The Alzheimer's Disease Amyloid Precursor Protein Modulates Copper-Induced Toxicity and Oxidative Stress in Primary Neuronal Cultures

Abstract

The amyloid precursor protein (APP) of Alzheimer's disease can reduce copper (II) to copper (I) in a cell-free system potentially leading to increased oxidative stress in neurons. We used neuronal cultures derived from APP knock-out (APP(-/-)) and wild-type (WT) mice to examine the role of APP in copper neurotoxicity. WT cortical, cerebellar, and hippocampal neurons were significantly more susceptible than their respective APP(-/-) neurons to toxicity induced by physiological concentrations of copper but not by zinc or iron. There was no difference in copper toxicity between APLP2(-/-) and WT neurons, demonstrating specificity for APP-associated copper toxicity. Copper uptake was the same in WT and APP(-/-) neurons, suggesting APP may interact with copper to induce a localized increase in oxidative stress through copper (I) production. This was supported by significantly higher levels of copper-induced lipid peroxidation in WT neurons. Treatment of neuronal cultures with a peptide corresponding to the human APP copper-binding domain (APP142-166) potentiated copper but not iron or zinc toxicity. Incubation of APP142-166 with low-density lipoprotein (LDL) and copper resulted in significantly increased lipid peroxidation compared to copper and LDL alone. Substitution of the copper coordinating histidine residues with asparagines (APP142-166(H147N, H149N, H151N)) abrogated the toxic effects. A peptide corresponding to the zinc-binding domain (APP181-208) failed to induce copper or zinc toxicity in neuronal cultures. These data support a role for the APP copper-binding domain in APP-mediated copper (I) generation and toxicity in primary neurons, a process that has important implications for Alzheimer's disease and other neurodegenerative disorders.

Early Synergy between Aβ42 and Oxidatively Damaged Membranes in Promoting Amyloid Fibril Formation by Aβ40

“…This observation brings to mind the associations previously noted between oxidative stress, metal ions, and the toxicity of A␤ or APP (26,27), and indirect measures of lipid peroxidation that have more recently showed that oxidative stress correlates with amyloid plaque formation in animal models (28), and with disease severity in humans (29). It is also noteworthy that vitamin E, a lipophilic antioxidant, is relatively deficient in the post-mortem brain tissue of patients of Alzheimer's disease (30), and its administration in pharmacological doses appears to slow the clinical progression of disease (31).…”

APP physiological and pathophysiological functions: insights from animal models

“…APP KO mice are viable and fertile but suffer from various defects and abnormalities, such as reduced body and brain weight, decreased size of forebrain commissures, increased frequency and severity of corpus callosum agenesis [28,30], reactive gliosis [28], increased sensitivity to kainate-induced seizures [36], increased copper and iron levels in the cerebral cortex and liver [37,38], upregulated cholesterol and sphingomyelin levels in the brain [39] and decreased plasma glucose levels as well as hyperinsulinemia [40]. Behavioral studies revealed that APP KO mice have decreased locomotor activity, reduced forelimb grip strength and deficits in the Morris water maze task as well as passive avoidance learning [41][42][43].…”

Protection against β-Amyloid-induced Apoptosis by Peptides Interacting with β-Amyloid

“…APP is an integral membrane protein with high affinity for copper (39,40). It has been suggested that APP is involved in neurodevelopment (41) and is essential for neuronal growth (42,43).…”