Electronic cigarettes: where to from here?

Stimulus mediation, specificity and impact of menthol in rats trained to discriminate puffs of nicotine e-cigarette aerosol from nicotine-free aerosol

RATIONALE

It is unclear if e-cigarettes have reduced abuse liability relative to traditional cigarettes, especially when considering advanced devices which deliver nicotine more efficiently. Translatable and predictive animal models are needed to addresses this question.

OBJECTIVES

Our goal was to explore the subjective stimulus effects of e-cigarettes by training rats to discriminate puffs of nicotine aerosol from vehicle aerosol using an aerosol delivery system designed to model e-cigarette use patterns in humans.

METHODS

Rats were trained to discriminate between ten, 10 s puffs of aerosol generated from 3 mg/ml nicotine e-liquid and nicotine-free e-liquid using a food-reinforced operant procedure. Following acquisition, tests were conducted to determine the specificity of the nicotine aerosol stimulus as well as the impact to the stimulus effects of nicotine resulting from the addition of menthol to e-liquid.

RESULTS

Rats learned the nicotine aerosol puff vs vehicle puff discrimination in a mean of 25 training sessions. Injected nicotine fully substituted for the stimulus effects of nicotine aerosol. The stimulus effects of nicotine aerosol were blocked by the nicotinic receptor antagonist mecamylamine. The nicotinic receptor partial agonist, varenicline as well as the stimulant d-amphetamine substituted more robustly for nicotine aerosol puffs than did the NMDA antagonist, ketamine. Menthol enhanced the stimulus effects of nicotine aerosol without altering nicotine blood plasma levels.

CONCLUSIONS

Nicotine aerosol puffs can function as a training stimulus in rats. The stimulus effects were CNS-mediated and receptor specific. Menthol appears to enhance the stimulus effects of nicotine aerosol through a pharmacodynamic rather than pharmacokinetic mechanism.

Implications of Switching from Conventional to Electronic Cigarettes on Quality of Life and Smoking Behaviour: Results from the EQualLife Trial

INTRODUCTION

Electronic cigarettes and "vaping" have become popular since their appearance in Europe and the USA in approximately 2006. They are often perceived as having fewer health risks than conventional cigarettes, which makes them of interest as a support tool in smoking cessation. However, its efficacy regarding cessation or reduction of smoking under real-life conditions remains controversial. Our objective was to clarify this question in an observational study of smoking habits after initiating vaping without targeted intervention, as compared to a validated cessation programme.

METHODS

From October 2015 to April 2018, 80 subjects (60 in the e-cigarette group and 20 in the supervised smoking cessation group) were included in two trial visits, one at the start of the trial and the second after 3 months, plus 4 questionnaire surveys: at the start of the trial and after a 1, 2, and 3 month period. The questionnaire included a nicotine use inventory, a modified Fagerström test for nicotine dependence, and the WHO-QOL-BREF survey.

RESULTS

E-cigarettes were effective, leading to a significant (p < 0.03) reduction (p < 0.03) in tobacco consumption and nicotine dependence, with an abstinence rate of 43% after 3 months. Compared to participants in the smoking cessation programme, their use was not associated with an improvement in quality of life during the quitting attempt, and there were no significant differences in clinical symptoms between groups. The reduction in nicotine dependence was more pronounced (p < 0.012) for the smoking cessation programme, with higher abstinence rates (p = 0.011 after 12 weeks) and lower (p < 0.003) remaining tobacco consumption compared to electronic cigarettes.

DISCUSSION/CONCLUSIONS

The use of electronic cigarettes reduced nicotine dependence and tobacco consumption, but a supervised smoking cessation programme was superior in terms of achieved cessation in both regards. Electronic cigarettes did not improve the quality of life. Since e-cigarettes could be associated with long-term health risks, their usefulness in smoking cessation remains questionable, and a professionally guided and validated smoking cessation programme still appears to be superior and preferable, in terms of achieved cessation. Although this trial is limited regarding the number of participants and follow-up time, it highlights the need for additional, large clinical trials evaluating the efficacy of e-cigarettes for smoking cessation in comparison to a professionally guided smoking cessation programme.

Human abuse liability assessment of e-cigarettes: Why, what and how?

