title: Serum amyloid A induces IL-8 secretion through a G protein-coupled receptor, FPRL1/LXA4R.
abstract: Host response to injury and infection is accompanied by a rapid rise in the blood of acute-phase proteins such as serum amyloid A (SAA). Although SAA has been used as a marker for inflammatory diseases, its role in the modulation of inflammation and immunity has not been defined. Human neutrophils respond to SAA with secretion of the proinflammatory cytokines interleukin 8 (IL-8) and, to a lesser extent, tumor necrosis factor alpha (TNF-alpha). The induction of IL-8 secretion by SAA involves both transcription and translation and correlates with activation of nuclear factor kappaB (NF-kappaB). The proximal signaling events induced by SAA include mobilization of intracellular Ca(2+) and activation of the mitogen-activated protein kinases ERK1/2 and p38, both required for the induced IL-8 secretion. Pertussis toxin effectively blocks SAA-induced IL-8 secretion indicating involvement of a Gi-coupled receptor. Overexpression of FPRL1/LXA4R in HeLa cells results in a significant increase of the expression of NF-kappaB and IL-8 luciferase reporters by SAA, and an antibody against the N-terminal domain of FPRL1/LXA4R inhibits IL-8 secretion. Lipoxin A4, which binds to FPRL1/LXA4R specifically, decreases SAA-induced IL-8 secretion significantly. Collectively, these results indicate that the cytokine-like property of SAA is manifested through activation of the Gi-coupled FPRL1/LXA4R, which has been known to mediate the anti-inflammatory effects of lipoxin A4. The ability of FPRL1/LXA4R to mediate 2 drastically different and opposite functions suggests that it plays a role in the modulation of inflammatory and immune responses.
authors.affiliation: Department of Pharmacology, College of Medicine, University of Illinois, Chicago 60012, USA.
authors.forename: Rong
authors.initials: R
authors.lastname: He
authors.forename: Hairong
authors.initials: H
authors.lastname: Sang
authors.forename: Richard D
authors.initials: RD
authors.lastname: Ye
mesh_terms: D001053:Apolipoproteins / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D015870:Gene Expression; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism*; D048748:MAP Kinase Kinase Kinase 3; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology; D014176:Protein Biosynthesis; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D044042:Receptors, Formyl Peptide; D044067:Receptors, Lipoxin; D000685:Serum Amyloid A Protein / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D001053:Apolipoproteins; C105101:FPR2 protein, human; D020672:I-kappa B Proteins; D016209:Interleukin-8; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D011956:Receptors, Cell Surface; D044042:Receptors, Formyl Peptide; D044067:Receptors, Lipoxin; D000685:Serum Amyloid A Protein; D000072000:NF-KappaB Inhibitor alpha; D003609:Dactinomycin; D004247:DNA; D003513:Cycloheximide; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048748:MAP Kinase Kinase Kinase 3; D020930:MAP Kinase Kinase Kinases; C482625:MAP3K3 protein, human; D002118:Calcium