Longitudinal study of angiotensin peptides in normal and pre-eclamptic pregnancy.

PURPOSE: To address whether differential regulation of the renin-angiotensin-aldosterone system occurs in pre-eclampsia, we performed an analysis of the time course of circulating and urinary profiles of the vasoconstrictor (Ang II) and the vasodilator [Ang-(1-7)] peptides in normal pregnant (NP) and pre-eclamptic (PE) women. METHODS: Urine and plasma samples from 86 nulliparous women were collected prospectively; 67 subjects continued as NP and 19 developed PE. Subjects were enrolled prior to 12 weeks of gestation and plasma and spot urine samples were obtained throughout gestation. Control samples were obtained at 6 weeks postpartum (PP). RESULTS: Mean blood pressure (p < 0.001) was elevated at 31-37 weeks of gestation in PE subjects as compared with NP subjects. Plasma Ang I and Ang II levels were elevated in NP subjects as early as 16 weeks of gestation and maintained throughout gestation. In PE subjects both plasma Ang I and Ang II were elevated at 16-33 weeks as compared with PP levels. PE subjects showed reduced plasma Ang I and Ang II (at 35-37 weeks of gestation) compared with NP subjects. Plasma Ang-(1-7) was unchanged in both groups. All three urinary peptides increased throughout gestation in NP subjects. In PE subjects urinary Ang I was increased at 23-26 weeks and was maintained throughout gestation. Urinary Ang II was increased at 27-29 and 31-33 weeks of gestation. PE subjects had no change in urinary Ang-(1-7). CONCLUSION: The activation of the RAS, particularly Ang II throughout normal gestation may contribute to the maintenance of vascular tone during normal pregnancy. However higher sensitivity to Ang II in pre-eclampsia may be potentiated by the higher circulating and urinary levels of Ang II, unopposed by local renal Ang-(1-7), and thus may contribute to the development of pre-eclampsia.

Downregulation of apelin in the human placental chorionic villi from preeclamptic pregnancies.

The role of the endogenous apelin system in pregnancy is not well understood. Apelin's actions in pregnancy are further complicated by the expression of multiple forms of the peptide. Using radioimmunoassay (RIA) alone, we established the expression of apelin content in the chorionic villi of preeclamptic (PRE) and normal pregnant women (NORM) at 36-38 wk of gestation. Total apelin content was lower in PRE compared with NORM chorionic villi (49.7±3.4 vs. 72.3±9.8 fmol/mg protein; n=20-22) and was associated with a trend for lower preproapelin mRNA in the PRE. Further characterization of apelin isoforms by HPLC-RIA was conducted in pooled samples from each group. The expression patterns of apelin peptides in NORM and PRE villi revealed little or no apelin-36 or apelin-17. Pyroglutamate apelin-13 [(Pyr1)-apelin-13] was the predominant form of the peptide in NORM and PRE villi. Angiotensin-converting enzyme 2 (ACE2) activity was higher in PRE villi (572.0±23.0 vs. 485.3±24.8 pmol·mg(-1)·min(-1); n=18-22). A low dose of ANG II (1 nM; 2 h) decreased apelin release in NORM villous explants that was blocked by the ANG II receptor 1 (AT1) antagonist losartan. Moreover, losartan enhanced apelin release above the 2-h baseline levels in both NORM and PRE villi (P<0.05). In summary, these studies are the first to demonstrate the lower apelin content in human placental chorionic villi of PRE subjects using quantitative RIA. (Pyr1)-apelin-13 is the predominant form of endogenous apelin in the chorionic villi of NORM and PRE. The potential mechanism of lower apelin expression in the PRE villi may involve a negative regulation of apelin by ANG II.

Hemodynamic responses to angiotensin-(1-7) in women in their third trimester of pregnancy.

BACKGROUND: To understand the role of Angiotensin-(1-7) (Ang-(1-7)) in vasculature of pregnant women, we compared cardiac output (CO), total peripheral resistance (TPR) and forearm blood flow (FBF) responses to Ang-(1-7) infusion between normotensive pregnant women in their third trimester and healthy age matched non-pregnant women. The responses of skin microcirculation to Ang-(1-7) were tested in preeclamptic, normotensive pregnant and non-pregnant women. Responses to Angiotensin II (Ang II) were also determined. METHODS: Non-invasive methods for systemic (bioimpedance and VascuMAP), FBF (venous occlusion strain gauge plethysmography), and skin (laser Doppler) hemodynamics assessments were used. RESULTS: Compared to non-pregnant women, systemic infusion of Ang-(1-7) (2000 pmol/min) resulted in a greater increase in CO (9.4 ± 6.4 versus -3.3 ± 2.1%, n = 9-10) in normotensive pregnant women. Brachial local infusion of Ang-(1-7) had no effect on FBF in either group. In non-pregnant and normotensive pregnant women, local Ang II induced a dose-dependent decrease in FBF and increase in forearm resistance at 50 and 100 pmol/min (p < 0.05 versus corresponding baseline, n = 7-10). Following iontophoretic application of 5 mmol/l dose of Ang-(1-7), the change in skin flow was higher in normotensive pregnant versus preeclamptic women (182.5 ± 93 versus 15.76 ± 19.46%, n = 14-15). Skin flow was lower in normotensive pregnant versus preeclamptic women (-46.5 ± 48.7 versus 108.7 ± 49.1%, n = 14-15) following Ang II infusion at 1.0 pmol/min. CONCLUSION: In the third trimester of pregnancy, Ang-(1-7) induces alterations in CO and differentially regulates micro- and macro-circulations, depending on the dose. Dysregulation in skin vasculature may contribute to the development of vascular dysfunction and hypertension in preeclampsia.

Candidate gene linkage approach to identify DNA variants that predispose to preterm birth.

BACKGROUND: The aim of this study was to identify genetic variants contributing to preterm birth (PTB) using a linkage candidate gene approach. METHODS: We studied 99 single-nucleotide polymorphisms (SNPs) for 33 genes in 257 families with PTBs segregating. Nonparametric and parametric analyses were used. Premature infants and mothers of premature infants were defined as affected cases in independent analyses. RESULTS: Analyses with the infant as the case identified two genes with evidence of linkage: CRHR1 (P = 0.0012) and CYP2E1 (P = 0.0011). Analyses with the mother as the case identified four genes with evidence of linkage: ENPP1 (P = 0.003), IGFBP3 (P = 0.006), DHCR7 (P = 0.009), and TRAF2 (P = 0.01). DNA sequence analysis of the coding exons and splice sites for CRHR1 and TRAF2 identified no new likely etiologic variants. CONCLUSION: These findings suggest the involvement of six genes acting through the infant and/or the mother in the etiology of PTB.

Single-nucleotide polymorphisms in the KCNN3 gene associate with preterm birth.

The objectives were to determine whether single-nucleotide polymorphisms (SNPs) in KCNN3 (encodes the small conductance calcium-activated potassium channel subfamily N, member 3), associate with preterm birth (PTB). In all, 602 preterm families with at least 1 preterm (<37 weeks gestation) infant were studied: DNA from the infant and one or both parents were genotyped for 16 SNPs in KCNN3. A region of interest within KCNN3 was sequenced in 512 Caucasian non-Hispanic mothers (412 with preterm deliveries;100 who delivered at term). Family-based association testing was used for genotyping analysis; Fisher exact test was used for sequencing analysis. Six SNPs (rs1218585, rs4845396, rs12058931, rs1218568, rs6426985, and rs4845394) were associated with PTB (all Ps < .05). These variations were all located within the intronic region between exons 1 and 2. Maternal sequencing revealed an association of 3 SNPs with spontaneous PTB; rs1218585 (P = .007), rs1218584 (P = .05), and a novel SNP at chromosome1:153099353 (P = .02). Polymorphisms in KCNN3 are associated with PTB and investigation into the functional significance of these allelic changes is warranted.

Angiotensin II and angiotensin-(1-7) decrease sFlt1 release in normal but not preeclamptic chorionic villi: an in vitro study.

BACKGROUND: During preeclampsia, placental angiogenesis is impaired. Factors released from the placenta including vascular endothelial growth factor (VEGF), placental growth factor (PLGF), soluble VEGF receptor 1 (sFlt1), and soluble endoglin (sEng) are regulatory molecules of placental development and function. While the renin angiotensin system has been shown to regulate angiogenic factors in other research fields, these mechanisms have not been extensively studied during pregnancy. METHODS: We evaluated the effects of angiotensin II (Ang II) and angiotensin-(1-7) [Ang-(1-7)] on the release of VEGF, PLGF, sFlt1, and sEng from placental chorionic villi (CV). CV were collected from nulliparous third-trimester normotensive and preeclamptic subjects. CV were incubated for 0, 2, 4, and 16 hours with or without Ang II (1 nM and 1 microM) or Ang-(1-7) (1 nM and 1 microM). The release of VEGF, PLGF, sFlt1, sEng, lactate dehydrogenase (LDH), and human placenta lactogen (HPL) was measured by ELISA. RESULTS: The release of sFlt1, PLGF, sEng from normal and preeclamptic CV increased over time. Release of sFlt1 and sEng was significantly higher from preeclamptic CV. VEGF was below the detectable level of the assay in normal and preeclamptic CV. After 2 hours, sFlt1 release from normal CV was significantly inhibited with Ang II (1 nM and 1 microM) and Ang-(1-7) (1 nM and 1 microM). There was a time-dependent increase in HPL indicating that the CV were functioning normally. CONCLUSIONS: Our study demonstrates a critical inhibitory role of angiotensin peptides on sFlt1 in normal pregnancy. Loss of this regulation in preeclampsia may allow sFlt1 to increase resulting in anti-angiogenesis and end organ damage in the mother.

The uterine placental bed Renin-Angiotensin system in normal and preeclamptic pregnancy.

Previously, we demonstrated activation of the renin-angiotensin system in the fetal placental chorionic villi, but it is unknown whether the immediately adjacent area of the maternal uterine placental bed is regulated similarly. This study measured angiotensin peptides, renin-angiotensin system component mRNAs, and receptor binding in the fundus from nonpregnant subjects (n = 19) and in the uterine placental bed from normal (n = 20) and preeclamptic (n = 14) subjects. In the uterine placental bed from normal pregnant women, angiotensin II peptide levels and angiotensinogen, angiotensin-converting enzyme, angiotensin receptor type 1 (AT(1)), AT(2), and Mas mRNA expression were lower as compared with the nonpregnant subjects. In preeclamptic uterine placental bed, angiotensin II peptide levels and renin and angiotensin-converting enzyme mRNA expression were significantly higher than normal pregnant subjects. The AT(2) receptor was the predominant receptor subtype in the nonpregnant fundus, whereas all angiotensin receptor binding was undetectable in normal and preeclamptic pregnant uterine placental bed compared with nonpregnant fundus. These findings suggest that the maternal uterine placental bed may play an endocrine role by producing angiotensin II, which acts in the adjacent placenta to vasoconstrict fetal chorionic villi vessels where we have shown previously that AT(1) receptors predominate. This would lead to decreased maternal-fetal oxygen exchange and fetal nutrition, a known characteristic of preeclampsia.

Insulin glargine versus neutral protamine Hagedorn insulin for treatment of diabetes in pregnancy.

We compared maternal and neonatal outcomes in diabetic pregnancies treated with either insulin glargine or neutral protamine Hagedorn (NPH) insulin. We performed a retrospective chart review of diabetic pregnant patients using the Diabetes Care Center of Wake Forest University during the years 2000 to 2005. Outcomes of interest included maternal hemoglobin A1C, average fasting and 2-hour postprandial blood sugars, mode of delivery, birth weight, 5-minute Apgar score < 7, umbilical artery pH < 7.20, incidence of neonatal hypoglycemia, and pregnancy complications. A total of 52 diabetic pregnant patients were included in this study. Twenty-seven women used insulin glargine. A total of 13 women used insulin glargine during the first trimester. Glycemic control was similar in women who used NPH insulin and insulin glargine, as determined by hemoglobin A1C levels and mean blood sugar values. There were no differences in mode of delivery, average birth weight, or neonatal outcomes. Maternal and fetal/neonatal outcomes appear similar in pregnant diabetic women who use either NPH insulin or insulin glargine in combination with a short-acting insulin analogue to achieve adequate glycemic control during pregnancy. Insulin glargine appears to be an effective insulin analogue for use in women whose pregnancies are complicated by diabetes.

Identifying risk factors for uterine rupture.

Uterine rupture, whether in the setting of a prior uterine incision or in an unscarred uterus, is an obstetric emergency with potentially catastrophic consequences for both mother and child. Numerous studies have been published regarding various risk factors associated with uterine rupture. Despite the mounting data regarding both antepartum and intrapartum factors, it currently is impossible to predict in whom a uterine rupture will occur. This article reviews the data regarding these antepartum and intrapartum predictors for uterine rupture. The author hopes that the information presented in this article will help clinicians assess an individual's risk for uterine rupture.

Activation of local chorionic villi angiotensin II levels but not angiotensin (1-7) in preeclampsia.

The chorionic villi in the placenta are responsible for the regulation of fetal oxygen and nutrient transport. Although the peripheral renin-angiotensin system is activated during normal pregnancy, the regulation of the local chorionic villi renin-angiotensin system remains unknown. Therefore, placental chorionic villous tissue was collected from nulliparous third-trimester normotensive or preeclamptic subjects and was analyzed for angiotensin peptide content, angiotensinogen, renin, angiotensin-converting enzyme (ACE), ACE2, neprilysin, angiotensin II type 1 (AT(1)), angiotensin II type 2, Mas receptor mRNAs, and angiotensin receptor density and subtype. Angiotensin II in chorionic villi was significantly higher in preeclamptic subjects, whereas angiotensin (1-7) was not different. Angiotensinogen and AT(1) receptor gene expression was significantly higher in preeclamptic subjects. No differences were observed in renin, ACE, ACE2, or neprilysin gene expression. Mas receptor mRNA in preeclamptic subjects was decreased. The AT(1) receptor was the predominant receptor subtype in normal and preeclamptic chorionic villi. There was no difference in the density of the AT(1,) angiotensin II type 2, and angiotensin (1-7) receptors. These results indicate that enhanced chorionic villous expression of angiotensin II may result from increased angiotensinogen. Elevated angiotensin II, acting through the AT(1) receptor, may favor vasoconstriction in placental chorionic villi and contribute to impaired fetal blood flow and decreased fetal nutrition observed during preeclampsia.

ACE2 and ANG-(1-7) in the rat uterus during early and late gestation.

The present study was designed to determine ANG peptide content [ANG I, ANG II, ANG-(1-7)], ACE2 mRNA, and the immunocytochemical distribution of ANG-(1-7) and ACE2 in the uteroembryonic unit during early and late gestation in Sprague-Dawley rats and in a rat model of pregnancy-induced hypertension, the reduced uterine perfusion pressure (RUPP) model. At early pregnancy ANG-(1-7) and ACE2 staining were localized in the primary and secondary decidual zone and luminal and glandular epithelial cells. During late gestation, ANG-(1-7) and ACE2 staining was visualized in the labyrinth placenta and amniotic and yolk sac epithelium. Uterine ANG II concentration at early pregnancy was significantly decreased by 21-55% in the implantation and interimplantation sites compared with virgin rats, whereas ANG-(1-7) levels were maintained at prepregnancy levels. At late gestation, uterine concentrations of ANG I and ANG II were significantly increased (30% and 25%, respectively). In RUPP animals, ANG-(1-7) concentration is significantly reduced in the uterus (181 +/- 16 vs. 372 +/- 74 fmol/g of tissue) and placenta (143 +/- 26 vs. 197 +/- 20 fmol/g of tissue). ACE2 mRNA increased in the uterus of early pregnant compared with virgin rats, yet within the implantation site it was downregulated. At late pregnancy, ACE2 mRNA is elevated by 58% in the uterus and decreased by 59% in RUPP animals. The regulation of ANG-(1-7) and ACE2 in early and late pregnancy supports the hypothesis that ANG-(1-7) and ACE2 may act as a local autocrine/paracrine regulator throughout pregnancy, participating in the early (angiogenesis, apoptosis, and growth) and late (uteroplacental blood flow) events of pregnancy.

Angiotensin-(1-7) inhibits in vitro endothelial cell tube formation in human umbilical vein endothelial cells through the AT(1-7) receptor.

Angiotensin-(1-7) is increased in the circulation during human pregnancy, but its functional role is unknown. Recent studies suggested that it opposes angiotensin II mediated vascular growth. Because angiogenesis is critical to normal embryonic development during human pregnancy, this study assessed the in vitro effects of angiotensin-(1-7) on human umbilical vein endothelial cell tube formation. The blocking effects of the angiotensin-(1-7) receptor antagonist, D-[Alanine7]-Ang-(1-7), and angiotensin II receptor AT1 and AT2 antagonists, losartan and PD123319, on tube formation were measured by counting tube branch points. Human umbilical vein endothelial cells were cultured in EGM-2 medium and treated with angiotensin-(1-7) (0.17 nM-17 microM) for 18 h. Angiotensin-(1-7) inhibited tube formation by 24% (P < 0.01) at all doses tested. Treatment with 1.7 microM angiotensin-(1-7) plus 17 microM D-[Alanine7]-Ang-(1-7) resulted in the reversal of angiotensin-(1-7) mediated inhibition of tube formation (P < 0.05). Losartan (17 microM) also reversed the angiotensin-(1-7) mediated inhibition of tube formation (P < 0.05). Tube formation was unaffected by PD123319. These results suggest that angiotensin-(1-7) has an anti-angiogenic effect on human umbilical vein endothelial cells through a unique AT(1-7) receptor that is sensitive to losartan, indicating that angiotensin-(1-7) may play an important role in the regulation of vascular growth in the placenta during pregnancy.

The importance of angiotensin II subtype receptors for blood pressure control during mouse pregnancy.

Pregnancy is characterized by a progressive increase in the different components of the renin angiotensin system (RAS) including angiotensin II, a potent vasoconstrictor. Pregnant women and experimental animals are resistant to the pressor effect of increased angiotensin II concentrations during pregnancy. In normal pregnancy, maternal blood pressure (BP) begins to fall in early gestation, reaches a nadir in midgestation, and then gradually increases to nonpregnant levels before term in both humans and C57BL/6J mice. The mechanism producing these changes is unknown. The present study investigates the roles of angiotensin II subtype receptors (AT1a and AT2) in hemodynamic regulation during pregnancy in mice. Female mice genetically or pharmacologically manipulated to alter angiotensin receptor stimulation were bred to 2 strains of males. Maternal BP was measured daily throughout pregnancy. Pup weight and number were determined. Pregnancy-induced hypertension was apparent in transgenic female mice expressing the human angiotensin gene bred with males expressing human renin. This effect was not apparent in the absence of the AT1a receptor (ie, in AT1a knockout mice). The midgestation BP decline in both C56BL/6J and AT1a(-/-) females was abolished by AT2 receptor antagonism. There was a linear, inverse relationship between average BP throughout pregnancy and the average pup weight and number per litter. In summary, these findings suggest that activation of the AT2 receptor may be an important factor in promoting the midgestation BP decline that occurs in several mammalian species and, furthermore, that angiotensin is an important modulator of BP during pregnancy.

