Event In Alzheimer's Disease Research Articles

Does retinoic acid reverse cell cycle dysregulation in Alzheimer's disease lymphocytes?

Aberrant re-entry of neurons into cell cycle appears to be an early event in Alzheimer's disease (AD) and targeting this dysregulation may have therapeutic potential. We have examined whether cell cycle dysregulation in AD can be detected using patient and control derived B-lymphocytes. Cell cycle analysis using flow cytometry demonstrated that cell cycle dysregulation occurs in AD lymphocytes, with a significant difference in the distribution of cells in G0/G1, S and G2/M phases of cell cycle as compared to control lymphocytes. Using global gene expression analysis by RNA sequencing and cell cycle analysis, we examined the role of Retinoic Acid (RA), a candidate molecule predicted to be of therapeutic potential in cell cycle dysregulation associated with AD. CCND1, CCNE2, E2F transcription factors which are known to be dysregulated in AD were among the 32 genes that showed differential expression in response to RA treatment thus suggesting a protective role of RA. However, the cell cycle analysis demonstrated that RA did not reverse the cellular phenotype in AD lymphocytes. This suggests that though RA might have a protective role by influencing the expression of cell cycle genes, it might not be able to arrest abnormal re-entry into cell cycle.

Noninvasive 40-Hz light flicker to recruit microglia and reduce amyloid beta load.

Microglia, the primary immune cells of the brain, play a key role in pathological and normal brain function. Growing efforts aim to reveal how these cells may be harnessed to treat both neurodegenerative diseases such as Alzheimer's and developmental disorders such as schizophrenia and autism. We recently showed that using noninvasive exposure to 40-Hz white-light (4,000 K) flicker to drive 40-Hz neural activity transforms microglia into an engulfing state and reduces amyloid beta, a peptide thought to initiate neurotoxic events in Alzheimer's disease (AD). This article describes how to construct an LED-based light-flicker apparatus, expose animals to 40-Hz flicker and control conditions, and perform downstream assays to study the effects of these stimuli. Light flicker is simple, faster to implement, and noninvasive, as compared with driving 40-Hz activity using optogenetics; however, it does not target specific cell types, as is achievable with optogenetics. This noninvasive approach to driving 40-Hz neural activity should enable further research into the interactions between neural activity, molecular pathology, and the brain's immune system. Construction of the light-flicker system requires ~1 d and some electronics experience or available guidance. The flicker manipulation and assessment can be completed in a few days, depending on the experimental design.

The effect of amyloid-β peptide on synaptic plasticity and memory is influenced by different isoforms, concentrations, and aggregation status.

The increase of oligomeric amyloid-beta (oAβ) has been related to synaptic dysfunction, thought to be the earliest event in Alzheimer's disease pathophysiology. Conversely, the suppression of endogenous Aβ impaired synaptic plasticity and memory, suggesting that the peptide is needed in the healthy brain. However, different species, aggregation forms and concentrations of Aβ might differently influence synaptic function/dysfunction. Here, we have tested the contribution of monomeric and oligomeric Aβ42 and Aβ40 at 200nM and 200 pM concentrations on hippocampal long-term potentiation and spatial memory. We found that, when at 200nM, oAβ40, oAβ42, and monomeric Aβ42 impaired long-term potentiation and memory, whereas only oAβ42 200 pM enhanced synaptic plasticity and memory and rescued the detrimental effect due to depletion of endogenous Aβ. Interestingly, quantification of monomer-like and oligomer-like species carried out by transmission electron microscopy revealed an increase of the monomer/oligomer ratio in the oAβ42 200 pM preparation, suggesting that the content of monomers and oligomers depends on the final concentration of the solution.

