Furthermore, significantly elevated levels of several proteins, which are directly or indirectly associated with ER stress including GRP78, GRP94, phosphorylated (p-) PERK, eIF2a, p-eIF2a, XBP1, CHOP, IRE1, p-IRE1 and inducible nitric oxide synthase NOS expression, and reduced levels of endothelial NOS expression are observed in preeclampsia versus control placentas [162]. This evidence concerns the gene XBP1 and preeclampsia.