Placental P-glycoprotein and breast cancer resistance protein: Influence of polymorphisms on fetal drug exposure and physiology

Successful Prediction of Fetal Exposure to Dual BCRP/P-gp Drug Substrates Using the Efflux Ratio-Relative Expression Factor Approach and PBPK M&S

To inform fetal drug safety, it is important to determine or predict fetal drug exposure throughout pregnancy. The former is not possible in the first or second trimester. In contrast, at the time of birth, fetal drug exposure, relative to maternal exposure, can be estimated as Kp,uu (unbound fetal umbilical venous (UV) plasma area under the curve (AUC)/unbound maternal plasma (MP) AUC), provided the observed UV/MP values, spanning the dosing interval, are available from multiple maternal-fetal dyads. However, this fetal Kp,uu cannot be extrapolated to other drugs. To overcome the above limitations, we have used an efflux ratio-relative expression factor (ER-REF) approach to successfully predict the fetal Kp,uu of P-gp substrates. Because many drugs taken by pregnant people are also BCRP substrates, here, we extend this approach to drugs that are effluxed by both placental BCRP and P-gp or P-gp alone. To verify our predictions, we chose drugs for which UV/MP data were available at term: glyburide and imatinib (both BCRP and P-gp substrates) and nelfinavir (only P-gp substrate). First, the ER of the drugs was determined using Transwells and MDCKII cells expressing either BCRP or P-gp. Then, the ER was scaled using the proteomics-informed REF value to predict the fetal Kp,uu of the drug at term. The ER-REF predicted fetal Kp,uu of glyburide (0.43), imatinib (0.42), and nelfinavir (0.40) fell within two-fold of the corresponding in vivo fetal Kp,uu (0.44, 0.37, and 0.46, respectively). These data confirm that the ER-REF approach can successfully predict fetal drug exposure to BCRP/P-gp and P-gp substrates, at term.

The Effect of Tobacco Use on the Expression of Placental Transporters in Alaska Native Women

Prenatal tobacco use among Alaska Native (AN) women has decreased substantially over the past two decades. Previous research suggests that providing AN women with feedback regarding fetal exposure to tobacco may further promote cessation. Transporters in the placenta regulate fetal exposure to nutrients and xenobiotics, including compounds associated with tobacco use. We examined whether prenatal tobacco use impacts transporter expression in the placenta, and whether this is influenced by fetal sex, degree of tobacco exposure, or transporter genotype. At delivery, we obtained placental samples from AN research participants who smoked cigarettes, used commercial chew or iqmik (oral tobacco), or did not use tobacco during pregnancy. Transporter expression was evaluated using qRT-PCR and Western blotting and tested for correlations between transcript levels and urinary biomarkers of tobacco use. The impact of BCRP/ABCG2 and OATP2B1/SLCO2B1 genotypes on protein expression was also examined. Oral tobacco use was associated with decreased P-gp and increased MRP1, MRP3, LAT1, and PMAT mRNA expression. Transcript levels of multiple transporters significantly correlated with tobacco biomarkers in maternal and fetal urine. In women carrying male fetuses, both smoking and oral tobacco were associated with decreased P-gp. Oral tobacco was also associated with decreased LAT1 in women carrying female fetuses. BCRP and OATP2B1 genotypes did not appear to impact protein expression. In conclusion, prenatal tobacco use is associated with altered expression of multiple placental transporters which differs by fetal sex. As transcript levels of multiple transporters were significantly correlated with tobacco use biomarkers, eliminating prenatal tobacco use should alleviate these changes.

Inter-individual variations and modulators of MDR1 transport activity in human placenta

INTRODUCTION

ATP binding cassette (ABC) membrane transporter multidrug resistance 1 (MDR1) is one of the most important efflux transporters in the human placenta protecting the fetus from exposure to xenobiotic toxicity. Recent studies have focused on placental MDR1 expression, but few studies have analyzed placental MDR1 transport activity. The purpose of this study was to investigate placental MDR1 transport activity using a relatively large sample size of human placentas. Furthermore, the effect of ABCB1 gene polymorphisms were investigated along with physiological factors including maternal age, times of pregnancy, BMI, delivery mode or pregnancy complications on placental MDR1 transport activity.

METHODS

A total of 252 human placentas were obtained after delivery. MDR1 transport activity was detected by N-methyl quinidine uptake in placental microvillus membrane vesicles (MVMVs). Nine common single nucleotide polymorphisms (SNPs) in ABCB1 genes were determined by Snapshot. The association between ABCB1 gene polymorphisms, maternal age, times of pregnancy, BMI, delivery mode or pregnancy complications, and transporter activity was investigated.

RESULTS

Inter-individual variations of MDR1 transport activity were observed among 252 subjects. The per unit protein activity was ranged from 0.05 to 0.15/mg. Nine SNPs in ABCB1 gene didn't exhibit significant association with transporter activity of MDR1. Likewise, neither age, times of pregnancy, delivery mode nor pregnancy complications showed any significant effect of placental MDR1 transport activity. But placental MDR1 transport activity in obese pregnant women was lower than those in non-obese pregnant women.

CONCLUSION

Inter-individual variations of MDR1 transport activity existed in human placentas. This may contribute to variations in drug exposure to the fetus affecting clinical outcomes. Maternal age, times of pregnancy, delivery mode nor pregnancy complications included in this study maybe not significantly impact placental MDR1 transport activity, but maternal obese could inhibit placental MDR1 activity.

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.

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.

Is bisphenol S a safer alternative to bisphenol A in terms of potential fetal exposure ? Placental transfer across the perfused human placenta

The aim of our study was to evaluate the bidirectional transfer of Bisphenol S (BPS) and its main metabolite, BPS Glucuronide (BPSG), using the model of perfused human placenta and to compare the obtained values with those of Bisphenol A (BPA) and BPA Glucuronide. Fourteen placentas at term were perfused in an open dual circuit with deuterated BPS (1 and 5 μM) and non-labelled BPSG (2.5 μM) and a freely diffusing marker antipyrine (800 ng/ml) in the presence of albumin (25 mg/ml). In a second experiment, the potential role of P-glycoprotein in the active efflux of BPS across the placental barrier was studied using the well-established P-glycoprotein inhibitor, PSC833 (2 and 4 μM). Placental transfer of BPS was much lower than that of BPA in both directions. The placental clearance index of BPS in the materno-fetal direction was three times lower than in the opposite direction, strongly suggesting some active efflux transport. However, our results show that P-glycoprotein is not involved in limiting the materno-fetal transfer of BPS. Placental transfer of BPSG in the fetal compartment was almost non-existent indicating that, in the fetal compartment, BPSG originates mainly from feto-placental metabolism. The feto-maternal clearance index for BPSG was 20-fold higher than the materno-fetal index. We conclude that the blood-placental barrier is much more efficient in limiting fetal exposure to BPS than to BPA, indicating that the placenta has a crucial role in protecting the human fetus from BPS exposure.

ABCB1 3435TT and ABCG2 421CC genotypes were significantly associated with longer progression-free survival in Chinese breast cancer patients

Objective

To investigate the distribution of ABCB1 C3435T and ABCG2 C421A gene polymorphisms in Chinese Han population and their influences on the susceptibility and prognosis of breast carcinoma.

Methods

A total of 200 female subjects were enrolled in this study, comprising 100 breast cancer patients and 100 healthy controls. Carcinoma and para-carcinoma tissues were collected from the breast cancer patients, while peripheral blood was collected from healthy controls. Single nucleotide polymorphisms (SNPs) were detected by the Taqman method. Progression-free survival (PFS) and 5-year survival rate of the patients were calculated.

Results

ABCB1 C3435T and ABCG2 C421A polymorphisms were not associated with disease susceptibility and 5-year survival rate in the study population (p>0.05). However, a high mutation rate of both ABCB1 C3435T and ABCG2 C421A (16% and 17%, respectively) was observed in breast cancer tissues. Patients with ABCB1 3435TT genotype or ABCG2 421CC genotype had longer PFS (p<0.05).

Conclusion

ABCB1 3435TT and ABCG2 421CC were significantly associated with longer PFS in Chinese breast cancer patients.

Placental Origins of Chronic Disease

Epidemiological evidence links an individual's susceptibility to chronic disease in adult life to events during their intrauterine phase of development. Biologically this should not be unexpected, for organ systems are at their most plastic when progenitor cells are proliferating and differentiating. Influences operating at this time can permanently affect their structure and functional capacity, and the activity of enzyme systems and endocrine axes. It is now appreciated that such effects lay the foundations for a diverse array of diseases that become manifest many years later, often in response to secondary environmental stressors. Fetal development is underpinned by the placenta, the organ that forms the interface between the fetus and its mother. All nutrients and oxygen reaching the fetus must pass through this organ. The placenta also has major endocrine functions, orchestrating maternal adaptations to pregnancy and mobilizing resources for fetal use. In addition, it acts as a selective barrier, creating a protective milieu by minimizing exposure of the fetus to maternal hormones, such as glucocorticoids, xenobiotics, pathogens, and parasites. The placenta shows a remarkable capacity to adapt to adverse environmental cues and lessen their impact on the fetus. However, if placental function is impaired, or its capacity to adapt is exceeded, then fetal development may be compromised. Here, we explore the complex relationships between the placental phenotype and developmental programming of chronic disease in the offspring. Ensuring optimal placentation offers a new approach to the prevention of disorders such as cardiovascular disease, diabetes, and obesity, which are reaching epidemic proportions.

Placental ABC Transporters: Biological Impact and Pharmaceutical Significance

The human placenta fulfills a variety of essential functions during prenatal life. Several ABC transporters are expressed in the human placenta, where they play a role in the transport of endogenous compounds and may protect the fetus from exogenous compounds such as therapeutic agents, drugs of abuse, and other xenobiotics. To date, considerable progress has been made toward understanding ABC transporters in the placenta. Recent studies on the expression and functional activities are discussed. This review discusses the placental expression and functional roles of several members of ABC transporter subfamilies B, C, and G including MDR1/P-glycoprotein, the MRPs, and BCRP, respectively. Since placental ABC transporters modulate fetal exposure to various compounds, an understanding of their functional and regulatory mechanisms will lead to more optimal medication use when necessary in pregnancy.

Association between ABCB1 C3435T polymorphism and breast cancer risk: a Moroccan case-control study and meta-analysis

BACKGROUND

Breast cancer is the most common cause of cancer death among women. Several studies have investigated the relationship between the C3435T polymorphism of ABCB1 gene and risk of breast cancer; but the results are conflicting. In the present study, we sought to assess the relationship between the C3435T polymorphism in ABCB1 gene and the risk of breast cancer in a sample of the Moroccan population.

METHODS

A case control study was performed on 60 breast cancer patients and 68 healthy women. The ABCB1 C3435T polymorphism was analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Furthermore, a meta-analysis including 16 studies with 6094 cases of breast cancer and 8646 controls was performed.

RESULTS

Genotype frequencies were 50 % for CC, 33.3 % for CT and 16.7 % for TT in patients and 41.2 % for CC, 48.5 % for CT and 10.3 % for TT respectively in the control group. This difference was not statistically significant. The same trend as observed in the allele distribution between patients and controls (P = 0.84). Findings from the meta-analysis showed that the ABCB1 C3435T polymorphism was not associated with an increased risk of breast cancer in the dominant model (OR = 0.907; 95 % CI = 0.767-1.073; P = 0.25) as well as in the recessive model (OR = 1.181; 95 % CI = 0.973-1.434; P = 0.093) and in the allele contrast model (OR = 1.098; 95 % CI = 0.972-1.240; P = 0.133). However, the stratification of studies on ethnic basis showed that the TT genotype was associated with the risk of breast cancer in Asians (OR = 1.405; 95 % CI = 1.145-1.725; P = 0.001), Caucasians (OR = 1.093; 95 % CI = 1.001-1.194; P = 0.048) and North African (OR = 2.028; 95 % CI = 1.220-3.371; P = 0.006).

CONCLUSIONS

We have noted that the implication of C3435T variant on the risk of breast cancer was ethnicity-dependent. However, there is no evidence that ABCB1 C3435T polymorphism could play a role in susceptibility to breast cancer in Morocco. Further studies with a larger sample size, extended to other polymorphisms are needed to understand the influence of ABCB1 genetic variants on the risk of breast cancer.

The xenoestrogens, bisphenol A and para-nonylphenol, decrease the expression of the ABCG2 transporter protein in human term placental explant cultures

Many endogenous and xenobiotic compounds are substrates and regulators of human placental ABC transporters. ABCG2 is protecting fetus against foreign chemicals. Environmental xenoestrogens, like bisphenol A (BPA) and p-nonylphenol (p-NP), mimic natural estrogens and can affect hormonal systems. Effects of BPA, p-NP, DES (diethylstilbestrol) and estradiol (E2), on ABCG2 expression were studied using human first trimester and term placental explants. Role of estrogen receptors (ER) in the effects of chemicals was studied by ER antagonist. Term placenta expressed less ABCG2 protein. In term placentas BPA (p < 0.05), p-NP (p < 0.01) and E2 (p < 0.05) decreased the ABCG2 protein expression after 48 h exposure while after 24 h exposure, only E2 decreased the expression (p < 0.05). The chemicals did not affect ABCG2 in first trimester placentas. The ER antagonist affected differently the responses of chemicals. In conclusion, environmental xenoestrogens downregulate placental ABCG2 protein expression depending on gestational age.

Classification, Treatment Strategy, and Associated Drug Resistance in Breast Cancer

Breast cancer is the second leading cause of cancer death in women, affecting 1.7 million patients every year worldwide. As a result of its heterogeneous nature, the genetic profile and associated clinical feature varies greatly among different breast cancer subtypes. With the advancement of molecular biology, our understanding of breast cancer has improved greatly in recent years. In this review, we examine different types of breast cancer and summarize their clinical features, current treatment schemes, and potential drug resistance profiles in response to treatments. We believe that the understanding of the molecular mechanisms of each treatment and subsequent drug resistance development will eventually lead to the discovery of more effective and efficient second-line therapeutics.

ATP-binding cassette transporters in reproduction: a new frontier

BACKGROUND

The transmembrane ATP-binding cassette (ABC) transporters actively efflux an array of clinically relevant compounds across biological barriers, and modulate biodistribution of many physiological and pharmacological factors. To date, over 48 ABC transporters have been identified and shown to be directly and indirectly involved in peri-implantation events and fetal/placental development. They efflux cholesterol, steroid hormones, vitamins, cytokines, chemokines, prostaglandins, diverse xenobiotics and environmental toxins, playing a critical role in regulating drug disposition, immunological responses and lipid trafficking, as well as preventing fetal accumulation of drugs and environmental toxins.

METHODS

This review examines ABC transporters as important mediators of placental barrier functions and key reproductive processes. Expression, localization and function of all identified ABC transporters were systematically reviewed using PubMed and Google Scholar websites to identify relevant studies examining ABC transporters in reproductive tissues in physiological and pathophysiological states. Only reports written in English were incorporated with no restriction on year of publication. While a major focus has been placed on the human, extensive evidence from animal studies is utilized to describe current understanding of the regulation and function of ABC transporters relevant to human reproduction.

RESULTS

ABC transporters are modulators of steroidogenesis, fertilization, implantation, nutrient transport and immunological responses, and function as 'gatekeepers' at various barrier sites (i.e. blood-testes barrier and placenta) against potentially harmful xenobiotic factors, including drugs and environmental toxins. These roles appear to be species dependent and change as a function of gestation and development. The best-described ABC transporters in reproductive tissues (primarily in the placenta) are the multidrug transporters p-glycoprotein and breast cancer-related protein, the multidrug resistance proteins 1 through 5 and the cholesterol transporters ABCA1 and ABCG1.

CONCLUSIONS

The ABC transporters have various roles across multiple reproductive tissues. Knowledge of efflux direction, tissue distribution, substrate specificity and regulation of the ABC transporters in the placenta and other reproductive tissues is rapidly expanding. This will allow better understanding of the disposition of specific substrates within reproductive tissues, and facilitate development of novel treatments for reproductive disorders as well as improved approaches to protecting the developing fetus.

