A label-free dually-amplified aptamer sensor for the specific detection of amyloid-beta peptide oligomers in cerebrospinal fluids.

Amyloid-beta peptide oligomer (Aßo) is widely acknowledged to be associated with Alzheimer's disease (AD). The immediate and accurate detection of Aßo may provide the index for tracking the progress of the state of the disease, as well as some useful information for investigating the pathology of AD. In this work, based on a triple helix DNA which triggers a series of circular amplified reactions in the presence of Aßo, we designed a simple and label-free colorimetric biosensor with dually-amplified signal for the specific detection of Aßo. The sensor displays some advantages including high specificity, high sensitivity, low detection limit down to 0.23 pM, and wide detection range with three orders of magnitude from 0.3472 to 694.44 pM. Furthermore, the proposed sensor was successfully applied for detecting Aßo in artificial and real cerebrospinal fluids with satisfactory results, suggesting the potential application of the proposed sensor for state-monitoring and pathological studies of AD.

Preventing the amyloid-beta peptides accumulation on the cell membrane by applying GHz electric fields: A molecular dynamic simulation.

Alzheimer's disease is associated with accumulating different amyloid peptides on the nerve cell membranes. The non-thermal effects of the GHz electric fields in this topic have yet to be well recognized. Hence, in this study, the impacts of 1 and 5 GHz electric fields on the amyloid peptide proteins accumulation on the cell membrane have been investigated, utilizing molecular dynamics (MD) simulation. The obtained results indicated that this range of electric fields did not significantly affect the peptide structure. Moreover, it was found that the peptide penetration into the membrane was increased as the field frequency was increased when the system was exposed to a 20 mv/nm oscillating electric field. In addition, it was observed that the protein-membrane interaction is reduced significantly in the presence of the 70 mv/nm electric field. The molecular level results reported in this study could be helpful in better understanding Alzheimer's disease.

Investigation of Cyclo-Z Therapeutic Effect on Insulin Pathway in Alzheimer's Rat Model: Biochemical and Electrophysiological Parameters.

Cyclo (his-pro-CHP) plus zinc (Zn+2) (Cyclo-Z) is the only known chemical that increases the production of insulin-degrading enzyme (IDE) and decreases the number of inactive insulin fragments in cells. The aim of the present study was to systematically characterize the effects of Cyclo-Z on the insulin pathway, memory functions, and brain oscillations in the Alzheimer's disease (AD) rat model. The rat model of AD was established by bilateral injection of Aß42 oligomer (2,5nmol/10µl) into the lateral ventricles. Cyclo-Z (10mg Zn+2/kg and 0.2mg CHP/kg) gavage treatment started seven days after Aß injection and lasted for 21 days. At the end of the experimental period, memory tests and electrophysiological recordings were performed, which were followed by the biochemical analysis. Aß42 oligomers led to a significant increase in fasting blood glucose, serum insulin, Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and phospho-tau-Ser356 levels. Moreover, Aß42 oligomers caused a significant decrement in body weight, hippocampal insulin, brain insulin receptor substrate (IRS-Ser612), and glycogen synthase kinase-3 beta (GSK-3ß) levels. Also, Aß42 oligomers resulted in a significant reduction in memory. The Cyclo-Z treatment prevented the observed alterations in the ADZ group except for phospho-tau levels and attenuated the increased Aß42 oligomer levels in the ADZ group. We also found that the Aß42 oligomer decreased the left temporal spindle and delta power during ketamine anesthesia. Cyclo-Z treatment reversed the Aß42 oligomer-related alterations in the left temporal spindle power. Cyclo-Z prevents Aß oligomer-induced changes in the insulin pathway and amyloid toxicity, and may contribute to the improvement of memory deficits and neural network dynamics in this rat model.

A near-infrared probe for detecting and interposing amyloid beta oligomerization in early Alzheimer's disease.

