Expression of growth arrest and DNA damage-inducible 45α and p38 mitogen-activated protein kinase in placentas of women complicated with preeclampsia

Abstract

Objective To evaluate the expression of Gadd45α and p38 MAPK in placentas and the correlations of Gadd45α protein and serum soluble vascular endothelial growth factor receptor-1 (sFlt-1) and soluble endoglin (sEng) in preeclampsia(PE). Methods Fifty-four pregnant women who delivered from September 2009 to March 2010 in the First Affiliated Hospital of Chongqing Medical University were chosen as the subjects. They were classified into mild preeclampsia group (n=20),severe preeclampsia group (n=16) and the control group (normal pregnant women underwent elective cesarean sections at term without labor and perinatal complications, n=18). Western blot and immunohistochemistry were employed to determine the expression and localization of Gadd45α and p-p38 MAPK protein respectively. Gadd45α mRNA level was determined by quantitative real-time PCR. The levels of seum sFlt-1 and sEng were measured by enzyme-linked immunosorbent assay (ELISA). One-way ANOVA and LSD-t test were applied for statistical analysis. Results (1)Immunohistochemistry identified that the positive stained cells were mostly located in trophoblast cells in normotensive placentas, whereas in preeclamptic placentas Gadd45α protein and p-p38 MAPK protein were detected in trophoblast and endothelial cells, as well as a few stromal cells at increased levels.(2)The mRNA levels of Gadd45α was significantly elevated in mild and severe preeclampsia groups compared to the control group (2.10±0.11 and 3.33±0.13 vs 1.01±0.18, P＜0.05), and Gadd45α mRNA level in severe group was significantly higher than in mild group (P＜0.05).(3)The data of Western blot revealed that the Gadd45α protein levels in each group were 0.22±0.11, 0.65±0.15 and 1.34±0.17, respectively, with significant differences between each group(P＜0.05). The p-p38 MAPK protein levels in each group were 0.32±0.08, 0.72±0.12 and 1.45±0.21, respectively, with significant differences between each group (P＜0.05). p38 MAPK protein levels in the total groups showed no difference(P＞0.05).(4)Compared with the control group, sFlt-1 and sEng concentrations in maternal circulation were significantly increasing in mild and severe preeclampsia groups, and concentrations in severe group were significantly higher than those in mild group (P＜0.05).(5) There were positive correlations between Gadd45α protein levels and the concentrations of serum sFlt-1 and sEng in each group( r=0.88 and 0.87, respectively all P＜0.05). Conclusions Upregulation of Gadd45α in preeclampsia placentas may play an important role in the pathogenesis of preeclampsia. It may induce the increased maternal serum levels of sFlt-l and sEng by activating p38 MAPK signaling pathway, leading to deficient cytotrophoblastic invasion and abnormal placental vascular reconstruction during pregnancy. Key words: Pre-eclampsia; Nuclear proteins; Cell cycle proteins; p38 Mitogen-activated protein kinases; Vascular endothelial growth factor receptor-1; Receptors, cell surface; Antigens, CD