Long-term administration of tenofovir or emtricitabine to pregnant rats; effect on Abcb1a, Abcb1b and Abcg2 expression in the placenta and in maternal and fetal organs.

OBJECTIVES: Tenofovir and emtricitabine are very effective and well-tolerated antiretrovirals representing current backbone of the antiretroviral combination regimens for the prevention of perinatal HIV transmission. The aim of our study was to determine whether tenofovir or emtricitabine administered in long-term fashion affect expression of two widely described pharmacokinetic determinants, P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2), in maternal or fetal biological tissues. METHODS: For this purpose, pregnant Wistar rats were administered tenofovir (2.25 mg/kg/day), emtricitabine (3.5 mg/kg/day) or saline i.m. for 10 days (from the 12th to 21st gestation day). On the 22nd day, the placenta and maternal/fetal intestine, brain, kidneys and liver were sampled and analysed for Abcb1a, Abcb1b and Abcg2 expression; placental and newborns' weights were also monitored. KEY FINDINGS: We found that long-term application of tenofovir or emtricitabine did not significantly affect expression of Abcb1a, Abcb1b and Abcg2 in either maternal or fetal organs. However, tenofovir administration significantly increased placenta-to-birthweight ratio, a strong indicator of various diseases occurring later in life. CONCLUSIONS: Our data broaden current knowledge on safety profile of tenofovir and emtricitabine use in pregnancy. Nevertheless, further research in other mammal species, including humans, is important to fully elucidate this issue.

Placental passage of olomoucine II, but not purvalanol A, is affected by p-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2) and multidrug resistance-associated proteins (ABCCs).

1. Purine cyclin-dependent kinase inhibitors have recently been recognised as promising candidates for the treatment of various cancers. While pharmacodynamic properties of these compounds are relatively well understood, their pharmacokinetics including possible interactions with placental transport systems have not been characterised to date. 2. In this study, we investigated transplacental passage of olomoucine II and purvalanol A in rat focusing on possible role of p-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2) and/or multidrug resistance-associated proteins (ABCCs). Employing the in situ method of dually perfused rat term placenta, we demonstrate transplacental passage of both olomoucine II and purvalanol A against the concentration gradient in foetus-to-mother direction. Using several ATP-binding cassette (ABC) drug transporter inhibitors, we confirm the participation of ABCB1, ABCG2 and ABCCs transporters in the placental passage of olomoucine II, but not purvalanol A. 3. Transplacental passage of olomoucine II and purvalanol A from mother to foetus is significantly reduced by active transporters, restricting thereby foetal exposure and providing protection against harmful effects of these xenobiotics. Importantly, we demonstrate that in spite of their considerable structural similarity, the two molecules utilise distinct placental transport systems. These facts should be kept in mind when introducing these prospective anticancer candidates and/or their analogues into the clinical area.

Role of ABCB1, ABCG2, ABCC2 and ABCC5 transporters in placental passage of zidovudine.

Zidovudine (AZT) is one of the most frequently used antiretroviral drugs in prevention of perinatal transmission of HIV. However, safety concerns on AZT use in pregnancy still persist as severe side effects are associated with AZT exposure in children. In our study we aimed to contribute to current knowledge on AZT transplacental transport and to evaluate potential involvement of the main human drug efflux ATP-binding cassette (ABC) transporters, p-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2) and multidrug resistance-associated proteins 2 and 5 (ABCC2 and ABCC5) in the disposition of AZT between mother and fetus. In order to elucidate this issue we investigated the effect of selected ABC transporters on AZT transepithelial transport across MDCKII cell monolayers. In addition we used the in situ method of dually perfused rat term placenta to further study the role of ABC transporters in AZT transplacental transport. In vitro studies revealed significant effect of ABCB1 and ABCG2 on AZT transport which was subsequently confirmed also on organ level. Lamivudine, an antiretroviral agent commonly co-administered with AZT, did not affect ABC transporter-mediated AZT transfer.

Effect of drug efflux transporters on placental transport of antiretroviral agent abacavir.

Abacavir is as a frequent part of combination antiretroviral therapy used in pregnant women. The aim of this study was to investigate, using in vitro, in situ and ex vivo experimental approaches, whether the transplacental pharmacokinetics of abacavir is affected by ATP-binding cassette (ABC) efflux transporters functionally expressed in the placenta: P-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2), multidrug resistance-associated protein 2 (ABCC2) and multidrug resistance-associated protein 5 (ABCC5). In vitro transport assays revealed that abacavir is a substrate of human ABCB1 and ABCG2 transporters but not of ABCC2 or ABCC5. In addition, in situ experiments using dually perfused rat term placenta confirmed interactions of abacavir with placental Abcb1/Abcg2. In contrast, uptake studies in human placental villous fragments did not reveal any interaction of abacavir with efflux transporters suggesting a large contribution of passive diffusion and/or influx mechanisms to net transplacental abacavir transfer.

Interactions of tenofovir and tenofovir disoproxil fumarate with drug efflux transporters ABCB1, ABCG2, and ABCC2; role in transport across the placenta.

OBJECTIVE AND DESIGN: Tenofovir (TFV) is used in pregnant women as a part of combination antiretroviral treatment to prevent mother-to-child transmission of HIV infection. We aimed to detect whether TFV and/or its prodrug, tenofovir disoproxil fumarate (TDF), are substrates of ATP-binding cassette (ABC) transporters that are functionally expressed in the placenta, namely P-glycoprotein (ABCB1/MDR1), Breast Cancer Resistance Protein (ABCG2/BCRP) and Multidrug Resistance-Associated Protein 2 (ABCC2/MRP2). We employed in-vitro cell-based assays and in-situ animal model to assess possible role of the efflux transporters in transplacental pharmacokinetics of TFV and TDF. METHODS: In-vitro transport assays were performed in MDCKII cells transduced with human ABCB1, ABCG2 or ABCC2. To quantify the effect of these transporters on TFV/TDF transplacental passage, we employed the in-situ model of dually perfused rat term placenta in open and closed setup. RESULTS: In-vitro assays revealed that TDF is a dual substrate of ABCB1 and ABCG2 but not of ABCC2. In contrast, TFV transport was not influenced by any of these transporters. Applying concentration-dependent studies and selective inhibitors, we further confirmed these findings in situ on the organ level; both ABCB1 and ABCG2 limited mother-to-fetus transfer of TDF whereas TFV transplacental passage was not affected by these ABC transporters. CONCLUSION: We propose limited mother-to-fetus transport of both TFV and TDF. While placental transport of TFV is restricted passively, by physical-chemical properties of the molecule, mother-to-fetus passage of TDF is actively hindered by placental ABCB1 and ABCG2 transporters, pumping this compound from trophoblast back to maternal circulation.

Organic cation transporter 3 (OCT3/SLC22A3) and multidrug and toxin extrusion 1 (MATE1/SLC47A1) transporter in the placenta and fetal tissues: expression profile and fetus protective role at different stages of gestation.

In our previous study, we described synchronized activity of organic cation transporter 3 (OCT3/SLC22A3) and multidrug and toxin extrusion 1 (MATE1/SLC47A1) transporter in the passage of organic cations across the rat placenta and the role of these transporters in fetal defense; in this study, we hypothesized that changes in placental levels of OCT3 and MATE1 throughout gestation might affect the fetal protection and detoxification. Using quantitative RT-PCR, Western blot analysis, and immunohistochemistry, we were able to detect Oct3/OCT3 and Mate1/MATE1 expression in the rat placenta as early as on Gestation Day (gd) 12 with increasing tendency toward the end of pregnancy. Comparing first versus third trimester human placenta, we observed stable expression of OCT1 and decreasing expression of OCT2 and OCT3 isoforms. Contrary to the current literature, we were able to detect also MATE1/MATE2 isoforms in the human placenta, however, with considerable inter- and intraindividual variability. Using infusion of 1-methyl-4-phenylpyridinium (MPP(+)), a substrate of OCT and MATE transporters, into pregnant dams, we investigated the protective function of the placenta against organic cations at different gds. The highest amount of MPP(+) reached the fetus on gd 12 while from gd 15 onward, maternal-to-fetal transport of MPP(+) decreased significantly. We conclude that increased expression of placental OCT3 and MATE1 along with general maturation of the placental tissues results in significantly lower transport of MPP(+) from mother to fetus. In contrast, decreasing expression of OCT3 and MATE1 in human placenta indicates these transporters may play a role in fetal protection preferentially at earlier stages of gestation.