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Mahley RW. Apolipoprotein E: from cardiovascular disease to neurodegenerative disorders. J Mol Med (Berl) 2016; 94:739-46. [PMID: 27277824 PMCID: PMC4921111 DOI: 10.1007/s00109-016-1427-y] [Citation(s) in RCA: 280] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 05/04/2016] [Accepted: 05/11/2016] [Indexed: 12/18/2022]
Abstract
Apolipoprotein (apo) E was initially described as a lipid transport protein and major ligand for low density lipoprotein (LDL) receptors with a role in cholesterol metabolism and cardiovascular disease. It has since emerged as a major risk factor (causative gene) for Alzheimer's disease and other neurodegenerative disorders. Detailed understanding of the structural features of the three isoforms (apoE2, apoE3, and apoE4), which differ by only a single amino acid interchange, has elucidated their unique functions. ApoE2 and apoE4 increase the risk for heart disease: apoE2 increases atherogenic lipoprotein levels (it binds poorly to LDL receptors), and apoE4 increases LDL levels (it binds preferentially to triglyceride-rich, very low density lipoproteins, leading to downregulation of LDL receptors). ApoE4 also increases the risk for neurodegenerative diseases, decreases their age of onset, or alters their progression. ApoE4 likely causes neurodegeneration secondary to its abnormal structure, caused by an interaction between its carboxyl- and amino-terminal domains, called domain interaction. When neurons are stressed or injured, they synthesize apoE to redistribute cholesterol for neuronal repair or remodeling. However, because of its altered structure, neuronal apoE4 undergoes neuron-specific proteolysis, generating neurotoxic fragments (12-29 kDa) that escape the secretory pathway and cause mitochondrial dysfunction and cytoskeletal alterations, including tau phosphorylation. ApoE4-associated pathology can be prevented by small-molecule structure correctors that block domain interaction by converting apoE4 to a molecule that resembles apoE3 both structurally and functionally. Structure correctors are a potential therapeutic approach to reduce apoE4 pathology in both cardiovascular and neurological disorders.
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Affiliation(s)
- Robert W Mahley
- Gladstone Institute of Neurological Disease, 1650 Owens Street, San Francisco, CA, 94158, USA.
- Departments of Pathology and Medicine, University of California, San Francisco, CA, 94143, USA.
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Enhancing GABA Signaling during Middle Adulthood Prevents Age-Dependent GABAergic Interneuron Decline and Learning and Memory Deficits in ApoE4 Mice. J Neurosci 2016; 36:2316-22. [PMID: 26888940 DOI: 10.1523/jneurosci.3815-15.2016] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
UNLABELLED Apolipoprotein E4 (apoE4) is the major genetic risk factor for Alzheimer's disease (AD). However, the underlying mechanisms are still poorly understood. We previously reported that female apoE4 knock-in (KI) mice had an age-dependent decline in hilar GABAergic interneurons that correlated with the extent of learning and memory deficits, as determined by Morris water maze (MWM), in aged mice. Enhancing GABA signaling by treating aged apoE4-KI mice with the GABAA receptor potentiator pentobarbital (PB) for 4 weeks before and during MWM rescued the learning and memory deficits. Here, we report that withdrawal of PB treatment for 2 weeks before MWM abolished the rescue in aged apoE4-KI mice, suggesting the importance of continuously enhancing GABA signaling in the rescue. However, treating apoE4-KI mice during middle adulthood (9-11 months of age) with PB for 6 weeks prevented age-dependent hilar GABAergic interneuron decline and learning and memory deficits, when examined at 16 month of age. These data imply that increasing inhibitory tone after substantial GABAergic interneuron loss may be an effective symptomatic, but not a disease-modifying, treatment for AD related to apoE4, whereas a similar intervention before substantial interneuron loss could be a disease-modifying therapeutic. SIGNIFICANCE STATEMENT We previously reported that female apoE4-KI mice had an age-dependent decline in hilar GABAergic interneurons that correlated with the extent of cognitive deficits in aged mice. The current study demonstrates that enhancing GABA signaling by treating aged apoE4-KI mice with a GABAA receptor potentiator pentobarbital (PB) before and during behavioral tests rescued the cognitive deficits; but withdrawal of PB treatment for 2 weeks before the tests abolished the rescue, suggesting the importance of continuously enhancing GABA signaling. However, treating apoE4-KI mice during middle adulthood with PB for a short period of time prevented age-dependent hilar GABAergic interneuron decline and cognitive deficits late in life, suggesting early intervention by enhancing GABA signaling as a potential strategy to prevent AD related to apoE4.
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Gillespie AK, Jones EA, Lin YH, Karlsson MP, Kay K, Yoon SY, Tong LM, Nova P, Carr JS, Frank LM, Huang Y. Apolipoprotein E4 Causes Age-Dependent Disruption of Slow Gamma Oscillations during Hippocampal Sharp-Wave Ripples. Neuron 2016; 90:740-51. [PMID: 27161522 DOI: 10.1016/j.neuron.2016.04.009] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2015] [Revised: 02/26/2016] [Accepted: 03/30/2016] [Indexed: 12/29/2022]
Abstract
Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer's disease (AD), but the mechanism by which it causes cognitive decline is unclear. In knockin (KI) mice, human apoE4 causes age-dependent learning and memory impairments and degeneration of GABAergic interneurons in the hippocampal dentate gyrus. Here we report two functional apoE4-KI phenotypes involving sharp-wave ripples (SWRs), hippocampal network events critical for memory processes. Aged apoE4-KI mice had fewer SWRs than apoE3-KI mice and significantly reduced slow gamma activity during SWRs. Elimination of apoE4 in GABAergic interneurons, which prevents learning and memory impairments, rescued SWR-associated slow gamma activity but not SWR abundance in aged mice. SWR abundance was reduced similarly in young and aged apoE4-KI mice; however, the full SWR-associated slow gamma deficit emerged only in aged apoE4-KI mice. These results suggest that progressive decline of interneuron-enabled slow gamma activity during SWRs critically contributes to apoE4-mediated learning and memory impairments. VIDEO ABSTRACT.
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Affiliation(s)
- Anna K Gillespie
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, CA 94158, USA; Biomedical Sciences Graduate Program, University of California, San Francisco, CA 94143, USA
| | - Emily A Jones
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, CA 94158, USA; Biomedical Sciences Graduate Program, University of California, San Francisco, CA 94143, USA
| | - Yuan-Hung Lin
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, CA 94158, USA; Neuroscience Graduate Program, University of California, San Francisco, CA 94143, USA
| | - Mattias P Karlsson
- Kavli Institute for Fundamental Neuroscience and Department of Physiology, University of California, San Francisco, CA 94158, USA
| | - Kenneth Kay
- Kavli Institute for Fundamental Neuroscience and Department of Physiology, University of California, San Francisco, CA 94158, USA; Bioengineering Graduate Program, University of California, San Francisco, CA 94143, USA
| | - Seo Yeon Yoon
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, CA 94158, USA
| | - Leslie M Tong
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, CA 94158, USA; Biomedical Sciences Graduate Program, University of California, San Francisco, CA 94143, USA
| | - Philip Nova
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, CA 94158, USA; Biomedical Sciences Graduate Program, University of California, San Francisco, CA 94143, USA
| | - Jessie S Carr
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, CA 94158, USA; Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, CA 94143, USA
| | - Loren M Frank
- Neuroscience Graduate Program, University of California, San Francisco, CA 94143, USA; Kavli Institute for Fundamental Neuroscience and Department of Physiology, University of California, San Francisco, CA 94158, USA; Bioengineering Graduate Program, University of California, San Francisco, CA 94143, USA
| | - Yadong Huang
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, CA 94158, USA; Biomedical Sciences Graduate Program, University of California, San Francisco, CA 94143, USA; Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, CA 94143, USA; Departments of Neurology and Pathology, University of California, San Francisco, CA 94143, USA.
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Adult Hippocampal Neurogenesis, Fear Generalization, and Stress. Neuropsychopharmacology 2016; 41:24-44. [PMID: 26068726 PMCID: PMC4677119 DOI: 10.1038/npp.2015.167] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 05/29/2015] [Accepted: 06/05/2015] [Indexed: 12/21/2022]
Abstract
The generalization of fear is an adaptive, behavioral, and physiological response to the likelihood of threat in the environment. In contrast, the overgeneralization of fear, a cardinal feature of posttraumatic stress disorder (PTSD), manifests as inappropriate, uncontrollable expression of fear in neutral and safe environments. Overgeneralization of fear stems from impaired discrimination of safe from aversive environments or discernment of unlikely threats from those that are highly probable. In addition, the time-dependent erosion of episodic details of traumatic memories might contribute to their generalization. Understanding the neural mechanisms underlying the overgeneralization of fear will guide development of novel therapeutic strategies to combat PTSD. Here, we conceptualize generalization of fear in terms of resolution of interference between similar memories. We propose a role for a fundamental encoding mechanism, pattern separation, in the dentate gyrus (DG)-CA3 circuit in resolving interference between ambiguous or uncertain threats and in preserving episodic content of remote aversive memories in hippocampal-cortical networks. We invoke cellular-, circuit-, and systems-based mechanisms by which adult-born dentate granule cells (DGCs) modulate pattern separation to influence resolution of interference and maintain precision of remote aversive memories. We discuss evidence for how these mechanisms are affected by stress, a risk factor for PTSD, to increase memory interference and decrease precision. Using this scaffold we ideate strategies to curb overgeneralization of fear in PTSD.
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Narváez M, Borroto-Escuela DO, Millón C, Gago B, Flores-Burgess A, Santín L, Fuxe K, Narváez JA, Díaz-Cabiale Z. Galanin receptor 2-neuropeptide Y Y1 receptor interactions in the dentate gyrus are related with antidepressant-like effects. Brain Struct Funct 2015; 221:4129-4139. [DOI: 10.1007/s00429-015-1153-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 11/19/2015] [Indexed: 11/30/2022]
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Potential of GABA-ergic cell therapy for schizophrenia, neuropathic pain, and Alzheimer's and Parkinson's diseases. Brain Res 2015; 1638:74-87. [PMID: 26423935 DOI: 10.1016/j.brainres.2015.09.019] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 08/26/2015] [Accepted: 09/08/2015] [Indexed: 12/17/2022]
Abstract
Several neurological and psychiatric disorders present hyperexcitability of neurons in specific regions of the brain or spinal cord, partly because of some loss and/or dysfunction of gamma-amino butyric acid positive (GABA-ergic) inhibitory interneurons. Strategies that enhance inhibitory neurotransmission in the affected brain regions may therefore ease several or most deficits linked to these disorders. This perception has incited a huge interest in testing the efficacy of GABA-ergic interneuron cell grafting into regions of the brain or spinal cord exhibiting hyperexcitability, dearth of GABA-ergic interneurons or impaired inhibitory neurotransmission, using preclinical models of neurological and psychiatric disorders. Interneuron progenitors from the embryonic ventral telencephalon capable of differentiating into diverse subclasses of interneurons have particularly received much consideration because of their ability for dispersion, migration and integration with the host neural circuitry after grafting. The goal of this review is to discuss the premise, scope and advancement of GABA-ergic cell therapy for easing neurological deficits in preclinical models of schizophrenia, chronic neuropathic pain, Alzheimer's disease and Parkinson's disease. As grafting studies in these prototypes have so far utilized either primary cells from the embryonic medial and lateral ganglionic eminences or neural progenitor cells expanded from these eminences as donor material, the proficiency of these cell types is highlighted. Moreover, future studies that are essential prior to considering the possible clinical application of these cells for the above neurological conditions are proposed. Particularly, the need for grafting studies utilizing medial ganglionic eminence-like progenitors generated from human pluripotent stem cells via directed differentiation approaches or somatic cells through direct reprogramming methods are emphasized. This article is part of a Special Issue entitled SI: PSC and the brain.
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McQuail JA, Frazier CJ, Bizon JL. Molecular aspects of age-related cognitive decline: the role of GABA signaling. Trends Mol Med 2015; 21:450-60. [PMID: 26070271 DOI: 10.1016/j.molmed.2015.05.002] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 05/12/2015] [Accepted: 05/14/2015] [Indexed: 12/19/2022]
Abstract
Alterations in inhibitory interneurons contribute to cognitive deficits associated with several psychiatric and neurological diseases. Phasic and tonic inhibition imparted by γ-aminobutyric acid (GABA) receptors regulates neural activity and helps to establish the appropriate network dynamics in cortical circuits that support normal cognition. This review highlights basic science demonstrating that inhibitory signaling is altered in aging, and discusses the impact of age-related shifts in inhibition on different forms of memory function, including hippocampus-dependent spatial reference memory and prefrontal cortex (PFC)-dependent working memory. The clinical appropriateness and tractability of select therapeutic candidates for cognitive aging that target receptors mediating inhibition are also discussed.
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Affiliation(s)
- Joseph A McQuail
- Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA; McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Charles J Frazier
- Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA; McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA; Department of Pharmacodynamics, University of Florida, Gainesville, FL 32610, USA
| | - Jennifer L Bizon
- Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA; McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA.
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Quarta E, Bravi R, Scambi I, Mariotti R, Minciacchi D. Increased anxiety-like behavior and selective learning impairments are concomitant to loss of hippocampal interneurons in the presymptomatic SOD1(G93A) ALS mouse model. J Comp Neurol 2015; 523:1622-38. [DOI: 10.1002/cne.23759] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 02/09/2015] [Accepted: 02/09/2015] [Indexed: 12/12/2022]
Affiliation(s)
- Eros Quarta
- Department of Experimental and Clinical Medicine, Physiological Sciences Section; University of Florence; Florence I-50134 Italy
| | - Riccardo Bravi
- Department of Experimental and Clinical Medicine, Physiological Sciences Section; University of Florence; Florence I-50134 Italy
| | - Ilaria Scambi
- Department of Neurological and Movement Sciences; University of Verona; Verona I-37134 Italy
| | - Raffaella Mariotti
- Department of Neurological and Movement Sciences; University of Verona; Verona I-37134 Italy
| | - Diego Minciacchi
- Department of Experimental and Clinical Medicine, Physiological Sciences Section; University of Florence; Florence I-50134 Italy
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59
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Tong LM, Fong H, Huang Y. Stem cell therapy for Alzheimer's disease and related disorders: current status and future perspectives. Exp Mol Med 2015; 47:e151. [PMID: 25766620 PMCID: PMC4351411 DOI: 10.1038/emm.2014.124] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 11/19/2014] [Indexed: 12/31/2022] Open
Abstract
Underlying cognitive declines in Alzheimer's disease (AD) are the result of neuron and neuronal process losses due to a wide range of factors. To date, all efforts to develop therapies that target specific AD-related pathways have failed in late-stage human trials. As a result, an emerging consensus in the field is that treatment of AD patients with currently available drug candidates might come too late, likely as a result of significant neuronal loss in the brain. In this regard, cell-replacement therapies, such as human embryonic stem cell- or induced pluripotent stem cell-derived neural cells, hold potential for treating AD patients. With the advent of stem cell technologies and the ability to transform these cells into different types of central nervous system neurons and glial cells, some success in stem cell therapy has been reported in animal models of AD. However, many more steps remain before stem cell therapies will be clinically feasible for AD and related disorders in humans. In this review, we will discuss current research advances in AD pathogenesis and stem cell technologies; additionally, the potential challenges and strategies for using cell-based therapies for AD and related disorders will be discussed.
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Affiliation(s)
- Leslie M Tong
- Gladstone Institute of Neurological Disease, University of California, San Francisco, CA, USA
- Biomedical Sciences Graduate Program, University of California, San Francisco, CA, USA
| | - Helen Fong
- Gladstone Institute of Neurological Disease, University of California, San Francisco, CA, USA
- Department of Neurology, University of California, San Francisco, CA, USA
| | - Yadong Huang
- Gladstone Institute of Neurological Disease, University of California, San Francisco, CA, USA
- Biomedical Sciences Graduate Program, University of California, San Francisco, CA, USA
- Department of Neurology, University of California, San Francisco, CA, USA
- Department of Pathology, University of California, San Francisco, CA, USA
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Apolipoprotein E4 produced in GABAergic interneurons causes learning and memory deficits in mice. J Neurosci 2015; 34:14069-78. [PMID: 25319703 DOI: 10.1523/jneurosci.2281-14.2014] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Apolipoprotein (apo) E4 is expressed in many types of brain cells, is associated with age-dependent decline of learning and memory in humans, and is the major genetic risk factor for AD. To determine whether the detrimental effects of apoE4 depend on its cellular sources, we generated human apoE knock-in mouse models in which the human APOE gene is conditionally deleted in astrocytes, neurons, or GABAergic interneurons. Here we report that deletion of apoE4 in astrocytes does not protect aged mice from apoE4-induced GABAergic interneuron loss and learning and memory deficits. In contrast, deletion of apoE4 in neurons does protect aged mice from both deficits. Furthermore, deletion of apoE4 in GABAergic interneurons is sufficient to gain similar protection. This study demonstrates a detrimental effect of endogenously produced apoE4 on GABAergic interneurons that leads to learning and memory deficits in mice and provides a novel target for drug development for AD related to apoE4.
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Hippocampal dysregulation of neurofibromin-dependent pathways is associated with impaired spatial learning in engrailed 2 knock-out mice. J Neurosci 2015; 34:13281-8. [PMID: 25274808 DOI: 10.1523/jneurosci.2894-13.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Genome-wide association studies indicated the homeobox-containing transcription factor Engrailed-2 (En2) as a candidate gene for autism spectrum disorders (ASD). Accordingly, En2 knock-out (En2(-/-)) mice show anatomical and behavioral "ASD-like" features, including decreased sociability and learning deficits. The molecular pathways underlying these deficits in En2(-/-) mice are not known. Deficits in signaling pathways involving neurofibromin and extracellular-regulated kinase (ERK) have been associated with impaired learning. Here we investigated the neurofibromin-ERK cascade in the hippocampus of wild-type (WT) and En2(-/-) mice before and after spatial learning testing. When compared with WT littermates, En2(-/-) mice showed impaired performance in the Morris water maze (MWM), which was accompanied by lower expression of the activity-dependent gene Arc. Quantitative RT-PCR, immunoblotting, and immunohistochemistry experiments showed a marked downregulation of neurofibromin expression in the dentate gyrus of both naive and MWM-treated En2(-/-) mice. ERK phosphorylation, known to be induced in the presence of neurofibromin deficiency, was increased in the dentate gyrus of En2(-/-) mice after MWM. Treatment of En2(-/-) mice with lovastatin, an indirect inhibitor of ERK phosphorylation, markedly reduced ERK phosphorylation in the dentate gyrus, but was unable to rescue learning deficits in MWM-trained mutant mice. Further investigation is needed to unravel the complex molecular mechanisms linking dysregulation of neurofibromin-dependent pathways to spatial learning deficits in the En2 mouse model of ASD.
