Role of the renin-angiotensin system in the pathogenesis of preeclampsia

Exploring the role of exosomal MicroRNAs as potential biomarkers in preeclampsia

The complex pathogenesis of preeclampsia (PE), a significant contributor to maternal and neonatal mortality globally, is poorly understood despite substantial research. This review explores the involvement of exosomal microRNAs (exomiRs) in PE, focusing on their impact on the protein kinase B (AKT)/hypoxia-inducible factor 1-α (HIF1α)/vascular endothelial growth factor (VEGF) signaling pathway as well as endothelial cell proliferation and migration. Specifically, this article amalgamates existing evidence to reveal the pivotal role of exomiRs in regulating mesenchymal stem cell and trophoblast function, placental angiogenesis, the renin-angiotensin system, and nitric oxide production, which may contribute to PE etiology. This review emphasizes the limited knowledge regarding the role of exomiRs in PE while underscoring the potential of exomiRs as non-invasive biomarkers for PE diagnosis, prediction, and treatment. Further, it provides valuable insights into the mechanisms of PE, highlighting exomiRs as key players with clinical implications, warranting further exploration to enhance the current understanding and the development of novel therapeutic interventions.

Regulation of vascular angiotensin II type 1 and type 2 receptor and angiotensin-(1-7)/MasR signaling in normal and hypertensive pregnancy

Normal pregnancy (Norm-Preg) is associated with a slight reduction in blood pressure (BP) and decreased BP response to vasoconstrictor stimuli such as angiotensin II (Ang II), although the renin-angiotensin-aldosterone system (RAAS) is upregulated. Preeclampsia (PE) is a complication of pregnancy manifested as hypertension-in-pregnancy (HTN-Preg), and dysregulation of angiotensin biosynthesis and signaling have been implicated. Ang II activates vascular Ang II type-1 receptor (AT1R) and Ang II type-2 receptor (AT2R), while angiotensin-(1-7) promotes Ang-(1-7)/MasR signaling. The role of AT1R in vasoconstriction and the activated cellular mechanisms are well-characterized. The sensitivity of vascular AT1R to Ang II and consequent activation of vasoconstrictor mechanisms decrease during Norm-Preg, but dramatically increase in HTN-Preg. Placental ischemia in late pregnancy could also initiate the release of AT1R agonistic autoantibodies (AT1AA) with significant impact on endothelial dysfunction and activation of contraction pathways in vascular smooth muscle including [Ca2+]c and protein kinase C. On the other hand, the role of AT2R and Ang-(1-7)/MasR in vascular relaxation, particularly during Norm-Preg and PE, is less clear. During Norm-Preg, increases in the expression/activity of vascular AT2R and Ang-(1-7)/MasR promote the production of endothelium-derived relaxing factors such as nitric oxide (NO), prostacyclin and endothelium-derived hyperpolarizing factor leading to generalized vasodilation. Aortic segments of Preg rats show prominent endothelial AT2R staining and increased relaxation and NO production in response to AT2R agonist CGP42112A, and treatment with AT2R antagonist PD123319 enhances phenylephrine-induced contraction. Decreased vascular AT2R and Ang-(1-7)/MasR expression and receptor-mediated mechanisms of vascular relaxation have been suggested in HTN-Preg animal models, but their role in human PE needs further testing. Changes in angiotensin-converting enzyme-2 (ACE2) have been observed in COVID-19 patients, and whether ACE2 influences the course of COVID-19 viral infection/immunity in Norm-Preg and PE is an intriguing area for research.

The Effects of Preeclamptic Milieu on Cord Blood Derived Endothelial Colony-Forming Cells

Preeclampsia is one of the leading causes of infant and maternal mortality worldwide. Many infants born from preeclamptic pregnancies are born prematurely with higher risk of developing cardiovascular later in their life. A key mechanism by which these complications occur is through stress-induced dysfunction of endothelial progenitor cells (EPCs), including endothelial colony-forming cells (ECFCs). To gain insight into this, cord blood derived ECFCs isolated from preeclamptic pregnancies (PRECs) were analyzed and compared to their healthy counterparts. While PRECs preserve key endothelial markers, they upregulate several markers associated with oxidative stress and inflammatory response. Compared to ECFCs, PRECs also exhibit lower migratory behaviors and impaired angiogenic potential. Interestingly, treatment of neuropilin-1 can improve tube formation in vitro. Collectively, this study reports that preeclamptic milieu influence phenotypes and functionality of PRECs, which can be rejuvenated using exogenous molecules. Promising results from this study warrant future investigations on the prospect of the rejuvenated PRECs to improve lung function of infants born from preeclamptic pregnancies.

The NADPH Link between the Renin Angiotensin System and the Antioxidant Mechanisms in Dopaminergic Neurons

The renin angiotensin system (RAS) has several components including signaling peptides, enzymes, and membrane receptors. The effort in characterizing this system in the periphery has led to the approval of a class of antihypertensives. Much less is known about RAS in the central nervous system. The production of RAS peptides and the expression of several RAS enzymes and receptors in dopaminergic neurons of the substantia nigra has raised expectations in the therapy of Parkinson's disease, a neurodegenerative condition characterized by lack of dopamine in the striatum, the motor control region of the mammalian brain. On the one hand, dopamine production requires reducing power. On the other hand, reducing power is required by mechanisms involved in REDOX homeostasis. This review focuses on the potential role of RAS in the regulation of neuronal/glial expression of glucose-6-phosphate dehydrogenase, which produces the NADPH required for dopamine synthesis and for reactive oxygen species (ROS) detoxification. It is known that transgenic expression of the gene coding for glucose-6-phosphate dehydrogenase prevents the death of dopaminergic nigral neurons. Signaling via angiotensin II G protein-coupled receptors, AT1 or AT2, leads to the activation of protein kinase A and/or protein kinase C that in turn can regulate glucose-6- phosphate dehydrogenase activity, by Ser/Thr phosphorylation/dephosphorylation events. Long-term effects of AT1 or AT2 receptor activation may also impact on the concentration of the enzyme via activation of transcription factors that participate in the regulation of gene expression in neurons (or glia). Future research is needed to determine how the system can be pharmacologically manipulated to increase the availability of NADPH to neurons degenerating in Parkinson's disease and to neuroprotective glia.

G-protein-coupled receptor MAS deletion produces a preeclampsia-like phenotype in FVB/N mice

BACKGROUND

An unbalance in the renin-angiotensin (Ang) system (RAS) between the Ang II/AT1 and Ang-(1-7)/Mas axis appears to be involved in preeclampsia (PE), in which a reduction in Ang-(1-7) was observed. Here, we tested whether the reduction in the activity of the Ang-(1-7)/Mas axis could be a contributing factor for the development of PE, using Mas-deficient (Mas-/-) mice.

METHODS AND RESULTS

Cardiovascular parameters were evaluated by telemetry before, during pregnancy and 4 days postpartum in 20-week-old Mas-/- and wild-type (WT) female mice. Mas-/- mice presented reduced arterial blood pressure (BP) at baseline (91.3 ± 0.8 in Mas-/- vs. 94.0 ± 0.9 mmHg in WT, Diastolic, P<0.05). However, after the 13th day of gestation, BP in Mas-/- mice started to increase, time-dependently, and at day 19 of pregnancy, these animals presented a higher BP in comparison with WT group (90.5 ± 0.7 in Mas-/- vs. 80.3 ± 3.5 mmHg in WT, Diastolic D19, P<0.0001). Moreover, pregnant Mas-/- mice presented fetal growth restriction, increase in urinary protein excretion as compared with nonpregnant Mas-/-, oliguria, increase in cytokines, endothelial dysfunction and reduced ACE, AT1R, ACE2, ET-1A, and eNOS placental mRNA, similar to some of the clinical manifestations found in the development of PE.

CONCLUSIONS

These results show that Mas-deletion produces a PE-like state in FVB/N mice.

RGS2 and female common diseases: a guard of women's health

Currently, women around the world are still suffering from various female common diseases with the high incidence, such as ovarian cancer, uterine fibroids and preeclampsia (PE), and some diseases are even with the high mortality rate. As a negative feedback regulator in G Protein-Coupled Receptor signaling (GPCR), the Regulator of G-protein Signaling (RGS) protein family participates in regulating kinds of cell biological functions by destabilizing the enzyme-substrate complex through the transformation of hydrolysis of G Guanosine Triphosphate (GTP). Recent work has indicated that, the Regulator of G-protein Signaling 2 (RGS2), a member belonging to the RGS protein family, is closely associated with the occurrence and development of certain female diseases, providing with the evidence that RGS2 functions in sustaining women's health. In this review paper, we summarize the current knowledge of RGS2 in female common diseases, and also tap and discuss its therapeutic potential by targeting multiple mechanisms.

Investigation of CD56, ADAM17 and FGF21 Expressions in the Placentas of Preeclampsia Cases

Objective: In the present study, we investigated the expression of CD56, ADAM17 and FGF21 antibodies (Ab), which we think have an effect on the pathophysiology of preeclampsia (PE), in pregnant patients with healthy placentas and placentas with PE. The expression of these antibodies has been investigated in a limited amount of former research, but their role in PE has not yet been clarified. With this study, we aimed to contribute to the elucidation of the pathophysiology of PE and the detection of new target molecules for treatment. Materials and Methods: Parturients with singleton pregnancy at 32 weeks or above without any maternal or fetal pathology who were admitted to the Department of Obstetrics and Gynecology, Zonguldak Bülent Ecevit University Practice and Research Hospital between 11 January 2020 and 7 January 2022 were included in the present study. Pregnant women with coexisting disease or a pathology related to the placenta (ablation placenta, vasa previa, hemangioma, etc.) were excluded. CD56, ADAM17 and FGF21 antibodies were histopathologically and immunohistochemically detected in 60 placentas with PE (study group) and 43 healthy placentas (control group). Results: CD56, ADAM17 and FGF21 proteins were all more intensely expressed in preeclamptic placentas and a statistically significant difference was found between the two groups for all three antibodies (p < 0.001). Deciduitis, perivillous fibrin deposition, intervillous fibrin, intervillous hemorrhage, infarct, calcification, laminar necrosis and syncytial node were found to be significantly more common in the study group (p < 0.001). Conclusions: We observed that CD56, ADAM17 and FGF21 expressions increased in preeclamptic placentas. These Ab may be responsible for the pathogenesis of PE, which can be illuminated with further studies.

The role of immune cells and mediators in preeclampsia

Preeclampsia is a hypertensive disorder of major concern in pregnancy than can lead to intrauterine growth restriction, placental abruption and stillbirth. The pathophysiology of preeclampsia is multifactorial, including not only kidney dysfunction but also endothelial dysfunction, as the maternal endothelium becomes exposed to placental factors that are released into the circulation and increase systemic levels of vasoconstrictors, oxidative stress, anti-angiogenic factors and inflammatory mediators. Importantly, inflammation can lead to insufficient placental perfusion and low birthweight in offspring. Various innate and adaptive immune cells and mediators have been implicated in the development of preeclampsia, in which oxidative stress is associated with activation of the maternal inflammatory response. Immune cells such as regulatory T cells, macrophages, natural killer cells, and neutrophils are known to have major causative roles in the pathology of preeclampsia, but the contributions of additional immune cells such as B cells, inflammatory cytokines and anti-angiotensin II type 1 receptor autoantibodies are also now recognized. Immunological interventions, therefore, have therapeutic potential in this disease. Here, we provide an overview of the immune responses that are involved in the pathogenesis of preeclampsia, including the role of innate and adaptive immune cells and mediators.

Increased angiotensin II coupled with decreased Adra1a expression enhances cardiac hypertrophy in pregnancy-associated hypertensive mice

Cardiac hypertrophy is a crucial risk factor for hypertensive disorders during pregnancy, but its progression during pregnancy remains unclear. We previously showed cardiac hypertrophy in a pregnancy-associated hypertensive (PAH) mouse model, in which an increase in angiotensin II (Ang II) levels was induced by human renin and human angiotensinogen, depending on pregnancy conditions. Here, to elucidate the factors involved in the progression of cardiac hypertrophy, we performed a comprehensive analysis of changes in gene expression in the hearts of PAH mice and compared them with those in control mice. We found that alpha-1A adrenergic receptor (Adra1a) mRNA levels in the heart were significantly reduced under PAH conditions, whereas the renin-angiotensin system was upregulated. Furthermore, we found that Adra1a-deficient PAH mice exhibited more severe cardiac hypertrophy than PAH mice. Our study suggests that Adra1a levels are regulated by renin-angiotensin system and that changes in Adra1a expression are involved in progressive cardiac hypertrophy in PAH mice.

COVID-19: Consequences on pregnant women and neonates

Introduction

Human species is confronting with a gigantic global COVID-19 pandemic. Initially, it was observed in Wuhan, China, and the COVID-19 cases spread across the globe with lightning speed and resulted in the 21st century pandemic. If scientific reports are taken care of, it is noteworthy that this virus possesses more specific characteristics due to its structure. The distinctive structure has a higher binding affinity with angiotensin-converting enzyme 2 (ACE2) protein, and this is used as an access point to gain access to hosts.

Methods

A complete literature search was conducted using PubMed, Google Scholar, SciFinder, and deep-diving Google Search using keywords such as "Pregnancy, COVID-19, Newborn, Fetus, Coronavirus 2019, Neonate, Pregnant women, and vertical transmission".

Result and discussion

The SARS-CoV-2 virus is unlike its former analogs: SARS-CoV, and MERS-CoV in 2002 and 2012, respectively, or anything mankind has faced earlier concerning viciousness, global spread, and gravity of a causative agent. The current review has delved into articles published in various journals worldwide including the latest studies on the impact of COVID-19 on pregnant women and neonates and has discussed complications and challenges, psychological health, immunological response, vertical transmission, concurrent disorders, vaccine debate, management recommendations, recent news of the approval of COVID-19 vaccine for 6 months and older babies, and future perspectives.

Effect of the number of parity on right heart chamber quantification

INTRODUCTION

Pregnancy is a process that can cause several physiologic changes to the cardiovascular system such as ventricular hypertrophy and dilation of cardiac chambers. Although there are studies about pregnancy-related changes in echocardiographic examination; there is no data about the long-term effects of parity on these alterations. Therefore, we evaluated the long-term effect of pregnancy on right ventricular (RV) dilation and RV hypertrophy and their relation to the parity number.

METHODS

This prospective study included a total of 600 women (200 consecutive women who had no parity, 200 women who had a parity number of 1 to 4 and 200 women who had a parity number of more than 4). Right chambers' measurements were compared between the groups.

RESULTS

In echocardiographic analysis, RV and right atrial dimensions and areas and RV wall thickness were higher in parous women. On the other hand, RV systolic function parameters were significantly lower in parous women. These significant changes showed a gradual increase or decrease by increasing parity number. By multivariate hierarchical logistic regression analysis, the four independent factors that increased the risk of RV dilation were age (OR: 1.16 CI: 1.10-1.20), body mass index (OR: 1.05, CI: 1.02-1.08), smoking (OR: 1.87, CI: 1.28-4.02), and giving a birth (OR: 3.94 CI: 1.82-8.81). There was also independent relationship between the number of parity and RV hypertrophy even after adjustment for several confounders.

CONCLUSION

Pregnancy-related physiological changes mostly resolve after delivery. This study about long-term effects of pregnancy on RV has demonstrated that there is a significant relation between the number of parity and either RV dilation or RV hypertrophy. Each parity had also additive effect on these changes.

Epigenetic processes during preeclampsia and effects on fetal development and chronic health

Preeclampsia (PE), the leading cause of maternal and fetal morbidity and mortality, is associated with poor fetal growth, intrauterine growth restriction (IUGR) and low birth weight (LBW). Offspring of women who had PE are at increased risk for cardiovascular (CV) disease later in life. However, the exact etiology of PE is unknown. Moreover, there are no effective interventions to treat PE or alleviate IUGR and the developmental origins of chronic disease in the offspring. The placenta is critical to fetal growth and development. Epigenetic regulatory processes such as histone modifications, microRNAs and DNA methylation play an important role in placental development including contributions to the regulation of trophoblast invasion and remodeling of the spiral arteries. Epigenetic processes that lead to changes in placental gene expression in PE mediate downstream effects that contribute to the development of placenta dysfunction, a critical mediator in the onset of PE, impaired fetal growth and IUGR. Therefore, this review will focus on epigenetic processes that contribute to the pathogenesis of PE and IUGR. Understanding the epigenetic mechanisms that contribute to normal placental development and the initiating events in PE may lead to novel therapeutic targets in PE that improve fetal growth and mitigate increased CV risk in the offspring.

