Abstract: Early embryonic death and abortion in dairy cows impair the reproductive performance and cause great economic losses. In this study, endometrial cells were treated with different concentrations of hydrogen peroxide (H₂O₂) for 6 h. The levels of intracellular reactive oxygen species (ROS) were measured by flow cytometry. The activities of superoxide dismutase (SOD) and catalase (CAT), and the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) were measured by microplate reader, which were to establish an oxidative stress model in endometrial cells. Then apoptosis and cell cycle were detected by flow cytometry, mRNA and protein expression of key genes in Fas/FasL signaling pathway were detected by fluorescent quantitative RT-PCR and Western blot, and lentivirus-mediated RNA interference (RNAi) was employed to inhibit Fas expression in endometrial cells to further verify whether the oxidative stress-induced apoptosis is mediated through Fas/FasL signaling pathway. All experiments were repeated more than three times. Results are as follows: Treatment of endometrial cells with 200 μmol·L^-1 H₂O₂ for 6 h resulted in an increase in the amount of intracellular ROS (P < 0.05), a significant decrease in the activities of SOD and CAT (P < 0.05), and the ratio of GSH to GSSG was significantly reduced (P < 0.05), which indicated that H₂O₂ caused oxidative stress damage in endometrial cells. Compared with control group, the proportion of S phase in cell cycle was significantly reduced (P < 0.05), and the proportion of apoptosis was significantly increased (P < 0.05). The levels of mRNA expressions of Fas, Caspase 8 and Caspase 3 in Fas/FasL signaling pathway significantly increased (P < 0.05); The concentration of FasL in the cultured medium significantly increased (P < 0.05) and the levels of protein expression of Fas, Caspase 8 and Caspase 3 significantly increased (P < 0.05). Further studies have found that interfering with Fas gene expression partly reduced the proportion of apoptosis and the levels of protein expression of key genes in Fas/FasL signaling pathway induced by oxidative stress. In conclusion, these results demonstrated that oxidative stress-induced apoptosis in bovine endometrial epithelial cells is mediated through Fas/FasL signaling pathway, which may provide new insights into the adverse effects of endometrial cells in response to oxidative stress.

Key words: oxidative stress, Fas/FasL signaling pathway, apoptosis, endometrial cells