Original Contribution IS INCREASED REDOX-ACTIVE IRON IN ALZHEIMER DISEASE A FAILURE OF THE COPPER-BINDING PROTEIN CERULOPLASMIN? RUDY J. CASTELLANI,* MARK A. SMITH, ² AKIHIKO NUNOMURA, ²,‡ PEGGY L. R. HARRIS, ² and GEORGE PERRY ² *Division of Neuropathology, Department of Pathology, University of Maryland at Baltimore, Baltimore, MD, USA; ² Institute of Pathology, Case Western Reserve University, Cleveland, OH, USA; and ‡ Department of Psychiatry and Neurology, Asahikawa Medical College, Asahikawa, Japan (Received 2 September 1998; Revised 30 November 1998; Accepted 7 January 1999) Abstract—One of the most striking features of Alzheimer disease (AD) is an accumulation of iron in neurofibrillary tangles and senile plaques. Intriguingly, this iron is found as both iron (II) and iron (III) and is redox-active. To address the issue of whether such iron participates in redox cycling, it was essential to investigate how iron (II) accumulates, since oxidation of iron (II) can lead to the generation of reactive oxygen species. To begin to address this issue, here we investigated ceruloplasmin, a key protein involved in the regulation of the redox state of iron by converting iron (II) to iron (III). Cases of AD and age-matched controls, obtained at autopsy with similar postmortem intervals, display similar levels of ceruloplasmin immunoreactivity that is mainly confined to neurons. However, in marked contrast, cases of AD show a significant increase in ceruloplasmin within the neuropil determined by immunoblot analysis of tissue homogenates as well as a generalized increased neuropil staining. Together, these findings suggest that neuronal induction of ceruloplasmin is feeble in AD, even while there is an increase in tissue ceruloplasmin. Therefore, a failure of neuronal ceruloplasmin to respond to iron may be an important factor that then leads to an accumulation of redox-active iron in neurons in AD. © 1999 Elsevier Science Inc. Key words—Alzheimer disease, Amyloid-, Ceruloplasmin, Copper, Free radicals, Iron, Neurofibrillary tangles, Oxidative stress, Senile plaques. INTRODUCTION Oxidative stress and injury from reactive oxygen species are important pathogenic factors in a variety of age- associated diseases, including many common neurode- generative diseases such as Alzheimer disease (AD) [1–3]. One striking oxidative abnormality in AD is an increase in redox-active iron associated with neurofibril- lary tangles and senile plaques, the primary lesions of the disease. The significance of such iron accumulation in AD is shown by the concurrent accumulation of transi- tion metal-dependent [4] oxidative damage to lipids [5,6] and protein [7,8]. Ceruloplasmin, a 132kDa blue protein containing 6 atoms of copper, is the major copper transport protein in plasma [9 –12] and contributes to antioxidant defense by scavenging H 2 O 2 [13] and inhibits superoxide- and fer- ritin-induced lipid peroxidation [14,15] as well as cata- lyzing the conversion of iron (II) to iron (III) (ferroxidase activity). Further, peroxynitrite, a product of superoxide and nitric oxide that is increased in AD [16,17], causes copper to be released from ceruloplasmin [18]. Indeed, while a variety of processes and molecules potentiate and are altered by oxidative stress, the metabolism of iron and its interaction with ceruloplasmin appears to be particularly relevant. It is iron (II) that is a potent reactive oxygen catalyst and, alternatively, it is through cerulo- plasmin that the iron (II) is oxidized without reactive oxygen production [19]. An acute phase reactive protein, ceruloplasmin is in- creased during inflammation [20] and, while primarily a plasma protein synthesized in the liver, ceruloplasmin is also expressed in a number of other sites, including the brain [21–23]. Ceruloplasmin can also enter the brain via the plasma when the blood brain barrier is compromised [24]. The importance of ceruloplasmin in disease is ex- Address correspondence to: George Perry, PhD, Institute of Pathol- ogy, Case Western Reserve University, 2085 Adelbert Road, Cleve- land, Ohio 44106, USA; Tel: (216) 368-2488; Fax: (216) 368-8964; E-Mail: gxp7@po.cwru.edu. Free Radical Biology & Medicine, Vol. 26, Nos. 11/12, pp. 1508 –1512, 1999 Copyright © 1999 Elsevier Science Inc. Printed in the USA. All rights reserved 0891-5849/99/$–see front matter PII S0891-5849(99)00016-7 1508