Acrolein inhalation alters arterial blood gases and triggers carotid body-mediated cardiovascular responses in hypertensive rats

Associations between specific volatile organic chemical exposures and cardiovascular disease risks: insights from NHANES

Introduction

An increasing body of research has demonstrated a correlation between pollutants from the environment and the development of cardiovascular diseases (CVD). However, the impact of volatile organic chemicals (VOC) on CVD remains unknown and needs further investigation.

Objectives

This study assessed whether exposure to VOC was associated with CVD in the general population.

Methods

A cross-sectional analysis was conducted utilizing data from five survey cycles (2005-2006, 2011-2012, 2013-2014, 2015-2016, and 2017-2018) of the National Health and Nutrition Examination Survey (NHANES) program. We analyzed the association between urinary VOC metabolites (VOCs) and participants by multiple logistic regression models, further Bayesian Kernel Machine Regression (BKMR) models and Weighted Quantile Sum (WQS) regression were performed for mixture exposure analysis.

Results

Total VOCs were found to be positively linked with CVD in multivariable-adjusted models (p for trend = 0.025), independent of established CVD risk variables, such as hypertension, diabetes, drinking and smoking, and total cholesterol levels. Compared with the reference quartile of total VOCs levels, the multivariable-adjusted odds ratios in increasing quartiles were 1.01 [95% confidence interval (CI): 0.78-1.31], 1.26 (95% CI: 1.05-1.21) and 1.75 (95% CI: 1.36-1.64) for total CVD. Similar positive associations were found when considering individual VOCs, including AAMA, CEMA, CYMA, 2HPMA, 3HPMA, IPM3 and MHBMA3 (acrolein, acrylamide, acrylonitrile, propylene oxide, isoprene, and 1,3-butadiene). In BKMR analysis, the overall effect of a mixture is significantly related to VOCs when all chemicals reach or exceed the 75th percentile. Moreover, in the WQS models, the most influential VOCs were found to be CEMA (40.30%), DHBMA (21.00%), and AMCC (19.70%).

Conclusion

The results of our study indicated that VOC was all found to have a significant association with CVD when comparing results from different models. These findings hold significant potential for public health implications and offer valuable insights for future research directions.

Impact of Wildfires on Cardiovascular Health

Wildfire smoke (WFS) is a mixture of respirable particulate matter, environmental gases, and other hazardous pollutants that originate from the unplanned burning of arid vegetation during wildfires. The increasing size and frequency of recent wildfires has escalated public and occupational health concerns regarding WFS inhalation, by either individuals living nearby and downstream an active fire or wildland firefighters and other workers that face unavoidable exposure because of their profession. In this review, we first synthesize current evidence from environmental, controlled, and interventional human exposure studies, to highlight positive associations between WFS inhalation and cardiovascular morbidity and mortality. Motivated by these findings, we discuss preventative measures and suggest interventions to mitigate the cardiovascular impact of wildfires. We then review animal and cell exposure studies to call attention on the pathophysiological processes that support the deterioration of cardiovascular tissues and organs in response to WFS inhalation. Acknowledging the challenges of integrating evidence across independent sources, we contextualize laboratory-scale exposure approaches according to the biological processes that they model and offer suggestions for ensuring relevance to the human condition. Noting that wildfires are significant contributors to ambient air pollution, we compare the biological responses triggered by WFS to those of other harmful pollutants. We also review evidence for how WFS inhalation may trigger mechanisms that have been proposed as mediators of adverse cardiovascular effects upon exposure to air pollution. We finally conclude by highlighting research areas that demand further consideration. Overall, we aspire for this work to serve as a catalyst for regulatory initiatives to mitigate the adverse cardiovascular effects of WFS inhalation in the community and alleviate the occupational risk in wildland firefighters.

Contributions of particulate and gas phases of simulated burn pit smoke exposures to impairment of respiratory function

OBJECTIVE

Inhalation of smoke from the burning of waste materials on military bases is associated with increased incidences of cardiopulmonary diseases. This study examined the respiratory and inflammatory effects of acute inhalation exposures in mice to smoke generated by military burn pit-related materials including plywood (PW), cardboard (CB), mixed plastics (PL), and a mixture of these three materials (MX) under smoldering (0.84 MCE) and flaming (0.97 MCE) burn conditions.

METHODS

Mice were exposed nose-only for one hour on two consecutive days to whole or filtered smoke or clean air alone. Smoldering combustion emissions had greater concentrations of PM (∼40 mg/m3) and VOCs (∼5-12 ppmv) than flaming emissions (∼4 mg/m3 and ∼1-2 ppmv, respectively); filtered emissions had equivalent levels of VOCs with negligible PM. Breathing parameters were assessed during exposure by head-out plethysmography.

RESULTS

All four smoldering burn pit emission types reduced breathing frequency (F) and minute volumes (MV) compared with baseline exposures to clean air, and HEPA filtration significantly reduced the effects of all smoldering materials except CB. Flaming emissions had significantly less suppression of F and MV compared with smoldering conditions. No acute effects on lung inflammatory cells, cytokines, lung injury markers, or hematology parameters were noted in smoke-exposed mice compared with air controls, likely due to reduced respiration and upper respiratory scrubbing to reduce the total deposited PM dose in this short-term exposure.

