Preferential Zn2+ influx through Ca2+-permeable AMPA/kainate channels triggers prolonged mitochondrial superoxide production.
Synaptically released Zn2+ can enter and cause injury to postsynaptic neurons. Microfluorimetric studies using the Zn2+-sensitive probe, Newport green, examined levels of [Zn2+]i attained in cultured cortical neurons on exposure to N-methyl-D-asparte, kainate, or high K+ (to activate voltage-sensitive Ca2+ channels) in the presence of 300 microM Zn2+. Indicating particularly high permeability through Ca2+-permeable alpha-amino3-hydroxy-5-methyl-4-isoxazolepropionic-acid/kainate (Ca-A/K) channels, micromolar [Zn2+]i rises were observed only after kainate exposures and only in neurons expressing these channels [Ca-A/K(+) neurons]. Further studies using the oxidation-sensitive dye, hydroethidine, revealed Zn2+-dependent reactive oxygen species (ROS) generation that paralleled the [Zn2+]i rises, with rapid oxidation observed only in the case of Zn2+ entry through Ca-A/K channels. Indicating a mitochondrial source of this ROS generation, hydroethidine oxidation was inhibited by the mitochondrial electron transport blocker, rotenone. Additional evidence for a direct interaction between Zn2+ and mitochondria was provided by the observation that the Zn2+ entry through Ca-A/K channels triggered rapid mitochondrial depolarization, as assessed by using the potential-sensitive dye tetramethylrhodamine ethylester. Whereas Ca2+ influx through Ca-A/K channels also triggers ROS production, the [Zn2+]i rises and subsequent ROS production are of more prolonged duration.
Sensi
S L
SL
Department of Neurology, University of California, Irvine, CA 92697-4292, USA.
Yin
H Z
HZ
Carriedo
S G
SG
Rao
S S
SS
Weiss
J H
JH
D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D004625:Embryo, Nonmammalian; D007608:Kainic Acid / Q000633:toxicity; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D016202:N-Methylaspartate / Q000494:pharmacology; D019579:Neocortex / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009498:Neurotoxins / Q000633:toxicity; D011188:Potassium / Q000494:pharmacology; D018091:Receptors, AMPA / Q000502:physiology*; D018092:Kainic Acid Receptors / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D013481:Superoxides / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism* / Q000494:pharmacology
D002118:Calcium; D015220:Calcium Channels; D007608:Kainic Acid; D016202:N-Methylaspartate; D009498:Neurotoxins; D011188:Potassium; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate; D013481:Superoxides; D015032:Zinc