title: Reoxygenation after severe hypoxia induces cardiomyocyte hypertrophy in vitro: activation of CREB downstream of GSK3beta.
abstract: In vivo, left ventricular remodeling after myocardial infarction involves hypertrophy generally attributed to increased cardiac workload. We hypothesized that hypoxia/reoxygenation directly induces cardiomyocyte hypertrophy and studied several participating kinases and transcription factors in isolated cardiomyocytes. Hypoxia for 6 h followed by 42 h reoxygenation induced cardiomyocyte hypertrophy assessed by 3H leucine incorporation and immunohistochemistry. Inhibition of reactive oxygen species (ROS), serine/threonine kinase AKT, and ERK abolished reoxygenation-induced hypertrophy. In addition, a beta2-adrenergic receptor (beta2-AR) antagonist, as well as Gi inhibitor pertussis toxin, blocked reoxygenation-induced hypertrophy. Hypoxia for 6 h increased transcription factors CREB, NF-kappaB, and GATA DNA binding activities. However, only CREB DNA-binding was sustained during reoxygenation. Inhibition of PI3-kinase, ERK, and PKA abrogated reoxygenation-induced CREB DNA-binding without affecting CREB serine-133 phosphorylation. These same pathways were found to regulate hypoxia/reoxygenation-induced GSK3beta kinase activity and CREB serine-129 de-phosphorylation. GSK3beta mutants resistant to phosphorylation blocked the stimulation of CRE-dependent transcription induced by hypoxia/reoxygenation. Transfection of cardiomyocytes with a dominant-negative mutant of CREB abrogated hypoxia/reoxygenation-induced hypertrophy. We suggest that hypoxia/reoxygenation induces cardiomyocyte hypertrophy through CREB activation. Inactivation of GSK3beta by hypoxia/reoxygenation, possibly integrating PI3-kinase and ERK pathways downstream of beta2-AR and ROS, is a prerequisite for CRE-dependent transcription. Transient hypoxia may contribute to cardiac hypertrophy in ischemic heart disease independent of cardiac workload.
authors.affiliation: Max Delbrück Center for Molecular Medicine, Berlin, Germany.
authors.forename: Amina
authors.initials: A
authors.lastname: El Jamali
authors.forename: Christian
authors.initials: C
authors.lastname: Freund
authors.forename: Cindy
authors.initials: C
authors.lastname: Rechner
authors.forename: Claus
authors.initials: C
authors.lastname: Scheidereit
authors.forename: Rainer
authors.initials: R
authors.lastname: Dietz
authors.forename: Martin W
authors.initials: MW
authors.lastname: Bergmann
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000096:biosynthesis / Q000235:genetics; D015687:Cell Hypoxia; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D050991:GATA4 Transcription Factor; D017930:Genes, Reporter; D038362:Glycogen Synthase Kinase 3 / Q000502:physiology*; D000071679:Glycogen Synthase Kinase 3 beta; D006984:Hypertrophy; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020672:I-kappa B Proteins / Q000235:genetics / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000502:physiology; D010100:Oxygen / Q000494:pharmacology; D016716:PC12 Cells / Q000187:drug effects / Q000378:metabolism; D037342:Pertussis Toxin / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000502:physiology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species; D011943:Receptors, Adrenergic, beta / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015398:Signal Transduction; D014157:Transcription Factors / Q000502:physiology; D014162:Transfection
chemical_list: D000319:Adrenergic beta-Antagonists; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D050991:GATA4 Transcription Factor; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606206:Nfkbia protein, rat; D017382:Reactive Oxygen Species; D011943:Receptors, Adrenergic, beta; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D000072000:NF-KappaB Inhibitor alpha; D009320:Atrial Natriuretic Factor; D037342:Pertussis Toxin; D011494:Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3; D010100:Oxygen