The Inhibitory Effect of Leptin on Angiotensin II-Induced Vasoconstriction in Vascular Smooth Muscle Cells Is Mediated via a Nitric Oxide-Dependent Mechanism

• Published in: Endocrinology (Philadelphia) 2007-01, Vol.148 (1), p.324-331
• Main Authors: Rodríguez, Amaia, Fortuño, Ana, Gómez-Ambrosi, Javier, Zalba, Guillermo, Díez, Javier, Frühbeck, Gema
• Format: Article
• Language: English
• Subjects: 1-Phosphatidylinositol 3-kinase; AKT protein; Angiotensin; Angiotensin II; Angiotensin II - pharmacology; Animals; Aorta; Aorta, Thoracic - cytology; Arginine; Bioavailability; Biological and medical sciences; Calcium (intracellular); Calcium - metabolism; Calcium ions; Calcium signalling; Cells, Cultured; Citrulline; Coronary vessels; Drug Interactions; Endothelium; Enzyme Activation - drug effects; Enzyme Inhibitors - pharmacology; Fundamental and applied biological sciences. Psychology; Fura-2; Intracellular signalling; Janus kinase 2; Janus Kinase 2 - metabolism; Kinases; Leptin; Leptin - metabolism; Leptin - pharmacology; Lysine; Male; Muscle contraction; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - drug effects; Muscle, Smooth, Vascular - physiology; Nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Synthase Type II - antagonists & inhibitors; Nitric Oxide Synthase Type II - metabolism; Nitric-oxide synthase; omega-N-Methylarginine - pharmacology; Phosphatidylinositol 3-Kinases - metabolism; Phosphorylation; Proteins; Proto-Oncogene Proteins c-akt - metabolism; Rats; Rats, Wistar; Smooth muscle; Stat3 protein; STAT3 Transcription Factor - metabolism; Transcription factors; Transducers; Vasoconstriction; Vasoconstriction - drug effects; Vasoconstriction - physiology; Vasoconstrictor Agents - pharmacology; Vertebrates: endocrinology; Wortmannin
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.2006-0940

Leptin inhibits the contractile response induced by angiotensin (Ang) II in vascular smooth muscle cells (VSMCs) of the aorta. We studied in vitro and ex vivo the role of nitric oxide (NO) in the effect of leptin on the Ang II-induced vasoconstriction of the aorta of 10-wk-old Wistar rats. NO and nitric oxide synthase (NOS) activity were assessed by the Griess and 3H-arginine/citrulline conversion assays, respectively. Stimulation of inducible NOS (iNOS) as well as Janus kinases/signal transducers and activators of transcription (JAK/STAT) and phosphoinositide 3-kinase (PI3K)/Akt signaling pathways were determined by Western blot. The contractile responses to Ang II were evaluated in endothelium-denuded aortic rings using the organ bath system. Changes in intracellular Ca2+ were measured in VSMCs using fura-2 fluorescence. Leptin significantly (P ≤ 0.01) stimulated NO release and NOS activity in VSMCs. Leptin’s effect on NO was abolished by the NOS inhibitor, NG-monomethyl l-arginine, or the iNOS selective inhibitor l-N6-(1-iminoethyl)-lysine. Accordingly, leptin increased iNOS protein expression, with a comparable time course with that of NO production and NOS activity. Leptin also significantly increased STAT3 (P ≤ 0.01) and Akt (P ≤ 0.001) phosphorylation. Moreover, either the JAK2 inhibitor, AG490, or the PI3K inhibitor, wortmannin, significantly (P ≤ 0.05) abrogated the leptin-induced increase in iNOS protein. Finally, both NG-monomethyl l-arginine and l-N6-(1-iminoethyl)-lysine inhibitors completely blunted (P ≤ 0.001) the leptin-mediated inhibition of the Ang II-induced VSMC activation and vasoconstriction. These findings suggest that the endothelium-independent depressor action of leptin is mediated by an increase of NO bioavailability in VSMCs. This process requires the up-regulation of iNOS through mechanisms involving JAK2/STAT3 and PI3K/Akt pathways.