Neuroprotective effects of two selenium-containing peptides, TSeMMM and SeMDPGQQ, derived from selenium-enriched rice protein hydrolysates on Pb2+-induced oxidative stress in HT22 cells

Abstract Immunomodulatory peptides with the sequences TSeMMM and SeMDPGQQ from selenium (Se)-enriched rice protein hydrolysates (SPHs) were identified in our previous study. We synthesized these two peptides to study whether they have neuroprotective effects on Pb2+-induced oxidative stress in mouse hippocampal HT22 cells, SPHs and a purified SPH fraction (SPHs-2) were used to compare the effects. Peptides pretreatments significantly suppressed Pb2+-induced cytotoxicity by increasing cell viability and decreasing cell apoptosis. TSeMMM and SeMDPGQQ reduced nitric oxide (NO) levels by 37.47% and 14.72% of Pb2+ group, as well as lactate dehydrogenase (LDH) release by 12.98% and 6.32% of Pb2+ group. TSeMMM and SeMDPGQQ could increase the activities of antioxidant enzymes; for example, the activity of superoxide dismutase (SOD) increased by 47.79% and 13.93%, respectively, and that of glutathione peroxidase (GSH-Px) increased by 94.7% and 78.73% of Pb2+ group. Additionally, nuclear factor erythroid 2-related factor (Nrf2) nuclear translocation and heme oxygenase 1 (HO-1) expression were triggered. These results suggest that TSeMMM and SeMDPGQQ can suppress oxidative damage caused by Pb2+; moreover, TSeMMM showed better neuroprotective potential than SeMDPGQQ.