Progesterone Inhibits Folic Acid Transport in Human Trophoblasts

The endocannabinoid 2-arachidonoylglycerol promotes endoplasmic reticulum stress in placental cells

Proliferation, differentiation and apoptosis of trophoblast cells are required for normal placental development. Impairment of those processes may lead to pregnancy-related diseases. Disruption of endoplasmic reticulum (ER) homeostasis has been associated with several reproductive pathologies including recurrent pregnancy loss and preeclampsia. In the unfolded protein response (UPR), specific ER-stress signalling pathways are activated to restore ER homeostasis, but if the adaptive response fails, apoptosis is triggered. Protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1 (IRE1) and Activating transcription factor 6 (ATF6) are central players in UPR and in ER-stress-induced apoptosis, as well as downstream transcription factors, as C/EBP homologous protein (CHOP). Our previous studies have shown that the endocannabinoid 2-arachidonoylglycerol (2-AG) modulates trophoblast cell turnover. Nevertheless, the role of ER-stress on 2-AG induced apoptosis and cannabinoid signalling in trophoblast has never been addressed. In this work, we used BeWo cells and human primary cytotrophoblasts isolated from term-placenta. The expression of ER-stress markers was analysed by qRT-PCR and Western blotting. ROS generation was assessed by fluorometric methods, while apoptosis was detected by the evaluation of caspase -3/-7 activities and Poly (ADP-ribose) polymerase (PARP) cleavage. Our findings indicate that 2-AG is able to induce ER-stress and apoptosis. Moreover, the eukaryotic initiation factor 2 (eIF2α)/CHOP pathway involved in ER-stress-induced apoptosis is triggered through a mechanism dependent on cannabinoid receptor CB2 activation. The results bring novel insights on the importance of ER-stress and cannabinoid signalling on 2-AG mechanisms of action in placenta.

Identification of placental nutrient transporters associated with intrauterine growth restriction and pre-eclampsia

Background

Gestational disorders such as intrauterine growth restriction (IUGR) and pre-eclampsia (PE) are main causes of poor perinatal outcomes worldwide. Both diseases are related with impaired materno-fetal nutrient transfer, but the crucial transport mechanisms underlying IUGR and PE are not fully elucidated. In this study, we aimed to identify membrane transporters highly associated with transplacental nutrient deficiencies in IUGR/PE.

Results

In silico analyses on the identification of differentially expressed nutrient transporters were conducted using seven eligible microarray datasets (from Gene Expression Omnibus), encompassing control and IUGR/PE placental samples. Thereby 46 out of 434 genes were identified as potentially interesting targets. They are involved in the fetal provision with amino acids, carbohydrates, lipids, vitamins and microelements. Targets of interest were clustered into a substrate-specific interaction network by using Search Tool for the Retrieval of Interacting Genes. The subsequent wet-lab validation was performed using quantitative RT-PCR on placentas from clinically well-characterized IUGR/PE patients (IUGR, n = 8; PE, n = 5; PE+IUGR, n = 10) and controls (term, n = 13; preterm, n = 7), followed by 2D-hierarchical heatmap generation. Statistical evaluation using Kruskal-Wallis tests was then applied to detect significantly different expression patterns, while scatter plot analysis indicated which transporters were predominantly influenced by IUGR or PE, or equally affected by both diseases. Identified by both methods, three overlapping targets, SLC7A7, SLC38A5 (amino acid transporters), and ABCA1 (cholesterol transporter), were further investigated at the protein level by western blotting. Protein analyses in total placental tissue lysates and membrane fractions isolated from disease and control placentas indicated an altered functional activity of those three nutrient transporters in IUGR/PE.

Conclusions

Combining bioinformatic analysis, molecular biological experiments and mathematical diagramming, this study has demonstrated systematic alterations of nutrient transporter expressions in IUGR/PE. Among 46 initially targeted transporters, three significantly regulated genes were further investigated based on the severity and the disease specificity for IUGR and PE. Confirmed by mRNA and protein expression, the amino acid transporters SLC7A7 and SLC38A5 showed marked differences between controls and IUGR/PE and were regulated by both diseases. In contrast, ABCA1 may play an exclusive role in the development of PE.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4518-z) contains supplementary material, which is available to authorized users.

