Plasma Abeta, homocysteine, and cognition: the Vitamin Intervention for Stroke Prevention (VISP) trial.

BACKGROUND: Amyloid-beta protein (Abeta) plays a key role in Alzheimer disease (AD) and is also implicated in cerebral small vessel disease. Serum total homocysteine (tHcy) is a risk factor for small vessel disease and cognitive impairment and correlates with plasma Abeta levels. To determine whether this association results from a common pathophysiologic mechanism, we investigated whether vitamin supplementation-induced reduction of tHcy influences plasma Abeta levels in the Vitamin Intervention in Stroke Prevention (VISP) study. METHODS: Two groups of 150 patients treated with either the high-dose or low-dose formulation of pyridoxine, cobalamin, and folic acid in a randomized, double-blind fashion were selected among the participants in the VISP study without recurrent stroke during follow-up and in the highest 10% of the distribution for baseline tHcy levels. Concentrations of plasma Abeta with 40 (Abeta40) and 42 (Abeta42) amino acids were measured at baseline and at the 2-year visit. RESULTS: tHcy levels significantly decreased with vitamin supplementation in both groups. tHcy were strongly correlated with Abeta40 but not Abeta42 concentrations. There was no difference in the change in Abeta40, Abeta42 (p = 0.40, p = 0.35), or the Abeta42/Abeta40 ratio over time (p = 0.86) between treatment groups. Abeta measures were not associated with cognitive change. CONCLUSIONS: This double-blind randomized controlled trial of vitamin therapy demonstrates a strong correlation between serum tHcy and plasma Abeta40 concentrations in subjects with ischemic stroke. Treatment with high dose vitamins does not, however, influence plasma levels of Abeta, despite their effect on lowering tHcy. Our results suggest that although tHcy is associated with plasma Abeta40, they may be regulated by independent mechanisms.

Serum cystatin C and the risk of Alzheimer disease in elderly men.

BACKGROUND: Multiple lines of research suggest that increased cystatin C activity in the brain protects against the development of Alzheimer disease (AD). METHODS: Serum cystatin C levels were analyzed at two examinations of the Uppsala Longitudinal Study of Adult Men, a longitudinal, community-based study of elderly men (age 70 years, n = 1,153 and age 77 years, n = 761, a subset of the age 70 examination). Cox regressions were used to examine associations between serum cystatin C and incident AD. AD cases were identified by cognitive screening and comprehensive medical chart review in all subjects. RESULTS: On follow-up (median 11.3 years), 82 subjects developed AD. At age 70 years, lower cystatin C was associated with higher risk of AD independently of age, APOE4 genotype, glomerular filtration rate, diabetes, hypertension, stroke, cholesterol, body mass index, smoking, education level, and plasma amyloid-beta protein 40 and 42 levels (hazard ratio [HR] for lowest [<1.12 micromol/L] vs highest [>1.30 micromol/L] tertile = 2.67, 95% CI 1.22-5.83, p < 0.02). The results were similar at age 77 years (43 participants developed AD during follow-up). Furthermore, a 0.1-mumol/L decrease of cystatin C between ages 70 and 77 years was associated with a 29% higher risk of incident AD (HR 1.29, 95% CI 1.03-1.63, p < 0.03). CONCLUSIONS: Low levels of serum cystatin C precede clinically manifest Alzheimer disease (AD) in elderly men free of dementia at baseline and may be a marker of future risk of AD. These findings strengthen the evidence for a role for cystatin C in the development of clinical AD.

Plasma F2A isoprostane levels in Alzheimer's and Parkinson's disease.

BACKGROUND: Oxidative damage is implicated in the pathophysiology of Alzheimer's disease (AD). F2-isoprostane is a marker of lipid peroxidation which is elevated in AD CSF. Plasma F2-isoprostane has been proposed as a diagnostic marker for AD and mild cognitive impairment (MCI). OBJECTIVE: To determine whether plasma F2-isoprostane levels differ between nondemented control individuals and patients with AD, MCI, or Parkinson's disease (PD). METHODS: We collected plasma from191 outpatients with a diagnosis of AD (49), MCI (47), nondemented PD (47), and no dementia (48). Plasma levels of the isoprostane iP2alpha-IV (F2A) were determined by gas chromatography/mass spectroscopy. RESULTS: Mean plasma levels of F2A isoprostane did not differ significantly between the four diagnostic groups. Within the MCI and AD groups, F2A levels did not correlate with duration of memory impairment or with cognitive test scores. F2A levels were marginally lower in users of cholinesterase inhibitors and individuals with an APOE epsilon4 allele. CONCLUSIONS: While CSF isoprostane levels are elevated in AD, plasma isoprostane measures were neither sensitive nor specific for the clinical diagnosis of MCI or AD.

