scholarly journals Synaptic Loss in Alzheimer's Disease: Mechanistic Insights Provided by Two-Photon in vivo Imaging of Transgenic Mouse Models

2020 ◽  
Vol 14 ◽  
Author(s):  
Jaichandar Subramanian ◽  
Julie C. Savage ◽  
Marie-Ève Tremblay
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Mouse Models ◽  
Synaptic Loss ◽  
Two Photon ◽  
Synapse Loss ◽  
Disease Mutations ◽  
The Brain

Synapse loss is the strongest correlate for cognitive decline in Alzheimer's disease. The mechanisms underlying synapse loss have been extensively investigated using mouse models expressing genes with human familial Alzheimer's disease mutations. In this review, we summarize how multiphoton in vivo imaging has improved our understanding of synapse loss mechanisms associated with excessive amyloid in the living animal brain. We also discuss evidence obtained from these imaging studies for the role of cell-intrinsic calcium dyshomeostasis and cell-extrinsic activities of microglia, which are the immune cells of the brain, in mediating synapse loss.

scholarly journals TRANSGENIC MOUSE MODELS OF ALZHEIMER’S DISEASE

2019 ◽  
Vol 3 (Supplement_1) ◽  
pp. S835-S835
Author(s):  
Charnae A Henry-Smith ◽  
Xianlin Han
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Mouse Models ◽  
Myelin Sheath ◽  
Thinking Skills ◽  
Drug Dosage ◽  
Whole Body ◽  
To Receive ◽  
The Brain

Abstract Alzheimer’s disease is a progressive brain disease that slowly destroys memory and thinking skills. Alzheimer’s is characterized by an increase in Aβ plaques , and tau tangles. Neurons in the brain have axons covered in myelin sheath that connect microglia and astrocytes. The myelin sheath is composed of about 70% lipid composition; Sulfatide contributing to 30% overall. Sulfatide changes the morphology of primary microglia to their activated form. To study the role of microglia activation and sulfatide levels, three different mouse models were created: APP KI mice, CST Whole Body Ko mice, and cCST (conditional) KO. In order to create the genotype of the APP KI mice, a breeding mouse line was created. The APP KI gene had to be introduced in Plp1-Cre and cCST KO crossed mice to receive a working mouse model. During the duration of breeding for the APP KI mice, a preliminary experiment was performed on the CST KO mice. These mice were given the PLX3397 diet with the aim to remove the microglia and to see the effect of Aβ plaques. The PLX3397 will reduce the microglia targeting the CSF1R. After consuming the diet, the mice were harvested to collect tissues from the brain and spinal cord. Lipidomics and immunohistology were performed. In conclusion, we will continue the breeding of the CST flox/flox / Plp1-Cre / APP KI mice, and the drug dosage and treatment to be used in our APP KI mice will be based on preliminary data from our CST mice.

scholarly journals Detection of Active Caspase-3 in Mouse Models of Stroke and Alzheimer’s Disease with a Novel Dual Positron Emission Tomography/Fluorescent Tracer [68Ga]Ga-TC3-OGDOTA

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Valeriy G. Ostapchenko ◽  
Jonatan Snir ◽  
Mojmir Suchy ◽  
Jue Fan ◽  
M. Rebecca Cobb ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Mouse Models ◽  
Caspase 3 ◽  
Single Cells ◽  
Glucose Deprivation ◽  
Apoptotic Cells ◽  
The Brain

Apoptosis is a feature of stroke and Alzheimer’s disease (AD), yet there is no accepted method to detect or follow apoptosis in the brain in vivo. We developed a bifunctional tracer [68Ga]Ga-TC3-OGDOTA containing a cell-penetrating peptide separated from fluorescent Oregon Green and 68Ga-bound labels by the caspase-3 recognition peptide DEVD. We hypothesized that this design would allow [68Ga]Ga-TC3-OGDOTA to accumulate in apoptotic cells. In vitro, Ga-TC3-OGDOTA labeled apoptotic neurons following exposure to camptothecin, oxygen-glucose deprivation, and β-amyloid oligomers. In vivo, PET showed accumulation of [68Ga]Ga-TC3-OGDOTA in the brain of mouse models of stroke or AD. Optical clearing revealed colocalization of [68Ga]Ga-TC3-OGDOTA and cleaved caspase-3 in brain cells. In stroke, [68Ga]Ga-TC3-OGDOTA accumulated in neurons in the penumbra area, whereas in AD mice [68Ga]Ga-TC3-OGDOTA was found in single cells in the forebrain and diffusely around amyloid plaques. In summary, this bifunctional tracer is selectively associated with apoptotic cells in vitro and in vivo in brain disease models and represents a novel tool for apoptosis detection that can be used in neurodegenerative diseases.

scholarly journals Nutrient signaling pathways regulate amyloid clearance and synaptic loss in Alzheimer’s disease

2020 ◽  
Author(s):  
Mrityunjoy Mondal ◽  
Jitin Bali ◽  
Makis Tzioras ◽  
Rosa C. Paolicelli ◽  
Ali Jawaid ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Β ◽  
Pathological State ◽  
Amyloid Formation ◽  
Synaptic Loss ◽  
Synapse Loss ◽  
Human Neurons ◽  
Nutrient Signaling

SummaryExtra-cellular accumulation of Amyloid-β (Aβ) plaques is causatively associated with Alzheimer’s disease (AD). However, mechanisms that mediate the pre-pathological state of amyloid plaque formation remain elusive. Here, using paired RNAi and kinase inhibitor screens, we discovered that AKT-mediated insulin/nutrient signaling suppresses lysosomal clearance of Aβ and promotes amyloid formation. This mechanism is cell-autonomous and functions in multiple systems, including iPSC-derived human neurons and in vivo. Nutrient signaling regulates amyloid formation via distinct lysosomal functional mechanisms, while enhanced amino acid signaling promotes amyloid formation by transcriptionally suppressing lysosome biogenesis, and high intracellular cholesterol levels suppress lysosomal clearance of amyloid by increasing the number of non-functional lysosomes. The nutrient signaling pathway, present in both neurons and microglia, regulates lysosomal clearance of amyloid and microglia mediated synapse loss, both in vitro and in vivo. Clinically, older hyperlipidemic patients showed less synapse loss through microglia and performed better in cognitive tests. Thus, our results reveal a bi-partite cellular quality control system regulated by the insulinnutrient signaling that in neurons regulates Aβ peptide clearance and in microglia regulates synaptic loss, both processes causally associated with AD. Our results also caution against reducing amyloid through such processes as this might also result in synapse loss.

scholarly journals MicroRNAs and Alzheimer's Disease Mouse Models: Current Insights and Future Research Avenues

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Charlotte Delay ◽  
Sébastien S. Hébert
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Clinical Trials ◽  
Animal Models ◽  
Mouse Models ◽  
Future Research ◽  
Neuronal Function ◽  
Key Genes

Evidence from clinical trials as well as from studies performed in animal models suggest that both amyloid and tau pathologies function in concert with other factors to cause the severe neurodegeneration and dementia in Alzheimer’s disease (AD) patients. Accumulating data in the literature suggest that microRNAs (miRNAs) could be such factors. These conserved, small nonprotein-coding RNAs are essential for neuronal function and survival and have been implicated in the regulation of key genes involved in genetic and sporadic AD. The study of miRNA changes in AD mouse models provides an appealing approach to address the cause-consequence relationship between miRNA dysfunction and AD pathology in humans. Mouse models also provide attractive tools to validate miRNA targetsin vivoand provide unique platforms to study the role of specific miRNA-dependent gene pathways in disease. Finally, mouse models may be exploited for miRNA diagnostics in the fight against AD.

scholarly journals Pinpointing Brain TREM2 Levels in Two Mouse Models of Alzheimer’s Disease

2021 ◽  
Author(s):  
Silvio R. Meier ◽  
Dag Sehlin ◽  
Greta Hultqvist ◽  
Stina Syvänen
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Transgenic Mice ◽  
Mouse Models ◽  
Microglial Activation ◽  
Bispecific Antibody ◽  
Ex Vivo ◽  
Transgenic Animals ◽  
The Brain

Abstract Purpose The triggering receptor expressed on myeloid cells 2 (TREM2) is expressed by brain microglia. Microglial activation, as observed in Alzheimer’s disease (AD) as well as in transgenic mice expressing human amyloid-beta, appears to increase soluble TREM2 (sTREM2) levels in CSF and brain. In this study, we used two different transgenic mouse models of AD pathology and investigated the potential of TREM2 to serve as an in vivo biomarker for microglial activation in AD. Procedures We designed and generated a bispecific antibody based on the TREM2-specific monoclonal antibody mAb1729, fused to a single-chain variable fragment of the transferrin receptor binding antibody 8D3. The 8D3-moiety enabled transcytosis of the whole bispecific antibody across the blood-brain barrier. The bispecific antibody was radiolabeled with I-125 (ex vivo) or I-124 (PET) and administered to transgenic AD and wild-type (WT) control mice. Radioligand retention in the brain of transgenic animals was compared to WT mice by isolation of brain tissue at 24 h or 72 h, or with in vivo PET at 24 h, 48 h, and 72 h. Intrabrain distribution of radiolabeled mAb1729-scFv8D3CL was further studied by autoradiography, while ELISA was used to determine TREM2 brain concentrations. Results Transgenic animals displayed higher total exposure, calculated as the AUC based on SUV determined at 24h, 48h, and 72h post injection, of PET radioligand [124I]mAb1729-scFv8D3CL than WT mice. However, differences were not evident in single time point PET images or SUVs. Ex vivo autoradiography confirmed higher radioligand concentrations in cortex and thalamus in transgenic mice compared to WT, and TREM2 levels in brain homogenates were considerably higher in transgenic mice compared to WT. Conclusion Antibody-based radioligands, engineered to enter the brain, may serve as PET radioligands to follow changes of TREM2 in vivo, but antibody formats with faster systemic clearance to increase the specific signal in relation to that from blood in combination with antibodies showing higher affinity for TREM2 must be developed to further progress this technique for in vivo use.

scholarly journals An isogenic panel of single App knock-in mouse models of Alzheimer's disease confers differential profiles of β-secretase inhibition and endosomal abnormalities

2021 ◽  
Author(s):  
Naoto Watamura ◽  
Kaori Sato ◽  
Gen Shiihashi ◽  
Ayami Iwasaki ◽  
Naoko Kamano ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Mouse Models ◽  
The Arctic ◽  
Secretase Inhibitor ◽  
Beta Secretase ◽  
Abeta Production ◽  
The Brain ◽  
Experimental Comparisons

We previously developed single App knock-in mouse models of Alzheimer's disease (AD) that harbor the Swedish and Beyreuther/Iberian mutations with or without the Arctic mutation (AppNL-G-F and AppNL-F mice). These models showed the development of amyloid We previously developed single App knock-in mouse models of AD that harbor the Swedish and Beyreuther/Iberian mutations with or without the Arctic mutation (AppNL-G-F and AppNL-F mice). We have now generated App knock-in mice devoid of the Swedish mutations (AppG-F mice) and some additional mutants to address the following two questions: [1] Do the Swedish mutations influence the mode of beta-secretase inhibitor action in vivo? [2] Does the quantity of C-terminal fragment of amyloid precursor protein (APP) generated by beta-secretase (CTF-beta) affect endosomal properties as previously reported as well as other pathological events? Abeta pathology was exhibited by AppG-F mice from 6 to 8 months of age, and was accompanied by microglial and astrocyte activation. We found that a beta-secretase inhibitor, verubecestat, inhibited Abeta production in AppG-F mice, but not in AppNL-G-F mice, indicating that the AppG-F mice are more suitable for preclinical studies of beta-secretase inhibition given that most AD patients do not carry Swedish mutations. We also found that the quantity of CTF-beta generated by various App knock-in mutants failed to correlate with endosomal alterations or enlargement, implying that CTF-beta, endosomal abnormalities, or both are unlikely to play a major role in AD pathogenesis. This is the first AD mouse model ever described that recapitulates amyloid pathology in the brain without the presence of Swedish mutations and without relying on the overexpression paradigm. Thus, experimental comparisons between different App knock-in mouse lines will potentially provide new insights into our understanding of the etiology of AD.

scholarly journals Towards Understanding the Roles of Heparan Sulfate Proteoglycans in Alzheimer’s Disease

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Gan-lin Zhang ◽  
Xiao Zhang ◽  
Xiao-min Wang ◽  
Jin-Ping Li
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Heparan Sulfate ◽  
Mouse Models ◽  
Transgenic Animal ◽  
Heparan Sulfate Proteoglycans ◽  
Molecular Structures ◽  
The Brain

Alzheimer’s disease (AD) is the most common form of dementia, characterized by progressive loss of memory and cognitive dysfunctions. A central pathological event of AD is accumulation and deposition of cytotoxic amyloid-βpeptide (Aβ) in the brain parenchyma. Heparan sulfate proteoglycans (HSPGs) and the side chains heparan sulfate (HS) are found associated with Aβdeposits in the brains of AD patients and transgenic animal models of AD. A growing body of evidence fromin vitroandin vivostudies suggests functional roles of HSPG/HS in Aβpathogenesis. Although the question of “how and why HSPG/HS is codeposited with Aβ?” still remains, it is within reach to understand the mechanisms of the events. Recent progress by immunohistochemical examination with advanced antibodies shed light on molecular structures of HS codeposited with Aβ. Several recent reports have provided important new insights into the roles of HSPG in Aβpathogenesis. Particularly, experiments on mouse models revealed indispensible functions of HSPG in modulating Aβ-associated neuroinflammation and clearance of Aβfrom the brain. Application of molecules to interfere with the interaction between HS and Aβpeptides has demonstrated beneficial effects on AD mouse models. Elucidating the functions of HSPG/HS in Aβdeposition and toxicity is leading to further understanding of the complex pathology of AD. The progress is encouraging development of new treatments for AD by targeting HS-Aβinteractions.

Electromagnetic field in Alzheimer’s disease: a literature review of recent preclinical and clinical studies

2020 ◽  
Vol 17 ◽  
Author(s):  
Reem Habib Mohamad Ali Ahmad ◽  
Marc Fakhoury ◽  
Nada Lawand
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Neurodegenerative Disorder ◽  
In Vivo Studies ◽  
Key Factors ◽  
Potential Benefits ◽  
Preclinical And Clinical Studies ◽  
The Brain

: Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by the progressive loss of neurons leading to cognitive and memory decay. The main signs of AD include the irregular extracellular accumulation of amyloidbeta (Aβ) protein in the brain and the hyper-phosphorylation of tau protein inside neurons. Changes in Aβ expression or aggregation are considered key factors in the pathophysiology of sporadic and early-onset AD and correlate with the cognitive decline seen in patients with AD. Despite decades of research, current approaches in the treatment of AD are only symptomatic in nature and are not effective in slowing or reversing the course of the disease. Encouragingly, recent evidence revealed that exposure to electromagnetic fields (EMF) can delay the development of AD and improve memory. This review paper discusses findings from in vitro and in vivo studies that investigate the link between EMF and AD at the cellular and behavioural level, and highlights the potential benefits of EMF as an innovative approach for the treatment of AD.

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