Rodent of the Week: Can having rheumatoid arthritis protect against Alzheimer’s disease?

A protein released when rheumatoid arthritis is present in the body may reduce the risk of Alzheimer’s disease. The surprise finding in a mouse study may explain why people with rheumatoid arthritis have lower rates of developing Alzheimer’s.

Experts used to think that the drugs that people took for rheumatoid arthritis -- called non-steroidal anti-inflammatory drugs, or NSAIDs -- also reduced the risk of Alzheimer’s disease. That led to clinical trials to see if NSAIDs reduced the risk of Alzheimer’s in a range of patients. However, those trials failed.

The new study, published online Monday in the Journal of Alzheimer’s Disease, suggests a different explanation: A signaling protein called GM-CSF that is released when people have arthritis may stimulate the body to attack and remove amyloid deposits in the brain.

Researchers injected the protein into two groups of mice -- a group that was genetically altered to develop memory problems mimicking Alzheimer’s disease and a group of normal, old-age mice. At the end of 20 days of injections with GM-CSF the memory-impaired mice performed much better on tests measuring their working memory and learning. Their performance was similar to the mice without dementia. The normal mice who received GM-CSF performed slightly better on memory tests than the normal mice who were not injected with the protein. The treated Alzheimer’s mice also had a 50% decrease in beta amyloid plaques in the brains, the hallmark characteristic of Alzheimer’s disease.

“Our findings provide a compelling explanation for why rheumatoid arthritis is a negative risk factor for Alzheimer’s disease,” the lead author of the study, Huntington Potter, professor of molecular medicine at the University of South Florida, said in a news release.

A recombinant form of GM-CSF, called Leukine, is already approved by the Food and Drug Administration for treating certain cancer patients. “Our study, along with the drug’s track record for safety, suggests Leukine should be tested in humans as a potential treatment for Alzheimer’s disease,” said Potter, who is also director of the Florida Alzheimer’s Disease Research Center.

Later this year, the USF Health Byrd Alzheimer’s Institute will launch a pilot-phase clinical trial investigating GM-CSF in patients with mild to moderate Alzheimer’s disease.

-- Shari Roan / Los Angeles Times

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