Cellular and molecular pathobiology of pulmonary arterial hypertension

Medical therapy for pulmonary arterial hypertension

Recent advances in the understanding of pulmonary arterial hypertension have led to new therapeutic options, although the disease remains incurable and continues to cause substantial morbidity and mortality. Disease-specific therapies have been approved for use in the US, including epoprostenol and its various analogs, endothelin receptor antagonists, and phosphodiesterase 5 inhibitors. The use of combination therapy with agents from more than one of these drug classes is becoming increasingly common, although guidelines establishing optimal combinations are lacking. Meanwhile, potential future therapeutic options are actively being pursued.

Peripheral blood B lymphocytes derived from patients with idiopathic pulmonary arterial hypertension express a different RNA pattern compared with healthy controls: a cross sectional study

BACKGROUND

Idiopathic pulmonary arterial hypertension (IPAH) is a progressive and still incurable disease. Research of IPAH-pathogenesis is complicated by the lack of a direct access to the involved tissue, the human pulmonary vasculature. Various auto-antibodies have been described in the blood of patients with IPAH. The purpose of the present work was therefore to comparatively analyze peripheral blood B lymphocyte RNA expression characteristics in IPAH and healthy controls.

METHODS

Patients were diagnosed having IPAH according to WHO (mean pulmonary arterial pressure > or = 25 mmHg, pulmonary capillary occlusion pressure < or = 15 mmHg, absence of another explaining disease). Peripheral blood B-lymphocytes of patients and controls were immediately separated by density gradient centrifugation and magnetic beads for CD19. RNA was thereafter extracted and analyzed by the use of a high sensitivity gene chip (Affymetrix HG-U133-Plus2) able to analyze 47000 transcripts and variants of human genes. The array data were analyzed by two different softwares, and up-and down-regulations were defined as at least 1.3 fold with standard deviations smaller than fold-changes.

RESULTS

Highly purified B-cells of 5 patients with IPAH (mean pulmonary artery pressure 51 +/- 13 mmHg) and 5 controls were analyzed. Using the two different analyzing methods we found 225 respectively 128 transcripts which were up-regulated (1.3-30.7 fold) in IPAH compared with healthy controls. Combining both methods, there were 33 overlapping up-regulated transcripts and no down-regulated B-cell transcripts.

CONCLUSION

Patients with IPAH have a distinct RNA expression profile of their peripheral blood B-lymphocytes compared to healthy controls with some clearly up-regulated genes. Our finding suggests that in IPAH patients B cells are activated.

Pulmonary hypertension in the critical care setting: classification, pathophysiology, diagnosis, and management

Pulmonary hypertension (PH) is common in the critical care setting, and may be a target for specific therapy. Moderate degrees of pulmonary hypertension are most often the consequence of acute or chronic heart failure, hypoxemia, or acute pulmonary embolism, and may be relatively rapidly reversible. The consequences of more severe forms of PH, both acute and chronic, can include hypotension; low cardiac output; right heart failure with congestion of the liver, gut, and kidneys; and varying degrees of hypoxemia, each of which can lead to death or severe disability. We review the physiology, definitions, classification, pathogenesis, diagnostic tools, and algorithms for diagnosis and specific treatments for the various causes of PH as seen in the critical care setting.

Effects of omega-hydroxylase product on distal human pulmonary arteries

The aim of the present study was to provide a mechanistic insight into how 20-hydroxyeicosatetraenoic acid (20-HETE) relaxes distal human pulmonary arteries (HPAs). This compound is produced by omega-hydroxylase from free arachidonic acid. Tension measurements, performed on either fresh or 1 day-cultured pulmonary arteries, revealed that the contractile responses to 1 microM 5-hydroxytryptamine were largely relaxed by 20-HETE in a concentration-dependent manner (0.01-10 microM). Iberiotoxin pretreatments (10 nM) partially decreased 20-HETE-induced relaxations. However, 10 microM indomethacin and 3 microM SC-560 pretreatments significantly reduced the relaxations to 20-HETE in these tissues. The relaxing responses induced by the eicosanoid were likely related to a reduced Ca2+ sensitivity of the myofilaments since free Ca2+ concentration ([Ca2+])-response curves performed on beta-escin-permeabilized cultured explants were shifted toward higher [Ca2+]. 20-HETE also abolished the tonic responses induced by phorbol-ester-dibutyrate (a PKC-sensitizing agent). Western blot analyses, using two specific primary antibodies against the PKC-potentiated inhibitory protein CPI-17 and its PKC-dependent phosphorylated isoform pCPI-17, confirmed that 20-HETE interferes with this intracellular process. We also investigated the effect of 20-HETE on the activation of Rho-kinase pathway-induced Ca2+ sensitivity. The data demonstrated that 20-HETE decreased U-46619-induced Ca2+ sensitivity on arteries. Hence, this observation was correlated with an increased staining of p116(Rip), a RhoA-binding protein. Together, these results strongly suggest that the 20-hydroxyarachidonic acid derivative is a potent modulator of tone in HPAs in vitro.

Rho kinase-mediated vasoconstriction in rat models of pulmonary hypertension

There is current controversy regarding whether vasoconstriction plays a significant role in the elevated pressure of severe, advanced stages of pulmonary hypertension. Results of acute vasodilator testing using conventional vasodilators in such patients suggest there is only a minor contribution of vasoconstriction. However, there is a possibility that these results may underestimate the contribution of vasoconstriction because the most effective vasodilators have not yet been tested. This issue has not been addressed even experimentally, due mainly to a lack of appropriate animal models. A few animal models that mimic the pathology of human severe pulmonary hypertension more closely (i.e., development of occlusive neointimal lesions in small pulmonary arteries/arterioles) have been introduced, including rat models of left lung pneumonectomy plus monocrotaline injection and vascular endothelial growth factor inhibition plus exposure to chronic hypoxia. We have observed that Rho kinase inhibitors, a novel class of potent vasodilators, reduce the high pulmonary artery pressure of these models acutely and markedly, suggesting that vasoconstriction can significantly be involved in pulmonary hypertension with severely remodeled (occluded) pulmonary vessels. This chapter describes methods used for evaluation of the involvement of Rho kinase-mediated vasoconstriction in rat models of pulmonary hypertension.

Smooth muscle protein 22alpha-mediated patchy deletion of Bmpr1a impairs cardiac contractility but protects against pulmonary vascular remodeling

Vascular expression of bone morphogenetic type IA receptor (Bmpr1a) is reduced in lungs of patients with pulmonary arterial hypertension, but the significance of this observation is poorly understood. To elucidate the role of Bmpr1a in the vascular pathology of pulmonary arterial hypertension and associated right ventricular (RV) dysfunction, we deleted Bmpr1a in vascular smooth muscle cells and in cardiac myocytes in mice using the SM22alpha;TRE-Cre/LoxP;R26R system. The LacZ distribution reflected patchy deletion of Bmpr1a in the lung vessels, aorta, and heart of SM22alpha;TRE-Cre;R26R;Bmpr1a(flox/+) and flox/flox mutants. This reduction in BMPR-IA expression was confirmed by Western immunoblot and immunohistochemistry in the flox/flox group. This did not affect pulmonary vasoreactivity to acute hypoxia (10% O2) or the increase in RV systolic pressure and RV hypertrophy following 3 weeks in chronic hypoxia. However, both SM22alpha;TRE-Cre;R26R;Bmpr1a(flox/+) and flox/flox mutant mice had fewer muscularized distal pulmonary arteries and attenuated loss of peripheral pulmonary arteries compared with age-matched control littermates in hypoxia. When Bmpr1a expression was reduced by short interference RNA in cultured pulmonary arterial smooth muscle cells, serum-induced proliferation was attenuated explaining decreased hypoxia-mediated muscularization of distal vessels. When Bmpr1a was reduced in cultured microvascular pericytes by short interference RNA, resistance to apoptosis was observed and this could account for protection against hypoxia-mediated vessel loss. The similar elevation in RV systolic pressure and RV hypertrophy, despite the attenuated remodeling with chronic hypoxia in the flox/flox mutants versus controls, was not a function of elevated left ventricular end diastolic pressure but was associated with increased periadventitial deposition of elastin and collagen, potentially influencing vascular stiffness.