CONCLUSION

Our data suggest that material and combustion type influences respiratory responses to burn pit combustion emissions. Furthermore, PM filtration provides significant protective effects only for certain material types.

Exposure to Volatile Organic Compounds Is Associated with Hypertension in Black Adults: The Jackson Heart Study

BACKGROUND

The prevalence of hypertension is higher among Black adults than among White and Hispanic adults. Nevertheless, reasons underlying the higher rates of hypertension in the Black population remain unclear but may relate to exposure to environmental chemicals such as volatile organic compounds (VOCs).

METHODS

We evaluated the associations of blood pressure (BP) and hypertension with VOC exposure in non-smokers and smokers in a subgroup of the Jackson Heart Study (JHS), consisting of 778 never smokers and 416 age- and sex-matched current smokers. We measured urinary metabolites of 17 VOCs by mass spectrometry.

RESULTS

After adjusting for covariates, we found that amoong non-smokers, metabolites of acrolein and crotonaldehyde were associated with a 1.6 mm Hg (95%CI: 0.4, 2.7; p = 0.007) and a 0.8 mm Hg (95%CI: 0.01, 1.6; p = 0.049) higher systolic BP, and the styrene metabolite was associated with a 0.4 mm Hg (95%CI: 0.09, 0.8, p = 0.02) higher diastolic BP. Current smokers had 2.8 mm Hg (95% CI 0.5, 5.1) higher systolic BP. They were at higher risk of hypertension (relative risk = 1.2; 95% CI, 1.1, 1.4), and had higher urinary levels of several VOC metabolites. Individuals who smoke had higher levels of the urinary metabolites of acrolein, 1,3-butadiene, and crotonaldehyde and were associated with higher systolic BP. The associations were stronger among participants who were <60 years of age and male. Using Bayesian kernel machine regression to assess the effects of multiple VOC exposures, we found that the relationship between VOCs and hypertension among non-smokers was driven primarily by acrolein and styrene in non-smokers, and crotonaldehyde in smokers.

CONCLUSIONS

Hypertension in Black individuals may be attributed, in part, to VOC exposure from the environment or tobacco smoke.

Impact of sub-acute acrolein inhalation on the molecular regulation of mitochondrial metabolism in rat lung

Nowadays, mitochondria are recognized as key players in the pathogenesis of a variety of smoking-associated lung diseases. Acrolein, a component of cigarette smoke, is a known driver of biological mechanisms underlying smoking-induced respiratory toxicity. The impact of sub-acute acrolein inhalation in vivo on key processes controlling mitochondrial homeostasis in cells of the airways however is unknown. In this study, we investigated the activity/abundance of a myriad of molecules critically involved in mitochondrial metabolic pathways and mitochondrial quality control processes (mitochondrial biogenesis and mitophagy) in the lungs of Sprague-Dawley rats that were sub-acutely exposed to filtered air or 3 ppm acrolein by whole-body inhalation (5 h/day, 5 days/week for 4 weeks). Acrolein exposure induced a general inflammatory response in the lung as gene expression analysis revealed an increased expression of Icam1 and Cinc1 (p < 0.1; p < 0.05). Acrolein significantly decreased enzyme activity of hydroxyacyl-Coenzyme A dehydrogenase (p < 0.01), and decreased Pdk4 transcript levels (p < 0.05), suggestive of acrolein-induced changes in metabolic processes. Investigation of constituents of the mitochondrial biogenesis pathways and mitophagy machinery revealed no pronounced alterations. In conclusion, sub-acute inhalation of acrolein did not affect the regulation of mitochondrial metabolism and quality control, which is in contrast to more profound changes after acute exposure in other studies.

E-cigarettes and their lone constituents induce cardiac arrhythmia and conduction defects in mice

E-cigarette use has surged, but the long-term health effects remain unknown. E-cigarette aerosols containing nicotine and acrolein, a combustion and e-cigarette byproduct, may impair cardiac electrophysiology through autonomic imbalance. Here we show in mouse electrocardiograms that acute inhalation of e-cigarette aerosols disturbs cardiac conduction, in part through parasympathetic modulation. We demonstrate that, similar to acrolein or combustible cigarette smoke, aerosols from e-cigarette solvents (vegetable glycerin and propylene glycol) induce bradycardia, bradyarrhythmias, and elevations in heart rate variability during inhalation exposure, with inverse post-exposure effects. These effects are slighter with tobacco- or menthol-flavored aerosols containing nicotine, and in female mice. Yet, menthol-flavored and PG aerosols also increase ventricular arrhythmias and augment early ventricular repolarization (J amplitude), while menthol uniquely alters atrial and atrioventricular conduction. Exposure to e-cigarette aerosols from vegetable glycerin and its byproduct, acrolein, diminish heart rate and early repolarization. The pro-arrhythmic effects of solvent aerosols on ventricular repolarization and heart rate variability depend partly on parasympathetic modulation, whereas ventricular arrhythmias positively associate with early repolarization dependent on the presence of nicotine. Our study indicates that chemical constituents of e-cigarettes could contribute to cardiac risk by provoking pro-arrhythmic changes and stimulating autonomic reflexes.

Xenobiotics Delivered by Electronic Nicotine Delivery Systems: Potential Cellular and Molecular Mechanisms on the Pathogenesis of Chronic Kidney Disease

Chronic kidney disease (CKD) is characterized as sustained damage to the renal parenchyma, leading to impaired renal functions and gradually progressing to end-stage renal disease (ESRD). Diabetes mellitus (DM) and arterial hypertension (AH) are underlying diseases of CKD. Genetic background, lifestyle, and xenobiotic exposures can favor CKD onset and trigger its underlying diseases. Cigarette smoking (CS) is a known modified risk factor for CKD. Compounds from tobacco combustion act through multi-mediated mechanisms that impair renal function. Electronic nicotine delivery systems (ENDS) consumption, such as e-cigarettes and heated tobacco devices, is growing worldwide. ENDS release mainly nicotine, humectants, and flavorings, which generate several byproducts when heated, including volatile organic compounds and ultrafine particles. The toxicity assessment of these products is emerging in human and experimental studies, but data are yet incipient to achieve truthful conclusions about their safety. To build up the knowledge about the effect of currently employed ENDS on the pathogenesis of CKD, cellular and molecular mechanisms of ENDS xenobiotic on DM, AH, and kidney functions were reviewed. Unraveling the toxic mechanisms of action and endpoints of ENDS exposures will contribute to the risk assessment and implementation of proper health and regulatory interventions.

Effect Comparison of E-Cigarette and Traditional Smoking and Association with Stroke-A Cross-Sectional Study of NHANES

Introduction: Tobacco use is one of the most significant risk factors for stroke. Besides traditional cigarettes and combustible products, the use of e-cigarettes and electronic nicotine delivery products has been widespread among young adults in the recent era. Furthermore, the trend of vaping has increased over the last decade. However, the relationship between e-cigarettes and stroke is largely unknown. The aim of this study was to evaluate the prevalence and identify the relationship between e-cigarette smoking and stroke. Methods: A cross-sectional study was performed using the NHANES database of the US population. Adults with a history of smoking were considered in our study and divided into three groups, e-cigarette users, traditional, and dual smokers. The Chi-squared test, Wilcoxon rank-sum test, and multivariable logistic regression analysis were used to identify the prevalence and association of e-cigarette consumption and stroke. Results: Out of a total of 266,058 respondents from 2015 to 2018, we found 79,825 respondents who smoked e-cigarettes (9.72%) or traditional (29.37%) or dual smoking (60.91%). Stroke prevalence among e-cigarette smokers was 1.57%. Stroke was more prevalent among traditional smokers than among e-cigarette smokers. (6.75% vs. 1.09%; p < 0.0001) E-cigarette smokers had early onset of stroke in comparison with traditional smokers. (median age: 48 vs. 59 years; p < 0.0001). Among females with stroke, the prevalence of e-cigarette use was higher in comparison with traditional smoking (36.36% vs. 33.91%; p < 0.0001). Among the stroke population, the prevalence of e-cigarette use was higher among Mexican-Americans (21.21% vs. 6.02%) and other Hispanics (24.24% vs. 7.70%) compared with traditional smoking (p < 0.0001). The regression analysis found higher odds of stroke history among e-cigarette users than traditional smokers [aOR: 1.15; 95% CI: 1.15−1.16)]. Conclusion: Though stroke was more prevalent in traditional smokers, the incidence of stroke was early-in-onset and was strongly associated with e-cigarette use compared to traditional smokers. We have also identified vascular effects of e-cigarettes components as possible triggers for the stroke.

Acrolein inhalation acutely affects the regulation of mitochondrial metabolism in rat lung

Exposure of the airways to cigarette smoke (CS) is the primary risk factor for developing several lung diseases such as Chronic Obstructive Pulmonary Disease (COPD). CS consists of a complex mixture of over 6000 chemicals including the highly reactive α,β-unsaturated aldehyde acrolein. Acrolein is thought to be responsible for a large proportion of the non-cancer disease risk associated with smoking. Emerging evidence suggest a key role for CS-induced abnormalities in mitochondrial morphology and function in airway epithelial cells in COPD pathogenesis. Although in vitro studies suggest acrolein-induced mitochondrial dysfunction in airway epithelial cells, it is unknown if in vivo inhalation of acrolein affects mitochondrial content or the pathways controlling this. In this study, rats were acutely exposed to acrolein by inhalation (nose-only; 0-4 ppm), 4 h/day for 1 or 2 consecutive days (n = 6/group). Subsequently, the activity and abundance of key constituents of mitochondrial metabolic pathways as well as expression of critical proteins and genes controlling mitochondrial biogenesis and mitophagy were investigated in lung homogenates. A transient decreasing response in protein and transcript abundance of subunits of the electron transport chain complexes was observed following acrolein inhalation. Moreover, acrolein inhalation caused a decreased abundance of key regulators associated with mitochondrial biogenesis, respectively a differential response on day 1 versus day 2. Abundance of components of the mitophagy machinery was in general unaltered in response to acrolein exposure in rat lung. Collectively, this study demonstrates that acrolein inhalation acutely and dose-dependently disrupts the molecular regulation of mitochondrial metabolism in rat lung. Hence, understanding the effect of acrolein on mitochondrial function will provide a scientifically supported reasoning to shortlist aldehydes regulation in tobacco smoke.

