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Stephen S. Hecht - One of the best experts on this subject based on the ideXlab platform.
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metabolism and dna adduct formation of carcinogenic tobacco specific Nitrosamines found in smokeless tobacco products
2020Co-Authors: Stephen S. HechtAbstract:Abstract Tobacco-Specific Nitrosamines are the most abundant strong carcinogens in smokeless tobacco products. This chapter focuses on three of the most important of these compounds: N′-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). The carcinogenic activities of NNN, NNK, and NNAL are discussed, and the metabolic pathways of these carcinogens are presented. Specific metabolite biomarkers have been developed to assess exposure to Tobacco-Specific Nitrosamines in smokeless tobacco users; these are presented and discussed. DNA and protein adduct formation by Tobacco-Specific Nitrosamines are also summarized, based mainly on studies in laboratory animals.
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recent studies on dna adducts resulting from human exposure to tobacco smoke
Toxics, 2019Co-Authors: Irina Stepanov, Stephen S. HechtAbstract:DNA adducts are believed to play a central role in the induction of cancer in cigarette smokers and are proposed as being potential biomarkers of cancer risk. We have summarized research conducted since 2012 on DNA adduct formation in smokers. A variety of DNA adducts derived from various classes of carcinogens, including aromatic amines, polycyclic aromatic hydrocarbons, Tobacco-Specific Nitrosamines, alkylating agents, aldehydes, volatile carcinogens, as well as oxidative damage have been reported. The results are discussed with particular attention to the analytical methods used in those studies. Mass spectrometry-based methods that have higher selectivity and specificity compared to 32P-postlabeling or immunochemical approaches are preferred. Multiple DNA adducts specific to tobacco constituents have also been characterized for the first time in vitro or detected in vivo since 2012, and descriptions of those adducts are included. We also discuss common issues related to measuring DNA adducts in humans, including the development and validation of analytical methods and prevention of artifact formation.
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analysis and identification of 2 deoxyadenosine derived adducts in lung and liver dna of f 344 rats treated with the tobacco specific carcinogen 4 methylnitrosamino 1 3 pyridyl 1 butanone and enantiomers of its metabolite 4 methylnitrosamino 1 3 pyridyl 1 butanol
Chemical Research in Toxicology, 2018Co-Authors: Erik S Carlson, Pramod Upadhyaya, Peter W Villalta, Stephen S. HechtAbstract:4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) are carcinogenic in animal models and are believed to play an important role in human lung carcinogenesis for cigarette smokers. Cytochrome P450-mediated metabolism of these Tobacco-Specific Nitrosamines produces reactive species that alkylate DNA in the form of pyridyloxobutyl (POB)- or pyridylhydroxybutyl (PHB)-DNA adducts. Understanding the formation mechanism and overall levels of these adducts can potentially enhance cancer prevention methods through the identification of particularly susceptible smokers. Previous studies have identified and measured a panel of POB- and PHB-DNA base adducts of dGuo, dCyd, and Thd; however, dAdo adducts have yet to be determined. In this study, we complete this DNA adduct panel by identifying and quantifying levels of NNK- and NNAL-derived dAdo adducts in vitro and in vivo. To accomplish this, we synthesized standards for expected dAdo-derived D...
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identification of 4 3 pyridyl 4 oxobutyl 2 deoxycytidine adducts formed in the reaction of dna with 4 acetoxymethylnitrosamino 1 3 pyridyl 1 butanone a chemically activated form of tobacco specific carcinogens
ACS omega, 2017Co-Authors: Anna K Michel, Pramod Upadhyaya, Adam T Zarth, Stephen S. HechtAbstract:Metabolic activation of the carcinogenic Tobacco-Specific Nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK, 1) and N′-nitrosonornicotine (NNN, 2) results in the formation of 4-(3-pyridyl)-4-oxobutyl (POB)-DNA adducts, several of which have been previously identified both in vitro and in tissues of laboratory animals treated with NNK or NNN. However, 2′-deoxycytidine adducts formed in this process have been incompletely examined in previous studies. Therefore, in this study we prepared characterized standards for the identification of previously unknown 2′-deoxycytidine and 2′-deoxyuridine adducts that could be produced in these reactions. The formation of these products in reactions of 4-(acetoxymethylnitrosamino)-1-(3-pyridyl)-1-butanone (NNKOAc, 3), a model 4-(3-pyridyl)-4-oxobutylating agent, with DNA was investigated. The major 2′-deoxycytidine adduct, identified as its stable cytosine analogue O2-[4-(3-pyridyl)-4-oxobut-1-yl]-cytosine (12), was O2-[4-(3-pyridyl)-4-oxobut-1-yl]-2′-deox...
