101
|
Montembeault M, Rouleau I, Provost JS, Brambati SM. Altered Gray Matter Structural Covariance Networks in Early Stages of Alzheimer's Disease. Cereb Cortex 2015; 26:2650-62. [PMID: 25994962 DOI: 10.1093/cercor/bhv105] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Clinical symptoms observed in Alzheimer's disease (AD) patients may reflect variations within specific large-scale brain networks, modeling AD as a disconnection syndrome. The present magnetic resonance imaging study aims to compare the organization of gray matter structural covariance networks between 109 cognitively unimpaired controls (CTRL) and 109 AD patients positive to beta-amyloid at the early stages of the disease, using voxel-based morphometry. The default-mode network (DMN; medial temporal lobe subsystem) was less extended in AD patients in comparison with CTRL, with a significant decrease in the structural association between the entorhinal cortex and the medial prefrontal and the dorsolateral prefrontal cortices. The DMN (midline core subsystem) was also less extended in AD patients. Trends toward increased structural association were observed in the salience and executive control networks. The observed changes suggest that early disruptions in structural association between heteromodal association cortices and the entorhinal cortex could contribute to an isolation of the hippocampal formation, potentially giving rise to the clinical hallmark of AD, progressive memory impairment. It also provides critical support to the hypothesis that the reduced connectivity within the DMN in early AD is accompanied by an enhancement of connectivity in the salience and executive control networks.
Collapse
Affiliation(s)
- Maxime Montembeault
- Centre de recherche de l'Institut universitaire de gériatrie de Montréal, Montréal, QC, Canada H3W 1W5 Département de psychologie, Université de Montréal, Montréal, QC, Canada H3C 3J7
| | - Isabelle Rouleau
- Département de psychologie, Université du Québec à Montréal (UQAM), Montréal, QC, Canada H3C 3P8
| | - Jean-Sébastien Provost
- Centre de recherche de l'Institut universitaire de gériatrie de Montréal, Montréal, QC, Canada H3W 1W5 Département de psychologie, Université de Montréal, Montréal, QC, Canada H3C 3J7
| | - Simona Maria Brambati
- Centre de recherche de l'Institut universitaire de gériatrie de Montréal, Montréal, QC, Canada H3W 1W5 Département de psychologie, Université de Montréal, Montréal, QC, Canada H3C 3J7
| | | |
Collapse
|
102
|
Mathur R, Ince PG, Minett T, Garwood CJ, Shaw PJ, Matthews FE, Brayne C, Simpson JE, Wharton SB. A reduced astrocyte response to β-amyloid plaques in the ageing brain associates with cognitive impairment. PLoS One 2015; 10:e0118463. [PMID: 25707004 PMCID: PMC4338046 DOI: 10.1371/journal.pone.0118463] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 12/18/2014] [Indexed: 12/18/2022] Open
Abstract
Aims β-amyloid (Aβ) plaques are a key feature of Alzheimer’s disease pathology but correlate poorly with dementia. They are associated with astrocytes which may modulate the effect of Aβ-deposition on the neuropil. This study characterised the astrocyte response to Aβ plaque subtypes, and investigated their association with cognitive impairment. Methods Aβ plaque subtypes were identified in the cingulate gyrus using dual labelling immunohistochemistry to Aβ and GFAP+ astrocytes, and quantitated in two cortical areas: the area of densest plaque burden and the deep cortex near the white matter border (layer VI). Three subtypes were defined for both diffuse and compact plaques (also known as classical or core-plaques): Aβ plaque with (1) no associated astrocytes, (2) focal astrogliosis or (3) circumferential astrogliosis. Results In the area of densest burden, diffuse plaques with no astrogliosis (β = -0.05, p = 0.001) and with focal astrogliosis (β = -0.27, p = 0.009) significantly associated with lower MMSE scores when controlling for sex and age at death. In the deep cortex (layer VI), both diffuse and compact plaques without astrogliosis associated with lower MMSE scores (β = -0.15, p = 0.017 and β = -0.81, p = 0.03, respectively). Diffuse plaques with no astrogliosis in layer VI related to dementia status (OR = 1.05, p = 0.025). In the area of densest burden, diffuse plaques with no astrogliosis or with focal astrogliosis associated with increasing Braak stage (β = 0.01, p<0.001 and β = 0.07, p<0.001, respectively), and ApoEε4 genotype (OR = 1.02, p = 0.001 and OR = 1.10, p = 0.016, respectively). In layer VI all plaque subtypes associated with Braak stage, and compact amyloid plaques with little and no associated astrogliosis associated with ApoEε4 genotype (OR = 1.50, p = 0.014 and OR = 0.10, p = 0.003, respectively). Conclusions Reactive astrocytes in close proximity to either diffuse or compact plaques may have a neuroprotective role in the ageing brain, and possession of at least one copy of the ApoEε4 allele impacts the astroglial response to Aβ plaques.
Collapse
Affiliation(s)
- Ryan Mathur
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, England, United Kingdom
| | - Paul G. Ince
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, England, United Kingdom
| | - Thais Minett
- Institute of Public Health, University of Cambridge, Cambridge, England, United Kingdom
| | - Claire J. Garwood
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, England, United Kingdom
| | - Pamela J. Shaw
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, England, United Kingdom
| | | | - Carol Brayne
- Institute of Public Health, University of Cambridge, Cambridge, England, United Kingdom
| | - Julie E. Simpson
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, England, United Kingdom
- * E-mail:
| | - Stephen B. Wharton
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, England, United Kingdom
| | | |
Collapse
|
103
|
Kato T, Konishi Y, Shimohama S, Beach TG, Akatsu H, Tooyama I. Alpha1-chimaerin, a Rac1 GTPase-activating protein, is expressed at reduced mRNA levels in the brain of Alzheimer's disease patients. Neurosci Lett 2015; 591:19-24. [PMID: 25676811 PMCID: PMC4382517 DOI: 10.1016/j.neulet.2015.02.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 02/03/2015] [Accepted: 02/06/2015] [Indexed: 12/21/2022]
Abstract
Alpha1-chimaerin is a GTPase-activating protein (GAP) for Rac1, a member of the Rho small GTPase family, whose action leads to the inactivation of Rac1. Rac1 activity is upregulated in Alzheimer's disease, but little is known about the role of α1-chimaerin. In this study, we investigated the expression and localization of α1-chimaerin mRNA in postmortem human brains from patients with Alzheimer's disease and control subjects. In situ hybridization studies demonstrated that α1-chimaerin was expressed by neurons in the neo-cortex of the temporal lobe and the hippocampus of both controls and Alzheimer's disease cases, with the signal intensity dramatically decreased in patients with Alzheimer's disease. Real-time PCR analysis confirmed a significant reduction of α1-chimaerin mRNA expression in the temporal cortex of Alzheimer's disease cases. In contrast, α2-chimaerin mRNA levels showed no significant difference between the groups. The present study showed reduced α1-chimaerin expression in the brain of Alzheimer's disease cases, suggesting a role in the upregulation of Rac1 activity during the disease process.
Collapse
Affiliation(s)
- Tomoko Kato
- Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu 520-2192, Japan
| | - Yoshihiro Konishi
- Department of Clinical Research, Nishi-tottori National Hospital, Tottori 689-0202, Japan
| | - Shun Shimohama
- Department of Neurology, Sapporo Medical University, Sapporo 060-8556, Japan
| | - Thomas G Beach
- Banner Sun Health Research Institute, Sun City, AZ 85372, USA
| | - Hiroyasu Akatsu
- Department of Community-Based Medical Education, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
| | - Ikuo Tooyama
- Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu 520-2192, Japan.
| |
Collapse
|
104
|
Abstract
In the past decades, a large number of neuropeptides with unknown functions have been identified in the brain. Among the newly discovered peptides, nociceptin or orphanin-FQ (N/OFQ) peptide has attracted considerable attention because of its sequence homology with the opioid peptide family. N/OFQ and its cognate receptor (NOP receptor) are distributed widely in the mammalian central nervous system, though particularly intense expression is found in corticolimbic structures. Such distinctive pattern of expression suggests a key role of N/OFQ system in higher brain functions, such as cognition and emotion. In this chapter, we will outline the findings supporting the role played by N/OFQ and NOP receptors in learning and memory and discuss the underlying mechanisms.
Collapse
|
105
|
Dlg5 regulates dendritic spine formation and synaptogenesis by controlling subcellular N-cadherin localization. J Neurosci 2014; 34:12745-61. [PMID: 25232112 DOI: 10.1523/jneurosci.1280-14.2014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Most excitatory synapses in the mammalian brain are formed on dendritic spines, and spine density has a profound impact on synaptic transmission, integration, and plasticity. Membrane-associated guanylate kinase (MAGUK) proteins are intracellular scaffolding proteins with well established roles in synapse function. However, whether MAGUK proteins are required for the formation of dendritic spines in vivo is unclear. We isolated a novel disc large-5 (Dlg5) allele in mice, Dlg5(LP), which harbors a missense mutation in the DLG5 SH3 domain, greatly attenuating its ability to interact with the DLG5 GUK domain. We show here that DLG5 is a MAGUK protein that regulates spine formation, synaptogenesis, and synaptic transmission in cortical neurons. DLG5 regulates synaptogenesis by enhancing the cell surface localization of N-cadherin, revealing a key molecular mechanism for regulating the subcellular localization of this cell adhesion molecule during synaptogenesis.
Collapse
|
106
|
Henriques AG, Oliveira JM, Carvalho LP, da Cruz E Silva OAB. Aβ Influences Cytoskeletal Signaling Cascades with Consequences to Alzheimer's Disease. Mol Neurobiol 2014; 52:1391-1407. [PMID: 25344315 DOI: 10.1007/s12035-014-8913-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 09/28/2014] [Indexed: 01/16/2023]
Abstract
Abnormal signal transduction events can impact upon the cytoskeleton, affecting the actin and microtubule networks with direct relevance to Alzheimer's disease (AD). Cytoskeletal anomalies, in turn, promote atypical neuronal responses, with consequences for cellular organization and function. Neuronal cytoskeletal modifications in AD include neurofibrillary tangles, which result from aggregates of hyperphosphorylated tau protein. The latter is a microtubule (MT)-binding protein, whose abnormal phosphorylation leads to MT instability and consequently provokes irregularities in the neuronal trafficking pathways. Early stages of AD are also characterized by synaptic dysfunction and loss of dendritic spines, which correlate with cognitive deficit and impaired brain function. Actin dynamics has a prominent role in maintaining spine plasticity and integrity, thus providing the basis for memory and learning processes. Hence, factors that disrupt both actin and MT network dynamics will compromise neuronal function and survival. The peptide Aβ is the major component of senile plaques and has been described as a pivotal mediator of neuronal dystrophy and synaptic loss in AD. Here, we review Aβ-mediated effects on both MT and actin networks and focus on the relevance of the elicited cytoskeletal signaling events targeted in AD pathology.
Collapse
Affiliation(s)
- Ana Gabriela Henriques
- Laboratório de Neurociências e Sinalização, Centro de Biologia Celular, SACS, Universidade de Aveiro, 3810-193, Aveiro, Portugal
| | - Joana Machado Oliveira
- Laboratório de Neurociências e Sinalização, Centro de Biologia Celular, SACS, Universidade de Aveiro, 3810-193, Aveiro, Portugal
| | - Liliana Patrícia Carvalho
- Laboratório de Neurociências e Sinalização, Centro de Biologia Celular, SACS, Universidade de Aveiro, 3810-193, Aveiro, Portugal
| | - Odete A B da Cruz E Silva
- Laboratório de Neurociências e Sinalização, Centro de Biologia Celular, SACS, Universidade de Aveiro, 3810-193, Aveiro, Portugal.
| |
Collapse
|
107
|
Segal M, Korkotian E. Endoplasmic reticulum calcium stores in dendritic spines. Front Neuroanat 2014; 8:64. [PMID: 25071469 PMCID: PMC4089118 DOI: 10.3389/fnana.2014.00064] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 06/23/2014] [Indexed: 12/14/2022] Open
Abstract
Despite decades of research, the role of calcium stores in dendritic spines structure, function and plasticity is still debated. The reasons for this may have to do with the multitude of overlapping calcium handling machineries in the neuron, including stores, voltage and ligand gated channels, pumps and transporters. Also, different cells in the brain are endowed with calcium stores that are activated by different receptor types, and their differential compartmentalization in dendrites, spines and presynaptic terminals complicates their analysis. In the present review we address several key issues, including the role of calcium stores in synaptic plasticity, their role during development, in stress and in neurodegenerative diseases. Apparently, there is increasing evidence for a crucial role of calcium stores, especially of the ryanodine species, in synaptic plasticity and neuronal survival.
Collapse
Affiliation(s)
- Menahem Segal
- Department of Neurobiology, The Weizman Institute Rehovot, Israel
| | - Eduard Korkotian
- Department of Neurobiology, The Weizman Institute Rehovot, Israel
| |
Collapse
|
108
|
Bellot A, Guivernau B, Tajes M, Bosch-Morató M, Valls-Comamala V, Muñoz FJ. The structure and function of actin cytoskeleton in mature glutamatergic dendritic spines. Brain Res 2014; 1573:1-16. [DOI: 10.1016/j.brainres.2014.05.024] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 05/12/2014] [Accepted: 05/13/2014] [Indexed: 12/01/2022]
|
109
|
Schafer DP, Lehrman EK, Heller CT, Stevens B. An engulfment assay: a protocol to assess interactions between CNS phagocytes and neurons. J Vis Exp 2014. [PMID: 24962472 DOI: 10.3791/51482] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Phagocytosis is a process in which a cell engulfs material (entire cell, parts of a cell, debris, etc.) in its surrounding extracellular environment and subsequently digests this material, commonly through lysosomal degradation. Microglia are the resident immune cells of the central nervous system (CNS) whose phagocytic function has been described in a broad range of conditions from neurodegenerative disease (e.g., beta-amyloid clearance in Alzheimer's disease) to development of the healthy brain (e.g., synaptic pruning)(1-6). The following protocol is an engulfment assay developed to visualize and quantify microglia-mediated engulfment of presynaptic inputs in the developing mouse retinogeniculate system(7). While this assay was used to assess microglia function in this particular context, a similar approach may be used to assess other phagocytes throughout the brain (e.g., astrocytes) and the rest of the body (e.g., peripheral macrophages) as well as other contexts in which synaptic remodeling occurs (e.g. ,brain injury/disease).
Collapse
Affiliation(s)
- Dorothy P Schafer
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School;
| | - Emily K Lehrman
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School
| | - Christopher T Heller
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School
| | - Beth Stevens
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School
| |
Collapse
|
110
|
Sun S, Zhang H, Liu J, Popugaeva E, Xu NJ, Feske S, White CL, Bezprozvanny I. Reduced synaptic STIM2 expression and impaired store-operated calcium entry cause destabilization of mature spines in mutant presenilin mice. Neuron 2014; 82:79-93. [PMID: 24698269 DOI: 10.1016/j.neuron.2014.02.019] [Citation(s) in RCA: 210] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/02/2014] [Indexed: 12/14/2022]
Abstract
Mushroom dendritic spine structures are essential for memory storage, and the loss of mushroom spines may explain memory defects in Alzheimer's disease (AD). Here we show a significant reduction in the fraction of mushroom spines in hippocampal neurons from the presenilin-1 M146V knockin (KI) mouse model of familial AD (FAD). The stabilization of mushroom spines depends on STIM2-mediated neuronal store-operated calcium influx (nSOC) and continuous activity of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). We demonstrate that STIM2-nSOC-CaMKII pathway is compromised in KI neurons, in aging neurons, and in sporadic AD brains due to downregulation of STIM2 protein. We further establish that overexpression of STIM2 rescues synaptic nSOC, CaMKII activity, and mushroom spine loss in KI neurons. Our results identify STIM2-nSOC-CaMKII synaptic maintenance pathway as a novel potential therapeutic target for treatment of AD and age-related memory decline.
Collapse
Affiliation(s)
- Suya Sun
- Department of Physiology, UT Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
| | - Hua Zhang
- Department of Physiology, UT Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
| | - Jie Liu
- Department of Physiology, UT Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
| | - Elena Popugaeva
- Laboratory of Molecular Neurodegeneration, Saint Petersburg State Polytechnical University, Saint Petersburg, 195251, Russia
| | - Nan-Jie Xu
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Stefan Feske
- Department of Pathology, New York University Langone Medical Center, New York, NY 10016, USA
| | - Charles L White
- Department of Pathology, UT Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
| | - Ilya Bezprozvanny
- Department of Physiology, UT Southwestern Medical Center at Dallas, Dallas, TX 75390, USA; Laboratory of Molecular Neurodegeneration, Saint Petersburg State Polytechnical University, Saint Petersburg, 195251, Russia.
| |
Collapse
|
111
|
Wang R, Palavicini JP, Wang H, Maiti P, Bianchi E, Xu S, Lloyd BN, Dawson-Scully K, Kang DE, Lakshmana MK. RanBP9 overexpression accelerates loss of dendritic spines in a mouse model of Alzheimer's disease. Neurobiol Dis 2014; 69:169-79. [PMID: 24892886 DOI: 10.1016/j.nbd.2014.05.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 04/14/2014] [Accepted: 05/22/2014] [Indexed: 01/08/2023] Open
Abstract
We previously demonstrated that RanBP9 overexpression increased Aβ generation and amyloid plaque burden, subsequently leading to robust reductions in the levels of several synaptic proteins as well as deficits in the learning and memory skills in a mouse model of Alzheimer's disease (AD). In the present study, we found striking reduction of spinophilin-immunoreactive puncta (52%, p<0.001) and spinophilin area (62.5%, p<0.001) in the primary cortical neurons derived from RanBP9 transgenic mice (RanBP9-Tg) compared to wild-type (WT) neurons. Similar results were confirmed in WT cortical neurons transfected with EGFP-RanBP9. At 6-months of age, the total spine density in the cortex of RanBP9 single transgenic, APΔE9 double transgenic and APΔE9/RanBP9 triple transgenic mice was similar to WT mice. However, in the hippocampus the spine density was significantly reduced (27%, p<0.05) in the triple transgenic mice compared to WT mice due to reduced number of thin spines (33%, p<0.05) and mushroom spines (22%, p<0.05). This suggests that RanBP9 overexpression in the APΔE9 mice accelerates loss of spines and that the hippocampus is more vulnerable. At 12-months of age, the cortex showed significant reductions in total spine density in the RanBP9 (22%, p<0.05), APΔE9 (19%, p<0.05) and APΔE9/RanBP9 (33%, p<0.01) mice compared to WT controls due to reductions in mushroom and thin spines. Similarly, in the hippocampus the total spine density was reduced in the RanBP9 (23%, p<0.05), APΔE9 (26%, p<0.05) and APΔE9/RanBP9 (39%, p<0.01) mice due to reductions in thin and mushroom spines. Most importantly, RanBP9 overexpression in the APΔE9 mice further exacerbated the reductions in spine density in both the cortex (14%, p<0.05) and the hippocampus (16%, p<0.05). Because dendritic spines are considered physical traces of memory, loss of spines due to RanBP9 provided the physical basis for the learning and memory deficits. Since RanBP9 protein levels are increased in AD brains, RanBP9 might play a crucial role in the loss of spines and synapses in AD.
Collapse
Affiliation(s)
- Ruizhi Wang
- Section of Neurobiology, Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port Saint Lucie, FL 34987, USA
| | - Juan Pablo Palavicini
- Section of Neurobiology, Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port Saint Lucie, FL 34987, USA
| | - Hongjie Wang
- Section of Neurobiology, Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port Saint Lucie, FL 34987, USA
| | - Panchanan Maiti
- University of Tennessee Health Science Center, Department of Neurology, 415 Link Building, TN, USA
| | - Elisabetta Bianchi
- Laboratory of Immuneregulation, Department of Immunology, Institut Pasteur, 25 rue du Dr. Roux, 75724 Paris, France
| | - Shaohua Xu
- Florida Institute of Technology, 150 West University Blvd, Melbourne, FL 32901, USA
| | - B N Lloyd
- Department of Biological Sciences, Charles E. Schmidt College of Science, Florida Atlantic University, Boca Raton, FL, USA
| | - Ken Dawson-Scully
- Department of Biological Sciences, Charles E. Schmidt College of Science, Florida Atlantic University, Boca Raton, FL, USA
| | - David E Kang
- Department of Molecular Medicine, USF Health Byrd Alzheimer's Institute, 4001 E. Fletcher Ave. - MDC36, Tampa, FL 33612, USA
| | - Madepalli K Lakshmana
- Section of Neurobiology, Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port Saint Lucie, FL 34987, USA.
| |
Collapse
|
112
|
Deng X, Li M, Ai W, He L, Lu D, Patrylo PR, Cai H, Luo X, Li Z, Yan X. Lipolysaccharide-Induced Neuroinflammation Is Associated with Alzheimer-Like Amyloidogenic Axonal Pathology and Dendritic Degeneration in Rats. ADVANCES IN ALZHEIMER'S DISEASE 2014; 3:78-93. [PMID: 25360394 PMCID: PMC4211261 DOI: 10.4236/aad.2014.32009] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Chronic neuroinflammation is thought to play an etiological role in Alzheimer's disease (AD), which is characterized pathologically by amyloid and tau formation, as well as neuritic dystrophy and synaptic degeneration. The causal relationship between these pathological events is a topic of ongoing research and discussion. Recent data from transgenic AD models point to a tight spatiotemporal link between neuritic and amyloid pathology, with the obligatory enzyme for β-amyloid (Aβ) production, namely β-secretase-1 (BACE1), is overexpressed in axon terminals undergoing dystrophic change. However, the axonal pathology inherent with BACE1 elevation seen in transgenic AD mice may be secondary to increased soluble Aβ in these genetically modified animals. Here we explored the occurrence of the AD-like axonal and dendritic pathology in adult rat brain affected by LPS-induced chronic neuroinflammation. Unilateral intracerebral LPS injection induced prominent inflammatory response in glial cells in the ipsilateral cortex and hippocampal formation. BACE1 protein levels were elevated the ipsilateral hippocampal lysates in the LPS treated animals relative to controls. BACE1 immunoreactive dystrophic axons appeared in the LPS-treated ipsilateral cortex and hippocampal formation, colocalizing with increased β-amyloid precursor protein and Aβ antibody (4G8) immunolabeling. Quantitative Golgi studies revealed reduction of dendritic branching points and spine density on cortical layer III and hippocampal CA3 pyramidal neurons in the LPS-treated ipsilateral cerebrum. These findings suggest that Alzheimer-like amyloidogenic axonal pathology and dendritic degeneration occur in wildtype mammalian brain in partnership with neuroinflammation following LPS injection.
Collapse
Affiliation(s)
- Xiaohua Deng
- Department of Anatomy and Neurobiology, Central South University School of Basic Medical Science, Changsha, China
| | - Meili Li
- Department of Anatomy and Neurobiology, Central South University School of Basic Medical Science, Changsha, China
| | - Weiming Ai
- Department of Anatomy and Neurobiology, Central South University School of Basic Medical Science, Changsha, China
- Department of Nursing in Internal Medicine, School of Nursing, Xiangtan Vocational and Technical College, Xiangtan, China
| | - Lixin He
- Department of Anatomy and Neurobiology, Central South University School of Basic Medical Science, Changsha, China
- Department of Anatomy and Physiology, School of Nursing, Xiangtan Vocational and technical College, Xiangtan, China
| | - Dahua Lu
- Department of Anatomy and Neurobiology, Central South University School of Basic Medical Science, Changsha, China
| | - Peter R. Patrylo
- Departments of Physiology, Anatomy and Center for Integrated Research in Cognitive and Neural Sciences, Southern Illinois University Carbondale, Carbondale, USA
| | - Huaibin Cai
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, USA
| | - Xuegang Luo
- Department of Anatomy and Neurobiology, Central South University School of Basic Medical Science, Changsha, China
| | - Zhiyuan Li
- Department of Anatomy and Neurobiology, Central South University School of Basic Medical Science, Changsha, China
| | - Xiaoxin Yan
- Department of Anatomy and Neurobiology, Central South University School of Basic Medical Science, Changsha, China
| |
Collapse
|
113
|
Szepesi Z, Hosy E, Ruszczycki B, Bijata M, Pyskaty M, Bikbaev A, Heine M, Choquet D, Kaczmarek L, Wlodarczyk J. Synaptically released matrix metalloproteinase activity in control of structural plasticity and the cell surface distribution of GluA1-AMPA receptors. PLoS One 2014; 9:e98274. [PMID: 24853857 PMCID: PMC4031140 DOI: 10.1371/journal.pone.0098274] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 04/29/2014] [Indexed: 01/13/2023] Open
Abstract
Synapses are particularly prone to dynamic alterations and thus play a major role in neuronal plasticity. Dynamic excitatory synapses are located at the membranous neuronal protrusions called dendritic spines. The ability to change synaptic connections involves both alterations at the morphological level and changes in postsynaptic receptor composition. We report that endogenous matrix metalloproteinase (MMP) activity promotes the structural and functional plasticity of local synapses by its effect on glutamate receptor mobility and content. We used live imaging of cultured hippocampal neurons and quantitative morphological analysis to show that chemical long-term potentiation (cLTP) induces the permanent enlargement of a subset of small dendritic spines in an MMP-dependent manner. We also used a superresolution microscopy approach and found that spine expansion induced by cLTP was accompanied by MMP-dependent immobilization and synaptic accumulation as well as the clustering of GluA1-containing AMPA receptors. Altogether, our results reveal novel molecular and cellular mechanisms of synaptic plasticity.
Collapse
Affiliation(s)
- Zsuzsanna Szepesi
- Department of Molecular and Cellular Neurobiology, Nencki Institute, Warsaw, Poland
| | - Eric Hosy
- Dynamic Organization and Function of Synapses, Interdisciplinary Institute for Neuroscience, Bordeaux, France
| | - Blazej Ruszczycki
- Department of Molecular and Cellular Neurobiology, Nencki Institute, Warsaw, Poland
| | - Monika Bijata
- Department of Molecular and Cellular Neurobiology, Nencki Institute, Warsaw, Poland
| | - Marta Pyskaty
- Department of Molecular and Cellular Neurobiology, Nencki Institute, Warsaw, Poland
| | - Arthur Bikbaev
- Department of Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Martin Heine
- Department of Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Daniel Choquet
- Dynamic Organization and Function of Synapses, Interdisciplinary Institute for Neuroscience, Bordeaux, France
| | - Leszek Kaczmarek
- Department of Molecular and Cellular Neurobiology, Nencki Institute, Warsaw, Poland
| | - Jakub Wlodarczyk
- Department of Molecular and Cellular Neurobiology, Nencki Institute, Warsaw, Poland
- * E-mail:
| |
Collapse
|
114
|
Remmers C, Sweet RA, Penzes P. Abnormal kalirin signaling in neuropsychiatric disorders. Brain Res Bull 2014; 103:29-38. [PMID: 24334022 PMCID: PMC3989394 DOI: 10.1016/j.brainresbull.2013.12.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 12/02/2013] [Accepted: 12/05/2013] [Indexed: 10/25/2022]
Abstract
Changes in dendritic spines structure and function play a critical role in a number of physiological processes, including synaptic transmission and plasticity, and are intimately linked to cognitive function. Alterations in dendritic spine morphogenesis occur in a number of neuropsychiatric disorders and likely underlie the cognitive and behavioral changes associated with these disorders. The neuronal guanine nucleotide exchange factor (GEF) kalirin is emerging as a key regulator of structural and functional plasticity at dendritic spines. Moreover, a series of recent studies have genetically and functionally linked kalirin signaling to several disorders, including schizophrenia and Alzheimer's disease. Kalirin signaling may thus represent a disease mechanism and provide a novel therapeutic target.
Collapse
Affiliation(s)
- Christine Remmers
- Department of Physiology, 303 E. Chicago Avenue, Chicago, IL 60611, USA
| | - Robert A Sweet
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA; VISN 4 Mental Illness Research, Education and Clinical Center, VA Pittsburgh Healthcare System, Pittsburgh, PA, USA
| | - Peter Penzes
- Department of Physiology, 303 E. Chicago Avenue, Chicago, IL 60611, USA; Department of Psychiatry and Behavioral Sciences, Northwestern University Feinberg School of Medicine, 303 E. Chicago Avenue, Chicago, IL 60611, USA.
| |
Collapse
|
115
|
Davis PR, Head E. Prevention approaches in a preclinical canine model of Alzheimer's disease: benefits and challenges. Front Pharmacol 2014; 5:47. [PMID: 24711794 PMCID: PMC3968758 DOI: 10.3389/fphar.2014.00047] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 02/28/2014] [Indexed: 12/30/2022] Open
Abstract
Aged dogs spontaneously develop many features of human aging and Alzheimer's disease (AD) including cognitive decline and neuropathology. In this review, we discuss age-dependent learning tasks, memory tasks, and functional measures that can be used in aged dogs for sensitive treatment outcome measures. Neuropathology that is linked to cognitive decline is described along with examples of treatment studies that show reduced neuropathology in aging dogs (dietary manipulations, behavioral enrichment, immunotherapy, and statins). Studies in canine show that multi-targeted approaches may be more beneficial than single pathway manipulations (e.g., antioxidants combined with behavioral enrichment). Aging canine studies show good predictive validity for human clinical trials outcomes (e.g., immunotherapy) and several interventions tested in dogs strongly support a prevention approach (e.g., immunotherapy and statins). Further, dogs are ideally suited for prevention studies as they the age because onset of cognitive decline and neuropathology strongly support longitudinal interventions that can be completed within a 3-5 year period. Disadvantages to using the canine model are that they lengthy, use labor-intensive comprehensive cognitive testing, and involve costly housing (almost as high as that of non-human primates). However, overall, using the dog as a preclinical model for testing preventive approaches for AD may complement work in rodents and non-human primates.
Collapse
Affiliation(s)
- Paulina R Davis
- Sanders-Brown Center on Aging, University of Kentucky Lexington, KY, USA ; Department of Molecular and Biomedical Pharmacology, University of Kentucky Lexington, KY, USA
| | - Elizabeth Head
- Sanders-Brown Center on Aging, University of Kentucky Lexington, KY, USA ; Department of Molecular and Biomedical Pharmacology, University of Kentucky Lexington, KY, USA
| |
Collapse
|
116
|
The case for involvement of spiroplasma in the pathogenesis of transmissible spongiform encephalopathies. J Neuropathol Exp Neurol 2014; 73:104-14. [PMID: 24423635 DOI: 10.1097/nen.0000000000000033] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Spiroplasma biofilm formation explains the role of these wall-less bacteria in the pathogenesis of transmissible spongiform encephalopathies (TSEs). Spiroplasma embedded in the biofilm polysaccharide matrix are markedly resistant to physical and chemical treatment, simulating the biologic properties of the TSE agent. Microcolonies of spiroplasma embedded in biofilm bound to clay are the likely mechanism of lateral transmission of scrapie in sheep and chronic wasting disease in deer via soil ingestion. Spiroplasma in biofilm bound to the stainless steel of surgical instruments may also cause iatrogenic transmission of Creutzfeldt-Jakob disease. Sessile spiroplasma in biofilm attach to the surface by curli-like fibrils, a functional amyloid that is important for spiroplasma entering cells. Curli fibers have been shown to interact with host proteins and initiate formation of a potentially toxic amyloid that multiplies by self-assembly. In TSE, this mechanism may explain how spiroplasma trigger the formation of prion amyloid. This possibility is supported by experiments that show spiroplasma produce α-synuclein in mammalian tissue cultures. The data linking spiroplasma to neurodegenerative diseases provide a rationale for developing diagnostic tests for TSE based on the presence of spiroplasma-specific proteins or nucleic acid. Research efforts should focus on this bacterium for development of therapeutic regimens for Creutzfeldt-Jakob disease.
