Including Nicotine Addiction Research Articles

Evaluating the effectiveness of recovery-oriented interventions for youth who vape nicotine: a systematic review protocol.

The increase in nicotine vaping among youth has emerged as a critical public health concern. Vaping among youth is linked to adverse health outcomes, including nicotine addiction, cardiovascular and pulmonary diseases and mental health challenges. Recently, there has been a growing demand for research to expand on treatments to enhance the recovery process from vaping nicotine in youth. To this date, no comprehensive review identifies all interventions available for vaping recovery and compares their effectiveness in youth. This proposed systematic review seeks to identify all recovery-oriented interventions for youth aged 10-24 that facilitate vaping recovery and evaluate the measured effectiveness. This review will serve to support healthcare practitioners, nurses and policymakers to further understand recovery interventions and aid in improving vaping recovery among youth. This protocol, registered with PROSPERO, adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocol (PRISMA-P) framework, and the final review will adhere to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines to ensure quality and replicability. The review will comprise studies including youth aged 10-24 engaging in nicotine vaping. A comprehensive search will be conducted across MEDLINE, Embase, PsycINFO, Scopus and CINAHL, with no restrictions on the date range due to the recency of the topic. Two independent reviewers will screen the identified research for eligibility at the title and abstract levels, with any disagreements resolved by a third reviewer. The review will include randomised control trials and quasi-experimental studies. Full-text review and data extraction will be standardised and completed by the primary researcher. Additionally, studies will be assessed for quality and potential biases. Given that this is a review of existing literature, no ethics approval is required. The focus on youth necessitates careful consideration of ethical standards. This review is committed to contributing responsibly to public health knowledge regarding youth vaping recovery. The results from this review will be disseminated through publication in an open-access, peer-reviewed journal and likely through posters and presentations at scientific conferences. CRD42024543994.

Effects of positive mGlu5 modulation on D2 signaling and nicotine-conditioned place preference: Mechanisms of epigenetic inheritance in a transgenerational model of drug abuse vulnerability in psychosis.

The metabotropic glutamate type 5 (mGlu5) receptor has emerged as a potential target for the treatment of psychosis that is suggested to have greater efficacy than antipsychotic medications that are currently utilized. This study sought to elucidate mechanisms of therapeutic action associated with the modulation of the mGlu5 receptor in a disordered system marked by dopamine dysfunction. We further explored epigenetic mechanisms contributing to heritable transmission of a psychosis-like phenotype in a novel heritable model of drug abuse vulnerability in psychosis. F1 generation male and female Sprague-Dawley rats that were the offspring of two neonatal quinpirole-treated (QQ) or two saline-treated (SS) animals were tested on nicotine-conditioned place preference (CPP). Regulators of G protein signaling 9 (RGS9) and β-arrestin 2 (βA2), which mediate dopamine (DA) D2 signaling, were measured in the nucleus accumbens shell, prelimbic and infralimbic cortices. Reduced Representation Bisulfite Sequencing (RRBS) was used to analyze the cytosine methylation in these brain regions. Pretreatment with the mGlu5-positive allosteric modulator 3-Cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (CDPPB) 20 min prior to conditioning trials blocked enhanced nicotine CPP and mitigated aberrant G protein-dependent and -independent signaling in QQ animals. RRBS analysis revealed region-specific changes in several pathways, including nicotine addiction, dopamine synapses, and neural connectivity. These results reveal an important region-specific mechanism of action for CDPPB in a system marked by enhanced DAD2 receptor signaling. Results additionally reveal DNA methylation as an epigenetic mechanism of heritability, further validating the current model as a useful tool for the study of psychosis and comorbid nicotine use.

