Differential regulation by beta-amyloid peptides of intracellular free Ca2+ concentration in cultured rat microglia.

We have previously shown that exposure to beta-amyloid peptides alters microglial activity and viability. It is thought that beta-amyloid peptides induce toxicity in neuronal cultures by destabilizing Ca2+ homeostasis. To investigate the effects of beta-amyloid peptides on intracellular free Ca2+ concentration ([Ca2+]i) in cultured microglia, we used Fura-2 imaging. Exposure to 25 microM beta-amyloid-(25-35) induced increases in 2+]i within 1 h. In contrast, exposure to 25 microM beta-amyloid-(1-42), the full-length homolog to the beta-amyloid protein deposited in plaques, does not, over the same time period. However, the average [Ca2+]i of microglia is increased by a 6 h exposure to beta-amyloid-(1-42). Thus, beta-amyloid-(25-35) can alter [Ca2+]i in microglia on a different time scale than beta-amyloid-(1-42), indicating a specificity in the response of these cells as compared to neurons.