Figure 2: Ligase IV is involved in the neuroprotective mechanisms of SB216763. (A) Ligase IV mRNA expression was significantly upregulated in serum-starved retinal neurons pretreated with SB216763 compared with control cells. (B, C) SB216763 pretreatment significantly upregulated ligase IV protein expression in serum-starved retinal neurons, as evidenced by western blot analysis. (D, E) siRNA interference assays were employed to downregulate ligase IV protein expression in serum-starved retinal neurons pretreated with SB216763 or DMSO. (F) SB216763 pretreatment significantly improved cell viability in serum-starved retinal neurons compared with control treatment; however, downregulation of ligase IV by siRNA assay markedly suppressed this effect. Data are expressed as mean ± SEM compared with the control group. n = 3 for each group. *P < 0.05, **P < 0.01, vs. control (Con) group (Student's t-test). DMSO: Dimethyl sulfoxide; Gapdh: glyceraldehyde 3-phosphate dehydrogenase; GSK-3β: glycogen synthase kinase-3β; SB216763: a GSK-3β inhibitor; siRNA: small interfering RNA.