Role of the Uteroplacental Renin-Angiotensin System in Placental Development and Function, and Its Implication in the Preeclampsia Pathogenesis

Placental development and function implicate important morphological and physiological adaptations to thereby ensure efficient maternal–fetal exchanges, as well as pregnancy-specific hormone secretion and immune modulation. Incorrect placental development can lead to severe pregnancy disorders, such as preeclampsia (PE), which endangers both the mother and the infant. The implication of the systemic renin–angiotensin system (RAS) in the pregnancy-related physiological changes is now well established. However, despite the fact that the local uteroplacental RAS has been described for several decades, its role in placental development and function seems to have been underestimated. In this review, we provide an overview of the multiple roles of the uteroplacental RAS in several cellular processes of placental development, its implication in the regulation of placental function during pregnancy, and the consequences of its dysregulation in PE pathogenesis.

The Involvement of MicroRNAs in SARS-CoV-2 Infection Comorbid with HIV-Associated Preeclampsia

Purpose of Review

This review investigated the potential role of microRNAs (miRNAs) in the synergy of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, preeclampsia (PE), and human immunodeficiency virus (HIV) infection. Maternal health is a great concern when treating pregnant women fighting this triad of diseases, which is highly prevalent in South Africa. MicroRNAs are involved in fine-tuning of physiological processes. Disruptions to the balance of this minute protein can lead to various physiological changes that are sometimes pathological.

Recent Findings

MicroRNAs have recently been implicated in PE and have been linked to the anti-angiogenic imbalance evident in PE. Recent in silico studies have identified potential host miRNAs with anti-viral properties against SARS-CoV-2 infection. Studies have demonstrated dysregulated expression of several miRNAs in HIV-1 infection along with the ability of HIV-1 to downregulate anti-viral host microRNAs.

Summary

This review has highlighted the significant gap in literature on the potential of miRNAs in women with HIV-associated PE in synergy with the novel SARS-CoV-2 infection. In addition, this review has provided evidence of the critical role that the epigenetic regulatory mechanism of miRNA plays in viral infections and PE, thereby providing a foundation for further research investigating the potential of therapeutic miRNA development with fewer side-effects for pregnant women.

A Longitudinal Pilot Study on Cognition and Cerebral Hemodynamics in a Mouse Model of Preeclampsia Superimposed on Hypertension: Looking at Mothers and Their Offspring

Preeclampsia is a common hypertensive disorder in pregnant women and whose causes and consequences have focused primarily on cardiovascular outcomes on the mother and offspring, often without taking into consideration the possible effects on the brain. One possible cause of preeclampsia has been attributed to alterations in the renin-angiotensin system, which has also been linked to cognitive decline. In this pilot study, we use a transgenic mouse model that chronically overexpresses human angiotensinogen and renin (R⁺A⁺ mice) that displayed characteristics of preeclampsia such as proteinuria during gestation. Offspring of these mothers as well as from control mothers were also examined. We were primarily interested in detecting whether cognitive deficits were present in the mothers and offspring in the long term and used a spatial learning and memory task as well as an object recognition task at three timepoints: 3, 8, and 12 months post-partum or post-natal, while measuring blood pressure and performing urine analysis after each timepoint. While we did not find significant deficits in preeclamptic mothers at the later timepoints, we did observe negative consequences in the pups of R⁺A⁺ mice that coincided with hemodynamic alterations whereby pups had higher whisker-evoked oxygenated hemoglobin levels and increased cerebral blood flow responses compared to control pups. Our study provides validation of this preeclampsia mouse model for future studies to decipher the underlying mechanisms of long-term cognitive deficits found in offspring.

STOX1 deficiency is associated with renin-mediated gestational hypertension and placental defects

The pathogenesis of preeclampsia and other hypertensive disorders of pregnancy remains poorly defined despite the substantial burden of maternal and neonatal morbidity associated with these conditions. In particular, the role of genetic variants as determinants of disease susceptibility is understudied. Storkhead-box protein 1 (STOX1) was first identified as a preeclampsia risk gene through family-based genetic linkage studies in which loss-of-function variants were proposed to underlie increased preeclampsia susceptibility. We generated a genetic Stox1 loss-of-function mouse model (Stox1 KO) to evaluate whether STOX1 regulates blood pressure in pregnancy. Pregnant Stox1-KO mice developed gestational hypertension evidenced by a significant increase in blood pressure compared with WT by E17.5. While severe renal, placental, or fetal growth abnormalities were not observed, the Stox1-KO phenotype was associated with placental vascular and extracellular matrix abnormalities. Mechanistically, we found that gestational hypertension in Stox1-KO mice resulted from activation of the uteroplacental renin-angiotensin system. This mechanism was supported by showing that treatment of pregnant Stox1-KO mice with an angiotensin II receptor blocker rescued the phenotype. Our study demonstrates the utility of genetic mouse models for uncovering links between genetic variants and effector pathways implicated in the pathogenesis of hypertensive disorders of pregnancy.

Aminopeptidase A (ENPEP) gene polymorphisms and preeclampsia: Descriptive analysis

OBJECTIVE

The etiology of preeclampsia (PE) remains elusive. Recent genome-wide association studies have identified a number of genetic variants associated with blood pressure variations in east Asians. One of the genetic variants is the aminopeptidase A (ENPEP) gene, which converts angiotensin II to angiotensin III. The C allele of rs6825911 is a risk for hypertension. The current study investigated whether genetic variants of ENPEP play a role in the pathogenesis of preeclampsia.

STUDY DESIGN

The study was a descriptive analysis of gene polymorphisms of ENPEP; 602 pregnant women of African ancestry [normotensive (n = 245) and PE (n = 357)] were recruited. The two groups were divided according to their HIV status. The PE group consisted of early- and late-onset sub-categories. A single nucleotide polymorphism of rs6825911 was analyzed using the TaqMan® Probe mix and by means of real time polymerase chain reaction.

RESULTS

The risk of C allele for PE was 1.07 (95 % CI 0.83-1.38, P = 0.589) for allele comparison and the risk for preeclampsia CC to CT/TT was 1.33 (95 % CI 0.96-1.85, P = 0.086). The sub analysis for the PE group without HIV infection the risk of C allele was 1.25 (95 % CI 0.838-1.78, P = 0.199) and the risk of PE of CC to CT/TT was 1.51 (95 %CI: 0.96-2.35, P = 0.071).

CONCLUSION

This is the first study in a homogenous South African population of African ancestry to show that the variant of ENPEP gene does not play a role in pathogenesis of preeclampsia.

Cardiac dysfunction after preeclampsia; an overview of pro- and anti-fibrotic circulating effector molecules

Preeclampsia (PE) is strongly associated with heart failure (HF) later in life. The aberrant cardiac remodelling is likely initiated or amplified during preeclamptic pregnancy. Aberrant remodelling often persists after delivery and is known to relate strongly to cardiac fibrosis. This review provides an overview of pro- and anti- fibrotic circulating effector molecules that are involved in cardiac fibrosis and their association with PE. Women with PE complicated pregnancies show increased ANG-II sensitivity and elevated levels of the pro-fibrotic factors IL-6, TNF-α, TGs and FFAs compared to uncomplicated pregnancies. In the postpartum period, PE pregnancies compared to uncomplicated pregnancies have increased ANG-II sensitivity, elevated levels of the pro-fibrotic factors IL-6, TNF-α, LDL cholesterol and leptin, as well as decreased levels of the anti-fibrotic factor adiponectin. The review revealed several profibrotic molecules that associate to cardiac fibrosis during and after PE. The role that these fibrotic factors have on the heart during and after PE may improve the understanding of the link between PE and HF. Furthermore they may provide insight into the pathways in which the relation between both diseases can be understood as potential mechanisms which interfere in the process of cardiovascular disease (CVD). Unravelling the molecular mechanism and pathways involved might bring the diagnostic and therapeutic abilities of those factors a step closer.

Is highly expressed ACE 2 in pregnant women "a curse" in times of COVID-19 pandemic?

Angiotensin-converting enzyme 2 (ACE 2) is a membrane-bound enzyme that cleaves angiotensin II (Ang II) into angiotensin (1-7). It also serves as an important binding site for SARS-CoV-2, thereby, facilitating viral entry into target host cells. ACE 2 is abundantly present in the intestine, kidney, heart, lungs, and fetal tissues. Fetal ACE 2 is involved in myocardium growth, lungs and brain development. ACE 2 is highly expressed in pregnant women to compensate preeclampsia by modulating angiotensin (1-7) which binds to the Mas receptor, having vasodilator action and maintain fluid homeostasis. There are reports available on Zika, H1N1 and SARS-CoV where these viruses have shown to produce fetal defects but very little is known about SARS-CoV-2 involvement in pregnancy, but it might have the potential to interact with fetal ACE 2 and enhance COVID-19 transmission to the fetus, leading to fetal morbidity and mortality. This review sheds light on a path of SARS-CoV-2 transmission risk in pregnancy and its possible link with fetal ACE 2.

The Role of the Renin-Angiotensin-Aldosterone System in Preeclampsia: a Review

PURPOSE OF REVIEW

Preeclampsia (PE) is a complex human pregnancy-specific condition and is clinically characterized by new onset hypertension and proteinuria in the second half of pregnancy. The precise etiology of PE is unknown, but much of the pathophysiology has been elucidated, and it is accepted that the disorder is multifactorial in nature. Historically, because of the presence of proteinuria, the role of the renin-angiotensin-aldosterone system (RAAS) has been considered in the etiology of PE. However, the results of studies (including maternal circulatory angiotensin II, urinary angiotensinogen, plasma renin and prorenin, AT1 receptor antibodies, and gene polymorphisms) on the role of the RAAS in the etiology of PE have proved controversial. The purpose of this narrative review was to evaluate the contemporary literature on the RAAS and its role in the pathophysiology of pregnancy.

RECENT FINDINGS

The current review shows that although the RAAS has a role in the development of normal pregnancy, it does not have a significant role in the pathophysiology of PE except for the AT1-AA components. Despite many researchers having measured increases in s[P}RR and [P]RR, this may be independent of the RAAS. Our view is in keeping with contemporary thinking that the placenta rather than the RAAS plays a central role in elaborating pro-inflammatory factors (antiangiogenic and angiogenic) into the maternal circulation resulting in widespread endothelial dysfunction in all organ systems including the renal system.

The role of LNPEP and ANPEP gene polymorphisms in the pathogenesis of pre-eclampsia

OBJECTIVE

The exact role of renin angiotensin system (RAS) in the pathogenesis of pre-eclampsia has not been established. Gene polymorphisms, however, have been implicated in the pathophysiology. Therefore, the aim of this study was to investigate the association of the Angiotensin IV receptor and aminopeptidase-N in the pathogenesis of pre-eclampsia.

STUDY DESIGN

Stored blood samples of 637 South African women of African ancestry were utilized. The study population was divided into controls (n = 280) and pre-eclampsia (n = 357). Pre-eclampsia was sub-divided into early (n = 187) and late (n = 170) onset subtypes. DNA was extracted from whole blood and genotyped. Odds ratio and 95 % confidence intervals were used to assess the association.

RESULTS

The allele and genotype frequencies of the angiotensin receptor IV and aminopeptidase-N showed no significant difference between the control versus the pre-eclampsia groups. Similarly, allele and genotype distributions of the control group versus the subtypes of pre-eclampsia (early onset and late onset pre-eclampsia) showed no significant differences.

CONCLUSION

The single nucleotide polymorphisms of angiotensin IV receptor (rs18059) and aminopeptidase-N (rs6496603) are not associated with the pathogenesis of pre-eclampsia in women of African ancestry.

An insertion-deletion polymorphism in angiotensin-converting enzyme is associated with a reduced risk of preeclampsia: an evidence-based meta-analysis from 44 studies

Objective An updated meta-analysis was performed to evaluate the relationship between an insertion/deletion (I/D) polymorphism in angiotensin-converting enzyme (ACE) and preeclampsia (PE) risk. Methods Pubmed, OVID and China National Knowledge Infrastructure databases were searched. Pooled odds ratios with 95% confidence intervals were calculated using fixed-effects or random-effects model. Results ACE I/D polymorphism decreased the risk of PE in overall analysis. Subgroup analysis revealed a significantly lower risk of PE with ACE I/D polymorphism in Asians, Caucasians. The decreased risk was also found in severe PE and early-onset PE. Conclusion ACE I/D polymorphism may protect against the development of PE.

Fetal renal artery impedance in pregnancies affected by preeclampsia

Background Preeclampsia (PE) is a pregnancy-specific vascular endothelial disorder characterized by multi-organ system involvement. This includes the maternal kidneys, with changes such as continuous vasospasm of renal arteries and reduced renal blood flow. However, it is unclear whether similar renal vascular changes are seen in the fetus. This study sought to compare renal artery impedance in fetuses of women with and without PE. Methods This was a prospective Doppler assessment study of the fetal renal artery impedance in 48 singleton fetuses. The group with PE consisted of 24 appropriately grown fetuses in pregnancy complicated by both mild and severe PE and a control group of 24 uncomplicated pregnancies. Doppler studies included renal artery systolic/diastolic (S/D) ratio, pulsatility index (PI), resistance index (RI), and identification of end-diastolic blood flow. Results Fetuses of mothers with PE were more likely to have a lower renal artery Doppler S/D ratio (7.85 [6.4-10.2] vs. 10.8 [7.75-22.5], P = 0.03) and lower RI (0.875 [0.842-0.898] vs. 0.905 [0.872-0.957], P = 0.03). However, there was no statistically significant difference in PI. There was also no difference in the incidence of absent end-diastolic flow. Conclusion This study suggests that PE results in changes in blood flow to the renal arteries of the fetus. This may be associated with long-term adverse health effects later in adulthood.

The association between maternal and foetal REN gene polymorphisms and preeclampsia/eclampsia: A hybrid design study

OBJECTIVES

Preeclampsia (PE)/eclampsia (E) is an important cause of foetal and maternal morbidity and mortality, and its aetiology is poorly understood. Good evidence suggests that renin (REN) might be associated with PE/E. The risk of PE/E is determined by both maternal and foetal genes, but most previous studies have focused on maternal contributions. This study aimed to explore the association of maternal and foetal REN polymorphisms with PE/E in pregnant Han Chinese women.

METHODS

A case-parents/mother-control study including 347 PE/E patients with their partners and offspring and 700 control mothers with their offspring was conducted. A log-linear model was used to investigate the association between maternal and foetal REN SNPs and PE/E simultaneously, as well as the interaction of REN SNPs and environmental factors on PE/E.

RESULTS

The foetal REN rs5707 AC genotype in combination with a pre-pregnancy BMI ≥ 24 kg/m² was significantly associated with an increased risk of PE/E, with an OR of 2.75 (95%CI = 1.50-5.06). Maternal and foetal rs5707 were significantly associated with an increased risk of PE/E under the recessive model (AA + AC/CC). In haplotype analyses, foetal CCT (in the order of rs2368564, rs5707, rs5705) and TAT genotypes were positively associated with the risk of PE/E. There was no significant association between maternal and foetal REN SNP genotypes and PE/E in the transmission disequilibrium test (TDT) and log-linear model analysis.

CONCLUSIONS

Findings from this study indicate that foetal rs5707 polymorphisms may play a significant role in PE/E development, especially among overweight or obese pregnant women in China.

