amyloid-beta-peptides and Amyloidosis

Aberrant proteins or peptide aggregates form soluble oligomers or nanofibrils that can cause a wide range of amyloidosis diseases, including Alzheimer's disease (AD). The mechanisms of their cytotoxicity, however, remain controversial and poorly understood, greatly hindering the development of AD drugs. Here we report a comprehensive evaluation of the cytotoxicity of the aggregates by meta-analysis. The analysis indicates that the cytotoxicity of the aggregates converges in a narrower range in the mass concentrations than in the molar concentrations, suggesting that it is the weight of the aggregates rather than the number of the molecules that dictates the cytotoxicity. This new perspective implies that these aggregates are likely to have non-specific interactions with cells to cause cell death. The comparison of several existing theories regarding cellular volumes supports that the aggregates may result in crowding effect and increase the free energy, thus resulting in instability of the cells.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Humans; Peptide Fragments; Protein Aggregates; Protein Aggregation, Pathological

The amyloid beta-protein (Abeta) E22Q mutation of the rare disorder hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D) causes severe cerebral amyloid angiopathy (CAA) with hemorrhagic strokes of mid-life onset and dementia. The mutation does not affect total Abeta production but may alter the Abeta1-42:Abeta1-40 ratio, and affect the proteolytic degradation of Abeta and its transport across the blood-brain barrier. Abeta E22Q aggregates faster into more stable amyloid-like fibrils than wild-type Abeta. Non-fibrillar Abeta(x-42) deposits precede the appearance of fibrils and the deposition of Abeta(x-40) in the vascular basement membrane. CAA severity tends to increase with age but may vary greatly among patients of comparable ages. Lumenal narrowing of affected blood vessels, leukoencephalopathy, CAA-associated vasculopathies, and perivascular astrocytosis, microgliosis, and neuritic degeneration complicate the development of HCHWA-D CAA. Parenchymal Abeta deposition is also enhanced in the HCHWA-D brain with non-fibrillar membrane-bound Abeta(x-42) deposits evolving into relatively fibrillar diffuse plaques variously associated with reactive astrocytes, activated microglia, and degenerating neurites. Plaque density tends to decrease with age. Neurofibrillary degeneration is absent or limited. HCHWA-D dementia is associated with CAA severity independently of Braak stage, age, and plaque density. Particularly, microaneurysms may contribute to the development of (small) hemorrhages/infarcts and the latter to cognitive decline in affected subjects. However, the relative importance of cerebral hemorrhages/infarcts, white matter damage and/or other CAA- or Abeta-related factors for cognitive deterioration in HCHWA-D remains to be determined.

Topics: Adult; Aged; Amyloid beta-Peptides; Amyloidosis; Animals; Brain; Cerebral Amyloid Angiopathy, Familial; Cerebral Hemorrhage; Humans; Mice; Middle Aged; Mutation; Peptide Fragments

Cerebral amyloid β (Aβ) proteostasis is compromised under neuronal overexcitation, long-term neuroinflammation and brain aging. Using the animal model of LPS-induced neuroinflammation we demonstrated that treatment with levetiracetam, a specific modulator of synaptic vesicle glycoprotein SV2A, rescues abnormal synaptic vesicle (SV) fusion and neurotransmitter release, decreasing elevated hippocampal APP levels in vivo. Therapy with levetiracetam upregulates the SV2A in hippocampus and restores the level of apolipoprotein E, involved in brain Aβ aggregation/clearance and resolution of inflammation. We demonstrated that oligomers of Aβ

Topics: Amyloid beta-Peptides; Amyloidosis; Animals; Cells, Cultured; Drug Delivery Systems; Hippocampus; Levetiracetam; Lipopolysaccharides; Male; Membrane Glycoproteins; Nerve Tissue Proteins; Nootropic Agents; Peptide Fragments; Rats; Rats, Wistar

A hallmark pathology of Alzheimer's disease (AD) is the formation of amyloid β (Aβ) deposits that exhibit diverse localization and morphologies, ranging from diffuse to cored-neuritic deposits in brain parenchyma, with cerebral vascular deposition in leptomeningeal and parenchymal compartments. Most AD brains exhibit the full spectrum of pathologic Aβ morphologies. In the course of studies to model AD amyloidosis, we have generated multiple transgenic mouse models that vary in the nature of the transgene constructs that are expressed; including the species origin of Aβ peptides, the levels and length of Aβ that is deposited, and whether mutant presenilin 1 (PS1) is co-expressed. These models recapitulate features of human AD amyloidosis, but interestingly some models can produce pathology in which one type of Aβ morphology dominates. In prior studies of mice that primarily develop cored-neuritic deposits, we determined that Aβ deposition is associated with changes in cytosolic protein solubility in which a subset of proteins become detergent-insoluble, indicative of secondary proteome instability. Here, we survey changes in cytosolic protein solubility across seven different transgenic mouse models that exhibit a range of Aβ deposit morphologies. We find a surprisingly diverse range of changes in proteome solubility across these models. Mice that deposit human Aβ40 and Aβ42 in cored-neuritic plaques had the most robust changes in proteome solubility. Insoluble cytosolic proteins were also detected in the brains of mice that develop diffuse Aβ42 deposits but to a lesser extent. Notably, mice with cored deposits containing only Aβ42 had relatively few proteins that became detergent-insoluble. Our data provide new insight into the diversity of biological effects that can be attributed to different types of Aβ pathology and support the view that fibrillar cored-neuritic plaque pathology is the more disruptive Aβ pathology in the Alzheimer's cascade.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Animals; Brain; Disease Models, Animal; Gliosis; Humans; Mice; Mice, Transgenic; Peptide Fragments; Plaque, Amyloid; Presenilin-1; Proteome; Solubility

Misfolding and fibrillogenesis of amyloid-β protein (Aβ) play a key role in the onset and progression of Alzheimer's disease (AD). Screening for inhibitors against Aβ amyloidogenesis is helpful for rational designing and developing new anti-AD drugs and therapeutic strategies. Dihydromyricetin, a natural flavonoid extracted from a Chinese herb,

Topics: Amyloid beta-Peptides; Amyloidosis; Animals; Cytotoxins; Dose-Response Relationship, Drug; Flavonoids; Flavonols; PC12 Cells; Peptide Fragments; Protein Structure, Secondary; Rats

Mutation is considered an important factor in the accumulation of amyloid-β (Aβ), which is a hallmark of Alzheimer's disease (AD). A2V Aβ40 shows a higher aggregation tendency; however, the existing knowledge is not sufficient to explain the mechanism. We performed replica-exchange molecular dynamics simulations (REMD) to investigate the structural properties of A2V Aβ40 monomers and consider the tautomerism of histidine. The collective effects of the mutation and tautomerism leads A2V Aβ40 to much higher β-sheet and lower α-helix contents than WT Aβ40, which may explain the enhanced aggregation kinetics of A2V Aβ40 with respect to WT Aβ40. The current research provides new insights on understanding the pathology of AD.

Topics: Amyloid beta-Peptides; Amyloidogenic Proteins; Amyloidosis; Histidine; Humans; Molecular Dynamics Simulation; Mutation; Peptide Fragments; Protein Aggregates; Protein Structure, Secondary; tau Proteins

The abnormal aggregation of amyloid β-protein (Aβ) is considered central in the pathogenesis of Alzheimer's disease. We focused on membrane-mediated amyloidogenesis and found that amyloid fibrils formed on monosialoganglioside GM1 clusters were more toxic than those formed in aqueous solution. In this study, we investigated the structure of the toxic fibrils by Aβ-(1-40) in detail in comparison with less-toxic fibrils formed in aqueous solution. The less-toxic fibrils contain in-resister parallel β-sheets, whereas the structure of the toxic fibrils is unknown. Atomic force microscopy revealed that the toxic fibrils had a flat, tape-like morphology composed of a single β-sheet layer. Isotope-edited infrared spectroscopy indicated that almost the entire sequence of Aβ is included in the β-sheet. Chemical cross-linking experiments using Cys-substituted Aβs suggested that the fibrils mainly contained both in-resister parallel and two-residue-shifted antiparallel β-sheet structures. Solid-state NMR experiments also supported this conclusion. Thus, the toxic fibrils were found to possess a novel unique structure.

