Isoflurane inhibits cardiac myocyte apoptosis during oxidative and inflammatory stress by activating Akt and enhancing Bcl-2 expression.
BACKGROUND
Volatile anesthetics attenuate apoptosis. The underlying mechanisms remain undefined. The authors tested whether isoflurane reduces apoptosis in cardiomyocytes subjected to oxidative or inflammatory stress by enhancing Akt and B-cell lymphoma-2 (Bcl-2).


METHODS
Adult and neonatal rat ventricular myocytes and atrial HL-1 myocytes were exposed to hypoxia, hydrogen peroxide, or neutrophils with or without isoflurane pretreatment. The authors assessed cell damage and investigated apoptosis using mitochondrial cytochrome c release, caspase activity, and TUNEL assay. They determined expression of phospho-Akt and Bcl-2 and tested their involvement by blocking phospho-Akt with wortmannin and Bcl-2 with HA14-1.


RESULTS
Isoflurane significantly reduced the cell damage and apoptosis induced by hypoxia, H2O2, and neutrophils. Isoflurane reduced hypoxia-induced mitochondrial cytochrome c release in HL-1 cells by 45 +/- 12% and caspase activity by 28 +/- 4%; in neonatal cells, it reduced caspase activity by 43 +/- 5% and TUNEL-positive cells by 50 +/- 2%. Isoflurane attenuated H2O2-induced caspase activity in HL-1 cells by 48 +/- 16% and TUNEL-positive cells by 78 +/- 3%; in neonatal cells, it reduced caspase activity by 30 +/- 3% and TUNEL-positive cells by 32 +/- 7%. In adult cardiomyocytes exposed to neutrophils, isoflurane decreased both mitochondrial cytochrome c and caspase activity by 47 +/- 3% and TUNEL-positive cells by 25 +/- 4%. Isoflurane enhanced phospho-Akt and Bcl-2 expression. Wortmannin and HA14-1 prevented the action of isoflurane (53 +/- 8% and 54 +/- 7% apoptotic cells vs. 18 +/- 1% without blockers).


CONCLUSIONS
Isoflurane protects cardiomyocytes against apoptosis induced by hypoxia, H2O2, or activated neutrophils through Akt activation and increased Bcl-2 expression. This suggests that a reduction in apoptosis contributes to the cardioprotective effects of isoflurane.
Jamnicki-Abegg
Marina
M
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
Weihrauch
Dorothee
D
Pagel
Paul S
PS
Kersten
Judy R
JR
Bosnjak
Zeljko J
ZJ
Warltier
David C
DC
Bienengraeber
Martin W
MW
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects*; D001711:Biotransformation / Q000187:drug effects; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002469:Cell Separation; D045304:Cytochromes c / Q000378:metabolism; D004285:Dogs; D019254:Genes, bcl-2 / Q000187:drug effects*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D000860:Hypoxia / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D007249:Inflammation / Q000473:pathology*; D007530:Isoflurane / Q000494:pharmacology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects*; D018375:Neutrophil Activation / Q000187:drug effects; D009504:Neutrophils / Q000187:drug effects; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013268:Stimulation, Chemical; D013778:Tetrazolium Salts / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism
D018685:Anesthetics, Inhalation; D013778:Tetrazolium Salts; D013844:Thiazoles; D045304:Cytochromes c; D006861:Hydrogen Peroxide; D007530:Isoflurane; D007770:L-Lactate Dehydrogenase; D051057:Proto-Oncogene Proteins c-akt; D020169:Caspases; C022616:thiazolyl blue