title: Tricarboxylic acid cycle substrates prevent PARP-mediated death of neurons and astrocytes.
abstract: The DNA repair enzyme, poly(ADP-ribose) polymerase-1 (PARP1), contributes to cell death during ischemia/reperfusion when extensively activated by DNA damage. The cell death resulting from PARP1 activation is linked to NAD+ depletion and energy failure, but the intervening steps are not well understood. Because glycolysis requires cytosolic NAD+, the authors tested whether PARP1 activation impairs glycolytic flux and whether substrates that bypass glycolysis can rescue cells after PARP1 activation. PARP1 was activated in mouse cortical astrocyte and astrocyte-neuron cocultures with the DNA alkylating agent, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Studies using the 2-deoxyglucose method confirmed that glycolytic flux was reduced by more than 90% in MNNG-treated cultures. The addition of 5 mmol/L of alpha-ketoglutarate, 5 mmol/L pyruvate, or other mitochondrial substrates to the cultures after MNNG treatment reduced cell death from approximately 70% to near basal levels, while PARP inhibitors and excess glucose had negligible effects. The mitochondrial substrates significantly reduced cell death, with delivery delayed up to 2 hours after MNNG washout. The findings suggest that impaired glycolytic flux is an important factor contributing to PARP1-mediated cell death. Delivery of alternative substrates may be a promising strategy for delayed treatment of PARP1-mediated cell death in ischemia and other disorders.
authors.affiliation: Department of Neurology, University of California at San Francisco and Veterans Affairs Medical Center, USA.
authors.forename: Weihai
authors.initials: W
authors.lastname: Ying
authors.forename: Yongmei
authors.initials: Y
authors.lastname: Chen
authors.forename: Conrad C
authors.initials: CC
authors.lastname: Alano
authors.forename: Raymond A
authors.initials: RA
authors.lastname: Swanson
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology / Q000201:enzymology*; D016923:Cell Death / Q000187:drug effects*; D002478:Cells, Cultured; D002952:Citric Acid Cycle; D018920:Coculture Techniques; D004789:Enzyme Activation / Q000187:drug effects; D006019:Glycolysis; D007656:Ketoglutaric Acids / Q000494:pharmacology; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology; D051379:Mice; D009243:NAD / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000201:enzymology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D019289:Pyruvic Acid / Q000494:pharmacology
chemical_list: D007656:Ketoglutaric Acids; D009243:NAD; D008769:Methylnitronitrosoguanidine; D019289:Pyruvic Acid; D011065:Poly(ADP-ribose) Polymerases