Cigarette smoking is the world's leading cause of preventable death and disease. Alternative nicotine products such as e-cigarettes have tobacco harm reduction potential, by providing smokers with an alternative form of nicotine delivery but with either the reduced presence or absence of the numerous harmful chemicals found in combustible cigarette smoke. One aspect of importance in determining the potential of e-cigarettes to provide a viable alternative to combustible cigarettes for smokers is their ability to cause dependence, also known as their abuse liability. E-cigarettes with little or no abuse liability would be unlikely to be used as a substitute for cigarettes, whereas at least some degree of abuse liability is acknowledged as supportive both to aiding cigarette substitution or complete cessation and to preventing relapse. Given this link between abuse liability and substitution efficacy, human studies assessing the abuse liability of e-cigarettes are important to determine their true harm reduction potential. In this review, the concept of tobacco product abuse liability is discussed, along with the primary elements-pharmacokinetics and pharmacodynamics (subjective effects)-that need to be assessed to determine abuse liability. The review also presents a number of human abuse liability study design considerations and discusses what existing studies in the literature tell us about the abuse liability and harm reduction potential of e-cigarettes.

Predicting the long-term effects of electronic cigarette use on population health: a systematic review of modelling studies

OBJECTIVE

To systematically review and synthesise the findings of modelling studies on the population impacts of e-cigarette use and to identify potential gaps requiring future investigation.

DATA SOURCE AND STUDY SELECTION

Four databases were searched for modelling studies of e-cigarette use on population health published between 2010 and 2023. A total of 32 studies were included.

DATA EXTRACTION

Data on study characteristics, model attributes and estimates of population impacts including health outcomes and smoking prevalence were extracted from each article. The findings were synthesised narratively.

DATA SYNTHESIS

The introduction of e-cigarettes was predicted to lead to decreased smoking-related mortality, increased quality-adjusted life-years and reduced health system costs in 29 studies. Seventeen studies predicted a lower prevalence of cigarette smoking. Models that predicted negative population impacts assumed very high e-cigarette initiation rates among non-smokers and that e-cigarette use would discourage smoking cessation by a large margin. The majority of the studies were based on US population data and few studies included factors other than smoking status, such as jurisdictional tobacco control policies or social influence.

CONCLUSIONS

A population increase in e-cigarette use may result in lower smoking prevalence and reduced burden of disease in the long run, especially if their use can be restricted to assisting smoking cessation. Given the assumption-dependent nature of modelling outcomes, future modelling studies should consider incorporating different policy options in their projection exercises, using shorter time horizons and expanding their modelling to low-income and middle-income countries where smoking rates remain relatively high.

Comparison of the effects of electronic cigarette vapours and tobacco smoke extracts on human neutrophils in vitro

Background

Electronic cigarettes (ECs) are electronic aerosol delivery systems composed of nicotine and various chemicals, which are widely used to facilitate smoking cessation. Although ECs are considered safer than cigarettes, they do, however, contain chemical toxicants, some of which may interact with cells of the host's innate immune system of which neutrophils constitute a key component.

Methods

The current study was designed to compare the effects of aqueous EC aerosol extracts (ECEs; with or without nicotine) with those of cigarette smoke extract (CSE) on neutrophil and platelet reactivity in vitro. Neutrophil reactivity is characterised by the generation of reactive oxygen species (ROS), degranulation (elastase release) and the release of extracellular DNA (neutrophil extracellular trap (NET) formation: NETosis), which were measured using chemiluminescence, spectrophotometric and microscopic procedures, respectively. Platelet reactivity was measured according to the magnitude of upregulated expression of the adhesion molecule CD62P on activated cells using a flow cytometric procedure.

Results

Exposure of neutrophils to either ECEs or CSE caused a significant inhibition of ROS generation and elastase release by N-formyl-l-methionyl-l-leucyl-l-phenylalanine (1 µM)-activated neutrophils. Pre-treatment of neutrophils with CSE also resulted in a marked attenuation of phorbol 12-myristate 13-acetate (6.25 nM)-mediated release of extracellular DNA, which was unaffected by the ECEs. Similarly, CSE, but not the ECEs, inhibited the expression of CD62P by platelets activated with ADP (100 µM).

Conclusions

These observations suggest that ECE aerosols may inhibit some of the immuno-protective activities of neutrophils such as ROS production and elastase release by activated cells, the effect of which was not enhanced by inclusion of nicotine. The inhibitory effects of CSE were significantly more pronounced than those of ECEs, especially so for suppression of NET formation and platelet activation. If operative in vivo, these harmful immunosuppressive effects of ECEs may compromise intrinsic pulmonary antimicrobial defence mechanisms, albeit less so than cigarette smoke.

A randomised, crossover, clinical study to assess nicotine pharmacokinetics and subjective effects of the BIDI® stick ENDS compared with combustible cigarettes and a comparator ENDS in adult smokers

BACKGROUND

Nicotine pharmacokinetic assessments of electronic nicotine delivery systems (ENDS) are crucial to understand their ability to provide an alternative to cigarette smoking. Subjective effects data also strongly contribute to this understanding. The BIDI® Stick is a disposable ENDS product which contains 59 mg/ml nicotine benzoate salt and various flavours.

METHODS

In this study, we assessed nicotine pharmacokinetics and subjective effects of 6 flavour variants of BIDI® Stick ENDS in adult smokers, compared to cigarettes and a comparator ENDS product. During each of eight study visits, 18 volunteer smoker subjects randomly used one of either their usual brand (UB) of cigarette, a BIDI® Stick ENDS, or a comparator ENDS (JUUL 59 mg/ml nicotine with Virginia Tobacco flavour), during both controlled (10 puffs, 30 s apart) and ad libitum (60 min) puffing sessions. Blood samples were collected at various time points and subjective effects questionnaires were administered.

RESULTS

Mean [SD] plasma nicotine Cmax 0-120 was not significantly different between BIDI® Stick ENDS with any flavour (range 15.3 [9.90] ng/ml for BIDI® Stick Winter to 17.6 [9.00] ng/ml for BIDI® Stick Classic) and UB cigarettes (16.2 [9.17] ng/ml). Mean [SD] AUC0-120 (range 569.7 [327.29] to 628.6 [408.99]  min*ng/ml for BIDI® Stick ENDS and 747.1 [325.48]  min*ng/ml for UB cigarettes) and median Tmax 0-120 (range 5-7 min for all BIDI® Stick ENDS and UB cigarettes) values were also not significantly different between BIDI® Stick ENDS and UB cigarettes, while subjective effects measures were also similar between BIDI® Stick ENDS and UB cigarettes. Mean [SD] plasma nicotine Cmax 0-120, AUC0-120, and median Tmax 0-120 were 6.8 [4.13] ng/ml, 243.6 [179.04] min*ng/ml, and 5 min, respectively, for JUUL ENDS. These values were significantly different compared with those for all BIDI® Stick ENDS and UB cigarettes for both Cmax 0-120 and AUC0-120 but not for Tmax 0-120.

CONCLUSIONS

BIDI® Stick ENDS delivered nicotine to users comparably to their UB combustible cigarette and higher than JUUL ENDS, and also elicited similar subjective effects such as satisfaction and relief. Thus, the BIDI® Stick ENDS may be a satisfying alternative to cigarettes among current smokers and may support their transitioning away from cigarette smoking.

TRIAL REGISTRATION

ClinicalTrials.gov (identifier number NCT05072925).

The vaping product use associated lung injury: is this a new pulmonary disease entity?

In the summer of 2019, an epidemic of e-cigarette or vaping product use associated lung injury (EVALI) broke out in the United States of America. EVALI is a lung disease that can be severe and life-threatening. It should be emphasized that EVALI is not a clinical diagnosis, but surveillance case definition. Due to the profile of users of such devices, the pathology mainly affects young adults, although cases of EVALI have been reported in almost all age groups, from teenage children to seniors. The worst prognosis is in patients over 35 years of age, with accompanying diseases. A significant number of patients declared the use of products containing tetrahydrocannabinol (THC). The most likely factor responsible for the occurrence of EVALI is vitamin E acetate, which is sometimes added to liquids necessary for the use of electronic cigarette type devices, especially those liquids that contain THC. Nevertheless, it is possible that other substances used in liquids may also be a causative factor. Typical for EVALI are respiratory, gastrointestinal and systemic symptoms, while in imaging tests, a characteristic feature of EVALI is the presence of opacities on the chest radiogram and ground-glass clouds on computed tomography scans. In the course of this disease, respiratory failure often occurs (58%). In the vast majority of cases oxygen substitution is necessary. Currently, the best treatment of EVALI is considered to be the administration of systemic glucocorticosteroids. Over 90% of patients with EVALI required hospitalization, while the mortality rate was about 2.42%. Median age of the fatalities was 51 years. The aim of this review is to summarise the available information on EVALI and to consider possible causative factors and pathomechanism.

