Nicotinic acetylcholine receptors and nicotinic cholinergic mechanisms of the central nervous system

In silico exploration of cholinergic activity and neuroprotection of novel caffeine analogues

Alzheimer's disease (AD) is characterized by a cholinergic deficit, prompting conventional therapies to elevate acetylcholine levels as a compensatory measure. Two main strategies involve the inhibition of acetylcholinesterase (AChE) and/or the stimulation of acetylcholine receptors (AChR). Caffeine (CFF), known as a partial agonist of nAChR and an AChE inhibitor, acts as a cholinergic enhancer. Additionally, it is suggested that CFF may exhibit neuroprotective capabilities through the inhibition of the human adenosine receptor type 2A (hA2AR) in the brain's striatum, potentially preventing cellular apoptosis. This study explores on the design and prediction of the bioactivity of CFF analogues with the aim of enhancing cholinergic signaling and providing neuroprotection to improve their therapeutic potential. We employed tools to predict pharmacokinetic and bioactivity properties, molecular docking, molecular dynamics, and target prediction to identify potential candidates among the designed CFF analogues capable of enhancing neurotransmission and providing cellular protection. In a novel approach, a normalized index is proposed for the combined analysis of the pharmacokinetic parameters and molecular docking binding affinities, which facilitates the systematic evaluation and comparison of the synthesized analogues and minimizes subjectivity in the selection of promising candidates. Results indicated that some analogues show promise in improving cholinergic activity and providing neuroprotection. These findings instill optimism, encouraging further research to corroborate their effects, while also representing a significant step towards the development of new therapeutic agents for AD.

Subtype-selective effect and molecular regulation of celastrol and triptolide at human nicotinic acetylcholine receptors

Celastrol and triptolide, bioactive compounds isolated from Tripterygium wilfordii Hook F, have demonstrated significant pharmacological effects across various biological pathways, making them subjects of extensive research for potential therapeutic applications. Celastrol and triptolide are known to have therapeutic use in neurodegenerative diseases including Alzheimer's disease and Parkinson's disease through neuroprotective action. Nicotinic acetylcholine receptors (nAChRs) are a subtype of cholinergic receptors and are ligand-gated ion channels that play an essential role in regulating synaptic transmission in the central nervous system. The results of this study indicate that celastrol and triptolide inhibit nAChR subtypes in a subtype-specific manner. This inhibitory effect was shown to be reversible, concentration-dependent, and noncompetitive. Mutation experiments were then performed to identify mutations in the binding site of nAChR determined by molecular docking studies and prioritize them based on binding energy, and it was found that triptolide had no inhibitory effect in double mutants of nAChR. These findings confirm that celastrol and triptolide selectively and effectively inhibit α3β2 and α3β4 nAChRs among various nAChR subtypes, and that celastrol and triptolide interact with a specific region of α3β4 nAChRs, which play a key role in the autonomic nervous system, without inhibiting the activity of α7 and α4β2, which act in neurodegenerative diseases.

Nicotinic α7 receptors on cholinergic neurons in the striatum mediate cocaine-reinforcement, but not food reward

The neurotransmitter acetylcholine has since long been implicated in reward learning and drug addiction. However, the role of specific cholinergic receptor subtypes on different neuronal populations remain elusive. Here, we studied the function of nicotinic acetylcholinergic alpha 7 receptors (α7 nAChRs) in cocaine and food-enforced behaviors. We found that global deletion of α7 nAChRs in mice attenuates cocaine seeking in a Pavlovian conditioned place preference paradigm and decreases operant responding to cocaine in a runway task and in self-administration, without influencing responding to palatable food. This effect can be attributed to alpha 7 receptor signaling in the striatum, as selective deletion of striatal α7 nAChRs using a viral vector approach resulted in a similar decrease in cocaine-preference as that of global deletion. To investigate which type of striatal neurons are responsible for this effect, we selectively targeted Cholinergic (ChAT-expressing) neurons and dopamine D1-receptor (D1R) expressing neurons. Mice with conditional deletion of α7 nAChRs in ChAT-neurons (α7 nAChR-ChATCre) exhibited decreased cocaine place preference and intact place preference for food, while α7 nAChR-D1RCre mice had no changes in reward learning to neither food nor cocaine. Cocaine induction of striatal immediate early gene expression of cFos, FosB, Arc and EGR2 was blocked in α7 nAChR-ChATCre mice, demonstrating the importance of α7 nAChRs on cholinergic neurons for striatal neuronal activity changes. Collectively, our findings show that α7 nAChRs on cholinergic interneurons in the striatum are pivotal for learning processes related to cocaine, but not food reward.

Nicotine Ameliorates α-Synuclein Preformed Fibril-Induced Behavioral Deficits and Pathological Features in Mice

Epidemiologic study suggests that nicotine reduces the risk of Parkinson's disease (PD) and thus could serve as a potential treatment. In this study, we aimed to investigate the effect of nicotine on the behavioral phenotypes and pathological characteristics of mice induced by human alpha-synuclein preformed fibers (α-syn-PFF). Mice were injected with 5 µg of human α-syn-PFF in the hippocampus while administering nicotine-containing drinking water (200 µg/mL). After 1 month, the motor ability, mood, spatial learning, and memory ability of the PD phenotype-like model mice were detected using open field, rotarod, Y maze, and O maze tests. The expression of pathological α-syn and apoptotic proteins, as well as the number of glial and neural stem cells in the hippocampus of mice, was detected using western blot and immunofluorescence. The results demonstrated that nicotine significantly reduced pathological α-syn accumulation, α-syn serine 129 phosphorylation, and apoptosis induced by α-syn-PFF injection in the hippocampus of mice. Nicotine also inhibited the increase in the number of glia, microglia, and neuronal apoptotic cells, and it decreased the expression of PI3K and Akt while also exhibiting significant memory impairment, motor deficits, and anxiety-like behavior. In conclusion, our findings suggest that nicotine ameliorates behavioral deficits and pathological changes in mice by inhibiting human α-syn-PFF-induced neuroinflammation and apoptosis.

Clinical, molecular, physiologic, and therapeutic feature of patients with CHRNA4 and CHRNB2 deficiency: A systematic review

The α4β2 nAChRs are crucial ion channels that control neurotransmitter release and play a role in various physiologic and pathologic processes. CHRNA4 encodes the α4-nAChRs, while CHRNB2 encodes the β2-nAChRs. Recent studies have found different variants of α4β2-nAChRs in individuals with conditions such as AD, ADHD, ALS, PD, and brain abnormalities. We conducted a scoping review following a six-stage methodology structure and adhering to PRISMA guidelines. We systematically reviewed articles using relevant keywords up to October 2, 2023. In this summary, we cover the clinical symptoms reported, the genes and protein structure of CHRNA4 and CHRNB2, mutations in these genes, inheritance patterns, the functional impact of mutations and polymorphisms in CHRNA4 and CHRNB2, and the epidemiology of these diseases. Recent research indicates that nAChRs may play a significant role in neurodegenerative disorders, possibly impacting neuronal function through yet undiscovered regulatory pathways. Studying how nAChRs interact with disease-related aggregates in neurodegenerative conditions may lead to new treatment options for these disorders.

Molecular determinants of the selectivity and potency of α-conotoxin Vc1.1 for human nicotinic acetylcholine receptors

The α-conotoxins (α-Ctxs) are short, disulfide-rich peptides derived from the venom of the Conus marine snails, primarily acting as antagonists of nicotinic acetylcholine receptors (nAChRs). Specifically, α-Ctx Vc1.1, a 16-amino acid peptide from Conus victoriae, competitively antagonizes non-muscle nAChRs, inhibits nicotine-induced currents in bovine chromaffin cells, and alleviates neuropathic pain in rat models. Although Vc1.1 selectively inhibits rat α9α10 nAChRs, its potency and selectivity across human nAChR subtypes remain unresolved. In this study, we assessed the activity of Vc1.1 on human (h) nAChRs heterologously expressed in Xenopus laevis oocytes using the two-electrode voltage clamp technique and simulated interactions using computational modeling. Vc1.1 selectively antagonized homomeric α9 and heteromeric α3β2 nAChRs, with half-maximal inhibitory concentrations (IC50) of 160 nM and 232 nM, respectively. At hα9[N179A]α10, Vc1.1 exhibited a 20-fold decrease in potency compared to hα9α10, due to the loss of hydrogen bonding with Vc1.1-D11. Conversely, Vc1.1 was four-fold more potent at hα3β2[E86A] compared to hα3β2, possibly influenced by the proximal residue β2-K104, as suggested by molecular dynamics (MD) simulations. Additionally, Vc1.1's potency doubled at hα9[N213K]α10, whereas it remained unchanged at hα9[N213R]α10 nAChRs. MD simulations indicate that altered interactions between the mutant hα9 N179A, N213K, and N213R side chains and Vc1.1-D5 may partly explain these changes in potency. The inhibitory action of Vc1.1 at α9-containing nAChRs is particularly relevant given their role in neuroinflammation, presenting a potential therapeutic pathway for alleviating neuropathic and inflammatory pain. This study provides valuable insights into the rational design of Vc1.1-derived α-Ctxs with enhanced nAChR subtype selectivity.

A tiered toxicity testing strategy for assessing early life stage toxicity in estuarine fish (Mugilogobius chulae): A case study on tris (1-chloro-2-propyl) phosphate ester

The estuarine ecological environment faces significant threats from contaminants of emerging concern (CECs); yet, the risk posed by CECs to resident organisms remains poorly understood. Here, we employed tiered toxicity testing to investigate the adverse effects and potential mechanisms of tris (1-chloro-2-propyl) phosphate (TCPP) on the early life stages of an estuarine fish, Mugilogobius chulae. TCPP affected the development of M. chulae embryos, including survival, morphology, hatching, and behavior. A concentration-dependent transcriptomic analysis showed that TCPP disrupted 12 neurodevelopment-related KEGG pathways in M. chulae embryos, with five of the 30 % top-ranked pathways related to neurotransmitter signaling. Besides the cholinergic synapse signaling pathway, the glutamatergic signaling pathway (including NMDAR and AMPAR subtypes) may also mediate TCPP-induced neurodevelopmental toxicity. The NMDAR subtype GRIN2B was downregulated at high concentrations. Molecular dynamics simulations revealed a strong interaction between TCPP and GRIN2B, with TCPP binding to the residues Ile153 and Ile188. The results suggest that NMDARs play a crucial role in TCPP-induced neurodevelopmental toxicity toward M. chulae. AOP network analysis predicted that TCPP may impact cognitive functions and memory. Our study provides a novel testing strategy for identifying the mechanisms of toxicity of CECs, a crucial component of ecological risk assessment.

Development of an Intravenously Stable Disulfide-Rich Peptide for the Treatment of Chemotherapy-Induced Neuropathic Pain

α-conotoxins (α-Ctxs), a class of disulfide-rich conopetides, are excellent drug leads due to their small size, high selectivity, and potency for specific membrane receptors and ion channels involved in pain transmission. However, their high susceptibility to proteolytic degradation limits their therapeutic potential. In this study, we designed and synthesized a series of conformationally stable analogues of α-Ctx Mr1.1[S4Dap] using various structural optimization strategies. The Mr1.1[S4Dap, C16Pen] analogue maintained potency at human α9α10 nicotinic acetylcholine receptors, with a half-maximal inhibitory concentration (IC50) of 4 nM. It exhibited over a 5-fold increase in serum stability compared to Mr1.1[S4Dap], without disrupting its overall conformation. Furthermore, intravenous application of Mr1.1[S4Dap, C16Pen] showed potent analgesic activity in oxaliplatin-induced cold allodynia, indicating a high potential for drug development. Overall, the results from this study provide valuable insights for optimizing the serum stability of disulfide-rich peptides in future therapeutic applications.

From Plaques to Pathways in Alzheimer's Disease: The Mitochondrial-Neurovascular-Metabolic Hypothesis

Alzheimer's disease (AD) presents a public health challenge due to its progressive neurodegeneration, cognitive decline, and memory loss. The amyloid cascade hypothesis, which postulates that the accumulation of amyloid-beta (Aβ) peptides initiates a cascade leading to AD, has dominated research and therapeutic strategies. The failure of recent Aβ-targeted therapies to yield conclusive benefits necessitates further exploration of AD pathology. This review proposes the Mitochondrial-Neurovascular-Metabolic (MNM) hypothesis, which integrates mitochondrial dysfunction, impaired neurovascular regulation, and systemic metabolic disturbances as interrelated contributors to AD pathogenesis. Mitochondrial dysfunction, a hallmark of AD, leads to oxidative stress and bioenergetic failure. Concurrently, the breakdown of the blood-brain barrier (BBB) and impaired cerebral blood flow, which characterize neurovascular dysregulation, accelerate neurodegeneration. Metabolic disturbances such as glucose hypometabolism and insulin resistance further impair neuronal function and survival. This hypothesis highlights the interconnectedness of these pathways and suggests that therapeutic strategies targeting mitochondrial health, neurovascular integrity, and metabolic regulation may offer more effective interventions. The MNM hypothesis addresses these multifaceted aspects of AD, providing a comprehensive framework for understanding disease progression and developing novel therapeutic approaches. This approach paves the way for developing innovative therapeutic strategies that could significantly improve outcomes for millions affected worldwide.

Exploring the therapeutic potential of tDCS, TMS and DBS in overcoming tobacco use disorder: an umbrella review

The purpose of the present study was to investigate the effects of neuromodulation techniques, including transcranial direct current stimulation, transcranial magnetic stimulation, and deep brain stimulation, on the treatments of nicotine dependence. Specifically, our objective was to assess the existing evidence by conducting an umbrella review of systematic reviews. The quality of the included studies was evaluated using the standardized tools designed to evaluate systematic reviews. The PubMed/MEDLINE database was queried for systematic reviews, and yielded 7 systematic reviews with a substantial sample size (N = 4,252), some of which included meta-analyses. A significant finding across these studies was the effectiveness of neuromodulation techniques to reduce nicotine cravings and consumption, through the evidence remains not yet conclusive. A significant efficacy of transcranial direct current stimulation and repetitive transcranial magnetic stimulation that targeted the dorsolateral prefrontal cortex was found, as well as the lateral prefrontal cortex and insula bilaterally, on smoking frequency and craving. Moreover, smoking behaviors may also be positively affected by the use of deep brain stimulation (DBS) targeting the nucleus accumbens. In conclusion, neuromodulation approaches hold promise as effective treatments for tobacco use disorder. Nonetheless, further research is required to comprehensively understand their effectiveness and to determine if combining them with other treatments can aid individuals to successfully quit smoking.

Activation of α7 nicotinic receptors attenuated hyperalgesia and anxiety induced by palatable obesogenic diet withdrawal

Consumption of palatable food (PF) can alleviate anxiety, and pain in humans. Contrary, spontaneous withdrawal of long-term PF intake produces anxiogenic-like behavior and abnormal pain sensation, causing challenges to weight-loss diet and anti-obesity agents. Thus, we examined α7-nicotinic acetylcholine receptors (α7nAChR) involvement since it plays essential role in nociception and psychological behaviors.

METHODS

Adult male C57BL/6 mice were placed on a Standard Chow (SC) alone or with PF on intermittent or continuous regimen for 6 weeks. Then, mice were replaced with normal SC (spontaneous withdrawal). Body weight, food intake, and calories intake with and without the obesogenic diet were measured throughout the study. During PF withdrawal, anxiety-like behaviors and pain sensitivity were measured with PNU-282987 (α7nAChR agonist) administration.

RESULTS

Six weeks of SC + PF-intermittent and continuous paradigms produced a significant weight gain. PF withdrawal displayed hyperalgesia and anxiety-like behaviors. During withdrawal, PNU-282987 significantly attenuated hyperalgesia and anxiety-like behaviors.

CONCLUSION

The present study shows that a PF can increase food intake and body weight. Also, enhanced pain sensitivity and anxiety-like behavior were observed during PF withdrawal. α7nAChR activation attenuated anxiolytic-like behavior and hyperalgesia in PF abstinent mice. These data suggest potential therapeutic effects of targeting α7 nAChRs for obesity-withdrawal symptoms in obese subjects.

The role of kynurenines in migraine-related neuroimmune pathways

Migraine, a primary headache disorder whose mechanism remains incompletely understood, appears to involve the activation of the trigeminovascular system (TS) during attacks. Research suggests that inflammatory processes mediated by the immune system may play a role in migraine pathophysiology. Neuroinflammation is often associated with migraine attacks, with cytokines serving as crucial mediators in the process. Elevated levels of pro-inflammatory cytokines, such as interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α), have been observed in the blood and cerebrospinal fluid of individuals experiencing migraine attacks. These cytokines have the capacity to sensitize pain pathways in the brain, thereby increasing sensitivity to pain stimuli. This phenomenon, known as central sensitization, is believed to contribute to the intensity and persistence of migraine pain. Kynurenines, endogenous mediators of glutamatergic mechanisms, can significantly influence the pathophysiology of primary headache disorders. The kynurenine system is collectively known as the kynurenine pathway (KP), which can act on multiple receptors, such as glutamate receptors, aryl hydrocarbon receptors (AhRs), G protein-coupled receptors 35 (GPR35), and α-7 nicotinic acetylcholine (α7 nACh) receptors. These receptors are also found on various cells of the immune system, so the role of the KP in the pathomechanism of primary headaches may also be mediated through them. In this review, our goal is to show a possible link between the receptors of the KP and immune system in the context of inflammation and migraine. Migraine research in recent years has focused on neuropeptides, such as calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP) as potential pathogenic factors and possible therapeutic approaches. These peptides share many similarities in their characteristics and roles. For instance, they exhibit potent vasodilation, occur in both the peripheral and central nervous systems, and play a role in transmitting nociception and neurogenic inflammation. The investigation of potential connections between the aforementioned neuropeptides and the kynurenine pathway could play a significant role in uncovering the pathomechanism of migraine and identifying new drug candidates.

The interaction between cannabinoids and long-term synaptic plasticity: A survey on memory formation and underlying mechanisms

Synaptic plasticity, including long-term potentiation (LTP) and long-term depression (LTD), is an essential phenomenon in memory formation as well as maintenance along with many other cognitive functions, such as those needed for coping with external stimuli. Synaptic plasticity consists of gradual changes in the biochemistry and morphology of pre- and postsynaptic neurons, particularly in the hippocampus. Consuming marijuana as a primary source of exocannabinoids immediately impairs attention and working memory-related tasks. Evidence regarding the effects of cannabinoids on LTP and memory is contradictory. While cannabinoids can affect a variety of specific cannabinoid receptors (CBRs) and nonspecific receptors throughout the body and brain, they exert miscellaneous systemic and local cerebral effects. Given the increasing use of cannabis, mainly among the young population, plus its potential adverse long-term effects on learning and memory processes, it could be a future global health challenge. Indeed, the impact of cannabinoids on memory is multifactorial and depends on the dosage, timing, formula, and route of consumption, plus the background complex interaction of the endocannabinoids system with other cerebral networks. Herein, we review how exogenously administrated organic cannabinoids, CBRs agonists or antagonists, and endocannabinoids can affect LTP and synaptic plasticity through various receptors in interaction with other cerebral pathways and primary neurotransmitters.

Structural bases for stoichiometry-selective calcium potentiation of a neuronal nicotinic receptor

BACKGROUND AND PURPOSE

α4β2 nicotinic acetylcholine (nACh) receptors assemble in two stoichiometric forms, one of which is potentiated by calcium. The sites of calcium binding that underpin potentiation are not known.

EXPERIMENTAL APPROACH

To identify calcium binding sites, we applied cryo-electron microscopy (cryo-EM) and molecular dynamics (MD) simulations to each stoichiometric form of the α4β2 nACh receptor in the presence of calcium ions. To test whether the identified calcium sites are linked to potentiation, we generated mutants of anionic residues at the sites, expressed wild type and mutant receptors in clonal mammalian fibroblasts, and recorded ACh-elicited single-channel currents with or without calcium.

KEY RESULTS

Both cryo-EM and MD simulations show calcium bound to a site between the extracellular and transmembrane domains of each α4 subunit (ECD-TMD site). Substituting alanine for anionic residues at the ECD-TMD site abolishes stoichiometry-selective calcium potentiation, as monitored by single-channel patch clamp electrophysiology. Additionally, MD simulation reveals calcium association at subunit interfaces within the extracellular domain. Substituting alanine for anionic residues at the ECD sites reduces or abolishes stoichiometry-selective calcium potentiation.

CONCLUSIONS AND IMPLICATIONS

Stoichiometry-selective calcium potentiation of the α4β2 nACh receptor is achieved by calcium association with topographically distinct sites framed by anionic residues within the α4 subunit and between the α4 and β2 subunits. Stoichiometry-selective calcium potentiation could result from the greater number of calcium sites in the stoichiometric form with three rather than two α4 subunits. The results are relevant to modulation of signalling via α4β2 nACh receptors in physiological and pathophysiological conditions.

Abundant extrasynaptic expression of α3β4-containing nicotinic acetylcholine receptors in the medial habenula-interpeduncular nucleus pathway in mice

Nicotinic acetylcholine receptors (nAChRs) in the medial habenula (MHb)-interpeduncular nucleus (IPN) pathway play critical roles in nicotine-related behaviors. This pathway is particularly enriched in nAChR α3 and β4 subunits, both of which are genetically linked to nicotine dependence. However, the cellular and subcellular expression of endogenous α3β4-containing nAChRs remains largely unknown because specific antibodies and appropriate detection methods were unavailable. Here, we successfully uncovered the expression of endogenous nAChRs containing α3 and β4 subunits in the MHb-IPN pathway using novel specific antibodies and a fixative glyoxal that enables simultaneous detection of synaptic and extrasynaptic molecules. Immunofluorescence and immunoelectron microscopy revealed that both subunits were predominantly localized to the extrasynaptic cell surface of somatodendritic and axonal compartments of MHb neurons but not at their synaptic junctions. Immunolabeling for α3 and β4 subunits disappeared in α5β4-knockout brains, which we used as negative controls. The enriched and diffuse extrasynaptic expression along the MHb-IPN pathway suggests that α3β4-containing nAChRs may enhance the excitability of MHb neurons and neurotransmitter release from their presynaptic terminals in the IPN. The revealed distribution pattern provides a molecular and anatomical basis for understanding the functional role of α3β4-containing nAChRs in the crucial pathway of nicotine dependence.

Pathogenic genes implicated in sleep-related hypermotor epilepsy: a research progress update

Sleep-related hypermotor epilepsy (SHE) is a focal epilepsy syndrome characterized by a variable age of onset and heterogeneous etiology. Current literature suggests a prevalence rate of approximately 1.8 per 100,000 persons. The discovery of additional pathogenic genes associated with SHE in recent years has significantly expanded the knowledge and understanding of its pathophysiological mechanisms. Identified SHE pathogenic genes include those related to neuronal ligand- and ion-gated channels (CHRNA4, CHRNB2, CHRNA2, GABRG2, and KCNT1), genes upstream of the mammalian target of rapamycin complex 1 signal transduction pathway (DEPDC5, NPRL2, NPRL3, TSC1, and TSC2), and other genes (CRH, CaBP4, STX1B, and PRIMA1). These genes encode proteins associated with ion channels, neurotransmitter receptors, cell signal transduction, and synaptic transmission. Mutations in these genes can result in the dysregulation of encoded cellular functional proteins and downstream neuronal dysfunction, ultimately leading to epileptic seizures. However, the associations between most genes and the SHE phenotype remain unclear. This article presents a literature review on the research progress of SHE-related pathogenic genes to contribute evidence to genotype-phenotype correlations in SHE and establish the necessary theoretical basis for future SHE treatments.

Explorations of Agonist Selectivity for the α9* nAChR with Novel Substituted Carbamoyl/Amido/Heteroaryl Dialkylpiperazinium Salts and Their Therapeutic Implications in Pain and Inflammation

There is an urgent need for nonopioid treatments for chronic and neuropathic pain to provide effective alternatives amid the escalating opioid crisis. This study introduces novel compounds targeting the α9 nicotinic acetylcholine receptor (nAChR) subunit, which is crucial for pain regulation, inflammation, and inner ear functions. Specifically, it identifies novel substituted carbamoyl/amido/heteroaryl dialkylpiperazinium iodides as potent agonists selective for human α9 and α9α10 over α7 nAChRs, particularly compounds 3f, 3h, and 3j. Compound 3h (GAT2711) demonstrated a 230 nM potency as a full agonist at α9 nAChRs, being 340-fold selective over α7. Compound 3c was 10-fold selective for α9α10 over α9 nAChR. Compounds 2, 3f, and 3h inhibited ATP-induced interleukin-1β release in THP-1 cells. The analgesic activity of 3h was fully retained in α7 knockout mice, suggesting that analgesic effects were potentially mediated through α9* nAChRs. Our findings provide a blueprint for developing α9*-specific therapeutics for pain.

Proteome profile of the cerebellum from α7 nicotinic acetylcholine receptor deficient mice

The alpha7 nicotinic acetylcholine receptor (α7 nAChR; CHRNA7) is expressed in the nervous system and in non-neuronal tissues. Within the central nervous system, it is involved in various cognitive and sensory processes such as learning, attention, and memory. It is also expressed in the cerebellum, where its roles are; however, not as well understood as in the other brain regions. To investigate the consequences of absence of CHRNA7 on the cerebellum proteome, we performed a quantitative nano-LC-MS/MS analysis of samples from CHRNA7 knockout (KO) mice and corresponding wild type (WT) controls. Liver, an organ which does not express this receptor, was analyzed, in comparison. While the liver proteome remained relatively unaltered (three proteins more abundant in KOs), 90 more and 20 less abundant proteins were detected in the cerebellum proteome of the KO mice. The gene ontology analysis of the differentially abundant proteins indicates that the absence of CHRNA7 leads to alterations in the glutamatergic system and myelin sheath in the cerebellum. In conclusion, our dataset provides new insights in the role of CHRNA7 in the cerebellum, which may serve as a basis for future in depth-investigations.

Western diet consumption impairs memory function via dysregulated hippocampus acetylcholine signaling

Western diet (WD) consumption during early life developmental periods is associated with impaired memory function, particularly for hippocampus (HPC)-dependent processes. We developed an early life WD rodent model associated with long-lasting HPC dysfunction to investigate the neurobiological mechanisms mediating these effects. Rats received either a cafeteria-style WD (ad libitum access to various high-fat/high-sugar foods; CAF) or standard healthy chow (CTL) during the juvenile and adolescent stages (postnatal days 26-56). Behavioral and metabolic assessments were performed both before and after a healthy diet intervention period beginning at early adulthood. Results revealed HPC-dependent contextual episodic memory impairments in CAF rats that persisted despite the healthy diet intervention. Given that dysregulated HPC acetylcholine (ACh) signaling is associated with memory impairments in humans and animal models, we examined protein markers of ACh tone in the dorsal HPC (HPCd) in CAF and CTL rats. Results revealed significantly lower protein levels of vesicular ACh transporter in the HPCd of CAF vs. CTL rats, indicating chronically reduced ACh tone. Using intensity-based ACh sensing fluorescent reporter (iAChSnFr) in vivo fiber photometry targeting the HPCd, we next revealed that ACh release during object-contextual novelty recognition was highly predictive of memory performance and was disrupted in CAF vs. CTL rats. Neuropharmacological results showed that alpha 7 nicotinic ACh receptor agonist infusion in the HPCd during training rescued memory deficits in CAF rats. Overall, these findings reveal a functional connection linking early life WD intake with long-lasting dysregulation of HPC ACh signaling, thereby identifying an underlying mechanism for WD-associated memory impairments.

