Brains Of Tg2576 Mice Research Articles

A Comparison between Extract Products of Magnolia officinalis on Memory Impairment and Amyloidogenesis in a Transgenic Mouse Model of Alzheimer's Disease

The components of Magnolia officinalis have well known to act anti-inflammatory, anti-oxidative and neuroprotective activities. These efficacies have been sold many products as nutritional supplement extracted from bark of Magnolia officinalis. Thus, to assess and compare neuroprotective effect in the nutritional supplement (Magnolia ExtractTM, Health Freedom Nutrition LLC, USA) and our ethanol extract of Magnolia officinalis (BioLand LTD, Korea), we investigated memorial improving and anti-Alzheimer’s disease effects of extract products of Magnolia officinalis in a transgenic AD mice model. Oral pretreatment of two extract products of Magnolia officinalis (10 mg/kg/day in 0.05% ethanol) into drinking water for 3 months ameliorated memorial dysfunction and prevented Aβ accumulation in the brain of Tg2576 mice. In addition, extract products of Magnolia officinalis also decreased expression of β-site APP cleaving enzyme 1 (BACE1), amyloid precursor protein (APP) and its product, C99. Although both two extract products of Magnolia officinalis could show preventive effect of memorial dysfunction and Aβ accumulation, our ethanol extract of Magnolia officinalis (BioLand LTD, Korea) could be more effective than Magnolia ExtractTM (Health Freedom Nutrition LLC, USA). Therefore, our results showed that extract products of Magnolia officinalis were effective for prevention and treatment of AD through memorial improving and anti-amyloidogenic effects via down-regulating β-secretase activity, and neuroprotective efficacy of Magnolia extracts could be differed by cultivating area and manufacturing methods.

Toxoplasma gondii infection in the brain inhibits neuronal degeneration and learning and memory impairments in a murine model of Alzheimer's disease.

Immunosuppression is a characteristic feature of Toxoplasma gondii-infected murine hosts. The present study aimed to determine the effect of the immunosuppression induced by T. gondii infection on the pathogenesis and progression of Alzheimer's disease (AD) in Tg2576 AD mice. Mice were infected with a cyst-forming strain (ME49) of T. gondii, and levels of inflammatory mediators (IFN-γ and nitric oxide), anti-inflammatory cytokines (IL-10 and TGF-β), neuronal damage, and β-amyloid plaque deposition were examined in brain tissues and/or in BV-2 microglial cells. In addition, behavioral tests, including the water maze and Y-maze tests, were performed on T. gondii-infected and uninfected Tg2576 mice. Results revealed that whereas the level of IFN-γ was unchanged, the levels of anti-inflammatory cytokines were significantly higher in T. gondii-infected mice than in uninfected mice, and in BV-2 cells treated with T. gondii lysate antigen. Furthermore, nitrite production from primary cultured brain microglial cells and BV-2 cells was reduced by the addition of T. gondii lysate antigen (TLA), and β-amyloid plaque deposition in the cortex and hippocampus of Tg2576 mouse brains was remarkably lower in T. gondii-infected AD mice than in uninfected controls. In addition, water maze and Y-maze test results revealed retarded cognitive capacities in uninfected mice as compared with infected mice. These findings demonstrate the favorable effects of the immunosuppression induced by T. gondii infection on the pathogenesis and progression of AD in Tg2576 mice.

Inhibitory Effect of Ethanol Extract of Magnolia officinalis on Memory Impairment and Amyloidogenesis in a Transgenic Mouse Model of Alzheimer's Disease via Regulating β‐Secretase Activity

Alzheimer's disease (AD) is the most common form of dementia and is characterized by deposition of amyloid beta (Aβ) in the brain. The components of the herb Magnolia officinalis are known to have antiinflammatory, antioxidative and neuroprotective activities. In this study we investigated the effects of ethanol extract of M. officinalis on memory dysfunction and amyloidogenesis in a transgenic mouse model of AD. Oral pretreatment of ethanol extract of M. officinalis (10 mg/kg in 0.05% ethanol) into drinking water for 3 months inhibited memory impairment and Aβ deposition in the brain of Tg2576 mice. Ethanol extract of M. officinalis also decreased activity of β-secretase, cleaving Aβ from amyloid precursor protein (APP), and expression of β-site APP cleaving enzyme 1 (BACE1), APP and its product, C99. Our results showed that ethanol extract of M. officinalis effectively prevented memory impairment via down-regulating β-secretase activity.

