Immunohistochemical characterization of placental nitric oxide synthase expression in preeclampsia

Altered uterine artery protein signature and function following E-cigarette exposure in pregnancy

OBJECTIVE

Over the past decade e-cigarette (e-cig) usage has become a growing public health concern, especially during pregnancy as many perceive e-cigs as a safer alternative to combustible cigarettes. Although human and animal models exhibit altered uterine artery Doppler velocimetry and waveform abnormalities following traditional smoking and buccal nicotine exposure, the effects of e-cig aerosols on pregnancy are incompletely researched and understood. We hypothesized that an altered uterine artery proteomic signature, accompanied by functional deficits, will be caused by e-cig vaping during pregnancy.

METHODS

In a validated timed pregnant Sprague-Dawley rat model system, a custom-engineered vaping system comprising a commercial atomizer and vape unit was utilized to generate and deliver e-cig aerosols that mimic the aerosols produced by commercial e-cigs, once daily, to pregnant dams.

RESULTS

Mean fetal weight, crown-rump length, and placental weight were significantly lower in the E-Cig group than those in the pair-fed Control group. Mass spectrometry followed by proteomic analysis detected a total of 2129 proteins; 36 significantly altered proteins were mostly related to immune system and vasodilation. Principal component analysis validated the protein signature. The uterine arteries of e-cig exposed rats demonstrated impaired concentration-dependent acetylcholine-induced uterine artery relaxation. Supplementation of N(ω)-nitro-L-arginine methyl ester (L-NAME) confirmed a role for the nitric oxide (NO) system. Immunofluorescence validated the localization to the uterine artery endothelium and the decreased levels of vasodilatory excitatory P-Ser1177 endothelial NO synthase.

CONCLUSIONS

Identifying the pathway(s) involved in the pathogenesis of uterine artery dysfunction creates a potential for pinpointing antagonistic and/or reversal medications, thereby preventing or reducing e-cigarette mediated uteroplacental dysfunction and fetal growth restriction.

Evidence of Nitric Oxide Impairment During Hypertensive Pregnancies

Hypertensive disorders of pregnancy complicate up to 10% of pregnancies worldwide, and they can be classified into (1) gestational hypertension, (2) preeclampsia, (3) chronic hypertension and (4) chronic hypertension with preeclampsia. Nitric oxide (NO) plays an essential role in the haemodynamic adaptations observed during pregnancy. It has been shown that the nitric oxide pathway's dysfunction during pregnancy is associated with placental- and vascular-related diseases such as hypertensive disorders of pregnancy. This review aims to present a brief definition of hypertensive disorders of pregnancy and physiological maternal cardiovascular adaptations during pregnancy. We also detail how NO signalling is altered in the (a) systemic vasculature, (b) uterine artery/spiral arteries, (c) implantation and (d) placenta of hypertensive disorders during pregnancy. We conclude by summarizing the anti-hypertensive therapy of hypertensive disorders of pregnancy as a specific management strategy.

Nitric Oxide Production and Effects in Group B Streptococcus Chorioamnionitis

Intrauterine infection, or chorioamnionitis, due to group B Streptococcus (GBS) is a common cause of miscarriage and preterm birth. To cause chorioamnionitis, GBS must bypass maternal-fetal innate immune defenses including nitric oxide (NO), a microbicidal gas produced by nitric oxide synthases (NOS). This study examined placental NO production and its role in host-pathogen interactions in GBS chorioamnionitis. In a murine model of ascending GBS chorioamnionitis, placental NOS isoform expression quantified by RT-qPCR revealed a four-fold expression increase in inducible NOS, no significant change in expression of endothelial NOS, and decreased expression of neuronal NOS. These NOS expression results were recapitulated ex vivo in freshly collected human placental samples that were co-incubated with GBS. Immunohistochemistry of wild type C57BL/6 murine placentas with GBS chorioamnionitis demonstrated diffuse inducible NOS expression with high-expression foci in the junctional zone and areas of abscess. Pregnancy outcomes between wild type and inducible NOS-deficient mice did not differ significantly although wild type dams had a trend toward more frequent preterm delivery. We also identified possible molecular mechanisms that GBS uses to survive in a NO-rich environment. In vitro exposure of GBS to NO resulted in dose-dependent growth inhibition that varied by serovar. RNA-seq on two GBS strains with distinct NO resistance phenotypes revealed that both GBS strains shared several detoxification pathways that were differentially expressed during NO exposure. These results demonstrate that the placental immune response to GBS chorioamnionitis includes induced NO production and indicate that GBS activates conserved stress pathways in response to NO exposure.

Expression of Endothelin-1 and Endothelial Nitric Oxide Synthase in Normal and Preeclamptic Placentae

OBJECTIVE

 To investigate the expression of endothelin-1 (ET-1) and endothelial nitric oxide (NO) synthase (eNOS) in normal and preeclamptic (PE) placentae.

METHODS

 The present cross-sectional analytical study was performed in normal and PE primigravidae (n = 10 in each group) who were admitted to the North Okkalapa General and Teaching Hospital from February 2019 to February 2020. Serum samples were collected immediately before delivery, and placental tissues were collected immediately after emergency or elective cesarean section. The expression of placental eNOS was measured by western blot, and the levels of ET-1 in placental tissue homogenates and in the serum were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

 The PE group had significantly higher serum levels of ET-1 (median: 116.56 pg/mL; IQR: 89.14-159.62 pg/mL) than the normal group (median: 60.02 pg/mL; IQR: 50.89-94.37 pg/mL) (p < 0.05). However, statistically significant differences were not observed in the levels of ET-1 in placental tissue homogenates between normal and PE placentae (median: 0.007 pg/µg of total protein; IQR: 0.002-0.0123 pg/µg of total protein; and median: 0.005 pg/µg of total protein; IQR: 0.003-0.016 pg/µg of total protein respectively). The median and IQR values of relative placental eNOS expression were significantly higher in the PE group than in the normal group (p < 0.05). The serum levels of ET-1 level were not significantly correlated with placental ET-1 expression, and neither there was a significant correlation between placental ET-1 and eNOS expression in any of the groups.

