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1. Breast cancer resistance protein (BCRP, ABCG2) is a drug efflux transporter that is believed to affect the drug disposition of several drugs and xenobiotics. In the present study, we evaluated the localization and functional expression of BCRP in the human choriocarcinoma cell line BeWo, an in vitro model of the human trophoblast, and compared it with the expression of P-glycoprotein (MDR1, ABCB1) as the most widely studied placental transporter. In addition, the expression of BCRP at the mRNA level was compared with that of MDR1 in the human term placenta. 2. Western blotting analysis revealed high endogenous expression of BCRP protein in BeWo cells. Using indirect immunofluorescence microscopy, we found that the BCRP transporter appears to be localized predominantly at the apical plasma membrane. Functional studies showed a significant effect of the BCRP inhibitors GF120918 (5 micromol/L) and Ko143 (1 micromol/L) on mitoxantrone accumulation and, thus, confirmed efflux activity of BCRP in BeWo cells. 3. Using absolute mRNA quantification with real-time reverse transcription-polymerase chain reaction, we found high expression of BCRP in BeWo cells, whereas no transcript of MDR1 (P-glycoprotein), the most extensively studied drug transporter, was detected. 4. In the human placenta, BCRP was localized predominantly in the syncytiotrophoblast layer; however, immunopositivity for the BXP-21 antibody was also observed in fetal vessels of the chorionic villi. The number of BCRP transcripts in the human term placenta was found to be more than 10-fold higher compared with the expression of MDR1. 5. In conclusion, we suggest that BeWo cells could serve as a suitable in vitro model to study trans-trophoblast transport of BCRP substrates and that placental BCRP can play an important role in preventing the accumulation of potentially toxic xenobiotics in the trophoblast cells.

Breast cancer resistance protein (BCRP/ABCG2) is a member of the ATP-binding cassette transporter family that recognizes a variety of chemically unrelated compounds. Its expression has been revealed in many mammal tissues, including placenta. The purpose of this study was to describe its role in transplacental pharmacokinetics using rat placental HRP-1 cell line and dually perfused rat placenta. In HRP-1 cells, expression of Bcrp, but not P-glycoprotein, was revealed at mRNA and protein levels. Cell accumulation studies confirmed Bcrp-dependent uptake of BODIPY FL prazosin. In the placental perfusion studies, a pharmacokinetic model was applied to distinguish between passive and Bcrp-mediated transplacental passage of cimetidine as a model substrate. Bcrp was shown to act in a concentration-dependent manner and to hinder maternal-tofetal transport of the drug. Fetal-to-maternal clearance of cimetidine was found to be 25 times higher than that in the opposite direction; this asymmetry was partly eliminated by BCRP inhibitors fumitremorgin C (2 M) or N- (4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918; 2 M) and abolished at high cimetidine concentrations (1000 M). When fetal perfusate was recirculated, Bcrp was found to actively remove cimetidine from the fetal compartment to the maternal compartment even against a concentration gradient and to establish a 2-fold maternal-to-fetal concentration ratio. Based on our results, we propose a two-level defensive role of Bcrp in the rat placenta in which the transporter 1) reduces passage of its substrates from mother to fetus but also 2) removes the drug already present in the fetal circulation.Placenta is an organ that brings maternal and fetal blood circulations into proximity, allowing mutual interchange of nutrients and waste products. Conversely, placenta forms a barrier to protect the fetus against harmful endo-and exogenous compounds from maternal circulation. As a barrier, the human and rodent placenta had for long been supposed to present only a mechanical obstruction formed by fetal endothelia, basal membranes, and syncytiotrophoblast. However, over the past two decades, a variety of metabolizing enzymes and drug efflux transporters of the ATP-binding cassette (ABC) transporter family have been localized in placental trophoblast (Marin et al., 2004;Syme et al., 2004). These proteins are thought to strengthen, in an active and capacitylimited manner, placental barrier role and help in protecting the fetus.Drug efflux transporters of the ABC family are membraneembedded proteins that limit intracellular concentration of substrates by pumping them out of cell through an active, energy-dependent mechanism (Schinkel and Jonker, 2003). The most intensively studied drug efflux transporters to date have been P-glycoprotein (P-gp; ABCB1), breast cancer resistance protein (BCRP; ABCG2) and multidrug resistance-associated proteins 1 and 2 (ABCC1 and ABCC2), all of which were found t...

Contrast-enhanced magnetic resonance imaging (CE-MRI) is a valuable technique for the diagnosis of liver diseases. As gadocoletic acid trisodium salt (B22956/1), a new contrast agent showing high biliary excretion, may be potentially advantageous in hepatobiliary imaging, the aim of the study was to investigate the molecular mechanisms of hepatic transport of the B22956 ion in a cellular model of hepatic tumor. B22956 ion uptake was measured in tumoral (HepG2) and nontumoral (Chang liver) hepatic cell lines. Absolute quantitative real-time reverse transcriptase (RT)-polymerase chain reaction (PCR) analyses, using cloned PCR products as standards, were performed on total RNA of both cell lines and normal liver to evaluate the transcription of 12 transport genes:

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Rhodamine 123 (Rho123), a model substrate of P-glycoprotein (P-gp), was used to evaluate the functional activity of P-gp efflux transporter in the rat placental barrier. The dually perfused rat-term placenta method was used. In our experiments, the materno-fetal transplacental passage of Rho123 did not meet the criteria of the first-order pharmacokinetics, suggesting an involvement of transporter-mediated process. Inhibitors of P-gp, such as [3Ј-keto-Bmt 1 ]-[Val 2 ]-cyclosporine (PSC833), cyclosporine (CsA), quinidine, and chlorpromazine, increased significantly the materno-fetal transplacental passage of Rho123 in the experiments under steady-state conditions. On the other hand, PSC833, CsA, and quinidine decreased the feto-maternal passage of Rho123. Similarly, in the experiments carried out under nonsteady-state conditions, CsA accelerated the passage of Rho123 in the materno-fetal direction and decreased its passage in the opposite direction. Feto-maternal transplacental clearances of Rho123 were found to be considerably higher than those in the materno-fetal course. Potent P-gp inhibitors, such as PSC833 or CsA, partially canceled the asymmetry. Negligible metabolism of Rho123 into its major demethylated metabolite rhodamine 110 was observed in the rat placenta. Expression of P-gp genes was detected using immunohistochemical, Western blotting, and reverse transcription-polymerase chain reaction methods preferentially in the second rat syncytiotrophoblast layer. In conclusion, these data suggest that P-gp limits the entry of Rho123 into fetuses and at the same time it accelerates the feto-maternal elimination of the model compound. Therefore, it seems plausible that pharmacokinetics of xenobiotics in the rat placental barrier could be controlled by P-gp in both directions.

Skin exposure to ultraviolet (UV) light evokes a complex stress response in keratinocytes. Keratin filament organization provides structural stability and mechanical integrity of keratinocytes. Involucrin is a transglutaminase substrate protein contributing to the formation of insoluble cornified envelopes. However, a more complex role for keratins and involucrin has been proposed, including the regulation of cell stress response. The aim was to evaluate modulations of keratin 1, 10 and involucrin expression in HaCaT in the light of the complex response of these cells to UV-B radiation, including effects on c-Jun and matrix metalloproteinase 1 (MMP-1) gene expression and production of interleukin (IL) 6 and 8. A UV-B (300±5 nm) dose of 10 mJ/cm2 was selected since this dose resulted in a partial decrease in cell viability in contrast to higher UV-B doses, which induced complete cell death 48 h after treatment. The UV-B radiation induced significant expression of keratin 1 and 10 and decreased expression of involucrin. This was accompanied by increased expression of c-Jun and MMP-1 and IL-6 and IL-8 production. The data suggest that the expression of keratin 1, 10 and involucrin is modulated in HaCaT keratinocytes as a part of the complex stress response to UV radiation.

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