Some aspects of IL-8 pathophysiology III: chemokine interaction with endothelial cells

Abstract

Chemokines have been convincingly implicated in driving leukocyte emigration in different inflammatory reactions. However, the cellular and molecular mechanisms of chemokine involvement in leukocyte emigration are not clear. We and others suggested that leukocyte adhesion to the endothelium and transmigration are induced by chemokines immobilized on the endothelial cell surface. This would require the presence of specific chemokine binding sites in this microanatomical location. Using an in situ binding assay we demonstrated the presence of binding sites for interleukin-8 (IL-8) and RANTES, but not monocyte inflammatory protein-1 alpha on the endothelium of postcapillary venules and small veins in human skin. In contrast, venules and veins in various anatomical locations showed dramatically differing IL-8 binding patterns. The subcellular distribution of IL-8 in the venular endothelial cells following its in vivo and ex vivo injections was studied by use of electron microscopy. Our results suggest that IL-8 was internalized by the endothelial cells, transported transcellularly via plasmalemmal vesicles, and released onto the luminal surface where it appeared located preferentially on tips of membrane protrusions. We were unable to study the endothelial IL-8 binding or transport in vitro because all the in vitro propagated endothelial cell lines and primary endothelial cells tested lacked IL-8 binding sites. This includes human umbilical vein endothelial cells (HUVECs), which also did not bind IL-8 in situ. However, HUVECs provided a satisfactory in vitro system to study the secretion of IL-8 by the endothelial cells. Two possible alternative pathways were described: secretion directly from the Golgi apparatus or following storage in Weibel-Palade bodies.

The Duffy Antigen Modifies Systemic and Local Tissue Chemokine Responses following Lipopolysaccharide Stimulation

“…Our data show that the Duffy Ag is involved in the preferential compartmentalization of KC in the plasma. Our findings are also consistent with the hypothesis set forth by Rot and colleagues (31)(32)(33) that endothelial Duffy Ag facilitates chemokine mobilization from the abluminal to luminal direction, as the WT3 KO mice show higher BAL concentrations of MIP-2 at 4 h and KC at 2 h (Fig. 4, A and B).…”

Expression of IFN-Inducible T Cell α Chemoattractant by Human Endothelial Cells Is Cyclosporin A-Resistant and Promotes T Cell Adhesion: Implications for Cyclosporin A-Resistant Immune Inflammation

“…The failure to detect bound I-TAC on cultured EC may be due to low sensitivity of the assay or, alternatively, to masking of the recognition epitope as a result of I-TAC binding to heparan sulfate or other surface proteins. We were also unable to detect bound I-TAC on freshly prepared fragments of umbilical vein treated with IFN-␥ (data not shown), suggesting that lack of detectable binding was not merely due to loss of binding sites on passaged cells (3,31).…”

“…It has been proposed that chemokines bind to the surface of EC through heparan-sulfate interactions (3,27). For example, IL-8, platelet factor 4 (PF4), macrophage-inflammatory protein-1␤, and IP-10 have all been shown in vitro to bind to EC (2,(27)(28)(29)(30)(31). Given the similarities between I-TAC and IP-10, it seems likely that I-TAC would also be secreted and captured at the EC surface.…”

Monomeric variants of IL-8: Effects of side chain substitutions and solution conditions upon dimer formation

“…While there is reason to think that these interactions are physiologically relevant (Rot et al, 1996), the specific consequences of IL-8 binding to these targets in vivo has not been established. For the DARC receptor, however, chemokine-binding is mediated in part through interactions with the Arg residue of the ELR motif as well as through interactions elsewhere within the structure (Hesselgesser et al, 1995).…”