title: CD73 regulates anti-inflammatory signaling between apoptotic cells and endotoxin-conditioned tissue macrophages.
abstract: The phagocytosis of apoptotic cells (efferocytosis) shifts macrophages to an anti-inflammatory state through a set of still poorly understood soluble and cell-bound signals. Apoptosis is a common feature of inflamed tissues, and efferocytosis by tissue macrophages is thought to promote the resolution of inflammation. However, it is not clear how the exposure of tissue macrophages to inflammatory cues (e.g., PAMPs, DAMPs) in the early stages of inflammation affects immune outcomes of macrophage-apoptotic cell interactions occurring at later stages of inflammation. To address this, we used low-dose endotoxin conditioning (LEC, 1 ng/ml LPS 18 h) of mouse resident peritoneal macrophages (RPMФ) to model the effects of suboptimal (i.e., non-tolerizing), antecedent TLR activation on macrophage inflammatory responses to apoptotic cells. Compared with unconditioned macrophages (MФ), LEC-MФ showed a significant enhancement of apoptotic cell-driven suppression of many inflammatory cytokines (e.g., TNF, MIP-1β, MCP-1). We then found that enzymatic depletion of adenosine or inhibition of the adenosine receptor A2a on LEC-MФ abrogated apoptotic cell suppression of TNF, and this suppression was entirely dependent on the ecto-enzyme CD73 (AMPadenosine) but not CD39 (ATPAMP), both of which are highly expressed on RPMФ. In addition to a requirement for CD73, we also show that Adora2a levels in macrophages are a critical determinant of TNF suppression by apoptotic cells. LEC treatment of RPMФ led to a ~3-fold increase in Adora2a and a ~28-fold increase in adenosine sensitivity. Moreover, in RAW264.7 cells, ectopic expression of both A2a and CD73 was required for TNF suppression by apoptotic cells. In mice, mild, TLR4-dependent inflammation in the lungs and peritoneum caused a rapid increase in macrophage Adora2a and Adora2b levels, and CD73 was required to limit neutrophil influx in this peritonitis model. Thus immune signaling via the CD73-A2a axis in macrophages links early inflammatory events to subsequent immune responses to apoptotic cells.
authors.affiliation: Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.|David H. Smith Center for Vaccine Biology and Immunology, University of Rochester School of Medicine and Dentistry,Rochester, NY, USA.
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Murphy
authors.affiliation: Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
authors.forename: Samir P
authors.identifier: 0000-0003-2330-4691
authors.initials: SP
authors.lastname: Bhagwat
authors.affiliation: Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.|Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
authors.forename: Joshua C
authors.initials: JC
authors.lastname: Munger
authors.affiliation: Department of Medicine, National Jewish Health and University of Colorado Denver Anschutz Campus, Denver, CO, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Janssen
authors.affiliation: Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.|Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
authors.forename: Terry W
authors.initials: TW
authors.lastname: Wright
authors.affiliation: Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.|David H. Smith Center for Vaccine Biology and Immunology, University of Rochester School of Medicine and Dentistry,Rochester, NY, USA.
authors.forename: Michael R
authors.identifier: 0000-0002-0642-482X
authors.initials: MR
authors.lastname: Elliott
mesh_terms: D015720:5'-Nucleotidase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000241:Adenosine / Q000378:metabolism; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D001081:Apyrase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D054357:Chemokine CXCL10 / Q000378:metabolism; D054426:Chemokine CXCL2 / Q000378:metabolism; D018920:Coculture Techniques; D016207:Cytokines / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity*; D008168:Lung / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000067996:RAW 264.7 Cells; D043705:Receptor, Adenosine A2A / Q000235:genetics / Q000378:metabolism; D043704:Receptor, Adenosine A2B / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D054357:Chemokine CXCL10; D054426:Chemokine CXCL2; D016207:Cytokines; D008070:Lipopolysaccharides; D043705:Receptor, Adenosine A2A; D043704:Receptor, Adenosine A2B; D051197:Toll-Like Receptor 4; D015720:5'-Nucleotidase; D001081:Apyrase; C067869:CD39 antigen; D000241:Adenosine