Neuroprotective therapeutics for Alzheimer's disease: progress and prospects

Functional near-infrared spectroscopy and vagus somatosensory evoked potentials add to the power of established parameters such as poor cognitive performance, dsyosmia and APOe genotype to predict cognitive decline over 8 years in the elderly

Alzheimer's dementia is the main cause of cognitive impairment in people over the age of 65, with Alzheimer's disease starting presumably 10-15 years before the onset of clinical symptoms. It is therefore important to recognize dementia at an early stage and identify possible predictors. The existing methods, like different parameters of ß-Amyloid and Tau quantification in cerebrospinal fluid (CSF) or the living brain by measure of PET, are invasive and expensive. Therefore, the present study investigates the predictive value of a battery of clinical, neuropsychological, and blood parameters as well as two neurophysiological methods (functional near-infrared spectroscopy [fNIRS] and vagus somatosensory evoked potentials [VSEP]) which are easy to perform, less invasive and cost-efficient, for developing cognitive impairments in the elderly.In this longitudinal, prospective study, we enrolled 604 healthy participants between 70 and 77 years of age. The participants were invited back after a mean time interval of 3 years and 11 months, and after 7 years and 8 months, and their cognitive impairments were determined.Here we show that the development of cognitive impairments after approximately 8 years can be predicted not only by previously known risk factors such as ApoE4 risk alleles, dysosmia, or poor cognitive performance at baseline but that latency prolongation in the VSEP and altered functional activation patterns measured by NIRS at baseline also provide additional predictive value.We therefore suggest that both neurophysiological parameters, VSEP and NIRS, should be included in future studies, investigating the prediction of dementia. Dementia ClinicalTrials.gov Identifier: NCT02224326.

Preliminary study on early diagnosis of Alzheimer's disease in APP/PS1 transgenic mice using multimodal magnetic resonance imaging

Alzheimer's disease (AD) has an insidious onset and lacks clear early diagnostic markers, and by the time overt dementia symptoms appear, the disease is already in the mid-to-late stages. The search for early diagnostic markers of AD may open a critical window for Alzheimer's treatment and facilitate early intervention to slow the progression of AD. In this study, we aimed to explore the imaging markers for early diagnosis of AD through the combined application of structural magnetic resonance imaging (sMRI), resting-state functional magnetic resonance imaging (rs-fMRI), and 1H-magnetic resonance spectroscopy (1H-MRS) multimodal magnetic resonance imaging (MRI) techniques at the animal experimental level, with the aim to provide a certain reference for early clinical diagnosis of AD. First, sMRI scans were performed on 4-month-old amyloid beta precursor protein/presenilin 1 (APP/PS1) transgenic AD model mice and wild type mice of the same litter using a 7.0 T animal MRI scanner to analyze the differential brain regions with structural changes in the gray matter of the brain by voxel-based morphometry (VBM). Next, rs-fMRI scans were performed to analyze the differential brain regions between groups for local spontaneous brain activity and functional connectivity (FC) between brain regions. Finally, 1H-MRS scans were performed to quantify and analyze intergroup differences in the relative concentrations of different metabolites within regions of interest (cortex and hippocampus). Compared with wild type mice, the volume of the left hippocampus, and right olfactory bulb of APP/PS1 transgenic AD model mice were reduced, the functional activity of the bilateral hippocampus, right piriform cortex and right caudate putamen was reduced, the functional network connectivity of the hippocampus was impaired, and the relative content of N-acetylaspartate (NAA)in the hippocampus was decreased. In addition, this study found that imaging changes in olfactory-related brain regions were closely associated with AD diagnosis, and these findings may provide some reference for the early diagnosis of AD.

[Ginkgolide B: mechanisms of neurobiological effects, prospects for use in the therapy of Alzheimer's disease]

The review presents an analysis of experimental data on the study of neurobiological effects of ginkgolide B, which may find application in the therapy of Alzheimer's disease (AD). Ginkgolide B is a diterpene trilactone isolated from the leaves of the relict woody plant Ginkgo biloba L., which has been used for thousands of years in traditional Chinese medicine as a neuroprotective agent. In recent years, this compound has attracted attention because of its wide range of neurobiological effects. The neuroprotective effect of ginkgolide B on brain neurons when exposed to various neurotoxins has been established. This compound has also been shown to effectively protect neurons from the effects of beta-amyloid. Studies have revealed the ability of ginkgolide B to reduce microglia activity and regulate neurotransmitter release. In vivo experiments have shown that this substance significantly increases the expression of brain-derived neurotrophic factor (BDNF) and improves cognitive functions, including memory and learning. It is concluded that ginkgolide B, apparently, may find application in the future as a multi-targeted agent of complex therapy of AD.

Application of the Mannich reaction in the structural modification of natural products

The Mannich reaction is commonly used to introduce N atoms into compound molecules and is thus widely applied in drug synthesis. The Mannich reaction accounts for a certain proportion of structural modifications of natural products. The introduction of Mannich bases can significantly improve the activity, hydrophilicity, and medicinal properties of compounds; therefore, the Mannich reaction is widely used for the structural modification of natural products. In this paper, the application of the Mannich reaction to the structural modification of natural products is reviewed, providing a method for the structural modification of natural products.

Unveiling the neuroprotective potential of dietary polysaccharides: a systematic review

Central nervous system (CNS) disorders present a growing and costly global health challenge, accounting for over 11% of the diseases burden in high-income countries. Despite current treatments, patients often experience persistent symptoms that significantly affect their quality of life. Dietary polysaccharides have garnered attention for their potential as interventions for CNS disorders due to their diverse mechanisms of action, including antioxidant, anti-inflammatory, and neuroprotective effects. Through an analysis of research articles published between January 5, 2013 and August 30, 2023, encompassing the intervention effects of dietary polysaccharides on Alzheimer's disease, Parkinson's disease, depression, anxiety disorders, autism spectrum disorder, epilepsy, and stroke, we have conducted a comprehensive review with the aim of elucidating the role and mechanisms of dietary polysaccharides in various CNS diseases, spanning neurodegenerative, psychiatric, neurodevelopmental disorders, and neurological dysfunctions. At least four categories of mechanistic bases are included in the dietary polysaccharides' intervention against CNS disease, which involves oxidative stress reduction, neuronal production, metabolic regulation, and gut barrier integrity. Notably, the ability of dietary polysaccharides to resist oxidation and modulate gut microbiota not only helps to curb the development of these diseases at an early stage, but also holds promise for the development of novel therapeutic agents for CNS diseases. In conclusion, this comprehensive review strives to advance therapeutic strategies for CNS disorders by elucidating the potential of dietary polysaccharides and advocating interdisciplinary collaboration to propel further research in this realm.

Implication of the cooking oil-peroxidation product "hydroxynonenal" for Alzheimer's disease

Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme that reduces cell injuries via detoxification of lipid-peroxidation product, 4-hydroxy-2-nonenal (hydroxynonenal). It is generated exogenously via deep-frying of linoleic acid-rich cooking oils and/or endogenously via oxidation of fatty acids involved in biomembranes. Although its toxicity for human health is widely accepted, the underlying mechanism long remained unknown. In 1998, Yamashima et al. have formulated the "calpain-cathepsin hypothesis" as a molecular mechanism of ischemic neuronal death. Subsequently, they found that calpain cleaves Hsp70.1 which became vulnerable after the hydroxynonenal-induced carbonylation at the key site Arg469. Since it is the pivotal aberration that induces lysosomal membrane rupture, they suggested that neuronal death in Alzheimer's disease similarly occurs by chronic ischemia via the calpain-cathepsin cascade triggered by hydroxynonenal. For nearly three decades, amyloid β (Aβ) peptide was thought to be a root substance of Alzheimer's disease. However, because of both the insignificant correlations between Aβ depositions and occurrence of neuronal death or dementia, and the negative results of anti-Aβ medicines tested so far in the patients with Alzheimer's disease, the strength of the "amyloid cascade hypothesis" has been weakened. Recent works have suggested that hydroxynonenal is a mediator of programmed cell death not only in the brain, but also in the liver, pancreas, heart, etc. Increment of hydroxynonenal was considered an early event in the development of Alzheimer's disease. This review aims at suggesting ways out of the tunnel, focusing on the implication of hydroxynonenal in this disease. Herein, the mechanism of Alzheimer neuronal death is discussed by focusing on Hsp70.1 with a dual function as chaperone protein and lysosomal stabilizer. We suggest that Aβ is not a culprit of Alzheimer's disease, but merely a byproduct of autophagy/lysosomal failure resulting from hydroxynonenal-induced Hsp70.1 disorder. Enhancing ALDH2 activity to detoxify hydroxynonenal emerges as a promising strategy for preventing and treating Alzheimer's disease.

Evaluation of In Vitro and In Silico Anti-Alzheimer Potential of Nonpolar Extracts and Essential Oil from Mentha piperita

The anticholinesterase and antioxidant activities with chemical composition and molecular docking of essential oil and nonpolar extracts of Mentha piperita were evaluated using enzymatic and chemical methods. Molecular docking tools were used to explain the interaction of the major chemical constituents with the enzymes. GC/MS analyses revealed that the main compounds in M. piperita essential oil were l-menthone (43.601%) followed by pulegone (21.610%), linolenic acid (25.628%), and l-menthone (10.957%), representing the major compounds of the petroleum ether extract. Imidazoquinoline (7.767%) and 17-N-acetyl-oroidine (5.363%) were the major constituents of the chloroform extract. Linolenic acid (19.397%) and l-menthone (6.336%) were the most abundant compounds in the hexane extract. The M. piperita essential oil and nonpolar extracts showed moderate antioxidant activity. The essential oil showed the most promising anticholinesterase activity with IC₅₀ = 10.66 ± 0.12 µg/mL and IC₅₀ = 16.33 ± 0.03 µg/mL against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), respectively, close to galantamine in AChE and more active in BChE, followed by the interesting activity in the petroleum ether extract with IC₅₀ = 23.42 ± 3.06 µg/mL in AChE and IC₅₀ = 62.00 ± 3.22 µg/mL in BChE. The docking experiments showed that among the seven major identified compounds, N-acetyl-17-oroidine showed the highest binding score (63.01 in AChE and 63.68 in BChE). This compound was found to bind the catalytic and peripheral sites, resulting in more potent inhibitory activity than galantamine, which only binds to the catalytic site. These findings suggested the possible use of M. piperita essential oil and nonpolar extracts as a potential source of alternative natural anti-Alzheimer compounds.

Antioxidant and Neuroprotective Effects of Paeonol against Oxidative Stress and Altered Carrier-Mediated Transport System on NSC-34 Cell Lines

Paeonol is a naturally occurring phenolic agent that attenuates neurotoxicity in neurodegenerative diseases. We aimed to investigate the antioxidant and protective effects of paeonol and determine its transport mechanism in wild-type (WT; NSC-34/hSOD1^WT) and mutant-type (MT; NSC-34/hSOD1^G93A) motor neuron-like amyotrophic lateral sclerosis (ALS) cell lines. Cytotoxicity induced by glutamate, lipopolysaccharides, and H₂O₂ reduced viability of cell; however, the addition of paeonol improved cell viability against neurotoxicity. The [³H]paeonol uptake was increased in the presence of H₂O₂ in both cell lines. Paeonol recovered ALS model cell lines by reducing mitochondrial oxidative stress induced by glutamate. The transport of paeonol was time-, concentration-, and pH-dependent in both NSC-34 cell lines. Kinetic parameters showed two transport sites with altered affinity and capacity in the MT cell line compared to the WT cell line. [³H]Paeonol uptake increased in the MT cell line transfected with organic anion transporter1 (Oat1)/Slc22a6 small interfering RNA compared to that in the control. Plasma membrane monoamine transporter (Pmat) was also involved in the uptake of paeonol by ALS model cell lines. Overall, paeonol exhibits neuroprotective activity via a carrier-mediated transport system and may be a beneficial therapy for preventing motor neuronal damage under ALS-like conditions.

4-(4-(((1H-Benzo[d][1,2,3]triazol-1-yl)oxy)methyl)-1H-1,2,3-triazol-1-yl)-7-chloroquinoline

The 1,2,3-triazole ring system can be easily obtained by widely used copper-catalyzed click reaction of azides with alkynes. 1,2,3-triazole exhibits myriad of biological activities, including antibacterial antimalarial, and antiviral activities. We herein reported the synthesis of quinoline-based [1,2,3]-triazole hybrid derivative via Cu(I)-catalyzed click reaction of 4-azido-7-chloroquinoline with alkyne derivative of hydroxybenzotriazole (HOBt). The compound was fully characterized by proton nuclear magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR), correlated spectroscopy (1H-1H-COSY), heteronuclear single quantum coherence (HSQC) and distortionless enhancement by polarization transfer (DEPT-135 and DEPT-90) NMR, ultraviolet (UV) and Fourier-transform infrared (FTIR) spectroscopies, and high-resolution mass spectrometry (HRMS). Computational studies were enrolled to predict the interaction of the synthesized compound with acetylcholinesterase, a target of primary relevance for developing new therapeutic options to counteract neurodegeneration. Moreover, the drug-likeness of the compound was also investigated by predicting its pharmacokinetic properties.

Inhibitory potential of nitrogen, oxygen and sulfur containing heterocyclic scaffolds against acetylcholinesterase and butyrylcholinesterase

Heterocycles are the key structures in organic chemistry owing to their immense applications in the biological, chemical, and pharmaceutical fields. Heterocyclic compounds perform various noteworthy functions in nature, medication, innovation etc. Most frequently, pure nitrogen heterocycles or various positional combinations of nitrogen, oxygen, and sulfur atoms in five or six-membered rings can be found. Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes is a popular strategy for the management of numerous mental diseases. In this context, cholinesterase inhibitors are utilized to relieve the symptoms of neurological illnesses like dementia and Alzheimer's disease (AD). The present review focuses on various heterocyclic scaffolds and their role in designing and developing new potential AChE and BChE inhibitors to treat AD. Moreover, a detailed structure-activity relationship (SAR) has been established for the future discovery of novel drugs for the treatment of AD. Most of the heterocyclic motifs have been used in the design of new potent cholinesterase inhibitors. In this regard, this review is an endeavor to summarize the biological and chemical studies over the past decade (2010-2022) describing the pursuit of new N, O and S containing heterocycles which can offer a rich supply of promising AChE and BChE inhibitory activities.

Alzheimer's Disease: Key Insights from Two Decades of Clinical Trial Failures

Given the acknowledged lack of success in Alzheimer’s disease (AD) drug development over the past two decades, the objective of this review was to derive key insights from the myriad failures to inform future drug development. A systematic and exhaustive review was performed on all failed AD compounds for dementia (interventional phase II and III clinical trials from ClinicalTrials.gov) from 2004 to the present. Starting with the initial ∼2,700 AD clinical trials, ∼550 trials met our initial criteria, from which 98 unique phase II and III compounds with various mechanisms of action met our criteria of a failed compound. The two recent reported phase III successes of aducanumab and oligomannate are very encouraging; however, we are awaiting real-world validation of their effectiveness. These two successes against the 98 failures gives a 2.0% phase II and III success rate since 2003, when the previous novel compound was approved. Potential contributing methodological factors for the clinical trial failures were categorized into 1) insufficient evidence to initiate the pivotal trials, and 2) pivotal trial design shortcomings. Our evaluation found that rational drug development principles were not always followed for AD therapeutics development, and the question remains whether some of the failed compounds may have shown efficacy if the principles were better adhered to. Several recommendations are made for future AD therapeutic development. The whole database of the 98 failed compounds is presented in the Supplementary Material.

Addressing Blood–Brain Barrier Impairment in Alzheimer’s Disease

The blood–brain barrier (BBB) plays a vital role in maintaining the specialized microenvironment of the brain tissue. It facilitates communication while separating the peripheral circulation system from the brain parenchyma. However, normal aging and neurodegenerative diseases can alter and damage the physiological properties of the BBB. In this review, we first briefly present the essential pathways maintaining and regulating BBB integrity, and further review the mechanisms of BBB breakdown associated with normal aging and peripheral inflammation-causing neurodegeneration and cognitive impairments. We also discuss how BBB disruption can cause or contribute to Alzheimer’s disease (AD), the most common form of dementia and a devastating neurological disorder. Next, we document overlaps between AD and vascular dementia (VaD) and briefly sum up the techniques for identifying biomarkers linked to BBB deterioration. Finally, we conclude that BBB breakdown could be used as a biomarker to help diagnose cognitive impairment associated with normal aging and neurodegenerative diseases such as AD.

Role of Clathrin and Dynamin in Clathrin Mediated Endocytosis/Synaptic Vesicle Recycling and Implications in Neurological Diseases

Endocytosis is a process essential to the health and well-being of cell. It is required for the internalisation and sorting of “cargo”—the macromolecules, proteins, receptors and lipids of cell signalling. Clathrin mediated endocytosis (CME) is one of the key processes required for cellular well-being and signalling pathway activation. CME is key role to the recycling of synaptic vesicles [synaptic vesicle recycling (SVR)] in the brain, it is pivotal to signalling across synapses enabling intracellular communication in the sensory and nervous systems. In this review we provide an overview of the general process of CME with a particular focus on two key proteins: clathrin and dynamin that have a central role to play in ensuing successful completion of CME. We examine these two proteins as they are the two endocytotic proteins for which small molecule inhibitors, often of known mechanism of action, have been identified. Inhibition of CME offers the potential to develop therapeutic interventions into conditions involving defects in CME. This review will discuss the roles and the current scope of inhibitors of clathrin and dynamin, providing an insight into how further developments could affect neurological disease treatments.

Inhibition of the formation of lysozyme fibrillar assemblies by the isoquinoline alkaloid coralyne

The isoquinoline alkaloid coralyne can efficiently attenuate fibrillogenesis in lysozyme.

Synthesis and biological evaluation of selective histone deacetylase 6 inhibitors as multifunctional agents against Alzheimer's disease

Histone deacetylase 6 (HDAC6) is a potential target for Alzheimer's disease (AD). In this study, a series of novel phenothiazine-, memantine-, and 1,2,3,4-tetrahydro-γ-carboline-based HDAC6 inhibitors with a variety of linker moieties were designed and synthesized. As a hydrochloride salt, the phenothiazine-based hydroxamic acid W5 with a pyridyl-containing linker motif was identified as a high potent and selective HDAC6 inhibitor. It inhibited HDAC6 with an IC₅₀ of 2.54 nM and was more than 290- to 3300-fold selective over other HDAC isoforms. In SH-SY5Y cells, W5 dose-dependently increased the acetylated α-tubulin levels and reduced the hyperphosphorylated tau proteins at Ser396. As an effective metal chelator, W5 inhibited Cu²⁺-induced Aβ_1-42 aggregation and disaggregated Cu²⁺-Aβ_1-42 oligomers, and showed protective effects on the SH-SY5Y cells against Aβ_1-42- as well as Cu²⁺-Aβ_1-42 induced cell damages, serving as a potential ligand to target AD metal dyshomeostasis. Moreover, W5 promoted the differentiated neuronal neurite outgrowth, increased the mRNA expression of the recognized neurogenesis markers, GAP43, N-myc, and MAP-2. Therefore, W5 might be a good lead for the development of novel HDAC6 inhibitors targeting multi-facets of AD.

Neuroprotective Potential of Mung Bean (Vigna radiata L.) Polyphenols in Alzheimer's Disease: A Review

Mung bean contains various neuroprotective polyphenols, so it might be a healthy food for Alzheimer's disease (AD) prevention. Totally, 19 major phenolic compounds were quantified in mung bean, including 10 phenolic acids and 9 flavonoids. After summarizing their contents and effective doses in rodent AD models, it was speculated that vitexin, isovitexin, sinapic acid, and ferulic acid might be the major bioactive compounds for mung bean-mediated neuroprotection. The mechanisms involved inhibition of β-amyloidogenesis, tau hyperphosphorylation, oxidative stress, and neuroinflammation, and promotion of autophagy and acetylcholinesterase enzyme activity. Notably, the neuroprotective phenolic profile in mung bean changed after germination, with decreased vitexin and isovitexin, and increased rutin, isoquercitrin, isorhamnetin, and caffeic acid detected. However, only studies of individual phenolic compounds in mung bean are published at present. Hence, further studies are needed to elucidate the neuroprotective activities and mechanisms of extractions of mung bean seeds and sprouts, and the synergism between different phenolic compounds.

Changes in the Morphology, Number, and Pathological Protein Levels of Plasma Exosomes May Help Diagnose Alzheimer's Disease

Exosomes are nano-sized extracellular vesicles that are secreted by cells and usually found in body fluids. Since they freely cross the blood-brain barrier, neuronal exosomes respond directly to changes in the brain's environment. Recent studies have shown that exosomes contain both amyloid-β (Aβ) and tau proteins and have a controversial role in the Alzheimer's disease (AD) process. In this study, enzyme-linked immunosorbent assay was used to detect the levels of P-S396-tau and Aβ1-42 in plasma exosomes. We found that levels of P-S396-tau and Aβ1-42 in plasma exosomes of AD patients were significantly higher compared to those in matched healthy controls. The difference between plasma exosomes of AD patients and those of matched healthy controls was determined using transmission electron microscopy and nanoparticle tracking analysis. Exosomes from AD patients were smaller and lower in quantity. These data together may provide a basis for early diagnosis of AD.

Design, synthesis, and biological evaluation of diosgenin-indole derivatives as dual-functional agents for the treatment of Alzheimer's disease

The complex pathogenesis of Alzheimer's disease (AD) has become a major obstacle in its treatment. An effective approach is to develop multifunctional agents that simultaneously target multiple pathological processes. Here, a series of diosgenin-indole compounds were designed, synthesized and evaluated for their neuroprotective effects against H₂O₂ (hydrogen peroxide), 6-OHDA (6-hydroxydopamine) and Aβ (beta amyloid) damages. Preliminary structure-activities relationship revealed that the introduction of indole fragment and electron-donating group at C-5 on ring indole could be beneficial for neuroprotective activities. Results indicated that compound 5b was the most promising candidate against cellular damage induced by H₂O₂ (52.9 ± 1.9%), 6-OHDA (38.4 ± 2.4%) and Aβ_1-42 (54.4 ± 2.7%). Molecular docking study suggested the affinity for 5b bound to Aβ_1-42 was -40.59 kcal/mol, which revealed the strong binding affinity of 5b to Aβ_1-42. The predicted values of brain/blood partition coefficient (-0.733) and polar surface area (85.118 Å²) indicated the favorable abilities of BBB permeation and absorption of 5b. In addition, 5b significantly decreased ROS (reactive oxygen species) production induced by H₂O₂. In the following in vivo experiment, 5b obviously attenuated memory and learning impairments of Aβ-injected mice. In summary, compound 5b could be considered as a promising dual-functional neuroprotective agent against AD.

Paeonol Derivatives and Pharmacological Activities: A Review of Recent Progress

Paeonol, 2-hydroxy-4-methoxy acetophenone, is one of the main active ingredients of traditional Chinese medicine such as Cynanchum paniculatum, Paeonia suffruticosa Andr and Paeonia lactiflora Pall. Modern medical research has shown that paeonol has a wide range of pharmacological activities. In recent years, a large number of studies have been carried out on the structure modification of paeonol and the mechanism of action of paeonol derivatives has been studied. Some paeonol derivatives exhibit good pharmacological activities in terms of antibacterial, anti-inflammatory, antipyretic analgesic, antioxidant and other pharmacological effects. Herein, the research progress on paeonol derivatives and their pharmacological activities were systematically reviewed.

LMDS-1, a potential TrkB receptor agonist provides a safe and neurotrophic effect for early-phase Alzheimer's disease

RATIONALE

The signaling pathways of tropomyosin-related kinase B (TrkB) receptor play a pivotal role in axonal sprouting, proliferation of dendritic arbor, synaptic plasticity, and neuronal differentiation. The levels of BDNF and TrkB receptor were reduced in patients with Alzheimer's disease (AD).

OBJECTIVES

The activation of TrkB signaling pathways is a potential strategy for AD therapies. We intended to identify potential TrkB agonists to activate the neuroprotective signaling to alleviate the pathological features of AD mice.

RESULTS

Both of the Aβ-deteriorated hippocampal primary neurons and mouse models were generated and showed AD characteristics. We first investigated 12 potential TrkB agonists with primary hippocampal neurons of mice. Both 7,8-DHF and LMDS-1 were identified to have better effect than the other compounds on dendritic arborization of the neurons and were further applied to the Aβ-injected mouse model. The short-term cognitive behavior and pathology in the mice were improved by LMDS-1. Further investigation indicated that LMDS-1 activated the TrkB through phosphorylation at Y516 rather than Y816. In addition, the ERK but not CaMKII or Akt was activated in the mouse hippocampus with LMDS-1 administration. LMDS-1 treatment also upregulated CREB and BDNF while downregulated the GSK3β active form and tau phosphorylation.

CONCLUSIONS

This study suggests that LMDS-1 upregulates the expression of BDNF and ameliorates the early-phase phenotypes of the AD-like mice through the pTrkB (Y516)-ERK-CREB pathway. In addition, LMDS-1 has better effect than 7,8-DHF in ameliorating the behavioral and pathological features of AD-like mice.

Gelatin grafted poly(D,L-lactide) as an inhibitor of protein aggregation: An in vitro case study

Amyloids are a group of proteins that are capable of forming aggregated amyloid fibrils, which is responsible for many neurodegenerative diseases including Alzheimer's disease (AD). In our previous study, synthesis and characterization of star-shaped poly(D,L-lactide)-b-gelatin (ss-pLG) have been reported. In the present work, we have extended our work to study ss-pLG against protein aggregation. To the best of our knowledge, this is the first report on the inhibition of amyloid fibrillation by protein grafted poly(D,L-lactide). Bovine serum albumin (BSA) was chosen as the model protein, which readily forms fibril under high temperature. We found that ss-pLG efficiently suppressed the fibril formation of BSA compared with gelatin (Gel), which was supported by Thioflavin T assay, circular dichroism (CD) spectroscopy and atomic force microscopy (AFM). In addition, ss-pLG significantly curtailed amyloid-induced hemolysis. We also found that incubation of ss-pLG with neuroblastoma cells (MC65) protected the cells from fibril-induced toxicity. The rescuing efficiency of ss-pLG was better than Gel, which could be attributed to the reduced lamella thickness in branched ss-pLG. These results suggest the significance of gelatin grafting, which probably allows gelatin to interact with the key residues of the amyloidogenic core of BSA effectively.

Molecular insights into the inhibitory mechanisms of gallate moiety on the Aβ1-40 amyloid aggregation: A molecular dynamics simulation study

Alzheimer's disease is the most common form of neurodegenerative disease and the formation of Aβ amyloid aggregates has been widely demonstrated to be the principal cause of Alzheimer's disease. Our previous study and other studies suggested that the gallate moiety played an obligatory role in the inhibition process of naturally occurring polyphenols on Aβ amyloid fibrils formation. However, the detailed mechanisms were still unknown. Thus, in the present study, the gallic acid (GA) was specially selected and the molecular recognition mechanisms between GA molecules and Aβ_1-40 monomer were examined and analyzed by molecular dynamics simulation. The in silico experiments revealed that GA significantly prevented the conformational changes of Aβ_1-40 monomer with no β-sheet structure during the whole 100 ns. By analyzing the binding sites of GA molecules to Aβ_1-40 monomer, we found that both hydrophilic and hydrophobic amino acid residues were participated in the binding of GA molecules to Aβ_1-40 monomer. Moreover, results from the binding free energy analysis further demonstrated that the strength of polar interactions was significantly stronger than that of nonpolar interactions. We believed that our results could help to elucidate the underlying mechanisms of gallate moiety on the anti-amyloidogenic effects of polyphenols at the atomic level.

Modeling and Targeting Alzheimer's Disease With Organoids

Human neurodegenerative diseases, such as Alzheimer’s disease (AD), are not easily modeled in vitro due to the inaccessibility of brain tissue and the level of complexity required by existing cell culture systems. Three-dimensional (3D) brain organoid systems generated from human pluripotent stem cells (hPSCs) have demonstrated considerable potential in recapitulating key features of AD pathophysiology, such as amyloid plaque- and neurofibrillary tangle-like structures. A number of AD brain organoid models have also been used as platforms to assess the efficacy of pharmacological agents in disease progression. However, despite the fact that stem cell-derived brain organoids mimic early aspects of brain development, they fail to model complex cell-cell interactions pertaining to different regions of the human brain and aspects of natural processes such as cell differentiation and aging. Here, we review current advances and limitations accompanying several hPSC-derived organoid methodologies, as well as recent attempts to utilize them as therapeutic platforms. We additionally discuss comparative benefits and disadvantages of the various hPSC-derived organoid generation protocols and differentiation strategies. Lastly, we provide a comparison of hPSC-derived organoids to primary tissue-derived organoids, examining the future potential and advantages of both systems in modeling neurodegenerative disorders, especially AD.

A Unique GSK-3β inhibitor B10 Has a Direct Effect on Aβ, Targets Tau and Metal Dyshomeostasis, and Promotes Neuronal Neurite Outgrowth

Due to the complicated pathogenesis of Alzheimer's disease (AD), the development of multitargeted agents to simultaneously interfere with multiple pathological processes of AD is a potential choice. Glycogen synthase kinase-3β (GSK-3β) plays a vital role in the AD pathological process. In this study, we discovered a novel 1H-pyrrolo[2,3-b]pyridine derivative B10 as a GSK-3β inhibitor that features with a quinolin-8-ol moiety to target the metal dyshomeostasis of AD. B10 potently inhibited GSK-3β with an IC₅₀ of 66 ± 2.5 nM. At the concentration of 20 μM, B10 increased β-catenin abundance (β-catenin/GAPDH: 0.83 ± 0.086 vs. 0.30 ± 0.016), phosphorylated GSK-3β at Ser9 (p-GSK-3β/GAPDH: 0.53 ± 0.045 vs. 0.35 ± 0.012), and decreased the phosphorylated tau level (p-tau/GAPDH: 0.33 ± 0.065 vs. 0.83 ± 0.061) in SH-SY5Y cells. Unlike other GSK-3β inhibitors, B10 had a direct effect on Aβ by inhibiting Aβ_1-42 aggregation and promoting the Aβ_1-42 aggregate disassociation. It selectively chelated with Cu²⁺, Zn²⁺, Fe^3+, and Al³⁺, and targeted AD metal dyshomeostasis. Moreover, B10 effectively increased the mRNA expression of the recognized neurogenesis markers, GAP43, N-myc, and MAP-2, and promoted the differentiated neuronal neurite outgrowth, possibly through the GSK-3β and β-catenin signal pathways. Therefore, B10 is a potent and unique GSK-3β inhibitor that has a direct on Aβ and serves as a multifunctional anti-AD agent for further investigations.

Multi-modal latent space inducing ensemble SVM classifier for early dementia diagnosis with neuroimaging data

Fusing multi-modality data is crucial for accurate identification of brain disorder as different modalities can provide complementary perspectives of complex neurodegenerative disease. However, there are at least four common issues associated with the existing fusion methods. First, many existing fusion methods simply concatenate features from each modality without considering the correlations among different modalities. Second, most existing methods often make prediction based on a single classifier, which might not be able to address the heterogeneity of the Alzheimer's disease (AD) progression. Third, many existing methods often employ feature selection (or reduction) and classifier training in two independent steps, without considering the fact that the two pipelined steps are highly related to each other. Forth, there are missing neuroimaging data for some of the participants (e.g., missing PET data), due to the participants' "no-show" or dropout. In this paper, to address the above issues, we propose an early AD diagnosis framework via novel multi-modality latent space inducing ensemble SVM classifier. Specifically, we first project the neuroimaging data from different modalities into a latent space, and then map the learned latent representations into the label space to learn multiple diversified classifiers. Finally, we obtain the more reliable classification results by using an ensemble strategy. More importantly, we present a Complete Multi-modality Latent Space (CMLS) learning model for complete multi-modality data and also an Incomplete Multi-modality Latent Space (IMLS) learning model for incomplete multi-modality data. Extensive experiments using the Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset have demonstrated that our proposed models outperform other state-of-the-art methods.

Aiding the discovery of new treatments for dementia by uncovering unknown benefits of existing medications

Introduction

There is a significant need for disease-modifying therapies to treat and prevent dementia, including Alzheimer's disease. Availability of real-world observational information and new analytic techniques to analyze large volumes of data can provide a path to aid drug discovery.

Methods

Using a self-controlled study design, we examined the association between 2181 medications and incidence of dementia across four US insurance claims databases. Medications associated with ≥50% reduction in risk of dementia in ≥2 databases were examined.

Results

A total of 117,015,066 individuals were included in the analysis. Seventeen medications met our threshold criteria for a potential protective effect on dementia and fell into five classes: catecholamine modulators, anticonvulsants, antibiotics/antivirals, anticoagulants, and a miscellaneous group.

Discussion

The biological pathways of the medications identified in this analysis may be targets for further research and may aid in discovering novel therapeutic approaches to treat dementia. These data show association not causality.

Preventive approach for overcoming dementia

Dementia is used as a general term to describe chronic disorders of mental processes caused by the deterioration of cognitive functions to the extent that one's ability to perform daily activities is impaired. Currently, age is known to be the main risk factor for dementia, suggesting that the risk of being diagnosed with dementia significantly increases later in one's life. Therefore, there are two approaches one can take when confronting dementia: to cure it when it occurs in late adulthood or to prevent the onset of symptoms beforehand. Recently, the latter strategy of delaying and preventing Alzheimer's disease, the most prevalent form and most studied type of dementia, through both pharmaceutical and nonpharmaceutical interventions is becoming increasingly recognized. In this review, we discuss studies conducted in various fields that addresses nonpharmaceutical lifestyle interventions, including diet, physical activity, cognitive stimulation, and social engagement, and their effects in preventing and inhibiting dementia.

Lysozyme-luteolin binding: molecular insights into the complexation process and the inhibitory effects of luteolin towards protein modification

In the proposed work, the complexation of bioactive flavonoid luteolin with hen egg white lysozyme (HEWL) along with its inhibitory influence on HEWL modification has been explored with the help of multi-spectroscopic and computational methods. The binding affinity has been observed to be moderate in nature (in the order of 10⁴ M^-1) and the static quenching mechanism was found to be involved in the fluorescence quenching process. The binding constant (K_b) shows a progressive increase with the increase in temperature from (4.075 ± 0.046 × 10⁴ M^-1) at 293 K to (6.962 ± 0.024 × 10⁴ M^-1) at 313 K under experimental conditions. Spectroscopic measurements along with molecular docking calculations suggest that Trp62 is involved in the binding site of luteolin within the geometry of HEWL. The positive changes in enthalpy (ΔH = +19.99 ± 0.65 kJ mol^-1) as well as entropy (ΔS = +156.28 ± 2.00 J K^-1 mol^-1) are indicative of the presence of hydrophobic forces that stabilize the HEWL-luteolin complex. The micro-environment around the Trp residues showed an increase in hydrophobicity as indicated by synchronous fluorescence (SFS), three dimensional fluorescence (3D) and red edge excitation (REES) studies. The % α-helix of HEWL showed a marked reduction upon binding with luteolin as indicated by circular dichroism (CD) and Fourier-transform infrared spectroscopy (FTIR) studies. Moreover, luteolin is situated at a distance of 4.275 ± 0.004 nm from the binding site as indicated by FRET theory, and the rate of energy transfer k_ET (0.063 ± 0.004 ns^-1) has been observed to be faster than the donor decay rate (1/τ_D = 0.606 ns^-1), which is indicative of the non-radiative energy transfer during complexation. Leaving aside the binding study, luteolin showed promising inhibitory effects towards the d-ribose mediated glycation of HEWL as well as towards HEWL fibrillation as studied by fluorescence emission and imaging studies. Excellent correlation with the experimental observations as well as precise location and dynamics of luteolin within the binding site has been obtained from molecular docking and molecular dynamics simulation studies.

Involvement of a Novel Organic Cation Transporter in Paeonol Transport Across the Blood-Brain Barrier

Paeonol has neuroprotective function, which could be useful for improving central nervous system disorder. The purpose of this study was to characterize the functional mechanism involved in brain transport of paeonol through blood-brain barrier (BBB). Brain transport of paeonol was characterized by internal carotid artery perfusion (ICAP), carotid artery single injection technique (brain uptake index, BUI) and intravenous (IV) injection technique in vivo. The transport mechanism of paeonol was examined using conditionally immortalized rat brain capillary endothelial cell line (TR-BBB) as an in vitro model of BBB. Brain volume of distribution (V_D) of [³H]paeonol in rat brain was about 6-fold higher than that of [¹⁴C]sucrose, the vascular space marker of BBB. The uptake of [3H]paeonol was concentration-dependent. Brain volume of distribution of paeonol and BUI as in vivo and inhibition of analog as in vitro studies presented significant reduction effect in the presence of unlabeled lipophilic compounds such as paeonol, imperatorin, diphenhydramine, pyrilamine, tramadol and ALC during the uptake of [³H]paeonol. In addition, the uptake significantly decreased and increased at the acidic and alkaline pH in both extracellular and intracellular study, respectively. In the presence of metabolic inhibitor, the uptake reduced significantly but not affected by sodium free or membrane potential disruption. Similarly, paeonol uptake was not affected on OCTN2 or rPMAT siRNA transfection BBB cells. Interestingly. Paeonol is actively transported from the blood to brain across the BBB by a carrier mediated transporter system.

Protein Assemblies: Nature-Inspired and Designed Nanostructures

Ordered protein assemblies are attracting interest as next-generation biomaterials with a remarkable range of structural and functional properties, leading to potential applications in biocatalysis, materials templating, drug delivery and vaccine development. This Review covers ordered protein assemblies including protein nanowires/nanofibrils, nanorings, nanotubes, designed two- and three-dimensional ordered protein lattices and protein-like cages including polyhedral virus-like cage structures. The main focus is on designed ordered protein assemblies, in which the spatial organization of the proteins is controlled by tailored noncovalent interactions (including metal ion binding interactions, electrostatic interactions and ligand–receptor interactions among others) or by careful design of modified (mutant) proteins or de novo constructs. The modification of natural protein assemblies including bacterial S-layers and cage-like and rod-like viruses to impart novel function, e.g. enzymatic activity, is also considered. A diversity of structures have been created using distinct approaches, and this Review provides a summary of the state-of-the-art in the development of these systems, which have exceptional potential as advanced bionanomaterials for a diversity of applications.

The Use of Pluripotent Stem Cell-Derived Organoids to Study Extracellular Matrix Development during Neural Degeneration

The mechanism that causes the Alzheimer's disease (AD) pathologies, including amyloid plaque, neurofibrillary tangles, and neuron death, is not well understood due to the lack of robust study models for human brain. Three-dimensional organoid systems based on human pluripotent stem cells (hPSCs) have shown a promising potential to model neurodegenerative diseases, including AD. These systems, in combination with engineering tools, allow in vitro generation of brain-like tissues that recapitulate complex cell-cell and cell-extracellular matrix (ECM) interactions. Brain ECMs play important roles in neural differentiation, proliferation, neuronal network, and AD progression. In this contribution related to brain ECMs, recent advances in modeling AD pathology and progression based on hPSC-derived neural cells, tissues, and brain organoids were reviewed and summarized. In addition, the roles of ECMs in neural differentiation of hPSCs and the influences of heparan sulfate proteoglycans, chondroitin sulfate proteoglycans, and hyaluronic acid on the progression of neurodegeneration were discussed. The advantages that use stem cell-based organoids to study neural degeneration and to investigate the effects of ECM development on the disease progression were highlighted. The contents of this article are significant for understanding cell-matrix interactions in stem cell microenvironment for treating neural degeneration.

Protective effects of silibinin on insulin amyloid fibrillation, cytotoxicity and mitochondrial membrane damage

A growing body of evidence suggests that secretion and assembly of insulin to amyloid fibrils reduce its efficacy in treating type II diabetes and may lead to dysfunctioning of several organs. The research presented here explores the effects of silibinin on the in vitro amyloid fibrillation and cytotoxicity of bovine insulin fibrils on SH-SY5Y human neuroblastoma cells. Interaction of the resulting structures with rat brain mitochondria was also investigated. Using a range of methods for amyloid detection we showed that insulin fibrillation was significantly inhibited by silibinin in a dose-dependent fashion. Moreover, we found that silibinin was very effective in attenuating insulin fibril-induced neuronal toxicity characterized by decrease of cell viability, the release of lactate dehydrogenase, intracellular reactive oxygen species enhancement, morphological alterations, and apoptotic cell death induction. While insulin fibrillation products showed the capacity to damage mitochondria, the resultant structures produced in the presence of silibinin were totally ineffective. Together, results demonstrate the capacity of insulin fibrils to cause SH-SY5Y cell death by inducing necrosis/apoptosis changes and suggest how silibinin may afford protection. It is concluded that elucidation of such protection may provide important insights into the development of preventive and therapeutic agents for amyloid-related diseases.

A cascade synthesis, in vitro cholinesterases inhibitory activity and docking studies of novel Tacrine-pyranopyrazole derivatives

In this work, we describe the preparation of some new Tacrine analogues modified with a pyranopyrazole moiety. A one-pot multicomponent reaction of 3-methyl-1H-pyrazol-5(4H)-one, aryl(or hetero)aldehydes, malononitrile and cyclohexanone involving a Friedländer condensation led to the title compounds. The synthesized heterocyclic analogues of this molecule were evaluated in vitro for their AChE and BChE inhibitory activities in search for potent cholinesterase enzyme inhibitors. Most of the synthesized compounds displayed remarkable AChE inhibitory activities with IC₅₀ values ranging from 0.044 to 5.80 µM, wherein compounds 5e and 5j were found to be most active inhibitors against AChE with IC₅₀ values of 0.058 and 0.044 µM respectively. Molecular modeling simulation on AChE and BChE receptors, showed good correlation between IC₅₀ values and binding interaction template of the most active inhibitors docked into the active site of their relevant enzymes.

Solvation-Guided Design of Fluorescent Probes for Discrimination of Amyloids

The deposition of insoluble protein aggregates in the brain is a hallmark of many neurodegenerative diseases. While their exact role in neurodegeneration remains unclear, the presence of these amyloid deposits often precedes clinical symptoms. As a result, recent progress in imaging methods that utilize amyloid-specific small molecule probes have become a promising avenue for antemortem disease diagnosis. Here, we present a series of amino-aryl cyanoacrylate (AACA) fluorophores that show a turn-on fluorescence signal upon binding to amyloids in solution and in tissue. Using a theoretical model for environmental sensitivity of fluorescence together with ab initio computational modeling of the effects of polar environment on electron density distribution and conformational dynamics, we designed, synthesized, and evaluated a set of fluorophores that (1) bind to aggregated forms of Alzheimer’s-related β-amyloid peptides with low micromolar to high nanomolar affinities and (2) have the capability to fluorescently discriminate different amyloids based on differences in amino acid composition within the binding pocket through exploitation of their solvatochromic properties. These studies showcase the rational design of a family of amyloid-binding imaging agents that could be integrated with new optical approaches for the clinical diagnosis of amyloidoses, where accurate identification of the specific neurodegenerative disease could aid in the selection of a proper course for treatment.

Intracellular cAMP Sensor EPAC: Physiology, Pathophysiology, and Therapeutics Development

This review focuses on one family of the known cAMP receptors, the exchange proteins directly activated by cAMP (EPACs), also known as the cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFs). Although EPAC proteins are fairly new additions to the growing list of cAMP effectors, and relatively "young" in the cAMP discovery timeline, the significance of an EPAC presence in different cell systems is extraordinary. The study of EPACs has considerably expanded the diversity and adaptive nature of cAMP signaling associated with numerous physiological and pathophysiological responses. This review comprehensively covers EPAC protein functions at the molecular, cellular, physiological, and pathophysiological levels; and in turn, the applications of employing EPAC-based biosensors as detection tools for dissecting cAMP signaling and the implications for targeting EPAC proteins for therapeutic development are also discussed.

Regioselective synthesis of 7-O-esters of the flavonolignan silibinin and SARs lead to compounds with overadditive neuroprotective effects

A series of neuroprotective hybrid compounds was synthesized by conjugation of the flavonolignan silibinin with natural phenolic acids, such as ferulic, cinnamic and syringic acid. Selective 7-O-esterfication without protection groups was achieved by applying the respective acyl chlorides. Sixteen compounds were obtained and SARs were established by evaluating antioxidative properties in the physicochemical FRAP assay, as well as in a cell-based neuroprotection assay using murine hippocampal HT-22 cells. Despite weak activities in the FRAP assay, esters of the α,β-unsaturated acids showed pronounced overadditive effects at low concentrations greatly exceeding the effects of equimolar mixtures of silibinin and the respective acids in the neuroprotection assay. Cinnamic and ferulic acid esters (5a and 6a) also showed overadditive effects regarding inhibition of microglial activation, PC12 cell differentiation, in vitro ischemia as well as anti-aggregating abilities against Aβ42 peptide and τ protein. Remarkably, the esters of ferulic acid with silybin A and silybin B (11a and 11b) showed a moderate but significant difference in both neuroprotection and in their anti-aggregating capacities. The results demonstrate that non-toxic natural antioxidants can be regioselectively connected as esters with medium-term stability exhibiting very pronounced overadditive effects in a portfolio of biological assays.