Matching Items (10)

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Dyrk1 inhibition improves Alzheimer's disease-like pathology

Description

There is an urgent need for the development of new therapeutic strategies for Alzheimer's disease (AD). The dual-specificity tyrosine phosphorylation-regulated kinase-1A (Dyrk1a) is a protein kinase that phosphorylates the amyloid

There is an urgent need for the development of new therapeutic strategies for Alzheimer's disease (AD). The dual-specificity tyrosine phosphorylation-regulated kinase-1A (Dyrk1a) is a protein kinase that phosphorylates the amyloid precursor protein (APP) and tau and thus represents a link between two key proteins involved in AD pathogenesis. Furthermore, Dyrk1a is upregulated in postmortem human brains, and high levels of Dyrk1a are associated with mental retardation. Here, we sought to determine the effects of Dyrk1 inhibition on AD-like pathology developed by 3xTg-AD mice, a widely used animal model of AD. We dosed 10-month-old 3xTg-AD and nontransgenic (NonTg) mice with a Dyrk1 inhibitor (Dyrk1-inh) or vehicle for eight weeks. During the last three weeks of treatment, we tested the mice in a battery of behavioral tests. The brains were then analyzed for the pathological markers of AD. We found that chronic Dyrk1 inhibition reversed cognitive deficits in 3xTg-AD mice. These effects were associated with a reduction in amyloid-β (Aβ) and tau pathology. Mechanistically, Dyrk1 inhibition reduced APP and insoluble tau phosphorylation. The reduction in APP phosphorylation increased its turnover and decreased Aβ levels. These results suggest that targeting Dyrk1 could represent a new viable therapeutic approach for AD.

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Created

Date Created
  • 2017-06-19

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Identification of learning-induced changes in protein networks in the hippocampi of a mouse model of Alzheimer’s disease

Description

Memory loss is the most profound clinical manifestation in Alzheimer’s disease (AD); however, the molecular mechanisms underlying these deficits are poorly understood. Identification of the molecular pathways involved in the

Memory loss is the most profound clinical manifestation in Alzheimer’s disease (AD); however, the molecular mechanisms underlying these deficits are poorly understood. Identification of the molecular pathways involved in the onset of cognitive deficits may lead to the identification of key events in the pathogenesis of AD. Using isobaric tags for relative and absolute quantitation (iTRAQ) and proteomic methods, here we identified learning-induced changes in the hippocampal proteome of non-transgenic (NonTg) and 3 × Tg-AD mice, a widely used animal model of AD. We found that expression of 192 proteins was differentially regulated by learning in NonTg mice. Notably, of these 192 proteins, only 28 were also differentially regulated by learning in 3 × Tg-AD mice, whereas the levels of 164 proteins were uniquely changed in NonTg mice but not in 3 × Tg-AD mice. These data suggest that during learning, 3 × Tg-AD mice fail to differentially regulate 164 proteins. Gene ontology and protein interaction analyses indicated that these proteins were overrepresented in RNA processing, specifically RNA transport, splicing and mRNA translation initiation pathways. These findings suggest that mRNA-processing events that take place during learning and memory are significantly altered in 3 × Tg-AD mice.

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Agent

Created

Date Created
  • 2016-07-05

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Role of S6K1 on structural and molecular changes in the brain of a mouse model of AD

Description

The aims of this project are: (i) to identify structural and molecular changes in the brains of 3xTg-AD mice and (ii) to determine whether decreasing S6K1 protects the brain from

The aims of this project are: (i) to identify structural and molecular changes in the brains of 3xTg-AD mice and (ii) to determine whether decreasing S6K1 protects the brain from these changes. To achieve our goals, we decided to remove one copy of the S6K1 gene in 3xTg-AD mice by breeding them with S6K1 knockout mice (S6K1+/-). In previous studies, we have seen that reducing S6K1 levels in 3xTg-AD mice improved spatial memory and synaptic plasticity which was associated with reduced A and tau pathology. Here, we used a multiparametric MRI to assess volumetric and blood flow changes in the brain of 20-month-old 3xTg-AD mice. We found that 3xTg-AD/S6K1+/- mice had higher blood flow and cortical volume compared to 3xTg-AD mice. However, we saw no significant differences between 3xTg-AD mice and NonTg mice. We further found A levels and plaque numbers were significantly lower in 3xTg-AD/S6K1+/- mice compared to 3xTg-AD mice. This reduction in plaques could account for the improvement in blood flow in 3xTg-AD/S6K1+/- mice. To try to understand the reason behind the increase in cortical volume in the 3xTg-AD/S6K1+/- when compared to the 3xTg-AD, we measured markers of synaptic density, PSD95, and synaptophysin. We found that PSD95 levels were not different between the four groups. However, synaptophysin levels were significantly lower in 3xTg-AD mice compared to NonTg levels and returned to baseline levels in 3xTg-AD mice lacking one copy of the S6K1 gene. This difference in synaptophysin could explain, at least in part, the difference in volume between the four groups analyzed. Overall, this represents the first evidence showing that reducing mTOR signaling improves blood flow and cortical volume in a mouse model of AD.

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Agent

Created

Date Created
  • 2018-05

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Elucidating the Effects of PRAS40 on Learning and Memory

Description

The mammalian target of rapamycin (mTOR) is integral in regulating cell growth as it maintains a homeostatic balance of proteins by modulating their synthesis and degradation. In the brain, mTOR

The mammalian target of rapamycin (mTOR) is integral in regulating cell growth as it maintains a homeostatic balance of proteins by modulating their synthesis and degradation. In the brain, mTOR regulates protein-driven neuroplastic changes that modulate learning and memory. Nevertheless, upregulation of mTOR can cause detrimental effect in spatial memory and synaptic plasticity. The proline-rich Akt-substrate 40 kDa (PRAS40) is a key negative regulator of mTOR, as it binds mTOR and directly reduces its activity. To investigate the role of PRAS40 on learning and memory, we generated a transgenic mouse model in which we used the tetracycline-off system to regulate the expression of PRAS40 specifically in neurons of the hippocampus. After induction, we found that mice overexpressing PRAS40 performed better than control mice in the Morris Water Maze behavioral test. We further show that the improvement in memory was associated with a decrease in mTOR signaling, an increase in dendritic spines in hippocampal pyramidal neurons, and an increase in the levels of brain-derived neurotrophic factor (BDNF), a neurotrophin necessary for learning and memory. This is the first evidence that shows that increasing PRAS40 in the mouse brain enhances learning and memory deficits.

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Agent

Created

Date Created
  • 2018-05

Acute tau knockdown in the hippocampus of adult mice causes learning and memory deficits

Description

To date, it has been difficult to elucidate the role of tau in learning and memory during adulthood due to developmental compensation of other microtubule associated proteins in Tau knockout

To date, it has been difficult to elucidate the role of tau in learning and memory during adulthood due to developmental compensation of other microtubule associated proteins in Tau knockout (KO) mice. Here, we generated an adeno-associated virus (AAV) expressing a doxycycline (doxy)-inducible short-hairpin (sh) RNA targeted to tau, and stereotaxically and bilaterally injected 7-month-old C57BL/6 mice with either the AAV-shRNAtau or an AAV expressing a scramble shRNA sequence. Seven days after the injections, all animals were administered doxy for thirty-five days to induce expression of shRNAs, after which they were tested in the open field, rotarod and Morris water maze (MWM) to assess anxiety like behavior, motor coordination and spatial reference memory, respectively. Our results show that reducing tau in the adult hippocampus produces significant impairments in motor coordination, endurance and spatial memory. Tissue analyses shows that tau knockdown reduces hippocampal dendritic spine density and the levels of BDNF and synaptophysin, two proteins involved in memory formation and plasticity. Our approach circumvents the developmental compensation issues observed in Tau KO models and shows that reducing tau levels during adulthood impairs cognition.

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Agent

Created

Date Created
  • 2018-05

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Mice Olfaction and Habituation on Strawberries through Utilization of an Odorized Hole-Board Arena

Description

The mammalian olfactory system is commonly studied by using the mouse as a model system. Odor habituation is used to investigate odor perception and learning processes. Most previous experimental preparations

The mammalian olfactory system is commonly studied by using the mouse as a model system. Odor habituation is used to investigate odor perception and learning processes. Most previous experimental preparations have been tedious, requiring a researcher to manually change odorants, record investigation time and duration at each odorant, or physical alteration on the mice to enable video tracking. These limitations were overcame by creating an odorized hole-board to allow for systematic and automatic recording of olfactory behavior in mice. A cohort of five male mice were utilized in these experiments and the responses to the odor of strawberries, a diet staple of wile mice, were examined. Experiment 1 showed that free-feeding mice exhibit a preference to locations with strawberry (over control locations), even when these locations can only be identified using olfaction. This preference habituates within a trial but not across days. Experiment 2 showed that strawberry odor without reward causes habituation or extinction to the odor both within trials and across days. From these experiments, it can be concluded that mice innately explore strawberry odor and this can be exploited to the study odor habituation using an odorized hole-board.

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Agent

Created

Date Created
  • 2016-12

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An Evaluation of the Cognitive Effects of a Short-Term and a Long-Term Ovarian Hormone Deprivation in a Transgenic Mouse Model of Alzheimer's Disease: Addressing the Critical Window

Description

With no known cure, Alzheimer's disease (AD) is the most common dementia, affecting more than 5.5 million Americans. Research has shown that women who undergo surgical menopause (i.e. removal of

With no known cure, Alzheimer's disease (AD) is the most common dementia, affecting more than 5.5 million Americans. Research has shown that women who undergo surgical menopause (i.e. removal of the ovaries) before the onset of natural menopause are at a greater risk for AD. It is hypothesized that this greater relative risk of developing AD is linked to ovarian hormone deprivation associated with surgical menopause. The purpose of these studies was to evaluate the behavioral changes that occur after a short-term (ST) and a long-term (LT) ovarian hormone deprivation in a mouse model of AD. Wildtype (Wt) or APP/PS1 (Tg) mutation mice underwent either a sham surgery or an ovariectomy (Ovx) surgery at three months of age. Study 1 consisted of a short-term cohort that was behaviorally tested one month following surgery on a battery of spatial memory tasks including, the Morris water maze, delayed matched-to-sample water maze, and visible platform task. Study 2 consisted of a long-term cohort that was behaviorally tested on the same cognitive battery three months following surgery. Results of Study 1 revealed that genotype interacted with surgical menopause status, such that after a short-term ovarian hormone deprivation, Ovx induced a genotype effect while Sham surgery did not. Results of Study 2 showed a similar pattern of effects, with a comparable interaction between genotypes and surgical menopause status. These findings indicate that the cognitive impact of ovarian hormone deprivation depends on AD-related genotype. Neuropathology evaluations in these mice will be done in the near future and will allow us to test relations between surgical menopause status, cognition, and AD-like neuropathology.

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Agent

Created

Date Created
  • 2017-12

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Pim1 inhibition as a novel therapeutic strategy for Alzheimer’s disease

Description

Background
Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder worldwide. Clinically, AD is characterized by impairments of memory and cognitive functions. Accumulation of amyloid-β (Aβ) and neurofibrillary tangles are

Background
Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder worldwide. Clinically, AD is characterized by impairments of memory and cognitive functions. Accumulation of amyloid-β (Aβ) and neurofibrillary tangles are the prominent neuropathologies in patients with AD. Strong evidence indicates that an imbalance between production and degradation of key proteins contributes to the pathogenesis of AD. The mammalian target of rapamycin (mTOR) plays a key role in maintaining protein homeostasis as it regulates both protein synthesis and degradation. A key regulator of mTOR activity is the proline-rich AKT substrate 40 kDa (PRAS40), which directly binds to mTOR and reduces its activity. Notably, AD patients have elevated levels of phosphorylated PRAS40, which correlate with Aβ and tau pathologies as well as cognitive deficits. Physiologically, PRAS40 phosphorylation is regulated by Pim1, a protein kinase of the protoconcogene family. Here, we tested the effects of a selective Pim1 inhibitor (Pim1i), on spatial reference and working memory and AD-like pathology in 3xTg-AD mice.
Results
We have identified a Pim1i that crosses the blood brain barrier and reduces PRAS40 phosphorylation. Pim1i-treated 3xTg-AD mice performed significantly better than their vehicle treated counterparts as well as non-transgenic mice. Additionally, 3xTg-AD Pim1i-treated mice showed a reduction in soluble and insoluble Aβ[subscript 40] and Aβ[subscript 42] levels, as well as a 45.2 % reduction in Aβ[subscript 42] plaques within the hippocampus. Furthermore, phosphorylated tau immunoreactivity was reduced in the hippocampus of Pim1i–treated 3xTg-AD mice by 38 %. Mechanistically, these changes were linked to a significant increase in proteasome activity.
Conclusion
These results suggest that reductions in phosphorylated PRAS40 levels via Pim1 inhibition reduce Aβ and Tau pathology and rescue cognitive deficits by increasing proteasome function. Given that Pim1 inhibitors are already being tested in ongoing human clinical trials for cancer, the results presented here may open a new venue of drug discovery for AD by developing more Pim1 inhibitors.

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Agent

Created

Date Created
  • 2016-07-02

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Removing Neuronal PRAS40 Exacerbates Alzheimer's Disease Pathology in a Mouse Model

Description

Alzheimer’s disease (AD) is characterized by the aberrant accumulation and aggregation of proteins that in turn contribute to learning and memory deficits. The mammalian target of rapamycin (mTOR) plays an

Alzheimer’s disease (AD) is characterized by the aberrant accumulation and aggregation of proteins that in turn contribute to learning and memory deficits. The mammalian target of rapamycin (mTOR) plays an essential role in regulating the synthesis and degradation of proteins that contribute to cell growth and learning and memory. Hyperactivity of mTOR can cause detrimental effects to protein homeostasis and has been linked to AD. The proline-rich Akt-substrate 40 kDa (PRAS40) is a negative regulator of mTOR, as it binds to mTOR directly, reducing its activity. Upon phosphorylation, PRAS40 detaches from mTOR thereby releasing its inhibitory effects. Increased phosphorylation of PRAS40, and a subsequent increase in mTOR activity has been linked to diabetes, cancer, and other conditions; however, PRAS40’s direct role in the pathogenesis of AD is still unclear. To investigate the role of PRAS40 in AD pathology, we generated a PRAS40 conditional knockout mouse model and, using a neuronal-specific Cre recombinase, selectively removed PRAS40 from APP/PS1 mice. Removing neuronal PRAS40 exacerbated Abeta levels and plaque load but paradoxically had no significant effects on mTOR signaling. Mechanistically, the increase in Abeta pathology was linked to a decrease in autophagy function. Our data highlight a primary role of PRAS40 in the pathogenesis of AD.

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Agent

Created

Date Created
  • 2019-05

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Antibody-based Diagnostics and Therapeutics for Alzheimer's disease and Frontotemporal Dementia

Description

Alzheimer’s Disease (AD) and Frontotemporal Dementia (FTD) are the leading causes of early onset dementia. There are currently no ways to slow down progression, to prevent or cure AD and

Alzheimer’s Disease (AD) and Frontotemporal Dementia (FTD) are the leading causes of early onset dementia. There are currently no ways to slow down progression, to prevent or cure AD and FTD. Both AD and FTD share a lot of the symptoms and pathology. Initial symptoms such as confusion, memory loss, mood swings and behavioral changes are common in both these dementia subtypes. Neurofibrillary tau tangles and intraneuronal aggregates of TAR DNA Binding Protein 43 (TDP-43) are also observed in both AD and FTD. Hence, FTD cases are often misdiagnosed as AD due to a lack of accurate diagnostics. Prior to the formation of tau tangles and TDP-43 aggregates, tau and TDP-43 exist as intermediate protein variants which correlate with cognitive decline and progression of these neurodegenerative diseases. Effective diagnostic and therapeutic agents would selectively recognize these toxic, disease-specific variants. Antibodies or antibody fragments such as single chain antibody variable domain fragments (scFvs), with their diverse binding capabilities, can aid in developing reagents that can selectively bind these protein variants. A combination of phage display library and Atomic Force Microscopy (AFM)-based panning was employed to identify antibody fragments against immunoprecipitated tau and immunoprecipitated TDP-43 from human postmortem AD and FTD brain tissue respectively. Five anti-TDP scFvs and five anti-tau scFvs were selected for characterization by Enzyme Linked Immunosorbent Assays (ELISAs) and Immunohistochemistry (IHC). The panel of scFvs, together, were able to identify distinct protein variants present in AD but not in FTD, and vice versa. Generating protein variant profiles for individuals, using the panel of scFvs, aids in developing targeted diagnostic and therapeutic plans, gearing towards personalized medicine.

Contributors

Agent

Created

Date Created
  • 2018