| Background and objective:Acute cerebral ischemia results in neural injuries in not only infarct focus but also distant areas. Base-excision repair, the main DNA repair mechanism is initiated after acute cerebral ischemia. APE (apurinic/apyrimidinic endonuclease, or redox factor-1, Ref-1) is a complex multi-functional biological macromolecule with DNA repair and redox functions. It is the rate-limiting enzyme in the process of base-excision repair, and plays a key role in DNA repair process. Our research will observe the expressions of APE and8-OHdG in CA1region of hippocampus after focal cerebral ischemia, discuss the relations between their variations and cell apoptosis, and the physiopathologic mechanisms in damage happened in distant areas.Methods:63healthy male SD rats weighting250-300g were randomly divided into sham and pMCAO groups(M2h、M6h、M12h、 M24h、M48h、M72h,9rats in each group). pMCAO groups were induced by middle cerebral artery occlusion (MCAO), and their neurological functional deficit were evaluated two hours later. After MCAO,3rats in each group were killed at a regular time as mentioned for measuring infarct size using TTC staining,6rats were killed for observing pathological changes using nissl’s staining and expression variations of APE and8-OHdG in hippocampus using immuno-histochemistry, and detecting cell apoptosis degrees using TUNEL staining.Results:1. TTC:Frontal, temporal, parietal lobes and part of subcortical tissues were dyed white(infarct focus) in ischemia side while other tissues were dyed red(normal tissues) in pMCAO groups. Brain tissues in sham group were also dyed red. Cerebral infarction scopes conformed to MCA blood supply areas, pMCAO models were well induced.2. Nissl’s staining:In sham group, a large quantity of deep dyeing and neatly arranged Nissl bodies were found in CA1region of hippocampus; in M2h、M6h groups, the number of nissl bodies in the same region were decreasing(P>0.05); in M12h、M24h、M48、M72h groups, cells in CA1areas of hippocampus became swelled in a mess, pyknosis of cell nucleus, reductions of nissl bodies and axons were found, which was statistically significant (P<0.05);3. Immunohistochemistry:Reductions of APE expressions in CA1region of hippocampus in ischemia side appeared at2hours after ischemia and were continuous with extended ischemia time; expressions of8-OHdG in the same region, which appeared at6hours after ischemia, were continuously increasing with extended ischemia time (P<0.05) and were at a nearly same level since24hours to72hours after ischemia;4.TUNEL staining:TUNEL positive cells in CA1areas of hippocampus in ischemia side, which appeared at6hours after ischemia, were continuously increasing with extended ischemia time (P<0.05) and were at a nearly same level since24hours to72hours after ischemia.Conclusions:1.DNA oxidative damage existed in distant areas after focal ischemia;2.Expressions of APE in distant areas were decreased after focal ischemia, accumulating and progressing of DNA oxidative damages induced cell apoptosis. |
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