Figure 6.

The antiapoptotic effect of 1,2-NQ is mediated via the epidermal growth factor receptor–PI3K–Akt pathway in A549 cells.A–D, cells were stimulated with the indicated concentrations of 1,2-NQ for 10 min and were then incubated with serum-free medium. After 72 h, cells were observed using a phase contrast microscope (A), and cell viability was then determined by a water soluble tetrazolium salt assay (B). The scale bar represents 100 μm. Cells were treated with Hoechst 33342 for 30 min and were then observed using a fluorescence microscope. The arrows show the apoptotic cells. C and D, the scale bar represents 50 μm. The data are expressed as the mean ± SEM values. ∗p < 0.05 and ∗∗p < 0.01 versus control. E, cells were incubated with serum-free medium for 12 h and were then stimulated with 1,2-NQ at indicated concentrations for 10 min. After the incubation of serum-free medium for 24 h, cells were stained by annexin V–FITC/propidium iodide and then observed using a fluorescence microscope. Annexin V/propidium iodide double positive cells were counted as apoptotic cells. The data are expressed as the mean ± SEM values. ∗p < 0.05 versus 0 μM 1,2-NQ. F, cells were cultured with serum-free medium for 24 h and were then exposed to 1,2-NQ (10 μM) for 10 min after treatment with LY294002 (10 μM) and OSU-03012 (5 μM) for 12 h. Cells were treated with tyrphostin A25 (100 μM) in serum-free medium for 24 h after stimulation with 10 μM 1,2-NQ. After 72 h, cell viability was determined by a water soluble tetrazolium salt assay. G and H, cells were stimulated with 1,2-NQ for 10 min and were then incubated with serum-free medium for 24 h. The lysates were analyzed by Western blotting with anti-PARP or anticleaved PARP antibodies. Statistical analysis was carried out by two-way ANOVA with Bonferroni's multiple comparisons test. The data are expressed as the mean ± SEM values. ∗p < 0.05 and ∗∗∗p < 0.001 between the two indicated groups. 1,2-NQ, 1,2-naphthoquinone; PARP, poly(ADP-ribose) polymerase.