Pharmacology of neuronal nicotinic acetylcholine recceptors: effects of acute and chronic nicotine

α4β2 Nicotinic receptor desensitizing compounds can decrease self-administration of cocaine and methamphetamine in rats

Sazetidine-A [6-(5(((S)-azetidine-2-yl)methoxy)pyridine-3-yl)hex-5-yn-1-ol] is a selective α4β2 nicotinic receptor desensitizing agent and partial agonist. Sazetidine-A has been shown in our previous studies to significantly reduce nicotine and alcohol self-administration in rats. The question arises whether sazetidine-A would reduce self-administration of other addictive drugs as well. Nicotinic receptors on the dopaminergic neurons in the ventral tegmental area play an important role in controlling the activity of these neurons and release of dopamine in the nucleus accumbens, which is critical mechanism for reinforcing value of drugs of abuse. Previously, we showed that the nonspecific nicotinic antagonist mecamylamine significantly reduces cocaine self-administration in rats. In this study, we acutely administered systemically sazetidine-A and two other selective α4β2 nicotinic receptor-desensitizing agents, VMY-2-95 and YL-2-203, to young adult female Sprague-Dawley rats and determined their effects on IV self-administration of cocaine and methamphetamine. Cocaine self-administration was significantly reduced by 0.3 mg/kg of sazetidine-A. In another set of rats, sazetidine-A (3 mg/kg) significantly reduced methamphetamine self-administration. VMY-2-95 significantly reduced both cocaine and methamphetamine self-administration with threshold effective doses of 3 and 0.3 mg/kg, respectively. In contrast, YL-2-203 did not significantly reduce cocaine self-administration at the same dose range and actually significantly increased cocaine self-administration at the 1 mg/kg dose. YL-2-203 (3 mg/kg) did significantly decrease methamphetamine self-administration. Sazetidine-A and VMY-2-95 are promising candidates to develop as new treatments to help addicts successfully overcome a variety of addictions including tobacco, alcohol as well as the stimulant drugs cocaine and methamphetamine.

An Official American Thoracic Society Research Statement: Current Understanding and Future Research Needs in Tobacco Control and Treatment

INTRODUCTION

Since the mid-20th century, the scientific community has substantially improved its understanding of the worldwide tobacco epidemic. Although significant progress has been made, the sheer enormity and scope of the global problem put it on track to take a billion lives this century. Curbing the epidemic will require maximizing the impact of proven tools as well as the development of new, breakthrough methods to help interrupt the spread of nicotine addiction and reduce the downstream morbidity.

METHODS

Members of the Tobacco Action Committee of the American Thoracic Society queried bibliographic databases, including Medline, Embase, and the Cochrane Collaborative, to identify primary sources and reviews relevant to the epidemic. Exploded search terms were used to identify evidence, including tobacco, addiction, smoking, cigarettes, nicotine, and smoking cessation. Evidence was consolidated into three thematic areas: (1) determinants of risk, (2) maternal-fetal exposure, and (3) current tobacco users. Expert panel consensus regarding current gaps in understanding and recommendations for future research priorities was generated through iterative discussion.

RESULTS

Although much has been accomplished, significant gaps in understanding remain. Implementation often lags well behind insight. This report identifies a number of investigative opportunities for significantly reducing the toll of tobacco use, including: (1) the need for novel, nonlinear models of population-based disease control; (2) refinement of "real-world" models of clinical intervention in trial design; and (3) understanding of mechanisms by which intrauterine smoke exposure may lead to persistent, tobacco-related chronic disease.

DISCUSSION

In the coming era of tobacco research, pooled talent from multiple disciplines will be required to further illuminate the complex social, environmental and biological codeterminants of tobacco dependence.

Correlates of cortisol in human hair: implications for epidemiologic studies on health effects of chronic stress

Assessment of cortisol concentrations in hair is one of the latest innovations for measuring long-term cortisol exposure. We performed a systematic review of correlates of cortisol in human hair to inform the design, analysis, and interpretation of future epidemiologic studies. Relevant publications were identified through electronic searches on PubMed, WorldCat, and Web of Science using keywords, "cortisol," "hair," "confounders," "chronic," "stress," and "correlates." Thirty-nine studies were included in this review. Notwithstanding scarce data and some inconsistencies, investigators have found hair cortisol concentrations to be associated with stress-related psychiatric symptoms and disorders (e.g., post-traumatic stress disorder), medical conditions indicating chronic activation of the hypothalamic-pituitary-adrenal axis (e.g., Cushing's syndrome), and other life situations associated with elevated risk of chronic stress (e.g., shiftwork). Results from some studies suggest that physical activity, adiposity, and substance abuse may be correlates of hair cortisol concentrations. In contrast to measures of short-term cortisol release (saliva, blood, and urine), cigarette smoking and use of oral contraceptives appear not to be associated with hair cortisol concentrations. Studies of pregnant women indicate increased hair cortisol concentrations across successive trimesters. The study of hair cortisol presents a unique opportunity to assess chronic alterations in cortisol concentrations in epidemiologic studies.

