RESUMEN
Pulmonary Hypertension (PH) is a pathophysiologic condition characterized by hypoxemia and right ventricular strain. Proliferation of fibroblasts, smooth muscle cells, and endothelial cells is central to the pathology of PH in animal models and in humans. Methionine aminopeptidase-2 (MetAP2) regulates proliferation in a variety of cell types including endothelial cells, smooth muscle cells, and fibroblasts. MetAP2 is inhibited irreversibly by the angiogenesis inhibitor fumagillin. We have previously found that inhibition of MetAP2 with fumagillin in bleomycin-injured mice decreased pulmonary fibrosis by selectively decreasing the proliferation of lung myofibroblasts. In this study, we investigated the role of fumagillin as a potential therapy in experimental PH. In vivo, treatment of rats with fumagillin early after monocrotaline injury prevented PH and right ventricular remodeling by decreasing the thickness of the medial layer of the pulmonary arteries. Treatment with fumagillin beginning two weeks after monocrotaline injury did not prevent PH but was associated with decreased right ventricular mass and decreased cardiomyocyte hypertrophy, suggesting a direct effect of fumagillin on right ventricular remodeling. Incubation of rat pulmonary artery smooth muscle cells (RPASMC) with fumagillin and MetAP2-targeting siRNA inhibited proliferation of RPASMC in vitro. Platelet-derived growth factor, a growth factor that is important in the pathogenesis of PH and stimulates proliferation of fibroblasts and smooth muscle cells, strongly increased expression of MetP2. By immunohistochemistry, we found that MetAP2 was expressed in the lesions of human pulmonary arterial hypertension. We propose that fumagillin may be an effective adjunctive therapy for treating PH in patients.
Asunto(s)
Aminopeptidasas/metabolismo , Ciclohexanos/administración & dosificación , Ácidos Grasos Insaturados/administración & dosificación , Glicoproteínas/metabolismo , Hipertensión Pulmonar/patología , Hipertensión Pulmonar/prevención & control , Aminopeptidasas/antagonistas & inhibidores , Aminopeptidasas/genética , Animales , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Modelos Animales de Enfermedad , Regulación de la Expresión Génica , Glicoproteínas/antagonistas & inhibidores , Glicoproteínas/genética , Ventrículos Cardíacos/efectos de los fármacos , Ventrículos Cardíacos/fisiopatología , Hemodinámica , Humanos , Hipertensión Pulmonar/inducido químicamente , Masculino , Monocrotalina/farmacología , Miocitos Cardíacos/efectos de los fármacos , Miocitos Cardíacos/metabolismo , Miocitos del Músculo Liso/citología , Miofibroblastos/efectos de los fármacos , Miofibroblastos/patología , Factor de Crecimiento Derivado de Plaquetas/genética , Factor de Crecimiento Derivado de Plaquetas/metabolismo , Arteria Pulmonar/citología , Arteria Pulmonar/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Sesquiterpenos/administración & dosificaciónRESUMEN
BACKGROUND: The B vitamin folic acid (FA) is important to mitochondrial protein and nucleic acid synthesis, is an antioxidant, and enhances nitric oxide synthase activity. Here, we tested whether FA reduces myocardial ischemic dysfunction and postreperfusion injury. METHODS AND RESULTS: Wistar rats were pretreated with either FA (10 mg/d) or placebo for 1 week and then underwent in vivo transient left coronary artery occlusion for 30 minutes with or without 90 minutes of reperfusion (total n=131; subgroups used for various analyses). FA (4.5x10(-6) mol/L i.c.) pretreatment and global ischemia/reperfusion (30 minutes/30 minutes) also were performed in vitro (n=28). After 30 minutes of ischemia, global function declined more in controls than in FA-pretreated rats (Delta dP/dtmax, -878+/-586 versus -1956+/-351 mm Hg/s placebo; P=0.03), and regional thickening was better preserved (37.3+/-5.3% versus 5.1+/-0.6% placebo; P=0.004). Anterior wall perfusion fell similarly (-78.4+/-9.3% versus -71.2+/-13.8% placebo at 30 minutes), yet myocardial high-energy phosphates ATP and ADP reduced by ischemia in controls were better preserved by FA pretreatment (ATP: control, 2740+/-58 nmol/g; ischemia, 947+/-55 nmol/g; ischemia plus FA, 1332+/-101 nmol/g; P=0.02). Basal oxypurines (xanthine, hypoxanthine, and urate) rose with FA pretreatment but increased less during ischemia than in controls. Ischemic superoxide generation declined (3124+/-280 cpm/mg FA versus 5898+/-474 cpm/mg placebo; P=0.001). After reperfusion, FA-treated hearts had smaller infarcts (3.8+/-1.2% versus 60.3+/-4.1% placebo area at risk; P<0.002) and less contraction band necrosis, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling positivity, superoxide, and nitric oxide synthase uncoupling. Infarct size declined similarly with 1 mg/d FA. CONCLUSIONS: FA pretreatment blunts myocardial dysfunction during ischemia and ameliorates postreperfusion injury. This is coupled to preservation of high-energy phosphates, reducing subsequent reactive oxygen species generation, eNOS-uncoupling, and postreperfusion cell death.
