Astroglia as metal depots: molecular mechanisms for metal accumulation, storage and release

The brain is an organ that concentrates metals, and these metals are often localized to astroglia. An examination of metal physiology of brain cells, particularly astroglia, offers insights into the developmental neurotoxicity of certain metals, including lead (Pb), mercury (Hg), manganese (Mn), and copper (Cu). Xenobiotic metals probably accumulate in cells by exploiting the normal functions of proteins that transport and handle essential metals. In addition, essential metals may become toxic by accumulating at levels that exceed the normal metal buffering capacity of the cell. This review considers the uptake, accumulation, storage, and release of two xenobiotic metals, Pb and Hg, as well as two essential nutrient metals that are neurotoxic in high amounts, Mn and Cu. Evidence that each metal accumulates in astroglia is evaluated, together with the mechanisms the host cell may invoke to protect itself from cytoxicity.