Inducible repair of oxidative DNA lesions in the rat brain after transient focal ischemia and reperfusion.
To determine the role of oxidative DNA damage and repair in brain injury after focal ischemia and reperfusion, the authors investigated DNA base damage and DNA base excision repair (BER) capacity, the predominant repair mechanism for oxidative DNA lesions, in the rat model of temporary middle cerebral artery occlusion. Contents of 8-hydroxyl-2'-deoxyguanosine (8-oxodG) and apurinic/apyrimidinic abasic site (AP site), hallmarks of oxidative DNA damage, were quantitatively measured in nuclear DNA extracts from brains 0.25 to 72 hours after 1 hour of middle cerebral artery occlusion. In parallel to the detection of DNA lesions, the capacity for 8-oxodG- or AP site-dependent DNA repair synthesis was measured in nuclear protein extracts using specific in vitro DNA repair assays. After postischemic reperfusion, the levels of 8-oxodG and AP sites were markedly increased in ischemic tissues. In frontal/parietal cortex, regions that survived ischemia, 8-oxodG and AP sites were efficiently repaired during reperfusion. However, in the caudate, a region that was destined to infarct, the DNA lesions were poorly repaired. In consistent with the patterns of endogenous lesion repair, a markedly induced and long-lasting (at least 72 hours) BER activity was detected in the cortex but not in the caudate after ischemia. The induced BER activity in ischemic cortex was attributed to the upregulation of gene expression and activation of selective BER enzymes, particularly DNA polymerase-beta and OGG1. These results strongly suggest that inducible DNA BER constitutes an important endogenous mechanism that protects brain against ischemia-induced oxidative neuronal injury.
Department of Neurology and Pittsburgh Institute of Neurodegenerative Disorders, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
Jing
J
Lan
Wenjin
W
Li
Feng
F
Zhang
Feng-Yan
FY
Sun
Tetsuya
T
Nagayama
Cristine
C
O'Horo
Jun
J
Chen
D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D001157:Arterial Occlusive Diseases / Q000473:pathology; D001921:Brain / Q000378:metabolism / Q000473:pathology; D002421:Caudate Nucleus / Q000473:pathology; D002467:Cell Nucleus / Q000737:chemistry; D002540:Cerebral Cortex / Q000473:pathology; D004249:DNA Damage; D045647:DNA Glycosylases / Q000096:biosynthesis; D019951:DNA Polymerase beta / Q000096:biosynthesis; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000032:analysis; D002546:Ischemic Attack, Transient / Q000473:pathology*; D008297:Male; D018384:Oxidative Stress; D051381:Rats; D017207:Rats, Sprague-Dawley; D015424:Reperfusion; D013997:Time Factors; D015854:Up-Regulation
D000080242:8-Hydroxy-2'-Deoxyguanosine; D019951:DNA Polymerase beta; D045647:DNA Glycosylases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D003849:Deoxyguanosine