title: Involvement of mitochondrial K+ release and cellular efflux in ischemic and apoptotic neuronal death.
abstract: We measured and manipulated intracellular potassium (K+) fluxes in cultured hippocampal neurons in an effort to understand the involvement of K+ in neuronal death under conditions of ischemia and exposure to apoptotic stimuli. Measurements of the intracellular K+ concentration using the fluorescent probe 1,3-benzenedicarboxylic acid, 4,4'-[1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diylbis(5-methoxy-6,2-benzofurandiyl)]bis-, tetrakis [(acetyloxy) methyl] ester (PBFI) revealed that exposure of neurons to cyanide (chemical hypoxia), glutamate (excitotoxic insult) or staurosporine (apoptotic stimulus) results in efflux of K+ and cell death. Treatment of neurons with 5-hydroxydecanoate (5HD), an inhibitor of mitochondrial K+ channels, reduced K+ fluxes in neurons exposed to each insult and increased the resistance of the cells to death. K+ efflux was attenuated, levels of oxyradicals were decreased, mitochondrial membrane potential was stabilized and release of cytochrome c from mitochondria was attenuated in neurons treated with 5HD. K+ was rapidly released into the cytosol from mitochondria when neurons were exposed to the K+ channel opener, diazoxide, or to the mitochondrial uncoupler, carbonyl cyanide 4(trifluoromethoxy)phenylhydrazone (FCCP), demonstrating that the intramitochondrial K+ concentration is greater than the cytosolic K+ concentration. The release of K+ from mitochondria was followed by efflux through plasma membrane K+ channels. In vivo studies showed that 5HD reduces ischemic brain damage without affecting cerebral blood flow in a mouse model of focal ischemic stroke. These findings suggest that intracellular K+ fluxes play a key role in modulating neuronal oxyradical production and cell survival under ischemic conditions, and that agents that modify K+ fluxes may have therapeutic benefit in stroke and related neurodegenerative conditions.
authors.affiliation: Laboratory of Neurosciences, National Institute on Aging Gerontology Research Center, Baltimore, Maryland, USA.
authors.forename: Dong
authors.initials: D
authors.lastname: Liu
authors.forename: John R
authors.initials: JR
authors.lastname: Slevin
authors.forename: Chengbiao
authors.initials: C
authors.lastname: Lu
authors.forename: Sic L
authors.initials: SL
authors.lastname: Chan
authors.forename: Magnus
authors.initials: M
authors.lastname: Hansson
authors.forename: Eskil
authors.initials: E
authors.lastname: Elmér
authors.forename: Mark P
authors.initials: MP
authors.lastname: Mattson
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002545:Brain Ischemia / Q000188:drug therapy / Q000378:metabolism*; D016923:Cell Death; D015687:Cell Hypoxia; D002478:Cells, Cultured; D003486:Cyanides / Q000633:toxicity; D003652:Decanoic Acids / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000633:toxicity; D005456:Fluorescent Dyes; D018698:Glutamic Acid / Q000633:toxicity; D006880:Hydroxy Acids / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D051381:Rats; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D003486:Cyanides; D003652:Decanoic Acids; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D006880:Hydroxy Acids; D018696:Neuroprotective Agents; D026902:Potassium Channel Blockers; D014665:Vasodilator Agents; D018698:Glutamic Acid; C052853:5-hydroxydecanoic acid; D003981:Diazoxide; D011188:Potassium