Acute and subacute inhalation toxicity assessment of WS-23 in Sprague-Dawley rats

Newly synthesized acridone derivatives targeting lung cancer: A toxicity and xenograft model study

AKT is one of the overexpressed targets in nonsmall cell lung cancer (NSCLC) and plays an important role in its progression and offers an attractive target for the therapy. The PI3K/AKT/mTOR pathway is upregulated in NSCLC. Acridone is an important heterocycle compound which treats cancer through various mechanisms including AKT as a target. In the present work, the study was designed to evaluate the safety profile of three acridone derivatives (AC-2, AC-7, and AC-26) by acute and repeated dose oral toxicity. In addition to this, we also checked the pAKT overexpression and its control by these derivatives in tumor xenograft model. The results from acute and repeated dose toxicity showed these compounds to be highly safe and free from any toxicity, mortality, or significant alteration in body weight, food, and water intake in the rats. In the repeated dose toxicity, compounds showed negligible variations in a few hematological parameters at 400 mg/kg. The histopathology, biochemical, and urine parameters remained unchanged. The xenograft model study demonstrated AC-2 to be inhibiting HOP-62 induced tumor via reduction in p-AKT1 (Ser473) expression significantly. In immunofluorescence staining AC-2 treated tissue section showed 2.5 fold reduction in the expression of p-AKT1 (Ser473). Histopathology studies showed the destruction of tumor cells with increased necrosis after treatment. The study concluded that AC-2 causes cell necrosis in tumor cells via blocking the p-AKT1 expression. The findings may provide a strong basis for further clinical applications of acridone derivatives in NSCLC.

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.

A synthetic coolant (WS-23) in disposable electronic cigarettes impairs cytoskeletal function in EpiAirway microtissues exposed at the air liquid interface

The design of popular disposable electronic cigarettes (ECs) was analyzed, and the concentrations of WS-23, a synthetic coolant, in EC fluids were determined for 22 devices from 4 different brands. All products contained WS-23 in concentrations that ranged from 1.0 to 40.1 mg/mL (mean = 21.4 ± 9.2 mg/mL). To determine the effects of WS-23 on human bronchial epithelium in isolation of other chemicals, we exposed EpiAirway 3-D microtissues to WS-23 at the air liquid interface (ALI) using a cloud chamber that generated aerosols without heating. Proteomics analysis of exposed tissues revealed that the cytoskeleton was a major target of WS-23. BEAS-2B cells were exposed to WS-23 in submerged culture to validate the main results from proteomics. F-actin, which was visualized with phalloidin, decreased concentration dependently in WS-23 treated BEAS-2B cells, and cells became immotile in concentrations above 1.5 mg/mL. Gap closure, which depends on both cell proliferation and migration, was inhibited by 0.45 mg/mL of WS-23. These data show that WS-23 is being added to popular EC fluids at concentrations that can impair processes dependent on the actin cytoskeleton and disturb homeostasis of the bronchial epithelium. The unregulated use of WS-23 in EC products may harm human health.

The role of synthetic coolants, WS-3 and WS-23, in modulating E-cigarette-induced reactive oxygen species (ROS) in lung epithelial cells

There has been a substantial rise in e-cigarette (e-cig) use or vaping in the past decade, prompting growing concerns about their adverse health effects. Recently, e-cig manufacturers have been using synthetic cooling agents, like WS-23 and WS-3, to provide a cooling sensation without the "menthol taste". Studies have shown that aerosols/vapes generated by e-cigs can contain significant levels of reactive oxygen species (ROS). However, studies investigating the role of synthetic coolants in modulating ROS levels generated by e-cigs are lacking. This study seeks to understand how synthetic coolants, e-cig additives that have become increasingly prevalent in e-liquids sold in the United States (US), impact acellular ROS production from e-liquid aerosols as well as cellular ROS levels from pulmonary epithelial cells exposed to these e-liquids. To further explain, our study aims to understand whether the addition of WS-3 and WS-23 to e-liquid base and e-liquid base with nicotine significantly modifies generated acellular ROS levels within aerosolized e-liquids, as well as cellular ROS within BEAS-2B cells treated with these same e-liquids. Aerosols were generated from e-liquids with and without synthetic coolants through a single-puff aerosol generator; subsequently, acellular ROS was semi-quantified in H2O2 equivalents via fluorescence spectroscopy. Our acellular ROS data suggest that adding WS-3 to e-liquid base (PG:VG), regardless of nicotine content, has a minimal impact on modifying e-cig generated acellular ROS levels. Additionally, we also measured cellular ROS in lung epithelial cells using both e-liquids containing and not containing synthetic coolants via the CellROX Green fluorescent sensor. Similar comparable results were found in BEAS2B cells though ROS was increased by WS-3 and WS-23 treated in e-cig nicotine groups. Altogether, our data suggest that neither the addition of WS-23 nor WS-3 to e-liquid base solution, with and without nicotine, significantly modifies e-cig generated acellular ROS levels within aerosolized e-liquids and cellular ROS levels within treated BEAS-2B cells. Together, our data provide insight into whether synthetic coolants added to e-liquids could impact vaping-induced oxidative stress in the lungs.

Disposable Puff Bar Electronic Cigarettes: Chemical Composition and Toxicity of E-liquids and a Synthetic Coolant

The popularity of disposable fourth-generation electronic cigarettes (ECs) among young adults and adolescents has been increasing since the ban on flavored cartridge EC products such as JUUL. Although the constituents and toxicity of some cartridge-based fourth-generation ECs, such as JUUL, have been studied, limited data exist for other disposable ECs such as Puff. The purpose of this study was to determine flavor chemicals, synthetic coolants, and nicotine concentrations in 16 disposable Puff devices, evaluate the cytotoxicity of the different flavors from the Puff brand using in vitro assays, and investigate the health risks of synthetic coolants in EC products. Gas chromatography/mass spectrometry was used to identify and quantify chemicals in Puff EC fluids. One hundred and twenty-six flavor chemicals were identified in Puff fluids, and 16 were >1 mg/mL. WS-23 (2-isopropyl-N,2,3-trimethylbutyramide) was present in all products, and concentrations ranged from 0.8 to 45.1 mg/mL. WS-3 (N-ethyl-p-menthane-3-carboxamide) concentrations ranged from 1.5 to 16.4 mg/mL in 6/16 products. Nicotine concentrations ranged from 40.6 to 52.4 (average 44.8 mg/mL). All unvaped fluids were cytotoxic at dilutions between 0.1 and 10% in the MTT and neutral red uptake assays when tested with BEAS-2B lung epithelial cells. The cytotoxicity of Puff fluids was highly correlated with total chemical concentrations, nicotine, WS-23, both synthetic coolants, and synthetic coolants plus ethyl maltol. Lower concentrations of WS-23 than those in the fluids adversely affected cell growth and morphology. Concentrations of synthetic coolants exceeded levels used in consumer products. The margin of exposure data showed that WS-3 and WS-23 concentrations were high enough in Puff products to present a health hazard. Our study demonstrates that disposable Puff ECs have high levels of cytotoxic chemicals. The data support the regulation of flavor chemicals and synthetic coolants in ECs to limit potentially harmful health effects.

Synthetic Cooling Agents in US-marketed E-cigarette Refill Liquids and Popular Disposable E-cigarettes: Chemical Analysis and Risk Assessment

INTRODUCTION

Menthol, through its cooling and pleasant sensory effects, facilitates smoking and tobacco product initiation, resulting in the high popularity of mint/menthol-flavored E-cigarettes. More recently, E-cigarette vendors started marketing synthetic cooling agents as additives that impart a cooling effect but lack a characteristic minty odor. Knowledge about content of synthetic coolants in US-marketed E-cigarette products and associated health risks is limited.

AIMS AND METHODS

E-liquid vendor sites were searched with the terms "koolada", "kool/cool", "ice", or WS-3/WS-23, denoting individual cooling agents, and relevant refill E-liquids were purchased. "Ice" flavor varieties of Puffbar, the most popular disposable E-cigarette brand, were compared with non-"Ice" varieties. E-liquids were characterized, and synthetic coolants quantified using GC/MS. Margin of exposure (MOE), a risk assessment parameter, was calculated to assess the risk associated with synthetic coolant exposure from E-cigarette use.

RESULTS

WS-3 was detected in 24/25 refill E-liquids analyzed. All Puffbar flavor varieties contained either WS-23 (13/14) or WS-3 (5/14), in both "Ice"- and non-"Ice" flavors. Modeling consumption of WS-3 from vaped E-liquids, resulted in MOEs below the safe margin of 100 for most daily use scenarios. MOEs for WS-23 were <100 for 10/13 Puffbar flavors in all use scenarios. Puffbar power specifications are identical to Juul devices.

CONCLUSIONS

Synthetic cooling agents (WS-3/WS-23) were present in US-marketed E-cigarettes, at levels that may result in consumer exposures exceeding safety thresholds set by regulatory agencies. Synthetic coolants are not only found in mint- or menthol-flavored products but also in fruit- and candy-flavored products, including popular disposable E-cigarette products such as Puffbar.

IMPLICATIONS

Synthetic cooling agents are widely used in "kool/cool"- and "ice"-flavored E-liquids and in E-liquids without these labels, both as a potential replacement for menthol or to add cooling "notes" to nonmenthol flavors. These agents may be used to bypass current and future regulatory limits on menthol content in tobacco products, and not just E-cigarettes. Because synthetic cooling agents are odorless, they may not fall under the category of "characterizing flavor", potentially circumventing regulatory measures based on this concept. Regulators need to consider the additional health risks associated with exposure to synthetic cooling agents.