The Cholinergic System, the Adrenergic System and the Neuropathology of Alzheimer's Disease

New insights into butyrylcholinesterase: Pharmaceutical applications, selective inhibitors and multitarget-directed ligands

Butyrylcholinesterase (BChE), also known as pseudocholinesterase and serum cholinesterase, is an isoenzyme of acetylcholinesterase (AChE). It mediates the degradation of acetylcholine, especially under pathological conditions. Proverbial pharmacological applications of BChE, its mutants and modulators consist of combating Alzheimer's disease (AD), influencing multiple sclerosis (MS), addressing cocaine addiction, detoxifying organophosphorus poisoning and reflecting the progression or prognosis of some diseases. Of interest, recent reports have shed light on the relationship between BChE and lipid metabolism. It has also been proved that BChE is going to increase abnormally as a compensator for AChE in the middle and late stages of AD, and BChE inhibitors can alleviate cognitive disorders and positively influence some pathological features in AD model animals, foreboding favorable prospects and potential applications. Herein, the selective BChE inhibitors and BChE-related multitarget-directed ligands published in the last three years were briefly summarized, along with the currently known pharmacological applications of BChE, aiming to grasp the latest research directions. Thereinto, some emerging strategies for designing BChE inhibitors are intriguing, and the modulators based on target combination of histone deacetylase and BChE against AD is unprecedented. Furthermore, the involvement of BChE in the hydrolysis of ghrelin, the inhibition of low-density lipoprotein (LDL) uptake, and the down-regulation of LDL receptor (LDLR) expression suggests its potential to influence lipid metabolism disorders. This compelling prospect likely stimulates further exploration in this promising research direction.

The impact of chelating compounds on Cu2+, Fe2+/3+, and Zn2+ ions in Alzheimer's disease treatment

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid - β extracellular plaques and tau interfibrillar tangles, leading to memory loss, cognitive decline, and behavioral changes. With dementia posing a growing global health concern, there is an urgent need for comprehensive strategies to address its challenges. The economic burden of dementia is projected to rise significantly, emphasizing the necessity for collaborative efforts in research and healthcare. In the United States alone, millions are affected by AD, with prevalence increasing with age and even affecting younger individuals. The complexity of AD involves intricate biological processes, including the aggregation of amyloid beta, oxidative stress, and metal ion dysregulation. Metal ions, particularly those from copper, iron, and zinc, play pivotal roles in AD pathology, influencing Aβ deposition and tau protein accumulation. Current treatments offer symptomatic relief but do not address the underlying disease mechanisms. This paper explores the potential of various chelating compounds to target metal ions involved in AD pathology. N-acylhydrazones, morpholine, chrysin, quinoline, oxindole, cyclam, catechol-based, and quinazolinone-based derivatives show promising chelation activity and therapeutic effects. Metal chelation therapy offers a targeted approach to AD treatment by addressing the core pathology. By selectively binding to metal ions implicated in disease progression, chelators may minimize side effects associated with broad-spectrum treatments. Additionally, chelators may offer neuroprotective effects beyond metal binding, further enhancing their therapeutic potential. Overall, metal chelation therapy presents a promising strategy in combating AD, with the potential to significantly impact disease progression and improve patient outcomes.

An Expanded Narrative Review of Neurotransmitters on Alzheimer's Disease: The Role of Therapeutic Interventions on Neurotransmission

Alzheimer's disease (AD) is a progressive neurodegenerative disease. The accumulation of amyloid-β (Aβ) plaques and tau neurofibrillary tangles are the key players responsible for the pathogenesis of the disease. The accumulation of Aβ plaques and tau affect the balance in chemical neurotransmitters in the brain. Thus, the current review examined the role of neurotransmitters in the pathogenesis of Alzheimer's disease and discusses the alterations in the neurochemical activity and cross talk with their receptors and transporters. In the presence of Aβ plaques and neurofibrillary tangles, changes may occur in the expression of neuronal receptors which in turn triggers excessive release of glutamate into the synaptic cleft contributing to cell death and neuronal damage. The GABAergic system may also be affected by AD pathology in a similar way. In addition, decreased receptors in the cholinergic system and dysfunction in the dopamine neurotransmission of AD pathology may also contribute to the damage to cognitive function. Moreover, the presence of deficiencies in noradrenergic neurons within the locus coeruleus in AD suggests that noradrenergic stimulation could be useful in addressing its pathophysiology. The regulation of melatonin, known for its effectiveness in enhancing cognitive function and preventing Aβ accumulation, along with the involvement of the serotonergic system and histaminergic system in cognition and memory, becomes remarkable for promoting neurotransmission in AD. Additionally, nitric oxide and adenosine-based therapeutic approaches play a protective role in AD by preventing neuroinflammation. Overall, neurotransmitter-based therapeutic strategies emerge as pivotal for addressing neurotransmitter homeostasis and neurotransmission in the context of AD. This review discussed the potential for neurotransmitter-based drugs to be effective in slowing and correcting the neurodegenerative processes in AD by targeting the neurochemical imbalance in the brain. Therefore, neurotransmitter-based drugs could serve as a future therapeutic strategy to tackle AD.

Neuroprotection of macamide in a mouse model of Alzheimer's disease involves Nrf2 signaling pathway and gut microbiota

The underlying mechanisms of macamide's neuroprotective effects in Alzheimer's disease (AD) were investigated in the paper. Macamides are considered as unique ingredients in maca. Improvement effects and mechanisms of macamide on cognitive impairment have not been revealed. In this study, Vina 1.1.2 was used for docking to evaluate the binding abilities of 12 main macamides to acetylcholinesterase (AChE). N-benzyl-(9Z,12Z)-octadecadienamide (M 18:2) was selected to study the following experiments because it can stably bind to AChE with a strong binding energy. The animal experiments showed that M 18:2 prevented the scopolamine (SCP)-induced cognitive impairment and neurotransmitter disorders, increased the positive rates of Nrf2 and HO-1 in hippocampal CA1, improved the synaptic plasticity by maintaining synaptic morphology and increasing the synapse density. Moreover, the contents of IL-1β, IL-6, and TNF-α in the hippocampus, serum, and colon were reduced by M 18:2. Furthermore, M 18:2 promoted colonic epithelial integrity and partially restored the composition of the gut microbiota to normal, including decreased genera Clostridiales_unclassified and Lachnospiraceae_unclassified, as well as increased genera Muribaculaceae_unclassified, Muribaculum, Alistipes, and Bacteroides, which may be the possible biomarkers of cognitive aging. In summary, M 18:2 exerted neuroprotective effects on SCP-induced AD mice possibly via activating the Nrf2/HO-1 signaling pathway and modulating the gut microbiota.

Insulin resistance as the molecular link between diabetes and Alzheimer's disease

Diabetes mellitus (DM) and Alzheimer's disease (AD) are two major health concerns that have seen a rising prevalence worldwide. Recent studies have indicated a possible link between DM and an increased risk of developing AD. Insulin, while primarily known for its role in regulating blood sugar, also plays a vital role in protecting brain functions. Insulin resistance (IR), especially prevalent in type 2 diabetes, is believed to play a significant role in AD's development. When insulin signalling becomes dysfunctional, it can negatively affect various brain functions, making individuals more susceptible to AD's defining features, such as the buildup of beta-amyloid plaques and tau protein tangles. Emerging research suggests that addressing insulin-related issues might help reduce or even reverse the brain changes linked to AD. This review aims to explore the rela-tionship between DM and AD, with a focus on the role of IR. It also explores the molecular mechanisms by which IR might lead to brain changes and assesses current treatments that target IR. Understanding IR's role in the connection between DM and AD offers new possibilities for treatments and highlights the importance of continued research in this interdisciplinary field.

Specific Mode Electroacupuncture Stimulation Mediates the Delivery of NGF Across the Hippocampus Blood-Brain Barrier Through p65-VEGFA-TJs to Improve the Cognitive Function of MCAO/R Convalescent Rats

Cognitive impairment frequently presents as a prevalent consequence following stroke, imposing significant burdens on patients, families, and society. The objective of this study was to assess the effectiveness and underlying mechanism of nerve growth factor (NGF) in treating post-stroke cognitive dysfunction in rats with cerebral ischemia-reperfusion injury (MCAO/R) through delivery into the brain using specific mode electroacupuncture stimulation (SMES). From the 28th day after modeling, the rats were treated with NGF mediated by SMES, and the cognitive function of the rats was observed after treatment. Learning and memory ability were evaluated using behavioral tests. The impact of SMES on blood-brain barrier (BBB) permeability, the underlying mechanism of cognitive enhancement in rats with MCAO/R, including transmission electron microscopy, enzyme-linked immunosorbent assay, immunohistochemistry, immunofluorescence, and TUNEL staining. We reported that SMES demonstrates a safe and efficient ability to open the BBB during the cerebral ischemia repair phase, facilitating the delivery of NGF to the brain by the p65-VEGFA-TJs pathway.

