Combined treatment with hyaluronan inhibitor Pep-1 and a selective adenosine A2 receptor agonist reduces inflammation in experimental arthritis

Investigations have suggested degradation of native hyaluronan (HA) into small oligosaccharides as being involved in the development and progression of inflammatory diseases, particularly rheumatoid arthritis (RA). Inflammatory responses occur by modulating the TLR4 and 2, and the CD44 natural HA receptor. As reported recently, the adenosine A2 receptor (A(2A)R) plays an important anti-inflammatory role in arthritis. TLR4, TLR2 and CD44 stimulation activate NF-B, which stimulates the production of pro-inflammatory cytokines and other mediators. In contrast, A(2A)R stimulation inhibits NF-B activation. The aim of this study was to investigate the effect of combined treatment of HA inhibitor Pep-1 and a selective A(2A)R agonist (CV-1808) in collagen-induced arthritis (CIA) in mice. Arthritis was induced via intradermal injection of bovine collagen-II. Mice were treated with Pep-1 plus CV-1808 intraperitoneally daily for 20d. CIA increased TLR4, TLR2, CD44 and A(2A)R mRNA expression and the related proteins in the joint cartilage of arthritic mice, where significantly increased concentrations were of TNF-, IL-1-, IL-17, matrix metalloprotease-13 and inducible nitric oxide synthase. Pep-1 with CV-1808 treatment significantly reduced CIA damage and all the up-regulated biochemical parameters. These reductions were supported by microscopic analysis and synovial fluid HA levels.