title: Mechanical Stretch Inhibits MicroRNA499 via p53 to Regulate Calcineurin-A Expression in Rat Cardiomyocytes.
abstract: BACKGROUND
  MicroRNAs play an important role in cardiac remodeling. MicroRNA 499 (miR499) is highly enriched in cardiomyocytes and targets the gene for Calcineurin A (CnA), which is associated with mitochondrial fission and apoptosis. The mechanism regulating miR499 in stretched cardiomyocytes and in volume overloaded heart is unclear. We sought to investigate the mechanism regulating miR499 and CnA in stretched cardiomyocytes and in volume overload-induced heart failure.
  
  
  RESULTS
  Rat cardiomyocytes grown on a flexible membrane base were stretched via vacuum to 20% of maximum elongation at 60 cycles/min. An in vivo model of volume overload with aorta-caval shunt in adult rats was used to study miR499 expression. Mechanical stretch downregulated miR499 expression, and enhanced the expression of CnA protein and mRNA after 12 hours of stretch. Expression of CnA and calcineurin activity was suppressed with miR499 overexpression; whereas, expression of dephosphorylated dynamin-related protein 1 (Drp1) was suppressed with miR499 overexpression and CnA siRNA. Adding p53 siRNA reversed the downregulation of miR499 when stretched. A gel shift assay and promoter-activity assay demonstrated that stretch increased p53 DNA binding activity but decreased miR499 promoter activity. When the miR499 promoter p53-binding site was mutated, the inhibition of miR499 promoter activity with stretch was reversed. The in vivo aorta-caval shunt also showed downregulated myocardial miR499 and overexpression of miR499 suppressed CnA and cellular apoptosis.
  
  
  CONCLUSIONS
  The miR499-controlled apoptotic pathway involving CnA and Drp1 in stretched cardiomyocytes may be regulated by p53 through the transcriptional regulation of miR499.
authors: Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.|Division of Cardiology, Department of Internal Medicine, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.|School of Medicine, Fu-Jen Catholic University, Taipei County, Taiwan.
authors: Su-Kiat
authors: SK
authors: Chua
authors: Division of Cardiology, Department of Internal Medicine, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.|School of Medicine, Fu-Jen Catholic University, Taipei County, Taiwan.
authors: Bao-Wei
authors: BW
authors: Wang
authors: School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.|Department of Neurology, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
authors: Li-Ming
authors: LM
authors: Lien
authors: Division of Cardiology, Department of Internal Medicine, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.|School of Medicine, Fu-Jen Catholic University, Taipei County, Taiwan.
authors: Huey-Ming
authors: HM
authors: Lo
authors: Division of Cardiology, Department of Internal Medicine, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.|School of Medicine, Fu-Jen Catholic University, Taipei County, Taiwan.
authors: Chiung-Zuan
authors: CZ
authors: Chiu
authors: Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.|Division of Cardiology, Department of Internal Medicine, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
authors: Kou-Gi
authors: KG
authors: Shyu
mesh_terms: D000818:Animals; D017209:Apoptosis; D019703:Calcineurin / Q000235:genetics* / Q000378:metabolism; D002306:Cardiac Volume; D034281:Dynamins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D040542:Mechanotransduction, Cellular; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D017208:Rats, Wistar; D013314:Stress, Mechanical; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism / Q000502:physiology*
chemical_list: C558425:MIRN499 microRNA, rat; D035683:MicroRNAs; D016159:Tumor Suppressor Protein p53; D019703:Calcineurin; C519851:Dnm1l protein, rat; D034281:Dynamins