Preeclampsia is associated with loss of neuronal nitric oxide synthase expression in vascular smooth muscle cells of the human umbilical cord

miR-31-5p from placental and peripheral blood exosomes is a potential biomarker to diagnose preeclampsia

Background

Preeclampsia, a multisystem disorder of unknown etiology, is one of the leading causes of maternal and perinatal morbidity and mortality. Identifying sensitive, noninvasive markers can aid its prevention and improve prognosis. microRNAs (miRs), which function as negative regulators of gene expression, are closely related to preeclampsia occurrence and development. Herein we investigated the relationship between the DLK1-Dio3 imprinted miR cluster derived from placental and peripheral blood exosomes of pregnant women with preeclampsia and routine clinical diagnostic indicators, and also determined its potential as a noninvasive diagnostic marker.

Methods

Exosomes were extracted from the placenta and peripheral blood of pregnant women with preeclampsia.

Results

qPCR data indicated that the expression level of miRs, such as miR-134, miR-31-5p, miR-655, miR-412, miR-539, miR-409, and miR-496, in pregnant women with preeclampsia was significantly lower than that in healthy controls; miR-31-5p expression was the most different. Gene ontology analysis predicted that genes negatively regulated by miR-31-5p were mainly enriched in cellular entity, cellular process, and binding; moreover, Kyoto Encyclopedia of Genes and Genomes pathway analyses indicated that genes were involved in gonadotropin-releasing hormone receptor pathway and other signaling pathways. Correlation analysis revealed that miR-31-5p was significantly negatively correlated with clinical indicators of preeclampsia, such as systolic and diastolic pressure, lactate dehydrogenase, and proteinuria.

Conclusion

We believe that exosome-derived miR-31-5p can serve as an effective and sensitive biomarker to determine the course of preeclampsia in pregnant women.

An autophagic deficit in the uterine vessel microenvironment provokes hyperpermeability through deregulated VEGFA, NOS1, and CTNNB1

The uterus undergoes vascular changes during the reproductive cycle and pregnancy. Steroid hormone deprivation induces macroautophagy/autophagy in major uterine cell types. Herein, we explored the functions of uterine autophagy using the Amhr2-Cre-driven atg7 deletion model. Deletion of Atg7 was confirmed by functional deficit of autophagy in uterine stromal, myometrial, and vascular smooth muscle cells, but not in endothelial cells. atg7d/d uteri exhibited enhanced stromal edema accompanied by dilation of blood vessels. Ovariectomized atg7d/d uteri showed decreased expression of endothelial junction-related proteins, such as CTNNB1/beta-catenin, with increased vascular permeability, and increased expression of VEGFA and NOS1. Nitric oxide (NO) was shown to mediate VEGFA-induced vascular permeability by targeting CTNNB1. NO involvement in maintaining endothelial junctional stability in atg7d/d uteri was confirmed by the reduction in extravasation following treatment with a NOS inhibitor. We also showed that atg7d/d uterine phenotype improved the fetal weight:placental weight ratio, which is one of the indicators of assessing the status of preeclampsia. We showed that autophagic deficit in the uterine vessel microenvironment provokes hyperpermeability through the deregulation of VEGFA, NOS1, and CTNNB1.Abbreviations: ACTA2: actin, alpha 2, smooth muscle, aortic; Amhr2: anti-Mullerian hormone type 2 receptor; ANGPT1: angiopoietin 1; ATG: autophagy-related; CDH5: cadherin 5; CLDN5: claudin 5; COL1A1: collagen, type I, alpha 1; CSPG4/NG2: chondroitin sulfate proteoglycan 4; CTNNB1: catenin (cadherin associated protein), beta 1; DES: desmin; EDN1: endothelin 1; EDNRB: endothelin receptor type B; F3: coagulation factor III; KDR/FLK1/VEGFR2: kinase insert domain protein receptor; LYVE1: lymphatic vessel endothelial hyaluronan receptor 1; MAP1LC3B: microtubule-associated protein 1 light chain 3 beta; MCAM/CD146: melanoma cell adhesion molecule; MYL2: myosin, light polypeptide 2, regulatory, cardiac, slow; MYLK: myosin, light polypeptide kinase; NOS1/nNOS: nitric oxide synthase 1, neuronal; NOS2/iNOS: nitric oxide synthase 2, inducible; NOS3/eNOS: nitric oxide synthase 3, endothelial cell; OVX: ovariectomy; PECAM1/CD31: platelet/endothelial cell adhesion molecule 1; POSTN: periostin, osteoblast specific factor; SQSTM1: sequestosome 1; TEK/Tie2: TEK receptor tyrosine kinase; TJP1/ZO-1: tight junction protein 1; TUBB1, tubulin, beta 1 class VI; USC: uterine stromal cell; VEGFA: vascular endothelial growth factor A; VSMC: vascular smooth muscle cell.

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.

Human umbilical cord and its vessels: a histomorphometric study in difference severity of hypertensive disorders of pregnancy

The umbilical cord (UC) is a platform for fetal nourishment and growth. The fetus, mother and placenta with UC form a triad, which contributes to pregnancy outcome. When pregnancy is complicated by a medical condition like hypertension, affects both maternal and fetal health. Being a fetal structure it can be used as a window to know the maternal dysfunctions and their impacts on fetal wellbeing. The present study is to explore the histomorphometric changes of the UC and its vessels involved in the development of hypertension during pregnancy. Sixty UCs were used and the following parameters, total UC area; total vessel area; jelly area; wall area, luminal area and wall thickness of umbilical arteries 1 and 2 and vein were studied using ImageJ software. From the results, the mean differences of above parameters of hypertensive UCs were found to be lesser than control and it was significantly higher in cases of severe preeclampsia (P≤0.05). From the present study, we conclude hypertensive cords and its vessels are associated with significant structural changes. Since it is a global health issue it is important to know the factors contributing it to diagnose and prevent.

Morphometric characteristics of the umbilical cord and vessels in fetal growth restriction and pre-eclampsia

BACKGROUND

Reports on the morphometric analysis of umbilical cord (UC) and its vessels have been inconsistent due to varying inclusion criteria and methodology. The current study tried to overcome the limitations of previous studies by comparing the UC in pregnancies complicated by fetal growth restriction (FGR), preeclampsia (PE) and FGR+PE, to healthy controls.

AIMS

Analyze the morphometric attributes of the UC in pregnancies complicated by FGR and PE.

STUDY DESIGN

Case-control.

SUBJECTS

The study groups consisted of 36 patients with FGR+PE, 72 with FGR (without PE) and 15 with PE (without FGR). They were compared to 50 patients without FGR or PE.

OUTCOME MEASURES

Histological cross-sections of the UC were photographed and measured. The following variables were recorded: cross-section area of UC, thickness and surface area of umbilical vessel walls, shortest distance between cord surface and nearest artery (DSA), distance between the arteries (DBA) and placental weight and measurements. The area of the Wharton's jelly (WJ) area was calculated.

RESULTS

UC and WJ cross-section areas were significantly smaller in FGR+PE and FGR, but not in PE. The umbilical vessel wall area was decreased in FGR+PE, but the thickness was not significantly decreased in all three study groups, compared to controls. DSA was smaller in all three groups, whereas DBA was not significantly different, compared to controls.

CONCLUSIONS

Smaller UC cross-section areas were seen in FGR and FGR+PE, but not in PE without FGR. However, there is no evidence to determine whether this reduction is a cause or consequence of FGR. Reduced DSA in PE, whose UC cross-section area was not smaller as in FGR and FGR+PE, might reflect alterations in UC induced by PE.

Preeclampsia serum-induced collagen I expression and intracellular calcium levels in arterial smooth muscle cells are mediated by the PLC-γ1 pathway

In women with preeclampsia (PE), endothelial cell (EC) dysfunction can lead to altered secretion of paracrine factors that induce peripheral vasoconstriction and proteinuria. This study examined the hypothesis that PE sera may directly or indirectly, through human umbilical vein ECs (HUVECs), stimulate phospholipase C-γ1-1,4,5-trisphosphate (PLC-γ1-IP₃) signaling, thereby increasing protein kinase C-α (PKC-α) activity, collagen I expression and intracellular Ca²⁺ concentrations ([Ca²⁺]_i) in human umbilical artery smooth muscle cells (HUASMCs). HUASMCs and HUVECs were cocultured with normal or PE sera before PLC-γ1 silencing. Increased PLC-γ1 and IP₃ receptor (IP₃R) phosphorylation was observed in cocultured HUASMCs stimulated with PE sera (P<0.05). In addition, PE serum significantly increased HUASMC viability and reduced their apoptosis (P<0.05); these effects were abrogated with PLC-γ1 silencing. Compared with normal sera, PE sera increased [Ca²⁺]_i in cocultured HUASMCs (P<0.05), which was inhibited by PLC-γ1 and IP₃R silencing. Finally, PE sera-induced PKC-α activity and collagen I expression was inhibited by PLC-γ1 small interfering RNA (siRNA) (P<0.05). These results suggest that vasoactive substances in the PE serum may induce deposition in the extracellular matrix through the activation of PLC-γ1, which may in turn result in thickening and hardening of the placental vascular wall, placental blood supply shortage, fetal hypoxia–ischemia and intrauterine growth retardation or intrauterine fetal death. PE sera increased [Ca²⁺]_i and induced PKC-α activation and collagen I expression in cocultured HUASMCs via the PLC-γ1 pathway.

