title: GSK-3β at the crossroads in the signalling of heart preconditioning: implication of mTOR and Wnt pathways.
abstract: OBJECTIVE
  Ischaemic preconditioning (IPC) protects the heart against prolonged lethal ischaemia through a signalling cascade involving Akt, glycogen synthase kinase-3β (GSK-3β), and mitochondrial ATP-sensitive potassium channels (mitoK(ATP)). We previously demonstrated the involvement of the Wnt pathway in IPC in vivo via GSK-3β. A downstream target might be mammalian target of rapamycin (mTOR) since Wnt can impair tuberous sclerosis complex-2 (TSC2) phosphorylation by inhibiting GSK-3β. Here, we investigate whether the mTOR pathway is involved in cardioprotection.
  
  
  RESULTS
  Isolated-perfused mouse hearts were subjected to IPC via four cycles of ischaemia/reperfusion or pharmacological preconditioning (PPC) by diazoxide, a selective mitoK(ATP) activator. IPC, like PPC, induced an inhibition/phosphorylation of GSK-3β through Akt activation. Preconditioning also induced phosphorylation of mTOR, p70S6K, and 4E-BP1 that correlated with a significant reduction in infarct size after 40-min ischaemia and 120-min reperfusion when compared with non-preconditioned controls. Preconditioning was impaired in GSK3 knock-in mice. In transgenic mice hearts overexpressing secreted frizzled protein 1 (sFRP1, a Wnt/Frz antagonist), GSK-3β phosphorylation, mTOR activation, and cardioprotection were impaired. Cardioprotection and its signalling were also inhibited by rapamycin (an mTOR inhibitor), 5-HD (a mitoK(ATP) blocker), and N-(2-mercaptopropionyl) glycine (MPG) as a reactive oxygen species (ROS) scavenger.
  
  
  CONCLUSIONS
  We propose that the preconditioning signalling pathway involving an amplification loop results in a downregulation of GSK-3β and a constant opening of mitoK(ATP) with ROS generation to activate the mTOR pathway and induce cardioprotection. The disruption of the Wnt/Frz pathway by sFRP1 modulates this loop, inducing GSK-3β activation. This study provides evidence that cardioprotection involves both a pro-survival mTOR pathway and a developmental Wnt pathway targeting GSK-3β.
authors.affiliation: Inserm Unit 828, Pessac, France.
authors.forename: François
authors.initials: F
authors.lastname: Vigneron
authors.forename: Pierre
authors.initials: P
authors.lastname: Dos Santos
authors.forename: Sandrine
authors.initials: S
authors.lastname: Lemoine
authors.forename: Maryline
authors.initials: M
authors.lastname: Bonnet
authors.forename: Liliane
authors.initials: L
authors.lastname: Tariosse
authors.forename: Thierry
authors.initials: T
authors.lastname: Couffinhal
authors.forename: Cécile
authors.initials: C
authors.lastname: Duplaà
authors.forename: Béatrice
authors.initials: B
authors.lastname: Jaspard-Vinassa
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins; D003981:Diazoxide / Q000494:pharmacology; D004195:Disease Models, Animal; D039642:Eukaryotic Initiation Factors; D016166:Free Radical Scavengers / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D047908:Intracellular Signaling Peptides and Proteins; D019157:Ischemic Preconditioning, Myocardial; D051379:Mice; D008822:Mice, Transgenic; D009203:Myocardial Infarction / Q000201:enzymology / Q000473:pathology / Q000517:prevention & control*; D015428:Myocardial Reperfusion Injury / Q000201:enzymology / Q000473:pathology / Q000517:prevention & control*; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology; D010477:Perfusion; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051153:Wnt Proteins / Q000378:metabolism*; D000099274:Frizzled-Related Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D003981:Diazoxide; D039642:Eukaryotic Initiation Factors; D016166:Free Radical Scavengers; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D015221:Potassium Channels; D047428:Protein Kinase Inhibitors; D011506:Proteins; D051057:Proto-Oncogene Proteins c-akt; D017382:Reactive Oxygen Species; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D051153:Wnt Proteins; D000099274:Frizzled-Related Proteins; C499527:Eif4ebp1 protein, mouse; C117780:mitochondrial K(ATP) channel; C546843:mTOR protein, mouse; C000605507:Gsk3b protein, mouse; C448021:glycogen synthase kinase 3 alpha