51
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Codadu NK, Graham RT, Burman RJ, Jackson‐Taylor RT, Raimondo JV, Trevelyan AJ, Parrish RR. Divergent paths to seizure-like events. Physiol Rep 2019; 7:e14226. [PMID: 31587522 PMCID: PMC6778598 DOI: 10.14814/phy2.14226] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 07/29/2019] [Accepted: 07/31/2019] [Indexed: 12/19/2022] Open
Abstract
Much debate exists about how the brain transitions into an epileptic seizure. One source of confusion is that there are likely to be critical differences between experimental seizure models. To address this, we have compared the evolving activity patterns in two widely used in vitro models of epileptic discharges. Brain slices from young adult mice were prepared in the same way and bathed either in 0 Mg2+ or 100 µmol/L 4AP artificial cerebrospinal fluid. We have found that while local field potential recordings of epileptiform discharges in the two models appear broadly similar, patch-clamp analysis reveals an important difference in the relative degree of glutamatergic involvement. 4AP affects parvalbumin-expressing interneurons more than other cortical populations, destabilizing their resting state and inducing spontaneous bursting behavior. Consequently, the most prominent pattern of transient discharge ("interictal event") in this model is almost purely GABAergic, although the transition to seizure-like events (SLEs) involves pyramidal recruitment. In contrast, interictal discharges in 0 Mg2+ are only maintained by a very large glutamatergic component that also involves transient discharges of the interneurons. Seizure-like events in 0 Mg2+ have significantly higher power in the high gamma frequency band (60-120Hz) than these events do in 4AP, and are greatly delayed in onset by diazepam, unlike 4AP events. We, therefore, conclude that the 0 Mg2+ and 4AP models display fundamentally different levels of glutamatergic drive, demonstrating how ostensibly similar pathological discharges can arise from different sources. We contend that similar interpretative issues will also be relevant to clinical practice.
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Affiliation(s)
- Neela K. Codadu
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
| | - Robert T. Graham
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
| | - Richard J. Burman
- Division of Cell BiologyDepartment of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular MedicineFaculty of Health SciencesUniversity of Cape TownCape TownSouth Africa
| | | | - Joseph V. Raimondo
- Division of Cell BiologyDepartment of Human Biology, Neuroscience Institute and Institute of Infectious Disease and Molecular MedicineFaculty of Health SciencesUniversity of Cape TownCape TownSouth Africa
| | - Andrew J. Trevelyan
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
| | - R. Ryley Parrish
- Institute of NeuroscienceMedical SchoolNewcastle UniversityNewcastle upon TyneUnited Kingdom
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52
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Siracusa R, Fusco R, Cuzzocrea S. Astrocytes: Role and Functions in Brain Pathologies. Front Pharmacol 2019; 10:1114. [PMID: 31611796 PMCID: PMC6777416 DOI: 10.3389/fphar.2019.01114] [Citation(s) in RCA: 182] [Impact Index Per Article: 36.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 08/30/2019] [Indexed: 12/16/2022] Open
Abstract
Astrocytes are a population of cells with distinctive morphological and functional characteristics that differ within specific areas of the brain. Postnatally, astrocyte progenitors migrate to reach their brain area and related properties. They have a regulatory role of brain functions that are implicated in neurogenesis and synaptogenesis, controlling blood-brain barrier permeability and maintaining extracellular homeostasis. Mature astrocytes also express some genes enriched in cell progenitors, suggesting they can retain proliferative potential. Considering heterogeneity of cell population, it is not surprising that their disorders are related to a wide range of different neuro-pathologies. Brain diseases are characterized by the active inflammatory state of the astrocytes, which is usually described as up-regulation of glial fibrillary acidic protein (GFAP). In particular, the loss of astrocytes function as a result of cellular senescence could have implications for the neurodegenerative disorders, such as Alzheimer disease and Huntington disease, and for the aging brain. Astrocytes can also drive the induction and the progression of the inflammatory state due to their Ca2+ signals and that it is strongly related to the disease severity/state. Moreover, they contribute to the altered neuronal activity in several frontal cortex pathologies such as ischemic stroke and epilepsy. There, we describe the current knowledge pertaining to astrocytes' role in brain pathologies and discuss the possibilities to target them as approach toward pharmacological therapies for neuro-pathologies.
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Affiliation(s)
- Rosalba Siracusa
- Department of Chemical, Biological, Pharmaceutical and Environmental Science, University of Messina, Messina, Italy
| | - Roberta Fusco
- Department of Chemical, Biological, Pharmaceutical and Environmental Science, University of Messina, Messina, Italy
| | - Salvatore Cuzzocrea
- Department of Chemical, Biological, Pharmaceutical and Environmental Science, University of Messina, Messina, Italy.,Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, Saint Louis, MO, United States
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53
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Role of the protease-activated receptor 1 in regulating the function of glial cells within central and peripheral nervous system. J Neural Transm (Vienna) 2019; 126:1259-1271. [DOI: 10.1007/s00702-019-02075-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 08/31/2019] [Indexed: 02/07/2023]
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54
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Liu J, McDaid L, Araque A, Wade J, Harkin J, Karim S, Henshall DC, Connolly NMC, Johnson AP, Tyrrell AM, Timmis J, Millard AG, Hilder J, Halliday DM. GABA Regulation of Burst Firing in Hippocampal Astrocyte Neural Circuit: A Biophysical Model. Front Cell Neurosci 2019; 13:335. [PMID: 31396055 PMCID: PMC6664076 DOI: 10.3389/fncel.2019.00335] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Accepted: 07/08/2019] [Indexed: 12/30/2022] Open
Abstract
It is now widely accepted that glia cells and gamma-aminobutyric acidergic (GABA) interneurons dynamically regulate synaptic transmission and neuronal activity in time and space. This paper presents a biophysical model that captures the interaction between an astrocyte cell, a GABA interneuron and pre/postsynaptic neurons. Specifically, GABA released from a GABA interneuron triggers in astrocytes the release of calcium (Ca2+) from the endoplasmic reticulum via the inositol 1, 4, 5-trisphosphate (IP3) pathway. This results in gliotransmission which elevates the presynaptic transmission probability rate (PR) causing weight potentiation and a gradual increase in postsynaptic neuronal firing, that eventually stabilizes. However, by capturing the complex interactions between IP3, generated from both GABA and the 2-arachidonyl glycerol (2-AG) pathway, and PR, this paper shows that this interaction not only gives rise to an initial weight potentiation phase but also this phase is followed by postsynaptic bursting behavior. Moreover, the model will show that there is a presynaptic frequency range over which burst firing can occur. The proposed model offers a novel cellular level mechanism that may underpin both seizure-like activity and neuronal synchrony across different brain regions.
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Affiliation(s)
- Junxiu Liu
- School of Computing, Engineering and Intelligent Systems, Ulster University, Derry, United Kingdom
| | - Liam McDaid
- School of Computing, Engineering and Intelligent Systems, Ulster University, Derry, United Kingdom
| | - Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, United States
| | - John Wade
- School of Computing, Engineering and Intelligent Systems, Ulster University, Derry, United Kingdom
| | - Jim Harkin
- School of Computing, Engineering and Intelligent Systems, Ulster University, Derry, United Kingdom
| | - Shvan Karim
- School of Computing, Engineering and Intelligent Systems, Ulster University, Derry, United Kingdom
| | - David C Henshall
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland.,FutureNeuro Research Centre, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Niamh M C Connolly
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Anju P Johnson
- Department of Electronic Engineering, University of York, York, United Kingdom
| | - Andy M Tyrrell
- Department of Electronic Engineering, University of York, York, United Kingdom
| | - Jon Timmis
- Department of Electronic Engineering, University of York, York, United Kingdom
| | - Alan G Millard
- Department of Electronic Engineering, University of York, York, United Kingdom
| | - James Hilder
- Department of Electronic Engineering, University of York, York, United Kingdom
| | - David M Halliday
- Department of Electronic Engineering, University of York, York, United Kingdom
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55
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Weiss S, Melom JE, Ormerod KG, Zhang YV, Littleton JT. Glial Ca 2+signaling links endocytosis to K + buffering around neuronal somas to regulate excitability. eLife 2019; 8:44186. [PMID: 31025939 PMCID: PMC6510531 DOI: 10.7554/elife.44186] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 04/25/2019] [Indexed: 12/30/2022] Open
Abstract
Glial-neuronal signaling at synapses is widely studied, but how glia interact with neuronal somas to regulate their activity is unclear. Drosophila cortex glia are restricted to brain regions devoid of synapses, providing an opportunity to characterize interactions with neuronal somas. Mutations in the cortex glial NCKXzydeco elevate basal Ca2+, predisposing animals to seizure-like behavior. To determine how cortex glial Ca2+ signaling controls neuronal excitability, we performed an in vivo modifier screen of the NCKXzydeco seizure phenotype. We show that elevation of glial Ca2+ causes hyperactivation of calcineurin-dependent endocytosis and accumulation of early endosomes. Knockdown of sandman, a K2P channel, recapitulates NCKXzydeco seizures. Indeed, sandman expression on cortex glial membranes is substantially reduced in NCKXzydeco mutants, indicating enhanced internalization of sandman predisposes animals to seizures. These data provide an unexpected link between glial Ca2+ signaling and the well-known role of glia in K+ buffering as a key mechanism for regulating neuronal excitability.
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Affiliation(s)
- Shirley Weiss
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Jan E Melom
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Kiel G Ormerod
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Yao V Zhang
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - J Troy Littleton
- Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
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56
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Ma T, Wu Y, Chen B, Zhang W, Jin L, Shen C, Wang Y, Liu Y. D-Serine Contributes to Seizure Development via ERK Signaling. Front Neurosci 2019; 13:254. [PMID: 30971878 PMCID: PMC6443828 DOI: 10.3389/fnins.2019.00254] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 03/04/2019] [Indexed: 12/22/2022] Open
Abstract
A seizure is one of the leading neurological disorders. NMDA receptor-mediated neuronal excitation has been thought to be essential for epileptogenesis. As an endogenous co-agonist of the NMDA receptor, D-serine has been suggested to play a role in epileptogenesis. However, the underlying mechanisms remain unclear. In the current study, we investigated the effects of antagonizing two key enzymes in D-serine metabolism on the development of seizures and the downstream signaling. Our results showed that serine racemase (SR), a key enzyme in regulating the L-to-D-serine conversion, was significantly up-regulated in hippocampal astrocytes in rats and patients who experienced seizure, in comparison with control rats and patients. L-aspartic acid β-hydroxamate (LaaβH), an inhibitor of SR, significantly prolonged the latencies of seizures, shortened the durations of seizures, and decreased the total EEG power in rats. In contrast, D-amino acid oxidase inhibitor 5-chlorobenzo[d]isoxazol-3-ol (CBIO), which can increase D-serine levels, showed the opposite effects. Furthermore, our data showed that LaaβH and CBIO significantly affected the phosphorylation of Extracellular Signal-regulated Kinase (ERK). Antagonizing or activating ERK could significantly block the effects of LaaβH/CBIO on the occurrence of seizures. In summary, our study revealed that D-serine is involved in the development of epileptic seizures, partially through ERK signaling, indicating that the metabolism of D-serine may be targeted for the treatment of epilepsy.
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Affiliation(s)
- Tie Ma
- Department of Neurology, Xijing Hospital, Air Force Military Medical University, Xi'an, China.,Department of Neurology, The Seventh Medical Center of PLA General Hospital, Beijing, China
| | - Yin Wu
- Department of Pharmacy, Xi'an High-tech Hospital, Xi'an, China
| | - Beibei Chen
- Department of Neurology, Xijing Hospital, Air Force Military Medical University, Xi'an, China
| | - Wenjuan Zhang
- Department of Neurology, Xijing Hospital, Air Force Military Medical University, Xi'an, China
| | - Lang Jin
- Department of Neurology, Xijing Hospital, Air Force Military Medical University, Xi'an, China
| | - Chenxi Shen
- Department of Neurology, Xijing Hospital, Air Force Military Medical University, Xi'an, China
| | - Yazhou Wang
- Department of Neurobiology and Institute of Neurosciences, School of Basic Medicine, Air Force Medical University, Xi'an, China
| | - Yonghong Liu
- Department of Neurology, Xijing Hospital, Air Force Military Medical University, Xi'an, China
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57
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Bedner P, Steinhäuser C. TNFα-Driven Astrocyte Purinergic Signaling during Epileptogenesis. Trends Mol Med 2018; 25:70-72. [PMID: 30581052 DOI: 10.1016/j.molmed.2018.12.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 12/05/2018] [Accepted: 12/05/2018] [Indexed: 12/21/2022]
Abstract
The etiology of temporal lobe epilepsy is unclear, but proinflammatory molecules and disturbed neuron-glia communications are emerging as potential causers. A recent study (Nikolic et al. Glia 2018; https://doi.org/10.1002/glia.23519) revealed that pathologically elevated tumor necrosis factor α contributes to epileptogenesis, by boosting hyperexcitation through an autocrine mechanism involving purinergic signaling, astrocyte glutamate release, and modulation of neuronal transmitter release.
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Affiliation(s)
- Peter Bedner
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany
| | - Christian Steinhäuser
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany.
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58
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Wellmann M, Álvarez-Ferradas C, Maturana CJ, Sáez JC, Bonansco C. Astroglial Ca 2+-Dependent Hyperexcitability Requires P2Y 1 Purinergic Receptors and Pannexin-1 Channel Activation in a Chronic Model of Epilepsy. Front Cell Neurosci 2018; 12:446. [PMID: 30542266 PMCID: PMC6277884 DOI: 10.3389/fncel.2018.00446] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 11/06/2018] [Indexed: 12/31/2022] Open
Abstract
Astrocytes from the hippocampus of chronic epileptic rats exhibit an abnormal pattern of intracellular calcium oscillations, characterized by an augmented frequency of long lasting spontaneous Ca2+ transients, which are sensitive to purinergic receptor antagonists but resistant to tetrodotoxin. The above suggests that alterations in astroglial Ca2+-dependent excitability observed in the epileptic tissue could arise from changes in astrocyte-to-astrocyte signaling, which is mainly mediated by purines in physiological and pathological conditions. In spite of that, how purinergic signaling contributes to astrocyte dysfunction in epilepsy remains unclear. Here, we assessed the possible contribution of P2Y1R as well as pannexin1 and connexin43 hemichannels—both candidates for non-vesicular ATP-release—by performing astroglial Ca2+ imaging and dye uptake experiments in hippocampal slices from control and fully kindled rats. P2Y1R blockade with MRS2179 decreased the mean duration of astroglial Ca2+ oscillations by reducing the frequency of slow Ca2+ transients, and thereby restoring the balance between slow (ST) and fast transients (FT) in the kindled group. The potential contribution of astroglial pannexin1 and connexin43 hemichannels as pathways for purine release (e.g., ATP) was assessed through dye uptake experiments. Astrocytes from kindled hippocampi exhibit three-fold more EtBr uptake than controls, whereby pannexin1 hemichannels (Panx1 HCs) accounts for almost all dye uptake with only a slight contribution from connexin43 hemichannels (Cx43 HCs). Confirming its functional involvement, Panx1 HCs inhibition decreased the mean duration of astroglial Ca2+ transients and the frequency of slow oscillations in kindled slices, but had no noticeable effects on the control group. As expected, Cx43 HCs blockade did not have any effects over the mean duration of astroglial Ca2+ oscillations. These findings suggest that P2Y1R and Panx1 HCs play a pivotal role in astroglial pathophysiology, which would explain the upregulation of glutamatergic neurotransmission in the epileptic brain and thus represents a new potential pharmacological target for the treatment of drug-refractory epilepsy.
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Affiliation(s)
- Mario Wellmann
- Centro de Neurobiología y Plasticidad Cerebral CNPC, Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.,Escuela de Fonoaudiología, Facultad de Medicina, Universidad de Valparaíso, Valparaíso, Chile
| | - Carla Álvarez-Ferradas
- Centro de Neurobiología y Plasticidad Cerebral CNPC, Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.,Escuela de Ciencias de la Salud, Universidad Viña del Mar, Valparaíso, Chile
| | - Carola J Maturana
- Departamento de Ciencias Fisiológicas, Facultad Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.,Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Juan C Sáez
- Departamento de Ciencias Fisiológicas, Facultad Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.,Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Christian Bonansco
- Centro de Neurobiología y Plasticidad Cerebral CNPC, Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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59
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Nikolic L, Shen W, Nobili P, Virenque A, Ulmann L, Audinat E. Blocking TNFα-driven astrocyte purinergic signaling restores normal synaptic activity during epileptogenesis. Glia 2018; 66:2673-2683. [DOI: 10.1002/glia.23519] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Revised: 07/19/2018] [Accepted: 07/20/2018] [Indexed: 12/14/2022]
Affiliation(s)
- Ljiljana Nikolic
- Neuron-glia interactions group, INSERM U1128; Paris Descartes University; Paris France
| | - Weida Shen
- Neuron-glia interactions group, INSERM U1128; Paris Descartes University; Paris France
- Department of Pharmacology; Zhejiang University City College; Hangzhou, Zhejiang China
| | - Paola Nobili
- Neuron-glia interactions group, INSERM U1128; Paris Descartes University; Paris France
| | - Anaïs Virenque
- Institute of Functional Genomics, University of Montpellier; CNRS, INSERM; Montpellier France
| | - Lauriane Ulmann
- Institute of Functional Genomics, University of Montpellier; CNRS, INSERM; Montpellier France
- LabEx Ion Channel Science and Therapeutics; Montpellier France
| | - Etienne Audinat
- Neuron-glia interactions group, INSERM U1128; Paris Descartes University; Paris France
- Institute of Functional Genomics, University of Montpellier; CNRS, INSERM; Montpellier France
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60
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New Roles for Old Glue: Astrocyte Function in Synaptic Plasticity and Neurological Disorders. Int Neurourol J 2018; 22:S106-114. [PMID: 30396259 PMCID: PMC6234728 DOI: 10.5213/inj.1836214.107] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 10/10/2018] [Indexed: 01/02/2023] Open
Abstract
Previously believed to solely play a supportive role in the central nervous system, astrocytes are now considered active players in normal brain function. Evidence in recent decades extends their contributions beyond the classically held brain glue role; it's now known that astrocytes act as a unique excitable component with functions extending into local network modulation, synaptic plasticity, and memory formation, and postinjury repair. In this review article, we highlight our growing understanding of astrocyte function and physiology, the increasing role of gliotransmitters in neuron-glia communication, and the role of astrocytes in modulating synaptic plasticity and cognitive function. Owing to the duality of both beneficial and deleterious roles attributed to astrocytes, we also discuss the implications of this new knowledge as it applies to neurological disorders including Alzheimer disease, epilepsy, and schizophrenia.
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61
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Gómez-Gonzalo M, Zehnder T, Requie LM, Bezzi P, Carmignoto G. Insights into the release mechanism of astrocytic glutamate evoking in neurons NMDA receptor-mediated slow depolarizing inward currents. Glia 2018; 66:2188-2199. [DOI: 10.1002/glia.23473] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 04/27/2018] [Accepted: 05/25/2018] [Indexed: 12/19/2022]
Affiliation(s)
- Marta Gómez-Gonzalo
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences; University of Padova; Padova Italy
| | - Tamara Zehnder
- Department of Fundamental Neurosciences; University of Lausanne; Lausanne Switzerland
| | - Linda Maria Requie
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences; University of Padova; Padova Italy
| | - Paola Bezzi
- Department of Fundamental Neurosciences; University of Lausanne; Lausanne Switzerland
| | - Giorgio Carmignoto
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences; University of Padova; Padova Italy
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62
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Liu Y, Chen J, Jin M, Li Z, Tian T, Li L, Ni H. Relationship between changes in mitochondrial function and hippocampal neuronal apoptosis after recurrent convulsion during developmental stage. Exp Ther Med 2018; 16:127-132. [PMID: 29896232 PMCID: PMC5995061 DOI: 10.3892/etm.2018.6147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 04/20/2018] [Indexed: 02/01/2023] Open
Abstract
The aim of the present study was to establish a recurrent convulsion model during the developmental stage using inhalation of flurothyl, and to observe the relationship between the changes in mitochondrial function in hippocampal neurons and hippocampal neuronal apoptosis after recurrent convulsion. A total of 36 Sprague-Dawley male rats were selected and randomly divided into the control (NS) group and recurrent-seizure (RS) group for 0, 1.5, 3, 12 and 24 h. After the last seizure the rats were subdivided with 6 animals in each group. Rats in the seizure group inhaled flurothyl repeatedly to induce status convulsivus, 30 min once daily, for 7 consecutive days, while the same operation was conducted in the control group without inhalation of flurothyl. At each time-point after the last seizure, blood was taken from the heart, followed by decapitation and immediate removal of the brain. Half of the brain tissue was immediately fixed in 10% paraformaldehyde to prepare paraffin-embedded tissues for hematoxylin and eosin (H&E) histological staining. Hippocampus was taken from the other half of the brain and stored at -80°C. Changes in mitochondrial membrane potential (ΔΨm) in hippocampal neurons were detected by flow cytometer. Dynamic changes of mitochondrial fusion and division-related genes, mitochondrial fusion protein 2 (Mfn2) and dynamin-related protein 1 (Drp1), in the hippocampus after recurrent convulsion were observed using reverse transcription-polymerase chain reaction (RT-PCR)and western blot analysis. The expression of caspase-3 and cytochrome c (Cyt c) was determined by RT-PCR and western blot analysis. After successful establishment of the recurrent convulsion model in rats during developmental stage using flurothyl, H&E staining results exhibited that in the CA1 region of hippocampus in the NS group, karyopyknosis occurred in nucleus that was stained to be brown and yellow, and the expression peak of apoptotic cells mainly existed at 24 h after the last convulsion. RT-PCR and western analysis revealed that apoptosis-related gene caspase-3 expression in the RS group was elevated at 1.5 h after the last convulsion, and lasted 24 h after convulsion. Detection results of mitochondrial ΔΨm revealed a significant reduction 1.5, 3 and 12 h after convulsion in hippocampal neurons of experimental rats, which reached the trough at 12 h, and rapidly increased after 24 h. The expression of Mfn2 mRNA in the RS group was significantly lower than that in the control group, while the expression of Drp1 mRNA in RS group was distinctly higher than that in the control group. RT-PCR and western blot analysis revealed that, mitochondrial apoptosis-related gene Cyt c expression was increased at 3 h after the last convulsion, and lasted 24 h after convulsion. Correlation analysis showed that the changes in mitochondrial function were closely related to neuronal apoptosis. The results of the study show that apoptosis exists in the hippocampus of rats after recurrent convulsion, which is closely related to the changes in mitochondrial function.
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Affiliation(s)
- Yueying Liu
- Neurology Laboratory, Institute of Pediatrics, Children's Hospital of Soochow University, Suzhou, Jiangsu 215003, P.R. China
| | - Jieru Chen
- Neurology Laboratory, Institute of Pediatrics, Children's Hospital of Soochow University, Suzhou, Jiangsu 215003, P.R. China
| | - Meifang Jin
- Neurology Laboratory, Institute of Pediatrics, Children's Hospital of Soochow University, Suzhou, Jiangsu 215003, P.R. China
| | - Zhenhong Li
- Neurology Laboratory, Institute of Pediatrics, Children's Hospital of Soochow University, Suzhou, Jiangsu 215003, P.R. China
| | - Tian Tian
- Neurology Laboratory, Institute of Pediatrics, Children's Hospital of Soochow University, Suzhou, Jiangsu 215003, P.R. China
| | - Lili Li
- Neurology Laboratory, Institute of Pediatrics, Children's Hospital of Soochow University, Suzhou, Jiangsu 215003, P.R. China
| | - Hong Ni
- Neurology Laboratory, Institute of Pediatrics, Children's Hospital of Soochow University, Suzhou, Jiangsu 215003, P.R. China
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63
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Christenson Wick Z, Krook-Magnuson E. Specificity, Versatility, and Continual Development: The Power of Optogenetics for Epilepsy Research. Front Cell Neurosci 2018; 12:151. [PMID: 29962936 PMCID: PMC6010559 DOI: 10.3389/fncel.2018.00151] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Accepted: 05/15/2018] [Indexed: 12/19/2022] Open
Abstract
Optogenetics is a powerful and rapidly expanding set of techniques that use genetically encoded light sensitive proteins such as opsins. Through the selective expression of these exogenous light-sensitive proteins, researchers gain the ability to modulate neuronal activity, intracellular signaling pathways, or gene expression with spatial, directional, temporal, and cell-type specificity. Optogenetics provides a versatile toolbox and has significantly advanced a variety of neuroscience fields. In this review, using recent epilepsy research as a focal point, we highlight how the specificity, versatility, and continual development of new optogenetic related tools advances our understanding of neuronal circuits and neurological disorders. We additionally provide a brief overview of some currently available optogenetic tools including for the selective expression of opsins.
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Affiliation(s)
- Zoé Christenson Wick
- Graduate Program in Neuroscience and Department of Neuroscience, University of Minnesota, Minneapolis, MN, United States
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64
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Dong Q, Liu Q, Li R, Wang A, Bu Q, Wang KH, Chang Q. Mechanism and consequence of abnormal calcium homeostasis in Rett syndrome astrocytes. eLife 2018; 7:33417. [PMID: 29595472 PMCID: PMC5902163 DOI: 10.7554/elife.33417] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 03/28/2018] [Indexed: 12/21/2022] Open
Abstract
Astrocytes play an important role in Rett syndrome (RTT) disease progression. Although the non-cell-autonomous effect of RTT astrocytes on neurons was documented, cell-autonomous phenotypes and mechanisms within RTT astrocytes are not well understood. We report that spontaneous calcium activity is abnormal in RTT astrocytes in vitro, in situ, and in vivo. Such abnormal calcium activity is mediated by calcium overload in the endoplasmic reticulum caused by abnormal store operated calcium entry, which is in part dependent on elevated expression of TRPC4. Furthermore, the abnormal calcium activity leads to excessive activation of extrasynaptic NMDA receptors (eNMDARs) on neighboring neurons and increased network excitability in Mecp2 knockout mice. Finally, both the abnormal astrocytic calcium activity and the excessive activation of eNMDARs are caused by Mecp2 deletion in astrocytes in vivo. Our findings provide evidence that abnormal calcium homeostasis is a key cell-autonomous phenotype in RTT astrocytes, and reveal its mechanism and consequence.
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Affiliation(s)
- Qiping Dong
- Waisman Center, University of Wisconsin-Madison, Madison, United States
| | - Qing Liu
- Unit on Neural Circuits and Adaptive Behaviors, National Institute of Mental Health, Bethesda, United States
| | - Ronghui Li
- Waisman Center, University of Wisconsin-Madison, Madison, United States
| | - Anxin Wang
- Waisman Center, University of Wisconsin-Madison, Madison, United States
| | - Qian Bu
- Waisman Center, University of Wisconsin-Madison, Madison, United States
| | - Kuan Hong Wang
- Unit on Neural Circuits and Adaptive Behaviors, National Institute of Mental Health, Bethesda, United States
| | - Qiang Chang
- Waisman Center, University of Wisconsin-Madison, Madison, United States.,Department of Medical Genetics, University of Wisconsin-Madison, Madison, United States.,Department of Neurology, University of Wisconsin-Madison, Madison, United States
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65
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Rossi LF, Kullmann DM, Wykes RC. The Enlightened Brain: Novel Imaging Methods Focus on Epileptic Networks at Multiple Scales. Front Cell Neurosci 2018; 12:82. [PMID: 29632475 PMCID: PMC5879108 DOI: 10.3389/fncel.2018.00082] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 03/08/2018] [Indexed: 11/24/2022] Open
Abstract
Epilepsy research is rapidly adopting novel fluorescence optical imaging methods to tackle unresolved questions on the cellular and circuit mechanisms of seizure generation and evolution. State of the art two-photon microscopy and wide-field fluorescence imaging can record the activity in epileptic networks at multiple scales, from neuronal microcircuits to brain-wide networks. These approaches exploit transgenic and viral technologies to target genetically encoded calcium and voltage sensitive indicators to subclasses of neurons, and achieve genetic specificity, spatial resolution and scalability that can complement electrophysiological recordings from awake animal models of epilepsy. Two-photon microscopy is well suited to study single neuron dynamics during interictal and ictal events, and highlight the differences between the activity of excitatory and inhibitory neuronal classes in the focus and propagation zone. In contrast, wide-field fluorescence imaging provides mesoscopic recordings from the entire cortical surface, necessary to investigate seizure propagation pathways, and how the unfolding of epileptic events depends on the topology of brain-wide functional connectivity. Answering these questions will inform pre-clinical studies attempting to suppress seizures with gene therapy, optogenetic or chemogenetic strategies. Dissecting which network nodes outside the seizure onset zone are important for seizure generation, propagation and termination can be used to optimize current and future evaluation methods to identify an optimal surgical strategy.
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Affiliation(s)
- L Federico Rossi
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
| | - Dimitri M Kullmann
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom
| | - Robert C Wykes
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom
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66
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Xu JH, Wang H, Zhang W, Tang FR. Alterations of L-type voltage dependent calcium channel alpha 1 subunit in the hippocampal CA3 region during and after pilocarpine-induced epilepsy. Neurochem Int 2018; 114:108-119. [DOI: 10.1016/j.neuint.2018.02.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 01/25/2018] [Accepted: 02/05/2018] [Indexed: 01/08/2023]
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67
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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68
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 942] [Impact Index Per Article: 157.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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69
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Boison D, Steinhäuser C. Epilepsy and astrocyte energy metabolism. Glia 2017; 66:1235-1243. [PMID: 29044647 DOI: 10.1002/glia.23247] [Citation(s) in RCA: 152] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 08/29/2017] [Accepted: 10/02/2017] [Indexed: 12/17/2022]
Abstract
Epilepsy is a complex neurological syndrome characterized by neuronal hyperexcitability and sudden, synchronized electrical discharges that can manifest as seizures. It is now increasingly recognized that impaired astrocyte function and energy homeostasis play key roles in the pathogenesis of epilepsy. Excessive neuronal discharges can only happen, if adequate energy sources are made available to neurons. Conversely, energy depletion during seizures is an endogenous mechanism of seizure termination. Astrocytes control neuronal energy homeostasis through neurometabolic coupling. In this review, we will discuss how astrocyte dysfunction in epilepsy leads to distortion of key metabolic and biochemical mechanisms. Dysfunctional glutamate metabolism in astrocytes can directly contribute to neuronal hyperexcitability. Closure of astrocyte intercellular gap junction coupling as observed early during epileptogenesis limits activity-dependent trafficking of energy metabolites, but also impairs clearance of the extracellular space from accumulation of K+ and glutamate. Dysfunctional astrocytes also increase the metabolism of adenosine, a metabolic product of ATP degradation that broadly inhibits energy-consuming processes as an evolutionary adaptation to conserve energy. Due to the critical role of astroglial energy homeostasis in the control of neuronal excitability, metabolic therapeutic approaches that prevent the utilization of glucose might represent a potent antiepileptic strategy. In particular, high fat low carbohydrate "ketogenic diets" as well as inhibitors of glycolysis and lactate metabolism are of growing interest for the therapy of epilepsy.
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Affiliation(s)
- Detlev Boison
- R.S. Dow Neurobiology Laboratories, Legacy Research Institute, Portland, Oregon
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70
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Manoochehri M, Mahmoudzadeh M, Bourel-Ponchel E, Wallois F. Cortical light scattering during interictal epileptic spikes in frontal lobe epilepsy in children: A fast optical signal and electroencephalographic study. Epilepsia 2017; 58:2064-2072. [PMID: 29034451 DOI: 10.1111/epi.13926] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/25/2017] [Indexed: 12/15/2022]
Abstract
OBJECTIVE Interictal epileptic spikes (IES) represent a signature of the transient synchronous and excessive discharge of a large ensemble of cortical heterogeneous neurons. Epilepsy cannot be reduced to a hypersynchronous activation of neurons whose functioning is impaired, resulting on electroencephalogram (EEG) in epileptic seizures or IES. The complex pathophysiological mechanisms require a global approach to the interactions between neural synaptic and nonsynaptic, vascular, and metabolic systems. In the present study, we focused on the interaction between synaptic and nonsynaptic mechanisms through the simultaneous noninvasive multimodal multiscale recording of high-density EEG (HD-EEG; synaptic) and fast optical signal (FOS; nonsynaptic), which evaluate rapid changes in light scattering related to changes in membrane configuration occurring during neuronal activation of IES. METHODS To evaluate changes in light scattering occurring around IES, three children with frontal IES were simultaneously recorded with HD-EEG and FOS. To evaluate change in synchronization, time-frequency representation analysis of the HD-EEG was performed simultaneously around the IES. To independently evaluate our multimodal method, a control experiment with somatosensory stimuli was designed and applied to five healthy volunteers. RESULTS Alternating increase-decrease-increase in optical signals occurred 200 ms before to 180 ms after the IES peak. These changes started before any changes in EEG signal. In addition, time-frequency domain EEG analysis revealed alternating decrease-increase-decrease in the EEG spectral power concomitantly with changes in the optical signal during IES. These results suggest a relationship between (de)synchronization and neuronal volume changes in frontal lobe epilepsy during IES. SIGNIFICANCE These changes in the neuronal environment around IES in frontal lobe epilepsy observed in children, as they have been in rats, raise new questions about the synaptic/nonsynaptic mechanisms that propel the neurons to hypersynchronization, as occurs during IES. We further demonstrate that this noninvasive multiscale multimodal approach is suitable for studying the pathophysiology of the IES in patients.
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Affiliation(s)
- Mana Manoochehri
- National Institute of Health and Medical Research Unit 1105, Research Group on Multimodal Analysis of Brain Function, University of Picardie Jules Verne, University Hospital Center South, Amiens, France
| | - Mahdi Mahmoudzadeh
- National Institute of Health and Medical Research Unit 1105, Research Group on Multimodal Analysis of Brain Function, University of Picardie Jules Verne, University Hospital Center South, Amiens, France
| | - Emilie Bourel-Ponchel
- National Institute of Health and Medical Research Unit 1105, Research Group on Multimodal Analysis of Brain Function, University of Picardie Jules Verne, University Hospital Center South, Amiens, France
| | - Fabrice Wallois
- National Institute of Health and Medical Research Unit 1105, Research Group on Multimodal Analysis of Brain Function, University of Picardie Jules Verne, University Hospital Center South, Amiens, France
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71
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Tight Coupling of Astrocyte pH Dynamics to Epileptiform Activity Revealed by Genetically Encoded pH Sensors. J Neurosci 2017; 36:7002-13. [PMID: 27358457 DOI: 10.1523/jneurosci.0664-16.2016] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 05/23/2016] [Indexed: 12/21/2022] Open
Abstract
UNLABELLED Astrocytes can both sense and shape the evolution of neuronal network activity and are known to possess unique ion regulatory mechanisms. Here we explore the relationship between astrocytic intracellular pH dynamics and the synchronous network activity that occurs during seizure-like activity. By combining confocal and two-photon imaging of genetically encoded pH reporters with simultaneous electrophysiological recordings, we perform pH measurements in defined cell populations and relate these to ongoing network activity. This approach reveals marked differences in the intracellular pH dynamics between hippocampal astrocytes and neighboring pyramidal neurons in rodent in vitro models of epilepsy. With three different genetically encoded pH reporters, astrocytes are observed to alkalinize during epileptiform activity, whereas neurons are observed to acidify. In addition to the direction of pH change, the kinetics of epileptiform-associated intracellular pH transients are found to differ between the two cell types, with astrocytes displaying significantly more rapid changes in pH. The astrocytic alkalinization is shown to be highly correlated with astrocytic membrane potential changes during seizure-like events and mediated by an electrogenic Na(+)/HCO3 (-) cotransporter. Finally, comparisons across different cell-pair combinations reveal that astrocytic pH dynamics are more closely related to network activity than are neuronal pH dynamics. This work demonstrates that astrocytes exhibit distinct pH dynamics during periods of epileptiform activity, which has relevance to multiple processes including neurometabolic coupling and the control of network excitability. SIGNIFICANCE STATEMENT Dynamic changes in intracellular ion concentrations are central to the initiation and progression of epileptic seizures. However, it is not known how changes in intracellular H(+) concentration (ie, pH) differ between different cell types during seizures. Using recently developed pH-sensitive proteins, we demonstrate that astrocytes undergo rapid alkalinization during periods of seizure-like activity, which is in stark contrast to the acidification that occurs in neighboring neurons. Rapid astrocytic pH changes are highly temporally correlated with seizure activity, are mediated by an electrogenic Na(+)/HCO3- cotransporter, and are more tightly coupled to network activity than are neuronal pH changes. As pH has profound effects on signaling in the nervous system, this work has implications for our understanding of seizure dynamics.