Maternal titanium dioxide nanomaterial inhalation exposure compromises placental hemodynamics

The fetal consequences of gestational engineered nanomaterial (ENM) exposure are unclear. The placenta is a barrier protecting the fetus and allowing transfer of substances from the maternal circulation. The purpose of this study was to determine the effects of maternal pulmonary titanium dioxide nanoparticle (nano-TiO₂) exposure on the placenta and umbilical vascular reactivity. We hypothesized that pulmonary nano-TiO₂ inhalation exposure increases placental vascular resistance and impairs umbilical vascular responsiveness. Pregnant Sprague-Dawley rats were exposed via whole-body inhalation to nano-TiO₂ with an aerodynamic diameter of 188 ± 0.36 nm. On gestational day (GD) 11, rats began inhalation exposures (6 h/exposure). Daily lung deposition was 87.5 ± 2.7 μg. Animals were exposed for 6 days for a cumulative lung burden of 525 ± 16 μg. On GD 20, placentas, umbilical artery and vein were isolated, cannulated, and treated with acetylcholine (ACh), angiotensin II (ANGII), S-nitroso-N-acetyl-DL-penicillamine (SNAP), or calcium-free superfusate (Ca²⁺-free). Mean outflow pressure was measured in placental units. ACh increased outflow pressure to 53 ± 5 mmHg in sham-controls but only to 35 ± 4 mmHg in exposed subjects. ANGII decreased outflow pressure in placentas from exposed animals (17 ± 7 mmHg) compared to sham-controls (31 ± 6 mmHg). Ca²⁺-free superfusate yielded maximal outflow pressures in sham-control (63 ± 5 mmHg) and exposed (30 ± 10 mmHg) rats. Umbilical artery endothelium-dependent dilation was decreased in nano-TiO₂ exposed fetuses (30 ± 9%) compared to sham-controls (58 ± 6%), but ANGII sensitivity was increased (-79 ± 20% vs -36 ± 10%). These results indicate that maternal gestational pulmonary nano-TiO₂ exposure increases placental vascular resistance and impairs umbilical vascular reactivity.

MicroRNAs in Preeclampsia

Preeclampsia (PE) continues to represent a worldwide problem and challenge for both clinicians and laboratory-based doctors. Despite many efforts, the knowledge acquired regarding its pathogenesis and pathophysiology does not allow us to treat it efficiently. It is not possible to arrest its progressive nature, and the available therapies are limited to symptomatic treatment. Furthermore, both the diagnosis and prognosis are frequently uncertain, whilst the ability to predict its occurrence is very limited. MicroRNAs are small non-coding RNAs discovered two decades ago, and present great interest given their ability to regulate almost every aspect of the cell function. A lot of evidence regarding the role of miRNAs in pre-eclampsia has been accumulated in the last 10 years. Differentially expressed miRNAs are characteristic of both mild and severe PE. In many cases they target signaling pathway-related genes that result in altered processes which are directly involved in PE. Immune system, angiogenesis and trophoblast proliferation and invasion, all fundamental aspects of placentation, are controlled in various degrees by miRNAs which are up- or downregulated. Finally, miRNAs represent a potential therapeutic target and a diagnostic tool.

Alterations in transcranial Doppler indices of pregnant women with complicated preeclampsia

OBJECTIVES

We aimed to investigate alterations in transcranial Doppler indices (TCD) of the cerebral arteries between normotensive and preeclampsia (PE) pregnancies according to the presence of cerebral symptoms.

STUDY DESIGN

This cross-sectional study included 48 PE and 20 normotensive pregnancies, respectively. Doppler indices of the anterior, middle, and posterior cerebral arteries (ACA, MCA, and PCA, respectively) were compared between the PE and normotensive group.

MAIN OUTCOME MEASURES

Mean cerebral velocity (MCV), pulsatility index (PI), and resistance index (RI) were calculated using cerebral velocities. The cerebral perfusion pressure (CPP), resistance area product (RAP), and cerebral flow index (CFI) were computed using velocity and blood pressure. The PE group was subdivided according to the presence of cerebral symptoms and the TCD indices were compared between these groups.

RESULTS

MCV and CFI of the PCA as well as CPP and RAP of all arteries were significantly higher, while PI and RI were significantly lower in PE group (P < 0.05). PI of the MCA had the highest sensitivity (91.7%), while PI of the PCA and RAP of the MCA had the highest specificity (95.0% each) for predicting PE-related cerebral complications. The positive likelihood ratio was highest in PI of the PCA (14.58). Among these parameters, CPP and RAP of the PCA were higher in PE patients showing cerebral symptoms than in those without symptoms.

CONCLUSIONS

These results suggest that pregnant women with PE had altered TCD indices and that prominent changes, thereof, especially in the PCA, contribute to the development of cerebral symptoms.

Decreased Ang-(1-7) and Downregulated Intrarenal RAS May Contribute to the Direct Podocyte Injury With Proteinuria in Preeclampsia

The mechanisms of proteinuria development in preeclampsia (PE) are still enigmatic. Renin-angiotensin system (RAS) components may play a role. Maternal serum and urinary concentrations of angiotensin-(1-7) [Ang-(1-7)], angiotensin II (Ang II), and angiotensinogen in women with PE (n = 14), gestational hypertension (n = 14), and normal pregnancy were quantified. The alteration in these concentrations was used to evaluate their relationships with podocyturia and proteinuria in PE. In addition, the podocytes cultured in vitro were interfered in serum of preeclamptic and normotensive pregnant women, with or without Ang-(1-7). The morphologic change in podocyte was observed using a microscope. The changes in podocyte-specific proteins (nephrin, CD2-associated protein [CD2AP]), the cytoskeletal protein F-actin, the tight junction protein (ZO-1), and Mas receptor (MasR) were examined by immunofluorescence. Western blot was used to examine the expression and variation of MasR. We found that the concentrations of RAS components were associated with prepartal urinary podocyte number, random urine albumin/creatinine ratio, blood pressure, and renal function. The expression of nephrin, F-actin, ZO-1, and MasR on podocytes interfered in serum of PE was significantly decreased compared to normal control and normal pregnant serum group in vitro, yet their expression was significantly increased after coculture by 10^-6 mol/L Ang-(1-7) and the preeclamptic serum. The expression of CD2AP had no significant difference. We concluded that decreased Ang-(1-7) and downregulated intrarenal RAS contributed to the direct podocyte injury with proteinuria in PE.

Investigation of elevation as a risk factor for hypertensive disorders of pregnancy among Colorado women between 2007 and 2015

OBJECTIVE

The purpose of this study is to determine the association between high elevation and hypertensive disorders of pregnancy (HDP).

METHODS

Retrospective cohort study using Colorado birth certificate data to compare HDP at high (≥8,000 ft), moderate (4,501-7,999 ft), or low (≤4,500 ft) elevation using logistic regression.

RESULTS

Among the cohort (n = 314,431), 3.4% of women developed a HDP. High or moderate elevation was not significantly associated with HDP relative to low elevation (adjusted odds ratio [aOR] 1.16, 95% confidence interval [CI] 0.93-1.43; aOR 1.14, 95% CI 0.98-1.31, respectively).

CONCLUSION

Women living at high or moderate elevation do not have higher odds of HDP.

A novel rodent model of pregnancy complications associated with genetically determined angiotensin-converting enzyme (ACE) activity

Brown Norway (BN) and Lewis (LW) inbred rat strains harbor different angiotensin-converting enzyme ( Ace) polymorphisms that result in higher ACE activity in BN than LW rats. Thus we hypothesized that pregnant BN rats would show pregnancy complications linked to angiotensin II (AII) activity. We performed longitudinal and cross-sectional studies in pregnant LW and BN rats. We found that BN rats have significantly higher ACE activity and AII levels at prepregnancy and throughout pregnancy compared with LW rats, except at midgestation. BN placentas and maternal kidneys had significantly higher expression of AII receptor 1 (AGTR1) and lower expression of AGTR2 than the respective LW placentas and maternal kidneys. Renin-angiotensin system activation in BN rats correlated with hypertension and proteinuria at gestational days 17-21, which were resolved after delivery. In addition, BN rat pregnancies were characterized by significant fetal loss, restricted growth in surviving fetuses, decreased uteroplacental blood flows, and decreased trophoblast remodeling of uterine arteries compared with LW pregnancies. Short-term losartan treatment significantly increased uteroplacental blood flow and fetal weight and decreased maternal blood pressure (BP) and proteinuria in BN pregnancies. In contrast, losartan treatment significantly decreased uteroplacental blood flow and fetal weight but had no significant effect on maternal BP in LW pregnancies. We conclude that Ace polymorphisms play an important role in the reproductive phenotype of BN and LW rats and that BN rats are a novel model of pregnancy complications in association with genetically controlled, increased ACE activity.

