title: Endothelin-1 induces endoplasmic reticulum stress by activating the PLC-IP(3) pathway: implications for placental pathophysiology in preeclampsia.
abstract: Recent evidence implicates placental endoplasmic reticulum (ER) stress in the pathophysiological characteristics of preeclampsia. Herein, we investigate whether endothelin (ET)-1, which induces Ca(2+) release from the ER, can induce placental ER stress. Loss of ER Ca(2+) homeostasis impairs post-translational modification of proteins, triggering ER stress-response pathways. IHC confirmed the presence of both ET-1 and its receptors in the syncytiotrophoblast. Protein levels and immunoreactivity of ET-1 and the endothelin B receptor (ETBR) were increased in preeclamptic samples compared with normotensive controls. JEG-3 and BeWo choriocarcinoma cells treated with ET-1 displayed an increase in ER stress markers. ET-1 induced phospho-activation of the ETBR. Treating cells with BQ788, an ETBR antagonist, or small-interfering RNA knockdown of the receptor inhibited induction of ER stress. ET-1 also stimulated p-phospholipase C (PLC)γ1 levels. By using inhibitors of PLC activation, U73122, and the inositol 1,4,5-triphosphate (IP(3)) receptor, xestospongin-C, we demonstrated that ET-1 induces ER stress via the PLC-IP(3) pathway. Furthermore, ET-1 levels increased in the syncytiotrophoblast of explants from normal placentas after hypoxia-reoxygenation in vitro. Conditioned medium from hypoxia-reoxygenation explants also contained higher ET-1 levels, which induced ER stress in JEG-3 cells that was abolished by an ET-1-neutralizing antibody. Collectively, the data show that ET-1 induced ER stress in trophoblasts via the ETBR and initiation of signaling through the PLC-IP(3) pathway, with the potential for autocrine stimulation.
authors.affiliation: Center for Trophoblast Research, Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Arjun
authors.initials: A
authors.lastname: Jain
authors.forename: Matts
authors.initials: M
authors.lastname: Olovsson
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Burton
authors.forename: Hong-wa
authors.initials: HW
authors.lastname: Yung
mesh_terms: D004305:Dose-Response Relationship, Drug; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000502:physiology*; D019332:Endothelin-1 / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D005260:Female; D055785:Gene Knockdown Techniques; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D010920:Placenta / Q000378:metabolism / Q000503:physiopathology*; D011225:Pre-Eclampsia / Q000378:metabolism / Q000503:physiopathology*; D011247:Pregnancy; D034741:RNA, Small Interfering / Q000235:genetics; D044022:Receptor, Endothelin A / Q000378:metabolism; D044023:Receptor, Endothelin B / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D046509:Tissue Culture Techniques; D014327:Trophoblasts / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000502:physiology
chemical_list: D019332:Endothelin-1; D053496:Inositol 1,4,5-Trisphosphate Receptors; D034741:RNA, Small Interfering; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D010738:Type C Phospholipases