Exploring the potential of quercetin in Alzheimer's Disease: Pharmacodynamics, Pharmacokinetics, and Nanodelivery systems

Alzheimer's disease (AD) is a primary cause of dementia that affects millions of people worldwide and its prevalence is likely to increase largely in the coming decades. Multiple complex pathways, such as oxidative stress, tau and amyloid-beta (Aβ) pathology, and cholinergic dysfunction, are involved in the pathogenesis of Alzheimer's disease. The conventional treatments provide only symptomatic relief and not a complete cure for the disease. On the other hand, recent studies have looked into the possibility of flavonoids as an effective therapeutic strategy for treating AD. Quercetin, a well-known flavonol, has been extensively studied for AD treatment. Therefore, this review mainly focuses on the pharmacokinetics properties of quercetin and its modes of action, such as antioxidant, anti-inflammatory, anti-amyloidogenic, and neuroprotective properties, which are beneficial in treating AD. It also highlights the nano delivery systems of quercetin, including liposomes, nanostructures lipid carriers, solid lipid nanoparticles, nanoemulsions, microemulsions, self-emulsifying drug delivery systems, and nanoparticles reported for AD treatment. The remarkable potential of quercetin nanocarriers has been reflected in enhancing its bioavailability and therapeutic efficacy. Therefore, clinical studies must be conducted to explore it as a therapeutic strategy for Alzheimer's disease.

Cerebellum in Alzheimer's disease and other neurodegenerative diseases: an emerging research frontier

The cerebellum is crucial for both motor and nonmotor functions. Alzheimer's disease (AD), alongside other dementias such as vascular dementia (VaD), Lewy body dementia (DLB), and frontotemporal dementia (FTD), as well as other neurodegenerative diseases (NDs) like Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), and spinocerebellar ataxias (SCA), are characterized by specific and non-specific neurodegenerations in central nervous system. Previously, the cerebellum's significance in these conditions was underestimated. However, advancing research has elevated its profile as a critical node in disease pathology. We comprehensively review the existing evidence to elucidate the relationship between cerebellum and the aforementioned diseases. Our findings reveal a growing body of research unequivocally establishing a link between the cerebellum and AD, other forms of dementia, and other NDs, supported by clinical evidence, pathological and biochemical profiles, structural and functional neuroimaging data, and electrophysiological findings. By contrasting cerebellar observations with those from the cerebral cortex and hippocampus, we highlight the cerebellum's distinct role in the disease processes. Furthermore, we also explore the emerging therapeutic potential of targeting cerebellum for the treatment of these diseases. This review underscores the importance of the cerebellum in these diseases, offering new insights into the disease mechanisms and novel therapeutic strategies.

Protective effect of cholecalciferol against cobalt-induced neurotoxicity in rats: ZO-1/iFABP, ChAT/AchE and antioxidant pathways as potential therapeutic targets

Cobalt (Co) toxicity has been reported to produce central nervous system and gastrointestinal abnormalities. This study assessed the therapeutic effect of cholecalciferol (Cho) supplementation against damages caused by sub-acute (14-day) cobalt chloride (CoCl2) exposure in the brain and intestines. Thirty-five male Wistar rats were divided equally into five groups: Group I (control) received no treatment; Group II received oral CoCl2 (100 mg/kg) only; Groups III, IV, and V received 1000, 3000 and 6000 IU/kg of cholecalciferol, respectively by oral gavage, and concurrently with CoCl2. Cobalt-treated rats showed neuronal vacuolation and presence of pyknotic nuclei in the cerebral cortex and hippocampus, depletion of Purkinje cells in the cerebellum, as well as inflammation and congestion in the intestinal mucosa. Cobalt also increased brain and intestinal hydrogen peroxide (H2O2) and malondialdehyde (MDA) concentrations, while simultaneously reducing glutathione (GSH) content, superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione S-transferase (GST) activities. Further, CoCl2 induced increases in brain acetylcholinesterase (AchE) activity and serum zonulin (ZO-1) levels. Conversely, Cho administration suppressed CoCl2-induced damages in the brain and intestines by reducing lipid peroxidation and increasing the activities of antioxidant enzymes. Remarkably, Cho produced stimulation of brain choline acetyltransferase (ChAT) and suppression of AchE activity, along with dose-dependent reduction in serum levels of ZO-1, intestinal fatty acid-binding protein (iFABP) and nitric oxide. In conclusion, the protective role of cholecalciferol against cobalt-induced toxicity occurred via modulation of cholinergic, intestinal permeability and antioxidant pathways. The results may prove significant in the context of the role of gut-brain connections in neuroprotection.

Neurotoxicities induced by micro/nanoplastics: A review focusing on the risks of neurological diseases

Pollution of micro/nano-plastics (MPs/NPs) is ubiquitously prevalent in the environment, leading to an unavoidable exposure of the human body. Despite the protection of the blood-brain barrier, MPs/NPs can be transferred and accumulated in the brain, which subsequently exert negative effects on the brain. Nevertheless, the potential neurodevelopmental and/or neurodegenerative risks of MPs/NPs remain largely unexplored. In this review, we provide a systematic overview of recent studies related to the neurotoxicity of MPs/NPs. It covers the environmental hazards and human exposure pathways, translocation and distribution into the brain, the neurotoxic effects, and the possible mechanisms of environmental MPs/NPs. MPs/NPs are widely found in different environment matrices, including air, water, soil, and human food. Ambient MPs/NPs can enter the human body by ingestion, inhalation and dermal contact, then be transferred into the brain via the blood circulation and nerve pathways. When MPs/NPs are present in the brain, they can initiate a series of molecular or cellular reactions that may harm the blood-brain barrier, cause oxidative stress, trigger inflammatory responses, affect acetylcholinesterase activity, lead to mitochondrial dysfunction, and impair autophagy. This can result in abnormal protein folding, loss of neurons, disruptions in neurotransmitters, and unusual behaviours, ultimately contributing to the initiation and progression of neurodegenerative changes and neurodevelopmental abnormalities. Key challenges and further research directions are also proposed in this review as more studies are needed to focus on the potential neurotoxicity of MPs/NPs under realistic conditions.

Protective effects of myricetin and morin on neurological damage in Aβ1-42/Al3+ -induced Alzheimer's disease model of rats

Alzheimer's disease (AD) is a degenerative neurological disorder with unclear pathogenesis. Single-target drugs have very limited efficacy in treating AD, but synthetic multi-target drugs have poor efficacy and safety. Therefore, finding suitable natural multi-target drugs against AD is of great interest for research studies. We chose two flavonols, myricetin and morin, for the relevant study. In this study, we used microinjection of Aβ1-42 oligomers into the CA1 region of rat hippocampus, combined with gavage of Aluminum chloride hexahydrate (AlCl3·6H2O) solution to establish AD rat models, and myricetin and morin were selected as intervening drugs to explore the protective effects against neurological impairment. Experimental results showed that myricetin or morin could reduce the production of Aβ, Tubulin-associated unit (Tau), and Phosphorylated tubulin-associated unit (p-Tau), down-regulate the expression of relevant inflammatory factors, reduce hippocampal cell apoptosis in rats. There was a significant increase in the activity of adenosine triphosphatase, catalase, total superoxide dismutase, and the content of glutathione in the brain tissue. However, the content of malondialdehyde, inducible nitric oxide synthase, and the activity of acetylcholinesterase were decreased in the brain tissue. These two flavonols can regulate the imbalance of monoamine and amino acid neurotransmitter levels. In conclusion, Myricetin or morin can effectively improve learning and memory dysfunction in AD rats induced by Aβ1-42/Al3+ through anti-oxidative stress and anti-apoptotic features.

Atrophy of the cholinergic regions advances from early to late mild cognitive impairment

PURPOSE

We investigated the volumetric changes in the components of the cholinergic pathway for patients with early mild cognitive impairment (EMCI) and those with late mild cognitive impairment (LMCI). The effect of patients' apolipoprotein 4 (APOE-ε4) allele status on the structural changes were analyzed.

METHODS

Structural magnetic resonance imaging data were collected. Patients' demographic information, plasma data, and validated global cognitive composite scores were included. Relevant features were extracted for constructing machine learning models to differentiate between EMCI (n = 312) and LMCI (n = 541) and predict patients' neurocognitive function. The data were analyzed primarily through one-way analysis of variance and two-way analysis of covariance.

