Preliminary Study On The Autophagy After Focal Cerebral Ischemia/reperfusion In Rat

Objective:To investigate the changes of autophagy and lysosome after focal cerebral ischemia/reperfusion in rats and approach the role of autophagy/lysosomal pathway in brain injury after focal cerebral ischemia/reperfusion.Methods:The middle cerebral artery ischemia and reperfusion model in rats was achieved by an intraluminal filament embolism.The formation of autophagosome and activation of lysosome were observed in neuron after cerebral ischemia/reperfusion by using transmission electron microscope (TEM),Immunohistochemistry was employed to determine the expression of Beclin l and cathepsin B in ischemic penumbra (cortex). Autophagy promoter (rapamycin) was used to interfere autophagy pathway before cerebral ischemia, its effects were analyzed by the score of neurological deficits and level of serous neuron specific enolase (NSE).Results:There were few number of autophagosomes and lysosomes in neuron of sham-operated group.The formation of autophagosomes and enhanced presence of lysosomes were detected by TEM at 2h in ischemic cortex after cerebral ischemia/ reperfusion,its number was significantly increased at 12h-24h,and still could be found at 5d. There was little expression of Beclin 1 and cathepsin B in neuron of sham-operated group. The expression of Beclin 1 detected by immunohistochemistry was significantly increased at 4h (P<0.01) and peaked at 24h after cerebral ischemia/reperfusion,its expression still could be found at 5d (P<0.01).Cathepsin B was activated at 2h (P<0.01),got to its peak at 12h,and kept a level of activating at 5d after cerebral ischemia/reperfusion (P<0.01). Rapamycin pretreatment improved the score of neurological deficits (P<0.05) and reduced the level of NSE in serum (P<0.05).Conclusions:1.There were few number of autophagosomes and lysosomes,low expression of Beclin 1 and cathepsin B were detected in normal neuron of rats;2. Autophagy/lysosomal pathway was activated after focal cerebral ischemia/reperfusion in rats.Its activation was manifested by the formation of autophagosomes,the activation of lysosomes and the robust elevation of Beclin 1,cathepsin B in ischemic penumbra with the time challenged by cerebral ischemia/reperfusion injury;3.Autophagy promoter (rapamycin) has protective effects on cerebral ischemia/reperfusion injury in rats. Activation of autophagy might play a protective role in the initial stage of cerebral ischemia/reperfusion; 4.It may be a therapeutic strategy to regulate the autophagy/lysosomal pathway in ischemic penumbra after cerebral ischemia/reperfusion injury.