Pain-Free Living

Deficiency in Serotonin Linked to Rheumatoid Arthritis

By Matt Mendenhall

A deficiency in serotonin, the neurotransmitter widely thought to contribute to feelings of happiness and well-being, has been found to worsen rheumatoid arthritis (RA), a chronic disease that causes inflammation, stiffness, and swelling of the joints. The findings may lay the groundwork for new treatment approaches for RA.

A report released March 9 in the American Journal of Pathology shows that experimentally induced RA in serotonin-deficient mice is worse than the disease reported in normal mice and that some effects of RA can be reduced by serotonin or compounds that activate serotonin receptors.

“Our study highlights that [serotonin] has a direct immuno-regulatory role in arthritis,” says Marie-Christine de Vernejoul, an investigator of the study from Université Paris Diderot.

The researchers studied mice with collagen-induced arthritis (CIA), a disease similar to what people with RA experience — cartilage and bone destruction, as well as the activation of cells responsible for bone resorption, known as osteoclasts. The scientists compared the effects of CIA in normal mice to those in mice genetically bred with a deficiency in an enzyme needed for serotonin production in peripheral tissues.

The investigators found that both the number and activity of osteoclasts were higher in serotonin-deficient mice with arthritis. In addition, more bone resorption was detected both at the affected joints and at remote sites.

The research, says de Vernejoul, could lead to treatments that “regulate the immune response in RA and open new perspectives to improve the therapeutic options for patients.”

Matt Mendenhall is the editor of Pain-Free Living.

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