation of antioxidant potential after PM exposure. Early detection of vascular disease is crucial to preventing cardiovascular deaths and future work will focus on further identification of bioactive therapeutic targets.

Inhalation of printer-emitted particles impairs cardiac conduction, hemodynamics, and autonomic regulation and induces arrhythmia and electrical remodeling in rats

BACKGROUND

Using engineered nanomaterial-based toners, laser printers generate aerosols with alarming levels of nanoparticles that bear high bioactivity and potential health risks. Yet, the cardiac impacts of printer-emitted particles (PEPs) are unknown. Inhalation of particulate matter (PM) promotes cardiovascular morbidity and mortality, and ultra-fine particulates (< 0.1 μm aerodynamic diameter) may bear toxicity unique from larger particles. Toxicological studies suggest that PM impairs left ventricular (LV) performance; however, such investigations have heretofore required animal restraint, anesthesia, or ex vivo preparations that can confound physiologic endpoints and/or prohibit LV mechanical assessments during exposure. To assess the acute and chronic effects of PEPs on cardiac physiology, male Sprague Dawley rats were exposed to PEPs (21 days, 5 h/day) while monitoring LV pressure (LVP) and electrocardiogram (ECG) via conscious telemetry, analyzing LVP and heart rate variability (HRV) in four-day increments from exposure days 1 to 21, as well as ECG and baroreflex sensitivity. At 2, 35, and 70 days after PEPs exposure ceased, rats received stress tests.

RESULTS

On day 21 of exposure, PEPs significantly (P < 0.05 vs. Air) increased LV end systolic pressure (LVESP, + 18 mmHg) and rate-pressure-product (+ 19%), and decreased HRV indicating sympathetic dominance (root means squared of successive differences [RMSSD], - 21%). Overall, PEPs decreased LV ejection time (- 9%), relaxation time (- 3%), tau (- 5%), RMSSD (- 21%), and P-wave duration (- 9%). PEPs increased QTc interval (+ 5%) and low:high frequency HRV (+ 24%; all P < 0.05 vs. Air), while tending to decrease baroreflex sensitivity and contractility index (- 15% and - 3%, P < 0.10 vs. Air). Relative to Air, at both 2 and 35 days after PEPs, ventricular arrhythmias increased, and at 70 days post-exposure LVESP increased. PEPs impaired ventricular repolarization at 2 and 35 days post-exposure, but only during stress tests. At 72 days post-exposure, PEPs increased urinary dopamine 5-fold and protein expression of ventricular repolarizing channels, Kv1.5, Kv4.2, and Kv7.1, by 50%.

CONCLUSIONS

Our findings suggest exposure to PEPs increases cardiovascular risk by augmenting sympathetic influence, impairing ventricular performance and repolarization, and inducing hypertension and arrhythmia. PEPs may present significant health risks through adverse cardiovascular effects, especially in occupational settings, among susceptible individuals, and with long-term exposure.

Metabolic Syndrome and Air Pollution: A Narrative Review of Their Cardiopulmonary Effects

Particulate matter (PM) exposure and metabolic syndrome (MetSyn) are both significant global health burdens. PM exposure has been implicated in the pathogenesis of MetSyn and cardiopulmonary diseases. Individuals with pre-existing MetSyn may be more susceptible to the detrimental effects of PM exposure. Our aim was to provide a narrative review of MetSyn/PM-induced systemic inflammation in cardiopulmonary disease, with a focus on prior studies of the World Trade Center (WTC)-exposed Fire Department of New York (FDNY). We included studies (1) published within the last 16-years; (2) described the epidemiology of MetSyn, obstructive airway disease (OAD), and vascular disease in PM-exposed individuals; (3) detailed the known mechanisms of PM-induced inflammation, MetSyn and cardiopulmonary disease; and (4) focused on the effects of PM exposure in WTC-exposed FDNY firefighters. Several investigations support that inhalation of PM elicits pulmonary and systemic inflammation resulting in MetSyn and cardiopulmonary disease. Furthermore, individuals with these preexisting conditions are more sensitive to PM exposure-related inflammation, which can exacerbate their conditions and increase their risk for hospitalization and chronic disease. Mechanistic research is required to elucidate biologically plausible therapeutic targets of MetSyn- and PM-induced cardiopulmonary disease.

Ambient fine particulate matter exposure induces reversible cardiac dysfunction and fibrosis in juvenile and older female mice

BACKGROUND

Cardiovascular disease is the leading cause of mortality in the advanced world, and age is an important determinant of cardiac function. The purpose of the study is to determine whether the PM2.5-induced cardiac dysfunction is age-dependent and whether the adverse effects can be restored after PM2.5 exposure withdrawal.

