THE IMPORTANCE OF IRON IN PATHOPHYSIOLOGIC CONDITIONS EDITED BY : Raffaella Gozzelino and Paolo Arosio PUBLISHED IN : Frontiers in Pharmacology 1 June 2015 | The Importance of Iron in Pathophysiologic Conditions Frontiers in Pharmacology Frontiers Copyright Statement © Copyright 2007-2015 Frontiers Media SA. All rights reserved. All content included on this site, such as text, graphics, logos, button icons, images, video/audio clips, downloads, data compilations and software, is the property of or is licensed to Frontiers Media SA (“Frontiers”) or its licensees and/or subcontractors. The copyright in the text of individual articles is the property of their respective authors, subject to a license granted to Frontiers. The compilation of articles constituting this e-book, wherever published, as well as the compilation of all other content on this site, is the exclusive property of Frontiers. For the conditions for downloading and copying of e-books from Frontiers’ website, please see the Terms for Website Use. If purchasing Frontiers e-books from other websites or sources, the conditions of the website concerned apply. Images and graphics not forming part of user-contributed materials may not be downloaded or copied without permission. Individual articles may be downloaded and reproduced in accordance with the principles of the CC-BY licence subject to any copyright or other notices. They may not be re-sold as an e-book. As author or other contributor you grant a CC-BY licence to others to reproduce your articles, including any graphics and third-party materials supplied by you, in accordance with the Conditions for Website Use and subject to any copyright notices which you include in connection with your articles and materials. All copyright, and all rights therein, are protected by national and international copyright laws. The above represents a summary only. For the full conditions see the Conditions for Authors and the Conditions for Website Use. ISSN 1664-8714 ISBN 978-2-88919-524-4 DOI 10.3389/978-2-88919-524-4 About Frontiers Frontiers is more than just an open-access publisher of scholarly articles: it is a pioneering approach to the world of academia, radically improving the way scholarly research is managed. The grand vision of Frontiers is a world where all people have an equal opportunity to seek, share and generate knowledge. Frontiers provides immediate and permanent online open access to all its publications, but this alone is not enough to realize our grand goals. Frontiers Journal Series The Frontiers Journal Series is a multi-tier and interdisciplinary set of open-access, online journals, promising a paradigm shift from the current review, selection and dissemination processes in academic publishing. All Frontiers journals are driven by researchers for researchers; therefore, they constitute a service to the scholarly community. At the same time, the Frontiers Journal Series operates on a revolutionary invention, the tiered publishing system, initially addressing specific communities of scholars, and gradually climbing up to broader public understanding, thus serving the interests of the lay society, too. Dedication to Quality Each Frontiers article is a landmark of the highest quality, thanks to genuinely collaborative interactions between authors and review editors, who include some of the world’s best academicians. Research must be certified by peers before entering a stream of knowledge that may eventually reach the public - and shape society; therefore, Frontiers only applies the most rigorous and unbiased reviews. Frontiers revolutionizes research publishing by freely delivering the most outstanding research, evaluated with no bias from both the academic and social point of view. By applying the most advanced information technologies, Frontiers is catapulting scholarly publishing into a new generation. What are Frontiers Research Topics? Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: researchtopics@frontiersin.org 2 June 2015 | The Importance of Iron in Pathophysiologic Conditions Frontiers in Pharmacology THE IMPORTANCE OF IRON IN PATHOPHYSIOLOGIC CONDITIONS Topic Editors: Raffaella Gozzelino, Chronic Diseases Research Center (CEDOC)/Faculty of Medical Sciences, NOVA University of Lisbon, Portugal Paolo Arosio, University of Brescia, Italy The iron element (Fe) is strictly required for the survival of most forms of life, including bacteria, plants and humans. Fine-tuned regulatory mechanisms for Fe absorption, mobilization and recycling operate to maintain Fe homeostasis, the disruption of which leads to Fe overload or Fe depletion. Whereas the deleterious effect of Fe deficiency relies on reduced oxygen transport and diminished activity of Fe-dependent enzymes, the cytotoxicity induced by Fe overload is due to the ability of this metal to act as a pro-oxidant and catalyze the formation of highly reactive hydroxyl radicals via the Fenton chemistry. This results in unfettered oxidative stress generation that, by inducing protein, lipid and DNA oxidation, leads to Fe-mediated programmed cell death and organ dysfunction. Major and systemic Fe overloads occurring in hemochromatosis and Fe-loading anemias have been extensively studied. However, localized tissue Fe overload was recently associated to a variety of pathologies, such as infection, inflammation, cancer, cardiovascular and neurodegenerative disorders. In keeping with the existence of cross-regulatory interactions between Fe homeostasis and the pathophysiology of these diseases, further investigations on the mechanisms that provide cellular and systemic adaptation to tissue Fe overload are instrumental for future therapeutic approaches. Thus, we encourage our colleagues to submit original research papers, reviews, perspectives, methods and technology reports to contribute their findings to a current state of the art on a comprehensive overview of the importance of iron metabolism in pathophysiologic conditions. Citation: Gozzelino, R., Arosio, P., eds. (2015). The Importance of Iron in Pathophysiologic Conditions. Lausanne: Frontiers Media. doi: 10.3389/978-2-88919-524-4 3 June 2015 | The Importance of Iron in Pathophysiologic Conditions Frontiers in Pharmacology Table of Contents 06 The importance of iron in pathophysiologic conditions Raffaella Gozzelino and Paolo Arosio Iron metabolism 09 Zebrafish in the sea of mineral (iron, zinc, and copper) metabolism Lu Zhao, Zhidan Xia and Fudi Wang 32 The physiological functions of iron regulatory proteins in iron homeostasis – an update De-Liang Zhang, Manik C. Ghosh and Tracey A. Rouault 44 Iron, hepcidin, and the metal connection Olivier Loréal,Thibault Cavey, Edouard Bardou-Jacquet, Pascal Guggenbuhl, Martine Ropert and Pierre Brissot 54 The IRP/IRE system in vivo: insights from mouse models Nicole Wilkinson and Kostas Pantopoulos 69 The role of hepatic transferrin receptor 2 in the regulation of iron homeostasis in the body Christal A. Worthen and Caroline A. Enns 77 Pathophysiology of the belgrade rat Tania Veuthey and Marianne Wessling-Resnick 90 Special delivery: distributing iron in the cytosol of mammalian cells Caroline C. Philpott and Moon-Suhn Ryu 98 Ferritin polarization and iron transport across monolayer epithelial barriers in mammals Esther G. Meyron-Holtz, Lyora A. Cohen, Lulu Fahoum, Yael Haimovich, Lena Lifshitz, Inbar Magid-Gold, Tanja Stuemler and Marianna Truman-Rosentsvit 105 The role of iron in the skin and cutaneous wound healing Josephine A. Wright, Toby Richards and Surjit K. S. Srai 113 Mechanisms of iron metabolism in Caenorhabditis elegans Cole P. Anderson and Elizabeth A. Leibold 121 Labile iron in cells and body fluids: physiology, pathology, and pharmacology Zvi Ioav Cabantchik Heme-Iron 132 Heme in pathophysiology: a matter of scavenging, metabolism and trafficking across cell membranes Deborah Chiabrando, Francesca Vinchi, Veronica Fiorito, Sonia Mercurio and Emanuela Tolosano 4 June 2015 | The Importance of Iron in Pathophysiologic Conditions Frontiers in Pharmacology 156 Like iron in the blood of the people: the requirement for heme trafficking in iron metabolism Tamara Korolnek and Iqbal Hamza 169 Expression of ABCG2 (BCRP) in mouse models with enhanced erythropoiesis Gladys O. Latunde-Dada, Abas H. Laftah, Patarabutr Masaratana, Andrew T. McKie and Robert J. Simpson Genetic disorders 175 Molecular basis of HFE-hemochromatosis MajaVujic ́ 181 The extrahepatic role of TFR2 in iron homeostasis Laura Silvestri, Antonella Nai, Alessia Pagani and Clara Camaschella Iron deficiency and anemia 187 The role of TMPRSS6/matriptase-2 in iron regulation and anemia Chia-YuWang, Delphine Meynard and Herbert Y. Lin 193 Iron deficiency in the elderly population, revisited in the hepcidin era Fabiana Busti, Natascia Campostrini, Nicola Martinelli and Domenico Girelli 202 Hemojuvelin and bone morphogenetic protein (BMP) signaling in iron homeostasis Amanda B. Core, Susanna Canali and Jodie L. Babitt 211 Hepcidin antagonists for potential treatments of disorders with hepcidin excess Maura Poli, Michela Asperti, Paola Ruzzenenti, Maria Regoni and Paolo Arosio Inflammation 224 Physiological implications of NTBI uptake by T iymphocytes Jorge P. Pinto, João Arezes, Vera Dias, Susana Oliveira, Inês Vieira, Mónica Costa, Matthijn Vos, Anna Carlsson, Yuri Rikers, Maria Rangel and Graça Porto 238 Iron at the interface of immunity and infection Manfred Nairz, David Haschka, Egon Demetz and Günter Weiss 248 Heme on innate immunity and inflammation Fabianno F. Dutra and MarceloT. Bozza 268 Iron, anemia and hepcidin in malaria Natasha Spottiswoode, Patrick E. Duffy and Hal Drakesmith 279 Influence of host iron status on Plasmodium falciparum