title: Poly(ADP-ribose) polymerase-1 causes mitochondrial damage and neuron death mediated by Bnip3.
abstract: Excessive pathophysiological activity of the nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP1) causes neuron death in brain hypoxia/ischemia by inducing mitochondrial permeability transition and nuclear translocation of apoptosis-inducing factor (AIF). Bcl-2/adenovirus E1B 19 kDa-interacting protein (Bnip3) is a prodeath BH3-only Bcl-2 protein family member that is induced in hypoxia, and has effects on mitochondrial permeability and neuronal survival similar to those caused by PARP1 activation. We hypothesized that Bnip3 is a critical mediator of PARP1-induced mitochondrial dysfunction and neuron death. Hypoxic death of mouse cortical neuron cultures was mitigated by deletion of either PARP1 or Bnip3, indicating that both factors are involved. Direct normoxic PARP1 activation by a DNA alkylating agent enhanced Bnip3 expression, and caused Bnip3-dependent mitochondrial membrane permeability, AIF translocation, and neuron death. Hypoxia produced PARP1-dependent depletion of nicotinamide adenine dinucleotide (NAD(+)) and inhibition of the NAD(+)-dependent class III histone deactelyase (HDAC) sirtuin-1 (SIRT1). This, in turn, led to hyperacetylation and nuclear localization of the forkhead box (Fox) protein FoxO3a, followed by enhanced association of FoxO3a with the Bnip3 upstream promoter region, increased levels of Bnip3 transcript, and elevated mitochondrial Bnip3 immunoreactivity. Finally, FoxO3a silencing using a lentiviral short hairpin RNA approach significantly reduced hypoxic Bnip3 expression, mitochondrial damage, and neuron death. Together, these data illustrate a direct PARP1-mediated hypoxic signaling pathway involving NAD(+) depletion, SIRT1 inhibition, FoxO3a-driven Bnip3 generation, and mitochondrial AIF release.
authors.affiliation: Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Winnipeg Health Sciences Centre and College of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0Z3, Canada, Department of Pharmacology and Therapeutics, College of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0T6, Canada, and.
authors.forename: Ping
authors.initials: P
authors.lastname: Lu
authors.affiliation: Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Winnipeg Health Sciences Centre and College of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0Z3, Canada, Department of Pharmacology and Therapeutics, College of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0T6, Canada, and.
authors.forename: Amit
authors.initials: A
authors.lastname: Kamboj
authors.affiliation: Manitoba Institute of Cell Biology, Winnipeg, Manitoba R3E 0T3, Canada.
authors.forename: Spencer B
authors.initials: SB
authors.lastname: Gibson
authors.affiliation: Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Winnipeg Health Sciences Centre and College of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0Z3, Canada, Department of Pharmacology and Therapeutics, College of Medicine, University of Manitoba, Winnipeg, Manitoba R3E 0T6, Canada, and chris.anderson@med.umanitoba.ca.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Anderson
mesh_terms: D000818:Animals; D016923:Cell Death / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis*; D051379:Mice; D057507:Mice, 129 Strain; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism* / Q000473:pathology; D024101:Mitochondrial Proteins / Q000096:biosynthesis*; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000502:physiology*
chemical_list: C508686:BNip3 protein, mouse; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; C499321:Parp1 protein, mouse; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases
keywords: Bnip3; PARP; apoptosis-inducing factor; ischemia; mitochondrial permeability; sirtuin