Expression and localization analyses of the cholinergic anti-inflammatory pathway and α7nAchR in different tissues of rats with rheumatoid arthritis

Rheumatoid arthritis (RA) is a complicated chronic multisystem autoimmune disease, wherein the inflammatory cascade leads to vasospasm and osteoclastogenesis, which ultimately results in bone and cartilage destruction. In this study, we investigated the expression and localization of the alpha-7 nicotinic receptor (alpha 7nAchR) gene CHRNA7 in the heart, liver, spleen, lung, kidney, and joints of the collagen-induced arthritis (CIA) rat model. The CHRNA7 mRNA and protein expression levels in these tissues of rats from CIA and normal groups were analyzed via real-time quantitative polymerase chain reaction (RT-qPCR) and western blotting, respectively. The cellular localization of CHRNA7 protein was determined via immunohistochemistry (IHC) assays. CHRNA7 was expressed at varying levels in different tissues of rats from the groups, among which joints showed significantly higher CHRNA7 expression levels than other tissues (P < 0.05). CIA rats had significantly higher CHRNA7 expression levels in the spleen and joints than the control group rats (P < 0.05). Positive expression signals for CHRNA7 were detected in various tissues of CIA and control group rats, among which strong positive signals were detected in joint fibroblast-like synoviocytes (FLSs), endothelial cells, stromal cells, and macrophages. Our results further confirmed the involvement of the CAP in the onset and development of inflammatory responses in RA, suggesting that CHRNA7 may be a new therapeutic target for RA. This study is of great clinical and theoretical significance for understanding the differential expression of CHRNA7 in various tissues and cholinergic anti-inflammatory pathway (CAP)-targeted treatment of RA.