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Albini M, Krawczun-Rygmaczewska A, Cesca F. Astrocytes and brain-derived neurotrophic factor (BDNF). Neurosci Res 2023; 197:42-51. [PMID: 36780947 DOI: 10.1016/j.neures.2023.02.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 01/17/2023] [Accepted: 02/02/2023] [Indexed: 02/13/2023]
Abstract
Astrocytes are emerging in the neuroscience field as crucial modulators of brain functions, from the molecular control of synaptic plasticity to orchestrating brain-wide circuit activity for cognitive processes. The cellular pathways through which astrocytes modulate neuronal activity and plasticity are quite diverse. In this review, we focus on neurotrophic pathways, mostly those mediated by brain-derived neurotrophic factor (BDNF). Neurotrophins are a well-known family of trophic factors with pleiotropic functions in neuronal survival, maturation and activity. Within the brain, BDNF is the most abundantly expressed and most studied of all neurotrophins. While we have detailed knowledge of the effect of BDNF on neurons, much less is known about its physiology on astroglia. However, over the last years new findings emerged demonstrating that astrocytes take an active part into BDNF physiology. In this work, we discuss the state-of-the-art knowledge about astrocytes and BDNF. Indeed, astrocytes sense extracellular BDNF through its specific TrkB receptors and activate intracellular responses that greatly vary depending on the brain area, stage of development and receptors expressed. Astrocytes also uptake and recycle BDNF / proBDNF at synapses contributing to synaptic plasticity. Finally, experimental evidence is now available describing deficits in astrocytic BDNF in several neuropathologies, suggesting that astrocytic BDNF may represent a promising target for clinical translation.
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Affiliation(s)
- Martina Albini
- Department of Experimental Medicine, University of Genova, Italy; IIT Center for Synaptic Neuroscience and Technology, Genova, Italy
| | - Alicja Krawczun-Rygmaczewska
- IIT Center for Synaptic Neuroscience and Technology, Genova, Italy; Department of Life Sciences, University of Trieste, Italy
| | - Fabrizia Cesca
- IIT Center for Synaptic Neuroscience and Technology, Genova, Italy; Department of Life Sciences, University of Trieste, Italy.
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2
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Kacher R, Mounier C, Caboche J, Betuing S. Altered Cholesterol Homeostasis in Huntington’s Disease. Front Aging Neurosci 2022; 14:797220. [PMID: 35517051 PMCID: PMC9063567 DOI: 10.3389/fnagi.2022.797220] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 03/18/2022] [Indexed: 12/25/2022] Open
Abstract
Huntington’s disease (HD) is an autosomal dominant genetic disorder caused by an expansion of the CAG repeat in the first exon of Huntingtin’s gene. The associated neurodegeneration mainly affects the striatum and the cortex at early stages and progressively spreads to other brain structures. Targeting HD at its earlier stages is under intense investigation. Numerous drugs were tested, with a rate of success of only 3.5% approved molecules used as symptomatic treatment. The restoration of cholesterol metabolism, which is central to the brain homeostasis and strongly altered in HD, could be an interesting disease-modifying strategy. Cholesterol is an essential membrane component in the central nervous system (CNS); alterations of its homeostasis have deleterious consequences on neuronal functions. The levels of several sterols, upstream of cholesterol, are markedly decreased within the striatum of HD mouse model. Transcription of cholesterol biosynthetic genes is reduced in HD cell and mouse models as well as post-mortem striatal and cortical tissues from HD patients. Since the dynamic of brain cholesterol metabolism is complex, it is essential to establish the best method to target it in HD. Cholesterol, which does not cross the blood-brain-barrier, is locally synthesized and renewed within the brain. All cell types in the CNS synthesize cholesterol during development but as they progress through adulthood, neurons down-regulate their cholesterol synthesis and turn to astrocytes for their full supply. Cellular levels of cholesterol reflect the dynamic balance between synthesis, uptake and export, all integrated into the context of the cross talk between neurons and glial cells. In this review, we describe the latest advances regarding the role of cholesterol deregulation in neuronal functions and how this could be a determinant factor in neuronal degeneration and HD progression. The pathways and major mechanisms by which cholesterol and sterols are regulated in the CNS will be described. From this overview, we discuss the main clinical strategies for manipulating cholesterol metabolism in the CNS, and how to reinstate a proper balance in HD.
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Affiliation(s)
- Radhia Kacher
- Institut du Cerveau - Paris Brain Institute (ICM), AP-HP, INSERM, CNRS, University Hospital Pitié-Salpêtrière, Sorbonne Université, Paris, France
- INSERM, U1216, Grenoble Institut Neurosciences, Université Grenoble Alpes, Grenoble, France
| | - Coline Mounier
- Neuroscience Paris Seine, Institut de Biologie Paris-Seine, Faculté des Sciences et Ingénierie, Sorbonne Université, Paris, France
- Centre National de la Recherche Scientifique, UMR 8246, Paris, France
- U1130, Institut National de la Santé et de la Recherche Médicale, Paris, France
| | - Jocelyne Caboche
- Neuroscience Paris Seine, Institut de Biologie Paris-Seine, Faculté des Sciences et Ingénierie, Sorbonne Université, Paris, France
- Centre National de la Recherche Scientifique, UMR 8246, Paris, France
- U1130, Institut National de la Santé et de la Recherche Médicale, Paris, France
| | - Sandrine Betuing
- Neuroscience Paris Seine, Institut de Biologie Paris-Seine, Faculté des Sciences et Ingénierie, Sorbonne Université, Paris, France
- Centre National de la Recherche Scientifique, UMR 8246, Paris, France
- U1130, Institut National de la Santé et de la Recherche Médicale, Paris, France
- *Correspondence: Sandrine Betuing,
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3
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Kasatkina LA, Rittchen S, Sturm EM. Neuroprotective and Immunomodulatory Action of the Endocannabinoid System under Neuroinflammation. Int J Mol Sci 2021; 22:ijms22115431. [PMID: 34063947 PMCID: PMC8196612 DOI: 10.3390/ijms22115431] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 05/17/2021] [Accepted: 05/18/2021] [Indexed: 12/17/2022] Open
Abstract
Endocannabinoids (eCBs) are lipid-based retrograde messengers with a relatively short half-life that are produced endogenously and, upon binding to the primary cannabinoid receptors CB1/2, mediate multiple mechanisms of intercellular communication within the body. Endocannabinoid signaling is implicated in brain development, memory formation, learning, mood, anxiety, depression, feeding behavior, analgesia, and drug addiction. It is now recognized that the endocannabinoid system mediates not only neuronal communications but also governs the crosstalk between neurons, glia, and immune cells, and thus represents an important player within the neuroimmune interface. Generation of primary endocannabinoids is accompanied by the production of their congeners, the N-acylethanolamines (NAEs), which together with N-acylneurotransmitters, lipoamino acids and primary fatty acid amides comprise expanded endocannabinoid/endovanilloid signaling systems. Most of these compounds do not bind CB1/2, but signal via several other pathways involving the transient receptor potential cation channel subfamily V member 1 (TRPV1), peroxisome proliferator-activated receptor (PPAR)-α and non-cannabinoid G-protein coupled receptors (GPRs) to mediate anti-inflammatory, immunomodulatory and neuroprotective activities. In vivo generation of the cannabinoid compounds is triggered by physiological and pathological stimuli and, specifically in the brain, mediates fine regulation of synaptic strength, neuroprotection, and resolution of neuroinflammation. Here, we review the role of the endocannabinoid system in intrinsic neuroprotective mechanisms and its therapeutic potential for the treatment of neuroinflammation and associated synaptopathy.
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Affiliation(s)
- Ludmila A. Kasatkina
- Otto Loewi Research Center, Division of Pharmacology, Medical University of Graz, 8010 Graz, Austria; (L.A.K.); (S.R.)
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Sonja Rittchen
- Otto Loewi Research Center, Division of Pharmacology, Medical University of Graz, 8010 Graz, Austria; (L.A.K.); (S.R.)
| | - Eva M. Sturm
- Otto Loewi Research Center, Division of Pharmacology, Medical University of Graz, 8010 Graz, Austria; (L.A.K.); (S.R.)
- Correspondence:
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4
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Goodnight AV, Kremsky I, Khampang S, Jung YH, Billingsley JM, Bosinger SE, Corces VG, Chan AWS. Chromatin accessibility and transcription dynamics during in vitro astrocyte differentiation of Huntington's Disease Monkey pluripotent stem cells. Epigenetics Chromatin 2019; 12:67. [PMID: 31722751 PMCID: PMC6852955 DOI: 10.1186/s13072-019-0313-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 10/25/2019] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Huntington's 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. RESULTS 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, and strong associations between E2F target gene expression and accessibility at nearby putative enhancers were observed. CONCLUSIONS The results suggest that chromatin accessibility and transcription are altered throughout in vitro HD astrocyte differentiation and provide evidence that E2F dysregulation contributes to aberrant cell-cycle re-entry and apoptosis throughout the progression from NPCs to astrocytes.
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Affiliation(s)
- Alexandra V Goodnight
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, 30322, USA
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA
- Genetics and Molecular Biology Program, Graduate Division of Biological and Biomedical Sciences, 1462 Clifton Rd, Atlanta, GA, 30322, USA
| | - Isaac Kremsky
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA
| | - Sujittra Khampang
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, 30322, USA
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA
- Embryonic Stem Cell Research Center, School of Biotechnology, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Yoon Hee Jung
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA
| | - James M Billingsley
- Division of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
| | - Steven E Bosinger
- Division of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
- Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA, USA
| | - Victor G Corces
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA.
- Genetics and Molecular Biology Program, Graduate Division of Biological and Biomedical Sciences, 1462 Clifton Rd, Atlanta, GA, 30322, USA.
| | - Anthony W S Chan
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, 30322, USA.
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA.
- Genetics and Molecular Biology Program, Graduate Division of Biological and Biomedical Sciences, 1462 Clifton Rd, Atlanta, GA, 30322, USA.
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Palpagama TH, Waldvogel HJ, Faull RLM, Kwakowsky A. The Role of Microglia and Astrocytes in Huntington's Disease. Front Mol Neurosci 2019; 12:258. [PMID: 31708741 PMCID: PMC6824292 DOI: 10.3389/fnmol.2019.00258] [Citation(s) in RCA: 109] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Accepted: 10/10/2019] [Indexed: 12/21/2022] Open
Abstract
Huntington's disease (HD) is an autosomal dominant neurodegenerative disease. HD patients present with movement disorders, behavioral and psychiatric symptoms and cognitive decline. This review summarizes the contribution of microglia and astrocytes to HD pathophysiology. Neuroinflammation in the HD brain is characterized by a reactive morphology in these glial cells. Microglia and astrocytes are critical in regulating neuronal activity and maintaining an optimal milieu for neuronal function. Previous studies provide evidence that activated microglia and reactive astrocytes contribute to HD pathology through transcriptional activation of pro-inflammatory genes to perpetuate a chronic inflammatory state. Reactive astrocytes also display functional changes in glutamate and ion homeostasis and energy metabolism. Astrocytic and microglial changes may further contribute to the neuronal death observed with the progression of HD. Importantly, the degree to which these neuroinflammatory changes are detrimental to neurons and contribute to the progression of HD pathology is not well understood. Furthermore, recent observations provide compelling evidence that activated microglia and astrocytes exert a variety of beneficial functions that are essential for limiting tissue damage and preserving neuronal function in the HD brain. Therefore, a better understanding of the neuroinflammatory environment in the brain in HD may lead to the development of targeted and innovative therapeutic opportunities.
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Affiliation(s)
- Thulani H Palpagama
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Henry J Waldvogel
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Richard L M Faull
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Andrea Kwakowsky
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
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Abstract
Our understanding of astrocytes and their role in neurological diseases has increased considerably over the past two decades as the diverse roles of these cells have become recognized. Our evolving understanding of these cells suggests that they are more than support cells for neurons and that they play important roles in CNS homeostasis under normal conditions, in neuroprotection and in disease exacerbation. These multiple functions make them excellent candidates for targeted therapies to treat neurological disorders. New technological advances, including in vivo imaging, optogenetics and chemogenetics, have allowed us to examine astrocytic functions in ways that have uncovered new insights into the dynamic roles of these cells. Furthermore, the use of induced pluripotent stem cell-derived astrocytes from patients with a host of neurological disorders can help to tease out the contributions of astrocytes to human disease. In this Review, we explore some of the technological advances developed over the past decade that have aided our understanding of astrocyte function. We also highlight neurological disorders in which astrocyte function or dysfunction is believed to have a role in disease pathogenesis or propagation and discuss how the technological advances have been and could be used to study each of these diseases.
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7
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Li K, Li J, Zheng J, Qin S. Reactive Astrocytes in Neurodegenerative Diseases. Aging Dis 2019; 10:664-675. [PMID: 31165009 PMCID: PMC6538217 DOI: 10.14336/ad.2018.0720] [Citation(s) in RCA: 234] [Impact Index Per Article: 46.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 07/20/2018] [Indexed: 12/17/2022] Open
Abstract
Astrocytes, the largest and most numerous glial cells in the central nervous system (CNS), play a variety of important roles in regulating homeostasis, increasing synaptic plasticity and providing neuroprotection, thus helping to maintain normal brain function. At the same time, astrocytes can participate in the inflammatory response and play a key role in the progression of neurodegenerative diseases. Reactive astrocytes are strongly induced by numerous pathological conditions in the CNS. Astrocyte reactivity is initially characterized by hypertrophy of soma and processes, triggered by different molecules. Recent studies have demonstrated that neuroinflammation and ischemia can elicit two different types of reactive astrocytes, termed A1s and A2s. However, in the case of astrocyte reactivity in different neurodegenerative diseases, the recently published research issues remain a high level of conflict and controversy. So far, we still know very little about whether and how the function or reactivity of astrocytes changes in the progression of different neurodegenerative diseases. In this review, we aimed to briefly discuss recent studies highlighting the complex contribution of astrocytes in the process of various neurodegenerative diseases, which may provide us with new prospects for the development of an excellent therapeutic target for neurodegenerative diseases.
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Affiliation(s)
- Kunyu Li
- 1Department of Anatomy, Histology and Embryology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Jiatong Li
- 1Department of Anatomy, Histology and Embryology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Jialin Zheng
- 2Center for Translational Neurodegeneration and Regenerative Therapy, Shanghai Tenth People's Hospital affiliated to Tongji University School of Medicine, Shanghai, China
| | - Song Qin
- 1Department of Anatomy, Histology and Embryology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
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8
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Chronic stress impairs the aquaporin-4-mediated glymphatic transport through glucocorticoid signaling. Psychopharmacology (Berl) 2019; 236:1367-1384. [PMID: 30607477 DOI: 10.1007/s00213-018-5147-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 12/03/2018] [Indexed: 12/12/2022]
Abstract
BACKGROUND The glymphatic system has recently been proposed to function as a brain-wide macroscopic system for the clearance of potentially harmful molecules, such as amyloid beta (e.g., Aβ), from the brain parenchyma. Previous literatures have established that the glymphatic function is dramatically suppressed by aging, traumatic brain injury, and some diseases. However, the effect of chronic stress on the glymphatic function and its underlying mechanism remains largely unknown. METHODS Adult mice were randomly divided into four groups: chronic unpredictable mild stress (CUMS)-treated group, CUMS simultaneously treated with mifepristone (MFP) group, dexamethasone (DEX)-treated group, and control group. Stress response was observed by assessing the change of body weight, plasma corticosterone level, and behavior tests. The level of Aβ42 in cerebral tissue was assessed by ELISA. The glymphatic function was determined by using fluorescence tracer injection. The expression and localization of aquaporin-4 (AQP4) were evaluated by immunohistochemistry and western blot. The transcription level of AQP4 and anchoring molecules was evaluated by real-time PCR. FINDINGS Compared with control group, CUMS-treated mice exhibited the impairment of global glymphatic function especially in the anterior brain. This change was accompanied by the decreased expression and polarization of AQP4, reduced transcription of AQP4, agrin, laminin, and dystroglycan in the anterior cortex. Similarly, the glucocorticoid receptor (GR) agonist DEX exposure could reduce the glymphatic function and AQP4 expression. Moreover, the GR antagonist MFP treatment could significantly rescue the glymphatic function and reverse the expression and polarization of AQP4 impaired by CUMS. CONCLUSION Chronic stress could impair the AQP4-mediated glymphatic transport in the brain through glucocorticoid signaling. Our results also suggest that GR antagonist could be beneficial to rescue the glymphatic function suppressed by chronic stress.
