The effect of air pollution on haemostasis

Evaluation of neural reflex activation as a potential mode of action for respiratory and cardiovascular effects of fine particulate matter

OBJECTIVES

Mortality from respiratory and cardiovascular health conditions contributes largely to the total mortality that has been associated with exposure to PM2.5 in epidemiology studies. A mode of action (MoA) for these underlying morbidities has not been established, but it has been proposed that some effects of PM2.5 occur through activation of neural reflexes.

MATERIALS AND METHODS

We critically reviewed the experimental studies of PM2.5 (including ambient PM2.5, diesel exhaust particles, concentrated ambient particles, diesel exhaust, and cigarette smoke) and neural reflex activation, and applied the principles of the International Programme on Chemical Safety (IPCS) MoA/human relevance framework to assess whether they support a biologically plausible and human-relevant MoA by which PM2.5 could contribute to cardiovascular and respiratory causes of death. We also considered whether the evidence from these studies supports a non-threshold MoA that operates at low, human-relevant PM2.5 exposure concentrations.

RESULTS AND DISCUSSION

We found that the proposed MoA of neural reflex activation is biologically plausible for PM2.5-induced respiratory effects at high exposure levels used in experimental studies, but further studies are needed to fill important data gaps regarding the relevance of this MoA to humans at lower PM2.5 exposure levels. A role for the proposed MoA in PM2.5-induced cardiovascular effects is plausible for some effects but not others.

CONCLUSIONS

Further studies are needed to determine whether neural reflex activation is the MoA by which PM2.5 could cause either respiratory or cardiovascular morbidities in humans, particularly at the ambient concentrations associated with total mortality in epidemiology studies.

Antithrombotic medication and endovascular interventions associated with short-term exposure to particulate air pollution: A nationwide case-crossover study

Short-term exposure to air pollution has pro-thrombotic effects and triggers thrombo-embolic events such as myocardial infarction or stroke in adults. This study evaluates the association between short-term variation in air pollution and treatments for acute thrombo-embolic events among the whole Belgian population. In a bidirectional time-stratified case-crossover design, we included 227,861 events treated with endovascular intervention and 74,942 with antithrombotic enzymes that were reimbursed by the Belgian Social Security between January 1st, 2009 and December 31st, 2013. We compared the concentrations of particulate matter (PM) air pollution (PM₁₀ and PM_2.5), as estimated at the municipality level on the day of the event (lag 0) and two days earlier (lag 1 and lag 2) with those of control days from the same month, matched by temperature and accounting for day of the week (weekend vs week days). We applied conditional logistic regression models to obtain odds ratios (OR) and their 95% CI for an increase of 10 μg/m³ (PM₁₀) or 5 μg/m³ (PM_2.5) in pollutant concentrations over three lag days (lag 0, 1 and 2). We observed significant associations of PM₁₀ and PM_2.5 with treatment of acute thrombo-embolic events at the three lags. The strongest associations were observed for air pollution concentrations on the day of the event (lag0). Increases of 10 μg/m³ PM₁₀ and 5 μg/m³ PM_2.5 on lag0 increased the odds of events treated with endovascular intervention by 2.7% (95%CI:2.3%-3.2%) and 1.3% (95%CI:1%-1.5%), respectively, and they increased the odds of events treated with antithrombotic enzymes by 1.9% (95%CI:1.1-2.7%) and 1.2% (95%CI:0.7%-1.6%), respectively. The associations were generally stronger during autumn months and among children. Our nationwide study confirms that acute exposure to outdoor air pollutants such as PM₁₀ or PM_2.5 increase the use of medication and interventions to treat thrombo-embolic events.

Air pollution and cardiovascular disease: car sick

The cardiovascular effects of inhaled particle matter (PM) are responsible for a substantial morbidity and mortality attributed to air pollution. Ultrafine particles, like those in diesel exhaust emissions, are a major source of nanoparticles in urban environments, and it is these particles that have the capacity to induce the most significant health effects. Research has shown that diesel exhaust exposure can have many detrimental effects on the cardiovascular system both acutely and chronically. This review provides an overview of the cardiovascular effects on PM in air pollution, with an emphasis on ultrafine particles in vehicle exhaust. We consider the biological mechanisms underlying these cardiovascular effects of PM and postulate that cardiovascular dysfunction may be implicated in the effects of PM in other organ systems. The employment of multiple strategies to tackle air pollution, and especially ultrafine particles from vehicles, is likely to be accompanied by improvements in cardiovascular health.

Pathway analysis of a genome-wide gene by air pollution interaction study in asthmatic children

OBJECTIVES

We aimed to investigate the role of genetics in the respiratory response of asthmatic children to air pollution, with a genome-wide level analysis of gene by nitrogen dioxide (NO2) and carbon monoxide (CO) interaction on lung function and to identify biological pathways involved.

METHODS

We used a two-step method for fast linear mixed model computations for genome-wide association studies, exploring whether variants modify the longitudinal relationship between 4-month average pollution and post-bronchodilator FEV1 in 522 Caucasian and 88 African-American asthmatic children. Top hits were confirmed with classic linear mixed-effect models. We used the improved gene set enrichment analysis for GWAS (i-GSEA4GWAS) to identify plausible pathways.

RESULTS

Two SNPs near the EPHA3 (rs13090972 and rs958144) and one in TXNDC8 (rs7041938) showed significant interactions with NO2 in Caucasians but we did not replicate this locus in African-Americans. SNP-CO interactions did not reach genome-wide significance. The i-GSEA4GWAS showed a pathway linked to the HO-1/CO system to be associated with CO-related FEV1 changes. For NO2-related FEV1 responses, we identified pathways involved in cellular adhesion, oxidative stress, inflammation, and metabolic responses.

CONCLUSION

The host lung function response to long-term exposure to pollution is linked to genes involved in cellular adhesion, oxidative stress, inflammatory, and metabolic pathways.

Pure ultra-fine carbon particles do not exert pro-coagulation and inflammatory effects on microvascular endothelial cells

Pro-thrombotic and inflammatory changes play an important role in cardiovascular morbidity and mortality, resulting from short-term exposure to fine particulate air-pollution. Part of those effects has been attributed to the ultra-fine particles (UFPs) that pass through the lung and directly contact blood-exposed and circulating cells. Despite UFP-induced platelet activation, it is unclear whether the penetrated particles exert any direct effect on endothelial cells. While exposure levels are boosting as a result of world-wide increases in economic development and desertification, which create more air-polluted regions, as well as increase in demands for synthetic UFPs in medicine and various industries, further studies on the health effects of these particles are required. In this study, human pulmonary and cardiac microvascular endothelial cells (MECs) have been exposed to 0.1, 1, 10, and 100 μg/ml suspensions of either a natural (carbon black) or a synthetic (multi-walled carbon nano-tubes) type of UFPs, in vitro. As a result, no changes in the levels of coagulation factor VIII, Von Willebrand factor, Interleukin 8, and P-selectin measured in the cells' supernatant were observed prior to and 6, 12, and 24 h after exposure. In parallel, the spatio-temporal effect of UFPs on cardiac MECs was evaluated by Transmission Electron Microscopy. Despite phagocytic uptake of pure UFPs observed on cellular sections of the treated cells, Weibel-Palade bodies remained intact in shape and similar in number when compared with the untreated cells. Our work shows that carbon itself is a non-toxic carrier for endothelial cells.

Ambient air pollution and thrombosis

Air pollution is a growing public health concern of global significance. Acute and chronic exposure is known to impair cardiovascular function, exacerbate disease and increase cardiovascular mortality. Several plausible biological mechanisms have been proposed for these associations, however, at present, the pathways are incomplete. A seminal review by the American Heart Association (2010) concluded that the thrombotic effects of particulate air pollution likely contributed to their effects on cardiovascular mortality and morbidity. The aim of the current review is to appraise the newly accumulated scientific evidence (2009-2016) on contribution of haemostasis and thrombosis towards cardiovascular disease induced by exposure to both particulate and gaseous pollutants.Seventy four publications were reviewed in-depth. The weight of evidence suggests that acute exposure to fine particulate matter (PM_2.5) induces a shift in the haemostatic balance towards a pro-thrombotic/pro-coagulative state. Insufficient data was available to ascertain if a similar relationship exists for gaseous pollutants, and very few studies have addressed long-term exposure to ambient air pollution. Platelet activation, oxidative stress, interplay between interleukin-6 and tissue factor, all appear to be potentially important mechanisms in pollution-mediated thrombosis, together with an emerging role for circulating microvesicles and epigenetic changes.Overall, the recent literature supports, and arguably strengthens, the contention that air pollution contributes to cardiovascular morbidity by promoting haemostasis. The volume and diversity of the evidence highlights the complexity of the pathophysiologic mechanisms by which air pollution promotes thrombosis; multiple pathways are plausible and it is most likely they act in concert. Future research should address the role gaseous pollutants play in the cardiovascular effects of air pollution mixture and direct comparison of potentially susceptible groups to healthy individuals.

Air pollution and admissions due to ST elevation myocardial infarction-a time-series study from northwest of Iran

We investigated the association between the levels of air pollutants and the number of daily admissions due to ST segment elevation myocardial infarction (STEMI) in a metropolitan in the northwest of Iran. Daily concentrations of common air pollutants were obtained for the greater city of Tabriz for a period of 2 years. These reports included sulfur dioxide (SO2), nitrogen dioxide (NO2), nitric oxide (NO), nitrogen byproducts (NOx), carbon monoxide (CO), ozone (O3), and particulate matters < 10 μm (PM10). The census of admissions for STEMI was retrieved for the same period from hospital registries. The association of daily variations in air pollutant levels and the daily number of STEMI admissions were investigated in a time-series analysis. In the multi-pollutant model adjusting for long-term trend, seasonality, and temperature, a significant association was found for 1-h [NO2] and 24-h [CO]. A marginally significant association was observed for 24-h [NO2] and 8-h [CO]. The 24-h [CO] had the strongest association with the number of admissions with STEMI. Maximum 1-h concentrations of NO2 on the same day and on the prior day as well as 24-h concentrations of CO on the prior day were independently associated with increased number of STEMI admissions. However, daily concentrations of SO2, NO, O3, and PM10 were not associated with the frequency of hospital admissions for STEMI.

Oxidative Stress and Cardiovascular Risk: Obesity, Diabetes, Smoking, and Pollution: Part 3 of a 3-Part Series

Oxidative stress occurs whenever the release of reactive oxygen species (ROS) exceeds endogenous antioxidant capacity. In this paper, we review the specific role of several cardiovascular risk factors in promoting oxidative stress: diabetes, obesity, smoking, and excessive pollution. Specifically, the risk of developing heart failure is higher in patients with diabetes or obesity, even with optimal medical treatment, and the increased release of ROS from cardiac mitochondria and other sources likely contributes to the development of cardiac dysfunction in this setting. Here, we explore the role of different ROS sources arising in obesity and diabetes, and the effect of excessive ROS production on the development of cardiac lipotoxicity. In parallel, contaminants in the air that we breathe pose a significant threat to human health. This paper provides an overview of cigarette smoke and urban air pollution, considering how their composition and biological effects have detrimental effects on cardiovascular health.

Fibrin clot structure is affected by levels of particulate air pollution exposure in patients with venous thrombosis

BACKGROUND

Particulate air pollution is a risk factor for cardiovascular diseases and thrombosis. Long-term exposure to particulate matter with a diameter<10μm (PM10) has been associated with an increased risk of venous thrombosis.

OBJECTIVES

The aim of this study was to investigate whether or not particulate air pollution alters fibrin clot structure and thus modulates thrombosis risk.

METHODS

We investigated fibrin polymerization by turbidity (maximum absorbance mOD), clot structure by confocal microscopy (fibre number per μm) and fibrin pore size by permeability (Ks×10(-10)cm(2)) in 103 patients with deep vein thrombosis and 121 healthy controls, for whom levels of air pollution exposure had been recorded. Exposure groups were defined by mean PM10 concentrations over the 730days before the event.

RESULTS

We found a higher average number of fibres per clot area in patients than controls, but no difference in Ks or fibre thickness. When the two groups were divided into high or low exposure to PM10, a significantly denser fibrin clot network structure with thicker fibres (higher maximum absorbance, p<0.05), decreased permeability (lower Ks value, p<0.05) and higher average fibre numbers per clot area (p<0.05) was observed in patients in the high exposure group compared to those with low exposure. There were no significant differences in fibrin clot structure between the two exposure levels in healthy subjects.

CONCLUSIONS

PM10 levels are associated with altered fibrin clot structure in patients with deep vein thrombosis but not in controls, suggesting that air pollution may trigger differences in fibrin clot structure only in patients predisposed to thrombotic disease.

Fine particulate matter potentiates type 2 diabetes development in high-fat diet-treated mice: stress response and extracellular to intracellular HSP70 ratio analysis

Exposure to fine particulate matter (PM_2.5) air pollution is a risk factor for type 2 diabetes (T2DM). We argue whether the potentiating effect of PM_2.5 over the development of T2DM in high-fat diet (HFD)-fed mice would be related to modification in cell stress response, particularly in antioxidant defenses and 70-kDa heat shock proteins (HSP70) status. Male mice were fed standard chow or HFD for 12 weeks and then randomly exposed to daily nasotropic instillation of PM_2.5 for additional 12 weeks under the same diet schedule, divided into four groups (n = 14-15 each): Control, PM_2.5, HFD, and HFD + PM_2.5 were evaluated biometric and metabolic profiles of mice, and cellular stress response (antioxidant defense and HSP70 status) of metabolic tissues. Extracellular to intracellular HSP70 ratio ([eHSP72]/[iHSP70]), viz. H-index, was then calculated. HFD + PM_2.5 mice presented a positive correlation between adiposity, increased body weight and glucose intolerance, and increased glucose and triacylglycerol plasma levels. Pancreas exhibited lower iHSP70 expression, accompanied by 3.7-fold increase in the plasma to pancreas [eHSP72]/[iHSP70] ratio. Exposure to PM_2.5 markedly potentiated metabolic dysfunction in HFD-treated mice and promoted relevant alteration in cell stress response assessed by [eHSP72]/[iHSP70], a relevant biomarker of chronic low-grade inflammatory state and T2DM risk.

Platelet activation independent of pulmonary inflammation contributes to diesel exhaust particulate-induced promotion of arterial thrombosis

BACKGROUND

Accelerated thrombus formation induced by exposure to combustion-derived air pollution has been linked to alterations in endogenous fibrinolysis and platelet activation in response to pulmonary and systemic inflammation. We hypothesised that mechanisms independent of inflammation contribute to accelerated thrombus formation following exposure to diesel exhaust particles (DEP).

METHODS

Thrombosis in rats was assessed 2, 6 and 24 h after administration of DEP, carbon black (CB; control carbon nanoparticle), DQ12 quartz microparticles (to induce pulmonary inflammation) or saline (vehicle) by either intra-tracheal instillation (0.5 mg, except Quartz; 0.125 mg) or intravenous injection (0.5 mg/kg). Thrombogenicity was assessed by carotid artery occlusion, fibrinolytic variables and platelet-monocyte aggregates. Measures of inflammation were determined in plasma and bronchoalveolar lavage fluid. Tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI)-1 were measured following direct in vitro exposure of human umbilical vein endothelial cells (HUVECs) to DEP (10-150 μg/mL).

RESULTS

Instillation of DEP reduced the time to thrombotic occlusion in vivo, coinciding with the peak of DEP-induced pulmonary inflammation (6 h). CB and DQ12 produced greater inflammation than DEP but did not alter time to thrombotic occlusion. Intravenous DEP produced an earlier (2 h) acceleration of thrombosis (as did CB) without pulmonary or systemic inflammation. DEP inhibited t-PA and PAI-1 release from HUVECs, and reduced the t-PA/PAI-1 ratio in vivo; similar effects in vivo were seen with CB and DQ12. DEP, but not CB or DQ12, increased platelet-monocyte aggregates.

CONCLUSION

DEP accelerates arterial thrombus formation through increased platelet activation. This effect is dissociated from pulmonary and systemic inflammation and from impaired fibrinolytic function.

Evaluation of atherosclerosis as a potential mode of action for cardiovascular effects of particulate matter

Epidemiology studies have consistently reported associations between PM2.5 exposure and cardiovascular (CV) morbidity and mortality, but the epidemiology evidence for associations between PM2.5 and subclinical measures of atherosclerosis is unclear. We critically reviewed the experimental studies of PM2.5 and effects associated with acceleration and exacerbation of atherosclerosis and evaluated whether they support a biologically plausible, human-relevant mode of action (MoA) for the associations between PM2.5 exposure and adverse CV outcomes reported in epidemiology studies. We focused on outcomes related to atherosclerotic plaque development, thrombosis, and coagulation, and we examined whether these outcomes were correlated with measures of oxidative stress and systemic or pulmonary inflammation, to evaluate whether these processes are likely to be key early events for atherogenic effects of PM. While the current experimental evidence indicates that the acceleration and exacerbation of atherosclerosis is a biologically plausible MoA in experimental animal models, we found that the human relevance of the key events in the proposed MoA is unclear and not well supported by the existing data. Further studies are needed to fill several important data gaps before the human relevance of this MoA can be established.

