Uncorrected Author Proof Journal of Alzheimer’s Disease 28 (2011) 1–15 DOI 10.3233/JAD-2011-110614 IOS Press 1 Modest Amyloid Deposition is Associated with Iron Dysregulation, Microglial Activation, and Oxidative Stress 1 2 3 Joseph J. Gallagher a,∗ , Mary E. Finnegan b , Belinda Grehan a , Jon Dobson c,d , Joanna F. Collingwood b,c and Marina A. Lynch a 4 5 a Department of Physiology, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland 6 b School of Engineering, University of Warwick, Coventry, UK 7 c Institute of Science and Technology in Medicine, Keele University, Stoke-on-Trent, UK 8 d Departments of Biomedical Engineering and Materials Science and Engineering, University of Florida, Gainesville, Florida, USA 9 10 Handling Associate Editor: Jane Flinn 11 Accepted 24 August 2011 Abstract. There is a well-established literature indicating a relationship between iron in brain tissue and Alzheimer’s disease (AD). More recently, it has become clear that AD is associated with neuroinflammatory and oxidative changes which probably result from microglial activation. In this study, we investigated the correlative changes in microglial activation, oxidative stress, and iron dysregulation in a mouse model of AD which exhibits early-stage amyloid deposition. Microfocus X-ray absorption spectroscopy analysis of intact brain tissue sections prepared from APP/PS1 transgenic mice revealed the presence of magnetite, a mixed-valence iron oxide, and local elevations in iron levels in tissue associated with amyloid--containing plaques. The evidence indicates that the expression of markers of microglial activation, CD11b and CD68, and astrocytic activation, GFAP, were increased, and were histochemically determined to be adjacent to amyloid--containing plaques. These findings support the contention that, in addition to glial activation and oxidative stress, iron dysregulation is an early event in AD pathology. 12 13 14 15 16 17 18 19 20 Keywords: Alzheimer’s disease, iron, microglia, oxidative stress, spectrometry, X-ray fluorescence 21 INTRODUCTION 22 Iron plays a pivotal role in many physiological pro- 23 cesses, for example in the transport of oxygen, electron 24 transport, and in the synthesis of certain neurotrans- 25 mitters [1]. Intracellular iron is stored in the cytosolic 26 protein ferritin, a 12 nm diameter 24-subunit protein 27 shell encasing a hollow interior capable of containing ∗ Correspondence to: Joseph J. Gallagher, Biological Imaging Centre, Beckman Institute, m/c 139-74, California Institute of Technology, Pasadena, California, USA. Tel.: 1 626 395 2004; Fax: 626 449 5163; E-mail: jjg@caltech.edu. a maximum of approximately 4,500 iron atoms. Iron 28 is normally taken up from the redox active Fe 2+ state 29 and converted to the less reactive ferric (Fe 3+ ) valence 30 state in a ferrihydrite-like hydrated iron oxide [2]. Non- 31 heme iron circulates in the blood mainly in a tight, 32 but reversible, bond with the glycoprotein, transferrin. 33 Blood brain barrier endothelial cells express a specific 34 transferrin receptor (TfR) which facilitates cellular 35 internalization of iron [3]. Ferritin, brain endogenous 36 transferrin and TfR are heterogeneously expressed in 37 different brain cell types and brain regions which fur- 38 ther complicates a currently poor understanding of 39 iron release into the brain and its subsequent regulation 40 ISSN 1387-2877/11/$27.50 © 2011 – IOS Press and the authors. All rights reserved