Fig. 2: Bcl-2 inhibits thapsigragin (TG)-induced ER stress-mediated apoptosis.

a, b Overexpression of control vector (C), wild-type Bcl-2 (WT), and Bcl-2 mutant (mt) in MDCK cells that were treated with 2 μM TG for 48 h and 72 h. a Representative images of cells as observed under a bright-field microscope (scale bar, 100 μm). b Quantitative analysis of the apoptosis ratio that was assessed from the hypodiploid DNA peak of propidium iodide (PI)-stained cells by flow cytometry from five independent experiments. The data were found to be statistically significant at p < 0.01 (indicated by **) and p < 0.001 (indicated by ***) compared to untreated cells (0 h) of the same cell line, and p < 0.05 (indicated by #) and p < 0.01 (indicated by ##) compared to control vector (C) overexpressing cells at the same time point (Student’s t-test). c, d Cells were treated with 2 μM TG, and the cell lysates were harvested at the indicated time points. The lysates were analyzed by SDS-PAGE and Western blotting for Grp78, caspase-12, and the internal control β-actin. Arrow and arrowhead indicate the inactive and active caspase-12, respectively. Representative pictures of three independent experiments. c Lower panel, densitometry was performed to quantify the relative level of Grp78 expression from three independent Western blots. The data were found to be statistically significant at p < 0.001 (indicated by ***) compared to control vector (C)-overexpressing cells at the same time point (Student’s t-test). e Caspase-3 activity was measured using the fluorogenic substrate DEVD-AFC cells treated with 2 μM TG for 6 h or 12 h. The data were found to be statistically significant at p < 0.01 (indicated by **) compared to control vector (C)-overexpressing cells at the same time point (Student’s t-test)