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Reichel JM, Nissel S, Rogel-Salazar G, Mederer A, Käfer K, Bedenk BT, Martens H, Anders R, Grosche J, Michalski D, Härtig W, Wotjak CT. Distinct behavioral consequences of short-term and prolonged GABAergic depletion in prefrontal cortex and dorsal hippocampus. Front Behav Neurosci 2015; 8:452. [PMID: 25628548 PMCID: PMC4292780 DOI: 10.3389/fnbeh.2014.00452] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 12/17/2014] [Indexed: 11/13/2022] Open
Abstract
GABAergic interneurons are essential for a functional equilibrium between excitatory and inhibitory impulses throughout the CNS. Disruption of this equilibrium can lead to various neurological or neuropsychiatric disorders such as epilepsy or schizophrenia. Schizophrenia itself is clinically defined by negative (e.g., depression) and positive (e.g., hallucinations) symptoms as well as cognitive dysfunction. GABAergic interneurons are proposed to play a central role in the etiology and progression of schizophrenia; however, the specific mechanisms and the time-line of symptom development as well as the distinct involvement of cortical and hippocampal GABAergic interneurons in the etiology of schizophrenia-related symptoms are still not conclusively resolved. Previous work demonstrated that GABAergic interneurons can be selectively depleted in adult mice by means of saporin-conjugated anti-vesicular GABA transporter antibodies (SAVAs) in vitro and in vivo. Given their involvement in schizophrenia-related disease etiology, we ablated GABAergic interneurons in the medial prefrontal cortex (mPFC) and dorsal hippocampus (dHPC) in adult male C57BL/6N mice. Subsequently we assessed alterations in anxiety, sensory processing, hyperactivity and cognition after long-term (>14 days) and short-term (<14 days) GABAergic depletion. Long-term GABAergic depletion in the mPFC resulted in a decrease in sensorimotor-gating and impairments in cognitive flexibility. Notably, the same treatment at the level of the dHPC completely abolished spatial learning capabilities. Short-term GABAergic depletion in the dHPC revealed a transient hyperactive phenotype as well as marked impairments regarding the acquisition of a spatial memory. In contrast, recall of a spatial memory was not affected by the same intervention. These findings emphasize the importance of functional local GABAergic networks for the encoding but not the recall of hippocampus-dependent spatial memories.
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Affiliation(s)
- Judith M Reichel
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
| | - Sabine Nissel
- Paul Flechsig Institute for Brain Research, University of Leipzig Leipzig, Germany
| | - Gabriela Rogel-Salazar
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
| | - Anna Mederer
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
| | - Karola Käfer
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
| | - Benedikt T Bedenk
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
| | | | - Rebecca Anders
- Paul Flechsig Institute for Brain Research, University of Leipzig Leipzig, Germany
| | - Jens Grosche
- Paul Flechsig Institute for Brain Research, University of Leipzig Leipzig, Germany ; Effigos AG Leipzig, Germany
| | | | - Wolfgang Härtig
- Paul Flechsig Institute for Brain Research, University of Leipzig Leipzig, Germany
| | - Carsten T Wotjak
- Department of Stress Neurobiology and Neurogenetics, Max Planck Institute of Psychiatry, Research Group "Neuronal Plasticity" Munich, Germany
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63
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Zhang Y, Qiao L, Song M, Wang L, Xie J, Feng H. Hplc-ESI-MS/MS analysis of the water-soluble extract from Ziziphi spinosae semen and its ameliorating effect of learning and memory performance in mice. Pharmacogn Mag 2014; 10:509-16. [PMID: 25422554 PMCID: PMC4239731 DOI: 10.4103/0973-1296.141777] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2013] [Revised: 12/06/2013] [Accepted: 09/26/2014] [Indexed: 12/15/2022] Open
Abstract
Background: Ziziphi Spinosae Semen (ZSS), the seed of Ziziphus jujuba var. spinosa (Bunge) Hu ex H. F. Chow., is a traditional herb for insomnia and anxiety in eastern Asia. However, few researches have been concerned with its effect on ameliorating memory and learning performance. Objective: To investigate the constituents of ZSS water soluble extract and its ameliorating learning and memory in mice. Materials and Methods: A new high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-ESI-MS/MS) method was developed and validated to determine the main constituents in the extract. The effect of ZSS water soluble extract on memory and learning performance was investigated in mice by Y-maze and passive avoidance test. Results: The extract could significantly decrease the number of errors (NOE), and increase the transfer latency time (TLT) and electrical stimuli time (EST). In addition, spinosin, jujuboside A (JuA) and jujuboside B (JuB) were simultaneously identified and quantified in the extract. Their contents in the extract were as followed: Spinosin (223.51mg/g), JuA (63.76mg/g) and JuB (26.29mg/g). Conclusion: The extract played a promising role in ameliorating memory in mice with alcohol induced memory retrieval disorders, and might help to improve learning capacity to some extent. Spinosin, JuA and JuB were the predominant constituents, which might be mainly responsible for the definite activity.
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Affiliation(s)
- Yanqing Zhang
- Department of Pharmaceutical Egineering, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, People's Republic of China ; Tianjin Key Laboratory of Food Biotechnology, Tianjin 300134, People's Republic of China
| | - Longdong Qiao
- Department of Pharmaceutical Egineering, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, People's Republic of China
| | - Mengyuan Song
- Department of Pharmaceutical Egineering, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, People's Republic of China
| | - Lijuan Wang
- Department of Pharmaceutical Egineering, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, People's Republic of China ; Tianjin Key Laboratory of Food Biotechnology, Tianjin 300134, People's Republic of China
| | - Junbo Xie
- Department of Pharmaceutical Egineering, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, People's Republic of China ; Tianjin Key Laboratory of Food Biotechnology, Tianjin 300134, People's Republic of China
| | - Hua Feng
- Department of Pharmaceutical Egineering, College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin 300134, People's Republic of China
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Inhibitory interneuron progenitor transplantation restores normal learning and memory in ApoE4 knock-in mice without or with Aβ accumulation. J Neurosci 2014; 34:9506-15. [PMID: 25031394 DOI: 10.1523/jneurosci.0693-14.2014] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Excitatory and inhibitory balance of neuronal network activity is essential for normal brain function and may be of particular importance to memory. Apolipoprotein (apo) E4 and amyloid-β (Aβ) peptides, two major players in Alzheimer's disease (AD), cause inhibitory interneuron impairments and aberrant neuronal activity in the hippocampal dentate gyrus in AD-related mouse models and humans, leading to learning and memory deficits. To determine whether replacing the lost or impaired interneurons rescues neuronal signaling and behavioral deficits, we transplanted embryonic interneuron progenitors into the hippocampal hilus of aged apoE4 knock-in mice without or with Aβ accumulation. In both conditions, the transplanted cells developed into mature interneurons, functionally integrated into the hippocampal circuitry, and restored normal learning and memory. Thus, restricted hilar transplantation of inhibitory interneurons restores normal cognitive function in two widely used AD-related mouse models, highlighting the importance of interneuron impairments in AD pathogenesis and the potential of cell replacement therapy for AD. More broadly, it demonstrates that excitatory and inhibitory balance are crucial for learning and memory, and suggests an avenue for investigating the processes of learning and memory and their alterations in healthy aging and diseases.
