Adrenomedullin induces endothelium-dependent vasorelaxation via the phosphatidylinositol 3-kinase/Akt-dependent pathway in rat aorta.
To study the mechanisms by which adrenomedullin (AM) induces endothelium-dependent vasorelaxation, we examined whether AM-induced endothelium-dependent vasodilation was mediated by the phosphatidylinositol 3-kinase (PI3K)/Akt-dependent pathway in rat aorta, because it was recently reported that PI3K/Akt was implicated in the activation of endothelial NO synthase. AM-induced vasorelaxation in thoracic aorta with intact endothelium was inhibited by pretreatment with PI3K inhibitors to the same level as that in endothelium-denuded aorta. AM elicited Akt phosphorylation in a time- and dose-dependent manner. AM-induced Akt phosphorylation was inhibited by pretreatment with a calmodulin-dependent protein kinase inhibitor as well as with PI3K inhibitors. When an adenovirus construct expressing a dominant-negative Akt mutant (Ad/dnAkt) was injected into abdominal aortas so that the mutant was expressed predominantly in the endothelium layer, AM-induced vasodilation was diminished to the same level as that in endothelium-denuded aortas. Finally, AM-induced cGMP production, which was used as an indicator for NO production, was suppressed by PI3K inhibition or by Ad/dnAkt infection into the endothelium. These results suggested that AM induced Akt activation in the endothelium via the Ca(2+)/calmodulin-dependent pathway and that this was implicated in the production of NO, which in turn induced endothelium-dependent vasodilation in rat aorta.
Nishimatsu
H
H
Department of Urology, Faculty of Medicine, University of Tokyo, Japan.
Suzuki
E
E
Nagata
D
D
Moriyama
N
N
Satonaka
H
H
Walsh
K
K
Sata
M
M
Kangawa
K
K
Matsuo
H
H
Goto
A
A
Kitamura
T
T
Hirata
Y
Y
D053607:Adrenomedullin; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000502:physiology; D002147:Calmodulin / Q000502:physiology; D046508:Culture Techniques; D006152:Cyclic GMP / Q000096:biosynthesis; D004730:Endothelium, Vascular / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008297:Male; D009154:Mutation; D009569:Nitric Oxide / Q000096:biosynthesis; D010455:Peptides / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D014664:Vasodilation / Q000187:drug effects
D053607:Adrenomedullin; D002118:Calcium; D002147:Calmodulin; D006152:Cyclic GMP; D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D010455:Peptides; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C494920:Akt1 protein, rat