Exposure to volatile organic compounds - acrolein, 1,3-butadiene, and crotonaldehyde - is associated with vascular dysfunction

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of mortality worldwide. Exposure to air pollution, specifically particulate matter of diameter ≤2.5 μm (PM2.5), is a well-established risk factor for CVD. However, the contribution of gaseous pollutant exposure to CVD risk is less clear.

OBJECTIVE

To examine the vascular effects of exposure to individual volatile organic compounds (VOCs) and mixtures of VOCs.

METHODS

We measured urinary metabolites of acrolein (CEMA and 3HPMA), 1,3-butadiene (DHBMA and MHBMA3), and crotonaldehyde (HPMMA) in 346 nonsmokers with varying levels of CVD risk. On the day of enrollment, we measured blood pressure (BP), reactive hyperemia index (RHI - a measure of endothelial function), and urinary levels of catecholamines and their metabolites. We used generalized linear models for evaluating the association between individual VOC metabolites and BP, RHI, and catecholamines, and we used Bayesian Kernel Machine Regression (BKMR) to assess exposure to VOC metabolite mixtures and BP.

RESULTS

We found that the levels of 3HPMA were positively associated with systolic BP (0.98 mmHg per interquartile range (IQR) of 3HPMA; CI: 0.06, 1.91; P = 0.04). Stratified analysis revealed an increased association with systolic BP in Black participants despite lower levels of urinary 3HPMA. This association was independent of PM2.5 exposure and BP medications. BKMR analysis confirmed that 3HPMA was the major metabolite associated with higher BP in the presence of other metabolites. We also found that 3HPMA and DHBMA were associated with decreased endothelial function. For each IQR of 3HPMA or DHBMA, there was a -4.4% (CI: -7.2, -0.0; P = 0.03) and a -3.9% (CI: -9.4, -0.0; P = 0.04) difference in RHI, respectively. Although in the entire cohort the levels of several urinary VOC metabolites were weakly associated with urinary catecholamines and their metabolites, in Black participants, DHBMA levels showed strong associations with urinary norepinephrine and normetanephrine levels.

DISCUSSION

Exposure to acrolein and 1,3-butadiene is associated with endothelial dysfunction and may contribute to elevated risk of hypertension in participants with increased sympathetic tone, particularly in Black individuals.

The Cardiovascular Effects of Electronic Cigarettes

PURPOSE OF REVIEW

Electronic cigarettes (e-cigarettes) are gaining rapid popularity among all age groups, especially among youth. They have evolved into technologically advanced devices capable of delivering nicotine concentration and other substances. In addition to nicotine, e-cigarettes' constituents possess variety of toxic chemicals that have adverse effects on human body.

RECENT FINDINGS

In recent years, steady downward trend in tobacco usage has been observed; however, e-cigarette use is on upward trend. E-cigarettes are advertised as "safer" alternatives to conventional smoking and as an aid to smoking cessation. Emerging studies have, however, shown that e-cigarettes have harmful effects on the cardiovascular system and that most of the e-cigarette users are dual users, concurrently using e-cigarettes and smoking conventional cigarettes. Despite a gap in clinical studies and randomized trials analyzing adverse cardiovascular effects of e-cigarette use, the existing literature supports that different constituents of e-cigarettes such as nicotine, carbonyls, and particulate matters carry potential risk for cardiovascular diseases (CVD) on its users.

Peat smoke inhalation alters blood pressure, baroreflex sensitivity, and cardiac arrhythmia risk in rats

Wildland fires (WF) are linked to adverse health impacts related to poor air quality. The cardiovascular impacts of emissions from specific biomass sources are however unknown. The purpose of this study was to assess the cardiovascular impacts of a single exposure to peat smoke, a key regional WF air pollution source, and relate these to baroreceptor sensitivity and inflammation. Three-month-old male Wistar-Kyoto rats, implanted with radiotelemeters for continuous monitoring of heart rate (HR), blood pressure (BP), and spontaneous baroreflex sensitivity (BRS), were exposed once, for 1-hr, to filtered air or low (0.38 mg/m³ PM) or high (4.04 mg/m³) concentrations of peat smoke. Systemic markers of inflammation and sensitivity to aconitine-induced cardiac arrhythmias, a measure of latent myocardial vulnerability, were assessed in separate cohorts of rats 24 hr after exposure. PM size (low peat = 0.4-0.5 microns vs. high peat = 0.8-1.2 microns) and proportion of organic carbon (low peat = 77% vs. high peat = 65%) varied with exposure level. Exposure to high peat and to a lesser extent low peat increased systolic and diastolic BP relative to filtered air. In contrast, only exposure to low peat elevated BRS and aconitine-induced arrhythmogenesis relative to filtered air and increased circulating levels of low-density lipoprotein cholesterol, complement components C3 and C4, angiotensin-converting enzyme (ACE), and white blood cells. Taken together, exposure to peat smoke produced overt and latent cardiovascular consequences that were likely influenced by physicochemical characteristics of the smoke and associated adaptive homeostatic mechanisms.

Air Pollution-Induced Autonomic Modulation

Air pollutants pose a serious worldwide health hazard, causing respiratory and cardiovascular morbidity and mortality. Pollutants perturb the autonomic nervous system, whose function is critical to cardiopulmonary homeostasis. Recent studies suggest that pollutants can stimulate defensive sensory nerves within the cardiopulmonary system, thus providing a possible mechanism for pollutant-induced autonomic dysfunction. A better understanding of the mechanisms involved would likely improve the management and treatment of pollution-related disease.

Biological Toxicity of the Compositions in Electronic-Cigarette on Cardiovascular System

Using electronic cigarette (e-cig) among youth is becoming a critical public health crisis in the USA. However, the biological impacts of the e-cig on multiple organ systems, especially in the cardiovascular system, are largely unknown. Unlike conventional tobacco, e-cig combines various chemical ingredients including nicotine and other add-on non-nicotine chemicals, such as the solvents (propylene glycol and/or vegetable glycerin) and flavoring chemicals, which dramatically increases the diversity of the potential implications. The recent outbreak of e-cig vaping-related tragic deaths in youth and multiple hospitalized patients raised a question on the safety of e-cig use and led to an urgent need for the knowledge of the health risk of the e-cig compositions. Therefore, in the review, we summarized the latest findings from both human and animal studies on the potential cardiovascular toxicological effects of e-cig on the cardiovascular system in terms of the systemic physiological implications and the cellular and molecular mechanisms involved.

Concomitant exposure to area-level poverty, ambient air volatile organic compounds, and cardiometabolic dysfunction: a cross-sectional study of U.S. adolescents

PURPOSE

A key to better understanding the influence of the place of residence on cardiometabolic function is the effect of concomitant exposure to both air pollution and residence in economically marginalized areas. We hypothesized that, among adolescents, the association between air pollution and cardiometabolic function is exacerbated among residents of economically marginalized areas.

METHODS

In this cross-sectional study, individual-level data on cardiometabolic function collected from a representative sample of U.S. adolescents in the National Health and Nutrition Examination Survey (n = 10,415) were merged with data on area-level poverty (U.S. decennial survey and American Community Survey) and air pollution levels (National-Scale Air Toxics Assessment ) using contemporary census-tract identifiers. We excluded respondents who were pregnant, had hypertension or diabetes or using medication for hypertension or diabetes, or with missing data on outcome variables.

RESULTS

We observed a significant interaction between area-level poverty and air pollution. Among residents of high-poverty areas, exposure to high levels of air pollution predicted a 30% elevated odds of cardiometabolic dysfunction (OR = 1.30; 95% CI: 1.04, 1.61), whereas in low-poverty areas, exposure to high levels of air pollution was not associated with elevated odds of cardiometabolic dysfunction (OR = 1.04; 95% CI: 0.85, 1.28).

CONCLUSIONS

Our findings suggest that the cardiometabolic consequences of air pollution are more readily realized among residents of economically marginalized areas. Structural remedies are discussed.

Cardiac toxicity of acrolein exposure in embryonic zebrafish (Danio rerio)

Acrolein is a widely distributed pollutant produced from various sources such as industrial waste, organic combustion, and power plant emissions. It is also intentionally released into irrigation canals to control invasive aquatic plants. Zebrafish (Danio rerio) has a good reputation for being an attractive model organism for developmental and toxicological research. In this study, zebrafish embryos were exposed to acrolein to investigate the cardiotoxic effects. The 96-h LC₅₀ (median lethal concentration) value of acrolein was determined as 654.385 μg/L. Then, the embryos were treated with the sublethal experimental concentrations of acrolein (1, 4, 16, 64, and 256 μg/L) for 96 h. Embryos were examined at 48, 72, and 96 h post-fertilization (hpf). Acrolein affected the cardiac morphology and function of the embryos. Sinus venosus-bulbus arteriosus (SV-BA) distance of 64 μg/L and 256 μg/L acrolein groups was elongated compared with the control samples. Immunostaining with MF20 antibody clearly exhibited that the atrium positioned posterior to the ventricle which indicated cardiac looping inhibition. Histological preparations also showed the mispositioning and the lumens of the chambers narrowed. Acrolein-induced increased heart rate was noted in the 4, 16, 64, and 256 μg/L treatment groups. Taken together, these results indicated that acrolein disrupted the heart development and cardiac function in zebrafish, suggesting that its water-borne risks should be considered seriously.

