Genotoxic risk of ethyl-paraben could be related to telomere shortening.

The ability of parabens to promote the appearance of multiple cancer hallmarks in breast epithelium cells provides grounds for regulatory review of the implication of the presence of parabens in human breast tissue. It is well documented that telomere dysfunction plays a significant role in the initiation of genomic instability during carcinogenesis in human breast cancer. In the present study, we evaluated the genotoxic effect of ethyl 4-hydroxybenzoate (ethyl-paraben), with and without metabolic activation (S9), in studies following OECD guidelines. We observed a significant increase in genotoxic damage using the Mouse Lymphoma Assay and in vitro micronucleus (MN) tests in the L5178Y cell line in the presence of S9 only after a short exposure. A high frequency of MN was observed in the TK6 cells after a short exposure (3 h) in the presence of S9 and a long exposure (26 h) without S9. We found significant increases in the MN frequency and induced chromosomal aberrations in the lymphocytes of only one donor after ethyl-paraben exposure in the presence of S9 after a short exposure. Cytogenetic characterization of the paraben-treated cells demonstrated telomere shortening associated with telomere loss and telomere deletions in L5178Y and TK6 cells and lymphocytes of the paraben sensitive-donor. In a control cohort of 68 human lymphocytes, telomere length and telomere aberrations were age-dependent and showed high inter-individual variation. This study is the first to link telomere shortening and the genotoxic effect of ethyl paraben in the presence of S9 and raises the possibility that telomere shortening may be a proxy for underlying inter-individual sensitivity to ethyl-paraben. Copyright © 2016 John Wiley & Sons, Ltd.

Use of primary cultures of rat hepatocytes to predict toxicity in the early development of new chemical entities.

The new strategies for development of pharmacologically interesting compounds pose some limitations for standard toxicity assessment approaches due to: (1) increase in the number of compounds to be tested and (2) decrease in the amount of substance available for testing. In vitro methods are thus the only way to overcome such limitations. In this communication we present a cell-based model, using primary rat hepatocyte cultures, which we have validated using 23 compounds of the MEIC list as well as several Synthélabo proprietary products, covering a wide range of therapeutic indications. Our results show that our in vitro model gives a sufficient prediction for general toxicity by the oral route of administration (up to 2-4 weeks of treatment) in the rat to aid in decisions during early development. We also suggest that the comparative evaluation of the different parameters of cell toxicity examined may point to potential organ-related toxicity which could be further studied either with more complex in vitro or in vivo models. In conclusion, our results show that cell-based models for toxicity can be used for general screening purposes to predict in vivo toxicity in the early development of new chemical entities.