Absorption and metabolism of nicotine from cigarettes

Unravelling the Risk of Poisoning From Nicotine-Containing Tobacco Products in Children Less Than Five Years of Age

For decades, young children in the United States have been accidentally poisoned by traditional tobacco products and the yearly incidence has slowly increased. More poisonings have accompanied the introduction of new products such as e-cigarettes and dissolvable tobacco, with renewed public attention. Using toxicological principles of human health risk assessment, published data from prior exposures, and information about the content and characteristics of specific products, I estimated the acute toxicological risk from exposure to various types and quantities of tobacco products for children <5 years old. Approximate reference levels for a non-lethal oral dose of nicotine were derived: A higher level potentially requiring medical care (0.2 mg per kg) and a lower level not potentially requiring medical care (0.04 mg per kg). A weight-based oral lowest lethal dose (LDLO) of 1-14 mg per kg in children <5 years old is estimated from the cited LDLOs in adults. I provide tables relating e-liquid concentration and volume to the oral LDLO in children <5 years old by weight and describing the amount of other tobacco products expected to result in lethality. Communications about safe storage practices should focus on the benefits of keeping any nicotine-containing product out of the reach of young children, and adults can be reminded to always reengage child-resistant closures on packages and call a poison center for accidental exposures. Healthcare providers, families, or any member of the public can also make reports about unexpected health or safety concerns related to tobacco products to the FDA using its online Safety Reporting Portal at https://www.fda.gov/TobaccoProducts/PublicHealthScienceResearch/ucm377563.htm. Tobacco products, particularly electronic nicotine delivery system (ENDS) liquids are highly toxic to children <5 years old in small amounts. Given that the concentration of nicotine in ENDS is 3 to 72 mg per mL, the lethal dose (LDLO) is expected to be 13-40 mL in a bottle containing a solution of 3 mg per mL liquid nicotine but may be as low as ½-2 mL in a bottle containing a highly concentrated solution of 72 mg per mL liquid nicotine. Features such as flow restrictors, child-resistant closures, and communication of safe storage practices to parents can help to lessen the morbidity and mortality from poisoning.

The fate of an inhaled cigarette puff in the human respiratory tract

OBJECTIVE

Cigarette smoking can lead to a host of adverse health effects such as lung and heart disease. Increased lung cancer risk is associated with inhalation of carcinogens present in a puff of smoke. These carcinogenic compounds deposit in the lung at different sites and trigger a cascade of events leading to adverse outcomes. Understanding the site-specific deposition of various smoke constituents will inform the study of respiratory diseases from cigarette smoking. We previously developed a deposition model for inhalation of aerosol from electronic nicotine delivery systems. In this study, the model was modified to simulate inhalation of cigarette smoke consisting of soluble and insoluble tar, nicotine, and cigarette-specific constituents that are known or possible human carcinogens.

MATERIALS AND METHODS

The deposition model was further modified to account for nicotine protonation and other cigarette-specific physics-based mechanisms that affect smoke deposition. Model predictions showed a total respiratory tract uptake in the lung for formaldehyde (99%), nicotine (80%), and benzo[a]pyrene (60%).

RESULTS

The site of deposition and uptake depended primarily on the constituent's saturation vapor pressure. High vapor pressure constituents such as formaldehyde were preferentially absorbed in the oral cavity and proximal lung regions, while low vapor pressure constituents such as benzo[a]pyrene were deposited in the deep lung regions. Model predictions of exhaled droplet size, droplet retention, nicotine retention, and uptake of aldehydes compared favorably with experimental data.

CONCLUSION

The deposition model can be integrated into exposure assessments and other studies that evaluate potential adverse health effects from cigarette smoking.

Association of environmental polycyclic aromatic hydrocarbons exposure with periodontitis in NHANES 2009-2014: A mixtures approach

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) can invade and cause harm to the human body through various pathways, but there is currently little research on the relationship between mixed-PAHs exposure and periodontitis. The purpose of this study was to examine the effects of mixed-urinary PAHs exposure on periodontitis in adults in the United States.

METHODS

The cross-sectional study included 2749 subjects selected from the National Health and Nutrition Examination Survey (NHANES) 2009-2014 cycles. A professional examination of the periodontal status was conducted to distinguish between periodontitis and non-periodontitis based on the Centers for Disease Control and Prevention/American Academy of Periodontology (CDC/AAP) case definition. Laboratory testing of urine samples was performed to obtain the levels of urinary PAHs. Pearson correlation coefficients were utilized to determine the degree of correlation between urinary PAHs, while weighted binary logistic regression and Bayesian kernel machine regression (BKMR) were employed to evaluate the relationship between urinary PAHs and periodontitis.

RESULTS

In a single-exposure model, 3-hydroxyfluorene (OH-3F), 2-hydroxyfluorene (OH-2F), 1-hydroxyphenanthrene (OH-1Ph), and 2-hydroxyphenanthrene and 3-hydroxyphenanthrene (OH-2,3Ph) were positively associated with periodontitis risk. In the mixed-exposure model, BKMR analysis demonstrated that mixed exposure to urinary PAHs was positively associated with periodontitis, with OH-2F being the most critical factor for the overall mixed effects (posterior inclusion probability [PIP] = 0.98). Univariate exposure-response function and univariate effects analysis revealed a positive correlation between urinary OH-2F levels and periodontitis.

CONCLUSIONS

The study reveals a significant positive correlation between exposure to mixed PAHs and periodontitis, with a particular emphasis on the pivotal role of OH-2F. Mitigating PAHs in the environment may serve as a preventive measure against periodontitis and alleviate its global public health burden.

Active smoking in urban households: An association between urinary cotinine metabolite level and serum eGFR concentration

INTRODUCTION

Smoking stands as a primary contributor to preventable deaths globally and is linked to an increased risk of developing kidney failure and other diseases. A few studies have focused on the negative correlation between serum cotinine and estimated glomerular filtration rate (eGFR), indicating decreased kidney function. This study investigated the associations between urinary cotinine metabolite concentration and serum eGFR among active smokers in urban households.

METHODS

This was a cross-sectional study of active smokers in urban households' community Bangkok, Thailand from January to April 2023. The study involved 85 participants aged ≥18 years who were active smokers. Both urinary cotinine and serum eGFR concentrations were used as biomarkers. Independent sample t-tests were used to compare the urinary cotinine metabolite based on differences in the characteristic variable. We used multiple linear regression to test the association between cotinine metabolite and characteristics variables. Spearman's analysis was used to test the correlation between cotinine metabolite and eGFR concentration.

RESULTS

The association between urinary cotinine metabolite and serum eGFR concentration decreased with increasing cotinine concentrations (r= -0.223, p=0.041), suggesting a decline in kidney function. However, this study found no significant difference between urinary cotinine metabolite and characteristic variables (p>0.05). Additionally, those who smoked for ≥10 years (117.40 ± 89.80 ng/mL), smoked ≥10 cigarettes per day (117.40 ± 89.80 ng/mL) and used conventional cigarettes (124.53 ± 115.10 ng/mL). The results of the multiple linear regression models analysis indicated that those who were smokers for ≥10 years (β=0.076; 95% CI: -31.575-59.715) and those who were smoked ≥10 cigarettes/day (β=0.126; 95% CI: -65.636-18.150) were not associated with urinary cotinine metabolite level.

CONCLUSIONS

This study shows that the urinary cotinine metabolite level is associated with serum eGFR concentration among active smokers in urban households. The current study suggests that clinical identification and a prospective cohort study are needed before robust conclusions about how tobacco affects kidney efficiency.

High-performance liquid chromatography-tandem mass spectrometry method for measuring cotinine and trans-3'-hydroxycotinine in bronchoalveolar lavage fluid of patients with e-cigarette, or vaping, product use-associated lung injury

In 2019, nearly 3000 U.S. residents developed severe lung injury associated with recent use of e-cigarette or vaping products. The Centers for Disease Control and Prevention responded to the outbreak, which was formally defined as e-cigarette, or vaping, product use-associated lung injury (EVALI). Centers for Disease Control and Prevention Laboratory rapidly developed assays to analyze potentially harmful and addictive substances in bronchoalveolar lavage (BAL) fluid collected from EVALI case patients. This report describes the development and validation of a high-throughput isotope-dilution high performance liquid chromatography-tandem mass spectrometry method for measuring two nicotine biomarkers, cotinine (COT) and trans-3'-hydroxycotinine (HCT), in bronchoalveolar lavage fluid samples. COT and HCT are the major metabolites of nicotine, the addictive alkaloid presents in tobacco products. This method had good specificity and sensitivity. The limit of detection is 0.033 and 0.0165 ng/mL for COT and HCT, respectively, using only 200 µL of sample volume. The within-run and between-run precision were 2-10%. The overall accuracy, calculated from recovery in three different sample matrices spiked at three concentrations, was 94.8% and 93.6% for COT and HCT, respectively. This novel HPLC-MS-MS method was utilized to characterize recent tobacco exposure in EVALI case patients. This method is useful for characterizing tobacco exposure that may be related to acute and chronic lung injury.

Molecular and functional changes in neutrophilic granulocytes induced by nicotine: a systematic review and critical evaluation

Background

Over 1.1 billion people smoke worldwide. The alkaloid nicotine is a prominent and addictive component of tobacco. In addition to tumors and cardiovascular disorders, tobacco consumption is associated with a variety of chronic-inflammatory diseases. Although neutrophilic granulocytes (neutrophils) play a role in the pathogenesis of many of these diseases, the impact of nicotine on neutrophils has not been systematically reviewed so far.

Objectives

The aim of this systematic review was to evaluate the direct influence of nicotine on human neutrophil functions, specifically on cell death/damage, apoptosis, chemotaxis, general motility, adhesion molecule expression, eicosanoid synthesis, cytokine/chemokine expression, formation of neutrophil extracellular traps (NETs), phagocytosis, generation of reactive oxygen species (ROS), net antimicrobial activity, and enzyme release.

Material and methods

This review was conducted according to the PRISMA guidelines. A literature search was performed in the databases NCBI Pubmed® and Web of Science™ in February 2023. Inclusion criteria comprised English written research articles, showing in vitro studies on the direct impact of nicotine on specified human neutrophil functions.

Results

Of the 532 originally identified articles, data from 34 articles were finally compiled after several evaluation steps. The considered studies highly varied in methodological aspects. While at high concentrations (>3 mmol/l) nicotine started to be cytotoxic to neutrophils, concentrations typically achieved in blood of smokers (in the nmol/l range) applied for long exposure times (24-72h) supported the survival of neutrophils. Smoking-relevant nicotine concentrations also increased the chemotaxis of neutrophils towards several chemoattractants, elevated their production of elastase, lipocalin-2, CXCL8, leukotriene B4 and prostaglandin E2, and reduced their integrin expression. Moreover, while nicotine impaired the neutrophil phagocytotic and anti-microbial activity, a range of studies demonstrated increased NET formation. However, conflicting effects were found on ROS generation, selectin expression and release of β-glucuronidase and myeloperoxidase.

Conclusion

Nicotine seems to support the presence in the tissue and the inflammatory and selected tissue-damaging activity of neutrophils and reduces their antimicrobial functions, suggesting a direct contribution of nicotine to the pathogenesis of chronic-inflammatory diseases via influencing the neutrophil biology.

Downregulation of Stem-Loop Binding Protein by Nicotine via α7-Nicotinic Acetylcholine Receptor and Its Role in Nicotine-Induced Cell Transformation

The use of electronic-cigarettes (e-cigs) has increased substantially in recent years, particularly among the younger generations. Liquid nicotine is the main component of e-cigs. Previous studies have shown that mice exposed to e-cig aerosols developed lung adenocarcinoma and bladder hyperplasia. These findings implicated a potential role for e-cig aerosols and nicotine in cancer development, although the underlying mechanisms are not fully understood. Here we report that exposure to liquid nicotine or nicotine aerosol generated from e-cig induces downregulation of Stem-loop binding protein (SLBP) and polyadenylation of canonical histone mRNAs in human bronchial epithelial cells and in mice lungs. Canonical histone mRNAs typically do not end in a poly(A) tail and the acquisition of such a tail via depletion of SLBP has been shown to causes chromosome instability. We show that nicotine-induced SLBP depletion is reversed by an inhibitor of α7-nicotinic acetylcholine receptors (α7-nAChR) or siRNA specific for α7-nAChR, indicating a nAChR-dependent reduction of SLBP by nicotine. Moreover, PI3K/AKT pathway is activated by nicotine exposure and CK2 and probably CDK1, 2 kinases well known for their function for SLBP phosphorylation and degradation, are shown to be involved, α7-nAChR-dependently, in nicotine-induced SLBP depletion. Importantly, nicotine-induced anchorage-independent cell growth is attenuated by inhibition of α7-nAChR and is rescued by overexpression of SLBP. We propose that the SLBP depletion and polyadenylation of canonical histone mRNAs via activation of α7-nAChR and a series of downstream signal transduction pathways are critical for nicotine-induced cell transformation and potential carcinogenesis.

Nicotine e-cigarette vapor inhalation and self-administration in a rodent model: Sex- and nicotine delivery-specific effects on metabolism and behavior

E-cigarettes, which deliver vaporized nicotine, have dramatically risen in popularity in recent years, despite many unanswered questions about safety, efficacy in reducing dependence, and overall impact on public health. Other factors, such as sex, also play an important role in determining behavioral and neurochemical responses to drugs of abuse. In these studies, we sought to develop a protocol for vaporized e-cigarette nicotine self-administration in rats, as a foundation to better understand the differing effects of nicotine exposure routes on behavior and physiological function. We report a novel method that elicits robust nicotine vapor self-administration in male and female rats. Our findings indicate that 5-mg/ml nicotine vape solution provides a high level of consistency in lever-pressing behavior for both males and females. Moreover, in male rats, we find that such e-cigarette nicotine vapor induces similar blood levels of nicotine's main metabolite, cotinine, as that found with intravenous nicotine self-administration. Therefore, the breathing pattern during vapor exposure in males leads to similar levels of titrated nicotine intake as with intravenous nicotine self-administration. Interestingly, a differential effect was found in the females, in which the same conditions of vapor exposure led to decreased cotinine levels with vapor compared to intravenous self-administration. Finally, differences in nicotine-mediated locomotion provide further support of the physiological effects of e-cigarette vapor inhalation. Taken together, our findings reveal important sex differences in nicotine intake based on the route of exposure, and we further establish a protocol for nicotine vapor self-administration in rats.

Comprehensive Parent-Metabolite PBPK/PD Modeling Insights into Nicotine Replacement Therapy Strategies

Background

Nicotine, the pharmacologically active substance in both tobacco and many electronic cigarette (e-cigarette) liquids, is responsible for the addiction that sustains cigarette smoking. With 8 million deaths worldwide annually, smoking remains one of the major causes of disability and premature death. However, nicotine also plays an important role in smoking cessation strategies.

Objectives

The aim of this study was to develop a comprehensive, whole-body, physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model of nicotine and its major metabolite cotinine, covering various routes of nicotine administration, and to simulate nicotine brain tissue concentrations after the use of combustible cigarettes, e-cigarettes, nicotine gums, and nicotine patches.

Methods

A parent–metabolite, PBPK/PD model of nicotine for a non-smoking and a smoking population was developed using 91 plasma and brain tissue concentration–time profiles and 11 heart rate profiles. Among others, cytochrome P450 (CYP) 2A6 and 2B6 enzymes were implemented, including kinetics for CYP2A6 poor metabolizers.

Results

The model is able to precisely describe and predict both nicotine plasma and brain tissue concentrations, cotinine plasma concentrations, and heart rate profiles. 100% of the predicted area under the concentration–time curve (AUC) and maximum concentration (C_max) values meet the twofold acceptance criterion with overall geometric mean fold errors of 1.12 and 1.15, respectively. The administration of combustible cigarettes, e-cigarettes, nicotine patches, and nicotine gums was successfully implemented in the model and used to identify differences in steady-state nicotine brain tissue concentration patterns.

Conclusions

Our PBPK/PD model may be helpful in further investigations of nicotine dependence and smoking cessation strategies. As the model represents the first nicotine PBPK/PD model predicting nicotine concentration and heart rate profiles after the use of e-cigarettes, it could also contribute to a better understanding of the recent increase in youth e-cigarette use.

Electronic supplementary material

The online version of this article (10.1007/s40262-020-00880-4) contains supplementary material, which is available to authorized users.

Glial cells as therapeutic targets for smoking cessation

Smoking remains the leading cause of morbidity and mortality in the United States, with less than 5% of smokers attempting to quit succeeding. This low smoking cessation success rate is thought to be due to the long-term adaptations and alterations in synaptic plasticity that occur following chronic nicotine exposure and withdrawal. Glial cells have recently emerged as active players in the development of dependence phenotypes due to their roles in modulating neuronal functions and synaptic plasticity. Fundamental studies have demonstrated that microglia and astrocytes are crucial for synapse formation and elimination in the developing brain, likely contributing to why glial dysfunction is implicated in numerous neurological and psychiatric disorders. Recently, there is increasing evidence for the involvement of glial cells in drug dependence and its associated behavioral manifestations. This review summarizes the newly evaluated role of microglia and astrocytes as molecular drivers of nicotine dependence and withdrawal phenotypes. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology.

History repeats itself: Role of characterizing flavors on nicotine use and abuse

The popularity of e-cigarettes has skyrocketed in recent years, and most vapers use flavored e-cigarette products. Consumption of flavored e-cigarettes exceeds that of combustible cigarettes and other tobacco products among adolescents, who are particularly vulnerable to becoming nicotine dependent. Flavorings have been used by the tobacco industry since the 17th century, but the use of flavors by the e-cigarette industry to create products with "characterizing" flavors (i.e. flavors other than tobacco or menthol) has sparked a public health debate. This review addresses the possibility that characterizing flavors make nicotine more appealing, rewarding and addictive. It also discusses ways in which preclinical and clinical studies could improve our understanding of the mechanisms by which flavors may alter nicotine reward and reinforcement. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.

More than Smoke and Patches: The Quest for Pharmacotherapies to Treat Tobacco Use Disorder

Tobacco use is a persistent public health issue. It kills up to half its users and is the cause of nearly 90% of all lung cancers. The main psychoactive component of tobacco is nicotine, primarily responsible for its abuse-related effects. Accordingly, most pharmacotherapies for smoking cessation target nicotinic acetylcholine receptors (nAChRs), nicotine's major site of action in the brain. The goal of the current review is twofold: first, to provide a brief overview of the most commonly used behavioral procedures for evaluating smoking cessation pharmacotherapies and an introduction to pharmacokinetic and pharmacodynamic properties of nicotine important for consideration in the development of new pharmacotherapies; and second, to discuss current and potential future pharmacological interventions aimed at decreasing tobacco use. Attention will focus on the potential for allosteric modulators of nAChRs to offer an improvement over currently approved pharmacotherapies. Additionally, given increasing public concern for the potential health consequences of using electronic nicotine delivery systems, which allow users to inhale aerosolized solutions as an alternative to smoking tobacco, an effort will be made throughout this review to address the implications of this relatively new form of nicotine delivery, specifically as it relates to smoking cessation. SIGNIFICANCE STATEMENT: Despite decades of research that have vastly improved our understanding of nicotine and its effects on the body, only a handful of pharmacotherapies have been successfully developed for use in smoking cessation. Thus, investigation of alternative pharmacological strategies for treating tobacco use disorder remains active; allosteric modulators of nicotinic acetylcholine receptors represent one class of compounds currently under development for this purpose.

Risk Factors for Asthma Exacerbation and Treatment Failure in Adults and Adolescents with Well-controlled Asthma during Continuation and Step-Down Therapy

RATIONALE

Although national and international guidelines recommend reduction of asthma controller therapy or "step-down" therapy in patients with well-controlled asthma, it is expected that some individuals may experience worsening of asthma symptoms or asthma exacerbations during step-down. Characteristics associated with subsequent exacerbations during step-down therapy have not been well defined. The effect of environmental tobacco smoke exposure on risk of treatment failure during asthma step-down therapy has not been reported.

OBJECTIVES

To identify baseline characteristics associated with treatment failure and asthma exacerbation during maintenance and guideline-based step-down therapy.

METHODS

The present analysis uses data collected from a completed randomized controlled trial of optimal step-down therapy in patients with well-controlled asthma taking moderate-dose combination inhaled corticosteroids/long-acting β-agonists. Participants were 12 years or older with physician-diagnosed asthma and were enrolled between December 2011 and May 2014.

RESULTS

An emergency room visit in the previous year was associated with subsequent treatment failure (hazard ratio, 1.53; 95% confidence interval, 1.06-2.21). For every 10% increase in baseline forced expiratory volume in one second percent predicted, the hazard ratio of treatment failure was 14% lower (hazard ratio, 0.86; 95% confidence interval, 0.74-0.99). There was no difference in the risk of treatment failure between adults and children, nor was the duration of asthma associated with the risk of treatment failure. Age of asthma onset was not associated with an increased risk of treatment failure. Unexpected emergency room visit in the previous year was the only risk factor significantly associated with subsequent asthma exacerbations requiring systemic corticosteroids. Time to treatment failure or exacerbation did not differ in participants with and without self-report of environmental tobacco smoke exposure.

CONCLUSIONS

The present findings can help clinicians identify adults and adolescents with asthma who are more likely to develop treatment failure and exacerbations and who may therefore require closer monitoring during asthma step-down treatment. Those with reduced pulmonary function, a history of exacerbations, and early-onset disease, even if otherwise well controlled, may require closer observation to prevent treatment failures and asthma exacerbations. Clinical trial registered with www.clinicaltrials.gov (NCT01437995).

A Public Health Crisis: Electronic Cigarettes, Vape, and JUUL

Electronic cigarettes (e-cigarettes) and vape devices have rapidly become the most common tobacco products used by youth, driven in large part by marketing and advertising by e-cigarette companies. There is substantial evidence that adolescent e-cigarette use leads to use of combustible tobacco products. E-cigarette companies commonly advertise that e-cigarettes contain nicotine, flavoring chemicals, and humectants (propylene glycol and/or vegetable glycerin), but toxicants, ultrafine particles, and carcinogens have also been found in e-cigarette solutions and emissions, many of which are known to cause adverse health effects. Most major e-cigarette brands are owned by big tobacco companies that use similar marketing and advertising strategies to attract youth users as they did with traditional tobacco products. In this review, we provide an overview of e-cigarettes and vape devices with an emphasis on the impact for the pediatric population. We describe the vast array of e-cigarette devices and solutions, concern for nicotine addiction, and the scientific background on the known health harms. There are accompanying visual depictions to assist in identifying these products, including newer e-cigarette products and JUUL. Because current federal regulations are insufficient to protect youth from e-cigarette use, exposure, and nicotine addiction, there are recommendations for pediatricians and pediatric health care providers to counsel and advocate for a tobacco-free lifestyle for patients and families.

Discriminative Stimulus Properties of S(-)-Nicotine: "A Drug for All Seasons"

S(-)-Nicotine is the major pharmacologically active substance in tobacco and can function as an effective discriminative stimulus in both experimental animals and humans. In this model, subjects must detect and communicate the nicotine drug state versus the non-drug state. This review describes the usefulness of the procedure to study nicotine, presents a general overview of the model, and provides some relevant methodological details for the establishment of this drug as a stimulus. Once established, the (-)-nicotine stimulus can be characterized for dose response and time course effects. Moreover, tests can be conducted to determine the similarity of effects produced by test drugs to those produced by the training dose of nicotine. Such tests have shown that the stimulus effects of nicotine are stereoselective [S(-)-nicotine >R(+)-nicotine] and that other "natural" tobacco alkaloids and (-)-nicotine metabolites can produce (-)-nicotine-like effects, but these drugs are much less potent than (-)-nicotine. Stimulus antagonism tests with mecamylamine and DHβE (dihydro-β-erythroidine) indicate that the (-)-nicotine stimulus is mediated via α4β2 nicotinic acetylcholine receptors (nAChRs) in brain; dopamine systems also are likely involved. Individuals who try to cease their use of nicotine-based products are often unsuccessful. Bupropion (Zyban®) and varenicline (Chantix®) may be somewhat effective as anti-smoking medications because they probably produce stimulus effects that serve as suitable substitutes for (-)-nicotine in the individual who is motivated to quit smoking. Finally, it is proposed that future drug discrimination studies should apply the model to the issue of maintenance of abstinence from (-)-nicotine-based products.

Role of α7-nicotinic acetylcholine receptor in nicotine-induced invasion and epithelial-to-mesenchymal transition in human non-small cell lung cancer cells

Nicotine via nicotinic acetylcholine receptors (nAChRs) stimulates non-small cell lung cancer (NSCLC) cell invasion and epithelial to mesenchymal transition (EMT) which underpin the cancer metastasis. However, the receptor subtype-dependent effects of nAChRs on NSCLC cell invasion and EMT, and the signaling pathway underlying the effects remain not fully defined. We identified that nicotine induced NSCLC cell invasion, migration, and EMT; the effects were suppressed by pharmacological intervention using α7-nAChR selective antagonists or by genetic intervention using α7-nAChR knockdown via RNA inference. Meanwhile, nicotine induced activation of MEK/ERK signaling in NSCLC cells; α7-nAChR antagonism or MEK/ERK signaling pathway inhibition suppressed NSCLC cell invasion and EMT marker expression. These results indicate that nicotine induces NSCLC cell invasion, migration, and EMT; the effects are mediated by α7-nAChRs and involve MEK/ERK signaling pathway. Delineating the effect of nicotine on the NSCLC cell invasion and EMT at receptor subtype level would improve the understanding of cancer biology and offer potentials for the exploitation of selective ligands for the control of the cancer metastasis.

Diverging effects of nicotine on motor learning performance: Improvement in deprived smokers and attenuation in non-smokers

Nicotine modulates cognition and neuroplasticity in smokers and non-smokers. A possible mechanism for its effect on learning and memory performance is its impact on long-term potentiation (LTP) and long-term depression (LTD). As neuroplasticity is closely connected to learning processes, we aimed to explore the effect of nicotine in healthy, young smokers and non-smokers on performance of the serial reaction time task (SRTT), a sequential motor learning paradigm. 20 nicotine-deprived smokers and 20 non-smokers participated in the study and were exposed to nicotine or placebo medication. Deprived smokers under placebo medication displayed reduced performance in terms of reaction time and error rates compared to the non-smoking group. After application of nicotine, performance in smokers improved while it deteriorated in non-smokers. These results indicate a restituting effect of nicotine in smokers in terms of cognitive parameters. This sheds further light on the proposed mechanism of nicotine on learning processes, which might be linked to the addictive component of nicotine, the probability of relapse and thus needs also be addressed in cessation treatment.

Environmental Tobacco Smoke and Periodontitis in United States Non-Smokers, 2009 to 2012

BACKGROUND

Epidemiologic studies using half-mouth designs for assessment of periodontal disease prevalence have reported that environmental tobacco smoke (ETS) exposure of non-smokers is associated with a two- to three-fold increase in the odds of developing periodontitis. In response to the possibility of under-reporting of periodontitis, the Centers for Disease Control updated periodontal examination procedures in 2009 for the National Health and Nutritional Examination Survey (NHANES), including full-mouth, six-site periodontal probing, and attachment loss assessment. Aims of this study are to estimate prevalence of periodontitis among United States non-smoking adults exposed to ETS, report the values of the improved methods for estimating disease prevalence, and evaluate the predictive contribution of ETS exposure to periodontitis.

METHODS

A cross-sectional study was conducted using NHANES data from the 2009 to 2012 examination cycle. To address these aims, oral examination data were used to determine prevalence of periodontitis among United States non-smoking adults and to test the influence of ETS exposure on occurrence of periodontitis.

RESULTS

There was a 28% increase in the odds of periodontitis for those with any ETS exposure compared with those with no measurable exposure (Wald χ2 test statistic [df] = 6.58 [1], P = 0.01; 95% confidence interval = 1.06 to 1.55).

CONCLUSION

ETS exposure increases the risk of an individual developing periodontitis.

Measurements of dermal uptake of nicotine directly from air and clothing

In this preliminary study, we have investigated whether dermal uptake of nicotine directly from air or indirectly from clothing can be a meaningful exposure pathway. Two participants wearing only shorts and a third participant wearing clean cotton clothes were exposed to environmental tobacco smoke (ETS), generated by mechanically "smoking" cigarettes, for three hours in a chamber while breathing clean air from head-enveloping hoods. The average nicotine concentration (420 μg/m³ ) was comparable to the highest levels reported for smoking sections of pubs. Urine samples were collected immediately before exposure and 60 hour post-exposure for bare-skinned participants. For the clothed participant, post-exposure urine samples were collected for 24 hour. This participant then entered the chamber for another three-hour exposure wearing a hood and clothes, including a shirt that had been exposed for five days to elevated nicotine levels. The urine samples were analyzed for nicotine and two metabolites-cotinine and 3OH-cotinine. Peak urinary cotinine and 3OH-cotinine concentrations for the bare-skinned participants were comparable to levels measured among non-smokers in hospitality environments before smoking bans. The amount of dermally absorbed nicotine for each bare-skinned participant was conservatively estimated at 570 μg, but may have been larger. For the participant wearing clean clothes, uptake was ~20 μg, and while wearing a shirt previously exposed to nicotine, uptake was ~80 μg. This study demonstrates meaningful dermal uptake of nicotine directly from air or from nicotine-exposed clothes. The findings are especially relevant for children in homes with smoking or vaping.

Do brand characteristics contribute significantly to variability in toxicant exposure in smokers? Data from NHANES 2007-2012

INTRODUCTION

This study sought to quantify the difference in serum cotinine and other biomarkers indicative of cigarette smoking in current US cigarette smokers attributable to brand level versus individual level factors.

METHODS

A total of 2,558 daily exclusive smokers, 20 years and older in the United States participated in the National Health and Nutrition Examination Surveys 2007-2012 and provided biospecimens and cigarette brand information. Biomakers of interest were serum cotinine, and urinary NNAL, PAHs, and heavy metals. Adjustments were made for person-level factors (e.g., sex, age, race, education), smoking behavior (cigarettes per day), brand, tar group (≤ 6mg, >6-15mg, >15mg), and menthol status.

RESULTS

The most commonly reported brands of US cigarettes were Marlboro, Newport, Camel, and Pall Mall. Cotinine levels differed by age (p=0.0065), race (p<0.0001), and cigarettes smoked per day (p<0.0001) but not brand, tar or menthol. Brand family was significantly associated with urinary levels of NNAL, 1HP, HFs, and HPHs. For NNAL. Person-level factors accounted for some of these differences. No consistent differences in metal exposure by brand were noted. Overall, brand information accounted for 2-8% of variance depending on the marker. Together, age, sex, race, education, and cigarettes smoked per day accounted for 20% in variance in cotinine levels, and adding the brand information (brand family, tar group, menthol) to the model accounted for an additional 0.5% (p<0.0948). In the full multivariate model, no significant difference in cotinine was seen by brand (p=0.2205), tar (p=0.2987) or menthol (p=0.1583).

CONCLUSIONS

Brand to brand differences seen in serum cotinine levels and other biomarkers indicative of cigarette smoking between the top US cigarette brands from 2007-2012 are primarily driven by individual differences among smokers, and to a lesser extent by differences among products.

Effects of nicotine in the presence and absence of vitamin E on morphology, viability and osteogenic gene expression in MG-63 osteoblast-like cells

BACKGROUND

Evidence shows that oxidative stress induced by nicotine plays an important role in bone loss. Vitamin E with its antioxidative properties may be able to reverse the effects of nicotine on bone. This study aimed to assess the effects of nicotine in the presence and absence of vitamin E on morphology, viability and osteogenic gene expression in MG-63 (osteosarcoma) human osteoblast-like cells.

METHODS

We treated the cells with 5 mM nicotine. The viability and morphology of cells were evaluated respectively using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT) and crystal violet assays. The effect of nicotine on osteogenic gene expression in MG-63 cells was assessed by real-time reverse-transcription polymerase chain reaction of osteoblast markers, namely, alkaline phosphatase, osteocalcin and bone sialoprotein.

RESULTS

The results revealed that survival and proliferation of MG-63 cells were suppressed following exposure to nicotine, and cytoplasm vacuolization occurred in the cells. Nicotine significantly down-regulated the expression of osteogenic marker genes. Such adverse effects on morphology, viability and osteogenic gene expression of MG-63 cells were reversed by vitamin E therapy.

CONCLUSIONS

In conclusion, vitamin E supplementation may play a role in proliferation and differentiation of osteoblasts, and vitamin E can be considered as an anabolic agent to treat nicotine-induced bone loss.

Development and characterization of self-assembling lecithin-based mixed polymeric micelles containing quercetin in cancer treatment and an in vivo pharmacokinetic study

Quercetin (Que) is known to have biological benefits including an anticancer effect, but low water solubility limits its clinical application. The aim of this study was to develop a lecithin-based mixed polymeric micelle (LMPM) delivery system to improve the solubility and bioavailability of Que. The optimal Que-LMPM, composed of Que, lecithin, Pluronic^® P123, and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy[poly(ethylene glycol)-2000] in a proportion of 3:1:17.5:2.5 (w/w), was prepared by a thin-film method. The average size, polydispersion index, encapsulating efficiency, and drug loading of Que-LMPM were 61.60±5.02 nm, 0.589±0.198, 96.87%±9.04%, and 12.18%±1.11%, respectively. The solubility of Que in the Que-LMPM system increased to 5.81 mg/mL, compared to that of free Que in water of 0.17–7.7 μg/mL. The Que-LMPM system presented a sustained-release property in vitro. The in vitro cytotoxicity assay showed that the 50% inhibitory concentration values toward MCF-7 breast cancer cells for free Que, blank LMPMs, and Que-LMPMs were >200, >200, and 110 μM, respectively, indicating the nontoxicity of the LMPM carrier, but the LMPM formulation enhanced the cytotoxicity of Que against MCF-7 cells. A cellular uptake assay also confirmed the intake of Que-LMPM by MCF-7 cells. An in vivo pharmacokinetic study demonstrated that Que-LMPMs had higher area under the concentration–time curve and a longer half-life, leading to better bioavailability compared to a free Que injection. Due to their nanosize, core–shell structure, and solubilization potential, LMPMs were successfully developed as a drug delivery system for Que to improve its solubility and bioavailability.

Smoking and Hand Dermatitis in the United States Adult Population

Background

Hand dermatitis is a common chronic relapsing skin disease resulting from a variety of causes, including endogenous predisposition and environmental exposures to irritants and allergens. Lifestyle factors such as smoking have been implicated in hand dermatitis.

Objective

To evaluate the association between tobacco exposure and hand dermatitis using the 2003~2004 National Health and Nutrition Examination Survey (NHANES) database.

Methods

Data were retrieved and analyzed from 1,301 participants, aged 20~59 years, from the 2003~2004 NHANES questionnaire study who completed health examination and blood tests. Diagnosis of hand dermatitis was based on standardized photographs of the dorsal and palmar views of the hands read by two dermatologists.

Results

There were 38 diagnosed cases of active hand dermatitis out of the 1,301 study participants (2.9%). Heavy smokers (>15 g tobacco daily) were 5.11 times more likely to have active hand dermatitis (odds ratio [OR], 5.11; 95% confidence interval [CI], 1.39~18.88; p=0.014). Those with serum cotinine >3 ng/ml were also more likely to have active hand dermatitis, compared with those with serum cotinine ≤3 ng/ml (OR, 2.50; 95% CI, 1.26~4.95; p=0.007). After adjusting for confounding factors such as age, atopic diathesis, occupational groups, and physical activity, the association between tobacco exposure and active hand dermatitis remained significant.

Conclusion

Smoking has a significant association with the presence of active hand dermatitis. It is important to consider smoking cessation as part of management of hand dermatitis.

Nicotine delivery, retention and pharmacokinetics from various electronic cigarettes

AIMS

To measure the systemic retention of nicotine, propylene glycol (PG) and vegetable glycerin (VG) in electronic cigarette (e-cigarette) users, and assess the abuse liability of e-cigarettes by characterizing nicotine pharmacokinetics.

DESIGN

E-cigarette users recruited over the internet participated in a 1-day research ward study. Subjects took 15 puffs from their usual brand of e-cigarette. Exhaled breath was trapped in gas-washing bottles and blood was sampled before and several times after use.

SETTING

San Francisco, California, USA.

PARTICIPANTS

Thirteen healthy, experienced adult e-cigarette users (six females and seven males).

MEASUREMENTS

Plasma nicotine was analyzed by gas chromatography-mass spectrometry (GC-MS/MS) and nicotine, VG and PG in e-liquids and gas traps were analyzed by LC-MS/MS. Heart rate changes and subjective effects were assessed.

FINDINGS

E-cigarettes delivered an average of 1.33 (0.87-1.79) mg [mean and 95% confidence interval (CI)] of nicotine, and 93.8% of the inhaled dose, 1.22 (0.80-1.66) was systemically retained. Average maximum plasma nicotine concentration (Cmax ) was 8.4 (5.4-11.5) ng/ml and time of maximal concentration (Tmax ) was 2-5 minutes. One participant had Tmax of 30 minutes. 84.4% and 91.7% of VG and PG, respectively, was systemically retained. Heart rate increased by an average of 8.0 beats per minute after 5 minutes. Withdrawal and urge to smoke decreased and the e-cigarettes were described as satisfying.

CONCLUSIONS

E-cigarettes can deliver levels of nicotine that are comparable to or higher than typical tobacco cigarettes, with similar systemic retention. Although the average maximum plasma nicotine concentration in experienced e-cigarette users appears to be generally lower than what has been reported from tobacco cigarette use, the shape of the pharmacokinetic curve is similar, suggesting addictive potential.

Nicotine and cotinine exposure from electronic cigarettes: a population approach

BACKGROUND AND OBJECTIVES

Electronic cigarettes (e-cigarettes) are a recent technology that has gained rapid acceptance. Still, little is known about them in terms of safety and effectiveness. A basic question is how effectively they deliver nicotine; however, the literature is surprisingly unclear on this point. Here, a population pharmacokinetic model was developed for nicotine and its major metabolite cotinine with the aim to provide a reliable framework for the simulation of nicotine and cotinine concentrations over time, based solely on inhalation airflow recordings and individual covariates [i.e., weight and breath carbon monoxide (CO) levels].

METHODS

This study included ten adults self-identified as heavy smokers (at least one pack of cigarettes per day). Plasma nicotine and cotinine concentrations were measured at regular 10-min intervals for 90 min while human subjects inhaled nicotine vapor from a modified e-cigarette. Airflow measurements were recorded every 200 ms throughout the session. A population pharmacokinetic model for nicotine and cotinine was developed based on previously published pharmacokinetic parameters and the airflow recordings. All of the analyses were performed with the non-linear mixed-effect modeling software NONMEM(®) version 7.2.

RESULTS

The results show that e-cigarettes deliver nicotine effectively, although the pharmacokinetic profiles are lower than those achieved with regular cigarettes. Our pharmacokinetic model effectively predicts plasma nicotine and cotinine concentrations from the inhalation volume, and initial breath CO.

