Mike McEwan

Measurement of oxidative DNA damage induced by mainstream cigarette smoke in cultured NCI-H292 human pulmonary carcinoma cells.

Cigarette smoke is a complex dynamic mixture of more than 4800 chemicals distributed between the particulate and vapour phases. It is widely acknowledged that cigarette smoke is capable of causing oxidative damage in DNA, either directly or through generation of reactive oxygen species. In this study, we have used a novel system for exposing cultured NCI-H292 human pulmonary carcinoma cells at the air-liquid interface, to investigate the potential effects of cigarette smoke on oxidative DNA damage by use of the modified comet assay with formamidopyrimidine N-glycosylase (FPG) and endonuclease III (Endo III) to reveal purine and pyrimidine lesions, respectively. The results demonstrate that NCI-H292 cells exposed to mainstream cigarette smoke from Kentucky reference-cigarettes show considerable DNA damage in terms of strand-breaks (SBs), alkali-labile sites (ALS) and oxidative DNA lesions. Initial measurements of FPG-sensitive oxidative lesions were confounded by high levels of SBs and ALS. Strand-breaks, but not oxidative lesions are repaired during a 20-h recovery period, which allows the semi-quantitative measurement of FPG-sensitive oxidative DNA lesions. We also conclude that mainstream cigarette smoke does not generate increased levels of Endo III-sensitive oxidative DNA lesions, or that they are not distinguishable from SBs and ALS in vitro in this system. Moreover, we demonstrate the viability and versatility of this exposure system in combination with in vitro techniques as an investigative tool for damage induced by cigarette smoke and smoke constituents.

Simultaneous determination of four tobacco-specific N-nitrosamines (TSNA) in human urine.

Tobacco-specific N-nitrosamines (TSNA) include 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosonornicotine (NNN), N-nitrosoanabasine (NAB) and N-nitrosoanatabine (NAT). TSNA are suggested to play an important role in tobacco smoke carcinogenesis. We have developed and validated an LC-MS/MS method for the determination of total (free and conjugated) TSNA in human urine. The limits of detection (LOD) were 2.0, 0.8, 1.1 and 0.7 pg/ml for NNAL, NNN, NAB and NAT, respectively. Smokers were found to have significantly higher levels of TSNA in their urine than nonsmokers. In conclusion, the newly developed method is suitable for assessing the tobacco use-related exposure to NNK, NNN, NAB and NAT.

A liquid chromatography/tandem mass spectrometry (LC-MS/MS) method for the determination of phenolic polycyclic aromatic hydrocarbons (OH-PAH) in urine of non-smokers and smokers

AbstractPolycyclic aromatic hydrocarbons (PAH) are products of the incomplete combustion of organic materials and, therefore, occur ubiquitously in the environment and also in tobacco smoke. Since some PAH have been classified as carcinogens, it is important to have access to suitable analytical methods for biomarkers of exposure to this class of compounds. Past experience has shown that measuring a profile of PAH metabolites is more informative than metabolites of a single PAH. Assessment of environmental and smoking-related exposure levels requires analytical methods with high sensitivity and specificity. In addition, these methods should be fast enough to allow high throughput. With these pre-conditions in mind, we developed and validated a high-performance liquid chromatographic method with tandem mass spectrometric detection (LC-MS/MS) for the determination of phenolic metabolites of naphthalene, fluorene, phenanthrene and pyrene in urine of smokers and non-smokers. Sample work-up comprised enzymatic hydrolysis of urinary conjugates and solid-phase extraction on C18 cartridges. The method showed good specificity, sensitivity, and accuracy for the intended purpose and was also sufficiently rapid with a sample throughput of about 350 per week. Application to urine samples of 100 smokers and 50 non-smokers showed significant differences between both groups for all measured PAH metabolites, and strong correlations with markers of daily smoke exposure in smoker urine. Urinary levels were in good agreement with previously reported data using different methodologies. In conclusion, the developed LC-MS/MS method is suitable for the quantification of phenolic PAH metabolites of naphthalene, fluorene, phenanthrene, and pyrene in smoker and non-smoker urine. FigureCumulative frequencies of urinary 4-OH-Phe (left, not significantly influenced by smoking) and 1-OH-Pyr (right, significantly elevated in smokers)

Determination of tobacco-specific N-nitrosamines in urine of smokers and non-smokers

Tobacco-specific N-nitrosamines (TSNA) include 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N′-nitrosonornicotine (NNN), N′-nitrosoanabasine (NAB) and N′-nitrosoanatabine (NAT) and are found in tobacco and tobacco smoke. TSNA are of interest for biomonitoring of tobacco-smoke exposure as they are associated with carcinogenesis. Both NNK and NNN are classified by IARC as Group 1 carcinogens. Samples of 24 h urine collections (n = 108) were analysed from smokers and non-smokers, using a newly developed and validated LC-MS/MS method for determining total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL, the major metabolite of NNK), and total NNN, NAB and NAT. TSNA levels in smokers’ urine were significantly higher than in non-smokers. In smokers, urinary excretion of total TSNA correlated significantly (r > 0.5) with markers of smoking dose, such as daily cigarette consumption, salivary cotinine and urinary nicotine equivalents and increased with the ISO tar yield of cigarettes smoked. The correlation between urinary total NNN and the smoking dose was weaker (r = 0.4–0.5). In conclusion, this new method is suitable for assessing tobacco use-related exposure to NNK, NNN, NAB and NAT.

Cardiovascular Biomarkers in Groups of Established Smokers after a Decade of Smoking

To investigate tools for evaluation of smoking-associated disease initiation and progression, we examined basic clinical parameters and biomarkers of cardiovascular disease risk, in a group of healthy volunteers with an average 10-year smoking history. A small cross-sectional study of never-smokers, moderate smokers and smokers was performed. Caucasians were recruited to match pre-defined cigarette tar yields and cigarettes smoked per day. For haematological parameters, significant differences between never-smokers and all female smokers combined were seen for haemoglobin concentration, haematocrit, total leucocyte count, neutrophil count and lymphocyte count. For all male smokers combined, only total leucocyte count was statistically different. Analysis of exhaled CO and other smoke exposure biomarker (nicotine and its metabolites) data showed a statistically significant increase in all groups of smokers with a trend related to the number of cigarettes smoked per day. Thromboxane urinary metabolites 11-dehydro-thromboxane B(2) and 2,3-dinor-thromboxane B(2) were statistically significantly elevated in smokers. Significant statistical differences between smokers with approximately 10 years of smoking history and non-smokers in white cells count, hemoglobin and thromboxane turnover were seen, although they did not reach levels associated with overt diseases. These data could provide insight into early biomarkers predictive of risk for coronary and vascular disease.

A cross-sectional investigation of biomarkers of risk after a decade of smoking

Two groups of 20 healthy volunteers with cigarettes of different tar yield were compared with a group of 20 never smokers over 24 h for several biomarkers. All groups were of similar mean ages and the smokers had smoked for a homogeneous period of approximately 10 yr. The groups were assessed using routine medical parameters as well as biomarkers of recent smoke exposure and other biomarkers that were under evaluation as possible markers of risk for smoking-associated diseases. All biomarkers of exposure—carbon monoxide, nicotine plus its five major metabolites, and 4-(methylnitrosamine)-1-(3-pyridyl)-1-butanol (NNAL)—were significantly elevated in smokers. For biomarkers of potential risk evaluated in the blood, white cells and immunoglobulin (Ig) G showed a decrease related to smoking status (p < .01). Interleukin 6 levels were higher in smoker groups compared to never smokers, with a significant increasing trend across the groups (p < .05). Among the urinary biomarkers studied, 11-deydro-thromboxane B2, 2,3-dinor-thromboxane B2, and thymidine glycol showed significant increasing trends across the groups (p < .01). The results suggest that after the first decade or less of smoking, changes in inflammatory, immunological, and cardiovascular function can be observed. However, further studies on larger groups will be required to better understand the kinetics of these subtle effects observed early in smokers and their relationship with the potential risk of subsequent smoking-associated disease.

E-cigarette Nicotine Delivery: Data and Learnings from Pharmacokinetic Studies.

OBJECTIVES E-cigarettes could potentially play a major role in tobacco harm reduction by delivering nicotine in a vapor containing significantly fewer toxicants than cigarette smoke and may aid smoking behavior changes such as reduction or cessation. METHODS We examined blood nicotine levels in smokers who were non-accustomed to e-cigarette use (Study 1) and accustomed e-cigarette users (Study 2). We compared nicotine levels when participants used a closed modular system e-cigarette to those when participants smoked a cigarette. RESULTS In Study 1, Cmax (geometric mean (CV)) during a 5-minute puffing period (10 puffs, 30 seconds apart) was 13.4 (51.4) ng/ ml for a regular cigarette. The e-cigarette Cmax was significantly lower (p .05) at 2.5 (67.8) ng/ml. In Study 2, during a 5-minute ad libitum puffing period, cigarette Cmax was 7.2 (130.8) ng/mL, and it was 7.8 (108.2) ng/mL for the e-cigarette. CONCLUSIONS Our data demonstrate heterogeneity of nicotine deliveries both between products and also with the same products used by different cohorts, eg, accustomed users versus smokers. Such differences must be taken into account when determining the likely behavioral impact, on smoking reduction and cessation, of nicotine delivery data and when planning e-cigarette nicotine pharmacokinetic studies.

Changes in Biomarkers of Exposure on Switching From a Conventional Cigarette to Tobacco Heating Products: A Randomized, Controlled Study in Healthy Japanese Subjects

Abstract Background Smoking is a leading cause of numerous human disorders including pulmonary disease, cardiovascular disease, and cancer. Disease development is primarily caused by exposure to cigarette smoke constituents, many of which are known toxicants. Switching smokers to modified risk tobacco products (MRTPs) has been suggested as a potential means to reduce the risks of tobacco use, by reducing such exposure. Methods This randomized, controlled study investigated whether biomarkers of toxicant exposure (BoE) were reduced when smokers switched from smoking combustible cigarettes to using a novel (glo™/THP1.0) or in-market comparator (iQOS/THS) tobacco heating product (THP). One hundred eighty Japanese smokers smoked combustible cigarettes during a 2-day baseline period, followed by randomization to either continue smoking cigarettes, switch to using mentholated or non-mentholated variants of glo™, switch to using a non-mentholated variant of iQOS, or quit nicotine and tobacco product use completely for 5 days. Baseline and post-randomization 24-h urine samples were collected for BoE analysis. Carbon monoxide was measured daily in exhaled breath (eCO). Results On day 5 after switching, urinary BoE (excluding for nicotine) and eCO levels were significantly (p < .05) reduced by medians between 20.9% and 92.1% compared with baseline in all groups either using glo™ or iQOS or quitting tobacco use. Between-group comparisons revealed that the reductions in the glo™ groups were similar (p > .05) to quitting in many cases. Conclusions glo™ or iQOS use for 5 days reduced exposure to smoke toxicants in a manner comparable to quitting tobacco use. THPs are reduced exposure tobacco products with the potential to be MRTPs. Implications This clinical study demonstrates that when smokers switched from smoking combustible cigarettes to using tobacco heating products their exposure to smoke toxicants was significantly decreased. In many cases, this was to the same extent as that seen when they quit smoking completely. This may indicate that these products have the potential to be reduced exposure and/or reduced risk tobacco products when used by smokers whose cigarette consumption is displaced completely. Clinical Trial Registrations ISRCTN14301360 and UMIN000024988.

Smoking Selectively Accelerates Carotid Atherosclerosis in Hypertensive Patients

AbstractBackground and objectives: Left ventricular hypertrophy, carotid atherosclerosis and renal dysfunction are indicators of target organ damage in hypertension, and independent risk factors for both fatal and non-fatal cardio- and cerebrovascular events. In the general population, smoking is associated with increases in left ventricular mass and carotid intima-media thickness (IMT), and impaired renal function. The aim of the present study was to evaluate whether smoking affects the development of target organ damage in patients with arterial hypertension. Methods: 3192 hypertensive patients referred to the Hypertension Clinic of the “Federico II” University of Naples from January 2000 to July 2006 were retrospectively analysed. Subjects were aged from 18 to 75 years. Among these patients, 1391 were smokers and 1801 non-smokers. Results: The duration and severity of hypertension was significantly shorter in smokers when compared with non-smokers. The maximum arterial IMT was significantly higher in smokers compared with non-smokers (1.7 ± 0.1 mm vs 1.5 ± 0.1, p < 0.0001), while left ventricular mass index was comparable between the two groups. In contrast, glomerular filtration rate was observed to be higher in smokers compared with non-smokers. Logistic regression analysis showed that smoking, age, sex, duration of hypertension, systolic blood pressure and diastolic blood pressure were significantly correlated with IMT. Furthermore, a strong correlation was found between the number of cigarettes smoked per day and IMT. Conclusions: Together, these data indicate that in hypertensive patients who have a high risk of developing atherosclerosis, smoking could potentiate the development of atherosclerotic plaques.

Nicotine pharmacokinetics of electronic cigarettes: A review of the literature

E-cigarettes are battery-powered electronic devices from which users can inhale nicotine following its aerosolisation from a liquid solution. Some regulators and public health bodies consider e-cigarettes as potentially playing a major role in tobacco harm reduction. Their ability to provide nicotine to smokers in both amount and in a manner and form generally similar to cigarette smoking have been proposed as key components to help smokers reduce or cease the use of combustible cigarettes. Nicotine pharmacokinetic studies of e-cigarettes have been performed for a number of years and are beginning to show how nicotine delivery is evolving as the products themselves evolve. In this review, we provide a critical overview of the literature to describe what is known about nicotine delivery from e-cigarettes. We will discuss how the progression of e-cigarette design, development, and user familiarity has allowed increases in nicotine availability to the user, in the context of how much and how rapidly nicotine is delivered during acute-use periods. This review will also provide insight into current research gaps and highlight the potential utility of modelling and the standardisation of methodologies used to assess nicotine delivery to facilitate identification of products that are best suited to displace cigarette smoking among adult smokers.