Monoamine oxidase and tobacco dependence

Psychopharmacology of smoking cessation medications: focus on patients with mental health disorders

The adverse effects of smoking cessation in individuals with mental health disorders have been a point of concern, and progress in the development of treatment has been slow. The primary first-line treatments for smoking cessation are Nicotine Replacement Therapy, Bupropion, Varenicline, and behavioural support. Nortriptyline and Clonidine are second-line treatments used when the first-line treatments are not effective or are contraindicated. Smoking cessation medications have been shown to be effective in reducing nicotine cravings and withdrawal symptoms and promoting smoking cessation among patients living with mental disorders. However, these medications may have implications for patients' mental health and need to be monitored closely. The efficacy and side effects of these medications may vary depending on the patient's psychiatric condition, medication regimen, substance use, or medical comorbidities. The purpose of this review is to synthesise the pharmacokinetics, pharmacodynamics, therapeutic effects, adverse effects, and pharmacological interactions of first- and second-line smoking cessation drugs, with an emphasis on patients suffering from mental illnesses. Careful consideration of the risks and benefits of using smoking cessation medications is necessary, and treatment plans must be tailored to individual patients' needs. Monitoring symptoms and medication regimens is essential to ensure optimal treatment outcomes.

Neurobiological associations between smoking and internalizing disorders

People with severe mental disorders have a higher mortality rate due to preventable conditions like cardiovascular diseases and respiratory diseases. Nicotine addiction is a preventable risk factor, with tobacco use being twice as high in people with mental disorders. An integrative model that divides mental disorders into externalising, internalising, and thought disorders could be useful for identifying common causalities and risk factors. This review aims to examine the interface between smoking and internalising disorders, specifically schizophrenia, depressive disorders, and anxiety disorders. The review finds that there is a clear association between smoking behaviour and these disorders. Schizophrenia is associated with polymorphisms that result in an imbalance between glutamate and GABA release and abnormalities of dopaminergic pathways. Nicotine improves dopaminergic signalling and balances glutamatergic and GABAergic pathways, improving symptoms and increasing the risk of nicotine dependence. In depressive disorders, smoking is associated with functional changes in brain regions affected by smoking and self-medication. In anxiety disorders, there is a bidirectional relationship with smoking, involving the amygdala and changes in dopaminergic pathways and cortisol production. Smoking poses a threat to people living with psychiatric disorders and calls for further research to assess the interactions between nicotine dependence and internalising and thought disorders.

Antidepressants for smoking cessation

BACKGROUND

The pharmacological profiles and mechanisms of antidepressants are varied. However, there are common reasons why they might help people to stop smoking tobacco: nicotine withdrawal can produce short-term low mood that antidepressants may relieve; and some antidepressants may have a specific effect on neural pathways or receptors that underlie nicotine addiction.

OBJECTIVES

To assess the evidence for the efficacy, harms, and tolerability of medications with antidepressant properties in assisting long-term tobacco smoking cessation in people who smoke cigarettes.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group Specialised Register, most recently on 29 April 2022.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in people who smoked, comparing antidepressant medications with placebo or no pharmacological treatment, an alternative pharmacotherapy, or the same medication used differently. We excluded trials with fewer than six months of follow-up from efficacy analyses. We included trials with any follow-up length for our analyses of harms.

DATA COLLECTION AND ANALYSIS

We extracted data and assessed risk of bias using standard Cochrane methods. Our primary outcome measure was smoking cessation after at least six months' follow-up. We used the most rigorous definition of abstinence available in each trial, and biochemically validated rates if available. Our secondary outcomes were harms and tolerance outcomes, including adverse events (AEs), serious adverse events (SAEs), psychiatric AEs, seizures, overdoses, suicide attempts, death by suicide, all-cause mortality, and trial dropouts due to treatment. We carried out meta-analyses where appropriate.

MAIN RESULTS

We included a total of 124 studies (48,832 participants) in this review, with 10 new studies added to this update version. Most studies recruited adults from the community or from smoking cessation clinics; four studies focused on adolescents (with participants between 12 and 21 years old). We judged 34 studies to be at high risk of bias; however, restricting analyses only to studies at low or unclear risk of bias did not change clinical interpretation of the results.  There was high-certainty evidence that bupropion increased smoking cessation rates when compared to placebo or no pharmacological treatment (RR 1.60, 95% CI 1.49 to 1.72; I2 = 16%; 50 studies, 18,577 participants). There was moderate-certainty evidence that a combination of bupropion and varenicline may have resulted in superior quit rates to varenicline alone (RR 1.21, 95% CI 0.95 to 1.55; I2 = 15%; 3 studies, 1057 participants). However, there was insufficient evidence to establish whether a combination of bupropion and nicotine replacement therapy (NRT) resulted in superior quit rates to NRT alone (RR 1.17, 95% CI 0.95 to 1.44; I2 = 43%; 15 studies, 4117 participants; low-certainty evidence). There was moderate-certainty evidence that participants taking bupropion were more likely to report SAEs than those taking placebo or no pharmacological treatment. However, results were imprecise and the CI also encompassed no difference (RR 1.16, 95% CI 0.90 to 1.48; I2 = 0%; 23 studies, 10,958 participants). Results were also imprecise when comparing SAEs between people randomised to a combination of bupropion and NRT versus NRT alone (RR 1.52, 95% CI 0.26 to 8.89; I2 = 0%; 4 studies, 657 participants) and randomised to bupropion plus varenicline versus varenicline alone (RR 1.23, 95% CI 0.63 to 2.42; I2 = 0%; 5 studies, 1268 participants). In both cases, we judged evidence to be of low certainty. There was high-certainty evidence that bupropion resulted in more trial dropouts due to AEs than placebo or no pharmacological treatment (RR 1.44, 95% CI 1.27 to 1.65; I2 = 2%; 25 studies, 12,346 participants). However, there was insufficient evidence that bupropion combined with NRT versus NRT alone (RR 1.67, 95% CI 0.95 to 2.92; I2 = 0%; 3 studies, 737 participants) or bupropion combined with varenicline versus varenicline alone (RR 0.80, 95% CI 0.45 to 1.45; I2 = 0%; 4 studies, 1230 participants) had an impact on the number of dropouts due to treatment. In both cases, imprecision was substantial (we judged the evidence to be of low certainty for both comparisons). Bupropion resulted in inferior smoking cessation rates to varenicline (RR 0.73, 95% CI 0.67 to 0.80; I2 = 0%; 9 studies, 7564 participants), and to combination NRT (RR 0.74, 95% CI 0.55 to 0.98; I2 = 0%; 2 studies; 720 participants). However, there was no clear evidence of a difference in efficacy between bupropion and single-form NRT (RR 1.03, 95% CI 0.93 to 1.13; I2 = 0%; 10 studies, 7613 participants). We also found evidence that nortriptyline aided smoking cessation when compared with placebo (RR 2.03, 95% CI 1.48 to 2.78; I2 = 16%; 6 studies, 975 participants), and some evidence that bupropion resulted in superior quit rates to nortriptyline (RR 1.30, 95% CI 0.93 to 1.82; I2 = 0%; 3 studies, 417 participants), although this result was subject to imprecision. Findings were sparse and inconsistent as to whether antidepressants, primarily bupropion and nortriptyline, had a particular benefit for people with current or previous depression.

AUTHORS' CONCLUSIONS

There is high-certainty evidence that bupropion can aid long-term smoking cessation. However, bupropion may increase SAEs (moderate-certainty evidence when compared to placebo/no pharmacological treatment). There is high-certainty evidence that people taking bupropion are more likely to discontinue treatment compared with people receiving placebo or no pharmacological treatment. Nortriptyline also appears to have a beneficial effect on smoking quit rates relative to placebo, although bupropion may be more effective. Evidence also suggests that bupropion may be as successful as single-form NRT in helping people to quit smoking, but less effective than combination NRT and varenicline. In most cases, a paucity of data made it difficult to draw conclusions regarding harms and tolerability. Further studies investigating the efficacy of bupropion versus placebo are unlikely to change our interpretation of the effect, providing no clear justification for pursuing bupropion for smoking cessation over other licensed smoking cessation treatments; namely, NRT and varenicline. However, it is important that future studies of antidepressants for smoking cessation measure and report on harms and tolerability.

Bioisosteric replacement based on 1,2,4-oxadiazoles in the discovery of 1H-indazole-bearing neuroprotective MAO B inhibitors

Following a hybridization strategy, a series of 5-substituted-1H-indazoles were designed and evaluated in vitro as inhibitors of human monoamine oxidase (hMAO) A and B. Among structural modifications, the bioisostere-based introduction of 1,2,4-oxadiazole ring returned the most potent and selective human MAO B inhibitor (compound 20, IC₅₀ = 52 nM, SI > 192). The most promising inhibitors were studied in cell-based neuroprotection models of SH-SY5Y and astrocytes line against H₂O₂. Moreover, preliminary drug-like features (aqueous solubility at pH 7.4; hydrolytic stability at acidic and neutral pH) were assessed for selected 1,2,4-oxadiazoles and compared to amide analogues through RP-HPLC methods. Molecular docking simulations highlighted the crucial role of molecular flexibility in providing a better shape complementarity for compound 20 within MAO B enzymatic cleft than rigid analogue 18. Enzymatic kinetics analysis along with thermal stability curves (T_m shift = +2.9 °C) provided clues of a tight-binding mechanism for hMAO B inhibition by 20.

A review of monoamine oxidase (MAO) inhibitors in tobacco or tobacco smoke

Tobacco smoking is reputed to be the most difficult addiction of all to give up, and nicotine has been noted as the major addictive agent in tobacco smoke. However, research shows that nicotine addiction is due to more than nicotine alone. One hypothesis is that monoamine oxidase (MAO) inhibition from non-nicotinic components in, or derived from, tobacco smoke contributes to nicotine addiction. Harman and norharman, have been recognised as major and potent MAO inhibitors in tobacco smoke, but these two inhibitors together comprise perhaps less than 10% of the total MAO A inhibitory activity in cigarette smoke suggesting other unidentified components may make significant contributions to total inhibitory activity. Therefore, we reviewed an index of the chemical components of tobacco and tobacco smoke and identified those known to be MAO inhibitors. Amongst these inhibitors, phenols and phenolic acids with MAO inhibitory activity are commonly reversible and selective MAO A inhibitors, whereas trans,trans-farnesol, 2-methyl-1,4-naphthoquinone (menadione), 1,4-naphthoquinone, scopoletin, and diosmetin with MAO inhibitory activity are reversible and selective MAO B inhibitors. The compound, 1,4-benzoquinone is an irreversible MAO A inhibitor and to the best of our knowledge, this is the first irreversible MAO A inhibitor to be reported in tobacco smoke. MAO inhibitors have been used clinically to treat depression, anxiety, and Parkinson's disease. The MAO inhibitors identified from tobacco and tobacco smoke and summarized in this review, are potential pharmacological candidates to be investigated further. This review will enhance our knowledge of the way tobacco smoke affects MAO activity in smokers and will also be important in helping to understand nicotine addiction.

Monoamine oxidase inhibition in cigarette smokers: From preclinical studies to tobacco product regulation

Monoamine oxidase (MAO) activity is reduced in cigarette smokers and this may promote the reinforcing actions of nicotine, thereby enhancing the addictive properties of cigarettes. At present, it is unclear how cigarette smoking leads to MAO inhibition, but preclinical studies in rodents show that MAO inhibition increases nicotine self-administration, especially at low doses of nicotine. This effect of MAO inhibition develops slowly, likely due to plasticity of brain monoamine systems; studies relying on acute MAO inhibition are unlikely to replicate what happens with smoking. Given that MAO inhibition may reduce the threshold level at which nicotine becomes reinforcing, it is important to consider this in the context of very low nicotine content (VLNC) cigarettes and potential tobacco product regulation. It is also important to consider how this interaction between MAO inhibition and the reinforcing actions of nicotine may be modified in populations that are particularly vulnerable to nicotine dependence. In the context of these issues, we show that the MAO-inhibiting action of cigarette smoke extract (CSE) is similar in VLNC cigarettes and cigarettes with a standard nicotine content. In addition, we present evidence that in a rodent model of schizophrenia the effect of MAO inhibition to enhance nicotine self-administration is absent, and speculate how this may relate to brain serotonin systems. These issues are relevant to the MAO-inhibiting effect of cigarette smoking and its implications to tobacco product regulation.

Harmane Potentiates Nicotine Reinforcement Through MAO-A Inhibition at the Dose Related to Cigarette Smoking

Nicotine is the primary addictive component in cigarette smoke, and dopamine release induced by nicotine is considered a significant cause of persistent smoking and nicotine dependence. However, the effects of nicotine replacement therapy on smoking cessation were less effective than expected, suggesting that other non-nicotine constituents may potentiate the reinforcing effects of nicotine. Harmane is a potent, selective monoamine oxidase A (MAO-A) inhibitor found in cigarette smoke, but showed no effect on nicotine self-administration in previous studies, possibly due to the surprisingly high doses used. In the present study, we found that harmane potentiated nicotine self-administration on the fixed ration schedule at the dose related to human cigarette smoking by the synergistic effects in up-regulating genes in addiction-related pathways, and the effect was reduced at doses 10 times higher or lower than the smoking-related dose. The smoking-related dose of harmane also enhanced the increase of locomotor activity induced by nicotine, accompanied by increased dopamine basal level and dopamine release in the nucleus accumbens through MAO-A inhibition. Our findings provided new evidence for the important role of non-nicotine ingredients of tobacco products in smoking addiction.

Biologically Active Compounds Present in Tobacco Smoke: Potential Interactions Between Smoking and Mental Health

Tobacco dependence remains one of the major preventable causes of premature morbidity and mortality worldwide. There are well over 8,000 compounds present in tobacco and tobacco smoke, but we do not know what effect, if any, many of them have on smokers. Major interest has been on nicotine, as well as on toxic and carcinogenic effects and several major and minor components of tobacco smoke responsible for the negative health effects of smoking have been elucidated. Smokers themselves report a variety of positive effects from smoking, including effects on depression, anxiety and mental acuity. Smoking has also been shown to have protective effects in Parkinson’s Disease. Are the subjective reports of a positive effect of smoking due to nicotine, of some other components of tobacco smoke, or are they a manifestation of the relief from nicotine withdrawal symptoms that smoking provides? This mini-review summarises what is currently known about the components of tobacco smoke with potential to have positive effects on smokers.

Association between cigarette smoking and Parkinson’s disease: a neuroimaging study

Background:

Mounting evidence has revealed an inverse association between cigarette smoking and the risk of Parkinson’s disease (PD). Meanwhile, cigarette smoking has been found to be associated with cognitive impairment in PD patients. However, the neural mechanisms of the association between cigarette smoking and PD are not fully understood.

Objective:

The aim of this study is to explore the neural mechanisms of the association between cigarette smoking and PD.

Methods:

A total of 129 PD patients and 69 controls were recruited from the Parkinson’s Progression Markers Initiative (PPMI) cohort, including 39 PD patients with regular smoking history (PD-S), 90 PD patients without regular smoking history (PD-NS), 26 healthy controls with regular smoking history (HC-S), and 43 healthy controls without regular smoking history (HC-NS). Striatal dopamine transporter (DAT) binding and gray matter (GM) volume of the whole brain were compared among the four groups.

Results:

PD patients showed significantly reduced striatal DAT binding compared with healthy controls, and HC-S showed significantly reduced striatal DAT binding compared with HC-NS. Moreover, smoking and PD showed a significant interaction effect in the left medial prefrontal cortex (mPFC). PD-S showed reduced GM volume in the left mPFC compared with PD-NS.

Conclusion:

The degeneration of dopaminergic neurons in PD results in a substantial reduction of the DAT and dopamine levels. Nicotine may act as a stimulant to inhibit the action of striatal DAT, increasing dopamine levels in the synaptic gap. The inverse alteration of dopamine levels between PD and nicotine addiction may be the reason for the inverse association between smoking and the risk of PD. In addition, the mPFC atrophy in PD-S may be associated with cognitive impairment.

Study protocol: evaluation of the addictive potential of e-cigarettes (EVAPE): neurobiological, sociological, and epidemiological perspectives

BACKGROUND

Tobacco use is the largest preventable cause of diseases and deaths; reducing tobacco intake is, therefore, an urgent public health goal. In recent years, e-cigarettes have been marketed as a 'healthier' alternative to tobacco smoking, whilst product features have evolved tremendously in the meantime. A lively scientific debate has developed regarding the potential benefits and risks of e-cigarettes although, surprisingly, there are few studies investigating the addictive potential of nicotine-containing e-cigarettes. The present work comprises three work packages investigating the addictive potential of e-cigarettes from different perspectives: (1) the neurobiological addictive potential of e-cigarettes; (2) the experience and perception of dependence symptoms among users of e-cigarettes in a social context; and (3) the epidemiological perspective regarding factors influencing the potential for dependence.

METHODS

Work package I: the neurobiological study will investigate the key elements of addiction in e-cigarettes compared to tobacco cigarettes using neurobiological and neuropsychological correlates associated with craving, incentive motivation, cue reactivity and attentional bias. Work package II: the sociological study part examines self-reports on the experience and perception of dependence symptoms in a social context, using focus group interviews and the analysis of posts in online discussion forums on e-cigarettes. Work package III: the epidemiological study part focuses on tolerance development and the role of psychosocial and product factors by analyzing longitudinal data from the International Tobacco Control Policy Evaluation Project (ITC).

DISCUSSION

The present study offers a chosen mix of three methodological approaches, thereby comprehensively examining core symptoms of positive and negative reinforcement in addiction. Whether e-cigarettes are as reinforcing and addictive as combustible tobacco cigarettes is an important public health issue with implications for prevention and treatment programs.

TRIAL REGISTRATION

Work package I: Registered at clinicaltrials.gov/ct2/show/NCT04772014. Work package II: Registered at OSF Registries: https://osf.io/dxgya (2021, January 14).

Smoking Addiction and Strategies for Cessation

Cigarette smoking is the leading cause of chronic obstructive pulmonary disease (COPD) worldwide. Smoking cessation is thus integral to the treatment of COPD. Nicotine addiction is a disease dependent on the complex interactions of neurotransmitter pathways, conditioned behaviors, environmental cues, genetic predisposition, and personal life circumstances, which render some more susceptible to tobacco abuse than others. The most successful smoking cessation programs are individualized, comprehensive, and utilize combinations of clinician counseling, behavioral reinforcement, community resources, advanced technology support (eg, smartphone apps, and Internet Web sites), and pharmacotherapy (both nicotine-based and nonnicotine medications). E-cigarettes were introduced to the US market in 2006 and touted as a safer alternative to tobacco cigarette smoking. Unfortunately, over the last 5 to 10 years, recreational e-cigarette use, or "vaping," has increased in popularity, especially among adolescents. This has introduced nicotine addiction to an entire generation of nonsmokers and resulted in numerous cases of acute lung disease, now known as e-cigarette or vape product use-associated lung injury (EVALI). In light of these adverse events, e-cigarettes and vape products are not currently recommended as a smoking cessation aid.

Smoking Is Associated with Pain in All Body Regions, with Greatest Influence on Spinal Pain

OBJECTIVE

Examine the interrelationship between smoking and pain in the US population.

DESIGN

A cross-sectional population-based study.

SETTING

Nationwide survey.

METHODS

Comprehensive pain reports categorically defined as head, spine, trunk, and limb pain; smoking history; demographics; medical history from a total of 2,307 subjects from the 2003-2004 National Health and Nutrition Examination Survey obtained from the Centers for Disease Control were analyzed. Unpaired t tests were used to analyze independent continuous variables, and chi-square tests were used to analyze categorical variables between smoker and nonsmoker groups. Weighted multivariate logistic regression analyses determined the association of current smoking with the presence of pain in various body regions.

RESULTS

Smoking is most strongly associated with spine pain (odds ratio [OR] = 2.89, 95% confidence interval [CI] = 2.21-3.77), followed by headache (OR = 2.47, 95% CI = 1.73-3.53), trunk pain (OR = 2.17, 95% CI = 1.45-2.74), and limb pain (OR = 1.99, 95% CI = 1.45-2.73).

CONCLUSIONS

Current smoking is associated with pain in every region of the body. This association is strongest for spine and head pain. Given that pain is a strong motivator and that current smoking was associated with pain in all body regions, we recommend that these results be used to further raise public awareness about the potential harms of smoking.

Effects of Nicotine and Tobacco-Related Products on the Feeding Behavior of the German Cockroach (Blattodea: Blattellidae)

Animals use olfaction to detect developmentally significant volatile organic compounds (VOCs) in their local environment. As part of a wider study aiming to demonstrate that the olfactory responses of animals to VOCs can be modified through the creation of a drug-addicted status and association with a selected VOC, we investigated nicotine and tobacco smoke particulate (TSP) extract as possible addictive compounds for male German cockroaches, Blattella germanica (Linnaeus). In feeding experiments using an artificial food stimulus, food treated with TSP extract was preferred over untreated food. Surprisingly, nicotine, which was expected to be the most important addictive tobacco component, did not induce noticeable effects on cockroach behavior. Both TSP extract and nicotine were shown to be phagostimulants. Olfactometry assays that measured odor-mediated insect behavior demonstrated that male B. germanica did not choose TSP-extract-treated food even when attempts were made specifically to train them via this modality. These results support a hypothesis that B. germanica needs to consume TSP-containing food to show a clear preference for this stimulus and that gustatory mechanisms are involved due to compounds present in the TSP extract.

Nicotine exposure during lactation causes disruption of hedonic eating behavior and alters dopaminergic system in adult female rats

Tobacco smoke during gestation is associated with increased consumption of palatable foods by the offspring in humans and rats. Postpartum relapse is observed in lactating women who quit smoking during pregnancy, putting their children at risk of adverse health outcomes caused by secondhand smoke. Nicotine is transferred through milk and alters the dopaminergic reward system of adult male rats, reducing dopamine action in the nucleus accumbens (NAc) and hypothalamic arcuate nucleus. Here, we evaluated the long-term effects of nicotine-only exposure during lactation on eating behavior, anxiety, locomotion, dopaminergic system, hypothalamic leptin signaling and nicotinic receptor in the adult female rat progeny. Two days after birth (PN2), Wistar rat dams were separated into control and nicotine (Nic) groups for implantation of osmotic minipumps that released respectively saline or 6 mg/kg nicotine. Lactating dams were kept with 6 pups. After weaning (PN21; nicotine withdrawal), only the female offspring were studied. Euthanasia occurred at PN180. Nic females showed hyperphagia, preference for a high-sucrose diet, increased anxiety-like behavior, lower tyrosine hydroxylase (TH), lower dopamine transporter and higher dopamine receptor (Drd2) in NAc; lower Drd1 in prefrontal cortex and lower TH in dorsal striatum (DS). These animals showed changes that can explain their hyperphagia, such as: lower leptin signaling pathway (Lepr^b, pJAK2, pSTAT3) and Chrna7 expression in hypothalamus. Neonatal nicotine exposure affects the brain reward system of the female progeny differently from males, mainly decreasing dopamine production in NAc and DS. Therefore, Nic females are more susceptible to develop food addiction and obesity.

The Relationship of Varenicline Agonism of α4β2 Nicotinic Acetylcholine Receptors and Nicotine-Induced Dopamine Release in Nicotine-Dependent Humans

INTRODUCTION

Cigarette smoking continues to be one of the most important behavioral causes of morbidity and mortality in the world. Varenicline, an α4β2 nicotinic acetylcholine receptor (nAChR) partial agonist, has been shown to increase smoking quit rates compared with nicotine-based products. This human laboratory, double-blind, placebo-controlled study examined varenicline and placebo effects on α4β2-nAChRs occupancy, nicotine-induced change in [11C]raclopride non-displaceable binding potential (BPND), and behavioral measures of cigarette smoking, nicotine craving, and withdrawal.

METHODS

Current nicotine dependent daily smokers (N = 17) were randomized to varenicline 1 mg twice daily or placebo for 13 days. Using positron emission tomography), we characterized α4β2-nAChRs occupancy using [18F]AZAN and dopamine receptor binding using [11C]raclopride as well as behavioral measures of cigarettes smoked, craving, and nicotine withdrawal.

RESULTS

Varenicline compared with placebo resulted in significant reductions in [18F]AZAN BPND in multiple brain regions including thalamus, midbrain, putamen, and ventral striatum. Following administration of a controlled-dose nicotine cigarette, dopamine release was significantly suppressed in the ventral striatum in the varenicline-treated compared with the placebo group. There was a significant relationship between α4β2-nAChRs BPND measured in thalamus during the [18F]AZAN scan and nicotine-induced change in raclopride BPND in the ventral striatum.

CONCLUSION

This is the first human study to demonstrate a direct relationship between the extent of varenicline occupancy of α4β2-nAChRs and the magnitude of dopamine release following nicotine use.

IMPLICATIONS

It has remained unclear how nicotinic receptor blockade through partial agonist medications such as varenicline promotes smoking cessation. One hypothesized mechanism is downstream dampening of the mesolimbic reward dopamine system. For the first time in human smokers, we observed a direct relationship between the extent of varenicline blockade of α4β2-nACh nicotinic receptors and the magnitude of dopamine release following smoking. This has mechanistic and therapeutic implications for improving smoking cessation interventions.

Antidepressants for smoking cessation

BACKGROUND

Whilst the pharmacological profiles and mechanisms of antidepressants are varied, there are common reasons why they might help people to stop smoking tobacco. Firstly, nicotine withdrawal may produce depressive symptoms and antidepressants may relieve these. Additionally, some antidepressants may have a specific effect on neural pathways or receptors that underlie nicotine addiction.

OBJECTIVES

To assess the evidence for the efficacy, safety and tolerability of medications with antidepressant properties in assisting long-term tobacco smoking cessation in people who smoke cigarettes.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Specialized Register, which includes reports of trials indexed in the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO, clinicaltrials.gov, the ICTRP, and other reviews and meeting abstracts, in May 2019.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that recruited smokers, and compared antidepressant medications with placebo or no treatment, an alternative pharmacotherapy, or the same medication used in a different way. We excluded trials with less than six months follow-up from efficacy analyses. We included trials with any follow-up length in safety analyses.

DATA COLLECTION AND ANALYSIS

We extracted data and assessed risk of bias using standard Cochrane methods. We also used GRADE to assess the certainty of the evidence. The primary outcome measure was smoking cessation after at least six months follow-up, expressed as a risk ratio (RR) and 95% confidence intervals (CIs). We used the most rigorous definition of abstinence available in each trial, and biochemically validated rates if available. Where appropriate, we performed meta-analysis using a fixed-effect model. Similarly, we presented incidence of safety and tolerance outcomes, including adverse events (AEs), serious adverse events (SAEs), psychiatric AEs, seizures, overdoses, suicide attempts, death by suicide, all-cause mortality, and trial dropout due to drug, as RRs (95% CIs).

MAIN RESULTS

We included 115 studies (33 new to this update) in this review; most recruited adult participants from the community or from smoking cessation clinics. We judged 28 of the studies to be at high risk of bias; however, restricting analyses only to studies at low or unclear risk did not change clinical interpretation of the results. There was high-certainty evidence that bupropion increased long-term smoking cessation rates (RR 1.64, 95% CI 1.52 to 1.77; I² = 15%; 45 studies, 17,866 participants). There was insufficient evidence to establish whether participants taking bupropion were more likely to report SAEs compared to those taking placebo. Results were imprecise and CIs encompassed no difference (RR 1.16, 95% CI 0.90 to 1.48; I² = 0%; 21 studies, 10,625 participants; moderate-certainty evidence, downgraded one level due to imprecision). We found high-certainty evidence that use of bupropion resulted in more trial dropouts due to adverse events of the drug than placebo (RR 1.37, 95% CI 1.21 to 1.56; I² = 19%; 25 studies, 12,340 participants). Participants randomized to bupropion were also more likely to report psychiatric AEs compared with those randomized to placebo (RR 1.25, 95% CI 1.15 to 1.37; I² = 15%; 6 studies, 4439 participants). We also looked at the safety and efficacy of bupropion when combined with other non-antidepressant smoking cessation therapies. There was insufficient evidence to establish whether combination bupropion and nicotine replacement therapy (NRT) resulted in superior quit rates to NRT alone (RR 1.19, 95% CI 0.94 to 1.51; I² = 52%; 12 studies, 3487 participants), or whether combination bupropion and varenicline resulted in superior quit rates to varenicline alone (RR 1.21, 95% CI 0.95 to 1.55; I² = 15%; 3 studies, 1057 participants). We judged the certainty of evidence to be low and moderate, respectively; in both cases due to imprecision, and also due to inconsistency in the former. Safety data were sparse for these comparisons, making it difficult to draw clear conclusions. A meta-analysis of six studies provided evidence that bupropion resulted in inferior smoking cessation rates to varenicline (RR 0.71, 95% CI 0.64 to 0.79; I² = 0%; 6 studies, 6286 participants), whilst there was no evidence of a difference in efficacy between bupropion and NRT (RR 0.99, 95% CI 0.91 to 1.09; I² = 18%; 10 studies, 8230 participants). We also found some evidence that nortriptyline aided smoking cessation when compared with placebo (RR 2.03, 95% CI 1.48 to 2.78; I² = 16%; 6 studies, 975 participants), whilst there was insufficient evidence to determine whether bupropion or nortriptyline were more effective when compared with one another (RR 1.30 (favouring bupropion), 95% CI 0.93 to 1.82; I² = 0%; 3 studies, 417 participants). There was no evidence that any of the other antidepressants tested (including St John's Wort, selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs)) had a beneficial effect on smoking cessation. Findings were sparse and inconsistent as to whether antidepressants, primarily bupropion and nortriptyline, had a particular benefit for people with current or previous depression.

AUTHORS' CONCLUSIONS

There is high-certainty evidence that bupropion can aid long-term smoking cessation. However, bupropion also increases the number of adverse events, including psychiatric AEs, and there is high-certainty evidence that people taking bupropion are more likely to discontinue treatment compared with placebo. However, there is no clear evidence to suggest whether people taking bupropion experience more or fewer SAEs than those taking placebo (moderate certainty). Nortriptyline also appears to have a beneficial effect on smoking quit rates relative to placebo. Evidence suggests that bupropion may be as successful as NRT and nortriptyline in helping people to quit smoking, but that it is less effective than varenicline. There is insufficient evidence to determine whether the other antidepressants tested, such as SSRIs, aid smoking cessation, and when looking at safety and tolerance outcomes, in most cases, paucity of data made it difficult to draw conclusions. Due to the high-certainty evidence, further studies investigating the efficacy of bupropion versus placebo are unlikely to change our interpretation of the effect, providing no clear justification for pursuing bupropion for smoking cessation over front-line smoking cessation aids already available. However, it is important that where studies of antidepressants for smoking cessation are carried out they measure and report safety and tolerability clearly.

Randomized Clinical Trials Investigating Innovative Interventions for Smoking Cessation in the Last Decade

Every year, billions of dollars are spent treating smoking and related conditions, yet smoking-related morbidity and mortality continue to rise. There are currently only three FDA-approved medications for smoking cessation: nicotine replacement therapy, bupropion, and varenicline. Although these medications increase abstinence rates, most individuals relapse following treatment. This chapter reviews clinical trials published within the past 10 years investigating novel smoking cessation pharmacotherapies. Among these pharmacotherapies, some showed promising results, such as cytisine and endocannabinoid modulators, whereas others failed to produce significant effects. More research is needed to develop drugs that produce higher rates of long-term abstinence and to determine which subgroups of patients benefit from a given treatment.

A haplotype-specific linkage disequilibrium pattern of monoamine oxidase A gene associated with regular smoking in women

BACKGROUND

Cigarette smoking in women is raising a public health problem. The X-linked monoamine oxidase A (MAOA) was considered as a susceptibility gene to substance abuse of tobacco, but the evolutionary effect of MAOA may lead to a positive or negative association between genetic variations and smoking development among study regions.

METHODS

Based on linkage disequilibrium (LD), we performed a haplotype-based association to explore the effect of MAOA gene on women's smoking risk in a case-control study.

RESULTS

Genotyped single nucleotide polymorphisms (SNPs) of MAOA gene, rs5953210G>A, rs2283725A>G and rs1137070T>C, were significantly associated with current smoking risk in women, and the increased level of plasma MAO-A activity was raised with per copy increment of risk allele in current smokers (P < .01). The haplotype patterns with minor haplotype frequency >.05 were constructed using the Expectation-Maximization algorithm, and the haplotype-specific A-G-C pattern raised the 2-fold risk to develop regular smoking (P = .0005). In the diplotype analysis based on X-inactivation mechanism relative to no and full dosage compensation, we showed that A-G-C haplotype not only increased regular smoking risk in a dose-dependent manner (P_trend = .0011) but also contributed to smoking risk in the dosage compensation mechanism. Compared to non-smokers, the effect of A-G-C haplotype on random X-activation was associated with the raised MAO-A activity in women smokers (P < .05) although the lifetime cigarette consumption showed a difference that was not statistically significant.

CONCLUSION

This study provides information on MAOA LD-based haplotype and diplotype patterns in women smoking.

Toxicological Aspects and Determination of the Main Components of Ayahuasca: A Critical Review

Ayahuasca is a psychoactive beverage prepared traditionally from a mixture of the leaves and stems of Psychotria viridis and Banisteriopsis caapi, respectively, being originally consumed by indigenous Amazonian tribes for ritual and medicinal purposes. Over the years, its use has spread to other populations as a means to personal growth and spiritual connection. Also, the recreational use of its isolated compounds has become prominent. The main compounds of this tea-like preparation are N,N-dimethyltryptamine (DMT), β-Carbolines, and harmala alkaloids, such as harmine, tetrahydroharmine, and harmaline. The latter are monoamine-oxidase inhibitors and are responsible for DMT psychoactive and hallucinogenic effects on the central nervous system. Although consumers defend its use, its metabolic effects and those on the central nervous system are not fully understood yet. The majority of studies regarding the effects of this beverage and of its individual compounds are based on in vivo experiments, clinical trials, and even surveys. This paper will not only address the toxicological aspects of the ayahuasca compounds but also perform a comprehensive and critical review on the analytical methods available for their determination in biological and non-biological specimens, with special focus on instrumental developments and sample preparation approaches.

Current advances in research in treatment and recovery: Nicotine addiction

The health harms of combusted tobacco use are undeniable. With market and regulatory pressures to reduce the harms of nicotine delivery by combustion, the tobacco product landscape has diversified to include smokeless, heated, and electronic nicotine vaping products. Products of tobacco combustion are the main cause of smoking-induced disease, and nicotine addiction sustains tobacco use. An understanding of the biology and clinical features of nicotine addiction and the conditioning of behavior that occurs via stimuli paired with frequent nicotine dosing, as with a smoked cigarette, is important for informing pharmacologic and behavioral treatment targets. We review current advances in research on nicotine addiction treatment and recovery, with a focus on conventional combustible cigarette use. Our review covers evidence-based methods to treat smoking in adults and policy approaches to prevent nicotine product initiation in youth. In closing, we discuss emerging areas of evidence and consider new directions for advancing the field.

Circulating serotonin levels in COPD patients: a pilot study

Background

Chronic obstructive pulmonary disease (COPD) is a major and increasing global health problem. Serotonin is a neurotransmitter that participates in several pulmonary functions and it has been involved in oxidative stress, which plays essential roles in the pathogenesis of COPD. The current study aimed at establishing the levels of circulating serotonin in COPD, and investigating eventual relations between serotonin and oxidative stress markers.

Methods

Whole blood serotonin was assessed in 43 consecutive patients with stable COPD and in 43 age and sex-matched healthy controls.

Results

Serotonin blood levels were significantly higher in COPD patients than in controls (median 0.81 μmol/L, IQR: 0.61–4.02 vs 0.65 μmol/L, IQR: 0.53–1.39, p = 0.02). The univariate logistic regression analysis evidenced that serotonin levels are independently associated with presence of COPD (crude OR = 7.29, 95% CI: 1.296–41.05, p = 0.003) and such an association was confirmed also after adjusting for several confounders (OR 21.92, 95% CI 2.02–237.83; p = 0.011).

Conclusions

Our study showed higher levels of circulating serotonin in COPD and an inverse correlation with the worsening of airway obstruction. Future studies are necessary to investigate the clinical utility of this finding.

Comprehensive, robust, and sensitive UPLC-MS/MS analysis of free biogenic monoamines and their metabolites in urine

Biogenic monoamines, including catecholamines and serotonin are important hormones and neurotransmitters. Abnormal urinary levels of biogenic monoamines and their metabolites are associated with smoking, neuroendocrine tumors, as well as neurological and cardiovascular diseases. Measurements of free biogenic monoamines and their metabolites have been challenging because of low concentrations in complex biological matrices. Current methods require extensive enrichment and removal of interfering substances and can analyze only basic or acidic compounds in a single run. We developed a simple and robust dilute-and-shoot method capable of measuring 10 analytes, including free biogenic monoamines and their metabolites in human urine. The assay enables sensitive measurements of analytes within expected sample concentration ranges. To assess the assay's efficacy, we measured urinary levels of free biogenic monoamines and their metabolites in 255 non-smokers and 191 smokers. Our data show that while smokers had significantly higher urinary levels of free catecholamines and metanephrines, there was a decrease in levels of biogenic amine metabolites synthesized through the monoamine oxidase pathway - homovanillic acid and vanillylmandelic acid. The method could be used for high throughput measurement of the range of free biogenic amines and their metabolites in urine under a variety of different conditions.

The genotypes and methylation of MAO genes as factors behind smoking behavior

OBJECTIVE

Smoking dependence is the main cause for tobacco-related illnesses. The addiction-causing substance in tobacco, nicotine, acts through the dopamine pathway in the brain, causing several pleasurable experiences through cigarette smoking. Thus, both genetic and epigenetic factors related to dopamine metabolism may play an important role in influencing an individual's smoking behavior.

MATERIALS AND METHODS

We studied the 1460 C/T variation and the variable number tandem repeat polymorphism in the MAOA gene and A/G variation in intron 13 in the MAOB gene together with four DNA methylation sites in both of these genes in relation to several smoking-related phenotypes in a study population of 1230 Whites of Russian origin.

RESULTS

The genotypes studied were found to be associated with smoking status in women; the MAOB G variant allele was more prevalent in female smokers than nonsmokers [odds ratio (OR): 2.16, 95% confidence interval (CI): 1.08-4.33], whereas a reverse relation was observed for the MAOA 1460 T-variant allele (OR: 0.44, 95% CI: 0.21-0.91) and variable number tandem repeat low-activity alleles (OR: 0.49, 95% CI: 0.24-0.98). Moreover, the mean methylation values of the CpG sites studied in the MAOA gene were related to smoking behavior in women. Similarly, several methylation patterns in the MAOB gene were associated with a smoking history, with each CpG site showing a remarkable sex dependence.

CONCLUSION

Smoking behavior seems to be related to the genetic and epigenetic profile of MAO genes, with considerable individual and sex-related differences.

Differences in vaping topography in relation to adherence to exclusive electronic cigarette use in veterans

Background

Understanding vaping patterns of electronic cigarette (EC) use is important to understand the real-life exposure to EC vapor. Long term information on vaping topography in relation to tobacco cigarette (TC) smoking cessation success has not been explored.

Methods

Observational non-blinded study where active TC smokers were asked to replace TC with EC over 4 weeks (replacement phase, RP) followed by exclusive EC use for an additional 12 weeks (maintenance phase, MP). TC use and EC compliance was monitored weekly. Subjects were classified as success or failure whether or not they completed the protocol. Vaping information was stored and downloaded directly from the EC device and averaged per calendar day for analysis.

Results

From 25 subjects that followed the protocol, sixteen succeeded in completing the RP and 8 the MP (32%). No significant differences in baseline characteristics were noted between subjects in the success and failure groups including markers of nicotine addiction, plasma cotinine levels or smoking history. Success subjects showed significantly longer puff duration (seconds per vape) and total overall vapor exposure (number of vapes x average vape duration or vape-seconds) in both study phases. Furthermore, subjects in the success group continued to increase the number of vapes, device voltage and wattage significantly as they transitioned into the MP. After an initial drop, subjects in the success group were able to regain plasma cotinine levels comparable to their TC use while subjects in the failure group could not. Cotinine levels significantly correlated with the average number of daily vapes and vapes-seconds, but not with other vaping parameters.

Conclusion

The topography of smokers who adhere to exclusive EC use reflects a progressive and dynamic device adaptation over weeks to maintain baseline cotinine levels. The higher inhaled volume over time should be considered when addressing the potential toxic effects of EC and the variable EC adherence when addressing public health policies regarding their use.

Animal Research on Nicotine Reduction: Current Evidence and Research Gaps

A mandated reduction in the nicotine content of cigarettes may improve public health by reducing the prevalence of smoking. Animal self-administration research is an important complement to clinical research on nicotine reduction. It can fill research gaps that may be difficult to address with clinical research, guide clinical researchers about variables that are likely to be important in their own research, and provide policy makers with converging evidence between clinical and preclinical studies about the potential impact of a nicotine reduction policy. Convergence between clinical and preclinical research is important, given the ease with which clinical trial participants can access nonstudy tobacco products in the current marketplace. Herein, we review contributions of preclinical animal research, with a focus on rodent self-administration, to the science of nicotine reduction. Throughout this review, we highlight areas where clinical and preclinical research converge and areas where the two differ. Preclinical research has provided data on many important topics such as the threshold for nicotine reinforcement, the likelihood of compensation, moderators of the impact of nicotine reduction, the impact of environmental stimuli on nicotine reduction, the impact of nonnicotine cigarette smoke constituents on nicotine reduction, and the impact of nicotine reduction on vulnerable populations. Special attention is paid to current research gaps including the dramatic rise in alternative tobacco products, including electronic nicotine delivery systems (ie, e-cigarettes). The evidence reviewed here will be critical for policy makers as well as clinical researchers interested in nicotine reduction.

IMPLICATIONS

This review will provide policy makers and clinical researchers interested in nicotine reduction with an overview of the preclinical animal research conducted on nicotine reduction and the regulatory implications of that research. The review also highlights the utility of preclinical research for research questions related to nicotine reduction.

Monoamine oxidase inhibitory activity in tobacco particulate matter: Are harman and norharman the only physiologically relevant inhibitors?

Monoamine oxidase inhibition is significant in smokers, but it is still unclear how the inhibition that is seen in the brains and bodies of smokers is brought about. Our aim was to test the contribution of the harman and norharman in tobacco smoke to MAO-A inhibition from tobacco smoke preparations, as part of a re-examination of harman and norharman as the cause of the inhibition of MAO-A inhibition in the brain. Tobacco smoke particulate matter and cigarette smoke particulate matter were prepared and the amounts of harman and norharman measured. The results were compared with the total monoamine oxidase-A inhibitory activity. At a nicotine concentration of 0.6μM (a "physiological" concentration in blood) the total monoamine oxidase-A inhibitory activity measured in these samples was sufficient to inhibit the enzyme by approximately 10%. Of this inhibitory activity, only a small proportion of the total was found to be due to harman and norharman. These results show that harman and norharman provide only a moderate contribution to the total monoamine oxidase-A inhibitory activity of tobacco smoke, perhaps under 10%. This suggests that other inhibitors (either known or unknown) may be more significant contributors to total inhibitory activity than has yet been established, and deserve closer examination.

An Inventory of Methods for the Assessment of Additive Increased Addictiveness of Tobacco Products

BACKGROUND

Cigarettes and other forms of tobacco contain the addictive drug nicotine. Other components, either naturally occurring in tobacco or additives that are intentionally added during the manufacturing process, may add to the addictiveness of tobacco products. As such, these components can make cigarette smokers more easily and heavily dependent.Efforts to regulate tobacco product dependence are emerging globally. Additives that increase tobacco dependence will be prohibited under the new European Tobacco Product Directive.

OBJECTIVE

This article provides guidelines and recommendations for developing a regulatory strategy for assessment of increase in tobacco dependence due to additives. Relevant scientific literature is summarized and criteria and experimental studies that can define increased dependence of tobacco products are described.

CONCLUSIONS

Natural tobacco smoke is a very complex matrix of components, therefore analysis of the contribution of an additive or a combination of additives to the level of dependence on this product is challenging. We propose to combine different type of studies analyzing overall tobacco product dependence potential and the functioning of additives in relation to nicotine. By using a combination of techniques, changes associated with nicotine dependence such as behavioral, physiological, and neurochemical alterations can be examined to provide sufficient information.Research needs and knowledge gaps will be discussed and recommendations will be made to translate current knowledge into legislation. As such, this article aids in implementation of the Tobacco Product Directive, as well as help enable regulators and researchers worldwide to develop standards to reduce dependence on tobacco products.

IMPLICATIONS

This article provides an overall view on how to assess tobacco product constituents for their potential contribution to use and dependence. It provides guidelines that help enable regulators worldwide to develop standards to reduce dependence on tobacco products and guide researches to set research priorities on this topic.

Damage to the insula leads to decreased nicotine withdrawal during abstinence

BACKGROUND AND AIMS

Current pharmacotherapies for tobacco dependence are generally well tolerated, but have relatively high rates of relapse. They target primarily the brains' mesocorticolimbic 'reward' pathway. However, recent evidence suggests that the insular cortex, a central cerebral hemispheric region historically overlooked in addiction models, may also play an important role in cognitive and emotional processes that facilitate drug use. We examined whether insular versus non-insular damage from ischemic stroke attenuated acute withdrawal from cigarette smoking and reduced the likelihood of nicotine replacement therapy (NRT) use during hospitalization.

DESIGN

Data were derived from a longitudinal study with 3 months' follow-up, beginning June 2013 and ending May 2014.

SETTING

Three acute care hospitals in Rochester, NY, USA.

PARTICIPANTS

One-hundred and fifty-six current smokers hospitalized for acute ischemic stroke (38 with insular infarctions and 118 with non-insular infarctions, assessed by three neuroradiologists).

MEASUREMENTS

The Wisconsin Smoking Withdrawal Scale (WSWS) and Minnesota Nicotine Withdrawal Scale (MNWS) were administered during hospitalization (a period of forced abstinence) to assess the frequency and severity of withdrawal symptoms. NRT use was also assessed during hospitalization.

FINDINGS

On average, smokers with insular damage had a lower WSWS score during admission [mean=5.89, standard deviation (SD)=4.72] compared with those with non-insular damage (mean=9.20, SD=4.71; P<0.001) [covariate-adjusted difference in means of -3.12, 95% confidence interval (CI)=-4.97, -1.27]. A similar difference was also noted when the MNWS was used (P=0.02). Furthermore, participants with insular lesions appeared to be less likely to use NRT during admission compared with those with non-insular lesions [odds ratio (OR)=0.72, 95% CI=0.32, 1.64].

CONCLUSIONS

Current smokers with damage to their insular cortex brain region appear to experience fewer and less severe tobacco withdrawal symptoms, and appear to be less likely to require nicotine replacement therapy during hospitalization, compared with smokers with non-insular damage. These findings support the potential role of the insular cortex in regulating withdrawal during abstinence, a motivator responsible for the maintenance of addictive behaviors.

Contribution of Monoamine Oxidase Inhibition to Tobacco Dependence: A Review of the Evidence

BACKGROUND

There is a hypothesis that substances present in, or derived from, tobacco smoke inhibit monoamine oxidase (MAO) in the brains of smokers, reducing the degradation of catecholamine neurotransmitters involved in central reward pathways and acting synergistically with nicotine to increase its addictive effects.

OBJECTIVE

The objective of this review was to evaluate the evidence for a role of MAO inhibition by tobacco-derived substances in tobacco dependence.

INVESTIGATIONAL PLAN

Relevant studies on the effects of tobacco use on MAO levels or activity in humans were identified by electronic searches.

RESULTS

The identified data show a clear association between smoking and lower density of MAO-A and MAO-B binding sites in the brains of smokers and strong evidence that MAO is inhibited by a substance or substances in, or derived from, tobacco smoke. There was little evidence to support the hypothesis that low MAO levels/activity is a predictive factor for tobacco use. Substances that inhibit MAO in in vitro assays have been isolated from tobacco leaves and tobacco smoke; however, no single substance has been shown to be absorbed from tobacco smoke and to inhibit MAO in the brains of human smokers. Nevertheless, it is possible that MAO inhibition in smokers could result from additive or synergistic effects of several tobacco-derived substances. MAO inhibition potentiates the reinforcing effects of intravenous nicotine in rodents; however, no data were identified to support the hypothesis that MAO inhibitors in or derived from tobacco or tobacco additives affect tobacco dependence in human smokers.

IMPLICATIONS

This comprehensive review describes the available evidence for the role of MAO inhibition in tobacco dependence and points the way for further research in this field. In view of the large number of MAO inhibitors identified in tobacco and tobacco smoke, identification of the putative inhibitors responsible for the lower level/activity of MAO in smokers may be impractical. Future studies must address whether the lower level/activity of MAO observed in smokers is also seen in users of other tobacco products and if this change is implicated in their dependence-inducing effects.

Effects of MAO inhibition and a combination of minor alkaloids, β-carbolines, and acetaldehyde on nicotine self-administration in adult male rats

INTRODUCTION

Although nicotine is the primary reinforcing constituent in cigarettes, there is evidence that other constituents in cigarette smoke may interact with nicotine to reinforce smoking behavior.

METHODS

The present experiments investigated whether a novel combination of these cigarette smoke constituents would increase nicotine self-administration in adult male rats. The constituents included five minor alkaloids (anabasine, nornicotine, cotinine, myosmine, and anatabine), two β-carbolines (harman and norharman), and acetaldehyde. All doses were indexed to be proportional to concentrations in cigarette smoke given a standard dose of nicotine used in rodent self-administration, or ten times higher than this standard. To model MAO inhibition seen in chronic smokers, some groups received separate injections of tranylcypromine prior to each self-administration session.

RESULTS

Tranylcypromine increased low-dose nicotine self-administration independent of other smoke constituents, which had no effect on self-administration behavior. The effect of tranylcypromine was confirmed across a large range of reinforcement schedules. The effect of tranylcypromine on low-dose nicotine self-administration was observed regardless of whether the injection was delivered 1-h or 23-h prior to the self-administration session, consistent with the interpretation that MAO inhibition was responsible for the increase in self-administration, instead of acute off-target effects.

CONCLUSIONS

These data suggest that this cocktail of constituents does not significantly alter the primary reinforcing effects of nicotine, but constituents that inhibit MAO may increase the primary reinforcing effects of nicotine, especially at low doses.

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.

Association between monoamine oxidase gene polymorphisms and smoking behavior: A meta-analysis

BACKGROUND

A number of studies have researched the association between monoamine oxidase gene (MAO) polymorphisms and smoking behavior, but the conclusion is quite inconsistent. A meta-analysis was conducted to assess the association of MAO-A C1460T, MAO-A VNTR and MAO-B G644A polymorphisms with smoking behavior.

METHODS

A comprehensive search was performed to identify all eligible studies. Meta-analysis was applied to calculate the pooled effect values and their 95% confidence intervals. Meta-regression and the 'leave one out' sensitivity analysis were used to explore potential sources of heterogeneity. The risk of bias was assessed by the Egger regression asymmetry test.

RESULTS

11 articles conformed to the inclusion criteria. The meta-analysis showed T allele in MAO-A C1460T reduced the risk of heavy smoking (OR=0.66, 95% CI: 0.52-0.84; I(2)=0.0%), especially in Caucasians; the active group in MAO-A VNTR increased the likelihood of failed smoking cessation in males (OR=1.49, 95% CI: 1.01-2.22; I(2)=0.0%); A allele in MAO-B G644A reduced the risk of heavy smoking in males (OR=0.20, 95% CI: 0.04-0.98).

CONCLUSION

Our findings indicate that the low activity of monoamine oxidase gene polymorphisms has a protective effect on smoking cessation and heaviness. Some associations and applications should be further confirmed.

Imaging of monoamine oxidase-A in the human brain with [11C]befloxatone: quantification strategies and correlation with mRNA transcription maps

INTRODUCTION

[C]Befloxatone is a highly specific, reversible, and selective radioligand for brain PET imaging of monoamine oxidase-A and can be quantified by a two-tissue compartment model (2TCM) and an arterial input function. The aims of the present study were the following: (a) to assess whether in-vivo protein concentration, as measured by [C]befloxatone total distribution volume (VT), is correlated with post-mortem mRNA expression; (b) to replicate in a population of tobacco smokers the results of a recent study on healthy nonsmokers, which showed that spectral analysis (SA) provides a highly accurate estimation of [C]befloxatone-VT at the voxel level; and (c) to validate the use of an input function that would not require arterial sampling.

MATERIALS AND METHODS

Healthy male nonsmokers (n=7) and smokers (n=8) were imaged with PET and [C]befloxatone. Binding was quantified at the regional and voxel level with the Logan plot, multilinear analysis (MA1), and SA. VT values were compared with the reference values obtained by 2TCM at the regional level. [C]Befloxatone binding was compared with mRNA transcription maps from the Allen Human Brain Atlas. A less-invasive input function was obtained with a population-based input function (PBIF) scaled with arterialized venous samples.

RESULTS

mRNA expression was highly correlated with in-vivo 2TCM-VT values both for nonsmokers (R=0.873; P<0.0001) and for smokers (R=0.851; P<0.0001). At the regional level, both Logan and MA1 showed a moderate negative bias (-5 to -10%) compared with the reference VT values. With the exception of a single outlying individual, SA showed little bias and variability (+4.4±3.5%). Although variability was higher than at the regional level, SA provided the most accurate VT estimations at the voxel level: all but one participant had an error of less than 20%. Parametric Logan and MA1 analyses gave highly biased or unusable results. PBIF provided good results in all participants in whom the arterialization of venous blood was successful (all errors of about 10% or less).

CONCLUSION

[C]Befloxatone binding is strongly correlated with the values of mRNA transcription measured in post-mortem brains. At the voxel level, SA is the best available choice for [C]befloxatone quantification, although a higher variability must be expected. When an arterial input function is not technically feasible, a PBIF scaled with arterialized venous samples may provide an acceptable alternative, provided an optimal arterialization can be achieved.

The separate and combined effects of monoamine oxidase inhibition and nicotine on P50 sensory gating

INTRODUCTION

The cognitive effects of nicotine in humans remain a topic of great interest, due to the continued prevalence of cigarette smoking in society as well as the hypothesis that cognitively impaired populations such as schizophrenia patients use nicotine as a means of self-medicating against deficits of sensory gating. However, chronic smoking can predispose individuals to robust monoamine oxidase (MAO) inhibition, and thus far, the effect of MAO inhibition on human sensory gating is unknown.

METHODS

In this study, we investigated the effects of both nicotine (6-mg gum) and pharmacologically induced MAO-A inhibition via moclobemide (75 mg) on P50 event-related potential-indexed sensory gating in a sample of 24 healthy non-smoking males.

RESULTS

Ratio score (rP50) measured gating revealed significant improvement in auditory stimulus suppression after combined nicotine and MAO-A inhibition compared to placebo and to the nicotine-alone condition. This nicotine + MAO-A inhibition-induced efficient gating was consistent regardless of participants' baseline (placebo) gating efficiency, despite the observation that nicotine in the absence of MAO-A inhibition exhibited a detrimental effect on gating in participants with high baseline suppression ratios.

CONCLUSION

Nicotine and monoamine oxidase-inhibiting agents in tobacco smoke appear to exert a synergistic effect on sensory gating, which may contribute to the elevated dependence rates seen in populations with cognitive deficits such as schizophrenia.

Empirically derived subtypes of serious emotional disturbance in a large adolescent sample

PURPOSE

The heterogeneity of serious emotional disturbance has been thoroughly documented among adolescents with nationally representative data derived from structured interviews, although use of these interviews may not be feasible within the context of brief and self-administered school surveys. This study seeks to identify distinct subtypes of serious emotional disturbance in a large school-based sample.

METHODS

A total of 108,736 students fully completed the K6 scale that was included on the 2012 Kentucky Incentives for Prevention Survey. Latent class analysis was used to derive subtypes of serious emotional disturbance among students receiving a positive screen (n = 15,147). To determine significant predictors of class membership, adjusted rate ratios and 95 % confidence intervals were calculated using multinomial logistic regression.

RESULTS

A four-class model was the most parsimonious, with four distinct subtypes emerging that varied by both symptom type and severity: comorbid moderate severity, comorbid high severity, anxious moderate severity, and depressed high severity. Age, gender, race/ethnicity, family structure, substance use, antisocial behavior, role impairments, and peer victimization were significant predictors of class membership, although the magnitude of these effects was stronger for the two high severity groups.

CONCLUSIONS

Our results suggest heterogeneity of serious emotional disturbance by both symptom type and severity. Prevention programs may benefit by shifting focus from specific disorders to the core features of serious emotional disturbance, including psychological distress, high comorbidity, and role impairments.

A Comprehensive Approach to Tobacco Dependence Interventions

Tobacco smoking remains the leading preventable cause of death and illness in the United States. Smoking cessation is particularly relevant for individuals with chronic obstructive pulmonary disease because it is known from multiple studies that individuals who quit smoking experience an initial improvement in pulmonary function, a decreased rate of normal age-related decline in FEV1, a lower risk of hospital admission, and improved survival. Tobacco dependence must be recognized as a chronic disease, and comprehensive treatment for the tobacco-dependent patient with chronic obstructive pulmonary disease begins with a physician's inquiry into smoking and encouragement to quit, followed by an assessment of the level of dependence and the severity of withdrawal symptoms during previous quit attempts. Combination pharmacotherapy is recommended for the initial treatment of most smokers, especially those with moderate to high baseline levels of tobacco dependence. The patient's history, combined with his or her personal preference, can guide the clinician in initiating an appropriate treatment regimen. Given the chronic nature of tobacco dependence, clinicians must anticipate relapses and the need for recurrent, long-term follow-up. Comprehensive tobacco treatment consultation should be sought whenever possible for patients with high levels of tobacco dependence and multiple relapses or failed quit attempts.

Influence of Altered Hormonal Status on Platelet 5-HT and MAO-B Activity in Cigarette Smokers

The present study was designed to understand the cigarette smoking-induced alterations in hormones and the resulting changes in platelet serotonin (5-hydroxytryptamine, 5-HT) and monoamine oxidase (MAO-B) activity in chronic smokers. Human male volunteers aged 35 ± 8 years, were divided into two groups, namely controls and smokers (12 ± 2 cigarettes per day for 7-10 years). Results showed that cigarette smoking significantly (p < 0.05) elevated plasma triiodothyronine (T3), cortisol and testosterone levels with significant (p < 0.05) reduction in plasma tryptophan and thyroxin (T4). Moreover, smokers showed reduced platelet 5-HT levels and MAO-B activity. In smokers, plasma cortisol was negatively correlated with tryptophan (r = -0.386), platelet MAO-B (r = -0.264), and 5-HT (r = -0.671), and positively correlated with testosterone (r = 0.428). However, testosterone was negatively correlated with platelet MAO-B (r = -0.315), and 5-HT (r = -.419) in smokers. Further, smokers plasma T3 levels were negatively correlated with platelet MAO-B (r = -0.398), and 5-HT (r = -0.541), whereas T4 levels were positively correlated with platelet MAO-B (r = 0.369), and 5-HT (r = 0.454). In conclusion, our study showed that altered testosterone and cortisol levels may aggravate behavior, mood disturbances and symptoms of depression by decreasing platelet 5-HT and MAO-B activity in smokers.

Targeting the noradrenergic system for gender-sensitive medication development for tobacco dependence

INTRODUCTION

Tobacco use remains the leading cause of morbidity and mortality for both women and men in the United States, and women often experience poorer smoking cessation outcomes than men. Preliminary evidence suggests there are sex differences in medication effectiveness for smoking cessation. However, current medications do not take into account gender-sensitive treatment development and efficacy, underscoring the importance of this underdeveloped area of research.

METHODS

We reviewed preclinical and clinical evidence for gender differences in the inability to quit smoking by examining (a) the effect of increased negative affect and stress reactivity on smoking outcomes in women and (b) smoking for nicotine reinforcement in men. We also reviewed the current literature targeting the noradrenergic system as a novel gender-sensitive treatment strategy for tobacco dependence.

RESULTS

We hypothesize that noradrenergic agents that normalize noradrenergic activity may differentially attenuate stress reactivity in women and nicotine-related reinforcement in men, indicating that targeting the noradrenergic system for smoking cessation may be effective for both genders, with benefits operating through sex-specific mechanisms.

CONCLUSIONS

Converging lines of preclinical and clinical evidence suggest that gender-sensitive approaches to medication development for smoking cessation are a critical next step for addressing low quit rates and exacerbated health risks among women. Evidence reviewed indicates that smoking activates different brain systems modulated by noradrenergic activity in women versus men, and noradrenergic compounds may preferentially target these gender-sensitive systems.

Tobacco particulate matter self-administration in rats: differential effects of tobacco type

Nicotine self-administration in rats is the most widely used animal model of tobacco dependence. There is increasing evidence, however, that non-nicotinic constituents in smoke contribute to addiction and that different tobacco products contain varying levels of these constituents. The present study firstly sought to compare self-administration of pure nicotine to tobacco particulate matter (TPM) to determine if there were differences in reward-efficacy attributable to the non-nicotine constituents. Secondly, cigarette and roll-your-own (RYO) TPM groups were included and compared to determine whether different formulations of non-nicotinic constituents could impact reward. Briefly, male Sprague Dawley rats were implanted with indwelling jugular catheters for self-administration (n = 76). The reinforcing efficacy of infusions of nicotine (0.0 or 30.0 μg/kg/infusion) versus cigarette/RYO TPM (with matched nicotine content) was determined using spontaneous acquisition of self-administration on a fixed ratio schedule. The progressive ratio schedule was then employed to determine the motivation to receive each drug and within-subject dose-response curves were also produced (7.5, 15.0, 30.0 and 60.0 μg/kg/infusion nicotine). The main finding was that the RYO TPM was more reinforcing and produced a different profile of reward-related behaviour compared with both the nicotine and the cigarette TPM groups. The conclusions were that non-nicotinic components have a role in tobacco dependence and that some tobacco products could have higher abuse liability, irrespective of nicotine levels.

Whole tobacco smoke extracts to model tobacco dependence in animals

Smoking tobacco is highly addictive and a leading preventable cause of death. The main addictive constituent is nicotine; consequently it has been administered to laboratory animals to model tobacco dependence. Despite extensive use, this model might not best reflect the powerful nature of tobacco dependence because nicotine is a weak reinforcer, the pharmacology of smoke is complex and non-pharmacological factors have a critical role. These limitations have led researchers to expose animals to smoke via the inhalative route, or to administer aqueous smoke extracts to produce more representative models. The aim was to review the findings from molecular/behavioural studies comparing the effects of nicotine to tobacco/smoke extracts to determine whether the extracts produce a distinct model. Indeed, nicotine and tobacco extracts yielded differential effects, supporting the initiative to use extracts as a complement to nicotine. Of the behavioural tests, intravenous self-administration experiments most clearly revealed behavioural differences between nicotine and extracts. Thus, future applications for use of this behavioural model were proposed that could offer new insights into tobacco dependence.

Kinetic analysis of [11C]befloxatone in the human brain, a selective radioligand to image monoamine oxidase A

BACKGROUND

[11C]Befloxatone measures the density of the enzyme monoamine oxidase A (MAO-A) in the brain. MAO-A is responsible for the degradation of different neurotransmitters and is implicated in several neurologic and psychiatric illnesses. This study sought to estimate the distribution volume (VT) values of [11C]befloxatone in humans using an arterial input function.

METHODS

Seven healthy volunteers were imaged with positron emission tomography (PET) after [11C]befloxatone injection. Kinetic analysis was performed using an arterial input function in association with compartmental modeling and with the Logan plot, multilinear analysis (MA1), and standard spectral analysis (SA) at both the regional and voxel level. Arterialized venous samples were drawn as an alternative and less invasive input function.

RESULTS

An unconstrained two-compartment model reliably quantified VT values in large brain regions. A constrained model did not significantly improve VT identifiability. Similar VT results were obtained using SA; however, the Logan plot and MA1 slightly underestimated VT values (about -10%). At the voxel level, SA showed a very small bias (+2%) compared to compartmental modeling, Logan severely underestimated VT values, and voxel-wise images obtained with MA1 were too noisy to be reliably quantified. Arterialized venous blood samples did not provide a satisfactory alternative input function as the Logan-VT regional values were not comparable to those obtained with arterial sampling in all subjects.

CONCLUSIONS

Binding of [11C]befloxatone to MAO-A can be quantified using an arterial input function and a two-compartment model or, in parametric images, with SA.

Electronic cigarettes and vaping: a new challenge in clinical medicine and public health. A literature review

Electronic cigarette (e-cigarette) use, or vaping, in the United States and worldwide is increasing. Their use is highly controversial from scientific, political, financial, psychological, and sociological ideologies. Given the controversial nature of e-cigarettes and vaping, how should medical care providers advise their patients? To effectively face this new challenge, health care professionals need to become more familiar with the existing literature concerning e-cigarettes and vaping, especially the scientific literature. Thus, the aim of this article is to present a review of the scientific evidence-based primary literature concerning electronic cigarettes and vaping. A search of the most current literature using the pubmed database dating back to 2008, and using electronic cigarette(s) or e-cigarette(s) as key words, yielded a total of 66 highly relevant articles. These articles primarily deal with (1) consumer-based surveys regarding personal views on vaping, (2) chemical analysis of e-cigarette cartridges, solutions, and mist, (3) nicotine content, delivery, and pharmacokinetics, and (4) clinical and physiological studies investigating the effects of acute vaping. When compared to the effects of smoking, the scant available literature suggests that vaping could be a “harm reduction” alternative to smoking and a possible means for smoking cessation, at least to the same degree as other Food and Drug Administration-approved nicotine replacement therapies. However, it is unclear if vaping e-cigarettes will reduce or increase nicotine addiction. It is obvious that more rigorous investigations of the acute and long-term health effects of vaping are required to establish the safety and efficacy of these devices; especially parallel experiments comparing the cardiopulmonary effects of vaping to smoking. Only then will the medical community be able to adequately meet the new challenge e-cigarettes and vaping present to clinical medicine and public health.

Evidence of sex differences in the relationship between current tobacco use and past-year serious psychological distress: 2005-2008 National Survey on Drug Use and Health

PURPOSE

Cigarette use is highly prevalent in psychiatric populations. Studies suggest that smokeless tobacco use is not significantly associated with past-year psychiatric morbidity, with evidence that tobacco use differ among sexes. The relationships between current tobacco use and past-year serious psychological distress, major depressive episode and anxiety disorder were therefore examined. Sex differences in the aforementioned relationship were also examined.

METHODS

A total of 133,221 adults from four successive independent samples of the 2005-2008 National Survey on Drug Use and Health were included. Prevalence odds ratios and 95 % confidence intervals were calculated using multivariable logistic regression adjusting for demographic factors, survey year, pregnancy (women only), past-year medical morbidity, past-year psychiatric comorbidity, and past-year substance use disorders.

RESULTS

No associations were demonstrated among smokeless tobacco users. Statistically significant sex differences were found for current tobacco use and serious psychological distress (p < 0.001). Both male and female smokers were significantly more likely to have serious psychological distress and anxiety disorder compared to never users, while only female smokers were more likely to have major depressive episode. The strongest associations were found for anxiety disorder among all adults as well as both sexes.

CONCLUSIONS

The null associations for both sexes for smokeless tobacco may support a reduced risk profile. Female cigarette smokers may be more vulnerable to subclinical distress and depression than males. Studies using other nationally representative samples are needed to confirm these data.

Enhanced smoking cue salience associated with depression severity in nicotine-dependent individuals: a preliminary fMRI study

The association between cigarette smoking and depression has been well documented; however, little research has been done to elucidate the neurobiological substrates of this highly prevalent comorbidity. We used multiple linear regression analysis to evaluate the relationship between depression severity as assessed by the Hamilton Depression Rating Scale (HAMD) and blood oxygen level-dependent (BOLD) responses to visual smoking cues in drug-free nicotine-dependent smokers (n=18). Two functional magnetic resonance imaging (fMRI) scans were completed over a single study day, following overnight smoking abstinence (pre-smoking scan) and after cigarette reinstatement (post-smoking scan). During the pre-smoking scan positive correlations between BOLD activity and HAMD scores were observed in areas of the mesocorticolimbic dopaminergic system [inferior frontal gyrus, middle frontal gyrus (MFG), hippocampus (HC), anterior cingulate gyrus] and areas of the visuospatial attention circuit (medial occipital lobe, middle cingulate cortex, superior frontal gyrus, angular gyrus). During the post-smoking scan positive correlations were observed in areas of the brain implicated in drug expectancy (MFG), memory (HC), attentional motivation (posterior cingulate cortex), and visual processing and attention (precuneus). These preliminary findings demonstrate that smokers with higher depression severity attribute greater incentive salience to smoking-related cues and this is especially pronounced during periods of acute abstinence. Such enhanced salience of smoking cues, even after smoking a cigarette, may play a critical role both in the maintenance of smoking in depression and in greater levels of nicotine dependence seen in this patient population.