Hindawi Publishing Corporation Oxidative Medicine and Cellular Longevity Volume 2013, Article ID 676425, 13 pages http://dx.doi.org/10.1155/2013/676425 Research Article Atherogenesis May Involve the Prooxidant and Proinflammatory Effects of Ferryl Hemoglobin László Potor, 1 Emese Bányai, 2 Gergely Becs, 2 Miguel P. Soares, 3 György Balla, 1,4 József Balla, 2 and Viktória Jeney 1,2 1 MTA-DE Vascular Biology, hrombosis and Hemostasis Research Group, Hungarian Academy of Sciences, 4012 Debrecen, Hungary 2 Department of Medicine, University of Debrecen, 4012 Debrecen, Hungary 3 Instituto Gulbenkian de Ciˆ encia, 2780-156 Oeiras, Portugal 4 Department of Pediatrics, University of Debrecen, 4012 Debrecen, Hungary Correspondence should be addressed to Vikt´ oria Jeney; jeneyv@internal.med.unideb.hu Received 27 February 2013; Accepted 23 April 2013 Academic Editor: Gregory M. Vercellotti Copyright © 2013 L´ aszl´ o Potor et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Oxidized cell-free hemoglobin (Hb), including covalently cross-linked Hb multimers, is present in advanced atherosclerotic lesions. Oxidation of Hb produces methemoglobin (Fe 3+ ) and ferryl hemoglobin (Fe 4+ = O 2− ). Ferryl iron is unstable and can return to the Fe 3+ state by reacting with speciic amino acids of the globin chains. In these reactions globin radicals are produced followed by termination reactions yielding covalently cross-linked Hb multimers. Despite the evanescent nature of the ferryl state, herein we refer to this oxidized Hb as “ferryl Hb.” Our aim in this work was to study formation and biological efects of ferrylHb. We demonstrate that ferrylHb, like metHb, can release its heme group, leading to sensitization of endothelial cells (ECs) to oxidant- mediated killing and to oxidation of low-density lipoprotein (LDL). Furthermore, we observed that both oxidized LDL and lipids derived from human atherosclerotic lesions trigger Hb oxidation and subsequent production of covalently cross-linked ferrylHb multimers. Previously we showed that ferrylHb disrupts EC monolayer integrity and induces expression of inlammatory cell adhesion molecules. Here we show that when exposed to ferrylHb, EC monolayers exhibit increased permeability and enhanced monocyte adhesion. Taken together, interactions between cell-free Hb and atheroma lipids engage in a vicious cycle, amplifying oxidation of plaque lipids and Hb. hese processes trigger EC activation and cytotoxicity. 1. Introduction Extracellular lipid accumulation is the main feature of type IV atherosclerotic lesions. hese can progress into more com- plicated lesions, in which there is rupture of the ibrous cap accompanied by either hematoma/hemorrhage and throm- bus formation or intraplaque hemorrhage in the neovascula- ture sprouting from the vasa vasorum. hese events provoke the clinical symptoms and are responsible for atherosclerosis- associated morbidity and mortality [1–5]. Li et al. describe the complicated lesion as a highly oxida- tive environment containing products of lipid peroxidation such as lipid hydroperoxides, aldehydes, and carbonyls [6]. he authors suggest that these oxidation products are toxic for incoming cells, especially macrophages, and constitute a “death zone,” perhaps explaining the persistence and growth of atherosclerotic lesions. Upon plaque rupture or intraplaque hemorrhage, red blood cells (RBCs) are brought into close contact with plaque materials. Hemoglobin within RBCs is protected from oxida- tion because erythrocytes are equipped with highly efective antioxidant defenses [7]. Based on our previous work, lipids derived from atheromatous plaque or oxidized low-density lipoprotein (LDL) can cause RBC lysis and subsequent oxidation of Hb into metHb [8]. he efect of oxLDL and plaque lipids can be mimicked by cumene hydroperoxide. Moreover, enzymatic conversion of lipidhydroperoxides to alcohol by GSH/GPx causes signiicant inhibition of RBC lysis and Hb oxidation triggered by oxLDL and plaque lipids, suggesting that lipid hydroperoxides play a major role in these