Pulmonary hypertension in patients with essential thrombocythemia and reactive thrombocytosis

Increased incidence of pulmonary hypertension (PH) has been reported in patients with chronic myeloproliferative disorders. The exact incidence of PH in essential thrombocythemia (ET) is unknown. Most of the reported literature consists of case reports or small studies. We designed this study to asses the incidence of PH in patients with ET and reactive thrombocytosis. Previously or newly diagnosed 46 patients with ET, and 40 patients with reactive thrombocytosis secondary to iron deficiency anemia were found to be eligible for this study. Diagnosis of PH was established via transthoracic echocardiography. PH was found in 22 (47.8%) out of 46 patients with ET. Seven patients with PH were newly diagnosed ET, 5 patients with PH were in low, and the other patients with PH were in intermediate or high risk category. We found statistically significant difference in terms of platelet counts between ET patients with PH and without PH (p = 0.027). None of the patients with reactive thrombocytosis had PH. In conclusion, PH appears to be common in patients with ET. Therefore, all patients with ET should be evaluated for PH. Larger and prospective studies are required to clarify the long-term impact of PH on the survival of these patients. Future studies are also needed to determine whether cytoreductive treatment and aspirin prevent the development of PH, and to determine the effects of cytoreductive treatments and aspirin on the prognosis of PH. The effect of PH on ET prognosis should also be determined in low risk ET patients.

Genetic basis for systemic sclerosis

Among the connective tissue diseases, systemic sclerosis is an orphan disease in which diffuse connective tissue alterations lead to multi-organ involvement. Environmental factors implicated in triggering this multifactorial disease include crystalline silica, chlorine solvents, welding vapors, and various other solvents. Clustering within families indicates a role for genetic factors. Although concordance for the disease among identical twins is low, concordance for autoantibodies associated with systemic sclerosis and for fibroblast gene expression profiles is higher. Because multiplex families are rare, association and candidate gene strategies are the most appropriate methods for investigating the genetics of systemic sclerosis. The most consistent data relate to the involvement of fibrosis genes, most notably the TGF-beta regulation pathway, secreted protein acid and rich in cysteine (SPARC) genes, and the fibrillin-1 gene (FBN1). Several variants of genes for cytokines or their receptors may be involved. Data on the vasculopathy characteristic of systemic sclerosis are somewhat conflicting. Investigations into the genetics of systemic sclerosis may shed light on the complex pathophysiology of this disease, help to identify factors that predict organ involvement, and suggest new treatment strategies.

Increased regulatory and decreased CD8+ cytotoxic T cells in the blood of patients with idiopathic pulmonary arterial hypertension

BACKGROUND

An association between pulmonary arterial hypertension (PAH) and various immune disorders is well established. Recently, the role of an intact immune system in protecting against pulmonary angioproliferation was shown in an animal model.

OBJECTIVE

To elucidate the role of T cells in human PAH, we comparatively studied T cell subclasses with emphasis on regulatory T cells (T(reg)) in the peripheral blood of patients with idiopathic pulmonary arterial hypertension (IPAH) and healthy controls.

METHODS

Isolated peripheral blood mononuclear cells from 36 patients diagnosed with IPAH and 33 healthy controls were stained with fluorescently labeled monoclonal antibodies against superficial T cell markers (CD3, CD4, CD8, CD25) and FoxP3, the intracellular marker of T(reg) cells. The relative cell distribution was analyzed by flow cytometry. The functionality of patient and control T(reg) cells was assessed by coculture of T(reg) with nonregulatory T cells from the same individual.

RESULTS

Significantly less CD8+ T cells (p = 0.02) and more CD25hi+ and FoxP3+CD4+ T cells were found in the peripheral blood of patients compared with controls (p = 0.009 and p < 0.001, respectively). The percentage of FoxP3+ cells within the CD25hi+CD4+ T(reg) cells was similar. T(reg) cell functionality was equal in patients and controls.

CONCLUSION

Our findings of decreased CD8+ T cells and increased T(reg) cells in the peripheral blood of patients with IPAH are novel and may have implications for directing future research in the field to elucidate the differential role of T cells and the immune system in IPAH.

Role of Endothelium-derived CC Chemokine Ligand 2 in Idiopathic Pulmonary Arterial Hypertension

RATIONALE

Inflammatory cytokines may affect pulmonary vascular remodeling in idiopathic pulmonary arterial hypertension (IPAH). CC chemokine ligand 2 (CCL2) is synthesized by vascular cells and can stimulate monocyte/macrophage migration and smooth muscle cell (SMC) proliferation.

OBJECTIVES

To investigate the role of CCL2 in IPAH.

METHODS

CCL2 levels in plasma, monocytes, lungs, and medium from pulmonary endothelial cell (P-EC) or pulmonary artery SMC (PA-SMC) cultures were measured by ELISA and Western blot analysis. CCL2 receptor CCR2 mRNA levels in monocytes, P-ECs, and PA-SMCs were measured by real-time polymerase chain reaction. Effect of CCL2 on PA-SMC proliferation and migration was assessed using [3H]thymidine incorporation and a modified Boyden's chamber. The effect of endothelial cell-derived CCL2 on monocyte migration was measured using a modified Boyden's chamber.

MEASUREMENTS AND MAIN RESULTS

Compared with control subjects, we found the following in patients with IPAH: elevated CCL2 protein levels in plasma and lung tissue, whereas monocyte CCL2 levels were similar between patients and control subjects, and elevated CCL2 release by P-ECs or PA-SMCs. P-ECs released twice as much CCL2 than did PA-SMCs. Monocyte migration was markedly increased in the presence of P-ECs, and the increase was larger with P-ECs from patients with IPAH. CCL2-blocking antibodies reduced P-ECs' chemotactic activity by 60%. Compared with controls, PA-SMCs from patients exhibited stronger migratory and proliferative responses to CCL2, in keeping with the finding that CCR2 was markedly increased in PA-SMCs from patients.

CONCLUSIONS

These results suggest that CCL2 overproduction may be a feature of the abnormal P-EC phenotype in IPAH, contributing to the inflammatory process and to pulmonary vascular remodeling.

Procoagulant membrane microparticles correlate with the severity of pulmonary arterial hypertension

RATIONALE

Procoagulant microparticles constitute valuable hallmarks of cell damage. Microparticles also behave as cellular effectors.

OBJECTIVES

We hypothesized that the extent of the vascular cell damage measured by circulating microparticles could be related to the severity of pulmonary arterial hypertension (PAH).

METHODS

Circulating biomarkers of vascular damage and cell activation were measured in blood samples from 20 patients with PAH. Samples were withdrawn from occluded pulmonary artery and jugular vein. Peripheral venous blood samples were obtained in 23 control subjects. The microparticle procoagulant abilities were quantified by functional prothrombinase and tissue factor assays and their cellular origin was determined.

MEASUREMENTS AND MAIN RESULTS

Soluble vascular cellular adhesion molecule-1 and proinflammatory markers, such as monocyte chemoattractant protein-1 and highly specific C-reactive protein, were elevated in patients with PAH compared with control subjects. Microparticles bearing active tissue factor and CD105 (endoglin) were also elevated in patients with PAH compared with control subjects (29 +/- 13 vs. 16 +/- 6 fmol/L, P < 0.001, and 1.10 +/- 0.46 vs. 0.49 +/- 0.33 nmol/L phosphatidylserine equivalent, P < 0.001, respectively). A further increase in endothelium-derived CD105 microparticles was observed in pulmonary arterial blood compared with venous blood in patients with PAH (1.73 +/- 0.77, P = 0.038). Microparticles bearing active tissue factor were at a higher level in patients in functional class III and IV and who were walking fewer than 380 m with the six-minute-walk test.

CONCLUSIONS

Circulating markers of endothelium damage, proinflammatory markers, and cell stimulation estimated with circulating microparticles appear to be valuable tools in determining the severity of PAH.

Raised LIGHT levels in pulmonary arterial hypertension: potential role in thrombus formation

RATIONALE

Thrombus formation and inflammation are involved in the pathogenesis of pulmonary arterial hypertension (PAH), and LIGHT (Lymphotoxin-like Inducible protein that competes with Glycoprotein D for Herpesvirus entry mediator on T lymphocytes) has been shown to promote vascular inflammation.

OBJECTIVES

We sought to investigate the role of the tumor necrosis factor superfamily ligand LIGHT in the pathogenesis of PAH.

METHODS

We studied 73 patients with severe PAH and 10 control subjects. LIGHT and pro- and antithrombotic markers were assessed by enzyme immunoassays.

MEASUREMENTS AND MAIN RESULTS

(1) Patients with idiopathic PAH (n = 21), patients with PAH related to risk factors or associated conditions (n = 31), and those with chronic thromboembolic PAH (n = 21) all had raised serum levels of LIGHT compared with control subjects (n = 10). (2) LIGHT levels in femoral artery were significantly related to mortality in the patients with PAH. (3) Immunostaining of LIGHT and its receptors was seen in alveolar macrophages, vascular smooth muscle cells, and endothelial cells in lungs from patients with PAH. (4) Thirteen patients received prostacyclin infusion (3 mo), and all showed hemodynamic improvement, accompanied by decreased LIGHT levels. (5) Prostacyclin abolished the release of LIGHT from activated platelets in vitro, suggesting that the decrease in LIGHT during prostacyclin therapy could involve direct effects on platelets. (6) LIGHT increased tissue factor and plasminogen activator inhibitor type 1 and decreased thrombomodulin levels in endothelial cells, inducing a prothrombotic state in these cells.

CONCLUSIONS

Our findings suggest prothrombotic effects of LIGHT in PAH involving endothelium-related mechanisms, potentially contributing to the progression of this disorder.

Statin therapy, alone or with rapamycin, does not reverse monocrotaline pulmonary arterial hypertension: the rapamcyin-atorvastatin-simvastatin study

Pulmonary arterial hypertension (PAH) is characterized by excessive pulmonary artery smooth muscle cell proliferation and impaired apoptosis leading to obstruction of resistance pulmonary arteries. We hypothesized that antiproliferative (rapamycin) and proapoptotic (statins) agents, already used clinically for other indications, would decrease experimental PAH, facilitating translation to human therapies. Prior studies in the rat monocrotaline-PAH model have indicated that simvastatin regresses and rapamycin prevents, but cannot reverse, PAH. Two PAH regression strategies (rapamycin monotherapy vs. rapamycin + atorvastatin) and one prevention strategy (simvastatin) were tested in a rat monocrotaline-PAH model. Adult male Sprague-Dawley rats were randomized to saline ( n = 6) or monocrotaline (60 mg/kg ip, n = 36) treatment groups. Monocrotaline rats were randomized to gavage with vehicle, rapamycin (2.5 mg·kg−1·day−1), or rapamycin + atorvastatin (10 mg·kg−1·day−1) treatment groups, beginning 12 days post-monocrotaline. Echocardiographic and hemodynamic end points were assessed 2 wk later. Additional monocrotaline-PAH rats ( n = 20) were randomized to vehicle or simvastatin (2 mg·kg−1·day−1) treatment groups and followed echocardiographically for 4 wk. Monocrotaline-PAH increased lung p70 S6 kinase phosphorylation, and this was reversed by rapamycin, confirming the biological activity of rapamycin. Despite the use of high doses, neither rapamcyin nor rapamycin + atorvastatin improved survival nor reduced PAH, vascular remodeling, and right ventricular hypertrophy. Although prophylactic simvastatin slowed PAH progression, by 4 wk PAH severity and mortality were not different from placebo. Apart from the new finding of p70 S6 kinase phosphorylation in monocrotaline-PAH, this is a negative therapeutic trial (none of these promising therapies improved monocrotaline-PAH). These negative results should be considered as human trials with these agents are underway (simvastatin) or proposed (rapamycin).

Management strategies for patients with pulmonary hypertension in the intensive care unit

OBJECTIVE

Pulmonary hypertension may be encountered in the intensive care unit in patients with critical illnesses such as acute respiratory distress syndrome, left ventricular dysfunction, and pulmonary embolism, as well as after cardiothoracic surgery. Pulmonary hypertension also may be encountered in patients with preexisting pulmonary vascular, lung, liver, or cardiac diseases. The intensive care unit management of patients can prove extremely challenging, particularly when they become hemodynamically unstable. The objective of this review is to discuss the pathogenesis and physiology of pulmonary hypertension and the utility of various diagnostic tools, and to provide recommendations regarding the use of vasopressors and pulmonary vasodilators in intensive care.

DATA SOURCES AND EXTRACTION

We undertook a comprehensive review of the literature regarding the management of pulmonary hypertension in the setting of critical illness. We performed a MEDLINE search of articles published from January 1970 to March 2007. Medical subject headings and keywords searched and cross-referenced with each other were: pulmonary hypertension, vasopressor agents, therapeutics, critical illness, intensive care, right ventricular failure, mitral stenosis, prostacyclin, nitric oxide, sildenafil, dopamine, dobutamine, phenylephrine, isoproterenol, and vasopressin. Both human and animal studies related to pulmonary hypertension were reviewed.

CONCLUSIONS

Pulmonary hypertension presents a particular challenge in critically ill patients, because typical therapies such as volume resuscitation and mechanical ventilation may worsen hemodynamics in patients with pulmonary hypertension and right ventricular failure. Patients with decompensated pulmonary hypertension, including those with pulmonary hypertension associated with cardiothoracic surgery, require therapy for right ventricular failure. Very few human studies have addressed the use of vasopressors and pulmonary vasodilators in these patients, but the use of dobutamine, milrinone, inhaled nitric oxide, and intravenous prostacyclin have the greatest support in the literature. Treatment of pulmonary hypertension resulting from critical illness or chronic lung diseases should address the primary cause of hemodynamic deterioration, and pulmonary vasodilators usually are not necessary.

Pathogenic mechanisms of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a complex disease that causes significant morbidity and mortality and is clinically characterized by an increase in pulmonary vascular resistance. The histopathology is marked by vascular proliferation/fibrosis, remodeling, and vessel obstruction. Development of PAH involves the complex interaction of multiple vascular effectors at all anatomic levels of the arterial wall. Subsequent vasoconstriction, thrombosis, and inflammation ensue, leading to vessel wall remodeling and cellular hyperproliferation as the hallmarks of severe disease. These processes are influenced by genetic predisposition as well as diverse endogenous and exogenous stimuli. Recent studies have provided a glimpse at certain molecular pathways that contribute to pathogenesis; these have led to the identification of attractive targets for therapeutic intervention. We will review our current understanding of the mechanistic underpinnings of the genetic and exogenous/acquired triggers of PAH. The resulting imbalance of vascular effectors provoking pathogenic vascular changes will also be discussed, with an emphasis on common and overarching regulatory pathways that may relate to the primary triggers of disease. The current conceptual framework should allow for future studies to refine our understanding of the molecular pathogenesis of PAH and improve the therapeutic regimen for this disease.

Pulmonary arterial hypertension: a rare complication of primary Sjögren syndrome: report of 9 new cases and review of the literature

Primary Sjögren syndrome (pSS) is a fairly common autoimmune disease with glandular and extraglandular manifestations. Pulmonary involvement mainly corresponds to small airways and interstitial lung disease. Pulmonary arterial hypertension (PAH) is rare: to our knowledge, only 32 cases have been reported in pSS patients to date. PAH is a disease of the small pulmonary arteries characterized by vascular proliferation and remodeling, resulting in a progressive increase in pulmonary vascular resistance, and, ultimately, right ventricular failure and death. We report 9 new cases of pSS-associated PAH with a complete assessment including clinical characteristics (of both PAH and pSS), hemodynamic parameters, medical management, and outcome. We also review the 19 fully documented PAH patients with pSS reported in the English-language literature, therefore analyzing a total of 28 cases (27 women; mean age at PAH diagnosis, 50 +/- 11 yr; range, 23-68 yr). Functional impairment at diagnosis was severe, with a New York Heart Association (NYHA) functional class of III or IV in most cases. Seven of 15 (47%) patients for whom data were available had history or evidence of right heart failure at PAH diagnosis. Hemodynamic parameters were moderate to severe with a mean pulmonary artery pressure of 44 +/- 11 mm Hg (range, 24-60 mm Hg) and a cardiac index of 2.91 +/- 0.72 Lmin(-1)m(-2) (range, 1.36-3.88 Lmin(-1)m(-2)). Standard PAH therapy (endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, or prostanoids) was initially effective in some patients but had short-term and long-term failures. Some patients were treated with first-line immunosuppressants alone leading to improvement in some, but second-line standard PAH therapy was added in all cases thereafter. The best treatment strategy remains to be defined. Estimated survival rates were low (73% and 66% at 1 and 3 years, respectively). Compared with pSS patients without PAH, patients with pSS-associated PAH had Raynaud phenomenon, cutaneous vasculitis, and interstitial lung disease significantly more frequently. They also more frequently had antinuclear, anti-Ro/SSA, and anti-RNP autoantibodies, as well as positive rheumatoid factor and hypergammaglobulinemia. These data suggest that systemic vasculopathy, B-cell activation, and autoimmunity could play a role in the pathophysiology of pSS-associated PAH. In conclusion, this report underlines the rarity and severity of PAH in pSS patients. The best therapeutic regimen remains to be defined but should include standard PAH therapy and/or immunosuppressants.

Early changes in rat hearts with developing pulmonary arterial hypertension can be detected with three-dimensional electrocardiography

The study aim was to assess three-dimensional electrocardiogram (ECG) changes during development of pulmonary arterial hypertension (PAH). PAH was induced in male Wistar rats ( n = 23) using monocrotaline (MCT; 40 mg/kg sc). Untreated healthy rats served as controls ( n = 5). ECGs were recorded with an orthogonal three-lead system on days 0, 14, and 25 and analyzed with dedicated computer software. In addition, left ventricular (LV)-to-right ventricular (RV) fractional shortening ratio was determined using echocardiography. Invasively measured RV systolic pressure was 49 (SD 10) mmHg on day 14 and 64 (SD 10) mmHg on day 25 vs. 25 (SD 2) mmHg in controls (both P < 0.001). Baseline ECGs of controls and MCT rats were similar, and ECGs of controls did not change over time. In MCT rats, ECG changes were already present on day 14 but more explicit on day 25: increased RV electromotive forces decreased mean QRS-vector magnitude and changed QRS-axis orientation. Important changes in action potential duration distribution and repolarization sequence were reflected by a decreased spatial ventricular gradient magnitude and increased QRS-T spatial angle. On day 25, LV-to-RV fractional shortening ratio was increased, and RV hypertrophy was found, but not on day 14. In conclusion, developing PAH is characterized by early ECG changes preceding RV hypertrophy, whereas severe PAH is marked by profound ECG changes associated with anatomical and functional changes in the RV. Three-dimensional ECG analysis appears to be very sensitive to early changes in RV afterload.

Effects of Combined Therapy With a Rho-Kinase Inhibitor and Prostacyclin on Monocrotaline-Induced Pulmonary Hypertension in Rats

Pulmonary hypertension (PH) is a fatal disease characterized by endothelial dysfunction, hypercontraction and proliferation of vascular smooth muscle cells, and migration of inflammatory cells, for which no satisfactory treatment has yet been developed. We have previously demonstrated that long-term inhibition of Rho-kinase, an effector of the small GTPase Rho, ameliorates monocrotaline-induced PH in rats and hypoxia-induced PH in mice. We also have reported that prostacyclin and its oral analogue, beraprost sodium (BPS), may lack direct inhibitory effect on Rho-kinase in vitro, suggesting that combination therapy with a Rho-kinase inhibitor and BPS is effective for the treatment of PH. In this study, we addressed this point in monocrotaline-induced PH model in rats. Male Sprague-Dawley rats were given a subcutaneous injection of monocrotaline (60 mg/kg). They were maintained with or without the treatment with a Rho-kinase inhibitor, fasudil (30 mg/kg/day), BPS (200 microg/kg/day), or a combination of both drugs for 3 weeks. The combination therapy, when compared with each monotherapy, showed significantly more improvement in PH, right ventricular hypertrophy, and pulmonary medial thickness without any adverse effects. Plasma concentrations of fasudil were not affected by BPS. These results suggest that combination therapy with a Rho-kinase inhibitor and prostacyclin exerts further beneficial effects on PH.

