title: NAD+ depletion is necessary and sufficient for poly(ADP-ribose) polymerase-1-mediated neuronal death.
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.
authors.affiliation: Department of Neurology, University of California, San Francisco, San Francisco Veterans Affairs Medical Center, San Francisco, California 94121, USA. mail: conrad.alano@ucsf.edu.
authors.forename: Conrad C
authors.initials: CC
authors.lastname: Alano
authors.forename: Philippe
authors.initials: P
authors.lastname: Garnier
authors.forename: Weihai
authors.initials: W
authors.lastname: Ying
authors.forename: Youichirou
authors.initials: Y
authors.lastname: Higashi
authors.forename: Tiina M
authors.initials: TM
authors.lastname: Kauppinen
authors.forename: Raymond A
authors.initials: RA
authors.lastname: Swanson
mesh_terms: D000818:Animals; D051033:Apoptosis Inducing Factor / Q000187:drug effects / Q000378:metabolism; D016923:Cell Death / Q000502:physiology; D019069:Cell Respiration / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D006019:Glycolysis / Q000187:drug effects / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D028361:Mitochondrial Diseases / Q000188:drug therapy / Q000201:enzymology / Q000503:physiopathology; D009243:NAD / Q000172:deficiency* / Q000494:pharmacology; D009410:Nerve Degeneration / Q000201:enzymology* / Q000503:physiopathology*; D009474:Neurons / Q000187:drug effects / Q000201:enzymology*; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000378:metabolism; D058486:Receptors, Purinergic P2X7
chemical_list: D051033:Apoptosis Inducing Factor; C546469:P2rx7 protein, mouse; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D009243:NAD; C499321:Parp1 protein, mouse; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases