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Cellular iron status influences the functional relationship between microglia and oligodendrocytes

Authors

  • X. Zhang,

    1. Department of Neurosurgery, College of Medicine, The Pennsylvania State University, M.S. Hershey Medical Center, Hershey, Pennsylvania
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  • N. Surguladze,

    1. Department of Neurosurgery, College of Medicine, The Pennsylvania State University, M.S. Hershey Medical Center, Hershey, Pennsylvania
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  • B. Slagle-Webb,

    1. Department of Neurosurgery, College of Medicine, The Pennsylvania State University, M.S. Hershey Medical Center, Hershey, Pennsylvania
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  • A. Cozzi,

    1. Biological and Technological Research Department, Istituto di Ricovero e Cura a Carattere Scientifico, H. San Raffaele, Via Olgettina 58, Milan, Italy
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  • J. R. Connor

    Corresponding author
    1. Department of Neurosurgery, College of Medicine, The Pennsylvania State University, M.S. Hershey Medical Center, Hershey, Pennsylvania
    • Department of Neurosurgery (H110), Director, G.M. Leader Family Alzheimer's Disease Laboratory, Penn State College of Medicine, M.S. Hershey Medical Center, 500 University Drive, PO Box 850, Hershey, PA 17033-0850, USA
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Abstract

Previously, we have reported that there is a spatiotemporal relationship between iron accumulation in microglia and oligodendrocytes during normal development and in remyelination following injury. This in vivo observation has prompted us to develop a cell culture model to test the relationship between iron status of microglia and survival of oligodendrocytes. We found that conditioned media from iron-loaded microglia increases the survival of oligodendrocytes; but conditioned media from iron loaded activated microglia is toxic to oligodendrocytes. In the trophic condition, one of the proteins released by iron-loaded microglia is H-ferritin, and transfecting the microglia with siRNA for H-ferritin blocks the trophic response on oligodendrocytes. Lipopolysaccharide (LPS) activation decreases the amount of H-ferritin that is released from microglia and increases the release of the proinflammatory cytokines tumor necrosis factor-α and interleukin-1. LPS activation of iron-enriched microglia results in the activation of NF-kB and greater release of cytokines when compared with that of control microglia; whereas treating microglia with an iron chelator is associated with less NF-kB activation and less release of cytokines. These results indicate that microglia play an important role in iron homoeostasis and that their iron status can influence how microglia influence growth and survival of oligodendrocytes. The results further indicate that ferritin, released by microglia, is a significant source of iron for oligodendrocytes. © 2006 Wiley-Liss, Inc.

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