Inhibition of DNA adduct formation and mutagenic action of 3-amino-1-methyl-5H-pyrido[4,3-b]indole by chlorophyllin-chitosan in rpsL transgenic mice

We have studied the inhibitory effect of chlorophyllin-chitosan (Chi-Chi) c omplex. an insoluble form of chlorophyllin, on the DNA adduct formation and mutagenesis by a heterocyclic food mutagen-carcinogen, 3-amino-1-methyl-5H -pyrido[4,3-b]indole (Trp-P-2), in mice carrying the E. coli rpsL gene as a mutagenesis reporter. Upon administration of a diet containing 0.002% or 0 .01% Trp-P-2, DNA adducts were formed in various tissues in a dose-dependen t manner, with the maximum level observed in the liver. Addition of 3% Chi- Chi to the diet reduced the Trp-P-2 adduct by up to 90%. The rpsL mutant fr equencies increased significantly in both the liver and spleen upon adminis tration of a 0.01% Trp-P-2 diet. Addition of Chl-Chi to the diet decreased these induced mutant frequencies to the background level. No harmful effect of Chi-Chi was detected during these experiments. The results show that Ch i-Chi may be a candidate chemopreventive agent against the genotoxic action of Trp-P-2, and possibly also other aromatic carcinogens in the diet.