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Amyloidogenic Proteins; Amyloidosis; G(M1) Ganglioside; Humans; Peptide Fragments; Protein Structure, Secondary

Amyloid imaging demonstrates the in vivo presence of amyloid-β (Aβ) deposits in the aging human brain but it is still unknown which structural forms and modifications of Aβ are detected. In Alzheimer's disease, most amyloid deposits are predominantly composed of Aβ ending at amino acid residues Val40 or Ala42. It has been reported that Aβ40 is largely restricted to neuritic plaques while Aβ42 may be deposited in amyloid plaques of all types, and is often the sole component of diffuse plaques. The distinction is important as it is mainly the neuritic plaques that correlate with cognitive impairment while diffuse plaques may be the initial type of Aβ deposited. Whether PET amyloid ligands such as florbetapir-18F (Amyvid) are partially or wholly selective for brain deposits of Aβ40 or Aβ42 is currently unknown. We compared antemortem florbetapir PET cortical/cerebellar signal intensity (SUVr) of 55 subjects with postmortem biochemical (ELISA) measurements employing specific antibodies against Aβ40 and Aβ42. Spearman's univariable correlations were significant for both Aβ40 and Aβ42, but were much stronger for Aβ42. Multiple linear regression showed significance only for Aβ42. These results suggest that florbetapir binds only weakly, if at all, to Aβ40. This may be in part due to the higher likelihood for Aβ42 to be present in a β-pleated sheet tertiary structure, or to differences between Aβ40 and Aβ42 in β-pleated sheet tertiary or quaternary structure.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Aniline Compounds; Autopsy; Brain; Ethylene Glycols; Humans; Linear Models; Peptide Fragments; Plaque, Amyloid; Positron-Emission Tomography

The multicomponent nature of neuronal plaques in Alzheimer's disease signifies the possible recruitment of non-Aβ candidates during the amyloid growth of Aβ peptides. Here, we show that amyloid fibrils of Aβ

Topics: Amyloid; Amyloid beta-Peptides; Amyloidosis; Humans; In Vitro Techniques; Models, Molecular; Molecular Docking Simulation; Peptide Fragments; Plaque, Amyloid; Protein Aggregates; Protein Aggregation, Pathological; Protein Interaction Domains and Motifs

Protein aggregation is a hallmark of several degenerative diseases, including Alzheimer's disease, Parkinson's disease and familial amyloidosis (Finnish type) (FAF). A method to isolate and detect amyloids is desired for the diagnosis of amyloid diseases. Here, we report the synthesis of pentameric thiophene amyloid ligand (p-FTAA) linked to agarose resin for selective purification of amyloid aggregates produced in vitro and in vivo. Using amyloid fibrils produced in vitro from α-synuclein, gelsolin, and Aβ

Topics: Acetates; alpha-Synuclein; Amyloid; Amyloid beta-Peptides; Amyloidosis; Animals; Corneal Dystrophies, Hereditary; Gelsolin; Humans; Mice; Peptide Fragments; Protein Aggregates; Sepharose; Thiophenes

Cerebrospinal fluid analysis and other measurements of amyloidosis, such as amyloid-binding positron emission tomography studies, are limited by cost and availability. There is a need for a more practical amyloid β (Aβ) biomarker for central nervous system amyloid deposition.. We adapted our previously reported stable isotope labeling kinetics protocol to analyze the turnover kinetics and concentrations of Aβ38, Aβ40, and Aβ42 in human plasma.. Aβ isoforms have a half-life of approximately 3 hours in plasma. Aβ38 demonstrated faster turnover kinetics compared with Aβ40 and Aβ42. Faster fractional turnover of Aβ42 relative to Aβ40 and lower Aβ42 and Aβ42/Aβ40 concentrations in amyloid-positive participants were observed.. Blood plasma Aβ42 shows similar amyloid-associated alterations as we have previously reported in cerebrospinal fluid, suggesting a blood-brain transportation mechanism of Aβ. The stability and sensitivity of plasma Aβ measurements suggest this may be a useful screening test for central nervous system amyloidosis.

Topics: Aged; Amyloid beta-Peptides; Amyloidosis; Area Under Curve; Biomarkers; Chromatography, Liquid; Humans; Immunoprecipitation; Isotope Labeling; Kinetics; Mass Spectrometry; Peptide Fragments; Prospective Studies; ROC Curve; Single-Blind Method

The self-assembly of two derivatives of KLVFF, a fragment Aβ(16-20) of the amyloid beta (Aβ) peptide, is investigated and recovery of viability of neuroblastoma cells exposed to Aβ (1-42) is observed at sub-stoichiometric peptide concentrations. Fluorescence assays show that NH

Topics: Amino Acid Sequence; Amyloid beta-Peptides; Amyloidosis; Animals; Cell Survival; Molecular Structure; Neurons; Peptide Fragments; Protein Aggregates; Protein Aggregation, Pathological; Protein Structure, Secondary; Rats; Spectrometry, Mass, Electrospray Ionization; Spectroscopy, Fourier Transform Infrared; X-Ray Diffraction

Intracerebral or intraperitoneal injections of brain extracts from the Alzheimer's disease patients result in the acceleration of cerebral β-amyloidosis in transgenic mice. Earlier, we have found that intravenous injections of synthetic full-length amyloid-β (Aβ) comprising the isomerized Asp7 trigger cerebral β-amyloidosis. In vitro studies have shown that isomerization of Asp7 promotes zinc-induced oligomerization of the Aβ metal-binding domain (Aβ1-16). Here we report that single intracerebral injection of the peptide Aβ1-16 with isomerized Asp7 (isoAβ1-16) but not the injection of Aβ1-16 significantly increases amyloid burden in 5XFAD transgenic mice. Our results provide evidence for a role of isoAβ1-16 as a minimal seeding agent of Aβ aggregation in vivo.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Analysis of Variance; Animals; Aspartic Acid; Disease Models, Animal; Gene Expression Regulation; Humans; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mutation; Peptide Fragments; Plaque, Amyloid; Presenilin-1

Many lines of evidence suggest a protective role for high-density lipoprotein (HDL) and its major apolipoprotein (apo)A-I in Alzheimer's Disease (AD). HDL/apoA-I particles are produced by the liver and intestine and, in addition to removing excess cholesterol from the body, are increasingly recognized to have vasoprotective functions. Here we tested the ability of reconstituted HDL (rHDL) consisting of human apoA-I reconstituted with soy phosphatidylcholine for its ability to lower amyloid beta (Aβ) levels in symptomatic APP/PS1 mice, a well-characterized preclinical model of amyloidosis. Animals were treated intravenously either with four weekly doses (chronic study) or a single dose of 60mg/kg of rHDL (acute study). The major finding of our acute study is that soluble brain Aβ40 and Aβ42 levels were significantly reduced within 24h of a single dose of rHDL. By contrast, no changes were observed in our chronic study with respect to soluble or deposited Aβ levels in animals assessed 7days after the final weekly dose of rHDL, suggesting that beneficial effects diminish as rHDL is cleared from the body. Further, rHDL-treated animals showed no change in amyloid burden, cerebrospinal fluid (CSF) Aβ levels, neuroinflammation, or endothelial activation in the chronic study, suggesting that the pathology-modifying effects of rHDL may indeed be acute and may be specific to the soluble Aβ pool. That systemic administration of rHDL can acutely modify brain Aβ levels provides support for further investigation of the therapeutic potential of apoA-I-based agents for AD. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Animals; Apolipoprotein A-I; Brain; Disease Models, Animal; Female; Humans; Lipoproteins, HDL; Male; Mice; Mice, Transgenic; Peptide Fragments

Increasing amounts of evidence suggest that Alzheimer's disease (AD) and type 2 diabetes (T2D) are linked to each other. We have recently identified in vitro a high affinity interaction between β-amyloid peptide (Aβ) of AD and islet amyloid polypeptide (IAPP) of T2D which results in the formation of non-fibrillar and non-cytotoxic Aβ-IAPP hetero-oligomers. The Aβ-IAPP interaction delays cytotoxic self-association of both polypeptides albeit it is unable to block it. In this context, IAPP-GI, a soluble conformationally constrained mimic of a non-amyloidogenic and non-toxic IAPP conformer, completely blocks Aβ amyloidogenesis and cytotoxicity. Here we studied the hetero-association pathways of Aβ with IAPP and with IAPP-GI. We found that preformed Aβ or IAPP fibrils and cytotoxic assemblies are able to seed amyloidogenesis and cytotoxicity in Aβ-IAPP but not in Aβ-IAPP-GI solutions. Initially non-fibrillar and non-toxic Aβ-IAPP but not Aβ-IAPP-GI hetero-oligomers were found to further aggregate into hetero-fibrils and cytotoxic assemblies in a process strongly enhanced under Aβ or IAPP self-assembly promoting conditions. Importantly, our studies provided evidence that initially non-fibrillar and non-toxic Aβ-IAPP hetero-oligomers are able to misfold into hetero-fibrils and indicated a crucial role of the strong amyloidogenic character of IAPP in this process. These results uncover a novel molecular property of the Aβ and IAPP sequences, i.e. their ability to form hetero-fibrils, and offer mechanistic support to a model linking Aβ and IAPP hetero-association to their cytotoxic self-association pathways and thus likely to the pathogenesis of AD and T2D.

