Amyloid β peptides appear to play a role in physiological processes; however, they are also involved in the pathogenesis of Alzheimer disease. Their actions under normal conditions are probably mediated by soluble monomeric L-isoforms at low concentrations, perhaps via highly specific interactions. On the contrary, toxic effects of aggregated natural L-isoforms/synthetic D-isoforms on membranes are very similar, but synthetic reverse/random L: -isoforms without pronounced aggregation properties are not toxic. Our previous work reported interactions of non-aggregated/aggregated L-isoforms of amyloid β peptides 1-40/1-42 with racemic 24-hydroxycholesterol. In this study, stereospecificity in the interactions of natural 24(S)hydroxycholesterol (cerebrosterol) or synthetic 24(R)hydroxycholesterol with soluble fragment 1-40 was evaluated by means of an in vitro test based on increased vulnerability of the hemicholinium-3 sensitive high-affinity choline uptake system in rat hippocampal cholesterol-depleted synaptosomes to the actions of amyloid β; computational simulations were also performed. Our results suggest that: (1) 24(S)hydroxycholesterol interacts with L-peptide 1-40 but not with the reverse L-peptide 40-1, (2) 24(R)hydroxycholesterol does not interact with L-peptide 1-40 or reverse 40-1, and (3) both enantiomers can probably interact with D-peptide 1-40. Therefore, the binding of 24(S)hydroxycholesterol is not fully stereospecific and the interaction could not reflect a physiological mechanism. Data from the computational simulation indicate that the hydrophobic core of the amyloid β molecule interacts with the hydrophobic part of 24(S)hydroxycholesterol, but no hydrogen bonds with high stability were found. Using this procedure, globular amyloid β could retain 24(S)hydroxycholesterol and thus contribute to its pathological accumulation in the brains of patients with Alzheimer disease.

• MeSH
• Amyloid beta-Peptides metabolism   MeSH
• Hippocampus metabolism   MeSH
• Hydroxycholesterols metabolism   MeSH
• Rats MeSH
• Peptide Fragments metabolism   MeSH
• Rats, Wistar MeSH
• Protein Binding MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Cíl: Cílem práce bylo porovnat metody ELISA pro stanovení hladin tripletu proteinů – celkového (t-tau) a fosforylovaného tau (p-tau) proteinů a β-amyloidu (1– 42) (Aβ42) v mozkomíšním moku (MMM) od dvou výrobců Fujirebio a EUROIMMUN a zároveň vytvořit orientační vodítka pro normální koncentrace u české populace od kognitivně zdravých starších osob. Soubor a metodika: Koncentrace likvorového tripletu proteinů od 38 kognitivně zdravých osob starších 55 let (19 mužů, průměrný věk 67 ± 8 let) byly změřeny jak soupravami ELISA INNOTEST, tak soupravami EUROIMMUN AG. Výsledky: Výsledky srovnání metod pro t-tau a p-tau proteiny a Aβ42 pomocí rozdílového grafu dle Blanda a Altmana ukazují, že hodnoty rozdílů mezi metodami ležely v rozsahu limitů shody (průměr ± 1,96 SD) až na ojedinělé výjimky odlehlých hodnot. Hodnoty korelačních koeficientů svědčí pro významnou shodu pro soupravy na stanovení t-tau proteinu. Na základě našich výsledků a zkušeností navrhujeme rozdělit koncentrace likvorového tripletu na tři skupiny: 1. snížené; 2. nerozhodné a hraniční; 3. zvýšené koncentrace v ng/ l na základě našeho konsenzu takto: t-tau protein < 280– 400 >, p181-tau protein < 50– 60 > a Aβ42 < 430– 480 >. Závěr: Soupravy ELISA obou výrobců jsou vhodné ke stanovení tripletu proteinů v MMM. Pro jejich referenční rozmezí lze orientačně využít naše výsledky, založené na reálném měření vzorků pečlivě vybraných a vyšetřených zdravých starších osob z ČR, nebo normy na základě našeho společného názoru.

Aim: The aim of the study was to compare ELISA methods for determination of triplet protein levels – total (t-tau) and phosphorylated tau (p-tau) proteins and β-amyloid (1– 42) (Aβ42) in cerebrospinal fl uid (CSF) from manufacturers Fujirebio and EUROIMMUN; and to provide guidance for normal concentrations from cognitively healthy elderly people. Patients and methods: The group consisted of 38 cognitively healthy persons over 55 years of age (19 men) whose average age was 67 ± 8 years. In each CSF sample, we examined the protein triplet by both ELISA INNOTEST and EUROIMMUN AG kits. Results: A comparison of ELISA methods for determination of t-tau and p-tau proteins and Aβ42 us ing the Bland and Altman difference graph shows that the differences between methods, with the exception of isolated outliers, were within the range of compliance (mean ± 1.96 SD). Cor relation coeffi cient values suggest significant agreement for t-tau protein as say kits. Based on our results and experience, we propose to clas sify CSF concentrations into three groups: 1. decreased; 2. questionable and borderline; 3. increased concentrations in ng/ L based on our consensus as follows: t-tau protein < 280– 400 >, p181-tau protein < 50– 60 > and Aβ42 < 430– 480 >. Conclusion: ELISA kits from two producers are suitable for determination of the triplet proteins in CSF. Our results based on real measurements of samples of carefully selected and examined healthy elderly people from the Czech Republic or the norms based on our consensus recom mendation can be used as reference range of the triplet.

• MeSH
• Alzheimer Disease * diagnosis   MeSH
• Amyloid beta-Peptides * analysis   MeSH
• Enzyme-Linked Immunosorbent Assay MeSH
• Clinical Studies as Topic MeSH
• Middle Aged MeSH
• Humans MeSH
• Cerebrospinal Fluid MeSH
• tau Proteins analysis   MeSH
• Cerebrospinal Fluid Proteins * analysis   MeSH
• Aged MeSH
• Check Tag
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged MeSH

Amyloid β is considered a key player in the development and progression of Alzheimer's disease (AD). Many studies investigating the effect of statins on lowering cholesterol suggest that there may be a link between cholesterol levels and AD pathology. Since cholesterol is one of the most abundant lipid molecules, especially in brain tissue, it affects most membrane-related processes, including the formation of the most dangerous form of amyloid β, Aβ42. The entire Aβ production system, which includes the amyloid precursor protein (APP), β-secretase, and the complex of γ-secretase, is highly dependent on membrane cholesterol content. Moreover, cholesterol can affect amyloidogenesis in many ways. Cholesterol influences the stability and activity of secretases, but also dictates their partitioning into specific cellular compartments and cholesterol-enriched lipid rafts, where the amyloidogenic machinery is predominantly localized. The most complicated relationships have been found in the interaction between cholesterol and APP, where cholesterol affects not only APP localization but also the precise character of APP dimerization and APP processing by γ-secretase, which is important for the production of Aβ of different lengths. In this review, we describe the intricate web of interdependence between cellular cholesterol levels, cholesterol membrane distribution, and cholesterol-dependent production of Aβ, the major player in AD.

• Publication type
• Journal Article MeSH
• Review MeSH

The accumulation of amyloid-β (Aβ) peptide is thought to be a major causative mechanism of Alzheimer's disease. Aβ accumulation could be caused by dysregulated processing of amyloid precursor protein, yielding excessive amounts of Aβ, and/or by inefficient proteolytic degradation of the peptide itself. Several proteases have been described as Aβ degradation enzymes, most notably metalloendopeptidases, aspartic endopeptidases, and some exopeptidases. Recently a report suggested that another metallopeptidase, glutamate carboxypeptidase II (GCPII), can also cleave Aβ. GCPII is a zinc exopeptidase that cleaves glutamate from N-acetyl-L-aspartyl-L-glutamate in the central nervous system and from pteroylpoly-γ-glutamate in the jejunum. GCPII has been proposed as a promising therapeutic target for disorders caused by glutamate neurotoxicity. However, an Aβ-degrading activity of GCPII would compromise potential pharmaceutical use of GCPII inhibitors, because the enzyme inhibition might lead to increased Aβ levels and consequently to Alzheimer's disease. Therefore, we analyzed the reported Aβ-degrading activity of GCPII using highly purified recombinant enzyme and synthetic Aβ. We did not detect any Aβ degradation activity of GCPII or its homologue even under prolonged incubation at a high enzyme to substrate ratio. These results are in good agreement with the current detailed structural understanding of the substrate specificity and enzyme-ligand interactions of GCPII.

• MeSH
• Amyloid beta-Peptides chemistry   metabolism   MeSH
• Antigens, Surface genetics   metabolism   MeSH
• Biocatalysis drug effects   MeSH
• Dipeptides metabolism   MeSH
• Glutamate Carboxypeptidase II antagonists & inhibitors   genetics   metabolism   MeSH
• Mass Spectrometry MeSH
• Hydrolysis MeSH
• Catalytic Domain MeSH
• Humans MeSH
• Molecular Structure MeSH
• Neprilysin genetics   metabolism   MeSH
• Organophosphorus Compounds pharmacology   MeSH
• Peptide Fragments chemistry   metabolism   MeSH
• Proteolysis MeSH
• Recombinant Proteins metabolism   MeSH
• Substrate Specificity MeSH
• Tritium MeSH
• Chromatography, High Pressure Liquid MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

OBJECTIVE: In a multicenter cohort of probable dementia with Lewy bodies (DLB), we tested the hypothesis that β-amyloid and tau biomarker positivity increases with age, which is modified by APOE genotype and sex, and that there are isolated and synergistic associations with the clinical phenotype. METHODS: We included 417 patients with DLB (age 45-93 years, 31% women). Positivity on β-amyloid (A+) and tau (T+) biomarkers was determined by CSF β-amyloid1-42 and phosphorylated tau in the European cohort and by Pittsburgh compound B and AV-1451 PET in the Mayo Clinic cohort. Patients were stratified into 4 groups: A-T-, A+T-, A-T+, and A+T+. RESULTS: A-T- was the largest group (39%), followed by A+T- (32%), A+T+ (15%), and A-T+ (13%). The percentage of A-T- decreased with age, and A+ and T+ increased with age in both women and men. A+ increased more in APOE ε4 carriers with age than in noncarriers. A+ was the main predictor of lower cognitive performance when considered together with T+. T+ was associated with a lower frequency of parkinsonism and probable REM sleep behavior disorder. There were no significant interactions between A+ and T+ in relation to the clinical phenotype. CONCLUSIONS: Alzheimer disease pathologic changes are common in DLB and are associated with the clinical phenotype. β-Amyloid is associated with cognitive impairment, and tau pathology is associated with lower frequency of clinical features of DLB. These findings have important implications for diagnosis, prognosis, and disease monitoring, as well as for clinical trials targeting disease-specific proteins in DLB. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that in patients with probable DLB, β-amyloid is associated with lower cognitive performance and tau pathology is associated with lower frequency of clinical features of DLB.

• MeSH
• Amyloid beta-Peptides cerebrospinal fluid   metabolism   MeSH
• Apolipoprotein E4 genetics   MeSH
• Biomarkers metabolism   MeSH
• Lewy Body Disease classification   complications   metabolism   physiopathology   MeSH
• Phenotype MeSH
• Cognitive Dysfunction etiology   physiopathology   MeSH
• Cohort Studies MeSH
• Middle Aged MeSH
• Humans MeSH
• Peptide Fragments cerebrospinal fluid   MeSH
• Positron-Emission Tomography MeSH
• tau Proteins cerebrospinal fluid   metabolism   MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Age Factors MeSH
• Check Tag
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Multicenter Study MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH

Multifunctional mitochondrial enzyme 17β-hydroxysteroid dehydrogenase type 10 plays a role in the development of Alzheimer's disease. However, changes in its expression in the brain or cerebrospinal fluid are not fully specific for this type of dementia. Our previous study revealed that complexes of the enzyme and amyloid β in cerebrospinal fluid could serve as a more specific biomarker of Alzheimer's disease than either the enzyme or amyloid β individually when compared to autoimmune multiple sclerosis. In this study, enzyme-linked immunosorbent assay and the surface plasmon resonance biosensor method were used to analyse cerebrospinal fluid of patients with various neuroinflammatory diseases. Significant differences in the levels of the total enzyme, complexes, amyloid β 1-42 and total τ/phospho-τ were found in Alzheimer's disease patients while differences in complexes, total amyloid β and amyloid β 1- 42 were observed in patients with neuroinflammatory diseases (except for multiple sclerosis) when compared to non-neuroinflammatory controls. The interactions of the enzyme with amyloid β appeared to depend strongly on neuroinflammation-sensitive amyloid β. Our data demonstrated that oligomerisation/aggregation of intracellular amyloid β peptides was important in Alzheimer's disease while extracellular amyloid β could play a role in neuroinflammatory diseases. Phospho-τ is currently the best biomarker of Alzheimer's disease.

• MeSH
• 17-Hydroxysteroid Dehydrogenases MeSH
• Alzheimer Disease complications   MeSH
• Amyloid beta-Peptides MeSH
• Enzyme-Linked Immunosorbent Assay MeSH
• Humans MeSH
• Central Nervous System Diseases complications   MeSH
• Vascular Diseases complications   MeSH
• Peripheral Nervous System Diseases complications   MeSH
• Statistics, Nonparametric MeSH
• Peptide Fragments MeSH
• Surface Plasmon Resonance MeSH
• Aged MeSH
• Inflammation complications   MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Mounting evidence suggests that the neuronal cell membrane is the main site of oligomer-mediated neuronal toxicity of amyloid-β peptides in Alzheimer's disease. To gain a detailed understanding of the mutual interference of amyloid-β oligomers and the neuronal membrane, we carried out microseconds of all-atom molecular dynamics (MD) simulations on the dimerization of amyloid-β (Aβ)42 in the aqueous phase and in the presence of a lipid bilayer mimicking the in vivo composition of neuronal membranes. The dimerization in solution is characterized by a random coil to β-sheet transition that seems on pathway to amyloid aggregation, while the interactions with the neuronal membrane decrease the order of the Aβ42 dimer by attenuating its propensity to form a β-sheet structure. The main lipid interaction partners of Aβ42 are the surface-exposed sugar groups of the gangliosides GM1. As the neurotoxic activity of amyloid oligomers increases with oligomer order, these results suggest that GM1 is neuroprotective against Aβ-mediated toxicity.

• MeSH
• Amyloid chemistry   MeSH
• Amyloid beta-Peptides chemistry   metabolism   MeSH
• Cell Membrane metabolism   MeSH
• G(M1) Ganglioside metabolism   MeSH
• Protein Conformation MeSH
• Humans MeSH
• Lipid Bilayers metabolism   MeSH
• Protein Multimerization * MeSH
• Neurons metabolism   MeSH
• Molecular Dynamics Simulation MeSH
• Protein Binding MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Alzheimer's disease (AD) is a neurodegenerative disorder that is one of the most devastating and widespread diseases worldwide, mainly affecting the aging population. One of the key factors contributing to AD-related neurotoxicity is the production and aggregation of amyloid β (Aβ). Many studies have shown the ability of Aβ to bind to the cell membrane and disrupt its structure, leading to cell death. Because amyloid damage affects different parts of the brain differently, it seems likely that not only Aβ but also the nature of the membrane interface with which the amyloid interacts, helps determine the final neurotoxic effect. Because cholesterol is the dominant component of the plasma membrane, it plays an important role in Aβ-induced toxicity. Elevated cholesterol levels and their regulation by statins have been shown to be important factors influencing the progression of neurodegeneration. However, data from many studies have shown that cholesterol has both neuroprotective and aggravating effects in relation to the development of AD. In this review, we attempt to summarize recent findings on the role of cholesterol in Aβ toxicity mediated by membrane binding in the pathogenesis of AD and to consider it in the broader context of the lipid composition of cell membranes.

• Publication type
• Journal Article MeSH
• Review MeSH

In this perspective we summarize current knowledge of the effect of monosialoganglioside GM1 on the membrane-mediated aggregation of the β-amyloid (Aβ) peptide. GM1 has been suggested to be actively involved in the development of Alzheimer's disease due to its ability to seed the aggregation of Aβ. However, GM1 is known to be neuroprotective against Aβ-induced toxicity. Here we suggest that the two scenarios are not mutually exclusive but rather complementary, and might depend on the organization of GM1 in membranes. Improving our understanding of the molecular details behind the role of gangliosides in neurodegenerative amyloidoses might help in developing disease-modifying treatments.

• MeSH
• Amyloid beta-Peptides chemistry   metabolism   MeSH
• G(M1) Ganglioside chemistry   metabolism   MeSH
• Humans MeSH
• Brain metabolism   MeSH
• Protein Aggregation, Pathological metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH

The overproduction of β-amyloid (Aβ) fragments in transgenic APPswe/PS1dE9 mice results in formation of amyloid deposits in the cerebral cortex and hippocampus starting around four months of age and leading to cognitive impairment much later. We have previously found an age and transgene-dependent weakening of muscarinic receptor-mediated transmission that was not present in young (6-10-week-old) animals but preceded both amyloid deposits and cognitive deficits. Now we investigated immediate and prolonged in vitro effects of non-aggregated Aβ(1-42) on coupling of individual muscarinic receptor subtypes expressed in CHO (Chinese hamster ovary) cells and their underlying mechanisms. Immediate application of 1 μM Aβ(1-42) had no effect on the binding of the muscarinic antagonist N-methylscopolamine or the agonist carbachol. In contrast, 4-day treatment of CHO cells expressing the M1 muscarinic receptor with 100 nM Aβ(1-42) significantly changed the binding characteristics of the muscarinic agonist carbachol and reduced the extent of the M1 receptor-stimulated breakdown of phosphatidylinositol while it did not demonstrate overt toxic effects. The treatment had no influence on the expression of either G-proteins or muscarinic receptors. In concert, we found no change in the gene expression of muscarinic receptor subtypes and gene or protein expression of the G(s), G(q/11), and G(i/o) G-proteins in the cerebral cortex of young adult APPswe/PS1dE9 mice that demonstrate high concentrations of soluble Aβ(1-42) and impaired muscarinic receptor-mediated G-protein activation. Our results provide strong evidence that the initial injurious effects of Aβ(1-42) on M1 muscarinic receptor-mediated transmissionis is due to compromised coupling of the receptor with G(q/11) G-protein.

• MeSH
• Amyloid beta-Peptides antagonists & inhibitors   metabolism   MeSH
• CHO Cells MeSH
• Cricetulus MeSH
• Cricetinae MeSH
• Cells, Cultured MeSH
• Humans MeSH
• Mice, Transgenic MeSH
• Mice MeSH
• Peptide Fragments antagonists & inhibitors   metabolism   MeSH
• Receptor, Muscarinic M1 metabolism   MeSH
• Receptors, G-Protein-Coupled antagonists & inhibitors   metabolism   MeSH
• Uncoupling Agents pharmacology   MeSH
• Protein Binding drug effects   physiology   MeSH
• Animals MeSH
• Check Tag
• Cricetinae MeSH
• Humans MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH