Surface Of Astrocytes Research Articles

Astroglial morphological changes in periaqueductal grey in different pain and itch mice models

BackgroundThe periaqueductal gray (PAG) plays a well-established pivotal role in the descending pain modulatory circuit. The objective of this study was to investigate morphological changes in the astroglia in models that are commonly used in pain and itch studies. MethodsFive different mouse models of pain, as well as two models of chronic itch, were established using complete Freund's adjuvant (CFA), spared nerve injury (SNI), bone cancer pain (BCP), cisplatin (CIS), and paclitaxel (PTX) for pain, and diphenylcyclopropenone (DCP) and acetone and diethyl ether followed by water (AEW) for chronic itch. von Frey tests and video recordings were employed to assess pain and itching behaviors. The immunofluorescence of S100β, pSTAT3, and glial fibrillary acidic protein (GFAP) was examined. Two- and three-dimensional studies were used to evaluate changes in astrocyte morphology. ResultsSignificant scratching was caused by DCP and AEW, whereas the administration of CFA, SNI, BCP, CIS, and PTX produced clear mechanical allodynia. The expression of GFAP in the lPAG/vlPAG was upregulated in CFA, SNI, BCP, CIS, PTX, and DCP mice but decreased in AEW mice. According to Sholl analysis, CFA, SNI, PTX, and BCP mice showed substantially higher astrocyte intersections in the vlPAG, whereas CFA, SNI, BCP, CIS, and DCP mice presented longer peak lengths. In three-dimensional analysis, CFA, SNI, PTX, and DCP mice showed increased astrocyte surface areas, while CIS and AEW mice showed both reduced surface areas and/or volumes of astrocytes. ConclusionThe findings showed that different pain and itching conditions have different astrocyte morphologies, and these variations in morphological changes help to explain the pathophysiology of these conditions.

GLT-1a glutamate transporter nanocluster localization is associated with astrocytic actin and neuronal Kv2 clusters at sites of neuron-astrocyte contact.

Introduction: Astrocytic GLT-1 glutamate transporters ensure the fidelity of glutamic neurotransmission by spatially and temporally limiting glutamate signals. The ability to limit neuronal hyperactivity relies on the localization and diffusion of GLT-1 on the astrocytic surface, however, little is known about the underlying mechanisms. We show that two isoforms of GLT-1, GLT-1a and GLT-1b, form nanoclusters on the surface of transfected astrocytes and HEK-293 cells. Methods: We used both fixed and live cell super-resolution imaging of fluorescent protein and epitope tagged proteins in co-cultures of rat astrocytes and neurons. Immunofluorescence techniques were also used. GLT1 diffusion was assessed via single particle tracking and fluorescence recovery after photobleach (FRAP). Results: We found GLT-1a, but not GLT-1b, nanoclusters concentrated adjacent to actin filaments which was maintained after addition of glutamate. GLT-1a nanocluster concentration near actin filaments was prevented by expression of a cytosolic GLT-1a C-terminus, suggesting the C-terminus is involved in the localization adjacent to cortical actin. Using super-resolution imaging, we show that astrocytic GLT-1a and actin co-localize in net-like structures around neuronal Kv2.1 clusters at points of neuron/astrocyte contact. Conclusion: Overall, these data describe a novel relationship between GLT-1a and cortical actin filaments, which localizes GLT-1a near neuronal structures responsive to ischemic insult.

Astrocyte DNA damage and response upon acute exposure to ethanol and corticosterone.

Introduction: Astrocytes are the glial cells responsible for brain homeostasis, but if injured, they could damage neural cells even deadly. Genetic damage, DNA damage response (DDR), and its downstream cascades are dramatic events poorly studied in astrocytes. Hypothesis and methods: We propose that 1h of 400mmol/L ethanol and/or 1μmol/L corticosterone exposure of cultured hippocampal astrocytes damages DNA, activating the DDR and eliciting functional changes. Immunolabeling against γH2AX (chromatin DNA damage sites), cyclin D1 (cell cycle control), nuclear (base excision repair, BER), and cytoplasmic (anti-inflammatory functions) APE1, ribosomal nucleolus proteins together with GFAP and S100β plus scanning electron microscopy studies of the astrocyte surface were carried out. Results: Data obtained indicate significant DNA damage, immediate cell cycle arrest, and BER activation. Changes in the cytoplasmic signals of cyclin D1 and APE1, nucleolus number, and membrane-attached vesicles strongly suggest a reactivity like astrocyte response without significant morphological changes. Discussion: Obtained results uncover astrocyte genome immediate vulnerability and DDR activation, plus a functional response that might in part, be signaled through extracellular vesicles, evidencing the complex influence that astrocytes may have on the CNS even upon short-term aggressions.

