Figure 1. Cytokinins acting on the A_2A-R prevent serum deprivation-induced PC12 cell apoptosis.

(A) Serum-contained and serum-deprived cells were treated with or without the indicated reagent(s) for 24 h. NGF were treated in 100 ng/ml. Besides, cells pretreated with zeatin riboside (100 µM) for 3 h were treated with or without H₂O₂ (25 µM) for 24 h. Cell viability was expressed as a percentage of the results from the MTT assay with respect to the mean value of the serum-contained control group. Data points represent the mean ± SEM (n = 3∼6). *p<0.05, compared to its serum-deprived group. #p<0.05, compared to the H₂O₂-treated group. (B) Serum-deprived cells were pretreated with or without the indicated reagents for 30 min. Zeatin riboside or CGS (0.1 µM) was added for another 24 h. Cell viability was expressed as a percentage of the results from the MTT and trypan blue exclusion assays with respect to the mean value of the serum-contained control group. Data points represent the mean ± SEM (n = 3∼6). *p<0.05, compared to its serum-deprived group. (C) Serum-deprived cells were pretreated with or without 1 µM ZM or 1 µM SCH for 30 min. Zeatin riboside was added for 24 h and followed by Annexin V-FITC staining. Cells were subjected to image and cytometry analysis. Bar represents 50 µm. Data points represent the mean ± SEM (n = 3∼6). *p<0.05, compared to the serum-contained control group. (D) Serum-contained or -deprived cells in the presence or absence of zeatin riboside were harvested and subjected to a Western blot analysis. The relative optical density of the bands were quantified by densitometry relative to actin and normalized to the levels in serum-contained control group or in serum-deprived for 24 h group. Data points (mean ± SEM) represent one out of three independent experiments that gave similar results. *p<0.05, compared to its serum-containing control group. #p<0.05, compared to its 24 h serum-deprived group. AU represents arbitrary unit.