The time dependency of ABCB1 mRNA expression in human RPTECs.A, temporal expression profiles of ABCB1 mRNA in mock-transduced and ADAR1-KD RPTECs after treatment with 100 nM DEX. The mRNA levels were assessed by quantitative real-time RT-PCR analysis and their expression levels were normalized to that of 18S rRNA. Values are the mean with S.D. (n = 4). The value of mock-transduced RPTECs before DEX treatment was set at 1.0. There were significant time-dependent variations in ABCB1 mRNA levels in mock-transduced and ADAR1-KD RPTECs (F5,18 = 12.280, p < 0.001 for mock-transduced, F5,18 = 9.835, p < 0.001 for ADAR1-KD; ANOVA). ∗p < 0.05; significant difference between the two groups (t6 = 2.994, p = 0.024; unpaired t-test, two-sided). B, the luciferase activity of ABCB1 [2.8kb]::Luc in RPTECs 32 and 44 h after DEX treatment. Values are the mean with S.D. (n = 4). C, the stability of ABCB1 mRNA in RPTECs 32 or 44 h after DEX treatment. Cells were treated with 5 μM ActD 32 or 44 h after DEX treatment, and then RNA was extracted at the indicated time points after ActD treatment. The mRNA levels were assessed by semiquantitative RT-PCR analysis and their expression levels were normalized to that of 18S rRNA. Values are the mean with S.D. (n = 6). The value at 0 h (the time of the initiation of ActD) was set at 1.0. ∗p < 0.05; significant difference between the two groups at the corresponding time point (F7,40 = 16.020, p < 0.001; ANOVA with Tukey–Kramer’s post hoc test).