Relative efficacies of amyloid β peptide (Aβ) binding proteins in Aβ aggregation

The aggregation of amyloid β peptide (Aβ) into its fibrillar, cross β-pleated configuration is generally viewed as a critical event in the pathophysiology of Alzheimer's disease (AD). A diverse group of molecules, the Aβ binding proteins, has been evaluated for their effects on this process. However, most of these studies have used micromolar or greater reagent concentrations, and their different methods have not permitted quantitative comparisons of the efficacy of different Aβ binding proteins in augmenting or inhibiting aggregation. In the present work we have undertaken a coherent analysis using fluorimetry of thioflavin T-stained experimental solutions. The complement protein C1q, serum amyloid P, and transthyretin significantly enhanced the formation of precipitable, cross β-pleated aggregates in solutions of 800 nM Aβ1–42. Under these same experimental conditions, α₁-antichymotrypsin had no significant effect on the aggregation process, and both the E3 and E4 isoforms of apolipoprotein E were significant inhibitors. There was a non-significant trend toward the E3 isoform exhibiting greater inhibition than the E4 isoform. Of the aggregation-facilitating molecules, C1q was substantially and significantly the most potent. © 1996 Wiley-Liss, Inc.     

Astrocytic Aβ1‐42 uptake is determined by Aβ‐aggregation state and the presence of amyloid‐associated proteins

Intracerebral accumulation of amyloid‐β (Aβ) leading to Aβ plaque formation, is the main hallmark of Alzheimer's disease and might be caused by defective Aβ‐clearance. We previously found primary human astrocytes and microglia able to bind and ingest Aβ1‐42 in vitro, which appeared to be limited by Aβ1‐42 fibril formation. We now confirm that astrocytic Aβ‐uptake depends on size and/or composition of Aβ‐aggregates as astrocytes preferably take up oligomeric Aβ over fibrillar Aβ. Upon exposure to either fluorescence‐labelled Aβ1‐42 oligomers (Aβ_oligo) or fibrils (Aβ_fib), a larger (3.7 times more) proportion of astrocytes ingested oligomers compared to fibrils, as determined by flow cytometry. Aβ‐internalization was verified using confocal microscopy and live‐cell imaging. Neither uptake of Aβ_oligo nor Aβ_fib, triggered proinflammatory activation of the astrocytes, as judged by quantification of interleukin‐6 and monocyte‐chemoattractant protein‐1 release. Amyloid‐associated proteins, including α1‐antichymotrypsin (ACT), serum amyloid P component (SAP), C1q and apolipoproteins E (ApoE) and J (ApoJ) were earlier found to influence Aβ‐aggregation. Here, astrocytic uptake of Aβ_fib increased when added to the cells in combination with SAP and C1q (SAP/C1q), but was unchanged in the presence of ApoE, ApoJ and ACT. Interestingly, ApoJ and ApoE dramatically reduced the number of Aβ_oligo‐positive astrocytes, whereas SAP/C1q slightly reduced Aβ_oligo uptake. Thus, amyloid‐associated proteins, especially ApoJ and ApoE, can alter Aβ‐uptake in vitro and hence may influence Aβ clearance and plaque formation in vivo. © 2010 Wiley‐Liss, Inc.     

Lack of effect of interleukins 1α and 1β, during in vitro perifusion,on anterior pituitary release of adrenocorticotropic hormone and β endorphin in the male rat

It has been demonstrated that interleukin 1 (IL1) injection provokes a great variety of biological effects, notably an activation of the corticotropic axis, increasing plasma adrenocorticotropic hormone (ACTH) and corticosterone. However, the primary site of action of IL1 is still controversial. In the present study, we first verified the in vivo capability of human interleukins 1α (hIL1α) and 1β (hIL1β) to release ACTH and β endorphin (β EP) in the normal male rat, before investigating, through an anterior pituitary (AP) perifusion system, the hIL1α and hIL1β effects on basal and corticotropin-releasing factor (CRF)-induced ACTH and β EP secretions. This system enabled the examination of a dynamic profile of hormones secretion, avoiding the possibility of feedback mechanisms, as is the case with the use of regular but very often longtime incubations. The results showed that in a perifusion system, with a short duration treatment (below 2 hr) compatible with the kinetics of action observed in vivo, basal and CRF-induced ACTH and β EP release were not modified in the presence of a broad range of concentrations (from 10^?12 to 10^?9 M) of hIL1α or hIL1β. Taken together, these results clearly show that in an in vitro situation close to physiological conditions, the primary site of action of hIL1α and hIL1β on ACTH and β EP release is not located at the AP level in the male rat. © 1993 Wiley-Liss, Inc.     

