amyloid-beta-peptides and Neurodegenerative-Diseases

The Amyloid Tau Neurodegeneration (ATN) framework was proposed to define the biological state underpinning Alzheimer's disease (AD). Blood-based biomarkers offer a scalable alternative to the costly and invasive currently available biomarkers.. In this meta-analysis we sought to assess the diagnostic performance of plasma amyloid (Aβ40, Aβ42, Aβ42/40 ratio), tangle (p-tau181), and neurodegeneration (total tau [t-tau], neurofilament light [NfL]) biomarkers.. Electronic databases were screened for studies reporting biomarker concentrations for AD and control cohorts. Biomarker performance was examined by random-effect meta-analyses based on the ratio between biomarker concentrations in patients and controls.. 83 studies published between 1996 and 2020 were included in the analyses. Aβ42/40 ratio as well as Aβ42 discriminated AD patients from controls when using novel platforms such as immunomagnetic reduction (IMR). We found significant differences in ptau-181 concentration for studies based on single molecule array (Simoa), but not for studies based on IMR or ELISA. T-tau was significantly different between AD patients and control in IMR and Simoa but not in ELISA-based studies. In contrast, NfL differentiated between groups across platforms. Exosome studies showed strong separation between patients and controls for Aβ42, t-tau, and p-tau181.. Currently available assays for sampling plasma ATN biomarkers appear to differentiate between AD patients and controls. Novel assay methodologies have given the field a significant boost for testing these biomarkers, such as IMR for Aβ, Simoa for p-tau181. Enriching samples through extracellular vesicles shows promise but requires further validation.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Humans; Neurodegenerative Diseases; Neurofibrillary Tangles; Neurofilament Proteins; Peptide Fragments; Phosphorylation; Plaque, Amyloid; tau Proteins

Easily accessible biomarkers for Alzheimer's disease (AD), Parkinson's disease (PD), frontotemporal dementia (FTD), and related neurodegenerative disorders are urgently needed in an aging society to assist early-stage diagnoses. In this study, we aimed to develop machine learning algorithms using the multiplex blood-based biomarkers to identify patients with different neurodegenerative diseases. Plasma samples (

Topics: Aged; Aged, 80 and over; alpha-Synuclein; Amyloid beta-Peptides; Biomarkers; Cognitive Dysfunction; Female; Humans; Machine Learning; Male; Middle Aged; Neurodegenerative Diseases; Peptide Fragments; tau Proteins

Cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) reflect brain biochemistry. Using combined immunoprecipitation and mass spectrometry, we have shown that amyloid beta 1-15 (Aβ1-15) is produced by concerted β- and α-secretase cleavage of amyloid precursor protein (APP) and that the relative levels of Aβ1-16 in AD compared to controls are increased. Furthermore, drug-induced γ-secretase inhibition enhances the relative levels of Aβ1-15 and Aβ1-16. Here, we investigate a novel immunoassay for Aβ1-15/16 in a broad range of neurodegenerative conditions. The CSF level of Aβ1-15/16 was measured by the bead-based amplified luminescent proximity homogeneous assay (Alpha technology). Concentrations of Aβ1-15/16 were analyzed in subjects with Parkinson disease (PD; n = 90), PD with dementia (PDD) (n = 32), dementia with Lewy bodies (DLB) (n = 68), AD (n = 48), progressive supranuclear palsy (PSP) (n = 45), multiple system atrophy (MSA) (n = 46), and corticobasal degeneration (CBD) (n = 12). The detecting antibody is specific to the C-terminal epitope of Aβ15. We found that a carboxypeptidase (CPB) present in fetal bovine serum (FBS), a component of the buffers used, degrades Aβ1-16 to Aβ1-15, which is then detected by the Aβ1-15/16 assay. Significantly, lower levels of Aβ1-15/16 were detected in PD, PDD, PSP, and MSA compared to other neurodegenerative diseases and controls. Using the specific Aβ1-15/16 assay, a reliable quantification of Aβ1-15 or Aβ1-15/16 in CSF samples is obtained. We found reduced levels of Aβ1-15 in parkinsonian disease groups. The molecular mechanism behind this reduction is at present unknown.

