Inflammatory diseases like rheumatoid arthritis cause fatigue because white blood cells — monocytes — infiltrate the brain, Canadian researchers said.
Senior author Dr. Mark Swain of the University of Calgary and colleagues found that in mice with inflamed livers monocytes infiltrated the brain. These findings support previous research demonstrating the presence of immune cells in the brain following organ inflammation, challenging the long-held belief that the blood-brain barrier prevents immune cells from accessing the brain.
Using an experimental model of liver inflammation, our group has demonstrated for the first time the existence of a novel communication pathway between the inflamed liver and the brain,
Swain said in a statement.
Swain and his colleagues found that liver inflammation triggered brain cells called microbial to produce CL2, a chemical that attracts monocytes. When the researchers blocked CL2 signaling, monocytes did not enter the brain despite ongoing inflammation in the liver.
Liver inflammation also stimulated cells in the blood to make an immune chemical. When the researchers blocked the signaling of this immune chemical, microbial produced less CL2, and monocytes stayed out of the brain.
The study, published in The Journal of Neuroscience, found that in the mice with inflamed livers, preventing the entry of monocytes into the brain reduced sickness behaviors; mice showed more mobility and social interaction.
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