Elevated plasma endothelin-1 and pulmonary arterial pressure in children exposed to air pollution

BACKGROUND

Controlled exposures of animals and humans to particulate matter (PM) or ozone air pollution cause an increase in plasma levels of endothelin-1, a potent vasoconstrictor that regulates pulmonary arterial pressure.

OBJECTIVES

The primary objective of this field study was to determine whether Mexico City children, who are chronically exposed to levels of PM and O(3) that exceed the United States air quality standards, have elevated plasma endothelin-1 levels and pulmonary arterial pressures.

METHODS

We conducted a study of 81 children, 7.9 +/- 1.3 years of age, lifelong residents of either northeast (n = 19) or southwest (n = 40) Mexico City or Polotitlán (n = 22), a control city with PM and O(3) levels below the U.S. air quality standards. Clinical histories, physical examinations, and complete blood counts were done. Plasma endothelin-1 concentrations were determined by immunoassay, and pulmonary arterial pressures were measured by Doppler echocardiography.

RESULTS

Mexico City children had higher plasma endothelin-1 concentrations compared with controls (p < 0.001). Mean pulmonary arterial pressure was elevated in children from both northeast (p < 0.001) and southwest (p < 0.05) Mexico City compared with controls. Endothelin-1 levels in Mexico City children were positively correlated with daily outdoor hours (p = 0.012), and 7-day cumulative levels of PM air pollution < 2.5 mum in aerodynamic diameter (PM(2.5)) before endothelin-1 measurement (p = 0.03).

CONCLUSIONS

Chronic exposure of children to PM(2.5) is associated with increased levels of circulating endothelin-1 and elevated mean pulmonary arterial pressure.

Perspectives on endothelial-to-mesenchymal transition: potential contribution to vascular remodeling in chronic pulmonary hypertension

All forms of pulmonary hypertension are characterized by structural changes in pulmonary arteries. Increased numbers of cells expressing α-smooth muscle (α-SM) actin is a nearly universal finding in the remodeled artery. Traditionally, it was assumed that resident smooth muscle cells were the exclusive source of these newly appearing α-SM actin-expressing cells. However, rapidly emerging experimental evidence suggests other, alternative cellular sources of these cells. One possibility is that endothelial cells can transition into mesenchymal cells expressing α-SM actin and that this process contributes to the accumulation of SM-like cells in vascular pathologies. We review the evidence that endothelial-mesenchymal transition is an important contributor to cardiac and vascular development as well as to pathophysiological vascular remodeling. Recent work has provided evidence for the role of transforming growth factor-β, Wnt, and Notch signaling in this process. The potential roles of matrix metalloproteinases and serine proteases are also discussed. Importantly, endothelial-mesenchymal transition may be reversible. Thus insights into the mechanisms controlling endothelial-mesenchymal transition are relevant to vascular remodeling and are important as we consider new therapies aimed at reversing pulmonary vascular remodeling.

Fluvastatin inhibits hypoxic proliferation and p38 MAPK activity in pulmonary artery fibroblasts

The earliest structural change in hypoxia-induced pulmonary hypertension is increased proliferation of adventitial fibroblasts. This fibroproliferative response occurs in acute and chronic hypoxic models, is dependent on p38 mitogen-activated protein (MAP) kinase activation, is selective for the pulmonary circulation, and would seem an important therapeutic target. Simvastatin attenuates pulmonary vascular remodeling in animal models, but additional information regarding mechanisms of action, differential antiproliferative effects and dose responses of available statins is required for appropriate clinical trial design. Our objectives were to determine the effects of statins on acute hypoxia-induced proliferation and p38 MAP kinase activation in pulmonary and systemic artery fibroblasts, to assess the effects of cholesterol intermediates, prenyltransferase and related inhibitors, and to determine the statin's mechanism of action. Atorvastatin, fluvastatin, and simvastatin inhibited adventitial fibroblast proliferation. At low doses (1 microM), this effect was selective for hypoxic (versus serum-induced) proliferation and was also selective for pulmonary (versus systemic) fibroblasts. Complete inhibition of hypoxia-induced p38 MAP kinase activity was achieved at this 1-microM dose. The lipophilic statins exhibited similar potency. The statin effect was reversed by geranylgeranyl pyrophosphate and mimicked by geranylgeranyl transferase and Rac1 inhibitors. Hypoxia-induced p38 MAP kinase activation and proliferation in pulmonary adventitial fibroblasts is dependent on a geranylgeranylated signaling protein, probably Rac1. One micromolar of fluvastatin exhibits a circulation- and stimulus-selective antiproliferative effect on pulmonary artery fibroblasts. The pharmacokinetics of fluvastatin would suggest that its antiproliferative effects may be useful in pulmonary hypertension associated with hypoxia.

Pulmonary hypertension: current diagnosis and treatment

Pulmonary hypertension (PH) is a devastating disease that - if untreated - is characterized by a poor prognosis. According to the current classification (Venice, 2003), pulmonary arterial hypertension (PAH) is distinguished from other forms of PH. Recent advances in drug therapy have led to a dramatic improvement of medical care particularly in patients with PAH. Hence, early establishment of the diagnosis appears increasingly important. This review article gives an overview on the definition, classification, pathophysiology, and clinical presentation of various forms of PH. Furthermore, it summarizes the recommended diagnostic work-up and the current treatment options particularly in PAH, with special emphasis on prostanoids, endothelin receptor antagonists (ERAs), and phosphopdiesterase type 5 (PDE5) inhibitors such as sildenafil. Finally, novel developments are being discussed which currently represent an exciting field of research.

Therapy of pulmonary arterial hypertension in systemic sclerosis: An update

Pulmonary arterial hypertension (PAH) affects 10% to 15% of patients with systemic sclerosis and is a major cause for disease-related morbidity and mortality. Over the past decade, significant progress has been made in the understanding of the pathophysiologic mechanisms underlying PAH. This progress led to the development of several new treatment options and, as a result, dramatically improved survival among this severely affected cohort. The outcome in patients with scleroderma-related PAH is much worse than that in patients with idiopathic PAH, and unfortunately only a few studies have assessed treatment and outcome among patients suffering from connective tissue disease-related PAH. In recent years, publications of connective tissue disease subgroup analysis from large trials in PAH have emerged. We review the current treatment options for PAH and the evidence for their use in scleroderma-related PAH.

Pulmonary arterial hypertension: current therapeutic strategies

The treatment of pulmonary arterial hypertension--once a lethal condition--has evolved considerably over the past few years as the number of therapeutic options available to treat this disease has increased. In this Review we attempt to summarize the current knowledge of the pathogenesis of pulmonary hypertension, in relation to the therapies presently available and those that could become available in the near future. The use of prostacyclin and its analogs, calcium-channel blockers, endothelin-receptor antagonists and phosphodiesterase type 5 inhibitors is reviewed. Newer concepts, such as the use of combination therapy, and the potential for long-term disease amelioration and improvement of outcomes, are also discussed. The role of supportive care and medications not specific to pulmonary hypertension is also examined. In addition, we review the novel emerging therapies, such as imatinib, fasudil, simvastatin, ghrelin and vasoactive intestinal peptide, which hold therapeutic potential for disease modification as well as treatment of symptoms.

