P1‐293: An investigation of mitochondrial oxidative stress in Alzheimer's disease

Abstract

Current therapy for Alzheimer's disease (AD) focuses on delaying progression, illustrating the need for more effective therapeutic targets. Increases in reactive oxygen species (ROS) in the brain link multiple hypotheses for the cause of AD. Mouse models display elevations in ROS prior to both Aß plaque and neurofibrillary tangle formation. In particular, elevations in mitochondrial ROS as a result of Aß aggregation have been observed throughout AD pathology. Antioxidant trials have produced mixed results in mouse models and patients, perhaps due to lack of specificity and targeting. Learning and memory deficits are present in the Tg2576 model of AD prior to plaque formation and ROS elevation. In addition, recent studies have linked mitochondria specific antioxidant, superoxide dismutase 2 (SOD2) with recovery of AD pathology in the Tg2576 mouse model of AD. When Tg2576 mice were crossed with mice that overexpress SOD2, (Tg2576/SOD2 mice) both learning and memory impairment as well as plaque burden were improved, indicating that mitochondrial ROS may play a large role in AD pathogenesis. In order to identify the possible source of ROS, we conducted an investigation in vitro using PC12 cells treated with Aß to examine changes in mitochondrial ROS using both cytosolic (DCFH) and mitochondrial (MitoSOX) ROS dyes. We show that Aß1-42 specifically increased ROS from the mitochondria in a dose dependent manner. Mean fluorescence intensity for DCFH was 220.578 [0uM], 278.258 [1uM], and 289.349 [5uM], whereas MitoSOX intensity was 325.17 [0uM], 363.415 [1uM], and 850.718 [5uM]. These results demonstrate both that the source of ROS likely mitochondrial superoxide and its relationship to a sub-lethal concentration of Aß1-42. In addition, using sub-cellular site-specific redox probes directed to the mitochondria we are assessing the contribution of mitochondrial superoxide (mito-cpYFP) and hydrogen peroxide (pHyper-dMito) to the Aß induced ROS burden in neurons. Our findings implicate the development of specific, targeted mitochondrial antioxidants for AD patients. Identifying the sub-cellular source, the specific ROS species produced, and the mechanisms by which increased mitochondrial ROS influence neuronal function in AD will allow for the development of more effective targeted therapeutic interventions to combat the deleterious effects of this devastating disease.