Abstract
Abstract: :
Purpose: To test the hypothesis that αA crystallin deficiency leads to increased susceptibility of RPE to cell death Methods: RPE cells were isolated from 4–6 week–old αA (–/–) and wild type (wt) 129 SvJ mice. Effect of 12 h exposure of early passages αA (–/–) and wt RPE cells to hydrogen peroxide (H2O2; 100–200 µM) on viability, membrane permeability transition (MPT), caspase 3 activation, and apoptosis (TUNEL) was determined. Effect of N–linked glycosylation inhibitor, Tunicamycin (TM; 100 µg/ml, 24 h), an ER stress inducer, on induction of apoptosis and MPT was assessed. Results:The cell viability of 12 h H2O2 treated RPE from αA (–/–) mice was significantly lower (p<0.01) as compared to untreated and 12 h H2O2 treated wt controls. RPE from αA (–/–) mice exhibited significantly increased MPT and apoptosis (p<0.01 vs wt). Caspase 3 activation with 100 µM H2O2 increased from 8% in wt to 34 % in αA (–/–) RPE. Concentration–dependency experiments in control RPE cells showed that TM caused a dose–dependent (25–200 µg/ml) increase in cell death. When cells were incubated with 100 µg/ml TM, apoptosis in αA (–/–) RPE (42.5%) was significantly higher than wt RPE (12.8%) (p<0.01). Conclusions: Absence of αA crystallin renders RPE more susceptible to mitochondrial and ER stress.
Keywords: apoptosis/cell death • retinal pigment epithelium • crystallins