N-nitroso compounds in cigarette tobacco and their occurrence in mainstream tobacco smoke

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.

Intake of tobacco nitrosamines of smokers in various provinces of China and their cancer risk: A meta-analysis

Nitrosamines are a class of carcinogens which have been detected widely in food, water, some pharmaceuticals as well as tobacco. The objectives of this paper include reviewing the basic information on tobacco consumption and nitrosamine contents, and assessing the health risks of tobacco nitrosamines exposure to Chinese smokers. We searched the publications in English from "Web of Science" and those in Chinese from the "China National Knowledge Infrastructure" in 2022 and collected 151 literatures with valid information. The content of main nitrosamines in tobacco, including 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosonornicotine (NNN), N-nitrosoanatabine (NAT), N-nitrosoanabasine (NAB), total tobacco-specific nitrosamines (TSNA), and N-nitrosodimethylamine (NDMA) were summarized. The information of daily tobacco consumption of smokers in 30 provinces of China was also collected. Then, the intakes of NNN, NNK, NAT, NAB, TSNAs, and NDMA via tobacco smoke were estimated as 1534 ng/day, 591 ng/day, 685 ng/day, 81 ng/day, 2543 ng/day, and 484 ng/day by adult smokers in 30 provinces, respectively. The cancer risk (CR) values for NNN and NNK inhalation intake were further calculated as 1.44 × 10-5 and 1.95 × 10-4. The CR value for NDMA intake via tobacco smoke (inhalation: 1.66 × 10-4) indicates that NDMA is similarly dangerous in tobacco smoke when compared with the TSNAs. In China, the CR values caused by average nitrosamines intake via various exposures and their order can be estimated as the following: smoke (3.75 × 10-4) > food (1.74 × 10-4) > drinking water (1.38 × 10-5). Smokers in China averagely suffer 200% of extra cancer risk caused by nitrosamines in tobacco when compared with non-smokers.

Exogenous of different elicitors: proline and ornithine on Sansevieria trifasciata under particulate matter (PM) and volatile organic compounds (VOC)

Phytoremediation has become famous for removing particulate matter (PM) and volatile organic compounds (VOC) in situ. Plants for removing PM and VOC were associated with botanical biofilters to attract pollution to the plant. On the other hand, persistent pollution exposure can lower plant health and phytoremediation effectiveness; therefore, improving plant tolerance against stress is necessary. Various elicitors can enhance plant tolerance to certain stressors. This study aims to investigate different elicitors to maintain plant health and improve the use of plants in phytoremediation for PM and VOC pollution. This experiment used Sansevieria trifasciata hort. ex Prain under PM and VOC stress. Exogenous elicitors, such as proline, ornithine, and a commercial product, were applied to the leaf parts before exposure to PM and VOC stress. The initial concentrations of PM1, PM2.5, and PM10 were 300-350, 350-450, and 400-500 µg m-3, respectively, while the VOC concentration was 2.5-3.0 mg m-3. The plant was stressed for 7 days. The result indicated that ornithine 10 mM is vital in improving plant tolerance and inducing antioxidant enzymes against PM and VOC, while proline 50 mM and a commercial product could not reduce plant stress. This study suggests that ornithine might be an important metabolite to improve plant tolerance to PM and VOC.

Sijunzi decoction ameliorates gastric precancerous lesions via regulating oxidative phosphorylation based on proteomics and metabolomics

ETHNOPHARMACOLOGICAL RELEVANCE

Sijunzi decoction (SJZD), a traditional Chinese medicine formula, is commonly used in clinical practice for the treatment of gastric precancerous lesions (GPL). However, the mechanism of gastric protection is not fully understood.

AIMS OF THE STUDY

The purpose of this study was to systematically evaluate the efficacy of SJZD in blocking the development of GPL and to reveal the underlying mechanism.

METHODS

First, we established a rat model of GPL, which was induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) combined with an irregular diet and 40% ethanol. The efficacy of SJZD was evaluated based on pathological sections and serum biochemical indices. Then, the pharmacodynamic mechanism of SJZD was revealed by quantitative proteomics based on stable isotope dimethyl labeling. At the same time, the pharmacodynamic mechanism was verified by quantitative metabolomics. In addition, the anti-gastritis effect of SJZD was confirmed by a serum pharmacology method in a cell model, and the functional mechanism was further verified.

RESULTS

We demonstrated that SJZD could block the development of GPL in the animal model. Proteomics and metabolomics revealed that SJZD blocks GPL development by regulating oxidative phosphorylation (OXPHOS). In addition, the serum pharmacology results showed that SJZD-containing serum (SJZD-CS) could inhibit apoptosis in MNNG-induced GES-1 cells. OXPHOS inhibitors could significantly reduce the protective effect of SJZD-CS.

CONCLUSION

SJZD effectively ameliorates GPL, and proteomics and metabolomics revealed that its protective effects are closely related to OXPHOS.

Harmful and Potentially Harmful Constituents in the Filler and Smoke of Tobacco-Containing Tobacco Products

The U.S. Food and Drug Administration established a list of 93 harmful and potentially harmful constituents (HPHCs) in tobacco products. While HPHCs are required to be submitted for tobacco products, knowledge gaps exist regarding which tobacco-containing tobacco product (TCTP, i.e., tobacco products that contain tobacco(s) as a component) types (cigarettes, cigars, roll-your-own tobaccos [RYOs], pipe tobaccos [pipes], smokeless tobacco products [STPs], waterpipe tobaccos [waterpipes]) and matrices (filler, smoke) contain which HPHCs. This study identified and addressed such gaps by conducting literature searches and measuring the amount of HPHCs in TCTP types and matrices. First, literature searches, performed for cigarettes, RYOs, and STPs for publications up to 2014 and for cigars, pipes, and waterpipes for publications up to 2016, identified knowledge gaps for the 93 HPHCs (or 119 HPHCs if cresols [o-, m-, p-cresol] are counted as 3 and chlorinated dioxins/furans as 25) across TCTP types and matrices. Then, three ISO 17025 accredited laboratories including two subcontracted laboratories performed the HPHC quantifications. Inclusion of the HPHCs, TCTP types, and matrices in the study scope was also determined by the availability of validated analytical methods in each laboratory. Eleven (9%) HPHCs are quantifiable in all brands for all TCTP types and matrices, 33 (28%) HPHCs are not quantifiable in any brands of any TCTP type and matrix, and 74 (63%) HPHCs are quantifiable only in some brands across TCTP types and matrices examined. Understanding the quantifiability of HPHCs in each TCTP type and matrix can inform the scientific basis for manufacturers regarding the regulatory requirements for reporting HPHCs. The quantity of HPHCs observed can also inform the evaluation of the public health impact of HPHCs and public communications regarding the health risks of tobacco products.

Inflammation and Gastric Cancer

Gastric cancer remains a major killer globally, although its incidence has declined over the past century. It is the fifth most common cancer and the third most common reason for cancer-related deaths worldwide. Gastric cancer is the outcome of a complex interaction between environmental, host genetic, and microbial factors. There is significant evidence supporting the association between chronic inflammation and the onset of cancer. This association is particularly robust for gastrointestinal cancers in which microbial pathogens are responsible for the chronic inflammation that can be a triggering factor for the onset of those cancers. Helicobacter pylori is the most prominent example since it is the most widespread infection, affecting nearly half of the world’s population. It is well-known to be responsible for inducing chronic gastric inflammation progressing to atrophy, metaplasia, dysplasia, and eventually, gastric cancer. This review provides an overview of the association of the factors playing a role in chronic inflammation; the bacterial characteristics which are responsible for the colonization, persistence in the stomach, and triggering of inflammation; the microbiome involved in the chronic inflammation process; and the host factors that have a role in determining whether gastritis progresses to gastric cancer. Understanding these interconnections may improve our ability to prevent gastric cancer development and enhance our understanding of existing cases.

Stereospecific Response of E/Z-isomers of N-Nitrososarcosine in LC-ESI-MS/MS

The carcinogenic compound N-nitrososarcosine (NSAR) is found in foods and tobacco products, and its quantification is of great interest. Although the presence of two stereoisomers, E- and Z-NSAR, is well-known, individual investigation of the isomers has not been reported so far. The present study by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) reveals that (i) the mass spectrometric responses of the isomers differ by a factor of approximately two and (ii) the isomer ratio is unstable in freshly prepared standard solutions. As a consequence, NSAR concentrations determined by LC-ESI-MS/MS are biased if those facts are not taken into account. The method described here overcomes the difficulty of stereospecific response by adjusting the isomer ratio and was applied to 100 tobacco products and fully validated for moist and dry snuff reference materials showing expanded measurement uncertainties of ~20% and limits of quantification of ~20 ng/g.

Quantification of nitromethane in mainstream smoke using gas chromatography and tandem mass spectrometry

Nitromethane is a volatile organic compound categorized as a Group 2B carcinogen by the International Agency for Research on Cancer. It has been detected in mainstream cigarette smoke, but few reliable methods have been reported for accurate quantification. We developed, a sensitive, selective, fully validated method for the targeted determination of nitromethane in mainstream tobacco smoke in ten U.S. domestic brands and two quality control materials (3R4F and CM6). The vapor phase portion of machine-generated cigarette mainstream smoke, under modified ISO 3308:2000 regime (ISO) and modified intense regime (HCI), from single cigarettes was collected using airtight polyvinylfluoride sampling bags. The bags' contents were extracted using methanol containing an isotopically labeled internal standard followed by gas chromatography-tandem mass spectrometry. This approach is sufficiently sensitive to measure nitromethane levels in the nanogram range, with a method limit of detection of 72.3 ng/cig. Within-product variability estimated from the replicate analysis of 10 products ranged from 4.6%-16.3% (n = 6) over the two different smoking regimes, and method reproducibility estimated from two products used as quality control materials (3R4F and CM6) yielded intermediate precision values ranging from 16.6 to 20.8% (n = 20). Under HCI, nitromethane yields in machine-generated cigarette smoke from ten different domestic cigarette products ranged from 3.2 to 12 μg/cig; under ISO yields ranged from 1.6 to 4.9 μg/cig under standardized smoking machine conditions. Nitromethane yields are related to both the smoke regime (blocking of vent holes, puff duration and puff volume) and the heterogeneity of tobacco mixtures. This method provides a selective and fully validated technique to accurately quantify nitromethane in mainstream cigarette smoke, with minimal waste generation. It is an improvement over previous methods with regards to specificity, throughput, and simplicity of the sample collection process.

Amelioration of oxidative stress, inflammation and liver function by nutraceuticals in rat model of hepatic cancer initiation induced by N-nitrosodiethylamine

Introduction: Nutraceuticals might serve as protective agent against liver cancer induced by pro-cancerous chemicals that initiate high oxidative stress, inflammation and affect DNA integrity. The aim of the present research was to study the prevention of hepatocellular carcinoma initiation induced by N-nitrosodiethylamine (NDEA) through treatment by nutraceuticals. Methods: Two nutraceuticals were prepared; the first (NI) was a mixture of different extracts of green tea, wheat germ and tomato, the second one (NII) was composed of extracts mixture of broccoli, hazelnuts and carrot. Total flavonoids and flavonols were determined in the nutraceuticals. Four groups of rats were run; the first served as control normal, the other three groups were treated by intraperitoneal injection of NDEA, one of these groups was designated as control NDEA, the other two groups (test groups) were treated daily with oral doses of NI and NII, respectively. The experiment continued for 8 weeks. Plasma transaminases, alkaline phosphatase and catalase activities, total protein, albumin, malondialdehyde (MDA) and tumor necrosis factor-α (TNF-α) along with liver MDA level and catalase activity were assessed. Results: NI showed higher flavonoids and lower flavonols than NII (P < 0.05). High oxidative stress and inflammation biomarkers, liver dysfunction, reduced plasma albumin and total protein were demonstrated in control NDEA compared to control normal (P < 0.05). Test groups showed significant improvement in all parameters (P < 0.05) compared to NDEA control. NI was superior in improving plasma transaminases and catalase activities, MDA and TNF-α levels and liver catalase activity compared to NII (P < 0.05). Conclusion: Both NI and NII might prevent liver cancer initiation during exposure to carcinogenic agents, NI being superior to NII.

Diethylnitrosamine-induced liver tumorigenesis in mice

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and the third leading cause of cancer related mortality with a 10 year survival rate of merely 22-35%. Tumorigenesis frequently occurs in patients with chronic liver disease where continued liver cell damage, compensatory proliferation and inflammation provide the basis for tumor initiation, promotion and progression. Animal models of HCC are particularly useful to better understand molecular events underlying liver tumorigenesis. To this end, chemical carcinogenesis protocols based on the injection of genotoxic compounds such as diethylnitrosamine (DEN) are widely used to model liver tumorigenesis in rodents. DEN injection into 2 week old mice is sufficient to cause liver tumorigenesis after 8-10 months. When injected into older mice, DEN has to be combined with administration of tumor promoting agents such as phenobarbital or feeding high fat diet. Such protocols allow to dissect the different steps of tumor formation (i.e., tumor initiation and promotion) experimentally and to model liver pathologies in mice which frequently lead to HCC in human patients such as non-alcoholic fatty liver disease. Here, we review several established chemical carcinogenesis protocols based on DEN injection into mice and discuss their advantages as well as potential limitations.

Critical review of major sources of human exposure to N-nitrosamines

More than 24 N-nitrosamine compounds contribute to the total N-nitrosamine (TNA) burden monitored routinely to assess human exposure to this important group of known and suspected human carcinogens. A literature review (n = 122) identified multiple sources of human exposure to TNAs, including waters (40 ± 10.5 ng/L; average ± standard deviation), food and beverages (6.7 ± 0.8 ng/g), tobacco (16,100 ± 3650 ng/g) and personal care products (1500 ± 750 ng/g). Due to source control interventions, levels of TNAs in beer have dropped by about 96% between 1980 and 1990, whereas N-nitrosamine levels in other known sources have shown little to no change. Maximum daily TNA exposure in the U.S. in units of ng/d is estimated at 25,000 ± 4,950, driven by consumption of tobacco products (22,000 ± 4350), food (1900 ± 380), alcohol (1000 ± 200), and drinking water (120 ± 24). Behavioral choices of individuals in non-occupational settings were calculated to result in a spectrum of exposure values ranging from a lower bound of 1900 ± 380 ng/d to a higher bound of 25,000 ± 4950 ng/d, indicating opportunities for a possible 12-fold reduction in TNA exposure to 8% of the above maximum through deliberate choices in diet and lifestyle.

Tobacco Smoke Exposure Impairs Brain Insulin/IGF Signaling: Potential Co-Factor Role in Neurodegeneration

BACKGROUND

Human studies suggest tobacco smoking is a risk factor for cognitive impairment and neurodegeneration, including Alzheimer's disease (AD). However, experimental data linking tobacco smoke exposures to underlying mediators of neurodegeneration, including impairments in brain insulin and insulin-like growth factor (IGF) signaling in AD are lacking.

OBJECTIVE

This study tests the hypothesis that cigarette smoke (CS) exposures can impair brain insulin/IGF signaling and alter expression of AD-associated proteins.

METHODS

Adult male A/J mice were exposed to air for 8 weeks (A8), CS for 4 or 8 weeks (CS4, CS8), or CS8 followed by 2 weeks recovery (CS8+R). Gene expression was measured by qRT-PCR analysis and proteins were measured by multiplex bead-based or direct binding duplex ELISAs.

RESULTS

CS exposure effects on insulin/IGF and insulin receptor substrate (IRS) proteins and phosphorylated proteins were striking compared with the mRNA. The main consequences of CS4 or CS8 exposures were to significantly reduce insulin R, IGF-1R, IRS-1, and tyrosine phosphorylated insulin R and IGF-1R proteins. Paradoxically, these effects were even greater in the CS8+R group. In addition, relative levels of S312-IRS-1, which inhibits downstream signaling, were increased in the CS4, CS8, and CS8+R groups. Correspondingly, CS and CS8+R exposures inhibited expression of proteins and phosphoproteins required for signaling through Akt, PRAS40, and/or p70S6K, increased AβPP-Aβ, and reduced ASPH protein, which is a target of insulin/IGF-1 signaling.

CONCLUSION

Secondhand CS exposures caused molecular and biochemical abnormalities in brain that overlap with the findings in AD, and many of these effects were sustained or worsened despite short-term CS withdrawal.

Assessment of tobacco specific nitrosamines (TSNAs) in oral fluid as biomarkers of cancer risk: A population-based study

BACKGROUND

Smoke-free laws are expected to reduce smoking habits and exposure to secondhand smoke. The objective of this study was the measurement of tobacco specific carcinogens (TSNAs) in oral fluid to assess the most suitable biomarker of cancer risk associated with tobacco smoke.

METHODS

TSNAs, N'-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), as well as nicotine and cotinine were measured in oral fluid samples from 166 smokers and 532 non-smokers of the adult population of Barcelona, Spain. A simple method with an alkaline single liquid-liquid extraction with dichloromethane/isopropanol was used and lower limits of quantification for cotinine, NNN, NNK and NNAL were set at 0.10ng/mL, 1.0, 2.0 and 0.50pg/mL respectively. The NNN/cotinine ratio was also calculated.

RESULTS

NNN was the most abundant TSNA present in oral fluid with a significant difference between smokers and non-smokers (mean concentrations of 118 and 5.3pg/mL, respectively, p<0.001). NNK and NNAL were detectable in fewer samples. NNN and cotinine concentrations had a moderate correlation within both groups (Spearman's rank correlation coefficient of 0.312, p<0.001 in smokers and 0.279, p=0.022 in non-smokers). NNN/cotinine ratio was significantly higher (p<0.001) in non-smokers than in smokers, in line with equivalent findings for the NNAL/cotinine ratio in urine.

CONCLUSIONS

TSNAs are detectable in oral fluid of smokers and non-smokers. NNN is the most abundant, in line with its association with esophageal and oral cavity cancers. The NNN/cotinine ratio confirms the relative NNN increase in second hand smoke. Findings provide a new oral fluid biomarker of cancer risk associated with exposure to tobacco smoke.

A competitive ELISA detecting 7-methylguanosine adduct induced by N-nitrosodimethylamine exposure

N-Nitrosodimethylamine is a chemical compound known to be carcinogenic to animals and probably to humans. It is widespread and it can be found in food, tobacco smoke and in industrial emissions, such as in the rubber industry. N-Nitrosodimethylamine exerts its biological effects after metabolic activation by forming methylating nucleic acids in DNA. The most formed adduct is 7-methylguanosine. Our laboratory has developed and validated a competitive enzyme-linked immunosorbent assay in order to detect this adduct in DNA exposed to N-nitrosodimethylamine in vitro or in vivo. The imidazole ring-opening (iro) of 7-methylguanosine was required because of its stability. When 7-methylguanosine iro and serum were incubated at 48C, the assay was 35 times more sensitive than at 378C (50% inhibition at 37 fmol 7-methylguanosine iro per well at 48C and 1.28 pmol at 378C) with a lower limit of detection at 1.58 fmol 7-methylguanosine iro. This assay is reproducible, can be routinely performed and is sensitive enough to detect 7-methylguanosine adduct in DNA samples from human exposed to N-nitrosodimethylamine. We aim to use this method in further studies on epidemiological assessment in people at high risk, such as smokers.

Evaluation of tobacco specific nitrosamines exposure by quantification of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in human hair of non-smokers

Chronic exposure to specific carcinogens present in secondhand smoke has been associated with different types of cancers. Hair is an ideal matrix to develop a proper biomarker as it absorbs substances in circulation and allows measuring their average concentration over long periods of time. A method was developed for the simultaneous quantification of nicotine, cotinine, NNN, NNK and NNAL in 20 mg human hair samples. Concentrations were significantly different depending on the declared exposure. This study shows for the first time that NNK is present in hair samples from non-smokers in concentrations much higher than any other tobacco specific nitrosamine. NNN could also be detected in samples from the most exposed non-smokers while, as previously reported, NNAL was undetectable. NNK correlates well with nicotine and cotinine (rsp = 0.774 and rsp = 0.792 respectively, p < 0.001 in both cases). However, NNN concentrations did not correlate with any of the other analytes. Ratios between NNK and nicotine show variability with different concentrations of NNK present in samples with similar nicotine values. NNK has proven to be the best marker of tobacco specific nitrosamines in hair. Monitoring NNK may provide a good estimation of cancer risk associated with exposure to secondhand smoke.

Tobacco Smoke-Induced Hepatic Injury with Steatosis, Inflammation, and Impairments in Insulin and Insulin-Like Growth Factor Signaling

Background

Alcoholic liver disease (ALD) is associated with impairments in hepatic insulin and insulin-like growth factor (IGF) signaling through cell growth, survival, and metabolic pathways. Since not all heavy drinkers develop ALD, co-factors may be important. Epidemiologic data indicate that most heavy drinkers smoke tobacco and experimental data revealed that low-level nitrosamine exposures, including those from tobacco, can cause steatohepatitis with hepatic insulin/IGF resistance and exacerbate ALD. We hypothesize that cigarette smoke (CS) exposures also cause liver injury with impaired hepatic insulin/IGF signaling, and thereby contribute to ALD.

Methods

Adult male A/J mice were exposed to air for 8 weeks (A8), CS for 4 (CS4) or 8 (CS8) weeks, or CS for 8 weeks with 2 weeks recovery (CS8+R).

Results

CS exposures caused progressive liver injury with disruption of the normal hepatic chord architecture, lobular inflammation, apoptosis or necrosis, micro-steatosis, sinusoidal dilatation, and nuclear pleomorphism. Histopathological liver injury scores increased significantly from A8 to CS4 and then further to CS8 (P<0.0001). The mean histological grade was also higher in CS8+R relative to A8 (P<0.0001) but lower than in CS4, reflecting partial resolution of injury by CS withdrawal. CS exposures impaired insulin and IGF-1 signaling through IRS-1, Akt, GSK-3β, and PRAS40. Livers from CS8+R mice had normalized or elevated levels of insulin receptor, pYpY-Insulin-R, 312S-IRS-1, 473S-Akt, S9-GSK-3β, and pT246-PRAS40 relative to A8, CS4, or CS8, reflecting partial recovery.

Conclusion

CS-mediated liver injury and steatohepatitis with impairments in insulin/IGF signalling are reminiscent of the findings in ALD. Therefore, CS exposures (either first or second-hand) may serve as a co-factor in ALD. The persistence of several abnormalities following CS exposure cessation suggests that some aspects of CS-mediated hepatic metabolic dysfunction are not readily reversible.

Preparation of molecularly imprinted polymers using theanine as dummy template and its application as SPE sorbent for the determination of eighteen amino acids in tobacco

In this paper, a novel dummy template molecularly imprinted polymer (DMIP) based on a vinyl-SiO2 microspheres surface for the simultaneous selective recognition and enrichment of 18 amino acids was prepared via a surface molecular imprinting technique using theanine as a dummy template. Compared to the imprinted polymers prepared using traditional polymerization techniques, the obtained DMIPs exhibited a regular spherical shape and were relatively monodisperse. The maximal sorption capacity (Qmax) of the resulting DMIPs for the 18 amino acids was up to 1444.3 mg g(-1). A kinetic binding study showed that the sorption capacity reached 85.40% of Qmax in 25 min and sorption equilibrium at 30 min. The imprint factors of the sorbents ranged from 2.86 to 6.9 for the 18 amino acids, which indicated that the DMIP sorbents have high selectivity. An HPLC-UV method for the simultaneous determination of 18 amino acids in tobacco and tobacco smoke was developed using the DMIPs as sorbents for solid phase extraction (SPE) in the sample pretreatment procedure. Under the optimum experimental conditions, the materials had enrichment factors of up to 200 for the amino acids, and the recoveries of the 18 amino acids in tobacco smoke were in the range from 79% to 104% with relative standard deviations of less than 7.4%. It indicated that the obtained DMIP sorbents could specifically recognize the amino acids from complicated samples.

Cigarette Smoke-Induced Alterations in Frontal White Matter Lipid Profiles Demonstrated by MALDI-Imaging Mass Spectrometry: Relevance to Alzheimer's Disease

BACKGROUND

Meta-analysis has shown that smokers have significantly increased risks for Alzheimer's disease (AD), and neuroimaging studies showed that smoking alters white matter (WM) structural integrity.

OBJECTIVE

Herein, we characterize the effects of cigarette smoke (CS) exposures and withdrawal on WM myelin lipid composition using matrix assisted laser desorption and ionization-imaging mass spectrometry (MALDI-IMS).

METHODS

Young adult male A/J mice were exposed to air (8 weeks; A8), CS (4 or 8 weeks; CS4, CS8), or CS8 followed by 2 weeks recovery (CS8 + R). Frontal lobe WM was examined for indices of lipid and protein oxidation and lipid profile alterations by MALDI-IMS. Lipid ions were identified by MS/MS with the LIPID MAPS prediction tools database. Inter-group comparisons were made using principal component analysis and R-generated heatmap.

RESULTS

CS increased lipid and protein adducts such that higher levels were present in CS8 compared with CS4 samples. CS8 + R reversed CS8 effects and normalized the levels of oxidative stress. MALDI-IMS demonstrated striking CS-associated alterations in WM lipid profiles characterized by either reductions or increases in phospholipids (phosphatidylinositol, phosphatidylserine, phosphatidylcholine, or phosphatidylethanolamine) and sphingolipids (sulfatides), and partial reversal of CS's inhibitory effects with recovery. The heatmap hierarchical dendrogram and PCA distinguished CS exposure, duration, and withdrawal effects on WM lipid profiles.

CONCLUSION

CS-mediated WM degeneration is associated with lipid peroxidation, protein oxidative injury, and alterations in myelin lipid composition, including shifts in phospholipids and sphingolipids needed for membrane integrity, plasticity, and intracellular signaling. Future goals are to delineate WM abnormalities in AD using MALDI-IMS, and couple the findings with MRI-mass spectroscopy to improve in vivo diagnostics and early detection of brain biochemical responses to treatment.

Tobacco Smoke-Induced Brain White Matter Myelin Dysfunction: Potential Co-Factor Role of Smoking in Neurodegeneration

BACKGROUND

Meta-analysis studies showed that smokers have increased risk for developing Alzheimer's disease (AD) compared with non-smokers, and neuroimaging studies revealed that smoking damages white matter structural integrity.

OBJECTIVE

The present study characterizes the effects of side-stream (second hand) cigarette smoke (CS) exposures on the expression of genes that regulate oligodendrocyte myelin-synthesis, maturation, and maintenance and neuroglial functions.

METHODS

Adult male A/J mice were exposed to air (8 weeks; A8), CS (4 or 8 weeks; CS4, CS8), or CS8 followed by 2 weeks recovery (CS8 + R). The frontal lobes were used for histology and qRT-PCR analysis.

RESULTS

Luxol fast blue, Hematoxylin and Eosin stained histological sections revealed CS-associated reductions in myelin staining intensity and narrowing of the corpus callosum. CS exposures broadly decreased mRNA levels of immature and mature oligodendrocyte myelin-associated, neuroglial, and oligodendrocyte-related transcription factors. These effects were more prominent in the CS8 compared with CS4 group, suggesting that molecular abnormalities linked to white matter atrophy and myelin loss worsen with duration of CS exposure. Recovery normalized or upregulated less than 25% of the suppressed genes; in most cases, inhibition of gene expression was either sustained or exacerbated.

CONCLUSION

CS exposures broadly inhibit expression of genes needed for myelin synthesis and maintenance. These adverse effects often were not reversed by short-term CS withdrawal. The results support the hypothesis that smoking contributes to white matter degeneration, and therefore could be a key risk factor for a number of neurodegenerative diseases, including AD.

Characterization of Pseudooxynicotine Amine Oxidase of Pseudomonas putida S16 that Is Crucial for Nicotine Degradation

Pseudooxynicotine amine oxidase (Pnao) is essential to the pyrrolidine pathway of nicotine degradation of Pseudomonas putida strain S16, which is significant for the detoxification of nicotine, through removing the CH₃NH₂ group. However, little is known about biochemical mechanism of this enzyme. Here, we characterized its properties and biochemical mechanism. Isotope labeling experiments provided direct evidence that the newly introduced oxygen atom in 3-succinoylsemialdehyde-pyridine is derived from H₂O, but not from O₂. Pnao was very stable at temperatures below 50 °C; below this temperature, the enzyme activity increased as temperature rose. Site-directed mutagenesis studies showed that residue 180 is important for its thermal stability. In addition, tungstate may enhance the enzyme activity, which has rarely been reported before. Our findings make a further understanding of the crucial Pnao in nicotine degradation.

Cigarette smoking and the risk of pancreatic cancer: a case-control study

We proposed to investigate the relationship between smoking and pancreatic cancer. From February 2000 to February 2010, we conducted a hospital-based case-control study on pancreatic cancer. Information was collected by questionnaire. Cases were 307 patients with pancreatic cancer, 1,228 were healthy matched controls. Multiple logistic regression was used to estimate the odds ratios (OR) and the corresponding 95% confidence intervals (CI). Compared to never smokers, current smokers had a significantly increased risk of pancreatic cancer, OR 1.71 (95% CI 1.25-2.35). Among smokers, a significant association with higher smoking intensity was shown (≥20 cigarettes/day: OR=2.18; 95% CI 1.66-3.69). A significantly decreasing trend in risk with increasing years after smoking cessation was observed (p<0.01). The ORs were 0.73 (95% CI 0.38-1.33) and 0.46 (95% CI 0.21-0.94) for those who had quit smoking for <10 and ≥10 years, respectively. Our case-control study confirmed that cigarette smoking was associated with an increased risk of death from pancreatic cancer.

Enhanced N-nitrosamine formation in pool water by UV irradiation of chlorinated secondary amines in the presence of monochloramine

N-Nitrosamines, in particular N-nitrosodimethylamine (NDMA), are carcinogens, which occur as chlorine disinfection by-products (DBPs) in swimming pools and hot tubs. UV treatment is a commonly used technique in swimming pools for disinfection and DBP attenuation. UV irradiation is known to efficiently degrade N-nitrosamines. However, UV irradiation (at λ = 254 nm) of chlorinated dimethylamine (CDMA) and monochloramine, two NDMA precursors present in swimming pool water, resulted in a substantial UV-induced NDMA formation (~1-2% molar yield based on initial CDMA concentration) simultaneously to NDMA photolysis. Maximum NDMA concentrations were found at UV doses in the range used for advanced oxidation (350-850 mJ cm(-2)). Very similar behaviour was found for other chlorinated secondary amines, namely diethylamine and morpholine. Effectiveness of UV irradiation for N-nitrosamine abatement depends on initial N-nitrosamine and precursor concentrations and the applied UV dose. N-Nitrosamine formation is hypothesized to occur via the reaction of nitric oxide or peroxynitrite with the secondary aminyl radical, which are products from the photolysis of monochloramine and chlorinated secondary amines, respectively. Experiments with pool water showed that similar trends were observed under pool water conditions. UV treatment (UV dose: ~360 mJ cm(-2)) slightly increased NDMA concentration in pool water instead of the anticipated 50% abatement in the absence of NDMA precursors.

Modulation of the activation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone by hamster liver microsomes to protein alkylating species

During incubation with hamster liver microsomes, the tobacco-specific N-nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was metabolized by alpha-carbon hydroxylation, pyridine N-oxidation and carbonyl reduction. The modulation of the activation of NNK to intermediates, alkylating microsomal proteins, by some compounds related to tobacco smoke, P-450 inhibitors, thiol and alcohol compounds, has been determined. Binding of both the pyridyloxobutyl and the methyl moieties of NNK was inhibited by more than 40% by N'-nitrosonornicotine or N-nitrosodimethylamine. In contrast, nicotine and 3-acetylpyridine inhibited only the binding of the pyridyloxobutyl moiety. Binding of both moieties of NNK was not inhibited by its deactivation metabolite, the NNK-N-oxide. Whereas the P-450 inhibitors metyrapone, [2-(diethylamino)ethyl 2,2-diphenyl pentenoate]hydrochloride and piperonyl butoxide inhibit the binding of the pyridyloxobutyl moiety selectively, carbon monoxide inhibits the binding of both moieties. Metyrapone reduced alpha-carbon hydroxylation but not pyridine N-oxidation, suggesting that in hamster livers pyridine N-oxidation is not mediated by P-450-dependent monooxygenases. The binding of the pyridyloxobutyl and methyl moieties was partially dependent on the presence of NADPH in the incubation mixture. Glutathione had no effect on the metabolism of NNK but inhibited the enzymatic and non-enzymatic binding of its pyridyloxobutyl moiety. It is concluded that the binding of NNK-derived intermediates to cellular proteins is inhibited by various substances present in tobacco smoke and by inhibitors of P-450 monooxygenases. Only part of this binding is enzymatically mediated.

O(6)-methylguanine-DNA methyltransferase (MGMT): impact on cancer risk in response to tobacco smoke

Tobacco, smoked, snuffed and chewed, contains powerful mutagens and carcinogens. At least three of them, N-dimethylnitrosamine, N'-nitrosonornicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, attack DNA at the O(6)-position of guanine. The resulting O(6)-alkylguanine adducts are repaired by the suicide enzyme O(6)-methylguanine-DNA methyltransferase (MGMT), which is known to protect against the mutagenic, genotoxic and carcinogenic effects of monofunctional alkylating agents. While in rat liver MGMT was shown to be subject to regulation by genotoxic stress leading to adaptive changes in its activity, in humans evidence of adaptive modulation of MGMT levels is still lacking. Several polymorphisms are known, which are suspected to impact on the risk of developing cancer. In this review we focus on three questions: (a) Has tobacco consumption by smoking or chewing an impact on MGMT expression and MGMT promoter methylation in normal and tumor tissue? (b) Is there an association between MGMT polymorphisms and cancer risk and is this risk related to smoking? (c) Does MGMT protect against tobacco-associated cancer? There are several lines of evidence for an increase of MGMT activity in the normal tissue of smokers compared to non-smokers. Furthermore, in tumors developed in smokers a tendency towards an increase of MGMT expression was found. The data points to the possibility that agents in tobacco smoke are able to trigger upregulation of MGMT in normal and tumor tissue. For MGMT promoter methylation data is conflicting. There is some evidence for an association between MGMT polymorphisms and smoking-induced cancer risk. The key question whether or not MGMT protects against tobacco smoke-induced cancer is difficult to answer since prospective studies on smokers versus non-smokers are lacking and appropriate animal studies with MGMT transgenic mice exposed to the complex mixture of tobacco smoke have not been performed, which indicates the need for further explorations.

A review of the analysis of tobacco-specific nitrosamines in biological matrices

Tobacco use constitutes a leading cause of mortality and morbidity worldwide. Tobacco-specific nitrosamines (TSNAs) are an important class of biomarkers for tobacco carcinogen uptake. The current review focuses on the issues and developments in analysis of these compounds in human biological matrices. The two most widely used techniques for TSNA bioanalysis are gas chromatography coupled with thermal energy analysis and liquid chromatography coupled with mass spectrometry, employing various sample preparation techniques. The review provides an overview of the tools and techniques currently available for TSNA bioanalysis that will help towards the ultimate goal of understanding the mechanisms of cancer caused by the use of tobacco products. A contrast and comparison of the important aspects of bioanalysis such as sample preparation, compound detection, and throughput is discussed for the thermal energy analysis- and mass spectrometry-based techniques. Complex sample extraction procedures, throughput, and the ability to validate are important issues of concern for the gas chromatography-thermal energy analysis-based methods. On the other hand, addressing ion suppression matrix effects remains an important challenge for hyphenated mass spectrometry-based methods. The review also provides an extensive summary of analytical procedures for various studies measuring tobacco-specific nitrosamines in different biological matrices.

Lung cancer risk and variation in MGMT activity and sequence

O(6)-Alkylguanine-DNA alkyltransferase (MGMT) repairs DNA adducts that result from alkylation at the O(6) position of guanine. These lesions are mutagenic and toxic and can be produced by a variety of agents including the tobacco-specific nitrosamines, carcinogens present in cigarette smoke. Here, we review some of our work in the context of inter-individual differences in MGMT expression and their potential influence on lung cancer risk. In humans there are marked inter-individual differences in not only levels of DNA damage in the lung (N7-methylguanine) that can arise from exposure to methylating agents but also in MGMT activity in lung tissues. In the presence of such exposure, this variability in MGMT activity may alter cancer susceptibility, particularly as animal models have demonstrated that the complete absence of MGMT activity predisposes to alkylating-agent induced cancer while overexpression is protective. Recent studies have uncovered a series of polymorphisms that affect protein activity or are associated with differences in expression levels. The associations between these (and other) polymorphisms and cancer risk are inconsistent, possibly because of small sample sizes and inter-study differences in lung cancer histology. We have recently analysed a consecutive series of case-control studies and found evidence that lung cancer risk was lower in subjects with the R178 allele.

Cigarettes and alcohol in relation to colorectal cancer: the Singapore Chinese Health Study

The relations were examined between colorectal cancer and cigarette smoking and alcohol consumption within the Singapore Chinese Health Study, a population-based, prospective cohort of 63 257 middle-aged and older Chinese men and women enrolled between 1993 and 1998, from whom baseline data on cigarette smoking and alcohol consumption were collected through in-person interviews. By 31 December 2004, 845 cohort participants had developed colorectal cancer (516 colon cancer, 329 rectal cancer). Compared with nondrinkers, subjects who drank seven or more alcoholic drinks per week had a statistically significant, 72% increase in risk of colorectal cancer hazard ratio (HR)=1.72; 95% confidence interval (CI)=1.33-2.22). Cigarette smoking was associated with an increased risk of rectal cancer only. Compared with nonsmokers, HRs (95% CIs) for rectal cancer were 1.43 (1.10-1.87) for light smokers and 2.64 (1.77-3.96) for heavy smokers. Our data indicate that cigarette smoking and alcohol use interact in the Chinese population in an additive manner in affecting risk of rectal cancer, thus suggesting that these two exposures may share a common etiologic pathway in rectal carcinogenesis.

Relationship between machine-derived smoke yields and biomarkers in cigarette smokers in Germany

In order to determine whether smokers of cigarettes in the contemporary yield ranges of the German market (0.1-1.0mg nicotine, 1-10mg tar) differ in their actual exposure to various smoke constituents, we performed a field study with 274 smokers and 100 non-smokers. The following biomarkers were determined: In 24-h urine: Nicotine equivalents (molar sum of nicotine, cotinine, trans-3'-hydroxycotinine and their respective glucuronides), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL, metabolite of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, NNK), 3-hydroxypropylmercapturic acid (metabolite of acrolein), trans,trans-muconic acid, S-phenylmercapturic acid (metabolites of benzene), 1-hydroxypyrene (metabolite of pyrene); in saliva: Cotinine and trans-3'-hydroxycotinine; in exhaled air: Carbon monoxide; in blood: Methyl-, hydroxyethyl-, cyanoethyl- (biomarker of acrylonitrile) and carbamoylethylvaline (biomarker of acrylamide) hemoglobin adducts. All biomarkers were found to be significantly higher in smokers compared to non-smokers and showed strong correlations with the daily cigarette consumption. Biomarker levels and per cigarette increases in smokers were at most weakly related to the machine-derived smoke yields. It is concluded that machine-derived yields of cigarettes from the contemporary German cigarette market have little or no impact on the actual smoking-related exposure determined by suitable biomarkers.

Development, validation and transfer of a hydrophilic interaction liquid chromatography/tandem mass spectrometric method for the analysis of the tobacco-specific nitrosamine metabolite NNAL in human plasma at low picogram per milliliter concentrations

A highly sensitive bioanalytical method based on a simple liquid/liquid extraction and hydrophilic interaction liquid chromatography with tandem mass spectrometry (HILIC/MS/MS) analysis has been developed, validated and transferred for the determination of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a tobacco-specific nitrosamine metabolite. Deuterated NNAL (NNAL-d(4)) was synthesized and used as the internal standard. This method can be used for the analysis of free and total NNAL (free NNAL plus NNAL-gluc) in K(3)-EDTA human plasma. Free NNAL and NNAL-d(4) are extracted from human plasma by liquid/liquid extraction. To analyze for total NNAL and the internal standard, a separate aliquot of the K(3)-EDTA human plasma is treated with beta-glucuronidase to deconjugate the NNAL-gluc; the total NNAL and internal standard are then extracted using liquid/liquid extraction. After drying down under nitrogen, the residue is reconstituted with acetonitrile and analyzed using positive ion electrospray and HILIC/MS/MS at a flow rate of 1.0 mL/min. The chromatographic run time is 1.0 min per injection, with retention time for both NNAL and NNAL-d(4) of 0.75 min with a capacity factor (k') of 2. The standard curve range for this assay is from 5.00-1000 pg/mL for both free and total NNAL, using a total plasma sample volume of 1.0 mL. The interday precision and accuracy of the quality control (QC) samples demonstrated <7.6% relative standard deviation (RSD) and <3.3% relative error (RE) for free NNAL. For total NNAL, the interday precision and accuracy of the QC samples demonstrated <11.7% RSD and <2.8% RE. Optimization of enzyme hydrolysis of NNAL-gluc is discussed in detail. The overall recoveries for free and total NNAL and IS were 68.2 and 71.5% (free) and 70.7 and 65.5% (total). No adverse matrix effects were noticed for this assay.

An analysis of the role of tobacco-specific nitrosamines in the carcinogenicity of tobacco smoke

Cigarette smoke is a complex mixture consisting of more than 4500 chemicals, including several tobacco-specific nitrosamines (TSNA). TSNA typically form in tobacco during the post-harvest period, with some fraction being transferred into mainstream smoke when a cigarette is burned during use. The most studied of the TSNA is 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). NNK has been shown to be carcinogenic in laboratory animals. Studies examining the carcinogenicity of NNK frequently are conducted by injecting rodents with a single dose of 2.5 to 10 mumol of pure NNK; the amount of NNK contained in all of the mainstream smoke from about 3700 to 14,800 typical U.S. cigarettes. Extrapolated to a 70-kg smoker, the carcinogenic dose of pure NNK administered to rodents would be equivalent to the amount of NNK in all of the mainstream smoke of 22 to 87 million typical U.S. cigarettes. Furthermore, extrapolating results from rodent studies based on a single injection of pure NNK to establish a causative role for NNK in the carcinogenicity of chronic tobacco smoke exposure in humans is not consistent with basic pharmacological and toxicological principles. For example, such an approach fails to consider the effect of other smoke constituents upon the toxicity of NNK. In vitro studies demonstrate that nicotine, cotinine, and aqueous cigarette "tar" extract (ACTE) all inhibit the mutagenic activity of NNK. In vivo studies reveal that the formation of pulmonary DNA adducts in mice injected with NNK is inhibited by the administration of cotinine and mainstream cigarette smoke. Cigarette smoke has been shown to modulate the metabolism of NNK, providing a mechanism for the inhibitory effects of cigarette smoke and cigarette smoke constituents on NNK-induced tumorigenesis. NNK-related pulmonary DNA adducts have not been detected in rodents exposed to cigarette smoke, nor has the toxicity of tobacco smoke or tobacco smoke condensate containing marked reductions in TSNA concentrations been shown to be reduced in any biological assay. In summary, there is no experimental evidence to suggest that reduction of TSNA will reduce the mutagenic, cytotoxic, or carcinogenic potential of tobacco smoke.

Liquid chromatographic/tandem mass spectrometric method for the determination of the tobacco-specific nitrosamine metabolite NNAL in smokers' urine

A specific and rapid liquid chromatographic/tandem mass spectrometric (LC/MS/MS) method was developed and validated for NNAL, a metabolite of the tobacco-specific nitrosamine metabolite NNK. The metabolite was detected in smokers' urine with a limit of quantitation (LOQ) of 20 pg ml(-1) and a linear range up to 1000 pg ml(-1). The method features a single solid-phase extraction step and MS/MS monitoring following electrospray ionization. Fragmentation pathways for the protonated molecular ion are proposed. The sample preparation is simpler than that for gas chromatographic methods reported in the literature and maintains sensitivity adequate for determining NNAL in smokers' urine. By using enzyme hydrolysis to determine total NNAL in urine, the amount of NNAL-glucuronide was calculated. A standard pooled smokers' urine sample used for development gave values of 176 +/- 8 pg ml(-1) free NNAL and 675 +/- 26 pg ml(-1) total NNAL following enzyme hydrolysis. The method was applied to a group of seven smokers; the free NNAL level for the group was 101-256 pg ml(-1) with NNAL-glucuronides at 247-566 pg ml(-1). The ratio of conjugated to free NNAL was in the range 0.98-2.95. The variability in total daily amount of NNAL excreted (ng per 24 h) had RSDs of 6-21% for free NNAL, 7-22% for conjugated NNAL and 6-20% for total NNAL excreted. When normalized to the number of cigarettes smoked, the amounts of NNAL excreted per cigarette smoked were in the range of amounts of NNK yields reported for cigarettes in the literature.

Molecular epidemiology of smoking and lung cancer

Lung cancer is the single most common cause of death, and almost all of it is due to tobacco smoking. Before the widespread use of cigarettes in this century, lung cancer was a rare illness. Tobacco smoke is a complex mixture of numerous mutagens and carcinogens. Over the last 40 years, the type of cigarettes most frequently used has been changing, namely the increased use of low tar and nicotine cigarettes. This has been accompanied by an increased risk of lung cancer due to a smokers' need to maintain blood nicotine levels, which in turn causes the need for smoking more cigarettes per day and deeper inhalation. This phenomena has led to the increasing rates of lung adenocarcinoma, compared to squamous cell carcinoma. It also probably explains, in part, the greater risk of lung cancer in women compared to men (in addition to some biological differences). The study of lung cancer involves many types of biomarkers, including those that measure exposure, the biologically effective dose and harm. The use of these has allowed us to understand many parts of lung carcinogenesis. Genetic susceptibilities play a large role in lung cancer risk. They govern smoking behavior (affecting dopamine reward mechanisms due to nicotine and nicotine metabolism), carcinogen metabolism and detoxification, DNA repair, cell cycle control and other cellular responses. The need for the study of lung cancer is highlighted by the need to improve cessation rates and reduce exposure among persons who cannot quit smoking, for better prevention strategies for former smokers and an understanding of environmental tobacco smoke risk.

Effect of nicotine, cotinine and phenethyl isothiocyanate on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) metabolism in the Syrian golden hamster

The effect of nicotine, cotinine and phenethyl isothiocyanate (PEITC) on metabolism of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was studied in the Syrian golden hamster. Urinary metabolite profiles were determined in 24 h urine after a single subcutaneous (s.c.) administration of [5-(3)H]NNK (80 nmol/kg, s.c.). Co-administration of either a 500-fold higher dose of nicotine (40 micromol/kg, s.c.) or a 5000-fold higher dose of cotinine (400 micromol/kg, s.c.) significantly (P<0.001) reduced metabolic activation of NNK by alpha-hydroxylation to 85 and 71% of control, respectively. Co-administration of a 300-fold higher dose of PEITC (1 micromol/g diet) slightly reduced alpha-hydroxylation of NNK (94% of control). Metabolism of NNK by reduction to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) was increased by nicotine (155%), and significantly increased by cotinine (670%, P<0.001) and PEITC (219%, P<0.01). Detoxification of NNAL by glucuronidation was also increased by all three test agents. Detoxification of NNK and NNAL by N-oxidation was marginally increased by nicotine, reduced by PEITC, and significantly reduced by cotinine. The urinary metabolite profiles suggest that nicotine, which occurs in concentrations up to 30000-fold higher than NNK in mainstream cigarette smoke, and cotinine, its proximal metabolite, may have a significant protective effect against in vivo metabolic activation of NNK.

"IARC Group 2B carcinogens" reported in cigarette mainstream smoke

In the third and final part of a series surveying the international literature on the "IARC carcinogens" in cigarette mainstream smoke, the "IARC Group 2B carcinogens" are reviewed. A search of the published literature shows that of 227 chemical components classified as Group 2B, that is, "possible carcinogens," by the International Agency for Research on Cancer (IARC), 48 have previously been reported in cigarette mainstream smoke. Owing to its highly interactive molecular nature, removal from or inhibition of a given mutagenic or carcinogenic chemical within the complex aerosol mixture cannot reliably be predicted to reduce either the overall mutagenicity or carcinogenicity. However, in the absence of experimental data demonstrating an increase in adverse biological activity resulting from removal or inhibition of a potentially carcinogenic constituent, negation of the activity of the potential carcinogen may be considered as a desirable circumstance.

Predicting the mutagenicity of tobacco-related N-nitrosamines in humans using 11 strains of Salmonella typhimurium YG7108, each coexpressing a form of human cytochrome P450 along with NADPH-cytochrome P450 reductase

Tobacco, including snuff and chewing tobacco, contains N-nitrosamines such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR), N-nitrosopiperidine (NPIP), N-nitrosomorpholine (NMOR), N-nitrosonornicotine (NNN), N-nitrosoanabasine (NABS), and N-nitrosoanatabine (NATB). The role of human cytochrome P450 (CYP) in the metabolic activation of these tobacco-related N-nitrosamines was examined by a Salmonella mutation test using genetically engineered Salmonella typhimurium (S. typhimurium) YG7108 cells each expressing a form of human CYP (CYP1A1, CYP1A2, CYP1B1, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4, or CYP3A5) together with human NADPH-cytochrome P450 reductase. Mutagen production from NNK was catalyzed by CYP in the following order: CYP1A2, CYP1A1, CYP1B1, CYP2A6, CYP2C19, CYP3A4. The metabolic activation of one of the N-alkylnitrosamines, NDEA, was mediated by CYP2A6, followed by CYP2E1. Cyclic N-nitrosamines such as NPYR, NPIP, and NMOR were also primarily activated by CYP2A6, and to a lesser extent by CYP2E1. NNN, a pyridine derivative of NPYR, was activated by CYP1A1 at an efficiency similar to that of CYP2A6. NABS, a pyridine derivative of NPIP, was mainly activated by CYP3A4, followed by CYP1A1 and CYP2A6. Thus, the addition of a pyridine ring to NPYR or NPIP altered the forms of CYP primarily responsible for mutagenic activation. NATB was metabolically activated solely by CYP2A6, whereas the genotoxicity of NATB was much lower than that of NNN or NPYR. Based on these data, we conclude that CYP2A6 was responsible for the mutagenic activation of essentially all tobacco-related N-nitrosamines tested in the present study.

"IARC group 2B Carcinogens" reported in cigarette mainstream smoke

In the third and final part of a series surveying the international literature on the "IARC carcinogens" in cigarette mainstream smoke, the "IARC Group 2B carcinogens" are reviewed. A search of the published literature shows that of 227 chemical components classified as Group 2B, that is, "possible carcinogens," by the International Agency for Research on Cancer (IARC), 48 have previously been reported in cigarette mainstream smoke. Owing to its highly interactive molecular nature, removal from or inhibition of a given mutagenic or carcinogenic chemical within the complex aerosol mixture cannot reliably be predicted to reduce either the overall mutagenicity or carcinogenicity. However, in the absence of experimental data demonstrating an increase in adverse biological activity resulting from removal or inhibition of a potentially carcinogenic constituent, negation of the activity of the potential carcinogen may be considered as a desirable circumstance.

The profile of urinary metabolites of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in rats is determined by its pulmonary metabolism

Metabolism of the tobacco specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in rats was compared to metabolism in primary lung and liver cells. Untreated rats and rats pretreated with phenobarbital, acetone or phenethyl isothiocyanate (PEITC) were used for all experiments. Also the influence of [-]-1-methyl-2-[3-pyridyl]-pyrrolidine (nicotine) administered concomitantly with NNK, or incubated with isolated cells, upon NNK metabolism was investigated and found to be only marginal upon alpha-hydroxylation and pyridine N-oxidation in vivo. In hepatocytes nicotine inhibited NNK pyridine N-oxidation, alpha-hydroxylation and glucuronidation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), whereas in lung cells the influence of nicotine was not as pronounced. In vivo phenobarbital induced alpha-hydroxylation and pyridine N-oxidation. In vitro the effects of the modulators were most pronounced upon hepatocytes, where phenobarbital greatly induced pyridine N-oxidation and PEITC inhibited alpha-hydroxylation. NNAL was conjugated to its beta-glucuronide in lung cells at four times higher rates than in hepatocytes. The ratios of the sum of N-oxides to the sum of alpha-hydroxylation products in vivo were similar to those in lung cells, especially at low NNK concentrations (1 microM), while in hepatocytes alpha-hydroxylation was more pronounced. The same correlation of metabolism in isolated lung cells with whole rats was observed if oxidative NNAL metabolism was related to oxidative NNK metabolism. Here hepatocytes showed a much higher formation of NNAL oxidation products than either lung cells formed, or rats excreted in urine. This was true despite a lower rate of metabolism in the lung than in liver if based on cell number, the rate based on mg protein was four times higher in lung than liver. Only after phenobarbital treatment was the contribution of hepatic metabolism to excreted metabolites important. In conclusion the lung which is also the target of NNK carcinogenesis, and not the liver, is the organ with the most important contribution to NNK and NNAL metabolism at concentrations relevant to human exposure.

Stress, hormonal changes, alcohol, food constituents and drugs: factors that advance the incidence of tobacco smoke-related cancer?

