title: Cocaine N-demethylation and the metabolism-related hepatotoxicity can be prevented by cytochrome P450 3A inhibitors.
abstract: Cocaine is eliminated and detoxified principally through the metabolism of nonspecific plasma and tissue esterases. Microsomal oxidative metabolism is of importance in cocaine N-demethylation, this being a principal pathway of cocaine bioactivation and hepatotoxicity. The contribution of different cytochrome P450 (CYP) enzymes to cocaine N-demethylase activity was studied in vitro with DBA/2 mouse and human liver microsomes, and cocaine hepatotoxicity was examined in vivo in DBA/2 male mice. Species dependent enzyme kinetics was observed. Cocaine N-demethylase displayed two Km values in murine liver (40-60 microM and 2-3 mM), whereas only one Km value was observed in human liver microsomes (2.3-2.7 mM). We suggest that CYP3A plays a prominent role in the N-demethylation of cocaine for the following reasons: (i) pregnenolone-16 alpha-carbonitrile, an inducer of CYP3As increases cocaine N-demethylase in parallel with testosterone 6 beta-hydroxylase activity and immunoreactive 3A protein in mouse liver; (ii) human and mouse cocaine N-demethylase and testosterone 6 beta-hydroxylase activities can be inhibited by triacetyloleandomycin, cannabidiol, or gestodene, all selective inhibitors of CYP3A P450s; (iii) antibodies directed against P450s within subfamilies 1A, 2A, 2B, 2C, or 2E inhibited cocaine N-demethylase activity only marginally, and finally, (iv) treatment of mice with triacetyloleandomycin or cannabidiol in vivo significantly attenuated the cocaine-elicited hepatotoxicity as assessed by the serum alanine aminotransferase activity and liver histology in parallel with decreased cocaine N-demethylase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology and Toxicology, University of Kuopio, Finland.
authors.forename: P
authors.initials: P
authors.lastname: Pellinen
authors.forename: P
authors.initials: P
authors.lastname: Honkakoski
authors.forename: F
authors.initials: F
authors.lastname: Stenbäck
authors.forename: M
authors.initials: M
authors.lastname: Niemitz
authors.forename: E
authors.initials: E
authors.lastname: Alhava
authors.forename: O
authors.initials: O
authors.lastname: Pelkonen
authors.forename: M A
authors.initials: MA
authors.lastname: Lang
authors.forename: M
authors.initials: M
authors.lastname: Pasanen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D001711:Biotransformation / Q000187:drug effects / Q000502:physiology; D002185:Cannabidiol / Q000494:pharmacology; D003042:Cocaine / Q000378:metabolism* / Q000633:toxicity*; D019392:Cytochrome P-450 CYP2E1; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000502:physiology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000502:physiology; D007700:Kinetics; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D008862:Microsomes, Liver / Q000201:enzymology; D008875:Middle Aged; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors* / Q000502:physiology; D010089:Oxidoreductases, N-Demethylating / Q000378:metabolism; D013045:Species Specificity; D014217:Troleandomycin / Q000494:pharmacology
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D007527:Isoenzymes; D002185:Cannabidiol; D003577:Cytochrome P-450 Enzyme System; D014217:Troleandomycin; D006899:Mixed Function Oxygenases; D019392:Cytochrome P-450 CYP2E1; D010089:Oxidoreductases, N-Demethylating; C054553:cocaine N-demethylase; D003042:Cocaine