Abstract
In the present study, we examined the role and the mechanism of poly(ADP-ribose) polymerase (PARP) and poly(ADP-ribose) glycohydrolase (PARG) activation in zinc-induced cell death in cortical culture. After brief exposure to 400 microM zinc, cortical cells exhibited DNA fragmentation, increased poly(ADP-ribosyl)ation, and decreased levels of nicotinamide adenine dinucleotide (NAD) and ATP and subsequently underwent cell death. Inhibitors of PARP/PARG attenuated both zinc-induced NAD/ATP depletion and cell death, thereby implicating the PARP/PARG cascade in these processes. The zinc-inducible enzymes NADPH oxidase and neuronal nitric oxide synthase (nNOS) contributed to PARP activation as their inhibitors attenuated zinc-induced poly(ADP-ribosyl)ation. Levels of nitric oxide and nitrites increased following zinc exposure, consistent with NOS activation. In addition, Western blots and RT-PCR analysis revealed that protein and mRNA levels of nNOS specifically increased following zinc exposure in a manner similar to that of NADPH oxidase. The present study demonstrates that induction of NADPH oxidase and nNOS actively contributes to PARP/PARG-mediated NAD/ATP depletion and cell death induced by zinc in cortical culture.
MeSH terms
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Adenosine Triphosphate / metabolism
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Animals
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Apoptosis* / drug effects
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Apoptosis* / physiology
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Astrocytes / cytology
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Astrocytes / drug effects
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Astrocytes / enzymology
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Cells, Cultured
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Cerebral Cortex / cytology
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Cerebral Cortex / drug effects*
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Cerebral Cortex / embryology
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Cerebral Cortex / enzymology
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Coculture Techniques
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DNA Fragmentation / drug effects
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Enzyme Activation / drug effects
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Enzyme Induction / drug effects
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Enzyme Inhibitors / pharmacology
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Glycoside Hydrolases / antagonists & inhibitors
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Glycoside Hydrolases / metabolism
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Mice
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NAD / metabolism
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NADPH Oxidases / antagonists & inhibitors
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NADPH Oxidases / metabolism*
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Neurons / cytology
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Neurons / drug effects
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Neurons / enzymology
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Nitric Oxide / metabolism
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Nitric Oxide Synthase / antagonists & inhibitors
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Nitric Oxide Synthase / metabolism*
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Nitric Oxide Synthase Type I
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Nitric Oxide Synthase Type II
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Nitric Oxide Synthase Type III
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Poly(ADP-ribose) Polymerase Inhibitors
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Poly(ADP-ribose) Polymerases / metabolism*
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Tyrosine / analogs & derivatives*
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Tyrosine / metabolism
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Zinc / toxicity*
Substances
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Enzyme Inhibitors
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Poly(ADP-ribose) Polymerase Inhibitors
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NAD
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Nitric Oxide
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3-nitrotyrosine
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Tyrosine
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Adenosine Triphosphate
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Nitric Oxide Synthase
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Nitric Oxide Synthase Type I
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Nitric Oxide Synthase Type II
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Nitric Oxide Synthase Type III
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Nos1 protein, mouse
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Nos2 protein, mouse
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Nos3 protein, mouse
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NADPH Oxidases
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Poly(ADP-ribose) Polymerases
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Glycoside Hydrolases
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poly ADP-ribose glycohydrolase
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Zinc