title: A role for oxidative stress in apoptosis: oxidation and externalization of phosphatidylserine is required for macrophage clearance of cells undergoing Fas-mediated apoptosis.
abstract: Exposure of phosphatidylserine (PS) on the surface of apoptotic cells has been suggested to serve as an important recognition signal for macrophages. In this work we show that triggering of the death receptor Fas on Jurkat cells results in the generation of reactive oxygen species with oxidation and externalization of PS but not of the other major aminophospholipid, phosphatidylethanolamine. These cells were readily ingested by several classes of macrophages, whereas Raji cells, which are defective for Fas-induced PS exposure, remained unengulfed. However, when Raji cells were incubated with the thiol-reactive agent N-ethylmaleimide to induce PS exposure in the absence of other features of apoptosis, these cells were also engulfed by macrophages. Phagocytosis of Fas-triggered Jurkat cells was inhibited by superoxide dismutase and catalase, which prevent oxidation of PS while allowing PS to remain externalized on these cells. Moreover, liposomes containing oxidized PS (PS-OX) were more potent inhibitors of phagocytosis than those containing its nonoxidized counterpart. Finally, enrichment of the plasma membrane of Jurkat or Raji cells, or myeloid leukemic HL-60 cells, with exogenous PS resulted in phagocytic cell clearance, and this process was further enhanced when PS was substituted for by PS-OX. Taken together, our data suggest that the presence of PS-OX in conjunction with nonoxidized PS on the cell surface is an important signal for macrophage clearance of apoptotic cells.
authors.affiliation: Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15260, USA. kagan@pitt.edu
authors.forename: Valerian E
authors.initials: VE
authors.lastname: Kagan
authors.forename: Bettina
authors.initials: B
authors.lastname: Gleiss
authors.forename: Yulia Y
authors.initials: YY
authors.lastname: Tyurina
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Tyurin
authors.forename: Carina
authors.initials: C
authors.lastname: Elenström-Magnusson
authors.forename: Shang-Xi
authors.initials: SX
authors.lastname: Liu
authors.forename: F Behice
authors.initials: FB
authors.lastname: Serinkan
authors.forename: Antonio
authors.initials: A
authors.lastname: Arroyo
authors.forename: Joya
authors.initials: J
authors.lastname: Chandra
authors.forename: Sten
authors.initials: S
authors.lastname: Orrenius
authors.forename: Bengt
authors.initials: B
authors.lastname: Fadeel
mesh_terms: D000276:Adjuvants, Immunologic / Q000378:metabolism; D000328:Adult; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D020169:Caspases / Q000502:physiology; D002374:Catalase / Q000494:pharmacology; D002460:Cell Line; D002478:Cells, Cultured; D018922:HL-60 Cells; D006801:Humans; D019169:Jurkat Cells / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000276:immunology*; D010587:Phagocytosis / Q000187:drug effects / Q000276:immunology*; D010714:Phosphatidylethanolamines / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism / Q000502:physiology*
chemical_list: D000276:Adjuvants, Immunologic; D000975:Antioxidants; D008563:Membrane Lipids; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D019014:fas Receptor; D002374:Catalase; D013482:Superoxide Dismutase; D020169:Caspases