Endothelial cell activation by leukocyte microparticles.
The ability of polymorphonuclear leukocytes (PMNs) to modulate endothelial cell (EC) activation was investigated. Adding PMNs to cultured HUVECs resulted in a release of IL-6 (888 +/- 71 pg/ml, a 35-fold increase over release by the two cell types alone) and IL-8 (45.2 +/- 14.5 ng/ml, a 6.4-fold over PMN release alone and a 173-fold increase over EC release alone). In contrast, the release of TNF-alpha, IL-1beta, and platelet-derived growth factor was not affected by the EC-PMN coculture. Neutralizing mAbs to ICAM-1 or beta2 integrins or a physical segregation of PMNs and ECs did not reduce EC stimulation. In contrast, cell-free supernatants of PMNs recapitulated EC activation with an 18-fold up-regulation of EC IL-6 mRNA. The filtration of PMN supernatant or PMN pretreatment with metabolic antagonists or membrane cross-linking agents all suppressed EC activation. By flow cytometry, PMNs released in the supernatant, heterogeneous membrane-derived microparticles containing discrete proteins of 28 to 250 kDa as resolved by SDS-PAGE. PMN microparticle formation was enhanced by inflammatory stimuli, including formyl peptide and phorbol ester, and was time-dependent, reaching a plateau after a 1-h incubation from stimulation. Purified PMN microparticles induced EC IL-6 release in a reaction that was quantitatively indistinguishable from that observed with unfractionated PMN supernatant and unaffected by a neutralizing Ab to soluble IL-6R. These findings demonstrate that membrane microparticles released from stimulated PMNs are competent inflammatory mediators to produce EC activation and cytokine gene induction.
Mesri
M
M
Department of Pathology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06536, USA.
Altieri
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DC
D002450:Cell Communication / Q000276:immunology*; D002478:Cells, Cultured; D018920:Coculture Techniques; D003594:Cytoplasmic Granules / Q000276:immunology; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology*; D006801:Humans; D015850:Interleukin-6 / Q000276:immunology; D009504:Neutrophils / Q000166:cytology / Q000276:immunology*
D015850:Interleukin-6