Nicotine encourages oxidative stress and impairment of rats' brain mitigated by Spirulina platensis lipopolysaccharides and low-dose ionizing radiation

Nicotine is a psychoactive alkaloid of tobacco, which is ingested during cigarettes or electronic cigarette smoking. Extensive consumption of nicotine induced oxidative stress. Accordingly, it is implicated in many pathophysiology brain disorders and triggers neurodegeneration. In this study, we investigated the protective role of Spirulina platensis-lipopolysaccharides (S.LPS) and the low dose-ionizing radiation (LD-IR) against the induced neurotoxicity in the rats' brain due to the prolonged administration of high nicotine levels. Rats treated with nicotine for two months showed alterations in the oxidative stress markers (malondialdehyde (MDA), reduced glutathione (GSH) and oxidized glutathione disulfide (GSSG)), antioxidant enzymes (superoxide dismutase (SOD), catalase (Cat), glutathione enzymes (GPx and GST)) as well as several pro-inflammatory markers (Tumor Necrosis Factor-alpha (TNF-α), Interleukin-17 (IL-17), and Nuclear Factor-kappa B (NF-κB)), and induced apoptosis through Caspase-3 activity. Nicotine also upregulated the mRNA gene expression of cytochrome P450 enzymes (CYP2B1 and CYP2E1), Cyclin-dependent kinase 5 (CDK5), Toll-Like Receptor 4 (TLR4), and phospho-Tau (p-Tau) protein expression. Besides, it downregulated the alpha-7 nicotinic receptor (α7nAChR) mRNA gene expression accompanied by a decline in the calcium (Ca2+) level. S.LPS exhibited antioxidant, anti-inflammatory, anti-apoptotic and neuroprotective activities, which counteracting the detrimental effects of chronic nicotine administration. LD-IR demonstrated comparable effects to S.LPS. Exposure of rats to LD-IR enhanced the neuroprotective effects of S.LPS against nicotine toxicity. The light microscopic examination of the brain tissues was in agreement with the biochemical investigations. These findings display that S.LPS and LD-IR mitigated the oxidative stress and the impairment of rats' brain induced by nicotine, due to regulation of the mRNA gene expression of cytochrome P450 enzymes (CYP2B1 and CYP2E1) and the signaling pathway of Tau protein phosphorylation.

Clinical and attentional effects of acute nicotine treatment in Tourette’s syndrome

Evidence from pre-clinical infrahuman investigations, open-label clinical trials, and a single controlled trial found acute nicotine treatment potentiated up to 4 weeks neuroleptic-induced reductions of dyskinetic symptoms characterizing Tourette’s syndrome (TS). Given the attentional disturbances associated with this syndrome, and the improvements in attentional processes reported with nicotine, this randomized, double-blind, placebo-controlled trial examined the acute (4 h) and sustained (2 weeks) effects of a single dose of transdermal nicotine on clinical (i.e., tics), attentional (continuous performance task, event-related potentials, patient and parental reports) and behavioral symptoms in 23 children and adolescents with TS receiving neuroleptic treatment. In the 14 evaluable patients with complete primary efficacy data, nicotine (compared to placebo) failed to alter symptoms at 4 h but counteracted ERP-P300 signs of diminished attention seen 2 weeks following placebo treatment. Secondary efficacy measures, including patient self-reports and parental ratings, found nicotine to reduce complex tics and improve behaviors related to inattention. Additional work with intermittent dosing schedules is required to characterize optimal clinical and cognitive effects with nicotine treatment.

Trait differences in response to chronic nicotine and nicotine withdrawal in rats

INTRODUCTION

Understanding an individual's vulnerability to drug addiction has important implications for the development of effective personal treatment plans. Although theories acknowledge impulsive behaviour as a key component of drug addiction, little is known about the influence of trait impulsivity on an individual's susceptibility to the effects of psychostimulants on impulsivity at critical phases of the addiction cycle.

METHODS

This study investigated the short and longer-term effects of chronic nicotine administration on impulsive choice in rats selected for high (HI) and low impulsivity (LI) on a delay discounting task. Rats prepared with subcutaneously osmotic mini-pumps received either nicotine (3.16 mg/kg/day [freebase]) or saline for 7 days. Performance was assessed during chronic treatment, early and late withdrawal, and in response to acute nicotine challenges following prolonged abstinence.

RESULTS

Chronic nicotine increased impulsive choice in LI but not HI animals. Spontaneous withdrawal was associated with a nicotine abstinence syndrome, the early stages of which were characterised by opposing effects on impulsive choice in HI and LI animals. A transient decrease in impulsivity was observed in HI animals whilst the LI group remained more impulsive for up to 1 week following drug termination. Following normalisation of behaviour, acute nicotine challenges (0.125, 0.25, 0.5 mg/kg, SC) markedly increased impulsive choice regardless of trait impulsivity and drug history.

CONCLUSION

The results indicate that only LI individuals are vulnerable to chronic drug- and withdrawal-induced impairments in self-control which may increase the likelihood of the transition to, and maintenance of, nicotine dependence.

Handling relapse in smoking cessation: strategies and recommendations

Once established, smoking is a very difficult addiction to break. Many smokers persist in tobacco use for several years and typically cycle through multiple periods of remission and relapse. Smoking cessation is not a single event but a process, and relapse is an ordinary component of this process. While international guidelines place great emphasis on relapse prevention, very little can be found about managing smokers who have relapsed. This article is intended to address the challenge of managing smokers who relapse in the course of a smoking cessation program. This knowledge may lead to an improved smoking cessation outcomes.

[The endocrine effects of smoking]

Almost one third of men and women smoke in Belgium. Besides the well known tobacco's neck and cardiopulmonary systems adverse effects as well as associated neoplasms, today we recognize other deleterious consequences of tobacco on the neuroendocrine, thyroid and reproductive systems. Not only active smokers but also the fetus carried by a smoking mother is at risk for important health problems. Tobacco is a recognized risk factor of occurrence of ophtalmopathy. Some of the active components of tobacco as the thiocyanates are goitrogenic. Tobacco is a risk factor for men and women's infertility. Newborns from parents that smoke are at risk for sudden death. These consequences represent a major public health issue. A campaign for smoking cessation has been recently launched by the Federation of Public Health Service and the INAMI in Belgium.

