Oligomeric and fibrillar Aβ42 increase levels of endogenous APP in mouse primary astrocyte cultures. C57BL/6J mouse primary astrocyte cultures were treated with 10 μM oligomeric or fibrillar Aβ42. Following treatment, cells were harvested for either APP immunoblot (A, B), immunofluorescence microscopy (C), or mRNA quantification by TaqMan RT-PCR (D). Treatment times are indicated, or are 24 h (C). Olig., Aβ42 oligomer treatment; Fibr., Aβ42 fibril treatment; OC, oligomer vehicle control; FC, fibril vehicle control. GFAP immunosignals served as loading controls. Aβ42 oligomers and fibrils dramatically increased APP protein levels to ~400-500% of controls at early treatment times (A-C) that correlated with an early rise in APP mRNA level (D). Levels of both APP protein and mRNA were transiently elevated by Aβ42, and returned to normal by 96 h. Asterisks indicate significant differences as compared to vehicle controls (*: p < 0.05; ***: p < 0.001; n = 3). Error bars, SEM.