title: Cyclooxygenase-2 induction in macrophages is modulated by docosahexaenoic acid via interactions with free fatty acid receptor 4 (FFA4).
abstract: Cyclooxygenase-2 (COX-2)-derived prostaglandins are implicated in numerous inflammatory disorders. The purpose of these studies was to examine previously unexplored interactions between COX-2 induction and docosahexaenoic acid (DHA) via the free fatty acid receptor 4 (FFA4) signaling pathway in murine RAW 264.7 cells and peritoneal macrophages challenged with lipopolysaccharide (LPS). DHA dose (IC50=18 μM)- and time-dependently reduced COX-2 expression, without affecting COX-1. DHA (25 μM for 24 h) decreased LPS-induced prostaglandin E2 (PGE2) synthesis by 81%, primarily through reducing COX-2 (60%), as well as down-regulating microsomal prostaglandin E synthase-1 (46%), but independently of peroxisome proliferator-activated receptors. FFA4 knockdown abrogated DHA effects on COX-2 induction, PGE2 production, and interleukin 6 (IL-6) gene expression. In the presence of inhibitors of eicosanoid metabolism via COX-2, 12/15-lipoxygenase and CYP450s (rofecoxib (1 μM), PD146176 (2 μM), or MS-PPOH (20 μM)), DHA was still effective in attenuating COX-2 induction. Moreover, Toll-like receptor 4 signaling via Akt/JNK phosphorylation and p65 nuclear translocation was repressed by DHA-activated FFA4 coupling with β-arrestin 2, which was reversed by FFA4 knockdown. These data support DHA modulation of COX-2 expression and activity, in part, via FFA4, which provides a new mechanistic explanation for some of the anti-inflammatory effects of DHA.
authors.affiliation: 1Department of Biomedical and Molecular Sciences, Queen's University, Botterell Hall, Rm. 433, 18 Stuart St., Kingston, ON, Canada, K7L 3N6. funkc@queensu.ca.
authors.forename: Xinzhi
authors.initials: X
authors.lastname: Li
authors.forename: Ying
authors.initials: Y
authors.lastname: Yu
authors.forename: Colin D
authors.initials: CD
authors.lastname: Funk
mesh_terms: D000818:Animals; D019390:Arrestins / Q000378:metabolism; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D065607:Cytochrome P-450 Enzyme Inhibitors; D015232:Dinoprostone / Q000096:biosynthesis; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D019746:Intramolecular Oxidoreductases / Q000378:metabolism; D007783:Lactones / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D047492:Peroxisome Proliferator-Activated Receptors / Q000378:metabolism; D000071876:Prostaglandin-E Synthases; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D013450:Sulfones / Q000494:pharmacology; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: C000605258:Arrb2 protein, mouse; D019390:Arrestins; D065607:Cytochrome P-450 Enzyme Inhibitors; C498007:FFAR4 protein, mouse; D015850:Interleukin-6; D007783:Lactones; D008070:Lipopolysaccharides; D016859:Lipoxygenase Inhibitors; D047492:Peroxisome Proliferator-Activated Receptors; D043562:Receptors, G-Protein-Coupled; D013450:Sulfones; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; C577686:interleukin-6, mouse; C116926:rofecoxib; D004281:Docosahexaenoic Acids; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D051057:Proto-Oncogene Proteins c-akt; D019892:eIF-2 Kinase; D048670:MAP Kinase Kinase 4; D019746:Intramolecular Oxidoreductases; D000071876:Prostaglandin-E Synthases; D015232:Dinoprostone
keywords: GPR120; inflammation; prostaglandin; ω3 polyunsaturated fatty acids