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Ovsepian SV, O'Leary VB, Martinez S. Selective vulnerability of motor neuron types and functional groups to degeneration in amyotrophic lateral sclerosis: review of the neurobiological mechanisms and functional correlates. Brain Struct Funct 2024; 229:1-14. [PMID: 37999738 PMCID: PMC10827929 DOI: 10.1007/s00429-023-02728-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 10/26/2023] [Indexed: 11/25/2023]
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative condition characterised by a progressive loss of motor neurons controlling voluntary muscle activity. The disease manifests through a variety of motor dysfunctions related to the extent of damage and loss of neurons at different anatomical locations. Despite extensive research, it remains unclear why some motor neurons are especially susceptible to the disease, while others are affected less or even spared. In this article, we review the neurobiological mechanisms, neurochemical profiles, and morpho-functional characteristics of various motor neuron groups and types of motor units implicated in their differential exposure to degeneration. We discuss specific cell-autonomous (intrinsic) and extrinsic factors influencing the vulnerability gradient of motor units and motor neuron types to ALS, with their impact on disease manifestation, course, and prognosis, as revealed in preclinical and clinical studies. We consider the outstanding challenges and emerging opportunities for interpreting the phenotypic and mechanistic variability of the disease to identify targets for clinical interventions.
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Affiliation(s)
- Saak V Ovsepian
- Faculty of Engineering and Science, University of Greenwich London, Chatham Maritime, Kent, ME4 4TB, UK.
| | - Valerie B O'Leary
- Department of Medical Genetics, Third Faculty of Medicine, Charles University, Ruská 87, 10000, Prague, Czech Republic
| | - Salvador Martinez
- Instituto de Neurociencias UMH-CSIC, Avda. Ramon y Cajal, 03550, San Juan de Alicante, Spain.
- Center of Biomedical Network Research on Mental Health (CIBERSAM), ISCIII, Madrid, Spain.
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2
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Dunn E, Zhang B, Sahota VK, Augustin H. Potential benefits of medium chain fatty acids in aging and neurodegenerative disease. Front Aging Neurosci 2023; 15:1230467. [PMID: 37680538 PMCID: PMC10481710 DOI: 10.3389/fnagi.2023.1230467] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Accepted: 08/07/2023] [Indexed: 09/09/2023] Open
Abstract
Neurodegenerative diseases are a large class of neurological disorders characterized by progressive dysfunction and death of neurones. Examples include Alzheimer's disease, Parkinson's disease, frontotemporal dementia, and amyotrophic lateral sclerosis. Aging is the primary risk factor for neurodegeneration; individuals over 65 are more likely to suffer from a neurodegenerative disease, with prevalence increasing with age. As the population ages, the social and economic burden caused by these diseases will increase. Therefore, new therapies that address both aging and neurodegeneration are imperative. Ketogenic diets (KDs) are low carbohydrate, high-fat diets developed initially as an alternative treatment for epilepsy. The classic ketogenic diet provides energy via long-chain fatty acids (LCFAs); naturally occurring medium chain fatty acids (MCFAs), on the other hand, are the main components of the medium-chain triglyceride (MCT) ketogenic diet. MCT-based diets are more efficient at generating the ketone bodies that are used as a secondary energy source for neurones and astrocytes. However, ketone levels alone do not closely correlate with improved clinical symptoms. Recent findings suggest an alternative mode of action for the MCFAs, e.g., via improving mitochondrial biogenesis and glutamate receptor inhibition. MCFAs have been linked to the treatment of both aging and neurodegenerative disease via their effects on metabolism. Through action on multiple disease-related pathways, MCFAs are emerging as compounds with notable potential to promote healthy aging and ameliorate neurodegeneration. MCFAs have been shown to stimulate autophagy and restore mitochondrial function, which are found to be disrupted in aging and neurodegeneration. This review aims to provide insight into the metabolic benefits of MCFAs in neurodegenerative disease and healthy aging. We will discuss the use of MCFAs to combat dysregulation of autophagy and mitochondrial function in the context of "normal" aging, Parkinson's disease, amyotrophic lateral sclerosis and Alzheimer's disease.
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Affiliation(s)
| | | | | | - Hrvoje Augustin
- Department of Biological Sciences, Centre for Biomedical Sciences, Royal Holloway University of London, Egham, United Kingdom
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3
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Lukáčová N, Hricová L, Kisucká A, Papcunová Š, Bimbová K, Bačová M, Pavel J, Marsala M, Vanický I, Dzurjašková Z, Matéffy S, Lukáčová V, Stropkovská A, Gálik J. Is Innervation of the Neuromuscular Junction at the Diaphragm Modulated by sGC/cGMP Signaling? Front Physiol 2020; 11:700. [PMID: 32655417 PMCID: PMC7324717 DOI: 10.3389/fphys.2020.00700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 05/28/2020] [Indexed: 11/15/2022] Open
Abstract
We previously reported NO/sGC signaling in the upper respiratory pathway, receiving input from the respiratory neurons of the brainstem to phrenic motoneurons in the C3–C6 spinal cord. In order to assess whether innervation of the neuromuscular junction (NMJ) at the diaphragm is modulated by sGC/cGMP signaling, we performed unilateral 8-day continuous ligation of the phrenic nerve in rats. We examined sGCβ1 within the lower bulbospinal pathway (phrenic motoneurons, phrenic nerves and NMJs at the diaphragm) and the cGMP level in the contra- and ipsilateral hemidiaphragm. Additionally, we characterized the extent of phrenic nerve axonal degeneration and denervation at diaphragm NMJs. The results of our study show that continuous 8-day phrenic nerve ligation caused a marked increase in sGCβ1 (immunoreactivity and the protein level) in the ipsilateral phrenic motor pool. However, the protein sGCβ1 level in the phrenic nerve below its ligation and the cGMP level in the ipsilateral hemidiaphragm were evidently decreased. Using confocal analysis we discovered a reduction in sGCβ1-IR boutons/synaptic vesicles at the ipsilateral MNJs. These findings are consistent with the marked axonal loss (∼47%) and significant NMJs degeneration in the ipsilateral diaphragm muscle. The remarkable unilateral decrease in cGMP level in the diaphragm and the failure of EMG recordings in the ipsilateral hemidiaphragm muscle can be attributed to the fact that sGC is involved in transmitter release at the diaphragm NMJs via the sGC-cGMP pathway.
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Affiliation(s)
- Nadežda Lukáčová
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia
| | - L'udmila Hricová
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia
| | - Alexandra Kisucká
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia
| | - Štefánia Papcunová
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia
| | - Katarína Bimbová
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia
| | - Mária Bačová
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia
| | - Jaroslav Pavel
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia
| | - Martin Marsala
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia.,Neuroregeneration Laboratory, Department of Anesthesiology, University of California, San Diego, La Jolla, CA, United States
| | - Ivo Vanický
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia
| | - Zuzana Dzurjašková
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia
| | - Stanislav Matéffy
- Diagnostic Center of Pathology in Prešov, Alpha Medical, s.r.o., Martin, Slovakia
| | - Viktória Lukáčová
- Faculty of Economics, Technical University of Košice, Košice, Slovakia
| | - Andrea Stropkovská
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia
| | - Ján Gálik
- Institute of Neurobiology, Biomedical Research Center of the Slovak Academy of Sciences, Košice, Slovakia
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4
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Zavodska M, Galik J, Marsala M, Papcunova S, Pavel J, Racekova E, Martoncikova M, Sulla I, Gajdos M, Lukac I, Kafka J, Ledecky V, Sulla I, Reichel P, Trbolova A, Capik I, Bimbova K, Bacova M, Stropkovska A, Kisucka A, Miklisova D, Lukacova N. Hypothermic treatment after computer-controlled compression in minipig: A preliminary report on the effect of epidural vs. direct spinal cord cooling. Exp Ther Med 2018; 16:4927-4942. [PMID: 30542449 PMCID: PMC6257352 DOI: 10.3892/etm.2018.6831] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2017] [Accepted: 06/29/2018] [Indexed: 11/24/2022] Open
Abstract
The aim of the present study was to investigate the therapeutic efficacy of local hypothermia (beginning 30 min post-injury persisting for 5 h) on tissue preservation along the rostro-caudal axis of the spinal cord (3 cm cranially and caudally from the lesion site), and the prevention of injury-induced functional loss in a newly developed computer-controlled compression model in minipig (force of impact 18N at L3 level), which mimics severe spinal cord injury (SCI). Minipigs underwent SCI with two post-injury modifications (durotomy vs. intact dura mater) followed by hypothermia through a perfusion chamber with cold (epidural t≈15°C) saline, DMEM/F12 or enriched DMEM/F12 (SCI/durotomy group) and with room temperature (t≈24°C) saline (SCI-only group). Minipigs treated with post-SCI durotomy demonstrated slower development of spontaneous neurological improvement at the early postinjury time points, although the outcome at 9 weeks of survival did not differ significantly between the two SCI groups. Hypothermia with saline (t≈15°C) applied after SCI-durotomy improved white matter integrity in the dorsal and lateral columns in almost all rostro-caudal segments, whereas treatment with medium/enriched medium affected white matter integrity only in the rostral segments. Furthermore, regeneration of neurofilaments in the spinal cord after SCI-durotomy and hypothermic treatments indicated an important role of local saline hypothermia in the functional outcome. Although saline hypothermia (24°C) in the SCI-only group exhibited a profound histological outcome (regarding the gray and white matter integrity and the number of motoneurons) and neurofilament protection in general, none of the tested treatments resulted in significant improvement of neurological status. The findings suggest that clinically-proven medical treatments for SCI combined with early 5 h-long saline hypothermia treatment without opening the dural sac could be more beneficial for tissue preservation and neurological outcome compared with hypothermia applied after durotomy.
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Affiliation(s)
- Monika Zavodska
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia
| | - Jan Galik
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia
| | - Martin Marsala
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia.,Department of Anesthesiology, Neuroregeneration Laboratory, University of California-San Diego, San Diego, CA 92093, USA
| | - Stefania Papcunova
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia
| | - Jaroslav Pavel
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia
| | - Eniko Racekova
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia
| | - Marcela Martoncikova
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia
| | - Igor Sulla
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia.,Hospital of Slovak Railways, 040 01 Košice, Slovakia
| | - Miroslav Gajdos
- Department of Neurosurgery, Faculty of Medicine, University of Pavol Jozef Safarik, 040 66 Košice, Slovakia
| | - Imrich Lukac
- Department of Neurosurgery, Faculty of Medicine, University of Pavol Jozef Safarik, 040 66 Košice, Slovakia
| | - Jozef Kafka
- Department of Neurosurgery, Faculty of Medicine, University of Pavol Jozef Safarik, 040 66 Košice, Slovakia
| | - Valent Ledecky
- Department of Small Animal Clinic, University of Veterinary Medicine and Pharmacy, 041 81 Košice, Slovakia
| | - Igor Sulla
- Department of Small Animal Clinic, University of Veterinary Medicine and Pharmacy, 041 81 Košice, Slovakia
| | - Peter Reichel
- Department of Small Animal Clinic, University of Veterinary Medicine and Pharmacy, 041 81 Košice, Slovakia
| | - Alexandra Trbolova
- Department of Small Animal Clinic, University of Veterinary Medicine and Pharmacy, 041 81 Košice, Slovakia
| | - Igor Capik
- Department of Small Animal Clinic, University of Veterinary Medicine and Pharmacy, 041 81 Košice, Slovakia
| | - Katarina Bimbova
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia
| | - Maria Bacova
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia
| | - Andrea Stropkovska
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia
| | - Alexandra Kisucka
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia
| | - Dana Miklisova
- Department of Vector-borne Diseases, Institute of Parasitology, Slovak Academy of Sciences, 040 01 Košice, Slovakia
| | - Nadezda Lukacova
- Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, 040 01 Košice, Slovakia
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Nijssen J, Comley LH, Hedlund E. Motor neuron vulnerability and resistance in amyotrophic lateral sclerosis. Acta Neuropathol 2017; 133:863-885. [PMID: 28409282 PMCID: PMC5427160 DOI: 10.1007/s00401-017-1708-8] [Citation(s) in RCA: 196] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/29/2017] [Accepted: 04/01/2017] [Indexed: 12/11/2022]
Abstract
In the fatal disease-amyotrophic lateral sclerosis (ALS)-upper (corticospinal) motor neurons (MNs) and lower somatic MNs, which innervate voluntary muscles, degenerate. Importantly, certain lower MN subgroups are relatively resistant to degeneration, even though pathogenic proteins are typically ubiquitously expressed. Ocular MNs (OMNs), including the oculomotor, trochlear and abducens nuclei (CNIII, IV and VI), which regulate eye movement, persist throughout the disease. Consequently, eye-tracking devices are used to enable paralysed ALS patients (who can no longer speak) to communicate. Additionally, there is a gradient of vulnerability among spinal MNs. Those innervating fast-twitch muscle are most severely affected and degenerate first. MNs innervating slow-twitch muscle can compensate temporarily for the loss of their neighbours by re-innervating denervated muscle until later in disease these too degenerate. The resistant OMNs and the associated extraocular muscles (EOMs) are anatomically and functionally very different from other motor units. The EOMs have a unique set of myosin heavy chains, placing them outside the classical characterization spectrum of all skeletal muscle. Moreover, EOMs have multiple neuromuscular innervation sites per single myofibre. Spinal fast and slow motor units show differences in their dendritic arborisations and the number of myofibres they innervate. These motor units also differ in their functionality and excitability. Identifying the molecular basis of cell-intrinsic pathways that are differentially activated between resistant and vulnerable MNs could reveal mechanisms of selective neuronal resistance, degeneration and regeneration and lead to therapies preventing progressive MN loss in ALS. Illustrating this, overexpression of OMN-enriched genes in spinal MNs, as well as suppression of fast spinal MN-enriched genes can increase the lifespan of ALS mice. Here, we discuss the pattern of lower MN degeneration in ALS and review the current literature on OMN resistance in ALS and differential spinal MN vulnerability. We also reflect upon the non-cell autonomous components that are involved in lower MN degeneration in ALS.
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6
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Barger SW. Gene regulation and genetics in neurochemistry, past to future. J Neurochem 2016; 139 Suppl 2:24-57. [PMID: 27747882 DOI: 10.1111/jnc.13629] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2015] [Revised: 03/01/2016] [Accepted: 03/30/2016] [Indexed: 12/14/2022]
Abstract
Ask any neuroscientist to name the most profound discoveries in the field in the past 60 years, and at or near the top of the list will be a phenomenon or technique related to genes and their expression. Indeed, our understanding of genetics and gene regulation has ushered in whole new systems of knowledge and new empirical approaches, many of which could not have even been imagined prior to the molecular biology boon of recent decades. Neurochemistry, in the classic sense, intersects with these concepts in the manifestation of neuropeptides, obviously dependent upon the central dogma (the established rules by which DNA sequence is eventually converted into protein primary structure) not only for their conformation but also for their levels and locales of expression. But, expanding these considerations to non-peptide neurotransmitters illustrates how gene regulatory events impact neurochemistry in a much broader sense, extending beyond the neurochemicals that translate electrical signals into chemical ones in the synapse, to also include every aspect of neural development, structure, function, and pathology. From the beginning, the mutability - yet relative stability - of genes and their expression patterns were recognized as potential substrates for some of the most intriguing phenomena in neurobiology - those instances of plasticity required for learning and memory. Near-heretical speculation was offered in the idea that perhaps the very sequence of the genome was altered to encode memories. A fascinating component of the intervening progress includes evidence that the central dogma is not nearly as rigid and consistent as we once thought. And this mutability extends to the potential to manipulate that code for both experimental and clinical purposes. Astonishing progress has been made in the molecular biology of neurochemistry during the 60 years since this journal debuted. Many of the gains in conceptual understanding have been driven by methodological progress, from automated high-throughput sequencing instruments to recombinant-DNA vectors that can convey color-coded genetic modifications in the chromosomes of live adult animals. This review covers the highlights of these advances, both theoretical and technological, along with a brief window into the promising science ahead. This article is part of the 60th Anniversary special issue.
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Affiliation(s)
- Steven W Barger
- Department of Geriatrics, Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA. .,Geriatric Research Education and Clinical Center, Central Arkansas Veterans Healthcare System, Little Rock, Arkansas, USA.
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King AE, Woodhouse A, Kirkcaldie MT, Vickers JC. Excitotoxicity in ALS: Overstimulation, or overreaction? Exp Neurol 2016; 275 Pt 1:162-71. [DOI: 10.1016/j.expneurol.2015.09.019] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 08/30/2015] [Accepted: 09/28/2015] [Indexed: 12/14/2022]
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Kaus A, Sareen D. ALS Patient Stem Cells for Unveiling Disease Signatures of Motoneuron Susceptibility: Perspectives on the Deadly Mitochondria, ER Stress and Calcium Triad. Front Cell Neurosci 2015; 9:448. [PMID: 26635528 PMCID: PMC4652136 DOI: 10.3389/fncel.2015.00448] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 11/02/2015] [Indexed: 12/11/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a largely sporadic progressive neurodegenerative disease affecting upper and lower motoneurons (MNs) whose specific etiology is incompletely understood. Mutations in superoxide dismutase-1 (SOD1), TAR DNA-binding protein 43 (TARDBP/TDP-43) and C9orf72, have been identified in subsets of familial and sporadic patients. Key associated molecular and neuropathological features include ubiquitinated TDP-43 inclusions, stress granules, aggregated dipeptide proteins from mutant C9orf72 transcripts, altered mitochondrial ultrastructure, dysregulated calcium homeostasis, oxidative and endoplasmic reticulum (ER) stress, and an unfolded protein response (UPR). Such impairments have been documented in ALS animal models; however, whether these mechanisms are initiating factors or later consequential events leading to MN vulnerability in ALS patients is debatable. Human induced pluripotent stem cells (iPSCs) are a valuable tool that could resolve this “chicken or egg” causality dilemma. Relevant systems for probing pathophysiologically affected cells from large numbers of ALS patients and discovering phenotypic disease signatures of early MN susceptibility are described. Performing unbiased ‘OMICS and high-throughput screening in relevant neural cells from a cohort of ALS patient iPSCs, and rescuing mitochondrial and ER stress impairments, can identify targeted therapeutics for increasing MN longevity in ALS.
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Affiliation(s)
- Anjoscha Kaus
- Board of Governors-Regenerative Medicine Institute, Cedars-Sinai Medical Center Los Angeles, CA, USA ; Department of Biomedical Sciences, Cedars-Sinai Medical Center Los Angeles, CA, USA
| | - Dhruv Sareen
- Board of Governors-Regenerative Medicine Institute, Cedars-Sinai Medical Center Los Angeles, CA, USA ; Department of Biomedical Sciences, Cedars-Sinai Medical Center Los Angeles, CA, USA ; iPSC Core, The David and Janet Polak Stem Cell Laboratory, Cedars-Sinai Medical Center Los Angeles, CA, USA
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9
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Joshi DC, Tewari BP, Singh M, Joshi PG, Joshi NB. AMPA receptor activation causes preferential mitochondrial Ca2+ load and oxidative stress in motor neurons. Brain Res 2015; 1616:1-9. [DOI: 10.1016/j.brainres.2015.04.042] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 04/18/2015] [Accepted: 04/22/2015] [Indexed: 01/05/2023]
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Krishnamurthy K, Mehta B, Singh M, Tewari BP, Joshi PG, Joshi NB. Depalmitoylation preferentially downregulates AMPA induced Ca2+ signaling and neurotoxicity in motor neurons. Brain Res 2013; 1529:143-53. [PMID: 23850769 DOI: 10.1016/j.brainres.2013.06.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 06/24/2013] [Accepted: 06/26/2013] [Indexed: 10/26/2022]
Abstract
Excessive activation of AMPA receptor has been implicated in motor neuron degeneration in amyotrophic lateral sclerosis (ALS). However, it is not clear why motor neurons are preferentially sensitive to AMPA receptor mediated excessive [Ca(2+)]i rise and excitotoxicity. In the present study we examined whether palmitoylation regulates Ca(2+) permeability of AMPA receptor and excitotoxicity in cultured spinal cord neurons. We adapted chronic 2-bromopalmitate (2-BrP) treatment to achieve depalmitoylation and examined its effect on the cytotoxicity in spinal cord neurons exposed to AMPA. The change in AMPA induced signaling and cytotoxicity in motor neurons and other spinal neurons under identical conditions of exposure to AMPA was studied. 2-BrP treatment inhibited AMPA induced rise in [Ca(2+)]i and cytotoxicity in both types of neurons but the degree of inhibition was significantly higher in motor neurons as compared to other spinal neurons. The AMPA induced [Na(+)]i rise was moderately affected in both type of neurons on depalmitoylation. Depalmitoylation reduced the expression levels of AMPA receptor subunits (GluR1 and GluR2) and also PSD-95 but stargazin levels remained unaffected. Our results demonstrate that 2-BrP attenuates AMPA receptor activated Ca(2+) signaling and cytotoxicity preferentially in motor neurons and suggest that AMPA receptor modulation by depalmitoylation could play a significant role in preventing motor neuron degeneration.
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Affiliation(s)
- Karthik Krishnamurthy
- Department of Biophysics, National Institute of Mental Health and Neuro Sciences, Bangalore 560029, India
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12
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Lukáčová N, Kisucká A, Pavel J, Hricová Ľ, Kucharíková A, Gálik J, Maršala M, Langfort J, Chalimoniuk M. Spinal cord transection modifies neuronal nitric oxide synthase expression in medullar reticular nuclei and in the spinal cord and increases parvalbumin immunopositivity in motoneurons below the site of injury in experimental rabbits. Acta Histochem 2012; 114:518-24. [PMID: 22000862 DOI: 10.1016/j.acthis.2011.09.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Revised: 09/09/2011] [Accepted: 09/22/2011] [Indexed: 10/16/2022]
Abstract
Using immunohistochemistry, we detected the expression of neuronal nitric oxide synthase (nNOS) in ventral medullary gigantocellular reticular nuclei and in the lumbosacral spinal cord 10 days after thoracic transection in experimental rabbits. We tried to determine whether neurons located below the site of injury are protected by the calcium binding protein parvalbumin (PV). Changes of nNOS immunoreactivity (IR) in spinal cord were correlated with the level of nNOS protein in dorsal and ventral horns. Ten days after transection, nNOS was upregulated predominantly in lateral gigantocellular nuclei. In the spinal cord, we revealed a significant increase of nNOS protein in the dorsal horn. This is consistent with a higher density of punctate and fiber-like immunostaining for nNOS in laminae III-IV and the up-regulation of nNOS-IR in neurons of the deep dorsal horn. After surgery, the perikarya of motoneurons remained nNOS immunonegative. Contrary to nNOS, the PV-IR was upregulated in α-motoneurons and small-sized neurons of the ventral horn. However, its expression was considerably reduced in neurons of the deep dorsal horn. The findings indicate that spinal transection affects nNOS and PV in different neuronal circuits.
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Chang PKY, Verbich D, McKinney RA. AMPA receptors as drug targets in neurological disease - advantages, caveats, and future outlook. Eur J Neurosci 2012; 35:1908-16. [DOI: 10.1111/j.1460-9568.2012.08165.x] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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14
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Cozzolino M, Carrì MT. Mitochondrial dysfunction in ALS. Prog Neurobiol 2011; 97:54-66. [PMID: 21827820 DOI: 10.1016/j.pneurobio.2011.06.003] [Citation(s) in RCA: 173] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 06/13/2011] [Accepted: 06/14/2011] [Indexed: 12/11/2022]
Abstract
In the present article, we review the many facets of mitochondrial dysfunction in amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease due to loss of upper motor neurons in cerebral cortex and lower motor neurons in brainstem and spinal cord. Accumulating evidence from recent studies suggests that the many, interconnected facets of mitochondrial dysfunction may play a more significant role in the etiopathogenesis of this disorder than previously thought. This notion stems from our expanding knowledge of the complex physiology of mitochondria and of alteration of their properties that might confer an intrinsic susceptibility to long-lived, post-mitotic motor neurons to energy deficit, calcium mishandling and oxidative stress. The wealth of evidence implicating mitochondrial dysfunction as a major event in the pathology of ALS has prompted new studies aimed to the development of new mitochondria-targeted therapies. However, it is now clear that drugs targeting more than one aspect of mitochondrial dysfunction are needed to fight this devastating disease.
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Affiliation(s)
- Mauro Cozzolino
- Fondazione Santa Lucia IRCCS, c/o CERC, Via del Fosso di Fiorano 64, 00143 Rome, Italy
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Joshi DC, Singh M, Krishnamurthy K, Joshi PG, Joshi NB. AMPA induced Ca2+ influx in motor neurons occurs through voltage gated Ca2+ channel and Ca2+ permeable AMPA receptor. Neurochem Int 2011; 59:913-21. [PMID: 21777635 DOI: 10.1016/j.neuint.2011.06.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 06/27/2011] [Accepted: 06/29/2011] [Indexed: 11/19/2022]
Abstract
The rise in intracellular Ca(2+) mediated by AMPA subtype of glutamate receptors has been implicated in the pathogenesis of motor neuron disease, but the exact route of Ca(2+) entry into motor neurons is not clearly known. In the present study, we examined the role of voltage gated calcium channels (VGCCs) in AMPA induced Ca(2+) influx and subsequent intracellular signaling events responsible for motor neuron degeneration. AMPA stimulation caused sodium influx in spinal neurons that would depolarize the plasma membrane. The AMPA induced [Ca(2+)](i) rise in motor neurons as well as other spinal neurons was drastically reduced when extracellular sodium was replaced with NMDG, suggesting the involvement of voltage gated calcium channels. AMPA mediated rise in [Ca(2+)](i) was significantly inhibited by L-type VGCC blocker nifedipine, whereas ω-agatoxin-IVA and ω-conotoxin-GVIA, specific blockers of P/Q type and N-type VGCC were not effective. 1-Napthyl-acetyl spermine (NAS), an antagonist of Ca(2+) permeable AMPA receptors partially inhibited the AMPA induced [Ca(2+)](i) rise but selectively in motor neurons. Measurement of AMPA induced currents in whole cell voltage clamp mode suggests that a moderate amount of Ca(2+) influx occurs through Ca(2+) permeable AMPA receptors in a subpopulation of motor neurons. The AMPA induced mitochondrial calcium loading [Ca(2+)](m), mitochondrial depolarization and neurotoxicity were also significantly reduced in presence of nifedipine. Activation of VGCCs by depolarizing concentration of KCl (30mM) in extracellular medium increased the [Ca(2+)](i) but no change was observed in mitochondrial Ca(2+) and membrane potential. Our results demonstrate that a subpopulation of motor neurons express Ca(2+) permeable AMPA receptors, however the larger part of Ca(2+) influx occurs through L-type VGCCs subsequent to AMPA receptor activation and consequent mitochondrial dysfunction is the trigger for motor neuron degeneration. Nifedipine is an effective protective agent against AMPA induced mitochondrial stress and degeneration of motor neurons.
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Affiliation(s)
- Dinesh C Joshi
- Department of Biophysics, National Institute of Mental Health and Neuro Sciences, Bangalore 560 029, India
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16
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Manuel M, Heckman CJ. Stronger is not always better: could a bodybuilding dietary supplement lead to ALS? Exp Neurol 2010; 228:5-8. [PMID: 21167830 DOI: 10.1016/j.expneurol.2010.12.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 12/07/2010] [Accepted: 12/08/2010] [Indexed: 12/11/2022]
Affiliation(s)
- Marin Manuel
- Northwestern University, Department of Physiology, 303 E Chicago Ave, Chicago, IL 60611, USA.
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17
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Tovar-y-Romo LB, Tapia R. VEGF protects spinal motor neurons against chronic excitotoxic degeneration in vivo by activation of PI3-K pathway and inhibition of p38MAPK. J Neurochem 2010; 115:1090-101. [DOI: 10.1111/j.1471-4159.2010.06766.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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18
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Bento-Abreu A, Van Damme P, Van Den Bosch L, Robberecht W. The neurobiology of amyotrophic lateral sclerosis. Eur J Neurosci 2010; 31:2247-65. [PMID: 20529130 DOI: 10.1111/j.1460-9568.2010.07260.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Amyotrophic lateral sclerosis is a degenerative disease affecting the motor neurons. In spite of our growing insights into its biology, it remains a lethal condition. The identification of the cause of several of the familial forms of ALS allowed generation of models to study this disease both in vitro and in vivo. Here, we summarize what is known about the pathogenic mechanisms of ALS induced by hereditary mutations, and attempt to identify the relevance of these findings for understanding the pathogenic mechanisms of the sporadic form of this disease.
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Affiliation(s)
- André Bento-Abreu
- Laboratory for Neurobiology, Experimental Neurology, K.U.Leuven, Herestraat, 3000 Leuven, Belgium.
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19
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Hsu CI, Wang TC, Hou SYT, Chin TY, Chang YC. Quantitative study of the developmental changes in calcium-permeable AMPA receptor-expressing neurons in the rat somatosensory cortex. J Comp Neurol 2010; 518:75-91. [DOI: 10.1002/cne.22211] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
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20
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Tovar-y-Romo LB, Santa-Cruz LD, Tapia R. Experimental models for the study of neurodegeneration in amyotrophic lateral sclerosis. Mol Neurodegener 2009; 4:31. [PMID: 19619317 PMCID: PMC2720968 DOI: 10.1186/1750-1326-4-31] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Accepted: 07/20/2009] [Indexed: 12/11/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of unknown cause, characterized by the selective and progressive death of both upper and lower motoneurons, leading to a progressive paralysis. Experimental animal models of the disease may provide knowledge of the pathophysiological mechanisms and allow the design and testing of therapeutic strategies, provided that they mimic as close as possible the symptoms and temporal progression of the human disease. The principal hypotheses proposed to explain the mechanisms of motoneuron degeneration have been studied mostly in models in vitro, such as primary cultures of fetal motoneurons, organotypic cultures of spinal cord sections from postnatal rodents and the motoneuron-like hybridoma cell line NSC-34. However, these models are flawed in the sense that they do not allow a direct correlation between motoneuron death and its physical consequences like paralysis. In vivo, the most widely used model is the transgenic mouse that bears a human mutant superoxide dismutase 1, the only known cause of ALS. The major disadvantage of this model is that it represents about 2%-3% of human ALS. In addition, there is a growing concern on the accuracy of these transgenic models and the extrapolations of the findings made in these animals to the clinics. Models of spontaneous motoneuron disease, like the wobbler and pmn mice, have been used aiming to understand the basic cellular mechanisms of motoneuron diseases, but these abnormalities are probably different from those occurring in ALS. Therefore, the design and testing of in vivo models of sporadic ALS, which accounts for >90% of the disease, is necessary. The main models of this type are based on the excitotoxic death of spinal motoneurons and might be useful even when there is no definitive demonstration that excitotoxicity is a cause of human ALS. Despite their difficulties, these models offer the best possibility to establish valid correlations between cellular alterations and motor behavior, although improvements are still necessary in order to produce a reliable and integrative model that accurately reproduces the cellular mechanisms of motoneuron degeneration in ALS.
