OATP1B1 Plays an Important Role in the Transport and Treatment Efficacy of Sorafenib in Hepatocellular Carcinoma.

BACKGROUND: Sorafenib is an anticancer drug used in the treatment of unresectable hepatocellular carcinoma and advanced renal cell carcinoma. It is a substrate for the human OATP1B1. This study is aimed at assessing the role of OATP1B1 in transportation and uptake of sorafenib in hepatocellular carcinoma and how OATP1B1 affects the pharmacodynamics of sorafenib in vitro and in vivo. METHODS: Sorafenib transport was measured in HepG2, HepG2-OATP1B1∗1a, HepG2-OATP1B1∗1b, HepG2-OATP1B1∗15, LO2, LO2-OATP1B1∗1a, LO2-OATP1B1∗1b, and LO2-OATP1B1∗15 cells, as well as in HepG2 cells transfected with miR-148a mimics. The viability and apoptosis rate of cells treated with sorafenib were evaluated. A liver cancer rat model was established to explore the pharmacokinetics and pharmacodynamics of sorafenib after overexpression of Oatp2. RESULTS: Changes in expression and genetic mutations of OATP1B1 significantly affected the uptake of sorafenib in HepG2 and LO2 transgenic cells, and the uptake of sorafenib was higher in HepG2 than LO2. Genetic mutations of OATP1B1 significantly affected the cell viability and apoptosis rate of HepG2 cells after sorafenib treatment. Compared to control group, the uptake of sorafenib in miR-148a mimic-transfected HepG2 cells was decreased, and the cell viability was increased. PCN significantly increased the expression of Oatp2 and affected the pharmacokinetics of sorafenib. Vascular endothelial growth factor levels and microvascular density in tumor-adjacent tissues decreased significantly, suggesting that increased Oatp2 expression improves the treatment effect of sorafenib in a rat model of liver cancer. CONCLUSIONS: OATP1B1 plays an important role in the pharmacokinetics and pharmacodynamics of sorafenib in hepatocellular carcinoma.

Therapeutic Effects of an Inhibitor of Thioredoxin Reductase on Liver Fibrosis by Inhibiting the Transforming Growth Factor-ß1/Smads Pathway.

Liver fibrosis is an important stage in the progression of liver injury into cirrhosis or even liver cancer. Hepatic stellate cells (HSCs) are induced by transforming growth factor-ß1 (TGF-ß1) to produce α-smooth muscle actin (α-SMA) and collagens in liver fibrosis. Butaselen (BS), which was previously synthesized by our group, is an organic selenium compound that exerts antioxidant and tumor cell apoptosis-promoting effects by inhibiting the thioredoxin (Trx)/thioredoxin reductase (TrxR) system. The aim of this study was to investigate the potential effects of BS on liver fibrosis and explore the underlying molecular mechanisms of its action. Liver fibrosis models were established using male BALB/c mice through intraperitoneal injection of CCl4. BS was administered orally once daily at a dose of 36, 90, or 180 mg/kg. Silymarin (Si), which is a drug used for patients with nonalcoholic fatty liver disease and nonalcoholic steatohepatitis, was administered at a dose of 30 mg/kg per day as a control. The action mechanisms of BS against liver fibrosis progression were examined in HSCs. The study revealed that the activity and expression levels of TrxR were elevated in the mouse liver and serum after CCl4-induced liver fibrosis. Oral administration of BS relieved the pathological state of mice with liver fibrosis, showing significant therapeutic effects against liver fibrosis. Moreover, BS not only induced HSC apoptosis but also inhibited the production of α-SMA and collagens by HSCs by downregulating the TGF-ß1 expression and blocking the TGF-ß1/Smads pathway. The results of the study indicated that BS inhibited liver fibrosis by regulating the TGF-ß1/Smads pathway.

Identification of cytochrome P450 isoenzymes involved in the metabolism of 23-hydroxybetulinic acid in human liver microsomes.

Context: 23-Hydroxybetulinic acid (23-HBA), a major active constituent of Pulsatilla chinensis (Bunge) Regel (Ranunculaceae), exhibits potential antitumor activity. Its metabolism, however, has not yet been studied.Objective: This study focuses on the metabolism of 23-HBA in vitro by human liver microsomes.Materials and methods: The metabolic kinetics of 23-HBA (0.5-100 µM) and the effects of selective CYP450 (CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4) inhibitors on metabolism of 23-HBA were evaluated in human liver microsomes incubation system and then determined by LC-MS method. The Michaelis-Menten parameters Km and Vmax were initially estimated by analysing Lineweaver-Burk plot. The clearance (CLint) was also calculated.Results: The Vmax, Km, and CLint of 23-HBA were 256.41 ± 11.20 pmol/min/mg, 11.10 ± 1.07 µM, and 23.10 ± 1.32 µL/min/mg, respectively. The metabolism of 23-HBA was significantly inhibited by furafylline (0.05 µM, p < 0.01) and ketoconazole (0.02 µM, p < 0.05). Ticlopidine (1.3 µM, p < 0.05) could inhibit the metabolism of 23-HBA, while the other inhibitors (sulfaphenazole and quinidine) showed nonsignificant inhibition on the metabolism of 23-HBA.Discussion and conclusions: This is the first investigation of the metabolism of 23-HBA in human liver microsomes. The in vitro study indicates that CYP1A2 and CYP3A4 are mainly involved in the metabolism of 23-HBA. Special attention should be given to the pharmacokinetic and clinical outcomes when 23-HBA was co-administrated with other compounds mainly undergoing CYP1A2/CYP3A4-mediated metabolism. Further studies are needed to evaluate the significance of this interaction and strengthen the understanding of traditional Chinese medicine.