Tau localises within mitochondrial sub-compartments and its caspase cleavage affects ER-mitochondria interactions and cellular Ca2+ handling

Intracellular neurofibrillary tangles (NFT) composed by tau and extracellular amyloid beta (Aβ) plaques accumulate in Alzheimer's disease (AD) and contribute to neuronal dysfunction. Mitochondrial dysfunction and neurodegeneration are increasingly considered two faces of the same coin and an early pathological event in AD. Compelling evidence indicates that tau and mitochondria are closely linked and suggests that tau-dependent modulation of mitochondrial functions might be a trigger for the neurodegeneration process; however, whether this occurs either directly or indirectly is not clear. Furthermore, whether tau influences cellular Ca2+ handling and ER-mitochondria cross-talk is yet to be explored. Here, by focusing on wt tau, either full-length (2N4R) or the caspase 3-cleaved form truncated at the C-terminus (2N4RΔC20), we examined the above-mentioned aspects. Using new genetically encoded split-GFP-based tools and organelle-targeted aequorin probes, we assessed: i) tau distribution within the mitochondrial sub-compartments; ii) the effect of tau on the short- (8–10 nm) and the long- (40–50 nm) range ER-mitochondria interactions; and iii) the effect of tau on cytosolic, ER and mitochondrial Ca2+ homeostasis. Our results indicate that a fraction of tau is found at the outer mitochondrial membrane (OMM) and within the inner mitochondrial space (IMS), suggesting a potential tau-dependent regulation of mitochondrial functions. The ER Ca2+ content and the short-range ER-mitochondria interactions were selectively affected by the expression of the caspase 3-cleaved 2N4RΔC20 tau, indicating that Ca2+ mis-handling and defects in the ER-mitochondria communications might be an important pathological event in tau-related dysfunction and thereby contributing to neurodegeneration. Finally, our data provide new insights into the molecular mechanisms underlying tauopathies.

SEQUENCE OF COGNITIVE DECLINE IN ADULTS WITH DOWN SYNDROME DURING PROGRESSION FROM PRECLINICAL TO PRODROMAL ALZHEIMER'S DISEASE

Down syndrome (DS, trisomy 21) is associated with a high risk of Alzheimer's disease (AD) due to triplication of the APP gene on chromosome 21. DS is therefore an important population in which to test the efficacy of drugs aimed at preventing or delaying onset of disease, before neurodegeneration occurs. However, there is lack of data on the early progression of AD in DS. We aimed to define the progression of aging-related decline associated with AD in DS using detailed cognitive phenotyping in a large cohort of older individuals with DS to identify tests that could be used as outcome measures, and to understand the sequence of cognitive decline, as well as effect of the APOE gene. Using cognitive test data and informant-rated questionnaires from 316 adults with DS aged 16 and older, we firstly compared individuals in the preclinical, prodromal and dementia stage of AD to identify cognitive domains most affected in each group and to estimate effect sizes of potential cognitive outcome measures for trials. We also used a data-driven approach, the Event-Based Model (EBM), to estimate the sequence of AD-related cognitive decline and assign participants to a disease stage. We demonstrated that individuals with DS experience significant cognitive decline before the onset of clinical dementia, with large effect sizes on several cognitive measures for the transition from preclinical to prodromal, and from prodromal to dementia stages. Decline in visuospatial memory and sustained attention are implicated as early events in AD in DS; informant measures defined later events. A staging model was identified, with older adults with an AD diagnosis and those with APOE e4 status being more likely to be staged later. We estimated sample sizes required for clinical trials to prevent or delay decline. Significant cognitive change occurs during the prodromal stages of AD in DS, highlighting the necessity for early assessment. Sample size calculations suggest that trials of treatment to prevent or delay dementia are feasible in DS individuals.

Glutamatergic synaptic plasticity and dysfunction in Alzheimer disease: Emerging mechanisms.

Impaired synaptic plasticity and dendritic loss in excitatory glutamatergic synapses are early events in Alzheimer disease (AD). These synaptic abnormalities are triggered by accumulation of soluble fibrillary β-amyloid (Aβ) oligomers, which bind to several postsynaptic and presynaptic partners. Many of the synaptic effects of Aβ oligomers involve NMDA receptors (NMDARs) and type 1 metabotropic glutamate receptor 5 (mGluR5). These receptors mediate use-dependent plasticity of glutamatergic synapses in the hippocampus and other brain regions. Synaptic plasticity includes long-term potentiation (LTP) and long-term depression (LTD) of efficacy of synaptic transmission. Studies both in vitro and in animal models indicate that Aβ oligomers disrupt LTP and promote LTD; these effects are associated with decreased density of dendritic spines. The mechanisms by which Aβ oligomers elicit these synaptic changes are similar to those normally utilized in the CNS during development and learning. In addition, interactions of β oligomers with extrasynaptic NMDARs and mGluR5 promote tau-hyperphosphorylation, leading to impaired mitochondrial transport to synapses and thus disrupting calcium homeostasis and energy-dependent processes. Via activation of glial cells, Aβ triggers complement-mediated pruning of vulnerable synapses. Loss of dendritic spines precedes the accumulation of neuritic plaques and neurofibrillary tangles and is potentially reversible. The multiple potential mechanisms by which Aβ oligomers may trigger dysfunction and loss of glutamatergic synapses provide multiple targets for neuroprotective therapy. There are several reviews focused on these topics.1–11 Only selected aspects of synaptic plasticity and its involvement in AD are reviewed here.

