Attenuation of iron‐binding proteins in ARPE‐19 cells reduces their resistance to oxidative stress. (11th June 2016)

• Record Type: Journal Article
• Authors: Karlsson, Markus; Kurz, Tino
• Is Part Of: Acta ophthalmologica. Volume 94:Number 6(2016)
• Page Start: 556
• Page End: 564
• Publication Date: 2016-06-11
• Subjects: age‐related macular degeneration -- ARPE‐19 -- ferritin -- HSP70 -- iron -- metallothionein -- oxidative stress -- retinal pigment epithelium; Ophthalmology -- Periodicals; 617.7005
• DOI: 10.1111/aos.13076
• Languages: English
• ISSNs: 1755-375X

Abstract

Abstract: Purpose: Oxidative stress‐related damage to retinal pigment epithelial (RPE) cells is an important feature in the development of age‐related macular degeneration. Iron‐catalysed intralysosomal production of hydroxyl radicals is considered a major pathogenic factor, leading to lipofuscin formation with ensuing depressed cellular autophagic capacity, lysosomal membrane permeabilization and apoptosis. Previously, we have shown that cultured immortalized human RPE (ARPE‐19) cells are extremely resistant to exposure to bolus doses of hydrogen peroxide and contain considerable amounts of the iron‐binding proteins metallothionein (MT), heat‐shock protein 70 (HSP70) and ferritin (FT). According to previous findings, autophagy of these proteins depresses lysosomal redox‐active iron. The aim of this study was to investigate whether up‐ or downregulation of these proteins would affect the resistance of ARPE‐19 cells to oxidative stress. Methods: The sensitivity of ARPE‐19 cells to H2 O2 exposure was tested following upregulation of MT, HSP70 and/or FT by pretreatment with ZnSO4, heat shock or FeCl3, as well as siRNA‐mediated downregulation of the same proteins. Results: Upregulation of MT, HSP70 and FT did not improve survival following exposure to H2 O2 . This was interpreted as existence of an already maximal protection. Combined siRNA‐mediated attenuation of both FT chains (H and L), or simultaneous downregulation of all three proteins, made the cells significantly more susceptible to oxidative stress confirming the importance of iron‐binding proteins. Conclusion: The findings support our hypothesis that the oxidative stress resistance exhibited by RPE cells may be explained by a high autophagic influx of iron‐binding proteins that would keep levels of redox‐active lysosomal iron low.