Serum amyloid A mediates human neutrophil production of reactive oxygen species through a receptor independent of formyl peptide receptor like-1.
Serum amyloid A (SAA) is one of the acute-phase reactants, a group of plasma proteins that increases immensely in concentration during microbial infections and inflammatory conditions, and a close relationship between SAA levels and disease activity in rheumatoid arthritis (RA) has been observed. RA is an inflammatory disease, where neutrophils play important roles, and SAA is thought to participate in the inflammatory reaction by being a neutrophil chemoattractant and inducer of proinflammatory cytokines. The biological effects of SAA are reportedly mediated mainly through formyl peptide receptor like-1 (FPRL1), a G protein-coupled receptor (GPCR) belonging to the formyl peptide receptor family. Here, we confirmed the affinity of SAA for FPRL1 by showing that stably transfected HL-60 cells expressing FPRL1 were activated by SAA and that the response was inhibited by the use of the FPRL1-specific antagonist WRWWWW (WRW4). We also show that SAA activates the neutrophil NADPH-oxidase and that a reserve pool of receptors is present in storage organelles mobilized by priming agents such as TNF-alpha and LPS from Gram-negative bacteria. The induced activity was inhibited by pertussis toxin, indicating the involvement of a GPCR. However, based on FPRL1-specific desensitization and use of FPRL1 antagonist WRW4, we found the SAA-mediated effects in neutrophils to be independent of FPRL1. Based on these findings, we conclude that SAA signaling in neutrophils is mediated through a GPCR, distinct from FPRL1. Future identification and characterization of the SAA receptor could lead to development of novel, therapeutic targets for treatment of RA.
Björkman
Lena
L
Department of Rheumatology and Inflammation Research, The Sahlgrenska Academy at Göteborg University, Göteborg, Sweden. lena.i.bjorkman@vgregion.se
Karlsson
Jennie
J
Karlsson
Anna
A
Rabiet
Marie-Josèphe
MJ
Boulay
Francois
F
Fu
Huamei
H
Bylund
Johan
J
Dahlgren
Claes
C
D020013:Calcium Signaling / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D018260:Gelsolin / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D019255:NADPH Oxidases / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D015388:Organelles / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D037342:Pertussis Toxin / Q000494:pharmacology; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D044042:Receptors, Formyl Peptide / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled / Q000187:drug effects / Q000502:physiology*; D044067:Receptors, Lipoxin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology; D016897:Respiratory Burst / Q000187:drug effects; D000685:Serum Amyloid A Protein / Q000494:pharmacology / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
C105101:FPR2 protein, human; D018260:Gelsolin; D008070:Lipopolysaccharides; D009842:Oligopeptides; D010446:Peptide Fragments; D019269:Phosphatidylinositol 4,5-Diphosphate; D017382:Reactive Oxygen Species; D044042:Receptors, Formyl Peptide; D043562:Receptors, G-Protein-Coupled; D044067:Receptors, Lipoxin; D011993:Recombinant Fusion Proteins; D000685:Serum Amyloid A Protein; D014409:Tumor Necrosis Factor-alpha; C527698:gelsolin (160-169); C440499:lipopolysaccharide, Escherichia coli O111 B4; C509690:tryptophyl-arginyl-tryptophyl-tryptophyl-tryptophyl-tryptophanamide; D019255:NADPH Oxidases; C022709:superoxide-forming enzyme; D037342:Pertussis Toxin