Acetaldehyde in mainstream tobacco smoke: formation and occurrence in smoke and bioavailability in the smoker

Coolants, organic acids, flavourings and other additives that facilitate inhalation of tobacco and nicotine products: implications for regulation

To inform regulatory policy, this article summarises findings on inhalation facilitation from the ninth report of the WHO Study Group on Tobacco Product Regulation. Some additives counteract the harshness and bitterness of tobacco and nicotine product aerosols, making them easier to inhale. Additives that promote inhalability may perpetuate and increase the use of inhaled tobacco and nicotine products, especially by young people. Thus, as a class, additives that facilitate inhalation are an important regulatory target to prevent tobacco and nicotine product uptake. We defined inhalation facilitation as modifications to products during manufacturing that enhance the sensory experience and (potentially) behaviours associated with inhalation (eg, deeper puffs, faster inhalation, larger puff volume, shorter intervals in between puffs and use episodes). Evidence review showed that: (a) menthol and synthetic coolants decrease irritation caused by aerosol constituents by activating sensory perception receptors (eg, cooling receptors) and may promote dependence in inexperienced users; (b) acid additives and sugars, which lower the pH of aerosols and shift nicotine from free-base to protonated salt forms, reduce harshness and increase blood nicotine yield; (c) e-cigarette flavourings perceived as sweet or fruity reduce subjective bitterness, increase attractiveness and may escalate use, although their effects on perceived harshness are inconclusive; (d) sugars in tobacco impart sweet sensations, but limited industry-independent data preclude strong conclusions for sugars' roles in inhalation facilitation. Given these findings, WHO policy recommendations suggest that regulators might consider banning ingredients that facilitate inhalation in all commercial inhaled tobacco and nicotine products.

A study of 9 common breath VOCs in 504 healthy subjects using PTR-TOF-MS

INTRODUCTION

This study employs Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) to analyze exhaled breath profiles of 504 healthy adults, focusing on nine common volatile organic compounds (VOCs): acetone, acetaldehyde, acetonitrile, ethanol, isoprene, methanol, propanol, phenol, and toluene. PTR-MS offers real-time VOC measurement, crucial for understanding breath biomarkers and their applications in health assessment.

OBJECTIVES

The study aims to investigate how demographic factors-gender, age, and smoking history-affect VOC concentrations in exhaled breath. The objective is to enhance our understanding of breath biomarkers and their potential for health monitoring and clinical diagnosis.

METHODS

Exhaled breath samples were collected using PTR-MS, measuring concentrations of nine VOCs. The data were analyzed to discern distribution patterns across demographic groups.

RESULTS

Males showed higher average VOC levels for certain compounds. Propanol and methanol concentrations significantly increased with age. Smoking history influenced VOC levels, with differences among non-smokers, current smokers, and ex-smokers.

CONCLUSION

This research provides valuable insights into demographic influences on exhaled VOC profiles, emphasizing the potential of breath analysis for health assessment. PTR-MS's real-time measurement capabilities are crucial for capturing dynamic VOC changes, offering advantages over conventional methods. These findings lay a foundation for advancements in non-invasive disease detection, highlighting the importance of considering demographics in breath biomarker research.

Harmful and Potentially Harmful Constituents in E-Liquids and Aerosols from Electronic Nicotine Delivery Systems (ENDS)

In 2012, the U.S. Food & Drug Administration (FDA) published an established list of 93 harmful and potentially harmful constituents (HPHCs) targeting four tobacco product types (cigarettes, cigarette tobacco, roll-your-own tobacco, smokeless tobacco). In 2016, the FDA finalized the deeming rule to regulate electronic nicotine delivery systems (ENDS). However, knowledge gaps exist regarding whether certain HPHCs are present in ENDS e-liquids and aerosols. We identified and addressed these gaps by conducting literature searches and then experimentally quantifying HPHCs in the e-liquid and aerosol of 37 ENDS brands based on gaps in the literature. The literature searches identified 66 e-liquid HPHCs and 68 aerosol HPHCs that have limited to no information regarding the quantifiability of these constituents. A contracted ISO 17025 accredited laboratory performed the HPHC quantifications. The availability of validated analytical methods in the contracted laboratory determined the HPHCs included in the study scope (63/66 for e-liquids, 64/68 for aerosols). Combining the results from the quantifications and literature searches, 36 (39%) and 34 (37%) HPHCs were found quantifiable (≥limit of quantification [LOQ]) in ENDS e-liquids and aerosols, respectively, with 25 HPHCs being quantifiable in both matrices. Quantifiability results imply potential HPHC transfers between matrices, leaching from components, or formations from aerosol generation. The study results can inform the scientific basis for manufacturers and regulators regarding regulatory requirements for HPHC reporting. The HPHC quantities can also inform evaluations of the public health impact of ENDS and public communications regarding ENDS health risks.

Heat-not-burn tobacco products and cardiovascular risk reduction: A systematic review of randomized controlled trials

BACKGROUND

Heat-not-burn (HNB) technology by the U.S. Food and Drug Administration has been classified as a modified risk tobacco product, which can be a better option for those populations who cannot give up the habit of smoking. The outlook on the effects of these products is quite controversial in the scientific world.

OBJECTIVE

To present the effect of HNB tobacco products on the cardiovascular system, with reference to the existence of possible benefits of the technology.

METHODS

The literature search was conducted in PubMed/Medline, the Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov databases, with reliance on a well-defined guiding research statement. Quality appraisal was performed using the CASP checklist for randomized controlled trials.

RESULTS

The search of three databases identified 167 records, and after selection process, 25 randomized controlled trials were eligible for our study's criteria. Twenty studies investigated the effects of HNB products on biomarkers of clinical relevance. Five studies evaluated other functional heart parameters rather than biomarkers.

CONCLUSION

With HNB tobacco products, significant reductions were found in biomarkers of exposure and biological effect related to pathways involved in cardiovascular disease, including inflammation, oxidative stress, lipid metabolism, platelet function, and endothelial dysfunction.

Malondialdehyde acetaldehyde adduction of surfactant protein D attenuates SARS-CoV-2 spike protein binding and virus neutralization

BACKGROUND

Over 43% of the world's population regularly consumes alcohol. Although not commonly known, alcohol can have a significant impact on the respiratory environment. Living in the time of the COVID-19 pandemic, alcohol misuse can have a particularly deleterious effect on SARS-CoV-2-infected individuals and, in turn, the overall healthcare system. Patients with alcohol use disorders have higher odds of COVID-19-associated hospitalization and mortality. Even though the detrimental role of alcohol on COVID-19 outcomes has been established, the underlying mechanisms are yet to be fully understood. Alcohol misuse has been shown to induce oxidative damage in the lungs through the production of reactive aldehydes such as malondialdehyde and acetaldehyde (MAA). MAA can then form adducts with proteins, altering their structure and function. One such protein is surfactant protein D (SPD), which plays an important role in innate immunity against pathogens.

METHODS AND RESULTS

In this study, we examined whether MAA adduction of SPD (SPD-MAA) attenuates the ability of SPD to bind SARS-CoV-2 spike protein, reversing SPD-mediated virus neutralization. Using ELISA, we show that SPD-MAA is unable to competitively bind spike protein and prevent ACE2 receptor binding. Similarly, SPD-MAA fails to inhibit entry of wild-type SARS-CoV-2 virus into Calu-3 cells, a lung epithelial cell line, as well as ciliated primary human bronchial epithelial cells isolated from healthy individuals.

CONCLUSIONS

Overall, MAA adduction of SPD, a consequence of alcohol overconsumption, represents one mechanism of compromised lung innate defense against SARS-CoV-2, highlighting a possible mechanism underlying COVID-19 severity and related mortality in patients who misuse alcohol.

Acetaldehyde makes a distinct mutation signature in single-stranded DNA

Acetaldehyde (AA), a by-product of ethanol metabolism, is acutely toxic due to its ability to react with various biological molecules including DNA and proteins, which can greatly impede key processes such as replication and transcription and lead to DNA damage. As such AA is classified as a group 1 carcinogen by the International Agency for Research on Cancer (IARC). Previous in vitro studies have shown that AA generates bulky adducts on DNA, with signature guanine-centered (GG→TT) mutations. However, due to its weak mutagenicity, short chemical half-life, and the absence of powerful genetic assays, there is considerable variability in reporting the mutagenic effects of AA in vivo. Here, we used an established yeast genetic reporter system and demonstrate that AA treatment is highly mutagenic to cells and leads to strand-biased mutations on guanines (G→T) at a high frequency on single stranded DNA (ssDNA). We further demonstrate that AA-derived mutations occur through lesion bypass on ssDNA by the translesion polymerase Polζ. Finally, we describe a unique mutation signature for AA, which we then identify in several whole-genome and -exome sequenced cancers, particularly those associated with alcohol consumption. Our study proposes a key mechanism underlying carcinogenesis by acetaldehyde—mutagenesis of single-stranded DNA.

Malondialdehyde Acetaldehyde-Adduction Changes Surfactant Protein D Structure and Function

Alcohol consumption with concurrent cigarette smoking produces malondialdehyde acetaldehyde (MAA)-adducted lung proteins. Lung surfactant protein D (SPD) supports innate immunity via bacterial aggregation and lysis, as well as by enhancing macrophage-binding and phagocytosis. MAA-adducted SPD (SPD-MAA) has negative effects on lung cilia beating, macrophage function, and epithelial cell injury repair. Because changes in SPD multimer structure are known to impact SPD function, we hypothesized that MAA-adduction changes both SPD structure and function. Purified human SPD and SPD-MAA (1 mg/mL) were resolved by gel filtration using Sephadex G-200 and protein concentration of each fraction determined by Bradford assay. Fractions were immobilized onto nitrocellulose by slot blot and assayed by Western blot using antibodies to SPD and to MAA. Binding of SPD and SPD-MAA was determined fluorometrically using GFP-labeled Streptococcus pneumoniae (GFP-SP). Anti-bacterial aggregation of GFP-SP and macrophage bacterial phagocytosis were assayed by microscopy and permeability determined by bacterial phosphatase release. Viral injury was measured as LDH release in RSV-treated airway epithelial cells. Three sizes of SPD were resolved by gel chromatography as monomeric, trimeric, and multimeric forms. SPD multimer was the most prevalent, while the majority of SPD-MAA eluted as trimer and monomer. SPD dose-dependently bound to GFP-SP, but SPD-MAA binding to bacteria was significantly reduced. SPD enhanced, but MAA adduction of SPD prevented, both aggregation and macrophage phagocytosis of GFP-SP. Likewise, SPD increased bacterial permeability while SPD-MAA did not. In the presence of RSV, BEAS-2B cell viability was enhanced by SPD, but not protected by SPD-MAA. Our results demonstrate that MAA adduction changes the quaternary structure of SPD from multimer to trimer and monomer leading to a decrease in the native anti-microbial function of SPD. These findings suggest one mechanism for increased pneumonia observed in alcohol use disorders.

Biologically Active Compounds Present in Tobacco Smoke: Potential Interactions Between Smoking and Mental Health

Tobacco dependence remains one of the major preventable causes of premature morbidity and mortality worldwide. There are well over 8,000 compounds present in tobacco and tobacco smoke, but we do not know what effect, if any, many of them have on smokers. Major interest has been on nicotine, as well as on toxic and carcinogenic effects and several major and minor components of tobacco smoke responsible for the negative health effects of smoking have been elucidated. Smokers themselves report a variety of positive effects from smoking, including effects on depression, anxiety and mental acuity. Smoking has also been shown to have protective effects in Parkinson’s Disease. Are the subjective reports of a positive effect of smoking due to nicotine, of some other components of tobacco smoke, or are they a manifestation of the relief from nicotine withdrawal symptoms that smoking provides? This mini-review summarises what is currently known about the components of tobacco smoke with potential to have positive effects on smokers.

Upper Gastrointestinal Cancer and Liver Cirrhosis

Simple Summary

There is a higher incidence rate of upper gastrointestinal cancer in those with liver cirrhosis. The contributing factors include gastric ulcers, congestive gastropathy, zinc deficiency, alcohol drinking, tobacco use and gut microbiota. Most of the de novo malignancies that develop after liver transplantation for cirrhotic patients are upper gastrointestinal cancers. The surgical risk of upper gastrointestinal cancers in cirrhotic patients with advanced liver cirrhosis is higher.

Abstract

The extended scope of upper gastrointestinal cancer can include esophageal cancer, gastric cancer and pancreatic cancer. A higher incidence rate of gastric cancer and esophageal cancer in patients with liver cirrhosis has been reported. It is attributable to four possible causes which exist in cirrhotic patients, including a higher prevalence of gastric ulcers and congestive gastropathy, zinc deficiency, alcohol drinking and tobacco use and coexisting gut microbiota. Helicobacter pylori infection enhances the development of gastric cancer. In addition, Helicobacter pylori, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans also contribute to the development of pancreatic cancer in cirrhotic patients. Cirrhotic patients (especially those with alcoholic liver cirrhosis) who undergo liver transplantation have a higher overall risk of developing de novo malignancies. Most de novo malignancies are upper gastrointestinal malignancies. The prognosis is usually poor. Considering the surgical risk of upper gastrointestinal cancer among those with liver cirrhosis, a radical gastrectomy with D1 or D2 lymph node dissection can be undertaken in Child class A patients. D1 lymph node dissection can be performed in Child class B patients. Endoscopic submucosal dissection for gastric cancer or esophageal cancer can be undertaken safely in selected cirrhotic patients. In Child class C patients, a radical gastrectomy is potentially fatal. Pancreatic radical surgery should be avoided in those with liver cirrhosis with Child class B or a MELD score over 15. The current review focuses on the recent reports on some factors in liver cirrhosis that contribute to the development of upper gastrointestinal cancer. Quitting alcohol drinking and tobacco use is important. How to decrease the risk of the development of gastrointestinal cancer in those with liver cirrhosis remains a challenging problem.

Content of toxic components of cigarette, cigarette smoke vs cigarette butts: A comprehensive systematic review

The commercially sold cigarettes contain more than 7000 chemicals, and their combustion produces potential toxicants in mainstream smoke (MS), sidestream smoke (SS), secondhand smoke (SHS), thirdhand smoke (THS), and discarded cigarette butts (CBs). We conducted a systematic review of published literature to compare the toxicants produced in each of these phases of tobacco combustion (MS, SS, and CBs). The initial search included 12,301 articles, but after screening and final restrictions considering the aims of this review, 159 published studies were selected for inclusion. Additionally, SHS and THS are briefly discussed here. Overall, polycyclic aromatic hydrocarbons (PAHs) and other aromatic hydrocarbons have been represented in more studies than other compounds. However, metals and nitrosamines were detected in higher concentrations than other components in SS. The concentrations of most PAHs and other aromatic hydrocarbons in MS and SS are higher compared to concentrations found in CBs. Also, the concentrations of all the studied carbonyl compounds, aldehydes and ketones in SS and MS were higher than in CBs. The mean levels of alcohols and phenols in SS were higher than those reported for both MS and CBs. Tobacco toxicants are inhaled by smokers and transmitted to the environment through SS, SHS, THS, and discarded CBs. However, further studies are necessary to assess adverse effects of toxicants found in CBs and THS not only on human health, but also on the environment and ecosystems. The results of this review provide updated information on the chemical contents of MS, SS, SHS, THS, and CBs. It adds to the growing understanding that smoking creates major health problems for smokers and passive smokers, but also that it generates environmental hazards with consequences to the ecosystems and human health through discarded CBs, SHS, and THS exposure.

Experimental and Kinetic Studies on Tobacco Pyrolysis under a Wide Range of Heating Rates

In the present work, experimental and kinetic studies are conducted to explore and model tobacco pyrolysis characteristics under a wide range of heating conditions. First, thermal decomposition processes of a tobacco sample were investigated using thermogravimetric analysis/difference thermogravimetry (TGA/DTG) experiments under a wide range of heating rates (10-500 K/min), and the TGA/DTG profiles were compared to highlight the effect of heating rate on the pyrolysis characteristics. The results showed that the tobacco sample was sufficiently devolatilized at 1173.15 K (900 °C) and the final volatiles yields were not sensitive to the heating rate. Moreover, it was illustrated that the DTG curve presents a polymerization trend with the increase in heating rate. Then, kinetic parameters, including total component mass fraction, preexponential factor, and activation energy, were derived by deconvolution from TG/DTG profiles for each component with a one-step kinetic framework, and the correlations between kinetic parameters and heating rates were further explored and modeled. The results illustrated that four subpeaks can be found in the deconvolution, indicating the four components (volatile components, hemicellulose, cellulose, and lignin). In addition, the activation energy of each component was found to be insensitive with heating rate (with standard deviation less than 20%). Therefore, an average activation energy was used for each component to avoid the compensation effect and a power correlation between the heating rate and the preexponential factor could be found. A posteriori analysis also confirmed the validity of this correlation.

