Analysis of clinical features and outcomes in patients with ocular myasthenia gravis according to anti-acetylcholine receptor antibody-seropositivity.

PURPOSE: To comparatively analyze the clinical characteristics of patients with ocular myasthenia gravis (OMG) referred to an ophthalmology clinic, according to anti-acetylcholine receptor antibody (AchR Ab)-seropositivity. STUDY DESIGN: Retrospective Cohort Study. METHODS: Medical records of patients with OMG who presented to a tertiary eye care center between 2003 and 2020 were retrospectively reviewed. Demographics, ophthalmologic characteristics, response to medical treatment, presence of autoimmune thyroid disease and thyroid autoantibody were compared between the AchR Ab seropositive and seronegative groups. RESULTS: A total of 130 patients with OMG were identified; among them, 46 patients (35.4%) had autoantibody against acetylcholine receptors. The mean age at symptom onset was 42.4 ± 18.9 years. There were no differences in mean age at symptom onset, gender ratio, and mean follow-up period between patients with seropositive and seronegative OMG. Graves ophthalmopathy was significantly more frequent in seronegative patients (p = 0.04), while thymic disease (p < 0.01) was more frequent in seropositive patients (p < 0.01). Among patients with seropositive OMG, 52.3% showed a good response to medical treatment, while only 31.4% of the seronegative patients were classified as good responders (p = 0.01). Thyroid dysfunction was found in 27.4% patients with OMG and the proportion of thyroid dysfunction was not different according to anti-acetylcholine receptor antibody-seropositivity. CONCLUSION: Seropositivity to acetylcholine receptor antibody is associated with a better response to medical treatment and lower risk of concomitant autoimmune thyroid disease in patients with OMG.

Safety and Usefulness of Intracoronary Acetylcholine 200 µg Into the Left Coronary Artery as Vasoreactivity Testing: Comparisons With Intracoronary Acetylcholine Maximum 100 µg.

OBJECTIVES: We retrospectively analyzed the usefulness and safety of intracoronary acetylcholine (ACh) 200 µg into the left coronary artery (LCA) as vasoreactivity testing compared with intracoronary ACh 100 µg. METHODS: We recruited 1433 patients who had angina-like chest pain and intracoronary ACh testing in the LCA, including 1234 patients with a maximum ACh 100 µg and 199 patients with a maximum ACh 200 µg. ACh was injected in incremental doses of 20/50/100/200 µg into the LCA. Positive spasm was defined as ≥ 90% stenosis, usual chest pain, and ischemic electrocardiogram (ECG) changes. RESULTS: The incidence of coronary constriction ≥ 90%, usual chest pain, and ischemic ECG changes with a maximum ACh of 100 µg was markedly higher than that with a maximum ACh of 200 µg. The frequency of unusual chest pain in patients with a maximum ACh of 200 µg was higher than that in those with a maximum ACh of 100 µg (13% vs. 3%, p < 0.001). In patients with rest angina, positive spasm of maximum ACh 100 µg was significantly higher than that of maximum ACh 200 µg, whereas there was no difference regarding positive spasm in patients with atypical chest pain between the two ACh doses. Major complications (1.38% vs. 1.51%, p = 0.8565) and the occurrence of paroxysmal atrial fibrillation (1.81% vs. 2.63%, p = 0.6307) during ACh testing in the LCA were not different between the two maximum ACH doses. CONCLUSIONS: Intracoronary ACh 200 µg into the LCA is clinically useful and safe for vasoreactivity testing when intracoronary ACh 100 µg dose not provoke spasms.

Molecular Recognition Properties of Nicotinic Ligands Determining Selectivity Between Insect and Mammalian Receptors.

This investigation defines the roles of various amino acids, neighboring key conserved amino acids in loops C and D of the nicotinic acetylcholine (ACh) receptor (nAChR), in the selective molecular recognition of nicotinic ligands with diverse pharmacophores using Aplysia californica ACh binding protein Y55W (Ac-AChBP) mutants (+Q57R; + Q57R+S189 V; + Q57R+S189E; + Q57T; + Q57T+S189 V; + Q57T+S189E) and Lymnaea stagnalis AChBP (Ls-AChBP) mutants (Q55T; Q55T+S186E; Q55R) as insect and mammalian nAChR structural surrogates, respectively. N-nitro/cyanoimine insecticides show high affinity to four Ac-AChBPs containing Arg57 or Thr57 and Ser189 or Val189, except for those with Glu189. Pyrazinoyl compound selectively interacts with the three Ac-AChBPs containing Arg57 and Ser189, Val189, or Glu189. Cationic ligands prefer three Ac-AChBPs with Thr57 and Ser189, Val189, or Glu189 and two Ls-AChBPs providing Thr55 ± Glu186 over the four Ac- and Ls-AChBPs with Arg57/55. Accordingly, loop C contributes to N-nitro/cyanoimine insecticide action, and loop D controls the affinity of the pyrazinoyl or cationic ligand.

