Pharmacogenetics of drug-induced birth defects: the role of polymorphisms of placental transporter proteins

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.

Non-Nutritive Sweeteners Acesulfame Potassium and Sucralose Are Competitive Inhibitors of the Human P-glycoprotein/Multidrug Resistance Protein 1 (PGP/MDR1)

Non-nutritive sweeteners (NNS) are popular sugar replacements used in foods, beverages, and medications. Although NNS are considered safe by regulatory organizations, their effects on physiological processes such as detoxification are incompletely understood. Previous studies revealed that the NNS sucralose (Sucr) altered P-glycoprotein (PGP) expression in rat colon. We also demonstrated that early-life exposure to NNS Sucr and acesulfame potassium (AceK) compromises mouse liver detoxification. Building upon these initial discoveries, we investigated the impact of AceK and Sucr on the PGP transporter in human cells to assess whether NNS influence its key role in cellular detoxification and drug metabolism. We showed that AceK and Sucr acted as PGP inhibitors, competing for the natural substrate-binding pocket of PGP. Most importantly, this was observed after exposure to concentrations of NNS within expected levels from common foods and beverage consumption. This may suggest risks for NNS consumers, either when taking medications that require PGP as the primary detoxification transporter or during exposure to toxic compounds.

Breastfeeding, pregnancy, medicines, neurodevelopment, and population databases: the information desert

Background

The pharmacoepidemiology of the long-term benefits and harms of medicines in pregnancy and breastfeeding has received little attention. The impact of maternal medicines on children is increasingly recognised as a source of avoidable harm. The focus of attention has expanded from congenital anomalies to include less visible, but equally important, outcomes, including cognition, neurodevelopmental disorders, educational performance, and childhood ill-health. Breastfeeding, whether as a source of medicine exposure, a mitigator of adverse effects or as an outcome, has been all but ignored in pharmacoepidemiology and pharmacovigilance: a significant ‘blind spot’.

Whole-population data on breastfeeding: why we need them

Optimal child development and maternal health necessitate breastfeeding, yet little information exists to guide families regarding the safety of medicine use during lactation. Breastfeeding initiation or success may be altered by medicine use, and breastfeeding may obscure the true relationship between medicine exposure during pregnancy and developmental outcomes. Absent or poorly standardised recording of breastfeeding in most population databases hampers analysis and understanding of the complex relationships between medicine, pregnancy, breastfeeding and infant and maternal health. The purpose of this paper is to present the arguments for breastfeeding to be included alongside medicine use and neurodevelopmental outcomes in whole-population database investigations of the harms and benefits of medicines during pregnancy, the puerperium and postnatal period. We review: 1) the current situation, 2) how these complexities might be accommodated in pharmacoepidemiological models, using antidepressants and antiepileptics as examples; 3) the challenges in obtaining comprehensive data.

Conclusions

The scarcity of whole-population data and the complexities of the inter-relationships between breastfeeding, medicines, co-exposures and infant outcomes are significant barriers to full characterisation of the benefits and harms of medicines during pregnancy and breastfeeding. This makes it difficult to answer the questions: ‘is it safe to breastfeed whilst taking this medicine’, and ‘will this medicine interfere with breastfeeding and/ or infants’ development’?

Disruption of small molecule transporter systems by Transporter-Interfering Chemicals (TICs)

Small molecule transporters (SMTs) in the ABC and SLC families are important players in disposition of diverse endo- and xenobiotics. Interactions of environmental chemicals with these transporters were first postulated in the 1990s, and since validated in numerous in vitro and in vivo scenarios. Recent results on the co-crystal structure of ABCB1 with the flame-retardant BDE-100 demonstrate that a diverse range of man-made and natural toxic molecules, hereafter termed transporter-interfering chemicals (TICs), can directly bind to SMTs and interfere with their function. TIC-binding modes mimic those of substrates, inhibitors, modulators, inducers, and possibly stimulants through direct and allosteric mechanisms. Similarly, the effects could directly or indirectly agonize, antagonize or perhaps even prime the SMT system to alter transport function. Importantly, TICs are distinguished from drugs and pharmaceuticals that interact with transporters in that exposure is unintended and inherently variant. Here, we review the molecular mechanisms of environmental chemical interaction with SMTs, the methodological considerations for their evaluation, and the future directions for TIC discovery.

