scholarly journals Distinct microglial response against Alzheimer's amyloid and tau pathologies characterized by P2Y12 receptor

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Jun Maeda ◽  
Takeharu Minamihisamatsu ◽  
Masafumi Shimojo ◽  
Xiaoyun Zhou ◽  
Maiko Ono ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Early Stage ◽  
Receptor Gene ◽  
Amyloid Β ◽  
Progressive Increase ◽  
P2y12 Receptor ◽  
Down Regulation ◽  
Disease Etiology ◽  
The Central Nervous System

Abstract Microglia are the resident phagocytes of the central nervous system, and microglial activation is considered to play an important role in the pathogenesis of neurodegenerative diseases. Recent studies with single-cell RNA analysis of CNS cells in Alzheimer’s disease and diverse other neurodegenerative conditions revealed that the transition from homeostatic microglia to disease-associated microglia was defined by changes of gene expression levels, including down-regulation of the P2Y12 receptor gene (P2Y12R). However, it is yet to be clarified in Alzheimer’s disease brains whether and when this down-regulation occurs in response to amyloid-β and tau depositions, which are core pathological processes in the disease etiology. To further evaluate the significance of P2Y12 receptor alterations in the neurodegenerative pathway of Alzheimer’s disease and allied disorders, we generated an anti-P2Y12 receptor antibody and examined P2Y12 receptor expressions in the brains of humans and model mice bearing amyloid-β and tau pathologies. We observed that the brains of both Alzheimer’s disease and non-Alzheimer’s disease tauopathy patients and tauopathy model mice (rTg4510 and PS19 mouse lines) displayed declined microglial P2Y12 receptor levels in regions enriched with tau inclusions, despite an increase in the total microglial population. Notably, diminution of microglial immunoreactivity with P2Y12 receptor was noticeable prior to massive accumulations of phosphorylated tau aggregates and neurodegeneration in rTg4510 mouse brains, despite a progressive increase of total microglial population. On the other hand, Iba1-positive microglia encompassing compact and dense-cored amyloid-β plaques expressed P2Y12 receptor at varying levels in amyloid precursor protein (APP) mouse models (APP23 and AppNL-F/NL-F mice). By contrast, neuritic plaques in Alzheimer’s disease brains were associated with P2Y12 receptor-negative microglia. These data suggest that the down-regulation of microglia P2Y12 receptor, which is characteristic of disease-associated microglia, is intimately associated with tau rather than amyloid-β pathologies from an early stage and could be a sensitive index for neuroinflammatory responses to Alzheimer’s disease-related neurodegenerative processes.

Advent of Proteomic Tools for Diagnostic Biomarker Analysis in Alzheimer’s Disease

2020 ◽  
Vol 21 (10) ◽  
pp. 965-977
Author(s):  
Manisha Singh ◽  
Surinder P. Singh ◽  
P.K. Dubey ◽  
R Rachana ◽  
Shalini Mani ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Early Stage ◽  
Imaging Techniques ◽  
Amyloid Β ◽  
Diagnostic Tools ◽  
Disease Etiology ◽  
Detection Model ◽  
Therapeutic Trials ◽  
Biomarker Analysis

: Locating remedies for Alzheimer’s disease (AD) has been majorly restricted by the inefficiency to establish a definitive detection model for early-stage diagnosis of pathological events. This current lapse in AD diagnosis also limits the therapeutic efficiency of the drugs, which might have been effective if given at the earlier stages of the disease. The indicated situation directs towards the burgeoned need for an effective biomarker technique that will help in early detection of AD and would be imminently useful to facilitate improved diagnosis and stimulate therapeutic trials. Till date, the major biomarkers, specifically associated with AD detection, may help in determining the early-stage AD diagnosis and identifying alterations in the cellular proteome, offering deeper insight into disease etiology. Currently existing multidisciplinary clinical diagnosis of AD is a very tedious, expensive procedure and requires highly trained and skilled professionals who are rarely available outside the specialty clinics. Mutations in amyloid precursor protein (APP) or Presenilin 1 and 2 (PSEN1 and PSEN2) are some biomarkers acting as critical checkpoints for AD diagnosis. However, the presence of some associated biomarkers in cerebrospinal fluid (CSF) such as total-Tau (tTau), phosphorylated- Tau (pTau) 181 and Amyloid-β (Aβ) 1-42 using structural or functional imaging techniques is considered for confirmatory diagnosis of AD. Furthermore, the molecular diagnosis of AD incorporates various sophisticated techniques including immuno-sensing, machine learning, nano conjugation-based detections, etc. In the current review description, we have summarized the various diagnostic approaches and their relevance in mitigating the long-standing urgency of targeted diagnostic tools for detection of AD.

