Caenorhabditis elegans as a predictive model for methylmercury-induced neurotoxicity

Abstract

Several targets and detoxifying components of methylmercury (MeHg) toxicity, including glutathione (GSH), metallothioneins (MTs), and heat shock proteins (HSPs), have been identified to date. In our most recent studies, we have used the model organism, Caenorhabditis elegans, to examine many of the unknown molecular mechanisms of MeHg neurotoxicity. While MeHg accumulated within C. Elegans was shown to cause a delay in development as well as a decreased pharyngeal pumping rate, many endpoints, including nervous system morphology, were unaffected. These findings led to the hypothesis that C. Elegans has unique mechanisms for protecting its nervous system from MeHg neurotoxicity. Therefore, we examined the involvement of GSH, MTs, and HSPs in MeHg toxicity in C. Elegans. We found that GSH levels were altered upon MeHg exposure, a glutathione s-transferase was highly upregulated upon exposure, and the lack of MTs resulted in increased sensitivity to the toxicant. We also demonstrated that MeHg induces hormesis in C. Elegans, which is most likely due, at least in part, to the involvement of glutathione transferases in MeHg toxicity. The molecular mechanisms of MeHg neuroprotection in C. Elegans, which we identify in this review, may prove valuable in developing effective strategies to protect human health.