Raloxifene Modulates Pulmonary Vascular Reactivity in Spontaneously Hypertensive Rats

Selective estrogen receptor modulators (SERMs) reduce vascular tone in the systemic circulation. Their effects on the pulmonary circulation are unknown. The present study examined the effect of oral treatment with raloxifene (a second-generation SERM) on vasomotor reactivity in pulmonary arteries from normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Pulmonary arterial rings were suspended in a multi-channel myograph, and changes in isometric tension were measured. WKY rings constricted less to U46619 than SHR rings, and the difference was eliminated after chronic treatment with raloxifene. More contraction to U46619 was obtained after inhibition of nitric oxide synthase (NOS) by L-NAME (as an index of basal NO release) in raloxifene-treated than in control SHR rings. Less U46619-induced contraction after raloxifene treatment occurred only in SHR rings with endothelium, and this effect was abolished upon removal of the endothelium. Raloxifene treatment did not enhance the contribution of basal NO to U46619-induced constriction in WKY rings. Raloxifene treatment did not modify endothelium-dependent relaxation to acetylcholine and endothelium-independent relaxation to nifedipine. The reduced relaxing sensitivity to sodium nitroprusside (SNP) in SHR rings was normalized by raloxifene treatment. Raloxifene treatment reduced CaCl2-induced tone in SHR but not in WKY rings. The results show that chronic treatment with raloxifene could improve pulmonary vascular function in hypertensive animals by (1) increasing basal NO release, (2) reducing vascular smooth muscle tone, and (3) improving the effect of NO on vascular smooth muscle in SHR. In contrast, raloxifene has little effect on vascular reactivity in pulmonary arteries from normotensive WKY rats.

Going to High Altitude with a Newborn Infant

Fetal life conditions the responses of a newborn infant to high altitude. The fetal circulation is characterized by high pulmonary vascular resistance and low pulmonary blood flow, as well as intra and extracardiac shunts that serve to route blood to and from the placenta and around the fetal lungs. At birth, rapid changes occur in the pulmonary circulation under normoxia; pulmonary vascular resistance falls, pulmonary blood flow increases dramatically, and the fetal shunts close functionally, then anatomically. Under conditions of hypoxia, the changes of circulatory transition occur more slowly, and pronounced hypoxia can cause a reversion to fetal circulatory patterns, albeit without the placenta to serve as the organ of oxygenation. Underlying medical conditions of newborn infants that combine exaggerated hypoxemia in response to high altitude hypoxia with an underlying predisposition to pulmonary hypertension can increase the likelihood of problems at high altitude. Awareness of risk factors and clinical signs of hypoxemia in newborn infants, as well as measurement of arterial oxygen saturation by pulse oximetry, can aid health professionals and parents in recognizing and preventing altitude-associated illness.

Prostanoid therapy for pulmonary arterial hypertension

Epoprostenol and the structurally related compounds treprostinil, iloprost, and beraprost are collectively referred to as prostanoids. The discovery of epoprostenol in 1976 and unequivocal demonstration of its efficacy in 1996 dramatically altered the approach to therapy for pulmonary arterial hypertension (PAH). Development of prostanoids available through multiple routes of administration and the discovery and development of other agents acting through alternative pathways continue to expand the array of therapeutic options. The use of prostanoids in combination with other PAH drugs and for treating pulmonary hypertensive disorders outside of the PAH classification are areas of ongoing research.

Endothelin receptor antagonists in the treatment of pulmonary arterial hypertension

The recognition that endothelin-1 contributes to the pathogenesis of pulmonary arterial hypertension has led to the development of clinically useful endothelin receptor antagonists that improve symptoms and functional capacity and alter the natural history of the disease in a beneficial way. The antagonists have varying degrees of selectivity for the two classes of endothelin receptor, termed ETA and ETB, and the varying degrees may translate into clinical differences. Endothelin receptor antagonists have become an integral part of therapy for pulmonary arterial hypertension, and the indications for their use are expanding.

Diverse signaling pathways regulate fibroblast differentiation and transformation through Rho kinase activation

This study examined the role of agonist-induced Rho kinase (ROCK) involvement in the morphological outcome of pulmonary-derived fibroblasts. Normal human lung fibroblasts (NHLF) spontaneously differentiate into network-like structures in a two-dimensional growth factor reduced Matrigel matrix-based assay. Sphingosine 1-phosphate (SPP), a bioactive phospholipid that regulates angiogenesis, inhibited fibroblast morphogenesis in a dose-dependent manner, virtually eliminating the presence of multi-cellular structures at 500 nM. Pretreatment with the Rho kinase-specific inhibitor, H1152, eradicated the high dose SPP-induced inhibition. Similarly, NHLFs transfected with Rho kinase siRNA prevented SPP-induced inhibition of the fibroblast morphogenesis. Alternatively, transforming growth factor-beta1 (TGF-beta1), a cytokine recognized as a key mediator of wound healing, terminally differentiates NHLF into myofibroblasts as evidenced by the expression of the smooth muscle cell isoform of alpha-actin (alpha-SMA). H1152 suppressed TGF-beta1-induced alpha-SMA expression in a dose-dependent manner. Similarly, treatment with Rho kinase siRNA reduced alpha-SMA expression by greater than 50%. SPP treatment had no effect on TGF-beta1-induced transformation into myofibroblasts, and TGF-beta1 treatment did not alter fibroblast morphogenesis. This study suggests a dual regulatory role for Rho kinase in cellular regulation of fibroblasts in which SPP-induced Rho kinase activation via a G-protein coupled receptor suppresses fibroblast morphogenesis while TGF-beta1-induced Rho kinase activation through a serine/threonine kinase receptor culminates in transformation into myofibroblasts.

α1-Adrenoceptor-dependent vascular hypertrophy and remodeling in murine hypoxic pulmonary hypertension

Excessive proliferation of vascular wall cells underlies the development of elevated vascular resistance in hypoxic pulmonary hypertension (PH), but the responsible mechanisms remain unclear. Growth-promoting effects of catecholamines may contribute. Hypoxemia causes sympathoexcitation, and prolonged stimulation of α1-adrenoceptors (α1-ARs) induces hypertrophy and hyperplasia of arterial smooth muscle cells and adventitial fibroblasts. Catecholamine trophic actions in arteries are enhanced when other conditions favoring growth or remodeling are present, e.g., injury or altered shear stress, in isolated pulmonary arteries from rats with hypoxic PH. The present study examined the hypothesis that catecholamines contribute to pulmonary vascular remodeling in vivo in hypoxic PH. Mice genetically deficient in norepinephrine and epinephrine production [dopamine β-hydroxylase−/− (DBH−/−)] or α1-ARs were examined for alterations in PH, cardiac hypertrophy, and vascular remodeling after 21 days exposure to normobaric 0.1 inspired oxygen fraction (FiO2). A decrease in the lumen area and an increase in the wall thickness of arteries were strongly inhibited in knockout mice (order of extent of inhibition: DBH−/− = α1D-AR−/− > α1B-AR−/−). Distal muscularization of small arterioles was also reduced (DBH−/− > α1D-AR−/− > α1B-AR−/− mice). Despite these reductions, increases in right ventricular pressure and hypertrophy were not attenuated in DBH−/− and α1B-AR−/− mice. However, hematocrit increased more in these mice, possibly as a consequence of impaired cardiovascular activation that occurs during reduction of FiO2. In contrast, in α1D-AR−/− mice, where hematocrit increased the same as in wild-type mice, right ventricular pressure was reduced. These data suggest that catecholamine stimulation of α1B- and α1D-ARs contributes significantly to vascular remodeling in hypoxic PH.

Phosphodiesterase 1 Upregulation in Pulmonary Arterial Hypertension

Background— Pulmonary arterial hypertension (PAH) is a life-threatening disease, characterized by vascular smooth muscle cell hyperproliferation. The calcium/calmodulin-dependent phosphodiesterase 1 (PDE1) may play a major role in vascular smooth muscle cell proliferation.

Methods and Results— We investigated the expression of PDE1 in explanted lungs from idiopathic PAH patients and animal models of PAH and undertook therapeutic intervention studies in the animal models. Strong upregulation of PDE1C in pulmonary arterial vessels in the idiopathic PAH lungs compared with healthy donor lungs was noted on the mRNA level by laser-assisted vessel microdissection and on the protein level by immunohistochemistry. In chronically hypoxic mouse lungs and lungs from monocrotaline-injected rats, PDE1A upregulation was detected in the structurally remodeled arterial muscular layer. Long-term infusion of the PDE1 inhibitor 8-methoxymethyl 3-isobutyl-1-methylxanthine in hypoxic mice and monocrotaline-injected rats with fully established pulmonary hypertension reversed the pulmonary artery pressure elevation, structural remodeling of the lung vasculature (nonmuscularized versus partially muscularized versus fully muscularized small pulmonary arteries), and right heart hypertrophy.

Conclusions— Strong upregulation of the PDE1 family in pulmonary artery smooth muscle cells is noted in human idiopathic PAH lungs and lungs from animal models of PAH. Inhibition of PDE1 reverses structural lung vascular remodeling and right heart hypertrophy in 2 animal models. The PDE1 family may thus offer a new target for therapeutic intervention in pulmonary hypertension.

Pulmonary vascular remodeling

The maladaptive response of the pulmonary vasculature that occurs in patients with congenital diaphragmatic hernia significantly impacts outcome. Muscularized distal pulmonary arterioles inhibit the ability of the neonate to adjust to extrauterine circulation, resulting in severe pulmonary hypertension. This review summarizes the current state of knowledge regarding normal and abnormal development of the lung vascular system and identifies current and potential therapies directed toward preserving or restoring proper pulmonary vascular function.

Pulmonary arterial hypertension in the pediatric age

Pulmonary hypertension is defined as a mean pulmonary artery pressure more than 25 mmHg at rest or 30 mmHg on exercise. Pathogenesis of pulmonary hypertension is recognized to be multifactorial: vasoconstriction, proliferation, inflammation, and thrombosis. The main point in the clinical management is to assess the potential causes, the degree of functional and hemodynamic impairment and the available therapeutic options. Treatment of children with idiopathic pulmonary hypertension is similar to that of adults, but the results are often difficult to predict, with clinical deterioration being very rapid in early symptomatic patients. However, the availability of chronic vasodilator therapy, in particular epoprostenol, has led to a significant improvement in survival of children with idiopathic pulmonary hypertension and oral vasodilator agents are currently being evaluated. Moreover, lung transplantation is, nowadays, a reality even in children. Survival for patients with idiopathic pulmonary hypertension undergoing lung transplantation is approximately 65% at 1 year and 45% at 5 years. Accepted indications are severe clinical deterioration (New York Heart Association class III or IV) despite available medical treatments including intravenous epoprostenol. Timing for listing the patient is a difficult issue that should take into account possible markers of poor prognosis on medical therapy together with mortality rate of lung transplantation, local organ availability and mean waiting time on the list before transplantation.

Pulmonary arterial hypertension: a disease of tethers, SNAREs and SNAPs?

Histological and electron microscopic studies over the past four decades have highlighted "plump," "enlarged" endothelial, smooth muscle, and fibroblastic cellular elements with increased endoplasmic reticulum, Golgi stacks, and vacuolation in pulmonary arterial lesions in human and in experimental (hypoxia and monocrotaline) pulmonary arterial hypertension. However, the contribution of disrupted intracellular membrane trafficking in the pathobiology of this disease has received insufficient attention. Recent studies suggest a pathogenetic role of the disruption of intracellular trafficking of vasorelevant proteins and cell-surface receptors in the development of this disease. The purpose of this essay is to highlight the molecular regulation of vesicular trafficking by membrane tethers, SNAREs and SNAPs, and to suggest how their dysfunction, directly and/or indirectly, might contribute to development of pulmonary arterial hypertension in experimental models and in humans, including that due to mutations in bone morphogenetic receptor type 2.

Absence of T cells confers increased pulmonary arterial hypertension and vascular remodeling

RATIONALE

Severe pulmonary arterial hypertension (SPH) is a frequently lethal condition characterized by pulmonary vascular remodeling and right heart strain or failure. SPH is also often associated with autoimmune and collagen vascular disorders.

OBJECTIVES

To study the effects of T cells on the development of experimental SPH.

METHODS

Athymic nude rats lacking T cells were treated with a single subcutaneous injection of vascular endothelial growth factor (VEGF) receptor blocker SU5416 (20 mg/kg) to induce pulmonary vascular endothelial cell apoptosis. Immunohistochemical analysis and IL-4 levels of the lung tissue were performed. Cell death and proliferation were assessed by Western blot and immunohistochemistry.

MEASUREMENTS AND MAIN RESULTS

In contrast to SU5416-treated euthymic rats that develop SPH only in combination with chronic hypoxia, athymic nude rats developed SPH and vascular remodeling (similar to clinical SPH) at normoxic conditions as demonstrated by measurements of pulmonary artery pressure and right ventricle hypertrophy. Pulmonary arterioles became occluded with proliferating endothelial cells and were surrounded by mast cells, B cells, and macrophages. IL-4, proliferating cell nuclear antigen, and collagen type I levels were markedly increased in SU5416-treated athymic rat lungs. Antibody deposition was noted along the vascular endothelium in rats with SPH. Finally, protection from SPH was conferred by immune challenge with spleen cells from euthymic nude rats.

CONCLUSIONS

These studies demonstrate the importance of a complete, intact immune system in protecting against pulmonary angioproliferation in this new model of SPH as well as the importance of intact VEGF receptor signaling for lung endothelial cell homeostasis.

Quality of life in pulmonary arterial hypertension: improvement and maintenance with bosentan

BACKGROUND

Bosentan (an oral dual endothelin receptor antagonist) improves symptoms and cardiac hemodynamics and reduces clinical worsening in patients with pulmonary arterial hypertension (PAH). The VITAL study assessed the effect of bosentan on quality of life in patients with WHO Functional Class III or IV PAH (idiopathic or associated with connective tissue diseases).

METHODS

Quality of life was assessed prospectively using the MOS SF-36 and AQOL questionnaires. Baseline readings and scores at 3 and 6 months were collected, in addition to other efficacy and safety data.

