Pairs of forward and reverse primers and TaqMan probes specic to each human cytochrome P450 isoform were prepared. Analysis of the mRNA level of each CYP isoform in total RNA from pooled specimens of various human or gans was performed by realtime reverse transcription PCR using an ABI PRISM 7700 sequence detector system. The ex pression of CYP3A4 mRNA was similar to that of CYP3A7 mRNA in the fetal liver, and CYP3A4 mRNA levels in the fetal liver were about 0.1 times lower than in the adult liver. CYP2E1 showed the highest level of mRNA expression in the liver. The mRNA expression of 30 CYP isoforms (CYP1A1, 1A2, 1B1, 2A6, 2A7, 2B6, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, 2J2, 3A4, 3A5, 3A7, 4A11, 4F2, 4F3, 5A1, 7B1, 8A1, 8B1, 17, 26A1, 27, 27B1, 39A1, 46, and 51) in the liver was successfully detected by this method. CYP2F1, 4B1, 4F8, 11s (11A, 11B1, and 11B2), 19, and 24 mRNA levels were the highest in the lung, lung, prostate, adrenal gland, placenta, and kidney, respectively; however, the mRNA expression of these eight CYP isoforms in the liver was not detected by this method. The mRNA levels of the CYP isoforms deter mined in various human tissues were in good agreement with previously reported data. The method described here has the advantages of high specicity and excellent quantication over a wide range of mRNA concentrations, making it suitable for the evaluation of a large number of samples in the assessment of the expression prole of drugmetabolizing enzymes.
In the present study, the induction of drug-metabolizing enzymes and transporters was evaluated by analyzing mRNA expression in human hepatocytes after exposure to various compounds. The compounds tested included typical enzyme inducers, rifampicin and omeprazole, and controls. All experiments were performed in the presence of 0.1% DMSO. Analysis was performed by the real-time reverse-transcription polymerase chain reaction method (RT PCR) in the presence of TaqMan probes using an ABI PRISM 7700 Sequence Detector system. A new analytic method to quantify mRNA levels in small numbers of human hepatocytes has been developed for phase I enzymes, phase II enzymes, and transporters. The levels of CYP1A1, CYP2B6, CYP2C8, CYP3A4, CYP3A5, ADH3, and ABCG1 mRNA in human hepatocytes increased after exposure to rifampicin. The levels of CYP1A1, CYP2B6, CYP3A4, CYP3A5, and ABCG1 mRNA recovered after a change to media without rifampicin. The levels of CYP1A1, CYP1A2, CYP1B1, ALDH3, and ALDH6 mRNA increased after exposure to omeprazole, and recovered after a change to media without omeprazole. On the other hand, the levels of ADH3 and ABCB4 mRNA decreased after exposure to omeprazole, and recovered after a change to media without omeprazole. In conclusion, these results demonstrate the applicability of quantitative real-time RT PCR to the evaluation of the gene induction and recovery of drug-metabolizing enzymes and transporters after exposure to drugs in human hepatocytes.
The novel compound NO-1886, 4-[(diethoxyphosphoryl)methyl]-N-(4-bromo-2-cyanophenyl)-ben zamide, is a hypolipidemic agent, which appears to increase lipoprotein lipase activity in rats. Various analogs of NO-1886 were synthesized to study the structure-activity relationship of this hypolipidemic drug. A novel series of quinazolines and 4(3H)-quinazolinones were prepared by cyclization of NO-1886 derivatives. Derivatives bearing a 4-[(diethoxyphosphoryl)-methyl]phenyl] group at the 2-position were found to lower triglyceride and total cholesterol levels. In accord with the decrease in log P*, quinazolines and 4(3H)-quinazolinones showed good absorption and hypolipidemic activity. When the quinazolinone ring system is substituted at positions 6 and 7 with methoxy groups, increased hypolipidemic activity was observed. The highest hypolipidemic activity was observed when the 3-position was substituted by a methyl or benzyl group.
The hepatic mRNA expression of human drug-metabolizing enzymes and transporters in chimeric mise with almost-completely humanized liver (replacement index: 71-89%) was investigated. The mRNAs of 58 human phase I enzymes, 26 human phase II enzymes, 23 human transporters, and five mouse Cyps were measured in the chimeric mice with humanized liver generated using hepatocytes from a Japanese donor. The mRNA expression of 52 human phase I enzymes, which includes 20 human CYPs, 26 human phase II enzymes and 21 human transporters was ascertained in the chimeric mouse liver. Among them, the expression of the target mRNAs vital for liver function such as the metabolism and secretion of endogenous compounds appeared to be maintained. The central value for the expression ratio in all target genes in chimeric mouse liver to the donor liver was 0.46, which was lower than the substitution rate of chimeric mouse liver by donor liver. The ratio of mouse Cyp mRNA expression of chimeric mouse liver to that of control mouse liver was 0.19 or less, except for that of Cyp2b10. There were good correlations between the mRNA expression levels of human hepatic albumin gene, the values of the rate of replacement of mouse liver by human liver, and the human blood albumin concentration in the chimeric mice. The chimeric mice with humanized liver may be a useful tool for the evaluation of drug-drug interactions such as the inhibition and induction of drug-metabolizing enzymes and transporters.
We investigated and compared the expression of human CYPs mRNA in primary cultures of cryopreserved human hepatocytes and in chimeric mice constructed by transplanting hepatocytes from the same human donors. Analysis was performed by real-time reverse-transcription polymerase chain reaction. Initial expression levels for the 12 human CYPs mRNA in chimeric mouse hepatocytes were higher than those in human hepatocytes, but a low correlation coefficient was observed (r=0.690). After 24 h of culture, the correlation remained low (r=0.699). The medium was replaced with fresh medium without human epidermal growth factor, and after 48 h of culture, expression of the 12 human CYPs mRNA were very similar in human hepatocytes and chimeric mouse hepatocytes, and a higher correlation coefficient was observed (r=0.809). After 72 h of culture, the correlation remained high (r=0.873). The ratio of human CYP1A2 mRNA to beta-actin mRNA in chimeric mouse hepatocytes decreased quickly during the first 24 h of culture, and then remained constant. Expression profiles of human CYP1A2 mRNA in chimeric mouse hepatocytes were similar to those in human hepatocytes after exposure of beta-naphthoflavone. CYP3A4 mRNA expression was increased significantly by rifampicin (Rif) exposure in human hepatocytes, whereas Rif-induced increases in CYP3A4 mRNA expression in chimeric mouse hepatocytes was seen for two of the three donors. In conclusion, we demonstrated that expression and induction of human CYPs in human hepatocytes can be reproduced in chimeric mouse hepatocytes.
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