Plasma Membrane Of Syncytiotrophoblast Research Articles

Functional characterization of dopamine and norepinephrine transport across the apical and basal plasma membranes of the human placental syncytiotrophoblast

The human placenta represents a unique non-neuronal site of monoamine transporter expression, with pathophysiological relevance during the prenatal period. Monoamines (serotonin, dopamine, norepinephrine) are crucial neuromodulators for proper placenta functions and fetal development, including cell proliferation, differentiation, and neuronal migration. Accumulating evidence suggests that even a transient disruption of monoamine balance during gestation may lead to permanent changes in the fetal brain structures and functions, projecting into adulthood. Nonetheless, little is known about the transfer of dopamine and norepinephrine across the placental syncytiotrophoblast. Employing the method of isolated membranes from the human term placenta, here we delineate the transport mechanisms involved in dopamine and norepinephrine passage across the apical microvillous (MVM) and basal membranes. We show that the placental uptake of dopamine and norepinephrine across the mother-facing MVM is mediated via the high-affinity and low-capacity serotonin (SERT/SLC6A4) and norepinephrine (NET/SLC6A2) transporters. In the fetus-facing basal membrane, however, the placental uptake of both monoamines is controlled by the organic cation transporter 3 (OCT3/SLC22A3). Our findings thus provide insights into physiological aspects of dopamine and norepinephrine transport across both the maternal and fetal sides of the placenta. As monoamine transporters represent targets for several neuroactive drugs such as antidepressants, our findings are pharmacologically relevant to ensure the safety of drug use during pregnancy.

Pre-eclampsia predictive ability of maternal miR-125b: a clinical and experimental study

Pre-eclampsia (PE) is a systemic maternal syndrome affecting 2-8% of pregnancies worldwide and involving poor placental perfusion and impaired blood supply to the foetus. It manifests after the 20th week of pregnancy as new-onset hypertension and substantial proteinuria and is responsible for severe maternal and newborn morbidity and mortality. Identifying biomarkers that predict PE onset prior to its establishment would critically help treatment and attenuate outcome severity. MicroRNAs are ubiquitous gene expression modulators found in blood and tissues. Trophoblast cell surface antigen (Trop)-2 promotes cell growth and is involved in several cancers. We assessed the PE predictive ability of maternal miR-125b in the first trimester of pregnancy by measuring its plasma levels in women with normal pregnancies and with pregnancies complicated by PE on the 12th week of gestation. To gain insight into PE pathogenesis we investigated whether Trop-2 is targeted by miR-125b in placental tissue. Data analysis demonstrated a significant association between plasma miR-125b levels and PE, which together with maternal body mass index before pregnancy provided a predictive model with an area under the curve of 0.85 (95% confidence interval, 0.70-1.00). We also found that Trop-2 is a target of miR-125b in placental cells; its localization in the basal part of the syncytiotrophoblast plasma membrane suggests a role for it in the early onset of PE. Altogether, maternal miR-125b proved a promising early biomarker of PE, suggesting that it may be involved in placental development through its action on Trop-2 well before the clinical manifestations of PE.

Insulin Stimulates GLUT4 Trafficking to the Syncytiotrophoblast Basal Plasma Membrane in the Human Placenta.

Placental transport capacity influences fetal glucose supply. The syncytiotrophoblast is the transporting epithelium in the human placenta, expressing glucose transporters (GLUTs) and insulin receptors (IRs) in its maternal-facing microvillous plasma membrane (MVM) and fetal-facing basal plasma membrane (BM). The objectives of this study were to (i) determine the expression of the insulin-sensitive GLUT4 glucose transporter and IR in the syncytiotrophoblast plasma membranes across gestation in normal pregnancy and in pregnancies complicated by maternal obesity, and (ii) assess the effect of insulin on GLUT4 plasma membrane trafficking in human placental explants. Placental tissue was collected across gestation from women with normal body mass index (BMI) and mothers with obesity with appropriate for gestational age and macrosomic infants. MVM and BM were isolated. Protein expression of GLUT4, GLUT1, and IR were determined by western blot. GLUT4 was exclusively expressed in the BM, and IR was predominantly expressed in the MVM, with increasing expression across gestation. BM GLUT1 expression was increased and BM GLUT4 expression was decreased in women with obesity delivering macrosomic babies. In placental villous explants, incubation with insulin stimulated Akt (S473) phosphorylation (+76%, P = 0.0003, n = 13) independent of maternal BMI and increased BM GLUT4 protein expression (+77%, P = 0.0013, n = 7) in placentas from lean women but not women with obesity. We propose that maternal insulin stimulates placental glucose transport by promoting GLUT4 trafficking to the BM, which may enhance glucose transfer to the fetus in response to postprandial hyperinsulinemia in women with normal BMI.

Relation of placental alkaline phosphatase expression in human term placenta with maternal and offspring fat mass.

Alkaline phosphatase is implicated in intestinal lipid transport and in the development of obesity. Placental alkaline phosphatase is localised to the microvillous plasma membrane of the placental syncytiotrophoblast at the maternal-fetal interface, but its role is unclear. We investigated the relations of placental alkaline phosphatase activity and mRNA expression with maternal body composition and offspring fat mass in humans. Term human placentas from the UK Birthright cohort (n = 52) and the Southampton Women's Survey (SWS) (n = 95) were studied. In the Birthright cohort, alkaline phosphatase activity was measured in placental microvillous plasma membrane vesicles. In the SWS, alkaline phosphatase mRNA was measured using Nanostring. Alkaline phosphatase gene expression was compared to other lipid-related genes. In Birthright samples placental microvillous plasma membrane alkaline phosphatase activity was positively associated with maternal triceps skinfold thickness and BMI (β = 0.04 (95% CI: 0.01-0.06) and β = 0.02 (0.00-0.03) µmol/mg protein/min per SD, P = 0.002 and P = 0.05, respectively) after adjusting for potential confounders. In SWS samples placental alkaline phosphatase mRNA expression in term placenta was positively associated with maternal triceps skinfold (β = 0.24 (0.04, 0.44) SD/SD, P = 0.02), had no association with neonatal %fat mass (β = 0.01 (-0.20 to 0.21) SD/SD, P = 0.93) and was negatively correlated with %fat mass at ages 4 (β = -0.28 (-0.52 to -0.04) SD/SD, P = 0.02), 6-7 (β = -0.25 (-0.49 to -0.02) SD/SD, P = 0.03) years. When compared with placental expression of other genes, alkaline phosphatase expression was positively related to genes including the lysophosphatidylcholine transporter MFSD2A (major facilitator superfamily domain containing 2A, P < 0.001) and negatively related to genes including the fatty acid transport proteins 2 and 3 (P = 0.001, P < 0.001). Our findings suggest relationships between placental alkaline phosphatase and both maternal and childhood adiposity. The inverse relationship between placental alkaline phosphatase gene expression and childhood %fat mass suggests that placental alkaline phosphatase may help to protect the foetus from the adverse effects of maternal obesity.

Nongenomic Effect of T3 on the Na, K-ATPase Activity of Syncytiotrophoblast from Human Term Placenta

Several ion transport enzymes are positively regulated by genomic mechanisms, through the thyroid hormones T3 and T4. However, there is evidence indicating that these hormones might also exert non genomic effects on different transporting enzymes. A normal activity of the Na, K-ATPase of syncytiotrophoblast is essential for ion homeostasis in this tissue, as well as for the growth and development of the fetus. In the current work it was studied the non genomic effect of thyroid hormones on the Na, K-ATPase activity of syncytiotrophoblast. The study was carried-out by incubating human term placental explants in the absence and presence of 10nMT3 or 350nMT4 and then isolating the syncytiotrophoblast plasma membranes and assaying them for Na, K-ATPase activity. The enzyme activity was also assayed for freshly prepared plasma membranes in the presence of (0–15)nMT3 or (0–500)nMT4.

Role of organic anion transporter 4 on the transport of olmesartan across the basal plasma membrane of human placental syncytiotrophoblast

Role of organic anion transporter 4 on the transport of olmesartan across the basal plasma membrane of human placental syncytiotrophoblast

Computational modelling of placental amino acid transfer as an integrated system

Placental amino acid transfer is essential for fetal development and its impairment is associated with poor fetal growth. Amino acid transfer is mediated by a broad array of specific plasma membrane transporters with overlapping substrate specificity. However, it is not fully understood how these different transporters work together to mediate net flux across the placenta. Therefore the aim of this study was to develop a new computational model to describe how human placental amino acid transfer functions as an integrated system. Amino acid transfer from mother to fetus requires transport across the two plasma membranes of the placental syncytiotrophoblast, each of which contains a distinct complement of transporter proteins. A compartmental modelling approach was combined with a carrier based modelling framework to represent the kinetics of the individual accumulative, exchange and facilitative classes of transporters on each plasma membrane. The model successfully captured the principal features of transplacental transfer. Modelling results clearly demonstrate how modulating transporter activity and conditions such as phenylketonuria, can increase the transfer of certain groups of amino acids, but that this comes at the cost of decreasing the transfer of others, which has implications for developing clinical treatment options in the placenta and other transporting epithelia.

Protein expression of fatty acid transporter 2 is polarized to the trophoblast basal plasma membrane and increased in placentas from overweight/obese women

BackgroundObese and overweight women are more likely to deliver a large infant or an infant with increased adiposity, however the underlying mechanisms are not well established. We tested the hypothesis that placental capacity to transport fatty acid is increased in overweight/obese women. MethodsPregnant women with body mass index (BMI) ranging from 18.4 to 54.3 kg/m2 and with uncomplicated term pregnancies were recruited for collection of blood samples and placental tissue. Maternal and fetal levels of non-esterified fatty acids (NEFAs) were measured in plasma. The expression and localization of CD36/fatty acid translocase (FAT), fatty acid transport protein (FATP)2, and FATP4 was determined in fixed placental tissue and in isolated syncytiotrophoblast plasma membranes from normal and high BMI mothers. ResultsMaternal and fetal plasma NEFA levels did not correlate (n = 42). FATP2 and FATP4 expressions were higher in the basal plasma membrane (BPM) compared to the microvillous membrane (P < 0.001; n = 7) per unit membrane protein. BPM expression of FATP2 correlated with maternal BMI (P < 0.01; n = 30); there was no association between CD36/FAT or FATP4 expression and maternal BMI. ConclusionThe polarization of FATPs to the BPM will facilitate fatty acid transfer across the placenta. In overweight/obese pregnancies, the increased FATP2 expression could contribute to increased fatty acid delivery to the fetus and while we have no direct data we speculate that this could lead accelerated fetal growth or increased fat deposition.

Preeclampsia and preeclampsia superimposed on chronic hypertension in Buenos Aires

Preeclampsia and preeclampsia superimposed on chronic hypertension in Buenos Aires

Magnesium sulfate affords protection against oxidative damage during severe preeclampsia

IntroductionMgSO4 is the drug of choice to prevent seizures in preeclamptic pregnant women, but its mechanism of action at the molecular level remains an enigma. In previous works, we found that treating preeclamptic women with MgSO4 reduces the lipid peroxidation of their red blood cell membranes to normal levels and leads to a significant reduction in the osmotic fragility of the red blood cells that is increased during preeclampsia. In addition, the increase in lipid peroxidation of red cell membranes induced by the Fenton reaction does not occur when MgSO4 is present. MethodsThe antioxidant protection of MgSO4 was evaluated in UV-C-treated red blood cell ghosts and syncytiotrophoblast plasma membranes by measuring their level of lipid peroxidation. The interaction of MgSO4 with free radicals was assessed for its association with the galvinoxyl radical, the quenching of H2O2-induced chemiluminescence and its effect on sensitized peroxidation of linoleic acid. Resultsa) MgSO4 protected red blood cell ghosts and the syncytiotrophoblast plasma membranes of normotensive pregnant women against lipid peroxidation induced by UV-C irradiation. b) MgSO4 does not seem to scavenge the galvinoxyl free radical. c) The quenching of the H2O2-enhanced luminol chemiluminescence is increased by the presence of MgSO4. d) The peroxidation of linoleic acid is significantly blocked by MgSO4. DiscussionMgSO4 may provide protection against oxidative damage of plasma membranes through interactions with alkyl radicals.

Na+, K+-ATPase and Ca2+-ATPase activities in basal and microvillous syncytiotrophoblast membranes from preeclamptic human term placenta

Objective: The aim of this study is to evaluate the effect of preeclampsia on the level of lipid peroxidation, activity and expression of both plasma membrane Ca2+- and Na+, K+-ATPases in syncytiotrophoblast. Methods: The level of lipid peroxidation was estimated by measuring TBARS. ATPase activities were quantified by a colorimetric method measuring the amount of inorganic phosphate during the assay. Expression of Ca2+- and Na+, K+-ATPases in syncytiotrophoblast plasma membranes and term placenta tissue sections was investigated using Western blot and immunohistochemistry, respectively. Results: Our results show a higher level of lipid peroxidation of syncytiotrophoblast plasma membranes from preeclamptic, as compared to uncomplicated pregnant women. Preeclampsia also significantly reduced the activity of Ca2+- and Na+, K+-ATPases; however, expression of both ATPases was unaffected. Conclusion: Our findings suggest that the reduction of Ca2+- and Na+, K+-ATPase activities during preeclampsia could be at least partially due to an increased level of lipid peroxidation of the syncytiotrophoblast plasma membranes.

Effect of hypoxia on the calcium and magnesium content, lipid peroxidation level, and Ca²⁺-ATPase activity of syncytiotrophoblast plasma membranes from placental explants.

In the current study the possible relationship between the Ca2+/Mg2+ ratio of human syncytiotrophoblast plasma membranes and their lipid peroxidation and Ca2+-ATPase activity was determined. Syncytiotrophoblast plasma membranes of placental explants cultured under hypoxia increased their lipid peroxidation and Ca2+ content, diminished their Ca2+-ATPase activity, and kept their Mg2+ content unchanged. Membranes preincubated with different concentrations of Ca2+ increased their Ca2+ content without changes in their Mg2+ content. There is a direct relationship between Ca2+ content and lipid peroxidation of the membranes, as well as an inverse relationship between their Ca2+ content and Ca2+-ATPase activity. On the contrary, preincubation of membranes with different concentrations of Mg2+ showed a higher Mg2+ content without changing their lipid peroxidation and Ca2+-ATPase activity. Explants cultured under hypoxia in the presence of 4 mM MgSO4 showed similar values of lipid peroxidation and Ca2+-ATPase activity of their membranes compared to those of explants cultured under normoxia. Increased Ca2+ content of the membranes by interacting with negatively charged phospholipids could result in destabilizing effects of the membrane structure, exposing hydrocarbon chains of fatty acids to the action of free radicals. Mg2+ might exert a stabilizing effect of the membranes, avoiding their exposure to free radicals.

Adaptations in placental nutrient supply capacity to meet fetal demand: implications for intrauterine programming

Fetal growth is absolutely dependent on supply of nutrients from mother via the placenta. A variety of human and mouse data together suggest that placental capacity to supply nutrient is adaptable in relation to fetal demand. (1) In normal human pregnancy the activity, per mg membrane protein, of the System A amino acid transporter in the microvillous plasma membrane (MVM) of the placental syncytiotrophoblast is inversely related to the birthweight and size of baby. (2) In mice with a deletion of the placental transcript of the insulin‐like growth factor 2 (igf2) gene, placental weight is reduced compared to wild type mice at e16 (term e20) but fetal weight is not reduced at this time, perhaps because System A expression and activity, per g placenta, is higher in the knockout conceptuses. (3) In the same knockout mice fetal calcium accretion is reduced compared to wild type at e17, but returns to normal by e19 apparently through an increased activity/expression of placental calcium transport mechanisms. (4) Most recently, we find apparent adaptations in placental transporter and vascular reactivity in pregnancies complicated by obesity and pre‐eclampsia respectively. The variable nature of the placental transfer adaptations in different situations, as found in these different studies, will variably affect the mix of nutrient transferred and so potentially variably programme fetal homeostatic mechanisms.

Differential Expression of Ezrin and CLP36 in the Two Layers of Syncytiotrophoblast in Rats

The syncytiotrophoblast, which regulates maternal-fetal transfer of drugs, consists of a single layer in humans, but two layers, i.e., SynI and SynII, in rodents. Polar distribution of transporters in the apical and basal plasma membranes of syncytiotrophoblast is important for placental function in terms of vectorial transport of substrates, but the mechanisms that control protein distribution in the syncytiotrophoblast remain unclear. We have previously established rat syncytiotrophoblast cell lines, TR-TBT 18d-1 and TR-TBT 18d-2, which retain characteristics of SynI and SynII, respectively. In this study, we aimed to characterize the gene expression profiles in the two layers by using these cell lines. DNA microarray analysis indicated that more than 25 mRNAs, including cytoskeleton binding proteins, ezrin and CLP36, are differentially expressed between TR-TBT 18d-1 and TR-TBT 18d-2. Quantitative real time-polymerase chain reaction (PCR) analysis indicated that mRNA expression of ezrin, CLP36, CCN1, and CCN2 is higher in TR-TBT 18d-1 and mRNA expression of elf-1a, hsc70 and flot2 is higher in TR-TBT 18d-2, compared with their counterparts. Immunohistochemical analysis indicated that ezrin is expressed in rat placental villi in vivo, and is located on the apical membranes of TR-TBT 18d-1, while CLP36 is located in the apical and basal sides of TR-TBT 18d-1. The expression of ezrin was highest at gestational days 14 and 18 and was highest among the ezrin/radixin/moesin (ERM) family members. These results may help to clarify the mechanisms controlling polarization of the syncytiotrophoblast and the significance of the double epithelial layers in rat and mouse.

Expression of folate transporters in human placenta and implications for homocysteine metabolism

Poor folate status during pregnancy can lead to elevated maternal plasma levels of homocysteine (Hcy) with associated pregnancy complications and adverse neonatal outcomes, suggesting placental metabolism of Hcy might be an important determinant in influencing fetal development. The metabolic pathways for Hcy in placenta are not well defined. In this study we examined the gene expression of key enzymes involved in Hcy metabolism in first trimester and term human placenta to determine which metabolic pathways prevail. Expression of mRNA for methionine synthase and 5,10-methylene tetrahydrofolate reductase, enzymes involved in the methionine cycle and responsible for the re-methylation of Hcy to methionine, were expressed at similar levels between first trimester and term and in comparison to human liver as positive control. In contrast, cystathionine β-synthase mRNA expression was markedly lower than that in liver at both gestational periods. Betaine–homocysteine methyltransferase mRNA was undetectable at either gestational age. These data suggest that re-methylation of Hcy using methyl donation from 5-methyltetrahydrofolate is the prevalent pathway, indicating a marked reliance on folate availability. This led to further investigations examining the expression and localisation of folate transporters in first trimester and term placenta. Folate receptor α (FRα) was highly polarised to the microvillous plasma membrane (MVM) of the syncytiotrophoblast at both gestational periods, a distribution shared by the proton-coupled folate transporter which co-localised with FRα. Reduced folate carrier was distributed to both MVM and basal syncytiotrophoblast plasma membranes at term suggesting a role at both loci, and in first trimester was localised to MVM as well as cytotrophoblast plasma membranes. These data support the concept that placental folate transport is established early in pregnancy, providing folate for utilisation in placental Hcy metabolism.

Maternal celiac disease autoantibodies bind directly to syncytiotrophoblast and inhibit placental tissue transglutaminase activity

BackgroundCeliac disease (CD) occurs in as many as 1 in 80 pregnant women and is associated with poor pregnancy outcome, but it is not known if this is an effect on maternal nutrient absorption or, alternatively, if the placenta is an autoimmune target. The major autoantigen, tissue transglutaminase (tTG), has previously been shown to be present in the maternal-facing syncytiotrophoblast plasma membrane of the placenta.MethodsELISA was used to demonstrate the presence of antibodies to tissue transglutaminase in a panel of CD sera. Immunohistochemistry was used to evaluate the binding of IgA autoantibodies from CD serum to term placenta. In addition, novel direct binding and activity assays were developed to mimic the in vivo exposure of the villous placenta to maternal autoantibody.Results and DiscussionCD IgA autoantibodies located to the syncytial surface of the placenta significantly more than IgA antibodies in control sera (P < 0.0001). The distribution of antigen was similar to that observed using a monoclonal antibody to tissue transglutaminase. Staining was reduced by pre-absorption of CD serum with recombinant human tissue transglutaminase. In direct binding assays, autoimmune immunoglobulin A (IgA) from the maternal compartment became associated with antigen at the syncytial surface of the placenta, as a result of which transglutaminase activity at this site was inhibited.ConclusionThese data indicate that direct immune effects in untreated CD women may compromise placental function.

Isolation of highly enriched apical plasma membranes of the placental syncytiotrophoblast

The human placenta is a complex organ whose proper function is crucial for the development of the fetus. The placenta contains within its structure elements of the maternal and fetal circulatory systems. The interface with maternal blood is the lining of the placenta, that is a unique compartment known as the syncytiotrophoblast. This large syncytial structure is a single cell layer in thickness, and the apical plasma membrane of the syncytiotrophoblast interacts directly with maternal blood. Relatively little is known about the proteins that reside in this unique plasma membrane or how they may change in various placental diseases. Our goal was to develop methods for isolating highly enriched preparations of this apical plasma membrane compatible with high-quality proteomics analysis and herein describe the properties of these isolated membranes.

The Mechanisms and Regulation of Placental Amino Acid Transport to the Human Foetus

The mechanisms by which amino acids are transferred across the human placenta are fundamental to our understanding of foetal nutrition. Amino acid transfer across the human placenta is dependent on transport across both the microvillous and basal plasma membranes of the placental syncytiotrophoblast, and on metabolism within the syncytiotrophoblast. Although the principles underlying uptake of amino acids across the microvillous plasma membrane are well understood, the extent to which amino acids are metabolised within human placenta and the mechanisms by which amino acids are transported out of the placenta across the basal plasma membrane are not well understood. Understanding the mechanisms and regulation of amino acid transport is necessary to understand the causes of intrauterine growth restriction in human pregnancy.

Antiepileptic Medication During Pregnancy: Does Fetal Genotype Affect Outcome?

Congenital abnormalities and impaired development in childhood are attributable to fetal exposure to antiepileptic drugs (AEDs). Pregnancy registries set up to obtain information about the potential risks of fetal exposure to AEDs, in particular major congenital malformations (MCMs), suggest that valproate exposure increases the frequency of congenital malformations more than other AEDs. Furthermore, follow-up studies have drawn attention to cognitive impairments in later childhood after prenatal exposure to valproate. Fetal exposure to AEDs may be influenced by drug transporting proteins in the placenta, including P-glycoprotein (P-gp), multidrug resistance protein (MRP) 1, and breast cancer resistance protein (BCRP). Their location in the syncytiotrophoblast plasma membrane, at the interface of the maternal and fetal circulations, allows these transport proteins to efflux xenobiotics back to the mother and offers the fetus protection from medications taken during pregnancy. Genetic variations in the expression and activity of these transport proteins may influence fetal exposure to AEDs and thus the risk of teratogenicity. Identification of a hierarchy of haplotypes ranging from susceptible to protective of congenital abnormalities could assist genetic counseling, in assessing fetal risks from exposure to AEDs.

Lipid Peroxidation and Ca-ATPase Activity of Basal Plasma Membranes of Syncytiotrophoblast from Normotensive Pregnant Women

Background: The Ca-ATPase activity of the plasma membranes of several tissues of preeclamptic pregnant women is significantly reduced when compared with the values of normotensive pregnant women. This has been explained considering the raise in the level of lipid peroxidation of the plasma membranes with preeclampsia. In this work we studied the effect of lipid peroxidation of syncytiotrophoblast basal (fetal facing) plasma membranes from normotensive pregnant women, on their level of Ca-ATPase activity. Methods: The syncytiotrophoblast basal (fetal facing) plasma membranes from normotensive pregnant women were isolated and irradiated with ultraviolet (UV) light (254 nm). The membranes were then assayed for Ca-ATPase activity and lipid peroxidation by TBARS. Results: The UV irradiation raises the level of lipid peroxidation of the membranes, producing a concomitant inhibition of their Ca-ATPase activity. Presence of the antioxidant butylated hydroxytoluene during the UV irradiation of the membranes prevents increase in their level of lipid peroxidation and hence the inhibition of their Ca-ATPase activity. Conclusion: These results give a strong support to the hypothesis that the lowered Ca-ATPase activity already described for plasma membranes of several tissues of preeclamptic women is the consequence of the increased level of lipid peroxidation shown by these membranes.