Adenoviral gene transfer of activated phosphatidylinositol 3'-kinase and Akt inhibits apoptosis of hypoxic cardiomyocytes in vitro.
BACKGROUND
The intracellular signaling pathways that control cardiomyocyte apoptosis have not been fully defined. Because insulin-like growth factor-1 (IGF-1) prevents cardiomyocyte apoptosis, we examined the role of its downstream signaling molecules in an in vitro model of hypoxia-induced cardiomyocyte apoptosis.


RESULTS
Treatment of rat neonatal cardiomyocytes with IGF-1 increased activity of both phosphatidylinositol 3' (PI 3)-kinase and its downstream target, Akt (also known as protein kinase B or PKB). Cardiomyocytes were subjected to hypoxia for 24 hours, and apoptosis was assessed by DNA laddering, TUNEL staining, and ELISA for histone-associated DNA fragments. IGF-1 treatment (100 nmol/L) reduced cardiomyocyte apoptosis, and this effect was inhibited by simultaneous treatment with a PI 3-kinase inhibitor. Cardiomyocytes were infected with either a control adenovirus (Ad.EGFP) or adenoviruses carrying constitutively active forms of PI 3-kinase (Ad.BD110) or Akt (Ad. myr-Akt-HA). Ad.BD110 significantly inhibited apoptosis of hypoxic cardiomyocytes compared with Ad.EGFP (61.0+/-4.6% less DNA fragmentation than in Ad.EGFP-infected cells, P<0.0001). Ad. myr-Akt-HA even more dramatically inhibited apoptosis of hypoxic cardiomyocytes (90.9+/-1.4% less DNA fragmentation than in controls, P<0.0001).


CONCLUSIONS
IGF-1 activates PI 3-kinase and Akt in cardiomyocytes. Activated PI 3-kinase and Akt are each sufficient to protect hypoxic cardiomyocytes against apoptosis in vitro. Adenoviral gene transfer provides a useful tool for investigating the role of these signaling pathways in cardiomyocyte apoptosis.
Matsui
T
T
Cardiovascular Research Center and Division of Cardiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02129, USA.
Li
L
L
del MonteF
Fukui
Y
Y
Franke
T F
TF
Hajjar
R J
RJ
Rosenzweig
A
A
D000256:Adenoviridae; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D015687:Cell Hypoxia / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D015967:Gene Expression Regulation, Viral; D018014:Gene Transfer Techniques; D020287:In Situ Nick-End Labeling; D066298:In Vitro Techniques; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D009025:Morpholines / Q000494:pharmacology; D018485:Muscle Fibers, Skeletal / Q000166:cytology; D017202:Myocardial Ischemia / Q000201:enzymology; D009206:Myocardium / Q000166:cytology; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D015398:Signal Transduction / Q000502:physiology
D002867:Chromones; D004791:Enzyme Inhibitors; D007334:Insulin-Like Growth Factor I; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494920:Akt1 protein, rat