Electronic cigarette exposure triggers neutrophil inflammatory responses

E-Cigarette effects on oral health: A molecular perspective

Electronic cigarettes (e-cigarettes) have emerged as a potential alternative to traditional smoking and may aid in tobacco harm reduction and smoking cessation. E-cigarette use has notably increased, especially among young non-tobacco users, raising concerns due to the unknown long-term health effects. The oral cavity is the first and one of the most crucial anatomical sites for the deposition of e-cigarette aerosols. E-cigarette aerosols contain nicotine, flavors, volatile organic compounds, heavy metals, carcinogens, and other hazardous substances. These aerosols impact the oral cavity, disrupting host-microbial interactions and triggering gingivitis and systemic diseases. Furthermore, oral inflammation and periodontitis can be caused by proinflammatory cytokines induced by e-cigarette aerosols. The toxic components of e-cigarette aerosols increase the cellular reactive oxygen species (ROS) levels, reduce antioxidant capacity, increase DNA damage, and disrupt repair processes, which may further contribute to harmful effects on oral epithelum, leading to inflammatory and pre-malignant oral epithelial lesions. In this review, we analyze the toxicological properties of compounds in e-cigarette aerosols, exploring their cytotoxic, genotoxic, and inflammatory effects on oral health and delving into the underlying molecular mechanisms. Further research is essential to understand the impact of e-cigarettes on oral health and make informed regulatory decisions based on reliable scientific evidence.

Immunological Effects of Electronic Cigarette Use: A Review of Current Evidence

Electronic cigarettes (EC) have emerged as a popular alternative to traditional tobacco products, but their impact on immune function has raised significant health concerns. This review explores the immunological effects of EC exposure, focusing on innate and adaptive immune responses. Electronic cigarette aerosol (ECA) induces widespread inflammation. These changes compromise immune cell function, impairing neutrophil chemotaxis, phagocytosis, and oxidative burst while increasing macrophage and dendritic cell recruitment and activation. ECA also disrupts epithelial barriers, increasing susceptibility to bacterial and viral infections. Studies show enhanced biofilm formation in bacteria such as Staphylococcus aureus and Streptococcus pneumoniae and impaired antiviral responses against pathogens like influenza A and SARS-CoV-2. Additionally, EC exposure modulates adaptive immunity, affecting T and B cell function and increasing systemic inflammatory markers. The long-term consequences of these immunological disruptions include heightened risks for chronic inflammatory diseases, respiratory infections, and potentially autoimmune conditions. The widespread adoption of EC, particularly among younger users, poses a growing public health challenge. As the popularity of vaping continues to rise, these immunological disruptions could result in increased healthcare burdens in the future, with higher rates of infections, chronic inflammatory diseases, and immune system-related disorders among those who begin using e-cigarettes at a young age. Understanding the full scope of EC-related health risks is essential for informing public health policies and protecting future generations from the potential long-term effects of vaping.

E-Cigarettes induce expression of procoagulant tissue factor in cultivated human endothelial cells

BACKGROUND

E-cigarettes (ECIG) are proposed as an alternative for regular tobacco users with less dangerous effects for health. Several studies demonstrated that ECIG exert deleterious cardiovascular effects and promote platelet dependent thrombosis. However, ECIG role on Tissue Factor-dependent thrombosis is still unknown. Dysfunctional endothelial cells (ECs) are known to express Tissue Factor (TF) on their surface. Aim of the present study was to investigate whether ECIG might promote TF expression in ECs, shifting them to a pro thrombotic phenotype.

METHODS

Human Umbilical Vein Endothelial Cells (HUVEC) were incubated with increasing doses of ECIG (commercially available and mix of propylene glycol/vegetable glycerine/nicotine 18 mg/mL) up to 1.8 mg/mL. TF gene expression and protein levels were assessed at different time points by Real Time PCR and Western Blot, respectively. TF surface expression and activity were also measured by FACS analysis and coagulation assay. Finally, NF-kB translocation was investigated as possible mechanism of action. Potential protective effects by Rosuvastatin were also investigated.

RESULTS

ECIG significantly increased TF expression at both gene and protein levels in a time and dose dependent manner. Surface expression and procoagulant activity were increased as well. These phenomena appeared modulated by the NF-κB pathway. Rosuvastatin reduced ECIG effects on TF-mRNA.

CONCLUSIONS

Although in vitro, we indicate that ECIG promote a pro thrombotic phenotype in ECs via expression of functional TF. Data of the present study permit to shed a brighter light on the still partially unresolved issue about the role of ECIG in development of cardiovascular diseases suggesting that they might represent a potential risk factor for thrombotic cardiovascular events.

Using single-cell RNA sequencing and bulk RNA sequencing data to reveal a correlation between smoking and neutrophil activation in esophageal carcinoma patients

BACKGROUND

Cigarette smoking is considered as a major risk factor for esophageal carcinoma (ESCA) patients. Neutrophil activation plays a key role in cancer development and progression. However, the relationship between cigarette smoking and neutrophils in ESCA patients remained unclear.

METHODS

Single-cell RNA sequencing (scRNA-seq) and bulk RNA sequencing data were obtained from public databases. Uniform manifold approximation and projection (UMAP) was used to perform downscaling and clustering based on scRNA-seq data. The module genes associated with smoking in ESCA patients were filtered by weighted gene co-expression network analysis (WGCNA). Using the "AUCell" package, the enrichment of different cell subpopulations and gene collections were assessed. "CellChat" and "CellphoneDB" were used to infer the probability and significance of ligand-receptor interactions between different cell subpopulations.

RESULTS

WGCNA was performed to screened module genes associated with smoking in ESCA patients from MEdarkquosie, MEturquoise, and MEgreenyellow. Next, eight cell clusters were identified, and using the AUCell score, we determined that neutrophil clusters were more active in the gene modules associated with smoking in ESCA patients. Two neutrophil subtypes, Neutrophils 1 and Neutrophils 2, exhibited greater enrichment in inflammatory response regulation, intercellular adhesion, and regulation of T cell activation. Furthermore, we found that neutrophils may pass through AMPT-(ITGA5 + ITGB1) and ICAM1-AREG in order to promote the development of ESCA, and that the expression levels of the receptor genes insulin-degrading enzyme and ITGB1 were significantly and positively correlated with cigarette smoking per day.

CONCLUSION

Combining smoking-related gene modules and scRNA-seq, the current findings revealed the heterogeneity of neutrophils in ESCA and a tumor-promoting role of neutrophils in the tumor microenvironment of smoking ESCA patients.

Impact of electronic cigarettes (e-cigs) and heat-not-burn/heated tobacco products (HnB/HTP) on asthma and chronic obstructive pulmonary disease: a viewpoint of the Italian Society of Internal Medicine

The association of cigarette smoking with several severe and very severe diseases (oncological, cardiovascular, respiratory) which have dramatic epidemiological, medical, and financial impact, is a well-known public threat. Asthma and chronic obstructive pulmonary disease (COPD) are highly prevalent diseases in Italy, posing significant public health challenges. Tobacco smoking, a primary risk factor for COPD and a common asthma trigger, remains a critical preventable public health issue. While universally acknowledged that quitting smoking drastically reduces the risk of smoking-related health issues, a significant portion of smokers and patients find quitting challenging or undesirable, hence a need for new ways to deal with it. A worth considering alternative might be the switch to electronic cigarettes (e-cig), and heat-not-burn/heated tobacco products (HnB/HTP). Emerging evidence suggests potential benefits in asthma and COPD management when transitioning from traditional smoking to e-cigs or HnB devices. However, the effectiveness of these products in facilitating smoking cessation is still debated, alongside concerns about their role in promoting smoking initiation among non-smokers. Internists are among the physicians who most frequently assist patients with smoking-related diseases, and in this perspective they cannot avoid paying attention to the progressive diffusion of smoking products alternative to the traditional cigarette, and to the controversies with respect to their use. In this context, the Italian Society of Internal Medicine, also recognizing a growing need for clarity for healthcare providers, has undertaken a comprehensive analysis of existing literature to offer an informed perspective on the health impact of e-cigs and HnB/HTP on asthma and COPD.

Advances in non-type 2 severe asthma: from molecular insights to novel treatment strategies

Asthma is a prevalent pulmonary disease that affects more than 300 million people worldwide and imposes a substantial economic burden. While medication can effectively control symptoms in some patients, severe asthma attacks, driven by airway inflammation induced by environmental and infectious exposures, continue to be a major cause of asthma-related mortality. Heterogeneous phenotypes of asthma include type 2 (T2) and non-T2 asthma. Non-T2 asthma is often observed in patients with severe and/or steroid-resistant asthma. This review covers the molecular mechanisms, clinical phenotypes, causes and promising treatments of non-T2 severe asthma. Specifically, we discuss the signalling pathways for non-T2 asthma including the activation of inflammasomes, interferon responses and interleukin-17 pathways, and their contributions to the subtypes, progression and severity of non-T2 asthma. Understanding the molecular mechanisms and genetic determinants underlying non-T2 asthma could form the basis for precision medicine in severe asthma treatment.

Molecular changes underlying pulmonary emphysema and chronic bronchitis in Chronic Obstructive Pulmonary Disease: An updated review

The aim of this review is to update and synthesize the molecular mechanisms that lead to the heterogeneous effect on tissue remodeling observed in the two most important clinical phenotypes of chronic obstructive pulmonary disease (COPD), pulmonary emphysema (PE) and chronic bronchitis (CB). Clinical and experimental evidence suggests that this heterogeneous response to promote PE, CB, or both, is related to differentiated genetic, epigenetic, and molecular conditions. Specifically, a tendency toward PE could be related to a variant in the DSP gene, SIRT1 downregulation, macrophage polarization to M1, as well as the involvement of the noncanonical Wnt5A signaling pathway, among other alterations. Additionally, in advanced stages of COPD, PE development is potentiated by dysregulations in autophagy, which promotes senescence and subsequently cell apoptosis, through exacerbated inflammasome activation and release of caspases. On the other hand, CB or the pro-fibrotic phenotype could be potentiated by the downregulated activity of HDAC2, the activation of the TGF-β/Smad or Wnt/β-catenin signaling pathways, macrophage polarization to M2, upregulation of TIMP-1, and/or the presence of the epithelial-mesenchymal transition (EMT) mechanism. Interestingly, the upregulated activity of MMPs, especially MMP-9, is widely involved in the development of both phenotypes. Furthermore, MMP-9 and MMP-12 enhance the severity, perpetuation, and exacerbation of COPD, as well as the development of autoimmunity in this disease.

Electronic cigarettes and cardiovascular disease: epidemiological and biological links

Electronic cigarettes (e-cigarettes), as alternative nicotine delivery methods, has rapidly increased among youth and adults in recent years. However, cardiovascular safety is an important consideration regarding e-cigarettes usage. e-cigarette emissions, including nicotine, propylene glycol, flavorings, nitrosamine, and metals, might have adverse effects on cardiovascular health. A large body of epidemiological evidence has indicated that e-cigarettes are considered an independent risk factor for increased rates of cardiovascular disease occurrence and death. The incidence and mortality of various types of cardiovascular disease, such as cardiac arrhythmia, hypertension, acute coronary syndromes, and heart failure, have a modest growth in vapers (users of e-cigarettes). Although the underlying biological mechanisms have not been fully understood, studies have validated that oxidative stress, inflammation, endothelial dysfunction, atherosclerosis, hemodynamic effects, and platelet function play important roles in which e-cigarettes work in the human body. This minireview consolidates and discusses the epidemiological and biological links between e-cigarettes and various types of cardiovascular disease.

A Chymotrypsin-Dependent Live-Attenuated Influenza Vaccine Provides Protective Immunity against Homologous and Heterologous Viruses

Influenza virus is one of the main pathogens causing respiratory diseases in humans. Vaccines are the most effective ways to prevent viral diseases. However, the limited protective efficacy of current influenza vaccines highlights the importance of novel, safe, and effective universal influenza vaccines. With the progress of the COVID-19 pandemic, live-attenuated vaccines delivered through respiratory mucosa have shown robustly protective efficacy. How to obtain a safe and effective live-attenuated vaccine has become a major challenge. Herein, using the influenza virus as a model, we have established a strategy to quickly obtain a live-attenuated vaccine by mutating the cleavage site of the influenza virus. This mutated influenza virus can be specifically cleaved by chymotrypsin. It has similar biological characteristics to the original strain in vitro, but the safety is improved by at least 100 times in mice. It can effectively protect against lethal doses of both homologous H1N1 and heterologous H5N1 viruses post mucosal administration, confirming that the vaccine generated by this strategy has good safety and broad-spectrum protective activities. Therefore, this study can provide valuable insights for the development of attenuated vaccines for respiratory viruses or other viruses with cleavage sites.

Deflamin Attenuated Lung Tissue Damage in an Ozone-Induced COPD Murine Model by Regulating MMP-9 Catalytic Activity

Chronic obstructive pulmonary disease (COPD) is comprised of histopathological alterations such as pulmonary emphysema and peribronchial fibrosis. Matrix metalloproteinase 9 (MMP-9) is one of the key enzymes involved in both types of tissue remodeling during the development of lung damage. In recent studies, it was demonstrated that deflamin, a protein component extracted from Lupinus albus, markedly inhibits the catalytic activity of MMP-9 in experimental models of colon adenocarcinoma and ulcerative colitis. Therefore, in the present study, we investigated for the first time the biological effect of deflamin in a murine COPD model induced by chronic exposure to ozone. Ozone exposure was carried out in C57BL/6 mice twice a week for six weeks for 3 h each time, and the treated group was orally administered deflamin (20 mg/kg body weight) after each ozone exposure. The histological results showed that deflamin attenuated pulmonary emphysema and peribronchial fibrosis, as evidenced by H&E and Masson's trichrome staining. Furthermore, deflamin administration significantly decreased MMP-9 activity, as assessed by fluorogenic substrate assay and gelatin zymography. Interestingly, bioinformatic analysis reveals a plausible interaction between deflamin and MMP-9. Collectively, our findings demonstrate the therapeutic potential of deflamin in a COPD murine model, and suggest that the attenuation of the development of lung tissue damage occurs by deflamin-regulated MMP-9 catalytic activity.

Exhaled nitric oxide levels in COPD patients who use electronic cigarettes

Emerging data from clinical studies have shown pro-inflammatory effects associated with e-cigarette use. Fractional exhaled nitric oxide (FeNO) is a biomarker of pulmonary type 2 (T2) inflammation. The effect of chronic e-cigarette use on FeNO is unclear. The aim of this study was to compare FeNO levels in COPD ex-smokers who use e-cigarettes (COPDE + e-cig) to COPDE ex-smokers (COPDE) and COPD current smokers (COPDS). FeNO levels were significantly higher in COPDE + e-cig (median 16.2 ppb) and COPDE (median 18.0 ppb) compared to COPDS (median 7.6 ppb) (p = 0.0003 and p < 0.0001 respectively). There was no difference in FeNO levels between COPDE + e-cig compared to COPDE (p > 0.9). The importance of our results is that electronic cigarette use does not alter the interpretation of FeNO results, and so does not interfere with the use of FeNO as a practical biomarker of T2 inflammation, unlike current cigarette smoking in COPD. Whilst the effect of electronic cigarette use on FeNO levels is not the same as cigarette smoke, this cannot be taken as evidence that electronic cigarettes are harmless. These differential pulmonary effects can be attributed to differences in the chemical composition of the two products.

