scholarly journals Single Nuclei Transcriptome Reveals Perturbed Brain Vascular Molecules in Alzheimer's Disease

2021 ◽  
Author(s):  
Ozkan Is ◽  
Xue Wang ◽  
Tulsi A. Patel ◽  
Zachary S. Quicksall ◽  
Michael G. Heckman ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Molecular Mechanisms ◽  
Temporal Cortex ◽  
Amyloid Β ◽  
Cell Types ◽  
Predictive Algorithm ◽  
Knowledge Based ◽  
Transcriptional Changes ◽  
Single Nucleus

Blood-brain barrier (BBB) dysfunction is well-known in Alzheimer's disease (AD), but the precise molecular changes contributing to its pathophysiology are unclear. To understand the transcriptional changes in brain vascular cells, we performed single nucleus RNA sequencing (snRNAseq) of temporal cortex tissue in 24 AD and control brains resulting in 79,751 nuclei, 4,604 of which formed three distinct vascular clusters characterized as activated pericytes, endothelia and resting pericytes. We identified differentially expressed genes (DEGs) and their enriched pathways in these clusters and detected the most transcriptional changes within activated pericytes. Using our data and a knowledge-based predictive algorithm, we discovered and prioritized molecular interactions between vascular and astrocyte clusters, the main cell types of the gliovascular unit (GVU) of the BBB. Vascular targets predicted to interact with astrocytic ligands have biological functions in signaling, angiogenesis, amyloid β metabolism and cytoskeletal structure. Top astrocytic and vascular interacting molecules include both novel and known AD risk genes such as APOE, APP and ECE1. Our findings provide information on transcriptional changes in predicted vascular-astrocytic partners at the GVU, bringing insights to the molecular mechanisms of BBB breakdown in AD.

scholarly journals Single-cell transcriptomic analysis elucidates APOE genotype specific changes across cell types in two brain regions in Alzheimer’s disease

2021 ◽  
Author(s):  
Stella Belonwu ◽  
Yaqiao Li ◽  
Daniel Bunis ◽  
Arjun Arkal Rao ◽  
Caroline Warly Solsberg ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Single Cell ◽  
Molecular Mechanisms ◽  
Apoe Genotype ◽  
Cell Types ◽  
Brain Regions ◽  
Single Cell Level ◽  
Cell Level ◽  
Single Nucleus

Abstract Alzheimer’s Disease (AD) is a complex neurodegenerative disease that gravely affects patients and imposes an immense burden on caregivers. Apolipoprotein E4 (APOE4) has been identified as the most common genetic risk factor for AD, yet the molecular mechanisms connecting APOE4 to AD are not well understood. Past transcriptomic analyses in AD have revealed APOE genotype-specific transcriptomic differences; however, these differences have not been explored at a single-cell level. Here, we leverage the first two single-nucleus RNA sequencing AD datasets from human brain samples, including nearly 55,000 cells from the prefrontal and entorhinal cortices. We observed more global transcriptomic changes in APOE4 positive AD cells and identified differences across APOE genotypes primarily in glial cell types. Our findings highlight the differential transcriptomic perturbations of APOE isoforms at a single-cell level in AD pathogenesis and have implications for precision medicine development in the diagnosis and treatment of AD.

scholarly journals Molecular and cellular pathology of monogenic Alzheimer’s disease at single cell resolution

2020 ◽  
Author(s):  
Federica Marinaro ◽  
Moritz Haneklaus ◽  
Zhechun Zhang ◽  
Alessio Strano ◽  
Lewis Evans ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Large Scale ◽  
Cell Types ◽  
Brain Cell ◽  
Metabolic Reprogramming ◽  
Brain Atlas ◽  
Transcriptional Changes ◽  
Single Nucleus ◽  
Cellular Pathology

AbstractCell and molecular biology analyses of sporadic Alzheimer’s disease brain are confounded by clinical variability, ageing and genetic heterogeneity. Therefore, we used single-nucleus RNA sequencing to characterize cell composition and gene expression in the cerebral cortex in early-onset, monogenic Alzheimer’s disease. Constructing a cellular atlas of frontal cortex from 8 monogenic AD individuals and 8 matched controls, provided insights into which neurons degenerate in AD and responses of different cell types to AD at the cellular and systems level. Such responses are a combination of positively adaptive and deleterious changes, including large-scale changes in synaptic transmission and marked metabolic reprogramming in neurons. The nature and scale of the transcriptional changes in AD emphasizes the global impact of the disease across all brain cell types.One Sentence SummaryAlzheimer’s disease brain atlas provides insights into disease mechanisms

Neuroprotective Role of Diosgenin, A NGF Stimulator, Against Aβ (1–42) Induced Neurotoxicity in Animal Model of Alzheimer’s Disease

2021 ◽  
Author(s):  
Swati Som ◽  
Justin Antony ◽  
Palanisamy Dhanabal ◽  
Ponnusankar Sivasankaran
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Learning And Memory ◽  
Spatial Learning ◽  
Molecular Mechanisms ◽  
Protective Action ◽  
Amyloid Β ◽  
Spatial Learning And Memory ◽  
Avoidance Task ◽  
Model Of Alzheimer’S Disease

Abstract Diosgenin is a neurosteroid derived from the plants and has been previously reported for its numerous health beneficial properties, such as anti-arrhythmic, hypolipidemic, and antiproliferative effects. Although several studies conducted earlier suggested cognition enhancement actions of diosgenin against neurodegenerative disorders, but the molecular mechanisms underlying are not clearly understood. In the present study, we investigated the neuroprotective effect of diosgenin in the wistar rats that received an intracerebroventricular injection of Amyloid-β (1–42) peptides, representing a rodent model of Alzheimer’s disease (AD). Animals were treated with 100 and 200 mg/kg/p.o of diosgenin for 28 days, followed by Amyloid-β (1–42) peptides infusion. Animals were assessed for the spatial learning and memory by using radial arm maze and passive avoidance task. Subsequently, animals were euthanized and brains were collected for biochemical estimations and histopathological studies. Our results revealed that, diosgenin administration dose dependently improved the spatial learning and memory and protected the animals from Amyloid-β (1–42) peptides induced disrupted cognitive functions. Further, biochemical analysis showed that diosgenin successfully attenuated Amyloid-β (1–42) mediated plaque load, oxidative stress, neuroinflammation and elevated acetylcholinesterase activity. In addition, histopathological evaluation also supported neuroprotective effects of diosgenin in hippocampus of rat brain when assessed using hematoxylin-eosin and Cresyl Violet staining. Thus, the aforementioned effects suggested protective action of diosgenin against Aβ (1–42) induced neuronal damage and thereby can serve as a potential therapeutic candidate for AD.

scholarly journals Molecular and Imaging Biomarkers in Alzheimer’s Disease: A Focus on Recent Insights

2020 ◽  
Vol 10 (3) ◽  
pp. 61 ◽  
Author(s):  
Chiara Villa ◽  
Marialuisa Lavitrano ◽  
Elena Salvatore ◽  
Romina Combi
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Molecular Mechanisms ◽  
Biological Fluids ◽  
Imaging Techniques ◽  
Amyloid Β ◽  
The Elderly ◽  
Diagnostic Methods ◽  
Imaging Biomarkers ◽  
Attractive Alternative

Alzheimer’s disease (AD) is the most common neurodegenerative disease among the elderly, affecting millions of people worldwide and clinically characterized by a progressive and irreversible cognitive decline. The rapid increase in the incidence of AD highlights the need for an easy, efficient and accurate diagnosis of the disease in its initial stages in order to halt or delay the progression. The currently used diagnostic methods rely on measures of amyloid-β (Aβ), phosphorylated (p-tau) and total tau (t-tau) protein levels in the cerebrospinal fluid (CSF) aided by advanced neuroimaging techniques like positron emission tomography (PET) and magnetic resonance imaging (MRI). However, the invasiveness of these procedures and the high cost restrict their utilization. Hence, biomarkers from biological fluids obtained using non-invasive methods and novel neuroimaging approaches provide an attractive alternative for the early diagnosis of AD. Such biomarkers may also be helpful for better understanding of the molecular mechanisms underlying the disease, allowing differential diagnosis or at least prolonging the pre-symptomatic stage in patients suffering from AD. Herein, we discuss the advantages and limits of the conventional biomarkers as well as recent promising candidates from alternative body fluids and new imaging techniques.

