Protection of bovine mammary epithelial cells from hydrogen peroxide-induced oxidative cell damage by selenium
The uncontrolled release of arachidonic acid (ARA) and its metabolism by lipoxygenase (LOX) pathway can induce and aggravate cellular oxidative stress. Selenium (Se) is an integral part of some antioxidative selenoproteins and may protect cells from oxidative damage by modulating ARA release and metabolism. The present study aimed to investigate the protective response of Se against hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>)-induced oxidative damage in bovine mammary epithelial cells (BMECs). The BMECs were incubated for 24 h in serum-free medium and then divided into four groups randomly. The cells in groups 1 and 2 were subsequently incubated for 30 h in serum-free medium containing 0 (control) and 50 nM Se (Se treatment group). The cells in groups 3 and 4 were incubated for 24 h in serum-free medium containing 0 and 50 nM Se, and then treated with 600 μM H<sub>2</sub>O<sub>2</sub> for 6 h (H<sub>2</sub>O<sub>2</sub> damage group and Se prevention group). The results showed that Se attenuated the H<sub>2</sub>O<sub>2</sub>-induced production of reactive oxygen species and the decrease of antioxidative enzymes as glutathione peroxidase (GPX), thioredoxin reductase (TrxR), selenoprotein P (SelP), superoxide dismutase, and catalase in BMECs. The preventive effects of Se on the decrease of selenoprotein activity were demonstrated further by the increase of mRNA expression for GPX1, TrxR1, and SelP, and protein expression for GPX1 and TrxR1. Pretreatment of cells with Se inhibited the H<sub>2</sub>O<sub>2</sub>-induced increase of mRNA expressions and activities for cytosolic phospholipase A2 and 5-lipoxygenase, ARA release, and 15-hydroperoxyeicosatetraenoic acid production. Se also blocked the H<sub>2</sub>O<sub>2</sub>-induced activation of p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase but not that of extracellular signal-regulated kinase. These results suggested that Se may protect BMECs against H<sub>2</sub>O<sub>2</sub>-induced oxidative damage by increasing selenoproteins synthesis, inhibiting MAPK pathway, and then decreasing ARA release and its metabolism by LOX pathway.
