BACKGROUND AND PURPOSE: The organic cation transporter 1 (OCT1) transports cationic drugs into hepatocytes. The high hepatic expression of OCT1 is controlled by the HNF4α and USF transcription factors. Pregnane X receptor (PXR) mediates induction of the principal xenobiotic metabolizing enzymes and transporters in the liver. Here, we have assessed the down-regulation of OCT1 expression by PXR activation. EXPERIMENTAL APPROACH: We used primary human hepatocytes and related cell lines to measure OCT1 expression and activity, by assaying MPP(+) accumulation. Western blotting, qRT-PCR, the OCT1 promoter gene reporter constructs and chromatin immunoprecipitation assays were also used. KEY RESULTS: OCT1 mRNA in human hepatocytes was down-regulated along with reduced [(3) H]MPP(+) accumulation in differentiated HepaRG cells after treatment with rifampicin. Rifampicin and hyperforin as well as the constitutively active PXR mutant T248D suppressed activity of the 1.8 kb OCT1 promoter construct in gene reporter assays. Silencing of both PXR and HNF4α in HepaRG cells blocked the PXR ligand-mediated down-regulation of OCT1 expression. The mutation of HNF4α and USF1 (E-box) responsive elements reversed the PXR-mediated inhibition in gene reporter assays. Chromatin immunoprecipitation assays indicated that PXR activation sequestrates the SRC-1 coactivator from the HNF4α response element and E-box of the OCT1 promoter. Consistent with these findings, exogenous overexpression of the SRC-1, but not the PGC1α coactivator, relieved the PXR-mediated repression of OCT1 transactivation. CONCLUSIONS AND IMPLICATIONS: PXR ligands reduced the HNF4α-mediated and USF-mediated transactivation of OCT1 gene expression by competing for SRC-1 and decreased delivery of a model OCT1 substrate into hepatocytes.

• MeSH
• buňky Hep G2 MeSH
• down regulace MeSH
• floroglucinol analogy a deriváty   farmakologie   MeSH
• hepatocyty metabolismus   MeSH
• koaktivátor 1 jaderných receptorů metabolismus   MeSH
• lidé MeSH
• nádorové buňky kultivované MeSH
• oktamerní transkripční faktor 1 genetika   metabolismus   MeSH
• pregnanový X receptor MeSH
• rifampin farmakologie   MeSH
• steroidní receptory metabolismus   MeSH
• terpeny farmakologie   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• vztahy mezi strukturou a aktivitou MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• floroglucinol MeSH
• hyperforin MeSH Prohlížeč
• koaktivátor 1 jaderných receptorů MeSH
• NCOA1 protein, human MeSH Prohlížeč
• oktamerní transkripční faktor 1 MeSH
• POU2F1 protein, human MeSH Prohlížeč
• pregnanový X receptor MeSH
• rifampin MeSH
• steroidní receptory MeSH
• terpeny MeSH

Entecavir (ETV) is one of the most potent agents for the treatment of the hepatitis B viral infection. The drug is principally eliminated by the kidney. The goal of this study was to investigate the potential of ETV to interact in vitro with the renal SLC transporters hOAT1, hOCT2, hCNT2 and hCNT3. Potential drug-drug interactions of ETV at the renal transporters with antiviral drugs known to be excreted by the kidney (adefovir, tenofovir, cidofovir) as well as transporter-dependent cytotoxicity were also examined. Interactions with the selected transporters along with cytotoxicity were studied in several transiently transfected cellular models using specific substrates and inhibitors. ETV was found to be both a substrate and inhibitor of hOAT1 (IC50 = 175.3 μM), hCNT2 (IC50 = 241.9 μM) and hCNT3 (IC50 = 278.4 μM) transporters, although it interacted with the transporters with relatively low affinities. ETV inhibited the cellular uptake of adefovir, tenofovir, and cidofovir by hOAT1; however, effective inhibition was shown at ETV concentrations exceeding therapeutic levels. In comparison with adefovir, tenofovir, and cidofovir, ETV displayed no transporter-mediated cytotoxicity in cells transfected with hOAT1, hCNT2, and hCNT3. No significant interaction of ETV with hOCT2 was detected. The study demonstrates interactions of ETV with several human renal transporters. For the first time, an interaction of ETV with the hCNTs was proved. We show that the potency of ETV to cause nephrotoxicity and/or clinically significant drug-drug interactions related to the tested transporters is considerably lower than that of adefovir, tenofovir, and cidofovir.

• Klíčová slova
• antivirals, drug–drug interactions, nephrotoxicity, renal disposition,
• Publikační typ
• časopisecké články MeSH

Amphotericin B (AmB) is excreted via the renal excretion route. This excretion process may result in nephrotoxicity. However, relevant information on the precise renal excretion mechanisms is not available. The aim of the study was to analyze the possible interaction of AmB or its prodrug AmB deoxycholate (AmB-DOC) with the typical renal organic anion transporters (OATs) and organic cation transporters (OCTs), using cellular and organ models. The relevant transport systems were then investigated in terms of the drug-drug interactions of AmB-DOC with antivirals that might potentially be used concomitantly. To analyze the renal excretion mechanisms of [(3)H]AmB, perfused rat kidney was employed. HeLa and MDCK II cells transiently transfected with human OAT1 (hOAT1) or hOCT2 were used as the cellular models. A significant tubular secretion of AmB was demonstrated in the perfused rat kidney. The cellular studies performed confirmed the active transport of AmB into cells. AmB did not interact with hOAT1 but strongly inhibited hOCT2. In contrast, AmB-DOC inhibited both hOAT1 and hOCT2. However, [(3)H]AmB cellular uptake by hOAT1 and hOCT2 was not found. AmB-DOC interacted significantly with adefovir, tenofovir, and cidofovir in hOAT1-transfected cells at supratherapeutic concentrations. In conclusion, the significant potency of AmB and AmB-DOC for inhibiting the transporters was demonstrated in this study. The secretion of AmB in the renal tubules is likely not related to the transporters here, since the drug was not proven to be a substrate for them. Drug-drug interactions of AmB and the antivirals used in this study on the investigated transporters are not probable.

• MeSH
• amfotericin B metabolismus   MeSH
• antivirové látky metabolismus   MeSH
• buněčné linie MeSH
• fixní kombinace léků MeSH
• HeLa buňky MeSH
• krysa rodu Rattus MeSH
• kyselina deoxycholová metabolismus   MeSH
• ledviny metabolismus   MeSH
• lékové interakce MeSH
• lidé MeSH
• potkani Wistar MeSH
• protein 1 přenášející organické anionty metabolismus   MeSH
• proteiny přenášející organické kationty metabolismus   MeSH
• psi MeSH
• teplota MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• mužské pohlaví MeSH
• psi MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• amfotericin B MeSH
• amphotericin B, deoxycholate drug combination MeSH Prohlížeč
• antivirové látky MeSH
• fixní kombinace léků MeSH
• kyselina deoxycholová MeSH
• protein 1 přenášející organické anionty MeSH
• proteiny přenášející organické kationty MeSH