Oxidative cellular damage and the reduction of APE/Ref-1 expression after experimental traumatic brain injury

The DNA repair enzyme, apurinic/apyrimidinic endonuclease (or redox effecto r factor-1, APE/Ref-1), is involved in base excision repair of apurinic/apy rimidinic sites after oxidative DNA damage. We investigated the expression of APE/Ref-1 and its relationship to oxidative stress after severe traumati c brain injury produced by controlled cortical impact in normal mice, and i n mice over- or underexpressing copper-zinc superoxide dismutase (SOD1TG an d SOD1KO, respectively). Oxygen free radical-mediated cellular injury was v isualized with 8-hydroxyguanine immunoreactivity as a marker for DNA oxidat ion, and in situ hydroethidine oxidation as a marker for superoxide product ion. After trauma there was a reduced expression of APE/Ref-1 in the ipsila teral cortex and hippocampus that correlated with the gene dosage levels of cytosolic superoxide dismutase. The decrease in APE/Ref-1 expression prece ded DNA fragmentation. There was also a close correlation between APE/Ref-1 protein levels 4 h after trauma and the volume of the lesion 1 week after injury. Our data have demonstrated that reduction of APE/Ref-1 protein leve ls correlates closely with the level of oxidative stress after traumatic br ain injury. We suggest that APE/Ref-1 immunoreactivity is a sensitive marke r for oxidative cellular injury. (C) 2001 Academic Press.