CONCLUSION

 The serum levels of ET-1 were significantly higher in PE pregnant women compared with normal pregnant women, while the ET-1 levels of placental tissue homogenates were not significantly different. Serum ET-1 rather than placental ET-1 might play a major role in the pathogenesis of PE.

Systems Pharmacology-Based Research on the Mechanism of Tusizi-Sangjisheng Herb Pair in the Treatment of Threatened Abortion

Threatened abortion (TA) is a common complication with high incidence in the first trimester of pregnancy, which will end in miscarriage if not treated properly. The Chinese herbs Cuscutae Semen (Tusizi in Chinese) and Herba Taxilli (Sangjisheng in Chinese) first recorded in the ancient classic medical book Shennong Bencao Jing are effective and widely used as an herb pair for the treatment of TA, while the active ingredients and the functional mechanism of Tusizi-Sangjisheng herb pair treating TA are still unknown. In order to exploit the relationship between those two herbs and TA, systems pharmacology analysis was carried out in this study. A total of 75 ingredients of Tusizi-Sangjisheng were collected from Traditional Chinese Medicine System Pharmacology Database and Analysis Platform (TCMSP). 12 bioactive compounds were screened, and 153 directly related targets were predicted by systematic models. Besides, Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were used to systematically explore the potential mechanisms of Tusizi-Sangjisheng treating TA. Meanwhile, Compound-Target (C-T), Target-Disease (T-D), and Target-Pathway (T-P) networks were constructed to further quest the underlying functional mechanisms of Tusizi-Sangjisheng. As a result, 31 targets and 3 key pathways were found to be directly related to TA that includes mitogen-activated protein kinases (MAPKs), phosphatidylinositol-3-kinase/protein kinase B (PI3K-Akt), and transforming growth factor-β (TGF-β) signaling pathways. The results in this study may provide some valuable clues about the molecular mechanisms of the efficient Chinese herb pair Tusizi-Sangjisheng in the treatment of TA.

Maternal supraphysiological hypercholesterolemia associates with endothelial dysfunction of the placental microvasculature

Maternal physiological or supraphysiological hypercholesterolemia (MPH, MSPH) occurs during pregnancy. MSPH is associated with foetal endothelial dysfunction and atherosclerosis. However, the potential effects of MSPH on placental microvasculature are unknown. The aim of this study was to determine whether MSPH alters endothelial function in the placental microvasculature both ex vivo in venules and arterioles from the placental villi and in vitro in primary cultures of placental microvascular endothelial cells (hPMEC). Total cholesterol < 280 mg/dL indicated MPH, and total cholesterol ≥280 mg/dL indicated MSPH. The maximal relaxation to histamine, calcitonin gene-related peptide and adenosine was reduced in MSPH venule and arteriole rings. In hPMEC from MSPH placentas, nitric oxide synthase (NOS) activity and L-arginine transport were reduced without changes in arginase activity or the protein levels of endothelial NOS (eNOS), human cationic amino acid 1 (hCAT-1), hCAT-2A/B or arginase II compared with hPMEC from MPH placentas. In addition, it was shown that adenosine acts as a vasodilator of the placental microvasculature and that NOS is active in hPMEC. We conclude that MSPH alters placental microvascular endothelial function via a NOS/L-arginine imbalance. This work also reinforces the concept that placental endothelial cells from the macro- and microvasculature respond differentially to the same pathological condition.

Differential regional fatty acid distribution in normotensive and preeclampsia placenta

Background

Long chain polyunsaturated fatty acids (LCPUFAs) are biologically active fatty acids which regulate placental angiogenesis, inflammation, and oxidative stress. Abnormalities in these aspects have been associated with preeclampsia (PE). Further, placenta has a heterogeneous structure with differential vascularization across different regions. We therefore hypothesize that the distribution of fatty acids in various regions of the placenta is altered in PE leading to poor fetal outcome.

Methods

In this cross-sectional study we recruited 69 normotensive control (NC) and 44 women with PE. PE women were further classified as those delivered preterm (PTPE, n = 24) and at term (TPE, n = 20). Fatty acid levels were analyzed from placental samples from four different regions (CF—central fetal, PF—peripheral fetal, CM—central maternal and PM—peripheral maternal).

Results

In the NC placenta, AA levels were lower (p < 0.05) in CM as compared with CF region. However, such differences were not seen in the TPE and PTPE. In contrast, the DHA levels varied between regions only in the PTPE placenta. Between groups, DHA levels were lower (p < 0.05 for both) in the CM and CF regions of the PTPE as compared with NC. The levels of DHA in TPE placenta were similar to NC. AA levels were lower (p < 0.05 for both) in CF region of TPE and PF region of PTPE placenta than NC.

Conclusions

There is differential pattern of LCPUFA distribution across various regions of the NC, TPE and PTPE placenta. This may have implications for placental growth and development as well as transfer of LCPUFA to the fetus.

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There are regional differences in fatty acid levels in normal placenta.

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Regional fatty acid distribution is further affected in preeclampsia.

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Preterm preeclampsia placenta is more affected than term preeclampsia and control.

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DHA of peripheral fetal region positively associated with baby weight in preeclampsia.

Placental expression of endothelial and inducible nitric oxide synthase and NO metabolism in gestational hypertension: a case-control study

OBJECTIVE

Hypertension is one of the most common medical disorders in pregnancy and a role of nitric oxide (NO) metabolism has been described. Thus, the present work aimed at determining placental gene expression of eNOS and iNOS, to measure NO and ONOO(-) levels in patients with gestational hypertension (GH).

METHODS

Fifteen patients with GH and 15 healthy pregnant controls were enrolled in the study. Placental tissue was taken immediately after delivery and was stored at -80 °C until analysis. A piece of frozen tissue was homogenized in the appropriate buffer. Total RNA was extracted and was reverse transcribed to obtain complementary DNA that was used for real-time PCR for iNOS and eNOS expression, whereas NO and ONOO(-) production were measured by commercially available kits.

