An exploratory, randomised, crossover study to investigate the effect of nicotine on cognitive function in healthy adult smokers who use an electronic cigarette after a period of smoking abstinence.

BACKGROUND: As well as being associated with serious negative health outcomes, smoking has been reported to have an array of physiological and psychological effects, including effects on mood and cognitive function. Post-cessation, loss of such effects (including temporary deficits in cognitive function) have been cited as reasons for resumption of smoking. The effects of e-cigarettes and nicotine delivered by e-cigarettes on these functions have not been widely researched but may play a role in the effectiveness of e-cigarettes as a satisfactory alternative to combustible cigarettes for people who smoke, and in encouraging individuals who would otherwise continue to smoke, to transition to e-cigarettes. METHODS: The study was an exploratory, randomised, partially-blinded, single-centre, five-arm crossover trial that recruited 40 healthy male and female people who smoke. At 5 study sessions, following a 12-h period of nicotine abstinence, participants were randomly assigned to use either a combustible cigarette, an e-cigarette of three varying nicotine strengths (18 mg/mL, 12 mg/mL or 0 mg/mL respectively) or observe a no product usage session. Participants completed pre- and post-product usage assessments to examine the product usage effect on cognitive performance (using the Cambridge Neuropsychological Test Automated Battery (CANTAB)), subjective mood and smoking urges. RESULTS: A significant improvement in sustained attention task performance was observed following use of both the nicotine containing e-cigarettes and combustible cigarette compared to no product use. Additionally, there were no significant differences between the nicotine containing products, indicating that nicotine use enhanced sustained attention regardless of delivery format. Nicotine containing e-cigarette and combustible cigarette use also significantly improved overall mood of participants compared to no product use, with no significant differences observed between the nicotine containing products. Nicotine containing e-cigarette and combustible cigarette use significantly reduced smoking urges compared to no product use, though combustible cigarette use elicited the greatest reduction in smoking urges. CONCLUSIONS: Overall, the nicotine containing products improved sustained attention and mood while reducing smoking urges, with the studied e-cigarettes having comparable effects to combustible cigarettes across the assessed cognitive parameters and mood measures. These results demonstrate the potential role of e-cigarettes to provide an acceptable alternative for combustible cigarettes among people who would otherwise continue to smoke. Trial registration ISRCTN (identifier: ISRCTN35376793).

Statistical analysis plan for "A randomised, controlled study to evaluate the effects of switching from cigarette smoking to using a tobacco heating product on health effect indicators in healthy subjects".

Tobacco harm reduction strategies aim to substitute smoking with potentially reduced risk products (PRRPs) such as e-cigarettes and tobacco-heating products (THPs). The health benefits of switching from smoking to PRRPs is unknown. A randomised controlled trial is being conducted to increase understanding of the health effects of switching from smoking to a THP in a 12-month long ambulatory study (ISRCTN81075760). Here we describe the study endpoints and the statistical analysis plan. Endpoints are divided into biomarkers of exposure (BoE) to tobacco smoke constituents and health effect indicators related to risk of lung cancer, cardiovascular and obstructive lung disease. These have been selected on the basis of extensive literature evidence. Three primary endpoints, augmentation index (risk factor for cardiovascular disease), total NNAL (linked to lung cancer) and 8-Epi-PGF2α type III (indicator of oxidative stress linked to various diseases), and multiple secondary endpoints will be analysed at 90, 180, and 360 days. Changes from baseline will be compared between study arms by specific contrasts in mixed models. Study wise multiple comparisons adjustments will be performed to account for multiplicity of timepoints and comparisons within timepoints. Generalisability of outcomes will be tested by a sensitivity analysis adjusting for age and gender. Importantly, an ancillary analysis will be performed to assess product compliance during the study based on plasma levels of CEVal, a surrogate marker for acrylonitrile exposure. The rationale underlying the selection of BoEs and health effect indicators, coupled with the statistical analysis plan will be central to understanding the potential health effects of replacing smoking with THP use for one year.

Evaluating the effects of switching from cigarette smoking to using a heated tobacco product on health effect indicators in healthy subjects: study protocol for a randomized controlled trial.

Tobacco heating products (THPs) are a potentially safer alternative to combustible cigarette smoking. Through continued use, THPs may reduce smoking-related disease risk, whilst maintaining the sensorial experience and nicotine delivery sought by smokers. While literature evidence of the biological effects of THP aerosol exposure is increasing, there remains a knowledge gap with respect to substantiation of THP reduced risk potential in longer term real-life use. This randomized, multi-centre, controlled clinical study will test the hypotheses that following a switch from combustible cigarettes to a THP for 1 year, participants will experience a sustained reduction in exposure to tobacco-related toxicants that will lead to favourable changes in health effect indicators associated with smoking-related disease development. Changes in such indicators will be contextualized against smoking cessation and never-smoker cohorts. Up to 280 participants who do not intend to quit smoking will be randomized to continued combustible smoking (arm A, up to n = 80) or a commercially available THP (arm B n = 200). Furthermore, up to 190 participants with a high intent to quit smoking will undergo smoking cessation (arm D), and 40 never smokers will serve as a control group (arm E). Recruitment numbers were determined to be sufficient to achieve n = 50 in arms A, B and D, at study end. Enrolment started in March 2018 and the trial is scheduled to be completed in March 2020. Data from this study will be a valuable addition to the growing body of evidence in the field of understanding the individual and public health impact of THPs.Clinical Trial Registration: https://www.isrctn.com/ISRCTN81075760.

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.

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.

A single-blinded, single-centre, controlled study in healthy adult smokers to identify the effects of a reduced toxicant prototype cigarette on biomarkers of exposure and of biological effect versus commercial cigarettes.

BACKGROUND: Despite universal acceptance that smoking is harmful, a substantial number of adults continue to smoke. The development of potential reduced exposure products (more recently termed modified risk tobacco products) has been suggested as a way to reduce the risks of tobacco smoking. This trial is designed to investigate whether changes in toxicant exposure after switching from a commercial to reduced toxicant prototype (RTP) cigarette (7 mg International Organisation for Standardisation (ISO) tar yield) can be assessed by measurement of biomarkers and other factors. The primary objective is to descriptively assess changes in selected biomarkers of exposure (BoE) and biomarkers of biological effect (BoBE) within participants and within and between groups after switching. Secondary objectives are to assess similarly changes in other biomarkers, quality of life, smoking behaviours, physiological measures, mouth-level exposure to toxicants and sensory perception. METHODS/DESIGN: This trial will assess current smokers, ex-smokers and never-smokers in a single-centre single-blind, controlled clinical trial with a forced-switching design and in-clinic (residential) and ambulatory (non-residential) periods. Smokers will be aged 23-55 years (minimum legal smoking age plus 5 years) and non-smokers 28-55 years (minimum legal smoking age plus 5 years, plus minimum 5 years since last smoked). Smokers will be allowed to smoke freely at all times. We will assess changes in selected BoE and BoBE and effective dose in urine and blood after switching. Creatinine concentrations in serum, creatinine clearance in urine, cotinine concentration in saliva, diaries and collection of spent cigarette filters will be used to assess compliance with the study protocol. Mouth-level exposure to toxins will be assessed by filter analysis. DISCUSSION: Data from this study are expected to improve scientific understanding of the effects of RTP cigarettes on BoE and BoBE, and give insights into study design for clinical assessment of potential MRTPs. TRIAL REGISTRATION: The study was registered in the Current Controlled Trials database under the reference ISRCTN81286286.

CYP1A1/1B1 and CYP2A6/2A13 activity is conserved in cultures of differentiated primary human tracheobronchial epithelial cells.

BACKGROUND: The respiratory tract is the primary route of exposure to inhaled toxicants such as environmental pollutants and tobacco smoke. Metabolic activation of xenobiotics is a contributor to the onset of lung diseases. Enzymes such as CYP1A1/1B1 and CYP2A6/2A13 activate polycyclic aromatic hydrocarbons and nitrosamines, respectively. Yet, few in vitro models retaining both adequate morphology and metabolic activities are currently available to investigate smoke toxicity. OBJECTIVE: We characterised the expression and activity of the toxicologically relevant metabolic enzymes CYP1A1/1B1 and CYP2A6/2A13 in polarised primary tracheobronchial epithelial cells cultured at the air-liquid interface. Metabolic activity was compared with NCI-H292 and A549, two commonly used lung epithelial cell models. RESULTS: We report that CYP activity and inducibility is conserved in polarised primary tracheobronchial epithelial cells for 7- and 28-days cultured at the air-liquid interface. In comparison, NCI-H292 cells did not show CYP2A6/2A13 activity whilst A549 cells did not display significant metabolic activity for CYP1A1/1B1 or CYP2A6/2A13. CONCLUSION: Primary tracheobronchial epithelial cells retain both a polarised morphology and significant metabolic activity over a prolonged period of time. On the other hand, although A549 cells and NCI-H292 cells have been extensively used as lung models for toxicological assessment, they lack critical metabolic activation capability.

Agents associated with lung inflammation induce similar responses in NCI-H292 lung epithelial cells.

The aim of this study was to investigate an in vitro lung epithelial model for assessment of potential inhalation toxicity. The selected NCI-H292 lung carcinoma cell line is sensitive to cigarette smoke, responds in a similar manner to primary human lung epithelial cells and produces airway mucins. The following agents associated with inhalation toxicity were tested in the model: cigarette smoke total particulate matter, fly ash, bleomycin, lipopolysaccharide, vanadyl sulphate, diesel exhaust particles and carbon black. Polystyrene, poly-methylmethacrylate and dimethyl sulphoxide were used as negative controls. Response markers were chosen on the basis of reported injurious effects of lung toxicants in humans, and included pro-inflammatory cytokines, matrix metalloprotease-1, the airway mucin MUC5AC and heparin-binding epidermal growth factor-like growth factor. Markers were quantified at the mRNA and/or protein level in control and treated cells. Many of the selected markers were regulated in a similar manner by cigarette smoke and the other toxic substances in the H292 cell model. By comparison, the negative control agents were largely ineffective. We conclude that, with further validation, this assay may form part of a tiered strategy for toxicological assessment of inhaled agents prior to more complex primary cell models and animal inhalation studies.