Inducible DNA repair via the base-excision repair pathway is an important prosurvival mechanism activated in response to oxidative DNA damage. Elevated levels of the essential base-excision repair enzyme apurinic/apyrimidinic endonuclease 1 (APE1)/redox effector factor-1 correlate closely with neuronal survival against ischemic insults, depending on the CNS region, protective treatments, and degree of insult. However, the precise mechanisms by which this multifunctional protein affords protection and is activated by upstream signaling pathways in postischemic neurons are not well delineated. Here we show that intracerebral administration of pituitary adenylate cyclase-activating polypeptide (PACAP), an endogenously occurring small neuropeptide, induces expression of APE1 in hippocampal neurons. Induction of APE1 expression requires PKAand p38-dependent phosphorylation of cAMP response-element binding and activating transcription factor 2, which leads to transactivation of the APE1 promoter. We further show that PACAP markedly reduces oxidative DNA stress and hippocampal CA1 neuronal death following transient global ischemia. These effects occurred,atleastinpart,viaenhancedAPE1expression.Furthermore, the DNA repair function of APE1 was required for PACAP-mediated neuroprotection. Thus, induction of DNA repair enzymes may be a uniquestrategy forneuroprotectionagainsthippocampalinjury.activating transcription factor 2 | cAMP response-element binding | delayed neurodegeneration | DNA repair | oxidative stress O xidative stress is a hallmark of neurological disorders, including cerebral ischemia. Ischemic injury rapidly elicits oxidative DNA damage either directly via reactive oxygen species attack or indirectly via oxidization of lipids or proteins (1-3). These actions induce DNA lesions, involving base modifications and damage to the sugar moiety in the DNA, formation of abasic (apurinic/apyrimidinic, AP) sites, single strand breaks, and DNA intra-or interstrand crosslinks. Of these lesions, AP sites and single strand breaks are highly prevalent types of DNA damage in insulted neurons (4). Whereas the accumulation of unrepaired DNA ultimately induces cell death, active repair of DNA promotes cell survival (4-6).In neurons, base-excision repair (BER) is the predominant mechanism for repair of oxidative DNA lesions (7). BER is a three-step process. First, 5′-acting AP endonuclease 1 (APE1, also known as redox-effector factor 1) cleaves the phosphodiester backbone, then β-polymerase or alternative repair proteins, such as FEN1 or PCNA, fill in the gap with newly synthesized nucleotides, and finally a DNA ligase seals the nick. In several models of ischemia, oxidative DNA damage is reversible in regions that survive (4,6,8), raising the possibility that repair of DNA damage via BER is required for cell survival following ischemia.APE1 is an attractive target for neuroprotection, as it is a critical component of the BER process (9) and as also has redox and transcription-regulation activities. Following cerebral ischemi...