Topics: Alzheimer Disease; Amino Acid Sequence; Amyloid; Amyloid beta-Peptides; Amyloidosis; Animals; Benzothiazoles; Cell Survival; Circular Dichroism; Diabetes Mellitus, Type 2; Islet Amyloid Polypeptide; Kinetics; Microscopy, Electron, Transmission; Molecular Sequence Data; PC12 Cells; Peptide Fragments; Protein Binding; Protein Folding; Protein Multimerization; Rats; Spectrometry, Fluorescence; Thiazoles

Abnormal accumulation of Aβ (amyloid β) within AEL (autophagy-endosomal-lysosomal) vesicles is a prominent neuropathological feature of AD (Alzheimer's disease), but the mechanism of accumulation within vesicles is not clear. We express secretory forms of human Aβ1-40 or Aβ1-42 in Drosophila neurons and observe preferential localization of Aβ1-42 within AEL vesicles. In young animals, Aβ1-42 appears to associate with plasma membrane, whereas Aβ1-40 does not, suggesting that recycling endocytosis may underlie its routing to AEL vesicles. Aβ1-40, in contrast, appears to partially localize in extracellular spaces in whole brain and is preferentially secreted by cultured neurons. As animals become older, AEL vesicles become dysfunctional, enlarge and their turnover appears delayed. Genetic inhibition of AEL function results in decreased Aβ1-42 accumulation. In samples from older animals, Aβ1-42 is broadly distributed within neurons, but only the Aβ1-42 within dysfunctional AEL vesicles appears to be in an amyloid-like state. Moreover, the Aβ1-42-containing AEL vesicles share properties with AD-like extracellular plaques. They appear to be able to relocate to extracellular spaces either as a consequence of age-dependent neurodegeneration or a non-neurodegenerative separation from host neurons by plasma membrane infolding. We propose that dysfunctional AEL vesicles may thus be the source of amyloid-like plaque accumulation in Aβ1-42-expressing Drosophila with potential relevance for AD.

Topics: Aging; Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Animals; Animals, Genetically Modified; Autophagy; Brain; Cell Membrane; Cells, Cultured; Cytoplasmic Vesicles; Drosophila melanogaster; Endocytosis; Endosomes; Extracellular Space; Humans; Lysosomes; Nerve Degeneration; Neurons; Peptide Fragments; Plaque, Amyloid

Familial hypercholesterolemia is caused by inherited genetic abnormalities that directly or indirectly affect the function of the low-density lipoprotein (LDL) receptor. This condition is characterized by defective catabolism of LDL which results in increased plasma cholesterol concentrations and premature coronary artery disease. Nevertheless, there is increasing preclinical and clinical evidence indicating that familial hypercholesterolemia subjects show a particularly high incidence of mild cognitive impairment. Moreover, the LDL receptor (LDLr) has been implicated as the main central nervous system apolipoprotein E receptor that regulates amyloid deposition in distinct mouse models of β-amyloidosis. In this regard, herein we hypothesized that the lack of LDLr would enhance the susceptibility to amyloid-β-(Aβ)-induced neurotoxicity in mice. Using the acute intracerebroventricular injection of aggregated Aβ(1-40) peptide (400 pmol/mouse), a useful approach for the investigation of molecular mechanisms involved in Aβ toxicity, we observed oxidative stress, neuroinflammation, and neuronal membrane damage within the hippocampus of C57BL/6 wild-type mice, which were associated with spatial reference memory and working memory impairments. In addition, our data show that LDLr knockout (LDLr(-/-)) mice, regardless of Aβ treatment, displayed memory deficits and increased blood-brain barrier permeability. Nonetheless, LDLr(-/-) mice treated with Aβ(1-40) peptide presented increased acetylcholinesterase activity, astrogliosis, oxidative imbalance, and cell permeability within the hippocampus in comparison with Aβ(1-40)-treated C57BL/6 wild-type mice. Overall, the present study shows that the lack of LDLr increases the susceptibility to Aβ-induced neurotoxicity in mice providing new evidence about the crosslink between familial hypercholesterolemia and cognitive impairment.

Topics: Acetylcholinesterase; Amyloid beta-Peptides; Amyloidosis; Animals; Antioxidants; Astrocytes; Blood-Brain Barrier; Capillary Permeability; Cell Membrane Permeability; Disease Models, Animal; Gliosis; Hippocampus; Memory Disorders; Memory, Short-Term; Mice, Inbred C57BL; Mice, Knockout; Neuroimmunomodulation; Oxidative Stress; Peptide Fragments; Prefrontal Cortex; Receptors, LDL; Spatial Memory; Superoxide Dismutase

In a previous in vitro study, the standardized turmeric extract, HSS-888, showed strong inhibition of Aβ aggregation and secretion in vitro, indicating that HSS-888 might be therapeutically important. Therefore, in the present study, HSS-888 was evaluated in vivo using transgenic 'Alzheimer' mice (Tg2576) over-expressing Aβ protein. Following a six-month prevention period where mice received extract HSS-888 (5mg/mouse/day), tetrahydrocurcumin (THC) or a control through ingestion of customized animal feed pellets (0.1% w/w treatment), HSS-888 significantly reduced brain levels of soluble (∼40%) and insoluble (∼20%) Aβ as well as phosphorylated Tau protein (∼80%). In addition, primary cultures of microglia from these mice showed increased expression of the cytokines IL-4 and IL-2. In contrast, THC treatment only weakly reduced phosphorylated Tau protein and failed to significantly alter plaque burden and cytokine expression. The findings reveal that the optimized turmeric extract HSS-888 represents an important step in botanical based therapies for Alzheimer's disease by inhibiting or improving plaque burden, Tau phosphorylation, and microglial inflammation leading to neuronal toxicity.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Analysis of Variance; Animals; Antioxidants; Curcuma; Cytokines; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Humans; Mice; Mice, Transgenic; Mutation; Peptide Fragments; Phosphorylation; Plant Extracts; tau Proteins

Although evidence is accumulating that diabetes mellitus is an important risk factor for sporadic Alzheimer's disease (AD), the mechanisms by which defects in insulin signaling may lead to the acceleration of AD progression remain unclear. In this study, we applied streptozotocin (STZ) to induce experimental diabetes in AD transgenic mice (5XFAD model) and investigated how insulin deficiency affects the β-amyloidogenic processing of amyloid precursor protein (APP). Two and half months after 5XFAD mice were treated with STZ (90 mg/kg, i.p., once daily for two consecutive days), they showed significant reductions in brain insulin levels without changes in insulin receptor expression. Concentrations of cerebral amyloid-β peptides (Aβ40 and Aβ42) were significantly increased in STZ-treated 5XFAD mice as compared with vehicle-treated 5XFAD controls. Importantly, STZ-induced insulin deficiency upregulated levels of both β-site APP cleaving enzyme 1 (BACE1) and full-length APP in 5XFAD mouse brains, which was accompanied by dramatic elevations in the β-cleaved C-terminal fragment (C99). Interestingly, BACE1 mRNA levels were not affected, whereas phosphorylation of the translation initiation factor eIF2α, a mechanism proposed to mediate the post-transcriptional upregulation of BACE1, was significantly elevated in STZ-treated 5XFAD mice. Meanwhile, levels of GGA3, an adapter protein responsible for sorting BACE1 to lysosomal degradation, are indistinguishable between STZ- and vehicle-treated 5XFAD mice. Moreover, STZ treatments did not affect levels of Aβ-degrading enzymes such as neprilysin and insulin-degrading enzyme (IDE) in 5XFAD brains. Taken together, our findings provide a mechanistic foundation for a link between diabetes and AD by demonstrating that insulin deficiency may change APP processing to favor β-amyloidogenesis via the translational upregulation of BACE1 in combination with elevations in its substrate, APP.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Amyloidosis; Animals; Aspartic Acid Endopeptidases; Behavior, Animal; Disease Models, Animal; Disease Progression; Hippocampus; Humans; Insulin; Mice; Mice, Transgenic; Peptide Fragments; Protein Multimerization; Protein Structure, Secondary; Time Factors

Alzheimer's disease is the most common form of senile dementia. This neurodegenerative disorder is characterized by an amyloid deposition in senile plaques, composed primarily of fibrils of an aggregated peptide, amyloid β (Aβ). The modeling of a senile plaque formation on a model neuronal membrane under the physiological condition is an attractive issue. In this study, we used anionic liposomes to model the senile plaque formation by Aβ. The growth behavior of amyloid Aβ fibrils was directly observed, revealing that the induction of the spherulitic Aβ aggregates could result from the growth of seeds in the presence of anionic liposomes. The seeds of Aβ fibrils strongly interacted with negatively charged liposome and the subsequent association of the seeds were induced to form the seed cluster with many growth ends, which is advantageous for the formation of spherulitic Aβ aggregates. Therefore, anionic liposomes mediated not only fibril growth but also the aggregation process. These results imply that anionic liposome membranes would affect the aggregate form of Aβ fibrils. The modeling of senile plaque reported here is considered to have great potential for study on the amyloidosis.

Topics: Amyloid beta-Peptides; Amyloidosis; Anions; Humans; Liposomes; Models, Chemical; Peptide Fragments; Plaque, Amyloid

Part of the inflammatory response in Alzheimer's disease (AD) is the upregulation of the inducible nitric oxide synthase (NOS2) resulting in increased NO production. NO contributes to cell signaling by inducing posttranslational protein modifications. Under pathological conditions there is a shift from the signal transducing actions to the formation of protein tyrosine nitration by secondary products like peroxynitrite and nitrogen dioxide. We identified amyloid β (Aβ) as an NO target, which is nitrated at tyrosine 10 (3NTyr(10)-Aβ). Nitration of Aβ accelerated its aggregation and was detected in the core of Aβ plaques of APP/PS1 mice and AD brains. NOS2 deficiency or oral treatment with the NOS2 inhibitor L-NIL strongly decreased 3NTyr(10)-Aβ, overall Aβ deposition and cognitive dysfunction in APP/PS1 mice. Further, injection of 3NTyr(10)-Aβ into the brain of young APP/PS1 mice induced β-amyloidosis. This suggests a disease modifying role for NOS2 in AD and therefore represents a potential therapeutic target.

Topics: Age Factors; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Animals; Biophysics; Brain; Disease Models, Animal; Drug Combinations; Electric Stimulation; Enzyme-Linked Immunosorbent Assay; Gene Expression Regulation; Hippocampus; Humans; Immunoprecipitation; In Vitro Techniques; Long-Term Potentiation; Maze Learning; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mutation; Neurons; Nitric Oxide Synthase Type II; Patch-Clamp Techniques; Peptide Fragments; Peroxynitrous Acid; Plaque, Amyloid; Presenilin-1; Tyrosine

Mitochondrial dysfunction and oxidative stress are involved in Alzheimer disease (AD) pathogenesis. In human AD brains, the activity of the alpha-ketoglutarate dehydrogenase enzyme complex (alpha-KGDHC) is reduced. KGDHC is mostly involved in NADH production. It can also participate in oxidative stress and reactive oxygen species (ROS) production. The mitochondrial dihydrolipoyl succinyltransferase enzyme (DLST) is a key subunit specific to the alpha-KGDHC. In cultured cells, reduction of DLST increased H(2)O(2)-induced ROS generation and cell death. Thus, we asked whether partial genetic deletion of DLST could accelerate the onset of AD pathogenesis, using a transgenic mouse model of amyloid deposition crossed with DLST(+/-) mice. Tg19959 mice, which carry the human amyloid precursor protein with two mutations, develop amyloid deposits and progressive behavioral abnormalities. We compared Tg19959 mice to Tg19959-DLST(+/-) littermates at 2-3 months of age and studied the effects of DLST deficiency on amyloid deposition, spatial learning and memory, and oxidative stress. We found that alpha-KGDHC activity was reduced in DLST(+/-) mice. We also found that DLST deficiency increased amyloid plaque burden, Abeta oligomers, and nitrotyrosine levels and accelerated the occurrence of spatial learning and memory deficits in female Tg19959 mice. Our data suggest that alpha-KGDHC may be involved in AD pathogenesis through increased mitochondrial oxidative stress.

Topics: Acyltransferases; Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Animals; Disease Models, Animal; Female; Male; Memory Disorders; Mice; Mice, Transgenic; Mitochondria; Oxidative Stress; Peptide Fragments

Amyloid beta-peptide (Abeta) is a major constituent of senile plaques in Alzheimer's disease (AD). Neurotoxicity results from the conformational transition of Abeta from random-coil to beta-sheet and its oligomerization. Among a series of ionic compounds able to interact with soluble Abeta, Tramiprosate (3-amino-1-propanesulfonic acid; 3APS; Alzhemedtrade mark) was found to maintain Abeta in a non-fibrillar form, to decrease Abeta(42)-induced cell death in neuronal cell cultures, and to inhibit amyloid deposition. Tramiprosate crosses the murine blood-brain barrier (BBB) to exert its activity. Treatment of TgCRND8 mice with Tramiprosate resulted in significant reduction (approximately 30%) in the brain amyloid plaque load and a significant decrease in the cerebral levels of soluble and insoluble Abeta(40) and Abeta(42) (approximately 20-30%). A dose-dependent reduction (up to 60%) of plasma Abeta levels was also observed, suggesting that Tramiprosate influences the central pool of Abeta, changing either its efflux or its metabolism in the brain. We propose that Tramiprosate, which targets soluble Abeta, represents a new and promising therapeutic class of drugs for the treatment of AD.

Topics: Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Animals; Brain; Cell Death; Cells, Cultured; Disease Models, Animal; Embryo, Mammalian; GABA Agonists; Humans; Mice; Mice, Transgenic; Neurons; Peptide Fragments; Rats; Rats, Sprague-Dawley; Taurine

Transgenic mice expressing mutant forms of both amyloid-beta (Abeta) precursor protein (APP) and presenilin (PS) 2 develop severe brain amyloidosis and cognitive deficits, two pathological hallmarks of Alzheimer's disease (AD). One-year-old APP/PS2 mice with high brain levels of Abeta and abundant Abeta plaques show disturbances in spatial learning and memory. Treatment of these deteriorated mice with a systemic slow-release formulation of insulin-like growth factor I (IGF-I) significantly ameliorated AD-like disturbances. Thus, IGF-I enhanced cognitive performance, decreased brain Abeta load, increased the levels of synaptic proteins, and reduced astrogliosis associated to Abeta plaques. The beneficial effects of IGF-I were associated to a significant increase in brain Abeta complexed to protein carriers such as albumin, apolipoprotein J or transthyretin. Since levels of APP were not modified after IGF-I therapy, and in vitro data showed that IGF-I increases the transport of Abeta/carrier protein complexes through the choroid plexus barrier, it seems that IGF-I favors elimination of Abeta from the brain, supporting a therapeutic use of this growth factor in AD.

Topics: Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Analysis of Variance; Animals; Behavior, Animal; Blood-Brain Barrier; Brain Chemistry; Brain Diseases; Cognition Disorders; Disease Models, Animal; Immunohistochemistry; Insulin-Like Growth Factor I; Maze Learning; Mice; Mice, Inbred C57BL; Mice, Transgenic; Peptide Fragments; Spatial Behavior

Cerebral beta-amyloidosis was found in 16/18 marmosets aged <10 yrs and 8/9 marmosets aged >10 yrs, injected intracerebrally with human or marmoset brain homogenate containing beta-amyloid 1-8 years previously. It was found in only 2/12 marmosets aged <10 yrs and 1/15 marmosets aged >10 yrs, injected with synthetic Abeta-peptides, CSF, or brain tissue which did not contain beta-amyloid. Cerebral beta-amyloidosis was found in 0/11 uninjected marmosets aged <10 yrs and in 5/29 uninjected marmosets aged >10 yrs. The beta-amyloidosis comprised small and large vessel angiopathy and some plaques throughout cortex and was qualitatively similar in injected marmosets and, when present, in uninjected marmosets. Of those injected marmosets which were positive, the amount of beta-amyloidosis was unrelated to age or incubation times but the 3 injected marmosets without beta-amyloidosis had incubation times of <3.5 years. We conclude that beta-amyloid, or associated factors, can initiate or accelerate the process of cerebral amyloidosis in primates.

Topics: Adult; Aging; Amyloid beta-Peptides; Amyloidosis; Animals; Brain; Callithrix; Down Syndrome; Female; Gerstmann-Straussler-Scheinker Disease; Humans; Male; Middle Aged; Peptide Fragments

Alzheimer's disease (AD) is characterized by pathological lesions, such as senile plaques (SPs) and cerebral amyloid angiopathy (CAA), both predominantly consisting of a proteolytic cleavage product of the amyloid-beta precursor protein (APP), the amyloid-beta peptide (Abeta). CAA is also the major pathological lesion in hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D), caused by a mutation in the gene coding for the Abeta peptide. Several members of the small heat shock protein (sHsp) family, such as alphaB-crystallin, Hsp27, Hsp20 and HspB2, are associated with the pathological lesions of AD, and the direct interaction between sHsps and Abeta has been demonstrated in vitro. HspB8, also named Hsp22 of H11, is a recently discovered member of the sHsp family, which has chaperone activity and is observed in neuronal tissue. Furthermore, HspB8 affects protein aggregation, which has been shown by its ability to prevent formation of mutant huntingtin aggregates. The aim of this study was to investigate whether HspB8 is associated with the pathological lesions of AD and HCHWA-D and whether there are effects of HspB8 on Abeta aggregation and Abeta-mediated cytotoxicity. We observed the expression of HspB8 in classic SPs in AD brains. In addition, HspB8 was found in CAA in HCHWA-D brains, but not in AD brains. Direct interaction of HspB8 with Abeta(1-42), Abeta(1-40) and Abeta(1-40) with the Dutch mutation was demonstrated by surface plasmon resonance. Furthermore, co-incubation of HspB8 with D-Abeta(1-40) resulted in the complete inhibition of D-Abeta(1-40)-mediated death of cerebrovascular cells, likely mediated by a reduction in both the beta-sheet formation of D-Abeta(1-40) and its accumulation at the cell surface. In contrast, however, with Abeta(1-42), HspB8 neither affected beta-sheet formation nor Abeta-mediated cell death. We conclude that HspB8 might play an important role in regulating Abeta aggregation and, therefore, the development of classic SPs in AD and CAA in HCHWA-D.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Brain; Cell Death; Cerebral Amyloid Angiopathy; Cerebral Hemorrhage; Heat-Shock Proteins; Humans; Molecular Chaperones; Mutation; Peptide Fragments; Plaque, Amyloid; Protein Serine-Threonine Kinases; Surface Plasmon Resonance; Tissue Distribution

Nicotine reduces beta-amyloidosis and has a beneficial effect against Alzheimer's disease (AD), but the underlying mechanism is not clear. The abnormal interactions of beta-amyloid (Abeta) with metal ions such as copper and zinc are implicated in the process of Abeta deposition in AD brains. In the present study, we investigated the effect of nicotine on metal homeostasis in the hippocampus and cortex of APP(V717I) (London mutant form of APP) transgenic mice. A significant reduction in the metal contents of copper and zinc in senile plaques and neuropil is observed after nicotine treatment. The densities of copper and zinc distributions in a subfield of the hippocampus CA1 region are also reduced after nicotine treatment. We further studied the mechanism of nicotine-mediated effect on metal homeostasis by using SH-SY5Y cells overexpressing the Swedish mutant form of human APP (APPsw). Nicotine treatment decreases the intracellular copper concentration and attenuates Abeta-mediated neurotoxicity facilitated by the addition of copper, and these effects are independent of the activation of nicotinic acetylcholine-receptor. These data suggest that the effect of nicotine on reducing beta-amyloidosis is partly mediated by regulating metal homeostasis.

