title: ASIC channel inhibition enhances excitotoxic neuronal death in an in vitro model of spinal cord injury.
abstract: In the spinal cord high extracellular glutamate evokes excitotoxic damage with neuronal loss and severe locomotor impairment. During the cell dysfunction process, extracellular pH becomes acid and may activate acid-sensing ion channels (ASICs) which could be important contributors to neurodegenerative pathologies. Our previous studies have shown that transient application of the glutamate analog kainate (KA) evokes delayed excitotoxic death of spinal neurons, while white matter is mainly spared. The present goal was to enquire if ASIC channels modulated KA damage in relation to locomotor network function and cell death. Mouse spinal cord slices were treated with KA (0.01 or 0.1mM) for 1h, and then washed out for 24h prior to analysis. RT-PCR results showed that KA (at 0.01mM concentration that is near-threshold for damage) increased mRNA expression of ASIC1a, ASIC1b, ASIC2 and ASIC3, an effect reversed by the ASIC inhibitor 4',6-diamidino-2-phenylindole (DAPI). A KA neurotoxic dose (0.1mM) reduced ASIC1a and ASIC2 expression. Cell viability assays demonstrated KA-induced large damage in spinal slices from mice with ASIC1a gene ablation. Likewise, immunohistochemistry indicated significant neuronal loss when KA was followed by the ASIC inhibitors DAPI or amiloride. Electrophysiological recording from ventral roots of isolated spinal cords showed that alternating oscillatory cycles were slowed down by 0.01mMKA, and intensely inhibited by subsequently applied DAPI or amiloride. Our data suggest that early rise in ASIC expression and function counteracted deleterious effects on spinal networks by raising the excitotoxicity threshold, a result with potential implications for improving neuroprotection.
authors.affiliation: Laboratorios de Investigación aplicada en Neurociencias (LIAN) - Fundación para la Lucha conntra las Enfermedades Neurológicas de la Infancia (FLENI), CONICET, Buenos Aires, Argentina. Electronic address: mazzone@fbmc.fcen.uba.ar.
authors.forename: Graciela L
authors.initials: GL
authors.lastname: Mazzone
authors.affiliation: Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy.
authors.forename: Priyadharishini
authors.initials: P
authors.lastname: Veeraraghavan
authors.affiliation: Instituto de Fisiología, Biología molecular y Neurociencias, CONICET, Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
authors.forename: Carlota
authors.initials: C
authors.lastname: Gonzalez-Inchauspe
authors.affiliation: Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy; Spinal Person Injury Neurorehabilitation Applied Laboratory (SPINAL), Istituto di Medicina Fisica e Riabilitazione, Udine, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Nistri
authors.affiliation: Instituto de Fisiología, Biología molecular y Neurociencias, CONICET, Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
authors.forename: Osvaldo D
authors.initials: OD
authors.lastname: Uchitel
mesh_terms: D062646:Acid Sensing Ion Channel Blockers / Q000633:toxicity; D062565:Acid Sensing Ion Channels / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016923:Cell Death / Q000187:drug effects / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D018698:Glutamic Acid / Q000378:metabolism; D007211:Indoles / Q000633:toxicity; D007608:Kainic Acid / Q000633:toxicity; D051379:Mice; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D011522:Protons; D012333:RNA, Messenger / Q000378:metabolism; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D013119:Spinal Cord Injuries / Q000378:metabolism* / Q000473:pathology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D046509:Tissue Culture Techniques
chemical_list: D062646:Acid Sensing Ion Channel Blockers; D062565:Acid Sensing Ion Channels; D007211:Indoles; D011522:Protons; D012333:RNA, Messenger; D018698:Glutamic Acid; C007293:DAPI; D007608:Kainic Acid
keywords: acid sensing ion channels (ASICs); fictive locomotion; kainic acid; neuroprotection; pH; spinal cord injury