Space-Time Analysis to Identify Areas at Risk of Mortality from Cardiovascular Disease

This study aimed at identifying areas that were at risk of mortality due to cardiovascular disease in residents aged 45 years or older of the cities of Cuiabá and Várzea Grande between 2009 and 2011. We conducted an ecological study of mortality rates related to cardiovascular disease. Mortality rates were calculated for each census tract by the Local Empirical Bayes estimator. High- and low-risk clusters were identified by retrospective space-time scans for each year using the Poisson probability model. We defined the year and month as the temporal analysis unit and the census tracts as the spatial analysis units adjusted by age and sex. The Mann-Whitney U test was used to compare the socioeconomic and environmental variables by risk classification. High-risk clusters showed higher income ratios than low-risk clusters, as did temperature range and atmospheric particulate matter. Low-risk clusters showed higher humidity than high-risk clusters. The Eastern region of Várzea Grande and the central region of Cuiabá were identified as areas at risk of mortality due to cardiovascular disease in individuals aged 45 years or older. High mortality risk was associated with socioeconomic and environmental factors. More high-risk clusters were observed at the end of the dry season.

Nanoparticles and the cardiovascular system: a critical review

Nanoparticles (NPs) are tiny particles with a diameter of less than 100 nm. Traffic exhaust is a major source of combustion-derived NPs (CDNPs), which represent a significant component in urban air pollution. Epidemiological, panel and controlled human chamber studies clearly demonstrate that exposure to CDNPs is associated with multiple adverse cardiovascular effects in both healthy individuals and those with pre-existing cardiovascular disease. NPs are also manufactured from a large range of materials for industrial use in a vast array of products including for use as novel imaging agents for medical use. There is currently little information available on the impacts of manufactured NPs in humans, but experimental studies demonstrate similarities to the detrimental cardiovascular actions of CDNPs. This review describes the evidence for these cardiovascular effects and attempts to resolve the paradox between the adverse effects of the unintentional exposure of CDNPs and the intentional delivery of manufactured NPs for medical purposes.

Imbalance of mitochondrial-nuclear cross talk in isocyanate mediated pulmonary endothelial cell dysfunction

Mechanistic investigations coupled with epidemiology, case-control, cohort and observational studies have increasingly linked isocyanate exposure (both chronic and acute) with pulmonary morbidity and mortality. Though ascribed for impairment in endothelial cell function, molecular mechanisms of these significant adverse pulmonary outcomes remains poorly understood. As preliminary studies conducted in past have failed to demonstrate a cause-effect relationship between isocyanate toxicity and compromised pulmonary endothelial cell function, we hypothesized that direct exposure to isocyanate may disrupt endothelial structural lining, resulting in cellular damage. Based on this premise, we comprehensively evaluated the molecular repercussions of methyl isocyanate (MIC) exposure on human pulmonary arterial endothelial cells (HPAE-26). We examined MIC-induced mitochondrial oxidative stress, pro-inflammatory cytokine response, oxidative DNA damage response and apoptotic index. Our results demonstrate that exposure to MIC, augment mitochondrial reactive oxygen species production, depletion in antioxidant defense enzymes, elevated pro-inflammatory cytokine response and induced endothelial cell apoptosis via affecting the balance of mitochondrial-nuclear cross talk. We herein delineate the first and direct molecular cascade of isocyanate-induced pulmonary endothelial cell dysfunction. The results of our study might portray a connective link between associated respiratory morbidities with isocyanate exposure, and indeed facilitate to discern the exposure-phenotype relationship in observed deficits of pulmonary endothelial cell function. Further, understanding of inter- and intra-cellular signaling pathways involved in isocyanate-induced endothelial damage would not only aid in biomarker identification but also provide potential new avenues to target specific therapeutic interventions.