The potential health effects associated with electronic-cigarette

A good old gateway theory that electronic-cigarettes (e-cigarettes) are widely recognized as safer tobacco substitutes. In actuality, demographics also show that vaping cannibalizes smoking, the best explanation of the data is the "common liability". However, the utilization of e-cigarette products remains a controversial topic at present. Currently, there has been a widespread and substantial growth in e-cigarette use worldwide owing to their endless new flavors and customizable characteristics. Furthermore, e-cigarette has grown widespread among smokers as well as non-smokers, including adolescents and young adults. And some studies have shown that e-cigarette users are at greater risk to start using combustible cigarettes while e-cigarettes use was also observed the potential benefits to people who want to quit smoking or not. Although it is true that e-cigarettes generally contain fewer toxic substances than combustible cigarettes, this does not mean that the chemical composition in e-cigarettes aerosols poses absolutely no risks. While concerns about toxic substances in e-cigarettes and their widespread use in the population are reasonable, it is also crucial to consider that e-cigarettes have been associated with the potential for promoting smoking cessation and the clinically relevant improvements in users with smoking-related pathologies. Meanwhile, there is still short of understanding of the health impacts associated with e-cigarette use. Therefore, in this review, we discussed the health impacts of e-cigarette exposure on oral, nasal, pulmonary, cardiovascular systems and brain. We aspire for this review to change people's previous perceptions of e-cigarettes and provide them with a more balanced perspective. Additionally, we suggest appropriate adjustments on regulation and policy for e-cigarette to gain greater public health benefits.

Evaluation of toxicity of heated tobacco products aerosol and cigarette smoke to BEAS-2B cells based on 3D biomimetic chip model

It is still a controversial topic about evaluating whether heated tobacco products (HTP) really reduce harm, which involves the choice of an experimental model. Here, a three-dimensional (3D) biomimetic chip model was used to evaluate the toxicity of aerosols came from HTP and smoke produced by cigarettes (Cig). Based on cell-related experiments, we found that the toxicity of Cig smoke extract diluted four times was also much higher than that of undiluted HTP, showing higher oxidative stress response and cause mitochondrial dysfunction. Meanwhile, both tobacco products all affect the tricarboxylic acid cycle (TCA), which is manifested by a significant decrease in the mRNA expression of TCA key rate-limiting enzymes. Summarily, 3D Biomimetic chip technology can be used as an ideal model to evaluate HTP. It can provide important data for tobacco risk assessment when 3D chip model was used. Our experimental results showed that HTP may be less harmful than tobacco cigarettes, but it does show significant cytotoxicity with the increase of dose. Therefore, the potential clinical effects of HTP on targeted organs such as lung should be further studied.

E-cigarette vapor renders neutrophils dysfunctional due to filamentous actin accumulation

BACKGROUND

Electronic cigarette (e-cigarette) use continues to rise despite concerns of long-term effects, especially the risk of developing lung diseases such as chronic obstructive pulmonary disease. Neutrophils are central to the pathogenesis of chronic obstructive pulmonary disease, with changes in phenotype and function implicated in tissue damage.

OBJECTIVE

We sought to measure the impact of direct exposure to nicotine-containing and nicotine-free e-cigarette vapor on human neutrophil function and phenotype.

METHODS

Neutrophils were isolated from the whole blood of self-reported nonsmoking, nonvaping healthy volunteers. Neutrophils were exposed to 40 puffs of e-cigarette vapor generated from e-cigarette devices using flavorless e-cigarette liquids with and without nicotine before functions, deformability, and phenotype were assessed.

RESULTS

Neutrophil surface marker expression was altered, with CD62L and CXCR2 expression significantly reduced in neutrophils treated with e-cigarette vapor containing nicotine. Neutrophil migration to IL-8, phagocytosis of Escherichia coli and Staphylococcus aureus pHrodo bioparticles, oxidative burst response, and phorbol 12-myristate 13-acetate-stimulated neutrophil extracellular trap formation were all significantly reduced by e-cigarette vapor treatments, independent of nicotine content. E-cigarette vapor induced increased levels of baseline polymerized filamentous actin levels in the cytoplasm, compared with untreated controls.

CONCLUSIONS

The significant reduction in effector neutrophil functions after exposure to high-power e-cigarette devices, even in the absence of nicotine, is associated with excessive filamentous actin polymerization. This highlights the potentially damaging impact of vaping on respiratory health and reinforces the urgency of research to uncover the long-term health implications of e-cigarettes.

Safety and efficacy of e-cigarettes in those with atherosclerotic disease: a review

Smoking cessation is the most effective intervention to reduce mortality in patients with established atherosclerotic cardiovascular disease (ASCVD), with 'e-cigarettes' becoming an increasingly used intervention to achieve smoking cessation. The current review aims to summarise the current evidence base for their efficacy and safety in the ASCVD cohort. A search of the PUBMED and MEDLINE databases using the terms 'e-cigarette', 'cessation', 'safety' and 'efficacy' since 2012 yielded 706 results. Both observational and experimental studies were included, while those with an unavailable full text, non-English or duplicates were excluded, yielding 78 relevant articles, with 13 subsequent additional articles included from a search of reference lists, for a total of 91 included papers. E-cigarette vapour contains many known pro-atherosclerotic substances and has been demonstrated to potentiate traditional atherosclerotic mechanisms. While e-cigarettes may be more effective in promoting smoking cessation in the general population over a medium term (>6 months), when compared with nicotine replacement therapy (NRT), few studies specifically examined those with ASCVD, despite the latter having a higher baseline quit rate (52% vs 2%). Most studies compare e-cigarettes with NRT alone and do not include pharmacotherapy, which may be more effective in the ASCVD cohort. The single randomised controlled trial addressing the research question favoured traditional methods. Those that successfully quit smoking using e-cigarettes are more likely to continue to use the intervention at 1 year (90% vs 9%). Conflicting advice exists regarding the utilisation of e-cigarettes for smoking cessation. E-cigarettes may be inferior to standard care for smoking cessation in those with ASCVD, and their use is likely to promote the key drivers of the atherosclerotic process already active in this cohort.

Multimodal Diagnostics of Changes in Rat Lungs after Vaping

(1) Background: The use of electronic cigarettes has become widespread in recent years. The use of e-cigarettes leads to milder pathological conditions compared to traditional cigarette smoking. Nevertheless, e-liquid vaping can cause morphological changes in lung tissue, which affects and impairs gas exchange. This work studied the changes in morphological and optical properties of lung tissue under the action of an e-liquid aerosol. To do this, we implemented the "passive smoking" model and created the specified concentration of aerosol of the glycerol/propylene glycol mixture in the chamber with the animal. (2) Methods: In ex vivo studies, the lungs of Wistar rats are placed in the e-liquid for 1 h. For in vivo studies, Wistar rats were exposed to the e-liquid vapor in an aerosol administration chamber. After that, lung tissue samples were examined ex vivo using optical coherence tomography (OCT) and spectrometry with an integrating sphere. Absorption and reduced scattering coefficients were estimated for the control and experimental groups. Histological sections were made according to the standard protocol, followed by hematoxylin and eosin staining. (3) Results: Exposure to e-liquid in ex vivo and aerosol in in vivo studies was found to result in the optical clearing of lung tissue. Histological examination of the lung samples showed areas of emphysematous expansion of the alveoli, thickening of the alveolar septa, and the phenomenon of plasma permeation, which is less pronounced in in vivo studies than for the exposure of e-liquid ex vivo. E-liquid aerosol application allows for an increased resolution and improved imaging of lung tissues using OCT. Spectral studies showed significant differences between the control group and the ex vivo group in the spectral range of water absorption. It can be associated with dehydration of lung tissue owing to the hyperosmotic properties of glycerol and propylene glycol, which are the main components of e-liquids. (4) Conclusions: A decrease in the volume of air in lung tissue and higher packing of its structure under e-liquid vaping causes a better contrast of OCT images compared to intact lung tissue.

