title: Differential inhibition of cytochromes P450 3A4 and 3A5 by the newly synthesized coumarin derivatives 7-coumarin propargyl ether and 7-(4-trifluoromethyl)coumarin propargyl ether.
abstract: The abilities of 7-coumarin propargyl ether (CPE) and 7-(4-trifluoromethyl)coumarin propargyl ether (TFCPE) to act as mechanism-based inactivators of P450 3A4 and 3A5 in the reconstituted system have been investigated using 7-benzyloxy-4-(trifluoromethyl)coumarin (BFC) and testosterone as probes. CPE inhibited the BFC O-debenzylation activity of P450 3A4 in a time-, concentration-, and NADPH-dependent manner characteristic of a mechanism-based inactivator with a half-maximal inactivation (K(I)) of 112 microM, a maximal rate of inactivation (k(inact)) of 0.05 min(-1), and a t(1/2) of 13.9 min. Similarly, TFCPE inhibited the BFC O-debenzylation activity of P450 3A4 in a time-, concentration-, and NADPH-dependent manner with a K(I) of 14 microM, a k(inact) of 0.04 min(-1), and a t(1/2) of 16.5 min. Parallel losses of P450 3A4 enzymatic activity and heme were observed with both compounds as measured by high-performance liquid chromatography and reduced CO spectra. Interestingly, neither compound inhibited the BFC O-debenzylation activity of P450 3A5. Reactive intermediates of CPE and TFCPE formed by P450 3A4 were trapped with glutathione, and the resulting adducts were identified using tandem mass spectral analysis. Metabolism studies using TFCPE resulted in the identification of a single metabolite that is formed by P450 3A4 but not by P450 3A5 and that may play a role in the mechanism-based inactivation.
authors.affiliation: Department of Pharmacology, The University of Michigan, 1150 West Medical Center Dr., Ann Arbor, MI 48109-5632, USA.
authors.forename: Chitra
authors.initials: C
authors.lastname: Sridar
authors.forename: Ute M
authors.initials: UM
authors.lastname: Kent
authors.forename: Kate
authors.initials: K
authors.lastname: Noon
authors.forename: Alecia
authors.initials: A
authors.lastname: McCall
authors.forename: Bill
authors.initials: B
authors.lastname: Alworth
authors.forename: Maryam
authors.initials: M
authors.lastname: Foroozesh
authors.forename: Paul F
authors.initials: PF
authors.lastname: Hollenberg
mesh_terms: D000480:Alkynes / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D003374:Coumarins / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D065692:Cytochrome P-450 CYP3A Inhibitors; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology; D004987:Ethers / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism
chemical_list: D000480:Alkynes; D003374:Coumarins; D065692:Cytochrome P-450 CYP3A Inhibitors; D004791:Enzyme Inhibitors; D004987:Ethers; D007093:Imidazoles; C517283:coumarin 7; C531209:propargyl ether; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human