title: The infection of microvascular endothelial cells with ExoU-producing Pseudomonas aeruginosa triggers the release of von Willebrand factor and platelet adhesion.
abstract: An increased plasma concentration of von Willebrand factor (vWF) is detected in individuals with many infectious diseases and is accepted as a marker of endothelium activation and prothrombotic condition. To determine whether ExoU, a Pseudomonas aeruginosa cytotoxin with proinflammatory activity, enhances the release of vWF, microvascular endothelial cells were infected with the ExoU-producing PA103 P. aeruginosa strain or an exoU-deficient mutant. Significantly increased vWF concentrations were detected in conditioned medium and subendothelial extracellular matrix from cultures infected with the wild-type bacteria, as determined by enzyme-linked immunoassays. PA103-infected cells also released higher concentrations of procoagulant microparticles containing increased amounts of membrane-associated vWF, as determined by flow cytometric analyses of cell culture supernatants. Both flow cytometry and confocal microscopy showed that increased amounts of vWF were associated with cytoplasmic membranes from cells infected with the ExoU-producing bacteria. PA103-infected cultures exposed to platelet suspensions exhibited increased percentages of cells with platelet adhesion. Because no modulation of the vWF mRNA levels was detected by reverse transcription-polymerase chain reaction assays in PA103-infected cells, ExoU is likely to have induced the release of vWF from cytoplasmic stores rather than vWF gene transcription. Such release is likely to modify the thromboresistance of microvascular endothelial cells.
authors.affiliation: Departamento de Microbiologia e Imunologia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brasil.
authors.forename: Carla
authors.initials: C
authors.lastname: Freitas
authors.forename: Maria-Cristina
authors.initials: MC
authors.lastname: Assis
authors.forename: Alessandra Mattos
authors.initials: AM
authors.lastname: Saliba
authors.forename: Veronica Maria
authors.initials: VM
authors.lastname: Morandi
authors.forename: Camila Castro
authors.initials: CC
authors.lastname: Figueiredo
authors.forename: Mirian
authors.initials: M
authors.lastname: Pereira
authors.forename: Maria-Cristina
authors.initials: MC
authors.lastname: Plotkowski
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D006801:Humans; D010973:Platelet Adhesiveness; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C111749:pseudomonas exoprotein A protein, Pseudomonas aeruginosa; D014841:von Willebrand Factor