title: Estrogen-Related Receptor α (ERRα) is required for adaptive increases in PGC-1 isoform expression during electrically stimulated contraction of adult cardiomyocytes in sustained hypoxic conditions.
abstract: OBJECTIVE
  In adult myocardium, Estrogen-Related Receptor α (ERRα) programs energetic capacity of cardiomyocytes by regulating expression of target genes required for mitochondrial biogenesis, fatty acid metabolism and oxidative phosphorylation. Transcriptional activation by ERRα is dependent on the α or β isoform of Peroxisome Proliferator-Activated Receptor γ Coactivator-1 (PGC-1). This study utilized a model of continuously contracting adult cardiomyocytes to determine the effects of sustained oxygen reduction (hypoxia) on ERRα target gene expression.
  
  
  RESULTS
  Adult feline cardiomyocytes in primary culture were electrically stimulated to contract at 1 Hz in either normoxia (21% O2) or hypoxia (0.5% O2). Compared to normoxia, hypoxia increased PGC-1α mRNA and PGC-1β mRNA levels by 16-fold and 14-fold after 24h. ERRα mRNA levels were increased 3-fold by hypoxia over the same time period. Treatment of cardiomyocytes with XCT-790, an ERRα inverse agonist, caused knockdown of ERRα protein expression. The increases in PGC-1 mRNA levels in response to hypoxia were blocked by XCT-790 treatment, which indicates that expression of PGC-1 isoforms is dependent on ERRα activity. The products of two ERRα target genes required for energy metabolism, Cox6c mRNA and Fabp3 mRNA, increased by 4.5-fold and 3.5 fold after 24h of hypoxia as compared to normoxic controls. These increases were blocked by XCT-790 treatment of hypoxic cardiomyocytes with a concomitant decrease in ERRα expression.
  
  
  CONCLUSIONS
  ERRα activity is required to increase expression of PGC-1 isoforms and downstream target genes as part of the adaptive response of contracting adult cardiomyocytes to sustained hypoxia.
authors.affiliation: Gazes Cardiac Research Institute, Department of Medicine, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Kathryn F
authors.initials: KF
authors.lastname: Cunningham
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Gyda C
authors.initials: GC
authors.lastname: Beeson
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Craig C
authors.initials: CC
authors.lastname: Beeson
authors.affiliation: Gazes Cardiac Research Institute, Department of Medicine, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Catalin F
authors.initials: CF
authors.lastname: Baicu
authors.affiliation: Gazes Cardiac Research Institute, Department of Medicine, Medical University of South Carolina, Charleston, SC, USA; Ralph H. Johnson Department of Veterans Affairs Medical Center, Charleston, SC, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Zile
authors.affiliation: Gazes Cardiac Research Institute, Department of Medicine, Medical University of South Carolina, Charleston, SC, USA; Ralph H. Johnson Department of Veterans Affairs Medical Center, Charleston, SC, USA. Electronic address: mcdermp@musc.edu.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: McDermott
mesh_terms: D000367:Age Factors; D000818:Animals; D002415:Cats; D004558:Electric Stimulation; D000860:Hypoxia; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000502:physiology; D020033:Protein Isoforms; D011960:Receptors, Estrogen / Q000502:physiology*; D014157:Transcription Factors / Q000096:biosynthesis*; D000097983:ERRalpha Estrogen-Related Receptor
chemical_list: D020033:Protein Isoforms; D011960:Receptors, Estrogen; D014157:Transcription Factors; D000097983:ERRalpha Estrogen-Related Receptor; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1
keywords: Cardiomyocyte; Contraction; Estrogen-Related Receptor; Hypoxia; Peroxisome Proliferator-Activated Receptor γ Coactivator-1