Toll-like Receptor 4/Nuclear Factor-κB Signaling in Synovial Tissue Is Involved in the Anti-inflammatory Effect of Moxibustion in Rats with Rheumatoid Arthritis

Abstract

To observe the effect of moxibustion on Toll-like receptor 4/nuclear factor-κB (TLR 4/NF-κB) signaling in the synovial tissue of the ankle joint in rats with rheumatoid arthritis (RA), so as to analyze its biological mechanism underlying improvement of RA. Fifty male SD rats were randomly divided into normal control, model, moxibustion, moxibustion ＋ TLR 4 agonist, and moxibustion ＋ TLR 4 antagonist groups (n＝10 rats in each). The RA model was established by subcutaneous injection of Freund's complete adjuvant (FCA, 0.1 mL/rat) at the right hind-paw and by being raised in a wind (air fan blowing), cold (about 10 ℃) and wet (purling) environment for 20 days. After 3 days of modeling, mild moxibustion was applied to bilateral "Shenshu" (BL 23) and "Zusanli" (ST 36) for 20 minutes, once daily for successive 10 days. The TLR 4 agonist (lipopolysaccharide) or TLR 4 antagonist (TAK-242) (1 mg/mL) was separately administered via the tail vein 30 min before performing moxibustion every time in the agonist group and the antagonist group. The expression of NF-κB inhibitory factor ɑ (IκBɑ), IκB kinase complex β(IκKβ), myeloid differentiation factor 88 (MyD 88), TLR 4, and NF-κB p 65 proteins in the synovial tissue of the ankle joint was detected by using Western blot. Following modeling, the girth of the swollen ankle joint was obviously bigger (P<0.01), and the expression levels of IκBɑ， IκKβ， TLR 4, MyD 88, and NF-κB p 65 proteins in the synovial tissue were considerably increased in the model group relevant to the normal control group (P<0.01). After moxibustion intervention, the girth of the swollen ankle joint and the expression levels of IκBɑ， IκKβ， TLR 4, MyD 88, and NF-κB p 65 proteins were significantly down-regulated in the moxibustion, moxibustion ＋TLR 4 agonist, moxibustion＋TLR 4 antagonist groups compared with the model group (P<0.01, P<0.05). Comparison among the 3 moxibustion groups showed that the lowered levels of ankle-joint girth, and IκBɑ， IκKβ， TLR 4, MyD 88, and NF-κB p 65 expression were significantly smaller in the moxibustion＋TLR 4 agonist group than in the simple moxibustion and moxibustion＋TLR 4 antagonist groups (P<0.05，P<0.01). No significant differences were found between the moxibustion and moxibustion＋TLR 4 antagonist groups in the decreased ankle joint girth and IκBɑ， IκKβ， TLR 4, MyD 88, and NF-κB p 65 expression levels (P>0.05), suggesting that activation of TLR 4 reduced the anti-inflammatory effect of moxibustion intervention. Moxibustion can reduce the ankle joint swelling in RA rats, which may be closely associated with its effect in down-regulating the expression of IκBɑ， IκKβ， TLR 4, MyD 88, and NF-κB p 65 proteins and in inhibiting TLR 4/NF-κB signaling in the synovial tissue of the ankle joint.