title: LPS from Neisseria meningitidis is crucial for inducing monocyte- and microparticle-associated tissue factor activity but not for tissue factor expression.
abstract: Neisseria meningitidis causes sepsis with coagulopathy. The present study evaluated the tissue factor (TF)-inducing capacity of bacterial LPS in different presentation forms, i.e. membrane-bound LPS versus purified LPS, and of non-LPS components of N. meningitidis. By using a wild-type N. meningitidis, a mutant N. meningitidis lacking LPS (LPS-deficient N. meningitidis), purified LPS from N. meningitidis and Escherichia coli, we measured TF-expression and TF-activity on human monocytes and microparticles (MPs). The effect of TF-modulators, such as phosphatidylserine (PS), tissue factor pathway inhibitor (TFPI) and recombinant IL-10 (rhIL-10) was investigated. In plasmas from meningococcal patients, fibrinopeptide A (FPA), LPS and IL-10 were quantified. Monocytes and MPs exposed to purified LPS or wild-type N. meningitidis had much higher TF-activity than monocytes and MPs exposed to LPS-deficient N. meningitidis (clot formation assay). Incubation with wild-type N. meningitidis, but also LPS-deficient N. meningitidis, resulted in TF-expression on monocytes (flow cytometry, qRT-PCR). Increased cellular TF-activity is associated with coincident surface-exposure of PS and the number of monocytes positive for both PS and TF was significantly higher for monocytes exposed to wild-type N. meningitidis (7.6%) compared with monocytes exposed to LPS-deficient N. meningitidis (1.8%). Treatment with rhIL-10 reduced monocyte- and MP-associated TF-activity, the number of monocytes positive for both TF and PS, and microvesiculation. Patients with meningococcal septicemia had significantly higher levels of LPS, FPA and IL-10 than patients with distinct meningitis. Our results indicate that LPS from N. meningitidis is crucial for inducing TF-activity, but not for monocyte- and MP-associated TF-expression. TF-activity seems to require coincident expression of TF and PS on monocytes, and LPS induces such double-positive monocytes.
authors.affiliation: Blood Cell Research Unit, Section for Research, Department of Medical Biochemistry, Oslo University Hospital, Ullevål, Norway. reidun.ovstebo@medisin.uio.no
authors.forename: Reidun
authors.initials: R
authors.lastname: Øvstebø
authors.forename: Hans C Dalsbotten
authors.initials: HC
authors.lastname: Aass
authors.forename: Kari Bente Foss
authors.initials: KB
authors.lastname: Haug
authors.forename: Anne-Marie Siebke
authors.initials: AM
authors.lastname: Trøseid
authors.forename: Unni
authors.initials: U
authors.lastname: Gopinathan
authors.forename: Peter
authors.initials: P
authors.lastname: Kierulf
authors.forename: Jens P
authors.initials: JP
authors.lastname: Berg
authors.forename: Petter
authors.initials: P
authors.lastname: Brandtzaeg
authors.forename: Carola E
authors.initials: CE
authors.lastname: Henriksson
mesh_terms: D001777:Blood Coagulation / Q000187:drug effects / Q000276:immunology; D055252:Cell-Derived Microparticles / Q000187:drug effects / Q000276:immunology*; D002478:Cells, Cultured; D004926:Escherichia coli / Q000276:immunology; D004927:Escherichia coli Infections / Q000276:immunology; D005344:Fibrinopeptide A / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D006801:Humans; D016753:Interleukin-10 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000276:immunology*; D008074:Lipoproteins / Q000494:pharmacology; D008585:Meningitis, Meningococcal / Q000097:blood / Q000276:immunology* / Q000382:microbiology; D008589:Meningococcal Infections / Q000097:blood / Q000276:immunology* / Q000382:microbiology; D009000:Monocytes / Q000187:drug effects / Q000276:immunology*; D038541:Neisseria meningitidis, Serogroup B / Q000276:immunology* / Q000378:metabolism; D010718:Phosphatidylserines / Q000494:pharmacology; D013925:Thromboplastin / Q000235:genetics / Q000378:metabolism*
chemical_list: D008070:Lipopolysaccharides; D008074:Lipoproteins; D010718:Phosphatidylserines; C051928:lipoprotein-associated coagulation inhibitor; D016753:Interleukin-10; D005344:Fibrinopeptide A; D013925:Thromboplastin