Intracellular antioxidant activity and apoptosis inhibition capacity of PEF-treated KDHCH in HepG2 cells

The effect of pulsed electric field (PEF) treatment on the intracellular antioxidant and apoptotic activity of the peptide Lys-Asp-His-Cys-His (KDHCH) was examined using model HepG2 cells. First, PEF treatment conditions specific for the antioxidant peptide were optimized, and it was found that PEF treatment could enhance DPPH, ABTS and hydroxyl radical scavenging capacity of KDHCH. Second, KDHCH subjected to PEF treatment at 1800 Hz and 15 kV/cm was investigated using various intracellular antioxidant assays. PEF treatment decreased the EC50 value and increased the protective ability of oxidative stress inhibition and reactive oxygen species (ROS) scavenging activity of KDHCH. Furthermore, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-PX) and glutathione reductase (GR) activities of KDHCH-pre-treated HepG2 cells increased significantly compared with those of the H2O2 damaged group, whereas lactate dehydrogenase (LDH) and malonaldehyde (MDA) content were decreased. PEF-treated KDHCH exhibited an increased capacity to maintain the stability of mitochondrial membrane potential (MMP) and reduced the level of caspase-3. These results indicate that PEF treatment can enhance the intracellular antioxidant activity of KDHCH, which can inhibit the effect of H2O2 oxidation on HepG2 cells by inhibiting the accumulation of intracellular ROS, regulating antioxidant related enzymes, and blocking the apoptotic mitochondrial pathways activated by ROS.