P4‐314: Inhibitors Of Catalase‐Amyloid Interactions Protect Cells From Oxidative Stress And Toxicity Induced By Aggregated Alzheimer’s‐Related beta‐Amyloid Peptides

While oxidative stress is commonly associated with aging, increased oxidative damage mediated by oxidative stress (such as increased oxidation of proteins, lipids and nucleic acids) and subsequent neuronal loss in β-amyloid (Aβ)-rich regions of the brain is a distinct feature of Alzheimer's disease (AD). Compelling evidence shows a strong correlation between accumulation of aggregated neurotoxic b-amyloid peptides and oxidative stress in the brains of patients afflicted with AD. One hypothesis for this correlation involves the direct and harmful interaction of aggregated Aβ peptides with cellular proteins responsible for maintaining normal, cellular levels of reactive oxygen species (ROS). To identify specific, destructive interactions of Ab peptides with cellular antioxidant enzymes and to inhibit these harmful protein-amyloid interactions. Using cell-free and cellular assays, in addition to fluorescence microscopy, we demonstrate that exposure of human neuroblastoma cells to cytotoxic preparations of aggregated Ab peptides results in significant intracellular co-localization of Ab with catalase-an antioxidant enzyme responsible for catalyzing the degradation of the ROS, hydrogen peroxide (H2O2)-and that these catalase-Ab interactions contribute to an observed increase in cellular levels of H2O2. Furthermore, we evaluate the effects of generating protein-resistive surface coatings on aggregated Ab peptides in cells by using two oligo(ethylene glycol) derivatives of 6-methylbenzothiazole aniline (BTA-EG4 and BTA-EG6) as synthetic molecular probes that exhibit the following characteristics: 1)capability of generating protein-resistive surface coatings on aggregated Ab peptides (to inhibit catalase-amyloid interactions in cells), 2)lack of toxicity, 3)cell permeability, 4)capability of localizing to the same subcellular compartments of cells as Ab, 5)intrinsic fluorescence properties (to visualize the intracellular localization of the molecules), and 6)chemical stability in oxidative environments. We show that these small molecule inhibitors of catalase-amyloid interactions protects the hydrogen peroxide-degrading activity of catalase in an Ab-rich environment, leading to reduction of the co-localization of catalase and Ab in cells, inhibition of Ab-induced increase in cellular levels of H2O2 (Figure 1), and neutralization of the toxicity of Ab peptides. These studies provide evidence for the important role of catalase-amyloid interactions in Ab-induced oxidative stress and propose a novel molecular strategy to inhibit such harmful interactions in AD.