Attenuation of β‐amyloid‐induced tauopathy via activation of CK2α/SIRT1: Targeting for cilostazol

β‐Amyloid (Aβ) deposits and hyperphosphorylated tau aggregates are the chief hallmarks in the Alzheimer's disease (AD) brains, but the strategies for controlling these pathological events remain elusive. We hypothesized that CK2‐coupled SIRT1 activation stimulated by cilostazol suppresses tau acetylation (Ac‐tau) and tau phosphorylation (P‐tau) by inhibiting activation of P300 and GSK3β. Aβ was endogenously overproduced in N2a cells expressing human APP Swedish mutation (N2aSwe) by exposure to medium containing 1% fetal bovine serum for 24 hr. Increased Aβ accumulation was accompanied by increased Ac‐tau and P‐tau levels. Concomitantly, these cells showed increased P300 and GSK3β P‐Tyr216 expression; their expressions were significantly reduced by treatment with cilostazol (3–30 μM) and resveratrol (20 μM). Moreover, decreased expression of SIRT1 and its activity by Aβ were significantly reversed by cilostazol as by resveratrol. In addition, cilostazol strongly stimulated CK2α phosphorylation and its activity, and then stimulated SIRT1 phosphorylation. These effects were confirmed by using the pharmacological inhibitors KT5720 (1 μM, PKA inhibitor), TBCA (20 μM, inhibitor of CK2), and sirtinol (20 μM, SIRT1 inhibitor) as well as by SIRT1 gene silencing and overexpression techniques. In conclusion, increased cAMP‐dependent protein kinase‐linked CK2/SIRT1 expression by cilostazol can be a therapeutic strategy to suppress the tau‐related neurodegeneration in the AD brain. © 2013 Wiley Periodicals, Inc.     

Effects of antiparkinsonian agents on β‐amyloid and α‐synuclein oligomer formation in vitro

The aggregation of β‐amyloid protein (Aβ) and α‐synuclein (αS) are hypothesized to be the key pathogenic event in Alzheimer's disease (AD) and Lewy body diseases (LBD), with oligomeric assemblies thought to be the most neurotoxic. Inhibitors of oligomer formation, therefore, could be valuable therapeutics for patients with AD and LBD. Here, we examined the effects of antiparkinsonian agents (dopamine, levodopa, trihexyphenidyl, selegiline, zonisamide, bromocriptine, peroxide, ropinirole, pramipexole, and entacapone) on the in vitro oligomer formation of Aβ40, Aβ42, and αS using a method of photo‐induced cross‐linking of unmodified proteins (PICUP), electron microscopy, and atomic force microscopy. The antiparkinsonian agents except for trihexyphenidyl inhibited both Aβ and αS oligomer formations, and, among them, dopamine, levodopa, pramipexole, and entacapone had the stronger in vitro activity. Circular dichroism and thioflavin T(S) assays showed that secondary structures of Aβ and αS assemblies inhibited by antiparkinsonian agents were statistical coil state and that their seeding activities had disappeared. The antiparkinsonian agents could be potential therapeutic agents to prevent or delay AD and LBD progression. © 2013 Wiley Periodicals, Inc.     

