Figure 3. Quinotrierixin inhibits X-box binding protein 1 splicing and C/EBP homologous protein expression in retinal pigment epithelium cells during endoplasmic reticulum stress. ARPE-19 cells were treated with endoplasmic reticulum stress inducer thapsigargin (TG) with or without quinotrierixin for 8 h. A: X-box binding protein 1 (XBP1) mRNA splicing was detected with reverse transcription polymerase chain reaction (RT–PCR). XBP1u: unspliced XBP1. XBP1s: spliced XBP1. B: Protein level of spliced XBP1 was detected with western blot analysis. NS: none specific. Quantitative data are expressed as mean±SD (n=3 independent experiments). **p<0.01 versus control, ††p<0.01 versus TG. C: Phosphorylation of PKR-like endoplasmic reticulum kinase (PERK) and eukaryotic translation initiation factor 2α (eIF2α) was detected with western blot analysis. D: Intracellular level of C/EBP homologous protein (CHOP) and nuclear levels of spliced XBP1 and CHOP were determined with western blot analysis. Lamin B was used as loading control for nuclear proteins. The concentrations of TG and quinotrierixin were both 0.5 μM unless otherwise indicated.