Genotoxic potential of montmorillonite clay mineral and alteration in the expression of genes involved in toxicity mechanisms in the human hepatoma cell line HepG2

Montmorillonite, also known as Cloisite (R) Na+ (CNa+), is a natural clay with a wide range of well-documented and novel applications, such as pharmaceutical products or food packaging. Although considered a low toxic product, the expected increased exposure to CNa+ arises concern on the potential consequences on human and environmental health especially as its genotoxicity has scarcely been investigated so far. Thus, we investigated, for the first time, the influence of non-cytotoxic concentrations of CNa+ (15.65, 31.25 and 62.5 mu g/mL) on genomic instability of human hepatoma cell line (HepG2) by determining the formation of micronuclei (MNi), nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) with the Cytokinesis block micronucleus cytome assay. Further on we studied the influence of CNa+ on the expression of several genes involved in toxicity mechanisms using the real-time quantitative PCR. The results showed that CNa+ increased the number of MNi, while the numbers of NBUDs and NPBs were not affected. In addition it deregulated genes in all the groups studied, mainly after longer time of exposure. These findings provide the evidence that CNa+ is potentially genotoxic. Therefore further studies that will elucidate the molecular mechanisms involved in toxic activity of CNa+ are needed for hazard identification and human safety assessment. (C) 2015 Elsevier B.V. All rights reserved.