Objective: To explore the effect of hydrogen peroxide (H2O2) on the expression of human leukocyte antigen-G (HLA-G) in placental trophoblasts in pregnant women with pre-eclampsia.

Methods: Forty pregnant women, delivered through cesarean section in the Department of Obstetrics of and Gynecology, the First Affiliated Hospital of Nanjing Medical University from October 2008 to October 2009, were enrolled, including 20 women with pre-eclampsia and 20 healthy gravidas (control group). Colorimetry and western blot were applied, respectively, to determine the level of H2O2 and the expression of HLA-G protein in placental tissues and the correlation between them were analyzed. After 24 hours of seeding, JEG-3 cells (the HLA-G positive cell line of choriocarcinoma) were divided into two groups: intervention group (exposure to 175 micromol/L H2O2) and control group (without H2O2). Immunofluorescence and western blot were used to investigate the expression of HLA-G protein in JEG-3 cells at 24 hours and 48 hours after incubation.

Results: (1) The level of H2O2 in placenta in the pre-eclampsia group was significantly higher than that in control group [(105+/-13) nmolxmg(-1)xprot(-1) vs (62+/-18) nmol.mg(-1)xprot(-1), P<0.05]. (2) The expression of HLA-G protein in placenta of the pre-eclampsia group was reduced by 88% compared with that of the control (0.20+/-0.08 vs 1.67+/-0.65, P<0.05). (3) Negative correlation was found between HLA-G level and H2O2 expression in the placenta in both groups (r=-0.895, P=0.000). (4) Compared with the control group, the expression of HLA-G protein in JEG-3 cells, after 24 hours and 48 hours exposure to H2O2, reduced by 39% and 80%, respectively, (3.21+/-0.33 vs 1.95+/-0.25 and 0.65+/-0.08, P<0.05, respectively) and 67% reduction was detected from 24 hours to 48 hours of H2O2 exposure (P<0.05). Fluorescence microscope observed reduced expression of HLA-G in JEG-E cells in the intervention group at 48 hours compared to the control group (P<0.05).

Conclusion: High level of H2O2 could down-regulate HLA-G expression in the placental trophoblasts in pre-eclampsia which may be involved in the pathogenesis of pre-eclampsia.