title: Oxidized low density lipoprotein acts on endothelial cells in culture to enhance endothelin secretion and monocyte migration.
abstract: Monocyte deposition on the endothelium is the initial step in atherogenesis. Oxidized low density lipoprotein (Ox-LDL) is involved in the development of the fatty streak which progresses to the atherosclerotic lesion. Our interest focussed on the question, does the endothelium react to Ox-LDL to produce humoral substances that might influence the migration of human blood monocytes? Chemotaxis of monocytes was assessed by the modified membrane-filter technique based on the Boyden chamber principle. Exposure of porcine aorta endothelial cells (ECs) to Ox-LDL (100 micrograms/ml) increased the directional migration of monocytes by 25% (p < 0.01) over that of ECs in the absence of Ox-LDL. Radioimmunoassay of the EC culture media revealed the presence of immunoreactive endothelin-1 (ir-ET-1). The endothelin converting enzyme inhibitor, phosphoramidone (10 microM), when incubated together with ECs and Ox-LDL, suppressed the synthesis of ir-ET-1 by 53% (p < 0.05) and the migration decreased by 12% (p < 0.05). Preincubation of monocytes with the ETA receptor-selective antagonist, BQ-123 (1 microM), followed by exposure to ECs plus Ox-LDL, lead to a decrease in their migration by 12% (p < 0.05) compared to monocytes not treated with BQ-123. These results show that Ox-LDL acts on ECs to enhance the synthesis of ir-ET-1 which in turn increases the directional migration of monocytes. Phosphoramidone decreased the synthesis of ir-ET-1 but migration was affected only modestly; monocyte ETA receptor blockade by BQ-123 also suppressed migration toward EC chemoattractants to a small extent. Both results suggest that in addition to ir-ET-1 other chemotactic factors are being released by the ECs; Ox-LDL appears to enhance their release or synthesis.
authors.affiliation: Institute of Clinical Biochemistry, University of Bonn, Germany.
authors.forename: T H
authors.initials: TH
authors.lastname: Achmad
authors.forename: A
authors.initials: A
authors.lastname: Winterscheidt
authors.forename: C
authors.initials: C
authors.lastname: Lindemann
authors.forename: G S
authors.initials: GS
authors.lastname: Rao
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D002634:Chemotaxis, Leukocyte / Q000187:drug effects*; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000032:analysis / Q000096:biosynthesis*; D000072396:Endothelin-Converting Enzymes; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D006020:Glycopeptides / Q000494:pharmacology; D006801:Humans; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008666:Metalloendopeptidases; D009000:Monocytes / Q000187:drug effects* / Q000502:physiology; D010084:Oxidation-Reduction; D010456:Peptides, Cyclic / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D011863:Radioimmunoassay; D013552:Swine
chemical_list: D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D006020:Glycopeptides; D008077:Lipoproteins, LDL; D010456:Peptides, Cyclic; D011480:Protease Inhibitors; C099252:oxidized low density lipoprotein; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; D000072396:Endothelin-Converting Enzymes; C072247:cyclo(Trp-Asp-Pro-Val-Leu); C008890:phosphoramidon