CONCLUSION

E-cigarettes are effective at delivering nicotine. This new pharmacokinetic model of e-cigarette usage might be used for pharmacodynamic analysis where the pharmacokinetic profiles are not available.

Nicotine Directly Induces Endoplasmic Reticulum Stress Response in Rat Placental Trophoblast Giant Cells

Nicotine exposure during pregnancy leads to placental insufficiency impairing both fetal and neonatal development. Previous studies from our laboratory have demonstrated that in rats, nicotine augmented endoplasmic reticulum (ER) stress in association with placental insufficiency; however, the underlying mechanisms remain elusive. Therefore, we sought to investigate the possible direct effect of nicotine on ER stress in Rcho-1 rat placental trophoblast giant (TG) cells during differentiation. Protein and/or mRNA expression of markers involved in ER stress (eg, phosphorylated PERK, eIF2α, CHOP, and BiP/GRP78) and TG cell differentiation and function (eg, Pl-1, placental growth factor [Pgf], Hsd11b1, and Hsd11b2) were quantified via Western blot or real-time polymerase chain reaction. Nicotine treatment led to dose-dependent increases in the phosphorylation of PERK[Thr981] and eIF2α[Ser51], whereas pretreatment with a nicotinic acetylcholine receptor (nAChR) antagonist (mecamylamine hydrochloride) blocked the induction of PERK phosphorylation, verifying the direct involvement of nicotine and nAChR binding. We next investigated select target genes known to play essential roles in placental TG cell differentiation and function (Pl-1, Pgf, Hsd11b1, and Hsd11b2), and found that nicotine significantly augmented the mRNA levels of Hsd11b1 in a dose-dependent manner. Furthermore, using tauroursodeoxycholic acid, a safe bile acid known to improve protein chaperoning and folding, we were able to prevent nicotine-induced increases in both PERK phosphorylation and Hsd11b1 mRNA levels, revealing a potential novel therapeutic approach to reverse the deleterious effects of nicotine exposure in pregnancy. Collectively, these results implicate that nicotine, acting through its receptor, can directly augment ER stress and impair placental function.

Smoking and inflammation: evidence for a synergistic role in chronic disease

Tobacco smoking is the most important preventable risk factor for periodontitis; however, the underlying biological mechanisms responsible for the detrimental effects of smoking on periodontal health remain largely unclear. It is also well established that smoking has a negative impact on several inflammatory diseases, including rheumatoid arthritis, multiple sclerosis and inflammatory bowel disease. The aim of this paper was to review smoking-related changes in local and systemic host responses with a focus on cellular and molecular effects that could explain a hyperinflammatory response leading to periodontal destruction. Biological mechanisms that may be common to periodontal disease and other chronic inflammatory diseases were also explored, together with gene-smoking interactions. An epidemiologic perspective on the burden of smoking on periodontal health and the potential for smoking cessation is also presented. Tobacco smoking seems to induce changes ranging from decreased leukocyte chemotaxis to decreased production of immunoglobulins. Smoking also seems to cause a stronger inflammatory reaction with an increased release of potentially tissue-destructive substances (e.g. reactive oxygen species, collagenase, serine proteases and proinflammatory cytokines). These findings support a hypothesis that periodontitis is a hyperinflammatory condition rather than a hypo-inflammatory condition.

Bacoside A: Role in Cigarette Smoking Induced Changes in Brain

Cigarette smoking (CS) is a major health hazard that exerts diverse physiologic and biochemical effects mediated by the components present and generated during smoking. Recent experimental studies have shown predisposition to several biological consequences from both active and passive cigarette smoke exposure. In particular, passive smoking is linked to a number of adverse health effects which are equally harmful as active smoking. A pragmatic approach should be considered for designing a pharmacological intervention to combat the adverse effects of passive smoking. This review describes the results from a controlled experimental condition, testing the effect of bacoside A (BA) on the causal role of passive/secondhand smoke exposure that caused pathological and neurological changes in rat brain. Chronic exposure to cigarette smoke induced significant changes in rat brain histologically and at the neurotransmitter level, lipid peroxidation states, mitochondrial functions, membrane alterations, and apoptotic damage in rat brain. Bacoside A is a neuroactive agent isolated from Bacopa monnieri. As a neuroactive agent, BA was effective in combating these changes. Future research should examine the effects of BA at molecular level and assess its functional effects on neurobiological and behavioral processes associated with passive smoke.

Nicotine Induces Tumor Growth and Chemoresistance through Activation of the PI3K/Akt/mTOR Pathway in Bladder Cancer

Continued smoking is highly associated with not only a higher incidence but also greater risk of tumor recurrence, progression, and acquired chemoresistance of urothelial carcinoma. We investigated whether nicotine affects urothelial carcinoma, and the detailed mechanism by which nicotine could induce tumor growth and any associated chemoresistance. Cell viability was evaluated in the human bladder cancer cell line T24 exposed to nicotine with or without cisplatin (CDDP) and NVP-BEZ235 as a PI3K/mTOR dual inhibitor by the WST-1 assay. Protein expression of the PI3K/Akt/mTOR pathway was investigated by Western blotting or immunohistochemical analysis. The influence of nicotine on tumor growth was also evaluated with or without CDDP and/or NVP-BEZ235 in a subcutaneous bladder tumor model. The result demonstrated that cell proliferation was increased in T24 cells after exposure to nicotine. Phospho-specific Akt (pAkt) and phospho-specific p70 S6 kinase (pS6) were significantly upregulated by nicotine exposure. Tumor growth in vivo was significantly induced by nicotine exposure in accordance with increased pS6 expression. Nicotine attenuated inhibition of T24 cell growth by CDDP and further upregulated pS6 expression in vitro and in vivo. NVP-BZE235 inhibited T24 cell proliferation and pAkt and pS6 expression induced after exposure to nicotine and/or CDDP. In conclusion, nicotine increases tumor growth and induces acquired chemoresistance through activation of the PI3K/Akt/mTOR pathway in bladder cancer.

Cigarette smoke condensate inhibits collagen gel contraction and prostaglandin E2 production in human gingival fibroblasts

BACKGROUND

Granulation tissue remodeling and myofibroblastic differentiation are critically important events during wound healing. Tobacco smoking has a detrimental effect in gingival tissue repair. However, studies evaluating the effects of cigarette smoke on these events are lacking.

MATERIAL AND METHODS

We used gingival fibroblasts cultured within free-floating and restrained collagen gels to simulate the initial and final steps of the granulation tissue phase during tissue repair. Collagen gel contraction was stimulated with serum or transforming growth factor-β1. Cigarette smoke condensate (CSC) was used to evaluate the effects of tobacco smoke on gel contraction. Protein levels of alpha-smooth muscle actin, β1 integrin, matrix metalloproteinase-3 and connective tissue growth factor were evaluated through Western blot. Prostaglandin E(2) (PGE(2)) levels were determined through ELISA. Actin organization was evaluated through confocal microscopy.

RESULTS

CSC reduced collagen gel contraction induced by serum and transforming growth factor-β1 in restrained collagen gels. CSC also altered the development of actin stress fibers in fibroblasts cultured within restrained collagen gels. PGE(2) levels were strongly diminished by CSC in three-dimensional cell cultures. However, other proteins involved in granulation tissue remodeling and myofibroblastic differentiation such as alpha-smooth muscle actin, β1 integrin, matrix metalloproteinase-3 and connective tissue growth factor, were unmodified by CSC.

CONCLUSIONS

CSC may alter the capacity of gingival fibroblasts to remodel and contract a collagen matrix. Inhibition of PGE(2) production and alterations of actin stress fibers in these cells may impair proper tissue maturation during wound healing in smokers.

Consumption patterns and biomarkers of exposure in cigarette smokers switched to Snus, various dissolvable tobacco products, Dual use, or tobacco abstinence

The objectives of this clinical study were to evaluate changes in tobacco product use behavior and levels of selected biomarkers of exposure (BOEs) for smokers who switched to one of six conditions during clinical confinement: exclusive use of; Camel Snus, Sticks, Strips or Orbs, controlled Dual use of cigarettes and Camel Snus, or tobacco abstinence. The controlled Dual use (DU) condition mandated a 60% reduction in cigarettes smoked per day (CPD). 167 healthy U.S. male and female smokers were randomized to the six groups (n=25-30/group). Subjects smoked their usual brand of cigarette for 1 day prior to switching to their designated intervention condition. Levels of thirty-two BOEs in plasma, whole blood, urine and feces were determined before and after switching. Questionnaires that scored nicotine dependence and withdrawal discomfort were also administered. After 5 days, exclusive Snus, Sticks, Strips, or Orbs use averaged 6.1, 5.9, 13.5, and 8.5 units/day, respectively. DU subjects smoked 7.6 CPD and used 3.2 Snus pouches/day, on average. After 5 days, substantial reductions of most biomarkers, including nicotine, were observed in all groups. Toxicant exposures were similar to being tobacco abstinent after switching exclusively to Camel Snus, Sticks, Strips or Orbs. DU reductions were more modest.

Nicotine patches and paranoid psychosis

A patient was admitted with an acute paranoid psychosis. Prior to her illness, she had been using Nicobate patches while still smoking. The relationship between the two are discussed.

The pro-proliferative effects of nicotine and its underlying mechanism on rat airway smooth muscle cells

Recent studies have shown that nicotine, a major component of cigarette smoke, can stimulate the proliferation of non-neuronal cells. Cigarette smoking can promote a variety of pulmonary and cardiovascular diseases, such as chronic obstructive pulmonary disease (COPD), atherosclerosis, and cancer. A predominant feature of COPD is airway remodeling, which includes increased airway smooth muscle (ASM) mass. The mechanisms underlying ASM remodeling in COPD have not yet been fully elucidated. Here, we show that nicotine induces a profound and time-dependent increase in DNA synthesis in rat airway smooth muscle cells (RASMCs) in vitro. Nicotine also significantly increased the number of RASMCs, which was associated with the increased expression of Cyclin D1, phosphorylation of the retinoblastoma protein (RB) and was dependent on the activation of Akt. The activation of Akt by nicotine occurred within minutes and depended upon the nicotinic acetylcholine receptors (nAchRs). Activated Akt increased the phosphorylation of downstream substrates such as GSK3β. Our data suggest that the binding of nicotine to the nAchRs on RASMCs can regulate cellular proliferation by activating the Akt pathway.

Nicotine-mediated cell proliferation and tumor progression in smoking-related cancers

Tobacco smoke contains multiple classes of established carcinogens including benzo(a)pyrenes, polycyclic aromatic hydrocarbons, and tobacco-specific nitrosamines. Most of these compounds exert their genotoxic effects by forming DNA adducts and generation of reactive oxygen species, causing mutations in vital genes such as K-Ras and p53. In addition, tobacco-specific nitrosamines can activate nicotinic acetylcholine receptors (nAChR) and to a certain extent β-adrenergic receptors (β-AR), promoting cell proliferation. Furthermore, it has been demonstrated that nicotine, the major addictive component of tobacco smoke, can induce cell-cycle progression, angiogenesis, and metastasis of lung and pancreatic cancers. These effects occur mainly through the α7-nAChRs, with possible contribution from the β-ARs and/or epidermal growth factor receptors. This review article will discuss the molecular mechanisms by which nicotine and its oncogenic derivatives such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N-nitrosonornicotine induce cell-cycle progression and promote tumor growth. A variety of signaling cascades are induced by nicotine through nAChRs, including the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway, phosphoinositide 3-kinase/AKT pathway, and janus-activated kinase/STAT signaling. In addition, studies have shown that nAChR activation induces Src kinase in a β-arrestin-1-dependent manner, leading to the inactivation of Rb protein and resulting in the expression of E2F1-regulated proliferative genes. Such nAChR-mediated signaling events enhance the proliferation of cells and render them resistant to apoptosis induced by various agents. These observations highlight the role of nAChRs in promoting the growth and metastasis of tumors and raise the possibility of targeting them for cancer therapy.

Nicotine exposure during differentiation causes inhibition of N-myc expression

Background

The ability of chemicals to disrupt neonatal development can be studied using embryonic stem cells (ESC). One such chemical is nicotine. Prenatal nicotine exposure is known to affect postnatal lung function, although the mechanisms by which it has this effect are not clear. Since fibroblasts are a critical component of the developing lung, providing structure and secreting paracrine factors that are essential to epithelialization, this study focuses on the differentiation of ESC into fibroblasts using a directed differentiation protocol.

Methods

Fibroblasts obtained from non-human primate ESC (nhpESC) differentiation were analyzed by immunohistochemistry, immunostaining, Affymetrix gene expression array, qPCR, and immunoblotting.

Results

Results of these analyses demonstrated that although nhpESCs differentiate into fibroblasts in the presence of nicotine and appear normal by some measures, including H&E and SMA staining, they have an altered gene expression profile. Network analysis of expression changes demonstrated an over-representation of cell-cycle related genes with downregulation of N-myc as a central regulator in the pathway. Further investigation demonstrated that cells differentiated in the presence of nicotine had decreased N-myc mRNA and protein expression and longer doubling times, a biological effect consistent with downregulation of N-myc.

Conclusions

This study is the first to use primate ESC to demonstrate that nicotine can affect cellular differentiation from pluripotency into fibroblasts, and in particular, mediate N-myc expression in differentiating ESCs. Given the crucial role of fibroblasts throughout the body, this has important implications for the effect of cigarette smoke exposure on human development not only in the lung, but in organogenesis in general.

Animal models of nicotine exposure: relevance to second-hand smoking, electronic cigarette use, and compulsive smoking

Much evidence indicates that individuals use tobacco primarily to experience the psychopharmacological properties of nicotine and that a large proportion of smokers eventually become dependent on nicotine. In humans, nicotine acutely produces positive reinforcing effects, including mild euphoria, whereas a nicotine abstinence syndrome with both somatic and affective components is observed after chronic nicotine exposure. Animal models of nicotine self-administration and chronic exposure to nicotine have been critical in unveiling the neurobiological substrates that mediate the acute reinforcing effects of nicotine and emergence of a withdrawal syndrome during abstinence. However, important aspects of the transition from nicotine abuse to nicotine dependence, such as the emergence of increased motivation and compulsive nicotine intake following repeated exposure to the drug, have only recently begun to be modeled in animals. Thus, the neurobiological mechanisms that are involved in these important aspects of nicotine addiction remain largely unknown. In this review, we describe the different animal models available to date and discuss recent advances in animal models of nicotine exposure and nicotine dependence. This review demonstrates that novel animal models of nicotine vapor exposure and escalation of nicotine intake provide a unique opportunity to investigate the neurobiological effects of second-hand nicotine exposure, electronic cigarette use, and the mechanisms that underlie the transition from nicotine use to compulsive nicotine intake.

The effect of transdermal nicotine on fracture healing in a rabbit model

OBJECTIVE

Cigarette smoking inhibits fracture healing and places the patient at a higher risk of delayed union and nonunion. Nicotine has been implicated as the primary ingredient responsible for these effects. However, an analysis of current published investigations reveals conflicting data, with some evidence that nicotine alone does not significantly affect healing. We undertook an animal study of the effects of transdermal nicotine on fracture healing.

METHODS

Twenty-two adult male New Zealand white rabbits were randomly assigned to the nicotine group or the control group. A midshaft tibial osteotomy was performed on the left tibiae of all 22 rabbits. The nicotine rabbits were exposed using a 10.5-mg transdermal patch applied daily to the ear. Radiographs were obtained, and the area of fracture callus was assessed. Rabbits were euthanized at 21 days. Fractures were stressed to failure, and load/deformation curves were recorded.

