Studies to further investigate the inhibition of human liver microsomal CYP2C8 by the acyl-beta-glucuronide of gemfibrozil.

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Jenkins SM, Zvyaga T, Johnson SR, Hurley J, Wagner A, Burrell R, Turley W, Leet JE, Philip T, Rodrigues AD

Studies to further investigate the inhibition of human liver microsomal CYP2C8 by the acyl-beta-glucuronide of gemfibrozil.

Drug Metab Dispos. 2011 Dec;39(12):2421-30. doi: 10.1124/dmd.111.041947. Epub 2011 Sep 12.

PubMed ID

21911547 [ View in PubMed

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Abstract

In previous studies, gemfibrozil acyl-beta-glucuronide, but not gemfibrozil, was found to be a mechanism-based inhibitor of cytochrome P450 2C8. To better understand whether this inhibition is specific for gemfibrozil acyl-beta-glucuronide or whether other glucuronide conjugates are potential substrates for inhibition of this enzyme, we evaluated several pharmaceutical compounds (as their acyl glucuronides) as direct-acting and metabolism-dependent inhibitors of CYP2C8 in human liver microsomes. Of 11 compounds that were evaluated as their acyl glucuronide conjugates, only gemfibrozil acyl-beta-glucuronide exhibited mechanism-based inhibition, indicating that CYP2C8 mechanism-based inhibition is very specific to certain glucuronide conjugates. Structural analogs of gemfibrozil were synthesized, and their glucuronide conjugates were prepared to further examine the mechanism of inhibition. When the aromatic methyl groups on the gemfibrozil moiety were substituted with trifluoromethyls, the resulting glucuronide conjugate was a weaker inhibitor of CYP2C8 and mechanism-based inhibition was abolished. However, the glucuronide conjugates of monomethyl gemfibrozil analogs were mechanism-based inhibitors of CYP2C8, although not as potent as gemfibrozil acyl-beta-glucuronide itself. The ortho-monomethyl analog was a more potent inhibitor than the meta-monomethyl analog, indicating that CYP2C8 favors the ortho position for oxidation and potential inhibition. Molecular modeling of gemfibrozil acyl-beta-glucuronide in the CYP2C8 active site is consistent with the ortho-methyl position being the favored site of covalent attachment to the heme. Moreover, hydrogen bonding to four residues (Ser100, Ser103, Gln214, and Asn217) is implicated.

DrugBank Data that Cites this Article

Drug Enzymes

Drug	Enzyme	Kind	Organism	Pharmacological Action	Actions
Mefenamic acid	Cytochrome P450 2C8	Protein	Humans	Unknown	Inhibitor	Details