ZnT-1 expression in astroglial cells protects against zinc toxicity and slows the accumulation of intracellular zinc.
Zinc ions are emerging as an important factor in the etiology of neurodegenerative disorders and in brain damage resulting from ischemia or seizure activity. High intracellular levels of zinc are toxic not only to neurons but also to astrocytes, the major population of glial cells in the brain. In the present study, the role of ZnT-1 in reducing zinc-dependent cell damage in astrocytes was assessed. Zinc-dependent cell damage was apparent within 2 h of exposure to zinc, and occurred within a narrow range of approximately 200 microM. Pretreatment with sublethal concentrations of zinc rendered astrocytes less sensitive to toxic zinc levels, indicating that preconditioning protects astrocytes from zinc toxicity. Fluorescence cell imaging revealed a steep reduction in intracellular zinc accumulation for the zinc-pretreated cells mediated by L-type calcium channels. Heterologous expression of ZnT-1 had similar effects; intracellular zinc accumulation was slowed down and the sensitivity of astrocytes to toxic zinc levels was reduced, indicating that this is specifically mediated by ZnT-1 expression. Immunohistochemical analysis demonstrated endogenous ZnT-1 expression in cultured astroglia, microglia, and oligodendrocytes. Pretreatment with zinc induced a 4-fold increase in the expression of the putative zinc transporter ZnT-1 in astroglia as shown by immunoblot analysis. The elevated ZnT-1 expression following zinc priming or after heterologous expression of ZnT-1 may explain the reduced zinc accumulation and the subsequent reduction in sensitivity toward toxic zinc levels. Induction of ZnT-1 may play a protective role when mild episodes of stroke or seizures are followed by a massive brain insult.
Nolte
Christiane
C
Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.
Gore
Ariel
A
Sekler
Israel
I
Kresse
Wolfgang
W
Hershfinkel
Michal
M
Hoffmann
Anja
A
Kettenmann
Helmut
H
Moran
Arie
A
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D001927:Brain Diseases / Q000378:metabolism* / Q000503:physiopathology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism; D027682:Cation Transport Proteins; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D007424:Intracellular Fluid / Q000378:metabolism; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism*; D008657:Metabolic Clearance Rate / Q000187:drug effects / Q000502:physiology; D017628:Microglia / Q000187:drug effects / Q000378:metabolism; D009410:Nerve Degeneration / Q000378:metabolism* / Q000503:physiopathology; D009836:Oligodendroglia / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology; D015032:Zinc / Q000378:metabolism / Q000633:toxicity*
D020746:Calcium Channels, L-Type; D027682:Cation Transport Proteins; D008565:Membrane Proteins; C092392:Slc30a1 protein, rat; D015032:Zinc