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At least 19 recordsLinked to original sources
PubMed2005

Pharmacokinetic analysis of the blood-brain barrier transport of 125I-amyloid beta protein 40 in wild-type and Alzheimer's disease transgenic mice (APP,PS1) and its implications for amyloid plaque formation.

Amyloid plaques are formed in the extracellular space of Alzheimer's disease (AD) brain due to the accumulation of amyloid beta (Abeta) proteins such as Abeta40. The relationship between Abeta40 pharmacokinetics and its accumulation within and clearance from the brain in both wild-type (WT) and AD transgenic mice (APP,PS1) was studied to understand the mechanism of amyloid plaque formation and the potential use of Abeta40 as a probe to target and detect amyloid plaques. In both WT and APP,PS1 mice, the (125)I-Abeta40 tracer exhibited biexponential disposition in plasma with very short first and second phase half-lives. The (125)I-Abeta40 was significantly metabolized in the liver kidney > spleen. Coadministration of exogenous Abeta40 inhibited the plasma clearance and the uptake of (125)I-Abeta40 at the blood-brain barrier (BBB) in WT animals but did not affect its elimination from the brain. The (125)I-Abeta40 was shown to be metabolized within and effluxed from the brain parenchyma. The rate of efflux from APP,PS1 brain slices was substantially lower compared with WT brain slices. Since the Abeta40 receptor at the BBB can be easily saturated, the blood-to-brain transport of Abeta40 is less likely to be a primary contributor to the amyloid plaque formation in APP,PS1 mice. The decreased elimination of Abeta40 from the brain is most likely responsible for the amyloid plaque formation in the brain of APP,PS1 mice. Furthermore, inadequate targeting of Abeta40 to amyloid plaques, despite its high BBB permeability, is due to the saturability of Abeta40 transporter at the BBB and its metabolism and efflux from the brain.

Alzheimer Disease↗
PubMed2006

Activation of beta2-adrenergic receptor stimulates gamma-secretase activity and accelerates amyloid plaque formation.

Amyloid plaque is the hallmark and primary cause of Alzheimer disease. Mutations of presenilin-1, the gamma-secretase catalytic subunit, can affect amyloid-beta (Abeta) production and Alzheimer disease pathogenesis. However, it is largely unknown whether and how gamma-secretase activity and amyloid plaque formation are regulated by environmental factors such as stress, which is mediated by receptors including beta(2)-adrenergic receptor (beta(2)-AR). Here we report that activation of beta(2)-AR enhanced gamma-secretase activity and thus Abeta production. This enhancement involved the association of beta(2)-AR with presenilin-1 and required agonist-induced endocytosis of beta(2)-AR and subsequent trafficking of gamma-secretase to late endosomes and lysosomes, where Abeta production was elevated. Similar effects were observed after activation of delta-opioid receptor. Furthermore, chronic treatment with beta(2)-AR agonists increased cerebral amyloid plaques in an Alzheimer disease mouse model. Thus, beta(2)-AR activation can stimulate gamma-secretase activity and amyloid plaque formation, which suggests that abnormal activation of beta(2)-AR might contribute to Abeta accumulation in Alzheimer disease pathogenesis.

Alzheimer Disease↗
PubMed1998

Amyloid plaques in Guam amyotrophic lateral sclerosis/parkinsonism-dementia complex contain species of A beta similar to those found in the amyloid plaques of Alzheimer's disease and pathological aging.

The Guamanian amyotrophic lateral sclerosis/parkinsonism-dementia complex (ALS/PDC) is characterized by abundant neurofibrillary pathology and neuron loss. In contrast to Alzheimer's disease (AD), where extensive neurofibrillary lesions always occur with deposits of A beta in numerous amyloid plaques, A beta-rich amyloid plaques are absent or rare in most ALS/PDC patients. To characterize the amyloid plaques in the latter patients, we probed plaque-rich sections of their brains by immunohistochemistry using well-characterized antibodies to specific epitopes in the N and C termini of A beta as well as to defined epitopes in hyperphosphorylated tau (PHFtau). The results indicate that the species of A beta in the amyloid plaques of ALS/PDC patients resemble those detected in the amyloid plaques of cognitively intact subjects with pathological aging as well as patients with AD. However, the paucity of PHFtau-positive neurites in the ALS/PDC plaques suggests that they reflect pathological aging rather than AD.

