Juniperonic Acid Incorporation into the Phospholipids of Murine Macrophage Cells Modulates Pro-Inflammatory Mediator Production.

Juniperonic acid (JPA; Δ5,11,14,17-20:4), originally identified in certain gymnosperm seeds, is a rare n-3 polyunsaturated fatty acid (PUFA) with lipid-modulating effects on rats and anti-proliferative effects on fibroblast cell proliferation. However, little is known how JPA exerted its immunosuppressive effect. The objective of this study was to investigate whether JPA inhibited the production of inflammatory mediators through the modulation of cellular phospholipid fatty acid compositions. Using standard lipid chemistry techniques in conjunction with argentated column chromatography, high-purity JPA (> 98%) was extracted, isolated, and purified from Biota kernels. When murine RAW264.7 macrophages were incubated with increasing concentrations of JPA, amounts of cellular phospholipid total PUFA, JPA, and Δ7-docosatetraenoic acid (Δ7-DTA; elongation product of JPA) increased in a dose-dependent manner; however, the proportions of total monounsaturated fatty acid (MUFA) and arachidonic acid (AA) decreased. JPA suppressed the production of nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) and the expression of inducible nitric oxide synthase (iNOS) up to 21, 75, 30, and 44%, respectively. The induction of cyclooxygenase-2 (COX-2) over-expression by JPA could account for the doubling of the PGE2 level. Furthermore, JPA suppressed the expression of phosphorylated mitogen-activated protein kinases (MAPK). In a separate study using the mouse ear edema model, we demonstrated that JPA also significantly suppressed inflammation, as measured by ear thickness and biopsy weight. The anti-inflammatory properties of JPA could be due, in part, to the incorporation of JPA into cellular phospholipids with subsequent modulation of membrane-mediated MAPK signaling.

Incorporation of eicosatrienoic acid exerts mild anti-inflammatory properties in murine RAW264.7 cells.

Eicosatrienoic acid (Δ11,14,17-20:3; ETrA) is a rare naturally occurring n-3 polyunsaturated fatty acid (PUFA). Using murine RAW264.7 cells, the objectives were to determine how ETrA modulated phospholipid fatty acid compositions and the production of pro-inflammatory mediators. Incubation cells with ETrA dose-dependently increased the proportions of phospholipid ETrA and its metabolites to 33 % of the fatty acid total. Incorporation of ETrA also reduced the proportions of total n-6 PUFA and monounsaturated fatty acids (MUFA) by 30 and 60 %, respectively. ETrA suppressed LPS-stimulated nuclear factor-kappa B (NF-κB)-mediated nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression. However, no such suppressive effect on the production of prostaglandin E2 (PGE2), cytokines, or expression of cyclooxygenase-2 (COX-2) was observed. As compared with ETrA, eicosapentaenoic acid (EPA) exerted a more potent anti-inflammatory effect. In conclusion, although ETrA suppresses significant NO synthesis and iNOS expression, this n-3 PUFA was a less potent anti-inflammatory agent than EPA.

PGE2 production is suppressed by chemically-synthesized Δ7-eicosatrienoic acid in macrophages through the competitive inhibition of COX-2.

Δ7-Eicosatrienoic acid (Δ7-ETrA; Δ7,11,14-20:3), an elongation metabolite of pinolenic acid (PNA; Δ5,9,12-18:3), is a rare polyunsaturated fatty acid (PUFA) originally from pine seeds. Incorporation of PNA and Δ7-ETrA into murine macrophages inhibited lipopolysaccharide (LPS)-stimulated prostaglandin E2 (PGE2) production. Due to the lack of availability of the naturally-occurring fatty acid, we synthesized Δ7-ETrA and demonstrated it was capable of suppressing PGE2 production. Using laboratory synthetic techniques involving 2-carbon elongation and argentated column chromatography, Δ7-ETrA was synthesized and isolated. Its identity and purity (>98%) were confirmed by gas chromatography (GC)/GC-mass spectroscopy. Incubation of murine RAW264.7 cells or rat primary peritoneal macrophages with Δ7-ETrA reduced PGE2 production by up to 84%, but slightly down-regulated type-2 cyclooxygenase (COX-2) expression. Δ7-ETrA blocked nuclear factor-kappa B (NF-κB) translocation into nucleus and inactivated mitogen-activated protein kinases (MAPK), however, these results might not directly account for its inhibitory effect. Furthermore, PGE2 production reduced by Δ7-ETrA was highly correlated with the extent of Δ7-ETrA incorporation into cellular phospholipids and appeared to be the result of competition between this unusual fatty acid and arachidonic acid (AA) for COX-2. In conclusion, Δ7-ETrA incorporation suppresses PGE2 production by macrophages through competition between Δ7-ETrA and AA for COX-2.