Astrocytes as modulators of mercury-induced neurotoxicity

The case for significant toxicity of methylmercury (MeHg) to the CNS is strongly supported by both in vivo and in vitro studies. MeHg perturbs a number of cellular processes which most certainly include astrocytic failure to maintain the composition of the extracellular fluid. Astrocytic predisposition to be damaged by MeHg offers a potential explanation for its neurotoxicity. Consistent with this concept is the ability of astrocytes to preferentially concentrate brain MeHg. The present commentary elaborates on the role of astrocytes in mediating MeHg-induced injuries, detailing their function in maintaining the extracellular concentrations of the excitatory amino acids glutamate and aspartate. It continues with a discussion on the effects of MeHg on astrocytic swelling and the ensuing regulatory volume decrease (RVD). Recent work demonstrating that primary astrocyte cultures constituitively express a cluster of sulfhydryl (-SH)-containing proteins, collectively referred to as metallothioneins (MTs), is also reviewed with particular reference to the role of MTs both as protectors and facilitators of MeHg intoxication.