Elevated Cellular Oxidative Stress in Circulating Immune Cells in Otherwise Healthy Young People Who Use Electronic Cigarettes in a Cross-Sectional Single-Center Study: Implications for Future Cardiovascular Risk

Assessing the association between e-cigarette use and cardiovascular disease: A meta-analysis of exclusive and dual use with combustible cigarettes

BACKGROUND

Growing evidence highlights the impact of e-cigarette use on cardiovascular health, prompting a crucial examination of its association with cardiovascular disease (CVD) in both exclusive e-cigarette and dual use scenarios with combustible cigarettes. This meta-analysis assessed the association between e-cigarette use and CVD by synthesizing the existing literature.

METHODS

Pertinent observational studies were identified using multiple electronic databases, from August 22nd, 2006, to April 10th, 2024. A meta-analysis was conducted using random-effect models. Risk of bias was assessed using the National Institutes of Health (NIH) Study Quality Assessment Tools.

FINDINGS

A total of 20 observational studies involving 8,499,444 participants were included in the meta-analysis. Dual use (e-cigarettes and combustible cigarette) increased the odds of CVD by 2.56 times (95 % CI: 2.11, 3.11) compared to never use of both. Current e-cigarette use combined with former combustible cigarette increased the odds of CVD by 2.02 times (95 % CI: 1.58, 2.58) compared to never use of either. Exclusive current e-cigarette use did not show a statistically significant association with CVD odds compared to never use of either (OR = 1.24, 95 % CI: 0.93, 1.67).

CONCLUSIONS

Dual use of e-cigarettes and combustible cigarettes was significantly associated with CVD, but results failed to show a significant association between exclusive e-cigarette use and CVD. Robust and longitudinal studies are needed to understand the long-term implications of e-cigarette use and CVD. Public health efforts should focus on awareness, smoking cessation, and regulating both e-cigarettes and combustible cigarettes.

Sex Differences in Oxidative Stress-Mediated Reductions in Microvascular Endothelial Function in Young Adult e-Cigarette Users

BACKGROUND

Chronic electronic-cigarette (EC) use is reported to decrease vascular endothelial function. However, the mechanism(s) mediating this reduction remain unclear. In this study, we examined endothelium- and NO-dependent dilation, and the role of oxidative stress in attenuating these responses, in healthy young EC users (n=20, 10 males/10 females) compared with healthy controls (n=20, 10 males/10 females). We hypothesized that EC would have reduced endothelium- and NO-dependent dilation and administration of the superoxide scavenger tempol would increase these responses in EC. We further hypothesized that female EC would have the greatest reductions in endothelium- and NO-dependent dilation.

METHODS

We assessed microvascular endothelium-dependent vasodilator function in vivo by measurement of cutaneous vascular conductance (%CVCmax) responses to a standardized local heating protocol in control and 10 μM tempol-treated sites. After full expression of the local heating response, 15 mM NG-nitro-L-arginine methyl ester (NO synthase inhibition) was perfused.

RESULTS

EC had significantly reduced endothelium- (73±15 versus 87±9%CVCmax; P<0.001) and NO-dependent (48±17% versus 62±15%; P=0.011) dilation. Tempol perfusion increased endothelium-dependent (84±12%CVCmax P=0.01) and NO-dependent (63±14% P=0.005) dilation in EC but had no effect in healthy control. Within female sex, EC had lower endothelium-dependent (71±13 versus 89±7%CVCmax; P=0.002) and NO-dependent (50±6 versus 69±11%; P=0.005) dilation compared with healthy control, and tempol augmented endothelium-dependent (83±13%CVCmax; P=0.002) and NO-dependent (62±13%; P=0.015) dilation. There were no group or treatment differences within male sex.

CONCLUSION

Healthy young adult EC users have reduced microvascular endothelium-dependent and NO-dependent dilation, driven by greater reductions in female EC users, and mediated in part by superoxide.

Sex Differences in E-Cigarette Use and Related Health Effects

BACKGROUND

Electronic cigarettes (e-cigarettes) comprise a variety of products designed to deliver nicotine, flavorings, and other substances. To date, multiple epidemiological and experimental studies have reported a variety of health issues associated with their use, including respiratory toxicity, exacerbation of respiratory conditions, and behavioral and physiological effects. While some of these effects appear to be sex- and/or gender-related, only a portion of the research has been conducted considering these variables. In this review, we sought to summarize the available literature on sex-specific effects and sex and gender differences, including predictors and risk factors, effects on organ systems, and behavioral effects.

METHODS

We searched and selected articles from 2018-2023 that included sex as a variable or reported sex differences on e-cigarette-associated effects.

RESULTS

We found 115 relevant studies published since 2018 that reported sex differences in a variety of outcomes. The main differences reported were related to reasons for initiation, including smoking history, types of devices and flavoring, polysubstance use, physiological responses to nicotine and toxicants in e-liquids, exacerbation of lung disease, and behavioral factors such as anxiety, depression, sexuality, and bullying.

CONCLUSIONS

The available literature supports the notion that both sex and gender influence the susceptibility to the negative effects of e-cigarette use. Future research needs to consider sex and gender variables when addressing e-cigarette toxicity and other health-related consequences.

Chronic Electronic Cigarette Use and Atherosclerosis Risk in Young People: A Cross-Sectional Study-Brief Report

BACKGROUND

Little is known whether electronic cigarettes (ECIG) increase vulnerability to future atherosclerotic cardiovascular disease. We determined, using an ex vivo mechanistic atherogenesis assay, whether proatherogenic changes including monocyte transendothelial migration and monocyte-derived foam cell formation are increased in people who use ECIGs.

METHODS

In a cross-sectional single-center study using plasma and peripheral blood mononuclear cells from healthy participants who are nonsmokers or with exclusive use of ECIGs or tobacco cigarettes (TCIGs), autologous peripheral blood mononuclear cells with patient plasma and pooled peripheral blood mononuclear cells from healthy nonsmokers with patient plasma were utilized to dissect patient-specific ex vivo proatherogenic circulating factors present in plasma and cellular factors present in monocytes. Our main outcomes were monocyte transendothelial migration (% of blood monocyte cells that undergo transendothelial migration through a collagen gel) and monocyte-derived foam cell formation as determined by flow cytometry and the median fluorescence intensity of the lipid-staining fluorochrome BODIPY in monocytes of participants in the setting of an ex vivo model of atherogenesis.

RESULTS

Study participants (N=60) had median age of 24.0 years (interquartile range [IQR], 22.0-25.0 years), and 31 were females. Monocyte transendothelial migration was increased in people who exclusively used TCIGs (n=18; median [IQR], 2.30 [ 1.29-2.82]; P<0.001) and in people who exclusively used ECIGs (n=21; median [IQR], 1.42 [ 0.96-1.91]; P<0.01) compared with nonsmoking controls (n=21; median [IQR], 1.05 [0.66-1.24]). Monocyte-derived foam cell formation was increased in people who exclusively used TCIGs (median [IQR], 2.01 [ 1.59-2.49]; P<0.001) and in people who exclusively used ECIGs (median [IQR], 1.54 [ 1.10-1.86]; P<0.001) compared with nonsmoker controls (median [IQR], 0.97 [0.86-1.22]). Both monocyte transendothelial migration and monocyte-derived foam cell formation were higher in TCIG smokers compared with ECIG users and in ECIG users who were former smokers versus ECIG users who were never smokers (P<0.05 for all comparisons).

CONCLUSIONS

The finding of alterations in proatherogenic properties of blood monocytes and plasma in TCIG smokers compared with nonsmokers validates this assay as a strong ex vivo mechanistic tool with which to measure proatherogenic changes in people who use ECIGs. Similar yet significantly less severe alterations in proatherogenic properties of monocytes and plasma were detected in the blood from ECIG users. Future studies are necessary to determine whether these findings are attributable to a residual effect of prior smoking or are a direct effect of current ECIG use.

Cardiopulmonary Impact of Electronic Cigarettes and Vaping Products: A Scientific Statement From the American Heart Association

Vaping and electronic cigarette (e-cigarette) use have grown exponentially in the past decade, particularly among youth and young adults. Cigarette smoking is a risk factor for both cardiovascular and pulmonary disease. Because of their more limited ingredients and the absence of combustion, e-cigarettes and vaping products are often touted as safer alternative and potential tobacco-cessation products. The outbreak of e-cigarette or vaping product use-associated lung injury in the United States in 2019, which led to >2800 hospitalizations, highlighted the risks of e-cigarettes and vaping products. Currently, all e-cigarettes are regulated as tobacco products and thus do not undergo the premarket animal and human safety studies required of a drug product or medical device. Because youth prevalence of e-cigarette and vaping product use was as high as 27.5% in high school students in 2019 in the United States, it is critical to assess the short-term and long-term health effects of these products, as well as the development of interventional and public health efforts to reduce youth use. The objectives of this scientific statement are (1) to describe and discuss e-cigarettes and vaping products use patterns among youth and adults; (2) to identify harmful and potentially harmful constituents in vaping aerosols; (3) to critically assess the molecular, animal, and clinical evidence on the acute and chronic cardiovascular and pulmonary risks of e-cigarette and vaping products use; (4) to describe the current evidence of e-cigarettes and vaping products as potential tobacco-cessation products; and (5) to summarize current public health and regulatory efforts of e-cigarettes and vaping products. It is timely, therefore, to review the short-term and especially the long-term implications of e-cigarettes and vaping products on cardiopulmonary health. Early molecular and clinical evidence suggests various acute physiological effects from electronic nicotine delivery systems, particularly those containing nicotine. Additional clinical and animal-exposure model research is critically needed as the use of these products continues to grow.

Ectodomain shedding of proteins important for SARS-CoV-2 pathogenesis in plasma of tobacco cigarette smokers compared to electronic cigarette vapers: a cross-sectional study

The impact of tobacco cigarette (TCIG) smoking and electronic cigarette (ECIG) vaping on the risk of development of severe COVID-19 is controversial. The present study investigated levels of proteins important for SARS-CoV-2 pathogenesis present in plasma because of ectodomain shedding in smokers, ECIG vapers, and non-smokers (NSs). Protein levels of soluble angiotensin-converting enzyme 2 (ACE2), angiotensin (Ang) II (the ligand of ACE2), Ang 1-7 (the main peptide generated from Ang II by ACE2 activity), furin (a protease that increases the affinity of the SARS-CoV-2 spike protein for ACE2), and products of ADAM17 shedding activity that predict morbidity in COVID-19 (IL-6/IL-6R alpha (IL-6/IL-6Rα) complex, soluble CD163 (sCD163), L-selectin) were determined in plasma from 45 NSs, 30 ECIG vapers, and 29 TCIG smokers using ELISA. Baseline characteristics of study participants did not differ among groups. TCIG smokers had increased sCD163, L-selectin compared to NSs and ECIG vapers (p < 0.001 for all comparisons). ECIG vapers had higher plasma furin compared to both NSs (p < 0.001) and TCIG smokers (p < 0.05). ECIG vaping and TCIG smoking did not impact plasma ACE2, Ang 1-7, Ang II, and IL-6 levels compared to NSs (p > 0.1 for all comparisons). Further studies are needed to determine if increased furin activity and ADAM17 shedding activity that is associated with increased plasma levels of sCD163 and L-selectin in healthy young TCIG smokers may contribute to the future development of severe COVID-19 and cardiovascular complications of post-acute COVID-19 syndrome.

Chronic health effects associated with electronic cigarette use: A systematic review

Introduction

Over the last decade, e-cigarette use has been on the rise but with growing health concerns. The objective of this systematic review was to update findings for chronic health outcomes associated with e-cigarette use from the 2018 National Academies of Sciences, Engineering, and Medicine (NASEM) report.

Methods

Three bibliographic databases were searched to identify studies comparing the chronic health effects of e-cigarette users (ECU) to non-smokers (NS), smokers, and/or dual users indexed between 31 August 2017 and 29 January 2021. Two independent reviewers screened abstracts and full texts. Data were extracted by one reviewer and verified by a second one. Outcomes were synthesized in a narrative manner using counts and based on statistical significance and direction of the association stratified by study design and exposure type. Risk of bias and certainty of evidence was assessed. The protocol was prospectively registered on Open Science Framework https://osf.io/u9btp.

Results

A total of 180 articles were eligible. This review focused on 93 studies for the 11 most frequently reported outcomes and from which 59 reported on daily e-cigarette use. The certainty of evidence for all outcomes was very low because of study design (84% cross-sectional) and exposure type (27% reported on exclusive ECU, i.e., never smoked traditional cigarettes). Overall, the summary of results for nearly all outcomes, including inflammation, immune response, periodontal and peri-implant clinical parameters, lung function, respiratory symptoms, and cardiovascular disease, suggested either non-significant or mixed results when daily ECU was compared to NS. This was also observed when comparing exclusive ECU to NS. The only notable exception was related to oral health where most (11/14) studies reported significantly higher inflammation among daily ECU vs. NS. Compared to the smokers, the exclusive-ECUs had no statistically significant differences in inflammation orperiodontal clinical parameters but had mixed findings for peri-implant clinical parameters.

Conclusions

This review provides an update to the 2018 NASEM report on chronic health effects of e-cigarette use. While the number of studies has grown, the certainty of evidence remains very low largely because of cross-sectional designs and lack of reporting on exclusive e-cigarette exposure. There remains a need for higher quality intervention and prospective studies to assess causality, with a focus on exclusive e-cigarette use.

Neural-hematopoietic-inflammatory axis in nonsmokers, electronic cigarette users, and tobacco smokers

Amygdala activity in context of the splenocardiac model has not been investigated in healthy, young adults and has not been compared between nonsmokers, electronic cigarette users, and smokers. The purpose of the current study was to determine whether fluorodeoxyglucose positron emission tomography/computer tomography (FDG PET/CT) scans would demonstrate positively correlated metabolic activity in the amygdala, bone marrow, spleen, and aorta, elucidating activation of the splenocardiac axis in otherwise healthy young people who use tobacco products compared to nonusers. Moreover, the study was conducted to evaluate whether electronic cigarette users and tobacco smokers have similar levels of inflammation compared to nonusers. In 45 healthy adults (mean age = 25 years), including nonsmoker (n = 15), electronic cigarette user (n = 16), and smoker (n = 14) groups, metabolic activity in the amygdala, spleen, aorta, bone marrow of thoracic vertebrae, and adjacent erector spinae skeletal muscle was quantified through visualization of radioactive glucose (18 FDG) uptake by FDG-PET/CT. The maximum standardized uptake value for each region was calculated for correlation analyses and comparisons between groups. In correlation analyses, metabolic activity of the amygdala correlated with metabolic activity in the aorta (r = 0.757), bone marrow (r = 0.750), and spleen (r = 0.665), respectively. Metabolic activity in the aorta correlated with 18 FDG uptake in the thoracic vertebrae (r = 0.703) and spleen (r = 0.594), respectively. Metabolic activity in the spleen also correlated with 18 FDG uptake in the bone marrow (r = 0.620). Metabolic activity in the adjacent erector spinae skeletal muscle (our control tissue) was not positively correlated with any other region of interest. Finally, there were no statistically significant mean differences in metabolic activity between the three groups: nonsmokers, electronic cigarette users, and smokers in any target tissue. Amygdala metabolic activity, as measured by 18 FDG uptake in FDG-PET/CT scans, positively correlated with inflammation in the splenocardiac tissues, including: the aorta, bone marrow, and spleen, underscoring the existence of a neural-hematopoietic-inflammatory axis in healthy, young adults.

An integral perspective of canonical cigarette and e-cigarette-related cardiovascular toxicity based on the adverse outcome pathway framework

BACKGROUND

Nowadays, cigarette smoking remains the leading cause of chronic disease and premature death, especially cardiovascular disease. As an emerging tobacco product, e-cigarettes have been advocated as alternatives to canonical cigarettes, and thus may be an aid to promote smoking cessation. However, recent studies indicated that e-cigarettes should not be completely harmless to the cardiovascular system.

AIM OF REVIEW

This review aimed to build up an integral perspective of cigarettes and e-cigarettes-related cardiovascular toxicity.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review adopted the adverse outcome pathway (AOP) framework as a pivotal tool and aimed to elucidate the association between the molecular initiating events (MIEs) induced by cigarette and e-cigarette exposure to the cardiovascular adverse outcome. Since the excessive generation of reactive oxygen species (ROS) has been widely approved to play a critical role in cigarette smoke-related CVD and may also be involved in e-cigarette-induced toxic effects, the ROS overproduction and subsequent oxidative stress are regarded as essential parts of this framework. As far as we know, this should be the first AOP framework focusing on cigarette and e-cigarette-related cardiovascular toxicity, and we hope our work to be a guide in exploring the biomarkers and novel therapies for cardiovascular injury.

Cardiopulmonary Consequences of Vaping in Adolescents: A Scientific Statement From the American Heart Association

Although the US Food and Drug Administration has not approved e-cigarettes as a cessation aid, industry has at times positioned their products in that way for adults trying to quit traditional cigarettes; however, their novelty and customizability have driven them into the hands of unintended users, particularly adolescents. Most new users of e-cigarette products have never smoked traditional cigarettes; therefore, understanding the respiratory and cardiovascular consequences of e-cigarette use has become of increasing interest to the research community. Most studies have been performed on adult e-cigarette users, but the majority of these study participants are either former traditional smokers or smokers who have used e-cigarettes to switch from traditional smoking. Therefore, the respiratory and cardiovascular consequences in this population are not attributable to e-cigarette use alone. Preclinical studies have been used to study the effects of naive e-cigarette use on various organ systems; however, almost all of these studies have used adult animals, which makes translation of health effects to adolescents problematic. Given that inhalation of any foreign substance can have effects on the respiratory and cardiovascular systems, a more holistic understanding of the pathways involved in toxicity could help to guide researchers to novel therapeutic treatment strategies. The goals of this scientific statement are to provide salient background information on the cardiopulmonary consequences of e-cigarette use (vaping) in adolescents, to guide therapeutic and preventive strategies and future research directions, and to inform public policymakers on the risks, both short and long term, of vaping.

An assessment of vaping-induced inflammation and toxicity: A feasibility study using a 2-stage zebrafish and mouse platform

It is currently understood that tobacco smoking is a major cause of pulmonary disease due to pulmonary/lung inflammation. However, due to a highly dynamic market place and an abundance of diverse products, less is known about the effects of e-cigarette (E-cig) use on the lung. In addition, varieties of E-cig liquids (e-liquids), which deliver nicotine and numerous flavor chemicals into the lungs, now number in the 1000s. Thus, a critical need exists for safety evaluations of these E-cig products. Herein, we employed a "2-stage in vivo screening platform" (zebrafish to mouse) to assess the safety profiles of e-liquids. Using the zebrafish, we collected embryo survival data after e-liquid exposure as well as neutrophil migration data, a key hallmark for a pro-inflammatory response. Our data indicate that certain e-liquids induce an inflammatory response in our zebrafish model and that e-liquid exposure alone results in pro-inflammatory lung responses in our C57BL/6J model, data collected from lung staining and ELISA analysis, respectively, in the mouse. Thus, our platform can be used as an initial assessment to ascertain the safety profiles of e-liquid using acute inflammatory responses (zebrafish, Stage 1) as our initial metric followed by chronic studies (C57BL/6J, Stage 2).

Instigators of COVID-19 in Immune Cells Are Increased in Tobacco Cigarette Smokers and Electronic Cigarette Vapers Compared With Nonsmokers

INTRODUCTION

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the virus responsible for the COVID-19 pandemic, gains entry into the host cell when its Spike protein is cleaved by host proteases TMPRSS2 and furin, thereby markedly increasing viral affinity for its receptor, angiotensin-converting enzyme-2 (ACE2). In rodent and diseased human lungs, tobacco cigarette (TCIG) smoke increases ACE2, but the effect of electronic cigarette vaping (ECIG) is unknown. It is unknown whether nicotine (in both TCIGs and ECIGs) or non-nicotine constituents unique to TCIG smoke increase expression of key proteins in COVID-19 pathogenesis.

METHODS

Immune (CD45+) cells collected before the pandemic in otherwise healthy young people, including TCIG smokers (n = 9), ECIG vapers (n = 12), or nonsmokers (NS) (n = 12), were studied. Using flow cytometry, expression of key proteins in COVID-19 pathogenesis were compared among these groups.

RESULTS

TCIG smokers and ECIG vapers had similar smoking or vaping burdens as indicated by similar plasma cotinine levels. TCIG smokers compared with NS had a significantly increased percentage of cells that were positive for ACE2 (10-fold, p < .001), TMPRSS2 (5-fold, p < .001), and ADAM17 (2.5-fold, p < .001). Additionally, the mean fluorescence intensity (MFI) consistently showed greater mean ACE2 (2.2-fold, p < .001), TMPRSS2 (1.5-fold, p < .001), furin (1.1-fold, p < .05), and ADAM17 (2-fold, p < .001) in TCIG smokers compared with NS. In ECIG vapers, furin MFI was increased (1.15-fold, p < .05) and TMPRSS2 MFI tended to be increased (1.1-fold, p = .077) compared with NS.

CONCLUSIONS

The finding that key instigators of COVID-19 infection are lower in ECIG vapers compared with TCIG smokers is intriguing and warrants additional investigation to determine if switching to ECIGs is an effective harm reduction strategy. However, the trend toward increased proteases in ECIG vapers remains concerning.

IMPLICATIONS

(1) This is the first human study to report a marked increase in proteins critical for COVID-19 infection, including ACE2, TMPRSS2, and ADAM17, in immune cells from healthy tobacco cigarette smokers without lung disease compared with e-cigarette vapers and nonsmokers. (2) These findings warrant additional investigation to determine whether switching to electronic cigarettes may be an effective harm reduction strategy in smokers addicted to nicotine who are unable or unwilling to quit. (3) The increase in proteases in electronic cigarette vapers remains concerning.

Association of 1 Vaping Session With Cellular Oxidative Stress in Otherwise Healthy Young People With No History of Smoking or Vaping: A Randomized Clinical Crossover Trial

This randomized clinical crossover trial evaluates the association of a single session of electronic cigarette vaping with cellular oxidative stress in healthy young people who do not smoke compared with individuals with long-term tobacco cigarette or electronic cigarette use.

Electronic and Tobacco Cigarettes Alter Polyunsaturated Fatty Acids and Oxidative Biomarkers

[Figure: see text].

Biomarkers of Inflammation and Oxidative Stress among Adult Former Smoker, Current E-Cigarette Users-Results from Wave 1 PATH Study

BACKGROUND

Former smokers who currently use e-cigarettes have lower concentrations of biomarkers of tobacco toxicant exposure than current smokers. It is unclear whether tobacco toxicant exposure reductions may lead to health risk reductions.

METHODS

We compared inflammatory biomarkers (high-sensitivity C-reactive protein, IL6, fibrinogen, soluble intercellular adhesion molecule-1) and an oxidative stress marker (F2-isoprostane) among 3,712 adult participants in Wave 1 (2013-2014) of the Population Assessment of Tobacco and Health Study by tobacco user groups: dual users of cigarettes and e-cigarettes; former smokers who currently use e-cigarettes-only; current cigarette-only smokers; former smokers who do not currently use any tobacco; and never tobacco users. We calculated geometric means (GM) and estimated adjusted GM ratios (GMR).

RESULTS

Dual users experienced greater concentration of F2-isoprostane than current cigarette-only smokers [GMR 1.09 (95% confidence interval, CI, 1.03-1.15)]. Biomarkers were similar between former smokers who currently use e-cigarettes and both former smokers who do not use any tobacco and never tobacco users, but among these groups most biomarkers were lower than those of current cigarette-only smokers. The concentration of F2-isoprostane decreased by time since smoking cessation among both exclusive e-cigarette users (P _trend = 0.03) and former smokers who do not currently use any tobacco (P _trend = 0.0001).

CONCLUSIONS

Dual users have greater concentration of F2-isoprostane than smokers. Exclusive e-cigarette users have biomarker concentrations that are similar to those of former smokers who do not currently use tobacco, and lower than those of exclusive cigarette smokers.

IMPACT

This study contributes to an understanding of the health effects of e-cigarettes.

Increased Expression of Proatherogenic Proteins in Immune Cell Subtypes in Tobacco Cigarette Smokers But Not in Electronic Cigarette Vapers

It is unclear how oxidative stress triggered by smoking and vaping may alter specific immune cell subsets. In this study, we showed that tobacco cigarette smoking, but not electronic-cigarette vaping, is associated with increased expression of major proteins in the toll-like receptor 4 (TLR4) inflammasome-interleukin (IL)-6 signalling axis in monocyte subtypes and T cells. TLR4 senses oxidative stress in immune cells caspase-1 is a key protein of inflammasome activation, and IL-6R-α is the receptor for IL-6 that drives proatherogenic IL-6 signalling. These findings implicate the non-nicotine, pro-oxidant toxicants in tobacco cigarette smoke as instigators of increased expression of key proteins in the TLR4-inflammasome-IL-6 axis that contribute to atherogenesis.

Atherosclerosis inflammation and burden in young adult smokers and vapers measured by PET/MR

BACKGROUND AND AIMS

Electronic cigarette (EC) use is popular among youth, touted as a safer alternative to smoking and promoted as a tool to aid in smoking cessation. EC cardiovascular safety however is not well established. The aim of this study was to examine cardiovascular consequences of EC use by evaluating their effect on the entire atherosclerotic cascade in young adults using noninvasive combined positron emission tomography (PET)/magnetic resonance imaging (MR) and comparing EC use with age matched smokers of traditional cigarettes and nonsmoking controls.

METHODS

Carotid PET/MR was applied to look at vascular inflammation (18-fluorodeoxyglucose (FDG)-PET) and plaque burden (multi-contrast MR of vessel wall) from 60 18-30 year-old subjects (20 electronic cigarette users, 20 traditional smokers and 20 nonsmokers).

RESULTS

Groups were reasonably well balanced in terms of age, gender, demographics, cardiovascular risk and most biomarkers. There were no differences in vascular inflammation as measured by 18-FDG-PET target to background ratios (TBR) between EC users, traditional cigarette smokers and nonsmokers. However, measures of carotid plaque burden - wall area, normalized wall index, and wall thickness - measured from MR were significantly higher in both traditional smokers and EC users than in nonsmokers.

CONCLUSIONS

Young adult EC users, smokers and nonsmokers in our study did not exhibit vascular inflammation as defined by 18-F-FDG-PET TBR max, but smokers and EC users had significantly more carotid plaque burden compared to matched nonsmokers. Results could indicate that vaping does not cause an increase in vascular inflammation as measured by FDG-PET.

Vaping and cardiac disease

Tobacco cigarette smoking is the most prevalent reversible risk factor for cardiovascular disease in the USA. Electronic cigarettes, invented as an alternative nicotine source for smokers unable or unwilling to stop smoking, have gained skyrocketing popularity, but their cardiovascular risk remains uncertain. Although data recently analysed in a Cochran report do support their superior effectiveness to other forms of nicotine replacement therapies for smoking cessation, electronic cigarettes are also frequently used by non-smokers-especially high school students. There are no long-term outcome studies on the cardiovascular risk of vaping electronic cigarettes, but the effects of electronic cigarettes on known risk factors for cardiovascular disease, including neurohumoural activation, oxidative stress and inflammation, endothelial function and thrombosis, have been studied. In this review, we summarise evidence in humans that supports the notion that while electronic cigarettes may be less harmful than traditional cigarettes, they are not harmless. Additionally, the increasing popularity of vaping marijuana with its unknown cardiovascular risks as well as the outbreak in 2019 of EVALI (electronic cigarette, or vaping, product use-associated lung injury) related to bootlegged vaping products raise further concerns. Before physicians can confidently advise their smoking patients about the role of electronic cigarettes as a means of smoking cessation to lower cardiovascular risk, improved regulation and quality control is necessary.

Elevated Cellular Oxidative Stress in Circulating Immune Cells in Otherwise Healthy Young People Who Use Electronic Cigarettes in a Cross-Sectional Single-Center Study: Implications for Future Cardiovascular Risk

Background

Tobacco cigarettes (TCs) increase oxidative stress and inflammation, both instigators of atherosclerotic cardiac disease. It is unknown if electronic cigarettes (ECs) also increase immune cell oxidative stress. We hypothesized an ordered, “dose‐response” relationship, with tobacco‐product type as “dose” (lowest in nonsmokers, intermediate in EC vapers, and highest in TC smokers), and the “response” being cellular oxidative stress (COS) in immune cell subtypes, in otherwise, healthy young people.

Methods and Results

Using flow cytometry and fluorescent probes, COS was determined in immune cell subtypes in 33 otherwise healthy young people: nonsmokers (n=12), EC vapers (n=12), and TC smokers (n=9). Study groups had similar baseline characteristics, including age, sex, race, and education level. A dose‐response increase in proinflammatory monocytes and lymphocytes, and their COS content among the 3 study groups was found: lowest in nonsmokers, intermediate in EC vapers, and highest in TC smokers. These findings were most striking in CD14_dimCD16⁺ and CD14⁺⁺CD16⁺ proinflammatory monocytes and were reproduced with 2 independent fluorescent probes of COS.

Conclusions

These findings portend the development of premature cardiovascular disease in otherwise healthy young people who chronically vape ECs. On the other hand, that the COS is lower in EC vapers compared with TC smokers warrants additional investigation to determine if switching to ECs may form part of a harm‐reduction strategy.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03823885.