Selenium suppressed the LPS-induced oxidative stress of bovine endometrial stromal cells through Nrf2 pathway with high cortisol background

Stress and infection seriously threaten the reproductive performance and health of dairy cows. Various perinatal stresses increase plasma cortisol concentrations in cows, and chronically high cortisol levels may increase the incidence and severity of the uterine diseases. Selenium (Se) enhances antioxidant capacity of cows. The aim of this study was to explore how Se affects the oxidative stress of primary bovine endometrial stromal cells (BESC) with high cortisol background. The levels of reactive oxygen species (ROS) and other biomarkers of oxidative stress were measured using flow cytometry and assay kits. The changes in nuclear NF-E2-related factor 2 (Nrf2) pathway were detected by Western blot, qPCR, and immunofluorescence. The result showed that lipopolysaccharide (LPS) increased (P < 0.01) ROS and malondialdehyde (MDA) content and reduced (P < 0.01) superoxide dismutase (SOD) concentration, provoking BESC oxidative stress. The elevated levels of cortisol resulted in the accumulation (P < 0.05) of ROS and MDA and inhibition (P < 0.05) of SOD in unstimulated BESC but demonstrated an antioxidative effect in LPS-stimulated cells. Pretreatment with Se reduced (P < 0.01) the levels of ROS and MDA, while increasing (P < 0.05) the antioxidant capacities and the relative abundance of gene transcripts and proteins related to the Nrf2 pathway in BESC. This antioxidant effect was more pronounced in the presence of high cortisol level. In conclusion, cortisol alone induced the oxidative damage but provided an antioxidant protection in the presence of LPS. Se alleviated the LPS-induced cellular oxidative stress, which is probably achieved through activating Nrf2 pathway. At high cortisol levels, Se supplement has a more significant protective effect on BESC oxidative stress. This study provided evidence for the protective role of Se in bovine endometrial oxidative damage of stressed animals and suggested the potential regulatory mechanism in vitro.