No abstract

No abstract

Objective-Substrates of placental efflux transporters could compete for a single transporter, which could result in an increase in the transfer of each substrate to the fetal circulation. Our aim was to determine the role of placental transporters in the biodisposition of oral hypoglycemic drugs that could be used as monotherapy or in combination therapy for gestational diabetes.Study design-Inside-out brush border membrane vesicles from term placentas were used to determine the efflux of glyburide, rosiglitazone, and metformin by P-gp, Breast Cancer Resistance Protein (BCRP), and Multidrug Resistance Protein (MRP1).Results-Glyburide was transported by MRP1 (43 ± 4%); BCRP (25 ± 5%); and P-gp (9 ± 5%). Rosiglitazone was transported predominantly by P-gp (71 ± 26%). Metformin was transported by Pgp (58 ± 20%) and BCRP (25 ± 14%).Conclusion-Multiple placental transporters contribute to efflux of glyburide, rosiglitazone, and metformin. Administration of drug combinations could lead to their competition for efflux transporters.

Objectives Determine the bidirectional transfer of pravastatin across the dually perfused term human placental lobule and its distribution between the tissue, maternal and fetal circuits. Study design The transfer of pravastatin was determined in the Maternal-to-Fetal (n=11) and Fetal-to-Maternal (n=10) directions. Pravastatin was co-perfused with its [3H]-isotope and the marker compound antipyrine (20 μg/mL) and its [14C]-isotope. The concentration of pravastatin in the perfused tissue, the maternal and fetal circuits was determined using liquid scintillation spectrometry. Inside-out vesicles prepared from placental brush border membranes were utilized to investigate the role of efflux transporters in transplacental transfer of pravastatin. Results Pravastatin was transferred from the maternal to the fetal circuit and vise versa. In the Maternal-to-Fetal direction, the distribution of pravastatin at the end of experiment was as follows: 14 ± 5% of the drug was retained by the tissue, 68 ± 5% remained in the maternal circuit, and 18±4% was transferred to the fetal circuit. The normalized transfer of pravastatin (Clearance index) to antipyrine in the Fetal-to-Maternal direction (0.48 ± 0.07) was higher than its transfer in the Maternal-to-Fetal direction (0.36 ± 0.07, p<0.01). Furthermore, pravastatin inhibited the ATP-dependent uptake of the paclitaxel and estrone sulfate. Conclusions The transfer of pravastatin across the dually perfused placental lobule suggests that fetal exposure to pravastatin is plausible. The higher transfer of pravastatin in the Fetal-to-Maternal direction than the reverse as well as its inhibition of the ATP-dependent uptake of [3H]-paclitaxel and [3H]-estrone sulfate strongly suggest the involvement of efflux transporters in decreasing its transfer across the placenta, and support pravastatin favorable pharmacokinetic profile in pregnancy.

The ABC transporter P-glycoprotein is a product of the MDR1 gene and its function in human placenta is to extrude xenobiotics from the tissue thus decreasing fetal exposure. The goal of this investigation was to examine the effect of three polymorphisms in the MDR1 gene on the expression and activity of placental P-gp. In 199 term placentas examined, the C1236T variant was associated with 11% lower P-gp protein expression than wild type, while the C3435T and G2677T/A variants each were associated with a 16% reduction (p < 0.05). Homozygotes for the C1236T and C3435T variant allele (TT) were associated with 42% and 47% increase in placental P-gp transport activity, respectively (p = 0.04 and p = 0.02) of the prototypic substrate, [ 3 H]-paclitaxel. These findings indicate that the C3435T and G2677T/A SNPs in MDR1 are significantly associated with decreased placental P-gp protein expression, while the C1236T and C3245T homozygous variants are significantly associated with an increase in its efflux activity.

BACKGROUND:The transfer of pathogenic immunoglobulin G antibodies from mother to fetus is a critical step in the pathophysiology of alloimmune and autoimmune diseases of the fetus and neonate. Immunoglobulin G transfer across the human placenta to the fetus is mediated by the neonatal Fc receptor, and blockade of the neonatal Fc receptor may provide a therapeutic strategy to prevent or minimize pathological events associated with immune-mediated diseases of pregnancy. M281 is a fully human, aglycosylated monoclonal immunoglobulin G1 antineonatal Fc receptor antibody that has been shown to block the neonatal Fc receptor with high affinity in nonclinical studies and in a phase 1 study in healthy volunteers. OBJECTIVE: The objective of the study was to determine the transplacental transfer of M281 and its potential to inhibit transfer of immunoglobulin G from maternal to fetal circulation. STUDY DESIGN: To determine the concentration of M281 required for rapid cellular uptake and complete saturation of the neonatal Fc receptor in placental trophoblasts, primary human villous trophoblasts were incubated with various concentrations of M281 in a receptor occupancy assay. The placental transfer of M281, immunoglobulin G, and immunoglobulin G in the presence of M281 was studied using the dually perfused human placental lobule model. Immunoglobulin G transfer was established using a representative immunoglobulin G molecule, adalimumab, a human immunoglobulin G1 monoclonal antibody, at a concentration of 270 mg/ mL. Inhibition of immunoglobulin G transfer by M281 was determined by cotransfusing 270 mg/mL of adalimumab with 10 mg/mL or 300 mg/mL of M281. Concentrations of adalimumab and M281 in sample aliquots from maternal and fetal circuits were analyzed using a sandwich enzyme-linked immunosorbent assay and Meso Scale Discovery assay, respectively. RESULTS: In primary human villous trophoblasts, the saturation of the neonatal Fc receptor by M281 was observed within 30e60 minutes at 0.15e5.0 mg/mL, suggesting rapid blockade of neonatal Fc receptor in placental cells. The transfer rate of adalimumab (0.23% AE 0.21%) across dually perfused human placental lobule was significantly decreased by 10 mg/mL and 300 mg/mL of M281 to 0.07 AE 0.01% and 0.06 AE 0.01%, respectively. Furthermore, the transfer rate of M281 was 0.002% AE 0.02%, approximately 100-fold lower than that of adalimumab. CONCLUSION: The significant inhibition of immunoglobulin G transfer across the human placental lobule by M281 and the minimal transfer of M281 supports the development of M281 as a novel agent for the treatment of fetal and neonatal diseases caused by transplacental transfer of alloimmune and autoimmune pathogenic immunoglobulin G antibodies.

The use of either methadone or buprenorphine for treatment of the pregnant opiate dependent patient improves maternal and neonatal outcome. However, patient outcomes are often complicated by neonatal abstinence syndrome (NAS). The incidence and severity of NAS should depend on opiate concentration in the fetal circulation. Efflux transporters expressed in human placental brush border membranes decrease fetal exposure to medications by their extrusion to the maternal circulation. Accordingly, the concentration of either methadone or buprenorphine in the fetal circulation is, in part, dependent on the activity of the efflux transporters. The objective of this study was to characterize the activity of P-gp and its interaction with opiates in the placental apical membrane. Therefore, brush border membrane vesicles were prepared from human placenta. The vesicles were oriented approximately 75% inside out, exhibited saturable ATP-dependent uptake of P-gp substrate [3H] paclitaxel with an apparent Kt of 66 ± 38 nM and Vmax of 20 ± 3 pmol*mg protein−1min−1. Methadone, buprenorphine, and morphine inhibited paclitaxel transport with apparent Ki of 18, 44, and 90 μM, respectively. Our data indicate that a method has been established to determine the activity of the efflux transporter P-gp, expressed in placental brush border membranes, and the kinetics for the transfer of its prototypic substrate paclitaxel. Furthermore, the method was used to determine the effects of methadone, buprenorphine, and morphine on paclitaxel transfer by placental P-gp and revealed that they have higher affinity to the transporter than its classical inhibitor verapamil (Ki, 300 μM).

The expression and activity of human placental transporters during pregnancy could be altered by several factors including pathological changes associated with preeclampsia. The aims of this study were to identify the placental efflux transporters involved in the bio-disposition of pravastatin, determine the protein expression of these transporters and their encoding genes as well as the activity of pravastatin uptake in placentas obtained from patients with preeclampsia. ATP-dependent uptake of [3H]-pravastatin by trophoblast tissue apical and basal membrane vesicles exhibited sigmoidal kinetics. The curved shapes of Eadie-Hofstee plots indicate that more than one placental transporter are involved in the uptake of pravastatin. ATP-dependent uptake of [3H]-pravastatin into vesicles expressing MRP1-5, BCRP, and P-gp, as well as the results of inhibition studies suggest that BCRP and MRP1 are the major placental efflux transporters responsible for the in vitro uptake of pravastatin. Compared to placentas from healthy pregnancies, preeclamptic placentas had increased number of syncytial knots with increased expression of BCRP in their apical membrane and increased expression of MRP1 in the cytoplasm of the syncytiotrophoblast and in cytoplasm of syncytial knots. There was a concomitant increase in ABCC1 but not in ABCG2 gene expressions in preeclamptic placentas. ATP-dependent uptake of [3H]-pravastatin by vesicles prepared from apical membranes of preeclamptic placentas was similar to the uptake by vesicles prepared from placentas obtained after uncomplicated pregnancies (13.9 ± 6.5 vs 14.1 ± 5.8 pmol·mg protein min). The transporter-specific changes in the expression of BCRP and MRP1 in preeclamptic placentas did not affect the efflux activity of transporters localized on the apical membrane of the syncytiotrophoblast.