Fig. 7

Aβ24 fragment diminishes Aβ42 clearance through the BBB. a Graphical representation of the in vitro BBB model composed by a monolayer of brain endothelial cells seeded and cultured on an inverted matrix-coated porous membrane, allowing an apical compartment (donor-“brain”-side) physically separated from the basolateral chamber (receiving-“blood”-side). b Representative images of brain endothelial cells tightly wedged together and c expressing cell type-specific tight junctional proteins claudin-5 (green) d and ZO-1 (green), and e the gap junction protein Connexin-43 (green). Nuclei counter-stained with DAPI (blue). Scale bars: 20 μm. f Barrier properties monitored in terms of gradual increase in transendothelial electrical resistance (TEER) during cell monolayer’s formation over time. g and h Apical-to-basolateral exchange across endothelial monolayer of fluorescent Aβ42 or scramble Aβ42 control peptide, 1 μM g) or 100 nM h), over 120 min in presence or absence of Aβ24 at equimolar concentration. Quantification of unidirectional trans-endothelial Aβ42 transport by fluorescence spectrophotometry n ≥ 3 experiments; statistical analysis was performed by One way Anova, followed by Bonferroni’s post hoc test for multiple comparisons (**P < 0.01; ***P < 0.001). i) Dot blot analysis of medium collected in the abluminal compartment 120 min after brain endothelial cell monolayers exposure to Aβ42 or Aβ42/Aβ24 mix. Histograms represent the densitometry quantification upon staining with anti-6E10 antibody. Results are expressed as mean values of triplicates in each experimental group ± SE. Values were normalized on control; statistical analysis was performed by unpaired T test (**P < 0.01). j Aβ42 (pg/ml) absolute values detected by ELISA in the serum of mice 1 week after H-Aβ42 intracranical injection. k Aβ42 serum level measured 1 week after the injection of vehicle, H-Aβ42 and H-Aβ42/H-Aβ24 mix (2pmol of H-Aβ24 plus 2pmol of H-Aβ42) or l H-Aβ42/H-Aβ24 mix (8pmol of H-Aβ24 plus 8pmol of H-Aβ42). N = 4 to 6 animals per experimental group. Values are normalized on vehicle. Statistical analysis was performed by unpaired T test (*P < 0.05)