AMPA/kainate receptor-triggered Zn2+ entry into cortical neurons induces mitochondrial Zn2+ uptake and persistent mitochondrial dysfunction.
Rapid Zn2+ influx through Ca2+-permeable AMPA/kainate (Ca-A/K) channels triggers reactive oxygen species (ROS) generation and is potently neurotoxic. The first aim of this study was to determine whether these effects might result from direct mitochondrial Zn2+ uptake. Adapting the mitochondrially sequestered divalent cation sensitive probe, rhod-2, to visualize mitochondrial Zn2+, present studies indicate that Zn2+ is taken up into these organelles. The specificity of the signal for Zn2+ was indicated by its reversal by Zn2+ chelation, and its mitochondrial origin indicated by its speckled extranuclear appearance and by its elimination upon pretreatment with the mitochondrial protonophore, carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP). Consistent with inhibition of mitochondrial Zn2+ uptake, FCCP also slowed the recovery of cytosolic Zn2+ elevations in Ca-A/K(+) neurons. Further studies sought clues to the high toxic potency of intracellular Zn2+. In experiments using the mitochondrial membrane polarization (DeltaPsi(m))-sensitive probe tetramethylrhodamine ethyl ester and the ROS-sensitive probe hydroethidine, brief kainate exposures in the presence of 300 microM Zn2+ (with or without Ca2+) resulted in prolonged loss of DeltaPsi(m) and corresponding prolonged ROS generation in Ca-A/K(+) neurons, in comparison to the more rapid recovery from loss of DeltaPsi(m) and transient ROS generation after kainate/1.8 mM Ca2+ exposures.
Sensi
S L
SL
Department of Neurology, University of California Irvine, Irvine, CA 92697-4292, USA.
Yin
H Z
HZ
Weiss
J H
JH
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000633:toxicity; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005333:Fetus; D005456:Fluorescent Dyes / Q000494:pharmacology; D006575:Heterocyclic Compounds, 3-Ring; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D009410:Nerve Degeneration / Q000378:metabolism / Q000503:physiopathology; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009498:Neurotoxins / Q000378:metabolism / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D018091:Receptors, AMPA / Q000187:drug effects* / Q000378:metabolism; D013569:Synapses / Q000378:metabolism / Q000473:pathology; D015032:Zinc / Q000378:metabolism* / Q000633:toxicity
D015220:Calcium Channels; D005456:Fluorescent Dyes; D006575:Heterocyclic Compounds, 3-Ring; D009498:Neurotoxins; D017382:Reactive Oxygen Species; D018091:Receptors, AMPA; C068483:rhod-2; D015032:Zinc; D002118:Calcium