Topics: Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Animals; Cell Survival; Copper; Hippocampus; Homeostasis; Humans; Metals; Mice; Mice, Transgenic; Molecular Chaperones; Neuroprotective Agents; Nicotine; Peptide Fragments; Plaque, Amyloid; Reactive Oxygen Species; Receptors, Nicotinic; Superoxide Dismutase; Superoxide Dismutase-1

Colostrinin (CLN), a mixture of proline-rich polypeptides, has shown a stabilizing effect on cognitive function in Alzheimer's patients measured by the Alzheimer's disease Assessment Scale-cognitive (ADAS-cog) and in Instrumental Activities of Daily Living (ILDL) in recently conducted clinical trials. The aim of this study was to elucidate a possible mode of action of CLN in the treatment of Alzheimer's disease. Here, we report that CLN prevents the aggregation of beta-amyloid peptide Abeta (1-40) in vitro. The impact of CLN on the fibril formation was monitored by optical and electron microscopy. The electron micrographs illustrate that, at 25 microM, Abeta (1-40) peptides formed fibrils after 24-48 h of incubation. The presence of 0.25 microM CLN completely abolished the fibril formation. Abeta (1-40) peptides grow into dense fibers when examined at the 20th day. In the presence of CLN, however, the fibrils are much shorter and less dense. Addition of CLN as late as the 17th day can still dissolves the preformed fibrils. These observations were compared to the effect of CLN on the neurotoxic activity of beta-amyloid peptides in the cell culture model (SHSY-5Y). The beta-amyloid peptides were pre-incubated with CLN at various times and used to treat SHSY-5Y neuroblastoma cells for up to 4 days. The cytotoxic effect was monitored by trypan blue exclusion. We demonstrated that 24-48 h treatment was the onset of toxicity of 10-50 microM of beta-amyloid peptides. Pre-incubation of 0.0025-0.25muM of CLN with 25 microM of beta-amyloid peptides leads to near-complete abolition of cytotoxicity. Low doses of CLN (2.5 nM) can attain cytotoxic protection levels similar to those of highest doses (0.25 microM). Thus, the time course for the appearance of beta-amyloid fibrils coincides with that for cytotoxicity, and that the reduction of fibrils of beta-amyloid peptides by CLN is concomitant with the reduction of the cytotoxic effects of beta-amyloid on SHSY-5Y neuroblastoma cells. Our studies suggest that the neuroprotective effects exerted by CLN are related to the reduction of beta-amyloid fibrils.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Cell Line, Tumor; Cell Survival; Humans; Intercellular Signaling Peptides and Proteins; Neuroblastoma; Neurons; Neuroprotective Agents; Peptide Fragments; Peptides; Protein Structure, Secondary

Recent epidemiological evidence indicates that insulin resistance, a proximal cause of Type II diabetes [a non-insulin dependent form of diabetes mellitus (NIDDM)], is associated with an increased relative risk for Alzheimer's disease (AD). In this study we examined the role of dietary conditions leading to NIDDM-like insulin resistance on amyloidosis in Tg2576 mice, which model AD-like neuropathology. We found that diet-induced insulin resistance promoted amyloidogenic beta-amyloid (Abeta) Abeta1-40 and Abeta1-42 peptide generation in the brain that corresponded with increased gamma-secretase activities and decreased insulin degrading enzyme (IDE) activities. Moreover, increased Abeta production also coincided with increased AD-type amyloid plaque burden in the brain and impaired performance in a spatial water maze task. Further exploration of the apparent interrelationship of insulin resistance to brain amyloidosis revealed a functional decrease in insulin receptor (IR)-mediated signal transduction in the brain, as suggested by decreased IR beta-subunit (IRbeta) Y1162/1163 autophosphorylation and reduced phosphatidylinositol 3 (PI3)-kinase/pS473-AKT/Protein kinase (PK)-B in these same brain regions. This latter finding is of particular interest given the known inhibitory role of AKT/PKB on glycogen synthase kinase (GSK)-3alpha activity, which has previously been shown to promote Abeta peptide generation. Most interestingly, we found that decreased pS21-GSK-3alpha and pS9-GSK-3beta phosphorylation, which is an index of GSK activation, positively correlated with the generation of brain C-terminal fragment (CTF)-gamma cleavage product of amyloid precursor protein, an index of gamma-secretase activity, in the brain of insulin-resistant relative to normoglycemic Tg2576 mice. Our study is consistent with the hypothesis that insulin resistance may be an underlying mechanism responsible for the observed increased relative risk for AD neuropathology, and presents the first evidence to suggest that IR signaling can influence Abeta production in the brain.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Amyloidosis; Animals; Aspartic Acid Endopeptidases; Brain; Cyclic AMP-Dependent Protein Kinase Type II; Cyclic AMP-Dependent Protein Kinases; Dietary Fats; Disease Models, Animal; Endopeptidases; Female; Glycogen Synthase Kinase 3; Humans; Insulin Resistance; Insulysin; Maze Learning; Mice; Mice, Transgenic; Nerve Tissue Proteins; Peptide Fragments; Phosphatidylinositol 3-Kinases; Phosphorylation; Plaque, Amyloid; Protein Processing, Post-Translational; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Receptor, Insulin; Signal Transduction; Spatial Behavior

Traumatic brain injury is a well-recognized environmental risk factor for developing Alzheimer's disease. Repetitive concussive brain injury (RCBI) exacerbates brain lipid peroxidation, accelerates amyloid (Abeta) formation and deposition, as well as cognitive impairments in Tg2576 mice. This study evaluated the effects of vitamin E on these four parameters in Tg2576 mice following RCBI. Eleven-month-old mice were randomized to receive either regular chow or chow-supplemented with vitamin E for 4 weeks, and subjected to RCBI (two injuries, 24 h apart) using a modified controlled cortical impact model of closed head injury. The same dietary regimens were maintained up to 8 weeks post-injury, when the animals were killed for biochemical and immunohistochemical analyses after behavioral evaluation. Vitamin E-treated animals showed a significant increase in brain vitamin E levels and a significant decrease in brain lipid peroxidation levels. After RBCI, compared with the group on regular chow, animals receiving vitamin E did not show the increase in Abeta peptides, and had a significant attenuation of learning deficits. This study suggests that the exacerbation of brain oxidative stress following RCBI plays a mechanistic role in accelerating Alphabeta accumulation and behavioral impairments in the Tg2576 mice.

Topics: Amyloid; Amyloid beta-Peptides; Amyloidosis; Animals; Antioxidants; Brain; Brain Chemistry; Brain Concussion; Cognition Disorders; Dietary Supplements; Dinoprost; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Female; Mice; Mice, Transgenic; Motor Activity; Oxidative Stress; Peptide Fragments; Vitamin E

Aging and apolipoprotein E (APOE) isoform are among the most consistent risks for the development of Alzheimer's disease (AD). Metabolic factors that modulate risk have been elusive, though oxidative reactions and their by-products have been implicated in human AD and in transgenic mice with overt histological amyloidosis. We investigated the relationship between the levels of endogenous murine amyloid beta (Abeta) peptides and the levels of a marker of oxidation in mice that never develop histological amyloidosis [i.e. APOE knockout (KO) mice with or without transgenic human APOEepsilon3 or human APOEepsilon4 alleles]. Aging-, gender-, and APOE-genotype-dependent changes were observed for endogenous mouse brain Abeta40 and Abeta42 peptides. Levels of the oxidized lipid F2-isoprostane (F2-isoPs) in the brains of the same animals as those used for the Abeta analyses revealed aging- and gender-dependent changes in APOE KO and in human APOEepsilon4 transgenic KO mice. Human APOEepsilon3 transgenic KO mice did not exhibit aging- or gender-dependent increases in F2-isoPs. In general, the changes in the levels of brain F2-isoPs in mice according to age, gender, and APOE genotype mirrored the changes in brain Abeta levels, which, in turn, paralleled known trends in the risk for human AD. These data indicate that there exists an aging-dependent, APOE-genotype-sensitive rise in murine brain Abeta levels despite the apparent inability of the peptide to form histologically detectable amyloid. Human APOEepsilon3, but not human APOEepsilon4, can apparently prevent the aging-dependent rise in murine brain Abeta levels, consistent with the relative risk for AD associated with these genotypes. The fidelity of the brain Abeta/F2-isoP relationship across multiple relevant variables supports the hypothesis that oxidized lipids play a role in AD pathogenesis, as has been suggested by recent evidence that F2-isoPs can stimulate Abeta generation and aggregation.

Topics: Aging; Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Animals; Apolipoprotein E3; Apolipoprotein E4; Apolipoproteins E; Astrocytes; Cell Count; Choline O-Acetyltransferase; Disease Models, Animal; Disease Progression; F2-Isoprostanes; Humans; Lipid Metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Neurons; Oxidative Stress; Peptide Fragments; Sex Factors

The E693Q mutation in the amyloid beta precursor protein (APP) leads to cerebral amyloid angiopathy (CAA), with recurrent cerebral hemorrhagic strokes and dementia. In contrast to Alzheimer disease (AD), the brains of those affected by hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D) show few parenchymal amyloid plaques. We found that neuronal overexpression of human E693Q APP in mice (APPDutch mice) caused extensive CAA, smooth muscle cell degeneration, hemorrhages and neuroinflammation. In contrast, overexpression of human wild-type APP (APPwt mice) resulted in predominantly parenchymal amyloidosis, similar to that seen in AD. In APPDutch mice and HCHWA-D human brain, the ratio of the amyloid-beta40 peptide (Abeta40) to Abeta42 was significantly higher than that seen in APPwt mice or AD human brain. Genetically shifting the ratio of AbetaDutch40/AbetaDutch42 toward AbetaDutch42 by crossing APPDutch mice with transgenic mice producing mutated presenilin-1 redistributed the amyloid pathology from the vasculature to the parenchyma. The understanding that different Abeta species can drive amyloid pathology in different cerebral compartments has implications for current anti-amyloid therapeutic strategies. This HCHWA-D mouse model is the first to develop robust CAA in the absence of parenchymal amyloid, highlighting the key role of neuronally produced Abeta to vascular amyloid pathology and emphasizing the differing roles of Abeta40 and Abeta42 in vascular and parenchymal amyloid pathology.

Topics: Age Factors; Aged; Aged, 80 and over; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Animals; Blood Vessels; Blotting, Western; Brain; Cerebral Hemorrhage; Cerebrovascular Circulation; Disease Models, Animal; Encephalitis; Enzyme-Linked Immunosorbent Assay; Glutamic Acid; Glutamine; Humans; Immunohistochemistry; In Situ Hybridization; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microscopy, Electron; Middle Aged; Mutation; Peptide Fragments; Pia Mater; Postmortem Changes; Thy-1 Antigens

The misfolding of the amyloid peptide, which is the result of a well-known alpha-to-beta transition, causes neurodegenerative disorder. Fluorinated alcohols have been described in the literature as potent solvents which can refold the beta-conformation. The present studies demonstrate the effectiveness of differently fluorinated alcohols for the beta-to-alpha refolding process on fibrillar aggregated amyloid beta(1-40). The regenerated helical structure is shown to be maintained in the absence of the fluoroalcohols, a behaviour which was found to contrast with immunoglobulin. We interpret this difference on the basis of the hydrophilic/hydrophobic domains in the amyloid sequence and present some speculations regarding the free-energy levels of the folded states of both proteins. The effect of the -CF(3) group on the observed conformational changes is interpreted as a result of alterations of the hydration shell of the peptides. Moreover, based on the results achieved with fluoroalcohols, we have used novel fluorinated amphiphiles possessing blood-compatibility properties and studied their effect on amyloid beta(1-40). First results point in the direction of a beta-to-alpha transition. Therefore, the use of fluorine groups in the development of new drugs is considered a new possibility requiring further investigation for the prevention of amyloidosis.

Topics: Amino Acid Sequence; Amyloid beta-Peptides; Amyloidosis; Circular Dichroism; Drug Design; Ethanol; Humans; Hydrophobic and Hydrophilic Interactions; Microscopy, Atomic Force; Molecular Sequence Data; Peptide Fragments; Propanols; Protein Conformation; Protein Folding; Protein Structure, Secondary; Solutions; Trifluoroethanol

Severe cognitive impairment is common in elderly patients with schizophrenia. Alzheimer's disease is the main cause of dementia among the elderly. Biochemical and genetic studies suggest that amyloid beta-peptide is central in Alzheimer's disease. The authors examined the possible involvement of amyloid beta-peptide in cognitive impairment in schizophrenia.. Specific antibodies against two major forms of amyloid beta-peptide, Abetax-40 and Abetax-42, were used in sandwich enzyme-linked immunosorbent assays to determine the levels of amyloid beta-peptide in postmortem brain samples from Alzheimer's disease patients (N=10), normal elderly comparison subjects (N=11), and schizophrenia patients with (N=7) or without (N=26) Alzheimer's disease.. The levels of amyloid beta-peptide were highest in the Alzheimer's disease patients, followed by the patients with schizophrenia and comparison subjects. The mean Abetax-42 level in the schizophrenia patients without Alzheimer's disease was similar to that in the comparison subjects, but the level in the schizophrenia patients with Alzheimer's disease was significantly higher than in those without Alzheimer's disease or the comparison subjects. The Abetax-42 level in the schizophrenia patients with Alzheimer's disease was significantly lower than the level in the Alzheimer's disease cohort.. In contrast to elderly schizophrenia patients with Alzheimer's disease pathology, those without Alzheimer's disease had amyloid beta-peptide levels that were not significantly different from those of normal subjects; hence amyloid beta-peptide does not account for the cognitive deficits in this group. These results suggest that the causes of cognitive impairment in "pure" schizophrenia are different from those in Alzheimer's disease.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Brain Chemistry; Brain Diseases; Cognition Disorders; Comorbidity; Enzyme-Linked Immunosorbent Assay; Female; Geriatric Assessment; Humans; Male; Peptide Fragments; Plaque, Amyloid; Prefrontal Cortex; Schizophrenia

A mirror image phage display approach was used to identify novel and highly specific ligands for Alzheimer's disease amyloid peptide Abeta(1-42). A randomized 12-mer peptide library presented on M13 phages was screened for peptides with binding affinity for the mirror image of Abeta(1-42). After four rounds of selection and amplification the peptides were enriched with a dominating consensus sequence. The mirror image of the most representative peptide (D-pep) was shown to bind Abeta(1-42) with a dissociation constant in the submicromolar range. Furthermore, in brain tissue sections derived from patients that suffered from Alzheimer's disease, amyloid plaques and leptomeningeal vessels containing Abeta amyloid were stained specifically with a fluorescence-labeled derivative of D-pep. Fibrillar deposits derived from other amyloidosis were not labeled by D-pep. Possible applications of this novel and highly specific Abeta ligand in diagnosis and therapy of Alzheimer's disease are discussed.

Topics: Alzheimer Disease; Amino Acid Sequence; Amyloid beta-Peptides; Amyloidosis; Brain; Humans; Ligands; Molecular Sequence Data; Peptide Fragments; Peptide Library; Plaque, Amyloid; Protein Binding

Reflectance Fourier transform infrared (FT-IR) microspectroscopy was applied to study the prevention of beta-sheet formation of amyloid beta (Abeta)(1-40) peptide by co-incubation with a hexapeptide containing a KLVFF sequence (Abeta(15-20) fragment). Second-derivative spectral analysis was used to locate the position of the overlapping components of the amide I band of Abeta peptide and assigned them to different secondary components. The result indicates that each intact sample of Abeta(15-20) fragment or Abeta(1-40) peptide previously incubated in distilled water at 37 degrees C transformed their secondary structure from 1649 (1651) or 1653cm(-1) to 1624cm(-1), suggesting the transformation from alpha-helix and/or random coil structures to beta-sheet structure. By co-incubating both samples with different molar ratio in distilled water at 37 degrees C, the structural transformation was not found for Abeta(1-40) peptide after 24h-incubation. But the beta-sheet formation of Abeta(1-40) peptide after 48h-incubation was evidenced from the appearance of the IR peak at 1626cm(-1) by adding a little amount of Abeta(15-20) fragment. There was no beta-sheet formation of Abeta(1-40) peptide after addition with much amount of Abeta(15-20) fragment, however, suggesting the higher amount of Abeta(15-20) fragment used might inhibit the beta-sheet formation of Abeta(1-40) peptide. The more Abeta(15-20) fragment used made the more stable structure of Abeta(1-40) peptide and the less beta-sheet formation of Abeta(1-40) peptide. The study indicates that the reflectance FT-IR microspectroscopy can easily evidence the prevention of beta-sheet formation of Abeta(1-40) peptide by a short amyloid fragment.

