title: Apoptotic cells, at all stages of the death process, trigger characteristic signaling events that are divergent from and dominant over those triggered by necrotic cells: Implications for the delayed clearance model of autoimmunity.
abstract: Current models of autoimmunity suggest that delayed clearance of apoptotic cells leads to the presentation of apoptotic antigens in the context of inflammatory signals, with resultant autoimmunity. These models implicitly assume that, in contrast to early apoptotic cells (that retain membrane integrity), late apoptotic cells (with compromised membranes) act like necrotic cells (which also lack intact membranes), possibly because of the release of proinflammatory intracellular contents. We showed previously that early apoptotic and necrotic cells induce distinct mitogen-activated protein kinase modules in macrophages with which they interact. Exposure to apoptotic cells led to nearly complete inhibition of both basal and macrophage colony-stimulating factor-induced ERK1/2 by macrophages. In contrast, necrotic cells induced ERK1/2. We show here that apoptotic cells also strongly induced both c-Jun N-terminal kinase and p38, whereas necrotic cells had no detectable effect on c-Jun N-terminal kinase and p38. We also compared the signaling events induced in macrophages by exposure to early apoptotic cells, late apoptotic cells, and necrotic cells. The signaling events induced by late apoptotic cells were identical to and just as potent as those induced by early apoptotic cells. Thus, apoptotic cells are functionally equivalent throughout the cell death process, irrespective of membrane integrity. Moreover, the effects of both early and late apoptotic cells on signaling were dominant over those of necrotic cells. These data show that apoptotic cells do not become proinflammatory upon the loss of membrane integrity and are inconsistent with the notion that delayed clearance alone can lead to autoimmunity.
authors.affiliation: Department of Medicine, Division of Nephrology, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
authors.forename: Vimal A
authors.initials: VA
authors.lastname: Patel
authors.forename: Angelika
authors.initials: A
authors.lastname: Longacre
authors.forename: Kevin
authors.initials: K
authors.lastname: Hsiao
authors.forename: Hanli
authors.initials: H
authors.lastname: Fan
authors.forename: Fanyong
authors.initials: F
authors.lastname: Meng
authors.forename: Justin E
authors.initials: JE
authors.lastname: Mitchell
authors.forename: Joyce
authors.initials: J
authors.lastname: Rauch
authors.forename: David S
authors.initials: DS
authors.lastname: Ucker
authors.forename: Jerrold S
authors.initials: JS
authors.lastname: Levine
mesh_terms: D000818:Animals; D017209:Apoptosis; D015551:Autoimmunity; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002468:Cell Physiological Phenomena; D049109:Cell Proliferation; D006801:Humans; D007249:Inflammation; D019169:Jurkat Cells; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D008954:Models, Biological; D009336:Necrosis; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4