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exposure and metabolic activation biomarkers of carcinogenic tobacco specific Nitrosamines
Accounts of Chemical Research, 2016Co-Authors: Stephen S. Hecht, Irina Stepanov, Steven G. CarmellaAbstract:ConspectusLung cancer is the leading cause of cancer death in the world, and cigarette smoking is its main cause. Oral cavity cancer is another debilitating and often fatal cancer closely linked to tobacco product use. While great strides have been made in decreasing tobacco use in the United States and some other countries, there are still an estimated 1 billion men and 250 million women in the world who are cigarette smokers and there are hundreds of millions of smokeless tobacco users, all at risk for cancer. Worldwide, lung cancer kills about three people per minute.This Account focuses on metabolites and biomarkers of two powerful Tobacco-Specific nitrosamine carcinogens, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N′-nitrosonornicotine (NNN), considered to be among the main causes of lung cancer and oral cavity cancer in people who use tobacco products. Three properties of NNK and NNN are critical for successful biomarker studies: they are present in all tobacco products, they are tobac...
Irina Stepanov - One of the best experts on this subject based on the ideXlab platform.
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recent studies on dna adducts resulting from human exposure to tobacco smoke
Toxics, 2019Co-Authors: Irina Stepanov, Stephen S. HechtAbstract:DNA adducts are believed to play a central role in the induction of cancer in cigarette smokers and are proposed as being potential biomarkers of cancer risk. We have summarized research conducted since 2012 on DNA adduct formation in smokers. A variety of DNA adducts derived from various classes of carcinogens, including aromatic amines, polycyclic aromatic hydrocarbons, Tobacco-Specific Nitrosamines, alkylating agents, aldehydes, volatile carcinogens, as well as oxidative damage have been reported. The results are discussed with particular attention to the analytical methods used in those studies. Mass spectrometry-based methods that have higher selectivity and specificity compared to 32P-postlabeling or immunochemical approaches are preferred. Multiple DNA adducts specific to tobacco constituents have also been characterized for the first time in vitro or detected in vivo since 2012, and descriptions of those adducts are included. We also discuss common issues related to measuring DNA adducts in humans, including the development and validation of analytical methods and prevention of artifact formation.
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exposure and metabolic activation biomarkers of carcinogenic tobacco specific Nitrosamines
Accounts of Chemical Research, 2016Co-Authors: Stephen S. Hecht, Irina Stepanov, Steven G. CarmellaAbstract:ConspectusLung cancer is the leading cause of cancer death in the world, and cigarette smoking is its main cause. Oral cavity cancer is another debilitating and often fatal cancer closely linked to tobacco product use. While great strides have been made in decreasing tobacco use in the United States and some other countries, there are still an estimated 1 billion men and 250 million women in the world who are cigarette smokers and there are hundreds of millions of smokeless tobacco users, all at risk for cancer. Worldwide, lung cancer kills about three people per minute.This Account focuses on metabolites and biomarkers of two powerful Tobacco-Specific nitrosamine carcinogens, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N′-nitrosonornicotine (NNN), considered to be among the main causes of lung cancer and oral cavity cancer in people who use tobacco products. Three properties of NNK and NNN are critical for successful biomarker studies: they are present in all tobacco products, they are tobac...
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increased pouch sizes and resulting changes in the amounts of nicotine and tobacco specific n Nitrosamines in single pouches of camel snus and marlboro snus
Nicotine & Tobacco Research, 2012Co-Authors: Irina Stepanov, Stephen S. Hecht, Joni Jensen, Lois Biener, Robin L Bliss, Dorothy K HatsukamiAbstract:Introduction: Initial analyses of the novel smokeless tobacco products Camel Snus and Marlboro Snus demonstrated that these products contain relatively low amounts of nicotine and the carcinogenic Tobacco-Specific Nitrosamines N’-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), as compared with traditional smokeless products. It is unknown whether the modifications in packaging, flavors, and pouch sizes that occurred for both Camel Snus and Marlboro Snus since their first introduction to the market were accompanied by any changes in nicotine or nitrosamine levels.
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carcinogenic tobacco specific n Nitrosamines in us cigarettes three decades of remarkable neglect by the tobacco industry
Tobacco Control, 2012Co-Authors: Irina Stepanov, Dorothy K Hatsukami, Clifford H. Watson, Liqin Zhang, Aleksandar Knezevich, Stephen S. HechtAbstract:Background Modification of tobacco curing methods and other changes in cigarette manufacturing techniques could substantially reduce the levels of Tobacco-Specific Nitrosamines (TSNA), a group of potent carcinogens, in cigarette smoke. In 1999, two major US cigarette manufacturers stated their intent to move towards using tobaccos low in TSNA. There is no information available on current TSNA levels in tobacco of various cigarettes available in the US, particularly in the newer varieties introduced over the past decade. Methods Seventeen brands of cigarettes were purchased in April of 2010 from retail stores in Minnesota. TSNA levels were measured in the tobacco filler and smoke of these cigarettes. Results In all brands, the sum of two potent carcinogenic TSNA - 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N9 -nitrosonornicotine - in cigarette filler averaged 2.54 (±1.05) μg/g tobacco. This value is virtually identical to the sum of these two carcinogens reported for the tobacco of a US filtered cigarette in 1979. TSNA levels in smoke positively correlated with those in tobacco filler of the same cigarettes. Conclusion We found no indication that any meaningful attempt was made to reduce or at least control TSNA levels in the new varieties of the popular brands Marlboro and Camel introduced over the last decade. In light of the recently granted regulatory authority to the FDA over tobacco products, regulation of TSNA levels in cigarette tobacco should be strongly considered to reduce the levels of these potent carcinogens in cigarette smoke.
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evidence for endogenous formation of n nitrosonornicotine in some long term nicotine patch users
Nicotine & Tobacco Research, 2009Co-Authors: Irina Stepanov, Steven G. Carmella, Angela Pinto, Andrew A Strasser, Caryn Lerman, Stephen S. HechtAbstract:Introduction: Nitrosation of nicotine or its metabolites in the human body could lead to formation of the 2 carcinogenic Tobacco-Specific Nitrosamines—N′-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK).
Clifford H. Watson - One of the best experts on this subject based on the ideXlab platform.
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Tobacco-Specific Nitrosamines in tobacco from U.S. brand and non-U.S. brand cigarettes
2016Co-Authors: David L. Ashley, Michelle D. Beeson, Diana R. Johnson, Joan M. Mccraw, Patricia Richter, James L. Pirkle, Terry F. Pechacek, Siqing Song, Clifford H. WatsonAbstract:Tobacco-Specific Nitrosamines (TSNAs) are one of the major classes of carcinogens found in tobacco products. As part of collaborative efforts to reduce tobacco use and resulting disease, the U.S. Centers for Disease Control and Prevention (CDC) carried out a two-phase investigation into the worldwide variation of the levels of TSNAs in cigarette tobacco. In the first phase, representatives of the World Health Organization (WHO) purchased cigarettes; scientists from the CDC subsequently measured the levels of TSNAs in tobacco from 21 different countries. Although the data collected from this initial survey suggested that globally marketed U.S.-brand cigarettes typically had higher TSNA levels than locally popular non-U.S. cigarettes in many countries, the number of samples limited the statistical power of the study. To improve statistical power and to ensure adequate sampling, the CDC conducted a second survey of 14 countries. In addition to the United States, the CDC selected the world’s 10 most populous countries and three additional countries, so that at least two countries from each of the six WHO regions were represented. For each country, the CDC compared 15 packs of Marlboro cigarettes, which is the world’s most popular brand of cigarettes, with 15 packs of a locally popular non-U.S. brand in the study country. Marlboro cigarettes purchased in 11/13 foreign countries had significantly higher tobacco TSNA levels than the locally popular non-U.S. brands purchased in the same country. The findings suggest that TSNA levels in tobacco can be substantially reduced in some cigarettes
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Semi-volatiles in mainstream smoke delivery from select charcoal-filtered cigarette brand variants
2016Co-Authors: Bryan A Hearn, Clifford H. Watson, Liqin Zhang, Yan S. Ding, Christina Vaughan, Gregory Polzin, Samuel P Caudill, David L. AshleyAbstract:Background It has been reported that charcoal added to cigarette filters selectively removes many of the more volatile chemicals, but it is not clear to what extent charcoal may reduce the delivery of important less volatile chemical constituents in mainstream cigarette smoke. Methods We analysed machine-derived mainstream smoke deliveries (under three smoking regimens) for variants of a charcoal-filtered cigarette commercially test-marketed in the USA, focusing on selected polycyclic aromatic hydrocarbons (PAHs), phenols and Tobacco-Specific Nitrosamines (TSNAs). Results While charcoal-containing filters selectively removed lower molecular weight PAHs from mainstream smoke, they did not significantly remove the heavier and more toxic PAHs studied, such as benzo[a]pyrene, a known carcinogen. Likewise, charcoal-containing filters removed phenols and TSNAs from mainstream smoke to differing amounts depending on the compound, filter design and the smoking regimen. Conclusions The addition of sufficient charcoal to cigarette filters is known to remove many volatile compounds and can potentially reduce deliveries of certain semi-volatile compounds under some machine smoking regimens. Less volatile compounds, with a significant portion in the particulate phase, are less available for selective filtration by charcoal-containing filters than the more volatile compounds that reside predominantly in the gas phase
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Tobacco-Specific Nitrosamines in the Tobacco and Mainstream Smoke of U.S. Commercial Cigarettes
2016Co-Authors: Selvin H. Edwards, Liqin Zhang, Lana M. Rossiter, Kenneth M. Taylor, Matthew R. Holman, Yan S. Ding, Clifford H. WatsonAbstract:Tobacco-Specific Nitrosamines (TSNAs) are N-nitroso-derivatives of pyridine-alkaloids (e.g., nicotine) present in tobacco and cigarette smoke. Two TSNAs, N′-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), are included on the Food and Drug Administration’s list of harmful and potentially harmful constituents (HPHCs) in tobacco products and tobacco. The amounts of four TSNAs (NNK, NNN, N-nitrosoanabasine (NAB), and N′-nitrosoanatabine (NAT)) in the tobacco and mainstream smoke from 50 U.S. commercial cigarette brands were measured from November 15, 2011 to January 4, 2012 using a validated HPLC/MS/MS method. Smoke samples were generated using the International Organization of Standardization (ISO) and Canadian Intense (CI) machine-smoking regimens. NNN and NAT were the most abundant TSNAs in tobacco filler and smoke across all cigarette brands, whereas NNK and NAB were present in lesser amounts. The average ratios for each TSNA in mainstream smoke to filler content is 29% by the CI smoking regimen and 13% for the ISO machine-smoking regimen. The reliability of individual TSNAs to predict total TSNA amounts in the filler and smoke was examined. NNN, NAT, and NAB have a moderate to high correlation (R2 = 0.61–0.98, p < 0.0001), and all three TSNAs individually predict total TSNAs with minimal difference between measured and predicted total TSNA amounts (error < 7.4%). NNK has weaker correlation (R2 = 0.56–0.82; p < 0.0001) and is a less reliable predictor of total TSNA quantities. Tobacco weight and levels of TSNAs in filler influence TSNA levels in smoke from the CI machine-smoking regimen. In contrast, filter ventilation is a major determinant of levels of TSNAs in smoke by the ISO machine-smoking regimen. Comparative analysis demonstrates substantial variability in TSNA amounts in tobacco filler and mainstream smoke yields under ISO and CI machine-smoking regimens among U.S. commercial cigarette brands
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carcinogenic tobacco specific n Nitrosamines in us cigarettes three decades of remarkable neglect by the tobacco industry
Tobacco Control, 2012Co-Authors: Irina Stepanov, Dorothy K Hatsukami, Clifford H. Watson, Liqin Zhang, Aleksandar Knezevich, Stephen S. HechtAbstract:Background Modification of tobacco curing methods and other changes in cigarette manufacturing techniques could substantially reduce the levels of Tobacco-Specific Nitrosamines (TSNA), a group of potent carcinogens, in cigarette smoke. In 1999, two major US cigarette manufacturers stated their intent to move towards using tobaccos low in TSNA. There is no information available on current TSNA levels in tobacco of various cigarettes available in the US, particularly in the newer varieties introduced over the past decade. Methods Seventeen brands of cigarettes were purchased in April of 2010 from retail stores in Minnesota. TSNA levels were measured in the tobacco filler and smoke of these cigarettes. Results In all brands, the sum of two potent carcinogenic TSNA - 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N9 -nitrosonornicotine - in cigarette filler averaged 2.54 (±1.05) μg/g tobacco. This value is virtually identical to the sum of these two carcinogens reported for the tobacco of a US filtered cigarette in 1979. TSNA levels in smoke positively correlated with those in tobacco filler of the same cigarettes. Conclusion We found no indication that any meaningful attempt was made to reduce or at least control TSNA levels in the new varieties of the popular brands Marlboro and Camel introduced over the last decade. In light of the recently granted regulatory authority to the FDA over tobacco products, regulation of TSNA levels in cigarette tobacco should be strongly considered to reduce the levels of these potent carcinogens in cigarette smoke.
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effect of differing levels of tobacco specific Nitrosamines in cigarette smoke on the levels of biomarkers in smokers
Cancer Epidemiology Biomarkers & Prevention, 2010Co-Authors: David L. Ashley, Dorothy K Hatsukami, Richard J Oconnor, Clifford H. Watson, Ram B Jain, John T Bernert, Gregory M Polzin, David Hammond, Gary A Giovino, Michael K CummingsAbstract:Background: Smokers are exposed to significant doses of carcinogens, including Tobacco-Specific Nitrosamines (TSNA). Previous studies have shown significant global differences in the levels of TSNAs in cigarette smoke because of the variation in tobacco blending and curing practices around the world. Methods: Mouth-level exposure to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) measured in cigarette butts and urinary concentrations of its major metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) were examined among 126 daily smokers in four countries over a 24-hour study period. Results: As mouth-level exposure of NNK increased, the urinary NNAL increased even after adjustment for other covariates ( β = 0.46, P = 0.004). The relationship between mouth-level exposure to nicotine and its salivary metabolite, cotinine, was not statistically significant ( β = 0.29, P = 0.057), likely because of the very limited range of differences in mouth-level nicotine exposure in this population. Conclusions: We have shown a direct association between the 24-hour mouth-level exposure of NNK resulting from cigarette smoking and the concentration of its primary metabolite, NNAL, in the urine of smokers. Internal dose concentrations of urinary NNAL are significantly lower in smokers in countries that have lower TSNA levels in cigarettes such as Canada and Australia in contrast to countries that have high levels of these carcinogens in cigarettes, such as the United States. Impact: Lowering the levels of NNK in the mainstream smoke of cigarettes through the use of specific tobacco types and known curing practices can significantly affect the exposure of smokers to this known carcinogen. Cancer Epidemiol Biomarkers Prev; 19(6); 1389–98. ©2010 AACR. This article is featured in Highlights of This Issue, [p. 1387][1] [1]: /lookup/volpage/19/1387
Gene I Gillman - One of the best experts on this subject based on the ideXlab platform.
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www.mdpi.com/journal/ijerph Article Nicotine Levels and Presence of Selected Tobacco-Derived Toxins in Tobacco Flavoured Electronic Cigarette Refill Liquids
2016Co-Authors: Konstantinos E Farsalinos, Gene I Gillman, Konstantinos Poulas, Matt S. Melvin, Amelia R. Paolantonio, Wendy J. Gardow, Kathy E. Humphries, Sherri E. Brown, Vassilis VoudrisAbstract:Abstract: Background. Some electronic cigarette (EC) liquids of tobacco flavour contain extracts of cured tobacco leaves produced by a process of solvent extraction and steeping. These are commonly called Natural Extract of Tobacco (NET) liquids. The purpose of the study was to evaluate nicotine levels and the presence of tobacco-derived toxins in tobacco-flavoured conventional and NET liquids. Methods. Twenty-one samples (10 conventional and 11 NET liquids) were obtained from the US and Greek market. Nicotine levels were measured and compared with labelled values. The levels of tobacco-derived chemicals were compared with literature data on tobacco products. Results. Twelve samples had nicotine levels within 10 % of the labelled value. Inconsistency ranged from −21 % to 22.1%, with no difference observed between conventional and NET liquids. Tobacco-Specific Nitrosamines (TSNAs) were present in all samples at ng/mL levels. Nitrates were present almost exclusively in NET liquids. Acetaldehyde was present predominantly i
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tobacco specific Nitrosamines in electronic cigarettes comparison between liquid and aerosol levels
International Journal of Environmental Research and Public Health, 2015Co-Authors: Konstantinos E Farsalinos, Gene I Gillman, Konstantinos Poulas, Vassilis VoudrisAbstract:Introduction: Although electronic cigarette (EC) liquids contain low levels of Tobacco-Specific Nitrosamines (TSNAs), studies evaluating the levels emitted to the aerosol are scarce. The purpose of this study was to compare the levels of TSNAs between liquids and generated aerosol. Methods: Three EC liquids were obtained from the market. An additional (spiked) sample was prepared by adding known amounts of standard TSNAs solutions to one of the obtained liquids. N-nitrosonornicotine (NNN), N-nitrosoanatabine (NAT), N-nitrosoanabasine (NAB) and 4-(methylnitrosamino)1-(3-pyridyl)-1-butanone (NNK) were measured. Three 100-puff sets from each liquid were trapped in filter pads and were subsequently analyzed for the presence of TSNAs. The expected levels of TSNAs (calculated based on the liquid consumption) were compared with the measured levels in the aerosol. Results: Only NAB was found at trace levels in two commercial liquids (1.2 and 2.3 ng/g), while the third contained 1.5 ng/g NAB and 7.7 ng/g NNN. The 100-puff sets resulted in 336–515 mg liquid consumption, with no TSNAs being detected in the aerosol. The spiked sample contained 42.0–53.9 ng/g of each of the TSNAs. All TSNAs were detected in the aerosol with the measured levels being statistically similar to the expected amounts. A significant correlation between expected and measured levels of TSNAs in the aerosol was found (r = 0.83, p < 0.001). Conclusion: The findings of this study show that exposure of EC users to TSNAs can be accurately assessed based on the levels present in the liquid, without the need to analyze the aerosol.
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development of a quantitative method for the analysis of tobacco specific Nitrosamines in mainstream cigarette smoke using isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry
Analytical Chemistry, 2005Co-Authors: Karl A Wagner, Nancy H Finkel, Eric J Fossett, Gene I GillmanAbstract:An improved method has been developed for the determination of the four major Tobacco-Specific Nitrosamines (TSNA) in mainstream cigarette smoke. The new method offers decreased sample preparation and analysis time as compared to traditional methodologies. This method uses isotope dilution liquid chromatography coupled to a tandem mass spectrometer with electrospray ionization and is significantly more sensitive than traditional methods. It also shows no evidence of artifactual formation of TSNA. Sample concentrations were determined for four TSNA in mainstream smoke using two isotopically labeled TSNA analogues as internal standards. Mainstream smoke was collected on an industry standard 44-mm Cambridge filter pad, extracted with an aqueous buffer solution, and analyzed without further sample cleanup. This method has been validated through intra- and interlaboratory studies and has shown excellent recoveries, sensitivity, and repeatability. The limits of detection of each TSNA varied from 0.01 to 0.1 ng/...
