Controlled exposure study of air pollution and T-wave alternans in volunteers without cardiovascular disease

Air Pollution and Temperature: a Systematic Review of Ubiquitous Environmental Exposures and Sudden Cardiac Death

PURPOSE OF REVIEW

Environmental exposures have been associated with increased risk of cardiovascular mortality and acute coronary events, but their relationship with out-of-hospital cardiac arrest (OHCA) and sudden cardiac death (SCD) remains unclear. SCD is an important contributor to the global burden of cardiovascular disease worldwide.

RECENT FINDINGS

Current literature suggests a relationship between environmental exposures and cardiovascular disease, but their relationship with OHCA/SCD remains unclear. A literature search was conducted in PubMed, Embase, Web of Science, and Global Health. Of 5138 studies identified by our literature search, this review included 30 studies on air pollution, 42 studies on temperature, 6 studies on both air pollution and temperature, and 1 study on altitude exposure and OHCA/SCD. Particulate matter air pollution, ozone, and both hot and cold temperatures are associated with increased risk of OHCA/SCD. Pollution and other exposures related to climate change play an important role in OHCA/SCD incidence.

Acute ozone exposure can cause cardiotoxicity: Mitochondria play an important role in mediating myocardial apoptosis

OBJECTIVE

To clarify the cardiotoxicity induced by acute exposure to different concentrations of ozone in both gender rats and explore the underlying mechanisms.

METHODS

A total of 240 rats were randomly sorted into 6 groups with equal numbers of male and female rats in each group. The rats were subjected to ozone inhalation at concentrations of 0, 0.12, 0.5, 1.0, 2.0 and 4.0 ppm, respectively, for 6 h. After ozone exposure, function indicators, myocardial injury indexes and risk factors of cardiovascular disease in blood were assayed.

RESULTS

High ozone exposure resulted in sustained ventricular tachycardia in male and female rats. Myocardial apoptosis in male rats started from 1.0 ppm ozone, and that in female rats started from 2.0 ppm ozone (p < 0.05). Caspase-9 increased significantly from 0.12 ppm ozone (p < 0.01) in both gender rats, while caspase-3 was initially activated at 0.5 ppm ozone. From 1.0 ppm ozone, mitochondrial cristae and myofilaments dissolved. The ratio of Bcl-2/Bax decreased significantly from 0.12 ppm and MRCC-IV decreased significantly from 2.0 ppm by ozone.

CONCLUSION

Acute ozone exposure can cause paroxysmal ventricular tachycardia in rats. Moreover, the changes of inflammatory factors in the heart tissues of female and male rats after ozone exposure were greater than those of oxidative stress. This study reported for the first time that 6 h ozone exposure does not cause acute cardiomyocyte necrosis, but promotes cardiomyocyte apoptosis in a mitochondrial-dependent manner. Ozone could regulate caspases-3 dependent cardiomyocyte apoptosis by affecting the balance between caspase-9 and XIAP.

Pathogenic Role of Air Pollution Particulate Matter in Cardiometabolic Disease: Evidence from Mice and Humans

Significance: Air pollution is a considerable global threat to human health that dramatically increases the risk for cardiovascular pathologies, such as atherosclerosis, myocardial infarction, and stroke. An estimated 4.2 million cases of premature deaths worldwide are attributable to outdoor air pollution. Among multiple other components, airborne particulate matter (PM) has been identified as the major bioactive constituent in polluted air. While PM-related illness was historically thought to be confined to diseases of the respiratory system, overwhelming clinical and experimental data have now established that acute and chronic exposure to PM causes a systemic inflammatory and oxidative stress response that promotes cardiovascular disease. Recent Advances: A large body of evidence has identified an impairment of redox metabolism and the generation of oxidatively modified lipids and proteins in the lung as initial tissue response to PM. In addition, the pathogenicity of PM is mediated by an inflammatory response that involves PM uptake by tissue-resident immune cells, the activation of proinflammatory pathways in various cell types and organs, and the release of proinflammatory cytokines as locally produced tissue response signals that have the ability to affect organ function in a remote manner. Critical Issues: In the present review, we summarize and discuss the functional participation of PM in cardiovascular pathologies and its risk factors with an emphasis on how oxidative stress, inflammation, and immunity interact and synergize as a response to PM. Future Directions: The impact of PM constituents, doses, and novel anti-inflammatory therapies against PM-related illness is also discussed.

Cytotoxicity of Air Pollutant 9,10-Phenanthrenequinone: Role of Reactive Oxygen Species and Redox Signaling

Atmospheric pollution has been a principal topic recently in the scientific and political community due to its role and impact on human and ecological health. 9,10-phenanthrenequinone (9,10-PQ) is a quinone molecule found in air pollution abundantly in the diesel exhaust particles (DEP). This compound has studied extensively and has been shown to develop cytotoxic effects both in vitro and in vivo. 9, 10-PQ has been proposed to play a critical role in the development of cytotoxicity via generation of reactive oxygen species (ROS) through redox cycling. This compound also reduces expression of glutathione (GSH), which is critical in Phase II detoxification reactions. Understanding the underlying cellular mechanisms involved in cytotoxicity can allow for the development of therapeutics designed to target specific molecules significantly involved in the 9,10-PQ-induced ROS toxicity. This review highlights the developments in the understanding of the cytotoxic effects of 9, 10-PQ with special emphasis on the possible mechanisms involved.

The effects of ozone on human health

Ozone is a highly reactive, oxidative gas associated with adverse health outcome, including mortality and morbidity. Data from monitoring sites worldwide show levels of ozone often exceeding EU legislation threshold and the more restrictive WHO guidelines for the protection of human health. Well-established evidence has been produced for short-term effects, especially on respiratory and cardiovascular systems, associated to ozone exposure. Less conclusive is the evidence for long-term effects, reporting suggestive associations with respiratory mortality, new-onset asthma in children and increased respiratory symptom effects in asthmatics. The growing epidemiological evidence and the increasing availability of routinely collected data on air pollutant concentrations and health statistics allow to produce robust estimates in health impact assessment routine. Most recent estimates indicate that in 2013 in EU-28, 16,000 premature deaths, equivalent to 192,000 years of life lost, are attributable to ozone exposure. Italy shows very high health impact estimates among EU countries, reporting 3380 premature deaths and 61 years of life lost (per 100,000 inhabitants) attributable to ozone exposure.

Cardiac pathophysiology in response to environmental stress: a current review

Purpose

Environmental stressors are disturbing our ecosystem at an accelerating rate. An increasingly relevant stressor are air pollutants, whose levels are increasing worldwide with threats to human health. These air pollutants are associated with increased mortality and morbidity from cardiovascular diseases. In this review we discuss environmental stressors focusing mainly on the various types of air pollutants, their short-term and long-term cardiovascular effects, and providing the epidemiological evidence associated with adverse cardiovascular outcomes. Direct and indirect pathophysiological mechanisms are also linked with cardiovascular complications such as thrombosis, fibrinolysis, hypertension, ischemic heart diseases and arrhythmias.

RESULTS

Evidence to date suggests that humans are constantly being exposed to unhealthy levels of environmental toxicants with the potential of serious health conditions. Environmental stressors adversely affect the cardiovascular system and pose an increased risk for cardiovascular diseases for those who reside in highly polluted areas.

CONCLUSION

People with existing risk factors and those with established cardiovascular disease have increased susceptibility to environmental stressors. The literature reviewed in this article thus support public health policies aimed at reducing pollutant exposure to benefit public health.

Cardiovascular effects of ozone in healthy subjects with and without deletion of glutathione-S-transferase M1

CONTEXT

Exposure to ozone has acute respiratory effects, but few human clinical studies have evaluated cardiovascular effects.

OBJECTIVE

We hypothesized that ozone exposure alters pulmonary and systemic vascular function, and cardiac function, with more pronounced effects in subjects with impaired antioxidant defense from deletion of the glutathione-S-transferase M1 gene (GSTM1 null).

METHODS

Twenty-four young, healthy never-smoker subjects (12 GSTM1 null) inhaled filtered air, 100 ppb ozone and 200 ppb ozone for 3 h, with intermittent exercise, in a double-blind, randomized, crossover fashion. Exposures were separated by at least 2 weeks. Vital signs, spirometry, arterial and venous blood nitrite levels, impedance cardiography, peripheral arterial tonometry, estimation of pulmonary capillary blood volume (Vc), and blood microparticles and platelet activation were measured at baseline and during 4 h after each exposure.

RESULTS

Ozone inhalation decreased lung function immediately after exposure (mean ± standard error change in FEV1, air: -0.03 ± 0.04 L; 200 ppb ozone: -0.30 ± 0.07 L; p < 0.001). The immediate post-exposure increase in blood pressure, caused by the final 15-min exercise period, was blunted by 200 ppb ozone exposure (mean ± standard error change for air: 16.7 ± 2.6 mmHg; 100 ppb ozone: 14.5 ± 2.4 mmHg; 200 ppb ozone: 8.5 ± 2.5 mmHg; p = 0.02). We found no consistent effects of ozone on any other measure of cardiac or vascular function. All results were independent of the GSTM1 genotype.

CONCLUSIONS

We did not find convincing evidence for early acute adverse cardiovascular consequences of ozone exposure in young healthy adults. The ozone-associated blunting of the blood pressure response to exercise is of unclear clinical significance.

Weight-of-evidence evaluation of short-term ozone exposure and cardiovascular effects

There is a relatively large body of research on the potential cardiovascular (CV) effects associated with short-term ozone exposure (defined by EPA as less than 30 days in duration). We conducted a weight-of-evidence (WoE) analysis to assess whether it supports a causal relationship using a novel WoE framework adapted from the US EPA's National Ambient Air Quality Standards causality framework. Specifically, we synthesized and critically evaluated the relevant epidemiology, controlled human exposure, and experimental animal data and made a causal determination using the same categories proposed by the Institute of Medicine report Improving the Presumptive Disability Decision-making Process for Veterans ( IOM 2008). We found that the totality of the data indicates that the results for CV effects are largely null across human and experimental animal studies. The few statistically significant associations reported in epidemiology studies of CV morbidity and mortality are very small in magnitude and likely attributable to confounding, bias, or chance. In experimental animal studies, the reported statistically significant effects at high exposures are not observed at lower exposures and thus not likely relevant to current ambient ozone exposures in humans. The available data also do not support a biologically plausible mechanism for CV effects of ozone. Overall, the current WoE provides no convincing case for a causal relationship between short-term exposure to ambient ozone and adverse effects on the CV system in humans, but the limitations of the available studies preclude definitive conclusions regarding a lack of causation. Thus, we categorize the strength of evidence for a causal relationship between short-term exposure to ozone and CV effects as "below equipoise."

Air pollution and arrhythmic risk: the smog is yet to clear

Epidemiologic evidence has demonstrated that air pollution may impair cardiovascular health, leading to potentially life-threatening arrhythmias. Efforts have been made, with the use of epidemiologic data and controlled exposures in diverse animal and human populations, to verify the relationship between air pollution and arrhythmias. The purpose of this review is to examine and contrast the epidemiologic and toxicologic evidence to date that relates airborne pollutants with cardiac arrhythmia. We have explored the potential biological mechanisms driving this association. Using the PubMed database, we conducted a literature search that included the terms "air pollution" and "arrhythmia" and eventually divergent synonyms such as "particulate matter," "bradycardia," and "atrial fibrillation." We reviewed epidemiologic studies and controlled human and animal exposures independently to determine whether observational conclusions were corroborated by toxicologic results. Numerous pollutants have demonstrated some arrhythmic capacity among healthy and health-compromised populations. However, some exposure studies have shown no significant correlation of air pollutants with arrhythmia, which suggests some uncertainty about the arrhythmogenic potential of air pollution and the mechanisms involved in arrhythmogenesis. While data from an increasing number of controlled exposures with human volunteers suggest a potential mechanistic link between air pollution and altered cardiac electrophysiology, definite conclusions regarding air pollution and arrhythmia are elusive as the direct arrhythmic effects of air pollutants are not entirely consistent across all studies.