Investigations into model systems of neurodegeneration: Organotypic brain slice culture and in vivo microdialysis

Abstract

The mechanisms behind neurodegeneration in disease and injury have yet to be fully defined. Many in vitro and in vivo model systems, have been developed to investigate the mechanisms of neurotoxicity and its relation to human disease and injury. There are a few resounding connections between most types of neurological disorder; namely oxidative stress and inflammation. The glutamate receptor agonist, N-methyl-D-aspartate, can be used to imitate excitotoxicity during stroke as it overstimulates the glutamate receptor, leading to rises in intracellular calcium levels, which in turn lead to oxidative stress within the cell. Amyloid-beta protein (Abeta) a useful in many of its isoforms in creating in vitro model systems of Alzheimer's disease (AD). Abeta can directly cause the production of potentially harmful free radicals. This study investigates the formation of model systems of neurodegeneration: in vivo microdialysis and organotypic brain slices culture in order to assess the role of oxidative stress and inflammation morphologically and biochemically. The effect of melatonin, an endogenous antioxident, on oxidative stress associated with NMDA and Abeta neurotoxicity was determined through morphological analysis and biochemical markers of oxidative stress. This study reports that both NMDA and Abeta(25--35) cause oxidative stress in an organotypic brain slice culture model system of stroke and Alzheimer's disease as established by: (1) morphological analysis of tissue and ultrastructure, (2) redox-active assay, (3) heme-oxygenase assay, (4) 8-hydroxyguanosine assay and (5) interleukin IL-1beta and IL-6 assay (Abeta only) These investigations also demonstrate that melatonin can attenuate the oxidative stress associated with NMDA and Abeta exposure. These findings expand upon previous evidence from cell culture analysis of oxidative stress induced by NMDA and Abeta. Therefore, this evidence supports the theory that oxidative stress is involved in neurodegeneration in both excitotoxicity in stroke and in Abeta-mediated damage in Alzheimer's disease, and that endogenous antioxidant treatment may be a useful therapeutic approach in such injury and disease.