Mechanisms of Genotoxicity of the Phytoestrogens Genistein and Daidzein

DI VIRGILIO A.L.; BOLT H.M

Congreso; 41 Congreso de la Sociedad Europea de Toxicología; 2003

Hormonally active chemicals in the human diet, such as man-made estrogenic chemicals or plant-derived compounds (phytoestrogens), have become a matter of public concern. A significant part of human exposure to phytoestrogens is attributable to soy isoflavones. Besides their estrogenic properties, soy isoflavones also exert genotoxic actions. In this study, the micronucleus (MN) assay in V79 cells was used to study chromosomal genotoxicity. Genistein caused a clear dose-related induction of MN within the range of 5–25
M; MN rates were declining at higher genistein concentrations. This was probably due to cytotoxicity of genistein since reduced neutral red uptake and MTT formation with an IC50 of about 75
M occurred. Daidzein induced a comparatively shallow increase in the number of MN between 25 and 100
M. Additional staining with anti-kinetochore (CREST) antibodies served to determine if the micronuclei contain whole chromosomes or acentric fragments. Genistein induced mostly CREST(−) micronuclei, i.e. MN with chromosomal fragments, thus indicative of a clastogenic mode of action. MN induced by high concentrations of daidzein were partly CREST(+) and CREST(−). These results point to a differential genotoxicity of phytoestrogens.