Placental endothelial nitric oxide synthase localization and expression in normal human pregnancy and pre-eclampsia

A Novel Dual-Function Nitric Oxide Donor Therapy for Preeclampsia-A Proof-of-Principle Study in a Murine Model

Background: Preeclampsia (PE) is a hypertensive disorder of pregnancy that is associated with substantial morbidity and mortality for the mother and fetus. Reduced nitric oxide bioavailability and oxidative stress contribute to the maternal and fetal pathophysiology of PE. In this study, we evaluated the efficacy of a novel dual-function nitric oxide donor/redox modulator, AKT-1005, in reducing PE symptoms in a mouse model of PE. Method: The potential therapeutic effect of AKT-1005 was tested in an animal model of Ad.sFlt-1-induced hypertension, proteinuria and glomerular endotheliosis, a model of PE. Pregnant Ad.sFlt-1-overexpressing CD1 mice were randomized into groups administered AKT-1005 (20 mg/kg) or a vehicle using a minipump on gd11 of pregnancy, and the impact on blood pressure and renal and placental damage were assessed. Results: In healthy female mice, ex vivo treatment of resistance vessels with AKT-1005 induced vasorelaxation, and 6 days of treatment in vivo did not significantly alter blood pressure with or without pregnancy. When given for 6 days during pregnancy along with Ad.sFlt-1-induced PE, AKT-1005 significantly increased plasma nitrate levels and reduced hypertension, renal endotheliosis and plasma cystatin C. In the placenta, AKT-1005 improved placental function, with reduced oxidative stress and increased endothelial angiogenesis, as measured by CD31 staining. As such, AKT-1005 treatment attenuated the Ad.sFlt-1-induced increase in placental and free plasma soluble endoglin expression. Conclusions: These data suggest that AKT-1005 significantly attenuates the sFlt-1-induced PE phenotypes by inhibiting oxidative stress, the anti-angiogenic response, and increasing NO bioavailability. Additional research is warranted to investigate the role of AKT-1005 as a novel therapeutic agent for vascular disorders such as preeclampsia.

Markers of Endothelial Dysfunction Are Attenuated by Resveratrol in Preeclampsia

Preeclampsia (PE) is characterized by great endothelial dysfunction, decreased nitric oxide (NO) bioavailability, and higher levels of arginase activity. In the present study, we investigated the potential modulatory effects of trans-resveratrol (RSV) on arginase and endothelial dysfunction biomarkers in endothelial cells exposed to plasma from patients with PE and healthy pregnant (HP) women, and umbilical arteries from patients with PE. Human umbilical vein endothelial cells (HUVECs) were incubated with pooled plasma from 10 HP or 10 PE pregnant women and RSV; umbilical arteries from patients with PE were incubated with RSV; intracellular NO and total reactive oxygen species (ROS) levels were assessed using a probe that interacted with these radicals; total arginase activity was evaluated measuring the urea produced; total antioxidant capacity was measured using the ferric reduction ability power (FRAP) assay; and endothelial dysfunction biomarkers were assessed using qPCR in endothelial cells and umbilical arteries. RSV increased NO levels and decreased total arginase activity in endothelial cells incubated with plasma from patients with PE. In addition, RSV increased total antioxidant capacity and downregulated endothelial dysfunction biomarkers, such as intercellular adhesion molecule-1 (ICAM-1), von Willebrand factor (vWF), and Caspase-3, (CASP-3), in endothelial cells and umbilical arteries from PE patients. RSV treatment positively modulated the L-arginine-NO pathway, decreased arginase activity, and increased antioxidant capacity, in addition to downregulating endothelial dysfunction biomarkers.

A metabolomic study on the effect of prenatal exposure to Benzophenone-3 on spontaneous fetal loss in mice

Benzophenone-3 (BP-3) is widely used in a variety of cosmetics and is prevalent in drinking water or food, and women were under notable high exposure burden of BP-3. Reports show the associations between prenatal exposure to BP-3 and the risk of fetal loss, but its underlying mechanism remains largely unknown. Pregnant ICR mice were gavaged with BP-3 from gestational day (GD) 0 to GD 6 at doses of 0.1, 10 and 1000 mg/kg/day. The samples were collected on GD 12. Ultra-performance liquid chromatography coupled with mass spectrometry-based metabolomics was used to detect metabolome changes in fetal mice, the uterus and the placenta to identify the underlying mechanism. The results showed that the body weight and relative organ weights of the liver, brain and uterus of pregnant mice were not significantly changed between the control group and the treatment group. BP-3 increased fetal loss, and induced placental thrombosis and tissue necrosis with enhancement of platelet aggregation. Metabolomic analysis revealed that fructose and mannose metabolism, the TCA cycle, arginine and proline metabolism in the fetus, arginine and proline metabolism and biotin metabolism in the uterus, and arginine biosynthesis and pyrimidine metabolism in the placenta were the key changed pathways involved in the above changes. Our study indicates that exposure to BP-3 can induce placental thrombosis and fetal loss via the disruption of maternal and fetal metabolism in mice, providing novel insights into the influence of BP-3 toxicity on the female reproductive system.

New views on endothelial dysfunction in gestational hypertension and potential therapy targets

The placenta has vital roles in metabolite exchange, fetal growth, and pre-eclampsia (PE). In this review, we discuss the pathogenesis of hypertension in pregnancy, focusing on four major theories to explain PE, discussing endothelial roles in those theories. We focus in particular on the roles of nitric oxide (NO) and prostacyclin (PGI₂) in placental endothelium, and propose new hypotheses for the influence and mechanisms of endothelial NO and PGI₂ signaling pathways in PE.

Association Between eNOS, MMP-9, BAG-6 Gene Polymorphisms and Risk of Hypertensive Disorders of Pregnancy in the Northern Chinese Population

The objective of this study was to investigate the role of endothelial nitric oxide synthase (eNOS), matrix metalloproteinases (MMP)-9, and Bcl2-associated oncogene 6 (BAG-6) gene polymorphisms, as well as the combined role of single nucleotide polymorphisms (SNPs) in hypertensive disorders of pregnancy (HDP) patients. This case-control study consisted of women with 326 HDP and 312 healthy pregnant controls. Multiplex PCR combined with next-generation sequencing method was used for determination of gene polymorphisms. Nine SNPs were analyzed, and we classified these case samples in depth by preeclampsia (PE) non-PE or blood pressure stages. We undertook allele and genotype haplotype association studies in all the cases and in the subgroups, as well as adjust age by binary logistic regression. Furthermore, the distribution of the haplotypes formed by the nine SNPs mentioned between the HDP patients and healthy pregnant controls were analyzed. There were no statistically significant differences in the nine SNPs of eNOS, MMP-9, and BAG-6 gene allele and genotype frequencies between HDP or subtypes and controls. However, for haplotype analyses, we found that the frequencies of AGACGCCGA (p = 3.67^e-005), AGACGCGCA (p = 0.03127), and GAACACCGA (p = 0.02449) were significantly lower in the cases than in the controls. However, the haplotype of GGACGCCGA (p = 0.000686) was higher in the cases than in the controls. Our results suggested protective effect of the haplotypes AGACGCCGA, AGACGCGCA, and GAACACCGA against the development of HDP, and the haplotype GGACGCCGA was the risk factor of HDP.

Placental endothelial nitric oxide synthase expression and role of oxidative stress in susceptibility to preeclampsia in Pakistani women

BACKGROUND

Preeclampsia (PE): a hypertensive disorder of pregnancy characterized by de novo development of concurrent hypertension and proteinuria. The prevailing theory determined that PE starts from the placenta and ends in the maternal endothelium. Role of endothelial dysfunction in the onset of PE has been reported in different populations. Therefore, present study was designed to investigate the localization and expression of endothelial nitric oxide synthase (eNOS) and role of oxidative stress markers in preeclamptic Pakistani women.

METHODS

A total of 400 blood samples (PE = 200, controls = 200) and 100 placental tissues (PE = 50, controls = 50) were recruited from pregnant women. Reactive oxygen species (ROS), thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), and guaiacol peroxidase (POD) levels were analyzed through spectrophotometer. Immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR) were carried out to estimate the localization and expression of eNOS in the placentas of PE patients and healthy pregnant women.

RESULTS

Significantly increased levels of POD (0.01), TBARS (0.04), and ROS (p ≤ .001) were determined in preeclamptic women while, nonsignificant change in SOD and CAT was observed in both groups. Reduced eNOS immunoreactivity (p ≤ .001) and mRNA abundance (p ≤ .001) was observed in preeclamptic group as compared to control group.

CONCLUSION

Considering the results of current study, it is concluded that decreased eNOS expression and oxidative stress could play a role in the pathology of PE seen both in placenta and ultimately in maternal endothelium. However, large studies are necessary to validate these findings to prevent maternal and neonatal morbidity and mortality in Pakistani population.

The Role of Nitric Oxide, ADMA, and Homocysteine in The Etiopathogenesis of Preeclampsia-Review

Preeclampsia is a serious, pregnancy-specific, multi-organ disease process of compound aetiology. It affects 3–6% of expecting mothers worldwide and it persists as a leading cause of maternal and foetal morbidity and mortality. In fact, hallmark features of preeclampsia (PE) result from vessel involvement and demonstrate maternal endothelium as a target tissue. Growing evidence suggests that chronic placental hypoperfusion triggers the production and release of certain agents that are responsible for endothelial activation and injury. In this review, we will present the latest findings on the role of nitric oxide, asymmetric dimethylarginine (ADMA), and homocysteine in the etiopathogenesis of preeclampsia and their possible clinical implications.

High glutathionylation of placental endothelial nitric oxide synthase in preeclampsia

Decreased nitric oxide (NO) bioavailability plays a critical role in the pathophysiology of preeclampsia (PE). Recent evidence indicates that S-glutathionylation may occur on the endothelial nitric oxide synthase (eNOS), leading to eNOS uncoupling, characterized by a decreased NO production and an increased generation of superoxide anion (O2•-). We hypothesized that eNOS glutathionylation may occur in PE placentas and participate in eNOS dysfunction. The glutathionylation of eNOS was investigated in thirteen PE-affected patients and in nine normal pregnancies. Immunofluorescence, confocal microscopy and western-blot experiments carried out on eNOS immunoprecipitates, revealed a high level of eNOS glutathionylation in PE placentas, mostly reversed by dithiotreitol (DTT), thus indicative of S-glutathionylation. In order to investigate whether eNOS glutathionylation may alter trophoblast migration, an important event occurring during early placentation, cultured HTR-8/SVneo human trophoblasts (HTR8) were exposed either to low pO2 (O2 1%) or to pO2 changes (O2 1-20%), in order to generate oxidative stress. Trophoblasts exposed to low pO2, did not undergo oxidative stress nor eNOS S-glutathionylation, and were able to generate NO and migrate in a wound closure model. In contrast, trophoblasts submitted to low/high pO2 changes, exhibited oxidative stress and a (DTT reversible) S-glutathionylation of eNOS, associated with reduced NO production and migration. The autonomous production of NO seemed necessary for the migratory potential of HTR8, as suggested by the inhibitory effect of eNOS silencing by small interfering RNAs, and the eNOS inhibitor L-NAME, in low pO2 conditions. Finally, the addition of the NO donor, NOC-18 (5 µM), restored in part the migration of HTR8, thereby emphasizing the role of NO in trophoblast homeostasis. In conclusion, the high level of eNOS S-glutathionylation in PE placentas provides new insights in the mechanism of eNOS dysfunction in this disease.

Circulating markers of nitric oxide homeostasis and cardiometabolic diseases: insights from population-based studies

Emerging data suggest that impaired nitric oxide (NO) homeostasis has a key role in development of cardiometabolic disorders. The association between circulating levels of NO metabolites, i.e. nitrate and nitrite (NOx), and risk of chronic diseases has not yet been fully clarified. This work aims to address epidemiologic aspects of NO metabolism and discusses different physiologic and pathophysiologic conditions influencing circulating NOx. Further, cross-sectional associations of serum NOx with metabolic disorders are described and along the way, potential short-term and long-term power of serum NOx for predicting cardiometabolic outcomes are reviewed. Results from population-based studies show that circulating NOx is affected by aging, smoking habits, pregnancy, menopause status, thyroid hormones, and various pathologic conditions including type 2 diabetes, insulin resistance, hypertension, and renal dysfunction. Lifestyle factors, especially dietary habits, but also smoking habits and the degree of physical activity influence NO homeostasis and the circulating levels of NOx. Elevated serum NOx, due to increased iNOS activity, is associated with increased incidence of metabolic syndrome, different obesity phenotypes, and cardiovascular events.

Deletion of GIT1 Impacts eNOS Activity To Aggravate sFlt-1-Induced Preeclampsia Phenotype in Mice

Preeclampsia, a serious multisystem disorder specific to human pregnancy, remains a considerable burden of disease worldwide. Reduced nitric oxide bioavailability is proved to be crucial in the maternal and fetal pathophysiology of preeclampsia. G-protein-coupled Receptor Kinase Interactor-1 (GIT1) is a novel endothelial nitric oxide synthases (eNOS) interactor mediator. The aim of this paper is to investigate the effect of GIT1 on preeclampsia. Blood pressure (BP) was measured using a carotid catheter-calibrated eight-chamber tail-cuff system (CODA) at the same time daily. Urinary albumin excretion (UAE) was determined using Albuwell-M kits (Exocell Inc) and creatinine clearance (CCr) was determined by measuring urinary creatinine concentration with tandem liquid chromatography–mass spectrometry. The release of nitrite was analyzed to detect nitric oxide (NO) production using a Sievers Chemiluminescence NO Analyzer. NOS activity was examined by measuring the conversion of ³H-labeled l-arginine to ³H-labeled l-citrulline. BP was significantly increased in GIT1^−/− mice with or without sFIT-1 treatment. In addition, GIT1−/− mice possessed higher UAE and lower CCr. Depletion of GIT1 impedes the NO production and placenta eNOS activity. Additional GIT1 attenuates sFlt-1-induced preeclampsia phenotypes. Our findings suggest that GIT1 significantly extenuates the sFlt-1-induced preeclampsia phenotypes by inhibiting eNOS activity, indicating a crucial role of GIT1 in the progression of preeclampsia.

Altered Endothelial Nitric Oxide Signaling as a Paradigm for Maternal Vascular Maladaptation in Preeclampsia

PURPOSE OF REVIEW

The goal of this review is to present the newest insights into what we view as a central failure of cardiovascular adaptation in preeclampsia (PE) by focusing on one clinically significant manifestation of maternal endothelial dysfunction: nitric oxide signaling. The etiology, symptoms, and current theories of the PE syndrome are described first, followed by a review of the available evidence, and underlying causes of reduced endothelial nitric oxide (NO) signaling in PE.

RECENT FINDINGS

PE maladaptations include, but are not limited to, altered physiological stimulatory inputs (e.g., estrogen; VEGF/PlGF; shear stress) and substrates (L-Arg; ADMA), augmented placental secretion of anti-angiogenic and inflammatory factors such as sFlt-1 and Eng, changes in eNOS (polymorphisms, expression), and reduced bioavailability of NO secondary to oxidative stress. PE is a complex obstetrical syndrome that is associated with maternal vascular dysfunction. Diminished peripheral endothelial vasodilator influence in general, and of NO signaling specifically, are key in driving disease progression and severity.

Review on role of progestogen (dydrogesterone) in the prevention of gestational hypertension

INTRODUCTION

Gestational hypertension remains one of the main causes of maternal deaths all over the world. Attempts to reduce/prevent the incidence had failed due to lack of understanding of the disease's aetiology. One of the early roles of natural progesterone in the first trimester of pregnancy is to promote formation of wide-calibre spiral vessels that invade into the myometrial layer of the gravid uterus. Theoretically, this will prevent or reduce the incidence of gestational hypertension in the latter half of the pregnancy.

REVIEW

The progestogen, dydrogesterone, has similar molecular structure and properties to natural progesterone. A pilot study was undertaken on primigravidae, who have higher risk of developing gestational hypertension. They were supplemented with dydrogesterone in the first trimester (Study Group) and compared with a similar number of primigravidae (Control Group) without supplementation with the progestogen. The incidence of gestational hypertension was significantly lower in the Study Group as compared to the Control Group (1.7% vs. 12.9%, respectively, p<0.001). The incidence of foetal distress was also significantly lower in the Study Group compared to the Control Group (4.3% vs. 18.1%, respectively, p<0.001).

CONCLUSION

Supplementation of the progestogen, dydrogesterone, in the first trimester to primigravidae has shown great potential in reducing or preventing the incidence of gestational hypertension.

Polymorphisms in the Endothelial Nitric Oxide Synthase Gene May Be Protective Against Preeclampsia in a Chinese Population

The association between the endothelial nitric oxide synthase (eNOS) gene with vascular diseases in Western populations and with severe preeclampsia (PE) in the Japanese population have been demonstrated, lacing the data in Chinese population. The authors examine the association between PE and 2 polymorphisms of the eNOS gene in a Chinese population, consisting of 92 pregnant women with PE and 256 healthy controls. All were genotyped for the Glu298Asp polymorphism in exon 7 and the number of 27 base pair repeats in intron 4 of the eNOS gene. The frequencies of both the variant T allele and eNOS 4a (small allele with 4 repeats of 27 bp) were significantly lower in the PE group than in the control group. The genotype distribution of Glu298Glu, Glu298Asp, and Asp298Asp in eNOS exon 7 and bb type and ab type in eNOS intron 4 revealed statistically significant differences between control and PE groups. This is the first study to evaluate the association between 2 polymorphisms in the maternal eNOS gene with PE simultaneously in a Chinese population. Similar to the findings in Western populations, polymorphisms in the eNOS gene may be protective against PE in a Chinese population, in contrast to the results in the Japanese population.

A pilot study to determine whether progestogen supplementation using dydrogesterone during the first trimester will reduce the incidence of gestational hypertension in primigravidae

BACKGROUND

Gestational hypertension (GH) remains one of the main causes of high maternal and perinatal morbidity and mortality worldwide with the highest incidence among primigravidae of about 10%-15%. However, it was noted that the incidence of GH in primigravidae who conceived following assisted reproductive technique (ART) or intrauterine insemination (IUI) supplemented with dydrogesterone during the first trimester was low.

AIM

To determine whether dydrogesterone supplementation during the first trimester can reduce the incidence of GH among primigravidae.

METHOD

A prospective cross-sectional comparative study was undertaken in 2010 on 116 primigravidae (study group) who conceived following ART or IUI and supplemented with dydrogesterone up to 16 weeks gestation. They were matched for age and race at 16 weeks gestation with a control patient from the early pregnancy clinic who were primigravidae (n = 116) who conceived spontaneously without dydrogesterone supplementation.

FINDINGS

The incidence of GH in the study group was significantly lower than the control group (1.7% versus 12.9%, p = 0.001). The incidence of fetal distress was also significantly lower in the study group compared to the control group (4.3% versus 18.1%, p = 0.001).

INTERPRETATION

Dydrogesterone supplementation during the first trimester significantly reduced the incidence of GH and fetal distress in primigravidae.

