The Cytotoxic Effect of Thymoquinone Enhance on HepG2 Cell Line due to Induction of Fenton Reaction by Hydrogen Peroxide: An In Vitro and In Silico Study

OBJECTIVE: Thymoquinone (TQ) is a component derived from the volatile oil of Nigella sativa. Fenton reaction induction is a well-known strategy to prevent the growth of cancer cells which can stimulate by hydrogen peroxide. This study was designed to investigate the TQ effects on hydrogen peroxide-induced cytotoxicity. METHODS: In this study, HepG2 cell survival, reactive oxygen species (ROS) production, cell membrane integrity, and changes of superoxide dismutase (SOD)/ catalase (CAT) activity were evaluated following incubation of HepG2 cells with 31 μM hydrogen peroxide and different concentrations of TQ (18.5, 37 and 75 μM). In addition, molecular docking studies on the interference of TQ with CAT/SOD enzymes were investigated. RESULTS: Our findings showed that TQ low concentration can increase the survival of HepG2 cells when exposed to hydrogen peroxide, and on the contrary, its high concentration can potentiate cytotoxicity induced by hydrogen peroxide. The TQ alongside hydrogen peroxide increased the production of ROS, which was related to increase CAT and SOD activity in the HepG2 cells. Molecular docking findings showed that TQ effects on the formation of free radicals were not related to its chemical interference with the structure of the SOD/CAT molecules. CONCLUSION: Fenton reaction induction may increase the effectiveness of TQ in preventing HepG2 cells proliferation.