The Effect of Cigarette Smoking Duration on Hemoglobin Level Measured with Cyanmethemoglobin Method

In Indonesia, cigarette consumption is quite prevalent and has been become more common over time. According to Riskesdas (Baseline Health Research from Agency of Health Research and Development) study in 2018, the national percentage of people aged who smoke increased from 2016-2018, namely from 3.39% in 2016, 3.9% in 2017 and 9.65% in 2018. Smoking habits will negatively affect human health. Cigarette smoke contains various of different chemicals that are harmful to health, including nicotine addiction, tar (carcinogen or cancer-causing), and carbon monoxide. When inhaled, they form carboxyhemoglobin with Hb (Hemoglobin). When this occurs, the amount of Hb available for oxygen transport is reduced. By way of compensation, the body will produce more red blood cells. The objective of the study was to determine the hemoglobin levels in smokers with smoking durations of 3 years, 4 years and 5 years. This study is quasi-experimental. Determine hemoglobin readings using a photometer 5010 with the Cyanmethemoglobin method. Up to 20 samples were analyzed with SPSS version 20 with Anova analysis at 95% confidence level. The results of statistical analysis showed p-value <0.05, which means that there is a significant effect between variables and vice versa. Hb level comparison between durations of smoking are of 3 years with an average value of 14.8, Hb levels of 4 years with an average value of 14.53, and Hb levels of 5 years with an average value 15.94. The results showed that there was an effect of smoking duration on the results of the examination of hemoglobin levels in smokers of 3,4 and 5 years with the greatest effect being smokers with a duration of 5 years. The duration of smoking impact on hemoglobin levels.

Nicotine addiction – a health problem in adolescents in a neurobiological context

Abstract Smoking is one of the leading causes of death which can be prevented in the developed countries. Smoking begins mainly in adolescence. Smoking in early adolescence is known to be associated with an increased risk of later addiction. Also the growing popularity of e-cigarettes, which attract young people with a variety of flavors, and are still little associated with harmful effects on health, unlike regular cigarettes. Exposure to nicotine in young people can affect learning, memory and attention, and lead to increased impulsivity, mood disorders and drug dependence. Nicotine and its derivatives are harmful to the human body, causing a significant increase in blood pressure, deterioration of blood supply to the vessels and acceleration of atherosclerotic processes, it has a detrimental effect on the gastric mucosa, causing gastric disorders. In addition, smoking is associated with the risk of many cancers: oral cavity, larynx, esophagus, lung, pancreas, kidney, liver and bladder. Nicotine addiction causes many health, social and financial consequences for the individual and the community as a whole. Multiple nicotine addiction risk SNPs were found in the CHRNA5/A3/B4 gene cluster, with the best reported results for the risk allele derived from the non-synonymous SNP, rs16969968, in CHRNA5. Therefore, in the problem of addiction, including nicotine addiction, it seems important to know the neurobiological factors, including genetic ones, involved in these processes. This could lead to the development of new pharmacological and behavioral treatment strategies in the future.

Biophysical characterization of lynx-nicotinic receptor interactions using atomic force microscopy.

Nicotinic acetylcholine receptors (nAChRs) are broadly expressed in the central and peripheral nervous systems, playing essential roles in cholinergic neurotransmission. The lynx family proteins, a subset of the Ly6/uPAR superfamily expressed in multiple brain regions, have been shown to bind to nAChRs and modulate their function via allosteric regulation. The binding interactions between lynx and nAChRs, however, have not been systematically quantified and compared. In this work, we characterized the interactions between lynx1 or lynx2 and α3β4‐ or α7‐nAChRs using single‐molecule atomic force microscopy (AFM). The AFM technique allows the quantification of the off‐rate of lynx‐nAChR binding and of the energetic barrier width between the bound state and transition state, providing a biophysical means to compare the selectivity of lynx proteins for nAChR subtypes. Results indicate that lynx1 has a marginal preference for α7‐ over α3β4‐nAChRs. Strikingly, lynx2 exhibits a two order of magnitude stronger affinity for α3β4‐ compared to α7‐nAChRs. Together, the AFM assay serves as a valuable tool for the biophysical characterization of lynx‐nAChR binding affinities. Revealing the differential affinities of lynx proteins for nAChR subtypes will help elucidate how lynx regulates nAChR‐dependent functions in the brain, including nicotine addiction and other critical pathways.

Interactions of Globular and Ribbon [γ4E]GID with α4β2 Neuronal Nicotinic Acetylcholine Receptor.

The α4β2 nAChR is implicated in a range of diseases and disorders including nicotine addiction, epilepsy and Parkinson’s and Alzheimer’s diseases. Designing α4β2 nAChR selective inhibitors could help define the role of the α4β2 nAChR in such disease states. In this study, we aimed to modify globular and ribbon α-conotoxin GID to selectively target the α4β2 nAChR through competitive inhibition of the α4(+)β2(−) or α4(+)α4(−) interfaces. The binding modes of the globular α-conotoxin [γ4E]GID with rat α3β2, α4β2 and α7 nAChRs were deduced using computational methods and were validated using published experimental data. The binding mode of globular [γ4E]GID at α4β2 nAChR can explain the experimental mutagenesis data, suggesting that it could be used to design GID variants. The predicted mutational energy results showed that globular [γ4E]GID is optimal for binding to α4β2 nAChR and its activity could not likely be further improved through amino-acid substitutions. The binding mode of ribbon GID with the (α4)3(β2)2 nAChR was deduced using the information from the cryo-electron structure of (α4)3(β2)2 nAChR and the binding mode of ribbon AuIB. The program FoldX predicted the mutational energies of ribbon [γ4E]GID at the α4(+)α4(−) interface, and several ribbon[γ4E]GID mutants were suggested to have desirable properties to inhibit (α4)3(β2)2 nAChR.

Cigarette smoke promotes oral leukoplakia via regulating glutamine metabolism and M2 polarization of macrophage

Oral immunosuppression caused by smoking creates a microenvironment to promote the occurrence and development of oral mucosa precancerous lesions. This study aimed to investigate the role of metabolism and macrophage polarization in cigarette-promoting oral leukoplakia. The effects of cigarette smoke extract (CSE) on macrophage polarization and metabolism were studied in vivo and in vitro. The polarity of macrophages was detected by flow cytometric analysis and qPCR. Liquid chromatography-mass spectrometry (LC-MS) was used to perform a metabolomic analysis of Raw cells stimulated with CSE. Immunofluorescence and flow cytometry were used to detect the polarity of macrophages in the condition of glutamine abundance and deficiency. Cell Counting Kit-8 (CCK-8), wound-healing assay, and Annexin V-FITC (fluorescein isothiocyanate)/PI (propidium iodide) double-staining flow cytometry were applied to detect the growth and transferability and apoptosis of Leuk-1 cells in the supernatant of Raw cells which were stimulated with CSE, glutamine abundance and deficiency. Hyperkeratosis and dysplasia of the epithelium were evident in smoking mice. M2 macrophages increased under CSE stimulation in vivo and in vitro. In total, 162 types of metabolites were detected in the CSE group. The metabolites of nicotine, glutamate, arachidic acid, and arginine changed significantly. The significant enrichment pathways were also selected, including nicotine addiction, glutamine and glutamate metabolism, and arginine biosynthesis. The results also showed that the supernatant of Raw cells stimulated by CSE could induce excessive proliferation of Leuk-1 and inhibit apoptosis. Glutamine abundance can facilitate this process. Cigarette smoke promotes oral leukoplakia via regulating glutamine metabolism and macrophage M2 polarization.

Genome-wide gene-smoking interaction study identified novel susceptibility loci for non-small cell lung cancer in Chinese populations.

Gene-smoking interactions play important roles in the development of non-small cell lung cancer (NSCLC). To identify single-nucleotide polymorphisms (SNPs) that modify the association of smoking behavior with NSCLC risk, we conducted a genome-wide gene-smoking interaction study in Chinese populations. The genome-wide interaction analysis between SNPs and smoking status (ever- versus never-smokers) was carried out using genome-wide association studies of NSCLC, which included 13 327 cases and 13 328 controls. Stratified analysis by histological subtypes was also conducted. We used a genome-wide significance threshold of 5 × 10-8 for identifying significant gene-smoking interactions and 1 × 10-6 for identifying suggestive results. Functional annotation was performed to identify potential functional SNPs and target genes. We identified three novel loci with significant or suggestive gene-smoking interaction. For NSCLC, the interaction between rs2746087 (20q11.23) and smoking status reached genome-wide significance threshold [odds ratio (OR) = 0.63, 95% confidence interval (CI): 0.54-0.74, P = 3.31 × 10-8], and the interaction between rs11912498 (22q12.1) and smoking status reached suggestive significance threshold (OR = 0.72, 95% CI: 0.63-0.82, P = 8.10 × 10-7). Stratified analysis by histological subtypes identified suggestive interactions between rs459724 (5q11.2) and smoking status (OR = 0.61, 95% CI: 0.51-0.73, P = 7.55 × 10-8) in the risk of lung squamous cell carcinoma. Functional annotation indicated that both classic and novel biological processes, including nicotine addiction and airway clearance, may modulate the susceptibility to NSCLC. These novel loci provide new insights into the biological mechanisms underlying NSCLC risk. Independent replication in large-scale studies is needed and experimental studies are warranted to functionally validate these associations.

Characterization of AN317, a novel selective agonist of α6β2-containing nicotinic acetylcholine receptors

Neuronal nicotinic acetylcholine receptors (nAChRs) are crucial mediators of central presynaptic, postsynaptic, and extrasynaptic signaling, and they are implicated in a range of CNS disorders. The numerous nAChR subtypes are differentially expressed and mediate distinct functions throughout the CNS, and thus there is considerable interest in developing subtype-selective nAChR modulators, both for use as pharmacological tools and as putative therapeutics. α6β2-containing (α6β2*) nAChRs are highly expressed in and regulate the activity of midbrain dopaminergic neurons, which makes them attractive drug targets in several psychiatric and neurological diseases, including nicotine addiction and Parkinson’s disease. This paper presents the preclinical characterization of AN317, a novel α6β2* agonist exhibiting functional selectivity toward other nAChRs, including α4β2, α3β4 and α7 receptors. AN317 induced [3H]dopamine release from rat striatal synaptosomes and augmented dopaminergic neuron activity in substantia nigra pars compacta brain slices in Ca2+ imaging and electrophysiological assays. In line with this, AN317 alleviated the high-frequency tremors arising from reserpine-mediated dopamine depletion in rats. Finally, AN317 mediated significant protective effects on cultured rat mesencephalic neurons treated with the dopaminergic neurotoxin MPP+. AN317 displays good bioavailability and readily crosses the blood–brain barrier, which makes it a unique tool for both in vitro and in vivo studies of native α6β2* receptors in the nigrostriatal system and other dopaminergic pathways. Altogether, these findings highlight the potential of selective α6β2* nAChR activation as a treatment strategy for symptoms and possibly even deceleration of disease progression in neurodegenerative diseases such as Parkinson’s disease.

Effects of lorcaserin (Belviq®) on nicotine- and food-maintained responding in non-human primates

BackgroundAccumulating evidence suggests that the FDA-approved serotonin 5-HT2C receptor agonist, lorcaserin (Belviq®), may be a promising candidate for the management of substance use disorders, including nicotine addiction. The present study was conducted to determine the efficacy and selectivity of acute or continuous lorcaserin treatment for decreasing the reinforcing effects of nicotine in a primate species. MethodsAdult rhesus monkeys (n=4) with a history of nicotine self-administration (>2years) responded for injections of nicotine (0.32–100μg/kg IV) or food pellets under a fixed-ratio schedule of reinforcement during daily 100-min sessions. When responding was stable, lorcaserin was administered either as an acute pretreatment (0.1–1.0mg/kg, IM) or by continuous infusion (0.1mg/kg/hr, SC for 3–5days). Daily activity patterns were also monitored immediately following experimental sessions. ResultsResults indicate that acute lorcaserin pretreatment produced significant and dose-dependent decreases in nicotine-maintained responding across a >100-fold range of self-administered nicotine doses. Continuous lorcaserin treatment decreased intake of 10μg/kg/inj nicotine to about 50% of baseline values. Food-maintained responding was only moderately decreased in 3 of 4 subjects after acute administration and unaffected in all subjects during continuous treatment. Daily activity also was significantly decreased—to ≤50% of control values—following experimental sessions in which acute lorcaserin was administered. ConclusionsThese data indicate that lorcaserin reduces IV self-administration of nicotine at a dose that decreases motoric activity but less consistently disrupts food-maintained responding. Further research into lorcaserin’s potential utility for the management of nicotine dependence is warranted.

The co-occurrence of nicotine and other substance use and addiction among youth and adults in the United States: implications for research, practice, and policy

ABSTRACTBackground: The increasing popularity of non-cigarette nicotine products, especially among youth, highlights the need for greater attention to their potential risks, including nicotine addiction and other substance use and addiction. Objectives: To examine the extent to which nicotine product use co-occurs with other substance use and addiction among youth and adults, describe the demographic groups and types of nicotine products associated with an increased risk of such co-occurrence, and discuss implications for research, prevention, clinical practice, and policy. Methods: Analyzing 2014 data from two nationally representative US surveys, the National Survey on Drug Use and Health (NSDUH) and the Monitoring the Future (MTF) study, we examined the co-occurrence between nicotine product use and alcohol and other drug use and addiction. Results: Individuals of all ages who reported using nicotine products of any kind were significantly more likely than nonusers to report alcohol, marijuana, other drug, and poly-substance use and to meet diagnostic criteria for a substance-use disorder. Users of multiple nicotine products generally were the most likely to engage in alcohol and other drug use and to be addicted to these other substances. Conclusions: The substantial co-occurrence of all forms of nicotine use and other substance use and addiction underscores the need to control the growing use of non-cigarette nicotine products among youth and to incorporate all forms of nicotine product use into substance use and addiction research, prevention, clinical practice, and policy efforts.

The changing tobacco landscape: What dental professionals need to know

BackgroundTobacco products in the United States and the patterns of tobacco use are changing. Although cigarette smoking prevalence has declined, dental professionals are likely to encounter substantial numbers of patients who have tried and are continuing to use new and alternative tobacco products, including cigars, water pipes (hookahs), and electronic cigarettes, as well as conventional and new smokeless tobacco products. MethodsThe authors reviewed conventional and new tobacco products in the United States, their adverse oral and systemic health effects, and their prevalence of use. ResultsTobacco products other than cigarettes account for a substantial portion of tobacco use. For this reason, tobacco-use prevention and cessation counseling provided by dental health care professionals must address all tobacco products, including cigarettes, cigars, water pipes, and electronic cigarettes, as well as conventional and new smokeless tobacco products. Cigarette smoking and smokeless tobacco use are associated with immediate and long-term adverse health effects, including nicotine addiction, oral and systemic disease, and death. Novel products may attract new tobacco users, potentially leading to addiction that results in enduring tobacco product use and associated adverse health effects. ConclusionsThis critical review of conventional, new, and emerging tobacco products presents information that dental professionals can use in providing tobacco-related counseling to patients who use or who are at risk for using tobacco products. Practical ImplicationsIt is essential that dental professionals are knowledgeable about tobacco products and are able to answer patients’ questions and provide them with evidence-based tobacco-related counseling. This information may prevent patients from initiating use or help reduce or cease use to avoid immediate and long-term adverse health effects, including nicotine addiction, oral and systemic disease, and death.

Nicotine-Upregulation of Alpha 7 nAChR in Xenopus Oocytes

The alpha 7 (α7) subtype of nAChR appears to play critical roles in learning, cognition, and various neuropathologies including nicotine addiction. Nicotine-upregulation of α7 Rs may play a significant role in the latter phenomenon. But whether nicotine-upregulation of α7 Rs reliably occurs, and its underlying mechanism(s), are largely unknown. Previous studies of α7 nAChRs heterologously expressed in Xenopus oocytes failed to observe nicotine-upregulation. These failures might have been due to intracellular accumulation of nicotine and its subsequent slow release from oocytes, resulting in desensitization of α7 Rs during functional assays. In our experiments, 12-14 hr exposure to nicotine (100 μM) 4-5 days post cRNA-injection (PI), followed by extensive washout, yielded statistically-significant ∼2-fold increases in peak α7 currents and net charge as determined by TEVC and α7-protein (by Western blot). Less-extensive washout, as well as 100 nM nicotine incubation, failed to produce upregulation. Instead, inactivated/desensitized currents were observed. GC/MS measurement of nicotine in the washout fluid confirmed that nicotine was continually released from oocytes. The concentration was ∼20 nM at 3-4 hr following washout onset, well in excess of the ∼ 3 nM IC50 value. Exposure of α7-expressing oocytes to cumulative washout fluid produced suppressed α7 currents (∼ 8% of controls). Similar to nicotine, methyllycaconitine, a cell-permeable competitive antagonist of α7 Rs, and carbachol, a stable membrane-impermeable agonist, also produced ∼ 2X-upregulation. However, ACh incubation (which can be hydrolyzed by the oocytes) failed to produce upregulation. We also found that chelation of intracellular Ca2+ by BAPTA-AM completely blocked nicotine upregulation. However, elimination of extracellular Ca2+ had no effect. These results suggest that persistent ligand-binding to α7 Rs (but not necessarily channel gating), leading to increases in [Ca2+]i, was critical for α7 R-upregulation. Several Ca2+-dependent signaling pathways were implicated in nicotine-upregulation of α7.

