The long-term goal of this project is to understand the effects of epileptic seizures on the developing brain. During the last grant period, we showed that severe seizures (status epilepticus, SE) can cause neuronal death in the immature brain, and that this death is often apoptotic, but can also be necrotic. The proportion of necrotic death increases with advancing age. Our results suggest that hypoxic neuronal necrosis starts with cytochrome liberation from mitochondria, and requires the activation of a cascade of caspases. The goal of the upcoming grant is to test the hypothesis that seizure-induced neuronal necrosis is an orderly process that does not involve gene expression, RNA or protein synthesis, but does involve the mitochondrial activation of a caspase cascade. This process is triggered by mitochondrial failure that liberates cytochrome C into the cytoplasm, thereby activating caspase-9, then (by specific, energy-sparing proteolysis), caspase-3 from their constitutionally expressed proenzymes. This hypothesis will be tested in P15 rats and in adult mice subjected to status epilepticus induced by lithium and pilocarpine or by kainic acid. We will use electron microscopy immunocytochemistry, biochemistry and other methods to test this sequence of program activation. We also predict that inhibitors of caspase-3 or caspase-9 activity will reduce seizure-induced neuronal necrosis, We expect that transgenic mice with a null mutation for caspase-3 will have less neuronal necrosis than matched controls, while KOs for p53 will not be affected. We also predict that transgenic mice expressing the baculovirus p35 caspase inhibitor will show a reduced amount of Se-induced neuronal necrosis (and apoptosis) in the hippocampus. This will be of great relevance to the problem of seizure-induced brain damage, since a better understanding of the mechanisms involved in seizure induced neuronal necrosis could help to prevent or minimize that damage.
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