Emerging Functions of Neuromodulation during Sleep.

Neuromodulators act on multiple timescales to affect neuronal activity and behavior. They function as synaptic fine-tuners and master coordinators of neuronal activity across distant brain regions and body organs. While much research on neuromodulation has focused on roles in promoting features of wakefulness and transitions between sleep and wake states, the precise dynamics and functions of neuromodulatory signaling during sleep have received less attention. This review discusses research presented at our minisymposium at the 2024 Society for Neuroscience meeting, highlighting how norepinephrine, dopamine, and acetylcholine orchestrate brain oscillatory activity, control sleep architecture and microarchitecture, regulate responsiveness to sensory stimuli, and facilitate memory consolidation. The potential of each neuromodulator to influence neuronal activity is shaped by the state of the synaptic milieu, which in turn is influenced by the organismal or systemic state. Investigating the effects of neuromodulator release across different sleep substates and synaptic environments offers unique opportunities to deepen our understanding of neuromodulation and explore the distinct computational opportunities that arise during sleep. Moreover, since alterations in neuromodulatory signaling and sleep are implicated in various neuropsychiatric disorders and because existing pharmacological treatments affect neuromodulatory signaling, gaining a deeper understanding of the less-studied aspects of neuromodulators during sleep is of high importance.

Assessment of the Interaction of Acetylcholinesterase Binding with Bioactive Compounds from Coffee and Coffee Fractions Digested In Vitro in the Gastrointestinal Tract.

The aim of the study was to evaluate the degree of acetylcholinesterase (AChE) inhibition by green and light- and dark-roasted coffee extracts and their fractions after digestion in a simulated gastrointestinal tract. The analysis was carried out using isothermal titration calorimetry, molecular docking, and dynamics simulations. The results showed that 3-O-caffeoylquinic acid binds strongly to AChE through hydrogen interactions with the amino acids ARG289A, HIS440A, and PHE288A and hydrophobic interactions with TYR121A in the active site of the enzyme. The Robusta green coffee extract (ΔG = -35.87 kJ/mol) and dichlorogenic acid fraction (ΔG = -19-29 kJ/mol) showed the highest affinity. Dichlorogenic acids (3,4-O-dicaffeoylquinic acid, 4,5-O-dicaffeoylquinic acid, and 3,4-O-dicaffeoylquinic acid) have high affinity for AChE as single compounds (ΔG(ITC) = -48.99-55.36 kJ/mol, ΔG(LF/AD) = -43.38-45.38 kJ/mol). The concentration necessary to reduce AChE activity by 50% amounted to 0.22 µmol/µmol chlorogenic acids to the enzyme.

Efficacy and safety of low-dose rituximab in the treatment of myasthenia gravis: a systemic review and meta-analysis.

Background: Rituximab (RTX) is a monoclonal antibody that has been increasingly used in the treatment of myasthenia gravis (MG). In most studies, the therapeutic protocol of RTX has been similar to that adopted for B cell lymphoma, with an increasing number of studies aimed at exploring the efficacy of low-dose RTX in MG. However, the beneficial effects of low-dose RTX in MG remain a subject of critical debate. Methods: This study was conducted following the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines. Two reviewers (Xishuai Yang and Bingxia Li) independently conducted searches across multiple databases, including PubMed, MEDLINE, EMBASE, Web of Science, Cochrane Library, and China National Knowledge Infrastructure (CNKI). A meta-analysis, utilizing representative forest plots, was performed to assess "Improved clinical status" and changes in the Quantitative Myasthenia Gravis (QMG) score before and after treatment. Results: A total of 17 studies involving 292 patients were included in the meta-analysis. A noticeable improvement in clinical status was observed in 91% of patients at the final follow-up after therapy (95% CI: 84-96%, P < 0.001). The QMG score showed a significant reduction following the treatment, with a standardized mean difference (SMD) of -1.69 (95% CI: -2.21 to -1.16, Z = 6.29, P < 0.001). In the acetylcholine receptor antibody-positive myasthenia gravis (AChR-MG) group, 90% of patients achieved improved clinical status (95% CI: 80-97%, P < 0.001) and the QMG score significantly decreased after low-dose RTX treatment, with an SMD of -1.51 (95% CI: -0.80 to -2.21, Z = 4.50, P < 0.001). In the muscle-specific kinase antibody-positive myasthenia gravis (MuSK-MG) group, 97% of patients achieved improved clinical status (95% CI: 89-100%, P < 0.001). The QMG score also significantly decreased following low-dose RTX treatment, with an SMD of -2.31 (95% CI: -2.99 to -1.62, Z = 6.60, P < 0.001). Adverse effects were reported in 29 out of 207 patients (14%, including infusion reactions in 22 patients (10.1%), infections in three patients (1.45%), cytopenia in two patients (0.96%), eosinophilia in one patient (0.48%), and hemiplegia in one patient (0.48%). Additionally, one patient (0.48%) succumbed to complications from invasive thymoma. Conclusion: Our meta-analysis shows that low-dose RTX is both effective and safe for treating MG. Systematic Review Registration: PROSPERO, identifier: CRD42024509951.

Acetylcholine receptor-ß inhibition by interleukin-6 in skeletal muscles contributes to modulating neuromuscular junction during aging.

BACKGROUND: Aging-related strength decline contributes to physiological deterioration and is a good predictor of poor prognosis. However, the mechanisms underlying neuromuscular junction disorders affecting contraction in aging are not well described. We hypothesized that the autocrine effect of interleukin (IL)-6 secreted by skeletal muscle inhibits acetylcholine receptor (AChR) expression, potentially causing aging-related strength decline. Therefore, we investigated IL-6 and AChR ß-subunit (AChR-ß) expression in the muscles and sera of aging C57BL/6J mice and verified the effect of IL-6 on AChR-ß expression. METHODS: Animal experiments, in vitro studies, bioinformatics, gene manipulation, dual luciferase reporter gene assays, and chromatin immunoprecipitation experiments were used to explore the role of the transcription cofactor peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC1α) and its interacting transcription factors in the IL-6-mediated regulation of AChR-ß expression. RESULTS: IL-6 expression gradually increased during aging, inhibiting AChR-ß expression, which was reversed by tocilizumab. Both tocilizumab and the PGC1α agonist reversed the inhibiting effect of IL-6 expression on AChR-ß. Compared to inhibition of signal transducer and activator of transcription 3, extracellular signal-regulated kinases 1/2 (ERK1/2) inhibition suppressed the effects of IL-6 on AChR-ß and PGC1α. In aging mouse muscles and myotubes, myocyte enhancer factor 2 C (MEF2C) was recruited by PGC1α, which directly binds to the AChR-ß promoter to regulate its expression. CONCLUSIONS: This study verifies AChR-ß regulation by the IL-6/IL-6R-ERK1/2-PGC1α/MEF2C pathway. Hence, evaluating muscle secretion, myokines, and AChRs at an earlier stage to determine pathological progression is important. Moreover, developing intervention strategies for monitoring, maintaining, and improving muscle structure and function is necessary.

Acute Hypobaric Hypoxia Causes Alterations in Acetylcholine-Mediated Signaling Through Varying Expression of Muscarinic Receptors in the Prefrontal Cortex and Cerebellum of Rats' Brain.

Sharma, Narendra Kumar, Mansi Srivastava, Tikam Chand Dakal, Vipin Ranga, and Pawan Kumar Maurya. Acute hypobaric hypoxia (HH) causes alterations in acetylcholine-mediated signaling through varying expression of muscarinic receptors in the PFC and cerebellum of rats' brain. High Alt Med Biol. 00:00-00, 2024. Background: Muscarinic receptor (CHRM) proteins are G-protein-associated acetylcholine receptors found in neuronal membranes. Five major subtypes, CHRM1-CHRM5, modulate acetylcholine in central nervous system signaling cascades. CHRM1, CHRM3, and CHRM5 are linked to Gαq/Gα11 proteins, whereas CHRM2 and CHRM4 are linked to Gαi/Gαo proteins. Objective: Limited research has been conducted to explore the impact of HH on CHRM gene expressions. It is caused by low oxygen availability at high altitudes, which impairs neurotransmission, cognitive performance, and physiological functions. Previous studies have shown that exposure to hypoxia leads to a reduction in CHRM receptors, which in turn causes alteration in signal transduction, physiological responses, cognitive deficits, and mood alterations. Method: In the present study, we have used semiquantitative PCR to measure muscarinic receptor gene expression after 6, 12, and 24 hours of HH exposure at 25,000 feet using a decompression chamber in rat brain's PFC and cerebellum. Result: We have found that CHRM1-CHRM5 downregulated after acute exposure to hypoxia until 12 hours, and then, the expression level of these receptors increased to 24 hours when compared with 12 hours in PFC. All subtypes have shown a similar pattern in PFC regions under hypoxia exposure. On the other hand, these receptors have shown altered expression at different time points in the cerebellum. CHRM1 and CHRM4 acutely downregulated, CHRM2 and CHRM5 downregulated, while CHRM3 upregulated after hypoxia exposure. Conclusion: Our study, for the first time, has shown the altered expressions of muscarinic receptors under temporal hypoxia exposure. The altered expression pattern has shown an association with acclimatization and protection against necrosis due to hypoxia. This study may pave further investigations for understanding and addressing the cognitive, behavioral, and physiological impacts of hypoxia and therapeutic development.

New treatment strategies in Myasthenia gravis.

Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disorder characterized by muscle weakness and fatigue. The disease is primarily caused by antibodies targeting acetylcholine receptors (AChR) and muscle-specific kinase (MuSK) proteins at the neuromuscular junction. Traditional treatments for MG, such as acetylcholinesterase inhibitors, corticosteroids, and immunosuppressants, have shown efficacy but are often associated with significant long-term side effects and variable patient response rates. Notably, approximately 15% of patients exhibit inadequate responses to these standard therapies. Recent advancements in molecular therapies, including monoclonal antibodies, B cell-depleting agents, complement inhibitors, Fc receptor antagonists, and chimeric antigen receptor (CAR) T cell-based therapies, have introduced promising alternatives for MG treatment. These novel therapeutic approaches offer potential improvements in targeting specific immune pathways involved in MG pathogenesis. This review highlights the progress and challenges in developing and implementing these molecular therapies. It discusses their mechanisms, efficacy, and the potential for personalized medicine in managing MG. The integration of new molecular therapies into clinical practice could significantly transform the treatment landscape of MG, offering more effective and tailored therapeutic options for patients who do not respond adequately to traditional treatments. These innovations underscore the importance of ongoing research and clinical trials to optimize therapeutic strategies and improve the quality of life for individuals with MG.

Cortical acetylcholine dynamics are predicted by cholinergic axon activity and behavior state.

Acetylcholine (ACh) is thought to play a role in driving the rapid, spontaneous brain-state transitions that occur during wakefulness; however, the spatiotemporal properties of cortical ACh activity during these state changes are still unclear. We perform simultaneous imaging of GRAB-ACh sensors, GCaMP-expressing basal forebrain axons, and behavior to address this question. We observed a high correlation between axon and GRAB-ACh activity around periods of locomotion and pupil dilation. GRAB-ACh fluorescence could be accurately predicted from axonal activity alone, and local ACh activity decreased at farther distances from an axon. Deconvolution of GRAB-ACh traces allowed us to account for sensor kinetics and emphasized rapid clearance of small ACh transients. We trained a model to predict ACh from pupil size and running speed, which generalized well to unseen data. These results contribute to a growing understanding of the precise timing and spatial characteristics of cortical ACh during fast brain-state transitions.

Conductance properties of the α9α10 nicotinic acetylcholine receptor of neonatal mouse inner and outer hair cells.

In the developing cochlea, just before the onset of hearing on postnatal day 12, the medial olivocochlear efferent axons in synaptic contact with the inner hair cells (IHCs) start withdrawing and new efferent synaptic connections are formed on the outer hair cells (OHCs), thereby progressing towards the adult pattern of medial olivocochlear efferent innervation. The synapses are inhibitory, calcium influx through the α9α10 nicotinic acetylcholine receptors (nAChRs) driving opening of calcium-dependent potassium channels. The nAChRs appear to function similarly in IHCs and OHCs, although with probable kinetic differences. Our aim was to assess their functional similarity in the neonatal mouse cochlea by making whole-cell recordings from both hair cell types between postnatal day 7 and 10 when nAChRs are expressed. ACh was applied to voltage-clamped hair cells by pressure-ejection from a pipette. The cells were dialysed with a Cs+-based solution designed to eliminate calcium-dependent potassium currents. There were differences in amplitude, voltage-sensitivity and reversal potential of the nAChR currents between IHCs and OHCs. There was also some indication that IHC nAChRs have slower activation and desensitization kinetics, although the relatively slow ACh application limited interpretation of this result. These differences, particularly concerning the reversal potential, might indicate the presence of different auxiliary protein subunits of the α9α10 receptor in neonatal IHCs and OHCs.

Concentration-dependent microvascular responses to repeated iontophoresis of acetylcholine.

BACKGROUND: Iontophoresis studies face challenges due to the unknown absolute drug dose delivered and the possible effect of the current used in drug delivery on the microvessels, known as current-induced vasodilation. This study aimed to investigate how various concentrations of acetylcholine (ACh), delivered through transdermal iontophoresis using repeated current pulses, impact the recovery profile of the microvascular response. METHODS: The study included fifteen healthy volunteers, and microvascular responses to five concentrations of iontophorised ACh (ranging from 0.0055 mM to 55 mM) and sterile water were assessed at six forearm skin sites using polarized reflectance spectroscopy. Iontophoresis at each concentration involved three consecutive pulses separated 8 recovery periods. RESULTS: Current-induced responses were more pronounced for lower concentrations of ACh and for sterile water. With repeated pulses, lower concentrations of ACh exhibited a recovery profile more akin to higher concentrations. PERSPECTIVE: Through repeated iontophoresis of ACh, microvascular responses exhibit variation based on the drug concentration and the number of pulses administered. These variations are likely attributed to changes in skin conductivity and permeability.

Alterations in Neuronal Nicotinic Acetylcholine Receptors in the Pathogenesis of Various Cognitive Impairments.

Cognitive impairment is a typical symptom of both neurodegenerative and certain other diseases. In connection with these different pathologies, the etiology and neurological and metabolic changes associated with cognitive impairment must differ. Until these characteristics and differences are understood in greater detail, pharmacological treatment of the different forms of cognitive impairment remains suboptimal. Neurotransmitter receptors, including neuronal nicotinic acetylcholine receptors (nAChRs), dopamine receptors, and glutamine receptors, play key roles in the functions and metabolisms of the brain. Among these, the role of nAChRs in the development of cognitive impairment has attracted more and more attention. The present review summarizes what is presently known concerning the structure, distribution, metabolism, and function of nAChRs, as well as their involvement in major cognitive disorders such as Alzheimer's disease, Parkinson's disease, vascular dementia, schizophrenia, and diabetes mellitus. As will be discussed, the relevant scientific literature reveals clearly that the α4ß2 and α7 nAChR subtypes and/or subunits of the receptors play major roles in maintaining cognitive function and in neuroprotection of the brain. Accordingly, focusing on these as targets of drug therapy can be expected to lead to breakthroughs in the treatment of cognitive disorders such as AD and schizophrenia.

The α3ß4 nAChR tissue distribution identified by fluorescent α-conotoxin [D11A]LvIA.

α3ß4, a vital subtype of neuronal nicotinic acetylcholine receptors (nAChRs), is widely distributed in the brain, ganglia, and adrenal glands, associated with addiction and neurological diseases. However, the lack of specific imaging tools for α3ß4 nAChRs has hindered the investigation of their tissue distribution and functions. [D11A]LvIA, a peptide derived from marine cone snails, demonstrates high affinity and potency for α3ß4 nAChRs, making it a valuable pharmacological tool for studying this receptor subtype. In this study, three fluorescent conjugates of [D11A]LvIA were synthesized using 6-TAMRA-SE (R), Cy3-NHS-ester (Cy3), and BODIPY-FL NHS ester (BDP) dyes. The electrophysiological activities were assessed in Xenopus laevis oocytes by two-electrodes voltage clamp (TEVC). [D11A]LvIA-Cy3 and [D11A]LvIA-BDP show improved selectivity and affinity, with IC50 values of 512.70 nM and 343.50 nM, respectively, and [D11A]LvIA-Cy3 exhibits better stability in cerebrospinal fluid (CSF). Utilizing [D11A]LvIA-Cy3, we successfully visualized the distribution of α3ß4 nAChRs in rat trigeminal ganglia, retina, adrenal glands, and various brain regions. This novel fluorescent peptide provides a significant pharmacological tool for the exploration and visualization in-situ distribution of α3ß4 nAChRs in different tissues and also assists in clarifying the function.

