title: Attenuated suppression of the oxidative burst by cells dying in the presence of oxidized low density lipoprotein.
abstract: Macrophages ingesting apoptotic cells attenuate inflammatory responses, such as reactive oxygen species (ROS) generation. In atherosclerosis, ongoing inflammation and accumulation of apoptotic/necrotic material are observed, suggesting defects of phagocytes in recognizing or responding to dying cells. Modified lipoproteins such as oxidized LDL (oxLDL) are known to promote inflammation and to interfere with apoptotic cell clearance. Here, we studied the impact of cells exposed to oxLDL on their ability to interfere with the oxidative burst in phagocytes. In contrast to apoptotic cells, cells dying in response to or in the presence of oxLDL failed to suppress ROS generation despite efficiently being taken up by phagocytes. In addition, apoptotic cells, but not oxLDL-treated cells, inhibited phosphorylation of extracellular signal-regulated kinase, which is important for NADPH oxidase activation. oxLDL treatment did not interfere with activation of the antiinflammatory transcriptional regulator peroxisome proliferator-activated receptor gamma by apoptotic cells. Moreover, cells exposed to oxLDL failed to suppress lipopolysaccharide- induced proinflammatory cytokine expression, whereas apoptotic cells attenuated these phagocyte responses. Thus, the presence of oxLDL during cell death impaired the ability of apoptotic cells to act antiinflammatory with regard to oxidative burst inhibition and cytokine expression in phagocytes.
authors.affiliation: Goethe-University, Faculty of Medicine, Institute of Biochemistry I/ZAFES, 60590 Frankfurt, Germany.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Namgaladze
authors.forename: Carla
authors.initials: C
authors.lastname: Jennewein
authors.forename: Stefan
authors.initials: S
authors.lastname: Preiss
authors.forename: Andreas
authors.initials: A
authors.lastname: von Knethen
authors.forename: Bernhard
authors.initials: B
authors.lastname: Brüne
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002460:Cell Line; D018932:Chemokine CCL2 / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics; D019169:Jurkat Cells; D008070:Lipopolysaccharides / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D047495:PPAR gamma / Q000378:metabolism; D010587:Phagocytosis / Q000187:drug effects; D010718:Phosphatidylserines / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D016897:Respiratory Burst / Q000187:drug effects*; D019311:Staurosporine / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D018932:Chemokine CCL2; D004791:Enzyme Inhibitors; D015850:Interleukin-6; D008070:Lipopolysaccharides; D008077:Lipoproteins, LDL; D047495:PPAR gamma; D010718:Phosphatidylserines; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; C099252:oxidized low density lipoprotein; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D019311:Staurosporine