RESUMO
OBJECTIVE: To investigate the effect of Chinese herbal formula Ermiao Powder (, EMP) on the expression of cholinergic anti-inflammatory pathway in rats with rheumatoid arthritis (RA). METHODS: Seventy-two rats were randomly divided into 6 groups according to body weight, including normal control group, collageninduced arthritis (CIA) group, three doses EMP groups, and methotrexate (MTX) group (n=12 per group). All of the rats except for those in the normal control group were given multipoint subcutaneous injection of bovine type II collagen to establish a CIA model. Three EMP groups received a high- (4.5 g/kg), medium- (3.0 g/kg), and low- (1.5 g/kg) doses of EMP by intragavage, respectively. MTX group was injected intraperitoneally MTX at 0.9 mg/kg once a week as the positive control. The administration was 3 consecutive weeks. Joint swelling, arthritis index, and body weight changes in different experimental groups of rats were tested. The joint damage was evaluated by masson staining. Quantitative real-time polymerase chain reaction, Western blot, and immunohistochemistry (IHC) were performed to evaluate the expression of CHRNA7, encoding α7 nicotinic acetylcholine receptor in the cholinergic anti-inflammatory pathway, in different tissues and their localization in the spleen and joints. RESULTS: CHRNA7 expression levels were significantly higher in the joints and spleens of CIA group than those in normal control group (both P<0.05). Moreover, the CHRNA7 mRNA and protein levels in the spleen and joints of MTX and three doses of EMP groups were significantly lower than CIA group (all P<0.05). Compared with the MTX group, treatment with low-dose EMP resulted in significant reduction of CHRNA7 mRNA and protein expression levels (P<0.05 or P<0.01). IHC showed positive signals of CHRNA7 in the white pulp and red pulp of the spleens of rats; CHRNA7 was expressed on fibroblast-like synoviocytes, macrophages, and endothelial cells in the joints of rats, and the expression in the joints of low-dose EMP group was significantly lower than that in the CIA group (P<0.01). CONCLUSIONS: Cholinergic anti-inflammatory pathway was involved in the generation of the inflammatory reaction in CIA rats, and EMP exerted therapeutic effect on RA through cholinergic anti-inflammatory pathway.