The Effects Of Hypothermia On Apoptosis And The Expression Of APE/Ref-1 Following Transient Forebrain ISchemia

[Objective]1. To explore the expression of apurinic/apyrimidinic endonuclease/redox factor l(APE/Ref-l) in the hippocampal CA1 subregion after transient global cerebral ischemia in rats .2. To study the neuronal apoptosis of the hippocampal CA1 subregion after transient global cerebral ischemia in rats .3. To explore the relationship between APE/Ref-1 and neuronal apoptosis in the hippocampal CA1 subregion after transient global cerebral ischemia in rats .4. To explore the effects of mild hypothermia on the expression of APE/Ref-1 and neuronal apoptosis in the hippocampal CA1 subregion after transient global cerebral ischemia in rats .5. To further explore the neuroprotective mechanism of mild hypothermia by studying the effects of mild hypothermia on the expression of APE/Ref-1 and neuronal apoptosis . [Methods]A model of transient global cerebral ischemia was made by 10min of bilateral common carotid artery occlusion and hypotension in rat. The neuronal absence in the CA1 subregion of the hippocampa was observed by nissel body stain. Expression of the APE/Ref-1 protein was measured by immunohistochemical analysis. Apoptosis after global ischemia was observed by in site end-labeling of fragmented DNA using the terminal deoxynucleotidyl transferase reaction (TUNEL). The cell types after global ischemia were distinguished by double staining with APE/Ref-1 and TUNEL. [Results]1. The hippocampa CA1 subregion neurons in normothermic ischemic group were significantly absent after transient global cerebral ischemia; and the absence in mild hypothermic ischemic group was obvious alleviative compared with normothermic group.2. The apoptotic neurons in hippocampal CA1 subregion were observed in normothermic and mild hypothermic ischemia groups, and the quantity of apoptotic neurons in mild hypothermic ischemia was less that of normothermic group(P<0.01).3. Immunohistochemistry showed the neuronal nucleus expressed widespread APE/Ref-1 in the control brains. Nuclear immunoreactivity of APE/Ref-1 decreased in the hippocampal CA1 subregion after transient global ischemia; mild hypothermic ischemic group was less decreased than that of normothermic group(P<0.01).4. Double staining with APE/Ref-1 and TUNEL clearly showed that there were three-type cell in hippocampal CA1 subregion : APE/Ref-1 positive celK TUNEL positive cell and neither APE/Ref-1 positive nor TUNEL positive cell.5. The change of APE/Ref-1 positive cell and TUNEL positive cell after transient global cerebral ischemia showed the decrease of APE/Ref-1 positive cell accompanying the increase of TUNEL positive cell.[Conclusions]1. The model of transient global cerebral ischemia made by 10mjn of bilateral common carotid artery occlusion and hypotension in rats was fittest for this study because of its invariance,reliability and good duplicability.2. The injury of neurons made by transient global cerebral ischemia was delayed neuronal death of hippocampal CA1 subregion.3. Delayed neuronal death of hippocampal CA1 subregion was apoptosis.4. The APE/Ref-1 decreased in hippocampal CA1 neurons after transient global ischemia and this reduction precedes apoptosis. The neurons which lost APE/Ref-1 immunoreactivity became TUNEL positive.5. The mild hypothermia had remarkable neuroprotection action. The inhibition of APE/Ref-1 reduction and ischemic neuronal apoptosis were assumed to be a neuroprotective mechanism of mild hypothermia.6. The failure of DNA repair might involve the mechanism of apoptosis after transientglobal ischemia. The mild hypothermia might possess the function which protected DNArepair mechanism after transient global ischemia.