GSK-3β at the crossroads in the signalling of heart preconditioning: implication of mTOR and Wnt pathways

Cardiovasc Res. 2011 Apr 1;90(1):49-56. doi: 10.1093/cvr/cvr002. Epub 2011 Jan 13.

Abstract

Aims: 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.

Methods and 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carrier Proteins / metabolism
  • Cell Cycle Proteins
  • Diazoxide / pharmacology
  • Disease Models, Animal
  • Eukaryotic Initiation Factors
  • Free Radical Scavengers / pharmacology
  • Glycogen Synthase Kinase 3 / antagonists & inhibitors
  • Glycogen Synthase Kinase 3 / genetics
  • Glycogen Synthase Kinase 3 / metabolism*
  • Glycogen Synthase Kinase 3 beta
  • Ischemic Preconditioning, Myocardial*
  • Mice
  • Mice, Transgenic
  • Myocardial Infarction / enzymology
  • Myocardial Infarction / pathology
  • Myocardial Infarction / prevention & control*
  • Myocardial Reperfusion Injury / enzymology
  • Myocardial Reperfusion Injury / pathology
  • Myocardial Reperfusion Injury / prevention & control*
  • Myocardium / enzymology*
  • Myocardium / pathology
  • Perfusion
  • Phosphoproteins / metabolism
  • Phosphorylation
  • Potassium Channels / drug effects
  • Potassium Channels / metabolism
  • Protein Kinase Inhibitors / pharmacology
  • Proteins / genetics
  • Proteins / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Reactive Oxygen Species / metabolism
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism
  • Signal Transduction* / drug effects
  • TOR Serine-Threonine Kinases / antagonists & inhibitors
  • TOR Serine-Threonine Kinases / metabolism*
  • Wnt Proteins / metabolism*

Substances

  • Carrier Proteins
  • Cell Cycle Proteins
  • Eif4ebp1 protein, mouse
  • Eukaryotic Initiation Factors
  • Free Radical Scavengers
  • Phosphoproteins
  • Potassium Channels
  • Protein Kinase Inhibitors
  • Proteins
  • Reactive Oxygen Species
  • WD repeat containing planar cell polarity effector
  • Wnt Proteins
  • mitochondrial K(ATP) channel
  • TOR Serine-Threonine Kinases
  • mTOR protein, mouse
  • Glycogen Synthase Kinase 3 beta
  • Gsk3b protein, mouse
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases, 70-kDa
  • Glycogen Synthase Kinase 3
  • glycogen synthase kinase 3 alpha
  • Diazoxide