Early-onset subicular microvascular amyloid and neuroinflammation correlate with behavioral deficits in vasculotropic mutant amyloid beta-protein precursor transgenic mice

Cerebral microvascular amyloid beta protein (Abeta) deposition and associated neuroinflammation are increasingly recognized as an important component leading to cognitive impairment in Alzheimer's disease and related cerebral amyloid angiopathy (CAA) disorders. Transgenic mice expressing the vasculotropic Dutch/Iowa (E693Q/D694N) mutant human Abeta precursor protein in brain (Tg-SwDI) accumulate abundant cerebral microvascular fibrillar amyloid deposits exhibiting robust neuroinflammation. In the present study, we sought to determine if the unique amyloid pathology of Tg-SwDI mice was associated with deficits in behavioral performance. Behavioral performance tests that assessed a variety of psychological functions, including overall activity, motor ability, balance and strength, anxiety, impulsivity, and learning were conducted on homozygous Tg-SwDI mice and similarly aged wild-type C57Bl/6 mice. Our results indicate that Tg-SwDI mice were impaired in the performance of the Barnes maze learning and memory task at 3, 9, and 12 months of age. While more widespread cerebral microvascular Abeta pathology was evident in older animals, the evaluation of the Abeta pathology in the 3 months old transgenic animals revealed specific accumulation of microvascular amyloid and markedly elevated numbers of reactive astrocytes and activated microglia restricted to the subiculum. These findings indicate that early-onset accumulation of subicular microvascular amyloid and accompanying neuroinflammation correlates with impaired performance in the learning and memory task in Tg-SwDI mice.     

Correlation between cognitive deficits and Abeta deposits in transgenic APP+PS1 mice

Doubly transgenic mAPP+mPS1 mice (15-16 months) had impaired cognitive function in a spatial learning and memory task that combined features of a water maze and a radial arm maze. Nontransgenic mice learned a new platform location each day during 4 consecutive acquisition trials, and exhibited memory for this location in a retention trial administered 30 min later. In contrast, transgenic mice were, on average, unable to improve their performance in finding the hidden platform over trials. The cognitive performance of individual mice within the transgenic group were inversely related to the amount of Abeta deposited in the frontal cortex and hippocampus. These findings imply that mAPP+mPS1 transgenic mice develop deficits in cognitive ability as Abeta deposits increase. These data argue that radial arm water maze testing of doubly transgenic mice may be a useful behavioral endpoint in evaluating the functional consequences of potential AD therapies, especially those designed to reduce Abeta load.     

Impaired synaptic plasticity and learning in aged amyloid precursor protein transgenic mice

We investigated synaptic communication and plasticity in hippocampal slices from mice overexpressing mutated 695-amino-acid human amyloid precursor protein (APP695SWE), which show behavioral and histopathological abnormalities simulating Alzheimer's disease. Although aged APP transgenic mice exhibit normal fast synaptic transmission and short term plasticity, they are severely impaired in in-vitro and in-vivo long-term potentiation (LTP) in both the CA1 and dentate gyrus regions of the hippocampus. The LTP deficit was correlated with impaired performance in a spatial working memory task in aged transgenics. These deficits are accompanied by minimal or no loss of presynaptic or postsynaptic elementary structural elements in the hippocampus, suggesting that impairments in functional synaptic plasticity may underlie some of the cognitive deficits in these mice and, possibly, in Alzheimer's patients.     

Deletion of the fcgamma receptor IIb in thymic stromal lymphopoietin transgenic mice aggravates membranoproliferative glomerulonephritis

Engagement of immunoglobulin-binding receptors (FcgammaR) on leukocytes and other cell types is one means by which immunoglobulins and immune complexes activate effector cells. One of these FcgammaRs, FcgammaRIIb, is thought to contribute to protection from autoimmune disease by down-regulation of B-cell responsiveness and myeloid cell activation. We assessed the role of FcgammaRIIb in a mouse model of cryoglobulin-associated membranoproliferative glomerulonephritis induced by overexpression of thymic stromal lymphopoietin (TSLP). TSLP transgenic mice were crossbred with animals deficient for FcgammaRIIb on the same genetic background (C57BL/6). Renal pathology was assessed in female and male animals (wild-type, FcgammaRIIb-/-, TSLP transgenic, and combined TSLP transgenic/FcgammaRIIb-/- mice) after 50 and 120 days, respectively. FcgammaRIIb-/- mice had no significant renal pathology, whereas overexpression of TSLP induced a membranoproliferative glomerulonephritis, as previously established. TSLP transgenic FcgammaRIIb-/- mice appeared sick with increased mortality. Kidney function was significantly impaired in male mice corresponding to aggravated glomerular pathology with increases in glomerular matrix and cellularity. This resulted from both a large influx of infiltrating macrophages and increased cellular proliferation. These results emphasize the important role of FcgammaRIIb in regulating immune responses and suggest that modulation of Fcgamma receptor activation or expression may be a useful therapeutic approach for treating glomerular diseases.     

Lamotrigine attenuates deficits in synaptic plasticity and accumulation of amyloid plaques in APP/PS1 transgenic mice

Hyperactivity and its compensatory mechanisms may causally contribute to synaptic and cognitive deficits in Alzheimer's disease (AD). Blocking the overexcitation of the neural network, with levetiracetam (LEV), a sodium channel blocker applied in the treatment of epilepsy, prevented synaptic and cognitive deficits in human amyloid precursor protein (APP) transgenic mice. This study has brought the potential use of antiepileptic drugs (AEDs) in AD therapy. We showed that the chronic treatment with lamotrigine (LTG), a broad-spectrum AED, suppressed abnormal spike activity, prevented the loss of spines, synaptophysin immunoreactivity, and neurons, and thus attenuated the deficits in synaptic plasticity and learning and memory in APP and presenilin 1 (PS1) mice, which express human mutant APP and PS1. In contrast with LEV, which failed to reduce the generation of amyloid β, the chronic LTG treatment reduced the cleavage of APP by β-secretase and thus the numbers and the size of amyloid plaques in the brains of APP and PS1 mice. Moreover, the levels of brain-derived neurotrophic growth factor (BDNF) and nerve growth factor (NGF) were enhanced in the brains of APP and PS1 mice by the chronic LTG treatment. Therefore, these observations demonstrate that LTG attenuates AD pathology through multiple mechanisms, including modulation of abnormal network activity, reduction of the generation of amyloid beta and upregulation of BDNF and NGF.     

Passive immunotherapy against Abeta in aged APP-transgenic mice reverses cognitive deficits and depletes parenchymal amyloid deposits in spite of increased vascular amyloid and microhemorrhage

BACKGROUND: Anti-Abeta immunotherapy in transgenic mice reduces both diffuse and compact amyloid deposits, improves memory function and clears early-stage phospho-tau aggregates. As most Alzheimer disease cases occur well past midlife, the current study examined adoptive transfer of anti-Abeta antibodies to 19- and 23-month old APP-transgenic mice. METHODS: We investigated the effects of weekly anti-Abeta antibody treatment on radial-arm water-maze performance, parenchymal and vascular amyloid loads, and the presence of microhemorrhage in the brain. 19-month-old mice were treated for 1, 2 or 3 months while 23-month-old mice were treated for 5 months. Only the 23-month-old mice were subject to radial-arm water-maze testing. RESULTS: After 3 months of weekly injections, this passive immunization protocol completely reversed learning and memory deficits in these mice, a benefit that was undiminished after 5 months of treatment. Dramatic reductions of diffuse Abeta immunostaining and parenchymal Congophilic amyloid deposits were observed after five months, indicating that even well-established amyloid deposits are susceptible to immunotherapy. However, cerebral amyloid angiopathy increased substantially with immunotherapy, and some deposits were associated with microhemorrhage. Reanalysis of results collected from an earlier time-course study demonstrated that these increases in vascular deposits were dependent on the duration of immunotherapy. CONCLUSIONS: The cognitive benefits of passive immunotherapy persist in spite of the presence of vascular amyloid and small hemorrhages. These data suggest that clinical trials evaluating such treatments will require precautions to minimize potential adverse events associated with microhemorrhage.     

Passive immunotherapy against Aβ in aged APP-transgenic mice reverses cognitive deficits and depletes parenchymal amyloid deposits in spite of increased vascular amyloid and microhemorrhage

Background  

Anti-Aβ immunotherapy in transgenic mice reduces both diffuse and compact amyloid deposits, improves memory function and clears early-stage phospho-tau aggregates. As most Alzheimer disease cases occur well past midlife, the current study examined adoptive transfer of anti-Aβ antibodies to 19- and 23-month old APP-transgenic mice.     

