Modulation of "Protective" Nicotine Perception and Use Profile by Flavorants: Preliminary Findings in E-cigarettes

Effects of Nicotine Content and Preferred Flavor on Subjective Responses to E-cigarettes: A Randomized, Placebo-controlled Laboratory Study

INTRODUCTION

Evidence suggests that e-liquid flavor and nicotine concentration are important factors in the initiation and maintenance of e-cigarette use (vaping). Flavors may increase the initiation and maintenance of vaping, and nicotine content is a factor in e-cigarette dependence and the efficacy of e-cigarettes for cigarette smoking cessation. Few human laboratory studies have assessed the joint and interactive effects of flavor and nicotine on subjective responses to e-cigarettes.

METHODS

Regular e-cigarette users (N = 89) completed a multi-session study involving a paced vaping procedure with e-liquid cartridges containing their preferred flavor (berry, menthol, or tobacco) or no flavor, with or without nicotine (18 mg). Subjective effects of vaping (satisfaction, reward, aversion, airway sensations, and craving relief) were assessed.

RESULTS

Nicotine significantly increased psychological reward and craving relief, whereas flavor significantly increased vaping satisfaction and taste. Nicotine dependence severity moderated the effect of nicotine on reward, such that those with the greatest dependence severity reported the greatest reward.

CONCLUSIONS

These findings support differential and noninteractive effects of e-liquid nicotine content and flavor on reinforcing effects of e-cigarettes.

IMPLICATIONS

E-liquid flavor and nicotine content have independent, non-interactive effects on subjective responses to vaping under controlled laboratory conditions. Among regular e-cigarette users, vaping a preferred flavor increased taste and satisfaction, but did not interact with nicotine to alter reward or craving. Further research on the ways in which these subjective effects may motivate vaping behavior among different populations of e-cigarette users would be useful to inform regulatory policy of ENDS products.

Effects of 'Ice' flavoured e-cigarettes with synthetic cooling agent WS-23 or menthol on user-reported appeal and sensory attributes

BACKGROUND

This clinical experiment tested the effects of exposure to e-cigarettes with WS-23 or menthol cooling additives on user appeal and sensory attributes, and, secondarily, whether WS-23 effects generalised across base characterising flavour, nicotine concentration, or nicotine/tobacco product use status.

METHODS

In this within-participant double-blind experiment, adult tobacco/nicotine users administered standardised puffs of 18 different e-cigarette solutions in randomised sequences using a pod-style device. Each of three base characterising e-cigarette flavour solutions ('bold tobacco', 'mango,' 'wintergreen') in both 2% and 4% concentrations of nicotine benzoate salt were manipulated by adding either: (1) Menthol (0.5%), (2) WS-23 (0.75%) or (3) No cooling agent. After each administration, participants rated 3 appeal and 5 sensory attributes (0-100 scales).

RESULTS

Participants (n=84; M(SD)=38.6 (13.6) years old) were either exclusive e-cigarette (25.0%), cigarette (36.9%) or dual (38.1%) users. WS-23 versus no coolant products produced higher liking, willingness to use again, smoothness, and coolness and lower disliking, bitterness, and harshness ratings (|B|difference range: 4.8 to 20.1; ps<0.005). Menthol (vs no coolant) increased willingness to use again and reduced harshness and coolness (ps<0.05). Flavours with WS-23 (vs menthol) were rated as smoother, cooler and less harsh (ps<0.05). Coolant effects did not differ by base flavour, nicotine concentration, or tobacco use status.

CONCLUSIONS

Adding synthetic coolant WS-23 to e-cigarettes appears to make the vaping user experience more appealing, regardless of characterising base flavour. Regulatory agencies should be aware that the manufacturing process of adding synthetic coolants may increase the attractiveness of various e-cigarette products.Cite Now.

The interactive effects of JUUL flavor and nicotine concentration on addiction potential

Prior research suggests that flavors can influence the pharmacological effects of nicotine. We used commercially available JUUL pods to examine whether preferred menthol versus tobacco flavor increased the addictive potential of nicotine per se. This study recruited 15 regular JUUL e-cigarette users to complete a 2 × 2 factorial crossover trial using an entirely remote video format. Participants completed a sampling baseline session to identify preferred JUUL flavor (menthol vs. tobacco) followed by four counterbalanced experimental sessions separated by ≥ 48 hr: (a) low-nicotine dose (3% JUUL)/nonpreferred flavor; (b) low dose/preferred flavor; (c) high-nicotine dose (5% JUUL)/nonpreferred flavor; and (d) high dose/preferred flavor. In each experimental session, participants completed a puffing procedure followed by subjective ratings of e-cigarette liking and wanting (ELW), urges, and reinforcement using a JUUL pod purchase task. There was a dose-by-flavor interaction for average ELW (F = 4.58, p = .041) in which ELW was significantly greater for the preferred than the nonpreferred flavor at the low-nicotine dose but not the high-nicotine dose. There were also dose-by-flavor interactions for pre- to post-puffing change in overall urge to vape (F = 5.97, p = .021) and urge strength (F = 4.96, p = .049), with greater reductions in overall urge/strength for the preferred compared to the nonpreferred flavor at the low but not the high dose. We found no significant interaction effects for purchase task outcomes. Using a fully remote experimental puffing procedure, our findings suggest preferred flavors increase the rewarding effects most for lower nicotine e-cigarettes. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Characterizing different-flavored e-cigarette solutions from user-reported sensory attributes and appeal

Scientists and regulators need parsimonious methods of characterizing flavored e-cigarettes which may vary widely in both chemical flavoring constituents and marketing descriptors. This laboratory experiment characterized user-reported appeal and experience of five cross-cutting sensory attributes (sweetness, bitterness, smoothness, harshness, coolness) of 10 common e-cigarette flavors. In a within-subject double-blind single-visit protocol, current nicotine/tobacco product users (N = 119) self-administered a single puff of each e-liquid flavor via a pod-style device and rated its appeal and sensory attributes on 0-100 scales. Custom-manufactured e-liquids, nicotine concentration: M (SD) = 23.4 (0.9) mg/mL, representative of commonly marketed fruit (green apple, strawberry), dessert (dark chocolate, vanilla), mint (peppermint, spearmint), nonmint cooling (menthol, koolada), and tobacco (subtle tobacco, full-flavored tobacco) flavor descriptors were used and their constituents were independently analyzed. Results largely demonstrated that a flavor's sensory attributes concorded with its marketed flavor descriptor. Among the 10 flavors, vanilla was rated sweetest (B[difference vs. mean of 9 other flavors] = 14.44, 95% CI [10.84, 18.03]), full-flavored tobacco was most bitter, B = 8.34, 95% CI [4.73, 11.96], subtle tobacco was most harsh, B = 5.69, 95% CI [1.70, 9.68], and peppermint scored highest in both smoothness, B = 6.98, 95% CI [3.13, 10.82], and coolness, B = 29.25, 95% CI [25.50, 33.01]. Flavors with higher appeal ratings tended to be sweeter, smoother, cooler, and less bitter and harsh. Chemical analysis found numerous flavoring constituents among study products without any clear differentiation of chemicals being present in particular flavor categories, which underscores the utility of using sensory ratings to characterize different-flavored e-cigarettes over and above constituent analyses. Characterizing e-cigarette flavors by subjective sensory attributes may be useful in future research and regulatory activities. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Expanding the E-Liquid Flavor Wheel: Classification of Emerging E-Liquid Flavors in Online Vape Shops

INTRODUCTION

Electronic cigarettes are the most popular tobacco product among U.S. youth, and over 80% of current youth users of e-cigarettes use flavored e-cigarettes, with fruit, mint/menthol, and candy/sweets being the most popular flavors. A number of new e-liquid flavors are currently emerging in the online e-cigarette market. Menthol and other flavored e-cigarettes could incentivize combustible tobacco smokers to transition to e-cigarette use.

METHODS

From February to May 2021, we scraped data of over 14,000 e-liquid products, including detailed descriptions of their flavors, from five national online vape shops. Building upon the existing e-liquid flavor wheel, we expanded the semantic databases (i.e., key terms) to identify flavors using WordNet-a major database for keyword matching and group discussion. Using the enriched databases, we classified 14,000+ e-liquid products into the following 11 main flavor categories: "fruit", "dessert/candy/sweets", "coffee/tea", "alcohol", "other beverages", "tobacco", "mint/menthol", "nuts", "spices/pepper", "other flavors", and "unspecified flavor".

RESULTS

We find that the most prominent flavor sold in the five online vape shop in 2021 was fruit flavored products, followed by dessert/candy/other sweets. Online vendors often label a product with several flavor profiles, such as fruit and menthol.

CONCLUSIONS

Given that online stores market products with multiple flavor profiles and most of their products contain fruit flavor, the FDA may have issued marketing denial orders to some of these products. It is important to further examine how online stores respond to the FDA flavor restrictions (e.g., compliance or non-compliance).

Alpha5 nicotinic acetylcholine receptor mediated immune escape of lung adenocarcinoma via STAT3/Jab1-PD-L1 signalling

Background

Immunotherapy has proven to be an emerging treatment for non-small-cell lung cancer in recent years. Notably, smokers show higher programmed cell death ligand-1 (PD-L1) expression and better responses to PD-1/PD-L1 inhibitors than nonsmokers. Genome-wide association studies show that the CHRNΑ5 encoding α5-nicotinic acetylcholine receptor (α5-nAChR) is especially relevant to lung cancer and nicotine dependence. Jab1 is a key regulatory factor and promotes the stabilization of PD-L1. Our previous study reported that α5-nAChR mediates lung adenocarcinoma (LUAD) epithelial-mesenchymal transition (EMT) and metastasis via STAT3/Jab1. However, the link between α5-nAChR and PD-L1 is unclear in LUAD.

Methods

We used various bioinformatics databases to analyze the expression of related genes and their correlations. Expression and clinicopathologic significance of α5-nAChR and PD-L1 were detected by immunohistochemistry in a tissue microarray. α5-nAChR regulated LUAD cell immune escape by targeting the STAT3/Jab1-PD-L1 signalling by Western-blotting and ChIP in vitro. We used T cell coculture, flow cytometry, ELISA, CCK8 assay and crystal violet staining to detect the expression of regulatory T cell (Tregs), IFN-γ, IL-2 and the ability of T cell-mediated tumour cell killing respectively. IF assays were performed in both cancer cells and tumour xenograft paraffin sections to analyze the protein expression. The in vivo experiments in mouse model were performed to show the α5-nAChR-mediated immune escape via PD-L1 pathway.

Results

The expression of α5-nAChR was correlated with PD-L1 expression, smoking status and lower survival of LUAD in vivo. In vitro, the expression of α5-nAChR mediated phosphorylated STAT3 (pSTAT3), Jab1 and PD-L1 expression. STAT3 bound to the Jab1 or PD-L1 promoter and mediated PD-L1 expression. Jab1 stabilized PD-L1 expression in LUAD cells. Furthermore, in primary T cell cocultured system, downregulation of α5-nAChR suppressed the function of CD4⁺CD25⁺FOXP3⁺ Tregs, enhanced IFN-γ secretion, and increased T cell-mediated killing of LUAD cells. In the Jurkat T cells and LUAD cells coculture assay, inhibition of α5-nAChR increased IL-2 secretion. In tumour xenograft tissues, α5-nAChR expression was related to PD-L1, Jab1, pSTAT3, CD4 and granzyme B expression (GB).

Conclusions

Our results suggest that the novel α5-nAChR/STAT3-Jab1-PD-L1 axis is involved in LUAD immune escape, which could lead to potential therapeutic strategies for cancer immunotherapy.

The Role of Nicotine and Flavor in the Abuse Potential and Appeal of Electronic Cigarettes for Adult Current and Former Cigarette and Electronic Cigarette Users: A Systematic Review

INTRODUCTION

Many adult cigarette smokers use electronic cigarettes (e-cigarettes) to cut down on or quit smoking cigarettes. E-cigarettes with higher abuse potential and appeal might facilitate complete switching. E-liquid nicotine concentration and flavor are two of the characteristics that may affect the abuse potential and appeal of e-cigarettes. The objective of this systematic review was to compile results from survey, animal, human laboratory, and clinical studies to understand the possible effects of nicotine concentration and flavor on abuse potential and appeal of e-cigarettes in adult current and former cigarette and e-cigarette users.

AIMS AND METHODS

A comprehensive literature search was conducted in Ovid Medline and PsycINFO followed by citation tracking in Web of Science Core Collection. Peer-reviewed studies published in English between 2007 and August 2020 were selected that analyzed differences between e-liquid nicotine concentration and/or flavors, had outcome measures related to abuse potential and/or appeal, and included adult humans (18+) or animals. A total of 1624 studies were identified and screened. A qualitative synthesis of results was performed.

RESULTS

Results from 104 studies included in this review suggest that higher nicotine concentration and access to a variety of flavors are likely to be associated with higher abuse potential and appeal of e-cigarettes for adult current and former cigarette and e-cigarette users.

CONCLUSIONS

Higher nicotine concentrations and the availability of a variety of flavors in e-cigarettes might facilitate complete substitution for cigarettes. Future e-cigarette regulations should take into account their impact on smokers, for whom e-cigarettes may be a cessation tool or reduced-harm alternative.

IMPLICATIONS

E-cigarettes may provide a reduced-harm alternative to cigarettes for smokers unwilling/unable to quit or serve as a path for quitting all nicotine products. Higher nicotine concentrations and flavor variety are associated with higher abuse potential and appeal of e-cigarettes. Higher abuse potential and appeal products may help facilitate complete switching from cigarettes to e-cigarettes. Regulation of nicotine concentration and flavors aimed at decreasing naïve uptake may inadvertently decrease uptake and complete switching among smokers, reducing the harm reduction potential of e-cigarettes. Evidence-based effects of regulating nicotine concentration and flavors must be considered for the population as a whole, including smokers.

Chemosensory Contributions of E-Cigarette Additives on Nicotine Use

While rates of smoking combustible cigarettes in the United States have trended down in recent years, use of electronic cigarettes (e-cigarettes) has dramatically increased, especially among adolescents. The vast majority of e-cigarette users consume "flavored" products that contain a variety of chemosensory-rich additives, and recent literature suggests that these additives have led to the current "teen vaping epidemic." This review, covering research from both human and rodent models, provides a comprehensive overview of the sensory implications of e-cigarette additives and what is currently known about their impact on nicotine use. In doing so, we specifically address the oronasal sensory contributions of e-cigarette additives. Finally, we summarize the existing gaps in the field and highlight future directions needed to better understand the powerful influence of these additives on nicotine use.

Plasma Menthol Glucuronide as a Biomarker for the Behavioral Effects of Menthol and Nicotine in Humans

This secondary analysis sought to determine if plasma menthol glucuronide (MG) concentrations predict changes in three outcomes, subjective drug effects, urges to smoke, and heart rate, following concurrent inhaled menthol and intravenous nicotine. A total of 45 menthol and non-menthol cigarettes smokers (36 male, nine female, 20 Black, and 23 White) were included in this double-blind, placebo-controlled study. Across three test sessions, participants were assigned to a different flavor condition for each session: 0% (no menthol), 0.5%, or 3.2% menthol. In each test session, participants received in a random order one intravenous delivery of saline and two intravenous deliveries of nicotine (0.25 mg/70 kg and 0.5 mg/70 kg), each 1 h apart, concurrent with menthol delivery by e-cigarettes. The main outcomes were subjective drug effects, urges to smoke, and heart rate. The results showed that following e-cigarette inhalation, changes in plasma MG concentrations or “menthol boost” increased proportionally to the menthol concentration in the e-liquids. While changes in plasma MG concentrations were not predictive of increases in heart rate or subjective drug effects that are reflective of acute effects from nicotine (i.e., feel good effects, stimulated, aversive effects), they were predictive of cooling effect, a typical effect of menthol, but only in menthol smokers in the absence of concurrent active nicotine infusion. These findings demonstrate the utility of plasma MG as a biomarker both for acute menthol exposure by e-cigarette inhalation and for the examination of the concentration-dependent behavioral and physiological effects of menthol in humans.

Evidence for Alpha7 Nicotinic Receptor Activation During the Cough Suppressing Effects Induced by Nicotine and Identification of ATA-101 as a Potential Novel Therapy for the Treatment of Chronic Cough

Studies performed in healthy smokers have documented a diminished responsiveness to tussive challenges, and several lines of experimental evidence implicate nicotine as an antitussive component in both cigarette smoke and the vapors generated by electronic cigarettes (eCigs). We set out to identify the nicotinic receptor subtype involved in the antitussive actions of nicotine and to further evaluate the potential of nicotinic receptor-selective agonists as cough-suppressing therapeutics. We confirmed an antitussive effect of nicotine in guinea pigs. We additionally observed that the alpha-4 beta-2 (α ₄ β ₂)-selective agonist Tc-6683 was without effect on evoked cough responses in guinea pigs, while the α ₇-selective agonist PHA 543613 dose-dependently inhibited evoked coughing. We subsequently describe the preclinical evidence in support of ATA-101, a potent and highly selective (α ₇) selective nicotinic receptor agonist, as a potential candidate for antitussive therapy in humans. ATA-101, formerly known as Tc-5619, was orally bioavailable and moderately central nervous system (CNS) penetrant and dose-dependently inhibited coughing in guinea pigs evoked by citric acid and bradykinin. Comparing the effects of airway targeted administration versus systemic dosing and the effects of repeated dosing at various times prior to tussive challenge, our data suggest that the antitussive actions of ATA-101 require continued engagement of α ₇ nicotinic receptors, likely in the CNS. Collectively, the data provide the preclinical rationale for α ₇ nicotinic receptor engagement as a novel therapeutic strategy for cough suppression. The data also suggest that α ₇ nicotinic acetylcholine receptor (nAChR) activation by nicotine may be permissive to nicotine delivery in a way that may promote addiction. SIGNIFICANCE STATEMENT: This study documents the antitussive actions of nicotine and identifies the α₇ nicotinic receptor subtype as the target for nicotine during cough suppression described in humans. We additionally present evidence suggesting that ATA-101 and other α₇ nicotinic receptor-selective agonists may be promising candidates for the treatment of chronic refractory cough.

A Simple Computational Approach to Identify Potential Drugs for Multiple Sclerosis and Cognitive Disorders from Expert Curated Resources

Multiple sclerosis, a disease of central nervous system leads to potential disability. In the USA, one million cases are diagnosed with multiple sclerosis in 2019. Multiple sclerosis is identified as one of the diseases causing global burden. Cognitive disorder is highly prevalent among 43-70% of multiple sclerosis patients. However, treating cognitive disorder in multiple sclerosis patients is mostly ignored and this leads to several complications. We utilized various expert curated resources to identify potential drugs for multiple sclerosis and cognitive disorder, with specific focus on identifying drugs that are capable of treating both the conditions. We used simple text mining techniques to compile two databases, disease-drug association database and gene-drug interaction database from various existing standard resources. Our study suggests four drugs, Baclofen, Levodopa, Minocycline, and Vitamin B12, for treating both multiple sclerosis and cognitive disorder. In addition, our approach suggests six drugs for multiple sclerosis and 10 drugs for cognitive disorder. We obtained pharmacologist opinion on the drugs suggested for each condition and provided literature evidence for our claim. Here, we present our computational approach as a protocol such that it can be applied to other comorbid diseases that did not gain much attention so far.

The effects of inhaled flavors on intravenous nicotine

Menthol is the only available flavor in combusted tobacco cigarettes; however, e-cigarettes are available in thousands of flavors. Research on flavors and rewarding properties of nicotine is limited. The present study sought to examine the acute rewarding effects of flavors inhaled from an e-cigarette, in combination with intravenous (IV) nicotine among cigarette smokers. In the present study, 24 menthol-preferring young adult (aged 18 to 30) cigarette smokers were tested under 3 different e-cigarette flavor conditions (menthol, green apple, or menthol + green apple) in a within-subject cross-over design. During each test session, each participant received 3 IV infusions (saline, 0.25 mg/70 kg nicotine, 0.5 mg/70 kg nicotine) administered 1 hr apart. The main outcome measures assessed cardiovascular, subjective, and cognitive domains. Compared with green apple or green apple + menthol, menthol produced higher ratings of "cooling" (ps < 0.01). Craving was rated higher following administration of green apple and the combined menthol + apple flavor compared to menthol alone (ps < 0.05). As expected, IV-nicotine dose-dependently increased the ratings of subjective liking/disliking and peak heart rate, improved cognitive performance, and reduced smoking urges (all ps < 0.05). These subjective, cognitive, and physiological effects of nicotine were not affected by any flavor condition. The present findings did not support an interaction between IV-nicotine dose and inhaled flavor for acute effects of nicotine. Green apple flavor, alone or in combination with menthol, could result in higher craving or insufficiently alleviate craving, relative to menthol flavor alone. Additional research is warranted to examine extended exposure to inhaled flavors on the rewarding and addictive effects of nicotine. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Influence of menthol and green apple e-liquids containing different nicotine concentrations among youth e-cigarette users

E-cigarettes are popular among adolescents. Given that flavors enhance e-cigarette appeal, this study examined the influence of flavors on nicotine in e-cigarettes. Youth e-cigarette users (average 26.2 days [SD = 3.6] in past 28 days) were randomized to use e-cigarettes containing 6 or 12 mg/mL of freebase nicotine and completed 4 test sessions. During the first 3 test sessions, participants completed 3 fixed puffing bouts (1 puffing bout = 10 puffs, 3 s each, 30-s interval), using menthol, green-apple, and unflavored e-liquids (50 propylene glycol [PG]/50 vegetable glycerin [VG]) with their assigned nicotine concentration in a random order using a ∼5.5-W V2 e-cigarette device. After each puffing bout, participants assessed subjective effects of nicotine and flavor. In the 4th test session, participants used any of the e-liquids they had tried in the earlier sessions, ad libitum for 60 min and the amount of e-liquid used for each flavor and the number of puffs was assessed. Participants (n = 49; 6 mg/mL [n = 24]; 12 mg/mL [n = 25]) were 63.3% male, 65.3% non-Hispanic White with an average age of 18.7 (SD = 0.9). Mixed models analysis revealed that green apple and 6 mg/mL of nicotine independently increased liking of e-cigarette taste. In addition, green apple produced higher ratings of fruitiness, sourness, sweetness, and menthol produced higher ratings of coolness. We did not observe any interactions between nicotine and flavor. Youth liked the taste of e-liquids containing green-apple flavor or low nicotine concentration which highlights the appeal of fruit flavors in e-cigarettes to adolescents. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The impact of flavored ENDS use among adolescents on daily use occasions and number of puffs, and next day intentions and willingness to vape

BACKGROUND

The FDA's policies restricting sale of sweet flavored cartridge-based and disposable electronic nicotine delivery systems (ENDS) comprise important steps toward curbing adolescent ENDS use. However, additional evidence is needed about the contribution of specific flavors to adolescents' ENDS use. This study investigated the effects of flavor use on same day vaping behaviors, and next day intentions and willingness.

METHODS

We collected ecological momentary assessments (EMA) from 50 adolescent past two-week vapers (ages 14-17) over 14 days. Daily EMA data were collected on vaping occasions, total puffs, vaping intentions, vaping willingness, and flavor used.

RESULTS

On average, data were obtained on 13.4 days per participant (670 observations). Participants vaped flavors on 87% of days (fruit = 55%; mint = 30%; tobacco = 6%; menthol = 5%, and candy, sweets, or chocolate = 5%). On days when participants vaped fruit flavors, they took more puffs (r = 0.13, p = .030). On days when they vaped tobacco flavor, they reported more vaping occasions (r = 0.20, p = .005) and more puffs (r = 0.15, p = .033). On days when they vaped because of flavor appeal, they reported more vaping occasions (r = 0.19, p = .001) and more puffs (r = 0.24, p < .001). On days when they vaped menthol flavor, they were less likely to report willingness to vape the next day (r = -0.14, p = .042). Adolescents who reported vaping due to flavor appeal were more likely to report intentions (OR = 5.63, p = .035) and willingness to vape the next day (r = 0.23, p < .001) CONCLUSION: These findings provide additional support for policies restricting the sale of flavored ENDS products to adolescents.

Cooling e-cigarette flavors and the association with e-cigarette use among a sample of high school students

INTRODUCTION

E-liquid flavor is typically presented by flavor category (e.g. menthol, mint, fruit, dessert). Cooling sensations produced by flavor additives such as menthol enhance appeal of e-cigarettes among youth, but not all e-liquids that produce cooling sensations are labeled as menthol. Sensory experiences produced by flavors may allow for a new way to capture e-cigarette flavor use. This study aims to examine use of flavors that produce cooling sensations among youth and its association with e-cigarette use behaviors.

METHODS

A 2019 survey of high school students (n = 4875) examined use of e-cigarette flavors that produced cooling sensations (cooling flavors) among past 30-day e-cigarette users. E-cigarette use behaviors (flavor use, nicotine use, frequency of use) were examined between those who did and did not use cooling flavors. A binary logistic regression was used to examine associations between vaping frequency, nicotine (vs. non-nicotine) use, and vaping cooling flavors while controlling for demographics, number of flavors vaped in the past month, and vaping age of onset.

RESULTS

51.6% (n = 473/916) of the analytic sample endorsed vaping cooling flavors. There were no demographic differences by vaping cooling flavors. Vaping cooling flavors was associated with vaping more frequently (AOR:1.04,95% CI:1.03,1.05) and vaping nicotine (AOR:2.37,95% CI:1.53,3.67).

CONCLUSION

Vaping cooling flavors was associated with greater nicotine vaping and frequency of e-cigarette use. Assessing sensory experience, such as cooling, in addition to flavor category may more fully capture e-cigarette flavor use and its impacts on youth e-cigarette use behaviors.

Abuse liability assessment of the JUUL system in two nicotine concentrations compared to combustible cigarette, nicotine gum and comparator electronic nicotine delivery system

BACKGROUND

To assess the abuse liability of the JUUL System (JS) in 5.0 % (59 mg/mL) and 3.0 % (35 mg/mL) nicotine concentrations.

METHODS

Adult smokers (N = 146; 45.9 % female; mean age = 41.29 years) were randomized to one of four study flavor arms and then to a within-subjects cross-over sequence for five test product categories: (1) JS 5.0 % nicotine concentration; (2) JS 3.0 % nicotine; (3) usual brand (UB) cigarette; (4) 4 mg mint nicotine gum; (5) comparator ENDS (VUSE Alto 5.0 % nicotine). Products were tested by ad libitum use (5 min for ENDS and cigarette; 30 min for gum); nicotine pharmacokinetic (PK) parameters and subjective effects were assessed following use.

RESULTS

Maximum plasma nicotine concentration (C_max-BL), rate of plasma nicotine rise and total nicotine exposure (AUC_0-60-BL) of UB cigarette were significantly greater than all other test products. The comparator ENDS was significantly greater than 5.0 % and 3.0 % JS and nicotine gum on C_max-BL, rate of plasma nicotine rise, and AUC_0-60-BL; C_max-BL of JS 5.0 % was significantly greater than JS 3.0 % and nicotine gum. Product liking and satisfying effects were significantly highest for the UB cigarette; JS products and comparator ENDS did not significantly differ and were rated higher than nicotine gum on most subjective measures.

CONCLUSIONS

These results suggest that the abuse liability of both 5.0 % and 3.0 % JS is: (1) substantially lower than UB cigarette; (2) somewhat lower than comparator ENDS; and (3) higher than nicotine gum. Additionally, the abuse liability of JS 5.0 % is somewhat higher than JS 3.0 %.

Menthol in electronic cigarettes: A contributor to respiratory disease?

Menthol is widely used in tobacco products. This study compared the effects of menthol on human bronchial epithelium using submerged cultures, a VITROCELL® cloud chamber that provides air liquid interface (ALI) exposure without solvents or heating, and a Cultex ALI system that delivers aerosol equivalent to that inhaled during vaping. In submerged culture, menthol significantly increased calcium influx and mitochondrial reactive oxygen species (ROS) via the TRPM8 receptor, responses that were inhibited by a TRPM8 antagonist. VITROCELL® cloud chamber exposure of BEAS-2B monolayers increased mitochondrial protein oxidation, expression of the antioxidant enzyme SOD2, activation of NF-κB, and secretion of inflammatory cytokines (IL-6 and IL-8). Proteomics data collected following ALI exposure of 3D EpiAirway tissue in the Cultex showed upregulation of NRF-2-mediated oxidative stress, oxidative phosphorylation, and IL-8 signaling. Across the three platforms, menthol adversely effected human bronchial epithelium in a manner that could lead to respiratory disease.