Collapse
|
117
|
Mukherjee S, Kim S, Ramanan VK, Gibbons LE, Nho K, Glymour MM, Ertekin-Taner N, Montine TJ, Saykin AJ, Crane PK. Gene-based GWAS and biological pathway analysis of the resilience of executive functioning. Brain Imaging Behav 2014; 8:110-8. [PMID: 24072271 PMCID: PMC3944472 DOI: 10.1007/s11682-013-9259-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Resilience in executive functioning (EF) is characterized by high EF measured by neuropsychological test performance despite structural brain damage from neurodegenerative conditions. We previously reported single nucleotide polymorphism (SNP) genome-wide association study (GWAS) results for EF resilience. Here, we report gene- and pathway-based analyses of the same resilience phenotype, using an optimal SNP-set (Sequence) Kernel Association Test (SKAT) for gene-based analyses (conservative threshold for genome-wide significance = 0.05/18,123 = 2.8 × 10(-6)) and the gene-set enrichment package GSA-SNP for biological pathway analyses (False discovery rate (FDR) < 0.05). Gene-based analyses found a genome-wide significant association between RNASE13 and EF resilience (p = 1.33 × 10(-7)). Genetic pathways involved with dendritic/neuron spine, presynaptic membrane, postsynaptic density, etc., were enriched with association to EF resilience. Although replication of these results is necessary, our findings indicate the potential value of gene- and pathway-based analyses in research on determinants of cognitive resilience.
Collapse
Affiliation(s)
- Shubhabrata Mukherjee
- Department of Medicine, University of Washington, Box 359780, 325 Ninth Avenue, Seattle, WA, 98104, USA,
| | | | | | | | | | | | | | | | | | | |
Collapse
|
118
|
Sala C, Segal M. Dendritic spines: the locus of structural and functional plasticity. Physiol Rev 2014; 94:141-88. [PMID: 24382885 DOI: 10.1152/physrev.00012.2013] [Citation(s) in RCA: 338] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The introduction of high-resolution time lapse imaging and molecular biological tools has changed dramatically the rate of progress towards the understanding of the complex structure-function relations in synapses of central spiny neurons. Standing issues, including the sequence of molecular and structural processes leading to formation, morphological change, and longevity of dendritic spines, as well as the functions of dendritic spines in neurological/psychiatric diseases are being addressed in a growing number of recent studies. There are still unsettled issues with respect to spine formation and plasticity: Are spines formed first, followed by synapse formation, or are synapses formed first, followed by emergence of a spine? What are the immediate and long-lasting changes in spine properties following exposure to plasticity-producing stimulation? Is spine volume/shape indicative of its function? These and other issues are addressed in this review, which highlights the complexity of molecular pathways involved in regulation of spine structure and function, and which contributes to the understanding of central synaptic interactions in health and disease.
Collapse
|
119
|
RanBP9 overexpression reduces dendritic arbor and spine density. Neuroscience 2014; 265:253-62. [PMID: 24486966 DOI: 10.1016/j.neuroscience.2014.01.045] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Revised: 01/22/2014] [Accepted: 01/22/2014] [Indexed: 11/21/2022]
Abstract
RanBP9 is a multi-domain scaffolding protein known to integrate extracellular signaling with intracellular targets. We previously demonstrated that RanBP9 enhances Aβ generation and amyloid plaque burden which results in loss of specific pre- and postsynaptic proteins in vivo in a transgenic mouse model. Additionally, we showed that the levels of spinophilin, a marker of dendritic spines were inversely proportional to the RanBP9 protein levels within the synaptosomes isolated from AD brains. In the present study, we found reduced dendritic intersections within the layer 6 pyramidal neurons of the cortex as well as the hippocampus of RanBP9 transgenic mice compared to age-matched wild-type (WT) controls at 12 months of age but not at 6months. Similarly, the dendritic spine numbers were reduced in the cortex at only 12 months of age by 30% (p<0.01), but not at 6months. In the hippocampus also the spine densities were reduced at 12 months of age (38%, p<0.01) in the RanBP9 transgenic mice. Interestingly, the levels of phosphorylated form of cofilin, an actin binding protein that plays crucial role in the regulation of spine numbers were significantly decreased in the cortical synaptosomes at only 12months of age by 26% (p<0.01). In the hippocampal synaptosomes, the decrease in cofilin levels were 36% (p<0.01) at 12 months of age. Thus dendritic arbor and spine density were directly correlated to the levels of phosphorylated form of cofilin in the RanBP9 transgenic mice. Similarly, cortical synaptosomes showed a 20% (p<0.01) reduction in the levels of spinophilin in the RanBP9 transgenic mice. These results provided the physical basis for the loss of synaptic proteins by RanBP9 and most importantly it also explains the impaired spatial learning and memory skills previously observed in the RanBP9 transgenic mice.
Collapse
|
120
|
|
121
|
Zhang HY, Yamakawa YI, Matsuya Y, Toyooka N, Tohda C, Awale S, Li F, Kadota S, Tezuka Y. Synthesis of long-chain fatty acid derivatives as a novel anti-Alzheimer's agent. Bioorg Med Chem Lett 2013; 24:604-8. [PMID: 24360558 DOI: 10.1016/j.bmcl.2013.12.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 11/20/2013] [Accepted: 12/02/2013] [Indexed: 11/29/2022]
Abstract
In order to develop new drugs for Alzheimer's disease, we prepared 17 fatty acid derivatives with different chain lengths and different numbers and positions of double bonds by using Wittig reaction and stereospecific hydrogenation of triple bonds as key reactions. Among them, (4Z,15Z)-octadecadienoic acid (10) and (23Z,34Z)-heptatriacontadienoic acid (16) showed the most potent neurite outgrowth activities on Aβ(25-35)-treated rat cortical neurons, which activities were comparable to that of a positive control, NGF. Both fatty acids 10 and 16 possess two (Z)-double bonds at the n-3 and n-14 positions, which might be important for the neurite outgrowth activity.
Collapse
Affiliation(s)
- Hong-Yan Zhang
- Division of Natural Products Chemistry, Institute of Natural Medicine, University of Toyama, Sugitani 2630, Toyama 930-0194, Japan
| | - Yu-ichiro Yamakawa
- Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Sugitani 2630, Toyama 930-0194, Japan
| | - Yuji Matsuya
- Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Sugitani 2630, Toyama 930-0194, Japan
| | - Naoki Toyooka
- Graduate School of Science and Technology for Research, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan; Graduate School of Innovative Life Science, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan.
| | - Chihiro Tohda
- Division of Division of Neuromedical Science, Institute of Natural Medicine, University of Toyama, Sugitani 2630, Toyama 930-0194, Japan
| | - Suresh Awale
- Frontier Research Core for Life Sciences, University of Toyama, Sugitani 2630, Toyama 930-0194, Japan
| | - Feng Li
- Research Promotion Office, Joint Usage/Research Center for Science-Based Natural Medicine, Institute of Natural Medicine, University of Toyama, Sugitani 2630, Toyama 930-0194, Japan
| | - Shigetoshi Kadota
- Division of Natural Products Chemistry, Institute of Natural Medicine, University of Toyama, Sugitani 2630, Toyama 930-0194, Japan
| | - Yasuhiro Tezuka
- Division of Natural Products Chemistry, Institute of Natural Medicine, University of Toyama, Sugitani 2630, Toyama 930-0194, Japan.
| |
Collapse
|
122
|
Song JM, DiBattista AM, Sung YM, Ahn JM, Turner RS, Yang J, Pak DTS, Lee HK, Hoe HS. A tetra(ethylene glycol) derivative of benzothiazole aniline ameliorates dendritic spine density and cognitive function in a mouse model of Alzheimer's disease. Exp Neurol 2013; 252:105-13. [PMID: 24316432 DOI: 10.1016/j.expneurol.2013.11.023] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 10/25/2013] [Accepted: 11/22/2013] [Indexed: 11/19/2022]
Abstract
We recently reported that the tetra(ethylene glycol) derivative of benzothiazole aniline, BTA-EG4, acts as an amyloid-binding small molecule that promotes dendritic spine density and cognitive function in wild-type mice. This raised the possibility that BTA-EG4 may benefit the functional decline seen in Alzheimer's disease (AD). In the present study, we directly tested whether BTA-EG4 improves dendritic spine density and cognitive function in a well-established mouse model of AD carrying mutations in APP, PS1 and tau (APPswe;PS1M146V;tauP301L, 3xTg AD mice). We found that daily injections of BTA-EG4 for 2 weeks improved dendritic spine density and cognitive function of 3xTg AD mice in an age-dependent manner. Specifically, BTA-EG4 promoted both dendritic spine density and morphology alterations in cortical layers II/III and in the hippocampus at 6-10 months of age compared to vehicle-injected mice. However, at 13-16 months of age, only cortical spine density was improved without changes in spine morphology. The changes in dendritic spine density correlated with Ras activity, such that 6-10 month old BTA-EG4 injected 3xTg AD mice had increased Ras activity in the cortex and hippocampus, while 13-16 month old mice only trended toward an increase in Ras activity in the cortex. Finally, BTA-EG4 injected 3xTg AD mice at 6-10 months of age showed improved learning and memory; however, only minimal improvement was observed at 13-16 months of age. This behavioral improvement corresponds to a decrease in soluble Aβ 40 levels. Taken together, these findings suggest that BTA-EG4 may be beneficial in ameliorating the synaptic loss seen in early AD.
Collapse
Affiliation(s)
- Jung Min Song
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC 20057, USA
| | | | - You Me Sung
- College of Pharmacy, Seoul National University, South Korea
| | - Joo Myung Ahn
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC 20057, USA
| | - R Scott Turner
- Department of Neurology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Jerry Yang
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA
| | - Daniel T S Pak
- Department of Pharmacology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Hey-Kyoung Lee
- Department of Neuroscience, Johns Hopkins University, Baltimore, MD 20218, USA; Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Hyang-Sook Hoe
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC 20057, USA; Department of Neurology, Georgetown University Medical Center, Washington, DC 20057, USA.
| |
Collapse
|
123
|
Sheng M, Ertürk A. Long-term depression: a cell biological view. Philos Trans R Soc Lond B Biol Sci 2013; 369:20130138. [PMID: 24298141 DOI: 10.1098/rstb.2013.0138] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Recent studies of the molecular mechanisms of long-term depression (LTD) suggest a crucial role for the signalling pathways of apoptosis (programmed cell death) in the weakening and elimination of synapses and dendritic spines. With this backdrop, we suggest that LTD can be considered as the electrophysiological aspect of a larger cell biological programme of synapse involution, which uses localized apoptotic mechanisms to sculpt synapses and circuits without causing cell death.
Collapse
Affiliation(s)
- Morgan Sheng
- Department of Neuroscience, Genentech, Inc., , 1 DNA Way, South San Francisco, CA 94080, USA
| | | |
Collapse
|
124
|
Tau causes synapse loss without disrupting calcium homeostasis in the rTg4510 model of tauopathy. PLoS One 2013; 8:e80834. [PMID: 24278327 PMCID: PMC3835324 DOI: 10.1371/journal.pone.0080834] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 10/15/2013] [Indexed: 01/23/2023] Open
Abstract
Neurofibrillary tangles (NFTs) of tau are one of the defining hallmarks of Alzheimer’s disease (AD), and are closely associated with neuronal degeneration. Although it has been suggested that calcium dysregulation is important to AD pathogenesis, few studies have probed the link between calcium homeostasis, synapse loss and pathological changes in tau. Here we test the hypothesis that pathological changes in tau are associated with changes in calcium by utilizing in vivo calcium imaging in adult rTg4510 mice that exhibit severe tau pathology due to over-expression of human mutant P301L tau. We observe prominent dendritic spine loss without disruptions in calcium homeostasis, indicating that tangles do not disrupt this fundamental feature of neuronal health, and that tau likely induces spine loss in a calcium-independent manner.
Collapse
|
125
|
Lai WB, Wang BJ, Hu MK, Hsu WM, Her GM, Liao YF. Ligand-dependent activation of EphA4 signaling regulates the proteolysis of amyloid precursor protein through a Lyn-mediated pathway. Mol Neurobiol 2013; 49:1055-68. [PMID: 24217950 DOI: 10.1007/s12035-013-8580-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 10/24/2013] [Indexed: 11/27/2022]
Abstract
Alzheimer's disease is the most common dementia afflicting the elderly in modern society. This disease arises from the neurotoxicity elicited by abnormal aggregates of amyloid-β (Aβ) protein. Such aggregates form through the cleavage of amyloid precursor protein (APP) by β-secretase and the subsequent proteolysis of the APP C-terminal fragment (APP-βCTF or C99) by γ-secretase to yield Aβ and APP intracellular domain (AICD). Recent evidence suggests that C99 and AICD may exert harmful effects on cells, suggesting that the proteolytic products of APP, including Aβ, C99, and AICD, could play a pivotal role in neuronal viability. Here, we demonstrate that ligand-activated EphA4 signaling governs the proteostasis of C99, AICD, and Aβ, without significantly affecting γ-secretase activity. EphA4 induced accumulation of C99 and AICD through a Lyn-dependent pathway; activation of this pathway triggered phosphorylation of EphA4, resulting in positive feedback of C99 and AICD proteostasis. Inhibition of EphA4 by dasatinib, a receptor tyrosine kinase inhibitor, effectively suppressed C99 and AICD accumulation. Furthermore, EphA4 signaling controlled C99 and AICD proteolysis through the ubiquitin-proteasome system. In conclusion, we have identified an EphA4-Lyn pathway that is essential for the metabolism of APP and its proteolytic derivatives, thereby providing novel pharmacological targets for the development of anti-Aβ therapeutics for AD.
Collapse
Affiliation(s)
- Wei-Bin Lai
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
| | | | | | | | | | | |
Collapse
|
126
|
Dickins EM, Salinas PC. Wnts in action: from synapse formation to synaptic maintenance. Front Cell Neurosci 2013; 7:162. [PMID: 24223536 PMCID: PMC3819050 DOI: 10.3389/fncel.2013.00162] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 08/04/2013] [Indexed: 11/13/2022] Open
Abstract
A proper balance between synapse assembly and disassembly is crucial for the formation of functional neuronal circuits and synaptic plasticity in the adult brain. During development, synaptogenesis generates a vast excess of synapses, which are subsequently eliminated. Importantly, aberrant synaptic disassembly during development underpins many neurological disorders. Wnt secreted proteins are robust synaptogenic factors that regulate synapse assembly and function in the developing and mature brain. Recent studies show that Wnt blockade with the antagonist Dickkopf-1 (Dkk1) induces the rapid disassembly of synapses in mature neurons. Importantly, Dkk1 mediates synaptic loss induced by Amyloid-ß, a key pathogenic molecule in Alzheimer's disease (AD). These findings provide new insights into the potential contribution of dysfunctional Wnt signaling to synaptic loss observed in neurodegenerative diseases. In this review, we discuss the role of Wnt signaling in vertebrate synaptic assembly, function and maintenance, and consider how dysfunction of Wnt signaling could contribute to synaptic disassembly in neurodegenerative diseases such as AD.
Collapse
Affiliation(s)
- Ellen M Dickins
- Department of Cell and Developmental Biology, University College London London, UK
| | | |
Collapse
|
127
|
Crowe SE, Ellis-Davies GCR. In vivo characterization of a bigenic fluorescent mouse model of Alzheimer's disease with neurodegeneration. J Comp Neurol 2013; 521:2181-94. [PMID: 23348594 DOI: 10.1002/cne.23306] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 12/14/2012] [Accepted: 01/17/2013] [Indexed: 11/11/2022]
Abstract
The loss of cognitive function in Alzheimer's disease (AD) patients is strongly correlated with the loss of neurons in various regions of the brain. We have created a new fluorescent bigenic mouse model of AD by crossing "H-line" yellow fluorescent protein (YFP) mice with the 5xFAD mouse model, which we call the 5XY mouse model. The 5xFAD mouse has been shown to have significant loss of L5 pyramidal neurons by 12 months of age. These neurons are transgenically labeled with YFP in the 5XY mouse, which enable longitudinal imaging of structural changes. In the 5XY mice, we observed an appearance of axonal dystrophies, with two distinct morphologies in the early stages of the disease progression. Simple swelling dystrophies are transient in nature and are not directly associated with amyloid plaques. Rosette dystrophies are more complex structures that remained stable throughout all imaging sessions, and always surrounded an amyloid plaque. Plaque growth was followed over 4 weeks, and significant growth was seen between weekly imaging sessions. In addition to axonal dystrophy appearance and plaque growth, we were able to follow spine stability in 4-month old 5XY mice, which revealed no significant loss of spines. 5XY mice also showed a striking shrinkage of the neocortex at older ages (12-14 months). The 5XY mouse model may be a valuable tool for studying specific events in the degeneration of the neocortex, and may suggest new avenues for therapeutic intervention.
Collapse
Affiliation(s)
- Sarah E Crowe
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York 10029, USA
| | | |
Collapse
|
128
|
Smolarkiewicz M, Skrzypczak T, Wojtaszek P. The very many faces of presenilins and the γ-secretase complex. PROTOPLASMA 2013; 250:997-1011. [PMID: 23504135 PMCID: PMC3788181 DOI: 10.1007/s00709-013-0494-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Accepted: 03/01/2013] [Indexed: 05/02/2023]
Abstract
Presenilin is a central, catalytic component of the γ-secretase complex which conducts intramembrane cleavage of various protein substrates. Although identified and mainly studied through its role in the development of amyloid plaques in Alzheimer disease, γ-secretase has many other important functions. The complex seems to be evolutionary conserved throughout the Metazoa, but recent findings in plants and Dictyostelium discoideum as well as in archeons suggest that its evolution and functions might be much more diversified than previously expected. In this review, a selective survey of the multitude of functions of presenilins and the γ-secretase complex is presented. Following a brief overview of γ-secretase structure, assembly and maturation, three functional aspects are analyzed: (1) the role of γ-secretase in autophagy and phagocytosis; (2) involvement of the complex in signaling related to endocytosis; and (3) control of calcium fluxes by presenilins.
Collapse
Affiliation(s)
- Michalina Smolarkiewicz
- Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Tomasz Skrzypczak
- Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Przemysław Wojtaszek
- Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| |
Collapse
|
129
|
Wei H, Alberts I, Li X. Brain IL-6 and autism. Neuroscience 2013; 252:320-5. [PMID: 23994594 DOI: 10.1016/j.neuroscience.2013.08.025] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Revised: 08/14/2013] [Accepted: 08/15/2013] [Indexed: 12/17/2022]
Abstract
Autism is a severe neurodevelopmental disorder characterized by impairments in social interaction, deficits in verbal and non-verbal communication, and repetitive behavior and restricted interests. Emerging evidence suggests that aberrant neuroimmune responses may contribute to phenotypic deficits and could be appropriate targets for pharmacologic intervention. Interleukin (IL)-6, one of the most important neuroimmune factors, has been shown to be involved in physiological brain development and in several neurological disorders. For instance, findings from postmortem and animal studies suggest that brain IL-6 is an important mediator of autism-like behaviors. In this review, a possible pathological mechanism behind autism is proposed, which suggests that IL-6 elevation in the brain, caused by the activated glia and/or maternal immune activation, could be an important inflammatory cytokine response involved in the mediation of autism-like behaviors through impairments of neuroanatomical structures and neuronal plasticity. Further studies to investigate whether IL-6 could be used for therapeutic interventions in autism would be of great significance.
Collapse
Affiliation(s)
- H Wei
- Central Laboratory, Shanxi Provincial People's Hospital, Affiliate of Shanxi Medical University, Taiyuan, China.
| | | | | |
Collapse
|
130
|
Kádár E, Huguet G, Aldavert-Vera L, Morgado-Bernal I, Segura-Torres P. Intracranial self stimulation upregulates the expression of synaptic plasticity related genes and Arc protein expression in rat hippocampus. GENES BRAIN AND BEHAVIOR 2013; 12:771-9. [PMID: 23898803 DOI: 10.1111/gbb.12065] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 05/31/2013] [Accepted: 07/25/2013] [Indexed: 11/30/2022]
Abstract
Post-training lateral hypothalamus (LH) intracranial self stimulation (ICSS) has a reliable enhancing effect on explicit memory formation evaluated in hippocampus-dependent tasks such as the Morris water maze. In this study, the effects of ICSS on gene expression in the hippocampus are examined 4.5 h post treatment by using oligonucleotide microarray and real-time PCR, and by measuring Arc protein levels in the different layers of hippocampal subfields through immunofluorescence. The microarray data analysis resulted in 65 significantly regulated genes in rat ICSS hippocampi compared to sham, including cAMP-mediated signaling as one of the most significantly enriched Database for Annotation, Visualization and Integrated Discovery (DAVID) functional categories. In particular, expression of CREB-dependent synaptic plasticity related genes (c-Fos, Arc, Bdnf, Ptgs-2 and Crem and Icer) was regulated in a time-dependent manner following treatment administration. Immunofluorescence results showed that ICSS treatment induced a significant increase in Arc protein expression in CA1 and DG hippocampal subfields. This empirical evidence supports our hypothesis that the effect of ICSS on improved or restored memory functions might be mediated by increased hippocampal expression of activity-dependent synaptic plasticity related genes, including Arc protein expression, as neural mechanisms related to memory consolidation.
