title: Extracellular spermine exacerbates ischemic neuronal injury through sensitization of ASIC1a channels to extracellular acidosis.
abstract: Ischemic brain injury is a major problem associated with stroke. It has been increasingly recognized that acid-sensing ion channels (ASICs) contribute significantly to ischemic neuronal damage, but the underlying mechanism has remained elusive. Here, we show that extracellular spermine, one of the endogenous polyamines, exacerbates ischemic neuronal injury through sensitization of ASIC1a channels to extracellular acidosis. Pharmacological blockade of ASIC1a or deletion of the ASIC1 gene greatly reduces the enhancing effect of spermine in ischemic neuronal damage both in cultures of dissociated neurons and in a mouse model of focal ischemia. Mechanistically, spermine profoundly reduces desensitization of ASIC1a by slowing down desensitization in the open state, shifting steady-state desensitization to more acidic pH, and accelerating recovery between repeated periods of acid stimulation. Spermine-mediated potentiation of ASIC1a activity is occluded by PcTX1 (psalmotoxin 1), a specific ASIC1a inhibitor binding to its extracellular domain. Functionally, the enhanced channel activity is accompanied by increased acid-induced neuronal membrane depolarization and cytoplasmic Ca(2+) overload, which may partially explain the exacerbated neuronal damage caused by spermine. More importantly, blocking endogenous spermine synthesis significantly attenuates ischemic brain injury mediated by ASIC1a but not that by NMDA receptors. Thus, extracellular spermine contributes significantly to ischemic neuronal injury through enhancing ASIC1a activity. Our data suggest new neuroprotective strategies for stroke patients via inhibition of polyamine synthesis and subsequent spermine-ASIC interaction.
authors.affiliation: Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Duan
authors.forename: Yi-Zhi
authors.initials: YZ
authors.lastname: Wang
authors.forename: Tao
authors.initials: T
authors.lastname: Yang
authors.forename: Xiang-Ping
authors.initials: XP
authors.lastname: Chu
authors.forename: Ye
authors.initials: Y
authors.lastname: Yu
authors.forename: Yu
authors.initials: Y
authors.lastname: Huang
authors.forename: Hui
authors.initials: H
authors.lastname: Cao
authors.forename: Jillian
authors.initials: J
authors.lastname: Hansen
authors.forename: Roger P
authors.initials: RP
authors.lastname: Simon
authors.forename: Michael X
authors.initials: MX
authors.lastname: Zhu
authors.forename: Zhi-Gang
authors.initials: ZG
authors.lastname: Xiong
authors.forename: Tian-Le
authors.initials: TL
authors.lastname: Xu
mesh_terms: D062565:Acid Sensing Ion Channels; D000138:Acidosis / Q000503:physiopathology*; D027182:Amino Acid Transport System y+ / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000378:metabolism; D000818:Animals; D001703:Biophysics; D001930:Brain Injuries / Q000139:chemically induced; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004347:Drug Interactions; D004558:Electric Stimulation; D004622:Embryo, Mammalian; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D045604:Extracellular Fluid / Q000187:drug effects*; D018756:GABA Antagonists / Q000009:adverse effects; D005947:Glucose / Q000172:deficiency; D006624:Hippocampus / Q000166:cytology; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia; D020244:Infarction, Middle Cerebral Artery / Q000473:pathology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D009841:Oligonucleotides / Q000494:pharmacology; D018408:Patch-Clamp Techniques / Q000379:methods; D010852:Picrotoxin / Q000009:adverse effects; D011700:Putrescine / Q000494:pharmacology; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*; D013096:Spermine / Q000009:adverse effects / Q000494:pharmacology*; D013778:Tetrazolium Salts; D013997:Time Factors; D014162:Transfection; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D062565:Acid Sensing Ion Channels; D027182:Amino Acid Transport System y+; D002118:Calcium; D004338:Drug Combinations; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D005947:Glucose; D007770:L-Lactate Dehydrogenase; D009419:Nerve Tissue Proteins; D009841:Oligonucleotides; D010852:Picrotoxin; D011700:Putrescine; D015222:Sodium Channels; D013096:Spermine; D013778:Tetrazolium Salts; D014633:Valine; C568267:ASIC1 protein, mouse; C412624:Slc7a10 protein, mouse; C056639:2-amino-5-phosphopentanoic acid; C009591:triphenyltetrazolium