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72
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Baird-Daniel E, Daniel AGS, Wenzel M, Li D, Liou JY, Laffont P, Zhao M, Yuste R, Ma H, Schwartz TH. Glial Calcium Waves are Triggered by Seizure Activity and Not Essential for Initiating Ictal Onset or Neurovascular Coupling. Cereb Cortex 2017; 27:3318-3330. [PMID: 28369176 PMCID: PMC6433182 DOI: 10.1093/cercor/bhx072] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 03/02/2017] [Indexed: 12/12/2022] Open
Abstract
It has been postulated that glia play a critical role in modifying neuronal activity, mediating neurovascular coupling, and in seizure initiation. We investigated the role of glia in ictogenesis and neurovascular coupling through wide-field multicell and 2-photon single cell imaging of calcium and intrinsic signal imaging of cerebral blood volume in an in vivo rat model of focal neocortical seizures. Ictal events triggered a slowly propagating glial calcium wave that was markedly delayed after both neuronal and hemodynamic onset. Glial calcium waves exhibited a stereotypical spread that terminated prior to seizure offset and propagated to an area ~60% greater than the propagation area of neural and vascular signals. Complete blockage of glial activity with fluoroacetate resulted in no change in either neuronal or hemodynamic activity. These ictal glial waves were blocked by carbenoxolone, a gap junction blocker. Our in vivo data reveal that ictal events trigger a slowly propagating, stereotypical glial calcium wave, mediated by gap junctions, that is spatially and temporally independent of neuronal and hemodynamic activities. We introduce a novel ictally triggered propagating glial calcium wave calling into question the criticality of glial calcium wave in both ictal onset and neurovascular coupling.
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Affiliation(s)
- Eliza Baird-Daniel
- Department of Neurological Surgery, Feil Family Brain and Mind Research Institute, Sackler Brain and Spine Institute, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY 10065, USA
| | - Andy G. S. Daniel
- Department of Neurological Surgery, Feil Family Brain and Mind Research Institute, Sackler Brain and Spine Institute, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY 10065, USA
| | - Michael Wenzel
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Dan Li
- Department of Neurological Surgery, Feil Family Brain and Mind Research Institute, Sackler Brain and Spine Institute, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY 10065, USA
- Department of Radiology, First Hospital of Jilin University, Changchun, Jilin 130021, China
| | - Jyun-You Liou
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Philippe Laffont
- Department of Neurological Surgery, Feil Family Brain and Mind Research Institute, Sackler Brain and Spine Institute, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY 10065, USA
| | - Mingrui Zhao
- Department of Neurological Surgery, Feil Family Brain and Mind Research Institute, Sackler Brain and Spine Institute, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY 10065, USA
| | - Rafael Yuste
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Hongtao Ma
- Department of Neurological Surgery, Feil Family Brain and Mind Research Institute, Sackler Brain and Spine Institute, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY 10065, USA
| | - Theodore H. Schwartz
- Department of Neurological Surgery, Feil Family Brain and Mind Research Institute, Sackler Brain and Spine Institute, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY 10065, USA
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73
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Losi G, Mariotti L, Sessolo M, Carmignoto G. New Tools to Study Astrocyte Ca 2+ Signal Dynamics in Brain Networks In Vivo. Front Cell Neurosci 2017; 11:134. [PMID: 28536505 PMCID: PMC5422467 DOI: 10.3389/fncel.2017.00134] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 04/20/2017] [Indexed: 11/19/2022] Open
Abstract
Sensory information processing is a fundamental operation in the brain that is based on dynamic interactions between different neuronal populations. Astrocytes, a type of glial cells, have been proposed to represent active elements of brain microcircuits that, through dynamic interactions with neurons, provide a modulatory control of neuronal network activity. Specifically, astrocytes in different brain regions have been described to respond to neuronal signals with intracellular Ca2+ elevations that represent a key step in the functional recruitment of astrocytes to specific brain circuits. Accumulating evidence shows that Ca2+ elevations regulate the release of gliotransmitters that, in turn, modulate synaptic transmission and neuronal excitability. Recent studies also provided new insights into the spatial and temporal features of astrocytic Ca2+ elevations revealing a surprising complexity of Ca2+ signal dynamics in astrocytes. Here we discuss how recently developed experimental tools such as the genetically encoded Ca2+ indicators (GECI), optogenetics and chemogenetics can be applied to the study of astrocytic Ca2+ signals in the living brain.
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Affiliation(s)
- Gabriele Losi
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of PadovaPadova, Italy
| | - Letizia Mariotti
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of PadovaPadova, Italy.,Division of Neurobiology, MRC Laboratory of Molecular BiologyCambridge, UK
| | - Michele Sessolo
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of PadovaPadova, Italy.,Center for Drug Discovery & Development, Aptuit inc.Verona, Italy
| | - Giorgio Carmignoto
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of PadovaPadova, Italy
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74
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Amar M, Singh A, Mallick BN. Noradrenergic β-Adrenoceptor-Mediated Intracellular Molecular Mechanism of Na-K ATPase Subunit Expression in C6 Cells. Cell Mol Neurobiol 2017; 38:441-457. [PMID: 28353187 DOI: 10.1007/s10571-017-0488-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 03/23/2017] [Indexed: 11/26/2022]
Abstract
Rapid eye movement sleep deprivation-associated elevated noradrenaline increases and decreases neuronal and glial Na-K ATPase activity, respectively. In this study, using C6 cell-line as a model, we investigated the possible intracellular molecular mechanism of noradrenaline-induced decreased glial Na-K ATPase activity. The cells were treated with noradrenaline in the presence or absence of adrenoceptor antagonists, modulators of extra- and intracellular Ca++ and modulators of intracellular signalling pathways. We observed that noradrenaline acting on β-adrenoceptor decreased Na-K ATPase activity and mRNA expression of the catalytic α2-Na-K ATPase subunit in the C6 cells. Further, cAMP and protein kinase-A mediated release of intracellular Ca++ played a critical role in such decreased α2-Na-K ATPase expression. In contrast, noradrenaline acting on β-adrenoceptor up-regulated the expression of regulatory β2-Na-K ATPase subunit, which although was cAMP and Ca++ dependent, was independent of protein kinase-A and protein kinase-C. Combining these with previous findings (including ours) we have proposed a working model for noradrenaline-induced suppression of glial Na-K ATPase activity and alteration in its subunit expression. The findings help understanding noradrenaline-associated maintenance of brain excitability during health and altered states, particularly in relation to rapid eye movement sleep and its deprivation when the noradrenaline level is naturally altered.
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Affiliation(s)
- Megha Amar
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Abhishek Singh
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
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75
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Buscemi L, Ginet V, Lopatar J, Montana V, Pucci L, Spagnuolo P, Zehnder T, Grubišić V, Truttman A, Sala C, Hirt L, Parpura V, Puyal J, Bezzi P. Homer1 Scaffold Proteins Govern Ca2+ Dynamics in Normal and Reactive Astrocytes. Cereb Cortex 2017; 27:2365-2384. [PMID: 27075036 PMCID: PMC5963825 DOI: 10.1093/cercor/bhw078] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In astrocytes, the intracellular calcium (Ca2+) signaling mediated by activation of metabotropic glutamate receptor 5 (mGlu5) is crucially involved in the modulation of many aspects of brain physiology, including gliotransmission. Here, we find that the mGlu5-mediated Ca2+ signaling leading to release of glutamate is governed by mGlu5 interaction with Homer1 scaffolding proteins. We show that the long splice variants Homer1b/c are expressed in astrocytic processes, where they cluster with mGlu5 at sites displaying intense local Ca2+ activity. We show that the structural and functional significance of the Homer1b/c-mGlu5 interaction is to relocate endoplasmic reticulum (ER) to the proximity of the plasma membrane and to optimize Ca2+ signaling and glutamate release. We also show that in reactive astrocytes the short dominant-negative splice variant Homer1a is upregulated. Homer1a, by precluding the mGlu5-ER interaction decreases the intensity of Ca2+ signaling thus limiting the intensity and the duration of glutamate release by astrocytes. Hindering upregulation of Homer1a with a local injection of short interfering RNA in vivo restores mGlu5-mediated Ca2+ signaling and glutamate release and sensitizes astrocytes to apoptosis. We propose that Homer1a may represent one of the cellular mechanisms by which inflammatory astrocytic reactions are beneficial for limiting brain injury.
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Affiliation(s)
- Lara Buscemi
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
- Stroke Laboratory, Neurology Service, Department of Clinical Neurosciences, University Hospital Centre and University of Lausanne, CH-1011 Lausanne, Switzerland
| | - Vanessa Ginet
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
- Division of Neonatology, Department of Paediatrics and Paediatric Surgery, University Hospital Centre and University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Jan Lopatar
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
| | - Vedrana Montana
- Department of Biotechnology, University of Rijeka, 51000 Rijeka, Croatia
- Department of Neurobiology, Center for Glial Biology in Medicine, Civitan International Research Center, Atomic Force Microscopy and Nanotechnology Laboratories, and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Luca Pucci
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
| | - Paola Spagnuolo
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Rende, Italy
| | - Tamara Zehnder
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
| | - Vladimir Grubišić
- Department of Neurobiology, Center for Glial Biology in Medicine, Civitan International Research Center, Atomic Force Microscopy and Nanotechnology Laboratories, and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Anita Truttman
- Division of Neonatology, Department of Paediatrics and Paediatric Surgery, University Hospital Centre and University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Carlo Sala
- CNR Institute of Neuroscience and Department of Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - Lorenz Hirt
- Stroke Laboratory, Neurology Service, Department of Clinical Neurosciences, University Hospital Centre and University of Lausanne, CH-1011 Lausanne, Switzerland
| | - Vladimir Parpura
- Department of Neurobiology, Center for Glial Biology in Medicine, Civitan International Research Center, Atomic Force Microscopy and Nanotechnology Laboratories, and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Julien Puyal
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
- Division of Neonatology, Department of Paediatrics and Paediatric Surgery, University Hospital Centre and University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Paola Bezzi
- Department of Fundamental Neurosciences, University of Lausanne, CH1005Lausanne, Switzerland
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76
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Gómez-Gonzalo M, Martin-Fernandez M, Martínez-Murillo R, Mederos S, Hernández-Vivanco A, Jamison S, Fernandez AP, Serrano J, Calero P, Futch HS, Corpas R, Sanfeliu C, Perea G, Araque A. Neuron-astrocyte signaling is preserved in the aging brain. Glia 2017; 65:569-580. [PMID: 28130845 DOI: 10.1002/glia.23112] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2016] [Revised: 11/23/2016] [Accepted: 12/21/2016] [Indexed: 12/18/2022]
Abstract
Astrocytes play crucial roles in brain homeostasis and are emerging as regulatory elements of neuronal and synaptic physiology by responding to neurotransmitters with Ca2+ elevations and releasing gliotransmitters that activate neuronal receptors. Aging involves neuronal and astrocytic alterations, being considered risk factor for neurodegenerative diseases. Most evidence of the astrocyte-neuron signaling is derived from studies with young animals; however, the features of astrocyte-neuron signaling in adult and aging brain remain largely unknown. We have investigated the existence and properties of astrocyte-neuron signaling in physiologically and pathologically aging mouse hippocampal and cortical slices at different lifetime points (0.5 to 20 month-old animals). We found that astrocytes preserved their ability to express spontaneous and neurotransmitter-dependent intracellular Ca2+ signals from juvenile to aging brains. Likewise, resting levels of gliotransmission, assessed by neuronal NMDAR activation by glutamate released from astrocytes, were largely preserved with similar properties in all tested age groups, but DHPG-induced gliotransmission was reduced in aged mice. In contrast, gliotransmission was enhanced in the APP/PS1 mouse model of Alzheimer's disease, indicating a dysregulation of astrocyte-neuron signaling in pathological conditions. Disruption of the astrocytic IP3 R2 mediated-signaling, which is required for neurotransmitter-induced astrocyte Ca2+ signals and gliotransmission, boosted the progression of amyloid plaque deposits and synaptic plasticity impairments in APP/PS1 mice at early stages of the disease. Therefore, astrocyte-neuron interaction is a fundamental signaling, largely conserved in the adult and aging brain of healthy animals, but it is altered in Alzheimer's disease, suggesting that dysfunctions of astrocyte Ca2+ physiology may contribute to this neurodegenerative disease. GLIA 2017 GLIA 2017;65:569-580.
