TY - JOUR. T1 - Infection of primary human fetal astrocytes by human herpesvirus 6. AU - Jun, H. E.. AU - McCarthy, Micheline. AU - Zhou, Y. I.. AU - Chandran, Bala. AU - Wood, Charles. PY - 1996/1/29. Y1 - 1996/1/29. N2 - Human herpesvirus 6 (HHV-6) is a lymphotropic betaherpesvirus which productively infects human CD4+ T cells and monocytes. HHV-6 is the etiologic agent for exanthem subitum (roseola), and it is well-known that central nervous system complications occur frequently during the course of HHV-6-associated disease. In addition, HHV-6 has been associated with encephalitis or encephalopathy. However, very little is known about its tropism for neural cells. There are reports that HHV-6 may infect some glial cell lines, but whether it can infect any primary neural cells is not known. Our studies show that both HHV-6A (GS) and HHV-6B (Z-29) can infect highly purified primary fetal astrocytes in vitro. Infected cells showed cytopathic effects, forming giant syncytia. In dual ...
We report here a novel live imaging approach to study astrocyte response to ischemic injury in the brains of living mice. Our results revealed marked effects of sex and estrogen on astrocyte response to ischemic injury. We report here that: (1) bioluminescent signal intensities/GFAP induction were significantly higher in female mice (out of estrus) compared with males (confirmed by immunohistochemistry); (2) in female mice, astrocyte response to ischemia/GFAP upregulation was strongly dependent on the estrus cycle and serum estrogen level; and (3) contrary to the findings in male mice, there was no correlation between bioluminescent signal intensity/GFAP upregulation and size of the ischemic lesion in female GFAP-luc mice.. GFAP is a 50-kDa intermediate filament, predominantly expressed by mature astrocytes in the central nervous system.24,25 Reactive astrogliosis is a key component of the inflammatory cellular response to central nervous system injury, including ischemia.2,26 It is ...
article{9714ffdf-1e21-475d-ac0b-daebdc2182ca, abstract = {Clearance of the amyloid-P peptide (A beta) as a remedy for Alzheimers disease (AD) is a major target in on-going clinical trials. In vitro studies confirmed that A beta is taken up by rodent astrocytes, but knowledge on human astrocyte-mediated A beta clearance is sparse. Therefore, by means of flow cytometry and confocal laser scanning microscopy (CLSM), we evaluated the binding and internalization of A beta 1-42 by primary human fetal astrocytes and adult astrocytes, isolated from nondemented subjects (n = 8) and AD subjects (n = 6). Furthermore, we analyzed whether alpha 1-antichymotrypsin (ACT), which is found in amyloid plaques and can influence A beta fibrillogenesis, affects the A beta uptake by human astrocytes. Upon over night exposure of astrocytes to FAM-labeled A beta 1-42 (10 mu M) preparations, (80.7 +/- 17.7)% fetal and (52.9 +/- 20.9)% adult A beta-positive astrocytes (P = 0.018) were observed. No significant difference ...
Astrocytes are the major glial subtype in the brain and mediate numerous functions ranging from metabolic support to gliotransmitter release through signaling mechanisms controlled by Ca2+. Despite intense interest, the Ca2+ influx pathways in astrocytes remain obscure, hindering mechanistic insights into how Ca2+ signaling is coupled to downstream astrocyte-mediated effector functions. Here, we identified store-operated Ca2+ release-activated Ca2+ (CRAC) channels encoded by Orai1 and STIM1 as a major route of Ca2+ entry for driving sustained and oscillatory Ca2+ signals in astrocytes after stimulation of metabotropic purinergic and protease-activated receptors. Using synaptopHluorin as an optical reporter, we showed that the opening of astrocyte CRAC channels stimulated vesicular exocytosis to mediate the release of gliotransmitters, including ATP. Furthermore, slice electrophysiological recordings showed that activation of astrocytes by protease-activated receptors stimulated interneurons in ...
Astrocytes derived from Y757F mutant mice defective in gp130-SHP2/SOCS3 signaling were investigated into their ability to respond to IL-6. Compared with WT astrocytes, Y757F astrocytes treated with hyper-IL6, had higher and more sustained activation of STAT3, while the levels of pY-SHP2 and pERK remained unchanged. Gene expression was investigated by Affymetrix gene chip analysis. At 2 hr, 306 genes were upregulated in WT astrocytes and of these, 28 did not increase in Y757F astrocytes. Of 238 genes upregulated in Y757F astrocytes, 9 were not upregulated in WT astrocytes. Some 99 genes were downregulated in WT astrocytes and of those 55 were not decreased in Y757F astrocytes. In WT astrocytes after 12 hrs the level of expression of many genes was reduced back to or near levels seen in the untreated cells, however, in Y757F astrocytes 109 genes either maintained their 2hr upregulated levels or were further increased. A number of candidate genes upregulated by hyper-IL6 in WT and Y757F astrocytes ...
Reactive astrocytes are associated with every form of neurological injury. Despite their ubiquity, the molecular mechanisms controlling their production and diverse functions remain poorly defined. Because many features of astrocyte development are recapitulated in reactive astrocytes, we investigated the role of nuclear factor I-A (NFIA), a key transcriptional regulator of astrocyte development whose contributions to reactive astrocytes remain undefined. Here, we show that NFIA is highly expressed in reactive astrocytes in human neurological injury and identify unique roles across distinct injury states and regions of the CNS. In the spinal cord, after white matter injury (WMI), NFIA-deficient astrocytes exhibit defects in blood-brain barrier remodeling, which are correlated with the suppression of timely remyelination. In the cortex, after ischemic stroke, NFIA is required for the production of reactive astrocytes from the subventricular zone (SVZ). Mechanistically, NFIA directly regulates the ...
Astrocyte activation is presumed to depress neuronal regeneration after CNS injury due to the glial scar, a formation of a physical barrier, and overproduction of multiple proinflammatory cytokines, including IL-1β, IL-6, and TNFα, which further aggravate the glial activation and injure the remaining neurons through positive feedback [4, 31, 38, 39]. The recombinant IL-1β used in the present study was shown to be biologically active as previously demonstrated by its ability to induce astrocyte activation in an in vitro astrocyte activation model [4, 40-42]. Therefore, we speculate that our IL-1β stimulation model is suitable and credible for the detection of the astrocyte activation in vitro. Upregulation of GFAP and hypertrophy of astrocyte cellular processes play a major and prominent role in astrocyte activation and the formation of glial scar [6, 12]. In the present study, the IL-1β stimulation triggered an elevated level of GFAP and induced the astrocyte hypertrophy; this phenomenon ...
The generation of human induced pluripotent stem cells (hiPSCs) represents an exciting advancement with promise for stem cell transplantation therapies as well as for neurological disease modeling. Based on the emerging roles for astrocytes in neurological disorders, we investigated whether hiPSC-derived astrocyte progenitors could be engrafted to the rodent spinal cord and how the characteristics of these cells changed between in vitro culture and after transplantation to the in vivo spinal cord environment. Our results show that human embryonic stem cell- and hiPSC-derived astrocyte progenitors survive long-term after spinal cord engraftment and differentiate to astrocytes in vivo with few cells from other lineages present. Gene profiling of the transplanted cells demonstrates the astrocyte progenitors continue to mature in vivo and upregulate a variety of astrocyte-specific genes. Given this mature astrocyte gene profile, this work highlights hiPSCs as a tool to investigate disease-related ...
TY - JOUR. T1 - Molecular diversity of astrocytes with implications for neurological disorders. AU - Bachoo, Robert M.. AU - Kim, Ryung S.. AU - Ligon, Keith L.. AU - Maher, Elizabeth A.. AU - Brennan, Cameron. AU - Billings, Nathan. AU - Chan, Suzanne. AU - Li, Cheng. AU - Rowitch, David H.. AU - Wong, Wing H.. AU - DePinho, Ronald A.. PY - 2004/6/1. Y1 - 2004/6/1. N2 - The astrocyte represents the most abundant yet least understood cell type of the CNS. Here, we use a stringent experimental strategy to molecularly define the astrocyte lineage by integrating microarray datasets across several in vitro model systems of astrocyte differentiation, primary astrocyte cultures, and various astrocyte-rich CNS structures. The intersection of astrocyte data sets, coupled with the application of nonastrocytic exclusion filters, yielded many astrocyte-specific genes possessing strikingly varied patterns of regional CNS expression. Annotation of these astrocyte-specific genes provides direct molecular ...
Introduction Astrocytes are the most abundant glial cell type. in C57BL/6 mice TNFSF11 astroglial cells in response to lipopolysaccharide (LPS) using reverse-transcription polymerase BMS-911543 BMS-911543 chain reaction (RT-PCR) method. Results We provide for the first time evidence that astrocytes can express IL-19 mRNA following LPS stimulation. Furthermore we have found the expression of IL-19 mRNA in the cortex of adult C57BL/6 mice following intraperitoneal (i.p.) administration of LPS. Discussion This finding will contribute to current knowledge on the function and behavior of cells and mediators during inflammatory conditions in BMS-911543 the brain. Keywords: IL-19 Mice Astroglial Cells brain Cortex Lipopolysaccharide 1 Introduction Glial cells play an important role in controlling of CNS inflammation. Astrocytes are the most abundant glial cell type in the brain (Kim Hong & BMS-911543 Ro 2011 BMS-911543 Astrocytes are multifunctional glial cells that regulate extracellular ion and ...
In the present study, we aim to elucidate the role of caveolin-1 in modulating astroglial differentiation of neural progenitor cells (NPCs) and the potential mechanisms involved. We first investigated astroglial differentiation and Notch signaling by detecting the expressions of S100β, GFAP, NICD and hairy enhancer of split 1 (Hes1) in the brains of wild-type and caveolin-1 knockout mice. Caveolin-1 knockout mice revealed remarkably less astroglial differentiation and lower levels of NICD and Hes1 expressions than wild type mice. We then studied the potential roles of caveolin-1 in modulating NICD and Hes1 expressions and astroglial differentiation in isolated cultured NPCs by using caveolin-1 peptide and caveolin-1 RNA silencing. In the differentiating NPCs, caveolin-1 peptide markedly promoted astroglial formation and up-regulated the expressions of NICD and Hes1. In contrast, the knockdown of caveolin-1 inhibited astroglial differentiation of NPCs and the expressions of NICD and Hes1. Taken ...
