Soniya Vaidya

Formation and efflux of ATP-binding cassette transporter substrate 2,4-dinitrophenyl-S-glutathione from cultured human term placental villous tissue fragments.

Upon exposure to 1-chloro-2,4-dinitrobenzene (CDNB), the human placental tissue forms its glutathione conjugate 2,4-dinitrophenyl-S-glutathione (DNP-SG). The purpose of this study was to investigate the involvement of human placental ATP-binding cassette (ABC) transporters in the efflux of DNP-SG. Placental tissue samples were obtained from pregnant patients undergoing C-section deliveries following normal pregnancies; villous tissue was cultured in suspension, and DNP-SG formation and efflux upon exposure to 100 microM CDNB were measured by HPLC. DNP-SG efflux decreased by 69.1 (+/-11.3)%, 51.1 (+/-5.4)%, 56.7 (+/-8.3)% and 53.6 (+/-10.8)% (p < 0.05) in the presence of 5 mM sodium orthovanadate (ATPase inhibitor), 100 microM MK571 (MRP-inhibitor), 1 mM dipyridamole (BCRP/P-gp/MRP1-inhibitor) and 100 microM verapamil (P-gp/MRP1 inhibitor) respectively, without any change in DNP-SG formation, total tissue glutathione, GSH/GSSG ratio, tissue integrity or tissue viability. These data clearly established the role of ABC transporters in the human placental efflux of DNP-SG. To investigate the contribution of various ABC transporters toward DNP-SG transport, ATP-dependent transport of 3H-DNP-SG was determined in Sf9 membrane vesicles overexpressing P-gp, BCRP and the MRP proteins. MRP1-mediated DNP-SG transport was inhibited in the presence of sodium orthovanadate, MK571, dipyridamole and verapamil in the presence of glutathione. Furthermore, MRP1-mediated transport [K(t) = 11.3 +/- 1.3 microM and v(max) = 86.7 +/- 1.9 pmol/mg/min] was a high-affinity process compared to MRP2-mediated transport [K(t) = 168 +/- 7 microM and v(max) = 1367 +/- 18 pmol/mg/min]. The inhibition pattern and the kinetics of DNP-SG efflux in the placental villous tissue were consistent with MRP1-mediated DNP-SG efflux, suggesting a functional role and an apical localization for an MRP1-like transporter in the human placental syncytiotrophoblast.

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.

Application of human placental villous tissue explants to study ABC transporter mediated efflux of 2,4-dinitrophenyl-S-glutathione.

OBJECTIVE The purpose of this study was to characterize the human term placental villous tissue explant culture model as a tool to study the formation and efflux of 1-chloro-2,4-dinitrobenzene (CDNB) conjugate 2,4-dinitrophenyl-S-glutathione (DNP-SG) as a model system for phase II metabolism and ATP-binding cassette (ABC) transporter-mediated cellular efflux. METHODS Placental tissue samples were obtained after cesarean section following normal pregnancies (n=9). Cultured villous tissue was monitored up to 48 h to study the effect of time in culture on biochemical parameters, formation and efflux of DNP-SG in the absence or presence of ATPase inhibitor sodium orthovanadate and the protein expression of ABC transporters - multidrug resistance associated protein 2 (MRP2), P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and enzyme glutathione-S-transferase isoform P1-1 (GSTP1-1). RESULTS Villous tissue structure, tissue viability and expression of BCRP, GSTP1-1 remained unchanged, while expression of MRP2, P-gp and total tissue glutathione decreased with time in culture. Tissue integrity was unchanged up to 24 h but declined at 48 h. However, DNP-SG formation, DNP-SG efflux, and the extent of inhibition of DNP-SG efflux by sodium orthovanadate showed only minor changes through 48 h. Sodium orthovanadate decreased DNP-SG efflux, consistent with inhibition of apical ABC transporters. CONCLUSION The results support the use of the cultured human term placental villous tissue explants model to study coordinated function of GSTP1-1 and apical ABC transporters in the formation and efflux of the model substrate DNP-SG.

Pharmacokinetics of QMF149 in Japanese versus Caucasian subjects: an open-label, randomized phase I study.

OBJECTIVES This study aimed to evaluate influence of ethnic factors on the pharmacokinetics of orally inhaled QMF149, a novel combination of an approved longacting β2-agonist, indacaterol (Onbrez® Breezhaler® for COPD), and an approved inhaled corticosteroid, mometasone furoate (MF), (Asmanex® Twisthaler® for asthma), following multiple dose administration of QMF149 (indacaterol acetate/MF) 150/80 μg and 150/320 μg via the Breezhaler® device in healthy Japanese and Caucasian subjects. METHODS This was a single-center, openlabel, multiple-dose, two-period, complete crossover study that randomized healthy Japanese and, age and weight matched Caucasian subjects to QMF149 150/80 μg or 150/320 μg once daily (o.d.) for 14 days in each period. Pharmacokinetics (PK) were assessed up to 24 hours on days 1 and 14. RESULTS 24 Japanese and 24 Caucasian healthy subjects were enrolled. Indacaterol and MF had similar PK profiles across both the doses and both ethnic groups. The maximum geometric mean ratios (90% confidence interval (CI)) for Japanese vs. Caucasian subjects for Cmax were 1.23 (1.11 - 1.38) and 1.24 (1.11 - 1.38) for indacaterol and MF, respectively. For AUC, the maximum ratios were 1.22 (1.09 - 1.36) and 1.30 (1.18 - 1.44) for indacaterol and MF, respectively. The mild trend towards higher exposure in Japanese subjects could be explained by the fact that the mean body weight was 14% higher for Caucasians compared to their Japanese counterparts. No serious adverse events or discontinuations related to study medication were reported. CONCLUSION The study demonstrated increase of mean exposure parameters in Japanese subjects vs. Caucasian subjects, which ranged between 19 - 23% and 17 - 30%, for indacaterol and MF components, respectively. Multiple doses of both the QMF149 dose levels were safe and well-tolerated in all subjects. Body weight was considered a key contributory factor for the observed difference in exposure. These results suggest no dose adjustment for QMF149 is required in Asian populations.

Lung Delivery of Indacaterol and Mometasone Furoate Following Inhalation of QMF149 in Healthy Volunteers

This single‐dose, 4‐period crossover study evaluated the pharmacokinetics (PK) of the β2‐agonist indacaterol maleate and the corticosteroid mometasone furoate (MF) after inhalation of a fixed‐dose combination (QMF149, indacaterol maleate/MF, 500/400 μg) via the Twisthaler (TH) device with and without activated charcoal and postdose mouth rinsing in healthy volunteers. The PK of indacaterol maleate 300 μg inhaled via the Breezhaler (BRZ) device was also characterized. Relative bioavailability of indacaterol and MF for inhalation with versus without charcoal, based on AUClast, was 0.25 (90% confidence interval [CI], 0.18–0.35) and 0.70 (90%CI, 0.52–0.93), respectively. Thus, 25% and 70% of systemic exposure of indacaterol and MF, respectively was due to pulmonary absorption and 75% and 30%, respectively, was due to gastrointestinal absorption. Mouth rinsing reduced the systemic exposure of indacaterol by approximately 35% but had no relevant effect on the exposure of MF. Dose‐normalized AUClast for indacaterol inhaled via the BRZ device was 2.3‐fold higher than QMF149 via the TH device. All treatments had a good safety profile and were well tolerated. Data from this study and comparison with inhalation of indacaterol via the BRZ device suggest that the latter was more efficient than the TH device regarding lung delivery of indacaterol.