XBP1 and Endoplasmic Reticulum Stress: It has also been shown that multiple PEs significantly regulate the unfolded protein response (complex adaptive or pro-apoptotic signaling triggered by endoplasmic reticulum stress) associated proteins glucose-regulated protein (GRP)78, X-box binding protein (XBP)-1, cleaved activating transcription factor (ATF)-6, inositol-requiring protein-1α (IRE1α), and C/EBP-homologous protein (CHOP), in the setting of myocardial I/R injury (Kim et al., 2008; Kim et al., 2010).