title: Characterization of the regulatory mechanisms of activating transcription factor 3 by hypertrophic stimuli in rat cardiomyocytes.
abstract: OBJECTIVE
  Activating transcription factor 3 (ATF3) is a stress-activated immediate early gene suggested to have both detrimental and cardioprotective role in the heart. Here we studied the mechanisms of ATF3 activation by hypertrophic stimuli and ATF3 downstream targets in rat cardiomyocytes.
  
  
  RESULTS
  When neonatal rat cardiomyocytes were exposed to endothelin-1 (ET-1, 100 nM) and mechanical stretching in vitro, maximal increase in ATF3 expression occurred at 1 hour. Inhibition of extracellular signal-regulated kinase (ERK) by PD98059 decreased ET-1- and stretch-induced increase of ATF3 protein but not ATF3 mRNA levels, whereas protein kinase A (PKA) inhibitor H89 attenuated both ATF3 mRNA transcription and protein expression in response to ET-1 and stretch. To characterize further the regulatory mechanisms upstream of ATF3, p38 mitogen-activated protein kinase (MAPK) signaling was investigated using a gain-of-function approach. Adenoviral overexpression of p38α, but not p38β, increased ATF3 mRNA and protein levels as well as DNA binding activity. To investigate the role of ATF3 in hypertrophic process, we overexpressed ATF3 by adenovirus-mediated gene transfer. In vitro, ATF3 gene delivery attenuated the mRNA transcription of interleukin-6 (IL-6) and plasminogen activator inhibitor-1 (PAI-1), and enhanced nuclear factor-κB (NF-κB) and Nkx-2.5 DNA binding activities. Reduced PAI-1 expression was also detected in vivo in adult rat heart by direct intramyocardial adenovirus-mediated ATF3 gene delivery.
  
  
  CONCLUSIONS
  These data demonstrate that ATF3 activation by ET-1 and mechanical stretch is partly mediated through ERK and cAMP-PKA pathways, whereas p38 MAPK pathway is involved in ATF3 activation exclusively through p38α isoform. ATF3 activation caused induction of modulators of the inflammatory response NF-κB and Nkx-2.5, as well as attenuation of pro-fibrotic and pro-inflammatory proteins IL-6 and PAI-1, suggesting cardioprotective role for ATF3 in the heart.
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Oulu, Oulu, Finland.
authors.forename: Elina
authors.initials: E
authors.lastname: Koivisto
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Oulu, Oulu, Finland.
authors.forename: Alicia
authors.initials: A
authors.lastname: Jurado Acosta
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Oulu, Oulu, Finland; Department of Pathology, Institute of Diagnostics, University of Oulu, Oulu, Finland.
authors.forename: Anne-Mari
authors.initials: AM
authors.lastname: Moilanen
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Oulu, Oulu, Finland; Department of Pathology, Institute of Diagnostics, University of Oulu, Oulu, Finland.
authors.forename: Heikki
authors.initials: H
authors.lastname: Tokola
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Oulu, Oulu, Finland.
authors.forename: Jani
authors.initials: J
authors.lastname: Aro
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Oulu, Oulu, Finland.
authors.forename: Harri
authors.initials: H
authors.lastname: Pennanen
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Oulu, Oulu, Finland.
authors.forename: Hanna
authors.initials: H
authors.lastname: Säkkinen
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Oulu, Oulu, Finland.
authors.forename: Leena
authors.initials: L
authors.lastname: Kaikkonen
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Oulu, Oulu, Finland; Division of Pharmacology and Pharmacotherapy, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland.
authors.forename: Heikki
authors.initials: H
authors.lastname: Ruskoaho
authors.affiliation: Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Oulu, Oulu, Finland; School of Pharmacy, University of Eastern Finland, Kuopio, Finland.
authors.forename: Jaana
authors.initials: J
authors.lastname: Rysä
mesh_terms: D051700:Activating Transcription Factor 3 / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena; D002312:Cardiomyopathy, Hypertrophic / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000502:physiology; D005260:Female; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000378:metabolism; D018836:Inflammation Mediators / Q000378:metabolism; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D051700:Activating Transcription Factor 3; C497108:Atf3 protein, rat; D019332:Endothelin-1; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; D018836:Inflammation Mediators; D007527:Isoenzymes; D016328:NF-kappa B; C524161:Nkx2-5 protein, rat; D017395:Plasminogen Activator Inhibitor 1; D047428:Protein Kinase Inhibitors; D014157:Transcription Factors; D048051:p38 Mitogen-Activated Protein Kinases