Abstract: BACKGROUND: The cholinergic anti-inflammatory pathway is widely involved in the development of rheumatoid arthritis. However, the immunoregulatory mechanism of choline acetyltransferase (ChAT)/α7 nicotinic acetylcholine receptor (α7nAChR)/nuclear factor (NF)-κB signaling pathway in the pathogenesis of rheumatoid arthritis has not been reported.
OBJECTIVE: To investigate the immunoregulatory mechanism of ChAT/α7nAChR/NF-κB signaling pathway in the pathogenesis of rheumatoid arthritis. 
METHODS: Thirty-two female Wistar rats were randomly divided into healthy control group, arthritis model group, vagotomy group and sham operation group, with eight rats in each group. Except for the healthy control group, other groups were treated with bovine type-all collagen and Freund’s complete/incomplete adjuvant to construct the rat arthritis model. After successful molding, the vagus nerve was severed from the left vagus nerve in the neck in the vagotomy group, while only the vagus nerve was isolated in the sham operation group. At 5 weeks after surgery, the body mass, arthritis score, joint swelling degree, pathological changes of the spleen and joint were detected. The levels of interleukin-1, interleukin-6 and tumor necrosis factor-α in serum were detected by ELISA. The mRNA and protein expression levels of ChAT/α7nAChR/NF-κB pathway core genes were detected by qRT-PCR and western blot, respectively, and analyzed by immunohistochemistry. 
RESULTS AND CONCLUSION: Compared with the healthy control group, the body mass of rats in the arthritis model group was significantly decreased (P < 0.05), the arthritis score was significantly increased (P < 0.01), the ankle swelling degree was aggravated, the joint space was reduced with inflammatory cell infiltration, and the white pulp and germinal center of the spleen were enlarged and increased. Moreover, the levels of interleukin-1, interleukin-6 and tumor necrosis factor-α were significantly increased, and the mRNA and protein expressions of α7nAChR, ChAT, IκBα, and NF-κBp50/p65 on the joint surface were also significantly increased in the arthritis model group compared with the healthy control group (P < 0.05, P < 0.01). Compared with the arthritis model group and the sham operation group, the body mass of rats in the vagotomy group was significantly decreased (P < 0.05), the arthritis score was significantly increased (P < 0.05, P < 0.01), the swelling degree of the ankle joint was aggravated with deformity, the joint space disappeared with inflammatory cell infiltration, the white pulp and germinal center of the spleen were enlarged and merged. Compared with the arthritis model group and the sham operation group, the levels of interleukin-1, interleukin-6 and tumor necrosis factor-α were significantly increased in the vagotomy group (P < 0.05, P < 0.01), as well as the mRNA and protein expressions of α7nAChR, ChAT, IκBα, and NF-κBp50/p65 were significantly increased on the joint surface (P < 0.05, P < 0.01). To conclude, the vagus nerve regulates the cholinergic anti-inflammatory pathway and stimulates the ChAT/α7nAChR/NF-κB signaling pathway to participate in the disease progression of rheumatoid arthritis. It indicates that the cholinergic anti-inflammatory pathway may be a potential target for the treatment of rheumatoid arthritis.

Key words: ChAT/α7nAChR/NF-κB, signaling pathway, rheumatoid arthritis, cholinergic anti-inflammatory pathway, the vagus nerve, immunoregulation