BODIPY-Based Molecular Probe for Imaging of Cerebral β-Amyloid Plaques

We designed and synthesized a BODIPY-based probe (BAP-1) for the imaging of β-amyloid plaques in the brain. In binding experiments in vitro, BAP-1 showed excellent affinity for synthetic Aβ aggregates. β-Amyloid plaques in Tg2576 mouse brain were clearly visualized with BAP-1. In addition, the labeling of β-amyloid plaques was demonstrated in vivo in Tg2576 mice. These results suggest BAP-1 to be a useful fluorescent probe for the optical imaging of cerebral β-amyloid plaques in patients with Alzheimer's disease.

Passive Immunization against Pyroglutamate-3 Amyloid-β Reduces Plaque Burden in Alzheimer-Like Transgenic Mice: A Pilot Study

Background: N-terminally truncated and modified pyroglutamate-3 amyloid-β protein (pE3-Aβ) is present in most, if not all, cerebral plaque and vascular amyloid deposits in human Alzheimer’s disease (AD). pE3-Aβ deposition is also found in AD-like transgenic (tg) mouse brain, albeit in lesser quantities than general Aβ. pE3-Aβ resists degradation, is neurotoxic, and may act as a seed for Aβ aggregation. Objective: We sought to determine if pE3-Aβ removal by passive immunization with a highly specific monoclonal antibody (mAb) impacts pathogenesis in a mouse model of Alzheimer’s amyloidosis. Methods: APPswe/PS1ΔE9 tg mice were given weekly intraperitoneal injections of a new anti-pE3-Aβ mAb (mAb07/1) or PBS from 5.8 to 13.8 months of age (prevention) or from 23 to 24.7 months of age (therapeutic). Multiple forms of cerebral Aβ were quantified pathologically and biochemically. Gliosis and microhemorrhage were examined. Results: Chronic passive immunization with an anti-pE3-Aβ mAb significantly reduced total plaque deposition and appeared to lower gliosis in the hippocampus and cerebellum in both the prevention and therapeutic studies. Insoluble Aβ levels in hemibrain homogenates were not significantly different between immunized and control mice. Microhemorrhage was not observed with anti-pE3-Aβ immunotherapy. Conclusions: Selective removal of pE3-Aβ lowered general Aβ plaque deposition suggesting a pro-aggregation or seeding role for pE3-Aβ.

Analysis of differential plaque depositions in the brains of Tg2576 and Tg-APPswe/PS1dE9 transgenic mouse models of Alzheimer disease

Adequate assessment of plaque deposition levels in the brain of mouse models of Alzheimer disease (AD) is required in many core issues of studies on AD, including studies on the mechanisms underlying plaque pathogenesis, identification of cellular factors modifying plaque pathology, and developments of anti-AD drugs. The present study was undertaken to quantitatively evaluate plaque deposition patterns in the brains of the two popular AD models, Tg2576 and Tg-APPswe/PS1dE9 mice. Coronally-cut brain sections of Tg2576 and Tg-APPswe/PS1dE9 mice were prepared and plaque depositions were visualized by staining with anti-amyloid β peptides antibody. Microscopic images of plaque depositions in the prefrontal cortex, parietal cortex, piriform cortex and hippocampus were obtained and the number of plaques in each region was determined by a computer-aided image analysis method. A series of optical images representing a gradual increase of plaque deposition levels were selected in the four different brain regions and were assigned in each with a numerical grade of 1-6, where +1 was lowest and +6, highest, so that plaques per unit in mm2 increased "sigmoidally" over the grading scales. Analyzing plaque depositions using the photographic plaque reference panels and a computer-aid image analysis method, it was demonstrated that the brains of Tg2576 mice started to accumulate predominantly small plaques, while the brains of Tg-APPswe/PS1dE9 mice deposited relatively large plaques.

