Affiliations: [a] Laboratory of Cellular, Molecular Biology and Neuroscience, Millennium Institute for Advanced Studies (CBB), Faculty of Science, Universidad de Chile, Chile | [b] Department of Neurological Science, Faculty of Medicine, Universidad de Chile, Chile | [c] Department of Psychology, Faculty of Social Science, Universidad de Chile, Chile | [d] Servicio de Neurología, Hospital Salvador, El Salvador | [e] Department of Chemical & Pharmaceutical Sciences, Arturo Prat University, Iquique, Chile
Correspondence:
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Corresponding author: Ricardo B. Maccioni, Department of Psychiatry, Faculty of Medicine, Avenida Salvador 486, 2do Piso, Providencia, Santiago, Chile. Tel.: 562 274 1560; Fax: 562 274 8855; E-mail: rmaccion@manquehue.net.
Abstract: Oxidative stress constitutes a hallmark of Alzheimer's disease (AD). Recent studies also point to redox active metals such as iron, copper and zinc in mediating oxidative stress in AD pathogenesis. However, the reactivity of cerebrospinal fluid (CSF) iron and its possible correlation with the severity of cognitive decline in both Alzheimer's patients and subjects with mild cognitive impairment (MCI) is still unknown. Here we show that different stages of cognitive and functional impairment are associated with changes in CSF reactive iron. In this work, we compared CSF samples from {56} elders, classified into 4 groups according to their scores on the Clinical Dementia Rating scale (CDR). Total CSF iron was analyzed by atomic absorption spectrometry. Redox-active iron was analyzed by a novel fluorimetric assay. One-way ANOVA was used to test differences in mean values, and Newman-Keuls Multiple Comparison Test was used for multi group comparisons. No difference in total CSF iron was found between different groups. Significant amounts of redox-active iron were found in CSF and their levels correlated with the extent of cognitive impairment. Redox-active CSF iron levels increased with the degree of cognitive impairment from normal to MCI subjects, while AD patients showed an abrupt decrease to levels close to zero. Given the relevance of oxidative damage in neurodegeneration, it might be possible to associate the development of cognitive and functional decline with the presence of redox-active iron in the CSF. The decrease in redox-active iron found in AD patients may represent a terminal situation, whereby the central nervous system attempts to minimize iron-associated toxicity.
