Brain and Joints May Share Similar Inflammatory Mediators in Rheumatoid Arthritis What are the main findings?

Response: It was found that MAO-B was simultaneously involved in joint inflammation and cognitive impairment in RA. First, MAO-B and by-products of MAO-B were present in the joint, which were proportional to inflammation. When the tissues of patients with rheumatoid arthritis were compared with osteoarthritis known to be relatively less inflammatory, MAO-B was aberrantly expressed in rheumatoid arthritis.

Furthermore, it was found that the hippocampal astrocytes cause cognitive impairment in the rheumatoid arthritis animal model. The hippocampal astrocytes were affected by an excessive IL-1beta in the whole body and at this time, the inhibitory neurotransmitter GABA is produced by the MAO-B of astrocytes, which suppresses neurons, causing cognitive impairment. 

Finally, the administration of reversible and selective MAO-B inhibitor, KDS2010, in the rheumatoid arthritis animal model restores both joint inflammation and cognitive impairment. What should readers take away from your report?

Response: Take home message of the report is that the cognitive impairment of rheumatoid arthritis is induced by MAO-B-dependent astrocytic GABA in the hippocampus. Moreover, MAO-B is also the cause of aggravated inflammation of the joints. Therefore, I hope that the newly developed reversible and selective MAO-B inhibitor will become an effective next-generation drug for the treatment of rheumatoid arthritis. What recommendations do you have for future research as a result of this study?

Response: For future research, it is possible to study whether astrocytes in the brain are also involved in psychiatric disorders accompanied by other autoimmune diseases in addition to rheumatoid arthritis. Furthermore, we could investigate whether MAO-B is also involved in inflammation in other cell types. Is there anything else you would like to add? Any disclosures?


Woojin Won, Hyun-Ji Choi, Ji-Young Yoo, Daeun Kim, Tai Young Kim, YeonHa Ju, Ki Duk Park, Hyunbeom Lee, Sang Youn Jung, C. Justin Lee. Inhibiting peripheral and central MAO-B ameliorates joint inflammation and cognitive impairment in rheumatoid arthritis. Experimental & Molecular Medicine, 2022; 54 (8): 1188 DOI: 10.1038/s12276-022-00830-z

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