Grape Seed Polyphenolic Extract Specifically Decreases Aβ*56 in the Brains of Tg2576 Mice

Amyloid-β (Aβ) oligomers, found in the brains of Alzheimer's disease (AD) patients and transgenic mouse models of AD, cause synaptotoxicity and memory impairment. Grape seed polyphenolic extract (GSPE) inhibits Aβ oligomerization in vitro and attenuates cognitive impairment and AD-related neuropathology in the brains of transgenic mice. In the current study, GSPE was administered to Tg2576 mice for a period of five months. Treatment significantly decreased brain levels of Aβ*56, a 56-kDa Aβ oligomer previously shown to induce memory dysfunction in rodents, without changing the levels of transgenic amyloid-β protein precursor, monomeric Aβ, or other Aβ oligomers. These results thus provide the first demonstration that a safe and affordable intervention can lower the levels of a memory-impairing Aβ oligomer in vivo and strongly suggest that GSPE should be further tested as a potential prevention and/or therapy for AD.

Binding of Curcumin to Senile Plaques and Cerebral Amyloid Angiopathy in the Aged Brain of Various Animals and to Neurofibrillary Tangles in Alzheimer's Brain

The binding of curcumin to senile plaques (SPs) and cerebral amyloid angiopathy (CAA) was examined in the aged brain of various animal species and a human patient with Alzheimer's disease (AD), together with its binding to neurofibrillary tangles (NFTs). Brain sections were immunostained with anti-amyloid β protein 1-42 (Aβ42) and anti-amyloid β protein 1-40 (Aβ40) antibodies. These sections were also stained with alkaline Congo red, periodic acid-methenamine silver (PAM), and curcumin (0.009% curcumin solution) with or without formic acid pretreatment. The sections from the AD brain were also immunostained for anti-paired helical filament-tau (PHF-tau), and were stained with Gallyas silver for NFTs. Some SPs in the AD, monkey, dog, bear, and amyloid precursor protein transgenic mouse (APP Tg-mouse) brains contained congophilic materials, and were intensely positive for curcumin. In addition, curcumin labeled some diffuse SPs negative for Congo red in the AD, monkey, bear, and APP Tg-mouse brains. In all animals, CAA was intensely positive for both Congo red and curcumin. The specific curcumin staining activity was lost by formic acid pretreatment. In the AD brain, NFTs positive for PHF-tau and Gallyas silver were moderately stained with curcumin. These findings indicate that curcumin specifically binds to the aggregated Aβ molecules in various animals, and further to phosphorylated tau protein, probably according to its conformational nature.

Suppression of Amyloid β A11 Antibody Immunoreactivity by Vitamin C: POSSIBLE ROLE OF HEPARAN SULFATE OLIGOSACCHARIDES DERIVED FROM GLYPICAN-1 BY ASCORBATE-INDUCED, NITRIC OXIDE (NO)-CATALYZED DEGRADATION

Amyloid β (Aβ) is generated from the copper- and heparan sulfate (HS)-binding amyloid precursor protein (APP) by proteolytic processing. APP supports S-nitrosylation of the HS proteoglycan glypican-1 (Gpc-1). In the presence of ascorbate, there is NO-catalyzed release of anhydromannose (anMan)-containing oligosaccharides from Gpc-1-nitrosothiol. We investigated whether these oligosaccharides interact with Aβ during APP processing and plaque formation. anMan immunoreactivity was detected in amyloid plaques of Alzheimer (AD) and APP transgenic (Tg2576) mouse brains by immunofluorescence microscopy. APP/APP degradation products detected by antibodies to the C terminus of APP, but not Aβ oligomers detected by the anti-Aβ A11 antibody, colocalized with anMan immunoreactivity in Tg2576 fibroblasts. A 50-55-kDa anionic, sodium dodecyl sulfate-stable, anMan- and Aβ-immunoreactive species was obtained from Tg2576 fibroblasts using immunoprecipitation with anti-APP (C terminus). anMan-containing HS oligo- and disaccharide preparations modulated or suppressed A11 immunoreactivity and oligomerization of Aβ42 peptide in an in vitro assay. A11 immunoreactivity increased in Tg2576 fibroblasts when Gpc-1 autoprocessing was inhibited by 3-β[2(diethylamino)ethoxy]androst-5-en-17-one (U18666A) and decreased when Gpc-1 autoprocessing was stimulated by ascorbate. Neither overexpression of Gpc-1 in Tg2576 fibroblasts nor addition of copper ion and NO donor to hippocampal slices from 3xTg-AD mice affected A11 immunoreactivity levels. However, A11 immunoreactivity was greatly suppressed by the subsequent addition of ascorbate. We speculate that temporary interaction between the Aβ domain and small, anMan-containing oligosaccharides may preclude formation of toxic Aβ oligomers. A portion of the oligosaccharides are co-secreted with the Aβ peptides and deposited in plaques. These results support the notion that an inadequate supply of vitamin C could contribute to late onset AD in humans.

