title: Phosphatidylinositol 3-kinase may mediate isoproterenol-induced vascular relaxation in part through nitric oxide production.
abstract: Phosphatidylinositol 3-kinase (PI3-K) has been shown to mediate insulin and insulin-like growth factor-1 (IGF-1)-induced nitric oxide (NO) generation and, thus, vascular tone. A role for PI3-K in G-protein-coupled receptor signal transduction has also been reported. As beta2 -adrenergic vascular actions are partly dependent on NO, this study the role of PI3-K on in vitro isoproterenol (Iso)-induced endothelial cell (EC) nitric oxide synthase (NOS) activation and rat aortic vascular relaxation. Cell lysates of rat aortic EC (RAEC), exposed to Iso (10 micromol/L) for 5 minutes, were immunoprecipitated with an antiphosphotyrosine antibody prior to assay for Western blot for the p85-kd regulatory subunit of PI3-K. Endothelial NOS activity was determined by measuring nitrite production. Endothelium-intact aortic rings from male Wistar rats were preincubated with the PI3-K inhibitors, wortmannin (WT), or LY294002 (LY), precontracted with phenylepinephrine (PE), and relaxation to graded doses of Iso was measured. NO contribution to vascular relaxation was assessed by L-N(G)-nitroarginine methyl ester (L-NAME), a NOS inhibitor. Both Iso and IGF-1 induced an increase in p85 subunit phosphorylation as demonstrated by Western analysis, effects inhibited by preincubation with WT. Iso also enhanced association of p85 with the Triton X-100-insoluble fraction of RAEC, reflecting translocation of this enzyme to a cytoskeletal fraction. In addition, Iso as well as IGF-1 significantly increased eNOS activity measured by nitrite production. Both WT and LY markedly inhibited relaxation to Iso, while L-NAME nearly abolished this beta-adrenergic-mediated vasorelaxation. These data indicate that both Iso and IGF-1 activate the EC PI3-K pathway which mediates, in part, the release of NO and subsequent vasorelaxation in response to this beta-agonist Iso as well as to IGF-1.
authors.affiliation: Department of Medicine and Cell Biology, SUNY-Health Science Center and Veterans Affairs Medical Center, Brooklyn, NY 11203, USA.
authors.forename: Esma
authors.initials: E
authors.lastname: Isenović
authors.forename: Mary F
authors.initials: MF
authors.lastname: Walsh
authors.forename: Ranganath
authors.initials: R
authors.lastname: Muniyappa
authors.forename: Mara
authors.initials: M
authors.lastname: Bard
authors.forename: Clement A
authors.initials: CA
authors.lastname: Diglio
authors.forename: James R
authors.initials: JR
authors.lastname: Sowers
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000502:physiology; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction / Q000502:physiology; D014664:Vasodilation / Q000502:physiology*; D000077191:Wortmannin
chemical_list: D000318:Adrenergic beta-Agonists; D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D007545:Isoproterenol; D009025:Morpholines; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000077191:Wortmannin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C496316:Nos3 protein, rat