New insights into pollution and the cardiovascular system: 2010 to 2012

Low-dose exposure of silica nanoparticles induces cardiac dysfunction via neutrophil-mediated inflammation and cardiac contraction in zebrafish embryos

The toxicity mechanism of nanoparticles on vertebrate cardiovascular system is still unclear, especially on the low-level exposure. This study was to explore the toxic effect and mechanisms of low-dose exposure of silica nanoparticles (SiNPs) on cardiac function in zebrafish embryos via the intravenous microinjection. The dosage of SiNPs was based on the no observed adverse effect level (NOAEL) of malformation assessment in zebrafish embryos. The mainly cardiac toxicity phenotypes induced by SiNPs were pericardial edema and bradycardia but had no effect on atrioventricular block. Using o-Dianisidine for erythrocyte staining, the cardiac output of zebrafish embryos was decreased in a dose-dependent manner. Microarray analysis and bioinformatics analysis were performed to screen the differential expression genes and possible pathway involved in cardiac function. SiNPs induced whole-embryo oxidative stress and neutrophil-mediated cardiac inflammation in Tg(mpo:GFP) zebrafish. Inflammatory cells were observed in atrium of SiNPs-treated zebrafish heart by histopathological examination. In addition, the expression of TNNT2 protein, a cardiac contraction marker in heart tissue had been down-regulated compared to control group using immunohistochemistry. Confirmed by qRT-PCR and western blot assays, results showed that SiNPs inhibited the calcium signaling pathway and cardiac muscle contraction via the down-regulated of related genes, such as ATPase-related genes (atp2a1l, atp1b2b, atp1a3b), calcium channel-related genes (cacna1ab, cacna1da) and the regulatory gene tnnc1a for cardiac troponin C. Moreover, the protein level of TNNT2 was decreased in a dose-dependent manner. For the first time, our results demonstrated that SiNPs induced cardiac dysfunction via the neutrophil-mediated cardiac inflammation and cardiac contraction in zebrafish embryos.

Zinc compound air releases from Toxics Release Inventory facilities and cardiovascular disease mortality rates

BACKGROUND

Inhaled zinc has been found in association with cardiopulmonary toxicity. However, limited human epidemiologic studies are available. This study analyzed the association between covariate-adjusted cardiovascular (CVD) mortality rates and zinc compound air releases in the United States.

METHODS

We conducted an ecological analysis on the association between zinc compound air releases for 1991-2000 using the Toxics Release Inventory database and average age-adjusted CVD mortality for 2006-2010, adjusting for race/ethnicity composition and several health and socioeconomic factors. Models were estimated for males and females and for metropolitan and nonmetropolitan counties.

RESULTS

Zinc compound air releases were positively associated with increased adjusted CVD mortality rates in all four models (β=0.0085, p<0.0001 for males in nonmetropolitan counties; β=0.0093, p<0.0001 for males in metropolitan counties; β=0.0145, p<0.0001 for females in nonmetropolitan counties; and β=0.0098, p<0.0001 for females in metropolitan counties). Results were largely robust to various sensitivity analyses.

CONCLUSION

This study provides epidemiological evidence for possible CVD health impacts of inhaled zinc in the United States. Although the strongest effect was found for females in nonmetropolitan counties, the associations were consistent in nonmetropolitan or metropolitan counties for both genders.

Chronic exposure to particulate matter and risk of cardiovascular mortality: cohort study from Taiwan

Background

Evidence on the association between long-term exposure to air pollution and cardiovascular mortality is limited in Asian populations.

Methods

We conducted a cohort study on the association between fine particulate matter (PM_2.5) and cardiovascular mortality using 43,227 individuals in a civil servants health service in Taiwan. Each participant was assigned an exposure level of particulate matter based on their district of residence using air pollution data collected by the Taiwan Environmental Protection Agency and with modeling using geographic information systems. The participants were followed up from 1989 to 2008 and the vital status was ascertained from death records. Cox regression models were used to adjust for confounding factors.

Results

The district-level average of PM_2.5 ranged from 22.8 to 32.9 μg/m³ in the study area. After a median follow-up of 18 years, 1992 deaths from all causes including 230 cardiovascular deaths occurred. After adjustment for potential confounders, PM_2.5 levels were not significantly associated with mortality from cardiovascular disease [Hazard Ratio (HR) 0.80; 95 % Confidence Interval (CI), 0.43 to 1.50 per 10 μg/m³ increase in PM_2.5] or all causes (HR 0.92; 95 % CI, 0.72 to 1.17 per 10 μg/m³ increase in PM_2.5). The results were similar when the analysis was restricted to the urban areas and when the PM_2.5 measurement was changed from the period average (2000–2008) to annual average.

