Astrocyte transcriptomic changes along the spatiotemporal progression of Alzheimer's disease.

Astrocytes are crucial to brain homeostasis, yet their changes along the spatiotemporal progression of Alzheimer's disease (AD) neuropathology remain unexplored. Here we performed single-nucleus RNA sequencing of 628,943 astrocytes from five brain regions representing the stereotypical progression of AD pathology across 32 donors spanning the entire normal aging to severe AD continuum. We mapped out several unique astrocyte subclusters that exhibited varying responses to neuropathology across the AD-vulnerable neural network (spatial axis) or AD pathology stage (temporal axis).

Landscape of brain myeloid cell transcriptome along the spatiotemporal progression of Alzheimer's disease reveals distinct sequential responses to Aβ and tau.

Human microglia are critically involved in Alzheimer's disease (AD) progression, as shown by genetic and molecular studies. However, their role in tau pathology progression in human brain has not been well described. Here, we characterized 32 human donors along progression of AD pathology, both in time-from early to late pathology-and in space-from entorhinal cortex (EC), inferior temporal gyrus (ITG), prefrontal cortex (PFC) to visual cortex (V2 and V1)-with biochemistry, immunohistochemistry, and single nuclei-RNA-sequencing, profiling a total of 337,512 brain myeloid cells, including microglia.

Distinct transcriptomic responses to Aβ plaques, neurofibrillary tangles, and APOE in Alzheimer's disease.

Introduction: Omics studies have revealed that various brain cell types undergo profound molecular changes in Alzheimer's disease (AD) but the spatial relationships with plaques and tangles and APOE-linked differences remain unclear.

Methods: We performed laser capture microdissection of amyloid beta (Aβ) plaques, the 50 μm halo around them, tangles with the 50 μm halo around them, and areas distant (> 50 μm) from plaques and tangles in the temporal cortex of AD and control donors, followed by RNA-sequencing.

Results: Aβ plaques exhibited upregulated microglial (neuroinflammation/phagocytosis) and downregulated neuronal (neurotransmission/energy metabolism) genes, whereas tangles had mostly downregulated neuronal genes.

Endothelial Cells Are Heterogeneous in Different Brain Regions and Are Dramatically Altered in Alzheimer's Disease.

Vascular endothelial cells play an important role in maintaining brain health, but their contribution to Alzheimer's disease (AD) is obscured by limited understanding of the cellular heterogeneity in normal aged brain and in disease. To address this, we performed single nucleus RNAseq on tissue from 32 human AD and non-AD donors (19 female, 13 male) each with five cortical regions: entorhinal cortex, inferior temporal gyrus, prefrontal cortex, visual association cortex, and primary visual cortex. Analysis of 51,586 endothelial cells revealed unique gene expression patterns across the five regions in non-AD donors.

Distinct Transcriptomic Responses to Aβ plaques, Neurofibrillary Tangles, and in Alzheimer's Disease.

Introduction: Omics studies have revealed that various brain cell types undergo profound molecular changes in Alzheimer's disease (AD) but the spatial relationships with plaques and tangles and -linked differences remain unclear.

Methods: We performed laser capture microdissection of Aβ plaques, the 50μm halo around them, tangles with the 50μm halo around them, and areas distant (>50μm) from plaques and tangles in the temporal cortex of AD and control donors, followed by RNA-sequencing.

Results: Aβ plaques exhibited upregulated microglial (neuroinflammation/phagocytosis) and downregulated neuronal (neurotransmission/energy metabolism) genes, whereas tangles had mostly downregulated neuronal genes.

Endothelial Cells are Heterogeneous in Different Brain Regions and are Dramatically Altered in Alzheimer's Disease.

Unlabelled: Vascular endothelial cells play an important role in maintaining brain health, but their contribution to Alzheimer's disease (AD) is obscured by limited understanding of the cellular heterogeneity in normal aged brain and in disease. To address this, we performed single nucleus RNAseq on tissue from 32 AD and non-AD donors each with five cortical regions: entorhinal cortex, inferior temporal gyrus, prefrontal cortex, visual association cortex and primary visual cortex. Analysis of 51,586 endothelial cells revealed unique gene expression patterns across the five regions in non-AD donors.

Microglia states and nomenclature: A field at its crossroads.

