Inhibition of GSK3beta by postconditioning is required to prevent opening of the mitochondrial permeability transition pore during reperfusion.
BACKGROUND
Opening of the mitochondrial permeability transition pore (mPTP) is a crucial event in lethal reperfusion injury. Phosphorylation (inhibition) of glycogen synthase kinase-3beta (GSK3beta) has been involved in cardioprotection. We investigated whether phosphorylated GSK3beta may protect the heart via the inhibition of mPTP opening during postconditioning.


RESULTS
Wild-type and transgenic GSK3beta-S9A mice (the cardiac GSK3beta activity of which cannot be inactivated) underwent 60 minutes of ischemia and 24 hours of reperfusion. At reperfusion, wild-type and GSK3beta-S9A mice received no intervention (control), postconditioning (3 cycles of 1 minute ischemia and 1 minute of reperfusion), the mPTP inhibitor cyclosporine A (CsA; 10 mg/kg IV), or the GSK3beta inhibitor SB216763 (SB21; 70 microg/kg IV). Infarct size was assessed by triphenyltetrazolium chloride staining. The resistance of the mPTP to opening after Ca(2+) loading was assessed by spectrofluorometry on mitochondria isolated from the area at risk. In wild-type mice, infarct size was significantly reduced by postconditioning, CsA, and SB21, averaging 39+/-2%, 35+/-5%, and 37+/-4%, respectively, versus 58+/-5% of the area at risk in control mice (P<0.05). In GSK3beta-S9A mice, only CsA, but not postconditioning or SB21, reduced infarct size. Postconditioning, CsA, and SB21 all improved the resistance of the mPTP in wild-type mice, but only CsA did so in GSK3beta-S9A mice.


CONCLUSIONS
These results suggest that S9-phosphorylation of GSK3beta is required for postconditioning and likely acts by inhibiting the opening of the mitochondrial permeability transition pore.
Gomez
Ludovic
L
INSERM U886, Université Claude Bernard Lyon, 69373 Lyon, France. ovize@sante.univ-lyon1.fr.
Paillard
Mélanie
M
Thibault
Hélène
H
Derumeaux
Geneviève
G
Ovize
Michel
M
D000818:Animals; D016572:Cyclosporine / Q000494:pharmacology; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D007211:Indoles / Q000494:pharmacology; D019157:Ischemic Preconditioning, Myocardial; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008854:Microscopy, Electron; D008928:Mitochondria / Q000201:enzymology / Q000648:ultrastructure; D033681:Mitochondrial Membrane Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D009203:Myocardial Infarction / Q000517:prevention & control; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000473:pathology / Q000648:ultrastructure; D010085:Oxidative Phosphorylation; D010766:Phosphorylation
D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; C417521:SB 216763; D016572:Cyclosporine; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3