ATBF1 protein and mRNA expression levels increased in primary cortical neurons after treatment with Aβ1-42 and DNA-damaging drugs, namely, etoposide (Etop) and homocysteine (Hom). A, primary cortical neurons were seeded at a density of 1 × 106 cells/ml in poly-d-lysine-coated 60 mm culture dishes. Three days after plating, the cells were treated for 16 h with 10 μM Aβ1-42, 1 μM etoposide, or 250 μM homocysteine, and the cells were then harvested. The expression levels of ATBF1 and p53 were determined by Western blot analysis using the anti-ATBF1 and anti-p53 antibodies. A, a representative immunoblot is shown (upper panel), and bands were quantified by densitometry, normalized to actin, and expressed as a value relative to that of the control (lower panel). B and C, primary cortical neurons were treated for 16 h with 0, 2.5, 5, or 10 μM Aβ1-42 (B), or 250 μM homocysteine or 1 μM etoposide (C). ATBF mRNA expression level was determined by real-time PCR analysis. The expression level of ATBF1 mRNA was normalized to the corresponding amount of actin mRNA and expressed as a value relative to that of the control. All the values are presented as the mean ± SEM of three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.001 vs control, as determined by Student's t-test.