Involvement of cytochrome P450 1A in sanguinarine detoxication.
Sanguinarine (SA), a member of the benzo[c]phenanthridine alkaloids, is a potent anti-microbial agent with anti-inflammatory and anti-neoplastic properties. However, toxicity of the alkaloid severely limits its medical applications. Recent report by Williams et al. implicated rat hepatic cytochrome P450 (CYP) 1A2 as a likely modulator of SA toxicity. Indeed, the in vitro toxicity of SA in primary culture of rat hepatocytes and human hepatic cell line HepG2, demonstrated as lactate dehydrogenase leakage and metabolic capability (MTT assay), was diminished following induction of CYP1A by 2,3,7,8-tetrachlorodibenzo-p-dioxin, 3-methylcholanthrene, and beta-naphtoflavone. Using microsomes containing recombinant CYP1A1 or CYP1A2 we show that SA causes non-competitive inhibition of the former and competitive inhibition of the latter as assessed by ethoxyresorufin de-ethylation (EROD). In human hepatic microsomes SA exhibits competitive inhibition of EROD activity with apparent K(i) of 2 microM, a value identical to that observed for CYP1A2 inhibition in recombinant system. Pre-incubation of SA with human liver microsomes resulted in time-dependent, but not dose-dependent decline in EROD activity suggesting CYP1A2 inhibition is not mechanism based. SA also inhibits activity of NADPH:CYP reductase, an enzyme required for CYP activity, with IC(50) very similar to that observed for EROD inhibition. Tentative mechanism for CYP1A involvement in decreased in vitro SA toxicity is discussed.
Vrba
Jirí
J
Institute of Medical Chemistry and Biochemistry, Faculty of Medicine, Palacký University, Hnevotínská 3, 77515 Olomouc, Czech Republic.
Kosina
Pavel
P
Ulrichová
Jitka
J
Modrianský
Martin
M
D000470:Alkaloids / Q000493:pharmacokinetics*; D000818:Animals; D000935:Antifungal Agents / Q000493:pharmacokinetics*; D053119:Benzophenanthridines; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019363:Cytochrome P-450 CYP1A1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism*; D065609:Cytochrome P-450 CYP1A2 Inhibitors; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics*; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D008658:Inactivation, Metabolic; D020128:Inhibitory Concentration 50; D007546:Isoquinolines; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D009251:NADPH-Ferrihemoprotein Reductase / Q000037:antagonists & inhibitors; D051381:Rats
D000470:Alkaloids; D000935:Antifungal Agents; D053119:Benzophenanthridines; D065609:Cytochrome P-450 CYP1A2 Inhibitors; D004791:Enzyme Inhibitors; D007546:Isoquinolines; C005705:sanguinarine; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D009251:NADPH-Ferrihemoprotein Reductase