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Affiliation(s)
- Luis B Tovar-y-Romo
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, AP 70-253, 04510-México, D.F., México
| | - Luz Diana Santa-Cruz
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, AP 70-253, 04510-México, D.F., México
| | - Ricardo Tapia
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, AP 70-253, 04510-México, D.F., México
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21
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Zagami CJ, Beart PM, Wallis N, Nagley P, O'Shea RD. Oxidative and excitotoxic insults exert differential effects on spinal motoneurons and astrocytic glutamate transporters: Implications for the role of astrogliosis in amyotrophic lateral sclerosis. Glia 2009; 57:119-35. [PMID: 18661557 DOI: 10.1002/glia.20739] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In amyotrophic lateral sclerosis (ALS) non-neuronal cells play key roles in disease etiology and loss of motoneurons via noncell-autonomous mechanisms. Reactive astrogliosis and dysfunctional transporters for L-glutamate [excitatory amino acid transporters, (EAATs)] are hallmarks of ALS pathology. Here, we describe mechanistic insights into ALS pathology involving EAAT-associated homeostasis in response to a destructive milieu, in which oxidative stress and excitotoxicity induce respectively astrogliosis and motoneuron injury. Using an in vitro neuronal-glial culture of embryonic mouse spinal cord, we demonstrate that EAAT activity was maintained initially, despite a loss of cellular viability induced by exposure to oxidative [3-morpholinosydnonimine chloride (SIN-1)] and excitotoxic [(S)-5-fluorowillardiine (FW)] conditions. This homeostatic response of EAAT function involved no change in the cell surface expression of EAAT1/2 at 0.5-4 h, but rather alterations in kinetic properties. Over this time-frame, EAAT1/2 both became more widespread across astrocytic arbors in concert with increased expression of glial fibrillary acidic protein (GFAP), although at 8-24 h there was gliotoxicity, especially with SIN-1 rather than FW. An opposite picture was found for motoneurons where FW, not SIN-1, produced early and extensive neuritic shrinkage and blebbing (> or =0.5 h) with somata loss from 2 h. We postulate that EAATs play an early homeostatic and protective role in the pathologic milieu. Moreover, the differential profiles of injury produced by oxidative and excitotoxic insults identify two distinct phases of injury which parallel important aspects of the pathology of ALS.
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Activation of the heat shock response in a primary cellular model of motoneuron neurodegeneration-evidence for neuroprotective and neurotoxic effects. Cell Mol Biol Lett 2009; 14:319-35. [PMID: 19183864 PMCID: PMC6275696 DOI: 10.2478/s11658-009-0002-8] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Accepted: 01/05/2009] [Indexed: 01/29/2023] Open
Abstract
Pharmacological up-regulation of heat shock proteins (hsps) rescues motoneurons from cell death in a mouse model of amyotrophic lateral sclerosis. However, the relationship between increased hsp expression and neuronal survival is not straightforward. Here we examined the effects of two pharmacological agents that induce the heat shock response via activation of HSF-1, on stressed primary motoneurons in culture. Although both arimoclomol and celastrol induced the expression of Hsp70, their effects on primary motoneurons in culture were significantly different. Whereas arimoclomol had survival-promoting effects, rescuing motoneurons from staurosporin and H2O2 induced apoptosis, celastrol not only failed to protect stressed motoneurons from apoptosis under same experimental conditions, but was neurotoxic and induced neuronal death. Immunostaining of celastrol-treated cultures for hsp70 and activated caspase-3 revealed that celastrol treatment activates both the heat shock response and the apoptotic cell death cascade. These results indicate that not all agents that activate the heat shock response will necessarily be neuroprotective.
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Chen P, Song J, Luo L, Gong S. Plastic changes of synapses and excitatory neurotransmitter receptors in facial nucleus following facial-facial anastomosis. JOURNAL OF HUAZHONG UNIVERSITY OF SCIENCE AND TECHNOLOGY. MEDICAL SCIENCES = HUA ZHONG KE JI DA XUE XUE BAO. YI XUE YING DE WEN BAN = HUAZHONG KEJI DAXUE XUEBAO. YIXUE YINGDEWEN BAN 2008; 28:714-718. [PMID: 19107374 DOI: 10.1007/s11596-008-0623-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2007] [Indexed: 05/27/2023]
Abstract
The remodeling process of synapses and neurotransmitter receptors of facial nucleus were observed. Models were set up by facial-facial anastomosis in rat. At post-surgery day (PSD) 0, 7, 21 and 60, synaptophysin (p38), NMDA receptor subunit 2A and AMPA receptor subunit 2 (GluR2) were observed by immunohistochemical method and semi-quantitative RT-PCR, respectively. Meanwhile, the synaptic structure of the facial motorneurons was observed under a transmission electron microscope (TEM). The intensity of p38 immunoreactivity was decreased, reaching the lowest value at PSD day 7, and then increased slightly at PSD 21. Ultrastructurally, the number of synapses in nucleus of the operational side decreased, which was consistent with the change in P38 immunoreactivity. NMDAR2A mRNA was down-regulated significantly in facial nucleus after the operation (P<0.05), whereas AMPAR2 mRNA levels remained unchanged (P>0.05). The synapses innervation and the expression of NMDAR2A and AMPAR2 mRNA in facial nucleus might be modified to suit for the new motor tasks following facial-facial anastomosis, and influenced facial nerve regeneration and recovery.
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Affiliation(s)
- Pei Chen
- Department of Otorhinolaryngology-Head and Neck Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
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24
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Buckingham S, Kwak S, Jones A, Blackshaw S, Sattelle D. Edited GluR2, a gatekeeper for motor neurone survival? Bioessays 2008; 30:1185-92. [DOI: 10.1002/bies.20836] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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25
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Morphological features and responses to AMPA receptor-mediated excitotoxicity of mouse motor neurons: comparison in purified, mixed anterior horn or motor neuron/glia cocultures. J Neurosci Methods 2008; 170:85-95. [DOI: 10.1016/j.jneumeth.2007.12.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2007] [Revised: 11/30/2007] [Accepted: 12/30/2007] [Indexed: 11/23/2022]
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26
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Prithviraj R, Kelly KM, Espinoza-Lewis R, Hexom T, Clark AB, Inglis FM. Differential regulation of dendrite complexity by AMPA receptor subunits GluR1 and GluR2 in motor neurons. Dev Neurobiol 2008; 68:247-64. [PMID: 18000827 DOI: 10.1002/dneu.20590] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Activity-dependent developmental mechanisms in many regions of the central nervous system are thought to be responsible for shaping dendritic architecture and connectivity, although the molecular mechanisms underlying these events remain obscure. Since AMPA glutamate receptors are developmentally regulated in spinal motor neurons, we have investigated the role of activation of AMPA receptors in dendritic outgrowth of spinal motor neurons by overexpression of two subunits, GluR1 and GluR2, and find that dendrite outgrowth is differentially controlled by expression of these subunits. Overexpression of GluR1 was associated with greater numbers of filopodia, and an increase in the length and complexity of dendritic arbor. In contrast, GluR2 expression did not alter dendritic complexity, but was associated with a moderate increase in length of arbor, and decreased numbers of filopodia. Neither GluR1 nor GluR2 had any effect on the motility of filopodia. In addition, GluR1 but not GluR2 expression increased the density of dendritic puncta incorporating a GFP-labeled PSD95, suggesting that GluR1 may mediate its effect in part by augmenting the number of excitatory synapses within motor neuron dendrites. Together these results suggest that in spinal motor neurons, AMPA receptors composed of GluR1 subunits may facilitate neurotrophic mechanisms in these neurons, permitting sustained dendrite outgrowth and synaptogenesis, whereas expression of AMPA receptors containing GluR2 acts to preserve existing dendritic arbor. Thus, the observed downregulation of GluR1 in motor neurons during postnatal development may limit the formation of new dendrite segments and synapses, promoting stabilized synaptic connectivity.
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Affiliation(s)
- Ranjini Prithviraj
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA
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27
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Corona JC, Tovar-y-Romo LB, Tapia R. Glutamate excitotoxicity and therapeutic targets for amyotrophic lateral sclerosis. Expert Opin Ther Targets 2007; 11:1415-28. [PMID: 18028007 DOI: 10.1517/14728222.11.11.1415] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Two forms of amyotrophic lateral sclerosis (ALS) are known, the familial (FALS), due in part to mutations in superoxide dismutase 1 (SOD1), and the sporadic (SALS), which accounts for > 90% of all cases. The cause of SALS is not known, but excitotoxicity due to overactivation of glutamate receptors may mediate the motor neuron degeneration in the spinal cord, which is the hallmark of this disease. Overactivation of calcium-permeable alpha-amino-3-hydroxy-5-isoxazole propionate receptors lacking the subunit glutamate receptor 2, leading to an increase in calcium cytoplasmic concentration, seems to play an important role in the mechanism of neuronal death. The knowledge of this mechanism, in addition to other factors, provides several possible targets for therapeutic strategies that are reviewed in this article. Some of these strategies have proven to be partially effective in both human mutant superoxide dismutase 1 transgenic rodents (FALS model) and the few existing in vivo models of spinal motor neurodegeneration induced by excitotoxicity (SALS models), although observable benefits are still to be shown in clinical trials.
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Affiliation(s)
- Juan C Corona
- Universidad Nacional Autönoma de México, Departamento de Neurociencias, Instituto de Fisiología Celular, AP 70-253, 04510-México, D.F., México
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28
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Ni X, Sullivan GJ, Martin-Caraballo M. Developmental characteristics of AMPA receptors in chick lumbar motoneurons. Dev Neurobiol 2007; 67:1419-32. [PMID: 17497695 DOI: 10.1002/dneu.20517] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Ca2+ fluxes through ionotropic glutamate receptors regulate a variety of developmental processes, including neurite outgrowth and naturally occurring cell death. In the CNS, NMDA receptors were originally thought to be the sole source of Ca2+ influx through glutamate receptors; however, AMPA receptors also allow a significant influx of Ca2+ ions. The Ca2+ permeability of AMPA receptors is regulated by the insertion of one or more edited GluR2 subunits. In this study, we tested the possibility that changes in GluR2 expression regulate the Ca2+ permeability of AMPA receptors during a critical period of neuronal development in chick lumbar motoneurons. GluR2 expression is absent between embryonic day (E) 5 and E7, but increases significantly by E8 in the chick ventral spinal cord. Increased GluR2 protein expression is correlated with parallel changes in GluR2 mRNA in the motoneuron pool. Electrophysiological recordings of kainate-evoked currents indicate a significant reduction in the Ca2(+)-permeability of AMPA receptors between E6 and E11. Kainate-evoked currents were sensitive to the AMPA receptor blocker GYKI 52466. Application of AMPA or kainate generates a significant increase in the intracellular Ca2+ concentration in E6 spinal motoneurons, but generates a small response in older neurons. Changes in the Ca(2+)-permeability of AMPA receptors are not mediated by age-dependent changes in the editing pattern of GluR2 subunits. These findings raise the possibility that Ca2+ influx through Ca(2+)-permeable AMPA receptors plays an important role during early embryonic development in chick spinal motoneurons.
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Affiliation(s)
- Xianglian Ni
- Department of Biology, University of Vermont, Burlington, Vermont 05405, USA
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29
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Van Damme P, Bogaert E, Dewil M, Hersmus N, Kiraly D, Scheveneels W, Bockx I, Braeken D, Verpoorten N, Verhoeven K, Timmerman V, Herijgers P, Callewaert G, Carmeliet P, Van Den Bosch L, Robberecht W. Astrocytes regulate GluR2 expression in motor neurons and their vulnerability to excitotoxicity. Proc Natl Acad Sci U S A 2007; 104:14825-30. [PMID: 17804792 PMCID: PMC1976195 DOI: 10.1073/pnas.0705046104] [Citation(s) in RCA: 159] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Influx of Ca(2+) ions through alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors contributes to neuronal damage in stroke, epilepsy, and neurodegenerative disorders such as ALS. The Ca(2+) permeability of AMPA receptors is largely determined by the glutamate receptor 2 (GluR2) subunit, receptors lacking GluR2 being permeable to Ca(2+) ions. We identified a difference in GluR2 expression in motor neurons from two rat strains, resulting in a difference in vulnerability to AMPA receptor-mediated excitotoxicity both in vitro and in vivo. Astrocytes from the ventral spinal cord were found to mediate this difference in GluR2 expression in motor neurons. The presence of ALS-causing mutant superoxide dismutase 1 in astrocytes abolished their GluR2-regulating capacity and thus affected motor neuron vulnerability to AMPA receptor-mediated excitotoxicity. These results reveal a mechanism through which astrocytes influence neuronal functioning in health and disease.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Nathalie Verpoorten
- Department of Molecular Genetics, Flanders Interuniversity Institute for Biotechnology, University of Antwerp, B-2610 Antwerpen, Belgium
| | - Kristien Verhoeven
- Department of Molecular Genetics, Flanders Interuniversity Institute for Biotechnology, University of Antwerp, B-2610 Antwerpen, Belgium
| | - Vincent Timmerman
- Department of Molecular Genetics, Flanders Interuniversity Institute for Biotechnology, University of Antwerp, B-2610 Antwerpen, Belgium
| | | | | | - Peter Carmeliet
- The Center for Transgene Technology and Gene Therapy, Flanders Interuniversity Institute for Biotechnology, University of Leuven, B-3000 Leuven, Belgium; and
| | - Ludo Van Den Bosch
- Laboratories of *Neurobiology
- To whom correspondence should be addressed at:
Campus Gasthuisberg Onderwijs & Navorsing 2 (O&N2), Herestraat 49, PB1022, B-3000 Leuven, Belgium. E-mail:
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30
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Corona JC, Tapia R. Ca2+-permeable AMPA receptors and intracellular Ca2+ determine motoneuron vulnerability in rat spinal cord in vivo. Neuropharmacology 2007; 52:1219-28. [PMID: 17320918 DOI: 10.1016/j.neuropharm.2006.12.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Revised: 12/07/2006] [Accepted: 12/24/2006] [Indexed: 01/12/2023]
Abstract
Excitotoxicity mediated by overactivation of glutamate receptors, particularly the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) type, has been implicated in motoneuron degeneration. AMPA receptors lacking the GluR2 subunit are permeable to Ca(2+) and the entrance of this cation might be responsible for the selective vulnerability of spinal motoneurons in amyotrophic lateral sclerosis (ALS). To evaluate this hypothesis in vivo, we have used a model of motoneuron death in which AMPA, perfused by microdialysis in the rat lumbar spinal cord, produces ipsilateral paralysis and a remarkable loss of spinal motoneurons. Perfusion of 1-naphthyl acetyl spermine, a selective blocker of the Ca(2+)-permeable AMPA receptors, and of the intracellular Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl ester) (BAPTA-AM), prevented the AMPA-induced paralysis and reduced by about 50% the loss of motoneurons. In addition, perfusion of pyruvate, an energy metabolic substrate, similarly prevented the paralysis and the motoneuron death. These results suggest that functional AMPA receptors lacking the GluR2 subunit are present in the rat spinal cord, and that motoneuron death is triggered by an increase of intracellular Ca(2+) via such Ca(2+)-permeable AMPA receptors. Our finding that pyruvate also protected against the excitotoxic effects of AMPA suggests that the increased intracellular Ca(2+) probably interferes with the mitochondrial energetic metabolism.
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Affiliation(s)
- Juan Carlos Corona
- Departamento de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, AP 70-253, 04510 México, DF, Mexico
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31
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Buldakova SL, Kim KK, Tikhonov DB, Magazanik LG. Selective blockade of Ca2+ permeable AMPA receptors in CA1 area of rat hippocampus. Neuroscience 2007; 144:88-99. [PMID: 17097234 DOI: 10.1016/j.neuroscience.2006.09.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Revised: 09/04/2006] [Accepted: 09/10/2006] [Indexed: 11/30/2022]
Abstract
Using whole cell patch-clamp recording from pyramidal cells and interneurons in the CA1 area of hippocampal slices, the effect of IEM-1460, a selective channel blocker of Ca2+ permeable AMPA receptors (AMPARs), on postsynaptic currents (PSCs) was studied. Excitatory postsynaptic currents (EPSCs) were evoked by stimulation of Schaffer collaterals (SCs) in the presence of APV and bicuculline to pharmacologically isolate the EPSCs mediated by AMPAR activation. IEM-1460 (50 microM) did not affect the amplitude of EPSCs in CA1 pyramidal cells but reversibly decreased their amplitude in interneurons of pyramidal layer (15 cells), radiatum (37 cells) and border radiatum-lacunosum-moleculare (R-LM) (55 cells) layers. The ability of IEM-1460 to decrease EPSC amplitude correlated with EPSC rectification properties in CA1 interneurons, providing evidence for synaptic localization of Ca2+ permeable AMPARs at the SC synaptic input. Independent of their localization, the majority of interneurons studied exhibited only modest sensitivity to IEM-1460 (EPSC amplitude decreased by less than 30%), while in 15% of interneurons IEM-1460 induced more than 50% reduction in EPSC amplitude. To reveal possible afferent-specific localization of Ca2+ permeable AMPARs on R-LM interneurons, the effect of IEM-1460 on EPSCs evoked by stimulation of SC was compared with that of perforant path (PP). Although average sensitivities did not differ significantly, in 61% of R-LM layer interneurons, the SC-evoked EPSCs exhibited higher sensitivity to IEM-1460 than the PP-evoked EPSCs. Moreover, in 54% of R-LM layer interneurons the EPSCs evoked by SC stimulation were complex, having an initial peak followed by one or several late components. Kinetics, latency distribution and reversal potential of late components suggest di- and polysynaptic origin of the late components. Late EPSCs were strongly and reversibly inhibited by IEM-1460 indicating that Ca2+ permeable AMPARs are involved in the indirect excitation of R-LM layer interneurons. Despite the ability to decrease the excitatory synaptic input to interneurons, IEM-1460 did not affect interneuron-mediated inhibitory postsynaptic currents (IPSCs) evoked in pyramidal neurons by SC stimulation. These data suggest that interneurons with a synaptic input highly sensitive to IEM-1460 do not contribute specifically to the feed-forward inhibition of hippocampal pyramidal neurons.
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Affiliation(s)
- S L Buldakova
- I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 Thorez pr., 194223, St. Petersburg, Russia
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32
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Rao SD, Banack SA, Cox PA, Weiss JH. BMAA selectively injures motor neurons via AMPA/kainate receptor activation. Exp Neurol 2006; 201:244-52. [PMID: 16764863 DOI: 10.1016/j.expneurol.2006.04.017] [Citation(s) in RCA: 177] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Revised: 04/06/2006] [Accepted: 04/08/2006] [Indexed: 01/12/2023]
Abstract
The toxin beta-methylamino-l-alanine (BMAA) has been proposed to contribute to amyotrophic lateral sclerosis-Parkinsonism Dementia Complex of Guam (ALS/PDC) based on its ability to induce a similar disease phenotype in primates and its presence in cycad seeds, which constituted a dietary item in afflicted populations. Concerns about the apparent low potency of this toxin in relation to estimated levels of human ingestion led to a slowing of BMAA research. However, recent reports identifying potential new routes of exposure compel a re-examination of the BMAA/cycad hypothesis. BMAA was found to induce selective motor neuron (MN) loss in dissociated mixed spinal cord cultures at concentrations ( approximately 30 muM) significantly lower than those previously found to induce widespread neuronal degeneration. The glutamate receptor antagonist NBQX prevented BMAA-induced death, implicating excitotoxic activation of AMPA/kainate receptors. Using microfluorimetric techniques, we further found that BMAA induced preferential [Ca(2+)](i) rises and selective reactive oxygen species (ROS) generation in MNs with minimal effect on other spinal neurons. Cycad seed extracts also triggered preferential AMPA/kainate-receptor-dependent MN injury, consistent with the idea that BMAA is a crucial toxic component in this plant. Present findings support the hypothesis that BMAA may contribute to the selective MN loss in ALS/PDC.
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MESH Headings
- Amino Acids, Diamino/administration & dosage
- Amino Acids, Diamino/toxicity
- Amyotrophic Lateral Sclerosis/etiology
- Amyotrophic Lateral Sclerosis/metabolism
- Amyotrophic Lateral Sclerosis/pathology
- Animals
- Calcium/metabolism
- Cell Survival/drug effects
- Cells, Cultured
- Cyanobacteria Toxins
- Cycas/chemistry
- Dose-Response Relationship, Drug
- Excitatory Amino Acid Agonists/administration & dosage
- Excitatory Amino Acid Agonists/toxicity
- Excitatory Amino Acid Antagonists/pharmacology
- Humans
- Mice
- Motor Neurons/cytology
- Motor Neurons/drug effects
- Motor Neurons/metabolism
- Neurotoxins/administration & dosage
- Neurotoxins/toxicity
- Plant Extracts/administration & dosage
- Plant Extracts/toxicity
- Plant Poisoning/etiology
- Plant Poisoning/metabolism
- Plant Poisoning/pathology
- Quinoxalines/pharmacology
- Reactive Oxygen Species/metabolism
- Receptors, AMPA/agonists
- Receptors, AMPA/antagonists & inhibitors
- Receptors, AMPA/metabolism
- Receptors, Kainic Acid/agonists
- Receptors, Kainic Acid/antagonists & inhibitors
- Receptors, Kainic Acid/metabolism
- Seeds/chemistry
- Spinal Cord/cytology
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Affiliation(s)
- Shyam D Rao
- Department of Anatomy and Neurobiology, 2101 Gillespie Building, University of California, Irvine, Irvine, CA 92697-4292, USA
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Tortarolo M, Grignaschi G, Calvaresi N, Zennaro E, Spaltro G, Colovic M, Fracasso C, Guiso G, Elger B, Schneider H, Seilheimer B, Caccia S, Bendotti C. Glutamate AMPA receptors change in motor neurons of SOD1G93A transgenic mice and their inhibition by a noncompetitive antagonist ameliorates the progression of amytrophic lateral sclerosis-like disease. J Neurosci Res 2006; 83:134-46. [PMID: 16323214 DOI: 10.1002/jnr.20715] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurological disorder involving the selective degeneration of motor neurons. In a small proportion of patients, ALS is caused by mutations in copper/zinc superoxide dismutase (SOD1), and mice overexpressing SOD1(G93A) mutant develop a syndrome that closely resembles the human disease. Excitotoxicity mediated by glutamate AMPA receptors has been suggested to be implicated in the selective susceptibility of motor neurons occurring in ALS. In SOD1(G93A) mice, we found that levels of GluR2 AMPA subunit, which plays a pivotal role in the maintenance of calcium impermeability of AMPA receptors, are decreased in spinal motor neurons before symptom onset in concomitance with a modest increase of GluR3 expression, a calcium-permeable AMPA subunit. This effect can result in a higher number of calcium-permeable AMPA receptors on motor neurons of SOD1(G93A) mice, predisposing these cells to be injured by AMPA-mediated glutamate firing. In support of this, we showed that treatment with a new noncompetitive AMPA antagonist, ZK 187638, partially protected motor neurons, improved motor function, and prolonged the survival of SOD1(G93A) mice.
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Kawahara Y, Kwak S. Excitotoxicity and ALS: what is unique about the AMPA receptors expressed on spinal motor neurons? ACTA ACUST UNITED AC 2006; 6:131-44. [PMID: 16183555 DOI: 10.1080/14660820510037872] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
It has been repeatedly reported that spinal motor neurons are selectively vulnerable to AMPA receptor-mediated excitotoxicity. Therefore, identifying the uniqueness of AMPA receptors that are expressed on motor neurons, especially in individuals affected with sporadic amyotrophic lateral sclerosis (ALS) is essential for elucidating the etiology of this disorder. The mechanism that initiates motor neuronal death appears to be an exaggerated influx of Ca(2+) through AMPA receptors. The determinants that affect this Ca(2+) influx are Ca(2+) permeability, which is regulated by the presence of the GluR2 subunit and by RNA editing at the Q/R site of GluR2; channel desensitization, which is regulated by alternative splicing at the flip/flop site and by RNA editing at the R/G site of GluR subunits; and receptor density on the cell surface, which is controlled by many factors including regulatory proteins, direct phosphorylation and RNA editing at the Q/R site. This review focuses on recent progress on the molecular dynamics of AMPA receptors and discusses the pathophysiology of selective motor neuron death mediated by AMPA receptors in individuals affected with sporadic ALS.
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Gryder DS, Castaneda DC, Rogawski MA. Evidence for low GluR2 AMPA receptor subunit expression at synapses in the rat basolateral amygdala. J Neurochem 2005; 94:1728-38. [PMID: 16045445 PMCID: PMC1352164 DOI: 10.1111/j.1471-4159.2005.03334.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fast excitatory synaptic responses in basolateral amygdala (BLA) neurons are mainly mediated by ionotropic glutamate receptors of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) subtype. AMPA receptors containing an edited GluR2 subunit are calcium impermeable, whereas those that lack this subunit are calcium permeable and also inwardly rectifying. Here, we sought to determine the extent to which synapses in the rat BLA have AMPA receptors with GluR2 subunits. We assessed GluR2 protein expression in the BLA by immunocytochemistry with a GluR2 subunit-specific antiserum at the light and electron microscopic level; for comparison, a parallel examination was carried out in the hippocampus. We also recorded from amygdala brain slices to examine the voltage-dependent properties of AMPA receptor- mediated evoked synaptic currents in BLA principal neurons. At the light microscopic level, GluR2 immunoreactivity was localized to the perikarya and proximal dendrites of BLA neurons; dense labeling was also present over the pyramidal cell layer of hippocampal subfields CA1 and CA3. In electron micrographs from the BLA, most of the synapses were asymmetrical with pronounced postsynaptic densities (PSD). They contained clear, spherical vesicles apposed to the PSD and were predominantly onto spines (86%), indicating that they are mainly with BLA principal neurons. Only 11% of morphological synapses in the BLA were onto postsynaptic elements that showed GluR2 immunoreactivity, in contrast to hippocampal subfields CA1 and CA3 in which 76% and 71% of postsynaptic elements were labeled (p < 0.001). Synaptic staining in the BLA and hippocampus, when it occurred, was exclusively postsynaptic, and particularly heavy over the PSD. In whole-cell voltage clamp recordings, 72% of BLA principal neurons exhibited AMPA receptor-mediated synaptic currents evoked by external capsule stimulation that were inwardly rectifying. Although BLA principal neurons express perikaryal and proximal dendritic GluR2 immunoreactivity, few synapses onto these neurons express GluR2, and a preponderance of principal neurons have inwardly rectifying AMPA-mediated synaptic currents, suggesting that targeting of GluR2 to synapses is restricted. Many BLA synaptic AMPA receptors are likely to be calcium permeable and could play roles in synaptic plasticity, epileptogenesis and excitoxicity.
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Affiliation(s)
| | | | - Michael A. Rogawski
- Address for correspondence: Michael A. Rogawski, M.D., Ph.D., Epilepsy Research Section, NINDS, NIH, Porter Neuroscience Research Center, Building 35, Room 1C-1002, 35 Convent Drive MSC 3702, Bethesda, MD 20892-3702, Telephone 301-496-8013, Fax 775-249-7715, E-mail:
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Sun H, Kawahara Y, Ito K, Kanazawa I, Kwak S. Expression profile of AMPA receptor subunit mRNA in single adult rat brain and spinal cord neurons in situ. Neurosci Res 2005; 52:228-34. [PMID: 15927724 DOI: 10.1016/j.neures.2005.03.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Revised: 03/17/2005] [Accepted: 03/18/2005] [Indexed: 11/30/2022]
Abstract
The differential expression of AMPA receptor subunit mRNA was analyzed in the adult rat brain and spinal cord using quantitative RT-PCR with laser capture microdissection. The expression of all four AMPA receptor subunits was demonstrable, with the mRNA expression level for GluR2 being the highest in all the brain areas and neuronal subsets examined. Both the absolute expression level of GluR2 mRNA and its expression relative to the other subunits were the lowest in motoneurons. The unique AMPA receptor expression profile of motoneurons may render them selectively vulnerable to AMPA receptor-mediated excitotoxicity.
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Affiliation(s)
- Hui Sun
- Department of Neurology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan
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Van Damme P, Braeken D, Callewaert G, Robberecht W, Van Den Bosch L. GluR2 Deficiency Accelerates Motor Neuron Degeneration in a Mouse Model of Amyotrophic Lateral Sclerosis. J Neuropathol Exp Neurol 2005; 64:605-12. [PMID: 16042312 DOI: 10.1097/01.jnen.0000171647.09589.07] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
AMPA receptor-mediated excitotoxicity has been implicated in the selective degeneration of motor neurons in amyotrophic lateral sclerosis (ALS). Motor neurons in vitro are particularly vulnerable to excessive AMPA receptor stimulation and one of the factors underlying this selective vulnerability is the presence of a large proportion of Ca2+ -permeable (i.e. GluR2-lacking) AMPA receptors. However, the precise role of GluR2-lacking AMPA receptors in motor neuron degeneration remains to be defined. We therefore studied the impact of GluR2 deficiency on motor neuron death in vitro and in vivo. Cultured motor neurons from GluR2-deficient embryos displayed an increased Ca2+ influx through AMPA receptors and an increased vulnerability to AMPA receptor-mediated excitotoxicity. We deleted the GluR2 gene in mutant SOD1G93A mice by crossbreeding them with GluR2 knockout mice. GluR2 deficiency clearly accelerated the motor neuron degeneration and shortened the life span of mutant SOD1G93A mice. These findings indicate that GluR2 plays a pivotal role in the vulnerability of motor neurons in vitro and in vivo, and that therapies that limit Ca2+ entry through AMPA receptors might be beneficial in ALS patients.
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Affiliation(s)
- Philip Van Damme
- Laboratory of Neurobiology, K. U. Leuven, Campus Gasthuisberg, Leuven, Belgium
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38
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Metzger F, Klapproth N, Kulik A, Sendtner M, Ballanyi K. Optical assessment of motoneuron function in a “twenty-four-hour” acute spinal cord slice model from fetal rats. J Neurosci Methods 2005; 141:309-20. [PMID: 15661313 DOI: 10.1016/j.jneumeth.2004.07.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2003] [Revised: 06/02/2004] [Accepted: 07/13/2004] [Indexed: 10/26/2022]
Abstract
In acute slice preparations of most brain regions, neuronal functions are preserved for only few hours. Since the effects of growth factors or neurotoxic agents are often manifested beyond this time scale, corresponding studies are typically performed on cultured cells. However, cell cultures are generated and maintained under vastly different conditions that can grossly alter neuronal properties. For example, glutamate application to motoneuronal cultures has been reported to modulate neurite formation in some studies while in others it has been reported to kill cells. Here, we have examined whether acute spinal cord slices from rat fetuses can be used within a time window of 24 h for assessment of long-term effects of neuromodulators. In these slices, we have studied the action of glutamate on lumbar motoneurons loaded with fura-2 and rhodamine-123 to monitor intracellular Ca2+ ([Ca2+]i) and mitochondrial potential (Deltapsi), respectively. Further, loading with fura-2 or propidium iodide allowed for morphological assessment of cell viability and death, respectively. Pulses (15 s) or 1 h application of glutamate (300 microM) evoked a moderate (approximately 500 nM) [Ca2+]i rise, but no change of Deltapsi. Even after 24 h, no glutamate-induced cell death was observed and glutamate pulse-evoked [Ca2+]i transients were comparable to controls. The data demonstrate that glutamate does not deregulate [Ca2+]i homeostasis in fetal motoneurons in situ. We propose that acute spinal cord slices from perinatal rodents are a robust model that allows for analysis of neuronal properties and cell viability within a time window of at least 24 h.
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Affiliation(s)
- Friedrich Metzger
- Klinische Forschergruppe Neuroregeneration, Neurologische Klinik, Universität Würzburg, Josef-Schneider-Strasse 11, D-97080 Würzburg, Germany
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Kwak S, Kawahara Y. Deficient RNA editing of GluR2 and neuronal death in amyotropic lateral sclerosis. J Mol Med (Berl) 2004; 83:110-20. [PMID: 15624111 DOI: 10.1007/s00109-004-0599-z] [Citation(s) in RCA: 176] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Accepted: 08/18/2004] [Indexed: 12/11/2022]
Abstract
One plausible hypothesis for selective neuronal death in sporadic amyotropic lateral sclerosis (ALS) is excitotoxicity mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors, which are a subtype of ionotropic glutamate receptors. The Ca2+ conductance of AMPA receptors differs markedly depending on whether the GluR2 (or GluR-B) subunit is a component of the receptor. The properties of GluR2 are generated posttranscriptionally by RNA editing at the Q/R site in the putative second membrane domain (M2), during which the glutamine (Q) codon is substituted by an arginine (R) codon. AMPA receptors containing the unedited form of GluR2Q have high Ca2+ permeability in contrast to the low Ca2+ conductance of those containing the edited form of GluR2R. The role of Ca(2+)-permeable AMPA receptors, particularly GluR2 Q/R site RNA editing status, in neuronal death has been clearly demonstrated both in mice deficient in editing at the GluR2 Q/R site and in mice transgenic for an artificial Ca(2+)-permeable GluR2 subunit. We analyzed the expression level of mRNA of each AMPA receptor subunit in individual motor neurons, as well as the editing efficiency of GluR2 mRNA at the Q/R site in the single neuron level in control subjects and ALS cases. There was no significant difference as to the expression profile of AMPA receptor subunits or the proportion of GluR2 mRNA to total GluRs mRNA between normal subjects and ALS cases. By contrast, the editing efficiency varied greatly, from 0% to 100%, among the motor neurons of each individual with ALS, and was not complete in 44 of them (56%), whereas it remained 100% in normal controls. In addition, GluR2 editing efficiency was more than 99% in the cerebellar Purkinje cells of ALS, spinocerebellar degeneration and normal control groups. Thus, GluR2 underediting occurs in a disease specific and region selective manner. GluR2 modification by RNA editing is a biologically crucial event for neuronal survival, and its deficiency is a direct cause of neuronal death. Therefore, marked reduction of RNA editing in ALS motor neurons may be a direct cause of the selective motor neuron death seen in ALS. It is likely that the molecular mechanism underlying the deficiency in RNA editing is a reduction in the activity of ADAR2, a double- strand RNA specific deaminase. The restoration of this enzyme activity in ALS motor neurons may open the novel strategy for specific ALS therapy.
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Affiliation(s)
- Shin Kwak
- Department of Neurology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-8655 Tokyo, Japan.
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Eybalin M, Caicedo A, Renard N, Ruel J, Puel JL. Transient Ca2+-permeable AMPA receptors in postnatal rat primary auditory neurons. Eur J Neurosci 2004; 20:2981-9. [PMID: 15579152 DOI: 10.1111/j.1460-9568.2004.03772.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Fast excitatory transmission in the nervous system is mostly mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors whose subunit composition governs physiological characteristics such as ligand affinity and ion conductance properties. Here, we report that AMPA receptors at inner hair cell (IHC) synapses lack the GluR2 subunit and are transiently Ca2+-permeable before hearing onset as evidenced using agonist-induced Co2+ accumulation, Western blots and GluR2 confocal microscopy in the rat cochlea. AMPA (100 microM) induced Co2+ accumulation in primary auditory neurons until postnatal day (PND) 10. This accumulation was concentration-dependent, strengthened by cyclothiazide (50 microM) and blocked by GYKI 52466 (80 microM) and Joro spider toxin (1 microM). It was unaffected by D-AP5 (50 microM), and it could not be elicited by 56 mM K+ or 1 mM NMDA + 10 microM glycine. Western blots showed that GluR1 immunoreactivity, present in homogenates of immature cochleas, had disappeared by PND12. GluR2 immunoreactivity was not detected until PND10 and GluR3 and GluR4 immunoreactivities were detected at all the ages examined. Confocal microscopy confirmed that the GluR2 immunofluorescence was not located postsynaptically to IHCs before PND10. In conclusion, AMPA receptors on maturing primary auditory neurons differ from those on adult neurons. They are probably composed of GluR1, GluR3 and GluR4 subunits and have a high Ca2+ permeability. The postsynaptic expression of GluR2 subunits may be continuously regulated by the presynaptic activity allowing for variations in the Ca2+ permeability and physiological properties of the receptor.
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Affiliation(s)
- Michel Eybalin
- INSERM U583, Institut des Neurosciences, Hôpital St. Eloi, 80, Avenue Augustin Fliche, BP 74103, 34091 Montpellier cedex 5, France.
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Santana RF, Reiner A, Britto LRG, Toledo CAB. Differential effects of aging on the distribution of calcium-binding proteins in a pretectal nucleus of the chicken brain. J Chem Neuroanat 2004; 26:195-208. [PMID: 14615028 DOI: 10.1016/j.jchemneu.2003.07.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The nucleus pretectalis (PT) of birds is an ovoid-shaped visuomotor cell group of the pretectum that receives tectal input and projects back to the optic tectum. We performed immunohistochemical single- and double-labeling to determine the distribution and abundance of neurons containing three calcium-binding proteins, parvalbumin (PV), calretinin (CR), and calbindin (CB), in the PT in chickens at three ages. We found that PV-positive and CR-positive cells co-localize and are largely found in the outer part of PT at all ages. The GluR4 subunit of the AMPA-type glutamate receptor was selectively localized to these neurons. CB-positive neurons, however, were largely absent from the PT in young and adult chickens. The abundance of PV-positive and CR-positive neurons in PT in old birds was indistinguishable from that in the younger birds, but CB-positive perikarya were 10-20-fold more common than in young birds, and were again mainly found in the outer part of PT. The overall abundance of neurons in PT was reduced to about 50% of its former abundance in the old birds, with this loss restricted to the central part of the nucleus. These data indicate that a cell loss process develops in PT as birds age, that parvalbuminergic and calretinergic neurons resist this process, and that this process is associated with increased expression of CB.
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Affiliation(s)
- Renato F Santana
- Laboratory of Neurosciences, City University of São Paulo, Rua Cesário Galeno 448, 03071-000 São Paulo, SP, Brazil
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Dekkers J, Bayley P, Dick JRT, Schwaller B, Berchtold MW, Greensmith L. Over-expression of parvalbumin in transgenic mice rescues motoneurons from injury-induced cell death. Neuroscience 2004; 123:459-66. [PMID: 14698753 DOI: 10.1016/j.neuroscience.2003.07.013] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Following nerve injury in neonatal rats, a large proportion of motoneurons die, possibly as a consequence of an increase in vulnerability to the excitotoxic effects of glutamate. Calcium-dependent glutamate excitotoxicity is thought to play a significant role not only in injury-induced motoneuron death, but also in motoneuron degeneration in diseases such as amyotrophic lateral sclerosis (ALS). Motoneurons are particularly vulnerable to calcium influx following glutamate receptor activation, as they lack a number of calcium binding proteins, such as calbindin-D(28k) and parvalbumin. Therefore, it is possible that increasing the ability of motoneurons to buffer intracellular calcium may protect them from cell death and prevent the decline in motor function that usually occurs as a consequence of motoneuron loss. In this study we have tested this possibility by examining the effect of neonatal axotomy on motoneuron survival and muscle force production in normal and transgenic mice that over-express parvalbumin in their motoneurons.The sciatic nerve was crushed in one hindlimb of new-born transgenic and wildtype mice. The effect on motoneuron survival was assessed 8 weeks later by retrograde labelling of motoneurons innervating the tibialis anterior muscle. Following nerve injury in wildtype mice, only 20.2% (+/-2.2, S.E.M.; n=4) of injured motoneurons survive long term compared with 47.2% (+/-4.4, S.E.M.; n=4) in parvalbumin over-expressing mice. Surprisingly, this dramatic increase in motoneuron survival was not reflected in a significant improvement in muscle function, since 8 weeks after injury there was no improvement in either maximal twitch and tetanic force, or muscle weights.Thus, inducing spinal motoneurons to express parvalbumin protects a large proportion of motoneurons from injury-induced cell death, but this is not sufficient to restore muscle function.
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Affiliation(s)
- J Dekkers
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square, London WC1N 3BG, UK
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Kawahara Y, Kwak S, Sun H, Ito K, Hashida H, Aizawa H, Jeong SY, Kanazawa I. Human spinal motoneurons express low relative abundance of GluR2 mRNA: an implication for excitotoxicity in ALS. J Neurochem 2003; 85:680-9. [PMID: 12694394 DOI: 10.1046/j.1471-4159.2003.01703.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
AMPA receptor-mediated neurotoxicity is currently the most plausible hypothesis for the etiology of amyotrophic lateral sclerosis (ALS). The mechanism initiating this type of neuronal death is believed to be exaggerated Ca2+-influx through AMPA receptors, which is critically determined by the presence or absence of the glutamate receptor subunit 2 (GluR2) in the assembly. We have provided the first quantitative measurements of the expression profile of AMPA receptor subunits mRNAs in human single neurons by means of quantitative RT-PCR with a laser microdissector. Among the AMPA subunits, GluR2 shared the vast majority throughout the neuronal subsets and tissues examined. Furthermore, both the expression level and the proportion of GluR2 mRNA in motoneurons were the lowest among all neuronal subsets examined, whereas those in motoneurons of ALS did not differ from the control group, implying that selective reduction of the GluR2 subunit cannot be a mechanism of AMPA receptor-mediated neurotoxicity in ALS. However, the low relative abundance of GluR2 might provide spinal motoneurons with conditions that are easily affected by changes of AMPA receptor properties including deficient GluR2 mRNA editing in ALS.
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Affiliation(s)
- Yukio Kawahara
- Department of Neurology, Graduate School of Medicine, The University of Tokyo, Hongo, Tokyo, Japan
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Chapter 15 Factors Underlying the Selective Vulnerability of Motor Neurons to Neurodegeneration. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1877-3419(09)70116-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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45
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Kim SH, Henkel JS, Beers DR, Sengun IS, Simpson EP, Goodman JC, Engelhardt JI, Siklós L, Appel SH. PARP expression is increased in astrocytes but decreased in motor neurons in the spinal cord of sporadic ALS patients. J Neuropathol Exp Neurol 2003; 62:88-103. [PMID: 12528821 DOI: 10.1093/jnen/62.1.88] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The evidence for increased oxidative stress and DNA damage in amyotrophic lateral sclerosis (ALS) prompted studies to determine if the expression of poly(ADP-ribose) polymerase (PARP) is increased in ALS. Using Western analyses of postmortem tissue, we demonstrated that PARP-immunoreactivity (PARP-IR) was increased 3-fold in spinal cord tissues of sporadic ALS (sALS) patients compared with non-neurological disease controls. Despite the increased PARP-IR, PARP mRNA expression was not increased significantly. Immunohistochemical analyses revealed PARP-IR was increased in both white and gray matter of sALS spinal cord. While PARP-IR was predominantly seen in astrocytes, large motor neurons displayed reduced staining compared with controls. This result contrasts sharply to the staining of Alzheimer and MPTP-induced Parkinson diseased tissue, where poly(ADP-ribose) (PAR)-IR was seen mostly in neurons, with little astrocytic staining. PARP-IR was increased in the pellet fraction of sALS homogenates compared with control homogenates, representing potential PARP binding to chromatin or membranes and suggesting a possible mechanism of PARP stabilization. The present results demonstrate glial alterations in sALS spinal cord tissue and support the role of glial alterations in sALS pathogenesis. Additionally, these results demonstrate differences in sALS spinal motor neurons and astrocytes compared to brain neurons and astrocytes in Alzheimer disease and MPTP-induced Parkinson disease despite the presence of markers for oxidative stress in all 3 diseases.
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Affiliation(s)
- Seung H Kim
- Department of Neurology, Baylor College of Medicine, Houston, Texas 77030, USA
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Mennini T, Bigini P, Ravizza T, Vezzani A, Calvaresi N, Tortarolo M, Bendotti C. Expression of glutamate receptor subtypes in the spinal cord of control and mnd mice, a model of motor neuron disorder. J Neurosci Res 2002; 70:553-60. [PMID: 12404509 DOI: 10.1002/jnr.10420] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We studied the expression and distribution of glutamate receptor subtypes in the spinal cord of mnd mice, a model of motor neuron disorders and neuronal ceroid lipofuscinosis, and control mice using immunocytochemistry and in situ hybridization. The constitutive subunit of the NMDA ionotropic glutamate receptor, NMDAR1, was expressed in all neurons of the grey matter and was not modified in the spinal cord of mnd mice in either its normal or phosphorylated form. The immunoreactivity of GluR2, but not its mRNA, was increased mainly in the substantia gelatinosa both in presymptomatic and in 8-month-old symptomatic mice, suggesting compensatory changes aimed at reducing the Ca2+ permeability of the receptor channel. In spinal cord of mnd mice, mRNA, and protein levels of GluR3 were low only at the symptomatic stage, possibly as a consequence of motor neuron dysfunction. This was not due to motoneuron degeneration, because the number of choline acetyltransferase (ChAT) immunopositive lumbar motor neurons and the ChAT activity in the spinal cord and hind leg muscles of symptomatic mnd mice were no different from control mice. GluR4 mRNA was increased throughout the grey matter, presumably in relation to the marked microglia activation reported in the grey matter of the lumbar spinal cord in mnd mice. These changes in ionotropic glutamate receptors may alter glutamatergic neurotransmission and play some role in the pathology of mnd mice.
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MESH Headings
- Animals
- Cell Count
- Choline O-Acetyltransferase/biosynthesis
- Disease Models, Animal
- Immunohistochemistry
- In Situ Hybridization
- Mice
- Mice, Neurologic Mutants
- Motor Neuron Disease/metabolism
- Motor Neuron Disease/pathology
- Motor Neurons/metabolism
- Motor Neurons/pathology
- Muscle, Skeletal/innervation
- Muscle, Skeletal/pathology
- Neuronal Ceroid-Lipofuscinoses/metabolism
- Neuronal Ceroid-Lipofuscinoses/pathology
- RNA, Messenger/biosynthesis
- Receptors, AMPA/biosynthesis
- Receptors, AMPA/genetics
- Receptors, Glutamate/biosynthesis
- Receptors, Glutamate/genetics
- Receptors, N-Methyl-D-Aspartate/biosynthesis
- Receptors, N-Methyl-D-Aspartate/genetics
- Spinal Cord/metabolism
- Spinal Cord/pathology
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Affiliation(s)
- Tiziana Mennini
- Istituto di Ricerche Farmacologiche Mario Negri, Milano, Italy.
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47
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Van Damme P, Van Den Bosch L, Van Houtte E, Callewaert G, Robberecht W. GluR2-dependent properties of AMPA receptors determine the selective vulnerability of motor neurons to excitotoxicity. J Neurophysiol 2002; 88:1279-87. [PMID: 12205149 DOI: 10.1152/jn.2002.88.3.1279] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
AMPA receptor-mediated excitotoxicity has been implicated in the selective motor neuron loss in amyotrophic lateral sclerosis. In some culture models, motor neurons have been shown to be selectively vulnerable to AMPA receptor agonists due to Ca(2+) influx through Ca(2+)-permeable AMPA receptors. Because the absence of GluR2 in AMPA receptors renders them highly permeable to Ca(2+) ions, it has been hypothesized that the selective vulnerability of motor neurons is due to their relative deficiency in GluR2. However, conflicting evidence exists about the in vitro and in vivo expression of GluR2 in motor neurons, both at the mRNA and at the protein level. In this study, we quantified electrophysiological properties of AMPA receptors, known to be dependent on the relative abundance of GluR2: sensitivity to external polyamines, rectification index, and relative Ca(2+) permeability. Cultured rat spinal cord motor neurons were compared with dorsal horn neurons (which are resistant to excitotoxicity) and with motor neurons that survived an excitotoxic insult. Motor neurons had a higher sensitivity to external polyamines, a lower rectification index, and a higher relative Ca(2+) permeability ratio than dorsal horn neurons. These findings confirm that motor neurons are relatively deficient in GluR2. The AMPA receptor properties correlated well with each other and with the selective vulnerability of motor neurons because motor neurons surviving an excitotoxic event had similar characteristics as dorsal horn neurons. These data indicate that the relative abundance of GluR2 in functional AMPA receptors may be a major determinant of the selective vulnerability of motor neurons to excitotoxicity in vitro.
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Affiliation(s)
- P Van Damme
- Laboratory for Neurobiology, University of Leuven, B-3000 Leuven, Belgium.
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48
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Toledo CAB, Britto LRG, Pires RS, Veenman CL, Reiner A. Interspecific differences in the expression of the AMPA-type glutamate receptors and parvalbumin in the nucleus of Edinger-Westphal of chicks and pigeons. Brain Res 2002; 947:122-30. [PMID: 12144860 DOI: 10.1016/s0006-8993(02)02919-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The distribution of AMPA-type glutamate receptor (GluR) subunits was studied in the Edinger-Westphal nucleus (EW) of chicks and pigeons. GluR1, GluR2, GluR3 and GluR4 subunits appeared to be present in EW neurons of both species, but interspecific differences were observed in the abundance of the different types of subunits found in EW neurons. Of particular note, GluR2 immunoreactivity was present in the vast majority (ca. 80%) of neurons of pigeon EW but was found in only a small fraction (ca. 15%) of chick EW neurons. Scarcity of the GluR2 subunit in chick EW was confirmed by in situ hybridization. Because of the tendency for parvalbumin to be localized to neurons that are selectively deficient in GluR2, we also studied the localization of parvalbumin, as well as other calcium-binding proteins, in EW of chick and pigeon. Parvalbumin was found in more than 50% of chick EW neurons but was not detected in pigeon EW neurons. Our results suggest that there are major glutamatergic inputs to EW neurons in both pigeons and chicks. Furthermore, there are likely to be more AMPA-type calcium-permeable glutamate receptors in EW neurons of chick than in pigeon, since it is known that the subtype containing the edited GluR2 subunit is not calcium permeable.
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Affiliation(s)
- Cláudio A B Toledo
- Laboratory of Neurosciences, City University of São Paulo, SP 03071-000, São Paulo, Brazil.
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49
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Van Damme P, Van Den Bosch L, Van Houtte E, Eggermont J, Callewaert G, Robberecht W. Na(+) entry through AMPA receptors results in voltage-gated k(+) channel blockade in cultured rat spinal cord motoneurons. J Neurophysiol 2002; 88:965-72. [PMID: 12163545 DOI: 10.1152/jn.2002.88.2.965] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor currents, evoked with the agonist kainate, were studied with the gramicidin perforated-patch-clamp technique in cultured rat spinal cord motoneurons. Kainate-induced currents could be blocked by the AMPA receptor antagonist LY 300164 and displayed an apparent strong inward rectification. This inward rectification was not a genuine property of AMPA receptor currents but was a result of a concomitant decrease in outward current at potentials positive to -40.5 +/- 1.3 mV. The AMPA receptor current itself was nearly linear (rectification index 0.91). The kainate-inhibited outward current had a reversal potential close to the estimated K(+) equilibrium potential and was blocked by 30 mM tetraethylammonium. When voltage steps were applied, it was found that kainate inhibited both the delayed rectifier K(+) current K(V) and the transient outward K(+) current, K(A). The kainate-induced inhibition of K(+) currents was dependent on ion flux through the AMPA receptor, because no change in the membrane conductance was noticed in the presence of LY 300164. Removing extracellular Ca(2+) had no effect, whereas replacing extracellular Na(+) or clamping the membrane close to the estimated Na(+) equilibrium potential during kainate application attenuated the inhibition of the K(+) current. Sustained Na(+) influx induced by application of the Na(+) ionophore monensin could mimic the effect of kainate on K(+) conductance. These findings demonstrate that Na(+) influx through AMPA receptors results in blockade of voltage-gated K(+) channels.
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Affiliation(s)
- P Van Damme
- Laboratory for Neurobiology, Department of Neuroscience, University of Leuven, Belgium.
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50
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Van Den Bosch L, Schwaller B, Vleminckx V, Meijers B, Stork S, Ruehlicke T, Van Houtte E, Klaassen H, Celio MR, Missiaen L, Robberecht W, Berchtold MW. Protective effect of parvalbumin on excitotoxic motor neuron death. Exp Neurol 2002; 174:150-61. [PMID: 11922657 DOI: 10.1006/exnr.2001.7858] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The mechanism responsible for the selective vulnerability of motor neurons in amyotrophic lateral sclerosis (ALS) is poorly understood. Several lines of evidence indicate that susceptibility of motor neurons to Ca(2+) overload induced by excitotoxic stimuli is involved. In this study, we investigated whether the high density of Ca(2+)-permeable AMPA receptors on motor neurons gives rise to higher Ca(2+) transients in motor neurons compared to dorsal horn neurons. Dorsal horn neurons were chosen as controls as these cells do not degenerate in ALS. In cultured spinal motor neurons, the rise of the cytosolic Ca(2+) concentration induced by kainic acid (KA) and mediated by the AMPA receptor was almost twice as high as in spinal neurons from the dorsal horn. Furthermore, we investigated whether increasing the motor neuron's cytosolic Ca(2+)-buffering capacity protects them from excitotoxic death. To obtain motor neurons with increased Ca(2+) buffering capacity, we generated transgenic mice overexpressing parvalbumin (PV). These mice have no apparent phenotype. PV overexpression was present in the central nervous system, kidney, thymus, and spleen. Motor neurons from these transgenic mice expressed PV in culture and were partially protected from KA-induced death as compared to those isolated from nontransgenic littermates. PV overexpression also attenuated KA-induced Ca(2+) transients, but not those induced by depolarization. We conclude that the high density of Ca(2+)-permeable AMPA receptors on the motor neuron's surface results in high Ca(2+) transients upon stimulation and that the low cytosolic Ca(2+)-buffering capacity of motor neurons may contribute to the selective vulnerability of these cells in ALS. Overexpression of a high-affinity Ca(2+) buffer such as PV protects the motor neuron from excitotoxicity and this protective effect depends upon the mode of Ca(2+) entry into the cell.
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Affiliation(s)
- L Van Den Bosch
- Neurobiology, Laboratory of Physiology, Campus Gasthuisberg, Herestraat 49, Leuven, Belgium
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