Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
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We review here some of our work focussing on the specific contribution of peroxide-derived free radicals to oxidative stress responses, using human cell and transgenic mouse models that overexpress selenium-dependent glutathione peroxidase-1 (GPx-1). Apoptosis induced by the superoxide/hydrogen peroxide-generator 6-hydroxydopamine was strongly inhibited by GPx-1 or iron[III] chelation in human neuroblastoma transfectants. This inhibition apparently occurred upstream of caspase activation and was not observed in staurosporine-treated cells. Since mitochondria play a central role in stress-related apoptotic processes, and mitochondrial dysfunction is a documented source of oxygen radicals in many neurotoxic processes, we investigated the role of intramitochondrial GPx-1 level in mitochondrial function homeostasis in conditions of oxidative stress. Intramitochondrial GPx-1 activity accounts for about 15% of total cellular activity in human WI38-VA13 fibroblasts and T47D carcinoma cells transfected or not by GPx-1 (high and low GPx activity). GPx-1 antigen detected by immuno-electron microscopy is about 20-fold more concentrated in mitochondria than in cytosol, irrespective of GPx-1 overexpression. Following 1h-oxidant challenge by menadione, both mtDNA strand breakage (relaxation) and 8-oxo-2'-deoxyguanosine formation in mtDNA were significantly lower in GPx-1-transfected T47D cells, suggesting reduced formation of hydroxyl radicals in GPx-1-rich mitochondria. Work supported by the National Cancer Institute of Canada with funds of the Canadian Cancer Society

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Presentation Number SAmirault0746
Keywords: Apoptosis, mitochondrial DNA, 8-oxoguanine, DNA strand breaks, neuroblastoma cells