title: Toxicity of oxysterols to human monocyte-macrophages.
abstract: We have investigated the toxicity of the cholesterol oxidation products (oxysterols), 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol, 7-ketocholesterol, 25-hydroxycholesterol and 26-hydroxycholesterol to human monocyte-macrophages in vitro. The 7-position derivatives are present in low density lipoprotein (LDL) oxidised with copper (II) sulphate and macrophages, and in extracts of human atherosclerotic lesions, which also contain 26-hydroxycholesterol. We have also assessed 25-hydroxycholesterol for toxicity because it has often been used in studies of 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibition and LDL receptor down-regulation. Measurement of radioactivity release from monocyte-macrophages preloaded with tritiated adenine, as a means of assessing cytotoxicity that all the oxysterols showed time- and concentration-dependent toxicity. The cytotoxic potency of 26-hydroxycholesterol was the greatest. The 7-position derivatives also produced marked cell damage, though at higher concentrations than for 26-hydroxycholesterol. Of the oxysterols assessed, the toxicity of 25-hydroxycholesterol was the least. The cytotoxicity of 7 beta-hydroxycholesterol and 26-hydroxycholesterol was also shown using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) dye reduction assay which confirmed that 26-hydroxycholesterol was more toxic than 7 beta-hydroxycholesterol. Incubation of monocyte-macrophages with cholesterol added to the different oxysterols gave varying results. Cholesterol, which was not itself toxic, inhibited the toxicity of 25-hydroxycholesterol and 26-hydroxycholesterol, but the toxicity of the 7-position derivatives was not affected. The possible relevance of these molecules to the death of macrophages seen in atherosclerosis is discussed.
authors.affiliation: University of Cambridge, Department of Pathology, UK.
authors.forename: K
authors.initials: K
authors.lastname: Clare
authors.forename: S J
authors.initials: SJ
authors.lastname: Hardwick
authors.forename: K L
authors.initials: KL
authors.lastname: Carpenter
authors.forename: N
authors.initials: N
authors.lastname: Weeratunge
authors.forename: M J
authors.initials: MJ
authors.lastname: Mitchinson
mesh_terms: D002478:Cells, Cultured; D006801:Humans; D006888:Hydroxycholesterols / Q000633:toxicity*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D013778:Tetrazolium Salts / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism
chemical_list: D006888:Hydroxycholesterols; D013778:Tetrazolium Salts; D013844:Thiazoles; C022616:thiazolyl blue