Microglial research has advanced considerably in recent decades yet has been constrained by a rolling series of dichotomies such as "resting versus activated" and "M1 versus M2." This dualistic classification of good or bad microglia is inconsistent with the wide repertoire of microglial states and functions in development, plasticity, aging, and diseases that were elucidated in recent years. New designations continuously arising in an attempt to describe the different microglial states, notably defined using transcriptomics and proteomics, may easily lead to a misleading, although unintentional, coupling of categories and functions.

Neurodegeneration and neuroinflammation are linked, but independent of alpha-synuclein inclusions, in a seeding/spreading mouse model of Parkinson's disease.

A key pathological process in Parkinson's disease (PD) is the transneuronal spreading of α-synuclein. Alpha-synuclein (α-syn) is a presynaptic protein that, in PD, forms pathological inclusions. Other hallmarks of PD include neurodegeneration and microgliosis in susceptible brain regions.

Distinct amyloid-β and tau-associated microglia profiles in Alzheimer's disease.

Alzheimer's disease (AD) is the most prevalent form of dementia and is characterized by abnormal extracellular aggregates of amyloid-β and intraneuronal hyperphosphorylated tau tangles and neuropil threads. Microglia, the tissue-resident macrophages of the central nervous system (CNS), are important for CNS homeostasis and implicated in AD pathology. In amyloid mouse models, a phagocytic/activated microglia phenotype has been identified.

Profiling Microglia From Alzheimer's Disease Donors and Non-demented Elderly in Acute Human Postmortem Cortical Tissue.

Microglia are the tissue-resident macrophages of the central nervous system (CNS). Recent studies based on bulk and single-cell RNA sequencing in mice indicate high relevance of microglia with respect to risk genes and neuro-inflammation in Alzheimer's disease (AD). Here, we investigated microglia transcriptomes at bulk and single-cell levels in non-demented elderly and AD donors using acute human postmortem cortical brain samples.

Detection of Synaptic Proteins in Microglia by Flow Cytometry.

A growing body of evidence indicates that microglia actively remove synapses , thereby playing a key role in synaptic refinement and modulation of brain connectivity. This phenomenon was mainly investigated in immunofluorescence staining and confocal microscopy. However, a quantification of synaptic material in microglia using these techniques is extremely time-consuming and labor-intensive.

Antidepressant treatment is associated with epigenetic alterations of Homer1 promoter in a mouse model of chronic depression.

Background: Understanding the neurobiology of depression and the mechanism of action of therapeutic measures is currently a research priority. We have shown that the expression of the synaptic protein Homer1a correlates with depression-like behavior and its induction is a common mechanism of action of different antidepressant treatments. However, the mechanism of Homer1a regulation is still unknown.

The neuroprotective role of microglial cells against amyloid beta-mediated toxicity in organotypic hippocampal slice cultures.

During Alzheimer's disease (AD) progression, microglial cells play complex roles and have potentially detrimental as well as beneficial effects. The use of appropriate model systems is essential for characterizing and understanding the roles of microglia in AD pathology. Here, we used organotypic hippocampal slice cultures (OHSCs) to investigate the impact of microglia on amyloid beta (Aβ)-mediated toxicity.

Enhanced adenosine A receptor and Homer1a expression in hippocampus modulates the resilience to stress-induced depression-like behavior.

Resilience to stress is critical for the development of depression. Enhanced adenosine A receptor (AR) signaling mediates the antidepressant effects of acute sleep deprivation (SD). However, chronic SD causes long-lasting upregulation of brain AR and increases the risk of depression.

Microglial Drug Targets in AD: Opportunities and Challenges in Drug Discovery and Development.

Alzheimer's disease (AD) is a large and increasing unmet medical need with no disease-modifying treatment currently available. Genetic evidence from genome-wide association studies (GWASs) and gene network analysis has clearly revealed a key role of the innate immune system in the brain, of which microglia are the most important element. Single-nucleotide polymorphisms (SNPs) in genes predominantly expressed in microglia have been associated with altered risk of developing AD.

Enhanced mGlu5 Signaling in Excitatory Neurons Promotes Rapid Antidepressant Effects via AMPA Receptor Activation.

Conventional antidepressants have limited efficacy and many side effects, highlighting the need for fast-acting and specific medications. Induction of the synaptic protein Homer1a mediates the effects of different antidepressant treatments, including the rapid action of ketamine and sleep deprivation (SD). We show here that mimicking Homer1a upregulation via intravenous injection of cell-membrane-permeable TAT-Homer1a elicits rapid antidepressant effects in various tests.

