Nicotinic Cholinergic Receptors Research Articles

Cholinergic Mechanisms in Gastrointestinal Neoplasia.

Acetylcholine-activated receptors are divided broadly into two major structurally distinct classes: ligand-gated ion channel nicotinic and G-protein-coupled muscarinic receptors. Each class encompasses several structurally related receptor subtypes with distinct patterns of tissue expression and post-receptor signal transduction mechanisms. The activation of both nicotinic and muscarinic cholinergic receptors has been associated with the induction and progression of gastrointestinal neoplasia. Herein, after briefly reviewing the classification of acetylcholine-activated receptors and the role that nicotinic and muscarinic cholinergic signaling plays in normal digestive function, we consider the mechanics of acetylcholine synthesis and release by neuronal and non-neuronal cells in the gastrointestinal microenvironment, and current methodology and challenges in measuring serum and tissue acetylcholine levels accurately. Then, we critically evaluate the evidence that constitutive and ligand-induced activation of acetylcholine-activated receptors plays a role in promoting gastrointestinal neoplasia. We focus primarily on adenocarcinomas of the stomach, pancreas, and colon, because these cancers are particularly common worldwide and, when diagnosed at an advanced stage, are associated with very high rates of morbidity and mortality. Throughout this comprehensive review, we concentrate on identifying novel ways to leverage these observations for prognostic and therapeutic purposes.

Microdose lithium improves behavioral deficits and modulates molecular mechanisms of memory formation in female SAMP-8, a mouse model of accelerated aging.

Alzheimer's disease (AD) is the most common neuronal disorder that leads to the development of dementia. Until nowadays, some therapies may alleviate the symptoms, but there is no pharmacological treatment. Microdosing lithium has been used to modify the pathological characteristics of the disease, with effects in both experimental and clinical conditions. The present work aimed to analyze the effects of this treatment on spatial memory, anxiety, and molecular mechanisms related to long-term memory formation during the aging process of a mouse model of accelerated aging (SAMP-8). Female SAMP-8 showed learning and memory impairments together with disruption of memory mechanisms, neuronal loss, and increased density of senile plaques compared to their natural control strain, the senescence-accelerated mouse resistant (SAMR-1). Chronic treatment with lithium promoted memory maintenance, reduction in anxiety, and maintenance of proteins related to memory formation and neuronal density. The density of senile plaques was also reduced. An increase in the density of gamma-aminobutyric acid A (GABAA) and α7 nicotinic cholinergic receptors was also observed and related to neuroprotection and anxiety reduction. In addition, this microdose of lithium inhibited the activation of glycogen synthase kinase-3beta (GSK-3β), the classical mechanism of lithium cell effects, which could contribute to the preservation of the memory mechanism and reduction in senile plaque formation. This work shows that lithium effects in neuroprotection along the aging process are not related to a unique cellular mechanism but produce multiple effects that slowly protect the brain along the aging process.

Nicotinic Acetylcholine Receptors in Glial Cells as Molecular Target for Parkinson's Disease.

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by resting tremor, bradykinesia, rigidity, and postural instability that also includes non-motor symptoms such as mood dysregulation. Dopamine (DA) is the primary neurotransmitter involved in this disease, but cholinergic imbalance has also been implicated. Current intervention in PD is focused on replenishing central DA, which provides remarkable temporary symptomatic relief but does not address neuronal loss and the progression of the disease. It has been well established that neuronal nicotinic cholinergic receptors (nAChRs) can regulate DA release and that nicotine itself may have neuroprotective effects. Recent studies identified nAChRs in nonneuronal cell types, including glial cells, where they may regulate inflammatory responses. Given the crucial role of neuroinflammation in dopaminergic degeneration and the involvement of microglia and astrocytes in this response, glial nAChRs may provide a novel therapeutic target in the prevention and/or treatment of PD. In this review, following a brief discussion of PD, we focus on the role of glial cells and, specifically, their nAChRs in PD pathology and/or treatment.

Current Progress on Central Cholinergic Receptors as Therapeutic Targets for Alzheimer's Disease.

Acetylcholine (ACh) is ubiquitously present in the nervous system and has been involved in the regulation of various brain functions. By modulating synaptic transmission and promoting synaptic plasticity, particularly in the hippocampus and cortex, ACh plays a pivotal role in the regulation of learning and memory. These procognitive actions of ACh are mediated by the neuronal muscarinic and nicotinic cholinergic receptors. The impairment of cholinergic transmission leads to cognitive decline associated with aging and dementia. Therefore, the cholinergic system has been of prime focus when concerned with Alzheimer's disease (AD), the most common cause of dementia. In AD, the extensive destruction of cholinergic neurons occurs by amyloid-β plaques and tau protein-rich neurofibrillary tangles. Amyloid-β also blocks cholinergic receptors and obstructs neuronal signaling. This makes the central cholinergic system an important target for the development of drugs for AD. In fact, centrally acting cholinesterase inhibitors like donepezil and rivastigmine are approved for the treatment of AD, although the outcome is not satisfactory. Therefore, identification of specific subtypes of cholinergic receptors involved in the pathogenesis of AD is essential to develop future drugs. Also, the identification of endogenous rescue mechanisms to the cholinergic system can pave the way for new drug development. In this article, we discussed the neuroanatomy of the central cholinergic system. Further, various subtypes of muscarinic and nicotinic receptors involved in the cognition and pathophysiology of AD are described in detail. The article also reviewed primary neurotransmitters that regulate cognitive processes by modulating basal forebrain cholinergic projection neurons.

Structural basis for the recognition of anthelmintic activity of bioactive metabolite in watery rose apple leaf through in silico investigation

This research is part of the research umbrella regarding the use of watery rose apple leaf [Eugenia aqueum (Burm. F) Alston] in the health sector. Infectious diseases of worms, are still a health problem with a high burden based on the incidence and mortality rates in Southeast Asian countries. Therefore, we tried to create a 3D structure of vital receptors of worms including Nicotinic Cholinergic Receptor (NCR), Acetylcholinesterase Enzymes (AE), and Phosphorylase Enzymes (PE) using homology modeling method through the SWISS-MODEL webserver, then conducted a molecular dynamics simulations using active metabolite of watery rose apple leaf i.e. 2',4'‑dihydroxy‑6'‑methoxy‑3',5'‑dimethylchalcone which was then compared with Piperazine Citrate and Pyrantel Pamoate which are anthelmintic drugs on the market. Based on the results of the study, the structure of the three receptors with high resolution was successfully obtained which was characterized by a good Ramachandran value, which was above 90%. Then the ligand structure was successfully modeled in a three-dimensional model and optimized geometrically using GaussView 5.0.8 and Gaussian09 software. In further, Root Mean Square Deviation (RMSD) and Root Mean Square Fluctuation (RMSF) analysis of molecular dynamics simulations ligand against the three receptors, compound 2',4'‑dihydroxy‑6'‑methoxy‑3',5'‑dimethylchalcone showed better stability than Piperazine Citrate and Pyrantel Pamoate at 50 ns simulation, although from the calculation of binding free energy Molecular Mechanics Poisson-Boltzmann Surface Area (MM/PBSA) is not better than the two comparisons. It can be concluded that the compound 2',4'‑dihydroxy‑6'‑methoxy‑3',5'‑dimethylchalcone from watery rose apple leaf showed potential as anthelmintic candidates. Communicated by Ramaswamy H. Sarma

Hypothalamic inflammation and the development of an obese phenotype induced by high-fat diet consumption is exacerbated in alpha7 nicotinic cholinergic receptor knockout mice

Hypothalamic inflammation and metabolic changes resulting from the consumption of high-fat diets have been linked to low grade inflammation and obesity. Inflammation impairs the hypothalamic expression of α7 nicotinic acetylcholine receptor (α7nAChR). The α7nAChR is described as the main component of the anti-inflammatory cholinergic pathway in different inflammation models. To assess whether the reduction in α7nAChR expression exacerbates hypothalamic inflammation induced by a high-fat diet (HFD), were used male and female global α7nAChR knockout mouse line in normal or high-fat diet for 4 weeks. Body weight gain, adiposity, glucose homeostasis, hypothalamic inflammation, food intake, and energy expenditure were evaluated. Insulin sensitivity was evaluated in neuronal cell culture. Consumption of an HFD for 4 weeks resulted in body weight gain and adiposity in male Chrna7-/- mice and the hypothalamus of male Chrna7-/- mice showed neuroinflammatory markers, with increased gene expression of pro-inflammatory cytokines and dysregulation in the nuclear factor kappa B pathway. Moreover, male Chrna7-/- mice consuming an HFD showed alterations in glucose homeostasis and serum of Chrna7-/- mice that consumed an HFD impaired insulin signalling in neuronal cell culture experiments. In general, female Chrna7-/- mice that consumed an HFD did not show the phenotypic and molecular changes found in male mice, indicating that there is sexual dimorphism in the analysed parameters. Thus, receptor deletion resulted in increased susceptibility to hypothalamic inflammation and metabolic damage associated with HFD consumption in male mice.

Non-neuronal acetylcholine is causal for cardioprotection by hypoxic preconditioning in adult rat cardiomyocytes

Abstract Introduction Brief episodes of non-lethal myocardial ischemia/reperfusion preceding more sustained ischemia and reperfusion reduce lethal ischemia/reperfusion injury. The underlying protective signaling mechanisms of such ischemic preconditioning are unclear in their details. Among other protective mediators, neuronal acetylcholine (ACh) and its signaling through cholinergic receptors is involved in protection by ischemic preconditioning. Recently, a non-neuronal cardiac cholinergic system (NNCCS) has been identified, suggesting that a nervous system-independent, cardiomyocyte-derived acetylcholine signaling with signal amplification by auto- and paracrine cholinergic receptor activation could also participate in ischemic preconditioning. Aim We aimed to examine the role of NNCCS-derived ACh as a mediator of ischemic preconditioning. We therefore, in a reductionist approach, used isolated adult cardiomyocytes with hypoxic preconditioning (HPC). Methods Adult ventricular rat cardiomyocytes were isolated (from n=9 hearts), and HPC was induced by one cycle of 10 min hypoxia / 20 min reoxygenation. Thirty min normoxia served as control. Cardiomyocytes were then exposed to 30 min sustained hypoxia / 5 min reoxygenation (H/R), or a 35 min time control (TC). Cardiomyocyte viability was quantified before and after H/R or TC, respectively, by trypan blue staining. In a subgroup of experiments (cardiomyocytes from n=6 hearts) in the presence of physostigmine (0.2 mmol/L), intracellular ACh was quantified before and after HPC or normoxia and after sustained hypoxia and reoxygenation or TC, respectively, via liquid chromatography-coupled tandem mass spectrometry. Experiments on cardiomyocyte viability (from n=9 hearts) were repeated with the addition of cholinergic receptor antagonists (nicotinic: hexamethonium [1 µmol/L], muscarinic: atropine [0.1 µmol/L]) a) during the first 30 min with HPC or normoxia, b) during H/R or TC (30-65 min), or c) throughout the total 65 min protocol. Results The viability of cardiomyocytes subjected to H/R was better preserved with HPC than without (Figure A), and intracellular ACh was increased during hypoxia after prior HPC (Figure B). Cholinergic receptor antagonists during HPC did not change HPC´s protection (Figure A). However, the combination of both antagonists during sustained hypoxia abrogated HPC´s protection (Figure A), whereas nicotinic or muscarinic cholinergic receptor antagonists alone did not. Cholinergic receptor antagonists throughout the total 65 min also abrogated HPC´s protection (Figure A). Conclusion: The NNCCS is activated by HPC and causal for HPC´s protection. HPC increases intracellular acetylcholine, and cardiomyocyte protection is mediated via both nicotinic and muscarinic cholinergic receptors, suggesting an auto- and paracrine signal amplification on the cardiomyocyte level.Figure

COMPUTER-AIDED DESIGN OF MUSCARINIC ACETYLCHOLINE RECEPTOR M3 INHIBITORS: PROMISING COMPOUNDS AMONG TRIFLUOROMETHYL CONTAINING HEXAHYDROPYRIMIDINONES/THIONES.

The new high selective mAChRs M3 inhibitors with IC 50 in nanomolecular ranges, which can be the prototypes for effective COPD and asthma treatment drugs, were discovered with computational approaches among trifluoromethyl containing hexahydropyrimidinones/thiones. Compounds [6-(4-ethoxy-3-methoxy-phenyl)-4-hydroxy-2-thioxo-4-(trifluoromethyl)hexahydropyrimidin-5-yl]-phenyl-methanone (THPT-1) and 5-benzoyl-6-(3,4-dimethoxyphenyl)-4-hydroxy-4-(trifluoromethyl)hexahydropyrimidin-2-one (THPO-4) have been proved to be a highly effective (with IC 50 values of 1.62·10 -7 M and 3.09·10 -9 M, respectively) at the same concentrations significantly competitive inhibit the signal conduction through mAChR3 in comparison with ipratropium bromide, without significant effect on mAChR2, nicotinic cholinergic and adrenergic receptors.

Dose-dependent effects of GAT107, a novel allosteric agonist-positive allosteric modulator (ago-PAM) for the α7 nicotinic cholinergic receptor: a BOLD phMRI and connectivity study on awake rats.

Alpha 7 nicotinic acetylcholine receptor (α7nAChR) agonists have been developed to treat schizophrenia but failed in clinical trials due to rapid desensitization. GAT107, a type 2 allosteric agonist-positive allosteric modulator (ago-PAM) to the α7 nAChR was designed to activate the α7 nAChR while reducing desensitization. We hypothesized GAT107 would alter the activity of thalamocortical neural circuitry associated with cognition, emotion, and sensory perception. The present study used pharmacological magnetic resonance imaging (phMRI) to evaluate the dose-dependent effect of GAT107 on brain activity in awake male rats. Rats were given a vehicle or one of three different doses of GAT107 (1, 3, and 10 mg/kg) during a 35 min scanning session. Changes in BOLD signal and resting state functional connectivity were evaluated and analyzed using a rat 3D MRI atlas with 173 brain areas. GAT107 presented with an inverted-U dose response curve with the 3 mg/kg dose having the greatest effect on the positive BOLD volume of activation. The primary somatosensory cortex, prefrontal cortex, thalamus, and basal ganglia, particularly areas with efferent connections from the midbrain dopaminergic system were activated as compared to vehicle. The hippocampus, hypothalamus, amygdala, brainstem, and cerebellum showed little activation. Forty-five min post treatment with GAT107, data for resting state functional connectivity were acquired and showed a global decrease in connectivity as compared to vehicle. GAT107 activated specific brain regions involved in cognitive control, motivation, and sensory perception using a BOLD provocation imaging protocol. However, when analyzed for resting state functional connectivity there was an inexplicable, general decrease in connectivity across all brain areas.

Long‐term nicotine treatment of mild cognitive impairment (The MIND Study): Baseline characteristics and study progress

AbstractBackgroundCognitive decline in AD/MCI is related to loss of cholinergic neurons. However, inhibition of acetylcholine degradation has not slowed progression. Treatment directly targeting nicotinic cholinergic receptors may be more helpful. We have shown proof of concept in a 6‐month multicenter trial that transdermal nicotine provides significant improvement in attention, episodic memory, and global ratings of functioning with minimal side effects in MCI. A larger and longer (2‐year) trial is underway to determine the persistence of improvement and attenuation of cognitive decline.MethodMCI participants were randomized 1:1 to either transdermal nicotine, beginning at 3.5 mg/day, increasing to 21 mg/day or matching placebo by 5 weeks. Participants were assessed at 0, 3, 6, 12, 18, and 24 months, with a subset undergoing MRI scans at 0, 12, and 24 months, and CSF collection at 0 and 24 months. Primary cognitive outcomes included reaction time standard error change‐from‐baseline (Connors CPT) for attention and delayed word recall (Cogstate) for memory. Primary clinical outcome is the CGIC. Secondary clinical measures include behavioral/functional scales and the CDR‐SOB. An MRI substudy is examining possible neural mechanisms.ResultTo date, 663 participants were screened and 309 were randomized including 133 females (43%) and 176 males (57%). Mean age was 73.7±7.1, education 16±2.8 years. Mean MMSE was 27.4±1.8 and CDR Global was 0.5. Randomization of ethnoracial underrepresented populations (URPs) was 9.4% (Black/African‐American 4%, Asian 2%, Hispanic/Latinx 3%). Treatment/Study discontinuations were higher than expected at 29% due in part to pandemic‐related disruptions. There are 87 completers thus far. Baseline MRI scans are 59 and LPs are 37. Safety results show that treatment has been generally well tolerated with no SAEs definitively or probably tied to study participation or investigational product thus far.ConclusionIf the hypotheses are validated, this will support a novel, broadly available, and inexpensive repurposed intervention for MCI and would encourage early treatment to improve symptoms, attenuate progression of cognitive impairment, and lead to combined trials with agents that interact with Aβ, tau or other mechanisms. Low URP recruitment and higher dropout rate remain challenging and will be specifically addressed in recruitment/enrollment/retention efforts moving forward.

Developmental exposure of zebrafish to neonicotinoid pesticides: Long-term effects on neurobehavioral function

Neonicotinoid compounds are commonly used insecticides which have become increasingly used as replacements of older generations of insecticides, such as organophosphates. Given the established neurotoxicity of cholinergic toxicants, developmental neurotoxicity studies are needed to identify in vertebrate species the potential toxicity of these insecticides which act on nicotinic cholinergic receptors. Previously, developmental exposure to a neonicotinoid insecticide imidacloprid was shown to cause persisting neurobehavioral toxicity in zebrafish. The current study evaluated neurobehavioral effects of embryonic exposure to two other neonicotinoid insecticides, clothianidin (1–100 µM) and dinotefuran (1–100 µM) in zebrafish (5–120 h post-fertilization), concentrations below the threshold for increased lethality and overt dysmorphogenesis. Neurobehavioral tests were conducted at larval (6 days), adolescent (10 weeks) and adult (8 months) ages. Both compounds caused short-term behavioral effects on larval motility, although these effects were distinct from one another. At a lower concentration (1 µM) clothianidin increased dark-induced locomotor stimulation the second time the lights turned off, while a higher concentration (100 µM) reduced activity in the dark at its second presentation. By contrast, dinotefuran (10–100 µM) caused a general decrease in locomotion. Specific longer-term neurobehavioral toxicity after early developmental exposure was also seen. clothianidin (100 µM) reduced locomotor activity in the novel tank in adolescence and adulthood, as well as reduced baseline activity in the tap startle test (1–100 µM) and reduced activity early (1–10 µM) or throughout the predator avoidance test session (100 µM). In addition to locomotor effects, clothianidin altered the diving response in a dose-, age- and time-block-dependent manner (1 µM, 100 µM), causing fish to remain further away from a fast predator cue (100 µM) relative to controls. Dinotefuran produced comparatively fewer effects, increasing the diving response in adulthood (10 µM), but not adolescence, and suppressing initial locomotor activity in the predator avoidance test (1–10 µM). These data indicate that neonicotinoid insecticides may carry some of the same risks for vertebrates posed by other classes of insecticides, and that these adverse behavioral consequences of early developmental exposure are evident well into adulthood.

Optogenetic stimulation of the brainstem dorsal motor nucleus ameliorates acute pancreatitis.

Inflammation is an inherently self-amplifying process, resulting in progressive tissue damage when unresolved. A brake on this positive feedback system is provided by the nervous system which has evolved to detect inflammatory signals and respond by activating anti-inflammatory processes, including the cholinergic anti-inflammatory pathway mediated by the vagus nerve. Acute pancreatitis, a common and serious condition without effective therapy, develops when acinar cell injury activates intrapancreatic inflammation. Prior study has shown that electrical stimulation of the carotid sheath, which contains the vagus nerve, boosts the endogenous anti-inflammatory response and ameliorates acute pancreatitis, but it remains unknown whether these anti-inflammatory signals originate in the brain. Here, we used optogenetics to selectively activate efferent vagus nerve fibers originating in the brainstem dorsal motor nucleus of the vagus (DMN) and evaluated the effects on caerulein-induced pancreatitis. Stimulation of the cholinergic neurons in the DMN significantly attenuates the severity of pancreatitis as indicated by reduced serum amylase, pancreatic cytokines, tissue damage, and edema. Either vagotomy or silencing cholinergic nicotinic receptor signaling by pre-administration of the antagonist mecamylamine abolishes the beneficial effects. These results provide the first evidence that efferent vagus cholinergic neurons residing in the brainstem DMN can inhibit pancreatic inflammation and implicate the cholinergic anti-inflammatory pathway as a potential therapeutic target for acute pancreatitis.

Double dissociation of perirhinal nicotinic acetylcholine receptors and dopamine D2 receptors in modulation of object memory consolidation by nicotine, cocaine and their conditioned stimuli

There are indications that drug conditioned stimuli (CS) may activate neurochemical systems of memory modulation that are activated by the drugs themselves. To directly test this hypothesis, a cholinergic nicotinic receptor antagonist (mecamylamine; MEC: 0, 10 or 30 µg/side) and a dopamine D2 receptor antagonist (l-741,626: 0, 0.63, 2.5 µg/side) were infused in the perirhinal cortex (PRh) to block modulation of object recognition memory consolidation induced by 0.4 mg/kg nicotine, 20 mg/kg cocaine, or their CSs. To establish these CSs, male Sprague-Dawley rats were confined for 2 h in a chamber, the CS+, after injections of 0.4 mg/kg nicotine, or 20 mg/kg cocaine, and in another chamber, the CS−, after injections of vehicle. This was repeated over 10 days (5 drug/CS+ and 5 vehicle/CS− pairings in total). It was found that the memory enhancing action of post-sample nicotine was blocked by intra-PRh infusions of both MEC doses, and 30 µg/side MEC also blocked the memory enhancing action of the nicotine CS. Interestingly, intra-PRh MEC did not block the memory enhancing effect of cocaine, nor that of the cocaine CS. In contrast, the memory enhancing action of post-sample cocaine administration was blocked by both l-741,626 doses, and 2.5 µg/side also blocked the effect of the cocaine CS, but not the memory effects of nicotine or of the nicotine CS. This functional double dissociation strongly indicates that drug CSs modulate memory consolidation by activating neural systems that are activated by the drugs themselves.

Smoking Cessation and Benefits to Cardiovascular Health: A Review of Literature.

Tobacco smoking is a chief cause of preventable deaths worldwide, accounting for various cancers, cardiovascular and respiratory diseases. Tobacco smoking accounts for more than seven million deaths every year. Worldwide statistics show that about 1.1 billion active smokers exist; 80% live in low- and middle-income countries. Nicotine is the addictive ingredient with the least harm compared to other active ingredients in tobacco, albeit not completely benign. Nicotine acts on the nicotinic cholinergic receptors (nAChRs) and produces the release of neurotransmitters. The mechanism by which it affects the cardiovascular system involves endothelial dysfunction by reducing nitrogen monoxide production, pro-thrombotic conditions, and activating inflammatory routes. These factors, along with the increased amounts of coronary atherosclerosis, have addictive adverse effects. Smoking has been shown to cause increased amounts of coronary atherosclerosis which may be responsible for the increased risk of hypertension, coronary heart disease, and atrial fibrillation, potentially contributing to the association of current smokers with a higher incidence of heart failure. This has led to worsened burdens and outcomes of cardiovascular disease among smokers. Smoking cessation has been associated with a reduction in cardiovascular mortality. This ranges from the reduction in the incidence of hypertension, type 2 diabetes, and heart failure. As regards behavioral and mental health, smoking cessation reduces the risk of cardiovascular disease in people experiencing mental illness. The prevalence of smoking continues to trend downward over the past couple of decades. Despite this downtrend, cigarette smoking is responsible for approximately half a million deaths per year in the United States and billions of dollars spent in healthcare. This buttresses the need to explore the various effects of smoking cessation on cardiovascular health and suggest ways to curb the disease burden.

You Don't Know Nicotine: Novel Applications of Nicotinic Therapeutics in Aging

Overall AbstractNicotine binds to nicotinic cholinergic receptors in the brain and the periphery. These receptors are ligand-gated ion channels that modulate other neurotransmitter systems and have important roles in cognitive and emotional functioning. Recent advances have expanded the understanding of how stimulation or blockade of nicotinic receptors affects brain activity, cortical networks, and behavior. While nicotine has been mostly thought of as a substance of abuse connected to tobacco smoking, the potential exists for utilizing nicotine and/or nicotinic stimulation as a therapeutic agent for the treatment of a variety of brain disorders. This symposium will present recent advances in the understanding of how nicotine and nicotinic drugs affect the brain and explore the possible utilization of nicotine for age-related brain disorders. While nicotinic therapeutics has a history dating back to the 1920s, work began in earnest in the 1980s with examining nicotine in Alzheimer's disease. This continued with the development of receptor-selective nicotinic agonists targeted towards Alzheimer’ disease, ADHD, and schizophrenia. These efforts failed, in part because of limited understanding of the appropriate brain system neural targets as well as lack of clarity as to whether the drugs engaged these targets in a meaningful way.Recent research has significantly expanded our understanding of the neural circuitry affected by nicotine and nicotinic stimulation and better human and animal models have offered new insights into the potential for nicotine therapeutics in areas as disparate as hearing loss and stress response mechanisms. Nicotine is now being investigated for its potential in age-related disorders including memory impairment, late life depression, cognitive impairment following cancer treatment and COVID, and age-related hearing loss. The symposium will examine how the effects of nicotine on cognitive functioning differ between older versus younger individuals to explore how nicotinic stimulation benefits may be age specific. We will also present the background and progress of the MIND study, a multi-center nicotine treatment study for mild cognitive impairment, the largest and longest nicotine study of non-smokers ever conducted. New clinical and neural evidence for nicotine as an augmentation treatment for late life depression and the cognitive deficits that accompany this condition will be discussed. Finally, the use of translational animal-human models for discerning the potential beneficial effects of nicotine and the potential for combination therapies to enhance the beneficial effects of nicotine will be presented. These studies of nicotine have broad clinical and scientific significance. If the hypotheses are validated, this will support a novel, broadly available, and inexpensive repurposed intervention for age-related brain disorders and would encourage early treatment to improve symptoms, retard progression of cognitive impairment or improve mood, and lead to combined trials with other agents for brain disorders of aging.

Different peripheral expression patterns of the nicotinic acetylcholine receptor in dementia with Lewy bodies and Alzheimer’s disease

BackgroundThe diffuse distribution of nicotinic cholinergic receptors (nAChRs) in both brain and peripheral immune cells points out their involvement in several pathological conditions. Indeed, the deregulated function of the nAChR was previously correlated with cognitive decline and neuropsychiatric symptoms in Alzheimer’s disease (AD) and Dementia with Lewy bodies (DLB).The evaluation in peripheral immune cells of nAChR subtypes, which could reflect their expression in brain regions, is a prominent investigation area.ObjectivesThis study aims to evaluate the expression levels of both the nAChR subunits and the main known inflammatory cytokines in peripheral blood mononuclear cells (PBMCs) of patients with DLB and AD to better characterize their involvement in these two diseases.ResultsHigher gene expression levels of TNFα, IL6 and IL1β were observed in DLB and AD patients in comparison with healthy controls (HC). In our cohort, a reduction of nAChRα4, nAChRβ2 and nAChRβ4 was detected in both DLB and AD with respect to HC. Considering nAChR gene expressions in DLB and AD, significant differences were observed for nAChRα3, nAChRα4, nAChRβ2 and nAChRβ4 between the two groups. Moreover, the acetylcholine esterase (AChE) gene expression was significantly higher in DLB than in AD. Correlation analysis points out the relation between different nAChR subtype expressions in DLB (nAChRβ2 vs nAChRα3; nAChRα4 vs nAChRα3) and AD (nAChRα4 vs nAChRα3; nAChRα4 vs nAChRβ4; nAChRα7 vs nAChRα3; nAChRα7 vs nAChRα4).ConclusionsDifferent gene expressions of both pro-inflammatory cytokines and nAChR subtypes may represent a peripheral link between inflammation and neurodegeneration. Inflammatory cytokines and different nAChRs should be valid and accurate peripheral markers for the clinical diagnosis of DLB and AD. However, although nAChRs show a great biological role in the regulation of inflammation, no significant correlation was detected between nAChR subtypes and the examined cytokines in our cohort of patients.

Muscarinic and Nicotinic Acetylcholine Receptors in the Regulation of the Cardiovascular System

Many different receptors and ion channels regulating ion currents are involved in the regulation of the cardiovascular system (CVS). The functioning of the CVS occurs via mechanisms of both nervous and humoral regulation, and in both cases, acetylcholine receptors of different families and subtypes with different localization participate in the regulation processes. It has been shown that acetylcholine receptors are located on the cell membranes directly of the heart and blood vessels; and this review examines the mechanisms of regulation of the functions of the CVS with the participation of only those cholinergic receptors that are located in the tissue of the heart and blood vessels. In general, both muscarinic and nicotinic cholinergic receptors are widely represented in the tissues of the CVS. While muscarinic acetylcholine receptors are generally involved in the regulation of vascular tonus and contractility of the heart, the nicotinic acetylcholine receptors are mainly involved in the regulation of a number of important pathophysiological processes directly affecting the functioning of the CVS. Regulation of the functioning of cholinergic receptors can be considered as an addition to existing methods for the treatment of diseases of the CVS, including such diseases as atherosclerosis and heart failure. The use of blockers and activators of cholinergic receptors for the study and/or treatment of pathological conditions of the CVS is discussed.

Meningeal mast cell-mediated mechanisms of cholinergic system modulation in neurogenic inflammation underlying the pathophysiology of migraine.

Growing evidence indicates that the parasympathetic system is implicated in migraine headache. However, the cholinergic mechanisms in the pathophysiology of migraine remain unclear. We investigated the effects and mechanisms of cholinergic modulation and a mast cell stabilizer cromolyn in the nitroglycerin-induced in vivo migraine model and in vitro hemiskull preparations in rats. Effects of cholinergic agents (acetylcholinesterase inhibitor neostigmine, or acetylcholine, and muscarinic antagonist atropine) and mast cell stabilizer cromolyn or their combinations were tested in the in vivo and in vitro experiments. The mechanical hyperalgesia was assessed by von Frey hairs. Calcitonin gene-related peptide (CGRP) and C-fos levels were measured by enzyme-linked immunosorbent assay. Degranulation and count of meningeal mast cells were determined by toluidine-blue staining. Neostigmine augmented the nitroglycerin-induced mechanical hyperalgesia, trigeminal ganglion CGRP levels, brainstem CGRP, and C-fos levels, as well as degranulation of mast cells in vivo. Atropine inhibited neostigmine-induced additional increases in CGRP levels in trigeminal ganglion and brainstem while it failed to do this in the mechanical hyperalgesia, C-fos levels, and the mast cell degranulation. However, all systemic effects of neostigmine were abolished by cromolyn. The cholinergic agents or cromolyn did not alter basal release of CGRP, in vitro, but cromolyn alleviated the CGRP-inducing effect of capsaicin while atropine failed to do it. These results ensure for a first time direct evidence that endogenous acetylcholine contributes to migraine pathology mainly by activating meningeal mast cells while muscarinic receptors are involved in CGRP release from trigeminal ganglion and brainstem, without excluding the possible role of nicotinic cholinergic receptors.

A Quantitative‐EEG Assessment of Alpha‐1062, a Novel Pro‐Drug of Galantamine for the Treatment of Mild to Moderate Dementia Associated with Alzheimer’s Disease.

AbstractBackgroundAcetylcholinesterase inhibitors (AChEIs) enhance cognitive functioning in Alzheimer’s disease (AD). The use of AChEIs at therapeutic doses is limited by gastrointestinal (GI) side effects, such as nausea, vomiting and diarrhea. Alpha‐1062 is a pharmacologically inactive prodrug of the AChEI galantamine specifically designed to reduce or eliminate GI side effects and provide increased safety. In addition to its activity as an AChEI, galantamine exhibits a second important mechanism of action, binding allosterically to nicotinic cholinergic receptors enhancing their responsiveness to acetylcholine. In Phase 1 single ascending dose (SAD) and multiple ascending dose (MAD) trials in young and elderly healthy subjects, Alpha‐1062 demonstrated both evidence of an improved GI side effect profile and enhanced cognition. Here we extend the findings of the SAD and MAD studies with an additional analysis of the effects of Alpha‐1062 on quantitative‐EEG (qEEG) data collected as part of the MAD study.MethodsSubjects (n = 12/dose) were administered two doses per day of Alpha‐1062 for 7 consecutive days. Pharmaco‐EEG measurements were performed for 4 min eyes closed / 4 min eyes open, on day 1 and day 7 at various timepoints both pre‐dose and post‐dose using a standard 10‐20 electrode montage with 21 channels. qEEG data analysis was conducted using qEEG indices developed using a machine learning algorithm based on the analysis of 39 AD patients administered galantamine (Sci Rep 7, 5775 [2017]). These were an AD index and a galantamine index, which were expected to be sensitive to the effects of Alpha 1062 administration.ResultsIn healthy elderly subjects, Alpha‐1062 administration improved response on the AD index (p <0.05) compared to placebo, at the pre‐dose timepoint on day 7. The AD index was also reduced at all post‐dose timepoints on day 7 relative to placebo. Changes in several other relevant measures of qEEG function suggested Alpha‐1062 improved brain function.ConclusionThese data demonstrate the potential benefit Alpha‐1062 in the treatment of AD. Alpha‐1062 was safe in the dose range investigated, and influenced pharmaco‐EEG outcomes in healthy elderly subjects that were consistent with the previously documented positive effects in tests related to sustained attention and working memory.

Hippocampal cholinergic receptors and the mTOR participation in fear-motivated inhibitory avoidance extinction memory

Evidence has demonstrated the hippocampal cholinergic system and the mammalian target of rapamycin (mTOR) participation during the memory formation of aversive events. This study assessed the role of these systems in the hippocampus for the extinction memory process by submitting male Wistar rats to fear-motivated step-down inhibitory avoidance (IA). The post-extinction session administration of the nicotinic and muscarinic cholinergic receptor antagonists, mecamylamine and scopolamine, respectively, both at doses of 2 µg/µl/side, and rapamycin, an mTOR inhibitor (0.02 µg/µl/side), into the CA1 region of the dorsal hippocampus, impaired the IA extinction memory. Furthermore, the nicotinic and muscarinic cholinergic receptor agonists, nicotine and muscarine, respectively, had a dose-dependent effect on the IA extinction memory when administered intra-CA1, immediately after the extinction session. Nicotine (0.6 µg/µl/side) and muscarine (0.02 µg/µl/side), respectively, had no effect, while the higher doses (6 and 2 µg/µl/side, respectively) impaired the IA extinction memory. Interestingly, the co-administration of muscarine at the lower dose blocked the impairment that was induced by rapamycin. This effect was not observed when nicotine at the lower dose was co-administered. These results have demonstrated the participation of the cholinergic receptors and mTOR in the hippocampus for IA extinction, and that the cholinergic agonists had a dose-dependent effect on the IA extinction memory. This study provides insights related to the behavioural aspects and the neurobiological properties underlying the early stage of fear-motivated IA extinction memory consolidation and suggests that there is hippocampal muscarinic receptor participation independent of mTOR in this memory process.