METHODS

Female C57BL/6 mice at different ages (4-week-old, 4-month-old, and 10-month-old) received oropharyngeal aspiration of 3 mg/kg b.w. PM2.5 every other day for 4 weeks. Then, 10-month-old and 4-week-old mice were exposed to PM2.5 for 4 weeks and withdrawal PM2.5 1 or 2 weeks. Heart rate and systolic blood pressure were measured using a tail-cuff system. Cardiac function was assessed by echocardiography. Left ventricles were processed for histology to assess myocardial fibrosis. ROS generation was detected by photocatalysis using 2',7'-dichlorodihydrofluorescein diacetate (DCFHDA). The expression of cardiac fibrosis markers (Col1a1, Col3a1) and possible signaling molecules, including NADPH oxidase 4 (NOX-4), transforming growth factor β1 (TGFβ1), and Smad3, were detected by qPCR and/ or Western blot.

RESULTS

PM2.5 exposure induced cardiac diastolic dysfunction of mice, elevated the heart rate and blood pressure, developed cardiac systolic dysfunction of 10-month-old mice, and caused fibrosis in both 4-week-old and 10-month-old mice. PM2.5 exposure increased the expression of Col1a1, Col3a1, NOX-4, and TGFβ1, activated Smad3, and generated more reactive oxygen species in the myocardium of 4-week-old and 10-month-old mice. The withdrawal from PM2.5 exposure restored blood pressure, heart rate, cardiac function, expression of collagens, and malonaldehyde (MDA) levels in hearts of both 10-month-old and 4-week-old mice.

CONCLUSION

Juvenile and older mice are more sensitive to PM2.5 than adults and suffer from cardiac dysfunction. PM2.5 exposure reversibly elevated heart rate and blood pressure, induced cardiac systolic dysfunction of older mice, and reversibly induced fibrosis in juvenile and older mice. The mechanism by which PM2.5 exposure resulted in cardiac lesions might involve oxidative stress, NADPH oxidase, TGFβ1, and Smad-dependent pathways.

Air pollution and diastolic function in elderly women - Results from the SALIA study cohort

BACKGROUND

Studies linking particulate matter (PM) with heart failure (HF) show inconsistent results. However, the association of air pollution with diastolic function, an important determinant of heart failure, has not been studied yet and is addressed in the presented study.

METHODS

402 women (69-79 years) of the clinical follow-up (2007-2010) of the ongoing population-based prospective SALIA (Study on the influence of Air pollution on Lung function, Inflammation and Ageing) cohort were examined using Doppler echocardiography: Of the 291 women with preserved ejection fraction, the ratio of peak early diastolic filling velocity and peak early diastolic mitral annulus velocity (E/E') was collected in 264 and left atrial volume index (LAVI) in 262 women. Residential long-term air pollution exposure (nitrogen oxides, size-fractioned PM) was modeled at baseline and at follow-up, applying land use regression models. We used linear regression to model the cross-sectional associations of air pollutants per interquartile range (IQR) with different measures of diastolic function, adjusting for personal risk factors.

RESULTS

Median concentrations of annual NOx, NO2, PM2.5, and PM10 at follow-up were 37.7, 25.9, 17.4 and 26.4μg/m(3), respectively. In the fully adjusted models, LAVI was associated with an IQR increase in PM2.5 (1.05 [0.99; 1.12]) and NOx (1.04 [1.00; 1.09]) at follow-up, and with NOx and NO2 (both 1.05 [1.00; 1.11]) at baseline. None of the pollutants were clearly associated with E/E'.

CONCLUSIONS

In this analysis of elderly women, we found suggestive evidence for an association of air pollution with impaired diastolic function.

Cardiac and mitochondrial dysfunction following acute pulmonary exposure to mountaintop removal mining particulate matter

Throughout the United States, air pollution correlates with adverse health outcomes, and cardiovascular disease incidence is commonly increased following environmental exposure. In areas surrounding active mountaintop removal mines (MTM), a further increase in cardiovascular morbidity is observed and may be attributed in part to particulate matter (PM) released from the mine. The mitochondrion has been shown to be central in the etiology of many cardiovascular diseases, yet its roles in PM-related cardiovascular effects are not realized. In this study, we sought to elucidate the cardiac processes that are disrupted following exposure to mountaintop removal mining particulate matter (PM MTM). To address this question, we exposed male Sprague-Dawley rats to PM MTM, collected within one mile of an active MTM site, using intratracheal instillation. Twenty-four hours following exposure, we evaluated cardiac function, apoptotic indices, and mitochondrial function. PM MTM exposure elicited a significant decrease in ejection fraction and fractional shortening compared with controls. Investigation into the cellular impacts of PM MTM exposure identified a significant increase in mitochondrial-induced apoptotic signaling, as reflected by an increase in TUNEL-positive nuclei and increased caspase-3 and -9 activities. Finally, a significant increase in mitochondrial transition pore opening leading to decreased mitochondrial function was identified following exposure. In conclusion, our data suggest that pulmonary exposure to PM MTM increases cardiac mitochondrial-associated apoptotic signaling and decreases mitochondrial function concomitant with decreased cardiac function. These results suggest that increased cardiovascular disease incidence in populations surrounding MTM mines may be associated with increased cardiac cell apoptotic signaling and decreased mitochondrial function.

Cardiomyopathy confers susceptibility to particulate matter-induced oxidative stress, vagal dominance, arrhythmia and pulmonary inflammation in heart failure-prone rats

Acute exposure to ambient fine particulate matter (PM2.5) is tied to cardiovascular morbidity and mortality, especially among those with prior cardiac injury. The mechanisms and pathophysiological events precipitating these outcomes remain poorly understood but may involve inflammation, oxidative stress, arrhythmia and autonomic nervous system imbalance. Cardiomyopathy results from cardiac injury, is the leading cause of heart failure, and can be induced in heart failure-prone rats through sub-chronic infusion of isoproterenol (ISO). To test whether cardiomyopathy confers susceptibility to inhaled PM2.5 and can elucidate potential mechanisms, we investigated the cardiophysiologic, ventilatory, inflammatory and oxidative effects of a single nose-only inhalation of a metal-rich PM2.5 (580 µg/m(3), 4 h) in ISO-pretreated (35 days × 1.0 mg/kg/day sc) rats. During the 5 days post-treatment, ISO-treated rats had decreased HR and BP and increased pre-ejection period (PEP, an inverse correlate of contractility) relative to saline-treated rats. Before inhalation exposure, ISO-pretreated rats had increased PR and ventricular repolarization time (QT) and heterogeneity (Tp-Te). Relative to clean air, PM2.5 further prolonged PR-interval and decreased systolic BP during inhalation exposure; increased tidal volume, expiratory time, heart rate variability (HRV) parameters of parasympathetic tone and atrioventricular block arrhythmias over the hours post-exposure; increased pulmonary neutrophils, macrophages and total antioxidant status one day post-exposure; and decreased pulmonary glutathione peroxidase 8 weeks after exposure, with all effects occurring exclusively in ISO-pretreated rats but not saline-pretreated rats. Ultimately, our findings indicate that cardiomyopathy confers susceptibility to the oxidative, inflammatory, ventilatory, autonomic and arrhythmogenic effects of acute PM2.5 inhalation.

Fine particulate matter results in hemodynamic changes in subjects with blunted nocturnal blood pressure dipping

Particulate matter with aerodynamic diameter of <2.5 μm (PM2.5) is associated with blood pressure and hemodynamic changes. Blunted nocturnal blood pressure dipping is a major risk factor for cardiovascular events; limited information is available on whether PM2.5 exposure-related hemodynamic changes vary with day-night blood pressure circadian rhythms. In this study, we enrolled 161 subjects and monitored the changes in ambulatory blood pressure and hemodynamics for 24h. The day-night blood pressure and cardiovascular metrics were calculated according to the sleep-wake cycles logged in the subject׳s diary. The effects of PM2.5 exposure on blood pressure and hemodynamic changes were analyzed using generalized linear mixed-effect model. After adjusting for potential confounders, a 10-μg/m(3) increase in PM2.5 was associated with 1.0 mmHg [95% confidence interval (CI): 0.2-1.8 mmHg] narrowing in the pulse pressure, 3.1% (95% CI: 1.4-4.8%) decrease in the maximum rate of left ventricular pressure rise, and 3.6% (95% CI: 1.6-5.7%) increase in systemic vascular resistance among 79 subjects with nocturnal blood pressure dip of <10%. In contrast, PM2.5 was not associated with any changes in cardiovascular metrics among 82 subjects with nocturnal blood pressure dip of ≥10%. Our findings demonstrate that short-term exposure to PM2.5 contributes to pulse pressure narrowing along with cardiac and vasomotor dysfunctions in subjects with nocturnal blood pressure dip of <10%.

Carbon black vs. black carbon and other airborne materials containing elemental carbon: physical and chemical distinctions

Airborne particles containing elemental carbon (EC) are currently at the forefront of scientific and regulatory scrutiny, including black carbon, carbon black, and engineered carbon-based nanomaterials, e.g., carbon nanotubes, fullerenes, and graphene. Scientists and regulators sometimes group these EC-containing particles together, for example, interchangeably using the terms carbon black and black carbon despite one being a manufactured product with well-controlled properties and the other being an undesired, incomplete-combustion byproduct with diverse properties. In this critical review, we synthesize information on the contrasting properties of EC-containing particles in order to highlight significant differences that can affect hazard potential. We demonstrate why carbon black should not be considered a model particle representative of either combustion soots or engineered carbon-based nanomaterials. Overall, scientific studies need to distinguish these highly different EC-containing particles with care and precision so as to forestall unwarranted extrapolation of properties, hazard potential, and study conclusions from one material to another.

Exposure to diesel exhaust particulates induces cardiac dysfunction and remodeling

Chronic exposure to diesel exhaust particulates (DEP) increases the risk of cardiovascular disease in urban residents, predisposing them to the development of several cardiovascular stresses, including myocardial infarctions, arrhythmias, thrombosis, and heart failure. DEP contain a high level of polycyclic aromatic hydrocarbons, which activate the aryl hydrocarbon receptor (AHR). We hypothesize that exposure to DEP elicits ventricular remodeling through the activation of the AHR pathway, leading to ventricular dilation and dysfunction. Male Sprague-Dawley rats were exposed by nose-only nebulization to DEP (SRM 2975, 0.2 mg/ml) or vehicle for 20 min/day × 5 wk. DEP exposure resulted in eccentric left ventricular dilation (8% increased left ventricular internal diameter at diastole and 23% decreased left ventricular posterior wall thickness at diastole vs. vehicle), as shown by echocardiograph assessment. Histological analysis using Picrosirius red staining revealed that DEP reduced cardiac interstitial collagen (23% decrease vs. vehicle). Further assessment of cardiac function using a pressure-volume catheter indicated impaired diastolic function (85% increased end-diastolic pressure and 19% decreased Tau vs. vehicle) and contractility (57 and 48% decreased end-systolic pressure-volume relationship and maximum change in pressure over time vs. end-diastolic volume compared with vehicle, respectively) in the DEP-exposed animals. Exposure to DEP significantly increased cardiac expression of AHR (19% increase vs. vehicle). In addition, DEP significantly decreased the cardiac expression of hypoxia inducible factor-1α, the competitive pathway to the AHR, and vascular endothelial growth factor, a downstream mediator of hypoxia inducible factor-1α (26 and 47% decrease vs. vehicle, respectively). These findings indicate that exposure to DEP induced left ventricular dilation by loss of collagen through an AHR-dependent mechanism.

Susceptibility of older adults to health effects induced by ambient air pollutants regulated by the European Union and the United States

Air pollution is a health concern for the general population, but a few subpopulations (e.g., children, individuals with preexisting cardiovascular or respiratory diseases, etc.) are considered more susceptible to the adverse health effects attributed to air pollution. There is sufficient evidence to suggest that older adults (≥65 years old) are more susceptible to air pollution-induced health effects compared to younger adults due to decreased physiological, metabolic and compensatory processes, and a greater incidence of cardiovascular and respiratory disease. This review examines health effects induced by exposures to common ambient air pollutants regulated by the European Union and the United States. Studies were evaluated that examined the potential susceptibility of older adults to air pollutant-induced health effects. This review focuses on epidemiologic studies that directly compared the health effects of older adults to younger adults and/or the general population in order to compare populations within the same study design. Supplementary information is used from controlled human exposure studies, which examined only older adults, and animal toxicological studies, which utilized animal models of senescence, to provide coherence and biological plausibility for the health effects observed in epidemiologic studies. Overall, evidence from available published studies demonstrates that older adults may be more susceptible to air pollution-induced health effects than younger adults and/or the general population. Clinicians and other health professionals should consider advising older adults on pollution-avoiding behaviors in order to decrease the risk of adverse air pollution-related health effects.

Diesel exhaust inhalation increases cardiac output, bradyarrhythmias, and parasympathetic tone in aged heart failure-prone rats

Acute air pollutant inhalation is linked to adverse cardiac events and death, and hospitalizations for heart failure. Diesel engine exhaust (DE) is a major air pollutant suspected to exacerbate preexisting cardiac conditions, in part, through autonomic and electrophysiologic disturbance of normal cardiac function. To explore this putative mechanism, we examined cardiophysiologic responses to DE inhalation in a model of aged heart failure-prone rats without signs or symptoms of overt heart failure. We hypothesized that acute DE exposure would alter heart rhythm, cardiac electrophysiology, and ventricular performance and dimensions consistent with autonomic imbalance while increasing biochemical markers of toxicity. Spontaneously hypertensive heart failure rats (16 months) were exposed once to whole DE (4h, target PM(2.5) concentration: 500 µg/m(3)) or filtered air. DE increased multiple heart rate variability (HRV) parameters during exposure. In the 4h after exposure, DE increased cardiac output, left ventricular volume (end diastolic and systolic), stroke volume, HRV, and atrioventricular block arrhythmias while increasing electrocardiographic measures of ventricular repolarization (i.e., ST and T amplitudes, ST area, T-peak to T-end duration). DE did not affect heart rate relative to air. Changes in HRV positively correlated with postexposure changes in bradyarrhythmia frequency, repolarization, and echocardiographic parameters. At 24h postexposure, DE-exposed rats had increased serum C-reactive protein and pulmonary eosinophils. This study demonstrates that cardiac effects of DE inhalation are likely to occur through changes in autonomic balance associated with modulation of cardiac electrophysiology and mechanical function and may offer insights into the adverse health effects of traffic-related air pollutants.

Effects of ozone and particulate matter on cardiac mechanics: role of the atrial natriuretic peptide gene

A positive association between air pollution exposure and increased human risk of chronic heart disease progression is well established. In the current study, we test two hypotheses: (1) the cardiac compensatory changes in response to air pollution are dependent on its composition and (2) specific cardiac adaptations are regulated by atrial natriuretic peptide (ANP). We address these hypotheses by initially examining the exposure effects of ozone (O(3)) and/or particulate matter (PM) on cardiac function in C57Bl/6J (B6) mice. Subsequently, the results are compared with cardiac functional changes to the same exposures in Nppa (the precursor gene for ANP) knockout (KO) mice. Separate groups of mice underwent 3 consecutive days of the same exposure sequence for 3h each consisting of the following: (1) 6h of filtered air (FAFA), (2) O(3) then FA (O(3)FA), (3) FA then carbon black (FACB), or (4) O(3) then CB. Cardiac function was assessed using a conductance catheter to generate cardiac pressure-volume loops 8-10h following each exposure sequence. As compared with FAFA, each sequence led to a substantial drop (as much as 33%) in stroke volume and cardiac output. However, these losses of cardiac function occurred by different compensatory mechanisms dependent on the pollutant composition. For example, O(3)FA exposure led to reductions in both end-systolic and end-diastolic left ventricular (LV) volumes, whereas FACB exposure led an increase in end-diastolic LV volume. These same cardiac compensatory changes were largely abolished in Nppa KO mice following O(3)FA or FACB exposure. These results suggest that cardiac functional changes in response to air pollution exposure are strongly dependent on the pollutant constituents, especially related to O(3) and/or PM. Furthermore, ANP regulation appears to be crucial to these cardiac compensatory mechanisms induced by air pollution.

Environmentally persistent free radicals decrease cardiac function and increase pulmonary artery pressure

Epidemiological studies have consistently linked inhalation of particulate matter (PM) to increased cardiac morbidity and mortality, especially in at risk populations. However, few studies have examined the effect of PM on baseline cardiac function in otherwise healthy individuals. In addition, airborne PM contain environmentally persistent free radicals (EPFR) capable of redox cycling in biological systems. The purpose of this study was to determine whether nose-only inhalation of EPFRs (20 min/day for 7 days) could decrease baseline left ventricular function in healthy male Sprague-Dawley rats. The model EPFR tested was 1,2-dichlorobenzene chemisorbed to 0.2-μm-diameter silica/CuO particles at 230°C (DCB230). Inhalation of vehicle or silica particles served as controls. Twenty-four hours after the last exposure, rats were anesthetized (isoflurane) and ventilated (3 l/min), and left ventricular function was assessed using pressure-volume catheters. Compared with controls, inhalation of DCB230 significantly decreased baseline stroke volume, cardiac output, and stroke work. End-diastolic volume and end-diastolic pressure were also significantly reduced; however, ventricular contractility and relaxation were not changed. DCB230 also significantly increased pulmonary arterial pressure and produced hyperplasia in small pulmonary arteries. Plasma levels of C-reactive protein were significantly increased by exposure to DCB230, as were levels of heme oxygenase-1 and SOD2 in the left ventricle. Together, these data show that inhalation of EPFRs, but not silica particles, decreases baseline cardiac function in healthy rats by decreasing cardiac filling, secondary to increased pulmonary resistance. These EPFRs also produced systemic inflammation and increased oxidative stress markers in the left ventricle.

Effects of particulate air pollution on cardiovascular health: a population health risk assessment

Particulate matter (PM) air pollution is increasingly recognized as an important and modifiable risk factor for adverse health outcomes including cardiovascular disease (CVD). However, there are still gaps regarding large population risk assessment. Results from the nationwide Behavioral Risk Factor Surveillance System (BRFSS) were used along with air quality monitoring measurements to implement a systematic evaluation of PM-related CVD risks at the national and regional scales. CVD status and individual-level risk factors were collected from more than 500,000 BRFSS respondents across 2,231 contiguous U.S. counties for 2007 and 2009. Chronic exposures to PM pollutants were estimated with spatial modeling from measurement data. CVD outcomes attributable to PM pollutants were assessed by mixed-effects logistic regression and latent class regression (LCR), with adjustment for multicausality. There were positive associations between CVD and PM after accounting for competing risk factors: the multivariable-adjusted odds for the multiplicity of CVD outcomes increased by 1.32 (95% confidence interval: 1.23–1.43) and 1.15 (1.07–1.22) times per 10 µg/m³ increase in PM_2.5 and PM₁₀ respectively in the LCR analyses. After controlling for spatial confounding, there were moderate estimated effects of PM exposure on multiple cardiovascular manifestations. These results suggest that chronic exposures to ambient particulates are important environmental risk factors for cardiovascular morbidity.

Phosphatase PTEN is critically involved in post-myocardial infarction remodeling through the Akt/interleukin-10 signaling pathway

The inflammatory cytokines interleukin (IL)-10 and tumor necrosis factor (TNF)-α play an important role in left ventricular (LV) remodeling after myocardial infarction (MI). Phosphatase and tensin homolog deleted on chromosome ten (PTEN) inactivates protein kinase Akt and promotes cell death in the heart. However, it is not known whether PTEN promotes post-MI remodeling by regulating IL-10 and TNF-α. MI was induced in wild-type (WT) mice and Pten heterozygous mutant (HET) mice. Pten adenoviruses (adPten) or empty vectors (adNull) were injected into the peri-infarct area of WT mice. LV dilation was attenuated and fractional shortening was increased in HET mice compared to WT mice. Survival rate and fractional shortening were decreased in adPten mice compared to adNull mice. Leukocyte infiltration into the peri-infarct area was attenuated in HET mice and worsened in adPten mice. PTEN expression was upregulated in the infarcted heart of WT mice. Partial inactivation of PTEN increased the production of IL-10 and decreased the expression of TNF-α and matrix metalloproteinase (MMP)-2 and -9 after MI in HET mice. PTEN overexpression caused opposite effects in the infarcted heart. Moreover in the infarcted heart of HET mice, Akt inhibition decreased Stat3 phosphorylation and IL-10 expression, and blockade of the IL-10 receptor increased TNF-α and MMP-2 expression. Both Akt inhibition and IL-10 receptor blockade abolished the attenuation of post-MI remodeling in HET mice. In conclusion, PTEN is critically involved in post-MI remodeling through the Akt/IL-10 signaling pathway. Therefore, targeting PTEN may be an effective approach to post-MI remodeling.

Environmentally persistent free radicals decrease cardiac function before and after ischemia/reperfusion injury in vivo

Exposure to airborne particles is associated with increased cardiovascular morbidity and mortality. During the combustion of chlorine-containing hazardous materials and fuels, chlorinated hydrocarbons chemisorb to the surface of transition metal-oxide-containing particles, reduce the metal, and form an organic free radical. These radical-particle systems can survive in the environment for days and are called environmentally persistent free radicals (EPFRs). This study determined whether EPFRs could decrease left ventricular function before and after ischemia and reperfusion (I/R) in vivo. Male Brown-Norway rats were dosed (8 mg/kg, intratracheal) 24 h prior to testing with particles containing the EPFR of 1, 2-dichlorobenzene (DCB230). DCB230 treatment decreased systolic and diastolic function. DCB230 also produced pulmonary and cardiac inflammation. After ischemia, systolic, but not diastolic function was significantly decreased in DCB230-treated rats. Ventricular function was not affected by I/R in control rats. There was greater oxidative stress in the heart and increased 8-isoprostane (biomarker of oxidative stress) in the plasma of treated vs. control rats after I/R. These data demonstrate for the first time that DCB230 can produce inflammation and significantly decrease cardiac function at baseline and after I/R in vivo. Furthermore, these data suggest that EPFRs may be a risk factor for cardiac toxicity in healthy individuals and individuals with ischemic heart disease. Potential mechanisms involving cytokines/chemokines and/or oxidative stress are discussed.

Particulate matter-induced health effects: who is susceptible?

BACKGROUND

Epidemiological, controlled human exposure, and toxicological studies have demonstrated a variety of health effects in response to particulate matter (PM) exposure with some of these studies indicating that populations with certain characteristics may be disproportionately affected.

OBJECTIVE

To identify populations potentially at greatest risk for PM-related health effects, we evaluated epidemiological studies that examined various characteristics that may influence susceptibility, while using results from controlled human exposure and toxicological studies as supporting evidence. Additionally, we formulated a definition of susceptibility, building from the varied and inconsistent definitions of susceptibility and vulnerability used throughout the literature.

DATA SYNTHESIS

We evaluated recent epidemiological studies to identify characteristics of populations potentially susceptible to PM-related health effects. Additionally, we evaluated controlled human exposure and toxicological studies to provide supporting evidence. We conducted a comprehensive review of epidemiological studies that presented stratified results (e.g., < 65 vs. ≥ 65 years of age), controlled human exposure studies that examined individuals with underlying disease, and toxicological studies that used animal models of disease. We evaluated results for consistency across studies, coherence across disciplines, and biological plausibility to assess the potential for increased susceptibility to PM-related health effects in a specific population or life stage.

CONCLUSIONS

We identified a diverse group of characteristics that can lead to increased risk of PM-related health effects, including life stage (i.e., children and older adults), preexisting cardiovascular or respiratory diseases, genetic polymorphisms, and low-socioeconomic status. In addition, we crafted a comprehensive definition of susceptibility that can be used to encompass all populations potentially at increased risk of adverse health effects as a consequence of exposure to an air pollutant.

Pulmonary exposure to carbon black nanoparticles and vascular effects

BACKGROUND

Exposure to small size particulates is regarded as a risk factor for cardiovascular diseases.

METHODS

We exposed young and aged apolipoprotein E knockout mice (apoE-/-) to carbon black (Printex 90, 14 nm) by intratracheal instillation, with different dosing and timing, and measured vasomotor function, progression of atherosclerotic plaques, and VCAM-1, ICAM-1, and 3-nitrotyrosine in blood vessels. The mRNA expression of VCAM-1, ICAM-1, HO-1, and MCP-1 was examined in lung tissue.

RESULTS

Young apoE-/- mice exposed to two consecutive 0.5 mg/kg doses of carbon black exhibited lower acetylcholine-induced vasorelaxation in aorta segments mounted in myographs, whereas single doses of 0.05-2.7 mg/kg produced no such effects. The phenylephrine-dependent vasocontraction response was shifted toward a lower responsiveness in the mice exposed once to a low dose for 24 hours. No effects were seen on the progression of atherosclerotic plaques in the aged apoE-/- mice or on the expression of VCAM-1 and ICAM-1 and the presence of 3-nitrotyrosine in the vascular tissue of either young or aged apoE-/- mice. The expression of MCP-1 mRNA was increased in the lungs of young apoE-/- mice exposed to 0.9-2.7 mg/kg carbon black for 24 hours and of aged apoE-/- mice exposed to two consecutive 0.5 mg/kg doses of carbon black seven and five weeks prior to sacrifice.

CONCLUSION

Exposure to nano-sized carbon black particles is associated with modest vasomotor impairment, which is associated neither with nitrosative stress nor with any obvious increases in the expression of cell adhesion proteins on endothelial cells or in plaque progression. Evidence of pulmonary inflammation was observed, but only in animals exposed to higher doses.

Variation in echocardiographic and cardiac hemodynamic effects of PM and ozone inhalation exposure in strains related to Nppa and Npr1 gene knock-out mice

Elevated levels of ambient co-pollutants are associated with adverse cardiovascular outcomes shown by epidemiology studies. The role of particulate matter (PM) and ozone (O3) as co-pollutants in this association is unclear. We hypothesize that cardiac function following PM and O3 exposure is variably affected by genetic determinants (Nppa and Npr1 genes) and age. Heart function was measured before and after 2 days each of the following exposure sequence; (1) 2-h filtered air (FA) and 3-h carbon black (CB; 0.5 microg/m(3)); (2) 2-h O3 (0.6 ppm) and 3-h FA; (3) 5-h FA; and, (4) 2-h O3 and 3-h CB. Two age groups (5 and 18 months old (mo)) were tested in C57Bl/6J (B6) and 129S1/SvImJ (129) mice using echocardiographic (echo) and in vivo hemodynamic (IVH) measurements. With echo, posterior wall thickness was significantly (P < 0.01) greater in 129 relative to B6 mice at baseline. With CB exposure, young B6 and older 129 mice show significant (P < 0.01) reductions in fractional shortening (FS) compared to FA. With O3 exposure, FS was significantly (P < 0.01) diminished in young 129, which was attributable to significant increases in end-systolic left ventricular diameter. With O3 and CB combined, notable (P < 0.01) declines in heart rate and end-systolic posterior wall thickness occurred in young 129 mice. The IVH measurements showed striking (P < 0.05) compromises in cardiac function after CB and O3 exposure; however, strain differences were undetectable. These results suggest that PM and O3 exposures, alone and combined, lead to different cardiac functional changes, and these unique changes are age-specific and dependent on Nppa and Npr1 genes.

Particulate matter air pollution and cardiovascular disease: An update to the scientific statement from the American Heart Association

In 2004, the first American Heart Association scientific statement on "Air Pollution and Cardiovascular Disease" concluded that exposure to particulate matter (PM) air pollution contributes to cardiovascular morbidity and mortality. In the interim, numerous studies have expanded our understanding of this association and further elucidated the physiological and molecular mechanisms involved. The main objective of this updated American Heart Association scientific statement is to provide a comprehensive review of the new evidence linking PM exposure with cardiovascular disease, with a specific focus on highlighting the clinical implications for researchers and healthcare providers. The writing group also sought to provide expert consensus opinions on many aspects of the current state of science and updated suggestions for areas of future research. On the basis of the findings of this review, several new conclusions were reached, including the following: Exposure to PM <2.5 microm in diameter (PM(2.5)) over a few hours to weeks can trigger cardiovascular disease-related mortality and nonfatal events; longer-term exposure (eg, a few years) increases the risk for cardiovascular mortality to an even greater extent than exposures over a few days and reduces life expectancy within more highly exposed segments of the population by several months to a few years; reductions in PM levels are associated with decreases in cardiovascular mortality within a time frame as short as a few years; and many credible pathological mechanisms have been elucidated that lend biological plausibility to these findings. It is the opinion of the writing group that the overall evidence is consistent with a causal relationship between PM(2.5) exposure and cardiovascular morbidity and mortality. This body of evidence has grown and been strengthened substantially since the first American Heart Association scientific statement was published. Finally, PM(2.5) exposure is deemed a modifiable factor that contributes to cardiovascular morbidity and mortality.

Effects of particulate matter (PM(10), PM(2.5) and PM(1)) on the cardiovascular system

Several studies have demonstrated that exposure to particulate matter (PM) of different size fractions is associated with an increased risk of cardiovascular disease (CVD). In this review, we have taken into consideration the possible correlation between the "short term" and "long term" effects of PM exposure and the onset of CVDs as well as the possible molecular mechanisms by which PM elicits the development of these events. Particularly, it is here underlined that these adverse health effects depend not only on the level of PM concentration in the air but also on its particular internal composition. Furthermore, we have also synthesized the findings gleaned from those few studies indicating that PM produced by tobacco smoke can give rise to cardiovascular injury.

Long-acting oral phosphodiesterase inhibition preconditions against reperfusion injury in an experimental lung transplantation model

OBJECTIVES

Ischemia-reperfusion injury remains a devastating complication of lung transplantation. Phosphodiesterase inhibitors have been shown to precondition tissues against ischemia-reperfusion injury. Little is known, however, about the utility of phosphodiesterase inhibition in reperfusion injury after lung transplantation. We evaluated the long-acting phosphodiesterase-5 inhibitor, tadalafil, in an ex vivo lung transplant model.

METHODS

New Zealand White rabbits (4 kg), were given oral tadalafil (n = 11) 24 hours before lung harvest and compared with rabbits given oral vehicle alone (n = 11). Lungs were recovered with Perfadex solution (Vitrolife, Kungsbacka, Sweden) and cold stored for 18 hours. After storage, lung blocks were reperfused with donor rabbit blood in an ex vivo apparatus. Pulmonary artery pressures were recorded with serial arterial and venous blood gas sampling and animals served as their own controls. Phosphodiesterase-5 and protein kinase G tissue activity assays confirmed drug effects. Luminol chemiluminescence assay was used to measure reactive oxygen species and levels of endothelial and inducible nitric oxide synthase were measured.

RESULTS

Extended cold storage, followed by reperfusion produced a consistent reproducible decrease in oxygenation and increase in pulmonary pressure. Tadalafil-treated animals exhibited greater Pao(2) throughout the course of reperfusion (P = .001) Mean pulmonary artery pressure was lower in tadalafil-treated animals (22 vs 40 mm Hg; P = .04). Phosphodiesterase-5 activity was decreased (143 +/- 8 vs 205 +/- 32 mP; P < .001) with protein kinase G activity increased (25 +/- 12 vs 12 +/- 2.4 fU/microg; P = .01) in the experimental group confirming that oral pretreatment resulted in active phosphodiesterase inhibition in the lung tissue. Reactive oxygen species (as measured by luminol activity) were decreased in tadalafil-treated animals (7.8 +/- 1.5 vs 10.2 +/- 1.2 relative light units; P = .003).

CONCLUSIONS

Our experimental model demonstrates that oral donor pretreatment with a long-acting phosphodiesterase inhibitor is an effective strategy for improving pulmonary performance after reperfusion. Importantly, phosphodiesterase enzymes and their downstream effectors may play a critical role in reperfusion injury after lung transplantation.

Interstrain variation in cardiac and respiratory adaptation to repeated ozone and particulate matter exposures

Increased ambient particulate matter (PM) is associated with adverse cardiovascular and respiratory outcomes, as demonstrated by epidemiology studies. Several studies have investigated the role of copollutants, such as ozone (O(3)), in this association. It is accepted that physiological adaptation involving the respiratory system occurs with repeated exposures to O(3). We hypothesize that adaptation to PM and O(3) varies among different inbred mouse strains, and cardiopulmonary adaptation to O(3) is a synchronized response between the cardiac and respiratory systems. Heart rate (HR), HR variability (HRV), and the magnitude and pattern of breathing were simultaneously measured by implanted telemeters and by plethysmography in three inbred mouse strains: C57Bl/6J (B6), C3H/HeJ (HeJ), and C3H/HeOuJ (OuJ). Physiological responses were assessed during dual exposures to filtered air (FA), O(3) (576 +/- 32 parts/billion), and/or carbon black (CB; 556 +/- 34 mug/m(3)). Exposures were repeated for 3 consecutive days. While each strain showed significant reductions in HR during CB with O(3) preexposure (O(3)CB) on day 1, prominent HRV responses were observed in only HeJ and OuJ mice. Each strain also differed in their adaptation profile in response to repeated O(3)CB exposures. Whereas B6 mice showed rapid adaptation in HR after day 1, HeJ mice generally showed more moderate HR and HRV adaptation after day 2 of exposure. Unlike either B6 or HeJ strains, OuJ mice showed little evidence of HR or HRV adaptation to repeated O(3)CB exposure. Adaptation profiles between HR regulation and breathing characteristics were strongly correlated, but these associations also varied significantly among strains. These findings suggest that genetic factors determine the responsivity and adaptation of the cardiac and respiratory systems to repeated copollutant exposures. During O(3)CB exposure, adaptation of cardiac and respiratory systems is markedly synchronized, which may explain a potential mechanism for adverse effects of PM on heart function.