Endothelial Cell Dysfunction in Pulmonary Hypertension
This study will examine and test healthy volunteers and patients with pulmonary hypertension to try to learn more about the disease and find better ways to detect, treat, and, if possible, slow progression. Pulmonary hypertension is a rare blood vessel disorder of the lung in which the pressure in the pulmonary artery (the blood vessel that leads from the heart to the lungs) rises above normal levels and may become life-threatening.
Normal volunteers and patients with pulmonary hypertension 18 years of age and older may be eligible for this study. All candidates are screened with a review of their medical records. Normal volunteers also have a medical history, electrocardiogram, echocardiogram (heart ultrasound), and pulmonary function test, in which the subject breathes in and out of a tube that measures lung volume, mechanics and function.
All participants undergo the following tests and procedures:
- Echocardiogram to measure heart function and blood pressure in the lungs. A small probe held against the chest uses sound waves to obtain pictures of the heart.
- Magnetic resonance imaging (MRI) to evaluate the heart's pumping action. Subjects lie on a stretcher that slides into a long, tube-shaped scanner. The machine uses a magnetic field and radio waves to obtain images of the heart.
- 6-minute walk to measure how far the subject can walk in 6 minutes. Subjects walk around the hospital for 6 minutes at a comfortable pace.
- Exercise testing to measure the ability to exercise and the subject's oxygen levels during exercise. Subjects exercise on a bike or treadmill while the oxygen and carbon dioxide they breathe are measured using a small device placed in the mouth.
- Right heart catheterization to measure pressure in the heart and lungs. A small catheter (plastic tube) is placed in an arm vein. A longer catheter called a central line is placed in a deeper vein in the neck or just below the neck, or in the leg or arm. A long, thin catheter that measures blood pressure directly is then inserted into the vein and advanced through the chambers of the heart into the lung artery to measure all the pressures in the heart and obtain blood samples.
- Genetic and protein studies. DNA, RNA, and proteins from blood samples are studied for genes and proteins that might predict the development or progression of pulmonary hypertension.
In addition to the above, patients whose pulmonary hypertension was caused by a blood vessel injury undergo the tests described below. The right heart catheter inserted for the catheterization procedure remains in place to obtain measurements of the effects of nitric oxide and nitrite in the following procedures:
- Inhalation of nitric oxide (a gas naturally produced by cells lining arteries) at 30-minute intervals to examine its effect on lung and heart pressures.
- Inhalation of aerosolized nitrite at 5-minute intervals to measure its effects on lung and heart pressures.
- Inhalation of nitric oxide for up to 24 hours to obtain multiple measurements of its effect on lung and heart pressures.
- Blood draws for laboratory tests.
In patients whose pulmonary hypertension was caused by a blood vessel injury, we also plan to follow response to standard therapy. After the initiation of standard therapy, we will restudy the same parameters (excluding NO and sodium nitrite studies) in these patients at approximately 4 months, and yearly for 5 years
Procedure: Heart Catheterization
Drug: Nitric Oxide
Drug: Nitric Oxide/INO Pulse Delivery
Drug: Sodium Nitrite
|Study Design:||Primary Purpose: Treatment|
|Official Title:||Endothelial Cell Dysfunction in Pulmonary Arterial Hypertension: Biomarkers, Mechanisms of Disease and Novel Therapeutic Targets|
|Study Start Date:||November 2004|
|Study Completion Date:||July 2009|
|Primary Completion Date:||July 2009 (Final data collection date for primary outcome measure)|
Procedure: Heart Catheterization
Introduction: Primary pulmonary hypertension, now known as idiopathic pulmonary arterial hypertension (IPAH), a subgroup of pulmonary arterial hypertension (PAH), is a rare disorder characterized by severe morbidity and high mortality rates. There are no routine screening tests or validated markers of disease activity in IPAH, or the broader group of PAH. Therefore, patients usually present at advanced stages of disease. The pathogenesis of IPAH and other forms of PAH remain unclear. Prior theories stressed a one-hit hypothesis. Current thinking focuses on a two-hit hypothesis: 1) genetic susceptibility, and 2) a triggering stimulus that initiates pulmonary vascular injury, resulting in endothelial cell (EC) dysfunction and the mobilization of endothelial progenitor cells (EPC). Loss of function mutations in the bone morphogenetic protein receptor 2 (BMPR2) gene, has been implicated in the pathogenesis of IPAH. EC dysfunction in IPAH has been associated with decreases in both endothelial nitric oxide synthase (eNOS) expression and nitric oxide (NO) production. Peripheral blood mononuclear cells (PBMCs) interact with an altered endothelial cell surface which may also be important in the disease process.
Objectives: We plan to define a subset of differentially regulated biomarkers in IPAH and PAH that may lead to earlier diagnosis and better methods for measuring responses to therapy. Specifically, we hope to identify biomarkers of IPAH and other forms of PAH that is suggestive of NO therapeutic response and which may be useful in titrating NO therapy. We also hope to identify novel targets for the development of new therapeutic strategies.
Methods: This study will consist of a pilot study and a primary study. The pilot study will enroll up to 30 patients and 30 controls in order to obtain completed studies on 10 normal subjects and 10 patients with PAH. The goal of the pilot study is to determine the best technique for circulating endothelial cell (CEC) and PBMC identification, quantification, and isolation and EPC identification and quantification. The subjects in the pilot phase undergo right heart catheterization to obtain hemodynamics and pulmonary artery blood. Pulmonary artery and peripheral blood will be used for EPC quantification and CEC and PBMC isolation. CECs and PBMC's will be studied in depth using high density oligonucleotide microarrays. In addition, plasma obtained from PAH patients will be applied to primary cultured ECs. Phenotypic expression will be studied by flow cytometry at baseline and after treatment in an effort to examine the feasibility of developing a bioassay.
The primary study will recruit the following subject groups: 1) patients with IPAH and other forms of PAH (vascular injury-induced pulmonary hypertension) who currently are on no therapy, less than or equal to 6 months of IV therapy, or less than or equal to one year of oral therapy, 2) patients with pulmonary hypertension (PH) ascribed to a nonvascular injury process and 3) normal individuals. The following baseline studies will be performed in all groups: 1) noninvasive assessment of right ventricular (RV) function by echocardiogram and magnetic resonance imaging (MRI), 2) determination of exercise capacity by cardiopulmonary stress test and six minute walk, 3) measurement of hemodynamic parameters by right heart catheterization and 4) characterization of disease phenotype by cell surface markers, oligonucleotide microarrays, and proteomics using peripheral and pulmonary arterial blood. EPC's will be quantitated and CECs and PBMCs will be isolated and analyzed by flow cytometry for expression of cell surface markers involved in coagulation, adhesion, and angiogenesis, as these are important processes in IPAH and PAH. Furthermore, ECs (identified by positive and negative selection and isolated by cell sorting) and PBMC's will be studied in depth using high density oligonucleotide microarrays to more fully characterize their transcriptome.
A major impediment to the widespread use of chronic home based inhaled NO are related to its delivery system and duration of effects. In PAH patients we plan to study a novel NO delivery system (INO pulse delivery device). Patients with PAH will be given inhaled NO (20 and 40 ppm) and then placed on inhaled NO using the INO pulse delivery device for 24 hours. Hemodynamics will be obtained serially with each dose and upon completion of 24 hours of therapy, pulmonary artery and peripheral blood will be drawn and reexamined by flow cytometry, microarrays, and proteomics.
We also plan to follow response to standard therapy (as determined by the referring physician). After the initial day 0 studies, we will restudy the same parameters (excluding NO studies) in patients with PAH at approximately 4 months, and yearly for 5 years after therapeutic intervention.
|United States, Maryland|
|National Institutes of Health Clinical Center, 9000 Rockville Pike|
|Bethesda, Maryland, United States, 20892|
|Principal Investigator:||Michael A Solomon, M.D.||National Institutes of Health Clinical Center (CC)|