Study on the mechanism of inhibiting autophagy by ischemic preconditioning on the neuroprotective effect of ischemia reperfusion rats

Qingyu Fan^*, Xinli Yang, Guilian Zhang, Jingjie Liu, Huqing Wang

Department of Neurology, Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, PR China

Objective: This study explores the mechanism of inhibiting autophagy during ischemia on the neuroprotective effect in ischemia-reperfusion rats.

Methods: Forty-five healthy male Sprague Dawley rats of clean grade were selected and randomly divided into five groups with nine rats in each group: the sham operation group, model group, and 24 h, 72 h and 120 h ischemic preconditioning groups. An animal experimental model was established. In the sham operation group, only the blood vessels were isolated and no sutures were inserted. In the model group, the rats were directly reperfused after 2 h of ischemia. The rats in the 24 h, 72 h and 120 h ischemic preconditioning groups underwent ischemia for 10 min and reperfusion for 10 min, with three cycles at intervals of 24 h, 72 h and 120 h, respectively, and then reperfused directly after 2 h of ischemia again. The neurological function of rats in each group was evaluated using the Zea-Longa neurological dysfunction score. The volume of cerebral infarction in each group was determined by the triphenyl tetrazolium chloride method. The HE staining method was used to detect the changes in the hippocampal nerve cells in each group of rats. The expression of autophagy-associated protein Beclin-1 and the microtubule-associated protein light chain 3-Ⅱ (LC3-Ⅱ) in rat hippocampal neurons in each group was detected using the immunohistochemistry method. 

Results: Compared with the sham operation group, the neurological dysfunction score, cerebral infarction volume, hippocampal nerve cell injury and the expression level of Beclin-1 and LC3-II were significantly increased in the model group (P<0.05). Compared with the model group, the neurological dysfunction score, cerebral infarction volume, hippocampal nerve cell injury and the expression level of Beclin-1 and LC3-II in the ischemic preconditioning group were remarkably lower (P<0.05). In the sham operation group, the hippocampal neurons were arranged closely, the morphology was normal, and the nucleolus was obvious. In the model group, the arrangement of hippocampal nerve cells was disordered, the number was lower, and karyopyknotic, intercellular oedema and vacuole-like changes were observed. The number of cells, intercellular oedema and vacuole-like changes in the ischemic preconditioning group were significantly improved compared with the model group. The improvement was the most obvious in the 72 h ischemic preconditioning group.

Conclusion: Ischemic preconditioning can play a neuroprotective role by inhibiting the expression of Beclin-1 and LC3-II and by suppressing autophagy, and was found to have the best effect at 72 h.