title: Toxicity of cholesterol oxidation products to Caco-2 and HepG2 cells: modulatory effects of alpha- and gamma-tocopherol.
abstract: Cholesterol can be oxidized to form a variety of cholesterol oxidation products also known as oxysterols. The aims of the present study were to compare the cytotoxic effects of four oxysterols, namely 25-hydroxycholesterol (25-OHC), 7beta-hydroxycholesterol (7beta-OHC), cholesterol-5beta,6beta-epoxide (beta-epox) and cholesterol-5alpha,6alpha-epoxide (alpha-epox), in two human cell culture models. Further, the ability of 10 and 100 micro m alpha- and gamma-tocopherol (alpha-TOC and gamma-TOC, respectively) to protect against oxysterol-induced cytotoxicity was also assessed. Human colonic adenocarcinoma Caco-2 and human hepatoma HepG2 cells were supplemented with increasing concentrations of 25-OHC, 7beta-OHC, beta-epox and alpha-epox (0-25 micro g ml(-1)) for 24, 48 or 96 h. Following 24-h and 48-h exposure, test media were replaced with normal growth media and the cells were maintained for 72 and 48 h, respectively. The 96-h exposure represented a constant challenge to the cells. Cytotoxicity was assessed using the neutral red uptake assay. The concentration of compound that inhibited cell viability by 50% (ic(50) value) was calculated. All four oxysterols investigated induced the greatest cytotoxic effects following 96 h of exposure. 25-Hydroxycholesterol exhibited the greatest cytotoxicity in both cell lines. Both beta-epox and alpha-epox were more toxic to HepG2 cells than to Caco-2 cells after the 48-h exposure. Pretreatment of cells with either alpha- or gamma-TOC did not protect against oxysterol-induced cytotoxicity. The caco-2 cells treated with the high concentration (100 micro m) of gamma-TOC were found to be more susceptible to oxysterol-induced toxicity under the conditions employed in this study.
authors.affiliation: Department of Food and Nutritional Sciences, University College Cork, Ireland.
authors.forename: A J
authors.initials: AJ
authors.lastname: O'Sullivan
authors.forename: Y C
authors.initials: YC
authors.lastname: O'Callaghan
authors.forename: J A
authors.initials: JA
authors.lastname: Woods
authors.forename: N M
authors.initials: NM
authors.lastname: O'Brien
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D018938:Caco-2 Cells; D002470:Cell Survival / Q000187:drug effects; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000633:toxicity*; D006801:Humans; D006888:Hydroxycholesterols / Q000633:toxicity*; D020128:Inhibitory Concentration 50; D009499:Neutral Red; D013997:Time Factors; D024502:alpha-Tocopherol / Q000494:pharmacology; D024504:gamma-Tocopherol / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D006888:Hydroxycholesterols; C002415:cholesterol alpha-oxide; D009499:Neutral Red; D024504:gamma-Tocopherol; D002784:Cholesterol; D024502:alpha-Tocopherol