Topics: Aged; Aged, 80 and over; Amyloid beta-Peptides; Animals; Antibody Specificity; Biomarkers; Biotinylation; Carboxypeptidases; Cattle; Diagnosis, Differential; Dose-Response Relationship, Immunologic; Epitopes; Female; Fetal Blood; Humans; Immunoassay; Luminescent Measurements; Male; Middle Aged; Neurodegenerative Diseases; Neuropsychological Tests; Peptide Fragments; Reagent Kits, Diagnostic

Self-aggregation of amyloid-β (Aβ) peptides has been known to play a vital role in the onset stage of neurodegenerative diseases, indicating the necessity of understanding the aggregation process of Aβ peptides. Despite previous studies on the aggregation process of Aβ peptides, the aggregation pathways of Aβ isoforms (i.e., Aβ40 and Aβ42) and their related structures have not been fully understood yet. Here, we study the aggregation pathways of Aβ40 and Aβ42, and the structures of Aβ40 and Aβ42 aggregates during the process, based on fluorescence and atomic force microscopy (AFM) experiments. It is shown that in the beginning of aggregation process for both Aβ40 and Aβ42, a number of particles (i.e., spherical oligomers) are formed. These particles are subsequently self-assembled together, resulting in the formation of different shapes of amyloid fibrils. Our finding suggests that the different aggregation pathways of Aβ isoforms lead to the amyloid fibrils with contrasting structure.

Topics: Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Benzothiazoles; Humans; Microscopy, Atomic Force; Microscopy, Fluorescence; Neurodegenerative Diseases; Peptide Fragments; Peptides; Protein Binding; Protein Conformation; Protein Isoforms

Imaging with β-amyloid (Aβ) positron emission tomography (PET) has the potential to aid the diagnosis of the cause of cognitive impairment affecting people living with HIV (PLWH) when neurodegenerative disorders are considered. We evaluated the clinical utility of [18F]Florbetaben (FBB) in PLWH with cognitive symptoms.. Imaging with FBB PET was performed in 20 patients with cognitive concerns about dementia. Neuropsychological testing, plasma neurofilament light protein, plasma Aβ40, Aβ42, and cerebrospinal fluid Aβ42, tau, and HIV RNA were obtained. FBB PET images were assessed visually by 3 readers blinded to the clinical diagnosis and quantitatively by obtaining a composite cortical to cerebellar cortex standardized uptake value ratio (SUVR). FBB SUVR from 10 age-matched healthy controls was compared with SUVR of PLWH.. Most participants were men (90%) of white ethnicity (90%) with a median age (interquartile range) of 59 (43-79) years. Median CD4 count was 682 (74-1056). All patients were on combination antiretroviral therapy with plasma and cerebrospinal fluid HIV RNA <40 copies/mL. Fourteen patients had objective cognitive impairment including 2 who met clinical criteria for a diagnosis of dementia. No significant differences in composite SUVRs between PLWH and controls [mean (SD): 1.18 (0.03) vs. 1.16 (0.09); P = 0.37] were observed. Four patients were FBB+ with the highest SUVR in the posterior cingulate, superior temporal, and frontal superior lobe. Amyloid PET results contributed to a change in diagnosis and treatment for 10 patients.. [18F]Florbetaben PET has potential as an adjunctive tool in the diagnosis of PLWH with cognitive impairment, increasing diagnostic certainty and optimizing management.

Topics: Adult; Aged; Amyloid beta-Peptides; Aniline Compounds; Brain; CD4 Lymphocyte Count; Cognitive Dysfunction; Drug Therapy, Combination; Female; HIV Infections; Humans; Male; Middle Aged; Neurodegenerative Diseases; Neuropsychological Tests; Peptide Fragments; Positron-Emission Tomography; RNA, Viral; Stilbenes; tau Proteins

To investigate whether tau phosphorylated at Thr217 (p-tau T217) assay in CSF can distinguish patients with Alzheimer disease (AD) from patients with other dementias and healthy controls.. We developed and validated a novel Simoa immunoassay to detect p-tau T217 in CSF. There was a total of 190 participants from 3 cohorts with AD (n = 77) and other neurodegenerative diseases (n = 69) as well as healthy participants (n = 44).. The p-tau T217 assay (cutoff 242 pg/mL) identified patients with AD with accuracy of 90%, with 78% positive predictive value (PPV), 97% negative predictive value (NPV), 93% sensitivity, and 88% specificity, compared favorably with p-tau T181 ELISA (52 pg/mL), showing 78% accuracy, 58% PPV, 98% NPV, 71% specificity, and 97% sensitivity. The assay distinguished patients with AD from age-matched healthy controls (cutoff 163 pg/mL, 98% sensitivity, 93% specificity), similarly to p-tau T181 ELISA (cutoff 60 pg/mL, 96% sensitivity, 86% specificity). In patients with AD, we found a strong correlation between p-tau T217 and p-tau T181, total tau and β-amyloid 40, but not β-amyloid 42.. This study demonstrates that p-tau T217 displayed better diagnostic accuracy than p-tau T181. The data suggest that the new p-tau T217 assay has potential as an AD diagnostic test in clinical evaluation.. This study provides Class III evidence that a CSF immunoassay for p-tau T217 distinguishes patients with AD from patients with other dementias and healthy controls.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Aphasia, Primary Progressive; Cohort Studies; Diagnosis, Differential; Female; Frontotemporal Dementia; Humans; Immunoassay; Male; Middle Aged; Neurodegenerative Diseases; Peptide Fragments; Predictive Value of Tests; Reproducibility of Results; Sensitivity and Specificity; Supranuclear Palsy, Progressive; tau Proteins; Tauopathies

Biomarkers have revolutionized scientific research on neurodegenerative diseases, in particular Alzheimer's disease, transformed drug trial design, and are also increasingly improving patient management in clinical practice. A few key cerebrospinal fluid biomarkers have been robustly associated with neurodegenerative diseases. Several novel biomarkers are very promising, especially blood-based markers. However, many biomarker findings have had low reproducibility despite initial promising results. In this perspective, we identify possible sources for low reproducibility of studies on fluid biomarkers for neurodegenerative diseases, with a focus on Alzheimer's disease. We suggest guidelines for researchers and journal editors, with the aim to improve reproducibility of findings.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Biomarkers; Humans; Neurodegenerative Diseases; Peptide Fragments; Reproducibility of Results; Sensitivity and Specificity; tau Proteins

Alzheimer's disease (AD) is a neurodegenerative disease that results in memory loss and the impairment of cognitive skills. Several mechanisms of AD's pathogenesis were proposed, such as the progressive accumulation of amyloid-β (Aβ) and τ pathology. Nevertheless, the exact neurodegenerative mechanism of the Aβ remains complex and not fully understood. This paper proposes an alternative hypothesis of the mechanism based on maintaining the neuron membrane's mechanical balance. The incorporation of Aβ decreases the lipid membrane's elastic properties, which eventually leads to the impairment of membrane clustering, disruption of mechanical wave propagation, and change in gamma oscillations. The first two disrupt the neuron's ability to function correctly while the last one decreases sensory encoding and perception enabling. To begin discussing this mechanical-balance hypothesis, we measured the effect of two selected peptides, Aβ-40 and Aβ-42, as well as their fluorescently labeled modification, on membrane mechanical properties. The decrease of bending rigidity, consistent for all investigated peptides, was observed using molecular dynamic studies and experimental flicker-noise techniques. Additionally, wave propagation was investigated with molecular dynamic studies in membranes with and without incorporated neurodegenerative peptides. A change in membrane behavior was observed in the membrane system with incorporated Aβ.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Brain; Cell Membrane; Humans; Lipid Bilayers; Membrane Lipids; Membrane Potentials; Microscopy, Confocal; Molecular Dynamics Simulation; Neurodegenerative Diseases; Neurons; Peptide Fragments; Phosphatidylcholines

Topics: alpha-Synuclein; Amyloid beta-Peptides; Cells, Cultured; Chromatography, Liquid; Humans; Kynurenine; Magnetic Resonance Spectroscopy; Neurodegenerative Diseases; Neurons; Peptide Fragments; Tandem Mass Spectrometry

Here we report the enzymologic characterization of recombinant human pitrilysin metallopeptidase 1 (Pitrm1) and derivative mutants including the arginine-to-glutamine substitution mutant Pitrm1 R183Q, which has been implicated in inherited amyloidogenic neuropathy. Recombinant Pitrm1 R183Q was readily expressed in and purified from Escherichia coli, but was less active than the recombinant wild-type enzyme against recombinant amyloid beta-peptide (Aβ 1-40). A novel fluorogenic substrate derived from the reported Aβ 1-40 core peptide cleavage sequence, Mca-KLVFFAEDK-(Dnp)-OH, was synthesized and applied to real-time kinetic study of Pitrm1 and derivative mutants including Pitrm1 R183Q. The Pitrm1 R183Q mutant exhibited significantly decreased rate of fluorogenic peptide hydrolysis, yet retained similar binding affinity by comparison with the wild-type enzyme. Targeted mutagenic analysis revealed a functional requirement for uncharged or electropositive residues in place of Pitrm1 R183. Residue R183 is positioned within an N-terminal strand-loop-strand motif that is conserved among M16C, but not M16A or M16B family metallopeptidases. Truncation analysis revealed that this strand-loop-strand motif inclusive of residue R183 is essential Pitrm1 function. A requirement for charged residues within 4.5 Å of residue R183 was demonstrated, and Pitrm1 R183Q was found to exhibit increased sensitivity to heat inactivation. Our findings indicate that charge sharing in the vicinity of Pitrm1 R183 is critical to enzyme activity, providing potential insight into a molecular basis of Pitrm1 dysfunction.

Topics: Amino Acid Motifs; Amino Acid Substitution; Amyloid beta-Peptides; Arginine; Fluorescence Resonance Energy Transfer; Humans; Hydrolysis; Metalloendopeptidases; Mutation; Neurodegenerative Diseases; Peptide Fragments; Recombinant Proteins; Static Electricity

The Caribbean vervet monkey (. To characterize biomarkers associated with neurodegeneration, we measured cerebrospinal fluid (CSF) concentrations of Aβ. Aβ. Overall, these results support the vervet as a non-human primate model of amyloid-related neurodegeneration, such as Alzheimer's disease and cerebral amyloid angiopathy, and highlight Aβ

Topics: Aging; Alzheimer Disease; Amyloid beta-Peptides; Animals; Biomarkers; Brain; Cerebral Amyloid Angiopathy; Chlorocebus aethiops; Chromosomes, Mammalian; Female; Genetic Linkage; Genome-Wide Association Study; Male; Models, Animal; Monkey Diseases; Neurodegenerative Diseases; Neuroimaging; Organ Size; Pedigree; Peptide Fragments; tau Proteins

Background and Purpose- Inflammation is involved in the pathogenesis of large artery atherosclerosis, ischemic stroke, and Alzheimer dementia. However, the role of inflammation in cerebral small vessel disease and neurodegeneration remains poorly understood. We hypothesize that CRP (C-reactive protein) is associated with brain structural changes and may interact with amyloid to produce vascular and degenerative damage. We examined the association of CRP levels with imaging markers of cerebral small vessel disease and neurodegeneration. Furthermore, we studied the association of CRP with plasma Aβ (amyloid-β) levels and their joint effects with imaging markers. Methods- We included 2814 persons (mean age, 56.9 years; 44.8% women) from the Rotterdam Study with complete data on CRP and 1.5 T brain magnetic resonance imaging scans. Aβ levels were measured in a subsample (n=736). Markers of cerebral small vessel disease included lacunes, white matter hyperintensities, microbleeds, and enlarged perivascular spaces. Neurodegeneration was assessed by smaller volumes of gray matter, white matter, and hippocampus. Plasma levels of Aβ1-38, Aβ1-40, and Aβ1-42 were assessed using ELISA. Results- Higher CRP levels were associated with larger white matter hyperintensities volume (β=0.07; 95% CI, 0.00-0.13), increasing lacunar (rate ratios, 1.61; 95% CI, 1.19-2.19), enlarged perivascular spaces (rate ratios, 1.01; 95% CI, 1.00-1.03), and deep/infratentorial microbleeds (rate ratios, 1.30; 95% CI, 1.00-1.69) counts. People with high CRP levels had small gray matter volume. We also found significant interaction between CRP and Aβ such that among persons in higher tertiles of Aβ1-42, a strong association was observed between CRP and lacunar ( P interaction, 0.004), enlarged perivascular spaces ( P interaction, 0.002), and microbleed counts ( P interaction, <0.001). Similarly, among persons in higher tertile of Aβ1-38, a strong association was observed between CRP and microbleed counts ( P interaction, 0.004). Conclusions- Higher CRP levels were associated with subclinical markers of cerebral small vessel disease and neurodegeneration. This effect was augmented by an interaction between CRP and Aβ levels. Future longitudinal studies focusing on joint effects of CRP and Aβ on progression of magnetic resonance imaging markers and cognitive decline are warranted.

Topics: Aged; Amyloid beta-Peptides; Brain; C-Reactive Protein; Cerebral Small Vessel Diseases; Female; Glymphatic System; Gray Matter; Hippocampus; Humans; Intracranial Hemorrhages; Magnetic Resonance Imaging; Male; Middle Aged; Neurodegenerative Diseases; Peptide Fragments; Stroke, Lacunar; White Matter

The outer mitochondrial membrane (OMM) protein, the translocator protein 18 kDa (TSPO), formerly named the peripheral benzodiazepine receptor (PBR), has been proposed to participate in the pathogenesis of neurodegenerative diseases. To clarify the TSPO function, we identified the Drosophila homolog, CG2789/dTSPO, and studied the effects of its inactivation by P-element insertion, RNAi knockdown, and inhibition by ligands (PK11195, Ro5-4864). Inhibition of dTSPO inhibited wing disk apoptosis in response to γ-irradiation or H2O2 exposure, as well as extended male fly lifespan and inhibited Aβ42-induced neurodegeneration in association with decreased caspase activation. Therefore, dTSPO is an essential mediator of apoptosis in Drosophila and plays a central role in controlling longevity and neurodegenerative disease, making it a promising drug target.

Topics: Amino Acid Sequence; Amyloid beta-Peptides; Animals; Apoptosis; Drosophila; Drosophila Proteins; Female; Humans; Longevity; Male; Mitochondrial Membranes; Molecular Sequence Data; Neurodegenerative Diseases; Peptide Fragments; Receptors, GABA

Pericytes are cells in the blood-brain barrier that degenerate in Alzheimer's disease (AD), a neurological disorder associated with neurovascular dysfunction, abnormal elevation of amyloid β-peptide (Aβ), tau pathology and neuronal loss. Whether pericyte degeneration can influence AD-like neurodegeneration and contribute to disease pathogenesis remains, however, unknown. Here we show that in mice overexpressing Aβ-precursor protein, pericyte loss elevates brain Aβ40 and Aβ42 levels and accelerates amyloid angiopathy and cerebral β-amyloidosis by diminishing clearance of soluble Aβ40 and Aβ42 from brain interstitial fluid prior to Aβ deposition. We further show that pericyte deficiency leads to the development of tau pathology and an early neuronal loss that is normally absent in Aβ-precursor protein transgenic mice, resulting in cognitive decline. Our data suggest that pericytes control multiple steps of AD-like neurodegeneration pathogenic cascade in Aβ-precursor protein-overexpressing mice. Therefore, pericytes may represent a novel therapeutic target to modify disease progression in AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Brain; Cell Death; Mice; Mice, Transgenic; Neurodegenerative Diseases; Neurons; Peptide Fragments; Pericytes; Phosphorylation; tau Proteins

Amyloid diseases such as Alzheimer, Parkinson, and prion diseases are associated with a specific form of protein misfolding and aggregation into oligomers and fibrils rich in β-sheet structure. The BRICHOS domain consisting of ∼100 residues is found in membrane proteins associated with degenerative and proliferative disease, including lung fibrosis (surfactant protein C precursor; pro-SP-C) and familial dementia (Bri2). We find that recombinant BRICHOS domains from Bri2 and pro-SP-C prevent fibril formation of amyloid β-peptides (Aβ(40) and Aβ(42)) far below the stoichiometric ratio. Kinetic experiments show that a main effect of BRICHOS is to prolong the lag time in a concentration-dependent, quantitative, and reproducible manner. An ongoing aggregation process is retarded if BRICHOS is added at any time during the lag phase, but it is too late to interfere at the end of the process. Results from circular dichroism and NMR spectroscopy, as well as analytical size exclusion chromatography, imply that Aβ is maintained as an unstructured monomer during the extended lag phase in the presence of BRICHOS. Electron microscopy shows that although the process is delayed, typical amyloid fibrils are eventually formed also when BRICHOS is present. Structural BRICHOS models display a conserved array of tyrosine rings on a five-stranded β-sheet, with inter-hydroxyl distances suited for hydrogen-bonding peptides in an extended β-conformation. Our data imply that the inhibitory mechanism is reliant on BRICHOS interfering with molecular events during the lag phase.

Topics: Amyloid; Amyloid beta-Peptides; Circular Dichroism; Humans; Models, Molecular; Neurodegenerative Diseases; Nuclear Magnetic Resonance, Biomolecular; Peptide Fragments; Protein Structure, Tertiary; Pulmonary Fibrosis

Amyloid deposits are pathological hallmarks of various neurodegenerative diseases including Alzheimer's disease (AD), where amyloid beta-peptide (Abeta) polymerizes into amyloid fibrils by a nucleation-dependent polymerization mechanism. The biological membranes or other interfaces as well as the convection of the extracellular fluids in the brain may influence Abeta amyloid fibril formation in vivo. Here, we examined the polymerization kinetics of 2.5, 5, 10 and 20 microM Abeta in the presence or absence of air-water interface (AWI) using fluorescence spectroscopy and fluorescence microscopy with the amyloid specific dye, thioflavin T. When the solutions were incubated with AWI and in quiescence, amyloid fibril formation was observed at all Abeta concentrations examined. In contrast, when incubated without AWI, amyloid fibril formation was observed only at higher Abeta concentrations (10 and 20 microM). Importantly, when the 5 microM Abeta solution was incubated with AWI, a ThT-reactive film was first observed at AWI without any other ThT-reactive aggregates in the bulk. When 5 microM Abeta solutions were voltexed or rotated with AWI, amyloid fibril formation was considerably accelerated, where a ThT-reactive film was first observed at AWI before ThT-reactive aggregates were observed throughout the mixture. When 5 microM Abeta solutions containing a polypropylene disc were rotated without AWI, amyloid fibril formation was also considerably accelerated, where fine ThT-reactive aggregates were first found attached at the edge of the disc. These results indicate the critical roles of interfaces and agitation for amyloid fibril formation. Furthermore, elimination of AWI may be essential for proper evaluation of the roles of various biological molecules in the amyloid formation studies in vitro.

Topics: Air; Alzheimer Disease; Amyloid; Amyloid beta-Peptides; Benzothiazoles; Brain Chemistry; Fluorescent Dyes; Humans; In Vitro Techniques; Microscopy, Electron, Transmission; Microscopy, Fluorescence; Neurodegenerative Diseases; Peptide Fragments; Protein Binding; Protein Conformation; Protein Multimerization; Solutions; Spectrometry, Fluorescence; Thiazoles; Water

