Methylmercury genotoxicity: a novel effect in human cell lines of the central nervous system

Methylmercury is an important source of environmental contamination and the central nervous system (CNS) is one of the main target organs. Methylmercury genotoxicity was already demonstrated in peripherical tissues but was never detected in the brain. Thus, the objective of this work was to verify its genotoxic effect using brain cell lines. Glioblastoma (U373) and neuroblastoma (B103) human cell lines were exposed to methylmercury (0-10 microM). By measuring cellular viability, concentrations inducing <20% of cellular death (P<0.05) were selected: 1 and 0.1 microM. To detect micronuclei, 200,000 cells were treated with methylmercury for 24 h, and then incubated with cytochalasin B (2 microg/ml) for 72 h (U373) or 48 h (B103). The binucleation index, frequency of micronucleated cells, micronucleation index, metaphasic index and index of nucleoplasmic bridges were determined. Statistical analysis showed indices and percentages significantly higher (P<0.05) in methylmercury-treated cells. Each cell line was shown to be differently sensitive to each biomarker of genotoxic damage, which seems to indicate the existence of different mechanisms of toxicity. This work demonstrates, for the first time, MeHg ability to provoke genotoxicity in cells of brain origin with relatively low levels of exposure.