Molecular Profiles of Amyloid-β Proteoforms in Typical and Rapidly Progressive Alzheimer’s Disease

AbstractThe molecular determinants of atypical clinical variants of Alzheimer’s disease, including the recently discovered rapidly progressive Alzheimer’s disease (rpAD), are unknown to date. Fibrilization of the amyloid-β (Aβ) peptide is the most frequently studied candidate in this context. The Aβ peptide can exist as multiple proteoforms that vary in their post-translational processing, amyloidogenesis, and toxicity. The current study was designed to identify these variations in Alzheimer’s disease patients exhibiting classical (sAD) and rapid progression, with the primary aim of establishing if these variants may constitute strains that underlie the phenotypic variability of Alzheimer’s disease. We employed two-dimensional polyacrylamide gel electrophoresis and MALDI-ToF mass spectrometry to validate and identify the Aβ proteoforms extracted from targeted brain tissues. The biophysical analysis was conducted using RT-QuIC assay, confocal microscopy, and atomic force microscopy. Interactome analysis was performed by co-immunoprecipitation. We present a signature of 33 distinct pathophysiological proteoforms, including the commonly targeted Aβ40, Aβ42, Aβ4-42, Aβ11-42, and provide insight into their synthesis and quantities. Furthermore, we have validated the presence of highly hydrophobic Aβ seeds in rpAD brains that seeded reactions at a slower pace in comparison to typical Alzheimer’s disease. In vitro and in vivo analyses also verified variations in the molecular pathways modulated by brain-derived Aβ. These variations in the presence, synthesis, folding, and interactions of Aβ among sAD and rpAD brains constitute important points of intervention. Further validation of reported targets and mechanisms will aid in the diagnosis of and therapy for Alzheimer’s disease.

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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 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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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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Increased levels of Stress-inducible phosphoprotein-1 accelerates amyloid-β deposition in a mouse model of Alzheimer’s disease

Acta Neuropathologica Communications ◽

10.1186/s40478-020-01013-5 ◽

2020 ◽

Vol 8 (1) ◽

Author(s):

Rachel E. Lackie ◽

Jose Marques-Lopes ◽

Valeriy G. Ostapchenko ◽

Sarah Good ◽

Wing-Yiu Choy ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Mouse Model ◽

Protein Quality ◽

Amyloid Β ◽

Amyloid Burden ◽

C Elegans ◽

Model Of Alzheimer’S Disease

Abstract Molecular chaperones and co-chaperones, which are part of the protein quality control machinery, have been shown to regulate distinct aspects of Alzheimer’s Disease (AD) pathology in multiple ways. Notably, the co-chaperone STI1, which presents increased levels in AD, can protect mammalian neurons from amyloid-β toxicity in vitro and reduced STI1 levels worsen Aβ toxicity in C. elegans. However, whether increased STI1 levels can protect neurons in vivo remains unknown. We determined that overexpression of STI1 and/or Hsp90 protected C. elegans expressing Aβ(3–42) against Aβ-mediated paralysis. Mammalian neurons were also protected by elevated levels of endogenous STI1 in vitro, and this effect was mainly due to extracellular STI1. Surprisingly, in the 5xFAD mouse model of AD, by overexpressing STI1, we find increased amyloid burden, which amplifies neurotoxicity and worsens spatial memory deficits in these mutants. Increased levels of STI1 disturbed the expression of Aβ-regulating enzymes (BACE1 and MMP-2), suggesting potential mechanisms by which amyloid burden is increased in mice. Notably, we observed that STI1 accumulates in dense-core AD plaques in both 5xFAD mice and human brain tissue. Our findings suggest that elevated levels of STI1 contribute to Aβ accumulation, and that STI1 is deposited in AD plaques in mice and humans. We conclude that despite the protective effects of STI1 in C. elegans and in mammalian cultured neurons, in vivo, the predominant effect of elevated STI1 is deleterious in AD.

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Netrin-1 Interrupts Amyloid-β Amplification, Increases sAβPPα in vitro and in vivo, and Improves Cognition in a Mouse Model of Alzheimer’s Disease

Journal of Alzheimer s Disease ◽

10.3233/jad-151046 ◽

2016 ◽

Vol 52 (1) ◽

pp. 223-242 ◽

Cited By ~ 9

Author(s):

Patricia R. Spilman ◽

Veronique Corset ◽

Olivia Gorostiza ◽

Karen S. Poksay ◽

Veronica Galvan ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Mouse Model ◽

Amyloid Β ◽

Model Of Alzheimer’S Disease

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Upregulation of Alzheimer’s Disease Amyloid-β Protein Precursor in Astrocytes Both in vitro and in vivo

Journal of Alzheimer s Disease ◽

10.3233/jad-200128 ◽

2020 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Yingxia Liang ◽

Frank Raven ◽

Joseph F. Ward ◽

Sherri Zhen ◽

Siyi Zhang ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Amyloid Β ◽

Amyloid Β Protein ◽

Protein Precursor ◽

Β Protein

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Microglia Activated with the Toll-Like Receptor 9 Ligand CpG Attenuate Oligomeric Amyloid β Neurotoxicity in in Vitro and in Vivo Models of Alzheimer’s Disease

American Journal Of Pathology ◽

10.2353/ajpath.2009.090418 ◽

2009 ◽

Vol 175 (5) ◽

pp. 2121-2132 ◽

Cited By ~ 90

Author(s):

Yukiko Doi ◽

Tetsuya Mizuno ◽

Yuki Maki ◽

Shijie Jin ◽

Hiroyuki Mizoguchi ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Amyloid Β ◽

Toll Like Receptor ◽

In Vivo Models

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Extraction of Polysaccharides From Bletilla Striata Using a Modified Low-temperature Method and Evaluation of Their Efficacy Against Alzheimer’s Disease

10.21203/rs.3.rs-643976/v1 ◽

2021 ◽

Author(s):

Yi-Wen Lin ◽

Chih-Hsiang Fang ◽

Hung-Hsiang Liao ◽

Feng Huei Lin

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Low Temperature ◽

Memory Loss ◽

Amyloid Β ◽

Ulcer Bleeding ◽

Bletilla Striata ◽

Temperature Method

Abstract Background: Amyloid-β (Aβ) peptides play a key role in Alzheimer’s disease (AD), the most common type of dementia. AD is characterized by progressive cognitive and memory loss accompanied by personality changes. Bletilla striata, a traditional Chinese medicine, has been widely used in Eastern Asian countries for alimentary canal damage, ulcer, bleeding, bruises, and burns. in this study, we investigated whether BSP could prevent the ROS from Aβ and the possibility to recover from the disease by memory improvement.Methods: In this study, a polysaccharide from Bletilla striata (BSP) with strong antioxidant and anti-inflammatory properties was extracted following a low-temperature method and tested for its efficacy against AD in vitro using N2a and BV-2 cells and in vivo using AD rats.Results: The characterization of the extracted BSP for its molecular structure and the functional group demonstrated the efficiency of the modified method to retain its bioactivity. In vitro, BSP reduced ROS levels in N2a cells and the expression levels of inflammatory-related genes in BV-2 cells treated with Aβ fibrils. In vivo, BSP recovered the learning memory, ameliorated the morphological damages in the hippocampus and cortex, and reduced the expression of the β-secretase protein in AlCl3-induced AD rats.Conclusions: To the best of our knowledge, this is the first study of BSP applicating in AD. Collectively, these findings demonstrated the efficacy of BSP to prevent and alleviate the effects of AD.

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