(LINE DENOTES CHANGES FROM A1) Pulmonary arterial hypertension (PAH) has been linked to reduced expression of bone morphogenetic protein receptor II (BMPRII). This proposal addresses our novel and potentially ground breaking findings that impaired BMPRII signaling can lead to abnormal synthesis and assembly of elastin fibers in the walls of pulmonary arteries (PA). Structural abnormalities in elastin assembly increase stiffness of the PAs, augmenting right ventricular work. They also result in the susceptibility of elastin fibers to degradation. If this occurs in response to proteolytic activity, the consequent release of elastin peptides and elastin fiber-bound growth factors can create a pro-proliferative and pro-inflammatory milieu in the PA wall. These features are associated with progressive PAH. In our Preliminary Studies we show, for the first time, that BMPRII ligands, in particular BMP4, can increase mRNA and protein levels of tropoelastin, the soluble precursor of elastin, in cultured human (h) PA SMC. We show that this results in the assembly of dense elastin. In contrast, while TGFss1 stimulates more tropoelastin production than BMP4, the elastin fibers are less well assembled, a feature described in PAs of animal models and patients with PAH. We attribute this difference to our observation that TGFss1 reduces Jagged1, a molecule judged necessary to organize elastin into a lamellar structure by its interaction with microfibrillar associated glycoprotein 2. To support our observations in cultured cells we have shown, that mice with deletion of BMPRII in SMC produce elastin lamellae that are more susceptible to degradation when compared to littermate controls. We also show that mice with compound heterozygosity for BMPRII and BMPRIA have more severe hypoxia-induced PAH when compared to single heterozygotes as judged by both heightened muscularity and loss of peripheral (P) PAs, features that we attribute to enhanced TGF? receptor signaling.
Our first aim i n this proposal is to use hPA SMC from elastic (EPA) and PPAs to determine how BMPs via BMPRII and IA transduce signals that stimulate tropoelastin synthesis and to establish how Jagged1 regulates elastin assembly. As part of this aim, we will determine whether the mechanism accounting for inability of EPA and PPA SMC from patients with advanced PAH to synthesize and repair tropoelastin is related to stabilization of transforming growth interacting factor (TGIF), a pSmad co- repressor.
Our second aim i s to determine whether, in mice with deletion of BMPRII in SMCs or with compound heterozygosity for BMPRII and either BMPRIA or BMP4, there is increased activation of the TGFss signaling pathway, and impaired neosynthesis and assembly of elastin. We will determine whether this enhances elastin susceptibility to degradation, is associated with increased PA stiffness, and with the propensity to develop elevated PA resistance and morphologic features of PAH, including the induction of a pro-proliferative and pro-inflammatory state in the PA wall. Our studies could lead to using elastin degradation products as biomarkers of early and progressive PAH, and to new treatments that stabilize the elastin matrix.

Public Health Relevance

New information has emerged from our studies supported during the current grant period that link abnormalities in bone morphogenetic protein receptor (BMPR)II in patients with pulmonary arterial (PA) hypertension (PAH), with a propensity to produce poorly assembled elastin fibers that are susceptible to degradation: these features contribute to vessel loss, occlusion and inflammation, hallmarks of PAH. We plan to discover how elastin production and assembly are dysregulated when there is a loss of function of BMPRII or a gain of function of TGFss1, by studying PA smooth muscle cells in culture from normal and PAH patients and by analyzing abnormalities in PA elastin in genetically modified mice, that we will relate to PA stiffness, and to proliferation and inflammation in the PA walls. These studies could produce new biomarkers of risk and progression of PAH related to elastin degradation, and may indicate that stabilizing elastin would be effective therapeutically in preventing or reversing PAH.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL074186-08
Application #
8402583
Study Section
Respiratory Integrative Biology and Translational Research Study Section (RIBT)
Program Officer
Colombini-Hatch, Sandra
Project Start
2003-07-01
Project End
2014-12-31
Budget Start
2013-01-01
Budget End
2013-12-31
Support Year
8
Fiscal Year
2013
Total Cost
$564,422
Indirect Cost
$215,402
Name
Stanford University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
009214214
City
Stanford
State
CA
Country
United States
Zip Code
94305
Liu, Aiping; Schreier, David; Tian, Lian et al. (2014) Direct and indirect protection of right ventricular function by estrogen in an experimental model of pulmonary arterial hypertension. Am J Physiol Heart Circ Physiol 307:H273-83
Rabinovitch, Marlene; Guignabert, Christophe; Humbert, Marc et al. (2014) Inflammation and immunity in the pathogenesis of pulmonary arterial hypertension. Circ Res 115:165-75
Sawada, Hirofumi; Saito, Toshie; Nickel, Nils P et al. (2014) Reduced BMPR2 expression induces GM-CSF translation and macrophage recruitment in humans and mice to exacerbate pulmonary hypertension. J Exp Med 211:263-80
Spiekerkoetter, Edda; Tian, Xuefei; Cai, Jie et al. (2013) FK506 activates BMPR2, rescues endothelial dysfunction, and reverses pulmonary hypertension. J Clin Invest 123:3600-13
Vanderpool, Rebecca R; El-Bizri, Nesrine; Rabinovitch, Marlene et al. (2013) Patchy deletion of Bmpr1a potentiates proximal pulmonary artery remodeling in mice exposed to chronic hypoxia. Biomech Model Mechanobiol 12:33-42
Kim, Yu-Mee; Haghighat, Leila; Spiekerkoetter, Edda et al. (2011) Neutrophil elastase is produced by pulmonary artery smooth muscle cells and is linked to neointimal lesions. Am J Pathol 179:1560-72
Perez, Vinicio A de Jesus; Ali, Ziad; Alastalo, Tero-Pekka et al. (2011) BMP promotes motility and represses growth of smooth muscle cells by activation of tandem Wnt pathways. J Cell Biol 192:171-88
Alvira, Cristina M; Guignabert, Christophe; Kim, Yu-Mee et al. (2011) Inhibition of transforming growth factor ýý worsens elastin degradation in a murine model of Kawasaki disease. Am J Pathol 178:1210-20
Spiekerkoetter, Edda; Guignabert, Christophe; de Jesus Perez, Vinicio et al. (2009) S100A4 and bone morphogenetic protein-2 codependently induce vascular smooth muscle cell migration via phospho-extracellular signal-regulated kinase and chloride intracellular channel 4. Circ Res 105:639-47, 13 p following 647
Guignabert, C; Alvira, C M; Alastalo, T-P et al. (2009) Tie2-mediated loss of peroxisome proliferator-activated receptor-gamma in mice causes PDGF receptor-beta-dependent pulmonary arterial muscularization. Am J Physiol Lung Cell Mol Physiol 297:L1082-90

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