title: PI3K-Akt signaling activates mTOR-mediated epileptogenesis in organotypic hippocampal culture model of post-traumatic epilepsy.
abstract: mTOR is activated in epilepsy, but the mechanisms of mTOR activation in post-traumatic epileptogenesis are unknown. It is also not clear whether mTOR inhibition has an anti-epileptogenic, or merely anticonvulsive effect. The rat hippocampal organotypic culture model of post-traumatic epilepsy was used to study the effects of long-term (four weeks) inhibition of signaling pathways that interact with mTOR. Ictal activity was quantified by measurement of lactate production and electrical recordings, and cell death was quantified with lactate dehydrogenase (LDH) release measurements and Nissl-stained neuron counts. Lactate and LDH measurements were well correlated with electrographic activity and neuron counts, respectively. Inhibition of PI3K and Akt prevented activation of mTOR, and was as effective as inhibition of mTOR in reducing ictal activity and cell death. A dual inhibitor of PI3K and mTOR, NVP-BEZ235, was also effective. Inhibition of mTOR with rapamycin reduced axon sprouting. Late start of rapamycin treatment was effective in reducing epileptic activity and cell death, while early termination of rapamycin treatment did not result in increased epileptic activity or cell death. The conclusions of the study are as follows: (1) the organotypic hippocampal culture model of post-traumatic epilepsy comprises a rapid assay of anti-epileptogenic and neuroprotective activities and, in this model (2) mTOR activation depends on PI3K-Akt signaling, and (3) transient inhibition of mTOR has sustained effects on epilepsy.
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts 02129, USA.
authors.forename: Yevgeny
authors.initials: Y
authors.lastname: Berdichevsky
authors.forename: Alexandra M
authors.initials: AM
authors.lastname: Dryer
authors.forename: Yero
authors.initials: Y
authors.lastname: Saponjian
authors.forename: Mark M
authors.initials: MM
authors.lastname: Mahoney
authors.forename: Corrin A
authors.initials: CA
authors.lastname: Pimentel
authors.forename: Corrina A
authors.initials: CA
authors.lastname: Lucini
authors.forename: Marija
authors.initials: M
authors.lastname: Usenovic
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Staley
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000633:toxicity; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D007736:Kynurenic Acid / Q000633:toxicity; D042844:L-Lactate Dehydrogenase (Cytochrome) / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D013997:Time Factors
chemical_list: D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D007736:Kynurenic Acid; D042844:L-Lactate Dehydrogenase (Cytochrome); D019344:Lactic Acid; D008869:Microtubule-Associated Proteins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases