Frazer Lowe

Evaluation of biomarkers of exposure and potential harm in smokers, former smokers and never-smokers

Abstract Background: The objective of this study was to obtain baseline data on biomarkers of exposure (BoE) and biomarkers of potential harm (BoPH) in smokers, former smokers and never-smokers. Methods: This was a cross-sectional study of 80 healthy male and female volunteers over 21 years old, self-selected for smoking status. Subjects were pre-screened by medical staff at an independent clinical research unit, within 1 week prior to a single overnight residential visit and sample collection. Results: All BoE were able to differentiate between the two smoking groups and smokers from all non-smokers. There was a strong correlation between cigarettes smoked per day and total urinary nicotine equivalents (TNE; r=0.85). TNE correlated better with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol levels than cigarettes smoked per day (r=0.75 and r=0.56, respectively). Of the BoPH included in this study, seven (11-dehydro-thromboxane B2, 2, 3-dinorthromboxane B2, 8-epi prostaglandin F2α, 8-hydroxy-2 deoxyguanosine, cis-thymidine glycol, low-density lipoprotein cholesterol and IgG) were significantly different between the group who smoked more cigarettes per day and never-smokers. These differences became more apparent and extended to the group who smoked 10 or less cigarettes per day, when total urinary recovery values were corrected for creatinine clearance. Conclusions: While BoE clearly differentiate between groups based on self-declared smoking status, most BoPH examined could not do so in a consistent manner. The dynamics of BoPH levels are not well understood. Future studies of BoPH should eliminate potential confounding factors and increase the number of subjects to allow the investigation of genetic polymorphism in metabolic pathways. Clin Chem Lab Med 2009;47:311–20.

E-cigarette aerosols induce lower oxidative stress in vitro when compared to tobacco smoke

Abstract Tobacco smoking is a risk factor for various diseases. The underlying cellular mechanisms are not fully characterized, but include oxidative stress, apoptosis, and necrosis. Electronic-cigarettes (e-cigarettes) have emerged as an alternative to and a possible means to reduce harm from tobacco smoking. E-cigarette vapor contains significantly lower levels of toxicants than cigarette smoke, but standardized methods to assess cellular responses to exposure are not well established. We investigated whether an in vitro model of the airway epithelium (human bronchial epithelial cells) and commercially available assays could differentiate cellular stress responses to aqueous aerosol extracts (AqE) generated from cigarette smoke and e-cigarette aerosols. After exposure to AqE concentrations of 0.063–0.500 puffs/mL, we measured the intracellular glutathione ratio (GSH:GSSG), intracellular generation of oxidant species, and activation of the nuclear factor erythroid-related factor 2 (Nrf2)-controlled antioxidant response elements (ARE) to characterize oxidative stress. Apoptotic and necrotic responses were characterized by increases in caspase 3/7 activity and reductions in viable cell protease activities. Concentration-dependent responses indicative of oxidative stress were obtained for all endpoints following exposure to cigarette smoke AqE: intracellular generation of oxidant species increased by up to 83%, GSH:GSSG reduced by 98.6% and transcriptional activation of ARE increased by up to 335%. Caspase 3/7 activity was increased by up to 37% and the viable cell population declined by up to 76%. No cellular stress responses were detected following exposure to e-cigarette AqE. The methods used were suitably sensitive to be employed for comparative studies of tobacco and nicotine products.

Lung cancer biomarkers for the assessment of modified risk tobacco products: an oxidative stress perspective

Abstract Manufacturers have developed prototype cigarettes yielding reduced levels of some tobacco smoke toxicants, when tested using laboratory machine smoking under standardised conditions. For the scientific assessment of modified risk tobacco products, tests that offer objective, reproducible data, which can be obtained in a much shorter time than the requirements of conventional epidemiology are needed. In this review, we consider whether biomarkers of biological effect related to oxidative stress can be used in this role. Based on published data, urinary 8-oxo-7,8-dihydro-2-deoxyguanosine, thymidine glycol, F2-isoprostanes, serum dehydroascorbic acid to ascorbic acid ratio and carotenoid concentrations show promise, while 4-hydroxynonenal requires further qualification.

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.

Assessing modified risk tobacco and nicotine products: Description of the scientific framework and assessment of a closed modular electronic cigarette

ABSTRACT Cigarette smoking causes many human diseases including cardiovascular disease, lung disease and cancer. Novel tobacco products with reduced yields of toxicants compared to cigarettes, such as tobacco‐heating products, snus and electronic cigarettes, hold great potential for reducing the harms associated with tobacco use. In the UK several public health agencies have advocated a potential role for novel products in tobacco harm reduction. Public Health England has stated that “The current best estimate is that e‐cigarettes are around 95% less harmful than smoking” and the Royal College of Physicians has urged public health to “Promote e‐cigarettes widely as substitute for smoking”. Health related claims on novel products such as ‘reduced exposure’ and ‘reduced risk’ should be substantiated using a weight of evidence approach based on a comprehensive scientific assessment. The US FDA, has provided draft guidance outlining a framework to assess novel products as Modified Risk Tobacco Products (MRTP). Based on this, we now propose a framework comprising pre‐clinical, clinical, and population studies to assess the risk profile of novel tobacco products. Additionally, the utility of this framework is assessed through the pre‐clinical and part of the clinical comparison of a commercial e‐cigarette (Vype ePen) with a scientific reference cigarette (3R4F) and the results of these studies suggest that ePen has the potential to be a reduced risk product. HighlightsDescription of a scientific framework to assess the risk profile of next generation products relative to cigarettes.Multi‐disciplinary studies comparing a commercial e‐cigarette (Vype ePen) with a scientific reference cigarette (3R4F).The test e‐cigarette aerosol is compositionally simpler, containing reduced levels of toxicants relative to cigarette smoke.Results from a range of multi‐disciplinary studies showed reduced responses for the test e‐cigarette relative to cigarettes.

Changes in levels of biomarkers of exposure and biological effect in a controlled study of smokers switched from conventional cigarettes to reduced-toxicant-prototype cigarettes

BACKGROUND Development of cigarettes that reduce exposure to harmful smoke constituents is a suggested tobacco harm reduction strategy, but robust methods for measurement of change are required. We investigated whether changes in biomarkers of exposure (BoE), effective dose (BoED) and biological effect (BoBE) could be detected after switching from conventional cigarettes to a reduced-toxicant-prototype cigarette (RTP). METHODS Regular smokers of 6-8mg ISO tar yield cigarettes were recruited in Hamburg, Germany, and supplied with a conventional 7mg ISO tar yield cigarette for 2weeks then switched to the same cigarette with a different tipping paper (control) or the RTP for 6months. Subjects smoked mostly at home and attended five residential clinic visits where urine and blood samples were collected for analysis. Primary endpoints were changes in specific biomarker levels compared with non-smoker background levels. Changes in daily cigarette consumption were also investigated. RESULTS BoE levels in controls generally increased over the study period, whereas most BoE and all BoED significantly declined in RTP smokers. Most BoBE data were similar across groups and/or too variable within individuals to detect changes. Increased daily cigarette consumption was affected by supply of free cigarettes, perceived shorter smoking time per cigarette than usual brands, and perceived reduced harm. CONCLUSIONS Despite increased cigarette consumption, reductions in BoE and BoED were detectable.

A cross-sectional analysis of candidate biomarkers of biological effect in smokers, never-smokers and ex-smokers.

Abstract Context: Biomarkers of biological effect (BOBE) have been proposed as potential tools to assess tobacco product use, toxicity and disease risk. Objective: To determine if candidate BOBE can distinguish between smokers, never-smokers and former smokers. Methods: Biomarker levels were compared from 143 smokers, 61 never-smokers and 61 ex-smokers. Results: In total, 27 candidate biomarkers were assessed, 14 were significantly different between smokers and never-smokers (p < 0.01) and of these 14 biomarkers, 12 were able to distinguish between smokers and former smokers (p < 0.05), which indicates the potential for reversibility. Conclusions: A total of 12 of 27 BOBE are potentially useful tools for future product assessment.

The Relationship Between Cigarette Smoking and Biomarkers of Exposure Across Two Study Centers in Europe~!2009-07-16~!2010-02-11~!2010-07-07~!

The relationship between biomarkers of exposure to cigarette smoke in 24h urine samples collected from groups of 80 smokers (44 males, 36 females) and 40 never smokers (17 males, 23 females) at two centers in Europe was studied. Eight biomarkers (nicotine, cotinine, hydroxycotinine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and all of the respective glucuronide conjugates) were measured. Subjects from the two centers were pooled and bio- marker data analyzed according to the machine smoked tar yield of the brand each subject smoked and the recorded num- ber of cigarettes smoked per day (CPD). A statistically significant relationship between CPD and all of the biomarkers analyzed was found. Smokers of less than 11 CPD had the lowest mean 24h urinary concentrations for all biomarkers measured. However, if the amount of constituent obtained from each cigarette smoked was calculated, then the amount of nicotine obtained per cigarette was highest in this group although the variation was also greatest for this group. The amount of NNK (4-(methylnitrosamino)-1-(3-pyridyl)-1 butanone, the parent molecule of NNAL) obtained per cigarette was not statistically significantly different across all groups. In conclusion, these results confirm the reliability of 24h uri- nary total nicotine and NNAL concentrations as biomarkers of exposure to specific cigarette smoke constituents across two centers in Europe. These measurements may provide an objective alternative to CPD when grouping smokers for are studies of other endpoints.

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.