Expression of APP products in differentiated SH-SY5Y neuroblastoma cells and in normal human astrocytes. The differentiated SH-SY5Y-cells were treated with IL-18 (100 ng/mL) without or with IL-18 bp (0.5 μg/mL) for described times. IL-18 treatment increased (A) APP synthesis during 6-h and 48-h treatment and (B) Thr668 phosphorylation of APP during 6-h treatment in SH-SY5Y cells. IL-18 treatment also increased the protein levels of (C) C99 (approximately 11 kD) and Aβ (approximately 4 kD) (WO-2 antibody), the BACE-1 and γ-secretase cleavage products of APP in (a) differentiated SH-SY5Y cells but also in (b) normal human astrocytes. When examined from the same SH-SY5Y culture medium, (D) total sAPP was only slightly increased by the IL-18 treatment (22C11 antibody detects sAPPα (76 kD) and sAPPβ (74 kD)). When WO-2 antibody was used (detects only sAPPα) for the same samples, the protein level of sAPPα was less in IL-18 treated culture medium, compared to untreated control (Ctrl), showing indirectly the increase in sAPPβ production by IL-18 in SH-SY5Y medium.