Figure 6

Both N2a cell- and human CSF-derived exosomes prevent AD brain-derived Aβ from inhibiting in vivo LTP. (A) Immunoprecipitation/Western blot analysis of TBS extracts of AD brain. Comparing to synthetic Aβ_1-42 loaded for control, AD-Aβ⁺ contained 2.2 ng/ml of Aβ monomer and 0.76 ng/ml of Aβ dimer whereas Aβ was completely removed from AD-Aβ^-. AD stands for the starting AD brain extract, TBS for buffer vehicle and N.S. denotes non-specific bands, presumably that arise due to the reaction of the IP antibody with the antibodies used for Western blotting. (B) Infusion of AD-Aβ⁺ disrupted LTP in vivo, but not by AD-Aβ^-. Animals were pre-injected with PBS (5μl, asterisk) followed by a second injection (hash) of either AD-Aβ^- or AD-Aβ⁺ containing ~18 pg Aβ. An arrow indicates HFS application and insets show representative traces at the color-matched time points. Calibration: 1.5 mV and 10 ms. (C) Cell-derived exosomes prevented AD-Aβ⁺ from disrupting LTP. In animals that received N2a cell-derived exosomes (4 μg in 5 μl, asterisk), AD-Aβ⁺ (6 μl, hash) no longer inhibited LTP, similar to animals injected with AD-Aβ^- (6 μl, hash). Arrow, insets and calibration as in B. (D) The exosomes prepared from human CSF were detected in fractions with a buoyant density around 1.149 g/ml and contained Flotillin-1 and PrP^C. (E) Infusion of human CSF-derived exosomes (huExo) abrogated the disruption of LTP by AD-Aβ⁺. Administration (asterisks, total 10 μl i.c.v., spread over two infusions) of samples of AD-Aβ⁺ extracts after 30 min pre-incubation with CSF exosomes (total 1 μg) no longer inhibited LTP. Arrow, insets and calibration as in B. (F) A summary histogram of the data in B, C and E with statistical comparisons. Error bars, ± SEM. Statistical significance was expressed as **, P < 0.01; ***, P < 0.001 comparing to respective control.