OXIDATIVE, ANTIOXIDANT AND TRACE ELEMENT STUDIES IN THE ALZHEIMER'S BRAIN

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Alzheimer's disease (AD), one of the major health problems of the elderly, afflicting 4 million Americans. The major barrier to progress in preventing or treating AD is a lack of understanding of the pathogenesis/etiology of the disease. A role for free radicals in AD has been proposed but is supported by minimal evidence. The basic hypotheses to be tested in this proposal are a) there is increased oxidative stress in the brain in AD and b) elevated iron (Fe) and other trace elements catalyze reactive oxygen species (ROS) formation, enhancing oxidative alterations in biomolecules, which play a role in the pathogenesis of neuron degeneration AD. Our previous studies showed a) an elevation of Al, Fe, Hg, and Si in various brain regions in AD, b) an increase in protein oxidation in the brain in aging and AD and a decline in oxidative-sensitive enzymes in AD, and c) an increase in lipid peroxidation and antioxidant activity in medial temporal lobe structures in AD. This study is designed to address major gaps in our understanding of the role of free radicals in AD by a) quantitating the levels of lipid peroxidation, (malondialdehyde, 4-hydroxynonenal and C3-C10 aldehydes by HPLC), polyunsaturated fatty acids (by HPLC), protein oxidation (protein carbonyl), and DNA oxidation by (GC-MS-SIM); b) quantitating the activity and messenger RNA levels (Northern blots) and protein analysis (Western blots) of superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase; c) determining the activity of glutamine synthetase and creatine kinase, oxidative-sensitive enzymes; d) quantitating bulk levels of Al, Cu, Fe, Hg, Se and Zn by instrumental neutron activation analysis and GFAAS and the cellular level by laser microprobe mass spectrometry and e) quantitating morphologic alterations (amyloid burden, neurofibrillary tangles, neuron and synapse density) by computerized image analysis, all in 4 neocortical regions, hippocampus, amygdala, nucleus basalis of Meynert and cerebellum of short postmortem interval autopsied AD and age-matched controls. These studies will be performed on immediately adjacent tissue segments to allow correlation of these parameters. In addition, the effect of Fe and Cu on ROS formation in synaptosomal membrane fractions from these brain regions will be performed using electron paramagnetic resonance. To define possible mechanisms of neuron degeneration, the effect of Fe and other trace elements on ROS formation, neuron survival and antioxidant enzyme activity in hippocampal neurons in vitro will be performed. This study will lead to a better understanding of one of the proposed pathogenetic mechanisms of neuron degeneration in AD and form a foundation for potential future therapeutic intervention in this disorder.