Effects of valproic acid on the placental barrier in the pregnant mouse: Optical imaging and transporter expression studies

Maternal exposure to nano-titanium dioxide impedes fetal development via endothelial-to-mesenchymal transition in the placental labyrinth in mice

BACKGROUND

Extensive production and usage of commercially available products containing TiO2 NPs have led to accumulation in the human body. The deposition of TiO2 NPs has even been detected in the human placenta, which raises concerns regarding fetal health. Previous studies regarding developmental toxicity have frequently focused on TiO2 NPs < 50 nm, whereas the potential adverse effects of large-sized TiO2 NPs received less attention. Placental vasculature is essential for maternal-fetal circulatory exchange and ensuring fetal growth. This study explores the impacts of TiO2 NPs (100 nm in size) on the placenta and fetal development and elucidates the underlying mechanism from the perspective of placental vasculature. Pregnant C57BL/6 mice were exposed to TiO2 NPs by gavage at daily dosages of 10, 50, and 250 mg/kg from gestational day 0.5-16.5.

RESULTS

TiO2 NPs penetrated the placenta and accumulated in the fetal mice. The fetuses in the TiO2 NP-exposed groups exhibited a dose-dependent decrease in body weight and length, as well as in placental weight and diameter. In vivo imaging showed an impaired placental barrier, and pathological examinations revealed a disrupted vascular network of the labyrinth upon TiO2 NP exposure. We also found an increase in gene expression related to the transforming growth factor-β (TGF-β) -SNAIL pathway and the upregulation of mesenchymal markers, accompanied by a reduction in endothelial markers. In addition, TiO2 NPs enhanced the gene expression responsible for the endothelial-to-mesenchymal transition (EndMT) in cultured human umbilical vein endothelial cells, whereas SNAIL knockdown attenuated the induction of EndMT phenotypes.

CONCLUSION

Our study revealed that maternal exposure to 100 nm TiO2 NPs disrupts placental vascular development and fetal mice growth through aberrant activation of EndMT in the placental labyrinth. These data provide novel insight into the mechanisms of developmental toxicity posed by NPs.

Placental disposition of cannabidiol: An ex vivo perfusion study

OBJECTIVE

In the absence of safety data in humans, the use of cannabidiol (CBD) is not recommended during pregnancy. Yet >50% of pregnancies in women with epilepsy are unintended, making fetal exposure to CBD possible. As a small-molecule, highly lipid-soluble drug, CBD is likely to be distributed into the placenta and cross it. To estimate the placental distribution profile of CBD and its potential short-term placental effects, we conducted an ex vivo perfusion study in human placentas.

METHODS

Placentas were obtained from healthy women undergoing cesarean deliveries. Selected cotyledons were cannulated and perfused for 180 min with a CBD-containing medium (250 ng/mL, .796 μmol·L-1 ; representative of a low therapeutic concentration; n = 8). CBD concentrations were determined at 180 min in the medium and placental tissue using liquid chromatography-tandem mass spectrometry. A customized gene panel array was used to analyze the expression of selected genes in the perfused placental cotyledons as well as in placentas perfused with 1000 ng/mL CBD (3.18 μmol·L-1 ; high therapeutic concentration; n = 8) and in those exposed to the vehicle.

RESULTS

CBD was sequestered in the placental tissue, exhibiting significant variability across samples (median = 5342 ng/g tissue, range = 1066-9351 ng/g tissue). CBD concentrations in the fetal compartment were one fifth of those measured in the maternal compartment (median = 59 ng/mL, range = 48-72 ng/mL vs. 280 = ng/mL, range = 159-388 ng/mL, respectively; p < .01). Placental gene expression was not significantly altered by CBD.

SIGNIFICANCE

The placenta acts as a depot compartment for CBD, slowing down its distribution to the fetus. This phenomenon might yield flatter but prolonged fetal CBD levels in vivo. The attenuated transplacental CBD transfer does not imply that its use by pregnant women is safe for the fetus. Only pregnancy registries and neurocognitive assessments would establish the risk of being antenatally exposed to CBD.

Lacosamide effects on placental carriers of essential compounds in comparison with valproate: Studies in perfused human placentas

OBJECTIVE

Lacosamide is increasingly being prescribed to pregnant women, although its effects on the developing fetus have not been fully clarified yet. Previously, we have shown that several antiseizure medications, particularly valproate, can affect the expression of carriers of essential compounds in placental cells. Here, our aim was to assess the effect of short ex vivo exposure of human placentas to lacosamide on the expression of carriers of essential nutrients required by the human fetus.

METHODS

Placentas were obtained from cesarean deliveries of women with no known epilepsy. Cotyledons were cannulated and perfused over 180 min in the presence of lacosamide at 2.5 μg/ml (10 μmol·L^-1 , n = 7) or 10 μg/ml (40 μmol·L^-1 , n = 6), representing low and high therapeutic concentrations, respectively, in the maternal perfusate. Valproate (83 μg/ml, 500 μmol·L^-1 , n = 6) and the perfusion solution (n = 6) were used as the respective positive and negative controls. A customized gene panel array was used to analyze the expression of carrier genes in the perfused cotyledons.

RESULTS

Following a 3-h perfusion, the mRNA expression of SLC19A1 (encoding the reduced folate carrier 1) was downregulated in placentas treated with 10 μg/ml lacosamide (50%) as compared with the vehicle (p < .05). Across all groups, a significant difference was observed in the expression of SLC19A3 (thiamine transporter 2; 52%, 20%, and 9% decrease by 10 μg/ml lacosamide, 83 μg/ml valproate, and 2.5 μg/ml lacosamide, respectively; p < .05).

SIGNIFICANCE

Lacosamide at high therapeutic concentrations exerted pharmacological effects on the human placenta. Our findings, if manifested in vivo, suggest that lacosamide could potentially affect folate supply to the fetus and support therapeutic monitoring and careful adjustment of lacosamide plasma concentrations during pregnancy.

Valproate Targets Mammalian Gastrulation Impairing Neural Tissue Differentiation and Development of the Placental Source In Vitro

The teratogenic activity of valproate (VPA), an antiepileptic and an inhibitor of histone deacetylase (HDACi), is dose-dependent in humans. Previous results showed that VPA impairs in vitro development and neural differentiation of the gastrulating embryo proper. We aimed to investigate the impact of a lower VPA dose in vitro and whether this effect is retained in transplants in vivo. Rat embryos proper (E9.5) and ectoplacental cones were separately cultivated at the air-liquid interface with or without 1 mM VPA. Embryos were additionally cultivated with HDACi Trichostatin A (TSA), while some cultures were syngeneically transplanted under the kidney capsule for 14 days. Embryos were subjected to routine histology, immunohistochemistry, Western blotting and pyrosequencing. The overall growth of VPA-treated embryos in vitro was significantly impaired. However, no differences in the apoptosis or proliferation index were found. Incidence of the neural tissue was lower in VPA-treated embryos than in controls. TSA also impaired growth and neural differentiation in vitro. VPA-treated embryos and their subsequent transplants expressed a marker of undifferentiated neural cells compared to controls where neural differentiation markers were expressed. VPA increased the acetylation of histones. Our results point to gastrulation as a sensitive period for neurodevelopmental impairment caused by VPA.

Folic Acid and Risk of Preterm Birth, Preeclampsia, and Fetal Growth Restriction Among Women With Epilepsy: A Prospective Cohort Study

BACKGROUND AND OBJECTIVES

Women with epilepsy treated with antiseizure medication (ASM) have increased risk of pregnancy complications including preterm birth, fetal growth restriction, and preeclampsia. We aimed to investigate whether folic acid supplementation is associated with these pregnancy complications in women with epilepsy using ASM.

METHODS

Singleton pregnancies in the prospective Norwegian Mother and Child Cohort Study (MoBa) (1999-2008) were included. Information on maternal epilepsy, ASM, folic acid supplementation, and pregnancy outcomes was obtained from the MoBa questionnaires and the Norwegian Medical Birth Registry. The main exposure, periconceptional folic acid supplementation, was defined as intake between 4 weeks before pregnancy and 12 weeks into pregnancy, retrospectively collected by recall of the mothers in weeks 17-19. The primary outcomes were preterm birth (gestational age <37 weeks at birth), small for gestational age (SGA), and preeclampsia.

RESULTS

The study included 100,105 pregnancies: 99,431 without maternal epilepsy, 316 with maternal epilepsy and ASM exposure in pregnancy, and 358 with untreated maternal epilepsy. Among ASM-treated women with epilepsy, the risk of preterm birth was higher in those who did not use periconceptional folic acid (n = 64) compared with those who did (n = 245, the reference) (adjusted odds ratio [aOR] 3.3, 95% CI 1.2-9.2), while the risk of preterm birth among the reference was similar to the risk among women without epilepsy using folic acid periconceptionally (aOR 0.9, 95% CI 0.5-1.6). ASM-treated women with epilepsy starting folic acid after the first trimester had a higher risk compared with women without epilepsy with similar timing of folic acid (aOR 2.6, 95% CI 1.1-6.5), and even higher if not using folic acid (aOR 9.4, 95% CI 2.6-34.8). Folic acid was not associated with risk of preterm birth among women with epilepsy without ASM or among women without epilepsy. Folic acid was not associated with risk of preeclampsia or SGA among women with epilepsy.

DISCUSSION

In women with epilepsy using ASM, periconceptional folic acid was associated with a lower risk of preterm birth. This finding supports the recommendation that ASM-treated women with epilepsy of childbearing potential should use folic acid supplementation on a regular basis.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that for women with epilepsy using ASM, periconceptional folic acid supplementation decreases the risk of preterm birth.

Effect of levetiracetam on the gene expression of placental transporters in a murine model

OBJECTIVE

Levetiracetam (LEV) is an antiseizure medication prescribed to women during childbearing age. The impact of LEV on placental transporters is poorly understood. This study aimed to assess the effect of LEV exposure on the messenger RNA (mRNA) expression of placental transporters for hormones and nutrients and to correlate their expression with the drug's serum concentration in pregnant mice.

METHODS

Studies were conducted on gestational days (GD) 13 and 18, following oral treatment with 100 mg/kg LEV or the vehicle every 24 h after weaning. Serum LEV measurements were performed by High-performance liquid chromatography with a UV detector (HPLC-UV). The weight, height, and width of the fetuses were also analyzed. In addition, the placental expression of transporters xCt, Lat1, Oatp4a1, Fr-α, Rfc, and Snat4 was evaluated through semi-quantitative real-time polymerase chain reaction (qPCR). The Kruskal-Wallis and the Mann-Whitney U tests were used to determine the statistical significance (p < .05). The correlation between serum LEV concentration and placental gene expression was evaluated using the Spearman test.

RESULTS

The weight, height, and width were lower in the fetuses exposed to LEV compared with the control group (p < .05). The number of fetuses was lower in the LEV-exposed group than in the control GD 13 group (p < .001). No significant differences were detected in the mRNA expression level at GD 13. At GD 18, the expression of Lat1, Oatp4a1, xCT, and Snat4 was higher in the group treated with LEV compared with the control group (p < .05), whereas the expression of Rfc was lower (p < .05). No correlation was identified between serum LEV concentrations and gene expression levels.

SIGNIFICANCE

The repression of the Rfc transcript by LEV at GD 18 suggests that the protein expression would be abolished contributing to the observed intrauterine growth restriction (IUGR). Furthermore, the significant increase in mRNA of xCt, Snat4, Oatp4a1, and Lat1 might be a compensatory mechanism for fetal survival at GD 18.

Transcriptomics and Other Omics Approaches to Investigate Effects of Xenobiotics on the Placenta

The conceptus is most vulnerable to developmental perturbation during its early stages when the events that create functional organ systems are being launched. As the placenta is in direct contact with maternal tissues, it readily encounters any xenobiotics in her bloodstream. Besides serving as a conduit for solutes and waste, the placenta possesses a tightly regulated endocrine system that is, of itself, vulnerable to pharmaceutical agents, endocrine disrupting chemicals (EDCs), and other environmental toxicants. To determine whether extrinsic factors affect placental function, transcriptomics and other omics approaches have become more widely used. In casting a wide net with such approaches, they have provided mechanistic insights into placental physiological and pathological responses and how placental responses may impact the fetus, especially the developing brain through the placenta-brain axis. This review will discuss how such omics technologies have been utilized to understand effects of EDCs, including the widely prevalent plasticizers bisphenol A (BPA), bisphenol S (BPS), and phthalates, other environmental toxicants, pharmaceutical agents, maternal smoking, and air pollution on placental gene expression, DNA methylation, and metabolomic profiles. It is also increasingly becoming clear that miRNA (miR) are important epigenetic regulators of placental function. Thus, the evidence to date that xenobiotics affect placental miR expression patterns will also be explored. Such omics approaches with mouse and human placenta will assuredly provide key biomarkers that may be used as barometers of exposure and can be targeted by early mitigation approaches to prevent later diseases, in particular neurobehavioral disorders, originating due to placental dysfunction.

Maternal-fetal transfer of indocyanine green: a systematic review

RATIONAL

In a survey of 1101 members of vitreoretinal trained physicians regarding the use of ICG angiography during pregnancy, 434 (83%) of 520 respondents had seen at least one pregnant woman requiring ICG angiography or fluorescein angiography. One hundred and five (24%) withheld ICG angiography, mostly because of fear of teratogenicity or lawsuit. Adverse reactions to fluorescein and ICG are rare and may be classified as toxic, hypersensitivity, and non-specific. This literature review aimed to review evaluate the maternal-to-fetal transfer of ICG and resume the most recent recommendations for ICG use in its obstetric applications.

METHODS

The available literature was examined using PubMed-Medline, and web of science, and using the MeSH terms "fluorescein," "Indocyanine green," and "pregnancy" according to PRISMA-P guidelines.

RESULTS

Studies in humans demonstrated that ICG is not detectable in fetal cord blood or umbilical vein blood collected immediately after birth. ICG maternal-to-fetal transfer is slow and is safe during pregnancy. ICG in the fetus accumulates in the liver and accumulation is enhanced by the administration of OATPs or P-gp inhibitors.

CONCLUSIONS

ICG's transplacental transfer is minimal and is probably medicine-mediated, like rifampin. The placenta is an effective protective barrier to ICG's distribution into the fetus.

Effects of antiseizure medications on placental cells: Focus on heterodimeric placental carriers

OBJECTIVE

Appropriate placental nutrient transfer is essential for optimal fetal development. We have previously shown that antiseizure medications (ASMs) can alter the expression of placental carriers for folate and thyroid hormones. Here we extended our analysis to heterodimeric carriers that mediate the placental uptake of amino acids and antioxidant precursors. We focused on the L-type amino acid transporter (LAT)2/SLC7A8, the cystine/glutamate antiporter xCT/SLC7A11, and their chaperone 4F2hc/SLC3A2.

METHODS

BeWo cells were exposed for two or five days to therapeutic concentrations of valproate, levetiracetam, carbamazepine, lamotrigine, or lacosamide. Transcript levels were measured by quantitative PCR. Levetiracetam effects on placental carriers were further explored using a tailored gene array.

RESULTS

At five days, 30 μg/mL levetiracetam (high therapeutic concentrations) significantly reduced the expression of all studied genes (p < 0.05). Carbamazepine treatment was associated with lower SLC7A8 (LAT2) expression (p < 0.05), whereas valproate increased the transcript levels of this transporter by up to 2.0-fold (p < 0.01). Some of these effects were already observed after two incubation days. Lamotrigine did not alter gene expression, and lacosamide slightly elevated SLC3A2 levels (p < 0.05). The array analysis confirmed the trends observed for levetiracetam and identified additional affected genes.

SIGNIFICANCE

Altered expression of placental heterodimeric transporters may represent a mechanism by which ASM affect fetal development. The placental effects are differential, with valproate, carbamazepine and levetiracetam as the more active compounds. The concentration-dependence of those ASM effects are in line with established dose-dependent teratogenicity implying that ASM doses should be adjusted during pregnancy with caution.

Antiseizure medications and fetal nutrients: Effects on choline transporters in a human placental cell line

OBJECTIVE

Many nutrients essential to the fetus and for proper function of the placenta itself cannot freely diffuse across membrane barriers, and their transplacental transfer depends on transporters. Our previous studies provided evidence for altered expression of transporters for folic acid in trophoblasts exposed to antiseizure medications (ASMs). The goal of the current study was to explore the effects of older and newer ASMs on the expression and function of uptake transporters for choline, which interacts with folate at pathways for methyl group donation.

METHODS

BeWo cells were incubated for 2 or 5 days with valproate (42, 83, or 166 µg/ml), carbamazepine (6 or 12 µg/ml), levetiracetam (10 or 30 µg/ml), lamotrigine (3 or 12 µg/ml), lacosamide (5, 10, or 20 µg/ml), or their vehicles (n = 6/treatment group). Quantitative polymerase chain reaction (PCR) analysis was utilized to study the effects of ASMs on the transcript levels of the choline transporters SLC44A1 (CTL1) and SLC44A2 (CTL2). Transporter protein expression in valproate-treated cells was assessed by western blot analysis. Choline and acetylcholine were quantified in cell lysates by a choline/acetylcholine assay kit.

RESULTS

Compared with controls, valproate and levetiracetam at high therapeutic concentrations (83 and 30 µg/ml, respectively) lowered choline transporter transcript levels by up to 42% and 26%, and total choline levels by 20% and 21%, respectively (p < .05). At 83 μg/ml, valproate additionally reduced CTL1 and CTL2 protein expression, by 39 ± 21% and 61 ± 13% (mean ± SD), respectively (p < .01). Carbamazepine reduced SLC44A1 transcript levels, whereas lacosamide modestly decreased the expression of SLC44A2. Lamotrigine did not alter choline transporter expression.

SIGNIFICANCE

Antiseizure medications, particularly at high therapeutic concentrations, can interfere with the placental uptake of choline. In line with current knowledge from pregnancy registries and clinical studies, the present in vitro findings further support careful adjustment of maternal ASM doses during pregnancy.

Effects of single and repetitive valproic acid administration on the gene expression of placental transporters in pregnant rats: An analysis by gestational period

The use of valproic acid (VPA), an antiepileptic drug, during pregnancy, is known to increase various fetal risks. Since VPA has been known to inhibit histone deacetylases (HDACs); its administration could alter gene transcription levels. However, in vivo effects of VPA administration on placental transporters have not been fully elucidated. The purpose of the present study was to comprehensively evaluate the effects of single and repetitive VPA administration on the expression of placental transporters and analyze them by gestational day. We investigated 18 transporters (8 ATP-binding cassette (ABC) and 10 solute carrier (SLC) transporters) in the placentas of pregnant rats that were orally administered 400 mg/kg/day VPA for one or four days, during mid- or late gestation. In the control rats, 4 ABC transporter genes (Abcb1a, 1b, Abcc2, Abcc4) were upregulated, 3 (Abcc3, Abcc5, Abcg2) downregulated through gestation, whereas 1 (Abcc1) was not changed. Regarding SLC transporters, 6 genes (Slc7a5, Slc16a3, Slc22a3, Slc22a4, Slco2b1, Slco4a1) were increased, 1 (Slc29a1) decreased through gestation, whereas 3 (Slc7a8, Slc22a5, Slco2a1) showed no significant change. Single VPA administration altered the expression of 9 transporters and repetitive administration, 13 transporters. In particular, VPA remarkably decreased Abcc4 and Slc22a4 in late gestation and increased Abcc5 during mid-gestation. Our findings indicated that VPA administration changed transporter expression levels in rat placenta, and suggested that sensitivity to VPA differs across gestational stages.

Effects of Valproic Acid on Cerebral Nutrient Carriers' Expression in the Rat

Objective: The antiepileptic drug valproate has been shown to affect the expression of carriers for essential compounds and drugs in extracerebral tissues. The aim of the current study was to evaluate in vivo the effect of valproate treatment on the cerebral expression of carriers and selected genes of the blood-brain barrier (BBB) in the rat.

Methods: Male Wistar rats were treated daily for 7 days by intraperitoneal injections of valproate (75, 150, or 300 mg/kg/day) or the vehicle. mRNA was isolated from the cerebral cortex and the hippocampus. Transcript levels of 37 genes were measured using a customized gene expression assay. Quantitative histone acetylation was evaluated by western blotting. Glucose6-phosphate (G6P) tissue levels were used as a surrogate of cerebral glucose concentrations.

Results: Valproate treatment was associated with significant reduction (up to 22%; P < 0.05) in cortical and hippocampal claudin 5-normalized Slc2a1 (Glut1) mRNA expression. G6P levels were not significantly altered, but were correlated with Slc2a1 transcript levels (r = 0.499; P < 0.02). None of the other 36 screened genes were significantly affected by valproate. Cortical histone hyperacetylation indicated cerebral activity of valproate on a major pathway regulating gene expression (P < 0.02).

Significance: The effect of valproate on nutrient carriers appears to be tissue-specific and even brain area-specific. If validated in humans, the changes in Glut1 expression might have clinical implications in positron emission tomography (PET) imaging. Further studies are required for elucidating the relevance of these findings to the clinic.

Adverse placental effects of valproic acid: Studies in perfused human placentas

OBJECTIVE

In utero exposure to valproic acid (VPA) has been associated with worse pregnancy outcomes compared to all other antiepileptic drugs. We have previously shown that VPA alters the expression of placental transporters for hormones and nutrients in vitro and in pregnant mice. Here, our aim was to characterize the effects of short exposure to VPA on the expression of carriers for compounds essential for fetal development in human placentas ex vivo, under controlled conditions.

METHODS

Placentas were obtained from cesarean deliveries of women with no known epilepsy. Cotyledons were cannulated and perfused in the absence or the presence of VPA (42, 83, or 166 μg/mL; n = 6/group) in the maternal perfusate over 180 minutes. A customized gene panel array was used to analyze the expression of carrier genes in the perfused cotyledons. We additionally measured in the perfused placentas folic acid concentrations and histone acetylation.

RESULTS

VPA significantly altered the mRNA levels of major carriers for folic acid, glucose, choline, thyroid hormones, and serotonin (P < .05) and reduced placental folate concentrations by 25%-35% (P = .059). The effects were observed at therapeutic concentrations sufficient to enhance placental histone acetylation, and some were concentration-dependent.

SIGNIFICANCE

Our results point to the placenta as a novel target of VPA, implying potential involvement of the placenta in VPA's adverse fetal outcomes.