scholarly journals Transcriptional, Behavioral and Biochemical Profiling in the 3xTg-AD Mouse Model Reveals a Specific Signature of Amyloid Deposition and Functional Decline in Alzheimer’s Disease

2020 ◽  
Vol 14 ◽  
Author(s):  
Wencheng Yin ◽  
Navei Cerda-Hernández ◽  
Atahualpa Castillo-Morales ◽  
Mayra L. Ruiz-Tejada-Segura ◽  
Jimena Monzón-Sandoval ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Molecular Mechanisms ◽  
Transcriptional Profiling ◽  
Differential Expression Analysis ◽  
Functional Decline ◽  
Insular Cortex ◽  
Learning Performance ◽  
Significant Enrichment ◽  
Transcriptional Changes

Alzheimer’s disease (AD)-related degenerative decline is associated to the presence of amyloid beta (Aβ) plaque lesions and neuro fibrillary tangles (NFT). However, the precise molecular mechanisms linking Aβ deposition and neurological decline are still unclear. Here we combine genome-wide transcriptional profiling of the insular cortex of 3xTg-AD mice and control littermates from early through to late adulthood (2–14 months of age), with behavioral and biochemical profiling in the same animals to identify transcriptional determinants of functional decline specifically associated to build-up of Aβ deposits. Differential expression analysis revealed differentially expressed genes (DEGs) in the cortex long before observed onset of behavioral symptoms in this model. Using behavioral and biochemical data derived from the same mice and samples, we found that down but not up-regulated DEGs show a stronger average association with learning performance than random background genes in control not seen in AD mice. Conversely, these same genes were found to have a stronger association with Aβ deposition than background genes in AD but not in control mice, thereby identifying these genes as potential intermediaries between abnormal Aβ/NFT deposition and functional decline. Using a complementary approach, gene ontology analysis revealed a highly significant enrichment of learning and memory, associative, memory, and cognitive functions only among down-regulated, but not up-regulated, DEGs. Our results demonstrate wider transcriptional changes triggered by the abnormal deposition of Aβ/NFT occurring well before behavioral decline and identify a distinct set of genes specifically associated to abnormal Aβ protein deposition and cognitive decline.

Impairment of the activity of the plasma membrane Ca2+-ATPase in Alzheimer's disease

2011 ◽  
Vol 39 (3) ◽  
pp. 819-822 ◽  
Author(s):  
Ana M. Mata ◽  
María Berrocal ◽  
M. Rosario Sepúlveda
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Plasma Membrane ◽  
Molecular Mechanisms ◽  
Neurodegenerative Disorder ◽  
Senile Plaques ◽  
Amyloid Β ◽  
Inhibitory Effect ◽  
Amyloid Β Peptide ◽  
Aβ Amyloid

AD (Alzheimer's disease) is an age-associated neurodegenerative disorder where the accumulation of neurotoxic Aβ (amyloid β-peptide) in senile plaques is a typical feature. Recent studies point out a relationship between Aβ neurotoxicity and Ca2+ dyshomoeostasis, but the molecular mechanisms involved are still under discussion. The PMCAs (plasma membrane Ca2+-ATPases) are a multi-isoform family of proteins highly expressed in brain that is implicated in the maintenance of low intraneural Ca2+ concentration. Therefore the malfunction of this pump may also be responsible for Ca2+ homoeostasis failure in AD. We have found that the Ca2+-dependence of PMCA activity is affected in human brains diagnosed with AD, being related to the enrichment of Aβ. The peptide produces an inhibitory effect on the activity of PMCA which is isoform-specific, with the greatest inhibition of PMCA4. Besides, cholesterol blocked the inhibitory effect of Aβ, which is consistent with the lack of any Aβ effect on PMCA4 found in cholesterol-enriched lipid rafts isolated from pig brain. These observations suggest that PMCAs are a functional component of the machinery that leads to Ca2+ dysregulation in AD and propose cholesterol enrichment in rafts as a protector of the Aβ-mediated inhibition on PMCA.

scholarly journals Role of Oxidative Damage in Alzheimer’s Disease and Neurodegeneration: From Pathogenic Mechanisms to Biomarker Discovery

Antioxidants ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1353
Author(s):  
Francesca Romana Buccellato ◽  
Marianna D’Anca ◽  
Chiara Fenoglio ◽  
Elio Scarpini ◽  
Daniela Galimberti
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Oxidative Damage ◽  
Molecular Mechanisms ◽  
Biomarker Discovery ◽  
Neurodegenerative Disorder ◽  
Amyloid Β ◽  
Antioxidant Defenses ◽  
Ageing Population

Alzheimer’s disease (AD) is a neurodegenerative disorder accounting for over 50% of all dementia patients and representing a leading cause of death worldwide for the global ageing population. The lack of effective treatments for overt AD urges the discovery of biomarkers for early diagnosis, i.e., in subjects with mild cognitive impairment (MCI) or prodromal AD. The brain is exposed to oxidative stress as levels of reactive oxygen species (ROS) are increased, whereas cellular antioxidant defenses are decreased. Increased ROS levels can damage cellular structures or molecules, leading to protein, lipid, DNA, or RNA oxidation. Oxidative damage is involved in the molecular mechanisms which link the accumulation of amyloid-β and neurofibrillary tangles, containing hyperphosphorylated tau, to microglia response. In this scenario, microglia are thought to play a crucial role not only in the early events of AD pathogenesis but also in the progression of the disease. This review will focus on oxidative damage products as possible peripheral biomarkers in AD and in the preclinical phases of the disease. Particular attention will be paid to biological fluids such as blood, CSF, urine, and saliva, and potential future use of molecules contained in such body fluids for early differential diagnosis and monitoring the disease course. We will also review the role of oxidative damage and microglia in the pathogenesis of AD and, more broadly, in neurodegeneration.

scholarly journals Hyperactivity Induced by Soluble Amyloid-β Oligomers in the Early Stages of Alzheimer's Disease

2021 ◽  
Vol 13 ◽  
Author(s):  
Audrey Hector ◽  
Jonathan Brouillette
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Molecular Mechanisms ◽  
Clinical Symptoms ◽  
Epileptiform Activity ◽  
Amyloid Β ◽  
Gamma Oscillations ◽  
Synaptic Activity ◽  
Early Stages ◽  
The Impact

Soluble amyloid-beta oligomers (Aβo) start to accumulate in the human brain one to two decades before any clinical symptoms of Alzheimer's disease (AD) and are implicated in synapse loss, one of the best predictors of memory decline that characterize the illness. Cognitive impairment in AD was traditionally thought to result from a reduction in synaptic activity which ultimately induces neurodegeneration. More recent evidence indicates that in the early stages of AD synaptic failure is, at least partly, induced by neuronal hyperactivity rather than hypoactivity. Here, we review the growing body of evidence supporting the implication of soluble Aβo on the induction of neuronal hyperactivity in AD animal models, in vitro, and in humans. We then discuss the impact of Aβo-induced hyperactivity on memory performance, cell death, epileptiform activity, gamma oscillations, and slow wave activity. We provide an overview of the cellular and molecular mechanisms that are emerging to explain how Aβo induce neuronal hyperactivity. We conclude by providing an outlook on the impact of hyperactivity for the development of disease-modifying interventions at the onset of AD.