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development of a quantitative method for the analysis of tobacco specific Nitrosamines in mainstream cigarette smoke using isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry
Analytical Chemistry, 2005Co-Authors: Karl A Wagner, Eric J Fossett, Nancy Finkel, Gene I GillmanAbstract:An improved method has been developed for the determination of the four major Tobacco-Specific Nitrosamines (TSNA) in mainstream cigarette smoke. The new method offers decreased sample preparation and analysis time as compared to traditional methodologies. This method uses isotope dilution liquid chromatography coupled to a tandem mass spectrometer with electrospray ionization and is significantly more sensitive than traditional methods. It also shows no evidence of artifactual formation of TSNA. Sample concentrations were determined for four TSNA in mainstream smoke using two isotopically labeled TSNA analogues as internal standards. Mainstream smoke was collected on an industry standard 44-mm Cambridge filter pad, extracted with an aqueous buffer solution, and analyzed without further sample cleanup. This method has been validated through intra- and interlaboratory studies and has shown excellent recoveries, sensitivity, and repeatability. The limits of detection of each TSNA varied from 0.01 to 0.1 ng/mL, and the linear calibration range of the instrument in sample matrix spanned 0.5-200 ng/ mL, which allowed for the determination of the TSNA levels in cigarettes with a wide range of deliveries. Data are also reported from two commercially available industry reference cigarettes and show excellent agreement and reproducibility over a six-month time period (n > 50).
Tsuichun Tsou - One of the best experts on this subject based on the ideXlab platform.
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metabolic effects of cyp2a6 and cyp2a13 on 4 methylnitrosamino 1 3 pyridyl 1 butanone nnk induced gene mutation a mammalian cell based mutagenesis approach
Toxicology and Applied Pharmacology, 2011Co-Authors: Huaichih Chiang, Hui-ling Lee, Chinying Wang, Tsuichun TsouAbstract:Abstract Both cytochrome P450 2A6 (CYP2A6) and cytochrome P450 2A13 (CYP2A13) are involved in metabolic activation of Tobacco-Specific Nitrosamines and may play important roles in cigarette smoking-induced lung cancer. Unlike CYP2A6, effects of CYP2A13 on the Tobacco-Specific nitrosamine-induced mutagenesis in lung cells remain unclear. This study uses a supF mutagenesis assay to examine the relative effects of CYP2A6 and CYP2A13 on metabolic activation of a Tobacco-Specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and its resulting mutagenesis in human lung cells. A recombinant adenovirus-mediated CYP2A6/CYP2A13 expression system was established to specifically address the relative effects of these two CYPs. Mutagenesis results revealed that both CYP2A6 and CYP2A13 significantly enhanced the NNK-induced supF mutation and that the mutagenic effect of CYP2A13 was markedly higher than that of CYP2A6. Analysis of NNK metabolism indicated that ≥ 70% of NNK was detoxified to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), either with or without CYP2A6/CYP2A13 expression. Both CYP2A6 and CYP2A13 significantly enhanced the α-hydroxylation of NNK; and the α-hydroxylation activity of CYP2A13 was significantly higher than that of CYP2A6. Analysis of the NNK-related DNA adduct formation indicated that, in the presence of CYP2A13, NNK treatments caused marked increases in O 6 -methylguanine (O 6 -MeG). The present results provide the first direct in vitro evidence demonstrating the predominant roles of CYP2A13 in NNK-induced mutagenesis, possibly via metabolic activation of NNK α-hydroxylation.