E-Cigarette or Vaping Product Use-Associated Lung Injury (EVALI) in an Active Duty Service Member

E-cigarette or vaping product use-associated lung injury (EVALI) is a developing serious pulmonary disease associated with the increasing use of vaping products in both civilian and active duty populations. This case study describes an active duty trainee using unbranded vaping products who developed acute respiratory distress syndrome necessitating intubation and multiday intensive care unit hospitalization. Diffuse ground glass opacities in imaging, lipid-laden macrophages found on bronchoalveolar lavage, negative infectious disease workup, and recent vaping indicate EVALI. This case demonstrates more work needs to be done within the Armed Forces to reduce use of vaping products given the danger of EVALI.

Electronic cigarette liquid substances propylene glycol and vegetable glycerin induce an inflammatory response in gingival epithelial cells

Information on the effects of propylene glycol (PG) and vegetable glycerin (VG) and on cytotoxicity and subsequent activation of the biological mediators is limited in periodontal diseases. This study analyzes the effect of unflavored PG/VG alone or in combination with nicotine on gingival epithelial cells. The cells were exposed to different PG/VG (± nicotine) concentrations for 24 h and cytotoxicity was evaluated by calorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromid assay. The expressions of interleukin (IL)-6, IL-8, and matrix metalloproteinases (MMPs)-9 were measured using an enzyme-linked immunosorbent assay and a western blotting. Stimulation with PG/VG mixtures reduced cell viability compared to nonexposed controls (p < 0.05). Adding PG/VG increased the levels of IL-6, IL-8, and MMP-9, and the amount of PG had more biological impact compared to the VG amount. The nicotine augmented this effect compared to its nicotine-free counterparts. In western blotting result, MMP-9 was clearly activated in almost all samples. These findings suggest that the main constituents PG/VG are cytotoxic and able to induce biological response in gingival cells in vitro. Despite being advertised as less harmful than conventional cigarettes, electronic cigarette liquid pose certain risks on periodontal cells. Awareness about the effects of electronic cigarettes on periodontal diseases must be increased.

Impact of tobacco control interventions on smoking initiation, cessation, and prevalence: a systematic review

This article investigates the effects of tobacco control policies on smoking initiation, cessation and prevalence by examining the papers published in the last 5 years. Twenty-one articles have been selected by two authors and sorted by four types of tobacco control: tobacco prices, anti-smoking campaigns for young people, mass media intervention and public smoking bans. Price/tax increase has deterrent effect on smoking initiation but does not promote smoking cessation; intervention on young people could reduce the smoking initiation if carried out at an early age and if acted on social skills and with peer-led approach, as opposed to restraining measures which hare generally easily circumvented by young people. The mass media campaigns showed positive effect on attempts to quit among smokers if carried forward over time and by involving multiple communication channels (TV, internet, radio). The bans in public have little effect on smoking cessation but could improve the overall well-being of non-smokers. Heterogeneous results have been described by different studies probably because of different research methodologies, cultural aspects and the really effective implementation of the rules for each country. In conclusion, comprehensive tobacco control interventions to reduce smoking prevalence and modify the smoking behavior are recommended. Moreover, the use of e-cigarettes and heat-not-burn (HnB) products, as possible helping tool for smoke cessation, currently remains controversial.

Vaping Cardiovascular Health Risks: an Updated Umbrella Review

Purpose of Review

Modified risk products (MRP) such as electronic vaping cigarettes (EVC) and heat-not-burn cigarettes (HNBC) are alternatives to traditional combustion cigarettes (TCC) with an expanding consumer base. Yet, their cardiovascular health risks are still unclear. We aimed to summarize the evidence base on this topic by conducting an updated umbrella review.

Recent Findings

We identified 7 systematic reviews, totaling 183 studies and reports, ranging from in vitro and in animal studies to clinical studies in apparently healthy volunteers and patients at risk of cardiovascular disease. Overall, acute EVC use was associated with several toxic effects at molecular, cellular, tissue, organ, and system level. In addition, EVC impacted adversely on blood pressure (BP) management, caused tachycardia, and worsened arterial stiffness. Finally, EVC use was associated with an increased risk of adverse clinical events, including atrial fibrillation and myocardial infarction, even if the causal link is still debated. Most reviews highlighted that the detrimental impact of EVC was of lesser magnitude of that of TCC. In addition, the differential impact of liquids and nicotine was not clearly disentangled. Finally, no review included studies on HNBC.

Summary

The present umbrella review suggests that EVC, and likely HNBC, despite clearly causing an increase in overall cardiovascular risk, may represent a temporary lesser evil than TCC in a risk-reduction or risk-modification strategy, aiming for eventual abstinence from all tobacco or nicotine products.