Fig. 2.

Hypoxia increases Aβ production by up-regulating BACE1 activity. (A) SH-SY5Y cells stably overexpressing Swedish mutant APP were exposed to 2% O₂ for 0, 12, or 24 h. C20 antibody was used to detect APP CTFs; 208 antibody was used to detect BACE1. (B and C) Quantification of C99 (B) and BACE1 protein (C) levels. ∗, P < 0.001 by ANOVA. (D and E) ELISA was performed to measure Aβ40 (D) and Aβ42 (E) in culture media from SH-SY5Y cells stably overexpressing Swedish mutant APP exposed to 2% O₂ (hypoxia) or 21% O₂ (normoxia) for 24 h. ∗, P < 0.0001 by Student's t test. (F) WT APP695 cell HAW1 was cultured under 2% O₂ for 12 h, and APP CTFs were detected with C20 antibody. (G) The levels of CTFβ including C99 and C89 were quantitated. ∗, P < 0.001 by Student's t test. (H and I) The conditioned media from the same hypoxia-treated cells were analyzed for Aβ40 (H) and Aβ42 (I) levels. The numbers represent mean ± SEM; n = 3; ∗, P < 0.0001 by Student's t test.