L-type Ca2+ channel-mediated Zn2+ toxicity and modulation by ZnT-1 in PC12cells

In view of evidence that Zn2+ neurotoxicity contributes to some forms of pa thological neuronal death, we developed a model of Zn2+ neurotoxicity in a cell line amenable to genetic manipulations. Exposure to 500 muM ZnCl2 for 15 min under depolarizing conditions resulted in modest levels of PC12 cell death, that was reduced by the L-type Ca2+ channel antagonist, nimodipine, and increased by the L-type Ca2+ channel opener, S(-)-Bay K 8644. At lower insult levels (200 muM Zn2++Bay K 8644), Zn2+-induced death appeared apopt otic under electron microscopy and was sensitive to the caspase inhibitor b enzyloxycarbonyl-Val-Ala-Asp-CH2F (Z-VAD); at higher insult levels (1000 mu M+Bay K 8644), cells underwent necrosis insensitive to Z-VAD. To test the h ypothesis that the plasma membrane transporter, ZnT-1, modulates Zn2+ neuro toxicity, we generated stable PC12 cell lines overexpressing wild type or d ominant negative forms of rat ZnT-1 (rZnT-1). Clones T9 and T23 overexpress ing wild type rZnT-1 exhibited enhanced Zn2+ efflux and reduced vulnerabili ty to Zn2+-induced death compared to the parental line, whereas clones D5 a nd D16 expressing dominant negative rZnT-1 exhibited the opposite character istics. Q 2000 Elsevier Science B.V. All rights reserved.