Antigen presentation reactions are dependent upon the expression of the class II major histocompatibility antigens (MHC), the T-cell receptor, and the presented antigen. Recent studies demonstrate that such processes also require the presence of adhesion molecules such as lymphocyte functional antigen 1 (LFA-1) and its cell surface ligand, intercellular adhesion molecule 1 (ICAM-1). It has been suggested that the brain astrocyte can function as a facultative antigen presenting cell (APC). This hypothesis is based upon the ability to induce the expression of the class II MHC antigens on astrocytes, and on their ability to present myelin basic protein to encephalitogenic T-cells in vitro. The best in vivo data showing that astrocytes serve as intracerebral APCs is the finding that astrocytes in multiple sclerosis plaques are DR+ (class II MHC in human). However, it still remains to be resolved whether the in vivo expression of the MHC antigens in disease states is instrumental to antigen presentation
TY - JOUR. T1 - Synergistic induction of astrocytic differentiation by factors secreted from meninges in the mouse developing brain. AU - Kawamura, Yoichiro. AU - Katada, Sayako. AU - Noguchi, Hirofumi. AU - Yamamoto, Hiroyuki. AU - Sanosaka, Tsukasa. AU - Iihara, Koji. AU - Nakashima, Kinichi. PY - 2017/11. Y1 - 2017/11. N2 - Astrocytes, which support diverse neuronal functions, are generated from multipotent neural stem/precursor cells (NS/PCs) during brain development. Although many astrocyte-inducing factors have been identified and studied in vitro, the regions and/or cells that produce these factors in the developing brain remain elusive. Here, we show that meninges-produced factors induce astrocytic differentiation of NS/PCs. Consistent with the timing when astrocytic differentiation of NS/PCs increases, expression of astrocyte-inducing factors is upregulated. Meningeal secretion-mimicking combinatorial treatment of NS/PCs with bone morphogenetic protein 4, retinoic acid and leukemia ...
In this study, we focused on four glial proteins that are abundant in amyloid plaques and/or that are known to interact with Abeta: alpha1-antichymotrypsin (ACT), interleukin-1beta (IL-1beta), S100beta, and butyrylcholinesterase (BChE). We examined the ability of these proteins to activate rat cortical astrocyte cultures and to influence the ability of Abeta to activate astrocytes. Treatment of astrocytes with ACT, IL-1beta, or S100beta resulted in glial activation, as assessed by reactive morphology, upregulation of IL-1beta, and production of inducible nitric oxide synthase and nitric oxide. The ability of Abeta to induce astrocyte activation was also enhanced in the presence of each of these three proteins. In contrast, BChE alone did not activate astrocytes and had no effect on Abeta-induced activation ...
Astrocytes, which constitute 40% to 70% of total cells in the CNS [1], perform key regulatory functions critical to brain function. The different CNS cell types are differentially infected with HIV; microglia being highly susceptible, astrocytes moderately restrictive, and neurons highly restrictive. Despite the lack of CD4 receptors, astrocytes become infected via CD4-independent mechanism [6,44]. In line with the earlier studies [1,2], we also found low level of HIV replication in astrocytes compared to microglia. After the initial productive phase, infection subsides to a persistent stage in astrocytes, which goes in hand with reports from other investigators [1,2,32]. Infected astrocytes produce very low levels of virus even in the acute phase in contrast to infection of T-lymphocytes [45,46]. Our results with pseudotyped virus confirm that regardless of the entry routes, there are post-entry blocks to infection in astrocytes. Though the introduction of potent HAART has significantly ...
OASIS is a member of the CREB/ATF family of transcription factors and modulates cell- or tissue-specific unfolded protein response signalling. Here we show that this modulation has a critical role in the differentiation of neural precursor cells into astrocytes. Cerebral cortices of mice specifically deficient in OASIS (Oasis−/−) contain fewer astrocytes and more neural precursor cells than those of wild-type mice during embryonic development. Furthermore, astrocyte differentiation is delayed in primary cultured Oasis−/− neural precursor cells. The transcription factor Gcm1, which is necessary for astrocyte differentiation in Drosophila, is revealed to be a target of OASIS. Introduction of Gcm1 into Oasis−/− neural precursor cells improves the delayed differentiation of neural precursor cells into astrocytes by accelerating demethylation of the Gfap promoter. Gcm1 expression is temporally controlled by the unfolded protein response through interactions between OASIS family members ...
We have used digital fluorescence imaging techniques to explore the interplay between mitochondrial Ca2+ uptake and physiological Ca2+ signaling in rat cortical astrocytes. A rise in cytosolic Ca2+ ([Ca2+]cyt), resulting from mobilization of ER Ca2+ stores was followed by a rise in mitochondrial Ca2+ ([Ca2+]m, monitored using rhod-2). Whereas [Ca2+]cyt recovered within ~1 min, the time to recovery for [Ca2+]m was ~30 min. Dissipating the mitochondrial membrane potential ( Dcm, using the mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxy-phenylhydrazone [FCCP] with oligomycin) prevented mitochondrial Ca2+ uptake and slowed the rate of decay of [Ca2+]cyt transients, suggesting that mitochondrial Ca2+ uptake plays a significant role in the clearance of physiological [Ca2+]cyt loads in astrocytes. Ca2+ signals in these cells initiated either by receptor-mediated ER Ca2+ release or mechanical stimulation often consisted of propagating waves (measured using fluo-3). In response to either ...
When DArcy Wentworth Thompsons On Growth and Form was published 100 years ago, it raised the question of how biological forms arise during development and across evolution. In light of the advances in molecular and cellular biology since then, a succinct modern view of the question states: how do genes encode geometry? Our new special issue is packed with articles that use mathematical and physical approaches to gain insights into cell and tissue patterning, morphogenesis and dynamics, and that provide a physical framework to capture these processes operating across scales.. Read the Editorial by guest editors Thomas Lecuit and L. Mahadevan, as they provide a perspective on the influence of DArcy Thompsons work and an overview of the articles in this issue.. ...
In the astrocyte lineage, Meteorin expression appears to be restricted to relatively immature cell populations. Meteorin expression is gradually lost in GLAST‐expressing astrocytes located in the postnatal cerebral parenchyma (Figure 2K and L), and is not detected in two major types of astrocytes in the adult cerebrum, fibrous astrocytes and protoplasmic astrocytes (Miller and Raff, 1984) (Supplementary Figure 3G). In the developing cerebellum, Meteorin is expressed in the VZ and GLAST‐positive migrating glial precursors. Among three subclasses of astrocytes in the adult cerebellar cortex, bushy protoplasmic astrocytes, smooth protoplasmic astrocytes, and Bergmann glia (Palay and Chan‐Palay, 1974), Meteorin expression is restricted to Bergmann glia (Figure 2M and N) (Supplementary Figure 3H and I). Expression of Meteorin in Bergmann glia may be regulated by neurons that interact with Bergmann glia. For instance, dendritic spines of Purkinje cells were completely enwrapped by Bergmann glial ...
The cells we identify here as primary precursors for new neurons in the adult hippocampus have the characteristics of astrocytes at the light and electron microscope. They contain multiple processes with intermediate filaments rich in GFAP. Results from three independent experiments support this conclusion. First, many proliferating SGL astrocytes rapidly convert to a cell type that is GFAP negative and that possesses characteristics of D cells. Second, anti-mitotic treatment resulted in the elimination of D cells from the SGL, but neurogenesis returned. Because new neurons are born at a time when [3H]thymidine-labeled astrocytes were observed, we infer that astrocytes function as primary precursors. Finally, we show that SGL astrocytes, specifically labeled with an avian retrovirus, give rise to granule neurons. We observed granule neurons at different stages of maturation by killing animals at different survivals after retroviral infection. Some SGL astrocytes remain labeled with thymidine ...
Tenascin-C is an extracellular matrix glycoprotein with trophic and repulsive properties on neuronal cells, involved in migratory processes of immature neurons. Previous reports demonstrated that this molecule is produced and secreted by astrocytes, in vitro after activation by bFGF or in vivo after CNS lesion. In injured brain the expression of tenascin-C has been correlated with the glial reaction since it was observed in regions suffering a dramatic glial proliferation and hypertrophy. In this report we show that the treatment of cultured hippocampal astrocytes with tenascin-C results in an increased fibronectin and NCAM immunoreactivities. In addition, treated astrocytes form longer extensions than control ones. The number of cells as well as the levels of GFAP mRNA and protein immunoreactivity are not modified after tenascin-C treatment. The present changes may, therefore, be related to the modification of the adhesive properties of astrocytes to the substrate. These observations are compatible
Repairing trauma to the central nervous system by replacement of glial support cells is an increasingly attractive therapeutic strategy. We have focused on the less-studied replacement of astrocytes, the major support cell in the central nervous system, by generating astrocytes from embryonic human glial precursor cells using two different astrocyte differentiation inducing factors. The resulting astrocytes differed in expression of multiple proteins thought to either promote or inhibit central nervous system homeostasis and regeneration. When transplanted into acute transection injuries of the adult rat spinal cord, astrocytes generated by exposing human glial precursor cells to bone morphogenetic protein promoted significant recovery of volitional foot placement, axonal growth and notably robust increases in neuronal survival in multiple spinal cord laminae. In marked contrast, human glial precursor cells and astrocytes generated from these cells by exposure to ciliary neurotrophic factor both failed
TY - JOUR. T1 - Transendothelial permeability of chlorpyrifos in RBE4 monolayers is modulated by astrocyte-conditioned medium. AU - Yang, Jian. AU - Mutkus, Lysette A.. AU - Sumner, Darrell. AU - Stevens, James T.. AU - Eldridge, J. Charles. AU - Strandhoy, Jack W.. AU - Aschner, Michael. PY - 2001/12/16. Y1 - 2001/12/16. N2 - The immortalized rat brain endothelium 4 (RBE4) cell line preserves many features of the in vivo brain endothelium. It has been used as an in vitro model of the blood-brain barrier (BBB). Astrocyte-endothelial cell interactions are crucial for maintenance of BBB characteristics. The present study investigated morphological and permeability properties of the RBE4 cell line. Immunohistochemical studies showed positive staining in RBE4 cells for E-cadherin, a Ca2+-dependent cell-cell adhesion molecule. Western blot immunoassay showed that RBE4 cells consistently express E-cadherin and that its expression significantly increased (P,0.001) in the presence of ...
One barrier to studying astrocytes has been the difficulty of isolating and culturing the mature cell from the brain. Most current protocols isolate precursor cells rather than mature astrocytes. These precursor cells proliferate in culture in the presence of serum, developing a flat, fibroblast-like appearance that bears little resemblance to astrocytes in the brain (see image above). Other isolation methods, such as fluorescence-activated cell sorting, are too harsh to produce viable cells, co-first author Ye Zhang told Alzforum.. To gently isolate mature astrocytes for culturing, Zhang and co-first author Steven Sloan developed an immunopanning protocol. In this procedure, dissociated cells from brain tissue were passed through several culture dishes coated with antibodies to specific cell-surface markers. The first several plates removed unwanted cell types, while the final plate contained anti-HepaCAM to capture astrocytes. After washing off contaminating cells, the authors detached the ...
The 14-3-3 protein family plays critical regulatory roles in signaling pathways in cell division and apoptosis. 14-3-3gamma is mainly expressed in brain. Using primary cultures of cerebral cortical astrocytes, we investigated the relationships between 14-3-3gamma proteins and actin in astrocytes in cell division and under ischemia. Our results showed that endogenous 14-3-3gamma proteins in immature astrocytes appeared filamentous and co-localized with filamentous actin (F-actin). During certain stages of mitosis, 14-3-3gamma proteins first aggregated and then formed a ring-like structure that surrounded the daughter nuclei and enclosed the F-actin. In 4-week-old cultures of astrocytes, 14-3-3gamma proteins appeared as punctate aggregates in the cytoplasm. Under ischemia, 14-3-3gamma proteins formed filamentous structures and were closely associated with F-actin in surviving astrocytes. However, in apoptotic astrocytes, the intensity of immunostaining of 14-3-3gamma proteins in the cytoplasm ...