RESULTS

Considerable differences were observed in cholinergic structural changes between patients with EMCI and LMCI. Cholinergic atrophy was more prominent in the LMCI cohort than in the EMCI cohort (P < 0.05 family-wise error corrected). APOE-ε4 differentially affected cholinergic atrophy in the LMCI and EMCI cohorts. For LMCI cohort, APOE-ε4 carriers exhibited increased brain atrophy (left amygdala: P = 0.001; right amygdala: P = 0.006, and right Ch123, P = 0.032). EMCI and LCMI patients showed distinctive associations of gray matter volumes in cholinergic regions with executive (R2 = 0.063 and 0.030 for EMCI and LMCI, respectively) and language (R2 = 0.095 and 0.042 for EMCI and LMCI, respectively) function.

CONCLUSIONS

Our data confirmed significant cholinergic atrophy differences between early and late stages of mild cognitive impairment. The impact of the APOE-ε4 allele on cholinergic atrophy varied between the LMCI and EMCI groups.

Somatostatin and the pathophysiology of Alzheimer's disease

Among the central features of Alzheimer's disease (AD) progression are altered levels of the neuropeptide somatostatin (SST), and the colocalisation of SST-positive interneurons (SST-INs) with amyloid-β plaques, leading to cell death. In this theoretical review, I propose a molecular model for the pathogenesis of AD based on SST-IN hypofunction and hyperactivity. Namely, hypofunctional and hyperactive SST-INs struggle to control hyperactivity in medial regions in early stages, leading to axonal Aβ production through excessive presynaptic GABAB inhibition, GABAB1a/APP complex downregulation and internalisation. Concomitantly, excessive SST-14 release accumulates near SST-INs in the form of amyloids, which bind to Aβ to form toxic mixed oligomers. This leads to differential SST-IN death through excitotoxicity, further disinhibition, SST deficits, and increased Aβ release, fibrillation and plaque formation. Aβ plaques, hyperactive networks and SST-IN distributions thereby tightly overlap in the brain. Conversely, chronic stimulation of postsynaptic SST2/4 on gulutamatergic neurons by hyperactive SST-INs promotes intense Mitogen-Activated Protein Kinase (MAPK) p38 activity, leading to somatodendritic p-tau staining and apoptosis/neurodegeneration - in agreement with a near complete overlap between p38 and neurofibrillary tangles. This model is suitable to explain some of the principal risk factors and markers of AD progression, including mitochondrial dysfunction, APOE4 genotype, sex-dependent vulnerability, overactive glial cells, dystrophic neurites, synaptic/spine losses, inter alia. Finally, the model can also shed light on qualitative aspects of AD neuropsychology, especially within the domains of spatial and declarative (episodic, semantic) memory, under an overlying pattern of contextual indiscrimination, ensemble instability, interference and generalisation.

The effects of carvacrol and p-cymene on Aβ1-42 -induced long-term potentiation deficit in male rats

AIMS

Alzheimer's disease (AD) is the most common type of dementia in which oxidative stress plays an important role. In this disease, learning and memory and the cellular mechanism associated with it, long-term potentiation (LTP), are impaired. Considering the beneficial effects of carvacrol (CAR) and p-cymene against AD, their effect was assessed on in vivo hippocampal LTP in the perforant pathway (PP)-dentate gyrus (DG) pathway in an Aβ1-42 -induced rat model of AD.

METHODS

Male Wistar rats were randomly assigned to five groups: sham: intracerebroventricular (ICV) injection of phosphate-buffered saline, Aβ: ICV Aβ1-42 injections, Aβ + CAR (50 mg/kg), Aβ + p-cymene (50 mg/kg), and Aβ + CAR + p-cymene. Administration of CAR and p-cymene was done by gavage daily 4 weeks before and 4 weeks after the Aβ injection. The population spike (PS) amplitude and field excitatory postsynaptic potentials (fEPSP) slope were determined in DG against the applied stimulation to the PP.

RESULTS

Aβ-treated rats exhibited impaired LTP induction in the PP-DG synapses, resulting in significant reduction in both fEPSP slope and PS amplitude compared to the sham animals. Aβ-treated rats consumed either CAR or p-cymene separately (but not their combination), and showed an enhancement in fEPSP slope and PS amplitude of the DG granular cells.

CONCLUSIONS

These data indicate that CAR or p-cymene can ameliorate Aβ-associated changes in synaptic plasticity. Surprisingly, the combination of CAR and p-cymene did not yield the same effect, suggesting a potential interaction between the two substances.

Phenyl-quinoline derivatives as lead structure of cholinesterase inhibitors with potency to reduce the GSK-3β level targeting Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder that leads to cognitive decline and memory loss. Unfortunately, there is no effective treatment for this condition, so there is a growing interest in developing new anti-AD agents. In this research project, a series of phenyl-quinoline derivatives were designed as potential anti-AD agents. These derivatives were substituted at two different positions on benzyl and phenyl rings. The structures of the derivatives were characterized using techniques such as IR spectroscopy, 1H NMR, 13C NMR, and elemental analysis. During the in vitro screening, the derivatives were tested against both acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). It was observed that most of the derivatives showed higher selectivity against BChE compared to AChE. Among the derivatives, analog 7n (with a methoxy group at R1 and a 4-bromine substituent at R2 exhibited the highest potency, with a 75-fold improvement in the activity compared to the positive control. Importantly, this potent analog demonstrated no toxicity at the tested concentration on SH-SY5Y cells, indicating its potential as a safe anti-AD agent. The level of GSK-3β was also reduced after treatments with 7n at 50 μM. Overall, this study highlights the design and evaluation of phenyl-quinoline derivatives as promising candidates for developing novel anti-AD agents.

Recent advancement in therapeutic strategies for Alzheimer's disease: Insights from clinical trials

Alzheimer's disease (AD) is the most prevalent form of dementia, characterized by the presence of plaques of amyloid beta and Tau proteins. There is currently no permanent cure for AD; the only medications approved by the FDA for mild to moderate AD are cholinesterase inhibitors, NMDA receptor antagonists, and immunotherapies against core pathophysiology, that provide temporary relief only. Researchers worldwide have made significant attempts to find new targets and develop innovative therapeutic molecules to treat AD. The FDA-approved drugs are palliative and couldn't restore the damaged neuron cells of AD. Stem cells have self-differentiation properties, making them prospective therapeutics to treat AD. The promising results in pre-clinical studies of stem cell therapy for AD seek attention worldwide. Various stem cells, mainly mesenchymal stem cells, are currently in different phases of clinical trials and need more advancements to take this therapy to the translational level. Here, we review research from the past decade that has identified several hypotheses related to AD pathology. Moreover, this article also focuses on the recent advancement in therapeutic strategies for AD treatment including immunotherapy and stem cell therapy detailing the clinical trials that are currently undergoing development.

Torreya grandis oil attenuates cognitive impairment in scopolamine-induced mice

The oil of Torreya grandis (TGO), a common nut in China, is considered to be a bioactive edible oil and has a great value in functional food development. In this study, the neuroprotective effects of TGO were investigated on a scopolamine (SCOP)-induced C57BL/6J mouse model. The mice were pretreated with TGO for 30 days (1000 mg per kg per day and 3000 mg per kg per day, i.g.). Behavioral tests showed that the supplementation of TGO could prevent the cognitive deficits induced by SCOP. TGO rebalanced the disorder of the cholinergic system by upgrading the level of acetylcholine. TGO also alleviated the over-activation of microglia and inhibited neuroinflammation and oxidative stress. Additionally, TGO could regulate the composition of gut microbiota, increase the production of short-chain fatty acids, and decrease the content of lipopolysaccharides in the serum. In conclusion, TGO has the potential to prevent loss of memory and impairment of cognition, which may be related to its regulation of the gut microbiota-metabolite-brain axis.

Nucleoside analogues: N-glycosylation methodologies, synthesis of antiviral and antitumor drugs and potential against drug-resistant bacteria and Alzheimer's disease

Nucleosides have gained significant attention since the discovery of the structure of DNA. Nucleoside analogues may be synthesized through multiple synthetic pathways, however the N-glycosylation of a nucleobase is the most common method. Amongst the different classical N-glycosylation methodologies, the Vorbrüggen glycosylation is the most popular method. This review focuses on the synthesis and therapeutic applications of several FDA approved nucleoside analogues as antiviral and anticancer agents. Moreover, this review also focuses on the potential of these compounds as new antibacterial and anti-Alzheimer's disease agents, offering an overview of the most recent research in these fields.

Imbalance of multiple neurotransmitter pathways leading to depression-like behavior and cognitive dysfunction in the triple transgenic mouse model of Alzheimer disease

Depression is among the most frequent psychiatric comorbid conditions in Alzheimer disease (AD). However, pharmacotherapy for depressive disorders in AD is still a big challenge, and the data on the efffcacy of current antidepressants used clinically for depressive symptoms in patients with AD remain inconclusive. Here we investigated the mechanism of the interactions between depression and AD, which we believe would aid in the development of pharmacological therapeutics for the comorbidity of depression and AD. Female APP/PS1/Tau triple transgenic (3×Tg-AD) mice at 24 months of age and age- and sex-matched wild-type (WT) mice were used. The shuttle-box passive avoidance test (PAT) were implemented to assess the abilities of learning and memory, and the open field test (OFT) and the tail suspension test (TST) were used to assess depression-like behavior. High-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) was used to detect the level of neurotransmitters related to depression in the hippocampus of mice. The data was identified by orthogonal projections to latent structures discriminant analysis (OPLS-DA). Most neurotransmitters exert their effects by binding to the corresponding receptor, so the expression of relative receptors in the hippocampus of mice was detected using Western blot. Compared to WT mice, 3×Tg-AD mice displayed significant cognitive impairment in the PAT and depression-like behavior in the OFT and TST. They also showed significant decreases in the levels of L-tyrosine, norepinephrine, vanillylmandelic acid, 5-hydroxytryptamine, and acetylcholine, in contrast to significant increases in 5-hydroxyindoleacetic acid, L-histidine, L-glutamine, and L-arginine in the hippocampus. Moreover, the expression of the alpha 1a adrenergic receptor (ADRA1A), serotonin 1 A receptor (5HT1A), and γ-aminobutyric acid A receptor subunit alpha-2 (GABRA2) was significantly downregulated in the hippocampus of 3×Tg-AD mice, while histamine H3 receptor (H3R) expression was significantly upregulated. In addition, the ratio of phosphorylated cAMP-response element-binding protein (pCREB) and CREB was significantly decreased in the hippocampus of 3×Tg-AD mice than WT mice. We demonstrated in the present study that aged female 3×Tg-AD mice showed depression-like behavior accompanied with cognitive dysfunction. The complex and diverse mechanism appears not only relevant to the imbalance of multiple neurotransmitter pathways, including the transmitters and receptors of the monoaminergic, GABAergic, histaminergic, and cholinergic systems, but also related to the changes in L-arginine and CREB signaling molecules.

Harnessing the Bioactive Potential of Limonium spathulatum (Desf.) Kuntze: Insights into Enzyme Inhibition and Phytochemical Profile

This study assessed the halophyte species Limonium spathulatum (Desf.) as a possible source of natural ingredients with the capacity to inhibit enzymes related to relevant human health disorders and food browning. Extracts using food-grade solvents such as water and ethanol were prepared by maceration from dried L. spathulatum leaves. They were evaluated for in vitro inhibition activity of enzymes such as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), α-glucosidase, tyrosinase and lipase, related to Alzheimer's disease, type-2-diabetes mellitus, skin hyperpigmentation, and obesity, respectively. These extracts were also appraised for in vitro acute toxicity on tumoral and non-tumoral cell lines and their chemical composition by high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS/MS). The extracts were more effective towards BChE than AChE. The best results were obtained with the hydroethanolic and water extracts, with IC50 values of 0.03 mg/mL and 0.06 mg/mL, respectively. The hydroethanolic extract had the highest capacity to inhibit α-glucosidase (IC50: 0.04 mg/mL), higher than the positive control used (acarbose, IC50 = 3.14 mg/mL). The ethanol extract displayed the best inhibitory activity against tyrosinase (IC50 = 0.34 mg/mL). The tested samples did not inhibit lipase and exhibited low to moderate cytotoxic activity against the tested cell lines. The hydroethanolic extract had a higher diversity of compounds, followed by the ethanol and water samples. Similar molecules were identified in all the extracts and were mainly hydroxybenzoic acids, hydroxycinnamic acids, and flavonoids. Taken together, these results suggest that L. spathulatum should be further explored as a source of bioactive ingredients for the food, cosmetic, and pharmaceutical industries.

Selective Noradrenaline Depletion in the Neocortex and Hippocampus Induces Working Memory Deficits and Regional Occurrence of Pathological Proteins

Noradrenaline (NA) depletion occurs in Alzheimer's disease (AD); however, its relationship with the pathological expression of Tau and transactive response DNA-binding protein 43 (TDP-43), two major hallmarks of AD, remains elusive. Here, increasing doses of a selective noradrenergic immunotoxin were injected into developing rats to generate a model of mild or severe NA loss. At about 12 weeks post-lesion, dose-dependent working memory deficits were detected in these animals, associated with a marked increase in cortical and hippocampal levels of TDP-43 phosphorylated at Ser 409/410 and Tau phosphorylated at Thr 217. Notably, the total levels of both proteins were largely unaffected, suggesting a direct relationship between neocortical/hippocampal NA depletion and the phosphorylation of pathological Tau and TDP-43 proteins. As pTD43 is present in 23% of AD cases and pTau Thr217 has been detected in patients with mild cognitive impairment that eventually would develop into AD, improvement of noradrenergic function in AD might represent a viable therapeutic approach with disease-modifying potential.

Neuroprotective, neurogenic, and anticholinergic evidence of Ganoderma lucidum cognitive effects: Crucial knowledge is still lacking

Ganoderma lucidum is a mushroom that has been widely used for centuries in Asian countries for its antiaging properties. It is popularly known as "Ling Zhi," "Reishi," and "Youngzhi," and because of its benefits, it is known as the "immortality mushroom." Pharmacological assays have revealed that G. lucidum ameliorates cognitive impairments through inhibition of β-amyloid and neurofibrillary tangle formation, antioxidant effect, reduction of inflammatory cytokine release and apoptosis, genic expression modulation, among other activities. Chemical investigations on G. lucidum have revealed the presence of metabolites such as triterpenes, which are the most explored in this field, as well as flavonoids, steroids, benzofurans, and alkaloids; in the literature, these have also been reported to have mnemonic activity. These properties of the mushroom make it a potential source of new drugs to prevent or reverse memory disorders, as actual medications are able to only alleviate some symptoms but are unable to stop the progress of cognitive impairments, with no impact on social, familiar, and personal relevance. In this review, we discuss the cognitive findings of G. lucidum reported in the literature, converging the proposed mechanisms through the several pathways that underlie memory and cognition processes. In addition, we highlight the gaps that deserve particular attention to support future studies.

Evidence of disturbed insulin signaling in animal models of Alzheimer's disease

Since glucose reuptake by neurons is mostly independent of insulin, it has been an intriguing question whether insulin has or not any roles in the brain. Consequently, the identification of insulin receptors in the central nervous system has fueled investigations of insulin functions in the brain. It is also already known that insulin can influence glucose reuptake by neurons, mostly during activities that have the highest energy demand. The identification of high density of insulin receptors in the hippocampus also suggests that insulin may present important roles related to memory. In this context, studies have reported worse performance in cognitive tests among diabetic patients. In addition, alterations in the regulation of central insulin pathways have been observed in the brains of Alzheimer's disease (AD) patients. In fact, some authors have proposed AD as a third type of diabetes and recently, our group proposed insulin resistance as a common link between different AD hypotheses. Therefore, in the present narrative review, we intend to revise and gather the evidence of disturbed insulin signaling in experimental animal models of AD.

Animal models of Alzheimer's disease: An originof innovativetreatments and insight to the disease's etiology

Alzheimer's disease (AD) is a progressive neurodegenerative disorder. The main pathogenic features are the development and depositionof senile plaques and neurofibrillary tangles in brain. Recent developments in the knowledge of the pathophysiological mechanisms behind Alzheimer's disease and other cognitive disorders have suggested new approaches to treatment development. These advancements have been significantly aided by the use of animal models, which are also essential for the assessment of therapies. Various approaches as transgenic animal model, chemical models, brain injury are used. This review will presentAD pathophysiology and emphasize several Alzheimer like dementia causingchemical substances, transgenic animal model and stereotaxy in order to enhance our existing knowledge of their mechanism of AD induction, dose, and treatment duration.

Neurotransmitter systems in the etiology of major neurological disorders: Emerging insights and therapeutic implications

Neurotransmitters serve as chemical messengers playing a crucial role in information processing throughout the nervous system, and are essential for healthy physiological and behavioural functions in the body. Neurotransmitter systems are classified as cholinergic, glutamatergic, GABAergic, dopaminergic, serotonergic, histaminergic, or aminergic systems, depending on the type of neurotransmitter secreted by the neuron, allowing effector organs to carry out specific functions by sending nerve impulses. Dysregulation of a neurotransmitter system is typically linked to a specific neurological disorder. However, more recent research points to a distinct pathogenic role for each neurotransmitter system in more than one neurological disorder of the central nervous system. In this context, the review provides recently updated information on each neurotransmitter system, including the pathways involved in their biochemical synthesis and regulation, their physiological functions, pathogenic roles in diseases, current diagnostics, new therapeutic targets, and the currently used drugs for associated neurological disorders. Finally, a brief overview of the recent developments in neurotransmitter-based therapeutics for selected neurological disorders is offered, followed by future perspectives in that area of research.

