scholarly journals The Many Faces of Astrocytes in Alzheimer's Disease

2021 ◽  
Vol 12 ◽  
Author(s):  
Michael D. Monterey ◽  
Haichao Wei ◽  
Xizi Wu ◽  
Jia Qian Wu
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Research Effort ◽  
Reactive Astrocytes ◽  
Sequencing Technologies ◽  
Recent Developments ◽  
Current Therapies ◽  
Pathological Development ◽  
The Many

Alzheimer's disease (AD) is a progressive neurodegenerative disease and is the most common cause of dementia in an aging population. The majority of research effort has focused on the role of neurons in neurodegeneration and current therapies have limited ability to slow disease progression. Recently more attention has been given to the role of astrocytes in the process of neurodegeneration. Specifically, reactive astrocytes have both advantageous and adverse effects during neurodegeneration. The ability to isolate and depict astrocyte phenotype has been challenging. However, with the recent development of single-cell sequencing technologies researchers are provided with the resource to delineate specific biomarkers associated with reactive astrocytes in AD. In this review, we will focus on the role of astrocytes in normal conditions and the pathological development of AD. We will further review recent developments in the understanding of astrocyte heterogeneity and associated biomarkers. A better understanding of astrocyte contributions and phenotypic changes in AD can ultimately lead to more effective therapeutic targets.

scholarly journals Regulation of cell distancing in peri-plaque glial nets by Plexin-B1 affects glial activation and amyloid compaction in Alzheimer’s disease

2021 ◽  
Author(s):  
Roland Friedel ◽  
Yong Huang ◽  
Minghui Wang ◽  
Shalaka Wahane ◽  
Mitzy Ríos de Anda ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Late Onset ◽  
Amyloid Plaque ◽  
Reactive Astrocytes ◽  
Glial Activation ◽  
Plaque Burden ◽  
Aβ Amyloid ◽  
Underlying Mechanisms

Abstract Communication between glial cells has a profound effect on the pathophysiology of Alzheimer’s disease (AD), but the underlying mechanisms remain unclear. Here, we reveal a role of reactive astrocytes in enforcing cell distancing in the glial nets surrounding amyloid plaques, which restricts microglial coverage of Aβ, a prerequisite to detect and engulf amyloid deposits. This process is mediated through guidance receptor Plexin-B1, which we identified as a key network regulator of late-onset AD. We show that Plexin-B1 is robustly upregulated in plaque-associated astrocytes in a corona-like pattern, and its expression levels correlate with plaque burden and disease severity in AD patients. In APP/PS1 mice, an amyloidogenic model of AD, removing Plexin-B1 led to smaller peri-plaque glial nets with relaxed cell distancing and enhanced glial coverage of Aβ plaques, as well as transcriptional changes in both reactive astrocytes and disease-associated microglia that are linked to glial activation and amyloid clearance. Furthermore, amyloid plaque burden was lowered, together with a shift towards dense-core plaques and reduced neuritic dystrophy. Our data thus support a role of Plexin-B1 in controlling glial net structure by imposing cell distancing, leading to poor glial coverage of Aβ, reduced amyloid clearance and compaction. Relaxing cell distancing by targeting guidance receptors may present an alternative strategy to alleviate neuroinflammation in AD by improving glial coverage of Aβ amyloid and plaque compaction.

scholarly journals The role of APOE4 in Alzheimer’s disease: strategies for future therapeutic interventions

2019 ◽  
Vol 3 (2) ◽  
Author(s):  
Holly C. Hunsberger ◽  
Priyanka D. Pinky ◽  
Warren Smith ◽  
Vishnu Suppiramaniam ◽  
Miranda N. Reed
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Synapse Formation ◽  
Late Onset ◽  
Therapeutic Interventions ◽  
Memory Decline ◽  
Current Therapies ◽  
Ε4 Allele ◽  
The Impact

Abstract Alzheimer’s disease (AD) is the leading cause of dementia affecting almost 50 million people worldwide. The ε4 allele of Apolipoprotein E (APOE) is the strongest known genetic risk factor for late-onset AD cases, with homozygous APOE4 carriers being approximately 15-times more likely to develop the disease. With 25% of the population being APOE4 carriers, understanding the role of this allele in AD pathogenesis and pathophysiology is crucial. Though the exact mechanism by which ε4 allele increases the risk for AD is unknown, the processes mediated by APOE, including cholesterol transport, synapse formation, modulation of neurite outgrowth, synaptic plasticity, destabilization of microtubules, and β-amyloid clearance, suggest potential therapeutic targets. This review will summarize the impact of APOE on neurons and neuronal signaling, the interactions between APOE and AD pathology, and the association with memory decline. We will then describe current treatments targeting APOE4, complications associated with the current therapies, and suggestions for future areas of research and treatment.

scholarly journals New diagnostic concepts in Alzheimer's disease

2013 ◽  
Vol 19 (4) ◽  
pp. 242-249 ◽  
Author(s):  
Anna Watkin ◽  
Sudip Sikdar ◽  
Biswadeep Majumdar ◽  
Anna V. Richman
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cognitive Impairment ◽  
Clinical Practice ◽  
Mild Cognitive Impairment ◽  
Diagnostic Criteria ◽  
Current Clinical Practice ◽  
Amnestic Mci ◽  
Recent Developments

SummaryThis article gives an overview of the profile of Alzheimer's disease, its pathophysiology and recent developments in technology that enable better understanding of the mechanism of disease. The diagnostic criteria and role of biomarkers proposed are explained. The new subgroups described are outlined in table form for easy reference. Subtypes of mild cognitive impairment (MCI) are reviewed and the conversion of amnestic MCI to Alzheimer's disease is considered. The implications and change to current clinical practice form the basis of the conclusion of the article.

scholarly journals Oxysterols Present in Alzheimer’s Disease Braininduce Synaptoxicity by Activating Astrocytes: A Major Role for Lipocalin-2

2020 ◽  
Author(s):  
Erica Staurenghi ◽  
Valentina Cerrato ◽  
Paola Gamba ◽  
Gabriella Testa ◽  
Serena Giannelli ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cholesterol Metabolism ◽  
Reactive Astrocytes ◽  
Cholesterol Oxidation ◽  
Neuronal Cultures ◽  
Lipocalin 2 ◽  
Brain Cholesterol ◽  
The Impact

Abstract Background: Among Alzheimer’s disease (AD) brain hallmarks, the presence of reactive astrocytes was demonstrated to correlate with neuronal loss and cognitive deficits. Evidence indeed supports the role of reactive astrocytes as mediators of changes in neurons, including synapses. However, the complexity and the outcomes of astrocyte reactivity are far from being completely elucidated. Another key role in AD pathogenesis is played by alterations in brain cholesterol metabolism. Oxysterols (cholesterol oxidation products) are crucial for brain cholesterol homeostasis, and we previously demonstrated that changes in the brain levels of various oxysterols correlate with AD progression. Moreover, oxysterols have been shown to contribute to various pathological mechanisms involved in AD pathogenesis.In order to deepen the role of oxysterols in AD, we investigated whether they could contribute to astrocyte reactivity, and consequently impact on neuronal health.Methods: Mouse primary astrocyte cultures were used to test the effect of two oxysterol mixtures, that represent the oxysterol composition respectively of mild or severe AD brains, on astrocyte morphology, markers of reactivity, and secretion profile. Co-culture experiments were performed to investigate the impact of oxysterol-treated astrocytes on neurons. Neuronal cultures were exposed to astrocyte conditioned media (ACM) deprived of lipocalin-2 (Lcn2) to investigate the contribution of this mediator to synaptotoxicity.Results: Results showed that oxysterols induce a clear morphological change in astrocytes, accompanied by the upregulation of some reactive astrocyte markers, including Lcn2. Moreover, ACM analysis revealed a significant increase in the release of Lcn2, cytokines, and chemokines in response to oxysterols. A significant reduction of postsynaptic density protein 95 (PSD95) and a concurrent increase in cleaved caspase-3 protein levels have been demonstrated in neurons co-cultured with oxysterol-treated astrocytes, pointing out that mediators released by astrocytes have an impact on neurons. Among these mediators, Lcn2 has been demonstrated to play a major role on synapses, affecting neurite morphology and decreasing dendritic spine density. Conclusions: These data demonstrated that oxysterols present in the AD brain promote astrocyte reactivity, determining the release of several mediators that affect neuronal health and synapses. Lcn2 has been shown to exert a key role in mediating the synaptotoxic effect of oxysterol-treated astrocytes.

scholarly journals The role of astrocytes in amyloid production and Alzheimer's disease

Open Biology ◽  
2017 ◽  
Vol 7 (12) ◽  
pp. 170228 ◽  
Author(s):  
Georgia R. Frost ◽  
Yue-Ming Li
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Neuronal Cell Death ◽  
Neuronal Cell ◽  
Reactive Astrocytes ◽  
Numerous Cell ◽  
Additional Role ◽  
The Brain ◽  
Aβ Production

