Mad Cow - Copper Shown
To Influence Prions -
Major Implications
NEW YORK (Reuters Health) - The elements copper and zinc may prompt prions -- the infectious proteins that cause "mad cow disease" and similar fatal neurological diseases -- to change shape, leading to the generation of different strains of prions.
The finding, from a study conducted by Dr. Jonathan D.F. Wadsworth of the Imperial College School of Medicine at St. Mary's in London, UK, and colleagues, suggests that drugs that control copper levels in the brain might be useful in treating prion disorders, such as Creutzfeldt-Jakob disease (CJD), which currently have no known treatment or cure, according to the report in the May issue of Nature Cell Biology.
Prion disorders -- including bovine spongiform encephalopathy, or "mad cow disease" in cattle, CJD in humans, and scrapie in sheep -- are all characterized by progressive neurological degeneration resulting in death.
These diseases are caused by a prion, an abnormal version of a naturally-occurring protein, but researchers have recognized different strains of prions that differ in incubation times, symptoms, and severity of illness.
The researchers came to the conclusion by studying two different human prion types that result in subtypes of CJD. There are four different types of CJD, including a new variant that has appeared in young adults in recent years in the UK and France, and is believed by some experts to be linked to consumption of cattle infected with bovine spongiform encephalopathy.
Wadsworth's team studied types 1 and 2 of classical CJD -- rare disorders that tend to strike in middle-age or later, causing dementia, muscle wasting, and involuntary movements. Type 1 tends to be more aggressive and death often occurs about 2 months after symptoms begin, while people with type 2 tend to survive for about 8 months.
In laboratory studies, the researchers found that one prion type could be converted into another in the presence of the copper or zinc ions.
The finding has "widespread implications" for both the classification and the study of prion diseases in humans and animals, the authors conclude.
SOURCE: Nature Cell Biology 1999;1:55-59.