Acrolein exerts a genotoxic effect in the Leydig cells by stimulating DNA damage-induced apoptosis

Acrolein is a highly reactive unsaturated organic molecule and has harmful effects on human health. Acrolein is generally formed in heat-treated foods above 150 °C, as well as in the combustion of gasoline, wood industry, plastic waste, and tobacco smoke. In this study, the effects of acrolein on genotoxicity in Leydig cells and the underlying mechanisms are aimed to be clarified. In addition, the toxicogenomic profile of acrolein was studied in terms of both apoptosis and steroidogenesis. Real-time PCR and ELISA tests were used to analyses of steroidogenic endpoints. Apoptosis was evaluated with double fluorescence staining and gene expression analyses of related genes. Comet assay was used to determine the genotoxicity. The results showed that acrolein caused concentration-dependent inhibition on cell viability at 8 μM and above concentrations, decreased testosterone production at 13.6 and 19.7 μM concentrations, and suppressed expression levels of genes that play an important role in steroidogenic pathway. Furthermore, acrolein downregulated expression of anti-apoptotic Bcl2 gene and upregulated expression of pro-apoptotic Bax, Casp3, and Trp53 gene after 24-h treatment in 7.4, 13.6, and 19.7 μM acrolein-exposed Leydig cells. The results of comet assay showed that acrolein significantly induced tail length, tail % DNA, and Olive tail moment. Overall, it was concluded that acrolein-induced cell damage in Leydig cells may be due to formation of genetic damage in steroidogenesis and apoptosis.

Ambient Particulate Matter and Acrolein Co-Exposure Increases Myocardial Dyssynchrony in Mice via TRPA1

Air pollution is a complex mixture of particulate matter and gases linked to adverse clinical outcomes. As such, studying responses to individual pollutants does not account for the potential biological responses resulting from the interaction of various constituents within an ambient air shed. We previously reported that exposure to high levels of the gaseous pollutant acrolein perturbs myocardial synchrony. Here, we examined the effects of repeated, intermittent co-exposure to low levels of concentrated ambient particulates (CAPs) and acrolein on myocardial synchrony and the role of transient receptor potential cation channel A1 (TRPA1), which we previously linked to air pollution-induced sensitization to triggered cardiac arrhythmia. Female B6129 and Trpa1-/- mice (n = 6/group) were exposed to filtered air (FA), CAPs (46 µg/m3 of PM2.5), Acrolein (0.42 ppm), or CAPs+Acrolein for 3 h/day, 2 days/week for 4 weeks. Cardiac ultrasound was conducted to assess cardiac synchronicity and function before and after the first exposure and after the final exposure. Heart rate variability (HRV), an indicator of autonomic tone, was assessed after the final exposure. Strain delay (time between peak strain in adjacent cardiac wall segments), an index of myocardial dyssynchrony, increased by 5-fold after the final CAPs+Acrolein exposure in B6129 mice compared with FA, CAPs, or Acrolein-exposed B6129 mice, and CAPs+Acrolein-exposed Trpa1-/- mice. Only exposure to acrolein alone increased the HRV high frequency domain (5-fold) in B6129 mice, but not in Trpa1-/- mice. Thus, repeated inhalation of pollutant mixtures may increase risk for cardiac responses compared with single or multiple exposures to individual pollutants through TRPA1 activation.

Cardiovascular injury induced by tobacco products: assessment of risk factors and biomarkers of harm. A Tobacco Centers of Regulatory Science compilation

Although substantial evidence shows that smoking is positively and robustly associated with cardiovascular disease (CVD), the CVD risk associated with the use of new and emerging tobacco products, such as electronic cigarettes, hookah, and heat-not-burn products, remains unclear. This uncertainty stems from lack of knowledge on how the use of these products affects cardiovascular health. Cardiovascular injury associated with the use of new tobacco products could be evaluated by measuring changes in biomarkers of cardiovascular harm that are sensitive to the use of combustible cigarettes. Such cardiovascular injury could be indexed at several levels. Preclinical changes contributing to the pathogenesis of disease could be monitored by measuring changes in systemic inflammation and oxidative stress, organ-specific dysfunctions could be gauged by measuring endothelial function (flow-mediated dilation), platelet aggregation, and arterial stiffness, and organ-specific injury could be evaluated by measuring endothelial microparticles and platelet-leukocyte aggregates. Classical risk factors, such as blood pressure, circulating lipoproteins, and insulin resistance, provide robust estimates of risk, and subclinical disease progression could be followed by measuring coronary artery Ca2+ and carotid intima-media thickness. Given that several of these biomarkers are well-established predictors of major cardiovascular events, the association of these biomarkers with the use of new and emerging tobacco products could be indicative of both individual and population-level CVD risk associated with the use of these products. Differential effects of tobacco products (conventional vs. new and emerging products) on different indexes of cardiovascular injury could also provide insights into mechanisms by which they induce cardiovascular harm.

