Endothelial Cell Mineralocorticoid Receptor (ECMR) deletion improves fetal growth and vascular function in the RUPP mouse model of preeclampsia.

Preeclampsia (PE), a hypertensive disorder of pregnancy, induces adverse pregnancy outcomes including fetal growth restriction (FGR) and afflicts ~5-10% of pregnancies. Compelling clinical data indicate that PE risk and severity in pregnant women is strongly associated with endothelial dysfunction. Previous work by our group shows that deletion of endothelial cell mineralocorticoid receptors (ECMR) improves endothelial function in premenopausal hypertensive female mice, however whether ECMR promotes endothelial dysfunction in PE is unknown. We tested the hypothesis that ECMR deletion improves FGR and endothelial function in a mouse model of PE, the reduced uterine perfusion pressure (RUPP) mouse. Pregnant ECMR-intact (WT) and ECMR-deficient (KO) mice were randomized to RUPP or sham surgery on GD13 and sacrificed on GD18 (WT Sham=6, WT RUPP=5, KO Sham=7, KO RUPP=6). Vascular function was measured via wire myography on 2 order mesenteric arteries. Conscious blood pressure was measured by radiotelemetry throughout pregnancy in a subset of mice. RUPP surgery did not decrease maternal weights in either WT or KO mice (P>0.05) at GD18. RUPP surgery significantly decreased GD18 pup weight, a measure of FGR, (726±20mg WT+Sham vs 660±11mg WT+RUPP, *P<0.05) and trended to decrease placental efficiency (pup/placenta weight) (8.23±0.23 WT+Sham vs 7.45±0.22 WT+RUPP P=0.13) in WT pregnant mice. ECMR deletion protected pregnant mice both from RUPP-induced reductions in pup weight (710±20mg KO+Sham vs 690±20mg KO+RUPP) and decreases in placental efficiency (7.63±0.19 KO+Sham vs 7.76±0.31 KO+RUPP). RUPP reduced acetylcholine-mediated relaxation (10 -3x10 M) in mesenteric arteries of WT pregnant mice but not KO pregnant mice (*P<0.05, 2-way ANOVA, repeated measures), indicating RUPP induced endothelial dysfunction in WT mice only. Preincubation with nitric oxide (NO) synthase inhibitor LNAME ablated differences in Ach-mediated relaxation between WT+sham and WT+RUPP mice (P>0.05), indicating that reductions in endothelial function in WT+RUPP mice were mediated by reduced NO. However, ECMR deletion as a variable increased Ach-mediated relaxation in the presence of LNAME in both Sham and RUPP mice (*P<0.05). Therefore, ECMR deletion may have protected pregnant mice from endothelial dysfunction via a non-NO mechanism. RUPP did not increase a-receptor agonist phenylephrine (Phe)-induced constriction in WT mice, however, ECMR deletion as a variable decreased Phe-mediated constriction independent of RUPP surgery indicating that ECMR deletion reduces smooth muscle-mediated vasoconstriction in pregnant sham and RUPP mice. These data indicate that specific deletion of ECMR improves vascular function to increase vasodilation and prevent constriction in PE pregnancy. Preliminary data further indicates that systolic blood pressure increased from GD8-18 (pre-post RUPP) in WT+RUPP but decreased in KO+RUPP pregnant mice (2.7 vs -8.6 DmmHg, respectively, N=1). Lastly RUPP surgery trended to increase plasma levels of the ECMR agonist corticosterone in WT pregnant mice (2.03±0.4pg/ml WT+Sham vs 3.33±0.95pg/ml WT+RUPP). Collectively, these data indicate that ECMR activation promotes FGR, vascular dysfunction and hypertension in the RUPP model of PE which may lead to clinical studies for the consideration of specific MR antagonists as therapeutic options for PE pregnancies.