title: Divergent Effects of miR-181 Family Members on Myocardial Function Through Protective Cytosolic and Detrimental Mitochondrial microRNA Targets.
abstract: BACKGROUND
  MicroRNA (miRNA) is a type of noncoding RNA that can repress the expression of target genes through posttranscriptional regulation. In addition to numerous physiologic roles for miRNAs, they play an important role in pathophysiologic processes affecting cardiovascular health. Previously, we reported that nuclear encoded microRNA (miR-181c) is present in heart mitochondria, and importantly, its overexpression affects mitochondrial function by regulating mitochondrial gene expression.
  
  
  RESULTS
  To investigate further how the miR-181 family affects the heart, we suppressed miR-181 using a miR-181-sponge containing 10 repeated complementary miR-181 "seed" sequences and generated a set of H9c2 cells, a cell line derived from rat myoblast, by stably expressing either a scrambled or miR-181-sponge sequence. Sponge-H9c2 cells showed a decrease in reactive oxygen species production and reduced basal mitochondrial respiration and protection against doxorubicin-induced oxidative stress. We also found that miR-181a/b targets phosphatase and tensin homolog (PTEN), and the sponge-expressing stable cells had increased PTEN activity and decreased PI3K signaling. In addition, we have used miR-181a/b-/-and miR-181c/d-/-knockout mice and subjected them to ischemia-reperfusion injury. Our results suggest divergent effects of different miR-181 family members: miR-181a/b targets PTEN in the cytosol, resulting in an increase in infarct size in miR-181a/b-/-mice due to increased PTEN signaling, whereas miR-181c targets mt-COX1 in the mitochondria, resulting in decreased infarct size in miR-181c/d-/-mice.
  
  
  CONCLUSIONS
  The miR-181 family alters the myocardial response to oxidative stress, notably with detrimental effects by targeting mt-COX1 (miR-181c) or with protection by targeting PTEN (miR-181a/b).
authors.affiliation: Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD sdas11@jhmi.edu.
authors.forename: Samarjit
authors.initials: S
authors.lastname: Das
authors.affiliation: Department of Environmental Health and Engineering, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD.
authors.forename: Mark
authors.initials: M
authors.lastname: Kohr
authors.affiliation: Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD.
authors.forename: Brittany
authors.initials: B
authors.lastname: Dunkerly-Eyring
authors.affiliation: Department of Cardiology, Johns Hopkins School of Medicine, Baltimore, MD.
authors.forename: Dong I
authors.initials: DI
authors.lastname: Lee
authors.affiliation: Department of Cardiology, Johns Hopkins School of Medicine, Baltimore, MD.|Faculty of Medicine and Health Sciences, Macquarie University, Sydney, Australia.
authors.forename: Djahida
authors.initials: D
authors.lastname: Bedja
authors.affiliation: Princess Margaret Cancer Centre, University of Toronto, Ontario, Canada.
authors.forename: Oliver A
authors.initials: OA
authors.lastname: Kent
authors.affiliation: Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD.
authors.forename: Anthony K L
authors.initials: AK
authors.lastname: Leung
authors.affiliation: Department of Pathology and Laboratory Medicine, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA.|Division of Transplant Immunology, Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA.|Institute for Immunology, Perelman School of Medicine, Philadelphia, PA.
authors.forename: Jorge
authors.initials: J
authors.lastname: Henao-Mejia
authors.affiliation: Department of Immunobiology, Yale University School of Medicine, New Haven, CT.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Flavell
authors.affiliation: Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD.
authors.forename: Charles
authors.initials: C
authors.lastname: Steenbergen
mesh_terms: D000818:Animals; D051545:Cyclooxygenase 1 / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000378:metabolism*; D032446:Myoblasts / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000235:genetics* / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018384:Oxidative Stress; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D051381:Rats
chemical_list: C581717:MIRN181 microRNA, rat; D008565:Membrane Proteins; D035683:MicroRNAs; C529100:mirn181 microRNA, mouse; D051545:Cyclooxygenase 1; C496512:Ptgs1 protein, mouse; D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse; C487216:Pten protein, rat
keywords: PI3 kinase; miR‐181; microRNA; mitochondria; mitochondrial miRNA; mitochondrial respiratory complex IV; mt‐COX1; oxidative stress; phosphatase and tensin homolog; reperfusion injury