DNA damage, DNA repair and carcinogenicity: Tobacco smoke versus electronic cigarette aerosol

The allure of tobacco smoking is linked to the instant gratification provided by inhaled nicotine. Unfortunately, tobacco curing and burning generates many mutagens including more than 70 carcinogens. There are two types of mutagens and carcinogens in tobacco smoke (TS): direct DNA damaging carcinogens and procarcinogens, which require metabolic activation to become DNA damaging. Recent studies provide three new insights on TS-induced DNA damage. First, two major types of TS DNA damage are induced by direct carcinogen aldehydes, cyclic-1,N2-hydroxy-deoxyguanosine (γ-OH-PdG) and α-methyl-1, N2-γ-OH-PdG, rather than by the procarcinogens, polycyclic aromatic hydrocarbons and aromatic amines. Second, TS reduces DNA repair proteins and activity levels. TS aldehydes also prevent procarcinogen activation. Based on these findings, we propose that aldehydes are major sources of TS induce DNA damage and a driving force for carcinogenesis. E-cigarettes (E-cigs) are designed to deliver nicotine in an aerosol state, without burning tobacco. E-cigarette aerosols (ECAs) contain nicotine, propylene glycol and vegetable glycerin. ECAs induce O6-methyl-deoxyguanosines (O6-medG) and cyclic γ-hydroxy-1,N2--propano-dG (γ-OH-PdG) in mouse lung, heart and bladder tissues and causes a reduction of DNA repair proteins and activity in lungs. Nicotine and nicotine-derived nitrosamine ketone (NNK) induce the same types of DNA adducts and cause DNA repair inhibition in human cells. After long-term exposure, ECAs induce lung adenocarcinoma and bladder urothelial hyperplasia in mice. We propose that E-cig nicotine can be nitrosated in mouse and human cells becoming nitrosamines, thereby causing two carcinogenic effects, induction of DNA damage and inhibition of DNA repair, and that ECA is carcinogenic in mice. Thus, this article reviews the newest literature on DNA adducts and DNA repair inhibition induced by nicotine and ECAs in mice and cultured human cells, and provides insights into ECA carcinogenicity in mice.

Development of bacterial biosensor for sensitive and selective detection of acetaldehyde

Acetaldehyde is a human carcinogen and widely existed in alcoholic beverages and polluted air. In this study, a simple, fast, convenient and sensitive acetaldehyde biosensor was developed based on an acetaldehyde dehydrogenase (AldDH) bacteria surface display system. The whole-cell catalyst facilitated the dehydrogenation of acetaldehyde, while coenzyme NAD⁺ was reduced and the resultant NADH can be detected spectrometrically at 340 nm. The correct location of AldDH on the bacteria surface was confirmed by the subcellular fraction and immunofluorescence analysis. By comparing the fusion protein expression level and whole-cell activity, the proper display system for anchoring AldDH on the cell surface was obtained. The results of kinetics analysis towards both surface-displayed AldDH and intracellular expressed AldDH demonstrated that the mass-transport resistance was dramatically alleviated by cell-surface display strategy. Under optimal conditions, AldDH-surface display strain with the highest whole-cell activity (3.41 ± 0.3 mU/OD₆₀₀) was applied to spectrophotometry acetaldehyde detection system. An excellent linear relationship between the increases of absorbance at 340 nm and acetaldehyde concentration over the range from 1 μM to 300 μM was reached. The proposed approach offered adequate sensitivity for the detection of acetaldehyde at 0.33 μM. Most importantly, the developed biosensor showed the narrowest substrate specificity towards acetaldehyde, which has been employed for quick determination of acetaldehyde in real samples with good accuracy. The total detection time was within 20 min. The method reported here provided a simple, rapid, and low-cost strategy for the sensitive and selective measurement of acetaldehyde. Therefore, genetically engineered cells may find broad application in biosensors and biocatalysts.

Comparison of cytotoxicity of cigarette smoke extract derived from heat-not-burn and combustion cigarettes in human vascular endothelial cells

The present study compared the properties of mainstream smoke generated from heat-not-burn (HNB) cigarettes and a combustion cigarette (hi-lite™ brand). Three types of cigarette heating devices were used to generate cigarette smoke at different heating temperatures [Ploom S™ (200 °C), glo™ (240 °C), and IQOS™ (300-350 °C)]. Mainstream smoke was generated using the following puffing regimen: volume, 55 mL; duration, 3 s; and interval, 30 s. The rank order of particulate phase (nicotine and tar) amounts trapped on a Cambridge filter was Ploom S < glo < IQOS < hi-lite. Heated cigarette-derived smoke extract (hCSE) from the devices except for Ploom S, and burned CSE (bCSE) decreased mitochondrial metabolic activity (glo < IQOS < hi-lite) in human vascular endothelial cells. Furthermore, the cytotoxicity was reduced by removing the particulate phase from the mainstream smoke. Endothelial nitric oxide synthase activity was reduced by nicotine- and tar-free CSE of IQOS and hi-lite (IQOS < hi-lite), but not Ploom S and glo. These inhibitory effects were diminished by removing the carbonyl compounds from the mainstream smoke. These results indicated that the cytotoxicity of hCSE was lower than that of bCSE in vascular endothelial cells.

L-Cysteine Containing Vitamin Supplement Which Prevents or Alleviates Alcohol-related Hangover Symptoms: Nausea, Headache, Stress and Anxiety

AIMS

Alcohol-related hangover symptoms: nausea, headache, stress and anxiety cause globally considerable amount of health problems and economic losses. Many of these harmful effects are produced by alcohol and its metabolite, acetaldehyde, which also is a common ingredient in alcohol beverages. The aim of the present study is to investigate the effect of the amino acid L-cysteine on the alcohol/acetaldehyde related aftereffects.

METHODS

Voluntary healthy participants were recruited through advertisements. Volunteers had to have experience of hangover and/or headache. The hangover study was randomized, double-blind and placebo-controlled. Nineteen males randomly swallowed placebo and L-cysteine tablets. The alcohol dose was 1.5 g/kg, which was consumed during 3 h.

RESULTS

The primary results based on correlational analysis showed that L-cysteine prevents or alleviates hangover, nausea, headache, stress and anxiety. For hangover, nausea and headache the results were apparent with the L-cysteine dose of 1200 mg and for stress and anxiety already with the dose of 600 mg.

CONCLUSIONS

L-cysteine would reduce the need of drinking the next day with no or less hangover symptoms: nausea, headache, stress and anxiety. Altogether, these effects of L-cysteine are unique and seem to have a future in preventing or alleviating these harmful symptoms as well as reducing the risk of alcohol addiction.

Use of a rapid human primary cell-based disease screening model, to compare next generation products to combustible cigarettes

A growing number of public health bodies, regulators and governments around the world consider electronic vapor products a lower risk alternative to conventional cigarettes. Of critical importance are rapid new approach methodologies to enable the screening of next generation products (NGPs) also known as next generation tobacco and nicotine products. In this study, the activity of conventional cigarette (3R4F) smoke and a range of NGP aerosols (heated tobacco product, hybrid product and electronic vapor product) captured in phosphate buffered saline, were screened by exposing a panel of human cell-based model systems using Biologically Multiplexed Activity Profiling (BioMAP® Diversity PLUS® Panel, Eurofins Discovery). Following exposure, the biological activity for a wide range of biomarkers in the BioMAP panel were compared to determine the presence of toxicity signatures that are associated with specific clinical findings. NGP aerosols were found to be weakly active in the BioMAP Diversity PLUS Panel (≤3/148 biomarkers) whereas significant activity was observed for 3R4F (22/148 biomarkers). Toxicity associated biomarker signatures for 3R4F included immunosuppression, skin irritation and thrombosis, with no toxicity signatures seen for the NGPs. BioMAP profiling could effectively be used to differentiate between complex mixtures of cigarette smoke or NGP aerosol extracts in a panel of human primary cell-based assays. Clinical validation of these results will be critical for confirming the utility of BioMAP for screening NGPs for potential adverse human effects.

SARS-CoV-2 infection and smoking: What is the association? A brief review

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The link between smoking and the expression of SARS-CoV-2 key entry genes is discussed.

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Smoking-related cardiac and respiratory diseases are risk factors for COVID-19.

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The impact of smoking on ACE-2 and TMPRSS2 receptors expression is controversial.

Susceptibility to severe illness from COVID-19 is anticipated to be associated with cigarette smoking as it aggravates the risk of cardiovascular and respiratory illness, including infections. This is particularly important with the advent of a new strain of coronaviruses, the severe acute respiratory syndrome coronavirus (SARS-CoV-2) that has led to the present pandemic, coronavirus disease 2019 (COVID-19). Although, the effects of smoking on COVID-19 are less described and controversial, we presume a link between smoking and COVID-19. Smoking has been shown to enhance the expression of the angiotensin-converting enzyme-2 (ACE-2) and transmembrane serine protease 2 (TMPRSS2) key entry genes utilized by SARS-CoV-2 to infect cells and induce a ‘cytokine storm’, which further increases the severity of COVID-19 clinical course. Nevertheless, the impact of smoking on ACE-2 and TMPRSS2 receptors expression remains paradoxical. Thus, further research is necessary to unravel the association between smoking and COVID-19 and to pursue the development of potential novel therapies that are able to constrain the morbidity and mortality provoked by this infectious disease. Herein we present a brief overview of the current knowledge on the correlation between smoking and the expression of SARS-CoV-2 key entry genes, clinical manifestations, and disease progression.

Comparison of the chemical composition of aerosols from heated tobacco products, electronic cigarettes and tobacco cigarettes and their toxic impacts on the human bronchial epithelial BEAS-2B cells

The electronic cigarettes (e-cigs) and more recently the heated tobacco products (HTP) provide alternatives for smokers as they are generally perceived to be less harmful than conventional cigarettes. However, it is crucial to compare the health risks of these different emergent devices, in order to determine which product should be preferred to substitute cigarette. The present study aimed to compare the composition of emissions from HTP, e-cigs and conventional cigarettes, regarding selected harmful or potentially harmful compounds, and their toxic impacts on the human bronchial epithelial BEAS-2B cells. The HTP emitted less polycyclic aromatic hydrocarbons and carbonyls than the conventional cigarette. However, amounts of these compounds in HTP aerosols were still higher than in e-cig vapours. Concordantly, HTP aerosol showed reduced cytotoxicity compared to cigarette smoke but higher than e-cig vapours. HTP and e-cig had the potential to increase oxidative stress and inflammatory response, in a manner similar to that of cigarette smoke, but after more intensive exposures. In addition, increasing e-cig power impacted levels of certain toxic compounds and related oxidative stress. This study provides important data necessary for risk assessment by demonstrating that HTP might be less harmful than tobacco cigarette but considerably more harmful than e-cig.

Smoking and COVID-19: Similar bronchial ACE2 and TMPRSS2 expression and higher TMPRSS4 expression in current versus never smokers

Uncertainties remain concerning the pathophysiology, epidemiology, and potential therapeutics for COVID-19. Among unsettled controversies is whether tobacco smoking increases or protects from severe COVID-19. Several epidemiological studies reported reduced COVID-19 hospitalizations among smokers, while other studies reported the opposite trend. Some authors assumed that smokers have elevated airway expression of ACE2, the cell recognition site of the SARS-Cov-2 spike protein, but this suggestion remains unverified. We therefore performed data mining of two independent NCBI GEO genome-wide RNA expression files (GSE7894 and GSE994) and report that in both data sets, current smokers and never smokers have, on average, closely similar bronchial epithelial cell mRNA levels of ACE2, as well as TMPRSS2, coding for a serine protease priming SARS-Cov-2 for cell entry, and ADAM17, coding for a protease implicated in ACE2 membrane shedding. In contrast, the expression levels of TMPRSS4, coding for a protease that primes SARS-CoV-2 for cell entry similarly to TMPRSS2, were elevated in bronchial epithelial cells from current smokers compared with never smokers, suggesting that higher bronchial TMPRSS4 levels in smokers might put them at higher SARS-Cov-2 infection risk. The effects of smoking on COVID-19 severity need clarification with larger studies. Additionally, the postulated protective effects of nicotine and nitric oxide, which may presumably reduce the risk of a "cytokine storm" in infected individuals, deserve assessment by controlled clinical trials.

Acetaldehyde-induced oxidative modifications and morphological changes in isolated human erythrocytes: an in vitro study

Acetaldehyde is a toxic, mutagenic and carcinogenic metabolite of alcohol which can bind to proteins, DNA and several other cellular macromolecules. Chronic alcohol consumption increases intracellular acetaldehyde levels which enhances the generation of reactive oxygen and nitrogen species (ROS and RNS). In this study, we have examined the effect of acetaldehyde on human erythrocytes under in vitro conditions. Treatment of human erythrocytes with different concentrations of acetaldehyde (0.05-2 mM) for 24 h at 37 °C increased intracellular generation of ROS and RNS. It also increased oxidation of proteins and lipids but decreased glutathione, total sulphhydryl and free amino group content. Methemoglobin level was increased accompanied by a decrease in methemoglobin reductase activity. Acetaldehyde impaired the antioxidant defence system and lowered the total antioxidant capacity of the cell. It decreased the activity of metabolic and membrane-bound enzymes and altered erythrocyte morphology. Our results show that acetaldehyde enhances the generation of ROS and RNS that results in oxidative modification of cellular components. This will lower the oxygen transporting ability of blood and shorten erythrocyte lifespan (red cell senescence).

Effects of "Essential AD2" Supplement on Blood Acetaldehyde Levels in Individuals Who Have Aldehyde Dehydrogenase (ALDH2) Deficiency

BACKGROUND

It is estimated that 1 billion people in the world have a point mutation in the gene encoding the aldehyde dehydrogenase 2 (ALDH2) enzyme, the primary enzyme responsible for the metabolism of acetaldehyde. The presence of this mutation is called ALDH2 deficiency. Because of limited ability to metabolize acetaldehyde, individuals with ALDH2 deficiency experience elevated levels of blood acetaldehyde after exposure to various common sources such as recreational alcohol. Because of higher levels of acetaldehyde, individuals with ALDH2 deficiency are at higher risk for numerous diseases, including liver cirrhosis, esophageal and gastric cancer, osteoporosis, and Alzheimer disease.

STUDY QUESTION

The present trial was designed to study the effectiveness, safety, and tolerability of a nutritional supplement (Essential AD2).

MEASURES AND OUTCOMES

The primary outcome was change in acetaldehyde levels in the blood after exposure to alcohol in individuals with ALDH2 deficiency before and after the use of study nutritional supplement.

STUDY DESIGN

This was a 28-day open-label trial, comparing initial acetaldehyde levels after alcohol ingestion to levels after 28 days of a nutritional supplement (Essential AD2). The study consisted of 12 subjects genotyped to be heterozygous for the ALDH2 gene mutation.

RESULTS AND CONCLUSIONS

ALDH2 deficient subjects showed a significant decrease in average blood acetaldehyde level 20 minutes after alcohol consumption (from 0.91 mg/dL to 0.71 mg/dL, P value = 0.02) after receiving 28 days of the nutritional supplement. Acetaldehyde levels taken at 10 minutes and 40 minutes also showed a decrease, although they were not statistically significant. In addition, safety tests looking at liver function tests showed a decrease in aspartate transaminase and alanine transaminase liver proteins from 27.3 to 15.2 and 20.9 to 13.2, respectively, over the 28 days. The treatment was well tolerated and no significant side effects were noted.

Behaviors of Cellulose-Based Activated Carbon Fiber for Acetaldehyde Adsorption at Low Concentration

The toxic nature of acetaldehyde renders its removal from a wide range of materials highly desirable. Removal of low-concentration acetaldehyde (a group 1 carcinogenic volatile organic compound) using an adsorbent of cellulose-based activated carbon fiber modified by amine functional group (A@CACF-H) is proposed, using 2 ppm of acetaldehyde balanced with N2/O2 (79/21% v/v) observed under continuous flow, with a total flow rate of 100 mL/min over 50 mg of A@CACF-H. The effective removal of the targeted acetaldehyde is achieved by introducing the functionalized amine at optimized content. The removal mechanism of A@CACF-H is elucidated using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (2D-GC TOF-MS), indicating the efficacy of the proposed acetaldehyde removal method.

Role of mouse cytochrome P450 enzymes of the CYP2ABFGS subfamilies in the induction of lung inflammation by cigarette smoke exposure

BACKGROUND

Many constituents of tobacco smoke (TS) require bioactivation to exert toxic effects; however, few studies have examined the role of bioactivation enzymes in the adverse effects of TS exposure. This knowledge gap is a major source of uncertainty for risk assessment and chemoprevention efforts.

OBJECTIVES

Our aim is to test the hypothesis that cytochrome P450 (P450) enzyme mediated bioactivation is essential to the development of TS exposure-induced lung toxicity, by determining the contributions of P450 enzymes in the mouse Cyp2abfgs gene subfamilies to environmental tobacco smoke (ETS)-induced lung inflammation.

METHODS

Adult female wildtype (WT) and Cyp2abfgs-null mice (both on C57BL/6J background) were exposed to filtered air or ETS, intermittently, for 1 or 2 weeks. Lung inflammation was assessed by quantification of inflammatory cells, cytokines, chemokines, proteins in bronchoalveolar lavage fluid (BALF), and histopathological analysis. Glutathione (GSH) conjugates of two ETS constituents, naphthalene (NA) and 3-methylindole (3MI), were measured in mice exposed to ETS for four hours.

RESULTS

Persistent macrophagic and neutrophilic lung inflammation was observed in ETS-exposed WT mice; the extent of which was significantly reduced in ETS-exposed Cyp2abfgs-null mice. Levels of proinflammatory cytokines and chemokines, along with the total protein concentration, were increased in cell-free BALF from ETS-exposed WT mice, but not Cyp2abfgs-null mice. Additionally, GSH-conjugates of NA and 3MI were detected in the lungs of WT, but not Cyp2abfgs-null, mice following ETS exposure.

CONCLUSIONS

These results provide the first in vivo evidence that the mouse Cyp2abfgs gene cluster plays an important role in ETS-induced lung inflammation.

Emission level of seven mainstream smoke toxicants from cigarette with variable tobacco leaf constituents

[Introduction] Seven smoke constituents, including hydrogen cyanide (HCN), ammonia (NH3), phenol, benzo[α]pyrene (B[a]P), carbon monoxide (CO)¸ crotonaldehyde, and 4-(methylnitrosamino)-1- (3-pyridyl)-1-butanone (NNK), are proposed be the most relevant constituents for smoking-related diseases. [Methods] Different combinations of leaf stalk positions, varieties and locations were used to create variable chemistry of cigarette filler and smoke. Experimental cigarettes were measured for emission level of seven smoke toxicants and content of seventy-three filler components. [Results] The ranges of coefficient of variation (CV) for seven smoke toxicants were 15.43%-43.15%. The emission pattern of NNK and crotonaldehyde were different from that of other five smoke toxicants. Most of the seven smoke toxicants were influenced in following order: stalk position > location > variety. The leaf constitutes closely correlated with seven smoke toxicants were analyzed. [Conclusions] The results showed that seven toxicants were significantly influenced by leaf position and location, and closely correlated with leaf components, such as potassium, malate and alkaloid contents. The results provide useful and comprehensive information on the affecting factors and correlating leaf constituents for the variations of seven smoke toxicants.

Cigarette smoke extract may induce lysosomal storage disease-like adverse health effects

Cigarette smoke is known to be associated with the incidence of a variety of pulmonary diseases, and alveolar macrophages are a key player in the defense mechanism against inhalable toxicants. Herein, we have found that a hydrophilic fraction in smoke extracts from 3R4F reference cigarettes (CSE) contains high concentrations of volatile substances compared to cigarette smoke condensate (amphoteric fraction). We also identified the toxic mechanism of CSE using MH-S, a mouse alveolar macrophage cell line. CSE decreased cell viability accompanying increased lactate dehydrogenase release. Additionally, mitochondrial volume and the potential increased along with enhanced expression of mitochondrial fusion proteins and decreased adenosine triphosphate production. Similarly, CSE clearly induced increase of catalase activity and intracellular calcium concentration and decrease of endoplasmic reticulum and lysosome volume at the highest dose. More interestingly, damaged organelles accumulated in the cytosol, and CSE-containing particles specifically penetrated to mitochondria. Meanwhile, any significant change in autophagy related protein expression was not found in CSE-treated cells. Subsequently, we evaluated the effects of CSE on secretion of inflammatory related cytokines and chemokines, considering the relationship between organelle damage and the disturbed immune response. Very importantly, we found that expression of innate and adaptive immunity related mediators is disrupted following CSE exposure. Taken together, we suggest that CSE may cause the accumulation of damaged organelles in the cytoplasm by impairing selective autophagic function. In addition, this accumulation is responsible for the inadequate ability of immune cells to repair the damage of lung tissue following exposure to CSE.

Redox regulation of motile cilia in airway disease

Motile cilia on airway cells are necessary for clearance of mucus-trapped particles out of the lung. Ciliated airway epithelial cells are uniquely exposed to oxidants through trapping of particles, debris and pathogens in mucus and the direct exposure to inhaled oxidant gases. Dynein ATPases, the motors driving ciliary motility, are sensitive to the local redox environment within each cilium. Several redox-sensitive cilia-localized proteins modulate dynein activity and include Protein Kinase A, Protein Kinase C, and Protein Phosphatase 1. Moreover, cilia are rich in known redox regulatory proteins and thioredoxin domain-containing proteins that are critical in maintaining a balanced redox environment. Importantly, a nonsense mutation in TXNDC3, which contains a thioredoxin motif, has recently been identified as disease-causing in Primary Ciliary Dyskinesia, a hereditary motile cilia disease resulting in impaired mucociliary clearance. Here we review current understanding of the role(s) oxidant species play in modifying airway ciliary function. We focus on oxidants generated in the airways, cilia redox targets that modulate ciliary beating and imbalances in redox state that impact health and disease. Finally, we review disease models such as smoking, asthma, alcohol drinking, and infections as well as the direct application of oxidants that implicate redox balance as a modulator of cilia motility.

Carbonyl emissions from a novel heated tobacco product (IQOS): comparison with an e-cigarette and a tobacco cigarette

AIMS

To measure carbonyl emissions from a heated tobacco product (IQOS) in comparison with an e-cigarette (Nautilus Mini) and a commercial tobacco cigarette (Marlboro Red).

DESIGN

Regular and menthol variants of the heated tobacco product were tested. A tank-type atomizer was tested with a tobacco-flavoured liquid at 10 and 14 W. Aerosol and smoke were collected in impingers containing 2,4-dinitrophenylhydrazine. Health Canada Intense and two more intense puffing regimens were used.

SETTING

Analytical laboratory in Greece.

MEASUREMENTS

Carbonyl levels in the aerosol and smoke.

FINDINGS

At the Health Canada Intense regimen, heated tobacco products emitted 5.0-6.4 μg/stick formaldehyde, 144.1-176.7 μg/stick acetaldehyde, 10.4-10.8 μg/stick acrolein, 11.0-12.8 μg/stick propionaldehyde and 1.9-2.0 μg/stick crotonaldehyde. Compared with the tobacco cigarette, levels were on average 91.6% lower for formaldehyde, 84.9% lower for acetaldehyde, 90.6% lower for acrolein, 89.0% lower for propionaldehyde and 95.3% lower for crotonaldehyde. The e-cigarette emitted 0.5-1.0 μg/12 puffs formaldehyde, 0.8-1.5 μg/12 puffs acetaldehyde and 0.3-0.4 μg/12 puffs acrolein, but no propionaldehyde and crotonaldehyde. At more intense puffing regimens, formaldehyde was increased in heated tobacco products, but levels were three-fourfold lower compared with the tobacco cigarette. Based on the findings from Health Canada Intense puffing regimen, use of 20 heated tobacco sticks would result in approximately 85% to 95% reduced carbonyl exposure compared with smoking 20 tobacco cigarettes; the respective reduction in exposure from use of 5 g e-cigarette liquid would be 97% to > 99%.

CONCLUSIONS

The IQOS heated tobacco product emits substantially lower levels of carbonyls than a commercial tobacco cigarette (Marlboro Red) but higher levels than a Nautilus Mini e-cigarette.

Quantification of 19 Aldehydes in Human Serum by Headspace SPME/GC/High-Resolution Mass Spectrometry

Sources of human aldehyde exposure include food additives, combustion of organic matter (tobacco smoke), water disinfection byproducts via ozonation, and endogenous processes. Aldehydes are potentially carcinogenic and mutagenic, and chronic human aldehyde exposure has raised concerns about potential deleterious health effects. To aid investigations of human aldehyde exposure, we developed a novel method to measure 19 aldehydes released from Schiff base protein adducts in serum using controlled acid hydrolysis, solid-phase microextraction (SPME), gas chromatography (GC), and high-resolution mass spectrometry (HRMS). Aldehydes are released from Schiff base protein adducts through acid hydrolysis, and are quantified in trace amounts (μg/L) using stable isotope dilution. Detection limits range from 0.1 to 50 μg/L, with calibration curves spanning 3 orders of magnitude. The analysis of fortified quality control material over a three-month period showed excellent precision and long-term stability (3-22% CV) for samples stored at -70 °C. The intraday precision is also excellent (CV, 1-10%). The method accuracy ranges from 89 to 108% for all measured aldehydes, except acrolein and crotonaldehyde, two aldehydes present in tobacco smoke; their analysis by this method is not considered robust due in part to their reactivity in vivo. However, results strongly suggest that propanal, butanal, isobutanal, and isopentanal levels in smokers are higher than levels in nonsmokers, and thus may be useful as biomarkers of tobacco smoke exposure. This method will facilitate large epidemiological studies involving aldehyde biomonitoring to examine nonoccupational environmental exposures.

The nicotine-degrading enzyme NicA2 reduces nicotine levels in blood, nicotine distribution to brain, and nicotine discrimination and reinforcement in rats

BACKGROUND

The bacterial nicotine-degrading enzyme NicA2 isolated from P. putida was studied to assess its potential use in the treatment of tobacco dependence.

RESULTS

Rats were pretreated with varying i.v. doses of NicA2, followed by i.v. administration of nicotine at 0.03 mg/kg. NicA2 had a rapid onset of action reducing blood and brain nicotine concentrations in a dose-related manner, with a rapid onset of action. A 5 mg/kg NicA2 dose reduced the nicotine concentration in blood by > 90% at 1 min after the nicotine dose, compared to controls. Brain nicotine concentrations were reduced by 55% at 1 min and 92% at 5 min post nicotine dose. To evaluate enzyme effects at a nicotine dosing rate equivalent to heavy smoking, rats pretreated with NicA2 at 10 mg/kg were administered 5 doses of nicotine 0.03 mg/kg i.v. over 40 min. Nicotine levels in blood were below the assay detection limit 3 min after either the first or fifth nicotine dose, and nicotine levels in brain were reduced by 82 and 84%, respectively, compared to controls. A 20 mg/kg NicA2 dose attenuated nicotine discrimination and produced extinction of nicotine self-administration (NSA) in most rats, or a compensatory increase in other rats, when administered prior to each daily NSA session. In rats showing compensation, increasing the NicA2 dose to 70 mg/kg resulted in extinction of NSA. An enzyme construct with a longer duration of action, via fusion with an albumin-binding domain, similarly reduced NSA in a 23 h nicotine access model at a dose of 70 mg/kg.

CONCLUSIONS

These data extend knowledge of NicA2's effects on nicotine distribution to brain and its ability to attenuate addiction-relevant behaviors in rats and support its further investigation as a treatment for tobacco use disorder.

Sugar and Aldehyde Content in Flavored Electronic Cigarette Liquids

Introduction

Sugars are major constituents and additives in traditional tobacco products, but little is known about their content or related toxins (formaldehyde, acetaldehyde, and acrolein) in electronic cigarette (e-cigarette) liquids. This study quantified levels of sugars and aldehydes in e-cigarette liquids across brands, flavors, and nicotine concentrations (n = 66).

Methods

Unheated e-cigarette liquids were analyzed using liquid chromatography mass spectrometry and enzymatic test kits. Generalized linear models, Fisher's exact test, and Pearson's correlation coefficient assessed sugar, aldehyde, and nicotine concentration associations.

Results

Glucose, fructose and sucrose levels exceeded the limits of quantification in 22%, 53% and 53% of the samples. Sucrose levels were significantly higher than glucose [χ2(1) = 85.9, p < .0001] and fructose [χ2(1) = 10.6, p = .001] levels. Formaldehyde, acetaldehyde, and acrolein levels exceeded the limits of quantification in 72%, 84%, and 75% of the samples. Acetaldehyde levels were significantly higher than formaldehyde [χ2(1) = 11.7, p = .0006] and acrolein [χ2(1) = 119.5, p < .0001] levels. Differences between nicotine-based and zero-nicotine labeled e-cigarette liquids were not statistically significant for sugars or aldehydes. We found significant correlations between formaldehyde and fructose (-0.22, p = .004) and sucrose (-0.25, p = .002) and acrolein and fructose (-0.26, p = .0006) and sucrose (-0.21, p = .0006). There were no significant correlations between acetaldehyde and any of the sugars or any of the aldehydes and glucose.

Conclusions

Sugars and related aldehydes were identified in unheated e-cigarette liquids and their composition may influence experimentation in naïve users and their potential toxicity.

Implications

The data can inform the regulation of specific flavor constituents in tobacco products as a strategy to protect young people from using e-cigarettes, while balancing FDA's interest in how these emerging products could potentially benefit adult smokers who are seeking to safely quit cigarette smoking. The data can also be used to educate consumers about ingredients in products that may contain nicotine and inform future FDA regulatory policies related to product standards and accurate and comprehensible labeling of e-cigarette liquids.

Cigarette Filter Ventilation and Smoking Protocol Influence Aldehyde Smoke Yields

The WHO study group on tobacco product regulation (TobReg) advised regulating and lowering toxicant levels in cigarette smoke. Aldehydes are one of the chemical classes on the TobReg smoke toxicants priority list. To provide insight in factors determining aldehyde yields, the levels of 12 aldehydes in mainstream cigarette smoke of 11 Dutch brands were quantified. Variations in smoking behavior and cigarette design affecting human exposure to aldehydes were studied by using four different machine testing protocols. Machine smoking was based on the International Standardization Organization (ISO) and Health Canada Intense (HCI) regime, both with and without taping the filter vents. The 11 cigarette brands differed in (i) design and blend characteristics; (ii) tar, nicotine, and carbon monoxide (TNCO) levels; (iii) popularity; and (iv) manufacturer. Cigarette smoke was trapped on a Cambridge filter pad and carboxen cartridge. After being dissolved in methanol/CS2 and derivatization with DNPH, the aldehyde yields were determined using HPLC-DAD. Using an intense smoking regime (increased puff volume, shorter puff interval) significantly increased aldehyde yields, following the pattern: ISO < ISO-taped < HCI-untaped < HCI. For all of the regimes, acetaldehyde and acrolein yields were strongly correlated ( r = 0.804). The difference in TNCO and aldehyde levels between regular and highly ventilated low-TNCO cigarettes (as measured using ISO) diminished when smoking intensely; this effect is stronger when combined with taping filter vents. The highly ventilated low-TNCO brands showed six times more aldehyde production per mg nicotine for the intense smoking regimes. In conclusion, acetaldehyde and acrolein can be used as representatives for the class of volatile aldehydes for the different brands and smoking regimes. The aldehyde-to-nicotine ratio increased when highly ventilated cigarettes were smoked intensely, similar to real smokers. Thus, a smoker of highly ventilated low-TNCO cigarettes has an increased potential for higher aldehyde exposures compared to a smoker of regular cigarettes.

Molecular Basis of Alcohol-Related Gastric and Colon Cancer

Many meta-analysis, large cohort studies, and experimental studies suggest that chronic alcohol consumption increases the risk of gastric and colon cancer. Ethanol is metabolized by alcohol dehydrogenases (ADH), catalase or cytochrome P450 2E1 (CYP2E1) to acetaldehyde, which is then further oxidized to acetate by aldehyde dehydrogenase (ALDH). Acetaldehyde has been classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen to humans. The acetaldehyde level in the stomach and colon is locally influenced by gastric colonization by Helicobacter pylori or colonic microbes, as well as polymorphisms in the genes encoding tissue alcohol metabolizing enzymes, especially ALDH2. Alcohol stimulates the uptake of carcinogens and their metabolism and also changes the composition of enteric microbes in a way to enhance the aldehyde level. Alcohol also undergoes chemical coupling to membrane phospholipids and disrupts organization of tight junctions, leading to nuclear translocation of β-catenin and ZONAB, which may contributes to regulation of genes involved in proliferation, invasion and metastasis. Alcohol also generates reactive oxygen species (ROS) by suppressing the expression of antioxidant and cytoprotective enzymes and inducing expression of CYP2E1 which contribute to the metabolic activation of chemical carcinogens. Besides exerting genotoxic effects by directly damaging DNA, ROS can activates signaling molecules involved in inflammation, metastasis and angiogenesis. In addition, alcohol consumption induces folate deficiency, which may result in aberrant DNA methylation profiles, thereby influencing cancer-related gene expression.

Self-administration of nicotine and cigarette smoke extract in adolescent and adult rats

Although smoking initiation typically occurs during adolescence, most preclinical studies of tobacco use involve adult animals. Furthermore, their focus is largely on nicotine alone, even though cigarette smoke contains thousands of constituents. The present study therefore aimed to determine whether aqueous constituents in cigarette smoke affect acquisition of nicotine self-administration during adolescence in rats. Adolescent and adult male rats, aged postnatal day (P) 25 and 85, respectively, were food trained on a fixed ratio 1 (FR1) schedule, then allowed to self-administer one of 5 doses of nicotine (0, 3.75, 7.5, 15, or 30 μg/kg) or aqueous cigarette smoke extract (CSE) with equivalent nicotine content. Three progressively more difficult schedules of reinforcement, FR1, FR2, and FR5, were used. Both adolescent and adult rats acquired self-administration of nicotine and CSE. Nicotine and CSE similarly increased non-reinforced responding in adolescents, leading to enhanced overall drug intake as compared to adults. When data were corrected for age-dependent alterations in non-reinforced responding, adolescents responded more for low doses of nicotine and CSE than adults at the FR1 reinforcement schedule. No differences in adolescent responding for the two drugs were seen at this schedule, whereas adults had fewer responses for CSE than for nicotine. However, when the reinforcement schedule was increased to FR5, animals dose-dependently self-administered both nicotine and CSE, but no drug or age differences were observed. These data suggest that non-nicotine tobacco smoke constituents do not influence the reinforcing effect of nicotine in adolescents.

Influence of cigarette circumference on smoke chemistry, biological activity, and smoking behaviour

Cigarettes with reduced circumference are increasingly popular in some countries, hence it is important to understand the effects of circumference reduction on their burning behaviour, smoke chemistry and bioactivity. Reducing circumference reduces tobacco mass burn rate, puff count and static burn time, and increases draw resistance and rod length burned during puff and smoulder periods. Smoulder temperature increases with decreasing circumference, but with no discernible effect on cigarette ignition propensity during a standard test. At constant packing density, mainstream (MS) and sidestream (SS) tar and nicotine yields decrease approximately linearly with decreasing circumference, as do the majority of smoke toxicants. However, volatile aldehydes, particularly formaldehyde, show a distinctly non-linear relationship with circumference and increases in the ratios of aldehydes to tar and nicotine have been observed as the circumference decreases. Mutagenic, cytotoxic and tumorigenic specific activities of smoke condensates (i.e. per unit weight of condensate) decrease as circumference decreases. Recent studies suggest that there is no statistical difference in mouth-level exposure to tar and nicotine among smokers of cigarettes with different circumferences. Commercially available slim cigarettes usually have changes in other cigarette design features compared with cigarettes with standard circumference, so it is difficult to isolate the effect of circumference on the properties of commercial products. However, available data shows that changes in cigarette circumference offer no discernible change to the harm associated with smoking.

Determination of two mercapturic acids related to crotonaldehyde in human urine: influence of smoking

Crotonaldehyde, an αβ-unsaturated aldehyde, and a potent alkylating agent, is present in many foods and beverages, ambient air and tobacco smoke. A previous study indicated that two metabolites, 3-hydroxy-1- methylpropylmercapturic acid (HMPMA) and 2-carboxy1-1-methylethylmercapturic acid (CMEMA), were excreted in rat urine after subcutaneous injection of crotonaldehyde. Herein, we report the development of a method based on liquid chromatography with tandem mass spectrometry (LC-MS/MS) and deuterated analytes as internal standards, for the determination of HMPMA and CMEMA in human urine. The limits of quantification of the method were 92 and 104 ng/mL for HMPMA and CMEMA, respectively. The calibration curves for both compounds were linear up to 7500 ng/mL with R2 >0.99. It was found that cigarette smokers excreted about three to five-fold more HMPMA, and only slightly elevated amounts of CMEMA, in their urine compared to non-smokers. In smokers, we also found significant correlations between the urinary excretion levels of HMPMA (but not CMEMA) and several markers of exposure for smoking, including the daily cigarette consumption, carbon monoxide in exhaled breath, salivary cotinine, and nicotine plus five of its major metabolites in urine. Smoking cessation or switching from smoking conventional cigarettes to experimental cigarettes with lower crotonaldehyde delivery led to significant reductions of urinary HMPMA excretion, but not CMEMA excretion. Alcohol consumption did not influence either urinary HMPMA or CMEMA excretion. We conclude that HMPMA is a potentially useful biomarker for smoking-related exposure to crotonaldehyde.

Contribution of Monoamine Oxidase Inhibition to Tobacco Dependence: A Review of the Evidence

BACKGROUND

There is a hypothesis that substances present in, or derived from, tobacco smoke inhibit monoamine oxidase (MAO) in the brains of smokers, reducing the degradation of catecholamine neurotransmitters involved in central reward pathways and acting synergistically with nicotine to increase its addictive effects.

OBJECTIVE

The objective of this review was to evaluate the evidence for a role of MAO inhibition by tobacco-derived substances in tobacco dependence.

INVESTIGATIONAL PLAN

Relevant studies on the effects of tobacco use on MAO levels or activity in humans were identified by electronic searches.

RESULTS

The identified data show a clear association between smoking and lower density of MAO-A and MAO-B binding sites in the brains of smokers and strong evidence that MAO is inhibited by a substance or substances in, or derived from, tobacco smoke. There was little evidence to support the hypothesis that low MAO levels/activity is a predictive factor for tobacco use. Substances that inhibit MAO in in vitro assays have been isolated from tobacco leaves and tobacco smoke; however, no single substance has been shown to be absorbed from tobacco smoke and to inhibit MAO in the brains of human smokers. Nevertheless, it is possible that MAO inhibition in smokers could result from additive or synergistic effects of several tobacco-derived substances. MAO inhibition potentiates the reinforcing effects of intravenous nicotine in rodents; however, no data were identified to support the hypothesis that MAO inhibitors in or derived from tobacco or tobacco additives affect tobacco dependence in human smokers.

IMPLICATIONS

This comprehensive review describes the available evidence for the role of MAO inhibition in tobacco dependence and points the way for further research in this field. In view of the large number of MAO inhibitors identified in tobacco and tobacco smoke, identification of the putative inhibitors responsible for the lower level/activity of MAO in smokers may be impractical. Future studies must address whether the lower level/activity of MAO observed in smokers is also seen in users of other tobacco products and if this change is implicated in their dependence-inducing effects.

High-resolution time and spatial imaging of tobacco and its pyrolysis products during a cigarette puff by microprobe sampling photoionisation mass spectrometry

The time- and space-resolved chemical signatures of gases and vapours formed in solid-state combustion processes are difficult to examine using recent analytical techniques. A machine-smoked cigarette represents a very reproducible model system for dynamic solid-state combustion. By using a special sampling system (microprobe unit) that extracts the formed gases from inside of the burning cigarette, which is coupled to a photoionisation mass spectrometer, it was possible to study the evolution of organic gases during a 2-s cigarette puff. The concentrations of various pyrolysis and combustion products such as 1,3-butadiene, toluene, acetaldehyde and phenol were monitored on-line at different sampling points within cigarettes. A near-microscopic-scale spatial resolution and a 200-ms time resolution were achieved. Finally, the recorded information was combined to generate time-resolved concentration maps, showing the formation and destruction zones of the investigated compounds in the burning cigarette. The combustion zone at the tip of cigarette, where e.g. 1,3-butadiene is predominately formed, was clearly separable from the pyrolysis zones. Depending on the stability of the precursor (e.g. lignin or cellulose), the position of pyrolytic formation varies. In conclusion, it was demonstrated that soft photoionisation mass spectrometry in conjunction with a microprobe sampling device can be used for time- and space-resolved analysis of combustion and pyrolysis reactions. In addition to studies on the model cigarette, further model systems may be studied with this approach. This may include further studies on the combustion of biomass or coal chunks, on heterogeneously catalysed reactions or on spray, dust and gas combustion processes.

Comparison of the reinforcing properties of nicotine and cigarette smoke extract in rats

Tobacco dependence is difficult to treat, with the vast majority of those who try to quit relapsing within the first year. Improvements in smoking cessation therapies may be achieved by improving current preclinical research methods. However, most experimental tests in animals use nicotine alone, ignoring the 8000 other constituents found in tobacco smoke. To improve on this model, we have used self-administration to test the reinforcing properties of aqueous cigarette smoke extract (CSE) in rats, made by bubbling cigarette smoke through a saline solution. CSE is more potent than nicotine alone in both the acquisition and maintenance of self-administration, but did not exhibit higher progressive ratio responding. Mecamylamine and varenicline had similar potencies to block nicotine and CSE self-administration, indicating the involvement of nicotinic receptors in CSE reinforcement. Following extinction of responding, reinstatement was triggered by exposing animals to a pharmacological stressor, yohimbine (2.5 mg/kg, i.p.), alone and in combination with cues. Animals that self-administered CSE were significantly more sensitive to stress-induced reinstatement than those that self-administered nicotine. Ligand binding autoradiography studies showed nicotine and CSE to have similar affinities for different nicotinic receptor types. CSE significantly reduced MAO-A and MAO-B activities in vitro, whereas nicotine did not. Although CSE inhibition of MAO-A activity in vitro was found to be partially irreversible, irreversible inhibition was not observed in vivo. These experiments show that CSE is an effective reinforcer acting via nicotinic receptors. Furthermore, it better models MAO inhibition and is more sensitive to stress-induced reinstatement than nicotine alone, which is a potent trigger for relapse in smokers.

Acetaldehyde is an oxidative stressor for gastric epithelial cells

Alcohol drinking and smoking contain the risk of a carcinogenesis. Acetaldehyde is content in cigarette smoke and an ethanol metabolite. However the clear evidence for reactive oxygen species (ROS) generation by acetaldehyde in gastric cells in vitro is none. In this study, we elucidated acetaldehyde is an oxidative stress inducer on rat gastric epithelial cells by electron paramagnetic resonance measurement in living cells. We also confirmed whether acetaldehyde-induced cellular ROS was derived from mitochondria or not. The results of cellular ROS determination showed that an increment of cellular ROS was shown for 15 min in living cells from exposing 0.1% (v/v) acetaldehyde. Lipid peroxidation in cellular membrane also induced by 0.1% ethanol and the tendency is same in the results of cellular ROS determination. JC-1 stained showed the decrement of mitochondrial membrane potential. These results indicated that acetaldehyde is not merely a necrotizing factor for gastric epithelial cells, but also an oxidative stress inducer via injured mitochondria.

An evaluation of sucrose as a possible contaminant in e-liquids for electronic cigarettes by hydrophilic interaction liquid chromatography-tandem mass spectrometry

The influence of sucrose combustion products on smoking and nicotine addiction is still controversial because the presence of the sucrose may be treated as a source of aldehydes and organic acids. In e-liquids used as refills for electronic cigarettes, which are made primarily of poly(propylene glycol), glycerine and ethanol, sucrose may be present at trace levels, and its impact on mainstream smoke formation, and hence on human health and smoking/nicotine addiction is unknown. An analytical method was developed where high-performance liquid chromatography in hydrophilic interaction liquid chromatography mode and tandem mass spectrometry were used for fast and simple determination of sucrose and other saccharides in e-liquids for electronic cigarettes. Minimal effort was required in the sample preparation step, and satisfactory results were obtained, and the sample matrix had an insignificant impact. The chromatographic separation was done using an Ascentis Express OH5 column (150 mm × 2.1 mm, 2.7 μm). The coefficients of variation for within-day precision for three concentrations were 2.4 %, 1.6 % and 2.3 %, and the between-day coefficients of variation for a single concentration were 2.1 %, 2.5 % and 1.7 % measured on the next 3 days. The detection limit was 0.73 μg/g, and the sucrose content in e-liquids ranged from 0.76 to 72.93 μg/g among 37 samples. Moreover, with the method presented it is possible to determine the presence of other saccharides such as fructose, glucose, maltose and lactose. However, only sucrose was found in all samples of e-liquids. The proposed method is rapid, simple and reliable in terms of high-performance liquid chromatography coupled with tandem mass spectrometry.

The GSTM1null (deletion) and MGMT84 rs12917 (Phe/Phe) haplotype are associated with bulky DNA adduct levels in human leukocytes

Tobacco smoke and air pollutants contain carcinogens, such as polycyclic aromatic hydrocarbons (PAHs) and tobacco specific nitrosamines (TSNA), that are substrates of metabolizing enzymes generating reactive metabolites that can bind to DNA. Variation in the activity of these enzymes may modify the extent to which these metabolites can interact with DNA. We compared the levels of bulky DNA adducts in blood leukocytes from 93 volunteers living in Mexico City with the presence of 13 single nucleotide polymorphisms (SNPs) in genes related to PAH and TSNA metabolism (AhR rs2044853, CYP1A1 rs1048943, CYP1A1 rs1048943, CYP1A1 rs1799814, EPHX1 rs1051740, EPHX1 rs2234922, GSTM1 null, GSTT1 null and GSTP1 rs947894), DNA repair (XRCC1 rs25487, ERCC2 rs13181 and MGMT rs12917) and cell cycle (TP53 rs1042522). (32)P-postlabeling analysis was used to quantify bulky DNA adduct formation. Genotyping was performed using PCR-RFLP. The mean levels of bulky DNA adducts were 8.51±3.66 adducts/10(8) nucleotides (nt) in smokers and 8.38±3.59 adducts/10(8) nt in non-smokers, being the difference not statistically significant. Without taking into account the smoking status, GSTM1 null individuals had a marginally significant lower adduct levels compared with GSTM1 volunteers (p=0.0433) and individuals heterozygous for MGMT Leu/Phe had a higher level of bulky adducts than those who were homozygous wild type (p=0.0170). A multiple regression analysis model showed a significant association between the GSTM1 (deletion) and MGMT rs12917 (Phe/Phe) haplotype and the formation of DNA adducts in smokers (R(2)=0.2401, p=0.0215). The presence of these variants conferred a greater risk for higher adduct levels in this Mexican population.

The composition of cigarette smoke determines inflammatory cell recruitment to the lung in COPD mouse models

COPD (chronic obstructive pulmonary disease) is caused by exposure to toxic gases and particles, most often CS (cigarette smoke), leading to emphysema, chronic bronchitis, mucus production and a subsequent decline in lung function. The disease pathogenesis is related to an abnormal CS-induced inflammatory response of the lungs. Similar to active (mainstream) smoking, second hand (sidestream) smoke exposure severely affects respiratory health. These processes can be studied in vivo in models of CS exposure of mice. We compared the acute inflammatory response of female C57BL/6 mice exposed to two concentrations [250 and 500 mg/m³ TPM (total particulate matter)] of sidestream and mainstream CS for 3 days and interpreted the biological effects based on physico-chemical differences in the gas and particulate phase composition of CS. BAL (bronchoalveolar lavage fluid) was obtained to perform differential cell counts and to measure cytokine release. Lung tissue was used to determine mRNA and protein expression of proinflammatory genes and to assess tissue inflammation. A strong acute inflammatory response characterized by neutrophilic influx, increased cytokine secretion [KC (keratinocyte chemoattractant), TNF-α (tumour necrosis factor α), MIP-2 (macrophage inflammatory protein 2), MIP-1α and MCP-1 (monocyte chemoattractant protein-1)], pro-inflammatory gene expression [KC, MIP-2 and MMP12 (matrix metalloproteinase 12)] and up-regulated GM-CSF (granulocyte macrophage colony-stimulating factor) production was observed in the mainstream model. After sidestream exposure there was a dampened inflammatory reaction consisting only of macrophages and diminished GM-CSF levels, most likely caused by elevated CO concentrations. These results demonstrate that the composition of CS determines the dynamics of inflammatory cell recruitment in COPD mouse models. Different initial inflammatory processes might contribute to COPD pathogenesis in significantly varying ways, thereby determining the outcome of the studies.

Preparation of phenyl group-functionalized magnetic mesoporous silica microspheres for fast extraction and analysis of acetaldehyde in mainstream cigarette smoke by gas chromatography-mass spectrometry

Acetaldehyde is regarded as a toxic mainstream cigarette smoke constituent, and measurement of acetaldehyde in complex real samples is difficult owing to its high volatility and reactivity. In this work, phenyl group-functionalized magnetic mesoporous microspheres were developed as the solid-phase extraction sorbents for enrichment and analysis of acetaldehyde in mainstream cigarette smoke. The functional magnetic microspheres were first synthesized through a facile one-pot co-condensation approach. The prepared nanomaterials possessed abundant silanol groups in the exterior surface and numerous phenyl groups in the interior pore-walls, as well as a large surface area (273.5m(2)/g), strong superparamagnetism and uniform mesopores (3.3 nm). Acetaldehyde in mainstream cigarette smoke was collected in water and derivatizated with O-2,3,4,5,6-(pentafluorobenzyl)hydroxylamine. The formed acetaldehyde oximes were extracted and enriched by the prepared adsorbents via π-π interactions and subsequently analyzed using GC-MS. Extraction conditions such as amounts of sorbents, eluting solvent, adsorption and desorption time were investigated and optimized to achieve the best efficiency. Method validations including linearity, recovery, repeatability, and limit of detection were also studied. It was found that the suggested methodology provided low detection limit of 0.04 mg/mL, good recovery of 88-92%, intra-day and inter-day RSD values of 4.5% and 10.1%, and linear range of 0.25-4 mg/mL (R(2)=0.999). The results indicated that the proposed method based on phenyl-functionalized magnetic mesoporous microspheres was rapid, efficient and convenient for the enrichment and analysis of acetaldehyde in tobacco.