The long-term effects of prenatal nicotine exposure on neurologic development

A large body of documented evidence has found that smoking during pregnancy is harmful to both the mother and the fetus. Prenatal exposure to nicotine in various forms alters neurologic development in experimental animals and may increase the risk for neurologic conditions in humans. There is a positive association between maternal smoking and sudden infant death syndrome (SIDS); however, the connection between nicotine addiction, depression, attention disorders, and learning and behavior problems in humans is not straightforward. Nicotine's action on the production and function of neurotransmitters makes it a prime suspect in the pathology of these diseases. Nicotine accentuates neurotransmitter function in adults but desensitizes these functions in prenatally exposed infants and children. This desensitization causes an abnormal response throughout the lifespan. Furthermore, nicotine use by adolescents and adults can alleviate some of the symptoms caused by these neurotransmitter problems while they increase the risk for nicotine addiction. Although nicotine replacement drugs are used by pregnant women, there is no clear indication that they improve outcomes during pregnancy, and they may add to the damage that occurs to the developing neurologic system in the fetus. Understanding the effects of nicotine exposure is important in providing safe care for pregnant women, children, and families and for developing appropriate smoking cessation programs during pregnancy.

Varenicline and suicidal behaviour: a cohort study based on data from the General Practice Research Database

OBJECTIVE

To determine whether varenicline, a recently licensed smoking cessation product, is associated with an increased risk of suicide and suicidal behaviour compared with alternative treatments bupropion and nicotine replacement therapy.

DESIGN

Cohort study nested within the General Practice Research Database.

SETTING

Primary care in the United Kingdom.

PARTICIPANTS

80,660 men and women aged 18-95 years were prescribed a new course of a smoking cessation product between 1 September 2006 and 31 May 2008; the initial drugs prescribed during follow-up were nicotine replacement products (n=63 265), varenicline (n=10 973), and bupropion (n=6422).

MAIN OUTCOME MEASURES

Primary outcomes were fatal and non-fatal self harm, secondary outcomes were suicidal thoughts and depression, all investigated with Cox's proportional hazards models.

RESULTS

There was no clear evidence that varenicline was associated with an increased risk of fatal (n=2) or non-fatal (n=166) self harm, although a twofold increased risk cannot be ruled out on the basis of the upper limit of the 95% confidence interval. Compared with nicotine replacement products, the hazard ratio for self harm among people prescribed varenicline was 1.12 (95% CI 0.67 to 1.88), and it was 1.17 (0.59 to 2.32) for people prescribed bupropion. There was no evidence that varenicline was associated with an increased risk of depression (n=2244) (hazard ratio 0.88 (0.77 to1.00)) or suicidal thoughts (n=37) (1.43 (0.53 to 3.85)).

CONCLUSION

Although a twofold increased risk of self harm with varenicline cannot be ruled out, these findings provide some reassurance concerning its association with suicidal behaviour.

Maternal tobacco smoking, nicotine replacement and neurobehavioural development

Abstract The adverse effects of prenatal cigarette smoke exposure on human reproductive outcomes are a major scientific and public health concern. In the United States, approximately 25% of women of childbearing age currently smoke cigarettes, and only a small percentage of these individuals quit after learning of their pregnancy. Women interested in smoking cessation during pregnancy have a number of options, including behavioural and pharmacological aids, but nicotine replacement therapy (NRT) is by far the most common approach. While NRT avoids exposure to the myriad compounds present in tobacco smoke, nicotine itself causes damage to the developing nervous system. The purpose of this article is to review the detrimental effects of developmental tobacco smoke exposure on short- and long-term outcomes with particular emphasis on neurobehavioural consequences. In conclusion based on the clear, adverse effects of nicotine on brain development observed in human and animal studies, we suggest that safer alternatives for smoking cessation in pregnancy are badly needed.

Dendritic cells in chronic obstructive pulmonary disease: new players in an old game

Dendritic cells (DCs) are professional antigen-presenting cells responsible for immune homeostasis. In the lung's responses to tissue damage or infection, they initiate and orchestrate innate and adaptive immunity. There are immature and mature states and at least three phenotypic and functional subsets. DCs circulate in the blood and localize to mucosal surfaces in immature form where they act as sentinels, sampling constituents of the external environment that breach the epithelium. With internalization of antigen, they are activated, mature, and migrate to draining lymph nodes to induce the proliferation and regulate the balance of Th1/Th2 T cells or to induce a state of tolerance, the last dependent on maturation status, extent of cell surface costimulatory molecule expression, and cytokine release. Cigarette smoke has modulatory effects varying with species, dose, the location examined within the lung, and the marker or technique used to identify DCs. Healthy smokers (and smokers with asthma) have reduced numbers of large airway mature DCs. In chronic obstructive pulmonary disease, the number of immature DCs is increased in small airways, whereas in smokers with chronic obstructive pulmonary disease, the total number of DCs appears to be reduced in large airways. We hypothesize that the long-term effects of cigarette smoke include reduction of DC maturation and function, changes that favor repeated infection, increased exacerbation frequency, and the altered (CD8(+) T-cell predominant) pattern of inflammation associated with this progressive chronic disease.

Nicotine increases the collagen-degrading ability of human gingival fibroblasts

BACKGROUND AND OBJECTIVE

The objective of this study was to determine the effects that nicotine and the combination of nicotine and Porphyromonas gingivalis supernatant have on human gingival fibroblast-mediated collagen degradation.

MATERIAL AND METHODS

Human gingival fibroblasts were cultured with 25-500 microg/ml of nicotine in collagen-coated six-well plates. On days 1-5, the conditioned media was collected for zymography and western blot analyses of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). The cells were then removed and the collagen cleavage visualized by Coomassie blue staining. To examine the combined effect, 250 microg/ml of nicotine and 10% v/v culture supernatant of P. gingivalis ATCC 33277 were added to the human gingival fibroblasts. The mRNA levels of multiple MMPs and TIMPs were monitored.