Pendrin Expression in Preeclampsia: A Prospective Immunohistochemical Staining Study on Placental Bed Biopsies

INTRODUCTION

To assess the pendrin expression density in placental bed biopsies from preeclampsia cases in comparison with healthy term controls.

MATERIAL AND METHODS

A prospective case-control study with 106 placental bed biopsies obtained during cesarean deliveries. Pendrin expression was evaluated by immunohistochemical staining in different hypertensive disorders of pregnancy.

RESULTS

Pendrin immunostaining frequency was higher in the hypertensive disorders group (p: 0.024), which was a result of the high frequency in the early-onset preeclampsia group. Uterine artery pulsatility indices were higher in pendrin positive patients than in the negatives in the case group. Gravidity was not found to affect the pendrin expression frequency in the placental bed.

CONCLUSION

Placental ischemia seems to be an important determinant of pendrin expression in pregnant decidua. Increased pendrin density in early-onset preeclampsia could be a pathogenetic mechanism in or a part of the adaptational response to the development of the hypertension.

Icariin improves acute kidney injury and proteinuria in a rat model of pregnancy‑induced hypertension

Icariin has previously been demonstrated to attenuate hyperglycemia-induced renal injury, however the renoprotective effects of icariin in a rat model of pregnancy-induced hypertension (PIH) remain to be elucidated. The present study aimed to investigate the effect of icariin on PIH-induced acute kidney injury (AKI) and proteinuria. Following 18 days of icariin treatment between day 1 and day 18 of gestation, which was combined with NG-nitro-L-arginine methyl ester (L-NAME) treatment between day 12 and day 18 of gestation to induce PIH, the 24 h urine protein level, blood urea nitrogen and serum creatinine were measured by using the Coomassie Brilliant Blue method, a commercial enzymatic kit and the picric acid method, respectively. Renal tissues were collected at day 18 of gestation for hematoxylin and eosin staining and immunohistochemistry. The mRNA expression of AGT and protein expression of angiotensin II (Ang II) in the kidneys of control and PIH rats was investigated by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively, to determine the effect of icariin on components of the renin-angiotensin system. The results demonstrated that L-NAME treatment in pregnant rats resulted in significant increases in systolic blood pressure (SBP) and diastolic blood pressure, in addition to the induction of severe proteinuria. The significant increase in SBP and proteinuria in PIH rats was prevented by icariin. L-NAME-induced AKI resulted in profound renal histological alterations, including mesangial expansion and glomerular lesions. L-NAME administration exerted a marked decrease in the mRNA and protein expression levels of nephrin in the kidneys from PIH rats compared with control group. Furthermore, upregulation of circulating and renal Ang II levels in PIH rats was observed. However, icariin treatment significantly reversed the L-NAME-induced downregulation of nephrin and upregulation of circulating and renal Ang II levels in PIH rats. These results demonstrated that icariin administration improved urinary protein excretion levels and renal tissue damage in PIH rats, and the underlying mechanism was mediated in part, via upregulation of nephrin expression and downregulation of Ang II.

Differential responses of mesenteric arterial bed to vasoactive substances in L-NAME-induced preeclampsia: Role of oxidative stress and endothelial dysfunction

To investigate the systemic and placental oxidant status as well as vascular function in experimental preeclampsia (PE) induced by nitro-L-arginine methyl ester (L-NAME). Fetal parameters and maternal blood pressure, proteinuria, mesenteric arterial bed (MAB) reactivity, and systemic and placental oxidative stress were compared between four groups: pregnant rats receiving L-NAME (60 mg/kg/day, orally) (P + L-NAME) or vehicle (P) from days 13 to 20 of pregnancy and nonpregnant rats receiving L-NAME (NP + L-NAME) or vehicle (NP) during 7 days. L-NAME administration during pregnancy induced some hallmarks of PE, such as hypertension and proteinuria. The P + L-NAME group presented lower weight gain and placental mass as well as reduced number and weight of live fetuses than P group. The vasodilator effect induced by acetylcholine (ACh) and angiotensin II (Ang II) was lower in the perfused MAB from NP + L-NAME and P + L-NAME than in control groups. Otherwise, the nitroglycerine-induced vasodilation and the phenylephrine- and Ang II-induced vasoconstriction were higher in MAB from NP + L-NAME and P + L-NAME groups than in the respective controls. Systemic and placental oxidative damage, assessed by malondialdehyde and carbonyl levels, was increased and activities of the antioxidant enzymes superoxide dismutase and glutathione peroxidase were reduced in P + L-NAME and NP + L-NAME groups compared to controls. The present data suggest that the oxidative stress and reduced bioavailability of nitric oxide may contribute to attenuation of vasodilator responses to ACh and Ang II, and hyperreactivity to Ang II in the mesentery of preeclamptic rat, which may contribute to the increased peripheral vascular resistance and BP, as well as intrauterine growth restriction in L-NAME-induced PE.

The expression of renin-angiotensin-aldosterone axis components in infantile hemangioma tissue and the impact of propranolol treatment

BackgroundPropranolol's mechanism of action for controlling infantile hemangioma (IH) remains unclear. We hypothesize that this nonselective beta antagonist downregulates renin-angiotensin-aldosterone (RAA) axis components, preventing angiogenic substrate induction of IH.MethodsIH tissue and serum were collected from children with propranolol-treated or -untreated IH during surgery. Normal skin and serum from demographically matched children were used as controls. Real-time PCR and western blot quantified RAA components in proliferative (n=10), involuting (n=10), propranolol-treated (n=12) IH, and normal specimens (n=11). Serum was analyzed by enzyme-linked immunosorbent assay (ELISA).ResultsThere were significantly greater messenger RNA (mRNA) levels of angiotensinogen (AGT) in proliferating IH, but not in involuting or treated IH, when compared with controls (P<0.05). Angiotensin-converting enzyme (ACE) and angiotensin II receptor 1 (AGTR1) mRNA expression was higher in all IH specimens when comparedwith controls (P<0.05). ACE and AGTR1 protein expression was greater in proliferating IH tissue compared with that in controls and in involuting and treated IH tissue (P<0.05). ELISA showed no significant difference in ACE serum levels but did show a significant reduction in renin in involuting compared with proliferating IH (P<0.05).ConclusionsThe protein and mRNA expression of several RAA pathway constituents is elevated in IH tissue when compared with that in normal tissue. The action of propranolol on IH may be the result of reductions in ACE and AGTR1.

Renin-angiotensin system transgenic mouse model recapitulates pathophysiology similar to human preeclampsia with renal injury that may be mediated through VEGF

Using a transgenic cross, we evaluated features of preeclampsia, renal injury and the sFlt1/VEGF changes. Transgenic hAGT and hREN, or wild-type (WT) C57Bl/6 mice were cross-bred: female hAGT × male hREN for preeclampsia (PRE) model and female WT × male WT for pregnant controls (WTP). Samples were collected for plasma VEGF, sFlt1, and urine albumin. Blood pressures (BP) were monitored by telemetry. Vascular reactivity was investigated by wire myography. Kidneys and placenta were immunostained for sFlt1 and VEGF. Eleven PRE and 9 WTP mice were compared. PRE more frequently demonstrated albuminuria, glomerular endotheliosis (80% vs. 11%; P = 0.02), and placental necrosis (60% vs. 0%; P < 0.01). PRE group demonstrated declining BPs with advancing gestation. Plasma sFlt1 increased across pregnancy in PRE; VEGF did not vary. IHC demonstrated the presence of sFlt1 in glomeruli, lymphatics, and collecting tubules of PRE kidneys, suggesting excretion. VEGF immunostaining was increased specifically in the glomeruli of PRE kidneys. Placenta in PRE showed marked immunostaining for sFlt1. We conclude that this transgenic model of preeclampsia recapitulates human preeclamptic state with high fidelity, and that, vascular adaptation to pregnancy is suggested by declining BPs and reduced vascular response to PE and increased response to acetylcholine. Placental damage with resultant increased release of sFlt1, proteinuria, deficient spiral artery remodeling, and glomerular endotheliosis were observed in this model of PRE. Increased VEGF binding to glomerular endothelial cells in this model of PRE is similar to human PRE and leads us to hypothesize that renal injury in preeclampsia may be mediated through local VEGF.

Agonistic Autoantibodies to the Angiotensin II Type 1 Receptor Enhance Angiotensin II-Induced Renal Vascular Sensitivity and Reduce Renal Function During Pregnancy

Preeclamptic women produce agonistic autoantibodies to the angiotensin II type 1 receptor (AT1-AA) and exhibit increased blood pressure (mean arterial pressure), vascular sensitivity to angiotensin II (ANG II), and display a decrease in renal function. The objective of this study was to examine the renal hemodynamic changes during pregnancy in the presence of AT1-AAs with or without a slow pressor dose of ANG II. In this study, mean arterial pressure was elevated in all pregnant rats treated with ANG II with or without AT1-AA. Glomerular filtration rate was reduced from 1.90±0.16 mL/min in normal pregnant (NP) to 1.20±0.08 in ANG II+AT1-AA rats. Renal blood flow was decreased in ANG II+AT1-AA versus NP rats to 7.4±1.09 versus 15.4±1.75 mL/min. Renal vascular resistance was drastically increased between ANG II+AT1-AA versus NP rats (18.4±2.91 versus 6.4±0.77 mm Hg/mL per minute). Isoprostane excretion was increased by 3.5-fold in ANG II+AT1-AA versus NP (1160±321 versus 323±52 pg/mL). In conclusion, ANG II and AT1-AA together significantly decrease glomerular filtration rate by 37% and renal blood flow by 50% and caused a 3-fold increase in renal vascular resistance and isoprostane levels versus NP rats. These data indicate the importance of AT1-AAs to enhance ANG II-induced renal vasoconstriction and reduce renal function as mechanisms to cause hypertension as observed during preeclampsia.

Soluble fms-like tyrosine kinase 1 promotes angiotensin II sensitivity in preeclampsia

Preeclampsia is a hypertensive disorder of pregnancy in which patients develop profound sensitivity to vasopressors, such as angiotensin II, and is associated with substantial morbidity for the mother and fetus. Enhanced vasoconstrictor sensitivity and elevations in soluble fms-like tyrosine kinase 1 (sFLT1), a circulating antiangiogenic protein, precede clinical signs and symptoms of preeclampsia. Here, we report that overexpression of sFlt1 in pregnant mice induced angiotensin II sensitivity and hypertension by impairing endothelial nitric oxide synthase (eNOS) phosphorylation and promoting oxidative stress in the vasculature. Administration of the NOS inhibitor l-NAME to pregnant mice recapitulated the angiotensin sensitivity and oxidative stress observed with sFlt1 overexpression. Sildenafil, an FDA-approved phosphodiesterase 5 inhibitor that enhances NO signaling, reversed sFlt1-induced hypertension and angiotensin II sensitivity in the preeclampsia mouse model. Sildenafil treatment also improved uterine blood flow, decreased uterine vascular resistance, and improved fetal weights in comparison with untreated sFlt1-expressing mice. Finally, sFLT1 protein expression inversely correlated with reductions in eNOS phosphorylation in placental tissue of human preeclampsia patients. These data support the concept that endothelial dysfunction due to high circulating sFLT1 may be the primary event leading to enhanced vasoconstrictor sensitivity that is characteristic of preeclampsia and suggest that targeting sFLT1-induced pathways may be an avenue for treating preeclampsia and improving fetal outcomes.

Placental Ischemia and Resultant Phenotype in Animal Models of Preeclampsia

Preeclampsia is new onset (or worsening of preexisting) hypertension that occurs during pregnancy. It is accompanied by chronic inflammation, intrauterine growth restriction, elevated anti-angiogenic factors, and can occur with or without proteinuria. Although the exact etiology is unknown, it is thought that preeclampsia begins early in gestation with reduced uterine spiral artery remodeling leading to decreased vasculogenesis of the placenta as the pregnancy progresses. Soluble factors, stimulated by the ischemic placenta, shower the maternal vascular endothelium and are thought to cause endothelial dysfunction and to contribute to the development of hypertension during pregnancy. Due to the difficulty in studying such soluble factors in pregnant women, various animal models have been designed. Studies from these models have contributed to a better understanding of how factors released in response to placental ischemia may lead to increased blood pressure and reduced fetal weight during pregnancy. This review will highlight various animal models and the major findings indicating the importance of placental ischemia to lead to the pathophysiology observed in preeclamptic patients.

Fetal and maternal angiotensin (1-7) are associated with preterm birth

BACKGROUND

Recent studies show that preterm birth is associated with hypertension in later life. The renin-angiotensin system (RAS) during pregnancy influences fetal growth and development. In the current study, we investigated the impact of fetal as well as maternal angiotensin (1-7) [Ang (1-7)] and angiotensin II (Ang II) plasma concentrations on the risk of preterm birth.

METHODS

Three hundred and nine pregnant women were prospectively included into the study. The pregnant women were divided into two groups, for example, preterm birth of lower than 37 gestational weeks (n = 17) and full-term birth of 37 gestational weeks or more (n = 292). Maternal and neonatal plasma Ang (1-7) and Ang II concentrations were analyzed at birth from maternal venous blood and umbilical cord blood, respectively. Risk factors for premature birth were determined by multiple logistic regression analysis.

RESULTS

Fetal and maternal plasma Ang (1-7) concentrations in the preterm group were lower than those of the term group fetal Ang (1-7) preterm birth: 486.15 ± 337.34  ng/l and fetal Ang (1-7) term birth: 833.84 ± 698.12  ng/l and maternal Ang (1-7) preterm birth: 399.86 ± 218.93  ng/l; maternal Ang (1-7) term birth: 710.34 ± 598.22  ng/l. Multiple logistic regression analysis considering confounding factors revealed that preeclampsia (P < 0.001), premature rupture of membranes (P = 0.001), lower concentration of maternal Ang (1-7) (P = 0.013) and fetal plasma Ang (1-7) (P = 0.032) were independently associated with preterm birth. We could furthermore demonstrate that the maternal Ang (1-7)/Ang II ratio is independently associated with gestational hypertension or preeclampsia, factors causing preterm birth.

CONCLUSIONS

Lower concentrations of maternal and fetal Ang (1-7) are independently associated with preterm birth - a risk factor of hypertension in later life.

Elevation of (Pro)Renin and (Pro)Renin Receptor in Preeclampsia

OBJECTIVE

Preeclampsia (preE), a syndrome of hypertension, proteinuria, and edema, has many elusive triggers. The renin-angiotensin system has been implicated in preE pathogenesis. In this study, we test the hypothesis that (pro)renin levels are increased in preE patients and that levels of (pro)renin and (pro)renin receptor ((P)RR) are elevated in a rat model of preE.

METHODS

We recruited 30 preE and 43 normal pregnant consenting patients. We used normally pregnant rats (NP, n = 10) and pregnant rats receiving weekly injections of desoxycorticosterone acetate and whose drinking water was replaced with 0.9% saline (preE, n = 10). Plasma and placental levels of (pro)renin were assayed by ELISA. Placental and kidney (P)RR was measured both by immunoblotting and immunohistochemistry.

RESULTS

The mean plasma (pro)renin of 27.1±5.2 in preE patients differs from that in patients without preE: 14.8±5.2 ng Ang I/ml/hour (P < 0.0001). In rats, both plasma (NP: 22.7±4.3 and preE: 49.2±10.0 ng Ang I/ml/hour) and placental (NP: 152±24 and preE: 302±39 ng/g tissue) levels of (pro)renin were higher (P < 0.001) in preE compared to NP rats. (P)RR expression was greater (P < 0.05) in placental tissue of preE rats, while kidney (P)RR expression was similar.

