Figure 1.

Effect of Aβ₄₂ on MKP1 expression in PC12 cells.

(A) PC12 cells were treated with the indicated concentrations of Aβ₄₂ for 24 hours. Cell viability was assessed with the cell counting kit-8 assay. (B) PC12 cells were treated with 10 μM Aβ₄₂. At the indicated time points, total RNA was extracted for quantitative real time-polymerase chain reaction for MKP1 mRNA expression with GAPDH as the internal control. The result is expressed as a percentage of the value at 0 hours. (C) PC12 cells were treated with 10 μM Aβ₄₂. At the indicated time points, total protein was extracted for immunoblotting of MKP1 protein with GAPDH as the loading control. The relative expression of MKP1 to GAPDH was assessed by densitometric analysis using ImageJ software. MKP1 expression is shown relative to that at time 0. Data are expressed as the mean ± SD (six separate experiments for each time point). Intergroup comparison was performed using analysis of variance. *P < 0.05, **P < 0.01, vs. control group (0 μM Aβ₄₂ or value at 0 hours). Aβ₄₂: Amyloid beta 42; MKP1: mitogen-activated protein kinase phosphatase 1.