Tea polyphenol (-)-epigallocatechin-3-gallate inhibits nicotine- and estrogen-induced α9-nicotinic acetylcholine receptor upregulation in human breast cancer cells

SCOPE

The aim of this research was to explore whether the tea-polyphenol (-)-epigallocatechin-3-gallate (EGCG) could be used as a potential agent for blocking smoking (nicotine, Nic)- or hormone (estradiol, E2)-induced breast cancer cell proliferation through inhibition of a common signaling pathway.

METHODS AND RESULTS

To explore whether Nic (>0.1 μM, 24 h) and E2 (>1 nM, 24 h) significantly increased α9-nicotinic acetylcholine (α9-nicotinic acetylcholine receptor (nAChR)) mRNA and protein expression levels, real-time PCR and immunoblotting analysis experiments were performed in human breast cancer (MCF-7) cells. Luciferase promoter activity experiment was performed to test the α9-nAChR promoter activity affected by Nic, E2 or EGCG. The results indicate that treatment with EGCG (1 μM) profoundly decreases Nic- and E2-induced MCF-7 proliferation by down regulating α9-nAChR expression. The α9-nAChR promoter activity is significantly induced by 24-h treatment with Nic (10 μM) or E2 (10 nM) (>1.8 and ∼2.3-fold, respectively) in MCF-7 cells. Pretreatment with EGCG eliminated the Nic- and E2-induced α9-nAChR promoter-dependent luciferase activity. We further demonstrate that combined treatment with EGCG profoundly inhibits [3H]-Nic/ α9-nAChR binding activity in breast cancer cells.

CONCLUSIONS

We found that the EGCG could be used as an agent for blocking smoking (Nic)- or hormone (E2)-induced breast cancer cell proliferation by inhibiting of α9-nAChR signaling pathway. This study reveals the novel antitumor mechanisms of EGCG, and these results may have significant applications for chemopreventive purposes in human breast cancer.

Review. Neurobiology of nicotine dependence

Nicotine is a psychoactive ingredient in tobacco that significantly contributes to the harmful tobacco smoking habit. Nicotine dependence is more prevalent than dependence on any other substance. Preclinical research in animal models of the various aspects of nicotine dependence suggests a critical role of glutamate, gamma-aminobutyric acid (GABA), cholinergic and dopamine neurotransmitter interactions in the ventral tegmental area and possibly other brain sites, such as the central nucleus of the amygdala and the prefrontal cortex, in the effects of nicotine. Specifically, decreasing glutamate transmission or increasing GABA transmission with pharmacological manipulations decreased the rewarding effects of nicotine and cue-induced reinstatement of nicotine seeking. Furthermore, early nicotine withdrawal is characterized by decreased function of presynaptic inhibitory metabotropic glutamate 2/3 receptors and increased expression of postsynaptic glutamate receptor subunits in limbic and frontal brain sites, while protracted abstinence may be associated with increased glutamate response to stimuli associated with nicotine administration. Finally, adaptations in nicotinic acetylcholine receptor function are also involved in nicotine dependence. These neuroadaptations probably develop to counteract the decreased glutamate and cholinergic transmission that is hypothesized to characterize early nicotine withdrawal. In conclusion, glutamate, GABA and cholinergic transmission in limbic and frontal brain sites are critically involved in nicotine dependence.

Synthesis and pharmacological evaluation of novel 9- and 10-substituted cytisine derivatives. Nicotinic ligands of enhanced subtype selectivity

We report the synthesis and pharmacological properties of several cytisine derivatives. Among them, two 10-substituted derivatives showed much higher selectivities for the alpha4beta2 nAChR subtype in binding assays than cytisine. The 9-vinyl derivative was found to have a very similar agonist activity profile to that of cytisine.

Smoking, cortisol and nicotine

Cigarette smoking is associated acutely with elevated cortisol levels. However, the results of comparisons of cortisol levels in smokers and non-smokers have been inconsistent, and the significance of cortisol responses in smoking cessation is unclear. Here we describe one study comparing the cortisol profiles of smokers and nonsmokers over the day, and a second investigation in which cortisol was monitored during smoking cessation. In the first study, we collected saliva samples from 196 middle-aged men and women on working and weekend days repeatedly through the day. On both working and weekend days, cortisol levels were significantly higher in smokers after adjustment for age, gender and grade of employment. Cortisol responses to waking (the increase between waking and 30 min) were also greater in smokers. The elevation in cortisol among smokers is generally attributed to nicotine exposure. Nicotine replacement therapy substantially improves abstinence rates, and has become a standard component of smoking cessation treatments, but the effects of nicotine replacement on cortisol are not known. In the second study, cortisol was monitored over 6 weeks of abstinence in 112 smokers treated with behavioural support and 15 mg nicotine patches. Smoking cessation was accompanied by an abrupt decrease in salivary cortisol, and this was sustained over the abstinence period. There was a marginal association between the decrease in cortisol and smoking relapse rates. These results suggest that the nicotine supplied through patches was not sufficient to block the cortisol reduction following smoking cessation. The contribution of these findings to understanding the role of neuroendocrine function in smoking is described.