The pre-protective effect of vitamin A on LPS-induced oxidative stress of bovine mammary epithelial cells

All-trans retinoic acid (RA, derivative of vitamin A) has been demonstrated to have anti-oxidative activity and is needed for the proper function of the immune system. In this study, the protective effects of RA against lipopolysaccharide (LPS)-induced oxidative stress on bovine mammary epithelial cells (BMECs) have been investigated. BMECs were divided into four equal groups with six replicates. The first group was used as a control without RA or LPS. The three experimental groups were treated with RA (1 μg/mL) alone, LPS (1 μg/mL) alone and RA plus LPS, respectively. The cells were treated for 30 h in all. Our results showed that cells in LPS-treated group have a significantly higher inflammatory cytokines concentration and NF-κBp50 and NF-κBp65 gene expression than the control (p < .01). Furthermore, compared with control, selenoproteins’ activity of glutathione peroxidase (GPx), thioredoxin reductase (TrxR), the concentration of SelP and the gene expression of Nrf2 were significantly decreased while the activity of inducible nitric oxide synthase (iNOS), the production of intracellular reactive oxygen species (ROS) and malonaldehyde (MDA) were elevated dramatically in LPS-treated group (p < .01). However, RA in combination with LPS enhanced the antioxidant enzyme activities of selenoprotein compared to LPS-treated group. In conclusion, RA ameliorated the LPS-induced BMECs damage by improving levels of antioxidant markers and reducing inflammatory cytokines contents, indicating that RA has the potential to counter measure the immunosuppressive condition on BMECs oxidative damage and to improve antioxidative function. However, further studies are still required to elucidate the molecular mechanisms underlying the protective effects of RA as an antioxidant.