Inhibition of glycogen synthase kinase or the apoptotic protein p53 lowers the threshold of helium cardioprotection in vivo: the role of mitochondrial permeability transition.
BACKGROUND
Prosurvival signaling kinases inhibit glycogen synthase kinase-3beta (GSK-3beta) activity and stimulate apoptotic protein p53 degradation. Helium produces cardioprotection by activating prosurvival kinases, but whether GSK and p53 inhibition mediate this process is unknown. We tested the hypothesis that inhibition of GSK or p53 lowers the threshold of helium cardioprotection via a mitochondrial permeability transition pore (mPTP)-dependent mechanism.


METHODS
Rabbits (n = 85) instrumented for hemodynamic measurement and subjected to a 30 min left anterior descending coronary artery (LAD) occlusion and 3 h reperfusion received 0.9% saline (control), or 1, 3, or 5 cycles of 70% helium-30% oxygen administered for 5 min interspersed with 5 min of an air-oxygen mixture (fraction of inspired oxygen concentration = 0.30) before LAD occlusion. Other rabbits received the GSK inhibitor SB 216763 (SB21; 0.2 or 0.6 mg/kg), the p53 inhibitor pifithrin-alpha (PIF; 1.5 or 3.0 mg/kg), or SB21 (0.2 mg/kg) or PIF (1.5 mg/kg) plus helium (1 cycle) before LAD occlusion in the presence or absence of the mPTP opener atractyloside (5 mg/kg).


RESULTS
Helium reduced (P < 0.05) myocardial infarct size (35 +/- 6 [n = 7], 25 +/- 4 [n = 7], and 20 +/- 3% [n = 6] of area at risk, 1, 3, and 5 cycles, respectively) compared with control (44 +/- 6% [n = 7]). SB21 (0.6 [n = 7] but not 0.2 mg/kg [n = 6]) and PIF (3.0 [n = 6] but not 1.5 mg/kg [n = 7]) also reduced necrosis. SB21 (0.2 mg/kg) or 1.5 mg/kg PIF (1.5 mg/kg) plus helium (1 cycle; n = 6 per group) decreased infarct size to an equivalent degree as three cycles of helium alone, and this cardioprotection was blocked by atractyloside (n = 7 per group).


CONCLUSIONS
Inhibition of GSK or p53 lowers the threshold of helium-induced preconditioning via a mPTP-dependent mechanism in vivo.
Pagel
Paul S
PS
Clement J. Zablocki Veterans Affairs Medical Center, Anesthesia Service, 5000 W. National Ave., Milwaukee, WI 53295, USA. pspagel@mcw.edu
Krolikowski
John G
JG
Pratt
Phillip F
PF
Shim
Yon Hee
YH
Amour
Julien
J
Warltier
David C
DC
Weihrauch
Dorothee
D
D000818:Animals; D017209:Apoptosis; D001278:Atractyloside / Q000494:pharmacology; D052160:Benzothiazoles / Q000378:metabolism; D002316:Cardiotonic Agents / Q000494:pharmacology*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D038341:Glycogen Synthase Kinases / Q000037:antagonists & inhibitors*; D006371:Helium / Q000737:chemistry / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010539:Permeability; D011817:Rabbits; D014050:Toluene / Q000031:analogs & derivatives / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D052160:Benzothiazoles; D002316:Cardiotonic Agents; D007211:Indoles; D008301:Maleimides; C417521:SB 216763; D016159:Tumor Suppressor Protein p53; D001278:Atractyloside; D006371:Helium; D014050:Toluene; C121565:pifithrin; D038341:Glycogen Synthase Kinases; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3; D010100:Oxygen