The lipolysis inhibitor acipimox reverses the cardiac phenotype induced by electronic cigarettes

Electronic cigarettes (e-cigarettes) are a prevalent alternative to conventional nicotine cigarettes among smokers and people who have never smoked. Increased concentrations of serum free fatty acids (FFAs) are crucial in generating lipotoxicity. We studied the effects of acipimox, an antilipolytic drug, on e-cigarette-induced cardiac dysfunction. C57BL/6J wild-type mice on high fat diet were treated with saline, e-cigarette with 2.4% nicotine [e-cigarette (2.4%)], and e-cigarette (2.4%) plus acipimox for 12 weeks. Fractional shortening and ejection fraction were diminished in mice exposed to e-cigarettes (2.4%) compared with saline and acipimox-treated mice. Mice exposed to e-cigarette (2.4%) had increased circulating levels of inflammatory cytokines and FFAs, which were diminished by acipimox. Gene Set Enrichment Analysis revealed that e-cigarette (2.4%)-treated mice had gene expression changes in the G2/M DNA damage checkpoint pathway that was normalized by acipimox. Accordingly, we showed that acipimox suppressed the nuclear localization of phospho-p53 induced by e-cigarette (2.4%). Additionally, e-cigarette (2.4%) increased the apurinic/apyrimidinic sites, a marker of oxidative DNA damage which was normalized by acipimox. Mice exposed to e-cigarette (2.4%) had increased cardiac Heme oxygenase 1 protein levels and 4-hydroxynonenal (4-HNE). These markers of oxidative stress were decreased by acipimox. Therefore, inhibiting lipolysis with acipimox normalizes the physiological changes induced by e-cigarettes and the associated increase in inflammatory cytokines, oxidative stress, and DNA damage.

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

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

The cardiovascular consequences of electronic cigarette smoking: a narrative review

INTRODUCTION

E-cigarettes have emerged as a popular alternative to traditional tobacco smoking in recent years. Despite their growing popularity, concerns have arisen regarding the cardiovascular implications of e-cigarette use.

AREAS COVERED

This narrative review aims to highlight the latest evidence on the impact of e-cigarettes on cardiovascular health.

EXPERT OPINION

Numerous studies have demonstrated that e-cigarette use can lead to acute adverse cardiovascular effects. Inhalation of e-cigarette aerosols exposes users to a wide range of potentially harmful substances that have been implicated in critical pathophysiologic pathways of cardiovascular disease, namely endothelial dysfunction, oxidative stress, inflammation, sympathetic overdrive, and arterial stiffness. While long-term epidemiological studies specifically focusing on the cardiovascular effects of e-cigarettes are still relatively scarce, early evidence suggests a potential association between e-cigarette use and an increased risk of adverse cardiovascular events. However, it is essential to recognize that e-cigarettes are relatively new products, and the full extent of their long-term cardiovascular impact has not been fully elucidated. In the meantime, promoting tobacco cessation strategies that are evidence-based and regulated, along with rigorous monitoring of e-cigarette use patterns and associated health outcomes, are essential steps in safeguarding cardiovascular health in the face of this emerging public health challenge.

The impact of e-cigarette exposure on different organ systems: A review of recent evidence and future perspectives

The use of electronic cigarettes (e-cigs) is rapidly increasing worldwide and is promoted as a smoking cessation tool. The impact of traditional cigs on human health has been well-defined in both animal and human studies. In contrast, little is known about the adverse effects of e-cigs exposure on human health. This review summarizes the impact of e-cigs exposure on different organ systems based on the rapidly expanding recent evidence from experimental and human studies. A number of growing studies have shown the adverse effects of e-cigs exposure on various organ systems. The summarized data in this review indicate that while e-cigs use causes less adverse effects on different organs compared to traditional cigs, its long-term exposure may lead to serious health effects. Data on short-term organ effects are limited and there is no sufficient evidence on long-term organ effects. Moreover, the adverse effects of secondhand and third hand e-cigs vapour exposure have not been thoroughly investigated in previous studies. Although some studies demonstrated e-cigs used as a smoking cessation tool, there is a lack of strong evidence to support it. While some researchers suggested e-cigs as a safer alternative to tobacco smoking, their long-term exposure health effects remain largely unknown. Therefore, more epidemiological and prospective studies including mechanistic studies are needed to address the potential adverse health effects of e-cigs to draw a firm conclusion about their safe use. A wide variation in e-cigs products and the lack of standardized testing methods are the major barriers to evaluating the existing data. Specific regulatory guidelines for both e-cigs components and the manufacturing process may be effective to protect consumer health.

An integral perspective of canonical cigarette and e-cigarette-related cardiovascular toxicity based on the adverse outcome pathway framework

BACKGROUND

Nowadays, cigarette smoking remains the leading cause of chronic disease and premature death, especially cardiovascular disease. As an emerging tobacco product, e-cigarettes have been advocated as alternatives to canonical cigarettes, and thus may be an aid to promote smoking cessation. However, recent studies indicated that e-cigarettes should not be completely harmless to the cardiovascular system.

AIM OF REVIEW

This review aimed to build up an integral perspective of cigarettes and e-cigarettes-related cardiovascular toxicity.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review adopted the adverse outcome pathway (AOP) framework as a pivotal tool and aimed to elucidate the association between the molecular initiating events (MIEs) induced by cigarette and e-cigarette exposure to the cardiovascular adverse outcome. Since the excessive generation of reactive oxygen species (ROS) has been widely approved to play a critical role in cigarette smoke-related CVD and may also be involved in e-cigarette-induced toxic effects, the ROS overproduction and subsequent oxidative stress are regarded as essential parts of this framework. As far as we know, this should be the first AOP framework focusing on cigarette and e-cigarette-related cardiovascular toxicity, and we hope our work to be a guide in exploring the biomarkers and novel therapies for cardiovascular injury.

Comparison of the effects of electronic cigarette vapours and tobacco smoke extracts on human neutrophils in vitro

Background

Electronic cigarettes (ECs) are electronic aerosol delivery systems composed of nicotine and various chemicals, which are widely used to facilitate smoking cessation. Although ECs are considered safer than cigarettes, they do, however, contain chemical toxicants, some of which may interact with cells of the host's innate immune system of which neutrophils constitute a key component.

Methods

The current study was designed to compare the effects of aqueous EC aerosol extracts (ECEs; with or without nicotine) with those of cigarette smoke extract (CSE) on neutrophil and platelet reactivity in vitro. Neutrophil reactivity is characterised by the generation of reactive oxygen species (ROS), degranulation (elastase release) and the release of extracellular DNA (neutrophil extracellular trap (NET) formation: NETosis), which were measured using chemiluminescence, spectrophotometric and microscopic procedures, respectively. Platelet reactivity was measured according to the magnitude of upregulated expression of the adhesion molecule CD62P on activated cells using a flow cytometric procedure.

Results

Exposure of neutrophils to either ECEs or CSE caused a significant inhibition of ROS generation and elastase release by N-formyl-l-methionyl-l-leucyl-l-phenylalanine (1 µM)-activated neutrophils. Pre-treatment of neutrophils with CSE also resulted in a marked attenuation of phorbol 12-myristate 13-acetate (6.25 nM)-mediated release of extracellular DNA, which was unaffected by the ECEs. Similarly, CSE, but not the ECEs, inhibited the expression of CD62P by platelets activated with ADP (100 µM).

Conclusions

These observations suggest that ECE aerosols may inhibit some of the immuno-protective activities of neutrophils such as ROS production and elastase release by activated cells, the effect of which was not enhanced by inclusion of nicotine. The inhibitory effects of CSE were significantly more pronounced than those of ECEs, especially so for suppression of NET formation and platelet activation. If operative in vivo, these harmful immunosuppressive effects of ECEs may compromise intrinsic pulmonary antimicrobial defence mechanisms, albeit less so than cigarette smoke.

Smoking cessation and vaccination

A significant proportion of COPD patients (∼40%) continue smoking despite knowing that they have the disease. Smokers with COPD exhibit higher levels of nicotine dependence, and have lower self-efficacy and self-esteem, which affects their ability to quit smoking. Treatment should be adapted to the needs of individual patients with different levels of tobacco dependence. The combination of counselling plus pharmacotherapy is the most effective cessation treatment for COPD. In patients with severe COPD, varenicline and bupropion have been shown to have the highest abstinence rates compared with nicotine replacement therapy. There is a lack of evidence to support that smoking cessation reduction or harm reduction strategies have benefits in COPD patients. The long-term efficacy and safety of electronic cigarettes for smoking cessation need to be evaluated in high-risk populations; therefore, it is not possible to recommend their use for smoking cessation in COPD. Future studies with the new generation of nicotine vaccines are necessary to determine their effectiveness in smokers in general and in COPD patients.

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.

