Abstract
The mammalian target of rapamycin (mTOR) has been demonstrated to mediate multidrug resistance in various tumors by inducing P-glycoprotein (P-gp) overexpression. Here, we investigated the correlation between the mTOR pathway and P-gp expression in pharmacoresistant epilepsy. Temporal cortex specimens were obtained from patients with refractory mesial temporal lobe epilepsy (mTLE) and age-matched controls who underwent surgeries at West China Hospital of Sichuan University between June 2014 and May 2015. We established a rat model of epilepsy kindled by coriaria lactone (CL) and screened pharmacoresistant rats (non-responders) using phenytoin. Non-responders were treated for 4 weeks with vehicle only or with the mTOR pathway inhibitor rapamycin at doses of 1, 3, and 6 mg/kg. Western blotting and immunohistochemistry were used to detect the expression of phospho-S6 (P-S6) and P-gp at different time points (1 h, 8 h, 1 day, 3 days, 1 weeks, 2 weeks, and 4 weeks) after the onset of treatment. Overexpression of P-S6 and P-gp was detected in both refractory mTLE patients and non-responder rats. Rapamycin showed an inhibitory effect on P-S6 and P-gp expression 1 week after treatment in rats. In addition, the expression levels of P-S6 and P-gp in the 6 mg/kg group were significantly lower than those in the 1 mg/kg or the 3 mg/kg group at the same time points (all P < 0.05). Moreover, rapamycin decreased the duration and number of CL-induced seizures, as well as the stage of non-responders (all P < 0.05). The current study indicates that the mTOR signaling pathway plays a critical role in P-gp expression in drug-resistant epilepsy. Inhibition of the mTOR pathway by rapamycin may be a potential therapeutic approach for pharmacoresistant epilepsy.
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Acknowledgements
This study was supported by the National Natural Science Foundation of China (Item Number: 81501127 and 81420108014).
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This study was approved by the Ethics Committee of West China Hospital. Informed consent forms were signed by patients and their legal guardians. The animal study was approved by the Experimental Animal Management Institute of Sichuan University and was conducted in compliance with the Chinese Animal Welfare Act.
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Xiaosa Chi and Cheng Huang contributed equally to the manuscript
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Figure S1
(A) Western blotting shows P-S6 expression in the hippocampus at various time points after the onset of vehicle treatment. (B) Western blotting shows P-gp expression in the hippocampus at various time points after the onset of vehicle treatment. (n = 3 for each time point per group. * P < 0.05, ** P < 0.005, *** P < 0.001 versus normal control; # P < 0.05, ## P < 0.005, ### P < 0.001 versus non-responders). (GIF 69 kb).
Figure S2
(A) Quantitative analysis of the P-S6 IOD value in hippocampal regions and cortex. (B) Quantitative analysis of the IRS of P-gp in hippocampal regions and cortex. (n = 6/group. * P < 0.05, ** P < 0.005, *** P < 0.001 versus normal control; # P < 0.05, ## P < 0.005, ### P < 0.001 versus responders). (GIF 46 kb).
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Chi, X., Huang, C., Li, R. et al. Inhibition of mTOR Pathway by Rapamycin Decreases P-glycoprotein Expression and Spontaneous Seizures in Pharmacoresistant Epilepsy. J Mol Neurosci 61, 553–562 (2017). https://doi.org/10.1007/s12031-017-0897-x
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DOI: https://doi.org/10.1007/s12031-017-0897-x