Abstract
Poly(ADP-ribose)-1 (PARP-1) is a key mediator of cell death in excitotoxicity, ischemia, and oxidative stress. PARP-1 activation leads to cytosolic NAD(+) depletion and mitochondrial release of apoptosis-inducing factor (AIF), but the causal relationships between these two events have been difficult to resolve. Here, we examined this issue by using extracellular NAD(+) to restore neuronal NAD(+) levels after PARP-1 activation. Exogenous NAD(+) was found to enter neurons through P2X(7)-gated channels. Restoration of cytosolic NAD(+) by this means prevented the glycolytic inhibition, mitochondrial failure, AIF translocation, and neuron death that otherwise results from extensive PARP-1 activation. Bypassing the glycolytic inhibition with the metabolic substrates pyruvate, acetoacetate, or hydroxybutyrate also prevented mitochondrial failure and neuron death. Conversely, depletion of cytosolic NAD(+) with NAD(+) glycohydrolase produced a block in glycolysis inhibition, mitochondrial depolarization, AIF translocation, and neuron death, independent of PARP-1 activation. These results establish NAD(+) depletion as a causal event in PARP-1-mediated cell death and place NAD(+) depletion and glycolytic failure upstream of mitochondrial AIF release.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Animals
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Apoptosis Inducing Factor / drug effects
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Apoptosis Inducing Factor / metabolism
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Cell Death / physiology
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Cell Respiration / drug effects
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Cell Respiration / physiology
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Cells, Cultured
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Energy Metabolism / drug effects
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Energy Metabolism / physiology
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Glycolysis / drug effects
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Glycolysis / physiology
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Mice
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Mice, Knockout
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Mitochondria / drug effects
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Mitochondria / enzymology
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Mitochondrial Diseases / drug therapy
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Mitochondrial Diseases / enzymology
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Mitochondrial Diseases / physiopathology
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NAD / deficiency*
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NAD / pharmacology
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Nerve Degeneration / enzymology*
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Nerve Degeneration / physiopathology*
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Neurons / drug effects
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Neurons / enzymology*
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Poly (ADP-Ribose) Polymerase-1
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Poly(ADP-ribose) Polymerases / genetics
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Poly(ADP-ribose) Polymerases / metabolism*
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Protein Transport / drug effects
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Protein Transport / physiology
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Receptors, Purinergic P2 / drug effects
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Receptors, Purinergic P2 / metabolism
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Receptors, Purinergic P2X7
Substances
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Apoptosis Inducing Factor
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P2rx7 protein, mouse
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Receptors, Purinergic P2
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Receptors, Purinergic P2X7
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NAD
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Parp1 protein, mouse
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Poly (ADP-Ribose) Polymerase-1
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Poly(ADP-ribose) Polymerases