scholarly journals Astrocytic transporters in Alzheimer's disease

2017 ◽  
Vol 474 (3) ◽  
pp. 333-355 ◽  
Author(s):  
Chris Ugbode ◽  
Yuhan Hu ◽  
Benjamin Whalley ◽  
Chris Peers ◽  
Marcus Rattray ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Early Stage ◽  
Neurological Diseases ◽  
Current Evidence ◽  
Specific Targeting ◽  
Disease Modifying Therapies ◽  
The Central Nervous System ◽  
Disease Modifying ◽  
And Function

Astrocytes play a fundamental role in maintaining the health and function of the central nervous system. Increasing evidence indicates that astrocytes undergo both cellular and molecular changes at an early stage in neurological diseases, including Alzheimer's disease (AD). These changes may reflect a change from a neuroprotective to a neurotoxic phenotype. Given the lack of current disease-modifying therapies for AD, astrocytes have become an interesting and viable target for therapeutic intervention. The astrocyte transport system covers a diverse array of proteins involved in metabolic support, neurotransmission and synaptic architecture. Therefore, specific targeting of individual transporter families has the potential to suppress neurodegeneration, a characteristic hallmark of AD. A small number of the 400 transporter superfamilies are expressed in astrocytes, with evidence highlighting a fraction of these are implicated in AD. Here, we review the current evidence for six astrocytic transporter subfamilies involved in AD, as reported in both animal and human studies. This review confirms that astrocytes are indeed a viable target, highlights the complexities of studying astrocytes and provides future directives to exploit the potential of astrocytes in tackling AD.

scholarly journals Microglia-Based Sex-Biased Neuropathology in Early-Stage Alzheimer’s Disease Model Mice and the Potential Pharmacologic Efficacy of Dioscin

Cells ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 3261
Author(s):  
Xiao Liu ◽  
Qian Zhou ◽  
Jia-He Zhang ◽  
Xiaoying Wang ◽  
Xiumei Gao ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Early Stage ◽  
Disease Model ◽  
Amyloid Β ◽  
Brain Lesions ◽  
Synaptic Dysfunction ◽  
Synaptic Loss ◽  
And Function ◽  
The Brain

Alzheimer’s disease (AD), the most common form of dementia, is characterized by amyloid-β (Aβ) accumulation, microglia-associated neuroinflammation, and synaptic loss. The detailed neuropathologic characteristics in early-stage AD, however, are largely unclear. We evaluated the pathologic brain alterations in young adult App knock-in model AppNL-G-F mice at 3 and 6 months of age, which corresponds to early-stage AD. At 3 months of age, microglia expression in the cortex and hippocampus was significantly decreased. By the age of 6 months, the number and function of the microglia increased, accompanied by progressive amyloid-β deposition, synaptic dysfunction, neuroinflammation, and dysregulation of β-catenin and NF-κB signaling pathways. The neuropathologic changes were more severe in female mice than in male mice. Oral administration of dioscin, a natural product, ameliorated the neuropathologic alterations in young AppNL-G-F mice. Our findings revealed microglia-based sex-differential neuropathologic changes in a mouse model of early-stage AD and therapeutic efficacy of dioscin on the brain lesions. Dioscin may represent a potential treatment for AD.

