Apoptotic nuclear morphology was assessed using Hoechst 33342 (Beijing Solarbio Science & Technology Co., Ltd., Beijing, China) in PBS buffer, as described previously (33 (link)). HepG2-mtGrx1-roGFP2 cells were grown in culture at 37°C for 12 h. Following 12 h of incubation at 37°C, the cells were perfused with oridonin (25 µM) in the presence or absence of SS31 (100 nM) at 37°C for 8 h. For morphological observation, cells were incubated with Hoechst 33342 (1 mg/ml) for 25 min at 37°C, washed and then examined using an Olympus FV1000 confocal laser scanning microscopy (Olympus Corporation) equipped with a ×40 objective at 350 nm excitation and 461 nm emission wavelengths.