Visualization and Analysis of Neuromuscular Junctions Using Immunofluorescence.

The neuromuscular junction (NMJ) is an interface between motor neurons and skeletal muscle fibers, facilitating the transmission of signals that initiate muscle contraction. Its pivotal role lies in ensuring efficient communication between the nervous system and muscles, allowing for precise and coordinated movements essential for everyday activities and overall motor function. To provide insights into neuromuscular disease and development, understanding the physiology of NMJ is essential. We target acetylcholine receptors (AChR) by immunofluorescence assay (IFA) with α-bungarotoxin (BTX; snake venom neurotoxins binding to AChR) to visualize and quantify the NMJ. Changes in AChR distribution or structure can indicate alterations in receptor density, which may be associated with neuromuscular disorders or conditions that affect synaptic transmission. This protocol provides the methodology for isolating and longitudinally sectioning gastrocnemius muscle for AChR-targeted IFA for confocal microscopy and performing quantitative analysis of NMJs. Key features • Visualizes and quantifies NMJs using α-bungarotoxin. • Utilizes high-resolution confocal microscopy for detailed imaging.

The changing landscape of autoantibody testing in myasthenia gravis in the setting of novel drug treatments.

Acquired myasthenia gravis (MG) is an autoimmune disease targeting the specific proteins in the postsynaptic muscle membrane. 50% of ocular and 80% of generalized MG have acetylcholine receptor antibodies (AChR Abs). 1-10% of MG patients have antibodies against muscle-specific kinase (MuSK), and 2-50 % of seronegative MG cases have antibodies against lipoprotein-receptor-related protein4 antibodies (LRP4 Abs). Serological testing is crucial for diagnosing and determining the appropriate therapeutic approach for MG patients. The radioimmunoprecipitation assay (RIPA) method is a historical standard test for detecting the AChR Abs and MuSK Abs. While it has nearly 100% specificity in the AChR Abs detection, its sensitivity is between 50--92%. The sensitivity and specificity of RIPA for detecting MuSK Abs is much lower. The fixed and live Cell-Based assays (f-CBA and L- CBA) have higher sensitivity than RIPA. With advancements in the serological diagnosis and management of MG, we now recommend a complete reflex testing algorithm on the first pretreatment sample of a suspected MG patient, starting with the binding and blocking assays for AChR Abs by RIPA and/ or f-CBA. If AChR Ab is negative, then reflex to MuSK Abs by RIPA and/ or CBAs. If AChR and MuSK Abs are negative, then use clustered L-CBA by request.

Investigation of the α9-nicotinic receptor single nucleotide polymorphisms induced oncogenic properties and molecular mechanisms in breast cancer.

α9-nAChR, a subtype of nicotinic acetylcholine receptor, is significantly overexpressed in female breast cancer tumor tissues compared to normal tissues. Previous studies have proposed that specific single nucleotide polymorphisms (SNPs) in the CHRNA9 (α9-nAChR) gene are associated with an increased risk of breast cancer in interaction with smoking. The study conducted a breast cancer risk assessment of the α9-nAChR SNP rs10009228 (NM_017581.4:c.1325A > G) in the Taiwanese female population, including 308 breast cancer patients and 198 healthy controls revealed that individuals with the heterozygous A/G or A/A wild genotype have an increased susceptibility to developing breast cancer in the presence of smoking compared to carriers of the G/G variant genotype. Our investigation confirmed the presence of this missense variation, resulting in an alteration of the amino acid sequence from asparagine (N442) to serine (S442) to facilitate phosphorylation within the α9-nAchR protein. Additionally, overexpression of N442 (A/A) in breast cancer cells significantly enhanced cell survival, migration, and cancer stemness compared to S442 (G/G). Four-line triple-negative breast cancer patient-derived xenograft (TNBC-PDX) models with distinct α9-nAChR rs10009228 SNP genotypes (A/A, A/G, G/G) further demonstrated that chronic nicotine exposure accelerated tumor growth through sustained activation of the α9-nAChR downstream oncogenic AKT/ERK/STAT3 pathway, particularly in individuals with the A/G or A/A genotype. Collectively, our study established the links between genetic variations in α9-nAChR and smoking exposure in promoting breast tumor development. This emphasizes the need to consider gene-environment interactions carefully while developing effective breast cancer prevention and treatment strategies.

