Transplacental passage of lamotrigine in a human placental perfusion system in vitro and in maternal and cord blood in vivo

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.

Transfer of anticonvulsants and lithium into amniotic fluid, umbilical cord blood & breast milk: A systematic review & combined analysis

OBJECTIVE

Data on the ability of anticonvulsants and lithium to enter fetal and newborn circulation has become increasingly available; here we estimated penetration ratios in a series of matrices from combined samples of pregnant/breastfeeding women treated with anticonvulsants or lithium.

METHODS

We conducted a systematic literature search in PubMed/EMBASE for studies with concentrations of anticonvulsants/lithium from maternal blood, amniotic fluid, umbilical cord blood and/or breast milk. Penetration ratios were calculated by dividing the concentrations in amniotic fluid, umbilical cord plasma or breast milk by the maternal concentrations. When data from multiple studies were available, we calculated combined penetration ratios, weighting studies' mean by study size.

RESULTS

Ninety-one eligible studies for brivaracetam, carbamazepine, clonazepam, ethosuximide, gabapentin, lacosamide, lamotrigine, levetiracetam, lithium, oxcarbazepine, perampanel, phenobarbital, phenytoin, pregabalin, primidone, topiramate, valproate, vigabatrin and zonisamide were identified. For amniotic fluid, the highest penetration ratios were estimated for levetiracetam (mean 3.56, range 1.27-5.85, n = 2) and lowest for valproate (mean 0.11, range 0.02-1.02, n = 57). For umbilical cord plasma, oxcarbazepine had the highest ratio (mean 1.59, range 0.11-4.33, n = 12) with clonazepam having the lowest (mean 0.55, range 0.52-0.59, n = 2). For breast milk, the highest ratios were observed for oxcarbazepine (mean 3.75, range 0.5-7.0, n = 2), whereas the lowest were observed for valproate (mean 0.04, range 0.01-0.22, n = 121).

DISCUSSION

We observed substantial variability between anticonvulsants and lithium regarding their ability to enter fetal/newborn circulation. Assessing concentrations of anticonvulsants and lithium in maternal samples can provide a surrogate of fetal/infant exposure, although patterns of concentration-dependent effects for maternal/neonatal safety are lacking.

A review of ex vivo placental perfusion models: an underutilized but promising method to study maternal-fetal interactions

Studying the placenta can provide information about the mechanistic pathways of pregnancy disease. However, analyzing placental tissues and manipulating placental function in real-time during pregnancy is not feasible. The ex vivo placental perfusion model allows observing important aspects of the physiology and pathology of the placenta, while maintaining its viability and functional integrity, and without causing harm to mother or fetus. In this review, we describe and compare setups for this technically complex model and summarize outcomes from various published studies. We hope that our review will encourage wider use of ex vivo placental perfusion, which in turn would generate more knowledge to improve pregnancy outcomes.

Monitoring of lamotrigine concentrations in mothers, colostrum, and breastfed newborns during the early postpartum period

OBJECTIVE

To analyse the concentrations of lamotrigine in maternal serum, colostrum, and serum of breastfed newborns, and to evaluate the effect of comedication with enzyme-inducing antiseizure medication and valproic acid.

METHODS

This cohort study collected data from 158 women and 143 breastfed newborns. Maternal serum, milk (i.e., colostrum), and newborn serum samples were collected between the 2nd and 5th postnatal days, and lamotrigine concentrations were measured by high-performance liquid chromatography.

RESULTS

The median lamotrigine concentrations were 2.7 mg/L in maternal serum, 1.4 mg/L in milk, and 1.7 mg/L in newborn serum. The median milk/maternal serum concentration ratio was 0.60, the median newborn/maternal serum concentration ratio was also 0.60, and the median newborn serum/milk concentration ratio was 1.00. A significant correlation was observed between milk and maternal serum concentrations and between newborn serum and milk concentrations, maternal serum concentrations, maternal daily dose, and dose related to maternal body weight.

CONCLUSIONS

Exposure to lamotrigine in breastfed newborns is lower than exposure during pregnancy. However, by the same dose by the same mother, lamotrigine concentrations in both maternal serum and milk increase significantly after delivery. This finding, together with the immature function of eliminating enzymes in newborns, may be the reason for reaching concentrations in the reference range used for the general epileptic population in breastfed newborns. Therapeutic monitoring of breastfed newborns serum concentrations of lamotrigine is not mandatory; however, if signs of possible adverse events are noted, newborn serum concentrations should be analysed.

Therapeutic concentration of ciprofloxacin and transfer across the human term placenta

BACKGROUND

Pregnant women have an increased risk of infections, and early and decisive treatment is preferred to prevent complications. Although ciprofloxacin is very commonly used, safety aspects of maternal treatment during pregnancy are limited, and avoidance of its use during late pregnancy is recommended.

OBJECTIVE

The aim is to estimate maternal-to-fetal transfer clearance of ciprofloxacin at a therapeutic concentration and to determine fetal exposure to maternally administered ciprofloxacin.

STUDY DESIGN

Transplacental pharmacokinetics were determined with an ex vivo placental model, which is a reliable experimental model for estimating fetal drug exposure. Human placentas from uncomplicated term pregnancies were collected after delivery and a suitable cotyledon was cannulated. Ciprofloxacin was added at a therapeutic concentration (1.6 μg/mL) to the maternal compartment, and antipyrine was included as a reference drug (10.0 μg/mL). Samples were collected from the maternal and fetal compartment at 12 time points (-2 to 180 minutes), and the integrity and metabolic parameters were measured consecutively. Drug concentrations were determined using ultra-performance liquid chromatography-tandem mass spectrometry.

RESULTS

A total of 5 human placentas from healthy term pregnancies were collected after delivery and cannulated with success. Ciprofloxacin crossed the placenta; its mean concentration in the fetal compartment was 0.3 μg/mL, accounting for 22% (0.29/1.30; range, 15%-31%) of the maternal concentration after 3 hours. The fetal/maternal ciprofloxacin concentration ratio increased gradually over time and reached 0.53. The transfer clearance for ciprofloxacin was 0.28 mL/min (range, 0.21-0.41 mL/min) during the first hour and 0.21 mL/min (range, 0.14-0.26 mL/min) during the following 2 hours. After end perfusion, the mean tissue concentration and proportion of ciprofloxacin were 0.7 μg/g and 11% (14/130; range, 7%-14%), respectively.

CONCLUSION

Ciprofloxacin crossed the placenta at a slow, constant rate, indicating moderate fetal exposure. This study verifies an accumulation of ciprofloxacin in the placenta that may lengthen the duration of fetal exposure. These results are an essential element of fetal risk assessment, but further studies are needed to estimate fetal safety.

Cellular uptake properties of lamotrigine in human placental cell lines: Investigation of involvement of organic cation transporters (SLC22A1-5)

Lamotrigine (LTG) is an important antiepileptic drug for the treatment of seizures in pregnant women with epilepsy. However, it is not known if the transport of LTG into placental cells occurs via a carrier-mediated pathway. The aim of this study was to investigate the uptake properties of LTG into placental cell lines (BeWo and JEG-3), and to determine the involvement of organic cation transporters (OCTs, SLC22A1-3) and organic cation/carnitine transporter (OCTNs, SLC22A4-5) in the uptake process. The uptake of LTG at 37 °C was higher than that at 4 °C. OCT1 and OCTNs were detected in both cell lines. The uptake of LTG was not greatly affected by the extracellular pH, Na⁺-free conditions, or the presence of l-carnitine, suggesting that OCTNs were not involved. Although several potent inhibitors of OCTs (chloroquine, imipramine, quinidine, and verapamil) inhibited LTG uptake, other typical inhibitors had no effect. In addition, siRNA targeted to OCT1 had no significant effect on LTG uptake. The mRNA expression in human term placenta followed the order OCTN2 > OCT3 > OCTN1 > OCT1 ≈ OCT2. These observations suggested that LTG uptake into placental cells was carrier-mediated, but that OCTs and OCTNs were not responsible for the placental transport process.

Drug transport across the human placenta: review of placenta-on-a-chip and previous approaches

In the past few decades, the placenta became a very controversial topic that has had many researchers and pharmacists discussing the significance of the effects of pharmaceutical drug intake and how it is a possible leading cause towards birth defects. The creation of an in vitro microengineered model of the placenta can be used to replicate the interactions between the mother and fetus, specifically pharmaceutical drug intake reactions. As the field of nanotechnology significantly continues growing, nanotechnology will become more apparent in the study of medicine and other scientific disciplines, specifically microengineering applications. This review is based on past and current research that compares the feasibility and testing of the placenta-on-a-chip microengineered model to the previous and underdeveloped in vivo and ex vivo approaches. The testing of the practicality and effectiveness of the in vitro, in vivo and ex vivo models requires the experimentation of prominent pharmaceutical drugs that most mothers consume during pregnancy. In this case, these drugs need to be studied and tested more often. However, there are challenges associated with the in vitro, in vivo and ex vivo processes when developing a practical placental model, which are discussed in further detail.

Congener-Specific Mother-Fetus Distribution, Placental Retention, and Transport of C10-13 and C14-17 Chlorinated Paraffins in Pregnant Women

Short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) are high-production-volume persistent and toxic industrial chemicals found ubiquitously in various environmental matrices. However, information is scarce regarding human internal exposure. The congener-specific SCCP and MCCP levels in matched maternal serum (n = 31), umbilical cord serum (n = 31), and placenta (n = 31) were studied to investigate the maternal-placenta-fetus distribution and the placental transport mechanisms of SCCPs and MCCPs. The results indicated that lower chlorinated and shorter carbon chain CPs were efficiently transported across placenta compared to highly chlorinated and longer carbon chain CPs. Meanwhile, ∑MCCP concentration followed the order of maternal sera > placentas > cord sera. The cord/maternal concentration fraction ratios (R_CM) of CPs exhibited similar values from C₁₀ to C₁₄, and then from C₁₅, a decreasing trend was observed with increasing carbon chain length. The log-normalized maternal SCCP concentrations were positively correlated (P < 0.01) with that in the cord, suggesting fetus exposure to SCCPs during pregnancy. Furthermore, the placenta/maternal concentration fraction ratio (R_PM) values for MCCPs were relatively higher than those for SCCPs, demonstrating that MCCPs were not efficiently transported and effectively retained in placenta tissues. These findings provide a better understanding of the maternal-fetal transmission and neonatal exposure to CPs.

Transplacental transfer and metabolism of diuron in human placenta

Diuron is a broad-spectrum phenylurea derived herbicide which is commonly used across the globe. Diuron is toxic to the reproductive system of animals and carcinogenic to rat urothelium, and recently found to be genotoxic in human cells. In in vivo, it is metabolized predominately into 3-(3,4-dichlorophenyl)-1-methyl urea (DCPMU) in humans and 3-(3, 4-dichlorophenyl)urea (DCPU) in animals. Information on diuron toxicokinetics and related toxicity in human placenta is absent. We have investigated the toxicokinetics of diuron in ex vivo human placental perfusion and in in vitro human placental microsomes and human trophoblastic cancer cells (BeWo). Diuron crossed human placenta readily in placental perfusion. Furthermore, diuron was metabolized into DCPMU in perfused placenta and in in vitro incubations using microsomes from placentas of smokers. In incubations with placental microsomes from non-smokers, and in BeWo cells, metabolism to DCPMU was detected but only with the highest used diuron concentration (100 μM). Diuron metabolism was inhibited upon addition of α-naphthoflavone, a CYP1A1 inhibitor, underscoring the role of CYP1A1 in the metabolism. In conclusion, it is evident that diuron crosses human placenta and diuron can be metabolized in the placenta to a toxic metabolite via CYP1A1. This implicates in vivo fetal exposure to diuron if pregnant women are exposed to diuron, which may result in fetotoxicity.

Soluble ST2, a preeclampsia-related cytokine receptor, is transported bi-directionally across the placenta

INTRODUCTION

We aimed to elucidate whether soluble ST2 (sST2), a preeclampsia (PE)-related cytokine, in the maternal or fetal circulation could be transported to the other circulatory system across the placenta.

METHODS

A placental perfusion model in a closed system was established and optimized. HPLC was performed to determine the dynamics of antipyrine levels in the perfusate. Placentas (n = 18) collected from healthy controls and PE patients were perfused without additional treatment or with added sST2 in the maternal or fetal circulation. The concentration of sST2 in the perfusate samples was quantified by ELISA.

RESULTS

Monitoring of the antipyrine levels were used as a quality control and showed each placenta established successfully. In the untreated group, sST2 could be produced by the placenta and enter into both the maternal and fetal circulations, and significantly higher levels were detected in the maternal circulation. In placentas perfused with additional sST2 in the maternal circulation, a similar trend was observed as for the untreated placentas. When sST2 was added to the fetal circulation, increased sST2 was detected in the maternal circulation. Compared with the healthy controls, significantly elevated sST2 in the maternal side of PE patients were detected.

CONCLUSION

Soluble ST2 could be bi-directionally transported across placentas. It was an active process that maintained a higher level of sST2 in the maternal circulation. Furthermore, the significant increase of sST2 in the maternal blood of PE patients was due to an impaired placental barrier as a result of PE.

Isomer-Specific Transplacental Transfer of Perfluoroalkyl Acids: Results from a Survey of Paired Maternal, Cord Sera, and Placentas

Currently, information regarding isomer-specific concentrations of PFHxS, PFOS, and PFOA in human placenta, and corresponding placental-maternal ratios (R_PM) of these compounds does not exist. The objective of the present study was to assess the occurrence, and distribution of different PFHxS, PFOS, and PFOA isomers in maternal serum, umbilical cord serum, and placenta to gain a better understanding of transplacental transport efficiency and prenatal exposure risks. The study involved quantitative determination of isomer-specific concentrations of PFHxS, PFOS, and PFOA in samples of maternal serum (n = 32), cord serum (n = 32), and placenta (n = 32) from pregnant women in Wuhan, China. The results indicate that both linear and branched PFHxS, PFOS and PFOA can be efficiently transported across the placenta, with exposure levels ordered maternal serum > cord serum > placenta. For PFOS isomers, the concentration ratios between cord serum and maternal serum (R_CM) were ordered n < iso < 4m < (3 + 5)m < 1m < ∑m₂. The R_PM values exhibited a similar trend for branched PFOS isomers: iso < 4m ≈ (3 + 5)m < 1m ≈ ∑m₂. Conversely, PFOA isomers did not exhibit an obvious structure-activity relationship for R_CM and R_PM. n-PFHxS transported across the placenta to a greater extent than br-PFHxS. To the best of our knowledge, this is the first study to report the occurrence of PFHxS, PFOS, and PFOA isomers in human placenta. Further, R_PM values of these compounds are reported here for the first time. The findings help to better understand the mechanisms of the placental transfer and neonatal exposure to these important contaminants of concern.

Transplacental transfer of 2-naphthol in human placenta

Objective

To determine the transfer of 2-naphthol (2-NPH) in fullterm human placental tissues.

Methods

Six placentas were studied. The ex-vivo dual closed-loop human placental cotyledon perfusion model was used. 2-NPH was added to the perfusate in the maternal compartment. Samples were obtained from the maternal and fetal up to 360 min measuring.

Results

The mean fetal weight was 2880 ± 304.2 g. Mean perfused cotyledon weight was 26.3 (±5.5) g. All unperfused placental tissue samples contained NPH with a mean level of 7.98 (±1.73) μg\g compared to a mean of 15.58 (±4.53) μg\g after 360 min perfusion. A rapid drop in maternal 2-NPH concentration was observed; from 5.54 μg\g in the first 15 min and 13.8 μg\g in 360 min. The fetal side increased from 0.65 μg\g in the initial 15 min to 1.5 μg\g in 360 min. The transfer rate of NPH was much lower than that of antipyrine.

Conclusion

2-NPH has the ability to rapidly across the placenta from the maternal to the fetal compartment within 15 min. The placenta seems to play a role in limiting the passage of 2-NPH in the fetal compartment.

Lamotrigine dosing for pregnant patients with bipolar disorder

OBJECTIVE

Little information is available on the need for dosage changes for lamotrigine in pregnant women with bipolar disorder. The authors present new data on serial serum levels of lamotrigine in pregnant patients on lamotrigine monotherapy. They also review the epilepsy literature on use of lamotrigine during pregnancy.

METHOD

Lamotrigine serum samples were obtained from eight mother-infant pairs at different time points during pregnancy and the postpartum period.

RESULTS

All of the women were taking lamotrigine throughout pregnancy. Serum-level-to-dose ratios were lower during pregnancy than the postpartum period. Lamotrigine was taken once daily in doses ranging from 100 mg to 300 mg. Three patients had an increase of 50 mg to their daily dose across pregnancy. The change in serum lamotrigine levels in the postpartum period ranged from a 30% decrease to a 640% increase compared with the first level obtained during pregnancy. Level-to-dose ratios obtained within 4 weeks after delivery reflected a mean level 402% greater than the baseline level during gestation. Compared with the third trimester, lamotrigine serum concentration increased an average of 154% within 5 weeks after delivery. The most dramatic increase in lamotrigine serum level early after delivery occurred at 1.5 weeks. The mean infant cord level was 66% of the maternal serum level at delivery. The mean breast-fed infant serum level was 32.5% of the maternal serum levels.

CONCLUSIONS

The pattern of lamotrigine changes during pregnancy in these women with bipolar disorder was consistent with that described in the epilepsy literature.

Pharmacotherapy in pregnancy; effect of ABC and SLC transporters on drug transport across the placenta and fetal drug exposure

Pharmacotherapy during pregnancy is often inevitable for medical treatment of the mother, the fetus or both. The knowledge of drug transport across placenta is, therefore, an important topic to bear in mind when deciding treatment in pregnant women. Several drug transporters of the ABC and SLC families have been discovered in the placenta, such as P-glycoprotein, breast cancer resistance protein, or organic anion/cation transporters. It is thus evident that the passage of drugs across the placenta can no longer be predicted simply on the basis of their physical-chemical properties. Functional expression of placental drug transporters in the trophoblast and the possibility of drug-drug interactions must be considered to optimize pharmacotherapy during pregnancy. In this review we summarize current knowledge on the expression and function of ABC and SLC transporters in the trophoblast. Furthermore, we put this data into context with medical conditions that require maternal and/or fetal treatment during pregnancy, such as gestational diabetes, HIV infection, fetal arrhythmias and epilepsy. Proper understanding of the role of placental transporters should be of great interest not only to clinicians but also to pharmaceutical industry for future drug design and development to control the degree of fetal exposure.

Fate of the teratogenic and carcinogenic ochratoxin A in human perfused placenta

Ochratoxin A (OTA) is one of the most frequent mycotoxins detected in human blood worldwide. Apart from its well known nephrotoxicity, OTA-induced teratogenicity and carcinogenicity proven in animals are potential effects also in humans. Pregnant women have been exposed to this food contaminant via dietary exposure in a continuous and widespread manner. Although the transplacental transfer of OTA has been demonstrated in laboratory animals and the presence of OTA in human fetal samples has been reported, little is known about the role of human placenta in OTA toxicokinetics. In this study, human perfused placenta was used to reveal the actual placental toxicokinetics of OTA using concentrations found in serum of pregnant women. Moreover, the effect of protein concentration and biological significance of placental transporters on the OTA transfer in human placenta were also determined. Our study is the first to pursue the transfer of OTA through perfused human placenta. The transfer of OTA through term human placenta was barely detectable in all perfusions. Inhibitors of neither ABCG2 nor ABCC2 increased the transport of OTA to fetal circulation in placental perfusion, and thus these transporters apparently do not have biological significance in inhibiting transplacental transfer of OTA. Human albumin has inhibited OTA transfer through a tight monolayer of BeWo b30 cells. Finding from this study clearly contradict the existing epidemiological studies reporting higher OTA levels in fetal than in maternal circulation in vivo.

Acute effects of ethanol on the transfer of nicotine and two dietary carcinogens in human placental perfusion

Many mothers use, against instructions, alcohol during pregnancy. Simultaneously mothers are exposed to a wide range of other environmental chemicals. These chemicals may also harm the developing fetus, because almost all toxic compounds can go through human placenta. Toxicokinetic effects of ethanol on the transfer of other environmental compounds through human placenta have not been studied before. It is known that ethanol has lytic properties and increases the permeability and fluidity of cell membranes. We studied the effects of ethanol on the transfer of three different environmental toxins: nicotine, PhIP (2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine) and NDMA (N-nitrosodimethylamine) in placental perfusion. We tested in human breast cancer adenocarcinoma cell line MCF-7 whether ethanol affects ABCG2/BCRP, which is also the major transporter in human placenta. We found that the transfer of ethanol is comparable to that of antipyrine, which points to passive diffusion as the transfer mechanism. Unexpectedly, ethanol had no statistically significant effect on the transfer of the other studied compounds. Neither did ethanol inhibit the function of ABCG2/BCRP. These experiments represent only the effects of acute exposure to ethanol and chronic exposure remains to be studied.

Placental transfer and DNA binding of benzo(a)pyrene in human placental perfusion

Benzo(a)pyrene (BP) is the best studied polycyclic aromatic hydrocarbon, classified as carcinogenic to humans. The carcinogenic metabolite, benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), binds covalently to DNA. The key enzyme in this metabolic reaction is CYP1A1, which has also been found in placenta and human trophoblastic cells. By using human placental perfusion we confirmed that BP added to the maternal circulation in concentrations of 0.1 and 1 microM reaches fetal compartment but somewhat slower than the freely diffusible reference substance antipyrine. A well-known P-glycoprotein (ABCB1/P-gp) antagonist verapamil did not affect the transfer more than it did in the case of antipyrine, indicating that ABCB1/P-gp does not have a role in BP transfer. In one of the two placentas perfused for 6 h with the higher concentration of BP (1 microM) BPDE specific DNA adducts were found in placental tissue after the perfusion, but not before. The ability of human trophoblastic cells to activate BP to BPDE-DNA adducts was confirmed in human trophoblastic BeWo cells. This study shows that maternal exposure to BP leads to the exposure of the fetus to BP and/or its metabolites and that placenta itself can activate BP to DNA adducts.

Drug transporters in the human blood-placental barrier

Studies on the increasing number of transporters found in the placental barrier are gaining momentum, because of their tissue-specific expression, significance in physiology and disease, and the possible utilization of the emerging knowledge in pharmacology. In the placenta, both syncytiotrophoblast and fetal capillary endothelium express transporters. Fetal exposure is determined by the net effect of combination of transporters, their nature and localization in relation to placental cells and their substrate specificity. Although the significance of placental transporters on human fetal drug exposure is almost an unstudied field so far, their potential use to design drugs that do not cross the placenta is already being pursued. It is thus of interest to review the existing knowledge of human placental transporters. Transporters in all groups which take part in drug transport are found in human placenta. Especially, ATP-binding cassette transporters ABCG2/breast cancer resistance protein, ABCB1/P-glycoprotein and ABCC2/MRP2 are all expressed at the apical surface of syncytiotrophoblast facing maternal blood and are putatively important protective proteins both for placental tissue and the fetus, because they are efflux transporters and their substrates include many drugs and also environmental chemicals. Such protective effect has been shown in animals, but these results cannot be directly extrapolated to humans due to interspecies differences in placental structure and function. Experimental models utilizing human placental tissue, especially human placental perfusion, offer valuable possibilities, which have been insufficiently studied so far.

Simultaneous determination of acrylamide, its metabolite glycidamide and antipyrine in human placental perfusion fluid and placental tissue by liquid chromatography-electrospray tandem mass spectrometry

A rapid and sensitive method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the simultaneous determination of acrylamide (AA) and its genotoxic metabolite glycidamide (GA) with a test marker antipyrine (AP) in placental tissue and perfusion medium used in human placental perfusion studies. An internal standard ((13)C-acrylamide) was added to the samples which were then deproteinized with acetonitrile. Chromatographic separation was performed on a reversed phase column with a gradient elution of acetonitrile and 0.01% formic acid at a flow rate of 0.3 mL/min. Detection and quantification of the analytes were carried out with a triple quadrupole mass spectrometer using positive electrospray ionization (ESI) and multiple reaction monitoring (MRM). The method was validated and linear over a concentration range of 0.5-20 microg/mL for acrylamide and glycidamide and 5-200 microg/mL for antipyrine. The lower limit of quantification for acrylamide and glycidamide was 0.5 microg/mL and for antipyrine 5 microg/mL. The method was selective, and good accuracy, precision, recovery, and stability were obtained for concentrations within the standard curve. The method was successfully used to analyze the placental perfusion medium and tissue samples in a toxicokinetic study for transplacental transfer of acrylamide and glycidamide. This is the first time that acrylamide, glycidamide and antipyrine are measured simultaneously.

In Vitro Models Using the Human Placenta to Study Fetal Exposure to Drugs

Over the recent years there has been a gradual rise in the use of pharmaceuticals during pregnancy. Knowledge on placental drug transfer and metabolism has increased during the past decades as well. Investigation of the transplacental transfer of any therapeutically useful drug is essential to the understanding of its metabolic processes and is a prerequisite for its use during pregnancy. The purpose of this review is to give insight on the various techniques that have been developed to evaluate transplacental transfer of drugs and xenobiotics.

ABCG2/BCRP decreases the transfer of a food-born chemical carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in perfused term human placenta

We have studied the role of ATP binding cassette (ABC) transporters in fetal exposure to carcinogens using 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) a known substrate for ABC transporters as a model compound. In perfusion of human term placenta, transfer of (14)C-PhIP (2 microM) through the placenta resulted in fetal-to-maternal concentration ratio (FM ratio) of 0.72+/-0.09 at 6 h. The specific ABCG2 inhibitor KO143 increased the transfer of (14)C-PhIP from maternal to fetal circulation (FM ratio 0.90+/-0.08 at 6 h, p<0.05) while the ABCC1/ABCC2 inhibitor probenecid had no effect (FM ratio at 6 h 0.75+/-0.10, p=0.84). There was a negative correlation between the expression of ABCG2 protein in perfused tissue and the FM ratio of (14)C-PhIP (R=-0.81, p<0.01) at the end of the perfusion. The expression of ABCC2 protein did not correlate with FM ratio of PhIP (R: -0.11, p=0.76). In addition, PhIP induced the expression of ABC transporters in BeWo cells at mRNA level. In conclusion, our data indicates that ABCG2 decreases placental transfer of (14)C-PhIP in perfused human placenta. Also, PhIP may modify ABC transporter expression in choriocarcinoma cells.

Lamotrigine in breast milk and nursing infants: determination of exposure

OBJECTIVE

Although lamotrigine use during pregnancy has substantially increased over the past decade secondary to accumulated reproductive safety data, systematic data on lamotrigine during breastfeeding remains sparse. We sought to characterize the determinants of lamotrigine concentrations in breast milk and nursing-infant plasma.

PATIENTS AND METHODS

Women who enrolled in a prospective investigation of perinatal medication pharmacokinetics, were treated with lamotrigine, and chose to continue lamotrigine while breastfeeding were included in the analysis. Breast milk samples were collected via breast pump from foremilk to hindmilk from a single breast to determine the excretion gradient and serial samples over 24 hours to determine the time course of excretion. Paired maternal/infant plasma samples were also collected. Lamotrigine concentrations in all of the samples were determined by using high-performance liquid chromatography with ultraviolet detection. Statistical analyses of breast milk and infant plasma concentrations and their determinants were conducted.

RESULTS

Thirty women and their nursing infants participated in the study, providing a total of 210 breast milk samples. The mean milk/plasma ratio was 41.3%. There was a nonsignificant trend for higher lamotrigine concentrations in breast milk 4 hours after the maternal dose. Infant plasma concentrations were 18.3% of maternal plasma concentrations. The theoretical infant lamotrigine dose was 0.51 mg/kg per day, and the relative infant lamotrigine dose was 9.2%. Mild thrombocytosis was present in 7 of 8 infants at the time of serum sampling. No other adverse events were observed or reported in the breastfed infants.

CONCLUSIONS

Consistent with previous investigations of medications in breast milk, the lamotrigine milk/plasma ratio is highly variable. The rate of lamotrigine excretion into human breast milk is similar to that observed with other antiepileptic drugs. These data expand the extant literature on lamotrigine in breastfeeding and demonstrate relatively comparable nursing-infant exposure to lamotrigine compared with other antiepileptic drugs.

Kinetics of gold nanoparticles in the human placenta

We studied the transfer of PEGylated gold nanoparticles through perfused human placenta. In 'once-through' perfusions using 15 and 30nm nanoparticles both maternal and fetal outflows were collected. Recirculating perfusions using 10 or 15nm nanoparticles lasted 6h. The gold concentration in samples was analysed on ICP-MS. The reference compound antipyrine crossed the placenta rapidly, as expected. In open perfusions nanoparticles were detected in maternal but not in fetal outflow, suggesting the lack of placental transfer. During 6h re-circulating perfusions, no particles were detected in fetal circulation. Using transmission electron microscopy (TEM) and silver enhancement, nanoparticles could be visualized in the placental tissue mainly in the trophoblastic cell layer. In in vitro experiments, nanoparticles were taken up by BeWo choriocarcinoma cells and retained inside the cells for an extended period of 48h. In conclusion, PEGylated gold nanoparticles of the size 10-30nm did not cross the perfused human placenta in detectable amounts into the fetal circulation within 6h. Whether PEGylated gold nanoparticles eventually are able to cross placenta and whether nanoparticles affect placental functions needs to be further studied.

The emerging importance of transporter proteins in the psychopharmacological treatment of the pregnant patient

P-glycoprotein, breast cancer resistance protein, and multidrug resistance proteins have physiological functions in placental tissue. Several antidepressants, antipsychotics, and anti-epileptic drugs have been found to be substrates of P-glycoprotein and other transporters. The extent that drugs pass through the placental barrier is likely influenced by drug transporters. The rational choice of psychoactive drugs to treat mental illness in women of child-bearing age should incorporate knowledge of both drug disposition as well as expected pharmacologic effects. This review summarizes the current data on drug transporters in the placental passage of medications, with a focus on medications used in clinical psychopharmacology.

The human placenta – An alternative for studying foetal exposure

Pregnant women are daily exposed to a wide selection of foreign substances. Sources are as different as lifestyle factors (smoking, daily care products, alcohol consumption, etc.), maternal medication or occupational/environmental exposures. The placenta provides the link between mother and foetus, and though its main task is to act as a barrier and transport nutrients and oxygen to the foetus, many foreign compounds are transported across the placenta to some degree and may therefore influence the unborn child. Foetal exposures to environmental and medicinal products may have impact on the growth of the foetus (e.g. cigarette smoke) and development of the foetal organs (e.g. methylmercury and thalidomide). The scope of this review is to give insight to the placental anatomy, development and function. Furthermore, the compounds physical properties and the transfer mechanism across the placental barrier are evaluated. In order to determine the actual foetal risk from exposure to a chemical many studies regarding the topic are necessary, including means of transportation, toxicological targets and effects. For this purpose several in vivo and in vitro models including the placental perfusion system are models of choice.

Structure-based modelling in reproductive toxicology: (Q)SARs for the placental barrier

The replacement of animal testing for endpoints such as reproductive toxicity is a long-term goal. This study describes the possibilities of using simple (quantitative) structure-activity relationships ((Q)SARs) to predict whether a molecule may cross the placental membrane. The concept is straightforward, if a molecule is not able to cross the placental barrier, then it will not be a reproductive toxicant. Such a model could be placed at the start of any integrated testing strategy. To develop these models the literature was reviewed to obtain data relating to the transfer of molecules across the placenta. A reasonable number of data were obtained and are suitable for the modelling of the ability of a molecule to cross the placenta. Clearance or transfer indices data were sought due to their ability to eliminate inter-placental variation by standardising drug clearance to the reference compound antipyrine. Modelling of the permeability data indicates that (Q)SARs with reasonable statistical fit can be developed for the ability of molecules to cross the placental barrier membrane. Analysis of the models indicates that molecular size, hydrophobicity and hydrogen-bonding ability are molecular properties that may govern the ability of a molecule to cross the placental barrier.

Phthalate monoesters in perfusate from a dual placenta perfusion system, the placenta tissue and umbilical cord blood

Fetal exposure to phthalates may be associated with adverse reproductive effects, including cryptorchidism and decreased semen quality. Information about human placental transfer is needed to qualify the hypotheses. A dual recirculating placenta perfusion system to monitor concentrations of eight phthalate monoesters in fetal and maternal perfusates was established. In addition to perfusate background measures of phthalate monoesters, the concentrations in umbilical cord plasma and placenta tissue were measured. Monomethyl phthalate (mMP), monoethyl phthalate (mEP), monobutyl phthalate (mBP), and mono (2-ethyl-hexyl) phthalate (mEHP) were detected in both maternal and fetal perfusate, demonstrating a release of compounds from tissue or blood to perfusates. The distribution of compounds between perfusate, umbilical cord plasma, and tissue was in accordance with the physical-chemical properties of the compounds. Results from the present study of compounds residing in the tissue are essential before studying human transplacental transfer, storage, and metabolism of selected phthalate monoesters.

Experimental methods to study human transplacental exposure to genotoxic agents

Human placenta differs more than any other organ between species. This is the primary reason to develop models utilizing human tissue to study placental functions. There are no major ethical restrictions using human placenta for scientific studies. Also, the size of human placenta enables a great number of different parameters to be studied in one placenta. The most important cell types considering transplacental transfer, are the trophoblasts differentiating into syncytiotrophoblasts facing maternal circulation, and endothelial cells of fetal vessels. Primary trophoblasts are difficult to culture and do not grow in monolayer thus inhibiting studies on the polarized functions of transport. Several cell lines originating from trophoblasts have been developed, of which BeWo cells seem most useful for transport studies, because they grow in a tight monolayer. Placental tissue can also be retained as explant cultures, although the trophoblast viability is very restricted despite of culture conditions. Cotyledons of human placenta can be retained viable in an isolated organ perfusion. Perfused placental tissue stays viable longer than placental tissue in tissue culture. Although human placental perfusion is the most tedious experimental method to study placental functions, there are several good reasons to develop it further: transplacental transfer and molecular mechanisms of genotoxic compounds can be studied. Placental perfusion is the only experimental method that retains fully the structure of placenta for polarized transport. Furthermore, perfusion of placentas from mothers, who smoke, use illegal drugs or have a disease, allows studies on the impact of such factors on fetal exposure to genotoxic agents.

Gender Aspects of Pharmacokinetics of New and Old AEDs

Alterations in drug disposition in pregnancy and drug transfer into breast milk during lactation are the most important gender-related aspects of the pharmacokinetics of antiepileptic drugs(AEDs). The effect of pregnancy on drug disposition has been fairly well characterized for the old AEDs. Total and unbound plasma concentrations of phenobarbital decline up to 50%. Total phenytoin levels may drop to approximately 40% of prepregnancy concentrations,but unbound concentrations considerably less. Unbound valproate levels remain unchanged despite a fairly marked decrease in total concentrations, and changes in unbound and total plasma concentrations of carbamazepine are minor. In contrast, pregnancy has a pronounced effect on lamotrigine, with a 300% increase in apparent clearance in the third trimester. Much less is known about the kinetics of other new AEDs during pregnancy. Umbilical cord/maternal plasma concentration ratios close to unity suggest free transplacental passage of most AEDs,whereas higher ratios indicate fetal accumulation of valproate and gabapentin. Milk/maternal plasma concentration ratios close to 1 demonstrate extensive transfer to breast milk of many AEDs including ethosuximide, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, topiramate, and zonisamide. Plasma levels are, however, in general low in the nursed infant, although pharmacological concentrations have been reported occasionally for carbamazepine, ethosuximide, lamotrigine, and phenobarbital. For most of the new-generation AEDs, there is an urgent need for further kinetic data from pregnancy and breast-feeding.

Bipolar disorder in women: reproductive events and treatment considerations

OBJECTIVE

Bipolar disorders are prevalent in women. Women with bipolar disorder often present with different clinical features than men. Reproductive events and hormonal treatments may impact the course of bipolar disorder. Our main objectives are to i) assess the impact of reproductive events on the course of the disorder, and ii) to discuss the relationships between reproductive events and psychiatric treatments.

METHOD

A literature search was conducted of MEDLINE journals from 1965 to present. Manual literature searches were also conducted. We review the presentation, clinical course, and treatment considerations of bipolar disorder in women, with emphasis on treatment considerations in the context of reproductive events. Treatment-related issues such as teratogenicity, breastfeeding, polycystic ovarian syndrome, weight gain and obesity, and medication interactions with oral contraceptives are reviewed.

RESULTS

Women with bipolar disorder may be more vulnerable to mood episodes in the context of reproductive events, particularly postpartum. In women of reproductive age, mood stabilizers must be selected with teratogenic risks in mind, with the highest reported risks in pregnancy with valproate, and the greatest concern during breastfeeding with lithium use. In the areas of the perimenopause and polycycstic ovarian syndrome, more data are needed to advise treatment decisions.

CONCLUSION

We urgently need further study in these areas to deliver care that is appropriate to women with bipolar disorder.

An examination of whether human placental perfusion allows accurate prediction of placental drug transport: Studies with diazepam

INTRODUCTION

Presently, no well-validated predictive tools are available for human placental transfer. We studied the transplacental passage of diazepam (DZP) in a recirculating dual human placental perfusion and compared the data with in vivo clinical data from the literature.

METHODS

Term placentas from healthy mothers without medication were used. The dual, recirculating perfusion technique was used. DZP (2 microg/ml, n = 4; 200 ng/ml, n = 3) and the reference compound antipyrine (100 microg/ml) were added into the maternal circulation simultaneously. The disappearance of drugs from the maternal circulation and appearance into the fetal circulation were followed every 15 min for 2 h.

RESULTS

DZP was detectable in the fetal circulation within 15 min in all of the perfusions indicating rapid transfer. DZP concentrations in the maternal circulation were higher than in the fetal circulation throughout the perfusion with both initial concentrations. At the end of the perfusion, the feto-maternal ratio was 0.48 +/- 0.11 (mean +/- S.D.) and the transfer from the maternal to the fetal compartment 18.4 +/- 3.6% with 2 microg/ml of DZP and 0.55 +/- 0.10 and 20.5 +/- 3.1% with 200 ng/ml of DZP, respectively. DZP concentrations in the perfused area of the placenta were in average 2 times higher than in the maternal perfusate and 3.6 times higher than in the fetal perfusate. Total recovery of DZP from samples, perfusion fluid, and perfused tissue was 37.6 +/- 21%.

DISCUSSION

Since animal studies in vivo do not accurately predict human placental transfer and it is problematic to study placental transfer of drugs in humans in vivo, the present human placental perfusion system could serve as one part of a test battery for fetotoxicity. However, although our earlier studies and those from the literature indicate a good correlation between in vivo and placental perfusion data, the present study shows this is not the case for all drugs.