The role of homocysteine, asymmetric dimethylarginine and nitric oxide in pre-eclampsia

Nitric oxide (NO) contributes to vasodilatation that is observed during normal pregnancy. Hyperhomocysteinaemia (HHcy) is a vascular risk factor associated with placental microvascular diseases and pre-eclampsia. Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of endothelial nitric oxide synthase (NOS) has been linked to endothelial dysfunction. Maternal ADMA has been reported to be higher in women with pre-eclampsia and HHcy leads to accumulation of ADMA. The aim of this presented study is to evaluate the alterations of plasma homocysteine, ADMA and NO levels in mild pre-eclampsia. A total of 40 pre-eclamptic women and 40 healthy controls were included into the study. Mean systolic and diastolic blood pressure, mean serum homocysteine and ADMA levels were significantly higher and NO level was lower in patients. Serum homocysteine, ADMA and NO levels found to be correlated among them and with blood pressure. In conclusion, we found that homocysteine and ADMA levels were increased and NO levels decreased in pre-eclampsia.

Role of arginase-2 and eNOS in the differential vascular reactivity and hypoxia-induced endothelial response in umbilical arteries and veins

The main vasodilator in the placenta is nitric oxide (NO), which is synthesized by endothelial NO synthase (eNOS). Arginase-2 competes with eNOS for l-arginine, and its activity has been related with vascular dysfunction. Recently, we showed that hypoxia induces arginase-2, and decreases eNOS activity in human umbilical vein endothelial cells (HUVEC). However there is evidence that vascular responses to hypoxia are not similar throughout the placental vascular tree. We studied whether arginase-2 plays a role controlling vascular tone in human umbilical vessels, and the changes in the expression of arginase-2 and eNOS proteins by hypoxia in endothelial cells from umbilical arteries (HUAEC) and veins (HUVEC). In isolated umbilical vessels the presence of eNOS and arginase-2 was determined in the endothelium, and the NO-dependent vasoactive responses in the presence and absence of S-(2-boronoethyl)-L-cysteine (BEC, arginase inhibitor) were studied. Additionally, HUAEC and HUVEC were exposed (0-24 h) to hypoxia (2% O2) or normoxia (5% O2), and protein levels of eNOS (total and phosphorylated at serine-1177) and arginase-2 were determined. In umbilical arteries and veins arginase-2 and eNOS were detected mainly at the endothelium. BEC induced a higher concentration-dependent relaxation in umbilical arteries than veins, and these responses were NOS-dependent. In HUAEC exposed to hypoxia there were no changes in eNOS and arginase-2 levels, however there was a significant increase of p-eNOS. In contrast, HUVEC showed an increase in arginase-2 and a reduction of p-eNOS in response to hypoxia. These results show that arginases have a vascular role in placental vessels counteracting the NOS-dependent relaxation, which is differentially regulated in placental artery and vein endothelial cells.

Mammalian Ste20-like protein kinase 3 plays a role in hypoxia-induced apoptosis of trophoblast cell line 3A-sub-E

Mammalian Ste20-like protein kinase 3 (Mst3) is a key player in inducing apoptosis in a variety of cell types and has recently been shown to participate in the signaling pathway of hypoxia-induced apoptosis of human trophoblast cell line 3A-sub-E (3A). It is believed that oxidative stress may occur during hypoxia and induce the expression of Mst3 in 3A cells via the activation of c-Jun N-terminal protein kinase 1 (JNK1). This hypothesis was demonstrated by the suppressive effect of dl-α-lipoic acid, a reactive oxygen species scavenger, in hypoxia-induced responses of 3A cells such as Mst3 expression, nitrotyrosine formation, JNK1 activation and apoptosis. Similar results were also observed in trophoblasts of human placental explants in both immunohistochemical studies and immunoblot analyses. These suggested that the activation of Mst3 might trigger the apoptotic process in trophoblasts by activating caspase 3 and possibly other apoptotic pathways. The role of nitric oxide synthase (NOS) and NADPH oxidase (NOX) in hypoxia-induced Mst3 up-regulation was also demonstrated by the inhibitory effect of N(G)-nitro-l-arginine and apocynin, which inhibits NOS and NOX, respectively. Oxidative stress was postulated to be induced by NOS and NOX in 3A cells during hypoxia. In conclusion, hypoxia induces oxidative stress in human trophoblasts by activating NOS and NOX. Subsequently, Mst3 is up-regulated and plays an important role in hypoxia-induced apoptosis of human trophoblasts.

