[Effects of heat-reinforcing needling on synovial inflammation and miR-155/TLR4/NF-κB signaling axis in rheumatoid arthritis rabbits with cold syndrome].

OBJECTIVE: To observe the effects of heat-reinforcing needling on synovial inflammation and microRNA-155 (miR-155)/Toll-like receptor 4 (TLR4)/nuclear transcription factor-κB (NF-κB) signaling axis, so as to investigate its anti-inflammatory mechanism in rabbits with cold syndrome of rheumatoid arthritis (RA). METHODS: A total of 36 rabbits were randomly divided into normal, model, agonist, inhibitor, heat-reinforcing needling (HRN) and agonist+heat-reinforcing needling (A+HRN) groups, with 6 rabbits in each group. The RA with cold syndrome model was induced by injecting ovalbumin dry powder and Freund's complete adjuvant combined with cold freezing. Rabbits in agonist group were intraperitoneally injected with miR-155 agomir 4.5 OD; rabbits in the inhibitor group were intraperitoneally injected with miR-155 antagomir 6.1 OD; rabbits in HRN group received heat-reinforcing needling at bilateral "Zusanli" (ST36) for 30 min；rabbits in A+HRN group received the same treatment as agonist group, and 30 min later, received the same treatment as the HRN group; rabbits in the normal and model groups were grasped and fixed in the same way, all groups received continuous treatment once a day for 7 d. After modeling, the knee joints of rabbits were examined by ultrasound, the pain threshold and the circumference were determined. After the interventions, the pain threshold and knee circumference were measured; the pathological morphology of synovial tissue of the knee joints were observed by HE staining; the mRNA levels of miR-155 and suppressor of cytokine signaling protein 1 (SOCS1), the expression levels of SOCS1, TLR4, NF-κB p65, interleukin (IL)-1ß and IL-17A proteins in synovial tissue of knee joints were detected by real-time PCR and Western blot respectively. RESULTS: Compared with the normal group, the pain threshold was significantly decreased (P<0.05), and the knee circumference was significantly increased (P<0.05); the synovial tissue of knee joints showed significant hyperplasia, abundant blood flow signal, joint cavity effusion and obvious inflammatory invasion, the pathological score was significantly increased (P<0.05), the expressions of miR-155 mRNA and IL-1ß, IL-17A, TLR4, NF-κB p65 proteins were significantly increased (P<0.05), the expressions of SOCS1 mRNA and protein were significantly decreased (P<0.05) in the model group. Compared with model group, the pain threshold was significantly increased (P<0.05), the circumference of knee joint was significantly decreased (P<0.05); in synovial tissue, the pathological score was decreased (P<0.05), the expression levels of miR-155 mRNA and IL-1ß, IL-17A, TLR4, NF-κB p65 proteins were significantly decreased (P<0.05), and the expressions of SOCS1 mRNA and protein were significantly increased (P<0.05) in inhibitor group and HRN group, while the above changes in agonist group were reversed (P<0.05). Compared with the agonist group, the pain threshold was significantly increased (P<0.05), the knee circumference was significantly decreased (P<0.05), the synovial pathological score was significantly decreased (P<0.05), the expressions of miR-155 mRNA and IL-1ß, IL-17A, TLR4, NF-κB proteins in synovial tissue were significantly decreased (P<0.05), and the expression levels of SOCS1 mRNA and protein were significantly increased (P<0.05) in A+HRN group. CONCLUSION: The heat-reinforcing needling can increase the pain threshold, reduce the knee circumference and inhibit the inflammatory response in rabbits with RA cold syndrome. The possible mechanism is related to the regulation of miR-155/TLR4/NF-κB signaling axis.