Topics: Amyloid beta-Peptides; Amyloidosis; Peptide Fragments; Protein Structure, Secondary; Spectroscopy, Fourier Transform Infrared

Amyloid-beta protein (A beta) deposition in the cerebral vascular walls is one of the key features of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). A beta(1-40) carrying the 'Dutch' mutation (HCHWA-D A beta(1-40)) induces pronounced degeneration of cultured human brain pericytes. In this study, we aimed to identify inhibitors of A beta-induced toxicity in human brain pericytes. The toxic effect of HCHWA-D A beta(1-40) on human brain pericytes was inhibited by co-incubation with catalase, but not with superoxide dismutase, glutathione or vitamin E analogue Trolox. Catalase interacts with A beta, both in cell cultures and in cell-free assays, and has a prominent effect on the amount and conformational state of A beta binding to the cell surface of human brain pericytes. This activity of catalase is likely based on its ability to bind and slowly degrade A beta and not by its usual capacity to convert hydrogen peroxide. Our data confirm that assembly of A beta at the cell surface of human brain pericytes is a crucial step in A beta-induced cellular degeneration of human brain pericytes. Inhibition of fibril formation at the cell surface could be an important factor in therapy aimed at reducing cerebral amyloid angiopathy.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Antioxidants; Blotting, Western; Brain; Catalase; Cell Death; Cells, Cultured; Chromans; Glutathione; Humans; In Vitro Techniques; Microscopy, Immunoelectron; Oxidative Stress; Peptide Fragments; Pericytes; Protein Binding; Superoxide Dismutase

1. We studied cerebrovascular sequestration and blood-brain barrier (BBB) permeability to [125I]- or [123I]-labeled amyloid-beta peptides (A beta) in aged rhesus and aged squirrel monkey, the nonhuman primate models of cerebral beta-amyloidosis and cerebrovascular amyloid angiopathy (CAA), respectively. 2. In aged rhesus, the half-time of elimination of [125I]A beta 1-40, t1/2e, was faster by 1.34 h, the systemic clearance, Clss, increased by 4.21 ml/min/kg and the mean residence time of intact peptide in the circulation shortened by 2 h. 3. Cerebrovascular sequestration of [125I]A beta 1-40 was significant in aged squirrel monkey (20.8 ml/g x 10(2)), but undetectable in the rhesus. 4. The permeability surface area product, PS, for [14C]inulin was low in both species (0.11-0.18 ml/g/s x 10(6)) indicating an intact barrier. 5. The BBB permeability to A beta 1-40 was 34.8- and 13.7-fold higher than for [14C]inulin in aged squirrel and rhesus, respectively, suggesting a specialized A beta transport across the BBB. 6. The single photon computed emission tomography studies confirmed a saturable [123I]A beta 1-40 transport at the BBB in primates (Km = 40 nM). 7. Brain autoradiographic analysis of [125I]A beta 1-42 or [125I]A beta 1-40 after intracarotid infusions of radiotracers confirmed co-localization of the signal with A beta-immunoreactive plaques in rhesus monkeys. 8. Metabolism of [125I]A beta 1-40 in brain and plasma was slower in aged squirrel compared to aged rhesus, by 2.9- and 2.6-fold, respectively. 9. Thus, transport of circulating A beta across the BBB contributes to brain parenchymal accumulation of amyloid in aged nonhuman primates. Negligible capillary binding, rapid systemic and brain degradation, and accelerated body elimination of blood-borne A beta, may prevent the development of CAA in rhesus in contrast to squirrel monkeys.

Topics: Adolescent; Aging; Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Animals; Blood-Brain Barrier; Cerebral Amyloid Angiopathy; Cerebrovascular Circulation; Disease Models, Animal; Humans; Immunohistochemistry; Macaca mulatta; Microcirculation; Peptide Fragments; Saimiri; Tomography, Emission-Computed, Single-Photon

More than 16 different proteins have been identified as amyloid in clinical diseases; among these, beta-amyloid (Abeta) of Alzheimer's disease is the best characterized. In the present study, we performed experiments with Abeta and calcitonin, another amyloid-forming peptide, to examine the role of G protein activation in amyloid toxicity. We demonstrated that the peptides, when prepared under conditions that promoted beta-sheet and amyloid fibril (or protofibril) formation, increased high affinity GTPase activity, but the nonamyloidogenic peptides had no discernible effects on GTP hydrolysis. These increases in GTPase activity were correlated to toxicity. In addition, G protein inhibitors significantly reduced the toxic effects of the amyloidogenic Abeta and calcitonin peptides. Our results further indicated that the amyloidogenic peptides significantly increased GTPase activity of purified Galpha(o) and Galpha(i) subunits and that the effect was not receptor-mediated. Collectively, these results imply that the amyloidogenic structure, regardless of the actual peptide or protein sequence, may be sufficient to cause toxicity and that toxicity is mediated, at least partially, through G protein activation. Our abilities to manipulate G protein activity may lead to novel treatments for Alzheimer's disease and the other amyloidoses.

Topics: Amyloid beta-Peptides; Amyloidosis; Animals; Calcitonin; Cattle; Cell Membrane; Enzyme Activation; GTP-Binding Proteins; Neuroprotective Agents; Neurotoxins; PC12 Cells; Peptide Fragments; Protein Binding; Protein Structure, Secondary; Rats

Oxidative stress is a key feature in the Alzheimer's disease (AD) brain and manifests as lipid peroxidation (LPO). Isoprostanes (iPs) are specific and sensitive markers of in vivo LPO. To determine whether amyloid beta (Abeta) deposition in vivo is associated with increased LPO, we examined iP levels in a transgenic mouse model (Tg2576) of AD amyloidosis. Urine, plasma, and brain tissues were collected from Tg2576 and littermate wild-type (WT) animals at different time points starting at 4 months of age and continuing until 18 months of age. Levels of urinary 8,12-iso-iPF(2alpha)-VI were higher in Tg2576 than in WT animals as early as 8 months of age and remained this high for the rest of the study. A similar pattern was observed for plasma levels of 8,12-iso-iPF(2alpha)-VI. Homogenates from the cerebral cortex and hippocampus of Tg2576 mice had higher levels of 8,12-iso-iPF(2alpha)-VI than those from WT mice starting at 8 months of age. In contrast, a surge of Abeta 1-40 and 1-42 levels as well as Abeta deposits in Tg2576 mouse brains occurred later, at 12 months of age. A direct correlation was observed between brain 8,12-iso-iPF(2alpha)-VI and Abeta 1-40 and 1-42. Because LPO precedes amyloid plaque formation in Tg2576 mice, this suggests that brain oxidative damage contributes to AD pathogenesis before Abeta accumulation in the AD brain.

Topics: Aging; Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Animals; Brain; Cerebellum; Cerebral Cortex; Dinoprost; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Female; Hippocampus; Lipid Peroxidation; Male; Mice; Mice, Transgenic; Peptide Fragments; Plaque, Amyloid

Amyloid-beta (A beta) deposition in cerebral vessels (cerebral amyloid angiopathy, CAA) is accompanied by degeneration of vascular cells, including pericytes and smooth muscle cells. Previous studies indicated that specific A beta protein isoforms are toxic for cultured human brain pericytes and smooth muscle cells. In particular, A beta 1-40 carrying the E22Q mutation, as in hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D), is toxic. We investigated the effects of the A beta-binding protein apolipoprotein E (ApoE) on the toxicity of A beta for cultured human brain pericytes. We compared the toxicity of HCHWA-D A beta 1-40 for pericyte cultures with different ApoE genotypes, studied the accumulation of A beta and ApoE in these different cell cultures, and investigated the effects of exogenous ApoE. Pericyte cultures with an ApoE epsilon 2/epsilon 3 genotype were more resistant to HCHWA-D A beta 1-40 treatment than cultures with a epsilon 3/epsilon 3 or epsilon 3/epsilon 4 genotype. Cell death was highest in cultures homozygous for ApoE epsilon 4. The extent to which both A beta ApoE accumulated at the cell surface was parallel to the degree of toxicity. The addition of purified ApoE resulted in a decrease in cell death. These data suggest that ApoE4 may direct A beta more efficiently than other ApoE isoforms into a pathological interaction with the HBP cell surface. The results of this study are in line with the observations that inheritance of the ApoE epsilon 4 allele increases the risk of developing Alzheimer's disease, and that the ApoE epsilon 2 allele has a relatively protective effect.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Amino Acid Substitution; Amyloid beta-Peptides; Amyloidosis; Apolipoproteins E; Cells, Cultured; Cerebral Hemorrhage; Cerebrovascular Circulation; Dementia, Multi-Infarct; Female; Genotype; Humans; Male; Middle Aged; Peptide Fragments; Pericytes; Point Mutation; Reference Values

Amyloid plaques composed of the peptide Abeta are an integral part of Alzheimer's disease (AD) pathogenesis. We have modeled the process of amyloid plaque growth by monitoring the deposition of soluble Abeta onto amyloid in AD brain tissue or synthetic amyloid fibrils and show that it is mediated by two distinct kinetic processes. In the first phase, "dock", Abeta addition to the amyloid template is fully reversible (dissociation t(1/2) approximately 10 min), while in the second phase, "lock", the deposited peptide becomes irreversibly associated (dissociation t(1/2) >> 1000 min) with the template in a time-dependent manner. The most recently deposited peptide dissociates first while Abeta previously deposited becomes irreversibly "locked" onto the template. Thus, the transition from monomer to neurotoxic amyloid is mediated by interaction with the template, a mechanism that has also been proposed for the prion diseases. Interestingly, two Abeta peptides bearing primary sequence alterations implicated in heritable Abeta amyloidoses displayed faster lock-phase kinetics than wild-type Abeta. Inhibiting the initial weak docking interaction between depositing Abeta and the template is a viable therapeutic target to prevent the critical conformational transition in the conversion of Abeta((solution)) to Abeta((amyloid)) and thus prevent stable amyloid accumulation. While thermodynamics suggest that inhibiting amyloid assembly would be difficult, the present study illustrates that the protein misfolding diseases are kinetically vulnerable to intervention.

