title: UV-A induced oxidative stress is more prominent in naturally pigmented aged human RPE cells compared to non-pigmented human RPE cells independent of zinc treatment.
abstract: To investigate the effects of zinc supplementation on human amelanotic (ARPE-19) and native pigmented retinal pigment epithelial cells (hRPE) under normal light conditions and after ultraviolet A light exposure. hRPE cells, containing both melanin and lipofuscin granules, were prepared from human donor eyes of 60-70 year old patients. Cells of the amelanotic ARPE-19 cell line and pigmented hRPE cells were treated with zinc chloride and subjected to oxidative stress by UV-A irradiation. Intracellular H(2)O(2) formation was measured using a fluorescence oxidation assay. Additionally, apoptosis and viability assays were performed. Control cells were treated identically except for irradiation and zinc supplementation. Under normal light conditions, zinc treated hRPE cells produced less H(2)O(2) than unsupplemented hRPE cells. Viability and apoptosis events did not change. After UV-A irradiation, ARPE and hRPE cells were greatly impaired in all tests performed compared to the non-irradiated controls. No differences were found after zinc supplementation. hRPE cells showed a higher apoptosis and mortality rate than non-pigmented cells when stressed by UV-A light. ARPE cells never showed any zinc related effects. In contrast, without irradiation, zinc supplementation reduced H(2)O(2) production in pigmented hRPE cells slightly. We did not find any zinc effect in irradiated hRPE cells. After UV light exposure, pigmented cells showed a higher apoptosis and mortality than cells lacking any pigmentation. We conclude that cells with pigmentation consisting of melanin and lipofuscin granules have more prooxidative than antioxidative capacity when stressed by UV light exposure compared to cells lacking any pigmentation.
authors.affiliation: Section of Experimental Vitreoretinal Surgery, University Eye Hospital Tuebingen, Schleichstr. 12/1, 72076 Tuebingen, Germany. antje.biesemeier@med.uni-tuebingen.de
authors.forename: Antje
authors.initials: A
authors.lastname: Biesemeier
authors.forename: Despina
authors.initials: D
authors.lastname: Kokkinou
authors.forename: Sylvie
authors.initials: S
authors.lastname: Julien
authors.forename: Peter
authors.initials: P
authors.lastname: Heiduschka
authors.forename: Mark
authors.initials: M
authors.lastname: Berneburg
authors.forename: Karl Ulrich
authors.initials: KU
authors.lastname: Bartz-Schmidt
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schraermeyer
mesh_terms: D000368:Aged; D017209:Apoptosis; D002470:Cell Survival; D016922:Cellular Senescence; D006801:Humans; D006861:Hydrogen Peroxide; D008875:Middle Aged; D018384:Oxidative Stress / Q000528:radiation effects*; D010857:Pigment Epithelium of Eye / Q000187:drug effects / Q000473:pathology* / Q000528:radiation effects; D010858:Pigmentation; D014466:Ultraviolet Rays / Q000009:adverse effects*; D015032:Zinc / Q000494:pharmacology*
chemical_list: D006861:Hydrogen Peroxide; D015032:Zinc