|
Prions Cause Heart Damage in Mouse Study
Brain-wasting diseases that kill by causing sponge-like holes in the brain
are believed to be caused by abnormal forms proteins called prions. Scrapie in
sheep, Creutzfeldt-Jacob disease in humans, mad cow disease in cattle and chronic
wasting disease in deer and elk are all examples of this family of diseases.
A new study shows that laboratory mice infected with the agent that causes scrapie
have high levels of scrapie in their hearts several hundred days after being
infected in their brains. Heart infection could be a new, previously unknown
aspect of this disease.
 |
|
| Damage from prion protein gives the brains of affected
cows a sponge-like appearance. Photo by Dr. Al Jenny, courtesy of the U.S.
Dept. of Agriculture Animal and Plant Health Inspection Service. |
|
Last year, researchers at the Rocky Mountain Laboratories (RML), part of NIH's
National Institute of Allergy and Infectious Diseases (NIAID), collaborated with
researchers at The Scripps Research Institute and learned that scrapie-infected
mice engineered without an "anchor" for the prion protein on the membrane of cells
regularly lived for more than 600 days, ultimately dying of old age. Wild mice
infected with scrapie typically die after about 150 days. In this earlier research,
signs of a prion protein buildup were most prominent near blood vessels in the
mouse brains.
In the new study, published online on July 6, 2006, by the journal Science,
the researchers, with the help of Dr. Kirk Knowlton of the University of California,
San Diego, report a similar prion protein accumulation in heart muscle. They
discovered that this protein buildup decreased the heart's ability to pump blood.
The new research provides cardiologists an animal model in which to study heart
amyloidosis, a family of heart diseases that affect humans, according to Dr.
Bruce Chesebro, an RML virologist and a senior author of the new paper. Amyloidoses
involve waxy protein deposits that stiffen the heart, limit its pumping ability
and typically lead to fatal heart stoppage.
"Although several types of protein are known to form heart amyloid, this is
the first time prion protein amyloid has been found in heart muscle and also
found to cause heart malfunction," says Dr. Chesebro.
Unusually high levels of the abnormal prion protein were also found in blood
of the mice used in the study. In the future, this finding could help scientists
develop a blood-based diagnostic test to identify brain-wasting diseases and
possibly lead to a way to filter or chemically treat blood to remove infectious
prion diseases, says Dr. Chesebro.
|
