Fig. 8
Neuronal cell death is induced by secreted microvesicles. Illustration of the experimental setup (a). Electron microscopy images of Aβ42 protofibril exposed co-cultures demonstrate microvesicle (*) secretion from a single astrocyte (b) and a larger (c) and smaller (d) microvesicle present in the cell culture medium. Western blot analysis show that the isolated microvesicles express Flotillin-1, but that the levels are unchanged in Aβ42 protofibril treated cultures, compared to controls (e). TUNEL assays demonstrate a significant increase (P < 0.001) in apoptotic neurons following treatment with microvesicles from Aβ42 protofibril exposed co-cultures (465.4 ± 150.4), compared to microvesicles from untreated co-cultures (308.3 ± 109.2) (f). The experiments were performed in triplicates with independent cell cultures and 10 images/experiment were analyzed. Microvesicles isolated from medium collected 6 and 12 days after Aβ42 protofibril exposure contain Aβ as revealed in Aβ1-x (396.9 ± 167.2 pM) and Aβx-42 (1239.0 ± 438.7 pM) ELISA. The Aβ1-x concentration is lower than Aβx-42, indicating that there is a truncation of the Aβ42 N-terminus (g). Duplicate samples from 3 independent experiments were analyzed. Mann–Whitney U-test ***P < 0.001. Scale bars: b = 1 μm, c–d = 100 nm