scholarly journals Effect of APOE ε4 genotype on amyloid-β and tau accumulation in Alzheimer’s disease

2020 ◽  
Author(s):  
Min Seok Baek ◽  
Hanna Cho ◽  
Hye Sun Lee ◽  
Jae Hoon Lee ◽  
Young Hoon Ryu ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Accumulation Rate ◽  
Temporal Cortex ◽  
Amyloid Β ◽  
Standardized Uptake Value ◽  
Linear Mixed Effect Model ◽  
Mixed Effect ◽  
Apoe Ε4 ◽  
Pet Scans

Abstract Background: To assess effects of apolipoprotein E (ApoE) ε4 genotype on Aβ and tau burden and their longitudinal changes in Alzheimer’s disease (AD) spectrum.Methods: Among 272 individuals who underwent PET scans (18F-florbetaben for Aβ and 18F-flortaucipir for tau) and ApoE genotyping, 187 individuals completed 2-year follow-up PET scans. After correcting for partial-volume effect, we compared the standardized uptake value ratio (SUVR) for Aβ and tau burden between the ε4+ and ε4- groups. By using a linear mixed-effect model, we measured changes in SUVR in the ApoE ε4+ and ε4- groups.Results: The ε4+ group showed greater baseline Aβ burden in the diffuse cortical regions and greater tau burden in the lateral, and medial temporal, cingulate, and insula cortices. Tau accumulation rate was higher in the parietal, occipital, lateral, and medial temporal cortices in the ε4+ group. In Aβ+ individuals, baseline tau burden was greater in the medial temporal cortex, while Aβ burden was conversely greater in the ε4- group. Tau accumulation rate was higher in the ε4+ group in a small region in the lateral temporal cortex. The effect of ApoE ε4 on enhanced tau accumulation persisted even after adjusting for the global cortical Aβ burden.Conclusions: Progressive tau accumulation may be more prominent in ε4 carriers, particularly in the medial and lateral temporal cortices. ApoE ε4 allele has differential effects on Aβ burden depending on the existing amyloidosis and enhances vulnerability to progressive tau accumulation in the AD spectrum independent of Aβ.

scholarly journals Astrocytic TSPO Upregulation Appears Before Microglial TSPO in Alzheimer’s Disease

2020 ◽  
Vol 77 (3) ◽  
pp. 1043-1056 ◽  
Author(s):  
Benjamin B. Tournier ◽  
Stergios Tsartsalis ◽  
Kelly Ceyzériat ◽  
Ben H. Fraser ◽  
Marie-Claude Grégoire ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Glial Cells ◽  
Binding Sites ◽  
Temporal Cortex ◽  
Population Expansion ◽  
Cell Types ◽  
Translocator Protein ◽  
Cellular Origin

Background: In vivo PET/SPECT imaging of neuroinflammation is primarily based on the estimation of the 18 kDa-translocator-protein (TSPO). However, TSPO is expressed by different cell types which complicates the interpretation. Objective: The present study evaluates the cellular origin of TSPO alterations in Alzheimer’s disease (AD). Methods: The TSPO cell origin was evaluated by combining radioactive imaging approaches using the TSPO radiotracer [125I]CLINDE and fluorescence-activated cell sorting, in a rat model of AD (TgF344-AD) and in AD subjects. Results: In the hippocampus of TgF344-AD rats, TSPO overexpression not only concerns glial cells but the increase is visible at 12 and 24 months in astrocytes and only at 24 months in microglia. In the temporal cortex of AD subjects, TSPO upregulation involved only glial cells. However, the mechanism of this upregulation appears different with an increase in the number of TSPO binding sites per cell without cell proliferation in the rat, and a microglial cell population expansion with a constant number of binding sites per cell in human AD. Conclusion: These data indicate an earlier astrocyte intervention than microglia and that TSPO in AD probably is an exclusive marker of glial activity without interference from other TSPO-expressing cells. This observation indicates that the interpretation of TSPO imaging depends on the stage of the pathology, and highlights the particular role of astrocytes.

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