Mammalian cell cultures as a model system for the determination of cytotoxicity induced by cholesterol oxidation products

Show simple item record

dc.contributor.advisor O'Brien, Nora M. en O'Callaghan, Yvonne C. 2014-07-29T09:15:55Z 2014-07-29T09:15:55Z 2001 2001
dc.identifier.citation O'Callaghan, Y. 2001. Mammalian cell cultures as a model system for the determination of cytotoxicity induced by cholesterol oxidation products. PhD Thesis, University College Cork. en
dc.description.abstract Oxysterols are products of cholesterol oxidation, which may be produced endogenously or may be absorbed from the diet where they are commonly found in foods of animal origin. Oxysterols are known to be cyctotoxic to cells in culture and mode of toxicity has been identified as apoptosis in certain cell lines. The cytotoxicity of the oxysterols 25-hydroxycholesterol (25-OH) and 7β-hydroxycholesterol (7β-OH) was examined in two human cell lines, HepG2, a hepatoma cell line, and U937, a monocytic cell line. Both 25-OH and 7β-OH were cytotoxic to the HepG2 cell line but apoptotic cells were not detected and it was concluded that cells underwent necrosis. 25-OH was not cytotoxic to the U937 cell line but it was found to have a cytostatic effect. 7β-OH was shown to induce apoptosis in the U937 line. The mechanism of oxysterol-induced apoptosis has not yet been fully elucidated, however the generation of an oxidative stress and the depletion of glutathione have been associated with the initial stages of the apoptotic process. The concentration of cellular antioxidant enzyme, superoxide dismutase (SOD) was increased in association with 7β-OH induced apoptosis in the U937 cell line. There was no change in the glutathione concentration or the SOD activity of HepG2 cells, which underwent necrosis in the presence of 7β-OH. Many apoptotic pathways center on the activation of caspase-3, which is the key executioner protease of apoptosis. Caspase-3 activity was also shown to increase in association with 7β-OH-induced apoptosis in U937 cells but there was no significant increase in caspase-3 activity in HepG2 cells. DNA fragmentation is regarded as the biochemical hallmark of apoptosis, therefore the comet assay as a measure of DNA fragmentation was assessed as a measure of apoptosis. The level of DNA fragmentation induced by 7β-OH, as measured using the comet assay, was similar for both cell lines. Therefore, it was concluded that the comet assay could not be used to distinguish between 7β-OH-induced apoptosis in U937 cells and 7β-OH-induced necrosis in HepG2 cells. The cytotoxicity and apoptotic potency of oxysterols 25-OH, 7β-OH, cholesterol- 5a,6a-epoxide (a-epoxide), cholesterol-5β,6β-epoxide (β-epoxide), 19-hydroxy-cholesterol (19-OH), and 7-ketocholesterol (7-keto) was compared in the U937 cell line. 7 β-OH, β-epoxide and 7-keto were found to induce apoptosis in U937 cells. 7β-OH-induced apoptosis was associated with a decrease in the cellular glutathione concentration and an increase in SOD activity, 7-keto and β-epoxide did not affect the glutathione concentration or the SOD activity of the cells.a-Epoxide, 19-OH and 25-OH were not cytotoxic to the U937 cell line. en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2001, Yvonne O'Callaghan en
dc.rights.uri en
dc.subject Cell death en
dc.subject Cytotoxicity en
dc.subject Oxysterol-induced apoptosis en
dc.subject DNA fragmentation en
dc.subject.lcsh Apoptosis en
dc.subject.lcsh Oxysterols en
dc.title Mammalian cell cultures as a model system for the determination of cytotoxicity induced by cholesterol oxidation products en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD (Food Science and Technology) en
dc.internal.availability Full text available en No embargo required en
dc.description.version Accepted Version
dc.description.status Not peer reviewed en Food and Nutritional Sciences en
dc.check.type No Embargo Required
dc.check.reason No embargo required en
dc.check.opt-out Not applicable en
dc.thesis.opt-out false
dc.check.embargoformat Not applicable en

Files in this item

This item appears in the following Collection(s)

Show simple item record

© 2001, Yvonne O'Callaghan Except where otherwise noted, this item's license is described as © 2001, Yvonne O'Callaghan
This website uses cookies. By using this website, you consent to the use of cookies in accordance with the UCC Privacy and Cookies Statement. For more information about cookies and how you can disable them, visit our Privacy and Cookies statement