Investigating the role of nicotinic acetylcholine receptors in menthol's effects in mice

The use of menthol in tobacco products has been linked to an increased likelihood of developing nicotine dependence. The widespread use of menthol can be attributed to its unique sensory characteristics; however, emerging evidence suggests that menthol also alters sensitivity to nicotine through modulation of nicotinic acetylcholine receptors (nAChRs). Nicotinic subunits, such as β2 and α5, are of interest due to their implications in nicotine reward, reinforcement, intake regulation, and aversion. This study, therefore, examined the in vivo relevance of β2 and α5 nicotinic subunits on the pharmacological and behavioral effects of menthol. Data suggests that the α5 nicotinic subunit modulates menthol intake in mice. Overall, deletion or a reduction in function of the α5 subunit lessened aversion to menthol. α5 KO mice and mice possessing the humanized α5 SNP, a variant that confers a nicotine dependence phenotype in humans, demonstrated increased menthol intake compared to their WT counterparts and in a sex-related fashion for α5 SNP mice. We further reported that the modulatory effects of the α5 subunit do not extend to other aversive tastants like quinine, suggesting that deficits in α5* nAChR signaling may not abolish general sensitivity to the aversive effects of other noxious chemicals. Further probing into the role of α5 in other pharmacological properties of menthol revealed that the α5 subunit does not modulate the antinociceptive properties of menthol in mice and suggests that the in vivo differences observed are likely not due to the direct effects of menthol on α5-containing nAChRs in vitro.

The protective effect of methanolic extract of Verbascum cheiranthifolium and Biebersteinia multifida DC on hippocampus damage induced by diazinon in male Wistar rats: An experimental study

Diazinon (DZN) an organophosphate (OP), with the most important mechanism of action of DZN being induction of oxidative stress (OS) and inhibition of the enzyme acetylcholinesterase (AChE). Verbascum cheiranthifolium (VER) and Biebersteinia multifida (BM) belong to the Scrophulariaceae and Biebersteiniaceae family respectively. These plants are widely used in Iranian traditional medicine due to their beneficial effects. Thus, this research aimed to appraise the protective effects of the methanolic extract of the VER and BM on changes in the level of expression of α7 and α4 subunits of nicotinic acetylcholine receptors (nAChRs) in hippocampus (HPC) of DZN-treated rats. In this research, 36 male Wistar rats were used and randomly divided into six groups: Control, DZN (40 mg/kg), VER (1 g/kg), DZN+VER (40 mg/kg+1 g/kg), BM (150 mg/kg), and DZN+BM (40 mg/kg+150 mg/kg). At the end of treatment periods, the animals of all groups underwent the Morris water maze (MWM) test. The rats were anesthetized, and blood sampling was performed. Eventually, the brain was removed for histological study and evaluation of OS parameters. The results indicated that DZN increased the extent of expression of nAChRs in the HPC and significantly inhibited cholinesterase (ChEs) activity plus OS parameters. Also, in MWM, the time to find the platform was significantly longer in the DZN group, while the time and the distance in the probe test were lower than in the control groups. VER and BM extract in the treatment groups simultaneously improved the extent of expression of nAChRs, ChEs activity, as well as the parameters of OS and spatial memory significantly. In conclusion, our results support the neuroprotective properties of VER and BM extract versus DZN in rats. Accordingly, the extracts of VER and BM may be useful as an approach for the treatment of learning disorders and memory enhancement.

Characterizing the binding of TC-5619 and encenicline on the alpha7 nicotinic acetylcholine receptor using PET imaging in the pig

The alpha7 nicotinic acetylcholine receptor (α7-nAChR) has has long been considered a promising therapeutic target for addressing cognitive impairments associated with a spectrum of neurological and psychiatric disorders, including Alzheimer's disease and schizophrenia. However, despite this potential, clinical trials employing α7-nAChR (partial) agonists such as TC-5619 and encenicline (EVP-6124) have fallen short in demonstrating sufficient efficacy. We here investigate the target engagement of TC-5619 and encenicline in the pig brain by use of the α7-nAChR radioligand 11C-NS14492 to characterize binding both with in vitro autoradiography and in vivo occupancy using positron emission tomography (PET). In vitro autoradiography demonstrates significant concentration-dependent binding of 11C-NS14492, and both TC-5619 and encenicline can block this binding. Of particular significance, our in vivo investigations demonstrate that TC-5619 achieves substantial α7-nAChR occupancy, effectively blocking approximately 40% of α7-nAChR binding, whereas encenicline exhibits more limited α7-nAChR occupancy. This study underscores the importance of preclinical PET imaging and target engagement analysis in informing clinical trial strategies, including dosing decisions.

Methods: A bioinformatic protocol for rapid analysis of zebrafish embryo photo-motory responses (PMR) in neurotoxicity testing

Chemobehavioural phenotyping presents unique opportunities for analyzing neurotoxicants and discovering behavior-modifying neuroceuticals in small aquatic model organisms such as zebrafish (Danio rerio). A recently popularized approach in this field involves the utilization of zebrafish embryos for a photo-motor response (PMR) bioassay. The PMR bioassay entails stimulating zebrafish embryos between 24 and 36 h post fertilization (hpf) with a high-intensity light stimulus, inducing a transient increase in the frequency of photo-induced embryo body flexions. These flexions can be computationally analyzed to derive behavioral signatures, enabling the categorization of neuromodulating chemicals. Despite the significant advantages of the PMR bioassay, its widespread implementation is hindered by lack of well described and straightforward high-throughput bioinformatic analysis of behavioral data. In this methods article, we present an easily implementable bioinformatics protocol specifically designed for rapid behavioral analysis of large cohorts of zebrafish specimens in PMR bioassays. We also address common pitfalls encountered during PMR analysis, discuss its limitations, and propose future directions for developing next-generation biometric analysis techniques in chemobehavioural assays utilizing zebrafish embryos.

Electronic Cigarette Vape Exposure Exacerbates Post-Ischemic Outcomes in Female but Not in Male Rats

BACKGROUND

Nicotine-containing electronic cigarette (EC) vaping has become popular worldwide, and our understanding of the effects of vaping on stroke outcomes is elusive. Using a rat model of transient middle cerebral artery occlusion, the current exploratory study aims to evaluate the sex-dependent effects of EC exposure on brain energy metabolism and stroke outcomes.

METHODS

Adult Sprague-Dawley rats of both sexes were randomly assigned to air/EC vapor (5% nicotine Juul pods) exposure for 16 nights, followed by randomization into 3 cohorts. The first cohort underwent exposure to air/EC preceding randomization to transient middle cerebral artery occlusion (90 minutes) or sham surgery, followed by survival for 21 days. During the survival period, rats underwent sensorimotor and Morris water maze testing. Subsequently, brains were collected for histopathology. A second cohort was exposed to air/EC after which brains were collected for unbiased metabolomics analysis. The third cohort of animals was exposed to air/EC and received transient middle cerebral artery occlusion/sham surgery, and brain tissue was collected 24 hours later for biochemical analysis.

RESULTS

In females, EC significantly increased (P<0.05) infarct volumes by 94% as compared with air-exposed rats, 165±50 mm3 in EC-exposed rats, and 85±29 mm3 in air-exposed rats, respectively, while in males such a difference was not apparent. Morris water maze data showed significant deficits in spatial learning and working memory in the EC sham or transient middle cerebral artery occlusion groups compared with the respective air groups in rats of both sexes (P<0.05). Thirty-two metabolites of carbohydrate, glycolysis, tricarboxylic acid cycle, and lipid metabolism were significantly altered (P≤0.05) due to EC, 23 of which were specific for females. Steady-state protein levels of hexokinase significantly decreased (P<0.05) in EC-exposed females; however, these changes were not seen in males.

CONCLUSIONS

Even brief EC exposure over 2 weeks impacts brain energy metabolism, exacerbates infarction, and worsens poststroke cognitive deficits in working memory more in female than male rats.

Real-time tilting and twisting motions of ligand-bound states of α7 nicotinic acetylcholine receptor

The α7 nicotinic acetylcholine receptor is a member of the nicotinic acetylcholine receptor family and is composed of five α7 subunits arranged symmetrically around a central pore. It is localized in the central nervous system and immune cells and could be a target for treating Alzheimer's disease and schizophrenia. Acetylcholine is a ligand that opens the channel, although prolonged application rapidly decreases the response. Ivermectin was reported as one of the positive allosteric modulators, since the binding of Ivermectin to the channel enhances acetylcholine-evoked α7 currents. One research has suggested that tilting motions of the nicotinic acetylcholine receptor are responsible for channel opening and activation. To verify this hypothesis applies to α7 nicotinic acetylcholine receptor, we utilized a diffracted X-ray tracking method to monitor the stable twisting and tilting motion of nAChR α7 without a ligand, with acetylcholine, with Ivermectin, and with both of them. The results show that the α7 nicotinic acetylcholine receptor twists counterclockwise with the channel transiently opening, transitioning to a desensitized state in the presence of acetylcholine and clockwise without the channel opening in the presence of Ivermectin. We propose that the conformational transition of ACh-bound nAChR α7 may be due to the collective twisting of the five α7 subunits, resulting in the compression and movement, either downward or upward, of one or more subunits, thus manifesting tilting motions. These tilting motions possibly represent the transition from the resting state to channel opening and potentially to the desensitized state.

Nicotine Abuse and Neurodegeneration: Novel Pharmacogenetic Targets to Aid Quitting and Reduce the Risk of Dementia

Nicotine dependence has deleterious neurological impacts. Previous studies found an association between cigarette smoking and accelerating age-related thinning of the brain's cortex and subsequent cognitive decline. Smoking is considered the third most common risk factor for dementia, which prompted the inclusion of smoking cessation in dementia prevention strategies. Traditional pharmacologic options for smoking cessation include nicotine transdermal patches, bupropion and varenicline. However, based on smokers' genetic makeup, pharmacogenetics can be used to develop novel therapies to replace these traditional approaches. Genetic variability of cytochrome P450 2A6 has a major impact on smokers' behavior and their response to quitting therapies. Gene polymorphism in nicotinic acetylcholine receptor subunits also has a great influence on the ability to quit smoking. In addition, polymorphism of certain nicotinic acetylcholine receptors was found to affect the risk of dementia and the impact of tobacco smoking on the development of Alzheimer's disease. Nicotine dependence involves the activation of pleasure response through the stimulation of dopamine release. Central dopamine receptors, catechol-o-methyltransferase and the dopamine transporter protein, regulate synaptic dopamine levels. The genes of these molecules are potential targets for novel smoking cessation drugs. Pharmacogenetic studies of smoking cessation also investigated other molecules, such as ANKK1 and dopamine-beta-hydroxylase (DBH). In this perspective article, we aim to highlight the promising role of pharmacogenetics in the development of effective drugs for smoking cessation, which can increase the success rate of smoking quitting plans and ultimately reduce the incidence of neurodegeneration and dementia.

Ionotropic and metabotropic responses by alpha 7 nicotinic acetylcholine receptors

Nicotinic acetylcholine receptors (nAChRs) belong to a superfamily of cys-loop receptors characterized by the assembly of five subunits into a multi-protein channel complex. Ligand binding to nAChRs activates rapid allosteric transitions of the receptor leading to channel opening and ion flux in neuronal and non-neuronal cell. Thus, while ionotropic properties of nAChRs are well recognized, less is known about ligand-mediated intracellular metabotropic signaling responses. Studies in neural and non-neural cells confirm ionotropic and metabotropic channel responses following ligand binding. In this review we summarize evidence on the existence of ionotropic and metabotropic signaling responses by homopentameric α7 nAChRs in various cell types. We explore how coordinated calcium entry through the ion channel and calcium release from nearby stores gives rise to signaling important for the modulation of cytoskeletal motility and cell growth. Amino acid residues for intracellular protein binding within the α7 nAChR support engagement in metabotropic responses including signaling through heterotrimeric G proteins in neural and immune cells. Understanding the dual properties of ionotropic and metabotropic nAChR responses is essential in advancing drug development for the treatment of various human disease.

Investigating Behavioral and Neuronal Changes in Adolescent Mice Following Prenatal Exposure to Electronic Cigarette (E-Cigarette) Vapor Containing Nicotine

A substantial percentage of pregnant smokers stop using traditional cigarettes and switch to alternative nicotine-related products such as e-cigarettes. Prenatal exposure to tobacco increases the risk of psychiatric disorders in children. Adolescence is a complex phase in which higher cognitive and emotional processes undergo maturation and refinement. In this study, we examined the behavioral and molecular effects of first-trimester prenatal exposure to e-cigarettes. Adult female mice were divided into normal air, vehicle, and 2.5%-nicotine-exposed groups. Our analyses indicated that the adolescents in the 2.5%-nicotine-exposed group exhibited a significant lack of normal digging behavior, elevated initial sucrose intake, and reduced recognition memory. Importantly, we identified a substantial level of nicotine self-administration in the 2.5%-nicotine-exposed group. At a molecular level, the mRNAs of metabotropic glutamate receptors and transporters in the nucleus accumbens were not altered. This previously undescribed work indicates that prenatal exposure to e-cigarettes might increase the risk of nicotine addiction during adolescence, reduce cognitive capacity, and alter normal adolescent behavior. The outcome will aid in translating research and assist healthcare practitioners in tackling addiction and mental issues caused by toxicological exposure. Further, it will inform relevant policymaking, such as recommended taxation, labeling e-cigarette devices with more detailed neurotoxic effects, and preventing their sale to pregnant women and adolescents.

Molecular docking and dynamic simulation studies of α4β2 and α7 nicotinic acetylcholine receptors with tobacco smoke constituents nicotine, NNK and NNN

Smoking constitutes a major global health problem. As it triggers various health hazards including cancers, cardiac and pulmonary illness, it is imperative to understand the mechanism of action of various smoke constituents on our cellular processes. Various in vitro studies have compiled the affinity of cigarette smoke constituents on various nicotinic acetylcholine receptors (nAChRs). But the nature of the intermolecular interactions contributing to this affinity and the key amino acids in the receptor active sites involved in this are not investigated so far. Here, we are examining the interaction of α7nAChR and α4β2nAChR on nicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N-nitrosornicotine (NNN), the physiologically significant constituents in smoke, through molecular docking and dynamics simulations study. The docking of α4β2nAChR structure with the ligands nicotine, NNK and NNN yielded docking scores of -41.45 kcal/mol, -59.28 kcal/mol and -54.60 kcal/mol, respectively, and that of α7nAChR receptor molecule with the ligands yielded docking scores of -59.54 kcal/mol, -71.06 kcal/mol and -70.86 kcal/mol, respectively. The study showed that NNK exhibited the highest affinity with the ligands which was confirmed by dynamics simulation. But higher stability of interactions as surmised from Molecular dynamics simulations was found for nicotine with α4β2nAChR and NNN with α7nAChR. The findings validate the in vitro studies comparing the affinities of these compounds. The study will be useful in formulating effective nAChR agonists to treat neurological disorders and antagonists for smoke deaddiction and improve health standards.Communicated by Ramaswamy H. Sarma.

Nicotine Decreases Nerve Regeneration and Pain Behaviors via PTEN and Downstream Inflammation-Related Pathway in Two Rat Nerve Injury Models

Neuropathic pain is stubborn and associated with the peripheral nerve regeneration process. Nicotine has been found to reduce pain, but whether it is involved in the regulation of nerve regeneration and the underlying mechanism are unknown. In this study, we examined the mechanical allodynia thermal hyperalgesia together with the peripheral nerve regeneration after nicotine exposure in two rat neuropathic pain models. In the spinal nerve ligation model, in which anatomic nerve regeneration can be easily observed, nicotine reduced anatomic measures of regeneration as well as expression of regeneration marker growth-associated protein 43 (GAP43). In the tibial nerve crush model, nicotine treatment significantly suppressed GAP43 expression and functional reinnervation as measured by myelinated action potential and electromyography of gastrocnemius. In both models, nicotine treatment reduced macrophage density in the sensory ganglia and peripheral nerve. These effects of nicotine were reversed by the selective α7 nicotinic acetylcholine receptor (nAChR) blocker methyllycaconitine. In addition, nicotine significantly elevated expression of PTEN (the phosphatase and tensin homolog deleted on chromosome 10), a key player in both regeneration and pain. Pharmacological interference of PTEN could regulate GAP43 expression, pain-related behaviors, and macrophage infiltration in a nicotine-treated nerve crush model. Our results reveal that nicotine and its α7-nAChR regulate both peripheral nerve regeneration process and pain though PTEN and the downstream inflammation-related pathway.

CHRNA5 gene variation affects the response of VTA dopaminergic neurons during chronic nicotine exposure and withdrawal

Nicotine is the principal psychoactive component in tobacco that drives addiction through its action on neuronal nicotinic acetylcholine receptors (nAChR). The nicotinic receptor gene CHRNA5, which encodes the α5 subunit, is associated with nicotine use and dependence. In humans, the CHRNA5 missense variant rs16969968 (G > A) is associated with increased risk for nicotine dependence and other smoking-related phenotypes. In rodents, α5-containing nAChRs in dopamine (DA) neurons within the ventral tegmental area (VTA) powerfully modulate nicotine reward and reinforcement. Although the neuroadaptations caused by long-term nicotine exposure are being actively delineated at both the synaptic and behavioral levels, the contribution of α5-containing nAChRs to the cellular adaptations associated with long-term nicotine exposure remain largely unknown. To gain insight into the mechanisms behind the influence of α5-containing nAChRs and the rs16969968 polymorphism on nicotine use and dependence, we used electrophysiological approaches to examine changes in nAChR function arising in VTA neurons during chronic nicotine exposure and multiple stages of nicotine withdrawal. Our results demonstrate that CHRNA5 mutation leads to profound changes in VTA nAChR function at baseline, during chronic nicotine exposure, and during short-term and prolonged withdrawal. Whereas nAChR function was suppressed in DA neurons from WT mice undergoing withdrawal relative to drug-naïve or nicotine-drinking mice, α5-null mice exhibited an increase in nAChR function during nicotine exposure that persisted throughout 5-10 weeks of withdrawal. Re-expressing the hypofunctional rs16969968 CHRNA5 variant in α5-null VTA DA neurons did not rescue the phenotype, with α5-SNP neurons displaying a similar increased response to ACh during nicotine exposure and early stages of withdrawal. These results demonstrate the importance of VTA α5-nAChRs in the response to nicotine and implicate them in the time course of withdrawal.

