title: Inhibition of cytochrome P450 enzymes participating in p-nitrophenol hydroxylation by drugs known as CYP2E1 inhibitors.
abstract: p-Nitrophenol hydroxylation is widely used as a probe for microsomal CYP2E1. Several drugs are known as CYP2E1 inhibitors because of their capability to inhibit p-nitrophenol hydroxylation. Our results suggest further participation of CYP2A6 and CYP2C19 enzymes in p-nitrophenol hydroxylation. Moreover, CYP2A6 and CYP2C19 may be considered as the primary catalysts, whereas CYP2E1 can also contribute to the hydroxylation of p-nitrophenol. Further aim of our study was to evaluate the selectivity of p-nitrophenol hydroxylase inhibitors towards cytochrome P450 enzymes. The effects of antifungals: bifonazole, econazole, clotrimazole, ketoconazole, miconazole; CNS-active drugs: chlorpromazine, desipramine, fluphenazine, thioridazine; and the non-steroidal anti-inflammatory drug: diclofenac were investigated on the enzyme activities selective for CYP2A6, CYP2C9, CYP2C19, CYP2E1 and CYP3A4. None of the drugs could be considered as a potent inhibitor of CYP2E1. Strong inhibition was observed for CYP3A4 by antifungals with IC(50) values in submicromolar range. However, ketoconazole was the only imidazole derivative that could be considered as a selective inhibitor of CYP3A4. The CNS-active drugs investigated were found to be weak inhibitors of CYP2A6, CYP2C9, CYP2C19, CYP2E1 and CYP3A4. Diclofenac efficiently inhibited CYP2C9 and to a less extent CYP3A4 enzyme.
authors.affiliation: Department of Biochemical Pharmacology, Chemical Research Center, Hungarian Academy of Sciences, P.O. Box 17, Pusztaszeri út 59-67, H-1025 Budapest, Hungary. monostor@chemres.hu
authors.forename: Katalin
authors.initials: K
authors.lastname: Monostory
authors.forename: Eszter
authors.initials: E
authors.lastname: Hazai
authors.forename: László
authors.initials: L
authors.lastname: Vereczkey
mesh_terms: D000328:Adult; D000935:Antifungal Agents / Q000494:pharmacology; D014150:Antipsychotic Agents / Q000494:pharmacology; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism; D065691:Cytochrome P-450 CYP2E1 Inhibitors; D004008:Diclofenac / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D006900:Hydroxylation; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D008875:Middle Aged; D009596:Nitrophenols / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D000935:Antifungal Agents; D014150:Antipsychotic Agents; D065691:Cytochrome P-450 CYP2E1 Inhibitors; D004791:Enzyme Inhibitors; D009596:Nitrophenols; D004008:Diclofenac; D019392:Cytochrome P-450 CYP2E1; C024836:4-nitrophenol