Current Perspectives on Characteristics, Compositions, and Toxicological Effects of E-Cigarettes Containing Tobacco and Menthol/Mint Flavors

e-Cigarette Tobacco Flavors, Public Health, and Toxicity: Narrative Review

BACKGROUND

Recently, the US Food and Drug Administration implemented enforcement priorities against all flavored, cartridge-based e-cigarettes other than menthol and tobacco flavors. This ban undermined the products' appeal to vapers, so e-cigarette manufacturers added flavorants of other attractive flavors into tobacco-flavored e-cigarettes and reestablished appeal.

OBJECTIVE

This review aims to analyze the impact of the addition of other flavorants in tobacco-flavored e-cigarettes on both human and public health issues and to propose further research as well as potential interventions.

METHODS

Searches for relevant literature published between 2018 and 2023 were performed. Cited articles about the toxicity of e-cigarette chemicals included those published before 2018, and governmental websites and documents were also included for crucial information.

RESULTS

Both the sales of e-cigarettes and posts on social media suggested that the manufacturers' strategy was successful. The reestablished appeal causes not only a public health issue but also threats to the health of individual vapers. Research has shown an increase in toxicity associated with the flavorants commonly used in flavored e-cigarettes, which are likely added to tobacco-flavored e-cigarettes based on tobacco-derived and synthetic tobacco-free nicotine, and these other flavors are associated with higher clinical symptoms not often induced solely by natural, traditional tobacco flavors.

CONCLUSIONS

The additional health risks posed by the flavorants are pronounced even without considering the toxicological interactions of the different tobacco flavorants, and more research should be done to understand the health risks thoroughly and to take proper actions accordingly for the regulation of these emerging products.

Vaping: Public Health, Social Media, and Toxicity

This viewpoint aims to provide a comprehensive understanding of vaping from various perspectives that contribute to the invention, development, spread, and consequences of e-cigarette products and vaping. Our analysis showed that the specific characteristics of e-cigarette products as well as marketing strategies, especially social media marketing, fostered the spread of vaping and the subsequent effects on human health and toxicity. We analyzed the components of e-cigarette devices and e-liquids, including the latest variants whose impacts were often overlooked. The different forms of nicotine, including salts and freebase nicotine, tobacco-derived nicotine, tobacco-free nicotine, and cooling agents (WS3 and WS23), have brought more choices for vapers along with more ways for e-cigarette manufacturers to advertise false understandings and present a greater threat to vapers' health. Our work emphasized the products of brands that have gained significant influence recently, which are contributing to severe public health issues. On the other hand, we also discussed in detail the toxicity of e-liquid components and proposed a toxicity mechanism. We also noticed that nicotine and other chemicals in e-liquids promote each other's negative effects through the oxidative stress and inflammatory nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway, a mechanism leading to pulmonary symptoms and addiction. The impact of government regulations on the products themselves, including flavor bans or regulations, has been limited. Therefore, we proposed further interventions or harm reduction strategies from a public health perspective.

Increased oxidative stress responses in murine macrophages exposed at the air-liquid interface to third- and fourth-generation electronic nicotine delivery system (ENDS) aerosols

Background

New fourth generation electronic nicotine delivery system (ENDS) devices contain high levels of nicotine salt (up to 60 mg/mL), whose cellular and molecular effects on immune cells are currently unknown. Here, we used a physiologically-relevant in vitro air-liquid interface (ALI) exposure model to assess the toxicity of distinct ENDS, a 3rd-generation electronic-cigarette (e-cig) and two 4th-generation ENDS devices (JUUL and Posh Plus).

Methods

Murine macrophages (RAW 264.7) were exposed at the ALI to either air, Menthol or Crème Brûlée-flavored ENDS aerosols generated from those devices for 1-hour per day for 1 or 3 consecutive days. Cellular and molecular toxicity was evaluated 24 h post-exposure.

Results

1-day of Menthol-flavored JUUL aerosol exposure significantly decreased cell viability and significantly increased lactate dehydrogenase (LDH) levels compared to air controls. Further, JUUL Menthol elicited significantly increased reactive oxygen species (ROS) and nitric oxide (NO) production compared to air controls. Posh Crème Brûlée-flavored aerosols displayed significant cytotoxicity - decreased cell viability and increased LDH levels -after 1- and 3-day exposures, while the Crème Brûlée-flavored aerosol produced by the 3rd-generation e-cig device only displayed significant cytotoxicity after 3 days compared to air controls. Further, both Posh and third-generation e-cig Crème Brûlée flavored-aerosols elicited significantly increased ROS plus high levels of 8-isoprostane after 1 and 3 days compared to air controls, indicating increased oxidative stress. Posh and third-generation e-cig Crème Brûlée flavored-aerosols elicited reduction in NO levels after one day, but elicited increase in NO after 3 days. Genes in common dysregulated by both devices after 1 day included α7nAChR, Cyp1a1, Ahr, Mmp12, and iNos.

Conclusion

Our results suggest that ENDS Menthol and Crème Brûlée-flavored aerosol exposures from both 3rd- and 4th-generation ENDS devices are cytotoxic to macrophages and cause oxidative stress. This can translate into macrophage dysfunction. Although 4th-generation disposable ENDS devices have no adjustable operational settings and are considered low-powered ENDS devices, their aerosols can induce cellular toxicity compared to air-exposed control cells. This study provides scientific evidence for regulation of nicotine salt-based disposable ENDS products.

Ice flavours and non-menthol synthetic cooling agents in e-cigarette products: a review

E-cigarettes with cooling flavours have diversified in ways that complicate tobacco control with the emergence of: (1) Ice-hybrid flavours (eg, 'Raspberry Ice') that combine cooling and fruity/sweet properties; and (2) Products containing non-menthol synthetic cooling agents (eg, Wilkinson Sword (WS), WS-3, WS-23 (termed 'koolada')). This paper reviews the background, chemistry, toxicology, marketing, user perceptions, use prevalence and policy implications of e-cigarette products with ice-hybrid flavours or non-menthol coolants. Scientific literature search supplemented with industry-generated and user-generated information found: (a) The tobacco industry has developed products containing synthetic coolants since 1974, (b) WS-3 and WS-23 are detected in mass-manufactured e-cigarettes (eg, PuffBar); (c) While safe for limited oral ingestion, inhalational toxicology and health effects from daily synthetic coolant exposure are unknown and merit scientific inquiry and attention from regulatory agencies; (d) Ice-hybrid flavours are marketed with themes incorporating fruitiness and/or coolness (eg, snow-covered raspberries); (e) WS-23/WS-3 concentrates also are sold as do-it-yourself additives, (f) Pharmacology research and user-generated and industry-generated information provide a premise to hypothesise that e-cigarette products with ice flavours or non-menthol cooling agents generate pleasant cooling sensations that mask nicotine's harshness while lacking certain aversive features of menthol-only products, (g) Adolescent and young adult use of e-cigarettes with ice-hybrid or other cooling flavours may be common and cross-sectionally associated with more frequent vaping and nicotine dependence in convenience samples. Evidence gaps in the epidemiology, toxicology, health effects and smoking cessation-promoting potential of using these products exist. E-cigarettes with ice flavours or synthetic coolants merit scientific and regulatory attention.

Preliminary study on the E-liquid and aerosol on the neurobehavior of C. elegans

E-cigarettes, also known as electronic nicotine delivery systems (ENDS), are mainly used among adolescents and young adults. Similar to traditional cigarettes, different concentrations of nicotine are also added to E-cigarette's liquid (E-liquid), but due to the supplementation of chemicals such as propylene glycol (PG), vegetable glycerin (VG) and flavors, it is difficult to determine the risk after using E-cigarettes. And given to the specificity of the aerosol particle composition and atomization process of E-cigarettes, it is necessary to assess the neurotoxic effects of long-term E-cigarettes use. In this study, two commercial nicotine-containing (5%) and nicotine-free E-liquids were diluted to investigate the neurobehavioral changes and addictive tendencies of developing C. elegans after sub-chronic exposure to E-liquid. The results showed that sub-chronic exposure of E-liquid could lead to impaired growth and development of nematodes, abnormal general neuromotor behavior and advanced learning and memory behavior, and nicotine-containing E-liquid could also lead to increased addiction tendency of nematodes. Although the damage effect of nicotine free E-liquid is smaller than that of the nicotine-containing group, its toxic effect cannot be ignored. Further analysis of the neurotoxicity mechanism found that redox imbalance-mediated mitochondrial stress and aging may be important causes of E-liquid-induced biological damage. The biosafety of e-cigarette aerosols was also included in the assessment. The study found that the heated atomization process did not alter the E-liquid components, and E-cigarette aerosols still have the effect of interfering with the growth and development of nematodes and neurobehavior, and its addictive nature is also of concern. This study can provide new ideas for future studies on the neurotoxic effects and safety assessment of the E-cigarettes, and provide theoretical reference for the study on the injury mechanism of E-cigarettes.

Detection of the Synthetic Coolant Menthone 1,2-Glycerol Ketal in an e-Liquid and in Electronic Waterpipe Aerosols Therefrom

The presence and toxicological risks of synthetic coolants in electronic nicotine delivery systems (ENDS) have not been thoroughly studied. We identified the synthetic coolant menthone 1,2-glycerol ketal (MGK) in a menthol-flavored e-liquid at a concentration of ∼170 μg/mL. We also detected MGK in aerosols resulting from heating the e-liquid with an electronic waterpipe. MGK was initially detected in the e-liquid by two-dimensional gas chromatography-time-of-flight mass spectrometry. To avoid potential analytical artifacts that could result from heating samples in the injection port of the gas chromatograph, quantitation of MGK in the e-liquid was accomplished using a liquid chromatography-tandem mass spectrometry method. Following recent reports identifying other synthetic coolants in e-liquids, these results add knowledge about inhalation exposures from ENDS use and suggest the importance of future research to study the potential inhalation toxicity related to the use of MGK-containing e-liquids in ENDS devices. Furthermore, the results demonstrate the ability to quantify ketals in e-liquids using liquid chromatography methods.

Interplay between proteasome function and inflammatory responses in e-cig vapor condensate-challenged lung epithelial cells

Exposure to cigarettes and other nicotine-based products results in persistent inflammation in the lung. In recent years, electronic cigarettes (e-cigs) have become extremely popular among adults and youth alike. E-cigarette vapor-induced oxidative stress promotes protein breakdown, DNA damage and cell death, culminating in a variety of respiratory diseases. The proteasome, a multi-catalytic protease, superintends protein degradation within the cell. When cells are stimulated with inflammatory cytokines such as IFN-γ and TNF-α, the constitutive catalytic proteasome subunits are replaced by the inducible subunits-low-molecular mass polypeptide (LMP)2 (β1i), multi-catalytic endopeptidase complex-like (MECL)1 (β2i), and LMP7 (β5i), which are required for the production of certain MHC class I-restricted T-cell epitopes. In this study, we used human alveolar epithelial cells (A549) and exposed them to filtered air or (1%) tobacco-flavored (TF) electronic cigarette vapor condensate (ECVC) ± nicotine (6 mg/ml) (TF-ECVC ± N) for 24 h. We observed an increase in the levels of IFN-γ, TNF-α, and inducible proteasome subunits (LMP7/PSMB8, LMP2/PSMB9, MECL1/PSMB10), and a reduced expression of constitutive proteasome subunits (β1/PSMB6 and β2/PSMB7) in challenged A549 cells. Interestingly, knockdown of the inducible proteasome subunit LMP7 reversed ECVC-induced expression of NADPH oxidase and immunoproteasome subunits in A549 cells. In addition, pre-exposure to an LMP7 inhibitor (ONX-0914) abrogated the mRNA expression of several NOX subunits and rescued the excessive production/release of inflammatory cytokines/chemokines (IL-6, IL-8, CCL2, and CCL5) in ECVC-challenged cells. Our findings suggest an important role of LMP7 in regulating the expression of inflammatory mediators during ECVC exposure. Overall, our results provide evidence for proteasome-dependent ROS-mediated inflammation in ECVC-challenged cells.

The AGE-RAGE Axis and the Pathophysiology of Multimorbidity in COPD

Chronic obstructive pulmonary disease (COPD) is a disease of the airways and lungs due to an enhanced inflammatory response, commonly caused by cigarette smoking. Patients with COPD are often multimorbid, as they commonly suffer from multiple chronic (inflammatory) conditions. This intensifies the burden of individual diseases, negatively affects quality of life, and complicates disease management. COPD and comorbidities share genetic and lifestyle-related risk factors and pathobiological mechanisms, including chronic inflammation and oxidative stress. The receptor for advanced glycation end products (RAGE) is an important driver of chronic inflammation. Advanced glycation end products (AGEs) are RAGE ligands that accumulate due to aging, inflammation, oxidative stress, and carbohydrate metabolism. AGEs cause further inflammation and oxidative stress through RAGE, but also through RAGE-independent mechanisms. This review describes the complexity of RAGE signaling and the causes of AGE accumulation, followed by a comprehensive overview of alterations reported on AGEs and RAGE in COPD and in important co-morbidities. Furthermore, it describes the mechanisms by which AGEs and RAGE contribute to the pathophysiology of individual disease conditions and how they execute crosstalk between organ systems. A section on therapeutic strategies that target AGEs and RAGE and could alleviate patients from multimorbid conditions using single therapeutics concludes this review.

Recent, national trends in US adolescent use of menthol and non-menthol cigarettes

OBJECTIVE

In light of the current U.S. Food and Drug Administration (FDA) proposal to ban menthol cigarettes, this study updates trends in menthol cigarette use among adolescents age 13-18 years up to the year 2020. The study considers a potential role for the ban to reduce black/non-black disparities in menthol cigarette use, as well as a counterargument that a ban is not necessary because menthol use is already diminishing.

METHODS

Data are from annual, cross-sectional, nationally representative Monitoring the Future (MTF) surveys of 85 547 8th, 10th and 12th grade students surveyed between 2012 and 2020. Analyses include trends in past 30-day menthol and non-menthol cigarette smoking among the total adolescent population, as well as stratified by race/ethnicity.

RESULTS

Declines in adolescent menthol and non-menthol cigarette smoking continued through 2020 so that in 2018-2020 past 30-day prevalence for each was less than 1% for non-Hispanic black adolescents and less than 2.2% for non-black adolescents. For non-Hispanic black adolescents no smoking declines in mentholated or non-mentholated cigarette use from 2015-2017 to 2018-2020 were statistically significant, in part because prevalence levels approached a floor effect and had little room to fall further. Menthol levels were lower for non-Hispanic black versus all other adolescents in all study years.

CONCLUSIONS

Continuing declines in adolescent menthol prevalence indicate that both menthol prevalence and also black/non-black disparities in its use are steadily decreasing. However, these decreases in adolescence will take decades to reach later ages through generational replacement. Efforts to accelerate menthol decreases will require new initiatives to increase cessation among adult menthol users.

Pod-based e-cigarette use among US college-aged adults: A survey on the perception of health effects, sociodemographic correlates, and interplay with other tobacco products

INTRODUCTION

E-cigarette use among youth and young adults remains of public health concern. Pod-based e-cigarettes, including JUUL, significantly changed the e-cigarette landscape in the US. Using an online survey, we explored the socio-behavioral correlates, predisposing factors, and addictive behaviors, among young adult pod-mod users within a University in Maryland, USA.

METHODS

In total, 112 eligible college students aged 18-24 years, recruited from a University in Maryland, who reported using pod-mods were included in this study. Participants were categorized into current/non-current users based on past-30-day use. Descriptive statistics were used to analyze participants' responses.

RESULTS

The mean age of the survey participants was 20.5 ± 1.2 years, 56.3% were female, 48.2% White, and 40.2% reported past-30-day (current) use of pod-mods. The mean age of first experimentation with pod-mods was 17.8 ± 1.4 years, while the mean age of regular use was 18.5 ± 1.4 years, with the majority (67.9%) citing social influence as the reason for initiation. Of the current users, 62.2% owned their own devices, and 82.2% predominantly used JUUL and menthol flavor (37.8%). A significant proportion of current users (73.3%) reported buying pods in person, 45.5% of whom were aged <21 years. Among all participants, 67% had had a past serious quit attempt. Among them, 89.3% neither used nicotine replacement therapy nor prescription medications. Finally, current use (adjusted odds ratio, AOR=4.52; 95% CI: 1.76-11.64), JUUL use (AOR=2.56; 95% CI: 1.08-6.03), and menthol flavor (AOR=6.52; 95% CI: 1.38-30.89) were associated with reduced nicotine autonomy, a measure of addiction.

CONCLUSIONS

Our findings provide specific data to inform the development of public health interventions targeted at college youth, including the need for more robust cessation support for pod-mod users.

Neuromodulatory and neurotoxic effects of e-cigarette vapor using a realistic exposure method

The most direct effects of inhaled harmful constituents are the effects on the airways. However, inhaled compounds can be rapidly absorbed and subsequently result in systemic effects. For example, e-cigarette vapor has been shown to evoke local effects in the lung, although little is known about subsequent effects in secondary target organs such as the brain. Traditionally, such effects are tested using in vivo models. As an alternative, we have combined two in vitro systems, which are Air-Liquid-Interface (ALI) cultured alveolar cells (A549) and rat primary cortical cultures grown on multi-well microelectrode arrays. This allows us to assess the neurological effects of inhaled compounds. We have used exposure to e-cigarette vapor, containing nicotine, menthol, or vanillin to test the model. Our results show that ALI cultured A549 cells respond to the exposure with the production of cytokines (IL8 and GROalpha). Furthermore, nicotine, menthol, and vanillin were found on the basolateral side of the cell culture, which indicates their translocation. Upon transfer of the basolateral medium to the primary cortical culture, exposure-related changes in spontaneous electrical activity were observed correlating with the presence of e-liquid components in the medium. These clear neuromodulatory effects demonstrate the feasibility of combining continuous exposure of ALI cultured cells with subsequent exposure of neuronal cells to assess neurotoxicity. Although further optimization steps are needed, such a combination of methods is important to assess the neurotoxic effects of inhaled compounds realistically. As such, an approach like this could play a role in future mechanism-based risk assessment strategies.

Cold stimuli, hot topic: An updated review on the biological activity of menthol in relation to inflammation

Background

Rising incidence of inflammation-related diseases is an increasing concern nowadays. However, while menthol is a wildly-used and efficacious complementary medicine, its pharmacological mechanism still remains uncertain. Superimposed upon that, the aim of this review is to summarize the contemporary evidence of menthol’s anti-inflammatory activity.

Methods

Using the pharmacopeias and electronic databases, including Web of Science, PubMed, and CNKI, this study analyzed the relevant research articles and review articles from 2002 to 2022 and concluded those results and conjectures to finish this article.

Results

The decrease in pro-inflammatory cytokines and related inflammatory markers, as well as associated pathway activation, was found to play the greatest role in the protective effects of menthol against inflammatory damage or association with protection against chronic inflammation.

Conclusion

This review mainly concludes the progress in menthol’s anti-inflammatory activity. Further studies are needed to establish relationships between the mechanisms of action and to clarify the clinical relevance of any anti-inflammatory effects.

