Elevation in glutathione in response to an oxidative stress: Significance for neuroprotection from oxidative damage.
Item
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Title
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Elevation in glutathione in response to an oxidative stress: Significance for neuroprotection from oxidative damage.
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Identifier
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AAI9618072
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identifier
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9618072
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Creator
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Han, Shan-Kuo D.
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Contributor
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Adviser: Gerald Cohen
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Date
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1996
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Neuroscience | Biology, Cell
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Abstract
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Glutathione (L-gamma-glutamyl-L-cysteinyl-glycine; GSH) plays an important role in protecting cells from oxidative stress. My studies focus on upregulation of GSH induced by L-DOPA or dopamine, which results in protection against damage by a toxic agent, t-butylhydroperoxide. Upregulation of GSH was found in mesencephalic cell cultures, as well as cultured glia, neuroblastoma cells, and pig kidney epithelium. Not only L-DOPA and dopamine, but other autoxidizable compounds such as hydroquinone, catechol, alpha-methyl-DOPA and apomorphine also evoked an increase in GSH. However, structural analogs that do not autoxidize failed to elevate GSH (3-O-methyl-DOPA, 2,4-dihydroxyphenylalanine, tyrosine, resorcinol). The rise in GSH was preceded by a rise in GSSG and could be blocked by ascorbate, which is an antioxidant. Inhibitors of DOPA decarboxylase or monoamine oxidase had no effect; added superoxide dismutase or catalase had no effect. Dopamine-receptor blocking agents failed to affect the rise in GSH evoked by dopamine. However, the disulfide form of dithiothreitol, which was used as a model disulfide, also induced an elevation in GSH. The results indicate that the rise in GSSG is a response to an oxidative stress due to autoxidation, and that formation of disulfides may play a role. Upregulation of GSH was linked to an increase in gamma-glutamylcysteine synthetase activity, the rate-limiting step in GSH biosynthesis. Inhibitors of protein kinase C (staurosporine and H-7) blocked the rise in GSH, showing that protein kinase C was part of signaling pathway. In comparison with mesencephalic cell cultures, pure neurons (no glia) failed to upregulate GSH and were badly damaged.;When mesencephalic cell cultures were treated with t-butylhydroperoxide, a progressive loss in viability was seen. Cells previously exposed to autoxidizing agents (L-DOPA or hydroquinone) were protected against the toxicity of t-butylhydroperoxide. However, when the rise in GSH was blocked with ascorbate, cell protection was no longer seen. These results show that upregulation of GSH provides protection in cell culture. Upregulation of GSH appears to be a response to a mild oxidative stress (autoxidation) and requires protein kinase C activity. The ability to upregulate GSH in brain may be an important factor in cell viability in neurodegenerative diseases, such as Parkinson's disease.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