Expression of NO synthases and redox enzymes in umbilical arteries from newborns born small, appropriate, and large for gestational age

BACKGROUND

Modified expression of nitric oxide synthases (NOSs) and an imbalance between the pro-oxidative and the antioxidative system accompany endothelial dysfunction, the first stage of atherosclerosis. Humans born small (SGA) or large (LGA) for gestational age are at higher risk of developing atherosclerosis later in life than humans born appropriate for gestational age (AGA). We hypothesized that indicators of endothelial dysfunction could be detectable at birth. The purpose of this study was to find out whether the expression patterns of NO synthases (endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS)), pro-oxidative enzymes (components of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, NADPH oxidase 1 (NOX1), NOX2, NOX4, p22phox, and p47phox), and antioxidative enzymes (superoxide dismutase 1-3 (SOD1-3), glutathione peroxidase 1 (GPX1), and catalase) in umbilical arteries differ among SGA, LGA, and AGA newborns.

METHODS

Thirty-six umbilical cords were obtained from healthy, normal, full-term SGA, AGA, and LGA newborns. The umbilical arteries were dissected and homogenized. mRNA expression was analyzed with quantitative real-time PCR. Western blotting was performed to determine protein expression.

RESULTS

mRNA and protein expression of NO synthases, pro-oxidative enzymes, and antioxidative enzymes did not differ in the umbilical arteries from newborns of the three groups.

CONCLUSION

Indicators of endothelial dysfunction in terms of differences in enzyme expression in SGA or LGA newborns vs. AGA newborns were not present at birth.

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 nitric oxide in placental vascular development and function

Nitric oxide (NO) is one of the most pleiotropic signaling molecules at systemic and cellular levels, participating in vascular tone regulation, cellular respiration, proliferation, apoptosis and gene expression. Indeed NO actively participates in trophoblast invasion, placental development and represents the main vasodilator in this tissue. Despite the large number of studies addressing the role of NO in the placenta, its participation in placental vascular development and the effect of altered levels of NO on placental function remains to be clarified. This review draws a time-line of the participation of NO throughout placental vascular development, from the differentiation of vascular precursors to the consolidation of vascular function are considered. The influence of NO on cell types involved in the origin of the placental vasculature and the expression and function of the nitric oxide synthases (NOS) throughout pregnancy are described. The developmental processes involved in the placental vascular bed are considered, such as the participation of NO in placental vasculogenesis and angiogenesis through VEGF and Angiopoietin signaling molecules. The role of NO in vascular function once the placental vascular tree has developed, in normal pregnancy as well as in pregnancy-related diseases, is then discussed.

Internal Mammary Artery Grafts Reactivity in Hypertensive Patients: Role of Stretching in Extraendothelial Nitric Oxide

BACKGROUND

The internal mammary artery (IMA) used in bypass coronary surgery remains efficient for a longer time than other grafts, such as saphenous veins; however, its biological characteristics are incompletely defined.

OBJECTIVE

To compare in IMA grafts from hypertensive (HT) and normotensive (NT) patients the presence of endothelium and their functionability, the response to passive stretching and basal tone, the reactivity to exogenous vasoconstrictors, the role of stretching in NO release, and the possible extraendothelial NO source.

METHODS AND RESULTS

IMA rings contractility, presence of endothelium, and nitrite release were studied. An endothelial dysfunction associated with hypertension was found. IMA rings from HT had an impaired response to passive stretching, resulting in a decreased relaxation. All IMA grafts had an increased basal tone demonstrated by relaxation to SNP; however, a lesser response was found in HT. Interestingly, it was demonstrated that NO release was present in IMA grafts, despite an endothelial dysfunction and that stretching increased NO release. This effect was inhibited by Ca2+ -free media, L-NAME and a specific neuronal NO synthase (nNOS) inhibitor. Furthermore, the demonstration of the presence of nNOS in smooth muscle cells by immunohistochemistry supports a role of extraendothelial NO.

