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 Controversial Role of 24-S-Hydroxycholesterol in Alzheimer’s Disease

Antioxidants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 740
Author(s):  
Paola Gamba ◽  
Serena Giannelli ◽  
Erica Staurenghi ◽  
Gabriella Testa ◽  
Barbara Sottero ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cholesterol Metabolism ◽  
Amyloid Β ◽  
Cholesterol Homeostasis ◽  
Oxidation Products ◽  
Cholesterol Oxidation ◽  
Brain Cholesterol ◽  
The Brain

The development of Alzheimer’s disease (AD) is influenced by several events, among which the dysregulation of cholesterol metabolism in the brain plays a major role. Maintenance of brain cholesterol homeostasis is essential for neuronal functioning and brain development. To maintain the steady-state level, excess brain cholesterol is converted into the more hydrophilic metabolite 24-S-hydroxycholesterol (24-OHC), also called cerebrosterol, by the neuron-specific enzyme CYP46A1. A growing bulk of evidence suggests that cholesterol oxidation products, named oxysterols, are the link connecting altered cholesterol metabolism to AD. It has been shown that the levels of some oxysterols, including 27-hydroxycholesterol, 7β-hydroxycholesterol and 7-ketocholesterol, significantly increase in AD brains contributing to disease progression. In contrast, 24-OHC levels decrease, likely due to neuronal loss. Among the different brain oxysterols, 24-OHC is certainly the one whose role is most controversial. It is the dominant oxysterol in the brain and evidence shows that it represents a signaling molecule of great importance for brain function. However, numerous studies highlighted the potential role of 24-OHC in favoring AD development, since it promotes neuroinflammation, amyloid β (Aβ) peptide production, oxidative stress and cell death. In parallel, 24-OHC has been shown to exert several beneficial effects against AD progression, such as preventing tau hyperphosphorylation and Aβ production. In this review we focus on the current knowledge of the controversial role of 24-OHC in AD pathogenesis, reporting a detailed overview of the findings about its levels in different AD biological samples and its noxious or neuroprotective effects in the brain. Given the relevant role of 24-OHC in AD pathophysiology, its targeting could be useful for disease prevention or slowing down its progression.

scholarly journals Cholesterol Dysmetabolism in Alzheimer’s Disease: A Starring Role for Astrocytes?

Antioxidants ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1890
Author(s):  
Erica Staurenghi ◽  
Serena Giannelli ◽  
Gabriella Testa ◽  
Barbara Sottero ◽  
Gabriella Leonarduzzi ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cholesterol Metabolism ◽  
Amyloid Β ◽  
Physiological Role ◽  
Cholesterol Oxidation ◽  
Peripheral Tissues ◽  
Functional Changes ◽  
Brain Cholesterol ◽  
The Impact

In recent decades, the impairment of cholesterol metabolism in the pathogenesis of Alzheimer’s disease (AD) has been intensively investigated, and it has been recognized to affect amyloid β (Aβ) production and clearance, tau phosphorylation, neuroinflammation and degeneration. In particular, the key role of cholesterol oxidation products, named oxysterols, has emerged. Brain cholesterol metabolism is independent from that of peripheral tissues and it must be preserved in order to guarantee cerebral functions. Among the cells that help maintain brain cholesterol homeostasis, astrocytes play a starring role since they deliver de novo synthesized cholesterol to neurons. In addition, other physiological roles of astrocytes are to modulate synaptic transmission and plasticity and support neurons providing energy. In the AD brain, astrocytes undergo significant morphological and functional changes that contribute to AD onset and development. However, the extent of this contribution and the role played by oxysterols are still unclear. Here we review the current understanding of the physiological role exerted by astrocytes in the brain and their contribution to AD pathogenesis. In particular, we focus on the impact of cholesterol dysmetabolism on astrocyte functions suggesting new potential approaches to develop therapeutic strategies aimed at counteracting AD development.

scholarly journals Abnormal brain cholesterol homeostasis in Alzheimer’s disease—a targeted metabolomic and transcriptomic study

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Vijay R. Varma ◽  
H. Büşra Lüleci ◽  
Anup M. Oommen ◽  
Sudhir Varma ◽  
Chad T. Blackshear ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Brain Tissue ◽  
Cholesterol Metabolism ◽  
Cholesterol Biosynthesis ◽  
Cholesterol Homeostasis ◽  
Transcriptomic Data ◽  
Brain Cholesterol ◽  
Cholesterol Levels

