Tau phosphorylation by glycogen synthase kinase 3β modulates enzyme acetylcholinesterase expression

Protein kinases in neurodegenerative diseases: current understandings and implications for drug discovery

Neurodegenerative diseases (e.g., Alzheimer's, Parkinson's, Huntington's disease, and Amyotrophic Lateral Sclerosis) are major health threats for the aging population and their prevalences continue to rise with the increasing of life expectancy. Although progress has been made, there is still a lack of effective cures to date, and an in-depth understanding of the molecular and cellular mechanisms of these neurodegenerative diseases is imperative for drug development. Protein phosphorylation, regulated by protein kinases and protein phosphatases, participates in most cellular events, whereas aberrant phosphorylation manifests as a main cause of diseases. As evidenced by pharmacological and pathological studies, protein kinases are proven to be promising therapeutic targets for various diseases, such as cancers, central nervous system disorders, and cardiovascular diseases. The mechanisms of protein phosphatases in pathophysiology have been extensively reviewed, but a systematic summary of the role of protein kinases in the nervous system is lacking. Here, we focus on the involvement of protein kinases in neurodegenerative diseases, by summarizing the current knowledge on the major kinases and related regulatory signal transduction pathways implicated in diseases. We further discuss the role and complexity of kinase-kinase networks in the pathogenesis of neurodegenerative diseases, illustrate the advances of clinical applications of protein kinase inhibitors or novel kinase-targeted therapeutic strategies (such as antisense oligonucleotides and gene therapy) for effective prevention and early intervention.

Triple-Target Inhibition of Cholinesterase, Amyloid Aggregation, and GSK3β to Ameliorate Cognitive Deficits and Neuropathology in the Triple-Transgenic Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) poses one of the most urgent medical challenges in the 21st century as it affects millions of people. Unfortunately, the etiopathogenesis of AD is not yet fully understood and the current pharmacotherapy options are somewhat limited. Here, we report a novel inhibitor, Compound 44, for targeting cholinesterases, amyloid-β (Aβ) aggregation, and glycogen synthase kinase 3β (GSK-3β) simultaneously with the aim of achieving symptomatic relief and disease modification in AD therapy. We found that Compound 44 had good inhibitory effects on all intended targets with IC50s of submicromolar or better, significant neuroprotective effects in cell models, and beneficial improvement of cognitive deficits in the triple transgenic AD (3 × Tg AD) mouse model. Moreover, we showed that Compound 44 acts as an autophagy regulator by inducing nuclear translocation of transcription factor EB through GSK-3β inhibition, enhancing the biogenesis of lysosomes and elevating autophagic flux, thus ameliorating the amyloid burden and tauopathy, as well as mitigating the disease phenotype. Our results suggest that triple-target inhibition via Compound 44 could be a promising strategy that may lead to the development of effective therapeutic approaches for AD.

Ionic and Non-Ionic Counterparts Based on Bis(Uracilyl)Alkane Moiety with Highest Selectivity Towards Acetylcholinesterase for Protection Against Organophosphate Poisoning and Treating Alzheimer's Disease

A series of bisuracils, in which uracil and 3,6-dimethyluracil moieties were bridged with a polymethylene spacer, and the uracil moiety contained a pentamethylene radical with ionic and non-ionic aminobenzyl groups, were synthesised. These bisuracils have been identified as cholinesterase inhibitors with exceptional selectivity for acetylcholinesterase (AChE) over butyrylcholinesterase (BuChE). These bisuracils, which have been identified as highly effective AChE inhibitors, demonstrated activity at nano- and sub-nanomolar concentrations, with exceptional selectivity for AChE over BuChE. In kinetic studies of lead bisuracils 2b and 3c, both compounds exhibited mixed-type inhibition against AChE and BuChE. Additionally, molecular dynamic simulations demonstrated robust and stable interactions of 2b and 3c with the binding sites of their target. Bisuracil 2b showed significant potential for protection of AChE from irreversible inhibition by paraoxon; the most effective dose of 0.01 mg/kg was shown to reduce mortality in paraoxon-poisoned mice. Bisuracil 3c effectively inhibited brain AChE activity, reversing scopolamine-induced amnesia in mice at a dose of 5 mg/kg, which indicates its potential for cognitive enhancement. These findings position ionic bisuracils as promising prophylactics against organophosphate poisoning and non-ionic bisuracils as viable candidates for Alzheimer's disease therapeutics.

