Different Involvement of OAT in Renal Disposition of Oral Anticoagulants Rivaroxaban, Dabigatran, and Apixaban.

This study aimed to investigate the interactions of 3 anticoagulants, rivaroxaban, apixaban, and dabigatran, with 5 human solute carrier transporters, hOAT1, hOAT3, hOCT2, hOATP1B1, and hOATP1B3. Apixaban inhibited hOAT3, hOATP1B1, and hOATP1B3, and rivaroxaban inhibited hOAT3 and hOATP1B3, with IC50 values of >20 and >5 µM, respectively. The effect of dabigatran was negligible or very weak, so significant drug interactions at therapeutic doses are unlikely. Specific uptake of rivaroxaban was observed only in human and mouse OAT3-expressing cells. The Km for mouse Oat3 (mOat3) was 1.01 ± 0.70 µM. A defect in mOat3 reduced the kidney-to-plasma concentration ratio of rivaroxaban by 38% in mice. Probenecid treatment also reduced the kidney-to-plasma concentration ratio of rivaroxaban in rats by 73%. Neither mOat3 defect nor probenecid administration in rats reduced the renal clearance of rivaroxaban. The uptake of rivaroxaban by monkey kidney slices was temperature dependent and inhibited by probenecid but not by tetraethylammonium. Taken together, organic anion transporters, mainly OAT3, may mediate basolateral uptake of rivaroxaban in kidneys. hOAT3 could be an additional factor that differentiates the potential drug-drug interactions of the 3 anticoagulants in the urinary excretion process in clinical settings.

Epigenetic regulation of organic anion transporting polypeptide 1B3 in cancer cell lines.

PURPOSE: The expression of a multispecific organic anion transporter, OATP1B3/SLCO1B3, is associated with clinical prognosis and survival of cancer cells. The aims of present study were to investigate the involvement of epigenetic regulation in mRNA expression of a cancer-type variant of OATP1B3 (Ct-OATP1B3) in cancer cell lines. METHODS: The membrane localization and transport functions of Ct-OATP1B3 were investigated in HEK293 cells transiently expressing Ct-OATP1B3. DNA methylation profiles around the transcriptional start site of Ct-OATP1B3 in cancer cell lines were determined. The effects of a DNA methyltransferase inhibitor and siRNA knockdown of methyl-DNA binding proteins (MBDs) on the expression of Ct-OATP1B3 mRNA were investigated. RESULTS: 5'-RACE identified the TSS of Ct-OATP1B3 in PK-8 cells. Ct-OATP1B3 was localized on the plasma membrane, and showed the transport activities of E217ßG, fluvastatin, rifampicin, and Gd-EOB-DTPA. The CpG dinucleotides were hypomethylated in Ct-OATP1B3-positive cell lines (DLD-1, TFK-1, PK-8, and PK-45P) but were hypermethylated in Ct-OATP1B3-negative cell lines (HepG2 and Caco-2). Treatment with a DNA methyltransferase inhibitor and siRNA knockdown of MBD2 significantly increased the expression of Ct-OATP1B3 mRNA in HepG2 and Caco-2. CONCLUSIONS: Ct-OATP1B3 is capable of transporting its substrates into cancer cells. Its mRNA expression is regulated by DNA methylation-dependent gene silencing involving MBD2.