Clinical and biochemical correlates of insoluble alpha-synuclein in dementia with Lewy bodies.

Alpha-synuclein is a major constituent of Lewy bodies, the fibrillar aggregates that form within neurons in Parkinson's disease and dementia with Lewy bodies (DLB). Recent biochemical data show that alpha-synuclein accumulates in Parkinson's disease in a detergent insoluble form. We now examine the relationship between detergent insoluble alpha-synuclein and the presence of Lewy bodies, clinical measures of dementia and biochemical parameters in a series of individuals with DLB. We found that Triton X-100 insoluble alpha-synuclein enriched nearly twofold in the temporal cortex of patients with DLB compared to age-matched controls. By contrast the total amount of alpha-synuclein protein was unchanged. Surprisingly, the degree of Triton X-100 insoluble alpha-synuclein did not correlate with either the duration of illness or the number of Lewy bodies counted using stereological methods from an adjacent block of tissue. However, the Triton X-100 soluble fraction of alpha-synuclein did correlate strongly with the expression of several heat shock proteins (HSPs) in DLB but not control cases, suggesting a coordinated HSP response in DLB neocortex.

Plasma beta-amyloid and white matter lesions in AD, MCI, and cerebral amyloid angiopathy.

BACKGROUND: Microvascular brain injury, typically measured by extent of white matter hyperintensity (WMH) on MRI, is an important contributor to cognitive impairment in the elderly. Recent studies suggest a role for circulating beta-amyloid peptide in microvascular dysfunction and white matter disease. METHODS: The authors performed a cross-sectional study of clinical, biochemical, and genetic factors associated with WMH in 54 subjects with Alzheimer disease (AD) or mild cognitive impairment (AD/MCI) and an independent group of 42 subjects with cerebral amyloid angiopathy (CAA). Extent of WMH was determined by computer-assisted volumetric measurement normalized to intracranial size (nWMH). Biochemical measurements included plasma concentrations of the 40- and 42-amino acid species of beta-amyloid (Abeta40 and Abeta42) detected by specific enzyme-linked immunosorbent assays. RESULTS: Plasma Abeta40 concentrations were associated with nWMH in both groups (correlation coefficient = 0.48 in AD/MCI, 0.42 in CAA, p < or = 0.005). Plasma Abeta40 remained independently associated with nWMH after adjustment for potential confounders among age, hypertension, diabetes, homocysteine, creatinine, folate, vitamin B12, and APOE genotype. The presence of lacunar infarctions was also associated with increased Abeta40 in both groups. nWMH was greater in CAA (19.8 cm3) than AD (11.1 cm3) or MCI (10.0 cm3; p < 0.05 for both comparisons). CONCLUSIONS: Plasma beta-amyloid 40 concentration is independently associated with extent of white matter hyperintensity in subjects with Alzheimer disease, mild cognitive impairment, or cerebral amyloid angiopathy. If confirmed in longitudinal studies, these data would suggest circulating beta-amyloid peptide as a novel biomarker or risk factor for microvascular damage in these common diseases of the elderly.

Association of homocysteine with plasma amyloid beta protein in aging and neurodegenerative disease.

