Microglia and the Generation of Beta-Amyloid in Alzheimer’s Disease

Alzheimer’s disease increases in incidence with age. This clearly links the disease to changes in the brain that occur with normal aging. One of the changes that occur in the brain is an increase in number of dystrophic microglia, and this change has been associated with an increased storage of the metal iron. We have been able to develop a microglial model that mimics the changes in microglia seen in aging by forcing cultured microglia to take up and store large amounts of iron. These “iron-fed” microglia show changes in iron storage, ferritin expression, and an increased release of neurotoxic substances. We have also shown that co-culture with these microglia causes an increase in amyloid precursor protein (APP) cleavage. Therefore we have been able to create a model to study increase beta-amyloid generation combined with an age related change to microglia. From our preliminary data it appears that iron-fed microglia specifically kill cells that have an increase level of APP cleavage. Consequently, we would also wish to assess whether the cell death is because of the presence of increased levels of beta-amyloid or whether the level of APP cleavage is linked to an increased susceptibility of the cells to toxic factors. This project will allow us to assess how an age related change could contribute to factors known to be important in Alzheimer’s disease. The student involved in this project will use a range of techniques to carry out the project which will include, ELISA assays of cytokines or beta-amyloid, fluorometric assays for detection of oxidative stress or luciferase assays to detect APP cleavage, western blots and other basic biochemical technques as well as extensive use of cell culture techniques and molecular biology. By the end of the project we hope to have developed a new model of APP cleavage that takes into account age related changes in microglia. Furthermore, we will have identified and assessed the importance of two new concepts to the Alzheimer’s field. First, whether age dependent factors need to be considered in Alzheimer’s disease models, and second, whether it is the generation of beta-amyloid by a cell rather than its presence that increases the likelihood of cell death.