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)-1β 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-1β

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-1β

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-1β

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.