The synthetic cannabinoid WIN-55,212 induced-apoptosis in cytotrophoblasts cells by a mechanism dependent on CB1 receptor

The endocannabinoid system has evolved as a key regulator in several pathological and physiological processes, including placentation, decidualization and implantation. In addition, it is known that Cannabis and cannabinoids negatively affect female reproduction. Although, the biological action of synthetic cannabinoids, such as WIN-55,212, in human fertility and pregnancy outcome remain to be unveiled. A tight balance between proliferation, differentiation and apoptosis of trophoblast cells is required for placental development and pregnancy outcome. Therefore, in this work, the effects of the synthetic cannabinoid WIN-55,212 in placental cytotrophoblast cells were explored. For that, it was used a human choriocarcinoma cell line, BeWo cells, and primary cultures of human cytotrophoblasts isolated from term placentas. Results demonstrate that this synthetic cannabinoid induces cell cycle arrest. We also observed that cell viability loss was associated with a disruption of mitochondrial membrane potential and activation of caspases -9 and -3/-7 independently of reactive oxygen species (ROS) production or recruitment of the endoplasmic reticulum stress marker CHOP. Moreover, these effects were prevented by pre-incubation with a selective cannabinoid receptor 1 (CBR1) antagonist (AM281). Thus, our results provide strong evidences of the apoptotic process induced by WIN-55,212 through the activation of the CBR1, which may reveal the impact of cannabinoids consumption during placental development.

The endocannabinoid 2-arachidonoylglycerol dysregulates the synthesis of proteins by the human syncytiotrophoblast

In recent years, endocannabinoids emerged as new players in various reproductive events. Recently, we demonstrated the involvement of 2-arachidonoylglycerol (2-AG) in human cytotrophoblast apoptosis and syncytialization. However, 2-AG impact in hormone production by the syncytiotrophoblast (hST) was never studied. In this work, we demonstrate that 2-AG activates cannabinoid (CB) receptors, exerting an inhibitory action on cyclic AMP/protein kinase A (cAMP/PKA) and mitogen-activated protein kinase (MAPK) p38 pathways, and enhancing ERK 1/2 phosphorylation. Furthermore, 2-AG affects the synthesis of human chorionic gonadotropin (hCG), leptin, aromatase, 3-β-hydroxysteroid dehydrogenase (3-β-HSD), and placental protein 13 (PP13). These 2-AG effects are mediated by the activation of CB receptors, in a mechanism that may involve p38, ERK 1/2 and cAMP/PKA pathways, which participate in the regulation of placental proteins expression. To our knowledge, this is the first study that associates the endocannabinoid signalling and endocrine placental function, shedding light on a role for 2-AG in the complex network of molecules that orchestrate the production of placental proteins essential for the gestational success.

The psychoactive compound of Cannabis sativa, Δ(9)-tetrahydrocannabinol (THC) inhibits the human trophoblast cell turnover

The noxious effects of cannabis consumption for fertility and pregnancy outcome are recognized for years. Its consumption during gestation is associated with alterations in foetal growth, low birth weight and preterm labor. The main psychoactive molecule of cannabis, Δ(9)-tetrahydrocannabinol (THC) impairs the production of reproductive hormones and is also able to cross the placenta barrier. However, its effect on the main placental cells, the trophoblasts, are unknown. Actually, the role of THC in cell survival/death of primary human cytotrophoblasts (CTs) and syncytiotrophoblasts (STs) and in the syncytialization process remains to be explored. Here, we show that THC has a dual effect, enhancing MTT metabolism at low concentrations, whereas higher doses decreased cell viability, on both trophoblast phenotypes, though the effects on STs were more evident. THC also diminished the generation of oxidative and nitrative stress and the oxidized form of glutathione, whereas the reduced form of this tripeptide was increased, suggesting that THC prevents ST cell death due to an antioxidant effect. Moreover, this compound enhanced the mitochondrial function of STs, as observed by the increased MTT metabolism and intracellular ATP levels. These effects were independent of cannabinoid receptors activation. Besides, THC impaired CT differentiation into STs, since it decreased the expression of biochemical and morphological biomarkers of syncytialization, through a cannabinoid receptor-dependent mechanism. Together, these results suggest that THC interferes with trophoblast turnover, preventing trophoblast cell death and differentiation, and contribute to disclose the cellular mechanisms that lead to pregnancy complications in women that consume cannabis-derived drugs during gestation.

