Apurinic/apyrimidinic endonuclease APE1 is required for PACAP-induced neuroprotection against global cerebral ischemia

Inducible DNA repair via the base-excision repair pathway is an important prosurvival mechanisma ctivated in response to oxidative DNA damage. Elevated levels of the essential base-excision repair enzyme apurinic/apyrimidinic endonuclease1(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 APE1expression requires PKA-and 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,viaenhanced APE1expression.Furthermore, the DNA repair function of APE1 was required for PACAP-mediated neuroprotection. Thus, induction of DNA repair enzymes may be a uniquestrategy for neuroprotection agains thippocampa linjury.