Alzheimer's disease (AD) is marked by the presence of extracellular amyloid beta (Aβ) plaques, intracellular neurofibrillary tangles (NFTs) and gliosis, activated glial cells, in the brain. It is thought that Aβ plaques trigger NFT formation, neuronal cell death, neuroinflammation and gliosis and, ultimately, cognitive impairment. There are increased numbers of reactive astrocytes in AD, which surround amyloid plaques and secrete proinflammatory factors and can phagocytize and break down Aβ. It was thought that neuronal cells were the major source of Aβ. However, mounting evidence suggests that astrocytes may play an additional role in AD by secreting significant quantities of Aβ and contributing to overall amyloid burden in the brain. Astrocytes are the most numerous cell type in the brain, and therefore even minor quantities of amyloid secretion from individual astrocytes could prove to be substantial when taken across the whole brain. Reactive astrocytes have increased levels of the three necessary components for Aβ production: amyloid precursor protein, β-secretase (BACE1) and γ-secretase. The identification of environmental factors, such as neuroinflammation, that promote astrocytic Aβ production, could redefine how we think about developing therapeutics for AD.

Role of Extracellular vesicles in Alzheimer’s disease: Current Advances

2021 ◽  
Vol 21 ◽  
Author(s):  
Smriti Sharma
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Extracellular Vesicles ◽  
Neurodegenerative Disorder ◽  
Future Research ◽  
Brain Pathology ◽  
Recent Developments ◽  
Available Information ◽  
Potential Use

: The recent developments in the field of extracellular vesicles (EVs) point to their potential use for predicting and treating neurodegenerative diseases. This reviews focusses on the importance and latest advances in this field especially with respect to Alzheimer’s disease (AD). Increasing evidence show that progression of amyloid-beta and tau brain pathology is correlated to the cognitive decline associated with AD. Lot of experimental data suggests involvement of EVs with these processes for instance EVs are known to circulate the misfolded proteins involved in AD. The currently available information on role of EVs in neurodegenerative disorder especially in AD and have also presented the knowledge gaps on which future research efforts should be focused.The recent developments in the field of extracellular vesicles (EVs) point to their potential use for predicting and treating neurodegenerative diseases. This reviews focusses on the importance and latest advances in this field especially with respect to Alzheimer’s disease (AD). Increasing evidence show that progression of amyloid-beta and tau brain pathology is correlated to the cognitive decline associated with AD. Lot of experimental data suggests involvement of EVs with these processes for instance EVs are known to circulate the misfolded proteins involved in AD. The currently available information on role of EVs in neurodegenerative disorder especially in AD and have also presented the knowledge gaps on which future research efforts should be focused.

Dissecting the role of Corticotropin-releasing hormone receptor type 1 in Alzheimer's Disease

2011 ◽  
Vol 44 (06) ◽  
Author(s):  
K Lerche ◽  
M Willem ◽  
K Kleinknecht ◽  
C Romberg ◽  
U Konietzko ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Hormone Receptor ◽  
Receptor Type ◽  
Corticotropin Releasing Hormone ◽  
Releasing Hormone

Role of melatonin in regulating neurogenesis: Implications for the neurodegenerative pathology and analogous therapeutics for Alzheimer’s disease

2020 ◽  
Vol 3 (2) ◽  
pp. 216-242 ◽  
Author(s):  
Mayuri Shukla ◽  
Areechun Sotthibundhu ◽  
Piyarat Govitrapong
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Adult Neurogenesis ◽  
Adult Brain ◽  
Therapeutic Approaches ◽  
Therapeutic Implications ◽  
Cell Proliferation And Differentiation ◽  
Proliferation And Differentiation ◽  
Progenitor Cell Proliferation

The revelation of adult brain exhibiting neurogenesis has established that the brain possesses great plasticity and that neurons could be spawned in the neurogenic zones where hippocampal adult neurogenesis attributes to learning and memory processes. With strong implications in brain functional homeostasis, aging and cognition, various aspects of adult neurogenesis reveal exuberant mechanistic associations thereby further aiding in facilitating the therapeutic approaches regarding the development of neurodegenerative processes in Alzheimer’s Disease (AD). Impaired neurogenesis has been significantly evident in AD with compromised hippocampal function and cognitive deficits. Melatonin the pineal indolamine augments neurogenesis and has been linked to AD development as its levels are compromised with disease progression. Here, in this review, we discuss and appraise the mechanisms via which melatonin regulates neurogenesis in pathophysiological conditions which would unravel the molecular basis in such conditions and its role in endogenous brain repair. Also, its components as key regulators of neural stem and progenitor cell proliferation and differentiation in the embryonic and adult brain would aid in accentuating the therapeutic implications of this indoleamine in line of prevention and treatment of AD.   

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