Reduction of Apurinic/Apyrimidinic Endonuclease Expression After Transient Global Cerebral Ischemia in Rats

Author:

Kawase Makoto1,Fujimura Miki1,Morita-Fujimura Yuiko1,Chan Pak H.1

Affiliation:

1. From the Department of Neurosurgery, Department of Neurology and Neurological Sciences, and Program in Neurosciences, Stanford University School of Medicine, Palo Alto, Calif.

Abstract

Background and Purpose —To clarify the relationship between apurinic/apyrimidinic endonuclease (APE/Ref-1), a multifunctional protein in the DNA base excision repair pathway, and delayed neuronal cell death associated with apoptosis, we examined the expression of APE/Ref-1 before and after transient global ischemia in rats. Methods —Global ischemia was induced by bilateral common carotid artery occlusion and hypotension. Expression of the APE/Ref-1 protein was evaluated by Western blot and immunohistochemical analyses. Apoptosis after global ischemia was observed by DNA electrophoresis and terminal deoxynucleotidyl transferase–mediated uridine 5′-triphosphate-biotin nick end labeling (TUNEL) staining. Results —Immunohistochemistry showed the nuclear expression of APE/Ref-1 in the control brains. Nuclear immunoreactivity of APE/Ref-1 was significantly decreased 2 days after 10 minutes of ischemia in the hippocampal CA1 subregion. Western blot analysis of a sample from the normal brains showed a characteristic 37-kDa band, which was reduced in the hippocampal CA1 subregion after ischemia. A significant amount of DNA fragmentation was observed at 3 days but not at 1 day after ischemia. Double staining with APE/Ref-1 and TUNEL clearly showed that the neurons that lost APE/Ref-1 immunoreactivity became TUNEL positive. Conclusions —Our data provide evidence that APE/Ref-1 decreased in hippocampal CA1 neurons after transient global ischemia and that this reduction precedes DNA fragmentation, which is destined to cause apoptosis. Our results suggest the possibility that a decrease of APE/Ref-1 activity and the failure of DNA repair may underlie the mechanism of apoptosis after transient focal ischemia.

Publisher

Ovid Technologies (Wolters Kluwer Health)

Subject

Advanced and Specialized Nursing,Cardiology and Cardiovascular Medicine,Neurology (clinical)

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