IL-8 specifically binds to endothelial but not to smooth muscle cells.
The proinflammatory cytokine and potent chemoattractant IL-8 is involved in regulation of infectious or inflammatory processes. Human vascular endothelial cells (EC) and smooth muscle cells (SMC) probably contribute to these responses by recognition and/or production of rIL-8. We demonstrate here in competitive binding studies with radiolabeled rIL-8 that EC and fibroblasts, but not SMC, specifically bind IL-8 with low affinity. The binding was not saturated by ligand concentrations up to 80 nM 125I-rIL-8. Unlabeled neutrophil-activating peptide-2 competed the binding of 125I-rIL-8, although less potently than unlabeled rIL-8, as reported previously for polymorphonuclear neutrophils. In contrast, connective tissue-activating peptide III, platelet factor 4, or lysozyme did not reduce binding of 125I-rIL-8 to EC or fibroblasts. In accordance with these binding studies, EC and fibroblasts, but not SMC, expressed human IL-8 receptor type I mRNA. Neither cell type expressed mRNA for IL-8 receptor type II. Stimulation with IL-1 alpha or LPS did not alter the results obtained in PCR or binding studies. Although SMC did not express specific binding sites for IL-8, Western blot experiments showed that IL-1 alpha-, TNF-, or LPS-stimulated SMC released two major immunoreactive isoforms of IL-8 in a time- and dose-dependent manner. The m.w. were similar to IL-8 isoforms released by EC or mononuclear cells. The differential capacity of EC and SMC to produce IL-8 and express IL-8 binding sites indicates that vascular cell-derived IL-8 may contribute to differential regulation of infectious and inflammatory responses in the vessel wall.
Schönbeck
U
U
Department of Immunology and Cell Biology, Forschungsinstitut Borstel, Germany.
Brandt
E
E
Petersen
F
F
Flad
H D
HD
Loppnow
H
H
D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D004730:Endothelium, Vascular / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D011509:Proteoglycans / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018123:Receptors, Interleukin / Q000235:genetics; D023062:Receptors, Interleukin-8A; D001620:beta-Thromboglobulin
D017931:DNA Primers; D016209:Interleukin-8; C061615:PPBP protein, human; D010455:Peptides; D011509:Proteoglycans; D012333:RNA, Messenger; D018123:Receptors, Interleukin; D023062:Receptors, Interleukin-8A; D001620:beta-Thromboglobulin; C009862:connective tissue-activating peptide