Soya isoflavones (SIF) and folic acid (FA) both confer the biological properties of antioxidation; however, the mechanism of their antioxidant effect on nervous system development is unclear. Our purpose is to investigate the neuroprotective effects of SIF, FA or co-administration of SIF with FA against beta-amyloid 1-40 (Abeta1-40)-induced learning and memory impairment in rats. In the present study, the learning and memory ability of rats and the amount of amyloid-positive neurons in the cerebral cortex and hippocampal CA1 area were measured. The levels of total antioxidant capacity (T-AOC), glutathione (GSH) and glutathione peroxidase (GSH-Px) in serum and brain tissue were also measured. The results showed that intracerebroventricular administration of Abeta1-40 resulted in a dramatic prolongation of the escape latency; however, in the SIF, FA and SIF+FA treatment groups, the functional deficits of learning and memory were significantly improved. Moreover, after Abeta1-40 injection, the levels of T-AOC and GSH were profoundly decreased, suggesting a decline of antioxidant activity in the rats. However, intragastric pre-treatment with SIF, or FA, or SIF+FA resulted in a significant increase of antioxidative activity. SIF, or FA, or SIF+FA treatments also reversed the Abeta1-40-induced increase in the amount of amyloid-positive neurons. These results suggest that: (1) learning or memory impairment in experimental rats was caused by Abeta1-40, which is probably attributed to Abeta-induced oxidative damage and deposition of beta-amyloid peptides in the brain; (2) pre-administration of SIF and/or FA may prevent the pathological alterations caused by Abeta1-40 treatment and the neuroprotective effects of SIF and/or FA are indicated.

Topics: Amyloid beta-Peptides; Animals; Antioxidants; Cerebral Cortex; Folic Acid; Glycine max; Hippocampus; Isoflavones; Male; Maze Learning; Memory; Models, Animal; Neurodegenerative Diseases; Neuroprotective Agents; Peptide Fragments; Random Allocation; Rats; Rats, Wistar

Neuronal models for Alzheimer's disease research frequently have limitations as a result of their nonhuman origin and/or transformed state. Here we examined the potential of readily accessible neural crest-derived human epidermal melanocytes isolated from elderly individuals as a model system for Alzheimer's disease research. The amyloidogenic isoforms of amyloid precursor protein (APP; isoforms APP751/770) and amyloid beta (Abeta)1-40 were detected in epidermal melanocytes using immunocytochemistry and western blotting. Incubation of epidermal melanocytes with aggregated Abeta1-40 peptide caused a concentration-dependent reduction in cell viability, whereas age-matched dermal fibroblasts remained unaffected. These findings suggest that epidermal melanocytes from elderly donors are capable of amyloidogenesis and are sensitive to Abeta1-40 cytotoxicity. Thus, these cells may provide a readily accessible human cell model for Alzheimer's disease research.

Topics: Age Factors; Aged; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Blotting, Western; Cell Survival; Cells, Cultured; Dose-Response Relationship, Drug; Epidermal Cells; Female; Fibroblasts; Humans; Immunohistochemistry; Melanocytes; Middle Aged; Neurodegenerative Diseases; Peptide Fragments

Although abundant evidence suggests that amyloid accumulation plays a significant role in the pathogenesis of degenerative disease, the mechanism of amyloid formation and toxicity remains elusive. Early hypotheses for disease pathogenesis proposed that large amyloid deposits, which are composed primarily of 6-10-nm mature amyloid fibrils, were the primary causative agent in pathogenesis, but this hypothesis required modification to consider the central role of oligomers or aggregation intermediates, because the accumulation of these large aggregates does not correlate well with pathogenesis. Recent evidence supports the hypothesis that small soluble aggregates representing intermediates in the fibril assembly process may represent the primary culprits in a variety of amyloid-related degenerative diseases. Investigating the role of soluble amyloid oligomers in pathogenesis presents a problem for distinguishing these aggregates from the mature fibrils, soluble monomer, and natively folded precursor proteins, especially in vivo and in complex mixtures. Recently, we generated a conformation-specific antibody that recognizes soluble oligomers from many types of amyloid proteins, regardless of sequence. These results indicate that soluble oligomers have a common, generic structure that is distinct from both fibrils and low-molecular-weight soluble monomer/dimer. Conformation-dependent, oligomer-specific antibodies represent powerful tools for understanding the role of oligomers in pathogenesis. The purpose of this chapter is to review the methods for the production, characterization, and application of this antibody to understanding the contribution of amyloid oligomers to the disease process.

Topics: Amino Acid Sequence; Amyloid; Amyloid beta-Peptides; Anilino Naphthalenesulfonates; Animals; Antibodies; Benzothiazoles; Circular Dichroism; Epitopes; Humans; Molecular Mimicry; Molecular Sequence Data; Neurodegenerative Diseases; Peptide Fragments; Protein Conformation; Protein Structure, Quaternary; Rabbits; Thiazoles

Accumulation of the amyloid-beta (Abeta) peptide depends on both its generation and clearance. To better define clearance pathways, we have evaluated the role of the tissue plasminogen activator (tPA)-plasmin system in Abeta degradation in vivo. In two different mouse models of Alzheimer's disease, chronically elevated Abeta peptide in the brain correlates with the upregulation of plasminogen activator inhibitor-1 (PAI-1) and inhibition of the tPA-plasmin system. In addition, Abeta injected into the hippocampus of mice lacking either tPA or plasminogen persists, inducing PAI-1 expression and causing activation of microglial cells and neuronal damage. Conversely, Abeta injected into wild-type mice is rapidly cleared and does not cause neuronal degeneration. Thus, the tPA-plasmin proteolytic cascade aids in the clearance of Abeta, and reduced activity of this system may contribute to the progression of Alzheimer's disease.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Disease Models, Animal; Enzyme Activation; Female; Hippocampus; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microglia; Neurodegenerative Diseases; Neurons; Peptide Fragments; Plasminogen; Plasminogen Activator Inhibitor 1; Tissue Plasminogen Activator; Up-Regulation

Chemokines are a diverse group of small proteins that effect cell signaling by binding to G-protein-coupled, seven-trans-membrane receptors. Our group had found previously that the chemokine receptor CCR1 was present in neurons and dystrophic processes in a small sample of Alzheimer's disease cases. This expanded immunohistochemical study shows that the number of CCR1-positive plaque-like structures in the hippocampus and entorhinal cortex is highly correlated to dementia state as measured by the clinical dementia rating score. CCR1 immunoreactivity is found in dystrophic, neurofilament-positive, synaptophysin-negative neurites that are associated with senile plaques containing amyloid beta peptides of the 1-42 species (Abeta42). CCR1 was not, however, associated with diffuse deposits of Abeta42. There was limited expression of CCR1 in neurofibrillary tangle-bearing neuritic processes. Astrocytes and microglia were typically negative for CCR1. Human brains from age-matched, nondemented individuals rarely displayed either CCR1 or Abeta42 immunoreactivity. Seven other types of dementing neurodegenerative diseases were examined, and all failed to demonstrate CCR1 immunopositivity unless Abeta42-positive plaques were also present. Thus, neuronal CCR1 is not a generalized marker of neurodegeneration. Rather, it appears to be part of the neuroimmune response to Abeta42-positive neuritic plaques.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Biomarkers; Brain; Disease Progression; Humans; Immunohistochemistry; Microscopy, Confocal; Neurodegenerative Diseases; Neurofibrillary Tangles; Peptide Fragments; Plaque, Amyloid; Receptors, CCR1; Receptors, Chemokine

We assessed the neuroprotective capabilities of S12024 (R,S 1-methyl 8-(2-morpholinylmethoxy)-1,2,3,4-tetrahydroquinoleine methane sulphonate) in a model of neuronal degeneration in the dentate gyrus of the rat hippocampus. Specific degeneration of a large part of neurons in the lateral blade of the gyrus dentatus occurred after small intrahippocampal injections of water with or without amyloid-beta 1-28 fragment. S12024 reduced the number of animals with neuronal loss in the hippocampus, diminished the extent of the lesion, and reversed deficits of passive avoidance learning acquisition in animals with deposits of amyloid-beta 1-28. These results suggest that S12024 has neuroprotective effects on hippocampal cells and that the neurodegeneration by fluid injection combined with deposit of amyloid-beta 1-28 may be used to assay the neuroprotective activity of pharmacological compounds.

Topics: Amyloid beta-Peptides; Animals; Dentate Gyrus; Disease Models, Animal; Female; Hippocampus; Injections, Intraventricular; Learning; Morpholines; Neurodegenerative Diseases; Peptide Fragments; Quinolines; Rats; Rats, Sprague-Dawley