Early life stress, prenatal secondhand smoke exposure, and the development of internalizing symptoms across childhood

BACKGROUND

Prior findings relating secondhand tobacco smoke (SHS) exposure and internalizing problems, characterized by heightened anxiety and depression symptoms, have been equivocal; effects of SHS on neurodevelopment may depend on the presence of other neurotoxicants. Early life stress (ELS) is a known risk factor for internalizing symptoms and is also often concurrent with SHS exposure. To date the interactive effects of ELS and SHS on children's internalizing symptoms are unknown. We hypothesize that children with higher exposure to both prenatal SHS and ELS will have the most internalizing symptoms during the preschool period and the slowest reductions in symptoms over time.

METHODS

The present study leveraged a prospective, longitudinal birth cohort of 564 Black and Latinx mothers and their children, recruited between 1998 and 2006. Cotinine extracted from cord and maternal blood at birth served as a biomarker of prenatal SHS exposure. Parent-reported Child Behavior Checklist (CBCL) scores were examined at four timepoints between preschool and eleven years-old. ELS exposure was measured as a composite of six domains of maternal stress reported at child age five. Latent growth models examined associations between SHS, ELS, and their interaction term with trajectories of children's internalizing symptoms. In follow-up analyses, weighted quintile sum regression examined contributions of components of the ELS mixture to children's internalizing symptoms at each time point.

RESULTS

ELS interacted with SHS exposure such that higher levels of ELS and SHS exposure were associated with more internalizing symptoms during the preschool period (β = 0.14, p = 0.03). The interaction between ELS and SHS was also associated with a less negative rate of change in internalizing symptoms over time (β=-0.02, p = 0.01). Weighted quintile sum regression revealed significant contributions of maternal demoralization and other components of the stress mixture to children's internalizing problems at each age point (e.g., age 11 WQS β = 0.26, p < 0.01).

CONCLUSIONS

Our results suggest that prior inconsistencies in studies of SHS on behavior may derive from unmeasured factors that also influence behavior and co-occur with exposure, specifically maternal stress during children's early life. Findings point to modifiable targets for personalized prevention.

Cardiopulmonary Impact of Electronic Cigarettes and Vaping Products: A Scientific Statement From the American Heart Association

Vaping and electronic cigarette (e-cigarette) use have grown exponentially in the past decade, particularly among youth and young adults. Cigarette smoking is a risk factor for both cardiovascular and pulmonary disease. Because of their more limited ingredients and the absence of combustion, e-cigarettes and vaping products are often touted as safer alternative and potential tobacco-cessation products. The outbreak of e-cigarette or vaping product use-associated lung injury in the United States in 2019, which led to >2800 hospitalizations, highlighted the risks of e-cigarettes and vaping products. Currently, all e-cigarettes are regulated as tobacco products and thus do not undergo the premarket animal and human safety studies required of a drug product or medical device. Because youth prevalence of e-cigarette and vaping product use was as high as 27.5% in high school students in 2019 in the United States, it is critical to assess the short-term and long-term health effects of these products, as well as the development of interventional and public health efforts to reduce youth use. The objectives of this scientific statement are (1) to describe and discuss e-cigarettes and vaping products use patterns among youth and adults; (2) to identify harmful and potentially harmful constituents in vaping aerosols; (3) to critically assess the molecular, animal, and clinical evidence on the acute and chronic cardiovascular and pulmonary risks of e-cigarette and vaping products use; (4) to describe the current evidence of e-cigarettes and vaping products as potential tobacco-cessation products; and (5) to summarize current public health and regulatory efforts of e-cigarettes and vaping products. It is timely, therefore, to review the short-term and especially the long-term implications of e-cigarettes and vaping products on cardiopulmonary health. Early molecular and clinical evidence suggests various acute physiological effects from electronic nicotine delivery systems, particularly those containing nicotine. Additional clinical and animal-exposure model research is critically needed as the use of these products continues to grow.

Nicotinic Acetylcholine Receptor Dysfunction in Addiction and in Some Neurodegenerative and Neuropsychiatric Diseases

The cholinergic system plays an essential role in brain development, physiology, and pathophysiology. Herein, we review how specific alterations in this system, through genetic mutations or abnormal receptor function, can lead to aberrant neural circuitry that triggers disease. The review focuses on the nicotinic acetylcholine receptor (nAChR) and its role in addiction and in neurodegenerative and neuropsychiatric diseases and epilepsy. Cholinergic dysfunction is associated with inflammatory processes mainly through the involvement of α7 nAChRs expressed in brain and in peripheral immune cells. Evidence suggests that these neuroinflammatory processes trigger and aggravate pathological states. We discuss the preclinical evidence demonstrating the therapeutic potential of nAChR ligands in Alzheimer disease, Parkinson disease, schizophrenia spectrum disorders, and in autosomal dominant sleep-related hypermotor epilepsy. PubMed and Google Scholar bibliographic databases were searched with the keywords indicated below.

Cholinergic-like neurons and cerebral spheroids bearing the PSEN1 p.Ile416Thr variant mirror Alzheimer's disease neuropathology

Familial Alzheimer's disease (FAD) is a complex neurodegenerative disorder for which there are no therapeutics to date. Several mutations in presenilin 1 (PSEN 1), which is the catalytic component of γ-secretase complex, are causal of FAD. Recently, the p.Ile416Thr (I416T) PSEN 1 mutation has been reported in large kindred in Colombia. However, cell and molecular information from I416T mutation is scarce. Here, we demonstrate that menstrual stromal cells (MenSCs)-derived planar (2D) PSEN 1 I416T cholinergic-like cells (ChLNS) and (3D) cerebral spheroids (CSs) reproduce the typical neuropathological markers of FAD in 4 post-transdifferentiating or 11 days of transdifferentiating, respectively. The models produce intracellular aggregation of APPβ fragments (at day 4 and 11) and phosphorylated protein TAU at residue Ser202/Thr205 (at day 11) suggesting that iAPPβ fragments precede p-TAU. Mutant ChLNs and CSs displayed DJ-1 Cys106-SO3 (sulfonic acid), failure of mitochondria membrane potential (ΔΨm), and activation of transcription factor c-JUN and p53, expression of pro-apoptotic protein PUMA, and activation of executer protein caspase 3 (CASP3), all markers of cell death by apoptosis. Moreover, we found that both mutant ChLNs and CSs produced high amounts of extracellular eAβ42. The I416T ChLNs and CSs were irresponsive to acetylcholine induced Ca2+ influx compared to WT. The I416T PSEN 1 mutation might work as dominant-negative PSEN1 mutation. These findings might help to understanding the recurring failures of clinical trials of anti-eAβ42, and support the view that FAD is triggered by the accumulation of other intracellular AβPP metabolites, rather than eAβ42.

Occurrence of changes in the auditory evoked potentials of smokers: systematic review of the literature

PURPOSE

To verify the occurrence of abnormal auditory evoked potentials (AEP) tests in adult smokers.

RESEARCH STRATEGIES

Systematic review of the literature according to the PRISMA guidelines, to answer the question: "Are there any changes in the AEP results in adult smokers?", PECOS strategy. Research carried out on PubMed, Embase, CINAHL, LIVIVO, Scopus, Web of Science, LILACS and Scielo databases. Additional search of gray literature: Google Scholar and ProQuest hand searching of reference lists of the included studies.

SELECTION CRITERIA

Cross-sectional studies were selected, without restriction on the year of publication and language.

DATA ANALYSIS

First, the titles and abstracts of all the studies were analyzed, followed by the full reading of the eligible studies.

RESULTS

898 articles were collected, after the duplicate studies were removed and after blind analysis by three researchers, 8 studies of the observational type were selected. Most studies have found an association between active smoking and changes in electrophysiological tests.

CONCLUSION

Normal hearing adult smokers present alterations in short and long AEP. In the auditory brainstem response, the main altered components were the increase in waves latencies of I and III and in the interpeaks I - III and III - V, as well as a decrease in the amplitude of the waves. In Mismatch Negativity, there was a significant increase in wave amplitude and latency. In the long latency potential, P300, there was an increase in latencies and decreased amplitudes in the components N1 (in Fz) and P3.

Bio-enhanced fraction from Clitoria ternatea root extract ameliorates cognitive functions and in vivo hippocampal neuroplasticity in chronic cerebral hypoperfusion rat model

Research employing a bio-enhanced fraction of Clitoria ternatea (CT) to treat cognitive decline in the animal model has not yet been found. This study aimed to determine the neuroprotective effect of CT root bioactive fraction (CTRF) in chronic cerebral hypoperfusion (CCH) rat model. CTRF and its major compound, clitorienolactones A (CLA), were obtained using column chromatography. A validated HPLC-UV method was employed for the standardization of CTRF. CCH rats were given orally either vehicle or fraction (10, 20 and 40 mg/kg). Behavioural and hippocampal neuroplasticity studies were conducted following 4 weeks post-surgery. The brain hippocampus was extracted for proteins and neurotransmitters analyses. HPLC analysis showed that CTRF contained 25% (w/w) of CLA. All tested doses of CTRF and CLA (10 mg/kg) significantly restored cognitive deficits and reversed the inhibition of neuroplasticity by CCH. However, only CTRF (40 mg/kg) and CLA (10 mg/kg) significantly reversed the elevation of amyloid-beta plaque. Subsequently, treatment with CTRF (40 mg/kg) and CLA (10 mg/kg) alleviated the downregulation of molecular synaptic signalling proteins levels caused by CCH. The neurotransmitters level was restored following treatment of CTRF and CLA. Our finding suggested that CTRF improves memory and neuroplasticity in CCH rats which was mainly contributed by CLA.

Central and peripheral actions of nicotine that influence blood glucose homeostasis and the development of diabetes

Cigarette smoking has long been recognized as a risk factor for type 2 diabetes (T2D), although the precise causal mechanisms underlying this relationship remain poorly understood. Recent evidence suggests that nicotine, the primary reinforcing component in tobacco, may play a pivotal role in connecting cigarette smoking and T2D. Extensive research conducted in both humans and animals has demonstrated that nicotine can elevate blood glucose levels, disrupt glucose homeostasis, and induce insulin resistance. The review aims to elucidate the genetic variants of nicotinic acetylcholine receptors associated with diabetes risk and provide a comprehensive overview of the available data on the mechanisms through which nicotine influences blood glucose homeostasis and the development of diabetes. Here we emphasize the central and peripheral actions of nicotine on the release of glucoregulatory hormones, as well as its effects on glucose tolerance and insulin sensitivity. Notably, the central actions of nicotine within the brain, which encompass both insulin-dependent and independent mechanisms, are highlighted as potential targets for intervention strategies in diabetes management.

Synthesis and Biological Activity of Novel α-Conotoxins Derived from Endemic Polynesian Cone Snails

α-Conotoxins are well-known probes for the characterization of the various subtypes of nicotinic acetylcholine receptors (nAChRs). Identifying new α-conotoxins with different pharmacological profiles can provide further insights into the physiological or pathological roles of the numerous nAChR isoforms found at the neuromuscular junction, the central and peripheral nervous systems, and other cells such as immune cells. This study focuses on the synthesis and characterization of two novel α-conotoxins obtained from two species endemic to the Marquesas Islands, namely Conus gauguini and Conus adamsonii. Both species prey on fish, and their venom is considered a rich source of bioactive peptides that can target a wide range of pharmacological receptors in vertebrates. Here, we demonstrate the versatile use of a one-pot disulfide bond synthesis to achieve the α-conotoxin fold [Cys 1-3; 2-4] for GaIA and AdIA, using the 2-nitrobenzyl (NBzl) protecting group of cysteines for effective regioselective oxidation. The potency and selectivity of GaIA and AdIA against rat nicotinic acetylcholine receptors were investigated electrophysiologically and revealed potent inhibitory activities. GaIA was most active at the muscle nAChR (IC₅₀ = 38 nM), whereas AdIA was most potent at the neuronal α6/3 β2β3 subtype (IC₅₀ = 177 nM). Overall, this study contributes to a better understanding of the structure-activity relationships of α-conotoxins, which may help in the design of more selective tools.

Nicotine's effect on cognition, a friend or foe?

Tobacco smoking is a preventable cause of morbidity and mortality throughout the world. Smoking comes in form of absorption of many compounds, among which nicotine is the main psychoactive component of tobacco and its positive and negative reinforcement effects are proposed to be the key mechanism for the initiation and maintenance of smoking. Growing evidence suggests that the cognitive enhancement effects of nicotine may also contribute to the difficulty of quitting smoking, especially in individuals with psychiatric disorders. In this review, we first introduce the beneficial effect of nicotine on cognition including attention, short-term memory and long-term memory. We next summarize the beneficial effect of nicotine on cognition under pathological conditions, including Alzheimer's disease, Parkinson's disease, Schizophrenia, Stress-induced Anxiety, Depression, and drug-induced memory impairment. The possible mechanism underlying nicotine's effect is also explored. Finally, nicotine's detrimental effect on cognition is discussed, including in the prenatal and adolescent periods, and high-dose nicotine- and withdrawal-induced memory impairment is emphasized. Therefore, nicotine serves as both a friend and foe. Nicotine-derived compounds could be a promising strategy to alleviate neurological disease-associated cognitive deficit, however, due to nicotine's detrimental effect, continued educational programs and public awareness campaigns are needed to reduce tobacco use among pregnant women and smoking should be quitted even if it is e-cigarette, especially for the adolescents.

Possible involvement of brain hydrogen sulphide in the inhibition of the rat micturition reflex induced by activation of brain alpha7 nicotinic acetylcholine receptors

We previously reported that brain α7 nicotinic acetylcholine receptors inhibited the rat micturition reflex. To elucidate the mechanisms underlying this inhibition, we focused on the relationship between α7 nicotinic acetylcholine receptors and hydrogen sulphide (H₂S) because we found that H₂S also inhibits the rat micturition reflex in the brain. Therefore, we investigated whether H₂S is involved in the inhibition of the micturition reflex induced by the activation of α7 nicotinic acetylcholine receptors in the brain. Cystometry was performed in male Wistar rats under urethane anesthesia (0.8 g/kg, ip) to examine the effects of icv pre-treated GYY4137 (H₂S donor, 1 or 3 nmol/rat) or aminooxyacetic acid (AOAA; non-selective H₂S synthesis inhibitor, 3 or 10 μg/rat) on PHA568487 (α7 nicotinic acetylcholine receptor agonist, icv)-induced prolongation of intercontraction intervals. PHA568487 administration at a lower dose (0.3 nmol/rat, icv) had no significant effect on intercontraction intervals, while under pre-treatment with GYY4137 (3 nmol/rat icv), PHA568487 (0.3 nmol/rat, icv) significantly prolonged intercontraction intervals. PHA568487 at a higher dose (1 nmol/rat, icv) induced intercontraction interval prolongation, and the PHA568487-induced prolongation was significantly suppressed by AOAA (10 μg/rat, icv). The AOAA-induced suppression of the PHA568487-induced intercontraction interval prolongation was negated by supplementing H₂S via GYY4137 at a lower dose (1 nmol/rat, icv) in the brain. GYY4137 or AOAA alone showed no significant effect on intercontraction intervals at each dose used in this study. These findings suggest a possible involvement of brain H₂S in inhibiting the rat micturition reflex induced by activation of brain alpha7 nicotinic acetylcholine receptors.

Comparison of fluorescence biosensors and whole-cell patch clamp recording in detecting ACh, NE, and 5-HT

The communication between neurons and, in some cases, between neurons and non-neuronal cells, through neurotransmission plays a crucial role in various physiological and pathological processes. Despite its importance, the neuromodulatory transmission in most tissues and organs remains poorly understood due to the limitations of current tools for direct measurement of neuromodulatory transmitters. In order to study the functional roles of neuromodulatory transmitters in animal behaviors and brain disorders, new fluorescent sensors based on bacterial periplasmic binding proteins (PBPs) and G-protein coupled receptors have been developed, but their results have not been compared to or multiplexed with traditional methods such as electrophysiological recordings. In this study, a multiplexed method was developed to measure acetylcholine (ACh), norepinephrine (NE), and serotonin (5-HT) in cultured rat hippocampal slices using simultaneous whole-cell patch clamp recordings and genetically encoded fluorescence sensor imaging. The strengths and weaknesses of each technique were compared, and the results showed that both techniques did not interfere with each other. In general, genetically encoded sensors GRAB_NE and GRAB_5HT1.₀ showed better stability compared to electrophysiological recordings in detecting NE and 5-HT, while electrophysiological recordings had faster temporal kinetics in reporting ACh. Moreover, genetically encoded sensors mainly report the presynaptic neurotransmitter release while electrophysiological recordings provide more information of the activation of downstream receptors. In sum, this study demonstrates the use of combined techniques to measure neurotransmitter dynamics and highlights the potential for future multianalyte monitoring.

Noradrenergic and cholinergic systems take centre stage in neuropsychiatric diseases of ageing

Noradrenergic and cholinergic systems are among the most vulnerable brain systems in neuropsychiatric diseases of ageing, including Alzheimer's disease, Parkinson's disease, Lewy body dementia, and progressive supranuclear palsy. As these systems fail, they contribute directly to many of the characteristic cognitive and psychiatric symptoms. However, their contribution to symptoms is not sufficiently understood, and pharmacological interventions targeting noradrenergic and cholinergic systems have met with mixed success. Part of the challenge is the complex neurobiology of these systems, operating across multiple timescales, and with non-linear changes across the adult lifespan and disease course. We address these challenges in a detailed review of the noradrenergic and cholinergic systems, outlining their roles in cognition and behaviour, and how they influence neuropsychiatric symptoms in disease. By bridging across levels of analysis, we highlight opportunities for improving drug therapies and for pursuing personalised medicine strategies.

