Modification of mononuclear cell function after incubation with albumin-bound unsaturated fatty acids or soybean oil emulsion

Administration of total parenteral nutrition (TPN) with soybean oil emulsion leads to a linoleic acid enrichment of the plasma membrane that may explain an tn vivo activation of mononuclear cells (MNC) seen in our previous studies. Fatty acids from the lipid emulsion may have been accessible to MNC after endocytosis of lipid particles, or by direct uptake of fatty acids after lipoprotein lipase hydrolyzation of the emulsion triglycerides. To resemble the incorporation of fatty acids in vivo, we have modified MNC membrane lipid composition by incubation with different albumin-bound unsaturated fatty acids (UFA) or soybean oil emulsion. After incubation with albumin-bound linoleic and oleic acid: the unstimulated release of superoxide anion was unchanged, while zymosan-stimulated release was 140% (n.s) and 112% (p<0.05) and phorbol-myristate-acetate (PMA)-stimulated release 148% (p<0.05) and 124% (p<0.05) of controls, respectively. Incubation with other UFAs or emulsion did not change superoxide anion release. Unstimulated lymphocyte proliferation increased 3 to 13-fold (p<0.05) after incubation with all UFAs compared to controls, while UFA incubation did not change phytohemagglutinin (PHA) or PMA-stimulated proliferation. Unstimulated lymphocyte proliferation was decreased after incubation with emulsion, while PHA/PMA-stimulated proliferation was unchanged. Increase in membrane fluidity was detectable only after incubation with emulsion. The increased reactivity may have been caused by changes in the lipid environment surrounding membrane-bound enzymes important for signal transduction through the plasma membrane.