Expression of the multidrug resistance P-glycoprotein, (ABCB1 glycoprotein) in the human placenta decreases with advancing gestation

Placental efflux transporters and antiseizure or antidepressant medication use impact birth weight in MoBa cohort

Low birth weight raises neonatal risks and lifelong health issues and is linked to maternal medication use during pregnancy. We examined data from the Norwegian Mother, Father, and Child Cohort Study and the Medical Birth Registry of Norway, including 69,828 offspring with genotype data and 81,189 with maternal genotype data. We identified genetic risk variants in placental efflux transporters, calculated genetic scores based on alleles related to transporter activity, and assessed their interaction with prenatal use of antiseizure or antidepressant medication on offspring birth weight. Our study uncovered possible genetic variants in both offspring (rs3740066) and mothers (rs10248420; rs2235015) in placental efflux transporters (MRP2-ABCC2 and MDR1-ABCB1) that modulated the association between prenatal exposure to antiseizure medication and low birth weight in the offspring. Antidepressant exposure was associated with low birth weight, but there were no gene-drug interactions. The interplay between MRP2-ABCC2 and MDR1-ABCB1 variants and antiseizure medication may impact neonatal birth weight.

Glucocorticoids and intrauterine programming of nonalcoholic fatty liver disease

Accumulating epidemiological and experimental evidence indicates that nonalcoholic fatty liver disease (NAFLD) has an intrauterine origin. Fetuses exposed to adverse prenatal environments (e.g., maternal malnutrition and xenobiotic exposure) are more susceptible to developing NAFLD after birth. Glucocorticoids are crucial triggers of the developmental programming of fetal-origin diseases. Adverse intrauterine environments often lead to fetal overexposure to maternally derived glucocorticoids, which can program fetal hepatic lipid metabolism through epigenetic modifications. Adverse intrauterine environments program the offspring's glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axis, which contributes to postnatal catch-up growth and disturbs glucose and lipid metabolism. These glucocorticoid-driven programming alterations increase susceptibility to NAFLD in the offspring. Notably, after delivery, offspring often face an environment distinct from their in utero life. The mismatch between the intrauterine and postnatal environments can serve as a postnatal hit that further disturbs the programmed endocrine axes, accelerating the onset of NAFLD. In this review, we summarize the current epidemiological and experimental evidence demonstrating that NAFLD has an intrauterine origin and discuss the underlying intrauterine programming mechanisms, focusing on the role of overexposure to maternally derived glucocorticoids. We also briefly discuss potential early life interventions that may be beneficial against fetal-originated NAFLD.

Obesity in pregnancy-Long-term effects on offspring hypothalamic-pituitary-adrenal axis and associations with placental cortisol metabolism: A systematic review

Obesity, affecting one in three pregnant women worldwide, is not only a major obstetric risk factor. The resulting low-grade inflammation may have a long-term impact on the offspring's HPA axis through dysregulation of maternal, placental and fetal corticosteroid metabolism, and children born of obese mothers have increased risk of diabetes and cardiovascular disease. The long-term effects of maternal obesity on offspring neurodevelopment are, however, undetermined and could depend on the specific effects on placental and fetal cortisol metabolism. This systematic review evaluates how maternal obesity affects placental cortisol metabolism and the offspring's HPA axis. Pubmed, Embase and Scopus were searched for original studies on maternal BMI, obesity, and cortisol metabolism and transfer. Fifteen studies were included after the screening of 4556 identified records. Studies were small with heterogeneous exposures and outcomes. Two studies found that maternal obesity reduced placental HSD11β2 activity. In one study, umbilical cord blood cortisol levels were affected by maternal BMI. In three studies, an altered cortisol response was consistently seen among offspring in childhood (n = 2) or adulthood (n = 1). Maternal BMI was not associated with placental HSD11β1 or HSD11β2 mRNA expression, or placental HSD11β2 methylation. In conclusion, high maternal BMI is associated with reduced placental HSD11β2 activity and a dampened cortisol level among offspring, but the data is sparse. Further investigations are needed to clarify whether the HPA axis is affected by prenatal factors including maternal obesity and investigate if adverse effects can be ameliorated by optimising the intrauterine environment.

A Literature Review of Changes in Phase II Drug-Metabolizing Enzyme and Drug Transporter Expression during Pregnancy

The purpose of this literature review is to comprehensively summarize changes in the expression of phase II drug-metabolizing enzymes and drug transporters in both the pregnant woman and the placenta. Using PubMed®, a systematic search was conducted to identify literature relevant to drug metabolism and transport in pregnancy. PubMed was searched with pre-specified terms during the period of 26 May 2023 to 10 July 2023. The final dataset of 142 manuscripts was evaluated for evidence regarding the effect of gestational age and hormonal regulation on the expression of phase II enzymes (n = 16) and drug transporters (n = 38) in the pregnant woman and in the placenta. This comprehensive review exposes gaps in current knowledge of phase II enzyme and drug transporter localization, expression, and regulation during pregnancy, which emphasizes the need for further research. Moreover, the information collected in this review regarding phase II drug-metabolizing enzyme and drug transporter changes will aid in optimizing pregnancy physiologically based pharmacokinetic (PBPK) models to inform dose selection in the pregnant population.

Genetics of ABCB1 in Cancer

ABCB1, also known as MDR1, is a gene that encodes P-glycoprotein (P-gp), a membrane-associated ATP-dependent transporter. P-gp is widely expressed in many healthy tissues-in the gastrointestinal tract, liver, kidney, and at the blood-brain barrier. P-gp works to pump xenobiotics such as toxins and drugs out of cells. P-gp is also commonly upregulated across multiple cancer types such as ovarian, breast, and lung. Overexpression of ABCB1 has been linked to the development of chemotherapy resistance across these cancers. In vitro work across a wide range of drug-sensitive and -resistant cancer cell lines has shown that upon treatment with chemotherapeutic agents such as doxorubicin, cisplatin, and paclitaxel, ABCB1 is upregulated. This upregulation is caused in part by a variety of genetic and epigenetic mechanisms. This includes single-nucleotide variants that lead to enhanced P-gp ATPase activity without increasing ABCB1 RNA and protein levels. In this review, we summarize current knowledge of genetic and epigenetic mechanisms leading to ABCB1 upregulation and P-gp-enhanced ATPase activity in the setting of chemotherapy resistance across a variety of cancers.

Changes in Expression and Function of Placental and Intestinal P-gp and BCRP Transporters during Pregnancy

ABC transporters are ubiquitous in the human body and are responsible for the efflux of drugs. They are present in the placenta, intestine, liver and kidney, which are the major organs that can affect the pharmacokinetic and pharmacologic properties of drugs. P-gp and BCRP transporters are the best-characterized transporters in the ABC superfamily, and they have a pivotal role in the barrier tissues due to their efflux mechanism. Moreover, during pregnancy, drug efflux is even more important because of the developing fetus. Recent studies have shown that placental and intestinal ABC transporters have great importance in drug absorption and distribution. Placental and intestinal P-gp and BCRP show gestational-age-dependent expression changes, which determine the drug concentration both in the mother and the fetus during pregnancy. They may have an impact on the efficacy of antibiotic, antiviral, antihistamine, antiemetic and oral antidiabetic therapies. In this review, we would like to provide an overview of the pharmacokinetically relevant expression alterations of placental and intestinal ABC transporters during pregnancy.

ABCB1 expression is increased in human first trimester placenta from pregnant women classified as overweight or obese

Obesity has become a global health challenge also affecting reproductive health. In pregnant women, obesity increases the risk of complications such as preterm birth, macrosomia, gestational diabetes, and preeclampsia. Moreover, obesity is associated with long-term adverse effects for the offspring, including increased risk of cardiovascular and metabolic diseases and neurodevelopmental difficulties. The underlying mechanisms are far from understood, but placental function is essential for pregnancy outcome. Transporter proteins P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) are important for trans-placental transport of endogenous substances like lipids and cortisol, a key hormone in tissue maturation. They also hold a protective function protecting the fetus from xenobiotics (e.g. pharmaceuticals). Animal studies suggest that maternal nutritional status can affect expression of placental transporters, but little is known about the effect on the human placenta, especially in early pregnancy. Here, we investigated if overweight and obesity in pregnant women altered mRNA expression of ABCB1 encoding P-gp or ABCG2 encoding BCRP in first trimester human placenta. With informed consent, 75 first trimester placental samples were obtained from women voluntarily seeking surgical abortion (< gestational week 12) (approval no.: 20060063). Villous samples (average gestational age 9.35 weeks) were used for qPCR analysis. For a subset (n = 38), additional villi were snap-frozen for protein analysis. Maternal BMI was defined at the time of termination of pregnancy. Compared to women with BMI 18.5-24.9 kg/m² (n = 34), ABCB1 mRNA expression was significantly increased in placenta samples from women classified as overweight (BMI 25-29.9 kg/m², n = 18) (p = 0.040) and women classified as obese (BMI ≥ 30 kg/m², n = 23) (p = 0.003). Albeit P-gp expression did not show statistically significant difference between groups, the effect of increasing BMI was the same in male and female pregnancies. To investigate if the P-gp increase was compensated, we determined the expression of ABCG2 which was unaffected by maternal obesity (p = 0.291). Maternal BMI affects ABCB1 but not ABCG2 mRNA expression in first trimester human placenta. Further studies of early placental function are needed to understand how the expression of placental transport proteins is regulated by maternal factors such as nutritional status and determine the potential consequences for placental-fetal interaction.

Maternal and Fetal Exposure to (-)-Δ9-tetrahydrocannabinol and Its Major Metabolites in Pregnant Mice Is Differentially Impacted by P-glycoprotein and Breast Cancer Resistance Protein

(-)-Δ9-tetrahydrocannabinol (THC) is the primary pharmacological active constituent of cannabis. 11-hydroxy-THC (11-OH-THC) and 11-nor-9-carboxy-THC (THC-COOH) are respectively the active and nonactive circulating metabolites of THC in humans. While previous animal studies reported that THC could be a substrate of mouse P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp), we have shown, in vitro, that only THC-COOH is a weak substrate of human BCRP, but not of P-gp. To confirm these findings and to investigate the role of P-gp and/or Bcrp in the maternal-fetal disposition of THC and its metabolites, we administrated 3 mg/kg of THC retro-orbitally to FVB wild-type (WT), P-gp -/-, Bcrp -/-, or P-gp-/- /Bcrp-/- pregnant mice on gestation day 18 and estimated the area under the concentration-time curve (AUC) of the cannabinoids in the maternal plasma, maternal brain, placenta, and fetus, as well as the tissue/maternal plasma AUC geometric mean ratios (GMRs) using a pooled data bootstrap approach. We found that the dose-normalized maternal plasma AUCs of THC in P-gp-/- and P-gp-/- /Bcrp-/- mice, and the placenta-to-maternal plasma AUC GMR of THC in Bcrp-/- mice were 279%, 271%, and 167% of those in WT mice, respectively. Surprisingly, the tissue-to-maternal plasma AUC GMRs of THC and its major metabolites in the maternal brain, placenta, or fetus in P-gp -/-, Bcrp -/- or P-gp-/- /Bcrp-/- mice were 28-78% of those in WT mice. This study revealed that P-gp and Bcrp do not play a role in limiting maternal brain and fetal exposure to THC and its major metabolites in pregnant mice. SIGNIFICANCE STATEMENT: This study systematically investigated whether P-gp and/or Bcrp in pregnant mice can alter the disposition of THC, 11-OH-THC, and THC-COOH. Surprisingly, except for Bcrp, which limits placental (but not fetal) exposure to THC, we found that P-gp-/- , Bcrp-/- , and/or P-gp-/- /Bcrp-/- significantly decreased exposure to THC and/or its metabolites in maternal brain, placenta, or fetus. The mechanistic basis for this decrease is unclear and needs further investigation. If replicated in humans, P-gp- or BCRP-based drug-cannabinoid interactions are not of concern.

The ATP-binding cassette proteins ABCB1 and ABCC1 as modulators of glucocorticoid action

Responses to hormones that act through nuclear receptors are controlled by modulating hormone concentrations not only in the circulation but also within target tissues. The role of enzymes that amplify or reduce local hormone concentrations is well established for glucocorticoid and other lipophilic hormones; moreover, transmembrane transporters have proven critical in determining tissue responses to thyroid hormones. However, there has been less consideration of the role of transmembrane transport for steroid hormones. ATP-binding cassette (ABC) proteins were first shown to influence the accumulation of glucocorticoids in cells almost three decades ago, but observations over the past 10 years suggest that differential transport propensities of both exogenous and endogenous glucocorticoids by ABCB1 and ABCC1 transporters provide a mechanism whereby different tissues are preferentially sensitive to different steroids. This Review summarizes this evidence and the new insights provided for the physiology and pharmacology of glucocorticoid action, including new approaches to glucocorticoid replacement.

Transplacental Therapeutic Drug Monitoring in Pregnant Women with Fetal Tachyarrhythmia Using HPLC-MS/MS

Fetal arrhythmia develops in 0.1-5% of pregnancies and may cause fetal heart failure and fetal hydrops, thus increasing fetal, neonatal, and infant mortality. The timely initiation of transplacental antiarrhythmic therapy (ART) promotes the conversion of fetal tachycardia to sinus rhythm and the regression of the concomitant non-immune fetal hydrops. The optimal treatment regimen search for the fetus with tachyarrhythmia is still of high value. Polymorphisms of these genes determines the individual features of the drug pharmacokinetics. The aim of this study was to study the pharmacokinetics of transplacental anti-arrhythmic drugs in the fetal therapy of arrhythmias using HPLC-MS/MS, as well as to assess the effect of the multidrug-resistance gene ABCB1 3435C > T polymorphism on the efficacy and maternal/fetal complications of digoxin treatment. The predisposition to a decrease in the bioavailability of the digoxin in patients with a homozygous variant of the CC polymorphism showed a probable association with the development of ART side effects. A pronounced decrease in heart rate in women with the 3435TT allele of the ABCB1 gene was found. The homozygous TT variant in the fetus showed a probable association with an earlier response to ART and rhythm disruptions on the digoxin dosage reduction. high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS) methods for digoxin and sotalol therapeutic drug monitoring in blood plasma, amniotic fluid, and urine were developed. The digoxin and sotalol concentrations were determined in the plasma blood, urine, and amniotic fluid of 30 pregnant women at four time points (from the beginning of the transplacental antiarrhythmic therapy to delivery) and the plasma cord blood of 30 newborns. A high degree of correlation between the level of digoxin and sotalol in maternal and cord blood was found. The ratio of digoxin and sotalol in cord blood to maternal blood was 0.35 (0.27 and 0.46) and 1.0 (0.97 and 1.07), accordingly. The digoxin concentration in the blood of the fetus at the moment of the first rhythm recovery episode, 0.58 (0.46, 0.8) ng/mL, was below the therapeutic interval. This confirms the almost complete transplacental transfer of sotalol and the significant limitation in the case of digoxin. Previously, ABCB1/P-glycoprotein had been shown to limit fetal exposure to drugs. Further studies (including multicenter ones) to clarify the genetic features of the transplacental pharmacokinetics of antiarrhythmic drugs are needed.

Infection and disruption of placental multidrug resistance (MDR) transporters: Implications for fetal drug exposure

P-glycoprotein (P-gp, encoded by the ABCB1 gene) and breast cancer resistance protein (BCRP/ABCG2) are efflux multidrug resistance (MDR) transporters localized at the syncytiotrophoblast barrier of the placenta and protect the conceptus from drug and toxin exposure throughout pregnancy. Infection is an important modulator of MDR expression and function. This review comprehensively examines the effect of infection on the MDR transporters, P-gp and BCRP in the placenta. Infection PAMPs such as bacterial lipopolysaccharide (LPS) and viral polyinosinic-polycytidylic acid (poly I:C) and single-stranded (ss)RNA, as well as infection with Zika virus (ZIKV), Plasmodium berghei ANKA (modeling malaria in pregnancy - MiP) and polymicrobial infection of intrauterine tissues (chorioamnionitis) all modulate placental P-gp and BCRP at the levels of mRNA, protein and or function; with specific responses varying according to gestational age, trophoblast type and species (human vs. mice). Furthermore, we describe the expression and localization profile of Toll-like receptor (TLR) proteins of the innate immune system at the maternal-fetal interface, aiming to better understand how infective agents modulate placental MDR. We also highlight important gaps in the field and propose future research directions. We conclude that alterations in placental MDR expression and function induced by infective agents may not only alter the intrauterine biodistribution of important MDR substrates such as drugs, toxins, hormones, cytokines, chemokines and waste metabolites, but also impact normal placentation and adversely affect pregnancy outcome and maternal/neonatal health.

Resolving the gene expression maps of human first-trimester chorionic villi with spatial transcriptome

The placenta is important for fetal development in mammals, and spatial transcriptomic profiling of placenta helps to resolve its structure and function. In this study, we described the landscape of spatial transcriptome of human placental villi obtained from two pregnant women at the first trimester using the modified Stereo-seq method applied for paraformaldehyde (PFA) fixation samples. The PFA fixation of human placenta villi was better than fresh villi embedded in optimum cutting temperature (OCT) compound, since it greatly improved tissue morphology and the specificity of RNA signals. The main cell types in chorionic villi such as syncytiotrophoblasts (SCT), villous cytotrophoblasts (VCT), fibroblasts (FB), and extravillous trophoblasts (EVT) were identified with the spatial transcriptome data, whereas the minor cell types of Hofbauer cells (HB) and endothelial cells (Endo) were spatially located by deconvolution of scRNA-seq data. We demonstrated that the Stereo-seq data of human villi could be used for sophisticated analyses such as spatial cell-communication and regulatory activity. We found that the SCT and VCT exhibited the most ligand-receptor pairs that could increase differentiation of the SCT, and that the spatial localization of specific regulons in different cell types was associated with the pathways related to hormones transport and secretion, regulation of mitotic cell cycle, and nutrient transport pathway in SCT. In EVT, regulatory pathways such as the epithelial to mesenchyme transition, epithelial development and differentiation, and extracellular matrix organization were identified. Finally, viral receptors and drug transporters were identified in villi according to the pathway analysis, which could help to explain the vertical transmission of several infectious diseases and drug metabolism efficacy. Our study provides a valuable resource for further investigation of the placenta development, physiology and pathology in a spatial context.

Thyroid Hormone Transporters in Pregnancy and Fetal Development

Thyroid hormone is essential for fetal (brain) development. Plasma membrane transporters control the intracellular bioavailability of thyroid hormone. In the past few decades, 15 human thyroid hormone transporters have been identified, and among them, mutations in monocarboxylate transporter (MCT)8 and organic anion transporting peptide (OATP)1C1 are associated with clinical phenotypes. Different animal and human models have been employed to unravel the (patho)-physiological role of thyroid hormone transporters. However, most studies on thyroid hormone transporters focus on postnatal development. This review summarizes the research on the thyroid hormone transporters in pregnancy and fetal development, including their substrate preference, expression and tissue distribution, and physiological and pathophysiological role in thyroid homeostasis and clinical disorders. As the fetus depends on the maternal thyroid hormone supply, especially during the first half of pregnancy, the review also elaborates on thyroid hormone transport across the human placental barrier. Future studies may reveal how the different transporters contribute to thyroid hormone homeostasis in fetal tissues to properly facilitate development. Employing state-of-the-art human models will enable a better understanding of their roles in thyroid hormone homeostasis.

Regulation of Placental Efflux Transporters during Pregnancy Complications

The placenta is essential for regulating the exchange of solutes between the maternal and fetal circulations. As a result, the placenta offers support and protection to the developing fetus by delivering crucial nutrients and removing waste and xenobiotics. ATP-binding cassette transporters, including multidrug resistance protein 1, multidrug resistance-associated proteins, and breast cancer resistance protein, remove chemicals through active efflux and are considered the primary transporters within the placental barrier. Altered transporter expression at the barrier could result in fetal exposure to chemicals and/or accumulation of xenobiotics within trophoblasts. Emerging data demonstrate that expression of these transporters is changed in women with pregnancy complications, suggesting potentially compromised integrity of placental barrier function. The purpose of this review is to summarize the regulation of placental efflux transporters during medical complications of pregnancy, including 1) placental inflammation/infection and chorioamnionitis, 2) hypertensive disorders of pregnancy, 3) metabolic disorders including gestational diabetes and obesity, and 4) fetal growth restriction/altered fetal size for gestational age. For each disorder, we review the basic pathophysiology and consider impacts on the expression and function of placental efflux transporters. Mechanisms of transporter dysregulation and implications for fetal drug and toxicant exposure are discussed. Understanding how transporters are up- or downregulated during pathology is important in assessing possible exposures of the fetus to potentially harmful chemicals in the environment as well as the disposition of novel therapeutics intended to treat placental and fetal diseases. SIGNIFICANCE STATEMENT: Diseases of pregnancy are associated with reduced expression of placental barrier transporters that may impact fetal pharmacotherapy and exposure to dietary and environmental toxicants.

Profiling the Influence of Gene Variants Related to Folate-Mediated One-Carbon Metabolism on the Outcome of In Vitro Fertilization (IVF) with Donor Oocytes in Recipients Receiving Folic Acid Fortification

Nutritional status and gene polymorphisms of one-carbon metabolism confer a well-known interaction that in pregnant women may affect embryo viability and the health of the newborn. Folate metabolism directly impacts nucleotide synthesis and methylation, which is of increasing interest in the reproductive medicine field. Studies assessing the genetic influence of folate metabolism on IVF treatments have currently been performed in women using their own oocytes. Most of these patients seeking to have a child or undergoing IVF treatments are advised to preventively intake folate supplies that restore known metabolic imbalances, but the treatments could lead to the promotion of specific enzymes in specific women, depending on their genetic variance. In the present study, we assess the influence of candidate gene variants related to folate metabolism, such as Serine Hydroxymethyltransferase 1 SHMT1 (rs1979276 and rs1979277), Betaine-Homocysteine S-Methyltransferase BHMT (rs3733890), Methionine synthase reductase MTRR (rs1801394), Methylenetetrahydrofolate reductase MTHFR (rs1801131 and rs1801133), methionine synthase MTR (rs12749581), ATP Binding Cassette Subfamily B Member 1 ABCB1 (rs1045642) and folate receptor alpha FOLR1 (rs2071010) on the success of IVF treatment performed in women being recipients of donated oocytes. The implication of such gene variants seems to have no direct impact on pregnancy consecution after IVF; however, several gene variants could influence pregnancy loss events or pregnancy maintenance, as consequence of folic acid fortification.

Predicting Human Fetal Drug Exposure Through Maternal-Fetal PBPK Modeling and In Vitro or Ex Vivo Studies

Medication (drug) use in human pregnancy is prevalent. Determining fetal safety and efficacy of drugs is logistically challenging. However, predicting (not measuring) fetal drug exposure (systemic and tissue) throughout pregnancy is possible through maternal-fetal physiologically based pharmacokinetic (PBPK) modeling and simulation. Such prediction can inform fetal drug safety and efficacy. Fetal drug exposure can be quantified in 2 complementary ways. First, the ratio of the steady-state unbound plasma concentration in the fetal plasma (or area under the plasma concentration-time curve) to the corresponding maternal plasma concentration (ie, Kp,uu ). Second, the maximum unbound peak (Cu,max,ss,f ) and trough (Cu,min,ss,f ) fetal steady-state plasma concentrations. We (and others) have developed a maternal-fetal PBPK model that can successfully predict maternal drug exposure. To predict fetal drug exposure, the model needs to be populated with drug specific parameters, of which transplacental clearances (active and/or passive) and placental/fetal metabolism of the drug are critical. Herein, we describe in vitro studies in cells/tissue fractions or the perfused human placenta that can be used to determine these drug-specific parameters. In addition, we provide examples whereby this approach has successfully predicted systemic fetal exposure to drugs that passively or actively cross the placenta. Apart from maternal-fetal PBPK models, animal studies also have the potential to estimate fetal drug exposure by allometric scaling. Whether such scaling will be successful is yet to be determined. Here, we review the above approaches to predict fetal drug exposure, outline gaps in our knowledge to make such predictions and map out future research directions that could fill these gaps.

ATP-binding cassette (ABC) drug transporters in the developing blood-brain barrier: role in fetal brain protection

The blood-brain barrier (BBB) provides essential neuroprotection from environmental toxins and xenobiotics, through high expression of drug efflux transporters in endothelial cells of the cerebral capillaries. However, xenobiotic exposure, stress, and inflammatory stimuli have the potential to disrupt BBB permeability in fetal and post-natal life. Understanding the role and ability of the BBB in protecting the developing brain, particularly with respect to drug/toxin transport, is key to promoting long-term brain health. Drug transporters, particularly P-gp and BCRP are expressed in early gestation at the developing BBB and have a crucial role in developmental homeostasis and fetal brain protection. We have highlighted several factors that modulate drug transporters at the developing BBB, including synthetic glucocorticoid (sGC), cytokines, maternal infection, and growth factors. Some factors have the potential to increase expression and function of drug transporters and increase brain protection (e.g., sGC, transforming growth factor [TGF]-β). However, others inhibit drug transporters expression and function at the BBB, increasing brain exposure to xenobiotics (e.g., tumor necrosis factor [TNF], interleukin [IL]-6), negatively impacting brain development. This has implications for pregnant women and neonates, who represent a vulnerable population and may be exposed to drugs and environmental toxins, many of which are P-gp and BCRP substrates. Thus, alterations in regulated transport across the developing BBB may induce long-term changes in brain health and compromise pregnancy outcome. Furthermore, a large portion of neonatal adverse drug reactions are attributed to agents that target or access the nervous system, such as stimulants (e.g., caffeine), anesthetics (e.g., midazolam), analgesics (e.g., morphine) and antiretrovirals (e.g., Zidovudine); thus, understanding brain protection is key for the development of strategies to protect the fetal and neonatal brain.

Contribution of child ABC-transporter genetics to prenatal MeHg exposure and neurodevelopment

BACKGROUND

There is emerging evidence that exposure to prenatal methylmercury (MeHg) from maternal fish consumption during pregnancy can differ between individuals due to genetic variation. In previous studies, we have reported that maternal polymorphisms in ABC-transporter genes were associated with maternal hair MeHg concentrations, and with children's early neurodevelopmental tests. In this study, we add to these findings by evaluating the contribution of genetic variation in children's ABC-transporter genes to prenatal MeHg exposure and early child neurodevelopmental tests.

METHODS

We genotyped six polymorphisms (rs2032582, rs10276499 and rs1202169 in ABCB1; rs11075290 and rs215088 in ABCC1; rs717620 in ABCC2) in DNA from cord blood and maternal blood of the Seychelles Child Development Study Nutrition Cohort 2. We determined prenatal MeHg exposure by measuring total mercury (Hg) in cord blood by atomic fluorescence spectrometry. We assessed neurodevelopment in children at approximately 20 months using the Bayley Scales of Infant Development (BSID-II). We used linear regression models to analyze covariate-adjusted associations of child genotype with cord MeHg and BSID-II outcomes (Mental Developmental and Psychomotor Developmental Indexes). We also evaluated interactions between genotypes, cord MeHg, and neurodevelopmental outcomes. All models were run with and without adjustment for maternal genotype.

RESULTS

Of the six evaluated polymorphisms, only ABCC1 rs11075290 was associated with cord blood MeHg; children homozygous for the T-allele had on average 29.99 µg/L MeHg in cord blood while those homozygous for the C-allele had on average 38.06 µg/L MeHg in cord blood (p < 0.001). No polymorphisms in the children were associated with either subscale of the BSID. However, the association between cord MeHg and the Mental Developmental Index (MDI) of the BSID differed significantly across the three genotypes of ABCB1 rs10276499 (2df F-test, p = 0.045). With increasing cord MeHg, the MDI decreased (slope=-0.091, p = 0.014) among children homozygous for the rare C-allele.

CONCLUSIONS

These findings support the possibility that child ABC genetics might influence prenatal MeHg exposure.

Impact of the ABCB1 Drug Resistance Gene on the Risk Factors of Patients with COVID-19 and Its Relationship with the Drugs Used

Objective

In the last two years progress was made in molecular, physio pathological understanding and the form of transmission of COVID-19, and different therapeutic strategies have been explored to deal with the situation of the pandemic. However, the evaluation of certain genes that participate in the metabolism and transport of these drugs has not been fully explored. A lack of response to treatment and a lower survival have been observed that may be due to the presence of the ABCB1 drug resistance gene. Our research group analyzed whether the expression levels of the ABCB1 gene are associated with comorbidities, treatments, overall survival and risk of death in patients with severe COVID-19.

Methods

The expression levels of the ABCB1 gene were analyzed by RT-qPCR in 61 patients diagnosed with COVID-19. The association between the levels of expression, the risk variables and different treatments were determined by the Chi-Square test and the Fisher’s exact test. Global Survival (GS) was determined by the Kaplan–Meier method. The impact of high levels of expression and the risk of death was performed by odds ratio.

Results

The different risk variables showed that patients with either high or absent levels of ABCB1 gene expression presented a greater risk of death (OR 3.08, 95%, CI 1.02–9.26) as well as need for ventilatory support (OR 2.8, 95%, CI 0.98 −8.5). Patients with diabetes and COVID-19, treated with metformin, were associated with a lower risk of death (OR 1.11, 95%, CI 0.38–3.22). OS with respect to high or absent levels of expression of the ABCB1 gene was lower.

Conclusion

High levels or null expression of the ABCB1 gene are associated with a higher risk of death or progression of the disease, the use of metformin in patients with COVID-19 confers a lower risk of death.

Gestational Age Variation in Human Placental Drug Transporters

Patient and providers’ fear of fetal exposure to medications may lead to discontinuation of treatment, disease relapse, and maternal morbidity. Placental drug transporters play a critical role in fetal exposure through active transport but the majority of data are limited to the 3rd trimester, when the majority of organogenesis has already occurred. Our objective was to define gestational age (GA) dependent changes in protein activity, expression and modifications of five major placental drug transporters: SERT, P-gp, NET, BCRP and MRP3. Apical brush border membrane fractions were prepared from fresh 1st, 2nd and 3rd trimester human placentas collected following elective pregnancy termination or planned cesarean delivery. A structured maternal questionnaire was used to identify maternal drug use and exclude exposed subjects. Changes in placental transporter activity and expression relative to housekeeping proteins were quantified. There was evidence for strong developmental regulation of SERT, NET, P-gp, BCRP and MRP3. P-gp and BCRP decreased with gestation (r = −0.72, p &lt; 0.001 and r = −0.77, p &lt; 0.001, respectively). Total SERT increased with gestation but this increase was due to a decrease in SERT cleavage products across trimesters. Uncleaved SERT increased with GA (r = 0.89, p &lt; 0.001) while cleaved SERT decreased with GA (r = −0.94, p &lt; 0.001). Apical membrane NET overall did not appear to be developmentally regulated (r = −0.08, p = 0.53). Two forms of MRP3 were identified; the 50 kD form did not change across GA; the 160 kD form was steady in the 1st and 2nd trimester and increased in the 3rd trimester (r = 0.24, p = 0.02). The 50 kD form was expressed at higher levels. The observed patterns of SERT, NET P-gp, BCRP and MRP3 expression and activity may be associated with transporter activity or decreased placental permeability in the 1st trimester to transporter specific substrates including commonly used psychoactive medications such as anti-depressants, anti-psychotics, and amphetamines, while transport of nutrients and serotonin is important in the 1st trimester. Overall these observations are consistent with a strong protective effect during organogenesis. 3rd trimester estimates of fetal exposure obtained from cord blood likely significantly overestimate early fetal exposure to these medications at any fixed maternal dose.

Preterm Birth Associates With Increased Placental Expression of MDR Transporters Irrespective of Prepregnancy BMI

CONTEXT

Preterm birth (PTB) and suboptimal prepregnancy body mass index (BMI) operate through inflammatory pathways to impair fetoplacental development. Placental efflux transporters mediate fetal protection and nutrition; however, few studies consider the effect of both PTB and BMI on fetal protection. We hypothesized that PTB would alter the expression of placental multidrug resistance (MDR) transporters and selected proinflammatory cytokines, and that maternal underweight and obesity would further impair placental phenotype.

OBJECTIVE

To determine whether placental MDR transporters P-glycoprotein (P-gp, encoded by ABCB1) and breast cancer resistance protein (BCRP/ABCG2), and proinflammatory cytokine levels are altered by PTB and maternal BMI.

METHODS

A cross-sectional study was conducted to assess the effect of PTB (with/without chorioamnionitis), or the effect of maternal prepregnancy BMI on placental MDR transporter and interleukin (IL)-6 and -8 expression in 60 preterm and 36 term pregnancies.

RESULTS

ABCB1 expression was increased in preterm compared to term placentae (P = .04). P-gp (P = .008) and BCRP (P = .01) immunolabeling was increased among all preterm compared to term placentae, with P-gp expression further increased in preterm pregnancies with chorioamnionitis (PTC, P = .007). Placental IL-6 mRNA expression was decreased in PTC compared to term placentae (P = .0005) and PTC associated with the greatest proportion of anti-inflammatory medications administered during pregnancy. Maternal BMI group did not influence placental outcomes.

CONCLUSION

PTB and infection, but not prepregnancy BMI, alter placental expression of MDR transporters and IL-6. This may have implications for fetal exposure to xenobiotics that may be present in the maternal circulation in pregnancies complicated by PTB.

Limited Impact of Murine Placental MDR1 on Fetal Exposure of Certain Drugs Explained by Bypass Transfer Between Adjacent Syncytiotrophoblast Layers

Purpose

Multidrug resistance protein 1 (MDR1) is located at the interface between two syncytiotrophoblast layers in rodent placenta, and may influence fetal drug distribution. Here, we quantitatively compare the functional impact per single MDR1 molecule of MDR1 at the placental barrier and blood-brain barrier in mice.

Methods

MDR1A and MDR1B proteins were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Paclitaxel or digoxin was continuously administered to pregnant Mdr1a^−/−/Mdr1b^−/− or wild-type mice, and the drug concentrations in the maternal and fetal plasma and maternal brain were quantified by LC-MS/MS.

Results

MDR1A and MDR1B proteins are expressed in the membrane of mouse placental labyrinth, and total MDR1 at the placental barrier amounts to about 30% of that at the blood-brain barrier. The fetal-to-maternal plasma concentration ratio of digoxin was only marginally affected in Mdr1a^−/−/Mdr1b^−/− mice, while that of paclitaxel showed a several-fold increase. No such difference between the two drugs was found in the maternal brain distribution. The impact per single MDR1 molecule on the fetal distribution of digoxin was calculated to be much lower than that on the brain distribution, but this was not the case for paclitaxel. Our pharmacokinetic model indicates that the impact of placental MDR1 is inversely correlated to the ratio of permeability through gap junctions connecting the two syncytiotrophoblast layers to passive diffusion permeability.

Conclusion

Our findings indicate that murine placental MDR1 has a minimal influence on the fetal concentration of certain substrates, such as digoxin, due to bypass transfer, probably via connexin26 gap junctions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-022-03165-6.

Fetal Membranes Contribute to Drug Transport across the Feto-Maternal Interface Utilizing the Breast Cancer Resistance Protein (BCRP)

During pregnancy, the placenta is established as a primary organ for drug transport at the maternal-fetal interface. The fetal membranes (FM) also form an interface with maternal tissues; however, their role in drug transport has not been previously investigated. Knowledge of drug transport across this feto-maternal interface along with the placenta can improve new drug development and testing for use during pregnancy. We also hypothesize that extracellular vesicles (exosomes 30–160 nm) released from the FM and placental cells may also contain drug transport proteins and might impact drug trafficking across the feto-maternal interfaces. The objectives were to (1) localize the breast cancer resistance protein (BCRP) in human FM; (2) determine the drug transport function of BCRP in chorion trophoblast cells (CTCs) of the FM; and (3) investigate the presence of BCRP in FM cell-derived exosomes, as a paracrine modifier of the tissue environment for transport functions. The gene and protein expressions of ABCG2/BCRP in FMs were determined by quantitative real-time PCR (qRT-PCR) and western blotting (WB) and were localized by immunohistochemistry (IHC). The surface expression of BCRP in FM cells was determined by flow cytometry. The functional role of BCRP was assessed by an EFFLUX dye multidrug resistance assay. The presence of BCRP in exosomes derived from CTCs and BeWo cells was examined using ExoView^®. Data derived from CTCs are compared with placental trophoblast cells (BeWo). BCRP is expressed and localized in the fetal membrane, primarily in the chorion trophoblast cell layer and scarcely in the amnion epithelial layer (AEC), and primarily localized on both AEC and CTC cell surfaces. Efflux assay data showed that FM cells have similar drug resistance activity as BeWo cells, suggesting that FM also have drug transportation capabilities. BeWo- and CTC-derived exosomes expressed limited BCRP protein on the surface, so it was predominantly contained in the exosomal lumen. As far as we are aware, this is the first study to report BCRP expression in fetal membrane cells and as cargo in fetal membrane-derived exosomes. We report that fetal membrane cells are capable of drug transportation. Based on these results, investigational drug trials should include the FM and its exosomes as possible drug transportation routes in pregnancy.

Ontogeny of renal, hepatic, and placental expression of ATP-binding cassette and solute carrier transporters in the rat and the rabbit

Species differences in developmental toxicity can be due to varying expression of xenobiotic transporters. Hence, knowledge on the ontogeny of these transporters, especially in human, rat and rabbit, is pivotal. Two superfamilies of transporters, the ATP-binding cassette (ABC) and the solute carrier (SLC) transporters, are well known for their role in the absorption, distribution and/or elimination of xenobiotics and endogenous substances. The aim of this study was to compare the expression levels of these xenobiotic transporters in liver, kidney and placenta of man, Wistar rat and New Zealand White rabbit during pre- and postnatal development. For this purpose, qPCR experiments were performed for rat and rabbit tissues and the gene expression profiles were compared with literature data from man, rat and rabbit. Data analysis showed large differences in transporter expression in development and between species. These results can be used to better understand developmental toxicity findings in non-clinical species and their relevance for man.

Overview of Drug Transporters in Human Placenta

The transport of drugs across the placenta is a point of great importance in pharmacotherapy during pregnancy. However, the knowledge of drug transport in pregnancy is mostly based on experimental clinical data, and the underlying biological mechanisms are not fully understood. In this review, we summarize the current knowledge of drug transporters in the human placenta. We only refer to human data since the placenta demonstrates great diversity among species. In addition, we describe the experimental models that have been used in human placental transport studies and discuss their availability. A better understanding of placental drug transporters will be beneficial for the health of pregnant women who need drug treatment and their fetuses.

A review of pregnancy-induced changes in opioid pharmacokinetics, placental transfer, and fetal exposure: Towards fetomaternal physiologically-based pharmacokinetic modeling to improve the treatment of neonatal opioid withdrawal syndrome

Physiologically-based pharmacokinetic (PBPK) modeling has emerged as a useful tool to study pharmacokinetics (PK) in special populations, such as pregnant women, fetuses, and newborns, where practical hurdles severely limit the study of drug behavior. PK in pregnant women is variable and everchanging, differing greatly from that in their nonpregnant female and male counterparts typically enrolled in clinical trials. PBPK models can accommodate pregnancy-induced physiological and metabolic changes, thereby providing mechanistic insights into maternal drug disposition and fetal exposure. Fueled by the soaring opioid epidemic in the United States, opioid use during pregnancy continues to rise, leading to an increased incidence of neonatal opioid withdrawal syndrome (NOWS). The severity of NOWS is influenced by a complex interplay of extrinsic and intrinsic factors, and varies substantially between newborns, but the extent of prenatal opioid exposure is likely the primary driver. Fetomaternal PBPK modeling is an attractive approach to predict in utero opioid exposure. To facilitate the development of fetomaternal PBPK models of opioids, this review provides a detailed overview of pregnancy-induced changes affecting the PK of commonly used opioids during gestation. Moreover, the placental transfer of these opioids is described, along with their disposition in the fetus. Lastly, the implementation of these factors into PBPK models is discussed. Fetomaternal PBPK modeling of opioids is expected to provide improved insights in fetal opioid exposure, which allows for prediction of postnatal NOWS severity, thereby opening the way for precision postnatal treatment of these vulnerable infants.

Mechanistic Modeling of Placental Drug Transfer in Humans: How Do Differences in Maternal/Fetal Fraction of Unbound Drug and Placental Influx/Efflux Transfer Rates Affect Fetal Pharmacokinetics?

Background: While physiologically based pharmacokinetic (PBPK) models generally predict pharmacokinetics in pregnant women successfully, the confidence in predicting fetal pharmacokinetics is limited because many parameters affecting placental drug transfer have not been mechanistically accounted for. Objectives: The objectives of this study were to implement different maternal and fetal unbound drug fractions in a PBPK framework; to predict fetal pharmacokinetics of eight drugs in the third trimester; and to quantitatively investigate how alterations in various model parameters affect predicted fetal pharmacokinetics. Methods: The ordinary differential equations of previously developed pregnancy PBPK models for eight drugs (acyclovir, cefuroxime, diazepam, dolutegravir, emtricitabine, metronidazole, ondansetron, and raltegravir) were amended to account for different unbound drug fractions in mother and fetus. Local sensitivity analyses were conducted for various parameters relevant to placental drug transfer, including influx/efflux transfer clearances across the apical and basolateral membrane of the trophoblasts. Results: For the highly-protein bound drugs diazepam, dolutegravir and ondansetron, the lower fraction unbound in the fetus vs. mother affected predicted pharmacokinetics in the umbilical vein by ≥10%. Metronidazole displayed blood flow-limited distribution across the placenta. For all drugs, umbilical vein concentrations were highly sensitive to changes in the apical influx/efflux transfer clearance ratio. Additionally, transfer clearance across the basolateral membrane was a critical parameter for cefuroxime and ondansetron. Conclusion: In healthy pregnancies, differential protein binding characteristics in mother and fetus give rise to minor differences in maternal-fetal drug exposure. Further studies are needed to differentiate passive and active transfer processes across the apical and basolateral trophoblast membrane.

Pharmacokinetics and placental transfer of dolutegravir in pregnancy

Dolutegravir is currently recommended by the WHO as the preferred first-line treatment for all people with HIV, including pregnant women. Estimates indicate that, by 2024, nearly 22 million adults in low- and middle-income countries will have transitioned to dolutegravir-based ART. It is therefore critical that there is a clear appreciation and understanding of the risks that may be associated with in utero exposure to dolutegravir. In this review we consolidate data from studies on dolutegravir and the placenta. The studies have largely focused on the pharmacokinetics and placental transfer of dolutegravir in pregnancy. These include studies on transplacental transfer of dolutegravir, ex vivo placenta perfusion models, physiologically based pharmacokinetic (PBPK) models and animal studies. The data available clearly demonstrate that placental transfer of dolutegravir occurs in moderate to high concentrations. Intracellular placental dolutegravir has been demonstrated in the placental villous tissue. There are limited data suggesting that pregnancy is associated with decreased maternal dolutegravir levels. In addition, PBPK models have great potential in predicting the passage of drugs through the placenta and further contributing towards the elucidation of fetal exposure. The animal studies available demonstrate that in utero dolutegravir exposure can be associated with neural tube defects. Taking into consideration that antiretroviral exposure may be associated with poor placental development or function and increased risk of adverse effects to the fetus, it is crucially important that these risks are evaluated, especially with the rapid scale up of dolutegravir-based ART into national treatment programmes.

Usage of Tacrolimus and Mycophenolic Acid During Conception, Pregnancy, and Lactation, and Its Implications for Therapeutic Drug Monitoring: A Systematic Critical Review

BACKGROUND

Conception, pregnancy, and lactation following solid organ transplantation require appropriate management. The most frequently used immunosuppressive drug combination after solid organ transplantation consists of tacrolimus (Tac) plus mycophenolic acid (MPA). Here, the effects of Tac and MPA on fertility, pregnancy, and lactation are systematically reviewed, and their implications for therapeutic drug monitoring (TDM) are discussed.

METHODS

A systematic literature search was performed (August 19, 2019) using Ovid MEDLINE, EMBASE, the Cochrane Central Register of controlled trials, Google Scholar, and Web of Science, and 102 studies were included. Another 60 were included from the reference list of the published articles.

RESULTS

As MPA is teratogenic, women who are trying to conceive are strongly recommended to switch from MPA to azathioprine. MPA treatment in men during conception seems to have no adverse effect on pregnancy outcomes. Nevertheless, in 2015, the drug label was updated with additional risk minimization measures in a pregnancy prevention program. Data on MPA pharmacokinetics during pregnancy and lactation are limited. Tac treatment during conception, pregnancy, and lactation seems to be safe in terms of the health of the mother, (unborn) child, and allograft. However, Tac may increase the risk of hypertension, preeclampsia, preterm birth, and low birth weight. Infants will ingest very small amounts of Tac via breast milk from mothers treated with Tac. However, no adverse outcomes have been reported in children exposed to Tac during lactation. During pregnancy, changes in Tac pharmacokinetics result in increased unbound to whole-blood Tac concentration ratio. To maintain Tac concentrations within the target range, increased Tac dose and intensified TDM may be required. However, it is unclear if dose adjustments during pregnancy are necessary, considering the higher concentration of (active) unbound Tac.

CONCLUSIONS

Tac treatment during conception, pregnancy and lactation seems to be relatively safe. Due to pharmacokinetic changes during pregnancy, a higher Tac dose might be indicated to maintain target concentrations. However, more evidence is needed to make recommendations on both Tac dose adjustments and alternative matrices than whole-blood for TDM of Tac during pregnancy. MPA treatment in men during conception seems to have no adverse effect on pregnancy outcomes, whereas MPA use in women during conception and pregnancy is strongly discouraged.

Effects of Maternal Obesity and Gestational Diabetes Mellitus on the Placenta: Current Knowledge and Targets for Therapeutic Interventions

Obesity and gestational diabetes mellitus (GDM) are becoming more common among pregnant women worldwide and are individually associated with a number of placenta-mediated obstetric complications, including preeclampsia, macrosomia, intrauterine growth restriction and stillbirth. The placenta serves several functions throughout pregnancy and is the main exchange site for the transfer of nutrients and gas from mother to fetus. In pregnancies complicated by maternal obesity or GDM, the placenta is exposed to environmental changes, such as increased inflammation and oxidative stress, dyslipidemia, and altered hormone levels. These changes can affect placental development and function and lead to abnormal fetal growth and development as well as metabolic and cardiovascular abnormalities in the offspring. This review aims to summarize current knowledge on the effects of obesity and GDM on placental development and function. Understanding these processes is key in developing therapeutic interventions with the goal of mitigating these effects and preventing future cardiovascular and metabolic pathology in subsequent generations.

The trophoblast clock controls transport across placenta in mice

In mammals, 24-h rhythms of physiology and behavior are organized by a body-wide network of clock genes and proteins. Despite the well-known function of the adult circadian system, the roles of maternal, fetal and placental clocks during pregnancy are poorly defined. In the mature mouse placenta, the labyrinth zone (LZ) is of fetal origin and key for selective nutrient and waste exchange. Recently, clock gene expression has been detected in LZ and other fetal tissues; however, there is no evidence of a placental function controlled by the LZ clock. Here, we demonstrate that specifically the trophoblast layer of the LZ harbors an already functional clock by late gestation, able to regulate in a circadian manner the expression and activity of the xenobiotic efflux pump, ATP-binding cassette sub-family B member 1 (ABCB1), likely gating the fetal exposure to drugs from the maternal circulation to certain times of the day. As more than 300 endogenous and exogenous compounds are substrates of ABCB1, our results might have implications in choosing the maternal treatment time when aiming either maximal/minimal drug availability to the fetus/mother.

Transfer of rhodamine-123 into the brain and cerebrospinal fluid of fetal, neonatal and adult rats

Background

Adenosine triphosphate binding cassette transporters such as P-glycoprotein (PGP) play an important role in drug pharmacokinetics by actively effluxing their substrates at barrier interfaces, including the blood-brain, blood-cerebrospinal fluid (CSF) and placental barriers. For a molecule to access the brain during fetal stages it must bypass efflux transporters at both the placental barrier and brain barriers themselves. Following birth, placental protection is no longer present and brain barriers remain the major line of defense. Understanding developmental differences that exist in the transfer of PGP substrates into the brain is important for ensuring that medication regimes are safe and appropriate for all patients.

Methods

In the present study PGP substrate rhodamine-123 (R123) was injected intraperitoneally into E19 dams, postnatal (P4, P14) and adult rats. Naturally fluorescent properties of R123 were utilized to measure its concentration in blood-plasma, CSF and brain by spectrofluorimetry (Clariostar). Statistical differences in R123 transfer (concentration ratios between tissue and plasma ratios) were determined using Kruskal-Wallis tests with Dunn’s corrections.

Results

Following maternal injection the transfer of R123 across the E19 placenta from maternal blood to fetal blood was around 20 %. Of the R123 that reached fetal circulation 43 % transferred into brain and 38 % into CSF. The transfer of R123 from blood to brain and CSF was lower in postnatal pups and decreased with age (brain: 43 % at P4, 22 % at P14 and 9 % in adults; CSF: 8 % at P4, 8 % at P14 and 1 % in adults). Transfer from maternal blood across placental and brain barriers into fetal brain was approximately 9 %, similar to the transfer across adult blood-brain barriers (also 9 %). Following birth when placental protection was no longer present, transfer of R123 from blood into the newborn brain was significantly higher than into adult brain (3 fold, p < 0.05).

Conclusions

Administration of a PGP substrate to infant rats resulted in a higher transfer into the brain than equivalent doses at later stages of life or equivalent maternal doses during gestation. Toxicological testing of PGP substrate drugs should consider the possibility of these patient specific differences in safety analysis.

Formulation effects on paclitaxel transfer and uptake in the human placenta

Diagnosis and treatment of breast cancer in pregnancy can result in morbidity and mortality for the mother and fetus. Many new paclitaxel nanoformulations commercially available worldwide for breast cancer treatment are being adopted due to favorable dosing regimens and side effect profiles, but their transplacental transport and resultant fetal exposure remain unknown. Here, we examine three formulations: Taxol (paclitaxel dissolved in Kolliphor EL and ethanol); Abraxane (albumin nanoparticle); and Genexol-PM (polymeric micelle). In the ex vivo dually perfused human placental cotyledon, placental accumulation of Genexol-PM is higher than Taxol, and both nanoformulations have lower maternal concentrations of paclitaxel over time. In vitro studies of these formulations and fluorescent nanoparticle analogs demonstrate that Genexol-PM allows paclitaxel to overcome P-glycoprotein efflux, but Abraxane behaves as a free drug formulation. We anticipate that these findings will impact future development of rational and safe treatment strategies for pregnancy-associated breast cancer and other diseases.

Social Determinants of Placental Health and Future Disease Risks for Babies

Birthweight is a well-known predictor of adult-onset chronic disease. The placenta plays a necessary role in regulating fetal growth and determining birth size. Maternal stressors that affect placental function and prenatal growth include maternal overnutrition and undernutrition, toxic social stress, and exposure to toxic chemicals. These stressors lead to increased vulnerability to disease within any population. This vulnerability arises from placental and fetal exposure to stressors during fetal life. The biological drivers linking various social determinants of health to compromised placental function and fetal development have been little studied.

Expression of P-gp in Glioblastoma: What we can Learn from Brain Development

P-Glycoprotein (P-gp) is a 170-kDa transmembrane glycoprotein that works as an efflux pump and confers multidrug resistance (MDR) in normal tissues and tumors, including nervous tissues and brain tumors. In the developing telencephalon, the endothelial expression of P-gp, and the subcellular localization of the transporter at the luminal endothelial cell (EC) plasma membrane are early hallmarks of blood-brain barrier (BBB) differentiation and suggest a functional BBB activity that may complement the placental barrier function and the expression of P-gp at the blood-placental interface. In early fetal ages, P-gp has also been immunolocalized on radial glia cells (RGCs), located in the proliferative ventricular zone (VZ) of the dorsal telencephalon and now considered to be neural progenitor cells (NPCs). RG-like NPCs have been found in many regions of the developing brain and have been suggested to give rise to neural stem cells (NSCs) of adult subventricular (SVZ) neurogenic niches. The P-gp immunosignal, associated with RG-like NPCs during cortical histogenesis, progressively decreases in parallel with the last waves of neuroblast migrations, while 'outer' RGCs and the deriving astrocytes do not stain for the efflux transporter. These data suggest that in human glioblastoma (GBM), P-gp expressed by ECs may be a negligible component of tumor MDR. Instead, tumor perivascular astrocytes may dedifferentiate and resume a progenitor-like P-gp activity, becoming MDR cells and contribute, together with perivascular P-gpexpressing glioma stem-like cells (GSCs), to the MDR profile of GBM vessels. In conclusion, the analysis of Pgp immunolocalization during brain development may contribute to identify the multiple cellular sources in the GBM vessels that may be involved in P-gp-mediated chemoresistance and can be responsible for GBM therapy failure and tumor recurrence.

Over-the-counter analgesics during pregnancy: a comprehensive review of global prevalence and offspring safety

BACKGROUND

Analgesia during pregnancy is often necessary. Due to their widespread availability, many mothers opt to use over-the-counter (OTC) analgesics. Those analgesic compounds and their metabolites can readily cross the placenta and reach the developing foetus. Evidence for safety or associations with adverse health outcomes is conflicting, limiting definitive decision-making for healthcare professionals.

OBJECTIVE AND RATIONALE

This review provides a detailed and objective overview of research in this field. We consider the global prevalence of OTC analgesia during pregnancy, explain the current mechanistic understanding of how analgesic compounds cross the placenta and reach the foetus, and review current research on exposure associations with offspring health outcomes.

SEARCH METHODS

A comprehensive English language literature search was conducted using PubMed and Scopus databases. Different combinations of key search terms were used including 'over-the-counter/non-prescription analgesics', 'pregnancy', 'self-medication', 'paracetamol', 'acetaminophen', 'diclofenac', 'aspirin', 'ibuprofen', 'in utero exposure', 'placenta drug transport', 'placental transporters', 'placenta drug metabolism' and 'offspring outcomes'.

OUTCOMES

This article examines the evidence of foetal exposure to OTC analgesia, starting from different routes of exposure to evidence, or the lack thereof, linking maternal consumption to offspring ill health. There is a very high prevalence of maternal consumption of OTC analgesics globally, which is increasing sharply. The choice of analgesia selected by pregnant women differs across populations. Location was also observed to have an effect on prevalence of use, with more developed countries reporting the highest consumption rates. Some of the literature focuses on the association of in utero exposure at different pregnancy trimesters and the development of neurodevelopmental, cardiovascular, respiratory and reproductive defects. This is in contrast to other studies which report no associations.

WIDER IMPLICATIONS

The high prevalence and the challenges of reporting exact consumption rates make OTC analgesia during pregnancy a pressing reproductive health issue globally. Even though some healthcare policy-making authorities have declared the consumption of some OTC analgesics for most stages of pregnancy to be safe, such decisions are often based on partial review of literature. Our comprehensive review of current evidence highlights that important knowledge gaps still exist. Those areas require further research in order to provide pregnant mothers with clear guidance with regard to OTC analgesic use during pregnancy.

Aberrant DNA Methylation of ABC Transporters in Cancer

ATP-binding cassette (ABC) transporters play a crucial role in multidrug resistance (MDR) of cancers. They function as efflux pumps, resulting in limited effectiveness or even failure of therapy. Increasing evidence suggests that ABC transporters are also involved in tumor initiation, progression, and metastasis. Tumors frequently show multiple genetic and epigenetic abnormalities, including changes in histone modification and DNA methylation. Alterations in the DNA methylation status of ABC transporters have been reported for a variety of cancer types. In this review, we outline the current knowledge of DNA methylation of ABC transporters in cancer. We give a brief introduction to structure, function, and gene regulation of ABC transporters that have already been investigated for their DNA methylation status in cancer. After giving an overview of the applied methodologies and the CpGs analyzed, we summarize and discuss the findings on aberrant DNA methylation of ABC transporters by cancer types. We conclude our review with the discussion of the potential to target aberrant DNA methylation of ABC transporters for cancer therapy.

Low oxygen tension differentially regulates the expression of placental solute carriers and ABC transporters

Low oxygen concentration, or hypoxia, is an important physiological regulator of placental function including chemical disposition. Here, we compared the ability of low oxygen tension to alter the expression of solute carriers (SLC) and ABC transporters in two human placental models, namely BeWo cells and term placental explants. We found that exposure to low oxygen concentration differentially regulates transporter expression in BeWo cells, including downregulation of ENT1, OATP4A1, OCTN2, BCRP, and MRP2/3/5, and upregulation of CNT1, OAT4, OATP2B1, SERT, SOAT, and MRP1. Similar upregulation of MRP1 and downregulation of MRP5 and BCRP were observed in explants, whereas uptake transporters were decreased or unchanged. Furthermore, a screening of transcriptional regulators of transporters revealed that hypoxia leads to a decrease in the mRNA levels of aryl hydrocarbon receptor, nuclear factor erythroid 2-related factor 2, and retinoid x receptor alpha in both human placental models. These data suggest that transporter expression is differentially regulated by oxygen concentration across experimental human placental models.

The impact of intrauterine growth restriction on cytochrome P450 enzyme expression and activity

With the increased prevalence of non-communicable disease and availability of medications to treat these and other conditions, a pregnancy free from prescribed medication exposure is rare. Up to 99% of women take at least one medication during pregnancy. These medications can be divided into those used to improve maternal health and wellbeing (e.g., analgesics, antidepressants, antidiabetics, antiasthmatics), and those used to promote the baby's wellbeing in either fetal (e.g., anti-arrhythmics) or postnatal life (e.g., antenatal glucocorticoids). These medications are needed for pre-existing or coincidental illnesses in the mother, maternal conditions induced by the pregnancy itself through to conditions that arise in the fetus or that will be encountered by the newborn. Thus, medications administered to the mother may be used to treat the mother, the fetus or both. Metabolism of medications is regulated by a range of physiological processes that change during pregnancy. Other pathological processes such as placental insufficiency can in turn have both immediate and lifelong adverse health consequences for babies. Individuals born growth restricted are more likely to require medications but may also have an altered ability to metabolise these medications in fetal and postnatal life. This review aims to determine the effect of suboptimal fetal growth on the fetal expression of the drug metabolising enzymes (DMEs) that convert medications into active or inactive metabolites, and the transporters that remove both these medications and their metabolites from the fetal compartment.

Safety of oral ivermectin during pregnancy: a systematic review and meta-analysis

Background

About 3·7 billion doses of ivermectin have been distributed in mass drug administration (MDA) campaigns globally over the past 30 years. At 10−100 times higher than current human doses, ivermectin is a known teratogen in mammals. During these campaigns with recommended doses, pregnant women might be inadvertently exposed. We therefore aimed to evaluate the existing evidence for serious and non-serious adverse events after ivermectin exposure in pregnant women.

Methods

For this systematic review and meta-analysis, we searched relevant databases and trial registry platforms on July 15, 2018, for randomised controlled trials (RCTs) and observational studies that reported adverse events in pregnant women. We did not use language or date restrictions. Outcomes of interest were spontaneous abortions, stillbirths, congenital anomalies, and neonatal death (serious adverse events), as well as maternal morbidity, preterm births, and low birthweight (adverse events). The risk of bias was assessed using the Newcastle-Ottawa Scale for observational studies and the Cochrane Risk of Bias Tool for RCTs. We did the meta-analysis of observational studies and RCTs separately. The quality of evidence was assessed using the GRADE approach. The study protocol is registered with PROSPERO, protocol CRD42016046914.

Findings

We identified 147 records, of which only five observational studies and one RCT were included for quantitative analysis; these studies were published between 1990 and 2008, and were done in six African countries. 893 women with 899 pregancy outcomes were included, of whom 496 pregnant women (500 pregnancy outcomes) received ivermectin inadvertently during MDA campaigns in the observational studies and 397 pregnant women (399 pregnancy outcomes) purposely received ivermectin as part of the open-label RCT. No study reported neonatal deaths, maternal morbidity, preterm births, or low birthweight. It is unclear whether exposure to ivermectin during pregnancy increases the risk of spontaneous abortions and stillbirths (odds ratio [OR] 1·15 [95% CI 0·75−1·78] with very low certainty of evidence for the four observational studies and 0·62 [0·18−2·14] with very low certainty of evidence for the RCT) or congenital anomalies (OR 1·69 [95% CI 0·83−3·41] with very low certainty of evidence for the five observational studies and 1·10 [0·07−17·65] with very low certainty of evidence for the RCT).

Interpretation

There is insufficient evidence to conclude on the safety profile of ivermectin during pregnancy. Treatment campaigns should focus additional efforts on preventing inadvertent treatment of pregnant women.

Funding

Unitaid.

Gestational Age-Dependent Abundance of Human Placental Transporters as Determined by Quantitative Targeted Proteomics

Some women take medication during pregnancy to address a variety of clinical conditions. Because of ethical and logistical concerns, it is impossible to determine fetal drug exposure, and therefore fetal risk, during pregnancy. Hence, alternative approaches need to be developed to predict maternal-fetal drug exposure throughout pregnancy. To do so, we previously developed and verified a maternal-fetal physiologically based pharmacokinetic model, which can predict fetal exposure to drugs that passively cross the placenta. However, many drugs are actively transported by the placenta (e.g., human immunodeficiency virus protease inhibitors). To extend our maternal-fetal physiologically based pharmacokinetic model to these actively transported drugs, we determined the gestational age–dependent changes in the protein abundance of placental transporters. Total cellular membrane fractions from first trimester (T1; n = 15), second trimester (T2; n = 19), and term (n = 15) human placentae obtained from uncomplicated pregnancies were isolated by ultracentrifugation. Transporter protein abundance was determined by targeted quantitative proteomics using liquid chromatography tandem mass specrometry. We observed that breast cancer resistance protein and P-glycoprotein abundance significantly decreased from T1 to term by 55% and 69%, respectively (per gram of tissue). Organic anion–transporting polypeptide (OATP) 2B1 abundance significantly decreased from T1 to T2 by 32%. In contrast, organic cation transporter (OCT) 3 and organic anion transporter 4 abundance significantly increased with gestational age (2-fold from T1 to term, 1.6-fold from T2 to term). Serotonin transporter and norepinephrine transporter did not change with gestational age. The abundance of bile salt export pump, multidrug resistance-associated protein 1-5, Na⁺-taurocholate cotransporting polypeptide, OATP1B1, OATP1B3, OCTN1-2, concentrative nucleoside transporter 1-3, equilibrative nucleoside transporter 2, and multidrug and toxin extrusion 1 could not be quantified. These data can be incorporated into our maternal-fetal physiologically based pharmacokinetic model to predict fetal exposure to drugs that are actively transported across the placenta.

Pregnancy and CYP3A5 Genotype Affect Day 7 Plasma Lumefantrine Concentrations

Pregnancy and pharmacogenetics variation alter drug disposition and treatment outcome. The objective of this study was to investigate the effect of pregnancy and pharmacogenetics variation on day 7 lumefantrine (LF) plasma concentration and therapeutic responses in malaria-infected women treated with artemether-lumefantrine (ALu) in Tanzania. A total of 277 (205 pregnant and 72 nonpregnant) women with uncomplicated Plasmodium falciparum malaria were enrolled. Patients were treated with ALu and followed up for 28 days. CYP3A4, CYP3A5, and ABCB1 genotyping were done. Day 7 plasma LF concentration and the polymerase chain reaction (PCR) - corrected adequate clinical and parasitological response (ACPR) at day 28 were determined. The mean day 7 plasma LF concentrations were significantly lower in pregnant women than nonpregnant women [geometric mean ratio = 1.40; 95% confidence interval (CI) of geometric mean ratio (1.119-1.1745), P < 0.003]. Pregnancy, low body weight, and CYP3A5*1/*1 genotype were significantly associated with low day 7 LF plasma concentration (P < 0.01). PCR-corrected ACPR was 93% (95% CI = 89.4-96.6) in pregnant women and 95.7% (95% CI = 90.7-100) in nonpregnant women. Patients with lower day 7 LF concentration had a high risk of treatment failure (mean 652 vs. 232 ng/ml, P < 0.001). In conclusion, pregnancy, low body weight, and CYP3A5*1 allele are significant predictors of low day 7 LF plasma exposure. In turn, lower day 7 LF concentration is associated with a higher risk of recrudescence. SIGNIFICANCE STATEMENT: This study reports a number of factors contributing to the lower day 7 lumefantrine (LF) concentration in women, which includes pregnancy, body weight, and CYP3A5*1/*1 genotype. It also shows that day 7 LF concentration is a main predictor of malaria treatment. These findings highlight the need to look into artemether-LF dosage adjustment in pregnant women so as to be able to maintain adequate drug concentration, which is required to reduce treatment failure rates in pregnant women.

Prediction of Maternal and Fetal Pharmacokinetics of Dolutegravir and Raltegravir Using Physiologically Based Pharmacokinetic Modeling

BACKGROUND

Predicting drug pharmacokinetics in pregnant women including placental drug transfer remains challenging. This study aimed to develop and evaluate maternal-fetal physiologically based pharmacokinetic models for two antiretroviral drugs, dolutegravir and raltegravir.

Drugs in pregnancy: Pharmacologic and physiologic changes that affect clinical care

Pharmacologic interventions play a major role in obstetrical care throughout pregnancy, labor and delivery and the postpartum. Traditionally, obstetrical providers have utilized standard dosing regimens developed for non-obstetrical indications based on pharmacokinetic knowledge from studies in men or non-pregnant women. With the recognition of pregnancy as a special pharmacokinetic population in the late 1990s, investigators have begun to study drug disposition in this unique patient dyad. Many of the basic physiologic changes that occur during pregnancy have significant impact on drug absorption, distribution and clearance. Activity of Phase I and Phase II drug metabolizing enzymes are differentially altered by pregnancy, resulting in drug concentrations sufficiently different for some medications that efficacy or toxicity is affected. Placental transporters play a major dynamic role in determining fetal drug exposure. In the past two decades, we have begun to expand our understanding of obstetrical pharmacology; however, to truly optimize pharmacologic care of our pregnant patients and their developing fetus, additional research is critically needed.

Placental transporter-mediated drug interactions and offspring congenital anomalies

Aims

P‐glycoprotein (P‐gp) and breast cancer resistance protein (BCRP) are efflux transporters expressed in the placenta, limiting their substrates from reaching the foetus. Our aim was to investigate if concomitant prenatal exposure to several substrates or inhibitors of these transporters increases the risk of congenital anomalies.

Methods

The national Drugs and Pregnancy database, years 1996–2014, was utilized in this population‐based birth cohort study. In the database, the Medical Birth Register, the Register on Induced Abortions, the Malformation register and the Register on Reimbursed Drug Purchases have been linked. The University of Washington Metabolism and Transport Drug Interaction Database was used to identify substrates and inhibitors of P‐gp and BCRP. We included singleton pregnancies ending in birth or elective termination of pregnancy due to foetal anomaly. Known teratogens were excluded. We identified women exposed 1 month before pregnancy or during the first trimester to P‐gp/BCRP polytherapy (n = 21 186); P‐gp/breast cancer resistance protein monotherapy (n = 97 906); non‐P‐gp/BCRP polytherapy (n = 78 636); and unexposed (n = 728 870). We investigated the association between the exposure groups and major congenital anomalies using logistic regression adjusting for several confounders.

Results

The prevalence of congenital anomalies was higher in the P‐gp/BCRP polytherapy group (5.5%) compared to the P‐gp/BCRP monotherapy (4.7%, OR 1.13; 95% CI 1.05–1.21), the non‐P‐gp/BCRP polytherapy (4.9%, OR 1.14; 95% CI 1.06–1.22), and to the unexposed groups (4.2%, OR 1.23; 95% CI 1.15–1.31).

Conclusion

The results suggest a role of placental transporter‐mediated drug interactions in teratogenesis.

Maternal malnutrition impacts placental morphology and transporter expression: an origin for poor offspring growth

The placenta promotes fetal growth through nutrient transfer and selective barrier systems. An optimally developed placenta can adapt to changes in the pregnancy environment, buffering the fetus from adverse exposures. We hypothesized that the placenta adapts differently to suboptimal maternal diets, evidenced by changes in placental morphology, developmental markers and key transport systems. Mice were fed a control diet (CON) during pregnancy, undernourished (UN) by 30% of control intake from gestational day (GD) 5.5-18.5 or fed 60% high-fat diet (HF) 8 weeks before and during pregnancy. At GD18.5, placental morphometry, development and transport were assessed. Junctional and labyrinthine areas of UN and HF placentae were smaller than CON by >10%. Fetal blood space area and fetal blood space:fetal weight ratios were reduced in HF vs. CON and UN. Trophoblast giant cell marker Ctsq mRNA expression was lower in UN vs. HF, and expression of glycogen cell markers Cx31.1 and Pcdh12 was lower in HF vs. UN. Efflux transporter Abcb1a mRNA expression was lower in HF vs. UN, and Abcg2 expression was lower in UN vs. HF. mRNA expression of fatty acid binding protein Fabp_pm was higher in UN vs. CON and HF. mRNA and protein levels of the lipid transporter FAT/CD36 were lower in UN, and FATP4 protein levels were lower in HF vs. UN. UN placentae appear less mature with aberrant transport, whereas HF placentae adapt to excessive nutrient supply. Understanding placental adaptations to common nutritional adversities may reveal mechanisms underlying the developmental origins of later disease.

Contributions of Drug Transporters to Blood-Placental Barrier

The placenta is the only organ linking two different individuals, mother and fetus, termed as blood-placental barrier. The functions of the blood-placental barrier are to regulate material transfer between the maternal and fetal circulation. The main functional units are the chorionic villi within which fetal blood is separated by only three or four cell layers (placental membrane) from maternal blood in the surrounding intervillous space. A series of drug transporters such as P-glycoprotein (P-GP), breast cancer resistance protein (BCRP), multidrug resistance-associated proteins (MRP1, MRP2, MRP3, MRP4, and MRP5), organic anion-transporting polypeptides (OATP4A1, OATP1A2, OATP1B3, and OATP3A1), organic anion transporter 4 (OAT4), organic cation transporter 3 (OCT3), organic cation/carnitine transporters (OCTN1 and OCTN2), multidrug and toxin extrusion 1 (MATE1), and equilibrative nucleoside transporters (ENT1 and ENT2) have been demonstrated on the apical membrane of syncytiotrophoblast, some of which also expressed on the basolateral membrane of syncytiotrophoblast or fetal capillary endothelium. These transporters are involved in transport of most drugs in the placenta, in turn, affecting drug distribution in fetus. Moreover, expressions of these transporters in the placenta often vary along with the gestational ages and are also affected by pathophysiological factor. This chapter will mainly illustrate function and expression of these transporters in placentas, their contribution to drug distribution in fetus, and their clinical significance.

Loss of Placental P-Glycoprotein May Be a Common Pathophysiologic Pathway for First Trimester Spontaneous Miscarriages

INTRODUCTION

P-glycoprotein the highly conserved mammalian adenosine triphosphate-binding cassette transmembrane multidrug protein transporter is involved in peri-implantation events and fetal placental development. Greater expression in early versus late pregnancy and localization in both syncytio- and cytotrophoblast indicate that P-glycoprotein transports substances across the uterine epithelium during early pregnancy and protects the conceptus from toxic substances during implantation and early embryogenesis. We hypothesized that P-glycoprotein is involved in the physiologic maintenance of early pregnancy and that P-glycoprotein dysregulation may be involved in early pregnancy pathologies.

METHODS

First trimester dilation and curettage specimens were selected retrospectively from the archives of the Department of Pathology from spontaneous miscarriages (n = 36) and elective termination of pregnancy (n = 20). Two P-glycoprotein specific monoclonal antibodies JSB1and C219 were used on formalin-fixed, paraffin-embedded 5µ tissue sections. The location, intensity, and percentage of P-glycoprotein chorionic villous immunostaining were semiquantitated.

RESULTS

Spontaneous miscarriages demonstrated absence or significant reduction in P-glycoprotein compared to elective terminations; 75% (27/36) showed total absence of P-glycoprotein, 19% (7/36) showed only rare villi with discontinuous immunostaining, and 6% (2/36) showed weak immunostaining. In contrast, 90% of elective terminations (18/20) showed positive immunostaining for P-glycoprotein and only 10% (2/20) showed loss of P-glycoprotein expression (P < .0001).

DISCUSSION

We report a dramatic loss/decrease of P-glycoprotein in first trimester spontaneous miscarriages. This finding in conjunction with the known high expression of P-glycoprotein in normal first trimester placental tissues suggests an important role of P-glycoprotein in the maintenance of early pregnancy.

Racial association and pharmacotherapy in neonatal opioid withdrawal syndrome

OBJECTIVE

To determine if racial differences are associated with Neonatal Opioid Withdrawal Syndrome (NOWS) severity.

STUDY DESIGN

A 10-year (2008-2017) retrospective cohort of infants ≥35 weeks gestation with prenatal exposure to opioids was included. The primary measure was the need for pharmacotherapy. Multivariable logistic regression and propensity score analysis were performed.

RESULTS

Among 345 infants with NOWS, 111 (32%) were black infants with 70% of them requiring pharmacotherapy as compared with 84% of white infants. Upon adjusting for significant covariates (methadone, benzodiazepine use, and gestational age), black infants were 57% less likely than whites to require pharmacotherapy (Odds ratio: 0.43, 95%CI: 0.22-0.80, p = 0.009). Similar results were observed with propensity score analysis.

CONCLUSIONS

Significant racial disparity observed may be secondary to genetic variations in opioid pharmacogenomics and/or extrinsic factors. Large-scale studies are warranted to include race in predictive models for early pharmacological intervention.