BACKGROUND: Elevated plasma total homocysteine (tHcy) is a risk factor for cardiovascular disease and is reported to be an independent risk factor for Alzheimer disease (AD) and cognitive decline. tHcy may potentiate neurotoxic and vasculopathic processes, including amyloid beta protein (Abeta) metabolism, implicated in neurodegenerative diseases. OBJECTIVE: To examine the relationship of plasma total tHcy levels with clinical, demographic, biochemical, and genetic factors in aging, mild cognitive impairment (MCI), AD, cerebral amyloid angiopathy (CAA), and Parkinson disease (PD). METHODS: Plasma tHcy, folate, vitamin B(12), creatinine, and Abeta levels were assessed in individuals evaluated in the Memory, Stroke, and Movement Disorders Units of Massachusetts General Hospital with diagnoses of AD (n = 145), MCI (n = 47), PD (n = 93), CAA (67), hypertensive intracerebral hemorrhage (hICH) (n = 25), and no dementia (n = 88). RESULTS: The tHcy levels did not differ across AD, MCI, CAA, hICH, and nondemented control subjects but were increased in the PD group (p < 0.01). The elevated levels within the PD group were due to high tHcy in individuals taking levodopa (p < 0.0001). Increasing tHcy was associated with worse cognition in the PD cases, but not the other diagnostic groups. tHcy levels positively correlated with plasma Abeta levels even after adjustments for age and creatinine (p < 0.0001). CONCLUSIONS: Mean tHcy levels increased with age but did not discriminate diagnostic groups aside from significant elevation in patients with PD taking levodopa. The positive association between tHcy and plasma Abeta levels raises the possibility that these circulating factors could interact to affect AD risk and cognition in PD.

Early Abeta accumulation and progressive synaptic loss, gliosis, and tangle formation in AD brain.

BACKGROUND: Pathologic changes in the Alzheimer disease (AD) brain occur in a hierarchical neuroanatomical pattern affecting cortical, subcortical, and limbic regions. OBJECTIVE: To define the time course of pathologic and biochemical changes-amyloid deposition, amyloid beta-peptide (Abeta) accumulation, neurofibrillary tangle (NFT) formation, synaptic loss, and gliosis-within the temporal association cortex of AD cases of varying disease duration, relative to control brains. METHODS: Stereologic assessments of amyloid burden and tangle density as well as ELISA-based measurements of Abeta, synaptophysin, and glial fibrillary acidic protein (GFAP) were performed in the superior temporal sulcus from a cohort of 83 AD and 26 nondemented control brains. RESULTS: Relative to control cases, AD brains were characterized by accumulation of NFT and amyloid plaques, increase of tris- and formic acid-extractable Abeta species, reduced levels of synaptophysin, and elevated levels of GFAP. In AD cases, the duration of dementia correlated with the degree of tangle formation, gliosis, and synaptic loss but not with any Abeta measures. Accumulation of Abeta, measured both neuropathologically and biochemically, was markedly increased in AD brains independent of disease duration, even in cases of short duration. CONCLUSIONS: These data support distinct processes in the initiation and progression of AD pathology within the temporal cortex: Deposition of Abeta reaches a "ceiling" early in the disease process, whereas NFT formation, synaptic loss, and gliosis continue throughout the course of the illness.

Neurotoxic effects of thioflavin S-positive amyloid deposits in transgenic mice and Alzheimer's disease.

Despite extensive deposition of putatively neurotoxic amyloid-beta (Abeta) protein in the brain, it has not been possible to demonstrate an association of Abeta deposits with neuronal loss in Alzheimer's disease (AD), and neuronal loss is minimal in transgenic mouse models of AD. Using triple immunostaining confocal microscopy and analyzing the images with the cross-correlation density map method from statistical physics, we directly compared Abeta deposition, Abeta morphology, and neuronal architecture. We found dramatic, focal neuronal toxicity associated primarily with thioflavin S-positive fibrillar Abeta deposits in both AD and PSAPP mice. These results, along with computer simulations, suggest that Abeta develops neurotoxic properties in vivo when it adopts a fibrillar beta-pleated sheet conformation.

Alzheimer disease therapeutics.

Alzheimer disease (AD) is characterized pathologically by cholinergic deficits, amyloid plaques, neurofibrillary tangles, gliosis, and neuronal and synaptic loss. The primary therapeutic approach that has arisen from the pathological analysis of AD brain has been cholinergic augmentation by cholinesterase inhibitors, which modestly improve cognitive function. Research on the underlying pathophysiological dysfunction have focussed on AD-specific processes such as amyloid precursor protein, tau, and cerebral apolipoprotein E metabolism, and more general neurodegenerative processes such as inflammation, oxidation, excitotoxicity, and apoptosis. Rational neuroprotective approaches have led to recent trials of estrogen, antioxidant and anti-inflammatory medications in AD, and to the development of anti-amyloid strategies for delaying progression or preventing development of AD.

