Fish oil augments macrophage cyclooxygenase II (COX-2) gene expression induced by endotoxin.
BACKGROUND
Fish oil-supplemented diets have anti-inflammatory and immunomodulating effects. Although fish oil is readily incorporated into the cell membrane and influences the production of eicosanoids, the exact mechanism is not clear. This study was designed to investigate the effects of eicosapentaenoic acid (EPA), a major component of fish oil, on macrophage (Mphi) cyclooxygenase (COX) gene expression induced by LPS.


METHODS
RAW 264.7 cells, a mouse Mphi cell line, were grown in EPA-rich media for 24 h. Mphi were washed and exposed to Escherichia coli LPS (10 microg/ml). Membrane lipid profile was determined by gas chromatographic analysis. COX-1 and COX-2 mRNA expressions were determined by Northern blot assays with mouse-specific cDNA probes. PGE(2) production of Mphi was measured by ELISA. Mphi production of COX-2 protein was determined by Western blot assays with an anti-COX-2 antibody.


RESULTS
Incubation in EPA-rich media increased membrane EPA and decreased arachidonic acid (AA) composition. COX-2 mRNA expression was induced by EPA and further augmented by LPS stimulation. EPA also augmented Mphi production of COX-2 protein. In comparison, COX-1 mRNA expression was not affected by either LPS stimulation or EPA incubation. EPA reduced PGE(2) production by LPS-stimulated Mphi. To further support that COX-2 mRNA was regulated by COX product, exogenous PGE(2) was added to Mphi prior to LPS stimulation. PGE(2) reduced COX-2 mRNA of LPS-stimulated Mphi.


CONCLUSIONS
EPA displaces AA and reduces PGE(2) production by LPS-stimulated Mphi. Fish oil inhibition of Mphi PGE(2) production induces COX-2 mRNA expression through a COX-2 product-mediated feedback mechanism.
Lo
C J
CJ
Department of Surgery, University of California, Los Angeles, Los Angeles, California 90095-6904, USA. clo@surgery.medsch.ucla.edu
Chiu
K C
KC
Fu
M
M
Lo
R
R
Helton
S
S
D000818:Animals; D002460:Cell Line; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000096:biosynthesis / Q000494:pharmacology; D004357:Drug Synergism; D015118:Eicosapentaenoic Acid / Q000494:pharmacology; D004731:Endotoxins / Q000494:pharmacology*; D005395:Fish Oils / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects*; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000201:enzymology*; D051379:Mice; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
D004731:Endotoxins; D005395:Fish Oils; D007527:Isoenzymes; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D015118:Eicosapentaenoic Acid; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone