Identification of Oxidized Proteins in Alzheimer's Disease

Joungil Choi, Identification of Oxidized Proteins in Alzheimer’s Disease. Doctor of Philosophy (Molecular Biology and Immunology). August, 2002. Pages-110. Tables 8. Figures 24. Oxidative modification of specific proteins is central to the pathology of Alzheimer’s disease (AD). The purpose of this study was to identify the oxidation-sensitive proteins in neuronal cells, fibroblasts from AD subjects, and in the blood of AD patients. In all cases, age-matched non-Alzheimer’s samples were used as controls. Proteomic methods were used to isolate and characterize the oxidized proteins. These included two-dimensional gel electrophoresis, immunolocalization of oxidized proteins and identification by MALDI-TOF mass spectroscopic methods. It was hypothesized that knowledge of these critical oxidation-sensitive proteins would shed light on the underlying mechanism of the disease. In addition, it was postulated that these proteins might prove to be biomarkers for early detection and monitoring the progress of the disease. The results show that two different oxidative stressors (H2O2 generated enzymatically, or the amyloid beta peptide, AB25-35) induce apoptotic cell death and oxidation of specific proteins (heat shock protein 60 and vimentin) in skin fibroblasts from AD subjects and in neuronal cells. In addition, the results indicate that susceptibility of these two proteins to oxidative stress is increased in fibroblasts from AD patients, compared to non-AD controls. Pretreatment with antioxidants (e.g., vitamin E or flavonoids) protect these proteins from oxidative damage. Both heat shock protein 60 and vimentin, have been suggested to function as antiapoptotic proteins. Thus, their oxidative damage could lead to the apoptotic neuronal cell death in Alzheimer’s disease. In the blood plasma of AD subjects, isoforms of fibrinogen gamma chain and alpha-1 antitrypsin were found to be oxidized. These proteins exhibited to a two- to six-fold greater specific oxidation index in plasma from AD subjects when compared to controls. Both of these proteins have been suggested to be implicated in oxidation-mediated damage of inflammation in the AD brain.