The Role Of P70S6K In Cognitive Dysfunction Of Diabetic Rats And Apoptosis Induced By High Glucose In SH-SY5Y Cells

OBJECTIVESTo investigate the connection of p-p70S6K changes in hippocampus and course of diabetes, diabetic cognitive dysfunction and hippocampus nerve cells apoptosis on the diabetic rats induced by streptozotocin;then culture SH-SY5Y cells in vitro, to analysis whether the high glucose by activating the mTOR/p70S6K signaling pathway to mediated nerve cell apoptosis.METHODSDiabetes was induced by a single intraperitoneal injection of streptozotocin at a dose of60mg/kg body weight dissolved in citrate buffer. The streptozotocin-injected rats with blood glucose levels>16.7mmol/l three days after injection were included in the study and were randomly divided into three groups:11weeks,15weeks and20weeks diabetic rats,each group of nine。Normal control group were divided into11weeks,15weeks and20weeks control rats, each group of seven.After the modeling of11weeks,15weeks and20weeks,used the Morris water maze experiment to test the learning and memory ability. After each Morris experiment, collected blood sample from heart, took the brain tissue, and collected bilateral hippocampus quickly,then tested the protein expression of p-p70S6K,Bax and Bcl-2with protein imprinting technique.Cultured SH-SY5Y cells in vitro,deal with serum-free medium containing glucose25mmol/1,50mmol/1,75mmol/1for72hours,and set75mmol/1mannitol control group at the same time. After that,used Hoechst staining to detect the cell apoptosis rate and tested the protein expression of mTOR (p-mTOR and t-mTOR)、 p-p70S6K, Bax and Bcl-2with protein imprinting technique.RESULTS1.The change of cognitive dysfunction on the diabetic rats induced by streptozotocin:the Morris water maze experiment showed that in11weeks group there was no statistically significant difference (P>0.05) in diabetic rats and control rats for escape incubation period and the target quadrant retention time.Compared the15and20weeks diabetic rats with the age-matched control rats,the escape incubation period was extended and the target quadrant retention time was shorter with the diabetes duration (P<0.05).2.The expression of Bax,Bcl-2protein change in diabetic rats hippocampus:in11weeks, the relevant protein of apoptosis Bax/Bcl-2ratio was no statistically significant difference with the age-matched control rats (P>0.05)。Compared the15and20weeks diabetic rats with the age-matched control rats,the relevant protein of apoptosis Bax/Bcl-2ratio was increased with the diabetes duration(P<0.05). 3.The expression of p-p70S6K protein change in diabetic rats hippocampus:in11weeks, the diabetic rats p-p70S6K protein expression were no statistically significant difference with the age-matched control rats (P>0.05)o Compared the15and20weeks diabetic rats with the age-matched control rats,the p-p70S6K protein expression were increased with the diabetes duration(P<0.05).4.SH-SY5Y cells cultured in vitro.Compared with the isotonic control group,the apoptotic protein ratio of Bax/Bcl-2and the rate of cell apoptosis were increased in the high glucose group(50mmol/L or75mmol/L,72hours)(P<0.05),but the expression of mTOR (p-mTOR and t-mTOR)and p-p70S6K protein were no statistically significant difference (P>0.05)CONCLUSION:1.With the extension of rats diabetic course, the expression of p-p70S6K in the hippocampus gradually increased,the change had the same trend with the relevant protein of apoptosis Bax/Bcl-2ratio and cognitive dysfunction.2.In cultured SH-SY5Y cells, high glucose dose not mediate nerve cells apoptosis through activate the mTOR/p70S6K signaling pathway.