RESULTS

The average area of callus formation was greater in the control group (

CONTROL

0.158 cm, Nicotine: 0.124 cm), but the difference was not statistically significant (P = 0.30). There was a significant difference between the 2 groups for mean normalized torque to failure (Nicotine: 36% of nonfractured side,

CONTROL

69% of nonfractured side, P = 0.028). The control group mean normalized stiffness was significantly greater than that for the nicotine rabbits (

CONTROL

87%, Nicotine: 43%, P = 0.036). There were 3 nonunions in the nicotine group (27%) compared with none in the control group (P = 0.062).

CONCLUSIONS

In a rabbit model of fracture healing, transdermal nicotine exposure resulted in decreased mechanical strength of healing fractures at 21 days and a higher rate of nonunion at 21 days compared with that of controls.

A multi-route model of nicotine-cotinine pharmacokinetics, pharmacodynamics and brain nicotinic acetylcholine receptor binding in humans

The pharmacokinetics of nicotine, the pharmacologically active alkaloid in tobacco responsible for addiction, are well characterized in humans. We developed a physiologically based pharmacokinetic/pharmacodynamic model of nicotine pharmacokinetics, brain dosimetry and brain nicotinic acetylcholine receptor (nAChRs) occupancy. A Bayesian framework was applied to optimize model parameters against multiple human data sets. The resulting model was consistent with both calibration and test data sets, but in general underestimated variability. A pharmacodynamic model relating nicotine levels to increases in heart rate as a proxy for the pharmacological effects of nicotine accurately described the nicotine related changes in heart rate and the development and decay of tolerance to nicotine. The PBPK model was utilized to quantitatively capture the combined impact of variation in physiological and metabolic parameters, nicotine availability and smoking compensation on the change in number of cigarettes smoked and toxicant exposure in a population of 10,000 people presented with a reduced toxicant (50%), reduced nicotine (50%) cigarette Across the population, toxicant exposure is reduced in some but not all smokers. Reductions are not in proportion to reductions in toxicant yields, largely due to partial compensation in response to reduced nicotine yields. This framework can be used as a key element of a dosimetry-driven risk assessment strategy for cigarette smoke constituents.

Transitions in smoking behaviour and the design of cessation schemes

The intake of nicotine by smoking cigarettes is modelled by a dynamical system of differential equations. The variables are the internal level of nicotine and the level of craving. The model is based on the dynamics of neural receptors and the way they enhance craving. Lighting of a cigarette is parametrised by a time-dependent Poisson process. The nicotine intake rate is assumed to be proportional with the parameter of this stochastic process. The effect of craving is damped by a control mechanism in which awareness of the risks of smoking and societal measures play a role. Fluctuations in this damping may cause transitions from smoking to non-smoking and vice versa. With the use of Monte Carlo simulation the effect of abrupt and gradual cessation therapies are evaluated. Combination of the two in a mixed scheme yields a therapy with a duration that can be set at wish.

Effects of cigarette smoke and nicotine on cell viability, migration and myofibroblastic differentiation

BACKGROUND AND OBJECTIVE

Several studies have analysed the role of nicotine as a prominent agent affecting wound repair in smokers. However, tobacco smoke contains several components that may alter gingival wound healing. The present study aimed to analyse the roles of cigarette smoke condensate (CSC) and nicotine on cell viability, cell migration/invasion and myofibroblastic differentiation using primary cultures of human gingival fibroblasts.

MATERIAL AND METHODS

To compare the effects of CSC and nicotine, gingival fibroblasts were stimulated with CSC (0.4–500 lg/mL) and the corresponding nicotine concentrations (0.025–32 lg/mL) present in research cigarettes (1R3F). Cell viability was evaluated through the MTS assay. Cell migration and invasion were assessed through scratch wound assays, collagen nested matrices and trans well migration. a-Smooth muscle actin production was evaluated by western blotting.

RESULTS

Cigarette smoke condensate at 50 lg/mL induced a moderate increase in cell viability, whereas the corresponding nicotine concentration (3.2 lg/mL) did not produce this response. Cigarette smoke condensate at 250 lg/mL, but not nicotine at 16 lg/mL (the corresponding nicotine concentration), induced cell death. Both nicotine and CSC stimulated cell migration (50 lg/mL CSC; 3.2 lg/mL nicotine). At 150 lg/mL, CSC inhibited cell migration; however, the corresponding concentration of nicotine (9.6 lg/mL), did not have this effect. Although both nicotine and CSC inhibited a-smooth muscle actin production, only the latter induced a statistically significant effect on this response.

CONCLUSION

Cigarette smoke condensate may stimulate cell survival and migration at low concentrations and inhibit these cell responses at higher levels of exposure. Moreover, CSC may interfere in myofibroblastic differentiation.These results show that cigarette smoke, but not nicotine, may significantly alter cell viability, cell migration and myofibroblastic differentiation in gingival mesenchymal cells.

Functional interaction between human papillomavirus type 16 E6 and E7 oncoproteins and cigarette smoke components in lung epithelial cells

The smoking habit is the most important, but not a sufficient cause for lung cancer development. Several studies have reported the human papillomavirus type 16 (HPV16) presence and E6 and E7 transcripts expression in lung carcinoma cases from different geographical regions. The possible interaction between HPV infection and smoke carcinogens, however, remains unclear. In this study we address a potential cooperation between tobacco smoke and HPV16 E6 and E7 oncoproteins for alterations in proliferative and tumorigenic properties of lung epithelial cells. A549 (alveolar, tumoral) and BEAS-2B (bronchial, non-tumoral) cell lines were stably transfected with recombinant pLXSN vectors expressing HPV16 E6 and E7 oncoproteins and exposed to cigarette smoke condensate (CSC) at different concentrations. HPV16 E6 and E7 expression was associated with loss of p53 stability, telomerase (hTERT) and p16(INK4A) overexpression in BEAS-2B cells as demonstrated by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting (WB). In A549 cells we observed downregulation of p53 but not a significant increase of hTERT transcripts. In addition, the HPV16 E6/E7 transfected cell lines showed an increased proliferation rate and anchorage-independent growth in a HPV16 E6 and E7 expression-dependent manner. Moreover, both HPV16 E6/E7 and mock transfected cells showed an increased proliferation rate and anchorage-independent growth in the presence of 0.1 and 10 µg/mL CSC. However, this increase was significantly greater in HPV16 E6/E7 transfected cells (p<0.001). Data were confirmed by FCSE proliferation assay. The results obtained in this study are suggestive of a functional interaction between tobacco smoke and HPV16 E6/E7 oncoproteins for malignant transformation and tumorigenesis of lung epithelial cells. More studies are warranted in order to dissect the molecular mechanisms involved in this cooperation.

A systematic review of nicotine by inhalation: is there a role for the inhaled route?

INTRODUCTION

A considerable minority of adults remain addicted to smoking cigarettes despite substantial education and public health efforts. Nicotine replacement therapies have only modest long-term quit rates. The pulmonary route of nicotine delivery has advantages over other routes. However, there are regulatory and technical barriers to the development of pulmonary nicotine delivery devices, and hence, none are commercially available. Current knowledge about pulmonary nicotine delivery is scattered throughout the literature and other sources such as patent applications. This review draws together what is currently known about pulmonary nicotine delivery and identifies potential ways that deep lung delivery can be achieved with a simple portable device.

AIMS

To systematically review clinical trials of nicotine inhalers, determine whether they delivered nicotine via the lung, and identify ways that pulmonary delivery of medicinal nicotine might be achieved and the technical issues involved.

METHODS

Systematic search of Medline and Embase.

RESULTS

Thirty-eight trials met the inclusion criteria. Cough, reflex interruption of smooth inspiration, and throat scratch limited the usefulness of nicotine inhalers. The pharmacokinetic profiles of portable nicotine inhalers were inferior to smoking, but among commercially available products, electronic cigarettes are currently the most promising.

CONCLUSIONS

Pulmonary nicotine delivery might be maximized by use of nicotine salts, which have a more physiological pH than pure nicotine, by ensuring the mass of the particles is optimal for alveolar absorption, and by adding flavoring agents. Metered-dose inhalers potentially can deliver nicotine more efficiently than other nicotine products, facilitating smoking cessation and improving smokers' lives.