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Goshen I. The optogenetic revolution in memory research. Trends Neurosci 2014; 37:511-22. [DOI: 10.1016/j.tins.2014.06.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 06/02/2014] [Accepted: 06/12/2014] [Indexed: 10/25/2022]
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Wang X, Gao F, Zhu J, Guo E, Song X, Wang S, Zhan RZ. Immunofluorescently labeling glutamic acid decarboxylase 65 coupled with confocal imaging for identifying GABAergic somata in the rat dentate gyrus-A comparison with labeling glutamic acid decarboxylase 67. J Chem Neuroanat 2014; 61-62:51-63. [PMID: 25058170 DOI: 10.1016/j.jchemneu.2014.07.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 07/11/2014] [Accepted: 07/12/2014] [Indexed: 01/23/2023]
Abstract
As γ-aminobutyric acid (GABA) is synthesized by two isoforms of glutamic acid decarboxylase (GAD), namely, GAD65 and GAD67, immunohistochemically targeting either isoform of GAD is theoretically useful for identifying GABAergic cell bodies. In practice, targeting GAD67 remains to be a popular choice. However, identifying GABAergic cell bodies with GAD67 immunoreactivity in the hippocampal dentate gyrus, especially in the hilus, is not without pitfalls. In the present study, we compared the characteristics of GAD65 immunoreactivity to GAD67 immunoreactivity in the rat dentate gyrus and examined perikaryal expression of GAD65 in four neurochemically prevalent subgroups of interneurons in the hilus. Experiments were done in normal adult Sprague-Dawley rats and GAD67-GFP knock-in mice. Horizontal hippocampal slices cut from the ventral portion of hippocampi were immunofluorescently stained and scanned using a confocal microscope. Immunoreactivity for both GAD67 and GAD65 was visible throughout the dentate gyrus. Perikaryal GAD67 immunoreactivity was denser but variable in terms of distribution pattern and intensity among cells whereas perikaryal GAD65 immunoreactivity displayed similar distribution pattern and staining intensity. Among different layers of the dentate gyrus, GAD67 immunoreactivity was densest in the hilus despite GAD65 immunoreactivity being more intense in the granule cell layer. Co-localization experiments showed that GAD65, but not GAD67, was expressed in all hilar calretinin (CR)-, neuronal nitric oxide synthase (nNOS)-, parvalbumin (PV)- or somatostatin (SOM)-positive somata. Labeling CR, nNOS, PV, and SOM in sections obtained from GAD67-GFP knock-in mice revealed that a large portion of SOM-positive cells had weak GFP expression. In addition, double labeling of GAD65/GABA and GAD67/GABA showed that nearly all of GABA-immunoreactive cells had perikaryal GAD65 expression whereas more than one-tenth of GABA-immunoreactive cells lacked perikaryal GAD67 immunoreactivity. Inhibition of axonal transport with colchicine dramatically improved perikaryal GAD65 immunoreactivity in GABAergic cells without significant augmentation to be seen in granule cells. Double labeling GAD65 and GAD67 in the sections obtained from colchicine-pretreated animals confirmed that a portion of GAD65-immunoreactive cells had weak or even no GAD67 immunoreactivity. We conclude that for confocal imaging, immunofluorescently labeling GAD65 for identifying GABAergic somata in the hilus of the dentate gyrus has advantages over labeling GAD67 in terms of easier recognition of perikaryal labeling and more consistent expression in GABAergic somata. Inhibition of axonal transport with colchicine further improves perikaryal GAD65 labeling, making GABAergic cells more distinguishable.
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Affiliation(s)
- Xiaochen Wang
- Department of Physiology, Shandong University School of Medicine, Jinan, China
| | - Fei Gao
- Department of Physiology, Shandong University School of Medicine, Jinan, China
| | - Jianchun Zhu
- Department of Physiology, Shandong University School of Medicine, Jinan, China
| | - Enpu Guo
- Division of General Surgery, The Second Affiliated Hospital, Shandong University of Traditional Chinese Medicine, China
| | - Xueying Song
- Department of Physiology, Shandong University School of Medicine, Jinan, China
| | - Shuanglian Wang
- Department of Physiology, Shandong University School of Medicine, Jinan, China
| | - Ren-Zhi Zhan
- Department of Physiology, Shandong University School of Medicine, Jinan, China.
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Xu K, Zhang Y, Wang Y, Ling P, Xie X, Jiang C, Zhang Z, Lian XY. Ginseng Rb fraction protects glia, neurons and cognitive function in a rat model of neurodegeneration. PLoS One 2014; 9:e101077. [PMID: 24971630 PMCID: PMC4074135 DOI: 10.1371/journal.pone.0101077] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 06/03/2014] [Indexed: 11/18/2022] Open
Abstract
The loss and injury of neurons play an important role in the onset of various neurodegenerative diseases, while both microgliosis and astrocyte loss or dysfunction are significant causes of neuronal degeneration. Previous studies have suggested that an extract enriched panaxadiol saponins from ginseng has more neuroprotective potential than the total saponins of ginseng. The present study investigated whether a fraction of highly purified panaxadiol saponins (termed as Rb fraction) was protective for both glia and neurons, especially GABAergic interneurons, against kainic acid (KA)-induced excitotoxicity in rats. Rats received Rb fraction at 30 mg/kg (i.p.), 40 mg/kg (i.p. or saline followed 40 min later by an intracerebroventricular injection of KA. Acute hippocampal injury was determined at 48 h after KA, and impairment of hippocampus-dependent learning and memory as well as delayed neuronal injury was determined 16 to 21 days later. KA injection produced significant acute hippocampal injuries, including GAD67-positive GABAergic interneuron loss in CA1, paralbumin (PV)-positive GABAergic interneuron loss, pyramidal neuron degeneration and astrocyte damage accompanied with reactive microglia in both CA1 and CA3 regions of the hippocampus. There was also a delayed loss of GAD67-positive interneurons in CA1, CA3, hilus and dentate gyrus. Microgliosis also became more severe 21 days later. Accordingly, KA injection resulted in hippocampus-dependent spatial memory impairment. Interestingly, the pretreatment with Rb fraction at 30 or 40 mg/kg significantly protected the pyramidal neurons and GABAergic interneurons against KA-induced acute excitotoxicity and delayed injury. Rb fraction also prevented memory impairments and protected astrocytes from KA-induced acute excitotoxicity. Additionally, microglial activation, especially the delayed microgliosis, was inhibited by Rb fraction. Overall, this study demonstrated that Rb fraction protected both astrocytes and neurons, especially GABAergic interneurons, and maintained microglial homeostasis against KA-induced excitotoxicity. Therefore, Rb fraction has the potential to prevent and treat neurodegenerative diseases.