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Affiliation(s)
| | | | | | | | | | - Stephanie Jamison
- Department of Neuroscience, University of Minnesota, Minneapolis, 55455
| | | | | | | | - Hunter S Futch
- College of Medicine, University of Florida, Gainesville, Florida, 32610-0261
| | - Rubén Corpas
- Aging and Neurodegeneration Unit, Biomedical Research Institute of Barcelona (IIBB), CSIC and IDIBAPS, Barcelona, 08036, Spain
| | - Coral Sanfeliu
- Aging and Neurodegeneration Unit, Biomedical Research Institute of Barcelona (IIBB), CSIC and IDIBAPS, Barcelona, 08036, Spain
| | | | - Alfonso Araque
- Department of Neuroscience, University of Minnesota, Minneapolis, 55455
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77
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Shigetomi E, Koizumi S. Visualization of diversity of calcium signals in astrocytes. Nihon Yakurigaku Zasshi 2017; 148:75-80. [PMID: 27478045 DOI: 10.1254/fpj.148.75] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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78
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Pompili E, Fabrizi C, Somma F, Correani V, Maras B, Schininà ME, Ciraci V, Artico M, Fornai F, Fumagalli L. PAR1 activation affects the neurotrophic properties of Schwann cells. Mol Cell Neurosci 2017; 79:23-33. [PMID: 28064059 DOI: 10.1016/j.mcn.2017.01.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 12/14/2016] [Accepted: 01/01/2017] [Indexed: 01/02/2023] Open
Abstract
Protease-activated receptor-1 (PAR1) is the prototypic member of a family of four G-protein-coupled receptors that signal in response to extracellular proteases. In the peripheral nervous system, the expression and/or the role of PARs are still poorly investigated. High PAR1 mRNA expression was found in the rat dorsal root ganglia and the signal intensity of PAR1 mRNA increased in response to sciatic nerve transection. In the sciatic nerve, functional PAR1 receptor was reported at the level of non-compacted Schwann cell myelin microvilli of the nodes of Ranvier. Schwann cells are the principal population of glial cells of the peripheral nervous system which myelinate axons playing an important role during axonal regeneration and remyelination. The present study was undertaken in order to determine if the activation of PAR1 affects the neurotrophic properties of Schwann cells. Our results suggest that the stimulation of PAR1 could potentiate the Schwann cell ability to favour nerve regeneration. In fact, the conditioned medium obtained from Schwann cell cultures challenged with a specific PAR1 activating peptide (PAR1 AP) displays increased neuroprotective and neurotrophic properties with respect to the culture medium from untreated Schwann cells. The proteomic analysis of secreted proteins in untreated and PAR1 AP-treated Schwann cells allowed the identification of factors differentially expressed in the two samples. Some of them (such as macrophage migration inhibitory factor, matrix metalloproteinase-2, decorin, syndecan 4, complement C1r subcomponent, angiogenic factor with G patch and FHA domains 1) appear to be transcriptionally regulated after PAR1 AP treatment as shown by RT-PCR.
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Affiliation(s)
- Elena Pompili
- Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Sapienza University of Rome, Rome, Italy.
| | - Cinzia Fabrizi
- Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Sapienza University of Rome, Rome, Italy
| | - Francesca Somma
- Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Sapienza University of Rome, Rome, Italy
| | - Virginia Correani
- Department of Biochemical Sciences, Sapienza University of Rome, Rome, Italy
| | - Bruno Maras
- Department of Biochemical Sciences, Sapienza University of Rome, Rome, Italy
| | | | - Viviana Ciraci
- Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Sapienza University of Rome, Rome, Italy
| | - Marco Artico
- Department of Sensory Organs, Sapienza University of Rome, Rome, Italy
| | - Francesco Fornai
- Department of Human Morphology and Applied Biology, University of Pisa, Pisa, Italy; IRCCS Neuromed, Pozzilli, Italy
| | - Lorenzo Fumagalli
- Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Sapienza University of Rome, Rome, Italy
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79
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Bang J, Kim HY, Lee H. Optogenetic and Chemogenetic Approaches for Studying Astrocytes and Gliotransmitters. Exp Neurobiol 2016; 25:205-221. [PMID: 27790055 PMCID: PMC5081467 DOI: 10.5607/en.2016.25.5.205] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 08/19/2016] [Accepted: 08/19/2016] [Indexed: 12/20/2022] Open
Abstract
The brain consists of heterogeneous populations of neuronal and non-neuronal cells. The revelation of their connections and interactions is fundamental to understanding normal brain functions as well as abnormal changes in pathological conditions. Optogenetics and chemogenetics have been developed to allow functional manipulations both in vitro and in vivo to examine causal relationships between cellular changes and functional outcomes. These techniques are based on genetically encoded effector molecules that respond exclusively to exogenous stimuli, such as a certain wavelength of light or a synthetic ligand. Activation of effector molecules provokes diverse intracellular changes, such as an influx or efflux of ions, depolarization or hyperpolarization of membranes, and activation of intracellular signaling cascades. Optogenetics and chemogenetics have been applied mainly to the study of neuronal circuits, but their use in studying non-neuronal cells has been gradually increasing. Here we introduce recent studies that have employed optogenetics and chemogenetics to reveal the function of astrocytes and gliotransmitters.
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Affiliation(s)
- Juwon Bang
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
| | - Hak Yeong Kim
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
| | - Hyosang Lee
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
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80
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Liu L, Liu L, Shi J, Tan M, Xiong J, Li X, Hu Q, Yi Z, Mao D. MicroRNA-34b mediates hippocampal astrocyte apoptosis in a rat model of recurrent seizures. BMC Neurosci 2016; 17:56. [PMID: 27514646 PMCID: PMC4981991 DOI: 10.1186/s12868-016-0291-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 07/21/2016] [Indexed: 01/03/2023] Open
Abstract
Background Recurrent convulsions can cause irreversible astrocyte death, impede neuron regeneration, and further aggravate brain damage. MicroRNAs have been revealed as players in the progression of numerous diseases including cancer and Alzheimer’s disease. Particularly, microRNA has been found linked to seizure-induced neuronal death. In this study, a rat model of recurrent convulsions induced by flurothyl treatments was utilised to assess the alterations of microRNA expressions in hippocampus tissues. We also applied an in vitro model in which primary astrocytes were exposed to kainic acid to verify the targets of miR-34b-5p identified in the animal model. Results We discovered that miR-34b-5p, a member of the miR-34 family, increased significantly in flurothyl-treated rat hippocampus tissue. More surprisingly, this upregulation occurred concurrently with accumulating astrocyte apoptosis, indicating the involvement of miR-34b-5p in seizures caused astrocyte apoptosis. Results from the in vitro experiments further demonstrated that miR-34b-5p directly targeted Bcl-2 mRNA, translationally repressed Bcl-2 protein, and thus modulated cell apoptosis by influencing Bcl-2, Bax, and Caspase-3. Conclusion Our findings prove microRNAs play a role in mediating recurrent convulsions-induced astrocyte death and further indicate that miR-34b-5p could acts as a regulator for astrocyte apoptosis induced by recurrent seizures. Electronic supplementary material The online version of this article (doi:10.1186/s12868-016-0291-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Liqun Liu
- Department of Pediatrics, The Second Xiangya Hospital of Central South University, 86 Renmin Middle Rd, Changsha, 410011, Hunan, People's Republic of China
| | - Lingjuan Liu
- Department of Pediatrics, The Second Xiangya Hospital of Central South University, 86 Renmin Middle Rd, Changsha, 410011, Hunan, People's Republic of China
| | - Jiayun Shi
- Department of Pediatrics, The Second Xiangya Hospital of Central South University, 86 Renmin Middle Rd, Changsha, 410011, Hunan, People's Republic of China
| | - Menglin Tan
- Department of Pediatrics, The Second Xiangya Hospital of Central South University, 86 Renmin Middle Rd, Changsha, 410011, Hunan, People's Republic of China
| | - Jie Xiong
- Department of Pediatrics, The Second Xiangya Hospital of Central South University, 86 Renmin Middle Rd, Changsha, 410011, Hunan, People's Republic of China
| | - Xingfang Li
- Department of Pediatrics, The Second Xiangya Hospital of Central South University, 86 Renmin Middle Rd, Changsha, 410011, Hunan, People's Republic of China
| | - Qingpeng Hu
- Department of Pediatrics, The Second Xiangya Hospital of Central South University, 86 Renmin Middle Rd, Changsha, 410011, Hunan, People's Republic of China
| | - Zhuwen Yi
- Department of Pediatrics, The Second Xiangya Hospital of Central South University, 86 Renmin Middle Rd, Changsha, 410011, Hunan, People's Republic of China
| | - Ding'an Mao
- Department of Pediatrics, The Second Xiangya Hospital of Central South University, 86 Renmin Middle Rd, Changsha, 410011, Hunan, People's Republic of China.
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81
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Trevelyan AJ. Do Cortical Circuits Need Protecting from Themselves? Trends Neurosci 2016; 39:502-511. [PMID: 27378547 DOI: 10.1016/j.tins.2016.06.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 05/09/2016] [Accepted: 06/09/2016] [Indexed: 01/27/2023]
Abstract
All hippocampal and neocortical networks can be driven to seize quite easily. This can be done using drugs, by altering the ionic constituency of the bathing medium [cerebrospinal fluid (CSF)], or by electrical stimulation (both experimentally and clinically, as in electroconvulsive therapy). It is worth asking why this is so, because this will both tell us more about potentially devastating neurological disorders and extend our understanding of cortical function and architecture. Here I review work examining the features of cortical networks that bias activity towards and away from hyperexcitability. I suggest that several cellular- and circuit-level features of rapidly responsive interneuron networks tip the balance away from seizure in the healthy brain.
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Affiliation(s)
- Andrew J Trevelyan
- Institute of Neuroscience, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
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82
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Logica T, Riviere S, Holubiec MI, Castilla R, Barreto GE, Capani F. Metabolic Changes Following Perinatal Asphyxia: Role of Astrocytes and Their Interaction with Neurons. Front Aging Neurosci 2016; 8:116. [PMID: 27445788 PMCID: PMC4921470 DOI: 10.3389/fnagi.2016.00116] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 05/03/2016] [Indexed: 11/13/2022] Open
Abstract
Perinatal Asphyxia (PA) represents an important cause of severe neurological deficits including delayed mental and motor development, epilepsy, major cognitive deficits and blindness. The interaction between neurons, astrocytes and endothelial cells plays a central role coupling energy supply with changes in neuronal activity. Traditionally, experimental research focused on neurons, whereas astrocytes have been more related to the damage mechanisms of PA. Astrocytes carry out a number of functions that are critical to normal nervous system function, including uptake of neurotransmitters, regulation of pH and ion concentrations, and metabolic support for neurons. In this work, we aim to review metabolic neuron-astrocyte interactions with the purpose of encourage further research in this area in the context of PA, which is highly complex and its mechanisms and pathways have not been fully elucidated to this day.
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Affiliation(s)
- Tamara Logica
- Laboratorio de Citoarquitectura y Plasticidad Neuronal, Facultad de Medicina, Instituto de Investigaciones Cardiológicas Prof. Dr. Alberto C. Taquini (ININCA), UBA-CONICET, CABA Buenos Aires, Argentina
| | - Stephanie Riviere
- Laboratorio de Biología Molecular, Facultad de Medicina, Instituto de Investigaciones cardiológicas Prof. Dr. Alberto C. Taquini (ININCA), UBA-CONICET, CABA Buenos Aires, Argentina
| | - Mariana I Holubiec
- Laboratorio de Citoarquitectura y Plasticidad Neuronal, Facultad de Medicina, Instituto de Investigaciones Cardiológicas Prof. Dr. Alberto C. Taquini (ININCA), UBA-CONICET, CABA Buenos Aires, Argentina
| | - Rocío Castilla
- Laboratorio de Biología Molecular, Facultad de Medicina, Instituto de Investigaciones cardiológicas Prof. Dr. Alberto C. Taquini (ININCA), UBA-CONICET, CABA Buenos Aires, Argentina
| | - George E Barreto
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana Bogotá Bogotá, Colombia
| | - Francisco Capani
- Laboratorio de Citoarquitectura y Plasticidad Neuronal, Facultad de Medicina, Instituto de Investigaciones Cardiológicas Prof. Dr. Alberto C. Taquini (ININCA), UBA-CONICET, CABABuenos Aires, Argentina; Departamento de Biología, Universidad Argentina JF KennedyBuenos Aires, Argentina; Investigador Asociado, Universidad Autónoma de ChileSantiago, Chile
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83
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Paredes JM, Idilli AI, Mariotti L, Losi G, Arslanbaeva LR, Sato SS, Artoni P, Szczurkowska J, Cancedda L, Ratto GM, Carmignoto G, Arosio D. Synchronous Bioimaging of Intracellular pH and Chloride Based on LSS Fluorescent Protein. ACS Chem Biol 2016; 11:1652-60. [PMID: 27031242 DOI: 10.1021/acschembio.6b00103] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Ion homeostasis regulates critical physiological processes in the living cell. Intracellular chloride concentration not only contributes in setting the membrane potential of quiescent cells but it also plays a role in modulating the dynamic voltage changes during network activity. Dynamic chloride imaging demands new tools, allowing faster acquisition rates and correct accounting of concomitant pH changes. Joining a long-Stokes-shift red-fluorescent protein to a GFP variant with high sensitivity to pH and chloride, we obtained LSSmClopHensor, a genetically encoded fluorescent biosensor optimized for the simultaneous chloride and pH imaging and requiring only two excitation wavelengths (458 and 488 nm). LSSmClopHensor allowed us to monitor the dynamic changes of intracellular pH and chloride concentration during seizure like discharges in neocortical brain slices. Only cells with tightly controlled resting potential revealed a narrow distribution of chloride concentration peaking at about 5 and 8 mM, in neocortical neurons and SK-N-SH cells, respectively. We thus showed that LSSmClopHensor represents a new versatile tool for studying the dynamics of chloride and proton concentration in living systems.