Restoration of home cage activity in Tg2576 mice by immunotherapy with the Ab-oligomer selective antibody A-887755

endogenous neurogenesis occurs, we hypothesized that the neurotrophic factors may improve cognition by increasing endogenous neurogenesis. Therefore, to test this hypothesis, we assessed whether stem cell transplants improved cognition by increasing neurogenesis in the brain. Methods: To test this hypothesis, wild-type neural stem cells derived from Tg2576 X B6SJL/F1 mice were stereotactically injected into the brains of Tg2576 mice (15 mo), followed by BrdU injections. After one month, mice behavior was assessed using various tasks (Morris watermaze, novel object, novel odor task). Mice were subsequently sacrificed. We examined the effect of stem cells on pathology and neurogenesis using stereology. Results: Stem cell transplants in Tg2576 mice rescued cognitive deficits observed in these animals at 15 mo. as assessed with various behavioral tasks. The improvement in cognitive deficits was correlated with neurogenesis in the brain. Conclusions: Here we show that stem cell transplants in AD transgenic mice rescue the cognitive deficits and that this is associated with an increase in neurogenesis.

Different distribution of soluble beta-amyloid assemblies in the Tg2576 mouse brain and Alzheimer disease autopsy brain

Different distribution of soluble beta-amyloid assemblies in the Tg2576 mouse brain and Alzheimer disease autopsy brain

O4‐08‐08: Progranulin gene therapy prevents plaque formation and synapse loss in a rodent model of AD

Progranulin (PGRN) is a multifunctional secreted protein expressed primarily by neurons and microglia. Evidence suggests that PGRN may function as a neurotrophic factor and may be essential for long-term neuronal survival, actively protecting neuronal cells from premature death. It also appears to be important for regulating neuroinflammation, consistent with its localization in microglial cells. Loss-of-function mutations in the PGRN gene have been identified as the cause of some forms of fronto-temporal dementia and mutations in PGRN have also been associated with AD and Lewy Body Dementia. Upregulated expression of PGRN has been reported in numerous neurodegenerative diseases involving microglial activation, including motor neuron disease, lysosomal storage disease, and Alzheimer's disease. In light of its role as a neurotrophic factor, this upregulation may represent an attempt to repair damage and protect cells. Here, we present data describing the effects of ND-602, a proprietary construct designed to target PGRN synthesis. The Tg2576 mouse model of AD expresses the Swedish mutation of APP (APPK67ON,M671L) at high levels under the control of the hamster prion protein promoter. These mice develop a progressive, age-related deposition in the form of amyloid plaques in the cortex and hippocampus. A rapid increase in insoluble Aß occurs around 6 months of age and plaques begin to form around 8-12 months of age, resulting in the development of memory deficits. At 8 months of age, Tg2576 mice received unilateral intracerebral injection of either a progranulin-expressing lentiviral vector (ND-602), or a control vector expressing green fluorescent protein (GFP), into the left dorsal hippocampus. At 12 months of age, animals were sacrificed and the brains assessed for pathology. ND-602 was capable of elevating PGRN expression in the dorsal hippocampus, frontal cortex, and entorhinal cortex. Elevations in PGRN expression were associated with increased neprilysin expression, reduced plaque burden, decreased neuroinflammation, and preservation of synapses. Together, the data reported here indicate that ND-602 treatment regulates Aß, a key causal factor in AD, by reducing tissue levels in Tg2576 mice as well as plaque deposition. Thus, ND-602, by targeting PGRN, may represent a potential therapy designed to slow or halt disease progression in AD. Hippocampal β-amyloid burden following lentiviral delivery. (A) Representative photomicrographs depicting β-amyloid immunolabeling in the hippocampal dentate gyrus of a Tg2576 mouse brain 6 months following unilateral intracerebral administration of either LV-GFP, or LV-PGRN (ND-602). (B) Amyloid burden was significantly reduced in the ipsilateral dentate gyrus of those animals receiving ND-602 administration. Each bar represents the mean (± S.E.M.) (n = 10) amyloid burden (% area) measured across 4 coronal sections. ∗∗ sig. diff. from GFP-treated controls, p<0.001.

In vivo detection of amyloid β deposition using 19F magnetic resonance imaging with a 19F-containing curcumin derivative in a mouse model of Alzheimer's disease

Amyloid β (Aβ) deposition in the brain is considered the initiating event in the progression of Alzheimer's disease (AD). Amyloid imaging is widely studied in diagnosing AD and evaluating the disease stage, with considerable advances achieved in recent years. We have developed a novel ¹⁹F-containing curcumin derivative (named FMeC1) as a potential imaging agent. This compound can exist in equilibrium between keto and enol tautomers, with the enol form able to bind Aβ aggregates while the keto form cannot. This study investigated whether FMeC1 is suitable as a ¹⁹F magnetic resonance imaging (MRI) probe to detect Aβ deposition in the Tg2576 mouse, a model of AD. In ¹⁹F nuclear magnetic resonance (NMR) spectra obtained from the whole head, a delayed decreased rate of F ¹⁹F signal was observed in Tg2576 mice that were peripherally injected with FMeC1 in comparison to wild-type mice. Furthermore, ¹⁹F MRI displayed remarkable levels of ¹⁹F signal in the brain of Tg2576 mice after the injection of FMeC1. Histological analysis of FMeC1-injected mouse brain showed penetration of the compound across the blood-brain barrier and binding to Aβ plaques in peripherally injected Tg2576 mice. Moreover, the distribution of Aβ deposits in Tg2576 mice was in accordance with the region of the brain in which the ¹⁹F signal was imaged. FMeC1 also exhibited an affinity for senile plaques in human brain sections. These findings suggest the usefulness of FMeC1 as a ¹⁹F MRI probe for the detection of amyloid deposition in the brain. Furthermore, the properties of FMeC1 could form the basis for further novel amyloid imaging probes.

Chronic exercise ameliorates the neuroinflammation in mice carrying NSE/htau23

The objective of the present study was to investigate whether chronic endurance exercise attenuates the neuroinflammation in the brain of mice with NSE/htau23. In this study, the tau-transgenic (Tg) mouse, Tg- NSE/htau23, which over expresses human Tau23 in its brain, was subjected to chronic exercise for 3 months, from 16 months of age. The brains of Tg mice exhibited increased immunoreactivity and active morphological changes in GFAP (astrocyte marker) and MAC-1 (microglia marker) expression in an age-dependent manner. To identify the effects of chronic exercise on gliosis, the exercised Tg mice groups were treadmill run at a speed of 12 m/min (intermediate exercise group) or 19 m/min (high exercise group) for 1 h/day and 5 days/week during the 3 month period. The neuroinflammatory response characterized by activated astroglia and microglia was significantly repressed in the exercised Tg mice in an exercise intensity-dependent manner. In parallel, chronic exercise in Tg mice reduced the increased expression of TNF-α, IL-6, IL-1β, COX-2, and iNOS. Consistently with these changes, the levels of phospho-p38 and phospho-ERK were markedly downregulated in the brain of Tg mice after exercise. In addition, nuclear NF-κB activity was profoundly reduced after chronic exercise in an exercise intensity-dependent manner. These findings suggest that chronic endurance exercise may alleviate neuroinflammation in the Tau pathology of Alzheimer’s disease.

Synthesis and Evaluation of 11C-Labeled Imidazo[2,1-b]benzothiazoles (IBTs) as PET Tracers for Imaging β-Amyloid Plaques in Alzheimer’s Disease

We report a novel series of (11)C-labeled imidazo[2,1-b]benzothiazoles (IBTs) as tracers for imaging of cerebral β-amyloid (Aβ) deposits in patients with Alzheimer's disease (AD) by means of positron emission tomography (PET). From a series of 11 compounds, candidates were identified to have a high binding affinity for Aβ. Selected compounds were prepared as O- or N-[(11)C]methyl derivatives and shown to have a high initial brain uptake in wild-type mice (range 1.9-9.2% I.D./g at 5 min). 2-(p-[(11)C]Methylaminophenyl)-7-methoxyimidazo[2,1-b] benzothiazole ([(11)C]5) was identified as a lead based on the combined favorable properties of high initial brain uptake, rapid clearance from normal brain, and high in vitro affinity for Aβ(1-40) (K(i) = 3.5 nM) and Aβ(1-42) (5.8 nM), which were superior to the Pittsburgh compound B (1a). In an APP/PS1 mouse model of AD (Tg), we demonstrate a specific uptake of [(11)C]5 in Aβ-containing telencephalic brain regions by means of small-animal PET that was confirmed by regional brain biodistribution, ex vivo autoradiography, and immunohistochemistry. Analysis of brain sections of Tg mice receiving a single bolus injection of [(11)C]5 and [(3)H]1a together revealed that the tracers bind to Aβ plaques in the brain of Tg mice in a comparable pattern. Taken together, these data suggest that IBTs represent useful PET imaging agents for high-sensitivity detection of Aβ plaques.

PKC ε Activation Prevents Synaptic Loss, Aβ Elevation, and Cognitive Deficits in Alzheimer's Disease Transgenic Mice

Among the pathologic hallmarks of Alzheimer's disease (AD) neurodegeneration, only synaptic loss in the brains of AD patients closely correlates with the degree of dementia in vivo. Here, we describe a molecular basis for this AD loss of synapses: pathological reduction of synaptogenic PKC isozymes and their downstream synaptogenic substrates, such as brain-derived neurotrophic factor. This reduction, particularly of PKC α and ε, occurs in association with elevation of soluble β amyloid protein (Aβ), but before the appearance of the amyloid plaques or neuronal loss in the Tg2576 AD transgenic mouse strain. Conversely, treatment of the Tg2576 mouse brain with the PKC activator, bryostatin-1, restores normal or supranormal levels of PKC α and ε, reduces the level of soluble Aβ, prevents and/or reverses the loss of hippocampal synapses, and prevents the memory impairment observed at 5 months postpartum. Similarly, the PKC ε-specific activator, DCP-LA, effectively prevents synaptic loss, amyloid plaques, and cognitive deficits (also prevented by bryostatin-1) in the much more rapidly progressing 5XFAD transgenic strain. These results suggest that synaptic loss and the resulting cognitive deficits depend on the balance between the lowering effects of Aβ on PKC α and ε versus the lowering effects of PKC on Aβ in AD transgenic mice.

Downregulation of CREB expression in Alzheimer's brain and in Aβ-treated rat hippocampal neurons

BackgroundOxidative stress plays an important role in neuronal dysfunction and neuron loss in Alzheimer's brain. Previous studies have reported downregulation of CREB-mediated transcription by oxidative stress and Aβ. The promoter for CREB itself contains cyclic AMP response elements. Therefore, we examined the expression of CREB in the hippocampal neurons of Tg2576 mice, AD post-mortem brain and in cultured rat hippocampal neurons exposed to Aβ aggregates.ResultsLaser Capture Microdissection of hippocampal neurons from Tg2576 mouse brain revealed decreases in the mRNA levels of CREB and its target, BDNF. Immunohistochemical analysis of Tg2576 mouse brain showed decreases in CREB levels in hippocampus and cortex. Markers of oxidative stress were detected in transgenic mouse brain and decreased CREB staining was observed in regions showing abundance of astrocytes. There was also an inverse correlation between SDS-extracted Aβ and CREB protein levels in Alzheimer's post-mortem hippocampal samples. The levels of CREB-regulated BDNF and BIRC3, a caspase inhibitor, decreased and the active cleaved form of caspase-9, a marker for the intrinsic pathway of apoptosis, was elevated in these samples. Exposure of rat primary hippocampal neurons to Aβ fibrils decreased CREB promoter activity. Decrease in CREB mRNA levels in Aβ-treated neurons was reversed by the antioxidant, N-acetyl cysteine. Overexpression of CREB by adenoviral transduction led to significant protection against Aβ-induced neuronal apoptosis.ConclusionsOur findings suggest that chronic downregulation of CREB-mediated transcription results in decrease of CREB content in the hippocampal neurons of AD brain which may contribute to exacerbation of disease progression.

