Abstract: Objective: This experiment was conducted to study the effect of Lactobacillus casei on antioxidant function of HepG2 cells under oxidative stress. Methods: HepG2 cells were randomly divided into 3 groups: control, model (H2O2 induced oxidative stress) and treatment (H2O2 plus Lactobacillus casei) groups. Antioxidant activity in culture supernatants and lysates of HepG2 cells at 12 and 48 h were measured. 4’,6-diamidino-2-phenylindole (DAPI) staining was applied to observe cell morphology in different groups by fluorescence microscopy. Results: Total antioxidant capacity (T-AOC), and glutathione peroxidase (GSH-Px) and catalase (CAT) activities in the culture supernatant, as well as superoxide dismutase (SOD) activity in the cell lysate at 12 h in the treatment group significantly increased by 80%, 30%, 124% and 22%, respectively when compared with their counterparts in the model group (P < 0.05). At 24 h, the activities of T-AOC, SOD, GSH-Px, CAT and peroxidase (POD) were significantly increased (P < 0.05), and the content of glutathione (GSH) and malondialdehyde (MDA) in the culture supernatant in the treatment group significantly decreased by 29% and 63% (P < 0.05); a significant decrease of 20% in SOD activity in the cell lysate was observed for the treatment group compared with the model group (P < 0.05). Moreover, the number of damaged cells was reduced in the treatment group than that in the model group, and most cells in the former group had normal morphology. Conclusion: The addition of Lactobacillus casei could increase antioxidant function of HepG2 cells under oxidative stress.

Key words: Lactobacillus casei, HepG2 cells, antioxidant, oxidative stress, cell lysates