AbstractThe role of brain cholesterol metabolism in Alzheimer’s disease (AD) remains unclear. Peripheral and brain cholesterol levels are largely independent due to the impermeability of the blood brain barrier (BBB), highlighting the importance of studying the role of brain cholesterol homeostasis in AD. We first tested whether metabolite markers of brain cholesterol biosynthesis and catabolism were altered in AD and associated with AD pathology using linear mixed-effects models in two brain autopsy samples from the Baltimore Longitudinal Study of Aging (BLSA) and the Religious Orders Study (ROS). We next tested whether genetic regulators of brain cholesterol biosynthesis and catabolism were altered in AD using the ANOVA test in publicly available brain tissue transcriptomic datasets. Finally, using regional brain transcriptomic data, we performed genome-scale metabolic network modeling to assess alterations in cholesterol biosynthesis and catabolism reactions in AD. We show that AD is associated with pervasive abnormalities in cholesterol biosynthesis and catabolism. Using transcriptomic data from Parkinson’s disease (PD) brain tissue samples, we found that gene expression alterations identified in AD were not observed in PD, suggesting that these changes may be specific to AD. Our results suggest that reduced de novo cholesterol biosynthesis may occur in response to impaired enzymatic cholesterol catabolism and efflux to maintain brain cholesterol levels in AD. This is accompanied by the accumulation of nonenzymatically generated cytotoxic oxysterols. Our results set the stage for experimental studies to address whether abnormalities in cholesterol metabolism are plausible therapeutic targets in AD.

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.

Alterations in Brain Cholesterol Metabolism in the APPSLxPS1mut mouse, a Model for Alzheimer's Disease

2010 ◽  
Vol 19 (1) ◽  
pp. 117-127 ◽  
Author(s):  
Tim Vanmierlo ◽  
Vincent W. Bloks ◽  
Leonie C. van Vark-van der Zee ◽  
Kris Rutten ◽  
Anja Kerksiek ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cholesterol Metabolism ◽  
Brain Cholesterol

scholarly journals A Crosstalk Between Brain Cholesterol Oxidation and Glucose Metabolism in Alzheimer’s Disease

2019 ◽  
Vol 13 ◽  
Author(s):  
Paola Gamba ◽  
Erica Staurenghi ◽  
Gabriella Testa ◽  
Serena Giannelli ◽  
Barbara Sottero ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Glucose Metabolism ◽  
Cholesterol Oxidation ◽  
Brain Cholesterol

The Role of Cholesterol Metabolism in Alzheimer’s Disease

2014 ◽  
Vol 51 (3) ◽  
pp. 947-965 ◽  
Author(s):  
Jia-Hao Sun ◽  
Jin-Tai Yu ◽  
Lan Tan
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cholesterol Metabolism

CYP46A1 variants influence Alzheimer’s disease risk and brain cholesterol metabolism

2009 ◽  
Vol 24 (3) ◽  
pp. 183-190 ◽  
Author(s):  
Heike Kölsch ◽  
Dieter Lütjohann ◽  
Frank Jessen ◽  
Julius Popp ◽  
Frank Hentschel ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Genetic Risk ◽  
Cholesterol Metabolism ◽  
Disease Risk ◽  
Brain Cholesterol ◽  
Increased Risk ◽  
Csf Levels ◽  
Interaction Term ◽  
Gene Variability

AbstractBackgroundCholesterol 24S-hydroxylase (CYP46) catalyzes the conversion of cholesterol to 24S-hydroxycholesterol, the primary cerebral cholesterol elimination product. Only few gene variations in CYP46 gene (CYP46A1) have been investigated for their relevance as genetic risk factors of Alzheimer’s disease (AD) and results are contradictory.MethodsWe performed a gene variability screening in CYP46A1 and investigated the effect of gene variants on the risk of AD and on CSF levels of cholesterol and 24S-hydroxycholesterol.ResultsTwo of the identified 16 SNPs in CYP46A1 influenced AD risk in our study (rs7157609: p = 0.016; rs4900442: p = 0.019). The interaction term of both SNPs was also associated with an increased risk of AD (p = 0.006). Haplotypes including both SNPs were calculated and haplotype G–C was identified to influence the risk of AD (p = 0.005). AD patients and non-demented controls, who were carriers of the G–C haplotype, presented with reduced CSF levels of 24S-hydroxycholesterol (p = 0.001) and cholesterol (p < 0.001).ConclusionOur results suggest that CYP46A1 gene variations might act as risk factor for AD via an influence on brain cholesterol metabolism.

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.

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