title: Poly(ADP-ribose) polymerase-1 protects neurons against apoptosis induced by oxidative stress.
abstract: In neurons, DNA is prone to free radical damage, although repair mechanisms preserve the genomic integrity. However, activation of the DNA repair system, poly(ADP-ribose) polymerase (PARP-1), is thought to cause neuronal death through NAD+ depletion and mitochondrial membrane potential (delta psi(m)) depolarization. Here, we show that abolishing PARP-1 activity in primary cortical neurons can either enhance or prevent apoptotic death, depending on the intensity of an oxidative stress. Only in severe oxidative stress does PARP-1 activation result in NAD+ and ATP depletion and neuronal death. To investigate the role of PARP-1 in an endogenous model of oxidative stress, we used an RNA interference (RNAi) strategy to specifically knock down glutamate-cysteine ligase (GCL), the rate-limiting enzyme of glutathione biosynthesis. GCL RNAi spontaneously elicited a mild type of oxidative stress that was enough to stimulate PARP-1 in a Ca2+-calmodulin kinase II-dependent manner. GCL RNAi-mediated PARP-1 activation facilitated DNA repair, although neurons underwent delta psi(m) loss followed by some apoptotic death. PARP-1 inhibition did not prevent delta psi(m) loss, but enhanced the vulnerability of neurons to apoptosis upon GCL silencing. Conversely, mild expression of PARP-1 partially prevented to GCL RNAi-dependent apoptosis. Thus, in the mild progressive damage likely occur in neurodegenerative diseases, PARP-1 activation plays a neuroprotective role that should be taken into account when considering therapeutic strategies.
authors.affiliation: Unidad de Investigación, Hospital Universitario de Salamanca-Instituto de Estudios Ciencias de la Salud de Castilla y León, Salamanca, Spain.
authors.forename: J I
authors.initials: JI
authors.lastname: Diaz-Hernandez
authors.forename: S
authors.initials: S
authors.lastname: Moncada
authors.forename: J P
authors.initials: JP
authors.lastname: Bolaños
authors.forename: A
authors.initials: A
authors.lastname: Almeida
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D004260:DNA Repair; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D016297:Mutagenesis, Site-Directed; D009243:NAD / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology*; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D011920:Rats, Inbred WF
chemical_list: D009243:NAD; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; D011065:Poly(ADP-ribose) Polymerases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione