VIP modulates IL-22R1 expression and prevents the contribution of rheumatoid synovial fibroblasts to IL-22-mediated joint destruction.

Rheumatoid arthritis (RA) and osteoarthritis are two rheumatic diseases whose progression is associated with a chronic synovitis. Fibroblast-like synoviocytes (FLS) have been shown to play a pivotal role in initiating and perpetuating inflammatory and destructive processes in the rheumatoid joint. Recently, the stimulating role of IL-22 has been reported on RA-FLS contribution to joint destruction by means of the increase of proliferation and matrix-metalloproteinase-1 (MMP-1) and alarmin S100A8/A9 production. Besides, mediators potentially present in inflamed joints have been shown to increase the expression of IL-22/IL-22R1 axis, amplifying the capacity of FLS to respond to IL-22 signalling. Since targeting cytokines that govern FLS activation would allow controlling their contribution to synovial inflammation, the present study was designed to analyze the potential immunoregulatory capacity of vasoactive intestinal peptide (VIP) to counterbalance IL-22 effects on FLS behavior. Our results showed that VIP is able to downregulate the augmented expression of IL-22 specific receptor in FLS subjected to a proinflammatory milieu. Moreover, this study revealed the ability of VIP to inhibit the IL-22 stimulatory effects on proliferation as well as on expression of both MMP-1 and alarmins in RA-FLS. The present findings reinforce the potential of this neuroimmunopeptide as a therapeutic agent in rheumatic diseases.