Synaptic plasticity and neuroprotection: The molecular impact of flavonoids on neurodegenerative disease progression

Flavonoids are a broad family of polyphenolic chemicals that are present in a wide variety of fruits, vegetables, and medicinal plants. Because of their neuroprotective qualities, flavonoids have attracted a lot of interest. The potential of flavonoids to control synaptic plasticity-a crucial process underlying memory, learning, and cognitive function-is becoming more and more clear. Dysregulation of synaptic plasticity is a feature of neurodegenerative diseases such as amyotrophic lateral sclerosis (0.4 %), Parkinson's (1-2 %), Alzheimer's (5-7 %), and Huntington's ((0.2 %)). This review discusses the molecular mechanisms via which flavonoids influence synaptic plasticity as well as their therapeutic potential in neurodegenerative diseases. Flavonoids modulate key signaling pathways such as MAPK/ERK and PI3K/Akt/mTOR to support neuroprotection, synaptic plasticity, and neuronal health, while also influencing neurotrophic factors (BDNF, NGF) and their receptors (TrkB, TrkA). They regulate neurotransmitter receptors like GABA, AMPA, and NMDA to balance excitatory and inhibitory transmission, and exert antioxidant effects via the Nrf2-ARE pathway and anti-inflammatory actions by inhibiting NF-κB signaling, highlighting their potential for treating neurodegenerative diseases. These varied reactions support the preservation of synapse function and neuronal integrity in the face of neurodegenerative insults. Flavonoids can reduce the symptoms of neurodegeneration, prevent synaptic loss, and enhance cognitive function, according to experimental studies. However, there are still obstacles to using these findings in clinical settings, such as limited bioavailability and the need for consistent dose. The focus of future research should be on improving flavonoid delivery systems and combining them with conventional medications.

Undifferentiated versus retinoic acid-differentiated SH-SY5Y cells in investigation of markers of neural function in toxicological research

The SH-SY5Y human neuroblastoma cell line is a standard in vitro experimental model of neuronal-like cells used in neuroscience and toxicological research. These cells can be differentiated into mature neurons, most commonly using retinoic acid (RA). Despite differences in characteristics, both undifferentiated and differentiated SH-SY5Y cells are used in research. However, due to uncertainties regarding the expression of specific markers of neural function in each culture, there is no definite conclusion on which culture is better suited for (neuro)toxicological and/or neuroscience investigations. To address this dilemma, we investigated the basal expression/activity of the key elements of acetylcholine, dopamine, serotonin, and GABA neurotransmitter pathways, along with the elements involved in exocytosis of neurotransmitters, and neuron electrophysiological activity in undifferentiated and in RA-differentiated SH-SY5Y cells using a six-day differentiation protocol. Our findings revealed that both SH-SY5Y cell types are functionally active. While undifferentiated SH-SY5Y cells exhibited greater multipotency in the expression of tested markers, most of those markers expressed in both cell types showed higher expression levels in RA-differentiated SH-SY5Y cells. Our results suggest that the six-day differentiation protocol with RA induces maturation, but not differentiation of the cells into specific neuron phenotype. The greater multipotency of undifferentiated cells in neural markers expression, together with their higher sensitivity to xenobiotic exposure and more simple cultivation protocols, make them a better candidate for high throughput toxicological screenings. Differentiated neurons are better suited for neuroscience researches that require higher expression of more specific neural markers and the specific types of neural cells.

ERRα and ERRγ coordinate expression of genes associated with Alzheimer's disease, inhibiting DKK1 to suppress tau phosphorylation

Alzheimer's disease (AD) is a prevalent neurodegenerative disease characterized by cognitive decline and learning/memory impairment associated with neuronal cell loss. Estrogen-related receptor α (ERRα) and ERRγ, which are highly expressed in the brain, have emerged as potential AD regulators, with unelucidated underlying mechanisms. Here, we identified genome-wide binding sites for ERRα and ERRγ in human neuronal cells. They commonly target a subset of genes associated with neurodegenerative diseases, including AD. Notably, Dickkopf-1 (DKK1), a Wnt signaling pathway antagonist, was transcriptionally repressed by both ERRα and ERRγ in human neuronal cells and brain. ERRα and ERRγ repress RNA polymerase II (RNAP II) accessibility at the DKK1 promoter by modulating a specific active histone modification, histone H3 lysine acetylation (H3K9ac), with the potential contribution of their corepressor. This transcriptional repression maintains Wnt signaling activity, preventing tau phosphorylation and promoting a healthy neuronal state in the context of AD.

Polymeric nanoparticles decorated with fragmented chitosan as modulation systems for neuronal drug uptake

This study aimed to modify chitosan (CS) by gamma irradiation and use it as a surface coating of nanoparticles (NPs) fabricated of poly lactic-co-glycolic acid (PLGA) to create mostly biocompatible nanosystems that can transport drugs to neurons. Gamma irradiation produced irradiated CS (CSγ) with a very low molecular weight (15.2-19.2 kDa). Coating NPs-PLGA with CSγ caused significant changes in their Z potential, making it slightly positive (from -21.7 ± 2.8 mV to +7.1 ± 2.3 mV) and in their particle size (184.4 0.4 ± 7.9 nm to 211.9 ± 14.04 nm). However, these changes were more pronounced in NPs coated with non-irradiated CS (Z potential = +54.0 ± 1.43 mV, size = 348.1 ± 16.44 nm). NPs coated with CSγ presented lower cytotoxicity and similar internalization levels in SH-SY5Y neuronal cells than NPs coated with non-irradiated CS, suggesting higher biocompatibility. Highly biocompatible NPs are desirable as nanocarriers to deliver drugs to the brain, as they help maintain the structure and function of the blood-brain barrier. Therefore, the NPs developed in this study could be evaluated as drug-delivery systems for treating brain diseases.

