Abstract
Background
Omega-3 fatty acid (ω-3 FA) lipid emulsion has been reported to inhibit nitric oxide
(NO) production and alter inducible nitric oxide synthase (iNOS) protein expression
in lipopolysaccharide (LPS)-stimulated murine macrophages. However, the role of cellular
uptake of l-arginine and iNOS transcription in ω-3 FA emulsion-induced inhibition of NO has not
been explored. In addition, cationic amino acid transporter-2 (CAT-2) can regulate
iNOS activity. The effect of ω-3 FA emulsion on CAT-2 expression is unknown. In the
present study, we hypothesized that ω-3 FA emulsion pretreatment would decrease the
production of NO in LPS-stimulated macrophages and that this effect would occur through
alterations in the cellular uptake of l-arginine and CAT-2 expression, in addition to iNOS expression.
Methods
Confluent immortalized murine macrophages (RAW264.7cells) were incubated with Dulbecco’s
modified Eagle’s medium, ω-3 FA emulsion, or an isoenergetic ω-6 lipid emulsion for
4 h. The cells were washed and then stimulated with LPS (1 μg/mL) or media alone for
12 or 24 h before harvesting. Greiss reagent was used to assess NO production of plate
well supernatants. Cellular uptake of l-arginine was assessed through [3H]-l-arginine. The expression of iNOS and CAT-2 mRNA in harvested RAW264.7 was quantified
by reverse transcriptase-polymerase chain reaction.
Results
NO production of unstimulated RAW264.7 cells was similar in all groups. After LPS
stimulation, ω-3 FA pretreatment at 12 and 24 h produced significantly less NO (P < 0.05) compared with ω-6 FA or media only. ω-3 FA pretreatment at 12 and 24 h resulted
in less l-arginine uptake. iNOS and CAT-2 mRNA was significantly decreased with ω-3 FA pretreatment
compared with ω-6 FA or media-only treatment (P < 0.05).
Conclusions
These experiments demonstrated that, in addition to other anti-inflammatory effects,
ω-3 FA lipid emulsion also significantly lowers NO production and l-arginine transport through altered expression of iNOS and CAT-2 in LPS-stimulated
RAW264.7 macrophage cells.
Keywords
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Article info
Publication history
Published online: March 29, 2012
Accepted:
February 13,
2012
Received in revised form:
January 18,
2012
Received:
August 28,
2011
Identification
Copyright
© 2013 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
