Oxidized low‐density lipoprotein is cytotoxic to human monocyte‐macrophages: protection with lipophilic antioxidants

Abstract

Human monocyte-macrophages were incubated for 24 h with low-density Hpoprotein (LDL) which had been previously oxidized for varying periods up to 24 h with copper ions, in the presence or absence of DL-ot-tocopberol or probucol. The release of radioactivity from cells preloaded with tritiated adenine was used as an assay of toxicity. Toxicity of oxidized LDL increased with duration of copper oxidation and with increasing evidence of lipid oxidation, measured by assay of thiobarbituric acid-reactive substances and by gas chromatography. Oxidation and toxicity were inhibited by DL-a-tocopherol (200/tM) and probucol (50 riM).

Cytotoxic and chemotactic potencies of several aldehydic components of oxidised low density lipoprotein for human monocyte‐macrophages

“…In previous studies with human monocyte-macrophages, we obtained reproducible cell-killing with copper-oxidised LDL at a concentration of 200 ~tg/ml in culture medium [9]. Analysis of this less extensively oxidised LDL (1 mg protein/ml using 5 p.M Cu 2+ for 24 h, resulting in consumption of approximately 70% of the polyunsaturated fatty acids) using the same analytical method as Esterbauer and colleagues indicated concentrations of hexanal, HNE and HHE as 71, 22 and 4 nmol/mg LDL protein (unpublished data).…”

“…Human monocyte-macrophages (HMM) were isolated from peripheral blood from healthy volunteers as described previously [9]. Blood was diluted with phosphate-buffered saline (PBS) and layered onto Lymphoprep (Nycomed Pharma AS, Oslo, Norway).…”

“…For the measurement of cytotoxicity HMM were preloaded with tritiated adenine (Amersham Radiochemicals, Amersham, Bucks, UK, 24 Ci/mmol) for 1 h (0.5 IxCi/well) using an established technique [9]. After washing with PBS, cells were incubated in Macrophage-SFM in the presence or absence of the various aldehydes.…”

“…Quinn and co-workers have shown that oxidised LDL induces chemotaxis in human monocytes, with lysophosphatidyl choline being one of its active components [3,4]. Further, oxidised LDL has been shown to be toxic for a variety of cell types including smooth muscle cells, fibroblasts [5] and more recently mouse peritoneal macrophages [6,7], the macrophage-like cell line P388D1 [8] and human monocyte-macrophages [9]. However, oxidised LDL is a complex mixture of various components including lipid hydroperoxides, oxysterols and aldehydes [10].…”

Uptake of Oxidized LDL by Macrophages Results in Partial Lysosomal Enzyme Inactivation and Relocation

“…[4][5][6] As to the effects of oxLDL on macrophage viability, however, there are a number of somewhat conflicting reports. [7][8][9][10][11] LDL is a lysosome-destined particle that is typically transported into cells via receptor-mediated endocytosis. Although most cells have LDL receptors on their plasma membrane, the expression of this receptor on macrophages is low.…”