Transport of salvianolic acid B via the human organic anion transporter 1B1 in the liver.

Salvianolic acid B (SAB) has a high concentration in the liver, but the mechanism of its distribution in the liver is unclear. The aim of this study was to investigate the mechanisms of hepatic uptake of SAB. In this study, we first explored the uptake features of SAB in HepG2 cells and the effect of rifampicin on uptake. Then, we explored the effects of SAB on the uptake of pitavastatin in HepG2 cells. Finally, we established an HEK239T-OATP1B1 cell model to confirm whether OATP1B1 mediated the transport of SAB. Results showed that the uptake kinetic parameters Vmax and Km for SAB in HepG2 cells were 21.28 ± 2.06 pmol mg-1 per protein min-1 and 28.47 ± 7.36 µM, respectively. Rifampicin inhibited the uptake of SAB in HepG2 cells (IC50 was 5.85 ± 1.70 µM), and SAB affected the uptake of pitavastatin in HepG2 cells (IC50 was 27.67 ± 1.90 µM). The uptake kinetic parameters Vmax and Km for SAB in HEK239T-OATP1B1 were 60.03 ± 6.16 pmol mg-1 per protein min-1 and 87.24 ± 15.28 µM, respectively, whereas in EGFP-HEK293 cells were 14.04 ± 2.53 pmol mg-1 per protein min-1 and 56.53 ± 15.50 µM. The SAB had no effect of on the expression of OATP1B1 in HEK239T-OATP1B1 cells. In conclusion, this study demonstrated that OATP1B1 contributes to the transport and accumulation of SAB in the liver.

Mulberroside A suppresses PXR-mediated transactivation and gene expression of P-gp in LS174T cells.

Mulberroside A (Mul A) is the main bioactive constituents of Sangbaipi, which is officially listed in the Chinese Pharmacopoeia. The pregnane X receptor (PXR) has been recognized as the critical mediator of human P-glycoprotein (P-gp) gene transactivation. In this study, the effect of Mul A on PXR-mediated transactivation and gene expression of P-gp was investigated. It was found that Mul A significantly suppressed PXR-mediated P-gp luciferase activity induced by rifampicin (Rif). Furthermore, Rif induced an elevation of P-gp expression and transport activity, which was apparently suppressed by Mul A. However, Mul A did not suppress the P-gp luciferase activity, P-gp expression, and function in the absence of Rif. These findings suggest that Mul A suppresses PXR-mediated transactivation and P-gp expression induced by Rif. This should be taken into consideration to predict any potential herb-drug interactions when Mul A or Sangbaipi are co-administered with Rif or other PXR agonist drugs.

[OATP1B1 in drug-drug interactions between traditional Chinese medicine Danshensu and rosuvastatin].

The study was designed to explore the drug-drug interactions mechanisms mediated by OATP1B1 between traditional Chinese medicine Danshensu and rosuvastatin. First, the changes of rosuvastatin pharmacokinetics were investigated in presence of Danshensu in rats. Then, the primary rat hepatocytes model was established to explore the effects of Danshensu on the uptake of rosuvastatin by hepatocytes. Finally, HEK293T cells with overexpression of OATP1B1*a and OATP1B1*5 were established using a lentiviral delivery system to explore the effects of Danshensu on the uptake of rosuvastatin. Rosuvastatin pharmacokinetic parameters of C(max0, AUCO(0-t), AUC(0-∞) were increased about 123%, 194% and 195%, by Danshensu in rats, while the CL z/F value was decreased by 60%. Uptake of rosuvastatin in the primary rat hepatocytes was decreased by 3.13%, 41.15% and 74.62%, respectively in the presence of 20, 40 and 80 µmol x L(-1) Danshensu. The IC50 parameters was (53.04 ± 2.43) µmol x L(-1). The inhibitory effect of Danshensu on OATP1B1 mediated transport of rosuvastatin was related to the OATP1B1 gene type. In OATP1B1*5-HEK293T mutant cells, transport of rosuvastatin were reduced by (39.11 ± 4.94)% and (63.61 ± 3.94)%, respectively, by Danshensu at 1 and 10 µmol x L(-1). While transport of rosuvastatin was reduced by (8.22 ± 2.40)% and (11.56 ± 3.04)% and in OATP1B1*1a cells, respectively. Danshensu significantly altered the pharmacokinetics of rosuvastatin in rats, which was related to competitive inhibition of transport by OATPJBI. Danshensu exhibited a significant activity in the inhibition of rosuvastatin transport by OATP1B1*5-HEK293T, but not by OATP1B1*1a, suggesting a dependence on OATP1B1 sequence.

The effect of herbal medicine danshensu and ursolic acid on pharmacokinetics of rosuvastatin in rats.

The aim of this study was to explore potential herb-drug interaction between danshensu or ursolic acid and rosuvastatin. Compared to the control group given rosuvastatin alone, the concurrent use of danshensu (46 mg/kg) or ursolic acid (80 mg/kg) prior to the oral administration of rosuvastatin (100 mg/kg) increased the systemic exposure of rosuvastatin more than twofold. The plasma clearance of rosuvastatin was reduced to more than 57% in the presence of danshensu or ursolic acid. Rosuvastatin is minimally metabolized in the CYP2C9 isoenzyme pathway and to an even lesser extent in the CYP2C19 isoenzyme pathway. Rosuvastatin is a substrate of drug transporters such as human OATP1B1, OATP 1B3, OATP 1A2, BCRP and NTCP. Therefore, the present results suggested that the potential drug interaction between danshensu or ursolic acid and rosuvastatin may be mediated by one or more transporters (OATP1B1, OATP 1B3, OATP 1A2, BCRP and NTCP) and/or CYPs.