Current Search:   Amyloid-Beta (x)

View All Items

  • CSV Spreadsheet
(1 - 8 of 8)
Pyroglutamylated amyloid beta peptides enhance non-fibrillogenic aggregation of the unmodified peptide
Title
Pyroglutamylated amyloid beta peptides enhance non-fibrillogenic aggregation of the unmodified peptide.
Creator
Goldblatt, Gregory, Tatulian, Suren, Chen, Bo, Teter, Kenneth, King, Stephen, University of Central Florida
Abstract / Description
Alzheimer's disease (AD) is accompanied by abnormal extracellular deposition of amyloid b (Ab) peptide. This has led to the amyloid cascade hypothesis, causatively relating Ab with AD. While Ab deposits assume a fibrillar cross-b structure, prefibrillar oligomers of Ab have been identified as the main cytotoxic agents in AD. Pyroglutamylated amyloid beta (AbpE) peptides are N-terminally truncated and pyroglutamylated (at Glu3 or Glu11) Ab molecules that display enhanced cytotoxicity and...
Show moreAlzheimer's disease (AD) is accompanied by abnormal extracellular deposition of amyloid b (Ab) peptide. This has led to the amyloid cascade hypothesis, causatively relating Ab with AD. While Ab deposits assume a fibrillar cross-b structure, prefibrillar oligomers of Ab have been identified as the main cytotoxic agents in AD. Pyroglutamylated amyloid beta (AbpE) peptides are N-terminally truncated and pyroglutamylated (at Glu3 or Glu11) Ab molecules that display enhanced cytotoxicity and represent up to 50% of total Ab in AD brains. AbpE significantly enhances the toxicity of unmodified Ab by an unknown mechanism. Although in situ Ab populations are heterogeneous, the majority of studies have been conducted on single Ab species. Here, we examined the structural and morphological changes that occur in mixed Ab/AbpE samples. Circular dichroism and transmission electron microscopy data indicate that AbpE3-42 forms b-sheet structure and undergoes delayed fibrillogenesis compared to unmodified Ab1-42. Further, AbpE3-42 decelerates b-sheet formation in mixed Ab1-42/AbpE3-42 samples. FTIR measurements, using 13C-labeled Ab1-42 and unlabeled AbpE3-42, indicate that AbpE3-42 inhibits cross-b-sheet formation by Ab1-42, which explains the retardation of fibrillogenesis. FTIR on peptides 13C-labeled at specific segments provided site specific structural information. Based on these data, the monomeric Ab structure has been modeled as a b-hairpin stabilized by intramolecular H-bonding with an N-terminal a-helix. These hairpins likely form higher order aggregates through ionic and hydrophobic interactions between the C-terminus of one hairpin and the N-terminus of another. Utilizing a novel technique, hydration from gas phase, we examined the a-helix to b-sheet transitions of these peptides. When combined, AbpE3-42 and Ab1-42 mutually inhibit intermolecular b-sheet formation, instead promoting formation of AbpE3-42/Ab1-42 hetero-oligomers of intramolecular H-bonding. These hetero-oligomers displayed enhanced toxicity to PC12 cells compared to individual peptides and induced greater calcium release from lipid vesicles than unmodified Ab. These results indicate that Ab and AbpE mutually inhibit fibrillogenesis and stabilize hetero-oligomers of enhanced cytotoxicity, possibly through a membrane permeabilization mechanism. Collectively, our findings lead to a new concept that Ab/AbpE hetero-oligomers, not just Ab or AbpE oligomers, are the main cytotoxic species in AD
Show less
Date Issued
2016
Identifier
CFE0006108, ucf:51195
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006108
In Vitro Characterization of Unmodified and Pyroglutamylated Alzheimer's Amyloid beta peptide
Title
In Vitro Characterization of Unmodified and Pyroglutamylated Alzheimer's Amyloid beta peptide.
Creator
Matos, Jason, Tatulian, Suren, Teter, Kenneth, Davidson, Victor, University of Central Florida
Abstract / Description
Plaques of amyloid ? peptide (A?) are a hallmark trait of Alzheimer's disease (AD). However, the precise role of A? aggregates is not well understood. Recent studies have identified that naturally occurring N-terminal truncation and pyroglutamylation of A? significantly increases its neurotoxicity by an unknown mechanism. Content of pyroglutamylated A? (pE-A?) in AD brains has been shown to reach up to 50% of total A?. Modified pE-A? co-aggregates with A? by a seeding mechanism and forms...
Show morePlaques of amyloid ? peptide (A?) are a hallmark trait of Alzheimer's disease (AD). However, the precise role of A? aggregates is not well understood. Recent studies have identified that naturally occurring N-terminal truncation and pyroglutamylation of A? significantly increases its neurotoxicity by an unknown mechanism. Content of pyroglutamylated A? (pE-A?) in AD brains has been shown to reach up to 50% of total A?. Modified pE-A? co-aggregates with A? by a seeding mechanism and forms structurally distinct and highly toxic oligomers. We studied structural transitions of the full-length A?1-42, its pyroglutamylated form A?pE3-42, their 9:1 (A?1-42/A?pE3-42) and 1:1 molar combinations. Transmission electron microscopy was used to directly visualize the fibrils of the samples in a buffer mimicking physiological environment. Atomic force microscopy measurements were done to determine rate of second nucleation events in fibrils. Thioflavin-T fluorescence indicated that low ionic strength suppressed the aggregation of A?pE3-42 but promoted that of A?1-42, suggesting different paths of fibrillogenesis of unmodified A? and pE-A?. Interestingly, A?pE3-42 at only 10% significantly facilitated the fibrillization of A?1-42 at near physiological ionic strength but had little effect at low salt. Circular dichroism and Fourier transform infrared (FTIR) spectroscopy were used to characterize the structural transitions during fibrillogenesis. In aqueous buffer, both unmodified A? and pE-A? peptides adopted parallel intermolecular ?-structure. Interestingly, A?pE3-42 contained lower ?-sheet content than 13C-A?1-42, while retaining significantly larger fractions of ?-helical and turn structures. Structural details of A? and pE-A? combinations were unveiled by isotope-edited FTIR spectroscopy, using 13C-labeled A?1-42 and unlabeled A?pE3-42. When exposed to environmental humidity, A?pE3-42 not only maintained an increased fraction of ?-helix but also was able to reverse 13C-A?1-42 ?-sheet structure. These data provide a novel structural mechanism for pE-A? hypertoxicity; pE-A? undergoes fasternucleation due to its increased hydrophobicity, thus promoting formation of smaller, hypertoxic oligomers of partial ?-helical structure.
Show less
Date Issued
2014
Identifier
CFE0005378, ucf:50465
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005378
STRUCTURAL TRANSITION DURING FIBRILLOGENESIS OF AMYLOID ? PEPTIDE
Title
STRUCTURAL TRANSITION DURING FIBRILLOGENESIS OF AMYLOID ? PEPTIDE.
Creator
Sidrak, George, Tatulian, Suren, University of Central Florida
Abstract / Description
Alzheimer's Disease (AD) is a neurodegenerative disease marked by progressive neuronal cell death, leading to dementia. AD is the most common disease that results in dementia and largely affects the elderly, with five million people in the United States diagnosed with the disease as of 2015 and approximately 35 million people worldwide. Diseases resulting in dementia cost the US healthcare system an estimated $172 billion in 2010 and that cost is expected to increase as the population ages...
Show moreAlzheimer's Disease (AD) is a neurodegenerative disease marked by progressive neuronal cell death, leading to dementia. AD is the most common disease that results in dementia and largely affects the elderly, with five million people in the United States diagnosed with the disease as of 2015 and approximately 35 million people worldwide. Diseases resulting in dementia cost the US healthcare system an estimated $172 billion in 2010 and that cost is expected to increase as the population ages and as diagnostic techniques improve so that more people are treated (Holtzman, 2011). The disease was first reported by psychiatrist Alois Alzheimer at the onset of the 20th century, when one of his patients "suffered memory loss, disorientation, hallucinations and delusions and died at the age of 55," then was found to have severe brain atrophy post-mortem (Cipriani, Dolciotti, Picchi, & Bonuccelli, 2011). There are palliative treatments available that marginally slow disease progression but there is currently no cure for the disease (Awasthi, Singh, Pandey, & Dwivedi, 2016). More research is needed to develop effective therapeutic strategies to combat the disease. Currently, AD cytotoxicity is believed to be caused by increased amyloid ? (A?) peptide plaque deposition in the brain, as described by the amyloid cascade hypothesis (Barage & Sonawane, 2015). The current understanding is that oligomers of A? peptide lead to neuronal death through multiple mechanisms, most notably hyper-phosphorylation of the tau protein. Having a better understanding of the structural changes in the fibrillization process of A? will provide a broader insight into mechanisms of cell death and open new possibilities for pharmacological treatments, which is what this research intends to provide.
Show less
Date Issued
2017
Identifier
CFH2000178, ucf:45994
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH2000178
AMELIORATION OF AMYLOID BURDEN IN ADVANCED HUMAN AND MOUSE ALZHEIMER'S DISEASE BRAINS BY ORAL DELIVERY OF MYELIN BASIC PROTEIN BIOENCAPSULATED IN PLANT CELLS
Title
AMELIORATION OF AMYLOID BURDEN IN ADVANCED HUMAN AND MOUSE ALZHEIMER'S DISEASE BRAINS BY ORAL DELIVERY OF MYELIN BASIC PROTEIN BIOENCAPSULATED IN PLANT CELLS.
Creator
Kohli, Neha, Daniell, Henry, Kim, Yoon-Seong, Cheng, Zixi, University of Central Florida
Abstract / Description
One of the pathological hallmarks of Alzheimer's disease (AD) is the amyloid plaque deposition in aging brains by aggregation of amyloid-? (A?) peptides. In this study, the effect of chloroplast derived myelin basic protein (MBP) fused with cholera toxin subunit B (CTB) was investigated in advanced diseased stage of human and mouse AD brains. The CTB-fusion protein in chloroplasts facilitates transmucosal delivery in the gut by the natural binding ability of CTB pentameric form with GM1...
Show moreOne of the pathological hallmarks of Alzheimer's disease (AD) is the amyloid plaque deposition in aging brains by aggregation of amyloid-? (A?) peptides. In this study, the effect of chloroplast derived myelin basic protein (MBP) fused with cholera toxin subunit B (CTB) was investigated in advanced diseased stage of human and mouse AD brains. The CTB-fusion protein in chloroplasts facilitates transmucosal delivery in the gut by the natural binding ability of CTB pentameric form with GM1 receptors on the intestinal epithelium. Further, bioencapsulation of the MBP within plant cells confers protection from enzymes and acids in the digestive system. Here, 12-14 months old triple transgenic AD mice were fed with CTB-MBP bioencapsulated in the plant cells for 3 months. A reduction of 67.3% and 33.3% amyloid levels in hippocampal and cortical regions, respectively were observed by immunostaining of brain sections with anti- A? antibody. Similarly, 70% decrease in plaque number and 40% reduction of plaque intensity was observed through thioflavin S (ThS) staining that specifically stains amyloid in the AD brain. Furthermore, ex vivo 3xTg AD mice brain sections showed up to 45% reduction of ThS stained amyloid levels when incubated with enriched CTB-MBP in a concentration dependent manner. Similarly, incubation of enriched CTB-MBP with ex vivo postmortem human brain tissue sections with advanced stage of AD resulted up to 47% decrease of ThS stained amyloid plaque intensity. Lastly, lyophilization of plant material facilitates dehydration and long term storage of capsules at room temperature, in addition to increasing CTB-MBP concentration by 17 fold. These observations offer a low cost solution for treatment of even advanced stages of the AD by facilitating delivery of therapeutic proteins to central nervous system to address other neurodegenerative disease.
Show less
Date Issued
2012
Identifier
CFE0004564, ucf:49237
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004564
AMYLOID-BETA42 TOXICITY REDUCTION IN HUMAN NEUROBLASTOMA CELLS USING CHOLERA TOXIN B SUBUNIT-MYELIN BASIC PROTEIN EXPRESSED IN CHLOROPLASTS
Title
AMYLOID-BETA42 TOXICITY REDUCTION IN HUMAN NEUROBLASTOMA CELLS USING CHOLERA TOXIN B SUBUNIT-MYELIN BASIC PROTEIN EXPRESSED IN CHLOROPLASTS.
Creator
Ayache, Alexandra, Daniell, Henry, University of Central Florida
Abstract / Description
Alzheimer's disease (AD) is an age progressive neurodegenerative brain disorder, affecting 37 million people worldwide. Cleavage of amyloid precursor protein by β- and γ-secretase produces the amyloid-beta (Aβ) protein, which significantly contributes to AD pathogenesis. The Aβ aggregates, formed at the surface of neurons and intracellularly, cause neurotoxicity and decrease synaptic function. Inhibiting or degrading Aβ accumulation is a key goal for development of new AD treatments. Evidence...
Show moreAlzheimer's disease (AD) is an age progressive neurodegenerative brain disorder, affecting 37 million people worldwide. Cleavage of amyloid precursor protein by β- and γ-secretase produces the amyloid-beta (Aβ) protein, which significantly contributes to AD pathogenesis. The Aβ aggregates, formed at the surface of neurons and intracellularly, cause neurotoxicity and decrease synaptic function. Inhibiting or degrading Aβ accumulation is a key goal for development of new AD treatments. Evidence shows that human Myelin Basic Protein (MBP) binds to and degrades Aβ thereby, preventing cytotoxicity. A potential method for oral drug delivery that will allow plant-derived bioencapsulated MBP to pass through intestinal epithelium and bypass denaturing stomach acidity is quite novel. Cholera Toxin B subunit (CTB), when fused with MBP, can serve as a vehicle for oral delivery of this chloroplast expressed therapeutic protein into the systemic circulation. Within chloroplast, CTB forms a pentameric structure that binds to GM1 ganglioside receptors, allowing receptor-mediated endocytosis. In order to investigate protein entry through neuronal GM1 receptors, we first created CTB fused to the green fluorescent protein (GFP). Incubation of this fusion protein with human neuroblastoma cells resulted in GFP entry into these cells whereas GFP alone was unable to enter. Similarly, co-incubation of CTB-MBP, via neuronal GM1 binding, allowed MBP to reduce neurotoxicity of Aβ42 treated cells by 37.1%. Delivery of CTB-MBP through GM1 receptor mediated binding should therefore facilitate oral administration, storage, heat stability and low cost AD treatment.
Show less
Date Issued
2012
Identifier
CFH0004249, ucf:44916
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH0004249
HYBRID ADULT NEURON CULTURE SYSTEMS FOR USE IN PHARMACOLOGICAL TESTING
Title
HYBRID ADULT NEURON CULTURE SYSTEMS FOR USE IN PHARMACOLOGICAL TESTING.
Creator
Edwards, Darin, Hickman, James, University of Central Florida
Abstract / Description
Neuronal culture systems have many applications, such as basic research into neuronal structure, function, and connectivity as well as research into diseases, conditions, and injuries affecting the brain and its components. In vitro dissociated neuronal systems have typically been derived from embryonic brain tissue, most commonly from the hippocampus of E18 rats. This practice has been motivated by difficulties in supporting regeneration, functional recovery and long-term survival of adult...
Show moreNeuronal culture systems have many applications, such as basic research into neuronal structure, function, and connectivity as well as research into diseases, conditions, and injuries affecting the brain and its components. In vitro dissociated neuronal systems have typically been derived from embryonic brain tissue, most commonly from the hippocampus of E18 rats. This practice has been motivated by difficulties in supporting regeneration, functional recovery and long-term survival of adult neurons in vitro. The overall focus of this dissertation research was to develop a dissociated neuronal culture system from human and animal adult brain tissue, one more functionally and developmentally correlative to the mature brain. To that end, this work was divided into five interrelated topics: development of an adult in vitro neuronal culture system comprised of electrically functional, mitotically stable, developmentally mature neurons from the hippocampus of adult rats; creation of stable two-cell neuronal networks for the study of synaptic communication in vitro; coupling of electrically active adult neurons to microelectrode arrays for high-throughput data collection and analysis; identification of inadequacies in embryonic neuronal culture systems and proving that adult neuronal culture systems were not deficient in similar areas; augmentation of the rat hippocampal culture system to allow for the culture and maintenance of electrically active human neurons for months in vitro. The overall hypothesis for this dissertation project was that tissue engineered in vitro systems comprised of neurons dissociated from mature adult brain tissue could be developed using microfabrication, defined medium formulations, optimized culture and maintenance parameters, and cell-cycle control. Mature differentiated glutamatergic neurons were extracted from hippocampal brain tissue and processed to purify neurons and remove tissue debris. Terminally differentiated rat hippocampal neurons recovered in vitro and displayed mature neuronal morphology. Extracellular glutamate in the culture medium promoted neuronal recovery of electrical function and activity. After recovery, essential growth factors in the culture medium caused adult neurons to reenter the cell cycle and divide multiple times. Only after reaching confluence did some neurons stop dividing. Strategies for inhibition of neuronal mitotic division were investigated, and manipulation of the cdk5 pathway was ultimately found to prevent division in vitro. Prevention of mitotic division as well as optimization of culture and maintenance parameters resulted in a neuronal culture system derived from adult rats in which the neuronal morphology, cytoskeleton and surface protein expression patterns, and electrical activity closely mirrored mature, terminally differentiated adult neurons in vivo. Improvements were also made to the growth surfaces on which neurons attached, regenerated, and survived long-term. Culture surfaces, in this case glass cover slips, were modified with the chemical substrate N-1 [3-(trimethoxysilyl) propyl]-diethylenetriamine (DETA) to create a covalently modified interface with exposed cell-adhesive triamine groups. DETA chemical surfaces were also further modified to create high-resolution patterns, useful in creating engineered two-cell networks of adult hippocampal neurons. Adult hippocampal neurons were also coupled to microelectrode array systems (MEAs) and recovered functionally, fired spontaneously, and reacted to synaptic antagonists in a manner consistent to adult neurons in vivo. Last, neurons from the brains of deceased Alzheimer's disease (AD) patients and from brain tissue excised during surgery for Parkinson's disease (PD), Essential Tremor (ET), and brain tumor were isolated and cultured, with these neurons morphological regenerating and electrically recovering in vitro.
Show less
Date Issued
2011
Identifier
CFE0004045, ucf:49127
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004045
Neurological profile of older ApoE-PON1 double knockout mice
Title
Neurological profile of older ApoE-PON1 double knockout mice.
Creator
Mitra, Connie, Parthasarathy, Sampath, Kim, Yoon-Seong, Zhao, Jihe, University of Central Florida
Abstract / Description
Atherosclerosis is a cardiovascular disease where plaques made up of lipids in the form of cholesterol ester build up in the carotid and innominate arteries that supply blood to the brain. Accumulation of the plaques limit the flow of blood and nutrients to the brain, leading to diminished oxygen supply, increased oxidative stress and cell death. All these have been implicated in Alzheimer's disease (AD). Alzheimer's disease, a chronic, progressive, age related neurodegenerative disorder is...
Show moreAtherosclerosis is a cardiovascular disease where plaques made up of lipids in the form of cholesterol ester build up in the carotid and innominate arteries that supply blood to the brain. Accumulation of the plaques limit the flow of blood and nutrients to the brain, leading to diminished oxygen supply, increased oxidative stress and cell death. All these have been implicated in Alzheimer's disease (AD). Alzheimer's disease, a chronic, progressive, age related neurodegenerative disorder is the most common form of dementia in the elderly accounting for 60-80% of the cases. Clinically, Alzheimer's disease is characterized by loss of memory, damage of brain tissues, and neuronal and synaptic loss. Pathologically, it is delineated by accumulation of amyloid beta and tau proteins forming senile plaques and neurofibrillary tangles respectively. Apolipoprotein E (ApoE) polymorphism, increased oxidative stress and products of lipid peroxidation are associated with atherosclerosis and Alzheimer's disease. ApoE is a glycosylated protein that mediates plasma lipoprotein metabolism. ApoE isoforms have differential effect on amyloid beta aggregation and clearance, thus playing an important role in Alzheimer's pathology. Serum paraoxonase 1 (PON1) is a lipoprotein associated antioxidant enzyme that prevents lipid peroxidation. S100B protein is a plasma biomarker, altered expression of which has been implied in AD. We propose the hypothesis that combined deficiencies in apolipoprotein E and antioxidant defense (established by the lack of PON1), together with dyslipidemia and development of carotid atherosclerosis in aging mice would reflect Alzheimer's pathology. The brains of young and old ApoE-PON1 double knockout (DKO) mice and control C57BL/6J mice were harvested. Atherosclerotic lesions were quantified by Image J. RNA was isolated, cDNA was synthesized and quantitative RT-PCR was performed to detect mRNA levels of S100B. Blood levels of S100B protein was measured by ELISA. Brain tissues were stained with Hematoxylin and Eosin stain and 4G8 immunostain to detect histopathological changes. The blood brain barrier (BBB) is altered in AD resulting in increased permeability and vascular dysfunction. The vascular permeability of BBB was analyzed by Evans Blue Dye (EBD) assay. The results showed that the older DKO mice had severe carotid atherosclerosis, increased levels of serum S100B protein and elevated mRNA levels of S100B. Histological examination showed the presence of characteristic hallmarks of AD. The leakage of EBD into brain parenchyma indicated disruption of BBB. The results suggest that diminished blood flow and nutrient supply to the brain due to atherosclerosis and increased oxidative stress might contribute to Alzheimer's pathology. We suggest that older ApoE-PON1 DKO mice may serve as a model of Alzheimer's disease and prevention of atherosclerosis might promote regression of Alzheimer's disease.
Show less
Date Issued
2016
Identifier
CFE0006483, ucf:51407
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006483
Development of human and rodent based in vitro systems toward better translation of bench to bedside in vivo results
Title
Development of human and rodent based in vitro systems toward better translation of bench to bedside in vivo results.
Creator
Berry, Bonnie, Hickman, James, Khaled, Annette, Lambert, Stephen, Sugaya, Kiminobu, University of Central Florida
Abstract / Description
Prospective medicinal compounds progress through multiple testing phases before becoming licensed drugs. Testing of novel compounds includes a preclinical phase where the potential therapeutic is tested in vitro and/or in animal models in vivo to predict its potential efficacy and/or toxicity in humans. The failure of preclinical models to accurately predict human drug responses can lead to potentially dangerous compounds being administered to humans, or potentially beneficial compounds being...
Show moreProspective medicinal compounds progress through multiple testing phases before becoming licensed drugs. Testing of novel compounds includes a preclinical phase where the potential therapeutic is tested in vitro and/or in animal models in vivo to predict its potential efficacy and/or toxicity in humans. The failure of preclinical models to accurately predict human drug responses can lead to potentially dangerous compounds being administered to humans, or potentially beneficial compounds being kept in development abeyance. Moreover, inappropriate choice in model organism for studying disease states may result in pushing forward inappropriate drug targets and/or compounds and wasting valuable time and resources in producing much-needed medications. In this dissertation, models for basic science research and drug testing are investigated with the intention of improving current preclinical models in order to drive drugs to market faster and more efficiently. We found that embryonic rat hippocampal neurons, commonly used to study neurodegenerative disease mechanisms in vitro, take 3-4 weeks to achieve similar, critical ion-channel expression profiles as seen in adult rat hippocampal cultures. We also characterized a newly-available commercial cell line of human induced pluripotent stem cell-derived neurons for their applicability in long-term studies, and used them to develop a more pathologically relevant model of early Alzheimer's Disease in vitro. Finally, we attempted to create an engineered, layered neural network of human neurons to study drug responses and synaptic mechanisms. Utilization of the results and methods described herein will help push forward the development of better model systems for translation of laboratory research to successful clinical human drug trials.
Show less
Date Issued
2015
Identifier
CFE0006261, ucf:51031
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006261