Extrinsic Apoptosis Pathway Altered by Glycogen Synthase Kinase-3β Inhibitor Influences the Net Drug Effect on NSC-34 Motor Neuron-Like Cell Survival

Figure 1

Effect of the glycogen synthase kinase-3β (GSK-3β) inhibitor VIII on viability of serum-deprived NSC-34 cells. (a) NSC-34 cell viability after serum deprivation was evaluated by the CCK-8 assay. NSC-34 cells were incubated for 72 h (h) under a serum withdrawal condition, and cell viability was measured with the CCK-8 assay. As serum deprivation time elapsed, cell viability decreased. Data are mean (% of viable cells of the control) ± standard error (SE). (compared with viability of control cells under normal conditions with growth factors). (b) GSK-3β activity was measured indirectly by measuring the immunoreactivity (IR) ratio of phosphorylated tau (Ser396)/total tau after GSK-3β inhibitor VIII treatment. NSC-34 cells were incubated in serum-deprived media with or without the GSK-3β inhibitor (0, 50, 200, and 1000 nM). Western blot results for phosphorylated tau (Ser396) and total tau are indicated following each concentration. As the GSK-3β inhibitor dose increased, the immunoreactivity (IR) ratio of phosphorylated tau (Ser396)/total tau decreased. Quantitative data of IR ratio is presented as arbitrary units. and (compared with control under serum deprivation only) and and (compared with groups treated with 50 nM GSK-3β inhibitor VIII). (c) CCK-8 assay after GSK-3β inhibitor treatment in 60 h serum-deprived NSC-34 cells. Cell viability at each GSK-3β inhibitor concentration is marked as mean (% of cell viability under normal conditions) ± SE. Protective effect was maximal at 200 nM of the GSK-3β inhibitor, but these protective effects decreased above 200 nM. (compared with control under serum deprivation only). (compared with 200 nM GSK-3β inhibitor-treated group).

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