Arsenic trioxide initiates ER stress responses, perturbs calcium signalling and promotes apoptosis in human lens epithelial cells

Identification of novel agents to eradicate the residual lens cell population following cataract surgery provides one mode of preventing PCO formation. The present study investigated the biological mechanism of As₂O₃ cytotoxicity in a human lens cell line and capsular bag system. FHL 124 cell survival was assessed by quantification of total protein content, a cell population measure. Gene changes were detected by Real-time PCR; apoptosis by TUNEL assays. Intracellular calcium was measured by real-time fluorimetric single-cell digital imaging techniques after Fura-2 incorporation. In vitro human capsular bags were generated from donor eyes, which involved sham cataract surgery then use of the Perfect Capsule device to form a closed system to deliver As₂O₃ for 2 min. On-going observations were by phase-contrast microscopy. Cellular architecture was examined by fluorescence immunocytochemistry. FHL 124 cells demonstrated a dose-dependent sensitivity to As₂O₃ exposure. A 2 min exposure of As₂O₃ to cells within the capsular bag, using the perfect capsule system, resulted in total cell death when used at 100 mM. As₂O₃ provoked an ER stress response identified through an upregulation of known genes. As₂O₃ depleted the calcium store and consequently lead to reduced calcium signalling. As₂O₃ increased rates of apoptosis. Arsenic trioxide provokes ER stress that leads to down-regulation of calcium signalling resulting in apoptosis. The application of As₂O₃ to cells within the capsular bag for a 2 min window using the Perfect Capsule system predicts putative therapeutic benefit in vivo.