title: Relaxin, a pregnancy hormone, is a functional endothelin-1 antagonist: attenuation of endothelin-1-mediated vasoconstriction by stimulation of endothelin type-B receptor expression via ERK-1/2 and nuclear factor-kappaB.
abstract: We have recently demonstrated that relaxin (RLX) acts as compensatory mediator in human heart failure. RLX inhibits the stimulation of endothelin-1, the most potent vasoconstrictor in heart failure. Upregulation of the endothelin type-B receptor (ET(B)), which mediates endothelin-1 clearance and endothelial release of NO, represents a pivotal mode of RLX action. However, signal transduction and abundance of this phenomenon are unknown. Therefore, we investigated RLX-induced regulation of ET(B) in human umbilical vein endothelial, epithelial (HeLa), and vascular smooth muscle cells. In human umbilical vein endothelial cells and HeLa cells, but not in human vascular smooth muscle cells, RLX upregulated ET(B) expression and activated extracellular signal-regulated kinase-1/2 (ERK-1/2) and nuclear factor-kappaB (NF-kappaB), a transcription factor. PD-98059, a selective inhibitor of the mitogen-activated protein kinase kinase-1 (MEK-1)-ERK-1/2 pathway, abolished ERK-1/2 and NF-kappaB activation and ET(B) upregulation. NF-kappaB inhibition also prevented RLX-mediated ET(B) stimulation. In NF-kappaB-luciferase reporter assays, we demonstrated complete inhibition of RLX-induced NF-kappaB activation in cells transfected with dominant-negative Raf-1, MEK-1, or ERK-1/2 constructs, whereas dominant-negative Ras had no effect. In rat aorta and mesenteric artery, RLX pretreatment, in an ET(B)-dependent fashion, mitigated the maximum contractile response to endothelin-1, by 38+/-4% and 43+/-6%, and the endothelin-1 sensitivity (-log[EC(50)]: aorta, 8.2+/-0.2 for vehicle versus 7.2+/-0.2 for RLX; mesenteric artery, 8.0+/-0.2 for vehicle versus 7.1+/-0.1 for RLX). RLX pretreatment augmented the dilator effect of the ET(B) agonist endothelin-3 by 100+/-8% and 133+/-13%. In conclusion, RLX stimulates endothelial and epithelial ET(B) via a Ras-independent Raf-1-MEK-1-ERK-1/2 pathway that activates NF-kappaB. On vascular smooth muscle cells, ET(B), a contributor to endothelin-mediated vasoconstriction, remains unaffected. This renders RLX a functional endothelin-1 antagonist.
authors.affiliation: Medizinische Klinik und Poliklinik (Kardiologie, Angiologie, Pulmologie) Charité, Campus Mitte, Berlin, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dschietzig
authors.forename: Cornelia
authors.initials: C
authors.lastname: Bartsch
authors.forename: Christoph
authors.initials: C
authors.lastname: Richter
authors.forename: Michael
authors.initials: M
authors.lastname: Laule
authors.forename: Gert
authors.initials: G
authors.lastname: Baumann
authors.forename: Karl
authors.initials: K
authors.lastname: Stangl
mesh_terms: D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D020536:Enzyme Activators / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D048369:MAP Kinase Kinase 1; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000378:metabolism*; D012065:Relaxin / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D015854:Up-Regulation / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects* / Q000502:physiology
chemical_list: D019332:Endothelin-1; D020536:Enzyme Activators; D016328:NF-kappa B; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D012065:Relaxin; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases