Pharmacotherapies and harm-reduction options for the treatment of tobacco dependence

Tobacco carcinogens and the methionine metabolism in human bladder cancer

Cigarette smoking is a strong risk factor for bladder cancer. It has been shown that the duration of smoking is associated with a poor prognosis and a higher risk of recurrence. This is due to tobacco carcinogens forming adducts with DNA and proteins that participate in the DNA repair mechanisms. Additionally, polymorphisms of genes responsible for methyl group transfer in the methionine cycle and dosages of vitamins (from diet and supplements) can cause an increased risk of bladder cancer. Upregulated DNA methyltransferase 1 expression and activity results in a high level of methylated products of metabolism, as well as hypermethylation of tumor suppressor genes. The development of a market that provides new inhibitors of DNA methyltransferase or alternatives for current smokers is essential not only for patients but also for people who are under the danger of secondhand smoking and can experience its long-term exposure consequences.

Attenuated nicotine-like effects of varenicline but not other nicotinic ACh receptor agonists in monkeys receiving nicotine daily

BACKGROUND AND PURPOSE

Chronic treatment can differentially impact the effects of pharmacologically related drugs that differ in receptor selectivity and efficacy.

EXPERIMENTAL APPROACH

The impact of daily nicotine treatment on the effects of nicotinic ACh receptor (nAChR) agonists was examined in two groups of rhesus monkeys discriminating nicotine (1.78 mg·kg-1 base weight) from saline. One group received additional nicotine treatment post-session (1.78 mg·kg-1 administered five times daily, each dose 2 h apart; i.e. Daily group), and the second group did not (Intermittent group).

KEY RESULTS

Daily repeated nicotine treatment produced a time-related increase in saliva cotinine. There was no significant difference in the ED50 values of the nicotine discriminative stimulus between the Daily and Intermittent group. Mecamylamine antagonized the effects of nicotine, whereas dihydro-β-erythroidine did not. Midazolam produced 0% nicotine-lever responding. The nAChR agonists epibatidine, RTI-36, cytisine and varenicline produced >96% nicotine-lever responding in the Intermittent group. The respective maximum effects in the Daily group were 100, 72, 59 and 28%, which shows that the ability of varenicline to produce nicotine-like responding was selectively decreased in the Daily as compared with the Intermittent group. When combined with nicotine, both varenicline and cytisine increased the potency of nicotine to produce discriminative stimulus effects.

CONCLUSION AND IMPLICATIONS

Nicotine treatment has a greater impact on the sensitivity to the effects of varenicline as compared with some other nAChR agonists. Collectively, these results strongly suggest that varenicline differs from nicotine in its selectivity for multiple nAChR subtypes.

Extracts from presumed "reduced harm" cigarettes induce equivalent or greater toxicity in antigen-presenting cells

The tobacco industry has promoted certain cigarette products with claims that their use may be less harmful to the smoker as they purportedly deliver lower amounts of toxic chemicals compared to conventional cigarettes. This study was designed to compare the relative antigen presenting cellular toxicity of Eclipse, a presumed reduced exposure product (PREP) cigarette, when compared with the reference research 3R4F cigarettes (Kentucky University). Utilizing a murine macrophage cell line, murine bone marrow derived dendritic cells (DCs) and human monocyte-derived DCs incubated with extracts generated from Eclipse and Kentucky reference 3R4F cigarettes, we determined the relative toxic effects of the different cigarette smoke extracts on cellular viability, oxidative stress, T-helper-1 (Th-1) polarizing cytokine production and general gene expression. Eclipse and 3R4F cigarette smoke extracts induced equivalent oxidatively-mediated cellular heme oxygenase-1 (HO-1) protein levels in macrophages and DCs. Cellular viability determination demonstrated greater induction of cell death by apoptosis and necrosis by Eclipse extracts in DCs. The production of the key Th-1 polarizing cytokine interleukin-12 (IL-12) by activated DCs or macrophages was suppressed to an equivalent or greater extent by Eclipse extracts. Microarray studies performed on bone marrow derived murine DCs incubated with Eclispe or 3R4F cigarette extracts showed identical genotoxic profiles. These studies imply that presumed reduced harm Eclipse cigarettes induce equivalent or greater antigen presenting cell dysfunction relative to 3R4F cigarettes and illustrate the importance of independent validation and testing of similar products claimed to be associated with reduced toxicity relative to other cigarettes.

Identifying Medication Targets for Psychostimulant Addiction: Unraveling the Dopamine D3 Receptor Hypothesis

The dopamine D3 receptor (D3R) is a target for developing medications to treat substance use disorders. D3R-selective compounds with high affinity and varying efficacies have been discovered, providing critical research tools for cell-based studies that have been translated to in vivo models of drug abuse. D3R antagonists and partial agonists have shown especially promising results in rodent models of relapse-like behavior, including stress-, drug-, and cue-induced reinstatement of drug seeking. However, to date, translation to human studies has been limited. Herein, we present an overview and illustrate some of the pitfalls and challenges of developing novel D3R-selective compounds toward clinical utility, especially for treatment of cocaine abuse. Future research and development of D3R-selective antagonists and partial agonists for substance abuse remains critically important but will also require further evaluation and development of translational animal models to determine the best time in the addiction cycle to target D3Rs for optimal therapeutic efficacy.

Exploratory survey study of long-term users of nicotine replacement therapy in Danish consumers

BACKGROUND

Long-term use of nicotine replacement therapy (NRT) has been approved in several countries for smokers who are unable or unwilling to quit smoking. However, information on basic characteristics, degree of nicotine dependence, health status and contentment with long-term use of NRT is scarce. The aim of this study was to collect information on the characteristics of long-term NRT users, having used NRT for at least 12 months, reasons for, and contentment with, their continued use of NRT including reasons for wishing to quit or sustain use and an estimation of their degree of nicotine dependence.

METHOD

Through advertisements in three national Danish newspapers, long-term NRT users were recruited to answer a short questionnaire about basic characteristics, health status and satisfaction with using NRT. A modified version of the Heaviness of Smoking Index (HSI) questionnaire was applied to estimate nicotine dependence. Linear regression was used to test association between time to first NRT and daily dosage of NRT.

RESULTS

A total of 92 respondents were included in the data analysis. A majority of 88% wished to quit NRT for the following reasons: costs of NRT, being tired of feeling addicted and fear of adverse health effects. Scoring on the modified HSI scale was 22.0% low, 68.0% moderate and 9.3% high dependent. Of the respondents, 67.0% used NRT within the first 30 min after waking. A validation check found a significant linear association between the two items in the modified HSI.

CONCLUSION

A significant majority of users wished to quit NRT because of the cost of products, being tired of feeling addicted and fear of adverse health consequences. The majority of these users were moderate to high nicotine dependent. The strong association found between time to first NRT and NRT dosages used per day gives reason to believe the validity of the modified HSI. Further studies are required for confirmation. Better counselling of long-term users on the benefits of using NRT compared to smoking should be provided, for those who are chronically dependent, as well as support to stop long-term use of NRT if wanted.

Nicotinic, glutamatergic and dopaminergic synaptic transmission and plasticity in the mesocorticolimbic system: focus on nicotine effects

Cigarette smoking is currently the leading cause of preventable deaths and disability throughout the world, being responsible for about five million premature deaths/year. Unfortunately, fewer than 10% of tobacco users who try to stop smoking actually manage to do so. The main addictive agent delivered by cigarette smoke is nicotine, which induces psychostimulation and reward, and reduces stress and anxiety. The use of new technologies (including optogenetics) and the development of mouse models characterised by cell-specific deletions of receptor subtype genes or the expression of gain-of-function nAChR subunits has greatly increased our understanding of the molecular mechanisms and neural substrates of nicotine addiction first revealed by classic electrophysiological, neurochemical and behavioural approaches. It is now becoming clear that various aspects of nicotine dependence are mediated by close interactions of the glutamatergic, dopaminergic and γ-aminobutyric acidergic systems in the mesocorticolimbic system. This review is divided into two parts. The first provides an updated overview of the circuitry of the ventral tegmental area, ventral striatum and prefrontal cortex, the neurotransmitter receptor subtypes expressed in these areas, and their physiological role in the mesocorticolimbic system. The second will focus on the molecular, functional and behavioural mechanisms involved in the acute and chronic effects of nicotine on the mesocorticolimbic system.

Is it safe to use smoking cessation therapeutics during pregnancy?

INTRODUCTION

Worldwide, 10 to 35% of pregnant women smoke. It is clear that smoking cessation has positive impacts for both the mother and child, yet many women are still unable to quit due to the addictive properties of nicotine. There are limited data surrounding their safety and efficacy in pregnancy.

AREAS COVERED

This review highlights evidence from clinical studies and animal experiments regarding the effects of smoking cessation therapeutics on pregnancy, neonatal and long-term postnatal outcomes.

EXPERT OPINION

There are insufficient data at this time to recommend the use of varenicline and/or bupropion for smoking cessation during pregnancy. In addition, the efficacy and safety of nicotine replacement therapy use for smoking cessation in pregnant women has not been clearly demonstrated. Until further studies are completed, there will continue to be considerable uncertainty regarding the use of these drugs in pregnancy despite the well-documented benefits of smoking cessation.

Optimizing treatments for nicotine dependence by increasing cognitive performance during withdrawal

INTRODUCTION

Current FDA-approved smoking cessation pharmacotherapies have limited efficacy and are associated with high rates of relapse. Therefore, there is a clear need to develop novel antismoking medications. Nicotine withdrawal is associated with cognitive impairments that predict smoking relapse. It has been proposed that these cognitive deficits are a hallmark of nicotine withdrawal that could be targeted in order to prevent smoking relapse. Thus, pharmacotherapies that increase cognitive performance during nicotine withdrawal may represent potential smoking cessation agents.

AREAS COVERED

The authors review the clinical literature demonstrating that nicotine withdrawal is associated with deficits in working memory, attention and response inhibition. They then briefly summarize different classes of compounds and strategies to increase cognitive performance during nicotine withdrawal. Particular emphasis has been placed on translational research in order to highlight areas for which there is strong rationale for pilot clinical trials of potential smoking cessation medications.

EXPERT OPINION

There is emerging evidence that supports deficits in cognitive function as a plausible nicotine withdrawal phenotype. The authors furthermore believe that the translational paradigms presented here may represent efficient and valid means for the evaluation of cognitive-enhancing medications as possible treatments for nicotine dependence.