Scavenging of Alzheimer's amyloid β-protein by microglia in culture

Deposits of amyloid β-protein (Aβ) form the cores of the pathological plaques which characterize Alzheimer's disease. The mechanism of formation of the deposits is unknown; one possibility is failure of a clearance mechanism that would normally remove the protein from brain parenchyma. This study has investigated the capacity of the central nervous system (CNS) phagocytes, microglia cells, to clear exogenous Aβ_1–42 from their environment. Cultured microglia from adult rat CNS have a high capacity to remove Aβ from serum-free medium, shown by immunoblotting experiments. Aβ from incubation medium was attached to the cell surface and could be identified by immunocytochemistry at the light or electron microscopic (EM) level; by EM, Aβ also appeared in phagosome-like intracellular vesicles. Light microscopic immunocytochemistry combined with computer-assisted image analysis showed that cells accumulated Aβ within 24 hr. from culture medium containing from 1 to 20 μg/ml Aβ. Microglial accumulation of Aβ was substantially reduced in the presence of fetal bovine serum. Addition of the protease inhibitor leupeptin to incubation medium with serum resulted in accumulation of Aβ in a membrane-bound intracellular compartment, but not at the cell surface. The increase in intracellular accumulation in the presence of the protease inhibitor indicates a microglial capacity for intracellular degradation of Aβ in the absence of inhibition. The change from predominantly cell-surface accumulation in serum-free medium to predominantly intracellular accumulation with serum may be explained by the presence in serum of carrier proteins that complex with Aβ and target it to cell surface receptors capable of stimulating endocytosis. Microglia were also cultured on unfixed cryostat sections of human brain tissue containing Alzheimer's plaques. Very little Aβ from the tissue was accumulated by the cells, although cultured microglia were found in direct contact with anti-Aβ immunopositive plaques. Possibly Aβ in tissue sections was complexed with other proteins which either inhibited its uptake by microglia or enhanced its proteolysis, preventing cellular accumulation of immunostainable Aβ. The results indicate that cultured microglia effectively remove Aβ from tissue culture medium and from the surface of the dish and concentrate monomer and aggregates of Aβ either on the cell surface or intracellularly. This process may be modified by proteins present in Alzheimer's brain sections. © 1996 Wiley-Liss, Inc.     

Active clearance of human amyloid β 1–42 peptide aggregates from the rat ventricular system

A major constituent of SP in the brains of Alzheimer's disease is 39–43 amino acid peptide called β‐amyloid peptide (Aβ). Recent data have demonstrated that Aβ has a strong tendency to form insoluble aggregates and that toxic effects of Aβ is based on its aggregation. In the current study, 100 µg of human synthetic Aβ 1–42 (sAβ 1–42) was infused into the lateral ventricle of rat brain using a short‐term infusion model. At 2 or 7 days following the infusion, sAβ 1–42 was found to form insoluble aggregates, scattering throughout the entire ventricular systems. The sAβ 1–42 aggregates were partially engulfed by phagocytic cells and deposited at the meningeal vessels or the choroid plexuses. However, these deposits mostly disappeared from the ventricles by 28 days post‐infusion. Here, it is reported for the first time that considerable amounts of sAβ 1–42 are almost cleared from the rat ventricular system by the mononuclear phagocytic system.     

Cyclin‐Dependent kinase 5 targeting prevents β‐Amyloid aggregation involving glycogen synthase kinase 3β and phosphatases

Inappropriate activation of cyclin‐dependent kinase 5 (CDK5) resulting from proteolytic release of the activator fragment p25 from the membrane contributes to the formation of neurofibrillary tangles, β‐amyloid (βA) aggregation, and chronic neurodegeneration. At 18 months of age, 3× Tg‐AD mice were sacrificed after either 3 weeks (short term) or 1 year (long term) of CDK5 knockdown. In short‐term‐treated animals, CDK5 knockdown reversed βA aggregation in the hippocampi via inhibitory phosphorylation of glycogen synthase kinase 3β Ser9 and activation of phosphatase PP2A. In long‐term‐treated animals, CDK5 knockdown induced a persistent reduction in CDK5 and prevented βA aggregation, but the effect on amyloid precursor protein processing was reduced, suggesting that yearly booster therapy would be required. These findings further validate CDK5 as a target for preventing or blocking amyloidosis in older transgenic mice. © 2015 Wiley Periodicals, Inc.     

A novel antibody targeting sequence 31–35 in amyloid β protein attenuates Alzheimer's disease‐related neuronal damage

Amyloid β protein (Aβ) plays a critical role in pathogenesis of Alzheimer's disease (AD). Our previous studies indicated that the sequence 31–35 in Aβ molecule is an effective active center responsible for Aβ neurotoxicity in vivo and in vitro. In the present study, we prepared a novel antibody specifically targeting the sequence 31–35 of amyloid β protein, and investigated the neuroprotection of the anti‐Aβ_31–35 antibody against Aβ_1–42‐induced impairments in neuronal viability, spatial memory, and hippocampal synaptic plasticity in rats. The results showed that the anti‐Aβ_31–35 antibody almost equally bound to both Aβ_31–35 and Aβ_1–42, and pretreatment with the antibody dose‐dependently prevented Aβ_1–42‐induced cytotoxicity on cultured primary cortical neurons. In behavioral study, intracerebroventricular (i.c.v.) injection of anti‐Aβ_31–35 antibody efficiently attenuated Aβ_1–42‐induced impairments in spatial learning and memory of rats. In vivo electrophysiological experiments further indicated that Aβ_1–42‐induced suppression of hippocampal synaptic plasticity was effectively reversed by the antibody. These results demonstrated that the sequence 31–35 of Aβ may be a new therapeutic target, and the anti‐Aβ_31–35 antibody could be a novel immunotheraputic approach for the treatment of AD. © 2016 Wiley Periodicals, Inc.     

Secreted amyloid precursor protein and holo‐APP bind amyloid β through distinct domains eliciting different toxic responses on hippocampal neurons

Amyloid β (Aβ) is a metabolic product of Aβ precursor protein (APP). Deposition of Aβ in the brain and neuronal degeneration are characteristic hallmarks of Alzheimer's disease (AD). Aβ induces neuronal degeneration, but the mechanism of neurotoxicity remains elusive. Increasing evidence implicates APP as a receptor‐like protein for Aβ fibrils (fAβ). In this study, we present further experimental support for the direct interaction of APP with fAβ and for its involvement in Aβ neurotoxicity. Using recombinant purified holo‐APP (h‐APP), we have shown that it directly binds fAβ. Employing deletion mutant forms of APP, we show that two different sequences are involved in the binding of APP to fAβ. One sequence in the n‐terminus of APP is required for binding of fAβ to secreted APP (s‐APP) but not to h‐APP. In addition, the extracellular juxtamembrane Aβ‐sequence mediates binding of fAβ to h‐APP but not to s‐APP. Deletion of the extracellular juxtamembrane Aβ sequence abolishes abnormal h‐APP accumulation and toxicity induced by fAβ deposition, whereas deletions in the n‐terminus of APP do not affect Aβ toxicity. These experiments show that interaction of toxic Aβ species with its membrane‐anchored parental protein promotes toxicity in hippocampal neurons, adding further support to an Aβ‐receptor‐like function of APP directly implicated in neuronal degeneration in AD. © 2010 Wiley‐Liss, Inc.     

γ‐Secretase binding sites in aged and Alzheimer's disease human cerebrum: the choroid plexus as a putative origin of CSF Aβ

Deposition of β ‐amyloid (Aβ) peptides, cleavage products of β‐amyloid precursor protein (APP) by β‐secretase‐1 (BACE1) and γ‐secretase, is a neuropathological hallmark of Alzheimer's disease (AD). γ‐Secretase inhibition is a therapeutical anti‐Aβ approach, although changes in the enzyme's activity in AD brain are unclear. Cerebrospinal fluid (CSF) Aβ peptides are thought to derive from brain parenchyma and thus may serve as biomarkers for assessing cerebral amyloidosis and anti‐Aβ efficacy. The present study compared active γ‐secretase binding sites with Aβ deposition in aged and AD human cerebrum, and explored the possibility of Aβ production and secretion by the choroid plexus (CP). The specific binding density of [³H]‐L‐685,458, a radiolabeled high‐affinity γ‐secretase inhibitor, in the temporal neocortex and hippocampal formation was similar for AD and control cases with similar ages and post‐mortem delays. The CP in post‐mortem samples exhibited exceptionally high [³H]‐L‐685,458 binding density, with the estimated maximal binding sites (Bmax) reduced in the AD relative to control groups. Surgically resected human CP exhibited APP, BACE1 and presenilin‐1 immunoreactivity, and β‐site APP cleavage enzymatic activity. In primary culture, human CP cells also expressed these amyloidogenic proteins and released Aβ40 and Aβ42 into the medium. Overall, our results suggest that γ‐secretase activity appears unaltered in the cerebrum in AD and is not correlated with regional amyloid plaque pathology. The CP appears to be a previously unrecognised non‐neuronal contributor to CSF Aβ, probably at reduced levels in AD.     

