Acupuncture ameliorates synovitis in mice with collagen-induced arthritis by repressing ferroptosis via butyric acid

It has been reported that the symptoms of rheumatoid arthritis (RA) can be ameliorated by acupuncture, an external treatment of traditional Chinese medicine. However, the immune mechanism underlying its action is elusive. Accordingly, this study investigated the role and mechanism of manual acupuncture (MA) in collagen-induced arthritis (CIA) in mice. The results demonstrated that MA or NaB treatment reduced Articular Index scores and right paw thickness and alleviated synovial inflammation and cartilage damage. MA or NaB treatment altered the content and relative abundance of short-chain fatty acids, particularly butyric and propionic acids, in feces. Additionally, MA or NaB treatment elevated SCD1, SREBP1, and GPX4 protein expression in synovial tissues and GSH-px contents in serum while decreasing ROS fluorescence intensity and MDA contents in peripheral blood. A linear correlation was found between the relative expression of SCD1 and SREBP1 in synovial tissues and the contents of propionic acids and butyric acids in feces, as well as between the contents of propionic acids and butyric acids. In summary, MA regulates butyric acids to inhibit ferroptosis, therefore suppressing inflammation in RA.