Hormonal Intervention Protects Axon-myelin to Promote Functional Recovery in SCI

Ralph H Johnson Va Medical Center, Charleston SC

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Abstract

DESCRIPTION (provided by applicant): Although better understanding of spinal cord injury (SCI) and its underlying mechanisms has been achieved, creating an effective therapy is still unrealized. Inflammation, intracellular Ca2+ influx, and oxidative damage are implicit in the initiation of secondary injury pathways leading to cell death following SCI. Since the only currently available treatment, methylprednisolone, has limited clinical efficacy, novel therapies to block inflammation, reduce cell and axon-myelin damage, and restore blood supply must be discovered. Neuroprotection has been achieved in acute SCI with a low dose of the multi-active agent estrogen. Estrogen suppresses Ca2+ influx and inflammation in SCI and cultured cells by blocking L-type Ca2+ channels. Preliminary data indicates that low dose estrogen reduces inflammation, inhibits calpain-caspase activity, protects cells, preserves axons and myelin, and restores locomotor function. These results indicate that estrogen may be used as a therapeutic agent for treatment of SCI. By understanding SCI pathophysiology, therapies with low dose estrogen (17¿-estradiol), alone or in combination, will be designed to prevent inflammation, axonal damage, and cell death in the spinal cord after injury. Because multiple pathways cause tissue destruction in SCI, blocking only one pathway may not be optimal. The goal of this proposal is to protect CNS cells and the axon-myelin unit from secondary damage by utilizing estrogen treatment and also by combining agents that preserve tissue and promote greater functional recovery. In addition to estrogen, treatment with angiogenesis-promoting factors, e.g. vascular endothelial growth factor (VEGF), will further increase the blood supply to the injured cord and aid in functional recovery. We hypothesize that estrogen will promote vascular growth, prevent Ca2+ influx, and attenuate cell and axon-myelin damage, lipid peroxidation, inflammation, and monocyte phagocytosis. Inhibition of these pathways will consequently block downstream calpain-mediated apoptotic events. Combination therapy with VEGF will further promote recovery by restoring tissue perfusion. Three specific aims will test the hypothesis: (1) investigate whether low dose estrogen therapy will preserve motor function following SCI by reducing inflammation and axonal damage, and protecting neuronal and glial cells from apoptotic events; (2) determine whether single therapy with low-dose estrogen or combination therapy with the angiogenic factor VEGF will further improve motor function long-term following SCI by promoting angiogenesis; and (3) examine the mechanisms of neuroprotection mediated by estrogen +/- VEGF in neurons and glia subjected to either excitotoxic or inflammatory stress. Results obtained from the proposed studies will have strong translational application to SCI, suggesting estrogen's therapeutic significance.