Lesions made of a previously unidentified protein have been found in the brains of Alzheimer's patients - a discovery that could shed light on the cause of the disease and offer a means of early diagnosis and perhaps even treatment.
"This is a spectacular lesion, never before seen, that tracks closely with the disease state," said Dr. John Q. Trojanowski, director of the Alzheimer's Disease Center at the University of Pennsylvania and senior author of the study, published in the July issue of the American Journal of Pathology.Alzheimer's is a mind-robbing brain disease that generally strikes people over 65. There is no known cure.
German neurologist Alois Alzheimer described the two primary characteristics of the disease - nerve fiber tangles and plaque coating the nerve cells - in 1907.
The plaque that Alzheimer found is formed by amyloid, or waxy, proteins. Trojanowski's team found new lesions made of different material.
"It occupies as much of the Alzheimer's brain as amyloid plaques do. As a result, we have every reason to suspect that this pathology will be found to play a crucial role in the development and progression of Alzheimer's disease," Trojanowski said.
During the two-year study, the team examined tissue from 81 brains - 40 from Alzheimer's patients and 41 from people who were normal or were victims of other forms of dementia. Some of the latter group showed signs of amyloid plaques, but the patients had not been diagnosed with Alz-hei-mer's.
The new lesions showed up only in brains that contained the amyloid plaques.
"This is quite illuminating and potentially very significant," said Zaven Khachaturian, director of Alzheimer's Association Ronald & Nancy Reagan Research Institute. "If confirmed, this finding may provide new insights to our understanding of the disease."
Khachaturian said the new protein may provide a new "marker" for diagnosis or a target for treatment.
So why wasn't this protein noticed before?
"The staining and chemical dye methods that have been used in the past to label Alzheimer's disease pathologies - primarily silver and thioflavin staining - do not pick up this lesion," said Virginia M.-Y. Lee, a professor of pathology and laboratory medicine who collaborated on the research.
The new plaque and its protein had not been named yet. Trojanowski referred to it as an "AMY-plaque," because an antibody called AMY117 was used in the laboratory to get a look at the new lesion.
"Perhaps one could develop an assay useful for diagnosis early in the disease state," he said. "One of the important goals of Alzheimer's research now is figuring out how to identify the disease years before you encounter problems."
He added: "If we learn more, we could make this protein a target of therapy - find a drug to block its formation."