Reperfusion-activated Akt kinase prevents apoptosis in transgenic mouse hearts overexpressing insulin-like growth factor-1.
Abstract -Hearts of wild-type and insulin-like growth factor-1 overexpressing (Igf-1(+/-)) transgenic mice were subjected to Langendorff perfusions and progressive periods of ischemia followed by reperfusion. Apoptosis was measured by DNA nucleosomal cleavage and a hairpin probe labeling assay to detect single-base overhang. Transgenic hearts subjected to 20 minutes of ischemia and 4 hours of reperfusion (I/R) sustained a rate of apoptosis of 1.8+/-0.3% compared with 4.6+/-1.1% for wild-type controls (n=4; P<0.03). Phosphorylation of the protein kinase Akt/protein kinase B was elevated 6.2-fold in transgenic hearts at baseline and increased another 4.4-fold within 10 minutes of reperfusion, remaining elevated for up to 2 hours. I/R activated Akt in wild-type hearts but to a lesser extent (1.6+/-0.3-fold). Pretreatment of transgenic hearts with wortmannin immediately before and during ischemia eliminated reperfusion-mediated activation of Akt and neutralized the resistance to apoptosis. The stress-activated kinase p38 was also activated during ischemia and reperfusion in both wild-type and transgenic hearts. Perfusion with the p38 inhibitor SB203580 (10 micromol/L) blocked both p38 activation and phosphorylation of Akt and differentially modulated apoptosis in wild-type and transgenic hearts. Pretreatment with SB203580 reduced apoptosis in wild-type hearts but increased apoptosis in transgenic hearts. These results demonstrate that Akt phosphorylation during I/R is modulated by IGF-1 and prevents apoptosis in hearts that overexpress the IGF-1 transgene.
Yamashita
K
K
Department of Molecular and Cellular Pharmacology, University of Miami Medical Center, Miami, Florida, USA.
Kajstura
J
J
Discher
D J
DJ
Wasserlauf
B J
BJ
Bishopric
N H
NH
Anversa
P
P
Webster
K A
KA
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005838:Genotype; D007093:Imidazoles / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D017202:Myocardial Ischemia / Q000503:physiopathology; D015425:Myocardial Reperfusion; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D010477:Perfusion; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D011725:Pyridines / Q000494:pharmacology; D000077191:Wortmannin; D048051:p38 Mitogen-Activated Protein Kinases
D000730:Androstadienes; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011518:Proto-Oncogene Proteins; D011725:Pyridines; D007334:Insulin-Like Growth Factor I; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580; D000077191:Wortmannin