Lack of mutagenicity of levofloxacin in lacZ transgenic mice

The mutagenic effects of levofloxacin in lacZ transgenicmice(Muta^TMMouse) have been investigated. Male Muta^TMMouse micewere administered levofloxacin i.p. at a dose of 300 or 600mg/kg. The higher dose corresponded to half the LD50 of thecompound in ddY strain mice. The mutant frequencies in the bonemarrow, liver (day 10 only), testis and sperm were examinedby the positive selection method for lacZ mutations on days1 and 10 after treatment Levofloxacin did not induce any statisticallysignificant increase in mutant frequency in any of the examinedtissues at either dose level or at either sampling time. Themutant frequency increases over the spontaneous values in thebone marrow, liver, testis and sperm were 1.0- to 1.2-fold,0.9-fold, 0.5- to 1.0-fold and 0.9- to 13-fold respectively.N-Ethyl-N-nitrosourea (100 mg/kg as a positive control), onthe other hand, induced significant increases in mutant frequenciesin both somatic cells (bone marrow and liver) and germ cells(testis and sperm) on day 10 after treatment. The mutagenicpotency for ENU was bone marrow >> liver testis sperm(50.1-fold, 3.4-fold, 2.9-fold and 23-fold respectively overthe spontaneous values). Levofloxacin was not mutagenic in thelacZ transgenic mice under the present experimental conditions. ¹To whom correspondence should be addressed. Tel: +81 3 5696 8294; Fax: +81 3 5696 8335; Email: itohsudk{at}daiichipharm.co.jp     

转铁蛋白受体1对淀粉样蛋白前体/早老素1转基因小鼠神经元的保护作用

目的 探讨转铁蛋白受体1(TfR1)在淀粉样蛋白前体（APP）/早老素1（PS1）转基因小鼠脑内异常表达情况及其对阿尔茨海默病（AD）神经元的保护作用。 方法 首先,利用免疫荧光及Western blotting技术检测出生后1月（P1M）至P12M各发育时间点,APP/PS1转基因小鼠与野生型小鼠大脑TfR1的表达情况;其次,取APP/PS1转基因与野生型新生小鼠原代海马神经元培养,培养12 d后利用TfR1 shRNA质粒干扰TfR1基因的表达,利用Western blotting技术检测干扰后细胞TfR1的表达变化;ELISA技术检测TfR1干扰前后细胞β-淀粉样蛋白(Aβ)_1-42的分泌量;利用微管相关蛋白2(MAP2)标记神经元突起,观察TfR1干扰前、后神经元突起的生长变化;最后,利用FM1-43染色观察由TfR1介导的轴质运输中囊泡的运输情况。 结果 在APP/PS1转基因小鼠生长发育过程中,随着年龄的增长TfR1的表达呈现先增加后减少的趋势,在P6M之后明显降低,且与对照组相比差异有显著性;TfR1 shRNA 干扰后可以使原代神经元细胞内TfR1基因沉默,使其突起明显变细、变长并影响囊泡的运输。与对照组相比,TfR1基因在APP/PS1转基因小鼠原代神经元中表达量减少,荧光减弱。 结论 APP、PS1基因突变可导致TfR1的表达下降;APP/PS1转基因小鼠原代神经元经TfR1 shRNA干扰Aβ_1-42分泌量增多,影响神经元突起的生长,使轴质运输速率减慢,囊泡的活动减缓,加重AD病情。故TfR1的表达可以对神经元起到保护作用。     

Dantrolene ameliorates cognitive decline and neuropathology in Alzheimer triple transgenic mice

Disruption of intracellular calcium homeostasis via abnormal and excessive activation of ryanodine receptors plays an important role in the neuropathology of Alzheimer's disease. We investigated the therapeutic effect of dantrolene, a ryanodine receptor antagonist, on cognitive dysfunction and neuropathology in the triple transgenic Alzheimer mouse model (3xTg-AD). 3xTg-AD mice were treated with dantrolene from 2 to 13 months of age. Learning and memory were measured with the Morris Water Maze at 6, 10, and 13 months of age. Amyloid and tau neuropathology and biomarkers for synaptic dysfunction and neurodegeneration were examined in the brain using immunoblotting or immunohistochemistry. Dantrolene treatment for 11 months significantly reduced both memory deficits and amyloid plaque load in the hippocampus in 13-month-old 3xTg-AD mice. Dantrolene treatment, however, had no effect on phosphorylated tau, phosphorylated or total GSK-3β, synaptic markers, or mitochondrial or cytosolic cytochrome C. Our results suggest that dantrolene significantly improves cognition in a murine model of Alzheimer's disease and is associated with a reduction in amyloid plaque burden, forming the basis for a novel therapeutic approach for Alzheimer's disease.     

Lashley maze learning deficits in NZB mice.

In a prior study we found excellent Lashley III maze learning in BXSB mice and poor learning in NZB mice, despite the fact that both strains are autoimmune and develop cortical ectopias. This prompted us to examine NZB Lashley maze performance in detail, including comparisons to other strains and attempts to improve performance by giving additional trials with or without additional intramaze visual cues. In conventional Lashley testing (10 trials), RF mice (non-autoimmune and nonectopic) and BXSBs performed well in the Lashley maze. They had high learning indices and few errors. NZB mice performed poorly, with low learning indices and many errors. Even with additional trials or additional trials plus intramaze cues, NZB performance remained poor. The number of backward and forward errors stayed high; learning indices were low. Since both BXSB and NZB mice develop autoimmune disorders and cortical ectopias, it is unlikely that differential Lashley performance is the result of the presence of these phenomena. NZB mice are known to have alterations in their hippocampal morphology, and this is a possible mediator of the Lashley deficit.     

Detecting spatial memory deficits beyond blindness in tg2576 Alzheimer mice

The retinal degeneration Pde6b^rd1 (rd) mutation can be a major pitfall in behavioral studies using tg2576 mice bred on a B6:SJL genetic background, 1 of the most widely used models of Alzheimer's disease. After a pilot study in wild type mice, performance of 8- and 16-month-old tg2576 mice were assessed in several behavioral tasks with the challenge of selecting 1 or more task(s) showing robust memory deficits on this genetic background. Water maze acquisition was impossible in rd homozygotes, whereas Y-maze alternation, object recognition, and olfactory discrimination were unaffected by both the transgene and the rd mutation. Spatial memory retention of 8- and 16-month-old tg2576 mice, however, was dramatically affected independently of the rd mutation when mice had to recognize a spatial configuration of objects or to perform the Barnes maze. Thus, the latter tasks appear extremely useful to evaluate spatial memory deficits and to test cognitive therapies in tg2576 mice and other mouse models bred on a background susceptible to visual impairment.     

Differential regulation of toll-like receptor mRNAs in amyloid plaque-associated brain tissue of aged APP23 transgenic mice

Alzheimer's disease (AD) is characterized by the pathological deposition of amyloid-β protein in the aged brain. Inefficient clearance of amyloid-β from brain tissue is believed to play a major role in the pathogenesis of these deposits. Since amyloid-β clearance likely involves activation of microglial cells via toll-like receptors and since these receptors and their signaling pathways are regarded as potential therapeutic targets, we have studied the expression of toll-like receptor (tlr) mRNAs in an animal model of AD (APP23 transgenic mice). Laser microdissection was used to harvest plaques, tissue surrounding plaques and plaque-free tissue from cortex of aged APP23 transgenic mice and age-matched controls. Real-time RT-PCR was employed to quantify expression levels of different tlr mRNAs in these tissues. This revealed a strong upregulation of tlr2, tlr4, tlr5, tlr7 and tlr9 mRNAs in plaque material compared to plaque-free tissue. In contrast, tlr3 was not significantly upregulated. Plaque-free tissue did not show an increased expression of any tlr mRNAs compared to age-matched control mice. Double-immunofluorescence for TLR2 and the microglial marker Iba1 was used to demonstrate localization of TLR2 on plaque-associated microglia. Taken together, these data show a strong upregulation of mRNAs encoding surface TLRs in plaque-associated brain tissue of aged APP23 transgenic mice. Since TLR-upregulation is restricted to plaques, modifying TLR-signaling may be a promising therapeutic strategy for plaque removal.     

