Abstract
BackgroundSuperoxide mediated oxidative stress is a key neuropathologic mechanism in acute central nervous system injuries. We have analyzed the neuroprotective efficacy of the transient overexpression of antioxidant enzyme Cu/Zn Superoxide dismutase (SOD) after excitotoxic injury to the immature rat brain by using a recently constructed modular protein vector for non-viral gene delivery termed NLSCt. For this purpose, animals were injected with the NLSCt vector carrying the Cu/Zn SOD or the control GFP transgenes 2 hours after intracortical N-methyl-D-aspartate (NMDA) administration, and daily functional evaluation was performed. Moreover, 3 days after, lesion volume, neuronal degeneration and nitrotyrosine immunoreactivity were evaluated.ResultsOverexpression of Cu/Zn SOD transgene after NMDA administration showed improved functional outcome and a reduced lesion volume at 3 days post lesion. In secondary degenerative areas, increased neuronal survival as well as decreased numbers of degenerating neurons and nitrotyrosine immunoreactivity was seen. Interestingly, injection of the NLSCt vector carrying the control GFP transgene also displayed a significant neuroprotective effect but less pronounced.ConclusionWhen the appropriate levels of Cu/Zn SOD are expressed transiently after injury using the non-viral modular protein vector NLSCt a neuroprotective effect is seen. Thus recombinant modular protein vectors may be suitable for in vivo gene therapy, and Cu/Zn SOD should be considered as an interesting therapeutic transgene.
Highlights
Superoxide mediated oxidative stress is a key neuropathologic mechanism in acute central nervous system injuries
In previous studies using N-methyl-D-aspartate (NMDA)-mediated excitotoxicity, a model for hypoxic-ischemic injury to the postnatal brain [14,15], we have shown an upregulation of inducible nitric oxide synthase and cyclooxygenase-2 (COX-2) [16] and increased levels of the oxidative marker nitrotyrosine [17]
Rat brains injected two hours after the lesion with the NLSCt vector carrying the antioxidant enzyme Cu/Zn Superoxide dismutase (SOD) transgene (NMDA+Cu/Zn SOD group) showed a pronounced reduction in the neurodegenerative area when compared to both the NMDA only group and the NMDA+saline group
Summary
Superoxide mediated oxidative stress is a key neuropathologic mechanism in acute central nervous system injuries. In previous studies using N-methyl-D-aspartate (NMDA)-mediated excitotoxicity, a model for hypoxic-ischemic injury to the postnatal brain [14,15], we have shown an upregulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) [16] and increased levels of the oxidative marker nitrotyrosine [17]. Dismuting metalloporphyrins have been shown to be neuroprotective [20] In this sense, several differences between immature and adult animals in terms of oxidative stress and antioxidant defenses have been described including: upregulation of gluthathione peroxidase in the damaged adult brain but not in the damaged immature brain after trauma [21], the rapid free iron accumulation within 4 hours after transient cerebral ischemia stimulating Fenton reactions in the immature brain [22,23], the lesser concentration of metallothioneins, potent metal-binding antioxidant enzymes in the immature brain [24,25]. In view of these contradictory findings of Cu/Zn SOD expression, we induced a transient post-injury overexpression of Cu/Zn SOD after excitotoxic damage to the immature rat brain using a novel non-viral gene therapy approach
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