Pulmonary exposure to peat smoke extracts in rats decreases expiratory time and increases left heart end systolic volume

Exposure to wildland fire-related particulate matter (PM) causes adverse health outcomes. However, the impacts of specific biomass sources remain unclear. The purpose of this study was to investigate cardiopulmonary responses in rats following exposure to PM extracts collected from peat fire smoke. We hypothesized that peat smoke PM would dose-dependently alter cardiopulmonary function. Male Sprague-Dawley rats (n = 8/group) were exposed to 35 µg (Lo PM) or 350 µg (Hi PM) of peat smoke PM extracts suspended in saline, or saline alone (Vehicle) via oropharyngeal aspiration (OA). Ventilatory expiration times, measured in whole-body plethysmographs immediately after OA, were the lowest in Hi PM exposed subjects at 6 min into recovery (p = .01 vs. Lo PM, p = .08 vs. Vehicle) and resolved shortly afterwards. The next day, we evaluated cardiovascular function in the same subjects via cardiac ultrasound under isoflurane anesthesia. Compared to Vehicle, Hi PM had 45% higher end systolic volume (p = .03) and 17% higher pulmonary artery blood flow acceleration/ejection time ratios, and both endpoints expressed significant increasing linear trends by dose (p = .01 and .02, respectively). In addition, linear trend analyses across doses detected an increase for end diastolic volume and decreases for ejection fraction and fractional shortening. These data suggest that exposure to peat smoke constituents modulates regulation of ventricular ejection and filling volumes, which could be related to altered blood flow in the pulmonary circulation. Moreover, early pulmonary responses to peat smoke PM point to irritant/autonomic mechanisms as potential drivers of later cardiovascular responses.

Respiratory Effects and Systemic Stress Response Following Acute Acrolein Inhalation in Rats

Previous studies have demonstrated that exposure to the pulmonary irritant ozone causes myriad systemic metabolic and pulmonary effects attributed to sympathetic and hypothalamus-pituitary-adrenal (HPA) axis activation, which are exacerbated in metabolically impaired models. We examined respiratory and systemic effects following exposure to a sensory irritant acrolein to elucidate the systemic and pulmonary consequences in healthy and diabetic rat models. Male Wistar and Goto Kakizaki (GK) rats, a nonobese type II diabetic Wistar-derived model, were exposed by inhalation to 0, 2, or 4 ppm acrolein, 4 h/d for 1 or 2 days. Exposure at 4 ppm significantly increased pulmonary and nasal inflammation in both strains with vascular protein leakage occurring only in the nose. Acrolein exposure (4 ppm) also caused metabolic impairment by inducing hyperglycemia and glucose intolerance (GK > Wistar). Serum total cholesterol (GKs only), low-density lipoprotein (LDL) cholesterol (both strains), and free fatty acids (GK > Wistar) levels increased; however, no acrolein-induced changes were noted in branched-chain amino acid or insulin levels. These responses corresponded with a significant increase in corticosterone and modest but insignificant increases in adrenaline in both strains, suggesting activation of the HPA axis. Collectively, these data demonstrate that acrolein exposure has a profound effect on nasal and pulmonary inflammation, as well as glucose and lipid metabolism, with the systemic effects exacerbated in the metabolically impaired GKs. These results are similar to ozone-induced responses with the exception of lung protein leakage and ability to alter branched-chain amino acid and insulin levels, suggesting some differences in neuroendocrine regulation of these two air pollutants.

Acrolein Can Cause Cardiovascular Disease: A Review

Acrolein is a highly reactive unsaturated aldehyde that is formed during the burning of gasoline and diesel fuels, cigarettes, woods and plastics. In addition, acrolein is generated during the cooking or frying of food with fats or oils. Acrolein is also used in the synthesis of many organic chemicals and as a biocide in agricultural and industrial water supply systems. The total emissions of acrolein in the United States from all sources are estimated to be 62,660 tons/year. Acrolein is classified by the Environmental Protection Agency as a high-priority air and water toxicant. Acrolein can exert toxic effects following inhalation, ingestion, and dermal exposures that are dose dependent. Cardiovascular tissues are particularly sensitive to the toxic effects of acrolein based primarily on in vitro and in vivo studies. Acrolein can generate free oxygen radical stress in the heart, decrease endothelial nitric oxide synthase phosphorylation and nitric oxide formation, form cytoplasmic and nuclear protein adducts with myocyte and vascular endothelial cell proteins and cause vasospasm. In this manner, chronic exposure to acrolein can cause myocyte dysfunction, myocyte necrosis and apoptosis and ultimately lead to cardiomyopathy and cardiac failure. Epidemiological studies of acrolein exposure and toxicity should be developed and treatment strategies devised that prevent or significantly limit acrolein cardiovascular toxicity.

Acrolein Inhalation Alters Myocardial Synchrony and Performance at and Below Exposure Concentrations that Cause Ventilatory Responses

Acrolein is an irritating aldehyde generated during combustion of organic compounds. Altered autonomic activity has been documented following acrolein inhalation, possibly impacting myocardial synchrony and function. Given the ubiquitous nature of acrolein in the environment, we sought to better define the immediate and delayed functional cardiac effects of acrolein inhalation in vivo. We hypothesized that acrolein inhalation would increase markers of cardiac mechanical dysfunction, i.e., myocardial dyssynchrony and performance index in mice. Male C57Bl/6J mice were exposed to filtered air (FA) or acrolein (0.3 or 3.0 ppm) for 3 h in whole-body plethysmography chambers (n = 6). Echocardiographic analyses were performed 1 day before exposure and at 1 and 24 h post-exposure. Speckle tracking echocardiography revealed that circumferential strain delay (i.e., dyssynchrony) was increased at 1 and 24 h following exposure to 3.0 ppm, but not 0.3 ppm, when compared to pre-exposure and/or FA exposure. Pulsed wave Doppler of transmitral blood flow revealed that acrolein exposure at 0.3 ppm, but not 3.0 ppm, increased the Tei index of myocardial performance (i.e., decreased global heart performance) at 1 and 24 h post-exposure compared to pre-exposure and/or FA exposure. We conclude that short-term inhalation of acrolein can acutely modify cardiac function in vivo and that echocardiographic evaluation of myocardial synchrony and performance following exposure to other inhaled pollutants could provide broader insight into the health effects of air pollution.

Effects of acrolein on aldosterone release from zona glomerulosa cells in male rats

A positive correlation between smoking and hypertension has been well established. Acrolein is a major toxic volatile compound found in cigarette smoke. Human exposure to low levels of acrolein is unavoidable due to its production in daily activities, such as smoke from industrial, hot oil cooking vapors, and exhaust fumes from vehicles. The toxicity and the action mechanism of acrolein to induce apoptosis have been extensively studied, but the effects of acrolein on hypertension are still unknown. The present study aimed to examine the effects of acrolein on aldosterone release both in vivo and in vitro. Male rats were divided into three groups, and intraperitoneally injected with normal saline, or acrolein (2mg/kg) for 1 (group A-1) or 3 (group A-3) days, respectively. After sacrificing, rat blood samples were obtained to measure plasma aldosterone and angiotensin II (Ang II) levels. Zona glomerulosa (ZG) cells were prepared from rat adrenal cortex, and were incubated with or without stimulants. We found that the serum aldosterone was increased by 1.2-fold (p<0.05) in A-3 group as compared to control group. Basal aldosterone release from ZG cells in A-3 group was also increased significantly. Moreover, acrolein enhanced the stimulatory effects of Ang II and 8-bromo-cyclic AMP on aldosterone secretion from ZG cells prepared in both A-1 and A-3 groups. Furthermore, the enzyme activity of P450scc, the rate-limiting step of aldosterone synthesis, was elevated after acrolein injection. Plasma level of Ang II was increased in both A-1 and A-3 groups. These results suggested that acrolein exposure increased aldosterone production, at least in part, through elevating the level of plasma Ang II and stimulating steroidogenesis pathways.

Acute cardiopulmonary toxicity of inhaled aldehydes: role of TRPA1

Inhalation of high-level volatile aldehydes, as present in smoke from wildfires and in tobacco smoke, is associated with both acute and chronic cardiopulmonary morbidity and mortality, but the underlying mechanisms are unclear. The transient receptor potential ankyrin 1 (TRPA1) protein forms a cation channel (irritant receptor) that mediates tobacco smoke-induced airway and lung injury, yet the role of TRPA1 in the cardiovascular toxicity of aldehyde exposure is unclear. Physiologically, airway-located TRPA1 activation triggers an irritant response (e.g., coughing and "respiratory braking") that alters the rate and depth of breathing to reduce exposure. Acrolein (2-propenal), a volatile, unsaturated aldehyde, activates TRPA1. Acrolein was used as a chemical weapon in World War I and is present at high levels in wildfires and tobacco smoke. Acrolein is thought to contribute to pulmonary and cardiovascular injury caused by tobacco smoke exposure, although the role of TRPA1 in cardiovascular toxicity is unclear. This minireview addresses this gap in our knowledge by exploring literature and recent data indicating a connection between TRPA1 and cardiovascular as well as pulmonary injury due to inhaled aldehydes.

Role of autonomic reflex arcs in cardiovascular responses to air pollution exposure

The body responds to environmental stressors by triggering autonomic reflexes in the pulmonary receptors, baroreceptors, and chemoreceptors to maintain homeostasis. Numerous studies have shown that exposure to various gases and airborne particles can alter the functional outcome of these reflexes, particularly with respect to the cardiovascular system. Modulation of autonomic neural input to the heart and vasculature following direct activation of sensory nerves in the respiratory system, elicitation of oxidative stress and inflammation, or through other mechanisms is one of the primary ways that exposure to air pollution affects normal cardiovascular function. Any homeostatic process that utilizes the autonomic nervous system to regulate organ function might be affected. Thus, air pollution and other inhaled environmental irritants have the potential to alter both local airway function and baro- and chemoreflex responses, which modulate autonomic control of blood pressure and detect concentrations of key gases in the body. While each of these reflex pathways causes distinct responses, the systems are heavily integrated and communicate through overlapping regions of the brainstem to cause global effects. This short review summarizes the function of major pulmonary sensory receptors, baroreceptors, and carotid body chemoreceptors and discusses the impacts of air pollution exposure on these systems.