E-cigarette synthetic cooling agent WS-23 and nicotine aerosols differentially modulate airway epithelial cell responses

Electronic cigarette (e-cig) aerosol exposures are strongly associated with pulmonary dysfunctions, and the airway epithelial cells (AECs) of respiratory passages play a pivotal role in understanding this association. However, not much is known about the effect of synthetic cooling agents such as WS-23 on AECs. WS-23 is a synthetic menthol-like cooling agent widely used to enhance the appeal of e-cigs and to suppress the harshness and bitterness of other e-cig constituents. Using primary human AECs, we compared the effects of aerosolized WS-23 with propylene glycol/vegetable glycerin (PG/VG) vehicle control and nicotine aerosol exposures. AECs treated with 3 % WS-23 aerosols showed a significant increase in viable cell numbers compared to PG/VG-vehicle aerosol exposed cells and cell growth was comparable following 2.5 % nicotine aerosol exposure. AEC inflammatory factors, IL-6 and ICAM-1 levels were significantly suppressed by WS-23 aerosols compared to PG/VG-controls. When differentiated AECs were challenged with WS-23 aerosols, there was a significant increase in secretory mucin MUC5AC expression with no discernible change in airway inflammatory SCGB1A1 expression. Compared to PG/VG-controls, WS-23 or nicotine aerosols presented with increased MUC5AC expression, but there was no synergistic effect of WS-23 + nicotine combination exposure. Thus, WS-23 and nicotine aerosols modulate the AEC responses and induce goblet cell hyperplasia, which could impact the airway physiology and susceptibility to respiratory diseases.

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.

E-Cigarettes Reexamined: Product Toxicity

The introduction of e-cigarettes, or electronic nicotine delivery systems (ENDS), has been accompanied by controversy regarding their safety and effectiveness as a cessation aid and by an explosion in their use by youth. Their use does not involve the combustion of tobacco and the creation of harmful combustion products; they have been seen as a "harm reduction" tool that may be of assistance in promoting smoking cessation. Recognition that ENDS can deliver an array of chemicals and materials with known adverse consequences has spurred more careful examination of these products. Nicotine, nitrosamines, carbonyl compounds, heavy metals, free radicals, reactive oxygen species, particulate matter, and "emerging chemicals of concern" are among the constituents of the heated chemical aerosol that is inhaled when ENDS are used. They raise concerns for cardiovascular and respiratory health that merit the attention of clinicians and regulatory agencies. Frequently cited concerns include evidence of disordered respiratory function, altered hemodynamics, endothelial dysfunction, vascular reactivity, and enhanced thrombogenesis. The absence of evidence of the consequences of their long-term use is of additional concern. Their effectiveness as cessation aids and beneficial impact on health outcomes continue to be examined. It is important to ensure that their production and availability are thoughtfully regulated to optimise their safety and permit their use as harm reduction devices and potentially as smoking-cessation aids. It is equally vital to effectively prevent them from becoming ubiquitous consumer products with the potential to rapidly induce nicotine addiction among large numbers of youth. Clinicians should understand the nature of these products and the implications of their use.

Menthol Flavor in E-Cigarette Vapor Modulates Social Behavior Correlated With Central and Peripheral Changes of Immunometabolic Signalings

The use of electronic cigarette (e-cigarette) has been increasing dramatically worldwide. More than 8,000 flavors of e-cigarettes are currently marketed and menthol is one of the most popular flavor additives in the electronic nicotine delivery systems (ENDS). There is a controversy over the roles of e-cigarettes in social behavior, and little is known about the potential impacts of flavorings in the ENDS. In our study, we aimed to investigate the effects of menthol flavor in ENDS on the social behavior of long-term vapor-exposed mice with a daily intake limit, and the underlying immunometabolic changes in the central and peripheral systems. We found that the addition of menthol flavor in nicotine vapor enhanced the social activity compared with the nicotine alone. The dramatically reduced activation of cellular energy measured by adenosine 5′ monophosphate-activated protein kinase (AMPK) signaling in the hippocampus were observed after the chronic exposure of menthol-flavored ENDS. Multiple sera cytokines including C5, TIMP-1, and CXCL13 were decreased accordingly as per their peripheral immunometabolic responses to menthol flavor in the nicotine vapor. The serum level of C5 was positively correlated with the alteration activity of the AMPK-ERK signaling in the hippocampus. Our current findings provide evidence for the enhancement of menthol flavor in ENDS on social functioning, which is correlated with the central and peripheral immunometabolic disruptions; this raises the vigilance of the cautious addition of various flavorings in e-cigarettes and the urgency of further investigations on the complex interplay and health effects of flavoring additives with nicotine in e-cigarettes.

Non-Invasive Systemic Biomarker of E-cigarette or Vaping use-Associated Lung Injury (EVALI): A pilot study

Background

Electronic cigarette (e-cigarette) vaping, containing nicotine and/or Δ⁸, Δ⁹ or Δ¹⁰ or Δ^o tetrahydrocannabinol (Δⁿ-THC), is associated with an outbreak of e-cigarette, or vaping, product use-associated lung injury (EVALI). Despite thousands being hospitalised with EVALI, much remains unknown about diagnosis, treatment and disease pathogenesis. Biomarkers of inflammation, oxidative stress and lipid mediators may help identify e-cigarette users with EVALI.

Methods

We collected plasma and urine along with demographic and vaping-related data of EVALI subjects (age 18–35 years) and non-users matched for sex and age in a pilot study. Biomarkers were assessed by ELISA/EIA and Luminex-based assays.

Results

Elevated levels of THC metabolite (11-nor-9-carboxy-Δ⁹-THC) were found in plasma from EVALI subjects compared to non-users. Levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG), an oxidative DNA damage biomarker, and 8-isoprostane, an oxidative stress marker, were slightly increased in urine samples from EVALI subjects compared to non-users. Conversely, plasma levels of lipid mediators, including resolvin D₁ (RvD₁) and prostaglandin E₂ (PGE₂), were significantly lower in EVALI subjects compared to non-users. Both pro-inflammatory biomarkers, such as tumour necrosis factor-α, macrophage inflammatory protein-1β, RANTES (regulated on activation, normal T-cell expressed and secreted) and granulocyte–macrophage colony-stimulating factor, as well as anti-inflammatory biomarkers, such as interleukin-9 and CC10/16, were decreased in plasma from EVALI subjects compared to non-users, supportive of a possible dysregulated inflammatory response in EVALI subjects.

Conclusions

Significant elevations in urine and plasma biomarkers of oxidative stress, as well as reductions in lipid mediators, were shown in EVALI subjects. These noninvasive biomarkers (8-OHdG, 8-isoprostane, RvD₁ and CC10/16), either individually or collectively, may serve as tools in diagnosing future EVALI subjects.

Biomarkers 8-OHdG, 8-isoprostane, RvD₁ and CC10/16 are associated with electronic cigarettes and vapinghttps://bit.ly/3tJJV71

Association of preferred flavorings and device type with box or pack purchase behavior of electronic nicotine delivery systems in the United States

This study examined the associations of preferred flavorings and device type of ENDS with box or pack purchase behavior. We analyzed current adult ENDS users in the United States who reported purchase of their own ENDS. Logistic regression revealed an increased likelihood of box/pack purchase behavior among users of menthol or mint-flavored ENDS, disposable, pod-based devices, and those who purchase ENDS from the Internet. A moderation analysis showed that the magnitude of the association between menthol or mint-flavored ENDS use and box/pack purchase was stronger among disposable and pod-based device users compared to tank or mods (customizable devices) users. In a subsequent stratified analysis menthol or mint flavor users were more likely than non-flavor users to engage in box/pack purchase among disposable and pod-based device users, but not among tank or mods users. Regulating flavors and maximum unit sale quantities of ENDS by device could thwart ENDS box/pack purchase behavior.

