Effects of GSK2606414 on cell proliferation and endoplasmic reticulum stress-associated gene expression in retinal pigment epithelial cells

GSK2606414 is a novel, highly selective inhibitor of protein kinase R-like endoplasmic reticulum kinase (PERK). GSK2606414 and its analogues have recently been demonstrated to delay tumor growth and prevent neurodegeneration. The present study investigated the effects of GSK2606414 on proliferation, apoptosis, and the expression of activating transcription factor 4 (ATF4), CCAAT/enhancer-binding protein homologous protein (CHOP) and vascular endothelial growth factor (VEGF) in human retinal pigment epithelial (RPE) cells under endoplasmic reticulum (ER) stress. ARPE-19 human RPE cells were treated with 0.01-50 mu M GSK2606414, and ER stress was induced by thapsigargin (TG) treatment. Cell proliferation was assessed using the Cell Counting kit-8 cell viability assay. Apoptosis was detected by Annexin-V/propidium iodide double staining using flow cytometry. Western blot analysis was used to measure eukaryotic initiation factor 2 alpha (eIF2 alpha) phosphorylation levels. ATF4, CHOP and VEGF mRNA expression levels were assessed using reverse transcription-quantitative polymerase chain reaction. GSK2606414 treatment inhibited RPE cell proliferation in a dose-dependent manner, however it did not induce apoptosis. In addition, GSK2606414 treatment inhibited eIF2 alpha phosphorylation and reduced CHOP and VEGF mRNA expression levels in RPE cells under TG-induced ER stress. To the best of our knowledge, the present study is the first to demonstrate that GSK2606414 has a potential antiproliferative effect in RPE cells in vitro. This effect appeared to be achieved via inhibition of the PERK/ATF4/CHOP signaling pathway and suppression of VEGF expression levels.