Flavor and Nicotine Effects on E-cigarette Appeal in Young Adults: Moderation by Reason for Vaping

Objectives: Effective regulations that reduce nicotine vaping among young adult dual (combustible and e-cigarette) users may differ depending on whether e-cigarettes are used for helping with smoking cessation. This laboratory experiment examined flavor and nicotine effects on e-cigarette product appeal among young adult dual users, stratified by reported use of e-cigarettes to quit smoking. Methods: Dual users aged 18-35 years that did (N = 31) or did not (N = 22) report vaping for the purpose of quitting smoking puffed e-cigarette solutions varied by a flavor (fruit, menthol, tobacco) and nicotine (nicotine-containing [6 mg/mL], nicotine-free) with-in-participant design. After puffing each solution, participants rated appeal. Results: In main effect analyses, non-tobacco (vs tobacco) flavors increased appeal and nicotine-containing (vs nicotine free) solutions reduced appeal similarly in dual users who did and did not vape to quit smoking. Interaction analyses found non-significant trend evidence that fruit and menthol flavors suppressed nicotine's appeal-reducing effects more powerfully in those that did not vape to quit smoking (flavor × nicotine × vape to quit smoking, ps = .05-.06). Conclusions: Non-tobacco flavors might increase e-cigarette product appeal in young adult dual users overall and disproportionately suppress nicotine's appeal-reducing effects in those that vape for purposes other than assisting with smoking cessation.

E-cigarette device power moderates the effects of non-tobacco flavors and nicotine on product appeal in young adults

BACKGROUND

Identifying e-cigarette product characteristics that moderate the effects of non-tobacco flavors and nicotine on user appeal can inform regulations issued in tandem with e-cigarette nicotine and flavor policies aimed to protect young adult health. An e-cigarette device's electrical power affects the amount of solution aerosolized per puff, leading to more concentrated or diluted aerosol, which may alter product appeal. This laboratory experiment tested whether e-cigarette device power moderated the independent and interactive effects of non-tobacco flavors and nicotine on appeal in young adults.

METHOD

In a within-subject design single-visit protocol, young adult e-cigarette users (N = 100) administered standardized doses of e-cigarette solutions varying in flavor (fruit, menthol, tobacco) and nicotine (nicotine-containing [6 mg/mL], nicotine-free). Solutions were administered via a variable-voltage tank-style device at low (7.3 W[3.3 V@1.5 Ω resistance]) and high (12.3 W[4.3 V@1.5 Ω resistance]) power settings. Participants rated each dose's appeal (0-100 scale).

RESULTS

The high (vs. low) power setting attenuated the appeal-enhancing effects of menthol (vs. tobacco) flavors (Menthol × Power, estimate = -5.44, P = .03). Power did not moderate the appeal-enhancing effects of fruit flavors. High (vs. low) power amplified the appeal-reducing effects of nicotine-containing (vs. nicotine-free) solutions (Nicotine × Power, estimate = 6.69, P < .001) and augmented the extent to which fruit and menthol flavors suppressed nicotine's appeal-reducing effects (Flavor × Nicotine × Power, estimates = 9.40-14.85, Ps≤0.03).

CONCLUSION

E-cigarette device power appears to moderate flavor- and nicotine-induced changes in product appeal in nuanced ways, including by augmenting the ability of non-tobacco flavors to mask nicotine's appeal-reducing effects. Regulatory restrictions on high-powered e-cigarette devices warrant consideration in efforts to protect young adult health.

Recent findings in the pharmacology of inhaled nicotine: Preclinical and clinical in vivo studies

INTRODUCTION

The rise of vaping in adolescents, the recent entrance of new inhaled nicotine products such as iQOS on the market and e-cigarette or vaping product use-associated lung injury cases has created concern for the use of inhaled non-combustible nicotine products. This narrative review discusses recent experimental in vivo studies that utilize human, rat and mouse models to understand the pharmacological impact of nicotine from non-combustible products.

METHODS

The search engine PubMed was utilized with the following search terms: inhaled nicotine, nicotine e-cigarette, heated tobacco products, iQOS, electronic cigarette, nicotine inhaler, nicotine vaping. This review highlights recent primary in vivo studies of inhaled nicotine administration experimental paradigms that occurred in laboratory settings using human and rodent (rats and mice) models that have been published from January 2017-December 2019.

RESULTS

The pharmacokinetics of nicotine via e-cigarettes is influenced by the PG/VG and flavor constituents in e-liquids, the presence of nicotine salts in e-liquids, puff topography of nicotine and tobacco product users and the power of the e-cigarette device. The pharmacodynamic impact of inhaled nicotine has cardiovascular, pulmonary and central nervous system implications.

CONCLUSION

The articles reviewed here highlight the importance of both animal and human models to fully understand the impact of inhaled nicotine pharmacology There is a need for more rodent pharmacokinetic inhaled nicotine studies to understand the influences of factors such as flavor and nicotine salts. Additionally, consensus on nicotine measurement in both human and rodent studies is greatly needed.

History repeats itself: Role of characterizing flavors on nicotine use and abuse

The popularity of e-cigarettes has skyrocketed in recent years, and most vapers use flavored e-cigarette products. Consumption of flavored e-cigarettes exceeds that of combustible cigarettes and other tobacco products among adolescents, who are particularly vulnerable to becoming nicotine dependent. Flavorings have been used by the tobacco industry since the 17th century, but the use of flavors by the e-cigarette industry to create products with "characterizing" flavors (i.e. flavors other than tobacco or menthol) has sparked a public health debate. This review addresses the possibility that characterizing flavors make nicotine more appealing, rewarding and addictive. It also discusses ways in which preclinical and clinical studies could improve our understanding of the mechanisms by which flavors may alter nicotine reward and reinforcement. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.

Sensory attributes of e-cigarette flavours and nicotine as mediators of interproduct differences in appeal among young adults

OBJECTIVE

To estimate the extent to which specific sensory attributes, for example, smoothness, mediate differences in electronic cigarette (e-cigarette) appeal between products in non-tobacco versus tobacco flavours and varying nicotine content in young adults.

METHOD

E-cigarette users (n=100; aged 18-34 years) administered standardised two-puff e-cigarette doses of different products varying in a flavour (fruit, menthol, tobacco) × nicotine (nicotine-containing (6 mg/mL freebase), nicotine-free) within-subject design. Participants rated sensory attributes (sweetness, bitterness, smoothness and harshness) and appeal on 100-unit visual analogue scales after administering each product. Sensory ratings were tested as simultaneous mediators of flavour, nicotine and flavour × nicotine effects on appeal.

RESULTS

Appeal preferences for fruit versus tobacco flavours were mediated by sweetness-enhancing (β_indirect=0.092), smoothness-enhancing (β_indirect=0.045) and bitterness-reducing (β_indirect=0.072) effects of fruit flavours. Appeal preferences for menthol versus tobacco flavours were mediated by menthol's smoothness-enhancing (β_indirect=0.039) and bitterness-reducing (β_indirect=0.034) effects. Lower appeal of nicotine-containing versus nicotine-free products was mediated by nicotine's sweetness-reducing (β_indirect=-0.036), smoothness-reducing (β_indirect=-0.156) and bitterness-increasing (β_indirect=0.045) effects. Flavour × nicotine interaction effects on appeal were explained by menthol-related suppression of nicotine's bitterness-enhancing and sweetness-reducing mediation pathways and fruit-related suppression of nicotine's bitterness-enhancing mediation pathway. Harshness did not mediate appeal after adjusting for other sensory attributes.

CONCLUSION

Bitterness and smoothness may be cross-cutting mediators of interproduct variation in the effects of types of non-tobacco flavours and nicotine on e-cigarette appeal in young adults. Sweetness may also mediate appeal-enhancing effects of fruit and appeal-reducing effects of nicotine. Non-tobacco flavours may suppress appeal-reducing effects of nicotine in e-cigarettes through attenuation of nicotine's aversive taste attributes.

Effects of non-tobacco flavors and nicotine on e-cigarette product appeal among young adult never, former, and current smokers

BACKGROUND

E-cigarette regulations targeting products that disproportionately appeal to never-smokers may optimize population health. This laboratory study of young adults tested whether differences in appeal between e-cigarettes with non-tobacco-flavored (vs. tobacco-flavored) and nicotine-containing (vs. nicotine-free) solutions varied by smoking history.

METHODS

Current (N = 53), former (N = 25), and never (N = 22) cigarette smokers who vape (Mean[SD] age = 25.4[4.4] years) administered standardized e-cigarette doses varied by a Flavor (fruit, menthol, tobacco) × Nicotine (nicotine-containing [6 mg/mL], nicotine-free) within-subject double-blind design. Participants rated each dose's appeal (0-100 scale). Covariate-adjusted interactions tested whether smoking history moderated flavor and nicotine effects.

RESULTS

Appeal was higher for fruit and menthol than tobacco flavors in each group. The fruit vs. tobacco appeal difference was greater in never smokers (fruit-tobacco estimate = 19.6) than current smokers (estimate = 12.1) but not former smokers (estimate = 12.6). The menthol vs. tobacco difference was greater in never smokers (menthol-tobacco estimate = 17.3) than former (estimate = 6.0) and current (estimate = 7.2) smokers. Appeal was lower for nicotine-containing than nicotine-free solutions in each group; this difference was greater in never smokers (nicotine-nicotine-free estimate = -17.3) than former (estimate = -7.0) and current (estimate = -10.6) smokers. Compared to tobacco flavors, nicotine's appeal-reducing effects were suppressed by fruit and menthol flavors in never smokers.

CONCLUSIONS

Higher appeal of non-tobacco-flavored (vs. tobacco-flavored) and lower appeal of nicotine-containing (vs. nicotine-free) e-cigarettes may be widespread in young adults but disproportionately amplified in never smokers. Non-tobacco flavors may suppress nicotine's appeal-lowering qualities in never smokers. The impact of regulating non-tobacco flavors in e-cigarettes may vary by smoking history.