title: Visualizing Metal Content and Intracellular Distribution in Primary Hippocampal Neurons with Synchrotron X-Ray Fluorescence.
abstract: Increasing evidence suggests that metal dyshomeostasis plays an important role in human neurodegenerative diseases. Although distinctive metal distributions are described for mature hippocampus and cortex, much less is known about metal levels and intracellular distribution in individual hippocampal neuronal somata. To solve this problem, we conducted quantitative metal analyses utilizing synchrotron radiation X-Ray fluorescence on frozen hydrated primary cultured neurons derived from rat embryonic cortex (CTX) and two regions of the hippocampus: dentate gyrus (DG) and CA1. Comparing average metal contents showed that the most abundant metals were calcium, iron, and zinc, whereas metals such as copper and manganese were less than 10% of zinc. Average metal contents were generally similar when compared across neurons cultured from CTX, DG, and CA1, except for manganese that was larger in CA1. However, each metal showed a characteristic spatial distribution in individual neuronal somata. Zinc was uniformly distributed throughout the cytosol, with no evidence for the existence of previously identified zinc-enriched organelles, zincosomes. Calcium showed a peri-nuclear distribution consistent with accumulation in endoplasmic reticulum and/or mitochondria. Iron showed 2-3 distinct highly concentrated puncta only in peri-nuclear locations. Notwithstanding the small sample size, these analyses demonstrate that primary cultured neurons show characteristic metal signatures. The iron puncta probably represent iron-accumulating organelles, siderosomes. Thus, the metal distributions observed in mature brain structures are likely the result of both intrinsic neuronal factors that control cellular metal content and extrinsic factors related to the synaptic organization, function, and contacts formed and maintained in each region.
authors.affiliation: Department of Biological Sciences, Interdisciplinary Graduate Program in Molecular and Cellular Biology, Neuroscience Program, Ohio University, Athens, Ohio, United States of America.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Colvin
authors.affiliation: Department of Physics & Astronomy, Northwestern University, Evanston, Illinois, United States of America.
authors.forename: Qiaoling
authors.initials: Q
authors.lastname: Jin
authors.affiliation: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois, United States of America.
authors.forename: Barry
authors.initials: B
authors.lastname: Lai
authors.affiliation: The Psychiatric Institute, Departments of Psychiatry and Pharmacology, the University of Illinois at Chicago, Chicago, Illinois, United States of America.
authors.forename: Lech
authors.initials: L
authors.lastname: Kiedrowski
mesh_terms: D000818:Animals; D056547:CA1 Region, Hippocampal / Q000378:metabolism / Q000648:ultrastructure*; D002118:Calcium / Q000032:analysis* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D002540:Cerebral Cortex / Q000378:metabolism / Q000648:ultrastructure; D003300:Copper / Q000032:analysis / Q000378:metabolism; D018891:Dentate Gyrus / Q000378:metabolism / Q000648:ultrastructure*; D004622:Embryo, Mammalian; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D005615:Freezing; D007501:Iron / Q000032:analysis* / Q000378:metabolism; D008345:Manganese / Q000032:analysis / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure*; D061251:Primary Cell Culture; D051381:Rats; D013052:Spectrometry, X-Ray Emission; D017356:Synchrotrons; D015032:Zinc / Q000032:analysis* / Q000378:metabolism
chemical_list: D008345:Manganese; D003300:Copper; D007501:Iron; D015032:Zinc; D002118:Calcium