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

One of the ongoing issues in perinatal medicine is the risk of birth defects associated with maternal drug use. The teratogenic effect of a drug depends, apart from other factors, on the exposition of the fetus to the drug. Transporter proteins are known to be involved in the pharmacokinetics of drugs and have an effect on drug level and fetal drug exposure. This condition may subsequently alter the risk of teratogenicity, which occurs in a dose-dependent manner. This review focuses on the clinically important polymorphisms of transporter proteins and their effects on the mRNA and protein expression in placental tissue. We also propose a novel approach on how the different genotypes of the polymorphism can be translated into phenotypes to facilitate genetic association studies. The last section looks into the recent studies exploring the association between P-glycoprotein polymorphisms and the risk of fetal birth defects associated with medication use during pregnancy.

Maternal medication use, fetal 3435 C>T polymorphism of the ABCB1 gene, and risk of isolated septal defects in a Han Chinese population

The fundamental etiology of the majority of nonsyndromic congenital heart defects is commonly believed to involve the interaction of multiple environmental and genetic factors. This study aimed to explore the joint effects of fetal 3435 C>T polymorphism in the ABCB1 gene and maternal medication use on the risk of septal defects in a Han Chinese population. An age- and gender-matched case-control study involving 265 pairs was conducted from March 2012 to September 2013. Information on maternal periconceptional medication use was obtained through questionnaires. The genotyping of 3435 C>T polymorphism was performed by sequencing. Logistic regression analysis was performed to assess the joint effects of ABCB1 gene 3435 C>T polymorphism and maternal medication use on the risk of septal defects. Use of maternal medication periconceptionally was significantly associated with an increased risk of septal defects [adjusted odds ratio (OR) 2.133; 95 % confidence interval (CI) 1.361-3.444; P = 0.001)]. The genotype distributions of 3435 C>T polymorphism differed significantly between cases and control subjects (P < 0.001). Meanwhile, more patients were carriers of the ABCB1 CC/CT genotypes, which were significantly associated with an increased risk of septal defects (OR 2.414; 95 % CI 1.418-4.110; P = 0.001). Children who carry the CC/CT genotype and have been exposed periconceptionally to medication have an almost fourfold increased risk of having septal defects than nonexposed children with the TT genotype (adjusted OR 3.932; 95 % CI 1.708-9.051), particularly perimembranous ventricular septal defects (VSD) (adjusted OR 4.070; 95 % CI 1.570-10.552). In conclusion, fetal 3435 C>T polymorphism in the ABCB1 gene increases the risk for isolated septal defects in the presence of maternal medication use periconceptionally, particularly for perimembranous VSD.

Serotonin reuptake inhibitors in pregnancy: can genes help us in predicting neonatal adverse outcome?

Lots has been written on use of SSRI during pregnancy and possible short and long term negative outcomes on neonates. the literature so far has described a various field of peripartum illness related to SSRI exposure during foetal life, such as increased incidence of low birth weight, respiratory distress, persistent pulmonary hypertension, poor feeding, and neurobehavioural disease. We know that different degrees of outcomes are possible, and not all the newborns exposed to SSRIs during pregnancy definitely will develop a negative outcome. So far, still little is known about the possible etiologic mechanism that could not only explain the adverse neonatal effects but also the degree of clinical involvement and presentation in the early period after birth. Pharmacogenetics and moreover pharmacogenomics, the study of specific genetic variations and their effect on drug response, are not widespread. This review describes possible relationship between SSRIs pharmacogenetics and different neonatal outcomes and summarizes the current pharmacogenetic inquiries in relation to maternal-foetal environment.

Cannabidiol changes P-gp and BCRP expression in trophoblast cell lines

Objectives. Marijuana is the most commonly used illicit drug during pregnancy. Due to high lipophilicity, cannabinoids can easily penetrate physiological barriers like the human placenta and jeopardize the developing fetus. We evaluated the impact of cannabidiol (CBD), a major non-psychoactive cannabinoid, on P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) expression, and P-gp function in a placental model, BeWo and Jar choriocarcinoma cell lines (using P-gp induced MCF7 cells (MCF7/P-gp) for comparison). Study design. Following the establishment of the basal expression of these transporters in the membrane fraction of all three cell lines, P-gp and BCRP protein and mRNA levels were determined following chronic (24-72 h) exposure to CBD, by Western Blot and qPCR. CBD impact on P-gp efflux function was examined by uptake of specific P-gp fluorescent substrates (calcein-AM, DiOC2(3) and rhodamine123(rh123)). Cyclosporine A (CsA) served as a positive control. Results. Chronic exposure to CBD resulted in significant changes in the protein and mRNA levels of both transporters. While P-gp was down-regulated, BCRP levels were up-regulated in the choriocarcinoma cell lines. CBD had a remarkably different influence on P-gp and BCRP expression in MCF7/P-gp cells, demonstrating that these are cell type specific effects. P-gp dependent efflux (of calcein, DiOC2(3) and rh123) was inhibited upon short-term exposure to CBD. Conclusions. Our study shows that CBD might alter P-gp and BCRP expression in the human placenta, and inhibit P-gp efflux function. We conclude that marijuana use during pregnancy may reduce placental protective functions and change its morphological and physiological characteristics.

Increased risk for congenital heart defects in children carrying the ABCB1 Gene C3435T polymorphism and maternal periconceptional toxicants exposure

Backgrounds

The etiology of congenital heart defect (CHD) is commonly believed to involve the interaction of multiple environmental and genetic factors. This study aimed to explore the joint effects of the ABCB1 gene C3435T polymorphism and maternal periconceptional toxicants exposure on the CHD risk in a Han Chinese population.

Methods

An age and gender matched case-control study with standardized data collection involving 201 pairs was conducted. Periconceptional toxicants exposure was obtained through a structured questionnaire. A job exposure matrix (JEM) was used for toxicants exposure assessment. Genotyping of the ABCB1 C3435T polymorphism was performed by sequencing. Logistic regression analysis was performed to assess the joint effects of the ABCB1 gene C3435T polymorphism and toxicants exposure on the risk of CHD. Placenta tissues and umbilical cords were collected to investigate the impact of C3435T polymorphism on the transcription and translation activities of ABCB1 gene.

Results

Maternal periconceptional exposures to phthalates (adjusted OR: 1.6; 95%CI: 1.0–2.6) and alkylphenolic compounds (adjusted OR:1.8; 95%CI:1.1–3.0) were associated with a higher incidence of CHDs in general. More cases were carriers of the ABCB1 CC/CT genotypes (OR: 2.0, 95%CI: 1.1–3.5, P-value: 0.021). Children carrying the CC/CT genotype and periconceptionally exposed to phthalates and alkylphenolic compounds suffered almost 3.5-fold increased risk of having CHD than non-exposed children with TT genotype (adjusted OR: 3.5, 95%CI: 1.5–7.9, P-value: 0.003), and the OR changed to 4.4 for septal defects (adjusted OR: 4.4,95%CI:1.8–10.9,P-value:0.001). The ABCB1 mRNA expression of the TT genotype was significantly higher than that of the CC genotype (P = 0.03). Compared with TT genotype, lower P-glycoprotein expression was observed for the CC/CT genotypes.

Conclusion

The C3435T polymorphism in the ABCB1 gene of fetus increases the risks of CHD in a Han Chinese population when the mothers are exposed to phthalates and alkylphenolic compounds during the periconceptional period, particularly for septal defects.

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

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

ATP-binding cassette efflux transporters in human placenta

Pregnant women are often complicated with diseases including viral or bacterial infections, epilepsy, hypertension, or pregnancy-induced conditions such as depression and gestational diabetes that require treatment with medication. In addition, substance abuse during pregnancy remains a major public health problem. Many drugs used by pregnant women are off label without the necessary dose, efficacy, and safety data required for rational dosing regimens of these drugs. Thus, a major concern arising from the widespread use of drugs by pregnant women is the transfer of drugs across the placental barrier, leading to potential toxicity to the developing fetus. Knowledge regarding the ATP-binding cassette (ABC) efflux transporters, which play an important role in drug transfer across the placental barrier, is absolutely critical for optimizing the therapeutic strategy to treat the mother while protecting the fetus during pregnancy. Such transporters include P-glycoprotein (P-gp, gene symbol ABCB1), the breast cancer resistance protein (BCRP, gene symbol ABCG2), and the multidrug resistance proteins (MRPs, gene symbol ABCCs). In this review, we summarize the current knowledge with respect to developmental expression and regulation, membrane localization, functional significance, and genetic polymorphisms of these ABC transporters in the placenta and their relevance to fetal drug exposure and toxicity.