CONCLUSION

We demonstrate the impact of hypertension in IMA grafts producing increased endothelial dysfunction, reduced response to passive stretching, increased basal tone, and impaired responsiveness to exogenous vasoconstrictors and NO release. A specific role of stretching in extraendothelial NO release was demonstrated, which may have an important role in the outcome of IMA grafts due to the protective actions of NO, even in the absence of the endothelium.

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.

Vasorelaxant action of 17 -estradiol in rat uterine arteries: role of nitric oxide synthases and estrogen receptors

The uterine vasculature plays an important role during pregnancy by providing adequate perfusion of the maternal-fetal interface. To this end, substantial remodeling of the uterine vasculature occurs with consequent changes in responsiveness to contractile agents. The purpose of our study was to characterize the vasorelaxant effects of estrogens on vascular smooth muscles of the rat uterine artery during pregnancy and to evaluate the involvement of estrogen receptors (ESR) and nitric oxide synthases (NOS). To do so, we measured NOS expression in the whole uterine and mesenteric circulatory bed by Western blotting. Vasorelaxant effects of 17beta-estradiol (17beta-E(2)) were assessed on endothelium-denuded uterine arteries with wire myographs in the absence and presence of pharmacological modulators [nitro-L-arginine methyl ester (L-NAME), ICI-182780, tamoxifen]. All experiments were performed on arteries from nonpregnant (NP) and late pregnant (P) rats. In the uterine vasculature of the latter group, NOS3 (endothelial NOS) expression was increased, while NOS1 (neuronal NOS) was reduced compared with NP rats. Expression of the NOS2 (inducible NOS) isoform was undetectable in the two groups. Both 17beta-E(2) and 17alpha-E(2) induced uterine artery relaxation, but the latter evoked lower responses. Endothelium-denuded arteries from NP rats showed larger relaxation with 17beta-E(2) than P rats. This larger relaxation disappeared in the presence of L-NAME. The ESR antagonist ICI-182780 did not affect acute relaxation with 17beta-E(2) and 17alpha-E(2). Moreover, membrane-nonpermeant 17beta-E(2):BSA (estradiol conjugated to bovine serum albumin) did not induce any vasorelaxation. Our results indicate that estrogens exert direct acute vasorelaxant effects in smooth muscles of the rat uterine artery that are mediated by mechanisms independent of ESR activation, but with some stereospecificity. Part of this effect, in NP rats only, is due to nitric oxide produced from muscle NOS1.

Early upregulation of iNOS mRNA expression and increase in NO metabolites in pressurized renal epithelial cells

Pressure is an important physiological regulator, but under abnormal conditions it may be a critical factor in the onset and progression of disease in many organs. In vivo, proximal tubular epithelial cells are subjected to pressure as a result of ureteral obstruction, which may influence the production of nitric oxide (NO), a ubiquitous multifunctional cytokine. To directly explore the effect of pressure on the expression and activity of NO synthase (NOS) in cultured proximal tubular epithelial cells, a novel pressure apparatus was developed. Cells were subjected to pressures of 20-120 mmHg over time (5 min-72 h). RT-PCR demonstrated an increase in inducible NOS (iNOS) and sGC, while endothelial NOS remained unchanged. Real-time PCR (qPCR) confirmed an earlier induction of iNOS transcript subjected to 60 mmHg compared with cytokine mix. iNOS protein expression was significantly increased following 60 mmHg of pressure for 24 h. Use of nuclear factor-kappaB inhibitors was shown to prevent the increase in iNOS expression following 60 mmHg for 2 h. NO and cGMP were increased with the application of pressure. The addition of the irreversible iNOS inhibitor (1400W) was shown to prevent this increase. We demonstrate that with the use of a simply designed apparatus, pressure led to an extremely early induction of iNOS and a rapid activation of NOS activity to increase NO and cGMP in proximal tubule epithelial cells. The rapid effects of pressure on iNOS may have important implications in the obstructed kidney.

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.

Effects of arecoline in relaxing human umbilical vessels and inhibiting endothelial cell growth

This study investigated the effects of arecoline, an active ingredient of the areca nut, on the tone of human umbilical arteries and veins and on the eNOS expression and cell proliferation of human umbilical vein endothelial cells (HUVECs). We found that arecoline relaxes the human umbilical artery and vein rings in a concentration-dependent manner; the higher the concentration of arecoline, the greater the relaxation of the rings. However, the relaxation decreases after the endothelium was removed or pretreated with L-NAME, a nitric oxide synthase inhibitor. Moreover, arecoline increases in a dose-dependent way the cGMP levels of human umbilical arteries and veins. In HUVECs, arecoline also increases the eNOS expression. Therefore, the relaxant effects of arecoline on the umbilical artery and vein rings were endothelium-dependent through the NO-cGMP systems. In addition, arecoline at higher doses (100-1000 microM) inhibits endothelial cell proliferation; the exposure toarecoline (100-1000 microM) for 24 and 48 h induces G2/M cell cycle arrest of HUVECs. Our results indicate that arecoline would decrease vascular tone, in part mediated by NO. Higher doses of arecoline inhibit endothelial cell growth, which suggest that long-term use or high doses of areca nut might induce endothelial dysfunction and associated diseases.

Nitric oxide stimulates growth hormone secretion from human fetal pituitaries and cultured pituitary adenomas

Nitric oxide (NO), a highly reactive free radical, has been identified as a neurotransmitter in the central and peripheral nervous system. NO synthase (NOS) is the enzyme responsible for NO production from L-arginine and plays an important role in regulating the release of several hypothalamic peptides. In the pituitary, NO was found to increase growth hormone (GH) secretion in several in vitro and in vivomodels. However, its role in human GH regulation is unknown. The aim of this study was to investigate the regulatory effects of NO on human GH and prolactin secretion using primary cell cultures of human fetal pituitaries and cultured hormone-secreting adenomas. Incubation of the human fetal pituitaries (21-24 wk gestation) in the presence of sodium nitroprusside (SNP; 1 mM), a NO donor, for 4 h resulted in a 50-75% increase in GH secretion, similar to the stimulatory effect evoked by growth hormone-releasing hormone (GHRH) (10 nM). However, fetal PRL secretion was not affected by SNP. GH release was also stimulated (40-70% increase) by SNP in 60% of the cultured GH-secreting adenomas studied. SNP-induced GH release was inhibited in both fetal and adenomatous cells by PTI0, a NO scavenger. The addition of cGMP (0.1-1 mM), the second messenger of multiple NO actions, enhanced fetal and adenomatous GH secretion by 55-95%. Neuronal NOS (nNOS) was expressed in normal (fetal and adult) human pituitary tissues and in GH-secreting adenomas. Examination of its functional expression using L-arginine (1 microM) yielded a 35% increase in GH release from cultured GH-secreting adenoma. This response was blocked by a NOS inhibitor with high selectivity for the neuronal enzyme and by a guanylyl cyclase inhibitor. In conclusion, NO stimulates human GH in cultured fetal pituitaries and GH-secreting adenomas. Cyclic GMP is probably involved in this hormonal regulation.

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.

Expression of endothelial NO synthase, inducible NO synthase, and estrogen receptors alpha and beta in placental tissue of normal, preeclamptic, and intrauterine growth-restricted pregnancies

In the physiology of placental blood circulation, nitric oxide (NO) synthases seem to play important roles, although their expression in pathological placentas and their role is still unclear. In addition, NO synthase activation seems to be related to estrogen receptor expression. Therefore, the aims of this study were to investigate the expression of estrogen receptors alpha (ERalpha), estrogen receptor beta (ER and the endothelial NO synthase (eNOS), and inducible NO synthase (iNOS) in intrauterine growth-restricted (IUGR) placentas, preeclamptic placentas, and in normal healthy control placentas. Slides of paraffin-embedded placental tissue were obtained after delivery from patients diagnosed with IUGR, preeclampsia, and normal term placentas and analyzed for eNOS, iNOS as well as ERalpha and ERbeta expression. Intensity of immunohistochemical reaction was analyzed using a semiquantitative score and statistical analysis was performed. In addition, Western blot experiments were performed for comparison of staining intensities obtained by immunohistochemistry and western blot. Expression of eNOS, iNOS, and ERbeta is significantly reduced in trophoblast cells of placentas with IUGR. However, preeclamptic placentas demonstrated a significant elevated expression intensity of these proteins compared with normal controls. A different expression of eNOS, iNOS, ERalpha, and ERbeta by human trophoblast cells seems to results in lower NO output and impaired trophoblast invasion. Results obtained in our study provide evidence that reduced expression of the investigated proteins is related to IUGR.