Oxidative Stress, PKC-delta Activation and Striatal Ischemic Cell Death

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DESCRIPTION (provided by applicant): Stroke is the third leading cause of morbidity and mortality in the US, yet effective therapeutic interventions for the treatment of ischemia-induced brain damage are not currently available. Numerous studies in experimental models of ischemia have implicated oxidative stress and apoptosis as key mediators of ischemia-induced cell death. The majority of these studies have focused on either cortical or hippocampal regions; however, the cellular mechanisms underlying ischemic damage to the striatum, a dopamine enriched brain region that is highly susceptible to oxidative damage, is unclear. Although dopamine is considered to be a key mediator of oxidative stress-induced neuronal injury to the striatum, its exact role in ischemia-induced cell death signaling pathways in the striatum remain to be clarified. Likewise, ROS generation, mitochondrial dysfunction and caspase-3 activation have been implicated in ischemia- induced brain damage; however, the downstream cellular events that lead to DNA fragmentation subsequent to caspase-3 activation are currently not well established. As outlined in the preliminary data, we have identified that protein kinase C-delta, a member of the novel PKC isoform family and an oxidative stress kinase is highly expressed in the striatal neurons and serves as a key substrate for caspase-3. Furthermore, the proteolytic activation of PKC-delta by caspase-3 results in the permanent dissociation of regulatory and catalytic subunits of the kinase, thereby resulting in persistently increased kinase activity, and potentiation of oxidative stress-induced apoptotic damage. Therefore, in the present proposal we will extend our preliminary findings, by investigating the following specific aims: 1) To systematically characterize the caspase-3 dependent proteolytic activation of PKC-delta cell death pathways in primary striatal neuronal cultures following oxygen-glucose deprivation (OGD). 2) To investigate whether dopamine-induced oxidative insult is a potential trigger for PKC-delta mediated cell death pathways in striatal neurons subjected to OGD. Pharmacological, cellular and molecular approaches will be utlilized to delineate these specific aims. The proposed studies will not only provide insights into the mechanism of PKC-delta mediated cell death and the influence of DA in modulating ischemia-induced striatal cellular collapse but may also lead to the development of novel thereapeutic interventions for the treatment of cerebral ischemia.