Correlation between superoxide dismutase expression and protection in selected models of injury

The expression of superoxide dismutase (SOD) has been associated with protection in many models of injury. Thus, practical approaches for increasing levels of SOD may beneficial to cells. Cortical spreading depression (CSD) induces neuronal tolerance to a subsequent episode of ischemia. A goal of this thesis was to test whether CSD induces tolerance to neurons by increasing levels of SOD-1 and SOD-2. The data presented in this thesis demonstrated that CSD does not upregulate the expression of SOD-1 or SOD2, suggesting that CSD-induced tolerance is independent of SOD-1 and SOD-2 expression. The thesis then examined whether the RNA-vector system is a feasible approach for increasing levels of SOD in cells. High and immediate expression of SOD-1 and SOD-2 was detected in cells after delivery of encoding RNAs. In vitro assays demonstrated that the SODs were enzymatically active. Accordingly, we examined whether the RNA-mediated expression of SOD-1 and SOD-2 could protect cells from apoptosis. The data demonstrated that wild-type SOD-1 and SOD-2 did not protect Chinese hamster ovarian (CHO) or human brain endothelial (BB19) cells from staurosporine or arsenite-induced apoptosis. Surprisingly, however, A4V SOD-1 (mutant SOD-1 with an alanine to valine substitution at codon 4) significantly protected the cells from the effects of staurosporine nor arsenite. The thesis also demonstrated that A4V SOD-1 interacted with the 70-kDa heat-shock protein (hsp70) whereas wild-type SOD-1 and other SOD-1 mutants did not. The possibility that A4V SOD-1-induced tolerance was mediated by HSP70 and the relevance of these findings to amyotrophic lateral sclerosis are discussed