Quaternary benzo[c]phenanthridine alkaloids (QBA) sanguinarine and chelerythrine exhibit a wide spectrum of biological activities whence they are used in dental care products. Recent studies indicated that cytochrome P450 CYP1A attenuates sanguinarine toxicity both in vivo [Williams, M.K., Dalvi, S., Dalvi, R.R., 2000. Influence of 3-methylcholanthrene pretreatment on sanguinarine toxicity in mice. Vet. Hum. Toxicol. 42, 196-198] and in vitro [Vrba, J., Kosina, P., Ulrichová, J., Modrianský, M., 2004. Involvement of cytochrome P450 1A in sanguinarine detoxication. Toxicol. Lett. 151, 375-387]. However, CYP1A converts sanguinarine to the products that form DNA adducts [Stiborová, M., Simánek, V., Frei, E., Hobza, P., Ulrichová, J., 2002. DNA adduct formation from quaternary benzo[c]phenanthridine alkaloids sanguinarine and chelerythrine as revealed by the 32P-postlabeling technique. Chem. Biol. Interact. 140, 231-242]. In our work we examined the effects of sanguinarine and chelerythrine on CYP1A1 expression and catalytic activity in human hepatoma cells-HepG2. Sanguinarine and chelerythrine did not affect basal and dioxin-inducible expression of CYP1A1 mRNA and protein in HepG2 cells. The enzymatic activity of CYP1A1 was assessed by the fluorescent measurement of 7-ethyxoresorufin-O-deethylase (EROD) activity. We observed a slight decrease of dioxin-induced EROD activity in HepG2 cells by sanguinarine and chelerythrine. This decrease was attributed to the inhibition of CYP1A1 catalytic activity, as revealed by enzyme kinetic studies on recombinant CYP1A1 protein. The IC50 values for the inhibition of CYP1A1 by sanguinarine and chelerythrine were 2.1 and 1.9muM, respectively. In conclusion, albeit the CYP1A modulates QBA cytotoxicity and genotoxicity, the QBA themselves do not affect CYP1A1 expression. The data indicate that studied alkaloids do not have specific cellular target and their biological effects are rather pleiotropic.

Institute of Medical Chemistry and Biochemistry Faculty of Medicine Palacký University Hnevotínská 3 775 15 Olomouc Czech Republic