Identification of novel drug targets for Alzheimer’s disease by integrating genetics and proteomes from brain and blood

AbstractBackgroundGenome‐wide association studies (GWASs) have discovered numerous risk genes for Alzheimer’s disease (AD), but how these genes confer AD risk is challenging to decipher.MethodTo efficiently transform genetic associations into drug targets for AD, we employed an integrative analytical pipeline using proteomes in brain and blood by systematically applying proteome‐wide association study (PWAS), Mendelian randomization (MR) and Bayesian colocalization.ResultCollectively, we identified the brain protein abundance of 7 genes (ACE, ICA1L, TOM1L2, SNX32, EPHX2, CTSH, and RTFDC1) are causal in AD (P<0.05/proteins identified for PWAS and MR; PPH4>80% for Bayesian colocalization). The proteins encoded by these genes were mainly expressed on the surface of glutamatergic neurons and astrocytes. Of them, ACE with its protein abundance was also identified in significant association with AD on the blood‐based studies and showed significance at the transcriptomic level. SNX32 was also found to be associated with AD at the blood transcriptomic level.ConclusionOur current study results on genetic, proteomic and transcriptomic approaches has identified compelling genes, which may provide important leads to design future functional studies and potential drug targets for AD.

Astrocytes and microglia-targeted Danshensu liposomes enhance the therapeutic effects on cerebral ischemia-reperfusion injury

Cerebral ischemia-reperfusion injury (CI/RI) is the main cause of disability and death in stroke without satisfactory therapeutic effect. Inflammation mediated by activation of astrocytes and microglia is the main pathological mechanism of CI/RI. Danshensu (DSS) has been shown to exert anti-inflammatory effects against brain injury. However, limited by its poor cellular permeability and low bioavailability, it is still needed the new DSS preparations with the ability to cross the blood–brain barrier (BBB) and target inflammatory glial cells. In this study, we developed phosphatidylserine (PS) and transferrin (TF) modified liposomes carrying DSS (TF/PS/DSS-LPs) to improve the therapeutic efficacy against ischemic stroke. First, TF molecules targeted transferrin receptor (TfR) that is overexpressed in the BBB. Following the liposomes enter the brain, PS modification allowed the liposomes to target and bind to the overexpressed phosphatidylserine-specific receptors (PSRs) on the surface of astrocytes and microglia. Furthermore, it enhanced the uptake of TF/PS/DSS-LPs by astrocytes and microglia, while polarizing astrocytes from A1 to A2 and microglia from M1 to M2, reducing neuronal inflammation, and ultimately ameliorating cerebral ischemic injury. Thus, TF/PS/DSS-LPs could potentially serve as a promising strategy for the CI/RI treatment.

Longitudinal scRNA-seq analysis in mouse and human informs optimization of rapid mouse astrocyte differentiation protocols.

Macroglia (astrocytes and oligodendrocytes) are required for normal development and function of the central nervous system, yet many questions remain about their emergence during the development of the brain and spinal cord. Here we used single-cell/single-nucleus RNA sequencing (scRNA-seq/snRNA-seq) to analyze over 298,000 cells and nuclei during macroglia differentiation from mouse embryonic and human-induced pluripotent stem cells. We computationally identify candidate genes involved in the fate specification of glia in both species and report heterogeneous expression of astrocyte surface markers across differentiating cells. We then used our transcriptomic data to optimize a previous mouse astrocyte differentiation protocol, decreasing the overall protocol length and complexity. Finally, we used multi-omic, dual single-nuclei (sn)RNA-seq/snATAC-seq analysis to uncover potential genomic regulatory sites mediating glial differentiation. These datasets will enable future optimization of glial differentiation protocols and provide insight into human glial differentiation.

Secretomics reveals gelatinase substrates at the blood-brain barrier that are implicated in astroglial barrier function.

The gelatinases, matrix metalloproteinase 2 (MMP-2) and MMP-9, are key for leukocyte penetration of the brain parenchymal border in neuroinflammation and the functional integrity of this barrier; however, it is unclear which MMP substrates are involved. Using a tailored, sensitive, label-free mass spectrometry-based secretome approach, not previously applied to nonimmune cells, we identified 119 MMP-9 and 21 MMP-2 potential substrates at the cell surface of primary astrocytes, including known substrates (β-dystroglycan) and a broad spectrum of previously unknown MMP-dependent events involved in cell-cell and cell-matrix interactions. Using neuroinflammation as a model of assessing compromised astroglial barrier function, a selection of the potential MMP substrates were confirmed in vivo and verified in human samples, including vascular cell adhesion molecule-1 and neuronal cell adhesion molecule. We provide a unique resource of potential MMP-2/MMP-9 substrates specific for the astroglia barrier. Our data support a role for the gelatinases in the formation and maintenance of this barrier but also in astrocyte-neuron interactions.

Glial cell response and microthrombosis in aneurysmal subarachnoid hemorrhage patients: An autopsy study.

Neuroinflammation and microthrombosis may be underlying mechanisms of brain injury after aneurysmal subarachnoid hemorrhage (aSAH), but they have not been studied in relation to each other. In postmortem brain tissue, we investigated neuroinflammation by studying the microglial and astrocyte response in the frontal cortex of 11 aSAH and 10 control patients. In a second study, we investigated the correlation between microthrombosis and microglia by studying the microglial surface area around vessels with and without microthrombosis in the frontal cortex and hippocampus of 8 other aSAH patients. In comparison with controls, we found increased numbers of microglia (mean ± SEM 50 ± 8 vs 20 ± 5 per 0.0026 mm³, p < 0.01), an increased surface area (%) of microglia (mean ± SEM 4.2 ± 0.6 vs 2.2 ± 0.4, p < 0.05), a higher intensity of the astrocytic intermediate filament protein glial fibrillary acidic protein (GFAP) (mean ± SEM 184 ± 28 vs 92 ± 23 arbitrary units, p < 0.05), and an increased GFAP surface area (%) (mean ± SEM 21.2 ± 2.6 vs 10.7 ± 2.1, p < 0.01) in aSAH tissue. Microglia surface area was approximately 40% larger around vessels with microthrombosis than those without microthrombosis (estimated marginal means [95% CI]; 6.1 [5.4-6.9] vs 4.3 [3.6-5.0], p < 0.001). Our results show that the microglial and astrocyte surface areas increased after aSAH and that microthrombosis and microglia are interrelated.

Dendrimer-enabled targeted delivery attenuates glutamate excitotoxicity and improves motor function in a rabbit model of cerebral palsy.

Glutamate carboxypeptidase II (GCPII), localized on the surface of astrocytes and activated microglia, regulates extracellular glutamate concentration in the central nervous system (CNS). We have previously shown that GCPII is upregulated in activated microglia in the presence of inflammation. Inhibition of GCPII activity could reduce glutamate excitotoxicity, which may decrease inflammation and promote a 'normal' microglial phenotype. 2-(3-Mercaptopropyl) pentanedioic acid (2-MPPA) is the first GCPII inhibitor that underwent clinical trials. Unfortunately, immunological toxicities have hindered 2-MPPA clinical translation. Targeted delivery of 2-MPPA specifically to activated microglia and astrocytes that over-express GCPII has the potential to mitigate glutamate excitotoxicity and attenuate neuroinflammation. In this study, we demonstrate that 2-MPPA when conjugated to generation-4, hydroxyl-terminated polyamidoamine (PAMAM) dendrimers (D-2MPPA) localize specifically in activated microglia and astrocytes only in newborn rabbits with cerebral palsy (CP), not in controls. D-2MPPA treatment led to higher 2-MPPA levels in the injured brain regions compared to 2-MPPA treatment, and the extent of D-2MPPA uptake correlated with the injury severity. D-2MPPA was more efficacious than 2-MPPA in decreasing extracellular glutamate level in ex vivo brain slices of CP kits, and in increasing transforming growth factor beta 1 (TGF-β1) level in primary mixed glial cell cultures. A single systemic intravenous dose of D-2MPPA on postnatal day 1 (PND1) decreased microglial activation and resulted in a change in microglial morphology to a more ramified form along with amelioration of motor deficits by PND5. These results indicate that targeted dendrimer-based delivery specifically to activated microglia and astrocytes can improve the efficacy of 2-MPPA by attenuating glutamate excitotoxicity and microglial activation.

