title: Relaxin protects cardiac muscle cells from hypoxia/reoxygenation injury: involvement of the Notch-1 pathway.
abstract: In animal models, the cardiotropic hormone relaxin has been shown to protect the heart against ischemia and reperfusion-induced damage, acting by multiple mechanisms that primarily involve the coronary vessels. This in vitro study evaluates whether relaxin also has a direct protective action on cardiac muscle cells. H9c2 rat cardiomyoblasts and primary mouse cardiomyocytes were subjected to hypoxia and reoxygenation. In some experiments, relaxin was added preventatively before hypoxia; in others, at reoxygenation. To elucidate its mechanisms of action, we focused on Notch-1, which is involved in heart pre- and postconditioning to ischemia. Inactivated RLX was used as negative control. Relaxin (17 nmol/L, EC50 4.7 nmol/L), added 24 h before hypoxia or at reoxygenation, protected against cardiomyocyte injury. In fact, relaxin significantly increased cell viability (assayed by trypan blue and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide), decreased apoptosis (assayed by TUNEL and bax/bcl-2 ratio), and reduced nitroxidative damage (assayed by nitrotyrosine expression and 8-hydroxy-deoxyguanosine levels). These effects were partly attributable to the ability of relaxin to upregulate Notch-1 signaling; indeed, blockade of Notch-1 activation with the specific inhibitor DAPT reduced relaxin-induced cardioprotection during hypoxia and reoxygenation. This study adds new mechanistic insights on the cardioprotective role of relaxin on ischemic and oxidative damage.
authors.affiliation: Department of Experimental and Clinical Medicine, Section of Anatomy and Histology, Research Unit of Histology and Embryology, University of Florence, Florence, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Boccalini
authors.affiliation: Department of Experimental and Clinical Medicine, Section of Anatomy and Histology, Research Unit of Histology and Embryology, University of Florence, Florence, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Sassoli
authors.affiliation: Department of Experimental and Clinical Medicine, Section of Anatomy and Histology, Research Unit of Histology and Embryology, University of Florence, Florence, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Formigli
authors.affiliation: Department of Experimental and Clinical Medicine, Section of Anatomy and Histology, Research Unit of Histology and Embryology, University of Florence, Florence, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Bani
authors.affiliation: Department of Experimental and Clinical Medicine, Section of Anatomy and Histology, Research Unit of Histology and Embryology, University of Florence, Florence, Italy silvia.nistri@unifi.it.
authors.forename: Silvia
authors.initials: S
authors.lastname: Nistri
mesh_terms: D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D002470:Cell Survival; D002478:Cells, Cultured; D004151:Dipeptides / Q000494:pharmacology; D051379:Mice; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000473:pathology / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D018384:Oxidative Stress; D051381:Rats; D051881:Receptor, Notch1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012065:Relaxin / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D004151:Dipeptides; C419410:N-(N-(3,5-difluorophenacetyl)alanyl)phenylglycine tert-butyl ester; C497762:Notch1 protein, mouse; C497763:Notch1 protein, rat; D051881:Receptor, Notch1; D012065:Relaxin
keywords: DAPT; H9c2; RXFP1; cardiomyocytes; oxidative injury