Highly Sensitive Near-Infrared Fluorophores for in Vivo Detection of Amyloid-β Plaques in Alzheimer’s Disease

AbstractThe abnormal deposition of beta-amyloid proteins in the brain is one of the major histopathological hallmarks of Alzheimer’s disease. Currently available intravital microscopy techniques for high-resolution plaque visualization commonly involve highly invasive procedures and are limited to a small field-of-view within the rodent brain. Here, we report the transcranial detection of amyloid-beta deposits at the whole brain scale with 20 μm resolution in APP/PS1 and arcAβ mouse models of Alzheimer’s disease amyloidosis using a large-field multifocal (LMI) fluorescence microscopy technique. Highly sensitive and specific detection of amyloid-beta deposits at a single plaque level in APP/PS1 and arcAβ mice was facilitated using luminescent conjugated oligothiophene HS-169. Immunohistochemical staining with HS-169, anti-Aβ antibody 6E10, and conformation antibodies OC (fibrillar) of brain tissue sections further showed that HS-169 resolved compact parenchymal and vessel-associated amyloid deposits. The novel imaging platform offers new prospects for in vivo studies into Alzheimer’s disease mechanisms in animal models as well as longitudinal monitoring of therapeutic responses at a single plaque level.

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Application of optogenetic Amyloid-β distinguishes between metabolic and physical damages in neurodegeneration

eLife ◽

10.7554/elife.52589 ◽

2020 ◽

Vol 9 ◽

Cited By ~ 3

Author(s):

Chu Hsien Lim ◽

Prameet Kaur ◽

Emelyne Teo ◽

Vanessa Yuk Man Lam ◽

Fangchen Zhu ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Disease Progression ◽

Biological Effects ◽

Amyloid Β ◽

Tissue Loss ◽

Amyloid Β Peptide ◽

Physical Damage ◽

Living Tissues

The brains of Alzheimer’s disease patients show a decrease in brain mass and a preponderance of extracellular Amyloid-β plaques. These plaques are formed by aggregation of polypeptides that are derived from the Amyloid Precursor Protein (APP). Amyloid-β plaques are thought to play either a direct or an indirect role in disease progression, however the exact role of aggregation and plaque formation in the aetiology of Alzheimer’s disease (AD) is subject to debate as the biological effects of soluble and aggregated Amyloid-β peptides are difficult to separate in vivo. To investigate the consequences of formation of Amyloid-β oligomers in living tissues, we developed a fluorescently tagged, optogenetic Amyloid-β peptide that oligomerizes rapidly in the presence of blue light. We applied this system to the crucial question of how intracellular Amyloid-β oligomers underlie the pathologies of A. We use Drosophila, C. elegans and D. rerio to show that, although both expression and induced oligomerization of Amyloid-β were detrimental to lifespan and healthspan, we were able to separate the metabolic and physical damage caused by light-induced Amyloid-β oligomerization from Amyloid-β expression alone. The physical damage caused by Amyloid-β oligomers also recapitulated the catastrophic tissue loss that is a hallmark of late AD. We show that the lifespan deficit induced by Amyloid-β oligomers was reduced with Li+ treatment. Our results present the first model to separate different aspects of disease progression.

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Elevated Expression of MiR-17 in Microglia of Alzheimer’s Disease Patients Abrogates Autophagy-Mediated Amyloid-β Degradation

Frontiers in Immunology ◽

10.3389/fimmu.2021.705581 ◽

2021 ◽

Vol 12 ◽

Author(s):

Shady Estfanous ◽

Kylene P. Daily ◽

Mostafa Eltobgy ◽

Nicholas P. Deems ◽

Midhun N. K. Anne ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Amyloid Β ◽

Therapeutic Interventions ◽

Tissue Sections ◽

Cargo Receptor ◽

5Xfad Mouse ◽

Aβ Degradation

Autophagy is a proposed route of amyloid-β (Aβ) clearance by microglia that is halted in Alzheimer’s Disease (AD), though mechanisms underlying this dysfunction remain elusive. Here, primary microglia from adult AD (5xFAD) mice were utilized to demonstrate that 5xFAD microglia fail to degrade Aβ and express low levels of autophagy cargo receptor NBR1. In 5xFAD mouse brains, we show for the first time that AD microglia express elevated levels of microRNA cluster Mirc1/Mir17-92a, which is known to downregulate autophagy proteins. By in situ hybridization in post-mortem AD human tissue sections, we observed that the Mirc1/Mir17-92a cluster member miR-17 is also elevated in human AD microglia, specifically in the vicinity of Aβ deposits, compared to non-disease controls. We show that NBR1 expression is negatively correlated with expression of miR-17 in human AD microglia via immunohistopathologic staining in human AD brain tissue sections. We demonstrate in healthy microglia that autophagy cargo receptor NBR1 is required for Aβ degradation. Inhibiting elevated miR-17 in 5xFAD mouse microglia improves Aβ degradation, autophagy, and NBR1 puncta formation in vitro and improves NBR1 expression in vivo. These findings offer a mechanism behind dysfunctional autophagy in AD microglia which may be useful for therapeutic interventions aiming to improve autophagy function in AD.

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The relationship between cortical microstructural changes and in vivo amyloid‐β and tau in aging and preclinical Alzheimer's disease

Alzheimer s & Dementia ◽

10.1002/alz.041626 ◽

2020 ◽

Vol 16 (S4) ◽

Author(s):

Elena Rodriguez‐Vieitez ◽

Victor Montal ◽

Jorge Sepulcre ◽

Cristina Lois ◽

Bernard Hanseeuw ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Amyloid Β ◽

Preclinical Alzheimer’S Disease ◽

Microstructural Changes ◽

The Relationship

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The inhibition of cellular toxicity of amyloid-β by dissociated transthyretin

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.013440 ◽

2020 ◽

Vol 295 (41) ◽

pp. 14015-14024 ◽

Cited By ~ 1

Author(s):

Qin Cao ◽

Daniel H. Anderson ◽

Wilson Y. Liang ◽

Joshua Chou ◽

Lorena Saelices

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Protective Effect ◽

Amyloid Β ◽

Inhibitory Effect ◽

Aβ Oligomers ◽

Cellular Toxicity ◽

Computational Docking

The protective effect of transthyretin (TTR) on cellular toxicity of β-amyloid (Aβ) has been previously reported. TTR is a tetrameric carrier of thyroxine in blood and cerebrospinal fluid, the pathogenic aggregation of which causes systemic amyloidosis. However, studies have documented a protective effect of TTR against cellular toxicity of pathogenic Aβ, a protein associated with Alzheimer's disease. TTR binds Aβ, alters its aggregation, and inhibits its toxicity both in vitro and in vivo. In this study, we investigate whether the amyloidogenic ability of TTR and its antiamyloid inhibitory effect are associated. Using protein aggregation and cytotoxicity assays, we found that the dissociation of the TTR tetramer, required for its amyloid pathogenesis, is also necessary to prevent cellular toxicity from Aβ oligomers. These findings suggest that the Aβ-binding site of TTR may be hidden in its tetrameric form. Aided by computational docking and peptide screening, we identified a TTR segment that is capable of altering Aβ aggregation and toxicity, mimicking TTR cellular protection. EM, immune detection analysis, and assessment of aggregation and cytotoxicity revealed that the TTR segment inhibits Aβ oligomer formation and also promotes the formation of nontoxic, nonamyloid amorphous aggregates, which are more sensitive to protease digestion. Finally, this segment also inhibits seeding of Aβ catalyzed by Aβ fibrils extracted from the brain of an Alzheimer's patient. Together, these findings suggest that mimicking the inhibitory effect of TTR with peptide-based therapeutics represents an additional avenue to explore for the treatment of Alzheimer's disease.

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Associations of Neprilysin Activity in CSF with Biomarkers for Alzheimer’s Disease

Neurodegenerative Diseases ◽

10.1159/000500811 ◽

2019 ◽

Vol 19 (1) ◽

pp. 43-50 ◽

Cited By ~ 1

Author(s):

Timo Grimmer ◽

Oliver Goldhardt ◽

Igor Yakushev ◽

Marion Ortner ◽

Christian Sorg ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Fdg Pet ◽

Amyloid Β ◽

Neuronal Injury ◽

Pittsburgh Compound B ◽

Positron Emission ◽

Amyloid Load ◽

Alzheimer’S Pathology

Background: Neprilysin (NEP) cleaves amyloid-β 1–42 (Aβ42) in the brain. Hence, we aimed to elucidate the effect of NEP on Aβ42 in cerebrospinal fluid (CSF) and on in vivo brain amyloid load using amyloid positron emission tomography (PET) with [11C]PiB (Pittsburgh compound B). In addition, associations with the biomarkers for neuronal injury, CSF-tau and FDG-PET, were investigated. Methods: Associations were calculated using global and voxel-based (SPM8) linear regression analyses in the same cohort of 23 highly characterized Alzheimer’s disease patients. Results: CSF-NEP was significantly inversely associated with CSF-Aβ42 and positively with the extent of neuronal injury as measured by CSF-tau and FDG-PET. Conclusions: Our results on CSF-NEP are compatible with the assumption that local degradation, amongst other mechanisms of amyloid clearance, plays a role in the development of Alzheimer’s pathology. In addition, CSF-NEP is associated with the extent and the rate of neurodegeneration.

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N,N′-Diacetyl-p-phenylenediamine restores microglial phagocytosis and improves cognitive defects in Alzheimer’s disease transgenic mice

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1916318116 ◽

2019 ◽

Vol 116 (47) ◽

pp. 23426-23436 ◽

Cited By ~ 6

Author(s):

Min Hee Park ◽

Misun Lee ◽

Geewoo Nam ◽

Mingeun Kim ◽

Juhye Kang ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Transgenic Mice ◽

Amyloid Β ◽

Causative Factor ◽

Central Feature ◽

Microglial Phagocytosis ◽

Cognitive Defects

As a central feature of neuroinflammation, microglial dysfunction has been increasingly considered a causative factor of neurodegeneration implicating an intertwined pathology with amyloidogenic proteins. Herein, we report the smallest synthetic molecule (N,N′-diacetyl-p-phenylenediamine [DAPPD]), simply composed of a benzene ring with 2 acetamide groups at the para position, known to date as a chemical reagent that is able to promote the phagocytic aptitude of microglia and subsequently ameliorate cognitive defects. Based on our mechanistic investigations in vitro and in vivo, 1) the capability of DAPPD to restore microglial phagocytosis is responsible for diminishing the accumulation of amyloid-β (Aβ) species and significantly improving cognitive function in the brains of 2 types of Alzheimer’s disease (AD) transgenic mice, and 2) the rectification of microglial function by DAPPD is a result of its ability to suppress the expression of NLRP3 inflammasome-associated proteins through its impact on the NF-κB pathway. Overall, our in vitro and in vivo investigations on efficacies and molecular-level mechanisms demonstrate the ability of DAPPD to regulate microglial function, suppress neuroinflammation, foster cerebral Aβ clearance, and attenuate cognitive deficits in AD transgenic mouse models. Discovery of such antineuroinflammatory compounds signifies the potential in discovering effective therapeutic molecules against AD-associated neurodegeneration.

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