title: Inhibition of carcinogen-bioactivating cytochrome P450 1 isoforms by amiloride derivatives.
abstract: We examined the effects of amiloride derivatives, especially 5-(N-ethyl-N-isopropyl)amiloride (EIPA), on the activity of cytochrome P450 (CYP) 1 isoforms, known to metabolize carcinogenic polycyclic aromatic hydrocarbons (PAHs), such as benzo(a)pyrene (BP), into mutagenic metabolites and whose cellular expression can be induced through interaction of PAHs with the arylhydrocarbon receptor. EIPA was found to cause a potent and dose-dependent inhibition of CYP1-related ethoxyresorufine O-deethylase (EROD) activity in both liver cells and microsomes. It also markedly reduced activity of human recombinant CYP1A1 enzyme through a competitive mechanism; activities of other human CYP1 isoforms, i.e. CYP1A2 and CYP1B1, were also decreased. However, EIPA did not affect BP-mediated induction of CYP1A1 mRNA and protein levels in rat liver cells, likely indicating that EIPA does not block activation of the arylhydrocarbon receptor by PAHs. Inhibition of CYP1 activity by EIPA was associated with a decreased metabolism of BP, a reduced formation of BP-derived DNA adducts and a diminished BP-induced apoptosis in liver cells. The present data suggest that amiloride derivatives, such as EIPA, may be useful for preventing toxicity of chemical carcinogens, such as PAHs, through inhibition of CYP1 enzyme activity.
authors.affiliation: INSERM U456, Détoxication et Réparation Tissulaire, Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes I, 2 avenue du Prof Léon Bernard, 35043 Rennes cédex, France. lydie.sparfel@rennes.inserm.fr
authors.forename: Lydie
authors.initials: L
authors.lastname: Sparfel
authors.forename: Laurence
authors.initials: L
authors.lastname: Huc
authors.forename: Marc
authors.initials: M
authors.lastname: Le Vee
authors.forename: Mireille
authors.initials: M
authors.lastname: Desille
authors.forename: Dominique
authors.initials: D
authors.lastname: Lagadic-Gossmann
authors.forename: Olivier
authors.initials: O
authors.lastname: Fardel
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors / Q000378:metabolism; D001564:Benzo(a)pyrene / Q000494:pharmacology*; D019363:Cytochrome P-450 CYP1A1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D065633:Cytochrome P-450 CYP1B1; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D004791:Enzyme Inhibitors; D007527:Isoenzymes; D001564:Benzo(a)pyrene; D000584:Amiloride; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; C585499:Cyp1b1 protein, rat; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1; C039614:ethylisopropylamiloride