Protective effects of rice dreg protein hydrolysates against hydrogen peroxide-induced oxidative stress in HepG-2 cells.

In this paper, the effects of rice dreg protein hydrolysates (RDPHs) obtained by various proteases on hydrogen peroxide-induced oxidative stress in HepG-2 cells were investigated. Cell cytotoxicity was evaluated through the aspects of cell viability, ROS level, antioxidant enzyme activity, and production of malondialdehyde (MDA). Cell apoptosis was assessed by flow cytometry. Molecular weight distribution was analyzed by gel permeation chromatography, and amino acid composition was measured using an automatic amino acid analyzer. The survival of cells and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were significantly increased through the pre-incubation of HepG-2 cells with RDPHs before H2O2 exposure. Additionally, these pretreatments also resulted in a reduction in ROS and MDA levels. As a result, apoptosis and loss of mitochondrial membrane potential of the HepG-2 cells were alleviated. Furthermore, the protective effects of protein hydrolysates obtained by various proteases were noticeably distinct, in which RDPHs prepared by alkaline protease showed higher antioxidant activities. The difference in the protective effects might be attributed to the specific peptide or amino acid composition. Therefore, enzymatic hydrolysis with different enzymes studied here could attenuate H2O2-induced cell damage, and the type of protease greatly influenced the anti-oxidative activity. Particularly, optimum use of Alcalase could produce peptides with higher antioxidant activity.