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Death‐signaling pathways in human myeloid cells by oxLDL and its cytotoxic components 7β‐hydroxycholesterol and cholesterol‐5β,6β‐epoxide
Author(s) -
Lordan Sinéad,
O'Callaghan Yvonne C.,
O'Brien Nora M.
Publication year - 2007
Publication title -
journal of biochemical and molecular toxicology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.526
H-Index - 58
eISSN - 1099-0461
pISSN - 1095-6670
DOI - 10.1002/jbt.20198
Subject(s) - u937 cell , apoptosis , chemistry , cell culture , low density lipoprotein , cholesterol , lipoprotein , epoxide , foam cell , western blot , programmed cell death , biochemistry , microbiology and biotechnology , biology , genetics , gene , catalysis
Oxidized low‐density lipoprotein contains many potentially proatherogenic molecules, including oxysterols, which have been shown to induce apoptosis in various cell lines. The aim of this study was to investigate the pathway of apoptosis induced by oxidized low‐density lipoprotein and the oxysterols, 7β‐hydroxycholesterol and cholesterol‐5β,6β‐epoxide, in two human monocytic cell lines. The HL‐60 cells appeared to be more sensitive to oxidized low‐density lipoprotein than U937 cells, whereas the isolated oxysterols were more potent inducers of apoptosis in the U937 cells. Caspase‐2 inhibition decreased the number of viable cells in oxidized low‐density lipoprotein‐treated samples; however, it protected against cholesterol‐5β,6β‐epoxide‐induced cell death. Western blot analysis was utilized to examine the effect of caspase‐2 inhibition on the expression of the antiapoptotic protein Bcl‐2. Pretreatment with the inhibitor protected against the decrease in Bcl‐2 expression in oxidized low‐density lipoprotein‐ and 7β‐hydroxycholesterol‐treated U937 cells. In HL‐60 cells, Bcl‐2 was overexpressed in oxidized low‐density lipoprotein‐treated cells, but in the presence of the inhibitor Bcl‐2 expression was returned to control levels. Depleted ATP concentrations in the cells suggest that both apoptosis and necrosis may have occurred simultaneously. Our results highlight differences in the signaling pathways induced by oxidized low‐density lipoprotein, 7β‐hydroxycholesterol, and cholesterol‐5β,6β‐epoxide in U937 and HL‐60 cells. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:362–372, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20198