2-Arachidonoylglycerol impairs human cytotrophoblast cells syncytialization: influence of endocannabinoid signalling in placental development

A balanced cytotrophoblast cell turnover is crucial for placental development and anomalies in this process associated with gestational diseases. The endocannabinoid system (ECS) has emerged as a new player in several biological processes. However, its influence during placental development is still unknown. We report here the expression of the endocannabinoid 2-arachidonoylglycerol (2-AG) main metabolic enzymes in human cytotrophoblasts and syncytiotrophoblast. We also showed that 2-AG induced a decrease in placental alkaline phosphatase activity, human chorionic gonadotropin secretion and Leptin mRNA levels. Moreover, 2-AG reduced glial cell missing 1 and syncytin-2 transcription and the number of nuclei in syncytium. These effects were mediated by cannabinoid receptors and may result from 2-AG inhibition of the cAMP/PKA signalling pathway. Our data suggest that 2-AG may interfere with the biochemical and morphological differentiation of human cytotrophoblasts, through a CB receptor-dependent mechanism, shedding light on a role for the ECS in placental development.

The endocannabinoid anandamide induces apoptosis in cytotrophoblast cells: involvement of both mitochondrial and death receptor pathways

INTRODUCTION

A balanced proliferation, apoptosis and differentiation in trophoblast cells of the human placenta is crucial for a proper placental development. Alteration in trophoblast apoptosis and differentiation are associated with gestational-related complications, such as preeclampsia, intrauterine growth restriction or miscarriages. The endocannabinoids (eCBs) have been recognized as new interveners in pregnancy events such as implantation and decidualization. However, their importance in placentation is poorly understood. We hypothesise that these novel lipid mediators may intervene in cytotrophoblast apoptosis and, concomitantly, have a role during placental development.

METHODS

primary human cytotrophoblasts (hCTs) and the human trophoblast-like choriocarcinoma cell line BeWo cells were exposed to Anandamide (AEA). It was investigated the cellular pathways involved in cell death, by the assessment of cell morphology, caspases activity, mitochondrial membrane potential (Δψm), reactive oxygen/nitrogen species (ROS/RNS) and western blot of cleaved Poly (ADP-ribose) polymerase 1 (PARP-1), truncated Bid (t-Bid) and IκB-α.

RESULTS

AEA decreased hCTs viability and induced morphological features of apoptosis (chromatin condensation and fragmentation), caspase-3/7 activation and PARP-1 cleavage. In BeWo, AEA also increased the activities of caspase-3/7 and 9, induced loss in Δψm and production of ROS/RNS. These effects were reversed by either CB1 or CB2 antagonists, whereas the increase in caspase-3/7 activity was only reversed with CB2 blockage. AEA-treated cells showed increased caspase-8 activation and formation of t-Bid, suggesting the interplay between intrinsic and extrinsic apoptotic pathways. AEA also increased IκB-α expression, a NF-κB regulatory protein.

CONCLUSION

Our results highlight the importance of eCBs in cytotrophoblast cell apoptosis and indicate that a crosstalk between intrinsic and extrinsic apoptotic pathways is involved in AEA-induced effects.

Transient receptor potential vanilloid 1 is expressed in human cytotrophoblasts: induction of cell apoptosis and impairment of syncytialization

The normal development of placenta relies essentially on a balanced proliferation, differentiation and apoptosis of cytotrophoblasts. These processes are tightly regulated by several hormones, cytokines, lipids and other molecules and anomalies in these events are associated with gestational complications. The cation channel transient receptor potential vanilloid 1 (TRPV1) is expressed in several organs and tissues and it participates in cellular events like nociception, inflammation and cell death. However, the expression and importance of this receptor in human placenta still remains unknown. In this work, we found that TRPV1 is expressed in human cytotrophoblasts and syncytiotrophoblasts. Furthermore, the TRPV1 agonists capsaicin and anandamide decreased cytotrophoblast viability and induced morphological alterations, such as chromatin condensation and fragmentation, which suggest the occurrence of apoptosis. Also, both TRPV1 agonists induced a loss of mitochondrial membrane potential and an increase of caspase 3/7 activity and production of reactive species of oxygen and nitrogen. Furthermore, capsaicin (10 μM) impaired the spontaneous in vitro differentiation of cytotrophoblasts into syncytiotrophoblasts by triggering TRPV1, as observed by the decrease in placental alkaline phosphatase activity and in human chorionic gonadotropin secretion. On the other hand, anandamide decreased placental alkaline phosphatase activity via a TRPV1-independent mechanism but did not influence the secretion of human chorionic gonadotropin. In conclusion, we showed that TRPV1 is expressed in human cytotrophoblasts and syncytiotrophoblasts and also reported the involvement of this receptor in cytotrophoblast apoptosis and differentiation.

2-arachidonoylglycerol effects in cytotrophoblasts: metabolic enzymes expression and apoptosis in BeWo cells

The major endocannabinoid (eCB) 2-arachidonoylglycerol (2-AG) is a member of the endocannabinoid system (ECS) that participates in cell proliferation and apoptosis, important events for the homoeostasis of biological systems. The formation of placenta is one of the most important stages of pregnancy and its development requires highly regulated proliferation, differentiation and apoptosis of trophoblasts. Anomalies in these processes are associated with gestational pathologies. In this work, we aimed to study the involvement of 2-AG in cytotrophoblast cell turnover. We found that 2-AG biosynthetic (diacylglycerol lipase A) and degradative (monoacylglycerol lipase) enzymes are expressed in human cytotrophoblasts and in BeWo cells. We also found that 2-AG induces a decrease in cell viability in a time- and concentration-dependent manner and exerts antiproliferative effects. The loss of cell viability induced by a 48-h treatment with 2-AG (10 μM) was accompanied by chromatin fragmentation and condensation, morphological features of apoptosis. Additionally, 2-AG induced an increase in caspase 3/7 and 9 activities, a loss of mitochondrial membrane potential (Δψm) and an increase in reactive oxygen species (ROS)/reactive nitrogen species (RNS) generation, suggesting the activation of the mitochondrial pathway. Moreover, whereas Δψm loss and ROS/RNS generation were significantly attenuated by the antagonists of both the cannabinoid receptors 1 and 2 (CB1 and CB2), the increase in caspase 3/7 and 9 activities and loss of cell viability were reversed only by the antagonist of CB2 receptor; the blockage of the eCB membrane transporter and the depletion of cholesterol failed to reverse the effects of 2-AG. Therefore, this work supports the importance of cannabinoid signalling during cytotrophoblast cell turnover and that its deregulation may be responsible for altered placental development and poor pregnancy outcomes.

L-methionine placental uptake: characterization and modulation in gestational diabetes mellitus

Our aim was to investigate the influence of gestational diabetes mellitus (GDM) and GDM-associated conditions upon the placental uptake of (14)C-l-methionine ((14)C-l-Met). The (14)C-l-Met uptake by human trophoblasts (TBs) obtained from normal pregnancies (normal trophoblast [NTB] cells) is mainly system l-type amino acid transporter 1 (LAT1 [L])-mediated, although a small contribution of system y(+)LAT2 is also present. Comparison of (14)C-l-Met uptake by NTB and by human TBs obtained from GDM pregnancies (diabetic trophoblast [DTB] cells) reveals similar kinetics, but a contribution of systems A, LAT2, and b(0+) and a greater contribution of system y(+)LAT1 appears to exist in DTB cells. Short-term exposure to insulin and long-term exposure to high glucose, tumor necrosis factor-α, and leptin decrease (14)C-l-Met uptake in a human TB (Bewo) cell line. The effect of leptin was dependent upon phosphoinositide 3-kinase, extracellular-signal-regulated kinase 1/2 (ERK/MEK 1/2), and p38 mitogen-activated protein kinase. In conclusion, GDM does not quantitatively alter (14)C-l-Met placental uptake, although it changes the nature of transporters involved in that process.

Folic acid uptake by the human syncytiotrophoblast is affected by gestational diabetes, hyperleptinemia, and TNF-α

BACKGROUND

The mechanisms whereby gestational diabetes mellitus (GDM) increases the risk of fetal overgrowth and development of metabolic diseases later in life are likely to involve changes in nutrient supply to the fetus. Hence, in this work, we hypothesize that GDM may affect folic acid (FA) supply to the placenta and fetus.

METHODS

We compared (3)H-FA uptake by human cytotrophoblasts isolated from normal pregnancies (normal trophoblasts; NTB cells) and GDM pregnancies (diabetic trophoblasts; DTB cells) and investigated the effect of GDM hallmarks on (3)H-FA uptake by BeWo cells.

RESULTS

(3)H-FA uptake by NTB and DTB cells was time dependent and acidic pH stimulated. When compared with NTB, (3)H-FA uptake by DTB cells was more sensitive to acidic pH changes and to 5-methyltetrahydrofolate and pemetrexed (PTX) inhibition, indicating a proportionally greater involvement of the proton-coupled folate transporter (PCFT). A 4-h exposure of BeWo cells to lipopolysaccharide (LPS, 1-10 μg/ml) or to high levels of tumor necrosis factor-α (TNF-α, 300 ng/l) significantly reduced (3)H-FA uptake. Moreover, hyperleptinemic conditions (100 ng/ml leptin) decreased (3)H-FA uptake by BeWo cells in a time-dependent manner when compared with normoleptinemic conditions (1 ng/ml leptin).

CONCLUSION

GDM modulates (3)H-FA uptake by the syncytiotrophoblast, and leptin as well as TNF-α downregulate it.

Folate transporter expression decreases in the human placenta throughout pregnancy and in pre-eclampsia

The transport of folate across the placenta involves a number of different receptors including folate receptor-alpha (FR-α), reduced folate carrier (RFC) and proton coupled folate transporter (PCFT). In addition there are a number of ATP-dependent transporters which have also recently been shown to be involved in folate transport; these include ABCB1, ABCC2 and BCRP (ABCG2). The aim of the current study was to characterise the placental mRNA and protein expression of these folate transporters throughout gestation and also to see if expression is altered in pre-eclampsia. Placental tissue was collected from women undergoing termination of pregnancy (TOP) and from women undergoing elective Caesarean section. To investigate mRNA expression quantitative real time PCR was used with gene specific oligonucleotide primers to FR-α, RFC, PCFT, ABCB1, ABCC2, BCRP and the reference gene YWHAZ. Protein expression was also characterised using immunohistochemistry of paraffin embedded placental tissue. Both protein and mRNA expression of all transporters examined decreased as the gestation progressed. Expression of FR-α and PCFT mRNA and protein were decreased in pre-eclampsia compared with normal term pregnancy. The higher levels of expression of FR-α, RFC, PCFT, ABCB1, ABCC2 and BCRP in early pregnancy indicate that these transporters may have an important role in the establishment and development of the placenta, with expression reducing in preparation for parturition. Reductions in FR-α and PCFT in pre-eclampsia may be a mechanism involved in the pathogenesis of pre-eclampsia by limiting placental folate uptake resulting in reduced levels of angiogenesis, cell proliferation and antioxidant protection.

The effects of human chorionic gonadotrophin, progesterone and oestradiol on trophoblast function

Remodelling of the uterine vasculature during the first trimester of human pregnancy requires invasion of trophoblast from the placenta into decidual spiral arterioles. The pregnancy-associated hormones human chorionic gonadotropin (hCG), progesterone (P(4)) and oestradiol (E(2)) are present at high concentrations at the maternal-fetal interface during the remodelling period and thus may contribute to the regulation of trophoblast movement. This study examined the effects of these hormones on trophoblast functions. HTR8/SVneo cells were treated with hCG (5-100mIU/mL), P(4) (20nM-20μM) or E(2) (0.07-734nM). hCG significantly stimulated migration and MMP-9 activity but did not affect cell numbers. P(4) significantly inhibited migration, MMP-2 and -9 activity and reduced cell numbers. E(2) had no effect on migration, MMP activity or cell numbers. We conclude that hCG and P(4), but not E(2), play direct roles in controlling trophoblast invasion, acting as positive and negative stimuli respectively to regulate trophoblast movement during vascular remodelling in early pregnancy.

Retrovirus-mediated multidrug resistance gene (MDR1) overexpression inhibits chemotherapy-induced toxicity of granulosa cells

OBJECTIVE

To protect granulosa cells from chemotherapy-induced toxicity by retrovirus-mediated multidrug resistance (MDR1) gene transfection.

DESIGN

Laboratory study.

SETTING

Academic research laboratory in a university hospital.

PATIENT(S)

None.

INTERVENTION(S)

KK15 immortalized murine granulosa cell line transiently transduced with sf91m3 retrovirus vector carrying MDR1 complementary DNA that encodes P-glycoprtoein (P-gp); transduced cells selected with colchicine and treated with doxorubicin or paclitaxel for 24-72 hours; expression and function of MDR1 and the messenger RNA (mRNA) expression of selected steroidogenesis enzymes evaluated by flow cytometry, cell viability assays, Western blot, and reverse-transcriptase polymerase chain reaction (RT-PCR).

MAIN OUTCOME MEASURE(S)

Viability of sf91m3-transduced KK15 cells after treatment with doxorubicin and paclitaxel.

RESULT(S)

The sf91m3-transduced KK15 demonstrated high expression of biologically active MDR1, as shown by flow cytometry analysis and immunoblotting using P-gp monoclonal antibody and Rhodamine 123 efflux assays. The sf91m3-transduced KK15 exhibited statistically significant resistance to toxicity of 10 μM paclitaxel. The MDR1-transduced KK15 cells were also protected from doxorubicin toxicity (10 nM to 2.5 μM), as shown by cell viability assay. Both flow cytometry and cell viability assays showed that the protection of KK15 from doxorubicin toxicity was lost at 5 μM of doxorubicin; equivalent to 500 times LD50. The sf91m3-transduced KK15 showed normal mRNA expression of a panel of selected steroidogenesis enzymes.

CONCLUSION(S)

Retroviral gene delivery of human MDR1 inhibited chemotherapy-induced granulosa cell toxicity and offered chemoprotection in an in vitro model.

Effect of polyphenols on the intestinal and placental transport of some bioactive compounds

Polyphenols are a group of widely distributed phytochemicals present in most foods of vegetable origin. A growing number of biological effects have been attributed to these molecules in the past few years and only recently has their interference with the transport capacity of epithelial barriers received attention. This review will present data obtained concerning the effect of polyphenols upon the transport of some compounds (organic cations, glucose and the vitamins thiamin and folic acid) at the intestinal and placental barriers. Important conclusions can be drawn: (i) different classes of polyphenols affect transport of these bioactive compounds at the intestinal epithelia and the placenta; (ii) different compounds belonging to the same phenolic family often possess opposite effects upon transport of a given molecule; (iii) the acute and chronic/short-term and long-term exposures to polyphenols do not produce parallel results and, therefore, care should be taken when extrapolating results; (iv) the effect of polyphenolics in combination may be very different from the expected ones taking into account the effect of each of these compounds alone, and so care should be taken when speculating on the effect of a drink based on the effect of one component only; (v) care should be taken in drawing conclusions for alcoholic beverages from results obtained with ethanol alone. Although most of the data reviewed in the present paper refer to in vitro experiments with cell-culture systems, these studies raise a concern about possible changes in the bioavailability of substrates upon concomitant ingestion of polyphenols.

cAMP efflux from human trophoblast cell lines: a role for multidrug resistance protein (MRP)1 transporter

Cyclic adenosine 3'-5'-monophosphate (cAMP) is a second messenger, which exerts an important role in the control of human first-trimester trophoblast functions. In the present study we demonstrate the existence of a mechanism that is able to extrude cAMP from trophoblast-derived cell lines, and show evidence indicating the involvement of multidrug resistance protein (MRP) 1, a transporter belonging to the ATP-binding cassette family, in cAMP egress. MRP1 is expressed in trophoblast cell lines and cAMP efflux is highly reduced by the MRP1 inhibitor, MK-571. In addition, interleukin-1beta and estrone are able to enhance MRP1 gene expression and influence extracellular cAMP concentration. The occurrence of a MRP1-dependent cAMP efflux is also shown in human first-trimester placenta explants. Extracellular cAMP could represent a source for adenosine formation, which in turn could regulate cAMP-dependent responses in placental tissue. Evidence is provided that adenosine receptor subtypes are present and functional in human trophoblast-derived cells. A role for cAMP egress mechanism in the fine modulation of the nucleotide homeostasis is therefore suggested.

Comparison of the transport characteristics of bioactive substances in IUGR and normal placentas

Knowing that IUGR is associated with altered placental transport, we aimed to characterize the placental transport of folic acid (FA), thiamine (THIAM), serotonin (5-HT), and 1-methyl-4-phenylpyridinium (MPP+) in IUGR. For this, we compared the transport characteristics of (3)H-FA, (3)H-THIAM, (3)H-5-HT, and (3)H-MPP+ in primary cultured human cytotrophoblasts isolated from IUGR and normal placentas (GRTB and NTB cells, respectively) and quantified mRNA expression of several placental transporters, by real-time RT-PCR. Our results show that GRTB cells take up (3)H-FA more efficiently (higher k(in) and A(max) values) and have higher transport capacity (higher V(max) values) for (3)H-FA, (3)H-5-HT, and (3)H-MPP+, when compared with NTB cells. In addition, GRTB cells take up (3)H-THIAM with higher affinity and (3)H-MPP+ with lower affinity than NTB cells. Finally, IUGR placentas have a generalized increase in mRNA expression of FA, THIAM, 5-HT, and MPP+ transporters, when compared with normal placentas, suggesting that the increase in transport capacity may be due to increased expression of placental transporters. These results point to an effect of "compensation for the weakness" of the IUGR placenta and pose the placenta as an active mediator of the communication between maternal and fetal environments.