NEURONAL DEGENERATION: MECHANISMS AND PREVENTION

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DESCRIPTION (provided by applicant): Neuronal degeneration and death are the hallmarks of many neurological diseases and there is considerable evidence that oxidative stress plays an important role in stroke/ischemia. The long term goals of this project are to elucidate the molecular mechanisms governing free radical-initiated apoptotic neuronal death and to utilize this molecular data for the design of therapeutic interventions. We have used the down-regulation of SOD1 in cultured primary neurons as a model of oxidative stress in which the pathways leading to neuronal apoptosis can be examined. Down-regulation of SOD1 leads to a death via a peroxynitrite-mediated pathway. This pathway requires activation of caspase-1 which in turn leads to the generation of IL-1beta which is released from the cell and acts in an autocrine manner on the IL-1 receptor to potentiate cell death. We also have evidence that activation of caspases-8 and -7, but unexpectedly not caspase-3, are required for death to proceed. This suggests a novel caspase cascade in which caspase-1 is the apical caspase leading to autocrine receptor activation followed by activation of caspase-8 and finally to activation of the executioner caspase, caspase-7. The failure to activate caspase-3 has not previously been seen in neuronal death cascades and supports the feasibility of designing specific agents to intervene in this pathway. We now propose the hypotheses that there is a feedback loop of NO and IL-1beta which is an essential component of the free radical death pathway and that there is a novel caspase cascade initiated by caspase-1 activation. These hypotheses will be examined with the following specific aims: 1. To determine the time course of induction/activation and localization of key molecules in the SOD1 down-regulation pathway and in ischemia. 2. To determine how the induction of nNOS is regulated after SOD1 down-regulation and after ischemia. 3. To determine how the induction of IL-1beta is regulated after SOD1 down-regulation and after ischemia. 4. To determine how caspases-8 and -7 are activated after SOD1 down-regulation. 5. To determine if there is activation/regulation of caspase-3 and other caspases after SOD1 down-regulation.