JUUL e-liquid exposure elicits cytoplasmic Ca2+ responses and leads to cytotoxicity in cultured airway epithelial cells

Impact of nicotine-free and nicotine-rich flavored electronic cigarette refill liquids on primary human melanocyte function

In this study, five popular EC liquid flavors-strawberry, banana, vanilla, tobacco, and menthol-were examined on human melanocyte functions. Each flavored e-liquid (in 80/20 PG/VG vehicle) was tested without or with 18 mg/mL nicotine. The effects of PG/VG and nicotine-containing vehicles were also evaluated. Results revealed that nicotine-free and nicotine-containing e-liquids had comparable cytotoxicity, with menthol> > banana> tobacco> vanilla> strawberry. This cytotoxicity was unrelated to either nicotine or the vehicle. PG/VG (1 and 2 %) increased melanin production without influencing cellular tyrosinase activity. The flavored e-liquids did not further affect melanin production, suggesting that the vehicle's effect, not the flavor, was responsible for the increased melanin production. Interestingly, nicotine at 2 % in the vehicle restored the stimulated melanin production to the control. Flavors suppressed cellular tyrosinase activity, with vanilla and banana flavors robustly inhibiting it. Vanilla and banana e-liquids also enhanced reactive oxygen species (ROS) production, which did not originate from the vehicle or nicotine-containing vehicle. Banana e-liquid with nicotine lowered ROS generation compared to nicotine-free banana e-liquid. Common flavors in e-liquids can cause cytotoxicity and influence melanogenesis even without nicotine, indicating that the use of ECs may not completely avoid the harmful effects of cigarette smoking. Further studies are warranted to investigate e-liquid aerosol effects on melanocytes.

The effects of flavored vaped e-liquids on cultured human macrophages derived from the central and peripheral nervous systems

The use of the electronic cigarette (e-cig) to consume an aerosol is referred to as "vaping" and has become the most popular method for nicotine consumption amongst youth and many adults worldwide. This popularity is at least partially attributable to the availability of 1000s of distinctly flavored e-liquids. At present, a large number of studies have evaluated the potential negative effects of e-cig use in relation to pulmonary disease. These studies have demonstrated that vaping can lead to immune activation and cell death but typically include only epithelial cell line studies. At present, significantly less is known about the effects of vaped e-liquids on the central nervous system (CNS) and peripheral nervous system (PNS). To investigate this gap, we utilized the human macrophage cell lines KG-1 (PNS-resident macrophages) and DBTRG-05MG (CNS-resident macrophages) and examined their exposure to vaped e-liquids. To carry out these investigations, measurements of: cell viability, expression of inflammatory cytokines, phagocytosis and reactive oxygen species (ROS) were employed. Our findings illustrate that when exposed to e-liquid, and especially flavored e-liquids, both peripheral and central macrophage cell lines decrease in cell viability, showcase an upregulated level of expression of pro-inflammatory cytokines, a diminished level of phagocytic activity and an overall increased level of reactive oxidative species. Thus, our study further indicates that the use of the e-cig can cause phenotype and immune disruptions within both the CNS and PNS.

GC/HRMS Analysis of E-Liquids Complements In Vivo Modeling Methods and can Help to Predict Toxicity

Tobacco smoking is a major risk factor for disease development, with the user inhaling various chemicals known to be toxic. However, many of these chemicals are absent before tobacco is "burned". Similar, detailed data have only more recently being reported for the e-cigarette with regards to chemicals present before and after the e-liquid is "vaped." Here, zebrafish were dosed with vaped e-liquids, while C57-BL/6J mice were vaped using nose-cone only administration. Preliminary assessments were made using e-liquids and GC/HRMS to identify chemical signatures that differ between unvaped/vaped and flavored/unflavored samples. Oxidative stress and inflammatory immune cell response assays were then performed using our in vivo models. Chemical signatures differed, e.g., between unvaped/vaped samples and also between unflavored/flavored e-liquids, with known chemical irritants upregulated in vaped and unvaped flavored e-liquids compared with unflavored e-liquids. However, when possible respiratory irritants were evaluated, these agents were predominantly present in only the vaped e-liquid. Both oxidative stress and inflammatory responses were induced by a menthol-flavored but not a tobacco-flavored e-liquid. Thus, chemical signatures differ between unvaped versus vaped e-liquid samples and also between unflavored versus flavored e-liquids. These flavors also likely play a significant role in the variability of e-liquid characteristics, e.g., pro-inflammatory and/or cytotoxic responses.

Vaping-Dependent Pulmonary Inflammation Is Ca2+ Mediated and Potentially Sex Specific

Here we use the SCIREQ InExpose system to simulate a biologically relevant vaping model in mice to investigate the role of calcium signaling in vape-dependent pulmonary disease as well as to investigate if there is a gender-based difference of disease. Male and female mice were vaped with JUUL Menthol (3% nicotine) using the SCIREQ InExpose system for 2 weeks. Additionally, 2-APB, a known calcium signaling inhibitor, was administered as a prophylactic for lung disease and damage caused by vaping. After 2 weeks, mice were exposed to lipopolysaccharide (LPS) to mimic a bacterial infection. Post-infection (24 h), mice were sacrificed, and bronchoalveolar lavage fluid (BALF) and lungs were taken. Vaping primed the lungs for worsened disease burden after microbial challenge (LPS) for both males and females, though females presented increased neutrophilia and inflammatory cytokines post-vape compared to males, which was assessed by flow cytometry, and cytokine and histopathological analysis. This increased inflammatory burden was controlled by calcium signaling inhibition, suggesting that calcium dysregulation may play a role in lung injury caused by vaping in a gender-dependent manner.

Electronic cigarette exposure disrupts airway epithelial barrier function and exacerbates viral infection

The use of electronic cigarettes (e-cigs), especially among teenagers, has reached alarming and epidemic levels, posing a significant threat to public health. However, the short- and long-term effects of vaping on the airway epithelial barrier are unclear. Airway epithelial cells are the forefront protectors from viruses and pathogens. They contain apical junctional complexes (AJCs), which include tight junctions (TJs) and adherens junctions (AJs) formed between adjacent cells. Previously, we reported respiratory syncytial virus (RSV) infection, the leading cause of acute lower respiratory infection-related hospitalization in children and high-risk adults, induces a "leaky airway" by disrupting the epithelial AJC structure and function. We hypothesized chemical components of e-cigs disrupt airway epithelial barrier and exacerbate RSV-induced airway barrier dysfunction. Using confluent human bronchial epithelial (16HBE) cells and well-differentiated normal human bronchial epithelial (NHBE) cells, we found that exposure to extract and aerosol e-cig nicotine caused a significant decrease in transepithelial electrical resistance (TEER) and the structure of the AJC even at noncytotoxic concentrations. Western blot analysis of 16HBE cells exposed to e-cig nicotine extract did not reveal significant changes in AJC proteins. Exposure to aerosolized e-cig cinnamon or menthol flavors also induced barrier disruption and aggravated nicotine-induced airway barrier dysfunction. Moreover, preexposure to nicotine aerosol increased RSV infection and the severity of RSV-induced airway barrier disruption. Our findings demonstrate that e-cig exposure disrupts the airway epithelial barrier and exacerbates RSV-induced damage. Knowledge gained from this study will provide awareness of adverse e-cig respiratory effects and positively impact the mitigation of e-cig epidemic.NEW & NOTEWORTHY Electronic cigarette (e-cig) use, especially in teens, is alarming and at epidemic proportions, threatening public health. Our study shows that e-cig nicotine exposure disrupts airway epithelial tight junctions and increases RSV-induced barrier dysfunction. Furthermore, exposure to aerosolized flavors exaggerates e-cig nicotine-induced airway barrier dysfunction. Our study confirms that individual and combined components of e-cigs deleteriously impact the airway barrier and that e-cig exposure increases susceptibility to viral infection.

Exposure, Retention, Exhalation, Symptoms, and Environmental Accumulation of Chemicals During JUUL Vaping

Little is known about the chemical exposures that electronic cigarette (EC) users receive and emit during JUUL vaping and if exposures produce symptoms dose dependently. This study examined chemical exposure (dose), retention, symptoms during vaping, and the environmental accumulation of exhaled propylene glycol (PG), glycerol (G), nicotine, and menthol in a cohort of human participants who vaped JUUL "Menthol" ECs. We refer to this environmental accumulation as "EC exhaled aerosol residue" (ECEAR). Chemicals were quantified using gas chromatography/mass spectrometry in JUUL pods before and after use, lab-generated aerosols, human exhaled aerosols, and in ECEAR. Unvaped JUUL "Menthol" pods contained ∼621.3 mg/mL of G, ∼264.9 mg/mL of PG, ∼59.3 mg/mL of nicotine, ∼13.3 mg/mL of menthol, and ∼0.1 mg/mL of the coolant WS-23. Eleven experienced male EC users (aged 21-26) provided exhaled aerosol and residue samples before and after vaping JUUL pods. Participants vaped ad libitum for 20 min, while their average puff count (22 ± 6.4) and puff duration (4.4 ± 2.0) were recorded. The transfer efficiency of nicotine, menthol, and WS-23 from the pod fluid into the aerosol varied with each chemical and was generally similar across flow rates (9-47 mL/s). At 21 mL/s, the average mass of each chemical retained by the participants who vaped 20 min was 53.2 ± 40.3 mg for G, 18.9 ± 14.3 mg for PG, 3.3 ± 2.7 mg for nicotine, and 0.5 ± 0.4 mg for menthol, with retention deduced to be ∼90-100% for each chemical. There was a significant positive relationship between the number of symptoms during vaping and total chemical mass retained. ECEAR accumulated on enclosed surfaces where it could contribute to passive exposure. These data will be valuable to researchers studying human exposure to EC aerosols and agencies that regulate EC products.

The relationship between the use of electronic nicotine delivery systems (ENDS) and effects on pulmonary immune responses-a literature review

INTRODUCTION

The use of electronic nicotine delivery systems (ENDS), or vaping, is a relatively recent phenomenon, and there are various gaps in our current knowledge regarding the specific effects of e-cigarettes, such as their immunological effects. The importance of this question became even more relevant in light of the COVID-19 pandemic.

OBJECTIVE

This literature review examines the relationship between the use of electronic nicotine delivery systems (ENDS) and immunological effects to examine available information and identify gaps in the current knowledge. Our search strategy included studies focusing on the effects of ENDS on the immune response during infectious respiratory diseases such as COVID-19 and pneumonia.

METHODS

Peer-reviewed studies presenting quantitative data published from 2007, the year that e-cigarettes were introduced to the US market until 2022 have been included. All studies were indexed in PubMed. We excluded papers on THC and EVALI (E-cigarette, or Vaping Product, Use Associated Lung Injury) as we wanted to focus on the effects of nicotine devices.

RESULTS

Among the 21 articles that assessed the relationship between ENDS and immunological health effects, we found eight studies based on cell models, two articles based on both cell and mouse models, five articles based on mouse models, and six studies of human populations. Most of the articles identified in our review demonstrated a potential association between vaping and adverse immunological health effects.

DISCUSSION

Overall, the evidence from the cell and animal studies indicates that there is a positive, statistically significant association between vaping and adverse immune response during infectious respiratory diseases. The evidence from human studies is not conclusive.

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

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

E-Cigarette (E-Cig) Liquid Composition and Operational Voltage Define the In Vitro Toxicity of Δ8Tetrahydrocannabinol/Vitamin E Acetate (Δ8THC/VEA) E-Cig Aerosols

The 2019 United States outbreak of E-cigarette (e-cig), or Vaping, Associated Acute Lung Injury (EVALI) has been linked to presence of vitamin E acetate (VEA) in Δ8tetrahydrocannabinol (Δ8THC)-containing e-liquids, as supported by VEA detection in patient biological samples. However, the pathogenesis of EVALI and the complex physicochemical properties of e-cig emissions remain unclear, raising concerns on health risks of vaping. This study investigates the effect of Δ8THC/VEA e-liquids and e-cig operational voltage on in vitro toxicity of e-cig aerosols. A novel E-cigExposure Generation System platform was used to generate and characterize e-cig aerosols from a panel of Δ8THC/VEA or nicotine-based e-liquids at 3.7 or 5 V. Human lung Calu-3 cells and THP-1 monocytes were exposed to cell culture media conditioned with collected e-cig aerosol condensate at doses of 85 and 257 puffs/m2 lung surface for 24 h, whereafter specific toxicological endpoints were assessed (including cytotoxicity, metabolic activity, reactive oxygen species generation, apoptosis, and inflammatory cytokines). Higher concentrations of gaseous volatile organic compounds were emitted from Δ8THC/VEA compared with nicotine-based e-liquids, especially at 5 V. Emitted PM2.5 concentrations in aerosol were higher for Δ8THC/VEA at 5 V and averagely for nicotine-based e-liquids at 3.7 V. Overall, aerosols from nicotine-based e-liquids showed higher bioactivity than Δ8THC/VEA aerosols in THP-1 cells, with no apparent differences in Calu-3 cells. Importantly, presence of VEA in Δ8THC and menthol flavoring in nicotine-based e-liquids increased cytotoxicity of aerosols across both cell lines, especially at 5 V. This study systematically investigates the physicochemical and toxicological properties of a model of Δ8THC/VEA and nicotine e-cigarette condensate exposure demonstrating that pyrolysis of these mixtures can generate hazardous toxicants whose synergistic actions potentially drive acute lung injury upon inhalation.

Calcium-Dependent Pulmonary Inflammation and Pharmacological Interventions and Mediators

Pulmonary diseases present a significant burden worldwide and lead to severe morbidity and mortality. Lung inflammation caused by interactions with either viruses, bacteria or fungi is a prominent characteristic of many pulmonary diseases. Tobacco smoke and E-cig use ("vaping") are considered major risk factors in the development of pulmonary disease as well as worsening disease prognosis. However, at present, relatively little is known about the mechanistic actions by which smoking and vaping may worsen the disease. One theory suggests that long-term vaping leads to Ca2+ signaling dysregulation. Ca2+ is an important secondary messenger in signal transduction. Cellular Ca2+ concentrations are mediated by a complex series of pumps, channels, transporters and exchangers that are responsible for triggering various intracellular processes such as cell death, proliferation and secretion. In this review, we provide a detailed understating of the complex series of components that mediate Ca2+ signaling and how their dysfunction may result in pulmonary disease. Furthermore, we summarize the recent literature investigating the negative effects of smoking and vaping on pulmonary disease, cell toxicity and Ca2+ signaling. Finally, we summarize Ca2+-mediated pharmacological interventions that could potentially lead to novel treatments for pulmonary diseases.

Acute vaping exacerbates microbial pneumonia due to calcium (Ca2+) dysregulation

As electronic cigarette (E-cig) use, also known as "vaping", has rapidly increased in popularity, data regarding potential pathologic effects are recently emerging. Recent associations between vaping and lung pathology have led to an increased need to scrutinize E-cigs for adverse health impacts. Our previous work (and others) has associated vaping with Ca2+-dependent cytotoxicity in cultured human airway epithelial cells. Herein, we develop a vaped e-liquid pulmonary exposure mouse model to evaluate vaping effects in vivo. Using this model, we demonstrate lung pathology through the use of preclinical measures, that is, the lung wet: dry ratio and lung histology/H&E staining. Further, we demonstrate that acute vaping increases macrophage chemotaxis, which was ascertained using flow cytometry-based techniques, and inflammatory cytokine production, via Luminex analysis, through a Ca2+-dependent mechanism. This increase in macrophage activation appears to exacerbate pulmonary pathology resulting from microbial infection. Importantly, modulating Ca2+ signaling may present a therapeutic direction for treatment against vaping-associated pulmonary inflammation.

Vaping Exacerbates Coronavirus-Related Pulmonary Infection in a Murine Model

Though the current preponderance of evidence indicates the toxicity associated with the smoking of tobacco products through conventional means, less is known about the role of "vaping" in respiratory disease. "Vaping" is described as the use of electronic cigarettes (E-Cigarettes or E-Cigs), which has only more recently been available to the public (∼10 years) but has quickly emerged as a popular means of tobacco consumption worldwide. The World Health Organization (WHO) declared the SARS-CoV-2 outbreak as a global pandemic in March 2020. SARS-CoV-2 can easily be transmitted between people in close proximity through direct contact or respiratory droplets to develop coronavirus infectious disease 2019 (COVID-19). Symptoms of COVID-19 range from a mild flu-like illness with high fever to severe respiratory distress syndrome and death. The risk factors for increased disease severity remain unclear. Herein, we utilize a murine-tropic coronavirus (beta coronavirus) MHV-A59 along with a mouse model and measures of pathology (lung weight/dry ratios and histopathology) and inflammation (ELISAs and cytokine array panels) to examine whether vaping may exacerbate the pulmonary disease severity of coronavirus disease. While vaping alone did result in some noted pathology, mice exposed with intranasal vaped e-liquid suffered more severe mortality due to pulmonary inflammation than controls when exposed to coronavirus infection. Our data suggest a role for vaping in increased coronavirus pulmonary disease in a mouse model. Furthermore, our data indicate that disease exacerbation may involve calcium (Ca2+) dysregulation, identifying a potential therapeutic intervention.

Calcium Signaling Derangement and Disease Development and Progression

The importance of intracellular calcium (Ca2+) in regulating integral biological functions such as cell division, cell motility, autophagy, apoptosis and gene transcription through its capacity as a ubiquitous second messenger is clear [...].

Effects of E-Cigarette Exposure on Prenatal Life and Childhood Respiratory Health: A Review of Current Evidence

In the last decade, widespread use of E-cigarettes (EC) has occurred all over the world. Whereas, a large amount of evidence on harm to children from conventional cigarette exposure is available, data on health effects in this population throughout different vulnerability windows are still a matter of concern. Exposure to EC during pregnancy may compromise placental function, resulting in fetal structural abnormalities. Specifically, this may cause physio-pathologic changes in the developing lung, which in turn may impair respiratory health later in life. Furthermore, there is evidence that using EC can cause both short- and long-term respiratory problems in the pediatric population and there is great concern for future young people with nicotine addiction. The low parental perception of the risks connected to EC exposure for children increases their susceptibility to harmful effects from passive vaping. This minireview aims to summarize the current evidence focusing on: (i) prenatal effects of EC passive exposure; (ii) post-natal respiratory effects of EC exposure in youth; (iii) parental attitudes toward EC use and perception of children's health risks connected to EC exposure; and (iv) addressing gaps in our current evidence.