Aged↗
PubMed2005

Collagenous Alzheimer amyloid plaque component assembles amyloid fibrils into protease resistant aggregates.

Recently, a novel plaque-associated protein, collagenous Alzheimer amyloid plaque component (CLAC), was identified in brains from patients with Alzheimer's disease. CLAC is derived from a type II transmembrane collagen precursor protein, termed CLAC-P (collagen XXV). The biological function and the contribution of CLAC to the pathogenesis of Alzheimer's disease and plaque formation are unknown. In vitro studies indicate that CLAC binds to fibrillar, but not to monomeric, amyloid beta-peptide (Abeta). Here, we examined the effects of CLAC on Abeta fibrils using assays based on turbidity, thioflavin T binding, sedimentation analysis, and electron microscopy. The incubation of CLAC with preformed Abeta fibrils led to increased turbidity, indicating that larger aggregates were formed. In support of this contention, more Abeta was sedimented in the presence of CLAC, as determined by gel electrophoresis. Moreover, electron microscopy revealed an increased amount of Abeta fibril bundles in samples incubated with CLAC. Importantly, the frequently used thioflavin T-binding assay failed to reveal these effects of CLAC. Digestion with proteinase K or trypsin showed that Abeta fibrils, incubated together with CLAC, were more resistant to proteolytic degradation. Therefore, CLAC assembles Abeta fibrils into fibril bundles that have an increased resistance to proteases. We suggest that CLAC may act in a similar way in vivo.

Alzheimer Disease↗
PubMedDate not supplied

Juvenile Alzheimer's disease with myoclonus: amyloid plaques and grumose alteration in the cerebellum.

A case of juvenile Alzheimer's disease is reported with onset at 34 years of age, a clinical course of 6 years, had myoclonic jerks, generalized convulsions, dysarthria and ataxic symptoms. The neuropathological examination indicated kuru-plaques, amyloid angiopathy and grumose alteration (degeneration) in the dentate nucleus. In this case, the plaques in Alzheimer disease is quite rare. This case also demonstrates the complex interrelationship between Alzheimer's disease and various multisystemic degeneration mainly involving the dentate nucleus.

Adult↗
PubMed1988

Immunohistochemical confirmation of Creutzfeldt-Jakob disease with a long clinical course with amyloid plaque core antibodies.

Amyloid plaques have been found in the brains of some patients with Creutzfeldt-Jakob disease (CJD) and all patients with Gerstmann-Sträussler syndrome (GSS). We examined paraffin sections from 45 patients with CJD or GSS and from 51 patients with other neurologic diseases, using an antiserum against GSS amyloid plaque cores. The GSS amyloid plaque core antiserum revealed not only birefringent amyloid plaques but also small plaques that cannot be detected by the staining with Congo red dye. Positive immunolabeling was demonstrated in 59% of 34 Japanese patients with CJD, in 100% of 11 patients with GSS, and in none with other neurologic diseases. All cases of CJD of short duration (less than 11 months) were evaluated as being negative, and 95% of 21 long survivors (over 12 months) were positive. This immunohistochemical approach revealed that amyloid plaque is a hallmark of CJD with a long clinical course.

Amyloid↗
PubMed1989

Alzheimer's disease: mismatch between amyloid plaques and neuritic plaques.

Isocortical amyloid deposits and neurofibrillary changes were studied using selective silver staining methods. Amyloid was found in plaque-like formations varying in size and shape. The distribution pattern of these plaques as seen in the silver-stained preparations was identical to that recognized by A4 protein (amyloid) immunostaining. Consecutive sections stained for amyloid and neurofibrillary changes revealed the absence of intraneuronal cytoskeleton abnormalities within the boundaries of many of the amyloid plaques. Congo red preparations did not show these plaques and the tissue within the range of the plaques did not reveal any conspicuous neuropil distortions and/or glial cell accumulations. Hence, a considerable proportion of the amyloid plaques do not correspond to and should carefully be distinguished from 'primitive', 'mature', and 'burned out' types of neuritic (senile) plaques.

Aged↗
PubMed2003

Negative association between amyloid plaques and cerebral amyloid angiopathy in Alzheimer's disease.

Cerebral amyloid angiopathy (CAA) is an important, though still relatively neglected, aspect of the pathology of Alzheimer's disease (AD), and both the source of amyloid beta protein (Abeta) in CAA, and its relationship to senile plaque (SP) Abeta, remain unclear. We have investigated the relationship between Abeta deposition in SP and CAA in four regions of brain from 69 patients with AD in order to gain insight into the pathogenetic mechanism(s) underlying these pathologies. CAA was present to some degree in all 69 patients, with the occipital cortex being affected more often and more severely than frontal, temporal and parietal cortices. By definition, SPs were present in all brain areas in all 69 patients, with greater uniformity of distribution than CAA, though the occipital cortex was less severely affected than the other brain regions. There was no significant (positive) correlation between CAA rating and that of SP for any one cortical region, but on combining data from all four regions there was a significant inverse correlation (P=0.037) between CAA and SP ratings. Such data suggest that the cellular sources and mechanisms leading to Abeta deposition as SP or CAA are likely to differ and may proceed independently of each other.

Aged↗
PubMed2006

Viral-induced inflammation is accompanied by beta-amyloid plaque reduction in brains of amyloid precursor protein transgenic Tg2576 mice.

Amyloid plaques, one of the neuropathological hallmarks of Alzheimer's disease, and their main constituent, the amyloid beta-peptide (Abeta), are triggers of the activation of innate inflammatory mechanisms involving the activation of microglia. To dissect the effects of a non-Abeta-specific microglial activation on the Abeta metabolism, we employed a viral infection-based model. Transgenic mice expressing a mutated form of the human amyloid precursor protein (Tg2576) were used. In preceding experiments, 2-week-old transgenic mice and non-transgenic littermates were infected intracerebrally with the neurotropic Borna disease virus and investigated at 2, 4 and 14 weeks post-infection. The Borna disease virus-inoculated mice showed a persisting, subclinical infection of cortical and limbic brain areas characterized by slight T-cell infiltrates, expression of cytokines and a massive microglial activation in the hippocampus and neocortex. Viral-induced effects reached their peak at 4 weeks post-infection. In 14-month-old Tg2576 mice, characterized by the deposition of diffuse and dense-core amyloid plaques in cortical brain regions, Borna disease virus-induced microglial activation in the vicinity of Abeta deposits was used to investigate the influence of a local inflammatory response on these deposits. At 4 weeks post-infection, histometric analyses employing Abeta immunohistochemistry revealed a decrease of the cortical and hippocampal Abeta-immunopositive area. This overall decrease was accompanied by a decrease of parenchymal thioflavin-S-positive amyloid deposits and an increase of such deposits in the walls of cerebral vessels, which indicates that the elicitation of a non-Abeta-specific microglial activation may contribute to a reduction of Abeta in the brain parenchyma.

Amyloid beta-Protein Precursor↗
PubMed1977

Histochemical similarity of senile plaque amyloid to apudamyloid.

Senile plaque amyloid of both isolated and perivascular (dyshoric) types was compared histochemically to other major types of amyloid. In contrast to most amyloids tested, senile plaque amyloid contained less tryptophan and tyrosine reactivity and more alcianophilia. These histochemical features indicate that senile plaque amyloid is similar to apudamyloid, and suggest that local factors are more important than systemic circulating factors in its genesis. The implications of these histochemical observations are discussed.

Aged↗
PubMed1992

Reversible in vitro growth of Alzheimer disease beta-amyloid plaques by deposition of labeled amyloid peptide.

The salient pathological feature of Alzheimer disease (AD) is the presence of a high density of amyloid plaques in the brain tissue of victims. The plaques are predominantly composed of human beta-amyloid peptide (beta A4), a 40-mer whose neurotoxicity is related to its aggregation. Radioiodinated human beta A4 is rapidly deposited in vitro from a dilute (less than 10 pM) solution onto neuritic and diffuse plaques and cerebrovascular amyloid in AD brain tissue, whereas no deposition is detectable in tissue without performed plaques. This growth of plaques by deposition of radiolabeled beta A4 to plaques is reversible, with a dissociation half-time of approximately 1 h. The fraction of grey matter occupied by plaques that bind radiolabeled beta A4 in vitro is dramatically larger in AD cortex (23 +/- 11%) than in age-matched normal controls (less than 2%). In contrast to the human peptide, rat/mouse beta A4 (differing at three positions from human beta A4) does not affect the deposition of radiolabeled human beta A4. beta A4 has no detectable interaction with tachykinin receptors in rat or human brain. The use of radioiodinated beta A4 provides an in vitro system for the quantitative evaluation of agents or conditions that may inhibit or enhance the growth or dissolution of AD plaques. This reagent also provides an extremely sensitive method for visualizing various types of amyloid deposits and a means for characterizing and locating sites of amyloid peptide binding to cells and tissues.

Aged↗
PubMed1980

Histochemical analysis of senile plaque amyloid and amyloid angiopathy.

Histochemical methods were used to obtain information on the chemical constituents of brain amyloid in senile dementia of the Alzheimer type. The staining properties of brain amyloid (senile plaque and amyloid angiopathy) were compared with those of extraneural amyloidosis and endocrine amyloid. We found no histochemical differences between amyloid in senile plaques and in amyloid angiopathy. The content of aromatic amino acids was higher in amyloid of plaques and in amyloid angiopathy than in endocrine amyloid. Furthermore, we found persistent birefringence and affinity of brain amyloid for Congo red after exposure to potassium permanganate, suggesting that AA amyloid is not a major constituent of cerebral amyloid.

APUD Cells↗
PubMed2002

CLAC: a novel Alzheimer amyloid plaque component derived from a transmembrane precursor, CLAC-P/collagen type XXV.

We raised monoclonal antibodies against senile plaque (SP) amyloid and obtained a clone 9D2, which labeled amyloid fibrils in SPs and reacted with approximately 50/100 kDa polypeptides in Alzheimer's disease (AD) brains. We purified the 9D2 antigens and cloned a cDNA encoding its precursor, which was a novel type II transmembrane protein specifically expressed in neurons. This precursor harbored three collagen-like Gly-X-Y repeat motifs and was partially homologous to collagen type XIII. Thus, we named the 9D2 antigen as CLAC (collagen-like Alzheimer amyloid plaque component), and its precursor as CLAC-P/collagen type XXV. The extracellular domain of CLAC-P/collagen type XXV was secreted by furin convertase, and the N-terminus of CLAC deposited in AD brains was pyroglutamate modified. Both secreted and membrane-tethered forms of CLAC-P/collagen type XXV specifically bound to fibrillized Abeta, implicating these proteins in beta-amyloidogenesis and neuronal degeneration in AD.

Alzheimer Disease↗
PubMed2001

Evidence that neurones accumulating amyloid can undergo lysis to form amyloid plaques in Alzheimer's disease.

AIMS: Amyloid has recently been shown to accumulate intracellularly in the brains of patients with Alzheimer's disease (AD), yet amyloid plaques are generally thought to arise from gradual extracellular amyloid deposition. We have investigated the possibility of a link between these two apparently conflicting observations. METHODS AND RESULTS: Immunohistochemistry and digital image analysis was used to examine the detailed localization of beta-amyloid(42) (A beta 42), a major component of amyloid plaques, in the entorhinal cortex and hippocampus of AD brains. A beta 42 first selectively accumulates in the perikaryon of pyramidal cells as discrete, granules that appear to be cathepsin D-positive, suggesting that they may represent lysosomes or lysosome-derived structures. AD brain regions abundantly populated with pyramidal neurones exhibiting excessive A beta 42 accumulations also contained evidence of neuronal lysis. Lysis of these A beta 42-burdened neurones apparently resulted in a local, radial dispersion of their cytoplasmic contents, including A beta 42 and lysosomal enzymes, into the surrounding extracellular space. A nuclear remnant was found at the dense core of many amyloid plaques, strengthening the idea that each amyloid plaque represents the end product of a single neuronal cell lysis. The inverse relationship between the amyloid plaque density and pyramidal cell density in the AD brain regions also supports this possibility, as does the close correlation between plaque size and the size of local pyramidal cells. CONCLUSIONS: Our findings suggest that excessive intracellular accumulation of A beta 42-positive material in pyramidal cells can result in cell lysis, and that cell lysis is an important source of amyloid plaques and neuronal loss in AD brains.