RESULTS

Nicotine increased the human gingival fibroblast-mediated collagen cleavage. The MMP-14 and MMP-2 produced by the nicotine-treated human gingival fibroblasts more readily underwent zymogen activation. Nicotine treatment resulted in TIMP-2 redistribution to the cell surface. The mRNAs of multiple MMPs and TIMPs were unaltered by nicotine. An additive collagen cleavage effect was observed when the human gingival fibroblasts were treated with both nicotine and P. gingivalis.

CONCLUSION

Nicotine increased human gingival fibroblast-mediated collagen degradation, in part through the activation of membrane-associated MMPs. Nicotine and P. gingivalis had an additive effect on human gingival fibroblast-mediated collagen degradation.

Nicotine, cotinine, withdrawal, and craving patterns during smoking and nicotine nasal spray use: results from a pilot study with African American men

Nicotine intake via smoking is highly variable. Individualized dosing of nicotine replacement therapy (NRT) may improve product efficacy, but a better understanding of the within-day and within-subject relationships between smoking, NRT use, nicotine and cotinine concentrations in blood, and cravings and withdrawal symptoms is needed to inform dosing algorithms. A pilot study was undertaken to collect data on these relationships and to assess the feasibility of the methods needed for this type of research, including a sophisticated statistical modeling technique (a two-part mixed-effects model with correlated random effects that accounts for clumping at zero). Because nicotine metabolism varies by gender and race, the sample was homogeneous with respect to these characteristics. In a within-subjects study, 27 African American adult male smokers carried a computerized cigarette dispenser for 1 week, capturing the time each cigarette was smoked. Subjects then entered an inpatient setting for 1 day of scheduled smoking (matched to data from the cigarette dispenser to create an ecologically valid schedule) and 4 days of ad libitum nicotine nasal spray use, while tobacco abstinent. Eight times per day, at 2-hour intervals, blood was drawn and ratings of cigarette cravings and withdrawal symptoms were obtained. On average, subjects used less than half of the manufacturer's recommended minimum daily dose of nicotine nasal spray. Large differences in nicotine and cotinine levels were observed between individuals. When predicting nicotine, cotinine, withdrawal, and cravings, we observed significant interactions between route of nicotine intake and a variety of independent variables.

Adrenergic blocker carvedilol attenuates the cardiovascular and aversive effects of nicotine in abstinent smokers

The cardiovascular response to nicotine is mediated mainly by noradrenergic activation. Whether noradrenergic activation mediates other effects of nicotine has not been well documented in humans. In this study, we examined the effects of an alpha and beta-adrenergic receptor blocker: carvedilol, on cardiovascular and subjective responses to nicotine lozenge and on the ability of nicotine lozenge to suppress tobacco withdrawal symptoms in overnight abstinent smokers. Fifteen smokers, nine men and six women, participated in a double-blind, placebo-controlled, crossover study. In each of the three experimental sessions, participants were treated orally with a single 25 or 50 mg dose of carvedilol or placebo. Two hours and 10 min following the medication treatment, participants received a single 4 mg nicotine lozenge. Carvedilol treatment attenuated the nicotine-induced heart rate, systolic and diastolic blood pressure increases. Carvedilol also attenuated the self-report rating of 'bad effects' in response to nicotine. Carvedilol, alone or in combination with nicotine lozenge, did not affect tobacco withdrawal symptoms. Carvedilol treatment did not affect performance on the Stroop Test. These results support the effectiveness of carvedilol for attenuating the cardiovascular effects of nicotine. Attenuation of the rating of 'bad effects' by carvedilol suggests that noradrenergic activation may also mediate the aversive effects of nicotine.

Non-treatment-seeking heavy drinkers: effects of chronic cigarette smoking on brain structure

We previously reported [Cardenas, V.A., Studholme, C., Meyerhoff, D.J., Song, E., Weiner, M.W., 2005. Chronic active heavy drinking and family history of problem drinking modulate regional brain tissue volumes. Psychiatry Res. 138, 115-130] that non-treatment-seeking, active heavy drinkers (HD) demonstrated smaller regional neocortical gray matter volumes compared to light drinking controls; however, the potential effects of chronic cigarette smoking on regional brain volumes were not addressed. The goal of this retrospective analysis was to determine if chronic smoking affected brain structure in the non-treatment-seeking heavy drinking sample from our earlier report (i.e., Cardenas et al., 2005). Regional volumetric comparisons were made among age-matched smoking HD (n=17), non-smoking HD (n=16), and non-smoking light drinkers (nsLD; n=20) from our original sample. Quantitative volumetric measures of neocortical gray matter (GM), white matter (WM), subcortical structures, and cerebral spinal fluid (CSF) were derived from high-resolution magnetic resonance imaging. Smoking HD demonstrated smaller volumes than nsLD in the frontal, parietal, temporal GM, and for total neocortical GM. Smoking HD also demonstrated smaller temporal and total GM volumes than non-smoking HD. Non-smoking HD and nsLD did not differ significantly on GM volumes. Further, the three groups did not differ on lobar WM, subcortical structures or regional CSF volumes. These retrospective analyses indicate neocortical GM volume reductions in non-treatment-seeking smoking HD, but not in non-smoking HD, which are consistent with our studies in recently detoxified treatment-seeking alcohol-dependent samples.

Efficacy of the nicotine inhaler in smoking reduction: A double-blind, randomized trial

Many smokers are not ready to quit but are interested in changing their smoking behavior, particularly if such a change is associated with a reduction in health risk. The present study evaluated the efficacy of the nicotine inhaler in reducing smoking. Exploratory studies assessed whether reduction in smoking was associated with reduction in markers of disease risk. A total of 429 healthy smokers (smoking at least 20 cigarettes/day) were randomly assigned to either nicotine-containing or placebo inhalers, which subjects were allowed to use ad libitum for up to 1 year. The nicotine inhaler was significantly superior to placebo in achieving reduction in daily cigarette consumption by at least 50% after 4 months, compared with baseline (18% vs. 8%, p = .004). Active treatment promoted smoking cessation: 8% of subjects in the nicotine group and 1% in the placebo group were abstinent at month 15. Throughout the study, smoking reduction, per se, independent of treatment group, was associated with a statistically significant decrease in exhaled carbon monoxide and serum cotinine and thiocyanate. Smoking reduction also improved established risk markers for cardiovascular disease over 4 months. The incidence of adverse events did not differ significantly between the active and placebo groups. The most common treatment-related adverse events were throat irritation and cough. In conclusion, the nicotine inhaler can help smokers who are unable or unwilling to quit to reduce daily cigarette consumption, which may be a health benefit on its own and may further promote quitting.

Airway irritation and cough evoked by inhaled cigarette smoke: role of neuronal nicotinic acetylcholine receptors

In a series of studies carried out in different experimental models, we investigated the type(s) of lung afferents and mechanism(s) underlying the cigarette smoke-induced airway irritation and cough. In healthy non-smokers, the intensity of airway irritation and cough evoked by cigarette smoke was markedly reduced after premedication with hexamethonium. A similar pattern of responses was also triggered by inhalation of nicotine aerosol. These studies in human subjects suggested nicotine as the primary causative agent in cigarette smoke that evokes airway irritation. Indeed, single-fiber recording experiments performed in anesthetized dogs showed that both C-fibers and rapidly adapting receptors in the lungs and airways were stimulated by inhalation of one puff of cigarette smoke, and the intensity of this stimulatory effect was related to the nicotine content in the cigarette and abolished by hexamethonium. To further study the direct effect of nicotine on these sensory nerves, we measured the change in intracellular calcium concentration ([Ca(2+)](i)) of pulmonary sensory neurons isolated from the nodose and jugular ganglia of adult rats. Our results showed that nicotine evoked an abrupt and transient increase in [Ca(2+)](i) in approximately 34% of the 522 neurons tested, and 1,1-dimethyl-4-phenylpiperazinium, a selective agonist of the neuronal nicotinic acetylcholine receptors (NnAChRs), evoked a similar pattern of response as that of nicotine in these neurons. In conclusion, results of these studies show that nicotine exerts a direct stimulatory effect on vagal pulmonary sensory neurons. This stimulatory effect of nicotine is primarily responsible for the airway irritation and cough evoked by inhaled cigarette smoke, and is mediated through an activation of the NnAChRs.

Environmental Tobacco Smoke and Risk of Spontaneous Abortion

BACKGROUND

Studies of exposure to environmental tobacco smoke (ETS) and risk of spontaneous abortion are limited to a few studies of self-reported exposure, and the results have been inconsistent. The aim of this study was to investigate risk of early spontaneous abortion related to ETS and active smoking as defined by plasma cotinine levels.

METHODS

We conducted a population-based case-control study in Uppsala County, Sweden, between January 1996 and December 1998. Cases were 463 women with spontaneous abortion at 6 to 12 completed weeks of gestation, and controls were 864 pregnant women matched to cases according to the week of gestation. Exposure status was defined by plasma cotinine concentrations: nonexposed, <0.1 ng/mL; ETS-exposed, 0.1-15 ng/mL; and exposed to active smoking, >15 ng/mL. Multivariable analysis was used to estimate the relative risk of spontaneous abortion associated with exposure to ETS and active smoking.

RESULTS

Nineteen percent of controls and 24% of cases were classified as having been exposed to ETS. Compared with nonexposed women, risk of spontaneous abortion was increased among both ETS-exposed women (adjusted odds ratio = 1.67; 95% confidence interval = 1.17-2.38) and active smokers (2.11; 1.36-3.27). We could not show a differential effect of exposure to ETS or active smoking between normal and abnormal fetal karyotype abortions.

CONCLUSIONS

Nonsmoking pregnant women exposed to ETS may be at increased risk of spontaneous abortion. Given the high prevalence of ETS exposure, the public health consequences of passive smoking regarding early fetal loss may be substantial.

Measuring impulsivity and modeling its association with cigarette smoking

Two types of behavioral measure are primarily used to examine impulsivity in humans and animals: Go/No-go tasks to assess inhibition and relative preference tasks to assess delay aversion. Several examples of each type of task are described so that common cognitive processes and variables affecting performance can be identified. Data suggest that smokers are more impulsive on each of these impulsivity measures than nonsmokers. Several models can be proposed to account for this group difference: (a) the differences predate and, possibly, are causally related to the initiation of cigarette smoking; (b) higher levels of impulsivity are associated with continued smoking, either through an association with heightened positive subjective effects of nicotine or heightened negative effects of nicotine abstinence (withdrawal); (c) nicotine causes neuroadaptations that result in elevated impulsivity in smokers. Studies relating to each of these models are reviewed, and it is concluded that all three models may contribute to the observed higher levels of impulsivity in smokers. However, pertinent studies are limited and additional systematic research is needed.

The up-regulation of heme oxygenase-1 expression in human gingival fibroblasts stimulated with nicotine

BACKGROUND

Cigarette smoking is a major risk factor in the development and further progression of periodontal diseases. Heme oxygenase-1 (HO-1) is known as a stress-inducible protein and functions as an antioxidant enzyme. There is limited information on the expression of HO-1 in smoking-associated periodontal disease.

OBJECTIVES

The aim of the present study was to investigate the effects of nicotine on the expression of HO-1 protein in cultured human gingival fibroblasts in vitro and further to compare HO-1 expression in gingival tissues obtained from cigarette smokers and non-smokers in vivo.

METHODS

Western blot assay was used to investigate the effects on human gingival fibroblasts exposed to nicotine. In addition, antioxidants catalase, superoxide dismutase (SOD), and N-acetyl-l-cysteine (NAC) were added to test how they modulated the effects on nicotine-induced HO-1 expression. Gingival biopsies taken from the flap surgery of 20 male patients with periodontal disease (10 cigarette smokers and 10 non-smokers) were examined by immunohistochemistry.

RESULTS

The exposure of quiescent human gingival fibroblasts to 10 mm nicotine resulted in the induction of HO-1 protein expression in a time-dependent manner (p < 0.05). The addition of glutathione (GSH) precursor NAC inhibited the nicotine-induced HO-1 protein expression (p < 0.05). However, SOD and catalase did not decrease the nicotine-induced HO-1 protein expression (p > 0.05). The results from immunohistochemistry demonstrated that HO-1 expression was significantly higher in cigarette smokers (p < 0.05). HO-1 was noted in the basal layers of epithelium, inflammatory cells, and fibroblasts in specimens from cigarette smoking.

CONCLUSIONS

Taken together, these results suggest that HO-1 expression is significantly up-regulated in gingival tissues from cigarette smokers, and nicotine may, among other constituents, be responsible for the enhanced HO-1 expression in vivo. The regulation of HO-1 expression induced by nicotine is critically dependent on the intracellular GSH concentration.

Human functional neuroimaging in nicotine and tobacco research: basics, background, and beyond

Modern functional neuroimaging techniques allow nicotine and tobacco researchers to investigate the neurobiological basis of addiction in humans. We introduce the methods and measures of the following neuroimaging techniques: Electroencephalography and event-related cortical potentials, positron emission tomography, and functional magnetic resonance imaging. We outline strengths and limitations across modalities and describe new and emerging technologies. We provide summaries of recent neuroimaging findings in the field of nicotine and tobacco research for neurochemistry, smoking and nicotine administration, craving and cue-reactivity, cognitive and affective information processing, and tobacco withdrawal. We address limitations of studies to date and identify opportunities for future research.

Latent class typology of nicotine withdrawal: genetic contributions and association with failed smoking cessation and psychiatric disorders

BACKGROUND

Nicotine withdrawal is associated with failed smoking cessation and thus contributes to continuance of the habit and increases risk of smoking-related illnesses. Withdrawal is also associated with psychiatric disorders such as depression and alcoholism. However, relatively little is known about how to characterize the severity of withdrawal, including whether withdrawal subtypes exist in male smokers. If so, do these subtypes represent quantitative or qualitative differences?

METHOD

Smoking and withdrawal data were obtained from 4112 male-male twin pairs of the Vietnam Era Twin Registry during a 1992 administration of the Diagnostic Interview Schedule. Latent Class Analysis (LCA) was used to derive significantly different nicotine withdrawal profiles, and their association with psychiatric disorders was assessed. Genetic and environmental contributions and the correlation between these contributions were evaluated using bivariate biometrical modeling of the withdrawal phenotype and failed smoking cessation.

RESULTS

The LCA model which best fit the data was a four-class severity continuum. Psychiatric disorders were significantly associated with more severe classes and the magnitude of the association increased as withdrawal severity increased. Genetics accounted for 31% and 51% of the variance in risk for withdrawal and failed cessation, respectively. The genetic contributions were significantly correlated (r = 0.37).

CONCLUSIONS

Nicotine withdrawal classes are characterized by quantitative differences. The strong association between psychiatric disorders and withdrawal severity and the significant genetic correlation between withdrawal and cessation highlight the importance of withdrawal severity. Further refinement of the DSM definition of withdrawal to incorporate severity ratings may be warranted.

Nicotine: from molecular mechanisms to behaviour

The addictive potential of nicotine is clearly recognized by the tenacity of tobacco smoking for most users, and has prompted extensive psychopharmacological studies in animals. In parallel, the interaction of nicotine with the many subtypes of its eponymous receptor has been the focus of molecular and cellular investigations. More recently, a convergence of these approaches has been stimulated by the generation of transgenic animals, which facilitates analysis of the impact of molecular changes on behaviour. Nicotine, like other addictive drugs including psychomotor stimulants, promotes dopamine release in the nucleus accumbens. This transmitter system has been a major focus of both neurochemical and behavioural investigations, although recently the pre-eminence of this system in nicotine dependence has been challenged. Complexities in the brain circuitry (including the subdivisions of the nucleus accumbens) and differences between behavioural models help to rationalise the current controversy.

The relationship between smoking cessation and mouth ulcers

Patients who stop smoking often complain of aphthous (mouth) ulcers. This symptom is sometimes attributed to the use of smoking cessation medications, but little is known about it. We investigated the incidence, severity, and time course of mouth ulcers in abstaining smokers and the effect of different smoking cessation medications on the symptom. The sample consisted of 1234 smokers who sought treatment at a large smoking cessation clinic, maintained at least 1 week of continuous biochemically validated abstinence, and provided usable data. Participants assessed their mouth ulcers by rating a mouth ulcer item added to the Mood and Physical Symptoms Scale. Subjects made ratings weekly on three occasions while still smoking and over 4 weeks following smoking cessation. After stopping smoking, some 40% of patients developed mouth ulcers, mostly in the first 2 weeks. The problem was generally mild, but 8% reported severe ulceration. The ulcers resolved within 4 weeks in 60% of patients affected. The ulcer ratings in patients using oral nicotine replacement products were higher than in those using patch, nasal spray or bupropion in the first week of abstinence but not afterward. Mouth ulcers were more prevalent in more dependent smokers, and the occurrence of ulcers correlated with other tobacco withdrawal symptoms. Our results confirm that mouth ulcers are a common result of stopping smoking, affecting two in five quitters. Patients should be reassured that the lesions are a result of stopping smoking and not a side-effect of smoking cessation medication.

Degeneration of intervertebral discs due to smoking: experimental assessment in a rat-smoking model

We have investigated the intervertebral discs of rat-smoking models to demonstrate that smoking is a cause of degenerative intervertebral disc disease. A smoking box was developed for this study. We exposed 8-week-old rats to indirect tobacco smoke inhalation. Each rat was forced to inhale the smoke from one cigarette per hour. The mean blood nicotine level of rodents exposed to cigarette smoke corresponds to about twice that of ordinary human smokers. Histological and immunological studies were then performed to assess the effects of smoking for varying periods of time. After 8 weeks, the chondrocytes in the disordered annulus fibrosus layer tended to grow larger and attain a rounder form than normal chondrocytes. The interleukin-1beta level in the 8-week smoking group was significantly higher than that of the control group. Tobacco smoke inhalation increased local production and release of inflammatory cytokines and resultant decomposition of chondrocyte activity.

Prolonged nicotine dependence associated with extended access to nicotine self-administration in rats

RATIONALE

Most nicotine self-administration (NSA) studies in rats are performed under limited-access conditions. Few studies have examined the relationship between nicotine dependence and NSA.

OBJECTIVES

To determine how NSA access conditions affect NSA and the duration of nicotine dependence during abstinence, as reflected in somatic signs of withdrawal precipitated by administration of the nicotinic receptor antagonist mecamylamine.

METHODS

The effects of different NSA access conditions (zero, 1 h/5 days, 1 h/7 days and 6 h/7 days per week) and non-contingent nicotine administration on NSA and somatic signs were examined.

RESULTS

Daily NSA access (30 days) resulted in spontaneous and mecamylamine-induced somatic signs. Both daily access groups (1 h/day and 6 h/day, 7 days/week) exhibited spontaneous somatic signs on day 25 of NSA (17 h post-NSA) and sensitivity to mecamylamine up to 2 and 4 weeks of abstinence, respectively. In contrast, the 1 h/day, 5 days/week access group exhibited mecamylamine-induced somatic signs only up to 1 week of abstinence. NSA behavior was stable in rats with 1 h/day 5 days/week and 1 h/day 7 days/week access, but decreased from initially high rates in the 6 h/day 7 days/week access group, and decreased in rats receiving non-contingent nicotine. In contrast, extended cocaine self-administration access resulted in a gradual escalation in cocaine intake.

CONCLUSION

There was no escalation in nicotine intake with extended access conditions, unlike cocaine self-administration. Nevertheless, daily nicotine self-administration seven days per week, for either 1 or 6 h per day, was sufficient to induce long-lasting adaptations in nicotinic acetylcholine receptor activity reflected in spontaneous and antagonist-precipitated somatic signs of withdrawal, possibly reflecting aspects of nicotine dependence.

Does the DRD2-Taq1 A polymorphism influence treatment response to bupropion hydrochloride for reduction of the nicotine withdrawal syndrome?

Bupropion hydrochloride is effective in promoting long-term abstinence from smoking and may reduce risk for relapse through attenuation of withdrawal symptoms and craving. Bupropion is a weak dopamine reuptake inhibitor, and individual genetic variation in the dopamine D2 receptor has been associated with nicotine dependence in case-control studies. Thirty smokers were randomly assigned to bupropion or placebo and interviewed using the Minnesota Nicotine Withdrawal Scale on two occasions: prior to starting medication and after 14 days on bupropion or placebo. The individual symptoms of craving, irritability, and anxiety were significantly reduced in the bupropion group, whereas no withdrawal symptoms were diminished in the placebo group. Within the bupropion group, subgroup analyses with stratification by genotype demonstrated that craving, irritability, and anxiety were significantly attenuated only among subjects with DRD2-Taq1 A2/A2 genotypes. In the DRD2-Taq1 A1/A1 and A1/A2 groups, no significant reduction was seen in any individual symptom of the nicotine withdrawal syndrome. These data suggest that bupropion attenuates specific symptoms of the nicotine withdrawal syndrome and that this effect may be modified by genotype for the dopamine D2 receptor.

Effects of nicotine on heart dimensions and blood volume in male and female rats

The adverse effects of tobacco smoking on the cardiovascular system are well established. Effects of nicotine on the heart, in contrast, are not well characterized. Understanding specific effects of nicotine on the heart and on blood volume is relevant to (a) elucidating the mechanisms by which nicotine may contribute to heart disease and (b) determining potential risks associated with nicotine products used in smoking cessation or to treat various medical conditions. The present experiment investigated effects of continuous nicotine administration for 14 days (0, 6, or 12 mg/kg/day) on heart histopathology and blood volume (a measure of hemoconcentration) in 59 male and 59 female rats of two strains (Sprague-Dawley and Long-Evans). Following nicotine administration, animals were sacrificed and blood volume was measured. Heart length; heart weight; left ventricle, right ventricle, lateral wall, anterior wall, and posterior wall thicknesses; and intraventricular width (i.e., septum) were measured. Nicotine reduced heart weight, heart length, and overall blood volume. Females were more sensitive than males to the effects of nicotine on heart weight. In contrast, males were more sensitive than females to the effects of nicotine on heart length. Together, these findings suggest that males and females differ in their sensitivity to nicotine's cardiac effects.

Prenatal nicotine increases testosterone levels in the fetus and female offspring

Epidemiological studies have shown that smoking during pregnancy markedly increases the risk for future tobacco use by adolescent female offspring. It has been hypothesized that the increased smoking risk in females is secondary to a nicotine-induced increase in fetal plasma testosterone levels that persist to adult life. To test this hypothesis, we randomized pregnant Sprague-Dawley rats to receive either saline or nicotine from Day 4 until the end of gestation. Blood samples for testosterone levels were obtained from 30- and 120-day-old offspring. In addition, blood samples for testosterone levels were obtained prior to and following a 2-day infusion of nicotine to chronically catheterized ovine fetuses. Maternal nicotine exposure resulted in increased plasma testosterone in 30-day-old female rat offspring, with no differences found in nicotine-exposed males. In addition, plasma testosterone levels increased in ovine fetuses in response to the nicotine infusion. We conclude that prenatal nicotine exposure increases plasma testosterone levels chronically in adolescent female rat offspring and acutely in both male and female ovine fetuses. Although our findings lack correlative behavioral information on the female offspring, these data are consistent with human epidemiological data suggesting that prenatal environmental influences may have marked effects on the subsequent smoking behaviors of offspring.

Acute effects of nicotine withdrawal syndrome in pilots during flight

BACKGROUND

Pilots who smoke are occasionally obliged to abstain from nicotine intake during flight and may during this period exhibit certain symptoms leading to performance decrement.

