Abstract 065: Reduction Of Endoplasmic Reticulum Stress By Treatment With Nifedipine In A Mouse Model Of Pre-eclampsia And In Human Placental Endothelial Cells

Abstract

Introduction: Pre-eclampsia (PE) is characterized by high blood pressure (BP) and metabolic disorders during pregnancy, being the leading cause of maternal-neonatal mortality worldwide. The causes of PE are still unclear. We observed enhanced endoplasmic reticulum (ER) stress and increased cytoplasmic mobility of calreticulin, a Ca2+ ion binding chaperone protein, in placental endothelial cells (pECs) of mice with PE, indicating changes in Ca2+ mobilization. We aimed to describe the effect of nifedipine, a Ca2+ channel blocker, on ER stress in placentas of mice with PE and in human pECs exposed to hypoxia. Methods: We used heterozygous mice overexpressing human renin and angiotensinogen, developing high BP from gestational day (GD) 13.5, and controls (C57BL/6). Nifedipine (1 mg/kg in 0.5 ml saline, s.c.) or saline was administered at GD14.5 and placentas removed at GD18.5 (n=8-12/group). Protein expressions of IREα, ATF6 and PERK were evaluated by western blot. ECs were extracted from human placentas of healthy pregnancies by magnetic sorting and exposed to hypoxia (0.5% O2) or control conditions (8% O2) for 24h while treated with nifedipine (0.1 μM) or DMSO. Angiogenesis was assessed by tube formation assay on matrigel. Results were compared by 2-way ANOVA (mean±SD). Results: IREα expression was higher in placentas of PE mice treated with saline versus control (+306±64%, p=0.020) and significantly reduced with nifedipine versus saline in PE mice (-235±66%, p=0.009). Results were similar with PERK, which was increased in placentas of saline-treated PE mice versus saline controls (116±40%, p=0.037) and significantly reduced with nifedipine versus saline in PE mice (-141±38%, p=0.006). ATF6 was not different between groups, but was significantly reduced by nifedipine versus saline in PE mice (-76±24%, p=0.022). In pECs, nifedipine increased 17x the numbers of tubes formed on matrigel of cells exposed to hypoxia in comparison to DMSO control (p<0.001). Conclusion: The results describe an enhanced ER stress in placentas of PE mice and a positive effect of nifedipine on this stress. The pro-angiogenic effect of nifedipine was shown in pECs exposed to hypoxia. Further investigations are needed to confirm a potential angiogenic effect of nifedipine in PE.