title: β2 integrin-mediated cell-cell contact transfers active myeloperoxidase from neutrophils to endothelial cells.
abstract: Atherosclerosis and vasculitis both feature inflammation mediated by neutrophil-endothelial cell (EC) contact. Neutrophil myeloperoxidase (MPO) can disrupt normal EC function, although the mechanism(s) by which MPO is transferred to ECs are unknown. We tested the hypothesis that close, β2 integrin-dependent neutrophil-EC contact mediates MPO transfer from neutrophils to ECs. We used sensitive MPO assays and flow cytometry to detect MPO in ECs and demonstrate that ECs acquired MPO when contacted by neutrophils directly but not when ECs and neutrophils were separated in Transwells. The transfer was dependent on neutrophil number, exposure time, and incubation temperature. Transfer occurred in several EC types, increased with endotoxin, was not accompanied by MPO release into the medium, and was not abrogated by inhibiting degranulation to secretagogues. Confocal microscopy showed MPO internalization by ECs with cytoplasmic and nuclear staining. Neutrophils and ECs formed intimate contact sites demonstrated by electron microscopy. Blocking CD11b or CD18 β2 integrin chains, or using neutrophils from CD11b gene-deleted mice, reduced MPO transfer. EC-acquired MPO was enzymatically active, as demonstrated by its ability to oxidize the fluorescent probe aminophenyl fluorescein in the presence of a hydrogen peroxide source. The data suggest an alternative to EC uptake of soluble MPO, namely the cell contact-dependent, β2 integrin-mediated transfer from neutrophils. The findings could be of therapeutic relevance in atherosclerosis and vasculitis.
authors.affiliation: Experimental and Clinical Research Center, Charité Medical Faculty, Berlin, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Jerke
authors.forename: Susanne
authors.initials: S
authors.lastname: Rolle
authors.forename: Bettina
authors.initials: B
authors.lastname: Purfürst
authors.forename: Friedrich C
authors.initials: FC
authors.lastname: Luft
authors.forename: William M
authors.initials: WM
authors.lastname: Nauseef
authors.forename: Ralph
authors.initials: R
authors.lastname: Kettritz
mesh_terms: D000818:Animals; D050197:Atherosclerosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000628:therapy; D039481:CD11b Antigen / Q000235:genetics / Q000378:metabolism; D018821:CD18 Antigens / Q000235:genetics / Q000378:metabolism*; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D015550:Cell Degranulation; D018920:Coculture Techniques; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism*; D009195:Peroxidase / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D014657:Vasculitis / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000628:therapy
chemical_list: D039481:CD11b Antigen; D018821:CD18 Antigens; C509295:ITGAM protein, human; D008070:Lipopolysaccharides; D009195:Peroxidase
keywords: Cell-Cell Interaction; Endothelium; Integrins; Myeloperoxidase; Neutrophil; Vascular Biology