NADPH oxidase-dependent generation of lysophosphatidylserine enhances clearance of activated and dying neutrophils via G2A.
Exofacial phosphatidylserine (PS) is an important ligand mediating apoptotic cell clearance by phagocytes. Oxidation of PS fatty acyl groups (oxPS) during apoptosis reportedly mediates recognition through scavenger receptors. Given the oxidative capacity of the neutrophil NADPH oxidase, we sought to identify oxPS signaling species in stimulated neutrophils. Using mass spectrometry analysis, only trace amounts of previously characterized oxPS species were found. Conversely, 18:1 and 18:0 lysophosphatidylserine (lyso-PS), known bioactive signaling phospholipids, were identified as abundant modified PS species following activation of the neutrophil oxidase. NADPH oxidase inhibitors blocked the production of lyso-PS in vitro, and accordingly, its generation in vivo by activated, murine neutrophils during zymosan-induced peritonitis was absent in mice lacking a functional NADPH oxidase (gp91phox-/-). Treatment of macrophages with lyso-PS enhanced the uptake of apoptotic cells in vitro, an effect that was dependent on signaling via the macrophage G2A receptor. Similarly, endogenously produced lyso-PS also enhanced the G2A-mediated uptake of activated PS-exposing (but non-apoptotic) neutrophils, raising the possibility of non-apoptotic mechanisms for removal of inflammatory cells during resolution. Finally, antibody blockade of G2A signaling in vivo prolonged zymosan-induced neutrophilia in wild-type mice, whereas having no effect in gp91phox-/- mice where lyso-PS are not generated. Taken together, we show that lyso-PS are modified PS species generated following activation of the NADPH oxidase and lyso-PS signaling through the macrophage G2A functions to enhance existing receptor/ligand systems for optimal resolution of neutrophilic inflammation.
Frasch
S Courtney
SC
Department of Pediatrics, National Jewish Health, Denver, Colorado 80206, USA. fraschc@njc.org
Berry
Karin Zemski
KZ
Fernandez-Boyanapalli
Ruby
R
Jin
Hyun-Sun
HS
Leslie
Christina
C
Henson
Peter M
PM
Murphy
Robert C
RC
Bratton
Donna L
DL
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D007249:Inflammation / Q000139:chemically induced / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D008246:Lysophospholipids / Q000235:genetics / Q000378:metabolism*; D017737:Macrophages, Peritoneal / Q000378:metabolism* / Q000473:pathology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D018375:Neutrophil Activation / Q000187:drug effects / Q000235:genetics; D009504:Neutrophils / Q000201:enzymology* / Q000473:pathology; D010084:Oxidation-Reduction / Q000187:drug effects; D010718:Phosphatidylserines / Q000378:metabolism / Q000494:pharmacology; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D015054:Zymosan / Q000633:toxicity
D000906:Antibodies; D018797:Cell Cycle Proteins; C115270:G2A receptor; D008246:Lysophospholipids; D008562:Membrane Glycoproteins; D010718:Phosphatidylserines; D043562:Receptors, G-Protein-Coupled; C025059:lysophosphatidylserine; D015054:Zymosan; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases