title: Identification of cytochrome P450 enzymes involved in the metabolism of the designer drugs N-(1-phenylcyclohexyl)-3-ethoxypropanamine and N-(1-phenylcyclohexyl)-3-methoxypropanamine.
abstract: The involvement of human hepatic cytochrome P450 isoenzymes (P450s) in the metabolism of the designer drugs N-(1-phenylcyclohexyl)-3-ethoxypropanamine (PCEPA) and N-(1-phenylcyclohexyl)-3-methoxypropanamine (PCMPA) to the common metabolite N-(1-phenylcyclohexyl)-3-hydroxypropanamine (PCHPA) was studied using insect cell microsomes with cDNA-expressed human P450s and human liver microsomes (HLMs). Incubation samples were analyzed by gas chromatography-mass spectrometry or liquid chromatography-mass spectrometry. Among the tested isoenzymes, P450 2B6, P450 2C19, P450 2D6, and P450 3A4 catalyzed PCEPA O-deethylation, and P450 2B6, P450 2C19, and P450 2D6 catalyzed PCMPA O-demethylation. According to the relative activity factor approach, these enzymes accounted for 22, 3, 30, and 45% of the net clearance for PCEPA and 51, 8, and 40% of the net clearance for PCMPA, respectively. At 1 microM PCEPA, the chemical inhibitors 4-(4-chlorobenzyl)pyridine for P450 2B6 and quinidine for P450 2D6 reduced metabolite formation in pooled HLMs by 37 and 73%, respectively, and at 10 microM PCEPA, they reduced metabolite formation by 57 and 26%, respectively. At 1 microM PCMPA, 4-(4-chlorobenzyl)pyridine and quinidine reduced metabolite formation in pooled HLMs by 25 and 39%, respectively, and at 10 microM PCMPA, they reduced metabolite formation by 62 and 27%, respectively. The experiments with the MAB inhibitory to P450 3A4 and the chemical inhibitor ketoconazole for P450 3A4 showed no inhibitory effect concerning PCEPA O-dealkylation. Experiments with HLMs from P450 2D6 poor metabolizers showed a reduction of metabolite formation as compared to pooled HLM of 73 and 25% (1 microM and 10 microM PCEPA) and 40 and 38% (1 microM and 10 microM PCMPA), respectively. In conclusion, the main metabolic step was catalyzed by different P450s.
authors.affiliation: Department of Experimental and Clinical Toxicology, Institute of Experimental and Clinical Pharmacology and Toxicology, Saarland University, D-66421 Homburg, Saar, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Sauer
authors.forename: Frank T
authors.initials: FT
authors.lastname: Peters
authors.forename: Andrea E
authors.initials: AE
authors.lastname: Schwaninger
authors.forename: Markus R
authors.initials: MR
authors.lastname: Meyer
authors.forename: Hans H
authors.initials: HH
authors.lastname: Maurer
mesh_terms: D003514:Cyclohexylamines / Q000737:chemistry / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D015195:Drug Design; D004353:Drug Evaluation, Preclinical; D006801:Humans; D007700:Kinetics; D013058:Mass Spectrometry; D008862:Microsomes, Liver / Q000201:enzymology
chemical_list: D003514:Cyclohexylamines; C522231:N-(1-phenylcyclohexyl)-3-ethoxypropanamine; D003577:Cytochrome P-450 Enzyme System