Evidence for a novel neuronal mechanism driving Alzheimer's disease, upstream of amyloid

This perspective offers an alternative to the amyloid hypothesis in the etiology of Alzheimer's disease (AD). We review evidence for a novel signaling mechanism based on a little-known peptide, T14. T14 could drive neurodegeneration as an aberrantly activated process of plasticity selective to interconnecting subcortical nuclei, the isodendritic core, where cell loss starts at the pre-symptomatic stages of the disease. Each of these cell groups has the capacity to form T14, which can stimulate production of p-Tau and β-amyloid, suggestive of an upstream driver of neurodegeneration. Moreover, results in an animal AD model show that antagonism of T14 with a cyclated variant, NBP14, prevents formation of β-amyloid, and restores cognitive function to that of wild-type counterparts. Any diagnostic and/or therapeutic strategy based on T14-NBP14 awaits validation in clinical trials. However, an understanding of this novel signaling system could bring much-needed fresh insights into the progression of cell loss underlying AD. HIGHLIGHTS: The possible primary mechanism of neurodegeneration upstream of amyloid. Primary involvement of selectively vulnerable subcortical nuclei, isodendritic core. Bioactive peptide T14 trophic in development but toxic in context of mature brain. Potential for early-stage biomarker to detect Alzheimer's disease. Effective therapeutic halting neurodegeneration, validated already in 5XFAD mice.

GSK3: A potential target and pending issues for treatment of Alzheimer's disease

Glycogen synthase kinase-3 (GSK3), consisting of GSK3α and GSK3β subtypes, is a complex protein kinase that regulates numerous substrates. Research has observed increased GSK3 expression in the brains of Alzheimer's disease (AD) patients and models. AD is a neurodegenerative disorder with diverse pathogenesis and notable cognitive impairments, characterized by Aβ aggregation and excessive tau phosphorylation. This article provides an overview of GSK3's structure and regulation, extensively analyzing its relationship with AD factors. GSK3 overactivation disrupts neural growth, development, and function. It directly promotes tau phosphorylation, regulates amyloid precursor protein (APP) cleavage, leading to Aβ formation, and directly or indirectly triggers neuroinflammation and oxidative damage. We also summarize preclinical research highlighting the inhibition of GSK3 activity as a primary therapeutic approach for AD. Finally, pending issues like the lack of highly specific and affinity-driven GSK3 inhibitors, are raised and expected to be addressed in future research. In conclusion, GSK3 represents a target in AD treatment, filled with hope, challenges, opportunities, and obstacles.

Exploring Tau Fibril-Disaggregating and Antioxidating Molecules Binding to Membrane-Bound Amyloid Oligomers Using Machine Learning-Enhanced Docking and Molecular Dynamics

Intracellular tau fibrils are sources of neurotoxicity and oxidative stress in Alzheimer's. Current drug discovery efforts have focused on molecules with tau fibril disaggregation and antioxidation functions. However, recent studies suggest that membrane-bound tau-containing oligomers (mTCOs), smaller and less ordered than tau fibrils, are neurotoxic in the early stage of Alzheimer's. Whether tau fibril-targeting molecules are effective against mTCOs is unknown. The binding of epigallocatechin-3-gallate (EGCG), CNS-11, and BHT-CNS-11 to in silico mTCOs and experimental tau fibrils was investigated using machine learning-enhanced docking and molecular dynamics simulations. EGCG and CNS-11 have tau fibril disaggregation functions, while the proposed BHT-CNS-11 has potential tau fibril disaggregation and antioxidation functions like EGCG. Our results suggest that the three molecules studied may also bind to mTCOs. The predicted binding probability of EGCG to mTCOs increases with the protein aggregate size. In contrast, the predicted probability of CNS-11 and BHT-CNS-11 binding to the dimeric mTCOs is higher than binding to the tetrameric mTCOs for the homo tau but not for the hetero tau-amylin oligomers. Our results also support the idea that anionic lipids may promote the binding of molecules to mTCOs. We conclude that tau fibril-disaggregating and antioxidating molecules may bind to mTCOs, and that mTCOs may also be useful targets for Alzheimer's drug design.

Cyanidin improves spatial memory and cognition in bisphenol A-induced rat model of Alzheimer's-like neuropathology by restoring canonical Wnt signaling

INTRODUCTION

Research has unveiled the neurotoxicity of Bisphenol A (BPA) linked to neuropathological traits of Alzheimer's disease (AD) through varied mechanisms. This study aims to investigate the neuroprotective properties of cyanidin, an anthocyanin, in an in vivo model of BPA-induced Alzheimer's-like neuropathology.

