P-Glycoprotein expression significantly increases the capability of human placental trophoblast cells to efflux xenobiotics

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University of Leeds (2002) J Physiol 544P, S116

Communications: P-Glycoprotein expression significantly increases the capability of human placental trophoblast cells to efflux xenobiotics

D.E. Atkinson, J.D. Glazier, C.P. Sibley, L.J. Fairbairn* and S.L. Greenwood

Academic Unit of Child Health, University of Manchester, St Mary's Hospital, Manchester M13 0JH and *Paterson Institute for Cancer Research, Christie Hospital, Manchester M20 4BX, UK

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We have previously shown that the trophoblast derived BeWo and JEG choriocarcinoma cell lines express MRP1 (multi-drug resistance related protein), whilst the JAr choriocarcinoma cell line and primary cytotrophoblast cells express both MRP1 and P-glycoprotein (P-gp, coded by the MDR1 gene) (Atkinson et al. 2000). The functional consequences of the absence of P-gp have also been determined and we have shown that the cyclosporin-sensitive accumulation of [3H] vinblastine by cells expressing only MRP1 is higher than that by cells expressing both drug efflux proteins (Atkinson et al. 2001).

In the present study we tested the hypothesis that the increased cyclosporin-sensitive [3H] vinblastine accumulation (i.e. reduced efflux) in BeWo cells is due to their lack of expression of MDR1 P-gp.

Using a retroviral vector based on the Moloney murine leukaemia virus we introduced MDR1 into BeWo cells by co-culture with the vector packaging cell line in transwell plates. MDR1 transduced cells (BeWo MDR) were then selected using 100 mg ml-1 of colchicine. To establish that transduction had been successful, Western blot analysis was performed using the F4 monoclonal antibody specific for human P-gp. The cells were then used in accumulation assays as previously described (Atkinson et al. 2001).

BeWo MDR cells express P-gp, whilst, as expected, native BeWo cells show no expression of the protein (Fig. 1). Cyclosporin-sensitive accumulation of [3H] vinblastine in BeWo MDR cells is significantly lower than in native BeWo cells and is very similar to that seen in cytotrophoblast cells which naturally express MDR1 (Fig. 2).

We conclude that the higher cyclosporin-sensitive accumulation in native BeWo cells resulting from a lower capacity to efflux substrate drugs is due to their lack of P-gp, and therefore that P-gp is important in xenobiotic handling by trophoblast cells. The expression of P-gp on the maternal facing plasma membrane of the placenta (Fig. 1, Atkinson et al. 2000) places it in an ideal position to protect the fetus from potentially harmful compounds in the maternal circulation.

This work was funded by the MRC. MVM and BM were kindly donated by Dr P. Speake.

All procedures accord with current local guidelines.

Where applicable, experiments conform with Society ethical requirements.

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