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Affiliation(s)
- Kangning Xu
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Yufen Zhang
- Anhui University of Chinese Medicine, Hefei, China
| | - Yan Wang
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Peng Ling
- Anhui University of Chinese Medicine, Hefei, China
| | - Xin Xie
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Chenyao Jiang
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Zhizhen Zhang
- Ocean College, Zhejiang University, Hangzhou, China
- * E-mail: (XYL); (ZZZ)
| | - Xiao-Yuan Lian
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
- * E-mail: (XYL); (ZZZ)
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Koh MT, Spiegel AM, Gallagher M. Age-associated changes in hippocampal-dependent cognition in Diversity Outbred mice. Hippocampus 2014; 24:1300-7. [PMID: 24909986 DOI: 10.1002/hipo.22311] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/30/2014] [Indexed: 11/05/2022]
Abstract
Episodic memory impairment due to aging has been linked to hippocampal dysfunction. Evidence exists for alterations in specific circuits within the hippocampal system that are closely coupled to individual differences in the presence and severity of such memory loss. Here, we used the newly developed Diversity Outbred (DO) mouse that was designed to model the genetic diversity in human populations. Young and aged DO mice were tested in a hippocampal-dependent water maze task. Young mice showed higher proficiency and more robust memory compared to the overall performance of aged mice. A substantial number of the older mice, however, performed on par with the normative performance of the younger mice. Stereological quantification of somatostatin-immunoreactive neurons in the dentate hilus showed that high-performing young and unimpaired aged mice had similar numbers of somatostatin-positive interneurons, while aged mice that were impaired in the spatial task had significantly fewer such neurons. These data in the DO model tie loss of hilar inhibitory network integrity to age-related memory impairment, paralleling data in other rodent models.
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Affiliation(s)
- Ming Teng Koh
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland
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69
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Berndt A, Lee SY, Ramakrishnan C, Deisseroth K. Structure-guided transformation of channelrhodopsin into a light-activated chloride channel. Science 2014; 344:420-4. [PMID: 24763591 PMCID: PMC4096039 DOI: 10.1126/science.1252367] [Citation(s) in RCA: 264] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Using light to silence electrical activity in targeted cells is a major goal of optogenetics. Available optogenetic proteins that directly move ions to achieve silencing are inefficient, pumping only a single ion per photon across the cell membrane rather than allowing many ions per photon to flow through a channel pore. Building on high-resolution crystal-structure analysis, pore vestibule modeling, and structure-guided protein engineering, we designed and characterized a class of channelrhodopsins (originally cation-conducting) converted into chloride-conducting anion channels. These tools enable fast optical inhibition of action potentials and can be engineered to display step-function kinetics for stable inhibition, outlasting light pulses and for orders-of-magnitude-greater light sensitivity of inhibited cells. The resulting family of proteins defines an approach to more physiological, efficient, and sensitive optogenetic inhibition.
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Affiliation(s)
- Andre Berndt
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Soo Yeun Lee
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Charu Ramakrishnan
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Karl Deisseroth
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305, USA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
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70
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Spiegel AM, Koh MT, Vogt NM, Rapp PR, Gallagher M. Hilar interneuron vulnerability distinguishes aged rats with memory impairment. J Comp Neurol 2014; 521:3508-23. [PMID: 23749483 DOI: 10.1002/cne.23367] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 04/30/2013] [Accepted: 05/23/2013] [Indexed: 01/24/2023]
Abstract
Hippocampal interneuron populations are reportedly vulnerable to normal aging. The relationship between interneuron network integrity and age-related memory impairment, however, has not been tested directly. That question was addressed in the present study using a well-characterized model in which outbred, aged, male Long-Evans rats exhibit a spectrum of individual differences in hippocampal-dependent memory. Selected interneuron populations in the hippocampus were visualized for stereological quantification with a panel of immunocytochemical markers, including glutamic acid decarboxylase-67 (GAD67), somatostatin, and neuropeptide Y. The overall pattern of results was that, although the numbers of GAD67- and somatostatin-positive interneurons declined with age across multiple fields of the hippocampus, alterations specifically related to the cognitive outcome of aging were observed exclusively in the hilus of the dentate gyrus. Because the total number of NeuN-immunoreactive hilar neurons was unaffected, the decline observed with other markers likely reflects a loss of target protein rather than neuron death. In support of that interpretation, treatment with the atypical antiepileptic levetiracetam at a low dose shown previously to improve behavioral performance fully restored hilar SOM expression in aged, memory-impaired rats. Age-related decreases in GAD67- and somatostatin-immunoreactive neuron number beyond the hilus were regionally selective and spared the CA1 field of the hippocampus entirely. Together these findings confirm the vulnerability of hippocampal interneurons to normal aging and highlight that the integrity of a specific subpopulation in the hilus is coupled with age-related memory impairment.
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Affiliation(s)
- Amy M Spiegel
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, 21218
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71
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Dihydromyricetin prevents fetal alcohol exposure-induced behavioral and physiological deficits: the roles of GABAA receptors in adolescence. Neurochem Res 2014; 39:1147-61. [PMID: 24676702 DOI: 10.1007/s11064-014-1291-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Revised: 03/18/2014] [Accepted: 03/20/2014] [Indexed: 10/25/2022]
Abstract
Fetal alcohol exposure (FAE) can lead to a variety of behavioral and physiological disturbances later in life. Understanding how alcohol (ethanol, EtOH) affects fetal brain development is essential to guide the development of better therapeutics for FAE. One of EtOH's many pharmacological targets is the γ-aminobutyric acid type A receptor (GABAAR), which plays a prominent role in early brain development. Acute EtOH potentiates inhibitory currents carried by certain GABAAR subtypes, whereas chronic EtOH leads to persistent alterations in GABAAR subunit composition, localization and function. We recently introduced a flavonoid compound, dihydromyricetin (DHM), which selectively antagonizes EtOH's intoxicating effects in vivo and in vitro at enhancing GABAAR function as a candidate for alcohol abuse pharmacotherapy. Here, we studied the effect of FAE on physiology, behavior and GABAAR function of early adolescent rats and tested the utility of DHM as a preventative treatment for FAE-induced disturbances. Gavage administration of EtOH (1.5, 2.5, or 5.0 g/kg) to rat dams on day 5, 8, 10, 12, and 15 of pregnancy dose-dependently reduced female/male offspring ratios (largely through decreased numbers of female offspring) and offspring body weights. FAE (2.5 g/kg) rats tested on postnatal days (P) 25-32 also exhibited increased anxiety and reduced pentylenetetrazol (PTZ)-induced seizure threshold. Patch-clamp recordings from dentate gyrus granule cells (DGCs) in hippocampal slices from FAE (2.5 g/kg) rats at P25-35 revealed reduced sensitivity of GABAergic miniature inhibitory postsynaptic currents (mIPSCs) and tonic current (Itonic) to potentiation by zolpidem (0.3 μM). Interestingly, potentiation of mIPSCs by gaboxadol increased, while potentiation of Itonic decreased in DGCs from FAE rats. Co-administration of EtOH (1.5 or 2.5 g/kg) with DHM (1.0 mg/kg) in pregnant dams prevented all of the behavioral, physiological, and pharmacological alterations observed in FAE offspring. DHM administration alone in pregnant rats had no adverse effect on litter size, progeny weight, anxiety level, PTZ seizure threshold, or DGC GABAAR function. Our results indicate that FAE induces long-lasting alterations in physiology, behavior, and hippocampal GABAAR function and that these deficits are prevented by DHM co-treatment of EtOH-exposed dams. The absence of adverse side effects and the ability of DHM to prevent FAE consequences suggest that DHM is an attractive candidate for development as a treatment for prevention of fetal alcohol spectrum disorders.
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72
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Circuit dynamics of adaptive and maladaptive behaviour. Nature 2014; 505:309-17. [PMID: 24429629 DOI: 10.1038/nature12982] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 11/08/2013] [Indexed: 02/08/2023]
Abstract
The recent development of technologies for investigating specific components of intact biological systems has allowed elucidation of the neural circuitry underlying adaptive and maladaptive behaviours. Investigators are now able to observe and control, with high spatio-temporal resolution, structurally defined intact pathways along which electrical activity flows during and after the performance of complex behaviours. These investigations have revealed that control of projection-specific dynamics is well suited to modulating behavioural patterns that are relevant to a broad range of psychiatric diseases. Structural dynamics principles have emerged to provide diverse, unexpected and causal insights into the operation of intact and diseased nervous systems, linking form and function in the brain.
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Ikrar T, Guo N, He K, Besnard A, Levinson S, Hill A, Lee HK, Hen R, Xu X, Sahay A. Adult neurogenesis modifies excitability of the dentate gyrus. Front Neural Circuits 2013; 7:204. [PMID: 24421758 PMCID: PMC3872742 DOI: 10.3389/fncir.2013.00204] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 12/10/2013] [Indexed: 01/24/2023] Open
Abstract
Adult-born dentate granule neurons contribute to memory encoding functions of the dentate gyrus (DG) such as pattern separation. However, local circuit-mechanisms by which adult-born neurons partake in this process are poorly understood. Computational, neuroanatomical and electrophysiological studies suggest that sparseness of activation in the granule cell layer (GCL) is conducive for pattern separation. A sparse coding scheme is thought to facilitate the distribution of similar entorhinal inputs across the GCL to decorrelate overlapping representations and minimize interference. Here we used fast voltage-sensitive dye (VSD) imaging combined with laser photostimulation and electrical stimulation to examine how selectively increasing adult DG neurogenesis influences local circuit activity and excitability. We show that DG of mice with more adult-born neurons exhibits decreased strength of neuronal activation and more restricted excitation spread in GCL while maintaining effective output to CA3c. Conversely, blockade of adult hippocampal neurogenesis changed excitability of the DG in the opposite direction. Analysis of GABAergic inhibition onto mature dentate granule neurons in the DG of mice with more adult-born neurons shows a modest readjustment of perisomatic inhibitory synaptic gain without changes in overall inhibitory tone, presynaptic properties or GABAergic innervation pattern. Retroviral labeling of connectivity in mice with more adult-born neurons showed increased number of excitatory synaptic contacts of adult-born neurons onto hilar interneurons. Together, these studies demonstrate that adult hippocampal neurogenesis modifies excitability of mature dentate granule neurons and that this non-cell autonomous effect may be mediated by local circuit mechanisms such as excitatory drive onto hilar interneurons. Modulation of DG excitability by adult-born dentate granule neurons may enhance sparse coding in the GCL to influence pattern separation.
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Affiliation(s)
- Taruna Ikrar
- Department of Anatomy and Neurobiology, School of Medicine, University of California Irvine, CA, USA
| | - Nannan Guo
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School Boston, MA, USA
| | - Kaiwen He
- Department of Biology, University of Maryland College Park, MD, USA ; The Solomon H. Snyder Department of Neuroscience, The Zanvyl-Krieger Mind/Brain Institute, Johns Hopkins University Baltimore, MD, USA
| | - Antoine Besnard
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School Boston, MA, USA
| | - Sally Levinson
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School Boston, MA, USA
| | - Alexis Hill
- Division of Integrative Neuroscience, Departments of Neuroscience and Psychiatry, Department of Pharmacology, Columbia University New York, NY, USA
| | - Hey-Kyoung Lee
- Department of Biology, University of Maryland College Park, MD, USA ; The Solomon H. Snyder Department of Neuroscience, The Zanvyl-Krieger Mind/Brain Institute, Johns Hopkins University Baltimore, MD, USA
| | - Rene Hen
- Division of Integrative Neuroscience, Departments of Neuroscience and Psychiatry, Department of Pharmacology, Columbia University New York, NY, USA
| | - Xiangmin Xu
- Department of Anatomy and Neurobiology, School of Medicine, University of California Irvine, CA, USA ; Department of Biomedical Engineering, University of California Irvine, CA, USA
| | - Amar Sahay
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School Boston, MA, USA ; Harvard Stem Cell Institute, Harvard University Boston, MA, USA ; Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School Boston, MA, USA
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Hunt RF, Girskis KM, Rubenstein JL, Alvarez-Buylla A, Baraban SC. GABA progenitors grafted into the adult epileptic brain control seizures and abnormal behavior. Nat Neurosci 2013; 16:692-7. [PMID: 23644485 PMCID: PMC3665733 DOI: 10.1038/nn.3392] [Citation(s) in RCA: 220] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 03/26/2013] [Indexed: 01/16/2023]
Abstract
Impaired GABA-mediated neurotransmission has been implicated in many neurologic diseases, including epilepsy, intellectual disability and psychiatric disorders. We found that inhibitory neuron transplantation into the hippocampus of adult mice with confirmed epilepsy at the time of grafting markedly reduced the occurrence of electrographic seizures and restored behavioral deficits in spatial learning, hyperactivity and the aggressive response to handling. In the recipient brain, GABA progenitors migrated up to 1,500 μm from the injection site, expressed genes and proteins characteristic for interneurons, differentiated into functional inhibitory neurons and received excitatory synaptic input. In contrast with hippocampus, cell grafts into basolateral amygdala rescued the hyperactivity deficit, but did not alter seizure activity or other abnormal behaviors. Our results highlight a critical role for interneurons in epilepsy and suggest that interneuron cell transplantation is a powerful approach to halting seizures and rescuing accompanying deficits in severely epileptic mice.
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Affiliation(s)
- Robert F Hunt
- Epilepsy Research Laboratory, University of California, San Francisco, California, USA.
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75
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Apolipoprotein e sets the stage: response to injury triggers neuropathology. Neuron 2013; 76:871-85. [PMID: 23217737 DOI: 10.1016/j.neuron.2012.11.020] [Citation(s) in RCA: 256] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2012] [Indexed: 01/04/2023]
Abstract
Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer's disease and is associated with poor clinical outcome following traumatic brain injury and other neuropathological disorders. Protein instability and an isoform-specific apoE property called domain interaction are responsible for these neuropathological effects. ApoE4 is the most neurotoxic isoform and can induce neuropathology through various cellular pathways. Neuronal damage or stress induces apoE synthesis as part of the repair response; however, when apoE4 is expressed in neurons, its unique conformation makes it susceptible to proteolysis, resulting in the generation of neurotoxic fragments. These fragments cause pathological mitochondrial dysfunction and cytoskeletal alterations. Here, we review data supporting the hypothesis that apoE4 (> apoE3 > apoE2) has direct neurotoxic effects and highlight studies showing that blocking domain interaction reverses these detrimental effects.
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76
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Leung L, Andrews-Zwilling Y, Yoon SY, Jain S, Ring K, Dai J, Wang MM, Tong L, Walker D, Huang Y. Apolipoprotein E4 causes age- and sex-dependent impairments of hilar GABAergic interneurons and learning and memory deficits in mice. PLoS One 2012; 7:e53569. [PMID: 23300939 PMCID: PMC3534053 DOI: 10.1371/journal.pone.0053569] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2012] [Accepted: 12/03/2012] [Indexed: 11/25/2022] Open
Abstract
Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer's disease (AD). ApoE4 has sex-dependent effects, whereby the risk of developing AD is higher in apoE4-expressing females than males. However, the mechanism underlying the sex difference, in relation to apoE4, is unknown. Previous findings indicate that apoE4 causes age-dependent impairments of hilar GABAergic interneurons in female mice, leading to learning and memory deficits. Here, we investigate whether the detrimental effects of apoE4 on hilar GABAergic interneurons are sex-dependent using apoE knock-in (KI) mice across different ages. We found that in female apoE-KI mice, there was an age-dependent depletion of hilar GABAergic interneurons, whereby GAD67- or somatostatin-positive–but not NPY- or parvalbumin-positive–interneuron loss was exacerbated by apoE4. Loss of these neuronal populations was correlated with the severity of spatial learning deficits at 16 months of age in female apoE4-KI mice; however, this effect was not observed in female apoE3-KI mice. In contrast, we found an increase in the numbers of hilar GABAergic interneurons with advancing age in male apoE-KI mice, regardless of apoE genotype. Moreover, male apoE-KI mice showed a consistent ratio of hilar inhibitory GABAergic interneurons to excitatory mossy cells approximating 1.5 that is independent of apoE genotype and age, whereas female apoE-KI mice exhibited an age-dependent decrease in this ratio, which was exacerbated by apoE4. Interestingly, there are no apoE genotype effects on GABAergic interneurons in the CA1 and CA3 subregions of the hippocampus as well as the entorhinal and auditory cortexes. These findings suggest that the sex-dependent effects of apoE4 on developing AD is in part attributable to inherent sex-based differences in the numbers of hilar GABAergic interneurons, which is further modulated by apoE genotype.
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Affiliation(s)
- Laura Leung
- Gladstone Institute of Neurological Disease, San Francisco, California, United States of America
- Department of Neurology, University of California San Francisco, San Francisco, California, United States of America
| | - Yaisa Andrews-Zwilling
- Gladstone Institute of Neurological Disease, San Francisco, California, United States of America
- Department of Neurology, University of California San Francisco, San Francisco, California, United States of America
| | - Seo Yeon Yoon
- Gladstone Institute of Neurological Disease, San Francisco, California, United States of America
| | - Sachi Jain
- Gladstone Institute of Neurological Disease, San Francisco, California, United States of America
- Biomedical Sciences Graduate Program, University of California San Francisco, San Francisco, California, United States of America
| | - Karen Ring
- Gladstone Institute of Neurological Disease, San Francisco, California, United States of America
- Biomedical Sciences Graduate Program, University of California San Francisco, San Francisco, California, United States of America
| | - Jessica Dai
- Gladstone Institute of Neurological Disease, San Francisco, California, United States of America
| | - Max Mu Wang
- Gladstone Institute of Neurological Disease, San Francisco, California, United States of America
| | - Leslie Tong
- Gladstone Institute of Neurological Disease, San Francisco, California, United States of America
- Biomedical Sciences Graduate Program, University of California San Francisco, San Francisco, California, United States of America
| | - David Walker
- Gladstone Institute of Neurological Disease, San Francisco, California, United States of America
- Gladstone Institute of Cardiovascular Disease, San Francisco, California, United States of America
| | - Yadong Huang
- Gladstone Institute of Neurological Disease, San Francisco, California, United States of America
- Gladstone Institute of Cardiovascular Disease, San Francisco, California, United States of America
- Department of Neurology, University of California San Francisco, San Francisco, California, United States of America
- Department of Pathology, University of California San Francisco, San Francisco, California, United States of America
- Biomedical Sciences Graduate Program, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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77
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Yu K, Wang J, Deng B, Wei X. Synchronization of neuron population subject to steady DC electric field induced by magnetic stimulation. Cogn Neurodyn 2012; 7:237-52. [PMID: 24427204 DOI: 10.1007/s11571-012-9233-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 10/31/2012] [Accepted: 12/01/2012] [Indexed: 12/18/2022] Open
Abstract
Electric fields, which are ubiquitous in the context of neurons, are induced either by external electromagnetic fields or by endogenous electric activities. Clinical evidences point out that magnetic stimulation can induce an electric field that modulates rhythmic activity of special brain tissue, which are associated with most brain functions, including normal and pathological physiological mechanisms. Recently, the studies about the relationship between clinical treatment for psychiatric disorders and magnetic stimulation have been investigated extensively. However, further development of these techniques is limited due to the lack of understanding of the underlying mechanisms supporting the interaction between the electric field induced by magnetic stimulus and brain tissue. In this paper, the effects of steady DC electric field induced by magnetic stimulation on the coherence of an interneuronal network are investigated. Different behaviors have been observed in the network with different topologies (i.e., random and small-world network, modular network). It is found that the coherence displays a peak or a plateau when the induced electric field varies between the parameter range we defined. The coherence of the neuronal systems depends extensively on the network structure and parameters. All these parameters play a key role in determining the range for the induced electric field to synchronize network activities. The presented results could have important implications for the scientific theoretical studies regarding the effects of magnetic stimulation on human brain.
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Affiliation(s)
- Kai Yu
- School of Electrical Engineering and Automation, Tianjin University, Tianjin, 300072 People's Republic of China
| | - Jiang Wang
- School of Electrical Engineering and Automation, Tianjin University, Tianjin, 300072 People's Republic of China
| | - Bin Deng
- School of Electrical Engineering and Automation, Tianjin University, Tianjin, 300072 People's Republic of China
| | - Xile Wei
- School of Electrical Engineering and Automation, Tianjin University, Tianjin, 300072 People's Republic of China
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