Routes of zinc entry in mouse cortical neurons: role in zinc-induced neurotoxicity.
Exposure of central neurons to Zn2+ triggers neuronal death. The routes of Zn2+ entry were investigated in living cortical neurons from the mouse using the specific Zn2+ fluorescent dye N-(6-methoxy-8-quinolyl)-p-toluene sulphonamide (TSQ), which preferentially detects membrane-bound Zn2+. Exposure of cortical neurons to increasing concentrations of Zn2+ (1-100 microM) induced a progressive increase in the fluorescence of TSQ. This fluorescence signal was not attenuated by the permeation of plasma membrane with digitonin. Accordingly, the major part of TSQ fluorescence (two-thirds) was associated to the particulate fraction of cortical neurons exposed to Zn2+. These results suggest that Zn2+ detected with TSQ in neurons is mainly bound to membranes. TSQ fluorescence measured in neurons exposed to 3 microM Zn2+ was enhanced by Na+-pyrithione, a Zn2+ ionophore, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N-methyl-D-aspartate (NMDA) or KCl-induced depolarization. However, in the absence of any treatment, TSQ labelling of neurons exposed to 3 microM Zn2+ was only decreased by NMDA receptor antagonists, whereas it remained unaltered in the presence of antagonists of AMPA receptors or L-type voltage-gated Ca2+ channels. Zn2+ entry through NMDA receptors did not contribute to Zn2+-induced neuronal death, as it was prevented by antagonists of NMDA receptors only when they were added after the Zn2+ exposure. Finally, Zn2+ induced a delayed accumulation of extracellular glutamate which might be responsible for the delayed NMDA receptor activation that leads to neuronal death.
Marin
P
P
Chaire de Neuropharmacologie, INSERM U114, Collège de France, 11, Place Marcelin Berthelot, 75231 Paris Cedex 05, France.
Israël
M
M
Glowinski
J
J
Prémont
J
J
D000255:Adenosine Triphosphate / Q000378:metabolism; D000634:Aminoquinolines; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology*; D004072:Digitonin / Q000494:pharmacology; D005456:Fluorescent Dyes; D018698:Glutamic Acid / Q000378:metabolism; D007211:Indoles; D051379:Mice; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D008928:Mitochondria / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009498:Neurotoxins / Q000493:pharmacokinetics / Q000633:toxicity; D010101:Oxygen Consumption; D014105:Tosyl Compounds; D015032:Zinc / Q000493:pharmacokinetics* / Q000633:toxicity
D000634:Aminoquinolines; D005456:Fluorescent Dyes; D007211:Indoles; D009498:Neurotoxins; D014105:Tosyl Compounds; D018698:Glutamic Acid; C061730:N-(6-methoxy-8-quinolyl)-4-toluenesulfonamide; D000255:Adenosine Triphosphate; D015032:Zinc; D004072:Digitonin; C048960:indo-1