While a diagnosis of rheumatoid arthritis can be scary, new research suggests that there's a silver lining to this inflammatory joint disease. A recent University of Florida study conducted on mice revealed that having rheumatoid arthritis offers protection against Alzheimer's disease, and offered a glimpse into the mechanisms behind this unlikely connection.
What's the link between rheumatoid arthritis and a lowered incidence of Alzheimer's? The researchers say it looks like a protein released when rheumatoid arthritis is present actually "cleans up" amyloid plaques in the brain, the deposits causing the cognitive impairment that is a hallmark of Alzheimer's. As part of the study, the protein, called GM-CSF, was injected daily into two groups of mice. One group was genetically bred to have memory problems and the other group was composed of normal mice. There were also two control groups consisting of memory-impaired mice and normal mice, who received only saline injections. After ten days of GM-CSF injections, the researchers began administering cognitive tests to see how well the mice were able to learn and remember things. They found that the memory-impaired mice had a significant boost in cognitive performance after receiving the GM-CSF injections, and the normal mice had a slight boost as well. None of the mice receiving saline saw any improvement.
Scientists have known for some time that people with rheumatoid arthritis are less likely than others to develop Alzheimer's. Based on their study, the researchers now theorize that when the immune system shifts into high gear, as it does with rheumatoid arthritis, it emits GM-CSF, which goes to work removing amyloid plaques in the brain. In the study, the mice treated with GM-CSF saw a more than 50-percent reduction in the substance that forms amyloid plaques. In addition, they had a higher level of inflammation-reducing immune cells in the brain.
The researchers are hopeful that upcoming clinical trials will allow them to further explore GM-CSF as an effective therapy for Alzheimer's disease.
Sources:
Boyd TD, Bennett SP, Mori T, Governatori N, Runfeldt M, Norden M, Padmanabhan J, Neame P, Wefes I, Sanchez-Ramos J, Arendash GW, et al. (2010). GM-CSF Upregulated in Rheumatoid Arthritis Reverses Cognitive Impairment and Amyloidosis in Alzheimer Mice. Journal of Alzheimer's Disease, 21(2010), 1-10.
