The Role Of Inhibition Of NEDD4-1-Mediated PTEN Nuclear Translocation In Hypoxic Ischemic Brain Damage

Objective: 1.Newborn rats were used to establish HIBD model.In order to observe the effect of polypeptide Tat-K13 on spatial memory retrieval and the neurons growth and the changes of NEDD4-related proteins after hypoxic ischemia,Tat-k13 peptide and the control peptide were administrated to HIBD model rats.2.To further determine the role and mechanism of NEDD4-mediated PTEN nuclear translocation after hypoxic ischemia.Methods: 1.7-day SPF newborn SD rats were divided into sham group and HIBD group randomly.After hypoxic,HIBD group were randomly divided into saline treatment group(HIBD+Saline),peptide treatment group(HIBD+K13)and control peptide treatment group(HIBD+K13R).Animals were subjected to intraperitoneal injection of saline or polypeptide at 0h,3h,24 h and 48 h after hypoxia ischemia,respectively.Morris water maze and Golgi staining were done when animals were 4 to 5 weeks old.Furthermore,hippocampal tissues were collected at 3 h,6 h,12 h,24 h,3 d,7 d after the blood vessels ligated,respectively.Total NEDD4-related proteins were detected at different time points.2.Forteen days' cultured cortical neurons were treated with NMDA at 25umol/L for 1 hour,and then the expressions of NEDD4-related proteins were detected,In addition,NEDD4-1 si RNA was used to treat SY5 Y cell,and then the expressions of NEDD4-1 and PTEN were detected.Results: 1.Morris water maze was used to detect spatial memory and the results showed that the time spend in the target quadrant in HIBD group was much shorter,the number of the rats through the platform was obviously reduce and the escape latency in HIBD group was much longer compared to SHAM group during the retrieval test,whereas Tat-K13 peptide can partially rescue the impairment.Similiarly,Golgi staining showed that the neurons was dramatically decreased in HIBD group compared with sham group,whereas Tat-K13 peptide treatment increased neurons compared to HIBD group.In addition,the levels of P34 and NEDD4-1 were reduced,but the level of NEDD4-2 was increased,at 3 to 12 h after HIBD compared to control.2.The level of NEDD4-1was decreased after the treatment of NMDA in primary cortical neurons.And the level of PTEN in the nucleoprotein was significantly increased after transfect NEDD4-1 si RNA into SY5 Y cell.Conclusion: 1.These results suggest that spatial memory and neuronal growth are impaired in HIBD model rats.While polypeptide Tat-K13 can partially rescue the impairment.Hypoxia ischemia decreases the expressions of P34 and NEDD4-1,and increases NEDD4-2 expression.2.The decreased NEDD4-1 leads to an increase in PTEN nuclear translocation.Objective: Placing rats on an elevated Plexiglas platform to establish stress model.Observing the effects of acute fluoxetine treatment on stress-facilitated hippocampal CA1 LTD and spatial memory retrieval impairment.Method: Adult male Sprague-Dawley rats(200–250 g)were used.Rats were palced on an elevated Plexiglas platform in a brightly lit room for 30 min.Fluoxetine treatment before or immediately after acute stress,or bath application of fluoxetine during electrophysiological recording.We firstly investigated the effects of acute fluoxetine treatment on stress-facilitated hippocampal CA1 LTD using in vitro electrophysiological.We then used Morris water maze test to observe spatial memory retrieval impairment induced by acute stress.The animals were trained in the spatial learning task for 4 trials per day for 6 consecutive days.24 hours after the final training trial,a retrieval test was performed.During retrieval test,rats were divided into 2 groups: non-stressed control(n = 8)and stressed group(n = 32).To determine the effect of fluoxetine on stress-induced spatial memory retrieval impairment,rats in stressed group were subdivided into 3 subgroups.Twelve rats were subjected to an acute injection of fluoxetine 30 min before elevated-platform stress(fluoxetine+ stress),and 10 rats were injected with fluoxetine immediately after stress(stress + fluoxetine).The remaining stressed rats were injected with saline vehicle(stress).Results: 1.Single fluoxetine treatment before acute stress inhibited stress-facilitated hippocampal CA1 LTD;2.Single fluoxetine treatment immediately after acute stress has no effect on stress-facilitated hippocampal CA1 LTD;3.Bath application of fluoxetine has no effect on acute stress-facilitated hippocampal CA1 LTD;4.Single fluoxetine treatment before acute stress prevents the impairment of spatial memory retrieval caused by stress.Conclusion: Single fluoxetine treatment before but not after acute stress can inhibit stress-facilitated LTD in the hippocampus and rescue stress-induced spatial memory retrieval impairment.