Premium
Attenuation of iron‐binding proteins in ARPE ‐19 cells reduces their resistance to oxidative stress
Author(s) -
Karlsson Markus,
Kurz Tino
Publication year - 2016
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/aos.13076
Subject(s) - downregulation and upregulation , oxidative stress , lipofuscin , autophagy , microbiology and biotechnology , heat shock protein , chemistry , ferritin , hsp70 , apoptosis , biochemistry , biology , gene
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 ( HSP 70) 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 H 2 O 2 exposure was tested following upregulation of MT , HSP 70 and/or FT by pretreatment with Zn SO 4 , heat shock or FeCl 3 , as well as si RNA ‐mediated downregulation of the same proteins. Results Upregulation of MT , HSP 70 and FT did not improve survival following exposure to H 2 O 2 . This was interpreted as existence of an already maximal protection. Combined si RNA ‐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.