Knockout of cytochrome P450 3A yields new mouse models for understanding xenobiotic metabolism
Antonius E. van Herwaarden, … , Jos H. Beijnen, Alfred H. Schinkel
Antonius E. van Herwaarden, … , Jos H. Beijnen, Alfred H. Schinkel
Published November 1, 2007
Citation Information: J Clin Invest. 2007;117(11):3583-3592. https://doi.org/10.1172/JCI33435.
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Technical Advance

Knockout of cytochrome P450 3A yields new mouse models for understanding xenobiotic metabolism

Abstract

Cytochrome P450 3A (CYP3A) enzymes constitute an important detoxification system that contributes to primary metabolism of more than half of all prescribed medications. To investigate the physiological and pharmacological roles of CYP3A, we generated Cyp3a-knockout (Cyp3a–/–) mice lacking all functional Cyp3a genes. Cyp3a–/– mice were viable, fertile, and without marked physiological abnormalities. However, these mice exhibited severely impaired detoxification capacity when exposed to the chemotherapeutic agent docetaxel, displaying higher exposure levels in response to both oral and intravenous administration. These mice also demonstrated increased sensitivity to docetaxel toxicity, suggesting a primary role for Cyp3a in xenobiotic detoxification. To determine the relative importance of intestinal versus hepatic Cyp3a in first-pass metabolism, we generated transgenic Cyp3a–/– mice expressing human CYP3A4 in either the intestine or the liver. Expression of CYP3A4 in the intestine dramatically decreased absorption of docetaxel into the bloodstream, while hepatic expression aided systemic docetaxel clearance. These results suggest that CYP3A expression determines impairment of drug absorption and efficient systemic clearance in a tissue-specific manner. The genetic models used in this study provide powerful tools to further study CYP3A-mediated xenobiotic metabolism, as well as interactions between CYP3A and other detoxification systems.

Authors

Antonius E. van Herwaarden, Els Wagenaar, Cornelia M.M. van der Kruijssen, Robert A.B. van Waterschoot, Johan W. Smit, Ji-Ying Song, Martin A. van der Valk, Olaf van Tellingen, José W.A. van der Hoorn, Hilde Rosing, Jos H. Beijnen, Alfred H. Schinkel

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Figure 2

CYP3A4 expression in transgenic mice.

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CYP3A4 expression in transgenic mice. (A) Schematic structure of villin ...
(A) Schematic structure of villin promoter–driven expression cassette, containing human CYP3A4 cDNA. (B) Western blot analysis of crude membrane fractions of liver and intestine of wild-type and Cyp3a–/– mice and transgenic mice with human CYP3A4 expression in liver (3a–/–A) or intestine (3a–/–V), in a Cyp3a–/– background. Blots were probed with an antibody raised against human CYP3A4. Cyp3a expression was found in wild-type but not in Cyp3a–/– tissues. Expression of human CYP3A4 was seen in liver and kidney, but not intestine, of transgenic Cyp3a–/–A mice. Expression of human CYP3A4 was seen in intestine and kidney, but not liver, of transgenic Cyp3a–/–V mice. 3A4, CYP3A4 standard (0.05 pmol). 20 μg of liver or intestinal protein was loaded, except in the case of the liver sample of Cyp3a–/–A and intestinal samples of Cyp3a–/–V mice, which had 2 μg loaded. 30 μg of kidney protein was loaded.