Impact of manganese on primary hippocampal neurons from rodents

ABSTRACTManganese‐enhanced magnetic resonance imaging (MEMRI) is a powerful tool for in vivo tract tracing or functional imaging of the central nervous system. However Mn2+ may be toxic at high levels. In this study, we addressed the impact of Mn2+ on mouse hippocampal neurons (HN) and neuron‐like N2a cells in culture, using several approaches. Both HN and N2a cells not exposed to exogenous MnCl2 were shown by synchrotron X‐ray fluorescence to contain 5 mg/g Mn. Concentrations of Mn2+ leading to 50% lethality (LC50) after 24 h of incubation were much higher for N2a cells (863 mM) than for HN (90 mM). The distribution of Mn2+ in both cell types exposed to Mn2+ concentrations below LC50 was perinuclear whereas that in cells exposed to concentrations above LC50 was more diffuse, suggesting an overloading of cell storage/detoxification capacity. In addition, Mn2+ had a cell‐type and dose‐dependent impact on the total amount of intracellular P, Ca, Fe and Zn measured by synchrotron X‐ray fluorescence. For HN neurons, immunofluorescence studies revealed that concentrations of Mn2+ below LC50 shortened neuritic length and decreased mitochondria velocity after 24 h of incubation. Similar concentrations of Mn2+ also facilitated the opening of the mitochondrial permeability transition pore in isolated mitochondria from rat brains. The sensitivity of primary HN to Mn2+ demonstrated here supports their use as a relevant model to study Mn2+‐induced neurotoxicity. © 2014 Wiley Periodicals, Inc.