Pilot Study to Detect Genes Involved in DNA Damage and Cancer in Humans: Potential Biomarkers of Exposure to E-Cigarette Aerosols

The Toxicological Effects of e-Cigarette Use in the Upper Airway: A Scoping Review

OBJECTIVE

While evidence continues to emerge on the negative health effects of electronic cigarettes (e-cigarettes) on the lungs, little is known regarding their deleterious effects on the upper airway. The purpose of this review is to summarize the toxicological effects of e-cigarettes, and their components, on the upper airway.

DATA SOURCES

PubMed, SCOPUS, EMBASE databases.

REVIEW METHODS

Systematic searches were performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines from 2003 to 2023. Studies were included if they investigated the toxicological effects of e-cigarette exposure on human or animal upper airway tissue. Two authors independently screened, reviewed, and appraised all included articles.

RESULTS

A total of 822 unique articles were identified, of which 53 met inclusion criteria and spanned subsites including the oral cavity (22/53 studies), nasal cavity/nasopharynx (13/53), multiple sites (10/53), larynx (5/53), trachea (2/53), and oropharynx (1/53). The most commonly observed consequences of e-cigarette use on the upper airway included: proinflammatory (15/53 studies), histological (13/53), cytotoxicity (11/53), genotoxicity (11/53), and procarcinogenic (6/53). E-cigarette humectants independently induced toxicity at multiple upper airway subsites, however, effects were generally amplified when flavoring(s) and/or nicotine were added. Across almost all studies, exposure to cigarette smoke exhibited increased toxicity in the upper airway compared with exposure to e-cigarette vapor.

CONCLUSION

Current data suggest that while e-cigarettes are generally less harmful than traditional cigarettes, they possess a distinct toxicological profile that is enhanced upon the addition of flavoring(s) and/or nicotine. Future investigations into underexamined subsites, such as the oropharynx and hypopharynx, are needed to comprehensively understand the effects of e-cigarettes on the upper airway.

Impact of electronic cigarettes on pediatric, adolescent and young adult leukemia patients

Electronic cigarettes, which deliver an aerosolized, nicotine-containing product upon inhalation, are a public health issue that continue to gain popularity among adolescents and young adults in the United States. Use of electronic cigarettes is wide, and extends to pediatric patients with multiple comorbidities, including childhood cancer, leaving them vulnerable to further negative health outcomes. Acute leukemias are the most common type of cancer in pediatric populations, and treatment outcomes for these patients are improving; consequently, there is an increased emphasis on the effect of behavioral lifestyle factors on quality of life in survivorship. The rate of electronic cigarette use is higher among pediatric patients with a history of cancer than those without a history of cancer. Because electronic cigarettes are relatively new, much about their acute and long-term consequences remains unknown, as is their effect on therapy outcomes and long-term survivorship. This review article summarizes current knowledge about electronic cigarettes, including their composition and the trends in use among pediatric patients. Furthermore, this review provides a comprehensive description of the impact electronic cigarettes have on leukemia development, treatment and survivorship and highlights gaps in knowledge that will be necessary for developing recommendations, management strategies, and tailored treatments for pediatric leukemia patients and survivors who use these nicotine products.

Sex-specific lung inflammation and mitochondrial damage in a model of electronic cigarette exposure in asthma

The prevalence of electronic cigarette (EC) use among adult with asthma has continued to increase over time, in part due to the belief of being less harmful than smoking. However, the extent of their toxicity and the involved mechanisms contributing to the deleterious impact of EC exposure on patients with preexisting asthma have not been delineated. In the present project, we tested the hypothesis that EC use contributes to respiratory damage and worsening inflammation in the lungs of patients with asthma. To define the consequences of EC exposure in established asthma, we used a mouse model with/without preexisting asthma for short-term exposure to EC aerosols. C57/BL6J mice were sensitized and challenged with a DRA (dust mite, ragweed, Aspergillus fumigates, 200 µg/mL) mixture and exposed daily to EC with nicotine (2% nicotine in 30:70 propylene glycol: vegetable glycerin) or filtered air for 2 wk. The mice were evaluated at 24 h after the final EC exposure. After EC exposure in asthmatic mice, lung inflammatory cell infiltration and goblet cell hyperplasia were increased, whereas EC alone did not cause airway inflammation. Our data also show that mitochondrial DNA (mtDNA) content and a key mtDNA regulator, mitochondrial transcription factor A (TFAM), are reduced in asthmatic EC-exposed mice in a sex-dependent manner. Together, these results indicate that TFAM loss in lung epithelium following EC contributes to male-predominant sex pathological differences, including mitochondrial damage, inflammation, and remodeling in asthmatic airways.NEW & NOTEWORTHY Respiratory immunity is dysregulated in preexisting asthma, and further perturbations by EC use could exacerbate asthma severity. However, the extent of their toxicity and the involved mechanisms contributing to the deleterious impact of EC exposure on patients with preexisting asthma have not been delineated. We found that EC has unique biological impacts in lungs and potential sex differences with loss of TFAM, a key mtDNA regulator, in lung epithelial region from our animal EC study.

Mechanisms of E-Cigarette Vape-Induced Epithelial Cell Damage

E-cigarette use has been reported to affect cell viability, induce DNA damage, and modulate an inflammatory response resulting in negative health consequences. Most studies focus on oral and lung disease associated with e-cigarette use. However, tissue damage can be found in the cardio-vascular system and even the bladder. While the levels of carcinogenic compounds found in e-cigarette aerosols are lower than those in conventional cigarette smoke, the toxicants generated by the heat of the vaping device may include probable human carcinogens. Furthermore, nicotine, although not a carcinogen, can be metabolized to nitrosamines. Nitrosamines are known carcinogens and have been shown to be present in the saliva of e-cig users, demonstrating the health risk of e-cigarette vaping. E-cig vape can induce DNA adducts, promoting oxidative stress and DNA damage and NF-kB-driven inflammation. Together, these processes increase the transcription of pro-inflammatory cytokines. This creates a microenvironment thought to play a key role in tumorigenesis, although it is too early to know the long-term effects of vaping. This review considers different aspects of e-cigarette-induced cellular changes, including the generation of reactive oxygen species, DNA damage, DNA repair, inflammation, and the possible tumorigenic effects.

DNA damage in human oral cells induced by use of e-cigarettes

The use of electronic cigarettes (e-cigarettes) has increased rapidly in the United States, especially among high school students. e-Cigarettes contain some recognized carcinogens and may induce DNA damage in oral cells. The aim of this review is to summarize studies reporting DNA adducts or other types of DNA damage in oral cells in vitro or in vivo upon exposure to e-cigarette vapor and to evaluate the possible connections between e-cigarette exposure and oral cancer. Three databases including PubMed, Scopus, and EMBASE and gray literature were searched for articles published up to April 24, 2022. After screening 321 articles, we extracted 27 for further investigation. Based on the inclusion criteria, 22 articles were eligible for this review. The in vitro studies demonstrate that e-cigarette liquid or vapor can induce DNA damage, oxidative stress, DNA double-stranded breaks, apoptosis, cytotoxicity, and genotoxicity in different types of oral cells. The clinical studies showed that e-cigarette users have significantly higher levels of N'-nitrosonornicotine, acrolein DNA adducts, metanuclear anomalies, gene regulation, and lactate dehydrogenase enzyme expression and significantly lower levels of apurinic/apyrimidinic sites than non-users. Comparison of micronuclei levels between e-cigarette users and non-users gave inconsistent results. e-Cigarettes are implicated in DNA damage to oral cells, but publications to date present limited evidence. Future studies with larger sample sizes are required to investigate the long-term consequences of e-cigarette use.

Molecular insights into the role of electronic cigarettes in oral carcinogenesis

Electronic cigarette (EC) usage or vaping has seen a significant rise in recent years across various parts of the world. They have been publicized as a safe alternative to smoking; however, this is not supported strongly by robust research evidence. Toxicological analysis of EC liquid and aerosol has revealed presence of several toxicants with known carcinogenicity. Oral cavity is the primary site of exposure of both cigarette smoke and EC aerosol. Role of EC in oral cancer is not as well-researched as that of traditional smoking. However, several recent studies have shown that it can lead to a wide range of potentially carcinogenic molecular events in oral cells. This review delineates the oral carcinogenesis potential of ECs at the molecular level, providing a summary of the effects of EC usage on cancer therapy resistance, cancer stem cells (CSCs), immune evasion, and microbiome dysbiosis, all of which may lead to increased tumor malignancy and poorer patient prognosis. This review of literature indicates that ECs may not be as safe as they are perceived to be, however further research is needed to definitively determine their oncogenic potential.

Impact of Electronic Cigarettes on the Upper Aerodigestive Tract: A Comprehensive Review for Otolaryngology Providers

Objective

The use and effects of electronic (e)-cigarettes (e-cigs) are particularly relevant for otolaryngology providers as tobacco plays a major role in benign and malignant diseases of the upper aerodigestive tract. This review aims to (1) summarize the recent policies regarding e-cigs and important patterns of use and (2) serve as a comprehensive resource for clinical providers on the known biologic and clinical effects of e-cigs on the upper aerodigestive tract.

Data Sources

PubMed/MEDLINE.

Review Methods

We conducted a narrative review on (1) general information on e-cig use and informative findings in the lower respiratory system and a comprehensive review on (2) the effects of e-cigs on cell and animal models and the clinical implications of these products on human health as is relevant to otolaryngology.

Conclusions

Although e-cigs are likely less harmful than conventional cigarettes, preliminary research on e-cigs suggest several deleterious effects including in the upper aerodigestive tract. Due to this, there has been increased interest in restricting e-cig usage, particularly among the adolescent population, and caution in recommending e-cigs to current smokers.

Implications for Practice

Chronic e-cig use is likely to have clinical implications. It is critical for otolaryngology providers to be aware of the rapidly changing regulations and use patterns regarding e-cigs and how e-cigs influence human health, particularly with regards to the upper aerodigestive tract, to accurately council patients regarding potential risks and benefits of use.

Electronic Cigarettes: A Pro-Con Review of the Current Literature

Electronic cigarettes (e-cigarettes, e-cigs, or electronic nicotine delivery systems) are battery-operated devices typically containing glycerol and/or propylene glycol-based solutions with varying nicotine content, known as e-liquids. Although e-cigarettes were originally developed as a potentially less harmful alternative to traditional combustible tobacco cigarette smokers, several factors have driven their popularity among smokers and nonsmokers alike, including their sleek product designs, innumerable appealing flavors, lack of combustible smoke and odor, and high potential nicotine concentrations. Furthermore, many advocates have promoted the idea that e-cigarettes are safe to use, or at least safer than conventional tobacco, despite limited longitudinal data to support these claims. Here, we examine what is known about the impacts of e-cigarette use on traditional cigarette smoking cessation, lung health, and youth and young adult tobacco product exposure. Upon review of the currently available literature, the negative effects of e-cigarette use seem to outweigh any potential benefit, because the available evidence does not confirm the use of e-cigarettes as an effective strategy for supporting traditional combustible tobacco cigarette smoking cessation, particularly given the emerging adverse effects on lung health and the potential future public health effects of e-cigarette adoption among a burgeoning new generation of tobacco product users.

E-Cigarette Toxicology

Since the spread of tobacco from the Americas hundreds of years ago, tobacco cigarettes and, more recently, alternative tobacco products have become global products of nicotine addiction. Within the evolving alternative tobacco product space, electronic cigarette (e-cigarette) vaping has surpassed conventional cigarette smoking among adolescents and young adults in the United States and beyond. This review describes the experimental and clinical evidence of e-cigarette toxicity and deleterious health effects. Adverse health effects related to e-cigarette aerosols are influenced by several factors, including e-liquid components, physical device factors, chemical changes related to heating, and health of the e-cigarette user (e.g., asthmatic). Federal, state, and local regulations have attempted to govern e-cigarette flavors, manufacturing, distribution, and availability, particularly to underaged youths. However, the evolving e-cigarette landscape continues to impede timely toxicological studies and hinder progress made toward our understanding of the long-term health consequence of e-cigarettes. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.