Abstract: Objective: Lowly and highly differentiated pheochromocytoma (PC12) cells were used to investigate the antioxidant capacity and underlying mechanism of curcumin. Methods: The relative proliferation rate of PC12 cells was measured by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay, and the concentration and duration of curcumin treatment were determined. The effect of curcumin on the total antioxidant capacity (T-AOC) of PC12 cells was detected by 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) cation radical scavenging and ferric ion reducing antioxidant power (FRAP) methods. The level of reactive oxygen species (ROS) was measured by the dichloro-dihydro-fluorescein diacetate assay. The activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) were determined using corresponding commercial kits, and the expression levels of antioxidant enzyme genes were detected by real-time fluorescent quantitative polymerase chain reaction. Results: Upon 10 μmol/L curcumin treatment for 24 h, the relative proliferation rate of lowly differentiated PC12 cells remained unchanged, while it was significantly inhibited in highly differentiated cells (P < 0.05). Treatment with curcumin at all concentrations tested significantly increased the T-AOC of both lowly and highly differentiated PC12 cells (P < 0.01), and reduced ROS level (P < 0.01). Furthermore, the activities and gene expression of SOD, CAT and GSH-Px were enhanced by curcumin. Conclusion: Curcumin can enhance the T-AOC, reduce ROS level, alleviate oxidative stress, and maintain cell homeostasis via increasing the activities and gene expression levels of SOD, CAT and GSH-Px.

Key words: plant polyphenols; pheochromocytoma cells; oxidative stress