Altered navigational strategy use and visuospatial deficits in hAPP transgenic mice

Navigation deficits are prominent in Alzheimer's disease (AD) patients and transgenic mice expressing familial AD-mutant hAPP and A beta peptides. To determine the impact of strategy use on these deficits, we assessed hAPP and nontransgenic mice in a cross maze that can be solved by allocentric (world-based) or egocentric (self-based) strategies. Most nontransgenic mice used allocentric strategies, whereas half of hAPP mice were egocentric. At 3 months, all mice learned the cross maze rapidly; at 6 months, only allocentric hAPP mice were impaired. At 3 and 6 months, hAPP mice had reduced hippocampal Fos expression, which correlated with cross maze learning in older mice. Striatal pCREB expression was unaltered in hAPP mice, suggesting striatal sparing. We conclude that egocentric strategy use may be an earlier indicator of hAPP/A beta-induced hippocampal impairment than spatial learning deficits. Persistent use of allocentric strategies when egocentric strategies are available is maladaptive when there is hippocampal damage. Interventions promoting flexibility in selecting learning strategies might help circumvent otherwise debilitating navigational deficits caused by AD-related hippocampal dysfunction.     

Age-related amyloid beta deposition in transgenic mice overexpressing both Alzheimer mutant presenilin 1 and amyloid beta precursor protein Swedish mutant is not associated with global neuronal loss

To analyze the relationship between the deposition of amyloid beta peptides (Abeta) and neuronal loss in transgenic models of Alzheimer's disease (AD), we examined the frontal neocortex (Fc) and CA1 portion of hippocampus (CA1) in PSAPP mice doubly expressing AD-associated mutant presenilin 1 (PS1) and Swedish-type mutant beta amyloid precursor protein (APPsw) by morphometry of Abeta burden and neuronal counts. Deposition of Abeta was detected as early as 3 months of age in the Fc and CA1 of PSAPP mice and progressed to cover 28.3% of the superior frontal cortex and 18.4% of CA1 at 12 months: approximately 20- (Fc) and approximately 40- (CA1) fold greater deposition than in APPsw mice. There was no significant difference in neuronal counts in either CA1 or the frontal cortex between nontransgenic (non-tg), PS1 transgenic, APPsw, and PSAPP mice at 3 to 12 months of age. In the PSAPP mice, there was disorganization of the neuronal architecture by compact amyloid plaques, and the average number of neurons was 8 to 10% fewer than the other groups (NS, P > 0.10) in CA1 and 2 to 20% fewer in frontal cortex (NS, P = 0.31). There was no loss of total synaptophysin immunoreactivity in the Fc or dentate gyrus molecular layer of the 12-month-old PSAPP mice. Thus, although co-expression of mutant PS1 with Swedish mutant betaAPP leads to marked cortical and limbic Abeta deposition in an age-dependent manner, it does not result in the dramatic neuronal loss in hippocampus and association cortex characteristic of AD.     

Microglial response to amyloid plaques in APPsw transgenic mice.

Microglial activation is central to the inflammatory response in Alzheimer's Disease (AD). A recently described mouse line, Tg(HuAPP695.K670N/M671L)2576, expressing human amyloid precursor protein with a familial AD gene mutation, age-related amyloid deposits, and memory deficits, was found to develop a significant microglial response using Griffonia simplicifolia lectin or phosphotyrosine probe to identify microglia Both Griffonia simplicifolia lectin and phosphotyrosine staining showed increased numbers of intensely labeled, often enlarged microglia clustered in and around plaques, consistent with microglial activation related to beta-amyloid formation. Using quantitative image analysis of coronal phosphotyrosine-immunostained sections, transgene-positive 10- to 16-month-old, hemizygous, hybrid Tg2576 (APPsw) animals showed significantly increased microglial density and size in plaque-forming areas of hippocampus and frontal, entorhinal, and occipital cortex. Quantitative analysis of microglia as a function of distance from the center of plaques (double labeled for A beta peptide and microglia) revealed highly significant, two- to fivefold elevations in microglial number and area within plaques compared with neighboring regions. Tg2576 beta-amyloid-plaque-forming mice should be a useful system for assessing the consequences of the microglial-mediated inflammatory response to beta-amyloid and developing anti-inflammatory therapeutic strategies for Alzheimer's disease. These results provide the first quantitative link between beta-amyloid plaque formation and microglial activation in an animal model with neuritic plaques and memory deficits.     

