Figure 5. LRP1 in brain endothelial cells substantially contributes to [¹²⁵I] Aβ_1–42 transcytosis in vitro.

[¹²⁵I] Aβ_1–42 transport across the primary mouse brain capillary endothelial cell monolayer was studied in the presence of 1 μCi/ml [¹⁴C]-inulin to determine the transcytosis quotient (TQ). Transcytosis was analyzed in the brain-to-blood direction (abluminal to luminal) by measuring the dpm for [¹⁴C]-inulin and the cpm for the TCA-precipitable [¹²⁵I] radioactivity. The TQ of Lrp1_BE^–/– brain endothelial cells was normalized to Lrp1_BE^fl/fl brain endothelial cells. (A) Transport at a physiological concentration of 0.1 nM Aβ (Lrp1_BE^fl/fl, n = 18; Lrp1_BE^–/–, n = 14; 4 independent experiments). (B) Higher contribution of LRP1 in transport of [¹²⁵I] Aβ_1–42 at higher Aβ concentrations (n = 6, n = 4, n = 5, n = 4, n = 3, n = 4, n = 3, n = 3 from left to right). Data represent mean ± SEM. For statistical analyses, unpaired t test was used. *P < 0.05, **P < 0.01, ***P < 0.001.