Schizophrenia Drugs for Treatment of Rheumatoid Arthritis
Dopamine receptors play a critical role in the progression of arthritis.
Posted Apr 12, 2020
You probably know someone with either schizophrenia or rheumatoid arthritis; however, it now appears that you probably do not know someone with both of these disorders. Over 22 million people in the world have been diagnosed with schizophrenia and almost 4 million have been diagnosed with rheumatoid arthritis. Given my title, your first question is almost certainly, “What do these two conditions have in common?”
Rheumatoid arthritis is characterized by chronic joint inflammation, bone erosion, and widespread pain. It can also affect many other organs and cause osteoporosis, vasculitis, and cardiovascular diseases as well as lung fibrosis. In contrast, schizophrenia is not associated with any of these conditions. Interestingly, patients with schizophrenia are much less likely to develop rheumatoid arthritis than the rest of the population. Why?
The answer is related to the normal actions of the neurotransmitter dopamine in the human body.
An imbalance in the activity of dopamine neurons in the different parts of the brain likely underlies with many of the symptoms associated with schizophrenia. In the U.S, schizophrenic patients are routinely treated with drugs that antagonize the action of dopamine in the brain. These drugs do not cure schizophrenia; they only reduce the incidence of some of the more debilitating symptoms. These dopamine receptors underlie the linkage between schizophrenia and rheumatoid arthritis.
Dopamine receptors exist outside of your brain. Dopamine receptors live on the surface of your immune cells and synovial cells, two cells that play a critical role in the development and progression of the symptoms of rheumatoid arthritis. Immune T-cells, B-cells, monocytes and Natural Killer cells all express dopamine receptors and all play a role in the degenerative changes associated with rheumatoid arthritis. Animal studies strongly suggest that the drugs currently being used to treat schizophrenia could be beneficial to treat arthritis because of their action at dopamine receptors.
The problem is that scientists are not yet sure which drugs, acting at which of the known dopamine receptors, are going to be most effective. Overall, all that is currently known with any certainty is that dopamine, the so-called pleasure molecule of the brain, has a direct effect on your body’s immune response, bone remodeling, and joint inflammation. Now that scientists are aware of this link between these two very different diseases there is hope that an effective therapeutic strategy for the treatment of rheumatoid arthritis might become a reality.
© Gary L. Wenk, Ph.D. Author of Your Brain on Food, 3rd Edition, 2019 (Oxford University Press)
Capellino S (2020) Dopaminergic agents in rheumatoid arthritis, Journal of Neuroimmune Pharmacology 15:48–56; https://doi.org/10.1007/s11481-019-09850-5