Abstract
We tested whether isoflurane preconditioning inhibits cardiomyocyte apoptosis and evaluated the role of the phosphatidylinositol-3-kinase (PI3K)/Akt pathway in anesthetic preconditioning and determined whether PI3K/Akt signaling modulates the expression of pro- and antiapoptotic proteins in anesthetic preconditioning. Six-month-old New Zealand rabbits subjected to 40 min of myocardial ischemia followed by 180 min of reperfusion were assigned to the following groups: ischemia-reperfusion (I/R), isoflurane preconditioning and isoflurane plus PI3K inhibitors, wortmannin and 2-(4-morpholinyl)-8-phenyl-4H-l-benzopyran-4-one (LY294002) (0.6 and 0.3 mg/kg i.v., respectively). Sham-operated, wortmannin + I/R, wortmannin + sham, LY294002 + I/R, and LY294002 + sham groups were also included. Infarct size was assessed by triphenyltetrazolium chloride staining. Apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and activated caspase-3 assays. Akt phosphorylation, Bax, Bcl-2, Bad, and phosphorylated Bad (phospho-Bad) expression was assessed by immunoblotting. Isoflurane preconditioning reduced infarct size compared with the I/R group: 22 ± 4 versus 41 ± 5% (p < 0.05). The percentage of apoptotic cells decreased in the isoflurane group (3.8 ± 1.2%) compared with the I/R group (12.4 ± 1.6%; p < 0.05). These results were also confirmed by the activated caspase-3 assay. Wortmannin and LY294002 inhibited the effects of isoflurane. Myocardial infarction increased to 44 ± 3 and 45 ± 2% and the percentage of apoptotic cells was 11.9 ± 2.1 and 11.7 ± 3.3%, respectively. Akt phosphorylation and Bcl-2 and phospho-Bad expression increased after isoflurane preconditioning, whereas Bax expression decreased. These effects were inhibited by wortmannin and LY294002. The data indicate that isoflurane preconditioning reduces infarct size and myocardial apoptosis after I/R. Activation of PI3K and modulation of the expression of pro- and antiapoptotic proteins may play a role in isoflurane-induced myocardial protection.
Footnotes
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.105.100537.
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ABBREVIATIONS: PI3K, phosphoinositol 3 kinase; phospho-Bad, phosphorylated Bad; I/R, ischemia reperfusion; Iso, isoflurane; LY294002, 2-(4-morpholinyl)-8-phenyl-4H-l-benzopyran-4-one; Wort, wortmannin; LY, LY294002; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling; LV, left ventricle; TBST, Tris-buffered saline containing 0.1% Tween 20; AR/LV, ratio of area at risk to left ventricular mass; MAC, minimum alveolar concentration; ERK, extracellular signal-regulated kinase.
- Received December 23, 2005.
- Accepted March 21, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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