Visual hallucinations in Parkinson's disease: spotlight on central cholinergic dysfunction.

Visual hallucinations are a common non-motor feature of Parkinson's disease and have been associated with accelerated cognitive decline, increased mortality and early institutionalisation. Despite their prevalence and negative impact on patient outcomes, the repertoire of treatments aimed at addressing this troubling symptom is limited. Over the last two decades, significant contributions have been made in uncovering the pathological and functional mechanisms of visual hallucinations, bringing us closer to the development of a comprehensive neurobiological framework. Convergent evidence now suggests that degeneration within the central cholinergic system may play a significant role in the genesis and progression of visual hallucinations. Here, we outline how cholinergic dysfunction may serve as a potential unifying neurobiological substrate underlying the multifactorial and dynamic nature of visual hallucinations. Drawing upon previous theoretical models, we explore the impact that alterations in cholinergic neurotransmission has on the core cognitive processes pertinent to abnormal perceptual experiences. We conclude by highlighting that a deeper understanding of cholinergic neurobiology and individual pathophysiology may help to improve established and emerging treatment strategies for the management of visual hallucinations and psychotic symptoms in Parkinson's disease.

Insights into the interaction between time and reward prediction on the activity of striatal tonically active neurons: A pilot study in rhesus monkeys.

Prior studies have documented the role of the striatum and its dopaminergic input in time processing, but the contribution of local striatal cholinergic innervation has not been specifically investigated. To address this issue, we recorded the activity of tonically active neurons (TANs), thought to be cholinergic interneurons in the striatum, in two male macaques performing self-initiated movements after specified intervals in the seconds range have elapsed. The behavioral data showed that movement timing was adjusted according to the temporal requirements. About one-third of all recorded TANs displayed brief depressions in firing in response to the cue that indicates the interval duration, and the strength of these modulations was, in some instances, related to the timing of movement. The rewarding outcome of actions also impacted TAN activity, as reflected by stronger responses to the cue paralleled by weaker responses to reward when monkeys performed correctly timed movements over consecutive trials. It therefore appears that TAN responses may act as a start signal for keeping track of time and reward prediction could be incorporated in this signaling function. We conclude that the role of the striatal cholinergic TAN system in time processing is embedded in predicting rewarding outcomes during timing behavior.

Acetylcholine regulates the melanogenesis of retinal pigment epithelia cells via a cAMP-dependent pathway: A non-neuronal function of cholinergic system in retina.

The turnover rate of melanogenesis in retinal pigment epithelium (RPE) and its molecular signaling remain unclear. This study aimed to investigate the role of cholinergic signaling in the process of melanogenesis of cultured RPE cells. Here, a human retinal pigment epithelia cell line, ARPE-19 cell, was used to study the process of melanogenesis. The mRNA and protein expressions of cholinergic molecules, e.g., acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and melanogenic molecules i.e., tyrosinase (TYR), microphthalmia-associated transcription factor (MITF), and melanin pigment were measured during melanogenesis of cultured ARPE-19 cells. Forskolin (a cAMP inducing agent), acetylcholine (ACh) and bethanechol (Bch; a muscarinic AChR agonist) were used to induce melanogenesis in the cultures. Muscarinic acetylcholine receptor (mAChR) antagonists were employed to identify the receptor subtype. During melanogenesis of ARPE-19 cells, the mRNA and protein expressions of cholinergic molecules, e.g., AChE and BChE, were increased along with melanogenic molecules, i.e., TYR, MITF and melanin pigment. Forskolin, ACh, and Bch induced an upregulation of melanogenesis in cultured ARPE-19 cultures: the induction was parallel to an increase of AChE expression. The Bch-induced enzymatic activities and mRNA levels of AChE and TYR were fully blocked by the treatments of gallamine (a M2 specific antagonist), tropicamide (a M4 specific antagonist) and atropine (non-specific antagonist for mAChRs). Cholinergic signaling via M2/M4 mAChRs regulates melanogenesis in cultured ARPE-19 cells through a cAMP-dependent pathway. This study provides insights into the regulation of RPE cell melanogenesis via a non-neuronal function of cholinergic system.