title: Toll-like receptor 4 senses oxidative stress mediated by the oxidation of phospholipids in extracellular vesicles.
abstract: Oxidative stress produced in response to infection or sterile injury activates the innate immune response. We found that extracellular vesicles (EVs) isolated from the plasma of patients with rheumatoid arthritis or secreted from cells subjected to oxidative stress contained oxidized phospholipids that stimulated cells expressing Toll-like receptor 4 (TLR4) in a manner dependent on its co-receptor MD-2. EVs from healthy subjects or reconstituted synthetic EVs subjected to limited oxidation gained the ability to stimulate TLR4-expressing cells, whereas prolonged oxidation abrogated this property. Furthermore, we found that 15-lipoxygenase generated hydro(pero)xylated phospholipids that stimulated TLR4-expressing cells. Molecular modeling suggested that the mechanism of activation of TLR4 by oxidized phospholipids in EVs was structurally similar to that of the TLR4 ligand lipopolysaccharide (LPS). This was supported by experiments showing that EV-mediated stimulation of cells required MD-2, that mutations that block LPS binding to TLR4 abrogated the stimulatory effect of EVs, and that EVs induced TLR4 dimerization. On the other hand, analysis of gene expression profiles showed that genes encoding factors that resolve inflammation were more abundantly expressed in responses to EVs than in response to LPS. Together, these data suggest that EVs act as an oxidative stress-induced endogenous danger signal that underlies the pervasive role of TLR4 in inflammatory diseases.
authors.affiliation: Department of Biotechnology, National Institute of Chemistry, 1000 Ljubljana, Slovenia. Excellent NMR Future Innovation for Sustainable Technologies, Centre of Excellence, 1000 Ljubljana, Slovenia. roman.jerala@ki.si mateja.mancek@ki.si.
authors.forename: Mateja
authors.initials: M
authors.lastname: Manček-Keber
authors.affiliation: Department of Rheumatology, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia.
authors.forename: Mojca
authors.initials: M
authors.lastname: Frank-Bertoncelj
authors.affiliation: Department of Biotechnology, National Institute of Chemistry, 1000 Ljubljana, Slovenia. Excellent NMR Future Innovation for Sustainable Technologies, Centre of Excellence, 1000 Ljubljana, Slovenia.
authors.forename: Iva
authors.initials: I
authors.lastname: Hafner-Bratkovič
authors.affiliation: Department of Biotechnology, National Institute of Chemistry, 1000 Ljubljana, Slovenia.
authors.forename: Anže
authors.initials: A
authors.lastname: Smole
authors.affiliation: Department of Biotechnology, National Institute of Chemistry, 1000 Ljubljana, Slovenia.
authors.forename: Mateja
authors.initials: M
authors.lastname: Zorko
authors.affiliation: Department of Biotechnology, National Institute of Chemistry, 1000 Ljubljana, Slovenia.
authors.forename: Nina
authors.initials: N
authors.lastname: Pirher
authors.affiliation: Division of Rheumatology, Department of Internal Medicine III, Medical University of Vienna, 1090 Vienna, Austria.
authors.forename: Silvia
authors.initials: S
authors.lastname: Hayer
authors.affiliation: Laboratoryof Clinical Biophysics, Faculty of Health Sciences, University of Ljubljana, 1000 Ljubljana, Slovenia.
authors.forename: Veronika
authors.initials: V
authors.lastname: Kralj-Iglič
authors.affiliation: Department of Rheumatology, University Medical Centre Ljubljana, 1000 Ljubljana, Slovenia.
authors.forename: Blaž
authors.initials: B
authors.lastname: Rozman
authors.affiliation: Faculty of Computer and Information Science, University of Ljubljana, 1000 Ljubljana, Slovenia.
authors.forename: Nejc
authors.initials: N
authors.lastname: Ilc
authors.affiliation: Department of Biotechnology, National Institute of Chemistry, 1000 Ljubljana, Slovenia. Department of Animal Science, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia.
authors.forename: Simon
authors.initials: S
authors.lastname: Horvat
authors.affiliation: Department of Biotechnology, National Institute of Chemistry, 1000 Ljubljana, Slovenia. Excellent NMR Future Innovation for Sustainable Technologies, Centre of Excellence, 1000 Ljubljana, Slovenia. roman.jerala@ki.si mateja.mancek@ki.si.
authors.forename: Roman
authors.initials: R
authors.lastname: Jerala
mesh_terms: D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D055252:Cell-Derived Microparticles / Q000235:genetics / Q000276:immunology*; D005260:Female; D057809:HEK293 Cells; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D051218:Lymphocyte Antigen 96 / Q000235:genetics / Q000276:immunology; D008297:Male; D018384:Oxidative Stress / Q000187:drug effects / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000819:agonists / Q000235:genetics / Q000276:immunology*
chemical_list: C495377:LY96 protein, human; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4