The genotoxicity of the most potent carcinogen in cigarette smoke [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)] is dependent on the relationship between its activation by cytochrome P450 enzymes and its detoxification by carbonyl reduction to NNK alcohol (NNAL) followed by glucuronidation. Recently, '11 beta-hydroxysteroid dehydrogenase' (11 beta-HSD 1) was identified to be responsible for NNK carbonyl reduction. It is now speculated that differences in tissue expression of 11 beta-HSD 1, as well as genetic polymorphisms, may have profound influences on the organospecificity and potency of NNK-induced cancerogenesis. Moreover, endogenous and exogenous substrates or inhibitors of 11 beta-HSD 1 may shift the NNK/NNAL equilibrium and favour NNK toxification in a variety of physiological and therapeutic situations. These issues are discussed here by Edmund Maser, who also describes how recent observations could provide the experimental base for epidemiological or clinical studies, which focus on polymorphisms in 11 beta-HSD 1 enzyme expression, as well as on implications of exposure to 11 beta-HSD 1 modulators and concurrent smoking.

Biomonitoring exposure to environmental tobacco smoke (ETS): a critical reappraisal

1 The most frequently used biomarkers for exposure to environmental tobacco smoke (ETS) are cotinine and thiocyanate in body fluids, carboxyhaemoglobin in red blood cells (COHb) and carbon monoxide in the expired air. Although not ideal, cotinine in blood, saliva or urine is an established biomarker for ETS exposure within the past 1-3 days. Comparison with cotinine concentrations in cigarette smokers reveals that passive smokers take up less than 1/100 of the nicotine dose of smokers. 2 Biomonitoring data available for the ETS-related exposure to genotoxic substances comprise uptake of benzene, polycyclic aromatic hydrocarbons (PAH), aromatic amines, tobacco-specific nifrosamines (TSNA), electrophilic compounds giving rise to urinary thioethers, mutagens causing urinary mutagenic activity and the formation of various DNA adducts. With the exception of TSNA, these biomarkers are related to chemicals occurring ubiquitously in the environment and in the food. As a consequence, the background levels in unexposed nonsmokers are high compared to the observed increases (if any) associated with ETS exposure. 3 Some markers of biological effects, which, by definition, are non-specific with regard to the underlying exposure, have also been investigated in relation to ETS exposure. These markers comprise cytogenetic effects, aryl hydrocarbon hydroxylase (AHH) induction, urinary hydroxyproline excretion and various factors indicative of cardiovascular risks. The available data suggest that passive smoking is associated with a small induction of placental AHH and also with effects on cardiovascular risk markers. The latter findings in particular may be confounded by other risk factors, which have been observed to be more frequent in passive smokers than in unexposed nonsmokers.

The identification of 11 beta-hydroxysteroid dehydrogenase as carbonyl reductase of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NC), which is generated by nitrosation of nicotine, requires enzymatic activation by cytochrome-P450-mediated alpha-carbon hydroxylation to yield particularly powerful carcinogenic alkylating intermediates. Pyridine-N-oxidation and carbonyl reduction are detoxification pathways, the latter by providing the functional hydroxy moiety necessary for glucuronosylation and final excretion of NC. For more than a decade, the enzyme responsible for NC carbonyl reduction has awaited characterization. In the present study, we demonstrate that the NC carbonyl reductase is identical to 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), the physiological function of which is the oxidoreduction of glucocorticoids. We conclude that the expression of 11 beta-HSD (together with glucuronosyl transferase) may have profound influence on the carcinogenic potency of NC and that many compounds of endogenous and exogenous origin, which are known to be substrates or inhibitors of 11 beta-HSD, may modulate NNK-induced carcinogenicity by competing for the same enzyme. In light of the known species and tissue differences in the expression of 11 beta-HSD isozymes, important aspects of NNK-induced tumorigenesis, such as metabolic activation versus inactivation or organospecificity, can now be re-evaluated.

Derivatization reactions for the determination of amines by gas chromatography and their applications in environmental analysis

The environmental analysis of amines is important to preserve human health because these compounds often have toxic effects. Gas chromatography (GC) of free amines is generally unsatisfactory owing to the adsorption and decomposition of the solutes on the column. Derivatization of amines is employed to reduce the polarity and to improve the GC properties. Derivatization reactions for the determination of amines by GC are reviewed with respect to reactivity, selectivity and sensitivity. Their applications to the determination of individual amines, ammonia and N-nitrosamines in various environmental samples are also described.

Selective determination of volatile N-nitrosamines by derivatization with diethyl chlorothiophosphate and gas chromatography with flame photometric detection

A selective and sensitive method was developed for the determination of volatile N-nitrosamines by gas chromatography (GC). After denitrosation of N-nitrosamines with hydrobromic acid, the resulting secondary amines were converted into their N-diethylthiophosphoryl derivatives and then measured by GC using a DB-1701 capillary column with flame photometric detection. The calibration graphs for N-nitrosamines in the range 0.05-1 nmol were linear and sufficiently reproducible for quantitative determination. This method was successfully applied to cigarette smoke samples without prior clean-up. N-Nitrosamines and secondary amines were completely separated by extraction with diethyl ether containing 25% 2-propanol. Overall recoveries of N-nitrosamines added to cigarette smoke samples were 83-110%. By using this method, N-nitrosamines in these samples could be determined without any interference from coexisting substances. Analytical results for the contents of N-nitrosamines and secondary amines in mainstream and sidestream smokes of several cigarettes are presented.

Airborne mutagens and carcinogens from cooking and other food preparation processes

The common food preparation processes, frying, broiling and baking, can give rise to air pollutants that are known to be mutagenic and carcinogenic in animal tests. A large number of persons can be exposed to such fumes as cooking is performed in most households and in many commercial enterprises. Additional studies on the emissions from these processes and exposure measurements are needed. Epidemiological studies on occupationally-exposed cooks and bakers with respect to cancer are equivocal.

Tobacco-specific N-nitrosamines and Areca-derived N-nitrosamines: chemistry, biochemistry, carcinogenicity, and relevance to humans

Nicotine and the minor tobacco alkaloids give rise to tobacco-specific N-nitrosamines (TSNA) during tobacco processing and during smoking. Chemical-analytical studies led to the identification of seven TSNA in smokeless tobacco (< or = 25 micrograms/g) and in mainstream smoke of cigarettes (1.3 micrograms TSNA/cigarette). Indoor air polluted by tobacco smoke may contain up to 24 pg/L of TSNA. In mice, rats, and hamsters, three TSNA, N'-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), are powerful carcinogens; two TSNA are moderately active as carcinogens; and two TSNA appear not to be carcinogenic. The TSNA are procarcinogens, agents that require metabolic activation. The active forms of the carcinogenic TSNA react with cellular components, including DNA, and with hemoglobin (Hb). The Hb adducts in chewers and smokers serve as biomarkers for the uptake and metabolic activation of carcinogenic TSNA and the urinary excretion of NNAL as free alcohol and as glucuronide for the uptake of TSNA. The review presents evidence that strongly supports the concept that TSNA contribute to the increased risk for cancer of the upper digestive tract in tobacco chewers and for the increased risk of lung cancer, especially pulmonary adenocarcinoma, in smokers. The high incidence of cancer of the upper digestive tract especially among men on the Indian subcontinent has been causally associated with chewing of betel quid mixed with tobacco. In addition to the TSNA, the betel quid chewers are exposed to four N-nitrosamines that are formed during chewing from the Areca alkaloids, two of these N-nitrosamines are carcinogens. The article also reviews approaches toward the reduction of the carcinogenic potency of smokeless tobacco, betel quid-tobacco mixtures, and cigarette smoke. Although the safest way to reduce the risk for tobacco-related cancers is to refrain from chewing and smoking, modifications of smokeless tobacco and of cigarettes are indicated to lead to less toxic products. Another more recent approach for reducing the carcinogenic effect of tobacco products is the application of chemopreventive agents, primarily of micronutrients. Future aspects in tobacco carcinogenesis, especially as it relates to TSNA, are expected in the field of molecular biochemistry and in biomarker studies, with the goal of identifying those tobacco and betel quid chewers and tobacco smokers who are at especially high risk for cancer.