Role of Amyloid-β and Tau Proteins in Alzheimer's Disease: Confuting the Amyloid Cascade.

The "Amyloid Cascade Hypothesis" has dominated the Alzheimer's disease (AD) field in the last 25 years. It posits that the increase of amyloid-β (Aβ) is the key event in AD that triggers tau pathology followed by neuronal death and eventually, the disease. However, therapeutic approaches aimed at decreasing Aβ levels have so far failed, and tau-based clinical trials have not yet produced positive findings. This begs the question of whether the hypothesis is correct. Here we have examined literature on the role of Aβ and tau in synaptic dysfunction, memory loss, and seeding and spreading of AD, highlighting important parallelisms between the two proteins in all of these phenomena. We discuss novel findings showing binding of both Aβ and tau oligomers to amyloid-β protein precursor (AβPP), and the requirement for the presence of this protein for both Aβ and tau to enter neurons and induce abnormal synaptic function and memory. Most importantly, we propose a novel view of AD pathogenesis in which extracellular oligomers of Aβ and tau act in parallel and upstream of AβPP. Such a view will call for a reconsideration of therapeutic approaches directed against Aβ and tau, paving the way to an increased interest toward AβPP, both for understanding the pathogenesis of the disease and elaborating new therapeutic strategies.

Effect of ferric citrate on amyloid-beta peptides behavior.

Amyloid beta (Aβ) aggregation and oxidative stress are two of the central events in Alzheimer's Disease (AD). Both these phenomena can be caused by the interaction of Aβ with metal ions. In the last years the interaction between ZnII , CuII , and Aβ was much studied, but between iron and Aβ it is still little known. In this work we determine how three Aβ peptides, present in AD, interact with FeIII -citrate. The three Aβ peptides are: full length Aβ1-42, an isoform truncated at Glutamic acid in position three, Aβ3-42, and its pyroglutamated form AβpE3-42. Conformation and morphology of the three peptides, aggregated with and without FeIII -citrate were studied. Besides, we have determined the strength of the interactions Aβ/FeIII -citrate studying the effect of ethylenediaminetetraacetic acid as chelator. Results reported here demonstrate that FeIII -citrate promotes the aggregation in all the three peptides. Moreover, Aspartic acid 1, Glutamic acid 3, and Tyrosine 10 have an important role in the coordination with iron, generating a more stable complex for Aβ1-42 compared to that for the truncated peptides.

Cellular Trafficking of Amyloid Precursor Protein in Amyloidogenesis Physiological and Pathological Significance.

The accumulation of excess intracellular or extracellular amyloid beta (Aβ) is one of the key pathological events in Alzheimer's disease (AD). Aβ is generated from the cleavage of amyloid precursor protein (APP) by beta secretase-1 (BACE1) and gamma secretase (γ-secretase) within the cells. The endocytic trafficking of APP facilitates amyloidogenesis while at the cell surface, APP is predominantly processed in a non-amyloidogenic manner. Several adaptor proteins bind to both APP and BACE1, regulating their trafficking and recycling along the secretory and endocytic pathways. The phosphorylation of APP at Thr668 and BACE1 at Ser498, also influence their trafficking. Neurotrophins and proneurotrophins also influence APP trafficking through their receptors. In this review, we describe the molecular trafficking pathways of APP and BACE1 that lead to Aβ generation, the involvement of different signaling molecules or adaptor proteins regulating APP and BACE1 subcellular localization. We have also discussed how neurotrophins could modulate amyloidogenesis through their receptors.

AMPA-ergic regulation of amyloid-\u03b2 levels in an Alzheimer\u2019s disease mouse model

BackgroundExtracellular aggregation of the amyloid-β (Aβ) peptide into toxic multimers is a key event in Alzheimer’s disease (AD) pathogenesis. Aβ aggregation is concentration-dependent, with higher concentrations of Aβ much more likely to form toxic species. The processes that regulate extracellular levels of Aβ therefore stand to directly affect AD pathology onset. Studies from our lab and others have demonstrated that synaptic activity is a critical regulator of Aβ production through both presynaptic and postsynaptic mechanisms. AMPA receptors (AMPA-Rs), as the most abundant ionotropic glutamate receptors, have the potential to greatly impact Aβ levels.MethodsIn order to study the role of AMPA-Rs in Aβ regulation, we used in vivo microdialysis in an APP/PS1 mouse model to simultaneously deliver AMPA and other treatments while collecting Aβ from the interstitial fluid (ISF). Changes in Aβ production and clearance along with inflammation were assessed using biochemical approaches. IL-6 deficient mice were utilized to test the role of IL-6 signaling in AMPA-R-mediated regulation of Aβ levels.ResultsWe found that AMPA-R activation decreases in ISF Aβ levels in a dose-dependent manner. Moreover, the effect of AMPA treatment involves three distinct pathways. Steady-state activity of AMPA-Rs normally promotes higher ISF Aβ. Evoked AMPA-R activity, however, decreases Aβ levels by both stimulating glutamatergic transmission and activating downstream NMDA receptor (NMDA-R) signaling and, with extended AMPA treatment, acting independently of NMDA-Rs. Surprisingly, we found this latter, direct AMPA pathway of Aβ regulation increases Aβ clearance, while Aβ production appears to be largely unaffected. Furthermore, the AMPA-dependent decrease is not observed in IL-6 deficient mice, indicating a role for IL-6 signaling in AMPA-R-mediated Aβ clearance.ConclusionThough basal levels of AMPA-R activity promote higher levels of ISF Aβ, evoked AMPA-R signaling decreases Aβ through both NMDA-R-dependent and -independent pathways. We find that evoked AMPA-R signaling increases clearance of extracellular Aβ, at least in part through enhanced IL-6 signaling. These data emphasize that Aβ regulation by synaptic activity involves a number of independent pathways that together determine extracellular Aβ levels. Understanding how these pathways maintain Aβ levels prior to AD pathology may provide insights into disease pathogenesis.

Strikingly different effects of cholesterol and 7-ketocholesterol on lipid bilayer-mediated aggregation of amyloid beta (1-42)

Oxidized cholesterol has been widely reported to contribute to the pathogenesis of Alzheimer's disease (AD). However, the mechanism by which they affect the disease is not fully understood. Herein, we aimed to investigate the effect of 7-ketocholesterol (7keto) on membrane-mediated aggregation of amyloid beta (Aβ-42), one of the critical pathogenic events in AD. We have shown that when cholesterol is present in lipid vesicles, kinetics of Aβ nuclei formation is moderately hindered while that of fibril growth was considerably accelerated. The partial substitution of cholesterol with 7keto slightly enhanced the formation of Aβ-42 nuclei and remarkably decreased fibril elongation, thus maintaining the peptide in protofibrillar aggregates, which are reportedly the most toxic species. These findings add in understanding of how cholesterol and its oxidation can affect Aβ-induced cytotoxicity.

Odor Enrichment Increases Hippocampal Neuron Numbers in Mouse.

The hippocampus and olfactory bulb incorporate new neurons migrating from neurogenic regions in the brain. Hippocampal atrophy is evident in numerous neurodegenerative disorders, and altered hippocampal neurogenesis is an early pathological event in Alzheimer's disease. We hypothesized that hippocampal neurogenesis is affected by olfactory stimuli through the neural pathway of olfaction-related memory. In this study, we exposed mice to novel pleasant odors for three weeks and then assessed the number of neurons, non-neuronal cells (mainly glia) and proliferating cells in the hippocampus and olfactory bulb, using the isotropic fractionator method. We found that the odor enrichment significantly increased the neuronal cell numbers in the hippocampus, and promoted cell proliferation and neurogenesis in the olfactory bulb. In contrast, the glial cell numbers remained unchanged in both of the regions. Our results suggest that exposure to novel odor stimuli promotes hippocampal neurogenesis and support the idea that enriched environments may delay the onset or slow down the progression of neurodegenerative disorders.

Supratherapeutic concentrations of cilostazol inhibits β-amyloid oligomerization in vitro

Alzheimer disease (AD) is the most common type of dementia, and is currently incurable. The efficacy of existing treatments for AD such as acetylcholinesterase inhibitors is limited to symptom improvement. Research on disease-modifying therapies (DMTs) has conventionally focused on amelioration of CNS pathogenesis. Two neuropathological changes correlate strongly with AD, the appearance of neurofibrillary tangles containing the microtubule-associated protein tau and extracellular amyloid deposits containing amyloid β-protein (Aβ). The aggregation of Aβ is believed to be the key pathogenic event in AD, with oligomeric assemblies thought to be the most neurotoxic form. Inhibitors of oligomer formation, therefore, could be valuable therapeutics for AD patients. The clinical phosphodiesterase type-3 inhibitor cilostazol (CSZ) was recently found to suppress the progression of cognitive decline in patients with stable AD receiving acetylcholinesterase inhibitors. Here we examined the effects of CSZ on in vitro aggregations of Aβ1-40 and Aβ1-42 including oligomerization, using the thioflavin T assay, photo-induced cross-linking of unmodified proteins, and electron microscopy. CSZ (25–100 μM) inhibited Aβ aggregation, especially oligomer formation. Considering that CSZ might be a key molecule for DMTs of AD, it cannot be ruled out that the low concentration of CSZ achievable in patient dosing may display some ant-oligomeric activity in synergy with its known therapeutic effects.

Prion-like propagation of \u03b2-amyloid aggregates in the absence of APP overexpression

The amyloid cascade hypothesis posits that the initiating event in Alzheimer’s disease (AD) is the aggregation and deposition of the β-amyloid (Aβ) peptide, which is a proteolytic cleavage product of the amyloid precursor protein (APP). Mounting evidence suggests that the formation and spread of prion-like Aβ aggregates during AD may contribute to disease progression. Inoculation of transgenic mice that overexpress APP with pre-formed Aβ aggregates results in the prion-like induction of cerebral Aβ deposition. To determine whether Aβ deposition can also be induced when physiological APP levels are present in the brain, we inoculated AppNL-F mice, a knock-in model of AD that avoids potential artifacts associated with APP overexpression, with Aβ aggregates derived from the brains of AD patients or transgenic mice. In all cases, induced Aβ deposition was apparent in the corpus callosum, olfactory bulb, and meningeal blood vessels of inoculated mice at 130–150 days post-inoculation, whereas uninoculated and buffer-inoculated animals exhibited minimal or no Aβ deposits at these ages. Interestingly, despite being predominantly composed of protease-resistant Aβ42 aggregates, the induced parenchymal Aβ deposits were largely diffuse and were unreactive to an amyloid-binding dye. These results demonstrate that APP overexpression is not a prerequisite for the prion-like induction of cerebral Aβ deposition. Accordingly, spreading of Aβ deposition may contribute to disease progression in AD patients.

Quantitative EEG during memory testing indicates pre‐symptomatic Alzheimer's disease and correlation with MRI

Background and ObjectivesIncreasing attention for Alzheimer's disease (AD) have been focused on pre‐symptomatic stage for potential effective treatment. We aim to explore the quantitative electroencephalography (qEEG) during memory testing and evaluate qEEG correlations with MRI volumetric data to investigate the underlying events of pre‐symptomatic AD.MethodsWe employed qEEG test to investigate brain activity during working memory processing (N‐back) in a pre‐symptomatic AD study. Study participants, age 60–100 years, with normal cognition were recruited from the local community, consisting of two subdivisions from cerebrospinal fluid proteins: cognitively healthy with normal amyloid/tau ratio (CH‐NAT, n=10) or pathological amyloid/tau ratio (CH‐PAT, n=14). Behavioral performance and spectral power from 21 recording head sensors were collected during testing. EEG signal (ir)regularity or “noise” levels were measured by spectral entropy (SE). To assess brain anatomical structures, MRI was collected from the same individuals. We analyzed the EEG data for all channels, and explored the spectral power correlations with MRI total gray matter and hippocampal volumes.Results & DiscussionThe behavioral performance was similar between the two groups during lower memory load, and CH‐PATs had significantly less accuracy of performance than CH‐NATs during higher memory load. The qEEG from several sensors were significantly different (p<0.01) between CH‐NAT and CH‐PAT groups during the lower load memory testing when behavioral performances did not differ. The CH‐PAT brain signals were “noisier” compared to CH‐NATs. We interpret the altered brain activity in the CH‐PAT group to indicate a compensation mechanism for the CH‐PATs. qEEG measures from specific sensors correlated with total gray matter volume (p<0.001) and hippocampal volumes (p<0.001); these unexpected results suggest neuroplasticity occurs in the pre‐symptomatic AD stage to compensate for reduction in brain regional volumes. We propose that intervention at the pre‐symptomatic phase of AD using strategies that improve cognitive efficiency may attenuate neurodegeneration.Support or Funding InformationThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

1,2,4-trihydroxynaphthalene-2-O-β-D-glucopyranoside delays amyloid-β42 aggregation and reduces amyloid cytotoxicity.

Presently, misfolding and aggregation of amyloid-β42 (Aβ42 ) are considered early events in Alzheimer's disease (AD) pathogenesis. The use of natural products to inhibit the aggregation process and to protect cells from cytotoxicity of early aggregate grown at the onset of the aggregation path is one of the promising strategies against AD. Recently, we have purified a new powerful antioxidant and inhibitor of Aβ42 aggregation from the leaves of Lawsonia inermis. The new compound was identified as a new Lawsoniaside; 1,2,4-trihydroxynaphthalene-2-O-β-D-glucopyranoside (THNG). Herein, we show that THNG interferes with Aβ42 aggregation, inhibits its conformational change to a β-sheet-rich structure, decreases its polymerization into large fibrillar species, reduces oxidative stress, and aggregate cytotoxicity. These results indicate that THNG has great potential as a neuroprotective and therapeutic agent against AD. © 2018 BioFactors, 44(3):272-280, 2018.

Aggregation kinetics in the presence of brain lipids of Aβ(1–40) cleaved from a soluble fusion protein

The cleavage of the amyloid precursor protein by β- and γ-secretases is a key event in Alzheimer's disease. A fusion protein was constructed to investigate the cleavage rate and aggregation kinetics of amyloid-beta (1–40) (Aβ(1–40)) peptides. The peptide was expressed with a Small Ubiquitin-Like Modifier (SUMO) on the N-terminus and cleaved by a SUMO protease Ulp1. The time course of the cleavage reaction was monitored by SDS-PAGE gel with 100:1 or 1000:1 SUMO-Aβ(1–40) to Ulp1 molar ratio and in the presence of brain total lipid extract unilamellar vesicles. Similarly, the aggregation of Aβ(1–40) peptides upon cleavage was monitored by thioflavin T fluorescence assays and by circular dichroism. The cleavage reaction was modulated by the concentration of Ulp1, with fast release of Aβ(1–40) peptides producing shorter lag time before fibril formation, but with similar elongation rate. The presence of lipids significantly reduced the cleavage completion at 1000:1, but reduced the lag time before fibril formation, while at 100:1 similar cleavage and aggregation kinetics were observed compared to the lipid-free condition. Overall, the results showed that the fusion protein SUMO-Aβ(1–40) is a means to study the cleavage and aggregation of amyloid peptides and that the presence of lipids and the fast release rate accelerated the aggregation of Aβ(1–40) peptides.

Early Presymptomatic Changes in the Proteome of Mitochondria-Associated Membrane in the APP/PS1 Mouse Model of Alzheimer's Disease.

Intracellular β-amyloid (Aβ) accumulation is an early event in Alzheimer's disease (AD) progression. Recently, it has been uncovered that presenilins (PSs), the key components of the amyloid precursor protein (APP) processing and the β-amyloid producing γ-secretase complex, are highly enriched in a special sub-compartment of the endoplasmic reticulum (ER) functionally connected to mitochondria, called mitochondria-associated ER membrane (MAM). A current hypothesis of pathogenesis of Alzheimer's diseases (AD) suggests that MAM is involved in the initial phase of AD. Since MAM supplies mitochondria with essential proteins, the increasing level of PSs and β-amyloid could lead to metabolic dysfunction because of the impairment of ER-mitochondrion crosstalk. To reveal the early molecular changes of this subcellular compartment in AD development MAM fraction was isolated from the cerebral cortex of 3months old APP/PS1 mouse model of AD and age-matched C57BL/6 control mice, then mass spectrometry-based quantitative proteome analysis was performed. The enrichment and purity of MAM preparations were validated with EM, LC-MS/MS and protein enrichment analysis. Label-free LC-MS/MS was used to reveal the differences between the proteome of the transgenic and control mice. We obtained 77 increased and 49 decreased protein level changes in the range of - 6.365 to + 2.988, which have mitochondrial, ER or ribosomal localization according to Gene Ontology database. The highest degree of difference between the two groups was shown by the ATP-binding cassette G1 (Abcg1) which plays a crucial role in cholesterol metabolism and suppresses Aβ accumulation. Most of the other protein changes were associated with increased protein synthesis, endoplasmic-reticulum-associated protein degradation (ERAD), oxidative stress response, decreased mitochondrial protein transport and ATP production. The interaction network analysis revealed a strong relationship between the detected MAM protein changes and AD. Moreover, it explored several MAM proteins with hub position suggesting their importance in Aβ induced early MAM dysregulation. Our identified MAM protein changes precede the onset of dementia-like symptoms in the APP/PS1 model, suggesting their importance in the development of AD.

Stoichiometric Zn2+ interferes with the self-association of Aβ42: Insights from size distribution analysis

The abnormal aggregation of amyloid β (Aβ) peptides in the brain has been recognized as a central event in Alzheimer's disease (AD). Divalent metal ions such as Zn2+ have been shown to be closely involved in modulating Aβ self-association. Although the link between Zn2+ dyshomeostasis and brain Aβ deposition has been established, the effect of Zn2+ on the aggregation of Aβ is still incompletely clarified. By combining analytical ultracentrifugation (AUC), circular dichroism (CD) spectroscopy, thioflavin T (ThT) assay and atomic force microscopy (AFM) imaging, we analyzed the impact of stoichiometric Zn2+ on the aggregation process of Aβ42, the main toxic isoform of Aβ species in the brain. Aβ42 aggregates found in the presence of Zn2+ were smaller in size, non-fibrillary and showed less β-sheet structures than aggregates formed in absence of Zn2+. AUC showed that Zn2+ was capable of retaining monomeric Aβ42 in solution. Zn2+ chelation by EDTA totally reversed the inhibitory effect of Zn2+ on Aβ42 fibrillation. Our results provide further evidence that Zn2+ shifts the self-association of Aβ42 toward a non-fibrillary pathway by interfering with the aggregation process at multiple levels.

LINGO-1 antibody ameliorates myelin impairment and spatial memory deficits in the early stage of 5XFAD mice.

Multiple evidence has indicated that myelin injury is common in Alzheimer's disease (AD). However, whether myelin injury is an early event in AD and the relationship between it and cognitive function is still elusive. Spatial memory of 5XFAD mice was determined by Morris water maze at 1 and 3months old. Meanwhile, the deposition of Aβ, the expression of myelin basic protein (MBP), LINGO-1, NgR, and myelin ultrastructure in many memory-associated brain regions were detected in one-month-old and three-month-old mice (before and after LINGO-1 antibody administration) using immunostaining, Western blot (WB), and transmission electron microscopy (TEM), respectively. No abnormal Aβ deposition was found in one-month-old 5XFAD mice. However, spatial memory deficits were proved in accordance with an obvious demyelination in memory-associated brain regions in one-month-old mice and both deteriorated with age. Administration of LINGO-1 antibody could obviously restore the myelin impairments in CA1 and DG region and partially ameliorate spatial memory deficits. Our results demonstrated that myelin injury was an early event in 5XFAD mice even prior to emergence of deposition of Aβ. Intervention with the LINGO-1 antibody could attenuate impaired spatial memory deficits by remyelination, which suggested that myelin injury was involved in spatial memory deficits and remyelination may be a potential therapeutic strategy in early stage of AD or mild cognitive impairments.