Inflammatory regulation of neurotrophin signaling in epileptogenesis

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PROJECT SUMMARY Epilepsy is a common neurological disorder that afflicts about 1% of the population. Although seizures can be partially controlled by current medications, there is no US FDA-approved drug that can provide disease prevention or modification despite remarkable advances in epilepsy treatment over the past decades. A major obstacle to finding such an antiepileptogenic drug is that the molecular mechanisms by which a normal brain is transformed to generate epileptic seizures remain unsolved. Accumulating evidence from recent clinical and preclinical studies suggests that the abnormal activation of the brain-derived neurotrophic factor (BDNF) receptor TrkB (tropomyosin-related kinase receptor B) and its downstream effector phospholipase Cγ1 (PLCγ1) is sufficient to produce epilepsy following status epilepticus (SE). As TrkB and PLCγ1 are emerging as attractive molecular targets to prevent acquired epilepsy, a key unsolved puzzle is the signaling events that are triggered by SE and cause the irregular BDNF/TrkA activity in the hippocampus, thereby leading to epileptogenesis. In preliminary studies we have demonstrated that the seizure-induced hippocampal BDNF/TrkB abnormality is largely suppressed by blocking prostaglandin E2 (PGE2) synthesis or signaling. Our main hypothesis is that PGE2 via a Gαs-dependent signaling pathway upregulates hippocampal BDNF/TrkB activity and contributes to epileptogenesis following prolonged seizures. Our general approach is to use biochemical, pharmacological, genetic tools, and multiple in vitro and in vivo model systems to test a hypothesis that PGE2 is involved in the hippocampal BDNF induction and TrkB activation after SE, to determine whether seizure-mediated BDNF/TrkB activity involves cAMP/PKA signaling and which Gαs-coupled PGE2 receptor is engaged, and to determine whether PGE2 signaling via its Gαs-coupled receptors plays a dominant role in the development of epilepsy and/or the associated behavioral comorbidities after SE. Successful completion of this project might lead to the discovery of novel molecular targets for the prevention strategies of acquired epilepsy.