METHODS

We studied 20 healthy male aviators, who were regular smokers, (mean age 33.7 +/- 1.4 yr) operating military fixed- and rotary-wing aircraft (C-47 Dakota, F-16, A. Bell 205). All pilots were subjected to a 12-h abstinence from cigarette smoking, during which time they performed flight duties. After landing, we studied the intensity of the nicotine withdrawal syndrome, as well as its effect on physiological parameters, psychological functions, and cognitive tasks. This was achieved by the completion of a questionnaire, measurement of BP and heart rate, and the execution of certain computerized performance assessment tests. These tests measure mental arithmetic, visual vigilance, and image free-recall. In a subsequent flight performed under similar conditions, every pilot repeated the procedure without smoking deprivation. Thus, each subject served as his own control. The Wilcoxon non-parametric test was applied for statistical analysis.

RESULTS

The most frequent symptoms reported during nicotine deprivation were nervousness, craving for tobacco, tension-anxiety, fatigue, difficulty in concentration, decrease in alertness, disorders of fine adjustments, prolonged reaction times, anger-irritability, drowsiness, increase in appetite, and impairment of judgement. Systolic BP and heart rate tended to decrease and diastolic BP tended to rise during withdrawal, although the differences were not statistically significant. Finally, all tests recorded an impairment of cognitive functions during abstinence.

CONCLUSION

Abrupt cessation of smoking may be detrimental to flight safety and the smoking withdrawal syndrome may influence flying parameters.

Nicotine and familial vulnerability to schizophrenia: a discordant twin study

Tobacco use is significantly associated with schizophrenia. However, it is not clear if smoking is associated with the illness itself, treatment, or underlying vulnerability to the disease. Smoking was studied in a sample of schizophrenic probands (n = 24), their unaffected co-twins (n = 24), and controls (n = 3,347). Unaffected co-twins had higher rates of daily smoking than controls. Probands and co-twins were more frequently unsuccessful in attempts to quit than controls. Probands reported shaky hands and depression following smoking cessation more often than controls, whereas unaffected co-twins reported difficulty concentrating, drowsiness, nervousness, and headache following smoking cessation more often than controls. Results are consistent with the hypothesis that nicotine use is influenced by familial vulnerability to schizophrenia, not just clinical schizophrenia per se.

Nicotine withdrawal syndrome: behavioural distress and selective up-regulation of the cyclic AMP pathway in the amygdala

Nicotine addiction is a major public health issue. The use of laboratory animal models is a crucial tool in research aiming at understanding the pathophysiological mechanisms of nicotine dependence and at proposing new therapies. In rodents, cessation of nicotine exposure or administration of the nicotinic antagonist mecamylamine induces a nicotine withdrawal syndrome. Antagonist-precipitated withdrawal from other abused drugs such as opiates or cannabinoids has been associated with region-specific modifications of the activity of the cyclic AMP pathway. Here we show that mecamylamine-precipitated nicotine withdrawal in the rat is characterized by an increase in thigmotaxis (time spent in the periphery of an open field) that may be indicative of behavioural distress and can be associated with a selective up-regulation of adenylyl cyclase activity in the amygdala, a region implicated in the regulation of negative affect in response to aversive stimuli, including withdrawal. Adenylyl cyclase activity that is increased during precipitated nicotine withdrawal is stimulated by calcium/calmodulin, as is also the case for opioid and cannabinoid abstinence. This suggests that directly or indirectly mediated increases in the activity of the cyclic AMP pathway could constitute a possible common molecular mechanism underlying neuroadaptive changes following abstinence from different abused drugs.

Opioid receptor involvement in the adaptation to motion sickness in Suncus murinus

The aim of the present study was to investigate an opioid receptor involvement in the adaptation response to motion sickness in Suncus murinus. Different groups of animals were treated intraperitoneally with either saline, morphine (0.1 and 1.0 mg/kg), naloxone (1.0, 10.0 and 5.0 mg/kg) or a combination of naloxone plus morphine in the absence or 30 min prior to a horizontal motion stimulus of 1 Hz and 40 mm amplitude. For the study of adaptation, different groups received saline on the first trial, and in subsequent trials (every 2 days) they received either saline, naloxone (1.0 and 10.0 mg/kg, i.p.) or morphine (0.1 mg/kg, i.p.) 30 min prior to the motion stimulus. Pretreatment with morphine caused a dose-related reduction in emesis induced by a single challenge to a motion stimulus. Pretreatment with naloxone alone did not induce emesis in its own right nor did it modify emesis induced by a single challenge to a motion stimulus. However, pretreatment with naloxone (5.0 mg/kg, i.p.) revealed an emetic response to morphine (P<.001) (1.0 mg/kg, i.p.) and antagonised the reduction of motion sickness induced by morphine. In animals that received saline or naloxone (1.0 mg/kg), a motion stimulus inducing emesis decreased the responsiveness of animals to a second and subsequent motion stimulus challenge when applied every 2 days for 11 trials. However, the animals receiving naloxone 10.0 mg/kg prior to the second and subsequent challenges showed no significant reduction in the intensity of emesis compared to the first trial. The data are revealing of an emetic potential of morphine when administered in the presence of a naloxone pretreatment. The administration of naloxone is also revealing of an additional inhibitory opioid system whose activation by endogenous opioid(s) may play a role in the adaptation to motion sickness on repeated challenge in S. murinus.

Effects of calcium channel blockers on nicotine-induced hyperglycemia in the rat

Effects of nifedipine and verapamil on nicotine-induced hyperglycemia were studied in fasted, anesthetized male rats. Blood glucose was measured using the glucose oxidase method. Nifedipine (0.05-0.20 mg/kg i.p.) significantly reduced nicotine-induced hyperglycemia in a dose-dependent manner. While lower doses (0.1.0-1.0 mg/kg i.p) of verapamil did not effect nicotine-induced hyperglycemia, higher doses 95.0-10 mg/kg i.p) of verapamil caused significant reduction but did not abolish it. Both nifedipine and verapamil had no significant effect on the basal blood glucose levels at any dose used. These results seem to suggest that the reduction in nicotine-induced hyperglycemia is related to inhibition of some of the processes by which nicotine induced hyperglycemia.

