Copper in the brain and Alzheimer's disease

Alzheimer's disease (AD) is the most common form of neurodegenerative disease. The brain is particularly vulnerable to oxidative damage induced by unregulated redox-active metals such as copper and iron, and the brains of AD patients display evidence of metal dyshomeostasis and increased oxidative stress. The colocalisation of copper and amyloid beta (A beta) in the glutamatergic synapse during NMDA-receptor-mediated neurotransmission provides a microenvironment favouring the abnormal interaction of redox-potent A beta with copper under conditions of copper dysregulation thought to prevail in the AD brain, resulting in the formation of neurotoxic soluble A beta oligomers. Interactions between A beta oligomers and copper can further promote the aggregation of A beta, which is the core component of extracellular amyloid plaques, a central pathological hallmark of AD. Copper dysregulation is also implicated in the hyperphosphorylation and aggregation of tau, the main component of neurofibrillary tangles, which is also a defining pathological hallmark of AD. Therefore, tight regulation of neuronal copper homeostasis is essential to the integrity of normal brain functions. Therapeutic strategies targeting interactions between A beta, tau and metals to restore copper and metal homeostasis are discussed.