Binding to heparan sulfate or heparin enhances neutrophil responses to interleukin 8.

Abstract

The interaction of interleukin 8 (IL-8) with heparin was studied by using synthetic IL-8 analogs with Cand N-terminal truncations. Elimination of the N-terminal region preceding the first cysteine, which constitutes the IL-8 receptor binding site, did not affect the afnity to heparinSepharose. Affinity, however, decreased with progressive truncation at the C terminus, and no binding was observed when the C-terminal a-helix was eliminated. The effect of heparin and other glycosaminoglycans on IL-8 activity was also tested.When IL-8 was applied together with heparan sulfate, neutrophil chemotaxis in vitro was enhanced up to 4-fold, and the stimulus-dependent increase in cytosolic free Ca2+ increased markedly in both rate and peak value. Heparin had a similar effect on the Ca2+ response but did not enhance chemotaxis. The glycosaminoglycans by themselves did not elicit neutrophil responses. Their enhancing effect was restricted to stimulation with IL-8 and was not observed when the unrelated chemoattractant fMet-Ile-Phe-Leu was used as the stimulus. Elastase released from stimulated neutrophils was inhibited by heparin, heparan sulfate, and, to a lesser extent, chondroitin sulfate B, conflrming previous observations. Taken together, these results suggest that heparan sulfate, which is present on the endothelial cell surface and in the basement membrane, may have a dual function in diapedesis, promotion of IL-8-dependent transmigration of neutrophils, and protection of the tissue microenvironment from damage by lytic enzymes released from the migrating cells.

The Epidermal Growth Factor-Seven Transmembrane (EGF-TM7) Receptor CD97 Is Required for Neutrophil Migration and Host Defense

“…This view has been challenged by studies showing that the formation of complexes with the GAG side chains of proteoglycans is generally needed for the in vivo activity of certain chemokines. Previously, it was found that IL-8 must bind GAG to elicit directed neutrophil migration (52). More recently, Li et al (53) could demonstrate that the release of complexes between the cell surface proteoglycan syndecan-1 and the chemokine KC from the epithelium in lung injury is regulated by the matrix metalloproteinase matrilysin (MMP-7).…”

Endothelial cell functions

“…Leukocytes are able to sense several distinct chemokine gradients, hence sustaining directed migration (Foxman et al, 1997). Endothelial cells contain a thick glycocalyx rich in proteoglycans, which serve as anchoring structures for chemokines (Tanaka et al, 1993;Webb et al, 1993). By this mechanism, retention of these molecules at the endothelial surface and presentation to leukocytes can be achieved.…”

Examination of MCP-1 (CCL2) partitioning and presentation during transendothelial leukocyte migration

“…Consequently, the discovery that chemokines are bound by cell surface GAG gave rise to the theory that haptotactic, or cell-bound, concentration gradients provide vectorial information in vivo. 5,47 A variety of experiments have shown that GAG are critically important for chemokine activity, 3,5,23,48 with loss of cell surface heparan sulfate severely limiting chemokine activity. 34,42,49 Soluble chemokine concentration gradients have been shown to direct immune cell migration in vitro.…”

“…2 Interaction with a low-affinity receptor, the cell surface glycosaminoglycans (GAG), is usually mediated via the C-terminus of the protein and often via a specific BBXB motif. 3,4 Chemokines display a range of affinities for the various glycosaminoglycan components of cell surface and extracellular proteoglycans, predominantly binding to the highly sulfated heparin-like species, heparan sulfate. 5 The ability to discriminate between different GAG molecules is believed to reside in paired glutamic acid residues within putative GAG-binding sites.…”