Novel anti-inflammatory peptides based on chemokine – glycosaminoglycan interactions reduce leukocyte migration and disease severity in a model of rheumatoid arthritis

Inflammation is characterised by the infiltration of leukocytes from the circulation and into the inflamed area. Leukocytes are guided throughout this process by chemokines. These are basic proteins which interact with leukocytes to initiate their activation and extravasation via chemokines receptors. This is enabled through chemokine immobilisation by glycosaminoglycans (GAGs) at the luminal endothelial surface of blood vessels. A specific stretch of basic amino acids on the chemokine, often at the C-terminus, interacts with the negatively charged GAGs which is considered an essential interaction for the chemokine function. Short chain peptides based on this GAG binding region of the chemokines CCL5, CXCL8 and CXCL12γ were synthesised using standard Fmoc chemistry. These peptides were found to bind to GAGs with high affinity which translated into a reduction of leukocyte migration across a cultured endothelial monolayer in response to chemokines. The leukocyte migration was inhibited upon removal of heparan sulphate (HS) from the endothelial surface and was found to reduce the ability of the chemokine and peptide to bind to endothelial cells in binding assays and to human rheumatoid arthritis (RA) tissue. Furthermore, control peptides lacking the basic amino acids showed reduced interaction with HS and no anti-chemotactic ability for leukocytes across an endothelial monolayer. The data suggest that the peptide competes with the wildtype (WT) chemokine for binding to GAGs such as HS and thereby reduces chemokine presentation and subsequent leukocyte migration. Furthermore, the lead peptide based on CXCL8 could reduce the disease severity and serum levels of the pro-inflammatory cytokine TNFα in a murine antigen induced arthritis model. Taken together, evidence is provided for interfering with the chemokine – GAG interaction as a relevant therapeutic approach. The use of site specific sequences of chemokines to target GAGs and compete with WT chemokines is a novel and promising avenue for the field.