Meeting national tobacco challenges: recommendations for smoking cessation groups

PURPOSE

To review the literature on model smoking cessation programs and provide an overview of the practice guidelines for intensive smoking cessation groups.

DATA SOURCES

Selected evidence-based literature and AHCPR/AHRQ clinical practice guidelines.

CONCLUSIONS

Smoking is the leading cause of preventable death in our global society and is expected to kill more people than any other disease within 20 years. Data support that most smokers want to quit and are more likely to succeed with a combination of behavioral and pharmacological support.

IMPLICATIONS FOR PRACTICE

Smoking cessation must be a priority in the delivery of patient care. Intensive interventions are more effective than brief interventions and should be available for all smokers.

Abstinence effects and reactivity to nicotine during 11 days of smoking deprivation

The purpose of the present study was to investigate smoking abstinence effects and the dissipation of tolerance (reactivity to nicotine) under controlled laboratory conditions. Seventeen male and female regular smokers were tested first in a session following ad libitum smoking and then in an additional five sessions over the course of 11 days during which they abstained from smoking. A metered dose of nicotine was administered via intranasal spray to ensure standard exposure, and pre- and post-dosing measures of heart rate, blood pressure, cortisol, galvanic skin response (GSR), craving, and several DSM-IV withdrawal symptoms (anxiety, irritability, restlessness, difficulty concentrating, and appetite) were collected. Prior to the nicotine test dose during deprivation sessions, heart rate and systolic blood pressure evinced elements of both an 'offset abstinence pattern' (deflection in a direction opposite to that produced by smoking) and a 'transient abstinence pattern' (deflection followed by a subsequent return); for cortisol, an offset pattern was observed, whereas for GSR and craving, a transient pattern was found. With respect to loss of tolerance, heart rate reactivity was found to increase significantly after 2 days' abstinence from nicotine, and the increase was sustained in subsequent sessions. Cortisol reactivity revealed more gradual dissipation, with significant differences evident only after 9 days of abstinence. These findings extend research on nicotine abstinence effects and on the dissipation of tolerance to nicotine deprivation intervals of nearly 2 weeks and confirm prior observations of variability across different response systems.

Environmental tobacco smoke and low birth weight: a hazard in the workplace?

Low birth weight (LBW) increases infant morbidity and mortality worldwide. One well-established risk factor is maternal smoking. Environmental tobacco smoke (ETS) exposure has recently been focused on as another potential risk factor. In this article, we review epidemiologic literature on the effects of ETS on LBW and intrauterine growth retardation (IUGR), the cause of LBW related to maternal smoking. As we consider the feasibility of modifying women's exposure, we focus our discussion on workplace exposure to ETS. The workplace is particularly important to consider because women of child-bearing age are present in the workplace in greater numbers now than ever before. In addition, certain subgroups of working women may be particularly at risk from the effects of ETS on pregnancy because they work in environments with higher exposure or they are more susceptible to its effects. We conclude that there is consistent evidence to relate maternal ETS exposure to an increased risk of adverse pregnancy outcomes and that this association may be generalized to the work environment. In studies with positive findings, infants exposed to ETS antenatally were 1.5-4 times more likely to be born with LBW, but few studies examined LBW. Most studies looked at measures of IUGR. ETS was associated with reductions in birth weight (adjusted for gestational age) ranging from 25 to 90 g. Infants born to women exposed to ETS were generally 2-4 times more likely to be born small-for-gestational age. ETS exposure in the workplace can and should be minimized to protect pregnant women from its adverse effects.

An oral formulation of nicotine for release and absorption in the colon: its development and pharmacokinetics

AIMS

Ulcerative colitis is predominantly a disease of nonsmokers and transdermal nicotine has therapeutic value in active disease; however side-effects are troublesome. The aim of this study was to develop an oral formulation of nicotine which would be slowly released in the colon over 6 h, and to examine its pharmacokinetic profile in 12 healthy volunteers, with measurements of serum nicotine and cotinine, its principal metabolite.

METHODS

Nicotine was combined with a polyacrylic carbomer, Carbopol 974P which was incorporated into 13 different vehicles and their release profiles examined in vitro. The polyglycolized glyceride, Gelucire 50/13, was chosen for subsequent kinetic studies because it consistently produced a suitable release pattern which was linear. Capsules containing 3 mg nicotine, combined with carbomer in Gelucire 50/13, were coated with an acrylic resin Eudragit L; this ensured the capsule would remain intact until the ileum. On 2 separate days, 6 and 15 mg nicotine, contained in 2 and 5 capsules, respectively, were administered to 12 subjects, all nonsmokers, mean age 28 years. Serial blood measurements were taken for 36 h, serum nicotine and cotinine concentrations were measured by gas liquid chromatography.

RESULTS

There was considerable intersubject variability in the nicotine and cotinine values. Plasma nicotine levels began to rise about 4 h after ingestion of the capsules, corresponding with the oro-caecal transit time. Cmax nicotine values were 2.2 and 5 ng ml-1, obtained 7 h after the ingestion of 6 and 15 mg, respectively, of the formulation. The corresponding Cmax values for cotinine were 37 and 94.4 ng ml-1, occurring after 9-10 h. The mean for elimination half-lives in the 24 studies, including the 6 and 15 mg doses, for nicotine were 4.3+/-2.7 h and for cotinine 16.8+/-7.5 h. With 6 mg nicotine-carbomer, only 1 of 12 volunteers had possible side-effects, but with the 15 mg dose 11 out of the 12 reported adverse effects which were systemic or gastrointestinal in nature-their timing corresponded with peak serum concentrations of nicotine.

CONCLUSIONS

An oral formulation of nicotine has been developed; in the ileum and colon, this becomes available for slow linear release over 6 h and delivers high concentrations of nicotine for topical effect on the colon. 6 mg Nicotine was well tolerated, whilst 15 mg gave both systemic and gastrointestinal side-effects. High concentrations of topical nicotine in the colon are achieved with relatively low systemic bioavailablity-reflected by the Cmax and AUC values for nicotine. This, or comparable formulations, may be of therapeutic value in ulcerative colitis.