Human neutrophils promote angiogenesis by a paracrine feedforward mechanism involving endothelial interleukin-8.
Neovascularization by sprouting angiogenesis is critical for inflammation-mediated tissue remodeling and wound healing. We report here that human polymorphonuclear neutrophils (PMN) stimulated for 1 h with 100 nM N-formyl-methionyl-leucyl-phenylalanine (fMLP) released a proangiogenic entity that induced sprouting of capillary-like structures in an in vitro angiogenesis assay. The effect was comparable to the response obtained on stimulation with 100 ng/ml basic FGF. The PMN-mediated response was inhibited by neutralizing antibodies against VEGF or IL-8. As measured by ELISA technique, we found that fMLP-activated PMN (5 x 10(6)/ml) released 78 pg/ml IL-8 and 39 pg/ml VEGF within 1 h after stimulation. IL-8 release was blocked by actinomycin D or cycloheximide, but the inhibitors had no effect on VEGF release, suggesting that IL-8 secretion required de novo synthesis whereas VEGF was secreted from preformed stores. Accordingly, RT-PCR analysis revealed that IL-8 mRNA was upregulated on PMN stimulation, whereas the expression of VEGF mRNA was not affected. Moreover, supernatant derived from activated PMN induced upregulation of endothelial IL-8 mRNA expression, suggesting that release of VEGF and IL-8 from activated PMN may activate a paracrine feedforward mechanism involving endothelial IL-8. Moreover, VEGF-induced upregulation of endothelial IL-8 expression as well as sprouting of capillary-like structures was inhibited by a neutralizing anti-IL-8 antibody. These findings suggest that bacteria-derived tripeptides stimulate human PMN to release VEGF and IL-8, which activate endothelial cells and induce angiogenesis by a paracrine feedforward mechanism involving endothelial IL-8 upregulation.
Schruefer
Ruth
R
Department of Physiology, Ludwig-Maximilians-Universität München, Schillerstrasse 44, D-80336 Munich, Germany.
Lutze
Nicola
N
Schymeinsky
Jürgen
J
Walzog
Barbara
B
D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology*; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D018919:Neovascularization, Physiologic / Q000276:immunology*; D018375:Neutrophil Activation / Q000502:physiology; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D019899:Paracrine Communication / Q000276:immunology; D012333:RNA, Messenger / Q000032:analysis; D014471:Umbilical Veins / Q000166:cytology; D015854:Up-Regulation / Q000276:immunology; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
D016209:Interleukin-8; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D009240:N-Formylmethionine Leucyl-Phenylalanine