Alzheimer’s disease is characterized by the formation of plaques between neurons. Scientists have made a new discovery: In the amyloid plaques, deposits of copper and iron in metallic form were detected.
Metallic Deposits in Plaques. Image Courtesy of James Everett, Scientific Reports
Overview
The symptoms of Alzheimer’s disease are due to the degeneration of neurons in the brain. The mechanisms that allow the abnormal formation of amyloid plaques between neurons and the neurofibrillary tangles within neurons have been described for more than a hundred years and are still not understood. The tangles sink neurons from the inside, while the amyloid plaques cause equally damaging inflammation.
Recently, an international team of researchers unraveled a new mystery at the heart of amyloid plaques. Using a state-of-the-art X-ray microscopy technique, they discovered the presence of copper and iron deposits. These two elements are not present in their ionic form, which is found throughout the human body, but in their metallic forms, a detection never before seen in human tissue.
Metal in the brain
The metallic deposits of copper and iron in amyloid plaques measure only a few nanometers. How did they form? Scientists hypothesize several things. The first is the direct reduction of copper and iron ions present in amyloid plaques to metals. They also suggest that an enzyme could catalyze this reduction, as is seen in microorganisms. A similar human reductase could exist in the brain but has not been observed.
In an Alzheimer’s brain, the level of oxidative stress on the cells is very high. The presence of these metal deposits could further increase this stress and thus the degeneration of neurons. Their detection in Alzheimer’s patients could be an additional diagnostic tool, and why not a therapeutic target to calm the brain inflammation associated with this pathology.
References
Biogenic metallic elements in the human brain?
