Purchase this article with an account.
G. Dou, P. G. Sreekumar, C. Spee, S. He, S. J. Ryan, R. Kannan, D. R. Hinton; Deficiency of B Crystallin Augments ER Stress-Induced Apoptosis by Accentuating Mitochondrial Dysfunction in RPE Cells. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1438.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Disturbance of endoplasmic reticulum (ER) homeostasis is being unveiled in several pathological conditions including age-related macular degeneration. Excessive ER stress initiates cell death, which could be orchestrated with mitochondrial dysfunction. This study aims to examine the cross talk between ER stress and mitochondrial dysfunction in RPE cells and to identify αB crystallin as a distinct anti-apoptotic regulator coordinating the interplay.
Expression levels of αB crystallin, GRP78, CHOP, caspase 12, caspase 3, Bcl-2 and Bax were examined in human fetal RPE (hRPE) cells treated with tunicamycin (TM, 1-10 µg/ml; 1-24h). Reactive oxygen species (ROS), free glutathione (GSH), release of cytochrome c and membrane permeability transition (MPT) were measured in TM-treated and untreated hRPE cells. The induction of apoptosis was evaluated by TUNEL and Annexin V assays in RPE cells from αB crystallin (-/-) mice, αB crystallin siRNA transfected hRPE, and ARPE-19 cells stably overexpressing αB crystallin.
TM treatment induced activation of caspase 3 and caspase 12 in hRPE. ER stress was verified by an increase in GRP78 and CHOP. Severe ER stress downregulated αB crystallin expression in ER and mitochondria. The reduction in αB crystallin expression occurred prior to caspase 3 activation. TM-treated hRPE exhibited an increase in ROS (p<0.05), decrease in cellular and mitochondrial GSH (p<0.05), and 50% increase of cytochrome c release from mitochondria into cytosol. Bcl-2 and Bcl-2/Bax ratio showed slight increases with TM treatment. RPE cells from αB crystallin (-/-) mice and from αB crystallin siRNA transfection exhibited increased susceptibility to ER stress-induced apoptosis, while αB crystallin overexpression promoted RPE cells survival by restoring changes of MPT(p<0.05) or regulating expression of Bax and caspase 12.
Our data show that αB crystallin plays a crucial role as a protective mediator in regard to mitochondrial function during ER stress-induced RPE apoptosis.
This PDF is available to Subscribers Only