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Abstract
Huntington's disease (HD) is a dominantly inherited neurodegenerative disease that results in motor, cognitive and psychiatric dysfunction. It is caused by a polyglutamine repeat expansion mutation in the widely expressed HTT protein. The clinical manifestations of HD have been largely attributed to the neurodegeneration of specific neuronal cell types in the brain. However, it has become clear that other cell types, including astrocytes, play important roles in the pathogenesis of HD. The mutant HTT (mHTT) protein is present in neuronal and non-neuronal cell types throughout the nervous system. Studies designed to understand the contribution of mHTT expression in non-neuronal cell types to HD pathogenesis has lagged considerably behind those focused on neurons. However, the role of astrocytes in HD has received more attention over the last 5-10 years. In this chapter we present an overview of HD and our current understanding of astrocytic involvement in this disease. We describe the neuropathological features of HD and provide evidence of morphological and molecular changes in mHTT expressing astrocytes. We review data from animal models and HD patients that implicate mHTT expressing astrocytes to the progression of HD.
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Affiliation(s)
- Michelle Gray
- Department of Neurology and Center for Neurodegeneration and Experimental Therapeutics, University of Alabama at Birmingham, 1720 2nd Ave S, CIRC 425B, Birmingham, AL 35294, USA.
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10
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Ferrer I. Diversity of astroglial responses across human neurodegenerative disorders and brain aging. Brain Pathol 2017; 27:645-674. [PMID: 28804999 PMCID: PMC8029391 DOI: 10.1111/bpa.12538] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 05/24/2017] [Indexed: 12/11/2022] Open
Abstract
Astrogliopathy refers to alterations of astrocytes occurring in diseases of the nervous system, and it implies the involvement of astrocytes as key elements in the pathogenesis and pathology of diseases and injuries of the central nervous system. Reactive astrocytosis refers to the response of astrocytes to different insults to the nervous system, whereas astrocytopathy indicates hypertrophy, atrophy/degeneration and loss of function and pathological remodeling occurring as a primary cause of a disease or as a factor contributing to the development and progression of a particular disease. Reactive astrocytosis secondary to neuron loss and astrocytopathy due to intrinsic alterations of astrocytes occur in neurodegenerative diseases, overlap each other, and, together with astrocyte senescence, contribute to disease-specific astrogliopathy in aging and neurodegenerative diseases with abnormal protein aggregates in old age. In addition to the well-known increase in glial fibrillary acidic protein and other proteins in reactive astrocytes, astrocytopathy is evidenced by deposition of abnormal proteins such as β-amyloid, hyper-phosphorylated tau, abnormal α-synuclein, mutated huntingtin, phosphorylated TDP-43 and mutated SOD1, and PrPres , in Alzheimer's disease, tauopathies, Lewy body diseases, Huntington's disease, amyotrophic lateral sclerosis and Creutzfeldt-Jakob disease, respectively. Astrocytopathy in these diseases can also be manifested by impaired glutamate transport; abnormal metabolism and release of neurotransmitters; altered potassium, calcium and water channels resulting in abnormal ion and water homeostasis; abnormal glucose metabolism; abnormal lipid and, particularly, cholesterol metabolism; increased oxidative damage and altered oxidative stress responses; increased production of cytokines and mediators of the inflammatory response; altered expression of connexins with deterioration of cell-to-cell networks and transfer of gliotransmitters; and worsening function of the blood brain barrier, among others. Increased knowledge of these aspects will permit a better understanding of brain aging and neurodegenerative diseases in old age as complex disorders in which neurons are not the only players.