Topics: Amino Acid Substitution; Amyloid beta-Peptides; Amyloidosis; Chromatography, High Pressure Liquid; Humans; Kinetics; Models, Chemical; Peptide Fragments; Plaque, Amyloid; Protein Conformation; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

The deposition of amyloid in the brain is a hallmark of Alzheimer disease (AD). Amyloid deposits consist of accumulations of beta-amyloid (Abeta), which is a 39-43 amino-acid peptide cleaved from the Abeta-protein precursor (APP). Another cleavage product of APP is the P3-peptide, which consists of the amino acids 17-42 of the Abeta-peptide. In order to study the deposition of N-terminal truncated forms of Abeta in the human entorhinal cortex, serial sections from 16 autopsy cases with AD-related pathology were immunostained with antibodies against Abeta1-40, Abeta1-42, Abeta17-23, and Abeta8-17, as well as with the Campbell-Switzer silver impregnation for amyloid. In the external entorhinal layers (pre-beta and pre-gamma), sharply delineated diffuse plaques were seen. They were labeled by silver impregnation and by all Abeta-antibodies used. By comparison, in the internal layers (pri-alpha, pri-beta, and pri-gamma) blurred, ill-defined clouds of amyloid existed, in addition to sharply delineated diffuse plaques. These clouds of amyloid were termed "fleecy amyloid." Immunohistochemically, fleecy amyloid was stained by Abeta17-23 and Abeta1-42 antibodies, but not with antibodies against Abeta8-17 and Abeta1-40. Using the Campbell-Switzer technique, the fleecy amyloid deposits were found to be fine argyrophilic amyloid fibrils. Thus, the internal entorhinal layers are susceptible to a distinct type of amyloid, namely fleecy amyloid. This fleecy amyloid obviously corresponds to N-terminal truncated fragments of Abeta1-42, probably representing the P3-peptide. These N-terminal truncated fragments of Abeta are capable of creating fine fibrillar "amyloid."

Topics: Aged; Aged, 80 and over; Amyloid beta-Peptides; Amyloidosis; Coloring Agents; Entorhinal Cortex; Female; Humans; Male; Middle Aged; Neurofibrillary Tangles; Peptide Fragments; Silver Staining; Staining and Labeling

Our previous studies have demonstrated that perlecan and perlecan-derived glycosaminoglycans (GAGs) not only bind beta-amyloid protein (Abeta) 1-40 and 1-42, but are also potent enhancers of Abeta fibril formation and stabilize amyloid fibrils once formed. However, it was not determined which moieties in perlecan heparan sulfate GAG chains may be responsible for the observed effects and whether other GAGs were also capable of a similar enhancement of Abeta fibril formation as observed with perlecan GAGs. In the present study, thioflavin T fluorometry (over a 1-week period) was used to extend our previous studies and to test the hypothesis that the sulfate moiety is critical for the enhancing effects of heparin/heparan sulfate GAGs on Abeta 1-40 fibrillogenesis. This hypothesis was confirmed when removal of all sulfates from heparin (i.e., completely desulfated N-acetylated heparin) led to a complete loss in the enhancement of Abeta fibrillogenesis as demonstrated in both thioflavin T fluorometry and Congo red staining studies. On the other hand, removal of O-sulfate from heparin (i.e., completely desulfated N-sulfated heparin), and to a lesser extent N-sulfate (i.e., N-desulfated N-acetylated heparin), resulted in only a partial loss of the enhancement of Abeta 1-40 fibril formation. These studies indicate that the sulfate moieties of GAGs are critical for enhancement of Abeta amyloid fibril formation. In addition, other sulfated molecules such as chondroitin-4-sulfate, dermatan sulfate, dextran sulfate, and pentosan polysulfate all significantly enhanced (greater than twofold by 3 days) Abeta amyloid fibril formation. These latter findings indicate that deposition and accumulation of other GAGs at sites of Abeta amyloid deposition in Alzheimer's disease brain may also participate in the enhancement of Abeta amyloidosis.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Animals; Coloring Agents; Congo Red; Fibrinolytic Agents; Glycosaminoglycans; Heparin; Neurofibrillary Tangles; Neurons; Peptide Fragments; Sulfates; Swine

Cerebrovascular amyloid beta-protein (A beta) deposition is a key pathological feature of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). A beta(1-40) containing the E22Q HCHWA-D mutation, but not wild-type A beta(1-40), potently induces several pathologic responses in cultured human cerebrovascular smooth muscle cells, including cellular degeneration and a robust increase in the levels of cellular A beta precursor. In the present study, we show by several quantitative criteria, including thioflavin T fluorescence binding, circular dichroism spectroscopy, and transmission electron microscopic analysis, that at a concentration of 25 microM neither HCHWA-D A beta(1-40) nor wild-type A beta(1-40) appreciably assembles into beta-pleated sheet-containing fibrils in solution over a 6-day incubation period. In contrast, at the same concentrations, HCHWA-D A beta(1-40), but not wild-type A beta(1-40), selectively binds and assembles into abundant fibrils on the surfaces of cultured human cerebrovascular smooth muscle cells. The simultaneous addition of an equimolar concentration of the dye Congo red prevents the cell surface fibril assembly of HCHWA-D A beta(1-40). Moreover, Congo red effectively blocks the key pathologic responses induced by HCHWA-D A beta(1-40) in these cells. The present findings suggest that the surface of human cerebrovascular smooth muscle cells may selectively orchestrate the assembly of pathogenic A beta fibrils and that cell surface A beta fibril formation plays an important role in causing the pathologic responses in these cells.

Topics: Amyloid beta-Peptides; Amyloidosis; Benzothiazoles; Cell Membrane; Cells, Cultured; Cerebral Hemorrhage; Cerebrovascular Circulation; Circular Dichroism; Coloring Agents; Congo Red; Fluorescent Dyes; Humans; Immunoblotting; Microscopy, Electron; Muscle, Smooth, Vascular; Mutation; Peptide Fragments; Thiazoles

Amyloid fibril formation is believed to be a nucleation-dependent polymerization process which may be influenced by various other factors with important consequences for the development, prevention or treatment of amyloidosis. We have previously shown that laminin inhibits A beta peptide fibril formation in vitro. Here we present a kinetic study that indicates laminin to be a potent anti-amyloidosis factor, as it not only inhibited A beta 1-40 fibril aggregation, but also inhibited the aggregation of the Dutch A beta 1-40 variant, a peptide with a higher capacity to aggregate than the wild-type A beta 1-40. The inhibitory effect of laminin on amyloid fibril formation was not overcome by the addition of pre-formed A beta fibrils, suggesting that laminin inhibits the fibril elongation process. At the present time, however, we cannot rule out the possibility that laminin also affects the initial nucleation process of A beta fibril formation. On other hand, laminin was not able to counteract the amyloid fibril formation promoted by acetylcholinesterase (AChE), another component of the amyloid deposits found in AD brains. The effect of laminin may be important as an inhibitor of A beta amyloidogenesis in vivo, specifically at the level of cerebral blood vessels.

Topics: Acetylcholinesterase; Amyloid beta-Peptides; Amyloidosis; Benzothiazoles; Fluorescence; Kinetics; Laminin; Nephelometry and Turbidimetry; Peptide Fragments; Plaque, Amyloid; Protein Binding; Thiazoles

Inhibition of cerebral amyloid beta-protein deposition seems to be an important target for Alzheimer's disease therapy. Amyloidogenesis could be inhibited by short synthetic peptides designed as beta-sheet breakers. Here we demonstrate a 5-residue peptide that inhibits amyloid beta-protein fibrillogenesis, disassembles preformed fibrils in vitro and prevents neuronal death induced by fibrils in cell culture. In addition, the beta-sheet breaker peptide significantly reduces amyloid beta-protein deposition in vivo and completely blocks the formation of amyloid fibrils in a rat brain model of amyloidosis. These findings may provide the basis for a new therapeutic approach to prevent amyloidosis in Alzheimer's disease.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloidosis; Animals; Brain; Disease Models, Animal; Humans; Male; Peptide Fragments; Peptides; Rats; Rats, Inbred F344; Tumor Cells, Cultured

A polyclonal antibody to a synthetic peptide representing a 28-amino-acid sequence of the previously isolated and described Alzheimer's disease amyloid precursor was raised in rabbits. The antibody was used in conjunction with an avidin-biotin-peroxidase technique to stain cerebral microvessels involved by amyloid angiopathy and senile "neuritic" plaque amyloid cores. The staining method has significant advantages over standard histologic techniques used to demonstrate brain amyloid and might have important practical applications in the study of microvascular lesions associated with cerebral amyloid angiopathy, as well as in studies on the pathogenesis of Alzheimer's disease or senile dementia of Alzheimer type.

Topics: Aged; Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloidosis; Cerebral Cortex; Cerebrovascular Disorders; Humans; Immune Sera; Immunoenzyme Techniques; Male; Peptide Fragments; Peptides