RESULTS

Placental eNOS and iNOS mRNA levels were significantly reduced in GH when compared to controls. NO and ONOO(-) production were both significantly higher in GH than controls.

CONCLUSIONS

The reduced eNOS and iNOS gene expression in women with GH reinforces the hypothesis that the mechanisms involving NO pathways, may promote oxidative damage, by contributing to the reduced blood flow and increased resistance in the feto-maternal circulation and suggests the use of NO modulators as useful tools in GH management.

Placental expression of eNOS, iNOS and the major protein components of caveolae in women with pre-eclampsia

Caveolae regulate many cardiovascular functions and thus could be of interest in relation to pre-eclampsia, a pregnancy specific disorder characterised by hypertension and proteinuria. We examined placental mRNA and protein expression/localisation of the caveolae components Caveolin 1-3, Cavin 1-4 as well as eNOS/iNOS in normotensive control (n = 24) and pre-eclamptic pregnancies (n = 19). Placental mRNA expression of caveolin-1, cavin 1-3, was lower and eNOS expression was increased in pre-eclampsia (P < 0.05 for all). Additionally Caveolin-1 protein expression was also reduced in pre-eclampsia (P = 0.007); this could be an adaptive response in pre-eclampsia, possibly to attenuate the oxidative stress/inflammation.

Is there a link between endothelial dysfunction, coagulation activation and nitric oxide synthesis in preeclampsia?

BACKGROUND

There may be a relationship between endothelial dysfunction, coagulation activation and nitric oxide (NO) synthesis in women with mild and severe preeclampsia (PE).

METHODS

Plasma thrombomodulin (TM), D-Dimer (D-Di), cyclic guanosine monophosphate (cGMP) and placental nitric oxide synthase activity (NOS) were investigated in 21 normotensive pregnant women (G1), 22 pregnant women with mild PE (G2) and 20 pregnant women with severe PE (G3).

RESULTS

TM and D-Di were significantly increased in G3 compared to G1 (P=0.001 and P=0.006, respectively) and G2 (P=0.001, in both cases). However, there was no significant difference when G1 was compared to G2. For total NOS, calcium independent NOS, calcium dependent NOS no significant difference was observed among the groups studied.

CONCLUSIONS

TM and D-Di levels are raised in women with severe PE compared to normotensive pregnant women and women with mild PE. While increased TM levels may reflect endothelial dysfunction, raised D-Di levels indicate a hypercoagulable state. NO assessed by 2 indirect methods did not show any significant difference among the groups studied. Due to current limitations with in vitro NO measurements and interferences associated with NO bioavailability, particularly in PE, such findings should not be over-interpreted.

Expression patterns of endothelial and inducible nitric oxide isoforms in the porcine umbilical cord

Stable fetal-placental blood pressure and flow are extremely important in fetal growth and development. Uncontrolled and long-standing increased or decreased vascular blood pressure in the umbilical cord (UC) affects hyperaemia or ischaemia and consequently causes fetal death. Nitric oxide (NO) is one of the most active factors controlling blood flow through relaxation of the vascular smooth muscle. In this study, we investigated endothelial (eNOS) and inducible (iNOS) nitric oxide synthase expression and NADPH-diaphorase activity (NADPH-d) in the porcine UC at various stages of pregnancy. The UCs were collected from pigs on days 40, 60, 75 and 90 of pregnancy and postpartum. Western blot analysis as well as immunohistochemical staining revealed protein presence for eNOS and iNOS in the UC of the pig. The eNOS expression was maintained at a significantly higher level in all analysed days of pregnancy when compared with postnatal stage. Additionally, a significant protein increase for eNOS was observed in a periplacental part of UC on day 90. There were no obvious differences in iNOS protein level in UC samples derived from different stages of pregnancy. NADPH-diaphorase histochemical activity was correlated with NOS immunoreactivity during all analysed days of pregnancy. These results suggest that NOS isoforms are responsible for regulation of blood circulation in UC and immune responses.

The human placenta from heavy smokers: evaluation of vasoactive peptides by immunohistochemistry

The study aimed to demonstrate the expression of nitric oxide converting enzyme, nitric oxide synthase (e-NOS), and endothelin-1 (Et-1) in formalin-fixed paraffin-embedded placental tissue, and to demonstrate a difference in staining intensity between heavy smokers and non-smokers. Term placentas from pregnancies from otherwise healthy women smoking 15 or more cigarettes per day (heavy smokers) and term placentas from a matching group of non-smokers were included. The antibodies for Et-1 and e-NOS are recommended for cryostat sections. We evaluated the antibodies on paraffin-embedded tissue combined with the streptavidin-biotin-peroxidase technique. Et-1 and e-NOS were demonstrated in the placental vasculature, the trophoblast, and the amnion. A blinded comparative study showed no reproducible significant differences in the staining intensity of the antigen-antibody reaction to Et-1 and e-NOS between the two groups.

Nitric oxide (NO) inhibits prostaglandin E2 9-ketoreductase (9-KPR) activity in human fetal membranes

Nitric oxide (NO) synthesized by fetal membranes may act either directly inhibiting myometrium contractility or indirectly interacting with tocolytic agents as prostaglandins (PGs). Here we examined if NO could modulate prostaglandin E(2) 9-ketoreductase (9-KPR) activity in human fetal membranes (HFM). 9-KPR is the enzyme that converts PGE(2) into PGF(2alpha), the main PGs known to induce uterine contractility at term. Chorioamnion explants obtained from elective caesareans were incubated with aminoguanidine (AG), an iNOS inhibitor, or NOC-18, a NO donor. NOC-18 (2mM) increased PGE(2) production and diminished PGF(2alpha) synthesis in HFM. AG presented the opposite effect. When we evaluated the activity of 9-KPR by the conversion of [(3)H]-PGE(2) into [(3)H]-PGF(2alpha) and 13,14-dihidro-15-keto prostaglandin F(2alpha) (the PGF(2alpha) metabolite), we found that NOC-18 inhibited 9-KPR activity. Interestingly, AG did not elicit any effect on 9-KPR but l-NAME, a non-selective NOS inhibitor, significantly increased its activity. Our data suggests that exogenous NO inhibits 9-KPR activity in HFM, thus modulating the synthesis of important labor mediators as PGF(2alpha).

Effect of in vivo administration of epidermal growth factor on prostaglandin production and NOS activity in term rat placentae. Possible participation of placental EGF receptors

Many authors hypothesize that the epidermal growth factor (EGF) is involved in the onset of labor. Previous reports from our laboratory showed that intrauterine administration of EGF delays the beginning of labor. The aims of this study were: 1) to analyze the effect of intrauterine administration of 500 ng EGF on placental prostaglandins and nitric oxide, and 2) to characterize the expression of EGF receptors (EGF-R) in pregnant rat placentae. Saline solution (sham group) and 500 ng EGF (EGF-treated group) were administered via intrauterine injection on day 21 of gestation, and both groups of animals were sacrificed on day 22 (sham rats delivered on day 22). Results showed that EGF treatment: 1) inhibited the production of prostaglandin E (p<0.001) and F(2alpha) (p<0.01), 2) increased the synthesis of nitric oxide (p<0.001), and 3) reduced the expression of cyclooxygenase-II, the enzyme responsible for PG synthesis. Placentae were found to express EGF-R and its activated form, and the expressions of both forms were higher at mid and term pregnancy. Hence, EGF is a very interesting molecule for studying the regulation of placental prostaglandin and nitric oxide production related to the parturition process.

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

AIMS

Umbilical blood vessels are not innervated and regulation of blood flow to the placenta must depend on structural changes and the effect of vasoactive factors. Failure to achieve these adaptations may result in reduced fetoplacental perfusion. The purpose of this study was to determine whether neuronal nitric oxide synthase (nNOS) is expressed in human vascular smooth muscle cells (VSMCs) of the fetoplacental circulation. nNOS has been described as a non-endothelial NOS counterregulating vasoconstriction only in the VSMCs of animal models. Therefore, we investigated nNOS expression in the fetoplacental unit from preeclamptic and healthy pregnancies.

METHODS AND RESULTS

We investigated nNOS regulation by immunohistochemistry, Western blotting and reverse transcriptase-polymerase chain reaction analysis. nNOS activity was determined by measuring the conversion of L-3H-arginine to L-3H-citrulline. nNOS expression was revealed only in VSMCs of the human umbilical veins, but not in umbilical arteries. A more direct assessment of nNOS activity showed that a small, but consistent amount of nNOS is present in the denuded media of the umbilical vein. In VSMCs of the umbilical veins during preeclampsia a total loss of nNOS protein expression and a significant decrease in mRNA expression were seen.

CONCLUSIONS

Loss of nNOS expression is associated with preeclampsia. It may alter the regulation of blood flow in the fetal and maternal placental vasculature in preeclampsia. However, the impact of NO produced by nNOS on the vascular tone of umbilical veins remains to be elucidated.

Lipopolysaccharide induces nitric oxide synthase expression and platelet-activating factor increases nitric oxide production in human fetal membranes in culture

BACKGROUND

Platelet-activating factor and nitric oxide may be involved in the initiation of human labour as inflammatory mediators. The aim of this study was to test whether platelet-activating factor and lipopolysaccharide were able to induce nitric oxide synthase expression and stimulate the production of nitric oxide in human fetal membrane explants in culture.

METHODS

Fetal membranes were collected from Caesarean sections at term. RNA was extracted from membranes and subjected to a qualitative RT-PCR to assess the baseline expression of iNOS. Discs of fetal membranes were cultured for 24 hours in the presence of platelet-activating factor at a dose range of 0.1 nanomolar--1 micomolar or 1 microgram/ml lipopolysaccharide. Nitric oxide production was measured via nitrite ions in the culture medium and mRNA for iNOS was detected by RT-PCR.

RESULTS

Culturing the membrane discs in medium containing serum induced nitric oxide synthase expression and platelet-activating factor significantly stimulated the production of nitric oxide under these conditions. When cultured without serum inducible nitric oxide synthase expression was induced by lipopolysaccharide, but not by platelet-activating factor.

CONCLUSION

Platelet-activating factor may have a role in the initiation of labour, at term or preterm, via the increased local production of nitric oxide as an inflammatory mediator. In this model of intrauterine infection, lipopolysaccharide was found to induce iNOS expression by fetal membranes, and this mechanism could be involved in preterm labour.

Expression of nitric oxide synthase isoforms in the human placenta is not altered by labor

Nitric oxide has various biological activities including smooth muscle relaxation, anti-inflammatory activity, anti-coagulatory activity. As the human placenta is known to express nitric oxide synthases, this study investigated the possible effect of labor on the expression of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) in human placental tissues at term. Both eNOS and iNOS mRNA expression in placental tissues in labor were significantly higher than those in the amnion, chorion laeve, decidua vera and myometrium. The eNOS mRNA and protein expressions in placental tissues in labor (n = 12) were 1.6023 +/- 0.1652 (eNOS/GAPDH, mean +/- SEM) and 12.8 +/- 1.3 arbitrary units (AU), respectively, which were similar to those not in labor (n = 10), 1.5806 +/- 0.2042 (eNOS/GAPDH) and 11.4 +/- 1.8 AU. The iNOS mRNA and protein expressions in the placental tissues in labor were 1.2831 +/- 0.2436 (iNOS/GAPDH) and 10.7 +/- 2.1 AU respectively, similar to those not in labor, 1.9254 +/- 0.8004 (iNOS/GAPDH) and 13.3 +/- 1.8 AU. The guanosine 3',5'-cyclic monophosphate (cGMP) concentration in the placental tissues in labor was 23.6 +/- 1.4 fmol/g wet tissue, similar to that not in labor, 26.1 +/- 2.0 fmol/g wet tissue. These findings suggest that nitric oxide production in the human placenta is maintained during labor.

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

1. The aim of the present study was to investigate whether pre-eclampisa, a state of placental hypoxia, is associated with placental abnormalities in the amount, distribution and expression of endothelial nitric oxide synthase (eNOS). 2. Localization and intensity of eNOS was determined by immunohistochemistry using an antibody specific for eNOS. The amount of eNOS mRNA expression was determined by reverse transcription-polymerase chain reaction (RT-PCR) and the densitometry of gel bands was expressed as a ratio of the band density of the housekeeping gene beta2-microglobulin. 3. Endothelial NOS staining was localized to syncytiotrophoblast cells within the villi and decidual trophoblast cells. It was not present in the endothelium of terminal villous vessels. There was no significant difference in eNOS villous or decidual staining intensity between normal pregnancy (NP; n = 12), pre-eclampsia (n = 14), or gestational hypertension (GH; n = 4). Staining for eNOS was not significantly different in the decidua compared with the villi in NP, GH or pre-eclampsia. Within the decidua, the depth of eNOS staining was similar in NP, pre-eclampisa and GH. 4. There was no significant difference in eNOS mRNA expression between NP (0.70 +/- 0.11), pre-eclampsia (0.5 +/- 0.07) or GH (0.69 +/- 0.26). 5. These findings suggest that the amount of eNOS in the placenta is not deficient in pre-eclampsia, excluding a possible pathogenic role for eNOS in this disease. Furthermore, placental hypoxia, which is associated with pre-eclampsia, did not induce an upregulation of eNOS

Immuno-electron microscopic localization of endothelial nitric oxide synthase in human placental terminal villous trophoblasts-normal and pre-eclamptic pregnancy

We demonstrated the subcellular localization of endothelial nitric oxide synthase (eNOS) in human placental terminal villous trophoblasts at near term period, and compared the distribution pattern with that in pre-eclamptic trophoblasts, using immunogold electron microscopy. Immunolabelling for eNOS was visible markedly in the syncytial microvilli and syncytial cytoplasm. Semiquantitative analysis showed that the concentration and the distribution pattern of gold particles for eNOS did not significantly differ between normal and pre-eclamptic placental trophoblasts. These results indicated that syncytiotrophoblastic microvilli and cytoplasm were the subcellular localization sites of syncytium-derived eNOS in terminal villi, and that there were no significant differences in this eNOS subcellular distribution pattern between normal and pre-eclamptic syncytiotrophoblasts in regard to immunohistochemically detectable eNOS.

Nitric oxide synthase immunoreactivity in human bladder carcinoma

AIMS

To study the expression of the endothelial and inducible isoforms of nitric oxide synthase (eNOS and iNOS, respectively) in human bladder carcinoma and schistosomal bladder disease, and to compare it with normal adult and fetal urothelium. Nitric oxide is thought to play a complex role in human carcinogenesis, but has only recently been investigated in bladder cancer.

METHODS

Immunohistochemistry was performed on paraffin wax embedded sections of 33 human bladder carcinomas and five bladder carcinoma cell lines; in addition, seven schistosomal bladder cases and normal and fetal urothelium were investigated. In the cell lines enzymatic activity was examined by the NADPH diaphorase reaction.

RESULTS

Immunoreactivity for eNOS was present in most cells of all 31 cases examined. Immunoreactivity for iNOS was less abundant and was seen in 23 of 25 cases. Similar findings were noted in schistosomal bladder cancer. In the normal bladder mucosa, eNOS immunoreactivity was found only in the superficial cell layer and iNOS was not expressed, whereas in the fetal urothelium immunoreactivity for both isoforms was seen in all cell layers. Enzymatic activity and immunoreactivity for eNOS and iNOS were evident in the five bladder carcinoma cell lines.

CONCLUSIONS

It is possible that NOS plays a role in the differentiation of the transitional epithelium in fetal life, has a biological function in the adult bladder mucosa, and is involved in bladder carcinogenesis. eNOS and iNOS immunoreactivity do not differ in schistosomal and non-schistosomal bladder carcinoma, but resemble the pattern of expression typical of fetal urothelium.

Nitric oxide synthase immunoreactivity in human bladder carcinoma

AIMS

To study the expression of the endothelial and inducible isoforms of nitric oxide synthase (eNOS and iNOS, respectively) in human bladder carcinoma and schistosomal bladder disease, and to compare it with normal adult and fetal urothelium. Nitric oxide is thought to play a complex role in human carcinogenesis, but has only recently been investigated in bladder cancer.

METHODS

Immunohistochemistry was performed on paraffin wax embedded sections of 33 human bladder carcinomas and five bladder carcinoma cell lines; in addition, seven schistosomal bladder cases and normal and fetal urothelium were investigated. In the cell lines enzymatic activity was examined by the NADPH diaphorase reaction.

RESULTS

Immunoreactivity for eNOS was present in most cells of all 31 cases examined. Immunoreactivity for iNOS was less abundant and was seen in 23 of 25 cases. Similar findings were noted in schistosomal bladder cancer. In the normal bladder mucosa, eNOS immunoreactivity was found only in the superficial cell layer and iNOS was not expressed, whereas in the fetal urothelium immunoreactivity for both isoforms was seen in all cell layers. Enzymatic activity and immunoreactivity for eNOS and iNOS were evident in the five bladder carcinoma cell lines.

CONCLUSIONS

It is possible that NOS plays a role in the differentiation of the transitional epithelium in fetal life, has a biological function in the adult bladder mucosa, and is involved in bladder carcinogenesis. eNOS and iNOS immunoreactivity do not differ in schistosomal and non-schistosomal bladder carcinoma, but resemble the pattern of expression typical of fetal urothelium.

Heme oxygenase expression in human placenta and placental bed: reduced expression of placenta endothelial HO-2 in preeclampsia and fetal growth restriction

In this study we tested the hypothesis that expression of heme oxygenases HO-1 and HO-2, which are responsible for the production of carbon monoxide, are reduced in the placenta and placental bed of pregnancies complicated by preeclampsia (PE) and fetal growth restriction (FGR) compared with control third-trimester pregnancies. Placental protein expression was determined by Western blotting (n=10 in each group) and immunohistochemistry (controls n=18, PE n=19, FGR n=10). Extravillous trophoblast expression was determined by immunohistochemistry of placental bed biopsy samples (controls n=17, PE n=19, FGR n=10). Western blot analysis of placental homogenates showed no overall differences in HO-2 among groups. However, immunohistochemical analysis showed a reduction in HO-2 expression in endothelial cells in both abnormal groups (PE P<0.01; FGR P<0.0005 vs. control group) but no differences in villous trophoblast staining. HO-1 was undetectable by Western blotting in control and abnormal pregnancies and immunoreactivity was very low, suggesting that there is little HO-1 in the placenta. Within the placental bed, HO-2 but not HO-1 was detected on all populations of extravillous trophoblast, but expression of HO-2 or HO-1 did not change in PE or FGR. The reduced expression of HO-2 on endothelial cells in PE and FGR may be responsible for reduced placental blood flow in these conditions. The data do not show changes in HO in the placental bed in PE or FGR.

Placental nitric oxide synthase (NOS) activity and nitric oxide (NO) production in normal pregnancy, pre-eclampsia and eclampsia

OBJECTIVES

To measure nitric oxide synthase (NOS) activity and total nitrites levels (as an index of nitric oxide 'NO' production) in placental villous homogenate of normal, pre-eclamptic and eclamptic pregnant women.

DESIGN

Two groups were studied cross-sectionally: late pregnant women with pre-eclampsia and eclampsia (n=31) and normal pregnant women (all late) as controls (n=32). Two tissue blocks of whole placenta, each 1 x 1 x 1 cm, were collected at delivery and assayed for NOS activity and total nitrite levels.

SETTING

Department of Obstetrics and Gynecology, Assiut University Hospitals, Egypt.

METHODS

Placental tissues were homogenized and villous homogenates were assayed for NO production by Griess reaction which measures the combined oxidation products for NO (nitrites and nitrates) after reduction with nitrate reductase. NOS activity was determined by measuring NO synthesis by tissue extracts spectrophotometrically using the oxidation of oxyhemoglobin to methemoglobin by NO.

RESULTS

Placental villous homogenates of pregnancies complicated by pre-eclampsia and eclampsia had significantly higher NOS activity and total nitrites levels compared with those of normal pregnancy [for NOS (P<0.0001) and for total nitrites (P<0.001)].

CONCLUSIONS

(1) Placental NOS activity and NO production are significantly increased in pre-eclampsia and eclampsia than those of normal pregnancy; this increase was directly related to the severity of this disorder. (2) Such increase possibly represents a physiologic adaptive response to overcome the increased placental vascular resistance and to minimize platelet and leukocyte adhesion to the surface of placental villi or within the intervillous spaces.

Phenotype of the endothelium in the human term placenta

The placental endothelium contributes to regulating transplacental exchange and maintaining the immunological maternofetal barrier. We characterized the endothelial phenotype in human normal term placentae with a panel of antibodies to endothelial antigens using a standardized immunofluorescence method. Placental endothelium strongly expressed vWF, PAL-E, H-antigen, thrombomodulin, PECAM-1, CD34, CD36, ICAM-1, CD44, thy-1, A10/33-1, VE-cadherin, caveolin-1 and HLA-G, whereas occludin, claudin-1, eNOS, angiotensin converting enzyme (ACE), ICAM-2, endoglin and integrin-alphathetabeta(3)were weakly expressed. PGI(2)synthase, tissue factor, E-selectin and VCAM-1 were not detected. Some antigens were heterogenously expressed along the vascular tree or within individual villi. Expression of ACE, eNOS, vWF, P-selectin, E-selectin, integrin alpha(v)beta(3)and endoglin was stronger in the maternal decidual vessels, while PECAM-1, CD44, thy-1 and caveolin-1 expression was stronger in fetal vessels. Some endothelial markers were present in trophoblasts and stroma. Endothelial proliferation was apparent in mature intermediate and terminal villi. There was limited inflammatory response to TNFalpha in explants, characterized by upregulation of vWF, P-selectin, PECAM-1 and CD44, downregulation of thrombomodulin, but no increase in ICAM-1 expression, nor induction of E-selectin, VCAM-1 or tissue factor. These patterns of heterogeneity, proliferative activity and inflammatory activation may underlie the specific physiological roles of the placental endothelium.

Expression of endothelial (type III) nitric oxide synthase in cytotrophoblastic cell lines: regulation by hypoxia and inflammatory cytokines

Expression of endothelial nitric oxide synthase (eNOS) has been localized to the villous syncytiotrophoblasts suggesting that NO release from these cells could prevent platelet adhesion and aggregation in the intervillous space. Hypoxia- or inflammation-dependent changes in the release of this vasoactive substance may result in thrombus formation and altered vascular resistance which occur in the placental bed of pre-eclamptic patients. To evaluate the influence of low-oxygen tension and inflammation on eNOS production in the trophoblast steady-state eNOS mRNA and protein levels were investigated in cytotrophoblastic BeWo and Jeg-3 cells cultured at 3.5 per cent oxygen and/or in the presence of the pro-inflammatory cytokines IL-1 and TNF-alpha. By RT-PCR and immunocytochemistry we demonstrate that BeWo cells produce eNOS mRNA and protein while eNOS polypeptide was undetectable in JEG-3 cells. In BeWo cells addition of both cytokines decreases eNOS mRNA and protein abundancies within 24 h of incubation while each substance alone had no effect. Compared to controls, the amount of eNOS transcripts was found to be elevated at low-oxygen tension, however, cNOS protein was downregulated after 24 h in the hypoxic environment, as shown by immunocytochemistry and Western blot analysis. Forskolin and methotrexate, which induce biochemical differentiation/ growth arrest in choriocarcinoma cells, stimulate eNOS mRNA and protein synthesis, but cannot overcome the decline of eNOS polypeptide levels during hypoxic incubation. It is speculated that acute hypoxia and inflammation impair eNOS/NO production of the trophoblast in vivo, which might contribute to pathological conditions of gestational diseases.

Etiology and pathogenesis of preeclampsia: current concepts

The etiology of preeclampsia is unknown. At present, 4 hypotheses are the subject of extensive investigation, as follows: (1) Placental ischemia-Increased trophoblast deportation, as a consequence of ischemia, may inflict endothelial cell dysfunction. (2) Very low-density lipoprotein versus toxicity-preventing activity-In compensation for increased energy demand during pregnancy, nonesterified fatty acids are mobilized. In women with low albumin concentrations, transporting extra nonesterified fatty acids from adipose tissues to the liver is likely to reduce albumin's antitoxic activity to a point at which very-low density lipoprotein toxicity is expressed. (3) Immune maladaptation-Interaction between decidual leukocytes and invading cytotrophoblast cells is essential for normal trophoblast invasion and development. Immune maladaptation may cause shallow invasion of spiral arteries by endovascular cytotrophoblast cells and endothelial cell dysfunction mediated by an increased decidual release of cytokines, proteolytic enzymes, and free radical species. (4) Genetic imprinting-Development of preeclampsia-eclampsia may be based on a single recessive gene or a dominant gene with incomplete penetrance. Penetrance may be dependent on fetal genotype. The possibility of genetic imprinting should be considered in future genetic investigations of preeclampsia.

Extracellular superoxide dismutase localization and activity within the human placenta

Maintenance of low vascular tone within the placenta is mediated by nitric oxide (NO). The half-life of NO is very short, as superoxide anion (O2-) rapidly inactivates NO to form peroxynitrite. Superoxide dismutases compete with NO for O2-. By scavenging O2-, superoxide dismutase promotes the vasodilatory action of NO. Extracellular superoxide dismutase (EC-SOD) is present in high concentrations within the extracellular matrix of systemic arteries and has been proposed to mediate vascular smooth muscle tone by increasing NO bioavailability. The localization and activity of EC-SOD within the human placenta has not been determined. Placental EC-SOD may be involved in placental vascular tone, and abnormal activity may lead to pre-eclampsia secondary to increased O2--mediated inactivation of NO. To investigate this possibility, the activity and localization of human placental EC-SOD was determined in normal women, and then compared to pre-eclamptic women. Placental EC-SOD localized within the villous extracellular matrix around arterioles, and there were no differences in distribution between normal and pre-eclamptic women. There were no differences in placental EC-SOD activity between normal and pre-eclamptic subjects in either center (33.7+/-4.1 versus 33.1+/-2.5, P=0.6), or peripheral (34.3+/-5.6 versus 34.0+/-3.5, P=0.9) samples. EC-SOD localization around villous vessels suggests that EC-SOD serves potentially to protect the fetal vasculature from O2-, in both normal and pre-eclamptic pregnancies. Placental EC-SOD distribution and activity is not different between pre-eclamptic and normal women, suggesting that EC-SOD is not involved in the vascular changes seen in pre-eclampsia.

Endothelial nitric oxide synthase immunoreactivity in early gestation and in trophoblastic disease

AIMS

To study the localisation of the endothelial nitric oxide synthase (eNOS) in the normal placenta, with special emphasis on the implantation site in the first trimester of pregnancy, and in the different subtypes of trophoblastic cells in gestational trophoblastic disease.

METHODS

The immunoperoxidase technique with an antibody directed against eNOS was applied to paraffin sections from first and second trimester placentas, placenta accreta, partial and complete hydatidiform moles, and choriocarcinoma. Immunoperoxidase staining for human placental lactogen (hPL) was performed on parallel sections.

RESULTS

Prominent immunoreactivity for eNOS was found to be present in the intermediate trophoblastic cells of the cell columns of the anchoring villi and in trophoblastic cells at the implantation site. Staining was also present in the syncytiotrophoblast, most conspicuous at the apical cell border. In trophoblastic disease, proliferating large mononuclear cells, which were strongly positive for hPL, were found to be immunoreactive for eNOS.

CONCLUSIONS

eNOS immunoreactivity is strongly positive in the extravillous trophoblastic cells and to a lesser extent in the syncytiotrophoblast. In the former it may play a role in implantation and vascular invasion. Cells with differentiation to intermediate trophoblast in complete hydatidiform mole and choriocarcinoma also show high levels of eNOS, which may be associated with the haematogenous mode of spread of trophoblastic disease.

Nitric oxide in preeclampsia: lack of evidence for decreased production

The purpose of our study was to determine the involvement of the L-arginine-NO system in preeclampsia. We studied 26 patients with preeclampsia and 27 normotensive pregnancies. Maternal and cord plasma, urine and amniotic fluid were assayed for nitric oxide metabolites (nitrite and nitrate) using the Griess reaction. Sections of placenta and fetal membranes were immunostained with polyclonal anti-endothelial and anti-neuronal nitric oxide synthase antibodies. The concentration of nitrate in the amniotic fluid of preeclamptic patients (median 10.3 mumol/mg creatinine) was significantly higher (P < 0.001) than in the normotensive group (5.6 mumol/mg creatinine). Nitrate concentrations in maternal and cord plasma and in urine were similar in the two groups. Endothelial cells of the villi of preeclamptic placentas showed a higher positivity in endothelial nitric oxide synthase immunostaining with respect to normotensive controls. Our results indicate that feto-placental NO production is not reduced in preeclampsia. In contrast, the increased concentrations of NO metabolites in amniotic fluid and the positive immunostaining of endothelial nitric oxide synthase in the placental villi suggest that the placental L-arginine-NO system is up-regulated in preeclampsia.

