917-94 Low Density Lipoprotein Stimulates Chemotaxis of Human Monocytes Through a Cyclooxygenase Dependent Pathway

Abstract

Monocyte migration into the vessel wall is an early step in atherogenesis. A number of chemotactic factors for monocytes have been identified, The regulation of the chemotactic response, however, is only poorly understood. We studied the influence of low density lipoprotein (LDL) on chemotactic mobility to a standardized stimulus. Migration of human monocytoid U937 cells was abolished by 30 h incubation in medium with 10% Iipoproteindeficient- serum. Human LDL, VLDL, HDL, or free cholesterol (5–20 μg/ml) were added for 0.5–12 h. At the end of each incubation period, chemotaxis to 1% human serum (modified Boyden chamber), viability (dye exclusion), and cellular cholesterol content (high performance thin layer chromatography) were measured. In the same experimental setting the effects of the pharmacological agents chloroquine (60 μM). indomethacin (20 μg/ml).or acetylsalicylic acid (ASS, 100 μM) on LDL mediated chemotaxis were studied. In some experiments the effect of fatty acids (linoleic acid, arachidonic acid, 10 μM for 2 hours) on restoration of chemotaxis was investigated. Chemotaxis was restored by LDL in a time and dose dependent manner starting at concentrations as low as 5 μg/ml and incubation periods of 30 minutes. Free cholesterol, VLDL, or HDL had no such effect on chemotaxis. Viability and total cholesterol was not different in all groups. Simultaneous incubation of cells with chloroquine, indomethacin or ASS reduced restitution of chemotaxis by LDL by 71%, 82% or 68% respectively. In contrast, the agents had only slight inhibitory effects on chemotactic mobility of control cells which were serum fed. Incubation with linoleic acid showed 60% restoration of chemotaxis, whereas arachidonic acid stimulated chemotaxis response to 140% of positive control. The data are consistent with a novel cyclooxygenase dependent regulation of chemotaxis by LDL.