BACKGROUND: The misfolding and deposition of amyloid beta (Aß) in human brain is the main hallmark of Alzheimer's disease (AD) pathology. One of the drivers of Alzheimer´s pathogenesis is the production of soluble oligomeric Aß, which could potentially serve as a biomarker of AD. METHODS: Given that the diphenylalanine (FF) at the C-terminus of Aß fragments plays a key role in inducing the AD pathology, based on the hydrophobic structure of FF, we synthesized a near-infrared BF2-dipyrrolmethane fluorescent imaging probe (NB) to detect both soluble and insoluble Aß. RESULTS: We found that NB not only binds Aß, particularly oligomeric Aß, but also interposes self-assembly of Aß through π-π interaction between NB and FF. CONCLUSION: This work holds great promise in the early detection of AD and may also provide an innovative approach to decelerate and even halt AD onset and progression.

Plasma amyloid-beta oligomer is related to subjective cognitive decline and brain amyloid status.

BACKGROUND: Subjective cognitive decline (SCD) is a target for Alzheimer's disease prediction. Plasma amyloid-beta oligomer (AßO), the pathogenic form of Aß in blood, has recently been proposed as a novel blood-based biomarker of AD prediction by representing brain Aß deposition. The relationship between plasma AßO, brain Aß deposition, and SCD in individuals with normal objective cognition has not been investigated. METHODS: In this cross-sectional study, we analyzed 126 participants with normal objective cognition. More SCD symptoms were expressed as higher scores of the Subjective Cognitive Decline Questionnaire (SCDQ) and Memory Age-associated Complaint Questionnaire (MACQ). The plasma AßO level of each participant was measured twice for validation and expressed as a concentration (ng/mL) and a ratio relative to the mean value of two internal standards. Brain Aß deposition was assessed by [18F] flutemetamol positron emission tomography (PET) and expressed as standard uptake value ratio (SUVR). Associations of SCDQ and MACQ with plasma AßO levels or SUVR were analyzed in multiple linear regression models. The association between plasma AßO level and flutemetamol PET positivity was assessed in logistic regression and receiver operative characteristic analyses. RESULTS: Overall, participants were 73.3 years old with female predominance (69.0%). After adjustment for confounders, high SCDQ and MACQ scores were associated with the high plasma AßO levels as both concentrations and ratios (ratios: standardized coefficient = 0.246 and p = 0.023 for SCDQ, standardized coefficient = 0.209 and p = 0.029 for MACQ; concentrations: standardized coefficient = 0.257 and p = 0.015 for SCDQ, standardized coefficient = 0.217 and p = 0.021 for MACQ). In contrast, SCDQ and MACQ were not significantly associated with SUVRs (p = 0.134 for SCDQ, p = 0.079 for MACQ). High plasma AßO levels were associated with flutemetamol PET (+) with an area under the curve of 0.694 (ratio) or 0.662 (concentration). Combined with APOE e4, plasma AßO presented area under the curves of 0.789 (ratio) and 0.783 (concentration). CONCLUSIONS: Our findings indicate that the high plasma AßO level could serve as a potential surrogate biomarker of severe SCD and the presence of brain Aß deposition in individuals with normal objective cognition.

Aß oligomer concentration in mouse and human brain and its drug-induced reduction ex vivo.

The elimination of amyloid beta (Aß) oligomers is a promising strategy for therapeutic drug development of Alzheimer's disease (AD). AD mouse models that develop Aß pathology have been used to demonstrate in vivo efficacy of compounds that later failed in clinical development. Here, we analyze the concentration and size distribution of Aß oligomers in different transgenic mouse models of AD and in human brain samples by surface-based fluorescence intensity distribution analysis (sFIDA), a highly sensitive method for detecting and quantitating protein aggregates. We demonstrate dose- and time-dependent oligomer elimination by the compound RD2 in mouse and human AD brain homogenates as sources of native Aß oligomers. Such ex vivo target engagement analyses with mouse- and human-brain-derived oligomers have the potential to enhance the translational value from pre-clinical proof-of-concept studies to clinical trials.

ACU193: An Immunotherapeutic Poised to Test the Amyloid ß Oligomer Hypothesis of Alzheimer's Disease.

Alzheimer's disease (AD) is an age-related neurodegenerative disease that affects 50 million people worldwide, with 10 million new cases occurring each year. The emotional and economic impacts of AD on patients and families are devastating. Approved treatments confer modest improvement in symptoms, and recently one treatment obtained accelerated approval from the United States Food and Drug Administration (FDA) and may have modest disease modifying benefit. Research over the past three decades has established a clear causal linkage between AD and elevated brain levels of amyloid ß (Aß) peptide, and substantial evidence now implicates soluble, non-fibrillar Aß oligomers (AßOs) as the molecular assemblies directly responsible for AD-associated memory and cognitive failure and accompanying progressive neurodegeneration. The widely recognized linkage of elevated Aß and AD spawned a comprehensive 20-year therapeutic campaign that focused primarily on two strategies - inhibition of the secretase enzymes responsible for Aß production and clearance of Aß peptide or amyloid plaques with Aß-directed immunotherapeutics. Unfortunately, all clinical trials of secretase inhibitors were unsuccessful. Of the completed phase 3 immunotherapy programs, bapineuzumab (targeting amyloid plaque) and solanezumab (targeting Aß monomers) were negative, and the crenezumab program (targeting Aß monomers and to a small extent oligomers) was stopped for futility. Aducanumab (targeting amyloid plaques), which recently received FDA accelerated approval, had one positive and one negative phase 3 trial. More than 25 negative randomized clinical trials (RCTs) have evaluated Aß-targeting therapeutics, yet none has directly evaluated whether selective blockage of disease-relevant AßOs can stop or reverse AD-associated cognitive decline. Here, we briefly summarize studies that establish the AD therapeutic rationale to target AßOs selectively, and we describe ACU193, the first AßO-selective immunotherapeutic to enter human clinical trials and the first positioned to test the AßO hypothesis of AD.

MicroRNA modulation is a potential molecular mechanism for neuroprotective effects of intranasal insulin administration in amyloid ßeta oligomer induced Alzheimer's like rat model.

Substantial evidence indicates that imbalance in the expression of miR-132-3p, miR-181b-5p, miR-125b-5p, miR-26a-5p, miR-124-3p, miR-146a-5p, miR-29a-3p, and miR-30a-5p in the AD brain are associated with amyloid-beta (Aß) aggregation, tau pathology, neuroinflammation, and synaptic dysfunction, the major pathological hallmarks of Alzheimer's disease)AD(. Several studies have reported that intranasal insulin administration ameliorates memory in AD patients and animal models. However, the underlying molecular mechanisms are not yet completely elucidated. Therefore, the aim of this study was to determine whether insulin is involved in regulating the expression of AD-related microRNAs. Pursuing this objective, we first investigated the therapeutic effect of intranasal insulin on Aß oligomer (AßO)-induced memory impairment in male rats using the Morris water maze task. Then, molecular and histological changes in response to AßO and/or insulin time course were assessed in the extracted hippocampi on days 1, 14, and 21 of the study using congo red staining, western blot and quantitative real-time PCR analyses. We observed memory impairment, Aß aggregation, tau hyper-phosphorylation, neuroinflammation, insulin signaling dys-regulation, and down-regulation of miR-26a, miR-124, miR-29a, miR-181b, miR-125b, miR-132, and miR-146a in the hippocampus of AßO-exposed rats 21 days after AßO injection. Intranasal insulin treatment ameliorated memory impairment and concomitantly increased miR-132, miR-181b, and miR-125b expression, attenuated tau phosphorylation levels, Aß aggregation, and neuroinflammation, and regulated the insulin signaling as well. In conclusion, our study suggest that the neuroprotective effects of insulin on memory observed in AD-like rats could be partially due to the restoration of miR-132, miR-181b, and miR-125b expression in the brain.

Intrathecal amyloid-beta oligomer administration increases tau phosphorylation in the medial temporal lobe in the African green monkey: A nonhuman primate model of Alzheimer's disease.