In cell migration assays, spheroids are seeded on an astrocyte monolayer culture, so the glioma cells do not penetrate the astrocyte culture and the migration is two-dimensional. This is the reason why we considered two layers in the model: one layer is the astrocyte on top of which lies the tumour cell layer. Thus, glioma cells and astrocytes can occupy the same position but on different planes. For all practical purposes, astrocytes in a confluent monolayer culture could be considered as non-motile cells. Time-lapse experiments registered only chaotic non-directional movements of negligible magnitude 1.24±0.36 μm in 5 h.. The rules of motion inside the layer of glioma cells are exactly the same as described before, for migration on a passive substrate: in the control situation we have p+=1, whereas in the treated situation we take p−=0.5. For the sake of coherency, we model the heterotype GJ communication as we did for homotype communication, i.e. with a parameter q which quantifies the ...
Functionally diversified neuronal populations have been efficiently generated from human pluripotent stem cells (hPSCs). rostral-caudal and dorsal-ventral identities with the same morphogens used for neuronal subtype specification generate immature astrocytes that carry distinct homeodomain transcription factors and display phenotypic differences. These human astroglial progenitors and immature astrocytes will be instrumental for studying astrocytes in brain development and function for revealing their roles in disease processes and for developing novel treatments for neurological disorders. INTRODUCTION Astroglial cells are the most abundant cell type in our brain and spinal cord and are now understood to be as important as neurons for brain function1 2 During development astroglial progenitors are specified after neurogenesis even though the identity of the progenitors isnt well described due to R935788 insufficient dependable markers3 4 These progenitors differentiate to immature astrocytes ...
We found that cultured mouse cortical astrocytes display circadian rhythms in extracellular ATP, in agreement with recent results from rat astrocyte cultures, SCN and SCN2.2 cells (Womac et al., 2009). We used a stabilized form of luciferase that allowed long-term recordings of extracellular ATP from the same cells without perturbations that can affect circadian clock-gene expression in astrocytes (Prolo et al., 2005). We found that Clock/Clock, Per1m Per2m, Cry1−/−Cry2−/− and Bmal1−/− astrocytes are arrhythmic, similar to the locomotor behavior deficits of these mice (Vitaterna et al., 1994; van der Horst et al., 1999; Bunger et al., 2000; Zheng et al., 2001). We found that Bmal1, Clock−/+ and Cry1−/−Cry2−/+ glia have abnormal periods, much like the heterozygous mouse behavior. The correlations between rhythmicity in clock genes, extracellular ATP in glia and locomotor behavior suggest they may be tightly related.. Most of the astrocyte cultures deficient for functional ...
The central finding of the present study is that Mt3 plays a key role in the clathrin-dependent endocytosis of Aβ in astrocytes. In Mt3 −/− astrocytes, clathrin-mediated endocytosis, the mechanism responsible for Aβ endocytosis, was markedly decreased, whereas caveolin-mediated endocytosis was not altered. Astrocytes are likely key players in the clearance of extracellular Aβ; thus, our results suggest that changes in the Mt3 expression in astrocytes may have clinical relevance in AD. Taken together with our previous findings that Mt3 helps to maintain lysosomal degradation in astrocytes, the reduction in Mt3 in astrocytes may aggravate Aβ accumulation in the extracellular space.. Early studies showed that AD brain extracts induce more neurite outgrowth in cell cultures than do control brain extracts [27], suggesting upregulation of a growth-inducing factor or downregulation of a growth-inhibitory factor (GIF) in AD brains. The latter was shown to be the case, and a subsequent study ...
TY - JOUR. T1 - N-cadherin and integrins. T2 - Two receptor systems that mediate neuronal process outgrowth on astrocyte surfaces. AU - Tomaselli, Kevin J.. AU - Neugebauer, Karla M.. AU - Bixby, John L.. AU - Lilien, Jack. AU - Reichard, Louis F.. PY - 1988/3. Y1 - 1988/3. N2 - Receptor-mediated interactions between neurons and astroglia are likely to play a crucial role in the growth and guidance of CNS axons. Using antibodies to neuronal cell surface proteins, we identified two receptor systems mediating neurite outgrowth on cultured astrocytes. N-cadherin, a Ca2+-dependent cell adhesion molecule, functions prominently in the outgrowth of neurites on astrocytes by E8 and E14 chick ciliary ganglion (CG) neurons. β1-class integrin ECM receptor heterodimers function less prominently in E8 and not at all in E14 neurite outgrowth on astrocytes. The lack of effect of integrin β1 antibodies on E14 neurite out-growth reflects an apparent loss of integrin function, as assayed by E14 neuronal ...
To better characterize the electrophysiological properties of neonatal astrocytes, we purposely narrowed the animal age to the dormant P1-3 period for examining potential diversity in ion channel expression among neonatal astrocytes. Interestingly, two electrophysiological phenotypes could be readily identified during this early postnatal age. The neonatal astrocytes in P1 homogeneously show a variably rectifying whole cell current profile, whereas electrophysiologically passive astrocytes (PAs) first appear in P2, and the percentage of PAs rapidly increased from 6.67 % in P2 to 20.83 % at P3. Interestingly, the appearance of PA in mice is 2 days earlier than rats [2], which seemingly follows a longer gestation time in rats (22 day) than mice (20 day).. We show that the passive behavior of neonatal astrocytes is solely attributable to gap junction coupling (Fig. 3). This differs fundamentally from the passive behavior of membrane conductance in mature astrocytes that is caused by intrinsic K+ ...