Replenishment of Organotypic Hippocampal Slice Cultures with Neonatal or Adult Microglia.

This protocol describes a method to deplete and repopulate organotypic hippocampal slice cultures with ramified microglia. We describe the slice culture preparation from newborn mice, standard culturing of neonatal microglia, and the acute isolation of microglia from adult mouse brain. Furthermore, we outline the technique for the replenishment of microglia-depleted slice cultures with different microglia populations and subsequent morphological analysis.

The role of adenosine receptors in mood and anxiety disorders.

Adenosine receptor subtypes, first described 40 years ago, are known to regulate diverse biological functions and have a role in various conditions, such as cerebral and cardiac ischemia, immune and inflammatory disorders and cancer. In the brain, they limit potentially dangerous over excitation, but also regulate mechanisms essential in sleep and psychiatric disorders. In this review, we discuss the role of adenosine receptors in mood and anxiety disorders.

Single-cell transcriptomics reveals distinct inflammation-induced microglia signatures.

Microglia are specialized parenchymal-resident phagocytes of the central nervous system (CNS) that actively support, defend and modulate the neural environment. Dysfunctional microglial responses are thought to worsen CNS diseases; nevertheless, their impact during neuroinflammatory processes remains largely obscure. Here, using a combination of single-cell RNA sequencing and multicolour flow cytometry, we comprehensively profile microglia in the brain of lipopolysaccharide (LPS)-injected mice.

Recent insights into antidepressant therapy: Distinct pathways and potential common mechanisms in the treatment of depressive syndromes.

There is an urgent, unmet clinical need for faster and more efficient antidepressant drugs with higher response rates. In animal models of depression it was shown in the last few years that inhibition of three signaling molecules (BDNF, p11 and Homer1a) prevents efficacy of antidepressant therapy. These data not only show the crucial role of these factors for the treatment of depression, but may also point towards a better understanding of the molecular changes responsible for successful antidepressant therapy.

Activation of EP receptor suppresses poly(I: C) and LPS-mediated inflammation in primary microglia and organotypic hippocampal slice cultures: Contributing role for MAPKs.

Brain inflammation is a critical factor involved in neurodegeneration. Recently, the prostaglandin E (PGE ) downstream members were suggested to modulate neuroinflammatory responses accompanying neurodegenerative diseases. In this study, we investigated the protective effects of prostaglandin E receptor 2 (EP ) during TLR3 and TLR4-driven inflammatory response using in vitro primary microglia and ex vivo organotypic hippocampal slice cultures (OHSCs).

Antidepressants Rescue Stress-Induced Disruption of Synaptic Plasticity via Serotonin Transporter-Independent Inhibition of L-Type Calcium Channels.

Background: Long-term synaptic plasticity is a basic ability of the brain to dynamically adapt to external stimuli and regulate synaptic strength and ultimately network function. It is dysregulated by behavioral stress in animal models of depression and in humans with major depressive disorder. Antidepressants have been shown to restore disrupted synaptic plasticity in both animal models and humans; however, the underlying mechanism is unclear.

Cellular and Molecular Characterization of Microglia: A Unique Immune Cell Population.

Microglia are essential for the development and function of the adult brain. Microglia arise from erythro-myeloid precursors in the yolk sac and populate the brain rudiment early during development. Unlike monocytes that are constantly renewed from bone marrow hematopoietic stem cells throughout life, resident microglia in the healthy brain persist during adulthood constant self-renewal.

Reestablishing microglia function: good news for Alzheimer's therapy?

Alzheimer's disease (AD) is the most common form of age‐related neurodegenerative disease resulting in dementia. The current notion is that AD is based on a pathological plaque‐forming accumulation of amyloid‐β (Aβ) peptides that originate from a disturbed balance between production and removal of Aβ peptides. Loss of Aβ uptake capacity by brain microglia is linked to Aβ plaque formation and AD onset.

GRIN3B missense mutation as an inherited risk factor for schizophrenia: whole-exome sequencing in a family with a familiar history of psychotic disorders.

Glutamate is the most important excitatory neurotransmitter in the brain. The N-methyl-D-aspartate (NMDA) receptor is a glutamate-gated ionotropic cation channel that is composed of several subunits and modulated by a glycine binding site. Many forms of synaptic plasticity depend on the influx of calcium ions through NMDA receptors, and NMDA receptor dysfunction has been linked to a number of neuropsychiatric disorders, including schizophrenia.