β‐Secretase inhibitor GRL‐8234 rescues age‐related cognitive decline in APP transgenic mice

Alzheimer disease is intimately linked to an excess amount of amyloid-β (Aβ) in the brain. Thus, therapeutic inhibition of Aβ production is an attractive clinical approach to treat this disease. Here we provide the first direct experimental evidence that the treatment of Tg2576 transgenic mice with an inhibitor of β-secretase, GRL-8234, rescues the age-related cognitive decline. We demonstrated that the injected GRL-8234 effectively enters the brain and rapidly decreases soluble Aβ in the brain of Tg2576 mice. The rescue of cognition, which was observed only after long-term inhibitor treatment ranging from 5 to 7.5 mo, was associated with a decrease of brain amyloid-β plaque load. We also found no accumulation of amyloid-β precursor protein after several months of inhibitor treatment. These observations substantiate the idea that Aβ accumulation plays a major role in the cognitive decline of Tg2576 mice and support the concept of Aβ reduction therapy as a treatment of AD.

SCFFbx2‐E3‐ligase‐mediated degradation of BACE1 attenuates Alzheimer’s disease amyloidosis and improves synaptic function

BACE1 (β-secretase) plays a central role in the β-amyloidogenesis of Alzheimer's disease (AD). The ubiquitin-proteasome system, a major intracellular protein quality control system, has been implicated recently in BACE1 metabolism. We report that the SCF(Fbx2) -E3 ligase is involved in the binding and ubiquitination of BACE1 via its Trp 280 residue of F-box-associated domain. Physiologically, we found that Fbx2 was expressed in various intracellular organelles in brain neurons and that BACE1 is colocalized with Fbx2 and the amyloid precursor protein (APP), mainly at the early endosome and endoplasmic reticulum. The former are believed to be the major intracellular compartments where the APP is cleaved by BACE1 and β-amyloid is produced. Importantly, we found that overexpression of Fbx2 in the primary cortical and hippocampal neurons derived from Tg2576 transgenic mice significantly promoted BACE1 degradation and reduced β-amyloid production. In the search for specific endogenous modulators of Fbx2 expression, we found that PPARγ coactivator-1α (PGC-1α) was capable of promoting the degradation of BACE1 through a mechanism involving Fbx2 gene expression. Interestingly, we found that the expression of both Fbx2 and PGC-1α was significantly decreased in the brains of aging Tg2576 mice. Our in vivo studies using a mouse model of AD revealed that exogenous adenoviral Fbx2 expression in the brain significantly decreased BACE1 protein levels and activity, coincidentally reducing β-amyloid levels and rescuing synaptic deficits. Our study is the first to suggest that promoting Fbx2 in the brain may represent a novel strategy for the treatment of AD.

Aβ Accelerates the Spatiotemporal Progression of Tau Pathology and Augments Tau Amyloidosis in an Alzheimer Mouse Model

Senile plaques formed by β-amyloid peptides (Aβ) and neurofibrillary tangles (NFTs) formed by hyperphosphorylated tau, a microtubule-associated protein, are the hallmark lesions of Alzheimer's disease (AD) in addition to loss of neurons. While several transgenic (Tg) mouse models have recapitulated aspects of AD-like Aβ and tau pathologies, a spatiotemporal mapping paradigm for progressive NFT accumulation is urgently needed to stage disease progression in AD mouse models. Braak and co-workers developed an effective and widely used NFT staging paradigm for human AD brains. The creation of a Braak-like spatiotemporal staging scheme for tau pathology in mouse models would facilitate mechanistic studies of AD-like tau pathology. Such a scheme would also enhance the reproducibility of preclinical AD therapeutic studies. Thus, we developed a novel murine model of Aβ and tau pathologies and devised a spatiotemporal scheme to stage the emergence and accumulation of NFTs with advancing age. Notably, the development of NFTs followed a spatiotemporal Braak-like pattern similar to that observed in authentic AD. More significantly, the presence of Aβ accelerated NFT formation and enhanced tau amyloidosis; however, tau pathology did not have the same effect on Aβ pathology. This novel NFT staging scheme provides new insights into the mechanisms of tau pathobiology, and we speculate that this scheme will prove useful for other basic and translational studies of AD mouse models.