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Angiopoietin/Tie2 pathway influences smooth muscle hyperplasia in idiopathic pulmonary hypertension.

Authors: Dewachter, L  Adnot, S  Fadel, E  Humbert, M  Maitre, B  Barlier-Mur, AM  Simonneau, G  Hamon, M  Naeije, R  Eddahibi, S 
Citation: Dewachter L, etal., Am J Respir Crit Care Med. 2006 Nov 1;174(9):1025-33. Epub 2006 Aug 17.
Pubmed: (View Article at PubMed) PMID:16917117
DOI: Full-text: DOI:10.1164/rccm.200602-304OC

RATIONALE: Angiopoietins are involved in blood vessel maturation and remodeling. OBJECTIVES: One consequence of endothelium-specific tyrosine kinase-2 (Tie2) receptor activation by angiopoietin-1 (Ang1) is the release of endothelium-derived growth factors that recruit vascular wall cells. We investigated this process in idiopathic pulmonary arterial hypertension (iPAH). METHODS: Ang1, Ang2, and total and phosphorylated Tie2 expression (mRNA and protein) was evaluated in human lung specimens and in cultured pulmonary artery smooth muscle cells (PA-SMCs) and pulmonary endothelial cells (P-ECs) isolated from patients with iPAH and control subjects. Media collected from Ang1-treated P-ECs were assessed for their PA-SMC growth-promoting effect. MEASUREMENTS AND MAIN RESULTS: Tie2 receptor was fourfold higher in lungs and P-ECs from patients with iPAH than in those from control subjects, with a parallel increase in phosphorylated lung Tie2 receptor. In contrast, Ang1 and Ang2 expression in lungs, P-ECs, and PA-SMCs did not differ. Incubation of PA-SMCs with medium collected from P-EC cultures induced marked proliferation, and this effect was stronger when using P-ECs from patients with iPAH than from control subjects. Ang1 pretreatment of P-ECs from either patients or control subjects induced a further increase in PA-SMC proliferation. Fluoxetine, an inhibitor of the mitogenic action of serotonin, reduced the growth-promoting effect of P-EC media. Ang1 added to P-ECs from patients with iPAH increased the production of endothelin-1 (ET-1) and serotonin, but not of platelet-derived growth factor-BB or epidermal growth factor, and increased the amount of mRNA encoding tryptophan hydroxylase-1 (the rate-limiting enzyme of serotonin synthesis), preproET-1, and ET-1-converting enzyme. CONCLUSIONS: The Ang1/Tie2 pathway is potentiated in iPAH, contributing to PA-SMC hyperplasia via increased stimulation of endothelium-derived growth factors synthesis by P-ECs.

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CRRD Object Information
CRRD ID: 1601487
Created: 2007-04-23
Species: All species
Last Modified: 2007-04-23
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.