CONCLUSION

Elevated levels of circulating (pro)renin have been observed in preE patients and in a rat model of preE. We also found the increased expression of placental (P)RR in preE rats.

Regulator of G Protein Signaling 2: A Versatile Regulator of Vascular Function

Regulators of G protein signaling (RGS) proteins of the B/R4 family are widely expressed in the cardiovascular system where their role in fine-tuning G protein signaling is critical to maintaining homeostasis. Among members of this family, RGS2 and RGS5 have been shown to play key roles in cardiac and smooth muscle function by tightly regulating signaling pathways that are activated through Gq/11 and Gi/o classes of heterotrimeric G proteins. This chapter reviews accumulating evidence supporting a key role for RGS2 in vascular function and the implication of changes in RGS2 function and/or expression in the pathogenesis of blood pressure disorders, particularly hypertension. With such understanding, RGS2 and the signaling pathways it controls may emerge as novel targets for developing next-generation antihypertensive drugs/agents.

Regulation of soluble fms-like tyrosine kinase-1 production in response to placental ischemia/hypoxia: role of angiotensin II

While soluble fms-like tyrosine-1 (sFlt-1) is implicated in the pathogenesis of hypertension during preeclampsia, the mechanisms leading to the enhanced sFlt-1 production remain unclear. A recent report suggests exogenous angiotensin II (ANGII) stimulates sFlt-1 production in pregnant rats, however, the role of endogenous ANGII in mediating the placental production of sFlt-1 in response to placental ischemia remains unknown. Therefore, the purpose of this study was to determine the role of endogenous ANGII in mediating the placental production of sFlt-1 in response to placental ischemia in pregnant Sprague–Dawley rats. To this end we compared sFlt-1 and ANGII levels from placental explants collected from normal pregnant (NP) and Reduced Uterine Perfusion Pressure (RUPP) rats. sFlt-1 (3271 ± 264 vs. 2228 ± 324 pg/mL, P < 0.05) and ANGII levels (43.2 ± 2.8 vs. 26.7 ± 1.9 pg/mL, P < 0.05) were higher in placental explants from RUPP rats versus NP rats. Administration of Losartan, an angiotensin type 1 (AT₁) receptor antagonist, (10 mg/day for 5 days) to RUPP rats significantly reduced plasma levels of sFlt-1 (1432 ± 255 pg/mL, P < 0.05) when compared with untreated control rats (3431 ± 454 pg/mL). In addition, RUPP-induced hypertension was significantly reduced (113 ± 2 mmHg vs. 139 ± 2 mmHg, P < 0.05). In conclusion, placental sFlt-1 and ANGII production are significantly elevated in response to placental ischemia in pregnant rats. In addition, AT₁ receptor activation, by endogenous ANGII, appears to play an important role in mediating the placental production of sFlt-1 in response to placental ischemia in pregnant rats.

Angiotensin-(1-7) attenuates damage to podocytes induced by preeclamptic serum through MAPK pathways

The underlying mechanisms of proteinuria, a main characteristic of preeclampsia (PE), have not yet been fully elucidated. Evidence indicates that the renin-angiotensin system (RAS) is involved in the pathogenesis of this disease, including decreased angiotensin-(1-7) [Ang-(1-7)] levels in the circulation and urine. In the present study, we examined the damage to podocytes induced by preeclamptic serum and the effects of Ang-(1-7) on podocytes treated with preeclamptic serum, as well as the underlying mechanisms. The podocytes were incubated with serum obtained from women with PE or with serum from women with normal pregnancies for different periods of time. Cell viability was determined by CCK-8 assay. The cells were treated with various concentrations of Ang-(1-7) and A779 [an (Ang-(1-7) antagonist]. The effects of Ang-(1-7) on the expression of podocyte-specific proteins [nephrin, Wilms tumor‑1 (WT-1) and podocin] and the phosphorylation of mitogen-activated protein kinases (MAPKs) were investigated by western blot analysis. Changes in F-actin rearrangement were determined by immunofluorescence. Podocyte apoptosis was determined by flow cytometry. The results revealed that in the cultured podocytes incubated with preeclamptic serum, there was a decrease in the expression of podocyte-specific proteins (nephrin and WT-1 but not podocin), a rearrangement of F-actin and apoptosis compared with the control group. However, treatment with Ang-(1-7) attenuated podocyte injury in the preeclamptic group, which may be mediated through the downregulation of MAPK (p38, ERK1/2 and JNK) phosphorylation. Thus, our data suggest that Ang-(1-7) plays a protective role in PE through the downregulation of MAPK phosphorylation.

The effects of S-nitrosoglutathione and S-nitroso-N-acetyl-D, L-penicillamine in a rat model of pre-eclampsia

BACKGROUND

Pre-eclampsia (PE) complicates approximately 5-7% of all pregnancies. This study investigates the effects of S-nitroso-N-acetylpenicillamine (SNAP) and S-nitrosoglutathione (GSNO) on the classical features of PE.

MATERIALS AND METHODS

On day 14 of gestation, female Sprague-Dawley rats were separated into five groups and treated intravenously for 7 days as follows: (i) 0.3 mL 0.9% saline (control, n = 11); (ii) 50 mg/kg Body Weight (BW) N-nitro-L-arginine methyl ester (L-NAME) in 0.3 mL saline (n = 10); (iii) 50 mg/kg BW L-NAME and 8 mg/kg BW GSNO in 0.15 mL saline (n = 6); (iv) 50 mg/kg BW L-NAME in 0.15 mL saline and 8 mg/kg BW SNAP in 0.15 mL DMSO (n = 9); and (v) 0.15 mL DMSO and 0.15 mL saline (SNAP control, n = 7). Blood pressures were measured on day 14 through day 20, a 4-h urine sample was taken on day 20, and animals were sacrificed on day 21. Pups were counted and weighed individually.

RESULTS

SNAP and GSNO significantly decreased systolic, diastolic, and mean arterial pressures in PE-induced rats from day 14 through day 20 (P < 0.05). Pup weights in SNAP and GSNO groups were higher than in L-NAME group but lower than in controls (P ≤ 0.001). SNAP and GSNO partially reversed growth retardation.

CONCLUSION

Elevated blood pressure, proteinuria, and intrauterine growth restriction associated with PE were induced in Sprague-Dawley rats using L-NAME. These were partially reversed with the use of GSNO and SNAP. The mechanism of action of these S-nitrosothiols (RSNOs) should be further explored.

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.

Long-term alterations in maternal plasma proteome after sFlt1-induced preeclampsia in mice

OBJECTIVE

Preeclampsia is associated with long-term adverse maternal health, such as cardiovascular and metabolic diseases. The objective of this study was to determine whether preeclampsia in a well-characterized animal model that was induced by overexpression of soluble fms-like tyrosine kinase-1 (sFlt1) results in alterations in the maternal circulating proteome that persist long after delivery.

STUDY DESIGN

CD-1 mice at day 8 of gestation were injected with adenovirus that carried sFlt1 or the murine immunoglobulin G2α Fc fragment as control. Depleted maternal plasma was analyzed 6 months after delivery by label-free liquid chromatography-mass spectrometry assay. The tandem mass spectrometry data were searched against a mouse database, and the resultant intensity data were used to compare abundance of proteins across disease/control plasma pool. Results were analyzed with ingenuity pathways analysis. Right-tailed Fisher exact test was used to calculate a probability value.

RESULTS

Of 150 proteins that are common for both groups, ingenuity pathways analysis determined 105 proteins that were ready for analysis. Diseases and disorders analysis showed significant enrichment of proteins that are associated with cardiovascular disease. Within this cluster, the most abundant proteins were associated with vascular disease, atherosclerosis, and atherosclerotic lesions. Other top disease clusters were inflammatory response, organismal injury and abnormalities, and hematologic and metabolic disease.

CONCLUSION

Exposure to sFlt1-induced preeclampsia alters multiple biologic functions in mothers that persist later in life. Our results suggest that some of the long-term adverse outcomes that are associated with preeclampsia actually may be a consequence rather than a mere unmasking of an underlying predisposition. If similar results are found in humans, the development of preventive strategies for preeclampsia should also improve long-term maternal health.