Comparative Reactive Oxygen Species (ROS) Content among Various Flavored Disposable Vape Bars, including Cool (Iced) Flavored Bars

Studies have shown that aerosols generated from flavored e-cigarettes contain Reactive Oxygen Species (ROS), promoting oxidative stress-induced damage within pulmonary cells. Our lab investigated the ROS content of e-cigarette vapor generated from disposable flavored e-cigarettes (vape bars) with and without nicotine. Specifically, we analyzed vape bars belonging to multiple flavor categories (Tobacco, Minty Fruit, Fruity, Minty/Cool (Iced), Desserts, and Drinks/Beverages) manufactured by various vendors and of different nicotine concentrations (0-6.8%). Aerosols from these vape bars were generated via a single puff aerosol generator; these aerosols were then individually bubbled through a fluorogenic solution to semi-quantify ROS generated by these bars in H2O2 equivalents. We compared the ROS levels generated by each vape bar as an indirect determinant of their potential to induce oxidative stress. Our results showed that ROS concentration (μM) within aerosols produced from these vape bars varied significantly among different flavored vape bars and identically flavored vape bars with varying nicotine concentrations. Furthermore, our results suggest that flavoring chemicals and nicotine play a differential role in generating ROS production in vape bar aerosols. Our study provides insight into the differential health effects of flavored vape bars, in particular cool (iced) flavors, and the need for their regulation.

Electronic cigarette aerosol increases the risk of organ dysfunction by enhancing oxidative stress and inflammation

An electronic cigarette is a rechargeable device that produces an inhaled aerosol containing varying levels of nicotine, and inorganic and organic toxicants and carcinogenic compounds. The aerosol is generated by heating a solution of propylene glycol and glycerin with nicotine and flavoring ingredients at a high temperature. The e-cigarette was developed and marketed as a safer alternative to the regular cigarette which is known to be injurious to human health. However, published studies suggest that the aerosol of e-cigarette can also have adverse health effects. The main objective of this review is to briefly describe some consequences of e-cigarette smoking, and to present data showing that the resulting increased oxidative stress and inflammation are likely to be involved in effecting to lung damage. Other organs are also likely to be affected. The aerosol contains varying amounts of organic and inorganic toxicants as well as carcinogens, which might serve as the source of such deleterious events. In addition, the aerosol also contains nicotine, which is known to be addictive. E-cigarette smoking releases these toxicants into the air leading to inhalation by nonsmokers in residential or work place areas. Unlike regular tobacco smoke, the long-term consequences of direct and secondhand exposure to e-cigarette aerosol have not been extensively studied but based on available data, e-cigarette aerosol should be considered harmful to human health.

Smoking and Methotrexate Inefficacy in Rheumatoid Arthritis: What About Underlying Molecular Mechanisms?

The study by Safy-Khan, et al in the current issue of The Journal of Rheumatology ¹ reports that in a methotrexate (MTX)-based treatment regimen for patients with early arthritis, current smoking was significantly associated with a smaller reduction of Disease Activity Score in 28 joints (DAS28) over time compared to noncurrent smoking. This negative effect of current smoking on DAS28 was dose-dependent: patients who smoked 10-19 cigarettes per day did worse than patients who smoked 1-9 cigarettes per day.

Perspectives on Epigenetics Alterations Associated with Smoking and Vaping

Epigenetic alterations, including DNA methylation, microRNA, and long noncoding RNA, play important roles in the pathogenesis of numerous respiratory health conditions and diseases. Exposure to tobacco smoking has been found to be associated with epigenetic changes in the respiratory tract. Marketed as a less harmful alternative to combustible cigarettes, electronic cigarette (e-cigarette) has rapidly gained popularity in recent years, especially among youth and young adults. Accumulative evidence from both animal and human studies has shown that e-cigarette use (vaping) is also linked to similar respiratory health conditions as observed with cigarette smoking, including wheezing, asthma, and COPD. This review aims to provide an overview of current studies on associations of smoking and vaping with epigenetic alterations in respiratory cells and provide future research directions in epigenetic studies related to vaping.