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Affiliation(s)
- Jose M. Paredes
- Institute of Biophysics, CNR, Via
alla Cascata 56/C, 38123 Trento, Italy
- Bruno Kessler Foundation, Via
Sommarive 18, 38123 Trento, Italy
| | - Aurora I. Idilli
- Institute of Biophysics, CNR, Via
alla Cascata 56/C, 38123 Trento, Italy
| | - Letizia Mariotti
- Neuroscience Institute, CNR, Viale
G. Colombo 3, 35121 Padova, Italy
| | - Gabriele Losi
- Neuroscience Institute, CNR, Viale
G. Colombo 3, 35121 Padova, Italy
| | - Lyaysan R. Arslanbaeva
- Institute of Biophysics, CNR, Via
alla Cascata 56/C, 38123 Trento, Italy
- CIBIO, University of Trento, Via delle Regole 101, 38123 Trento, Italy
| | | | | | | | | | - Gian Michele Ratto
- Nanoscience Institute, CNR, Pisa, Italy
- Scuola Normale Superiore, Pisa, Italy
| | | | - Daniele Arosio
- Institute of Biophysics, CNR, Via
alla Cascata 56/C, 38123 Trento, Italy
- CIBIO, University of Trento, Via delle Regole 101, 38123 Trento, Italy
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84
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Rassendren F, Audinat E. Purinergic signaling in epilepsy. J Neurosci Res 2016; 94:781-93. [PMID: 27302739 DOI: 10.1002/jnr.23770] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 04/28/2016] [Accepted: 04/29/2016] [Indexed: 12/24/2022]
Abstract
Until recently, analysis of the mechanisms underlying epilepsy was centered on neuron dysfunctions. Accordingly, most of the available pharmacological treatments aim at reducing neuronal excitation or at potentiating neuronal inhibition. These therapeutic options can lead to obvious secondary effects, and, moreover, seizures cannot be controlled by any known medication in one-third of the patients. A purely neurocentric view of brain functions and dysfunctions has been seriously questioned during the past 2 decades because of the accumulation of experimental data showing the functional importance of reciprocal interactions between glial cells and neurons. In the case of epilepsy, our current knowledge of the human disease and analysis of animal models clearly favor the involvement of astrocytes and microglial cells during the progression of the disease, including at very early stages, opening the way to the identification of new therapeutic targets. Purinergic signaling is a fundamental feature of neuron-glia interactions, and increasing evidence indicates that modifications of this pathway contribute to the functional remodeling of the epileptic brain. This Review discusses the recent experimental results indicating the roles of astrocytic and microglial P2X and P2Y receptors in epilepsy. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- François Rassendren
- CNRS, UMR 5203, Institut de Génomique Fonctionnelle, Montpellier, France.,INSERM, U1191, Montpellier, France.,Université de Montpellier, UMR5203, Montpellier, France.,Labex ICST, Montpellier, France
| | - Etienne Audinat
- INSERM, U1128, Paris, France.,Laboratory of Neurophysiology and New Microscopies, Paris Descartes University, Paris, France
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85
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Henneberger C. Does rapid and physiological astrocyte-neuron signalling amplify epileptic activity? J Physiol 2016; 595:1917-1927. [PMID: 27106234 DOI: 10.1113/jp271958] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Accepted: 02/26/2016] [Indexed: 12/11/2022] Open
Abstract
The hippocampus is a key brain region in the pathophysiology of mesial temporal lobe epilepsy. Long-term changes of its architecture and function on the network and cellular level are well documented in epilepsy. Astrocytes can control many aspects of neuronal function and their long-term alterations over weeks, months and years play an important role in epilepsy. However, a pathophysiological transformation of astrocytes does not seem to be required for astrocytes to contribute to epileptic activity. Some of the properties of physiological astrocyte-neuron communication could allow these cells to exacerbate or synchronize neuronal firing on shorter time scales of milliseconds to minutes. Therefore, these astrocyte-neuron interactions are increasingly recognized as potential contributors to epileptic activity. Fast and reciprocal communication between astrocytes and neurons is enabled by a diverse set of mechanisms that could both amplify and counteract epileptic activity. They may thus promote or cause development of epileptic activity or inhibit it. Mechanisms of astrocyte-neuron interactions that can quickly increase network excitability involve, for example, astrocyte Ca2+ and Na+ signalling, K+ buffering, gap junction coupling and metabolism. However, rapid changes of astrocyte neurotransmitter uptake and morphology may also underlie or support development of network hyperexcitability. The temporal characteristics of these interactions, their ability to synchronize neuronal activity and their net effect on network activity will determine their contribution to the emergence or maintenance of epileptic activity.
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Affiliation(s)
- Christian Henneberger
- Institute of Cellular Neurosciences, University of Bonn Medical School, Germany.,German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany.,UCL Institute of Neurology, London, UK
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86
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Crucial role of astrocytes in temporal lobe epilepsy. Neuroscience 2016; 323:157-69. [DOI: 10.1016/j.neuroscience.2014.12.047] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 12/25/2014] [Accepted: 12/30/2014] [Indexed: 11/30/2022]
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87
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Dallérac G, Rouach N. Astrocytes as new targets to improve cognitive functions. Prog Neurobiol 2016; 144:48-67. [PMID: 26969413 DOI: 10.1016/j.pneurobio.2016.01.003] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 01/07/2016] [Accepted: 01/24/2016] [Indexed: 01/09/2023]
Abstract
Astrocytes are now viewed as key elements of brain wiring as well as neuronal communication. Indeed, they not only bridge the gap between metabolic supplies by blood vessels and neurons, but also allow fine control of neurotransmission by providing appropriate signaling molecules and insulation through a tight enwrapping of synapses. Recognition that astroglia is essential to neuronal communication is nevertheless fairly recent and the large body of evidence dissecting such role has focused on the synaptic level by identifying neuro- and gliotransmitters uptaken and released at synaptic or extrasynaptic sites. Yet, more integrated research deciphering the impact of astroglial functions on neuronal network activity have led to the reasonable assumption that the role of astrocytes in supervising synaptic activity translates in influencing neuronal processing and cognitive functions. Several investigations using recent genetic tools now support this notion by showing that inactivating or boosting astroglial function directly affects cognitive abilities. Accordingly, brain diseases resulting in impaired cognitive functions have seen their physiopathological mechanisms revisited in light of this primary protagonist of brain processing. We here provide a review of the current knowledge on the role of astrocytes in cognition and in several brain diseases including neurodegenerative disorders, psychiatric illnesses, as well as other conditions such as epilepsy. Potential astroglial therapeutic targets are also discussed.
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Affiliation(s)
- Glenn Dallérac
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé et de la Recherche Médicale U1050, Labex Memolife, PSL Research University, Paris, France.
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique UMR 7241, Institut National de la Santé et de la Recherche Médicale U1050, Labex Memolife, PSL Research University, Paris, France.
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88
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Plasticity of Hippocampal Excitatory-Inhibitory Balance: Missing the Synaptic Control in the Epileptic Brain. Neural Plast 2016; 2016:8607038. [PMID: 27006834 PMCID: PMC4783563 DOI: 10.1155/2016/8607038] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 01/20/2016] [Accepted: 01/31/2016] [Indexed: 11/24/2022] Open
Abstract
Synaptic plasticity is the capacity generated by experience to modify the neural function and, thereby, adapt our behaviour. Long-term plasticity of glutamatergic and GABAergic transmission occurs in a concerted manner, finely adjusting the excitatory-inhibitory (E/I) balance. Imbalances of E/I function are related to several neurological diseases including epilepsy. Several evidences have demonstrated that astrocytes are able to control the synaptic plasticity, with astrocytes being active partners in synaptic physiology and E/I balance. Here, we revise molecular evidences showing the epileptic stage as an abnormal form of long-term brain plasticity and propose the possible participation of astrocytes to the abnormal increase of glutamatergic and decrease of GABAergic neurotransmission in epileptic networks.
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89
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De Stasi AM, Farisello P, Marcon I, Cavallari S, Forli A, Vecchia D, Losi G, Mantegazza M, Panzeri S, Carmignoto G, Bacci A, Fellin T. Unaltered Network Activity and Interneuronal Firing During Spontaneous Cortical Dynamics In Vivo in a Mouse Model of Severe Myoclonic Epilepsy of Infancy. Cereb Cortex 2016; 26:1778-94. [PMID: 26819275 PMCID: PMC4785957 DOI: 10.1093/cercor/bhw002] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Severe myoclonic epilepsy of infancy (SMEI) is associated with loss of function of the SCN1A gene encoding the NaV1.1 sodium channel isoform. Previous studies in Scn1a−/+ mice during the pre-epileptic period reported selective reduction in interneuron excitability and proposed this as the main pathological mechanism underlying SMEI. Yet, the functional consequences of this interneuronal dysfunction at the circuit level in vivo are unknown. Here, we investigated whether Scn1a−/+ mice showed alterations in cortical network function. We found that various forms of spontaneous network activity were similar in Scn1a−/+ during the pre-epileptic period compared with wild-type (WT) in vivo. Importantly, in brain slices from Scn1a−/+ mice, the excitability of parvalbumin (PV) and somatostatin (SST) interneurons was reduced, epileptiform activity propagated more rapidly, and complex synaptic changes were observed. However, in vivo, optogenetic reduction of firing in PV or SST cells in WT mice modified ongoing network activities, and juxtasomal recordings from identified PV and SST interneurons showed unaffected interneuronal firing during spontaneous cortical dynamics in Scn1a−/+ compared with WT. These results demonstrate that interneuronal hypoexcitability is not observed in Scn1a−/+ mice during spontaneous activities in vivo and suggest that additional mechanisms may contribute to homeostatic rearrangements and the pathogenesis of SMEI.
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Affiliation(s)
- Angela Michela De Stasi
- Optical Approaches to Brain Function Laboratory Neural Coding Laboratory, Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
| | - Pasqualina Farisello
- Optical Approaches to Brain Function Laboratory Fondazione EBRI "Rita Levi-Montalcini", Roma, Italy
| | - Iacopo Marcon
- CNR Neuroscience Institute and University of Padova, Padova, Italy
| | - Stefano Cavallari
- Neural Coding Laboratory, Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy Neural Computation Laboratory, Istituto Italiano di Tecnologia, Rovereto, Italy
| | - Angelo Forli
- Optical Approaches to Brain Function Laboratory Neural Coding Laboratory, Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
| | - Dania Vecchia
- Optical Approaches to Brain Function Laboratory Neural Coding Laboratory, Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
| | - Gabriele Losi
- CNR Neuroscience Institute and University of Padova, Padova, Italy
| | - Massimo Mantegazza
- Institute of Molecular and Cellular Pharmacology (IPMC), CNRS UMR7275 and University of Nice-Sophia Antipolis, Valbonne, France
| | - Stefano Panzeri
- Neural Coding Laboratory, Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy Neural Computation Laboratory, Istituto Italiano di Tecnologia, Rovereto, Italy
| | | | - Alberto Bacci
- Fondazione EBRI "Rita Levi-Montalcini", Roma, Italy Sorbonne Universités UPMC Paris 06, UMR S 1127, Inserm U 1127, CNRS UMR 7225, Paris, France ICM-Institut du Cerveau et de la Moelle épinière, Paris, France
| | - Tommaso Fellin
- Optical Approaches to Brain Function Laboratory Neural Coding Laboratory, Neuroscience and Brain Technologies Department, Istituto Italiano di Tecnologia, Genova, Italy
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90
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Mariotti L, Losi G, Sessolo M, Marcon I, Carmignoto G. The inhibitory neurotransmitter GABA evokes long-lasting Ca(2+) oscillations in cortical astrocytes. Glia 2015; 64:363-73. [PMID: 26496414 PMCID: PMC5057345 DOI: 10.1002/glia.22933] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 09/28/2015] [Indexed: 12/31/2022]
Abstract
Studies over the last decade provided evidence that in a dynamic interaction with neurons glial cell astrocytes contribut to fundamental phenomena in the brain. Most of the knowledge on this derives, however, from studies monitoring the astrocyte Ca2+ response to glutamate. Whether astrocytes can similarly respond to other neurotransmitters, including the inhibitory neurotransmitter GABA, is relatively unexplored. By using confocal and two photon laser‐scanning microscopy the astrocyte response to GABA in the mouse somatosensory and temporal cortex was studied. In slices from developing (P15‐20) and adult (P30‐60) mice, it was found that in a subpopulation of astrocytes GABA evoked somatic Ca2+ oscillations. This response was mediated by GABAB receptors and involved both Gi/o protein and inositol 1,4,5‐trisphosphate (IP3) signalling pathways. In vivo experiments from young adult mice, revealed that also cortical astrocytes in the living brain exibit GABAB receptor‐mediated Ca2+ elevations. At all astrocytic processes tested, local GABA or Baclofen brief applications induced long‐lasting Ca2+ oscillations, suggesting that all astrocytes have the potential to respond to GABA. Finally, in patch‐clamp recordings it was found that Ca2+ oscillations induced by Baclofen evoked astrocytic glutamate release and slow inward currents (SICs) in pyramidal cells from wild type but not IP3R2−/− mice, in which astrocytic GABAB receptor‐mediated Ca2+ elevations are impaired. These data suggest that cortical astrocytes in the mouse brain can sense the activity of GABAergic interneurons and through their specific recruitment contribut to the distinct role played on the cortical network by the different subsets of GABAergic interneurons. GLIA 2016;64:363–373
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Affiliation(s)
- Letizia Mariotti
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of Padova, via U.Bassi 58/B, Padova, 35121, Italy
| | - Gabriele Losi
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of Padova, via U.Bassi 58/B, Padova, 35121, Italy
| | - Michele Sessolo
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of Padova, via U.Bassi 58/B, Padova, 35121, Italy
| | - Iacopo Marcon
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of Padova, via U.Bassi 58/B, Padova, 35121, Italy
| | - Giorgio Carmignoto
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of Padova, via U.Bassi 58/B, Padova, 35121, Italy
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91
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Abstract
We delineate perspectives for the design and discovery of antiepileptic drugs (AEDs) with fewer side effects by focusing on astroglial modulation of spatiotemporal seizure dynamics. It is now recognized that the major inhibitory neurotransmitter of the brain, γ-aminobutyric acid (GABA), can be released through the reversal of astroglial GABA transporters. Synaptic spillover and subsequent glutamate (Glu) uptake in neighboring astrocytes evoke replacement of extracellular Glu for GABA, driving neurons away from the seizure threshold. Attenuation of synaptic signaling by this negative feedback through the interplay of Glu and GABA transporters of adjacent astroglia can result in shortened seizures. By contrast, long-range activation of astroglia through gap junctions may promote recurrent seizures on the model of pharmacoresistant temporal lobe epilepsy. From their first detection to our current understanding, we identify various targets that shape both short- and long-range neuro-astroglia coupling, as these are manifest in epilepsy phenomena and in the associated research promotions of AED.
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Affiliation(s)
- Julianna Kardos
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117 Budapest, Hungary
| | - Zsolt Szabó
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117 Budapest, Hungary
| | - László Héja
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117 Budapest, Hungary
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92
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Parvalbumin-Positive Inhibitory Interneurons Oppose Propagation But Favor Generation of Focal Epileptiform Activity. J Neurosci 2015; 35:9544-57. [PMID: 26134638 DOI: 10.1523/jneurosci.5117-14.2015] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Parvalbumin (Pv)-positive inhibitory interneurons effectively control network excitability, and their optogenetic activation has been reported to block epileptic seizures. An intense activity in GABAergic interneurons, including Pv interneurons, before seizures has been described in different experimental models of epilepsy, raising the hypothesis that an increased GABAergic inhibitory signal may, under certain conditions, initiate seizures. It is therefore unclear whether the activity of Pv interneurons enhances or opposes epileptiform activities. Here we use a mouse cortical slice model of focal epilepsy in which the epileptogenic focus can be identified and the role of Pv interneurons in the generation and propagation of seizure-like ictal events is accurately analyzed by a combination of optogenetic, electrophysiological, and imaging techniques. We found that a selective activation of Pv interneurons at the focus failed to block ictal generation and induced postinhibitory rebound spiking in pyramidal neurons, enhancing neuronal synchrony and promoting ictal generation. In contrast, a selective activation of Pv interneurons distant from the focus blocked ictal propagation and shortened ictal duration at the focus. We revealed that the reduced ictal duration was a direct consequence of the ictal propagation block, probably by preventing newly generated afterdischarges to travel backwards to the original focus of ictal initiation. Similar results were obtained upon individual Pv interneuron activation by intracellular depolarizing current pulses. The functional dichotomy of Pv interneurons here described opens new perspectives to our understanding of how local inhibitory circuits govern generation and spread of focal epileptiform activities.
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93
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Daniel AGS, Laffont P, Zhao M, Ma H, Schwartz TH. Optical electrocorticogram (OECoG) using wide-field calcium imaging reveals the divergence of neuronal and glial activity during acute rodent seizures. Epilepsy Behav 2015; 49:61-5. [PMID: 25976183 DOI: 10.1016/j.yebeh.2015.04.036] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 04/18/2015] [Indexed: 11/26/2022]
Abstract
The role of glia in epilepsy has been widely debated. Using in vivo bulk loading of calcium dyes, we imaged neuronal and glial activity in an acute pharmacologic rodent model of neocortical seizures. Optical calcium-based ECoG maps revealed that neuronal waves propagated rapidly and remained mostly confined to the seizure focus. Glial waves were triggered by ictal onset but propagated slowly in a stereotypical fashion far beyond the seizure focus. Although related at their onset, the divergence of these two phenomena during seizure evolution calls into question their interdependence and the criticality of the role of glia in seizure onset and neurovascular coupling. This article is part of a Special Issue entitled "Status Epilepticus".
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Affiliation(s)
- Andy G S Daniel
- Weill Cornell Medical College, New York Presbyterian Hospital, Department of Neurological Surgery, Brain and Mind Research Institute, Brain and Spine Center, 1300 York Avenue, Box 99, New York, NY 10021, USA
| | - Philippe Laffont
- Weill Cornell Medical College, New York Presbyterian Hospital, Department of Neurological Surgery, Brain and Mind Research Institute, Brain and Spine Center, 1300 York Avenue, Box 99, New York, NY 10021, USA; The Browning School, 52 E 62nd St, New York, NY 10065, USA
| | - Mingrui Zhao
- Weill Cornell Medical College, New York Presbyterian Hospital, Department of Neurological Surgery, Brain and Mind Research Institute, Brain and Spine Center, 1300 York Avenue, Box 99, New York, NY 10021, USA
| | - Hongtao Ma
- Weill Cornell Medical College, New York Presbyterian Hospital, Department of Neurological Surgery, Brain and Mind Research Institute, Brain and Spine Center, 1300 York Avenue, Box 99, New York, NY 10021, USA.
| | - Theodore H Schwartz
- Weill Cornell Medical College, New York Presbyterian Hospital, Department of Neurological Surgery, Brain and Mind Research Institute, Brain and Spine Center, 1300 York Avenue, Box 99, New York, NY 10021, USA
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94
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Kékesi O, Ioja E, Szabó Z, Kardos J, Héja L. Recurrent seizure-like events are associated with coupled astroglial synchronization. Front Cell Neurosci 2015; 9:215. [PMID: 26150770 PMCID: PMC4471369 DOI: 10.3389/fncel.2015.00215] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 05/20/2015] [Indexed: 01/22/2023] Open
Abstract
Increasing evidence suggest that astrocytes significantly modulate neuronal function at the level of the tripartite synapse both in physiological and pathophysiological conditions. The global control of the astrocytic syncytium over neuronal networks, however, is still less recognized. Here we examined astrocytic signaling during epileptiform activity which is generally attributed to large-scale neuronal synchronization. We show that seizure-like events in the low-[Mg(2+)] in vitro epilepsy model initiate massive, long-range astrocytic synchronization which is spatiotemporally coupled to the synchronized neuronal activity reaching its maximum at the electrographic tonic/clonic transition. Cross-correlation analysis of neuronal and astrocytic Ca(2+) signaling demonstrates that high degree of synchronization arises not only among astrocytes, but also between neuronal and astrocyte populations, manifesting in astrocytic seizure-like events. We further show that astrocytic gap junction proteins contribute to astrocytic synchronization since their inhibition by carbenoxolone (CBX) or Cx43 antibody increased the interictal interval and in 41% of slices completely prevented recurrent seizure-like activity. In addition, CBX also induced unsynchronized Ca(2+) transients associated with decreasing incidence of epileptiform discharges afterwards. We propose therefore that local, unsynchronized astrocytic Ca(2+) transients inhibit, while long-range, synchronized Ca(2+) signaling contributes to the propagation of recurrent seizure-like events.
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Affiliation(s)
- Orsolya Kékesi
- Research Centre for Natural Sciences, Hungarian Academy of Sciences, Institute of Organic Chemistry, Functional Pharmacology Group Budapest, Hungary
| | - Enikö Ioja
- Research Centre for Natural Sciences, Hungarian Academy of Sciences, Institute of Organic Chemistry, Functional Pharmacology Group Budapest, Hungary
| | - Zsolt Szabó
- Research Centre for Natural Sciences, Hungarian Academy of Sciences, Institute of Organic Chemistry, Functional Pharmacology Group Budapest, Hungary
| | - Julianna Kardos
- Research Centre for Natural Sciences, Hungarian Academy of Sciences, Institute of Organic Chemistry, Functional Pharmacology Group Budapest, Hungary
| | - László Héja
- Research Centre for Natural Sciences, Hungarian Academy of Sciences, Institute of Organic Chemistry, Functional Pharmacology Group Budapest, Hungary
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95
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Hongo Y, Takasu K, Ikegaya Y, Hasegawa M, Sakaguchi G, Ogawa K. Heterogeneous effects of antiepileptic drugs in an in vitro epilepsy model--a functional multineuron calcium imaging study. Eur J Neurosci 2015; 42:1818-29. [PMID: 25967117 DOI: 10.1111/ejn.12945] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 04/28/2015] [Accepted: 05/06/2015] [Indexed: 01/17/2023]
Abstract
Epilepsy is a chronic brain disease characterised by recurrent seizures. Many studies of this disease have focused on local neuronal activity, such as local field potentials in the brain. In addition, several recent studies have elucidated the collective behavior of individual neurons in a neuronal network that emits epileptic activity. However, little is known about the effects of antiepileptic drugs on neuronal networks during seizure-like events (SLEs) at single-cell resolution. Using functional multineuron Ca(2+) imaging (fMCI), we monitored the activities of multiple neurons in the rat hippocampal CA1 region on treatment with the proconvulsant bicuculline under Mg(2+) -free conditions. Bicuculline induced recurrent synchronous Ca(2+) influx, and the events were correlated with SLEs. Other proconvulsants, such as 4-aminopyridine, pentetrazol, and pilocarpine, also induced synchronous Ca(2+) influx. We found that the antiepileptic drugs phenytoin, flupirtine, and ethosuximide, which have different mechanisms of action, exerted heterogeneous effects on bicuculline-induced synchronous Ca(2+) influx. Phenytoin and flupirtine significantly decreased the peak, the amount of Ca(2+) influx and the duration of synchronous events in parallel with the duration of SLEs, whereas they did not abolish the synchronous events themselves. Ethosuximide increased the duration of synchronous Ca(2+) influx and SLEs. Furthermore, the magnitude of the inhibitory effect of phenytoin on the peak synchronous Ca(2+) influx level differed according to the peak amplitude of the synchronous event in each individual cell. Evaluation of the collective behavior of individual neurons by fMCI seems to be a powerful tool for elucidating the profiles of antiepileptic drugs.
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Affiliation(s)
- Yoshie Hongo
- Pain & Neuroscience, Discovery Research Laboratory for Core Therapeutic Areas, Shionogi Co. Ltd., 1-1 Futaba-cho 3-chome, Toyonaka, Osaka, 561-0825, Japan
| | - Keiko Takasu
- Pain & Neuroscience, Discovery Research Laboratory for Core Therapeutic Areas, Shionogi Co. Ltd., 1-1 Futaba-cho 3-chome, Toyonaka, Osaka, 561-0825, Japan
| | - Yuji Ikegaya
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, University of Tokyo, Bunkyo-ku, Tokyo, Japan.,Center for Information and Neural Networks, Suita City, Osaka, Japan
| | - Minoru Hasegawa
- Pain & Neuroscience, Discovery Research Laboratory for Core Therapeutic Areas, Shionogi Co. Ltd., 1-1 Futaba-cho 3-chome, Toyonaka, Osaka, 561-0825, Japan
| | - Gaku Sakaguchi
- Pain & Neuroscience, Discovery Research Laboratory for Core Therapeutic Areas, Shionogi Co. Ltd., 1-1 Futaba-cho 3-chome, Toyonaka, Osaka, 561-0825, Japan
| | - Koichi Ogawa
- Pain & Neuroscience, Discovery Research Laboratory for Core Therapeutic Areas, Shionogi Co. Ltd., 1-1 Futaba-cho 3-chome, Toyonaka, Osaka, 561-0825, Japan
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96
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Álvarez-Ferradas C, Morales JC, Wellmann M, Nualart F, Roncagliolo M, Fuenzalida M, Bonansco C. Enhanced astroglial Ca2+ signaling increases excitatory synaptic strength in the epileptic brain. Glia 2015; 63:1507-21. [PMID: 25980474 DOI: 10.1002/glia.22817] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 02/21/2015] [Accepted: 02/23/2015] [Indexed: 01/24/2023]
Abstract
The fine-tuning of synaptic transmission by astrocyte signaling is crucial to CNS physiology. However, how exactly astroglial excitability and gliotransmission are affected in several neuropathologies, including epilepsy, remains unclear. Here, using a chronic model of temporal lobe epilepsy (TLE) in rats, we found that astrocytes from astrogliotic hippocampal slices displayed an augmented incidence of TTX-insensitive spontaneous slow Ca(2+) transients (STs), suggesting a hyperexcitable pattern of astroglial activity. As a consequence, elevated glutamate-mediated gliotransmission, observed as increased slow inward current (SICs) frequency, up-regulates the probability of neurotransmitter release in CA3-CA1 synapses. Selective blockade of spontaneous astroglial Ca(2+) elevations as well as the inhibition of purinergic P2Y1 or mGluR5 receptors relieves the abnormal enhancement of synaptic strength. Moreover, mGluR5 blockade eliminates any synaptic effects induced by P2Y1R inhibition alone, suggesting that the Pr modulation via mGluR occurs downstream of P2Y1R-mediated Ca(2+)-dependent glutamate release from astrocyte. Our findings show that elevated Ca(2+)-dependent glutamate gliotransmission from hyperexcitable astrocytes up-regulates excitatory neurotransmission in epileptic hippocampus, suggesting that gliotransmission should be considered as a novel functional key in a broad spectrum of neuropathological conditions.
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Affiliation(s)
- Carla Álvarez-Ferradas
- Centro De Neurobiología Y Plasticidad Cerebral CNPC, Instituto De Fisiología, Facultad De Ciencias, Universidad De Valparaíso, Chile
| | - Juan Carlos Morales
- Centro De Neurobiología Y Plasticidad Cerebral CNPC, Instituto De Fisiología, Facultad De Ciencias, Universidad De Valparaíso, Chile
| | - Mario Wellmann
- Centro De Neurobiología Y Plasticidad Cerebral CNPC, Instituto De Fisiología, Facultad De Ciencias, Universidad De Valparaíso, Chile
| | - Francisco Nualart
- Departamento De Biología Celular, Centro De Microscopía Avanzada CMA BIOBIO, Facultad De Ciencias Biológicas, Universidad De Concepción, Concepción, Chile
| | - Manuel Roncagliolo
- Centro De Neurobiología Y Plasticidad Cerebral CNPC, Instituto De Fisiología, Facultad De Ciencias, Universidad De Valparaíso, Chile
| | - Marco Fuenzalida
- Centro De Neurobiología Y Plasticidad Cerebral CNPC, Instituto De Fisiología, Facultad De Ciencias, Universidad De Valparaíso, Chile
| | - Christian Bonansco
- Centro De Neurobiología Y Plasticidad Cerebral CNPC, Instituto De Fisiología, Facultad De Ciencias, Universidad De Valparaíso, Chile
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97
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Morquette P, Verdier D, Kadala A, Féthière J, Philippe AG, Robitaille R, Kolta A. An astrocyte-dependent mechanism for neuronal rhythmogenesis. Nat Neurosci 2015; 18:844-54. [PMID: 25938883 DOI: 10.1038/nn.4013] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 04/02/2015] [Indexed: 12/22/2022]
Abstract
Communication between neurons rests on their capacity to change their firing pattern to encode different messages. For several vital functions, such as respiration and mastication, neurons need to generate a rhythmic firing pattern. Here we show in the rat trigeminal sensori-motor circuit for mastication that this ability depends on regulation of the extracellular Ca(2+) concentration ([Ca(2+)]e) by astrocytes. In this circuit, astrocytes respond to sensory stimuli that induce neuronal rhythmic activity, and their blockade with a Ca(2+) chelator prevents neurons from generating a rhythmic bursting pattern. This ability is restored by adding S100β, an astrocytic Ca(2+)-binding protein, to the extracellular space, while application of an anti-S100β antibody prevents generation of rhythmic activity. These results indicate that astrocytes regulate a fundamental neuronal property: the capacity to change firing pattern. These findings may have broad implications for many other neural networks whose functions depend on the generation of rhythmic activity.
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Affiliation(s)
- Philippe Morquette
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - Dorly Verdier
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - Aklesso Kadala
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - James Féthière
- Faculté de Pharmacie, Université de Montréal, Montréal, Québec, Canada
| | - Antony G Philippe
- 1] Faculté des Sciences du Sport, Université Montpellier 1, Montpellier, France. [2] Institut National de la Recherche Agronomique, UMR866 Dynamique Musculaire Et Métabolisme, Montpellier, France
| | - Richard Robitaille
- Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada
| | - Arlette Kolta
- 1] Département de Neurosciences and Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec, Canada. [2] Faculté de Médecine Dentaire and Réseau de Recherche en Santé Bucco-dentaire et Osseuse du Fonds de Recherche Québec-Santé, Université de Montréal, Montréal, Québec, Canada
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98
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Wu XL, Tang YC, Lu QY, Xiao XL, Song TB, Tang FR. Astrocytic Cx 43 and Cx 40 in the mouse hippocampus during and after pilocarpine-induced status epilepticus. Exp Brain Res 2015; 233:1529-39. [PMID: 25690864 DOI: 10.1007/s00221-015-4226-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2014] [Accepted: 02/09/2015] [Indexed: 12/15/2022]
Abstract
Astrocytes have now been well accepted to play important roles in epileptogenesis by controlling gliotransmitter release and neuronal excitability, contributing to blood-brain barrier dysfunction and involving in brain inflammation. Recent studies indicate that abnormal expression of gap junction protein connexin (Cx) may also be a contributing factor for seizure generation. To further address this issue, we investigated the progressive changes of Cx 43 and Cx 40 in the mouse hippocampus at 4 h, 1 day, 1 week and 2 months during and after pilocarpine-induced status epilepticus (PISE). The co-localization of Cx 43 and Cx 40 with glial fibrillary acidic protein (GFAP) was also examined. We observed that Cx 43 and Cx 40 protein expression remained unaltered at 4 h during and at 1 day (acute stage) after PISE. However, their expression was significantly increased in CA1 and CA3 areas and in the dentate gyrus at 1 week (latent stage) and 2 months (chronic stage) after PISE. Double immunofluorescence labeling indicated the localization of Cx 43 and Cx 40 in astrocytes. Combined with progressive neuronal loss in the mouse hippocampus, our results suggest that the increase in gap junctions in the neuronoglial syncytium of reactive astrocytes may be implicated in synchronization of hippocampal hyperactivity leading to neuronal loss and epileptogenesis.
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Affiliation(s)
- X L Wu
- Department of Human Anatomy, Histology and Embryology, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, People's Republic of China
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99
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Astrocyte physiopathology: At the crossroads of intercellular networking, inflammation and cell death. Prog Neurobiol 2015; 130:86-120. [PMID: 25930681 DOI: 10.1016/j.pneurobio.2015.04.003] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 04/15/2015] [Accepted: 04/20/2015] [Indexed: 12/11/2022]
Abstract
Recent breakthroughs in neuroscience have led to the awareness that we should revise our traditional mode of thinking and studying the CNS, i.e. by isolating the privileged network of "intelligent" synaptic contacts. We may instead need to contemplate all the variegate communications occurring between the different neural cell types, and centrally involving the astrocytes. Basically, it appears that a single astrocyte should be considered as a core that receives and integrates information from thousands of synapses, other glial cells and the blood vessels. In turn, it generates complex outputs that control the neural circuitry and coordinate it with the local microcirculation. Astrocytes thus emerge as the possible fulcrum of the functional homeostasis of the healthy CNS. Yet, evidence indicates that the bridging properties of the astrocytes can change in parallel with, or as a result of, the morphological, biochemical and functional alterations these cells undergo upon injury or disease. As a consequence, they have the potential to transform from supportive friends and interactive partners for neurons into noxious foes. In this review, we summarize the currently available knowledge on the contribution of astrocytes to the functioning of the CNS and what goes wrong in various pathological conditions, with a particular focus on Amyotrophic Lateral Sclerosis, Alzheimer's Disease and ischemia. The observations described convincingly demonstrate that the development and progression of several neurological disorders involve the de-regulation of a finely tuned interplay between multiple cell populations. Thus, it seems that a better understanding of the mechanisms governing the integrated communication and detrimental responses of the astrocytes as well as their impact towards the homeostasis and performance of the CNS is fundamental to open novel therapeutic perspectives.
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100
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Losi G, Marcon I, Mariotti L, Sessolo M, Chiavegato A, Carmignoto G. A brain slice experimental model to study the generation and the propagation of focally-induced epileptiform activity. J Neurosci Methods 2015; 260:125-31. [PMID: 25863141 PMCID: PMC4751973 DOI: 10.1016/j.jneumeth.2015.04.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 04/01/2015] [Accepted: 04/02/2015] [Indexed: 11/30/2022]
Abstract
We propose a model of seizure-like events in temporal cortex slices from young mice. In the model local NMDA stimulations induce multiple seizure-like events. Electrophysiological, Ca2+ imaging and optogenetics are combined in the model. Seizures generation and propagation are separately studied. The role of specific cell population on these events can be accurately analyzed.
The early cellular events that in a brain network lead to seizure generation and govern seizure propagation are probably based on different cellular mechanisms. Experimental models in which these events can be separately studied would contribute to improve our understanding of epilepsy. We recently described an in vitro model in entorhinal cortex slices from young rats in which focal seizure-like discharges (SLDs) can be induced in spatially defined regions and at predictable times by local NMDA applications performed in the presence of 4-amimopyridine (4-AP) and low extracellular Mg2+. Through the use of single-dual cell patch-clamp and field potential recordings, and Ca2+ imaging from large ensembles of neurons, interneurons and astrocytes, we here extend this model to entorhinal and temporal cortex slices of rat and mouse brain, providing evidence that multiple SLDs exhibiting the typical tonic–clonic discharge pattern can be also evoked in these cortical regions by successive NMDA applications. Importantly, the temporal cortex is more accessible to viral vector injections than the entorhinal cortex: this makes it feasible in the former region the selective expression in inhibitory interneurons or principal neurons of genetically encoded Ca2+ indicators (GECI) or light-gated opsins. In this model, an optogenetic approach allows to activate specific neuronal types at spatially defined locations, i.e., the focus or the propagating region, and at precise time, i.e., before or during SLD. The NMDA/4-AP model can, therefore, represent a valuable tool to gain insights into the role of specific cell populations in seizure generation, propagation and cessation.
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Affiliation(s)
- Gabriele Losi
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of Padova, via U. Bassi 58/b, 35121 Padova, Italy.
| | - Iacopo Marcon
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of Padova, via U. Bassi 58/b, 35121 Padova, Italy
| | - Letizia Mariotti
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of Padova, via U. Bassi 58/b, 35121 Padova, Italy
| | - Michele Sessolo
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of Padova, via U. Bassi 58/b, 35121 Padova, Italy
| | - Angela Chiavegato
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of Padova, via U. Bassi 58/b, 35121 Padova, Italy
| | - Giorgio Carmignoto
- Neuroscience Institute, National Research Council (CNR) and Department of Biomedical Sciences, University of Padova, via U. Bassi 58/b, 35121 Padova, Italy
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