METHODS

Three-week-old Sprague-Dawley rats were randomly assigned to four groups: vehicle control, negative control (BPA exposure), low-dose cyanidin treatment (BPA + cyanidin 5 mg/kg), and high-dose cyanidin treatment (BPA + cyanidin 10 mg/kg). Spatial memory was assessed through behavioral tests, including the Y-maze, novel object recognition, and Morris water maze. After behavioral tests, animals were euthanized, and brain regions were examined for acetylcholinesterase inhibition, p-tau, Wnt3, GSK3β, and β-catenin levels, antioxidant activities, and histopathological changes.

RESULTS

BPA-exposed groups displayed memory impairments, while cyanidin-treated groups showed significant memory improvement (p < 0.0001). Cyanidin down regulated p-tau and glycogen synthase kinase-3β (GSK3β) and restored Wnt3 and β-catenin levels (p < 0.0001). Moreover, cyanidin exhibited antioxidant properties, elevating catalase and superoxide dismutase levels. The intervention significantly reduced the concentrations of acetylcholinesterase in the cortex and hippocampus in comparison to the groups treated with BPA (p < 0.0001). Significant gender-based disparities were not observed.

CONCLUSION

Cyanidin demonstrated potent neuroprotection against BPA-induced Alzheimer's-like neuropathology by enhancing antioxidant defenses, modulating tau phosphorylation by restoring the Wnt/β-catenin pathway, and ameliorating spatial memory deficits. This study highlights the therapeutic potential of cyanidin in countering neurotoxicity linked to BPA exposure.

Design, Synthesis, and Biological Evaluation of Novel Tetrahydroacridin Hybrids with Sulfur-Inserted Linkers as Potential Multitarget Agents for Alzheimer's Disease

Alzheimer's disease (AD) is a complex neurodegenerative disease that can lead to the loss of cognitive function. The progression of AD is regulated by multiple signaling pathways and their associated targets. Therefore, multitarget strategies theoretically have greater potential for treating AD. In this work, a series of new hybrids were designed and synthesized by the hybridization of tacrine (4, AChE: IC50 = 0.223 μM) with pyrimidone compound 5 (GSK-3β: IC50 = 3 μM) using the cysteamine or cystamine group as the connector. The biological evaluation results demonstrated that most of the compounds exhibited moderate to good inhibitory activities against acetylcholinesterase (AChE) and glycogen synthase kinase 3β (GSK-3β). The optimal compound 18a possessed potent dual AChE/GSK-3β inhibition (AChE: IC50 = 0.047 ± 0.002 μM, GSK-3β: IC50 = 0.930 ± 0.080 μM). Further molecular docking and enzymatic kinetic studies revealed that this compound could occupy both the catalytic anionic site and the peripheral anionic site of AChE. The results also showed a lack of toxicity to SH-SY5Y neuroblastoma cells at concentrations of up to 25 μM. Collectively, this work explored the structure-activity relationships of novel tetrahydroacridin hybrids with sulfur-inserted linkers, providing a reference for the further research and development of new multitarget anti-AD drugs.

Dual-target inhibitors of cholinesterase and GSK-3β to modulate Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease that affects over 55 million patients worldwide. Most of the approved small-molecule drugs for AD have been designed to tackle a single pathological hallmark, such as cholinergic dysfunction or amyloid toxicity, and thus may not fully address the multifactorial nature of the disease. Inhibition of both cholinesterase and glycogen synthase kinase-3β (GSK-3β) has emerged as a promising strategy to modulate AD. However, the dual inhibition of these two targets posts challenges in molecular design: issues related to target engagements and biopharmaceutical properties in particular must be overcome. In this review, we discuss the physiopathological roles and structures of cholinesterase and GSK-3β as well as recently reported dual-target inhibitors. We critically evaluate the current status of the discovery of dual-target inhibitors of cholinesterase and GSK-3β, and highlight further perspectives.

GSK-3β activation mediates apolipoprotein E4-associated cognitive impairment in type 2 diabetes mellitus: A multicenter, cross-sectional study

AIM

Both the activation of glycogen synthase kinase-3β (GSK-3β) and the presence of ApoE ε4 genotype have been found to respectively correlate with cognitive decline in patients with type 2 diabetes mellitus (T2DM), who further show a high incidence of developing Alzheimer's disease. However, the relationship between ApoE ε4 and GSK-3β in the cognitive impairment of T2DM patients remains unclear.

METHODS

ApoE genotypes and platelet GSK-3β level were measured in 1139 T2DM patients recruited from five medical centers in Wuhan, China. Cognitive functions were assessed by Mini-Mental State Examination (MMSE). The association and the relationships among apolipoprotein E (ApoE) genotypes, GSK-3β activity and cognitive function were analyzed by regression and mediating effect analyses, respectively.

RESULTS

T2DM patients with ApoE ε4 but not ApoE ε2 haplotype showed poorer cognitive function and elevated platelet GSK-3β activity, when using ApoE ε3 as reference. The elevation of GSK-3β activity was positively correlated the diabetes duration, as well as plasma glycated hemoglobin (HbA1c) and glucose levels. Moreover, correlation and regression analysis also revealed significant pairwise correlations among GSK-3β activity, ApoE gene polymorphism and cognitive function. Lastly, using Baron and Kenny modeling, we unveiled a mediative role of GSK-3β activity between ApoE ε4 and cognitive impairment.

CONCLUSION

We reported here that the upregulation of GSK-3β activity mediates the exacerbation of cognitive impairment by ApoE ε4-enhanced cognitive impairment in T2DM patients, suggesting GSK-3β inhibitors as promising drugs for preserving cognitive function in T2DM patients, especially to those with ApoE ε4 genotype.

Stalling the Course of Neurodegenerative Diseases: Could Cyanobacteria Constitute a New Approach toward Therapy?

Neurodegenerative diseases (NDs) are characterized by progressive and irreversible neuronal loss, accompanied by a range of pathological pathways, including aberrant protein aggregation, altered energy metabolism, excitotoxicity, inflammation, and oxidative stress. Some of the most common NDs include Alzheimer's Disease (AD), Parkinson's Disease (PD), Multiple Sclerosis (MS), Amyotrophic Lateral Sclerosis (ALS), and Huntington's Disease (HD). There are currently no available cures; there are only therapeutic approaches that ameliorate the progression of symptoms, which makes the search for new drugs and therapeutic targets a constant battle. Cyanobacteria are ancient prokaryotic oxygenic phototrophs whose long evolutionary history has resulted in the production of a plethora of biomedically relevant compounds with anti-inflammatory, antioxidant, immunomodulatory, and neuroprotective properties, that can be valuable in this field. This review summarizes the major NDs and their pathophysiology, with a focus on the anti-neurodegenerative properties of cyanobacterial compounds and their main effects.

Study on multi-target effects of PIMPC on Aβ/Cu2+-induced Alzheimer's disease model of rats

Glycogen synthase kinase-3 (GSK-3), a key role in the pathogenesis of Alzheimer's disease (AD), has been linked with the formation of β-amyloid (Aβ), tubulin-associated unit (tau) protein phosphorylation and apoptosis. Moreover, the excessive presence of elements such as copper (Cu) can promote Aβ aggregation and increase the risk of AD. Combined with the role of GSK-3 and metal elements in AD, a metal-chelating imine GSK-3 inhibitor N-(4-{[(2-amino-5-phenylpyridin-3-ylidene)imino]methyl}pyridin-2-yl)cyclopropanecarboxamide (PIMPC) was designed and synthesized. In our study, Aβ/Cu²⁺-induced AD rat model was established and treated with PIMPC. The results indicated that PIMPC can not only down-regulate the high expression levels of Aβ, tau and p-tau proteins of the AD rats, but also chelate Cu and aluminum (Al) elements in the brain. In addition, PIMPC may play an anti-apoptotic effect by down-regulating the high expression of cleaved Caspase-3 protein, and it can modulate ATPase and nitric oxide synthase (NOS) levels, oxidative stress and neurotransmitter disturbance. In summary, PIMPC acts on multiple targets to relieve the learning and memory impairment of AD rats induced by Aβ/Cu²⁺.

Nanodelivery of Histamine H3/H4 Receptor Modulators BF-2649 and Clobenpropit with Antibodies to Amyloid Beta Peptide in Combination with Alpha Synuclein Reduces Brain Pathology in Parkinson's Disease

Parkinson's disease (PD) in military personnel engaged in combat operations is likely to develop in their later lives. In order to enhance the quality of lives of PD patients, exploration of novel therapy based on new research strategies is highly warranted. The hallmarks of PD include increased alpha synuclein (ASNC) and phosphorylated tau (p-tau) in the cerebrospinal fluid (CSF) leading to brain pathology. In addition, there are evidences showing increased histaminergic nerve fibers in substantia niagra pars compacta (SNpc), striatum (STr), and caudate putamen (CP) associated with upregulation of histamine H3 receptors and downregulation of H4 receptors in human brain. Previous studies from our group showed that modulation of potent histaminergic H3 receptor inverse agonist BF-2549 or clobenpropit (CLBPT) partial histamine H4 agonist with H3 receptor antagonist induces neuroprotection in PD brain pathology. Recent studies show that PD also enhances amyloid beta peptide (AβP) depositions in brain. Keeping these views in consideration in this review, nanowired delivery of monoclonal antibodies to AβP together with ASNC and H3/H4 modulator drugs on PD brain pathology is discussed based on our own observations. Our investigation shows that TiO₂ nanowired BF-2649 (1 mg/kg, i.p.) or CLBPT (1 mg/kg, i.p.) once daily for 1 week together with nanowired delivery of monoclonal antibodies (mAb) to AβP and ASNC induced superior neuroprotection in PD-induced brain pathology. These observations are the first to show the modulation of histaminergic receptors together with antibodies to AβP and ASNC induces superior neuroprotection in PD. These observations open new avenues for the development of novel drug therapies for clinical strategies in PD.

The Role of Aldose Reductase in Beta-Amyloid-Induced Microglia Activation

The occurrence of Alzheimer's disease has been associated with the accumulation of beta-amyloid (β-amyloid) plaques. These plaques activate microglia to secrete inflammatory molecules, which damage neurons in the brain. Thus, understanding the underlying mechanism of microglia activation can provide a therapeutic strategy for alleviating microglia-induced neuroinflammation. The aldose reductase (AR) enzyme catalyzes the reduction of glucose to sorbitol in the polyol pathway. In addition to mediating diabetic complications in hyperglycemic environments, AR also helps regulate inflammation in microglia. However, little is known about the role of AR in β-amyloid-induced inflammation in microglia and subsequent neuronal death. In this study, we confirmed that AR inhibition attenuates increased β-amyloid-induced reactive oxygen species and tumor necrosis factor α secretion by suppressing ERK signaling in BV₂ cells. In addition, we are the first to report that AR inhibition reduced the phagocytotic capability and cell migration of BV₂ cells in response to β-amyloid. To further investigate the protective role of the AR inhibitor sorbinil in neurons, we co-cultured β-amyloid-induced microglia with stem cell-induced neurons. sorbinil ameliorated neuronal damage in both cells in the co-culture system. In summary, our findings reveal AR regulation of microglia activation as a novel therapeutic target for Alzheimer's disease.

Understanding the Intricate Role of Exosomes in Pathogenesis of Alzheimer's Disease

Alzheimer's disease causes loss of memory and deterioration of mental abilities is utmost predominant neurodegenerative disease accounting 70-80% cases of dementia. The appearance of plaques of amyloid-β and neurofibrillary tangles in the brain post-mortems of Alzheimer's patients established them as key participants in the etiology of Alzheimer's disease. Exosomes exist as extracellular vesicles of nano-size which are present throughout the body. Exosomes are known to spread toxic hyperphosphorylated tau and amyloid-β between the cells and are linked to the loss of neurons by inducing apoptosis. Exosomes have progressed from cell trashcans to multifunctional organelles which are involved in various functions like internalisation and transmission of macromolecules such as lipids, proteins, and nucleic acids. This review covers current findings on relationship of exosomes in biogenesis and angiogenesis of Alzheimer's disease and functions of exosomes in the etiology of AD. Furthermore, the roles of exosomes in development, diagnosis, treatment, and its importance as therapeutic targets and biomarkers for Alzheimer's disease have also been highlighted.

Combined Effects of Cadmium- and Cyanide-Contaminated Diet on Oxidative Stress Biomarkers in Different Tissues of Rats

Background. Several toxicants present simultaneously in the environment have combined toxicological effects. In addition, various xenobiotics have distinct effects on oxidative stress biomarkers in animal cells and tissues. The aim of this study was to analyze the effect of cadmium (Cd) and cyanide (CN) through the food chain on some antioxidant indices in the tissues (lungs, testes, heart, and brain) of male Wistar rats. Materials and Methods. The study included sixty African catfish allocated to four groups, each comprising fifteen fish, treated with potassium cyanide (KCN) and cadmium chloride (CdCl2), held at a temperature of 25°C in a 100-litre fish tank aquarium with water contaminated with 0.4 mg of both cyanide and cadmium/100 ml of water. All the fish were later killed, dried, and used to prepare diet for experimental animals. Twenty male rats divided into four groups, each comprising five rats, were used for this study as well, and fed for 28 days as follows: Group A - control diet; Group B - cyanide-contaminated diet; Group C - cadmium-contaminated diet; Group D - diet contaminated with cyanide + cadmium. Subsequently, they were sacrificed. Biochemical analysis of the tissues excised from the rats was done. Results. There was a significant (p < 0.05) increase in lipid peroxidation level and a significant decrease in superoxide dismutase, catalase and reduced glutathione activities in the lungs, testes, heart, and brain of rats fed a catfish diet containing both cyanide and cadmium as compared to controls. In addition, contaminated diet altered acetylcholinesterase activity in the brain, glutathione peroxidase activity, glutathione-S-transferase activity, and glutathione reductase activity in the tissues of experimental rats. Conclusions. Cadmium and cyanide, via the food chain, induce oxidative stress in the lungs, testes, heart, and brain of rats.

Study on the Potential Mechanism of Semen Strychni against Myasthenia Gravis Based on Network Pharmacology and Molecular Docking with Experimental Verification

Background

Semen Strychni (SS) is an effective Chinese medicine formula for treating myasthenia gravis (MG) in clinics. Nonetheless, its molecular mechanism is largely unknown.

Objective

Using network pharmacology, molecular docking, and experimental validation, we aim to identify the therapeutic effect of SS on MG and its underlying mechanism.

Methods

The main ingredients of SS and their targets and potential disease targets for MG were extracted from public databases. The protein-protein interaction (PPI) network was constructed using the STRING 11.0 database, and Cytoscape was used to identify the hub targets. In addition, Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to identify molecular biological processes and signaling pathways. Then, AutoDock Via conducted molecular docking. The experimental autoimmune myasthenia gravis (EAMG) model in female Lewis rats, quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and enzyme-linked immunosorbent assay (ELISA) were performed to confirm the effect and mechanism of SS on MG.

Results

The following active compounds and hub targets were identified by screening and analyzing: isobrucine, vomicine, (S)-stylopine, strychnine, brucine-N-oxide, brucine and AKT1, MAPK1, MAPK14, CHRM1, ACHE, and CHRNA4. KEGG enrichment analyses indicated that the cholinergic synapse and neuroactive ligand-receptor interaction signaling pathway may be necessary. The results of molecular docking revealed that the main active ingredients bind well to the hub targets. In vivo experiments proved that SS could improve the weight loss and Lennon scores in the EAMG model. Experiments in molecular biology showed that SS could treat MG by affecting the cholinergic synapse through the respective antibody, receptor, and key enzymes in the cholinergic pathway.

Conclusion

This study provided a preliminary overview of the active constituents, primary targets, and potential pathways of SS against MG. SS ameliorated EAMG by regulating the cholinergic synaptic junction.

Design, Synthesis, and Biological Evaluation of Notopterol Derivatives as Triple Inhibitors of AChE/BACE1/GSK3β for the Treatment of Alzheimer's Disease

The pathogenesis of Alzheimer's disease (AD) is very complex, and there are many hypotheses. Therefore, the development of a multi-target-directed-ligand may be an effective therapeutic strategy. Our previous study showed that notopterol (a natural product from Notopterygium) is a dual BACE1/GSK3β inhibitor. In this study, we designed and synthesized 48 notopterol derivatives with furacoumarin as a scaffold in order to enhance their balanced AChE/BACE1/GSK3β inhibitory activity. Fortunately, 1c showed effective inhibitory activity against AChE (58.7% at 1.0 μM), BACE1 (48.3% at 20 μM), and GSK3β (40.3% at 10 μM). Furthermore, 1c showed good blood-brain barrier penetrability, suitable bioavailability, and oral safety. More importantly, 1c could ameliorate the impaired learning and memory in Aβ-induced AD mice. In conclusion, we reported the triple inhibitor of AChE/BACE1/GSK3β lead compounds based on a furocoumarin scaffold of notopterol for the first time, which provides a potential new strategy for the treatment of AD.

Imidazopyridazine Acetylcholinesterase Inhibitors Display Potent Anti-Proliferative Effects in the Human Neuroblastoma Cell-Line, IMR-32

Imidazo[1,2-b]pyridazine compounds are a new class of promising lead molecules to which we have incorporated polar nitro and amino moieties to increase the scope of their biological activity. Two of these substituted 3-nitro-6-amino-imidazo[1,2-b]pyridazine compounds (5c and 5h) showed potent acetylcholinesterase (AChE) inhibitory activity (IC₅₀ 40–50 nM), which we have previously reported. In this study, we wanted to test the biological efficacy of these compounds. Cytotoxicity assays showed that compound 5h mediated greater cell death with over 43% of cells dead at 100 μM and activation of caspase 3-mediated apoptosis. On the other hand, compound 5c mediated a dose-dependent decrease in cell proliferation. Both compounds showed cell cycle arrest in the G₀/G₁ phase and reduced cellular ATP levels leading to activation of adenosine monophosphate-activated protein kinase (AMPK) and enhanced mitochondrial oxidative stress. It has to be noted that all these effects were observed at doses beyond 10 μM, 200-fold above the IC₅₀ for AChE inhibition. Both compounds also inhibited bacterial lipopolysaccharide-mediated cyclooxygenase-2 and nitric oxide release in primary rat microglial cells. These results suggested that the substituted imidazo (1,2-b) pyridazine compounds, which have potent AChE inhibitory activity, were also capable of antiproliferative, anti-migratory, and anti-inflammatory effects at higher doses.

Acetylcholinesterase Inhibitors in the Treatment of Neurodegenerative Diseases and the Role of Acetylcholinesterase in their Pathogenesis

Acetylcholinesterase (AChE) plays an important role in the pathogenesis of neurodegenerative diseases by influencing the inflammatory response, apoptosis, oxidative stress and aggregation of pathological proteins. There is a search for new compounds that can prevent the occurrence of neurodegenerative diseases and slow down their course. The aim of this review is to present the role of AChE in the pathomechanism of neurodegenerative diseases. In addition, this review aims to reveal the benefits of using AChE inhibitors to treat these diseases. The selected new AChE inhibitors were also assessed in terms of their potential use in the described disease entities. Designing and searching for new drugs targeting AChE may in the future allow the discovery of therapies that will be effective in the treatment of neurodegenerative diseases.

Medial septum tau accumulation induces spatial memory deficit via disrupting medial septum-hippocampus cholinergic pathway

Tau accumulation and cholinergic impairment are characteristic pathologies in Alzheimer's disease (AD). However, the causal role of tau accumulation in cholinergic lesion is elusive. Here, we observed an aberrant tau accumulation in the medial septum (MS) of 3xTg and 5xFAD mice, especially in their cholinergic neurons. Overexpressing hTau in mouse MS (MShTau ) for 6 months but not 3 months induced spatial memory impairment without changing object recognition and anxiety-like behavior, indicating a specific and time-dependent effect of MS-hTau accumulation on spatial cognitive functions. With increasing hTau accumulation, the MShTau mice showed a time-dependent cholinergic neuron loss with reduced cholinergic projections to the hippocampus. Intraperitoneal administration of donepezil, a cholinesterase inhibitor, for 1 month ameliorated the MS-hTau-induced spatial memory deficits with preservation of MS-hippocampal cholinergic pathway and removal of tau load; and the beneficial effects of donepezil was more prominent at low dose. Proteomics revealed that MS-hTau accumulation deregulated multiple signaling pathways with numerous differentially expressed proteins (DEPs). Among them, the vacuolar protein sorting-associated protein 37D (VP37D), an autophagy-related protein, was significantly reduced in MShTau mice; the reduction of VP37D was restored by donepezil, and the effect was more significant at low dose than high dose. These novel evidences reveal a causal role of tau accumulation in linking MS cholinergic lesion to hippocampus-dependent spatial cognitive damages as seen in the AD patients, and the new tau-removal and autophagy-promoting effects of donepezil may extend its application beyond simple symptom amelioration to potential disease modification.

Epigallocatechin-3-Gallate Provides Protection Against Alzheimer's Disease-Induced Learning and Memory Impairments in Rats

Purpose

Recent evidence has highlighted the anti-inflammatory properties of the constituent of Green Tea Polyphenols (GTP), epigallocatechin-3-gallate (EGCG) which has been suggested to exert a neuroprotective effect on Alzheimer’s disease (AD). The current study aimed to elucidate the effect of EGCG on memory function in rats with AD.

Methods

AD rat models were initially established through an injection with Aβ 25–35 solution, followed by gavage with EGCG at varying doses to determine the effect of EGCG on learning and cognitive deficits in AD. Morris water maze test was conducted to evaluate the spatial memory function of the rats. Immunohistochemistry and Western blot analysis were performed to identify Tau phosphorylation. The expression of β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) mRNA and protein in rat hippocampus was measured by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis. Acetylcholinesterase (AchE) activity, Aβ1-42 expression and Ach content were all detected using enzyme-linked immunosorbent assay (ELISA).

Results

EGCG intervention brought about a decrease in the escape latency period while increasing the time at the target quadrant among the AD rats. EGCG decreased the hyperphosphorylation of Tau in hippocampus. BACE1 expression and activity as well as the expression of Aβ1-42 were suppressed by EGCG. Moreover, EGCG promoted Ach content by diminishing the activity of AchE.

Conclusion

The current study demonstrates that EGCG may diminish the hyperphosphorylation of the Tau protein, downregulate BACE1 and Aβ1-42 expression to improve the antioxidant system and learning and memory function of rats with AD.

Tau phosphorylation by glycogen synthase kinase 3β modulates enzyme acetylcholinesterase expression

In Alzheimer's disease (AD), the enzyme acetylcholinesterase (AChE) co‐localizes with hyperphosphorylated tau (P‐tau) within neurofibrillary tangles. Having demonstrated that AChE expression is increased in the transgenic mouse model of tau Tg‐VLW, here we examined whether modulating phosphorylated tau levels by over‐expressing wild‐type human tau and glycogen synthase kinase‐3β (GSK3β) influences AChE expression. In SH‐SY5Y neuroblastoma cells expressing higher levels of P‐tau, AChE activity and protein increased by (20% ± 2%) and (440% ± 150%), respectively. Western blots and qPCR assays showed that this increment mostly corresponded to the cholinergic ACHE‐T variant, for which the protein and transcript levels increased ~60% and ~23%, respectively. Moreover, in SH‐SY5Y cells differentiated into neurons by exposure to retinoic acid (10 µM), over‐expression of GSK3β and tau provokes an imbalance in cholinergic activity with a decrease in the neurotransmitter acetylcholine in the cell (45 ± 10%). Finally, we obtained cerebrospinal fluid (CSF) from AD patients enrolled on a clinical trial of tideglusib, an irreversible GSK3β inhibitor. In CSF of patients that received a placebo, there was an increase in AChE activity (35 ± 16%) respect to basal levels, probably because of their treatment with AChE inhibitors. However, this increase was not observed in tideglusib‐treated patients. Moreover, CSF levels of P‐tau at the beginning measured by commercially ELISA kits correlated with AChE activity. In conclusion, this study shows that P‐tau can modulate AChE expression and it suggests that AChE may possibly increase in the initial phases of AD.