Abstract: OBJECTIVE: To explore the effect of quercetin on the expressions of Bcl-2/Bax apoptotic proteins in endometrial cells in mice with abortion induced by lipopolysaccharide.METHODS: For in vivo experiment, twenty five Kunming mice were randomly divided into five groups at day 4 of pregnancy, with 5 mice per group. The mice were treated with lipopolysaccharide(LPS)through tail vein intravenous injection at day 4 of pregnancy, followed by different concentrations of quercetin by oral gavage consecutively at days 5 to6 of pregnancy. On day 7 of gestation, the mice were sacrificed and the histopathological changes of the uterus tissues were observed. Immunohistochemical staining was applied to the detection of Bcl-2/Bax apoptotic proteins in the endometrial cells. For in vitro experiment, the primary endometrial cells werecultured using a uterus tissue mass culturing method sampled at day 4.5 of pregnancy. The cells were treated with LPS with or without different dosages of quercetin, respectively, for 12 h after 80% confluence. The expression of Bcl-2/Bax apoptotic proteins were detected by western blotting.RESULTS: Both the in vivo and in vitro experiments showed decreased expression of Bcl-2 and enhanced expression of Bax after LPS treatment, leading to a decreased Bcl-2/Bax ratio. The expression of Bcl-2 significantly increased while the expression of Bax was significantly elevated, in the LPS plus quercetin group compared to the LPS only group.CONCLUSION: These results suggest that quercetin has protective effect by partially regulating the expression of Bcl-2/Bax proteins, which in turn inhibits endometrial cell apoptosis and benefits the embryo implantation.

Key words: Quercetin, Lipopolysaccharides, Abortion,spontaneous, Endometrium, Bcl2 protein,mouse, Bcl-2-associated X protein