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J.S. Hurst, G.–F. Jin, M. Saini, Y.C. Awasthi, F.J. G. M. van Kuijk; Toxicity of Carotenoid Oxidative Breakdown Products to Cultured Human Retinal Pigmented Epithelial cells . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1297.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Carotenoids are potent antioxidants in vitro and have been included in large–scale clinical trials for the mitigation and/or prevention of diseases associated with aging, and/or chronic oxidative stress, such as cataract and age–related macular degeneration (ARMD). However, carotenoids are also susceptible to autoxidation which can generate volatile aldehydes and ketones which are biologically active. We previously showed that autoxidized ß–carotene inhibited Na+–K+–ATPase activity more effectively than the lipid peroxidation derived aldehyde 4–hydroxy–nonenal. Similarly autoxidized carotenoids were reported to oxidize DNA in fibroblasts, and promote apoptosis in various human cell lines. In the present studies, we have investigated whether autoxidized carotenoids induce death of human retinal pigment epithelial (RPE) cells. Methods: We compared the cellular viability of subconfluent cultured human 28 SV4 RPE and K562 erythroleukemic cells in response to different concentrations (0–100 µM) of carotenoid derived aldehydes (CDA) secondary to oxidative degradation. CDA were generated from the oxidation of 5 mg ß–carotene by 80 mM NaOCl. CDA were extracted according to the Bligh and Dyer method and quantified from spectrophotometric absorbance at 220 nm. Cellular viability was assessed as mitochondrial function determined from the reduction of 3–(4,5 dimethyl–thiazol–2–yl)–2,5–diphenyltetrazolium bromide (MTT cytotoxicity assay). Results: K562 cells were more sensitive to CDA than the RPE 28 SV4 cells. Concentrations ranging from 16–25 µM were toxic to K 562 cells, whereas RPE 28 SV4 cells were sensitive only to concentration > 50 µM. Mitochondrial function in K562 cells was inhibited by 30 and 87 percent respectively, in response to 20 and 25 µM CDA. Mitochondrial function in RPE 28 SV4 cells was 25 percent of the control values as shown at 100 µM CDA. Conclusions: The data showed that oxidized carotenoids are cytotoxic and that the mitochondrial function of K562 cells was more sensitive to CDA than that of RPE cells, which are known to have very high levels of antioxidants and are apparently less sensitive to this form of oxidative stress than K562 cells.
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