Role of the Death Receptor and Endoplasmic Reticulum Stress Signaling Pathways in Polyphyllin I-Regulated Apoptosis of Human Hepatocellular Carcinoma HepG2 Cells

Figure 4

ER stress inhibitor promotes cell death. HepG2 cells were pretreated with 4-PBA (20 μM) for 2 h, followed by incubation with or without PPI(2.5μM) for 12 h. Analysis of IRE-1 and GRP78 protein expression was conducted via western blotting (a). Cell morphology was observed via microscopy (magnification, x100) and cells stained with Hoechst 33258 were observed under a fluorescence microscope (magnification, x400), white arrows indicated the apoptotic cell (b). Apoptotic cells were detected by flow cytometry (c). The experiments were repeated three times. The results were presented as the mean ± standard deviation. p < 0.05 and p < 0.01, vs. the negative control group; p < 0.01 vs. 2.5 μM PPI group. ER, endoplasmic reticulum; IRE-1, endoribonuclease inositol-requiring enzyme 1; PPI, polyphyllin I.

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