Role of Astrocytes in Epilepsy and Schizophrenia

The dangers of epilepsy and schizophrenia are increasingly being noticed. Its economic burden, social harm and harm to patients cannot be ignored. However, little is known about the pathogenesis of psychiatric disorders. Relevant treatment is limited to symptomatic treatment. Research suggests astrocytes play a role in seizures and schizophrenia. In the occurrence and development of mental diseases such as epilepsy and schizophrenia, astrocytes cannot be ignored. The article introduces the current findings and theories on role and function of astrocytes, and their connection with epilepsy and schizophrenia. It describes the positive effects and negative effects of astrocytes and their basic mechanisms that are now believed. And those mechanisms include glutamate-glutamine cycle which is related to the synthesizing of gama-aminobutyric acid (GABA), blood brain barrier which is controlling the matter exchange between vessels and brain, several molecules and inflammatory factors effect on the channel expressing on the surface of astrocytes and other main paths that could contribute to neuronal disorders. The article also includes several chemicals and their effects on inhibiting astrocytes of isolated sample, from chliroquine, calmodulin-trifluoperazin, gamma globulin and anticardiolipin antibodies. Last, the present study on the relationship between epilepsy and schizophrenia is discussed.

Inhibition of Neuromyelitis Optica Immunoglobulin G Binding to Aquaporin-4 by the Small Molecule Blocker Melanthioidine.

Neuromyelitis optica (NMO) is a severe neurological demyelinating autoimmune disease affecting the optic nerves and spinal cord. The binding of neuromyelitis optica immunoglobulin G (NMO-IgG) and aquaporin-4 (AQP4) on the surface of astrocytes in the serum and cerebrospinal fluid is the main pathogenesis of NMO. Currently, therapeutic strategies for NMO include a reduction of the secondary inflammation response and the number of NMO-IgG, which can only alleviate clinical symptoms rather than fundamentally preventing a series of pathological processes caused by NMO-IgG binding to AQP4. The purpose of this study was to investigate the blocking effect of melanthioidine on the binding of NMO-IgG to AQP4 and its potential cytotoxicity. The current study developed a cell-based high-throughput screening approach to identify a molecular blocker of NMO-IgG binding to AQP4 using the Chinese hamster lung fibroblast (V79) cells expressing M23-AQP4. By screening ~400 small molecules, we identified melanthioidine with blocking effects without affecting AQP4 expression or its water permeability. Melanthioidine effectively blocked the binding of NMO-IgG to AQP4 in immunofluorescence assays and reduced complement-dependent cytotoxicity against both NMO-IgG/complement-treated Fischer rat thyroid-AQP4 cells and primary astrocytes. The docking computations identified the putative sites of blocker binding at the extracellular surface of AQP4. This study serves as proof of a potential NMO therapy by using a small-molecule blocker to target NMO pathogenesis.

Immunohistochemical Localization of MD2, a Co-Receptor of TLR4, in the Adult Mouse Brain.

Myeloid differentiation factor 2 (MD2) is a co-receptor of a classical proinflammatory protein TLR4 whose activation leads to neuroinflammation. It is widely accepted that TLR4 is expressed on the cell surface of microglia and astrocytes, and MD2 is expected to be expressed by these cells as well. However, our previous study showed that neurons from certain nuclei also expressed MD2. Whether MD2 is expressed by other brain nuclei is still unknown. It is the aim of the present study to map the distribution of MD2-positive cells in the adult mouse brain. Immunohistochemical staining against MD2 was completed to localize MD2-positive cells in the mouse brain by comparing the location of positive cells with the mouse brain atlas. MD2-positive cells were found in the majority of mouse brain nuclei with clusters of cells in the olfactory bulb, cortices, the red nucleus, and cranial nuclei. Subcortical nuclei had heterogeneous staining of MD2 with more prominent cells in the basolateral and the central amygdaloid nuclei. The ventral pallidum and the diagonal bands had positive cells with similar density and shape. Prominent cells were present in thalamic nuclei which were nearly homogeneous and in reticular formation of the brainstem where cells were dispersed with similar density. The hypothalamus had fewer outstanding cells compared with the thalamus. The red nucleus, the substantia nigra, and the ventral tegmental area in the pretectum had outstanding cells. Motor cranial nuclei also had outstanding MD2-positive cells, whereas raphe, sensory cranial, and deep cerebellar nuclei had MD2-positive cells with moderate density. The presence of MD2 in these nuclei may suggest the involvement of MD2 in their corresponding physiological functions.

Neuromyelitis-optica-Spektrum-Erkrankungen (NMOSD) und Anti-Myelin-Oligodendrozyten-Glykoprotein-Antikörper-assoziierte Erkrankungen (MOGAD)

Wiederkehrende Episoden entzündlicher Schädigungen des Sehnervs und des Rückenmarks sind als eigenständige Erkrankung schon aus historischen Überlieferungen bekannt. Im Jahr 2004 gelang die Identifikation des pathognomonischen, gegen Aquaporin‑4 auf Astrozyten gerichteten Antikörpers. Zugehörige klinische Manifestationen werden als Neuromyelitis-optica-Spektrum-Erkrankungen („neuromyelitis optica spectrum disorders“, NMOSD) zusammengefasst. Diagnostische Kriterien basieren auf der klinischen Präsentation sowie der Bildgebung und berücksichtigen den Antikörperstatus. Histologisch sind NMOSD durch eine primäre Schädigung der Astrozyten mit sekundärer Demyelinisierung charakterisiert. Nach Gabe von Methylprednisolon und evtl. Anwendung von Plasmapherese in der Akutsituation schließt sich die langdauernde Immunsuppression zur Schubprophylaxe an. Diese basiert auf B‑Zell-Depletion, Interleukin-6-Antagonismus oder Komplementhemmung. Klinisch ähnlich können sich Erkrankungen präsentieren, die mit Antikörpern gegen Myelin-Oligodendrozyten-Glykoprotein assoziiert sind („anti-MOG-antibody-associated diseases“, MOGAD). Hier kommt es zur primären entzündlichen Demyelinisierung im zentralen Nervensystem. Im Gegensatz zu mit Aquaporin-4-Antikörpern assoziierten NMOSD gibt es für MOGAD bisher keine kontrollierten Therapiestudien.

P2R Inhibitors Prevent Antibody-Mediated Complement Activation in an Animal Model of Neuromyelitis Optica

Purinergic 2 receptors (P2Rs) contribute to disease-related immune cell signaling and are upregulated in various pathological settings, including neuroinflammation. P2R inhibitors have been used to treat inflammatory diseases and can protect against complement-mediated cell injury. However, the mechanisms behind these anti-inflammatory properties of P2R inhibitors are not well understood, and their potential in CNS autoimmunity is underexplored. Here, we tested the effects of P2R inhibitors on glial toxicity in a mouse model of neuromyelitis optica spectrum disorder (NMOSD). NMOSD is a destructive CNS autoimmune disorder, in which autoantibodies against astrocytic surface antigen Aquaporin 4 (AQP4) mediate complement-dependent loss of astrocytes. Using two-photon microscopy in vivo, we found that various classes of P2R inhibitors prevented AQP4-IgG/complement-dependent astrocyte death. In vitro, these drugs inhibited the binding of AQP4-IgG or MOG-IgG to their antigen in a dose-dependent manner. Size-exclusion chromatography and circular dichroism spectroscopy revealed a partial unfolding of antibodies in the presence of various P2R inhibitors, suggesting a shared interference with IgG antibodies leading to their conformational change. Our study demonstrates that P2R inhibitors can disrupt complement activation by direct interaction with IgG. This mechanism is likely to influence the role of P2R inhibitors in autoimmune disease models and their therapeutic impact in human disease.

Identification of novel proteins for lacunar stroke by integrating genome-wide association data and human brain proteomes