Pharmacogenetics of Nicotine Addiction: Role of Dopamine

The neurotransmitter dopamine (DA) plays a central role in addictive disorders, including nicotine addiction. Specific DA-related gene variants have been studied to identify responsiveness to treatment for nicotine addiction. Genetic variants in DRD2, DRD4, ANKK1, DAT1, COMT and DBH genes show some promise in informing personalized prescribing of smoking cessation pharmacotherapies. However, many trials studying these variants had small samples, used retrospective design or were composed of mainly self-identified Caucasian individuals. Furthermore, many of these studies lacked a comprehensive measurement of nicotine metabolism rate, did not assess the roles of sex or the menstrual cycle, and did not investigate the role of rare variants and/or epigenetic factors. Future work should be conducted addressing these limitations to more effectively utilize DA genetic information to unlock the potential of smoking cessation pharmacogenetics.

Nicotinic Receptors as Therapeutic Targets for Drug Addictive Disorders

Drug addiction is a chronic neuropsychiatric disorder which is characterized by a compulsion to take drugs and loss of control in limiting intake. The worldwide impact of drug addiction on morbidity and mortality is very high. Evidence from preclinical and clinical studies suggests that brain nicotinic acetylcholine receptors (nAChRs), play a critical role in various addictive disorders, including nicotine addiction and alcoholism. Thus, there is an increasing impetus in developing new therapeutics for addictive disorders by targeting brain nAChRs. This review highlights the important preclinical findings involving nAChR ligands in regulating nicotine, alcohol and other addictive drug-induced neurobiological changes in animal models and humans. A number of partial agonists or antagonists targeting nAChRs have shown therapeutic benefit in nicotine addiction and alcohol use disorders are also discussed. Furthermore, the role of nAChRs in other addictive disorders is reviewed. Overall, novel pharmacological agents that target brain nAChRs for future drug development are discussed.

Characterization of a Novel α-Conotoxin from Conus textile That Selectively Targets α6/α3β2β3 Nicotinic Acetylcholine Receptors

α6β2 Nicotinic acetylcholine receptors (nAChRs) expressed by dopaminergic neurons in the CNS are potential therapeutic targets for the treatment of several neuropsychiatric diseases, including nicotine addiction and Parkinson disease. However, recent studies indicate that the α6 subunit can also associate with the β4 subunit to form α6β4 nAChRs that are difficult to pharmacologically distinguish from α6β2, α3β4, and α3β2 subtypes. The current study characterized a novel 16-amino acid α-conotoxin (α-CTx) TxIB from Conus textile whose sequence is GCCSDPPCRNKHPDLC-amide as deduced from gene cloning. The peptide and an analog with an additional C-terminal glycine were chemically synthesized and tested on rat nAChRs heterologously expressed in Xenopus laevis oocytes. α-CTx TxIB blocked α6/α3β2β3 nAChR with an IC(50) of 28 nm. In contrast, the peptide showed little or no block of other tested subtypes at concentrations up to 10 μm. The three-dimensional solution structure of α-CTx TxIB was determined using NMR spectroscopy. α-CTx TxIB represents a uniquely selective ligand for probing the structure and function of α6β2 nAChRs.

