β-Amyloid (Aβ) 1–42, implicated in the pathogenesis of Alzheimer's disease, forms an oligomeric complex that binds copper at a CuZn superoxide dismutase-like binding site. Aβ·Cu complexes generate neurotoxic H₂O₂ from O₂ through Cu²⁺ reduction, but the reaction mechanism has been unclear. We now report that Aβ1–42, when binding up to 2 eq of Cu²⁺, generates the H₂O₂catalytically by recruiting biological reducing agents as substrates under conditions where the Cu²⁺ or reducing agents will not form H₂O₂ themselves. Cholesterol is an important substrate for this activity, as are vitamin C,l-DOPA, and dopamine (V _maxfor dopamine = 34.5 nm/min, K _m = 8.9 μm). The activity was inhibited by anti-Aβ antibodies, Cu²⁺ chelators, and Zn²⁺. Toxicity of Aβ in neuronal culture was consistent with catalytic H₂O₂ production. Aβ was not toxic in cell cultures in the absence of Cu²⁺, and dopamine (5 μm) markedly exaggerated the neurotoxicity of 200 nm Aβ1–42·Cu. Therefore, microregional catalytic H₂O₂ production, combined with the exhaustion of reducing agents, may mediate the neurotoxicity of Aβ in Alzheimer's disease, and inhibitors of this novel activity may be of therapeutic value.

Increased brain metal levels have been associated with normal aging and a variety of diseases, including Alzheimer's disease (AD). Copper and iron levels both show marked increases with age and may adversely interact with the amyloid-β (Aβ) peptide causing its aggregation and the production of neurotoxic hydrogen peroxide (H₂O₂), contributing to the pathogenesis of AD. Amyloid precursor protein (APP) possesses copper/zinc binding sites in its amino-terminal domain and in the Aβ domain. Here we demonstrate that overexpression of the carboxyl-terminal fragment of APP, containing Aβ, results in significantly reduced copper and iron levels in transgenic mouse brain, while overexpression of the APP in Tg2576 transgenic mice results in significantly reduced copper, but not iron, levels prior to the appearance of amyloid neuropathology and throughout the lifespan of the mouse. Concomitant increases in brain manganese levels were observed with both transgenic strains. These findings, complemented by our previous findings of elevated copper levels in APP knock-out mice, support roles for APP and Aβ in physiological metal regulation.

The importance of transition metals in biological processes has been well established. Copper (Cu) is a transition metal that can exist in oxidised an

Cognitive decline in Alzheimer's disease (AD) involves pathological accumulation of synaptotoxic amyloid-β (Aβ) oligomers and hyperphosphorylated tau. Because recent evidence indicates that glycogen synthase kinase 3β (GSK3β) activity regulates these neurotoxic pathways, we developed an AD therapeutic strategy to target GSK3β. The strategy involves the use of copper- bis (thiosemicarbazonoto) complexes to increase intracellular copper bioavailability and inhibit GSK3β through activation of an Akt signaling pathway. Our lead compound Cu ^II (gtsm) significantly inhibited GSK3β in the brains of APP/PS1 transgenic AD model mice. Cu ^II (gtsm) also decreased the abundance of Aβ trimers and phosphorylated tau, and restored performance of AD mice in the Y-maze test to levels expected for cognitively normal animals. Improvement in the Y-maze correlated directly with decreased Aβ trimer levels. This study demonstrates that increasing intracellular copper bioavailability can restore cognitive function by inhibiting the accumulation of neurotoxic Aβ trimers and phosphorylated tau.

Biometals play an important role in Alzheimer disease, and recent reports have described the development of potential therapeutic agents based on modulation of metal bioavailability. The metal ligand clioquinol (CQ) has shown promising results in animal models and small phase clinical trials; however, the actual mode of action in vivo has not been determined. We now report a novel effect of CQ on amyloid beta-peptide (Abeta) metabolism in cell culture. Treatment of Chinese hamster ovary cells overexpressing amyloid precursor protein with CQ and Cu(2+) or Zn(2+) resulted in an approximately 85-90% reduction of secreted Abeta-(1-40) and Abeta-(1-42) compared with untreated controls. Analogous effects were seen in amyloid precursor protein-overexpressing neuroblastoma cells. The secreted Abeta was rapidly degraded through up-regulation of matrix metalloprotease (MMP)-2 and MMP-3 after addition of CQ and Cu(2+). MMP activity was increased through activation of phosphoinositol 3-kinase and JNK. CQ and Cu(2+) also promoted phosphorylation of glycogen synthase kinase-3, and this potentiated activation of JNK and loss of Abeta-(1-40). Our findings identify an alternative mechanism of action for CQ in the reduction of Abeta deposition in the brains of CQ-treated animals and potentially in Alzheimer disease patients.