Aged↗
PubMed1996

Amyloid load and neural elements in Alzheimer's disease and nondemented individuals with high amyloid plaque density.

The amyloid burden and relationship between amyloid deposits and neural elements were investigated in sections of prefrontal neocortex from eight Alzheimer's disease (AD) patients and four age-matched nondemented controls with high amyloid plaque density (HPND). Computer-based image analysis revealed that the total area occupied by betaA4 immunoreactivity was significantly greater (P < 0.031) in AD (27.1%) than in HPND (14.5%) sections. The total betaA4-positive area occupied by nondiffuse plaques was significantly greater (P < 0.05) in AD (13.6%) than in HPND (5.2%) sections. The percentage of diffuse (DPs) and nondiffuse plaques (NDPs) which contained neurons, astrocytes, microglia, dystrophic neurites, and amyloid precursor protein (APP) was also determined. The frequency of association between betaA4 and these neural elements was similar between AD and HPND cases in both diffuse and nondiffuse plaques. Forty percent of DPs in AD and HPND sections contained neuronal perikarya. Microglia, dystrophic neurites, and APP were detected in most nondiffuse plaques in both AD and HPND sections. While astrocyte cell bodies were not present in either diffuse or nondiffuse plaques, their processes were detected in most. These findings indicate that amyloid deposition and nondiffuse plaques are greater in AD than in HPND sections. The association between microglia and nondiffuse plaques supports the hypothesis that these resident immune cells participate in aggregation and redistribution of amyloid deposits and possibly formation of dystrophic neurites.

Age Factors↗
PubMed1989

Complement activation in amyloid plaques in Alzheimer's dementia.

Amyloid plaques in Alzheimer's dementia contain complement factors C1q, C4 and C3. In the present study we demonstrate complement activation in amyloid plaques using immunoenzymatical techniques and specific antibodies against subunits of individual complement components and activated complement products. Amyloid plaques contain C1q and activated C3 fragments (C3c and C3d, g) but no C1s and C3a. These findings demonstrate that the complement components are not passively bound to the amyloid plaque structures but are the result of an activation process. The role of complement activation in the genesis of senile plaques is discussed.

Aged↗
PubMed1992

Serial reconstruction of beta-protein amyloid plaques: relationship to microvessels and size distribution.

The suggestion that the amyloid plaques in Alzheimer disease are formed by abnormal leakage from microvessels is mainly based on the finding that many plaques are topographically associated with microvessels. However, because the microvessel network is dense and amyloid plaques are numerous, the frequently observed association may result from chance contact, especially for larger plaques. Therefore, we determined the frequency of this association as a variable of plaque size. If all the amyloid plaques are associated with microvessels, a constant and high rate of association would be expected for all plaque sizes. On the other hand, if the association is a chance contact, larger plaques would show more frequent contact than smaller ones. Sections were double-immunostained for amyloid plaques and microvessels with antibodies raised against beta-protein and collagen type IV, respectively. Amyloid plaques were reconstructed using 12 serial sections (7 microns thick) from the entorhinal cortex of two Alzheimer patients. With reconstruction we determined the size distribution of amyloid plaques as well as the influence of size on vascular association. All the amyloid plaques larger than 42 microns were associated with microvessels, however, the smaller the amyloid plaques, the less frequently they were associated with microvessels. Interestingly, although diffuse amyloid plaques occur in all size classes, core-containing amyloid plaques have a more discrete size. We conclude that the topographical relationship between amyloid deposition and capillaries does not support the leakage theory for amyloid plaque formation.

Aged↗