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OBJECTIVE Accumulating data have demonstrated that seizures induced by kainate or pilocarpine activate the mammalian target of rapamycin(mTOR) pathway and mTOR inhibitor rapamycin can inhibit mTOR activation which subsequently has potential anti-epileptic effects.However,a preliminary study showed a paradoxical exacerbation of increased mTOR pathway activity reflected by S6 phosphorylation when rapamycin was administrated within a short period before kainate injection.In the present study,we examined this paradoxical effect of rapamycin in more detail,both in normal rats and kainate-injected animals.METHODS The expression of mTOR signaling target both of phosphorylated and unphosphorylated forms were detected by Western Blotting analysis.Seizure onset and duration was monitored by Video.Neuronal cell death was detected by Fluoro-Jade B staining.RESULTS In normal rats,we found that rapamycin showed the expected dose-dependent inhibition of S6 phosphorylation 3~24 h after injection,while a paradoxical elevation of S6 phosphorylation was observed 1 h after rapamycin.Similarly,pretreatment with rapamycin over 10 h prior to kainate inhibits the kainate-induced mTOR activation.In contrast,rapamycin administered 1-6 h before kainate causes a paradoxical increase in the kainate-induced mTOR activation.Rats pretreated with rapamycin 1h prior to kainate showed an increase in severity and duration of seizures and more neuronal cell death as compared to vehicle treated groups.In contrast,rapamycin pretreated 10 h prior to KA had no effect on the seizures and decreased neuronal cell death.The paradoxical effect of rapamycin on S6 phosphorylation was correlated with upstream mTOR signaling and reversed by pre-treatment of perifosine,an akt inhibitor.CONCLUSION These data indicate the complexity of S6 regulation and its effect on epilepsy.Paradoxical effects of rapamycin need to be considered in clinical applications,such as potential treatments for epilepsy and other neurological disorders.
OBJECTIVE Accumulating data have demonstrated that seizures induced by kainate or pilocarpine activate the mammalian target of rapamycin (mTOR) pathway and mTOR inhibitor rapamycin can inhibit mTOR activation which has has potential anti-epileptic effects. However, a preliminary study showed a paradoxical exacerbation of increased mTOR pathway activity reflected by S6 phosphorylation when rapamycin was administered within a short period before kainate injection. in the present study, we examined this paradoxical effect of rapamycin in more detail, both in normal rats and kainate-injected animals. METHODS The expression of mTOR signaling target both of phosphorylated and unphosphorylated forms were detected by Western Blotting analysis. Determination of duration and duration was monitored by Video. Neuronal cell death was detected by Fluoro-Jade B staining. RESULTS In normal rats, we found that rapamycin showed the expected dose- dependent inhibition of S6 phosphorylation 3 ~ 24 h after injection, while a paradoxical elevation of S6 phosphorylation was observed 1 h after rapamycin.Similarly, pretreatment with rapamycin over 10 h prior to kainate inhibits the kainate-induced mTOR activation.In contrast, rapamycin administered 1-6 h before kainate causes a paradoxical increase in the kainate -induced mTOR activation. Rats pretreated with rapamycin 1h prior to kainate showed an increase in severity and duration of seizures and more neuronal cell death as compared to vehicle treated groups. contrast, rapamycin pretreated 10 h prior to KA had no effect on the seizures and decreased neuronal cell death. The paradoxical effect of rapamycin on S6 phosphorylation was correlated with upstream mTOR signaling and reversed by pre-treatment of perifosine, an akt inhibitor. CONCLUSION These data indicate the complexity of S6 regulation and its effect on epilepsy. Paradoxical effects of rapamycin need to be considered in clinical applications, such as potential treatments for epilepsy and other neurologicaldisorders.