Quantitative prediction of CYP3A-mediated drug-drug interactions by correctly estimating fraction metabolized using human liver chimeric mice.

BACKGROUND AND PURPOSE: Fraction metabolized (fm ) and fraction transported (ft ) are important for understanding drug-drug interactions (DDIs) in drug discovery and development. However, current in vitro systems cannot accurately estimate in vivo fm due to inability to reflect the ft by efflux transporters (ft,efflux ). This study demonstrates how CYP3A-mediated DDI for CYP3A/P-gp substrates can be predicted using Hu-PXB mice as human liver chimeric mice. EXPERIMENTAL APPROACH: For estimating human in vitro fm by CYP3A enzyme (fm,CYP3A,in vitro ), six drugs, including CYP3A/P-gp substrates (alprazolam, cyclosporine, docetaxel, midazolam, prednisolone, and theophylline) and human hepatocytes were incubated with or without ketoconazole as a CYP3A inhibitor. We calculated fm,CYP3A,in vitro based on hepatic intrinsic clearance. To estimate human in vivo fm,CYP3A (fm,CYP3A,in vivo ), we collected information on clinical DDI caused by ketoconazole for these six drugs. We calculated fm,CYP3A,in vivo using the change of total clearance (CLtotal ). For evaluating the human DDI predictability, the six drugs were administered intravenously to Hu-PXB and SCID mice with or without ketoconazole. We calculated the change of CLtotal caused by ketoconazole. We compared the CLtotal change in humans with that in Hu-PXB and SCID mice. KEY RESULTS: The fm,CYP3A,in vitro was overestimated compared to the fm,CYP3A,in vivo . Hu-PXB mice showed much better correlation in the change of CLtotal with humans (R2 = 0.95) compared to SCID mice (R2 = 0.0058). CONCLUSIONS AND IMPLICATIONS: CYP3A-mediated DDI can be predicted by correctly estimating human fm,CYP3A,in vivo using Hu-PXB mice. These mice could be useful predicting hepatic fm and ft,efflux .

Acceleration of murine hepatocyte proliferation by imazalil through the activation of nuclear receptor PXR.

The nuclear receptor pregnane X receptor (PXR) plays a major role in the xenobiotic-induced expression of drug-metabolizing enzymes. PXR activation is also associated with several adverse events in the liver. Especially, the receptor enhances hepatocyte proliferation mediated by chemical liver tumor promoters, suggesting that exposure to PXR activators increases the risk of liver cancer. In this study, we have investigated the influences of food additives on PXR to understand their potential adverse effects when they are taken in combination with other chemical compounds. We first screened 25 food additives and related compounds for their PXR-activating ability using reporter assays in HepG2 cells expressing mouse PXR, and found that imazalil dose-dependently activated mouse PXR. Next, to investigate whether imazalil could activate mouse PXR in vivo, mice were treated with imazalil and we found that imazalil treatment increased hepatic mRNA levels of Cyp3a11, a PXR target gene. Finally, to investigate the influence of imazalil exposure on the hepatocyte proliferation induced by nuclear receptor constitutive active/androstane receptor (CAR), mice were treated with imazalil with or without mouse CAR activator TCPOBOP. Although imazalil alone did not induce hepatocyte proliferation, co-treatment with imazalil facilitated the TCPOBOP-dependent proliferation, indicated by the increases in cell proliferation marker levels, Ki-67-positive nuclei and Mcm2 mRNA levels. These results suggest that in mice imazalil activates PXR to enhance hepatocyte proliferation mediated by CAR-activating liver tumor promoters.

Quantitative analysis of the number of antigens immobilized on a glass surface by AFM.

To develop force measurements using an atomic force microscope (AFM) in a quantitative manner, it is necessary to estimate the number density of target molecules on a sample surface, and for this, the sensitivity of detection should be known. In this study, the AFM was used as a mechanical detector and an antigen and its antibody were used as a model to evaluate the sensitivity of detection. Antigens were immobilized on a glass surface and number density was estimated by monitoring optical absorbance due to product formation by the reaction of crosslinkers. The concentration of antigen was controlled by mixing control peptides. A microbead was used as a probe and antibodies were immobilized on the bead. AFM force measurements were then made for a range of number densities in the order of 10-10(6) antigen molecules per square micrometer of surface and were compared to evaluate the sensitivity of detection. Our result establishes the reliability of estimating a number of molecules like receptors on the cell surface, and indicates that the AFM is useful as a mechanical detector with high sensitivity.

Reduction of bitterness of antihistaminic drugs by complexation with ß-cyclodextrins.

Reduction of bitterness of antihistaminic drugs by cyclodextrin (CyD) complexation was examined. The stability constant (Kc) of the 1:1 CyD inclusion complexes with antihistaminic drugs increased in the order of 2-hydroxypropyl-ß-CyD (HP-ß-CyD) ≈ ß-CyD > γ-CyD > α-CyD for diphenhydramine and epinastine, and HP-ß-CyD ≈ ß-CyD > α-CyD > γ-CyD for hydroxyzine, cetirizine, and dl-chlorpheniramine. The inclusion complexes inhibited the adsorption of antihistaminic drugs to lipid membrane using liposomes, as the magnitude of Kc increased. From human gustatory sensation tests, ß-CyD and HP-ß-CyD potently suppressed the bitterness of antihistaminic drugs in a dose-dependent manner. Further, an artificial taste sensor analysis revealed that ß-CyD and HP-ß-CyD inhibited the bitterness of antihistaminic drugs in solution. The results suggest that CyDs suppress the bitterness of antihistaminic drugs in solutions through the formation of inclusion complexes. These results may provide useful information for masking or elimination of bitterness of drugs using CyDs.

High glucose stimulates hepatic stellate cells to proliferate and to produce collagen through free radical production and activation of mitogen-activated protein kinase.

BACKGROUND: Nonalcoholic steatohepatitis is a clinicopathologic condition that may progress to liver fibrosis. Hyperglycemia is supposed to be one of the factors inducing hepatic fibrogenesis, but the mechanism has not been fully clarified. Oxidative stress is increasingly found in patients with diabetes/hyperglycemia in which conditions reactive oxygen species (ROS) are produced. METHODS: We performed experiments using hepatic stellate cells (HSCs) in culture in order to confirm the effect of high glucose concentrations on cell proliferation, type I collagen production, ROS production and activation of mitogen-activated protein (MAP) kinase pathway. RESULTS: High glucose stimulated cell growth of HSCs and up-regulated the levels of activated/phosphorylated extracellular signal-regulated kinase 1/2 and free radical production in HSCs. The MAP kinase phosphorylation and cell proliferation were suppressed by diphenylene iodonium chloride, an NADPH oxidase inhibitor, and by calphostin C, a protein kinase C (PKC)-specific inhibitor. Increased type I collagen mRNA and protein levels were also observed in HSCs at high glucose concentrations. CONCLUSIONS: Our findings indicate that high glucose concentrations may stimulate ROS production through PKC-dependent activation of NADPH oxidase, and induce MAP kinase phosphorylation subsequent to proliferation and type I collagen production by HSCs.