The Positively Charged COOH-terminal Glycosaminoglycan-binding CXCL9(74–103) Peptide Inhibits CXCL8-induced Neutrophil Extravasation and Monosodium Urate Crystal-induced Gout in Mice

The ELR−CXC chemokine CXCL9 is characterized by a long, highly positively charged COOH-terminal region, absent in most other chemokines. Several natural leukocyte- and fibroblast-derived COOH-terminally truncated CXCL9 forms missing up to 30 amino acids were identified. To investigate the role of the COOH-terminal region of CXCL9, several COOH-terminal peptides were chemically synthesized. These peptides display high affinity for glycosaminoglycans (GAGs) and compete with functional intact chemokines for GAG binding, the longest peptide (CXCL9(74–103)) being the most potent. The COOH-terminal peptide CXCL9(74–103) does not signal through or act as an antagonist for CXCR3, the G protein-coupled CXCL9 receptor, and does not influence neutrophil chemotactic activity of CXCL8 in vitro. Based on the GAG binding data, an anti-inflammatory role for CXCL9(74–103) was further evidenced in vivo. Simultaneous intravenous injection of CXCL9(74–103) with CXCL8 injection in the joint diminished CXCL8-induced neutrophil extravasation. Analogously, monosodium urate crystal-induced neutrophil migration to the tibiofemural articulation, a murine model of gout, is highly reduced by intravenous injection of CXCL9(74–103). These data show that chemokine-derived peptides with high affinity for GAGs may be used as anti-inflammatory peptides; by competing with active chemokines for binding and immobilization on GAGs, these peptides may lower chemokine presentation on the endothelium and disrupt the generation of a chemokine gradient, thereby preventing a chemokine from properly performing its chemotactic function. The CXCL9 peptide may serve as a lead molecule for further development of inhibitors of inflammation based on interference with chemokine-GAG interactions. Background: Chemokines, such as CXCL8 and CXCL9, drive leukocyte migration to an inflammation site. Results: CXCL9(74–103), derived from CXCL9, lacks leukocyte-attracting activity but competes with CXCL8 for GAG binding and inhibits neutrophil migration in two murine acute inflammation models. Conclusion: Through inhibition of chemokine-GAG interaction, CXCL9(74–103) blocks neutrophil migration. Significance: CXCL9(74–103) may be a lead molecule for development of anti-inflammatory agents.