BINDING TO HEPARAN-SULFATE OR HEPARIN ENHANCES NEUTROPHIL RESPONSES TO INTERLEUKIN-8

The interaction of interleukin 8 (IL-8) with heparin was studied by us ing synthetic IL-8 analogs with C- and N-terminal truncations. Elimina tion of the N-terminal region preceding the first cysteine, which cons titutes the IL-8 receptor binding site, did not affect the affinity to heparin-Sepharose. Affinity, however, decreased with progressive trun cation at the C terminus, and no binding was observed when the C-termi nal alpha-helix was eliminated. The effect of heparin and other glycos aminoglycans on IL-8 activity was also tested. When IL-8 was applied t ogether with heparan sulfate, neutrophil chemotaxis in vitro was enhan ced up to 4-fold, and the stimulus-dependent increase in cytosolic fre e Ca2+ increased markedly in both rate and peak value. Heparin had a s imilar 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 wa s not observed when the unrelated chemoattractant fMet-Ile-Phe-Leu was used as the stimulus. Elastase released from stimulated neutrophils w as inhibited by heparin, heparan sulfate, and, to a lesser extent, cho ndroitin sulfate B, confirming previous observations. Taken together, these results suggest that heparan sulfate, which is present on the en dothelial cell surface and in the basement membrane, may have a dual f unction in diapedesis, promotion of IL-8-dependent transmigration of n eutrophils, and protection of the tissue microenvironment from damage by lytic enzymes released from the migrating cells.