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In Situ Oxidative Catalysis by Neurofibrillary Tangles and Senile Plaques in Alzheimer’s Disease
Author(s) -
Sayre Lawrence M.,
Perry George,
Harris Peggy L. R.,
Liu Yahua,
Schubert Kathryn A.,
Smith Mark A.
Publication year - 2000
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2000.0740270.x
Subject(s) - senile plaques , chemistry , oxidative stress , redox , deferoxamine , biochemistry , alzheimer's disease , reactive oxygen species , antioxidant , oxidative phosphorylation , biophysics , pathology , disease , biology , inorganic chemistry , medicine
There is a great deal of evidence to support a pathogenic role of oxidative stress in Alzheimer’s disease (AD), but the sources of reactive oxygen species have not been directly demonstrated. In this study, using a novel in situ detection system, we show that neurofibrillary tangles and senile plaques are major sites for catalytic redox reactivity. Pretreatment with deferoxamine or diethylenetriaminepentaacetic acid abolishes the ability of the lesions to catalyze the H 2 O 2 ‐dependent oxidation of 3,3′‐diaminobenzidine (DAB), strongly suggesting the involvement of associated transition metal ions. Indeed, following chelated removal of metals, incubation with iron or copper salts reestablished lesion‐dependent catalytic redox reactivity. Although DAB oxidation can also detect peroxidase activity, this was inactivated by H 2 O 2 pretreatment before use of DAB, as shown by a specific peroxidase detection method. Model studies confirmed the ability of certain copper and iron coordination complexes to catalyze the H 2 O 2 ‐dependent oxidation of DAB. Also, the microtubule‐associated protein τ, as an in vitro model for proteins relevant to AD pathology, was found capable of adventitious binding of copper and iron in a redox‐competent manner. Our findings suggest that neurofibrillary tangles and senile plaques contain redox‐active transition metals and may thereby exert prooxidant or possibly antioxidant activities, depending on the balance among cellular reductants and oxidants in the local microenvironment.