Principles of Pharmacokinetics in the Pregnant Woman and Fetus

Pregnancy profoundly alters a woman's physiology. These changes alter drug absorption, distribution, metabolism, and elimination and emphasize the pharmacologic complexity of pregnancy. They also emphasize the dangers of extrapolating pharmacologic expectations from nonpregnant populations to pregnant women and their fetuses. Although concerns about fetal safety have historically limited pharmacokinetic studies during pregnancy, it is important to recognize that many medications are clinically indicated for various maternal or fetal conditions, and it is particularly important that these therapies be evidence-based with appropriate study, including short-term and long-term outcomes data.

Placental P-glycoprotein inhibition enhances susceptibility to Di-(2-ethylhexyl)-phthalate induced cardiac malformations in mice: A possibly promising target for congenital heart defects prevention

Backgrounds

Reducing toxicants transplacental rates could contribute to the prevention of congenital heart defects (CHDs). Placental P-glycoprotein (P-gp) plays a vital role in fetal toxicants exposure and subsequently affects the risk of toxicants-induced birth defects. However, data on the role of placental P-gp in decreasing toxicants-induced cardiac anomalies is extremely limited. This study aimed to explore the protective role of placental P-gp in reducing the risk of Di-(2-ethylhexyl)-phthalate (DEHP) induced cardiac anomalies in mice.

Methods

The C57BL mice were randomly divided into four groups: the vehicle group (corn oil, n = 10), 500mg/Kg DEHP group (n = 15), 3mg/Kg verapamil group (n = 10) and 500mg/Kg DEHP & 3mg/Kg verapamil group (n = 20). Pregnant dams in different group received respective intervention by gavage once daily from E6.5–14.5. Maternal weights were monitored every day and samples were collected at E15.5. HE staining was used to examine fetal cardiac malformations. Real-time quantitative PCR (RT-qPCR) and Western-Blot were applied to detect Nkx2.5/Gata4/Tbx5/Mef2c/Chf1 mRNA and protein expression, respectively. The mRNA expression of peroxisome proliferator-activated receptor γ (PPARγ) was also determined using RT-qPCR.

Results

Co-administration of verapamil and DEHP significantly elevated fetal cardiac malformation rates, in comparison with the DEHP group, the verapamil group and the vehicle group. Different phenotypes of cardiac anomalies, including septal defects and ventricular myocardium noncompaction, were noted both in the DEHP group and the DEHP & verapamil group. The ventricular myocardium noncompaction appeared to be more severe in the DEHP & verapamil group. Fetal cardiac PPARγ mRNA expression was notably increased and Gata4/Mef2c/Chf1 expression was markedly decreased in the DEHP & verapamil group.

Conclusion

Placental P-gp inhibition enhances susceptibility to DEHP induced cardiac malformations in mice.

Recent Developments in Understanding Barrier Mechanisms in the Developing Brain: Drugs and Drug Transporters in Pregnancy, Susceptibility or Protection in the Fetal Brain?

Efflux mechanisms situated in various brain barrier interfaces control drug entry into the adult brain; this review considers the effectiveness of these protective mechanisms in the embryo, fetus, and newborn brain. The longstanding belief that the blood-brain barrier is absent or immature in the fetus and newborn has led to many misleading statements with potential clinical implications. The immature brain is undoubtedly more vulnerable to damage by drugs and toxins; as is reviewed here, some developmentally regulated normal brain barrier mechanisms probably contribute to this vulnerability. We propose that the functional status of brain barrier efflux mechanisms should be investigated at different stages of brain development to provide a rational basis for the use of drugs in pregnancy and in newborns, especially in those prematurely born, where protection usually provided by the placenta is no longer present.

The Role of PXR Genotype and Transporter Expression in the Placental Transport of Lopinavir in Mice

Lopinavir (LPV), an antiretroviral protease inhibitor frequently prescribed in HIV-positive pregnancies, is a substrate of Abcb1 and Abcc2. As differences in placental expression of these transporters were seen in Pregnane X Receptor (PXR) −/− mice, we examined the impact of placental transporter expression and fetal PXR genotype on the fetal accumulation of LPV. PXR +/− dams bearing PXR +/+, PXR +/−, and PXR −/− fetuses were generated by mating PXR +/− female mice with PXR +/− males. On gestational day 17, dams were administered 10 mg/kg LPV (i.v.) and sacrificed 30 min post injection. Concentrations of LPV in maternal plasma and fetal tissue were measured by LC-MS/MS, and transporter expression was determined by quantitative RT-PCR. As compared to the PXR +/+ fetal units, placental expression of Abcb1a, Abcc2, and Abcg2 mRNA were two- to three-fold higher in PXR −/− fetuses (p < 0.05). Two-fold higher fetal:maternal LPV concentration ratios were also seen in the PXR +/+ as compared to the PXR −/− fetuses (p < 0.05), and this significantly correlated to the placental expression of Abcb1a (r = 0.495; p < 0.005). Individual differences in the expression of placental transporters due to genetic or environmental factors can impact fetal exposure to their substrates.

The risks associated with prenatal antidepressant exposure: time for a precision medicine approach

INTRODUCTION

The prevalence of depression in pregnancy is over 10% and a significant proportion of pregnant women use antidepressant medication. The safety of antidepressants in pregnancy is controversial, partly due to methodological challenges. The conflicting results in the literature may, however, also be due to differences in risks between the study populations related to variations in e.g. degree of depression, type of antidepressant, and lifestyle. Areas covered: The literature on the safety of antidepressants in pregnancy is vast and thousands of papers have been published mainly in the last decades. This paper summarizes the evidence on important outcomes, including malformations, obstetric and neonatal outcomes, and long-term effects. It further describes results indicating that genetic variations in e.g. metabolism need to be taken into account. Expert opinion: Use of antidepressants during pregnancy must balance between the risks related to the underlying disease and the risks of antidepressant use. This balance needs to include information on a number of factors, including degree of depression and life-style. More data are required on how to include genetic information in the counseling. Overall, emerging evidence points to the need for a precision medicine approach to the treatment of pregnant women with depression.

Prenatal exposure to serotonin reuptake inhibitors and congenital heart anomalies: an exploratory pharmacogenetics study

AIM

To explore the role of pharmacogenetics in determining the risk of congenital heart anomalies (CHA) with prenatal use of serotonin reuptake inhibitors.

METHODS

We included 33 case-mother dyads and 2 mother-only (child deceased) cases of CHA in a case-only study. Ten genes important in determining fetal exposure to serotonin reuptake inhibitors were examined: CYP1A2, CYP2C9, CYP2C19, CYP2D6, ABCB1, SLC6A4, HTR1A, HTR1B, HTR2A and HTR3B.

RESULTS

Among the exposed cases, polymorphisms that tended to be associated with an increased risk of CHA were SLC6A4 5-HTTLPR and 5-HTTVNTR, HTR1A rs1364043, HTR1B rs6296 and rs6298 and HTR3B rs1176744, but none reached statistical significance due to our limited sample sizes.

CONCLUSION

We identified several polymorphisms that might potentially affect the risk of CHA among exposed fetuses, which warrants further investigation.

Prenatal pharmacogenomics: a promising area for research

Clinical applications of prenatal genetic screening currently focus on detection of aneuploidy and other genetic diseases in the developing fetus. Growing evidence suggests that the fetal genome may also be informative about fetal exposures, through contributions to placental transport as well as placental and fetal metabolism. Possible clinical applications of prenatal pharmacogenomic screening include prospective optimization of medication selection and dosage, as well as retrospective assessment of whether a fetus was previously exposed to significant risk. Newly available non-invasive methods of prenatal genetic screening mean that relevant fetal genotypes could be made available to obstetricians for use in management of a current pregnancy. This promising area for research merits more attention than it has thus far received.

Pharmacogenomics of preterm birth prevention and treatment

Pharmacogenomics and personalised medicine incorporate genetic factors, historical data, and environmental exposures to predict individual variation in response to medications. The study of pharmacology and pharmacogenomics is challenging in obstetrics, and our knowledge in this area lags behind other disciplines of medicine. Some preliminary data, however, suggest that some of the interindividual variation seen in response to medications given for the prevention (progesterone) and the treatment (nifedipine, terbutaline, and others) of preterm labour may be caused by pharmacogenomic effects. A comprehensive approach, integrating clinical data, environmental factors, including concomitant medications and genotype, to optimise the prevention and treatment strategies for preterm birth, is urgently needed.

TWEETABLE ABSTRACT

Some of the variation to meds for prematurity prevention/treatment may arise from pharmacogenomic effects.

Genetic determinants of fetal opiate exposure and risk of neonatal abstinence syndrome: Knowledge deficits and prospects for future research

Opiate-dependent pregnant women receive opiate maintenance medications to prevent illicit use and withdrawal. Fetal opiate exposure causes central nervous system (CNS) alterations which manifest as postnatal physical withdrawal. The extensive variability in the Neonatal Abstinence Syndrome phenotype remains unexplained and may be related to variability in fetal exposure and response. Improved understanding of functionally significant genetic variants in pathways influencing placental opiate transfer and fetal response can lead to personalized maternal therapy and optimized neonatal outcomes.