Neuronal trauma model: in search of Thanatos.
Trauma to the nervous system triggers responses that include oxidative stress due to the generation of reactive oxygen species (ROS). DNA is a major macromolecular target of ROS, and ROS-induced DNA strand breaks activate poly(ADP-ribose)polymerase-1 (PARP-1). Upon activation PARP-1 uses NAD(+) as a substrate to catalyze the transfer of ADP-ribose subunits to a host of nuclear proteins. In the face of extensive DNA strand breaks, PARP-1 activation can lead to depletion of intracellular NAD(P)(H) pools, large decreases in ATP, that threaten cell survival. Accordingly, inhibition of PARP-1 activity after acute oxidative injury has been shown to increase cell survival. When NGF-differentiated PC12 cells, an in vitro neuronal model, are exposed to H(2)O(2) there is increased synthesis of poly ADP-ribose and decreases in intracellular NAD(P)(H) and ATP. Addition of the chemical PARP inhibitor 3-aminobenzamide (AB) prior to H(2)O(2) exposure blocks the synthesis of poly ADP-ribose and maintains intracellular NAD(P)(H) and ATP levels. H(2)O(2) injury is characterized by an immediate, necrotic cell death 2h after injury and a delayed apoptotic-like death 12-24h after injury. This apoptotic-like death is characterized by apoptotic membrane changes and apoptotic DNA fragmentation but is not associated with measurable caspase-3 activity. AB delays cell death beyond 24h and increases cell survival by approximately 25%. This protective effect is accompanied by significantly decreased necrosis and the apoptotic-like death associated with H(2)O(2) exposure. AB also restores caspase-3 which can be attributed to the activation of the upstream activator of caspase-3, caspase-9. Thus, the maintenance of intracellular ATP levels associated with PARP-1 inhibition shifts cell death from necrosis to apoptosis and from apoptosis to cell survival. Furthermore, the shift from necrosis to apoptosis may be explained, in part, by an energy-dependent activation of caspase-9.
Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, TX 77555, USA.
Kasie
K
Cole
J Regino
JR
Perez-Polo
D000818:Animals; D017209:Apoptosis; D001549:Benzamides / Q000494:pharmacology; D004249:DNA Damage; D004195:Disease Models, Animal; D004734:Energy Metabolism / Q000187:drug effects; D006801:Humans; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D000071137:Poly (ADP-Ribose) Polymerase-1; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020196:Trauma, Nervous System / Q000378:metabolism*
D001549:Benzamides; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D017382:Reactive Oxygen Species; C025160:3-aminobenzamide; C499321:Parp1 protein, mouse; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases