APOPTOSIS IN TRAUMATIC SPINAL CORD INJURY

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The studies proposed in this grant application focus on identifying and characterizing the molecular signaling events involved in apoptotic cell death following traumatic spinal cord injury (SCI). Despite the recent evidence of widespread apoptosis in neurons and glia after SCI, the molecular components of the apoptotic pathway remain largely unknown. The proposed experiments will provide evidence of components in the apoptotic machinery responsible for initiating and executing this cell death process. In addition, experiments are proposed to demonstrate that blocking steps involved in the apoptotic cell death pathway provides neuroprotection and promotes functional recovery in acute SCI. We hypothesize that calcineurin-mediated BAD dephosphorylation is one of the initial upstream events in the apoptotic cascade and is linked to caspase-3 activation. Glutamate-induced Ca2+ influx leads to calcineurin activation and high levels of glutamate are released soon after SCI. Therefore, we will examine whether intrathecal injections of selective glutamate receptor agonists into uninjured spinal cord lead to calcineurin- mediated BAD dephosphorylation. In addition, we will demonstrate that injections of glutamate receptor antagonists reduce activation of the caspase-3 apoptotic cascade. Finally, the contribution of apoptosis to the functional deficits observed following SCI is not clear at this time. Therefore, we will treat injured animals with inhibitors targeting calcineurin and caspase-3 and use morphological, histological, and behavioral criteria to measure indices of apoptotic cell death and functional recovery. The outcome of these studies will have clear clinical implications for minimizing secondary neuronal and glial cell death and promoting recovery of function following SCI.