Nitric oxide mediates the antiapoptotic effect of insulin in myocardial ischemia-reperfusion: the roles of PI3-kinase, Akt, and endothelial nitric oxide synthase phosphorylation.

Abstract

BACKGROUND:

Recent evidence from cultured endothelial cell studies suggests that phosphorylation of endothelial nitric oxide synthase (eNOS) through the PI3-kinase-Akt pathway increases NO production. This study was designed to elucidate the signaling pathway involved in the antiapoptotic effect of insulin in vivo and to test the hypothesis that phosphorylation of eNOS by insulin may participate in the cardioprotective effect of insulin after myocardial ischemia and reperfusion.

METHODS AND RESULTS:

Male Sprague-Dawley rats were subjected to 30 minutes of myocardial ischemia and 4 hours of reperfusion. Rats were randomized to receive vehicle, insulin, insulin plus wortmannin, or insulin plus L-NAME. Treatment with insulin resulted in 2.6-fold and 4.3-fold increases in Akt and eNOS phosphorylation and a significant increase in NO production in ischemic/reperfused myocardial tissue. Phosphorylation of Akt and eNOS and increase of NO production by insulin were completely blocked by wortmannin, a PI3-kinase inhibitor. Pretreatment with L-NAME, a nonselective NOS inhibitor, had no effect on Akt and eNOS phosphorylation but significantly reduced NO production. Moreover, treatment with insulin markedly reduced myocardial apoptotic death (P<0.01 versus vehicle). Pretreatment with wortmannin abolished the antiapoptotic effect of insulin. Most importantly, pretreatment with L-NAME also significantly reduced the antiapoptotic effect of insulin (P<0.01 versus insulin).

CONCLUSIONS:

These results demonstrated that in vivo administration of insulin activated Akt through the PI3-kinase-dependent mechanism and reduced postischemic myocardial apoptotic death. Phosphorylation of eNOS and the concurrent increase of NO production contribute significantly to the antiapoptotic effect of insulin.

• Authors: Feng Gao, Erhe Gao, Tian-Li Yue, Eliot H Ohlstein, Bernard L Lopez, Theodore A Christopher, Xin-Liang Ma
• Journal: Circulation (Circulation) Vol. 105 Issue 12 Pg. 1497-502 (Mar 26 2002) ISSN: 1524-4539 [Electronic] United States
• PMID: 11914261 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Androstadienes
• Enzyme Inhibitors
• Insulin
• Phosphoinositide-3 Kinase Inhibitors
• Proto-Oncogene Proteins
• Nitric Oxide
• Nitric Oxide Synthase
• Nitric Oxide Synthase Type III
• Nos3 protein, rat
• Akt1 protein, rat
• Protein Serine-Threonine Kinases
• Proto-Oncogene Proteins c-akt
• Glucose
• Potassium
• NG-Nitroarginine Methyl Ester
• Wortmannin

Topics

• Androstadienes (pharmacology)
• Animals
• Apoptosis (drug effects)
• Cells, Cultured
• Enzyme Activation (drug effects)
• Enzyme Inhibitors (pharmacology)
• Glucose (pharmacology)
• Insulin (pharmacology)
• Male
• Myocardial Ischemia (drug therapy, metabolism, pathology)
• Myocardium (cytology, metabolism)
• NG-Nitroarginine Methyl Ester (pharmacology)
• Nitric Oxide (metabolism)
• Nitric Oxide Synthase (antagonists & inhibitors, metabolism)
• Nitric Oxide Synthase Type III
• Phosphatidylinositol 3-Kinases (metabolism)
• Phosphoinositide-3 Kinase Inhibitors
• Phosphorylation (drug effects)
• Potassium (pharmacology)
• Protein Serine-Threonine Kinases
• Proto-Oncogene Proteins (metabolism)
• Proto-Oncogene Proteins c-akt
• Rats
• Rats, Sprague-Dawley
• Reperfusion Injury (metabolism, prevention & control)
• Signal Transduction (drug effects)
• Wortmannin