Abstract
Recently, a chimeric mouse line in which the liver could be replaced by more than 80% with human hepatocytes was established in Japan. Because the chimeric mouse produces human albumin (hAlb), replacement by human hepatocytes could be estimated by the hAlb concentration in the blood of chimeric mice. In this study, we investigated human major cytochrome P450 (P450) in the livers of chimeric mice by mRNA, protein, and enzyme activity using real-time polymerase chain reaction, Western blot analysis, and high-performance liquid chromatography, respectively. Chimeric mice with humanized liver generated using hepatocytes from a Japanese and white donor were used. Human P450 mRNAs were expressed in the liver of chimeric mice, and major human P450 proteins such as CYP1A2, CYP2C9, and CYP3A4 were detected. The expression of P450 mRNA and protein was correlated with the hAlb concentration in the blood. The enzyme activities such as diclofenac 4′-hydroxylase activity, dexamethasone 6-hydroxylase activity, and coumarin 7-hydroxylase activity, activities that are specific to human P450 but not to murine P450, were increased in a hAlb concentration-dependent manner. The chimeric mice with nearly 90% replacement by human hepatocytes demonstrated almost the same protein contents of human P450s and drug-metabolizing enzyme activity as those of the donor. It was confirmed that genomic DNA from the livers of the chimeric mice and that from the liver of the donor exhibited the same genotype. In conclusion, the chimeric mice exhibited a similarly efficient capacity of drug metabolism as humans, suggesting that they could be a useful animal model for drug development.
Footnotes
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This work was supported by a Research on Advanced Medical Technology, Health, and Labor Sciences Research grant from the Ministry of Health, Labor, and Welfare of Japan.
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doi:10.1124/dmd.104.001347.
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ABBREVIATIONS: P450, cytochrome P450; HLM, human liver microsomes; uPA, urokinase-type plasminogen activator; SCID, severe combined immunodeficient; hAlb, human albumin; RI, replacement index; PCR, polymerase chain reaction; COH, coumarin 7-hydroxylase activity; HPLC, high-performance liquid chromatography; PTXOH, paclitaxel 6α-hydroxylase activity; DICOH, diclofenac 4′-hydroxylase activity; MPOH, S-mephenytoin 4′-hydroxylase activity; DBOH, debrisoquine 4′-hydroxylase activity; DEXOH, dexamethasone 6-hydroxylase activity.
- Received July 4, 2004.
- Accepted September 14, 2004.
- The American Society for Pharmacology and Experimental Therapeutics
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