Inactivity-induced increase in nAChRs upregulates Shal K+ channels to stabilize synaptic potentials

Long–term synaptic changes, which are essential for learning and memory, are dependent on homeostatic mechanisms that stabilize neural activity. Homeostatic responses have also been implicated in pathological conditions, including nicotine addiction. Although multiple homeostatic pathways have been described, little is known about how compensatory responses are tuned to prevent them from overshooting their optimal range of activity. We show that prolonged inhibition of nicotinic acetylcholine receptors (nAChRs), the major excitatory receptor in the Drosophila CNS, results in a homeostatic increase in the Dα7 nAChR. This response then induces an increase in the transient A–type K+ current carried by Shal/Kv4 channels. While increasing Dα7 boosts mEPSCs, the ensuing increase in Shal channels serves to stabilize postsynaptic potentials. This identifies a novel mechanism to fine–tune the homeostatic response.

Nicotinic α5 receptor subunit mRNA expression is associated with distant 5′ upstream polymorphisms

CHRNA5, encoding the nicotinic α5 subunit, is implicated in multiple disorders, including nicotine addiction and lung cancer. Previous studies demonstrate significant associations between promoter polymorphisms and CHRNA5 mRNA expression, but the responsible sequence variants remain uncertain. To search for cis-regulatory variants, we measured allele-specific mRNA expression of CHRNA5 in human prefrontal cortex autopsy tissues and scanned the CHRNA5 locus for regulatory variants. A cluster of six frequent single-nucleotide polymorphisms (rs1979905, rs1979906, rs1979907, rs880395, rs905740, and rs7164030), in complete linkage disequilibrium (LD), fully account for a >2.5-fold allelic expression difference and a fourfold increase in overall CHRNA5 mRNA expression. This proposed enhancer region resides more than 13 kilobases upstream of the CHRNA5 transcription start site. The same upstream variants failed to affect CHRNA5 mRNA expression in peripheral blood lymphocytes, indicating tissue-specific gene regulation. Other promoter polymorphisms were also correlated with overall CHRNA5 mRNA expression in the brain, but were inconsistent with allelic mRNA expression ratios, a robust and proximate measure of cis-regulatory variants. The enhancer region and the nonsynonymous polymorphism rs16969968 generate three main haplotypes that alter the risk of developing nicotine dependence. Ethnic differences in LD across the CHRNA5 locus require consideration of upstream enhancer variants when testing clinical associations.

Understanding of nicotinic acetylcholine receptors

Understanding of nicotinic acetylcholine receptors

An Allosteric Modulator of α7 Nicotinic Receptors, N-(5-Chloro-2,4-dimethoxyphenyl)-N′-(5-methyl-3-isoxazolyl)-urea (PNU-120596), Causes Conformational Changes in the Extracellular Ligand Binding Domain Similar to Those Caused by Acetylcholine

Nicotinic acetylcholine receptors are implicated in several neuropsychiatric disorders, including nicotine addiction, Alzheimer's, schizophrenia, and depression. Therefore, they represent a critical molecular target for drug development and targeted therapeutic intervention. Understanding the molecular mechanisms by which allosteric modulators enhance activation of these receptors is crucial to the development of new drugs. We used the substituted cysteine accessibility method to study conformational changes induced by the positive allosteric modulator N-(5-chloro-2,4-dimethoxyphenyl)-N'-(5-methyl-3-isoxazolyl)-urea (PNU-120596) in the extracellular ligand binding domain of alpha7 nicotinic receptors carrying the L247T mutation. PNU-120596 caused changes in cysteine accessibility at the inner beta sheet, transition zone, and agonist binding site. These changes in accessibility are similar to but not identical to those caused by ACh alone. In particular, PNU-120596 induced changes in MTSEA accessibility at N170C (in the transition zone) that were substantially different from those evoked by acetylcholine (ACh). We found that PNU-120596 induced changes at position E172C in the absence of allosteric modulation. We identified a cysteine mutation of the agonist binding site (W148C) that exhibited an unexpected phenotype in which PNU-120596 acts as a full agonist. In this mutant, ACh-evoked currents were more sensitive to thiol modification than PNU-evoked currents, suggesting that PNU-120596 does not bind at unoccupied agonist-binding sites. Our results provide evidence that binding sites for PNU-120596 are not in the agonist-binding sites and demonstrate that positive allosteric modulators such as PNU-120596 enhance agonist-evoked gating of nicotinic receptors by eliciting conformational effects that are similar but nonidentical to the gating conformations promoted by ACh.