Gadolinium-staining reveals amyloid plaques in the brain of Alzheimer's transgenic mice

Detection of amyloid plaques in the brain by in vivo neuroimaging is a very promising biomarker approach for early diagnosis of Alzheimer's disease (AD) and evaluation of therapeutic efficacy. Here we describe a new method to detect amyloid plaques by in vivo magnetic resonance imaging (MRI) based on the intracerebroventricular injection of a nontargeted gadolinium (Gd)-based contrast agent, which rapidly diffuses throughout the brain and increases the signal and contrast of magnetic resonance (MR) images by shortening the T1 relaxation time. This gain in image sensitivity after in vitro and in vivo Gd staining significantly improves the detection and resolution of individual amyloid plaques in the cortex and hippocampus of AD transgenic mice. The improved image resolution is sensitive enough to demonstrate an age-dependent increase of amyloid plaque load and a good correlation between the amyloid load measured by μMRI and histology. These results provide the first demonstration that nontargeted Gd staining can enhance the detection of amyloid plaques to follow the progression of AD and to evaluate the activity of amyloid-lowering therapeutic strategies in longitudinal studies.     

3D-Reconstruction of microglia and amyloid in APP23 transgenic mice: no evidence of intracellular amyloid

Microglia cells are closely associated with compact amyloid plaques in Alzheimer's disease (AD) brains. Although activated microglia seem to play a central role in the pathogenesis of AD, mechanisms of microglial activation by beta-amyloid as well as the nature of interaction between amyloid and microglia remain poorly understood. We previously reported a close morphological association between activated microglia and congophilic amyloid plaques in the brains of APP23 transgenic mice at both the light and electron microscopic levels [25]. In the present study, we have further examined the structural relationship between microglia and amyloid deposits by using postembedding immunogold labeling, serial ultrathin sectioning, and 3-dimensional reconstruction. Although bundles of immunogold-labeled amyloid fibrils were completely engulfed by microglial cytoplasm on single sections, serial ultrathin sectioning and three-dimensional reconstruction revealed that these amyloid fibrils are connected to extracellular amyloid deposits. These data demonstrate that extracellular amyloid fibrils form a myriad of finger-like channels with the widely branched microglial cytoplasm. We conclude that in APP23 mice a role of microglia in amyloid phagocytosis and intracellular production of amyloid is unlikely.     

Reversal of presynaptic deficits of apolipoprotein E-deficient mice in human apolipoprotein E transgenic mice

Apolipoprotein E genotype is an important risk factor of Alzheimer's disease, which is associated with the degeneration of distinct brain neuronal systems. In the present study we employed apolipoprotein E-deficient mice and human apolipoprotein E3 and apolipoprotein E4 transgenic mice on a null mouse apolipoprotein E background, to examine the extent to which distinct brain neuronal systems are affected by apolipoprotein E and the isoform specificity of this effect. This was pursued by histological and autoradiographic measurements utilizing neuron specific presynaptic markers. The results thus obtained revealed significant reductions in the levels of brain cholinergic and noradrenergic nerve terminals in young apolipoprotein E-deficient mice and no changes in brain dopaminergic nerve terminals. These cholinergic and noradrenergic presynaptic derangements were ameliorated similarly in human apolipoprotein E3 and apolipoprotein E4 transgenic mice. In the case of the cholinergic system, this resulted in complete reversal of the presynaptic deficits, whereas in the case of the noradrenergic neurons the amelioration was partial.These findings suggest that brain cholinergic and noradrenergic neurons are markedly more dependent on brain apolipoprotein E than brain dopaminergic neurons and that the isoform specificity of these effects is not apparent at a young age under non-challenged conditions.     

Intracellular Abeta and cognitive deficits precede beta-amyloid deposition in transgenic arcAbeta mice

The brain pathology of Alzheimer's disease is characterized by abnormally aggregated Abeta in extracellular beta-amyloid plaques and along blood vessel walls, but the relation to intracellular Abeta remains unclear. To address the role of intracellular Abeta deposition in vivo, we expressed human APP with the combined Swedish and Arctic mutations in mice (arcAbeta mice). Intracellular punctate deposits of Abeta occurred concomitantly with robust cognitive impairments at the age of 6 months before the onset of beta-amyloid plaque formation and cerebral beta-amyloid angiopathy. beta-Amyloid plaques from arcAbeta mice had distinct dense-core morphologies with blood vessels appearing as seeding origins, suggesting reduced clearance of Abeta across blood vessels in arcAbeta mice. The co-incidence of intracellular Abeta deposits with behavioral deficits support an early role of intracellular Abeta in the pathophysiological cascade leading to beta-amyloid formation and functional impairment.