Asunto(s)
Adenosina Difosfato/metabolismo , Adenosina Trifosfato/metabolismo , Cardiotónicos/uso terapéutico , Oclusión Coronaria/tratamiento farmacológico , Ácido Fólico/uso terapéutico , Daño por Reperfusión Miocárdica/prevención & control , Profármacos/uso terapéutico , Animales , Cardiotónicos/farmacología , Oclusión Coronaria/metabolismo , Evaluación Preclínica de Medicamentos , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/metabolismo , Ácido Fólico/administración & dosificación , Ácido Fólico/farmacología , Hiperhomocisteinemia/tratamiento farmacológico , Infarto del Miocardio/etiología , Infarto del Miocardio/patología , Óxido Nítrico/metabolismo , Óxido Nítrico Sintasa de Tipo II/metabolismo , Óxido Nítrico Sintasa de Tipo III , Estrés Oxidativo/efectos de los fármacos , Premedicación , Profármacos/administración & dosificación , Profármacos/farmacología , Purinas/biosíntesis , Ratas , Ratas Wistar , Superóxidos/metabolismoRESUMEN
RATIONALE: Pulmonary arterial hypertension is a progressive disease characterized by an elevation in the mean pulmonary artery pressure leading to right heart failure and a significant risk of death. Alterations in two transforming growth factor (TGF) signaling pathways, bone morphogenetic protein receptor II and the TGF-beta receptor I, Alk1, have been implicated in the pathogenesis of pulmonary hypertension (PH). However, the role of TGF-beta family signaling in PH and pulmonary vascular remodeling remains unclear. OBJECTIVES: To determine whether inhibition of TGF-beta signaling will attenuate and reverse monocrotaline-induced PH (MCT-PH). METHODS: We have used an orally active small-molecule TGF-beta receptor I inhibitor, SD-208, to determine the functional role of this pathway in MCT-PH. MEASUREMENTS AND MAIN RESULTS: The development of MCT-PH was associated with increased vascular cell apoptosis, which paralleled TGF-beta signaling as documented by psmad2 expression. Inhibition of TGF-beta signaling with SD-208 significantly attenuated the development of the PH and reduced pulmonary vascular remodeling. These effects were associated with decreased early vascular cell apoptosis, adventitial cell proliferation, and matrix metalloproteinase expression. Inhibition of TGF-beta signaling with SD-208 in established MCT-PH resulted in a small but significant improvement in hemodynamic parameters and medial remodeling. CONCLUSIONS: These findings provide evidence that increased TGF-beta signaling participates in the pathogenesis of experimental severe PH.
Asunto(s)
Hipertensión Pulmonar/fisiopatología , Proteínas Serina-Treonina Quinasas/fisiología , Receptores de Factores de Crecimiento Transformadores beta/fisiología , Factor de Crecimiento Transformador beta/fisiología , Animales , Modelos Animales de Enfermedad , Células Endoteliales , Hepatocitos , Hipertensión Pulmonar/inducido químicamente , Masculino , Monocrotalina/administración & dosificación , Monocrotalina/toxicidad , Extractos Vegetales/administración & dosificación , Extractos Vegetales/toxicidad , Ratas , Ratas Sprague-Dawley , Receptor Tipo I de Factor de Crecimiento Transformador beta , Transducción de Señal , Células Tumorales CultivadasRESUMEN
CONTEXT: The amino acid L-arginine is a substrate for nitric oxide synthase and is increasingly used as a health supplement. Prior studies suggest that L-arginine has the potential to reduce vascular stiffness. OBJECTIVE: To determine whether the addition of L-arginine to standard postinfarction therapy reduces vascular stiffness and improves ejection fraction over 6-month follow-up in patients following acute ST-segment elevation myocardial infarction. DESIGN AND SETTING: Single-center, randomized, double-blind, placebo-controlled trial with enrollment from February 2002 to June 2004. PATIENTS: A total of 153 patients following a first ST-segment elevation myocardial infarction were enrolled; 77 patients were 60 years or older. INTERVENTION: Patients were randomly assigned to receive L-arginine (goal dose of 3 g 3 times a day) or matching placebo for 6 months. MAIN OUTCOME MEASURES: Change in gated blood pool-derived ejection fraction over 6 months in patients 60 years or older randomized to receive L-arginine compared with those assigned to receive placebo. Secondary outcomes included change in ejection fraction in all patients enrolled, change in noninvasive measures of vascular stiffness, and clinical events. RESULTS: Baseline characteristics, vascular stiffness measurements, and left ventricular function were similar between participants randomized to receive placebo or L-arginine. The mean (SD) age was 60 (13.6) years; of the participants, 104 (68%) were men. There was no significant change from baseline to 6 months in the vascular stiffness measurements or left ventricular ejection fraction in either of the 2 groups, including those 60 years or older and the entire study group. However, 6 participants (8.6%) in the L-arginine group died during the 6-month study period vs none in the placebo group (P = .01). Because of the safety concerns, the data and safety monitoring committee closed enrollment. CONCLUSIONS: L-arginine, when added to standard postinfarction therapies, does not improve vascular stiffness measurements or ejection fraction and may be associated with higher postinfarction mortality. L-arginine should not be recommended following acute myocardial infarction. Clinical Trial Registration ClinicalTrials.gov, NCT00051376.