Ectodomain shedding of proteins important for SARS-CoV-2 pathogenesis in plasma of tobacco cigarette smokers compared to electronic cigarette vapers: a cross-sectional study

The impact of tobacco cigarette (TCIG) smoking and electronic cigarette (ECIG) vaping on the risk of development of severe COVID-19 is controversial. The present study investigated levels of proteins important for SARS-CoV-2 pathogenesis present in plasma because of ectodomain shedding in smokers, ECIG vapers, and non-smokers (NSs). Protein levels of soluble angiotensin-converting enzyme 2 (ACE2), angiotensin (Ang) II (the ligand of ACE2), Ang 1-7 (the main peptide generated from Ang II by ACE2 activity), furin (a protease that increases the affinity of the SARS-CoV-2 spike protein for ACE2), and products of ADAM17 shedding activity that predict morbidity in COVID-19 (IL-6/IL-6R alpha (IL-6/IL-6Rα) complex, soluble CD163 (sCD163), L-selectin) were determined in plasma from 45 NSs, 30 ECIG vapers, and 29 TCIG smokers using ELISA. Baseline characteristics of study participants did not differ among groups. TCIG smokers had increased sCD163, L-selectin compared to NSs and ECIG vapers (p < 0.001 for all comparisons). ECIG vapers had higher plasma furin compared to both NSs (p < 0.001) and TCIG smokers (p < 0.05). ECIG vaping and TCIG smoking did not impact plasma ACE2, Ang 1-7, Ang II, and IL-6 levels compared to NSs (p > 0.1 for all comparisons). Further studies are needed to determine if increased furin activity and ADAM17 shedding activity that is associated with increased plasma levels of sCD163 and L-selectin in healthy young TCIG smokers may contribute to the future development of severe COVID-19 and cardiovascular complications of post-acute COVID-19 syndrome.

Electronic Cigarette Exposure Increases the Severity of Influenza a Virus Infection via TRAIL Dysregulation in Human Precision-Cut Lung Slices

The use of electronic nicotine dispensing systems (ENDS), also known as electronic cigarettes (ECs), is common among adolescents and young adults with limited knowledge about the detrimental effects on lung health such as respiratory viral infections and underlying mechanisms. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a protein of the TNF family involved in cell apoptosis, is upregulated in COPD patients and during influenza A virus (IAV) infections, but its role in viral infection during EC exposures remains unclear. This study was aimed to investigate the effect of ECs on viral infection and TRAIL release in a human lung precision-cut lung slices (PCLS) model, and the role of TRAIL in regulating IAV infection. PCLS prepared from lungs of nonsmoker healthy human donors were exposed to EC juice (E-juice) and IAV for up to 3 days during which viral load, TRAIL, lactate dehydrogenase (LDH), and TNF-α in the tissue and supernatants were determined. TRAIL neutralizing antibody and recombinant TRAIL were utilized to determine the contribution of TRAIL to viral infection during EC exposures. E-juice increased viral load, TRAIL, TNF-α release and cytotoxicity in IAV-infected PCLS. TRAIL neutralizing antibody increased tissue viral load but reduced viral release into supernatants. Conversely, recombinant TRAIL decreased tissue viral load but increased viral release into supernatants. Further, recombinant TRAIL enhanced the expression of interferon-β and interferon-λ induced by E-juice exposure in IAV-infected PCLS. Our results suggest that EC exposure in human distal lungs amplifies viral infection and TRAIL release, and that TRAIL may serve as a mechanism to regulate viral infection. Appropriate levels of TRAIL may be important to control IAV infection in EC users.

The main e-cigarette component vegetable glycerin enhances neutrophil migration and fibrosis in endotoxin-induced lung injury via p38 MAPK activation

We investigated the effects of vegetable glycerin (VG), a main e-cigarette constituent, on endotoxin-induced acute lung injury (ALI). Mice received intratracheal administration of 30% VG in phosphate buffered saline (PBS) vehicle or only PBS (control) for 4 days. On Day 5, mice received an intratracheal instillation of lipopolysaccharide (LPS) (LPS group and VG + LPS group) or PBS (VG group and control group). Lung histopathology, expression of chemokine receptors, and regulatory signaling were analyzed 24 h after the Day 5 treatment. VG significantly increased ALI-associated histopathological and fibrotic changes in both the VG group and LPS-induced ALI mice (VG + LPS group). Immunohistochemistry (IHC) and western blot analyses revealed that VG administration resulted in upregulation of neutrophil markers [lymphocyte antigen 6 complex locus G6D (Ly6G) and myeloperoxidase (MPO)] as well as upregulation of the expression of transforming growth factor-β (TGF-β), a central mediator of fibrogenesis, in the lungs of both VG and VG + LPS groups. VG enhanced the expression of adhesion molecules [very late antigen 4 (VLA-4) and vascular cell adhesion molecule 1 (VCAM-1)] and increased activation of p38 mitogen-activated protein kinase (p38 MAPK) to prompt neutrophil recruitment in the lungs of mice with ALI. Intraperitoneal administration of a p38 inhibitor attenuated these histopathological changes significantly as well as VG-induced upregulation in expression of Ly6G, MPO, VLA-4, VCAM-1, TGF-β, and collagen-1 in mice with ALI. In conclusion, VG enhances neutrophil chemotaxis and fibrosis and it amplifies the inflammatory response associated with LPS-induced ALI in the lungs via enhancement of p38 MAPK activity.

Electronic Cigarettes: A Narrative Review and Cohort Study of Electronic Cigarette Users in the Otolaryngology Clinic

Electronic nicotine delivery systems (ENDSs) are growing in popularity, particularly in young adults. While in vitro and murine models have demonstrated potentially harmful health effects of ENDSs, long-term health effects and clinical outcomes are generally unknown. Use as a smoking cessation aid is propagated by studies of potential harm reduction compared to conventional cigarette smoking. We present a review of the current controversies of ENDS use and present a novel cohort of patients visiting the otolaryngology clinic with known ENDS use to understand their clinical and demographic characteristics and the prevalence of otolaryngologic inflammatory diagnoses. Eighty-eight patients had 105 diagnoses. Forty-three (48.9%) ENDS users had at least 1 inflammatory diagnosis. ENDS use was more common in White, male patients between the ages of 18 and 35 years. The most common inflammatory diagnoses were chronic otitis media (17.4%) and allergic rhinitis (13.0%). While the rate of inflammatory disease was significantly higher in male than in female patients (60.7% vs 28.1% p = 0.003), no significant association was seen between inflammatory disease and age, race/ethnicity, or length of ENDS use. The identification and description of patients with ENDS use will help clinicians' better risk-stratify otolaryngologic diagnoses associated with this novel health behavior. Additionally, further clinical research is necessary to elucidate long-term health outcomes of ENDS use.

E-cigarette Flavors, Sensory Perception, and Evoked Responses

The chemosensory experiences evoked by flavors encompass a number of unique sensations that include olfactory stimuli (smell), gustatory stimuli (taste, i.e., salty, sweet, sour, bitter, and umami (also known as "savoriness")), and chemesthesis (touch). As such, the responses evoked by flavors are complex and, as briefly stated above, involve multiple perceptive mechanisms. The practice of adding flavorings to tobacco products dates back to the 17th century but is likely much older. More recently, the electronic cigarette or "e-cigarette" and its accompanying flavored e-liquids emerged on to the global market. These new products contain no combustible tobacco but often contain large concentrations (reported from 0 to more than 50 mg/mL) of nicotine as well as numerous flavorings and/or flavor chemicals. At present, there are more than 400 e-cigarette brands available along with potentially >15,000 different/unique flavored products. However, surprisingly little is known about the flavors/flavor chemicals added to these products, which can account for >1% by weight of some e-liquids, and their resultant chemosensory experiences, and the US FDA has done relatively little, until recently, to regulate these products. This article will discuss e-cigarette flavors and flavor chemicals, their elicited responses, and their sensory effects in some detail.

In Vitro Biological Effects of E-Cigarette on the Cardiovascular System-Pro-Inflammatory Response Enhanced by the Presence of the Cinnamon Flavor

The potential cardiovascular effects of e-cigarettes remain largely unidentified and poorly understood. E-liquids contain numerous chemical compounds and can induce exposure to potentially toxic ingredients (e.g., nicotine, flavorings, etc.). Moreover, the heating process can also lead to the formation of new thermal decomposition compounds that may be also hazardous. Clinical as well as in vitro and in vivo studies on e-cigarette toxicity have reported potential cardiovascular damages; however, results remain conflicting. The aim of this study was to assess, in vitro, the toxicity of e-liquids and e-cigarette aerosols on human aortic smooth muscle cells. To that purpose, cells were exposed either to e-liquids or to aerosol condensates obtained using an e-cigarette device at different power levels (8 W or 25 W) to assess the impact of the presence of: (i) nicotine, (ii) cinnamon flavor, and (iii) thermal degradation products. We observed that while no cytotoxicity and no ROS production was induced, a pro-inflammatory response was reported. In particular, the production of IL-8 was significantly enhanced at a high power level of the e-cigarette device and in the presence of the cinnamon flavor (confirming the suspected toxic effect of this additive). Further investigations are required, but this study contributes to shedding light on the biological effects of vaping on the cardiovascular system.

E-cigarette aerosol impairs male mouse skeletal muscle force development and prevents recovery from injury

To date, there has been a lag between the rise in E-cigarette use and an understanding of the long-term health effects. Inhalation of E-cigarette aerosol delivers high doses of nicotine, raises systemic cytokine levels, and compromises cardiopulmonary function. The consequences for muscle function have not been thoroughly investigated. The present study tests the hypothesis that exposure to nicotine-containing aerosol impairs locomotor muscle function, limits exercise tolerance, and interferes with muscle repair in male mice. Nicotine-containing aerosol reduced the maximal force produced by the extensor digitorum longus (EDL) by 30%-40% and, the speed achieved in treadmill running by 8%. Nicotine aerosol exposure also decreased adrenal and increased plasma epinephrine and norepinephrine levels, and these changes in catecholamines manifested as increased muscle and liver glycogen stores. In nicotine aerosol exposed mice, muscle regenerating from overuse injury only recovered force to 80% of noninjured levels. However, the structure of neuromuscular junctions (NMJs) was not affected by e-cigarette aerosols. Interestingly, the vehicle used to dissolve nicotine in these vaping devices, polyethylene glycol (PG) and vegetable glycerin (VG), decreased running speed by 11% and prevented full recovery from a lengthening contraction protocol (LCP) injury. In both types of aerosol exposures, cardiac left ventricular systolic function was preserved, but left ventricular myocardial relaxation was altered. These data suggest that E-cigarette use may have a negative impact on muscle force and regeneration due to compromised glucose metabolism and contractile function in male mice.NEW & NOTEWORTHY In male mice, nicotine-containing E-cigarette aerosol compromises muscle contractile function, regeneration from injury, and whole body running speeds. The vehicle used to deliver nicotine, propylene glycol, and vegetable glycerin, also reduces running speed and impairs the restoration of muscle function in injured muscle. However, the predominant effects of nicotine in this inhaled aerosol are evident in altered catecholamine levels, increased glycogen content, decreased running capacity, and impaired recovery of force following an overuse injury.

High prevalence of hypertension among smokers of conventional and e-cigarette: Using the nationally representative community dwelling survey

This study aimed to clarify the association between hypertension and conventional cigarette and electronic cigarette (e-cigarette) use, together or individually. A total of 275,762 participants were included, of which 120,766 were men and 154,996 were women. The data were drawn from the Korea Community Health Survey conducted in 2019. A multiple logistic regression model was used to examine the association between hypertension and types of smoking. Hypertension was defined as systolic blood pressure higher than 140 mmHg or diastolic blood pressure higher than 90 mmHg. Based on the types of smoking, participants were grouped as dual smokers of conventional and e-cigarettes, e-cigarette only smokers, conventional cigarette only smokers, past-smokers, and non-smokers. Compared to non-smokers, dual smokers presented the highest odds ratio for hypertension in the male [odds ratio (OR): 1.24, confidence interval (CI): 1.10 to 1.39] and female groups (OR: 1.44 CI: 0.96 to 2.15). According to the Cochran-Mantel-Haenszel test, the two-sided p-value of < 0.001 indicated an overall statistically significant association between types of smoking and hypertension. Use of both cigarette types was statistically significant in the male group, but only the use of conventional cigarettes and past smoking were statistically significant in the female group. Among smokers of the two cigarette types, those who were dual smokers of e-cigarettes and conventional cigarettes were the most likely to have the highest prevalence of hypertension.

Assessment of inhalation toxicity of cigarette smoke and aerosols from flavor mixtures: 5-week study in A/J mice

Most flavors used in e-liquids are generally recognized as safe for oral consumption, but their potential effects when inhaled are not well characterized. In vivo inhalation studies of flavor ingredients in e-liquids are scarce. A structure-based grouping approach was used to select 38 flavor group representatives (FGR) on the basis of known and in silico-predicted toxicological data. These FGRs were combined to create prototype e-liquid formulations and tested against cigarette smoke (CS) in a 5-week inhalation study. Female A/J mice were whole-body exposed for 6 h/day, 5 days/week, for 5 weeks to air, mainstream CS, or aerosols from (1) test formulations containing propylene glycol (PG), vegetable glycerol (VG), nicotine (N; 2% w/w), and flavor (F) mixtures at low (4.6% w/w), medium (9.3% w/w), or high (18.6% w/w) concentration or (2) base formulation (PG/VG/N). Male A/J mice were exposed to air, PG/VG/N, or PG/VG/N/F-high under the same exposure regimen. There were no significant mortality or in-life clinical findings in the treatment groups, with only transient weight loss during the early exposure adaptation period. While exposure to flavor aerosols did not cause notable lung inflammation, it caused only minimal adaptive changes in the larynx and nasal epithelia. In contrast, exposure to CS resulted in lung inflammation and moderate-to-severe changes in the epithelia of the nose, larynx, and trachea. In summary, the study evaluates an approach for assessing the inhalation toxicity potential of flavor mixtures, thereby informing the selection of flavor exposure concentrations (up to 18.6%) for a future chronic inhalation study.

Vegetable glycerin e-cigarette aerosols cause airway inflammation and ion channel dysfunction

Vegetable glycerin (VG) and propylene glycol (PG) serve as delivery vehicles for nicotine and flavorings in most e-cigarette (e-cig) liquids. Here, we investigated whether VG e-cig aerosols, in the absence of nicotine and flavors, impact parameters of mucociliary function in human volunteers, a large animal model (sheep), and air-liquid interface (ALI) cultures of primary human bronchial epithelial cells (HBECs). We found that VG-containing (VG or PG/VG), but not sole PG-containing, e-cig aerosols reduced the activity of nasal cystic fibrosis transmembrane conductance regulator (CFTR) in human volunteers who vaped for seven days. Markers of inflammation, including interleukin-6 (IL6), interleukin-8 (IL8) and matrix metalloproteinase-9 (MMP9) mRNAs, as well as MMP-9 activity and mucin 5AC (MUC5AC) expression levels, were also elevated in nasal samples from volunteers who vaped VG-containing e-liquids. In sheep, exposures to VG e-cig aerosols for five days increased mucus concentrations and MMP-9 activity in tracheal secretions and plasma levels of transforming growth factor-beta 1 (TGF-β1). In vitro exposure of HBECs to VG e-cig aerosols for five days decreased ciliary beating and increased mucus concentrations. VG e-cig aerosols also reduced CFTR function in HBECs, mechanistically by reducing membrane fluidity. Although VG e-cig aerosols did not increase MMP9 mRNA expression, expression levels of IL6, IL8, TGFB1, and MUC5AC mRNAs were significantly increased in HBECs after seven days of exposure. Thus, VG e-cig aerosols can potentially cause harm in the airway by inducing inflammation and ion channel dysfunction with consequent mucus hyperconcentration.

