Effect of pregnane X receptor ligands on transport mediated by human OATP1B1 and OATP1B3

Abstract

The pregnane X receptor is a ligand-activated transcription factor that is abundantly expressed in hepatocytes. Numerous drugs are pregnane X receptor ligands. To bind to their receptor they must cross the sinusoidal membrane. Organic anion transporting polypeptides 1B1 and 1B3 (OATP1B1 and OATP1B3) are polyspecific transporters expressed at the sinusoidal membrane of human hepatocytes. They mediate transport of a variety of drugs including the pregnane X receptor ligands rifampicin and dexamethasone. To test whether additional pregnane X receptor ligands interact with OATP1B1- and 1B3-mediated transport, we developed Chinese Hamster Ovary (CHO) cell lines stably expressing OATP1B1 or 1B3 at high levels. OATP1B1- and 1B3-mediated estradiol-17beta-glucuronide uptake was inhibited by several pregnane X receptor ligands in a concentration dependent way. IC(50) values for rifampicin, paclitaxel, mifepristone, and troglitazone were within their respective pharmacological free plasma concentrations. Kinetic analysis revealed that clotrimazole inhibits OATP1B1-mediated estradiol-17beta-glucuronide transport with a K(i) of 7.7+/-0.3 microM in a competitive way. However, uptake of OATP1B3-mediated estradiol-17beta-glucuronide was stimulated and this stimulation was due to an increased apparent affinity. Transport of estrone-3-sulfate was hardly affected while all other substrates tested were inhibited. Additional azoles like fluconazole, ketoconazole and miconazole did not stimulate OATP1B3-mediated estradiol-17beta-glucuronide transport. In summary, these results demonstrate that pregnane X receptor ligands, by inhibiting or stimulating OATP-mediated uptake, can lead to drug-drug interactions at the transporter level.

Polymorphisms in cytochromes P450 2C8 and 3A5 are associated with paclitaxel neurotoxicity

“…We studied 13 polymorphisms from six key paclitaxel elimination genes in 118 patients treated with paclitaxel, finding a statistically significant association for three cytochrome P450 functional genetic variants. The strategy followed was to select the most relevant polymorphisms, based on their functionality and allele frequency, in the genes essential for paclitaxel hepatic metabolism (CYP2C8, CYP3A4 and CYP3A5) 19,20 and transport (SLCO1B1, SLCO1B3 and ABCB1) [21][22][23][24] ( Figure 1) and assess their association with the paclitaxel dose that caused grade 2 neurotoxicity in our patients. Our data suggests a possible genetic predisposition to the occurrence of paclitaxelinduced neuropathy.…”

“…[16][17][18] In the liver paclitaxel is hydroxylated at the 6a position by cytochrome P450 2C8 (CYP2C8), forming the major metabolite, and at the C3 0 position by CYP3A4/5. 19,20 Concerning transport, paclitaxel uptake into the hepatocytes is mediated by the organic anion transporting polypeptide (OATP) 1B3 and, to some extent, (OATP) 1B1, 21,22 and efflux is mediated by P-glycoprotein. 23,24 The genes encoding these proteins are subjected to relevant genetic variation, which can alter drug metabolism and disposition, as we and others have shown.…”

Transporters involved in the hepatic uptake of 99mTc-mebrofenin and indocyanine green

“…Cell Lines Chinese hamster ovary (CHO) cell lines stably expressing human OATP1B1, OATP1B3, and OATP2B1 have been described (17,18). CHO wild type (CHO-WT) cells were used as control.…”

“…fetal calf serum, 0.05mg/mL L-proline, 100U/mL penicillin/streptomycin, and 500Pg/mL geneticin G- (17,18). Flp-In CHO cells (pcDNA5/FRT and NTCP) were grown in HAM F-12 medium containing 10% fetal calf serum, 1mM L-glutamine, 100U/mL penicillin/streptomycin, and 500Pg/mL hygromycin B.…”

“…Tc-Mebrofenin and ICG in Stably Transfected CHO Cells Transport experiments were performed in OATP-expressing CHO cells and NTCP-expressing Flp-In CHO cells as described before (17,20). Briefly, cells were washed 3× with pre-warmed (37°C) sodium buffer or choline buffer.…”