BackgroundPrevious genome-wide association studies (GWAS) have identified numerous risk genes for lacunar stroke, but it is challenging to decipher how they confer risk for the disease. We employed an integrative analytical pipeline to efficiently transform genetic associations to identify novel proteins for lacunar stroke.MethodsWe systematically integrated lacunar stroke genome-wide association study (GWAS) (N=7338) with human brain proteomes (N=376) to perform proteome-wide association studies (PWAS), Mendelian randomization (MR), and Bayesian colocalization. We also used an independent human brain proteomic dataset (N=152) to annotate the new genes.ResultsWe found that the protein abundance of seven genes (ICA1L, CAND2, ALDH2, MADD, MRVI1, CSPG4, and PTPN11) in the brain was associated with lacunar stroke. These seven genes were mainly expressed on the surface of glutamatergic neurons, GABAergic neurons, and astrocytes. Three genes (ICA1L, CAND2, ALDH2) were causal in lacunar stroke (P < 0.05/proteins identified for PWAS; posterior probability of hypothesis 4 ≥ 75 % for Bayesian colocalization), and they were linked with lacunar stroke in confirmatory PWAS and independent MR. We also found that ICA1L is related to lacunar stroke at the brain transcriptome level.ConclusionsOur present proteomic findings have identified ICA1L, CAND2, and ALDH2 as compelling genes that may give key hints for future functional research and possible therapeutic targets for lacunar stroke.

Implementation of tissue clearing and 3‐dimensional volumetric imaging approaches for visualization of anatomical structures in autonomic nuclei

Alterations within central nervous system (CNS) autonomic nuclei contribute to a wide array of diseases. In this context, significant advancements have been made into disease‐related molecular mechanisms in autonomic brain regions. While helpful, it is important to consider that information processing within the CNS occurs through dynamic micro‐architectural structural interactions, such astrocyte‐neuron synaptic connections. However the traditional method for evaluating CNS morphology and synaptic contacts between cells is performed with immunohistochemistry on thin brain sections. An inherent limitation of this approach is not only the narrow 2‐dimensional field of view, but also the lack of optical transparency that minimizes high‐resolution imaging of anatomical structures and cell‐cell interactions. To overcome these limitations, here we sought to optimize tissue clearing approaches combined with 3D volumetric imaging for autonomic CNS nuclei. We focused our initial efforts on the forebrain subfornical organ (SFO), a region lacking a blood‐brain‐barrier, given: 1 Alterations in the SFO have been described to contribute to numerous disease conditions; and 2 The SFO represents a unique technical challenge for 3D imaging due to the complexity of cellular processes and surrounding lateral ventricle space. As a first step, we used a “passive” CLARITY tissue approach in 8‐week‐old C57Bl/6J male mice. Mice were transcardially perfused with an acrylamide‐based hydrogel in standard fixative. Subsequently, a brain section encompassing the entire SFO (~1mm) was obtained, and a series of thermal diffusion steps was performed to place existing protein structures in a “scaffold” and remove the lipid contents ‐ rendering the tissue transparent. Whole‐mount immunohistochemistry for astrocytes was then conducted using GFAP and DAPI as a nuclei marker, followed by 3D volumetric multiphoton imaging to acquire high‐resolution visualization of the entire SFO in three planes (Figure top). In brief, this approach proved to be a significant advancement beyond standard 2D histology, and 3D visualization of intricate astrocyte processes throughout the whole SFO was possible. However, a major limitation was the extensive amount of time required to process a single sample; 2 weeks for tissue clearing and 2 weeks for primary and secondary antibody incubation. Based on this, we adapted our protocol to an “active” CLARITY approach and employed electrophoretic‐based clearing of large brain sections (n=5), which resulted in a reduction in clearing time from 2 weeks to 4 hours. It was also readily apparent that this approach rendered the tissue more transparent than passive clearing, allowing for greater visualization of astrocyte processes (Figure middle). Preliminary analysis with IMARIS software to analyze astrocyte surface area and dendritic processing (Figure bottom) revealed highly complex SFO astrocytic structures with some dendrites extending from soma at the lateral ventricle throughout and surrounding nearly the entire SFO; these processes are not visualized with standard histology. Collectively, these approaches highlight the utility of tissue‐based clearing for 3D visualization of anatomical structures within autonomic nuclei and provide a framework to understand structure‐function relationships within these brain regions in the regulation of physiological and pathophysiological conditions.

An Outside-In Switch in Integrin Signaling Caused by Chemical and Mechanical Signals in Reactive Astrocytes.

Astrocyte reactivity is associated with poor repair capacity after injury to the brain, where chemical and physical changes occur in the damaged zone. Astrocyte surface proteins, such as integrins, are upregulated, and the release of pro-inflammatory molecules and extracellular matrix (ECM) proteins upon damage generate a stiffer matrix. Integrins play an important role in triggering a reactive phenotype in astrocytes, and we have reported that αVβ3 Integrin binds to the Thy-1 (CD90) neuronal glycoprotein, increasing astrocyte contractility and motility. Alternatively, αVβ3 Integrin senses mechanical forces generated by the increased ECM stiffness. Until now, the association between the αVβ3 Integrin mechanoreceptor response in astrocytes and changes in their reactive phenotype is unclear. To study the response to combined chemical and mechanical stress, astrocytes were stimulated with Thy-1-Protein A-coated magnetic beads and exposed to a magnetic field to generate mechanical tension. We evaluated the effect of such stimulation on cell adhesion and contraction. We also assessed traction forces and their effect on cell morphology, and integrin surface expression. Mechanical stress accelerated the response of astrocytes to Thy-1 engagement of integrin receptors, resulting in cell adhesion and contraction. Astrocyte contraction then exerted traction forces onto the ECM, inducing faster cell contractility and higher traction forces than Thy-1 alone. Therefore, cell-extrinsic chemical and mechanical signals regulate in an outside-in manner, astrocyte reactivity by inducing integrin upregulation, ligation, and signaling events that promote cell contraction. These changes in turn generate cell-intrinsic signals that increase traction forces exerted onto the ECM (inside-out). This study reveals αVβ3 Integrin mechanoreceptor as a novel target to regulate the harmful effects of reactive astrocytes in neuronal healing.

Identification of novel drug targets for Alzheimer's disease by integrating genetics and proteomes from brain and blood.

Genome-wide association studies (GWASs) have discovered numerous risk genes for Alzheimer's disease (AD), but how these genes confer AD risk is challenging to decipher. To efficiently transform genetic associations into drug targets for AD, we employed an integrative analytical pipeline using proteomes in the brain and blood by systematically applying proteome-wide association study (PWAS), Mendelian randomization (MR) and Bayesian colocalization. Collectively, we identified the brain protein abundance of 7 genes (ACE, ICA1L, TOM1L2, SNX32, EPHX2, CTSH, and RTFDC1) are causal in AD (P < 0.05/proteins identified for PWAS and MR; PPH4 >80% for Bayesian colocalization). The proteins encoded by these genes were mainly expressed on the surface of glutamatergic neurons and astrocytes. Of them, ACE with its protein abundance was also identified in significant association with AD on the blood-based studies and showed significance at the transcriptomic level. SNX32 was also found to be associated with AD at the blood transcriptomic level. Collectively, our current study results on genetic, proteomic, and transcriptomic approaches has identified compelling genes, which may provide important leads to design future functional studies and potential drug targets for AD.

Glial decline and loss of homeostatic support rather than inflammation defines cognitive aging.

Glial decline and loss of homeostatic support rather than inflammation defines cognitive aging.

The Role of Platelets in the Stimulation of Neuronal Synaptic Plasticity, Electric Activity, and Oxidative Phosphorylation: Possibilities for New Therapy of Neurodegenerative Diseases.

The central nervous system (CNS) is highly vascularized where neuronal cells are located in proximity to endothelial cells, astroglial limitans, and neuronal processes constituting integrated neurovascular units. In contrast to many other organs, the CNS has a blood-brain barrier (BBB), which becomes compromised due to infection, neuroinflammation, neurodegeneration, traumatic brain injury, and other reasons. BBB disruption is presumably involved in neuronal injury during epilepsy and psychiatric disorders. Therefore, many types of neuropsychological disorders are accompanied by an increase in BBB permeability leading to direct contact of circulating blood cells in the capillaries with neuronal cells in the CNS. The second most abundant type of blood cells are platelets, which come after erythrocytes and outnumber ~100-fold circulating leukocytes. When BBB becomes compromised, platelets swiftly respond to the vascular injury and become engaged in thrombosis and hemostasis. However, more recent studies demonstrated that platelets could also enter CNS parenchyma and directly interact with neuronal cells. Within CNS, platelets become activated by recognizing major brain gangliosides on the surface of astrocytes and neurons and releasing a milieu of pro-inflammatory mediators, neurotrophic factors, and neurotransmitters. Platelet-derived factors directly stimulate neuronal electric and synaptic activity and promote the formation of new synapses and axonal regrowth near the site of damage. Despite such active involvement in response to CNS damage, the role of platelets in neurological disorders was not extensively studied, which will be the focus of this review.