Oxytocin for induction of labor.

Oxytocin is the most common pharmacologic agent used for the induction and augmentation of labor. Oxytocin protocols can be divided into high-dose and low-dose protocols depending on the initial dose and the amount and rate of sequential increase in dose. Despite the frequency with which oxytocin in used in clinical practice, there is little consensus regarding which protocol is most appropriate. The purpose of this chapter is to review the most current data concerning recommendations for the use of oxytocin in the induction of labor, including cases of intrauterine fetal demise and vaginal birth after cesarean.

Angiotensin-(1-7) in normal and preeclamptic pregnancy.

Angiotensin-(1-7) (Ang-[1-7]) is a bioactive component of the renin-angiotensin system, which has depressor, vasodilatory, and antihypertensive actions. In normal pregnancy, we questioned whether the known rise in plasma angiotensin II (Ang II) is counterbalanced by an increase in plasma Ang-(1-7) and whether Ang-(1-7) levels are decreased in preeclampsia and may thus be a factor involved in the development of hypertension. Nulliparous preeclamptic subjects, third-trimester normotensive pregnant subjects, and a nonpregnant group were enrolled (n = 15/group). Preeclamptic subjects had no previous history of hypertension or renal, connective-tissue, or metabolic disease, but at the time of delivery had significant hypertension (159 +/- 3/98 +/- 3 mmHg) and > or = 3+ proteinuria. Plasma Ang-(1-7) was increased by 51% in normal pregnancy (p < 0.05). Plasma Ang I, Ang II, and renin activity were also significantly elevated in normal pregnancy. In preeclamptic subjects, Ang-(1-7) was significantly decreased (p < 0.01) compared with normal pregnant subjects. All other components of the renin-angiotensin-aldosterone system, except serum angiotensin-converting enzyme, were reduced in preeclamptic subjects compared with normal pregnant subjects; only plasma Ang II remained elevated in preeclamptic compared with nonpregnant subjects. These studies demonstrate, for the first time, increased plasma Ang-(1-7) in normal pregnant subjects compared with nonpregnant subjects and decreased Ang-(1-7) in preeclamptic subjects compared with normal pregnant subjects. In preeclampsia the decreased plasma Ang-(1-7) in the presence of elevated Ang II is consistent with the development of hypertension.

Discovery of a spontaneous genetic mouse model of preeclampsia.

Preeclampsia remains a leading cause of maternal and fetal morbidity and mortality but has an unknown etiology. Women with elevated baseline blood pressure have an increased risk of this disorder. We hypothesized that BPH/5 mice, an inbred mouse strain with mildly elevated blood pressure, would develop a pregnancy-induced hypertensive syndrome. Nonpregnant female BPH/5 and C57BL/6 mice underwent thoracic aortic implantation of telemeters. After 7 days of recovery and 5 days of baseline mean arterial blood pressure (MAP) recording, strain-matched timed matings were carried out. MAP was recorded continuously during pregnancy and for 1 week after birth. In separate mice in metabolic cages, urinary protein was tracked, followed by renal histological analysis. Before pregnancy, the BPH/5 strain had elevated baseline MAP compared with the C57BL/6 strain, but both strains had similar total urinary protein levels and renal histology. MAP remained stable in both groups during the first 2 weeks of pregnancy. However, at the start of the last trimester, MAP began to rise further in the BPH/5 mice; it rose to peak levels just before delivery and returned to prepregnancy levels by 2 days after delivery. This was accompanied by late-gestational proteinuria and progressive glomerulosclerosis. No changes were observed in the C57BL/6 group except for a small decrease in MAP at mid gestation. The BPH/5 group delivered significantly smaller litters despite normal numbers of fetuses early in gestation, and longitudinal ultrasound studies documented fetal demise before the onset of hypertension and renal disease. This is the first report of an animal model that spontaneously develops a syndrome that bears close resemblance to preeclampsia, and it should have an impact on our understanding of the pathophysiology of this disorder.