infection Martha A. Clark, Morgan M. Goheen and Carla Cerami 291 Iron overload in Plasmodium berghei -infected placenta as a pathogenesis mechanism of fetal death Carlos Penha-Gonçalves, Raffaella Gozzelino and Luciana V. de Moraes 304 Behavioral decline and premature lethality upon pan-neuronal ferritin overexpression in Drosophila infected with a virulent form of Wolbachia Stylianos Kosmidis, Fanis Missirlis, Jose A. Botella, Stephan Schneuwly, Tracey A. Rouault and Efthimios M. C. Skoulakis Cardiotoxicity 312 The role of iron in anthracycline cardiotoxicity Elena Gammella, Federica Maccarinelli, Paolo Buratti, Stefania Recalcati and Gaetano Cairo 5 June 2015 | The Importance of Iron in Pathophysiologic Conditions Frontiers in Pharmacology 318 Epidemiological associations between iron and cardiovascular disease and diabetes Debargha Basuli, Richard G. Stevens, Frank M.Torti and Suzy V. Torti 328 Atherogenesis and iron: from epidemiology to cellular level Francesca Vinchi, Martina U. Muckenthaler, Milene C. Da Silva, György Balla, József Balla and Viktória Jeney 348 The role of iron metabolism as a mediator of macrophage inflammation and lipid handling in atherosclerosis Anwer Habib and Aloke V. Finn 354 H-ferritin ferroxidase induces cytoprotective pathways and inhibits microvascular stasis in transgenic sickle mice Gregory M.Vercellotti, Fatima B. Khan, Julia Nguyen, Chunsheng Chen, Carol M. Bruzzone, Heather Bechtel, Graham Brown, Karl A. Nath, Clifford J. Steer, Robert P. Hebbel and John D. Belcher 364 Randomized controlled trials of iron chelators for the treatment of cardiac siderosis in thalassaemia major A. John Baksi and Dudley J. Pennell Neurodegeneration 368 The iron regulatory capability of the major protein participants in prevalent neurodegenerative disorders Bruce X. Wong and James A. Duce 378 Neurodegeneration with brain iron accumulation: update on pathogenic mechanisms Sonia Levi and Dario Finazzi 398 The interplay between iron accumulation, mitochondrial dysfunction, and inflammation during the execution step of neurodegenerative disorders Pamela J. Urrutia, Natalia P. Mena and Marco T. Núñez 410 Mitochondrial ferritin in the regulation of brain iron homeostasis and neurodegenerative diseases Guofen Gao and Yan-Zhong Chang 417 Mitochondrial iron–sulfur cluster dysfunction in neurodegenerative disease Grazia Isaya 424 Dysregulation of cellular iron metabolism in Friedreich ataxia: from primary iron-sulfur cluster deficit to mitochondrial iron accumulation Alain Martelli and Hélène Puccio 435 HFE gene variants, iron, and lipids: a novel connection in Alzheimer’s disease Fatima Ali-Rahman, Cara-Lynne Schengrund and James R. Connor 454 The role of iron in neurodegenerative disorders: insights and opportunities with synchrotron light Joanna F. Collingwood and Mark R. Davidson 473 Regional siderosis: a new challenge for iron chelation therapy Zvi Ioav Cabantchik, Arnold Munnich, Moussa B. Youdim and David Devos EDITORIAL published: 24 February 2015 doi: 10.3389/fphar.2015.00026 The importance of iron in pathophysiologic conditions Raffaella Gozzelino 1 * and Paolo Arosio 2 * 1 Inflammation Laboratory, Instituto Gulbenkian de Ciência, Oeiras, Portugal 2 Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy *Correspondence: rgozzelino@igc.gulbenkian.pt; paolo.arosio@unibs.it Edited and reviewed by: Jaime Kapitulnik, The Hebrew University of Jerusalem, Israel Keywords: iron, iron metabolism, iron and genetic disorders, iron deficiency and anemia, iron and inflammation, iron and cardiotoxicity, iron and neurodegeneration, heme iron Biological iron is necessary for vital functions and also potentially toxic to the organisms. This dual effect raised the interest of many investigators to study the mechanisms controlling its homeosta- sis that are altered in many pathologic conditions. Recently the understanding of iron metabolism significantly improved with the discovery of genes responsible for genetic disorders, such as hemochromatosis, the IRE/IRPs machinery and the hepcidin- ferroportin axis, which allowed to elucidate the basis of cellular and systemic iron homeostasis. In addition, these advances dis- closed a causal link between deregulation of iron homeostasis, inflammation and oxidative stress, often induced by the iron accumulation that is commonly observed in many pathologic conditions. Hence, believing this was time to provide a current state-of- the-art on the importance of iron in pathophysiologic conditions, we thought to promote a Research Topic with the contribu- tion of top-leading scientists who studied the effects of iron homeostasis disruption on the outcome of genetic, inflamma- tory, infectious, cardiovascular, and neurodegenerative diseases. Encountering an interest even larger than our ambitions, we successfully collected 42 manuscripts, which cover the major aspects of iron metabolism, from the essential role of iron for cell survival to its contribution in the pathogenesis of vari- ous disorders. They have been organized in an e-book in 7 sections. The first section of the Research Topic includes 11 papers that cover the importance of iron in cellular proliferation, dif- ferentiation and functioning, and its crucial role in essential processes such as oxygen transport, DNA synthesis, metabolic energy and cellular respiration. They describe the expression and regulation of the main players involved in the mechanisms of iron absorption, recycling, and mobilization (Zhang et al., 2014), the cooperation among different cellular compartments that facilitates iron mobilization/storage and prevents the dele- terious effects induced by its accumulation, the role of iron in the Fenton chemistry and its effects on oxidative stress and pro- grammed cell death. Of interest is the study of the different types of circulating iron and the strategies more commonly used for its detection (Cabantchik, 2014). The papers also present updates on iron metabolism in zebrafish, in C. elegans , the role of iron in the skin and the regulatory mechanisms devoted to iron uptake, recycling and mobilization. Altogether they provide the infor- mation for a better understanding of the iron involvement in pathophysiologic conditions. The second section includes three papers dealing with the role of heme inside cells and its cytotoxicity when it is released from hemoproteins. In fact, most body iron is contained within the protoporphyrin ring that acts as prosthetic group in many hemoproteins essential to cellular functions. The different aspects related to heme synthesis, intracellular trafficking, scavenging and catabolism are reviewed together with the protective mech- anisms that cooperate to prevent the deleterious effects induced by heme accumulation and the pathological conditions in which heme plays a dominant role (Chiabrando et al., 2014). The expression and regulation of the main heme scavengers and trans- porters identified are also reviewed, together with the notion that maintenance of heme homeostasis is essential to prevent the deleterious effect induced by its overload (Korolnek and Hamza, 2014). The following sections are devoted to describe how disruption of iron homeostasis is associated with a series of syndromes and dictates the outcomes and severity of these disorders. The third section deals with hemochromatosis, the genetic dis- ease that has a fundamental importance for identifying the actors responsible for systemic iron regulation. It includes two reviews on the origin and genetic mutations characterizing this pathology as well as the incidence and different types of hemochromato- sis identified so far (Vujic, 2014). The symptoms and mani- festations that characterize these disorders and the alteration of the responsible proteins are also described (Silvestri et al., 2014). The forth section deals with anemia and iron deficiency, prob- lems that are common worldwide, and includes four papers. The distribution of iron deficiency in the population and in partic- ular during aging are reviewed (Busti et al., 2014). The etiology of anemia, caused by genetic disorders, inflammation, infections, bleeding due to the development of ulcers, drug administra- tion or cancers are covered. The roles of TMPRSS6 and of its substrate, hemojuvelin, in the regulation of BMP signaling and hepcidin expression are reviewed (Core et al., 2014; Wang et al., 2014). Finally, the increasing number of therapeutic approaches targeting the various steps involved in hepcidin regulation are summarized together with the promising results capable to cor- rect altered hematological parameters in animal models (Poli et al., 2014). The fifth section deals with one of the hottest topics of the field, which is the connection between iron and inflam- mation, largely mediated by hepcidin expression. Seven papers www.frontiersin.org February 2015 | Volume 6 | Article 26 | 6 Gozzelino and Arosio The importance of iron in pathophysiologic conditions are included. One is an updated review on the known bat- tle between host and pathogen for access to the iron neces- sary for proliferation, particular reference to the very complex malaria infection (Spottiswoode et al., 2014). The molecular mechanisms leading to disruption of iron homeostasis upon infections caused by parasites (Penha-Goncalves et al., 2014), intracellular or extracellular pathogens are also detailed (Nairz et al., 2014). Of importance are the effects of iron supplemen- tation therapy to individuals suffering from infectious diseases (Clark et al., 2014) and the role of proteins that restricting iron availability to microbes may modify the outcome of the infection. The sixth section discusses the role of iron overload in car- diovascular diseases, which includes six papers. One is a review on the long-standing and obscure relationship between iron availability and anthracycline cardiotoxicity, stressing the role of chelating agents and ferritins as agents protecting against the pro-oxidant activity of the drug (Gammella et al., 2014). A detailed overview on the pathways leading to the disruption of iron homeostasis and impairing heart functioning is described (Basuli et al., 2014). The toxicity of iron was addressed in dif- ferent cell types, emphasizing in particular the effects exerted on macrophages for the development and progression of atheroscle- rotic plaque. In this section, a special attention is also given to the occurrence of cardiovascular abnormalities and death in hemochromatosis patients, thus further confirming the role of iron in the pathogenesis of these diseases (Vinchi et al., 2014). Finally, the seventh section discusses the role of iron in neurodegenerative diseases and includes nine papers. Although the regulation of iron homeostasis in the brain remains rather obscure, its alteration has been observed in a variety of brain dis- orders, including Parkinson’s, Alzheimer’s, Huntington’s, Prion and neurodegeneration with brain iron accumulation (NBIA). This stimulated many studies to verify if the local iron overload is one, or the main contributor to neuronal death (Wong and Duce, 2014). The pathogenic mechanisms leading to neurode- generation that are associated to gene mutations of NBIAs are reviewed and they pose another tight connection between iron deregulation and oxidative damage (Levi and Finazzi, 2014), The involvement of inflammation in the establishment and progres- sion of these pathologic conditions and its correlation to the disruption of iron homeostasis was also addressed (Urrutia et al., 2014). The beneficial effect of an oral iron chelator able to pass through the blood-brain barrier, the deferiprone, in scavenging excess iron from regional foci of siderosis is reviewed together with the ongoing clinical trials. The chelator is claimed to be able to relocate efficiently iron and to replenish iron-deprived regions, thus ameliorating the symptoms of iron maldistribution and sup- pressing the deleterious effects of its overload (Cabantchik et al., 2013). In summary, this research topic enjoys the con- tribution of top-leading scientists aimed at providing a current state of the art on the importance of iron metabolism and its contribution in a variety of human disorders. ACKNOWLEDGMENTS We would like to heartily acknowledge all the authors for the valuable sharing of their findings, knowledge, and opinions. REFERENCES Basuli, D., Stevens, R. G., Torti, F. M., and Torti, S. V. (2014). Epidemiological asso- ciations between iron and cardiovascular disease and diabetes. Front. Pharmacol. 5:117. doi: 10.3389/fphar.2014.00117 Busti, F., Campostrini, N., Martinelli, N., and Girelli, D. (2014). Iron deficiency in the elderly population, revisited in the hepcidin era. Front. Pharmacol. 5:83. doi: 10.3389/fphar.2014.00083 Cabantchik, Z. I. (2014). Labile iron in cells and body fluids: physiology, pathology, and pharmacology. Front. Pharmacol. 5:45. doi: 10.3389/fphar.2014. 00045 Cabantchik, Z. I., Munnich, A., Youdim, M. B., and Devos, D. (2013). Regional siderosis: a new challenge for iron chelation therapy. Front. Pharmacol. 4:167. doi: 10.3389/fphar.2013.00167 Chiabrando, D., Vinchi, F., Fiorito, V., Mercurio, S., and Tolosano, E. (2014). Heme in pathophysiology: a matter of scavenging, metabolism and traffick- ing across cell membranes. Front. Pharmacol. 5:61. doi: 10.3389/fphar.2014. 00061 Clark, M. A., Goheen, M. M., and Cerami, C. (2014). Influence of host iron status on Plasmodium falciparum infection. Front. Pharmacol. 5:84. doi: 10.3389/fphar.2014.00084 Core, A. B., Canali, S., and Babitt, J. L. (2014). Hemojuvelin and bone morpho- genetic protein (BMP) signaling in iron homeostasis. Front. Pharmacol. 5:104. doi: 10.3389/fphar.2014.00104 Gammella, E., Maccarinelli, F., Buratti, P., Recalcati, S., and Cairo, G. (2014). The role of iron in anthracycline cardiotoxicity. Front. Pharmacol. 5:25. doi: 10.3389/fphar.2014.00025 Korolnek, T., and Hamza, I. (2014). Like iron in the blood of the people: the requirement for heme trafficking in iron metabolism. Front. Pharmacol. 5:126. doi: 10.3389/fphar.2014.00126 Levi, S., and Finazzi, D. (2014). Neurodegeneration with brain iron accu- mulation: update on pathogenic mechanisms. Front. Pharmacol. 5:99. doi: 10.3389/fphar.2014.00099 Nairz, M., Haschka, D., Demetz, E., and Weiss, G. (2014). Iron at the interface of immunity and infection. Front. Pharmacol. 5:152. doi: 10.3389/fphar.2014.00152 Penha-Goncalves, C., Gozzelino, R., and de Moraes, L. V. (2014). Iron over- load in Plasmodium berghei -infected placenta as a pathogenesis mech- anism of fetal death. Front. Pharmacol. 5:155. doi: 10.3389/fphar.2014. 00155 Poli, M., Asperti, M., Ruzzenenti, P., Regoni, M., and Arosio, P. (2014). Hepcidin antagonists for potential treatments of disorders with hepcidin excess. Front. Pharmacol. 5:86. doi: 10.3389/fphar.2014.00086 Silvestri, L., Nai, A., Pagani, A., and Camaschella, C. (2014). The extra- hepatic role of TFR2 in iron homeostasis. Front. Pharmacol. 5:93. doi: 10.3389/fphar.2014.00093 Spottiswoode, N., Duffy, P. E., and Drakesmith, H. (2014). Iron, anemia and hepcidin in malaria. Front. Pharmacol. 5:125. doi: 10.3389/fphar.2014. 00125 Urrutia, P. J., Mena, N. P., and Nunez, M. T. (2014). The interplay between iron accumulation, mitochondrial dysfunction, and inflammation during the execution step of neurodegenerative disorders. Front. Pharmacol. 5:38. doi: 10.3389/fphar.2014.00038 Vinchi, F., Muckenthaler, M. U., Da Silva, M. C., Balla, G., Balla, J., and Jeney, V. (2014). Atherogenesis and iron: from epidemiology to cellular level. Front. Pharmacol. 5:94. doi: 10.3389/fphar.2014.00094 Vujic, M. (2014). Molecular basis of HFE-hemochromatosis. Front. Pharmacol. 5:42. doi: 10.3389/fphar.2014.00042 Wang, C. Y., Meynard, D., and Lin, H. Y. (2014). The role of TMPRSS6/matriptase- 2 in iron regulation and anemia. Front. Pharmacol. 5:114. doi: 10.3389/fphar.2014.00114 Wong, B. X., and Duce, J. A. (2014). The iron regulatory capability of the major pro- tein participants in prevalent neurodegenerative disorders. Front. Pharmacol. 5:81. doi: 10.3389/fphar.2014.00081 Frontiers in Pharmacology | Drug Metabolism and Transport February 2015 | Volume 6 | Article 26 | 7 Gozzelino and Arosio The importance of iron in pathophysiologic conditions Zhang, D. L., Ghosh, M. C., and Rouault, T. A. (2014). The physiological functions of iron regulatory proteins in iron homeostasis - an update. Front. Pharmacol. 5:124. doi: 10.3389/fphar.2014.00124 Conflict of Interest Statement: The authors declare that the research was con- ducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Received: 23 December 2014; accepted: 30 January 2015; published online: 24 February 2015. Citation: Gozzelino R and Arosio P (2015) The importance of iron in pathophysiologic conditions. Front. Pharmacol. 6 :26. doi: 10.3389/fphar.2015.00026 This article was submitted to Drug Metabolism and Transport, a section of the journal Frontiers in Pharmacology. Copyright © 2015 Gozzelino and Arosio. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, dis- tribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. www.frontiersin.org February 2015 | Volume 6 | Article 26 | 8 REVIEW ARTICLE published: 06 March 2014 doi: 10.3389/fphar.2014.00033 Zebrafish in the sea of mineral (iron, zinc, and copper) metabolism Lu Zhao 1,2 , Zhidan Xia 1,2 and Fudi Wang 1,2 * 1 Department of Nutrition, Center for Nutrition and Health, School of Public Health, School of Medicine, Zhejiang University, Hangzhou, China 2 Institute of Nutrition and Food Safety, Zhejiang University, Hangzhou, China Edited by: Raffaella Gozzelino, Instituto Gulbenkian de Ciência, Portugal Reviewed by: Andrei Adrian Tica, University Of Medicine Craiova, Romania Constantin Ion Mircioiu, Carol Davila “University of Medicine and Pharmacy” , Romania *Correspondence: Fudi Wang, Department of Nutrition, Center for Nutrition and Health, School of Public Health, School of Medicine, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China e-mail: fwang@zju.edu.cn; fudiwang.lab@gmail.com Iron, copper, zinc, and eight other minerals are classified as essential trace elements because they present in minute in vivo quantities and are essential for life. Because either excess or insufficient levels of trace elements can be detrimental to life (causing human diseases such as iron-deficiency anemia, hemochromatosis, Menkes syndrome and Wilson’s disease), the endogenous levels of trace minerals must be tightly regulated. Many studies have demonstrated the existence of systems that maintain trace element homeostasis, and these systems are highly conserved in multiple species ranging from yeast to mice. As a model for studying trace mineral metabolism, the zebrafish is indispensable to researchers. Several large-scale mutagenesis screens have been performed in zebrafish, and these screens led to the identification of a series of metal transporters and the generation of several mutagenesis lines, providing an in-depth functional analysis at the system level. Moreover, because of their developmental advantages, zebrafish have also been used in mineral metabolism-related chemical screens and toxicology studies. Here, we systematically review the major findings of trace element homeostasis studies using the zebrafish model, with a focus on iron, zinc, copper, selenium, manganese, and iodine. We also provide a homology analysis of trace mineral transporters in