A group of scientists say they’ve made a surprising and potentially very important discovery in the brains of two people with Alzheimer’s disease: traces of a particular form of iron and copper deep inside deposits of amyloid plaque, a key marker of the fatal disease. The find raises more questions about how Alzheimer’s develops and may one day point to a new avenue of detecting or treating the underlying dysfunction that causes it.
Iron and copper are elements found in tiny amounts throughout the body, including in the brain. They can serve many important functions, such as being parts of enzymes crucial to our healthy function. Both can come in different oxidation states when they’re part of a compound, meaning they lose or gain electrons. Because some forms of these elements can be dangerous to us, triggering chemical reactions that damage cells, the body usually does a good job of regulating which kinds of iron and copper should be present in our system at any one time.
The regulation of these metals doesn’t seem to work so great in the brains of people with Alzheimer’s disease, though. Those with the disorder develop deposits of misfolded amyloid beta and tau, which are called plaques and tangles, respectively. And some evidence has suggested that toxic forms of iron and copper can be found inside these plaques.
To better understand this possible link, researchers in the UK, Germany, and the U.S. collaborated for a new study, published Wednesday in Science Advances. They used a type of X-ray imaging to analyse the specific chemical composition of plaques taken from the brains of two deceased donors with severe Alzheimer’s. They then found elemental and metallic nanoparticles of iron and copper in the cores of these plaques, meaning that the elements had no oxidation — no electrons missing or added.
Though some species of bacteria, fungi, and plants are known to produce these sorts of metals, it’s the first time this kind of iron and copper has been documented in human tissue, according to the authors. And it may help explain how plaques damage the brain.
“The metallic forms of iron and copper we observed have distinctly different chemical and magnetic properties from their less reactive oxide forms, in which iron and copper are predominately stored in the human body,” senior author Neil Telling, a professor of biomedical nanophysics at Keele University in the UK, told Gizmodo in an email. “The surfaces of metallic copper and iron are highly unstable and readily react with their surroundings, with potential to cause damage to brain cells.”
Of course, potential discoveries like this have to be further studied and validated by other researchers before they should be accepted as true. Even if this is a genuine find, there are many unanswered questions. It’s not yet confirmed, for instance, whether these metals can only be found in the brains of Alzheimer’s patients. Beyond that, their exact origin is still a mystery, though past research from Telling’s team and others does suggest that amyloid plaques can trigger chemical reactions capable of converting less reactive forms of these elements into something more dangerous. Some studies have also raised the possibility that amyloid plaques may be protecting us from these toxic metals, Telling noted, so the relationship between all these factors may be more complicated than we think.
In any case, Telling and his team plan to keep digging further into this. And should this area continue to show promise, it could very well lead to new directions in understanding Alzheimer’s and other neurological disorders linked to rogue proteins, such as Parkinson’s disease.
“This line of research could ultimately lead to new treatments that target metals as well as the amyloid proteins currently under consideration,” he said. “The existence of tiny magnetic iron particles within plaques could also help with diagnosis and to monitor disease progression, as they could in principle be detected by MRI scanners.”