Recent progress toward the understanding of the pathophysiology of hypertension during preeclampsia

Recent insights into the pathophysiology of preeclampsia

Preeclampsia, characterized by new-onset gestational hypertension and proteinuria, is a common and serious complication of pregnancy. Evidence from both animal and human studies has implicated placental ischemia and hypoxia as a central causative factor in the etiology of the disorder. The ischemic placenta in turn initiates a cascade of secondary effector mechanisms, including altered proangiogenic and antiangiogenic factor balance, increase in maternal oxidative stress and endothelial and immunological dysfunction. The full elucidation of these mechanisms will hopefully lead to a more complete understanding of the etiology of preeclampsia and lead to successful therapeutic intervention through the targeted disruption of new and novel pathways.

Tissue transglutaminase contributes to the pathogenesis of preeclampsia and stabilizes placental angiotensin receptor type 1 by ubiquitination-preventing isopeptide modification

Preeclampsia is a life-threatening pregnancy disorder that is widely thought to be triggered by impaired placental development. However, the placenta-related pathogenic factors are not fully identified, and their underlying mechanisms in disease development remain unclear. Here, we report that the protein level and enzyme activity of tissue transglutaminase (TG2 or tTG), the most ubiquitous member of a family of enzymes that conducts post-translational modification of proteins by forming ε-(γ-glutamyl)-lysine isopeptide bonds, are significantly elevated in placentas of preeclamptic women. TG2 is localized in the placental syncytiotrophoblasts of patients with preeclampsia where it catalyzes the isopeptide modification of the angiotensin receptor type 1 (AT1). To determine the role of elevated TG2 in preeclampsia, we used a mouse model of preeclampsia based on injection of AT1-agonistic autoantibody. A pathogenic role for TG2 in preeclampsia is suggested by in vivo experiments in which cystamine, a potent transglutaminase inhibitor, or small interfering RNA-mediated TG2 knockdown significantly attenuated autoantibody-induced hypertension and proteinuria in pregnant mice. Cystamine treatment also prevented isopeptide modification of placental AT1 receptors in preeclamptic mice. Mechanistically, we revealed that AT1-agonistic autoantibody stimulation enhances the interaction between AT1 receptor and TG2 and results in increased AT1 receptor stabilization via transglutaminase-mediated isopeptide modification in trophoblasts. Mutagenesis studies further demonstrated that TG2-mediated isopeptide modification of AT1 receptors prevents ubiquitination-dependent receptor degradation. Taken together, our studies not only identify a novel pathogenic involvement of TG2 in preeclampsia but also suggest a previously unrecognized role of TG2 in the regulation of G protein-coupled receptor stabilization by inhibiting ubiquitination-dependent degradation.

Endothelin-1 is not a Mechanism of IL-17 Induced Hypertension during Pregnancy

Preeclampsia is characterized as new onset maternal hypertension and proteinuria after 20 weeks gestation. Studies suggest that endothelin (ET-1) is a regulator of vascular function in preeclampsia and plays a major role in mediating chronic reduction in uterine perfusion pressure (RUPP)-induced hypertension. We recently demonstrated a role for the autoimmune cytokine interleukin 17 (IL-17) in causing placental oxidative stress and hypertension during pregnancy. In this current study, we investigated the role of ET-1 as a potential mechanism by which T_H17 cells and IL-17 mediate hypertension in preeclampsia. While IL-17 infusion into normal pregnant rats increased blood pressure in a dose-responsive manner (98+/-2 mmHg in NP (n=20) to 105+/-3 mmHg in IL-17 (50pg/day, n=20) to 120+/-4 mmHg in IL-17 (100pg/day, n=10) to 123+/-3 mmHg in IL-17 (150 pg/day, n=7), it decreased local endothelin in placentas (NP (n=10) 7.5±0.3; IL-17 (100 pg/day, n=5) 6.4±0.2; IL-17 (150 pg/day, n=12) 4.5+1.5) and renal cortices (NP (n=8) 7.9 + 0.4; IL-17 (100 pg/day, n=6) 7.1±0.4; IL-17 (150 pg/day, n=4) 1.6 +0.7 during pregnancy. In addition, increasing IL-17 directly reduced secretion of ET-1 by human umbilical venous endothelial cells (HUVECs). HUVEC ET-1 secretion decreased from that seen in serum free media 42.7±7.7 pg/ml to 36.2 ± 5.9 pg/ml at 10 pg IL-17 to 31.3 ± 5.1 pg/ml at 10 μg IL-17. Our observations suggest that IL-17 negatively regulates the ET-1 pathway in local tissues and cultured endothelial cells and that the ET-1 pathway is not a mechanism by which IL-17 causes hypertension during pregnancy.

Endothelin-1, oxidative stress, and endogenous angiotensin II: mechanisms of angiotensin II type I receptor autoantibody-enhanced renal and blood pressure response during pregnancy

Hypertension during preeclampsia is associated with increased maternal vascular sensitivity to angiotensin II (ANGII). This study was designed to determine mechanisms whereby agonistic autoantibodies to the ANGII type I receptor (AT1-AA) enhance blood pressure (mean arterial pressure [MAP]) and renal vascular sensitivity to ANGII during pregnancy. First, we examined MAP and renal artery resistance index in response to chronic administration of ANGII or AT1-AA or AT1-AA+ANGII in pregnant rats compared with control pregnant rats. To examine mechanisms of heightened sensitivity in response to AT1-AA during pregnancy, we examined the role of endogenous ANGII in AT1-AA-infused pregnant rats, and that of endothelin-1 and oxidative stress in AT1-AA+ANGII-treated rats. Chronic ANGII increased MAP from 95±2 in normal pregnant rats to 115±2 mm Hg; chronic AT1-AA increased MAP to 118±1 mm Hg in normal pregnant rats, which further increased to 123±2 mm Hg with AT1-AA+ANGII. Increasing ANGII from 10(-11) to 10(-8) decreased afferent arteriole diameter from 15% to 20% but sharply decreased afferent arteriole diameter to 60% in AT1-AA-pretreated vessels. Renal artery resistance index increased from 0.67 in normal pregnant rats to 0.70 with AT1-AA infusion, which was exacerbated to 0.74 in AT1-AA+ANGII-infused rats. AT1-AA-induced hypertension decreased with enalapril but was not attenuated. Both tissue endothelin-1 and reactive oxygen species increased with AT1-AA+ANGII compared with AT1-AA alone, and blockade of either of these pathways had significant effects on MAP or renal artery resistance index. These data support the hypothesis that AT1-AA, via activation of endothelin-1 and oxidative stress and interaction with endogenous ANGII, is an important mechanism whereby MAP and renal vascular responses are enhanced during preeclampsia.

Matrix metalloproteinases as drug targets in preeclampsia

Preeclampsia is an important syndrome complicating pregnancy. While the pathogenesis of preeclampsia is not entirely known, poor placental perfusion leading to widespread maternal endothelial dysfunction is accepted as a major mechanism. It has been suggested that altered placental expression of matrix metalloproteinases (MMPs) may cause shallow cytotrophoblastic invasion and incomplete remodeling of the spiral arteries. MMPs are also thought to link placental ischemia to the cardiovascular alterations of preeclampsia. In fact, MMPs may promote vasoconstriction and surface receptors cleavage affecting the vasculature. Therefore, the overall goal of this review article is to provide an overview of the pathophisiology of preeclampsia, more specifically regarding the role of MMPs in the pathogenesis of preeclampsia and the potential of MMP inhibitors as therapeutic options.

Pathophysiology of hypertension in pre-eclampsia: a lesson in integrative physiology

Despite being one of the leading causes of maternal death and a major contributor of maternal and perinatal morbidity, the mechanisms responsible for the pathogenesis of pre-eclampsia have yet to be fully elucidated. However, it is evident that this is a complex disorder involving multiple organ systems, and by using integrative approaches, enormous progress has been made towards understanding the pathophysiology of pre-eclampsia. Growing evidence supports the concept that the placenta plays a central role in the pathogenesis of pre-eclampsia and that reduced uteroplacental perfusion, which develops as a result of abnormal cytotrophoblast invasion of spiral arterioles, triggers the cascade of events leading to the maternal disorder. Placental ischaemia leads to release of soluble placental factors, many of which are classified as anti-angiogenic or pro-inflammatory. Once these ischaemic placental factors reach the maternal circulation, they cause widespread activation and dysfunction of the maternal vascular endothelium that results in enhanced formation of endothelin-1 and superoxide, increased vascular sensitivity to angiotensin II and decreased formation of vasodilators such as nitric oxide. This review highlights these links between placental ischaemia, maternal endothelial activation and renal dysfunction in the pathogenesis of hypertension in pre-eclampsia.

Dietary vitamin D restriction in pregnant female mice is associated with maternal hypertension and altered placental and fetal development

Epidemiology has linked vitamin D deficiency with preeclampsia in humans. We hypothesized that low vitamin D status in pregnant mice may lead to symptoms of preeclampsia. Female BL6 mice were raised on vitamin D-sufficient or -deficient diets from weeks 4 of age and then mated with vitamin D-sufficient BL6 males at week 8. The resulting pregnant mice were either allowed to deliver pups and monitored for blood pressure (BP) and weight of offspring or euthanized at day 14 or 18 of gestation (E14 or E18) for analysis of serum, placental/kidney tissues, and fetuses. At E14 serum concentrations of 25-hydroxyvitamin D (30.1 ± 5.0 vs 1.8 ± 0.6 ng/mL, P < .001) and 1,25-dihydroxyvitamin D (119.5 ± 18.7 vs 37.4 ± 5.1 pg/mL, P < .01) were higher in sufficient vs deficient pregnant mice. At E14 BP was significantly elevated in vitamin D-deficient pregnant mice relative to vitamin D-sufficient mice for both systolic BP (124.89 ± 2.28 vs 105.34 ± 3.61 mm Hg, P < .001) and mean arterial pressure (115.33 ± 1.93 vs 89.33 ± 5.02 mm Hg, P < .001). This elevation continued through pregnancy until 7 days postpartum (PP7) but returned to baseline by PP14. Analysis of maternal kidneys showed increased expression of mRNA for renin and the angiotensin II receptor (3- and 4-fold, respectively) in vitamin D-deficient vs -sufficient mice at E14. Histological analysis of E14 placentas from vitamin D-deficient mice showed decreased vascular diameter within the labyrinth region. E14 and E18 fetuses from vitamin D-deficient mice were larger than those from vitamin D-sufficient mothers. However, by PP14 pups from vitamin D-deficient mothers weighed significantly less than those from vitamin D-sufficient mothers. Resupplementation of vitamin D periconceptually partially reversed the effects of vitamin D deficiency. These data provide further evidence that low vitamin D status may predispose pregnant women to dysregulated placental development and elevated blood pressure.

Soluble fms-like tyrosine kinase-1 and soluble endoglin in HIV-associated preeclampsia

OBJECTIVE

Preeclampsia is characterized by endothelial dysfunction combined with increased concentrations of sFlt1, which antagonizes the biological effects of VEGF and PlGF, and of sEng, which antagonizes TGFβ1. This angiogenic imbalance may have a role in its etiology. This study evaluated the expression of VEGF, PlGF, sFlt1 and sEng amongst third trimester pregnancies in women with HIV-associated pre-eclampsia.

METHOD

Serum and placental tissue were obtained from 76 pregnancies in women who were normotensive and HIV negative (N-) or positive (N+), and in women who were pre-eclamptic and HIV negative (P-) or positive (P+). The serum and placental samples were quantitatively evaluated using ELISAs and RT-PCR respectively.

RESULTS

Placental sFlt1 expression differed significantly between the N- and P- groups (p=0.001). Similarly, sEng expression differed between the N- and P- groups (p=0.001). No significant effect was shown between HIV status and pregnancy. Serum sFlt1 (p=0.02) and sEng (p=0.001) were up-regulated in the P- compared to the N- groups. Similarly, no significant effect was shown between HIV status and pregnancy. Both VEGF and PlGF did not differ significantly between groups. Notably, sEng expression was elevated in both placenta and serum, whilst placental sFlt1 differed from serum. A weak but significant correlation between serum and placental concentration for sFlt1, sEng and PlGF (r=0.26, p=0.031; r=0.42, p<0.001 and r=-0.3, p=0.014) was observed.

CONCLUSIONS

This novel study demonstrates an up-regulation of serum sFlt1 and sEng in preeclamptic compared to normotensive groups irrespective of the HIV status of the pregnancy. This implicates a contributory role of sFlt1 and sEng in preeclampsia development. The serum reduction of sFlt1 and sEng within the HIV positive compared to HIV negative cohorts may imply a neutralization of the immune hyperreactivity of preeclampsia.

Prevention and endothelial therapy of coronary artery disease

Functional integrity of endothelial cells is an indicator and a prerequisite for vascular health and counteracts the development of atherosclerosis. This concept of 'endothelial therapy' was developed in the late 1990s as an approach to preserve or restore endothelial cell health given that 'the knowledge of the mechanisms involved in 'endothelial dysfunction' allows us to interfere specifically with pathogenic pathways at very early time points and to slow down the progression of disease'. In the present review, the principles underlying endothelial cell health will be discussed as well as the role of endothelial therapy as a preventive measure to reduce the prevalence of coronary artery disease or to delay disease progression in patients with chronic coronary artery disease. This article also highlights the importance of active participation, the need to reduce the number of future patients in view of the rising prevalence of childhood obesity, and the potential of endothelial therapy to improve survival, reduce disability and health costs, and to improve overall quality of life in patients at risk for or already diagnosed with coronary artery disease. The preventive and therapeutic approaches and considerations described herein can be applied by physicians, patients, parents, educators, health agencies, and political decision makers to help reducing the global cardiovascular disease burden in the decades to come.

Differential expression of β-catenin and Dickkopf-1 in the third trimester placentas from normal and preeclamptic pregnancies: a comparative study

BACKGROUND

Beta-catenin is a key nuclear effector of Wnt signaling which could be antagonized by dickkopf-1(DKK1). Beta-catenin and DKK1 are involved in a variety of biological processes; however, their expression in the placenta with severe preeclampsia (PE) has not been elucidated. This study was aimed to detect the localization and compare the expression of beta-catenin and DKK1 in normal and preeclamptic placenta.

