Protein folding pathology in domestic animals*

PubMed Central

Gruys, Erik

2004-01-01

Fibrillar proteins form structural elements of cells and the extracellular matrix. Pathological lesions of fibrillar microanatomical structures, or secondary fibrillar changes in globular proteins are well known. A special group concerns histologically amorphous deposits, amyloid. The major characteristics of amyloid are: apple green birefringence after Congo red staining of histological sections, and non-branching 7–10 nm thick fibrils on electron microscopy revealing a high content of cross beta pleated sheets. About 25 different types of amyloid have been characterised. In animals, AA-amyloid is the most frequent type. Other types of amyloid in animals represent: AIAPP (in cats), AApoAI, AApoAII, localised AL-amyloid, amyloid in odontogenic or mammary tumors and amyloid in the brain. In old dogs Aβ and in sheep APrPsc-amyloid can be encountered. AA-amyloidosis is a systemic disorder with a precursor in blood, acute phase serum amyloid A (SAA). In chronic inflammatory processes AA-amyloid can be deposited. A rapid crystallization of SAA to amyloid fibrils on small beta-sheeted fragments, the ‘amyloid enhancing factor’ (AEF), is known and the AEF has been shown to penetrate the enteric barrier. Amyloid fibrils can aggregate from various precursor proteins in vitro in particular at acidic pH and when proteolytic fragments are formed. Molecular chaperones influence this process. Tissue data point to amyloid fibrillogenesis in lysosomes and near cell surfaces. A comparison can be made of the fibrillogenesis in prion diseases and in enhanced AA-amyloidosis. In the reactive form, acute phase SAA is the supply of the precursor protein, whereas in the prion diseases, cell membrane proteins form a structural source. Aβ-amyloid in brain tissue of aged dogs showing signs of dementia forms a canine counterpart of senile dementia of the Alzheimer type (ccSDAT) in man. Misfolded proteins remain potential food hazards. Developments concerning prevention of amyloidogenesis and therapy of amyloid deposits are shortly commented. PMID:15362194

Modulation of beta-amyloid precursor protein trafficking and processing by the low density lipoprotein receptor family.

PubMed

Cam, Judy A; Bu, Guojun

2006-08-18

Amyloid-beta peptide (Abeta) accumulation in the brain is an early, toxic event in the pathogenesis of Alzheimer's disease (AD). Abeta is produced by proteolytic processing of a transmembrane protein, beta-amyloid precursor protein (APP), by beta- and gamma-secretases. Mounting evidence has demonstrated that alterations in APP cellular trafficking and localization directly impact its processing to Abeta. Recent studies have shown that members of the low-density lipoprotein receptor family, including LRP, LRP1B, SorLA/LR11, and apolipoprotein E (apoE) receptor 2, interact with APP and regulate its endocytic trafficking. Another common feature of these receptors is their ability to bind apoE, which exists in three isoforms in humans and the presence of the epsilon4 allele represents a genetic risk factor for AD. In this review, we summarize the current understanding of the function of these apoE receptors with a focus on their role in APP trafficking and processing. Knowledge of the interactions between these distinct low-density lipoprotein receptor family members and APP may ultimately influence future therapies for AD.

Amyloid precursor protein and Presenilin 1 interaction studied by FRET in human H4 cells.

PubMed

Nizzari, Mario; Venezia, Valentina; Bianchini, Paolo; Caorsi, Valentina; Diaspro, Alberto; Repetto, Emanuela; Thellung, Stefano; Corsaro, Alessandro; Carlo, Pia; Schettini, Gennaro; Florio, Tullio; Russo, Claudio

2007-01-01

The mayor pathologic hallmarks of Alzheimer's disease (AD) are senile plaque and neurofibrillary tangles. Senile plaque are primarily made up of deposits of amyloid-beta protein, a proteolytic product derived from the amyloid precursor protein (APP). APP is a transmembrane protein detected into the endoplasmic reticulum, in the Golgi apparatus, at the cell surface, recycled by endocytosis to endosomes, whose physiological function is unclear. Presenilins (PS), are a component of gamma-secretase complex that cleave alpha-CTFs (carboxy-terminal fragment), or beta-CTFs, leaving 40 or 42 amino acids amyloid-beta peptides and 58 or 56 amino acids intracellular domains (AICD). Where the amyloid-beta peptides is generated is not clear. The study of APP-PS interaction in specific cell compartments provides a good opportunity to light upon the molecular mechanisms regulating the activity of the "gamma-secretase complex," and where beta-amyloid is generated. In our study we used a biophysical assay of protein proximity: fluorescence resonance energy transfer (FRET), that can provide information about molecular interactions when two proteins are in the close proximity (<10 nm), to examine the subcellular localization and interaction between APP and PS1 in human neuroglioma cells (H4). Confocal microscopic analysis reveals extensive colocalization in different cells' compartment, and centrosomal or microtubule organizing center (MTOC) localization of APP and PS1, but not necessarily a close molecular interaction. We used FRET to determine if APP and PS1 interact at the cell centrosome. FRET data suggest a close interaction between APP and PS1 in subcellular compartments and at the centrosome of H4 cells. Using this approach we show that APP and PS1 are closely associated in the centrosomes of the H4 cell.

First demonstration of cerebrospinal fluid and plasma A beta lowering with oral administration of a beta-site amyloid precursor protein-cleaving enzyme 1 inhibitor in nonhuman primates.

PubMed

Sankaranarayanan, Sethu; Holahan, Marie A; Colussi, Dennis; Crouthamel, Ming-Chih; Devanarayan, Viswanath; Ellis, Joan; Espeseth, Amy; Gates, Adam T; Graham, Samuel L; Gregro, Allison R; Hazuda, Daria; Hochman, Jerome H; Holloway, Katharine; Jin, Lixia; Kahana, Jason; Lai, Ming-tain; Lineberger, Janet; McGaughey, Georgia; Moore, Keith P; Nantermet, Philippe; Pietrak, Beth; Price, Eric A; Rajapakse, Hemaka; Stauffer, Shaun; Steinbeiser, Melissa A; Seabrook, Guy; Selnick, Harold G; Shi, Xiao-Ping; Stanton, Matthew G; Swestock, John; Tugusheva, Katherine; Tyler, Keala X; Vacca, Joseph P; Wong, Jacky; Wu, Guoxin; Xu, Min; Cook, Jacquelynn J; Simon, Adam J

2009-01-01

beta-Site amyloid precursor protein (APP)-cleaving enzyme (BACE) 1 cleavage of amyloid precursor protein is an essential step in the generation of the potentially neurotoxic and amyloidogenic A beta 42 peptides in Alzheimer's disease. Although previous mouse studies have shown brain A beta lowering after BACE1 inhibition, extension of such studies to nonhuman primates or man was precluded by poor potency, brain penetration, and pharmacokinetics of available inhibitors. In this study, a novel tertiary carbinamine BACE1 inhibitor, tertiary carbinamine (TC)-1, was assessed in a unique cisterna magna ported rhesus monkey model, where the temporal dynamics of A beta in cerebrospinal fluid (CSF) and plasma could be evaluated. TC-1, a potent inhibitor (IC(50) approximately 0.4 nM), has excellent passive membrane permeability, low susceptibility to P-glycoprotein transport, and lowered brain A beta levels in a mouse model. Intravenous infusion of TC-1 led to a significant but transient lowering of CSF and plasma A beta levels in conscious rhesus monkeys because it underwent CYP3A4-mediated metabolism. Oral codosing of TC-1 with ritonavir, a potent CYP3A4 inhibitor, twice daily over 3.5 days in rhesus monkeys led to sustained plasma TC-1 exposure and a significant and sustained reduction in CSF sAPP beta, A beta 40, A beta 42, and plasma A beta 40 levels. CSF A beta 42 lowering showed an EC(50) of approximately 20 nM with respect to the CSF [TC-1] levels, demonstrating excellent concordance with its potency in a cell-based assay. These results demonstrate the first in vivo proof of concept of CSF A beta lowering after oral administration of a BACE1 inhibitor in a nonhuman primate.

The amyloid precursor protein and postnatal neurogenesis/neuroregeneration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Yanan; Tang, Bor Luen

2006-03-03

The amyloid precursor protein (APP) is the source of amyloid-beta (A{beta}) peptide, produced via its sequential cleavage {beta}- and {gamma}-secretases. Various biophysical forms of A{beta} (and the mutations of APP which results in their elevated levels) have been implicated in the etiology and early onset of Alzheimer's disease. APP's evolutionary conservation and the existence of APP-like isoforms (APLP1 and APLP2) which lack the A{beta} sequence, however, suggest that these might have important physiological functions that are unrelated to A{beta} production. Soluble N-terminal fragments of APP have been known to be neuroprotective, and the interaction of its cytoplasmic C-terminus with amore » myriad of proteins associates it with diverse processes such as axonal transport and transcriptional regulation. The notion for an essential postnatal function of APP has been demonstrated genetically, as mice deficient in both APP and APLP2 or all three APP isoforms exhibit early postnatal lethality and neuroanatomical abnormalities. Recent findings have also brought to light two possible functions of the APP family in Brain-regulation of neural progenitor cell proliferation and axonal outgrowth after injury. Interestingly, these two apparently related neurogenic/neuroregenerative functions of APP involve two separate domains of the molecule.« less

Trafficking of cell surface beta-amyloid precursor protein: retrograde and transcytotic transport in cultured neurons

PubMed Central

1995-01-01

Amyloid beta-protein (A beta), the principal constituent of senile plaques seen in Alzheimer's disease (AD), is derived by proteolysis from the beta-amyloid precursor protein (beta PP). The mechanism of A beta production in neurons, which are hypothesized to be a rich source of A beta in brain, remains to be defined. In this study, we describe a detailed localization of cell surface beta PP and its subsequent trafficking in primary cultured neurons. Full-length cell surface beta PP was present primarily on perikarya and axons, the latter with a characteristic discontinuous pattern. At growth cones, cell surface beta PP was inconsistently detected. By visualizing the distribution of beta PP monoclonal antibodies added to intact cultures, beta PP was shown to be internalized from distal axons or terminals and retrogradely transported back to perikarya in organelles which colocalized with fluid-phase endocytic markers. Retrograde transport of beta PP was shown in both hippocampal and peripheral sympathetic neurons, the latter using a compartment culture system that isolated cell bodies from distal axons and terminals. In addition, we demonstrated that beta PP from distal axons was transcytotically transported to the surface of perikarya from distal axons in sympathetic neurons. Indirect evidence of this transcytotic pathway was obtained in hippocampal neurons using antisense oligonucleotide to the kinesin heavy chain to inhibit anterograde beta PP transport. Taken together, these results demonstrate novel aspects of beta PP trafficking in neurons, including retrograde axonal transport and transcytosis. Moreover, the axonal predominance of cell surface beta PP is unexpected in view of the recent report of polarized sorting of beta PP to the basolateral domain of MDCK cells. PMID:7721945

Clinical observations with AN-1792 using TAPIR analyses.

PubMed

Hock, Christoph; Nitsch, Roger M

2005-01-01

Clinical observations with AN-1792 using tissue amyloid plaque immunoreactivity (TAPIR) analyses established for the first time evidence in humans that antibodies against beta-amyloid-related epitopes are capable of slowing progression in Alzheimer's disease. Antibodies derived upon TAPIR assay selection may specifically target the pathologic neoepitopes of aggregated A beta species present in amyloid plaques and some of their aggregated, protofibrillar and low molecular weight oligomeric precursors. We briefly summarize here how the proof of concept was established and why it provides the basis for a potential cure for Alzheimer's disease. Copyright 2005 S. Karger AG, Basel.

Metabolic Characterization of Intact Cells Reveals Intracellular Amyloid Beta but Not Its Precursor Protein to Reduce Mitochondrial Respiration

PubMed Central

Schaefer, Patrick M.; von Einem, Bjoern; Walther, Paul; Calzia, Enrico; von Arnim, Christine A. F.

2016-01-01

One hallmark of Alzheimer´s disease are senile plaques consisting of amyloid beta (Aβ), which derives from the processing of the amyloid precursor protein (APP). Mitochondrial dysfunction has been linked to the pathogenesis of Alzheimer´s disease and both Aβ and APP have been reported to affect mitochondrial function in isolated systems. However, in intact cells, considering a physiological localization of APP and Aβ, it is pending what triggers the mitochondrial defect. Thus, the aim of this study was to dissect the impact of APP versus Aβ in inducing mitochondrial alterations with respect to their subcellular localization. We performed an overexpression of APP or beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), increasing APP and Aβ levels or Aβ alone, respectively. Conducting a comprehensive metabolic characterization we demonstrate that only APP overexpression reduced mitochondrial respiration, despite lower extracellular Aβ levels compared to BACE overexpression. Surprisingly, this could be rescued by a gamma secretase inhibitor, oppositionally indicating an Aβ-mediated mitochondrial toxicity. Analyzing Aβ localization revealed that intracellular levels of Aβ and an increased spatial association of APP/Aβ with mitochondria are associated with reduced mitochondrial respiration. Thus, our data provide marked evidence for a prominent role of intracellular Aβ accumulation in Alzheimer´s disease associated mitochondrial dysfunction. Thereby it highlights the importance of the localization of APP processing and intracellular transport as a decisive factor for mitochondrial function, linking two prominent hallmarks of neurodegenerative diseases. PMID:28005987

The NACP/synuclein gene: chromosomal assignment and screening for alterations in Alzheimer disease.

PubMed

Campion, D; Martin, C; Heilig, R; Charbonnier, F; Moreau, V; Flaman, J M; Petit, J L; Hannequin, D; Brice, A; Frebourg, T

1995-03-20

The major component of the vascular and plaque amyloid deposits in Alzheimer disease is the amyloid beta peptide (A beta). A second intrinsic component of amyloid, the NAC (non-A beta component of amyloid) peptide, has recently been identified, and its precursor protein was named NACP. A computer homology search allowed us to establish that the human NACP gene was homologous to the rat synuclein gene. We mapped the NACP/synuclein gene to chromosome 4 and cloned three alternatively spliced transcripts in lymphocytes derived from a normal subject. We analyzed by RT-PCR and direct sequencing the entire coding region of the NACP/synuclein gene in a group of patients with familial early onset Alzheimer disease. No mutation was found in 26 unrelated patients. Further studies are required to investigate the implication of the NACP/synuclein gene in Alzheimer disease.

The NACP/synuclein gene: Chromosomal assignment and screening for alterations in Alzheimer disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campion, D.; Martin, C.; Charbonnier, F.

1995-03-20

The major component of the vascular and plaque amyloid deposits in Alzheimer disease is the amyloid {beta} peptide (A{beta}). A second intrinsic component of amyloid, the NAC (non-A{beta} component of amyloid) peptide, has recently been identified, and its precursor protein was named NACP. A computer homology search allowed us to establish that the human NACP gene was homologous to the rat synuclein gene. We mapped the NACP/synuclein gene to chromosome 4 and cloned three alternatively spliced transcripts in lymphocytes derived from a normal subject. We analyzed by RT-PCR and direct sequencing the entire coding region of the NACP/synuclein gene inmore » a group of patients with familial early onset Alzheimer disease. No mutation was found in 26 unrelated patients. Further studies are required to investigate the implication of the NACP/synuclein gene in Alzheimer disease. 21 refs., 3 tabs.« less

Increased production of 4 kDa amyloid beta peptide in serum deprived human primary neuron cultures: possible involvement of apoptosis.

PubMed

LeBlanc, A

1995-12-01

The etiology of the amyloid beta peptide in sporadic Alzheimer's disease (AD) is not known. Amyloid beta peptide (A beta), a proteolytic product of the amyloid precursor protein (APP), is deposited in the senile plaques and cerebrovascular tissues of individuals with either sporadic or familial AD (FAD). Increased A beta production from mutant APPs in FAD fosters the hypothesis that overexpression of A beta plays a primary role in the pathogenesis of AD. The absence of APP mutations in sporadic AD which displays identical pathological features than FAD such as synapse and neuronal loss, senile plaques and neurofibrillary tangles, suggests other causes for overexpression and/or deposition of A beta. To investigate the effect of neuronal death on APP metabolism and A beta secretion, human primary neuron cultures were induced to undergo apoptosis by serum deprivation. Serum deprived neurons display shrunken and rounded morphology, contain condensed chromatine and fragmented DNA, which are characteristic of apoptosis. In serum deprived neurons, metabolism of APP through the nonamyloidogenic secretory pathway is decreased to 20% from 40% in control cultures whereas 4kDa A beta is increased three- to fourfold. The results suggest that human neurons undergoing apoptosis generate excess A beta and indicates a possible mechanism for increased A beta in the absence of APP mutations.

Why Alzheimer trials fail: removing soluble oligomeric beta amyloid is essential, inconsistent, and difficult.

PubMed

Rosenblum, William I

2014-05-01

Before amyloid formation, peptides cleaved from the amyloid precursor protein (APP) exist as soluble oligomers. These are extremely neurotoxic. Their concentration is strongly correlated with synaptic impairment in animals and parallel cognitive decline in animals and humans. Clinical trials have largely been aimed at removing insoluble beta amyloid in senile plaques and have not reduced soluble load. Even treatment that should remove soluble oligomers has not consistently reduced the load. Failure to significantly improve cognition has frequently been attributed to failure of the amyloid hypothesis or to irreversible alteration in the brain. Instead, trial failures may be because of failure to significantly reduce load of toxic Aβ oligomers. Moreover, targeting only synthesis of Aβ peptides, only the oligomers themselves, or only the final insoluble amyloid may fail to significantly reduce soluble load because of the interrelationship between these 3 points in the amyloid cascade. Thus, treatments may fail unless trials target simultaneously all 3 points in the equation-"triple therapy". Cerebrospinal fluid analysis and other monitoring tools may in the future provide reliable measurement of soluble load. But currently, only analysis of autopsied brains can provide this data and thus enable proper evaluation and explanation of the outcome of clinical trials. These data are essential before attributing trial failures to the advanced nature of the disease or asserting that failures prove that the theory linking Alzheimer's disease to products of amyloid precursor protein is incorrect. Copyright © 2014 Elsevier Inc. All rights reserved.

Amyloid-degrading ability of nattokinase from Bacillus subtilis natto.

PubMed

Hsu, Ruei-Lin; Lee, Kung-Ta; Wang, Jung-Hao; Lee, Lily Y-L; Chen, Rita P-Y

2009-01-28

More than 20 unrelated proteins can form amyloid fibrils in vivo which are related to various diseases, such as Alzheimer's disease, prion disease, and systematic amyloidosis. Amyloid fibrils are an ordered protein aggregate with a lamellar cross-beta structure. Enhancing amyloid clearance is one of the targets of the therapy of these amyloid-related diseases. Although there is debate on whether the toxicity is due to amyloids or their precursors, research on the degradation of amyloids may help prevent or alleviate these diseases. In this study, we explored the amyloid-degrading ability of nattokinase, a fibrinolytic subtilisin-like serine protease, and determined the optimal conditions for amyloid hydrolysis. This ability is shared by proteinase K and subtilisin Carlsberg, but not by trypsin or plasmin.

Current concepts on selected plant secondary metabolites with promising inhibitory effects against enzymes linked to Alzheimer's disease.

PubMed

Orhan, I Erdogan

2012-01-01

Alzheimer's disease (AD) has become one of the deadliest diseases for human beings with special incidence in elderly population. It is a progressive neurodegenerative disease and the most prevalent cause of dementia. The neuropathology of AD has not been fully elucidated yet, however, cholinergic hypothesis is the most accepted theory nowadays, resulting from the cholinergic deficit emerging in the brains of AD patients. Shortage of the neurotransmitters, acetylcholine and butyrylcholine has been demonstrated, and therefore, inhibition of the enzymes; acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) that break down acetylcholine and butyrylcholine has become a standard approach for AD treatment. However, cholinesterase inhibitors are only effective in symptomatic treatment and have no ability to impede the disease. The pathogenesis of AD is highly complex and another hypothesis is the formation of amyloid plaques containing beta-amyloid peptide, which causes neurolesions in the brains of AD patients. Beta-amyloid peptide is generated after the sequential cleavage of amyloid precursor protein, especially by the beta- and gamma-secretase in the amyloidogenic pathway. The secretases involved in the processing of amyloid precursor protein are of particular interest and, consequently, the inhibition of secretase enzyme family of protease type has become another desired treatment strategy for AD. On the other hand, medicinal plants are attractive sources for drug research and development as they produce chemically-varying molecules with preferred biological activities. The aim of this article is to review the available data on selected inhibitors from plant secondary metabolites with emphasis on cholinesterase, prolyl endopeptidase, and secretase enzyme families as being the current treatments of AD.

Loss of function of ATXN1 increases amyloid beta-protein levels by potentiating beta-secretase processing of beta-amyloid precursor protein.

PubMed

Zhang, Can; Browne, Andrew; Child, Daniel; Divito, Jason R; Stevenson, Jesse A; Tanzi, Rudolph E

2010-03-19

Alzheimer disease (AD) is a devastating neurodegenerative disease with complex and strong genetic inheritance. Four genes have been established to either cause familial early onset AD (APP, PSEN1, and PSEN2) or to increase susceptibility for late onset AD (APOE). To date approximately 80% of the late onset AD genetic variance remains elusive. Recently our genome-wide association screen identified four novel late onset AD candidate genes. Ataxin 1 (ATXN1) is one of these four AD candidate genes and has been indicated to be the disease gene for spinocerebellar ataxia type 1, which is also a neurodegenerative disease. Mounting evidence suggests that the excessive accumulation of Abeta, the proteolytic product of beta-amyloid precursor protein (APP), is the primary AD pathological event. In this study, we ask whether ATXN1 may lead to AD pathogenesis by affecting Abeta and APP processing utilizing RNA interference in a human neuronal cell model and mouse primary cortical neurons. We show that knock-down of ATXN1 significantly increases the levels of both Abeta40 and Abeta42. This effect could be rescued with concurrent overexpression of ATXN1. Moreover, overexpression of ATXN1 decreased Abeta levels. Regarding the underlying molecular mechanism, we show that the effect of ATXN1 expression on Abeta levels is modulated via beta-secretase cleavage of APP. Taken together, ATXN1 functions as a genetic risk modifier that contributes to AD pathogenesis through a loss-of-function mechanism by regulating beta-secretase cleavage of APP and Abeta levels.

Mechanisms of A beta plaque clearance following passive A beta immunization.

PubMed

Morgan, Dave

2005-01-01

Alzheimer's disease is a major health problem with limited available medical treatment options. Immunotherapy is one approach with the potential to slow or reverse the disease process. In transgenic mouse models of amyloid deposition, anti-A beta immunotherapy is remarkably effective at diminishing the amyloid burden and reversing the memory deficiency phenotype present in these mice. Three distinct mechanisms of antibody action have been proposed to mediate these benefits of anti-A beta immunotherapy. The first is a catalytic dissolution of the A beta fibrils, proposed by Beka Solomon and colleagues. A second mechanism is opsonization of the amyloid by the antibody and subsequent phagocytosis by macrophages proposed by Dale Schenk and the Elan group. A third mechanism proposed by DeMattos, Holtzman and colleagues is the peripheral sink hypothesis, arguing that circulating antibodies sequester A beta and favor efflux of A beta from the CNS over influx to the CNS. None of these mechanisms are mutually exclusive. Our research group has evaluated these mechanisms using intracranial injection and systemic administration of anti-A beta antibodies. We found evidence supporting all three mechanisms, and suggest they may act synergistically to achieve the large effect size of the immunotherapeutic approach. However, in aged amyloid precursor protein transgenic mice administered anti-A beta antibodies systemically, there is a redistribution of the amyloid from the parenchyma to vascular elements. This increase in congophilic angiopathy is associated with increased risk of microhemorrhage. Thus, although we favor continued testing of the immunotherapy to treat Alzheimer's disease, we believe caution should be taken to minimize the risk of vascular leakage. Copyright 2005 S. Karger AG, Basel.

Tetrahydroxystilbene glucoside modulates amyloid precursor protein processing via activation of AKT-GSK3β pathway in cells and in APP/PS1 transgenic mice.

PubMed

Yin, Xiaomin; Chen, Chen; Xu, Ting; Li, Lin; Zhang, Lan

2018-01-01

Alternative splicing of amyloid precursor protein (APP) exon 7 generates the isoforms containing a Kunitz protease inhibitor (KPI) domain. APP-KPI levels in the brain are correlated with amyloid beta (Aβ) production. Here, we determined the effect of Tetrahydroxystilbene glucoside (TSG) on the AKT-GSK3β pathway. We found GSK3β increased APP-KPI inclusion level and interacted with the splicing factor ASF. TSG was intragastrically administered to 5-month-old APP/PS1 transgenic mice for 12 months. We found that the activated the AKT-GSK3β signaling pathway suppressed APP-KPI inclusion. Moreover, TSG treatment attenuated amyloid deposition in APP/PS1 mice. This study demonstrates the neuroprotective effect of TSG on APP expression, suggesting that TSG may be beneficial for AD prevention and treatment. Copyright © 2017 Elsevier Inc. All rights reserved.

Amyloid precursor protein and Presenilin1 interact with the adaptor GRB2 and modulate ERK 1,2 signaling.

PubMed

Nizzari, Mario; Venezia, Valentina; Repetto, Emanuela; Caorsi, Valentina; Magrassi, Raffaella; Gagliani, Maria Cristina; Carlo, Pia; Florio, Tullio; Schettini, Gennaro; Tacchetti, Carlo; Russo, Tommaso; Diaspro, Alberto; Russo, Claudio

2007-05-04

The amyloid precursor protein (APP) and the presenilins 1 and 2 are genetically linked to the development of familial Alzheimer disease. APP is a single-pass transmembrane protein and precursor of fibrillar and toxic amyloid-beta peptides, which are considered responsible for Alzheimer disease neurodegeneration. Presenilins are multipass membrane proteins, involved in the enzymatic cleavage of APP and other signaling receptors and transducers. The role of APP and presenilins in Alzheimer disease development seems to be related to the formation of amyloid-beta peptides; however, their physiological function, reciprocal interaction, and molecular mechanisms leading to neurodegeneration are unclear. APP and presenilins are also involved in multiple interactions with intracellular proteins, the significance of which is under investigation. Among the different APP-interacting proteins, we focused our interest on the GRB2 adaptor protein, which connects cell surface receptors to intracellular signaling pathways. In this study we provide evidence by co-immunoprecipitation experiments, confocal and electron microscopy, and by fluorescence resonance energy transfer experiments that both APP and presenilin1 interact with GRB2 in vesicular structures at the centrosome of the cell. The final target for these interactions is ERK1,2, which is activated in mitotic centrosomes in a PS1- and APP-dependent manner. These data suggest that both APP and presenilin1 can be part of a common signaling pathway that regulates ERK1,2 and the cell cycle.

Fetzima (levomilnacipran), a drug for major depressive disorder as a dual inhibitor for human serotonin transporters and beta-site amyloid precursor protein cleaving enzyme-1.

PubMed

Rizvi, Syed Mohd Danish; Shaikh, Sibhghatulla; Khan, Mahiuddin; Biswas, Deboshree; Hameed, Nida; Shakil, Shazi

2014-01-01

Pharmacological management of Major Depressive Disorder includes the use of serotonin reuptake inhibitors which targets serotonin transporters (SERT) to increase the synaptic concentrations of serotonin. Beta-site amyloid precursor protein cleaving enzyme-1 (BACE-1) is responsible for amyloid β plaque formation. Hence it is an interesting target for Alzheimer's disease (AD) therapy. This study describes molecular interactions of a new Food and Drug Administration approved antidepressant drug named 'Fetzima' with BACE-1 and SERT. Fetzima is chemically known as levomilnacipran. The study has explored a possible link between the treatment of Depression and AD. 'Autodock 4.2' was used for docking study. The free energy of binding (ΔG) values for 'levomilnacipran-SERT' interaction and 'levomilnacipran-BACE1' interaction were found to be -7.47 and -8.25 kcal/mol, respectively. Levomilnacipran was found to interact with S438, known to be the most important amino acid residue of serotonin binding site of SERT during 'levomilnacipran-SERT' interaction. In the case of 'levomilnacipran-BACE1' interaction, levomilnacipran interacted with two very crucial aspartic acid residues of BACE-1, namely, D32 and D228. These residues are accountable for the cleavage of amyloid precursor protein and the subsequent formation of amyloid β plaques in AD brain. Hence, Fetzima (levomilnacipran) might act as a potent dual inhibitor of SERT and BACE-1 and expected to form the basis of a future dual therapy against depression and AD. It is an established fact that development of AD is associated with Major Depressive Disorder. Therefore, the design of new BACE-1 inhibitors based on antidepressant drug scaffolds would be particularly beneficial.

The low density lipoprotein receptor-related protein 1B retains beta-amyloid precursor protein at the cell surface and reduces amyloid-beta peptide production.

PubMed

Cam, Judy A; Zerbinatti, Celina V; Knisely, Jane M; Hecimovic, Silva; Li, Yonghe; Bu, Guojun

2004-07-09

The low density lipoprotein (LDL) receptor-related protein 1B (LRP1B) is a newly identified member of the LDL receptor family that shares high homology with the LDL receptor-related protein (LRP). LRP1B was originally described as a putative tumor suppressor in lung cancer cells; however, its expression profile in several regions of adult human brain suggests it may have additional functions in the central nervous system. Since LRP1B has overlapping ligand binding properties with LRP, we investigated whether LRP1B, like LRP, could interact with the beta-amyloid precursor protein (APP) and modulate its processing to amyloid-beta peptides (Abetas). Using an LRP1B minireceptor (mLRP1B4) generated to study the trafficking of LRP1B, we found that mLRP1B4 and APP form an immunoprecipitable complex. Furthermore mLRP1B4 bound and facilitated the degradation of a soluble isoform of APP containing a Kunitz proteinase inhibitor domain but not soluble APP lacking a Kunitz proteinase inhibitor domain. A functional consequence of mLRP1B4 expression was a significant accumulation of APP at the cell surface, which is likely related to the slow endocytosis rate of LRP1B. More importantly, mLRP1B4-expressing cells that accumulated cell surface APP produced less Abeta and secreted more soluble APP. These findings reveal that LRP1B is a novel binding partner of APP that functions to decrease APP processing to Abeta. Consequently LRP1B expression could function to protect against the pathogenesis of Alzheimer's disease.

A single dose of the γ-secretase inhibitor semagacestat alters the cerebrospinal fluid peptidome in humans.

PubMed

Hölttä, Mikko; Dean, Robert A; Siemers, Eric; Mawuenyega, Kwasi G; Sigurdson, Wendy; May, Patrick C; Holtzman, David M; Portelius, Erik; Zetterberg, Henrik; Bateman, Randall J; Blennow, Kaj; Gobom, Johan

2016-03-07

In Alzheimer's disease, beta-amyloid peptides in the brain aggregate into toxic oligomers and plaques, a process which is associated with neuronal degeneration, memory loss, and cognitive decline. One therapeutic strategy is to decrease the production of potentially toxic beta-amyloid species by the use of inhibitors or modulators of the enzymes that produce beta-amyloid from amyloid precursor protein (APP). The failures of several such drug candidates by lack of effect or undesired side-effects underscore the importance to monitor the drug effects in the brain on a molecular level. Here we evaluate if peptidomic analysis in cerebrospinal fluid (CSF) can be used for this purpose. Fifteen human healthy volunteers, divided into three groups, received a single dose of placebo or either 140 mg or 280 mg of the γ-secretase inhibitor semagacestat (LY450139). Endogenous peptides in CSF, sampled prior to administration of the drug and at six subsequent time points, were analyzed by liquid chromatography coupled to mass spectrometry, using isobaric labeling based on the tandem mass tag approach for relative quantification. Out of 302 reproducibly detected peptides, 11 were affected by the treatment. Among these, one was derived from APP and one from amyloid precursor-like protein 1. Nine peptides were derived from proteins that may not be γ-secretase substrates per se, but that are regulated in a γ-secretase-dependent manner. These results indicate that a CSF peptidomic approach may be a valuable tool both to verify target engagement and to identify other pharmacodynamic effects of the drug. Data are available via ProteomeXchange with identifier PXD003075. NCT00765115 , registered 30/09/2008.

L-type calcium channel blockers and substance P induce angiogenesis of cortical vessels associated with beta-amyloid plaques in an Alzheimer mouse model.

PubMed

Daschil, Nina; Kniewallner, Kathrin M; Obermair, Gerald J; Hutter-Paier, Birgit; Windisch, Manfred; Marksteiner, Josef; Humpel, Christian

2015-03-01

It is well established that L-type calcium channels (LTCCs) are expressed in astroglia. However, their functional role is still speculative, especially under pathologic conditions. We recently showed that the α1 subunit-like immunoreactivity of the CaV1.2 channel is strongly expressed in reactive astrocytes around beta-amyloid plaques in 11-month-old Alzheimer transgenic (tg) mice with the amyloid precursor protein London and Swedish mutations. The aim of the present study was to examine the cellular expression of all LTCC subunits around beta-amyloid plaques by in situ hybridization using (35)S-labeled oligonucleotides. Our data show that messenger RNAs (mRNAs) of the LTCC CaV1.2 α1 subunit as well as all auxiliary β and α2δ subunits, except α2δ-4, were expressed in the hippocampus of age-matched wild-type mice. It was unexpected to see, that cells directly located in the plaque core in the cortex expressed mRNAs for CaV1.2 α1, β2, β4, and α2δ-1, whereas no expression was detected in the halo. Furthermore, cells in the plaque core also expressed preprotachykinin-A mRNA, the precursor for substance P. By means of confocal microscopy, we demonstrated that collagen-IV-stained brain vessels in the cortex were associated with the plaque core and were immunoreactive for substance P. In cortical organotypic brain slices of adult Alzheimer mice, we could demonstrate that LTCC blockers increased angiogenesis, which was further potentiated by substance P. In conclusion, our data show that brain vessels associated with beta-amyloid plaques express substance P and an LTCC and may play a role in angiogenesis. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Familial Alzheimer's disease mutations in presenilin 1 do not alter levels of the secreted amyloid-beta protein precursor generated by beta-secretase cleavage.

PubMed

Zhang, Can; Browne, Andrew; Kim, Doo Yeon; Tanzi, Rudolph E

2010-02-01

Alzheimer's disease (AD) is an insidious and progressive disease with a genetically complex and heterogenous etiology. More than 200 fully penetrant mutations in the amyloid beta-protein precursor (APP), presenilin 1 (or PSEN1), and presenilin 2 (PSEN2) have been linked to early-onset familial AD (FAD). 177 PSEN1 FAD mutations have been identified so far and account for more than approximately 80% of all FAD mutations. All PSEN1 FAD mutations can increase the Abeta42:Abeta40 ratio with seemingly different and incompletely understood mechanisms. A recent study has shown that the 286 amino acid N-terminal fragment of APP (N-APP), a proteolytic product of beta-secretase-derived secreted form of APP (sAPPbeta), could bind the death receptor, DR6, and lead to neurodegeneration. Here we asked whether PSEN1 FAD mutations lead to neurodegeneration by modulating sAPPbeta levels. All four different PSEN1 FAD mutations tested (in three mammalian cell lines) did not alter sAPPbeta levels. Therefore PS1 mutations do not appear to contribute to AD pathogenesis via altered production of sAPPbeta.

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

PubMed

Mochizuki, A; Peterson, J W; Mufson, E J; Trapp, B D

1996-11-01

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

Increased T cell recruitment to the CNS after amyloid beta 1-42 immunization in Alzheimer's mice overproducing transforming growth factor-beta 1.

PubMed

Buckwalter, Marion S; Coleman, Bronwen S; Buttini, Manuel; Barbour, Robin; Schenk, Dale; Games, Dora; Seubert, Peter; Wyss-Coray, Tony

2006-11-01

Immunotherapy targeting the amyloid beta (Abeta) peptide is a novel therapy under investigation for the treatment of Alzheimer's disease (AD). A clinical trial using Abeta(1-42) (AN1792) as the immunogen was halted as a result of development of meningoencephalitis in a small number of patients. The cytokine TGF-beta1 is a key modulator of immune responses that is increased in the brain in AD. We show here that local overexpression of TGF-beta1 in the brain increases both meningeal and parenchymal T lymphocyte number. Furthermore, TGF-beta1 overexpression in a mouse model for AD [amyloid precursor protein (APP) mice] leads to development of additional T cell infiltrates when mice were immunized at a young but not old age with AN1792. Notably, only mice overproducing both Abeta (APP mice) and TGF-beta1 experienced a rise in T lymphocyte number after immunization. One-third of infiltrating T cells were CD4 positive. We did not observe significant differences in B lymphocyte numbers in any of the genotypes or treatment groups. These results demonstrate that TGF-beta1 overproduction in the brain can promote T cell infiltration, in particular after Abeta(1-42) immunization. Likewise, levels of TGF-beta1 or other immune factors in brains of AD patients may influence the response to Abeta(1-42) immunization.

Unfolding story of inclusion-body myositis and myopathies: role of misfolded proteins, amyloid-beta, cholesterol, and aging.

PubMed

Askanas, Valerie; Engel, W King

2003-03-01

Sporadic inclusion-body myositis and hereditary inclusion-body myopathies are progressive muscle diseases leading to severe disability. We briefly summarize their clinical pictures and pathologic diagnostic criteria and discuss the latest advances in illuminating their pathogenic mechanism(s). We emphasize how different etiologies might lead to the strikingly similar pathology and possibly similar pathogenic cascade. On the basis of our research, several processes seem to be important in relation to the still speculative pathogenesis, including (a) increased transcription and accumulation of amyloid-beta precursor protein and accumulation of its proteolytic fragment amyloid-beta; (b) abnormal accumulation of components related to lipid metabolism, for example, cholesterol, accumulation of which is possibly owing to its abnormal trafficking; (c) oxidative stress; (d) accumulations of other Alzheimer's disease-related proteins; and (e) a milieu of muscle cellular aging in which these changes occur. We discuss a potentially very important role of unfolded and/or misfolded proteins as a possible mechanism in the formations of the inclusion bodies and other abnormalities.

Genetic cathepsin B deficiency reduces beta-amyloid in transgenic mice expressing human wild-type amyloid precursor protein.

PubMed

Hook, Vivian Y H; Kindy, Mark; Reinheckel, Thomas; Peters, Christoph; Hook, Gregory

2009-08-21

Neurotoxic beta-amyloid (Abeta) peptides participate in Alzheimer's disease (AD); therefore, reduction of Abeta generated from APP may provide a therapeutic approach for AD. Gene knockout studies in transgenic mice producing human Abeta may identify targets for reducing Abeta. This study shows that knockout of the cathepsin B gene in mice expressing human wild-type APP (hAPPwt) results in substantial decreases in brain Abeta40 and Abeta42 by 67% and decreases in levels of the C-terminal beta-secretase fragment (CTFbeta) derived from APP. In contrast, knockout of cathepsin B in mice expressing hAPP with the rare Swedish (Swe) and Indiana (Ind) mutations had no effect on Abeta. The difference in reduction of Abeta in hAPPwt mice, but not in hAPPSwe/Ind mice, shows that the transgenic model can affect cathepsin B gene knockout results. Since most AD patients express hAPPwt, these data validate cathepsin B as a target for development of inhibitors to lower Abeta in AD.

Acute γ-secretase Inhibition of Nonhuman Primate CNS Shifts Amyloid Precursor Protein (APP) Metabolism from Amyloid-β Production to Alternative APP Fragments without Amyloid-β Rebound

PubMed Central

Cook, Jacquelynn J.; Wildsmith, Kristin R.; Gilberto, David B.; Holahan, Marie A.; Kinney, Gene G.; Mathers, Parker D.; Michener, Maria S.; Price, Eric A.; Shearman, Mark S.; Simon, Adam J.; Wang, Jennifer X.; Wu, Guoxin; Yarasheski, Kevin E.; Bateman, Randall J.

2010-01-01

The accumulation of amyloid beta (Aβ) in Alzheimer’s disease is caused by an imbalance of production and clearance, which leads to increased soluble Aβ species and extracellular plaque formation in the brain. Multiple Aβ-lowering therapies are currently in development: an important goal is to characterize the molecular mechanisms of action and effects on physiological processing of Aβ, as well as other amyloid precursor protein (APP) metabolites, in models which approximate human Aβ physiology. To this end, we report the translation of the human in vivo stable-isotope-labeling kinetics (SILK) method to a rhesus monkey cisterna magna ported (CMP) nonhuman primate model, and use the model to test the mechanisms of action of a γ-secretase inhibitor (GSI). A major concern of inhibiting the enzymes which produce Aβ (β- and γ-secretase) is that precursors of Aβ may accumulate and cause a rapid increase in Aβ production when enzyme inhibition discontinues. In this study, the GSI MK-0752 was administered to conscious CMP rhesus monkeys in conjunction with in vivo stable isotope labeling, and dose-dependently reduced newly generated CNS Aβ. In contrast to systemic Aβ metabolism, CNS Aβ production was not increased after the GSI was cleared. These results indicate that most of the CNS APP was metabolized to products other than Aβ, including C-terminal truncated forms of Aβ: 1–14, 1–15 and 1–16; this demonstrates an alternative degradation pathway for CNS amyloid precursor protein during γ-secretase inhibition. PMID:20463236

Dietary (−)-epicatechin as a potent inhibitor of βγ-secretase amyloid precursor protein processing☆

PubMed Central

Cox, Carla J.; Choudhry, Fahd; Peacey, Eleanor; Perkinton, Michael S.; Richardson, Jill C.; Howlett, David R.; Lichtenthaler, Stefan F.; Francis, Paul T.; Williams, Robert J.

2015-01-01

Flavonoids, a group of dietary polyphenols have been shown to possess cognitive health benefits. Epidemiologic evidence suggests that they could play a role in risk reduction in dementia. Amyloid precursor protein processing and the subsequent generation of amyloid beta (Aβ) are central to the pathogenesis of Alzheimer's disease, as soluble, oligomeric Aβ is thought to be the toxic species driving disease progression. We undertook an in vitro screen to identify flavonoids with bioactivity at βγ-mediated amyloid precursor protein processing, which lead to identification of a number of flavonoids bioactive at 100 nM. Because of known bioavailability, we investigated the catechin family further and identified epigallocatechin and (−)-epicatechin as potent (nanomolar) inhibitors of amyloidogenic processing. Supporting this finding, we have shown reduced Aβ pathology and Aβ levels following short term, a 21-day oral delivery of (−)-epicatechin in 7-month-old TASTPM mice. Further, in vitro mechanistic studies suggest this is likely because of indirect BACE1 inhibition. Taken together, our results suggest that orally delivered (−)-epicatechin may be a potential prophylactic for Alzheimer's disease. PMID:25316600

A single amino acid difference between the intracellular domains of amyloid precursor protein and amyloid-like precursor protein 2 enables induction of synaptic depression and block of long-term potentiation.

PubMed

Trillaud-Doppia, Emilie; Paradis-Isler, Nicolas; Boehm, Jannic

2016-07-01

Alzheimer disease (AD) is initially characterized as a disease of the synapse that affects synaptic transmission and synaptic plasticity. While amyloid-beta and tau have been traditionally implicated in causing AD, recent studies suggest that other factors, such as the intracellular domain of the amyloid-precursor protein (APP-ICD), can also play a role in the development of AD. Here, we show that the expression of APP-ICD induces synaptic depression, while the intracellular domain of its homolog amyloid-like precursor protein 2 (APLP2-ICD) does not. We are able to show that this effect by APP-ICD is due to a single alanine vs. proline difference between APP-ICD and APLP2-ICD. The alanine in APP-ICD and the proline in APLP2-ICD lie directly behind a conserved caspase cleavage site. Inhibition of caspase cleavage of APP-ICD prevents the induction of synaptic depression. Finally, we show that the expression of APP-ICD increases and facilitates long-term depression and blocks induction of long-term potentiation. The block in long-term potentiation can be overcome by mutating the aforementioned alanine in APP-ICD to the proline of APLP2. Based on our results, we propose the emergence of a new APP critical domain for the regulation of synaptic plasticity and in consequence for the development of AD. Copyright © 2016 Elsevier Inc. All rights reserved.

Arf6 controls beta-amyloid production by regulating macropinocytosis of the Amyloid Precursor Protein to lysosomes.

PubMed

Tang, Weihao; Tam, Joshua H K; Seah, Claudia; Chiu, Justin; Tyrer, Andrea; Cregan, Sean P; Meakin, Susan O; Pasternak, Stephen H

2015-07-14

Alzheimer's disease (AD) is characterized by the deposition of Beta-Amyloid (Aβ) peptides in the brain. Aβ peptides are generated by cleavage of the Amyloid Precursor Protein (APP) by the β - and γ - secretase enzymes. Although this process is tightly linked to the internalization of cell surface APP, the compartments responsible are not well defined. We have found that APP can be rapidly internalized from the cell surface to lysosomes, bypassing early and late endosomes. Here we show by confocal microscopy and electron microscopy that this pathway is mediated by macropinocytosis. APP internalization is enhanced by antibody binding/crosslinking of APP suggesting that APP may function as a receptor. Furthermore, a dominant negative mutant of Arf6 blocks direct transport of APP to lysosomes, but does not affect classical endocytosis to endosomes. Arf6 expression increases through the hippocampus with the development of Alzheimer's disease, being expressed mostly in the CA1 and CA2 regions in normal individuals but spreading through the CA3 and CA4 regions in individuals with pathologically diagnosed AD. Disruption of lysosomal transport of APP reduces both Aβ40 and Aβ42 production by more than 30 %. Our findings suggest that the lysosome is an important site for Aβ production and that altering APP trafficking represents a viable strategy to reduce Aβ production.

Characterization of the beta amyloid precursor protein-like gene in the central nervous system of the crab Chasmagnathus. Expression during memory consolidation.

PubMed

Fustiñana, Maria Sol; Ariel, Pablo; Federman, Noel; Freudenthal, Ramiro; Romano, Arturo

2010-09-01

Human β-amyloid, the main component in the neuritic plaques found in patients with Alzheimer's disease, is generated by cleavage of the β-amyloid precursor protein. Beyond the role in pathology, members of this protein family are synaptic proteins and have been associated with synaptogenesis, neuronal plasticity and memory, both in vertebrates and in invertebrates. Consolidation is necessary to convert a short-term labile memory to a long-term and stable form. During consolidation, gene expression and de novo protein synthesis are regulated in order to produce key proteins for the maintenance of plastic changes produced during the acquisition of new information. Here we partially cloned and sequenced the beta-amyloid precursor protein like gene homologue in the crab Chasmagnathus (cappl), showing a 37% of identity with the fruit fly Drosophila melanogaster homologue and 23% with Homo sapiens but with much higher degree of sequence similarity in certain regions. We observed a wide distribution of cappl mRNA in the nervous system as well as in muscle and gills. The protein localized in all tissues analyzed with the exception of muscle. Immunofluorescence revealed localization of cAPPL in associative and sensory brain areas. We studied gene and protein expression during long-term memory consolidation using a well characterized memory model: the context-signal associative memory in this crab species. mRNA levels varied at different time points during long-term memory consolidation and correlated with cAPPL protein levels cAPPL mRNA and protein is widely distributed in the central nervous system of the crab and the time course of expression suggests a role of cAPPL during long-term memory formation.

Lovastatin inhibits amyloid precursor protein (APP) beta-cleavage through reduction of APP distribution in Lubrol WX extractable low density lipid rafts.

PubMed

Won, Je-Seong; Im, Yeong-Bin; Khan, Mushfiquddin; Contreras, Miguel; Singh, Avtar K; Singh, Inderjit

2008-05-01

Previous studies have described that statins (inhibitors of cholesterol and isoprenoid biosynthesis) inhibit the output of amyloid-beta (Abeta) in the animal model and thus decrease risk of Alzheimer's disease. However, their action mechanism(s) in Abeta precursor protein (APP) processing and Abeta generation is not fully understood. In this study, we report that lovastatin treatment reduced Abeta output in cultured hippocampal neurons as a result of reduced APP levels and beta-secretase activities in low density Lubrol WX (non-ionic detergent) extractable lipid rafts (LDLR). Rather than altering cholesterol levels in lipid raft fractions and thus disrupting lipid raft structure, lovastatin decreased Abeta generation through down-regulating geranylgeranyl-pyrophosphate dependent endocytosis pathway. The inhibition of APP endocytosis by treatment with lovastatin and reduction of APP levels in LDLR fractions by treatment with phenylarsine oxide (a general endocytosis inhibitor) support the involvement of APP endocytosis in APP distribution in LDLR fractions and subsequent APP beta-cleavage. Moreover, lovastatin-mediated down-regulation of endocytosis regulators, such as early endosomal antigen 1, dynamin-1, and phosphatidylinositol 3-kinase activity, indicates that lovastatin modulates APP endocytosis possibly through its pleiotropic effects on endocytic regulators. Collectively, these data report that lovastatin mediates inhibition of LDLR distribution and beta-cleavage of APP in a geranylgeranyl-pyrophosphate and endocytosis-dependent manner.

Development and characterization of a TAPIR-like mouse monoclonal antibody to amyloid-beta.

PubMed

Wang, Jun; Hara, Hideo; Makifuchi, Takao; Tabira, Takeshi

2008-06-01

Tissue amyloid plaque immuno-reactive (TAPIR) antibody was better related to the effect of immunotherapy in Alzheimer's disease (AD) than ELISA antibody. Here we used a hybridoma technique to develop a TAPIR-like anti-human amyloid-beta (Abeta) mouse monoclonal antibody. The obtained monoclonal antibody, 3.4A10, was an IgG2b isotype and recognized N-terminal portion of Abeta1-42 without binding denatured or native amyloid-beta protein precursor. It had higher affinity to Abeta1-42 than to Abeta1-40 by Biacore affinity analysis and stained preferably the peripheral part of senile plaques and recognized the plaque core less than 4G8. It inhibited the Abeta1-42 fibril formation as well as degraded pre-aggregated Abeta1-42 peptide in a thioflavin T fluorescence spectrophotometry assay. The in vivo studies showed that 3.4A10 treatment decreased amyloid burden compared to the control group and significantly reduced Abeta42 levels rather than Abeta40 levels in brain lysates as well as the Abeta*56 oligomer (12mer) in TBS fraction of the brain lysates. 3.4A10 entered brain and decorated some plaques, which is surrounded by more Iba1-positive microglia. 3.4A10 therapy did not induce lymphocytic infiltration and obvious increase in microhemorrhage. We conclude that 3.4A10 is a TAPIR-like anti-human amyloid monoclonal antibody, and has a potential of therapeutic application for AD.

Rapid endocytosis of the low density lipoprotein receptor-related protein modulates cell surface distribution and processing of the beta-amyloid precursor protein.

PubMed

Cam, Judy A; Zerbinatti, Celina V; Li, Yonghe; Bu, Guojun

2005-04-15

The low density lipoprotein receptor-related protein (LRP) is a approximately 600-kDa multifunctional endocytic receptor that is highly expressed in the brain. LRP and its ligands apolipoprotein E, alpha2-macroglobulin, and beta-amyloid precursor protein (APP), are genetically linked to Alzheimer disease and are found in characteristic plaque deposits in brains of patients with Alzheimer disease. To identify which extracellular domains of LRP interact with APP, we used minireceptors of each of the individual LRP ligand binding domains and assessed their ability to bind and degrade a soluble APP fragment. LRP minireceptors containing ligand binding domains II and IV, but not I or III, interacted with APP. To test whether APP trafficking is directly related to the rapid endocytosis of LRP, we generated stable Chinese hamster ovary cell lines expressing either a wild-type LRP minireceptor or its endocytosis mutants. Chinese hamster ovary cells stably expressing wild-type LRP minireceptor had less cell surface APP than pcDNA3 vector-transfected cells, whereas those stably expressing endocytosis-defective LRP minireceptors accumulated APP at the cell surface. We also found that the steady-state levels of the amyloid beta-peptides (Abeta) is dictated by the relative expression levels of APP and LRP, probably reflecting the dual roles of LRP in both Abeta production and clearance. Together, these data establish a relationship between LRP rapid endocytosis and APP trafficking and proteolytic processing to generate Abeta.

Olfactory dysfunction correlates with amyloid-beta burden in an Alzheimer's disease mouse model.

PubMed

Wesson, Daniel W; Levy, Efrat; Nixon, Ralph A; Wilson, Donald A

2010-01-13

Alzheimer's disease often results in impaired olfactory perceptual acuity-a potential biomarker of the disorder. However, the usefulness of olfactory screens to serve as informative indicators of Alzheimer's is precluded by a lack of knowledge regarding why the disease impacts olfaction. We addressed this question by assaying olfactory perception and amyloid-beta (Abeta) deposition throughout the olfactory system in mice that overexpress a mutated form of the human amyloid-beta precursor protein. Such mice displayed progressive olfactory deficits that mimic those observed clinically-some evident at 3 months of age. Also, at 3 months of age, we observed nonfibrillar Abeta deposition within the olfactory bulb-earlier than deposition within any other brain region. There was also a correlation between olfactory deficits and the spatial-temporal pattern of Abeta deposition. Therefore, nonfibrillar, versus fibrillar, Abeta-related mechanisms likely contribute to early olfactory perceptual loss in Alzheimer's disease. Furthermore, these results present the odor cross-habituation test as a powerful behavioral assay, which reflects Abeta deposition and thus may serve to monitor the efficacy of therapies aimed at reducing Abeta.

Short-term effects of beta-amyloid25-35 peptide aggregates on transmitter release in neuromuscular synapses.

PubMed

Garcia, Neus; Santafé, Manel M; Tomàs, Marta; Lanuza, Maria A; Tomàs, Josep

2008-03-01

The beta-amyloid (AB) peptide25-35 contains the functional domain of the AB precursor protein that is both required for neurotrophic effects in normal neural tissues and is involved in the neurotoxic effects in Alzheimer disease. We demonstrated the presence of the amyloid precursor protein/AB peptide in intramuscular axons, presynaptic motor nerve terminals, terminal and myelinating Schwann cells, and the postsynaptic and subsarcolemmal region in the Levator auris longus muscle of adult rats by immunocytochemistry. Using intracellular recording, we investigated possible short-term functional effects of the AB fragment (0.1-10 micromol/L) on acetylcholine release in adult and newborn motor end plates. We found no change in evoked, spontaneous transmitter release or resting membrane potential of the muscle cells. A previous block of the presynaptic muscarinic receptor subtypes and a previous block or stimulation of protein kinase C revealed no masked effect of the peptide on the regulation of transmitter release. The aggregated form of AB peptide25-35, however, interfered acutely with acetylcholine release (quantal content reduction) when synaptic activity was maintained by electric stimulation. The possible relevance of this inhibition of neurotransmission by AB peptide25-35 to the pathogenesis of Alzheimer remains to be determined.

Amyloid precursor protein-induced axonopathies are independent of amyloid-beta peptides.

PubMed

Stokin, Gorazd B; Almenar-Queralt, Angels; Gunawardena, Shermali; Rodrigues, Elizabeth M; Falzone, Tomás; Kim, Jungsu; Lillo, Concepción; Mount, Stephanie L; Roberts, Elizabeth A; McGowan, Eileen; Williams, David S; Goldstein, Lawrence S B

2008-11-15

Overexpression of amyloid precursor protein (APP), as well as mutations in the APP and presenilin genes, causes rare forms of Alzheimer's disease (AD). These genetic changes have been proposed to cause AD by elevating levels of amyloid-beta peptides (Abeta), which are thought to be neurotoxic. Since overexpression of APP also causes defects in axonal transport, we tested whether defects in axonal transport were the result of Abeta poisoning of the axonal transport machinery. Because directly varying APP levels also alters APP domains in addition to Abeta, we perturbed Abeta generation selectively by combining APP transgenes in Drosophila and mice with presenilin-1 (PS1) transgenes harboring mutations that cause familial AD (FAD). We found that combining FAD mutant PS1 with FAD mutant APP increased Abeta42/Abeta40 ratios and enhanced amyloid deposition as previously reported. Surprisingly, however, this combination suppressed rather than increased APP-induced axonal transport defects in both Drosophila and mice. In addition, neuronal apoptosis induced by expression of FAD mutant human APP in Drosophila was suppressed by co-expressing FAD mutant PS1. We also observed that directly elevating Abeta with fusions to the Familial British and Danish Dementia-related BRI protein did not enhance axonal transport phenotypes in APP transgenic mice. Finally, we observed that perturbing Abeta ratios in the mouse by combining FAD mutant PS1 with FAD mutant APP did not enhance APP-induced behavioral defects. A potential mechanism to explain these findings was suggested by direct analysis of axonal transport in the mouse, which revealed that axonal transport or entry of APP into axons is reduced by FAD mutant PS1. Thus, we suggest that APP-induced axonal defects are not caused by Abeta.

Trans fatty acids enhance amyloidogenic processing of the Alzheimer amyloid precursor protein (APP).

PubMed

Grimm, Marcus O W; Rothhaar, Tatjana L; Grösgen, Sven; Burg, Verena K; Hundsdörfer, Benjamin; Haupenthal, Viola J; Friess, Petra; Kins, Stefan; Grimm, Heike S; Hartmann, Tobias

2012-10-01

Hydrogenation of oils and diary products of ruminant animals leads to an increasing amount of trans fatty acids in the human diet. Trans fatty acids are incorporated in several lipids and accumulate in the membrane of cells. Here we systematically investigate whether the regulated intramembrane proteolysis of the amyloid precursor protein (APP) is affected by trans fatty acids compared to the cis conformation. Our experiments clearly show that trans fatty acids compared to cis fatty acids increase amyloidogenic and decrease nonamyloidogenic processing of APP, resulting in an increased production of amyloid beta (Aβ) peptides, main components of senile plaques, which are a characteristic neuropathological hallmark for Alzheimer's disease (AD). Moreover, our results show that oligomerization and aggregation of Aβ are increased by trans fatty acids. The mechanisms identified by this in vitro study suggest that the intake of trans fatty acids potentially increases the AD risk or causes an earlier onset of the disease. Copyright © 2012 Elsevier Inc. All rights reserved.

Natural Modulators of Amyloid-Beta Precursor Protein Processing

PubMed Central

Zhang, Can; Tanzi, Rudolph E.

2013-01-01

Alzheimer’s disease (AD) is a devastating neurodegenerative disease and the primary cause of dementia, with no cure currently available. The pathogenesis of AD is believed to be primarily driven by Aβ, the principal component of senile plaques. Aβ is an ~4 kDa peptide generated from the amyloid-β precursor protein (APP) through proteolytic secretases. Natural products, particularly those utilized in traditional Chinese medicine (TCM), have a long history alleviating common clinical disorders, including dementia. However, the cell/molecular pathways mediated by these natural products are largely unknown until recently when the underlying molecular mechanisms of the disorders begin to be elucidated. Here, the mechanisms with which natural products modulate the pathogenesis of AD are discussed, in particular, by focusing on their roles in the processing of APP. PMID:22998566

Senile plaques in an aged western lowland gorilla.

PubMed

Kimura, N; Nakamura, S; Goto, N; Narushima, E; Hara, I; Shichiri, S; Saitou, K; Nose, M; Hayashi, T; Kawamura, S; Yoshikawa, Y

2001-01-01

Senile plaques (SPs) were found in the cerebral cortex of a 44-year-old Western lowland gorilla (Gorilla gorilla gorilla). All the SPs were obtained as dense assemblies consisting of fibrous materials by silver impregnation, but were not detected by Congo red. More SPs were detected by immunostaining for amyloid beta protein (A beta) and a half of A beta-positive-SPs were also immunoreactive for apolipoprotein E. Moreover, all SPs were immunoreactive for A beta 42 and A beta 43, but not for A beta 40. SPs also did not contain A beta precursor protein-positive structures. These findings suggested that SPs in this case were diffuse plaques. To our knowledge, this is the first report of SPs in the gorilla.

Regulation of gamma-Secretase in Alzheimer's Disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Shuxia; Zhou, Hua; Walian, Peter

2007-02-07

The {gamma}-secretase complex is an intramembrane aspartyl protease that cleaves its substrates along their transmembrane regions. Sequential proteolytic processing of amyloid precursor protein by {beta}- and {gamma}-secretase produces amyloid {beta}-peptides, which are the major components of amyloid plaques in the brains of Alzheimer's disease patients. The {gamma}-secretase complex is therefore believed to be critical in the pathogenesis of Alzheimer's disease. Here we review the range of factors found to affect the nature and degree of {gamma}-secretase complex activity; these include {gamma}-secretase complex assembly and activation, the integral regulatory subunit CD147, transient or weak binding partners, the levels of cholesterol andmore » sphingolipids in cell membranes, and inflammatory cytokines. Integrated knowledge of the molecular mechanisms supporting the actions of these factors is expected to lead to a comprehensive understanding of the functional regulation of the {gamma}-secretase complex, and this, in turn, should facilitate the development of novel therapeutic strategies for the treatment of Alzheimer's disease.« less

Generation of amyloid-β is reduced by the interaction of calreticulin with amyloid precursor protein, presenilin and nicastrin.

PubMed

Stemmer, Nina; Strekalova, Elena; Djogo, Nevena; Plöger, Frank; Loers, Gabriele; Lutz, David; Buck, Friedrich; Michalak, Marek; Schachner, Melitta; Kleene, Ralf

2013-01-01

Dysregulation of the proteolytic processing of amyloid precursor protein by γ-secretase and the ensuing generation of amyloid-β is associated with the pathogenesis of Alzheimer's disease. Thus, the identification of amyloid precursor protein binding proteins involved in regulating processing of amyloid precursor protein by the γ-secretase complex is essential for understanding the mechanisms underlying the molecular pathology of the disease. We identified calreticulin as novel amyloid precursor protein interaction partner that binds to the γ-secretase cleavage site within amyloid precursor protein and showed that this Ca(2+)- and N-glycan-independent interaction is mediated by amino acids 330-344 in the C-terminal C-domain of calreticulin. Co-immunoprecipitation confirmed that calreticulin is not only associated with amyloid precursor protein but also with the γ-secretase complex members presenilin and nicastrin. Calreticulin was detected at the cell surface by surface biotinylation of cells overexpressing amyloid precursor protein and was co-localized by immunostaining with amyloid precursor protein and presenilin at the cell surface of hippocampal neurons. The P-domain of calreticulin located between the N-terminal N-domain and the C-domain interacts with presenilin, the catalytic subunit of the γ-secretase complex. The P- and C-domains also interact with nicastrin, another functionally important subunit of this complex. Transfection of amyloid precursor protein overexpressing cells with full-length calreticulin leads to a decrease in amyloid-β42 levels in culture supernatants, while transfection with the P-domain increases amyloid-β40 levels. Similarly, application of the recombinant P- or C-domains and of a synthetic calreticulin peptide comprising amino acid 330-344 to amyloid precursor protein overexpressing cells result in elevated amyloid-β40 and amyloid-β42 levels, respectively. These findings indicate that the interaction of calreticulin with amyloid precursor protein and the γ-secretase complex regulates the proteolytic processing of amyloid precursor protein by the γ-secretase complex, pointing to calreticulin as a potential target for therapy in Alzheimer's disease.

Cerebrospinal fluid and neuroimaging biomarker abnormalities suggest early neurological injury in a subset of individuals during primary HIV infection.

PubMed

Peluso, Michael J; Meyerhoff, Dieter J; Price, Richard W; Peterson, Julia; Lee, Evelyn; Young, Andrew C; Walter, Rudy; Fuchs, Dietmar; Brew, Bruce J; Cinque, Paola; Robertson, Kevin; Hagberg, Lars; Zetterberg, Henrik; Gisslén, Magnus; Spudich, Serena

2013-06-01

Cerebrospinal fluid (CSF) and neuroimaging abnormalities demonstrate neuronal injury during chronic AIDS, but data on these biomarkers during primary human immunodeficiency virus (HIV) infection is limited. We compared CSF concentrations of neurofilament light chain, t-tau, p-tau, amyloid precursor proteins, and amyloid-beta 42 in 92 subjects with primary HIV infection and 25 controls. We examined relationships with disease progression and neuroinflammation, neuropsychological testing, and proton-magnetic resonance spectroscopy (MRS)-based metabolites. Neurofilament light chain was elevated in primary HIV infection compared with controls (P = .0004) and correlated with CSF neopterin (r = 0.38; P = .0005), interferon gamma-induced protein 10 (r = 0.39; P = .002), white blood cells (r = 0.32; P = .004), protein (r = 0.59; P < .0001), and CSF/plasma albumin ratio (r = 0.60; P < .0001). Neurofilament light chain correlated with decreased N-acteylaspartate/creatine and glutamate/creatine in the anterior cingulate (r = -0.35, P = .02; r = -0.40, P = .009, respectively), frontal white matter (r = -0.43, P = .003; r = -0.30, P = .048, respectively), and parietal gray matter (r = -0.43, P = .003; r = -0.47, P = .001, respectively). Beta-amyloid was elevated in the primary infection group (P = .0005) and correlated with time infected (r = 0.34; P = .003). Neither marker correlated with neuropsychological abnormalities. T-tau and soluble amyloid precursor proteins did not differ between groups. Elevated neurofilament light chain and its correlation with MRS-based metabolites suggest early neuronal injury in a subset of participants with primary HIV infection through mechanisms involving central nervous system inflammation.

The Role of Oxidative Stress-Induced Epigenetic Alterations in Amyloid-β Production in Alzheimer's Disease

PubMed Central

Best, Thomas M.

2015-01-01

An increasing number of studies have proposed a strong correlation between reactive oxygen species (ROS)-induced oxidative stress (OS) and the pathogenesis of Alzheimer's disease (AD). With over five million people diagnosed in the United States alone, AD is the most common type of dementia worldwide. AD includes progressive neurodegeneration, followed by memory loss and reduced cognitive ability. Characterized by the formation of amyloid-beta (Aβ) plaques as a hallmark, the connection between ROS and AD is compelling. Analyzing the ROS response of essential proteins in the amyloidogenic pathway, such as amyloid-beta precursor protein (APP) and beta-secretase (BACE1), along with influential signaling programs of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and c-Jun N-terminal kinase (JNK), has helped visualize the path between OS and Aβ overproduction. In this review, attention will be paid to significant advances in the area of OS, epigenetics, and their influence on Aβ plaque assembly. Additionally, we aim to discuss available treatment options for AD that include antioxidant supplements, Asian traditional medicines, metal-protein-attenuating compounds, and histone modifying inhibitors. PMID:26543520

The Role of Oxidative Stress-Induced Epigenetic Alterations in Amyloid-β Production in Alzheimer's Disease.

PubMed

Zuo, Li; Hemmelgarn, Benjamin T; Chuang, Chia-Chen; Best, Thomas M

2015-01-01

An increasing number of studies have proposed a strong correlation between reactive oxygen species (ROS)-induced oxidative stress (OS) and the pathogenesis of Alzheimer's disease (AD). With over five million people diagnosed in the United States alone, AD is the most common type of dementia worldwide. AD includes progressive neurodegeneration, followed by memory loss and reduced cognitive ability. Characterized by the formation of amyloid-beta (Aβ) plaques as a hallmark, the connection between ROS and AD is compelling. Analyzing the ROS response of essential proteins in the amyloidogenic pathway, such as amyloid-beta precursor protein (APP) and beta-secretase (BACE1), along with influential signaling programs of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and c-Jun N-terminal kinase (JNK), has helped visualize the path between OS and Aβ overproduction. In this review, attention will be paid to significant advances in the area of OS, epigenetics, and their influence on Aβ plaque assembly. Additionally, we aim to discuss available treatment options for AD that include antioxidant supplements, Asian traditional medicines, metal-protein-attenuating compounds, and histone modifying inhibitors.

Enzymatic characteristics of I213T mutant presenilin-1/gamma-secretase in cell models and knock-in mouse brains: familial Alzheimer disease-linked mutation impairs gamma-site cleavage of amyloid precursor protein C-terminal fragment beta.

PubMed

Shimojo, Masafumi; Sahara, Naruhiko; Mizoroki, Tatsuya; Funamoto, Satoru; Morishima-Kawashima, Maho; Kudo, Takashi; Takeda, Masatoshi; Ihara, Yasuo; Ichinose, Hiroshi; Takashima, Akihiko

2008-06-13

Presenilin (PS)/gamma-secretase-mediated intramembranous proteolysis of amyloid precursor protein produces amyloid beta (Abeta) peptides in which Abeta species of different lengths are generated through multiple cleavages at the gamma-, zeta-, and epsilon-sites. An increased Abeta42/Abeta40 ratio is a common characteristic of most cases of familial Alzheimer disease (FAD)-linked PS mutations. However, the molecular mechanisms underlying amyloid precursor protein proteolysis leading to increased Abeta42/Abeta40 ratios still remain unclear. Here, we report our findings on the enzymatic analysis of gamma-secretase derived from I213T mutant PS1-expressing PS1/PS2-deficient (PS(-/-)) cells and from the brains of I213T mutant PS1 knock-in mice. Kinetics analyses revealed that the FAD mutation reduced de novo Abeta generation, suggesting that mutation impairs the total catalytic rate of gamma-secretase. Analysis of each Abeta species revealed that the FAD mutation specifically reduced Abeta40 levels more drastically than Abeta42 levels, leading to an increased Abeta42/Abeta40 ratio. By contrast, the FAD mutation increased the generation of longer Abeta species such as Abeta43, Abeta45, and >Abeta46. These results were confirmed by analyses of gamma-secretase derived from I213T knock-in mouse brains, in which the reduction of de novo Abeta generation was mutant allele dose-dependent. Our findings clearly indicate that the mechanism underlying the increased Abeta42/Abeta40 ratio observed in cases of FAD mutations is related to the differential inhibition of gamma-site cleavage reactions, in which the reaction producing Abeta40 is subject to more inhibition than that producing Abeta42. Our results also provide novel insight into how enhancing the generation of longer Abetas may contribute to Alzheimer disease onset.

Fluorescence Microspectroscopy for Testing the Dimerization Hypothesis of BACE1 Protein in Cultured HEK293 Cells

NASA Astrophysics Data System (ADS)

Gardeen, Spencer; Johnson, Joseph L.; Heikal, Ahmed A.

2016-06-01

Alzheimer's Disease (AD) is a neurodegenerative disorder that results from the formation of beta-amyloid plaques in the brain that trigger the known symptoms of memory loss in AD patients. The beta-amyloid plaques are formed by the proteolytic cleavage of the amyloid precursor protein (APP) by the proteases BACE1 and gamma-secretase. These enzyme-facilitated cleavages lead to the production of beta-amyloid fragments that aggregate to form plaques, which ultimately lead to neuronal cell death. Recent detergent protein extraction studies suggest that BACE1 protein forms a dimer that has significantly higher catalytic activity than its monomeric counterpart. In this contribution, we examine the dimerization hypothesis of BACE1 in cultured HEK293 cells using complementary fluorescence spectroscopy and microscopy methods. Cells were transfected with a BACE1-EGFP fusion protein construct and imaged using confocal, and differential interference contrast to monitor the localization and distribution of intracellular BACE1. Complementary fluorescence lifetime and anisotropy measurements enabled us to examine the conformational and environmental changes of BACE1 as a function of substrate binding. Using fluorescence correlation spectroscopy, we also quantified the diffusion coefficient of BACE1-EGFP on the plasma membrane as a means to test the dimerization hypothesis as a fucntion of substrate-analog inhibitition. Our results represent an important first towards examining the substrate-mediated dimerization hypothesis of BACE1 in live cells.

Amyloid beta (Aβ) peptide modulators and other current treatment strategies for Alzheimer’s disease (AD)

PubMed Central

Lukiw, Walter J.

2012-01-01

Introduction Alzheimer’s disease (AD) is a common, progressive neurological disorder whose incidence is reaching epidemic proportions. The prevailing ‘amyloid cascade hypothesis’, which maintains that the aberrant proteolysis of beta-amyloid precursor protein (βAPP) into neurotoxic amyloid beta (Aβ)-peptides is central to the etiopathology of AD, continues to dominate pharmacological approaches to the clinical management of this insidious disorder. This review is a compilation and update on current pharmacological strategies designed to down-regulate Aβ42-peptide generation in an effort to ameliorate the tragedy of AD. Areas Covered This review utilized on-line data searches at various open online-access websites including the Alzheimer Association, Alzheimer Research Forum; individual drug company databases; the National Institutes of Health (NIH) Medline; Pharmaprojects database; Scopus; inter-University research communications and unpublished research data. Expert Opinion Aβ immunization-, anti-acetylcholinesterase-, β-secretase-, chelation-, γ-secretase-, N-methyl D-aspartate (NMDA) receptor antagonist-, statin-based and other strategies to modulate βAPP processing have dominated pharmacological approaches directed against AD-type neurodegenerative pathology. Cumulative clinical results of these efforts remain extremely disappointing, and have had little overall impact on the clinical management of AD. While a number of novel approaches are in consideration and development, to date there is still no effective treatment or cure for this expanding healthcare concern. PMID:22439907

Intracellular trafficking of the β-secretase and processing of amyloid precursor protein.

PubMed

Zhi, Pei; Chia, Pei Zhi Cheryl; Chia, Cheryl; Gleeson, Paul A

2011-09-01

The main component of the amyloid plaques found in the brains of those with Alzheimer's disease (AD) is a polymerized form of the β-amyloid peptide (Aβ) and is considered to play a central role in the pathogenesis of this neurodegenerative disorder. Aβ is derived from the proteolytic processing of the amyloid precursor protein (APP). Beta site APP-cleaving enzyme, BACE1 (also known as β-secretase) is a membrane-bound aspartyl protease responsible for the initial step in the generation of Aβ peptide and is thus a prime target for therapeutic intervention. Substantive evidence now indicates that the processing of APP by BACE1 is regulated by the intracellular sorting of the enzyme and, moreover, perturbations in these intracellular trafficking pathways have been linked to late-onset AD. In this review, we highlight the recent advances in the understanding of the regulation of the intracellular sorting of BACE1 and APP and illustrate why the trafficking of these cargos represent a key issue for understanding the membrane-mediated events associated with the generation of the neurotoxic Aβ products in AD. Copyright © 2011 International Union of Biochemistry and Molecular Biology, Inc.

EFRH-phage immunization of Alzheimer's disease animal model improves behavioral performance in Morris water maze trials.

PubMed

Lavie, Vered; Becker, Maria; Cohen-Kupiec, Rachel; Yacoby, Iftach; Koppel, Rela; Wedenig, Manuela; Hutter-Paier, Birgit; Solomon, Beka

2004-01-01

We have developed an immunization procedure for the production of effective anti-beta-amyloid (anti-Abeta) antibodies, using filamentous phage displaying only 4 amino acids. The EFRH sequence, encompassing amino acids 3-6 of the 42 residues of Abeta peptide, was found previously to be the main regulatory site for amyloid modulation and the epitope of anti-aggregating antibodies. Engineered filamentous phage enable the display of various numbers of EFRH copies on the phage and serve as potent carriers of antigens. In the present study we have found that phage displaying high EFRH copy number are effective in eliciting humoral response against the EFRH sequence, which in turn relieves the amyloid burden in the brains of amyloid precursor protein Tg mice and improves their ability to perform cognitive tasks. Copyright 2004 Humana Press Inc.

Proposal for novel curcumin derivatives as potent inhibitors against Alzheimer's disease: Ab initio molecular simulations on the specific interactions between amyloid-beta peptide and curcumin

NASA Astrophysics Data System (ADS)

Ota, Shintaro; Fujimori, Mitsuki; Ishimura, Hiromi; Shulga, Sergiy; Kurita, Noriyuki

2017-10-01

Accumulation of amyloid-β (Aβ) peptides in a brain is closely related with the pathogenesis of Alzheimer's disease. To suppress the production of Aβ peptides, we propose novel curcumin derivatives and investigate their binding properties with the amyloid precursor protein (APP), using protein-ligand docking as well as ab initio molecular simulations. Our proposed derivative (curcumin XIV) is found to have a large binding energy with APP and interacts strongly with the cleavage site Ala19 by secretase. It is thus expected that curcumin XIV can protect APP from the secretase attack and be a potent inhibitor against the production of Aβ peptides.

Curcumin-derived pyrazoles and isoxazoles: Swiss army knives or blunt tools for Alzheimer's disease?

PubMed

Narlawar, Rajeshwar; Pickhardt, Marcus; Leuchtenberger, Stefanie; Baumann, Karlheinz; Krause, Sabine; Dyrks, Thomas; Weggen, Sascha; Mandelkow, Eckhard; Schmidt, Boris

2008-01-01

Curcumin binds to the amyloid beta peptide (Abeta) and inhibits or modulates amyloid precursor protein (APP) metabolism. Therefore, curcumin-derived isoxazoles and pyrazoles were synthesized to minimize the metal chelation properties of curcumin. The decreased rotational freedom and absence of stereoisomers was predicted to enhance affinity toward Abeta(42) aggregates. Accordingly, replacement of the 1,3-dicarbonyl moiety with isosteric heterocycles turned curcumin analogue isoxazoles and pyrazoles into potent ligands of fibrillar Abeta(42) aggregates. Additionally, several compounds are potent inhibitors of tau protein aggregation and depolymerized tau protein aggregates at low micromolar concentrations.

Molecular modelling indicates that the pathological conformations of prion proteins might be beta-helical.

PubMed Central

Downing, D T; Lazo, N D

1999-01-01

Creutzfeldt-Jakob disease, kuru, scrapie and bovine spongiform encephalopathy are diseases of the mammalian central nervous system that involve the conversion of a cellular protein into an insoluble extracellular isoform. Spectroscopic studies have shown that the precursor protein contains mainly alpha-helical and random-coil conformations, whereas the prion isoform is largely in the beta conformation. The pathogenic prion is resistant to denaturation and protease digestion and can promote the conversion of the precursor protein to the pathogenic form. These properties have yet to be explained in terms of the structural conformations of the proteins. In the present study, molecular modelling showed that prion proteins could adopt the beta-helical conformation, which has been established for a number of fibrous proteins and has been suggested previously as the basis of amyloid fibrils. The beta-helical conformation provides explanations for the biophysical and biochemical stability of prions, their ability to form templates for the transmission of pathological conformation, and the existence of phenotypical strains of the prion diseases. PMID:10510313

SIRT3 activator Honokiol attenuates β-Amyloid by modulating amyloidogenic pathway

PubMed Central

Lynd, Tyler; Briggs, Gwyneth; Adamek, Danielle; Jones, Ellery; Heiner, Jake; Majrashi, Mohammed; Moore, Timothy; Amin, Rajesh; Suppiramaniam, Vishnu

2018-01-01

Honokiol (poly-phenolic lignan from Magnolia grandiflora) is a Sirtuin-3 (SIRT3) activator which exhibit antioxidant activity and augment mitochondrial functions in several experimental models. Modern evidence suggests the critical role of SIRT3 in the progression of several metabolic and neurodegenerative diseases. Amyloid beta (Aβ), the precursor to extracellular senile plaques, accumulates in the brains of patients with Alzheimer’s disease (AD) and is related to the development of cognitive impairment and neuronal cell death. Aβ is generated from amyloid-β precursor protein (APP) through sequential cleavages, first by β-secretase and then by γ-secretase. Drugs modulating this pathway are believed to be one of the most promising strategies for AD treatment. In the present study, we found that Honokiol significantly enhanced SIRT3 expression, reduced reactive oxygen species generation and lipid peroxidation, enhanced antioxidant activities, and mitochondrial function thereby reducing Aβ and sAPPβ levels in Chinese Hamster Ovarian (CHO) cells (carrying the amyloid precursor protein-APP and Presenilin PS1 mutation). Mechanistic studies revealed that Honokiol affects neither protein levels of APP nor α-secretase activity. In contrast, Honokiol increased the expression of AMPK, CREB, and PGC-1α, thereby inhibiting β-secretase activity leading to reduced Aβ levels. These results suggest that Honokiol is an activator of SIRT3 capable of improving antioxidant activity, mitochondrial energy regulation, while decreasing Aβ, thereby indicating it to be a lead compound for AD drug development. PMID:29324783

Vitamin D receptor is present on the neuronal plasma membrane and is co-localized with amyloid precursor protein, ADAM10 or Nicastrin.

PubMed

Dursun, Erdinç; Gezen-Ak, Duygu

2017-01-01

Our recent study indicated that vitamin D and its receptors are important parts of the amyloid processing pathway in neurons. Yet the role of vitamin D receptor (VDR) in amyloid pathogenesis is complex and all regulations over the production of amyloid beta cannot be explained solely with the transcriptional regulatory properties of VDR. Given that we hypothesized that VDR might exist on the neuronal plasma membrane in close proximity with amyloid precursor protein (APP) and secretase complexes. The present study primarily focused on the localization of VDR in neurons and its interaction with amyloid pathology-related proteins. The localization of VDR on neuronal membranes and its co-localization with target proteins were investigated with cell surface staining followed by immunofluorescence labelling. The FpClass was used for protein-protein interaction prediction. Our results demonstrated the localization of VDR on the neuronal plasma membrane and the co-localization of VDR and APP or ADAM10 or Nicastrin and limited co-localization of VDR and PS1. E-cadherin interaction with APP or the γ-secretase complex may involve NOTCH1, NUMB, or FHL2, according to FpClass. This suggested complex might also include VDR, which greatly contributes to Ca+2 hemostasis with its ligand vitamin D. Consequently, we suggested that VDR might be a member of this complex also with its own non-genomic action and that it can regulate the APP processing pathway in this way in neurons.

Hypoperfusion induces overexpression of beta-amyloid precursor protein mRNA in a focal ischemic rodent model.

PubMed

Shi, J; Yang, S H; Stubley, L; Day, A L; Simpkins, J W

2000-01-17

Silent stroke is one of the risk factors of dementia. In the present study, we used a novel focal ischemic animal model to investigate the effects of comparatively small changes of cerebral blood flow (CBF) on the expression of beta-amyloid precursor protein (APP) mRNA. Focal ischemia was achieved by introducing a 4-0 monofilament to the bifurcation of anterior and middle cerebral arteries. Brain samples were harvested from ischemic core and penumbra of cortices at 1, 4 and 7 days following ischemia. The expression of APP mRNA was assessed by RT-PCR. The CBF was decreased to 50% for 1 day after stroke and recovered to 90% at the fourth day after stroke. The changes of CBF were accompanied by an increase in the expression of APP mRNA. APP mRNA increased to 208% and 152% in the penumbra and core ischemic regions, respectively, on the fourth day after MCAO and remained high through the seventh day of ischemia. This study suggests brain hypoperfusion enhances APP mRNA expression and may contribute to the progression of cognitive impairment after silent stroke.

Cerebrospinal Fluid and Neuroimaging Biomarker Abnormalities Suggest Early Neurological Injury in a Subset of Individuals During Primary HIV Infection

PubMed Central

Peluso, Michael J.; Meyerhoff, Dieter J.; Price, Richard W.; Peterson, Julia; Lee, Evelyn; Young, Andrew C.; Walter, Rudy; Fuchs, Dietmar; Brew, Bruce J.; Cinque, Paola; Robertson, Kevin; Hagberg, Lars; Zetterberg, Henrik; Gisslén, Magnus; Spudich, Serena

2013-01-01

Background. Cerebrospinal fluid (CSF) and neuroimaging abnormalities demonstrate neuronal injury during chronic AIDS, but data on these biomarkers during primary human immunodeficiency virus (HIV) infection is limited. Methods. We compared CSF concentrations of neurofilament light chain, t-tau, p-tau, amyloid precursor proteins, and amyloid-beta 42 in 92 subjects with primary HIV infection and 25 controls. We examined relationships with disease progression and neuroinflammation, neuropsychological testing, and proton-magnetic resonance spectroscopy (MRS)–based metabolites. Results. Neurofilament light chain was elevated in primary HIV infection compared with controls (P = .0004) and correlated with CSF neopterin (r = 0.38; P = .0005), interferon gamma-induced protein 10 (r = 0.39; P = .002), white blood cells (r = 0.32; P = .004), protein (r = 0.59; P < .0001), and CSF/plasma albumin ratio (r = 0.60; P < .0001). Neurofilament light chain correlated with decreased N-acteylaspartate/creatine and glutamate/creatine in the anterior cingulate (r = −0.35, P = .02; r = −0.40, P = .009, respectively), frontal white matter (r = −0.43, P = .003; r = −0.30, P = .048, respectively), and parietal gray matter (r = −0.43, P = .003; r = −0.47, P = .001, respectively). Beta-amyloid was elevated in the primary infection group (P = .0005) and correlated with time infected (r = 0.34; P = .003). Neither marker correlated with neuropsychological abnormalities. T-tau and soluble amyloid precursor proteins did not differ between groups. Conclusions. Elevated neurofilament light chain and its correlation with MRS-based metabolites suggest early neuronal injury in a subset of participants with primary HIV infection through mechanisms involving central nervous system inflammation. PMID:23460748

Chronic antioxidant therapy reduces oxidative stress in a mouse model of Alzheimer's disease.

PubMed

Siedlak, Sandra L; Casadesus, Gemma; Webber, Kate M; Pappolla, Miguel A; Atwood, Craig S; Smith, Mark A; Perry, George

2009-02-01

Oxidative modifications are a hallmark of oxidative imbalance in the brains of individuals with Alzheimer's, Parkinson's and prion diseases and their respective animal models. While the causes of oxidative stress are relatively well-documented, the effects of chronically reducing oxidative stress on cognition, pathology and biochemistry require further clarification. To address this, young and aged control and amyloid-beta protein precursor-over-expressing mice were fed a diet with added R-alpha lipoic acid for 10 months to determine the effect of chronic antioxidant administration on the cognition and neuropathology and biochemistry of the brain. Both wild type and transgenic mice treated with R-alpha lipoic acid displayed significant reductions in markers of oxidative modifications. On the other hand, R-alpha lipoic acid had little effect on Y-maze performance throughout the study and did not decrease end-point amyloid-beta load. These results suggest that, despite the clear role of oxidative stress in mediating amyloid pathology and cognitive decline in ageing and AbetaPP-transgenic mice, long-term antioxidant therapy, at levels within tolerable nutritional guidelines and which reduce oxidative modifications, have limited benefit.

In Situ FTIR Microspectroscopy of Brain Tissue from a Transgenic Mouse Model of Alzheimer Disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rak,M.; Del Bigio, M.; Mai, S.

2007-01-01

Plaques composed of the A{beta} peptide are the main pathological feature of Alzheimer's disease. Dense-core plaques are fibrillar deposits of A{beta}, showing all the classical properties of amyloid including {beta}-sheet secondary structure, while diffuse plaques are amorphous deposits. We studied both plaque types, using synchrotron infrared (IR) microspectroscopy, a technique that allows the chemical composition and average protein secondary structure to be investigated in situ. We examined plaques in hippocampal, cortical and caudal tissue from 5- to 21-month-old TgCRND8 mice, a transgenic model expressing doubly mutant amyloid precursor protein, and displaying impaired hippocampal function and robust pathology from an earlymore » age. Spectral analysis confirmed that the congophilic plaque cores were composed of protein in a {beta}-sheet conformation. The amide I maximum of plaque cores was at 1623 cm-1, and unlike for in vitro A{beta} fibrils, the high-frequency (1680-1690 cm-1) component attributed to antiparallel {beta}-sheet was not observed. A significant elevation in phospholipids was found around dense-core plaques in TgCRND8 mice ranging in age from 5 to 21 months. In contrast, diffuse plaques were not associated with IR detectable changes in protein secondary structure or relative concentrations of any other tissue components.« less

In situ hybridization of nucleus basalis neurons shows increased. beta. -amyloid mRNA in Alzheimer disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cohen, M.L.; Golde, T.E.; Usiak, M.F.

1988-02-01

To determine which cells within the brain produce ..beta..-amyloid mRNA and to assess expression of the ..beta..-amyloid gene in Alzheimer disease, the authors analyzed brain tissue from Alzheimer and control patients by in situ hybridization. The results demonstrate that ..beta..-amyloid mRNA is produced by neurons in the nucleus basalis of Meynert and cerebral cortex and that nuclues basalis perikarya from Alzheimer patients consistently hybridize more ..beta..-amyloid probe than those from controls. These observations support the hypothesis that increased expression of the ..beta..-amyloid gene plays an important role in the deposition of amyloid in the brains of patients with Alzheimer disease.

The role of astrocytes in amyloid production and Alzheimer's disease

PubMed Central

Frost, Georgia R.

2017-01-01

Alzheimer's disease (AD) is marked by the presence of extracellular amyloid beta (Aβ) plaques, intracellular neurofibrillary tangles (NFTs) and gliosis, activated glial cells, in the brain. It is thought that Aβ plaques trigger NFT formation, neuronal cell death, neuroinflammation and gliosis and, ultimately, cognitive impairment. There are increased numbers of reactive astrocytes in AD, which surround amyloid plaques and secrete proinflammatory factors and can phagocytize and break down Aβ. It was thought that neuronal cells were the major source of Aβ. However, mounting evidence suggests that astrocytes may play an additional role in AD by secreting significant quantities of Aβ and contributing to overall amyloid burden in the brain. Astrocytes are the most numerous cell type in the brain, and therefore even minor quantities of amyloid secretion from individual astrocytes could prove to be substantial when taken across the whole brain. Reactive astrocytes have increased levels of the three necessary components for Aβ production: amyloid precursor protein, β-secretase (BACE1) and γ-secretase. The identification of environmental factors, such as neuroinflammation, that promote astrocytic Aβ production, could redefine how we think about developing therapeutics for AD. PMID:29237809

GMP-compliant automated synthesis of [(18)F]AV-45 (Florbetapir F 18) for imaging beta-amyloid plaques in human brain.

PubMed

Yao, Cheng-Hsiang; Lin, Kun-Ju; Weng, Chi-Chang; Hsiao, Ing-Tsung; Ting, Yi-Shu; Yen, Tzu-Chen; Jan, Tong-Rong; Skovronsky, Daniel; Kung, Mei-Ping; Wey, Shiaw-Pyng

2010-12-01

We report herein the Good Manufacturing Practice (GMP)-compliant automated synthesis of (18)F-labeled styrylpyridine, AV-45 (Florbetapir), a novel tracer for positron emission tomography (PET) imaging of beta-amyloid (Abeta) plaques in the brain of Alzheimer's disease patients. [(18)F]AV-45 was prepared in 105 min using a tosylate precursor with Sumitomo modules for radiosynthesis under GMP-compliant conditions. The overall yield was 25.4+/-7.7% with a final radiochemical purity of 95.3+/-2.2% (n=19). The specific activity of [(18)F]AV-45 reached as high as 470+/-135 TBq/mmol (n=19). The present studies show that [(18)F]AV-45 can be manufactured under GMP-compliant conditions and could be widely available for routine clinical use. Copyright 2010 Elsevier Ltd. All rights reserved.

The quest for fragile X biomarkers.

PubMed

Westmark, Cara J

2014-12-01

Fragile X is the most common form of inherited intellectual disability and the leading known genetic cause of autism. There is currently no cure or approved medication for fragile X although various drugs target specific disease symptoms and a large number of therapeutics are in various stages of clinical development. Multiple recent clinical trials have failed on their primary endpoints indicating that there is a compelling need for validated biomarkers and outcome measures in fragile X. There are currently no validated blood-based biomarkers to assess disease severity or to monitor drug efficacy in fragile X syndrome. Herein, we review candidate blood protein biomarkers including extracellular-regulated kinase, phosphoinositide 3-kinase, matrix metalloproteinase 9, amyloid-beta and amyloid-beta protein precursor. Bench-to-bedside plans for fragile X syndrome are severely limited by the lack of validated outcome measures. The reviewed candidate biomarkers are at early stages of validation and deserve further investigation.

CD147 is a regulatory subunit of the gamma-secretase complex inAlzheimer's disease amyloid beta-peptide production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Shuxia; Zhou, Hua; Walian, Peter J.

2005-04-06

{gamma}-secretase is a membrane protein complex that cleaves the {beta}-amyloid precursor protein (APP) within the transmembrane region, following prior processing by {beta}-secretase, producing amyloid {beta}-peptides (A{beta}{sub 40} and A{beta}{sub 42}). Errant production of A{beta}-peptides that substantially increases A{beta}{sub 42} production has been associated with the formation of amyloid plaques in Alzheimer's disease patients. Biophysical and genetic studies indicate that presenilin-1 (Psn-1), which contains the proteolytic active site, and three other membrane proteins, nicastrin (Nct), APH-1, and PEN-2 are required to form the core of the active {gamma}-secretase complex. Here, we report the purification of the native {gamma}-secretase complexes from HeLamore » cell membranes and the identification of an additional {gamma}-secretase complex subunit, CD147, a transmembrane glycoprotein with two immunoglobulin-like domains. The presence of this subunit as an integral part of the complex itself was confirmed through co-immunoprecipitation studies of the purified protein from HeLa cells and solubilized complexes from other cell lines such as neural cell HCN-1A and HEK293. Depletion of CD147 by RNA interference was found to increase the production of A{beta} peptides without changing the expression level of the other {gamma}-secretase components or APP substrates while CD147 overexpression had no statistically significant effect on amyloid {beta}-peptide production, other {gamma}-secretase components or APP substrates, indicating that the presence of the CD147 subunit within the {gamma}-secretase complex directly down-modulates the production of A{beta}-peptides. {gamma}-secretase was first recognized through its role in the production of the A{beta} peptides that are pathogenic in Alzheimer's disease (AD) (1). {gamma}-secretase is a membrane protein complex with unusual aspartyl protease activity that cleaves a variety of type I membrane proteins, such as APP, CD44, DCC, ErbB4, E-cadherin, LRP, N-cadherin, Nectin-1, and Notch, within their transmembranous regions (2-11); therefore, in addition to its role in AD, {gamma}-secretase has been found to participate in other important biological functions, such as intracellular signaling. {gamma}-secretase processing of APP requires prior removal of a major fragment of the APP extracellular domain (sAPP{sub {beta}}) by {beta}-secretase to yield a membrane bound fragment (APP CTF{sub {beta}}). Subsequent cleavage of this membrane bound fragment by {gamma}-secretase results in the release of the Alzheimer's disease (AD) associated amyloid {beta}-peptides (12). The proteolytic activity of {gamma}-secretase is found not to be critically dependent on the specific sequence, but instead on the size of the extracellular domain (13); such sequence independent characteristics of the substrate are reminiscent of those of the 26S proteasome complex that cleaves substrates in a non-sequence specific manner. {gamma}-secretase is present in almost all animal species, vertebrates and invertebrates; it is expressed in many human organs and tissues.« less

Conformational changes of the amyloid beta-peptide (1-40) adsorbed on solid surfaces.

PubMed

Giacomelli, Carla E; Norde, Willem

2005-05-23

The conformational change of the 39-43 residues of the amyloid beta-peptide (Abeta) toward a beta-sheet enriched state promotes self-aggregation of the peptide molecules and constitutes the major peptide component of the amyloid plaques in Alzheimer patients. The crucial question behind the self-aggregation of Abeta is related to the different pathways the peptide may take after cleavage from the amyloid precursor proteins at cellular membranes. This work is aiming at determining the conformation of the Abeta (1-40) adsorbed on hydrophobic Teflon and hydrophilic silica particles, as model sorbent surfaces mimicking the apolar transmembrane environment and the polar, charged membrane surface, respectively. The mechanism by which the Abeta interacts with solid surfaces strongly depends on the hydrophobic/hydrophilic character of the particles. Hydrophobic and electrostatic interactions contribute differently in each case, causing a completely different conformational change of the adsorbed molecules on the two surfaces. When hydrophobic interactions between the peptide and the sorbent prevail, the adsorbed Abeta (1-40) mainly adopts an alpha-helix conformation due to H-bonding in the apolar part of the peptide that is oriented towards the surface. On the other hand, when the peptide adsorbs by electrostatic interactions beta-sheet formation is promoted due to intermolecular association between the apolar parts of the adsorbed peptide. Irrespective of the characteristics of the solid sorbent, crowding the surface results in intermolecular association between adsorbed molecules leading to a strong aggregation tendency of the Abeta (1-40). [Diagram: see text] CD spectra of Abeta (1-40) at pH 7: A) in solution ([Abeta]=0.2 mg.ml(-1)) freshly prepared (line) and after overnight incubation (symbols);B) on Teflon (Gamma=0.5 mg.m(-2)).

The APP-Interacting Protein FE65 is Required for Hippocampus-Dependent Learning and Long-Term Potentiation

ERIC Educational Resources Information Center

Wang, Yan; Zhang, Ming; Moon, Changjong; Hu, Qubai; Wang, Baiping; Martin, George; Sun, Zhongsheng; Wang, Hongbing

2009-01-01

FE65 is expressed predominantly in the brain and interacts with the C-terminal domain of [beta]-amyloid precursor protein (APP). We examined hippocampus-dependent memory and in vivo long-term potentiation (LTP) at the CA1 synapses with isoform-specific FE65 knockout (p97FE65[superscript -/-]) mice. When examined using the Morris water maze,…

Pharmacological evidences for DFK167-sensitive presenilin-independent gamma-secretase-like activity.

PubMed

Sevalle, Jean; Ayral, Erwan; Hernandez, Jean-François; Martinez, Jean; Checler, Frédéric

2009-07-01

Amyloid-beta (Abeta) peptides production is thought to be a key event in the neurodegenerative process ultimately leading to Alzheimer's disease (AD) pathology. A bulk of studies concur to propose that the C-terminal moiety of Abeta is released from its precursor beta-amyloid precursor protein by a high molecular weight enzymatic complex referred to as gamma-secretase, that is composed of at least, nicastrin (NCT), Aph-1, Pen-2, and presenilins (PS) 1 or 2. They are thought to harbor the gamma-secretase catalytic activity. However, several lines of evidence suggest that additional gamma-secretase-like activities could potentially contribute to Abeta production. By means of a quenched fluorimetric substrate (JMV2660) mimicking the beta-amyloid precursor protein sequence targeted by gamma-secretase, we first show that as expected, this probe allows monitoring of an activity detectable in several cell systems including the neuronal cell line telencephalon specific murine neurons (TSM1). This activity is reduced by DFK167, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), and LY68458, three inhibitors known to functionally interact with PS. Interestingly, JMV2660 but not the unrelated peptide JMV2692, inhibits Abeta production in an in vitrogamma-secretase assay as expected from a putative substrate competitor. This activity is enhanced by PS1 and PS2 mutations known to be responsible for familial forms of AD and reduced by aspartyl mutations inactivating PS or in cells devoid of PS or NCT. However, we clearly establish that residual JMV2660-hydrolysing activity could be recovered in PS- and NCT-deficient fibroblasts and that this activity remained inhibited by DFK167. Overall, our study describes the presence of a proteolytic activity displaying gamma-secretase-like properties but independent of PS and still blocked by DFK167, suggesting that the PS-dependent complex could not be the unique gamma-secretase activity responsible for Abeta production and delineates PS-independent gamma-secretase activity as a potential additional therapeutic target to fight AD pathology.

Abeta42-driven cerebral amyloidosis in transgenic mice reveals early and robust pathology.

PubMed

Radde, Rebecca; Bolmont, Tristan; Kaeser, Stephan A; Coomaraswamy, Janaky; Lindau, Dennis; Stoltze, Lars; Calhoun, Michael E; Jäggi, Fabienne; Wolburg, Hartwig; Gengler, Simon; Haass, Christian; Ghetti, Bernardino; Czech, Christian; Hölscher, Christian; Mathews, Paul M; Jucker, Mathias

2006-09-01

We have generated a novel transgenic mouse model on a C57BL/6J genetic background that coexpresses KM670/671NL mutated amyloid precursor protein and L166P mutated presenilin 1 under the control of a neuron-specific Thy1 promoter element (APPPS1 mice). Cerebral amyloidosis starts at 6-8 weeks and the ratio of human amyloid (A)beta42 to Abeta40 is 1.5 and 5 in pre-depositing and amyloid-depositing mice, respectively. Consistent with this ratio, extensive congophilic parenchymal amyloid but minimal amyloid angiopathy is observed. Amyloid-associated pathologies include dystrophic synaptic boutons, hyperphosphorylated tau-positive neuritic structures and robust gliosis, with neocortical microglia number increasing threefold from 1 to 8 months of age. Global neocortical neuron loss is not apparent up to 8 months of age, but local neuron loss in the dentate gyrus is observed. Because of the early onset of amyloid lesions, the defined genetic background of the model and the facile breeding characteristics, APPPS1 mice are well suited for studying therapeutic strategies and the pathomechanism of amyloidosis by cross-breeding to other genetically engineered mouse models.

Insights into the phosphoregulation of beta-secretase sorting signal by the VHS domain of GGA1.

PubMed

Shiba, Tomoo; Kametaka, Satoshi; Kawasaki, Masato; Shibata, Masahiro; Waguri, Satoshi; Uchiyama, Yasuo; Wakatsuki, Soichi

2004-06-01

BACE (beta-site amyloid precursor protein cleaving enzyme, beta-secretase) is a type-I membrane protein which functions as an aspartic protease in the production of beta-amyloid peptide, a causative agent of Alzheimer's disease. Its cytoplasmic tail has a characteristic acidic-cluster dileucine motif recognized by the VHS domain of adaptor proteins, GGAs (Golgi-localizing, gamma-adaptin ear homology domain, ARF-interacting). Here we show that BACE is colocalized with GGAs in the trans-Golgi network and peripheral structures, and phosphorylation of a serine residue in the cytoplasmic tail enhances interaction with the VHS domain of GGA1 by about threefold. The X-ray crystal structure of the complex between the GGA1-VHS domain and the BACE C-terminal peptide illustrates a similar recognition mechanism as mannose 6-phosphate receptors except that a glutamine residue closes in to fill the gap created by the shorter BACE peptide. The serine and lysine of the BACE peptide point their side chains towards the solvent. However, phosphorylation of the serine affects the lysine side chain and the peptide backbone, resulting in one additional hydrogen bond and a stronger electrostatic interaction with the VHS domain, hence the reversible increase in affinity.

Conservation of the sequence of the Alzheimer's disease amyloid peptide in dog, polar bear and five other mammals by cross-species polymerase chain reaction analysis.

PubMed

Johnstone, E M; Chaney, M O; Norris, F H; Pascual, R; Little, S P

1991-07-01

Neuritic plaque and cerebrovascular amyloid deposits have been detected in the aged monkey, dog, and polar bear and have rarely been found in aged rodents (Biochem. Biophy. Res. Commun., 12 (1984) 885-890; Proc. Natl. Acad. Sci. U.S.A., 82 (1985) 4245-4249). To determine if the primary structure of the 42-43 residue amyloid peptide is conserved in species that accumulate plaques, the region of the amyloid precursor protein (APP) cDNA that encodes the peptide region was amplified by the polymerase chain reaction and sequenced. The deduced amino acid sequence was compared to those species where amyloid accumulation has not been detected. The DNA sequences of dog, polar bear, rabbit, cow, sheep, pig and guinea pig were compared and a phylogenetic tree was generated. We conclude that the amino acid sequence of dog and polar bear and other mammals which may form amyloid plaques is conserved and the species where amyloid has not been detected (mouse, rat) may be evolutionarily a distinct group. In addition, the predicted secondary structure of mouse and rat amyloid that differs from that of amyloid bearing species is its lack of propensity to form a beta sheeted structure. Thus, a cross-species examination of the amyloid peptide may suggest what is essential for amyloid deposition.

Novel approaches for immunotherapeutic intervention in Alzheimer's disease.

PubMed

Vasilevko, Vitaly; Cribbs, David H

2006-07-01

Immunotherapy can attenuate amyloid neuropathology and improve cognitive function in transgenic models of Alzheimer's disease. However, the first clinical trial was halted when 6% of the Alzheimer's patients developed aseptic meningoencephalitis. Postmortem analysis of two cases with meningoencephalitis showed robust glial activation, T-cell infiltration and sporadic clearance of Abeta. Interestingly, transgenic mouse models of Alzheimer's disease failed as predictors of these adverse inflammatory events. However there are now several studies with amyloid precursor protein transgenic mice that have reported an increased risk of microhemorrhages at sites of cerebrovascular amyloid deposits and because approximately 80% of Alzheimer's patient's have cerebrovascular pathology, there is concern regarding clinical trials using passive administration of humanized anti-Abeta antibodies. Although many studies have now been published on immunotherapy in mouse models, the mechanism(s) of antibody-mediated clearance of beta-amyloid from the brain, and the cause of the antibody-induced microhemorrhages remain unclear. In this review, we will discuss the most recent results from the first clinical trial, offer speculation on possible causes for the failure of the trial, review data on antibody-mediated clearance mechanisms, explore the role of complement and inflammation in the clearance of beta-amyloid, and suggest novel strategies for avoiding problems in future clinical trials. The central hypothesis being proposed in this review is that anti-Abeta antibodies delivered directly to the CNS at the sites of amyloid deposits will be far more effective at clearing Abeta and safer than active or passive immunization strategies where the majority of the antibodies are in the periphery.

Distinct prion-like strains of amyloid beta implicated in phenotypic diversity of Alzheimer's disease.

PubMed

Cohen, Mark; Appleby, Brian; Safar, Jiri G

2016-01-01

Vast evidence on human prions demonstrates that variable disease phenotypes, rates of propagation, and targeting of distinct brain structures are determined by unique conformers (strains) of pathogenic prion protein (PrP(Sc)). Recent progress in the development of advanced biophysical tools that inventory structural characteristics of amyloid beta (Aβ) in the brain cortex of phenotypically diverse Alzheimer's disease (AD) patients, revealed unique spectrum of oligomeric particles in the cortex of rapidly progressive cases, implicating these structures in variable rates of propagation in the brain, and in distict disease manifestation. Since only ∼30% of phenotypic diversity of AD can be explained by polymorphisms in risk genes, these and transgenic bioassay data argue that structurally distinct Aβ particles play a major role in the diverse pathogenesis of AD, and may behave as distinct prion-like strains encoding diverse phenotypes. From these observations and our growing understanding of prions, there is a critical need for new strain-specific diagnostic strategies for misfolded proteins causing these elusive disorders. Since targeted drug therapy can induce mutation and evolution of prions into new strains, effective treatments of AD will require drugs that enhance clearance of pathogenic conformers, reduce the precursor protein, or inhibit the conversion of precursors into prion-like states.

Inclusion-body myositis and myopathies: different etiologies, possibly similar pathogenic mechanisms.

PubMed

Askanas, Valerie; Engel, W King

2002-10-01

Sporadic inclusion-body myositis (s-IBM) and hereditary inclusion body myopathies are progressive muscle diseases that lead to severe disability. We discuss recent advances in illuminating their pathogenic mechanism(s). We emphasize how different etiologies might lead to the strikingly similar pathology and possibly similar pathogenic cascade. Our basic hypothesis is that over-expression of amyloid-beta precursor protein within aging muscle fibers is an early upstream event causing the subsequent pathogenic cascade. On the basis of our research, several processes seem to be important in relation to the still speculative pathogenesis: (a) increased transcription and accumulation of amyloid-beta precursor protein, and accumulation of its proteolytic fragment Abeta; (b) accumulations of phosphorylated tau and other Alzheimer-related proteins; (c) accumulation of cholesterol and low-density lipoprotein receptors, the cholesterol accumulation possibly due to its abnormal trafficking; (d) oxidative stress; and (e) a milieu of muscle cellular aging in which these changes occur. We discuss unfolded and/or misfolded proteins as a possible mechanism in formation of the inclusion bodies and their consequences. The remarkable pathologic similarities between s-IBM muscle and Alzheimer disease brain are discussed. Unfolding knowledge of the various pathogenetic aspects of the s-IBMs and hereditary inclusion body myopathies may lead to new therapeutic avenues.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kosicek, Marko, E-mail: marko.kosicek@irb.hr; Malnar, Martina, E-mail: martina.malnar@irb.hr; Goate, Alison, E-mail: goate@icarus.wustl.edu

It has been suggested that cholesterol may modulate amyloid-{beta} (A{beta}) formation, a causative factor of Alzheimer's disease (AD), by regulating distribution of the three key proteins in the pathogenesis of AD ({beta}-amyloid precursor protein (APP), {beta}-secretase (BACE1) and/or presenilin 1 (PS1)) within lipid rafts. In this work we tested whether cholesterol accumulation upon NPC1 dysfunction, which causes Niemann Pick type C disease (NPC), causes increased partitioning of APP into lipid rafts leading to increased CTF/A{beta} formation in these cholesterol-rich membrane microdomains. To test this we used CHO NPC1{sup -/-} cells (NPC cells) and parental CHOwt cells. By sucrose density gradientmore » centrifugation we observed a shift in fl-APP/CTF compartmentalization into lipid raft fractions upon cholesterol accumulation in NPC vs. wt cells. Furthermore, {gamma}-secretase inhibitor treatment significantly increased fl-APP/CTF distribution in raft fractions in NPC vs. wt cells, suggesting that upon cholesterol accumulation in NPC1-null cells increased formation of APP-CTF and its increased processing towards A{beta} occurs in lipid rafts. Our results support that cholesterol overload, such as in NPC disease, leads to increased partitioning of APP/CTF into lipid rafts resulting in increased amyloidogenic processing of APP in these cholesterol-rich membranes. This work adds to the mechanism of the cholesterol-effect on APP processing and the pathogenesis of Alzheimer's disease and supports the role of lipid rafts in these processes.« less

The common inhalation anesthetic isoflurane induces caspase activation and increases amyloid beta-protein level in vivo.

PubMed

Xie, Zhongcong; Culley, Deborah J; Dong, Yuanlin; Zhang, Guohua; Zhang, Bin; Moir, Robert D; Frosch, Matthew P; Crosby, Gregory; Tanzi, Rudolph E

2008-12-01

An estimated 200 million patients worldwide have surgery each year. Anesthesia and surgery have been reported to facilitate emergence of Alzheimer's disease. The commonly used inhalation anesthetic isoflurane has previously been reported to induce apoptosis, and to increase levels and aggregation of Alzheimer's disease-associated amyloid beta-protein (Abeta) in cultured cells. However, the in vivo relevance has not been addressed. We therefore set out to determine effects of isoflurane on caspase activation and levels of beta-site amyloid precursor protein-cleaving enzyme (BACE) and Abeta in naive mice, using Western blot, immunohistochemistry, and reverse transcriptase polymerase chain reaction. Here we show for the first time that a clinically relevant isoflurane anesthesia (1.4% isoflurane for 2 hours) leads to caspase activation and modest increases in levels of BACE 6 hours after anesthesia in mouse brain. Isoflurane anesthesia induces caspase activation, and increases levels of BACE and Abeta up to 24 hours after anesthesia. Isoflurane may increase BACE levels by reducing BACE degradation. Moreover, the Abeta aggregation inhibitor, clioquinol, was able to attenuate isoflurane-induced caspase-3 activation in vivo. Given that transient insults to brain may lead to long-term brain damage, these findings suggest that isoflurane may promote Alzheimer's disease neuropathogenesis and, as such, have implications for use of isoflurane in humans, pending human study confirmation.

In vitro streptozotocin model for modeling Alzheimer-like changes: effect on amyloid precursor protein secretases and glycogen synthase kinase-3.

PubMed

Plaschke, Konstanze; Kopitz, Jürgen

2015-04-01

There is accumulating evidence for a pathogenetic link between sporadic Alzheimer's disease (AD) and diabetes mellitus (DM). At subdiabetogenic doses, the cerebral administration of the diabetogenic substance streptozotocin (STZ) induces an insulin-resistant brain state (IRBS). The aim of the present pilot study was to investigate the effect of STZ on Alzheimer-like characteristics such as amyloid precursor protein (APP) cleavage secretases, betaA4 fragment, and glycogen synthase kinase (GSK) in vitro. Different STZ concentrations (0-5 mM) and incubation intervals (0-48 h) were tested to find appropriate cell culture conditions for further biochemical analyses in human neuroblastoma cells (SK-N-MC). Lactate dehydrogenase (LDH) was measured spectrophotometrically. Intracellular ATP was determined using bioluminescent luciferase assay. Secretase activity (alpha, beta, and gamma) was measured by employing commercial fluorometric secretase activity assay kits, betaA4 fragment by immunoprecipitation. Glycogen synthase kinase-3alpha/beta (total and phospho-GSK) content was assayed by ELISA technique. In vitro STZ administration (1 mM) induced a significant reduction in intracellular ATP concentration without pronounced cell death after 24 and 48 h as measured by LDH. Under these experimental conditions, a significant increase in beta-secretase and a significant drop in alpha-secretase were obtained, whereas gamma-secretase was not changed significantly. Simultaneously, the betaA4 concentration was increased by about threefold. Furthermore, STZ significantly increased total GSK and markedly decreased phospho-GSK. A direct link between STZ, intracellular ATP deficit, and Alzheimer-related enzymes was shown in this in vitro pilot study. Thus, these results support the hypothesis that sporadic AD is being recognized as an IRBS, which can be modulated by in vitro STZ model. Continuing investigations relating pathogenetic mechanisms and AD-like hallmarks are necessary to modulate different cascades of the IRBS using in vitro models.

Toward the treatment and prevention of Alzheimer's disease: rational strategies and recent progress.

PubMed

Gandy, Sam; DeKosky, Steven T

2013-01-01

Alzheimer's disease (AD) is the major cause of late-life brain failure. In the past 25 years, autosomal dominant forms of AD were found to be primariy attributable to mutations in one of two presenilins, polytopic proteins that contain the catalytic site of the γ-secretase protease that releases the amyloid beta (Aβ) peptide. Some familial AD is also due to mutations in the amyloid precursor protein (APP), but recently a mutation in APP was discovered that reduces Aβ generation and is protective against AD, further implicating amyloid metabolism. Prion-like seeding of amyloid fibrils and neurofibrillary tangles has been invoked to explain the stereotypical spread of AD within the brain. Treatment trials with anti-Aβ antibodies have shown target engagement, if not significant treatment effects. Attention is increasingly focused on presymptomatic intervention, because Aβ mismetabolism begins up to 25 years before symptoms begin. AD trials deriving from new biological information involve extraordinary international collaboration and may hold the best hope for success in the fight against AD.

Radiolabeled probes for imaging Alzheimer’s plaques

NASA Astrophysics Data System (ADS)

Kulkarni, P. V.; Arora, V.; Roney, A. C.; White, C.; Bennett, M.; Antich, P. P.; Bonte, F. J.

2005-12-01

Alzheimer's disease (AD) is a debilitating disease characterized by the presence of extra-cellular plaques and intra-cellular neurofibrillary tangles (NFTs) in the brain. The major protein component of these plaques is beta amyloid peptide (Aβ), a 40-42 amino acid peptide cleaved from amyloid precursor protein (APP) by β-secretase and a putative γ-secretase. We radioiodinated quinoline derivatives (clioquinol and oxine) and evaluated them as potential amyloid imaging agents based on their ability to cross the blood brain barrier (BBB) and on their selectivity to metal binding sites on amyloid plaques. The uptake of theses tracers in the brains of normal swiss-webster mice was rapid and so was the clearance. Selectivity was demonstrated by higher binding to AD brain homogenates compared to normal brain. Autoradiographic studies demonstrated the localization of the tracers in the plaque regions of the AD brain sections as well as in liver tissue with amyloidosis. Further optimization and evaluations would likely lead to development of these molecules as AD plaque imaging agents.

Amyloid fibril formation from sequences of a natural beta-structured fibrous protein, the adenovirus fiber.

PubMed

Papanikolopoulou, Katerina; Schoehn, Guy; Forge, Vincent; Forsyth, V Trevor; Riekel, Christian; Hernandez, Jean-François; Ruigrok, Rob W H; Mitraki, Anna

2005-01-28

Amyloid fibrils are fibrous beta-structures that derive from abnormal folding and assembly of peptides and proteins. Despite a wealth of structural studies on amyloids, the nature of the amyloid structure remains elusive; possible connections to natural, beta-structured fibrous motifs have been suggested. In this work we focus on understanding amyloid structure and formation from sequences of a natural, beta-structured fibrous protein. We show that short peptides (25 to 6 amino acids) corresponding to repetitive sequences from the adenovirus fiber shaft have an intrinsic capacity to form amyloid fibrils as judged by electron microscopy, Congo Red binding, infrared spectroscopy, and x-ray fiber diffraction. In the presence of the globular C-terminal domain of the protein that acts as a trimerization motif, the shaft sequences adopt a triple-stranded, beta-fibrous motif. We discuss the possible structure and arrangement of these sequences within the amyloid fibril, as compared with the one adopted within the native structure. A 6-amino acid peptide, corresponding to the last beta-strand of the shaft, was found to be sufficient to form amyloid fibrils. Structural analysis of these amyloid fibrils suggests that perpendicular stacking of beta-strand repeat units is an underlying common feature of amyloid formation.

Candidate genes for Alzheimer's disease are associated with individual differences in plasma levels of beta amyloid peptides in adults with Down syndrome.

PubMed

Schupf, Nicole; Lee, Annie; Park, Naeun; Dang, Lam-Ha; Pang, Deborah; Yale, Alexander; Oh, David Kyung-Taek; Krinsky-McHale, Sharon J; Jenkins, Edmund C; Luchsinger, José A; Zigman, Warren B; Silverman, Wayne; Tycko, Benjamin; Kisselev, Sergey; Clark, Lorraine; Lee, Joseph H

2015-10-01

We examined the contribution of candidates genes for Alzheimer's disease (AD) to individual differences in levels of beta amyloid peptides in adults with Down syndrom, a population at high risk for AD. Participants were 254 non-demented adults with Down syndrome, 30-78 years of age. Genomic deoxyribonucleic acid was genotyped using an Illumina GoldenGate custom array. We used linear regression to examine differences in levels of Aβ peptides associated with the number of risk alleles, adjusting for age, sex, level of intellectual disability, race and/or ethnicity, and the presence of the APOE ε4 allele. For Aβ42 levels, the strongest gene-wise association was found for a single nucleotide polymorphism (SNP) on CAHLM1; for Aβ40 levels, the strongest gene-wise associations were found for SNPs in IDE and SOD1, while the strongest gene-wise associations with levels of the Aβ42/Aβ40 ratio were found for SNPs in SORCS1. Broadly classified, variants in these genes may influence amyloid precursor protein processing (CALHM1, IDE), vesicular trafficking (SORCS1), and response to oxidative stress (SOD1). Copyright © 2015 Elsevier Inc. All rights reserved.

Neurotoxicity of a Fragment of the Amyloid Precursor Associated with Alzheimer's Disease

NASA Astrophysics Data System (ADS)

Yankner, Bruce A.; Dawes, Linda R.; Fisher, Shannon; Villa-Komaroff, Lydia; Oster-Granite, Mary Lou; Neve, Rachael L.

1989-07-01

Amyloid deposition in senile plaques and the cerebral vasculature is a marker of Alzheimer's disease. Whether amyloid itself contributes to the neurodegenerative process or is simply a by-product of that process is unknown. Pheochromocytoma (PC12) and fibroblast (NIH 3T3) cell lines were transfected with portions of the gene for the human amyloid precursor protein. Stable PC12 cell transfectants expressing a specific amyloid-containing fragment of the precursor protein gradually degenerated when induced to differentiate into neuronal cells with nerve growth factor. Conditioned medium from these cells was toxic to neurons in primary hippocampal cultures, and the toxic agent could be removed by immunoabsorption with an antibody directed against the amyloid polypeptide. Thus, a peptide derived from the amyloid precursor may be neurotoxic.

Rescue of Hypovitaminosis A Induces Non-Amyloidogenic Amyloid Precursor Protein (APP) Processing.

PubMed

Reinhardt, Sven; Grimm, Marcus O W; Stahlmann, Christoph; Hartmann, Tobias; Shudo, Koichi; Tomita, Taisuke; Endres, Kristina

2016-01-01

Retinoic acid, the bioactive metabolite of beta-carotene or vitamin A, plays a pleiotropic, multifunctional role in vertebrate development. Studies in rodents revealed that a diet deficient in vitamin A results in a complex neonatal syndrome (the VAD syndrome), manifested in many organs. In humans, the function of retinoic acid (RA) extends into adulthood, where it has important roles in fertility, vision, and suppression of neoplastic growth. In recent years, it has also been suggested that retinoic acid might potentially act as a therapeutically relevant drug in attenuating or even preventing neurodegenerative diseases such as Alzheimer's disease (AD). Here, we report that VAD leads to an increase in A-beta peptide levels while only minor effects were observed on expression levels of the amyloid precursor protein (APP) processing proteinases in wild type mice. In line with these findings, rescue of hypovitaminosis reduced A-beta amount to baseline and induced sApp-alpha secretion in combination with an increase of alpha-secretase Adam10. By comparing retinoic acid treatment starting from a full nutrition status and a "VAD" situation in human neuroblastoma cells, we show that while intensities of differential gene expression were higher in replenished cells, a large overlap in AD-related, regulated genes was observed. Our data suggest that hypovitaminosis A can contribute to onset or progression of AD by increasing synthesis of A-beta peptides and that several AD-related genes such as ADAM10 or BDNF are regulated by retinoic acid. We suggest that dietary supplementation with retinoic acid derivatives is likely to have a beneficial effect on AD-pathology in individuals with hypovitaminosis and patients with normal vitamin A status.

Insight into inhibition of the human amyloid beta protein precursor (APP: PDB ID ) using (E)-N-(pyridin-2-ylmethylene)arylamine (LR) models: structure elucidation of a family of ZnX2-LR complexes.

PubMed

Basu Baul, Tushar S; Kundu, Sajal; Singh, Palwinder; Shaveta; Guedes da Silva, M Fátima C

2015-02-07

The amyloid beta precursor protein (APP) and its neurotoxic cleavage product amyloid beta (Aβ) are a cause of Alzheimer's disease and appear essential for neuronal development and cell homeostasis. Proteolytic processing of APP is influenced by metal ions and protein ligands, however the structural and functional mechanism of APP regulation is not known so far. In this context, molecular modeling studies were performed to understand the molecular behavior of (E)-N-(pyridin-2-ylmethylene)arylamines (LR) with an E2 domain of the APP in its complex with zinc (APP; PDB ID: ). Docking results indeed confirmed that the LR interacts with Zn in the binding site of the protein between two α-helical chains. In view of these findings, LR was further investigated for complexation reactions with Zn(2+) in order to establish the structural models in solution and in the solid state. Five new Zn(2+) complexes of compositions viz. [Zn(Br)2(L2-Me)] (), [Zn(Br)2(L2-OMe)] (), [Zn(i)2(L2-OMe)] (), [Zn(NO3)2(L2-OMe)(H2O)] () and [Zn(L4-Me)2(H2O)2](NO3)2 () were synthesized and their structures were ascertained by microanalysis, IR and (1)H NMR spectroscopy, and single-crystal X-ray diffraction. The zinc atom in complex exhibits a distorted tetrahedral geometry while the crystal structures of complexes and show distorted square pyramidal geometries. The zinc cation in and has an octahedral coordination environment, but in the zinc coordination geometry is less distorted. The Zn(ii) cations take part in one ( and ) or two () 5-membered metallacycles imposed by the NN or NNO chelation modes of LR. The significant intermolecular ππ interactions are also discussed.

Reducing iron in the brain: a novel pharmacologic mechanism of huperzine A in the treatment of Alzheimer's disease.

PubMed

Huang, Xiao-Tian; Qian, Zhong-Ming; He, Xuan; Gong, Qi; Wu, Ka-Chun; Jiang, Li-Rong; Lu, Li-Na; Zhu, Zhou-Jing; Zhang, Hai-Yan; Yung, Wing-Ho; Ke, Ya

2014-05-01

Huperzine A (HupA), a natural inhibitor of acetylcholinesterase derived from a plant, is a licensed anti-Alzheimer's disease (AD) drug in China and a nutraceutical in the United States. In addition to acting as an acetylcholinesterase inhibitor, HupA possesses neuroprotective properties. However, the relevant mechanism is unknown. Here, we showed that the neuroprotective effect of HupA was derived from a novel action on brain iron regulation. HupA treatment reduced insoluble and soluble beta amyloid levels, ameliorated amyloid plaques formation, and hyperphosphorylated tau in the cortex and hippocampus of APPswe/PS1dE9 transgenic AD mice. Also, HupA decreased beta amyloid oligomers and amyloid precursor protein levels, and increased A Disintegrin And Metalloprotease Domain 10 (ADAM10) expression in these treated AD mice. However, these beneficial effects of HupA were largely abolished by feeding the animals with a high iron diet. In parallel, we found that HupA decreased iron content in the brain and demonstrated that HupA also has a role to reduce the expression of transferrin-receptor 1 as well as the transferrin-bound iron uptake in cultured neurons. The findings implied that reducing iron in the brain is a novel mechanism of HupA in the treatment of Alzheimer's disease. Copyright © 2014 Elsevier Inc. All rights reserved.

Increased KPI containing amyloid precursor protein in experimental autoimmune encephalomyelitis brains.

PubMed

Beilin, Orit; Karussis, Dimitrios M; Korczyn, Amos D; Gurwitz, David; Aronovich, Ramona; Mizrachi-Kol, Rachel; Chapman, Joab

2007-04-16

Amyloid precursor protein can be translated from three alternatively spliced mRNAs. We measured levels of amyloid precursor protein isoforms containing the Kunitz protease inhibitor domain (KPIAPP), and amyloid precursor protein without the Kunitz protease inhibitor domain (KPIAPP) in brain homogenates of acute experimental autoimmune encephalomyelitis mice. At the preclinical phase of the disease, both KPIAPP and KPIAPP levels were significantly higher in homogenates from brains of autoimmune encephalomyelitis mice, whereas at the acute phase of the disease only KPIAPP remained significantly elevated compared with controls. At the recovery phase, no differences were observed between the groups. The early and isoform-specific elevation of KPIAPP in autoimmune encephalomyelitis mice suggests a possible role for amyloid precursor protein in the immune response mediating the disease.

Apolipoprotein E-mimetics inhibit neurodegeneration and restore cognitive functions in a transgenic Drosophila model of Alzheimer's disease.

PubMed

Sarantseva, Svetlana; Timoshenko, Svetlana; Bolshakova, Olga; Karaseva, Eugenia; Rodin, Dmitry; Schwarzman, Alexander L; Vitek, Michael P

2009-12-07

Mutations of the amyloid precursor protein gene (APP) are found in familial forms of Alzheimer's disease (AD) and some lead to the elevated production of amyloid-beta-protein (Abeta). While Abeta has been implicated in the causation of AD, the exact role played by Abeta and its APP precursor are still unclear. In our study, Drosophila melanogaster transgenics were established as a model to analyze AD-like pathology caused by APP overexpression. We demonstrated that age related changes in the levels and pattern of synaptic proteins accompanied progressive neurodegeneration and impairment of cognitive functions in APP transgenic flies, but that these changes may be independent from the generation of Abeta. Using novel peptide mimetics of Apolipoprotein-E, COG112 or COG133 proved to be neuroprotective and significantly improved the learning and memory of APP transgenic flies. The development of neurodegeneration and cognitive deficits was corrected by injections of COG112 or COG133, novel mimetics of apolipoprotein-E (apoE) with neuroprotective activities.

The amyloid precursor protein locus and very-late-onset Alzheimer disease.

PubMed

Olson, J M; Goddard, K A; Dudek, D M

2001-10-01

Although mutations in the amyloid-beta precursor protein (APP) gene are known to confer high risk of Alzheimer disease (AD) to a small percentage of families in which it has early onset, convincing evidence of a major role for the APP locus in late-onset AD has not been forthcoming. In this report, we have used a covariate-based affected-sib-pair linkage method to analyze the chromosome 21 clinical and genetic data obtained on affected sibships by the National Institute of Mental Health Alzheimer Disease Genetics Initiative. The baseline model (without covariates) gave a LOD score of 0.02, which increases to 1.43 when covariates representing the additive effects of E2 and E4 are added. Larger increases in LOD scores were found when age at last examination/death (LOD score 5.54; P=.000002) or age at onset plus disease duration (LOD score 5.63; P=.000006) were included in the linkage model. We conclude that the APP locus may predispose to AD in the very elderly.

The Alzheimer's Disease Mitochondrial Cascade Hypothesis: Progress and Perspectives

PubMed Central

Swerdlow, Russell H.; Burns, Jeffrey M.; Khan, Shaharyar M.

2013-01-01

Ten years ago we first proposed the Alzheimer's disease (AD) mitochondrial cascade hypothesis. This hypothesis maintains gene inheritance defines an individual's baseline mitochondrial function; inherited and environmental factors determine rates at which mitochondrial function changes over time; and baseline mitochondrial function and mitochondrial change rates influence AD chronology. Our hypothesis unequivocally states in sporadic, late-onset AD, mitochondrial function affects amyloid precursor protein (APP) expression, APP processing, or beta amyloid (Aβ) accumulation and argues if an amyloid cascade truly exists, mitochondrial function triggers it. We now review the state of the mitochondrial cascade hypothesis, and discuss it in the context of recent AD biomarker studies, diagnostic criteria, and clinical trials. Our hypothesis predicts biomarker changes reflect brain aging, new AD definitions clinically stage brain aging, and removing brain Aβ at any point will marginally impact cognitive trajectories. Our hypothesis, therefore, offers unique perspective into what sporadic, late-onset AD is and how to best treat it. PMID:24071439

Formononetin attenuates Aβ25-35-induced cytotoxicity in HT22 cells via PI3K/Akt signaling and non-amyloidogenic cleavage of APP.

PubMed

Chen, Lizhi; Ou, Shanshan; Zhou, Lingqi; Tang, Hai; Xu, Jie; Guo, Kaihua

2017-02-03

Amyloid beta (Aβ) is the main component of the amyloid plaques that accumulate in the brains of Alzheimer patients. Here, we reported the protective role of Formononetin (Form) against Aβ 25-35 -induced neurotoxicity in HT22 cells. We found that Form significantly increased the viability of HT22 cells but decreased the cell apoptosis when challenging with Aβ 25-35. The inhibitory effects of Form were associated with PI3K/Akt signaling pathway as PI3K inhibitor (LY294002) or ERα specific inhibitor (MPP) blocked the effects. Form also accelerated the non-amyloidogenic process of amyloid precursor protein (APP) by enhancing α-secretase activity and sAPPα release. Altogether, our findings may provide a novel therapeutic target to treat AD sufferers. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Quantification of beta A4 protein deposition in the medial temporal lobe: a comparison of Alzheimer's disease and senile dementia of the Lewy body type.

PubMed

Gentleman, S M; Williams, B; Royston, M C; Jagoe, R; Clinton, J; Perry, R H; Ince, P G; Allsop, D; Polak, J M; Roberts, G W

1992-08-03

The distribution of beta-amyloid protein (beta A4) was examined in the medial temporal lobes from cases of Alzheimer's disease (AD) (n = 13), senile dementia of Lewy body type (SDLT) (n = 12) and age matched controls (n = 9). Using a previously described image analysis technique the extent of beta A4 pathology was determined in ten distinct anatomical sites within the medial temporal lobe. AD and SDLT cases contained very similar amounts of beta A4 in the areas sampled and both contained significantly more beta A4 than the age matched controls, particularly in the dentate and parahippocampal gyri. The similarity of the beta A4 load in the two conditions is in contrast to reported differences in the number of neurofibrillary tangles which can be observed. It is suggested that AD and SDLT represent a spectrum of pathology which centres around the aberrant processing of the beta A4 precursor protein.

Numb endocytic adapter proteins regulate the transport and processing of the amyloid precursor protein in an isoform-dependent manner: implications for Alzheimer disease pathogenesis.

PubMed

Kyriazis, George A; Wei, Zelan; Vandermey, Miriam; Jo, Dong-Gyu; Xin, Ouyang; Mattson, Mark P; Chan, Sic L

2008-09-12

Central to the pathogenesis of Alzheimer disease is the aberrant processing of the amyloid precursor protein (APP) to generate amyloid beta-peptide (Abeta), the principle component of amyloid plaques. The cell fate determinant Numb is a phosphotyrosine binding domain (PTB)-containing endocytic adapter protein that interacts with the carboxyl-terminal domain of APP. The physiological relevance of this interaction is unknown. Mammals produce four alternatively spliced variants of Numb that differ in the length of their PTB and proline-rich region. In the current study, we determined the influence of the four human Numb isoforms on the intracellular trafficking and processing of APP. Stable expression of Numb isoforms that differ in the PTB but not in the proline-rich region results in marked differences in the sorting of APP to the recycling and degradative pathways. Neural cells expressing Numb isoforms that lack the insert in the PTB (short PTB (SPTB)) exhibited marked accumulation of APP in Rab5A-labeled early endosomal and recycling compartments, whereas those expressing isoforms with the insertion in the PTB (long PTB (LPTB)) exhibited reduced amounts of cellular APP and its proteolytic derivatives relative to parental control cells. Neither the activities of the beta- and gamma-secretases nor the expression of APP mRNA were significantly different in the stably transfected cells, suggesting that the differential effects of the Numb proteins on APP metabolism is likely to be secondary to altered APP trafficking. In addition, the expression of SPTB-Numb increases at the expense of LPTB-Numb in neuronal cultures subjected to stress, suggesting a role for Numb in stress-induced Abeta production. Taken together, these results suggest distinct roles for the human Numb isoforms in APP metabolism and may provide a novel potential link between altered Numb isoform expression and increased Abeta generation.

Oxygen-glucose deprivation regulates BACE1 expression through induction of autophagy in Neuro-2a/APP695 cells

PubMed Central

Chen, Rong-fu; Zhang, Ting; Sun, Yin-yi; Sun, Ya-meng; Chen, Wen-qi; Shi, Nan; Shen, Fang; Zhang, Yan; Liu, Kang-yong; Sun, Xiao-jiang

2015-01-01

Our previous findings have demonstrated that autophagy regulation can alleviate the decline of learning and memory by eliminating deposition of extracellular beta-amyloid peptide (Aβ) in the brain after stroke, but the exact mechanism is unclear. It is presumed that the regulation of beta-site APP-cleaving enzyme 1 (BACE1), the rate-limiting enzyme in metabolism of Aβ, would be a key site. Neuro-2a/amyloid precursor protein 695 (APP695) cell models of cerebral ischemia were established by oxygen-glucose deprivation to investigate the effects of Rapamycin (an autophagy inducer) or 3-methyladenine (an autophagy inhibitor) on the expression of BACE1. Either oxygen-glucose deprivation or Rapamycin down-regulated the expression of BACE1 while 3-methyladenine up-regulated BACE1 expression. These results confirm that oxygen-glucose deprivation down-regulates BACE1 expression in Neuro-2a/APP695 cells through the introduction of autophagy. PMID:26604904

Diagnostics and therapy of Alzheimer's disease.

PubMed

Mikiciuk-Olasik, Elzbieta; Szymański, Paweł; Zurek, Elzbieta

2007-04-01

Alzheimer's Disease (AD) is described as a degenerative disease of the central nervous system characterized by a noticeable cognitive decline defined by a loss of memory and learning ability, together with a reduced ability to perform basic activities of daily living. In the brain of an AD patients is the dramatic decrease in cholinergic innervation in the cortex and hippocampus due to the loss of neurons in the basal forebrain. The above findings led to the development of the cholinergic hypothesis, which proposes that the cognitive loss associated with AD is related to decreased cortical cholinergic neurotransmission. In brain of Alzheimer's patient's one ascertained presence of neuritic plaques containing the beta-amyloid peptide and protein tau. Biochemical and genetics studies implicated a central role for beta-amyloid in the pathological cascade of events in AD. The most therapeutic strategies in AD have been directed to two main targets: the beta-amyloid peptide and the cholinergic neurotransmission. The first approach is to act on the amyloid precursor protein (APP) processing. The second main approach is to slow of decline of neuronal degeneration or increasing cholinergic transmission. Diagnosis of AD is very difficult and to date no specific diagnostic tests of the disease are available. Intellectual function testing to determine the degree of cognitive status during routine medical examination is a useful supplementary method of diagnosing dementia. The permissible result, come down from radiopharmacy, which is an integral part of a nuclear medicine. A radiopharmaceutical may be defined as a pharmaceutical substance containing radioactive atoms. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are capable of mapping the distribution of radionuclides in three dimensions, producing maps of brain biochemical and physiological processes. The techniques are reasonably sensitive and specific in differentiating AD from other dementias.

Immunohistochemical localization of beta-amyloid precursor protein sequences in Alzheimer and normal brain tissue by light and electron microscopy.

PubMed

McGeer, P L; Akiyama, H; Kawamata, T; Yamada, T; Walker, D G; Ishii, T

1992-03-01

Immunohistochemical staining with antibodies directed against four segments of the amyloid precursor protein (APP) was studied by light and electron microscopy in normal and Alzheimer (AD) brain tissue. The segments according to the Kang et al. sequence were: 18-38 (T97); 527-540 (R36); 597-620 (1-24 of beta-amyloid protein [BAP], R17); and 681-695 (R37) (Kang et al. [1987]: Nature 325:733-736). The antibodies recognized full length APP in Western blots of extracts of APP transfected cells. They stained cytoplasmic granules in some pyramidal neurons in normal appearing tissue from control and AD cases. In AD affected tissue, the antibodies to amino terminal sections of APP stained tangled neurons and neuropil threads, and intensely stained dystrophic neurites in senile plaques. By electron microscopy, this staining was localized to abnormal filaments. The antibody to the carboxy terminal segment failed to stain neurofibrillary tangles or neuropil threads; it did stain some neurites with globular swellings. It also stained globular and elongated deposits in senile plaque areas. The antibody against the BAP intensely stained extracellular material in senile plaques and diffuse deposits. By electron microscopy, the antibodies all stained intramicroglial deposits. Some of the extracellular and intracellular BAP-positive deposits were fibrillary. Communication between intramicroglial and extracellular fibrils was detected in plaque areas. These data suggest the following sequence of events. APP is normally concentrated in intraneuronal granules. In AD, it accumulates in damaged neuronal fibers. The amino terminal portion binds to abnormal neurofilaments. Major fragments of APP are phagocytosed and processed by microglia with the BAP portion being preserved. The preserved BAP is then extruded and accumulates in extracellular tissue.

PPARgamma agonist curcumin reduces the amyloid-beta-stimulated inflammatory responses in primary astrocytes.

PubMed

Wang, Hong-Mei; Zhao, Yan-Xin; Zhang, Shi; Liu, Gui-Dong; Kang, Wen-Yan; Tang, Hui-Dong; Ding, Jian-Qing; Chen, Sheng-Di

2010-01-01

Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder. Accumulating data indicate that astrocytes play an important role in the neuroinflammation related to the pathogenesis of AD. It has been shown that microglia and astrocytes are activated in AD brain and amyloid-beta (Abeta) can increase the expression of cyclooxygenase 2 (COX-2), interleukin-1, and interleukin-6. Suppressing the inflammatory response caused by activated astrocytes may help to inhibit the development of AD. Curcumin is a major constituent of the yellow curry spice turmeric and proved to be a potential anti-inflammatory drug in arthritis and colitis. There is a low age-adjusted prevalence of AD in India, a country where turmeric powder is commonly used as a culinary compound. Curcumin has been shown to suppress activated astroglia in amyloid-beta protein precursor transgenic mice. The real mechanism by which curcumin inhibits activated astroglia is poorly understood. Here we report that the expression of COX-2 and glial fibrillary acidic protein were enhanced and that of peroxisome proliferator-activated receptor gamma (PPARgamma) was decreased in Abeta(25-35)-treated astrocytes. In line with these results, nuclear factor-kappaB translocation was increased in the presence of Abeta. All these can be reversed by the pretreatment of curcumin. Furthermore, GW9662, a PPARgamma antagonist, can abolish the anti-inflammatory effect of curcumin. These results show that curcumin might act as a PPARgamma agonist to inhibit the inflammation in Abeta-treated astrocytes.

p53-dependent control of cell death by nicastrin: lack of requirement for presenilin-dependent gamma-secretase complex.

PubMed

Pardossi-Piquard, Raphaëlle; Dunys, Julie; Giaime, Emilie; Guillot-Sestier, Marie-Victoire; St George-Hyslop, Peter; Checler, Frédéric; Alves da Costa, Cristine

2009-04-01

Nicastrin (NCT) is a component of the presenilin (PS)-dependent gamma-secretase complexes that liberate amyloid beta-peptides from the beta-Amyloid Precursor Protein. Several lines of evidence indicate that the members of these complexes could also contribute to the control of cell death. Here we show that over-expression of NCT increases the viability of human embryonic kidney (HEK293) cells and decreases staurosporine (STS)- and thapsigargin (TPS)-induced caspase-3 activation in various cell lines from human and neuronal origins by Akt-dependent pathway. NCT lowers p53 expression, transcriptional activity and promoter transactivation and reduces p53 phosphorylation. NCT-associated protection against STS-stimulated cell death was completely abolished by p53 deficiency. Conversely, the depletion of NCT drastically enhances STS-induced caspase-3 activation and p53 pathway and favored p53 nuclear translocation. We examined whether NCT protective function depends on PS-dependent gamma-secretase activity. First, a 29-amino acid deletion known to reduce NCT-dependent amyloid beta-peptide production did not affect NCT-associated protective phenotype. Second, NCT still reduces STS-induced caspase-3 activation in fibroblasts lacking PS1 and PS2. Third, the gamma-secretase inhibitor DFK167 did not affect NCT-mediated reduction of p53 activity. Altogether, our study indicates that NCT controls cell death via phosphoinositide 3-kinase/Akt and p53-dependent pathways and that this function remains independent of the activity and molecular integrity of the gamma-secretase complexes.

Glyburide - Novel Prophylaxis and Effective Treatment for Blast-Traumatic Brain Injury

DTIC Science & Technology

2013-10-01

determine the safety of the SUR1 blocker , glyburide (glibenclamide), as it might be used as prophylaxis against blast-TBI. During the 4th year of...We completed evaluation of the prophylaxis treatment with SUR1 blocker , glyburide in the neurobehavioral outcome after blast-TBI (Obj. 1d, c...APP ( Beta -amyloid precursor protein) 64 qPCR Casp 3 (caspase 3) 28 Tissue hemoglobin detection SP1 (ischemic, hypoxic marker) 7 ED1

Two different immunostaining patterns of beta-amyloid precursor protein (APP) may distinguish traumatic from nontraumatic axonal injury.

PubMed

Hayashi, Takahito; Ago, Kazutoshi; Nakamae, Takuma; Higo, Eri; Ogata, Mamoru

2015-09-01

Immunostaining for beta-amyloid precursor protein (APP) is recognized as an effective tool for detecting traumatic axonal injury, but it also detects axonal injury due to ischemic or other metabolic causes. Previously, we reported two different patterns of APP staining: labeled axons oriented along with white matter bundles (pattern 1) and labeled axons scattered irregularly (pattern 2) (Hayashi et al. (Leg Med (Tokyo) 11:S171-173, 2009). In this study, we investigated whether these two patterns are consistent with patterns of trauma and hypoxic brain damage, respectively. Sections of the corpus callosum from 44 cases of blunt head injury and equivalent control tissue were immunostained for APP. APP was detected in injured axons such as axonal bulbs and varicose axons in 24 of the 44 cases of head injuries that also survived for three or more hours after injury. In 21 of the 24 APP-positive cases, pattern 1 alone was observed in 14 cases, pattern 2 alone was not observed in any cases, and both patterns 1 and 2 were detected in 7 cases. APP-labeled injured axons were detected in 3 of the 44 control cases, all of which were pattern 2. These results suggest that pattern 1 indicates traumatic axonal injury, while pattern 2 results from hypoxic insult. These patterns may be useful to differentiate between traumatic and nontraumatic axonal injuries.

K+ channel openers prevent global ischemia-induced expression of c-fos, c-jun, heat shock protein, and amyloid beta-protein precursor genes and neuronal death in rat hippocampus.

PubMed Central

Heurteaux, C; Bertaina, V; Widmann, C; Lazdunski, M

1993-01-01

Transient global forebrain ischemia induces in rat brain a large increase of expression of the immediate early genes c-fos and c-jun and of the mRNAs for the 70-kDa heat-shock protein and for the form of the amyloid beta-protein precursor including the Kunitz-type protease-inhibitor domain. At 24 hr after ischemia, this increased expression is particularly observed in regions that are vulnerable to the deleterious effects of ischemia, such as pyramidal cells of the CA1 field in the hippocampus. In an attempt to find conditions which prevent the deleterious effects of ischemia, representatives of three different classes of K+ channel openers, (-)-cromakalim, nicorandil, and pinacidil, were administered both before ischemia and during the reperfusion period. This treatment totally blocked the ischemia-induced expression of the different genes. In addition it markedly protected neuronal cells against degeneration. The mechanism of the neuroprotective effects involves the opening of ATP-sensitive K+ channels since glipizide, a specific blocker of that type of channel, abolished the beneficial effects of K+ channel openers. The various classes of K+ channel openers seem to deserve attention as potential drugs for cerebral ischemia. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:8415718

Amyloid precursor protein mRNA levels in Alzheimer's disease brain.

PubMed

Preece, Paul; Virley, David J; Costandi, Moheb; Coombes, Robert; Moss, Stephen J; Mudge, Anne W; Jazin, Elena; Cairns, Nigel J

2004-03-17

Insoluble beta-amyloid deposits in Alzheimer's disease (AD) brain are proteolytically derived from the membrane bound amyloid precursor protein (APP). The APP gene is differentially spliced to produce isoforms that can be classified into those containing a Kunitz-type serine protease inhibitor domain (K(+), APP(751), APP(770), APRP(365) and APRP(563)), and those without (K(-), APP(695) and APP(714)). Given the hypothesis that Abeta is a result of aberrant catabolism of APP, differential expression of mRNA isoforms containing protease inhibitors might play an active role in the pathology of AD. We took 513 cerebral cortex samples from 90 AD and 81 control brains and quantified the mRNA isoforms of APP with TaqMan real-time RT-PCR. After adjustment for age at death, brain pH and gender we found a change in the ratio of KPI(+) to KPI(-) mRNA isoforms of APP. Three separate probes, designed to recognise only KPI(+) mRNA species, gave increases of between 28% and 50% in AD brains relative to controls (p=0.002). There was no change in the mRNA levels of KPI-(APP 695) (p=0.898). Therefore, whilst KPI-mRNA levels remained stable the KPI(+) species increased specifically in the AD brains.

Filamentous bacteriophage as a novel therapeutic tool for Alzheimer's disease treatment.

PubMed

Solomon, Beka

2008-10-01

Antibodies towards the N-terminal region of the amyloid-beta peptide (AbetaP) bind to Abeta fibrils, leading to their disaggregation. We developed an immunization procedure using filamentous phages displaying the only four amino acids EFRH encompassing amino acids 3-6 of the 42 residues of AbetaP, found to be the main regulatory site for Abeta formation. Phages displaying EFRH epitope are effective in eliciting humoral response against AbetaP which, in turn, relieves amyloid burden in brains of amyloid-beta protein precursor transgenic mice, improving their ability to perform cognitive tasks. In order to overcome the low permeability of the blood brain barrier for targeting 'anti-aggregating' monoclonal antibodies (mAbs) to Abeta plaques in the brain, we applied antibody engineering methods to minimize the size of mAbs while maintaining their biological activity. Single-chain antibodies displayed on the surface of filamentous phage showed the ability to enter the central nervous system (CNS). The genetically engineered filamentous bacteriophage proved to be an efficient, nontoxic viral delivery vector to the brain, offering an obvious advantage over other mammalian vectors. The feasibility of these novel strategies for production and targeting of anti-aggregating antibodies against Abeta plaques to disease affected regions in the CNS may have clinical potential for treatment of Alzheimer's disease.

LRP in amyloid-beta production and metabolism.

PubMed

Bu, Guojun; Cam, Judy; Zerbinatti, Celina

2006-11-01

Amyloid-beta peptide (Abeta) production and accumulation in the brain is a central event in the pathogenesis of Alzheimer's disease (AD). Recent studies have shown that apolipoprotein E (apoE) receptors, members of the low-density lipoprotein receptor (LDLR) family, modulate Abeta production as well as Abeta cellular uptake. Abeta is derived from proteolytic processing of the amyloid precursor protein (APP), which interacts with several members of the LDLR family. Studies from our laboratory have focused on two members of the LDLR family, the LDLR-related protein (LRP) and LRP1B. Our in vitro studies have shown that while LRP's rapid endocytosis facilitates APP endocytic trafficking and processing to Abeta, LRP1B's slow endocytosis inhibits these processes. In addition to modulating APP endocytic trafficking, LRP's rapid endocytosis also facilitates Abeta cellular uptake by binding to Abeta either directly or via LRP ligands such as apoE. Our in vivo studies using transgenic mice have shown that overexpression of LRP in central nervous system (CNS) neurons increases soluble brain Abeta and this increase correlates with deficits in memory. Together our studies demonstrate that members of the LDLR family modulate APP processing and Abeta metabolism by several independent mechanisms. Understanding the pathways that modulate brain Abeta metabolism may enable the rational design of molecular medicine to treat AD.

The pathogenesis of senile plaques.

PubMed

Dickson, D W

1997-04-01

Senile plaques (SP) are complicated lesions composed of diverse amyloid peptides and associated molecules, degenerating neuronal processes,a nd reactive glia. Evidence suggests that diffuse, neurocentric amyloid deposits evolve over time with formation of discrete niduses that eventually become neuritic SP. The evidence for differential amyloid precursor protein metabolism that may favor deposition of A beta 17-42 in this early, possibly aging-related lesion is discussed. This latter molecule, also known as P3, may represent a benign form of amyloid, since it lacks domains associated with activation and recruitment of glia to SP. Subsequent to deposition of A beta 1-42 and then growth of the amyloid with precipitation of soluble A beta 1-40, in an Alzheimer disease-specific process, SP increasingly become associated with activated microglia and reactive astrocytes. In response to interaction with amyloid peptides and possibly glycated proteins, microglia and astrocytes produce a number of molecules that may be locally toxic to neuronal processes in the vicinity of SP, including cytokines, reactive oxygen and nitrogen intermediates, and proteases. They also produce factors that lead to their reciprocal activation and growth, which potentiate a local inflammatory cascade. Paired helical filament- (PHF) type neurites appear to be associated with SP only in so far as neurofibrillary degeneration has progressed to affect neurons in those regions where the plaque forms. Thus, PHF-type neurites are readily apparent in SP in the amygdala at an early stage, while they are late in primary cortices and never detected in cerebellar plaques; where only dystrophic neurites are detected. If the various stages of SP pathogenesis can be further clarified, it may be possible to develop rational approaches to therapy directed at site-, cell type-, and stage-specific interventions. Although controlling the local inflammatory microenvironment of SP may hold promise for slowing lesion pathogenesis, it still remains a fundamental challenge to determine the mechanism of neurodegeneration that results in widespread neurofibrillary degeneration and eventual synaptic and neuronal loss, which is considered to be the proximate cause of the clinical dementia syndrome.

Serum amyloid A secretion from monocytic leukaemia cell line THP-1 and cultured human peripheral monocytes.

PubMed

Yamada, T; Wada, A; Itoh, K; Igari, J

2000-07-01

Serum amyloid A (SAA), an acute-phase protein and a precursor of fibrous components in reactive amyloid deposits, is synthesized mainly in the liver under the stimulation of inflammation-related cytokines. In addition, the SAA gene is expressed in monocytes/macrophages, which are believed to play a central role in amyloid fibrillogenesis. Consequently, the pathogenic implication of SAA produced from these cells has been of major concern. Because SAA synthesis at the protein level in such cells has never been analyzed quantitatively, in this study an enzyme-linked immunosorbent assay was generated with a detection level sufficiently high to measure SAA concentrations in the culture supernatants of the human monocytic leukaemia cell line THP-1. SAA secretion by THP-1 with interleukin (IL)-1beta required the presence of dexamethasone as proposed previously. We also found that unidentified components in fetal calf serum (FCS) could induce SAA production by THP-1 in the presence of dexamethasone. These findings are in contrast to the results obtained from hepatoma cell line HepG2, in which IL-1beta alone could induce SAA secretion, while dexamethasone-supplemented FCS could not. The method was able to quantify SAA secreted from cultured human peripheral monocytes. The findings suggest that monocytes produce SAA in almost the same manner as THP-1. Thus, THP-1 cells can be utilized to investigate a distinctive manner of SAA production from monocytes.

BACE1, a major determinant of selective vulnerability of the brain to amyloid-beta amyloidogenesis, is essential for cognitive, emotional, and synaptic functions.

PubMed

Laird, Fiona M; Cai, Huaibin; Savonenko, Alena V; Farah, Mohamed H; He, Kaiwen; Melnikova, Tatyana; Wen, Hongjin; Chiang, Hsueh-Cheng; Xu, Guilian; Koliatsos, Vassilis E; Borchelt, David R; Price, Donald L; Lee, Hey-Kyoung; Wong, Philip C

2005-12-14

A transmembrane aspartyl protease termed beta-site APP cleavage enzyme 1 (BACE1) that cleaves the amyloid-beta precursor protein (APP), which is abundant in neurons, is required for the generation of amyloid-beta (Abeta) peptides implicated in the pathogenesis of Alzheimer's disease (AD). We now demonstrate that BACE1, enriched in neurons of the CNS, is a major determinant that predisposes the brain to Abeta amyloidogenesis. The physiologically high levels of BACE1 activity coupled with low levels of BACE2 and alpha-secretase anti-amyloidogenic activities in neurons is a major contributor to the accumulation of Abeta in the CNS, whereas other organs are spared. Significantly, deletion of BACE1 in APPswe;PS1DeltaE9 mice prevents both Abeta deposition and age-associated cognitive abnormalities that occur in this model of Abeta amyloidosis. Moreover, Abeta deposits are sensitive to BACE1 dosage and can be efficiently cleared from the CNS when BACE1 is silenced. However, BACE1 null mice manifest alterations in hippocampal synaptic plasticity as well as in performance on tests of cognition and emotion. Importantly, memory deficits but not emotional alterations in BACE1(-/-) mice are prevented by coexpressing APPswe;PS1DeltaE9 transgenes, indicating that other potential substrates of BACE1 may affect neural circuits related to emotion. Our results establish BACE1 and APP processing pathways as critical for cognitive, emotional, and synaptic functions, and future studies should be alert to potential mechanism-based side effects that may occur with BACE1 inhibitors designed to ameliorate Abeta amyloidosis in AD.

Familial Danish dementia: a novel form of cerebral amyloidosis associated with deposition of both amyloid-Dan and amyloid-beta.

PubMed

Holton, Janice L; Lashley, Tammaryn; Ghiso, Jorge; Braendgaard, Hans; Vidal, Ruben; Guerin, Christopher J; Gibb, Graham; Hanger, Diane P; Rostagno, Agueda; Anderton, Brian H; Strand, Catherine; Ayling, Hilary; Plant, Gordon; Frangione, Blas; Bojsen-Møller, Marie; Revesz, Tamas

2002-03-01

Familial Danish dementia (FDD) is pathologically characterized by widespread cerebral amyloid angiopathy (CAA), parenchymal protein deposits, and neurofibrillary degeneration. FDD is associated with a mutation of the BRI2 gene located on chromosome 13. In FDD there is a decamer duplication, which abolishes the normal stop codon, resulting in an extended precursor protein and the release of an amyloidogenic fragment, ADan. The aim of this study was to describe the major neuropathological changes in FDD and to assess the distribution of ADan lesions, neurofibrillary pathology, glial, and microglial response using conventional techniques, immunohistochemistry, confocal microscopy, and immunoelectron microscopy. We showed that ADan is widely distributed in the central nervous system (CNS) in the leptomeninges, blood vessels, and parenchyma. A predominance of parenchymal pre-amyloid (non-fibrillary) lesions was found. Abeta was also present in a proportion of both vascular and parenchymal lesions. There was severe neurofibrillary pathology, and tau immunoblotting revealed a triplet electrophoretic migration pattern comparable with PHF-tau. FDD is a novel form of CNS amyloidosis with extensive neurofibrillary degeneration occurring with parenchymal, predominantly pre-amyloid rather than amyloid, deposition. These findings support the notion that parenchymal amyloid fibril formation is not a prerequisite for the development of neurofibrillary tangles. The significance of concurrent ADan and Abeta deposition in FDD is under further investigation.

Glycation induces formation of amyloid cross-beta structure in albumin.

PubMed

Bouma, Barend; Kroon-Batenburg, Loes M J; Wu, Ya-Ping; Brünjes, Bettina; Posthuma, George; Kranenburg, Onno; de Groot, Philip G; Voest, Emile E; Gebbink, Martijn F B G

2003-10-24

Amyloid fibrils are components of proteinaceous plaques that are associated with conformational diseases such as Alzheimer's disease, transmissible spongiform encephalopathies, and familial amyloidosis. Amyloid polypeptides share a specific quarternary structure element known as cross-beta structure. Commonly, fibrillar aggregates are modified by advanced glycation end products (AGE). In addition, AGE formation itself induces protein aggregation. Both amyloid proteins and protein-AGE adducts bind multiligand receptors, such as receptor for AGE, CD36, and scavenger receptors A and B type I, and the serine protease tissue-type plasminogen activator (tPA). Based on these observations, we hypothesized that glycation induces refolding of globular proteins, accompanied by formation of cross-beta structure. Using transmission electron microscopy, we demonstrate here that glycated albumin condensates into fibrous or amorphous aggregates. These aggregates bind to amyloid-specific dyes Congo red and thioflavin T and to tPA. In contrast to globular albumin, glycated albumin contains amino acid residues in beta-sheet conformation, as measured with circular dichroism spectropolarimetry. Moreover, it displays cross-beta structure, as determined with x-ray fiber diffraction. We conclude that glycation induces refolding of initially globular albumin into amyloid fibrils comprising cross-beta structure. This would explain how glycated ligands and amyloid ligands can bind to the same multiligand "cross-beta structure" receptors and to tPA.

Aging increases amyloid beta-peptide-induced 8-iso-prostaglandin F2alpha release from rat brain.

PubMed

Brunetti, Luigi; Michelotto, Barbara; Orlando, Giustino; Recinella, Lucia; Di Nisio, Chiara; Ciabattoni, Giovanni; Vacca, Michele

2004-01-01

In order to investigate whether amyloid beta-peptide-induced oxidative damage in the brain could be related to aging, we studied the release of 8-iso-prostaglandin (PG)F2alpha, a stable marker of cellular oxidative stress, in brain synaptosomes from Wistar rats of different ages (3, 6, 12, 18 months old), both basally and after amyloid beta-peptide (1-40) perfusion. We found that basal release of 8-iso-PGF2alpha was not significantly different among all age groups of rats. Either phospholipase A2 activation induced by calcium ionophore A23187 (10 nM) or amyloid beta-peptide (5 microM) did not modify isoprostane release, when these substances were used alone. In contrast, amyloid beta-peptide (1-5 microM) preincubation caused a dose-dependent increase of A23187-stimulated 8-iso-PGF2alpha release in each age group, which was also strikingly correlated to aging of rats. Furthermore, ferric ammonium sulfate stimulates isoprostane production to levels comparable to those induced by amyloid beta-peptide. In conclusion, although 8-iso-PGF2alpha production from rat brain synaptosomes is independent from aging in the basal state, aging renders neurons more vulnerable to amyloid beta-peptide-induced oxidative toxicity.

Curcumin derivatives inhibit or modulate beta-amyloid precursor protein metabolism.

PubMed

Narlawar, Rajeshwar; Baumann, Karlheinz; Schubenel, Robert; Schmidt, Boris

2007-01-01

Curcumin-derived oxazoles and pyrazoles were synthesized in order to minimize the metal chelation properties of curcumin. The reduced rotational freedom and the absence of stereoisomers was anticipated to enhance the inhibition of gamma-secretase. Accordingly, the replacement of the 1,3-dicarbonyl moiety by isosteric heterocycles turned curcumin analogue oxazoles and pyrazoles into potent gamma-secretase inhibitors. Compounds 4a-i were found to be potent inhibitors of gamma-secretase and displayed activity in the low micromolar range. 2007 S. Karger AG, Basel

Nicergoline, a drug used for age-dependent cognitive impairment, protects cultured neurons against beta-amyloid toxicity.

PubMed

Caraci, Filippo; Chisari, Mariangela; Frasca, Giuseppina; Canonico, Pier Luigi; Battaglia, Angelo; Calafiore, Marco; Battaglia, Giuseppe; Bosco, Paolo; Nicoletti, Ferdinando; Copani, Agata; Sortino, Maria Angela

2005-06-14

Nicergoline, a drug used for the treatment of Alzheimer's disease and other types of dementia, was tested for its ability to protect neurons against beta-amyloid toxicity. Pure cultures of rat cortical neurons were challenged with a toxic fragment of beta-amyloid peptide (betaAP(25-35)) and toxicity was assessed after 24 h. Micromolar concentrations of nicergoline or its metabolite, MDL, attenuated betaAP(25-35)-induced neuronal death, whereas MMDL (another metabolite of nicergoline), the alpha1-adrenergic receptor antagonist, prazosin, or the serotonin 5HT-2 receptor antagonist, methysergide, were inactive. Nicergoline increased the basal levels of Bcl-2 and reduced the increase in Bax levels induced by beta-amyloid, indicating that the drug inhibits the execution of an apoptotic program in cortical neurons. In mixed cultures of rat cortical cells containing both neurons and astrocytes, nicergoline and MDL were more efficacious than in pure neuronal cultures in reducing beta-amyloid neurotoxicity. Experiments carried out in pure cultures of astrocytes showed that a component of neuroprotection was mediated by a mechanism of glial-neuronal interaction. The conditioned medium of cultured astrocytes treated with nicergoline or MDL for 72-96 h (collected 24 h after drug withdrawal) was neuroprotective when transferred to pure neuronal cultures challenged with beta-amyloid. In cultured astrocytes, nicergoline increased the intracellular levels of transforming-growth factor-beta and glial-derived neurotrophic factor, two trophic factors that are known to protect neurons against beta-amyloid toxicity. These results raise the possibility that nicergoline reduces neurodegeneration in the Alzheimer's brain.

Synaptic transmission block by presynaptic injection of oligomeric amyloid beta

PubMed Central

Moreno, Herman; Yu, Eunah; Pigino, Gustavo; Hernandez, Alejandro I.; Kim, Natalia; Moreira, Jorge E.; Sugimori, Mutsuyuki; Llinás, Rodolfo R.

2009-01-01

Early Alzheimer's disease (AD) pathophysiology is characterized by synaptic changes induced by degradation products of amyloid precursor protein (APP). The exact mechanisms of such modulation are unknown. Here, we report that nanomolar concentrations of intraaxonal oligomeric (o)Aβ42, but not oAβ40 or extracellular oAβ42, acutely inhibited synaptic transmission at the squid giant synapse. Further characterization of this phenotype demonstrated that presynaptic calcium currents were unaffected. However, electron microscopy experiments revealed diminished docked synaptic vesicles in oAβ42-microinjected terminals, without affecting clathrin-coated vesicles. The molecular events of this modulation involved casein kinase 2 and the synaptic vesicle rapid endocytosis pathway. These findings open the possibility of a new therapeutic target aimed at ameliorating synaptic dysfunction in AD. PMID:19304802

Neurobehavioral characterization of APP23 transgenic mice with the SHIRPA primary screen.

PubMed

Lalonde, R; Dumont, M; Staufenbiel, M; Strazielle, C

2005-02-10

The SHIRPA primary screen comprises 40 measures covering various reflexes and basic sensorimotor functions. This multi-test battery was used to compare non-transgenic controls with APP23 transgenic mice, expressing the 751 isoform of human beta-amyloid precursor protein and characterized by amyloid deposits in parenchyma and vessel walls. The APP23 mice were distinguishable from controls by pathological limb reflexes, myoclonic jumping, seizure activity, and tail malformation. In addition, this mouse model of Alzheimer's disease was also marked by a crooked swimming trajectory. APP23 mice were also of lighter weight and were less inclined to stay immobile during a transfer arousal test. Despite the neurologic signs, APP23 transgenic mice were not deficient in stationary beam, coat-hanger, and rotorod tests, indicating intact motor coordination abilities.

Hyperforin prevents beta-amyloid neurotoxicity and spatial memory impairments by disaggregation of Alzheimer's amyloid-beta-deposits.

PubMed

Dinamarca, M C; Cerpa, W; Garrido, J; Hancke, J L; Inestrosa, N C

2006-11-01

The major protein constituent of amyloid deposits in Alzheimer's disease (AD) is the amyloid beta-peptide (Abeta). In the present work, we have determined the effect of hyperforin an acylphloroglucinol compound isolated from Hypericum perforatum (St John's Wort), on Abeta-induced spatial memory impairments and on Abeta neurotoxicity. We report here that hyperforin: (1) decreases amyloid deposit formation in rats injected with amyloid fibrils in the hippocampus; (2) decreases the neuropathological changes and behavioral impairments in a rat model of amyloidosis; (3) prevents Abeta-induced neurotoxicity in hippocampal neurons both from amyloid fibrils and Abeta oligomers, avoiding the increase in reactive oxidative species associated with amyloid toxicity. Both effects could be explained by the capacity of hyperforin to disaggregate amyloid deposits in a dose and time-dependent manner and to decrease Abeta aggregation and amyloid formation. Altogether these evidences suggest that hyperforin may be useful to decrease amyloid burden and toxicity in AD patients, and may be a putative therapeutic agent to fight the disease.

Schisandrin B protects PC12 cells by decreasing the expression of amyloid precursor protein and vacuolar protein sorting 35★

PubMed Central

Yan, Mingmin; Mao, Shanping; Dong, Huimin; Liu, Baohui; Zhang, Qian; Pan, Gaofeng; Fu, Zhiping

2012-01-01

PC12 cell injury was induced using 20 μM amyloid β-protein 25–35 to establish a model of Alzheimer's disease. The cells were then treated with 5, 10, and 25 μM Schisandrin B. Methylthiazolyldiphenyl-tetrazolium bromide assays and Hoechst 33342 staining results showed that with increasing Schisandrin B concentration, the survival rate of PC12 cells injured by amyloid β-protein 25–35 gradually increased and the rate of apoptosis gradually decreased. Reverse transcription-PCR, immunocytochemical staining and western blot results showed that with increasing Schisandrin B concentration, the mRNA and protein expression of vacuolar protein sorting 35 and amyloid precursor protein were gradually decreased. Vacuolar protein sorting 35 and amyloid precursor protein showed a consistent trend for change. These findings suggest that 5, 10, and 25 μM Schisandrin B antagonizes the cellular injury induced by amyloid β-protein 25–35 in a dose-dependent manner. This may be caused by decreasing the expression of vacuolar protein sorting 35 and amyloid precursor protein. PMID:25745458

Ablation of Prion Protein in Wild Type Human Amyloid Precursor Protein (APP) Transgenic Mice Does Not Alter The Proteolysis of APP, Levels of Amyloid-β or Pathologic Phenotype

PubMed Central

Baybutt, Herbert; Diack, Abigail B.; Kellett, Katherine A. B.; Piccardo, Pedro; Manson, Jean C.

2016-01-01

The cellular prion protein (PrPC) has been proposed to play an important role in the pathogenesis of Alzheimer’s disease. In cellular models PrPC inhibited the action of the β-secretase BACE1 on wild type amyloid precursor protein resulting in a reduction in amyloid-β (Aβ) peptides. Here we have assessed the effect of genetic ablation of PrPC in transgenic mice expressing human wild type amyloid precursor protein (line I5). Deletion of PrPC had no effect on the α- and β-secretase proteolysis of the amyloid precursor protein (APP) nor on the amount of Aβ38, Aβ40 or Aβ42 in the brains of the mice. In addition, ablation of PrPC did not alter Aβ deposition or histopathology phenotype in this transgenic model. Thus using this transgenic model we could not provide evidence to support the hypothesis that PrPC regulates Aβ production. PMID:27447728

The pathogenic implication of abnormal interaction between apolipoprotein E isoforms, amyloid-beta peptides, and sulfatides in Alzheimer's disease.

PubMed

Han, Xianlin

2010-06-01

Alzheimer's disease (AD) is the most common cause of dementia in the aging population. Prior work has shown that the epsilon4 allele of apolipoprotein E (apoE4) is a major risk factor for "sporadic" AD, which accounts for >99% of AD cases without a defined underlying mechanism. Recently, we have demonstrated that sulfatides are substantially and specifically depleted at the very early stage of AD. To identify the mechanism(s) of sulfatide loss concurrent with AD onset, we have found that: (1) sulfatides are specifically associated with apoE-associated particles in cerebrospinal fluid (CSF); (2) apoE modulates cellular sulfatide levels; and (3) the modulation of sulfatide content is apoE isoform dependent. These findings not only lead to identification of the potential mechanisms underlying sulfatide depletion at the earliest stages of AD but also serve as mechanistic links to explain the genetic association of apoE4 with AD. Moreover, our recent studies further demonstrated that (1) apoE mediates sulfatide depletion in amyloid-beta precursor protein transgenic mice; (2) sulfatides enhance amyloid beta (Abeta) peptides binding to apoE-associated particles; (3) Abeta42 content notably correlates with sulfatide content in CSF; (4) sulfatides markedly enhance the uptake of Abeta peptides; and (5) abnormal sulfatide-facilitated Abeta uptake results in the accumulation of Abeta in lysosomes. Collectively, our studies clearly provide a link between apoE, Abeta, and sulfatides in AD and establish a foundation for the development of effective therapeutic interventions for AD.

Detection of isolated cerebrovascular beta-amyloid with Pittsburgh compound B.

PubMed

Greenberg, Steven M; Grabowski, Thomas; Gurol, M Edip; Skehan, Maureen E; Nandigam, R N Kaveer; Becker, John A; Garcia-Alloza, Monica; Prada, Claudia; Frosch, Matthew P; Rosand, Jonathan; Viswanathan, Anand; Smith, Eric E; Johnson, Keith A

2008-11-01

Imaging of cerebrovascular beta-amyloid (cerebral amyloid angiopathy) is complicated by the nearly universal overlap of this pathology with Alzheimer's pathology. We performed positron emission tomographic imaging with Pittsburgh Compound B on 42-year-old man with early manifestations of Iowa-type hereditary cerebral amyloid angiopathy, a form of the disorder with little or no plaque deposits of fibrillar beta-amyloid. The results demonstrated increased Pittsburgh Compound B retention selectively in occipital cortex, sparing regions typically labeled in Alzheimer's disease. These results offer compelling evidence that Pittsburgh Compound B positron emission tomography can noninvasively detect isolated cerebral amyloid angiopathy before overt signs of tissue damage such as hemorrhage or white matter lesions.

Increased β-amyloid deposition in Tg-SWDI transgenic mouse brain following in vivo lead exposure.

PubMed

Gu, Huiying; Robison, Gregory; Hong, Lan; Barrea, Raul; Wei, Xing; Farlow, Martin R; Pushkar, Yulia N; Du, Yansheng; Zheng, Wei

2012-09-03

Previous studies in humans and animals have suggested a possible association between lead (Pb) exposure and the etiology of Alzheimer's disease (AD). Animals acutely exposed to Pb display an over-expressed amyloid precursor protein (APP) and the ensuing accumulation of beta-amyloid (Aβ) in brain extracellular spaces. This study was designed to examine whether in vivo Pb exposure increased brain concentrations of Aβ, resulting in amyloid plaque deposition in brain tissues. Human Tg-SWDI APP transgenic mice, which genetically over-express amyloid plaques at age of 2-3 months, received oral gavages of 50mg/kg Pb acetate once daily for 6 weeks; a control group of the same mouse strain received the same molar concentration of Na acetate. ELISA results revealed a significant increase of Aβ in the CSF, brain cortex and hippocampus. Immunohistochemistry displayed a detectable increase of amyloid plaques in brains of Pb-exposed animals. Neurobehavioral test using Morris water maze showed an impaired spatial learning ability in Pb-treated mice, but not in C57BL/6 wild type mice with the same age. In vitro studies further uncovered that Pb facilitated Aβ fibril formation. Moreover, the synchrotron X-ray fluorescent studies demonstrated a high level of Pb present in amyloid plaques in mice exposed to Pb in vivo. Taken together, these data indicate that Pb exposure with ensuing elevated Aβ level in mouse brains appears to be associated with the amyloid plaques formation. Pb apparently facilitates Aβ fibril formation and participates in deposition of amyloid plaques. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

The glucagon-like peptides: a new genre in therapeutic targets for intervention in Alzheimer's disease.

PubMed

Perry, TracyAnn; Greig, Nigel H

2002-12-01

Glucagon-like peptide-1 (7-36)-amide (GLP-1) is an insulinotropic hormone, secreted from the enteroendocrine L cells of the intestinal tract in response to nutrient ingestion. It enhances pancreatic islet beta-cell proliferation and glucose-dependent insulin secretion, and lowers blood glucose in patients with type 2 diabetes mellitus. GLP-1 receptors, which are coupled to the cyclic AMP second messenger pathway, are expressed throughout the brains of rodents and humans. The chemoarchitecture of receptor distribution in the brain correlates well with a central role for GLP-1 in the regulation of food intake and response to aversive stress. We have recently reported that GLP-1 and several longer acting analogs that bind at the GLP-1 receptor, possess neurotrophic properties, and offer protection against glutamate-induced apoptosis and oxidative injury in cultured neuronal cells. Furthermore, GLP-1 can modify processing of the amyloid beta- protein precursor in cell culture and dose-dependently reduces amyloid beta-peptide levels in the brain in vivo. As such, this review discusses the known role of GLP-1 within the central nervous system, and considers the potential of GLP-1 and analogs as novel therapeutic targets for intervention in Alzheimer's disease (AD) and potentially other central and peripheral neurodegenerative conditions.

Differential regulation of amyloid-. beta. -protein mRNA expression within hippocampal neuronal subpopulations in Alzheimer disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Higgins, G.A.; Lewis, D.A.; Bahmanyar, S.

1988-02-01

The authors have mapped the neuroanatomical distribution of amyloid-..beta..-protein mRNA within neuronal subpopulations of the hippocampal formation in the cynomolgus monkey (Macaca fascicularis), normal aged human, and patients with Alzheimer disease. Amyloid-..beta..-protein mRNA appears to be expressed in all hippocampal neurons, but at different levels of abundance. In the central nervous system of monkey and normal aged human, image analysis shows that neurons of the dentate gyrus and cornu Ammonis fields contain a 2.5-times-greater hybridization signal than is present in neurons of the subiculum and entorhinal cortex. In contrast, in the Alzheimer disease hippocampal formation, the levels of amyloid-..beta..-protein mRNAmore » in the cornu Ammonis field 3 and parasubiculum are equivalent. These findings suggest that within certain neuronal subpopulations cell type-specific regulation of amyloid-..beta..-protein gene expression may be altered in Alzheimer disease.« less

Procollagen C-proteinase enhancer-1 (PCPE-1) interacts with beta2-microglobulin (beta2-m) and may help initiate beta2-m amyloid fibril formation in connective tissues.

PubMed

Morimoto, Hisanori; Wada, Jun; Font, Bernard; Mott, Joni D; Hulmes, David J S; Ookoshi, Tadakazu; Naiki, Hironobu; Yasuhara, Akihiro; Nakatsuka, Atsuko; Fukuoka, Kousuke; Takatori, Yuji; Ichikawa, Haruo; Akagi, Shigeru; Nakao, Kazushi; Makino, Hirofumi

2008-04-01

Dialysis related amyloidosis (DRA) is a progressive and serious complication in patients under long-term hemodialysis and mainly leads to osteo-articular diseases. Although beta(2)-microglobulin (beta2-m) is the major structural component of beta2-m amyloid fibrils, the initiation of amyloid formation is not clearly understood. Here, we have identified procollagen C-proteinase enhancer-1 (PCPE-1) as a new interacting protein with beta2-m by screening a human synovium cDNA library. The interaction of beta2-m with full-length PCPE-1 was confirmed by immunoprecipitation, solid-phase binding and pull-down assays. By yeast two-hybrid analysis and pull-down assay, beta2-m appeared to interact with PCPE-1 via the NTR (netrin-like) domain and not via the CUB (C1r/C1s, Uegf and BMP-1) domain region. In synovial tissues derived from hemodialysis patients with DRA, beta2-m co-localized and formed a complex with PCPE-1. beta2-m did not alter the basal activity of bone morphogenetic protein-1/procollagen C-proteinase (BMP-1/PCP) nor BMP-1/PCP activity enhanced by PCPE-1. PCPE-1 did not stimulate beta2-m amyloid fibril formation from monomeric beta2-m in vitro under acidic and neutral conditions as revealed by thioflavin T fluorescence spectroscopy and electron microscopy. Since PCPE-1 is abundantly expressed in connective tissues rich in type I collagen, it may be involved in the initial accumulation of beta2-m in selected tissues such as tendon, synovium and bone. Furthermore, since such preferential deposition of beta2-m may be linked to subsequent beta2-m amyloid fibril formation, the disruption of the interaction between beta2-m and PCPE-1 may prevent beta2-m amyloid fibril formation and therefore PCPE-1 could be a new target for the treatment of DRA.

Amyloid beta precursor protein regulates male sexual behavior.

PubMed

Park, Jin Ho; Bonthius, Paul J; Tsai, Houng-Wei; Bekiranov, Stefan; Rissman, Emilie F

2010-07-28

Sexual behavior is variable between individuals, ranging from celibacy to sexual addictions. Within normal populations of individual men, ranging from young to middle aged, testosterone levels do not correlate with libido. To study the genetic mechanisms that contribute to individual differences in male sexual behavior, we used hybrid B6D2F1 male mice, which are a cross between two common inbred strains (C57BL/6J and DBA/2J). Unlike most laboratory rodent species in which male sexual behavior is highly dependent upon gonadal steroids, sexual behavior in a large proportion of these hybrid male mice after castration is independent of gonadal steroid hormones and their receptors; thus, we have the ability to discover novel genes involved in this behavior. Gene expression arrays, validation of gene candidates, and transgenic mice that overexpress one of the genes of interest were used to reveal genes involved in maintenance of male sexual behavior. Several genes related to neuroprotection and neurodegeneration were differentially expressed in the hypothalamus of males that continued to mate after castration. Male mice overexpressing the human form of one of these candidate genes, amyloid beta precursor protein (APP), displayed enhanced sexual behavior before castration and maintained sexual activity for a longer duration after castration compared with controls. Our results reveal a novel and unexpected relationship between APP and male sexual behavior. We speculate that declining APP during normal aging in males may contribute to the loss of sexual function.

Mitochondria-targeted catalase reduces abnormal APP processing, amyloid β production and BACE1 in a mouse model of Alzheimer's disease: implications for neuroprotection and lifespan extension.

PubMed

Mao, Peizhong; Manczak, Maria; Calkins, Marcus J; Truong, Quang; Reddy, Tejaswini P; Reddy, Arubala P; Shirendeb, Ulziibat; Lo, Herng-Hsiang; Rabinovitch, Peter S; Reddy, P Hemachandra

2012-07-01

The purpose of this study was to investigate the protective effects of the mitochondria-targeted antioxidant catalase (MCAT) and lifespan extension in mice that express amyloid beta (Aβ). Using immunoblotting and immunostaining analyses, we measured the production of full-length amyloid precursor protein (APP), soluble APPα, C-terminal fragments CTF99 and CTF83, monomeric and oligomeric Aβ, Aβ deposits and beta site amyloid precursor protein cleaving enzyme 1 (BACE1), in different stages of disease progression in MCAT/AβPP and AβPP mice. Using quantitative reverse transcriptase polymerase chain reaction and immunostaining analyses, we studied the expression of catalase, BACE1, the Alzheimer's disease (AD) markers, synaptophysin, APP, neprilysin, insulin-degrading enzyme and transthyretin in MCAT, AβPP, MCAT/AβPP and wild-type (WT) mice. Using the high pressure liquid chromatography analysis of 8-hydroxy-2-deoxyguanosine, we measured oxidative DNA damage in the cerebral cortical tissues from MCAT, AβPP, MCAT/AβPP and WT mice. We found that the AβPP transgenic mice that carried the human MCAT gene lived 5 months longer than did the AβPP mice. We also found that the overexpression of MCAT in the brain sections from the MCAT/AβPP transgenic mice significantly correlated with a reduction in the levels of full-length APP, CTF99, BACE1, Aβ levels (40 and 42), Aβ deposits and oxidative DNA damage relative to the brain sections from the AβPP mice. Interestingly, we found significantly increased levels of soluble APPα and CTF83 in the MCAT/AβPP mice, relative to the AβPP mice. These data provide direct evidence that oxidative stress plays a primary role in AD etiopathology and that in MCAT mice express Aβ, MCAT prevents abnormal APP processing, reduces Aβ levels and enhances Aβ-degrading enzymes in mice at different ages, corresponding to different stages of disease progression. These findings indicate that mitochondria-targeted molecules may be an effective therapeutic approach to treat patients with AD.

Mitochondria-targeted catalase reduces abnormal APP processing, amyloid β production and BACE1 in a mouse model of Alzheimer's disease: implications for neuroprotection and lifespan extension

PubMed Central

Mao, Peizhong; Manczak, Maria; Calkins, Marcus J.; Truong, Quang; Reddy, Tejaswini P.; Reddy, Arubala P.; Shirendeb, Ulziibat; Lo, Herng-Hsiang; Rabinovitch, Peter S.; Reddy, P. Hemachandra

2012-01-01

The purpose of this study was to investigate the protective effects of the mitochondria-targeted antioxidant catalase (MCAT) and lifespan extension in mice that express amyloid beta (Aβ). Using immunoblotting and immunostaining analyses, we measured the production of full-length amyloid precursor protein (APP), soluble APPα, C-terminal fragments CTF99 and CTF83, monomeric and oligomeric Aβ, Aβ deposits and beta site amyloid precursor protein cleaving enzyme 1 (BACE1), in different stages of disease progression in MCAT/AβPP and AβPP mice. Using quantitative reverse transcriptase polymerase chain reaction and immunostaining analyses, we studied the expression of catalase, BACE1, the Alzheimer's disease (AD) markers, synaptophysin, APP, neprilysin, insulin-degrading enzyme and transthyretin in MCAT, AβPP, MCAT/AβPP and wild-type (WT) mice. Using the high pressure liquid chromatography analysis of 8-hydroxy-2-deoxyguanosine, we measured oxidative DNA damage in the cerebral cortical tissues from MCAT, AβPP, MCAT/AβPP and WT mice. We found that the AβPP transgenic mice that carried the human MCAT gene lived 5 months longer than did the AβPP mice. We also found that the overexpression of MCAT in the brain sections from the MCAT/AβPP transgenic mice significantly correlated with a reduction in the levels of full-length APP, CTF99, BACE1, Aβ levels (40 and 42), Aβ deposits and oxidative DNA damage relative to the brain sections from the AβPP mice. Interestingly, we found significantly increased levels of soluble APPα and CTF83 in the MCAT/AβPP mice, relative to the AβPP mice. These data provide direct evidence that oxidative stress plays a primary role in AD etiopathology and that in MCAT mice express Aβ, MCAT prevents abnormal APP processing, reduces Aβ levels and enhances Aβ-degrading enzymes in mice at different ages, corresponding to different stages of disease progression. These findings indicate that mitochondria-targeted molecules may be an effective therapeutic approach to treat patients with AD. PMID:22492996

Inflammation occurs early during the Abeta deposition process in TgCRND8 mice.

PubMed

Dudal, Sherri; Krzywkowski, Pascale; Paquette, Julie; Morissette, Céline; Lacombe, Diane; Tremblay, Patrick; Gervais, Francine

2004-08-01

Alzheimer's disease (AD) is characterized by a progressive cognitive decline leading to dementia and involves the deposition of amyloid-beta (Abeta) peptides into senile plaques. Other neuropathological features that accompany progression of the disease include a decrease in synaptic density, neurofibrillary tangles, dystrophic neurites, inflammation, and neuronal cell loss. In this study, we report the early kinetics of brain amyloid deposition and its associated inflammation in an early onset transgenic mouse model of AD (TgCRND8) harboring the human amyloid precursor protein gene with the Indiana and Swedish mutations. Both diffuse and compact plaques were detected as early as 9-10 weeks of age. Abeta-immunoreactive (Abeta-IR) plaques (4G8-positive) appeared first in the neocortex and amygdala, then in the hippocampal formation, and lastly in the thalamus. Compact plaques (ThioS-positive) with an amyloid core were observed as early as diffuse plaques were detected, but in lower numbers. Amyloid deposition increased progressively with age. The formation of plaques was concurrent with the appearance of activated microglial cells and shortly followed by the clustering of activated astrocytes around plaques at 13-14 weeks of age. This TgCRND8 mouse model allows for a rapid, time-dependent study of the relationship between the fibrillogenic process and the inflammatory response during the brain amyloidogenic process.

Amyloid and tau cerebrospinal fluid biomarkers in HIV infection.

PubMed

Gisslén, Magnus; Krut, Jan; Andreasson, Ulf; Blennow, Kaj; Cinque, Paola; Brew, Bruce J; Spudich, Serena; Hagberg, Lars; Rosengren, Lars; Price, Richard W; Zetterberg, Henrik

2009-12-22

Because of the emerging intersections of HIV infection and Alzheimer's disease, we examined cerebrospinal fluid (CSF) biomarkers related of amyloid and tau metabolism in HIV-infected patients. In this cross-sectional study we measured soluble amyloid precursor proteins alpha and beta (sAPPalpha and sAPPbeta), amyloid beta fragment 1-42 (Abeta1-42), and total and hyperphosphorylated tau (t-tau and p-tau) in CSF of 86 HIV-infected (HIV+) subjects, including 21 with AIDS dementia complex (ADC), 25 with central nervous system (CNS) opportunistic infections and 40 without neurological symptoms and signs. We also measured these CSF biomarkers in 64 uninfected (HIV-) subjects, including 21 with Alzheimer's disease, and both younger and older controls without neurological disease. CSF sAPPalpha and sAPPbeta concentrations were highly correlated and reduced in patients with ADC and opportunistic infections compared to the other groups. The opportunistic infection group but not the ADC patients had lower CSF Abeta1-42 in comparison to the other HIV+ subjects. CSF t-tau levels were high in some ADC patients, but did not differ significantly from the HIV+ neuroasymptomatic group, while CSF p-tau was not increased in any of the HIV+ groups. Together, CSF amyloid and tau markers segregated the ADC patients from both HIV+ and HIV- neuroasymptomatics and from Alzheimer's disease patients, but not from those with opportunistic infections. Parallel reductions of CSF sAPPalpha and sAPPbeta in ADC and CNS opportunistic infections suggest an effect of CNS immune activation or inflammation on neuronal amyloid synthesis or processing. Elevation of CSF t-tau in some ADC and CNS infection patients without concomitant increase in p-tau indicates neural injury without preferential accumulation of hyperphosphorylated tau as found in Alzheimer's disease. These biomarker changes define pathogenetic pathways to brain injury in ADC that differ from those of Alzheimer's disease.

Differential effects of amyloid-beta 1-40 and 1-42 fibrils on 5-HT1A serotonin receptors in rat brain.

PubMed

Verdurand, Mathieu; Chauveau, Fabien; Daoust, Alexia; Morel, Anne-Laure; Bonnefoi, Frédéric; Liger, François; Bérod, Anne; Zimmer, Luc

2016-04-01

Evidence accumulates suggesting a complex interplay between neurodegenerative processes and serotonergic neurotransmission. We have previously reported an overexpression of serotonin 5-HT1A receptors (5-HT(1A)R) after intrahippocampal injections of amyloid-beta 1-40 (Aβ40) fibrils in rats. This serotonergic reactivity paralleled results from clinical positron emission tomography studies with [(18)F]MPPF revealing an overexpression of 5-HT(1A)R in the hippocampus of patients with mild cognitive impairment. Because Aβ40 and Aβ42 isoforms are found in amyloid plaques, we tested in this study the hypothesis of a peptide- and region-specific 5-HT(1A)R reactivity by injecting them, separately, into the hippocampus or striatum of rats. [(18)F]MPPF in vitro autoradiography revealed that Aβ40 fibrils, but not Aβ42, were triggering an overexpression of 5-HT(1A)R in the hippocampus and striatum of rat brains after 7 days. Immunohistochemical approaches targeting neuronal precursor cells, mature neurons, and astrocytes showed that Aβ42 fibrils caused more pathophysiological damages than Aβ40 fibrils. The mechanisms of Aβ40 fibrils-induced 5-HT(1A)R expression remains unknown, but hypotheses including neurogenesis, glial expression, and axonal sprouting are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

Amyloidosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glenner, G.G.; Osserman, E.F.

1986-01-01

The subjects covered in this Symposium range through almost every clinical medical specialty. From an average of one paper in each of the past three Symposiums, the explosive interest in cerebral amyloidosis has led to the presentation of 12 papers on this subject in the present volume. The genetically predisposed familial amyloidotic processes, such as the polyneuropathies and familial Mediterranean fever have also stimulated extensive and intriguing investigations which have revealed the striking effect of a single amino acid substitution in transforming a normal protein into a lethal ''amyloidogenic'' one. This Symposium clearly depicts the advances since the first amyloidmore » fibril protein was definitively identified and defined 14 years ago. Since all amyloid fibril proteins so far described are variants of normal proteins, attention to gene abnormalities now becomes a significant focus as well as the pathogenic sequences which lead in these cases to twisted BETA-pleated sheet (amyloid) fibril formation. Tentative concepts such as the ''amyloidogenic protein precursor of the fibril,'' ''proteolysis as one mechanism of fibril formation,'' ''Congo red birefringence as a marker for the twisted BETA-pleated sheet protein'' are now substantiated by recurring confirmation. Even a prophylactic treatment for one of the amyloidotic conditions, familial Mediterranean fever, is now available. Predictably, as the pathogeneses of the amyloid diseases are individually deciphered, highly specific and directed therapies will evolve to treat their devastated victims.« less

Cerebrospinal Fluid Amyloid Beta and Tau Concentrations Are Not Modulated by 16 Weeks of Moderate- to High-Intensity Physical Exercise in Patients with Alzheimer Disease.

PubMed

Steen Jensen, Camilla; Portelius, Erik; Siersma, Volkert; Høgh, Peter; Wermuth, Lene; Blennow, Kaj; Zetterberg, Henrik; Waldemar, Gunhild; Gregers Hasselbalch, Steen; Hviid Simonsen, Anja

2016-01-01

Physical exercise may have some effect on cognition in patients with Alzheimer disease (AD). However, the underlying biochemical effects are unclear. Animal studies have shown that amyloid beta (Aβ), one of the pathological hallmarks of AD, can be altered with high levels of physical activity. The objective of this study was to elucidate the effect of 16 weeks of moderate- to high-intensity physical exercise on the biomarkers of AD, with special emphasis on the amyloidogenic pathway. From a total of 53 patients with AD participating in the Preserving Cognition, Quality of Life, Physical Health and Functional Ability in Alzheimer's Disease: The Effect of Physical Exercise (ADEX) study we analyzed cerebrospinal fluid samples for Aβ species, total tau (t-tau), phosphorylated tau (p-tau) and soluble amyloid precursor protein (sAPP) species. We also assessed the patients for apolipoprotein E ε4 (ApoE ε4) genotype. We found no effect of 16 weeks of physical exercise on the selected biomarkers, and no effect of ApoE ε4 genotype. Our findings suggest that the possible effect of physical exercise on cognition in patients with AD is not due to modulation of Aβ, t-tau, p-tau and sAPP species. © 2016 S. Karger AG, Basel.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallant,M.; Rak, M.; Szeghalmi, A.

The creatine/phosphocreatine system, regulated by creatine kinase, plays an important role in maintaining energy balance in the brain. Energy metabolism and the function of creatine kinase are known to be affected in Alzheimer diseased brain and in cells exposed to the {beta}-amyloid peptide. We used infrared microspectroscopy to examine hippocampal, cortical, and caudal tissue from 21-89-week-old transgenic mice expressing doubly mutant (K670N/M671L and V717F) amyloid precursor protein and displaying robust pathology from an early age. Microcrystalline deposits of creatine, suggestive of perturbed energetic status, were detected by infrared microspectroscopy in all animals with advanced plaque pathology. Relatively large creatine depositsmore » were also found in hippocampal sections from post-mortem Alzheimer diseased human brain, compared with hippocampus from non-demented brain. We therefore speculate that this molecule is a marker of the disease process.« less

Nucleation Process of a Fibril Precursor in the C-Terminal Segment of Amyloid-β

NASA Astrophysics Data System (ADS)

Baftizadeh, Fahimeh; Pietrucci, Fabio; Biarnés, Xevi; Laio, Alessandro

2013-04-01

By extended atomistic simulations in explicit solvent and bias-exchange metadynamics, we study the aggregation process of 18 chains of the C-terminal segment of amyloid-β, an intrinsically disordered protein involved in Alzheimer’s disease and prone to form fibrils. Starting from a disordered aggregate, we are able to observe the formation of an ordered nucleus rich in beta sheets. The rate limiting step in the nucleation pathway involves crossing a barrier of approximately 40kcal/mol and is associated with the formation of a very specific interdigitation of the side chains belonging to different sheets. This structural pattern is different from the one observed experimentally in a microcrystal of the same system, indicating that the structure of a “nascent” fibril may differ from the one of an “extended” fibril.

Development of magnetic resonance imaging based detection methods for beta amyloids via sialic acid-functionalized magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Kouyoumdjian, Hovig

The development of a non-invasive method for the detection of Alzheimer's disease is of high current interest, which can be critical in early diagnosis and in guiding preventive treatment of the disease. The aggregates of beta amyloids are a pathological hallmark of Alzheimer's disease. Carbohydrates such as sialic acid terminated gangliosides have been shown to play significant roles in initiation of amyloid aggregation. Herein, we report a biomimetic approach using sialic acid coated iron oxide superparamagnetic nanoparticles for in vitro detection in addition to the assessment of the in vivo mouse-BBB (Blood brain barrier) crossing of the BSA (bovine serum albumin)-modified ones. The sialic acid functionalized dextran nanoparticles were shown to bind with beta amyloids through several techniques including ELISA (enzyme linked immunosorbent assay), MRI (magnetic resonance imaging), TEM (transmission electron microscopy), gel electrophoresis and tyrosine fluorescence assay. The superparamagnetic nature of the nanoparticles allowed easy detection of the beta amyloids in mouse brains in both in vitro and ex vivo model by magnetic resonance imaging. Furthermore, the sialic acid nanoparticles greatly reduced beta amyloid induced cytotoxicity to SH-SY5Y neuroblastoma cells, highlighting the potential of the glyconanoparticles for detection and imaging of beta amyloids. Sialic acid functionalized BSA (bovine serum albumin) nanoparticles also showed significant binding to beta amyloids, through ELISA and ex vivo mouse brain MRI experiments. Alternatively, the BBB crossing was demonstrated by several techniques such as confocal microscopy, endocytosis, exocytosis assays and were affirmed by nanoparticles transcytosis assays through bEnd.3 endothelial cells. Finally, the BBB crossing was confirmed by analyzing the MRI signal of nanoparticle-injected CD-1 mice.

Cdk5: one of the links between senile plaques and neurofibrillary tangles?

PubMed

Lee, Ming-Sum; Tsai, Li-Huei

2003-04-01

The relationship between amyloid plaques and neurofibrillary tangles, the two pathologic hallmarks of Alzheimer's disease (AD), is an unknown and controversial subject. However, emerging evidence from genetic and biochemical studies suggests that accumulation of amyloid beta peptides may play a causative role in AD pathogenesis. This led to the amyloid hypothesis, which proposes that amyloid beta peptides disrupt neuronal metabolic and ionic homeostasis and cause aberrant activation of kinases and/or inhibition of phosphatases. The resulting alteration in kinase and phosphatase activities ultimately leads to hyperphosphorylation of tau and formation of neurofibrillary tangles. Cyclin-dependent kinase 5 (Cdk5) is a tau kinase whose activity is induced by amyloid beta peptides. Its deregulation may represent one of the signal transduction pathways that connect amyloid beta toxicity to tau hyperphosphorylation. This article reviews the functions and regulation of Cdk5. Evidence that suggests deregulation of Cdk5 activity in AD by virtue of calpain cleavage of its activator p35 to p25 will be discussed.

Recent progress on understanding the mechanisms of amyloid nucleation.

PubMed

Chatani, Eri; Yamamoto, Naoki

2018-04-01

Amyloid fibrils are supramolecular protein assemblies with a fibrous morphology and cross-β structure. The formation of amyloid fibrils typically follows a nucleation-dependent polymerization mechanism, in which a one-step nucleation scheme has widely been accepted. However, a variety of oligomers have been identified in early stages of fibrillation, and a nucleated conformational conversion (NCC) mechanism, in which oligomers serve as a precursor of amyloid nucleation and convert to amyloid nuclei, has been proposed. This development has raised the need to consider more complicated multi-step nucleation processes in addition to the simplest one-step process, and evidence for the direct involvement of oligomers as nucleation precursors has been obtained both experimentally and theoretically. Interestingly, the NCC mechanism has some analogy with the two-step nucleation mechanism proposed for inorganic and organic crystals and protein crystals, although a more dramatic conformational conversion of proteins should be considered in amyloid nucleation. Clarifying the properties of the nucleation precursors of amyloid fibrils in detail, in comparison with those of crystals, will allow a better understanding of the nucleation of amyloid fibrils and pave the way to develop techniques to regulate it.

Towards Alzheimer's beta-amyloid vaccination.

PubMed

Frenkel, D; Solomon, B

2001-01-01

Beta-amyloid pathology, the main hallmark of Alzheimer's disease (AD), has been linked to its conformational status and aggregation. We recently showed that site-directed monoclonal antibodies (mAbs) towards the N-terminal region of the human beta-amyloid peptide bind to preformed beta-amyloid fibrils (Abeta), leading to disaggregation and inhibition of their neurotoxic effect. Here we report the development of a novel immunization procedure to raise effective anti-aggregating amyloid beta-protein (AbetaP) antibodies, using as antigen filamentous phages displaying the only EFRH peptide found to be the epitope of these antibodies. Due to the high antigenicity of the phage no adjuvant is required to obtain high affinity anti-aggregating IgG antibodies in animals model, that exhibit identity to human AbetaP. Such antibodies are able to sequester peripheral AbetaP, thus avoiding passage through the blood brain barrier (BBB) and, as recently shown in a transgenic mouse model, to cross the BBB and dissolve already formed beta-amyloid plaques. To our knowledge, this is the first attempt to use as a vaccine a self-anti-aggregating epitope displayed on a phage, and this may pave the way to treat abnormal accumulation-peptide diseases, such as Alzheimer's disease or other amyloidogenic diseases. Copyright 2001 The International Association for Biologicals.

A Novel Amyloid Designable Scaffold and Potential Inhibitor Inspired by GAIIG of Amyloid Beta and the HIV-1 V3 loop.

PubMed

Kokotidou, C; Jonnalagadda, S V R; Orr, A A; Seoane-Blanco, M; Apostolidou, C P; van Raaij, M J; Kotzabasaki, M; Chatzoudis, A; Jakubowski, J M; Mossou, E; Forsyth, V T; Mitchell, E P; Bowler, M W; Llamas-Saiz, A L; Tamamis, P; Mitraki, A

2018-05-17

The GAIIG sequence, common to the amyloid beta peptide (residues 29-33) and to the HIV gp 120 (residues 24-28 in a typical V3 loop) self-assembles into amyloid fibrils, as suggested by theory and the experiments presented here. The longer YATGAIIGNII sequence from the V3 loop also self-assembles into amyloid fibrils, of which the first three and the last two residues are outside the amyloid GAIIG core. We postulate that this sequence, with suitable selected replacements at the flexible positions, can serve as a designable scaffold for novel amyloid-based materials. Moreover, we report the single X-ray crystal structure of the beta-breaker peptide GAIPIG at 1.05 Å resolution. This structural information could serve as the basis for structure-based design of potential inhibitors of amyloid formation. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Caffeine Blocks HIV-1 Tat-Induced Amyloid Beta Production and Tau Phosphorylation.

PubMed

Soliman, Mahmoud L; Geiger, Jonathan D; Chen, Xuesong

2017-03-01

The increased life expectancy of people living with HIV-1 who are taking effective anti-retroviral therapeutics is now accompanied by increased Alzheimer's disease (AD)-like neurocognitive problems and neuropathological features such as increased levels of amyloid beta (Aβ) and phosphorylated tau proteins. Others and we have shown that HIV-1 Tat promotes the development of AD-like pathology. Indeed, HIV-1 Tat once endocytosed into neurons can alter morphological features and functions of endolysosomes as well as increase Aβ generation. Caffeine has been shown to have protective actions against AD and based on our recent findings that caffeine can inhibit endocytosis in neurons and can prevent neuronal Aβ generation, we tested the hypothesis that caffeine blocks HIV-1 Tat-induced Aβ generation and tau phosphorylation. In SH-SY5Y cells over-expressing wild-type amyloid beta precursor protein (AβPP), we demonstrated that HIV-1 Tat significantly increased secreted levels and intracellular levels of Aβ as well as cellular protein levels of phosphorylated tau. Caffeine significantly decreased levels of secreted and cellular levels of Aβ, and significantly blocked HIV-1 Tat-induced increases in secreted and cellular levels of Aβ. Caffeine also blocked HIV-1 Tat-induced increases in cellular levels of phosphorylated tau. Furthermore, caffeine blocked HIV-1 Tat-induced endolysosome dysfunction as indicated by decreased protein levels of vacuolar-ATPase and increased protein levels of cathepsin D. These results further implicate endolysosome dysfunction in the pathogenesis of AD and HAND, and by virtue of its ability to prevent and/or block neuropathological features associated with AD and HAND caffeine might find use as an effective adjunctive therapeutic agent.

Electromagnetic pulse exposure induces overexpression of beta amyloid protein in rats.

PubMed

Jiang, Da-peng; Li, Jing; Zhang, Jie; Xu, Sheng-long; Kuang, Fang; Lang, Hai-yang; Wang, Ya-feng; An, Guang-zhou; Li, Jin-hui; Guo, Guo-zhen

2013-04-01

With the developing and widely used electromagnetic field (EMF) technology, more and more studies are focusing on the relationship between EMF and Alzheimer's disease (AD). Electromagnetic pulse (EMP) is one type of widely used EMF. This study aimed to clarify whether EMP exposure could induce cognitive and memory impairment, thus finding a possible relationship between EMP and AD. Forty healthy male Sprague Dawley rats were randomly divided into four groups. Animals, respectively, received 100, 1000, and 10,000 pulses EMP (field strength 50 kV/m, repetition rate 100 Hz) exposure and sham exposure when 2 months old. Monthly Morris water maze (MWM) was used to test the changes of cognitive and memory ability. Superoxide dismutase (SOD) activity and glutathione (GSH) content were used as oxidative stress indexes. Expressions of some types of Alzheimer's disease-related proteins were also detected. After exposure, EMP exposure caused clear cognitive and memory impairment compared with sham exposure group (p <0.05). Determination of oxidation indexes showed decreased SOD activity and GSH content in exposure groups compared with sham group. Immunohistochemical (IHC) staining showed increased beta amyloid protein (Aβ) in EMP exposure groups compared with sham group. Western blot experiments showed increased expressions of Aβ oligomer and beta amyloid protein precursor (APP) in EMP exposure groups. Increased expression of microtubule-associated protein 1 light chain 3-II (LC3-II) was also found. The present results showed that EMP exposure can cause long-term impairment in impaired cognition and memory of rats, resulting in AD-like symptoms. This may be induced by enhancing oxidative stress and is related to autophagy dysfunction. Copyright © 2013 IMSS. Published by Elsevier Inc. All rights reserved.

Mitochondria-targeted antioxidants protect against amyloid-beta toxicity in Alzheimer's disease neurons.

PubMed

Manczak, Maria; Mao, Peizhong; Calkins, Marcus J; Cornea, Anda; Reddy, Arubala P; Murphy, Michael P; Szeto, Hazel H; Park, Byung; Reddy, P Hemachandra

2010-01-01

The purpose of our study was to investigate the effects of the mitochondria-targeted antioxidants, MitoQ and SS31, and the anti-aging agent resveratrol on neurons from a mouse model (Tg2576 line) of Alzheimer's disease (AD) and on mouse neuroblastoma (N2a) cells incubated with the amyloid-beta (Abeta) peptide. Using electron and confocal microscopy, gene expression analysis, and biochemical methods, we studied mitochondrial structure and function and neurite outgrowth in N2a cells treated with MitoQ, SS31, and resveratrol, and then incubated with Abeta. In N2a cells only incubated with the Abeta, we found increased expressions of mitochondrial fission genes and decreased expression of fusion genes and also decreased expression of peroxiredoxins. Electron microscopy of the N2a cells incubated with Abeta revealed a significantly increased number of mitochondria, indicating that Abeta fragments mitochondria. Biochemical analysis revealed that function is defective in mitochondria. Neurite outgrowth was significantly decreased in Abeta-incubated N2a cells, indicating that Abeta affects neurite outgrowth. However, in N2a cells treated with MitoQ, SS31, and resveratrol, and then incubated with Abeta, abnormal expression of peroxiredoxins and mitochondrial structural genes were prevented and mitochondrial function was normal; intact mitochondria were present and neurite outgrowth was significantly increased. In primary neurons from amyloid-beta precursor protein transgenic mice that were treated with MitoQ and SS31, neurite outgrowth was significantly increased and cyclophilin D expression was significantly decreased. These findings suggest that MitoQ and SS31 prevent Abeta toxicity, which would warrant the study of MitoQ and SS31 as potential drugs to treat patients with AD.

AbetaPP/APLP2 family of Kunitz serine proteinase inhibitors regulate cerebral thrombosis.

PubMed

Xu, Feng; Previti, Mary Lou; Nieman, Marvin T; Davis, Judianne; Schmaier, Alvin H; Van Nostrand, William E

2009-04-29

The amyloid beta-protein precursor (AbetaPP) is best recognized as the precursor to the Abeta peptide that accumulates in the brains of patients with Alzheimer's disease, but less is known about its physiological functions. Isoforms of AbetaPP that contain a Kunitz-type serine proteinase inhibitor (KPI) domain are expressed in brain and, outside the CNS, in circulating blood platelets. Recently, we showed that KPI-containing forms of AbetaPP regulates cerebral thrombosis in vivo (Xu et al., 2005, 2007). Amyloid precursor like protein-2 (APLP2), a closely related homolog to AbetaPP, also possesses a highly conserved KPI domain. Virtually nothing is known of its function. Here, we show that APLP2 also regulates cerebral thrombosis risk. Recombinant purified KPI domains of AbetaPP and APLP2 both inhibit the plasma clotting in vitro. In a carotid artery thrombosis model, both AbetaPP(-/-) and APLP2(-/-) mice exhibit similar significantly shorter times to vessel occlusion compared with wild-type mice indicating a prothrombotic phenotype. Similarly, in an experimental model of intracerebral hemorrhage, both AbetaPP(-/-) and APLP2(-/-) mice produce significantly smaller hematomas with reduced brain hemoglobin content compared with wild-type mice. Together, these results indicate that AbetaPP and APLP2 share overlapping anticoagulant functions with regard to regulating thrombosis after cerebral vascular injury.

The E2 Domains of APP and APLP1 Share a Conserved Mode of Dimerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

S Lee; Y Xue; J Hulbert

2011-12-31

Amyloid precursor protein (APP) is genetically linked to Alzheimer's disease. APP is a type I membrane protein, and its oligomeric structure is potentially important because this property may play a role in its function or affect the processing of the precursor by the secretases to generate amyloid {beta}-peptide. Several independent studies have shown that APP can form dimers in the cell, but how it dimerizes remains controversial. At least three regions of the precursor, including a centrally located and conserved domain called E2, have been proposed to contribute to dimerization. Here we report two new crystal structures of E2, onemore » from APP and the other from APLP1, a mammalian APP homologue. Comparison with an earlier APP structure, which was determined in a different space group, shows that the E2 domains share a conserved and antiparallel mode of dimerization. Biophysical measurements in solution show that heparin binding induces E2 dimerization. The 2.1 {angstrom} resolution electron density map also reveals phosphate ions that are bound to the protein surface. Mutational analysis shows that protein residues interacting with the phosphate ions are also involved in heparin binding. The locations of two of these residues, Arg-369 and His-433, at the dimeric interface suggest a mechanism for heparin-induced protein dimerization.« less

A {beta}{sub 2}-microglobulin cleavage variant fibrillates at near-physiological pH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Corlin, Dorthe B.; Johnsen, Christina K.; Nissen, Mogens H.

2009-04-03

{beta}{sub 2}-microglobulin ({beta}{sub 2}m) deposits as amyloid in dialysis-related amyloidosis (DRA), predominantly in joints. The molecular mechanisms underlying the amyloidogenicity of {beta}{sub 2}m are still largely unknown. In vitro, acidic conditions, pH < 4.5, induce amyloid fibrillation of native {beta}{sub 2}m within several days. Here, we show that amyloid fibrils are generated in less than an hour when a cleavage variant of {beta}{sub 2}m-found in the circulation of many dialysis patients-is exposed to pH levels (pH 6.6) occurring in joints during inflammation. Aggregation and fibrillation, including seeding effects with intact, native {beta}{sub 2}m were studied by Thioflavin T fluorescence spectroscopy,more » turbidimetry, capillary electrophoresis, and electron microscopy. We conclude that a biologically relevant variant of {beta}{sub 2}m is amyloidogenic at slightly acidic pH. Also, only a very small amount of preformed fibrils of this variant is required to induce fibrillation of native {beta}{sub 2}m. This may explain the apparent lack of detectable amounts of the variant {beta}{sub 2}m in extracts of amyloid from DRA patients.« less

Stereoselective determination of amino acids in beta-amyloid peptides and senile plaques.

PubMed

Thorsén, G; Bergquist, J; Westlind-Danielsson, A; Josefsson, B

2001-06-01

A novel method for the determination of the enantiomeric composition of peptides is presented. In this paper, the focus has been on beta-amyloid peptides from deceased Alzheimer's disease patients. The peptides are hydrolyzed using mineral acid. The free amino acids are derivatized with the chiral reagent (+)- or (-)-1-(9-anthryl)-2-propyl chloroformate and subsequently separated using micellar electrokinetic chromatography (MEKC) and detected using laser-induced fluorescence (LIF) detection. The high separation efficiency of the MEKC-LIF system, yielding approximately 1 million theoretical plates/m for most amino acids, facilitates the simultaneous chiral determination of nine amino acids. The samples that have been analyzed were standard 1-40 beta-amyloid peptides, in vitro precipitated beta-amyloid fibrils, and human senile plaque samples.

Activation of Ras-ERK Signaling and GSK-3 by Amyloid Precursor Protein and Amyloid Beta Facilitates Neurodegeneration in Alzheimer's Disease.

PubMed

Kirouac, Lisa; Rajic, Alexander J; Cribbs, David H; Padmanabhan, Jaya

2017-01-01

It is widely accepted that amyloid β (Aβ) generated from amyloid precursor protein (APP) oligomerizes and fibrillizes to form neuritic plaques in Alzheimer's disease (AD), yet little is known about the contribution of APP to intracellular signaling events preceding AD pathogenesis. The data presented here demonstrate that APP expression and neuronal exposure to oligomeric Aβ42 enhance Ras/ERK signaling cascade and glycogen synthase kinase 3 (GSK-3) activation. We find that RNA interference (RNAi)-directed knockdown of APP in B103 rat neuroblastoma cells expressing APP inhibits Ras-ERK signaling and GSK-3 activation, indicating that APP acts upstream of these signal transduction events. Both ERK and GSK-3 are known to induce hyperphosphorylation of tau and APP at Thr668, and our findings suggest that aberrant signaling by APP facilitates these events. Supporting this notion, analysis of human AD brain samples showed increased expression of Ras, activation of GSK-3, and phosphorylation of APP and tau, which correlated with Aβ levels in the AD brains. Furthermore, treatment of primary rat neurons with Aβ recapitulated these events and showed enhanced Ras-ERK signaling, GSK-3 activation, upregulation of cyclin D1, and phosphorylation of APP and tau. The finding that Aβ induces Thr668 phosphorylation on APP, which enhances APP proteolysis and Aβ generation, denotes a vicious feedforward mechanism by which APP and Aβ promote tau hyperphosphorylation and neurodegeneration in AD. Based on these results, we hypothesize that aberrant proliferative signaling by APP plays a fundamental role in AD neurodegeneration and that inhibition of this would impede cell cycle deregulation and neurodegeneration observed in AD.

Spirocyclic β-site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitors: from hit to lowering of cerebrospinal fluid (CSF) amyloid β in a higher species.

PubMed

Hunt, Kevin W; Cook, Adam W; Watts, Ryan J; Clark, Christopher T; Vigers, Guy; Smith, Darin; Metcalf, Andrew T; Gunawardana, Indrani W; Burkard, Michael; Cox, April A; Geck Do, Mary K; Dutcher, Darrin; Thomas, Allen A; Rana, Sumeet; Kallan, Nicholas C; DeLisle, Robert K; Rizzi, James P; Regal, Kelly; Sammond, Douglas; Groneberg, Robert; Siu, Michael; Purkey, Hans; Lyssikatos, Joseph P; Marlow, Allison; Liu, Xingrong; Tang, Tony P

2013-04-25

A hallmark of Alzheimer's disease is the brain deposition of amyloid beta (Aβ), a peptide of 36-43 amino acids that is likely a primary driver of neurodegeneration. Aβ is produced by the sequential cleavage of APP by BACE1 and γ-secretase; therefore, inhibition of BACE1 represents an attractive therapeutic target to slow or prevent Alzheimer's disease. Herein we describe BACE1 inhibitors with limited molecular flexibility and molecular weight that decrease CSF Aβ in vivo, despite efflux. Starting with spirocycle 1a, we explore structure-activity relationships of core changes, P3 moieties, and Asp binding functional groups in order to optimize BACE1 affinity, cathepsin D selectivity, and blood-brain barrier (BBB) penetration. Using wild type guinea pig and rat, we demonstrate a PK/PD relationship between free drug concentrations in the brain and CSF Aβ lowering. Optimization of brain exposure led to the discovery of (R)-50 which reduced CSF Aβ in rodents and in monkey.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong,Z.; Bennett, D.; Chapman, D.

We explored diffraction enhanced imaging (DEI) in both planar and computed tomography (CT) modes for early detection of beta amyloid deposition, a hallmark feature in Alzheimer's disease (AD). Since amyloid plaques precede clinical symptoms by years, their early detection is of great interest. These findings were correlated with results from synchrotron infrared microspectroscopic imaging and X-ray fluorescence microscopy, to determine the secondary structure of the amyloid beta protein and metal concentration in the amyloid plaques, respectively.

Alpha-2 macroglobulin is genetically associated with Alzheimer disease.

PubMed

Blacker, D; Wilcox, M A; Laird, N M; Rodes, L; Horvath, S M; Go, R C; Perry, R; Watson, B; Bassett, S S; McInnis, M G; Albert, M S; Hyman, B T; Tanzi, R E

1998-08-01

Alpha-2-macroglobulin (alpha-2M; encoded by the gene A2M) is a serum pan-protease inhibitor that has been implicated in Alzheimer disease (AD) based on its ability to mediate the clearance and degradation of A beta, the major component of beta-amyloid deposits. Analysis of a deletion in the A2M gene at the 5' splice site of 'exon II' of the bait region (exon 18) revealed that inheritance of the deletion (A2M-2) confers increased risk for AD (Mantel-Haenzel odds ratio=3.56, P=0.001). The sibship disequilibrium test (SDT) also revealed a significant association between A2M and AD (P=0.00009). These values were comparable to those obtained for the APOE-epsilon4 allele in the same sample, but in contrast to APOE-epsilon4, A2M-2 did not affect age of onset. The observed association of A2M with AD did not appear to account for the previously published linkage of AD to chromosome 12, which we were unable to confirm in this sample. A2M, LRP1 (encoding the alpha-2M receptor) and the genes for two other LRP ligands, APOE and APP (encoding the amyloid beta-protein precursor), have now all been genetically linked to AD, suggesting that these proteins may participate in a common neuropathogenic pathway leading to AD.

Novel Roles of Amyloid-Beta Protein Precursor Metabolites in Fragile X Syndrome and Autism

PubMed Central

Westmark, Cara J.; Sokol, Deborah K.; Maloney, Bryan; Lahiri, Debomoy K.

2017-01-01

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and is associated with up to 5% of autism cases. Several promising drugs are in preclinical testing for FXS; however, bench-to-bedside plans for the clinic are severely limited due to lack of validated biomarkers and outcome measures. Published work from our laboratories has demonstrated altered levels of amyloid-beta (Aβ) protein precursor (APP) and its metabolites in FXS and idiopathic autism. Westmark and colleagues have focused on β-secretase (amyloidogenic) processing and the accumulation of Aβ peptides in adult FXS models while Lahiri and Sokol have studied α-secretase (nonamyloidogenic or anabolic) processing and altered levels of sAPPα and Aβ in pediatric autism and FXS. Thus, our groups have hypothesized a pivotal role for these Alzheimer’s disease (AD)-related proteins in the neurodevelopmental disorders of FXS and autism. In this review, we discuss the contribution of APP metabolites to FXS and autism pathogenesis as well as the potential use of these metabolites as blood-based biomarkers and therapeutic targets. Our future focus is to identify key underlying mechanisms through which APP metabolites contribute to FXS and autism condition-to-disease pathology. Positive outcomes will support utilizing APP metabolites as blood-based biomarkers in clinical trials as well as testing drugs that modulate APP processing as potential disease therapeutics. Our studies to understand the role of APP metabolites in developmental conditions such as FXS and autism are a quantum leap for the neuroscience field, which has traditionally restricted any role of APP to AD and aging. PMID:27573877

Fluorescence fluctuation analysis of BACE1-GFP fusion protein in cultured HEK293 cells

NASA Astrophysics Data System (ADS)

Gardeen, Spencer; Johnson, Joseph L.; Heikal, Ahmed A.

2016-10-01

Beta-site APP cleaving enzyme 1 (BACE1) is a type I transmembrane aspartyl protease. In the amyloidogenic pathway, BACE1 provides β-secretase activity that cleaves the amyloid precursor protein (APP) that leads to amyloid beta (Aβ) peptides. The aggregation of these Aβ will ultimately results in amyloid plaque formation, a hallmark of Alzheimer's disease (AD). Amyloid aggregation leads to progressive memory impairment and neural loss. Recent detergent protein extraction studies suggest that the untreated BACE1 protein forms a dimer that has significantly higher catalytic activity than its monomeric counterpart. Here, we examine the dimerization hypothesis of BACE1 in cultured HEK293 cells using fluorescence correlation spectroscopy (FCS). Cells were transfected with a BACE1-EGFP fusion protein construct and imaged using confocal and DIC microscopy to monitor labeled BACE1 localization and distribution within the cell. Our one-photon fluorescence fluctuation autocorrelation of BACE1- EGFP on the plasma membrane of HEK cells is modeled using two diffusing species on the plasma membrane with estimated diffusion coefficients of 1.39 x 10-7 cm2/sec and 2.8 x 10-8 cm2/sec under resting conditions and STA-200 inhibition, respectively. Anomalous diffusion model also provided adequate description of the observed autocorrelation function of BACE1- EGFP on the plasma membrane with an estimate exponent (α) of 0.8 and 0.5 for resting and STA-200 treated cells, respectively. The corresponding hydrodynamic radius of this transmembrane fusion protein was estimated using the measured diffusion coefficients assuming both Stokes-Einstein and Saffman-Delbruck models. Our results suggest a complex diffusion pattern of BACE1-EGFP on the plasma membrane of HEK cells with the possibility for dimer formation, especially under STA-200 inhibition.

Amyloid precursor protein expression is enhanced in human platelets from subjects with Alzheimer's disease and frontotemporal lobar degeneration: a real-time PCR study.

PubMed

Vignini, Arianna; Morganti, Stefano; Salvolini, Eleonora; Sartini, Davide; Luzzi, Simona; Fiorini, Rosamaria; Provinciali, Leandro; Di Primio, Roberto; Mazzanti, Laura; Emanuelli, Monica

2013-12-01

Frontotemporal lobar degeneration (FTLD) and Alzheimer's disease (AD) represent the most frequent causes of early-onset and late-onset degenerative dementia, respectively. A correct diagnosis entails the choice of appropriate therapies. In this view the present study aimed to identify biomarkers that could improve the differential diagnosis. We recently found an overexpression of platelet amyloid precursor protein (APP) in AD; furthermore, recent studies have suggested the presence of changes in APP processing in FTLD. In this context, we analyzed the mRNA expression level of Total APP (TOT) and APP containing a Kunitz-type serine protease inhibitor domain (KPI) in platelets obtained from AD patients, subjects with FTLD, and healthy subjects. In addition, we evaluated the correlation between platelet APP mRNA expression levels and cognitive impairment.Differential gene expression measurements revealed a significant up-regulation of APP TOT and APP KPI in both AD and FTLD patients compared to the controls (being AD/Controls: 1.67 for APP TOT and 1.47 for APP KPI; FTLD/Controls: 1.62 for APP TOT and 1.51 for APP KPI; p < 0.05), although it is interesting to note that in FTLD patients this expression did not correlate with the severity of cognitive impairment.This could be related to a reduced beta-amyloid (Aβ) formation, caused by an alteration of secretase enzymatic activity, even though a post-transcriptional regulation of APP mRNAs in FTLD cannot be excluded.

Amyloid precursor protein expression is enhanced in human platelets from subjects with Alzheimer's disease and Frontotemporal lobar degeneration: A Real-time PCR study.

PubMed

Vignini, Arianna; Morganti, Stefano; Salvolini, Eleonora; Sartini, Davide; Luzzi, Simona; Fiorini, Rosamaria; Provinciali, Leandro; Di Primio, Roberto; Mazzanti, Laura; Emanuelli, Monica

2013-10-26

Frontotemporal lobar degeneration (FTLD) and Alzheimer's disease (AD) represent the most frequent causes of early-onset and late-onset degenerative dementia, respectively. A correct diagnosis entails the choice of appropriate therapies. In this view the present study aimed to identify biomarkers that could improve the differential diagnosis. We recently found an overexpression of platelet amyloid precursor protein (APP) in AD; furthermore, recent studies have suggested the presence of changes in APP processing in FTLD. In this context, we analyzed the mRNA expression level of Total APP (TOT) and APP containing a Kunitz-type serine protease inhibitor domain (KPI) in platelets obtained from AD patients, subjects with FTLD, and healthy subjects. In addition, we evaluated the correlation between platelet APP mRNA expression levels and cognitive impairment. Differential gene expression measurements revealed a significant up-regulation of APP TOT and APP KPI in both AD and FTLD patients compared to the controls (being AD/Controls: 1.67 for APP TOT and 1.47 for APP KPI; FTLD/Controls: 1.62 for APP TOT and 1.51 for APP KPI; p<0.05) , although it is interesting to note that in FTLD patients this expression did not correlate with the severity of cognitive impairment. This could be related to a reduced beta-amyloid (Aβ) formation, caused by an alteration of secretase enzymatic activity, even though a post-transcriptional regulation of APP mRNAs in FTLD cannot be excluded. © 2013.

GGA1 regulates signal-dependent sorting of BACE1 to recycling endosomes, which moderates Aβ production

PubMed Central

Toh, Wei Hong; Chia, Pei Zhi Cheryl; Hossain, Mohammed Iqbal; Gleeson, Paul A.

2018-01-01

The diversion of the membrane-bound β-site amyloid precursor protein–(APP) cleaving enzyme (BACE1) from the endolysosomal pathway to recycling endosomes represents an important transport step in the regulation of amyloid beta (Aβ) production. However, the mechanisms that regulate endosome sorting of BACE1 are poorly understood. Here we assessed the transport of BACE1 from early to recycling endosomes and have identified essential roles for the sorting nexin 4 (SNX4)-mediated, signal-independent pathway and for a novel signal-mediated pathway. The signal-mediated pathway is regulated by the phosphorylation of the DXXLL-motif sequence DISLL in the cytoplasmic tail of BACE1. The phosphomimetic S498D BACE1 mutant was trafficked to recycling endosomes at a faster rate compared with wild-type BACE1 or the nonphosphorylatable S498A mutant. The rapid transit of BACE1 S498D from early endosomes was coupled with reduced levels of amyloid precursor protein processing and Aβ production, compared with the S498A mutant. We show that the adaptor, GGA1, and retromer are essential to mediate rapid trafficking of phosphorylated BACE1 to recycling endosomes. In addition, the BACE1 DISLL motif is phosphorylated and regulates endosomal trafficking, in primary neurons. Therefore, post-translational phosphorylation of DISLL enhances the exit of BACE1 from early endosomes, a pathway mediated by GGA1 and retromer, which is important in regulating Aβ production. PMID:29142073

Sortilin-related receptor 1 interacts with amyloid precursor protein and is activated by 6-shogaol, leading to inhibition of the amyloidogenic pathway.

PubMed

Na, Ji-Young; Song, Kibbeum; Lee, Ju-Woon; Kim, Sokho; Kwon, Jungkee

2017-03-18

Sortilin-related receptor 1 (SORL1) is a neuronal sorting protein that reduces amyloid precursor protein (APP) trafficking to secretases that generate amyloid beta (Aβ). Although 6-shogaol, a constituent of ginger, has been reported to have anti-inflammatory and anti-oxidant effects on neuronal cells, research regarding the activation of SORL1 has not yet been reported. Here, we aimed to investigate whether 6-shogaol contributes to the increases in SORL1 that are related to Alzheimer's disease (AD). To clarify the effect of 6-shogaol as a possible activator of SORL1, we used SORL1 siRNA as a blockade of SORL1 in hippocampal neuronal cells (HT22). We found that SORL1 siRNA treatment naturally inhibited SORL1 and led to increases in β-secretase APP cleaving enzyme (BACE), secreted APP-β (sAPPβ) and Aβ. In contrast, 6-shogaol-mediated activation of SORL1 significantly downregulated BACE, sAPPβ, and Aβ in both in vitro HT22 cells and in vivo APPSw/PS1-dE9 Tg mice. Therefore, SORL1 activation by 6-shogaol provides neuronal cell survival through the inhibition of Aβ production. These results indicate that 6-shogaol should be regarded as an SORL1 activator and a potential preventive agent for the treatment of AD. Copyright © 2017 Elsevier Inc. All rights reserved.

Pittsburgh Compound B and AV-1451 positron emission tomography assessment of molecular pathologies of Alzheimer's disease in progressive supranuclear palsy.

PubMed

Whitwell, Jennifer L; Ahlskog, J Eric; Tosakulwong, Nirubol; Senjem, Matthew L; Spychalla, Anthony J; Petersen, Ronald C; Jack, Clifford R; Lowe, Val J; Josephs, Keith A

2018-03-01

Little is known about Alzheimer's disease molecular proteins, beta-amyloid and paired helical filament (PHF) tau, in progressive supranuclear palsy (PSP). Recent techniques have been developed to allow for investigations of these proteins in PSP. We determined the frequency of beta-amyloid deposition in PSP, and whether beta-amyloid deposition in PSP is associated with PHF-tau deposition pattern, or clinical features. Thirty probable PSP participants underwent MRI, [ 18 F]AV-1451 PET and Pittsburgh compound B (PiB) PET. Apolipoprotein (APOE) genotyping was also performed. A global PiB standard-uptake value ratio (SUVR) was calculated. AV-1451 SUVRs were calculated for a set of Alzheimer's disease (AD)-related regions and a set of PSP-related regions. Voxel-level analyses were conducted to assess for differences in AV-1451 uptake patterns and MRI atrophy between PiB(+) and PiB(-) cases compared to 60 normal PiB(-) controls. Statistical testing for correlations and associations between variables of interest were also performed. Twelve subjects (40%) showed beta-amyloid deposition. Higher PiB SUVR correlated with older age but not with AV-1451 SUVR in the AD- or PSP-related regions. Higher AV-1451 SUVR in AD-related regions was associated with higher AV-1451 SUVR in PSP-related regions. We found little evidence for beta-amyloid related differences in clinical metrics, proportion of APOE e4 carriers, pattern of AV-1451 uptake, or pattern of atrophy. Beta-amyloid deposition occurs in a relatively high proportion of PSP subjects. Unlike in Alzheimer's disease, however, there is little evidence that beta-amyloid, and PHF-tau, play a significant role in neurodegeneration in PSP. Copyright © 2017 Elsevier Ltd. All rights reserved.

Beta amyloid and hyperphosphorylated tau deposits in the pancreas in type 2 diabetes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miklossy, J.; Miller, L.; Qing, H.

2008-08-25

Strong epidemiologic evidence suggests an association between Alzheimer disease (AD) and type 2 diabetes. To determine if amyloid beta (A{beta}) and hyperphosphorylated tau occurs in type 2 diabetes, pancreas tissues from 21 autopsy cases (10 type 2 diabetes and 11 controls) were analyzed. APP and tau mRNAs were identified in human pancreas and in cultured insulinoma beta cells (INS-1) by RT-PCR. Prominent APP and tau bands were detected by Western blotting in pancreatic extracts. Aggregated A{beta}, hyperphosphorylated tau, ubiquitin, apolipoprotein E, apolipoprotein(a), IB1/JIP-1 and JNK1 were detected in Langerhans islets in type 2 diabetic patients. A{beta} was co-localized with amylinmore » in islet amyloid deposits. In situ beta sheet formation of islet amyloid deposits was shown by infrared microspectroscopy (SIRMS). LPS increased APP in non-neuronal cells as well. We conclude that A{beta} deposits and hyperphosphorylated tau are also associated with type 2 diabetes, highlighting common pathogenetic features in neurodegenerative disorders, including AD and type 2 diabetes and suggesting that A{beta} deposits and hyperphosphorylated tau may also occur in other organs than the brain.« less

{alpha}-Lipoic acid exhibits anti-amyloidogenicity for {beta}-amyloid fibrils in vitro

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ono, Kenjiro; Hirohata, Mie; Yamada, Masahito

2006-03-24

Inhibition of the formation of {beta}-amyloid fibrils (fA{beta}), as well as the destabilization of preformed fA{beta} in the CNS would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of {alpha}-lipoic acid (LA) and the metabolic product of LA, dihydrolipoic acid (DHLA), on the formation, extension, and destabilization of fA{beta} at pH 7.5 at 37 {sup o}C in vitro. LA and DHLA dose-dependently inhibited fA{beta} formation from amyloid {beta}-protein, as well as their extension. Moreover, they destabilized preformed fA{beta}s. LA and DHLA couldmore » be key molecules for the development of therapeutics for AD.« less

Discovery of isonicotinamide derived beta-secretase inhibitors: in vivo reduction of beta-amyloid.

PubMed

Stanton, Matthew G; Stauffer, Shaun R; Gregro, Alison R; Steinbeiser, Melissa; Nantermet, Philippe; Sankaranarayanan, Sethu; Price, Eric A; Wu, Guoxin; Crouthamel, Ming-Chih; Ellis, Joan; Lai, Ming-Tain; Espeseth, Amy S; Shi, Xiao-Ping; Jin, Lixia; Colussi, Dennis; Pietrak, Beth; Huang, Qian; Xu, Min; Simon, Adam J; Graham, Samuel L; Vacca, Joseph P; Selnick, Harold

2007-07-26

beta-Secretase inhibition offers an exciting opportunity for therapeutic intervention in the progression of Alzheimer's disease. A series of isonicotinamides derived from traditional aspartyl protease transition state isostere inhibitors has been optimized to yield low nanomolar inhibitors with sufficient penetration across the blood-brain barrier to demonstrate beta-amyloid lowering in a murine model.

The role of insulin receptor signaling in the brain.

PubMed

Plum, Leona; Schubert, Markus; Brüning, Jens C

2005-03-01

The insulin receptor (IR) is expressed in various regions of the developing and adult brain, and its functions have become the focus of recent research. Insulin enters the central nervous system (CNS) through the blood-brain barrier by receptor-mediated transport to regulate food intake, sympathetic activity and peripheral insulin action through the inhibition of hepatic gluconeogenesis and reproductive endocrinology. On a molecular level, some of the effects of insulin converge with those of the leptin signaling machinery at the point of activation of phosphatidylinositol 3-kinase (PI3K), resulting in the regulation of ATP-dependent potassium channels. Furthermore, insulin inhibits neuronal apoptosis via activation of protein kinase B in vitro, and it regulates phosphorylation of tau, metabolism of the amyloid precursor protein and clearance of beta-amyloid from the brain in vivo. These findings indicate that neuronal IR signaling has a direct role in the link between energy homeostasis, reproduction and the development of neurodegenerative diseases.

Mitochondria, Cybrids, Aging, and Alzheimer’s Disease

PubMed Central

Swerdlow, Russell H.; Koppel, Scott; Weidling, Ian; Hayley, Clay; Ji, Yan; Wilkins, Heather M.

2018-01-01

Mitochondrial and bioenergetic function change with advancing age and may drive aging phenotypes. Mitochondrial and bioenergetic changes are also documented in various age-related neurodegenerative diseases, including Alzheimer’s disease (AD). In some instances AD mitochondrial and bioenergetic changes are reminiscent of those observed with advancing age, but are greater in magnitude. Mitochondrial and bioenergetic dysfunction could, therefore, link neurodegeneration to brain aging. Interestingly, mitochondrial defects in AD patients are not brain-limited, and mitochondrial function can be linked to classic AD histologic changes including amyloid precursor protein processing to beta amyloid. Also, transferring mitochondria from AD subjects to cell lines depleted of endogenous mitochondrial DNA (mtDNA) creates cytoplasmic hybrid (cybrid) cell lines that recapitulate specific biochemical, molecular, and histologic AD features. Such findings have led to the formulation of a “mitochondrial cascade hypothesis” that places mitochondrial dysfunction at the apex of the AD pathology pyramid. Data pertinent to this premise are reviewed. PMID:28253988

Modulation of ABCA1 by an LXR Agonist Reduces Beta-Amyloid Levels and Improves Outcome after Traumatic Brain Injury

PubMed Central

Loane, David J.; Washington, Patricia M.; Vardanian, Lilit; Pocivavsek, Ana; Hoe, Hyang-Sook; Duff, Karen E.; Cernak, Ibolja; Rebeck, G. William; Faden, Alan I.

2011-01-01

Abstract Traumatic brain injury (TBI) increases brain beta-amyloid (Aβ) in humans and animals. Although the role of Aβ in the injury cascade is unknown, multiple preclinical studies have demonstrated a correlation between reduced Aβ and improved outcome. Therefore, therapeutic strategies that enhance Aβ clearance may be beneficial after TBI. Increased levels of ATP-binding cassette A1 (ABCA1) transporters can enhance Aβ clearance through an apolipoprotein E (apoE)-mediated pathway. By measuring Aβ and ABCA1 after experimental TBI in C57BL/6J mice, we found that Aβ peaked early after injury (1–3 days), whereas ABCA1 had a delayed response (beginning at 3 days). As ABCA1 levels increased, Aβ levels returned to baseline levels—consistent with the known role of ABCA1 in Aβ clearance. To test if enhancing ABCA1 levels could block TBI-induced Aβ, we treated TBI mice with the liver X-receptor (LXR) agonist T0901317. Pre- and post-injury treatment increased ABCA1 levels at 24 h post-injury, and reduced the TBI-induced increase in Aβ. This reduction in Aβ was not due to decreased amyloid precursor protein processing, or a shift in the solubility of Aβ, indicating enhanced clearance. T0901317 also limited motor coordination deficits in injured mice and reduced brain lesion volume. These data indicate that activation of LXR can reduce Aβ accumulation after TBI, and is accompanied by improved functional recovery. PMID:21175399

Chronic Sleep Restriction Induces Cognitive Deficits and Cortical Beta-Amyloid Deposition in Mice via BACE1-Antisense Activation.

PubMed

Zhao, Hong-Yi; Wu, Hui-Juan; He, Jia-Lin; Zhuang, Jian-Hua; Liu, Zhen-Yu; Huang, Liu-Qing; Zhao, Zhong-Xin

2017-03-01

To clarify the correlation between chronic sleep restriction (CSR) and sporadic Alzheimer disease (AD), we determined in wild-type mice the impact of CSR, on cognitive performance, beta-amyloid (Aβ) peptides, and its feed-forward regulators regarding AD pathogenesis. Sixteen nine-month-old C57BL/6 male mice were equally divided into the CSR and control groups. CSR was achieved by application of a slowly rotating drum for 2 months. The Morris water maze test was used to assess cognitive impairment. The concentrations of Aβ peptides, amyloid precursor protein (APP) and β-secretase 1 (BACE1), and the mRNA levels of BACE1 and BACE1-antisense (BACE1-AS) were measured. Following CSR, impairments of spatial learning and memory consolidation were observed in the mice, accompanied by Aβ plaque deposition and an increased Aβ concentration in the prefrontal and temporal lobe cortex. CSR also upregulated the β-secretase-induced cleavage of APP by increasing the protein and mRNA levels of BACE1, particularly the BACE1-AS. This study shows that a CSR accelerates AD pathogenesis in wild-type mice. An upregulation of the BACE1 pathway appears to participate in both cortical Aβ plaque deposition and memory impairment caused by CSR. BACE1-AS is likely activated to initiate a cascade of events that lead to AD pathogenesis. Our study provides, therefore, a molecular mechanism that links CSR to sporadic AD. © 2017 John Wiley & Sons Ltd.

The metabolic enhancer piracetam ameliorates the impairment of mitochondrial function and neurite outgrowth induced by beta-amyloid peptide.

PubMed

Kurz, C; Ungerer, I; Lipka, U; Kirr, S; Schütt, T; Eckert, A; Leuner, K; Müller, W E

2010-05-01

beta-Amyloid peptide (Abeta) is implicated in the pathogenesis of Alzheimer's disease by initiating a cascade of events from mitochondrial dysfunction to neuronal death. The metabolic enhancer piracetam has been shown to improve mitochondrial dysfunction following brain aging and experimentally induced oxidative stress. We used cell lines (PC12 and HEK cells) and murine dissociated brain cells. The protective effects of piracetam in vitro and ex vivo on Abeta-induced impairment of mitochondrial function (as mitochondrial membrane potential and ATP production), on secretion of soluble Abeta and on neurite outgrowth in PC12 cells were investigated. Piracetam improves mitochondrial function of PC12 cells and acutely dissociated brain cells from young NMRI mice following exposure to extracellular Abeta(1-42). Similar protective effects against Abeta(1-42) were observed in dissociated brain cells from aged NMRI mice, or mice transgenic for mutant human amyloid precursor protein (APP) treated with piracetam for 14 days. Soluble Abeta load was markedly diminished in the brain of those animals after treatment with piracetam. Abeta production by HEK cells stably transfected with mutant human APP was elevated by oxidative stress and this was reduced by piracetam. Impairment of neuritogenesis is an important consequence of Abeta-induced mitochondrial dysfunction and Abeta-induced reduction of neurite growth in PC12 cells was substantially improved by piracetam. Our findings strongly support the concept of improving mitochondrial function as an approach to ameliorate the detrimental effects of Abeta on brain function.

Laser-induced propagation and destruction of amyloid beta fibrils.

PubMed

Yagi, Hisashi; Ozawa, Daisaku; Sakurai, Kazumasa; Kawakami, Toru; Kuyama, Hiroki; Nishimura, Osamu; Shimanouchi, Toshinori; Kuboi, Ryoichi; Naiki, Hironobu; Goto, Yuji

2010-06-18

The amyloid deposition of amyloid beta (Abeta) peptides is a critical pathological event in Alzheimer disease (AD). Preventing the formation of amyloid deposits and removing preformed fibrils in tissues are important therapeutic strategies against AD. Previously, we reported the destruction of amyloid fibrils of beta(2)-microglobulin K3 fragments by laser irradiation coupled with the binding of amyloid-specific thioflavin T. Here, we studied the effects of a laser beam on Abeta fibrils. As was the case for K3 fibrils, extensive irradiation destroyed the preformed Abeta fibrils. However, irradiation during spontaneous fibril formation resulted in only the partial destruction of growing fibrils and a subsequent explosive propagation of fibrils. The explosive propagation was caused by an increase in the number of active ends due to breakage. The results not only reveal a case of fragmentation-induced propagation of fibrils but also provide insights into therapeutic strategies for AD.

Absence of beta-amyloid in cortical cataracts of donors with and without Alzheimer's disease.

PubMed

Michael, Ralph; Rosandić, Jurja; Montenegro, Gustavo A; Lobato, Elvira; Tresserra, Francisco; Barraquer, Rafael I; Vrensen, Gijs F J M

2013-01-01

Eye lenses from human donors with and without Alzheimer's disease (AD) were studied to evaluate the presence of amyloid in cortical cataract. We obtained 39 lenses from 21 postmortem donors with AD and 15 lenses from age-matched controls provided by the Banco de Ojos para Tratamientos de la Ceguera (Barcelona, Spain). For 17 donors, AD was clinically diagnosed by general physicians and for 4 donors the AD diagnosis was neuropathologically confirmed. Of the 21 donors with AD, 6 had pronounced bilateral cortical lens opacities and 15 only minor or no cortical opacities. As controls, 7 donors with pronounced cortical opacities and 8 donors with almost transparent lenses were selected. All lenses were photographed in a dark field stereomicroscope. Histological sections were analyzed using a standard and a more sensitive Congo red protocol, thioflavin staining and beta-amyloid immunohistochemistry. Brain tissue from two donors, one with cerebral amyloid angiopathy and another with advanced AD-related changes and one cornea with lattice dystrophy were used as positive controls for the staining techniques. Thioflavin, standard and modified Congo red staining were positive in the control brain tissues and in the dystrophic cornea. Beta-amyloid immunohistochemistry was positive in the brain tissues but not in the cornea sample. Lenses from control and AD donors were, without exception, negative after Congo red, thioflavin, and beta-amyloid immunohistochemical staining. The results of the positive control tissues correspond well with known observations in AD, amyloid angiopathy and corneas with lattice dystrophy. The absence of staining in AD and control lenses with the techniques employed lead us to conclude that there is no beta-amyloid in lenses from donors with AD or in control cortical cataracts. The inconsistency with previous studies of Goldstein et al. (2003) and Moncaster et al. (2010), both of which demonstrated positive Congo red, thioflavin, and beta-amyloid immunohistochemical staining in AD and Down syndrome lenses, is discussed. Copyright © 2012 Elsevier Ltd. All rights reserved.

Ferulic acid destabilizes preformed {beta}-amyloid fibrils in vitro

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ono, Kenjiro; Hirohata, Mie; Yamada, Masahito

2005-10-21

Inhibition of the formation of {beta}-amyloid fibrils (fA{beta}), as well as the destabilization of preformed fA{beta} in the CNS, would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). We reported previously that curcumin (Cur) inhibits fA{beta} formation from A{beta} and destabilizes preformed fA{beta} in vitro. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of ferulic acid (FA) on the formation, extension, and destabilization of fA{beta} at pH 7.5 at 37 deg C in vitro. We next compared the anti-amyloidogenic activities of FA with Cur, rifampicin, and tetracycline. Ferulic acid dose-dependentlymore » inhibited fA{beta} formation from amyloid {beta}-peptide, as well as their extension. Moreover, it destabilized preformed fA{beta}s. The overall activity of the molecules examined was in the order of: Cur > FA > rifampicin = tetracycline. FA could be a key molecule for the development of therapeutics for AD.« less

The role of beta amyloid in Alzheimer's disease: still a cause of everything or the only one who got caught?

PubMed

Verdile, Giuseppe; Fuller, Stephanie; Atwood, Craig S; Laws, Simon M; Gandy, Samuel E; Martins, Ralph N

2004-10-01

The beta amyloid (A beta) protein is a key molecule in the pathogenesis of Alzheimer's disease (AD). The tendency of the A beta peptide to aggregate, its reported neurotoxicity, and genetic linkage studies, have led to a hypothesis of AD pathogenesis that many AD researchers term the amyloid cascade hypothesis. In this hypothesis, an increased production of A beta results in neurodegeneration and ultimately dementia through a cascade of events. In the past 15 years, debate amongst AD researchers has arisen as to whether A beta is a cause or an effect of the pathogenic process. Recent in vitro and in vivo research has consolidated the theory that A beta is the primary cause, initiating secondary events, culminating in the neuropathological hallmarks associated with AD. This research has led to the development of therapeutic agents, currently in human clinical trials, which target A beta.

Adherence to the Mediterranean Diet Is not Related to Beta-Amyloid Deposition: Data from the Women's Healthy Ageing Project.

PubMed

Hill, E; Szoeke, C; Dennerstein, L; Campbell, S; Clifton, P

2018-01-01

Research has indicated the neuroprotective potential of the Mediterranean diet. Adherence to the Mediterranean diet has shown preventative potential for Alzheimer's disease incidence and prevalence, yet few studies have investigated the impact of Mediterranean diet adherence on the hallmark protein; beta-amyloid. To investigate the association between Mediterranean diet adherence and beta-amyloid deposition in a cohort of healthy older Australian women. This study was a cross-sectional investigation of participants from the longitudinal, epidemiologically sourced Women's Healthy Ageing Project which is a follow-up of the Melbourne Women's Midlife Health Project. Assessments were conducted at the Centre for Medical Research, Royal Melbourne Hospital in Melbourne, Australia. F-18 Florbetaben positron emission tomography scanning was conducted at the Austin Centre for PET in Victoria, Australia. One hundred and eleven Women's Healthy Ageing Project participants were included in the study. Mediterranean diet adherence scores for all participants were calculated from the administration of a validated food frequency questionnaire constructed by the Cancer Council of Victoria. Beta-amyloid deposition was measured using positron emission tomography standardised uptake value ratios. Gamma regression analysis displayed no association between Mediterranean diet adherence and beta-amyloid deposition. This result was consistent across APOE-ε4 +/- cohorts and with the inclusion of covariates such as age, education, body mass index and cognition. This study found no association between adherence to the Mediterranean diet and beta-amyloid deposition in a cohort of healthy Australian women.

Effects of intracerebroventricular administration of beta-amyloid on the dynamics of learning in purebred and mongrel rats.

PubMed

Stepanov, I I; Kuznetsova, N N; Klement'ev, B I; Sapronov, N S

2007-07-01

The effects of intracerebroventricular administration of the beta-amyloid peptide fragment Abeta(25-35) on the dynamics of the acquisition of a conditioned reflex in a Y maze were studied in Wistar and mongrel rats. The dynamics of decreases in the number of errors were assessed using an exponential mathematical model describing the transfer function of a first-order system in response to stepped inputs using non-linear regression analysis. This mathematical model provided a good approximation to the learning dynamics in inbred and mongrel mice. In Wistar rats, beta-amyloid impaired learning, with reduced memory between the first and second training sessions, but without complete blockade of learning. As a result, learning dynamics were no longer approximated by the mathematical model. At the same time, comparison of the number of errors in each training sessions between the control group of Wistar rats and the group given beta-amyloid showed no significant differences (Student's t test). This result demonstrates the advantage of regression analysis based on a mathematical model over the traditionally used statistical methods. In mongrel rats, the effect of beta-amyloid was limited to an a slowing of the process of learning as compared with control mongrel rats, with retention of the approximation by the mathematical model. It is suggested that mongrel animals have some kind of innate, genetically determined protective mechanism against the harmful effects of beta-amyloid.

Amyloid formation and inhibition of an all-beta protein: A study on fungal polygalacturonase

NASA Astrophysics Data System (ADS)

Chinisaz, Maryam; Ghasemi, Atiyeh; Larijani, Bagher; Ebrahim-Habibi, Azadeh

2014-02-01

Theoretically, all proteins can adopt the nanofibrillar structures known as amyloid, which contain cross-beta structures. The all-beta folded proteins are particularly interesting in this regard, since they appear to be naturally more predisposed toward this structural arrangement. In this study, methanol has been used to drive the beta-helix protein polygalacturonase (PG), toward amyloid fibril formation. Congo red absorbance, thioflavin T fluorescence, circular dichroism (CD) and transmission electron microscopy have been used to characterize this process. Similar to other all-beta proteins, PG shows a non-cooperative fibrillation mechanism, but the structural changes that are monitored by CD indicate a different pattern. Furthermore, several compounds containing aromatic components were tested as potential inhibitors of amyloid formation. Another protein predominantly composed of alpha-helices (human serum albumin) was also targeted by these ligands, in order to get an insight into their potential anti-aggregation property toward structurally different proteins. Among tested compounds, silibinin and chlorpropamide were able to considerably affect both proteins fibrillation process.

Beta-Amyloid Deposition and Alzheimer's Type Changes Induced by Borrelia Spirochetes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miklossy,J.; Kis, A.; Radenovic, A.

2006-01-01

The pathological hallmarks of Alzheimer's disease (AD) consist of {beta}-amyloid plaques and neurofibrillary tangles in affected brain areas. The processes, which drive this host reaction are unknown. To determine whether an analogous host reaction to that occurring in AD could be induced by infectious agents, we exposed mammalian glial and neuronal cells in vitro to Borrelia burgdorferi spirochetes and to the inflammatory bacterial lipopolysaccharide (LPS). Morphological changes analogous to the amyloid deposits of AD brain were observed following 2-8 weeks of exposure to the spirochetes. Increased levels of {beta}-amyloid presursor protein (A{beta}PP) and hyperphosphorylated tau were also detected by Westernmore » blots of extracts of cultured cells that had been treated with spirochetes or LPS. These observations indicate that, by exposure to bacteria or to their toxic products, host responses similar in nature to those observed in AD may be induced.« less

Acorus tatarinowii Schott extract protects PC12 cells from amyloid-beta induced neurotoxicity.

PubMed

An, Hong-Mei; Li, Guo-Wen; Lin, Chen; Gu, Chao; Jin, Miao; Sun, Wen-Xian; Qiu, Ming-Feng; Hu, Bing

2014-05-01

Amyloid-beta induced neurotoxicity has been identified as a major cause of Alzheimer's disease. Acorus tatarinowii Schott is one of the most frequently used Chinese herbs for Alzheimer's disease treatment. However, the effects of Acorus tatarinowii Schott on amyloid-beta mediated nerve cell damage remains unknown. In the present study, neuronal differentiated PC12 cells were used as a model to evaluate the effects of A. tatarinowii Schott extract (ATSE) against Abeta25-35 induced neurotoxicity. The results showed pretreatment with ATSE significantly protected PC12 cells from Abeta25-35 induced cell death, lactate dehydrogenase release, DNA damage, mitochondrial dysfunction and cytochrome c release from mitochondria. In addition, pretreatment with ATSE also significantly inhibited Abeta25-35 induced caspase-3 activation and reactive oxygen species generation in PC12 cells. These observations suggested that ATSE protects PC12 cells from amyloid-beta induced neurotoxicity.

Amyloid beta precursor protein and ubiquitin epitopes in human and experimental dystrophic axons. Ultrastructural localization.

PubMed Central

Bacci, B.; Cochran, E.; Nunzi, M. G.; Izeki, E.; Mizutani, T.; Patton, A.; Hite, S.; Sayre, L. M.; Autilio-Gambetti, L.; Gambetti, P.

1994-01-01

Dystrophic axons (DA) represent a major pathological feature of several neurodegenerative disorders, including infantile neuroaxonal dystrophy (INAD) and Alzheimer disease. We have previously presented evidence that amyloid beta precursor protein (BPP) and ubiquitin (Ub) are present in DA of different origin. We have now characterized the immunoreactivity of DA experimentally induced in rat by the administration of parabromophenylacetylurea (BPAU) and examined the subcellular localization of Ub and BPP in BPAU-induced DA and in DA present in subjects affected by INAD. BPAU-induced DA strongly immunoreacted with antisera to Ub and to COOH- and NH2-terminal regions of BPP. Immunoblots of DA-enriched brain regions were consistent with an increase in the amount of Ub and BPP in DA. Moreover, BPAU-induced DA immunoreacted with antibodies to PGP 9.5, a neuronal-specific Ub COOH-terminal hydrolase, and to the inducible heat shock protein 70. Antigenic characterization also indicated that the tubulovesicular membranes within DA derived largely from the smooth endoplasmic reticulum rather than from the Golgi system or the synaptic vesicles. Subcellular immunolocalization of Ub and BPP in both INAD- and BPAU-induced DA revealed that Ub and BPP colocalize in granulovesicular material in both conditions. In INAD DA intense Ub immunoreactivity was also detected in nonmembranous electron dense structures that were present only in these DA, probably because of the chronic course of INAD. Although BPP immunostaining may be related to accumulation of BPP-containing membranes in DA, Ub immunostaining is likely to result from activation of the Ub system by the neuron in the attempt to remove excessive and possibly abnormal proteins. A similar pathogenesis can be postulated for DA of Alzheimer disease. Images Figure 1 Figure 2 Figure 3 Figure 4 PMID:7512790

Metabolic and Structural Imaging at 7 Tesla After Repetitive Mild Traumatic Brain Injury in Immature Rats.

PubMed

Fidan, Emin; Foley, Lesley M; New, Lee Ann; Alexander, Henry; Kochanek, Patrick M; Hitchens, T Kevin; Bayır, Hülya

2018-01-01

Mild traumatic brain injury (mTBI) in children is a common and serious public health problem. Traditional neuroimaging findings in children who sustain mTBI are often normal, putting them at risk for repeated mTBI (rmTBI). There is a need for more sensitive imaging techniques capable of detecting subtle neurophysiological alterations after injury. We examined neurochemical and white matter changes using diffusion tensor imaging of the whole brain and proton magnetic resonance spectroscopy of the hippocampi at 7 Tesla in 18-day-old male rats at 7 days after mTBI and rmTBI. Traumatic axonal injury was assessed by beta-amyloid precursor protein accumulation using immunohistochemistry. A significant decrease in fractional anisotropy and increase in axial and radial diffusivity were observed in several brain regions, especially in white matter regions, after a single mTBI versus sham and more prominently after rmTBI. In addition, we observed accumulation of beta-amyloid precursor protein in the external capsule after mTBI and rmTBI. mTBI and rmTBI reduced the N-acetylaspartate/creatine ratio (NAA/Cr) and increased the myoinositol/creatine ratio (Ins/Cr) versus sham. rmTBI exacerbated the reduction in NAA/Cr versus mTBI. The choline/creatine (Cho/Cr) and (lipid/Macro Molecule 1)/creatine (Lip/Cr) ratios were also decreased after rmTBI versus sham. Diffusion tensor imaging findings along with the decrease in Cho and Lip after rmTBI may reflect damage to axonal membrane. NAA and Ins are altered at 7 days after mTBI and rmTBI likely reflecting neuro-axonal damage and glial response, respectively. These findings may be relevant to understanding the extent of disability following mTBI and rmTBI in the immature brain and may identify possible therapeutic targets.

Amyloid precursor protein modulates ERK-1 and -2 signaling.

PubMed

Venezia, Valentina; Nizzari, Mario; Repetto, Emanuela; Violani, Elisabetta; Corsaro, Alessandro; Thellung, Stefano; Villa, Valentina; Carlo, Pia; Schettini, Gennaro; Florio, Tullio; Russo, Claudio

2006-12-01

The amyloid precursor protein (APP) is a transmembrane protein with a short cytoplasmic tail whose physiological function is unclear, although it is well documented that the proteolytic processing of APP could influence the development of Alzheimer's disease (AD) through the formation of membrane-bound C-terminal fragments (CTFs) and of beta-amyloid peptides (Abeta). We have recently shown that tyrosine-phosphorylated APP and CTFs may interact with Grb2 and ShcA adaptor proteins and that this coupling occurs at a higher extent in AD subjects only. To study the interaction between APP or CTFs and ShcA/Grb2 and to investigate their molecular target we have used as experimental model two different cell lines: H4 human neuroglioma cells and APP/APLP null mouse embryonic fibroblast cells (MEFs). Here we show that in H4 cells APP interacts with Grb2; conversely in APP/APLP-null MEF cells this interaction is possible only after the reintroduction of human APP by transfection. We have also shown that in MEF cells the transfection of a plasmid encoding for human APP wild-type enhances the phosphorylation of ERK-1 and -2 as revealed by Western blotting and immunofluorescence experiments. Finally, also in H4 cells the overexpression of APP upregulates the levels of phospho-ERK-1 and -2. In summary our data suggest that APP may influence phospho-ERK-1 and -2 signaling through its binding with Grb2 and ShcA adaptors. The meaning of this event is not clear, but APP interaction with these adaptors could be relevant to regulate mitogenic pathway.

Substance P activates ADAM9 mRNA expression and induces α-secretase-mediated amyloid precursor protein cleavage.

PubMed

Marolda, R; Ciotti, M T; Matrone, C; Possenti, R; Calissano, P; Cavallaro, S; Severini, C

2012-04-01

Altered levels of Substance P (SP), a neuropeptide endowed with neuroprotective and anti-apoptotic properties, were found in brain areas and spinal fluid of Alzheimer's disease (AD) patients. One of the hallmarks of AD is the abnormal extracellular deposition of neurotoxic beta amyloid (Aβ) peptides, derived from the proteolytic processing of amyloid precursor protein (APP). In the present study, we confirmed, the neurotrophic action of SP in cultured rat cerebellar granule cells (CGCs) and investigated its effects on APP metabolism. Incubation with low (5 mM) potassium induced apoptotic cell death of CGCs and amyloidogenic processing of APP, whereas treatment with SP (200 nM) reverted these effects via NK1 receptors. The non-amyloidogenic effect of SP consisted of reduction of Aβ(1-42), increase of sAPPα and enhanced α-secretase activity, without a significant change in steady-state levels of cellular APP. The intracellular mechanisms whereby SP alters APP metabolism were further investigated by measuring mRNA and/or steady-state protein levels of key enzymes involved with α-, β- and γ-secretase activity. Among them, Adam9, both at the mRNA and protein level, was the only enzyme to be significantly down-regulated following the induction of apoptosis (K5) and up-regulated after SP treatment. In addition to its neuroprotective properties, this study shows that SP is able to stimulate non-amyloidogenic APP processing, thereby reducing the possibility of generation of toxic Aβ peptides in brain. Copyright © 2011 Elsevier Ltd. All rights reserved.

Structural Characterization of the E2 Domain of APL-1, a C. Elegans Homolog of Human Amyloid Precursor Protein, and its Heparin Binding Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoopes, J.; Liu, X; Xu, X

2010-01-01

The amyloid {beta}-peptide deposit found in the brain tissue of patients with Alzheimer disease is derived from a large heparin-binding protein precursor APP. The biological function of APP and its homologs is not precisely known. Here we report the x-ray structure of the E2 domain of APL-1, an APP homolog in Caenorhabditis elegans, and compare it to the human APP structure. We also describe the structure of APL-1 E2 in complex with sucrose octasulfate, a highly negatively charged disaccharide, which reveals an unexpected binding pocket between the two halves of E2. Based on the crystal structure, we are able tomore » map, using site-directed mutagenesis, a surface groove on E2 to which heparin may bind. Our biochemical data also indicate that the affinity of E2 for heparin is influenced by pH: at pH 5, the binding appears to be much stronger than that at neutral pH. This property is likely caused by histidine residues in the vicinity of the mapped heparin binding site and could be important for the proposed adhesive function of APL-1.« less

Withanamides in Withania somnifera fruit protect PC-12 cells from beta-amyloid responsible for Alzheimer's disease.

PubMed

Jayaprakasam, Bolleddula; Padmanabhan, Kaillathe; Nair, Muraleedharan G

2010-06-01

Alzheimer's disease (AD) is an irreversible neurodegenerative disorder with symptoms of confusion, memory loss, and mood swings. The beta-amyloid peptide, with 39-42 amino acid residues (BAP), plays a significant role in the development of AD. Although there is no cure for AD, it can be managed with available drugs to some degree. Several studies have revealed that natural antioxidants, such as vitamin E, vitamin C and beta-carotene, may help in scavenging free radicals generated during the initiation and progression of this disease. Therefore, there has been considerable interest in plant phytochemicals with antioxidant property as potential agents to prevent the progression of AD. Our earlier investigations of the Withania somnifera fruit afforded lipid peroxidation inhibitory withanamides that are more potent than the commercial antioxidants. In this study, we have tested two major withanamides A (WA) and C (WC) for their ability to protect the PC-12 cells, rat neuronal cells, from beta-amyloid induced cell damage. The cell death caused by beta-amyloid was negated by withanamide treatment. Molecular modeling studies showed that withanamides A and C uniquely bind to the active motif of beta-amyloid (25-35) and suggest that withanamides have the ability to prevent the fibril formation. Further understanding of the mechanism of action and in vivo efficacy of these withanamides may facilitate its development as a prophylaxis. (c) 2009 John Wiley & Sons, Ltd.

The Common Inhalational Anesthetic Sevoflurane Induces Apoptosis and Increases β-Amyloid Protein Levels

PubMed Central

Dong, Yuanlin; Zhang, Guohua; Zhang, Bin; Moir, Robert D.; Xia, Weiming; Marcantonio, Edward R.; Culley, Deborah J.; Crosby, Gregory; Tanzi, Rudolph E.; Xie, Zhongcong

2009-01-01

Objective: To assess the effects of sevoflurane, the most commonly used inhalation anesthetic, on apoptosis and β-amyloid protein (Aβ) levels in vitro and in vivo. Subjects: Naive mice, H4 human neuroglioma cells, and H4 human neuroglioma cells stably transfected to express full-length amyloid precursor protein. Interventions: Human H4 neuroglioma cells stably transfected to express full-length amyloid precursor protein were exposed to 4.1% sevoflurane for 6 hours. Mice received 2.5% sevoflurane for 2 hours. Caspase-3 activation, apoptosis, and Aβ levels were assessed. Results: Sevoflurane induced apoptosis and elevated levels of β-site amyloid precursor protein-cleaving enzyme and Aβ in vitro and in vivo. The caspase inhibitor Z-VAD decreased the effects of sevoflurane on apoptosis and Aβ. Sevoflurane-induced caspase-3 activation was attenuated by the γ-secretase inhibitor L-685,458 and was potentiated by Aβ. These results suggest that sevoflurane induces caspase activation which, in turn, enhances β-site amyloid precursor protein–cleaving enzyme and Aβ levels. Increased Aβ levels then induce further rounds of apoptosis. Conclusions: These results suggest that inhalational anesthetic sevoflurane may promote Alzheimer disease neuropathogenesis. If confirmed in human subjects, it may be prudent to caution against the use of sevoflurane as an anesthetic, especially in those suspected of possessing excessive levels of cerebral Aβ. PMID:19433662

Mitochondrion-Derived Reactive Oxygen Species Lead to Enhanced Amyloid Beta Formation

PubMed Central

Schütt, Tanja; Kurz, Christopher; Eckert, Schamim H.; Schiller, Carola; Occhipinti, Angelo; Mai, Sören; Jendrach, Marina; Eckert, Gunter P.; Kruse, Shane E.; Palmiter, Richard D.; Brandt, Ulrich; Dröse, Stephan; Wittig, Ilka; Willem, Michael; Haass, Christian; Reichert, Andreas S.; Müller, Walter E.

2012-01-01

Abstract Aims: Intracellular amyloid beta (Aβ) oligomers and extracellular Aβ plaques are key players in the progression of sporadic Alzheimer's disease (AD). Still, the molecular signals triggering Aβ production are largely unclear. We asked whether mitochondrion-derived reactive oxygen species (ROS) are sufficient to increase Aβ generation and thereby initiate a vicious cycle further impairing mitochondrial function. Results: Complex I and III dysfunction was induced in a cell model using the respiratory inhibitors rotenone and antimycin, resulting in mitochondrial dysfunction and enhanced ROS levels. Both treatments lead to elevated levels of Aβ. Presence of an antioxidant rescued mitochondrial function and reduced formation of Aβ, demonstrating that the observed effects depended on ROS. Conversely, cells overproducing Aβ showed impairment of mitochondrial function such as comprised mitochondrial respiration, strongly altered morphology, and reduced intracellular mobility of mitochondria. Again, the capability of these cells to generate Aβ was partly reduced by an antioxidant, indicating that Aβ formation was also ROS dependent. Moreover, mice with a genetic defect in complex I, or AD mice treated with a complex I inhibitor, showed enhanced Aβ levels in vivo. Innovation: We show for the first time that mitochondrion-derived ROS are sufficient to trigger Aβ production in vitro and in vivo. Conclusion: Several lines of evidence show that mitochondrion-derived ROS result in enhanced amyloidogenic amyloid precursor protein processing, and that Aβ itself leads to mitochondrial dysfunction and increased ROS levels. We propose that starting from mitochondrial dysfunction a vicious cycle is triggered that contributes to the pathogenesis of sporadic AD. Antioxid. Redox Signal. 16, 1421–1433. PMID:22229260

Blocking beta 2-adrenergic receptor inhibits dendrite ramification in a mouse model of Alzheimer's disease.

PubMed

Wu, Qin; Sun, Jin-Xia; Song, Xiang-He; Wang, Jing; Xiong, Cun-Quan; Teng, Fei-Xiang; Gao, Cui-Xiang

2017-09-01

Dendrite ramification affects synaptic strength and plays a crucial role in memory. Previous studies revealed a correlation between beta 2-adrenergic receptor dysfunction and Alzheimer's disease (AD), although the mechanism involved is still poorly understood. The current study investigated the potential effect of the selective β 2 -adrenergic receptor antagonist, ICI 118551 (ICI), on Aβ deposits and AD-related cognitive impairment. Morris water maze test results demonstrated that the performance of AD-transgenic (TG) mice treated with ICI (AD-TG/ICI) was significantly poorer compared with NaCl-treated AD-TG mice (AD-TG/NaCl), suggesting that β 2 -adrenergic receptor blockage by ICI might reduce the learning and memory abilities of mice. Golgi staining and immunohistochemical staining revealed that blockage of the β 2 -adrenergic receptor by ICI treatment decreased the number of dendritic branches, and ICI treatment in AD-TG mice decreased the expression of hippocampal synaptophysin and synapsin 1. Western blot assay results showed that the blockage of β 2 -adrenergic receptor increased amyloid-β accumulation by downregulating hippocampal α-secretase activity and increasing the phosphorylation of amyloid precursor protein. These findings suggest that blocking the β 2 -adrenergic receptor inhibits dendrite ramification of hippocampal neurons in a mouse model of AD.

ACE inhibition with captopril retards the development of signs of neurodegeneration in an animal model of Alzheimer's disease.

PubMed

AbdAlla, Said; Langer, Andreas; Fu, Xuebin; Quitterer, Ursula

2013-08-16

Increased generation of reactive oxygen species (ROS) is a significant pathological feature in the brains of patients with Alzheimer's disease (AD). Experimental evidence indicates that inhibition of brain ROS could be beneficial in slowing the neurodegenerative process triggered by amyloid-beta (Abeta) aggregates. The angiotensin II AT1 receptor is a significant source of brain ROS, and AD patients have an increased brain angiotensin-converting enzyme (ACE) level, which could account for an excessive angiotensin-dependent AT1-induced ROS generation. Therefore, we analyzed the impact of ACE inhibition on signs of neurodegeneration of aged Tg2576 mice as a transgenic animal model of AD. Whole genome microarray gene expression profiling and biochemical analyses demonstrated that the centrally active ACE inhibitor captopril normalized the excessive hippocampal ACE activity of AD mice. Concomitantly, the development of signs of neurodegeneration was retarded by six months of captopril treatment. The neuroprotective profile triggered by captopril was accompanied by reduced amyloidogenic processing of the amyloid precursor protein (APP), and decreased hippocampal ROS, which is known to enhance Abeta generation by increased activation of beta- and gamma-secretases. Taken together, our data present strong evidence that ACE inhibition with a widely used cardiovascular drug could interfere with Abeta-dependent neurodegeneration.

ACE Inhibition with Captopril Retards the Development of Signs of Neurodegeneration in an Animal Model of Alzheimer’s Disease

PubMed Central

AbdAlla, Said; Langer, Andreas; Fu, Xuebin; Quitterer, Ursula

2013-01-01

Increased generation of reactive oxygen species (ROS) is a significant pathological feature in the brains of patients with Alzheimer’s disease (AD). Experimental evidence indicates that inhibition of brain ROS could be beneficial in slowing the neurodegenerative process triggered by amyloid-beta (Abeta) aggregates. The angiotensin II AT1 receptor is a significant source of brain ROS, and AD patients have an increased brain angiotensin-converting enzyme (ACE) level, which could account for an excessive angiotensin-dependent AT1-induced ROS generation. Therefore, we analyzed the impact of ACE inhibition on signs of neurodegeneration of aged Tg2576 mice as a transgenic animal model of AD. Whole genome microarray gene expression profiling and biochemical analyses demonstrated that the centrally active ACE inhibitor captopril normalized the excessive hippocampal ACE activity of AD mice. Concomitantly, the development of signs of neurodegeneration was retarded by six months of captopril treatment. The neuroprotective profile triggered by captopril was accompanied by reduced amyloidogenic processing of the amyloid precursor protein (APP), and decreased hippocampal ROS, which is known to enhance Abeta generation by increased activation of beta- and gamma-secretases. Taken together, our data present strong evidence that ACE inhibition with a widely used cardiovascular drug could interfere with Abeta-dependent neurodegeneration. PMID:23959119

Blocking beta 2-adrenergic receptor inhibits dendrite ramification in a mouse model of Alzheimer's disease

PubMed Central

Wu, Qin; Sun, Jin-xia; Song, Xiang-he; Wang, Jing; Xiong, Cun-quan; Teng, Fei-xiang; Gao, Cui-xiang

2017-01-01

Dendrite ramification affects synaptic strength and plays a crucial role in memory. Previous studies revealed a correlation between beta 2-adrenergic receptor dysfunction and Alzheimer's disease (AD), although the mechanism involved is still poorly understood. The current study investigated the potential effect of the selective β2-adrenergic receptor antagonist, ICI 118551 (ICI), on Aβ deposits and AD-related cognitive impairment. Morris water maze test results demonstrated that the performance of AD-transgenic (TG) mice treated with ICI (AD-TG/ICI) was significantly poorer compared with NaCl-treated AD-TG mice (AD-TG/NaCl), suggesting that β2-adrenergic receptor blockage by ICI might reduce the learning and memory abilities of mice. Golgi staining and immunohistochemical staining revealed that blockage of the β2-adrenergic receptor by ICI treatment decreased the number of dendritic branches, and ICI treatment in AD-TG mice decreased the expression of hippocampal synaptophysin and synapsin 1. Western blot assay results showed that the blockage of β2-adrenergic receptor increased amyloid-β accumulation by downregulating hippocampal α-secretase activity and increasing the phosphorylation of amyloid precursor protein. These findings suggest that blocking the β2-adrenergic receptor inhibits dendrite ramification of hippocampal neurons in a mouse model of AD. PMID:29089997

Genetic engineering combined with deep UV resonance Raman spectroscopy for structural characterization of amyloid-like fibrils.

PubMed

Sikirzhytski, Vitali; Topilina, Natalya I; Higashiya, Seiichiro; Welch, John T; Lednev, Igor K

2008-05-07

Elucidating the structure of the cross-beta core in large amyloid fibrils is a challenging problem in modern structural biology. For the first time, a set of de novo polypeptides was genetically engineered to form amyloid-like fibrils with similar morphology and yet different strand length. Differential ultraviolet Raman spectroscopy allowed for separation of the spectroscopic signatures of the highly ordered beta-sheet strands and turns of the fibril core. The relationship between Raman frequencies and Ramachandran dihedral angles of the polypeptide backbone indicates the nature of the beta-sheet and turn structural elements.

Preformed {beta}-amyloid fibrils are destabilized by coenzyme Q{sub 10} in vitro

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ono, Kenjiro; Hasegawa, Kazuhiro; Naiki, Hironobu

2005-04-29

Inhibition of the formation of {beta}-amyloid fibrils (fA{beta}), as well as the destabilization of preformed fA{beta} in the CNS, would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). We reported previously that nordihydroguaiaretic acid (NDGA) and wine-related polyphenol, myricetin (Myr), inhibit fA{beta} formation from A{beta} and destabilize preformed fA{beta} in vitro. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of coenzyme Q{sub 10} (CoQ{sub 10}) on the formation, extension, and destabilization of fA{beta} at pH 7.5 at 37 deg C in vitro. We next compared the anti-amyloidogenic activities of CoQ{submore » 10} with NDGA and Myr. CoQ{sub 10} dose-dependently inhibited fA{beta} formation from amyloid {beta}-peptide (A{beta}), as well as their extension. Moreover, it destabilized preformed fA{beta}s. The anti-amyloidogenic effects of CoQ{sub 10} were slightly weaker than those of NDGA and Myr. CoQ{sub 10} could be a key molecule for the development of therapeutics for AD.« less

In silico study of full-length amyloid beta 1-42 tri- and penta-oligomers in solution.

PubMed

Masman, Marcelo F; Eisel, Ulrich L M; Csizmadia, Imre G; Penke, Botond; Enriz, Ricardo D; Marrink, Siewert Jan; Luiten, Paul G M

2009-08-27

Amyloid oligomers are considered to play causal roles in the pathogenesis of amyloid-related degenerative diseases including Alzheimer's disease. Using MD simulation techniques, we explored the contributions of the different structural elements of trimeric and pentameric full-length Abeta1-42 aggregates in solution to their stability and conformational dynamics. We found that our models are stable at a temperature of 310 K, and converge toward an interdigitated side-chain packing for intermolecular contacts within the two beta-sheet regions of the aggregates: beta1 (residues 18-26) and beta2 (residues 31-42). MD simulations reveal that the beta-strand twist is a characteristic element of Abeta-aggregates, permitting a compact, interdigitated packing of side chains from neighboring beta-sheets. The beta2 portion formed a tightly organized beta-helix, whereas the beta1 portion did not show such a firm structural organization, although it maintained its beta-sheet conformation. Our simulations indicate that the hydrophobic core comprising the beta2 portion of the aggregate is a crucial stabilizing element in the Abeta aggregation process. On the basis of these structure-stability findings, the beta2 portion emerges as an optimal target for further antiamyloid drug design.

Towards a Pharmacophore for Amyloid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landau, Meytal; Sawaya, Michael R.; Faull, Kym F.

2011-09-16

Diagnosing and treating Alzheimer's and other diseases associated with amyloid fibers remains a great challenge despite intensive research. To aid in this effort, we present atomic structures of fiber-forming segments of proteins involved in Alzheimer's disease in complex with small molecule binders, determined by X-ray microcrystallography. The fiber-like complexes consist of pairs of {beta}-sheets, with small molecules binding between the sheets, roughly parallel to the fiber axis. The structures suggest that apolar molecules drift along the fiber, consistent with the observation of nonspecific binding to a variety of amyloid proteins. In contrast, negatively charged orange-G binds specifically to lysine sidemore » chains of adjacent sheets. These structures provide molecular frameworks for the design of diagnostics and drugs for protein aggregation diseases. The devastating and incurable dementia known as Alzheimer's disease affects the thinking, memory, and behavior of dozens of millions of people worldwide. Although amyloid fibers and oligomers of two proteins, tau and amyloid-{beta}, have been identified in association with this disease, the development of diagnostics and therapeutics has proceeded to date in a near vacuum of information about their structures. Here we report the first atomic structures of small molecules bound to amyloid. These are of the dye orange-G, the natural compound curcumin, and the Alzheimer's diagnostic compound DDNP bound to amyloid-like segments of tau and amyloid-{beta}. The structures reveal the molecular framework of small-molecule binding, within cylindrical cavities running along the {beta}-spines of the fibers. Negatively charged orange-G wedges into a specific binding site between two sheets of the fiber, combining apolar binding with electrostatic interactions, whereas uncharged compounds slide along the cavity. We observed that different amyloid polymorphs bind different small molecules, revealing that a cocktail of compounds may be required for future amyloid therapies. The structures described here start to define the amyloid pharmacophore, opening the way to structure-based design of improved diagnostics and therapeutics.« less

Ameliorating effect of anti-Alzheimer's drugs on the bidirectional association between type 2 diabetes mellitus and Alzheimer's disease.

PubMed

Ahmed, Amira S; Elgharabawy, Rehab M; Al-Najjar, Amal H

2017-07-01

Mild to severe forms of nervous system damage were exhibited by approximately 60-70% of diabetics. It is important to understand the association between type 2 diabetes mellitus and Alzheimer's disease. The aim of the present work is to understand the bidirectional association between type 2 diabetes and Alzheimer's disease pathogenesis, that was monitored by glycaemic status, lipid profile, amyloid beta 40 and 42 (Aβ40 and Aβ42), C-reactive protein, total creatine kinase, total lactate dehydrogenase, D-dimer and magnesium measurements, to assess the association between theses biochemical markers and each other, to estimate the possibility of utilizing the amyloid beta as biochemical marker of T2D in Alzheimer's patients, and to evaluate the effect of piracetam and memantine drugs on diabetes mellitus. This study involved 120 subjects divided into 20 healthy control (group I), 20 diabetic patients (group II), 20 Alzheimer's patients (group III), 20 diabetic Alzheimer's patients with symptomatic treatment (group IV), 20 diabetic Alzheimer's patients treated with memantine (group V), and 20 diabetic Alzheimer's patients treated with piracetam (group VI). The demographic characteristics, diabetic index, and lipid profile were monitored. Plasma amyloid beta 40 and amyloid beta 42, C-reactive protein, total creatine kinase, total lactate dehydrogenase, D-dimer, and magnesium were assayed. The levels of amyloid beta 40 and amyloid beta 42 were significantly elevated in diabetic Alzheimer's patients with symptomatic treatment (group IV) compared to group II (by 50.5 and 7.5 fold, respectively) and group III (by 25.4 and 2.8 fold, respectively). In groups II, III, IV, V and VI, significant and positive associations were monitored between insulin and amyloid beta 40, amyloid beta 42, C-reactive protein, total creatine kinase, and D-dimer. Diabetic markers were significantly decreased in diabetic Alzheimer's patients treated with anti-Alzheimer's drugs (especially piracetam) compared to group IV. This study reveals the role of amyloid beta 40, amyloid beta 42, insulin, HbA1c, lipid profile disturbance, C-reactive protein, D-dimer, and magnesium in the bidirectional correlation between T2D and pathogenesis of Alzheimer's disease, that is powered by their correlations, and therefore the possibility of utilizing Aβ as a biochemical marker of T2D in Alzheimer's patients is recommended. Impact statement Several aspects associated with T2D that contribute to AD and vice versa were investigated in this study. Additionally, this work reveals the role of Aβ40, Aβ42, insulin, HbA1c, lipid profile disturbance, CRP, D-dimer, and magnesium in the bidirectional association between T2D and the pathogenesis of AD, that is powered by their correlations, and therefore the possibility of utilizing Aβ as a biochemical marker of T2D in Alzheimer's patients is recommended. Furthermore, the ameloriating effect of anti-Alzheimer's drugs on diabetes mellitus confirms this association. Hereafter, a new approach for treating insulin resistance and diabetes may be developed by new therapeutic potentials such as neutralization of Aβ by anti-Aβ antibodies.

Engineering Neprilysin Activity and Specificity to Create a Novel Therapeutic for Alzheimer’s Disease

PubMed Central

Webster, Carl I.; Burrell, Matthew; Olsson, Lise-Lotte; Fowler, Susan B.; Digby, Sarah; Sandercock, Alan; Snijder, Arjan; Tebbe, Jan; Haupts, Ulrich; Grudzinska, Joanna; Jermutus, Lutz; Andersson, Christin

2014-01-01

Neprilysin is a transmembrane zinc metallopeptidase that degrades a wide range of peptide substrates. It has received attention as a potential therapy for Alzheimer’s disease due to its ability to degrade the peptide amyloid beta. However, its broad range of peptide substrates has the potential to limit its therapeutic use due to degradation of additional peptides substrates that tightly regulate many physiological processes. We sought to generate a soluble version of the ectodomain of neprilysin with improved activity and specificity towards amyloid beta as a potential therapeutic for Alzheimer’s disease. Extensive amino acid substitutions were performed at positions surrounding the active site and inner surface of the enzyme and variants screened for activity on amyloid beta 1–40, 1–42 and a variety of other physiologically relevant peptides. We identified several mutations that modulated and improved both enzyme selectivity and intrinsic activity. Neprilysin variant G399V/G714K displayed an approximately 20-fold improved activity on amyloid beta 1–40 and up to a 3,200-fold reduction in activity on other peptides. Along with the altered peptide substrate specificity, the mutant enzyme produced a markedly altered series of amyloid beta cleavage products compared to the wild-type enzyme. Crystallisation of the mutant enzyme revealed that the amino acid substitutions result in alteration of the shape and size of the pocket containing the active site compared to the wild-type enzyme. The mutant enzyme offers the potential for the more efficient degradation of amyloid beta in vivo as a therapeutic for the treatment of Alzheimer’s disease. PMID:25089527

Amyloid-like aggregation of provasopressin in diabetes insipidus and secretory granule sorting.

PubMed

Beuret, Nicole; Hasler, Franziska; Prescianotto-Baschong, Cristina; Birk, Julia; Rutishauser, Jonas; Spiess, Martin

2017-01-26

Aggregation of peptide hormone precursors in the trans-Golgi network is an essential process in the biogenesis of secretory granules in endocrine cells. It has recently been proposed that this aggregation corresponds to the formation of functional amyloids. Our previous finding that dominant mutations in provasopressin, which cause cell degeneration and diabetes insipidus, prevent native folding and produce fibrillar aggregates in the endoplasmic reticulum (ER) might thus reflect mislocalized amyloid formation by sequences that evolved to mediate granule sorting. Here we identified two sequences responsible for fibrillar aggregation of mutant precursors in the ER: the N-terminal vasopressin nonapeptide and the C-terminal glycopeptide. To test their role in granule sorting, the glycopeptide was deleted and/or vasopressin mutated to inactivate ER aggregation while still permitting precursor folding and ER exit. These mutations strongly reduced sorting into granules and regulated secretion in endocrine AtT20 cells. The same sequences - vasopressin and the glycopeptide - mediate physiological aggregation of the wild-type hormone precursor into secretory granules and the pathological fibrillar aggregation of disease mutants in the ER. These findings support the amyloid hypothesis for secretory granule biogenesis.

Positive evolutionary selection of an HD motif on Alzheimer precursor protein orthologues suggests a functional role.

PubMed

Miklós, István; Zádori, Zoltán

2012-02-01

HD amino acid duplex has been found in the active center of many different enzymes. The dyad plays remarkably different roles in their catalytic processes that usually involve metal coordination. An HD motif is positioned directly on the amyloid beta fragment (Aβ) and on the carboxy-terminal region of the extracellular domain (CAED) of the human amyloid precursor protein (APP) and a taxonomically well defined group of APP orthologues (APPOs). In human Aβ HD is part of a presumed, RGD-like integrin-binding motif RHD; however, neither RHD nor RXD demonstrates reasonable conservation in APPOs. The sequences of CAEDs and the position of the HD are not particularly conserved either, yet we show with a novel statistical method using evolutionary modeling that the presence of HD on CAEDs cannot be the result of neutral evolutionary forces (p<0.0001). The motif is positively selected along the evolutionary process in the majority of APPOs, despite the fact that HD motif is underrepresented in the proteomes of all species of the animal kingdom. Position migration can be explained by high probability occurrence of multiple copies of HD on intermediate sequences, from which only one is kept by selective evolutionary forces, in a similar way as in the case of the "transcription binding site turnover." CAED of all APP orthologues and homologues are predicted to bind metal ions including Amyloid-like protein 1 (APLP1) and Amyloid-like protein 2 (APLP2). Our results suggest that HDs on the CAEDs are most probably key components of metal-binding domains, which facilitate and/or regulate inter- or intra-molecular interactions in a metal ion-dependent or metal ion concentration-dependent manner. The involvement of naturally occurring mutations of HD (Tottori (D7N) and English (H6R) mutations) in early onset Alzheimer's disease gives additional support to our finding that HD has an evolutionary preserved function on APPOs.

Positive Evolutionary Selection of an HD Motif on Alzheimer Precursor Protein Orthologues Suggests a Functional Role

PubMed Central

Miklós, István; Zádori, Zoltán

2012-01-01

HD amino acid duplex has been found in the active center of many different enzymes. The dyad plays remarkably different roles in their catalytic processes that usually involve metal coordination. An HD motif is positioned directly on the amyloid beta fragment (Aβ) and on the carboxy-terminal region of the extracellular domain (CAED) of the human amyloid precursor protein (APP) and a taxonomically well defined group of APP orthologues (APPOs). In human Aβ HD is part of a presumed, RGD-like integrin-binding motif RHD; however, neither RHD nor RXD demonstrates reasonable conservation in APPOs. The sequences of CAEDs and the position of the HD are not particularly conserved either, yet we show with a novel statistical method using evolutionary modeling that the presence of HD on CAEDs cannot be the result of neutral evolutionary forces (p<0.0001). The motif is positively selected along the evolutionary process in the majority of APPOs, despite the fact that HD motif is underrepresented in the proteomes of all species of the animal kingdom. Position migration can be explained by high probability occurrence of multiple copies of HD on intermediate sequences, from which only one is kept by selective evolutionary forces, in a similar way as in the case of the “transcription binding site turnover.” CAED of all APP orthologues and homologues are predicted to bind metal ions including Amyloid-like protein 1 (APLP1) and Amyloid-like protein 2 (APLP2). Our results suggest that HDs on the CAEDs are most probably key components of metal-binding domains, which facilitate and/or regulate inter- or intra-molecular interactions in a metal ion-dependent or metal ion concentration-dependent manner. The involvement of naturally occurring mutations of HD (Tottori (D7N) and English (H6R) mutations) in early onset Alzheimer's disease gives additional support to our finding that HD has an evolutionary preserved function on APPOs. PMID:22319430

Methods to uncover an antibody epitope in the KPI domain of Alzheimer's amyloid precursor protein for immunohistochemistry in human brain.

PubMed

Campbell, E; Pearson, R C; Parkinson, D

1999-11-15

A novel polyclonal antibody (Ab993), specific for a KPI domain epitope of APP, was characterised for use in immunoprecipitation, Western blotting and immunohistochemistry. Conditioned medium from NTera2/D1 cells was used for immunoprecipitation and Western blots. Paraffin-embedded human brain sections were used for immunohistochemistry. The antibody recognised KPI-containing APP on Western blots after standard solubilisation but immunoprecipitation of soluble APP required reduction with 2-mercaptoethanol followed by alkylation of reduced sulphydryl bonds with sodium iodoacetate. Immunohistochemical staining of human brain sections was significantly enhanced by this pre-treatment. Microwaving of sections also increased immunolabelling, by a mechanism that was additive to reduction and alkylation. Incubation in 80% formic acid did not confer any enhancement of immunoreactivity. Ab993, applied with the methods reported here, is expected to be valuable in investigations of the pathogenesis of Alzheimer's disease to determine the source of the beta-amyloid peptide.

Platelets are responsible for the accumulation of β-amyloid in blood clots inside and around blood vessels in mouse brain after thrombosis.

PubMed

Kucheryavykh, Lilia Y; Dávila-Rodríguez, Josué; Rivera-Aponte, David E; Zueva, Lidia V; Washington, A Valance; Sanabria, Priscilla; Inyushin, Mikhail Y

2017-01-01

Platelets contain beta-amyloid precursor protein (APP) as well as Aβ peptide (Aβ) that can be released upon activation. During thrombosis, platelets are concentrated in clots and activated. We used in vivo fluorescent analysis and electron microscopy in mice to determine to what degree platelets are concentrated in clots. We used immunostaining to visualize Aβ after photothrombosis in mouse brains. Both in vivo results and electron microscopy revealed that platelets were 300-500 times more concentrated in clots than in non-clotted blood. After thrombosis in control mice, but not in thrombocytopenic animals, Aβ immunofluorescence was present inside blood vessels in the visual cortex and around capillaries in the entorhinal cortex. The increased concentration of platelets allows enhanced release of Aβ during thrombosis, suggesting an additional source of Aβ in the brains of Alzheimer's patients that may arise if frequent micro-thrombosis events occur in their brains. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Intracellular APP Domain Regulates Serine-Palmitoyl-CoA Transferase Expression and Is Affected in Alzheimer's Disease

PubMed Central

Grimm, Marcus O. W.; Grösgen, Sven; Rothhaar, Tatjana L.; Burg, Verena K.; Hundsdörfer, Benjamin; Haupenthal, Viola J.; Friess, Petra; Müller, Ulrike; Fassbender, Klaus; Riemenschneider, Matthias; Grimm, Heike S.; Hartmann, Tobias

2011-01-01

Lipids play an important role as risk or protective factors in Alzheimer's disease (AD), a disease biochemically characterized by the accumulation of amyloid beta peptides (Aβ), released by proteolytic processing of the amyloid precursor protein (APP). Changes in sphingolipid metabolism have been associated to the development of AD. The key enzyme in sphingolipid de novo synthesis is serine-palmitoyl-CoA transferase (SPT). In the present study we identified a new physiological function of APP in sphingolipid synthesis. The APP intracellular domain (AICD) was found to decrease the expression of the SPT subunit SPTLC2, the catalytic subunit of the SPT heterodimer, resulting in that decreased SPT activity. AICD function was dependent on Fe65 and SPTLC2 levels are increased in APP knock-in mice missing a functional AICD domain. SPTLC2 levels are also increased in familial and sporadic AD postmortem brains, suggesting that SPT is involved in AD pathology. PMID:21660213

Identification of Human Islet Amyloid Polypeptide as a BACE2 Substrate

PubMed Central

Rulifson, Ingrid C.; Cao, Ping; Miao, Li; Kopecky, David; Huang, Linda; White, Ryan D.; Samayoa, Kim; Gardner, Jonitha; Wu, Xiaosu; Chen, Kui; Tsuruda, Trace; Homann, Oliver; Baribault, Helene; Yamane, Harvey; Carlson, Tim; Wiltzius, Jed; Li, Yang

2016-01-01

Pancreatic amyloid formation by islet amyloid polypeptide (IAPP) is a hallmark pathological feature of type 2 diabetes. IAPP is stored in the secretory granules of pancreatic beta-cells and co-secreted with insulin to maintain glucose homeostasis. IAPP is innocuous under homeostatic conditions but imbalances in production or processing of IAPP may result in homodimer formation leading to the rapid production of cytotoxic oligomers and amyloid fibrils. The consequence is beta-cell dysfunction and the accumulation of proteinaceous plaques in and around pancreatic islets. Beta-site APP-cleaving enzyme 2, BACE2, is an aspartyl protease commonly associated with BACE1, a related homolog responsible for amyloid processing in the brain and strongly implicated in Alzheimer’s disease. Herein, we identify two distinct sites of the mature human IAPP sequence that are susceptible to BACE2-mediated proteolytic activity. The result of proteolysis is modulation of human IAPP fibrillation and human IAPP protein degradation. These results suggest a potential therapeutic role for BACE2 in type 2 diabetes-associated hyperamylinaemia. PMID:26840340

APP with Kunitz type protease inhibitor domain (KPI) correlates with neuritic plaque density but not with cortical synaptophysin immunoreactivity in Alzheimer's disease and non-demented aged subjects: a multifactorial analysis.

PubMed

Zhan, S S; Sandbrink, R; Beyreuther, K; Schmitt, H P

1995-01-01

The formation of beta A4 amyloid protein in neuritic plaques in Alzheimer's disease (AD) and advanced age is a complex process that involves a number of both cellular and molecular mechanisms, the interrelations of which are not yet completely understood. We have examined quantitatively, in AD and aged controls an extended spectrum of amyloid plaque-related cellular and molecular factors and the cortical synaptophysin immunoreactivity (synaptic density) in order to check for interrelations between them by multifactorial analysis. In 3 cases of senile dementia of the Alzheimer type (SDAT) aged 72, 80 and 82 years, and 9 controls aged 43-88 (mean age 65) years, the cortical synaptophysin immunoreactivity was assessed, together with the numbers of neurons, astrocytes and microglial cells, senile plaques, of tangle-bearing neurons, and the amount of beta A4 amyloid precursor protein (APP) with and without the Kunitz type serine protease inhibitor (KPI) domain. The main results were: APP including the KPI domain (KPI-APP) correlated with the number of neuritic plaques, regardless of whether they occurred in SDAT or non-demented controls. There was no significant difference in the amount of KPI-APP between SDAT and controls. Conversely, APP695 (without KPI) was significantly reduced in SDAT. KPI-APP did not correlate with the synaptophysin immunoreactivity (RGVA), while APP695 showed a significant correlation with the latter in all evaluations. It also correlated with the neuron counts, which was not true for KPI-APP. These results support previous findings indicating that KPI-APP is an important local factor for amyloid deposition in the neuritic plaques, both in AD and in non-demented aged people. On the contrary, KPI-APP does not seem to be significantly involved in the mechanisms of synaptic change outside of the plaques.

Selective vulnerability of dentate granule cells prior to amyloid deposition in PDAPP mice: digital morphometric analyses.

PubMed

Wu, Chi-Cheng; Chawla, Faisal; Games, Dora; Rydel, Russell E; Freedman, Stephen; Schenk, Dale; Young, Warren G; Morrison, John H; Bloom, Floyd E

2004-05-04

Increasing evidence from mouse models of Alzheimer's disease shows that overexpression of a mutant form of the amyloid precursor protein (APP) and its product, beta-amyloid peptide, initiate pathological changes before amyloid deposition. To evaluate the cytological basis for one of these early changes, namely reduced volume of the dentate gyrus (DG), we have used high-throughput diOlistic cell loading and 3D neuronal reconstruction to investigate potential dendritic pathology of granule cells (GCs) in 90-day-old PDAPP mice. Labeled GCs from fixed hippocampal slices were selected randomly and imaged digitally by using confocal laser-scanning microscopy. The dendritic complexity of GCs was quantified according to subordinate morphological parameters, including soma position within the granule cell layer (superficial versus deep) and topographic location within the DG (dorsal versus ventral blade) along the anterior-posterior hippocampal axis. Initial analysis, which included all sampled GC types, revealed a 12% reduction of total dendritic length in PDAPP mice compared with littermate controls. Further analysis, performed with refined subgroups, found that superficially located GCs in the dorsal blade were profoundly altered, exhibiting a 23% loss in total dendritic length, whereas neurons in the ventral blade were unaffected. Superficial GCs were particularly vulnerable (a 32% reduction) in the posterior region of the DG. Furthermore, the dendritic reductions of this select group were uniformly localized within middle-to-outer portions of the dentate molecular layer. We conclude that substantial dendritic pathology is evident in 90-day-old PDAPP mice for a spatially defined subset of GCs well before amyloid accumulation occurs.

Aging, cortical injury and Alzheimer's disease-like pathology in the guinea pig brain.

PubMed

Bates, Kristyn; Vink, Robert; Martins, Ralph; Harvey, Alan

2014-06-01

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized histopathologically by the abnormal deposition of the proteins amyloid-beta (Aβ) and tau. A major issue for AD research is the lack of an animal model that accurately replicates the human disease, thus making it difficult to investigate potential risk factors for AD such as head injury. Furthermore, as age remains the strongest risk factor for most of the AD cases, transgenic models in which mutant human genes are expressed throughout the life span of the animal provide only limited insight into age-related factors in disease development. Guinea pigs (Cavia porcellus) are of interest in AD research because they have a similar Aβ sequence to humans and thus may present a useful non-transgenic animal model of AD. Brains from guinea pigs aged 3-48 months were examined to determine the presence of age-associated AD-like pathology. In addition, fluid percussion-induced brain injury was performed to characterize mechanisms underlying the association between AD risk and head injury. No statistically significant changes were detected in the overall response to aging, although we did observe some region-specific changes. Diffuse deposits of Aβ were found in the hippocampal region of the oldest animals and alterations in amyloid precursor protein processing and tau immunoreactivity were observed with age. Brain injury resulted in a strong and sustained increase in amyloid precursor protein and tau immunoreactivity without Aβ deposition, over 7 days. Guinea pigs may therefore provide a useful model for investigating the influence of environmental and non-genetic risk factors on the pathogenesis of AD. Copyright © 2014 Elsevier Inc. All rights reserved.

Herpes simplex virus interferes with amyloid precursor protein processing.

PubMed

Shipley, Suzanne J; Parkin, Edward T; Itzhaki, Ruth F; Dobson, Curtis B

2005-08-18

The early events underlying Alzheimer's disease (AD) remain uncertain, although environmental factors may be involved. Work in this laboratory has shown that the combination of herpes simplex virus type 1 (HSV1) in brain and carriage of the APOE-epsilon4 allele of the APOE gene strongly increases the risk of developing AD. The development of AD is thought to involve abnormal aggregation or deposition of a 39-43 amino acid protein--beta amyloid (Abeta)--within the brain. This is cleaved from the much larger transmembranal protein 'amyloid precursor protein' (APP). Any agent able to interfere directly with Abeta or APP metabolism may therefore have the capacity to contribute towards AD. One recent report showed that certain HSV1 glycoprotein peptides may aggregate like Abeta; a second study described a role for APP in transport of virus in squid axons. However to date the effects of acute herpesvirus infection on metabolism of APP in human neuronal-type cells have not been investigated. In order to find if HSV1 directly affects APP and its degradation, we have examined this protein from human neuroblastoma cells (normal and transfected with APP 695) infected with the virus, using Western blotting. We have found that acute HSV1 (and also HSV2) infection rapidly reduces full length APP levels--as might be expected--yet surprisingly markedly increases levels of a novel C-terminal fragment of APP of about 55 kDa. This band was not increased in cells treated with the protein synthesis inhibitor cycloheximide Herpes virus infection leads to rapid loss of full length APP from cells, yet also causes increased levels of a novel 55 kDa C-terminal APP fragment. These data suggest that infection can directly alter the processing of a transmembranal protein intimately linked to the aetiology of AD.

Cholinergic neurodegeneration in an Alzheimer mouse model overexpressing amyloid-precursor protein with the Swedish-Dutch-Iowa mutations.

PubMed

Foidl, Bettina Maria; Do-Dinh, Patricia; Hutter-Schmid, Bianca; Bliem, Harald R; Humpel, Christian

2016-12-01

Alzheimer's disease (AD) is a chronic neurodegenerative disorder that is mainly characterized by beta-amyloid (Aβ) plaque deposition, Tau pathology and dysfunction of the cholinergic system causing memory impairment. The aim of the present study was to examine (1) anxiety and cognition, (2) Aβ plaque deposition and (3) degeneration of cholinergic neurons in the nucleus basalis of Meynert (nbM) and cortical cholinergic innervation in an Alzheimer mouse model (APP_SweDI; overexpressing amyloid precursor protein (APP) with the Swedish K670N/M671L, Dutch E693Q, and Iowa D694N mutations). Our results show that 12-month-old APP_SweDI mice were more anxious and had more memory impairment. A large number of Aβ plaques were already visible at the age of 6 months and increased with age. A significant decrease in cholinergic neurons was seen in the transgenic mouse model in comparison to the wild-type mice, identified by immunohistochemistry against choline acetyltransferase (ChAT) and p75 neurotrophin receptor as well as by in situ hybridization. Moreover, a significant decrease in cortical cholinergic fiber density was found in the transgenic mice as compared to the wild-type. In the cerebral cortex of APP_SweDI mice, swollen cholinergic varicosities were seen in the vicinity of Aβ plaques. In conclusion, the present study shows that in an AD mouse model (APP_SweDI mice) a high Aβ plaque load in the cortex causes damage to cholinergic axons in the cortex, followed by subsequent retrograde-induced cell death of cholinergic neurons and some forms of compensatory processes. This degeneration was accompanied by enhanced anxiety and impaired cognition. Copyright © 2016 Elsevier Inc. All rights reserved.

Protein-induced Photophysical Changes to the Amyloid Indicator Dye Thioflavin T

DOE Office of Scientific and Technical Information (OSTI.GOV)

L Wolfe; M Calabrese; A Nath

2011-12-31

The small molecule thioflavin T (ThT) is a defining probe for the identification and mechanistic study of amyloid fiber formation. As such, ThT is fundamental to investigations of serious diseases such as Alzheimer's disease, Parkinson disease, and type II diabetes. For each disease, a different protein undergoes conformational conversion to a {beta}-sheet rich fiber. The fluorescence of ThT exhibits an increase in quantum yield upon binding these fibers. Despite its widespread use, the structural basis for binding specificity and for the changes to the photophysical properties of ThT remain poorly understood. Here, we report the co-crystal structures of ThT withmore » two alternative states of {beta}-2 microglobulin ({beta}2m); one monomeric, the other an amyloid-like oligomer. In the latter, the dye intercalates between {beta}-sheets orthogonal to the {beta}-strands. Importantly, the fluorophore is bound in such a manner that a photophysically relevant torsion is limited to a range of angles generally associated with low, not high, quantum yield. Quantum mechanical assessment of the fluorophore shows the electronic distribution to be strongly stabilized by aromatic interactions with the protein. Monomeric {beta}2m gives little increase in ThT fluorescence despite showing three fluorophores, at two binding sites, in configurations generally associated with high quantum yield. Our efforts fundamentally extend existing understanding about the origins of amyloid-induced photophysical changes. Specifically, the {beta}-sheet interface that characterizes amyloid acts both sterically and electronically to stabilize the fluorophore's ground state electronic distribution. By preventing the fluorophore from adopting its preferred excited state configuration, nonradiative relaxation pathways are minimized and quantum yield is increased.« less

Protein-induced photophysical changes to the amyloid indicator dye thioflavin T

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolfe, Leslie S.; Calabrese, Matthew F.; Nath, Abhinav

2010-10-04

The small molecule thioflavin T (ThT) is a defining probe for the identification and mechanistic study of amyloid fiber formation. As such, ThT is fundamental to investigations of serious diseases such as Alzheimer's disease, Parkinson disease, and type II diabetes. For each disease, a different protein undergoes conformational conversion to a {beta}-sheet rich fiber. The fluorescence of ThT exhibits an increase in quantum yield upon binding these fibers. Despite its widespread use, the structural basis for binding specificity and for the changes to the photophysical properties of ThT remain poorly understood. Here, we report the co-crystal structures of ThT withmore » two alternative states of {beta}-2 microglobulin ({beta}2m); one monomeric, the other an amyloid-like oligomer. In the latter, the dye intercalates between {beta}-sheets orthogonal to the {beta}-strands. Importantly, the fluorophore is bound in such a manner that a photophysically relevant torsion is limited to a range of angles generally associated with low, not high, quantum yield. Quantum mechanical assessment of the fluorophore shows the electronic distribution to be strongly stabilized by aromatic interactions with the protein. Monomeric {beta}2m gives little increase in ThT fluorescence despite showing three fluorophores, at two binding sites, in configurations generally associated with high quantum yield. Our efforts fundamentally extend existing understanding about the origins of amyloid-induced photophysical changes. Specifically, the {beta}-sheet interface that characterizes amyloid acts both sterically and electronically to stabilize the fluorophore's ground state electronic distribution. By preventing the fluorophore from adopting its preferred excited state configuration, nonradiative relaxation pathways are minimized and quantum yield is increased.« less

Phosphate and HEPES buffers potently affect the fibrillation and oligomerization mechanism of Alzheimer's A{beta} peptide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garvey, Megan; Tepper, Katharina; Haupt, Caroline

Highlights: {yields} Sodium phosphate buffer accelerated A{beta}(1-40) nucleation relative to HEPES. {yields} A{beta}(1-40) fibrils formed in the two buffers show only minor structural differences. {yields} NMR revealed that A{beta}(1-40) histidine residues mediate buffer dependent changes. -- Abstract: The oligomerization of A{beta} peptide into amyloid fibrils is a hallmark of Alzheimer's disease. Due to its biological relevance, phosphate is the most commonly used buffer system for studying the formation of A{beta} and other amyloid fibrils. Investigation into the characteristics and formation of amyloid fibrils frequently relies upon material formed in vitro, predominantly in phosphate buffers. Herein, we examine the effects onmore » the fibrillation and oligomerization mechanism of A{beta} peptide that occur due solely to the influence of phosphate buffer. We reveal that significant differences in amyloid fibrillation are observed due to fibrillation being initiated in phosphate or HEPES buffer (at physiological pH and temperature). Except for the differing buffer ions, all experimental parameters were kept constant. Fibril formation was assessed using fluorescently monitored kinetic studies, microscopy, X-ray fiber diffraction and infrared and nuclear magnetic resonance spectroscopies. Based on this set up, we herein reveal profound effects on the mechanism and speed of A{beta} fibrillation. The three histidine residues at positions 6, 13 and 14 of A{beta}(1-40) are instrumental in these mechanistic changes. We conclude that buffer plays a more significant role in fibril formation than has been generally acknowledged.« less

LRP-mediated clearance of Abeta is inhibited by KPI-containing isoforms of APP.

PubMed

Moir, Robert D; Tanzi, Rudolph E

2005-04-01

The pathogenesis of Alzheimer's disease (AD) involves the abnormal accumulation and deposition of beta-amyloid in cerebral blood vessels and in the brain parenchyma. Critical in modulating beta-amyloid deposition in brain is the flux of Abeta across the blood brain barrier. The low-density lipoprotein receptor-related protein (LRP), is a large endocytic receptor that mediates the efflux of Abeta out of brain and into the periphery. The first step in the LRP-mediated clearance of Abeta involves the formation of a complex between Abeta and the LRP ligands apolipoprotein E (apoE) or alpha(2)-macroglobulin (alpha(2)M). The Abeta/chaperone complexes then bind to LRP via binding sites on apoE or alpha(2)M. The efflux of Abeta/chaperone complexes out of the neuropil and into the periphery may be attenuated by LRP-ligands that compete with apoE or alpha(2)M for LRP binding. LRP is also the cell surface receptor for Kunitz Protease Inhibitor (KPI) containing isoforms of Abeta's parent protein, the amyloid protein precursor (APP). Protein and mRNA levels of KPI-containing APP isoforms (APP-KPI) are elevated in AD brain and are associated with increased Abeta production. In this study we show that soluble non-amyloidogenic APP-KPI can also inhibit the uptake of Abeta/alpha(2)M in a cell culture model of LRP mediated Abeta clearance. Clearance of Abeta/apoE complexes was not inhibited by APP-KPI. Our findings are consistent with studies showing that apoE and alpha(2)M have discrete binding sites on LRP. Most significantly, our data suggests that the elevated levels of APP-KPI in AD brain may attenuate the clearance of Abeta, the proteins own amyloidogenic catabolic product.

Cerebral amyloid-beta protein accumulation with aging in cotton-top tamarins: a model of early Alzheimer's disease?

PubMed

Lemere, Cynthia A; Oh, Jiwon; Stanish, Heather A; Peng, Ying; Pepivani, Imelda; Fagan, Anne M; Yamaguchi, Haruyasu; Westmoreland, Susan V; Mansfield, Keith G

2008-04-01

Alzheimer's disease (AD) is the most common progressive form of dementia in the elderly. Two major neuropathological hallmarks of AD include cerebral deposition of amyloid-beta protein (Abeta) into plaques and blood vessels, and the presence of neurofibrillary tangles in brain. In addition, activated microglia and reactive astrocytes are often associated with plaques and tangles. Numerous other proteins are associated with plaques in human AD brain, including Apo E and ubiquitin. The amyloid precursor protein and its shorter fragment, Abeta, are homologous between humans and non-human primates. Cerebral Abeta deposition has been reported previously for rhesus monkeys, vervets, squirrel monkeys, marmosets, lemurs, cynomologous monkeys, chimpanzees, and orangutans. Here we report, for the first time, age-related neuropathological changes in cotton-top tamarins (CTT, Saguinus oedipus), an endangered non-human primate native to the rainforests of Colombia and Costa Rica. Typical lifespan is 13-14 years of age in the wild and 15-20+ years in captivity. We performed detailed immunohistochemical analyses of Abeta deposition and associated pathogenesis in archived brain sections from 36 tamarins ranging in age from 6-21 years. Abeta plaque deposition was observed in 16 of the 20 oldest tamarins (>12 years). Plaques contained mainly Abeta42, and in the oldest animals, were associated with reactive astrocytes, activated microglia, Apo E, and ubiquitin-positive dystrophic neurites, similar to human plaques. Vascular Abeta was detected in 14 of the 20 aged tamarins; Abeta42 preceded Abeta40 deposition. Phospho-tau labeled dystrophic neurites and tangles, typically present in human AD, were absent in the tamarins. In conclusion, tamarins may represent a model of early AD pathology.

Dysregulation of cellular calcium homeostasis in Alzheimer's disease: bad genes and bad habits.

PubMed

Mattson, M P; Chan, S L

2001-10-01

Calcium is one of the most important intracellular messengers in the brain, being essential for neuronal development, synaptic transmission and plasticity, and the regulation of various metabolic pathways. The findings reviewed in the present article suggest that calcium also plays a prominent role in the pathogenesis of Alzheimer's disease (AD). Associations between the pathological hallmarks ofAD (neurofibrillary tangles [NFT] and amyloid plaques) and perturbed cellular calcium homeostasis have been established in studies of patients, and in animal and cell culture models of AD. Studies of the effects of mutations in the beta-amyloid precursor protein (APP) and presenilins on neuronal plasticity and survival have provided insight into the molecular cascades that result in synaptic dysfunction and neuronal degeneration in AD. Central to the neurodegenerative process is the inability of neurons to properly regulate intracellular calcium levels. Increased levels of amyloid beta-peptide (Abeta) induce oxidative stress, which impairs cellular ion homeostasis and energy metabolism and renders neurons vulnerable to apoptosis and excitotoxicity. Subtoxic levels of Abeta may induce synaptic dysfunction by impairing multiple signal transduction pathways. Presenilin mutations perturb calcium homeostasis in the endoplasmic reticulum in a way that sensitizes neurons to apoptosis and excitotoxicity; links between aberrant calcium regulation and altered APP processing are emerging. Environmental risk factors for AD are being identified and may include high calorie diets, folic acid insufficiency, and a low level of intellectual activity (bad habits); in each case, the environmental factor impacts on neuronal calcium homeostasis. Low calorie diets and intellectual activity may guard against AD by stimulating production of neurotrophic factors and chaperone proteins. The emerging picture of the cell and molecular biology of AD is revealing novel preventative and therapeutic strategies for eradicating this growing epidemic of the elderly.

Obesity in aging exacerbates blood-brain barrier disruption, neuroinflammation, and oxidative stress in the mouse hippocampus: effects on expression of genes involved in beta-amyloid generation and Alzheimer's disease.

PubMed

Tucsek, Zsuzsanna; Toth, Peter; Sosnowska, Danuta; Gautam, Tripti; Mitschelen, Matthew; Koller, Akos; Szalai, Gabor; Sonntag, William E; Ungvari, Zoltan; Csiszar, Anna

2014-10-01

There is growing evidence that obesity has deleterious effects on the brain and cognitive function in the elderly population. However, the specific mechanisms through which aging and obesity interact to promote cognitive decline remain unclear. To test the hypothesis that aging exacerbates obesity-induced cerebromicrovascular damage and neuroinflammation, we compared young (7 months) and aged (24 months) high fat diet-fed obese C57BL/6 mice. Aging exacerbated obesity-induced systemic inflammation and blood-brain barrier disruption, as indicated by the increased circulating levels of proinflammatory cytokines and increased presence of extravasated immunoglobulin G in the hippocampus, respectively. Obesity-induced blood-brain barrier damage was associated with microglia activation, upregulation of activating Fc-gamma receptors and proinflammatory cytokines, and increased oxidative stress. Treatment of cultured primary microglia with sera derived from aged obese mice resulted in significantly more pronounced microglia activation and oxidative stress, as compared with treatment with young sera. Serum-induced activation and oxidative stress were also exacerbated in primary microglia derived from aged animals. Hippocampal expression of genes involved in regulation of the cellular amyloid precursor protein-dependent signaling pathways, beta-amyloid generation, and the pathogenesis of tauopathy were largely unaffected by obesity in aged mice. Collectively, obesity in aging is associated with a heightened state of systemic inflammation, which exacerbates blood-brain barrier disruption. The resulting neuroinflammation and oxidative stress in the mouse hippocampus likely contribute to the significant cognitive decline observed in aged obese animals. © The Author 2013. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Effects of combined radiofrequency field exposure on amyloid-beta–induced cytotoxicity in HT22 mouse hippocampal neurones

PubMed Central

Lee, Jong-Sun; Kim, Jeong-Yub; Kim, Hee-Jin; Kim, Jeong Cheol; Lee, Jae-Seon; Kim, Nam; Park, Myung-Jin

2016-01-01

Alzheimer's disease (AD) is the most common progressive and irreversible neurodegenerative disease and it is caused by neuronal death in the brain. Recent studies have shown that non-ionizing radiofrequency (RF) radiation has some beneficial cognitive effects in animal models of AD. In this study, we examined the effect of combined RF radiation on amyloid-beta (Aβ)–induced cytotoxicity in HT22 rat hippocampal neurons. Treatment with Aβ suppressed HT22 cell proliferation in a concentration-dependent manner. RF exposure did not affect cell proliferation, and also had a marginal effect on Aβ-induced suppression of growth in HT22 cells. Cell cycle analysis showed that Aβ decreased the G1 fraction and increased the subG1 fraction, indicating increased apoptosis. Accordingly, Aβ increased the annexin V/propidium iodide (PI)–positive cell fraction and the degradation of poly (ADP ribose) polymerase and caspase-3 in HT22 cells. However, RF alone and the combination of Aβ and RF did not affect these events significantly. Aβ increased reactive oxygen species (ROS) generation, thereby suppressing cell proliferation. This was abrogated by N-acetylcysteine (NAC) treatment, indicating that Aβ-induced ROS generation is the main cause of suppression of proliferation. NAC also restored Aβ-induced annexin V/PI–positive cell populations. However, RF did not have a significant impact on these events. Finally, Aβ stimulated the ataxia telangiectasia and Rad3-related protein/checkpoint kinase 1 DNA single-strand breakage pathway, and enhanced beta-site amyloid precursor protein expression; RF had no effect on them. Taken together, our results demonstrate that RF exposure did not significantly affect the Aβ-induced decrease of cell proliferation, increase of ROS production, or induction of cell death in these cells. PMID:27325640

A second locus for very-late-onset Alzheimer disease: a genome scan reveals linkage to 20p and epistasis between 20p and the amyloid precursor protein region.

PubMed

Olson, Jane M; Goddard, Katrina A B; Dudek, Doreen M

2002-07-01

We used a covariate-based linkage method to reanalyze genome scan data from affected sibships collected by the Alzheimer Disease (AD) Genetics Initiative of the National Institute of Mental Health. As reported in an earlier article, the amyloid-beta precursor protein (APP) region is strongly linked to affected sib pairs of the oldest current age (i.e., age either at last exam or at death) who lack E4 alleles at the apolipoprotein E (ApoE) locus. We now report that a region on 20p shows the same pattern. A model that includes current age and the number of E2 alleles as covariates gives a LOD score of 4.1. The signal on 20p is near the location of the gene coding for cystatin-C, previously shown to be associated with late-onset AD and to codeposit with APP in the brains of patients with AD. Two-locus analysis provides evidence of strong epistasis between 20p and the APP region, limited to the oldest age group and to those lacking ApoE4 alleles. We speculate that high-risk polymorphisms in both regions produce a biological interaction between these two proteins that increases susceptibility to a very-late-onset form of AD.

Molecular genetics of Alzheimer disease.

PubMed

St George-Hyslop, P H

1999-01-01

Epidemiological and individual case studies indicate that genetic factors play a significant role in the genesis of Alzheimer Disease (AD). To date, molecular genetic studies in families multiply affected with AD have identified three genes (Presenilin 1-PS1, Presenilin 2-PS2, and beta-amyloid precursor protein--betaAPP) associated with highly penetrant early onset AD, and one gene (Apolipoprotein E) associated with late onset AD. A fifth potential AD susceptibility locus has been mapped to a broad region of chromosome 12, but the responsible gene defect has not yet been identified. Case-control studies comparing the frequency of alleles in numerous other candidate genes have identified a number of additional potential AD genes. However, methodological difficulties and conflicting results in follow-up studies, make it unclear whether allelic variations in these genes are truly pathogenic. Nevertheless, analysis of the biochemical effects of mutations in PS1, PS2, betaAPP at least, suggest a common biochemical effect-namely disturbances in the processing of betaAPP protein. In addition to utility in defining potential therapeutic targets, in some circumstances these genes can also potentially be used as adjunctives in clinical presymptomatic, symptomatic or pharmacogenomic diagnosis.

Zinc(II) binds to the neuroprotective peptide humanin.

PubMed

Armas, Ambar; Sonois, Vanessa; Mothes, Emmanuelle; Mazarguil, Honoré; Faller, Peter

2006-10-01

The abnormal accumulation of the peptide amyloid-beta in the form of senile (or amyloid) plaques is one of the hallmarks of Alzheimer's disease (AD). Zinc ions have been implicated in AD and plaques formation. Recently, the peptide humanin has been discovered. Humanin showed neuroprotective activity against amyloid-beta insults. Here the question investigated is if humanin could interact directly with Zn(II). It is shown that Zn(II) and its substitutes Cd(II)/Co(II) bind to humanin via a thiolate bond from the side chain of the single cysteine at position 8. The low intensity of the d-d bands of Co(II)-humanin indicated an octahedral coordination geometry. Titration experiments suggest that Zn(II) binds to humanin with an apparent affinity in the low muM range. This apparent Zn-binding affinity is in the same order as for amyloid-beta and glutathione and could thus be of physiological relevance.

Methanolic extract of Piper nigrum fruits improves memory impairment by decreasing brain oxidative stress in amyloid beta(1-42) rat model of Alzheimer's disease.

PubMed

Hritcu, Lucian; Noumedem, Jaurès A; Cioanca, Oana; Hancianu, Monica; Kuete, Victor; Mihasan, Marius

2014-04-01

The present study analyzed the possible memory-enhancing and antioxidant proprieties of the methanolic extract of Piper nigrum L. fruits (50 and 100 mg/kg, orally, for 21 days) in amyloid beta(1-42) rat model of Alzheimer's disease. The memory-enhancing effects of the plant extract were studied by means of in vivo (Y-maze and radial arm-maze tasks) approaches. Also, the antioxidant activity in the hippocampus was assessed using superoxide dismutase-, catalase-, glutathione peroxidase-specific activities and the total content of reduced glutathione, malondialdehyde, and protein carbonyl levels. The amyloid beta(1-42)-treated rats exhibited the following: decrease of spontaneous alternations percentage within Y-maze task and increase of working memory and reference memory errors within radial arm-maze task. Administration of the plant extract significantly improved memory performance and exhibited antioxidant potential. Our results suggest that the plant extract ameliorates amyloid beta(1-42)-induced spatial memory impairment by attenuation of the oxidative stress in the rat hippocampus.

Octylphenol (OP) alters the expression of members of the amyloid protein family in the hypothalamus of the snapping turtle, Chelydra serpentina serpentina.

PubMed Central

Trudeau, Vance L; Chiu, Suzanne; Kennedy, Sean W; Brooks, Ronald J

2002-01-01

The gonadal estrogen estradiol-17beta (E(2)) is important for developing and regulating hypothalamic function and many aspects of reproduction in vertebrates. Pollutants such as octylphenol (OP) that mimic the actions of estrogens are therefore candidate endocrine-disrupting chemicals. We used a differential display strategy (RNA-arbitrarily primed polymerase chain reaction) to isolate partial cDNA sequences of neurotransmitter, developmental, and disease-related genes that may be regulated by OP or E(2) in the snapping turtle Chelydra serpentina serpentina hypothalamus. Hatchling and year-old male snapping turtles were exposed to a 10 ng/mL nominal concentration of waterborne OP or E(2) for 17 days. One transcript [421 base pairs (bp)] regulated by OP and E(2) was 93% identical to human APLP-2. APLP-2 and the amyloid precursor protein (APP) regulate neuronal differentiation and are also implicated in the genesis of Alzheimer disease in humans. Northern blot analysis determined that the turtle hypothalamus contains a single APLP-2 transcript of 3.75 kb in length. Exposure to OP upregulated hypothalamic APLP-2 mRNA levels 2-fold (p < 0.05) in month-old and yearling turtles. E(2) did not affect APLP-2 mRNA levels in hatchlings but stimulated a 2-fold increase (p < 0.05) in APLP-2 mRNA levels in yearling males. The protein beta-amyloid, a selectively processed peptide derived from APP, is also involved in neuronal differentiation, and accumulation of this neurotoxic peptide causes neuronal degeneration in the brains of patients with Alzheimer disease. Therefore, we also sought to determine the effects of estrogens on the expression of beta-amyloid. Using homology cloning based on known sequences, we isolated a cDNA fragment (474 bp) from turtle brain with 88% identity to human APP. Northern blot analysis determined that a single 3.5-kb transcript was expressed in the turtle hypothalamus. Waterborne OP also increased the expression of hypothalamic APP after 35 days of exposure. Our results indicate that low levels of OP are bioactive and can alter the expression of APLP-2 and APP. Because members of the APP gene family are involved in neuronal development, we hypothesize that OP exposure may disrupt hypothalamic development in young turtles. PMID:11882478

Octylphenol (OP) alters the expression of members of the amyloid protein family in the hypothalamus of the snapping turtle, Chelydra serpentina serpentina.

PubMed

Trudeau, Vance L; Chiu, Suzanne; Kennedy, Sean W; Brooks, Ronald J

2002-03-01

The gonadal estrogen estradiol-17beta (E(2)) is important for developing and regulating hypothalamic function and many aspects of reproduction in vertebrates. Pollutants such as octylphenol (OP) that mimic the actions of estrogens are therefore candidate endocrine-disrupting chemicals. We used a differential display strategy (RNA-arbitrarily primed polymerase chain reaction) to isolate partial cDNA sequences of neurotransmitter, developmental, and disease-related genes that may be regulated by OP or E(2) in the snapping turtle Chelydra serpentina serpentina hypothalamus. Hatchling and year-old male snapping turtles were exposed to a 10 ng/mL nominal concentration of waterborne OP or E(2) for 17 days. One transcript [421 base pairs (bp)] regulated by OP and E(2) was 93% identical to human APLP-2. APLP-2 and the amyloid precursor protein (APP) regulate neuronal differentiation and are also implicated in the genesis of Alzheimer disease in humans. Northern blot analysis determined that the turtle hypothalamus contains a single APLP-2 transcript of 3.75 kb in length. Exposure to OP upregulated hypothalamic APLP-2 mRNA levels 2-fold (p < 0.05) in month-old and yearling turtles. E(2) did not affect APLP-2 mRNA levels in hatchlings but stimulated a 2-fold increase (p < 0.05) in APLP-2 mRNA levels in yearling males. The protein beta-amyloid, a selectively processed peptide derived from APP, is also involved in neuronal differentiation, and accumulation of this neurotoxic peptide causes neuronal degeneration in the brains of patients with Alzheimer disease. Therefore, we also sought to determine the effects of estrogens on the expression of beta-amyloid. Using homology cloning based on known sequences, we isolated a cDNA fragment (474 bp) from turtle brain with 88% identity to human APP. Northern blot analysis determined that a single 3.5-kb transcript was expressed in the turtle hypothalamus. Waterborne OP also increased the expression of hypothalamic APP after 35 days of exposure. Our results indicate that low levels of OP are bioactive and can alter the expression of APLP-2 and APP. Because members of the APP gene family are involved in neuronal development, we hypothesize that OP exposure may disrupt hypothalamic development in young turtles.

Conditional Depletion of Hippocampal Brain-Derived Neurotrophic Factor Exacerbates Neuropathology in a Mouse Model of Alzheimer's Disease.

PubMed

Braun, David J; Kalinin, Sergey; Feinstein, Douglas L

2017-01-01

Damage occurring to noradrenergic neurons in the locus coeruleus (LC) contributes to the evolution of neuroinflammation and neurodegeneration in a variety of conditions and diseases. One cause of LC damage may be loss of neurotrophic support from LC target regions. We tested this hypothesis by conditional unilateral knockout of brain-derived neurotrophic factor (BDNF) in adult mice. To evaluate the consequences of BDNF loss in the context of neurodegeneration, the mice harbored familial mutations for human amyloid precursor protein and presenilin-1. In these mice, BDNF depletion reduced tyrosine hydroxylase staining, a marker of noradrenergic neurons, in the rostral LC. BDNF depletion also reduced noradrenergic innervation in the hippocampus, the frontal cortex, and molecular layer of the cerebellum, assessed by staining for dopamine beta hydroxylase. BDNF depletion led to an increase in cortical amyloid plaque numbers and size but was without effect on plaque numbers in the striatum, a site with minimal innervation from the LC. Interestingly, cortical Iba1 staining for microglia was reduced by BDNF depletion and was correlated with reduced dopamine beta hydroxylase staining. These data demonstrate that reduction of BDNF levels in an LC target region can cause retrograde damage to LC neurons, leading to exacerbation of neuropathology in distinct LC target areas. Methods to reduce BDNF loss or supplement BDNF levels may be of value to reduce neurodegenerative processes normally limited by LC noradrenergic activities.

[Noopept improves the spatial memory and stimulates prefibrillar beta-amyloid(25-35) antibody production in mice].

PubMed

Bobkova, N V; Gruden', M A; Samokhin, A N; Medvinskaia, N I; Morozova-Roch, L; Uudasheva, T A; Ostrovskaia, R U; Seredinin, S B

2005-01-01

The effects of the novel proline-containing nootropic and neuroprotective dipeptide noopept (GVS-111, N-phenylacetyl-L-prolylglycine ethyl ester) were studied on NMRI mice upon olfactory bulbectomy, which had been previously shown to imitate the main morphological and biochemical signs of Alzheimer's disease (AD). The spatial memory was assessed using the Morris (water maze) test; the immunological status was characterized by ELISA with antibodies to prefibrillar beta-amyloid(25-35), S100b protein, and protofilaments of equine lysozyme, which are the molecular factors involved in the pathogenesis of AD. The control (sham-operated) animals during the Morris test preferred a sector where the safety platform was placed during the learning session. Bulbectomized animals treated with saline failed to recognize this sector, while bulbectomized animals treated with noopept (0.01 mg/kg for 21 days) restored this predominance, thus demonstrating the improvement of the spatial memory. These animals also demonstrated an increase in the level of antibodies to beta-amyloid(25-35)--the effect, which was more pronounced in the sham-operated than in bulbectomized mice. The latter demonstrated a profound decrease of immunological reactivity in a large number of tests. Noopept, stimulating the production of antibodies to beta-amyloid(25-35), can attenuate the well-known neurotoxic effects of beta-amyloid. The obtained data on the mnemotropic and immunostimulant effects noopept are indicative of good prospects for the clinical usage of this drug in the therapy of patients with neurodegenerative diseases.

Screening of plants used in the European traditional medicine to treat memory disorders for acetylcholinesterase inhibitory activity and anti amyloidogenic activity.

PubMed

Lobbens, Eva S B; Vissing, Karina J; Jorgensen, Lene; van de Weert, Marco; Jäger, Anna K

2017-03-22

Plants used in the traditional medicine of Europe to treat memory dysfunction and/or to enhance memory were investigated for activity against the underlying mechanisms of Alzheimer's disease. To investigate 35 ethanolic extracts of plants, selected using an ethnopharmacological approach, for anti-amyloidogenic activity as well as an ability to inhibit the enzymatic activity of acetylcholinesterase. The anti-amyloidogenic activity of the extracts against amyloid beta was investigated by Thioflavin T fibrillation assays and the ability to inhibit the enzymatic activity of acetylcholinesterase was evaluated monitoring the hydrolysis of acetylthiocholine RESULTS: Under the experimental conditions investigated, extracts of two plants, Carum carvi and Olea sylvestris, inhibited amyloid beta fibrillation considerably, eight plant extracts inhibited amyloid beta fibrillation to some extent, 16 plant extracts had no effect on amyloid beta fibrillation and nine extracts accelerated fibrillation of amyloid beta. Furthermore, five plant extracts from Corydalis species inhibited the enzymatic activity of acetylcholinesterase considerably, one plant extract inhibited the enzymatic activity of acetylcholinesterase to some extent and 29 plant extract had no effect on the enzymatic activity of acetylcholinesterase. An optimal extract in this study would possess acetylcholinesterase inhibitory activity as well as anti-amyloidogenic activity in order to address multiple facets of Alzheimer's disease, until the molecular origin of the disease is unraveled. Unfortunately no such extract was found. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

Impaired JIP3-dependent axonal lysosome transport promotes amyloid plaque pathology

PubMed Central

Gowrishankar, Swetha; Wu, Yumei

2017-01-01

Lysosomes robustly accumulate within axonal swellings at Alzheimer’s disease (AD) amyloid plaques. However, the underlying mechanisms and disease relevance of such lysosome accumulations are not well understood. Motivated by these problems, we identified JNK-interacting protein 3 (JIP3) as an important regulator of axonal lysosome transport and maturation. JIP3 knockout mouse neuron primary cultures accumulate lysosomes within focal axonal swellings that resemble the dystrophic axons at amyloid plaques. These swellings contain high levels of amyloid precursor protein processing enzymes (BACE1 and presenilin 2) and are accompanied by elevated Aβ peptide levels. The in vivo importance of the JIP3-dependent regulation of axonal lysosomes was revealed by the worsening of the amyloid plaque pathology arising from JIP3 haploinsufficiency in a mouse model of AD. These results establish the critical role of JIP3-dependent axonal lysosome transport in regulating amyloidogenic amyloid precursor protein processing and support a model wherein Aβ production is amplified by plaque-induced axonal lysosome transport defects. PMID:28784610

A specific RAGE-binding peptide biopanning from phage display random peptide library that ameliorates symptoms in amyloid β peptide-mediated neuronal disorder.

PubMed

Cai, Cuizan; Dai, Xiaoyong; Zhu, Yujie; Lian, Mengyang; Xiao, Fei; Dong, Fangyuan; Zhang, Qihao; Huang, Yadong; Zheng, Qing

2016-01-01

Alzheimer's disease (AD) is an age-related neurodegenerative disorder in which amyloid β (Aβ) peptide accumulates in the brain. The receptor for advanced glycation end product (RAGE) is a cellular binding site for Aβ peptide and mediates amyloid β-induced perturbations in cerebral vessels, neurons, and microglia in AD. Here, we identified a specific high-affinity RAGE inhibitor (APDTKTQ named RP-1) from a phage display library. RP-1 bound to RAGE and inhibited Aβ peptide-induced cellular stress in human neuroblastoma SH-SYSY cells in vitro. Three amino acids in RP-1 are identical to those in the Aβ peptide. RP-1 shows high homology to the 16-23 (KLVFFAED) regions in Aβ peptide and high-affinity RAGE. Functional analyses indicated that RP-1 significantly reduced the level of reactive oxygen species (ROS) and ROS products and that it enhanced catalase and glutathione peroxidase (GPx) activity. Furthermore, it inactivated caspase3 and caspase9 and inhibited the upregulation of RAGE, nuclear factor-κB (NF-κB), and beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1) protein expression. In addition, RP-1 activated the PI3K/AKT signaling pathway, inhibiting the interaction between Bax and Bcl-2. Our data suggest that RP-1 is a potent RAGE blocker that effectively controls the progression of Aβ peptide-mediated brain disorders and that it may have potential as a disease-modifying agent for AD.

2-Deoxy-D-glucose treatment induces ketogenesis, sustains mitochondrial function, and reduces pathology in female mouse model of Alzheimer's disease.

PubMed

Yao, Jia; Chen, Shuhua; Mao, Zisu; Cadenas, Enrique; Brinton, Roberta Diaz

2011-01-01

Previously, we demonstrated that mitochondrial bioenergetic deficits preceded Alzheimer's disease (AD) pathology in the female triple-transgenic AD (3xTgAD) mouse model. In parallel, 3xTgAD mice exhibited elevated expression of ketogenic markers, indicating a compensatory mechanism for energy production in brain. This compensatory response to generate an alternative fuel source was temporary and diminished with disease progression. To determine whether this compensatory alternative fuel system could be sustained, we investigated the impact of 2-deoxy-D-glucose (2-DG), a compound known to induce ketogenesis, on bioenergetic function and AD pathology burden in brain. 6-month-old female 3xTgAD mice were fed either a regular diet (AIN-93G) or a diet containing 0.04% 2-DG for 7 weeks. 2-DG diet significantly increased serum ketone body level and brain expression of enzymes required for ketone body metabolism. The 2-DG-induced maintenance of mitochondrial bioenergetics was paralleled by simultaneous reduction in oxidative stress. Further, 2-DG treated mice exhibited a significant reduction of both amyloid precursor protein (APP) and amyloid beta (Aβ) oligomers, which was paralleled by significantly increased α-secretase and decreased γ-secretase expression, indicating that 2-DG induced a shift towards a non-amyloidogenic pathway. In addition, 2-DG increased expression of genes involved in Aβ clearance pathways, degradation, sequestering, and transport. Concomitant with increased bioenergetic capacity and reduced β-amyloid burden, 2-DG significantly increased expression of neurotrophic growth factors, BDNF and NGF. Results of these analyses demonstrate that dietary 2-DG treatment increased ketogenesis and ketone metabolism, enhanced mitochondrial bioenergetic capacity, reduced β-amyloid generation and increased mechanisms of β-amyloid clearance. Further, these data link bioenergetic capacity with β-amyloid generation and demonstrate that β-amyloid burden was dynamic and reversible, as 2-DG reduced activation of the amyloidogenic pathway and increased mechanisms of β-amyloid clearance. Collectively, these data provide preclinical evidence for dietary 2-DG as a disease-modifying intervention to delay progression of bioenergetic deficits in brain and associated β-amyloid burden.

Detecting beta-amyloid aggregation from time-resolved emission spectra

NASA Astrophysics Data System (ADS)

Alghamdi, A.; Vyshemirsky, V.; Birch, D. J. S.; Rolinski, O. J.

2018-04-01

The aggregation of beta-amyloids is one of the key processes responsible for the development of Alzheimer’s disease. Early molecular-level detection of beta-amyloid oligomers may help in early diagnosis and in the development of new intervention therapies. Our previous studies on the changes in beta-amyloid’s single tyrosine intrinsic fluorescence response during aggregation demonstrated a four-exponential fluorescence intensity decay, and the ratio of the pre-exponential factors indicated the extent of the aggregation in the early stages of the process before the beta-sheets were formed. Here we present a complementary approach based on the time-resolved emission spectra (TRES) of amyloid’s tyrosine excited at 279 nm and fluorescence in the window 240-450 nm. TRES have been used to demonstrate sturctural changes occuring on the nanosecond time scale after excitation which has significant advantages over using steady-state spectra. We demonstrate this by resolving the fluorescent species and revealing that beta-amyloid’s monomers show very fast dielectric relaxation, and its oligomers display a substantial spectral shift due to dielectric relaxation, which gradually decreases when the oligomers become larger.

Differential regulation of amyloid precursor protein sorting with pathological mutations results in a distinct effect on amyloid-β production.

PubMed

Lin, Yen-Chen; Wang, Jia-Yi; Wang, Kai-Chen; Liao, Jhih-Ying; Cheng, Irene H

2014-11-01

The deposition of amyloid-β (Aβ) peptide, which is generated from amyloid precursor protein (APP), is the pathological hallmark of Alzheimer's disease (AD). Three APP familial AD mutations (D678H, D678N, and H677R) located at the sixth and seventh amino acid of Aβ have distinct effect on Aβ aggregation, but their influence on the physiological and pathological roles of APP remain unclear. We found that the D678H mutation strongly enhances amyloidogenic cleavage of APP, thus increasing the production of Aβ. This enhancement of amyloidogenic cleavage is likely because of the acceleration of APPD678H sorting into the endosomal-lysosomal pathway. In contrast, the APPD678N and APPH677R mutants do not cause the same effects. Therefore, this study indicates a regulatory role of D678H in APP sorting and processing, and provides genetic evidence for the importance of APP sorting in AD pathogenesis. The internalization of amyloid precursor protein (APP) increases its opportunity to be processed by β-secretase and to produce Amyloid-β (Aβ) that causes Alzheimer's disease (AD). We report a pathogenic APPD678H mutant that enhances APP internalization into the endosomal-lysosomal pathway and thus promotes the β-secretase cleavage and Aβ production. This study provides genetic evidence for the importance of APP sorting in AD pathogenesis. © 2014 International Society for Neurochemistry.

75 FR 75681 - Peripheral and Central Nervous System Drugs Advisory Committee; Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-06

... of [beta]-amyloid (beta-amyloid) aggregates in the brain to help rule out Alzheimer's disease. On... children (2 years of age and older) to detect and visualize areas with disrupted blood brain barrier (BBB... bloodstream into the brain. FDA intends to make background material available to the public no later than 2...

The Prevalence and Management of Systemic Amyloidosis in Western Countries.

PubMed

Nienhuis, Hans L A; Bijzet, Johan; Hazenberg, Bouke P C

2016-04-01

Amyloidosis has been a mystery for centuries, but research of the last decennia has clarified many of the secrets of this group of diseases. A protein-based classification of amyloidosis helps to understand problems that were part of the obsolete clinical classification in primary, secondary, and familial amyloidosis. All types of amyloid are secondary to some underlying precursor-producing process: each type is caused by a misfolded soluble precursor protein that becomes deposited as insoluble amyloid fibrils. The incidence of amyloidosis is not well documented, but probably falls between 5 and 13 per million per year. Prevalence data are scarce, but one UK study indicates about 20 per million inhabitants. Amyloidosis can be localized (amyloid deposited in the organ or tissue of precursor production) or systemic (amyloid at one or more sites distant from the site of precursor production). The major systemic types of amyloidosis are AL (associated with a light chain-producing plasma cell dyscrasia), AA (associated with longstanding inflammation), wild-type ATTR (associated with normal transthyretin and old age), and hereditary ATTR (associated with a transthyretin mutation) amyloidosis. Imaging techniques, such as cardiac ultrasound, magnetic resonance imaging, bone scintigraphy, and serum amyloid P component scintigraphy, are useful both for diagnosing amyloidosis and for assessing disease severity. Serologic markers are useful for detecting organ disease and disease monitoring during follow-up. Current treatment modalities are directed against the ongoing supply of precursor proteins and thereby aim to stop further accumulation of amyloid. Novel treatment modalities, such as interference with amyloid formation and even removal of amyloid, are being studied. A well-thought and planned monitoring during follow-up helps to assess the effect of treatment and to early detect possible progression of amyloidosis. Clinical management comprises histologic proof of amyloid, evidence of systemic deposition, reliable typing, precursor assessment, severity of organ disease, risk assessment and prognosis, choice of treatment, and planned monitoring during follow-up. (1) AL amyloidosis is the most prevalent type of amyloidosis accounting for 65% of the amyloidosis-diagnosed patients in the UK and for 93% of the amyloidosis-diagnosed patients in China. The predisposition of men over women to develop AL amyloidosis might be higher in China than in Western countries (2:1 vs. 1.3:1). Both in the East and West, incidence increases with age. At the time of diagnosis, edema is twice as frequent and the proportion of renal involvement is higher in Chinese compared to Western patients. (2) Melphalan followed by autologous stem cell transplantation (ASCT) is the current standard therapy but is restricted to eligible patients. The efficacy and safety of bortezomib combined with dexamethasone were proven in Western patients and recently confirmed in a Chinese cohort. Recent studies in China and the US indicate that bortezomib induction prior to ASCT increases the response rate. Thalidomide and lenalidomide have shown benefit, but toxicity and lack of clinical evidence exclude these agents from first-line therapy. The green tea extract epigallocatechin-3-gallate is under investigation as an inhibitor of AL amyloid formation and a compound that might dissolve amyloid.

Dynamics of beta-amyloid peptide in cholesterol superlattice domain

NASA Astrophysics Data System (ADS)

Smirnov, Anton; Zhu, Qing; Vaughn, Mark; Khare, Rajesh; Cheng, K.

2006-10-01

Presence of beta-amyloid peptide (beta-A) plagues in membranes of neuron cells is a clinical signature of Alzheimer disease. The onset of beta-A peptide aggregation occurs via a conformational transition from an alpha-helix state to a beta-sheet state. A gradual build-up of beta-A content in the neuronal extracellular space is another characteristic of the beta-A plague formation. Hypothetically, both the pathological conformation and the predominant localization of the beta-A can be a result of specific dynamic characteristics of the interphase between cellular membrane and extracellular milieu. In this study, the beta-A interphase problem has been investigated using a virtual membrane model implemented on the base of GROMACS molecular dynamics simulation package. The detailed folding pattern of beta-A has been examined using a novice interphase model comprised of a cholesterol supperlattice membrane and two water layers.

Comparison of imaging biomarkers for Alzheimer's disease: amyloid imaging with [18F]florbetapir positron emission tomography and magnetic resonance imaging voxel-based analysis for entorhinal cortex atrophy.

PubMed

Tateno, Amane; Sakayori, Takeshi; Kawashima, Yoshitaka; Higuchi, Makoto; Suhara, Tetsuya; Mizumura, Sunao; Mintun, Mark A; Skovronsky, Daniel M; Honjo, Kazuyoshi; Ishihara, Keiichi; Kumita, Shinichiro; Suzuki, Hidenori; Okubo, Yoshiro

2015-05-01

We compared amyloid positron emission tomography (PET) and magnetic resonance imaging (MRI) in subjects clinically diagnosed with Alzheimer's disease (AD), mild cognitive impairment (MCI), and older healthy controls (OHC) in order to test how these imaging biomarkers represent cognitive decline in AD. Fifteen OHC, 19 patients with MCI, and 19 patients with AD were examined by [(18)F]florbetapir PET to quantify the standard uptake value ratio (SUVR) as the degree of amyloid accumulation, by MRI and the voxel-based specific regional analysis system for AD to calculate z-score as the degree of entorhinal cortex atrophy, and by mini-mental state examination (MMSE) and Alzheimer's Disease Assessment Scale-cognitive component--Japanese version (ADAS-Jcog) for cognitive functions. Both cutoff values for measuring AD-like levels of amyloid (1.099 for SUVR) and entorhinal cortex atrophy (1.60 for z-score) were well differentially diagnosed and clinically defined AD from OHC (84.2% for SUVR and 86.7% for z-score). Subgroup analysis based on beta-amyloid positivity revealed that z-score significantly correlated with MMSE (r = -0.626, p < 0.01) and ADAS-Jcog (r = 0.691, p < 0.01) only among subjects with beta-amyloid. This is the first study to compare [(18)F]florbetapir PET and MRI voxel-based analysis of entorhinal cortex atrophy for AD. Both [(18)F]florbetapir PET and MRI detected changes in AD compared with OHC. Considering that entorhinal cortex atrophy correlated well with cognitive decline only among subjects with beta-amyloid, [18F]florbetapir PET makes it possible to detect AD pathology in the early stage, whereas MRI morphometry for subjects with beta-amyloid provides a good biomarker to assess the severity of AD in the later stage. Copyright © 2014 John Wiley & Sons, Ltd.

Aβ1-16 conformational changes induced by heavy metals, antioxidants, and corn zeins: CD, AFM, SEM, and FT-IR studies

NASA Astrophysics Data System (ADS)

Murariu, Manuela; Mihai, Marcela; Zaharia, Marius; Drochioiu, Gabi

2014-10-01

Amyloid-beta (known also as Aβ or A-beta or beta-amyloid) is a peptide of 36-43 amino acids that appears to be the main constituent of amyloid plaques in the brains of Alzheimer's disease (AD) patients. The transformation process from α-helix to β-sheet structures appears to be one of the major factors in the genesis and evolution of a variety of neurodegenerative diseases such as AD, Parkinson's disease (PD), and several prion diseases [1,2]. Metal-based reactions of some polypeptides and proteins are considered as a common denominator for neurodegenerative diseases (Figure 1) [3,4]. Amyloid-β (Aβ) aggregates are associated with Alzheimer's disease (AD), and may be promoted by the trace amounts of metal ions like aluminium, iron, zinc or copper [5-11]. For example, copper ions cause the peptide aggregation to a great extent and highly increase the neurotoxicity exhibited by Aβ1-40 in cell culture [11].

Differential cerebral deposition of IDE and NEP in sporadic and familial Alzheimer's disease.

PubMed

Dorfman, Verónica Berta; Pasquini, Laura; Riudavets, Miguel; López-Costa, Juan José; Villegas, Andrés; Troncoso, Juan Carlos; Lopera, Francisco; Castaño, Eduardo Miguel; Morelli, Laura

2010-10-01

Alzheimer's disease (AD) is characterized by amyloid beta (A beta) accumulation in the brain and is classified as familial early-onset (FAD) or sporadic late-onset (SAD). Evidences suggest that deficits in the brain expression of insulin degrading enzyme (IDE) and neprilysin (NEP), both proteases involved in amyloid degradation, may promote A beta deposition in SAD. We studied by immunohistochemistry IDE and NEP cortical expression in SAD and FAD samples carrying the E280A presenilin-1 missense mutation. We showed that IDE, a soluble peptidase, is linked with aggregated A beta 40 isoform while NEP, a membrane-bound protease, negatively correlates with amyloid angiopathy and its expression in the senile plaques is independent of aggregated amyloid and restricted to SAD cases. NEP, but not IDE, is over-expressed in dystrophic neurites, both proteases are immunoreactive in activated astrocytes but not in microglia and IDE was the only one detected in astrocytes of white matter from FAD cases. Collectively, our results support the notion that gross conformational changes involved in the modification from "natively folded-active" to "aggregated-inactive" IDE and NEP may be a relevant pathogenic mechanism in SAD. (c) 2008 Elsevier Inc. All rights reserved.

Docosahexaenoic Acid and the Aging Brain1–3

PubMed Central

Lukiw, Walter J.; Bazan, Nicolas G.

2008-01-01

The dietary essential PUFA docosahexaenoic acid [DHA; 22:6(n-3)] is a critical contributor to cell structure and function in the nervous system, and deficits in DHA abundance are associated with cognitive decline during aging and in neurodegenerative disease. Recent studies underscore the importance of DHA-derived neuroprotectin D1 (NPD1) in the homeostatic regulation of brain cell survival and repair involving neurotrophic, antiapoptotic and antiinflammatory signaling. Emerging evidence suggests that NPD1 synthesis is activated by growth factors and neurotrophins. Evolving research indicates that NPD1 has important determinant and regulatory interactions with the molecular-genetic mechanisms affecting β-amyloid precursor protein (βAPP) and amyloid beta (Aβ) peptide neurobiology. Deficits in DHA or its peroxidation appear to contribute to inflammatory signaling, apoptosis, and neuronal dysfunction in Alzheimer disease (AD), a common and progressive age-related neurological disorder unique to structures and processes of the human brain. This article briefly reviews our current understanding of the interactions of DHA and NPD1 on βAPP processing and Aβ peptide signaling and how this contributes to oxidative and pathogenic processes characteristic of aging and AD pathology. PMID:19022980

Apoptosis in Alzheimer's disease: an understanding of the physiology, pathology and therapeutic avenues.

PubMed

Obulesu, M; Lakshmi, M Jhansi

2014-12-01

Alzheimer's disease (AD) is a devastative neurodegenerative disorder with complex etiology. Apoptosis, a biological process that plays an essential role in normal physiology to oust a few cells and contribute to the normal growth, when impaired or influenced by various factors such as Bcl2, Bax, caspases, amyloid beta, tumor necrosis factor-α, amyloid precursor protein intracellular C-terminal domain, reactive oxygen species, perturbation of enzymes leads to deleterious neurodegenerative disorders like AD. There are diverse pathways that provoke manifold events in mitochondria and endoplasmic reticulum (ER) to execute the process of cell death. This review summarizes the crucial apoptotic mechanisms occurring in both mitochondria and ER. It gives substantial summary of the diverse mechanisms studied in vivo and in vitro. A brief account on neuroprotection of several bioactive components, flavonoids and antioxidants of plants against apoptotic events of both mitochondria and ER in both in vitro and in vivo has been discussed. In light of this, the burgeoning need to develop animal models to study the efficacy of various therapeutic effects has been accentuated.

Investigating structural details of lipid-cholesterol-A β interactions

NASA Astrophysics Data System (ADS)

Rai, Durgesh; Anunciado, Divina; Heller, William; O'Neill, Hugh; Urban, Volker; Qian, Shuo

2015-03-01

Alzheimer's disease (AD) is the most common form of dementia and is predicted to affect 1 in 85 people around the world by 2050. Amyloid beta (A β) -peptide, a peptide composed of 40- 42 amino acids that is the product of cleavage from the amyloid precursor protein (APP), is regarded to play a major role in the development of AD. In addition, accumulating evidence points to a positive association between cholesterol and AD. Here, we present results from our studies about A β-peptide and cholesterol in bilayer by small-angle neutron scattering (SANS) using a combination of dimyristoyl, phosphocholine (DMPC) and partially deuterated cholesterol (cholesterol-d7) with and without A β. We compare the results using grazing incidence and transmission SANS on lipid bilayer films and unilamellar vesicles respectively. The structural details on vesicles and bilayers work in conjunction with the circular dichroism on peptide in solution and oriented circular dichroism in bilayer films. The studies confirm a positive association of A β with the membrane layers. The results from different studies will be compared and contrasted in presentation.

APP mRNA splicing is upregulated in the brain of biglycan transgenic mice.

PubMed

Bjelik, Annamária; Pákáski, Magdolna; Bereczki, Erika; Gonda, Szilvia; Juhász, Anna; Rimanóczy, Agnes; Zana, Marianna; Janka, Zoltán; Sántha, Miklós; Kálmán, János

2007-01-01

Many of the risk factors for cerebrovascular disease and atherosclerosis also increase the risk of Alzheimer's disease, characterized by the cerebral deposition of beta-amyloid plaques resulting from the abnormal processing of the transmembrane amyloid precursor protein (APP). The initiating event of cholesterol-induced atherosclerosis is the retention and accumulation of atherogenic apolipoprotein B (apoB) together with low-density lipoproteins in the vascular intima. Biglycan, a member of the small leucine-rich protein family, was suspected of contributing to this process. The individual and combined overexpressions of biglycan and apoB-100 were therefore examined on the cortical APP mRNA levels of transgenic mice by means of semiquantitative PCR. As compared with the control littermates, transgenic biglycan mice had significantly increased cortical APP695 (122%) and APP770 (157%) mRNA levels, while the double transgenic (apoB(+/-)xbiglycan(+/-)) mice did not exhibit any changes. These results provide the first experimental evidence that the atherogenic risk factor biglycan alters APP splicing and may participate in the pathogenesis of both Alzheimer and vascular dementias.

Impairments of long-term depression induction and motor coordination precede Aβ accumulation in the cerebellum of APPswe/PS1dE9 double transgenic mice.

PubMed

Kuwabara, Yuki; Ishizeki, Masato; Watamura, Naoto; Toba, Junya; Yoshii, Aya; Inoue, Takafumi; Ohshima, Toshio

2014-08-01

Alzheimer's disease (AD) is a neurodegenerative disorder that represents the most common type of dementia among elderly people. Amyloid beta (Aβ) peptides in extracellular Aβ plaques, produced from the amyloid precursor protein (APP) via sequential processing by β- and γ-secretases, impair hippocampal synaptic plasticity, and cause cognitive dysfunction in AD patients. Here, we report that Aβ peptides also impair another form of synaptic plasticity; cerebellar long-term depression (LTD). In the cerebellum of commonly used AD mouse model, APPswe/PS1dE9 mice, Aβ plaques were detected from 8 months and profound accumulation of Aβ plaques was observed at 18 onths of age. Biochemical analysis revealed relatively high levels of APP protein and Aβ in the cerebellum of APPswe/PS1dE9 mice. At pre-Aβ accumulation stage, LTD induction, and motor coordination are disturbed. These results indicate that soluble Aβ oligomers disturb LTD induction and cerebellar function in AD mouse model. © 2014 International Society for Neurochemistry.

Genetic dissection of Alzheimer disease, a heterogeneous disorder.

PubMed

Schellenberg, G D

1995-09-12

The genetics of Alzheimer disease (AD) are complex and not completely understood. Mutations in the amyloid precursor protein gene (APP) can cause early-onset autosomal dominant AD. In vitro studies indicate that cells expressing mutant APPs overproduce pathogenic forms of the A beta peptide, the major component of AD amyloid. However, mutations in the APP gene are responsible for 5% or less of all early-onset familial AD. A locus on chromosome 14 is responsible for AD in other early-onset AD families and represents the most severe form of the disease in terms of age of onset and rate of decline. Attempts to identify the AD3 gene by positional cloning methods are underway. At least one additional early-onset AD locus remains to be located. In late-onset AD, the apolipoprotein E gene allele epsilon 4 is a risk factor for AD. This allele appears to act as a dose-dependent age-of-onset modifier. The epsilon 2 allele of this gene may be protective. Other late-onset susceptibility factors remain to be identified.

Association of late-onset Alzheimer disease with a genotype of PLAU, the gene encoding urokinase-type plasminogen activator on chromosome 10q22.2.

PubMed

Finckh, U; van Hadeln, K; Müller-Thomsen, T; Alberici, A; Binetti, G; Hock, C; Nitsch, R M; Stoppe, G; Reiss, J; Gal, A

2003-08-01

Urokinase-type plasminogen activator (uPA) converts plasminogen to plasmin. Plasmin is involved in processing of amyloid precursor protein and degrades secreted and aggregated amyloid-beta, a hallmark of Alzheimer disease (AD). PLAU, the gene encoding uPA, maps to chromosome 10q22.2 between two regions showing linkage to late-onset AD (LOAD). We genotyped a frequent C/T single nucleotide polymorphism in codon 141 of PLAU (P141L) in 347 patients with LOAD and 291 control subjects. LOAD was associated with homozygous C/C PLAU genotype in the whole sample (chi2=15.7, P=0.00039, df 2), as well as in all sub-samples stratified by gender or APOE epsilon4 carrier status (chi2> or = 6.84, P< or =0.033, df 2). Odds ratio for LOAD due to homozygosity C/C was 1.89 (95% confidence interval 1.37-2.61). PLAU is a promising new candidate gene for LOAD, with allele C (P141) being a recessive risk allele or allele T (L141) conferring protection.

Cholesterol as a Causative Factor in Alzheimer Disease: A Debatable Hypothesis

PubMed Central

Wood, W. Gibson; Li, Ling; Müller, Walter E.; Eckert, Gunter P.

2014-01-01

High serum/plasma cholesterol levels have been suggested as a risk factor for Alzheimer disease (AD). Some reports, mostly retrospective epidemiological studies, have observed a decreased prevalence of AD in patients taking the cholesterol lowering drugs, statins. The strongest evidence causally linking cholesterol to AD is provided by experimental studies showing that adding/reducing cholesterol alters amyloid precursor protein (APP) and amyloid beta-protein (Aβ) levels. However, there are problems with the cholesterol-AD hypothesis. Cholesterol levels in serum/plasma and brain of AD patients do not support cholesterol as a causative factor in AD. Prospective studies on statins and AD have largely failed to show efficacy. Even the experimental data are open to interpretation given that it is well-established that modification of cholesterol levels has effects on multiple proteins, not only APP and Aβ. The purpose of this review, therefore, is to examine the above-mentioned issues and discuss the pros and cons of the cholesterol-AD hypothesis, and the involvement of other lipids in the mevalonate pathway, such as isoprenoids and oxysterols, in AD. PMID:24329875

Abnormal Mitochondrial Dynamics and Synaptic Degeneration as Early Events in Alzheimer’s Disease: Implications to Mitochondria-Targeted Antioxidant Therapeutics

PubMed Central

Reddy, P. Hemachandra; Tripathy, Raghav; Troung, Quang; Thirumala, Karuna; Reddy, Tejaswini P.; Anekonda, Vishwanath; Shirendeb, Ulziibat P.; Calkins, Marcus J.; Reddy, Arubala P.; Mao, Peizhong; Manczak, Maria

2011-01-01

Synaptic pathology and mitochondrial oxidative damage are early events in Alzheimer’s disease (AD) progression. Loss of synapses and synaptic damage are the best correlate of cognitive deficits found in AD patients. Recent research on amyloid bet (Aβ) and mitochondria in AD revealed that Aβ accumulates in synapses and synaptic mitochondria, leading to abnormal mitochondrial dynamics and synaptic degeneration in AD neurons. Further, recent studies using live-cell imaging and primary neurons from amyloid beta precursor protein (AβPP) transgenic mice revealed that reduced mitochondrial mass, defective axonal transport of mitochondria and synaptic degeneration, indicating that Aβ is responsible for mitochondrial and synaptic deficiencies. Tremendous progress has been made in studying antioxidant approaches in mouse models of AD and clinical trials of AD patients. This article highlights the recent developments made in Aβ-induced abnormal mitochondrial dynamics, defective mitochondrial biogenesis, impaired axonal transport and synaptic deficiencies in AD. This article also focuses on mitochondrial approaches in treating AD, and also discusses latest research on mitochondria-targeted antioxidants in AD. PMID:22037588

Apolipoprotein E in the genetics and epidemiology of Alzheimer`s disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hardy, J.

1995-10-09

The role of apolipoprotein E (ApoE) alleles and isoforms in the etiology and pathogenesis of Alzheimer`s disease is discussed. The possibility that ApoE itself is not involved in the disease pathogenesis but is merely in genetic disequilibrium with the real locus is discussed and dismissed. The data showing that the {epsilon}4 allele is associated with an increased risk of developing the disease and with an earlier onset age are reviewed. The data showing that, at least in some circumstances, the {epsilon}2 allele is associated with a decrease in the risk of developing the disease, and with a later onset agemore » are also reviewed. Data from the genetic analysis of other disorders are reviewed and presented, and it is suggested that the genetic data support the notion that the role of ApoE in the etiology of the disease directly relates to {beta}-amyloid deposition and plaque formation. This suggestion is in concordance with the most likely mechanism for the role of P-amyloid precursor protein gene mutations as other risk factors for the disease. 68 refs.« less

Early Alzheimer's disease-type pathology in the frontal cortex of wild mountain gorillas (Gorilla beringei beringei).

PubMed

Perez, Sylvia E; Sherwood, Chet C; Cranfield, Michael R; Erwin, Joseph M; Mudakikwa, Antoine; Hof, Patrick R; Mufson, Elliott J

2016-03-01

Amyloid beta (Aβ) and tau pathology have been described in the brains of captive aged great apes, but the natural progression of these age-related pathologies from wild great apes, including the gorilla, is unknown. In our previous study of Western lowland gorillas (Gorilla gorilla gorilla) who were housed in American Zoos and Aquariums-accredited facilities, we found an age-related increase in Aβ-positive plaques and vasculature, tau-positive astrocytes, oligodendrocyte coiled bodies, and neuritic clusters in the neocortex as well as hippocampus in older animals. Here, we demonstrate that aged wild mountain gorillas (Gorilla beringei beringei), who spent their entire lives in their natural habitat, also display an age-related increase in amyloid precursor protein (APP) and/or Aβ-immunoreactive blood vessels and plaques, but very limited tau pathology, in the frontal cortex. These results indicate that Aβ and tau lesions are age-related events that occur in the brain of gorillas living in captivity and in the wild. Copyright © 2016 Elsevier Inc. All rights reserved.

Meningocerebrovascular amyloidosis associated with a novel transthyretin mis-sense mutation at codon 18 (TTRD 18G)

PubMed Central

Vidal, R.; Garzuly, F.; Budka, H.; Lalowski, M.; Linke, R. P.; Brittig, F.; Frangione, B.; Wisniewski, T.

1996-01-01

We describe a novel transthyretin mutation at codon 18 where Asp is replaced by Gly (D18G) in a Hungarian kindred. This mutation is associated with meningocerebrovascular amyloidosis, producing dementia, ataxia, and spasticity. Fifty different transthyretin mutations are related to amyloid deposition, typically producing a peripheral neuropathy or cardiac dysfunction. These symptoms are absent in this family. Up to now, amyloid-beta (A beta), cystatin C, and prion proteins have been known to be deposited as amyloid in the brain, leading to stroke or dementia. With this report we establish that transthyretin amyloid deposition can also produce central nervous system dysfunction as the major clinical symptom. Images Figure 2 Figure 4 PMID:8579098

Tannoid principles of Emblica officinalis renovate cognitive deficits and attenuate amyloid pathologies against aluminum chloride induced rat model of Alzheimer's disease.

PubMed

Justin Thenmozhi, Arokiasamy; Dhivyabharathi, Mathiyazahan; William Raja, Tharsius Raja; Manivasagam, Thamilarasan; Essa, Musthafa Mohamed

2016-07-01

Emblica officinalis is mentioned as a maharasayana in many Ayurvedic texts and promotes intelligence, memory, freedom from disease, longevity, and strength of the senses. The present study has been designed to explore the memory-enhancing effect of the tannoid principles of E. officinalis (EoT) at the biochemical, anatomical, behavioral, and molecular levels against aluminum chloride (AlCl3) induced Alzheimer's disease (AD) in rats. Aluminum is reported to have an important role in the etiology, pathogenesis, and development of AD. Male Wistar rats were divided into control, AlCl3 treated, AlCl3 and EoT (50, 100, and 200 mg/kg bw) co-treated, and EoT (200 mg/kg bw) alone treated groups. In control and experimental rats, behavior tests including water maze and open field test, estimation of aluminum, assay of acetylcholinesterase (AChE) activity, and expression of amyloidogenic proteins were performed. Intraperitonial injection of AlCl3 (100 mg/kg bw) for 60 days significantly elevated the concentration of aluminum (Al), activity of AChE and protein expressions of amyloid precursor protein, A-beta1-42, beta-, and gamma-secretases as compared to control group in hippocampus and cortex. Co-administration of EoT orally to AlCl3 rats for 60 days significantly revert back the Al concentration, AChE activity, and A-beta synthesis-related molecules in the studied brain regions. The spatial learning, memory, and locomotor impairments observed in AlCl3 treated rats were significantly attenuated by EoT. Therefore, EoT may be a promising therapy in ameliorating neurotoxicity of aluminum, however further studies are warranted to elucidate the exact mechanism of action of EoT.

Association of gamma-secretase with lipid rafts in post-Golgi and endosome membranes.

PubMed

Vetrivel, Kulandaivelu S; Cheng, Haipeng; Lin, William; Sakurai, Takashi; Li, Tong; Nukina, Nobuyuki; Wong, Philip C; Xu, Huaxi; Thinakaran, Gopal

2004-10-22

Alzheimer's disease-associated beta-amyloid peptides (Abeta) are generated by the sequential proteolytic processing of amyloid precursor protein (APP) by beta- and gamma-secretases. There is growing evidence that cholesterol- and sphingolipid-rich membrane microdomains are involved in regulating trafficking and processing of APP. BACE1, the major beta-secretase in neurons is a palmitoylated transmembrane protein that resides in lipid rafts. A subset of APP is subject to amyloidogenic processing by BACE1 in lipid rafts, and this process depends on the integrity of lipid rafts. Here we describe the association of all four components of the gamma-secretase complex, namely presenilin 1 (PS1)-derived fragments, mature nicastrin, APH-1, and PEN-2, with cholesterol-rich detergent insoluble membrane (DIM) domains of non-neuronal cells and neurons that fulfill the criteria of lipid rafts. In PS1(-/-)/PS2(-/-) and NCT(-/-) fibroblasts, gamma-secretase components that still remain fail to become detergent-resistant, suggesting that raft association requires gamma-secretase complex assembly. Biochemical evidence shows that subunits of the gamma-secretase complex and three TGN/endosome-resident SNAREs cofractionate in sucrose density gradients, and show similar solubility or insolubility characteristics in distinct non-ionic and zwitterionic detergents, indicative of their co-residence in membrane microdomains with similar protein-lipid composition. This notion is confirmed using magnetic immunoisolation of PS1- or syntaxin 6-positive membrane patches from a mixture of membranes with similar buoyant densities following Lubrol WX extraction or sonication, and gradient centrifugation. These findings are consistent with the localization of gamma-secretase in lipid raft microdomains of post-Golgi and endosomes, organelles previously implicated in amyloidogenic processing of APP.

Specific Inhibition of β-Secretase Processing of the Alzheimer Disease Amyloid Precursor Protein.

PubMed

Ben Halima, Saoussen; Mishra, Sabyashachi; Raja, K Muruga Poopathi; Willem, Michael; Baici, Antonio; Simons, Kai; Brüstle, Oliver; Koch, Philipp; Haass, Christian; Caflisch, Amedeo; Rajendran, Lawrence

2016-03-08

Development of disease-modifying therapeutics is urgently needed for treating Alzheimer disease (AD). AD is characterized by toxic β-amyloid (Aβ) peptides produced by β- and γ-secretase-mediated cleavage of the amyloid precursor protein (APP). β-secretase inhibitors reduce Aβ levels, but mechanism-based side effects arise because they also inhibit β-cleavage of non-amyloid substrates like Neuregulin. We report that β-secretase has a higher affinity for Neuregulin than it does for APP. Kinetic studies demonstrate that the affinities and catalytic efficiencies of β-secretase are higher toward non-amyloid substrates than toward APP. We show that non-amyloid substrates are processed by β-secretase in an endocytosis-independent manner. Exploiting this compartmentalization of substrates, we specifically target the endosomal β-secretase by an endosomally targeted β-secretase inhibitor, which blocked cleavage of APP but not non-amyloid substrates in many cell systems, including induced pluripotent stem cell (iPSC)-derived neurons. β-secretase inhibitors can be designed to specifically inhibit the Alzheimer process, enhancing their potential as AD therapeutics without undesired side effects. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

BACE1 elevation engendered by GGA3 deletion increases β-amyloid pathology in association with APP elevation and decreased CHL1 processing in 5XFAD mice.

PubMed

Kim, WonHee; Ma, Liang; Lomoio, Selene; Willen, Rachel; Lombardo, Sylvia; Dong, Jinghui; Haydon, Philip G; Tesco, Giuseppina

2018-02-02

β-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the rate-limiting enzyme in the production of amyloid beta (Aβ), the toxic peptide that accumulates in the brains of Alzheimer's disease (AD) patients. Our previous studies have shown that the clathrin adaptor Golgi-localized γ-ear-containing ARF binding protein 3 (GGA3) plays a key role in the trafficking of BACE1 to lysosomes, where it is normally degraded. GGA3 depletion results in BACE1 stabilization both in vitro and in vivo. Moreover, levels of GGA3 are reduced and inversely related to BACE1 levels in post-mortem brains of AD patients. In order to assess the effect of GGA3 deletion on AD-like phenotypes, we crossed GGA3 -/- mice with 5XFAD mice. BACE1-mediated processing of APP and the cell adhesion molecule L1 like protein (CHL1) was measured as well as levels of Aβ42 and amyloid burden. In 5XFAD mice, we found that hippocampal and cortical levels of GGA3 decreased while BACE1 levels increased with age, similar to what is observed in human AD brains. GGA3 deletion prevented age-dependent elevation of BACE1 in GGA3KO;5XFAD mice. We also found that GGA3 deletion resulted in increased hippocampal levels of Aβ42 and amyloid burden in 5XFAD mice at 12 months of age. While levels of BACE1 did not change with age and gender in GGAKO;5XFAD mice, amyloid precursor protein (APP) levels increased with age and were higher in female mice. Moreover, elevation of APP was associated with a decreased BACE1-mediated processing of CHL1 not only in 12 months old 5XFAD mice but also in human brains from subjects affected by Down syndrome, most likely due to substrate competition. This study demonstrates that GGA3 depletion is a leading candidate mechanism underlying elevation of BACE1 in AD. Furthermore, our findings suggest that BACE1 inhibition could exacerbate mechanism-based side effects in conditions associated with APP elevation (e.g. Down syndrome) owing to impairment of BACE1-mediated processing of CHL1. Therefore, therapeutic approaches aimed to restore GGA3 function and to prevent the down stream effects of its depletion (e.g. BACE1 elevation) represent an attractive alternative to BACE inhibition for the prevention/treatment of AD.

Amyloid Form of Ovalbumin Evokes Native Antigen-specific Immune Response in the Host

PubMed Central

Tufail, Saba; Owais, Mohammad; Kazmi, Shadab; Balyan, Renu; Kaur Khalsa, Jasneet; Faisal, Syed Mohd.; Sherwani, Mohd. Asif; Gatoo, Manzoor Ahmad; Umar, Mohd. Saad; Zubair, Swaleha

2015-01-01

Amyloids are highly organized protein aggregates that arise from inappropriately folded versions of proteins or polypeptides under both physiological as well as simulated ambiences. Once thought to be irreversible assemblies, amyloids have begun to expose their more dynamic and reversible attributes depending upon the intrinsic properties of the precursor protein/peptide and experimental conditions such as temperature, pressure, structural modifications in proteins, or presence of chemicals in the reaction mixture. It has been repeatedly proposed that amyloids undergo transformation to the bioactive peptide/protein forms under specific conditions. In the present study, amyloids assembled from the model protein ovalbumin (OVA) were found to release the precursor protein in a slow and steady manner over an extended time period. Interestingly, the released OVA from amyloid depot was found to exhibit biophysical characteristics of native protein and reacted with native-OVA specific monoclonal as well as polyclonal antibodies. Moreover, antibodies generated upon immunization of OVA amyloidal aggregates or fibrils were found to recognize the native form of OVA. The study suggests that amyloids may act as depots for the native form of the protein and therefore can be exploited as vaccine candidates, where slow antigen release over extended time periods is a pre-requisite for the development of desired immune response. PMID:25512377

Quantifying the pattern of beta/A4 amyloid protein distribution in Alzheimer's disease by image analysis.

PubMed

Bruce, C V; Clinton, J; Gentleman, S M; Roberts, G W; Royston, M C

1992-04-01

We have undertaken a study of the distribution of the beta/A4 amyloid deposited in the cerebral cortex in Alzheimer's disease. Previous studies which have examined the differential distribution of amyloid in the cortex in order to determine the laminar pattern of cortical pathology have not proved to be conclusive. We have developed an alternative method for the solution of this problem. It involves the immunostaining of sections followed by computer-enhanced image analysis. A mathematical model is then used to describe both the amount and the pattern of amyloid across the cortex. This method is both accurate and reliable and also removes many of the problems concerning inter and intra-rater variability in measurement. This method will provide the basis for further quantitative studies on the differential distribution of amyloid in Alzheimer's disease and other cases of dementia where cerebral amyloidosis occurs.

Dynamics of beta-cell turnover: evidence for beta-cell turnover and regeneration from sources of beta-cells other than beta-cell replication in the HIP rat.

PubMed

Manesso, Erica; Toffolo, Gianna M; Saisho, Yoshifumi; Butler, Alexandra E; Matveyenko, Aleksey V; Cobelli, Claudio; Butler, Peter C

2009-08-01

Type 2 diabetes is characterized by hyperglycemia, a deficit in beta-cells, increased beta-cell apoptosis, and islet amyloid derived from islet amyloid polypeptide (IAPP). These characteristics are recapitulated in the human IAPP transgenic (HIP) rat. We developed a mathematical model to quantify beta-cell turnover and applied it to nondiabetic wild type (WT) vs. HIP rats from age 2 days to 10 mo to establish 1) whether beta-cell formation is derived exclusively from beta-cell replication, or whether other sources of beta-cells (OSB) are present, and 2) to what extent, if any, there is attempted beta-cell regeneration in the HIP rat and if this is through beta-cell replication or OSB. We conclude that formation and maintenance of adult beta-cells depends largely ( approximately 80%) on formation of beta-cells independent from beta-cell duplication. Moreover, this source adaptively increases in the HIP rat, implying attempted beta-cell regeneration that substantially slows loss of beta-cell mass.

Unusual death of a transvestite: identification of crime weapon and survival time*.

PubMed

Cornetta, Sandra; Addante, Annalisa; Zotti, Fiorenza; Dell'Erba, Alessandro

2009-09-01

The authors report a case of a transvestite found murdered near his automobile with several lacerated contused wounds to the face and cranial fractures. Autopsy revealed that the cause of death was a serious head trauma with subdural and subarachnoidal hemorrhages. In order to identify the crime weapon, a scanning electron microscopy (SEM) was used which revealed metallic residue on the skin fragments with the same molecular composition of the car paint. As for survival time, antibody anti-beta-amyloid precursor protein (APP) was applied to brain fragments and brainstem tissue, allowing for axonal varicosities (which form 2 to 3 h following death) to be observed under the optic microscope. So, by using SEM we understood that the fatal cranial-encephalic lesions were the result of the victim's head being repeatedly struck against the car door while anti-betaAPP led to the understanding that the time elapsed between injury and death was less than 2 to 3 h.

Amyloid Precursor Protein (APP) Mediated Regulation of Ganglioside Homeostasis Linking Alzheimer's Disease Pathology with Ganglioside Metabolism

PubMed Central

Grimm, Marcus O. W.; Zinser, Eva G.; Grösgen, Sven; Hundsdörfer, Benjamin; Rothhaar, Tatjana L.; Burg, Verena K.; Kaestner, Lars; Bayer, Thomas A.; Lipp, Peter; Müller, Ulrike; Grimm, Heike S.; Hartmann, Tobias

2012-01-01

Gangliosides are important players for controlling neuronal function and are directly involved in AD pathology. They are among the most potent stimulators of Aβ production, are enriched in amyloid plaques and bind amyloid beta (Aβ). However, the molecular mechanisms linking gangliosides with AD are unknown. Here we identified the previously unknown function of the amyloid precursor protein (APP), specifically its cleavage products Aβ and the APP intracellular domain (AICD), of regulating GD3-synthase (GD3S). Since GD3S is the key enzyme converting a- to b-series gangliosides, it therefore plays a major role in controlling the levels of major brain gangliosides. This regulation occurs by two separate and additive mechanisms. The first mechanism directly targets the enzymatic activity of GD3S: Upon binding of Aβ to the ganglioside GM3, the immediate substrate of the GD3S, enzymatic turnover of GM3 by GD3S was strongly reduced. The second mechanism targets GD3S expression. APP cleavage results, in addition to Aβ release, in the release of AICD, a known candidate for gene transcriptional regulation. AICD strongly down regulated GD3S transcription and knock-in of an AICD deletion mutant of APP in vivo, or knock-down of Fe65 in neuroblastoma cells, was sufficient to abrogate normal GD3S functionality. Equally, knock-out of the presenilin genes, presenilin 1 and presenilin 2, essential for Aβ and AICD production, or of APP itself, increased GD3S activity and expression and consequently resulted in a major shift of a- to b-series gangliosides. In addition to GD3S regulation by APP processing, gangliosides in turn altered APP cleavage. GM3 decreased, whereas the ganglioside GD3, the GD3S product, increased Aβ production, resulting in a regulatory feedback cycle, directly linking ganglioside metabolism with APP processing and Aβ generation. A central aspect of this homeostatic control is the reduction of GD3S activity via an Aβ-GM3 complex and AICD-mediated repression of GD3S transcription. PMID:22470521

Inhibition of Wnt signaling induces amyloidogenic processing of amyloid precursor protein and the production and aggregation of Amyloid-β (Aβ)42 peptides.

PubMed

Tapia-Rojas, Cheril; Burgos, Patricia V; Inestrosa, Nibaldo C

2016-12-01

Alzheimer's disease (AD) is the most common neurodegenerative disorder and the most frequent cause of dementia in the aged population. According to the amyloid hypothesis, the amyloid-β (Aβ) peptide plays a key role in the pathogenesis of AD. Aβ is generated from the amyloidogenic processing of amyloid precursor protein and can aggregate to form oligomers, which have been described as a major synaptotoxic agent in neurons. Dysfunction of Wnt signaling has been linked to increased Aβ formation; however, several other studies have argued against this possibility. Herein, we use multiple experimental approaches to confirm that the inhibition of Wnt signaling promoted the amyloidogenic proteolytic processing of amyloid precursor protein. We also demonstrate that inhibiting Wnt signaling increases the production of the Aβ 42 peptide, the Aβ 42 /Aβ 40 ratio, and the levels of Aβ oligomers such as trimers and tetramers. Moreover, we show that activating Wnt signaling reduces the levels of Aβ 42 and its aggregates, increases Aβ 40 levels, and reduces the Aβ 42 /Aβ 40 ratio. Finally, we show that the protective effects observed in response to activation of the Wnt pathway rely on β-catenin-dependent transcription, which is demonstrated experimentally via the expression of various 'mutant forms of β-catenin'. Together, our findings indicate that loss of the Wnt signaling pathway may contribute to the pathogenesis of AD. © 2016 International Society for Neurochemistry.

Curcumin Decreases Amyloid-β Peptide Levels by Attenuating the Maturation of Amyloid-β Precursor Protein*

PubMed Central

Zhang, Can; Browne, Andrew; Child, Daniel; Tanzi, Rudolph E.

2010-01-01

Alzheimer disease (AD) is a devastating neurodegenerative disease with no cure. The pathogenesis of AD is believed to be driven primarily by amyloid-β (Aβ), the principal component of senile plaques. Aβ is an ∼4-kDa peptide generated via cleavage of the amyloid-β precursor protein (APP). Curcumin is a compound in the widely used culinary spice, turmeric, which possesses potent and broad biological activities, including anti-inflammatory and antioxidant activities, chemopreventative effects, and effects on protein trafficking. Recent in vivo studies indicate that curcumin is able to reduce Aβ-related pathology in transgenic AD mouse models via unknown molecular mechanisms. Here, we investigated the effects of curcumin on Aβ levels and APP processing in various cell lines and mouse primary cortical neurons. We show for the first time that curcumin potently lowers Aβ levels by attenuating the maturation of APP in the secretory pathway. These data provide a mechanism of action for the ability of curcumin to attenuate amyloid-β pathology. PMID:20622013

Amyloid-beta protofibrils differ from amyloid-beta aggregates induced in dilute hexafluoroisopropanol in stability and morphology.

PubMed

Nichols, Michael R; Moss, Melissa A; Reed, Dana Kim; Cratic-McDaniel, Stephanie; Hoh, Jan H; Rosenberry, Terrone L

2005-01-28

The brains of Alzheimer's disease (AD) patients contain large numbers of amyloid plaques that are rich in fibrils composed of 40- and 42-residue amyloid-beta (Abeta) peptides. Several lines of evidence indicate that fibrillar Abeta and especially soluble Abeta aggregates are important in the etiology of AD. Recent reports also stress that amyloid aggregates are polymorphic and that a single polypeptide can fold into multiple amyloid conformations. Here we demonstrate that Abeta-(1-40) can form soluble aggregates with predominant beta-structures that differ in stability and morphology. One class of aggregates involved soluble Abeta protofibrils, prepared by vigorous overnight agitation of monomeric Abeta-(1-40) at low ionic strength. Dilution of these aggregation reactions induced disaggregation to monomers as measured by size exclusion chromatography. Protofibril concentrations monitored by thioflavin T fluorescence decreased in at least two kinetic phases, with initial disaggregation (rate constant approximately 1 h(-1)) followed by a much slower secondary phase. Incubation of the reactions without agitation resulted in less disaggregation at slower rates, indicating that the protofibrils became progressively more stable over time. In fact, protofibrils isolated by size exclusion chromatography were completely stable and gave no disaggregation. A second class of soluble Abeta aggregates was generated rapidly (<10 min) in buffered 2% hexafluoroisopropanol (HFIP). These aggregates showed increased thioflavin T fluorescence and were rich in beta-structure by circular dichroism. Electron microscopy and atomic force microscopy revealed initial globular clusters that progressed over several days to soluble fibrous aggregates. When diluted out of HFIP, these aggregates initially were very unstable and disaggregated completely within 2 min. However, their stability increased as they progressed to fibers. Relative to Abeta protofibrils, the HFIP-induced aggregates seeded elongation by Abeta monomer deposition very poorly. The techniques used to distinguish these two classes of soluble Abeta aggregates may be useful in characterizing Abeta aggregates formed in vivo.

Reversal effects of crocin on amyloid β-induced memory deficit: Modification of autophagy or apoptosis markers.

PubMed

Asadi, Farideh; Jamshidi, Amir Hossein; Khodagholi, Fariba; Yans, Asal; Azimi, Leila; Faizi, Mehrdad; Vali, Leila; Abdollahi, Mohammad; Ghahremani, Mohammad Hossein; Sharifzadeh, Mohammad

2015-12-01

Crocin, as a carotenoid, is one of the main and active constituents of saffron stigmas (Crocus sativus L.) that is widely used in folk medicine. Several studies have pointed out the potent antioxidant and neuroprotective properties of crocin which may have therapeutic values for management of neurodegenerative disorders such as Alzheimer's disease. Alzheimer's disease is the most common form of dementia among the elderly and is characterized by massive neuronal loss and progressive cognitive impairment. Beta amyloid hypothesis is the main theoretical research framework for Alzheimer's disease which states that extracellular aggregation of beta amyloid results in synaptic loss and eventually cell apoptosis. Recent findings suggest that autophagy and apoptosis are extensively involved in Alzheimer's disease. In order to investigate therapeutic values of crocin, we examined the effect of crocin on memory, cell apoptosis, and autophagy using in vivo models of Alzheimer's disease. We also compared the effect of crocin administration on spatial memory with nicotine as positive control. Morris water maze results show that intra-peritoneal and intra-hippocampal administration of crocin significantly improve spatial memory indicators such as escape latency, traveled distance and time spent in target quadrant when compared to beta amyloid injection. Furthermore, we measured certain biomarkers of cell autophagy and apoptosis using Western blot analysis. Our results reveal that crocin administration does not cause any significant alteration in Beclin-1 and ratio of LC3-II/LC3-I compared to the group received beta amyloid by hippocampal injection. However, in contrast to autophagy, crocin administration significantly decreases Bax/Bcl-2 ratio and cleaved Caspase-3 level. This demonstrates that crocin inhibits beta amyloid induced apoptosis, which is possibly associated with its antioxidant properties. Our results further confirm the neuroprotective properties of crocin as a potential pharmaceutical agent for management of Alzheimer's disease. Copyright © 2015 Elsevier Inc. All rights reserved.

Impact of membrane curvature on amyloid aggregation.

PubMed

Terakawa, Mayu S; Lin, Yuxi; Kinoshita, Misaki; Kanemura, Shingo; Itoh, Dai; Sugiki, Toshihiko; Okumura, Masaki; Ramamoorthy, Ayyalusamy; Lee, Young-Ho

2018-04-28

The misfolding, amyloid aggregation, and fibril formation of intrinsically disordered proteins/peptides (or amyloid proteins) have been shown to cause a number of disorders. The underlying mechanisms of amyloid fibrillation and structural properties of amyloidogenic precursors, intermediates, and amyloid fibrils have been elucidated in detail; however, in-depth examinations on physiologically relevant contributing factors that induce amyloidogenesis and lead to cell death remain challenging. A large number of studies have attempted to characterize the roles of biomembranes on protein aggregation and membrane-mediated cell death by designing various membrane components, such as gangliosides, cholesterol, and other lipid compositions, and by using various membrane mimetics, including liposomes, bicelles, and different types of lipid-nanodiscs. We herein review the dynamic effects of membrane curvature on amyloid generation and the inhibition of amyloidogenic proteins and peptides, and also discuss how amyloid formation affects membrane curvature and integrity, which are key for understanding relationships with cell death. Small unilamellar vesicles with high curvature and large unilamellar vesicles with low curvature have been demonstrated to exhibit different capabilities to induce the nucleation, amyloid formation, and inhibition of amyloid-β peptides and α-synuclein. Polymorphic amyloidogenesis in small unilamellar vesicles was revealed and may be viewed as one of the generic properties of interprotein interaction-dominated amyloid formation. Several mechanical models and phase diagrams are comprehensively shown to better explain experimental findings. The negative membrane curvature-mediated mechanisms responsible for the toxicity of pancreatic β cells by the amyloid aggregation of human islet amyloid polypeptide (IAPP) and binding of the precursors of the semen-derived enhancer of viral infection (SEVI) are also described. The curvature-dependent binding modes of several types of islet amyloid polypeptides with high-resolution NMR structures are also discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

Amyloid-beta aggregates formed at polar-nonpolar interfaces differ from amyloid-beta protofibrils produced in aqueous buffers.

PubMed

Nichols, Michael R; Moss, Melissa A; Reed, Dana Kim; Hoh, Jan H; Rosenberry, Terrone L

2005-07-01

The deposition of aggregated amyloid-beta (Abeta) peptides in the brain as senile plaques is a pathological hallmark of Alzheimer's disease (AD). Several lines of evidence indicate that fibrillar and, in particular, soluble aggregates of these 40- and 42-residue peptides are important in the etiology of AD. Recent studies also stress that amyloid aggregates are polymorphic and that a single polypeptide can fold into multiple amyloid conformations. Here we review our recent reports that Abeta(1-40) in vitro can form soluble aggregates with predominant beta-structures that differ in stability and morphology. One class of aggregates involved soluble Abeta protofibrils, prepared by vigorous overnight agitation of monomeric Abeta(1-40) in low ionic strength buffers. These aggregates were quite stable and disaggregated to only a limited extent on dilution. A second class of soluble Abeta aggregates was generated at polar-nonpolar interfaces. Aggregation in a two-phase system of buffer over chloroform occurred more rapidly than in buffer alone. In buffered 2% hexafluoroisopropanol (HFIP), microdroplets of HFIP were formed and the half-time for aggregation was less than 10 minutes. Like Abeta protofibrils, these interfacial aggregates showed increased thioflavin T fluorescence and were rich in beta-structure by circular dichroism. However, electron microscopy and atomic force microscopy revealed very different morphologies. The HFIP aggregates formed initial globular clusters that progressed over several days to soluble fibrous aggregates. When diluted out of HFIP these aggregates initially were very unstable and disaggregated completely within 2 minutes. However, their stability increased as they progressed to fibers. It is important to determine whether similar interfacial Abeta aggregates are produced in vivo.

Beta-amyloid and phosphorylated tau metabolism changes in narcolepsy over time.

PubMed

Liguori, Claudio; Placidi, Fabio; Izzi, Francesca; Nuccetelli, Marzia; Bernardini, Sergio; Sarpa, Maria Giovanna; Cum, Fabrizio; Marciani, Maria Grazia; Mercuri, Nicola Biagio; Romigi, Andrea

2016-03-01

The aim od this study is to test whether metabolism of beta-amyloid and tau proteins changes in narcolepsy along with the disease course. We analyzed a population of narcoleptic drug-naïve patients compared to a sample of healthy controls. Patients and controls underwent lumbar puncture for assessment of cerebrospinal fluid (CSF) beta-amyloid1-42 (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau) levels. Moreover, based on the median disease duration of the whole narcolepsy group, the patients were divided into two subgroups: patients with a short disease duration (SdN, <5 years) and patients with a long disease duration (LdN, >5 years). We found significantly lower CSF Aβ42 levels in the whole narcolepsy group with respect to controls. Taking into account the patient subgroups, we documented reduced CSF Aβ42 levels in SdN compared to both LdN and controls. Even LdN patients showed lower CSF Aβ42 levels with respect to controls. Moreover, we documented higher CSF p-tau levels in LdN patients compared to both SdN and controls. Finally, a significant positive correlation between CSF Aβ42 levels and disease duration was evident. We hypothesize that beta-amyloid metabolism and cascade may be impaired in narcolepsy not only at the onset but also along with the disease course, although they show a compensatory profile over time. Concurrently, also CSF biomarkers indicative of neural structure (p-tau) appear to be altered in narcolepsy patients with a long disease duration. However, the mechanism underlying beta-amyloid and tau metabolism impairment in narcolepsy remains still unclear and deserves to be better elucidated.

Conditional Depletion of Hippocampal Brain-Derived Neurotrophic Factor Exacerbates Neuropathology in a Mouse Model of Alzheimer’s Disease

PubMed Central

Braun, David J.; Kalinin, Sergey

2017-01-01

Damage occurring to noradrenergic neurons in the locus coeruleus (LC) contributes to the evolution of neuroinflammation and neurodegeneration in a variety of conditions and diseases. One cause of LC damage may be loss of neurotrophic support from LC target regions. We tested this hypothesis by conditional unilateral knockout of brain-derived neurotrophic factor (BDNF) in adult mice. To evaluate the consequences of BDNF loss in the context of neurodegeneration, the mice harbored familial mutations for human amyloid precursor protein and presenilin-1. In these mice, BDNF depletion reduced tyrosine hydroxylase staining, a marker of noradrenergic neurons, in the rostral LC. BDNF depletion also reduced noradrenergic innervation in the hippocampus, the frontal cortex, and molecular layer of the cerebellum, assessed by staining for dopamine beta hydroxylase. BDNF depletion led to an increase in cortical amyloid plaque numbers and size but was without effect on plaque numbers in the striatum, a site with minimal innervation from the LC. Interestingly, cortical Iba1 staining for microglia was reduced by BDNF depletion and was correlated with reduced dopamine beta hydroxylase staining. These data demonstrate that reduction of BDNF levels in an LC target region can cause retrograde damage to LC neurons, leading to exacerbation of neuropathology in distinct LC target areas. Methods to reduce BDNF loss or supplement BDNF levels may be of value to reduce neurodegenerative processes normally limited by LC noradrenergic activities. PMID:28266222

Identification of sexually dimorphic gene expression in brain tissue of the fish Leporinus macrocephalus through mRNA differential display and real time PCR analyses.

PubMed

Alves-Costa, Fernanda A; Wasko, A P

2010-03-01

Differentially expressed genes in males and females of vertebrate species generally have been investigated in gonads and, to a lesser extent, in other tissues. Therefore, we attempted to identify sexually dimorphic gene expression in the brains of adult males and females of Leporinus macrocephalus, a gonochoristic fish species that presents a ZZ/ZW sex determination system, throughout a comparative analysis using differential display reverse transcriptase-PCR and real-time PCR. Four cDNA fragments were characterized, representing candidate genes with differential expression between the samples. Two of these fragments presented no significant identity with previously reported gene sequences. The other two fragments, isolated from male specimens, were associated to the gene that codes for the protein APBA2 (amyloid beta (A4) precursor protein-binding, family A, member 2) and to the Rab 37 gene, a member of the Ras oncogene family. The overexpression of these genes has been associated to a greater production of the beta-amyloid protein which, in turns, is the major factor that leads to Alzheimer's disease, and to the development of brain-tumors, respectively. Quantitative RT-PCR analyses revealed a higher Apba2 gene expression in males, thus validating the previous data on differential display. L. macrocephalus may represent an interesting animal model to the understanding of the function of several vertebrate genes, including those involved in neurodegenerative and cancer diseases.

Sildenafil Decreases BACE1 and Cathepsin B Levels and Reduces APP Amyloidogenic Processing in the SAMP8 Mouse.

PubMed

Orejana, Lourdes; Barros-Miñones, Lucía; Jordan, Joaquin; Cedazo-Minguez, Angel; Tordera, Rosa M; Aguirre, Norberto; Puerta, Elena

2015-06-01

The senescence-accelerated mouse-prone 8 (SAMP8), used as a model of aging, displays many established pathological features of Alzheimer's disease. Cognitive impairments and increased levels of hyperphosphorylated tau are found in the hippocampus of SAMP8 mice along with an increased β-secretase activity and amyloid-β (Aβ) depositions that increase in number and extent with age. Based on a previous study from our laboratory showing an amelioration of cognitive impairments and tau pathology by sildenafil, in this study we tested whether this drug could also modulate the amyloid precursor protein amyloidogenic processing in this mouse model. Our results show that the protein levels of the β-secretases β-site amyloid precursor protein cleaving enzyme 1 and cathepsin B are higher in the hippocampus of 9-month-old SAMP8 mice than those of age-matched senescence-resistant-1. Sildenafil (7.5mg/kg for 4 weeks) attenuated learning and memory impairments shown by SAMP8 mice in the passive avoidance test. The increased expression of β-site amyloid precursor protein cleaving enzyme 1 was also reduced by sildenafil, an effect paralleled to decreases in the activities of two β-site amyloid precursor protein cleaving enzyme 1 modulators, calpain and cyclin-dependent kinase 5 protein. Interestingly, sildenafil enhanced both Akt and glycogen synthase kinase-3β (ser9) phosphorylation, which could be mediating the reduction in cathepsin B levels found in the hippocampus of sildenafil-treated SAMP8 mice. Sildenafil-induced reduction in β-site amyloid precursor protein cleaving enzyme 1 and cathepsin B expression in SAMP8 mice was associated with a decrease in hippocampal Aβ42 levels which, in turn, could mediate the parallel decline in glial fibrillary acidic protein expression observed in these animals. These findings highlight the therapeutic potential of sildenafil in Alzheimer's disease pathogenesis. © The Author 2014. Published by Oxford University Press on behalf of the Gerontological Society of America. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Is Congo red an amyloid-specific dye?

PubMed

Khurana, R; Uversky, V N; Nielsen, L; Fink, A L

2001-06-22

Congo red (CR) binding, monitored by characteristic yellow-green birefringence under crossed polarization has been used as a diagnostic test for the presence of amyloid in tissue sections for several decades. This assay is also widely used for the characterization of in vitro amyloid fibrils. In order to probe the structural specificity of Congo red binding to amyloid fibrils we have used an induced circular dichroism (CD) assay. Amyloid fibrils from insulin and the variable domain of Ig light chain demonstrate induced CD spectra upon binding to Congo red. Surprisingly, the native conformations of insulin and Ig light chain also induced Congo red circular dichroism, but with different spectral shapes than those from fibrils. In fact, a wide variety of native proteins exhibited induced CR circular dichroism indicating that CR bound to representative proteins from different classes of secondary structure such as alpha (citrate synthase), alpha + beta (lysozyme), beta (concavalin A), and parallel beta-helical proteins (pectate lyase). Partially folded intermediates of apomyoglobin induced different Congo red CD bands than the corresponding native conformation, however, no induced CD bands were observed with unfolded protein. Congo red was also found to induce oligomerization of native proteins, as demonstrated by covalent cross-linking and small angle x-ray scattering. Our data suggest that Congo red is sandwiched between two protein molecules causing protein oligomerization. The fact that Congo red binds to native, partially folded conformations and amyloid fibrils of several proteins shows that it must be used with caution as a diagnostic test for the presence of amyloid fibrils in vitro.

Generation and initial characterization of FDD knock in mice.

PubMed

Giliberto, Luca; Matsuda, Shuji; Vidal, Ruben; D'Adamio, Luciano

2009-11-18

Mutations in the integral membrane protein 2B, also known as BRI(2), a type II trans-membrane domain protein cause two autosomal dominant neurodegenerative diseases, Familial British and Danish Dementia. In these conditions, accumulation of a C-terminal peptide (ABri and ADan) cleaved off from the mutated precursor protein by the pro-protein convertase furin, leads to amyloid deposition in the walls of blood vessels and parenchyma of the brain. Recent advances in the understanding of the generation of amyloid in Alzheimer's disease has lead to the finding that BRI(2) interacts with the Amyloid Precursor Protein (APP), decreasing the efficiency of APP processing to generate Abeta. The interaction between the two precursors, APP and BRI(2), and possibly between Abeta and ABri or ADan, could be important in influencing the rate of amyloid production or the tendency of these peptides to aggregate. We have generated the first BRI(2) Danish Knock-In (FDD(KI)) murine model of FDD, expressing the pathogenic decamer duplication in exon 6 of the BRI(2) gene. FDD(KI) mice do not show any evident abnormal phenotype, with normal brain histology and no detectable amyloid deposition in blood vessel walls or parenchyma. This new murine mouse model will be important to further understand the interaction between APP and BRI(2), and to provide insights into the molecular basis of FDD.

Effect of beta-amyloid block of the fast-inactivating K+ channel on intracellular Ca2+ and excitability in a modeled neuron.

PubMed

Good, T A; Murphy, R M

1996-12-24

beta-Amyloid peptide (A beta), one of the primary protein components of senile plaques found in Alzheimer disease, is believed to be toxic to neurons by a mechanism that may involve loss of intracellular calcium regulation. We have previously shown that A beta blocks the fast-inactivating potassium (A) current. In this work, we show, through the use of a mathematical model, that the A beta-mediated block of the A current could result in increased intracellular calcium levels and increased membrane excitability, both of which have been observed in vitro upon acute exposure to A beta. Simulation results are compared with experimental data from the literature; the simulations quantitatively capture the observed concentration dependence of the neuronal response and the level of increase in intracellular calcium.

Structural model of the amyloid fibril formed by beta(2)-microglobulin #21-31 fragment based on vibrational spectroscopy.

PubMed

Hiramatsu, Hirotsugu; Goto, Yuji; Naiki, Hironobu; Kitagawa, Teizo

2005-06-08

A structural model of amyloid fibril formed by the #21-31 fragment of beta2-microglobulin is proposed from microscope IR measurements on specifically 13C-labeled peptide fibrils and Raman spectra of the dispersed fibril solution. The 13C-shifted amide frequency indicated the secondary structure of the labeled residues. The IR spectra have demonstrated that the region between F22 and V27 forms the core part with the extended beta-sheet structure. Raman spectra indicated the formation of a dimer with a disulfide bridge between C25 residues.

Kinetics of the neuroinflammation-oxidative stress correlation in rat brain following the injection of fibrillar amyloid-beta onto the hippocampus in vivo.

PubMed

Rosales-Corral, Sergio; Tan, Dun-Xian; Reiter, Russel J; Valdivia-Velázquez, Miguel; Acosta-Martínez, J Pablo; Ortiz, Genaro G

2004-05-01

The purpose of this study was to describe-following the injection of a single intracerebral dose of fibrillar amyloid-beta(1-40) in vivo-some correlations between proinflammatory cytokines and oxidative stress indicators in function of time, as well as how these variables fit in a regression model. We found a positive, significant correlation between interleukin (IL)-1beta or IL-6 and the activity of the glutathione peroxidase enzyme (GSH-Px), but IL-1beta or IL-6 maintained a strong, negative correlation with the lipid peroxidation (LPO). The first 12 h marked a positive correlation between IL-6 and tumor necrosis factor-alpha (TNF-alpha), but starting from the 36 h, this relationship became negative. We found also particular patterns of behavior through the time for IL-1beta, nitrites and IL-6, with parallel or sequential interrelationships. Results shows clearly that, in vivo, the fibrillar amyloid-beta (Abeta) disrupts the oxidative balance and initiate a proinflammatory response, which in turn feeds the oxidative imbalance in a coordinated, sequential way. This work contributes to our understanding of the positive feedbacks, focusing the "cytokine cycle" along with the oxidative stress mediators in a complex, multicellular, and interactive environment.

Intravenous injection of beta-amyloid seeds promotes cerebral amyloid angiopathy (CAA).

PubMed

Burwinkel, Michael; Lutzenberger, Manuel; Heppner, Frank L; Schulz-Schaeffer, Walter; Baier, Michael

2018-03-05

Seeding and spread of beta-amyloid (Aβ) pathologies have been considered to be based on prion-like mechanisms. However, limited transmissibility of Aβ seeding activity upon peripheral exposure would represent a key difference to prions, not only in terms of pathogenesis but also in terms of potential transmission of disease. We partially characterized the seeded Aβ amyloidosis after intracerebral injection of various brain homogenates in APP/PS1 mice. One particularly seed-laden homogenate was selected to investigate the development of Aβ pathologies after intravenous exposure. We report here that a single intravenous injection of an Alzheimer disease patient's-brain extract into APP/PS1 recipient mice led to cerebral amyloid angiopathy within 180 days post injection. Thus, vascular proteinopathies such as CAA are transmissible in mice via the intravenous route of peripheral exposure.

Zinc-Amyloid Interactions on a Millisecond Time-Scale Stabilize Non-Fibrillar Alzheimer Related Species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noy,D.; Solomonov, I.; Sinkevich, O.

2008-01-01

The role of zinc, an essential element for normal brain function, in the pathology of Alzheimer's disease (AD) is poorly understood. On one hand, physiological and genetic evidence from transgenic mouse models supports its pathogenic role in promoting the deposition of the amyloid {beta}-protein (A{beta}) in senile plaques. On the other hand, levels of extracellular ('free') zinc in the brain, as inferred by the levels of zinc in cerebrospinal fluid, were found to be too low for inducing A{beta} aggregation. Remarkably, the release of transient high local concentrations of zinc during rapid synaptic events was reported. The role of suchmore » free zinc pulses in promoting A{beta} aggregation has never been established. Using a range of time-resolved structural and spectroscopic techniques, we found that zinc, when introduced in millisecond pulses of micromolar concentrations, immediately interacts with A{beta} 1-40 and promotes its aggregation. These interactions specifically stabilize non-fibrillar pathogenic related aggregate forms and prevent the formation of A{beta} fibrils (more benign species) presumably by interfering with the self-assembly process of A{beta}. These in vitro results strongly suggest a significant role for zinc pulses in A{beta} pathology. We further propose that by interfering with A{beta} self-assembly, which leads to insoluble, non-pathological fibrillar forms, zinc stabilizes transient, harmful amyloid forms. This report argues that zinc represents a class of molecular pathogens that effectively perturb the self-assembly of benign A{beta} fibrils, and stabilize harmful non-fibrillar forms.« less

Structure-based discovery of fiber-binding compounds that reduce the cytotoxicity of amyloid beta

DOE PAGES

Jiang, Lin; Liu, Cong; Leibly, David; ...

2013-07-16

Amyloid protein aggregates are associated with dozens of devastating diseases including Alzheimer’s, Parkinson’s, ALS, and diabetes type 2. While structure-based discovery of compounds has been effective in combating numerous infectious and metabolic diseases, ignorance of amyloid structure has hindered similar approaches to amyloid disease. Here we show that knowledge of the atomic structure of one of the adhesive, steric-zipper segments of the amyloid-beta (Aβ) protein of Alzheimer’s disease, when coupled with computational methods, identifies eight diverse but mainly flat compounds and three compound derivatives that reduce Aβ cytotoxicity against mammalian cells by up to 90%. Although these compounds bind tomore » Aβ fibers, they do not reduce fiber formation of Aβ. Structure-activity relationship studies of the fiber-binding compounds and their derivatives suggest that compound binding increases fiber stability and decreases fiber toxicity, perhaps by shifting the equilibrium of Aβ from oligomers to fibers.« less

Cartilage acidic protein 1, a new member of the beta-propeller protein family with amyloid propensity.

PubMed

Anjos, Liliana; Morgado, Isabel; Guerreiro, Marta; Cardoso, João C R; Melo, Eduardo P; Power, Deborah M

2017-02-01

Cartilage acidic protein1 (CRTAC1) is an extracellular matrix protein of chondrogenic tissue in humans and its presence in bacteria indicate it is of ancient origin. Structural modeling of piscine CRTAC1 reveals it belongs to the large family of beta-propeller proteins that in mammals have been associated with diseases, including amyloid diseases such as Alzheimer's. In order to characterize the structure/function evolution of this new member of the beta-propeller family we exploited the unique characteristics of piscine duplicate genes Crtac1a and Crtac1b and compared their structural and biochemical modifications with human recombinant CRTAC1. We demonstrate that CRTAC1 has a beta-propeller structure that has been conserved during evolution and easily forms high molecular weight thermo-stable aggregates. We reveal for the first time the propensity of CRTAC1 to form amyloid-like structures, and hypothesize that the aggregating property of CRTAC1 may be related to its disease-association. We further contribute to the general understating of CRTAC1's and beta-propeller family evolution and function. Proteins 2017; 85:242-255. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Methyl Salicylate Lactoside Protects Neurons Ameliorating Cognitive Disorder Through Inhibiting Amyloid Beta-Induced Neuroinflammatory Response in Alzheimer’s Disease

PubMed Central

Li, Jinze; Ma, Xiaowei; Wang, Yu; Chen, Chengjuan; Hu, Min; Wang, Linlin; Fu, Junmin; Shi, Gaona; Zhang, Dongming; Zhang, Tiantai

2018-01-01

Neuroinflammatory reactions mediated by microglia and astrocytes have been shown to play a key role in early progression of Alzheimer’s disease (AD). Increased evidences have demonstrated that neurons exacerbate local inflammatory reactions by producing inflammatory mediators and act as an important participant in the pathogenesis of AD. Methyl salicylate lactoside (MSL) is an isolated natural product that is part of a class of novel non-steroidal anti-inflammatory drugs (NSAID). In our previous studies, we demonstrated that MSL exhibited therapeutic effects on arthritis-induced mice and suppressed the activation of glial cells. In the current study, we investigated the effects of MSL on cognitive function and neuronal protection induced by amyloid-beta peptides (Aβ) and explored potential underlying mechanisms involved. Amyloid precursor protein (APP) and presenilin 1 (PS1) double transgenic mice were used to evaluate the effects of MSL through behavioral testing and neuronal degenerative changes. In addition, copper-injured APP Swedish mutation overexpressing SH-SY5Y cells were used to determine the transduction of cyclooxygenase (COX) and mitogen-activated protein kinase (MAPK) pathways. Our results indicated that at an early stage, MSL treatment ameliorated cognitive impairment and neurodegeneration in APP/PS1 mice. Moreover, in an in vitro AD model, MSL treatment protected injured cells by increasing cell viability, improving mitochondrial dysfunction, and decreasing oxidative damage. In addition, MSL inhibited the phosphorylated level of c-Jun N-terminal kinase (JNK) and p38 MAPK, and suppressed the expression of COX-1/2. As a novel NSAIDs and used for the treatment in early stage of AD, MSL clearly demonstrated cognitive preservation by protecting neurons via a pleiotropic anti-inflammatory effect in the context of AD-associated deficits. Therefore, early treatment of anti-inflammatory therapy may be an effective strategy for treating AD. PMID:29636677

Messenger RNA-based therapeutics for brain diseases: An animal study for augmenting clearance of beta-amyloid by intracerebral administration of neprilysin mRNA loaded in polyplex nanomicelles.

PubMed

Lin, Chin-Yu; Perche, Federico; Ikegami, Masaru; Uchida, Satoshi; Kataoka, Kazunori; Itaka, Keiji

2016-08-10

Alzheimer's disease (AD) pathogenesis is considered to be the metabolic imbalance between anabolism and clearance of amyloid-beta (Aβ), and the strategy of breaking the equilibrium between soluble and insoluble forms of Aβ is likely to help prevent the progression of AD. Neprilysin (NEP) plays a major role in the clearance of Aβ in the brain, and its supplementation using viral vectors has shown to decrease Aβ deposition and prevent pathogenic changes in the brain. In this study, we developed a new therapeutic strategy by mRNA-based gene introduction. mRNA has the advantages of negligible risk of random integration into genome and not needing to be transcribed precludes the need for nuclear entry. This allows efficient protein expression in slowly-dividing or non-dividing cells, such as neural cells. We constructed mRNA encoding the mouse NEP protein and evaluated its ability degrade Aβ. In vitro transfection of NEP mRNA to primary neurons exhibited Amyloid Precursor Protein (APP) degradation activity superior to that of NEP encoding plasmid DNA. We then evaluated the in vivo activity of NEP mRNA by intracerebroventricular (i.c.v.) infusion using a cationic polymer-based PEGylated nanocarrier to form polyplex nanomicelles, which have been shown to have a high potential to deliver mRNA to various target tissues and organs. Nanomicelles carrying a GFP-NEP fusion mRNA produced efficient protein expression in a diffuse manner surrounding the ventricular space. An ELISA evaluation revealed that the mRNA infusion significantly augmented NEP level and effectively reduced the concentration of Aβ that had been supplemented in the mouse brain. To the best of our knowledge, this is the first study to demonstrate the therapeutic potential of introducing exogenous mRNA for the treatment of brain diseases, opening the new era of mRNA-based therapeutics. Copyright © 2016 Elsevier B.V. All rights reserved.

Biomarkers for early diagnosis of Alzheimer disease: 'ALZheimer ASsociated gene'--a new blood biomarker?

PubMed

Jellinger, Kurt A; Janetzky, Bernd; Attems, Johannes; Kienzl, Elisabeth

2008-08-01

Simple, non-invasive tests for an early detection of degenerative dementia by use of biomarkers are urgently required. However, up to the present, no validated extracerebral diagnostic markers (plasma/serum, platelets, urine, connective tissue) for the early diagnosis of Alzheimer disease (AD) are available. In disease stages with evident cognitive disturbances, the clinical diagnosis of probable AD is made with around 90% accuracy using modern clinical, neuropsychological and imaging methods. Diagnostic sensitivity and specificity even in early disease stages are improved by CSF markers, in particular combined tau and amyloid beta peptides (Abeta) and plasma markers (eg, Abeta-42/Abeta-40 ratio). Recently, a novel gene/protein--ALZAS (Alzheimer Associated Protein)--with a 79 amino acid sequence, containing the amyloid beta-42 fragment (Abeta-42), the amyloid precursor protein (APP) transmembrane signal and a 12 amino acid C-terminal, not present in any other known APP alleles, has been discovered on chromosome 21 within the APP region. Reverse transcriptase-PCR revealed the expression of the transcript of this protein in the cortex and hippocampal regions as well as in lymphocytes of human AD patients. The expression of ALZAS is mirrored by a specific autoimmune response in AD patients, directed against the ct-12 end of the ALZAS-peptide but not against the Abeta-sequence. ELISA studies of plasma detected highest titers of ALZAS in patients with mild cognitive impairment (presymptomatic AD), but only moderately increased titers in autopsy-confirmed AD, whereas low or undetectable ct-12 titers were found in cognitively intact age-matched subjects and young controls. The antigen, ALZAS protein, was detected in plasma in later clinical stages of AD. It is suggested that ALZAS represents an indicator in a dynamic equilibrium between both peripheral and brain degenerative changes in AD and may become a useful "non-invasive" diagnostic marker via a simple blood test.

Neuroprotective potential of high-dose biotin.

PubMed

McCarty, Mark F; DiNicolantonio, James J

2017-11-01

A recent controlled trial has established that high-dose biotin supplementation - 100 mg, three times daily - has a stabilizing effect on progression of multiple sclerosis (MS). Although this effect has been attributed to an optimization of biotin's essential cofactor role in the brain, a case can be made that direct stimulation of soluble guanylate cyclase (sGC) by pharmacological concentrations of biotin plays a key role in this regard. The utility of high-dose biotin in MS might reflect an anti-inflammatory effect of cGMP on the cerebral microvasculature, as well on oligodendrocyte differentiation and on Schwann cell production of neurotrophic factors thought to have potential for managing MS. But biotin's ability to boost cGMP synthesis in the brain may have broader neuroprotective potential. In many types of neurons and neural cells, cGMP exerts neurotrophic-mimetic effects - entailing activation of the PI3K-Akt and Ras-ERK pathways - that promote neuron survival and plasticity. Hippocampal long term potentiation requires nitric oxide synthesis, which in turn promotes an activating phosphorylation of CREB via a pathway involving cGMP and protein kinase G (PKG). In Alzheimer's disease (AD), amyloid beta suppresses this mechanism by inhibiting sGC activity; agents which exert a countervailing effect by boosting cGMP levels tend to restore effective long-term potentiation in rodent models of AD. Moreover, NO/cGMP suppresses amyloid beta production within the brain by inhibiting expression of amyloid precursor protein and BACE1. In conjunction with cGMP's ability to oppose neuron apoptosis, these effects suggest that high-dose biotin might have potential for the prevention and management of AD. cGMP also promotes neurogenesis, and may lessen stroke risk by impeding atherogenesis and hypertrophic remodeling in the cerebral vasculature. The neuroprotective potential of high-dose biotin likely could be boosted by concurrent administration of brain-permeable phosphodiesterase-5 inhibitors. Copyright © 2017 Elsevier Ltd. All rights reserved.

Impact Mediated Loading Cytoplasmic Loading of Macromolecules into Adherent Cells

NASA Technical Reports Server (NTRS)

Clarke, Mark S. F.; Feeback, Daniel L.; Vanderburg, Charles R.

2003-01-01

The advent of modern molecular biology, including the development of gene array technologies, has resulted in an explosion of information concerning the specific genes activated during normal cellular development, as well as those associated with a variety of pathological conditions. These techniques have served as a highly efficient, broacI.-based screening approach for those specific genes involved. in regulating normal cellular physiology and identifying candidate genes directly associated with the etiology of specific disease states. However, this approach provides information at the transcriptional' level only and does not necessarily indicate . that the gene in question is in fact translated ito a protein, or whether or not post-translational modification of the protein occurs. The critical importance of post-translational modification (i.e. phosphorylation, glycosylation, sialyation, etc.) to protein function has been recognized with regard to a number of proteins involved in a variety of important disease states. For example, altered glycosylation of beta-amyloid precursor protein results in an increase in the amount of beta-amyloid peptide generated and hence secreted as insoluble extracellular amyloid deposits (Georgopoulou, McLaughlin et al. 2001; Walter, Fluhrer et al. 2001), a pathological hal1nark of Alzheimer's disease. Abnormal phosphorylaion of synapsin I has been linked to alterations in synaptic vesicle trafficking leading to defective neurotransmission in Huntington's disease (Lievens, Woodman et al. 2002). Altered phosphorylation of the TAU protein involved in microtubule function has been linked to a number of neurodegenative diseases such as Alzheimer's disease (Billingsley and Kincaid 1997; Sanchez, Alvarez-Tllada et a1. 2001). Aberrant siaIyation of cell/I surface antigens has been detected in a number of different tumor cell types and has been linked to the acquisition of a neoplastic phenotype (Sell 1990), while improper' sia1yation of sodium channels in cardiac tissue has been linked to heart failure (Ufret-Vincenty, Baro et al. 2001; Fozzard and Kyle 2002).

Amyloid protein-mediated differential DNA methylation status regulates gene expression in Alzheimer's disease model cell line

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sung, Hye Youn; Choi, Eun Nam; Ahn Jo, Sangmee

2011-11-04

Highlights: Black-Right-Pointing-Pointer Genome-wide DNA methylation pattern in Alzheimer's disease model cell line. Black-Right-Pointing-Pointer Integrated analysis of CpG methylation and mRNA expression profiles. Black-Right-Pointing-Pointer Identify three Swedish mutant target genes; CTIF, NXT2 and DDR2 gene. Black-Right-Pointing-Pointer The effect of Swedish mutation on alteration of DNA methylation and gene expression. -- Abstract: The Swedish mutation of amyloid precursor protein (APP-sw) has been reported to dramatically increase beta amyloid production through aberrant cleavage at the beta secretase site, causing early-onset Alzheimer's disease (AD). DNA methylation has been reported to be associated with AD pathogenesis, but the underlying molecular mechanism of APP-sw-mediated epigenetic alterationsmore » in AD pathogenesis remains largely unknown. We analyzed genome-wide interplay between promoter CpG DNA methylation and gene expression in an APP-sw-expressing AD model cell line. To identify genes whose expression was regulated by DNA methylation status, we performed integrated analysis of CpG methylation and mRNA expression profiles, and identified three target genes of the APP-sw mutant; hypomethylated CTIF (CBP80/CBP20-dependent translation initiation factor) and NXT2 (nuclear exporting factor 2), and hypermethylated DDR2 (discoidin domain receptor 2). Treatment with the demethylating agent 5-aza-2 Prime -deoxycytidine restored mRNA expression of these three genes, implying methylation-dependent transcriptional regulation. The profound alteration in the methylation status was detected at the -435, -295, and -271 CpG sites of CTIF, and at the -505 to -341 region in the promoter of DDR2. In the promoter region of NXT2, only one CpG site located at -432 was differentially unmethylated in APP-sw cells. Thus, we demonstrated the effect of the APP-sw mutation on alteration of DNA methylation and subsequent gene expression. This epigenetic regulatory mechanism may contribute to the pathogenesis of AD.« less

Evidence for novel beta-sheet structures in Iowa mutant beta-amyloid fibrils.

PubMed

Tycko, Robert; Sciarretta, Kimberly L; Orgel, Joseph P R O; Meredith, Stephen C

2009-07-07

Asp23-to-Asn mutation within the coding sequence of beta-amyloid, called the Iowa mutation, is associated with early onset, familial Alzheimer's disease and cerebral amyloid angiopathy, in which patients develop neuritic plaques and massive vascular deposition predominantly of the mutant peptide. We examined the mutant peptide, D23N-Abeta40, by electron microscopy, X-ray diffraction, and solid-state NMR spectroscopy. D23N-Abeta40 forms fibrils considerably faster than the wild-type peptide (k = 3.77 x 10(-3) min(-1) and 1.07 x 10(-4) min(-1) for D23N-Abeta40 and the wild-type peptide WT-Abeta40, respectively) and without a lag phase. Electron microscopy shows that D23N-Abeta40 forms fibrils with multiple morphologies. X-ray fiber diffraction shows a cross-beta pattern, with a sharp reflection at 4.7 A and a broad reflection at 9.4 A, which is notably smaller than the value for WT-Abeta40 fibrils (10.4 A). Solid-state NMR measurements indicate molecular level polymorphism of the fibrils, with only a minority of D23N-Abeta40 fibrils containing the in-register, parallel beta-sheet structure commonly found in WT-Abeta40 fibrils and most other amyloid fibrils. Antiparallel beta-sheet structures in the majority of fibrils are indicated by measurements of intermolecular distances through (13)C-(13)C and (15)N-(13)C dipole-dipole couplings. An intriguing possibility exists that there is a relationship between the aberrant structure of D23N-Abeta40 fibrils and the unusual vasculotropic clinical picture in these patients.

Structure activity relationship study of curcumin analogues toward the amyloid-beta aggregation inhibitor.

PubMed

Endo, Hitoshi; Nikaido, Yuri; Nakadate, Mamiko; Ise, Satomi; Konno, Hiroyuki

2014-12-15

Inhibition of the amyloid β aggregation process could possibly prevent the onset of Alzheimer's disease. In this article, we report a structure-activity relationship study of curcumin analogues for anti amyloid β aggregation activity. Compound 7, the ideal amyloid β aggregation inhibitor in vitro among synthesized curcumin analogues, has not only potent anti amyloid β aggregation effects, but also water solubility more than 160 times that of curcumin. In addition, new approaches to improve water solubility of curcumin-type compounds are proposed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Review: history of the amyloid fibril.

PubMed

Sipe, J D; Cohen, A S

2000-06-01

Rudolph Virchow, in 1854, introduced and popularized the term amyloid to denote a macroscopic tissue abnormality that exhibited a positive iodine staining reaction. Subsequent light microscopic studies with polarizing optics demonstrated the inherent birefringence of amyloid deposits, a property that increased intensely after staining with Congo red dye. In 1959, electron microscopic examination of ultrathin sections of amyloidotic tissues revealed the presence of fibrils, indeterminate in length and, invariably, 80 to 100 A in width. Using the criteria of Congophilia and fibrillar morphology, 20 or more biochemically distinct forms of amyloid have been identified throughout the animal kingdom; each is specifically associated with a unique clinical syndrome. Fibrils, also 80 to 100 A in width, have been isolated from tissue homogenates using differential sedimentation or solubility. X-ray diffraction analysis revealed the fibrils to be ordered in the beta pleated sheet conformation, with the direction of the polypeptide backbone perpendicular to the fibril axis (cross beta structure). Because of the similar dimensions and tinctorial properties of the fibrils extracted from amyloid-laden tissues and amyloid fibrils in tissue sections, they have been assumed to be identical. However, the spatial relationship of proteoglycans and amyloid P component (AP), common to all forms of amyloid, to the putative protein only fibrils in tissues, has been unclear. Recently, it has been suggested that, in situ, amyloid fibrils are composed of proteoglycans and AP as well as amyloid proteins and thus resemble connective tissue microfibrils. Chemical and physical definition of the fibrils in tissues will be needed to relate the in vitro properties of amyloid protein fibrils to the pathogenesis of amyloid fibril formation in vivo. Copyright 2000 Academic Press.

Impact of amyloid-beta changes on cognitive outcomes in Alzheimer's disease: analysis of clinical trials using a quantitative systems pharmacology model.

PubMed

Geerts, Hugo; Spiros, Athan; Roberts, Patrick

2018-02-02

Despite a tremendous amount of information on the role of amyloid in Alzheimer's disease (AD), almost all clinical trials testing this hypothesis have failed to generate clinically relevant cognitive effects. We present an advanced mechanism-based and biophysically realistic quantitative systems pharmacology computer model of an Alzheimer-type neuronal cortical network that has been calibrated with Alzheimer Disease Assessment Scale, cognitive subscale (ADAS-Cog) readouts from historical clinical trials and simulated the differential impact of amyloid-beta (Aβ40 and Aβ42) oligomers on glutamate and nicotinic neurotransmission. Preclinical data suggest a beneficial effect of shorter Aβ forms within a limited dose range. Such a beneficial effect of Aβ40 on glutamate neurotransmission in human patients is absolutely necessary to reproduce clinical data on the ADAS-Cog in minimal cognitive impairment (MCI) patients with and without amyloid load, the effect of APOE genotype effect on the slope of the cognitive trajectory over time in placebo AD patients and higher sensitivity to cholinergic manipulation with scopolamine associated with higher Aβ in MCI subjects. We further derive a relationship between units of Aβ load in our model and the standard uptake value ratio from amyloid imaging. When introducing the documented clinical pharmacodynamic effects on Aβ levels for various amyloid-related clinical interventions in patients with low Aβ baseline, the platform predicts an overall significant worsening for passive vaccination with solanezumab, beta-secretase inhibitor verubecestat and gamma-secretase inhibitor semagacestat. In contrast, all three interventions improved cognition in subjects with moderate to high baseline Aβ levels, with verubecestat anticipated to have the greatest effect (around ADAS-Cog value 1.5 points), solanezumab the lowest (0.8 ADAS-Cog value points) and semagacestat in between. This could explain the success of many amyloid interventions in transgene animals with an artificial high level of Aβ, but not in AD patients with a large variability of amyloid loads. If these predictions are confirmed in post-hoc analyses of failed clinical amyloid-modulating trials, one should question the rationale behind testing these interventions in early and prodromal subjects with low or zero amyloid load.

Determining the Effect of Aluminum Oxide Nanoparticles on the Aggregation of Amyloid-Beta in Transgenic Caenorhabditis elegans

NASA Astrophysics Data System (ADS)

Patel, Suhag; Matticks, John; Howell, Carina

2014-03-01

The cause of Alzheimer's disease has been linked partially to genetic factors but the predicted environmental components have yet to be determined. In Alzheimer's, accumulation of amyloid-beta protein in the brain forms plaques resulting in neurodegeneration and loss of mental functions. It has been postulated that aluminum influences the aggregation of amyloid-beta. To test this hypothesis, transgenic Caenorhabditis elegans, CL2120, was used as a model organism to observe neurodegeneration in nematodes exposed to aluminum oxide nanoparticles. Behavioral testing, fluorescent staining, and fluorescence microscopy were used to test the effects of aggregation of amyloid-beta in the nervous systems of effected nematodes exposed to aluminum oxide nanoparticles. Energy-dispersive x-ray spectroscopy was used to quantify the total concentration of aluminum oxide that the worms were exposed to during the experiment. Exposure of transgenic and wild type worms to a concentration of 4 mg mL-1 aluminum oxide showed a decrease in the sinusoidal motion, as well as an infirmity of transgenic worms when compared to control worms. These results support the hypothesis that aluminum may play a role in neurodegeneration in C. elegans, and may influence and increase the progression of Alzheimer's disease. This work was supported by National Science Foundation grants DUE-1058829, DMR-0923047 DUE-0806660 and Lock Haven FPDC grants.

Generation and Initial Characterization of FDD Knock In Mice

PubMed Central

Giliberto, Luca; Matsuda, Shuji; Vidal, Ruben; D'Adamio, Luciano

2009-01-01

Background Mutations in the integral membrane protein 2B [1], also known as BRI2 [2], a type II trans-membrane domain protein cause two autosomal dominant neurodegenerative diseases, Familial British and Danish Dementia [3]. In these conditions, accumulation of a C-terminal peptide (ABri and ADan) cleaved off from the mutated precursor protein by the pro-protein convertase furin [4], leads to amyloid deposition in the walls of blood vessels and parenchyma of the brain. Recent advances in the understanding of the generation of amyloid in Alzheimer's disease has lead to the finding that BRI2 interacts with the Amyloid Precursor Protein (APP), decreasing the efficiency of APP processing to generate Aβ [5], [6], [7]. The interaction between the two precursors, APP and BRI2, and possibly between Aβ and ABri or ADan, could be important in influencing the rate of amyloid production or the tendency of these peptides to aggregate. Methodology/Principal Findings We have generated the first BRI2 Danish Knock-In (FDDKI) murine model of FDD, expressing the pathogenic decamer duplication in exon 6 of the BRI2 gene. FDDKI mice do not show any evident abnormal phenotype, with normal brain histology and no detectable amyloid deposition in blood vessel walls or parenchyma. Conclusions/Significance This new murine mouse model will be important to further understand the interaction between APP and BRI2, and to provide insights into the molecular basis of FDD. PMID:19924302

Resveratrol, a neuroprotective supplement for Alzheimer's disease.

PubMed

Li, Fei; Gong, Qihai; Dong, Hongxin; Shi, Jingshan

2012-01-01

The polyphenolic compound resveratrol (3,4',5-trihydroxystilbene) is a naturally occurring phytochemical which has been found in more than 70 plant species, including herbs and human food products such as grapes, berries, and peanuts. Resveratrol was first isolated in 1940; however, little attention was paid to it until its benefits in coronary heart disease were studied in 1992. Since then, increasing evidence has indicated that resveratrol may be useful in treating cardiovascular diseases, cancers, pain, inflammation, tissue injury, and in reducing the risk of neurodegenerative disorders, especially Alzheimer's disease (AD). AD is characterized by a progressive dementia, and is one of the most common neurodegenerative disorders in the elderly. It has been reported that resveratrol exhibits neuroprotective benefits in animal models of AD. Resveratrol promotes the non-amyloidogenic cleavage of the amyloid precursor protein, enhances clearance of amyloid beta-peptides, and reduces neuronal damage. Despite the effort spent trying to understand the mechanisms by which resveratrol functions, the research work in this field is still incomplete. Many concerns such as bioavailability, biotransformation, synergism with other dietary factors, and risks inherent to its possible pro-oxidant activities still need to be addressed. This review summarizes and discusses the neuroprotective effects of resveratrol on AD, and their potential mechanisms.

Metal Dyshomeostasis and Inflammation in Alzheimer's and Parkinson's Diseases: Possible Impact of Environmental Exposures

PubMed Central

Myhre, Oddvar; Utkilen, Hans; Duale, Nur; Brunborg, Gunnar; Hofer, Tim

2013-01-01

A dysregulated metal homeostasis is associated with both Alzheimer's (AD) and Parkinson's (PD) diseases; AD patients have decreased cortex and elevated serum copper levels along with extracellular amyloid-beta plaques containing copper, iron, and zinc. For AD, a putative hepcidin-mediated lowering of cortex copper mechanism is suggested. An age-related mild chronic inflammation and/or elevated intracellular iron can trigger hepcidin production followed by its binding to ferroportin which is the only neuronal iron exporter, thereby subjecting it to lysosomal degradation. Subsequently raised neuronal iron levels can induce translation of the ferroportin assisting and copper binding amyloid precursor protein (APP); constitutive APP transmembrane passage lowers the copper pool which is important for many enzymes. Using in silico gene expression analyses, we here show significantly decreased expression of copper-dependent enzymes in AD brain and metallothioneins were upregulated in both diseases. Although few AD exposure risk factors are known, AD-related tauopathies can result from cyanobacterial microcystin and β-methylamino-L-alanine (BMAA) intake. Several environmental exposures may represent risk factors for PD; for this disease neurodegeneration is likely to involve mitochondrial dysfunction, microglial activation, and neuroinflammation. Administration of metal chelators and anti-inflammatory agents could affect disease outcomes. PMID:23710288

Visualization of APP and BACE-1 approximation in neurons: new insights into the amyloidogenic pathway

PubMed Central

Das, Utpal; Wang, Lina; Ganguly, Archan; Saikia, Junmi M.; Wagner, Steven L.; Koo, Edward H.; Roy, Subhojit

2016-01-01

Cleavage of APP (amyloid precursor protein) by BACE-1 (β-site APP cleaving enzyme-1) is the rate-limiting step in amyloid-beta (Aβ) production and a neuropathologic hallmark of Alzheimer's disease (AD); thus physical approximation of this substrate-enzyme pair is a critical event with broad biological and therapeutic implications. Despite much research, neuronal locales of APP/BACE-1 convergence and APP-cleavage remain unclear. Here we report an optical assay – based on fluorescence complementation – to visualize in-cellulo APP/BACE-1 interactions as a simple on/off signal. Combined with other assays tracking the fate of internalized APP in hippocampal neurons, we found that APP/BACE-1 interact in both biosynthetic and endocytic compartments; particularly along recycling-microdomains such as dendritic spines and presynaptic boutons. In axons, APP and BACE-1 are co-transported, and also interact during transit. Finally, our assay reveals that the AD-protective “Icelandic” mutation greatly attenuates APP/BACE-1 interactions, suggesting a mechanistic basis for protection. Collectively, the data challenge canonical models and provide concrete insights into long-standing controversies in the field. PMID:26642089

Anxiety-like behavior as an early endophenotype in the TgF344-AD rat model of Alzheimer's disease.

PubMed

Pentkowski, Nathan S; Berkowitz, Laura E; Thompson, Shannon M; Drake, Emma N; Olguin, Carlos R; Clark, Benjamin J

2018-01-01

Alzheimer's disease (AD) is characterized by progressive cognitive decline and the presence of aggregates of amyloid beta (plaques) and hyperphosphorylated tau (tangles). Early diagnosis through neuropsychological testing is difficult due to comorbidity of symptoms between AD and other types of dementia. As a result, there is a need to identify the range of behavioral phenotypes expressed in AD. In the present study, we utilized a transgenic rat (TgF344-AD) model that bears the mutated amyloid precursor protein as well as presenilin-1 genes, resulting in progressive plaque and tangle pathogenesis throughout the cortex. We tested young adult male and female TgF344-AD rats in a spatial memory task in the Morris water maze and for anxiety-like behavior in the elevated plus-maze. Results indicated that regardless of sex, TgF344-AD rats exhibited increased anxiety-like behavior in the elevated plus-maze, which occurred without significant deficits in the spatial memory. Together, these results indicate that enhanced anxiety-like behavior represents an early-stage behavioral marker in the TgF344-AD rat model. Copyright © 2017 Elsevier Inc. All rights reserved.

Protection against β-amyloid neurotoxicity by a non-toxic endogenous N-terminal β-amyloid fragment and its active hexapeptide core sequence.

PubMed

Forest, Kelly H; Alfulaij, Naghum; Arora, Komal; Taketa, Ruth; Sherrin, Tessi; Todorovic, Cedomir; Lawrence, James L M; Yoshikawa, Gene T; Ng, Ho-Leung; Hruby, Victor J; Nichols, Robert A

2018-01-01

High levels (μM) of beta amyloid (Aβ) oligomers are known to trigger neurotoxic effects, leading to synaptic impairment, behavioral deficits, and apoptotic cell death. The hydrophobic C-terminal domain of Aβ, together with sequences critical for oligomer formation, is essential for this neurotoxicity. However, Aβ at low levels (pM-nM) has been shown to function as a positive neuromodulator and this activity resides in the hydrophilic N-terminal domain of Aβ. An N-terminal Aβ fragment (1-15/16), found in cerebrospinal fluid, was also shown to be a highly active neuromodulator and to reverse Aβ-induced impairments of long-term potentiation. Here, we show the impact of this N-terminal Aβ fragment and a shorter hexapeptide core sequence in the Aβ fragment (Aβcore: 10-15) to protect or reverse Aβ-induced neuronal toxicity, fear memory deficits and apoptotic death. The neuroprotective effects of the N-terminal Aβ fragment and Aβcore on Aβ-induced changes in mitochondrial function, oxidative stress, and apoptotic neuronal death were demonstrated via mitochondrial membrane potential, live reactive oxygen species, DNA fragmentation and cell survival assays using a model neuroblastoma cell line (differentiated NG108-15) and mouse hippocampal neuron cultures. The protective action of the N-terminal Aβ fragment and Aβcore against spatial memory processing deficits in amyloid precursor protein/PSEN1 (5XFAD) mice was demonstrated in contextual fear conditioning. Stabilized derivatives of the N-terminal Aβcore were also shown to be fully protective against Aβ-triggered oxidative stress. Together, these findings indicate an endogenous neuroprotective role for the N-terminal Aβ fragment, while active stabilized N-terminal Aβcore derivatives offer the potential for therapeutic application. © 2017 International Society for Neurochemistry.

Fructo-oligosaccharide improved brain β-amyloid, β-secretase, cognitive function, and plasma antioxidant levels in D-galactose-treated Balb/cJ mice.

PubMed

Yen, Chi-Hua; Wang, Cheng-Hsin; Wu, Wen-Tzu; Chen, Hsiao-Ling

2017-05-01

Long-term d-galactose injection induces accelerated aging in experimental rodent models. The aim of this study was to determine the effects of dietary fructo-oligosaccharide (FO) on the brain β-amyloid (Aβ), amyloid-associated enzymes, cognitive function, and plasma antioxidant levels in d-galactose-treated Balb/c mice. The subcutaneous (s.c.) injection and the dietary treatment were conducted simultaneously for 49 days. Mice (12 weeks of age) were divided into five groups (n = 14/group): control (s.c. saline, control diet) serving as a young control, DG (s.c. 1.2 g d-galactose/kg body weight, control diet), DG + LFO (2.5% w/w FO, low-dose FO diet), DG + HFO (5% w/w FO, high-dose FO diet), and DG + E (α-tocopherol 0.2% w/w, vitamin E diet) as an antioxidant reference group. Another group of older mice (64 weeks of age) without any injection served as a natural aging (NA) group. The DG and NA groups had greater Aβ levels in the cortex, hippocampus, and the whole brain. High-dose FO, similar to α-tocopherol, attenuated the d-galactose-induced Aβ density in the cortex and hippocampus. In addition, FO attenuated the d-galactose-induced protein expression of Aβ and beta-site amyloid precursor cleaving enzyme of the whole brain in a dose-response manner. Either dose of FO supplementation, similar to α-tocopherol, attenuated the d-galactose-induced cognitive dysfunction. In addition, FO improved the plasma ascorbic acid level in a dose-response manner. Dietary FO (2.5-5% w/w diet) could attenuate the development of Alzheimer's disease, which was likely to be associated with its systematic antioxidant effects.

Cerebrospinal fluid Alzheimer's biomarker profiles in CNS infections.

PubMed

Krut, Jan Jessen; Zetterberg, Henrik; Blennow, Kaj; Cinque, Paola; Hagberg, Lars; Price, Richard W; Studahl, Marie; Gisslén, Magnus

2013-02-01

The cerebrospinal fluid (CSF) biomarker profile in Alzheimer's disease (AD) is characterized by decreased beta amyloid (Aβ(1-42)), increased total and hyperphosphorylated tau (t-tau and p-tau, respectively), which is a useful diagnostic tool and gives insight in the pathogenesis of AD. It is of importance to study how these biomarkers react in other CNS diseases; therefore, we decided to analyse amyloid and tau biomarkers in different CNS infections. We also included analysis of soluble amyloid precursor proteins (sAPPα and -β). CSF Aβ(1-42), sAPPα and -β, t-tau and p-tau were analysed in bacterial meningitis (n = 12), Lyme neuroborreliosis (n = 13), herpes simplex virus type 1 (HSV-1) encephalitis (n = 10), HIV-associated dementia (HAD) (n = 21), AD (n = 21) and healthy controls (n = 42). Concurrent with AD, Aβ(1-42) was decreased in all groups except neuroborreliosis compared to controls. HSV-1 encephalitis, bacterial meningitis and HAD showed lower concentrations of sAPPα and -β compared to AD. T-tau was increased in AD and HSV-1 encephalitis compared to all other groups. P-tau was higher in AD and HSV-1 encephalitis compared to bacterial meningitis, HAD and control. Decreased CSF Aβ(1-42), sAPPα and -β in various CNS infections imply an effect of neuroinflammation on amyloid metabolism which is similar in regard to AD concerning Aβ(1-42), but differs concerning sAPPα and -β. These results clearly indicate different pathologic pathways in AD and infectious CNS disease and may provide help in the differential biomarker diagnostics. Increased p-tau in HSV-1 encephalitis probably reflect acute neuronal damage and necrosis.

The Psen1-L166P-knock-in mutation leads to amyloid deposition in human wild-type amyloid precursor protein YAC transgenic mice

PubMed Central

Vidal, Ruben; Sammeta, Neeraja; Garringer, Holly J.; Sambamurti, Kumar; Miravalle, Leticia; Lamb, Bruce T.; Ghetti, Bernardino

2012-01-01

Genetically engineered mice have been generated to model cerebral β-amyloidosis, one of the hallmarks of Alzheimer disease (AD) pathology, based on the overexpression of a mutated cDNA of the amyloid-β precursor protein (AβPP) or by knock-in of the murine Aβpp gene alone or with presenilin1 mutations. Here we describe the generation and initial characterization of a new mouse line based on the presence of 2 copies of the human genomic region encoding the wild-type AβPP and the L166P presenilin 1 mutation. At ∼6 mo of age, double-mutant mice develop amyloid pathology, with signs of neuritic dystrophy, intracellular Aβ accumulation, and glial inflammation, an increase in AβPP C-terminal fragments, and an 8 times increase in Aβ42 levels with a 40% decrease in Aβ40 levels, leading to a significant increase (14 times) of Aβ42/Aβ40 ratios, with minimal effects on presenilin or the Notch1 pathway in the brain. We conclude that in mice, neither mutations in AβPP nor overexpression of an AβPP isoform are a prerequisite for Aβ pathology. This model will allow the study of AD pathogenesis and testing of therapeutic strategies in a more relevant environment without experimental artifacts due to the overexpression of a single-mutant AβPP isoform using exogenous promoters.—Vidal, R., Sammeta, N., Garringer, H. J., Sambamurti, K., Miravalle, L., Lamb B. T., Ghetti, B. The Psen1-L166P-knock-in mutation leads to amyloid deposition in human wild-type amyloid precursor protein YAC transgenic mice. PMID:22459153

Expression of amyloid-β protein and amyloid-β precursor protein after primary brain-stem injury in rats.

PubMed

Yang, Shudong; Sun, Rongchao; Zhou, Zhiyi; Zhou, Jing; Liang, Jiabei; Mu, Huijun

2014-09-01

Amyloid-β (Aβ) protein and its precursor, amyloid-β precursor protein (β-APP), have traditionally been used in the diagnosis of Alzheimer disease. Their use in diagnosis of traumatic brain injury by forensic analysis is becoming more widespread. However, to date, no reliable small animal model exists to evaluate these brain injury indicators. To address this, we have studied primary brain-stem injury in rats to assess the appearance of diffuse axonal injury in brain sections and correlate these findings with appearance of Aβ and relative β-APP mRNA levels. Using an EnVision 2-step immunohistochemical staining method to measure axon diameter, we found that there was significant difference in axon diameters within the medulla oblongata and several time points after brain injury, ranging from 3 to 24 hours. In addition, mRNA expression levels of β-APP increased following brain injury, peaking 3 hours following injury and decreasing back to baseline levels by 24 hours after injury. These results suggest that using immunohistochemistry and reverse transcription-polymerase chain reaction to detect changes in Aβ-associated axonal changes and β-APP mRNA levels, respectively, can be useful for the diagnosis of diffuse axonal injury during autopsy at early time points following fatal brain injury.

Amyloidosis: A cancer-derived paraproteinemia and kidney involvement.

PubMed

Małyszko, Jolanta; Kozłowska, Klaudia; Małyszko, Jacek Stanisław

2017-03-01

Amyloidosis is the general term describing the extracellular tissue deposition of fibrils composed of low molecular weight subunits of a variety of proteins. There are multiple different human protein precursors of amyloid fibrils. Amyloid deposits are stained using Congo Red and show typical apple-green birefringence in polarized microscopy. Nowadays, a novel technique LMD/MS technique or laser microdissection combined with mass spectrometry help to diagnose amyloidosis. Amyloidosis of the kidney is typically classified as being either one of two types: AL or AA. Less common is the hereditary amyloidosis. Clinical manifestations are usually determined by the type of precursor protein, the tissue distribution, and the amount of amyloid deposition. Renal manifestation is usually present as asymptomatic proteinuria or clinically apparent nephrotic syndrome. In some patients clinical presentation include impaired kidney function with no or mild proteinuria. Patients with renal amyloidosis who progress to end-stage renal disease (ESRD) can be treated with either dialysis or renal transplantation. Diagnosis of amyloidosis is prerequisite to consider treatment options to avoid unnecessary chemotherapy. Treatment of amyloidosis is aimed at decreasing the precursors of fibrillary proteins and/or decrease in synthesis/deposition of amyloid fibrils. It depends upon the type of amyloidosis and cause of excess fibril production. Copyright © 2016 Medical University of Bialystok. Published by Elsevier B.V. All rights reserved.

Amyloid-beta-sheet formation at the air-water interface.

PubMed Central

Schladitz, C; Vieira, E P; Hermel, H; Möhwald, H

1999-01-01

An amyloid(1-40) solution rich in coil, turn, and alpha-helix, but poor in beta-sheet, develops monolayers with a high beta-sheet content when spread at the air-water interface. These monolayers are resistant to repeated compression-dilatation cycles and interaction with trifluoroethanol. The secondary structure motifs were detected by circular dichroism (CD) in solution and with infrared reflection-absorption spectroscopy (IRRAS) at the interface. Hydrophobic influences are discussed for the structure conversion in an effort to understand the completely unknown reason for the natural change of the normal prion protein cellular (PrP(C)) into the abnormal prion protein scrapie (PrP(Sc)). PMID:10585952

Inhibition of beta-amyloid aggregation by fluorescent dye labels

NASA Astrophysics Data System (ADS)

Amaro, Mariana; Wellbrock, Thorben; Birch, David J. S.; Rolinski, Olaf J.

2014-02-01

The fluorescence decay of beta-amyloid's (Aβ) intrinsic fluorophore tyrosine has been used for sensing the oligomer formation of dye-labelled Aβ monomers and the results compared with previously studied oligomerization of the non-labelled Aβ peptides. It has been demonstrated that two different sized, covalently bound probes 7-diethylaminocoumarin-3-carbonyl and Hilyte Fluor 488 (HLF), alter the rate and character of oligomerization to different extents. The ability of HLF to inhibit formation of highly ordered structures containing beta-sheets was also shown. The implications of our findings for using fluorescence methods in amyloidosis research are discussed and the advantages of this auto-fluorescence approach highlighted.

Multiple Targets for the Management of Alzheimer's Disease.

PubMed

Ahmad, Syed Sayeed; Akhtar, Salman; Jamal, Qazi Mohammad Sajid; Rizvi, Syed Mohd Danish; Kamal, Mohammad A; Khan, M Kalim A; Siddiqui, Mohd Haris

2016-01-01

AD is a progressive and irreversible neurodegenerative disease and the most common cause of dementia in the elderly population. Βeta- amyloid cascade formation along with several cytoskeleton abnormalities succeeding to the hyperphosphorylation of microtubule-associated tau protein in neurons leads to the elicitation of several neurotoxic incidents. As an outcome of these phenomena, steady growth of dementia in aged population is becoming ubiquitous in both developed and developing countries. Thus, the key aspiration is to endow with stable daily life functionality to the person suffering from dementia and to cut down or slower the symptoms of disease leading to disruptive behavior. In sight of this, the proteins amyloid-beta, BACE-1, RAGE and AChE are being aimed for the treatment of AD successfully. Currently, there are several medicines for the treatment of AD under survey like Galangin, Cymserine, Tolserine, Bisnorcymserine and Huperzine A. The article emphasizes clinical and neurobiological aspects of AD. The purpose of this review article is to provide a brief introduction of AD along with the related concept of beta-secretase, beta amyloid and neurotransmitter in the progression of disease. In the present review, we summarize the available evidence on the new therapeutic approaches that target amyloid and neurotransmitter in the AD.

Non-fibrillar amyloid-{beta} peptide reduces NMDA-induced neurotoxicity, but not AMPA-induced neurotoxicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niidome, Tetsuhiro, E-mail: tniidome@pharm.kyoto-u.ac.jp; Goto, Yasuaki; Kato, Masaru

2009-09-04

Amyloid-{beta} peptide (A{beta}) is thought to be linked to the pathogenesis of Alzheimer's disease. Recent studies suggest that A{beta} has important physiological roles in addition to its pathological roles. We recently demonstrated that A{beta}42 protects hippocampal neurons from glutamate-induced neurotoxicity, but the relationship between A{beta}42 assemblies and their neuroprotective effects remains largely unknown. In this study, we prepared non-fibrillar and fibrillar A{beta}42 based on the results of the thioflavin T assay, Western blot analysis, and atomic force microscopy, and examined the effects of non-fibrillar and fibrillar A{beta}42 on glutamate-induced neurotoxicity. Non-fibrillar A{beta}42, but not fibrillar A{beta}42, protected hippocampal neurons frommore » glutamate-induced neurotoxicity. Furthermore, non-fibrillar A{beta}42 decreased both neurotoxicity and increases in the intracellular Ca{sup 2+} concentration induced by N-methyl-D-aspartate (NMDA), but not by {alpha}-amino-3-hydrozy-5-methyl-4-isoxazole propionic acid (AMPA). Our results suggest that non-fibrillar A{beta}42 protects hippocampal neurons from glutamate-induced neurotoxicity through regulation of the NMDA receptor.« less

Competing pathways determine fibril morphology in the self-assembly of beta2-microglobulin into amyloid.

PubMed

Gosal, Walraj S; Morten, Isobel J; Hewitt, Eric W; Smith, D Alastair; Thomson, Neil H; Radford, Sheena E

2005-08-26

Despite its importance in biological phenomena, a comprehensive understanding of the mechanism of amyloid formation remains elusive. Here, we use atomic force microscopy to map the formation of beta2-microglobulin amyloid fibrils with distinct morphologies and persistence lengths, when protein concentration, pH and ionic strength are varied. Using the resulting state-diagrams, we demonstrate the existence of two distinct competitive pathways of assembly, which define an energy landscape that rationalises the sensitivity of fibril morphology on the solution conditions. Importantly, we show that semi-flexible (worm-like) fibrils, which form rapidly during assembly, are kinetically trapped species, formed via a non-nucleated pathway that is explicitly distinct from that leading to the formation of the relatively rigid long-straight fibrils classically associated with amyloid. These semi-flexible fibrils also share an antibody epitope common to other protein oligomers that are known to be toxic species linked to human disease. The results demonstrate the heterogeneity of amyloid assembly, and have important implications for our understanding of the importance of oligomeric states in amyloid disease, the origins of prion strains, and the development of therapeutic strategies.

The crystal structure of DR6 in complex with the amyloid precursor protein provides insight into death receptor activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Kai; Olsen, Olav; Tzvetkova-Robev, Dorothea

The amyloid precursor protein (APP) has garnered considerable attention due to its genetic links to Alzheimer's disease. Death receptor 6 (DR6) was recently shown to bind APP via the protein extracellular regions, stimulate axonal pruning, and inhibit synapse formation. Here, we report the crystal structure of the DR6 ectodomain in complex with the E2 domain of APP and show that it supports a model for APP-induced dimerization and activation of cell surface DR6.

The crystal structure of DR6 in complex with the amyloid precursor protein provides insight into death receptor activation

DOE PAGES

Xu, Kai; Olsen, Olav; Tzvetkova-Robev, Dorothea; ...

2015-04-02

The amyloid precursor protein (APP) has garnered considerable attention due to its genetic links to Alzheimer's disease. Death receptor 6 (DR6) was recently shown to bind APP via the protein extracellular regions, stimulate axonal pruning, and inhibit synapse formation. Here, we report the crystal structure of the DR6 ectodomain in complex with the E2 domain of APP and show that it supports a model for APP-induced dimerization and activation of cell surface DR6.

MALDI, AP/MALDI and ESI techniques for the MS detection of amyloid [beta]-peptides

NASA Astrophysics Data System (ADS)

Grasso, Giuseppe; Mineo, Placido; Rizzarelli, Enrico; Spoto, Giuseppe

2009-04-01

Amyloid [beta]-peptides (A[beta]s) are involved in several neuropathological conditions such as Alzheimer's disease and considerable experimental evidences have emerged indicating that different proteases play a major role in regulating the accumulation of A[beta]s in the brain. Particularly, insulin-degrading enzyme (IDE) has been shown to degrade A[beta]s at different cleavage sites, but the experimental results reported in the literature and obtained by mass spectrometry methods are somehow fragmentary. The detection of A[beta]s is often complicated by solubility issues, oxidation artifacts and spontaneous aggregation/cleavage and, in order to rationalize the different reported results, we analyzed A[beta]s solutions by three different MS approaches: matrix assisted laser desorption ionization-time of flight (MALDI-TOF), atmospheric pressure (AP) MALDI ion trap and electrospray ionization (ESI) ion trap. Differences in the obtained results are discussed and ESI is chosen as the most suitable MS method for A[beta]s detection. Finally, cleavage sites produced by interaction of A[beta]s with IDE are identified, two of which had never been reported in the literature.

Circulating form of beta-2-microglobulin in dialysis patients.

PubMed

Gagnon, R F; Somerville, P; Thomson, D M

1988-01-01

The circulating profile of beta-2-microglobulin (beta 2M) was determined in 8 end-stage renal disease patients on long-term dialysis (6 on hemodialysis, 2 on CAPD) by measuring beta 2M in different fraction after molecular sieve separation of their sera. Four patients had carpal tunnel syndrome with demonstrated amyloid in excised wrist tissues of which 2 were positive for beta 2M. In all patients despite very high blood levels (34.3-63.1 mg/l), beta 2M eluted exclusively as a single peak in the molecular weight region of about 12,000 daltons on a calibrated Sephacryl S-200 column. Recoveries from within the peak accounted for 96% of the applied beta 2M serum concentrations. These results were confirmed by molecular sieve separation of the enriched beta 2M-containing fractions by high-pressure liquid chromatography. We conclude that immunoreactive beta 2M in dialysis patients circulates as an intact monomer without evidence for the formation of aggregates or fragments. The pathogenesis of tissue deposition of this low-molecular-weight protein and its polymerisation to form a specific amyloid remains to be defined.

[Relation between expression of cerebral beta-APP in the chronic alcoholism rats and death caused by TSAH].

PubMed

Wei, Lai; Lei, Huai-Cheng; Yu, Xiao-Jun; Lai, Xiao-Ping; Qian, Hong; Xu, Xiao-Hu; Zhu, Fang-Cheng

2013-04-01

By observing the cerebral beta-amyloid precursor protein (beta-APP) expression in the chronic alcoholism rats with slight cerebral injury, to discuss the correlation of chronic alcoholism and death caused by traumatic subarachnoid haemorrhage (TSAH). Sixty male SD rats were randomly divided into watering group, watering group with strike, alcoholism group and alcoholism group with strike. Among them, the alcohol was used for continuous 4 weeks in alcoholism groups and the concussion was made in groups with strike. In each group, HE staining and immunohistochemical staining of the cerebral tissues were done and the results were analyzed by the histopathologic image system. In watering group, there was no abnormal. In watering group with strike, mild neuronic congestion was found. In alcoholism group, vascular texture on cerebral surface was found. And the neurons arranged in disorder with dilated intercellular space. In alcoholism group with strike, diffuse congestion on cerebral surface was found. And there was TSAH with thick-layer patches around brainstem following irregular axonotmesis. The quantity of beta-APP IOD in alcoholism group was significantly higher in the frontal lobe, hippocampus, cerebellum, brainstem than those in watering group with strike and alcoholism group with strike. The cerebral tissues with chronic alcoholism, due to the decreasing tolerance, could cause fatal TSAH and pathological changes in cerebral tissues of rats under slight cerebral injury.

Rate Kinetics and Molecular Dynamics of the Structural Transitions in Amyloidogenic Proteins

NASA Astrophysics Data System (ADS)

Steckmann, Timothy M.

Amyloid fibril aggregation is associated with several horrific diseases such as Alzheimer's, Creutzfeld-Jacob, diabetes, Parkinson's and others. The process of amyloid aggregation involves forming myriad different metastable intermediate aggregates. Amyloid fibrils are composed of proteins that originate in an innocuous alpha-helix or random-coil structure. The alpha-helices convert their structure to beta-strands that aggregate into beta-sheets, and then into protofibrils, and ultimately into fully formed amyloid fibrils. On the basis of experimental data, I have developed a mathematical model for the kinetics of the reaction pathways and determined rate parameters for peptide secondary structural conversion and aggregation during the entire fibrillogenesis process from random coil to fibrils, including the molecular species that accelerate the conversions. The specific steps of the model and the rate constants that are determined by fitting to experimental data provide insight on the molecular species involved in the fibril formation process. To better understand the molecular basis of the protein structural transitions and aggregation, I report on molecular dynamics (MD) computational studies on the formation of amyloid protofibrillar structures in the small model protein ccbeta, which undergoes many of the structural transitions of the larger, naturally occurring amyloid forming proteins. Two different structural transition processes involving hydrogen bonds are observed for aggregation into fibrils: the breaking of intrachain hydrogen bonds to allow beta-hairpin proteins to straighten, and the subsequent formation of interchain hydrogen bonds during aggregation into amyloid fibrils. For my MD simulations, I found that the temperature dependence of these two different structural transition processes results in the existence of a temperature window that the ccbeta protein experiences during the process of forming protofibrillar structures. Both the mathematical modeling of the kinetics and the MD simulations show that molecular structural heterogeneity is a major factor in the process. The MD simulations also show that intrachain and interchain hydrogen bonds breaking and forming is strongly correlated to the process of amyloid formation.

Neuroinflammation is increased in the parietal cortex of atypical Alzheimer's disease.

PubMed

Boon, Baayla D C; Hoozemans, Jeroen J M; Lopuhaä, Boaz; Eigenhuis, Kristel N; Scheltens, Philip; Kamphorst, Wouter; Rozemuller, Annemieke J M; Bouwman, Femke H

2018-05-29

While most patients with Alzheimer's disease (AD) present with memory complaints, 30% of patients with early disease onset present with non-amnestic symptoms. This atypical presentation is thought to be caused by a different spreading of neurofibrillary tangles (NFT) than originally proposed by Braak and Braak. Recent studies suggest a prominent role for neuroinflammation in the spreading of tau pathology. We aimed to explore whether an atypical spreading of pathology in AD is associated with an atypical distribution of neuroinflammation. Typical and atypical AD cases were selected based on both NFT distribution and amnestic or non-amnestic clinical presentation. Immunohistochemistry was performed on the temporal pole and superior parietal lobe of 10 typical and 9 atypical AD cases. The presence of amyloid-beta (N-terminal; IC16), pTau (AT8), reactive astrocytes (GFAP), microglia (Iba1, CD68, and HLA-DP/DQ/DR), and complement factors (C1q, C3d, C4b, and C5b-9) was quantified by image analysis. Differences in lobar distribution patterns of immunoreactivity were statistically assessed using a linear mixed model. We found a temporal dominant distribution for amyloid-beta, GFAP, and Iba1 in both typical and atypical AD. Distribution of pTau, CD68, HLA-DP/DQ/DR, C3d, and C4b differed between AD variants. Typical AD cases showed a temporal dominant distribution of these markers, whereas atypical AD cases showed a parietal dominant distribution. Interestingly, when quantifying for the number of amyloid-beta plaques instead of stained surface area, atypical AD cases differed in distribution pattern from typical AD cases. Remarkably, plaque morphology and localization of neuroinflammation within the plaques was different between the two phenotypes. Our data show a different localization of neuroinflammatory markers and amyloid-beta plaques between AD phenotypes. In addition, these markers reflect the atypical distribution of tau pathology in atypical AD, suggesting that neuroinflammation might be a crucial link between amyloid-beta deposits, tau pathology, and clinical symptoms.

Changes of Functional and Directed Resting-State Connectivity Are Associated with Neuronal Oscillations, ApoE Genotype and Amyloid Deposition in Mild Cognitive Impairment

PubMed Central

Michels, Lars; Muthuraman, Muthuraman; Anwar, Abdul R.; Kollias, Spyros; Leh, Sandra E.; Riese, Florian; Unschuld, Paul G.; Siniatchkin, Michael; Gietl, Anton F.; Hock, Christoph

2017-01-01

The assessment of effects associated with cognitive impairment using electroencephalography (EEG) power mapping allows the visualization of frequency-band specific local changes in oscillatory activity. In contrast, measures of coherence and dynamic source synchronization allow for the study of functional and effective connectivity, respectively. Yet, these measures have rarely been assessed in parallel in the context of mild cognitive impairment (MCI) and furthermore it has not been examined if they are related to risk factors of Alzheimer’s disease (AD) such as amyloid deposition and apolipoprotein ε4 (ApoE) allele occurrence. Here, we investigated functional and directed connectivities with Renormalized Partial Directed Coherence (RPDC) in 17 healthy controls (HC) and 17 participants with MCI. Participants underwent ApoE-genotyping and Pittsburgh compound B positron emission tomography (PiB-PET) to assess amyloid deposition. We observed lower spectral source power in MCI in the alpha and beta bands. Coherence was stronger in HC than MCI across different neuronal sources in the delta, theta, alpha, beta and gamma bands. The directed coherence analysis indicated lower information flow between fronto-temporal (including the hippocampus) sources and unidirectional connectivity in MCI. In MCI, alpha and beta RPDC showed an inverse correlation to age and gender; global amyloid deposition was inversely correlated to alpha coherence, RPDC and beta and gamma coherence. Furthermore, the ApoE status was negatively correlated to alpha coherence and RPDC, beta RPDC and gamma coherence. A classification analysis of cognitive state revealed the highest accuracy using EEG power, coherence and RPDC as input. For this small but statistically robust (Bayesian power analyses) sample, our results suggest that resting EEG related functional and directed connectivities are sensitive to the cognitive state and are linked to ApoE and amyloid burden. PMID:29081745

Islet amyloid polypeptide (IAPP):cDNA cloning and identification of an amyloidogenic region associated with the species-specific occurrence of age-related diabetes mellitus.

PubMed

Betsholtz, C; Svensson, V; Rorsman, F; Engström, U; Westermark, G T; Wilander, E; Johnson, K; Westermark, P

1989-08-01

We have cloned and sequenced a human islet amyloid polypeptide (IAPP) cDNA. A secretory 89 amino acid IAPP protein precursor is predicted from which the 37 amino acid IAPP molecule is formed by amino- and carboxyterminal proteolytic processing. The IAPP peptide is 43-46% identical in amino acid sequence to the two members of the calcitonin gene-related peptide (CGRP) family. Evolutionary conserved proteolytic processing sites indicate that similar proteases are involved in the maturation of IAPP and CGRP and that the IAPP amyloid polypeptide is identical to the normal proteolytic product of the IAPP precursor. A synthetic peptide corresponding to a carboxyteminal fragment of human IAPP is shown to spontaneously form amyloid-like fibrils in vitro. Antibodies against this peptide cross-react with IAPP from species that develop amyloid in pancreatic islets in conjunction with age-related diabetes mellitus (human, cat, racoon), but do not cross-react with IAPP from other tested species (mouse, rat, guinea pig, dog). Thus, a species-specific structural motif in the putative amyloidogenic region of IAPP is associated with both amyloid formation and the development of age-related diabetes mellitus. This provides a new molecular clue to the pathogenesis of this disease.

A novel DYRK1A (dual specificity tyrosine phosphorylation-regulated kinase 1A) inhibitor for the treatment of Alzheimer's disease: effect on Tau and amyloid pathologies in vitro.

PubMed

Coutadeur, Séverine; Benyamine, Hélène; Delalonde, Laurence; de Oliveira, Catherine; Leblond, Bertrand; Foucourt, Alicia; Besson, Thierry; Casagrande, Anne-Sophie; Taverne, Thierry; Girard, Angélique; Pando, Matthew P; Désiré, Laurent

2015-05-01

The dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) gene is located within the Down Syndrome (DS) critical region on chromosome 21 and is implicated in the generation of Tau and amyloid pathologies that are associated with the early onset Alzheimer's Disease (AD) observed in DS. DYRK1A is also found associated with neurofibrillary tangles in sporadic AD and phosphorylates key AD players (Tau, amyloid precursor, protein, etc). Thus, DYRK1A may be an important therapeutic target to modify the course of Tau and amyloid beta (Aβ) pathologies. Here, we describe EHT 5372 (methyl 9-(2,4-dichlorophenylamino) thiazolo[5,4-f]quinazoline-2-carbimidate), a novel, highly potent (IC50 = 0.22 nM) DYRK1A inhibitor with a high degree of selectivity over 339 kinases. Models in which inhibition of DYRK1A by siRNA reduced and DYRK1A over-expression induced Tau phosphorylation or Aβ production were used. EHT 5372 inhibits DYRK1A-induced Tau phosphorylation at multiple AD-relevant sites in biochemical and cellular assays. EHT 5372 also normalizes both Aβ-induced Tau phosphorylation and DYRK1A-stimulated Aβ production. DYRK1A is thus as a key element of Aβ-mediated Tau hyperphosphorylation, which links Tau and amyloid pathologies. EHT 5372 and other compounds in its class warrant in vivo investigation as a novel, high-potential therapy for AD and other Tau opathies. Inhibition of the dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) is a new high-potential therapeutic approach for Alzheimer disease. Here we describe EHT 5372, a novel potent and selective DYRK1A inhibitor. EHT 5372 inhibits DYRK1A-induced Tau phosphorylation, Aβ production and Aβ effects on phospho-Tau, including Tau aggregation. © 2014 International Society for Neurochemistry.

Traditional Chinese Nootropic Medicine Radix Polygalae and Its Active Constituent Onjisaponin B Reduce β-Amyloid Production and Improve Cognitive Impairments

PubMed Central

Li, Xiaohang; Cui, Jin; Yu, Yang; Li, Wei; Hou, Yujun; Wang, Xin; Qin, Dapeng; Zhao, Cun; Yao, Xinsheng; Zhao, Jian; Pei, Gang

2016-01-01

Decline of cognitive function is the hallmark of Alzheimer’s disease (AD), regardless of the pathological mechanism. Traditional Chinese medicine has been used to combat cognitive impairments and has been shown to improve learning and memory. Radix Polygalae (RAPO) is a typical and widely used herbal medicine. In this study, we aimed to follow the β-amyloid (Aβ) reduction activity to identify active constituent(s) of RAPO. We found that Onjisaponin B of RAPO functioned as RAPO to suppress Aβ production without direct inhibition of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) and γ-secretase activities. Our mechanistic study showed that Onjisaponin B promoted the degradation of amyloid precursor protein (APP). Further, oral administration of Onjisaponin B ameliorated Aβ pathology and behavioral defects in APP/PS1 mice. Taken together, our results indicate that Onjisaponin B is effective against AD, providing a new therapeutic agent for further drug discovery. PMID:26954017

Traditional Chinese Nootropic Medicine Radix Polygalae and Its Active Constituent Onjisaponin B Reduce β-Amyloid Production and Improve Cognitive Impairments.

PubMed

Li, Xiaohang; Cui, Jin; Yu, Yang; Li, Wei; Hou, Yujun; Wang, Xin; Qin, Dapeng; Zhao, Cun; Yao, Xinsheng; Zhao, Jian; Pei, Gang

2016-01-01

Decline of cognitive function is the hallmark of Alzheimer's disease (AD), regardless of the pathological mechanism. Traditional Chinese medicine has been used to combat cognitive impairments and has been shown to improve learning and memory. Radix Polygalae (RAPO) is a typical and widely used herbal medicine. In this study, we aimed to follow the β-amyloid (Aβ) reduction activity to identify active constituent(s) of RAPO. We found that Onjisaponin B of RAPO functioned as RAPO to suppress Aβ production without direct inhibition of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) and γ-secretase activities. Our mechanistic study showed that Onjisaponin B promoted the degradation of amyloid precursor protein (APP). Further, oral administration of Onjisaponin B ameliorated Aβ pathology and behavioral defects in APP/PS1 mice. Taken together, our results indicate that Onjisaponin B is effective against AD, providing a new therapeutic agent for further drug discovery.

Neurodegeneration in Alzheimer disease: role of amyloid precursor protein and presenilin 1 intracellular signaling.

PubMed

Nizzari, Mario; Thellung, Stefano; Corsaro, Alessandro; Villa, Valentina; Pagano, Aldo; Porcile, Carola; Russo, Claudio; Florio, Tullio

2012-01-01

Alzheimer disease (AD) is a heterogeneous neurodegenerative disorder characterized by (1) progressive loss of synapses and neurons, (2) intracellular neurofibrillary tangles, composed of hyperphosphorylated Tau protein, and (3) amyloid plaques. Genetically, AD is linked to mutations in few proteins amyloid precursor protein (APP) and presenilin 1 and 2 (PS1 and PS2). The molecular mechanisms underlying neurodegeneration in AD as well as the physiological function of APP are not yet known. A recent theory has proposed that APP and PS1 modulate intracellular signals to induce cell-cycle abnormalities responsible for neuronal death and possibly amyloid deposition. This hypothesis is supported by the presence of a complex network of proteins, clearly involved in the regulation of signal transduction mechanisms that interact with both APP and PS1. In this review we discuss the significance of novel finding related to cell-signaling events modulated by APP and PS1 in the development of neurodegeneration.

Silencing of Amyloid Precursor Protein Expression Using a New Engineered Delta Ribozyme

PubMed Central

Ben Aissa, Manel; April, Marie-Claude; Bergeron, Lucien-Junior; Perreault, Jean-Pierre; Levesque, Georges

2012-01-01

Alzheimer's disease (AD) etiological studies suggest that an elevation in amyloid-β peptides (Aβ) level contributes to aggregations of the peptide and subsequent development of the disease. The major constituent of these amyloid peptides is the 1 to 40–42 residue peptide (Aβ 40−42) derived from amyloid protein precursor (APP). Most likely, reducing Aβ levels in the brain may block both its aggregation and neurotoxicity and would be beneficial for patients with AD. Among the several possible ways to lower Aβ accumulation in the cells, we have selectively chosen to target the primary step in the Aβ cascade, namely, to reduce APP gene expression. Toward this end, we engineered specific SOFA-HDV ribozymes, a new generation of catalytic RNA tools, to decrease APP mRNA levels. Additionally, we demonstrated that APP-ribozymes are effective at decreasing APP mRNA and protein levels as well as Aβ levels in neuronal cells. Our results could lay the groundwork for a new protective treatment for AD. PMID:22482079

Tyrosine Binding Protein Sites Regulate the Intracellular Trafficking and Processing of Amyloid Precursor Protein through a Novel Lysosome-Directed Pathway

PubMed Central

Tam, Joshua H. K.; Cobb, M. Rebecca; Seah, Claudia; Pasternak, Stephen H.

2016-01-01

The amyloid hypothesis posits that the production of β-amyloid (Aβ) aggregates leads to neurodegeneration and cognitive decline associated with AD. Aβ is produced by sequential cleavage of the amyloid precursor protein (APP) by β- and γ-secretase. While nascent APP is well known to transit to the endosomal/ lysosomal system via the cell surface, we have recently shown that APP can also traffic to lysosomes intracellularly via its interaction with AP-3. Because AP-3 interacts with cargo protein via interaction with tyrosine motifs, we mutated the three tyrosines motif in the cytoplasmic tail of APP. Here, we show that the YTSI motif interacts with AP-3, and phosphorylation of the serine in this motif disrupts the interaction and decreases APP trafficking to lysosomes. Furthermore, we show that phosphorylation at this motif can decrease the production of neurotoxic Aβ 42. This demonstrates that reducing APP trafficking to lysosomes may be a strategy to reduce Aβ 42 in Alzheimer’s disease. PMID:27776132

Tyrosine Binding Protein Sites Regulate the Intracellular Trafficking and Processing of Amyloid Precursor Protein through a Novel Lysosome-Directed Pathway.

PubMed

Tam, Joshua H K; Cobb, M Rebecca; Seah, Claudia; Pasternak, Stephen H

2016-01-01

The amyloid hypothesis posits that the production of β-amyloid (Aβ) aggregates leads to neurodegeneration and cognitive decline associated with AD. Aβ is produced by sequential cleavage of the amyloid precursor protein (APP) by β- and γ-secretase. While nascent APP is well known to transit to the endosomal/ lysosomal system via the cell surface, we have recently shown that APP can also traffic to lysosomes intracellularly via its interaction with AP-3. Because AP-3 interacts with cargo protein via interaction with tyrosine motifs, we mutated the three tyrosines motif in the cytoplasmic tail of APP. Here, we show that the YTSI motif interacts with AP-3, and phosphorylation of the serine in this motif disrupts the interaction and decreases APP trafficking to lysosomes. Furthermore, we show that phosphorylation at this motif can decrease the production of neurotoxic Aβ 42. This demonstrates that reducing APP trafficking to lysosomes may be a strategy to reduce Aβ 42 in Alzheimer's disease.

Human apoB overexpression and a high-cholesterol diet differently modify the brain APP metabolism in the transgenic mouse model of atherosclerosis.

PubMed

Bjelik, Annamária; Bereczki, Erika; Gonda, Szilvia; Juhász, Anna; Rimanóczy, Agnes; Zana, Marianna; Csont, Tamás; Pákáski, Magdolna; Boda, Krisztina; Ferdinandy, Péter; Dux, László; Janka, Zoltán; Sántha, Miklós; Kálmán, János

2006-09-01

Epidemiological and biochemical data suggest a link between the cholesterol metabolism, the amyloid precursor protein (APP) processing and the increased cerebral beta-amyloid (Abeta) deposition in Alzheimer's disease (AD). The individual and combined effects of a high-cholesterol (HC) diet and the overexpression of the human apoB-100 gene were therefore examined on the cerebral expression and processing of APP in homozygous apoB-100 transgenic mice [Tg (apoB(+/+))], a validated model of atherosclerosis. When fed with 2% cholesterol for 17 weeks, only the wild-type mice exhibited significantly increased APP695 (123%) and APP770 (138%) mRNA levels in the cortex. The HC diet-induced hypercholesterolemia significantly increased the APP isoform levels in the membrane-bound fraction, not only in the wild-type animals (114%), but also in the Tg apoB(+/+) group (171%). The overexpression of human apoB-100 gene by the liver alone reduced the brain APP isoform levels in the membrane-bound fraction (78%), whereas the levels were increased by the combined effect of HC and the overexpression of the human apoB-100 gene (134%). The protein kinase C and beta-secretase protein levels were not altered by the individual or combined effects of these two factors. Our data indicate that the two atherogenic factors, the HC diet and the overexpression of the human apoB-100 gene by the liver, could exert different effects on the processing and expression of APP in the mice brain.

Direct exposure of guinea pig CNS to human luteinizing hormone increases cerebrospinal fluid and cerebral beta amyloid levels.

PubMed

Wahjoepramono, Eka J; Wijaya, Linda K; Taddei, Kevin; Bates, Kristyn A; Howard, Matthew; Martins, Georgia; deRuyck, Karl; Matthews, Paul M; Verdile, Giuseppe; Martins, Ralph N

2011-01-01

Luteinizing hormone (LH) has been shown to alter the metabolism of beta amyloid (Aβ), a key protein in Alzheimer's disease (AD) pathogenesis. While LH and components required for LH receptor signalling are present in the brain, their role in the CNS remains unclear. In vitro, LH has been shown to facilitate neurosteroid production and alter Aβ metabolism. However, whether LH can directly modulate cerebral Aβ levels in vivo has not previously been studied. In this study, we investigated the effect of chronic administration of LH to the guinea pig CNS on cerebral Aβ levels. Gonadectomised male animals were administered, via cortical placement, either placebo or LH slow-release pellets. At 14 and 28 days after treatment, animals were sacrificed. Brain, plasma and CSF were collected and Aβ levels measured via ELISA. Levels of the Aβ precursor protein (APP) and the neurosteroidogenic enzyme cytochrome P450 side-chain cleavage enzyme (P450scc) were also assayed. An increase in CSF Aβ40 levels was observed 28 days following treatment. These CSF data also reflected changes in Aβ40 levels observed in brain homogenates. No change was observed in plasma Aβ40 levels but APP and its C-terminal fragments (APP-CTF) were significantly increased in response to LH exposure. Protein expression of P450scc was increased after 28 days of LH exposure, suggesting activation of the LH receptor. These data indicate that direct exposure of guinea pig CNS to LH results in altered brain Aβ levels, perhaps due to altered APP expression/metabolism. Copyright © 2011 S. Karger AG, Basel.

Iron overload accelerates neuronal amyloid-β production and cognitive impairment in transgenic mice model of Alzheimer's disease.

PubMed

Becerril-Ortega, Javier; Bordji, Karim; Fréret, Thomas; Rush, Travis; Buisson, Alain

2014-10-01

Iron dyshomeostasis is proving increasingly likely to be involved in the pathology of Alzheimer's disease (AD); yet, its mechanism is not well understood. Here, we investigated the AD-related mechanism(s) of iron-sulfate exposure in vitro and in vivo, using cultured primary cortical neurons and APP/PS1 AD-model mice, respectively. In both systems, we observed iron-induced disruptions of amyloid precursor protein (APP) processing, neuronal signaling, and cognitive behavior. Iron overload increased production of amyloidogenic KPI-APP and amyloid beta. Further, this APP misprocessing was blocked by MK-801 in vitro, suggesting the effect was N-methyl-D-aspartate receptor (NMDAR) dependent. Calcium imaging confirmed that 24 hours iron exposure led to disrupted synaptic signaling by augmenting GluN2B-containing NMDAR expression-GluN2B messenger RNA and protein levels were increased and promoting excessing extrasynaptic NMDAR signaling. The disrupted GluN2B expression was concurrent with diminished expression of the splicing factors, sc35 and hnRNPA1. In APP/PS1 mice, chronic iron treatment led to hastened progression of cognitive impairment with the novel object recognition discrimination index, revealing a deficit at the age of 4 months, concomitant with augmented GluN2B expression. Together, these data suggest iron-induced APP misprocessing and hastened cognitive decline occur through inordinate extrasynaptic NMDAR activation. Copyright © 2014 Elsevier Inc. All rights reserved.

Substance P and Alzheimer's Disease: Emerging Novel Roles.

PubMed

Severini, Cinzia; Petrella, Carla; Calissano, Pietro

2016-01-01

Alzheimer`s disease (AD) is an irreversible neurodegenerative disease, clinically characterized by progressive impairments of memory and cognition. The hallmarks of AD are neurofibrillary tangles, mainly constituted by altered phosphorylated and truncated portions of tau protein, and the abnormal extracellular deposition of neurotoxic beta amyloid (Aβ) peptides, derived from the proteolytic processing of amyloid precursor protein (APP). According to the amyloid hypothesis, Aβ is considered to be linked to the selective neurodegeneration seen in AD. Recent evidence points to an increase in voltage-gated potassium (Kv) channel currents in the etiology of Aβ-induced neuronal apoptosis. Substance P (SP) is an 11-aa neuropeptide, member of the tachykinin family, broadly distributed in the Central Nervous System where it acts as a neurotransmitter, neuromodulator, and neurotrophic factor. This peptide may play an important role in neurodegenerative disorders, since reduced levels of SP were found in brain areas and spinal fluid of AD patients. In addition to its neuroprotective properties, it was recently demonstrated that SP is able to stimulate non-amyloidogenic APP processing, thereby reducing the possibility of generation of toxic Aβ peptides in the brain. Recent studies, using in vitro and in vivo models, have also shown that the neuroprotective role of SP against Aβ could be related to its ability of modulate Kv channel currents. In this review, we briefly summarized the current findings on the neurotrophic and neuroprotective effects of SP, providing information about its anti-amyloidogenic and anti-Aβ toxicity role.

Treatment strategies in Alzheimer's disease: a review with focus on selenium supplementation.

PubMed

Aaseth, Jan; Alexander, Jan; Bjørklund, Geir; Hestad, Knut; Dusek, Petr; Roos, Per M; Alehagen, Urban

2016-10-01

Alzheimer's disease (AD) is a neurodegenerative disorder presenting one of the biggest healthcare challenges in developed countries. No effective treatment exists. In recent years the main focus of AD research has been on the amyloid hypothesis, which postulates that extracellular precipitates of beta amyloid (Aβ) derived from amyloid precursor protein (APP) are responsible for the cognitive impairment seen in AD. Treatment strategies have been to reduce Aβ production through inhibition of enzymes responsible for its formation, or to promote resolution of existing cerebral Aβ plaques. However, these approaches have failed to demonstrate significant cognitive improvements. Intracellular rather than extracellular events may be fundamental in AD pathogenesis. Selenate is a potent inhibitor of tau hyperphosphorylation, a critical step in the formation of neurofibrillary tangles. Some selenium (Se) compounds e.g. selenoprotein P also appear to protect APP against excessive copper and iron deposition. Selenoproteins show anti-inflammatory properties, and protect microtubules in the neuronal cytoskeleton. Optimal function of these selenoenzymes requires higher Se intake than what is common in Europe and also higher intake than traditionally recommended. Supplementary treatment with N-acetylcysteine increases levels of the antioxidative cofactor glutathione and can mediate adjuvant protection. The present review discusses the role of Se in AD treatment and suggests strategies for AD prevention by optimizing selenium intake, in accordance with the metal dysregulation hypothesis. This includes in particular secondary prevention by selenium supplementation to elderly with mild cognitive impairment.

Somatostatin: a novel substrate and a modulator of insulin-degrading enzyme activity.

PubMed

Ciaccio, Chiara; Tundo, Grazia R; Grasso, Giuseppe; Spoto, Giuseppe; Marasco, Daniela; Ruvo, Menotti; Gioia, Magda; Rizzarelli, Enrico; Coletta, Massimo

2009-02-06

Insulin-degrading enzyme (IDE) is an interesting pharmacological target for Alzheimer's disease (AD), since it hydrolyzes beta-amyloid, producing non-neurotoxic fragments. It has also been shown that the somatostatin level reduction is a pathological feature of AD and that it regulates the neprilysin activity toward beta-amyloid. In this work, we report for the first time that IDE is able to hydrolyze somatostatin [k(cat) (s(-1))=0.38 (+/-0.05); K(m) (M)=7.5 (+/-0.9) x 10(-6)] at the Phe6-Phe7 amino acid bond. On the other hand, somatostatin modulates IDE activity, enhancing the enzymatic cleavage of a novel fluorogenic beta-amyloid through a decrease of the K(m) toward this substrate, which corresponds to the 10-25 amino acid sequence of the Abeta(1-40). Circular dichroism spectroscopy and surface plasmon resonance imaging experiments show that somatostatin binding to IDE brings about a concentration-dependent structural change of the secondary and tertiary structure(s) of the enzyme, revealing two possible binding sites. The higher affinity binding site disappears upon inactivation of IDE by ethylenediaminetetraacetic acid, which chelates the catalytic Zn(2+) ion. As a whole, these features suggest that the modulatory effect is due to an allosteric mechanism: somatostatin binding to the active site of one IDE subunit (where somatostatin is cleaved) induces an enhancement of IDE proteolytic activity toward fluorogenic beta-amyloid by another subunit. Therefore, this investigation on IDE-somatostatin interaction contributes to a more exhaustive knowledge about the functional and structural aspects of IDE and its pathophysiological implications in the amyloid deposition and somatostatin homeostasis in the brain.

Nicergoline stimulates protein kinase C mediated alpha-secretase processing of the amyloid precursor protein in cultured human neuroblastoma SH-SY5Y cells.

PubMed

Cedazo-Minguez, A; Bonecchi, L; Winblad, B; Post, C; Wong, E H; Cowburn, R F; Benatti, L

1999-10-01

We investigated the ability of the antidementia agents, nicergoline, aniracetam and hydergine to stimulate PKC mediated alpha-secretase amyloid precursor protein (APP) processing in cultured human neuroblastoma SH-SY5Y cells. Western immunoblotting of cell conditioned media using the Mabs 22C11 and 6E10 revealed the presence of 2 bands with molecular mass of 90 and 120 kDa, corresponding to possible alternatively glycosylated forms of secreted APP (APPs). Short-term (30 min and 2 h) treatment of cells with nicergoline gave an increased intensity of both bands, compared to non-treated cells. Maximal nicergoline effects, of the order of 150-200% over basal APPs release, were seen at concentrations between 1 and 10 microM. Under the same condition, 1 microM PdBu, used as a positive control, gave 500-1000% increases of basal APPs release. In contrast, aniracetam and hydergine, did not show any effect on APPs secretion. 2 h treatment with nicergoline had no effect on cellular full-length APP levels, as determined by immunoblotting of cell extracts with 22C11 and CT15 antibodies. Immunoblotting with PKC isoform specific antibodies of soluble and membrane fractions prepared from 2 h treated cells, showed that nicergoline (50 microM) and PdBu (1 microM) both induced translocation of PKC alpha, gamma and epsilon, but not PKC beta. The involvement of PKC in mediating nicergoline stimulated APPs release was also studied using specific inhibitors. 1 microM calphostin C, a broad range PKC inhibitor, significantly reduced both PdBu (1 microM) and nicergoline (10 microM) induced APPs release. In contrast, Go6976 (1 microM), a selective PKC alpha and beta1 inhibitor, as well as the cAMP-dependent protein kinase inhibitor, H89 (1 microM) were without effect. These results indicate that nicergoline can modulate alpha-secretase APP processing by a PKC dependent mechanism that is likely to involve the gamma and epsilon isoforms of this enzyme.

The Amyloid Precursor Protein is rapidly transported from the Golgi apparatus to the lysosome and where it is processed into beta-amyloid

PubMed Central

2014-01-01

Background Alzheimer’s disease (AD) is characterized by cerebral deposition of β-amyloid peptide (Aβ). Aβ is produced by sequential cleavage of the Amyloid Precursor Protein (APP) by β- and γ-secretases. Many studies have demonstrated that the internalization of APP from the cell surface can regulate Aβ production, although the exact organelle in which Aβ is produced remains contentious. A number of recent studies suggest that intracellular trafficking also plays a role in regulating Aβ production, but these pathways are relatively under-studied. The goal of this study was to elucidate the intracellular trafficking of APP, and to examine the site of intracellular APP processing. Results We have tagged APP on its C-terminal cytoplasmic tail with photoactivatable Green Fluorescent Protein (paGFP). By photoactivating APP-paGFP in the Golgi, using the Golgi marker Galactosyltranferase fused to Cyan Fluorescent Protein (GalT-CFP) as a target, we are able to follow a population of nascent APP molecules from the Golgi to downstream compartments identified with compartment markers tagged with red fluorescent protein (mRFP or mCherry); including rab5 (early endosomes) rab9 (late endosomes) and LAMP1 (lysosomes). Because γ-cleavage of APP releases the cytoplasmic tail of APP including the photoactivated GFP, resulting in loss of fluorescence, we are able to visualize the cleavage of APP in these compartments. Using APP-paGFP, we show that APP is rapidly trafficked from the Golgi apparatus to the lysosome; where it is rapidly cleared. Chloroquine and the highly selective γ-secretase inhibitor, L685, 458, cause the accumulation of APP in lysosomes implying that APP is being cleaved by secretases in the lysosome. The Swedish mutation dramatically increases the rate of lysosomal APP processing, which is also inhibited by chloroquine and L685, 458. By knocking down adaptor protein 3 (AP-3; a heterotetrameric protein complex required for trafficking many proteins to the lysosome) using siRNA, we are able to reduce this lysosomal transport. Blocking lysosomal transport of APP reduces Aβ production by more than a third. Conclusion These data suggests that AP-3 mediates rapid delivery of APP to lysosomes, and that the lysosome is a likely site of Aβ production. PMID:25085554

A Native to Amyloidogenic Transition Regulated by a Backbone Trigger

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eakin,C.; Berman, A.; Miranker, A.

2006-01-01

Many polypeptides can self-associate into linear, aggregated assemblies termed amyloid fibers. High-resolution structural insights into the mechanism of fibrillogenesis are elusive owing to the transient and mixed oligomeric nature of assembly intermediates. Here, we report the conformational changes that initiate fiber formation by beta-2-microglobulin (beta2m) in dialysis-related amyloidosis. Access of beta2m to amyloidogenic conformations is catalyzed by selective binding of divalent cations. The chemical basis of this process was determined to be backbone isomerization of a conserved proline. On the basis of this finding, we designed a beta2m variant that closely adopts this intermediate state. The variant has kinetic, thermodynamicmore » and catalytic properties consistent with its being a fibrillogenic intermediate of wild-type beta2m. Furthermore, it is stable and folded, enabling us to unambiguously determine the initiating conformational changes for amyloid assembly at atomic resolution.« less

Amyloid-beta aggregation: selective inhibition of aggregation in mixtures of amyloid with different chain lengths.

PubMed Central

Snyder, S W; Ladror, U S; Wade, W S; Wang, G T; Barrett, L W; Matayoshi, E D; Huffaker, H J; Krafft, G A; Holzman, T F

1994-01-01

One of the clinical manifestations of Alzheimer's disease is the deposition of the 39-43 residue amyloid-beta (A beta) peptide in aggregated fibrils in senile plaques. Characterization of the aggregation behavior of A beta is one of the critical issues in understanding the role of A beta in the disease process. Using solution hydrodynamics, A beta was observed to form three types of species in phosphate-buffered saline: insoluble aggregates with sedimentation coefficients of approximately 50,000 S and molecular masses of approximately 10(9) Da, "soluble aggregates" with sedimentation coefficients of approximately 30 S and masses of approximately 10(6) Da, and monomer. When starting from monomer, the aggregation kinetics of A beta 1-40 (A beta 40) and A beta 1-42 (A beta 42), alone and in combination, reveal large differences in the tendency of these peptides to aggregate as a function of pH and other solution conditions. At pH 4.1 and 7.0-7.4, aggregation is significantly slower than at pH 5 and 6. Under all conditions, aggregation of the longer A beta 42 was more rapid than A beta 40. Oxidation of Met-35 to the sulfoxide in A beta 40 enhances the aggregation rate over that of the nonoxidized peptide. Aggregation was found to be dependent upon temperature and to be strongly dependent on peptide concentration and ionic strength, indicating that aggregation is driven by a hydrophobic effect. When A beta 40 and A beta 42 are mixed together, A beta 40 retards the aggregation of A beta 42 in a concentration-dependent manner. Shorter fragments have a decreasing ability to interfere with A beta 42 aggregation. Conversely, the rate of aggregation of A beta 40 can be significantly enhanced by seeding slow aggregating solutions with preformed aggregates of A beta 42. Taken together, the inhibition of A beta 42 aggregation by A beta 40, the seeding of A beta 40 aggregation by A beta 42 aggregates, and the chemical oxidation of A beta 40 suggest that the relative abundance and rates of production of different-length A beta and its exposure to radical damage may be factors in the accumulation of A beta in plaques in vivo. Images FIGURE 6 PMID:7811936

A physical chemical approach to understanding cellular dysfunction in type II diabetes

NASA Astrophysics Data System (ADS)

Miranker, Andrew

2013-03-01

The conversion of soluble protein into b-sheet rich amyloid fibers is the hallmark of a number of serious diseases. Precursors for many of these systems (e.g. Ab from Alzheimer's disease) reside in close association with a biological membranes. Membrane bilayers are reported to accelerate the rate of amyloid assembly. Furthermore, membrane permeabilization by amyloidogenic peptides can lead to toxicity. Given the b-sheet rich nature of mature amyloid, it is seemingly paradoxical that many precursors are either intrinsically b-helical, or transiently adopt an a-helical state upon association with membrane. We have investigated these phenomena in islet amyloid polypeptide (IAPP). IAPP is a 37-residue peptide hormone which forms amyloid fibers in individuals with type II diabetes. We report here the discovery of an oligomeric species that arises through stochastic nucleation on membranes, and results in disruption of the lipid bilayer. These species are stable, result in all-or-none leakage, and represent a definable protein/lipid phase that equilibrates over time. To characterize the reaction pathway of assembly, we apply an experimental design that includes ensemble and single particle evaluations in vitro and correlate these with quantitative measures of cellular toxicity.

Fluid Mechanics of the Vascular Basement Membrane in the Brain

NASA Astrophysics Data System (ADS)

Coloma, Mikhail; Hui, Jonathan; Chiarot, Paul; Huang, Peter; Carare, Roxana; McLeod, Kenneth; Schaffer, David

2013-11-01

Beta-amyloid is a normal product of brain metabolic function and is found within the interstitial fluid of the brain. Failure of the clearance of beta-amyloid from the aging brain leads to its accumulation within the walls of arteries and to Alzheimer's disease. The vascular basement membrane (VBM) within the walls of cerebral arteries surrounds the spirally arranged smooth muscle cells and represents an essential pathway for removal of beta-amyloid from the brain. This process fails with the stiffening of arterial walls associated with aging. In this study we hypothesize that the deformation of the VBM associated with arterial pulsations drives the interstitial fluid to drain in the direction opposite of the arterial blood flow. This hypothesis is theoretically investigated by modeling the VBM as a thin, coaxial, fluid-filled porous medium surrounding a periodically deforming cylindrical tube. Flow and boundary conditions required to achieve such a backward clearance are derived through a control volume analysis of mass, momentum, and energy.

Massive accumulation of luminal protease-deficient axonal lysosomes at Alzheimer's disease amyloid plaques.

PubMed

Gowrishankar, Swetha; Yuan, Peng; Wu, Yumei; Schrag, Matthew; Paradise, Summer; Grutzendler, Jaime; De Camilli, Pietro; Ferguson, Shawn M

2015-07-14

Through a comprehensive analysis of organellar markers in mouse models of Alzheimer's disease, we document a massive accumulation of lysosome-like organelles at amyloid plaques and establish that the majority of these organelles reside within swollen axons that contact the amyloid deposits. This close spatial relationship between axonal lysosome accumulation and extracellular amyloid aggregates was observed from the earliest stages of β-amyloid deposition. Notably, we discovered that lysosomes that accumulate in such axons are lacking in multiple soluble luminal proteases and thus are predicted to be unable to efficiently degrade proteinaceous cargos. Of relevance to Alzheimer's disease, β-secretase (BACE1), the protein that initiates amyloidogenic processing of the amyloid precursor protein and which is a substrate for these proteases, builds up at these sites. Furthermore, through a comparison between the axonal lysosome accumulations at amyloid plaques and neuronal lysosomes of the wild-type brain, we identified a similar, naturally occurring population of lysosome-like organelles in neuronal processes that is also defined by its low luminal protease content. In conjunction with emerging evidence that the lysosomal maturation of endosomes and autophagosomes is coupled to their retrograde transport, our results suggest that extracellular β-amyloid deposits cause a local impairment in the retrograde axonal transport of lysosome precursors, leading to their accumulation and a blockade in their further maturation. This study both advances understanding of Alzheimer's disease brain pathology and provides new insights into the subcellular organization of neuronal lysosomes that may have broader relevance to other neurodegenerative diseases with a lysosomal component to their pathology.

Massive accumulation of luminal protease-deficient axonal lysosomes at Alzheimer’s disease amyloid plaques

PubMed Central

Gowrishankar, Swetha; Yuan, Peng; Wu, Yumei; Schrag, Matthew; Paradise, Summer; Grutzendler, Jaime; De Camilli, Pietro; Ferguson, Shawn M.

2015-01-01

Through a comprehensive analysis of organellar markers in mouse models of Alzheimer’s disease, we document a massive accumulation of lysosome-like organelles at amyloid plaques and establish that the majority of these organelles reside within swollen axons that contact the amyloid deposits. This close spatial relationship between axonal lysosome accumulation and extracellular amyloid aggregates was observed from the earliest stages of β-amyloid deposition. Notably, we discovered that lysosomes that accumulate in such axons are lacking in multiple soluble luminal proteases and thus are predicted to be unable to efficiently degrade proteinaceous cargos. Of relevance to Alzheimer’s disease, β-secretase (BACE1), the protein that initiates amyloidogenic processing of the amyloid precursor protein and which is a substrate for these proteases, builds up at these sites. Furthermore, through a comparison between the axonal lysosome accumulations at amyloid plaques and neuronal lysosomes of the wild-type brain, we identified a similar, naturally occurring population of lysosome-like organelles in neuronal processes that is also defined by its low luminal protease content. In conjunction with emerging evidence that the lysosomal maturation of endosomes and autophagosomes is coupled to their retrograde transport, our results suggest that extracellular β-amyloid deposits cause a local impairment in the retrograde axonal transport of lysosome precursors, leading to their accumulation and a blockade in their further maturation. This study both advances understanding of Alzheimer’s disease brain pathology and provides new insights into the subcellular organization of neuronal lysosomes that may have broader relevance to other neurodegenerative diseases with a lysosomal component to their pathology. PMID:26124111

Structural and Functional Properties of Peptides Based on the N-terminus of HIV-1 gp41 and the C-terminus of the Amyloid-Beta Protein

PubMed Central

Gordon, Larry M.; Nisthal, Alex; Lee, Andy B.; Eskandari, Sepehr; Ruchala, Piotr; Jung, Chun-Ling; Waring, Alan J.; Mobley, Patrick W.

2008-01-01

Given their high alanine and glycine levels, plaque formation, α-helix to β-sheet interconversion and fusogenicity, FP (i.e., the N-terminal fusion peptide of HIV-1 gp41; 23 residues) and amyloids were proposed as belonging to the same protein superfamily. Here, we further test whether FP may exhibit ‘amyloid-like’ characteristics, by contrasting its structural and functional properties with those of Aβ(26–42), a 17-residue peptide from the C-terminus of the amyloid-beta protein responsible for Alzheimer’s. FTIR spectroscopy, electron microscopy, light scattering and predicted amyloid structure aggregation (PASTA) indicated that aqueous FP and Aβ(26–42) formed similar networked β-sheet fibrils, although the FP fibril interactions were weaker. FP and Aβ(26–42) both lysed and aggregated human erythrocytes, with the hemolysis-onsets correlated with the conversion of α-helix to β-sheet for each peptide in liposomes. Congo red (CR), a marker of amyloid plaques in situ, similarly inhibited either FP- or Aβ(26–42)-induced hemolysis, and surface plasmon resonance indicated that this may be due to direct CR-peptide binding. These findings suggest that membrane-bound β-sheets of FP may contribute to the cytopathicity of HIV in vivo through an amyloid-type mechanism, and support the classification of HIV-1 FP as an ‘amyloid homolog’ (or ‘amylog’). PMID:18515070

Intracellular amyloid beta expression leads to dysregulation of the mitogen-activated protein kinase and bone morphogenetic protein-2 signaling axis

PubMed Central

Cruz, Eric; Kumar, Sushil; Yuan, Li; Arikkath, Jyothi

2018-01-01

Alzheimer’s disease (AD) is a neurodegenerative syndrome classically depicted by the parenchymal accumulation of extracellular amyloid beta plaques. However, recent findings suggest intraneuronal amyloid beta (iAβ1–42) accumulation precedes extracellular deposition. Furthermore, the pathologic increase in iAβ1–42 has been implicated in dysregulation of cellular mechanisms critically important in axonal transport. Owing to neuronal cell polarity, retrograde and anterograde axonal transport are essential trafficking mechanism necessary to convey membrane bound neurotransmitters, neurotrophins, and endosomes between soma and synaptic interfaces. Although iAβ1–42 disruption of axonal transport has been implicated in dysregulation of neuronal synaptic transmission, the role of iAβ1–42 and its influence on signal transduction involving the mitogen-activated protein kinase (MAPK) and morphogenetic signaling axis are unknown. Our biochemical characterization of intracellular amyloid beta accumulation on MAPK and morphogenetic signaling have revealed increased iAβ1–42 expression leads to significant reduction in ERK 1/2 phosphorylation and increased bone morphogenetic protein 2 dependent Smad 1/5/8 phosphorylation. Furthermore, rescue of iAβ1–42 mediated attenuation of MAPK signaling can be accomplished with the small molecule PLX4032 as a downstream enhancer of the MAPK pathway. Consequently, our observations regarding the dysregulation of these gatekeepers of neuronal viability may have important implications in understanding the iAβ1–42 mediated effects observed in AD. PMID:29470488

Anti-acetylcholinesterase and Antioxidant Activities of Inhaled Juniper Oil on Amyloid Beta (1-42)-Induced Oxidative Stress in the Rat Hippocampus.

PubMed

Cioanca, Oana; Hancianu, Monica; Mihasan, Marius; Hritcu, Lucian

2015-05-01

Juniper volatile oil is extracted from Juniperus communis L., of the Cupressaceae family, also known as common juniper. Also, in aromatherapy the juniper volatile oil is used against anxiety, nervous tension and stress-related conditions. In the present study, we identified the effects of the juniper volatile oil on amyloid beta (1-42)-induced oxidative stress in the rat hippocampus. Rats received a single intracerebroventricular injection of amyloid beta (1-42) (400 pmol/rat) and then were exposed to juniper volatile oil (200 μl, either 1 or 3 %) for controlled 60 min period, daily, for 21 continuous days. Also, the antioxidant activity in the hippocampus was assessed using superoxide dismutase, glutathione peroxidase and catalase specific activities, the total content of the reduced glutathione, protein carbonyl and malondialdehyde levels. Additionally, the acetylcholinesterase activity in the hippocampus was assessed. The amyloid beta (1-42)-treated rats exhibited the following: increase of the acetylcholinesterase, superoxide dismutase and catalase specific activities, decrease of glutathione peroxidase specific activity and the total content of the reduced glutathione along with an elevation of malondialdehyde and protein carbonyl levels. Inhalation of the juniper volatile oil significantly decreases the acetylcholinesterase activity and exhibited antioxidant potential. These findings suggest that the juniper volatile oil may be a potential candidate for the development of therapeutic agents to manage oxidative stress associated with Alzheimer's disease through decreasing the activity of acetylcholinesterase and anti-oxidative mechanism.

Alzheimer's Disease: APP, Gamma Secretase, APOE, CLU, CR1, PICALM, ABCA7, BIN1, CD2AP, CD33, EPHA1, and MS4A2, and Their Relationships with Herpes Simplex, C. Pneumoniae, Other Suspect Pathogens, and the Immune System

PubMed Central

Carter, Chris

2011-01-01

Alzheimer's disease susceptibility genes, APP and gamma-secretase, are involved in the herpes simplex life cycle, and that of other suspect pathogens (C. pneumoniae, H. pylori, C. neoformans, B. burgdorferri, P. gingivalis) or immune defence. Such pathogens promote beta-amyloid deposition and tau phosphorylation and may thus be causative agents, whose effects are conditioned by genes. The antimicrobial effects of beta-amyloid, the localisation of APP/gamma-secretase in immunocompetent dendritic cells, and gamma secretase cleavage of numerous pathogen receptors suggest that this network is concerned with pathogen disposal, effects which may be abrogated by the presence of beta-amyloid autoantibodies in the elderly. These autoantibodies, as well as those to nerve growth factor and tau, also observed in Alzheimer's disease, may well be antibodies to pathogens, due to homology between human autoantigens and pathogen proteins. NGF or tau antibodies promote beta-amyloid deposition, neurofibrillary tangles, or cholinergic neuronal loss, and, with other autoantibodies, such as anti-ATPase, are potential agents of destruction, whose formation is dictated by sequence homology between pathogen and human proteins, and thus by pathogen strain and human genes. Pathogen elimination in the ageing population and removal of culpable autoantibodies might reduce the incidence and offer hope for a cure in this affliction. PMID:22254144

Levels of amyloid-beta-42 and CSF pressure are directly related in patients with Alzheimer's disease.

PubMed

Schirinzi, Tommaso; Di Lazzaro, Giulia; Sancesario, Giulia Maria; Colona, Vito Luigi; Scaricamazza, Eugenia; Mercuri, Nicola Biagio; Martorana, Alessandro; Sancesario, Giuseppe

2017-12-01

Experimental data suggest that the cerebrospinal fluid (CSF) dynamic is involved in the clearance of beta-amyloid, a key event in the pathogenesis of Alzheimer's disease (AD). At this regard no evidence still exists in vivo. In this study we explored the relationships between CSF pressure and AD pathology, as measured with CSF core biomarkers. We enrolled 16 patients with probable AD and 21 controls, collecting demographics, clinical data, CSF opening pressure and CSF levels of beta-amyloid-42 fragment (Aβ42), total-tau (t-tau), phosphorylated-tau-181 (p-tau), albumin and albumin ratio. Differences between the groups were calculated with non-parametric tests, while correlations among all parameters were separately calculated with Spearman's test in each group. The groups significantly differed in biomarkers' concentration with lower Aβ42, and higher t-tau and p-tau in AD patients. Moreover, CSF pressure was significantly lower in AD group (11.0 ± 2.8 vs. 13.3 ± 3.0 mmHg, p < 0.05) and directly correlated with Aβ42 levels (R = 0.512; p < 0.05), but not with other biomarkers or parameters. No significant correlations emerged for biomarkers in control group. AD patients exhibit low CSF pressure whose values are directly and selectively related to CSF Aβ42 levels. This interesting correlation may confirm in vivo the association between CSF dynamic and beta-amyloid metabolism occurring in AD.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Cong; Sawaya, Michael R.; Eisenberg, David

{beta}{sub 2}-microglobulin ({beta}{sub 2}-m) is the light chain of the type I major histocompatibility complex. It deposits as amyloid fibrils within joints during long-term hemodialysis treatment. Despite the devastating effects of dialysis-related amyloidosis, full understanding of how fibrils form from soluble {beta}{sub 2}-m remains elusive. Here we show that {beta}{sub 2}-m can oligomerize and fibrillize via three-dimensional domain swapping. Isolating a covalently bound, domain-swapped dimer from {beta}{sub 2}-m oligomers on the pathway to fibrils, we were able to determine its crystal structure. The hinge loop that connects the swapped domain to the core domain includes the fibrillizing segment LSFSKD, whosemore » atomic structure we also determined. The LSFSKD structure reveals a class 5 steric zipper, akin to other amyloid spines. The structures of the dimer and the zipper spine fit well into an atomic model for this fibrillar form of {beta}{sub 2}-m, which assembles slowly under physiological conditions.« less

Beta-structures in fibrous proteins.

PubMed

Kajava, Andrey V; Squire, John M; Parry, David A D

2006-01-01

The beta-form of protein folding, one of the earliest protein structures to be defined, was originally observed in studies of silks. It was then seen in early studies of synthetic polypeptides and, of course, is now known to be present in a variety of guises as an essential component of globular protein structures. However, in the last decade or so it has become clear that the beta-conformation of chains is present not only in many of the amyloid structures associated with, for example, Alzheimer's Disease, but also in the prion structures associated with the spongiform encephalopathies. Furthermore, X-ray crystallography studies have revealed the high incidence of the beta-fibrous proteins among virulence factors of pathogenic bacteria and viruses. Here we describe the basic forms of the beta-fold, summarize the many different new forms of beta-structural fibrous arrangements that have been discovered, and review advances in structural studies of amyloid and prion fibrils. These and other issues are described in detail in later chapters.

HIV-1 stimulates nuclear entry of amyloid beta via dynamin dependent EEA1 and TGF-β/Smad signaling

DOE Office of Scientific and Technical Information (OSTI.GOV)

András, Ibolya E., E-mail: iandras@med.miami; Toborek, Michal, E-mail: mtoborek@med.miami.edu

Clinical evidence indicates increased amyloid deposition in HIV-1-infected brains, which contributes to neurocognitive dysfunction in infected patients. Here we show that HIV-1 exposure stimulates amyloid beta (Aβ) nuclear entry in human brain endothelial cells (HBMEC), the main component of the blood–brain barrier (BBB). Treatment with HIV-1 and/or Aβ resulted in concurrent increase in early endosomal antigen-1 (EEA1), Smad, and phosphorylated Smad (pSmad) in nuclear fraction of HBMEC. A series of inhibition and silencing studies indicated that Smad and EEA1 closely interact by influencing their own nuclear entry; the effect that was attenuated by dynasore, a blocker of GTP-ase activity ofmore » dynamin. Importantly, inhibition of dynamin, EEA1, or TGF-β/Smad effectively attenuated HIV-1-induced Aβ accumulation in the nuclei of HBMEC. The present study indicates that nuclear uptake of Aβ involves the dynamin-dependent EEA1 and TGF-β/Smad signaling pathways. These results identify potential novel targets to protect against HIV-1-associated dysregulation of amyloid processes at the BBB level. - Highlights: • HIV-1 induces nuclear accumulation of amyloid beta (Aβ) in brain endothelial cells. • EEA-1 and TGF-Β/Smad act in concert to regulate nuclear entry of Aβ. • Dynamin appropriates the EEA-1 and TGF-Β/Smad signaling. • Dynamin serves as a master regulator of HIV-1-induced nuclear accumulation of Aβ.« less

Hereditary cerebral hemorrhage with amyloidosis in patients of Dutch origin is related to Alzheimer disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Duinen, S.G.; Castano, E.M.; Prelli, F.

1987-08-01

Hereditary cerebral hemorrhage with amyloidosis in Dutch patients is an autosomal dominant form of vascular amyloidosis restricted to the leptomeninges and cerebral cortex. Clinically the disease is characterized by cerebral hemorrhages leading to an early death. Immunohistochemical studies of five patients revealed that the vascular amyloid deposits reacted intensely with an antiserum raised against a synthetic peptide homologous to the Alzheimer disease-related ..beta..-protein. Silver stain-positive, senile plaque-like structures were also labeled by the antiserum, yet these lesions lacked the dense amyloid cores present in typical plaques of Alzheimer disease. No neurofibrillary tangles were present. Amyloid fibrils were purified from themore » leptomeningeal vessels of one patient who clinically had no signs of dementia. The protein had a molecular weight of approx. 4000 and its partial amino acid sequence to position 21 showed homology to the ..beta..-protein of Alzheimer disease and Down syndrome. These results suggest that hereditary cerebral hemorrhage with amyloidosis of Dutch origin is pathogenetically related to Alzheimer disease and support the concept that the initial amyloid deposition in this disorder occurs in the vessel walls before damaging the brain parenchyma. Thus, deposition of ..beta..-protein in brain tissue seems to be related to a spectrum of diseases involving vascular syndromes, progressive dementia, or both.« less

Are Aβ and Its Derivatives Causative Agents or Innocent Bystanders in AD?

PubMed Central

Robakis, Nikolaos K.

2010-01-01

Alzheimer's disease (AD) is characterized by neurodegeneration in neocortical regions of the brain. Currently, Aβ-based theories, including amyloid depositions and soluble Aβ, form the basis of most therapeutic approaches to AD. It remains unclear, however, whether Aβ and its derivatives are the primary causative agents of neuronal loss in AD. Reported studies show no significant correlations between brain amyloid depositions and either degree of dementia or loss of neurons, and brain amyloid loads similar to AD are often found in normal individuals. Furthermore, behavioral abnormalities in animal models overexpressing amyloid precursor protein seem independent of amyloid depositions. Soluble Aβ theories propose toxic Aβ42 or its oligomers as the agents that promote cell death in AD. Aβ peptides, however, are normal components of human serum and CSF, and it is unclear under what conditions these peptides become toxic. Presently, there is little evidence of disease-associated abnormalities in soluble Aβ and no toxic oligomers specific to AD have been found. That familial AD mutations of amyloid precursor protein, PS1 and PS2 promote neurodegeneration suggests the biological functions of these proteins play critical roles in neuronal survival. Evidence shows that the PS/γ-secretase system promotes production of peptides involved in cell surface-to-nucleus signaling and gene expression, providing support for the hypothesis that familial AD mutations may contribute to neurodegeneration by inhibiting PS-dependent signaling pathways. PMID:20160455

Porphyrin Cyclodextrin Conjugates Modulate Amyloid Beta Peptide Aggregation and Cytotoxicity.

PubMed

Oliveri, Valentina; Zimbone, Stefania; Giuffrida, Maria Laura; Bellia, Francesco; Tomasello, Marianna Flora; Vecchio, Graziella

2018-04-25

Although fibrillar amyloid beta peptide (Aβ) aggregates are one of the major hallmarks of Alzheimer's disease, increasing evidence suggests that soluble Aβ oligomers are the primary toxic species. Targeting the oligomeric species could represent an effective strategy to interfere with Aβ toxicity. In this work, the biological properties of 5[4-(6-O-β-cyclodextrin)-phenyl],10,15,20-tri(4-hydroxyphenyl)-porphyrin and its zinc complex were tested, as new molecules that interact with Aβ and effectively prevent its cytotoxicity. We found that these systems can cross the cell membrane to deliver Aβ intracellularly and promote its clearance. Our results provide evidence for the use of cyclodextrin-porphyrin derivatives as a promising strategy to target amyloid aggregation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antagonist of peroxisome proliferator-activated receptor {gamma} induces cerebellar amyloid-{beta} levels and motor dysfunction in APP/PS1 transgenic mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Jing; Sun, Bing; Chen, Kui

2009-07-03

Recent evidences show that peroxisome proliferator-activated receptor {gamma} (PPAR{gamma}) is involved in the modulation of the amyloid-{beta} (A{beta}) cascade causing Alzheimer's disease (AD) and treatment with PPAR{gamma} agonists protects against AD pathology. However, the function of PPAR{gamma} steady-state activity in A{beta} cascade and AD pathology remains unclear. In this study, an antagonist of PPAR{gamma}, GW9662, was injected into the fourth ventricle of APP/PS1 transgenic mice to inhibit PPAR{gamma} activity in cerebellum. The results show that inhibition of PPAR{gamma} significantly induced A{beta} levels in cerebellum and caused cerebellar motor dysfunction in APP/PS1 transgenic mice. Moreover, GW9662 treatment markedly decreased the cerebellarmore » levels of insulin-degrading enzyme (IDE), which is responsible for the cellular degradation of A{beta}. Since cerebellum is spared from significant A{beta} accumulation and neurotoxicity in AD patients and animal models, these findings suggest a crucial role of PPAR{gamma} steady-state activity in protection of cerebellum against AD pathology.« less

Etiology of sporadic Alzheimer's disease: somatostatin, neprilysin, and amyloid beta peptide.

PubMed

Hama, E; Saido, T C

2005-01-01

We recently demonstrated that amyloid beta peptide (Abeta) is catabolized primarily by a neutral endopeptidase, neprilysin, in the brain and that a neuropeptide, somatostatin (SST), regulates brain Abeta level via modulation of neprilysin activity. Because SST expression in the brain declines upon aging in various mammals including rodents, apes and humans, we hypothesize that the aging-dependent reduction of SST triggers accumulation of Abeta in the brain by suppressing neprilysin action. This hypothesis accounts for the fact that aging is the predominant risk factor for Sporadic Alzheimer's disease.

Catalytic antibodies to amyloid beta peptide in defense against Alzheimer disease.

PubMed

Taguchi, Hiroaki; Planque, Stephanie; Nishiyama, Yasuhiro; Szabo, Paul; Weksler, Marc E; Friedland, Robert P; Paul, Sudhir

2008-05-01

Immunoglobulins (Igs) that bind amyloid beta peptide (Abeta) are under clinical trials for immunotherapy of Alzheimer disease (AD). We have identified IgMs and recombinant Ig fragments that hydrolyze Abeta. Hydrolysis of peripheral Abeta by the IgMs may induce increased Abeta release from the brain. The catalytic IgMs are increased in AD patients, presumably reflecting a protective autoimmune response. Reduced Abeta aggregation and neurotoxicity attributable to the catalytic function were evident. These findings provide a foundation for development of catalytic Igs for AD immunotherapy.

Consequences of inhibiting amyloid precursor protein processing enzymes on synaptic function and plasticity.

PubMed

Wang, Hui; Megill, Andrea; He, Kaiwen; Kirkwood, Alfredo; Lee, Hey-Kyoung

2012-01-01

Alzheimer's disease (AD) is a neurodegenerative disease, one of whose major pathological hallmarks is the accumulation of amyloid plaques comprised of aggregated β-amyloid (Aβ) peptides. It is now recognized that soluble Aβ oligomers may lead to synaptic dysfunctions early in AD pathology preceding plaque deposition. Aβ is produced by a sequential cleavage of amyloid precursor protein (APP) by the activity of β- and γ-secretases, which have been identified as major candidate therapeutic targets of AD. This paper focuses on how Aβ alters synaptic function and the functional consequences of inhibiting the activity of the two secretases responsible for Aβ generation. Abnormalities in synaptic function resulting from the absence or inhibition of the Aβ-producing enzymes suggest that Aβ itself may have normal physiological functions which are disrupted by abnormal accumulation of Aβ during AD pathology. This interpretation suggests that AD therapeutics targeting the β- and γ-secretases should be developed to restore normal levels of Aβ or combined with measures to circumvent the associated synaptic dysfunction(s) in order to have minimal impact on normal synaptic function.

Postischemic dementia with Alzheimer phenotype: selectively vulnerable versus resistant areas of the brain and neurodegeneration versus β-amyloid peptide.

PubMed

Pluta, Ryszard; Jabłoński, Mirosław; Czuczwar, Stanisław J

2012-01-01

The road to clarity for postischemic dementia mechanisms has been one fraught with a wide range of complications and numerous revisions with a lack of a final solution. Importantly, brain ischemia is a leading cause of death and cognitive impairment worldwide. However, the mechanisms of progressive cognitive decline following brain ischemia are not yet certain. Data from animal models and clinical pioneering studies of brain ischemia have demonstrated an increase in expression and processing of amyloid precursor protein to a neurotoxin oligomeric β-amyloid peptide. Functional and memory brain restoration after ischemic brain injury is delayed and incomplete due to a lesion related increase in the amount of the neurotoxin amyloid protein. Moreover, ischemic injury is strongly accelerated by aging, too. In this review, we will present our current thinking about biogenesis of amyloid from the amyloid precursor protein in ischemic brain injury, and how this factor presents etiological, therapeutic and diagnostic targets that are now under consideration. Progressive injury of the ischemic brain parenchyma may be caused not only by degeneration of selectively vulnerable neurons destroyed during ischemia but also by acute and chronic damage of resistant areas of the brain and progressive damage in the blood-brain barrier. We propose that in postischemic dementia an initial ischemic injury precedes the cerebrovascular and brain parenchyma accumulation of Alzheimer disease related neurotoxin β-amyloid peptide, which in turn amplifies the neurovascular dysfunction triggering focal ischemic episodes as a vicious cycle preceding final neurodegenerative pathology. Persistent ischemic blood-brain barrier insufficiency with accumulation of neurotoxin β-amyloid protein in the brain tissue, especially in extracellular perivascular space and blood-brain barrier microvessels, may gradually, over a lifetime, progress to brain atrophy and to full-blown ischemic dementia with Alzheimer phenotype.

The intact Kunitz domain protects the amyloid precursor protein from being processed by matriptase-2.

PubMed

Beckmann, Anna-Madeleine; Glebov, Konstantin; Walter, Jochen; Merkel, Olaf; Mangold, Martin; Schmidt, Frederike; Becker-Pauly, Christoph; Gütschow, Michael; Stirnberg, Marit

2016-08-01

Proteolytic processing of the amyloid precursor protein (APP) leads to amyloid-β (Aβ) peptides. So far, the mechanism of APP processing is insufficiently characterized at the molecular level. Whereas the knowledge of Aβ generation by several proteases has been expanded, the contribution of the Kunitz-type protease inhibitor domain (KPI) present in two major APP isoforms to the complex proteolytic processing of APP is poorly understood. In this study, we have identified KPI-containing APP as a very potent, slow-binding inhibitor for the membrane-bound proteolytic regulator of iron homeostasis matriptase-2 by forming stable complexes with its target protease in HEK cells. Inhibition and complex formation depend on the intact KPI domain. By inhibiting matriptase-2, KPI-containing APP is protected from matriptase-2-mediated proteolysis within the Aβ region, thus preventing the generation of N-terminally truncated Aβ.

Amyloid Precursor Protein Processing and Alzheimer’s Disease

PubMed Central

O’Brien, Richard J.; Wong, Philip C.

2011-01-01

Alzheimer’s disease (AD), the leading cause of dementia worldwide, is characterized by the accumulation of the β-amyloid peptide (Aβ) within the brain along with hyperphosphorylated and cleaved forms of the microtubule-associated protein tau. Genetic, biochemical, and behavioral research suggest that physiologic generation of the neurotoxic Aβ peptide from sequential amyloid precursor protein (APP) proteolysis is the crucial step in the development of AD. APP is a single-pass transmembrane protein expressed at high levels in the brain and metabolized in a rapid and highly complex fashion by a series of sequential proteases, including the intramembranous γ-secretase complex, which also process other key regulatory molecules. Why Aβ accumulates in the brains of elderly individuals is unclear but could relate to changes in APP metabolism or Aβ elimination. Lessons learned from biochemical and genetic studies of APP processing will be crucial to the development of therapeutic targets to treat AD. PMID:21456963

Trehalose Alters Subcellular Trafficking and the Metabolism of the Alzheimer-associated Amyloid Precursor Protein*

PubMed Central

Tien, Nguyen T.; Karaca, Ilker; Tamboli, Irfan Y.

2016-01-01

The disaccharide trehalose is commonly considered to stimulate autophagy. Cell treatment with trehalose could decrease cytosolic aggregates of potentially pathogenic proteins, including mutant huntingtin, α-synuclein, and phosphorylated tau that are associated with neurodegenerative diseases. Here, we demonstrate that trehalose also alters the metabolism of the Alzheimer disease-related amyloid precursor protein (APP). Cell treatment with trehalose decreased the degradation of full-length APP and its C-terminal fragments. Trehalose also reduced the secretion of the amyloid-β peptide. Biochemical and cell biological experiments revealed that trehalose alters the subcellular distribution and decreases the degradation of APP C-terminal fragments in endolysosomal compartments. Trehalose also led to strong accumulation of the autophagic marker proteins LC3-II and p62, and decreased the proteolytic activation of the lysosomal hydrolase cathepsin D. The combined data indicate that trehalose decreases the lysosomal metabolism of APP by altering its endocytic vesicular transport. PMID:26957541

A canine model of Alzheimer's disease generated by overexpressing a mutated human amyloid precursor protein.

PubMed

Lee, Geun-Shik; Jeong, Yeon Woo; Kim, Joung Joo; Park, Sun Woo; Ko, Kyeong Hee; Kang, Mina; Kim, Yu Kyung; Jung, Eui-Man; Moon, Changjong; Hyun, Sang Hwan; Hwang, Kyu-Chan; Kim, Nam-Hyung; Shin, Taeyoung; Jeung, Eui-Bae; Hwang, Woo Suk

2014-04-01

Canines are considered the most authentic model for studying multifactorial human diseases, as these animals typically share a common environment with man. Somatic cell nuclear transfer (SCNT) technology along with genetic engineering of nuclear donor cells provides a unique opportunity for examining human diseases using transgenic canines. In the present study, we generated transgenic canines that overexpressed the human amyloid precursor protein (APP) gene containing well-characterized familial Alzheimer's disease (AD) mutations. We successfully obtained five out of six live puppies by SCNT. This was confirmed by observing the expression of green fluorescence protein in the body as a visual transgenic marker and the overexpression of the mutated APP gene in the brain. The transgenic canines developed AD-like symptoms, such as enlarged ventricles, an atrophied hippocampus, and β-amyloid plaques in the brain. Thus, the transgenic canines we created can serve as a novel animal model for studying human AD.

The insulin and islet amyloid polypeptide genes contain similar cell-specific promoter elements that bind identical beta-cell nuclear complexes.

PubMed Central

German, M S; Moss, L G; Wang, J; Rutter, W J

1992-01-01

The pancreatic beta cell makes several unique gene products, including insulin, islet amyloid polypeptide (IAPP), and beta-cell-specific glucokinase (beta GK). The functions of isolated portions of the insulin, IAPP, and beta GK promoters were studied by using transient expression and DNA binding assays. A short portion (-247 to -197 bp) of the rat insulin I gene, the FF minienhancer, contains three interacting transcriptional regulatory elements. The FF minienhancer binds at least two nuclear complexes with limited tissue distribution. Sequences similar to that of the FF minienhancer are present in the 5' flanking DNA of the human IAPP and rat beta GK genes and also the rat insulin II and mouse insulin I and II genes. Similar minienhancer constructs from the insulin and IAPP genes function as cell-specific transcriptional regulatory elements and compete for binding of the same nuclear factors, while the beta GK construct competes for protein binding but functions poorly as a minienhancer. These observations suggest that the patterns of expression of the beta-cell-specific genes result in part from sharing the same transcriptional regulators. Images PMID:1549125

Premature hippocampus-dependent memory decline in middle-aged females of a genetic rat model of depression.

PubMed

Lim, Patrick H; Wert, Stephanie L; Tunc-Ozcan, Elif; Marr, Robert; Ferreira, Adriana; Redei, Eva E

2018-02-25

Aging and major depressive disorder are risk factors for dementia, including Alzheimer's Disease (AD), but the mechanism(s) linking depression and dementia are not known. Both AD and depression show greater prevalence in women. We began to investigate this connection using females of the genetic model of depression, the inbred Wistar Kyoto More Immobile (WMI) rat. These rats consistently display depression-like behavior compared to the genetically close control, the Wistar Kyoto Less Immobile (WLI) strain. Hippocampus-dependent contextual fear memory did not differ between young WLI and WMI females, but, by middle-age, female WMIs showed memory deficits compared to same age WLIs. This deficit, measured as duration of freezing in the fear provoking-context was not related to activity differences between the strains prior to fear conditioning. Hippocampal expression of AD-related genes, such as amyloid precursor protein, amyloid beta 42, beta secretase, synucleins, total and dephosphorylated tau, and synaptophysin, did not differ between WLIs and WMIs in either age group. However, hippocampal transcript levels of catalase (Cat) and hippocampal and frontal cortex expression of insulin-like growth factor 2 (Igf2) and Igf2 receptor (Igf2r) paralleled fear memory differences between middle-aged WLIs and WMIs. This data suggests that chronic depression-like behavior that is present in this genetic model is a risk factor for early spatial memory decline in females. The molecular mechanisms of this early memory decline likely involve the interaction of aging processes with the genetic components responsible for the depression-like behavior in this model. Copyright © 2018 Elsevier B.V. All rights reserved.

Reduced Aβ secretion by human neurons under conditions of strongly increased BACE activity.

PubMed

Scholz, Diana; Chernyshova, Yana; Ückert, Anna-Katharina; Leist, Marcel

2018-05-27

The initial step in the amyloidogenic cascade of amyloid precursor protein (APP) processing is catalyzed by beta-site APP-cleaving enzyme (BACE), and this protease has increased activities in affected areas of Alzheimer's disease brains. We hypothesized that altered APP processing, due to augmented BACE activity, would affect the actions of direct and indirect BACE inhibitors. We therefore compared postmitotic human neurons (LUHMES) with their BACE-overexpressing counterparts (BLUHMES). Although β-cleavage of APP was strongly increased in BLUHMES, they produced less full-length and truncated amyloid beta (Aβ) than LUHMES. Moreover, low concentrations of BACE inhibitors decreased cellular BACE activity as expected, but increased Aβ 1-40 levels. Several other approaches to modulate BACE activity led to a similar, apparently paradoxical, behavior. For instance, reduction of intracellular acidification by bepridil increased Aβ production in parallel with decreased BACE activity. In contrast to BLUHMES, the respective control cells (LUHMES or BLUHMES with catalytically inactive BACE) showed conventional pharmacological responses. Other non-canonical neurochemical responses (so-called 'rebound effects') are well-documented for the Aβ pathway, especially for γ-secretase: a partial block of its activity leads to an increased Aβ secretion by some cell types. We therefore compared LUHMES and BLUHMES regarding rebound effects of γ-secretase inhibitors and found an Aβ rise in LUHMES but not in BLUHMES. Thus, different cellular factors are responsible for the γ-secretase- vs. BACE-related Aβ rebound. We conclude that increased BACE activity, possibly accompanied by an altered cellular localization pattern, can dramatically influence Aβ generation in human neurons and affect pharmacological responses to secretase inhibitors. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Pregnenolone protects the PC-12 cell line against amyloid beta peptide toxicity but its sulfate ester does not.

PubMed

Akan, Pinar; Kizildag, Servet; Ormen, Murat; Genc, Sermin; Oktem, Mehmet Ali; Fadiloglu, Meral

2009-01-15

Pregnenolone (P), the main precursor of the steroids, and its sulfate ester, pregnenolone sulfate (PS), are the major neurosteroids produced in the neural tissue. Many neuroendocrinological studies stressed the neuroprotective role of neurosteroids although it has been suggested that the inhibition of P and PS synthesis can delay neuronal cell death. The potential roles of P and PS in vital neuronal functions and in amyloid beta peptide (Abeta) toxicity are not clearly identified. This work aims to investigate the effects of P and PS on cell viability and Abeta peptide toxicity in a concentration and exposure time-dependent manner in rat PC-12 cells. The cells were treated with 20muM Abeta peptide 25-35 and variable concentrations of P and PS ranging from 0.5muM to 100muM. To examine the effects of steroid treatment on Abeta peptide toxicity, 0.5muM (low) and 50muM (high) neurosteroids were used. The cell viability and lactate dehydrogenase release of cells were evaluated after 24, 48 and 72h. Morphological changes of cells were also examined. The treatment with higher than 1muM concentrations of P and PS significantly decreased the cell viability comparing to untreated cells. At lower concentrations, P and PS had no toxic actions until 72h. The Abeta treatment resulted in a significant decrease in cell viability comparing to untreated cells. P showed a dose-dependent protective effect against Abeta peptide in PC-12 cells. But its sulfate ester did not have the same effect on Abeta peptide toxicity, even it significantly decreased cell viability in Abeta-treated cells. Consequently, the discrepant effects of P and PS on Abeta peptide toxicity may provide insight on the pathogenesis of Alzheimer's disease.

Site-activated chelators derived from anti-Parkinson drug rasagiline as a potential safer and more effective approach to the treatment of Alzheimer's disease.

PubMed

Zheng, Hailin; Fridkin, Mati; Youdim, Moussa B H

2010-12-01

chelators can modulate β-amyloid accumulation, protect against tau hyperphosphorylation, and block metal-related oxidative stress, and thereby hold considerable promise as effective anti-AD drugs. At present, a growing interest is focusing on increasing the efficacy and targeting of chelators through drug design. To this end, we have developed a new class of multifunctional prochelators from three FDA- approved drugs rasagiline, rivastigmine, and donepezil or tacrine. HLA20 A was designed by merging the important pharmacophores of rasagiline, rivastigmine, and donepezil into our newly developed multifunctional chelator HLA20. M30D was constructed using the key pharmacophoric moieties from rasagiline, rivastigmine, and tacrine. Experiments showed that both compounds possess potent anti-acetylcholinesterase (AChE) activity in vitro with weak inhibition of butyrylcholinesterase (BuChE), and without significant metal-binding activity. M30D was found also to be a highly potent MAO A inhibitor with moderate inhibition of MAO B in vitro. Both HLA20 and M30D can be activated by inhibition of AChE to release active chelators HLA20 and M30, respectively. HLA20 and M30 have been shown to be able to modulate amyloid precursor protein regulation and beta-amyloid reduction, suppress oxidative stress, and passivate excess metal ions (Fe, Cu, and Zn). Compared with the activated chelator HLA20 or M30, both HLA20A and M30D exhibited lower cytotoxicity in SH-SY5Y neuroblastoma cells, substantiating the prochelator strategy for minimizing toxicity associated with poor targeted chelators.

Age-dependent postoperative cognitive impairment and Alzheimer-related neuropathology in mice

NASA Astrophysics Data System (ADS)

Xu, Zhipeng; Dong, Yuanlin; Wang, Hui; Culley, Deborah J.; Marcantonio, Edward R.; Crosby, Gregory; Tanzi, Rudolph E.; Zhang, Yiying; Xie, Zhongcong

2014-01-01

Post-operative cognitive dysfunction (POCD) is associated with increased cost of care, morbidity, and mortality. However, its pathogenesis remains largely to be determined. Specifically, it is unknown why elderly patients are more likely to develop POCD and whether POCD is dependent on general anesthesia. We therefore set out to investigate the effects of peripheral surgery on the cognition and Alzheimer-related neuropathology in mice with different ages. Abdominal surgery under local anesthesia was established in the mice. The surgery induced post-operative elevation in brain β-amyloid (Aβ) levels and cognitive impairment in the 18 month-old wild-type and 9 month-old Alzheimer's disease transgenic mice, but not the 9 month-old wild-type mice. The Aβ accumulation likely resulted from elevation of beta-site amyloid precursor protein cleaving enzyme and phosphorylated eukaryotic translation initiation factor 2α. γ-Secretase inhibitor compound E ameliorated the surgery-induced brain Aβ accumulation and cognitive impairment in the 18 month-old mice. These data suggested that the peripheral surgery was able to induce cognitive impairment independent of general anesthesia, and that the combination of peripheral surgery with aging- or Alzheimer gene mutation-associated Aβ accumulation was needed for the POCD to occur. These findings would likely promote more research to investigate the pathogenesis of POCD.

Effects of short-term Western diet on cerebral oxidative stress and diabetes related factors in APP x PS1 knock-in mice.

PubMed

Studzinski, Christa M; Li, Feng; Bruce-Keller, Annadora J; Fernandez-Kim, Sun Ok; Zhang, Le; Weidner, Adam M; Markesbery, William R; Murphy, M Paul; Keller, Jeffrey N

2009-02-01

A chronic high fat Western diet (WD) promotes a variety of morbidity factors although experimental evidence for short-term WD mediating brain dysfunction remains to be elucidated. The amyloid precursor protein and presenilin-1 (APP x PS1) knock-in mouse model has been demonstrated to recapitulate some key features of Alzheimer's disease pathology, including amyloid-beta (Abeta) pathogenesis. In this study, we placed 1-month-old APP x PS1 mice and non-transgenic littermates on a WD for 4 weeks. The WD resulted in a significant elevation in protein oxidation and lipid peroxidation in the brain of APP x PS1 mice relative to non-transgenic littermates, which occurred in the absence of increased Abeta levels. Altered adipokine levels were also observed in APP x PS1 mice placed on a short-term WD, relative to non-transgenic littermates. Taken together, these data indicate that short-term WD is sufficient to selectively promote cerebral oxidative stress and metabolic disturbances in APP x PS1 knock-in mice, with increased oxidative stress preceding alterations in Abeta. These data have important implications for understanding how WD may potentially contribute to brain dysfunction and the development of neurodegenerative disorders such as Alzheimer's disease.

Par3 and aPKC regulate BACE1 endosome-to-TGN trafficking through PACS1.

PubMed

Sun, Miao; Zhang, Huaye

2017-12-01

The cleavage of amyloid precursor protein (APP) by β-site APP cleaving enzyme 1 (BACE1) is the rate-limiting step in beta amyloid generation during Alzheimer's disease (AD) pathogenesis. In AD brains, BACE1 is abnormally accumulated in endocytic compartments, where the acidic pH is optimal for its activity. However, mechanisms regulating the endosome-to-trans-Golgi network (TGN) retrieval of BACE1 remain unclear. Here, we show that partitioning defective 3 (Par3) facilitates BACE1 retrograde trafficking from endosomes to the TGN. Par3 functions through aPKC-mediated phosphorylation of BACE1 on Ser498, which in turn promotes the interaction between BACE1 and phosphofurin acidic cluster sorting protein 1 and facilitates the retrograde trafficking of BACE1 to the TGN. In human AD brains, there is a significant decrease in Ser498 phosphorylation of BACE1 suggesting that defective phosphorylation-dependent retrograde transport of BACE1 is important in AD pathogenesis. Together, our studies provide mechanistic insight into a novel role for Par3 and aPKC in regulating the retrograde endosome-to-TGN trafficking of BACE1 and shed light on the mechanisms of AD pathogenesis. Copyright © 2017 Elsevier Inc. All rights reserved.

The structure and function of Alzheimer's gamma secretase enzyme complex.

PubMed

Krishnaswamy, Sudarsan; Verdile, Giuseppe; Groth, David; Kanyenda, Limbikani; Martins, Ralph N

2009-01-01

The production and accumulation of the beta amyloid protein (Abeta) is a key event in the cascade of oxidative and inflammatory processes that characterizes Alzheimer's disease (AD). A multi-subunit enzyme complex, referred to as gamma (gamma) secretase, plays a pivotal role in the generation of Abeta from its parent molecule, the amyloid precursor protein (APP). Four core components (presenilin, nicastrin, aph-1, and pen-2) interact in a high-molecular-weight complex to perform intramembrane proteolysis on a number of membrane-bound proteins, including APP and Notch. Inhibitors and modulators of this enzyme have been assessed for their therapeutic benefit in AD. However, although these agents reduce Abeta levels, the majority have been shown to have severe side effects in pre-clinical animal studies, most likely due to the enzymes role in processing other proteins involved in normal cellular function. Current research is directed at understanding this enzyme and, in particular, at elucidating the roles that each of the core proteins plays in its function. In addition, a number of interacting proteins that are not components of gamma-secretase also appear to play important roles in modulating enzyme activity. This review will discuss the structural and functional complexity of the gamma-secretase enzyme and the effects of inhibiting its activity.

Neurotrophic and Neurotoxic Effects of Amyloid |beta Protein: Reversal by Tachykinin Neuropeptides

NASA Astrophysics Data System (ADS)

Yankner, Bruce A.; Duffy, Lawrence K.; Kirschner, Daniel A.

1990-10-01

The amyloid β protein is deposited in the brains of patients with Alzheimer's disease but its pathogenic role is unknown. In culture, the amyloid β protein was neurotrophic to undifferentiated hippocampal neurons at low concentrations and neurotoxic to mature neurons at higher concentrations. In differentiated neurons, amyloid β protein caused dendritic and axonal retraction followed by neuronal death. A portion of the amyloid β protein (amino acids 25 to 35) mediated both the trophic and toxic effects and was homologous to the tachykinin neuropeptide family. The effects of the amyloid β protein were mimicked by tachykinin antagonists and completely reversed by specific tachykinin agonists. Thus, the amyloid β protein could function as a neurotrophic factor for differentiating neurons, but at high concentrations in mature neurons, as in Alzheimer's disease, could cause neuronal degeneration.

Inflammation in Alzheimer's disease: amyloid-beta oligomers trigger innate immunity defence via pattern recognition receptors.

PubMed

Salminen, Antero; Ojala, Johanna; Kauppinen, Anu; Kaarniranta, Kai; Suuronen, Tiina

2009-02-01

The inflammatory process has a fundamental role in the pathogenesis of Alzheimer's disease (AD). Recent studies indicate that inflammation is not merely a bystander in neurodegeneration but a powerful pathogenetic force in the disease process. Increased production of amyloid-beta peptide species can activate the innate immunity system via pattern recognition receptors (PRRs) and evoke Alzheimer's pathology. We will focus on the role of innate immunity system of brain in the initiation and the propagation of inflammatory process in AD. We examine here in detail the significance of amyloid-beta oligomers and fibrils as danger-associated molecular patterns (DAMPs) in the activation of a wide array of PRRs in glial cells and neurons, such as Toll-like, NOD-like, formyl peptide, RAGE and scavenger receptors along with complement and pentraxin systems. We also characterize the signaling pathways triggered by different PRRs in evoking inflammatory responses. In addition, we will discuss whether AD pathology could be the outcome of chronic activation of the innate immunity defence in the brain of AD patients.

Beta-amyloid immunotherapy prevents synaptic degeneration in a mouse model of Alzheimer's disease.

PubMed

Buttini, Manuel; Masliah, Eliezer; Barbour, Robin; Grajeda, Henry; Motter, Ruth; Johnson-Wood, Kelly; Khan, Karen; Seubert, Peter; Freedman, Stephen; Schenk, Dale; Games, Dora

2005-10-05

Alzheimer's disease neuropathology is characterized by key features that include the deposition of the amyloid beta peptide (Abeta) into plaques, the formation of neurofibrillary tangles, and the loss of neurons and synapses in specific brain regions. The loss of synapses, and particularly the associated presynaptic vesicle protein synaptophysin in the hippocampus and association cortices, has been widely reported to be one of the most robust correlates of Alzheimer's disease-associated cognitive decline. The beta-amyloid hypothesis supports the idea that Abeta is the cause of these pathologies. However, the hypothesis is still controversial, in part because the direct role of Abeta in synaptic degeneration awaits confirmation. In this study, we show that Abeta reduction by active or passive Abeta immunization protects against the progressive loss of synaptophysin in the hippocampal molecular layer and frontal neocortex of a transgenic mouse model of Alzheimer's disease. These results, substantiated by quantitative electron microscopic analysis of synaptic densities, strongly support a direct causative role of Abeta in the synaptic degeneration seen in Alzheimer's disease and strengthen the potential of Abeta immunotherapy as a treatment approach for this disease.

(I) Pharmacological profiling of a novel modulator of the α7 nicotinic receptor: Blockade of a toxic acetylcholinesterase-derived peptide increased in Alzheimer brains.

PubMed

Garcia-Ratés, Sara; Morrill, Paul; Tu, Henry; Pottiez, Gwenael; Badin, Antoine-Scott; Tormo-Garcia, Cristina; Heffner, Catherine; Coen, Clive W; Greenfield, Susan A

2016-06-01

The primary cause of Alzheimer's disease is unlikely to be the much studied markers amyloid beta or tau. Their widespread distribution throughout the brain does not account for the specific identity and deep subcortical location of the primarily vulnerable neurons. Moreover an unusual and intriguing feature of these neurons is that, despite their diverse transmitters, they all contain acetylcholinesterase. Here we show for the first time that (1) a peptide derived from acetylcholinesterase, with independent trophic functions that turn toxic in maturity, is significantly raised in the Alzheimer midbrain and cerebrospinal fluid; (2) a synthetic version of this peptide enhances calcium influx and eventual production of amyloid beta and tau phosphorylation via an allosteric site on the α7 nicotinic receptor; (3) a synthetic cyclic version of this peptide is neuroprotective against the toxicity not only of its linear counterpart but also of amyloid beta, thereby opening up the prospect of a novel therapeutic approach. Copyright © 2016 Elsevier Ltd. All rights reserved.

PB1-F2 influenza A virus protein adopts a beta-sheet conformation and forms amyloid fibers in membrane environments.

PubMed

Chevalier, Christophe; Al Bazzal, Ali; Vidic, Jasmina; Février, Vincent; Bourdieu, Christiane; Bouguyon, Edwige; Le Goffic, Ronan; Vautherot, Jean-François; Bernard, Julie; Moudjou, Mohammed; Noinville, Sylvie; Chich, Jean-François; Da Costa, Bruno; Rezaei, Human; Delmas, Bernard

2010-04-23

The influenza A virus PB1-F2 protein, encoded by an alternative reading frame in the PB1 polymerase gene, displays a high sequence polymorphism and is reported to contribute to viral pathogenesis in a sequence-specific manner. To gain insights into the functions of PB1-F2, the molecular structure of several PB1-F2 variants produced in Escherichia coli was investigated in different environments. Circular dichroism spectroscopy shows that all variants have a random coil secondary structure in aqueous solution. When incubated in trifluoroethanol polar solvent, all PB1-F2 variants adopt an alpha-helix-rich structure, whereas incubated in acetonitrile, a solvent of medium polarity mimicking the membrane environment, they display beta-sheet secondary structures. Incubated with asolectin liposomes and SDS micelles, PB1-F2 variants also acquire a beta-sheet structure. Dynamic light scattering revealed that the presence of beta-sheets is correlated with an oligomerization/aggregation of PB1-F2. Electron microscopy showed that PB1-F2 forms amorphous aggregates in acetonitrile. In contrast, at low concentrations of SDS, PB1-F2 variants exhibited various abilities to form fibers that were evidenced as amyloid fibers in a thioflavin T assay. Using a recombinant virus and its PB1-F2 knock-out mutant, we show that PB1-F2 also forms amyloid structures in infected cells. Functional membrane permeabilization assays revealed that the PB1-F2 variants can perforate membranes at nanomolar concentrations but with activities found to be sequence-dependent and not obviously correlated with their differential ability to form amyloid fibers. All of these observations suggest that PB1-F2 could be involved in physiological processes through different pathways, permeabilization of cellular membranes, and amyloid fiber formation.

Toward a reliable distinction between patients with mild cognitive impairment and Alzheimer-type dementia versus major depression.

PubMed

Post, Anke; Ackl, Nibal; Rücker, Monika; Schreiber, Yvonne; Binder, Elisabeth B; Ising, Marcus; Sonntag, Annette; Holsboer, Florian; Almeida, Osborne F X

2006-05-01

Cerebrospinal fluid (CSF) levels of soluble amyloid precursor protein (sAPP) and its alpha-secreted form (alpha-sAPP) were investigated as a means to distinguish between individuals with mild cognitive impairment (MCI) and Alzheimer-type dementia (DAT) and those with major depressive episode (MDE) showing secondary memory deficits. Twenty-seven patients with MCI, 32 with probable DAT, and 24 with MDE attending a memory clinic were studied. Cerebrospinal fluid levels of sAPP/amyloid precursor-like protein 2 (APLP2) and alpha-sAPP were detected by Western blotting. Patients with MDE had the highest CSF levels of total sAPP/APLP2 as compared with MCI and DAT patients (p < .001); sAPP/APLP2 levels were higher in MCI than in DAT subjects. Whereas alpha-sAPP levels did not differ between the MCI and DAT groups, median levels of this peptide were significantly lower in MCI and DAT versus MDE patients. Soluble amyloid precursor protein/APLP2 and alpha-sAPP concentrations in CSF can differentiate between DAT and MCI versus MDE, facilitating early ameliorative interventions and appropriate treatment regimens.

Redundancy and divergence in the amyloid precursor protein family.

PubMed

Shariati, S Ali M; De Strooper, Bart

2013-06-27

Gene duplication provides genetic material required for functional diversification. An interesting example is the amyloid precursor protein (APP) protein family. The APP gene family has experienced both expansion and contraction during evolution. The three mammalian members have been studied quite extensively in combined knock out models. The underlying assumption is that APP, amyloid precursor like protein 1 and 2 (APLP1, APLP2) are functionally redundant. This assumption is primarily supported by the similarities in biochemical processing of APP and APLPs and on the fact that the different APP genes appear to genetically interact at the level of the phenotype in combined knockout mice. However, unique features in each member of the APP family possibly contribute to specification of their function. In the current review, we discuss the evolution and the biology of the APP protein family with special attention to the distinct properties of each homologue. We propose that the functions of APP, APLP1 and APLP2 have diverged after duplication to contribute distinctly to different neuronal events. Our analysis reveals that APLP2 is significantly diverged from APP and APLP1. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Copper(II) ions and the Alzheimer's amyloid-β peptide: Affinity and stoichiometry of binding

NASA Astrophysics Data System (ADS)

Tõugu, Vello; Friedemann, Merlin; Tiiman, Ann; Palumaa, Peep

2014-10-01

Deposition of amyloid beta (Aβ) peptides into amyloid plaques is the hallmark of Alzheimer's disease. According to the amyloid cascade hypothesis this deposition is an early event and primary cause of the disease, however, the mechanisms that cause this deposition remain elusive. An increasing amount of evidence shows that the interactions of biometals can contribute to the fibrillization and amyloid formation by amyloidogenic peptides. From different anions the copper ions deserve the most attention since it can contribute not only toamyloid formation but also to its toxicity due to the generation of ROS. In this thesis we focus on the affinity and stoichiometry of copper(II) binding to the Aβ molecule.

Diet rich in date palm fruits improves memory, learning and reduces beta amyloid in transgenic mouse model of Alzheimer's disease.

PubMed

Subash, Selvaraju; Essa, Musthafa Mohamed; Braidy, Nady; Awlad-Thani, Kathyia; Vaishnav, Ragini; Al-Adawi, Samir; Al-Asmi, Abdullah; Guillemin, Gilles J

2015-01-01

At present, the treatment options available to delay the onset or slow down the progression of Alzheimer's disease (AD) are not effective. Recent studies have suggested that diet and lifestyle factors may represent protective strategies to minimize the risk of developing AD. Date palm fruits are a good source of dietary fiber and are rich in total phenolics and natural antioxidants, such as anthocyanins, ferulic acid, protocatechuic acid and caffeic acid. These polyphenolic compounds have been shown to be neuroprotective in different model systems. We investigated whether dietary supplementation with 2% and 4% date palm fruits (grown in Oman) could reduce cognitive and behavioral deficits in a transgenic mouse model for AD (amyloid precursor protein [APPsw]/Tg2576). The experimental groups of APP-transgenic mice from the age of 4 months were fed custom-mix diets (pellets) containing 2% and 4% date fruits. We assessed spatial memory and learning ability, psychomotor coordination, and anxiety-related behavior in all the animals at the age of 4 months and after 14 months of treatment using the Morris water maze test, rota-rod test, elevated plus maze test, and open-field test. We have also analyzed the levels of amyloid beta (Aβ) protein (1-40 and 1-42) in plasma of control and experimental animals. Standard diet-fed Tg mice showed significant memory deficits, increased anxiety-related behavior, and severe impairment in spatial learning ability, position discrimination learning ability and motor coordination when compared to wild-type on the same diet and Tg mice fed 2% and 4% date supplementation at the age of 18 months. The levels of both Aβ proteins were significantly lowered in date fruits supplemented groups than the Tg mice without the diet supplement. The neuroprotective effect offered by 4% date fruits diet to AD mice is higher than 2% date fruits diet. Our results suggest that date fruits dietary supplementation may have beneficial effects in lowering the risk, delaying the onset or slowing down the progression of AD.

Minimalist design of water-soluble cross-[beta] architecture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biancalana, Matthew; Makabe, Koki; Koide, Shohei

Demonstrated successes of protein design and engineering suggest significant potential to produce diverse protein architectures and assemblies beyond those found in nature. Here, we describe a new class of synthetic protein architecture through the successful design and atomic structures of water-soluble cross-{beta} proteins. The cross-{beta} motif is formed from the lamination of successive {beta}-sheet layers, and it is abundantly observed in the core of insoluble amyloid fibrils associated with protein-misfolding diseases. Despite its prominence, cross-{beta} has been designed only in the context of insoluble aggregates of peptides or proteins. Cross-{beta}'s recalcitrance to protein engineering and conspicuous absence among the knownmore » atomic structures of natural proteins thus makes it a challenging target for design in a water-soluble form. Through comparative analysis of the cross-{beta} structures of fibril-forming peptides, we identified rows of hydrophobic residues ('ladders') running across {beta}-strands of each {beta}-sheet layer as a minimal component of the cross-{beta} motif. Grafting a single ladder of hydrophobic residues designed from the Alzheimer's amyloid-{beta} peptide onto a large {beta}-sheet protein formed a dimeric protein with a cross-{beta} architecture that remained water-soluble, as revealed by solution analysis and x-ray crystal structures. These results demonstrate that the cross-{beta} motif is a stable architecture in water-soluble polypeptides and can be readily designed. Our results provide a new route for accessing the cross-{beta} structure and expanding the scope of protein design.« less

Minimalist design of water-soluble cross-beta architecture.

PubMed

Biancalana, Matthew; Makabe, Koki; Koide, Shohei

2010-02-23

Demonstrated successes of protein design and engineering suggest significant potential to produce diverse protein architectures and assemblies beyond those found in nature. Here, we describe a new class of synthetic protein architecture through the successful design and atomic structures of water-soluble cross-beta proteins. The cross-beta motif is formed from the lamination of successive beta-sheet layers, and it is abundantly observed in the core of insoluble amyloid fibrils associated with protein-misfolding diseases. Despite its prominence, cross-beta has been designed only in the context of insoluble aggregates of peptides or proteins. Cross-beta's recalcitrance to protein engineering and conspicuous absence among the known atomic structures of natural proteins thus makes it a challenging target for design in a water-soluble form. Through comparative analysis of the cross-beta structures of fibril-forming peptides, we identified rows of hydrophobic residues ("ladders") running across beta-strands of each beta-sheet layer as a minimal component of the cross-beta motif. Grafting a single ladder of hydrophobic residues designed from the Alzheimer's amyloid-beta peptide onto a large beta-sheet protein formed a dimeric protein with a cross-beta architecture that remained water-soluble, as revealed by solution analysis and x-ray crystal structures. These results demonstrate that the cross-beta motif is a stable architecture in water-soluble polypeptides and can be readily designed. Our results provide a new route for accessing the cross-beta structure and expanding the scope of protein design.

Nerve Growth Factor Increases mRNA Levels for the Prion Protein and the β -amyloid Protein Precursor in Developing Hamster Brain

NASA Astrophysics Data System (ADS)

Mobley, William C.; Neve, Rachael L.; Prusiner, Stanley B.; McKinley, Michael P.

1988-12-01

Deposition of amyloid filaments serves as a pathologic hallmark for some neurodegenerative disorders. The prion protein (PrP) is found in amyloid of animals with scrapie and humans with Creutzfeldt-Jakob disease; the β protein is present in amyloid deposits in Alzheimer disease and Down syndrome patients. These two proteins are derived from precursors that in the brain are expressed primarily in neurons and are membrane bound. We found that gene expression for PrP and the β -protein precursor (β -PP) is regulated in developing hamster brain. Specific brain regions showed distinct patterns of ontogenesis for PrP and β -PP mRNAs. The increases in PrP and β -PP mRNAs in developing basal forebrain coincided with an increase in choline acetyltransferase activity, raising the possibility that these markers might be coordinately controlled in cholinergic neurons and regulated by nerve growth factor (NGF). Injections of NGF into the brains of neonatal hamsters increased both PrP and β -PP mRNA levels. Increased PrP and β -PP mRNA levels induced by NGF were confined to regions that contain NGF-responsive cholinergic neurons and were accompanied by elevations in choline acetyltransferase. It remains to be established whether or not exogenous NGF acts to increase PrP and β -PP gene expression selectively in forebrain cholinergic neurons in the developing hamster and endogenous NGF regulates expression of these genes.

A Helical Structural Nucleus Is the Primary Elongating Unit of Insulin Amyloid Fibrils

PubMed Central

Roessle, Manfred; Kastrup, Jette S; van de Weert, Marco; Flink, James M; Frokjaer, Sven; Gajhede, Michael; Svergun, Dmitri I

2007-01-01

Although amyloid fibrillation is generally believed to be a nucleation-dependent process, the nuclei are largely structurally uncharacterized. This is in part due to the inherent experimental challenge associated with structural descriptions of individual components in a dynamic multi-component equilibrium. There are indications that oligomeric aggregated precursors of fibrillation, and not mature fibrils, are the main cause of cytotoxicity in amyloid disease. This further emphasizes the importance of characterizing early fibrillation events. Here we present a kinetic x-ray solution scattering study of insulin fibrillation, revealing three major components: insulin monomers, mature fibrils, and an oligomeric species. Low-resolution three-dimensional structures are determined for the fibril repeating unit and for the oligomer, the latter being a helical unit composed of five to six insulin monomers. This helical oligomer is likely to be a structural nucleus, which accumulates above the supercritical concentration used in our experiments. The growth rate of the fibrils is proportional to the amount of the helical oligomer present in solution, suggesting that these oligomers elongate the fibrils. Hence, the structural nucleus and elongating unit in insulin amyloid fibrillation may be the same structural component above supercritical concentrations. A novel elongation pathway of insulin amyloid fibrils is proposed, based on the shape and size of the fibrillation precursor. The distinct helical oligomer described in this study defines a conceptually new basis of structure-based drug design against amyloid diseases. PMID:17472440

Are Abeta and its derivatives causative agents or innocent bystanders in AD?

PubMed

Robakis, Nikolaos K

2010-01-01

Alzheimer's disease (AD) is characterized by neurodegeneration in neocortical regions of the brain. Currently, Abeta-based theories, including amyloid depositions and soluble Abeta, form the basis of most therapeutic approaches to AD. It remains unclear, however, whether Abeta and its derivatives are the primary causative agents of neuronal loss in AD. Reported studies show no significant correlations between brain amyloid depositions and either degree of dementia or loss of neurons, and brain amyloid loads similar to AD are often found in normal individuals. Furthermore, behavioral abnormalities in animal models overexpressing amyloid precursor protein seem independent of amyloid depositions. Soluble Abeta theories propose toxic Abeta42 or its oligomers as the agents that promote cell death in AD. Abeta peptides, however, are normal components of human serum and CSF, and it is unclear under what conditions these peptides become toxic. Presently, there is little evidence of disease-associated abnormalities in soluble Abeta and no toxic oligomers specific to AD have been found. That familial AD mutations of amyloid precursor protein, PS1 and PS2 promote neurodegeneration suggests the biological functions of these proteins play critical roles in neuronal survival. Evidence shows that the PS/gamma-secretase system promotes production of peptides involved in cell surface-to-nucleus signaling and gene expression, providing support for the hypothesis that familial AD mutations may contribute to neurodegeneration by inhibiting PS-dependent signaling pathways. Copyright 2010 S. Karger AG, Basel.

Yeast prion architecture explains how proteins can be genes

NASA Astrophysics Data System (ADS)

Wickner, Reed

2013-03-01

Prions (infectious proteins) transmit information without an accompanying DNA or RNA. Most yeast prions are self-propagating amyloids that inactivate a normally functional protein. A single protein can become any of several prion variants, with different manifestations due to different amyloid structures. We showed that the yeast prion amyloids of Ure2p, Sup35p and Rnq1p are folded in-register parallel beta sheets using solid state NMR dipolar recoupling experiments, mass-per-filament-length measurements, and filament diameter measurements. The extent of beta sheet structure, measured by chemical shifts in solid-state NMR and acquired protease-resistance on amyloid formation, combined with the measured filament diameters, imply that the beta sheets must be folded along the long axis of the filament. We speculate that prion variants of a single protein sequence differ in the location of these folds. Favorable interactions between identical side chains must hold these structures in-register. The same interactions must guide an unstructured monomer joining the end of a filament to assume the same conformation as molecules already in the filament, with the turns at the same locations. In this way, a protein can template its own conformation, in analogy to the ability of a DNA molecule to template its sequence by specific base-pairing. Bldg. 8, Room 225, NIH, 8 Center Drive MSC 0830, Bethesda, MD 20892-0830, wickner@helix.nih.gov, 301-496-3452

Production of recombinant human beta2-microglobulin for scintigraphic diagnosis of amyloidosis in uremia and hemodialysis.

PubMed

Linke, R P; Schäeffer, J; Gielow, P; Lindner, P; Lottspeich, F; Plückthun, A; Weiss, E H

2000-02-01

Amyloid of beta2-microglobulin (beta2m) origin can be diagnosed using 131I-radiolabelled-beta2m scintigraphy in patients with uremia and hemodialysis treatment. As the tracer beta2m is isolated from another patient, it carries the common risks, including viral infections such as Hepatitis B, C and HIV, which are associated with human plasma products. In order to exclude these risks we have produced recombinant human beta2m (rhbeta2m) in Escherichia coli. The expression vector pASK40DeltaLbeta2m(His)5 contains a C-terminal (His)5-tag for purification via immobilized metal ion affinity chromatography (IMAC). Size exclusion chromatography on a Superose 12 column represents the second step of purification. The isolated rhbeta2mH5 reacted in an immunochemically identical manner to native human beta2m, and showed a single band of approximately 11.8 kDa in Western blot analysis and revealed a single spot in two-dimensional gel electrophoresis. Mass spectrometry analysis revealed a single peak at the expected molecular mass of 12 415.8 Da. Uniformity was further proven by crystallization and N-terminal amino-acid sequence analysis. The rhbeta2mH5 protein was then produced under conditions that allow the intravenous use in humans. Intraveneously applied indium-111-labelled rhbeta2mH5 was monitored in hemodialysed patients with and without known beta2m-amyloidosis. The tracer was localized specifically to particular areas known to contain amyloid. Thus, this rhbeta2mH5 preparation is suitable for detecting amyloid-containing organs of the beta2m-class in vivo and fulfils the requirements of a tracer for common use. Finally, the use of indium-111 instead of iodine-131 has reduced the radioactive load and resulted in higher resolution.

The genetics of Alzheimer disease: current status and future prospects.

PubMed

Blacker, D; Tanzi, R E

1998-03-01

Four genes involved in the development of Alzheimer disease have been identified. Three fully penetrant (deterministic) genes lead to the development of Alzheimer disease in patients younger than 60 years: the amyloid beta-protein precursor on chromosome 21, presenilin 1 on chromosome 14, and presenilin 2 on chromosome 1. Together, they account for about half of this early-onset form of the disease. One genetic risk factor--apolipoprotein E-4--is associated with late-onset Alzheimer disease. It accounts for a substantial fraction of disease burden but seems to act primarily to lower the age of disease onset. In general, none of these genes can be easily adapted for use as a diagnostic or predictive test for Alzheimer disease. Research activity includes searching for additional genes, especially for late-onset disease, and elucidating the mechanism of action of all identified genes as part of a long-term effort to develop more effective therapeutic and preventive strategies.

Metal ions differentially influence the aggregation and deposition of Alzheimer's beta-amyloid on a solid template.

PubMed

Ha, Chanki; Ryu, Jungki; Park, Chan Beum

2007-05-22

The abnormal deposition and aggregation of beta-amyloid (Abeta) on brain tissues are considered to be one of the characteristic neuropathological features of Alzheimer's disease (AD). Environmental conditions such as metal ions, pH, and cell membranes are associated with Abeta deposition and plaque formation. According to the amyloid cascade hypothesis of AD, the deposition of Abeta42 oligomers as diffuse plaques in vivo is an important earliest event, leading to the formation of fibrillar amyloid plaques by the further accumulation of soluble Abeta under certain environmental conditions. In order to characterize the effect of metal ions on amyloid deposition and plaque growth on a solid surface, we prepared a synthetic template by immobilizing Abeta oligomers onto a N-hydroxysuccinimide ester-activated solid surface. According to our study using ex situ atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), and thioflavin T (ThT) fluorescence spectroscopy, Cu2+ and Zn2+ ions accelerated both Abeta40 and Abeta42 deposition but resulted only in the formation of "amorphous" aggregates. In contrast, Fe3+ induced the deposition of "fibrillar" amyloid plaques at neutral pH. Under mildly acidic environments, the formation of fibrillar amyloid plaques was not induced by any metal ion tested in this work. Using secondary ion mass spectroscopy (SIMS) analysis, we found that binding Cu ions to Abeta deposits on a solid template occurred by the possible reduction of Cu ions during the interaction of Abeta with Cu2+. Our results may provide insights into the role of metal ions on the formation of fibrillar or amorphous amyloid plaques in AD.

Effect of Surfaces on Amyloid Fibril Formation

PubMed Central

Moores, Bradley; Drolle, Elizabeth; Attwood, Simon J.; Simons, Janet; Leonenko, Zoya

2011-01-01

Using atomic force microscopy (AFM) we investigated the interaction of amyloid beta (Aβ) (1–42) peptide with chemically modified surfaces in order to better understand the mechanism of amyloid toxicity, which involves interaction of amyloid with cell membrane surfaces. We compared the structure and density of Aβ fibrils on positively and negatively charged as well as hydrophobic chemically-modified surfaces at physiologically relevant conditions. We report that due to the complex distribution of charge and hydrophobicity amyloid oligomers bind to all types of surfaces investigated (CH3, COOH, and NH2) although the charge and hydrophobicity of surfaces affected the structure and size of amyloid deposits as well as surface coverage. Hydrophobic surfaces promote formation of spherical amorphous clusters, while charged surfaces promote protofibril formation. We used the nonlinear Poisson-Boltzmann equation (PBE) approach to analyze the electrostatic interactions of amyloid monomers and oligomers with modified surfaces to complement our AFM data. PMID:22016789

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lashuel, Hilal A.; Aljabari, Bayan; Sigurdsson, Einar M.

We demonstrate herein that human macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine expressed in the brain and not previously considered to be amyloidogenic, forms amyloid fibrils similar to those derived from the disease associated amyloidogenic proteins {beta}-amyloid and {alpha}-synuclein. Acid denaturing conditions were found to readily induce MIF to undergo amyloid fibril formation. MIF aggregates to form amyloid-like structures with a morphology that is highly dependent on pH. The mechanism of MIF amyloid formation was probed by electron microscopy, turbidity, Thioflavin T binding, circular dichroism spectroscopy, and analytical ultracentrifugation. The fibrillar structures formed by MIF bind Congo red andmore » exhibit the characteristic green birefringence under polarized light. These results are consistent with the notion that amyloid fibril formation is not an exclusive property of a select group of amyloidogenic proteins, and contribute to a better understanding of the factors which govern protein conformational changes and amyloid fibril formation in vivo.« less

Corticosteroidogenesis in the toad Bufo arenarum H: evidence for a precursor role for an aldosterone 3 beta-hydroxy-5-ene analogue (3 beta, 11 beta, 21-trihydroxy-20-oxo-5-pregnen-18-al).

PubMed Central

Ceballos, N R; Shackleton, C H; Harnik, M; Cozza, E N; Gros, E G; Lantos, C P

1993-01-01

A material isolated following pregnenolone incubations with toad (Bufo arenarum) inter-renal tissue at 28 degrees C has been identified as a 3 beta-hydroxy-5-ene analogue of aldosterone (3 beta, 11 beta, 21-trihydroxy-20-oxo-5-pregnen-18-al). The initial identification was made by enzymic and m.s. methods, and structural confirmation was achieved through comparison with chemically synthesized authentic material. The relative efficacy of corticosterone, 18-hydroxycorticosterone and the 3 beta-hydroxy-5-ene aldosterone analogue as aldosterone precursors was evaluated. In the in vitro situation studied, the 3 beta-hydroxy-5-ene steroid was by far the best precursor. PMID:8503841

Corticosteroidogenesis in the toad Bufo arenarum H: evidence for a precursor role for an aldosterone 3 beta-hydroxy-5-ene analogue (3 beta, 11 beta, 21-trihydroxy-20-oxo-5-pregnen-18-al).

PubMed

Ceballos, N R; Shackleton, C H; Harnik, M; Cozza, E N; Gros, E G; Lantos, C P

1993-05-15

A material isolated following pregnenolone incubations with toad (Bufo arenarum) inter-renal tissue at 28 degrees C has been identified as a 3 beta-hydroxy-5-ene analogue of aldosterone (3 beta, 11 beta, 21-trihydroxy-20-oxo-5-pregnen-18-al). The initial identification was made by enzymic and m.s. methods, and structural confirmation was achieved through comparison with chemically synthesized authentic material. The relative efficacy of corticosterone, 18-hydroxycorticosterone and the 3 beta-hydroxy-5-ene aldosterone analogue as aldosterone precursors was evaluated. In the in vitro situation studied, the 3 beta-hydroxy-5-ene steroid was by far the best precursor.

Anxiolytic and antidepressant profile of the methanolic extract of Piper nigrum fruits in beta-amyloid (1-42) rat model of Alzheimer's disease.

PubMed

Hritcu, Lucian; Noumedem, Jaurès A; Cioanca, Oana; Hancianu, Monica; Postu, Paula; Mihasan, Marius

2015-03-29

Piper nigrum L. (Piperaceae) is employed in traditional medicine of many countries as analgesic, antiinflammatory, anticonvulsant, antioxidant, antidepressant and cognitive-enhancing agent. This study was undertaken in order to evaluate the possible anxiolytic, antidepressant and antioxidant properties of the methanolic extract of Piper nigrum fruits in beta-amyloid (1-42) rat model of Alzheimer's disease. The anxiolytic- and antidepressant-like effects of the methanolic extract were studied by means of in vivo (elevated plus-maze and forced swimming tests) approaches. Also, the antioxidant activity in the amygdala was assessed using superoxide dismutase, glutathione peroxidase and catalase specific activities, the total content of the reduced glutathione, protein carbonyl and malondialdehyde levels. Statistical analyses were performed using one-way analysis of variance (ANOVA). Significant differences were determined by Tukey's post hoc test. F values for which p < 0.05 were regarded as statistically significant. Pearson's correlation coefficient and regression analysis were used in order to evaluate the connection between behavioral measures, the antioxidant defence and lipid peroxidation. The beta-amyloid (1-42)-treated rats exhibited the following: decrease of the exploratory activity, the percentage of the time spent and the number of entries in the open arm within elevated plus-maze test and decrease of swimming time and increase of immobility time within forced swimming test. Administration of the methanolic extract significantly exhibited anxiolytic- and antidepressant-like effects and also antioxidant potential. Taken together, our results suggest that the methanolic extract ameliorates beta-amyloid (1-42)-induced anxiety and depression by attenuation of the oxidative stress in the rat amygdala.

Assessment of cerebral microbleeds by susceptibility-weighted imaging in Alzheimer's disease patients: A neuroimaging biomarker of the disease.

PubMed

Sparacia, Gianvincenzo; Agnello, Francesco; La Tona, Giuseppe; Iaia, Alberto; Midiri, Federico; Sparacia, Benedetta

2017-08-01

Purpose The objective of this study was to correlate the presence and distribution of cerebral microbleeds in Alzheimer's disease patients with cerebrospinal fluid biomarkers (amyloid-beta and phosphorylated tau 181 protein levels) and cognitive decline by using susceptibility-weighted imaging magnetic resonance sequences at 1.5 T. Material and methods Fifty-four consecutive Alzheimer's disease patients underwent brain magnetic resonance imaging at 1.5 T to assess the presence and distribution of cerebral microbleeds on susceptibility-weighted imaging images. The images were analyzed in consensus by two neuroradiologists, each with at least 10 years' experience. Dementia severity was assessed with the Mini-Mental State Examination score. A multiple regression analysis was performed to assess the associations between the number and location of cerebral microbleed lesions with the age, sex, duration of the disease, cerebrospinal fluid amyloid-beta and phosphorylated tau 181 protein levels, and cognitive functions. Results A total of 296 microbleeds were observed in 54 patients; 38 patients (70.4%) had lobar distribution, 13 patients (24.1%) had non-lobar distribution, and the remaining three patients (5.6%) had mixed distribution, demonstrating that Alzheimer's disease patients present mainly a lobar distribution of cerebral microbleeds. The age and the duration of the disease were correlated with the number of lobar cerebral microbleeds ( P < 0.001). Cerebrospinal fluid amyloid-beta, phosphorylated tau 181 protein levels, and cognitive decline were correlated with the number of lobar cerebral microbleeds in Alzheimer's disease patients ( P < 0.001). Conclusion Lobar distribution of cerebral microbleeds is associated with Alzheimer's disease and the number of lobar cerebral microbleeds directly correlates with cerebrospinal fluid amyloid-beta and phosphorylated tau 181 protein levels and with the cognitive decline of Alzheimer's disease patients.

Ellagic acid ameliorates learning and memory deficits in a rat model of Alzheimer's disease: an exploration of underlying mechanisms.

PubMed

Kiasalari, Zahra; Heydarifard, Rana; Khalili, Mohsen; Afshin-Majd, Siamak; Baluchnejadmojarad, Tourandokht; Zahedi, Elham; Sanaierad, Ashkan; Roghani, Mehrdad

2017-06-01

Alzheimer's disease (AD) is a neurodegenerative disorder with irreversible loss of intellectual abilities. Current therapies for AD are still insufficient. In this study, the effect of ellagic acid on learning and memory deficits was evaluated in intrahippocampal amyloid beta (Aβ 25-35 )-microinjected rats and its modes of action were also explored. AD rat model was induced by bilateral intrahippocampal microinjection of Aβ 25-35 and ellagic acid was daily administered (10, 50, and 100 mg/kg), and learning, recognition memory, and spatial memory were evaluated in addition to histochemical assessment, oxidative stress, cholinesterases activity, and level of nuclear factor-kappaB (NF-κB), Toll-like receptor 4 (TLR4), and nuclear factor (erythroid-derived 2)-like 2 (Nrf2). The amyloid beta-microinjected rats showed a lower discrimination ratio in novel object and alternation score in Y maze tasks and exhibited an impairment of retention and recall capability in passive avoidance paradigm and higher working and reference memory errors in radial arm maze (RAM). In addition, amyloid beta group showed a lower number of Nissl-stained neurons in CA1 area in addition to enhanced oxidative stress, higher activity of cholinesterases, greater level of NF-κB and TLR4, and lower level of nuclear/cytoplasmic ratio for Nrf2 and ellagic acid at a dose of 100 mg/kg significantly prevented most of these abnormal alterations. Ellagic acid pretreatment of intrahippocampal amyloid beta-microinjected rats could dose-dependently improve learning and memory deficits via neuronal protection and at molecular level through mitigation of oxidative stress and acetylcholinesterase (AChE) activity and modulation of NF-κB/Nrf2/TLR4 signaling pathway.

Immunotherapy of Alzheimer's disease (AD): from murine models to anti-amyloid beta (Abeta) human monoclonal antibodies.

PubMed

Geylis, Valeria; Steinitz, Michael

2006-01-01

The deposition of amyloid beta (Abeta) protein is a key pathological feature in Alzheimer's disease (AD). In murine models of AD, both active and passive immunization against Abeta induce a marked reduction in amyloid brain burden and an improvement in cognitive functions. Preliminary results of a prematurely terminated clinical trial where AD patients were actively vaccinated with aggregated Abeta bear resemblance to those documented in murine models. Passive immunization of AD patients with anti-Abeta antibodies, in particular human antibodies, is a strategy that provides a more cautious management and control of any undesired side effects. Sera of all healthy adults contain anti-Abeta IgG autoimmune antibodies. Hence antigen-committed human B-cells are easily immortalized by Epstein-Barr virus (EBV) into anti-Abeta secreting cell lines. Two anti-Abeta human monoclonal antibodies which we recently prepared bind to the N-terminus of Abeta peptide and were shown to stain amyloid plaques in non-fixed brain sections from an AD patient. It is anticipated that specifically selected anti-Abeta human monoclonal antibodies could reduce and inhibit deposits of amyloid in brain while avoiding the cognitive decline that characterizes AD. In the future, this type of antibody may prove to be a promising immune therapy for the disease.

Hemin as a generic and potent protein misfolding inhibitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yanqin; Carver, John A.; Ho, Lam H.

2014-11-14

Highlights: • Hemin prevents Aβ42, α-synuclein and RCM-κ-casein forming amyloid fibrils. • Hemin inhibits the β-sheet structure formation of Aβ42. • Hemin reduces the cell toxicity caused by fibrillar Aβ42. • Hemin dissociates partially formed Aβ42 fibrils. • Hemin prevents amorphous aggregation by ADH, catalase and γs-crystallin. - Abstract: Protein misfolding causes serious biological malfunction, resulting in diseases including Alzheimer’s disease, Parkinson’s disease and cataract. Molecules which inhibit protein misfolding are a promising avenue to explore as therapeutics for the treatment of these diseases. In the present study, thioflavin T fluorescence and transmission electron microscopy experiments demonstrated that hemin preventsmore » amyloid fibril formation of kappa-casein, amyloid beta peptide and α-synuclein by blocking β-sheet structure assembly which is essential in fibril aggregation. Further, inhibition of fibril formation by hemin significantly reduces the cytotoxicity caused by fibrillar amyloid beta peptide in vitro. Interestingly, hemin degrades partially formed amyloid fibrils and prevents further aggregation to mature fibrils. Light scattering assay results revealed that hemin also prevents protein amorphous aggregation of alcohol dehydrogenase, catalase and γs-crystallin. In summary, hemin is a potent agent which generically stabilises proteins against aggregation, and has potential as a key molecule for the development of therapeutics for protein misfolding diseases.« less

Origin of life. Primordial genetics: Information transfer in a pre-RNA world based on self-replicating beta-sheet amyloid conformers.

PubMed

Maury, Carl Peter J

2015-10-07

The question of the origin of life on Earth can largely be reduced to the question of what was the first molecular replicator system that was able to replicate and evolve under the presumably very harsh conditions on the early Earth. It is unlikely that a functional RNA could have existed under such conditions and it is generally assumed that some other kind of information system preceded the RNA world. Here, I present an informational molecular system that is stable, self-replicative, environmentally responsive, and evolvable under conditions characterized by high temperatures, ultraviolet and cosmic radiation. This postulated pregenetic system is based on the amyloid fold, a functionally unique polypeptide fold characterized by a cross beta-sheet structure in which the beta strands are arranged perpendicular to the fiber axis. Beside an extraordinary structural robustness, the amyloid fold possesses a unique ability to transmit information by a three-dimensional templating mechanism. In amyloidogenesis short peptide monomers are added one by one to the growing end of the fiber. From the same monomeric subunits several structural variants of amyloid may be formed. Then, in a self-replicative mode, a specific amyloid conformer can act as a template and confer its spatially encoded information to daughter molecular entities in a repetitive way. In this process, the specific conformational information, the spatially changed organization, is transmitted; the coding element is the steric zipper structure, and recognition occurs by amino acid side chain complementarity. The amyloid information system fulfills several basic requirements of a primordial evolvable replicator system: (i) it is stable under the presumed primitive Earth conditions, (ii) the monomeric building blocks of the informational polymer can be formed from available prebiotic compounds, (iii) the system is self-assembling and self-replicative and (iv) it is adaptive to changes in the environment and evolvable. Copyright © 2015 The Author. Published by Elsevier Ltd.. All rights reserved.

Nicotinamide mononucleotide inhibits JNK activation to reverse Alzheimer disease.

PubMed

Yao, Zhiwen; Yang, Wenhao; Gao, Zhiqiang; Jia, Peng

2017-04-24

Amyloid-β (Aβ) oligomers have been accepted as major neurotoxic agents in the therapy of Alzheimer's disease (AD). It has been shown that the activity of nicotinamide adenine dinucleotide (NAD+) is related with the decline of Aβ toxicity in AD. Nicotinamide mononucleotide (NMN), the important precursor of NAD+, is produced during the reaction of nicotinamide phosphoribosyl transferase (Nampt). This study aimed to figure out the potential therapeutic effects of NMN and its underlying mechanisms in APPswe/PS1dE9 (AD-Tg) mice. We found that NMN gave rise to a substantial improvement in behavioral measures of cognitive impairments compared to control AD-Tg mice. In addition, NMN treatment significantly decreased β-amyloid production, amyloid plaque burden, synaptic loss, and inflammatory responses in transgenic animals. Mechanistically, NMN effectively controlled JNK activation. Furthermore, NMN potently progressed nonamyloidogenic amyloid precursor protein (APP) and suppressed amyloidogenic APP by mediating the expression of APP cleavage secretase in AD-Tg mice. Based on our findings, it was suggested that NMN substantially decreases multiple AD-associated pathological characteristically at least partially by the inhibition of JNK activation. Copyright © 2017 Elsevier B.V. All rights reserved.

Alzheimer's disease: molecular concepts and therapeutic targets

NASA Astrophysics Data System (ADS)

Fassbender, K.; Masters, C.; Beyreuther, K.

2001-06-01

The beta amyloid peptide is the major component of the neuritic plaques, the characteristic lesions in Alzheimer's disease. Mutations in three genes (APP, PS-1, and PS-2) cause familial Alzheimer's disease by alteration of the rate of generation of amyloid peptide or the length of this peptide. However, in the 90% non-familial cases, other factors play a major pathogenetic role. These include the apolipoprotein E genotype, the "plaque-associated" proteins promoting the formation of toxic fibrillar aggregates or the chronic inflammatory responses. The aim of this review is to explain the steps in the complex cascade leading to Alzheimer's disease and, based on this, to report the current efforts to intervene in these different pathophysiological events in order to prevent progression of Alzheimer's disease. Whereas acetylcholine substitution is currently used in clinical practice, future therapeutical strategies to combat Alzheimer's disease may include anti-inflammatory treatments, vaccination against beta amyloid peptide, or treatment with cholesterol-lowering drugs.

T-cell brain infiltration and immature antigen-presenting cells in transgenic models of Alzheimer's disease-like cerebral amyloidosis.

PubMed

Ferretti, M T; Merlini, M; Späni, C; Gericke, C; Schweizer, N; Enzmann, G; Engelhardt, B; Kulic, L; Suter, T; Nitsch, R M

2016-05-01

Cerebral beta-amyloidosis, one of the pathological hallmarks of Alzheimer's disease (AD), elicits a well-characterised, microglia-mediated local innate immune response. In contrast, it is not clear whether cells of the adaptive immune system, in particular T-cells, react to cerebral amyloidosis in AD. Even though parenchymal T-cells have been described in post-mortem brains of AD patients, it is not known whether infiltrating T-cells are specifically recruited to the extracellular deposits of beta-amyloid, and whether they are locally activated into proliferating, effector cells upon interaction with antigen-presenting cells (APCs). To address these issues we have analysed by confocal microscopy and flow-cytometry the localisation and activation status of both T-cells and APCs in transgenic (tg) mice models of AD-like cerebral amyloidosis. Increased numbers of infiltrating T-cells were found in amyloid-burdened brain regions of tg mice, with concomitant up-regulation of endothelial adhesion molecules ICAM-1 and VCAM-1, compared to non-tg littermates. The infiltrating T-cells in tg brains did not co-localise with amyloid plaques, produced less interferon-gamma than those in controls and did not proliferate locally. Bona-fide dendritic cells were virtually absent from the brain parenchyma of both non-tg and tg mice, and APCs from tg brains showed an immature phenotype, with accumulation of MHC-II in intracellular compartments. These results indicate that cerebral amyloidosis promotes T-cell infiltration but interferes with local antigen presentation and T-cell activation. The inability of the brain immune surveillance to orchestrate a protective immune response to amyloid-beta peptide might contribute to the accumulation of amyloid in the progression of the disease. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Zn(II)- and Cu(II)-induced non-fibrillar aggregates of amyloid-beta (1-42) peptide are transformed to amyloid fibrils, both spontaneously and under the influence of metal chelators.

PubMed

Tõugu, Vello; Karafin, Ann; Zovo, Kairit; Chung, Roger S; Howells, Claire; West, Adrian K; Palumaa, Peep

2009-09-01

Aggregation of amyloid-beta (Abeta) peptides is a central phenomenon in Alzheimer's disease. Zn(II) and Cu(II) have profound effects on Abeta aggregation; however, their impact on amyloidogenesis is unclear. Here we show that Zn(II) and Cu(II) inhibit Abeta(42) fibrillization and initiate formation of non-fibrillar Abeta(42) aggregates, and that the inhibitory effect of Zn(II) (IC(50) = 1.8 micromol/L) is three times stronger than that of Cu(II). Medium and high-affinity metal chelators including metallothioneins prevented metal-induced Abeta(42) aggregation. Moreover, their addition to preformed aggregates initiated fast Abeta(42) fibrillization. Upon prolonged incubation the metal-induced aggregates also transformed spontaneously into fibrils, that appear to represent the most stable state of Abeta(42). H13A and H14A mutations in Abeta(42) reduced the inhibitory effect of metal ions, whereas an H6A mutation had no significant impact. We suggest that metal binding by H13 and H14 prevents the formation of a cross-beta core structure within region 10-23 of the amyloid fibril. Cu(II)-Abeta(42) aggregates were neurotoxic to neurons in vitro only in the presence of ascorbate, whereas monomers and Zn(II)-Abeta(42) aggregates were non-toxic. Disturbed metal homeostasis in the vicinity of zinc-enriched neurons might pre-dispose formation of metal-induced Abeta aggregates, subsequent fibrillization of which can lead to amyloid formation. The molecular background underlying metal-chelating therapies for Alzheimer's disease is discussed in this light.

Immunoglobulin light chains, glycosaminoglycans and amyloid.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevens, F. J.; Kisilevsky, R.; Biosciences Division

2000-03-01

Immunoglobulin light chains are the precursor proteins for fibrils that are formed during primary amyloidosis and in amyloidosis associated with multiple myeloma. As found for the approximately 20 currently described forms of focal, localized, or systemic amyloidoses, light chain-related fibrils extracted from physiological deposits are invariably associated with glycosaminoglycans, predominantly heparan sulfate. Other amyloid-related proteins are either structurally normal, such as g2-microglobulin and islet amyloid polypeptide, fragments of normal proteins such as serum amyloid A protein or the precursor protein of the g peptide involved in Alzheimer's disease, or are inherited forms of single amino acid variants of a normalmore » protein such as found in the familial forms of amyloid associated with transthyretin. In contrast, the primary structures of light chains involved in fibril formation exhibit extensive mutational diversity rendering some proteins highly amyloidogenic and others non-pathological. The interactions between light chains and glycosaminoglycans are also affected by amino acid variation and may influence the clinical course of disease by enhancing fibril stability and contributing to resistance to protease degradation. Relatively little is currently known about the mechanisms by which glycosaminoglycans interact with light chains and light-chain fibrils. It is probable that future studies of this uniquely diverse family of proteins will continue o shed light on the processes of amyloidosis, and contribute as well to a greater understanding of the normal physiological roles of glycosaminoglycans.« less

Self-Assembly of Large Amyloid Fibers

NASA Astrophysics Data System (ADS)

Ridgley, Devin M.

Functional amyloids found throughout nature have demonstrated that amyloid fibers are potential industrial biomaterials. This work introduces a new "template plus adder" cooperative mechanism for the spontaneous self-assembly of micrometer sized amyloid fibers. A short hydrophobic template peptide induces a conformation change within a highly alpha-helical adder protein to form beta-sheets that continue to assemble into micrometer sized amyloid fibers. This study utilizes a variety of proteins that have template or adder characteristics which suggests that this mechanism may be employed throughout nature. Depending on the amino acid composition of the proteins used the mixtures form amyloid fibers of a cylindrical ( 10 mum diameter, 2 GPa Young's modulus) or tape (5- 10 mum height, 10-20 mum width and 100-200 MPa Young's modulus) morphology. Processing conditions are altered to manipulate the morphology and structural characteristics of the fibers. Spectroscopy is utilized to identify certain amino acid groups that contribute to the self-assembly process. Aliphatic amino acids (A, I, V and L) are responsible for initiating conformation change of the adder proteins to assemble into amyloid tapes. Additional polyglutamine segments (Q-blocks) within the protein mixtures will form Q hydrogen bonds to reinforce the amyloid structure and form a cylindrical fiber of higher modulus. Atomic force microscopy is utilized to delineate the self-assembly of amyloid tapes and cylindrical fibers from protofibrils (15-30 nm width) to fibers (10-20 mum width) spanning three orders of magnitude. The aliphatic amino acid content of the adder proteins' alpha-helices is a good predictor of high density beta-sheet formation within the protein mixture. Thus, it is possible to predict the propensity of a protein to undergo conformation change into amyloid structures. Finally, Escherichia coli is genetically engineered to express a template protein which self-assembles into large amyloid fibers when combined with extracellular myoglobin, an adder protein. The goal of this thesis is to produce, manipulate and characterize the self-assembly of large amyloid fibers for their potential industrial biomaterial applications. The techniques used throughout this study outline various methods to design and engineer amyloid fibers of a tailored modulus and morphology. Furthermore, the mechanisms described here may offer some insight into naturally occurring amyloid forming systems.

Differential mode of interaction of ThioflavinT with native β structural motif in human α 1-acid glycoprotein and cross beta sheet of its amyloid: Biophysical and molecular docking approach

NASA Astrophysics Data System (ADS)

Ajmal, Mohammad Rehan; Nusrat, Saima; Alam, Parvez; Zaidi, Nida; Badr, Gamal; Mahmoud, Mohamed H.; Rajpoot, Ravi Kant; Khan, Rizwan Hasan

2016-08-01

The present study details the interaction mechanism of Thioflavin T (ThT) to Human α1-acid glycoprotein (AAG) applying various spectroscopic and molecular docking methods. Fluorescence quenching data revealed the binding constant in the order of 104 M-1 and the standard Gibbs free energy change value, ΔG = -6.78 kcal mol-1 for the interaction between ThT and AAG indicating process is spontaneous. There is increase in absorbance of AAG upon the interaction of ThT that may be due to ground state complex formation between ThT and AAG. ThT impelled rise in β-sheet structure in AAG as observed from far-UV CD spectra while there are minimal changes in tertiary structure of the protein. DLS results suggested the reduction in AAG molecular size, ligand entry into the central binding pocket of AAG may have persuaded the molecular compaction in AAG. Isothermal titration calorimetric (ITC) results showed the interaction process to be endothermic with the values of standard enthalpy change ΔH0 = 4.11 kcal mol-1 and entropy change TΔS0 = 10.82 kcal.mol- 1. Moreover, docking results suggested hydrophobic interactions and hydrogen bonding played the important role in the binding process of ThT with F1S and A forms of AAG. ThT fluorescence emission at 485 nm was measured for properly folded native form and for thermally induced amyloid state of AAG. ThT fluorescence with native AAG was very low, while on the other hand with amyloid induced state of the protein AAG showed a positive emission peak at 485 nm upon the excitation at 440 nm, although it binds to native state as well. These results confirmed that ThT binding alone is not responsible for enhancement of ThT fluorescence but it also required beta stacked sheet structure found in protein amyloid to give proper signature signal for amyloid. This study gives the mechanistic insight into the differential interaction of ThT with beta structures found in native state of the proteins and amyloid forms, this study reinforce the notion that ThT is amyloid specific dye and interacts differently with the beta structures in native protein and that of the structures found in aggregated form of the same protein.

Toxic β-Amyloid (Aβ) Alzheimer's Ion Channels: From Structure to Function and Design

NASA Astrophysics Data System (ADS)

Nussinov, Ruth

2012-02-01

Full-length amyloid beta peptides (Aβ1-40/42) form neuritic amyloid plaques in Alzheimer's disease (AD) patients and are implicated in AD pathology. Recent biophysical and cell biological studies suggest a direct mechanism of amyloid beta toxicity -- ion channel mediated loss of calcium homeostasis. Truncated amyloid beta fragments (Aβ11-42 and Aβ17-42), commonly termed as non-amyloidogenic are also found in amyloid plaques of Alzheimer's disease (AD) and in the preamyloid lesions of Down's syndrome (DS), a model system for early onset AD study. Very little is known about the structure and activity of these smaller peptides although they could be key AD and DS pathological agents. Using complementary techniques of explicit solvent molecular dynamics (MD) simulations, atomic force microscopy (AFM), channel conductance measurements, cell calcium uptake assays, neurite degeneration and cell death assays, we have shown that non-amyloidogenic Aβ9-42 and Aβ17-42 peptides form ion channels with loosely attached subunits and elicit single channel conductances. The subunits appear mobile suggesting insertion of small oligomers, followed by dynamic channel assembly and dissociation. These channels allow calcium uptake in APP-deficient cells and cause neurite degeneration in human cortical neurons. Channel conductance, calcium uptake and neurite degeneration are selectively inhibited by zinc, a blocker of amyloid ion channel activity. Thus truncated Aβ fragments could account for undefined roles played by full length Aβs and provide a novel mechanism of AD and DS pathology. The emerging picture from our large-scale simulations is that toxic ion channels formed by β-sheets are highly polymorphic, and spontaneously break into loosely interacting dynamic units (though still maintaining ion channel structures as imaged with AFM), that associate and dissociate leading to toxic ion flux. This sharply contrasts intact conventional gated ion channels that consist of tightly interacting α-helices that robustly prevent ion leakage, rather than hydrogen-bonded β-strands. Moreover, in comparison with β-rich antimicrobial peptide (AMP) such as a protegrin-1 (PG-1), both Aβ and PG-1 are cytotoxic, and capable of forming fibrils and dynamic channels which consist of subunits with similar dimensions. These combined properties support a functional relationship between amyloidogenic peptides and β-sheet-rich cytolytic AMPs, suggesting that PG-1 is amyloidogenic and amyloids may have an antimicrobial function.

Modulation of neuroinflammation and pathology in the 5XFAD mouse model of Alzheimer's disease using a biased and selective beta-1 adrenergic receptor partial agonist.

PubMed

Ardestani, Pooneh Memar; Evans, Andrew K; Yi, Bitna; Nguyen, Tiffany; Coutellier, Laurence; Shamloo, Mehrdad

2017-04-01

Degeneration of noradrenergic neurons occurs at an early stage of Alzheimer's Disease (AD). The noradrenergic system regulates arousal and learning and memory, and has been implicated in regulating neuroinflammation. Loss of noradrenergic tone may underlie AD progression at many levels. We have previously shown that acute administration of a partial agonist of the beta-1 adrenergic receptor (ADRB1), xamoterol, restores behavioral deficits in a mouse model of AD. The current studies examined the effects of chronic low dose xamoterol on neuroinflammation, pathology, and behavior in the pathologically aggressive 5XFAD transgenic mouse model of AD. In vitro experiments in cells expressing human beta adrenergic receptors demonstrate that xamoterol is highly selective for ADRB1 and functionally biased for the cAMP over the β-arrestin pathway. Data demonstrate ADRB1-mediated attenuation of TNF-α production with xamoterol in primary rat microglia culture following LPS challenge. Finally, two independent cohorts of 5XFAD and control mice were administered xamoterol from approximately 4.0-6.5 or 7.0-9.5 months, were tested in an array of behavioral tasks, and brains were examined for evidence of neuroinflammation, and amyloid beta and tau pathology. Xamoterol reduced mRNA expression of neuroinflammatory markers (Iba1, CD74, CD14 and TGFβ) and immunohistochemical evidence for microgliosis and astrogliosis. Xamoterol reduced amyloid beta and tau pathology as measured by regional immunohistochemistry. Behavioral deficits were not observed for 5XFAD mice. In conclusion, chronic administration of a selective, functionally biased, partial agonist of ADRB1 is effective in reducing neuroinflammation and amyloid beta and tau pathology in the 5XFAD model of AD. Copyright © 2017 Elsevier Ltd. All rights reserved.

Calycosin improves cognitive function in a transgenic mouse model of Alzheimer's disease by activating the protein kinase C pathway.

PubMed

Song, Lei; Li, Xiaoping; Bai, Xiao-Xue; Gao, Jian; Wang, Chun-Yan

2017-11-01

The major pathological changes in Alzheimer's disease are beta amyloid deposits and cognitive impairment. Calycosin is a typical phytoestrogen derived from radix astragali that binds to estrogen receptors to produce estrogen-like effects. Radix astragali Calycosin has been shown to relieve cognitive impairment induced by diabetes mellitus, suggesting calycosin may improve the cognitive function of Alzheimer's disease patients. The protein kinase C pathway is upstream of the mitogen-activated protein kinase pathway and exerts a neuroprotective effect by regulating Alzheimer's disease-related beta amyloid degradation. We hypothesized that calycosin improves the cognitive function of a transgenic mouse model of Alzheimer's disease by activating the protein kinase C pathway. Various doses of calycosin (10, 20 and 40 mg/kg) were intraperitoneally injected into APP/PS1 transgenic mice that model Alzheimer's disease. Calycosin diminished hippocampal beta amyloid, Tau protein, interleukin-1beta, tumor necrosis factor-alpha, acetylcholinesterase and malondialdehyde levels in a dose-dependent manner, and increased acetylcholine and glutathione activities. The administration of a protein kinase C inhibitor, calphostin C, abolished the neuroprotective effects of calycosin including improving cognitive ability, and anti-oxidative and anti-inflammatory effects. Our data demonstrated that calycosin mitigated oxidative stress and inflammatory responses in the hippocampus of Alzheimer's disease model mice by activating the protein kinase C pathway, and thereby improving cognitive function.

Molecular architecture of human prion protein amyloid: a parallel, in-register beta-structure.

PubMed

Cobb, Nathan J; Sönnichsen, Frank D; McHaourab, Hassane; Surewicz, Witold K

2007-11-27

Transmissible spongiform encephalopathies (TSEs) represent a group of fatal neurodegenerative diseases that are associated with conformational conversion of the normally monomeric and alpha-helical prion protein, PrP(C), to the beta-sheet-rich PrP(Sc). This latter conformer is believed to constitute the main component of the infectious TSE agent. In contrast to high-resolution data for the PrP(C) monomer, structures of the pathogenic PrP(Sc) or synthetic PrP(Sc)-like aggregates remain elusive. Here we have used site-directed spin labeling and EPR spectroscopy to probe the molecular architecture of the recombinant PrP amyloid, a misfolded form recently reported to induce transmissible disease in mice overexpressing an N-terminally truncated form of PrP(C). Our data show that, in contrast to earlier, largely theoretical models, the con formational conversion of PrP(C) involves major refolding of the C-terminal alpha-helical region. The core of the amyloid maps to C-terminal residues from approximately 160-220, and these residues form single-molecule layers that stack on top of one another with parallel, in-register alignment of beta-strands. This structural insight has important implications for understanding the molecular basis of prion propagation, as well as hereditary prion diseases, most of which are associated with point mutations in the region found to undergo a refolding to beta-structure.

Regulation of amyloid precursor protein processing by its KFERQ motif.

PubMed

Park, Ji-Seon; Kim, Dong-Hou; Yoon, Seung-Yong

2016-06-01

Understanding of trafficking, processing, and degradation mechanisms of amyloid precursor protein (APP) is important because APP can be processed to produce β-amyloid (Aβ), a key pathogenic molecule in Alzheimer's disease (AD). Here, we found that APP contains KFERQ motif at its C-terminus, a consensus sequence for chaperone-mediated autophagy (CMA) or microautophagy which are another types of autophagy for degradation of pathogenic molecules in neurodegenerative diseases. Deletion of KFERQ in APP increased C-terminal fragments (CTFs) and secreted N-terminal fragments of APP and kept it away from lysosomes. KFERQ deletion did not abolish the interaction of APP or its cleaved products with heat shock cognate protein 70 (Hsc70), a protein necessary for CMA or microautophagy. These findings suggest that KFERQ motif is important for normal processing and degradation of APP to preclude the accumulation of APP-CTFs although it may not be important for CMA or microautophagy. [BMB Reports 2016; 49(6): 337-342].

Trehalose Alters Subcellular Trafficking and the Metabolism of the Alzheimer-associated Amyloid Precursor Protein.

PubMed

Tien, Nguyen T; Karaca, Ilker; Tamboli, Irfan Y; Walter, Jochen

2016-05-13

The disaccharide trehalose is commonly considered to stimulate autophagy. Cell treatment with trehalose could decrease cytosolic aggregates of potentially pathogenic proteins, including mutant huntingtin, α-synuclein, and phosphorylated tau that are associated with neurodegenerative diseases. Here, we demonstrate that trehalose also alters the metabolism of the Alzheimer disease-related amyloid precursor protein (APP). Cell treatment with trehalose decreased the degradation of full-length APP and its C-terminal fragments. Trehalose also reduced the secretion of the amyloid-β peptide. Biochemical and cell biological experiments revealed that trehalose alters the subcellular distribution and decreases the degradation of APP C-terminal fragments in endolysosomal compartments. Trehalose also led to strong accumulation of the autophagic marker proteins LC3-II and p62, and decreased the proteolytic activation of the lysosomal hydrolase cathepsin D. The combined data indicate that trehalose decreases the lysosomal metabolism of APP by altering its endocytic vesicular transport. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Membrane microdomain switching: a regulatory mechanism of amyloid precursor protein processing

PubMed Central

Sakurai, Takashi; Kaneko, Kumi; Okuno, Misako; Wada, Koji; Kashiyama, Taku; Shimizu, Hideaki; Akagi, Takumi; Hashikawa, Tsutomu; Nukina, Nobuyuki

2008-01-01

Neuronal activity has an impact on β cleavage of amyloid precursor protein (APP) by BACE1 to generate amyloid-β peptide (Aβ). However, the molecular mechanisms underlying this effect remain to be elucidated. Cholesterol dependency of β cleavage prompted us to analyze immunoisolated APP-containing detergent-resistant membranes from rodent brains. We found syntaxin 1 as a key molecule for activity-dependent regulation of APP processing in cholesterol-dependent microdomains. In living cells, APP associates with syntaxin 1–containing microdomains through X11–Munc18, which inhibits the APP–BACE1 interaction and β cleavage via microdomain segregation. Phosphorylation of Munc18 by cdk5 causes a shift of APP to BACE1-containing microdomains. Neuronal hyperactivity, implicated in Aβ overproduction, promotes the switching of APP microdomain association as well as β cleavage in a partially cdk5-dependent manner. We propose that microdomain switching is a mechanism of cholesterol- and activity-dependent regulation of APP processing in neurons. PMID:18936252

Transgenic Mice Overexpressing Amyloid Precursor Protein Exhibit Early Metabolic Deficits and a Pathologically Low Leptin State Associated with Hypothalamic Dysfunction in Arcuate Neuropeptide Y Neurons

PubMed Central

Ishii, Makoto; Wang, Gang; Racchumi, Gianfranco; Dyke, Jonathan P.

2014-01-01

Weight loss is a prominent early feature of Alzheimer's disease (AD) that often precedes the cognitive decline and clinical diagnosis. While the exact pathogenesis of AD remains unclear, accumulation of amyloid-β (Aβ) derived from the amyloid precursor protein (APP) in the brain is thought to lead to the neuronal dysfunction and death underlying the dementia. In this study, we examined whether transgenic mice overexpressing the Swedish mutation of APP (Tg2576), recapitulating selected features of AD, have hypothalamic leptin signaling dysfunction leading to early body weight deficits. We found that 3-month-old Tg2576 mice, before amyloid plaque formation, exhibit decreased weight with markedly decreased adiposity, low plasma leptin levels, and increased energy expenditure without alterations in feeding behavior. The expression of the orexigenic neuropeptide Y (NPY) in the hypothalamus to the low leptin state was abnormal at basal and fasting conditions. In addition, arcuate NPY neurons exhibited abnormal electrophysiological responses to leptin in Tg2576 hypothalamic slices or wild-type slices treated with Aβ. Finally, the metabolic deficits worsened as Tg2576 mice aged and amyloid burden increased in the brain. These results indicate that excess Aβ can potentially disrupt hypothalamic arcuate NPY neurons leading to weight loss and a pathologically low leptin state early in the disease process that progressively worsens as the amyloid burden increases. Collectively, these findings suggest that weight loss is an intrinsic pathological feature of Aβ accumulation and identify hypothalamic leptin signaling as a previously unrecognized pathogenic site of action for Aβ. PMID:24990930

Amyloid-β Peptide Exacerbates the Memory Deficit Caused by Amyloid Precursor Protein Loss-of-Function in Drosophila

PubMed Central

Bourdet, Isabelle; Lampin-Saint-Amaux, Aurélie; Preat, Thomas; Goguel, Valérie

2015-01-01

The amyloid precursor protein (APP) plays a central role in Alzheimer’s disease (AD). APP can undergo two exclusive proteolytic pathways: cleavage by the α-secretase initiates the non-amyloidogenic pathway while cleavage by the β-secretase initiates the amyloidogenic pathway that leads, after a second cleavage by the γ-secretase, to amyloid-β (Aβ) peptides that can form toxic extracellular deposits, a hallmark of AD. The initial events leading to AD are still unknown. Importantly, aside from Aβ toxicity whose molecular mechanisms remain elusive, several studies have shown that APP plays a positive role in memory, raising the possibility that APP loss-of-function may participate to AD. We previously showed that APPL, the Drosophila APP ortholog, is required for associative memory in young flies. In the present report, we provide the first analysis of the amyloidogenic pathway’s influence on memory in the adult. We show that transient overexpression of the β-secretase in the mushroom bodies, the center for olfactory memory, did not alter memory. In sharp contrast, β-secretase overexpression affected memory when associated with APPL partial loss-of-function. Interestingly, similar results were observed with Drosophila Aβ peptide. Because Aβ overexpression impaired memory only when combined to APPL partial loss-of-function, the data suggest that Aβ affects memory through the APPL pathway. Thus, memory is altered by two connected mechanisms—APPL loss-of-function and amyloid peptide toxicity—revealing in Drosophila a functional interaction between APPL and amyloid peptide. PMID:26274614

Alzheimer's disease: neuritic plaques and neurofibrillary tangles in human brain identified by FTIR spectroscopy

NASA Astrophysics Data System (ADS)

Choo, Lin-P'ing; Jackson, Michael; Halliday, William C.; Mantsch, Henry H.

1994-01-01

The abnormal abundance of (beta) -amyloid plaques and neurofibrillary tangles are the hallmark of Alzheimer's disease (AD). Human central nervous system (CNS) grey matter was probed for characteristics arising from these pathological features. In AD but not normal grey matter, an IR band at 1615 cm-1 is seen, characteristic of a protein in an aggregated state. We speculate that this band arises from (beta) A4-amyloid protein. AD, and 18q- grey matter spectra show increased intensity of phosphate bands in accordance with known hyperphosphorylation of proteins found in neurofibrillary tangles. These spectral features may be useful in the diagnosis of AD.

Overnutrition Determines LPS Regulation of Mycotoxin Induced Neurotoxicity in Neurodegenerative Diseases.

PubMed

Martins, Ian James

2015-12-10

Chronic neurodegenerative diseases are now associated with obesity and diabetes and linked to the developing and developed world. Interests in healthy diets have escalated that may prevent neurodegenerative diseases such as Parkinson's and Alzheimer's disease. The global metabolic syndrome involves lipoprotein abnormalities and insulin resistance and is the major disorder for induction of neurological disease. The effects of bacterial lipopolysaccharides (LPS) on dyslipidemia and NAFLD indicate that the clearance and metabolism of fungal mycotoxins are linked to hypercholesterolemia and amyloid beta oligomers. LPS and mycotoxins are associated with membrane lipid disturbances with effects on cholesterol interacting proteins, lipoprotein metabolism, and membrane apo E/amyloid beta interactions relevant to hypercholesterolemia with close connections to neurological diseases. The influence of diet on mycotoxin metabolism has accelerated with the close association between mycotoxin contamination from agricultural products such as apple juice, grains, alcohol, and coffee. Cholesterol efflux in lipoproteins and membrane cholesterol are determined by LPS with involvement of mycotoxin on amyloid beta metabolism. Nutritional interventions such as diets low in fat/carbohydrate/cholesterol have become of interest with relevance to low absorption of lipophilic LPS and mycotoxin into lipoproteins with rapid metabolism of mycotoxin to the liver with the prevention of neurodegeneration.

Noopept efficiency in experimental Alzheimer disease (cognitive deficiency caused by beta-amyloid25-35 injection into Meynert basal nuclei of rats).

PubMed

Ostrovskaya, R U; Belnik, A P; Storozheva, Z I

2008-07-01

Experiments on adult Wistar rats showed that injection of beta-amyloid25-35 (2 microg) into Meynert basal nuclei caused long-term memory deficiency which was detected 24 days after this injection by the memory trace retrieval in conditioned passive avoidance reflex (CPAR). The effects of noopept, an original nootropic and neuroprotective dipeptide, on the severity of this cognitive deficiency were studied. Preventive (for 7 days before the injury) intraperitoneal injections of noopept in a dose of 0.5 mg/kg completely prevented mnestic disorders under conditions of this model. Noopept exhibited a significant normalizing effect, if the treatment was started 15 days after the injury, when neurodegenerative changes in the basal nuclei, cortex, and hippocampus were still acutely pronounced. The mechanisms of this effect of the drug are studied, including, in addition to the choline-positive effect, its multicomponent neuroprotective effect and stimulation of production of antibodies to beta-amyloid25-35. Noopept efficiency in many models of Alzheimer disease, its high bioavailability and low toxicity suggest this dipeptide for further studies as a potential agent for the treatment of this condition (initial and moderate phases).

Novel strategies for Alzheimer's disease treatment: An overview of anti-amyloid beta monoclonal antibodies.

PubMed

Rygiel, Katarzyna

2016-01-01

Alzheimer's disease (AD) is a multifactorial, progressive neurodegenerative disorder with a poor prognosis, and thus, novel therapies for AD are certainly needed in a growing population of elderly patients or asymptomatic individuals, who are at risk for AD, worldwide. It has been established that some AD biomarkers such as amyloid-beta load in the brain, precede the onset of the disease, by approximately 20 years. Therefore, the therapy to prevent or effectively treat AD has to be initiated before the emergence of symptoms. A goal of this review is to present the results of recent clinical trials on monoclonal antibodies against amyloid beta, used for the treatment of AD and also to address some of the current challenges and emerging strategies to prevent AD. In recent trials, a monoclonal antibody, i.e. solanezumab has shown some beneficial cognitive effects among mild AD patients. Ongoing studies with gantenerumab and crenezumab will examine when exactly the AD treatment, aimed at modifying the disease course has to be started. This review was based on Medline database search for trials on passive anti-AD immunotherapy, for which the main timeframe was set from 2012 to 2015.

Overnutrition Determines LPS Regulation of Mycotoxin Induced Neurotoxicity in Neurodegenerative Diseases

PubMed Central

Martins, Ian James

2015-01-01

Chronic neurodegenerative diseases are now associated with obesity and diabetes and linked to the developing and developed world. Interests in healthy diets have escalated that may prevent neurodegenerative diseases such as Parkinson’s and Alzheimer’s disease. The global metabolic syndrome involves lipoprotein abnormalities and insulin resistance and is the major disorder for induction of neurological disease. The effects of bacterial lipopolysaccharides (LPS) on dyslipidemia and NAFLD indicate that the clearance and metabolism of fungal mycotoxins are linked to hypercholesterolemia and amyloid beta oligomers. LPS and mycotoxins are associated with membrane lipid disturbances with effects on cholesterol interacting proteins, lipoprotein metabolism, and membrane apo E/amyloid beta interactions relevant to hypercholesterolemia with close connections to neurological diseases. The influence of diet on mycotoxin metabolism has accelerated with the close association between mycotoxin contamination from agricultural products such as apple juice, grains, alcohol, and coffee. Cholesterol efflux in lipoproteins and membrane cholesterol are determined by LPS with involvement of mycotoxin on amyloid beta metabolism. Nutritional interventions such as diets low in fat/carbohydrate/cholesterol have become of interest with relevance to low absorption of lipophilic LPS and mycotoxin into lipoproteins with rapid metabolism of mycotoxin to the liver with the prevention of neurodegeneration. PMID:26690419

Multiscale Molecular Dynamics Simulations of Beta-Amyloid Interactions with Neurons

NASA Astrophysics Data System (ADS)

Qiu, Liming; Vaughn, Mark; Cheng, Kelvin

2012-10-01

Early events of human beta-amyloid protein interactions with cholesterol-containing membranes are critical to understanding the pathogenesis of Alzheimer's disease (AD) and to exploring new therapeutic interventions of AD. Atomistic molecular dynamics (AMD) simulations have been extensively used to study the protein-lipid interaction at high atomic resolutions. However, traditional MD simulations are not efficient in sampling the phase space of complex lipid/protein systems with rugged free energy landscapes. Meanwhile, coarse-grained MD (CGD) simulations are efficient in the phase space sampling but suffered from low spatial resolutions and from the fact that the energy landscapes are not identical to those of the AMD. Here, a multiscale approach was employed to simulate the protein-lipid interactions of beta-amyloid upon its release from proteolysis residing in the neuronal membranes. We utilized a forward (AMD to CGD) and reverse (CGD-AMD) strategy to explore new transmembrane and surface protein configuration and evaluate the stabilization mechanisms by measuring the residue-specific protein-lipid or protein conformations. The detailed molecular interactions revealed in this multiscale MD approach will provide new insights into understanding the early molecular events leading to the pathogenesis of AD.

Amyloid precursor protein and endosomal-lysosomal dysfunction in Alzheimer's disease: inseparable partners in a multifactorial disease.

PubMed

Nixon, Ralph A

2017-07-01

Abnormalities of the endosomal-lysosomal network (ELN) are a signature feature of Alzheimer's disease (AD). These include the earliest known cytopathology that is specific to AD and that affects endosomes and induces the progressive failure of lysosomes, each of which are directly linked by distinct mechanisms to neurodegeneration. The origins of ELN dysfunction and β-amyloidogenesis closely overlap, which reflects their common genetic basis, the established early involvement of endosomes and lysosomes in amyloid precursor protein (APP) processing and clearance, and the pathologic effect of certain APP metabolites on ELN functions. Genes that promote β-amyloidogenesis in AD (APP, PSEN1/2, and APOE4) have primary effects on ELN function. The importance of primary ELN dysfunction to pathogenesis is underscored by the mutations in more than 35 ELN-related genes that, thus far, are known to cause familial neurodegenerative diseases even though different pathogenic proteins may be involved. In this article, I discuss growing evidence that implicates AD gene-driven ELN disruptions as not only the antecedent pathobiology that underlies β-amyloidogenesis but also as the essential partner with APP and its metabolites that drive the development of AD, including tauopathy, synaptic dysfunction, and neurodegeneration. The striking amelioration of diverse deficits in animal AD models by remediating ELN dysfunction further supports a need to integrate APP and ELN relationships, including the role of amyloid-β, into a broader conceptual framework of how AD arises, progresses, and may be effectively therapeutically targeted.-Nixon, R. A. Amyloid precursor protein and endosomal-lysosomal dysfunction in Alzheimer's disease: inseparable partners in a multifactorial disease. © FASEB.

Caspase-6 Activation in Familial Alzheimer Disease Brains Carrying Amyloid Precursor Protein, Presenilin I or Presenilin II Mutations

PubMed Central

Albrecht, Steffen; Bogdanovic, Nenad; Ghetti, Bernardino; Winblad, Bengt; LeBlanc, Andréa C.

2010-01-01

We previously demonstrated the activation of Caspase-6 in the hippocampus and cortex in cases of mild, moderate, severe and very severe Alzheimer disease (AD). To determine whether Caspase-6 is also activated in familial AD, we performed an immunohistochemical analysis of active Caspase-6 and Tau cleaved by Caspase-6 in temporal cortex and hippocampal tissue sections from cases of familial AD. The cases included 5 carrying the amyloid precursor protein K670N, M671L Swedish mutation, 1 carrying the amyloid precursor protein E693G Arctic mutation, 2 each carrying the Presenilin I M146V, F105L, A431E, V261F, Y115C mutations, and 1 with the Presenilin II N141I mutation. Active Caspase-6 immunoreactivity was found in all cases. Caspase-6 immunoreactivity was observed in neuritic plaques or cotton wool plaques in some cases, neuropil threads and neurofibrillary tangles. These results indicate that Caspase-6 is activated in familial forms of AD, as previously observed in sporadic forms. Since sporadic and familial AD cases have similar pathological features, these results support a fundamental role of Caspase-6 in the pathophysiology of both familial and sporadic AD. PMID:19915487

[Rheumatologic and radiologic symptoms of dialysis-associated beta 2-microglobulin amyloidosis: long-term retrospective study of 175 chronic hemodialysis patients].

PubMed

Hermann, E; Mayet, W J; Wandel, E; Scherer, G; Schadmand, S; Klose, K J; Poralla, T; Meyer zum Büschenfelde, K H; Köhler, H

1991-01-01

beta 2-microglobulin amyloidosis is a major complication in chronic hemodialysis patients. Destructive arthropathy, spondylarthropathy, and carpal tunnel syndrome are clinical manifestations of beta 2M amyloid depositions within the joints, intervertebral discs, and tendon sheets. We have investigated the prevalence of beta 2M amyloidosis associated radiological joint lesions in a population of 175 patients on chronic hemodialysis. In 32 of 175 patients the diagnosis of amyloidosis arthropathy and spondylarthropathy was made by radiomorphological criteria. These 32 patients were asked about rheumatic symptoms (localisation and character of pain, synovitis, carpal tunnel syndrome, influence of dialysis membrane on pain) and examined clinically. Bilateral pain of the shoulders or wrists was complained by most of the patients. 24 of the 32 patients had signs of secondary hyperparathyroidism besides beta 2M-amyloidosis. 29 patients had a carpal tunnel syndrome, 23 of whom had to be operated. beta 2M-amyloid was histochemically demonstrated in all of these 23 cases. Renal transplantation led to immediate pain relief in 3 out of 3 patients, a change of the dialysis membrane (high-flux membrane) improved chronic pain in the majority of patients.

Amyloid Plaques in PSAPP Mice Bind Less Metal than Plaques in Human Alzheimer's Disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leskovjan, A.; Lanzirotti, A; Miller, L

2009-01-01

Amyloid beta (A{Beta}) is the primary component of Alzheimer's disease (AD) plaques, a key pathological feature of the disease. Metal ions of zinc (Zn), copper (Cu), iron (Fe), and calcium (Ca) are elevated in human amyloid plaques and are thought to be involved in neurodegeneration. Transgenic mouse models of AD also exhibit amyloid plaques, but fail to exhibit the high degree of neurodegeneration observed in humans. In this study, we imaged the Zn, Cu, Fe, and Ca ion distribution in the PSAPP transgenic mouse model representing end-stage AD (N = 6) using synchrotron X-ray fluorescence (XRF) microprobe. In order tomore » account for differences in density in the plaques, the relative protein content was imaged with synchrotron Fourier transform infrared microspectroscopy (FTIRM) on the same samples. FTIRM results revealed a 61% increase in protein content in the plaques compared to the surrounding tissue. After normalizing to protein density, we found that the PSAPP plaques contained only a 29% increase in Zn and there was actually less Cu, Fe, and Ca in the plaque compared to the surrounding tissue. Since metal binding to A{beta} is thought to induce redox chemistry that is toxic to neurons, the reduced metal binding in PSAPP mice is consistent with the lack of neurodegeneration in these animals. These findings were in stark contrast to the high metal ion content observed in human AD plaques, further implicating the role of metal ions in human AD pathology.« less

Amyloid and the origin of life: self-replicating catalytic amyloids as prebiotic informational and protometabolic entities.

PubMed

Maury, Carl Peter J

2018-05-01

A crucial stage in the origin of life was the emergence of the first molecular entity that was able to replicate, transmit information, and evolve on the early Earth. The amyloid world hypothesis posits that in the pre-RNA era, information processing was based on catalytic amyloids. The self-assembly of short peptides into β-sheet amyloid conformers leads to extraordinary structural stability and novel multifunctionality that cannot be achieved by the corresponding nonaggregated peptides. The new functions include self-replication, catalytic activities, and information transfer. The environmentally sensitive template-assisted replication cycles generate a variety of amyloid polymorphs on which evolutive forces can act, and the fibrillar assemblies can serve as scaffolds for the amyloids themselves and for ribonucleotides proteins and lipids. The role of amyloid in the putative transition process from an amyloid world to an amyloid-RNA-protein world is not limited to scaffolding and protection: the interactions between amyloid, RNA, and protein are both complex and cooperative, and the amyloid assemblages can function as protometabolic entities catalyzing the formation of simple metabolite precursors. The emergence of a pristine amyloid-based in-put sensitive, chiroselective, and error correcting information-processing system, and the evolvement of mutualistic networks were, arguably, of essential importance in the dynamic processes that led to increased complexity, organization, compartmentalization, and, eventually, the origin of life.

Clinical features of early onset, familial Alzheimer`s disease linked to chromosome 14

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mullan, M.; Bennett, C.; Figueredo, C.

1995-02-27

Early onset familial Alzheimer`s disease (AD) has an autosomal dominant mode of inheritance. Two genes are responsible for the majority of cases of this subtype of AD. Mutations in the {beta}-amyloid precursor protein ({beta}APP) gene on chromosome 21 have been shown to completely cosegregate with the disease. We and others have previously described the clinical features of families with {beta}APP mutations at the codon 717 locus in an attempt to define the phenotype associated with a valine to isoleucine (Val {r_arrow} Ile) or a valine to glycine (Val {r_arrow} Gly) change. More recently, a second locus for very early onsetmore » disease has been localized to chromosome 14. The results of linkage studies in some families suggesting linkage to both chromosomes have been explained by the suggestion of a second (centromeric) locus on chromosome 21. Here we report the clinical features and genetic analysis of a British pedigree (F74) with early onset AD in which neither the {beta}APP locus nor any other chromosome 21 locus segregates with the disease, but in which good evidence is seen for linkage on the long arm of chromosome 14. In particular we report marker data suggesting that the chromosome 14 disease locus is close to D14S43 and D14S77. Given the likelihood that F74 represents a chromosome 14 linked family, we describe the clinical features and make a limited clinical comparison with the {beta}APP717 Val {r_arrow} Ile and {beta}APP717 Val {r_arrow} Gly encoded families that have been previously described. We conclude that although several previously reported clinical features occur to excess in early onset familial AD, no single clinical feature demarcates either the chromosome 14 or {beta}APP codon 717 mutated families except mean age of onset. 52 refs., 2 figs., 5 tabs.« less

Total flavonoid extract from Dracoephalum moldavica L. attenuates β-amyloid-induced toxicity through anti-amyloidogenesic and neurotrophic pathways.

PubMed

Liu, Qing-Shan; Jiang, Hai-Lun; Wang, Yu; Wang, Lin-Lin; Zhang, Jun-Xia; He, Cheng-Hui; Shao, Shuai; Zhang, Tian-Tai; Xing, Jian-Guo; Liu, Rui

2018-01-15

Alzheimer's disease (AD) is an incurable neurodegenerative disorder characterized by global cognitive impairment that involves accumulation of amyloid-beta peptides (Aβ) in the brain. Herbal approaches can be used as alternative medicines to slow the progression of AD. This study aimed to determine the beneficial effects and potential underlying mechanisms of total flavonoid extract from Dracoephalum moldavica L. (TFDM) for attenuating Alzheimer-related deficits induced by Aβ. We used amyloid precursor protein (APP) and presenilin 1 (PS1) double transgenic mice and copper-injured APP Swedish mutation overexpressing SH-SY5Y cells to evaluate the beneficial effects of TFDM. Further, identifying the mechanisms of action was conducted on anti-amyloidogenic and neurotrophic transductions. Our results indicated that TFDM treatment ameliorated cognitive impairments and neurodegeneration and improved the antioxidant defense system in APP/PS1 mice. TFDM also reduced Aβ burden by relieving Aβ deposition, decreasing insoluble Aβ levels, and inhibiting β-amyloidogenic processing pathway involving downregulation of β-secretase and β-C-terminal fragment in the brain. In the in vitro model of AD, TFDM treatment protected injured cells, and combined with the beneficial effects of decreasing APP levels, lowered Aβ 1-42 and regulated the redox imbalance. Moreover, TFDM preserved the extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor pathway both in vitro and in vivo. In conclusion, TFDM clearly demonstrated neuroprotective effects by restoring the anti-amyloidogenic and neurotrophic transductions in the context of AD-associated deficits. These findings indicate the potential use of herb-based substances as supplements or potential alternative supplements for attenuating the progression of AD. Copyright © 2017. Published by Elsevier Inc.

Amyloid-β expression in retrosplenial cortex of 3xTg-AD mice: relationship to cholinergic axonal afferents from medial septum

PubMed Central

Robertson, Richard T.; Baratta, Janie; Yu, Jen; LaFerla, Frank M.

2009-01-01

Triple transgenic (3xTg-AD) mice harboring the presenilin 1, amyloid precursor protein, and tau transgenes (Oddo et al., 2003) display prominent levels of amyloid-beta (Aβ) immunoreactivity in forebrain regions. The Aβ immunoreactivity is first seen intracellularly in neurons and later as extracellular plaque deposits. The present study examined Aβ immunoreactivity that occurs in layer III of the granular division of retrosplenial cortex (RSg). This pattern of Aβ immunoreactivity in layer III of RSg develops relatively late, and is seen in animals older than 14 mo. The appearance of the Aβ immunoreactivity is similar to an axonal terminal field and thus may offer a unique opportunity to study the relationship between afferent projections and the formation of Aβ deposits. Axonal tract tracing techniques demonstrated that the pattern of axon terminal labeling in layer III of RSg, following placement of DiI in medial septum, is remarkably similar to the pattern of cholinergic axons in RSg, as detected by acetylcholinesterase histochemical staining, choline acetyltransferase immunoreactivity, or p75 receptor immunoreactivity; this pattern also is strikingly similar to the band of Aβ immunoreactivity. In animals sustaining early damage to the medial septal nucleus (prior to the advent of Aβ immunoreactivity), the band of Aβ in layer III of RSg does not develop; the corresponding band of cholinergic markers also is eliminated. In older animals (after the appearance of the Aβ immunoreactivity) damage to cholinergic afferents by electrolytic lesions, immunotoxin lesions, or cutting the cingulate bundle, result in a rapid loss of the cholinergic markers and a slower reduction of Aβ immunoreactivity. These results suggest that the septal cholinergic axonal projections transport Aβ or APP to layer III of RSg. PMID:19772895

The Ames dwarf mutation attenuates Alzheimer's disease phenotype of APP/PS1 mice.

PubMed

Puig, Kendra L; Kulas, Joshua A; Franklin, Whitney; Rakoczy, Sharlene G; Taglialatela, Giulio; Brown-Borg, Holly M; Combs, Colin K

2016-04-01

APP/PS1 double transgenic mice expressing human mutant amyloid precursor protein (APP) and presenilin-1 (PS1) demonstrate robust brain amyloid beta (Aβ) peptide containing plaque deposition, increased markers of oxidative stress, behavioral dysfunction, and proinflammatory gliosis. On the other hand, lack of growth hormone, prolactin, and thyroid-stimulating hormone due to a recessive mutation in the Prop 1 gene (Prop1df) in Ames dwarf mice results in a phenotype characterized by potentiated antioxidant mechanisms, improved learning and memory, and significantly increased longevity in homozygous mice. Based on this, we hypothesized that a similar hormone deficiency might attenuate disease changes in the brains of APP/PS1 mice. To test this idea, APP/PS1 mice were crossed to the Ames dwarf mouse line. APP/PS1, wild-type, df/+, df/df, df/+/APP/PS1, and df/df/APP/PS1 mice were compared at 6 months of age through behavioral testing and assessing amyloid burden, reactive gliosis, and brain cytokine levels. df/df mice demonstrated lower brain growth hormone and insulin-like growth factor 1 concentrations. This correlated with decreased astrogliosis and microgliosis in the df/df/APP/PS1 mice and, surprisingly, reduced Aβ plaque deposition and Aβ 1-40 and Aβ 1-42 concentrations. The df/df/APP/PS1 mice also demonstrated significantly elevated brain levels of multiple cytokines in spite of the attenuated gliosis. These data indicate that the df/df/APP/PS1 line is a unique resource in which to study aging and resistance to disease and suggest that the affected pituitary hormones may have a role in regulating disease progression. Copyright © 2016 Elsevier Inc. All rights reserved.

Interhemispheric EEG differences in olfactory bulbectomized rats with different cognitive abilities and brain beta-amyloid levels.

PubMed

Bobkova, Natalia; Vorobyov, Vasily; Medvinskaya, Natalia; Aleksandrova, Irina; Nesterova, Inna

2008-09-26

Alterations in electroencephalogram (EEG) asymmetry and deficits in interhemispheric integration of information have been shown in patients with Alzheimer's disease (AD). However, no direct evidence of an association between EEG asymmetry, morphological markers in the brain, and cognition was found either in AD patients or in AD models. In this study we used rats with bilateral olfactory bulbectomy (OBX) as one of the AD models and measured their learning/memory abilities, brain beta-amyloid levels and EEG spectra in symmetrical frontal and occipital cortices. One year after OBX or sham-surgery, the rats were tested with the Morris water paradigm and assigned to three groups: sham-operated rats, SO, and OBX rats with virtually normal, OBX(+), or abnormal, OBX(-), learning (memory) abilities. In OBX vs. SO, the theta EEG activity was enhanced to a higher extent in the right frontal cortex and in the left occipital cortex. This produced significant interhemispheric differences in the frontal cortex of the OBX(-) rats and in the occipital cortex of both OBX groups. The beta1 EEG asymmetry in SO was attenuated in OBX(+) and completely eliminated in OBX(-). OBX produced highly significant beta2 EEG decline in the right frontal cortex, with OBX(-)>OBX(+) rank order of strength. The beta-amyloid level, examined by post-mortem immunological DOT-analysis in the cortex-hippocampus samples, was about six-fold higher in OBX(-) than in SO, but significantly less (enhanced by 82% vs. SO) in OBX(+) than in OBX(-). The involvement of the brain mediatory systems in the observed EEG asymmetry differences is discussed.

Destruction of {alpha}-synuclein based amyloid fibrils by a low temperature plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karakas, Erdinc; Laroussi, Mounir; Munyanyi, Agatha

2010-10-04

Amyloid fibrils are ordered beta-sheet aggregates that are associated with a number of neurodegenerative diseases such as Alzheimer and Parkinson. At present, there is no cure for these progressive and debilitating diseases. Here we report initial studies that indicate that low temperature atmospheric pressure plasma can break amyloid fibrils into smaller units in vitro. The plasma was generated by the 'plasma pencil', a device capable of emitting a long, low temperature plasma plume/jet. This avenue of research may facilitate the development of a plasma-based medical treatment.

Towards revealing the structure of bacterial inclusion bodies.

PubMed

Wang, Lei

2009-01-01

Protein aggregation is a widely observed phenomenon in human diseases, biopharmaceutical production, and biological research. Protein aggregates are generally classified as highly ordered, such as amyloid fibrils, or amorphous, such as bacterial inclusion bodies. Amyloid fibrils are elongated filaments with diameters of 6-12 nm, they are comprised of residue-specific cross-beta structure, and display characteristic properties, such as binding with amyloid-specific dyes. Amyloid fibrils are associated with dozens of human pathological conditions, including Alzheimer disease and prion diseases. Distinguished from amyloid fibrils, bacterial inclusion bodies display apparent amorphous morphology. Inclusion bodies are formed during high-level recombinant protein production, and formation of inclusion bodies is a major concern in biotechnology. Despite of the distinctive morphological difference, bacterial inclusion bodies have been found to have some amyloid-like properties, suggesting that they might contain structures similar to amyloid-like fibrils. Recent structural data further support this hypothesis, and this review summarizes the latest progress towards revealing the structural details of bacterial inclusion bodies.

Peroxisome proliferator-activated receptor {gamma} is expressed in hippocampal neurons and its activation prevents {beta}-amyloid neurodegeneration: role of Wnt signaling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inestrosa, Nibaldo C.; Godoy, Juan A.; MIFAB, Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Santiago

2005-03-10

The molecular pathogenesis of Alzheimer's disease (AD) involves the participation of the amyloid-{beta}-peptide (A{beta}), which plays a critical role in the neurodegeneration that triggers the disease. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors, which are members of the nuclear receptor family. We report here that (1) PPAR{gamma} is present in rat hippocampal neurons in culture. (2) Activation of PPAR{gamma} by troglitazone and rosiglitazone protects rat hippocampal neurons against A{beta}-induced neurodegeneration, as shown by the 3-[4,5 -2yl]-2,5-diphenyltetrazolium bromide (MTT) reduction assay, immunofluorescence using an anti-heavy neurofilament antibody, and quantitative electron microscopy. (3) Hippocampal neurons treated with several PPAR{gamma} agonists, includingmore » troglitazone, rosiglitazone, and ciglitazone, prevent the excitotoxic A{beta}-induced rise in bulk-free Ca{sup 2+}. (4) PPAR{gamma} activation results in the modulation of Wnt signaling components, including the inhibition of glycogen synthase kinase-3{beta} (GSK-3{beta}) and an increase of the cytoplasmic and nuclear {beta}-catenin levels. We conclude that the activation of PPAR{gamma} prevents A{beta}-induced neurodegeneration by a mechanism that may involve a cross talk between neuronal PPAR{gamma} and the Wnt signaling pathway. More important, the fact that the activation of PPAR{gamma} attenuated A{beta}-dependent neurodegeneration opens the possibility to fight AD from a new therapeutic perspective.« less

Self-Assembling Protein Nanostructures - Towards Active Functionality

DTIC Science & Technology

2011-04-22

the (alpha-beta)8 barrel. A model thermophilic enzyme , natively a tetramer, was engineered as a monomer, a dimer (submitted to Biochimica et...problem. Objective one successfully built high surface area nanoscaffolds from amyloid fibrils, and demonstrated that enzyme activity could be attached...quaternary structure, amyloid fibril, organophosphorous hydrolase, enzyme Juliet Gerrard University of Canterbury 20 Kirkwood Ave Ilam 8041 - REPORT

Plasma Membrane Protein Profiling in Beta-Amyloid-Treated Microglia Cell Line.

PubMed

Correani, Virginia; Di Francesco, Laura; Mignogna, Giuseppina; Fabrizi, Cinzia; Leone, Stefano; Giorgi, Alessandra; Passeri, Alessia; Casata, Roberto; Fumagalli, Lorenzo; Maras, Bruno; Schininà, M Eugenia

2017-09-01

In the responsiveness of microglia to toxic stimuli, plasma membrane proteins play a key role. In this study we treated with a synthetic beta amyloid peptide murine microglial cells metabolically differently labelled with stable isotope amino acids (SILAC). The plasma membrane was selectively enriched by a multi-stage aqueous two-phase partition system. We were able to identify by 1D-LC-MS/MS analyses 1577 proteins, most of them are plasma membrane proteins according to the Gene Ontology annotation. An unchanged level of amyloid receptors in this data set suggests that microglia preserve their responsiveness capability to the environment even after 24-h challenge with amyloid peptides. On the other hand, 14 proteins were observed to change their plasma membrane abundance to a statistically significant extent. Among these, we proposed as reliable biomarkers of the inflammatory microglia phenotype in AD damaged tissues MAP/microtubule affinity-regulating kinase 3 (MARK3), Interferon-induced transmembrane protein 3 (IFITM3), Annexins A5 and A7 (ANXA5, ANXA7) and Neuropilin-1 (NRP1), all proteins known to be involved in the inflammation processes and in microtubule network assembly rate. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Heat-shock protein HSP70 protects neuroblastoma cells SK-N-SH from the neurotoxic effects hydrogen peroxide and the β-amyloid peptide].

PubMed

Yurinskaya, M M; Mit'kevich, V A; Barykin, E P; Garbuz, D G; Evgen'ev, M B; Makarov, A A; Vinokurov, M G

2015-01-01

Neuronal cell death in Alzheimer's disease is associated with the development of oxidative stress caused by the reactive oxygen species (ROS), which can be generated as a result of the effect of beta-amyloid peptides. One of the sources of ROS is hydrogen peroxide, inducing the apoptosis and necrosis of neural tissue cells. The mechanism of hydrogen peroxide apoptotic action includes launching signaling pathways that involve protein kinases PI3K, p38MAPK, JNK and ERK. Oxidative stress leads to increased synthesis of heat-shock proteins in the cells including HSP70. It was shown that the exogenous HSP70 could reduce generation of ROS in cells. In this study, we determined how HSP70 affected apoptosis and necrosis in human neuroblastoma cells SK-N-SH, induced by hydrogen peroxide and β-amyloid peptide Aβ(1-42). It was shown that HSP70 reduces the cytotoxic effects of hydrogen peroxide and beta-amyloid, and protein kinases PI3K and JNK play an important role in the mechanism of HSP70 protective effect on the peroxide induced apoptosis in SK-N-SH cells.

Transient increase in sAPPα secretion in response to Aβ1-42 oligomers: an attempt of neuronal self-defense?

PubMed

Rose, Christiane; Dorard, Emilie; Audrain, Mickael; Gorisse-Hussonnois, Lucie; Cartier, Nathalie; Braudeau, Jérome; Allinquant, Bernadette

2018-01-01

Amyloid precursor protein (APP), a key molecule of Alzheimer disease, is metabolized in 2 antagonist pathways generating the soluble APP alpha (sAPPα) having neuroprotective properties and the beta amyloid (Aβ) peptide at the origin of neurotoxic oligomers, particularly Aβ1-42. Whether extracellular Aβ1-42 oligomers modulate the formation and secretion of sAPPα is not known. We report here that the addition of Aβ1-42 oligomers to primary cortical neurons induced a transient increase in α-secretase activity and secreted sAPPα 6-9 hours later. Preventing the generation of sAPPα by using small interfering RNAs (siRNAs) for the α-secretases ADAM10 and ADAM17 or for APP led to increased Aβ1-42 oligomer-induced cell death after 24 hours. Neuronal injuries due to oxidative stress or growth factor deprivation also generated sAPPα 7 hours later. Finally, acute injection of Aβ1-42 oligomers into wild-type mouse hippocampi induced transient secretion of sAPPα 48-72 hours later. Altogether, these data suggest that neurons respond to stress by generating sAPPα for their survival. These data must be taken into account when interpreting sAPPα levels as a biomarker in neurological disorders. Copyright © 2017 Elsevier Inc. All rights reserved.

Longitudinal noninvasive magnetic resonance imaging of brain microhemorrhages in BACE inhibitor-treated APP transgenic mice.

PubMed

Beckmann, Nicolau; Doelemeyer, Arno; Zurbruegg, Stefan; Bigot, Karine; Theil, Diethilde; Frieauff, Wilfried; Kolly, Carine; Moulin, Pierre; Neddermann, Daniel; Kreutzer, Robert; Perrot, Ludovic; Brzak, Irena; Jacobson, Laura H; Staufenbiel, Matthias; Neumann, Ulf; Shimshek, Derya R

2016-09-01

Currently, several immunotherapies and BACE (Beta Site APP Cleaving Enzyme) inhibitor approaches are being tested in the clinic for the treatment of Alzheimer's disease. A crucial mechanism-related safety concern is the exacerbation of microhemorrhages, which are already present in the majority of Alzheimer patients. To investigate potential safety liabilities of long-term BACE inhibitor therapy, we used aged amyloid precursor protein (APP) transgenic mice (APP23), which robustly develop cerebral amyloid angiopathy. T2*-weighted magnetic resonance imaging (MRI), a translational method applicable in preclinical and clinical studies, was used for the detection of microhemorrhages throughout the entire brain, with subsequent histological validation. Three-dimensional reconstruction based on in vivo MRI and serial Perls' stained sections demonstrated a one-to-one matching of the lesions thus allowing for their histopathological characterization. MRI detected small Perls' positive areas with a high spatial resolution. Our data demonstrate that volumetric assessment by noninvasive MRI is well suited to monitor cerebral microhemorrhages in vivo. Furthermore, 3 months treatment of aged APP23 with the potent BACE-inhibitor NB-360 did not exacerbate microhemorrhages in contrast to Aβ-antibody β1. These results substantiate the safe use of BACE inhibitors regarding microhemorrhages in long-term clinical studies for the treatment of Alzheimer's disease. Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.

Modulation of inflammation in transgenic models of Alzheimer’s disease

PubMed Central

2014-01-01

Over the past decade the process of inflammation has been a focus of increasing interest in the Alzheimer’s disease (AD) field, not only for its potential role in neuronal degeneration but also as a promising therapeutic target. However, recent research in this field has provided divergent outcomes, largely due to the use of different models and different stages of the disease when the investigations have been carried out. It is now accepted that microglia, and possibly astrocytes, change their activation phenotype during ageing and the stage of the disease, and therefore these are important factors to have in mind to define the function of different inflammatory components as well as potential therapies. Modulating inflammation using animal models of AD has offered the possibility to investigate inflammatory components individually and manipulate inflammatory genes in amyloid precursor protein and tau transgenics independently. This has also offered some hints on the mechanisms by which these factors may affect AD pathology. In this review we examine the different transgenic approaches and treatments that have been reported to modulate inflammation using animal models of AD. These studies have provided evidence that enhancing inflammation is linked with increases in amyloid-beta (Aβ) generation, Aβ aggregation and tau phosphorylation. However, the alterations on tau phosphorylation can be independent of changes in Aβ levels by these inflammatory mediators. PMID:24490742

Effects of cannabidiol interactions with Wnt/β-catenin pathway and PPARγ on oxidative stress and neuroinflammation in Alzheimer's disease.

PubMed

Vallée, Alexandre; Lecarpentier, Yves; Guillevin, Rémy; Vallée, Jean-Noël

2017-10-01

Alzheimer's disease (AD) is a neurodegenerative disease, in which the primary etiology remains unknown. AD presents amyloid beta (Aβ) protein aggregation and neurofibrillary plaque deposits. AD shows oxidative stress and chronic inflammation. In AD, canonical Wingless-Int (Wnt)/β-catenin pathway is downregulated, whereas peroxisome proliferator-activated receptor γ (PPARγ) is increased. Downregulation of Wnt/β-catenin, through activation of glycogen synthase kinase-3β (GSK-3β) by Aβ, and inactivation of phosphatidylinositol 3-kinase/Akt signaling involve oxidative stress in AD. Cannabidiol (CBD) is a non-psychotomimetic phytocannabinoid from Cannabis sativa plant. In PC12 cells, Aβ-induced tau protein hyperphosphorylation is inhibited by CBD. This inhibition is associated with a downregulation of p-GSK-3β, an inhibitor of Wnt pathway. CBD may also increase Wnt/β-catenin by stimulation of PPARγ, inhibition of Aβ and ubiquitination of amyloid precursor protein. CBD attenuates oxidative stress and diminishes mitochondrial dysfunction and reactive oxygen species generation. CBD suppresses, through activation of PPARγ, pro-inflammatory signaling and may be a potential new candidate for AD therapy. © The Author 2017. Published by Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Amyloid-β production via cleavage of amyloid-β protein precursor is modulated by cell density.

PubMed

Zhang, Can; Browne, Andrew; Divito, Jason R; Stevenson, Jesse A; Romano, Donna; Dong, Yuanlin; Xie, Zhongcong; Tanzi, Rudolph E

2010-01-01

Mounting evidence suggests that Alzheimer's disease (AD) is caused by the accumulation of the small peptide, amyloid-β (Aβ), a proteolytic cleavage product of amyloid-β protein precursor (AβPP). Aβ is generated through a serial cleavage of AβPP by β- and γ-secretase. Aβ40 and Aβ42 are the two main components of amyloid plaques in AD brains, with Aβ42 being more prone to aggregation. AβPP can also be processed by α-secretase, which cleaves AβPP within the Aβ sequence, thereby preventing the generation of Aβ. Little is currently known regarding the effects of cell density on AβPP processing and Aβ generation. Here we assessed the effects of cell density on AβPP processing in neuronal and non-neuronal cell lines, as well as mouse primary cortical neurons. We found that decreased cell density significantly increases levels of Aβ40, Aβ42, total Aβ, and the ratio of Aβ42: Aβ40. These results also indicate that cell density is a significant modulator of AβPP processing. Overall, these findings carry profound implications for both previous and forthcoming studies aiming to assess the effects of various conditions and genetic/chemical factors, e.g., novel drugs on AβPP processing and Aβ generation in cell-based systems. Moreover, it is interesting to speculate whether cell density changes in vivo may also affect AβPP processing and Aβ levels in the AD brain.

Amyloid Precursor Protein and Alpha Synuclein Translation, Implications for Iron and Inflammation in Neurodegenerative diseases

PubMed Central

Cahill, Catherine M.; Lahiri, Debomoy K.; Huang, Xudong; Rogers, Jack T.

2014-01-01

Summary Recent studies that alleles in the hemochromatosis gene may accelerate the onset of Alzheimer's disease (AD) by five years have validated interest in the model in which metals (particularly iron) accelerate disease course. Biochemical and biophysical measurements demonstrated the presence of elevated levels of neurotoxic copper, zinc and iron in the brains of AD patients. Intracellular levels of amyloid precursor protein (APP) holoprotein were shown to be modulated via iron by a mechanism that is similar to the translation control of the ferritin L- and H mRNAs by Iron-responsive Element (IRE) RNA stem loops in their 5′untranslated regions (5′UTRs). Recently, we reported a putative IRE-like sequence to be present in the 5′UTR of the Parkinson's disease (PD) specific alpha synuclein (ASYN) transcript. ASYN encodes the non-Aβ component (NAC) of amyloid plaques. The demonstration of iron-dependent translation of APP mRNA, the involvement of metals in the plaque of AD patients and of increased iron in striatal neurons in the Substantia nigra (SN) of PD patients, have each encouraged the development of metal attenuating agents and iron chelators as a major new therapeutic strategy for the treatment of these neurodegenerative diseases. In the case of AD, metal based therapeutics may ultimately prove more cost effective than the use of an amyloid vaccine as the preferred anti-amyloid therapeutic strategy to ameliorate the cognitive decline of AD patients. PMID:19166904

An Aberrant Phosphorylation of Amyloid Precursor Protein Tyrosine Regulates Its Trafficking and the Binding to the Clathrin Endocytic Complex in Neural Stem Cells of Alzheimer's Disease Patients

PubMed Central

Poulsen, Ebbe T.; Iannuzzi, Filomena; Rasmussen, Helle F.; Maier, Thorsten J.; Enghild, Jan J.; Jørgensen, Arne L.; Matrone, Carmela

2017-01-01

Alzheimer's disease (AD) is the most common cause of dementia and is likely caused by defective amyloid precursor protein (APP) trafficking and processing in neurons leading to amyloid plaques containing the amyloid-β (Aβ) APP peptide byproducts. Understanding how APP is targeted to selected destinations inside neurons and identifying the mechanisms responsible for the generation of Aβ are thus the keys for the advancement of new therapies. We previously developed a mouse model with a mutation at tyrosine (Tyr) 682 in the C-terminus of APP. This residue is needed for APP to bind to the coating protein Clathrin and to the Clathrin adaptor protein AP2 as well as for the correct APP trafficking and sorting in neurons. By extending these findings to humans, we found that APP binding to Clathrin is decreased in neural stem cells from AD sufferers. Increased APP Tyr phosphorylation alters APP trafficking in AD neurons and it is associated to Fyn Tyr kinase activation. We show that compounds affecting Tyr kinase activity and counteracting defects in AD neurons can control APP location and compartmentalization. APP Tyr phosphorylation is thus a potential therapeutic target for AD. PMID:28360834

Proactive Semantic Interference is Associated with Total and Regional Abnormal Amyloid Load in Non-Demented Community-Dwelling Elders: A Preliminary Study.

PubMed

Loewenstein, David A; Greig, Maria T; Curiel, Rosie; Rodriguez, Rosemarie; Wicklund, Meredith; Barker, Warren W; Hidalgo, Jacqueline; Rosado, Marian; Duara, Ranjan

2015-12-01

To evaluate the relationship between susceptibility to proactive semantic interference (PSI) and retroactive semantic interference (RSI) and brain amyloid load in non-demented elders. 27 participants (11 cognitively normal [CN] with subjective memory complaints, 8 CN without memory complaints, and 8 with mild cognitive impairment [MCI]) underwent complete neurological and neuropsychological evaluations. Participants also received the Semantic Interference Test (SIT) and AV-45 amyloid PET imaging. High levels of association were present between total amyloid load, regional amyloid levels, and the PSI measure (in the entire sample and a subsample excluding MCI subjects). RSI and other memory measures showed much weaker associations or no associations with total and regional amyloid load. No associations between amyloid levels and non-memory performance were observed. In non-demented individuals, vulnerability to PSI was highly associated with total and regional beta-amyloid load and may be an early cognitive marker of brain pathology. Copyright © 2015 American Association for Geriatric Psychiatry. Published by Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vitiello, Giuseppe; CSGI; Grimaldi, Manuela

Highlights: Black-Right-Pointing-Pointer iA{beta}5p shows a significant tendency to deeply penetrates the hydrophobic core of lipid membrane. Black-Right-Pointing-Pointer A{beta}(25-35) locates in the external region of the membrane causing a re-positioning of CHOL. Black-Right-Pointing-Pointer iA{beta}5p withholds cholesterol in the inner hydrophobic core of the lipid membrane. Black-Right-Pointing-Pointer iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane. -- Abstract: Alzheimer's disease is characterized by the deposition of aggregates of the {beta}-amyloid peptide (A{beta}) in the brain. A potential therapeutic strategy for Alzheimer's disease is the use of synthetic {beta}-sheet breaker peptides, which are capable of binding A{beta} but unable to become part ofmore » a {beta}-sheet structure, thus inhibiting the peptide aggregation. Many studies suggest that membranes play a key role in the A{beta} aggregation; consequently, it is strategic to investigate the interplay between {beta}-sheet breaker peptides and A{beta} in the presence of lipid bilayers. In this work, we focused on the effect of the {beta}-sheet breaker peptide acetyl-LPFFD-amide, iA{beta}5p, on the interaction of the A{beta}(25-35) fragment with lipid membranes, studied by Electron Spin Resonance spectroscopy, using spin-labeled membrane components (either phospholipids or cholesterol). The ESR results show that iA{beta}5p influences the A{beta}(25-35) interaction with the bilayer through a cholesterol-mediated mechanism: iA{beta}5p withholds cholesterol in the inner hydrophobic core of the bilayer, making the interfacial region more fluid and capable to accommodate A{beta}(25-35). As a consequence, iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane, which is the first step of the {beta}-amyloid aggregation process.« less

The amyloid fold of Gad m 1 epitopes governs IgE binding

PubMed Central

Sánchez, Rosa; Martínez, Javier; Castro, Ana; Pedrosa, María; Quirce, Santiago; Rodríguez-Pérez, Rosa; Gasset, María

2016-01-01

Amyloids are polymeric structural states formed from locally or totally unfolded protein chains that permit surface reorganizations, stability enhancements and interaction properties that are absent in the precursor monomers. β-Parvalbumin, the major allergen in fish allergy, forms amyloids that are recognized by IgE in the patient sera, suggesting a yet unknown pathological role for these assemblies. We used Gad m 1 as the fish β-parvalbumin model and a combination of approaches, including peptide arrays, recombinant wt and mutant chains, biophysical characterizations, protease digestions, mass spectrometry, dot-blot and ELISA assays to gain insights into the role of amyloids in the IgE interaction. We found that Gad m 1 immunoreactive regions behave as sequence-dependent conformational epitopes that provide a 1000-fold increase in affinity and the structural repetitiveness required for optimal IgE binding and cross-linking upon folding into amyloids. These findings support the amyloid state as a key entity in type I food allergy. PMID:27597317

Therapeutic approaches of leptin in Alzheimer's disease.

PubMed

Carro, Eva M

2009-11-01

Novel approaches in the understanding of the neurodegeneration observed in Alzheimer's disease (AD), involving neurochemical as well as biochemical techniques are being developed, opening up new possibilities in the direction of a metabolic degeneration. Indeed, brain lipids are closely involved in amyloid beta-related pathogenic pathways. An important modulator of lipid homeostasis is the pluripotent peptide leptin, which has been shown to reduce amyloid beta levels and tau-related pathological pathways, the major pathological hallmarks of AD. These data suggest that leptin holds promise as a novel therapeutic tool for AD. In this article, with some patent literature we will review here some of the most promising approaches involving leptin to cure and prevent, rather than to treat, AD symptoms.

Subjective cognitive complaints, personality and brain amyloid-beta in cognitively normal older adults

PubMed Central

Snitz, Beth E.; Weissfeld, Lisa A.; Cohen, Ann D.; Lopez, Oscar L.; Nebes, Robert D.; Aizenstein, Howard J.; McDade, Eric; Price, Julie C.; Mathis, Chester A.; Klunk, William E.

2015-01-01

Objectives Subjective cognitive complaints in otherwise normal aging are common but may be associated with preclinical Alzheimer Disease in some individuals. Little is known about who is mostly likely to show associations between cognitive complaints and preclinical Alzheimer pathology. We sought to 1) demonstrate associations between subjective complaints and brain amyloid-β in cognitively normal older adults; 2) to explore personality factors as potential moderators of this association. Design Cross-sectional observational study. Setting Clinical neuroimaging research center. Participants Community volunteer sample of 92 healthy older adults, screened for normal cognition with comprehensive neuropsychological evaluation. Measurements Subjective cognitive self-report measures included the Memory Functioning Questionnaire, Cognitive Failures Questionnaire, and the Subjective Cognitive Complaint Scale. Personality was measured with the NEO Five Factor Inventory. Brain amyloid-β deposition was assessed with Pittsburgh compound B (PiB)-PET imaging. Results One of three cognitive complaint measures, the Memory Functioning Questionnaire, was associated with global PiB retention (standardized beta =−.230, p=.046, adjusting for age, sex and depressive symptoms). Neuroticism moderated this association such that only high neuroticism individuals showed the predicted pattern of high complaint – high amyloid-β association. Conclusions Evidence for association between subjective cognition and brain amyloid-β deposition in healthy older adults is demonstrable but measure-specific. Neuroticism may moderate the MFQ – amyloid-β association such that it is observed in the context of higher trait neuroticism. Subjective cognitive complaints and neuroticism may reflect a common susceptibility toward psychological distress and negative affect, which are in turn risk factors for cognitive decline in aging and incident Alzheimer Disease. PMID:25746485

Tuning the stereo-hindrance of a curcumin scaffold for the selective imaging of the soluble forms of amyloid beta species.

PubMed

Li, Yuyan; Yang, Jian; Liu, Hongwu; Yang, Jing; Du, Lei; Feng, Haiwei; Tian, Yanli; Cao, Jianqin; Ran, Chongzhao

2017-11-01

Amyloid peptides and proteins are associated with the pathologies of numerous diseases. In the progression of a disease, amyloids exist in soluble and insoluble forms, which are the dominant species at different stages of the disease and they have different degrees of toxicity. However, differentiating between the soluble and insoluble forms is very challenging with small molecule probes due to multiple obstacles that need to be overcome. Inspired by the recognition principle of antibodies for sAβ, we hypothesized that the accessibility/tightness of soluble and insoluble amyloids could be utilized to design imaging probes to recognize different amyloid forms and the stereo-hindrance tuning strategy could be used to design imaging probes for selectively detecting the soluble amyloid beta (sAβ) species in Alzheimer's disease (AD). Herein, we demonstrated that tuning the stereo-hindrance of the phenoxy-alkyl chains at the 4-position of a curcumin scaffold could lead to certain selectivity for sAβ over insoluble Aβs (insAβ). Among the designed compounds, CRANAD-102 showed a 68-fold higher affinity for sAβ than for insAβ (7.5 ± 10 nM vs. 505.9 ± 275.9 nM). Moreover, our imaging data indicated that CRANAD-102 was indeed capable of detecting sAβ in vivo using 4 month old APP/PS1 mice, in which sAβ is the predominant species in the brain. In addition, we also demonstrated that CRANAD-102 could be used to monitor the increase in sAβ loading from the ages of 4 months old to 12 months old. We believe that CRANAD-102 can be a useful probe for selectively detecting sAβ species in AD and that our probe designing strategy can be applied to other amyloids and will have tremendous impact on AD drug development and other amyloid research.

Direct interaction of beta-amyloid with Na,K-ATPase as a putative regulator of the enzyme function

NASA Astrophysics Data System (ADS)

Petrushanko, Irina Yu.; Mitkevich, Vladimir A.; Anashkina, Anastasia A.; Adzhubei, Alexei A.; Burnysheva, Ksenia M.; Lakunina, Valentina A.; Kamanina, Yulia V.; Dergousova, Elena A.; Lopina, Olga D.; Ogunshola, Omolara O.; Bogdanova, Anna Yu.; Makarov, Alexander A.

2016-06-01

By maintaining the Na+ and K+ transmembrane gradient mammalian Na,K-ATPase acts as a key regulator of neuronal electrotonic properties. Na,K-ATPase has an important role in synaptic transmission and memory formation. Accumulation of beta-amyloid (Aβ) at the early stages of Alzheimer’s disease is accompanied by reduction of Na,K-ATPase functional activity. The molecular mechanism behind this phenomenon is not known. Here we show that the monomeric Aβ(1-42) forms a tight (Kd of 3 μM), enthalpy-driven equimolar complex with α1β1 Na,K-ATPase. The complex formation results in dose-dependent inhibition of the enzyme hydrolytic activity. The binding site of Aβ(1-42) is localized in the “gap” between the alpha- and beta-subunits of Na,K-ATPase, disrupting the enzyme functionality by preventing the subunits from shifting towards each other. Interaction of Na,K-ATPase with exogenous Aβ(1-42) leads to a pronounced decrease of the enzyme transport and hydrolytic activity and Src-kinase activation in neuroblastoma cells SH-SY5Y. This interaction allows regulation of Na,K-ATPase activity by short-term increase of the Aβ(1-42) level. However prolonged increase of Aβ(1-42) level under pathological conditions could lead to chronical inhibition of Na,K-ATPase and disruption of neuronal function. Taken together, our data suggest the role of beta-amyloid as a novel physiological regulator of Na,K-ATPase.

Molecular organization of amyloid protofilament-like assembly of betabellin 15D: helical array of beta-sandwiches.

PubMed Central

Inouye, Hideyo; Bond, Jeremy E; Deverin, Sean P; Lim, Amareth; Costello, Catherine E; Kirschner, Daniel A

2002-01-01

Betabellin is a 32-residue peptide engineered to fold into a four-stranded antiparallel beta-sheet protein. Upon air oxidation, the betabellin peptides can fold and assemble into a disulfide-bridged homodimer, or beta-sandwich, of 64 residues. Recent biophysical and ultrastructural studies indicate that betabellin 15D (B15D) (a homodimer of HSLTAKIpkLTFSIAphTYTCAVpkYTAKVSH, where p = DPro, k = DLys, and h = DHis) forms unbranched, 35-A wide assemblies that resemble the protofilaments of amyloid fibers. In the present study, we have analyzed in detail the X-ray diffraction patterns of B15D prepared from acetonitrile. The fiber diffraction analysis indicated that the B15D fibril was composed of a double helix defined by the selection rule l = n + 7m (where l is even, and n and m are any integers), and having a 199-A period and pitch, 28-A rise per unit, and 10-A radius. This helical model is equivalent to a reverse-handed, single helix with half the period and defined by the selection rule l = -3n + 7m (where l is any integer). The asymmetric unit is the single B15D beta-sandwich molecule. These results suggest that the betabellin assembly that models the protofilaments of amyloid fibers is made up of discrete subunits on a helical array. Multiple intersheet hydrogen bonds in the axial direction and intersandwich polar interactions in the lateral direction stabilize the array. PMID:12202394

Tyrosine gated electron transfer is key to the toxic mechanism of Alzheimer's disease beta-amyloid.

PubMed

Barnham, Kevin J; Haeffner, Fredrik; Ciccotosto, Giuseppe D; Curtain, Cyril C; Tew, Deborah; Mavros, Christine; Beyreuther, Konrad; Carrington, Darryl; Masters, Colin L; Cherny, Robert A; Cappai, Roberto; Bush, Ashley I

2004-09-01

Alzheimer's disease (AD) is characterized by the presence of neurofibrillary tangles and amyloid plaques, which are abnormal protein deposits. The major constituent of the plaques is the neurotoxic beta-amyloid peptide (Abeta); the genetics of familial AD support a direct role for this peptide in AD. Abeta neurotoxicity is linked to hydrogen peroxide formation. Abeta coordinates the redox active transition metals, copper and iron, to catalytically generate reactive oxygen species. The chemical mechanism underlying this process is not well defined. With the use of density functional theory calculations to delineate the chemical mechanisms that drive the catalytic production of H2O2 by Abeta/Cu, tyrosine10 (Y10) was identified as a pivotal residue for this reaction to proceed. The relative stability of tyrosyl radicals facilitates the electron transfers that are required to drive the reaction. Confirming the theoretical results, mutation of the tyrosine residue to alanine inhibited H2O2 production, Cu-induced radicalization, dityrosine cross-linking, and neurotoxicity.

Functional Hydrogel Materials Inspired by Amyloid

NASA Astrophysics Data System (ADS)

Schneider, Joel

2012-02-01

Protein assembly resulting in the formation of amyloid fibrils, assemblies rich in cross beta-sheet structure, is normally thought of as a deleterious event associated with disease. However, amyloid formation is also involved in a diverse array of normal biological functions such as cell adhesion, melanin synthesis, insect defense mechanism and modulation of water surface tension by fungi and bacteria. These findings indicate that Nature has evolved to take advantage of large, proteinaceous fibrillar assemblies to elicit function. We are designing functional materials, namely hydrogels, from peptides that self-assembled into fibrillar networks, rich in cross beta-sheet structure. These gels can be used for the direct encapsulation and delivery of small molecule-, protein- and cell-based therapeutics. Loaded gels exhibit shear-thinning/self-healing mechanical properties enabling their delivery via syringe. In addition to their use for delivery, we have found that some of these gels display antibacterial activity. Although cytocompatible towards mammalian cells, the hydrogels can kill a broad spectrum of bacteria on contact.

Is Beta-Amyloid Accumulation a Cause or Consequence of Alzheimer’s Disease?

PubMed Central

Wang, Shaoxun; Mims, Paige N.; Roman, Richard J.; Fan, Fan

2017-01-01

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that is characterized by the pathological hallmarks of extracellular beta-amyloid (Aβ) plaques and intraneuronal tau-containing neurofibrillary tangles in the brain. Intraneuronal accumulation of Aβ also plays a role to accelerate AD progression by promoting neurodegeneration. Additionally, AD is associated with the development of amyloid angiopathy (CAA), in which Aβ builds up on the walls of the cerebral arteries, which augments the development of cerebral vascular disease (CVD). Conversely, CVD promotes Aβ deposition and the development of AD by affecting the balance of Aβ production and clearance. However, it remains to be determined whether the accumulation of Aβ is a cause or consequence of AD. The interaction between AD and CVD is a topic of considerable current interest. Here, we discuss the role of CVD in Aβ accumulation and the development of AD to provide a new point of view that combination therapies that address the accompanying cerebral microvascular disease may potentiate the efficacy of emerging treatment for AD. PMID:28815226

Alzheimer disease amyloid beta protein forms calcium channels in bilayer membranes: blockade by tromethamine and aluminum.

PubMed Central

Arispe, N; Rojas, E; Pollard, H B

1993-01-01

Amyloid beta protein (A beta P) is the 40- to 42-residue polypeptide implicated in the pathogenesis of Alzheimer disease. We have incorporated this peptide into phosphatidylserine liposomes and then fused the liposomes with a planar bilayer. When incorporated into bilayers the A beta P forms channels, which generate linear current-voltage relationships in symmetrical solutions. A permeability ratio, PK/PCl, of 11 for the open A beta P channel was estimated from the reversal potential of the channel current in asymmetrical KCl solutions. The permeability sequence for different cations, estimated from the reversal potential of the A beta P-channel current for each system of asymmetrical solutions, is Pcs > PLi > PCa > or = PK > PNa. A beta P-channel current (either CS+ or Ca2+ as charge carriers) is blocked reversibly by tromethamine (millimolar range) and irreversibly by Al3+ (micromolar range). The inhibition of the A beta P-channel current by these two substances depends on transmembrane potential, suggesting that the mechanism of blockade involves direct interaction between tromethamine (or Al3+) and sites within the A beta P channel. Hitherto, A beta P has been presumed to be neurotoxic. On the basis of the present data we suggest that the channel activity of the polypeptide may be responsible for some or all of its neurotoxic effects. We further propose that a useful strategy for drug discovery for treatment of Alzheimer disease may include screening compounds for their ability to block or otherwise modify A beta P channels. PMID:8380642

Aggregate Size Dependence of Amyloid Adsorption onto Charged Interfaces

PubMed Central

2017-01-01

Amyloid aggregates are associated with a range of human neurodegenerative disorders, and it has been shown that neurotoxicity is dependent on aggregate size. Combining molecular simulation with analytical theory, a predictive model is proposed for the adsorption of amyloid aggregates onto oppositely charged surfaces, where the interaction is governed by an interplay between electrostatic attraction and entropic repulsion. Predictions are experimentally validated against quartz crystal microbalance–dissipation experiments of amyloid beta peptides and fragmented fibrils in the presence of a supported lipid bilayer. Assuming amyloids as rigid, elongated particles, we observe nonmonotonic trends for the extent of adsorption with respect to aggregate size and preferential adsorption of smaller aggregates over larger ones. Our findings describe a general phenomenon with implications for stiff polyions and rodlike particles that are electrostatically attracted to a surface. PMID:29284092

Cellular demise and inflammatory microglial activation during beta-amyloid toxicity are governed by Wnt1 and canonical signaling pathways.

PubMed

Chong, Zhao Zhong; Li, Faqi; Maiese, Kenneth

2007-06-01

Initially described as a modulator of embryogenesis for a number of organ systems, Wnt1 has recently been linked to the development of several neurodegenerative disorders, none being of greater significance than Alzheimer's disease. We therefore examined the ability of Wnt1 to oversee vital pathways responsible for cell survival during beta-amyloid (Abeta1-42) exposure. Here we show that Wnt1 is critical for protection in the SH-SY5Y neuronal cell line against genomic DNA degradation, membrane phosphatidylserine (PS) exposure, and microglial activation, since these neuroprotective attributes of Wnt1 are lost during gene silencing of Wnt1 protein expression. Intimately tied to Wnt1 protection is the presence and activation of Akt1. Pharmacological inhibition of the PI 3-K pathway or gene silencing of Akt1 expression can abrogate the protective capacity of Wnt1. Closely aligned with Wnt1 and Akt1 are the integrated canonical pathways of synthase kinase-3beta (GSK-3beta) and beta-catenin. Through Akt1 dependent pathways, Wnt1 phosphorylates GSK-3beta and maintains beta-catenin integrity to insure its translocation from the cytoplasm to the nucleus to block apoptosis. Our work outlines a highly novel role for Wnt1 and its integration with Akt1, GSK-3beta, and beta-catenin to foster neuronal cell survival and repress inflammatory microglial activation that can identify new avenues of therapy against neurodegenerative disorders.

In vivo neuronal synthesis and axonal transport of Kunitz protease inhibitor (KPI)-containing forms of the amyloid precursor protein.

PubMed

Moya, K L; Confaloni, A M; Allinquant, B

1994-11-01

We have shown previously that the amyloid precursor protein (APP) is synthesized in retinal ganglion cells and is rapidly transported down the axons, and that different molecular weight forms of the precursor have different developmental time courses. Some APP isoforms contain a Kunitz protease inhibitor (KPI) domain, and APP that lacks the KPI domain is considered the predominant isoform in neurons. We now show that, among the various rapidly transported APPs, a 140-kDa isoform contains the KPI domain. This APP isoform is highly expressed in rapidly growing retinal axons, and it is also prominent in adult axon endings. This 140-kDa KPI-containing APP is highly sulfated compared with other axonally transported isoforms. These results show that APP with the KPI domain is a prominent isoform synthesized in neurons in vivo, and they suggest that the regulation of protease activity may be an important factor during the establishment of neuronal connections.

Folding of Cu/Zn superoxide dismutase suggests structural hotspots for gain of neurotoxic function in ALS: Parallels to precursors in amyloid disease

PubMed Central

Nordlund, Anna; Oliveberg, Mikael

2006-01-01

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease linked to misfolding of the ubiquitous enzyme Cu/Zn superoxide dismutase (SOD). In contrast to other protein-misfolding disorders with similar neuropathogenesis, ALS is not always associated with the in vivo deposition of protein aggregates. Thus, under the assumption that all protein-misfolding disorders share at primary level a similar disease mechanism, ALS constitutes an interesting disease model for identifying the yet-mysterious precursor states from which the cytotoxic pathway emerges. In this study, we have mapped out the conformational repertoire of the apoSOD monomer through analysis of its folding behavior. The results allow us to target the regions of the SOD structure that are most susceptible to unfolding locally under physiological conditions, leading to the exposure of structurally promiscuous interfaces that are normally hidden in the protein’s interior. The structure of this putative ALS precursor is strikingly similar to those implicated in amyloid disease. PMID:16798882

Pioglitazone and exenatide enhance cognition and downregulate hippocampal beta amyloid oligomer and microglia expression in insulin-resistant rats.

PubMed

Gad, Enas S; Zaitone, Sawsan A; Moustafa, Yasser M

2016-08-01

Insulin resistance is known to be a risk factor for cognitive impairment, most likely linked to insulin signaling, microglia overactivation, and beta amyloid (Aβ) deposition in the brain. Exenatide, a long lasting glucagon-like peptide-1 (GLP-1) analogue, enhances insulin signaling and shows neuroprotective properties. Pioglitazone, a peroxisome proliferated-activated receptor-γ (PPAR-γ) agonist, was previously reported to enhance cognition through its effect on Aβ accumulation and clearance. In the present study, insulin resistance was induced in male rats by drinking fructose for 12 weeks. The effect of monotherapy with pioglitazone (10 mg·kg(-1)) and exenatide or their combination on memory dysfunction was determined and some of the probable underlying mechanisms were studied. The current results confirmed that (1) feeding male rats with fructose syrup for 12 weeks resulted in a decline of learning and memory registered in eight-arm radial maze test; (2) treatment with pioglitazone or exenatide enhanced cognition, reduced hippocampal neurodegeneration, and reduced hippocampal microglia expression and beta amyloid oligomer deposition in a manner that is equal to monotherapies. These results may give promise for the use of pioglitazone or exenatide for ameliorating the learning and memory deficits associated with insulin resistance in clinical setting.

Pauling and Corey's alpha-pleated sheet structure may define the prefibrillar amyloidogenic intermediate in amyloid disease.

PubMed

Armen, Roger S; DeMarco, Mari L; Alonso, Darwin O V; Daggett, Valerie

2004-08-10

Transthyretin, beta(2)-microglobulin, lysozyme, and the prion protein are four of the best-characterized proteins implicated in amyloid disease. Upon partial acid denaturation, these proteins undergo conformational change into an amyloidogenic intermediate that can self-assemble into amyloid fibrils. Many experiments have shown that pH-mediated changes in structure are required for the formation of the amyloidogeneic intermediate, but it has proved impossible to characterize these conformational changes at high resolution using experimental means. To probe these conformational changes at atomic resolution, we have performed molecular dynamics simulations of these proteins at neutral and low pH. In low-pH simulations of all four proteins, we observe the formation of alpha-pleated sheet secondary structure, which was first proposed by L. Pauling and R. B. Corey [(1951) Proc. Natl. Acad. Sci. USA 37, 251-256]. In all beta-sheet proteins, transthyretin and beta(2)-microglobulin, alpha-pleated sheet structure formed over the strands that are highly protected in hydrogen-exchange experiments probing amyloidogenic conditions. In lysozyme and the prion protein, alpha-sheets formed in the specific regions of the protein implicated in the amyloidogenic conversion. We propose that the formation of alpha-pleated sheet structure may be a common conformational transition in amyloidosis.

Reducing the Levels of Akt Activation by PDK1 Knock-in Mutation Protects Neuronal Cultures against Synthetic Amyloid-Beta Peptides.

PubMed

Yang, Shaobin; Pascual-Guiral, Sònia; Ponce, Rebeca; Giménez-Llort, Lydia; Baltrons, María A; Arancio, Ottavio; Palacio, Jose R; Clos, Victoria M; Yuste, Victor J; Bayascas, Jose R

2017-01-01

The Akt kinase has been widely assumed for years as a key downstream effector of the PI3K signaling pathway in promoting neuronal survival. This notion was however challenged by the finding that neuronal survival responses were still preserved in mice with reduced Akt activity. Moreover, here we show that the Akt signaling is elevated in the aged brain of two different mice models of Alzheimer Disease. We manipulate the rate of Akt stimulation by employing knock-in mice expressing a mutant form of PDK1 (phosphoinositide-dependent protein kinase 1) with reduced, but not abolished, ability to activate Akt. We found increased membrane localization and activity of the TACE/ADAM17 α-secretase in the brain of the PDK1 mutant mice with concomitant TNFR1 processing, which provided neurons with resistance against TNFα-induced neurotoxicity. Opposite to the Alzheimer Disease transgenic mice, the PDK1 knock-in mice exhibited an age-dependent attenuation of the unfolding protein response, which protected the mutant neurons against endoplasmic reticulum stressors. Moreover, these two mechanisms cooperatively provide the mutant neurons with resistance against amyloid-beta oligomers, and might singularly also contribute to protect these mice against amyloid-beta pathology.

A hydrogel biosensor for high selective and sensitive detection of amyloid-beta oligomers.

PubMed

Sun, Liping; Zhong, Yong; Gui, Jie; Wang, Xianwu; Zhuang, Xiaorong; Weng, Jian

2018-01-01

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive and memory impairment. It is the most common neurological disease that causes dementia. Soluble amyloid-beta oligomers (AβO) in blood or cerebrospinal fluid (CSF) are the pathogenic biomarker correlated with AD. A simple electrochemical biosensor using graphene oxide/gold nanoparticles (GNPs) hydrogel electrode was developed in this study. Thiolated cellular prion protein (PrP C ) peptide probe was immobilized on GNPs of the hydrogel electrode to construct an AβO biosensor. Electrochemical impedance spectroscopy was utilized for AβO analysis. The specific binding between AβO and PrP C probes on the hydrogel electrode resulted in an increase in the electron-transfer resistance. The biosensor showed high specificity and sensitivity for AβO detection. It could selectively differentiate AβO from amyloid-beta (Aβ) monomers or fibrils. Meanwhile, it was highly sensitive to detect as low as 0.1 pM AβO in artificial CSF or blood plasma. The linear range for AβO detection is from 0.1 pM to 10 nM. This biosensor could be used as a cost-effective tool for early diagnosis of AD due to its high electrochemical performance and bionic structure.

Genetic Aspects of Alzheimer Disease

PubMed Central

Williamson, Jennifer; Goldman, Jill; Marder, Karen S.

2011-01-01

Background Alzheimer disease (AD) is a genetically complex disorder. Mutations in 3 genes, presenilin 1, amyloid precursor protein, and presenilin 2, lead to early-onset familial AD in rare families with onset of disease occurring prior to age 65. Specific polymorphisms in apolipoprotein E are associated with the more common, late-onset AD occurring after age 65. In this review, we discuss current advances in AD genetics, the implications of the known AD genes, presenilin 1, presenilin 2, amyloid precursor protein, and apolipoprotein E, and other possible genes on the clinical diagnosis, treatment, and genetic counseling of patients and families with early- and late-onset AD. Review Summary In addition to the mutations in 4 known genes associated with AD, mutations in other genes may be implicated in the pathogenesis of the disease. Most recently, 2 different research groups have reported genetic association between 2 genes, sortilin-related receptor and GAB2, and AD. These associations have not changed the diagnostic and medical management of AD. Conclusions New research in the genetics of AD have implicated novel genes as having a role in the disease, but these findings have not been replicated nor have specific disease causing mutations been identified. To date, clinical genetic testing is limited to familial early-onset disease for symptomatic individuals and asymptomatic relatives and, although not recommended, amyloid precursor protein apolipoprotein E testing as an adjunct to diagnosis of symptomatic individuals. PMID:19276785

Differentiating the Influences of Aging and Adiposity on Brain Weights, Levels of Serum and Brain Cytokines, Gastrointestinal Hormones, and Amyloid Precursor Protein.

PubMed

Banks, William A; Abrass, Christine K; Hansen, Kim M

2016-01-01

Aging and obesity exert important effects on disease. Differentiating these effects is difficult, however, because weight gain often accompanies aging. Here, we used a nested design of aged, calorically restricted, and refed rats to measure changes in brain and blood levels of cytokines and gastrointestinal hormones, brain amyloid precursor protein levels, and brain and body weights. By comparing groups and using path analysis, we found divergent influences of chronological aging versus body weight, our main findings being (i) changes in whole brain weight and serum macrophage colony-stimulating factor levels correlated better with body weight than with chronological aging, (ii) a decrease in brain cytokines and brain plasminogen activator inhibitor levels correlated better with chronological aging than with body weight, (iii) serum erythropoietin levels were influenced by both body weight and aging, (iv) serum plasminogen activator inhibitor, serum cytokines, and brain tumor necrosis factor were not influenced by aging or body weight, and (v) brain amyloid precursor protein more closely related to body weight and serum levels of gastrointestinal hormones than to brain weight, chronological aging, or cytokines. These findings show that although aging and body weight interact, their influences are distinct not only among various cytokines and hormones but also between the central nervous system and the peripheral tissue compartments. Published by Oxford University Press on behalf of the Gerontological Society of America 2014.

Current perspectives on cardiac amyloidosis

PubMed Central

Guan, Jian; Mishra, Shikha; Falk, Rodney H.

2012-01-01

Amyloidosis represents a group of diseases in which proteins undergo misfolding to form insoluble fibrils with subsequent tissue deposition. While almost all deposited amyloid fibers share a common nonbranched morphology, the affected end organs, clinical presentation, treatment strategies, and prognosis vary greatly among this group of diseases and are largely dependent on the specific amyloid precursor protein. To date, at least 27 precursor proteins have been identified to result in either local tissue or systemic amyloidosis, with nine of them manifesting in cardiac deposition and resulting in a syndrome termed “cardiac amyloidosis” or “amyloid cardiomyopathy.” Although cardiac amyloidosis has been traditionally considered to be a rare disorder, as clinical appreciation and understanding continues to grow, so too has the prevalence, suggesting that this disease may be greatly underdiagnosed. The most common form of cardiac amyloidosis is associated with circulating amyloidogenic monoclonal immunoglobulin light chain proteins. Other major cardiac amyloidoses result from a misfolding of products of mutated or wild-type transthyretin protein. While the various cardiac amyloidoses share a common functional consequence, namely, an infiltrative cardiomyopathy with restrictive pathophysiology leading to progressive heart failure, the underlying pathophysiology and clinical syndrome varies with each precursor protein. Herein, we aim to provide an up-to-date overview of cardiac amyloidosis from nomenclature to molecular mechanisms and treatment options, with a particular focus on amyloidogenic immunoglobulin light chain protein cardiac amyloidosis. PMID:22058156

Inactivation of Nitric Oxide Synthesis Exacerbates the Development of Alzheimer Disease Pathology in APPPS1 Mice (Amyloid Precursor Protein/Presenilin-1).

PubMed

Cifuentes, Diana; Poittevin, Marine; Bonnin, Philippe; Ngkelo, Anta; Kubis, Nathalie; Merkulova-Rainon, Tatyana; Lévy, Bernard I

2017-07-31

The epidemiological link between hypertension and Alzheimer disease is established. We previously reported that hypertension aggravates the Alzheimer-like pathology in APPPS1 mice (amyloid precursor protein/presenilin-1, mouse model of Alzheimer disease) with angiotensin II-induced hypertension, in relation with hypertension and nitric oxide deficiency. To provide further insights into the role of nitric oxide in the hypertension-Alzheimer disease cross-talk, we studied the effects of nitric oxide blockade in APPPS1 mice using N (ω)-nitro-l-arginine methyl ester (l-NAME) alone or in combination with hydralazine, to normalize blood pressure. Compared with normotensive APPPS1 mice, those with l-NAME-induced hypertension had greater amyloid burden ( P <0.05), increased cortical amyloid angiopathy ( P <0.01), decreased regional microvascular density ( P <0.05), and deficient long-term spatial reference memory ( P <0.001). Blood pressure normalization with hydralazine did not protect APPPS1 mice from l-NAME-induced deterioration except for cortical amyloid angiopathy, linked to hypertension-induced arterial wall remodeling. By testing the cerebrovascular response to hypercapnic breathing, we evidenced early functional impairment of cerebral vasomotor activity in APPPS1 mice. Whereas in control wild-type normotensive mice, carbon dioxide breathing resulted in 15±1.3% increase in the mean blood flow velocity ( P <0.001), paradoxical mild decrease (1.5±0.4%) was recorded in normotensive APPPS1 mice ( P <0.001). Carbon dioxide-induced decrease in mean blood flow velocity was not significantly modified in l-NAME-treated hypertensive APPPS1 mice (2.5±1.2%) and partly reversed to mild vasodilation by hydralazine (3.2±1.5%, P <0.01). These results suggest that impaired nitric oxide bioavailability exacerbates the pathophysiology of Alzheimer disease, essentially impacting amyloid load and cognitive impairment, independently of l-NAME-induced hypertension. Only cerebral amyloid angiopathy seems to be dependent on hypertension. © 2017 American Heart Association, Inc.

New insights into potential functions for the protein 4.1superfamily of proteins in kidney epithelium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calinisan, Venice; Gravem, Dana; Chen, Ray Ping-Hsu

2005-06-17

Members of the protein 4.1 family of adapter proteins are expressed in a broad panel of tissues including various epithelia where they likely play an important role in maintenance of cell architecture and polarity and in control of cell proliferation. We have recently characterized the structure and distribution of three members of the protein 4.1 family, 4.1B, 4.1R and 4.1N, in mouse kidney. We describe here binding partners for renal 4.1 proteins, identified through the screening of a rat kidney yeast two-hybrid system cDNA library. The identification of putative protein 4.1-based complexes enables us to envision potential functions for 4.1more » proteins in kidney: organization of signaling complexes, response to osmotic stress, protein trafficking, and control of cell proliferation. We discuss the relevance of these protein 4.1-based interactions in kidney physio-pathology in the context of their previously identified functions in other cells and tissues. Specifically, we will focus on renal 4.1 protein interactions with beta amyloid precursor protein (beta-APP), 14-3-3 proteins, and the cell swelling-activated chloride channel pICln. We also discuss the functional relevance of another member of the protein 4.1 superfamily, ezrin, in kidney physiopathology.« less

Chemical Kinetics for Bridging Molecular Mechanisms and Macroscopic Measurements of Amyloid Fibril Formation.

PubMed

Michaels, Thomas C T; Šarić, Anđela; Habchi, Johnny; Chia, Sean; Meisl, Georg; Vendruscolo, Michele; Dobson, Christopher M; Knowles, Tuomas P J

2018-04-20

Understanding how normally soluble peptides and proteins aggregate to form amyloid fibrils is central to many areas of modern biomolecular science, ranging from the development of functional biomaterials to the design of rational therapeutic strategies against increasingly prevalent medical conditions such as Alzheimer's and Parkinson's diseases. As such, there is a great need to develop models to mechanistically describe how amyloid fibrils are formed from precursor peptides and proteins. Here we review and discuss how ideas and concepts from chemical reaction kinetics can help to achieve this objective. In particular, we show how a combination of theory, experiments, and computer simulations, based on chemical kinetics, provides a general formalism for uncovering, at the molecular level, the mechanistic steps that underlie the phenomenon of amyloid fibril formation.

Chemical Kinetics for Bridging Molecular Mechanisms and Macroscopic Measurements of Amyloid Fibril Formation

NASA Astrophysics Data System (ADS)

Michaels, Thomas C. T.; Šarić, Anđela; Habchi, Johnny; Chia, Sean; Meisl, Georg; Vendruscolo, Michele; Dobson, Christopher M.; Knowles, Tuomas P. J.

2018-04-01

Understanding how normally soluble peptides and proteins aggregate to form amyloid fibrils is central to many areas of modern biomolecular science, ranging from the development of functional biomaterials to the design of rational therapeutic strategies against increasingly prevalent medical conditions such as Alzheimer's and Parkinson's diseases. As such, there is a great need to develop models to mechanistically describe how amyloid fibrils are formed from precursor peptides and proteins. Here we review and discuss how ideas and concepts from chemical reaction kinetics can help to achieve this objective. In particular, we show how a combination of theory, experiments, and computer simulations, based on chemical kinetics, provides a general formalism for uncovering, at the molecular level, the mechanistic steps that underlie the phenomenon of amyloid fibril formation.

Bloodstream Amyloid-beta (1-40) Peptide, Cognition, and Outcomes in Heart Failure.

PubMed

Bayes-Genis, Antoni; Barallat, Jaume; de Antonio, Marta; Domingo, Mar; Zamora, Elisabet; Vila, Joan; Subirana, Isaac; Gastelurrutia, Paloma; Pastor, M Cruz; Januzzi, James L; Lupón, Josep

2017-11-01

In the brain, amyloid-beta generation participates in the pathophysiology of cognitive disorders; in the bloodstream, the role of amyloid-beta is uncertain but may be linked to sterile inflammation and senescence. We explored the relationship between blood levels of amyloid-beta 1-40 peptide (Aβ40), cognition, and mortality (all-cause, cardiovascular, and heart failure [HF]-related) in ambulatory patients with HF. Bloodstream Aβ40 was measured in 939 consecutive patients with HF. Cognition was evaluated with the Pfeiffer questionnaire (adjusted for educational level) at baseline and during follow-up. Multivariate Cox regression analyses and measurements of performance (discrimination, calibration, and reclassification) were used, with competing risk for specific causes of death. Over 5.1 ± 2.9 years, 471 patients died (all-cause): 250 from cardiovascular causes and 131 HF-related. The median Aβ40 concentration was 519.1 pg/mL [Q1-Q3: 361.8-749.9 pg/mL]. The Aβ40 concentration correlated with age, body mass index, renal dysfunction, and New York Heart Association functional class (all P < .001). There were no differences in Aβ40 in patients with and without cognitive impairment at baseline (P = .97) or during follow-up (P = .20). In multivariable analysis, including relevant clinical predictors and N-terminal pro-B-type natriuretic peptide, Aβ40 remained significantly associated with all-cause death (HR, 1.22; 95%CI, 1.10-1.35; P < .001) and cardiovascular death (HR, 1.18; 95%CI, 1.03-1.36; P = .02), but not with HF-related death (HR, 1.13; 95%CI, 0.93-1.37; P = .22). Circulating Aβ40 improved calibration and patient reclassification. Blood levels of Aβ40 are not associated with cognitive decline in HF. Circulating Aβ40 was predictive of mortality and may indicate systemic aging. Copyright © 2017 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

Amyloid precursor protein expression and processing are differentially regulated during cortical neuron differentiation.

PubMed

Bergström, Petra; Agholme, Lotta; Nazir, Faisal Hayat; Satir, Tugce Munise; Toombs, Jamie; Wellington, Henrietta; Strandberg, Joakim; Bontell, Thomas Olsson; Kvartsberg, Hlin; Holmström, Maria; Boreström, Cecilia; Simonsson, Stina; Kunath, Tilo; Lindahl, Anders; Blennow, Kaj; Hanse, Eric; Portelius, Erik; Wray, Selina; Zetterberg, Henrik

2016-07-07

Amyloid precursor protein (APP) and its cleavage product amyloid β (Aβ) have been thoroughly studied in Alzheimer's disease. However, APP also appears to be important for neuronal development. Differentiation of induced pluripotent stem cells (iPSCs) towards cortical neurons enables in vitro mechanistic studies on human neuronal development. Here, we investigated expression and proteolytic processing of APP during differentiation of human iPSCs towards cortical neurons over a 100-day period. APP expression remained stable during neuronal differentiation, whereas APP processing changed. α-Cleaved soluble APP (sAPPα) was secreted early during differentiation, from neuronal progenitors, while β-cleaved soluble APP (sAPPβ) was first secreted after deep-layer neurons had formed. Short Aβ peptides, including Aβ1-15/16, peaked during the progenitor stage, while processing shifted towards longer peptides, such as Aβ1-40/42, when post-mitotic neurons appeared. This indicates that APP processing is regulated throughout differentiation of cortical neurons and that amyloidogenic APP processing, as reflected by Aβ1-40/42, is associated with mature neuronal phenotypes.

Protein Folding and Aggregation into Amyloid: The Interference by Natural Phenolic Compounds

PubMed Central

Stefani, Massimo; Rigacci, Stefania

2013-01-01

Amyloid aggregation is a hallmark of several degenerative diseases affecting the brain or peripheral tissues, whose intermediates (oligomers, protofibrils) and final mature fibrils display different toxicity. Consequently, compounds counteracting amyloid aggregation have been investigated for their ability (i) to stabilize toxic amyloid precursors; (ii) to prevent the growth of toxic oligomers or speed that of fibrils; (iii) to inhibit fibril growth and deposition; (iv) to disassemble preformed fibrils; and (v) to favor amyloid clearance. Natural phenols, a wide panel of plant molecules, are one of the most actively investigated categories of potential amyloid inhibitors. They are considered responsible for the beneficial effects of several traditional diets being present in green tea, extra virgin olive oil, red wine, spices, berries and aromatic herbs. Accordingly, it has been proposed that some natural phenols could be exploited to prevent and to treat amyloid diseases, and recent studies have provided significant information on their ability to inhibit peptide/protein aggregation in various ways and to stimulate cell defenses, leading to identify shared or specific mechanisms. In the first part of this review, we will overview the significance and mechanisms of amyloid aggregation and aggregate toxicity; then, we will summarize the recent achievements on protection against amyloid diseases by many natural phenols. PMID:23765219

Specific interactions between amyloid-β peptide and curcumin derivatives: Ab initio molecular simulations

NASA Astrophysics Data System (ADS)

Ishimura, Hiromi; Kadoya, Ryushi; Suzuki, Tomoya; Murakawa, Takeru; Shulga, Sergiy; Kurita, Noriyuki

2015-07-01

Alzheimer's disease is caused by accumulation of amyloid-β (Aβ) peptides in a brain. To suppress the production of Aβ peptides, it is effective to inhibit the cleavage of amyloid precursor protein (APP) by secretases. However, because the secretases also play important roles to produce vital proteins for human body, inhibitors for the secretases may have side effects. To propose new agents for protecting the cleavage site of APP from the attacking of the γ-secretase, we have investigated here the specific interactions between a short APP peptide and curcumin derivatives, using protein-ligand docking as well as ab initio molecular simulations.

DNA damage in nasal and brain tissues of canines exposed to air pollutants is associated with evidence of chronic brain inflammation and neurodegeneration.

PubMed

Calderón-Garcidueñas, Lilian; Maronpot, Robert R; Torres-Jardon, Ricardo; Henríquez-Roldán, Carlos; Schoonhoven, Robert; Acuña-Ayala, Hilda; Villarreal-Calderón, Anna; Nakamura, Jun; Fernando, Reshan; Reed, William; Azzarelli, Biagio; Swenberg, James A

2003-01-01

Acute, subchronic, or chronic exposures to particulate matter (PM) and pollutant gases affect people in urban areas and those exposed to fires, disasters, and wars. Respiratory tract inflammation, production of mediators of inflammation capable of reaching the brain, systemic circulation of PM, and disruption of the nasal respiratory and olfactory barriers are likely in these populations. DNA damage is crucial in aging and in age-associated diseases such as Alzheimer's disease. We evaluated apurinic/apyrimidinic (AP) sites in nasal and brain genomic DNA, and explored by immunohistochemistry the expression of nuclear factor NFkappaB p65, inducible nitric oxide synthase (iNOS), cyclo-oxygenase 2 (COX2), metallothionein I and II, apolipoprotein E, amyloid precursor protein (APP), and beta-amyloid(1-42) in healthy dogs naturally exposed to urban pollution in Mexico City. Nickel (Ni) and vanadium (V) were measured by inductively coupled plasma mass spectrometry (ICP-MS). Forty mongrel dogs, ages 7 days-10 years were studied (14 controls from Tlaxcala and 26 exposed to urban pollution in South West Metropolitan Mexico City (SWMMC)). Nasal respiratory and olfactory epithelium were found to be early pollutant targets. Olfactory bulb and hippocampal AP sites were significantly higher in exposed than in control age matched animals. Ni and V were present in a gradient from olfactory mucosa > olfactory bulb > frontal cortex. Exposed dogs had (a) nuclear neuronal NFkappaB p65, (b) endothelial, glial and neuronal iNOS, (c) endothelial and glial COX2, (d) ApoE in neuronal, glial and vascular cells, and (e) APP and beta amyloid(1-42) in neurons, diffuse plaques (the earliest at age 11 months), and in subarachnoid blood vessels. Increased AP sites and the inflammatory and stress protein brain responses were early and significant in dogs exposed to urban pollution. Oil combustion PM-associated metals Ni and V were detected in the brain. There was an acceleration of Alzheimer's-type pathology in dogs chronically exposed to air pollutants. Respiratory tract inflammation and deteriorating olfactory and respiratory barriers may play a role in the observed neuropathology. These data suggest that Alzheimer's disease may be the sequela of air pollutant exposures and the resulting systemic inflammation.

Cu(II) potentiation of Alzheimer Abeta1-40 cytotoxicity and transition on its secondary structure.

PubMed

Dai, Xue-Ling; Sun, Ya-Xuan; Jiang, Zhao-Feng

2006-11-01

Mounting evidence has shown that dyshomeostasis of the redox-active biometals such as Cu and Fe can lead to oxidative stress, which plays a key role in the neuropathology of Alzheimer' disease (AD). Here we demonstrate that with the formation of Cu(II).beta1-40 complexes, copper markedly potentiates the neurotoxicity exhibited by beta-amyloid peptide (Ab). A greater amount of hydrogen peroxide was released when Cu(II).beta1-40 complexes was added to the xanthine oxidase/xanthine system detected by potassium iodide spectrophotometry. Copper bound to Abeta1-40 was observed by electron paramagnetic resonance (EPR) spectroscopy. Circular dichroism (CD) studies indicated that copper chelation could cause a structural transition of Abeta. The addition of copper to Ab introduced an increase on beta-sheet as well as alpha-helix, which may be responsible for the aggregation of Abeta. We hypothesized that Abeta aggregation induced by copper may be responsible for local injury in AD. The interaction between Cu(2+) and Ab also provides a possible mechanism for the enrichment of metal ions in amyloid plaques in the AD brain.

A multipurpose fusion tag derived from an unstructured and hyperacidic region of the amyloid precursor protein

PubMed Central

Sangawa, Takeshi; Tabata, Sanae; Suzuki, Kei; Saheki, Yasushi; Tanaka, Keiji; Takagi, Junichi

2013-01-01

Expression and purification of aggregation-prone and disulfide-containing proteins in Escherichia coli remains as a major hurdle for structural and functional analyses of high-value target proteins. Here, we present a novel gene-fusion strategy that greatly simplifies purification and refolding procedure at very low cost using a unique hyperacidic module derived from the human amyloid precursor protein. Fusion with this polypeptide (dubbed FATT for Flag-Acidic-Target Tag) results in near-complete soluble expression of variety of extracellular proteins, which can be directly refolded in the crude bacterial lysate and purified in one-step by anion exchange chromatography. Application of this system enabled preparation of functionally active extracellular enzymes and antibody fragments without the need for condition optimization. PMID:23526492

Structure-activity relationships of β-hairpin mimics as modulators of amyloid β-peptide aggregation.

PubMed

Tonali, Nicolo; Kaffy, Julia; Soulier, Jean-Louis; Gelmi, Maria Luisa; Erba, Emanuela; Taverna, Myriam; van Heijenoort, Carine; Ha-Duong, Tap; Ongeri, Sandrine

2018-05-18

Aggregation of amyloid proteins is currently involved in more than 20 serious human diseases that are actually untreated, such as Alzheimer's disease (AD). Despite many efforts made to target the amyloid cascade in AD, finding an aggregation inhibiting compound and especially modulating early oligomerization remains a relevant and challenging strategy. We report herein the first examples of small and non-peptide mimics of acyclic beta-hairpins, showing an ability to delay the fibrillization of amyloid-β (Aβ 1-42 ) peptide and deeply modify its early oligomerization process. Modifications providing better druggability properties such as increased hydrophilicity and reduced peptidic character were performed. We also demonstrate that an appropriate balance between flexibility and stability of the β-hairpin must be reached to adapt to the different shape of the various aggregated forms of the amyloid peptide. This strategy can be investigated to target other challenging amyloid proteins. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Failure of Alzheimer's Aβ(1-40) amyloid nanofibrils under compressive loading

NASA Astrophysics Data System (ADS)

Paparcone, Raffaella; Buehler, Markus J.

2010-04-01

Amyloids are associated with severe degenerative diseases and show exceptional mechanical properties, in particular great stiffhess. Amyloid fibrils, forming protein nanotube structures, are elongated fibers with a diameter of ≈8 nm with a characteristic dense hydrogen-bond (H-bond)patterning in the form of beta-sheets (β-sheets). Here we report a series of molecular dynamics simulations to study mechanical failure properties of a twofold symmetric Aβ(l-40) amyloid fibril, a pathogen associated with Alzheimer’s disease. We carry out computational experiments to study the response of the amyloid fibril to compressive loading. Our investigations reveal atomistic details of the failure process, and confirm that the breakdown of H-bonds plays a critical role during the failure process of amyloid fibrils. We obtain a Young’s modulus of ≈12.43 GPa, in dose agreement with earlier experimental results. Our simulations show that failure by buck-ling and subsequent shearing in one of the layers initiates at ≈1% compressive strain, suggesting that amyloid fibrils can be rather brittle mechanical elements.

Natural Dietary Supplementation of Anthocyanins via PI3K/Akt/Nrf2/HO-1 Pathways Mitigate Oxidative Stress, Neurodegeneration, and Memory Impairment in a Mouse Model of Alzheimer's Disease.

PubMed

Ali, Tahir; Kim, Taehyun; Rehman, Shafiq Ur; Khan, Muhammad Sohail; Amin, Faiz Ul; Khan, Mehtab; Ikram, Muhammad; Kim, Myeong Ok

2017-11-23

Well-established studies have shown an elevated level of reactive oxygen species (ROS) that induces oxidative stress in the Alzheimer's disease (AD) patient's brain and an animal model of AD. Herein, we investigated the underlying anti-oxidant neuroprotective mechanism of natural dietary supplementation of anthocyanins extracted from Korean black beans in the amyloid precursor protein/presenilin-1 (APP/PS1) mouse model of AD. Both in vivo (APP/PS1 mice) and in vitro (mouse hippocampal HT22 cells) results demonstrated that anthocyanins regulate the phosphorylated-phosphatidylinositol 3-kinase-Akt-glycogen synthase kinase 3 beta (p-PI3K/Akt/GSK3β) pathways and consequently attenuate amyloid beta oligomer (AβO)-induced elevations in ROS level and oxidative stress via stimulating the master endogenous anti-oxidant system of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (Nrf2/HO-1) pathways and prevent apoptosis and neurodegeneration by suppressing the apoptotic and neurodegenerative markers such as activation of caspase-3 and PARP-1 expression as well as the TUNEL and Fluoro-Jade B-positive neuronal cells in the APP/PS1 mice. In vitro ApoTox-Glo™ Triplex assay results also showed that anthocyanins act as a potent anti-oxidant neuroprotective agent and reduce AβO-induced neurotoxicity in the HT22 cells via PI3K/Akt/Nrf2 signaling. Importantly, anthocyanins improve memory-related pre- and postsynaptic protein markers and memory functions in the APP/PS1 mice. In conclusion, our data suggested that consumption and supplementation of natural-derived anti-oxidant neuroprotective agent such as anthocyanins may be beneficial and suggest new dietary-supplement strategies for intervention in and prevention of progressive neurodegenerative diseases, such as AD.

Exposure to As-, Cd-, and Pb-mixture induces Aβ, amyloidogenic APP processing and cognitive impairments via oxidative stress-dependent neuroinflammation in young rats.

PubMed

Ashok, Anushruti; Rai, Nagendra Kumar; Tripathi, Sachin; Bandyopadhyay, Sanghamitra

2015-01-01

Environmental pollutants act as risk factors for Alzheimer's disease (AD), mainly affecting the aging population. We investigated early manifestations of AD-like pathology by a mixture of arsenic (As), cadmium (Cd), and lead (Pb), reported to impair neurodevelopment. We treated rats with As+Cd+Pb at their concentrations detected in groundwater of India, ie, 0.38, 0.098, and 0.22 ppm or 10 times of each, respectively, from gestation-05 to postnatal day-180. We identified dose-dependent increase in amyloid-beta (Aβ) in frontal cortex and hippocampus as early as post-weaning. The effect was strongly significant during early-adulthood, reaching levels comparable to an Aβ-infused AD-like rat model. The metals activated the proamyloidogenic pathway, mediated by increase in amyloid precursor protein (APP), and subsequent beta secretase (BACE) and presenilin (PS)-mediated APP-processing. Investigating the mechanism of Aβ-induction revealed an augmentation in oxidative stress-dependent neuroinflammation that stimulated APP expression through interleukin-responsive-APP-mRNA 5'-untranslated region. We then examined the effects of individual metals and binary mixtures in comparison with the tertiary. Among individual metals, Pb triggered maximum induction of Aβ, whereas individual As or Cd had a relatively non-significant effect on Aβ despite enhanced APP, owing to reduced induction of BACE and PS. Interestingly, when combined the metals demonstrated synergism, with a major contribution by As. The synergistic effect was significant and consistent in tertiary mixture, resulting in the augmentation of Aβ. Eventually, increase in Aβ culminated in cognitive impairments in the young rats. Together, our data demonstrate that exposure to As+Cd+Pb induces premature manifestation of AD-like pathology that is synergistic, and oxidative stress and inflammation dependent. © The Author 2014. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Cerebrospinal Fluid (CSF) Neuronal Biomarkers across the Spectrum of HIV Infection: Hierarchy of Injury and Detection

PubMed Central

Peterson, Julia; Gisslen, Magnus; Zetterberg, Henrik; Fuchs, Dietmar; Shacklett, Barbara L.; Hagberg, Lars; Yiannoutsos, Constantin T.; Spudich, Serena S.; Price, Richard W.

2014-01-01

The character of central nervous system (CNS) HIV infection and its effects on neuronal integrity vary with evolving systemic infection. Using a cross-sectional design and archived samples, we compared concentrations of cerebrospinal fluid (CSF) neuronal biomarkers in 143 samples from 8 HIV-infected subject groups representing a spectrum of untreated systemic HIV progression and viral suppression: primary infection; four groups of chronic HIV infection neuroasymptomatic (NA) subjects defined by blood CD4+ T cells of >350, 200–349, 50–199, and <50 cells/µL; HAD; treatment-induced viral suppression; and ‘elite’ controllers. Samples from 20 HIV-uninfected controls were also examined. The neuronal biomarkers included neurofilament light chain protein (NFL), total and phosphorylated tau (t-tau, p-tau), soluble amyloid precursor proteins alpha and beta (sAPPα, sAPPβ) and amyloid beta (Aβ) fragments 1–42, 1–40 and 1–38. Comparison of the biomarker changes showed a hierarchy of sensitivity in detection and suggested evolving mechanisms with progressive injury. NFL was the most sensitive neuronal biomarker. Its CSF concentration exceeded age-adjusted norms in all HAD patients, 75% of NA CD4<50, 40% of NA CD4 50–199, and 42% of primary infection, indicating common neuronal injury with untreated systemic HIV disease progression as well as transiently during early infection. By contrast, only 75% of HAD subjects had abnormal CSF t-tau levels, and there were no significant differences in t-tau levels among the remaining groups. sAPPα and β were also abnormal (decreased) in HAD, showed less marked change than NFL with CD4 decline in the absence of HAD, and were not decreased in PHI. The CSF Aβ peptides and p-tau concentrations did not differ among the groups, distinguishing the HIV CNS injury profile from Alzheimer's disease. These CSF biomarkers can serve as useful tools in selected research and clinical settings for patient classification, pathogenetic analysis, diagnosis and management. PMID:25541953

Cerebrospinal fluid (CSF) neuronal biomarkers across the spectrum of HIV infection: hierarchy of injury and detection.

PubMed

Peterson, Julia; Gisslen, Magnus; Zetterberg, Henrik; Fuchs, Dietmar; Shacklett, Barbara L; Hagberg, Lars; Yiannoutsos, Constantin T; Spudich, Serena S; Price, Richard W

2014-01-01

The character of central nervous system (CNS) HIV infection and its effects on neuronal integrity vary with evolving systemic infection. Using a cross-sectional design and archived samples, we compared concentrations of cerebrospinal fluid (CSF) neuronal biomarkers in 143 samples from 8 HIV-infected subject groups representing a spectrum of untreated systemic HIV progression and viral suppression: primary infection; four groups of chronic HIV infection neuroasymptomatic (NA) subjects defined by blood CD4+ T cells of >350, 200-349, 50-199, and <50 cells/µL; HAD; treatment-induced viral suppression; and 'elite' controllers. Samples from 20 HIV-uninfected controls were also examined. The neuronal biomarkers included neurofilament light chain protein (NFL), total and phosphorylated tau (t-tau, p-tau), soluble amyloid precursor proteins alpha and beta (sAPPα, sAPPβ) and amyloid beta (Aβ) fragments 1-42, 1-40 and 1-38. Comparison of the biomarker changes showed a hierarchy of sensitivity in detection and suggested evolving mechanisms with progressive injury. NFL was the most sensitive neuronal biomarker. Its CSF concentration exceeded age-adjusted norms in all HAD patients, 75% of NA CD4<50, 40% of NA CD4 50-199, and 42% of primary infection, indicating common neuronal injury with untreated systemic HIV disease progression as well as transiently during early infection. By contrast, only 75% of HAD subjects had abnormal CSF t-tau levels, and there were no significant differences in t-tau levels among the remaining groups. sAPPα and β were also abnormal (decreased) in HAD, showed less marked change than NFL with CD4 decline in the absence of HAD, and were not decreased in PHI. The CSF Aβ peptides and p-tau concentrations did not differ among the groups, distinguishing the HIV CNS injury profile from Alzheimer's disease. These CSF biomarkers can serve as useful tools in selected research and clinical settings for patient classification, pathogenetic analysis, diagnosis and management.

Association studies in late onset sporadic Alzheimer`s disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goate, A.M.; Lendon, C.; Talbot, C.

1994-09-01

Alzheimer`s disease (AD) is characterized by an adult onset progressive dementia and the presence of numerous plaques and tangles within the brain at autopsy. The senile plaques are composed of a proteinaceous core surrounded by dystrophic neurites. The major protein component of the core is {beta}-amyloid but antibodies to many other proteins bind to senile plaques, e.g., antibodies to apolioprotein E (ApoE) and to {alpha}1-antichymotrypsin (AACT). Genetic studies have implicated mutations within the {beta}-amyloid precursor protein gene as the cause of AD in a small number of early onset AD families. More recently, assocition studies in late onset AD havemore » demonstrated a positive association between ApoE-{epsilon}4 and AD. We report evidence for a negative association between ApoE-{epsilon}2 and AD in a large sample of sporadic late onset AD cases and matched controls supporting the role of ApoE in the etiology of AD. Ninety-three patients with sporadic AD (average age = 75 years, s.d. 8 yrs.) and 67 normal controls from the same ethnic background (age = 77 yrs., s.d. 10 yrs.) were recruited through the patient registry of the Washington University Alzheimer`s Disease Research Center. We found a statistically significant increase in ApoE-{epsilon}4 allele frequency in patients compared with controls ({chi}{sup 2}=7.75, 1 d.f., one tailed p=0.0027) and a significant decrease in {epsilon}2 allele frequency (Fisher`s exact test, one tailed p=0.0048), whereas the decreased frequency of {epsilon}3 in the patient groups was not statistically significant. Allele {epsilon}2 conferred a strong protective effect in our sample, with the odds ratio for AD for subjects possessing this allele being 0.08 (85% confidence interval 0.01-0.69). Similar studies using a polymorphism within the AACT gene showed no association with alleles at this locus in the entire AD sample or in AD cases homozygous for ApoE-{epsilon}3.« less

Changes in lipid membranes may trigger amyloid toxicity in Alzheimer's disease

PubMed Central

Drolle, Elizabeth; Negoda, Alexander; Hammond, Keely; Pavlov, Evgeny

2017-01-01

Amyloid-beta peptides (Aβ), implicated in Alzheimer’s disease (AD), interact with the cellular membrane and induce amyloid toxicity. The composition of cellular membranes changes in aging and AD. We designed multi-component lipid models to mimic healthy and diseased states of the neuronal membrane. Using atomic force microscopy (AFM), Kelvin probe force microscopy (KPFM) and black lipid membrane (BLM) techniques, we demonstrated that these model membranes differ in their nanoscale structure and physical properties, and interact differently with Aβ1–42. Based on our data, we propose a new hypothesis that changes in lipid membrane due to aging and AD may trigger amyloid toxicity through electrostatic mechanisms, similar to the accepted mechanism of antimicrobial peptide action. Understanding the role of the membrane changes as a key activating amyloid toxicity may aid in the development of a new avenue for the prevention and treatment of AD. PMID:28767712

Different disease-causing mutations in transthyretin trigger the same conformational conversion.

PubMed

Steward, Robert E; Armen, Roger S; Daggett, Valerie

2008-03-01

Transthyretin (TTR)-containing amyloid fibrils are deposited in cardiac tissue as a natural consequence of aging. A large number of inherited mutations lead to amyloid diseases by accelerating TTR deposition in other organs. Amyloid formation is preceded by a disruption of the quaternary structure of TTR and conformational changes in the monomer. To study conformational changes preceding the formation of amyloid, we performed molecular dynamics simulations of the wild-type monomer, amyloidogenic variants (V30M, L55P, V122I) and a protective variant (T119M) at neutral and low pH. At low pH, the D strand dissociated from the beta-sheet to expose the A strand, consistent with experimental studies. In amyloidogenic variants and in the wild-type at low pH, there was a conformational change in the beta-sheets into alpha-sheet via peptide bond flips that was not observed at neutral pH in the wild-type monomer. The same residues participated in conversion in each amyloidogenic variant simulation, originating in the G strand between residues 106 and 109, with accelerated conversion at low pH. The T119M protective variant changed the local conformation of the H strand and suppressed the conversion observed in amyloidogenic variants.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ngo, Sam; Guo, Zhefeng, E-mail: zhefeng@ucla.edu

Highlights: Black-Right-Pointing-Pointer A{beta} oligomers are neurotoxins and likely the causing agents for Alzheimer's disease. Black-Right-Pointing-Pointer A{beta}42 fusion protein form globular oligomers. Black-Right-Pointing-Pointer A{beta}42 fusion protein oligomers contain SDS-resistant tetramers and hexamers. Black-Right-Pointing-Pointer Cysteine substitutions at residues 31, 32, 34, 39-41 disrupt A{beta}42 oligomerization. -- Abstract: Deposition of amyloid fibrils consisting of amyloid {beta} (A{beta}) protein as senile plaques in the brain is a pathological hallmark of Alzheimer's disease. However, a growing body of evidence shows that soluble A{beta} oligomers correlate better with dementia than fibrils, suggesting that A{beta} oligomers may be the primary toxic species. The structure and oligomerization mechanismmore » of these A{beta} oligomers are crucial for developing effective therapeutics. Here we investigated the oligomerization of A{beta}42 in the context of a fusion protein containing GroES and ubiquitin fused to the N-terminus of A{beta} sequence. The presence of fusion protein partners, in combination with a denaturing buffer containing 8 M urea at pH 10, is unfavorable for A{beta}42 aggregation, thus allowing only the most stable structures to be observed. Transmission electron microscopy showed that A{beta}42 fusion protein formed globular oligomers, which bound weakly to thioflavin T and Congo red. SDS-PAGE shows that A{beta}42 fusion protein formed SDS-resistant hexamers and tetramers. In contrast, A{beta}40 fusion protein remained as monomers on SDS gel, suggesting that the oligomerization of A{beta}42 fusion protein is not due to the fusion protein partners. Cysteine scanning mutagenesis at 22 residue positions further revealed that single cysteine substitutions of the C-terminal hydrophobic residues (I31, I32, L34, V39, V40, and I41) led to disruption of hexamer and tetramer formation, suggesting that hydrophobic interactions between these residues are most critical for A{beta}42 oligomerization.« less

The stability of monomeric intermediates controls amyloid formation: Abeta25-35 and its N27Q mutant.

PubMed

Ma, Buyong; Nussinov, Ruth

2006-05-15

The structure and stabilities of the intermediates affect protein folding as well as misfolding and amyloid formation. By applying Kramer's theory of barrier crossing and a Morse-function-like energy landscape, we show that intermediates with medium stability dramatically increase the rate of amyloid formation; on the other hand, very stable and very unstable intermediates sharply decrease amyloid formation. Remarkably, extensive molecular dynamics simulations and conformational energy landscape analysis of Abeta25-35 and its N27Q mutant corroborate the mathematical description. Both experimental and current simulation results indicate that the core of the amyloid structure of Abeta25-35 formed from residues 28-35. A single mutation of N27Q of Abeta25-35 makes the Abeta25-35 N27Q amyloid-free. Energy landscape calculations show that Abeta25-35 has extended intermediates with medium stability that are prone to form amyloids, whereas the extended intermediates for Abeta25-35 N27Q split into stable and very unstable species that are not disposed to form amyloids. The results explain the contribution of both alpha-helical and beta-strand intermediates to amyloid formation. The results also indicate that the structure and stability of the intermediates, as well as of the native folded and the amyloid states can be targeted in drug design. One conceivable approach is to stabilize the intermediates to deter amyloid formation.

Increased CSF-BACE 1 Activity Is Associated with ApoE-[Epsilon]4 Genotype in Subjects with Mild Cognitive Impairment and Alzheimer's Disease

ERIC Educational Resources Information Center

Ewers, Michael; Zhong, Zhenyu; Burger, Katharina; Wallin, Anders; Blennow, Kaj; Teipel, Stefan J.; Shen, Yong; Hampel, Harald

2008-01-01

The Apolipoprotein (ApoE) [epsilon]4 allele is a major genetic risk factor of Alzheimer's disease, and may affect the production of amyloid beta (A[beta][subscript 1-42]). Recently, we have shown that [beta]-secretase (BACE 1) activity can be reliably detected within the brain and human CSF. Here, we have examined an association between the ApoE…

The Alzheimer's Prevention Initiative Generation Program: Evaluating CNP520 Efficacy in the Prevention of Alzheimer's Disease.

PubMed

Lopez Lopez, C; Caputo, A; Liu, F; Riviere, M E; Rouzade-Dominguez, M-L; Thomas, R G; Langbaum, J B; Lenz, R; Reiman, E M; Graf, A; Tariot, P N

2017-01-01

Alzheimer's disease pathology begins decades before the onset of clinical symptoms. This provides an opportunity for interventional clinical trials to potentially delay or prevent the onset of cognitive impairment or dementia. CNP520 (a beta-site-amyloid precursor protein-cleaving enzyme inhibitor) is in clinical development for the treatment of preclinical Alzheimer's disease under the Alzheimer's Prevention Initiative Generation Program. The Alzheimer's Prevention Initiative is a public-private partnership intended to accelerate the evaluation of Alzheimer's disease prevention therapies. The Generation Program comprises two pivotal phase II/III studies with similar designs to assess the efficacy and safety of investigational treatments in a cognitively unimpaired population at increased risk for developing Alzheimer's disease based on age and apolipoprotein E (APOE) genotype (i.e., presence of the APOE ε4 allele). The program has been designed to maximize benefit to Alzheimer's disease research. Generation Study 1 (NCT02565511) and Generation Study 2 (NCT03131453) are currently enrolling; their key features are presented here.

Preparation of powders suitable for conversion to useful .beta.-aluminas

DOEpatents

Morgan, Peter E. D.

1982-01-01

A process for forming a precursor powder which, when suitably pressed and sintered forms highly pure, densified .beta.- or .beta."-alumina, comprising the steps of: (1) forming a suspension (or slurry) of Bayer-derived Al(OH).sub.3 in a water-miscible solvent; (2) adding an aqueous solution of a Mg compound, a Li compound, a Na compound or mixtures thereof to the Bayer-derived Al(OH).sub.3 suspension while agitating the mixture formed thereby, to produce a gel; (3) drying the gel at a temperature above the normal boiling point of water to produce a powder material; (4) lightly ball milling and sieving said powder material; and (5) heating the ball-milled and sieved powder material at a temperature of between 350.degree. to 900.degree. C. to form the .beta.- or .beta."-alumina precursor powder. The precursor powder, thus formed, may be subsequently isopressed at a high pressure and sintered at an elevated temperature to produce .beta.- or .beta."-alumina. BACKGROUND OF THE INVENTION

Amyloid-β Production Via Cleavage of Amyloid-β Protein Precursor is Modulated by Cell Density

PubMed Central

Zhang, Can; Browne, Andrew; DiVito, Jason R.; Stevenson, Jesse A.; Romano, Donna; Dong, Yuanlin; Xie, Zhongcong; Tanzi, Rudolph E.

2012-01-01

Mounting evidence suggests that Alzheimer disease (AD) is caused by the accumulation of the small peptide, Aβ, a proteolytic cleavage product of amyloid-β protein precursor (AβPP; or APP). Aβ is generated through a serial cleavage of APP by β- and γ-secretase. Aβ40 and Aβ42 are the two main components of amyloid plaques in AD brains, with Aβ42 being more prone to aggregation. APP can also be processed by α-secretase, which cleaves APP within the Aβ sequence, thereby preventing the generation of Aβ. Little is currently known regarding the effects of cell density on APP processing and Aβ generation. Here we assessed the effects of cell density on APP processing in neuronal and non-neuronal cell lines, as well as mouse primary cortical neurons. We found that decreased cell density significantly increases levels of Aβ40, Aβ42, total Aβ, and the ratio of Aβ42:Aβ40. These results also indicate that cell density is a significant modulator of APP processing. Overall, these findings carry profound implications for both previous and forthcoming studies aiming to assess the effects of various conditions and genetic/chemical factors, e.g. novel drugs on APP processing and Aβ generation in cell-based systems. Moreover, it is interesting to speculate whether cell density changes in vivo may also affect APP processing and Aβ levels in the AD brain. PMID:20847415

Platelets, lymphocytes and erythrocytes from Alzheimer's disease patients: the quest for blood cell-based biomarkers.

PubMed

Pluta, Ryszard; Ułamek-Kozioł, Marzena; Januszewski, Sławomir; Czuczwar, Stanisław J

2018-01-01

In elderly population, Alzheimer's disease is a common neurodegenerative disorder and accounts for about 70% of all cases of dementia. The neurodegenerative processes of this disease start presumably 20 years ahead of the clinical beginning of the disorder. The postmortem histopathological examination, brains from Alzheimer's disease patients with characteristic features like amyloid plaques and neurofibrillary tangles, neuronal and synaptic disintegration confirm the final diagnosis of Alzheimer's disease. Senile plaques are composed of -amyloid peptide, deriving from the amyloid protein precursor, which is present not only in the brain tissue, but also in other non-neuronal tissues. Some investigations reported that platelets possess amyloid protein precursor and all the enzymatic activities required for the metabolism of this protein throughout the same pathways present in the brain. Thus, platelets may be a good peripheral blood cell-based biomarker to study the onset of Alzheimer's disease. Another line of research indicated molecular and cellular aberrations in blood lymphocytes and erythrocytes from Alzheimer's disease patients and emphasizes the systemic nature of the disease. In this review, we will summarize the recent knowledge on the involvement and/or response of platelets, lymphocytes and red blood cells in the circulation during Alzheimer's disease development. The facts will be reviewed with the special possibility for applying the above blood cells as Alzheimer's disease preclinical and antemortem blood cell-based biomarkers.

Aβ42-driven cerebral amyloidosis in transgenic mice reveals early and robust pathology

PubMed Central

Radde, Rebecca; Bolmont, Tristan; Kaeser, Stephan A; Coomaraswamy, Janaky; Lindau, Dennis; Stoltze, Lars; Calhoun, Michael E; Jäggi, Fabienne; Wolburg, Hartwig; Gengler, Simon; Haass, Christian; Ghetti, Bernardino; Czech, Christian; Hölscher, Christian; Mathews, Paul M; Jucker, Mathias

2006-01-01

We have generated a novel transgenic mouse model on a C57BL/6J genetic background that coexpresses KM670/671NL mutated amyloid precursor protein and L166P mutated presenilin 1 under the control of a neuron-specific Thy1 promoter element (APPPS1 mice). Cerebral amyloidosis starts at 6–8 weeks and the ratio of human amyloid (A)β42 to Aβ40 is 1.5 and 5 in pre-depositing and amyloid-depositing mice, respectively. Consistent with this ratio, extensive congophilic parenchymal amyloid but minimal amyloid angiopathy is observed. Amyloid-associated pathologies include dystrophic synaptic boutons, hyperphosphorylated tau-positive neuritic structures and robust gliosis, with neocortical microglia number increasing threefold from 1 to 8 months of age. Global neocortical neuron loss is not apparent up to 8 months of age, but local neuron loss in the dentate gyrus is observed. Because of the early onset of amyloid lesions, the defined genetic background of the model and the facile breeding characteristics, APPPS1 mice are well suited for studying therapeutic strategies and the pathomechanism of amyloidosis by cross-breeding to other genetically engineered mouse models. PMID:16906128