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Affiliation(s)
- Isidro Ferrer
- Department of Pathology and Experimental TherapeuticsUniversity of BarcelonaBarcelonaSpain
- Institute of NeuropathologyPathologic Anatomy Service, Bellvitge University Hospital, IDIBELL, Hospitalet de LlobregatBarcelonaSpain
- Institute of NeurosciencesUniversity of BarcelonaBarcelonaSpain
- Biomedical Network Research Center on Neurodegenerative Diseases (CIBERNED), Institute Carlos IIIMadridSpain
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Mutant Huntingtin Impairs BDNF Release from Astrocytes by Disrupting Conversion of Rab3a-GTP into Rab3a-GDP. J Neurosci 2017; 36:8790-801. [PMID: 27559163 DOI: 10.1523/jneurosci.0168-16.2016] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 06/06/2016] [Indexed: 02/03/2023] Open
Abstract
UNLABELLED Brain-derived neurotrophic factor (BDNF) is essential for neuronal differentiation and survival. We know that BDNF levels decline in the brains of patients with Huntington's disease (HD), a neurodegenerative disease caused by the expression of mutant huntingtin protein (mHtt), and furthermore that administration of BDNF in HD mice is protective against HD neuropathology. BDNF is produced in neurons, but astrocytes are also an important source of BDNF in the brain. Nonetheless, whether mHtt affects astrocytic BDNF in the HD brain remains unknown. Here we investigated astrocytes from HD140Q knock-in mice and uncovered evidence that mHtt decreases BDNF secretion from astrocytes, which is mediated by exocytosis in astrocytes. Our results demonstrate that mHtt associates with Rab3a, a small GTPase localized on membranes of dense-core vesicles, and prevents GTP-Rab3a from binding to Rab3-GAP1, disrupting the conversion of GTP-Rab3a into GDP-Rab3a and thus impairing the docking of BDNF vesicles on plasma membranes of astrocytes. Importantly, overexpression of Rab3a rescues impaired BDNF vesicle docking and secretion from HD astrocytes. Moreover, ATP release and the number of ATP-containing dense-core vesicles docking are decreased in HD astrocytes, suggesting that the exocytosis of dense-core vesicles is impaired by mHtt in HD astrocytes. Further, Rab3a overexpression reduces reactive astrocytes in the striatum of HD140Q knock-in mice. Our results indicate that compromised exocytosis of BDNF in HD astrocytes contributes to the decreased BDNF levels in HD brains and underscores the importance of improving glial function in the treatment of HD. SIGNIFICANCE STATEMENT Huntington's disease (HD) is an inherited neurodegenerative disorder that affects one in every 10,000 Americans. To date, there is no effective treatment for HD, in part because the pathogenic mechanism driving the disease is not fully understood. The dysfunction of astrocytes is known to contribute to the pathogenesis of HD. One important role of astrocytes is to synthesize and release brain-derived neurotrophic factor (BDNF), which is vital for neuronal survival, development, and function. We found that mutant huntingtin protein (mHtt) at the endogenous level decreases BDNF secretion from astrocytes by disrupting the conversion of GTP-Rab3a into GDP-Rab3a and that overexpressing Rab3a can rescue this deficient BDNF release and early neuropathology in HD knock-in mouse brain. Our study suggests that astrocytic Rab3a is a potential therapeutic target for HD treatment.
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Destination Brain: the Past, Present, and Future of Therapeutic Gene Delivery. J Neuroimmune Pharmacol 2017; 12:51-83. [PMID: 28160121 DOI: 10.1007/s11481-016-9724-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 12/12/2016] [Indexed: 12/20/2022]
Abstract
Neurological diseases and disorders (NDDs) present a significant societal burden and currently available drug- and biological-based therapeutic strategies have proven inadequate to alleviate it. Gene therapy is a suitable alternative to treat NDDs compared to conventional systems since it can be tailored to specifically alter select gene expression, reverse disease phenotype and restore normal function. The scope of gene therapy has broadened over the years with the advent of RNA interference and genome editing technologies. Consequently, encouraging results from central nervous system (CNS)-targeted gene delivery studies have led to their transition from preclinical to clinical trials. As we shift to an exciting gene therapy era, a retrospective of available literature on CNS-associated gene delivery is in order. This review is timely in this regard, since it analyzes key challenges and major findings from the last two decades and evaluates future prospects of brain gene delivery. We emphasize major areas consisting of physiological and pharmacological challenges in gene therapy, function-based selection of a ideal cellular target(s), available therapy modalities, and diversity of viral vectors and nanoparticles as vehicle systems. Further, we present plausible answers to key questions such as strategies to circumvent low blood-brain barrier permeability and most suitable CNS cell types for targeting. We compare and contrast pros and cons of the tested viral vectors in the context of delivery systems used in past and current clinical trials. Gene vector design challenges are also evaluated in the context of cell-specific promoters. Key challenges and findings reported for recent gene therapy clinical trials, assessing viral vectors and nanoparticles are discussed from the perspective of bench to bedside gene therapy translation. We conclude this review by tying together gene delivery challenges, available vehicle systems and comprehensive analyses of neuropathogenesis to outline future prospects of CNS-targeted gene therapies.
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Phatnani H, Maniatis T. Astrocytes in neurodegenerative disease. Cold Spring Harb Perspect Biol 2015; 7:cshperspect.a020628. [PMID: 25877220 DOI: 10.1101/cshperspect.a020628] [Citation(s) in RCA: 267] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Astrocytes contribute to the maintenance of the health and function of the central nervous system (CNS). Thus, it is not surprising that these multifunctional cells have been implicated in the onset and progression of several neurodegenerative diseases. The involvement of astrocytes in the neuropathology of these diseases is likely a consequence of both the loss of normal homeostatic functions and gain of toxic functions. Intracellular aggregates in astrocytes are a common feature of various neurodegenerative diseases, and these aggregates perturb normal astrocytic functions in ways that can be harmful to neuronal viability. Here, we review the role of astrocytes in neurodegenerative diseases, focusing on their dysfunction in Huntington's disease (HD), Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS).
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Affiliation(s)
- Hemali Phatnani
- Columbia University Medical Center, Department of Biochemistry and Molecular Biophysics, New York, New York 10032
| | - Tom Maniatis
- Columbia University Medical Center, Department of Biochemistry and Molecular Biophysics, New York, New York 10032
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McFarland KN, Huizenga MN, Darnell SB, Sangrey GR, Berezovska O, Cha JHJ, Outeiro TF, Sadri-Vakili G. MeCP2: a novel Huntingtin interactor. Hum Mol Genet 2013; 23:1036-44. [PMID: 24105466 DOI: 10.1093/hmg/ddt499] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Transcriptional dysregulation has been proposed to play a major role in the pathology of Huntington's disease (HD). However, the mechanisms that cause selective downregulation of target genes remain unknown. Previous studies have shown that mutant huntingtin (Htt) protein interacts with a number of transcription factors thereby altering transcription. Here we report that Htt directly interacts with methyl-CpG binding protein 2 (MeCP2) in mouse and cellular models of HD using complimentary biochemical and Fluorescent Lifetime Imaging to measure Förster Resonance Energy Transfer approaches. Htt-MeCP2 interactions are enhanced in the presence of the expanded polyglutamine (polyQ) tract and are stronger in the nucleus compared with the cytoplasm. Furthermore, we find increased binding of MeCP2 to the promoter of brain-derived neurotrophic factor (BDNF), a gene that is downregulated in HD, in the presence of mutant Htt. Finally, decreasing MeCP2 levels in mutant Htt-expressing cells using siRNA increases BDNF levels, suggesting that MeCP2 downregulates BDNF expression in HD. Taken together, these findings suggest that aberrant interactions between Htt and MeCP2 contribute to transcriptional dysregulation in HD.
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Affiliation(s)
- Karen N McFarland
- Department of Neurology and The McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
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