METHODS

Sixty pregnant women who underwent cesarean section were enrolled in this study, including 30 healthy pregnant women in the control group and 30 preeclamptic women in the severe PE group. Real-time polymerase chain reaction (real-time-PCR) and western blot were employed to detect the beta-catenin and DKK1 mRNA and protein expression levels, respectively, and their locations were evaluated by immunohistochemistry (IHC).

RESULTS

Our results indicated that beta-catenin and DKK1 were expressed predominantly in the syncytiotrophoblast and the extravillous trophoblast (EVT). The beta-catenin mRNA and protein expressions were significantly decreased, whereas the DKK1 significantly increased in preeclamptic placental tissues compared to normal placental controls.

CONCLUSIONS

In conclusion, decreased beta-catenin expression, as well as DKK1 over-expression might be associated with the process of the pathogenesis of PE. Further studies would elucidate their exact roles in the pathogenesis of PE.

Exercise training attenuates placental ischemia-induced hypertension and angiogenic imbalance in the rat

An imbalance between proangiogenic (vascular endothelial growth factor) and antiangiogenic (soluble fms-like tyrosine kinase 1) factors plays an important role in hypertension associated with reduced uteroplacental perfusion (RUPP). Exercise has been shown to stimulate proangiogenic factors, such as vascular endothelial growth factor, in both the pregnant and nonpregnant state; thus, we hypothesized that exercise training would attenuate both angiogenic imbalance and hypertension attributed to RUPP. Four groups of animals were studied, RUPP and normal pregnant controls and normal pregnant and RUPP+exercise training. Exercise training attenuated RUPP-induced hypertension (P<0.05), decreased soluble fms-like tyrosine kinase 1 (P<0.05), increased VEGF (P<0.05), and elevated the soluble fms-like tyrosine kinase 1:vascular endothelial growth factor ratio. The positive effects of exercise on angiogenic balance in the RUPP rats were confirmed by restoration (P<0.05) of the RUPP-induced decrease in endothelial tube formation in human umbilical vascular endothelial cells treated with serum from each of the experimental groups. Placental prolyl hydroxylase 1 was increased (P<0.05) in RUPP+exercise training rats. Decreased trolox equivalent antioxidant capacity in the placenta, amniotic fluid, and kidney of the RUPP rats was reversed by exercise. RUPP-induced increase in renal thiobarbituric acid reactive species was attenuated by exercise. The present data show that exercise training before and during pregnancy attenuates placental ischemia-induced hypertension, angiogenic imbalance, and oxidative stress in the RUPP rat and reveals that increased prolyl hydroxylase 1 is associated with decreased soluble fms-like tyrosine kinase 1, thus revealing several potential pathways for exercise training to mitigate the effects of placental ischemia-induced hypertension. Lastly, the present study demonstrates that exercise training may be a useful approach to attenuate the development of placental ischemia-induced hypertension during pregnancy.

Brain cell apoptosis and enhancement of nervous excitability in pregnant rats with high plasma levels of homocysteine

Hyperhomocysteinemia is an important risk factor for preeclampsia-eclampsia. This study established a pregnant rat model of hyperhomocysteinemia, in which blood plasma homocysteine concentrations were twice or three times greater than that of normal pregnant rats. TUNEL revealed an increase in the number of apoptotic cells in the frontal cortex of pregnant rats with hyperhomocysteinemia. In addition, immunohistochemical staining detected activated nuclear factor-κB-positve cells in the frontal cortex. Reverse transcription-PCR detected that mRNA expression of the anti-apoptotic gene bcl-2 diminished in the frontal cortex. In situ hybridization and western blotting revealed that N-methyl-D-aspartate receptor 1 mRNA and protein expression was upregulated in the frontal cortex and hippocampus. These results indicate that hyperhomocysteinemia can induce brain cell apoptosis, increase nerve excitability, and promote the occurrence of preeclampsia in pregnant rats.

Agonistic autoantibodies to the angiotensin II type I receptor cause pathophysiologic characteristics of preeclampsia

BACKGROUND

Preeclampsia (PE), new-onset hypertension with proteinuria during pregnancy, is associated with increased reactive oxygen species, the vasoactive peptide endothelin-1 (ET-1), T and B lymphocytes, soluble antiangiogenic factors sFlt-1 and sEndoglin (sFlt-1 and sEng), and agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA).

OBJECTIVES

One important area of investigation for our laboratory was to determine what role AT1-AA plays in the pathophysiology associated with PE.

METHODS

To achieve this goal, we examined the effect of AT1-AA suppression on hypertension in response to placental ischemia as well as the effect of AT1-AA on increased blood pressure, ET-1, reactive oxygen species, and sFlt-1 in normal pregnant rats (NP).

RESULTS

We demonstrated reductions in uterine perfusion pressure (RUPP) to be a stimulus for AT1-AA during pregnancy. We utilized the technique of B-cell depletion to suppress circulating AT1-AA in RUPP rats and found that AT1-AA suppression in RUPP rats was associated with lower blood pressure and ET-1 activation. To determine a role for AT1-AA to mediate hypertension during pregnancy, we infused purified rat AT1-AA (1:50) into NP rats, and analyzed blood pressure and soluble factors. We consistently found that AT1-AA infused rats had significantly increased AT1-AA and blood pressure above NP rats. This hypertension was associated with significantly increased ET-1 in renal cortices (11-fold) and placenta (4-fold), and there was an approximately 2- to 3-fold increase in placental oxidative stress. Furthermore, antiangiogenic factors sFlt-1 and sEng were significantly increased in the AT1-AA induced hypertensive group compared with the NP controls.

CONCLUSIONS

Collectively, these data indicated an important role for AT1-AA stimulated in response to placental ischemia that caused hypertension during pregnancy.

Normal pregnancy: mechanisms underlying the paradox of a ouabain-resistant state with elevated endogenous ouabain, suppressed arterial sodium calcium exchange, and low blood pressure

Endogenous cardiotonic steroids (CTS) raise blood pressure (BP) via vascular sodium calcium exchange (NCX1.3) and transient receptor-operated channels (TRPCs). Circulating CTS are superelevated in pregnancy-induced hypertension and preeclampsia. However, their significance in normal pregnancy, where BP is low, is paradoxical. Here we test the hypothesis that vascular resistance to endogenous ouabain (EO) develops in normal pregnancy and is mediated by reduced expression of NCX1.3 and TRPCs. We determined plasma and adrenal levels of EO and the impact of exogenous ouabain in pregnancy on arterial expression of Na(+) pumps, NCX1.3, TRPC3, and TRPC6 and BP. Pregnant (embryonic day 4) and nonpregnant rats received infusions of ouabain or vehicle. At 14-16 days, tissues and plasma were collected for blotting and EO assay by radioimmunoassay (RIA), liquid chromatography (LC)-RIA, and LC-multidimensional mass spectrometry (MS3). BP (-8 mmHg; P < 0.05) and NCX1.3 expression fell (aorta -60% and mesenteric artery -30%; P < 0.001) in pregnancy while TRPC expression was unchanged. Circulating EO increased (1.14 ± 0.13 nM) vs. nonpregnant (0.6 ± 0.08 nM; P < 0.05) and was confirmed by LC-MS3 and LC-RIA. LC-MS3 revealed two previously unknown isomers of EO; one increased ∼90-fold in pregnancy. Adrenal EO but not isomers were increased in pregnancy. In nonpregnant rats, similar infusions of ouabain raised BP (+24 ± 3 mmHg; P < 0.001). In ouabain-infused rats, impaired fetal and placental growth occurred with no BP increase. In summary, normal pregnancy is an ouabain-resistant state associated with low BP, elevated circulating levels of EO, two novel steroidal EO isomers, and increased adrenal mass and EO content. Ouabain raises BP only in nonpregnant animals. Vascular resistance to the chronic pressor activity of endogenous and exogenous ouabain is mediated by suppressed NCX1.3 and reduced sensitivity of events downstream of Ca(2+) entry. The mechanisms of EO resistance and the impaired fetal and placental growth due to elevated ouabain may be important in pregnancy-induced hypertension (PIH) and preeclampsia (PE).

B Cell in Autoimmune Diseases

The role of B cells in autoimmune diseases involves different cellular functions, including the well-established secretion of autoantibodies, autoantigen presentation and ensuing reciprocal interactions with T cells, secretion of inflammatory cytokines, and the generation of ectopic germinal centers. Through these mechanisms B cells are involved both in autoimmune diseases that are traditionally viewed as antibody mediated and also in autoimmune diseases that are commonly classified as T cell mediated. This new understanding of the role of B cells opened up novel therapeutic options for the treatment of autoimmune diseases. This paper includes an overview of the different functions of B cells in autoimmunity; the involvement of B cells in systemic lupus erythematosus, rheumatoid arthritis, and type 1 diabetes; and current B-cell-based therapeutic treatments. We conclude with a discussion of novel therapies aimed at the selective targeting of pathogenic B cells.

Receptor-activating autoantibodies and disease: preeclampsia and beyond

The research reviewed in this article provides examples of autoantibody-mediated receptor activation that likely contributes to disease. The classic example is Graves' hyperthyroidism, in which autoantibodies activate the thyroid-stimulating hormone receptor resulting in overproduction of thyroid hormones. Other compelling examples come from the cardiovascular literature and include agonistic autoantibodies targeting the cardiac β(1)-adrenergic receptor, which are associated with dilated cardiomyopathy. Autoantibodies capable of activating α(1)-adrenergic receptors are associated with refractory hypertension and cardiomyopathy. A prominent example is preeclampsia, a hypertensive disease of pregnancy, characterized by the presence of autoantibodies that activate the major angiotensin receptor, AT(1). AT(1) receptor-activating autoantibodies are also observed in kidney transplant recipients suffering from severe vascular rejection and malignant hypertension. AT(1) receptor-activating autoantibodies and antibodies that activate the endothelin-1 receptor, ET(A), are prevalent in individuals diagnosed with systemic sclerosis. Thus, the presence of agonistic autoantibodies directed to G protein-coupled receptors has been observed in numerous cardiovascular disease states. Rapidly emerging evidence indicates that receptor-activating autoantibodies contribute to disease, and that efforts to detect and remove these pathogenic autoantibodies or block their actions will provide promising therapeutic possibilities.

Vitamin D, the placenta and pregnancy

Impaired vitamin D status is common to many populations around the world. However, data suggest that this is a particular problem for specific groups such as pregnant women. This has raised important questions concerning the physiological and clinical impact of low vitamin D levels during pregnancy, with implications for classical skeletal functions of vitamin D, as well as its diverse non-classical actions. The current review will discuss this with specific emphasis on the classical calciotropic effects of vitamin D as well as the less well established immunological functions of vitamin D that may influence pregnancy outcome. The review also describes the pathways that are required for metabolism and function of vitamin D, and the various clinical complications that have been linked to impaired vitamin D status during pregnancy.

Alterations in maternal and fetal heart functions accompany failed spiral arterial remodeling in pregnant mice

OBJECTIVE

Our goal was to define mechanisms that protect murine pregnancies deficient in spiral arterial remodeling from hypertension, hypoxia, and intrauterine growth restriction.

STUDY DESIGN

Microultrasound analyses were conducted on virgin, gestation day 2, 4, 7, 9, 10, 12, 14, 16, 18, and postpartum BALB/c (wild type) mice and BALB/c-Rag2(-/-)/Il2rg(-/-) mice, an immunodeficient strain lacking spiral arterial remodeling.

RESULTS

Rag2(-/-)/Il2rg(-/-) dams had normal spiral arterial flow velocities, greatly elevated uterine artery flow velocities between gestational day 10-16 and smaller areas of placental flow from gestational day 14 to term than controls. Maternal heart weight and output increased transiently. Conceptus alterations included higher flow velocities in the umbilical-placental circulation that became normal before term and bradycardia persistent to term.

CONCLUSION

Transient changes in maternal heart weight and function accompanied by fetal circulatory changes successfully compensate for deficient spiral arterial modification in mice. Similar compensations may contribute to the elevated risk for cardiovascular diseases seen in women and their children who experience preeclamptic pregnancies.

Role of angiotensin II type I receptor agonistic autoantibodies (AT1-AA) in preeclampsia

Despite being one of the leading causes of maternal death and a major contributor of maternal and perinatal morbidity, the mechanisms responsible for the pathogenesis of preeclampsia are unclear. One important initiating event in preeclampsia is thought to be reduced placental perfusion leading to the production of a variety of factors that cause widespread dysfunction of the maternal vasculature. The major objective of this review is to discuss the potential role of a novel agonistic autoantibody to the angiotensin II type I receptor (AT1-AA) in mediating hypertension during pregnancy. Although animal studies suggest that increasing plasma AT1-AA concentration in pregnant rats to levels observed in preeclamptic women or placental ischemic rats result in significant increases in arterial pressure, the quantitative importance of AT1-AA in the pathophysiology of preeclampsia in humans has yet to be fully elucidated.

Primary hypertension and special aspects of hypertension in older children and adolescents

The prevalence of hypertension has increased at an accelerated rate in older children and adolescents. This has raised great concern about premature development of cardiovascular disease, which has major long-term health and financial implications. While obesity and sedentary habits largely explain this phenomenon, there are other social and cultural influences that may unmask genetic susceptibility to hypertension in the pediatric population. While it is essential to exclude numerous causes of secondary hypertension in every child, these disorders are not discussed in this review. Rather, the aim of this review is to familiarize pediatricians with casual and ambulatory blood pressure measurement, epidemiology, pathophysiology, and management of several common conditions that play a role in the development of hypertension in children and adolescents. Besides primary hypertension and obesity-related hypertension, emphasis is given to epidemiology, measurement of blood pressure, including ambulatory blood pressure monitoring, hypertension associated with drug use, teenage pregnancy, and video and computer games. Lastly, because pediatricians are increasingly confronted with special issues concerning the management of the hypertensive athlete, this topic is also addressed.

Advances in metal-induced oxidative stress and human disease

Detailed studies in the past two decades have shown that redox active metals like iron (Fe), copper (Cu), chromium (Cr), cobalt (Co) and other metals undergo redox cycling reactions and possess the ability to produce reactive radicals such as superoxide anion radical and nitric oxide in biological systems. Disruption of metal ion homeostasis may lead to oxidative stress, a state where increased formation of reactive oxygen species (ROS) overwhelms body antioxidant protection and subsequently induces DNA damage, lipid peroxidation, protein modification and other effects, all symptomatic for numerous diseases, involving cancer, cardiovascular disease, diabetes, atherosclerosis, neurological disorders (Alzheimer's disease, Parkinson's disease), chronic inflammation and others. The underlying mechanism of action for all these metals involves formation of the superoxide radical, hydroxyl radical (mainly via Fenton reaction) and other ROS, finally producing mutagenic and carcinogenic malondialdehyde (MDA), 4-hydroxynonenal (HNE) and other exocyclic DNA adducts. On the other hand, the redox inactive metals, such as cadmium (Cd), arsenic (As) and lead (Pb) show their toxic effects via bonding to sulphydryl groups of proteins and depletion of glutathione. Interestingly, for arsenic an alternative mechanism of action based on the formation of hydrogen peroxide under physiological conditions has been proposed. A special position among metals is occupied by the redox inert metal zinc (Zn). Zn is an essential component of numerous proteins involved in the defense against oxidative stress. It has been shown, that depletion of Zn may enhance DNA damage via impairments of DNA repair mechanisms. In addition, Zn has an impact on the immune system and possesses neuroprotective properties. The mechanism of metal-induced formation of free radicals is tightly influenced by the action of cellular antioxidants. Many low-molecular weight antioxidants (ascorbic acid (vitamin C), alpha-tocopherol (vitamin E), glutathione (GSH), carotenoids, flavonoids, and other antioxidants) are capable of chelating metal ions reducing thus their catalytic activity to form ROS. A novel therapeutic approach to suppress oxidative stress is based on the development of dual function antioxidants comprising not only chelating, but also scavenging components. Parodoxically, two major antioxidant enzymes, superoxide dismutase (SOD) and catalase contain as an integral part of their active sites metal ions to battle against toxic effects of metal-induced free radicals. The aim of this review is to provide an overview of redox and non-redox metal-induced formation of free radicals and the role of oxidative stress in toxic action of metals.

Hypertension in response to placental ischemia during pregnancy: role of B lymphocytes

Preeclampsia is associated with innate inflammatory response resulting in elevated tumor necrosis factor-α, agonistic autoantibodies to the angiotensin II type I receptor, and activation of endothelin 1 (ET-1). This study was designed to determine the role of B-cell depletion, resulting in agonistic autoantibodies to the angiotensin II type I receptor suppression to mediate hypertension via activation of ET-1 in the placental ischemic reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. To achieve this goal we examined the effect of RUPP on mean arterial pressure and ET-1 in the presence and absence of chronically infused rituximab (R; 250 mg/kg), a B-lymphocyte-suppressive agent used clinically to treat autoimmune diseases. Mean arterial pressure was 103±1 mm Hg in normal pregnant (NP) rats; 103±3 mm Hg in NP+R versus 133±2 mm Hg in RUPP rats, and 118±2 mm Hg in RUPP+R rats (P<0.001 vs RUPP controls). B lymphocytes decreased from 6.0±0.5% gated cells in RUPP to 3.7±0.8% gated cells in RUPP+R rats. Importantly, agonistic autoantibodies to the angiotensin II type I receptor decreased from 18±1 bpm in RUPP rats to 10±1 bpm in RUPP+R rats. ET-1 decreased 1.5-fold in kidneys and 4-fold in the placenta (P<0.01) of RUPP+R versus RUPP rats. Media ET-1 excretion from endothelial cells exposed to serum from NP, RUPP, NP+R, or RUPP+R rats was determined. ET-1 from endothelial cells treated with NP serum was 53+13 pg/mg and increased to 75+10 pg/mg with RUPP serum. In contrast, ET-1 secretion decreased in response to B-cell-depleted RUPP serum to 50±8 pg/mg and was unchanged in response to NP+R sera (46±12 pg/mg). These data demonstrate the important roles that B-lymphocyte activation and agonistic autoantibodies to the angiotensin II type I receptors play in the pathophysiology of hypertension in response to placental ischemia.

Effect of pre-eclampsia-eclampsia on major cardiovascular events among peripartum women in Taiwan

There is no large-scale population-based study to clarify the association between major adverse cardiovascular events (MACEs) and pre-eclampsia/eclampsia. A population-based Taiwanese cohort study was performed in 1,132,064 parturients from 1999 to 2003 using a dataset linking birth certificates and National Health Insurance hospital discharge data. Sociodemographic factors and obstetric complications were used in multivariate logistic regression models to determine adjusted hazard ratios of pre-eclampsia/eclampsia on risks of MACEs and mortality during pregnancy to at least the third year postpartum. Incidence rates of MACEs and all maternal mortality in women with pre-eclampsia/eclampsia were 16.21 and 40.38 per 100,000 patients per year, respectively. Women with pre-eclampsia/eclampsia had a 13.0-fold higher incidence of myocardial infarction, a 8.3-fold higher incidence of heart failure, a 14.5-fold higher incidence of stroke, a 12.6-fold higher incidence of MACEs, a 7.3-fold higher incidence of MACEs without stroke, a 2.3-fold higher incidence of MACE-related deaths, and a 6.4-fold higher incidence of overall death than women without pre-eclampsia/eclampsia. Kaplan-Meier survival curve discriminated in MACEs, nonstroke MACEs, MACE related death and overall death. In conclusion, women with pre-eclampsia/eclampsia have a significantly higher risk of MACEs, especially myocardial infarction and stroke, during pregnancy and their risk remains significant to ≥36 months postpartum. Our results suggest that women with pre-eclampsia/eclampsia should be closely monitored during pregnancy and for up to ≥3 years postpartum.

Recognizing and improving health care disparities in the prevention of cardiovascular disease in women

Innate differences in gender physiology result in unique exposures, risk, and protection that are specific to women. Recognition and appreciation of these differences results in better treatment adaptations for women and better outcomes. Disparities between genders in the treatment of major cardiovascular risk factors still exist and are mostly secondary to underestimating or misunderstanding a woman's risk. Preventive therapies are less often recommended to women. Women are more likely to be diagnosed and treated for hypertension, but are less likely to reach treatment goals. High-risk women-including diabetic women-are less likely to be on lipid-lowering agents and reach a low-density lipoprotein level less than 100 mg/dL. Diabetic women are less likely to achieve a hemoglobin A(1c) level less than 7%. Through understanding these disparities, health care providers will be better able to screen female patients and institute evidence-based therapies for the prevention of cardiovascular disease.

Could uric acid have a pathogenic role in pre-eclampsia?

Interest has been renewed over the role of uric acid in the pathogenesis of hypertension, endothelial dysfunction and renal dysfunction, which are all features of pre-eclampsia. Uric acid is not a consistent predictive factor for the development of pre-eclampsia but its levels generally increase once the disease manifests, and plasma levels of uric acid approximately correlate with disease severity. Hyperuricemia in pre-eclampsia was once thought to result solely from reduced renal clearance, but levels of uric acid are now also thought to increase through increased uric acid production caused by trophoblast breakdown, cytokine release and ischemia. Uric acid can promote endothelial dysfunction, damage and inflammation, which leads to oxidation. Pre-eclampsia, which is characterized by widespread endothelial dysfunction and inflammation, might be propagated by uric acid through these known in vitro activities. Of note, however, uric acid can also act as a scavenger of oxygen free radicals. Plasma urate measurements are currently used to support the diagnosis of pre-eclampsia during pregnancy. As further studies define the role of uric acid in the development of pre-eclampsia, monitoring levels of this factor may again become essential to the future treatment of pre-eclampsia.

Increased risk of pre-eclampsia (PE) among women with the history of migraine

The Objective of this study was to assess possible association of history of migraine with pre-eclampsia (PE). This was a retrospective study to compare history of migraine in 90 women affected by PE with 90 women without PE as the control group. They recruited by a nonrandomized consecutive sampling method. Data were collected by a questionnaire including demographic, medical, obstetrics, and migraine assessment sections. Data were analyzed using SPSS. Results showed an increased risk of PE in women with history of migraine (odds ratio: 2.87; p < 0.05). Result demonstrated that migraine history in the case group is 14/4% and in control group is 5/6%. Gestational age (GA) at delivery and weight of neonate (WN) were significantly lower compared to control (GA: 37.3 +/- 2.6 vs. 38.7+/- 1.3 weeks T test; P < 0.01) (WN: 2930 +/- 690 vs. 3330 +/- 420; T test; P < 0.0). Cesarean section was more frequent in the PE group compared to the control group [37 (42%) vs. 14 (15.6%)]; chi square; p < 0.01]. The association of migraine with PE is the result of some similar mechanism leading to endothelial dysfunction. Frequent reports of an association between migraine and PE in different populations suggest a history of migraine as a risk factor for PE/gestational hypertension (GH).

The effect of immune factors, tumor necrosis factor-alpha, and agonistic autoantibodies to the angiotensin II type I receptor on soluble fms-like tyrosine-1 and soluble endoglin production in response to hypertension during pregnancy

BACKGROUND

Preeclampsia is considered a disease of immunological origin associated with abnormalities in inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha), and activated lymphocytes secreting autoantibodies to the angiotensin II receptor (AT1-AA). Recent studies have also demonstrated that an imbalance of angiogenic factors, soluble fms-like tyrosine kinase (sFlt-1), and sEndoglin, exists in preeclampsia; however, the mechanisms that initiate their overproduction are unclear.

METHODS

To determine the role of immune regulation of these factors, circulating and placental sFlt-1 and/or sEndoglin was examined from pregnant rats chronically treated with TNF-alpha or AT1-AA. On day 19 of gestation blood pressure was analyzed and serum and tissues were collected. Placental villous explants were excised and cultured on matrigel coated inserts for 24 h and sFlt-1 and sEndoglin was measured from media.

RESULTS

In response to TNF-alpha-induced hypertension, sFlt-1 increased from 180 +/- 5 to 2,907 +/- 412 pg/ml. sFlt-1 was also increased from cultured placental explants of TNF-alpha induced hypertensive pregnant rats (n = 12) (2,544 +/- 1,132 pg/ml) vs. explants from normal pregnant (NP) rats (n = 12) (2,189 +/- 586 pg/ml) where as sEng was undetectable. Circulating sFlt-1 increased from 245 +/- 38 to 3,920 +/- 798 pg/ml in response to AT1-AA induced hypertension. sFlt-1 levels were higher (3,400 +/- 350 vs. 2,480 +/- 900 pg/ml) in placental explants from AT1-AA infused rats (n = 12) than NP rats (n = 7). In addition, sEndoglin increased from 30 +/- 2.7 to 44 +/- 3.3 pg/ml (P < 0.047) in AT1-AA infused rats but was undetectable in the media of the placental explants.

CONCLUSIONS

These data suggest that immune factors may serve as an important stimulus for both sFlt-1 and sEndoglin production in response to placental ischemia.

Increased urinary orosomucoid excretion predicts preeclampsia in pregnant women with pregestational type 1 diabetes

AIMS

We evaluated the urinary orosomucoid excretion (UOE) as a biomarker of preeclampsia and preterm delivery in pregnant women with type 1 diabetes.

METHODS

Singleton pregnant women with pregestational type 1 diabetes were included provided one urine sample had been collected before 17 gestational weeks. Serum and urinary orosomucoid were analysed by immunoturbidimetry. Primary outcome measurements were development of preeclampsia (blood pressure>140/90mmHg and proteinuria) and preterm delivery before 37 weeks.

RESULTS

In total 173 women were included. The UOE increased during pregnancy. Preeclampsia developed in 20 women and 65 women delivered preterm. Using logistic regression analysis we found that UOE>1.37mg/l (OR: 6.85 (95% CI: 1.97-23.88; p<0.003)), nulliparity (3.88 (1.10-13.72); p<0.04), systolic blood pressure>120mmHg (4.12 (1.35-12.59); p<0.02) and duration of diabetes>20 years (3.69 (1.18-11.52); p<0.03) independently predicted the development of preeclampsia. Independent predictors of preterm delivery were duration of diabetes and HbA1c>7%. The remaining covariates included in the regression models were BMI, serum creatinine, smoking and microalbuminuria.

CONCLUSIONS

Increased UOE early in pregnancy predicted preeclampsia in women with pregestational type 1 diabetes independently of albuminuria and other known risk factors. No association to preterm delivery was found.

Risk factors and mediators of the vascular dysfunction associated with hypertension in pregnancy

Normal pregnancy is associated with significant hemodynamic changes and vasodilation in the uterine and systemic circulation in order to meet the metabolic demands of the mother and developing fetus. Hypertension in pregnancy (HTN-Preg) and preeclampsia (PE) are major complications and life-threatening conditions to both the mother and fetus. PE is precipitated by various genetic, dietary and environmental factors. Although the initiating events of PE are unclear, inadequate invasion of cytotrophoblasts into the uterine artery is thought to reduce uteroplacental perfusion pressure and lead to placental ischemia/hypoxia. Placental hypoxia induces the release of biologically active factors such as growth factor inhibitors, anti-angiogenic proteins, inflammatory cytokines, reactive oxygen species, hypoxia-inducible factors, and antibodies to vascular angiotensin II receptor. These bioactive factors affect the production/activity of various vascular mediators in the endothelium, smooth muscle and extracellular matrix, leading to severe vasoconstriction and HTN. As an endothelial cell disorder, PE is associated with decreased vasodilator mediators such as nitric oxide, prostacyclin and hyperpolarizing factor and increased vasoconstrictor mediators such as endothelin, angiotensin II and thromboxane A(2). PE also involves enhanced mechanisms of vascular smooth muscle contraction including intracellular free Ca(2+) concentration ([Ca(2+)](i)), and [Ca(2+)](i) sensitization pathways such as protein kinase C, Rho-kinase and mitogen-activated protein kinase. Changes in extracellular matrix composition and matrix metalloproteases activity also promote vascular remodeling and further vasoconstriction in the uterine and systemic circulation. Characterization of the predisposing risk factors, the biologically active factors, and the vascular mediators associated with PE holds the promise for early detection, and should help design specific genetic and pharmacological tools for the management of the vascular dysfunction associated with HTN-Preg.

Effects of circulating and local uteroplacental angiotensin II in rat pregnancy

The renin-angiotensin (Ang) system is important during placental development. Dysregulation of the renin-Ang system is important in preeclampsia (PE). Female rats transgenic for the human angiotensinogen gene crossed with males transgenic for the human renin gene develop the PE syndrome, whereas those of the opposite cross do not. We used this model to study the role of Ang II in trophoblast invasion, which is shallow in human PE but deeper in this model. We investigated the following groups: PE rats, opposite-cross rats, Ang II-infused rats (1000 ng/kg per day), and control rats. Ang II infusion increased only circulating Ang II levels (267.82 pg/mL), opposite cross influenced only uteroplacental Ang II (13.52 fmol/mg of protein), and PE increased both circulating (251.09 pg/mL) and uteroplacental (19.24 fmol/mg of protein) Ang II. Blood pressure and albuminuria occurred in the models with high circulating Ang II but not in the other models. Trophoblast invasion increased in PE and opposite-cross rats but not in Ang II-infused rats. Correspondingly, uterine artery resistance index increased in Ang II-infused rats but decreased in PE rats. We then studied human trophoblasts and villous explants from first-trimester pregnancies with time-lapse microscopy. Local Ang II dose-dependently increased migration by 75%, invasion by 58%, and motility by 282%. The data suggest that local tissue Ang II stimulates trophoblast invasion in vivo in the rat and in vitro in human cells, a hitherto fore unrecognized function. Conceivably, upregulation of tissue Ang II in the maternal part of the placenta represents an important growth factor for trophoblast invasion and migration.

Application of a first-trimester prediction model for pre-eclampsia based on uterine arteries and maternal history in high-risk pregnancies

OBJECTIVE

To assess the value of a prediction model for pre-eclampsia (PE) in the first trimester (Ultrasound Obstet Gynecol 2007;30:742-794) for the prediction of late (>34 weeks) and early (< or =34 weeks) PE in a high-risk population.

METHODS

Longitudinal study performed in 152 high-risk pregnancies with at least one high-risk condition: previous PE, hypertension, pregestational diabetes, renal disease, obesity, hyperlipidemia, autoimmune disorders, thrombophilia or recurrent pregnancy loss. Mean uterine artery pulsatility index at 11 to 13 + 6 weeks and a series of maternal variables were combined in order to obtain the estimated 'a posteriori risk for PE' in each woman. This risk for unaffected women was compared with that for patients who subsequently developed late and early PE. The performance of such approach was described by receiver-operating characteristic curves.

RESULTS

Late PE developed in 13 (8.6%) pregnancies and early PE in seven (4.6%). The median 'a posteriori risk for PE' in the unaffected, late PE, and early PE groups was 0.62%, 1.22%, and 2.49% (P < 0.01), respectively. For a false-positive rate of 10%, the detection rates of late and early PE were 23.1 and 42.9%, respectively.

CONCLUSIONS

This referenced model shows a modest performance when applied to high-risk women.

Recombinant vascular endothelial growth factor 121 infusion lowers blood pressure and improves renal function in rats with placentalischemia-induced hypertension

Antagonism of vascular endothelial growth factor (VEGF) signaling by soluble fms-like tyrosine kinase 1 occurs during preeclampsia and is proposed to play an important role in the pathogenesis of preeclampsia. We reported recently that hypertension associated with chronic reductions in uteroplacental perfusion pressure (RUPP) is associated with increased soluble fms-like tyrosine kinase 1 and decreased free VEGF. Whether restoration of circulating VEGF can restore renal function and chronically decrease arterial pressure associated with placental ischemia remains unknown. We hypothesized that chronic infusion of VEGF(121) would attenuate hypertension, increase glomerular filtration rate, and reverse the endothelial dysfunction associated with chronic RUPP. VEGF(121) (at either 90 or 180 microg/kg per day) was administered for 5 days via osmotic minipump placed IP. Mean arterial pressure, renal function, and tissues were obtained on day 19 of pregnancy from RUPP+VEGF, RUPP, and normal pregnant dams. Mean arterial pressure was increased in the RUPP (131+/-3 mm Hg) compared with the normal pregnant (102+/-1 mm Hg) rats, and infusion of VEGF(121) resolved the hypertension (105+/-5 mm Hg). Glomerular filtration rate was decreased in the RUPP dams (1.5+/-0.3 mL/min) and restored to normal pregnant levels (3.1+/-0.5 mL/min) by VEGF(121) treatment (3.1+/-0.4 mL/min). Effective renal plasma flow, decreased by RUPP, was also increased by VEGF(121) infusion. Relaxation to acetylcholine was enhanced by the VEGF treatment (P<0.05). These data demonstrate that chronic infusion of VEGF(121) during late gestation restores glomerular filtration rate and endothelial function and reduces high blood pressure associated with placental ischemia. The present results suggest that VEGF(121) may be a candidate molecule for management of preeclampsia and its related complications.

Role of endothelin in mediating soluble fms-like tyrosine kinase 1-induced hypertension in pregnant rats

Although soluble fms-like tyrosine kinase 1 (sFlt-1), an antagonist of vascular endothelial growth factor and placental growth factor, has been implicated in the pathogenesis of hypertension during preeclampsia, the mechanisms whereby enhanced sFlt-1 production leads to hypertension remain unclear. Both sFlt-1 and endothelin 1 productions are elevated in women with preeclampsia and in placental ischemic animal models of preeclampsia; however, the importance of endothelin 1 and sFlt-1 interactions in the control of blood pressure during pregnancy is unknown. The purpose of this study was to determine the role of endothelin 1 in mediating sFlt-1-induced hypertension in pregnant rats. To achieve this goal, sFlt-1 (3.7 microg/kg per day for 6 days) was infused into normal pregnant rats and pregnant rats treated with a selective endothelin type A receptor antagonist, ABT 627 (5 mg/kg per day for 6 days). Plasma concentration of sFlt-1 increased from 735+/-34 pg/mL in normal pregnant rats to 2498+/-645 pg/mL (P<0.05) with infusion of sFlt-1. Arterial pressure increased from 100+/-1 mm Hg in normal pregnant rats to 122+/-3 mm Hg (P<0.05) in sFlt-1-infused rats. Chronic increases in plasma sFlt-1 in normal pregnant rats increased preproendothelin mRNA expression in the renal cortices by approximately 3-fold. In addition, chronic endothelin type A receptor blockade completely abolished the blood pressure response to sFlt-1 in pregnant rats (104+/-3 versus 100+/-1 mm Hg; P<0.05), whereas the endothelin A receptor antagonist had no effect on arterial pressure in NP rats (105+/-2 versus 100+/-1 mm Hg). In conclusion, this study demonstrates that endothelin 1, via endothelin type A receptor activation, plays an important role in mediating the hypertension in response to excess sFlt-1 during pregnancy.

Effects of hyperhomocysteinemia on arterial pressure and nitric oxide production in pregnant rats

BACKGROUND

An elevated plasma level of homocysteine (hyperhomocysteinemia) is thought to be an important risk factor for a variety of cardiovascular diseases including preeclampsia. Although clinical studies have reported a two- to threefold elevation in plasma levels of homocysteine in women who developed preeclampsia, the importance of hyperhomocysteinemia in causing endothelial dysfunction and increases in arterial pressure during pregnancy is unknown.

METHODS

Therefore, the purpose of this study was to determine the effects of a two- to threefold elevation in plasma homocysteine levels on arterial pressure, chronic pressure-natriuresis relationship, and endothelial factors during pregnancy in the rat. Homocysteine treatment for 4 weeks increased plasma homocysteine levels in pregnant rats from 7.1 +/- 1.9 to 16.7 +/- 2.3 micromol/l.

RESULTS

Homocysteine treatment decreased urinary nitrate/nitrite levels from 53 +/- 7 vs. 39 +/- 5 (micromol/24 h/kg body weight) in pregnant rats whereas having no effect on urinary excretion of endothelin. Homocysteine treatment had no effect on mean arterial pressure (MAP) in pregnant rats (104 +/- 2 vs. 107 +/- 3 mm Hg) nor on the chronic pressure-natriuresis relationship.

CONCLUSIONS

These results suggest that although hyperhomocysteinemia decreases nitric oxide (NO) production in pregnant rats, hyperhomocysteinemia does not affect MAP, the chronic pressure-natriuresis relationship, or urinary excretion of endothelin in pregnant rats. Moreover, the reported two- to threefold elevation in plasma level of homocysteine in women with preeclampsia is unlikely to contribute to the hypertension of preeclampsia.

Effects of 17-hydroxyprogesterone on tumor necrosis factor-alpha-induced hypertension during pregnancy

BACKGROUND

Inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) may be an important link between placental ischemia and hypertension in preeclampsia. We examined the effect of 17-hydroxyprogesterone caproate (17-OHP) on TNF-alpha-stimulated endothelin (ET) production and hypertension during pregnancy.

METHODS

TNF-alpha-stimulated ET was examined from endothelial cells cultured in the presence and absence of progesterone. Blood pressure and tissue ET-1 were measured in the following groups of pregnant rats: controls, 17-OHP (3.32 mg/kg), TNF-alpha treated (50 ng/day), TNF-alpha treated+17-OHP.

RESULTS

Progesterone abolished TNF-alpha-stimulated ET-1 from endothelial cells. TNF-alpha-induced hypertension was associated with significant increases in renal and placental ET-1. Administration of 17-OHP attenuated TNF-alpha-induced hypertension and decreased renal ET-1.

CONCLUSION

Progesterone directly abolished TNF-alpha-stimulated ET-1 and attenuated TNF-alpha-induced hypertension, possibly via suppression of the renal ET-1 system. These data suggest that treatment with progesterone of hypertension associated with elevated cytokines during pregnancy may be worthy of further consideration.

Hypertension in response to autoantibodies to the angiotensin II type I receptor (AT1-AA) in pregnant rats: role of endothelin-1

Agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) and endothelin -1 (ET-1) are suggested to be important links between placental ischemia and hypertension during preeclampsia. Activation of the angiotensin II type 1 receptor (AT1R) increases endothelial cell production of ET-1; however, the importance of ET-1 in response to AT1-AA-mediated AT1 R activation during preeclampsia is unknown. Furthermore, the role of AT1-AA-mediated increases in blood pressure during pregnancy remains unclear. The objective of this study was to test the hypothesis that AT1-AA, increased to levels observed in preeclamptic women and placental ischemic rats, increases mean arterial pressure (MAP) by activation of the ET-1 system. Chronic infusion of purified rat AT1-AA into normal pregnant (NP) rats for 7 days increased AT1-AA from 0.68+/-0.5 to 10.88+/-1.1 chronotropic units (P<0.001). The increased AT1-AA increased MAP from 99+/-1 to 119+/-2 mm Hg (P<0.001). The hypertension was associated with significant increases in renal cortices (11-fold) and placental (4-fold) ET-1. To determine whether ET-1 mediates AT1-AA-induced hypertension, pregnant rats infused with AT1-AA and NP rats were treated with an ET(A) receptor antagonist. MAP was 100+/-1 mm Hg in AT1-AA+ET(A) antagonist-treated rats versus 98+/-2 mm Hg in ET(A) antagonist-treated rats. Collectively, these data support the hypothesis that one potential pathway whereby AT1-AAs increase blood pressure during pregnancy is by an ET-1-dependent mechanism.

17-Hydroxyprogesterone blunts the hypertensive response associated with reductions in uterine perfusion pressure in pregnant rats

OBJECTIVE

Reduction in uteroplacental perfusion (RUPP) in pregnant rats is associated with hypertension, elevated cytokines, and activation of the endothelin (ET-1) system. Our objective was to determine whether the antiinflammatory properties of 17-alpha-hydroxyprogesterone caproate (17 OHP) reduce cytokine-stimulated vasoactive pathways that are associated with hypertension in response to placental ischemia.

STUDY DESIGN

Mean arterial pressure (MAP), tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, and renal ET-1 were measured in the following: pregnant controls, pregnant controls plus 17 OHP (6.6 mg/kg), RUPP rats, and RUPP rats plus 17 OHP.

RESULTS

MAP increased 29 mm Hg in RUPP rats compared with pregnant controls (P < .001), whereas in RUPP plus 17 OHP rats, MAP increased only 19 mm Hg (P < .05). TNF-alpha and IL-6 increased 2- to 3-fold, respectively, in response to placental ischemia but was normalized in RUPP rats treated with 17 OHP. ET-1 increased 3-fold in RUPP rats but was markedly less in RUPP plus 17 OHP rats.

CONCLUSION

17 OHP blunts hypertension associated with RUPP, possibly via suppression of cytokine-stimulated ET-1 activation.

Vitamin D deficiency during pregnancy may impair maternal and fetal outcomes

Over the past decade, new evidence has shown that vitamin D deficiency may contribute to the risk of developing a wide range of common chronic diseases that are different from the classic action on calcium and bone homeostasis. Acting through the vitamin D receptor, vitamin D can produce a wide array of favorable biological effects via genomic, non-genomic or intracrine mechanisms and, therefore, contributes to the improvement of human health in humans. We hypothesize that some of these effects may be even more critical during pregnancy. The focus of this paper is to review the data on the classic and non-classic actions of vitamin D with regards to pregnancy. It appears that vitamin D insufficiency during pregnancy is potentially associated with increased risk of preeclampsia, insulin resistance and gestational diabetes mellitus. Furthermore, experimental data also anticipate that vitamin D sufficiency is critical for fetal development, and especially for fetal brain development and immunological functions. Vitamin D deficiency during pregnancy may, therefore, not only impair maternal skeletal preservation and fetal skeletal formation but also be vital to the fetal "imprinting" that may affect chronic disease susceptibility soon after birth as well as later in life.