Endoplasmic reticulum stress and subsequent endothelial cell apoptosis, involving activation of eukaryotic initiation factor 2α (EIF2α), X-box-binding protein 1 (XBP1), CCAAT-enhancer-binding protein homologous protein (CHOP), and NF-κB, can induce endothelial dysfunction. Here, XBP1 is linked to endothelial dysfunction.