Study Of Reformation Of Synapses Regulated By Simvastatin And Chlorquine In A Rat Traumatic Brain Injury Model

Objectives The relationship between the activity of autophagy and the reformation of synapses afer TBI(traumatic brain injury) is not quite clear. Administration of simvastatin, an agonist of autophagy, and CQ, an inhibitor of autophagy was given to regulate the activity of autophagy in the hippocampal neuron of rat after TBI, which was indicated by the expression of autophagy related protein LC3 and Beclin-1. The expression of synaptic protein PSD-95 and synaptophysin was recorded to indicate the refomation of synapses. To research the mechanism underlying the functional recovery after TBI, providing new target for clinical treatment.Methods 200 Sprague Dawley rats were randomly divided into four groups:1 Sham group(n=50);2 TBI group(n=50);3 simvastatin group(n=50);4 CQ group(n=50). Each group was divided into 4 subgroups based on the time relative to the time of surgery. The TBI model was built with Marmarou’s method. Following variables were measured:1 The morphological change of neuron in the hippocampus was observed by H&E stain. 2 Colocalization of LC3 and Neu N was observed by the method of immunofluorescence. 3 50 Sprague Dawley rats were subjected to Morris Water Maze test. The results of Western blot were quantified by Gel-Doc software. Q-test was used. P<0.05 was considered significantly different. Data was analyzed by SPSS 18.0 software.Results 1 Pathological changes observed by H&E stain. Sham group: no obvious changes were found, neuron has quite clear boundary with an intact structure. TBI group: number of neurons were reduced. Brain tissue was loosely arranged, edema was observed. Intercellular space was widen compared with the sham group. Sructure of neuron was damaged. Simvastatin group: Reduction of neurons was less than TBI group, edema was mild. CQ group: no obvious difference with the TBI group. 2 Spatial learning and memory: Escape latency of the TBI group were extended, crossing, percent path length and percent quadrant time reduced. Escape latency of the simvastatin group were shorten, crossing, percent path length and percent quadrant time increased compared the TBI group. Escape latency of the CQ group were extended, crossing, percent path length and percent quadrant time reduced compared the TBI group. 3 Expression of LC3 II. sham group: expressionwas weak, showed no difference in each time point. TBI group: compared with the TBI group, showed a significant increase at 1d(P<0.05), reach peak at 3d, still higher expressed at 7d. simvastatin group: expression was significantly higher than the TBI group at 1d and 3d(P<0.05). CQ group: expression was significantly lower than the TBI group at 3d and 5d(P<0.05). 4 Expression of Beclin-1. sham group: expression was weak, showed no difference in each time point. TBI group: compared with the TBI group, showed a significant increase at 1d(P<0.05), reach peak at 3d, still higher expressed at 7d. simvastatin group: expression was significantly higher than the TBI group at 1d, 3d and 5d(P<0.05). CQ group: expression was significantly lower than the TBI group at 3d(P<0.05). 5 Expression of PSD-95. sham group: expression was strong, showed no difference in each time point. TBI group: compared with the TBI group, showed a significant downfall at 1d(P<0.05), slowly increased, still lower expressed at 7d. simvastatin group: expression was significantly higher than the TBI group at 5d and 7d(P<0.05). CQ group: expression was significantly lower than the TBI group at 7d(P<0.05). 6 Expression of synaptophysin. sham group: expression was strong, showed no difference in each time point. TBI group: compared with the TBI group, showed a significant downfall at 1d(P<0.05), slowly increased, still lower expressed at 5d and 7d. simvastatin group: expression was significantly higher than the TBI group at 5d and 7d(P<0.05). CQ group: expression was significantly lower than the TBI group at 5d and 7d(P<0.05). 7 Co-localization of Neu N and LC3. LC3 in cytoplasm was labeled by red fluorescent, Neu N was labeled as green. LC 3 and Neu N were collocated in hippocampus.Conclusions Treatment with simvastatin could improve neurological outcome after TBI, may significantly recovery the functional loss, upregulate the expression of synaptic protein. The possible underlying mechanism is an enhanced plasticity of the neural network by activating the pathway of autophagy, more synapses were formaed, the integrity of neural network was better reconstructed.