fish, mice and humans. Finally, we discuss the evidence that zebrafish is an ideal experimental tool for uncovering novel mechanisms of trace mineral metabolism and for improving approaches to treat mineral imbalance-related diseases. Keywords: zebrafish, trace elements, minerals, iron, copper, zinc, metabolism INTRODUCTION As children of the Earth, humans are intimately connected to our surroundings in many ways, and the relationship between humans and minerals is perhaps the most enigmatic. Based on their necessity for life and their limited quantities with the human body, 11 elements are classified as trace minerals, including iron (Fe), zinc (Zn), copper (Cu), selenium(Se), man- ganese(Mn), iodine(I), molybdenum(Mo), fluorine (F), cobalt (Co), chromium (Cr), and vanadium (V) (Fraga, 2005). Metal trace minerals are biologically active primarily as metal- loproteins formed by conjugating or binding with various protein partners. Metalloproteins account for approximately half of all proteins and perform a wide range of biological functions as enzymes, transporters and signal transducers. In metallopro- teins, metal trace minerals are essential components, acting at the enzyme’s active site or by stabilizing the protein’s structure. Trace mineral deficiencies can cause a number of diseases that can be mild, severe, or even fatal. Conversely, excess levels of trace min- erals can be toxic. For example, excess iron or copper produces reactive oxygen species (ROS) via the Fenton reaction, resulting in lipid peroxidation, DNA damage, altered calcium homeostasis, and cell death (Stohs and Bagchi, 1995). Excess levels of redox- inactive metals such as zinc are also harmful; the accumulation of zinc triggers neuronal death in the brain and induces copper deficiency. Thus, the balance of endogenous trace minerals must be tightly regulated. Organisms have evolved comprehensive systems for main- taining trace element homeostasis; these systems are composed primarily of transport proteins, storage proteins, and some hor- mones. Our current knowledge regarding these regulatory factors has come primarily from studies using model organisms rang- ing from yeast to mice. Among these species, the zebrafish ( Danio rerio ) has been a valuable vertebrate system with several unique advantages. First, their small size, high fertility rate, and rapid development make zebrafish an ideal model for large-scale genetic screens. Secondly, because they are fertilized ex vivo and are optically transparent, zebrafish embryos are ideally suited for experimental techniques such as gene knockout/knockdown and overexpression. Because the embryos develop ex utero , zebrafish are also an excellent model for studying pharmacology and tox- icology in early developmental stages. Finally, the zebrafish is a vertebrate species, and many of its genes and metabolic systems are highly conserved with humans; indeed, 80% of genes and expressed sequence tags (ESTs) are present in conserved synteny groups between fish and humans (Barbazuk et al., 2000). Here, we systematically review the major findings obtained from zebrafish studies of trace element homeostasis, with a focus on iron, zinc, copper, selenium, manganese, and iodine. We also www.frontiersin.org March 2014 | Volume 5 | Article 33 | 9 Zhao et al. Zebrafish in mineral metabolism performed a homology analysis of trace mineral transporters in fish, mice and humans, and we summarize the available zebrafish mutant models in the field. This review demonstrates that zebrafish are an ideal experimental tool for investigating novel mechanisms of trace mineral metabolism and for improving therapeutic approaches for treating mineral imbalance-related diseases. ZEBRAFISH AND IRON METABOLISM OVERVIEW OF IRON METABOLISM Iron is present in nearly all living organisms. As an essential com- ponent of heme and iron-sulfur cluster–containing proteins, iron plays a central role in many biological activities, including oxygen transport, cellular respiration, and DNA synthesis (Muckenthaler and Lill, 2012). Of all the trace elements, the iron homeostasis system is one of the best characterized, primarily because of iron’s role in erythropoiesis and its causative relationships with iron- deficiency anemia and hematochromatosis. To date, many major proteins involved in the uptake, transport, storage and release of iron have been identified ( Figure 1 ). Under normal conditions, dietary iron is absorbed by ente- rocytes through Divalent Metal Transporter 1 (DMT1); from there, it is exported to the circulation through Ferroportin 1 (Fpn1). In the blood, iron is transported in the form of Transferrin (Tf)-Fe 3 + , which is taken up by endocytosis into cells with surface Transferrin receptors (TfRs). Iron in the endo- somes is then released to the cytoplasm and delivered to the mitochondria, where it is used