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Mechanisms of Zn2+-Induced HT-22 Neuronal Cell Injury.

Berry, Elizabeth V. (2005) Mechanisms of Zn2+-Induced HT-22 Neuronal Cell Injury. Doctoral thesis, University of Surrey (United Kingdom)..

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Abstract

Elevated intracellular Zn2+ levels have been reported to induce neuronal death during acute CNS ischaemia. Despite several proposed mechanisms, the precise molecular events that induce Zn2+ neurotoxicity remain currently unclear. The present study utilised the murine hippocampal neuronal cell line, HT-22, to dissect the mechanism of cytotoxic Zn2+ insults. Increased extracellular Zn2+ concentrations induced both dose- and time-dependent cytotoxicity. Exogenously applied Zn2+ (200μM) increased intracellular Zn2+ levels as assessed by FluoZin-3 fluorescence and rapidly induced cell death. Zn2+ cytotoxicity was attenuated by the Zn2+ chelators, Ca. EDTA and N,N,N',N'-Tetrakis (2-pyridylmethyl) ethylenediamine (TPEN), but was unaffected by either KCl, or the L-type or T-type voltage-sensitive Ca2+ channel inhibitors, nimodipine and mibefradil respectively. In contrast to staurosporine, an inducer of apoptosis, Zn2+-induced cell death was insensitive to the pan-caspase inhibitor, zVAD-fmk, and was not accompanied by significant caspase 3 activation. Intriguingly, Zn2+ significantly reduced the mitochondrial membrane potential despite an apparent absence of reactive oxygen species (ROS) generation, although significant intracellular glutathione depletion was observed. Furthermore, pre-treatment with either of the antioxidants, trolox or N,N'-diphenyl-1,4-phenylenediamine (DPPD), limited Zn2+ cytotoxicity during 6hr, but not 24hr Zn2+ exposure paradigms. Both the energy substrates pyruvate and oxaloacetate however, afforded neuroprotection against Zn2+ cytotoxic insults without influencing acute intracellular Zn2+ uptake. It is concluded that HT-22 neurons are vulnerable to Zn2+ cytotoxic insults via a mechanism involving mitochondrial perturbation and energy inhibition, although independent of caspase-mediated apoptosis, but involving cellular oxidative stress.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors : Berry, Elizabeth V.
Date : 2005
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 2005.
Depositing User : EPrints Services
Date Deposited : 24 Apr 2020 15:27
Last Modified : 24 Apr 2020 15:27
URI: http://epubs.surrey.ac.uk/id/eprint/854876

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