AIMS: An obstacle to developing new treatment strategies for Alzheimer's disease (AD) has been the inadequate translation of findings in current AD transgenic rodent models to the prediction of clinical outcomes. By contrast, nonhuman primates (NHPs) share a close neurobiology with humans in virtually all aspects relevant to developing a translational AD model. The present investigation used African green monkeys (AGMs) to refine an inducible NHP model of AD based on the administration of amyloid-beta oligomers (AßOs), a key upstream initiator of AD pathology. METHODS: AßOs or vehicle were repeatedly delivered over 4 weeks to age-matched young adult AGMs by intracerebroventricular (ICV) or intrathecal (IT) injections. Induction of AD-like pathology was assessed in subregions of the medial temporal lobe (MTL) by quantitative immunohistochemistry (IHC) using the AT8 antibody to detect hyperphosphorylated tau. Hippocampal volume was measured by magnetic resonance imaging (MRI) scans prior to, and after, intrathecal injections. RESULTS: IT administration of AßOs in young adult AGMs revealed an elevation of tau phosphorylation in the MTL cortical memory circuit compared with controls. The largest increases were detected in the entorhinal cortex that persisted for at least 12 weeks after dosing. MRI scans showed a reduction in hippocampal volume following AßO injections. CONCLUSIONS: Repeated IT delivery of AßOs in young adult AGMs led to an accelerated AD-like neuropathology in MTL, similar to human AD, supporting the value of this translational model to de-risk the clinical trial of diagnostic and therapeutic strategies.

Amyloid-beta oligomers induce Parkin-mediated mitophagy by reducing Miro1.

Alzheimer's disease (AD) is a neurodegenerative disease associated with the accumulation of amyloid-beta oligomers (AßO). Recent studies have demonstrated that mitochondria-specific autophagy (mitophagy) contributes to mitochondrial quality control by selectively eliminating the dysfunctional mitochondria. Mitochondria motility, which is regulated by Miro1, is also associated with neuronal cell functions. However, the role played by Miro1 in the mitophagy mechanism, especially relative to AßO and neurodegenerative disorders, remains unknown. In this study, AßO induced mitochondrial dysfunction, enhanced Parkin-mediated mitophagy, and reduced mitochondrial quantities in hippocampal neuronal cells (HT-22 cells). We demonstrated that AßO-induced mitochondrial fragmentation could be rescued to the elongated mitochondrial form and that mitophagy could be mitigated by the stable overexpression of Miro1 or by pretreatment with N-acetylcysteine (NAC)-a reactive oxygen species (ROS) scavenger-as assessed by immunocytochemistry. Moreover, using time-lapse imaging, under live cell-conditions, we verified that mitochondrial motility was rescued by the Miro1 overexpression. Finally, in hippocampus from amyloid precursor protein (APP)/presenilin 1 (PS1)/Tau triple-transgenic mice, we noted that the co-localization between mitochondria and LC3B puncta was increased. Taken together, these results indicated that up-regulated ROS, induced by AßO, increased the degree of mitophagy and decreased the Miro1 expression levels. In contrast, the Miro1 overexpression ameliorated AßO-mediated mitophagy and increased the mitochondrial motility. In AD model mice, AßO induced mitophagy in the hippocampus. Thus, our results would improve our understanding of the role of mitophagy in AD toward facilitating the development of novel therapeutic agents for the treatment of AßO-mediated diseases.

Nanomechanical insights: Amyloid beta oligomer-induced senescent brain endothelial cells.

Senescent cells accumulate in various peripheral tissues during aging and have been shown to exacerbate age-related inflammatory responses. We recently showed that exposure to neurotoxic amyloid ß (Aß1-42) oligomers can readily induce a senescence phenotype in human brain microvascular endothelial cells (HBMECs). In the present work, we used atomic force microscopy (AFM) to further characterize the morphological properties such as cell membrane roughness and cell height and nanomechanical properties such as Young's modulus of the membrane (membrane stiffness) and adhesion resulting from the interaction between AFM tip and cell membrane in Aß1-42 oligomer-induced senescent human brain microvascular endothelial cells. Morphological imaging studies showed a flatter and spread-out nucleus in the senescent HBMECs, both characteristic features of a senescent phenotype. Furthermore, the mean cell body roughness and mean cell height were lower in senescent HBMECs compared to untreated normal HBMECs. We also observed increased stiffness and alterations in the adhesion properties in Aß1-42 oligomer-induced senescent endothelial cells compared to the untreated normal HBMECs suggesting dynamic reorganization of cell membrane. We then show that vascular endothelial growth factor receptor 1 (VEGFR-1) knockdown or overexpression of Rho GTPase Rac 1 in the endothelial cells inhibited senescence and reversed these nanomechanical alterations, confirming a direct role of these pathways in the senescent brain endothelial cells. These results illustrate that nanoindentation and topographic analysis of live senescent brain endothelial cells can provide insights into cerebrovascular dysfunction in neurodegenerative diseases such as Alzheimer's disease.

Peroxiredoxin 4 ameliorates amyloid beta oligomer-mediated apoptosis by inhibiting ER-stress in HT-22 hippocampal neuron cells.

Alzheimer's disease (AD) is a neurodegenerative disorder caused by amyloid beta oligomers (AßO), which induce cell death by triggering oxidative stress and endoplasmic reticulum (ER) stress. Oxidative stress is regulated by antioxidant enzymes, including peroxiredoxins. Peroxiredoxins (Prx) are classified into six subtypes, based on their localization and cysteine residues, and protect cells by scavenging hydrogen peroxide (H2O2). Peroxiredoxin 4 (Prx4) is unique in being localized to the ER; however, whether Prx4 protects neuronal cells from AßO-induced toxicity remains unclear, although Prx4 expression is upregulated in AßO-induced oxidative stress and ER stress. In this study, we established HT-22 cells in which Prx4 was either overexpressed or silenced to investigate its role in AßO-induced toxicity. AßO-stimulation of HT-22 cells with overexpressed Prx4 caused decreases in both AßO-induced ROS and ER stress (followed by ER expansion). In contrast, AßO stimulation caused increases in both ROS and ER stress that were notably higher in HT-22 cells with silenced Prx4 expression than in HT-22 cells. Consequently, Prx4 overexpression decreased apoptotic cell death and ameliorated the AßO-induced increase in intracellular Ca2+. Therefore, we conclude that Prx4 has a protective effect against AßO-mediated oxidative stress, ER stress, and neuronal cell death. Furthermore, these results suggest that Prx4 may be a target for preventing AßO toxicity in AD. Graphical abstract .

Monitoring of early diagnosis of Alzheimer's disease using the cellular prion protein and poly(pyrrole-2-carboxylic acid) modified electrode.

Amyloid-beta oligomers (AßΟ) are considered to be reliable biomarkers for the diagnosis of Alzheimer' disease (AD), and the cellular prion protein (PrPC) is identified as a receptor for AßO. We demonstrated a label and antibody-free electrochemical biosensor for the selective detection of AßO using an electrically conductive poly(pyrrole-2-carboxylic acid) (PPyCOOH) linking agent and PrPC receptor. In the fabrication of the biosensor, each step was characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The developed PrPc/PPyCOOH biosensor exhibited extremely low detection limit of 10-4 pM with high sensitivity which is desirable for the early diagnosis of AD. The sensing performance was further confirmed by the mice infected with AD. The proposed sensor emerged as a promising tool for the early detection of AßO.

A hydrogel biosensor for high selective and sensitive detection of amyloid-beta oligomers.

