Toxicity of oxysterols to human monocyte-macrophages.
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.
Clare
K
K
University of Cambridge, Department of Pathology, UK.
Hardwick
S J
SJ
Carpenter
K L
KL
Weeratunge
N
N
Mitchinson
M J
MJ
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
D006888:Hydroxycholesterols; D013778:Tetrazolium Salts; D013844:Thiazoles; C022616:thiazolyl blue