期刊
DRUG METABOLISM AND DISPOSITION
卷 36, 期 3, 页码 490-499出版社
AMER SOC PHARMACOLOGY EXPERIMENTAL THERAPEUTICS
DOI: 10.1124/dmd.107.016501
关键词
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资金
- NIDDK NIH HHS [P30DK26743, P30 DK026743, R01 DK026506, DK26506, R56 DK026506, R01 DK026506-27] Funding Source: Medline
- NIGMS NIH HHS [R01 GM058883, GM44037, R01 GM044037-16A1, R01 GM044037, GM58883] Funding Source: Medline
Carbamazepine (CBZ) is a widely prescribed anticonvulsant whose use is often associated with idiosyncratic hypersensitivity. Sera of CBZ-hypersensitive patients often contain anti-CYP3A antibodies, including those to a CYP3A23 K-helix peptide that is also modified during peroxidative CYP3A4 heme-fragmentation. We explored the possibility that cytochromes P450 (P450s) such as CYP3A4 bioactivate CBZ to reactive metabolite(s) that irreversibly modify the P450 protein. Such CBZ-P450 adducts, if stable in vivo, could engender corresponding serum P450 autoantibodies. Incubation with CBZ not only failed to inactivate functionally reconstituted, purified recombinant CYP3A4 or CYP3A4 Supersomes in a time-dependent manner, but the inclusion of CBZ (0-1 mM) also afforded a concentration-dependent protection to CYP3A4 from inactivation by NADPH-induced oxidative uncoupling. Incubation of CYP3A4 Supersomes with H-3-CBZ resulted in its irreversible binding to CYP3A4 protein with a stoichiometry of 1.58 +/- 0.15 pmol H-3-CBZ bound/pmol CYP3A4. Inclusion of glutathione (1.5 mM) in the incubation reduced this level to 1.09. Similar binding (1.0 +/- 0.4 pmol H-3-CBZ bound/pmol CYP3A4) was observed after H-3-CBZ incubation with functionally reconstituted, purified recombinant CYP3A4(His)(6). The CBZ-modified CYP3A4 retained its functional activity albeit at a reduced level, but its testosterone 6 beta-hydroxylase kinetics were altered from sigmoidal (a characteristic profile of substrate cooperativity) to near-hyperbolic (Michaelis-Menten) type, suggesting that CBZ may have modified CYP3A4 within its active site.
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