Scientists Find Biogenic Iron Minerals in Amyloid Plaques of Alzheimer’s Patients

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In brains affected by Alzheimer’s disease, an international group of scientists has identified several chemically-reduced iron species, with mineral forms including a magnetic iron oxide called magnetite. Understanding the impact and management of these minerals could lead to more effective future therapies for the neurodegenerative condition.

Everett et al scanned amyloid plaque cores using state-of-the-art X-ray microscopy to determine the chemical properties of the minerals within them. Image credit: University of Warwick.

Everett et al scanned amyloid plaque cores using state-of-the-art X-ray microscopy to determine the chemical properties of the minerals within them. Image credit: University of Warwick.

The team, led by researchers at the University of Warwick and Keele University, characterized iron species associated with the formation of amyloid protein plaques in the human brain — abnormal clusters of proteins in the brain.

The formation of these plaques is associated with toxicity which causes cell and tissue death, leading to mental deterioration in Alzheimer’s patients.

The scientists found that in brains affected by Alzheimer’s, several chemically-reduced iron species including a proliferation of magnetite — which is not commonly found in the human brain — occur in the amyloid protein plaques.

They had previously shown that these minerals can form when iron and the amyloid protein interact with each other.

Thanks to advanced measurement capabilities at synchrotron X-ray facilities in the UK and the United States, they have now shown detailed evidence that these processes took place in the brains of individuals who had Alzheimer’s disease.

The study authors analyzed the magnetic state of the iron species in the amyloid plaques to confirm the presence of various iron minerals including magnetite.

They also made unique observations about the forms of calcium minerals present in the plaques.

The researchers propose that interactions between iron and amyloid that produce the chemically reduced iron species may account for toxicity that contributes to the development and progression of Alzheimer’s.

“Iron is an essential element in the brain, so it is critical to understand how its management is affected in Alzheimer’s disease,” said co-lead author Dr. Joanna Collingwood, from the School of Engineering at the University of Warwick.

“We are excited to have these new insights into how amyloid plaque formation influences iron chemistry in the human brain, as our findings coincide with efforts by others to treat Alzheimer’s disease with iron-modifying drugs.”

The findings are published in the journal Nanoscale.

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James Everett et al. Nanoscale synchrotron X-ray speciation of iron and calcium compounds in amyloid plaque cores from Alzheimer’s disease subjects. Nanoscale, published online April 24, 2018; doi: 10.1039/C7NR06794A