PET Imaging of Tau Pathology and Amyloid-β, and MRI for Alzheimer’s Disease Feature Fusion and Multimodal Classification

2021 ◽  
pp. 1-18
Author(s):  
Mehdi Shojaie ◽  
Solale Tabarestani ◽  
Mercedes Cabrerizo ◽  
Steven T. DeKosky ◽  
David E. Vaillancourt ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Feature Selection ◽  
Mutual Information ◽  
Feature Fusion ◽  
Early Stage ◽  
Model Performance ◽  
Amyloid Β ◽  
Feature Ranking ◽  
Promising Tool

Background: Machine learning is a promising tool for biomarker-based diagnosis of Alzheimer’s disease (AD). Performing multimodal feature selection and studying the interaction between biological and clinical AD can help to improve the performance of the diagnosis models. Objective: This study aims to formulate a feature ranking metric based on the mutual information index to assess the relevance and redundancy of regional biomarkers and improve the AD classification accuracy. Methods: From the Alzheimer’s Disease Neuroimaging Initiative (ADNI), 722 participants with three modalities, including florbetapir-PET, flortaucipir-PET, and MRI, were studied. The multivariate mutual information metric was utilized to capture the redundancy and complementarity of the predictors and develop a feature ranking approach. This was followed by evaluating the capability of single-modal and multimodal biomarkers in predicting the cognitive stage. Results: Although amyloid-β deposition is an earlier event in the disease trajectory, tau PET with feature selection yielded a higher early-stage classification F1-score (65.4%) compared to amyloid-β PET (63.3%) and MRI (63.2%). The SVC multimodal scenario with feature selection improved the F1-score to 70.0% and 71.8% for the early and late-stage, respectively. When age and risk factors were included, the scores improved by 2 to 4%. The Amyloid-Tau-Neurodegeneration [AT(N)] framework helped to interpret the classification results for different biomarker categories. Conclusion: The results underscore the utility of a novel feature selection approach to reduce the dimensionality of multimodal datasets and enhance model performance. The AT(N) biomarker framework can help to explore the misclassified cases by revealing the relationship between neuropathological biomarkers and cognition.

Prions and Neurodegenerative Diseases: A Focus on Alzheimer’s Disease

2021 ◽  
pp. 1-16
Author(s):  
Alessio Crestini ◽  
Francesca Santilli ◽  
Stefano Martellucci ◽  
Elena Carbone ◽  
Maurizio Sorice ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Neurodegenerative Diseases ◽  
Protein Misfolding ◽  
Amyloid Β ◽  
Specific Protein ◽  
Cellular Prion Protein ◽  
Aβ Oligomers ◽  
The Central Nervous System ◽  
Induced Signal

Specific protein misfolding and aggregation are mechanisms underlying various neurodegenerative diseases such as prion disease and Alzheimer’s disease (AD). The misfolded proteins are involved in prions, amyloid-β (Aβ), tau, and α-synuclein disorders; they share common structural, biological, and biochemical characteristics, as well as similar mechanisms of aggregation and self-propagation. Pathological features of AD include the appearance of plaques consisting of deposition of protein Aβ and neurofibrillary tangles formed by the hyperphosphorylated tau protein. Although it is not clear how protein aggregation leads to AD, we are learning that the cellular prion protein (PrPC) plays an important role in the pathogenesis of AD. Herein, we first examined the pathogenesis of prion and AD with a focus on the contribution of PrPC to the development of AD. We analyzed the mechanisms that lead to the formation of a high affinity bond between Aβ oligomers (AβOs) and PrPC. Also, we studied the role of PrPC as an AβO receptor that initiates an AβO-induced signal cascade involving mGluR5, Fyn, Pyk2, and eEF2K linking Aβ and tau pathologies, resulting in the death of neurons in the central nervous system. Finally, we have described how the PrPC-AβOs interaction can be used as a new potential therapeutic target for the treatment of PrPC-dependent AD.

scholarly journals Revisiting the Amyloid Cascade Hypothesis: From Anti-Aβ Therapeutics to Auspicious New Ways for Alzheimer’s Disease

2020 ◽  
Vol 21 (16) ◽  
pp. 5858 ◽  
Author(s):  
Md. Sahab Uddin ◽  
Md. Tanvir Kabir ◽  
Md. Sohanur Rahman ◽  
Tapan Behl ◽  
Philippe Jeandet ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Clinical Trials ◽  
Clinical Symptoms ◽  
Neurodegenerative Disorder ◽  
Early Stage ◽  
Amyloid Β ◽  
Aβ Oligomers ◽  
Aβ Aggregation ◽  
Clinical Benefits

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder related to age, characterized by the cerebral deposition of fibrils, which are made from the amyloid-β (Aβ), a peptide of 40–42 amino acids. The conversion of Aβ into neurotoxic oligomeric, fibrillar, and protofibrillar assemblies is supposed to be the main pathological event in AD. After Aβ accumulation, the clinical symptoms fall out predominantly due to the deficient brain clearance of the peptide. For several years, researchers have attempted to decline the Aβ monomer, oligomer, and aggregate levels, as well as plaques, employing agents that facilitate the reduction of Aβ and antagonize Aβ aggregation, or raise Aβ clearance from brain. Unluckily, broad clinical trials with mild to moderate AD participants have shown that these approaches were unsuccessful. Several clinical trials are running involving patients whose disease is at an early stage, but the preliminary outcomes are not clinically impressive. Many studies have been conducted against oligomers of Aβ which are the utmost neurotoxic molecular species. Trials with monoclonal antibodies directed against Aβ oligomers have exhibited exciting findings. Nevertheless, Aβ oligomers maintain equivalent states in both monomeric and aggregation forms; so, previously administered drugs that precisely decrease Aβ monomer or Aβ plaques ought to have displayed valuable clinical benefits. In this article, Aβ-based therapeutic strategies are discussed and several promising new ways to fight against AD are appraised.

scholarly journals The Retinal Inner Plexiform Synaptic Layer Mirrors Grey Matter Thickness of Primary Visual Cortex with Increased Amyloid β Load in Early Alzheimer’s Disease

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Lília Jorge ◽  
Nádia Canário ◽  
Ricardo Martins ◽  
Beatriz Santiago ◽  
Isabel Santana ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Early Stage ◽  
Amyloid Β ◽  
Synaptic Function ◽  
Binding Potential ◽  
Inner Plexiform Layer ◽  
Pet Tracer

The retina may serve as putative window into neuropathology of synaptic loss in Alzheimer’s disease (AD). Here, we investigated synapse-rich layers versus layers composed by nuclei/cell bodies in an early stage of AD. In addition, we examined the associations between retinal changes and molecular and structural markers of cortical damage. We recruited 20 AD patients and 17 healthy controls (HC). Combining optical coherence tomography (OCT), magnetic resonance (MR), and positron emission tomography (PET) imaging, we measured retinal and primary visual cortex (V1) thicknesses, along with V1 amyloid β (Aβ) retention ([11C]-PiB PET tracer) and neuroinflammation ([11C]-PK11195 PET tracer). We found that V1 showed increased amyloid-binding potential, in the absence of neuroinflammation. Although thickness changes were still absent, we identified a positive association between the synapse-rich inner plexiform layer (IPL) and V1 in AD. This retinocortical interplay might reflect changes in synaptic function resulting from Aβ deposition, contributing to early visual loss.

scholarly journals Alzheimer’s disease: many failed trials, so where do we go from here?

2020 ◽  
Vol 68 (6) ◽  
pp. 1135-1140 ◽  
Author(s):  
Allison Bethanne Reiss ◽  
Amy D Glass ◽  
Thomas Wisniewski ◽  
Benjamin Wolozin ◽  
Irving H Gomolin ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Current Knowledge ◽  
Memory Loss ◽  
Treatment Strategies ◽  
Amyloid Β ◽  
Tau Proteins ◽  
Brain Disorder ◽  
The Central Nervous System ◽  
Progressive Cognitive Impairment

Alzheimer’s disease (AD) is a neurodegenerative brain disorder associated with relentlessly progressive cognitive impairment and memory loss. AD pathology proceeds for decades before cognitive deficits become clinically apparent, opening a window for preventative therapy. Imbalance of clearance and buildup of amyloid β and phosphorylated tau proteins in the central nervous system is believed to contribute to AD pathogenesis. However, multiple clinical trials of treatments aimed at averting accumulation of these proteins have yielded little success, and there is still no disease-modifying intervention. Here, we discuss current knowledge of AD pathology and treatment with an emphasis on emerging biomarkers and treatment strategies.

scholarly journals Decoupling of Global Brain Activity and Cerebrospinal Fluid Flow Is Linked to Alzheimer's Pathology

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. 637-638
Author(s):  
Feng Han ◽  
Jing Chen ◽  
Aaron Belkin-Rosen ◽  
Yameng Gu ◽  
Liying Luo ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cerebrospinal Fluid ◽  
Resting State ◽  
Early Stage ◽  
Adult Population ◽  
Critical Role ◽  
Low Frequency ◽  
Amyloid Β ◽  
Blood Oxygenation

Abstract Alzheimer’s disease (AD) is the most common cause of dementia in the old adult population. AD pathogenesis has been linked to the aggregation of toxic proteins, e.g., amyloid-β and tau. The glymphatic system may play an important role in clearing out these proteins via cerebrospinal fluid (CSF) flows through perivascular and interstitial spaces. Recent studies have suggested low-frequency (<0.1 Hz), sleep-dependent global blood-oxygenation-dependent-level (gBOLD; global resting-state functional MRI signal) during resting state is coupled with CSF movements, suggesting their potential link to glymphatic function. Here, we directly investigated whether the coupling between the gBOLD and CSF signals is related to AD-related pathology. By analyzing neuroimaging, neurobiological, and neuropsychological data from 118 human subjects (58-90 years of age; AD, early-stage AD, and control subjects included) collected in the Alzheimer's Disease Neuroimaging Initiative project, we found a strong coupling between the gBOLD and CSF signals. More importantly, the strength of this gBOLD-CSF coupling was significantly correlated with cortical amyloid-β level (p = 0.019), cognitive decline in the subsequent two years (p = 0.013), disease severity (p = 0.035), and several AD-related risk factors, including aging (p = 0.011), and gender (p = 0.026). These findings provide initial evidence for the critical role of resting-state low-frequency (<0.1 Hz) neural/physiological dynamics in AD pathology. They also suggest that the gBOLD-CSF coupling may serve as a non-invasive imaging marker for gauging the glymphatic function.

scholarly journals Microglia, TREM2, and Therapeutic Methods of Alzheimer’s Disease

2021 ◽  
Author(s):  
Siwei Xu ◽  
Yaya Ji ◽  
Tianle Sha ◽  
Haoming Li
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Dynamic Change ◽  
Amyloid Β ◽  
Neuronal Loss ◽  
Pathological Process ◽  
Amyloid Β Protein ◽  
Transmembrane Glycoprotein ◽  
Β Protein ◽  
The Central Nervous System

Alzheimer’s disease (AD) is one of the most common causes of dementia all around the world. It is characterized by the deposition of amyloid-β protein (Aβ) and the formation of neurofibrillary tangles (NFTs), which contribute to neuronal loss and cognitive decline. Microglia, as innate immune cells in brain, plays dual roles in the pathological process of AD. Expression in different subtypes of microglia is diverse in AD genes. Triggering receptor expressed on myeloid cells 2 (TREM2) is a transmembrane glycoprotein mainly expressed on microglia in the central nervous system (CNS). Soluble TREM2 (sTREM2), a proteolytic product of TREM2, which is abundant in the cerebrospinal fluid, shows a dynamic change in different stages and ameliorates the pathological process of AD. The interplay between the different subtypes of apolipoprotein and TREM2 is closely related to the mechanism of AD and serves as important regulatory sites. Moreover, several therapeutic strategies targeting TREM2 have shown positive outcomes during clinical trials and some novel therapies at different points are in progress. In this review, we mainly talk about the interrelationships among microglia, TREM2, and AD, and hope to give an overview of the strategies of AD.

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