Determining the oxidation states of manganese in PC12 and nerve growth factor-induced PC12 cells

Abstract

Excessive brain Mn can produce toxicity with symptoms resembling parkinsonism. This syndrome, called “manganism,” correlates with loss of dopamine in the striatum and cell death in the striatum and globus pallidus. A common hypothesis is that cell damage in Mn toxicity is caused by oxidation of important cell components by Mn 3+. Determination of the amount of Mn 3+ present, under a range of conditions, in neuronal cells and brain mitochondria represents an important step in evaluating the “damage through oxidation by Mn 3+ hypothesis.” In an earlier paper we used X-ray absorption near-edge structure (XANES) spectroscopy to determine the amount of Mn 2+ and Mn 3+ in brain mitochondria under a range of conditions. Here we extend the study to investigate the evidence for formation of Mn 3+ through oxidation of Mn 2+ by ROS in PC12 cells and in PC12 cells induced with nerve growth factor (NGF) to display a phenotype more like that of neurons. Although the results suggest that very small amounts of Mn 3+ might be present at low Mn levels, probably in Mn superoxide dismutase, Mn 3+ is not stabilized by complex formation in these cells and therefore does not accumulate to detectable amounts.