Acute Outcomes of Cigarette Smoke and Electronic Cigarette Aerosol Inhalation in a Murine Model

Cigarette smoking throughout life causes serious health issues in the lungs. The electronic cigarette (E-Cig) use increased, since it was first introduced in the world. This research work compared the short-term exposure consequences to e-cigarette vapor and cigarette smoke in male mice. Forty-five C57BL/6 mice were randomized into control (C) in an ambient air exposition cigarette smoke (CS) and aerosol electronic cigarette (EC), both were exposed to 120 puffs, 3 times/day during five days. Then, in the experimental protocol, the euthanized mice had their tissues removed for analysis. Our study showed that CS and EC resulted in higher cell influx into the airways, and an increase in macrophage counts in CS (209.25 ± 7.41) and EC (220.32 ± 8.15) when compared to C (108.40 ± 4.49) (p < 0.0001). The CS (1.92 ± 0.23) displayed a higher pulmonary lipid peroxidation as opposed to C (0.93 ± 0.06) and EC (1.23 ± 0.17) (p < 0.05). The EC (282.30 ± 25.68) and CS (368.50 ± 38.05) promoted increased levels of interleukin 17 when compared to C (177.20 ± 10.49) (p < 0.05). The EC developed shifts in lung histoarchitecture, characterized by a higher volume density in the alveolar air space (60.21; 55.00-65.83) related to C (51.25; 18.75-68.75) and CS (50.26; 43.75-62.08) (p =0.002). The EC (185.6 ± 9.01) presented a higher respiratory rate related to CS (133.6 ± 10.2) (p < 0.002). Therefore, our findings demonstrated that the short-term exposure to e-cig promoted more acute inflammation comparing to cigarette smoke in the ventilatory parameters of the animals.

Electronic Cigarette and Atherosclerosis: A Comprehensive Literature Review of Latest Evidences

Coronary artery diseases (CAD), also known as coronary heart disease (CHD), are the world’s leading cause of death. The basis of coronary artery disease is the narrowing of the heart coronary artery lumen due to atherosclerosis. The use of electronic cigarettes has increased significantly over the years. However, harmful effects of electronic cigarettes are still not firm. The aim of this article is to review the impact of electronic cigarette and its role in the pathogenesis of atherosclerosis from recent studies. The results showed that several chemical compounds, such as nicotine, propylene glycol, particulate matters, heavy metals, and flavorings, in electronic cigarette induce atherosclerosis with each molecular mechanism that lead to atherosclerosis progression by formation of ROS, endothelial dysfunction, and inflammation. Further research is still needed to determine the exact mechanism and provide more clinical evidence.

A systematic review examining the pulmonary effects of electronic vapor delivery systems

STUDY OBJECTIVE

Despite the popularity of vaping and electronic vapor delivery systems (EVDS), the healthcare community remains largely unfamiliar with their potential to induce harm. The purpose of this systematic review is to identify how EVDS use affects the pulmonary system in order to support future anesthetic guidelines for patients who vape.

DESIGN

Systematic Review. An electronic search of databases CINAHL and PubMed was performed in October 2020.

STUDY ELIGIBILITY CRITERIA

Studies were included if they were deemed original research published in English, if they were performed exclusively in humans or on human tissue, if they examined the effects of EVDS on pulmonary function or tissue, and/or if they produced quantitative data. Studies were excluded if they utilized animal samples, studied subjects under the age of 18, presented expert opinions or reviews, offered qualitative data, reported case studies, or only evaluated EVDS' efficacy as a smoking cessation tool.

MAIN RESULTS

This review identified six EVDS-induced pulmonary implications warranting anesthetic consideration: alterations in pulmonary function tests, disrupted ventilation, impaired mucociliary clearance, tissue destruction, a disrupted immune response, and oxidative stress with DNA fragmentation.

CONCLUSION

A total of 38 studies described the effects of EVDS on pulmonary function, airway epithelial tissue, and inflammatory mechanisms that may lead to chronic pulmonary disease. Anesthesia providers are encouraged to assess patients for EVDS use during the preoperative period and use the information generated by this systematic review to drive subsequent care.

Nose-Only Exposure to Cherry- and Tobacco-Flavored E-Cigarettes Induced Lung Inflammation in Mice in a Sex-Dependent Manner

Flavoring chemicals in electronic nicotine delivery systems have been shown to cause cellular inflammation; meanwhile, the effects of fruit and tobacco flavors on lung inflammation by nose-only exposures to mice are relatively unknown. We hypothesized that exposure to flavored e-cigarettes would cause lung inflammation in C57BL/6 J mice. The mice were exposed to air, propylene glycol/vegetable glycerin, and flavored e-liquids: Apple, Cherry, Strawberry, Wintergreen, and Smooth & Mild Tobacco, one hour per day for three days. Quantification of flavoring chemicals by proton nuclear magnetic resonance spectroscopy (1H NMR), differential cell counts by flow cytometry, pro-inflammatory cytokines/chemokines by ELISA, and matrix metalloproteinase levels by western blot were performed. Exposure to PG/VG increased neutrophil cell count in lung bronchoalveolar lavage fluid (BALF). KC and IL6 levels were increased by PG/VG exposure and female mice exposed to Cherry flavored e-cigarettes, in lung homogenate. Mice exposed to PG/VG, Apple, Cherry, and Wintergreen increased MMP2 levels. Our results revealed flavor- and sex-based e-cigarette effects in female mice exposed to cherry-flavored e-liquids and male mice exposed to tobacco-flavored e-liquids, namely, increased lung inflammation.

A Review of Toxicity Mechanism Studies of Electronic Cigarettes on Respiratory System

Electronic cigarettes (e-cigarettes) have attracted much attention as a new substitute for conventional cigarettes. E-cigarettes are first exposed to the respiratory system after inhalation, and studies on the toxicity mechanisms of e-cigarettes have been reported. Current research shows that e-cigarette exposure may have potentially harmful effects on cells, animals, and humans, while the safety evaluation of the long-term effects of e-cigarette use is still unknown. Similar but not identical to conventional cigarettes, the toxicity mechanisms of e-cigarettes are mainly manifested in oxidative stress, inflammatory responses, and DNA damage. This review will summarize the toxicity mechanisms and signal pathways of conventional cigarettes and e-cigarettes concerning the respiratory system, which could give researchers a better understanding and direction on the effects of e-cigarettes on our health.

Toxicological Assessment of Flavor Ingredients in E-Vapor Products

Many flavor ingredients are often used in potentially reduced-risk tobacco products (such as e-vapor products). Although most are “generally recognized as safe (GRAS)” when used in food, there is limited information available on their long-term health effects when delivered by inhalation. While obtaining route-of-exposure-specific toxicological data on flavor ingredients is critical to product evaluation, the large number of individual flavor ingredients available and their potential combinations render classical toxicological assessment approaches impractical, as they may require years of preclinical investigations and thousands of laboratory animals. Therefore, we propose a pragmatic approach in which flavor ingredients are initially assigned to groups of structurally related compounds (Flavor Groups), from which flavor group representatives (FGR) are then selected and tested individually and as a mixture in vitro and in vivo. The premise is that structurally related compounds would have comparable metabolic and biological activity and that the data generated using FGRs could support the toxicological assessment of other structurally related flavor ingredients of their respective Flavor Groups. This approach is explained in a step-wise manner and exemplified by a case study, along with its strengths, limitations as well as recommendations for further confirmatory testing. Once completed, this FGR approach could significantly reduce the time and resources required for filling the data gap in understanding the health risks of many flavor ingredients while also minimizing the need for laboratory animals.

Predicting the pulmonary effects of long-term e-cigarette use: are the clouds clearing?

Commercially available since 2007, e-cigarettes are a popular electronic delivery device of ever-growing complexity. Given their increasing use by ex-smokers, smokers and never-smokers, it is important to evaluate evidence of their potential pulmonary effects and predict effects of long-term use, since there has been insufficient time to study a chronic user cohort. It is crucial to evaluate indicators of harm seen in cigarette use, and those potentially unique to e-cigarette exposure. Evaluation must also account for the vast variation in e-cigarette devices (now including at least five generations of devices) and exposure methods used in vivo and in vitroThus far, short-term use cohort studies, combined with in vivo and in vitro models, have been used to probe for the effects of e-cigarette exposure. The effects and mechanisms identified, including dysregulated inflammation and decreased pathogen resistance, show concerning overlaps with the established effects of cigarette smoke exposure. Additionally, research has identified a signature of dysregulated lipid processing, which is unique to e-cigarette exposure.This review will evaluate the evidence of pulmonary effects of, and driving mechanisms behind, e-cigarette exposure, which have been highlighted in emerging literature, and highlight the gaps in current knowledge. Such a summary allows understanding of the ongoing debate into e-cigarette regulation, as well as prediction and potential mitigation of future problems surrounding e-cigarette use.

