Increased lysophosphatidylinositol levels in raw 264.7 macrophage tumor cells during stimulation by a monosaccharide precursor of Escherichia coli lipid

N2,O3-diacylglucosamine-1-phosphate (lipid X), a biosynthetic precursor of E. coli lipid A, has been isolated from a mutant strain of E. coli, and has also been chemically synthesized. These compounds were used to stimulate macrophage tumor cells in culture to examine their effects on animal cell lipid metabolism. The addition of either substance (2-5 μM) to cells that had been labeled for several generations with 32P/sub i/ resulted in a 4-6 fold increase in the labeling of lysophosphatidylinositol (LPI). A decrease in the labeling of phosphatidylinositol was the only other significant change in the phospholipid profile. LPI labeling reached a maximum at 45 minutes after the addition of lipid X, followed by a decline to near control values within 2 hours. This effect was dependent upon extracellular calcium and was inhibited by 95% when cycloheximide (5 μg/ml) was added at the time of stimulation. The addition of lipopolysaccharide (1 μg/ml), phorbol 12-myristate 13-acetate (2 x 10-7 M) and calcium ionophore (10-6 M) also resulted in an increase in LPI labeling. The effect of calcium ionophore on LPI labeling was not inhibited by cycloheximide. The ability of an agent to elicit this response did not correlate with its ability to induce the release of prostaglandins