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Lombardo J, Sun J, Harrington MA. Rapid activity-dependent modulation of the intrinsic excitability through up-regulation of KCNQ/Kv7 channel function in neonatal spinal motoneurons. PLoS One 2018; 13:e0193948. [PMID: 29579068 PMCID: PMC5868771 DOI: 10.1371/journal.pone.0193948] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 02/21/2018] [Indexed: 11/25/2022] Open
Abstract
Activity-dependent changes in the properties of the motor system underlie the necessary adjustments in its responsiveness on the basis of the environmental and developmental demands of the organism. Although plastic changes in the properties of the spinal cord have historically been neglected because of the archaic belief that the spinal cord is constituted by a hardwired network that simply relays information to muscles, plenty of evidence has been accumulated showing that synapses impinging on spinal motoneurons undergo short- and long-term plasticity. In the brain, brief changes in the activity level of the network have been shown to be paralleled by changes in the intrinsic excitability of the neurons and are suggested to either reinforce or stabilize the changes at the synaptic level. However, rapid activity-dependent changes in the intrinsic properties of spinal motoneurons have never been reported. In this study, we show that in neonatal mice the intrinsic excitability of spinal motoneurons is depressed after relatively brief but sustained changes in the spinal cord network activity. Using electrophysiological techniques together with specific pharmacological blockers of KCNQ/Kv7 channels, we demonstrate their involvement in the reduction of the intrinsic excitability of spinal motoneurons. This action results from an increased M-current, the product of the activation of KCNQ/Kv7 channels, which leads to a hyperpolarization of the resting membrane potential and a decrease in the input resistance of spinal motoneurons. Computer simulations showed that specific up-regulations in KCNQ/Kv7 channels functions lead to a modulation of the intrinsic excitability of spinal motoneurons as observed experimentally. These results indicate that KCNQ/Kv7 channels play a fundamental role in the activity-dependent modulation of the excitability of spinal motoneurons.
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Affiliation(s)
- Joseph Lombardo
- Department of Biology, Delaware State University, Dover, Delaware, United States of America
| | - Jianli Sun
- Department of Biology, Delaware State University, Dover, Delaware, United States of America
| | - Melissa A. Harrington
- Department of Biology, Delaware State University, Dover, Delaware, United States of America
- * E-mail:
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Kremeyer B, Lopera F, Cox JJ, Momin A, Rugiero F, Marsh S, Woods CG, Jones NG, Paterson KJ, Fricker FR, Villegas A, Acosta N, Pineda-Trujillo NG, Ramírez JD, Zea J, Burley MW, Bedoya G, Bennett DL, Wood JN, Ruiz-Linares A. A gain-of-function mutation in TRPA1 causes familial episodic pain syndrome. Neuron 2010; 66:671-80. [PMID: 20547126 PMCID: PMC4769261 DOI: 10.1016/j.neuron.2010.04.030] [Citation(s) in RCA: 326] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/16/2010] [Indexed: 12/12/2022]
Abstract
Human monogenic pain syndromes have provided important insights into the molecular mechanisms that underlie normal and pathological pain states. We describe an autosomal-dominant familial episodic pain syndrome characterized by episodes of debilitating upper body pain, triggered by fasting and physical stress. Linkage and haplotype analysis mapped this phenotype to a 25 cM region on chromosome 8q12-8q13. Candidate gene sequencing identified a point mutation (N855S) in the S4 transmembrane segment of TRPA1, a key sensor for environmental irritants. The mutant channel showed a normal pharmacological profile but altered biophysical properties, with a 5-fold increase in inward current on activation at normal resting potentials. Quantitative sensory testing demonstrated normal baseline sensory thresholds but an enhanced secondary hyperalgesia to punctate stimuli on treatment with mustard oil. TRPA1 antagonists inhibit the mutant channel, promising a useful therapy for this disorder. Our findings provide evidence that variation in the TRPA1 gene can alter pain perception in humans.
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Affiliation(s)
- Barbara Kremeyer
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK
| | - Francisco Lopera
- Grupo de Neurociencias, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | - James J. Cox
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK
- Department of Medical Genetics, Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge CB2 0XY, UK
| | - Aliakmal Momin
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK
| | - Francois Rugiero
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK
| | - Steve Marsh
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - C. Geoffrey Woods
- Department of Medical Genetics, Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge CB2 0XY, UK
| | - Nicholas G. Jones
- Department of Neurorestoration, Wolfson CARD, Hodgkin Building, Guy's Campus, King's College London, London SE1 1UL, UK
| | - Kathryn J. Paterson
- Department of Neurorestoration, Wolfson CARD, Hodgkin Building, Guy's Campus, King's College London, London SE1 1UL, UK
| | - Florence R. Fricker
- Department of Neurorestoration, Wolfson CARD, Hodgkin Building, Guy's Campus, King's College London, London SE1 1UL, UK
| | - Andrés Villegas
- Grupo de Neurociencias, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | - Natalia Acosta
- Grupo de Neurociencias, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | | | - Juan Diego Ramírez
- Grupo de Neurociencias, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | - Julián Zea
- Grupo de Neurociencias, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | - Mari-Wyn Burley
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK
| | - Gabriel Bedoya
- Grupo de Mapeo Genético, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | - David L.H. Bennett
- Department of Neurorestoration, Wolfson CARD, Hodgkin Building, Guy's Campus, King's College London, London SE1 1UL, UK
| | - John N. Wood
- Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK
- World Class University Department of Molecular Medicine and Biopharmaceutical Sciences, Seoul National University, Korea
| | - Andrés Ruiz-Linares
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK
- Grupo de Mapeo Genético, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
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Li GY, Fan B, Su GF. Acute energy reduction induces caspase-dependent apoptosis and activates p53 in retinal ganglion cells (RGC-5). Exp Eye Res 2009; 89:581-9. [PMID: 19524568 DOI: 10.1016/j.exer.2009.06.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Revised: 05/24/2009] [Accepted: 06/02/2009] [Indexed: 10/20/2022]
Abstract
The energy reduction-induced death of retinal ganglion cells is associated with many ophthalmic diseases. The present study was designed to investigate the apoptosis pathway of retinal ganglion cells (RGC-5) following acute ATP reduction by using glucose deprivation (GD). RGC-5 cells were cultured in glucose-free or normal DMEM for 3 days. The changes in intracellular ATP and cell viability were monitored by ATP assay and MTT assay. APOPercentage and in situ TUNEL assays were used to determine the cell death pattern. The involvement of oxidative stress was assessed by measuring intracellular ROS generation, the HO-1 expression, the effect of antioxidants, and the ratio of GSSG to total GSH. The activation of p53 and apoptosis markers was evaluated by Western blotting. We found that glucose deprivation caused an acute decline of intracellular ATP level, concomitantly decreasing cell viability. The cell death exhibited typical features indicative of apoptosis, including cell shrinkage, phosphatidylserine externalization and DNA fragmentation. Oxidative stress was involved in the cell death process; an antioxidant significantly protected the cells against glucose deprivation. p53 and apoptosis markers, caspase-3 and PARP-1 were activated after RGC-5 cells were cultured in glucose-free media for 32 h. Z-VAD-fmk, a pan-caspase inhibitor, was sufficient to prevent apoptosis. These results suggest that acute energy reduction induced by glucose deprivation triggers caspase-dependent apoptosis and activates p53. Blocking the critical steps in this cell death pathway may have therapeutic effects, rescuing the retinal ganglion cells from damages associated with acute energy reduction.
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Affiliation(s)
- Guang-Yu Li
- Department of Ophthalmology, Second Hospital of JiLin University, ChangChun 130041, China.
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