RESULTS

Among the 177 study patients, SF-36 scores were significantly improved at 3 months in the domains of physical functioning (27.3 to 34.8; p < 0.0001), role-physical (16.6 to 30.9; p < 0.0001), vitality (35.2 to 41.1; p = 0.0003), social functioning (48.0 to 58.6; p < 0.0001), mental health (64.2 to 72.0; p = 0.005) and role-emotional (44.8 to 58.1; p = 0.001). Improvements were seen in all etiologic sub-groups and were maintained in patients who remained on bosentan. An improvement in AQOL measures at 3 months was also noted for patients with baseline WHO Functional Class III.

CONCLUSIONS

Bosentan significantly improves quality of life in patients with idiopathic PAH or PAH associated with connective tissue diseases.

Acute vasodilator effect of fasudil, a Rho-kinase inhibitor, in monocrotaline-induced pulmonary hypertension in rats

Pulmonary arterial hypertension is a progressive and fatal disease for which Rho-kinase may be substantially involved. In this study, we examined the acute vasodilator effects of fasudil, a Rho-kinase inhibitor, in monocrotaline (MCT)-induced pulmonary hypertension (PH) in rats. Three weeks after a single subcutaneous injection of MCT (60 mg/kg), hemodynamic variables were measured under conscious and free-moving conditions before and after oral administration of fasudil. MCT caused a significant elevation of mean pulmonary arterial pressure (mPAP). Although a low dose of fasudil (3 mg/kg) had no effect on mPAP, a middle dose (10 mg/kg) caused a significant reduction in mPAP without change in mean systemic arterial pressure (mSAP), and a high dose (30 mg/kg) significantly reduced both mPAP and mSAP. Rho-kinase activity was significantly increased by MCT injection in pulmonary arteries but not in the aorta. Fasudil (10 mg/kg) inhibited only the Rho-kinase activity in pulmonary arteries without any effect in the aorta. Plasma concentration of hydroxyfasudil, a metabolite of fasudil, was within its clinical range in humans. These results demonstrate that fasudil exerts effective and selective vasodilatation of pulmonary arteries in rats with MCT-induced PH at a given dose, suggesting its usefulness for the treatment of the fatal disorder.

Modèles animaux d’hypertension artérielle pulmonaire

INTRODUCTION

Pulmonary arterial hypertension (PAH) is a rare syndrome of fatigue and dyspnoea, caused by increased pulmonary vascular resistance and right heart failure without an identifiable pulmonary or cardiac cause. Despite important recent advances in treatment the condition remains incurable.

BACKGROUND

Experimental animal models of PAH rely on hypoxic or monocrotaline injected rodents, the creation of left to right shunts in lambs or piglets, ligation of the ductus arteriosus in newborn lambs, genetically manipulated rodents and tissue culture. Hypoxic pulmonary hypertension is usually only moderate and limited to medial hypertrophy with varying degrees of adventitial change, but may progress to extensive remodelling in some species. Monocrotaline induced pulmonary hypertension is severe with prominent medial hypertrophy, inflammatory adventitial remodelling and, initially, pulmonary oedema and endothelial apoptosis. Pulmonary hypertension induced by shunting remains the most realistic model of PAH but causes only moderate increase in vascular resistance due to medial hypertrophy. Pulmonary hypertension of the newborn is severe but largely vasospastic, with predominant medial hypertrophy. An increasing number of genetically manipulated rodents are becoming available for the investigation of specific signalling pathways.

VIEWPOINT

While none of the models has yet reproduced PAH each allows investigation of a specific hypothesis. Recent progress has resulted from genetic manipulation and molecular and cellular approaches.

CONCLUSIONS

Animal models of PAH share basic biological abnormalities which, together with the study of lung tissue from patients with severe disease should lead to better understanding of the pathology and therapeutic innovation.

Combined endothelin receptor antagonist and transcatheter interventional therapy of patent ductus arteriosus with severe pulmonary artery hypertension

The natural history of congenital heart disease (CHD) with left to right shunt and high pulmonary blood flow, is characterized by development of severe Pulmonary Artery Hypertension (PAH); this condition usually contraindicates any type of surgical or interventional cardiac correction because of bad results. We here report the case of an adult patient with a patent ductus arteriosus and severe PAH, treated uneventfully with a staged combined therapy: Bosentan for 3 months and then percutaneous closure with amplatzer duct occluder (AGA Med. Co. Golden Valley, MN). The patient showed a dramatic improvement both of pulmonary hemodynamics and functional capacity at 8 months follow up confirming the efficacy of pulmonary vasodilator therapy in PAH associated to congenital heart disease.

[Pulmonary arterial hypertension in collagenoses: clinical features, epidemiology, pathogenesis, diagnosis and treatment]

Pulmonary arterial hypertension (PAH) is a severe vasculopathy, which is characterised by progressive narrowing and obliteration of the pulmonary arterioles and increased endothelin-1 levels. The increase of vascular resistance in the lung vessels leads to chronic pressure overload and to right heart failure, if untreated. PAH often occurs in association with rheumatic-inflammatory diseases (e.g., in 15% of patients with systemic sclerosis (SSc), especially in the limited form or in CREST patients) and determines their prognosis: in advanced stages, untreated patients die within a short period. Therefore all SSc patients, particularly the newly diagnosed ones, should be screened for PAH with echocardiography. If PAH is suspected, a right heart catheter should be performed, and if PAH is confirmed, adequate treatment should be initiated. While few years ago lung transplantation was the only option for patients with severe PAH, in recent years enormous progress was seen in drug treatment. Today prostanoids (Ventavis) and the endothelin receptor antagonist bosentan (Tracleer) are available for patients with PAH in WHO/NYHA stage III: they have substantially improved the prognosis of PAH in the last years. Since few months, also the phosphodiesterase inhibitor sildenafil (Revatio) is available. The combination of drugs with different mode of action will likely further improve the prognosis of PAH patients.

Dysfunctional intracellular trafficking in the pathobiology of pulmonary arterial hypertension

Discussions of the initiation of pulmonary arterial hypertension (PAH) in man and in experimental models have centered around intimal and medial proliferation in medium-sized pulmonary arteries. The histologic events are thought to include disordered proliferation of enlarged, vacuolated endothelial cells, neo-muscularization of the affected blood vessels, and vascular pruning. The discovery of the association of familial and sporadic PAH with mutations in BMPR2 has generated intense interest in cytokine receptor trafficking and function in the endothelial cell and how this might be disrupted to yield an enlarged proliferative cell phenotype. Nevertheless, considerations of the subcellular machinery of membrane trafficking in the endothelial cell and consequences of the disruption of this outward and inward membrane trafficking are largely absent from discussions of the pathobiology of PAH. Long-standing electron microscopy data in the PAH field has demonstrated marked disruptions of intracellular membrane trafficking in human and experimental PAH. Further, a role of the membrane-trafficking regulator Nef in simian HIV-induced PAH in macaques and in HIV-induced PAH in man is now evident. Additionally, monocrotaline and hypoxia are known to disrupt the function of Golgi tethers, SNAREs, SNAPs, and N-ethylmaleimide-sensitive factor ("the Golgi blockade hypothesis"). These results, along with recent reports demonstrating the trapping of PAH-associated human BMPR2 mutants in the Golgi, highlight the implications of disrupted intracellular membrane trafficking in the pathobiology of PAH. The purpose of this review is to present a brief overview of the molecular basis of intracellular trafficking and relate these considerations to the pathobiology of PAH.