BACKGROUND: Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive and memory impairment. It is the most common neurological disease that causes dementia. Soluble amyloid-beta oligomers (AßO) in blood or cerebrospinal fluid (CSF) are the pathogenic biomarker correlated with AD. METHODS: A simple electrochemical biosensor using graphene oxide/gold nanoparticles (GNPs) hydrogel electrode was developed in this study. Thiolated cellular prion protein (PrPC) peptide probe was immobilized on GNPs of the hydrogel electrode to construct an AßO biosensor. Electrochemical impedance spectroscopy was utilized for AßO analysis. RESULTS: The specific binding between AßO and PrPC probes on the hydrogel electrode resulted in an increase in the electron-transfer resistance. The biosensor showed high specificity and sensitivity for AßO detection. It could selectively differentiate AßO from amyloid-beta (Aß) monomers or fibrils. Meanwhile, it was highly sensitive to detect as low as 0.1 pM AßO in artificial CSF or blood plasma. The linear range for AßO detection is from 0.1 pM to 10 nM. CONCLUSION: This biosensor could be used as a cost-effective tool for early diagnosis of AD due to its high electrochemical performance and bionic structure.

EGCG inhibits the oligomerization of amyloid beta (16-22) hexamer: Theoretical studies.

An extensive replica exchange molecular dynamics (REMD) simulation was performed to investigate the progress patterns of the inhibition of (-)-epigallocatechin-3-gallate (EGCG) on the Aß16-22 hexamer. Structural variations of the oligomers without and with EGCG were monitored and analyzed in detail. It has been found that EGCG prevents the formation of Aß oligomer through two different ways by either accelerating the Aß oligomerization or reducing the ß-content of the hexamer. It also decreases the potential "highly toxic" conformations of Aß oligomer, which is related to the conformations having high order ß-sheet sizes. Both electrostatic and van der Waals interaction energies are found to be involved to the binding process. Computed results using quantum chemical methods show that the π-π stacking is a critical factor of the interaction between EGCG and the peptides. As a result, the binding free energy of the EGCG to the Aß peptides is slightly larger than that of the curcumin.

White Ginseng Protects Mouse Hippocampal Cells Against Amyloid-Beta Oligomer Toxicity.

Amyloid-beta oligomer (AßO) is a soluble oligomer form of the Aß peptide and the most potent amyloid-beta form that induces neuronal damage in Alzheimer's disease. We investigated the effect of dried white ginseng extract (WGE) on neuronal cell damage and memory impairment in intrahippocampal AßO (10 µM)-injected mice. Mice were treated with WGE (100 and 500 mg/kg/day, p.o.) for 12 days after surgery. WGE improved memory impairment by inhibiting hippocampal cell death caused by AßO. In addition, AßO-injected mice treated with WGE showed restoration of reduced synaptophysin and choline acetyltransferase intensity and lower levels of ionized calcium-binding adaptor molecule 1 in the hippocampus compared with those of vehicle-treated controls. These results suggest that WGE reverses memory impairment in Alzheimer's disease by attenuating neuronal damage and neuroinflammation in the AßO-injected mouse hippocampus. Copyright © 2017 John Wiley & Sons, Ltd.

Spinosin, a C-Glucosylflavone, from Zizyphus jujuba var. spinosa Ameliorates Abeta1-42 Oligomer-Induced Memory Impairment in Mice

Alzheimer's disease (AD) is a neurodegenerative disorder associated with progressive memory loss and neuronal cell death. Although numerous previous studies have been focused on disease progression or reverse pathological symptoms, therapeutic strategies for AD are limited. Alternatively, the identification of traditional herbal medicines or their active compounds has received much attention. The aims of the present study were to characterize the ameliorating effects of spinosin, a C-glucosylflavone isolated from Zizyphus jujuba var. spinosa, on memory impairment or the pathological changes induced through amyloid-beta1-42 oligomer (AbetaO) in mice. Memory impairment was induced by intracerebroventricular injection of AbetaO (50 muM) and spinosin (5, 10, and 20 mg/kg) was administered for 7 days. In the behavioral tasks, the subchronic administration of spinosin (20 mg/kg, p.o.) significantly ameliorated AbetaO-induced cognitive impairment in the passive avoidance task or the Y-maze task. To identify the effects of spinosin on the pathological changes induced through AbetaO, immunohistochemistry and Western blot analyses were performed. Spinosin treatment also reduced the number of activated microglia and astrocytes observed after AbetaO injection. In addition, spinosin rescued the AbetaO-induced decrease in choline acetyltransferase expression levels. These results suggest that spinosin ameliorated memory impairment induced through AbetaO, and these effects were regulated, in part, through neuroprotective activity via the anti-inflammatory effects of spinosin. Therefore, spinosin might be a useful agent against the amyloid b protein-induced cognitive dysfunction observed in AD patients.

6-Shogaol, an active constituent of ginger, attenuates neuroinflammation and cognitive deficits in animal models of dementia.

Recently, increased attention has been directed towards medicinal extracts as potential new drug candidates for dementia. Ginger has long been used as an important ingredient in cooking and traditional herbal medicine. In particular, ginger has been known to have disease-modifying effects in Alzheimer's disease (AD). However, there is no evidence of which constituents of ginger exhibit therapeutic effects against AD. A growing number of experimental studies suggest that 6-shogaol, a bioactive component of ginger, may play an important role as a memory-enhancing and anti-oxidant agent against neurological diseases. 6-Shogaol has also recently been shown to have anti-neuroinflammatory effects in lipopolysaccharide (LPS)-treated astrocytes and animal models of Parkinson's disease, LPS-induced inflammation and transient global ischemia. However, it is still unknown whether 6-shogaol has anti-inflammatory effects against oligomeric forms of the Aß (AßO) in animal brains. Furthermore, the effects of 6-shogaol against memory impairment in dementia models are also yet to be investigated. In this study, we found that administration of 6-shogaol significantly reduced microgliosis and astrogliosis in intrahippocampal AßO-injected mice, ameliorated AßO and scopolamine-induced memory impairment, and elevated NGF levels and pre- and post-synaptic marker in the hippocampus. All these results suggest that 6-shogaol may play a role in inhibiting glial cell activation and reducing memory impairment in animal models of dementia.

Donepezil inhibits the amyloid-beta oligomer-induced microglial activation in vitro and in vivo.

Recent studies on Alzheimer's disease (AD) have focused on soluble oligomeric forms of amyloid-beta (Aß oligomer, AßO) that are directly associated with AD-related pathologies, such as cognitive decline, neurodegeneration, and neuroinflammation. Donepezil is a well-known anti-dementia agent that increases acetylcholine levels through inhibition of acetylcholinesterase. However, a growing body of experimental and clinical studies indicates that donepezil may also provide neuroprotective and disease-modifying effects in AD. Additionally, donepezil has recently been demonstrated to have anti-inflammatory effects against lipopolysaccharides and tau pathology. However, it remains unknown whether donepezil has anti-inflammatory effects against AßO in cultured microglial cells and the brain in animals. Further, the effects of donepezil against AßO-mediated neuronal death, astrogliosis, and memory impairment have also not yet been investigated. Thus, in the present study, we examined the anti-inflammatory effect of donepezil against AßO and its neuroinflammatory mechanisms. Donepezil significantly attenuated the release of inflammatory mediators (prostaglandin E2, interleukin-1 beta, tumor necrosis factor-α, and nitric oxide) from microglia. Donepezil also decreased AßO-induced up-regulation of inducible nitric oxide synthase and cyclooxygenase-2 protein and phosphorylation of p38 mitogen-activated protein kinase as well as translocation of nuclear factor-kappa B. We next showed that donepezil suppresses activated microglia-mediated toxicity in primary hippocampal cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. In intrahippocampal AßO-injected mice, donepezil significantly inhibited microgliosis and astrogliosis. Furthermore, behavioral tests revealed that donepezil (2 mg/kg/day, 5 days, p.o.) significantly ameliorated AßO-induced memory impairment. These results suggest that donepezil directly inhibits microglial activation induced by AßO through blocking MAPK and NF-κB signaling and, in part, contributing to the amelioration of neurodegeneration and memory impairment.