The Mechanism Study Of IGF-1 On Cognitive Impairment And MEK/ERK Signaling Pathway In Rats With Global Cerebral Ischemia

Objects: The experiment was performed to observe cognitive impairment, the changes of morphology in hippocampal CA1 area and the expression of p-MEK1、p-ERK1/2 protein in rats with global cerebral ischemia.The purpose of this study was to investigate the IGF-1 influenced spatial learning and memory ability of rats with global cerebral ischemia by regulating MEK/ERK signaling pathway, to provide new basis on clinical improvement of cognitive impairment.Methods:(1)The Wistar rats were divided into normal control group, sham operation group, model control group,model+ IGF-1 group,model +IGF-1+PPP group by completely random methods.(2)In addition to normal control group, the other groups were embedded micro-injection catheter into the lateral ventricle. After six days, we adopted the Modified Pulsinelli four-vessel occlusion(4-VO)method to establish rat with global cerebral ischemia.(3)The rats were given different drugs basing on different groups after 4-VO.The rats in normal control group stained blank, the rats in sham operation group, model control group and the MC+IGF-1 group received intraperitoneal injection DMSO 1ml, the MC+IGF-1+PPP group received intraperitoneal injection PPP 1ml(2mg/kg). After 30 min, the rats in sham operation group,model group received intracerebroventricular injection NS 10 ul,the rats in the MC+IGF-1 and MC+IGF-1+PPP groups received intracerebroventricular injection IGF-1 10μl(0.2μg/μl),once a day and continuous injection seven days.(4)We did respectively the Morris water maze test before surgery, seven days after drug intervention.(5). To observe the morphological changes in hippocampal CA1 by HE staining. Immunohistochemical method and western blot to detect the expression of p-MEK1 and p-ERK1/2 protein in hippocampal.Results:1) There were 100 rats who were embedded micro-injection catheter into the lateral ventricle.The survival rate was:87%(87/100);There were 78 rats who were carried out 4-VO method, The success and survival rate of model was 41.03%(32/78).2) The results of morris water maze test: The swimming speed of the rats in five groups had no statistical significance(P>0.05). After drug intervention, the average escape latency of the model control group, the MC+IGF-1 group and MC+IGF-1+PPP group were significantly longer than the normal control and sham operation groups(P<0.05).Compared with model control group, the average escape latency of the MC+IGF-1 group was significantly shorter(P<0.05).Compared with MC+IGF-1 group, the average escape latency of the MC+IGF-1+PPP group was significantly longer(P<0.05).The average escape latency of the MC+IGF-1+PPP group and model control group were almost identical(P>0.05).The spanning platform times of the model control group, the MC+IGF-1 group and the MC+IGF-1+PPP were less than the normal control and sham operation groups(P<0.05). The spanning platform times of the model control group was less than the MC+IGF-1 group, the original platform quadrant swimming time was shorter(P<0.05).The spanning platform times of the MC+IGF-1+PPP was less than the MC+IGF-1 group, the original platform quadrant swimming time was shorter(P<0.05), Tthe spanning platform times and the original platform quadrant swimming time of both the model control groups and the MC+IGF-1+PPP group were almost same, the difference had no statistical significance(P>0.05).3) The results of HE staining: The cells in hippocampal CA1 area in normal control and sham operation groups were big large and round, neatly arranged. The cells in hippocampal CA1 area had different degree of degeneration and necrosis in model control group, the example cell numbers decreased, disordered arrangement, Cytoplasm staining thick and irregular nucleus. The cells degeneration and necrosis of CA1 area in hippocampal of the MC+IGF-1 group were lighter than model control groups. The cells degeneration and necrosis of CA1 area in hippocampal of the MC+IGF-1+PPP group and model control groups were almost same.4) The results of immunohistochemical staining: After drug intervention, the expression of p-MEK1、p-ERK1/2 protein in hippocampal CA1 area of model control group and MC+IGF-1 group and MC+IGF-1+PPP group were less than normal control group(P<0.05).The expression of p-MEK1、p-ERK1/2 protein in hippocampal CA1 area of the MC+IGF-1 group were more than model control group(P<0.05).The expression of p-MEK1 、p-ERK1/2 protein in hippocampal CA1 area of the MC+IGF-1 group were more than the MC+IGF-1+PPP group(P<0.05).The difference of the expression of p-MEK1、p-ERK1/2 protein in hippocampal CA1 area of model control group and the MC+IGF-1+PPP group had no statistical significance(P>0.05).5) The results of western blot in hippocampus: After drug intervention, the gray value ratio of p-MEK1、p-ERK1/2 protein and GAPDH of the model control group and the MC+IGF-1 group and the MC+IGF-1+PPP group were less than the normal control and sham operation groups(P<0.05).The gray value ratio of p-MEK1、p-ERK1/2 protein and GAPDH of the MC+IGF-1 group was more than the model control group(P<0.05).The gray value ratio of p-MEK1、p-ERK1/2 protein and GAPDH of the MC+IGF-1 group was more than the MC+IGF-1+PPP group(P<0.05).The gray value ratio of p-MEK1、p-ERK1/2 protein and GAPDH of the model control group and MC+IGF-1+PPP group had no statistical significance(P>0.05).Conclusion: The expression of p-MEK1 、 p-ERK1/2 protein in hippocampus reduced could be a potential mechanism of global cerebral ischemia with cognitive impairment in rats;IGF-1 can improve the spatial learning and memory ability;The effect may had a relationship with increasing the expression of p-MEK1、p-ERK1/2 protein in hippocampal, activating MEK/ERK signal pathway.