Vasodilator factors in the systemic and local adaptations to pregnancy

We postulate that an orchestrated network composed of various vasodilatory systems participates in the systemic and local hemodynamic adaptations in pregnancy. The temporal patterns of increase in the circulating and urinary levels of five vasodilator factors/systems, prostacyclin, nitric oxide, kallikrein, angiotensin-(1-7) and VEGF, in normal pregnant women and animals, as well as the changes observed in preeclamptic pregnancies support their functional role in maintaining normotension by opposing the vasoconstrictor systems. In addition, the expression of these vasodilators in the different trophoblastic subtypes in various species supports their role in the transformation of the uterine arteries. Moreover, their expression in the fetal endothelium and in the syncytiotrophoblast in humans, rats and guinea-pigs, favour their participation in maintaining the uteroplacental circulation. The findings that sustain the functional associations of the various vasodilators, and their participation by endocrine, paracrine and autocrine regulation of the systemic and local vasoactive changes of pregnancy are abundant and compelling. However, further elucidation of the role of the various players is hampered by methodological problems. Among these difficulties is the complexity of the interactions between the different factors, the likelihood that experimental alterations induced in one system may be compensated by the other players of the network, and the possibility that data obtained by manipulating single factors in vitro or in animal studies may be difficult to translate to the human. In addition, the impossibility of sampling the uteroplacental interface along normal pregnancy precludes obtaining longitudinal profiles of the various players. Nevertheless, the possibility of improving maternal blood pressure regulation, trophoblast invasion and uteroplacental flow by enhancing vasodilation (e.g. L-arginine, NO donors, VEGF transfection) deserves unravelling the intricate association of vasoactive factors and the systemic and local adaptations to pregnancy.

Placental infection by two subpopulations of Trypanosoma cruzi is conditioned by differential survival of the parasite in a deleterious placental medium and not by tissue reproduction

Chagas disease is caused by Trypanosoma cruzi, which can be transmitted to the fetus via the transplacental route. Factors that may be involved in transplacental transmission include parasite strain and placental immunological competence. The aim of this work was to compare the biological differences between two subpopulations of T. cruzi with respect to their interaction with the human placenta in vitro. We found that the Tulahuen strain (sublineage TcIIe) and another strain isolated from a congenitally infected newborn child had similar rates of productive infection in human chorionic villi in vitro, with similar deleterious nitric oxide levels between the two strains. We also found that the congenital T. cruzi stock had a greater ability than the Tulahuen strain to survive in the placental deleterious media, with the difference acquiring more importance considering the low reproductive rate of both subpopulations of T. cruzi within placental cells. As the presence of T. cruzi is a necessary condition to produce congenital transmission, we propose that the different survival rates of strains of T. cruzi in an adverse placental environment offer an opportunity for the parasite to infect the placenta in order to produce a sustainable infection during pregnancy, with the subsequent possibility of infecting the fetus.

Potential biomarkers of preeclampsia: inverse correlation between hydrogen peroxide and nitric oxide early in maternal circulation and at term in placenta of women with preeclampsia

Preeclampsia (PE) is a pregnancy-specific disease that has been associated with future cardiovascular disease for the mother and her child. The etiology of PE is unclear but oxidative stress seems to play a major role in endothelial dysfunction and permanent systemic vasoconstriction shown in PE. Hydrogen peroxide (H(2)O(2)), a terminal metabolite of the cellular oxidative stress cascade, is also revealed as a component of oxidative ischemia/reperfusion stress in placenta. We were the first to show an increase in the levels of H(2)O(2) in the serum of preeclamptic women at term. H(2)O(2) is already known to reduce the production of NO by increasing the metabolism of arginases. The objective of this study was to investigate a possible correlation between nitric oxide (NO), a potent vasodilator, and H(2)O(2) throughout pregnancy. Thus, we simultaneously assessed the levels of NO and H(2)O(2) in the serum of normal and preeclamptic women at 10-15 and 37-40 weeks of pregnancy, and in placentas at delivery. Our findings showed an inverse correlation between increased levels of H(2)O(2) and decreased levels of NO early in maternal circulation and at term in placenta. This relationship is confirmed by our in vitro experiments which demonstrate that H(2)O(2) inhibits NO synthesis of cytotrophoblasts. In conclusion, our findings highlight an inverse correlation between H(2)O(2) and NO early in maternal circulation and in placenta of women with preeclampsia, paving the way for further studies examining the potential use of NO and H(2)O(2) as biomarkers in the prediction of preeclampsia.

Gabor Than Award Lecture 2008: pre-eclampsia - from placental oxidative stress to maternal endothelial dysfunction

Pre-eclampsia is the most important complication of human pregnancy worldwide and a major contributor to maternal and fetal morbidity and mortality. Strong evidence exists that generation of placental oxidative stress, secondary to deficient spiral artery remodelling, is a key intermediary event, triggering the secretion of a mixture of placental factors that culminate in an enhanced maternal inflammatory response. Reactive oxygen species (ROS) have been recognised as secondary messengers in intracellular signalling cascades. Experiments studying placental ischaemia-reperfusion in vitro or in vivo during labour provide strong evidence suggesting that oxidative stress and ROS production can activate downstream stress-signalling pathways, p38 and SAPK/JNK MAPK, and the pro-inflammatory NF-kappaB signalling pathway, culminating in the release of inflammatory mediators, apoptotic debris, anti-angiogenic factors and other mediators, which then stimulate a maternal inflammatory reaction that manifests in endothelial dysfunction and the symptoms of pre-eclampsia. Addition of anti-oxidants or blocking the stress or inflammatory pathways in vitro attenuates these effects and opens possibilities for therapeutic intervention.