Role of the L-arginine nitric oxide pathway in hypoxic fetoplacental vasoconstriction

The role of nitric oxide in hypoxic fetoplacental vasoconstriction (HFPV) was investigated using dually perfused human placental cotyledons. Standard medium (Earle's salt solution with added dextran and L-arginine) was equilibrated with 95 per cent O2 and 5 per cent CO2 (maternal side) and 94 per cent N2 and 6 per cent CO2 (fetal side). Part 1 consisted of perfusion for 1 h, then maternal perfusate equilibrated with a 95 per cent N2 and 5 per cent CO2 for 20 min (hypoxia), and then the original perfusion conditions resumed for 40 min. In part 2, this sequence was repeated with standard medium alone (n = 6), or with added N-nitro-L-arginine methyl ester (L-NAME) (n = 6), or L-NAME and nitroglycerin (n = 6). When standard medium was used throughout, basal fetal perfusion pressure (30 +/- 2 mmHg) and the hypoxia-induced increase in perfusion pressure (18 +/- 1 mmHg) did not change significantly between parts 1 and 2. L-NAME increased basal perfusion pressure from 33 +/- 3 to 56 +/- 2 mmHg whereas perfusion pressure remained unchanged with L-NAME and nitroglycerin or nitroglycerin alone. The hypoxic vasoconstriction observed during part 1 in the L-NAME (14 +/- 3 mmHg) and the L-NAME with nitroglycerin groups (18 +/- 2 mmHg) was abolished during part 2 (to - 4 +/- 1 and 0.4 +/- 0.5 mmHg, respectively) whereas nitroglycerin alone significantly blunted the response (21 +/- 3 to 6 +/- 1 mmHg). Results suggest that a reduction in basal NO release mediates hypoxic fetoplacental vasoconstriction in the perfused human placental cotyledon in vitro.

Amniotic fluid nitric oxide and uteroplacental blood flow in pregnancy complicated by intrauterine growth retardation

OBJECTIVE

To examine the correlation between placental nitric oxide production and uteroplacental blood flow.

PARTICIPANTS

Thirty-one pregnant women with fetuses with intrauterine growth retardation and 27 normal pregnancies as controls.

DESIGN

Correlation between amniotic fluid measurements of nitrite metabolite in the third trimester and flow velocimetry waveforms recorded from uterine, umbilical and fetal middle cerebral arteries. Intrauterine growth retarded pregnancies were compared with controls.

MAIN OUTCOME MEASURES

Concentrations of nitric oxide metabolites (NO2- and NO3-) in amniotic fluid were correlated with flow velocimetry waveforms findings by the determination of correlation coefficient.

RESULTS

Overall median nitrite values in amniotic fluid were higher (P < 0.01) in intrauterine growth retarded patients (median 8.6 micromol/mg creatinine) than in controls (5.6 micromol/mg creatinine). Pathologic uterine flow velocimetry waveforms in uterine artery (-2SD) were observed in 12 women of the intrauterine growth retarded group, and the concentration of amniotic fluid nitrite was significantly lower (P < 0.01) in these patients (median 4.45 micromol/mg creatinine) than in those with normal flow velocity waveforms (median 11.43 micromol/mg creatinine). A significant negative correlation was observed between nitrite concentrations and uterine artery resistance index, umbilical artery pulsatility index and umbilical artery pulsatility index:middle cerebral artery pulsatility index ratio.

CONCLUSIONS

We conclude that placental nitric oxide is significantly associated with uteroplacental blood flow and may be important in maintaining adequate uteroplacental perfusion in intrauterine growth retarded pregnancies.

Evaluation of nitric oxide as a mediator of severe preeclampsia

OBJECTIVE

Our purpose was to determine whether a reduction in nitric oxide synthesis occurs in women with severe preeclampsia as a consequence of soluble serum factors.

STUDY DESIGN

Circulating nitrate and nitrite levels were compared between women who met standard clinical criteria for severe preeclampsia (n = 21) and maternal or gestational age-matched, normotensive, primagravid control subjects (n = 21). End-products of nitric oxide synthesis were measured from venous blood samples using nitrate reduction and chemiluminescence. To detect in vitro suppression of nitric oxide synthesis, human umbilical vein endothelial cell monolayers were grown to confluence and exposed to culture media containing 20% severe preeclamptic or control sera. Nitrate and nitrite production were compared in duplicate monolayers for each experimental condition, expressed as means +/- SEM in picomoles per 10(6) cells. Data were compared by Student's t or Mann-Whitney U tests, when appropriate, along with Spearman correlations for comparisons of laboratory and clinical data.

RESULTS

Circulating nitrate and nitrite levels were similar in normotensive and preeclamptic cohorts (976 +/- 88 vs 1009 +/- 41 pmol/ml, respectively; p = 0.22), and no correlations between blood pressure and nitric oxide metabolite levels were observed for the control or severely preeclamptic subsets. Similar patterns of in vitro endothelial nitrite production were observed after 1-, 12-, and 24-hour incubations with 20% control or preeclamptic sera.

CONCLUSIONS

Circulating nitrate and nitrite levels are not reduced in patients with severe preeclampsia compared with normotensive controls, and sera from these women do not suppress endothelial cell nitric oxide synthesis in vitro.

Nitric oxide concentrations are increased in the feto-placental circulation in intrauterine growth restriction

The aim of this study was to measure plasma concentrations of total nitrites, as an index of nitric oxide (NO) synthesis, in the fetal circulation of normal pregnancies and in pregnancies complicated by intrauterine growth restriction. Plasma was prepared from umbilical venous blood collected from 13 placentae from normal pregnancies complicated by intrauterine growth restriction. Plasma NO concentrations were determined using the Greiss reaction by measuring combined oxidation products of NO, plasma nitrite (NO2-) and nitrate (NO3-) after reduction with nitrate reductase. Significantly higher NO2-concentrations were found in umbilical venous plasma in the group complicated by intrauterine growth restriction compared to the control group (65.6 mumol/1, P < 0.001. These results support the hypothesis that increased NO production may be a compensatory response to improve blood flow in the placenta and/or may play a role in limiting platelet adhesion and aggregation.