Peer-Reviewed Journal Details
Mandatory Fields
Lordan, S;O'Brien, NM;Mackrill, JJ
2009
January
Journal of Biochemical and Molecular Toxicology
The Role of Calcium in Apoptosis Induced by 7 beta-Hydroxycholesterol and Cholesterol-5 beta,6 beta-Epoxide
Validated
WOS: 20 ()
Optional Fields
CELL-LINE INTRACELLULAR CALCIUM CHOLESTEROL OXIDATION ENDOPLASMIC-RETICULUM U937 CELLS CA2+ OXYSTEROLS INVOLVEMENT ATHEROSCLEROSIS PATHWAYS
23
324
332
Oxysterols, such as 7 beta-hydroxycholesterol (7 beta-OH) and cholesterol-5 beta,6 beta-epoxide (beta-epoxide), may have a central role in promoting atherogenesis. This is thought to be predominantly due to their ability to induce apoptosis in cells of the vascular wall and in monocytes/macrophages. Although there has been extensive research regarding the mechanisms through which oxysterols induce apoptosis, much remains to be clarified. Given that experimental evidence has long associated alterations of calcium (Ca(2+)) homeostasis to apoptotic cell death, the aim of the present study was to determine the influence of intracellular Ca(2+) changes on apoptosis induced by 7 beta-OH and P-epoxide. Ca(2+) responses in differentiated U937 cells were assessed by epifluorescence video microscopy, using the. ratiometric dye fura-2. Over 15-min exposure of differentiated U937 cells to 30 mu M of 7 beta-OH induced a slow but significant rise in fura-2 ratio. The Ca(2+) channel blocker nifedipine and the chelating agent EGTA blocked the increase in cytoplasmic Ca(2+). Moreover, dihydropyridine (DHP) binding sites identified with BODIPY-FLX-DHP were blocked following pretreatment with nifedipine, indicating that the influx of Ca(2+) occurred through L-type channels. However, following long-term incubation with 7 beta-OH, elevated levels of cytoplasmic Ca(2+) were not maintained and nifedipine did not provide protection against apoptotic cell death. Our results indicate that the increase in Ca(2+) may be an initial trigger of 7 beta-OH-induced apoptosis, but following chronic exposure to the oxysterol, the influence of Ca(2+) on apoptotic cell death appears to be less significant. In contrast, Ca(2+) did not appear to be involved in beta-epoxide-induced apoptosis. (C) 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:324-332, 2009; Published onhne in Wiley InterScience (www.interscience.wiley.com). DOI 10:1002/jbt.20295
HOBOKEN
1095-6670
10.1002/jbt.20295
Grant Details