Discussion

Our findings are different from those in prior cohort studies conducted in Asia where ambient air pollutionwas associated with an increased risk of cardiovascular mortality. The high background level of air pollutionin our study area and the small number of event cases limited the power of this study.

Conclusions

In this population-based cohort study in Taiwan, we found no evidence of increased risk for all-cause or cardiovascular mortality with long-term exposure to PM_2.5.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-2272-6) contains supplementary material, which is available to authorized users.

Impact of Fine Particulate Matter (PM2.5) Exposure During Wildfires on Cardiovascular Health Outcomes

Background

Epidemiological studies investigating the role of fine particulate matter (PM_2.5; aerodynamic diameter <2.5 μm) in triggering acute coronary events, including out-of-hospital cardiac arrests and ischemic heart disease (IHD), during wildfires have been inconclusive.

Methods and Results

We examined the associations of out-of-hospital cardiac arrests, IHD, acute myocardial infarction, and angina (hospital admissions and emergency department attendance) with PM_2.5 concentrations during the 2006–2007 wildfires in Victoria, Australia, using a time-stratified case-crossover study design. Health data were obtained from comprehensive health-based administrative registries for the study period (December 2006 to January 2007). Modeled and validated air exposure data from wildfire smoke emissions (daily average PM_2.5, temperature, relative humidity) were also estimated for this period. There were 457 out-of-hospital cardiac arrests, 2106 emergency department visits, and 3274 hospital admissions for IHD. After adjusting for temperature and relative humidity, an increase in interquartile range of 9.04 μg/m³ in PM_2.5 over 2 days moving average (lag 0-1) was associated with a 6.98% (95% CI 1.03% to 13.29%) increase in risk of out-of-hospital cardiac arrests, with strong association shown by men (9.05%,95%CI 1.63% to 17.02%) and by older adults (aged ≥65 years) (7.25%, 95% CI 0.24% to 14.75%). Increase in risk was (2.07%, 95% CI 0.09% to 4.09%) for IHD-related emergency department attendance and (1.86%, 95% CI: 0.35% to 3.4%) for IHD-related hospital admissions at lag 2 days, with strong associations shown by women (3.21%, 95% CI 0.81% to 5.67%) and by older adults (2.41%, 95% CI 0.82% to 5.67%).

Conclusion

PM_2.5 exposure was associated with increased risk of out-of-hospital cardiac arrests and IHD during the 2006–2007 wildfires in Victoria. This evidence indicates that PM_2.5 may act as a triggering factor for acute coronary events during wildfire episodes.

Associations between short-term exposure to particulate matter and ultrafine particles and myocardial infarction in Augsburg, Germany

BACKGROUND

Short-term exposure to increased particulate matter (PM) concentration has been reported to trigger myocardial infarction (MI). However, the association with ultrafine particles remains unclear.

OBJECTIVES

We aimed to assess the effects of short-term air pollution and especially ultrafine particles on registry-based MI events and coronary deaths in the area of Augsburg, Germany.

METHODS

Between 1995 and 2009, the MONICA/KORA myocardial infarction registry recorded 15,417 cases of MI and coronary deaths. Concentrations of PM<10μm (PM10), PM<2.5μm (PM2.5), particle number concentration (PNC) as indicator for ultrafine particles, and meteorological parameters were measured in the study region. Quasi-Poisson regression adjusting for time trend, temperature, season, and weekday was used to estimate immediate, delayed and cumulative effects of air pollutants on the occurrence of MI. The daily numbers of total MI, nonfatal and fatal events as well as incident and recurrent events were analysed.

RESULTS

We observed a 1.3% risk increase (95%-confidence interval: [-0.9%; 3.6%]) for all events and a 4.4% [-0.4%; 9.4%] risk increase for recurrent events per 24.3μg/m(3) increase in same day PM10 concentrations. Nonfatal events indicated a risk increase of 3.1% [-0.1%; 6.5%] with previous day PM10. No association was seen for PM2.5 which was only available from 1999 on. PNC showed a risk increase of 6.0% [0.6%; 11.7%] for recurrent events per 5529 particles/cm(3) increase in 5-day average PNC.

CONCLUSIONS

Our results suggested an association between short-term PM10 concentration and numbers of MI, especially for nonfatal and recurrent events. For ultrafine particles, risk increases were notably high for recurrent events. Thus, persons who already suffered a MI seemed to be more susceptible to air pollution.

Hypothetical exposure limits for oil-based metalworking fluids and cardiovascular mortality in a cohort of autoworkers: structural accelerated failure time models in a public health framework

Occupational exposure to aerosolized particles of oil-based metalworking fluid was recently linked to deaths from ischemic heart disease. The current recommended exposure limits might be insufficient. Studying cardiovascular mortality is challenging because symptoms can induce sicker workers to reduce their exposure, causing healthy-worker survivor bias. G-estimation of accelerated failure time models reduces this bias and permits comparison of multiple exposure interventions. Michigan autoworkers from the United AutoWorkers–General Motors cohort (n = 38,666) were followed from 1941 through 1994. Separate binary variables indicated whether annual exposure exceeded a series of potential limits. Separate g-estimation analyses for each limit yielded the total number of life-years that could have been saved among persons who died from specific cardiovascular causes by enforcing that exposure limit. Banning oil-based fluids would have saved an estimated 4,003 (95% confidence interval: 2,200, 5,807) life-years among those who died of ischemic heart disease. Estimates for cardiovascular disease overall, acute myocardial infarction, and cerebrovascular disease were 3,500 (95% confidence interval: 1,350, 5,651), 2,932 (95% confidence interval: 1,587, 4,277), and 917 (95% confidence interval: −80, 1,913) life-years, respectively. A limit of 0.01 mg/m³ would have had a similar impact on cerebrovascular disease but one only half as great on ischemic heart disease. Analyses suggest that limiting exposure to metalworking fluids could have saved many life-years lost to cardiovascular diseases in this cohort.

A Review of the Health Benefits of Greenness

Researchers are increasingly exploring how neighborhood greenness, or vegetation, may affect health behaviors and outcomes. Greenness may influence health by promoting physical activity and social contact; decreasing stress; and mitigating air pollution, noise, and heat exposure. Greenness is generally measured using satellite-based vegetation indices or land-use databases linked to participants' addresses. In this review, we found fairly strong evidence for a positive association between greenness and physical activity, and a less consistent negative association between greenness and body weight. Research suggests greenness is protective against adverse mental health outcomes, cardiovascular disease, and mortality, though most studies were limited by cross-sectional or ecological design. There is consistent evidence that greenness exposure during pregnancy is positively associated with birth weight, though findings for other birth outcomes are less conclusive. Future research should follow subjects prospectively, differentiate between greenness quantity and quality, and identify mediators and effect modifiers of greenness-health associations.

Controlled exposure to particulate matter from urban street air is associated with decreased vasodilation and heart rate variability in overweight and older adults

Background

Exposure to particulate matter (PM) is generally associated with elevated risk of cardiovascular morbidity and mortality. Elderly and obese subjects may be particularly susceptible, although short-term effects are poorly described.

Methods

Sixty healthy subjects (25 males, 35 females, age 55 to 83 years, body mass index > 25 kg/m²) were included in a cross-over study with 5 hours of exposure to particle- or sham-filtered air from a busy street using an exposure-chamber. The sham- versus particle-filtered air had average particle number concentrations of ~23.000 versus ~1800/cm³ and PM_2.5 levels of 24 versus 3μg/m³, respectively. The PM contained similar fractions of elemental and black carbon (~20-25%) in both exposure scenarios. Reactive hyperemia and nitroglycerin-induced vasodilation in finger arteries and heart rate variability (HRV) measured within 1 h after exposure were primary outcomes. Potential explanatory mechanistic variables included markers of oxidative stress (ascorbate/dehydroascorbate, nitric oxide-production cofactor tetrahydrobiopterin and its oxidation product dihydrobiopterin) and inflammation markers (C-reactive protein and leukocyte differential counts).

Results

Nitroglycerin-induced vasodilation was reduced by 12% [95% confidence interval: −22%; −1.0%] following PM exposure, whereas hyperemia-induced vasodilation was reduced by 5% [95% confidence interval: −11.6%; 1.6%]. Moreover, HRV measurements showed that the high and low frequency domains were significantly decreased and increased, respectively. Redox and inflammatory status did not change significantly based on the above measures.

Conclusions

This study indicates that exposure to real-life levels of PM from urban street air impairs the vasomotor function and HRV in overweight middle-aged and elderly adults, although this could not be explained by changes in inflammation, oxidative stress or nitric oxide-cofactors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-015-0081-9) contains supplementary material, which is available to authorized users.

Comparative cardiopulmonary toxicity of exhausts from soy-based biofuels and diesel in healthy and hypertensive rats

Increased use of renewable energy sources raise concerns about health effects of new emissions. We analyzed relative cardiopulmonary health effects of exhausts from (1) 100% soy biofuel (B100), (2) 20% soy biofuel + 80% low sulfur petroleum diesel (B20), and (3) 100% petroleum diesel (B0) in rats. Normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats were exposed to these three exhausts at 0, 50, 150 and 500 μg/m(3), 4 h/day for 2 days or 4 weeks (5 days/week). In addition, WKY rats were exposed for 1 day and responses were analyzed 0 h, 1 day or 4 days later for time-course assessment. Hematological parameters, in vitro platelet aggregation, bronchoalveolar lavage fluid (BALF) markers of pulmonary injury and inflammation, ex vivo aortic ring constriction, heart and aorta mRNA markers of vasoconstriction, thrombosis and atherogenesis were analyzed. The presence of pigmented macrophages in the lung alveoli was clearly evident with all three exhausts without apparent pathology. Overall, exposure to all three exhausts produced only modest effects in most endpoints analyzed in both strains. BALF γ-glutamyl transferase (GGT) activity was the most consistent marker and was increased in both strains, primarily with B0 (B0 > B100 > B20). This increase was associated with only modest increases in BALF neutrophils. Small and very acute increases occurred in aorta mRNA markers of vasoconstriction and thrombosis with B100 but not B0 in WKY rats. Our comparative evaluations show modest cardiovascular and pulmonary effects at low concentrations of all exhausts: B0 causing more pulmonary injury and B100 more acute vascular effects. BALF GGT activity could serve as a sensitive biomarker of inhaled pollutants.

Silica nanoparticles enhance autophagic activity, disturb endothelial cell homeostasis and impair angiogenesis

Background

Given that the effects of ultrafine fractions (<0.1 μm) on ischemic heart diseases (IHD) and other cardiovascular diseases are gaining attention, this study is aimed to explore the influence of silica nanoparticles (SiNPs)-induced autophagy on endothelial cell homeostasis and angiogenesis.

Methods and results

Ultrastructural changes of autophagy were observed in both vascular endothelial cells and pericytes in the heart of ICR mice by TEM. Autophagic activity and impaired angiogenesis were further confirmed by the immunohistochemistry staining of LC3 and VEGFR2. In addition, the immunohistochemistry results showed that SiNPs had an inhibitory effect on ICAM-1 and VCAM-1, but no obvious effect on E-selectin in vivo. The disruption of F-actin cytoskeleton occurred as an initial event in SiNPs-treated endothelial cells. The depolarized mitochondria, autophagic vacuole accumulation, LC3-I/LC3-II conversion, and the down-regulation of cellular adhesion molecule expression were all involved in the disruption of endothelial cell homeostasis in vitro. Western blot analysis indicated that the VEGFR2/PI3K/Akt/mTOR and VEGFR2/MAPK/Erk1/2/mTOR signaling pathway was involved in the cardiovascular toxicity triggered by SiNPs. Moreover, there was a crosstalk between the VEGFR2-mediated autophagy signaling and angiogenesis signaling pathways.

Conclusions

In summary, the results demonstrate that SiNPs induce autophagic activity in endothelial cells and pericytes, subsequently disturb the endothelial cell homeostasis and impair angiogenesis. The VEGFR2-mediated autophagy pathway may play a critical role in maintaining endothelium and vascular homeostasis. Our findings may provide experimental evidence and explanation for cardiovascular diseases triggered by nano-sized particles.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-014-0050-8) contains supplementary material, which is available to authorized users.

Ultrafine carbon particle mediated cardiovascular impairment of aged spontaneously hypertensive rats

Background

Studies provide compelling evidences for particulate matter (PM) associated cardiovascular health effects. Elderly individuals, particularly those with preexisting conditions like hypertension are regarded to be vulnerable. Experimental data are warranted to reveal the molecular pathomechanism of PM related cardiovascular impairments among aged/predisposed individuals. Thus we investigated the cardiovascular effects of ultrafine carbon particles (UfCP) on aged (12–13 months) spontaneously hypertensive rats (SHRs) and compared the findings with our pervious study on adult SHRs (6–7 months) to identify age related predisposition events in cardiovascular compromised elderly individuals.

Methods

Aged SHRs were inhalation exposed to UfCP for 24 h (~180 μg/m³) followed by radio-telemetric assessment for blood pressure (BP) and heart rate (HR). Bronchoalveolar lavage (BAL) fluid cell differentials, interleukin 6 (IL-6) and other proinflammatory cytokines; serum C-reactive protein (CRP) and haptoglobin (HPT); and plasma fibrinogen were measured. Transcript levels of hemeoxygenase 1 (HO-1), endothelin 1 (ET1), endothelin receptors A, B (ETA, ETB), tissue factor (TF), and plasminogen activator inhibitor-1 (PAI-1) were measured in the lung and heart to assess oxidative stress, endothelial dysfunction and coagulation cascade.

Result

UfCP exposed aged SHRs exhibited increased BP (4.4%) and HR (6.3%) on 1^st recovery day paralleled by a 58% increase of neutrophils and 25% increase of IL-6 in the BAL fluid. Simultaneously higher CRP, HPT and fibrinogen levels in exposed SHRs indicate systemic inflammation. HO-1, ET1, ET-A, ET-B, TF and PAI-1 were induced by 1.5-2.0 folds in lungs of aged SHRs on 1^st recovery day. However, in UfCP exposed adult SHRs these markers were up-regulated (2.5-6 fold) on 3^rd recovery day in lung without detectable pulmonary/systemic inflammation.

Conclusions

The UfCP induced pulmonary and systemic inflammation in aged SHRs is associated with oxidative stress, endothelial dysfunction and disturbed coagulatory hemostasis. UfCP exposure increased BP and HR in aged SHRs rats which was associated with lung inflammation, and increased expression of inflammatory, vasoconstriction and coagulation markers as well as systemic changes in biomarkers of thrombosis in aged SHRs. Our study provides further evidence for potential molecular mechanisms explaining the increased risk of particle mediated cardiac health effects in cardiovascular compromised elderly individuals.

The "New Deadly Quartet" for cardiovascular disease in the 21st century: obesity, metabolic syndrome, inflammation and climate change: how does statin therapy fit into this equation?

Despite population-based improvements in cardiovascular risk factors, such as blood pressure, cholesterol and smoking, cardiovascular disease still remains the number-one cause of mortality in the United States. In 1989, Kaplan coined the term "Deadly Quartet" to represent a combination of risk factors that included upper body obesity, glucose intolerance, hypertriglyceridemia and hypertension [Kaplan in Arch Int Med 7:1514-1520, 1989]. In 2002, the third report of the National Cholesterol Education Program Adult Treatment Panel (NCEP-ATP III) essentially added low HDL-C criteria and renamed this the "metabolic syndrome." [The National Cholesterol Education Program (NCEP) in JAMA 285:2486-2497, 2001] However, often forgotten was that a pro-inflammatory state and pro-thrombotic state were also considered components of the syndrome, albeit the panel did not find enough evidence at the time to recommend routine screening for these risk factors [The National Cholesterol Education Program (NCEP) in JAMA 285:2486-2497, 2001]. Now over a decade later, it may be time to reconsider this deadly quartet by reevaluating the roles of obesity and subclinical inflammation as they relate to the metabolic syndrome. To complete this new quartet, the addition of increased exposure to elevated levels of particulate matter in the atmosphere may help elucidate why this cardiovascular pandemic continues, despite our concerted efforts. In this article, we will summarize the evidence, focusing on how statin therapy may further impact this new version of the "deadly quartet".

Controlled exposures to air pollutants and risk of cardiac arrhythmia

BACKGROUND

Epidemiological studies have reported associations between air pollution exposure and increases in cardiovascular morbidity and mortality. Exposure to air pollutants can influence cardiac autonomic tone and reduce heart rate variability, and may increase the risk of cardiac arrhythmias, particularly in susceptible patient groups.

OBJECTIVES

We investigated the incidence of cardiac arrhythmias during and after controlled exposure to air pollutants in healthy volunteers and patients with coronary heart disease.

METHODS

We analyzed data from 13 double-blind randomized crossover studies including 282 participants (140 healthy volunteers and 142 patients with stable coronary heart disease) from whom continuous electrocardiograms were available. The incidence of cardiac arrhythmias was recorded for each exposure and study population.

RESULTS

There were no increases in any cardiac arrhythmia during or after exposure to dilute diesel exhaust, wood smoke, ozone, concentrated ambient particles, engineered carbon nanoparticles, or high ambient levels of air pollution in either healthy volunteers or patients with coronary heart disease.

CONCLUSIONS

Acute controlled exposure to air pollutants did not increase the short-term risk of arrhythmia in participants. Research employing these techniques remains crucial in identifying the important pathophysiological pathways involved in the adverse effects of air pollution, and is vital to inform environmental and public health policy decisions.