Melatonin, a novel selective ATF-6 inhibitor, induces human hepatoma cell apoptosis through COX-2 downregulation

Figure 5 Effects of activating transcription factor 6 siRNA on cell apoptosis in HepG2 cells under endoplasmic reticulum stress. A: HepG2 cells were transfected with ATF-6 siRNA for 24 h after pretreatment by tunicamycin (TM) for 8 h. Apoptotic cells were determined by FACS, and the data are expressed as the mean ± SD. A1, Untreated HepG2 cells; A2, HepG2 cells treated by TM only; A3, HepG2 cells treated by combination of TM and ATF-6 siRNA negative control; A4, HepG2 cells treated by ATF-6 siRNA and melatonin; B: Data are presented as the mean ± SD for the independent experiments (^aP < 0.05 vs untreated HepG2 cells; ^bP < 0.01 vs untreated HepG2 cells; ^cP < 0.01 vs HepG2 cells treated with TM and ATF-6 siRNA negative control); C: Cell morphology and percentage of apoptotic cells was examined by TUNEL staining. C1, Untreated HepG2 cells; C2, HepG2 cells treated by TM only; C3, HepG2 cells treated by combination of TM and ATF-6 siRNA negative control; C4, HepG2 cells treated by ATF-6 siRNA and melatonin; D: Data are presented as the mean ± SD for the independent experiments (^bP < 0.01 vs untreated HepG2 cells; ^cP < 0.01 vs HepG2 cells treated with TM and ATF-6 siRNA negative control). ATF-6: Activating transcription factor 6; NC: Negative control.