Angiogenic, hyperpermeability and vasodilator network in utero-placental units along pregnancy in the guinea-pig (Cavia porcellus)

BACKGROUND

The angiogenic and invasive properties of the cytotrophoblast are crucial to provide an adequate area for feto-maternal exchange. The present study aimed at identifying the localization of interrelated angiogenic, hyperpermeability and vasodilator factors in the feto-maternal interface in pregnant guinea-pigs.

METHODS

Utero-placental units were collected from early to term pregnancy. VEGF, Flt-1, KDR, B2R and eNOS were analyzed by immunohistochemistry, and the intensity of the signals in placenta and syncytial streamers was digitally analysed. Flt1 and eNOS content of placental homogenates was determined by western blotting. Statistical analysis used one-way analysis of variance and Tukey's Multiple Comparison post-hoc test.

RESULTS

In the subplacenta, placental interlobium and labyrinth VEGF, Flt-1, KDR, B2R and eNOS were expressed in all stages of pregnancy. Syncytial streamers in all stages of gestation, and cytotrophoblasts surrounding myometrial arteries in early and mid pregnancy - and replacing the smooth muscle at term - displayed immunoreactivity for VEGF, Flt-1, KDR, eNOS and B2R. In partly disrupted mesometrial arteries in late pregnancy cytotrophoblasts and endothelial cells expressed VEGF, Flt-1, KDR, B2R and eNOS. Sections incubated in absence of the first antibody, or in presence of rabbit IgG fraction and mouse IgG serum, yielded no staining. According to the digital analysis, Flt-1 increased in the placental interlobium in days 40 and 60 as compared to day 20 (P = 0.016), and in the labyrinth in day 60 as compared to days 20 and 40 (P = 0.026), while the signals for VEGF, KDR, B2R, and eNOS showed no variations along pregnancy. In syncytial streamers the intensity of VEGF immunoreactivity was increased in day 40 in comparison to day 20 (P = 0.027), while that of B2R decreased in days 40 and 60 as compared to day 20 (P = 0.011); VEGF, Flt-1, KDR, B2R and eNOS expression showed no variations. Western blots for eNOS and Flt-1 in placental homogenates showed no significant temporal differences along pregnancy.

CONCLUSION

The demonstration of different angiogenic, hyperpermeability and vasodilator factors in the same cellular protagonists of angiogenesis and invasion in the pregnant guinea-pig, supports the presence of a functional network, and strengthens the argument that this species provides an adequate model to understand human pregnancy.

Hormonal regulation of placental nitric oxide and pathogenesis of pre-eclampsia

The placenta is central to foetal growth and development in mammalian pregnancy. Compromised placental function (as found in pre-eclampsia) often results in life-threatening situations for both mother and foetus. The nitric-oxide (NO) signalling cascade is important for placental function, in particular for the development of the vascular network and for maintaining vascular tone. This pathway seems to be regulated by multiple hormonal signals. Emerging evidence suggests that pathogenic mechanisms that are involved in abnormal placental function target specific molecules, such as hormone receptors, that regulate NO release and have subsequent dramatic consequences. Here, we discuss the current knowledge of NO function in the placenta, its hormonal regulation in normal pregnancy and in the pathophysiology of pre-eclampsia, its potential pathogenic mechanisms and possible use as a therapeutic target.

Mechanisms of Disease: pre-eclampsia

Pre-eclampsia, a syndrome of pregnant women, is one of the leading causes of maternal and fetal morbidity and mortality. Despite active research, the etiology of this disorder remains an enigma. Recent work has, however, provided promising explanations for the causation of the disorder and some of its phenotypes. Evidence indicates that the symptoms of hypertension and proteinuria, upon which the diagnosis of pre-eclampsia is based, have several underlying causes. Nevertheless, the treatment of pre-eclampsia has not changed significantly in over 50 years. This review describes the most recent insights into the pathophysiology of pre-eclampsia from both basic and clinical research, and attempts to provide a unifying hypothesis to reconcile the abnormalities at the feto-placental level and the clinical features of the maternal syndrome. The novel findings outlined in this review provide a rationale for potential future prophylactic and therapeutic interventions for pre-eclampsia.

Polymorphisms of the Nos3 gene and unexplained late intrauterine fetal death

OBJECTIVE

Genetic polymorphisms associated with vascular diseases have been proposed to be involved in the pathogenesis of late unexplained intrauterine fetal death (IUFD). The Nos3 gene is known to regulate vascular tone via the endothelial nitric oxide synthase/nitric oxide pathway.

STUDY DESIGN

In a multicenter case-control study, we evaluated two Nos3 polymorphisms (exon 7 Glu298Asp and a 27bp-repeat in intron 4) in 92 women with IUFD and 92 healthy control women.

