The effects of gypenosides on the inhibition of N-
acetyltransferase (
NAT) activity, AF-
DNA adduct formation and
NAT gene expression in a human
cervix cancer cell line (Ca Ski) were studied. Various concentrations of gypenosides were added to the cytosols or individually to the culture medium of human
cervix cancer cells. The
NAT activity was determined by high performance liquid chromatography, assaying for the amounts of acetylated
2-aminofluorene (AAF) and non-acetylated
2-aminofluorene (AF). The
NAT activity in the human cervix intact
cancer cells and cytosols was suppressed by gypenosides in a dose-dependent manner. The results also demonstrated that gene expression (NAT1
mRNA) in human
cervix cancer cells was decreased by gypenosides in a dose-dependent manner. The apparent values of Km and Vmax of
NAT of human
cervix cancer cells were also decreased by gypenosides in cytosols. Gypenosides may act as noncompetitive inhibitors. After the incubation of human
cervix cancer cells with 30 or 60 microM AF and with or without 350 micrograms/ml gypenosides co-treatment, the cells were recovered,
DNA was prepared and hydrolyzed to
nucleotides; adducted
nucleotides were extracted in
butanol and AF-
DNA adducts were analyzed by HPLC. The results demonstrated that gypenosides decreased the levels of AF-
DNA adduct formation in these cells. The
NAT PCR and
cDNA microarray also demonstrated that gypenosides inhibited
NAT mRNA expression in human
cervix cancer cells.