title: Role of cytochromes P450 and peroxidases in metabolism of the anticancer drug ellipticine: additional evidence of their contribution to ellipticine activation in rat liver, lung and kidney.
abstract: OBJECTIVE
  Ellipticine is a potent antineoplastic agent exhibiting multiple mechanisms of action. This anticancer agent should be considered a pro-drug, whose pharmacological efficiency and/or genotoxic side effects are dependent on its cytochrome P450 (CYP)- and/or peroxidase-mediated activation to species forming covalent DNA adducts. The target of this study was to investigate a role of CYP and peroxidase enzymes in ellipticine oxidative activation in rats, a suitable model mimicking the fate of ellipticine in humans, in details. The contribution of pulmonary and renal CYP- and peroxidase enzymes to ellipticine metabolic activation is investigated and compared with that found in the liver.
  
  
  METHODS
  Ellipticine oxidation and DNA adduct formation in vitro were investigated using microsomes isolated from liver, lung and kidney of rats, either control (untreated) or treated i.p. with a single dose of 40 mg of ellipticine per kg of body weight. HPLC with UV detection was employed for the separation and characterization of ellipticine metabolites. Inhibitors of CYPs and cyclooxygenase (prostaglandin H synthase, COX) were used to characterize the enzymes participating in ellipticine oxidative activation in rat liver, lung and kidney. Ellipticine-derived DNA adducts were detected by 32P-postlabeling.
  
  
  RESULTS
  Using α-naphthoflavone, furafylline and ketoconazole, inhibitors of CYP1A, 1A2 and 3A, respectively, we found that the CYP1A and 3A enzymes play a major role in ellipticine activation to species forming DNA adducts in liver microsomes. Because of lower expression of these enzymes in lungs and kidneys, even after their induction by ellipticine, they play a minor role in ellipticine activation in these extrahepatic tissues. Arachidonic acid, a cofactor of COX, increased ellipticine activation in the microsomes of extrahepatic tissues. In addition, indomethacin, an inhibitor of COX, efficiently inhibited formation of ellipticine-derived DNA adduct in these microsomes. Based on these results, we attribute the higher activation of ellipticine in lung and kidney microsomes to COX than to CYP enzymes.
  
  
  CONCLUSIONS
  The results demonstrate that whereas CYP enzymes of 1A and 3A subfamilies are the major enzymes activating ellipticine in rat livers, peroxidase COX plays a significant role in this process in lungs and kidneys.
authors.affiliation: Department of Biochemistry, Faculty of Science, Charles University, Prague, Czech Republic. stiborov@natur.cuni.cz
authors.forename: Marie
authors.initials: M
authors.lastname: Stiborova
authors.forename: Michaela
authors.initials: M
authors.lastname: Moserova
authors.forename: Barbora
authors.initials: B
authors.lastname: Mrazova
authors.forename: Vera
authors.initials: V
authors.lastname: Kotrbova
authors.forename: Eva
authors.initials: E
authors.lastname: Frei
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism*; D001711:Biotransformation / Q000187:drug effects; D003577:Cytochrome P-450 Enzyme System / Q000502:physiology*; D018736:DNA Adducts / Q000187:drug effects; D004611:Ellipticines / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008168:Lung / Q000378:metabolism*; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D023421:Models, Animal; D010084:Oxidation-Reduction / Q000187:drug effects; D010544:Peroxidases / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000970:Antineoplastic Agents; D018736:DNA Adducts; D004611:Ellipticines; C034192:ellipticine; D003577:Cytochrome P-450 Enzyme System; D010544:Peroxidases