Fig. 5

Relevant mechanisms of RA In RA, reduced PNS activity can inhibit the vagus pathway, contributing to the formation of inflammatory lesions. The overactivated SNS, as well as sema3C, sema3F, and TNF secreted by macrophages play important roles in the reduction in sympathetic nerve fibers. Then, the concentration of NE is decreased. Decreased NE promotes the secretion of IL-22 and IL-17 by Th17 cells. In addition, NE can activate α-AR and reduce the expression of β-AR. The latter inhibits the β2-AR-cAMP-PKA pathway and suppresses NE and β-AR binding to Gαs-coupled proteins by transforming Gαs to Gαi. All these processes are beneficial to the formation and persistence of inflammation in RA