Lipopolysaccharide-stimulated RAW 264.7 macrophage inducible nitric oxide synthase and nitric oxide production is decreased by an omega-3 fatty acid lipid emulsion.
BACKGROUND
Omega-3 fatty acids (omega-3 FA) have been demonstrated to have anti-inflammatory properties, postulated to occur through several principal mechanisms, including (1) displacement of arachidonic acid from the cellular membrane; (2) shifting of prostaglandin E(2) and leukotriene B(4) production; and (3) molecular level alterations including decreased activation of nuclear factor kappa B and activator protein-1. An additional regulator that is likely associated is the production of nitric oxide (NO) by nitric oxide synthetase. NO is a short-lived free radical involved in many biological functions. However, excessive NO production can lead to complications, suggesting that decreased NO production is a potential target for some inflammatory diseases. We hypothesized that pretreating with an omega-3 FA lipid emulsion would decrease the production of NO in macrophages and that this effect would occur through alterations in inducible nitric oxide synthetase (iNOS).


METHODS
Greiss reagent was used to assess NO production in RAW 264.7 macrophages following omega-3 or omega-6 FA treatment alone or in combination with lipopolysaccharide (LPS) stimulation for 12 h/24 h. iNOS levels were determined by Western blot. Tumor necrosis factor-alpha levels were determined by enzyme-linked immunosorbent assay.


RESULTS
Following LPS-stimulation, omega-3 FA pretreatment at 12 and 24 h produced significantly less NO (P < 0.05) compared to omega-6 FA or media-only conditions. omega-3 FA pretreatment at 12 and 24 h also had less iNOS protein expression compared to omega-6 FA or media-only conditions. Tumor necrosis factor-alpha production was significantly decreased with omega-3 FA treatment compared to omega-6 FA treatment (P < 0.05) after 24 h LPS stimulation.


CONCLUSIONS
These experiments demonstrate that, in addition to other anti-inflammatory effects, omega-3 FA lipid emulsions also significantly lower NO production in LPS-stimulated macrophages through altered iNOS protein expression.
Aldridge
Christopher
C
Department of Surgery, University of Illinois at Chicago, Chicago, Illinois, USA.
Razzak
Anthony
A
Babcock
Tricia A
TA
Helton
W Scott
WS
Espat
N Joseph
NJ
D000818:Animals; D002460:Cell Line; D004655:Emulsions; D015525:Fatty Acids, Omega-3 / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects* / Q000201:enzymology; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D004655:Emulsions; D015525:Fatty Acids, Omega-3; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II