The Role of Adopted Orphan Nuclear Receptors in the Regulation of an Organic Anion Transporting Polypeptide 1B1 (OATP1B1) under the Action of Sex Hormones

Organic anion transporting polypeptide 1B1 (OATP1B1) is an influx transporter protein of the SLC superfamily, expressed mainly in the liver and some tumor cells. The mechanisms of its regulation are being actively studied. In the present study, the effect of sex hormones (estradiol, progesterone and testosterone) on OATP1B1 expression in HepG2 cells was examined. The role of adopted orphan receptors, farnasoid X receptor (FXR), constitutive androstane receptor (CAR), pregnane X receptor (PXR) and liver X receptor subtype alpha (LXRa), was also evaluated. Hormones were used in concentrations of 1, 10 and 100 mu M, with incubation for 24 h. The protein expression of OATP1B1, FXR, CAR, PXR and LXRa was analyzed by Western blot. It was shown that estradiol (10 and 100 mu M) increased the expression of OATP1B1, acting through CAR. Testosterone (1, 10 and 100 mu M) increased the expression of OATP1B1, acting through FXR, PXR and LXRa. Progesterone (10 and 100 mu M) decreased the expression of OATP1B1 (10 and 100 mu M) and adopted orphan receptors are not involved in this process. The obtained results have important practical significance and determine ways for targeted regulation of the transporter, in particular in cancer.