Neurogenesis is restricted in the adult mammalian brain; most neurons are neither exchanged during normal life nor replaced in pathological situations. We report that stroke elicits a latent neurogenic program in striatal astrocytes in mice. Notch1 signaling is reduced in astrocytes after stroke, and attenuated Notch1 signaling is necessary for neurogenesis by striatal astrocytes. Blocking Notch signaling triggers astrocytes in the striatum and the medial cortex to enter a neurogenic program, even in the absence of stroke, resulting in 850 ± 210 (mean ± SEM) new neurons in a mouse striatum. Thus, under Notch signaling regulation, astrocytes in the adult mouse brain parenchyma carry a latent neurogenic program that may potentially be useful for neuronal replacement strategies. ...
Astrocytes are now recognized as dynamic signaling elements in the brain. Bidirectional communication between neurons and astrocytes involves integration of neuronal inputs by astrocytes and release of gliotransmitters that modulate neuronal excitability and synaptic transmission. The ovarian steroid hormone, 17\beta-estradiol, in addition to its rapid actions on neuronal electrical activity can rapidly alter astrocyte intracellular calcium concentration $([Ca^{2+}]_i)$ through a membrane-associated estrogen receptor. Using calcium imaging and electrophysiological techniques, we investigated the functional consequences of acute treatment with estradiol on astrocyte-astrocyte and astrocyte-neuron communication in mixed hippocampal cultures. Mechanical stimulation of an astrocyte evoked a $[Ca^{2+}]_i$ rise in the stimulated astrocyte, which propagated to the surrounding astrocytes as a $[Ca^{2+}]_i$ wave. Following acute treatment with estradiol, the amplitude of the $([Ca^{2+}]_i)$ elevation in ...
Aquaporin-4 (AQP4) is the predominant water channel in brain and is selectively expressed in astrocytes. Astrocytic endfoot membranes exhibit tenfold higher densities of AQP4 than non-endfoot membranes, making AQP4 an excellent marker of astrocyte polarization. Loss of astrocyte polarization is known to compromise astrocytic function and to be associated with impaired water and K+ homeostasis. Here we investigate by a combination of light and electron microscopic immunocytochemistry whether amyloid deposition is associated with a loss of astrocyte polarization, using AQP4 as a marker. We used the tg-ArcSwe mouse model of Alzheimers disease, as this model displays perivascular plaques as well as plaques confined to the neuropil. 3D reconstructions were done to establish the spatial relation between plaques and astrocytic endfeet, the latter known to contain the perivascular pool of AQP4. Changes in AQP4 expression emerge just after the appearance of the first plaques. Typically, there is a loss ...
This cellular imaging study in animal models will explore whether two genetically determined forms of autism spectrum disorder (ASD) have similar deleterious alterations in star-shaped cells, called "astrocytes," that adversely affect brain development. Two genetic forms of ASD are Retts syndrome, which occurs almost exclusively in girls, and Fragile X syndrome, which occurs predominately in boys. Prior research showed that defects occur in neurons. More recent research indicates that defects occur as well in other types of cells in the brain, including astrocytes. While there are billions of nerve cells in the brain, there are even more astrocytes. Research suggests that astrocytes can produce both advantageous and deleterious effects. In the developing brain, astrocytes have a key role in regulating nerve cells functions. If astrocytes are altered, however, they may adversely affect brain development. The investigators hypothesize that both in Retts syndrome and Fragile X syndrome, as well ...
There is now growing evidence that astrocytes, like neurons, can release transmitters. One transmitter that in a vast number of studies has been shown to be released from astrocytes is glutamate. Although asytrocytic glutamate may be released by several mechanisms, the evidence in favor of exocytosis is most compelling. Astrocytes may respond to neuronal activity by such exocytotic release of glutamate. The astrocyte derived glutamate can in turn activate neuronal glutamate receptors, in particular N-methyl-D-aspartate (NMDA) receptors. Here we review the morphological data supporting that astrocytes possess the machinery for exocytosis of glutamate. We describe the presence of small synaptic-like microvesicles, SNARE proteins and vesicular glutamate transporters in astrocytes, as well as NMDA receptors situated in vicinity of the astrocytic vesicles.
The pathophysiology of a traumatic brain injury (TBI) involves the dysfunction of the blood-brain barrier (BBB). The lumen of the BBB is lined with cerebrovascular endothelial cells (CVEC) that are ensheathed with perivascular astrocyte endfeet. We investigated the cellular response of human-astrocytes and human-CVEC following trauma in vitro. Astrocytes and CVEC were subjected to a concussive injury (CI; mechanical stretch), then assessed for markers of injury (monolayer retraction) and activation (mitogen-activated protein kinases (MAPK) phosphorylation). CI induces astrocyte monolayer retraction and activation, with predominant phosphorylation of JNK1/2 MAPK. Interfering with JNK1/2 activation (selective JNK inhibitors) reduces trauma-induced astrocyte retraction. On the contrary, CI does not induce CVEC retraction, however up-regulates CVEC pro-adhesive phenotype resulting in increased polymorphonuclear leukocyte (PMN) adhesion. These findings indicate that CI elicits differential BBB cell responses
We used the pH-sensitive fluorescent dye BCECF to study intracellular pH (pHi) regulation in primary cultures of rat astrocytes and C6 glioma cells. Both cell types contain three pH-regulating transporters: (1) alkalinizing Na+/H+ exchange; (2) alkalinizing Na+ + HCO3 −/Cl−exchange; and (3) acidifying Cl−/HCO3− exchange. Na+/H+ exchange was most evident in the absence of CO2; recovery from acidification was Na+ dependent and amiloride sensitive. Exposure to CO2 caused a cell alkalinization that was inhibited by DIDS, dependent on external Na+, and inhibited 75% in the absence of Cl− (thus mediated by Na+ + HCO3−/Cl− exchange). When pHi was increased above the normal steady-state pHi, a DIDS-inhibitable and Na+ -independent acidifying recovery was evident, indicating the presence of Cl− /HCO3−exchange. Astrocytes, but not C6 cells, contain a fourth pH-regulating transporter, Na+ −HCO3− cotransport; in the presence of CO2, depolarization caused an alkalinization of 0.12 +− 0.01 (n
In recent literature, lymphokines have been reported to be able to promote both proliferation and maturation of some glial populations. In this paper, we compare the effect of rIL-1 on newborn and adult rat astroglial cells in vitro. In newborn, but not in adult astrocytes, 100 U/ml of rIL-1 beta increase [3H]thymidine incorporation with a maximal response by 3 days as compared to the control untreated culture. In contrast, rIL-1 beta induces an increase of GFAP immunoreactivity both in newborn and in adult astrocytes, as compared to the control untreated cells. These data indicate that, while both newborn and adult astroglial cells are capable of responding to rIL-1 beta, only newborn astrocytes can respond to this lymphokine with proliferation. Thus, it appears likely that different factors, other than rIL-1 beta, are needed by adult astrocytes to proliferate.
Blood-brain barrier (BBB) function is regulated by dynamic interactions among cell types within the neurovascular unit, including astrocytes and endothelial cells. Co-culture models of the BBB typically involve astrocytes seeded on two-dimensional (2D) surfaces, which recent studies indicate cause astrocytes to express a phenotype similar to that of reactive astrocytes in situ. We hypothesized that the culture conditions of astrocytes would differentially affect their ability to modulate BBB function in vitro. Brain endothelial cells were grown alone or in co-culture with astrocytes.
Huntingtons Disease (HD) is a fatal neurodegenerative disorder caused by a CAG repeat expansion, resulting in a mutant huntingtin protein. While it is now clear that astrocytes are affected by HD and significantly contribute to neuronal dysfunction and pathogenesis, the alterations in the transcriptional and epigenetic profiles in HD astrocytes have yet to be characterized. Here, we examine global transcription and chromatin accessibility dynamics during in vitro astrocyte differentiation in a transgenic non-human primate model of HD. We found global changes in accessibility and transcription across different stages of HD pluripotent stem cell differentiation, with distinct trends first observed in neural progenitor cells (NPCs), once cells have committed to a neural lineage. Transcription of p53 signaling and cell cycle pathway genes was highly impacted during differentiation, with depletion in HD NPCs and upregulation in HD astrocytes. E2F target genes also displayed this inverse expression pattern,
In this study, we investigated the role of the Arp2/3 complex and associated signaling in astrocytes. We demonstrate that the expansion of astrocytic cell bodies and processes is triggered by Arp2/3 inhibition in dissociated cultures and brain tissue. This phenomenon requires the activity of myosin II in conjunction with increased RhoA activity. Furthermore, we identified N-WASP and PICK1 as crucial Arp2/3 regulators in astrocyte morphological plasticity, and show that this mechanism underlies the rapid and drastic morphological changes exhibited by astrocytes under ischemic conditions.. In most studied cell types, inactivation of the Arp2/3 complex leads mainly to disappearance, outgrowth-inhibition or shrinkage of subcellular structures such as lamellipodia in fibroblasts and cancer cells (Steffen et al., 2006; Wu et al., 2012), or neurites and dendritic spines in neurons (Korobova and Svitkina, 2008; Hotulainen et al., 2009; Tahirovic et al., 2010; Nakamura et al., 2011; Yang et al., 2012). ...
Glutamate transporters (GluTs) maintain a low ambient level of glutamate in the central nervous system (CNS) and shape the activation of glutamate receptors at synapses. Nevertheless, the mechanisms that regulate the trafficking and localization of transporters near sites of glutamate release are poorly understood. Here, we examined the subcellular distribution and dynamic remodeling of the predominant GluT GLT-1 (excitatory amino acid transporter 2, EAAT2) in developing hippocampal astrocytes. Immunolabeling revealed that endogenous GLT-1 is concentrated into discrete clusters along branches of developing astrocytes that were apposed preferentially to synapsin-1 positive synapses. Green fluorescent protein (GFP)-GLT-1 fusion proteins expressed in astrocytes also formed distinct clusters that lined the edges of astrocyte processes, as well as the tips of filopodia and spine-like structures. Time-lapse three-dimensional confocal imaging in tissue slices revealed that GFP-GLT-1 clusters were ...
Astrocytes. Astrocytes are the most abundant cell type of the CNS, and exhibit broad morphological and functional heterogeneity. Astrocytes regulate ion and glutamate homeostasis, control the number and function of synapses, contribute to wound healing, form the blood-brain-barrier, and modulate cerebral blood flow. Astroglial cells also act as adult neural stem cells in the subventricular zone of the lateral ventricles lateral wall and in the subgranular layer of the dentate gyrus. GLAST is the most abundant glutamate transporter and a specific astrocyte marker in the developing and neonatal mammalian CNS. Radial glia and stem cells also express GLAST. The ACSA-2 antigen is specifically expressed on GLAST (ACSA-1)-positive astrocytes and is a second astrocyte-specific surface marker (PMID: 28317180). The antigen targeted by Anti-ACSA-2 is ATP1B2 (PMID: 28373281).. Oligodendrocytes. Oligodendrocytes form the myelin sheath around neuronal axons, which facilitates the fast saltatory propagation ...
TY - JOUR. T1 - ATP released from astrocytes mediates glial calcium waves. AU - Guthrie, Peter B.. AU - Knappenberger, Joshua. AU - Segal, Menahem. AU - Bennett, Michael V.L.. AU - Charles, Andrew C.. AU - Kater, Stanley B.. PY - 1999/1/15. Y1 - 1999/1/15. N2 - Calcium waves represent a widespread form of intercellular communication. Although they have been thought for a long time to require gap junctions, we recently demonstrated that mouse cortical astrocytes use an extracellular messenger for calcium wave propagation. The present experiments identify ATP as a major extracellular messenger in this system. Medium collected from astrocyte cultures during (but not before) calcium wave stimulation contains ATP. The excitatory effects of medium samples and of ATP are blocked by purinergic receptor antagonists and by pretreatment with apyrase; these same purinergic receptor antagonists block propagation of electrically evoked calcium waves. ATP, applied at the concentration measured in medium ...
The activation of those Ca2+ waves can be induced, as it has been said before, by neurotransmitters which are released into the synaptic space surrounded by astrocytes terminations. Evidence of this mechanisms has been provided by research into the role of mGluR5 in astrocytes in the nucleus accumbens. This type of glutamate receptor has a major role in regulating Ca2+ signaling in astrocytes and, as a consequence, the Ca2+ dependent release of excitatory transmitters from these glia: activation of mGluR5 induces Ca2+ oscillations in NAcc astrocytes with the correlated appearance of NMDA receptor-dependent slow inward currents detected in nucleus accumbens neurons. In other words, glutamatergic afferents cause the sustained activation of astrocytes, which in turn excite the surrounding through extrasynaptic NMDA receptors: this might be involved in amplificating neuronal signals (mGluR5 stimulates gliotransmission in the nucleus accumbens, 2007).. The release of gliotransmitters can be mediated ...
Purpose: While antiretroviral therapy (ART) has improved the quality of life and survival of HIV-1-infected patients, HIV-1-associated neurocognitive disorders (HAND) remain a major problem in over 30% of cases. All forms of HAND are associated with CNS inflammation. Astrocytes, the principal type of glial cells, are involved in signaling, homeostasis, and repair during CNS pathology. Some astrocytes become non-productively infected by HIV-1. The balance between matrix metalloproteinases (MMP) and their inhibitors must be tightly regulated during CNS inflammation. In the brain, tissue inhibitor of MMPs (TIMP)-1 protects human neurons from HIV-1-induced apoptosis and is mainly produced by astrocytes. Further, astrocyte TIMP-1 is differentially regulated during acute and chronic IL-1β-activation. However, the direct or indirect effects of astrocyte HIV-1 protein expression on TIMP-1 regulation are not well studied. Here, we investigated downstream effects of HIV-1 Tat and gp120 expression in astrocytes
A new study published by the team of Naguib Mechawar, Ph.D., a researcher with the McGill Group for Suicide Studies (MGSS) of the Douglas Institute (CIUSSS de lOuest-de-lÎle de Montréal) and Associate Professor in the Department of Psychiatry at McGill University, sheds new light on the disruption of astrocytes in depression. Astrocytes, a class of non-neuronal cells, have previously been implicated in depression and suicide. However, it was not known whether these cells were affected throughout the brain or only in certain regions. This research provides evidence that networks of astrocytes are altered specifically in areas of the brain associated with mood regulation. In addition, in describing the existence of new subtypes of astrocyte, this study reveals features specific to the human brain.. The diversity and functional and morphological complexity of cortical astrocytes in humans, as well as their involvement in normal and pathological brain function, have only recently begun to be ...
An in-depth bioinformatic search for astrocyte-specific genes comprised three different methods: (i) a biased search for genes with an expression pattern similar to the best known astrocyte marker, GFAP, (ii) an unbiased search by a class prediction tool, recursive-supervised machine (R-SVM) analysis, and (iii) an empirical threshold approach to identify a common set of genes among complementary data sets. In the GFAP cluster analysis, GFAP captured a group of 393 genes that were differentially expressed by all in vitro astrocyte samples (Fig. 1 A ). Whereas this cluster likely represents a potential source of novel astrocyte genes (see Table 2 for a complete list), it is notable that no clear GFAP subcluster emerged, and correspondingly, a random sampling of genes among the GFAP cluster revealed their limited expression in CNS astrocytes by RNA ISH (see below). Next, to avoid the bias of so-called signature genes, R-SVM analysis was used to identify genes that "as a group" (unlike genes found ...
Cells and cell culture. Four GSCs were established and identified by our previous work, and were cultured in serum-free stem cell medium (SFM) (Neurobasal, Gibco, Thermo Fisher Scientific) containing 20 ng/mL basic fibroblast growth factor (bFGF; catalog 100-18B-50UG, PeproTech), 20 ng/mL epidermal growth factor (EGF; catalog AF-100-15-100UG, PeproTech), 10 μg/mL heparin (catalog 9041-08-1, Sigma-Aldrich), 2% B27 (Gibco, Thermo Fihser Scientific), and 2 mmol/L l-glutamine (catalog SH30034.01, HyClone). The induced human neural stem cells, H1-NSCs obtained from D.Q. Peis laboratory (Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China) and ReNcell-CX cells (ATCC), were cultured in medium as for the GSCs with the extra addition of 1% N-2 supplement (Gibco, Thermo Fisher Scientific). We purchased a normal human astrocyte cell line (HA) from ScienCell and cultured it using commercial astrocyte medium (catalog 1801, ScienCell) supplemented with 2% FBS ...