Mechanism of moxibustion in inhibiting synovial inflammation of rheumatoid arthritis by regulating macrophage polarization based on the Tim-3/Gal-9 signaling pathway

To observe the effects of moxibustion at “Shenshu” (BL23) and “Zusanli” (ST36) on the T-cell immunoglobulin and mucin domain-containing molecule 3/galectin-9 (Tim-3/Gal-9) signaling pathway and macrophage polarization in rats with rheumatoid arthritis (RA), so as to explore the mechanism by which moxibustion ameliorates synovial inflammation in RA.

Male Sprague-Dawley (SD) rats were randomly divided into the blank control, model, moxibustion, and Tim-3 knockdown (Tim-3 KD) group, with 8 rats in each group. The RA model was established by subcutaneous injection of Freund′s complete adjuvant (FCA) into the plantar region. The Tim-3 KD group received a single multi-point subcutaneous injection of Tim-3 lentivirus into the plantar region. Both the moxibustion group and Tim-3 KD group were treated with grain-sized moxibustion at BL23 and ST36, 5 cones per acupoint, once daily, with 6 treatments as one course and 1 day of rest after each course, totaling 3 courses. The thickness of bilateral plantar regions was measured on days 1, 7, 14, 21, 28, and 35 of the experiment. HE staining was used to observe joint pathological changes and pathological scores were evaluated. ELISA was employed to detect the serum contents of interleukin (IL)-4 and vascular endothelial growth factor (VEGF). Immunofluorescence staining was used to determine the expression of Tim-3, Gal-9, and macrophage polarization-related molecules (CD86, CD206) in synovial tissue.

Compared with the blank control group, the model group showed increased thickness of bilateral plantar regions (P<0.01), narrowed joint space, proliferation of synovial and fibrous tissues, elevated scores of synovial hyperplasia, fibrous tissue proliferation, and inflammatory cell infiltration (P<0.01), decreased serum IL-4 content (P<0.05), increased serum VEGF content (P<0.01), up-regulated expression of Tim-3, Gal-9, and CD86 (P<0.01, P<0.05) and down-regulated expression of CD206 (P<0.01) in synovial tissue. Compared with the model group, the moxibustion group exhibited reduced thickness of bilateral plantar regions (P<0.01), alleviated joint space narrowing, decreased proliferation of synovial and fibrous tissues, lowered scores of synovial hyperplasia, fibrous tissue proliferation, and inflammatory cell infiltration (P<0.01), increased serum IL-4 content (P<0.05), decreased serum VEGF content (P<0.01), up-regulated expression of Tim-3, Gal-9, and CD206 (P<0.05, P<0.01) and down-regulated expression of CD86 (P<0.05) in synovial tissue. Compared with the moxibustion group, the Tim-3 KD group showed narrowed joint space, increased score of synovial hyperplasia and inflammatory cell infiltration (P<0.05), decreased serum IL-4 content, and down-regulated expression of Tim-3, Gal-9, and CD206 (P<0.05, P<0.01), along with up-regulated CD86 expression (P<0.05) in synovial tissue.

Moxibustion can ameliorate synovial inflammation in RA rats, and its mechanism may be related to regulating the expression of the Tim-3/Gal-9 signaling pathway, inhibiting M1 macrophage polarization, and promoting M2 macrophage polarization.