Collapse
Affiliation(s)
- E Kádár
- Departament de Biologia, Universitat de Girona, Girona, Spain
| | | | | | | | | |
Collapse
|
131
|
Abstract
Synaptic activity initiates biochemical processes that have various outcomes, including the formation of memories, increases in neuronal survival and the development of chronic pain and addiction. Virtually all activity-induced, long-lasting adaptations of brain functions require a dialogue between synapses and the nucleus that results in changes in gene expression. Calcium signals that are induced by synaptic activity and propagate into the nucleus are a major route for synapse-to-nucleus communication. Recent findings indicate that diverse forms of neuroadaptation require calcium transients in the nucleus to switch on the necessary genomic programme. Deficits in nuclear calcium signalling as a result of a reduction in synaptic activity or increased extrasynaptic NMDA receptor signalling may underlie the aetiologies of various diseases, including neurodegeneration and cognitive dysfunction.
Collapse
Affiliation(s)
- Hilmar Bading
- Department of Neurobiology, Interdisciplinary Centre for Neurosciences (IZN), University of Heidelberg, INF 364, 69120 Heidelberg, Germany. Hilmar.Bading@ uni-hd.de
| |
Collapse
|
132
|
Foolad F, Khodagholi F. Dietary supplementation with Salvia sahendica attenuates acetylcholinesterase activity and increases mitochondrial transcription factor A and antioxidant proteins in the hippocampus of amyloid beta-injected rats. ACTA ACUST UNITED AC 2013; 65:1555-62. [PMID: 24028623 DOI: 10.1111/jphp.12116] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 06/20/2013] [Indexed: 12/13/2022]
Abstract
OBJECTIVES We evaluated the acetylcholinesterase (AChE) inhibitory and potential antioxidant effects of Salvia sahendica extract to investigate whether these molecules are involved in learning and memory improvement in rats injected with fibrillar amyloid beta (Aβ) peptide in the CA1 region of their hippocampus. METHODS Rats were fed with S. sahendica (100 mg/kg/day) for 1 week before Aβ injection. Western blot analysis and enzymatic assays were carried out 7 days after injections. KEY FINDINGS Our results indicated that S. sahendica extract decreased AChE activity. Besides, S. sahendica prevented reduction in the level of nuclear respiratory factor-1 and mitochondrial transcription factor A (TFAM). Our data indicated the lack of sensitivity in citrate synthase and reduction in the activity of malate dehydrogenase in the presence of Aβ that was prevented with S. sahendica consumption. Pretreatment with S. sahendica extract impeded reduction of glutathione redox ratio, catalase and superoxide dismutase activity, while decreased the malondialdehyde level. CONCLUSIONS Based on the importance of AChE activity inhibition and increased TFAM level in the prevention of cognitive impairment, the use of S. sahendica could open a new protective issue in therapeutic fields of neurodegenerative disease.
Collapse
Affiliation(s)
- Forough Foolad
- Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | | |
Collapse
|
133
|
Walker KR, Tesco G. Molecular mechanisms of cognitive dysfunction following traumatic brain injury. Front Aging Neurosci 2013; 5:29. [PMID: 23847533 PMCID: PMC3705200 DOI: 10.3389/fnagi.2013.00029] [Citation(s) in RCA: 179] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 06/18/2013] [Indexed: 12/12/2022] Open
Abstract
Traumatic brain injury (TBI) results in significant disability due to cognitive deficits particularly in attention, learning and memory, and higher-order executive functions. The role of TBI in chronic neurodegeneration and the development of neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic Lateral Sclerosis (ALS) and most recently chronic traumatic encephalopathy (CTE) is of particular importance. However, despite significant effort very few therapeutic options exist to prevent or reverse cognitive impairment following TBI. In this review, we present experimental evidence of the known secondary injury mechanisms which contribute to neuronal cell loss, axonal injury, and synaptic dysfunction and hence cognitive impairment both acutely and chronically following TBI. In particular we focus on the mechanisms linking TBI to the development of two forms of dementia: AD and CTE. We provide evidence of potential molecular mechanisms involved in modulating Aβ and Tau following TBI and provide evidence of the role of these mechanisms in AD pathology. Additionally we propose a mechanism by which Aβ generated as a direct result of TBI is capable of exacerbating secondary injury mechanisms thereby establishing a neurotoxic cascade that leads to chronic neurodegeneration.
Collapse
Affiliation(s)
- Kendall R Walker
- Alzheimer's Disease Research Laboratory, Department of Neuroscience, Tufts University School of Medicine Boston, MA, USA
| | | |
Collapse
|
134
|
Xu F, Piett C, Farkas S, Qazzaz M, Syed NI. Silver nanoparticles (AgNPs) cause degeneration of cytoskeleton and disrupt synaptic machinery of cultured cortical neurons. Mol Brain 2013; 6:29. [PMID: 23782671 PMCID: PMC3695839 DOI: 10.1186/1756-6606-6-29] [Citation(s) in RCA: 114] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 06/15/2013] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND Silver nanoparticles (AgNPs), owing to their effective antimicrobial properties, are being widely used in a broad range of applications. These include, but are not limited to, antibacterial materials, the textile industry, cosmetics, coatings of various household appliances and medical devices. Despite their extensive use, little is known about AgNP safety and toxicity vis-à-vis human and animal health. Recent studies have drawn attention towards potential neurotoxic effects of AgNPs, however, the primary cellular and molecular targets of AgNP action/s remain to be defined. RESULTS Here we examine the effects of ultra fine scales (20 nm) of AgNPs at various concentrations (1, 5, 10 and 50 μg/ml) on primary rat cortical cell cultures. We found that AgNPs (at 1-50 μg/ml) not only inhibited neurite outgrowth and reduced cell viability of premature neurons and glial cells, but also induced degeneration of neuronal processes of mature neurons. Our immunocytochemistry and confocal microscopy studies further demonstrated that AgNPs induced the loss of cytoskeleton components such as the β-tubulin and filamentous actin (F-actin). AgNPs also dramatically reduced the number of synaptic clusters of the presynaptic vesicle protein synaptophysin, and the postsynaptic receptor density protein PSD-95. Finally, AgNP exposure also resulted in mitochondria dysfunction in rat cortical cells. CONCLUSIONS Taken together, our data show that AgNPs induce toxicity in neurons, which involves degradation of cytoskeleton components, perturbations of pre- and postsynaptic proteins, and mitochondrial dysfunction leading to cell death. Our study clearly demonstrates the potential detrimental effects of AgNPs on neuronal development and physiological functions and warns against its prolific usage.
Collapse
|
135
|
Wippel C, Maurer J, Förtsch C, Hupp S, Bohl A, Ma J, Mitchell TJ, Bunkowski S, Brück W, Nau R, Iliev AI. Bacterial cytolysin during meningitis disrupts the regulation of glutamate in the brain, leading to synaptic damage. PLoS Pathog 2013; 9:e1003380. [PMID: 23785278 PMCID: PMC3681734 DOI: 10.1371/journal.ppat.1003380] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Accepted: 04/08/2013] [Indexed: 12/20/2022] Open
Abstract
Streptococcus pneumoniae (pneumococcal) meningitis is a common bacterial infection of the brain. The cholesterol-dependent cytolysin pneumolysin represents a key factor, determining the neuropathogenic potential of the pneumococci. Here, we demonstrate selective synaptic loss within the superficial layers of the frontal neocortex of post-mortem brain samples from individuals with pneumococcal meningitis. A similar effect was observed in mice with pneumococcal meningitis only when the bacteria expressed the pore-forming cholesterol-dependent cytolysin pneumolysin. Exposure of acute mouse brain slices to only pore-competent pneumolysin at disease-relevant, non-lytic concentrations caused permanent dendritic swelling, dendritic spine elimination and synaptic loss. The NMDA glutamate receptor antagonists MK801 and D-AP5 reduced this pathology. Pneumolysin increased glutamate levels within the mouse brain slices. In mouse astrocytes, pneumolysin initiated the release of glutamate in a calcium-dependent manner. We propose that pneumolysin plays a significant synapto- and dendritotoxic role in pneumococcal meningitis by initiating glutamate release from astrocytes, leading to subsequent glutamate-dependent synaptic damage. We outline for the first time the occurrence of synaptic pathology in pneumococcal meningitis and demonstrate that a bacterial cytolysin can dysregulate the control of glutamate in the brain, inducing excitotoxic damage.
Collapse
Affiliation(s)
- Carolin Wippel
- DFG Membrane/Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
| | - Jana Maurer
- DFG Membrane/Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
| | - Christina Förtsch
- DFG Membrane/Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
| | - Sabrina Hupp
- DFG Membrane/Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
| | - Alexandra Bohl
- DFG Membrane/Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
| | - Jiangtao Ma
- Division of Infection and Immunity, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow, United Kingdom
| | - Timothy J. Mitchell
- Division of Infection and Immunity, Glasgow Biomedical Research Centre, University of Glasgow, Glasgow, United Kingdom
- Chair of Microbial Infection and Immunity, School of Immunity and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Stephanie Bunkowski
- Department of Neuropathology, Georg-August-University of Göttingen, Göttingen, Germany
| | - Wolfgang Brück
- Department of Neuropathology, Georg-August-University of Göttingen, Göttingen, Germany
| | - Roland Nau
- Department of Neuropathology, Georg-August-University of Göttingen, Göttingen, Germany
- Department of Geriatrics, Evangelisches Krankenhaus Göttingen-Weende, Göttingen, Germany
| | - Asparouh I. Iliev
- DFG Membrane/Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
| |
Collapse
|
136
|
Compensating for synaptic loss in Alzheimer’s disease. J Comput Neurosci 2013; 36:19-37. [DOI: 10.1007/s10827-013-0462-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 05/10/2013] [Accepted: 05/14/2013] [Indexed: 01/08/2023]
|
137
|
Tan M, Ma S, Huang Q, Hu K, Song B, Li M. GSK-3α/β-mediated phosphorylation of CRMP-2 regulates activity-dependent dendritic growth. J Neurochem 2013; 125:685-97. [PMID: 23470087 DOI: 10.1111/jnc.12230] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 02/25/2013] [Accepted: 02/28/2013] [Indexed: 12/15/2022]
Abstract
Neuronal activity shapes the dendritic arbour; however, most of the molecular players in this process remain to be identified. We observed that depolarization-induced neuronal activity causes an increase in the phosphorylation of glycogen synthase kinase-3 (GSK-3)α/β on Ser21/9 in cerebellar granule neurons. Using several approaches, including gene knockdown and GSK-3α/β(S21A/S21A/S9A/S9A) double knockin mice, we demonstrated that both GSK-3β and GSK-3α mediate activity-dependent dendritic growth and that Ser21/9 phosphorylation of GSK-3α/β plays an important role in this process. Collapsin response mediator protein-2 (CRMP-2), which is crucial for axon development, is phosphorylated at Thr514 and inactivated by GSK-3. We found CRMP-2 was located mainly in the dendrites of cerebellar granule neurons, in contrast to the axonal distribution in hippocampal neurons. Over-expression of CRMP-2 promoted and knockdown of CRMP-2 impaired dendritic growth, suggesting that CRMP-2 is necessary and sufficient for activity-dependent dendritic development. Furthermore, silencing CRMP-2 completely blocked the dendritic growth-promoting effects of GSK-3 knockdown, and expression of Thr514 nonphosphorylated form of CRMP-2 counteracted the inhibitory effect of constitutively active GSK-3. This data indicate that CRMP-2 functions downstream of GSK-3. Together, these findings identify a novel GSK-3/CRMP-2 pathway that connects neuronal activity to dendritic growth.
Collapse
Affiliation(s)
- Minghui Tan
- Department of Pharmacology and the Proteomics Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | | | | | | | | | | |
Collapse
|
138
|
Spine pruning in 5xFAD mice starts on basal dendrites of layer 5 pyramidal neurons. Brain Struct Funct 2013; 219:571-80. [PMID: 23417057 DOI: 10.1007/s00429-013-0518-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 02/01/2013] [Indexed: 12/19/2022]
Abstract
Transgenic mice with Alzheimer's disease (AD) mutations have been widely used to model changes in neuronal structure and function. While there are clear gross structural changes in post-mortem brains of AD patients, most mouse models of AD do not recapitulate the considerable loss of neurons. Furthermore, possible connections between early subtle structural changes and the loss of neurons are difficult to study. In an attempt to start unraveling how neurons are affected during the early stages of what becomes full neurodegeneration, we crossed a mouse model of familial AD, which displays massive neocortical neurodegeneration (the 5xFAD mouse), with the fluorescent H-line YFP mouse. This novel bigenic mouse model of AD, which we have named the 5XY mouse, expresses YFP in principal neurons in the cortex such that even fine details of cells are clearly visible. Such bright fluorescence allowed us to use high-resolution confocal microscopy to quantify changes in spine density in the somatosensory cortex, prefrontal cortex, and hippocampus at 2, 4, and 6 months of age. A significant loss of spines on basal dendrites in the somatosensory and prefrontal cortices of 6-month-old 5XY female mice was found. There was no observed spine loss at 6 months of age on the oblique dendrites of the hippocampus in the same mice. These data suggest that spine loss is an early event in the degeneration of the neocortical neurons in 5xFAD mice and a likely contributor to the cognitive impairments reported previously in this AD mouse model.
Collapse
|
139
|
Toledo JB, Da X, Bhatt P, Wolk DA, Arnold SE, Shaw LM, Trojanowski JQ, Davatzikos C. Relationship between plasma analytes and SPARE-AD defined brain atrophy patterns in ADNI. PLoS One 2013; 8:e55531. [PMID: 23408997 PMCID: PMC3568142 DOI: 10.1371/journal.pone.0055531] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 12/27/2012] [Indexed: 01/18/2023] Open
Abstract
Different inflammatory and metabolic pathways have been associated with Alzheimeŕs disease (AD). However, only recently multi-analyte panels to study a large number of molecules in well characterized cohorts have been made available. These panels could help identify molecules that point to the affected pathways. We studied the relationship between a panel of plasma biomarkers (Human DiscoveryMAP) and presence of AD-like brain atrophy patterns defined by a previously published index (SPARE-AD) at baseline in subjects of the ADNI cohort. 818 subjects had MRI-derived SPARE-AD scores, of these subjects 69% had plasma biomarkers and 51% had CSF tau and Aβ measurements. Significant analyte-SPARE-AD and analytes correlations were studied in adjusted models. Plasma cortisol and chromogranin A showed a significant association that did not remain significant in the CSF signature adjusted model. Plasma macrophage inhibitory protein-1α and insulin-like growth factor binding protein 2 showed a significant association with brain atrophy in the adjusted model. Cortisol levels showed an inverse association with tests measuring processing speed. Our results indicate that stress and insulin responses and cytokines associated with recruitment of inflammatory cells in MCI-AD are associated with its characteristic AD-like brain atrophy pattern and correlate with clinical changes or CSF biomarkers.
Collapse
Affiliation(s)
- Jon B. Toledo
- Department of Pathology & Laboratory Medicine, Institute on Aging, Center for Neurodegenerative Disease Research, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Xiao Da
- Section of Biomedical Image Analysis, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Priyanka Bhatt
- Section of Biomedical Image Analysis, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - David A. Wolk
- Penn Memory Center, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Steven E. Arnold
- Penn Memory Center, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Leslie M. Shaw
- Department of Pathology & Laboratory Medicine, Institute on Aging, Center for Neurodegenerative Disease Research, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - John Q. Trojanowski
- Department of Pathology & Laboratory Medicine, Institute on Aging, Center for Neurodegenerative Disease Research, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Christos Davatzikos
- Section of Biomedical Image Analysis, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | | |
Collapse
|
140
|
Neuroprotective Effects of Resveratrol Against Aβ Administration in Rats are Improved by Lipid-Core Nanocapsules. Mol Neurobiol 2013; 47:1066-80. [DOI: 10.1007/s12035-013-8401-2] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2012] [Accepted: 01/03/2013] [Indexed: 10/27/2022]
|
141
|
Structural networks in Alzheimer's disease. Eur Neuropsychopharmacol 2013; 23:63-77. [PMID: 23294972 DOI: 10.1016/j.euroneuro.2012.11.010] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 11/07/2012] [Accepted: 11/24/2012] [Indexed: 12/29/2022]
Abstract
Alzheimer's disease (AD) appears to be a uniquely human condition, which is possibly attributable to our expanded longevity and peculiar capacity for episodic memory. Due to a lack of naturally-occurring animal model for investigating AD pathogenesis, our knowledge about the disease must be derived from correlational observation of humans, or from animal models produced by genetic manipulation of known risk factors in humans. Advances in neuroimaging, cellular and molecular science, and computational methods have proven useful for the improvement of such techniques, but the general limitation persists; as a result we remain without clear answers to some of the fundamental questions posed by AD. On the other hand, much progress has been made in characterizing the longitudinal progression of AD pathology, which includes the formation of "plaques and tangles", a distinct topological pattern of atrophy of grey and white matter, and the concurrent decline of specific cognitive functions, beginning with mild memory impairments and ending with general debilitating dementia. In this review, we first discuss the existing literature which characterizes AD etiology, pathology, and pathogenesis, with the intention of framing the disease as primarily a "disconnection syndrome". We next describe methodologies for investigating the topological properties of human brain networks, using graph theoretical techniques and connectivity information derived from anatomical and diffusion-weighted MR imaging. Finally, we discuss how these methodologies have been applied to systems-level analyses of AD, to help characterize the network changes underlying the disease process, and how these patterns relate to specific cognitive outcome measures.
Collapse
|
142
|
Abstract
1-42 β-Amyloid (Aβ(1-42)) peptide is a key molecule involved in the development of Alzheimer's disease. Some of its effects are manifested at the neuronal morphological level. These morphological changes involve loss of neurites due to cytoskeleton alterations. However, the mechanism of Aβ(1-42) peptide activation of the neurodegenerative program is still poorly understood. Here, Aβ(1-42) peptide-induced transduction of cellular death signals through the phosphatidylinositol 3-kinase (PI3K)/phosphoinositol-dependent kinase (PDK)/novel protein kinase C (nPKC)/Rac 1 axis is described. Furthermore, pharmacological inhibition of PDK1 and nPKC activities blocks Rac 1 activation and neuronal cell death. Our results provide insights into an unsuspected connection between PDK1, nPKCs and Rac 1 in the same signal-transduction pathway and points out nPKCs and Rac 1 as potential therapeutic targets to block the toxic effects of Aβ(1-42) peptide in neurons.
Collapse
|
143
|
|
144
|
Fasano C, Bourque MJ, Lapointe G, Leo D, Thibault D, Haber M, Kortleven C, Desgroseillers L, Murai KK, Trudeau LÉ. Dopamine facilitates dendritic spine formation by cultured striatal medium spiny neurons through both D1 and D2 dopamine receptors. Neuropharmacology 2012; 67:432-43. [PMID: 23231809 DOI: 10.1016/j.neuropharm.2012.11.030] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Revised: 11/23/2012] [Accepted: 11/26/2012] [Indexed: 01/01/2023]
Abstract
Variations of dopamine (DA) levels induced by drugs of abuse or in the context of Parkinson's disease modulate the number of dendritic spines in medium spiny neurons (MSNs) of the striatum, showing that DA plays a major role in the structural plasticity of MSNs. However, little is presently known regarding early spine development in MSNs occurring before the arrival of cortical inputs and in particular about the role of DA and D1 (D1R) and D2 (D2R) DA receptors. A cell culture model reconstituting early cellular interactions between MSNs, intrinsic cholinergic interneurons and DA neurons was used to study the role of DA in spine formation. After 5 or 10 days in vitro, the presence of DA neurons increased the number of immature spine-like protrusions. In MSN monocultures, chronic activation of D1R or D2R also increased the number of spines and spinophilin expression in MSNs, suggesting a direct role for these receptors. In DA-MSN cocultures, chronic blockade of D1R or D2R reduced the number of dendritic spines. Interestingly, the combined activation or blockade of both D1R and D2R failed to elicit more extensive spine formation, suggesting that both receptors act through a mechanism that is not additive. Finally, we found increased ionotropic glutamate receptor responsiveness and miniature excitatory postsynaptic current (EPSC) frequency in DA-MSN co-cultures, in parallel with a higher number of spines containing PSD-95, suggesting that the newly formed spines present functional post-synaptic machinery preparing the MSNs to receive additional glutamatergic contacts. These results represent a first step in the understanding of how dopamine neurons promote the structural plasticity of MSNs during the development of basal ganglia circuits.
Collapse
Affiliation(s)
- Caroline Fasano
- Department of Pharmacology, Faculty of Medicine, Université de Montréal, Montréal, Québec, Canada
| | | | | | | | | | | | | | | | | | | |
Collapse
|
145
|
Amyloid plaque formation precedes dendritic spine loss. Acta Neuropathol 2012; 124:797-807. [PMID: 22993126 PMCID: PMC3508278 DOI: 10.1007/s00401-012-1047-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 09/07/2012] [Accepted: 09/09/2012] [Indexed: 11/01/2022]
Abstract
Amyloid-beta plaque deposition represents a major neuropathological hallmark of Alzheimer's disease. While numerous studies have described dendritic spine loss in proximity to plaques, much less is known about the kinetics of these processes. In particular, the question as to whether synapse loss precedes or follows plaque formation remains unanswered. To address this question, and to learn more about the underlying kinetics, we simultaneously imaged amyloid plaque deposition and dendritic spine loss by applying two-photon in vivo microscopy through a cranial window in double transgenic APPPS1 mice. As a result, we first observed that the rate of dendritic spine loss in proximity to plaques is the same in both young and aged animals. However, plaque size only increased significantly in the young cohort, indicating that spine loss persists even many months after initial plaque appearance. Tracking the fate of individual spines revealed that net spine loss is caused by increased spine elimination, with the rate of spine formation remaining constant. Imaging of dendritic spines before and during plaque formation demonstrated that spine loss around plaques commences at least 4 weeks after initial plaque formation. In conclusion, spine loss occurs, shortly but with a significant time delay, after the birth of new plaques, and persists in the vicinity of amyloid plaques over many months. These findings hence give further hope to the possibility that there is a therapeutic window between initial amyloid plaque deposition and the onset of structural damage at spines.
Collapse
|
146
|
Age-dependent alterations in the presynaptic active zone in a Drosophila model of Alzheimer's disease. Neurobiol Dis 2012; 51:161-7. [PMID: 23149068 DOI: 10.1016/j.nbd.2012.11.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 10/08/2012] [Accepted: 11/02/2012] [Indexed: 11/23/2022] Open
Abstract
The accumulation of beta amyloid (Aβ) can cause synaptic impairments, but the characteristics and mechanisms of the synaptic impairment induced by the accumulation of Aβ in Alzheimer's disease (AD) remain unclear. In identified single neurons in a newly developed Drosophila AD model, in which Aβ accumulates intraneuronally, we found an age-dependent reduction in the synaptic vesicle release probability that was associated with a decrease in the density of presynaptic calcium channel clusters and an increase in the presynaptic and postsynaptic contact length. Moreover, these alterations occurred in the absence of presynaptic bouton loss. In addition, we found that Aβ expression also produced an age-dependent decrease in the amount of Bruchpilot (Brp), which plays an important role in controlling Ca(2+) channel clustering and synaptic vesicle release in the presynaptic active zone. Our study indicates that the chronic accumulation of intraneuronal Aβ can induce functional and structural changes in the presynaptic active zone prior to a loss of presynaptic buttons in the same neuron.
Collapse
|
147
|
Yadav A, Gao YZ, Rodriguez A, Dickstein DL, Wearne SL, Luebke JI, Hof PR, Weaver CM. Morphologic evidence for spatially clustered spines in apical dendrites of monkey neocortical pyramidal cells. J Comp Neurol 2012; 520:2888-902. [PMID: 22315181 DOI: 10.1002/cne.23070] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The general organization of neocortical connectivity in rhesus monkey is relatively well understood. However, mounting evidence points to an organizing principle that involves clustered synapses at the level of individual dendrites. Several synaptic plasticity studies have reported cooperative interaction between neighboring synapses on a given dendritic branch, which may potentially induce synapse clusters. Additionally, theoretical models have predicted that such cooperativity is advantageous, in that it greatly enhances a neuron's computational repertoire. However, largely because of the lack of sufficient morphologic data, the existence of clustered synapses in neurons on a global scale has never been established. The majority of excitatory synapses are found within dendritic spines. In this study, we demonstrate that spine clusters do exist on pyramidal neurons by analyzing the three-dimensional locations of ∼40,000 spines on 280 apical dendritic branches in layer III of the rhesus monkey prefrontal cortex. By using clustering algorithms and Monte Carlo simulations, we quantify the probability that the observed extent of clustering does not occur randomly. This provides a measure that tests for spine clustering on a global scale, whenever high-resolution morphologic data are available. Here we demonstrate that spine clusters occur significantly more frequently than expected by pure chance and that spine clustering is concentrated in apical terminal branches. These findings indicate that spine clustering is driven by systematic biological processes. We also found that mushroom-shaped and stubby spines are predominant in clusters on dendritic segments that display prolific clustering, independently supporting a causal link between spine morphology and synaptic clustering.
Collapse
Affiliation(s)
- Aniruddha Yadav
- Fishberg Department of Neuroscience and Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York 10029, USA
| | | | | | | | | | | | | | | |
Collapse
|
148
|
Neurite sprouting and synapse deterioration in the aging Caenorhabditis elegans nervous system. J Neurosci 2012; 32:8778-90. [PMID: 22745480 DOI: 10.1523/jneurosci.1494-11.2012] [Citation(s) in RCA: 137] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Caenorhabditis elegans is a powerful model for analysis of the conserved mechanisms that modulate healthy aging. In the aging nematode nervous system, neuronal death and/or detectable loss of processes are not readily apparent, but because dendrite restructuring and loss of synaptic integrity are hypothesized to contribute to human brain decline and dysfunction, we combined fluorescence microscopy and electron microscopy (EM) to screen at high resolution for nervous system changes. We report two major components of morphological change in the aging C. elegans nervous system: (1) accumulation of novel outgrowths from specific neurons, and (2) physical decline in synaptic integrity. Novel outgrowth phenotypes, including branching from the main dendrite or new growth from somata, appear at a high frequency in some aging neurons, but not all. Mitochondria are often associated with age-associated branch sites. Lowered insulin signaling confers some maintenance of ALM and PLM neuron structural integrity into old age, and both DAF-16/FOXO and heat shock factor transcription factor HSF-1 exert neuroprotective functions. hsf-1 can act cell autonomously in this capacity. EM evaluation in synapse-rich regions reveals a striking decline in synaptic vesicle numbers and a diminution of presynaptic density size. Interestingly, old animals that maintain locomotory prowess exhibit less synaptic decline than same-age decrepit animals, suggesting that synaptic integrity correlates with locomotory healthspan. Our data reveal similarities between the aging C. elegans nervous system and mammalian brain, suggesting conserved neuronal responses to age. Dissection of neuronal aging mechanisms in C. elegans may thus influence the development of brain healthspan-extending therapies.
Collapse
|
149
|
Oligomeric forms of insulin amyloid aggregation disrupt outgrowth and complexity of neuron-like PC12 cells. PLoS One 2012; 7:e41344. [PMID: 22848469 PMCID: PMC3407202 DOI: 10.1371/journal.pone.0041344] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2012] [Accepted: 06/20/2012] [Indexed: 11/19/2022] Open
Abstract
Formation of protein amyloid fibrils consists of a series of intermediates including oligomeric aggregates, proto-fibrillar structures, and finally mature fibrils. Recent studies show higher toxicity for oligomeric and proto-fibrillar intermediates of protein relative to their mature fibrils. Here the kinetic of the insulin amyloid fibrillation was evaluated using a variety of techniques including ThT fluorescence, Congo red absorbance, circular dichroism, and atomic force microscopy (AFM). The solution surface tension changes were attributed to hydrophobic changes in insulin structure and were detected by Du Noüy Ring method. Determination of the surface tension of insulin oligomeric, proto-fibrillar and fibrillar forms indicated that the hydrophobicity of solution is enhanced by the formation of the oligomeric forms of insulin compared to other forms. In order to investigate the toxicity of the different forms of insulin we monitored morphological alterations of the differentiated neuron-like PC12 cells following incubation with native, oligomeric aggregates, proto-fibrillar, and fibrillar forms of insulin. The cell body area, average neurite length, neurite width, number of primary neurites, and percent of bipolar cells and node/primary neurite ratios were used to assess the growth and complexity of PC12 cells exposed to different forms of insulin. We observed that the oligomeric form of insulin impaired the growth and complexity of PC12 cells compared to other forms. Together our data suggest that the lower surface tension of oligomers and their perturbation affects the morphology of PC12 cells, mainly due to their enhanced hydrophobicity and detergent-like structures.
Collapse
|
150
|
Culmone V, Migliore M. Progressive effect of beta amyloid peptides accumulation on CA1 pyramidal neurons: a model study suggesting possible treatments. Front Comput Neurosci 2012; 6:52. [PMID: 22837746 PMCID: PMC3402026 DOI: 10.3389/fncom.2012.00052] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 07/05/2012] [Indexed: 12/24/2022] Open
Abstract
Several independent studies show that accumulation of β-amyloid (Aβ) peptides, one of the characteristic hallmark of Alzheimer's Disease (AD), can affect normal neuronal activity in different ways. However, in spite of intense experimental work to explain the possible underlying mechanisms of action, a comprehensive and congruent understanding is still lacking. Part of the problem might be the opposite ways in which Aβ have been experimentally found to affect the normal activity of a neuron; for example, making a neuron more excitable (by reducing the A- or DR-type K+ currents) or less excitable (by reducing synaptic transmission and Na+ current). The overall picture is therefore confusing, since the interplay of many mechanisms makes it difficult to link individual experimental findings with the more general problem of understanding the progression of the disease. This is an important issue, especially for the development of new drugs trying to ameliorate the effects of the disease. We addressed these paradoxes through computational models. We first modeled the different stages of AD by progressively modifying the intrinsic membrane and synaptic properties of a realistic model neuron, while accounting for multiple and different experimental findings and by evaluating the contribution of each mechanism to the overall modulation of the cell's excitability. We then tested a number of manipulations of channel and synaptic activation properties that could compensate for the effects of Aβ. The model predicts possible therapeutic treatments in terms of pharmacological manipulations of channels' kinetic and activation properties. The results also suggest how and which mechanisms can be targeted by a drug to restore the original firing conditions.
Collapse
Affiliation(s)
- Viviana Culmone
- Institute of Biophysics, National Research Council Palermo, Italy
| | | |
Collapse
|