RESULTS

The investigated Nos3 polymorphisms were not associated with the occurrence of IUFD. In the subgroup of pregnancies affected by IUFD, women with at least one mutant allele of the Nos3 intron 4 polymorphism were diagnosed with IUFD at a significantly earlier gestational age (31.8 [standard deviation (S.D.) = 4.9] weeks versus 34.6 [S.D. = 4.8] weeks, p = 0.02) and showed a significantly reduced birth weight (2113 g [S.D. = 1028] versus 1571 g [S.D. = 568], p = 0.03).

CONCLUSION

We are the first to report on Nos3 polymorphisms and IUFD. While not being associated with the incidence of IUFD overall, the intron 4 Nos3 polymorphism might modulate the timing of IUFD in affected pregnancies.

Expression of endothelial nitric oxide synthase traffic inducer in the placentas of women with pre-eclampsia

OBJECTIVE

To investigate the expression of endothelial nitric oxide synthase traffic inducer (NOSTRIN) in the placenta of women with pre-eclampsia (PE) and discuss its role in the pathogenesis of PE.

METHODS

Western blot analysis was used to detect the expression of NOSTRIN and endothelial nitric oxide synthase (eNOS). The activity of eNOS in placental tissue was assayed by spectrophotometry. Serum and placental NO(2)/NO(3), the stable metabolic end product of NO, was measured using nitrate reductase.

RESULTS

Western blot analysis showed that the protein level of NOSTRIN was significantly higher in women with PE than in the control group (P<0.01). However, no significant difference between groups was observed in the expression of placental eNOS (P>0.05). The activity of eNOS was significantly decreased in women with PE (13.727+/-3.58 U/mg) compared with the control group (21.69+/-3.84 U/mg) (P<0.01). The placental levels of NO(2)/NO(3) were significantly lower in women with PE (27.53+/-8.51 micromol/mg) than in the control group (44.38+/-9.59 micromol/mg) (P<0.01). The levels of serum NO(2)/NO(3) were significantly lower in women with PE (48.56+/-8.49 micromol/L) than in the control group (65.37+/-9.61 micromol/L) (P<0.01). A significant negative correlation existed between the expression of NOSTRIN protein and the activity of eNOS in the placental tissues of women with PE (r=-0.57, P<0.01).

CONCLUSION

The level of NOSTRIN expression in the placental tissues of women with PE is increased and is negatively correlated with the activity of eNOS-which may play an important role in the pathogenesis of PE.

Pathophysiological basis for the prophylaxis of preeclampsia through early supplementation with antioxidant vitamins

Preeclampsia (PE) is a multisystem disorder that remains a major cause of maternal and foetal morbidity and death. To date, no treatment has been found that prevents the development of the disease. Endothelial dysfunction is considered to underlie its clinical manifestations, such as maternal hypertension, proteinuria, and edema; however, the precise biochemical pathways involved remain unclear. A current hypothesis invokes the occurrence of oxidative stress as pathogenically important, as suggested by the fact that in PE, the placental and circulating levels of lipid peroxidation products (F2-isoprostanes and malondialdehyde [MDA]) are increased and endothelial cells are activated. A potential mechanism for endothelial dysfunction may occur via nuclear transcription factor kappa B (NF-kappaB) activation by oxidative stress. Alternatively, the idea that the antiangiogenic placental soluble fms-like tyrosine kinase 1 factor (sFlt1) is involved in the pathogenesis of this disease is just emerging; however, other pathophysiological events seem to precede its increased production. This review is focused on evidence providing a pathophysiological basis for the beneficial effect of early antioxidant therapy in the prevention of PE, mainly supported by the biological effects of vitamins C and E.

Reduced L-arginine level and decreased placental eNOS activity in preeclampsia

Nitric oxide is produced enzymatically by the nitric oxide synthase (NOS), which converts L-arginine in the presence of oxygen to L-citrulline and NO. Moreover, it has been reported that asymmetric dimethylarginine (ADMA) acts as is an endogenous inhibitor of endothelial NOS (eNOS) by competing with the enzyme for L-arginine. In this study, we measured L-arginine and ADMA in normal and preeclamptic women, and also investigated the association between the Glu298Asp eNOS gene polymorphism and preeclampsia. Finally, we assessed eNOS expression levels in the placentas of both normal and preeclamptic patients, using Western blot and immunohistochemistry. L-arginine levels were found to be significantly lower in the preeclamptic women than in the normal pregnant women (p=0.02) but there were no significant differences in ADMA levels between the normal and preeclamptic women. We also determined there to be no association between the Glu298Asp eNOS gene and preeclampsia. With regard to placental eNOS expression, we detected a lower degree of eNOS expression in the preeclamptic syncytiotrophoblasts than in the normal syncytiotrophoblasts. We suggest that reduced L-arginine levels, rather than increased ADMA levels, contribute to the development of preeclampsia, and also that decreased placental eNOS expression constitutes a characteristic finding in preeclamptic placentas.