J Neurochem. 2018 Oct 31. doi: 10.1111/jnc.14621. [Epub ahead of...

J Neurochem. 2018 Oct 31. doi: 10.1111/jnc.14621. [Epub ahead of print]
Iron-induced energy supply deficiency and mitochondrial fragmentation in neurons.

Huang XT¹, Liu X¹, Ye CY¹, Tao LX¹, Zhou H¹, Zhang HY^1,2.
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Abstract

Iron dyshomeostasis and mitochondrial impairments are both vitally important for the progression of many neurodegenerative diseases, including Parkinson's disease and Alzheimer's disease. Nevertheless, how these two pathological phenomena are linked with one another remains unclear, especially in neurons. To address the question, a model of iron overload was established with exposure of rat primary cortical neurons to excessive iron. We first verified that iron overload resulted in a decrease in ATP production in neurons. Meanwhile, the release of mitochondrial cytochrome c was significantly increased after iron overload and consequently triggered an apoptosis signal, as revealed by Caspase 3 cleavage. To explore the potential underlying molecular mechanisms, an unlabeled quantitative proteomics approach was applied to primary neurons. Gene Ontology enrichment analysis revealed that 58 mitochondria-associated proteins were found to be significantly altered, including three subunits of mitochondrial complex I and OPA1. Increased Ndufs1 and decreased NDUFA10 levels were further validated by a Western blot, and more importantly, complex I activity markedly declined. Iron-induced downregulation on the OPA1 level was also validated by a Western blot, which was not reversed by the anti-oxidant but was reversed by the iron chelator. Moreover, an OPA1-associated key downstream effect, mitochondrial fragmentation, was found to be aggravated in neurons exposed to excessive iron, which is consistent with the downregulation of OPA1. Furthermore, the protein level of PINK1, an important protein closely related to complex I activity and mitochondrial fragmentation, also significantly declined in neurons by iron overload. Thus, our findings may shed new light on the linkage between iron toxicity and mitochondrial impairments, such as energy supply deficiency and mitochondrial fragmentation, and further expand the toxic repertoire of iron in the central nerve system.​