284

ANGPT1

AGP1|AGPT|ANG1;angiopoietin 1;ANGPT1;angiopoietin 1

ANG-1|angiopoietin-1

8q23.1

protein-coding

Count: ANGPT1; 284

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.

BACKGROUND: Angiopoietin-1 gene expression in human pulmonary hypertensive lungs is directly proportional to increasing pulmonary vascular resistance. We hypothesized that targeted overexpresssion of angiopoietin-1 in the lung would cause persistent pulmonary hypertension in an animal model. METHODS: We injected 2 x 10(10) genomic particles of adeno-associated virus-angiopoietin-1 (AAV-Ang-1) into the right ventricular outflow tract of 30 Fischer rats while using adeno-associated virus-lacZ (AAV-lacZ) injected rats and carrier-injected rats as our control groups. All animals underwent survival surgery and were sacrificed at serial timepoints postgene delivery. At each timepoint, pulmonary artery pressures were measured and pulmonary angiography using the Microfil polymer perfusion technique was performed. The lungs were harvested for pathologic analysis, mRNA analysis, Western blot assays, and in situ RNA hybridization to localize gene expression. RESULTS: Pulmonary artery pressures of AAV-Ang-1 injected rats were significantly increased compared with the control groups (p < 0.01) at all timepoints. Pathologic analysis of AAV-Ang-1 lung specimens demonstrated increased smooth muscle cell proliferation within the medial layer of arterioles with obliteration of small vessels similar to that seen in human pulmonary hypertension. Angiograms of AAV-Ang-1 injected lungs showed blunting of small peripheral arterioles consistent with advanced pulmonary hypertension. In situ RNA hybridization localized angiopoietin-1 expression to the vascular wall of small-caliber pulmonary vessels. Protein and mRNA assays confirmed persistent angiopoietin-1 expression in the lung for up to 60 days postgene delivery. CONCLUSIONS: Overexpression of angiopoietin-1 using an adeno-associated virus vector causes pulmonary hypertension in rats. These data provide a novel physiologic animal model for pulmonary hypertension.

Angiogenic factors such as vascular endothelial growth factor (VEGF) are implicated in pulmonary hypertension (PH). However, the pathway of angiogenic factor-mediated pathologic angiogenesis in PH remains unclear. In this study, we evaluated the temporal expression of angiopoietin (Ang) 1, Ang2, and their receptor (Tie2) as well as VEGF, endothelial nitric oxide synthase (eNOS), inducible NOS (iNOS), and heme oxygenase 1 (HO1) in the monocrotaline-induced PH model. Histologic evaluation showed pathologic vascular remodeling in the arteries of lung sections 1 wk after monocrotaline treatment. Protein levels of Ang1, Ang2, eNOS, iNOS, HO1, and VEGF were increased 1 wk after monocrotaline treatment but Tie2 protein levels were decreased 2 wk afterward. These results suggest that Ang2 mediates vascular remodeling in PH by decreasing Tie2 expression. Therefore, the Ang-Tie2 system may play a role in the pathophysiology of PH.

The molecular basis and pathophysiology of pulmonary hypertension (PH) are rapidly evolving areas. Recently discovered angiopoietins (Ang) constitute a family of growth factors, and whether they play a causal or protective role in pulmonary hypertension has not been fully elucidated. Since left heart disease probably represents the most frequent cause of PH, we sought to determine whether there was a relationship between serum Ang-1 levels and pulmonary hypertension caused by mitral stenosis (MS). The study population was composed of 49 patients with isolated MS. These patients were then divided into group 1 [31 patients with severe MS: mitral valve area (MVA) PH is not severe (PAPs <50 mmHg). In conclusion, the findings of this study are distinctive in the sense that they clearly demonstrate a negative correlation between serum Ang-1 levels and the degree of PH.