The two‐hydrophobic domain tertiary structure of reticulon proteins is critical for modulation of β‐secretase BACE1

β‐Site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is a membrane‐bound protease that is essential for the production of β‐amyloid protein (Aβ). Given the crucial role of Aβ accumulation in Alzheimer's disease (AD), inhibition of BACE1 activity may represent a feasible therapeutic strategy in the treatment of AD. Recently, we and others identified reticulon 3 (RTN3) and reticulon 4‐B/C (RTN4‐B/C or Nogo‐B/C) as membrane proteins that interact with BACE1 and inhibit its ability to produce Aβ. In this study, we employed various mutants of RTN3 and RTN4‐C and C. elegans RTN to investigate the molecular mechanisms by which RTNs regulate BACE1. We found that RTN3 mutants lacking the N‐terminal or C‐terminal or loop domain as well as a RTN4‐C mutant lacking the C‐terminal domain bound to BACE1 comparably to wild‐type RTN3 and RTN4‐C. Furthermore, overexpression of wild‐type RTN3, RTN4‐C, and these RTN mutants similarly reduced Aβ40 and Aβ42 secretion by cells expressing Swedish mutant APP. C. elegans RTN, which has low homology to human RTNs, also interacted with BACE1 and inhibited Aβ secretion. In contrast, two RTN3 mutants containing deletions of the first or second potential transmembrane domains and an RTN3 swap mutant of the second transmembrane domain bound BACE1 but failed to inhibit Aβ secretion. Collectively, these results suggest that the two‐transmembrane‐domain tertiary structure of RTN proteins is critical for the ability of RTNs to modulate BACE1 activity, whereas N‐terminal, C‐terminal and loop regions are not essential for this function. © 2009 Wiley‐Liss, Inc.     

Sex Hormone Decline and Amyloid β Synthesis,Transport and Clearance in the Brain

Sex hormones (SH) are essential regulators of the central nervous system. The decline in SH levels along with ageing may contribute to compromised neuroprotection and set the grounds for neurodegeneration and cognitive impairments. In Alzheimer's disease, besides other pathological features, there is an imbalance between amyloid β (Aβ) production and clearance, leading to its accumulation in the brain of older subjects. Aβ accumulation is a primary cause for brain inflammation and degeneration, as well as concomitant cognitive decline. There is mounting evidence that SH modulate Aβ production, transport and clearance. Importantly, SH regulate most of the molecules involved in the amyloidogenic pathway, their transport across brain barriers for elimination, and their degradation in the brain interstitial fluid. This review brings together data on the regulation of Aβ production, metabolism, degradation and clearance by SH.     

A critical role of TRPM2 channel in Aβ42‐induced microglial activation and generation of tumor necrosis factor‐α

Amyloid β (Aβ)‐induced neuroinflammation plays an important part in Alzheimer's disease (AD). Emerging evidence supports a role for the transient receptor potential melastatin‐related 2 (TRPM2) channel in Aβ‐induced neuroinflammation, but how Aβ induces TRPM2 channel activation and this relates to neuroinflammation remained poorly understood. We investigated the mechanisms by which Aβ₄₂ activates the TRPM2 channel in microglial cells and the relationships to microglial activation and generation of tumor necrosis factor‐α (TNF‐α), a key cytokine implicated in AD. Exposure to 10–300 nM Aβ₄₂ induced concentration‐dependent microglial activation and generation of TNF‐α that were ablated by genetically deleting (TRPM2 knockout ;TRPM2‐KO) or pharmacologically inhibiting the TRPM2 channel, revealing a critical role of this channel in Aβ₄₂‐induced microglial activation and generation of TNF‐α. Mechanistically, Aβ₄₂ activated the TRPM2 channel via stimulating generation of reactive oxygen species (ROS) and activation of poly(ADPR) polymerase‐1 (PARP‐1). Aβ₄₂‐induced generation of ROS and activation of PARP‐1 and TRPM2 channel were suppressed by inhibiting protein kinase C (PKC) and NADPH oxidases (NOX). Aβ₄₂‐induced activation of PARP‐1 and TRPM2 channel was also reduced by inhibiting PYK2 and MEK/ERK. Aβ₄₂‐induced activation of PARP‐1 was attenuated by TRPM2‐KO and moreover, the remaining PARP‐1 activity was eliminated by inhibiting PKC and NOX, but not PYK2 and MEK/ERK. Collectively, our results suggest that PKC/NOX‐mediated generation of ROS and subsequent activation of PARP‐1 play a role in Aβ₄₂‐induced TRPM2 channel activation and TRPM2‐dependent activation of the PYK2/MEK/ERK signalling pathway acts as a positive feedback to further facilitate activation of PARP‐1 and TRPM2 channel. These findings provide novel insights into the mechanisms underlying Aβ‐induced AD‐related neuroinflammation.     

Macrophage colony stimulating factor is associated with excretion of amyloid‐β peptides from cerebrospinal fluid to peripheral blood

Background: The process of aggregation of brain amyloid‐β peptides (Aβ) is thought to be associated with the pathogenesis of Alzheimer's disease (AD). Amyloid‐β peptides are produced by sequential endoproteolysis by β‐site amyloid‐β protein precursor‐cleaving enzyme (BACE) followed by presenilin (PS)/γ‐secretase. There are several species of Aβ due to cleavage diversity of PS/γ‐secretase. The predominant species in human cerebrospinal fluid (CSF) or plasma is Aβ40, whereas Aβ42 is much more aggregatable and accumulated in senile plaques. The level of Aβ in the brain is determined by the balance between the generation and clearance of Aβ, including transport across the brain–blood barrier (BBB). Although the processes of Aβ generation and degradation have been studied in some detail, knowledge of the Aβ transport process across the BBB is limited. So far, low‐density lipoprotein receptor‐related protein (LRP1), P‐glycoprotein (P‐gp), and insulin‐like growth factor‐1 (IGF‐1) have been identified to modify the excretion of brain Aβ to the blood. Methods: To investigate whether macrophage colony stimulating factor (M‐CSF) has a role in the Aβ transport process, human Aβ was injected into the lateral ventricle of the brain of M‐CSF‐deficient (op/op) mice. Then, plasma and brain Aβ levels were measured by ELISA to determine the time‐course of Aβ movement from the brain to the plasma. Result: When human Aβ40 was injected into mouse lateral ventricles, the efflux of Aβ from the CSF to the blood was transiently decreased and delayed in M‐CSF‐deficient mice. Moreover, endogenous plasma Aβ40 levels were lower in M‐CSF‐deficient mice. Conclusion: The results indicate that M‐CSF deficiency impairs excretion of human‐type Aβ40 from the CSF to blood. We propose that M‐CSF may be a novel factor that facilitates the excretion of Aβ from the CSF to the blood via the BBB.     

δ‐Catenin/NPRAP: A new member of the glycogen synthase kinase‐3β signaling complex that promotes β‐catenin turnover in neurons

Through a multiprotein complex, glycogen synthase kinase‐3β (GSK‐3β) phosphorylates and destabilizes β‐catenin, an important signaling event for neuronal growth and proper synaptic function. δ‐Catenin, or NPRAP (CTNND2), is a neural enriched member of the β‐catenin superfamily and is also known to modulate neurite outgrowth and synaptic activity. In this study, we investigated the possibility that δ‐catenin expression is also affected by GSK‐3β signaling and participates in the molecular complex regulating β‐catenin turnover in neurons. Immunofluorescent light microscopy revealed colocalization of δ‐catenin with members of the molecular destruction complex: GSK‐3β, β‐catenin, and adenomatous polyposis coli proteins in rat primary neurons. GSK‐3β formed a complex with δ‐catenin, and its inhibition resulted in increased δ‐catenin and β‐catenin expression levels. LY294002 and amyloid peptide, known activators of GSK‐3β signaling, reduced δ‐catenin expression levels. Furthermore, δ‐catenin immunoreactivity increased and protein turnover decreased when neurons were treated with proteasome inhibitors, suggesting that the stability of δ‐catenin, like that of β‐catenin, is regulated by proteasome‐mediated degradation. Coimmunoprecipitation experiments showed that δ‐catenin overexpression promoted GSK‐3β and β‐catenin interactions. Primary cortical neurons and PC12 cells expressing δ‐catenin treated with proteasome inhibitors showed increased ubiquitinated β‐catenin forms. Consistent with the hypothesis that δ‐catenin promotes the interaction of the destruction complex molecules, cycloheximide treatment of cells overexpressing δ‐catenin showed enhanced β‐catenin turnover. These studies identify δ‐catenin as a new member of the GSK‐3β signaling pathway and further suggest that δ‐catenin is potentially involved in facilitating the interaction, ubiquitination, and subsequent turnover of β‐catenin in neuronal cells. © 2010 Wiley‐Liss, Inc.     

Aluminum chloride does not facilitate deposition of human synthetic amyloid β1–42 peptide in the rat ventricular system of a short‐term infusion model

Recent data have demonstrated that a 39–43 amino acid peptide called β‐amyloid peptide (Aβ), which predominantly contains 42 residues (Aβ1–42), has a strong tendency to form insoluble aggregates and that the toxic effects of Aβ are based on its aggregation. In a previous study, we reported that infusion of 100 µg of human synthetic Aβ1–42 (sAβ1–42), which is a main component of diffuse plaques, into the lateral ventricle of the rat brain of a short‐term infusion model resulted in almost complete disappearance of sAβ1–42 aggregates from the ventricles by 28 days. In addition, aluminum is considered a potential etiological factor in Alzheimer's disease (AD). Neurotoxicity from excess brain exposure to aluminum has been documented from both clinical observations and animal experiments, although a direct relationship between aluminum and AD has yet to be clearly established. We therefore investigated the effects of sAβ1–42 aggregates with aluminum chloride (AlCl₃) in the ventricular system of the rat brain of a short‐term infusion model. At either 2 or 7 days following infusion, sAβ1–42 formed aggregates with AlCl₃ that spread throughout the entire ventricular system. However, sAβ1–42 aggregates with AlCl₃ had almost disappeared from the ventricles by 28 days, resulting in similarities with respect to the time‐course and the neuropathological changes observed in sAβ1–42 aggregation without AlCl₃. We herein report for the first time that considerable amounts of sAβ1–42 aggregates with AlCl₃ almost disappear from the rat ventricular system by 28 days post‐infusion.     

Characteristics of cerebral β amyloid deposition in four non-demented patients in their forties with a high apolipoprotein E ε4 allele frequency

Four autopsied brains from mentally normal patients aged 43–49 who had cerebral β amyloid deposition were examined. Three patients had breast cancer, and in one of these cases it was associated with brain metastasis and brain radiation therapy. One other case had pulmonary small cell carcinoma. In two patients, small β amyloid deposits were only found in the frontal cortex. In another two patients, β amyloid deposits were found in many cortical areas and the density of plaques was higher than in the former two patients. No β amyloid deposition was found in the cerebella, basal ganglia, or brain stem in any of the four patients. When examined with end-specific antisera for the C-terminal of amyloid β protein (Aβ), Aβ42 was predominant in the diffuse plaques and immunoreactions for Aβ40 varied among the patients. The N-terminal of Aβ was truncated in a subset of plaques. Tau- and phosphorylated tau-reactive fine neurites were only found in the entorhinal cortex of Case 3. The apoE genotype of these four patients were 3/4, 3/4, 4/4 and 3/3, and therefore, the ε4 allele frequency (50%) was as high as that in AD. Three out of four patients had at least one ε4 allele, a risk factor of AD. There is a possibility that these subjects might develop AD when in their seventies. It may take 30 years from the beginning of Aβ deposition to the clinical manifestation of dementia.     

Operational dissection of β‐amyloid cytopathic effects on cultured neurons

Alzheimer disease (AD) affects mainly people over the age of 65 years, suffering from different clinical symptoms such as progressive decline in memory, thinking, language, and learning capacity. The toxic role of β‐amyloid peptide (Aβ) has now shifted from insoluble Aβ fibrils to smaller, soluble oligomeric Aβ aggregates. The urgent need for efficient new therapies is high; robust models dissecting the physiopathological aspects of the disease are needed. We present here a model allowing study of four cytopathic effects of Aβ oligomers (AβO): oxidative stress, loss of synapses, disorganization of the neurite network, and cellular death. By generating a solution of AβO and playing on the concentration of and time of exposure to AβO, we have shown that it was possible to reproduce early effects (oxidative stress) and the long‐term development of structural alterations (death of neurons). We have shown that 1) all toxic events were linked to AβO according to a specific timing and pathway and 2) AβO were probably the key intermediates in AD pathogenesis. The present model, using Aβ peptide solution containing AβO, reproduced essential neuropathological features of AD; the effects involved were similar whatever the kind of neurons tested (cortical vs. hippocampal). By using a single system, it was possible to embrace all toxic mechanisms at defined times and concentrations, to study each involved pathway, and to study the effects of new molecules on the different neurotoxic pathways responsible for development of AD. © 2013 Wiley Periodicals, Inc.