The role of dopamine transporter in selective toxicity of manganese and rotenone

The dopamine transporter has been shown to be the most relevant target site for the specificity of 1-methyl-4-phenylpyridinium ion (MPP+), a neurotoxin for dopaminergic neurons. In contrast, the mechanisms underlying the selective toxicity of manganese and rotenone, potentially toxic agents implicated in dopaminergic neuronal cell death, remain unknown. The aim of this study was to determine the cellular mechanisms of manganese or rotenone uptake in dopaminergic cells via the dopamine transporter. PC12 cells overexpressing the dopamine transporter, which were exposed to 10 μM MPP+, showed extensive DNA fragmentation, a biochemical hallmark of apoptosis, whereas wild-type PC12 cells or vector-transfected PC12 cells, which were exposed to 5 mM MPP+, did not show DNA fragmentation. In contrast, manganese and rotenone induced DNA fragmentation at slightly lower concentrations in PC12 cells overexpressing the dopamine transporter compared to control cells. Dopamine transporter inhibitors, such as mazindol, nomifensine, or GBR12909, inhibited MPP+-induced DNA fragmentation but did not affect manganese- and rotenone-induced DNA fragmentation in PC12 cells overexpressing the dopamine transporter. Finally, manganese accumulated to similar levels in PC12 cells overexpressing the dopamine transporter and control PC12 cells following incubation with manganese chloride. These results suggested that the dopamine transporter dose not confer cytotoxicity to manganese and rotenone.