Phospholipids in oxidized low density lipoproteins perturb the ability of macrophages to degrade internalized macromolecules and reduce intracellular cathepsin B activity

• Published in: Atherosclerosis Vol. 169; no. 2; pp. 215 - 224
• Main Authors: O'Neil, June, Hoppe, George, Hoff, Henry F.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ireland Ltd 01.08.2003; Elsevier
• Subjects: Animals; Atherosclerosis (general aspects, experimental research); Biological and medical sciences; Blood and lymphatic vessels; Cardiology. Vascular system; Cathepsin B; Cathepsin B - antagonists & inhibitors; Cathepsin B - metabolism; Cattle; Cells, Cultured; Chromatography, Gel; Degradation; Endopeptidases - metabolism; Lipoproteins, LDL - analysis; Lipoproteins, LDL - metabolism; Lysosomes - enzymology; Macromolecular Substances; Macrophages; Macrophages, Peritoneal - drug effects; Macrophages, Peritoneal - physiology; Mass spectrometry; Medical sciences; Methylated bovine serum albumin; Mice; Mice, Inbred C57BL; Oxidation-Reduction; Oxidized phospholipids; Phosphatidylcholines - pharmacology; Phospholipids - analysis; Phospholipids - physiology; HNE, 4-hydroxynonenal; Macrophages; DTT, dithiothreitol; Degradation; ACN, acetonitrile; Cathepsin B; TCA, trichloroacetic acid; Methylated bovine serum albumin; LDL, low density lipoprotein; LP, lipoprotein; PC, phosphatidylcholine; Oxidized phospholipids; BSA, bovine serum albumin; malBSA, maleylated bovine serum albumin; vx-LDL, vortexed LDL; MPM, mouse peritoneal macrophages; CLN, Na-CBZ- l-lysine p-nitrophenyl ester; FBS, fetal bovine serum; PBS, phosphate buffered saline; BHT, butylated hydroxytoluene; Acetyl LDL, acetylated LDL; PLPC, 1-palmitoyl 2-linoleoyl phosphatidylcholine; LC/ESI/MS, liquid chromatography/electrospray ionization/mass spectrometry; Mass spectrometry; ox-LDL, oxidized LDL; Pathogenesis; Cysteine endopeptidases; Phospholipid; Cardiovascular disease; Vascular disease; Lipoprotein LDL; Atherosclerosis; Oxidation; Enzyme; Rodentia; Peptidases; Vertebrata; Mammalia; Mouse; Macromolecule; Animal; Hydrolases; Intracellular; Macrophage
• ISSN: 0021-9150; 1879-1484
• DOI: 10.1016/S0021-9150(03)00104-7

Previous studies showed that pre-treatment of mouse peritoneal macrophages (MPM) with oxidized low density lipoprotein (oxLDL) repressed subsequent degradation of oxLDL following uptake. Parallel studies on the activity of the lysosomal protease, cathepsin B in MPM and in vitro indicate that oxLDL also induces a reduction in this activity. We now report that pre-treatment of MPM with the lipid portion of oxLDL induced a reduction both in the degradation of internalized small macromolecules such as maleylated (mal) BSA (30%) or larger ones such as aggregated LDL (100%), and in cellular cathepsin B activity (42%). Binding and uptake of malBSA were not affected. Pre-treatment of MPM for 2 h with oxidized phosphatidylcholine (oxPC) isolated from oxLDL or generated from Cu 2+-treated 1-palmitoyl-2-linoleoyl phosphatidylcholine (oxPLPC), also inhibited 125I-malBSA degradation and reduced cathepsin B activity in MPM and in vitro. Further separation of oxPLPC and oxPC from oxLDL by thin layer chromatography led to the isolation of a polar lipid fraction possessing most of the biological activity in oxPC. Partial characterization of this fraction from oxPLPC using liquid chromatography/electrospray ionization/mass spectrometry indicated that this polar fraction containing fragmentation products of linoleate, was still comprised of multiple bioactive molecular ions. Collectively, these results suggest that specific oxPC fractions in oxLDL are partially responsible for the alterations in MPM metabolism under study induced by oxLDL.