Control of Synaptic Levels of Nicotinic Acetylcholine Receptor by the Sequestering Subunit Dα5 and Secreted Scaffold Protein Hig

The presentation of nicotinic acetylcholine receptors (nAChRs) on synaptic membranes is crucial for generating cholinergic circuits, some of which are associated with memory function and neurodegenerative disorders. Although the physiology and structure of nAChR, a cation channel comprising five subunits, have been extensively studied, little is known about how the receptor levels in interneuronal synapses are determined and which nAChR subunits participate in the regulatory process in cooperation with synaptic cleft matrices and intracellular proteins. By a genetic screen of Drosophila, we identified mutations in the nAChR subunit Dα5 gene as suppressors that restored the mutant phenotypes of hig, which encodes a secretory matrix protein localized to cholinergic synaptic clefts in the brain. Only the loss of function of Dα5 among the 10 nAChR subunits suppressed hig mutant phenotypes in both male and female flies. Dα5 behaved as a lethal factor when Hig was defective; loss of Dα5 in hig mutants rescued lethality, upregulating Dα6 synaptic levels. By contrast, levels of Dα5, Dα6, and Dα7 subunits were all reduced in hig mutants. These three subunits have distinct properties for interaction with Hig or trafficking, as confirmed by chimeric subunit experiments. Notably, the chimeric Dα5 protein, which has the extracellular sequences that display no positive interaction with Hig, exhibited abnormal distribution and lethality even in the presence of Hig. We propose that the sequestering subunit Dα5 functions by reducing synaptic levels of nAChR through internalization, and this process is blocked by Hig, which tethers Dα5 to the synaptic cleft matrix.SIGNIFICANCE STATEMENT Because the cholinergic synapse is one of the major synapses that generate various brain functions, numerous studies have sought to reveal the physiology and structure of the nicotinic acetylcholine receptor (nAChR). However, little is known about how synaptic levels of nAChR are controlled and which nAChR subunits participate in the regulatory process in cooperation with synaptic cleft matrices. By a genetic screen of Drosophila, we identified mutations in the nAChR subunit Dα5 gene as suppressors that restored the mutant phenotypes of hig, which encodes a secretory matrix protein localized to cholinergic synaptic clefts. Our data indicate that Dα5 functions in reducing synaptic levels of nAChR, and this process is blocked by Hig, which tethers Dα5 to the synaptic cleft matrix.

SARS-CoV-2 spike ectodomain targets α7 nicotinic acetylcholine receptors

Virus entry into animal cells is initiated by attachment to target macromolecules located on host cells. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) trimeric spike glycoprotein targets host angiotensin converting enzyme 2 to gain cellular access. The SARS-CoV-2 glycoprotein contains a neurotoxin-like region that has sequence similarities to the rabies virus and the HIV glycoproteins, as well as to snake neurotoxins, which interact with nicotinic acetylcholine receptor (nAChR) subtypes via this region. Using a peptide of the neurotoxin-like region of SARS-CoV-2 (SARS-CoV-2 glycoprotein peptide [SCoV2P]), we identified that this area moderately inhibits α3β2, α3β4, and α4β2 subtypes, while potentiating and inhibiting α7 nAChRs. These nAChR subtypes are found in target tissues including the nose, lung, central nervous system, and immune cells. Importantly, SCoV2P potentiates and inhibits ACh-induced α7 nAChR responses by an allosteric mechanism, with nicotine enhancing these effects. Live-cell confocal microscopy was used to confirm that SCoV2P interacts with α7 nAChRs in transfected neuronal-like N2a and human embryonic kidney 293 cells. The SARS-CoV-2 ectodomain functionally potentiates and inhibits the α7 subtype with nanomolar potency. Our functional findings identify that the α7 nAChR is a target for the SARS-CoV-2 glycoprotein, providing a new aspect to our understanding of SARS-CoV-2 and host cell interactions, in addition to disease pathogenesis.

Smoking status ameliorates cholinergic impairments in cortical inhibition in patients with schizophrenia

Rationale Modulation of cortical excitability, in particular inhibition, is impaired in patients with schizophrenia. Chronic nicotine consumption, which is prevalent in this group, has been shown to alter cortical excitability in healthy individuals and to increase inhibitory activity. Thus, beneficial effects of smoking on impaired cortical excitability in patients with schizophrenia have been proposed, though direct experimental evidence is still lacking.

OBJECTIVES

We aimed to explore the effect of chronic smoking on cortical excitability by comparing smoking and non-smoking patients with schizophrenia.

METHOD

Twenty-six smoking and 19 non-smoking patients diagnosed with schizophrenia were included. Transcranial magnetic stimulation (TMS) applied to the primary motor cortex served as experimental paradigm for measuring corticospinal and intracortical excitability as follows: Resting motor threshold (RMT) and the input/output curve (I/O curve) were obtained to assess corticospinal excitability. Intracortical excitability was explored using paired-pulse TMS techniques (intracortical facilitation (ICF), short-latency intracortical inhibition (SICI) and short-latency afferent inhibition (SAI)).

RESULTS

A significantly stronger inhibition in the cholinergically driven SAI protocol was observed in smokers compared to non-smokers. All other measures did not show significant differences between groups.

CONCLUSION

Our results suggest an increased inhibition within cholinergic circuits due to chronic nicotine consumption in schizophrenia. This increase may compensate impaired cholinergic neurotransmission and could explain the high rate of smokers in schizophrenia.

Effect of Cigarette Smoke Exposure and Aspirin Treatment on Neurotransmitters’ Tissue Content in Rats’ Hippocampus and Amygdala

Cigarette smoke withdrawal can cause anxiety-like behavior and modulate neurotransmitter-related proteins in the brain. We examined the effects of cigarette smoke with and without aspirin treatment on the concentrations of neurotransmitters, including dopamine, serotonin, glutamate, glutamine, and GABA in the amygdala and hippocampus. Sprague-Dawley rats were randomly assigned to four different groups: (1) control group exposed only to standard room air, (2) cigarette smoke exposed group treated with saline vehicle, (3) cigarette smoke exposed group treated with aspirin (30 mg/kg), and (4) control group treated only with aspirin (30 mg/kg). Cigarette smoke exposure was performed for 2 h/day, 5 days/week, for 31 days. Behavioral testing was carried out weekly, 24 h after cigarette smoke exposure, during acute withdrawal. At the end of week 4, rats were given either distilled water (1 mL) or aspirin 45 min before cigarette exposure for 11 days. Dopamine, serotonin, glutamate, glutamine, and GABA were extracted from both the amygdala and hippocampus and were separated and quantified using a developed and validated HPLC-MS/MS method. Cigarette smoke withdrawal induced anxiety behaviors, and aspirin treatment reduced this effect. Cigarette smoke exposure increased tissue content of dopamine, serotonin, glutamate, glutamine, and GABA, and aspirin treatment reversed this effect. Cigarette smoke caused an increase in tissue content of several neurotransmitters as well as anxiety-like behavior, and these effects were normalized by aspirin treatment.

Basal forebrain cholinergic signalling: development, connectivity and roles in cognition

Acetylcholine plays an essential role in fundamental aspects of cognition. Studies that have mapped the activity and functional connectivity of cholinergic neurons have shown that the axons of basal forebrain cholinergic neurons innervate the pallium with far more topographical and functional organization than was historically appreciated. Together with the results of studies using new probes that allow release of acetylcholine to be detected with high spatial and temporal resolution, these findings have implicated cholinergic networks in 'binding' diverse behaviours that contribute to cognition. Here, we review recent findings on the developmental origins, connectivity and function of cholinergic neurons, and explore the participation of cholinergic signalling in the encoding of cognition-related behaviours.

The importance of ligand gated ion channels in sleep and sleep disorders

On average, humans spend about 26 years of their life sleeping. Increased sleep duration and quality has been linked to reduced disease risk; however, the cellular and molecular underpinnings of sleep remain open questions. It has been known for some time that pharmacological modulation of neurotransmission in the brain can promote either sleep or wakefulness thereby providing some clues about the molecular mechanisms at play. However, the field of sleep research has developed an increasingly detailed understanding of the requisite neuronal circuitry and key neurotransmitter receptor subtypes, suggesting that it may be possible to identify next generation pharmacological interventions to treat sleep disorders within this same space. The aim of this work is to examine the latest physiological and pharmacological findings highlighting the contribution of ligand gated ion channels including the inhibitory GABA_A and glycine receptors and excitatory nicotinic acetylcholine receptors and glutamate receptors in the sleep-wake cycle regulation. Overall, a better understanding of ligand gated ion channels in sleep will help determine if these highly druggable targets could facilitate a better night's sleep.

BNC210: an investigational α7-nicotinic acetylcholine receptor modulator for the treatment of anxiety disorders

INTRODUCTION

Anxiety disorders are common, disabling psychiatric conditions associated with excessive worry, irritability, and physiological symptoms of stress. Following insufficient response to psychological therapies, first-line pharmacological treatments for anxiety disorders suffer from inconsistent efficacy, addiction, and intolerable side-effect profiles (e.g. sedation), especially when used inappropriately or contrary to evidence-based guidelines. Developing anxiolytics acting via cholinergic modulation may provide novel options for the treatment of anxiety disorders, without the drawbacks of existing anxiolytics.

AREAS COVERED

We review pharmacological treatment of anxiety disorders and proposed mechanisms of action in relation to the associated neural circuitry. We then consider the mechanism of action, pharmacodynamics, and pharmacokinetics of the negative-allosteric modulator of the alpha7 nicotinic receptor BNC210, an investigational anxiolytic so far employed in studies of those with social anxiety disorder, post-traumatic stress disorder, and agitation in hospitalized elderly. Lastly, we consider the environment of competitor compounds for this indication, and BNC210's place within it, in both the present and near-future.

EXPERT OPINION

: There is a relative paucity of data regarding BNC210, albeit the small amount of mostly non-peer reviewed data indicate it is a well-tolerated, effective anxiolytic. Phase III trials are required for proper appraisal of its utility.