Vaping and Lung Inflammation and Injury

The use of electronic (e)-cigarettes was initially considered a beneficial solution to conventional cigarette smoking cessation. However, paradoxically, e-cigarette use is rapidly growing among nonsmokers, including youth and young adults. In 2019, this rapid growth resulted in an epidemic of hospitalizations and deaths of e-cigarette users (vapers) due to acute lung injury; this novel disease was termed e-cigarette or vaping use-associated lung injury (EVALI). Pathophysiologic mechanisms of EVALI likely involve cytotoxicity and neutrophilic inflammation caused by inhaled chemicals, but further details remain unknown. The undiscovered mechanisms of EVALI are a barrier to identifying biomarkers and developing therapeutics. Furthermore, adverse effects of e-cigarette use have been linked to chronic lung diseases and systemic effects on multiple organs. In this comprehensive review, we discuss the diverse spectrum of vaping exposures, epidemiological and clinical reports, and experimental findings to provide a better understanding of EVALI and the adverse health effects of chronic e-cigarette exposure.

Inflammatory phenotype modulation in the respiratory tract and systemic circulation of e-cigarette users: a pilot study

Over 40 million people use e-cigarettes worldwide, but the impact of chronic e-cigarette use on health has not been adequately defined. In particular, effects of e-cigarette aerosol inhalation on inflammation and host defenses across the body are not fully understood. We conducted a longitudinal cohort pilot study to explore changes in the inflammatory state and monocyte function of e-cigarette users (n = 20) versus healthy controls (n = 13) and to evaluate effects of e-cigarette use reduction on the same. Saliva, sputum, and blood were obtained from e-cigarette users at baseline and after a 2-wk intervention of decreased e-cigarette use. Overall, across 38 proteins quantified by multiplex, airway samples from e-cigarette users tended to have decreased levels of immunomodulatory proteins relative to healthy controls, whereas levels of cytokines, chemokines, and growth factors in the circulation tended to be elevated. Specifically, e-cigarette users had lower levels of IL-1 receptor antagonist (IL-1Ra) in saliva (P < 0.0001), with higher IL-1Ra and growth-regulated oncogene (GRO) levels in sputum (P < 0.01 and P < 0.05, respectively), and higher levels of both TNFβ (P < 0.0001) and VEGF (P < 0.0001) in plasma. Circulating monocytes from e-cigarette users had alterations in their inflammatory phenotype in response to reduced e-cigarette use, with blunted IL-8 and IL-6 release upon challenge with bacterial lipopolysaccharide (P < 0.001 and P < 0.05, respectively), suggesting a decreased ability to appropriately respond to bacterial infection. Based on these findings, chronic inhalation of e-cigarette aerosols alters the inflammatory state of the airways and systemic circulation, raising concern for the development of both inflammatory and infectious diseases in chronic users of e-cigarettes.

E-Cigarette Use: Device Market, Study Design, and Emerging Evidence of Biological Consequences

Electronic cigarettes are frequently viewed as a safer alternative to conventional cigarettes; however, evidence to support this perspective has not materialized. Indeed, the current literature reports that electronic cigarette use is associated with both acute lung injury and subclinical dysfunction to the lung and vasculature that may result in pathology following chronic use. E-cigarettes can alter vascular dynamics, polarize innate immune populations towards a proinflammatory state, compromise barrier function in the pulmonary endothelium and epithelium, and promote pre-oncogenic phenomena. This review will summarize the variety of e-cigarette products available to users, discuss current challenges in e-cigarette study design, outline the range of pathologies occurring in cases of e-cigarette associated acute lung injury, highlight disease supporting tissue- and cellular-level changes resulting from e-cigarette exposure, and briefly examine how these changes may promote tumorigenesis. Continued research of the mechanisms by which e-cigarettes induce pathology benefit users and clinicians by resulting in increased regulation of vaping devices, informing treatments for emerging diseases e-cigarettes produce, and increasing public awareness to reduce e-cigarette use and the onset of preventable disease.

Effects of E-Cigarette Flavoring Chemicals on Human Macrophages and Bronchial Epithelial Cells

E-cigarettes utilize a wide range of flavoring chemicals with respiratory health effects that are not well understood. In this study, we used pulmonary-associated cell lines to assess the in vitro cytotoxic effects of 30 flavoring chemicals. Human bronchial epithelial cells (BEAS-2B) and both naïve and activated macrophages (THP-1) were treated with 10, 100, and 1000 µM of flavoring chemicals and analyzed for changes in viability, cell membrane damage, reactive oxygen species (ROS) production, and inflammatory cytokine release. Viability was unaffected for all chemicals at the 10 and 100 µM concentrations. At 1000 µM, the greatest reductions in viability were seen with decanal, hexanal, nonanal, cinnamaldehyde, eugenol, vanillin, alpha-pinene, and limonene. High amounts of ROS were elicited by vanillin, ethyl maltol, and the diketones (2,3-pentanedione, 2,3-heptanedione, and 2,3-hexanedione) from both cell lines. Naïve THP-1 cells produced significantly elevated levels of IL-1β, IL-8, and TNF-α when exposed to ethyl maltol and hexanal. Activated THP-1 cells released increased IL-1β and TNF-α when exposed to ethyl maltol, but many flavoring chemicals had an apparent suppressive effect on inflammatory cytokines released by activated macrophages, some with varying degrees of accompanying cytotoxicity. The diketones, L-carvone, and linalool suppressed cytokine release in the absence of cytotoxicity. These findings provide insight into lung cell cytotoxicity and inflammatory cytokine release in response to flavorings commonly used in e-cigarettes.

E-cig vapor condensate alters proteome and lipid profiles of membrane rafts: impact on inflammatory responses in A549 cells

Electronic cigarettes (e-cigs) are battery-operated heating devices that aerosolize e-liquid, typically containing nicotine and several other chemicals, which is then inhaled by a user. Over the past decade, e-cigs have gained immense popularity among both smokers and non-smokers. One reason for this is that they are advertised as a safe alternative to conventional cigarettes. However, the recent reports of e-cig use associated lung injury have ignited a considerable debate about the relative harm and benefits of e-cigs. The number of reports about e-cig-induced inflammation and pulmonary health is increasing as researchers seek to better understand the effects of vaping on human health. In line with this, we investigated the molecular events responsible for the e-cig vapor condensate (ECVC)-mediated inflammation in human lung adenocarcinoma type II epithelial cells (A549). In an attempt to limit the variables caused by longer ingredient lists of flavored e-cigs, tobacco-flavored ECVC (TF-ECVC±nicotine) was employed for this study. Interestingly, we observed significant upregulation of cytokines and chemokines (IL-6, IL-8, and MCP-1) in A549 cells following a 48 h TF-ECVC challenge. Furthermore, there was a significant increase in the expression of pattern recognition receptors TLR-4 and NOD-1, lipid raft-associated protein caveolin-1, and transcription factor NF-кB in TF-ECVC with and/or without nicotine-challenged lung epithelial cells. Our results further demonstrate the harboring of TLR-4 and NOD-1 in the caveolae of TF-ECVC-challenged A549 cells. Proteomic and lipidomic analyses of lipid raft fractions from control and challenged cells revealed a distinct protein and lipid profile in TF-ECVC (w/wo nicotine)-exposed A549 cells. Interestingly, the inflammatory effects of TF-ECVC (w/wo nicotine) were inhibited following the caveolin-1 knockdown, thus demonstrating a critical role of caveolae raft-mediated signaling in eliciting inflammatory responses upon TF-ECVC challenge. Graphical Abstract Graphical Abstract.

Electronic and Tobacco Cigarettes Alter Polyunsaturated Fatty Acids and Oxidative Biomarkers

[Figure: see text].