Therapeutic Strategies Aimed at Improving Neuroplasticity in Alzheimer Disease

Alzheimer disease (AD) is the most prevalent form of dementia among elderly people. Owing to its varied and multicausal etiopathology, intervention strategies have been highly diverse. Despite ongoing advances in the field, efficient therapies to mitigate AD symptoms or delay their progression are still of limited scope. Neuroplasticity, in broad terms the ability of the brain to modify its structure in response to external stimulation or damage, has received growing attention as a possible therapeutic target, since the disruption of plastic mechanisms in the brain appear to correlate with various forms of cognitive impairment present in AD patients. Several pre-clinical and clinical studies have attempted to enhance neuroplasticity via different mechanisms, for example, regulating glucose or lipid metabolism, targeting the activity of neurotransmitter systems, or addressing neuroinflammation. In this review, we first describe several structural and functional aspects of neuroplasticity. We then focus on the current status of pharmacological approaches to AD stemming from clinical trials targeting neuroplastic mechanisms in AD patients. This is followed by an analysis of analogous pharmacological interventions in animal models, according to their mechanisms of action.

Combined Donepezil with Astaxanthin via Nanostructured Lipid Carriers Effective Delivery to Brain for Alzheimer's Disease in Rat Model

Introduction

Donepezil (DPL), a specific acetylcholinesterase inhibitor, is used as a first-line treatment to improve cognitive deficits in Alzheimer's disease (AD) and it might have a disease modifying effect. Astaxanthin (AST) is a natural potent antioxidant with neuroprotective, anti-amyloidogenic, anti-apoptotic, and anti-inflammatory effects. This study aimed to prepare nanostructured lipid carriers (NLCs) co-loaded with donepezil and astaxanthin (DPL/AST-NLCs) and evaluate their in vivo efficacy in an AD-like rat model 30 days after daily intranasal administration.

Methods

DPL/AST-NLCs were prepared using a hot high-shear homogenization technique, in vitro examined for their physicochemical parameters and in vivo evaluated. AD induction in rats was performed by aluminum chloride. The cortex and hippocampus were isolated from the brain of rats for biochemical testing and histopathological examination.

Results

DPL/AST-NLCs showed z-average diameter 149.9 ± 3.21 nm, polydispersity index 0.224 ± 0.017, zeta potential -33.7 ± 4.71 mV, entrapment efficiency 81.25 ±1.98% (donepezil) and 93.85 ±1.75% (astaxanthin), in vitro sustained release of both donepezil and astaxanthin for 24 h, spherical morphology by transmission electron microscopy, and they were stable at 4-8 ± 2°C for six months. Differential scanning calorimetry revealed that donepezil and astaxanthin were molecularly dispersed in the NLC matrix in an amorphous state. The DPL/AST-NLC-treated rats showed significantly lower levels of nuclear factor-kappa B, malondialdehyde, β-site amyloid precursor protein cleaving enzyme-1, caspase-3, amyloid beta (Aβ1‑42), and acetylcholinesterase, and significantly higher levels of glutathione and acetylcholine in the cortex and hippocampus than the AD-like untreated rats and that treated with donepezil-NLCs. DPL/AST-NLCs showed significantly higher anti-amyloidogenic, antioxidant, anti-acetylcholinesterase, anti-inflammatory, and anti-apoptotic effects, resulting in significant improvement in the cortical and hippocampal histopathology.

Conclusion

Nose-to-brain delivery of DPL/AST-NLCs is a promising strategy for the management of AD.

Polygoni Multiflori Radix Praeparata and Acori Tatarinowii Rhizoma ameliorate scopolamine-induced cognitive impairment by regulating the cholinergic and synaptic associated proteins

ETHNOPHARMACOLOGICAL RELEVANCE

The combination of Polygoni Multiflori Radix Praeparata (PMRP) and Acori Tatarinowii Rhizoma (ATR) is often used in traditional Chinese medicine to prevent and treat Alzheimer's disease (AD). However, it is not clear whether the effects and mechanisms of the decoction prepared by traditional decocting method (PA) is different from that prepared by modern decocting method (P + A).

AIM OF THE STUDY

The present study aimed to investigate the differences in the protective effects of PA and P + A on scopolamine induced cognitive impairment, and to explore its potential mechanism.

MATERIALS AND METHODS

To assess the protective effect of PA and P + A on cognitive dysfunction, the mice were orally administrated with PA (1.56, 6.24 g kg^-1•day^-1) and P + A (1.56, 6.24 g kg^-1•day^-1) for 26 days before co-treatment with scopolamine (4 mg kg^-1•day^-1, i.p.). The learning and memory abilities of mice were examined by Morris water maze test, and the expressions of proteins related to cholinergic system and synaptic function were detected by the methods of ELISA, real-time PCR and Western blotting. Then, molecular docking technique was used to verify the effect of active compounds in plasma after PA administration on Acetylcholinesterase (AChE) protein. Finally, the Ellman method was used to evaluate the effects of different concentrations of PA, P + A (1 μg/mL-100 mg/mL) and the compounds (1-100 μM) on AChE activity in vitro.

RESULTS

On one hand, in the scopolamine-induced cognitive impairment mouse model, both of PA and P + A could improve the cognitive impairment, while the effect of PA on cognitive amelioration was better than that of P + A. Moreover, PA regulated the cholinergic and synaptic functions by enhancing the concentration of acetylcholine (ACh), the mRNA levels of CHT1, Syn, GAP-43 and PSD-95, and the related proteins (CHT1, VACHT, Syn, GAP-43 and PSD-95), and significantly inhibiting the expression of AChE protein. Meanwhile, P + A only up-regulated the mRNA levels of GAP-43 and PSD-95, increased the expressions of CHT1, VACHT, Syn, GAP-43 and PSD-95 proteins, and inhibited the expression of AChE protein. On the other hand, the in vitro study showed that some compounds including emodin-8-o-β-d-Glucopyranoside, THSG and α-Asarone inhibited AChE protein activity with the IC₅₀ values 3.65 μM, 5.42 μM and 9.43 μM, respectively.

CONCLUSIONS

These findings demonstrate that both of PA and P + A can ameliorate the cognitive deficits by enhancing cholinergic and synaptic related proteins, while PA has the stronger improvement effect on the cholinergic function, which may be attributed to the compounds including THSG, emodin, emodin-8-O-β-D-glucopyranoside and α-asarone. The present study indicated that PA has more therapeutic potential in the treatment of neurodegenerative diseases such as AD. The results provide the experimental basis for the clinical use of PA.

Profiling Chemobiological Connection between Natural Product and Target Space Based on Systematic Analysis

Natural products provide valuable starting points for new drugs with unique chemical structures. Here, we retrieve and join the LOTUS natural product database and ChEMBL interaction database to explore the relations and rhythm between chemical features of natural products and biotarget spaces. Our analysis revealed relations between the biogenic pathways of natural products and species taxonomy. Nitrogen-containing natural products were more likely to achieve high activity and have a higher potential to become candidate compounds. An apparent trend existed in the target space of natural products originating from different biological sources. Highly active alkaloids were more related to targets of neurodegenerative or neural diseases. Oligopeptides and polyketides were mainly associated with protein phosphorylation and HDAC receptors. Fatty acids readily intervened in various physiological processes involving prostanoids and leukotrienes. We also used FusionDTA, a deep learning model, to predict the affinity between all LOTUS natural products and 622 therapeutic drug targets, exploring the potential target space for natural products. Our data exploration provided a global perspective on the gaps in the chemobiological space of natural compounds through systematic analysis and prediction of their target space, which can be used for new drug design or natural drug repurposing.

Design and synthesis of multi-functional small-molecule based inhibitors of amyloid-β aggregation: Molecular modeling and in vitro evaluation

Amyloid-β1-42 (Aβ42) peptide aggregate formation in the brain plays a crucial role in the onset and progression of Alzheimer's disease. According to published research, the Aβ monomer's amino acid residues KLVFF (16-20) self-associate to create antiparallel β-sheet fibrils. Small compounds can prevent self-assembly and destroy Aβ fibrils by attaching to the Aβ16-20 regions of Aβ42. To enhance biological characteristics and binding affinity to the amyloid beta peptide, β-sheet breaker small molecules can be developed and modified with various scaffolds. In the current study, a novel series of 2,3-disubstitutedbenzofuran derivatives was designed and created by fusing the benzofuran core of a known iron chelator, neuroprotective, and neurorestorative agent, like VK-28, with a motif found in the structure of a known muscarinic inhibitor and amyloid binding agent, like SKF-64346. Measurements of the binding affinity and in vitro aggregation inhibition of the Aβ42 peptide were made using the thioflavin T (ThT) test. Using AutoDock 4.2 software, molecular docking studies of the synthesized compounds were performed on the monomer and fibril structures of amyloid beta peptide. The compounds 8a-8g exhibited strong binding energy and affinity to Aβ fibrils as well as a 50%-67% reduction of the growth of Aβ aggregation. Finally, the positive traits of our recently synthesized compounds make them excellent candidates for additional in vivo testing as a "β-sheet breaking agent."

Assessment of Purity, Functionality, Stability, and Lipid Composition of Cyclofos-nAChR-Detergent Complexes from Torpedo californica Using Lipid Matrix and Macroscopic Electrophysiology

The main objective of the present study was to find detergents that can maintain the functionality and stability of the Torpedo californica nicotinic acetylcholine receptor (Tc-nAChR). We examined the functionality, stability, and purity analysis of affinity-purified Tc-nAChR solubilized in detergents from the Cyclofos (CF) family [cyclofoscholine 4 (CF-4), cyclofoscholine 6 (CF-6), and cyclofloscholine 7 (CF-7)]. The functionality of the CF-Tc-nAChR-detergent complex (DC) was evaluated using the Two Electrode Voltage Clamp (TEVC) method. To assess stability, we used the florescence recovery after photobleaching (FRAP) in Lipidic Cubic Phase (LCP) methodology. We also performed a lipidomic analysis using Ultra-Performance Liquid Chromatography (UPLC) coupled to electrospray ionization mass spectrometry (ESI-MS/MS) to evaluate the lipid composition of the CF-Tc-nAChR-DCs. The CF-4-Tc-nAChR-DC displayed a robust macroscopic current (- 200 ± 60 nA); however, the CF-6-Tc-nAChR-DC and CF-7-Tc-nAChR-DC displayed significant reductions in the macroscopic currents. The CF-6-Tc-nAChR and CF-4-Tc-nAChR displayed higher fractional florescence recovery. Addition of cholesterol produced a mild enhancement of the mobile fraction on the CF-6-Tc-nAChR. The lipidomic analysis revealed that the CF-7-Tc-nAChR-DC displayed substantial delipidation, consistent with the lack of stability and functional response of this complex. Although the CF-6-nAChR-DC complex retained the largest amount of lipids, it showed a loss of six lipid species [SM(d16:1/18:0); PC(18:2/14:1); PC(14:0/18:1); PC(16:0/18:1); PC(20:5/20:4), and PC(20:4/20:5)] that are present in the CF-4-nAChR-DC. Overall, the CF-4-nAChR displayed robust functionality, significant stability, and the best purity among the three CF detergents; therefore, CF-4 is a suitable candidate to prepare Tc-nAChR crystals for structural studies.

G protein-coupled receptors in neurodegenerative diseases and psychiatric disorders

Neuropsychiatric disorders are multifactorial disorders with diverse aetiological factors. Identifying treatment targets is challenging because the diseases are resulting from heterogeneous biological, genetic, and environmental factors. Nevertheless, the increasing understanding of G protein-coupled receptor (GPCR) opens a new possibility in drug discovery. Harnessing our knowledge of molecular mechanisms and structural information of GPCRs will be advantageous for developing effective drugs. This review provides an overview of the role of GPCRs in various neurodegenerative and psychiatric diseases. Besides, we highlight the emerging opportunities of novel GPCR targets and address recent progress in GPCR drug development.

Cholinergic dysfunction in COVID-19: frantic search and hoping for the best

A novel coronavirus known as severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is a potential cause of acute respiratory infection called coronavirus disease 2019 (COVID-19). The binding of SARS-CoV-2 with angiotensin-converting enzyme 2 (ACE2) induces a series of inflammatory cellular events with cytopathic effects leading to cell injury and hyperinflammation. Severe SARS-CoV-2 infection may lead to dysautonomia and sympathetic storm due to dysfunction of the autonomic nervous system (ANS). Therefore, this review aimed to elucidate the critical role of the cholinergic system (CS) in SARS-CoV-2 infection. The CS forms a multi-faceted network performing diverse functions in the body due to its distribution in the neuronal and non-neuronal cells. Acetylcholine (ACh) acts on two main types of receptors which are nicotinic receptors (NRs) and muscarinic receptors (MRs). NRs induce T cell anergy with impairment of antigen-mediated signal transduction. Nicotine through activation of T cell NRs inhibits the expression and release of the pro-inflammatory cytokines. NRs play important anti-inflammatory effects while MRs promote inflammation by inducing the release of pro-inflammatory cytokines. SARS-CoV-2 infection can affect the morphological and functional stability of CS through the disruption of cholinergic receptors. SARS-CoV-2 spike protein is similar to neurotoxins, which can bind to nicotinic acetylcholine receptors (nAChR) in the ANS and brain. Therefore, cholinergic receptors mainly nAChR and related cholinergic agonists may affect the pathogenesis of SARS-CoV-2 infection. Cholinergic dysfunction in COVID-19 is due to dysregulation of nAChR by SARS-CoV-2 promoting the central sympathetic drive with the development of the sympathetic storm. As well, nAChR activators through interaction with diverse signaling pathways can reduce the risk of inflammatory disorders in COVID-19. In addition, nAChR activators may mitigate endothelial dysfunction (ED), oxidative stress (OS), and associated coagulopathy in COVID-19. Similarly, nAChR activators may improve OS, inflammatory changes, and cytokine storm in COVID-19. Therefore, nAChR activators like varenicline in virtue of its anti-inflammatory and anti-oxidant effects with direct anti-SARS-CoV-2 effect could be effective in the management of COVID-19.

An Overview of 1,2,3-triazole-Containing Hybrids and Their Potential Anticholinesterase Activities

Acetylcholine (ACh) neurotransmitter of the cholinergic system in the brain is involved in learning, memory, stress responses, and cognitive functioning. It is hydrolyzed into choline and acetic acid by two key cholinesterase enzymes, viz., acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). A loss or degeneration of cholinergic neurons that leads to a reduction in ACh levels is considered a significant contributing factor in the development of neurodegenerative diseases (NDs) such as Alzheimer's disease (AD). Numerous studies have shown that cholinesterase inhibitors can raise the level of ACh and, therefore, enhance people's quality of life, and, at the very least, it can temporarily lessen the symptoms of NDs. 1,2,3-triazole, a five-membered heterocyclic ring, is a privileged moiety, that is, a central scaffold, and is capable of interacting with a variety of receptors and enzymes to exhibit a broad range of important biological activities. Recently, it has been clubbed with other pharmacophoric fragments/molecules in hope of obtaining potent and selective AChE and/or BuChE inhibitors. The present updated review succinctly summarizes the different synthetic strategies used to synthesize the 1,2,3-triazole moiety. It also highlights the anticholinesterase potential of various 1,2,3-triazole di/trihybrids reported in the past seven years (2015-2022), including a rationale for hybridization and with an emphasis on their structural features for the development and optimization of cholinesterase inhibitors to treat NDs.

Evidence for a protective effect of the loss of α4-containing nicotinic acetylcholine receptors on Aβ-related neuropathology in Tg2576 mice

Introduction

Loss of cholinergic neurons as well as α4β2* (* = containing) nicotinic acetylcholine receptors (nAChRs) is a prominent feature of Alzheimer's disease (AD). Specifically, amyloid β (Aβ), the principal pathogenic factor of AD, is a high affinity ligand for nAChRs. Yet, the pathophysiological role of nAChRs in AD is not well established.

Methods

In the present study, we have investigated the effects of the loss of α4* nAChRs on the histological alterations of the Tg2576 mouse model of AD (APPswe) crossing hemizygous APPswe mice with mice carrying the genetic inactivation of α4 nAChR subunit (α4KO).

Results

A global decrease in Aβ plaque load was observed in the forebrain of APPswe/α4KO mice in comparison with APPswe mice, that was particularly marked in neocortex of 15 month-old mice. At the same age, several alterations in synaptophysin immunoreactivity were observed in cortico-hippocampal regions of APPswe mice that were partially counteracted by α4KO. The analysis of the immunoreactivity of specific astroglia (glial fibrillary acidic protein, GFAP) and microglia (ionized calcium-binding adapter molecule, Iba1) markers showed an increase in the number as well as in the area occupied by these cells in APPswe mice that were partially counteracted by α4KO.

Conclusion

Overall, the present histological study points to a detrimental role of α4* nAChRs that may be specific for Aβ-related neuropathology.

The Aqueous Extract of Humulus japonicus Ameliorates Cognitive Dysfunction in Alzheimer's Disease Models via Modulating the Cholinergic System

Humulus japonicus (HJ) is an herbal medicine, which has been reported as being antioxidative and anti-inflammatory. The present study aimed to investigate the effect of oral administration of HJ water extract (HJW) on cognitive function through the cholinergic system in Alzheimer's disease (AD) mouse models. Institute of Cancer Research mice injected with beta-amyloid (Aβ) (1-42) (i.c.v.) and APP/PS1 transgenic (TG) mice were orally administered with HJW at 500 mg/kg/day for 3 weeks. Aβ-injected mice and APP/PS1 TG mice showed cognitive dysfunction, which was evaluated by various behavioral tests. HJW treatment significantly attenuated memory impairments in Aβ-injected mice and APP/PS1 TG mice. Aβ injection decreased acetylcholine (ACh) concentrations and choline acetyltransferase (ChAT) activity, and increased acetylcholinesterase (AChE) activity. These cholinergic impairments were also found in APP/PS1 TG mice. HJW significantly attenuated cholinergic alterations in Aβ-injected mice and TG mice. In addition, HJW significantly decreased Aβ plaque deposition in the cerebral cortex and hippocampus of TG mice. Therefore, the present study demonstrated that HJW protected against AD-related memory impairments via enhancing the cholinergic system and inhibiting Aβ plaque deposition.

Inhibition of Cholinesterases by Benzothiazolone Derivatives

Thirteen benzothiazolone derivatives (M1–M13) were synthesized and evaluated for their inhibitory activity against cholinesterases (ChEs) and monoamine oxidases (MAOs). All the compounds inhibited ChEs more effectively than MAOs. In addition, most of the compounds showed higher inhibitory activities against butyrylcholinesterase (BChE) than acetylcholinesterase (AChE). Compound M13 most potently inhibited BChE with an IC50 value of 1.21 μM, followed by M2 (IC50 = 1.38 μM). Compound M2 had a higher selectivity index (SI) value for BChE over AChE (28.99) than M13 (4.16). The 6-methoxy indole group of M13 was expected to have a greater effect on BChE inhibitory activity than the other groups. Kinetics and reversibility tests showed that M13 was a reversible noncompetitive BChE inhibitor with a Ki value of 1.14 ± 0.21 μM. In a docking simulation, M13 is predicted to form a hydrogen bond with the backbone carbonyl group of Ser287 of BChE through its methoxy indole moiety and π−π interactions between its benzothiazolone group and the side chain of Trp82 with the five-membered pyrrole ring and with the six-membered benzene ring. From these results, it is suggested that M13 is a BChE inhibitor and a potential candidate agent for the treatment of Alzheimer’s disease.

Bioinformatics-Based Approach for Exploring the Immune Cell Infiltration Patterns in Alzheimer's Disease and Determining the Intervention Mechanism of Liuwei Dihuang Pill

Traditional Chinese medicine (TCM) compounds have recently garnered attention for the regulation of immune cell infiltration and the prevention and treatment of Alzheimer's disease (AD). The Liuwei Dihuang Pill (LDP) has potential in this regard; however, its specific molecular mechanism currently remains unclear. Therefore, we adopted a bioinformatics approach to investigate the infiltration patterns of different types of immune cells in AD and explored the molecular mechanism of LDP intervention, with the aim of providing a new basis for improving the clinical immunotherapy of AD patients. We found that M1 macrophages showed significantly different degrees of infiltration between the hippocampal tissue samples of AD patients and healthy individuals. Four immune intersection targets of LDP in the treatment of AD were identified; they were enriched in 206 biological functions and 30 signaling pathways. Quercetin had the best docking effect with the core immune target PRKCB. Our findings suggest that infiltrated immune cells may influence the course of AD and that LDP can regulate immune cell infiltration through multi-component, multi-target, and multi-pathway approaches, providing a new research direction regarding AD immunotherapy.

Bioavailability of Hesperidin and Its Aglycone Hesperetin—Compounds Found in Citrus Fruits as a Parameter Conditioning the Pro-Health Potential (Neuroprotective and Antidiabetic Activity)—Mini-Review

Hesperidin and hesperetin are polyphenols that can be found predominantly in citrus fruits. They possess a variety of pharmacological properties such as neuroprotective and antidiabetic activity. However, the bioavailability of these compounds is limited due to low solubility and restricts their use as pro-healthy agents. This paper described the limitations resulting from the low bioavailability of the presented compounds and gathered the methods aiming at its improvement. Moreover, this work reviewed studies providing pieces of evidence for neuroprotective and antidiabetic properties of hesperidin and hesperetin as well as providing a detailed look into the significance of reported modes of action in chronic diseases. On account of a well-documented pro-healthy activity, it is important to look for ways to overcome the problem of poor bioavailability.

Alzheimer's Disease, Hearing Loss, and Deviance Detection

Age-related hearing loss is a widespread condition among the elderly, affecting communication and social participation. Given its high incidence, it is not unusual that individuals suffering from age-related hearing loss also suffer from other age-related neurodegenerative diseases, a scenario which severely impacts their quality of life. Furthermore, recent studies have identified hearing loss as a relevant risk factor for the development of dementia due to Alzheimer’s disease, although the underlying associations are still unclear. In order to cope with the continuous flow of auditory information, the brain needs to separate repetitive sounds from rare, unexpected sounds, which may be relevant. This process, known as deviance detection, is a key component of the sensory perception theory of predictive coding. According to this framework, the brain would use the available incoming information to make predictions about the environment and signal the unexpected stimuli that break those predictions. Such a system can be easily impaired by the distortion of auditory information processing that accompanies hearing loss. Changes in cholinergic neuromodulation have been found to alter auditory deviance detection both in humans and animal models. Interestingly, some theories propose a role for acetylcholine in the development of Alzheimer’s disease, the most common type of dementia. Acetylcholine is involved in multiple neurobiological processes such as attention, learning, memory, arousal, sleep and/or cognitive reinforcement, and has direct influence on the auditory system at the levels of the inferior colliculus and auditory cortex. Here we comment on the possible links between acetylcholine, hearing loss, and Alzheimer’s disease, and association that is worth further investigation.

Evidence for Rosa damascena efficacy in mental disorders in preclinical animal studies and clinical trials: A systematic review

The aim of this systematic review was to identify animal preclinical studies and randomized controlled trials that looked at the effects of R. damascena in any form on different mental diseases. Up to September 2021, the online databases of PubMed, Scopus, Embase, Web of Science, and Cochrane trials, as well as SID and MagIran, were searched. This study included 10 animal studies. Except for one research, the rest of the studies confirmed the positive effects of the plant in treatment of mental disorders. A total of 38 studies met the criteria for inclusion. Individuals who have encountered various sorts of mental problems, such as anxiety, sleep disturbance, and depressive disorder, were studied. R. damascena essential oil (EO), essence, extract, and dried plant were used in aromatherapy and oral administration. A decrease in sympathetic nervous system activity, induction of neurotransmitters, induction of nerve growth factors by neurogenesis and synaptogenesis mechanisms, a decrease in prolactin and an increase in noradrenaline, estradiol, and progesterone secretion are some of the mechanisms of action. In general, R. damascena is an effective herb for the treatment of mental disorders. However, further research timing and duration of intervention are needed to extrapolate the findings.

Hypoxic and Hypercapnic Responses in Transgenic Murine Model of Alzheimer’s Disease Overexpressing Human AβPP: The Effects of Pretreatment with Memantine and Rivastigmine

Despite the severe respiratory problems reducing the quality of life for Alzheimer’s disease (AD) patients, their causes are poorly understood. We aimed to investigate hypoxic and hypercapnic respiratory responses in a transgenic mouse model of AD (AβPP V717I) overexpressing AβPP and mimicking early-onset AD. The cholinesterase inhibitor rivastigmine and the NMDA receptor antagonist memantine were used to investigate the effects of drugs, used to treat AD cognitive dysfunction, on breathing in hypoxia and hypercapnia. We found a significant increase in the respiratory response to hypercapnia and no difference in the hypoxic response in APP+ mice, compared with the control group (APP−). Memantine had no effect on respiration in either group, including responses to hypoxia and hypercapnia. Rivastigmine depressed resting ventilation and response to hypercapnia irrespective of the mice genotype. Reduction in hypoxia-augmented ventilation by rivastigmine was observed only in APP+ mice, which exhibited lower acetylcholinesterase activity in the hippocampus. Treatment with rivastigmine reduced the enzyme activity in both groups equally in the hippocampus and brainstem. The increased ventilatory response to hypercapnia in transgenic mice may indicate alterations in chemoreceptive respiratory nuclei, resulting in increased CO₂ sensitivity. Rivastigmine is a potent reductant of normoxic and hypercapnic respiration in APP+ and APP− mice.

Bioactive Compounds and Their Derivatives: An Insight into Prospective Phytotherapeutic Approach against Alzheimer’s Disease

Alzheimer's disease (AD) is a common neurodegenerative brain disorder that causes cellular response alterations, such as impaired cholinergic mechanism, amyloid-beta (Aβ) AD aggregation, neuroinflammation, and several other pathways. AD is still the most prevalent form of dementia and affects many individuals across the globe. The exact cause of the disorder is obscure. There are yet no effective medications for halting, preventing, or curing AD's progress. Plenty of natural products are isolated from several sources and analyzed in preclinical and clinical settings for neuroprotective effects in preventing and treating AD. In addition, natural products and their derivatives have been promising in treating and preventing AD. Natural bioactive compounds play an active modulatory role in the pathological molecular mechanisms of AD development. This review focuses on natural products from plant sources and their derivatives that have demonstrated neuroprotective activities and maybe promising to treat and prevent AD. In addition, this article summarizes the literature pertaining to natural products as agents in the treatment of AD. Rapid metabolism, nonspecific targeting, low solubility, lack of BBB permeability, and limited bioavailability are shortcomings of most bioactive molecules in treating AD. We can use nanotechnology and nanocarriers based on different types of approaches.

Trigonella foenum-graecum Methanolic Extract on Isolated Smooth Muscles and Acetylcholinesterase Enzyme: An In Vitro and Mechanistic In Silico Investigation

Background and Objective. Trigonella foenum-graecum Linn., also called fenugreek, is a popular medicinal plant cultivated all over the globe. Fenugreek seeds are known for their many medicinal properties. We present our findings on the effect of a 70% aqueous methanolic fenugreek seed extract (Tfg.Cr) on isolated GI smooth muscles (rabbit jejunum and rat ileum) and the effect of extract and its constituent diosgenin on acetylcholinesterase (AChE) enzyme. Results. When tested on the baseline of isolated tissues, Tfg.Cr was devoid of any activity (stimulant or relaxant) till 10 mg/ml. This is an interesting finding, keeping in mind that the fenugreek seeds are used to alleviate constipation and diarrhoea. When Tfg.Cr was tried for any potential AChE inhibitory activity, it did show an inhibitory effect in increasing concentrations (47-380 μg/ml). This inhibitory effect was comparable to the effect produced by a standard AChE inhibitor physostigmine. One of the known fenugreek constituents, diosgenin, was also tested, and it also showed an AChE inhibitory effect in a concentration-dependent manner (11-190 μg/ml). Interaction between diosgenin and AChE was further investigated by molecular docking and molecular dynamics simulations for 100 ns, which showed that diosgenin interacted with the active-site gorge of AChE through hydrophobic, pi-pi stacking, and hydrogen bonds with various amino acids of the AChE enzyme. Conclusion. The results show that the fenugreek extract does not possess any GI stimulant or relaxant activity even though it is used traditionally in GI motility disorders. The extract and diosgenin could inhibit the AChE enzyme pointing towards their benefit to enhance the memory.

Targeting the M1 muscarinic acetylcholine receptor in Alzheimer’s disease

Alzheimer’s disease (AD) remains a major cause of morbidity and mortality worldwide, and despite extensive research, only a few drugs are available for management of the disease. One strategy has been to up-regulate cholinergic neurotransmission to improve cognitive function, but this approach has dose-limiting adverse effects. To avoid these adverse effects, new drugs that target specific receptor subtypes of the cholinergic system are needed, and the M1 subtype of muscarinic acetylcholine receptor (M1-mAChR) has been shown to be a good target for this approach. By using several strategies, M1-mAChR ligands have been developed and trialled in preclinical animal models and in human studies, with varying degrees of success. This article reviews the different approaches to targeting the M1-mAChR in AD and discusses the advantages and limitations of these strategies. The factors to consider in targeting the M1-mAChR in AD are also discussed.

Amorphous Inclusion Complexes: Molecular Interactions of Hesperidin and Hesperetin with HP-Β-CD and Their Biological Effects

This study aimed at obtaining hesperidin (Hed) and hesperetin (Het) systems with HP-β-CD by means of the solvent evaporation method. The produced systems were identified using infrared spectroscopy (FT-IR), X-ray powder diffraction (XRPD), and differential scanning calorimetry (DSC). Moreover, in silico docking and molecular dynamics studies were performed to assess the most preferable site of interactions between tested compounds and HP-β-CD. The changes of physicochemical properties (solubility, dissolution rate, and permeability) were determined chromatographically. The impact of modification on biological activity was tested in an antioxidant study as well as with regards to inhibition of enzymes important in pathogenesis of neurodegenerative diseases. The results indicated improvement in solubility over 1000 and 2000 times for Hed and Het, respectively. Permeability studies revealed that Hed has difficulties in crossing biological membranes, in contrast with Het, which can be considered to be well absorbed. The improved physicochemical properties influenced the biological activity in a positive manner by the increase in inhibitory activity on the DPPH radical and cholinoesterases. To conclude the use of HP-β-CD as a carrier in the formation of an amorphous inclusion complex seems to be a promising approach to improve the biological activity and bioavailability of Hed and Het.

Role of Cholinergic Signaling in Alzheimer's Disease

Acetylcholine, a neurotransmitter secreted by cholinergic neurons, is involved in signal transduction related to memory and learning ability. Alzheimer’s disease (AD), a progressive and commonly diagnosed neurodegenerative disease, is characterized by memory and cognitive decline and behavioral disorders. The pathogenesis of AD is complex and remains unclear, being affected by various factors. The cholinergic hypothesis is the earliest theory about the pathogenesis of AD. Cholinergic atrophy and cognitive decline are accelerated in age-related neurodegenerative diseases such as AD. In addition, abnormal central cholinergic changes can also induce abnormal phosphorylation of ttau protein, nerve cell inflammation, cell apoptosis, and other pathological phenomena, but the exact mechanism of action is still unclear. Due to the complex and unclear pathogenesis, effective methods to prevent and treat AD are unavailable, and research to explore novel therapeutic drugs is various and active in the world. This review summaries the role of cholinergic signaling and the correlation between the cholinergic signaling pathway with other risk factors in AD and provides the latest research about the efficient therapeutic drugs and treatment of AD.

Pantao Pill Improves the Learning and Memory Abilities of APP/PS1 Mice by Multiple Mechanisms

Background: To explore the effect and mechanisms of Pantao Pill (PTP) on cognitive impairment.

Methods: Network pharmacology was performed to analyze the mechanism of PTP treating cognitive impairment. The targets of PTP and cognitive impairment were predicted and used to construct protein-protein interaction (PPI) networks. The intersection network was selected, and the core network was obtained through topological analysis. Enrichment analysis was conducted to obtain the GOBP terms and KEGG pathways. We then performed experiments to validate the results of the network pharmacology by using an APP/PS1 transgenic mouse model. The APP/PS1 mice were divided into four groups: the model group, the high-dose PTP (3.6 g/kg·d) group, the low-dose PTP (1.8 g/kg·d) group, and the positive control group (donepezil hydrochloride, 2 mg/kg·d). Wild-type (WT) C57 mice served as a normal control group. PTP and donepezil were administered by gavage for 8 weeks.

Results: Network pharmacology showed that PTP might improve cognitive impairment by regulating autophagy, apoptosis, and oxidative stress. For the Morris water maze test, a significant difference was shown in the total swimming distance among groups (p < 0.05) in the positioning navigation experiment, and with training time extension, the swimming speed increased (p < 0.01). In the space probe test, PTP administration significantly reduced the swimming path length and the escape latency of APP/PS1 mice (p < 0.05 or p < 0.01), whereas it had no effect on the swimming speed (p > 0.05). PTP (3.6 g/kg/d) rescued the reduction of norepinephrine and acetylcholine levels (p < 0.05), and increased the acetylcholinesterase concentration (p < 0.05) in the brain tissue. PTP (1.8 g/kg/d) increased the norepinephrine level (p < 0.01). PTP rescued the activity reduction of superoxide dismutase in the brain tissue (p < 0.01) and the neuron cell pyknosis in the hippocampal CA region (p < 0.05). PTP reduced ATG12 and PS1 expression (p < 0.05 or p < 0.01), and increased Bcl-2 expression in the brain tissue (p < 0.05).

Conclusion: PTP can significantly improve the learning and memory abilities of APP/PS1 mice, and the mechanism may be related to the increase of neurotransmitter acetylcholine and norepinephrine levels, the reduction of the excessive autophagic activation, and the suppression of oxidative stress and excessive apoptotic activity.