Alpha-synuclein has an altered conformation and shows a tight intermolecular interaction with ubiquitin in Lewy bodies.

Alpha-synuclein, a protein in which two mutations have been identified that cause autosomal dominant Parkinson's disease, is thought to serve as a nidus for the development of a Lewy body. We hypothesized that alpha-synuclein would display different intra- and intermolecular associations in Lewy bodies than it does in its normal intracellular compartments. Using sensitive fluorescence resonance energy transfer (FRET) techniques, we found evidence that alpha-synuclein is more compact and in closer association with other alpha-synuclein molecules in Lewy bodies than it is in the neuropil. In addition, we found evidence of a close, direct intermolecular interaction between the N terminus of alpha-synuclein and ubiquitin. These observations provide support for the hypothesis that in Lewy bodies alpha-synuclein adopts an altered three-dimensional structure and undergoes N-terminal ubiquitination.

Elevation of cystatin C in susceptible neurons in Alzheimer's disease.

A common polymorphism in the cystatin C gene is associated with increased risk of developing Alzheimer's disease (AD). To explore possible neuropathological consequences of this genetic association, we examined expression of cystatin C in brains from 22 AD and 11 control patients by immunohistochemistry. In the temporal cortex of all AD brains, there was strong cystatin C immunostaining of neurons and activated glia, whereas staining was absent or minimal in 7 of the 11 control brains. Neuronal staining of cystatin C in AD brains was primarily limited to pyramidal neurons in cortical layers III and V, which are the neurons most susceptible to cell death in AD. The increase in cystatin C staining in AD was independent of cystatin C genotype. Immunostaining of cystatin C within neurons showed a punctate distribution, which co-localized with the endosomal/lysosomal proteinase, cathepsin B. A primarily glial source for cystatin C was suggested by parallel studies using in situ hybridization of mouse brain. In human AD brain, there was little co-localization of cystatin C with parenchymal Abeta deposits, although a small fraction of cerebral blood vessels and neurofibrillary tangles were cystatin C-positive. The regional distribution of cystatin C neuronal immunostaining also duplicated the pattern of neuronal susceptibility in AD brains: the strongest staining was found in the entorhinal cortex, in the hippocampus, and in the temporal cortex; fewer pyramidal neurons were stained in frontal, parietal, and occipital lobes. These neuropathological observations reinforce the association between cystatin C and AD, and support a model of cystatin C involvement in the process of neuronal death in AD.

Plaque-induced abnormalities in neurite geometry in transgenic models of Alzheimer disease: implications for neural system disruption.

Neurites that pass through amyloid-beta deposits in Alzheimer disease (AD) undergo 3 changes: they develop phosphorylated tau immunoreactivity; the density of SMI-32-positive dendrites diminishes; and they also develop a marked alteration in their geometric features, changing from being nearly straight to being quite curvy. The extent to which the latter 2 phenomena are related to phosphorylated tau is unknown. We have now examined whether amyloid-beta deposits in APP695Sw transgenic mice, which have only rare phosphorylated tau containing neurites. develop these changes. We found that dendritic density is diminished within the boundaries of amyloid-beta plaques, with the greatest loss (about 80%, p < 0.001) within the boundaries of thioflavine S cores. Remaining dendrites within plaques develop substantial morphological alterations quantitatively similar to those seen in AD. A statistically significant but smaller degree of change in geometry was seen in the immediate vicinity around plaques, suggesting a propagation of cytoskeletal disruption from the center of the plaque outward. We examined the possible physiological consequences of this change in dendritic geometry using a standard cable-theory model. We found a predicted delay of several milliseconds in about one quarter of the dendrites passing through a thioflavine S plaque. These results are consistent with previous observations in AD, and suggest that thioflavine S-positive amyloid-beta deposits have a marked effect on dendritic microarchitecture in the cortex, even in the relative absence of phosphorylated tau alterations.

Uptake of fibrillar beta-amyloid by microglia isolated from MSR-A (type I and type II) knockout mice.

To characterize the receptors involved in binding fibrillar amyloid A-beta (fA beta), we compared the uptake of fA beta in microglia from wildtype (MSR-A+/+) and MSR-A knockout (MSR-A-/-) mice. On average, there was a 60% reduction in the uptake of Cy3-fA beta in microglia from the MSR-A-/- mice. Cy3-fA beta uptake in the MSR-A-/- mice was still competable by scavenger receptor ligands, including acetylated low-density lipoprotein (Ac-LDL) and fucoidan. This indicates that uptake by MSR-B and/or other MSRs is also involved in the uptake of fA beta by microglia. However, the significant reduction in the uptake of fA beta in the MSR-A-/- microglia suggests that fA beta gets internalized mostly by MSR-As in microglia. Uptake of modified fA beta (ClqA beta) was similar in the MSR-A-/- microglia as in the wildtype indicating that the uptake of the opsonized fA beta is independent of MSR-A.

Glutamate receptor dysregulation in the hippocampus of transgenic mice carrying mutated human amyloid precursor protein.

Alzheimer's disease transgenic mice overexpressing human amyloid precursor protein (hAPP) with the Swedish double mutation (hAPP(Sw)) develop age-related amyloid deposition and behavioral and electrophysiologic changes by an unknown mechanism. Analysis of glutamatergic receptor subtypes in 4- and 15-month-old heterozygous hAPP(Sw) transgenic mice revealed a selective increase in AMPA receptor binding in the hippocampus of 15-month-old transgenic mice, which have established cortical and hippocampal amyloid deposits. There were no significant alterations of GluR1, GluR2, and GluR4 protein expression by semiquantitative confocal analysis or GluR1 mRNA by in situ hybridization. There was no significant alteration in NMDA, in group I and II metabotropic glutamate and in muscarinic receptor binding, or in striatal dopamine and adenosine receptor binding in 15-month-old mice. These data suggest that mutant APP overexpression or age-related amyloid deposition produce a subtle specific alteration in hippocampal glutamate receptors with aging.

beta-site APP cleaving enzyme mRNA expression in APP transgenic mice: anatomical overlap with transgene expression and static levels with aging.

The principal enzyme responsible for the beta-site cleavage of amyloid precursor protein (APP) in the brain is a membrane-bound aspartyl protease beta-site APP cleaving enzyme (BACE). We examined human APP (hAPP) and BACE mRNA expression by in situ hybridization in young and old hAPP transgenic mice from two lines: Tg2576, hAPP KM670-671NL (hAPP(Sw)) at 4 and 15 months; and PDAPP, hAPP V717F, at 4 and 11 months. In transgene-positive mice from both lines, hAPP expression was most prominent in cortical, cerebellar, and hippocampal neuronal populations. Cingulate, entorhinal, and hippocampal amyloid burden in transgene-positive 16-month Tg2576 mice was 4 to 8%, and in 12-month PDAPP mice, 2 to 4%; there was no cerebellar amyloid deposition. BACE expression in transgenic and nontransgenic mice was highest in the cerebellar granule cell layer and hippocampal neuronal layers, intermediate in cortex, lower in subcortical regions, and minimal or absent in white matter of the cerebellum. Emulsion-dipped sections confirmed a predominantly neuronal pattern of expression. The amount of hybridization signal did not differ between transgenic and nontransgenic mice, or young and old mice, within each line. Thus, hAPP and endogenous BACE expression in similar anatomical localizations allow for processing of hAPP and Abeta formation in hAPP transgenic mice, but these are modified by additional age-related and anatomical factors.

Apolipoprotein E affects the amount, form, and anatomical distribution of amyloid beta-peptide deposition in homozygous APP(V717F) transgenic mice.

Apolipoprotein E (apoE) has been implicated as a risk factor for Alzheimer's disease and in the deposition, fibrillogenesis, and clearance of the amyloid beta-peptide (Abeta). To examine the in vivo interactions between apoE and Abeta deposition, we examined 12-month-old transgenic (tg) mice expressing human amyloid precursor protein (APP) with the V717F mutation (APP(V717F) homozygous) on an APOE null background. Elimination of APOE resulted in a redistribution and alteration in the character of Abeta deposition in homozygous APP(V717F) tg mice, with a dramatic reduction in cortical and dentate gyrus deposition, prominent increase in diffuse CA1 and CA3 deposition, and prevention of the formation of thioflavin-S-positive deposits. These alterations in Abeta deposition were not mediated by significant changes in regional APP expression, low-density lipoprotein receptor-related protein expression, or soluble Abeta levels. Thus, apoE in APP(V717F) tg mice not only affects the amount and form of Abeta deposition, but also the anatomical distribution of diffuse Abeta deposits. The APP(V717F) tg mouse can serve as a model to investigate genetic influences on the vulnerability of specific neuroanatomical regions to Abeta deposition.

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.

Apolipoprotein E facilitates neuritic and cerebrovascular plaque formation in an Alzheimer's disease model.

The epsilon4 allele of apolipoprotein E (ApoE) is an important genetic risk factor for Alzheimer's disease (AD). Increasing evidence suggests that this association may be linked to the ability of ApoE to interact with the amyloid-beta (Abeta) peptide and influence its concentration and structure. To determine the effect of ApoE on Abeta and other AD pathology in vivo, we used APPsw transgenic mice and ApoE knockout (-/-) mice to generate APPsw animals that carried two (ApoE +/+), one (ApoE +/-), or no copies (ApoE -/-) of the normal mouse ApoE gene. At 12 months of age, Abeta deposition was present in the cortex and hippocampus and was also prominent within leptomeningeal and cortical blood vessels of all APPsw ApoE +/+ mice. Importantly, although Abeta deposition still occurred in APPsw ApoE -/- mice, no fibrillar Abeta deposits were detected in the brain parenchyma or cerebrovasculature. There was also no neuritic degeneration associated with Abeta deposition in the absence of ApoE. These data demonstrate that ApoE facilitates the formation of both neuritic and cerebrovascular plaques, which are pathological hallmarks of AD and cerebral amyloid angiopathy.

alpha-Synuclein immunoreactivity in dementia with Lewy bodies: morphological staging and comparison with ubiquitin immunostaining.

alpha-Synuclein is a presynaptic protein recently identified as a specific component of Lewy bodies (LB) and Lewy neurites. The aim of this study was to assess the morphology and distribution of alpha-synuclein immunoreactivity in cases of dementia with LB (DLB), and to compare alpha-synuclein with ubiquitin immunostaining. We examined substantia nigra, paralimbic regions (entorhinal cortex, cingulate gyrus, insula and hippocampus), and neocortex (frontal and occipital association cortices) with double alpha-synuclein and ubiquitin immunostaining in 25 cases meeting neuropathological criteria for DLB. alpha-Synuclein immunostaining was more specific than ubiquitin immunostaining in that it differentiated LB from globose tangles. It was also slightly more sensitive, staining 4-5% more intracytoplasmic structures, especially diffuse alpha-synuclein deposits that were ubiquitin negative. In addition to LB, alpha-synuclein staining showed filiform and globose neurites in the substantia nigra, CA2-3 regions of the hippocampus, and entorhinal cortex. A spectrum of alpha-synuclein staining was seen in substantia nigra: from diffuse "cloud-like" inclusions to aggregated intracytoplasmic inclusions with variable ubiquitin staining to classic LB. We hypothesize that these represent different stages in LB formation.

Modulation of A beta deposition in APP transgenic mice by an apolipoprotein E null background.

Several lines of evidence implicate apolipoprotein E (apoE) and its receptor--the low density lipoprotein receptor related protein (LRP)--in Alzheimer's disease (AD) pathogenesis, including increased amyloid deposition in human AD brains of people containing the apoE epsilon 4 allele, presence of apoE and LRP in amyloid plaques, and in vitro uptake of amyloid precursor protein (APP) and amyloid beta protein (A beta) by LRP. Studies of crosses of apoE knockout mice with APP transgenic mice support a complex interaction between apoE and A beta deposition. In the Tg2576 mice expressing human APPK670N-M671L, apoE determines the amount, morphology, vascular pattern, and neuropil response to A beta deposits. In the PDAPP mice expressing human APPV717F, apoE also affects the anatomical localization of cerebral A beta deposits. Thus, APP transgenic mice can serve as models to investigate genetic influences on the amount and timing of cerebral amyloidosis, the morphology of amyloid plaques, and the vulnerability of specific neuroanatomical regions to A beta deposition.