to make iron-sulfur (Fe-S) clus- ters, to synthesize heme, or to be stored as Ferritin. Most of the iron used for producing hemoglobin in erythrocytes is obtained from the recycling iron pool released from senescent red blood cells that are phagocytized by macrophages. Aside from transport and storage proteins, Hepcidin—a peptide hor- mone released by the liver—plays an important role in regulating iron levels by binding to Fpn1 and promoting its internal- ization. Other factors such as oxidoreductases [e.g., Duodenal Cytochrome b (Dytb), Ceruloplasmin (Cp), Hephaestin (Heph), and STEAP3) and modulatory proteins (e.g., Hemochromatosis (HFE), Hemojuvelin (HJV), Iron Regulatory Protein (IRP) 1/2, and Transmembrane Serine Protease 6 (TMPRSS6)] also play an active role in iron metabolism (Muckenthaler and Lill, 2012; Srai and Sharp, 2012). An overview of the protein homology and expression patterns among fish and mammalian iron-regulating proteins is provided in Table 1 FIGURE 1 | Generalized overview of iron metabolism in vertebrate cells. Dietary iron is absorbed by enterocytes through the concerted activity of the reductase DCYTB and the transporter DMT1. Iron is then oxidized by HEPH and exits the enterocytes through the iron exporter FPN1. Iron is transferred as a complex with Transferrin (TF) in the bloodstream and is delivered to target cells that express Transferrin receptors (TFRs) on their plasma membrane. TF-Iron-TFR complexes are then endocytosed. In the endosome, iron is released from TF by STEAP3 and then transported out of the endosome through DMT1. The cytoplasmic iron then enters the labile iron pool and is delivered by MFRN and siderophores to the mitochondria to be used for the synthesis of heme and Fe-S clusters. Excess iron is stored in Ferritin. Iron leaves the cell through FPN1, the plasma expression of which is negatively regulated by Hepcidin. Proteins for which zebrafish knockout and/or knockdown models are available are written in red. Frontiers in Pharmacology | Drug Metabolism and Transport March 2014 | Volume 5 | Article 33 | 10 Zhao et al. Zebrafish in mineral metabolism Table 1 | Iron metabolism–related proteins in zebrafish, mice, and humans. Gene/Protein Function/Related diseases Tissue distribution Protein identity (vs. H) M% Z% SLC11A2 /DMT1 Intestinal iron absorption, intracellular iron release/Hypochromic microcytic anemia H Ubiquitous 89 71 M Yolk sac, intestine Z Blood, gill, gut, lens, liver, YSL SLC40A1 /FPN 1 Cellular iron efflux/Hemochromatosis type 4 H Duodenum, macrophages, KCs, placenta, kidney 91 68 M Placenta, intestine, bone marrow, erythrocytes, liver, spleen Z CNS, yolk syncytial layer, gill, gut, liver HAMP /Hepcidin Cellular iron homeostasis/Hemochromatosis type 2B H Liver, heart 59 31 a /32 b M Liver, lung, heart Z Hamp1 : gut, liver; hamp2 : N.D. HFE /HFE Regulator of Tf-TfR interaction/Hemochromatosis type 1 H Ubiquitous 68 N.D. M Ubiquitous Z N.D. HFE2 /HJV Modulator of hepcidin expression/Hemochromatosis type 2A H Ubiquitous 87 44 M Skeletal muscle, liver, heart, prostate Z Skeletal muscle, liver, notochord TF /Transferrin Transport iron/atransferrinemia H Liver, spinal cord, lung, hypothalamus 72 41 M Liver, spinal cord, cerebellum, lung, placenta, ovary, bladder Z Liver, trunk musculature TFRC /TFR1 Cellular iron uptake / N.D. H Fetal liver, pancreas, muscle, placenta, early erythroid cells 77 44 c /39 d M Placenta, intestine, muscle, osteoclasts, microglia, bone marrow, liver, kidney Z Tfr1a : blood, blood island; tfr1b : ubiquitous TFR2 /TFR2 Mediates cellular uptake of Tf-bound iron/Hemochromatosis, type 3 H Liver, early erythroid cells 85 53 M Liver, bone, bone marrow Z Liver TMPRSS6 /TMPRSS6 Iron homeostasis/Iron-refractory iron deficiency anemia H Ubiquitous 83 N.D. M Liver Z N.D. SLC25A37 /Mitoferrin Mitochondrial iron transport/N.D. H Bone marrow, fetal liver, fetal lung, blood, prostate, early erythroid cells 91 69 M Umbilical cord, spleen, bone, bone marrow Z Blood island, lateral plate mesoderm CYBRD1 /DCYTB Dietary iron absorption/N.D. H Ubiquitous 75 58 M Ubiquitous Z N.D. STEAP3 / STEAP3 Ferric-chelate reductase activity/Anemia, hypochromic microcytic, with iron overload 2 H Ubiquitous 87 53 M Ubiquitous Z N.D. (Continued) www.frontiersin.org March 2014 | Volume 5 | Article 33 | 11 Zhao et al. Zebrafish in mineral metabolism Table 1 | Continued Gene/Protein Function/Related diseases Tissue distribution Protein identity (vs. H) M% Z% CP /Ceruloplasmin Oxidizes Fe(II) to Fe(III)/aceruloplasminemia H Ubiquitous 83 55 M Mammary gland, lung, liver, lens Z Liver, gut, pancreas HEPH /Hephaestin Transport of dietary iron from epithelial cells of the intestinal lumen into the circulatory system/N.D. H Ubiquitous 86 N.D. M Intestine, stomach, ovary, brown adipose Z N.D. FTH1 /Ferritin Store of iron in a soluble and nontoxic state/hemoc