title: Concentration dependence of vitamin C in combinations with vitamin E and zeaxanthin on light-induced toxicity to retinal pigment epithelial cells.
abstract: The purpose of this study was to determine the effects of increasing concentration of ascorbate alone and in combinations with α-tocopherol and zeaxanthin on phototoxicity to the retinal pigment epithelium. ARPE-19 cells were exposed to rose bengal and visible light in the presence and absence of antioxidants. Toxicity was quantified by an assay of cell-reductive activity. A 20 min exposure to visible light and photosensitizer decreased cell viability to ca 42%. Lipophilic antioxidants increased viabilities to ca 70%, 61% and 75% for α-tocopherol, zeaxanthin and their combination, respectively. Cell viabilities were ca 70%, 56% and 5% after exposures in the presence of 0.35, 0.7 and 1.4 mm ascorbate, respectively. A 45 min exposure increased cell death to ca 74% and >95% in the absence and presence of ascorbate, respectively. In the presence of ascorbate, zeaxanthin did not significantly affect phototoxicity. α-Tocopherol and its combination with zeaxanthin enhanced protective effects of ascorbate, but did not prevent from ascorbate-mediated deleterious effects. In conclusion, there is a narrow range of concentrations and exposure times where ascorbate exerts photoprotective effects, exceeding which leads to ascorbate-mediated increase in photocytotoxicity. Vitamin E and its combination with zeaxanthin can enhance protective effects of ascorbate, but do not ameliorate its deleterious effects.
authors.affiliation: School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, UK. rozanowskamb@cf.ac.uk
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Różanowska
authors.forename: Linda
authors.initials: L
authors.lastname: Bakker
authors.forename: Michael E
authors.initials: ME
authors.lastname: Boulton
authors.forename: Bartosz
authors.initials: B
authors.lastname: Różanowski
mesh_terms: D001205:Ascorbic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D004847:Epithelial Cells / Q000502:physiology / Q000528:radiation effects*; D006801:Humans; D008027:Light / Q000009:adverse effects*; D055213:Retinal Pigment Epithelium / Q000166:cytology*; D014810:Vitamin E / Q000008:administration & dosage / Q000494:pharmacology*; D024502:alpha-Tocopherol / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D014810:Vitamin E; D024502:alpha-Tocopherol; D001205:Ascorbic Acid