Neuroscientists have found twice the amount of aluminum deposits in the brains of Alzheimer’s patients for over 40 years, but have never been able to find the missing link between the exposure to this particular metal and neurodegenerative diseases.
In a cooperative study led by Emery University and involving several other research centers, found that metal ions cause toxicity in brain cells because they are binding themselves to amyloid fibrils. These amyloid fibrils have been linked to the development of such neurodegenerative diseases as Parkinson’s and Alzheimer’s.
The 2007 study was published in the Proceedings of the National Academy of Sciences. It says that copper, zinc and iron ions are found naturally in the brain. They produce an electrical charge by gaining or losing one or more electrons. Metal ions, especially copper, bind to amyloid in several different and specific ways, but only one way can produce toxicity, according to researchers. Typically hard, waxy deposits, amyloids containing mostly protein are found in body tissue.
“There is increasing evidence that links the ions in the brain to amyloid assembly and Alzheimer’s disease,†says David Lynn, Emory chair of chemistry and principal investigator of the study. “Not all amyloid fibrils are toxic,” says Lynn. “Amyloid is made of proteins, and proteins are normally fold into beautiful structures. However, for whatever reason, some misfold, and the resulting misfolded structures, are also beautiful – but sticky. They stick to themselves and then propagate to form fibrils, but only some of the fibrils turn out to be toxic.â€
Little is known as to how these amyloid fibrils are formed, the study does suggest that the exact way amyloid binds to copper ions affects the structure of the fibers, the rate in which they multiply, and what sort of effect they may have on surrounding neurons.Â
Folded proteins normally decompose shortly after being produced. Abnormal folds, however, accumulate and interfere with the brain’s structure and function over a period of time.
The scientists were able to determine the toxicity of the whole amyloid fibrils by examining the chemical properties of individual units of amino acid’s when binding with metal.
“We showed that the activity of this minimal unit actually replicates the activity of the whole fibril on the neuronal cell. And it does so by binding the metal in a specific way,†says Lynn. They also found individual units of amino acids could be assembled from several distinct types of structures. “We found that we could build lots of different types of structures with an individual unit: fettuccine-shaped structures, tubes, vesicles, and so on, not just fibers. And this is remarkable,†says Lynn.
“Like many scientific findings, we know about amyloid because of the diseases it’s associated with rather than because of its benefits,†says Lynn. “However, researchers are also finding situations in which amyloid is beneficial, such as in long-term memory and synapse maintenance in the marine snail.â€
“Our findings now lead us to ask what other types of structures these individual units can make, what exactly happens when the units bind to one another, and whether these individual units are important to neurodegenerative diseases or whether the entire fibril must be involved,†says Lynn.
About the author:
Ron White is a two-time U.S.A. Memory Champion and memory expert. As a memory speaker he travels the world to speak before large groups or small company seminars, demonstrating his memory skills and teaching others how to improve their memory, and how important a good memory is in all phases of your life.
Sources:
Wikipedia – Neurodegeneration: http://en.wikipedia.org/wiki/Neurodegeneration
Center for Neurodegenerative Disease – Emery-led Study links Alzheimer’s to Lead: http://www.emory.edu/news/Releases/Metals_to_Alzheimers1186774207.html
Proceedings of the National Academy of Sciences, Early Edition online during the week of Aug. 6-10, and in the print edition Aug. 14, 2007