Endothelin-1 in pulmonary hypertension

Peroxisome Proliferator-Activated Receptor γ and microRNA 98 in Hypoxia-Induced Endothelin-1 Signaling

Endothelin-1 (ET-1) plays a critical role in endothelial dysfunction and contributes to the pathogenesis of pulmonary hypertension (PH). We hypothesized that peroxisome proliferator-activated receptor γ (PPARγ) stimulates microRNAs that inhibit ET-1 and pulmonary artery endothelial cell (PAEC) proliferation. The objective of this study was to clarify molecular mechanisms by which PPARγ regulates ET-1 expression in vitro and in vivo. In PAECs isolated from patients with pulmonary arterial hypertension, microRNA (miR)-98 expression was reduced, and ET-1 protein levels and proliferation were increased. Similarly, hypoxia reduced miR-98 and increased ET-1 levels and PAEC proliferation in vitro. In vivo, hypoxia reduced miR-98 expression and increased ET-1 and proliferating cell nuclear antigen (PCNA) levels in mouse lung, derangements that were aggravated by treatment with the vascular endothelial growth factor receptor antagonist Sugen5416. Reporter assays confirmed that miR-98 binds directly to the ET-1 3'-untranslated region. Compared with littermate control mice, miR-98 levels were reduced and ET-1 and PCNA expression were increased in lungs from endothelial-targeted PPARγ knockout mice, whereas miR-98 levels were increased and ET-1 and PCNA expression was reduced in lungs from endothelial-targeted PPARγ-overexpression mice. Gain or loss of PPARγ function in PAECs in vitro confirmed that alterations in PPARγ were sufficient to regulate miR-98, ET-1, and PCNA expression. Finally, PPARγ activation with rosiglitazone regimens that attenuated hypoxia-induced PH in vivo and human PAEC proliferation in vitro restored miR-98 levels. The results of this study show that PPARγ regulates miR-98 to modulate ET-1 expression and PAEC proliferation. These results further clarify molecular mechanisms by which PPARγ participates in PH pathogenesis and therapy.

Beneficial Effects of Renal Denervation on Pulmonary Vascular Remodeling in Experimental Pulmonary Artery Hypertension

INTRODUCTION AND OBJECTIVES

Activation of both the sympathetic nervous system and the renin-angiotensin-aldosterone system is closely associated with pulmonary arterial hypertension. We hypothesized that renal denervation decreases renin-angiotensin-aldosterone activity and inhibits the progression of pulmonary arterial hypertension.

METHODS

Twenty-two beagles were randomized into 3 groups. The dogs' pulmonary dynamics were measured before and 8 weeks after injection of 0.1mL/kg dimethylformamide (control dogs) or 2mg/kg dehydromonocrotaline (pulmonary arterial hypertension and pulmonary arterial hypertension + renal denervation dogs). Eight weeks after injection, neurohormone levels and pulmonary tissue morphology were measured.

RESULTS

Levels of plasma angiotensin II and endothelin-1 were significantly increased after 8 weeks in the pulmonary arterial hypertension dogs and were higher in the lung tissues of these dogs than in those of the control and renal denervation dogs (mean [standard deviation] angiotensin II: 65 [9.8] vs 38 [6.7], 46 [8.1]; endothelin-1: 96 [10.3] vs 54 [6.2], 67 [9.4]; P < .01). Dehydromonocrotaline increased the mean pulmonary arterial pressure (16 [3.4] mmHg vs 33 [7.3] mmHg; P < .01), and renal denervation prevented this increase. Pulmonary smooth muscle cell proliferation was higher in the pulmonary arterial hypertension dogs than in the control and pulmonary arterial hypertension + renal denervation dogs.

CONCLUSIONS

Renal denervation attenuates pulmonary vascular remodeling and decreases pulmonary arterial pressure in experimental pulmonary arterial hypertension. The effect of renal denervation may contribute to decreased neurohormone levels.

Inhibition of ENaC by endothelin-1

The amiloride-sensitive epithelial Na(+) channel (ENaC) is a key player in the regulation of Na(+) homeostasis. Its functional activity is under continuous control by a variety of signaling molecules, including bioactive peptides of endothelin family. Since ENaC dysfunction is causative for disturbances in total body Na(+) levels associated with the abnormal regulation of blood volume, blood pressure, and lung fluid balance, uncovering the molecular mechanisms of inhibitory modulation or inappropriate activation of ENaC is crucial for the successful treatment of a variety of human diseases including hypertension. The precise regulation of ENaC is particularly important for normal Na(+) and fluid homeostasis in organs where endothelins are known to act: the kidneys, lung, and colon. Inhibition of ENaC by endothelin-1 (ET-1) has been established in renal cells, and several molecular mechanisms of inhibition of ENaC by ET-1 are proposed and will be reviewed in this chapter.

Endothelin-1 stimulates catalase activity through the PKCδ-mediated phosphorylation of serine 167

Our previous studies have shown that endothelin-1 (ET-1) stimulates catalase activity in endothelial cells and in lambs with acute increases in pulmonary blood flow (PBF), without altering gene expression. The purpose of this study was to investigate the molecular mechanism by which this occurs. Exposing pulmonary arterial endothelial cells to ET-1 increased catalase activity and decreased cellular hydrogen peroxide (H2O2) levels. These changes correlated with an increase in serine-phosphorylated catalase. Using the inhibitory peptide δV1.1, this phosphorylation was shown to be protein kinase Cδ (PKCδ) dependent. Mass spectrometry identified serine 167 as the phosphorylation site. Site-directed mutagenesis was used to generate a phospho-mimic (S167D) catalase. Activity assays using recombinant protein purified from Escherichia coli or transiently transfected COS-7 cells demonstrated that S167D catalase had an increased ability to degrade H2O2 compared to the wild-type enzyme. Using a phospho-specific antibody, we were able to verify that pS167 catalase levels are modulated in lambs with acute increases in PBF in the presence and absence of the ET receptor antagonist tezosentan. S167 is located on the dimeric interface, suggesting it could be involved in regulating the formation of catalase tetramers. To evaluate this possibility we utilized analytical gel filtration to examine the multimeric structure of recombinant wild-type and S167D catalase. We found that recombinant wild-type catalase was present as a mixture of monomers and dimers, whereas S167D catalase was primarily tetrameric. Further, the incubation of wild-type catalase with PKCδ was sufficient to convert wild-type catalase into a tetrameric structure. In conclusion, this is the first report indicating that the phosphorylation of catalase regulates its multimeric structure and activity.

Aldosterone inactivates the endothelin-B receptor via a cysteinyl thiol redox switch to decrease pulmonary endothelial nitric oxide levels and modulate pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is characterized, in part, by decreased endothelial nitric oxide (NO(·)) production and elevated levels of endothelin-1. Endothelin-1 is known to stimulate endothelial nitric oxide synthase (eNOS) via the endothelin-B receptor (ET(B)), suggesting that this signaling pathway is perturbed in PAH. Endothelin-1 also stimulates adrenal aldosterone synthesis; in systemic blood vessels, hyperaldosteronism induces vascular dysfunction by increasing endothelial reactive oxygen species generation and decreasing NO(·) levels. We hypothesized that aldosterone modulates PAH by disrupting ET(B)-eNOS signaling through a mechanism involving increased pulmonary endothelial oxidant stress.

METHODS AND RESULTS

In rats with PAH, elevated endothelin-1 levels were associated with elevated aldosterone levels in plasma and lung tissue and decreased lung NO(·) metabolites in the absence of left-sided heart failure. In human pulmonary artery endothelial cells, endothelin-1 increased aldosterone levels via peroxisome proliferator-activated receptor gamma coactivator-1α/steroidogenesis factor-1-dependent upregulation of aldosterone synthase. Aldosterone also increased reactive oxygen species production, which oxidatively modified cysteinyl thiols in the eNOS-activating region of ET(B) to decrease endothelin-1-stimulated eNOS activity. Substitution of ET(B)-Cys405 with alanine improved ET(B)-dependent NO(·) synthesis under conditions of oxidant stress, confirming that Cys405 is a redox-sensitive thiol that is necessary for ET(B)-eNOS signaling. In human pulmonary artery endothelial cells, mineralocorticoid receptor antagonism with spironolactone decreased aldosterone-mediated reactive oxygen species generation and restored ET(B)-dependent NO(·) production. Spironolactone or eplerenone prevented or reversed pulmonary vascular remodeling and improved cardiopulmonary hemodynamics in 2 animal models of PAH in vivo.

CONCLUSIONS

Our findings demonstrate that aldosterone modulates an ET(B) cysteinyl thiol redox switch to decrease pulmonary endothelium-derived NO(·) and promote PAH.

The PPARγ ligand rosiglitazone attenuates hypoxia-induced endothelin signaling in vitro and in vivo

Peroxisome proliferator-activated receptor (PPAR) γ activation attenuates hypoxia-induced pulmonary hypertension (PH) in mice. The current study examined the hypothesis that PPARγ attenuates hypoxia-induced endothelin-1 (ET-1) signaling to mediate these therapeutic effects. To test this hypothesis, human pulmonary artery endothelial cells (HPAECs) were exposed to normoxia or hypoxia (1% O(2)) for 72 h and treated with or without the PPARγ ligand rosiglitazone (RSG, 10 μM) during the final 24 h of exposure. HPAEC proliferation was measured with MTT assays or cell counting, and mRNA and protein levels of ET-1 signaling components were determined. To explore the role of hypoxia-activated transcription factors, selected HPAECs were treated with inhibitors of hypoxia-inducible factor (HIF)-1α (chetomin) or nuclear factor (NF)-κB (caffeic acid phenethyl ester, CAPE). In parallel studies, male C57BL/6 mice were exposed to normoxia (21% O(2)) or hypoxia (10% O(2)) for 3 wk with or without gavage with RSG (10 mg·kg(-1)·day(-1)) for the final 10 days of exposure. Hypoxia increased ET-1, endothelin-converting enzyme-1, and endothelin receptor A and B levels in mouse lung and in HPAECs and increased HPAEC proliferation. Treatment with RSG attenuated hypoxia-induced activation of HIF-1α, NF-κB activation, and ET-1 signaling pathway components. Similarly, treatment with chetomin or CAPE prevented hypoxia-induced increases in HPAEC ET-1 mRNA and protein levels. These findings indicate that PPARγ activation attenuates a program of hypoxia-induced ET-1 signaling by inhibiting activation of hypoxia-responsive transcription factors. Targeting PPARγ represents a novel therapeutic strategy to inhibit enhanced ET-1 signaling in PH pathogenesis.

Etiology, diagnosis, and pharmacologic treatment of pediatric pulmonary hypertension

Major advances have been made in the understanding and treatment of pulmonary hypertension in the last few years. Without treatment (medication) for idiopathic pulmonary arterial hypertension, which is a rare and potentially fatal condition, the survival time is only about 3 years after diagnosis. However, if pulmonary hypertension is secondary to other causes such as congenital heart disease, it is possible to survive for 30 years or more without treatment. The condition can affect children at any age, from fetal life to adulthood. Patients with pulmonary hypertension can present to the respiratory pediatrician with unresponsive asthma, to the neurologist with faints, or to the general pediatrician with failure to thrive. Over the last few years there have been significant developments in the available therapy for managing this complicated disease. There is now a generally recognized ladder of long-term therapy for chronic pulmonary hypertension. Treatment can start with oxygen at home at night or even during the day. Next is the use of oral phosphodiesterase inhibitors, mostly type V, such as sildenafil, which enhance endogenous nitric oxide. More potent are the endothelin receptor antagonists and the most potent are the prostanoids, especially epoprostenol, which is given by constant intravenous infusion. In addition to interventional catheterization with atrial septostomy, these agents have improved the prognostic outlook. This article reviews the current knowledge about the etiology, investigation, and treatment of children with pulmonary hypertension in the clinical setting.

Treatment of pediatric pulmonary hypertension

Pulmonary hypertension was once thought to be a rare condition and only managed in specialized centers. Now however, with the advent of echocardiography, it is found in many clinical scenarios, in the neonate with chronic lung disease, in the acute setting in the intensive care unit, in connective tissue disease and in cardiology pre- and postoperatively. We have a better understanding of the pathological process and have a range of medication which is starting to be able to palliate this previously fatal condition. This review describes the areas that are known in this condition and those that are less familiar. The basic physiology behind pulmonary hypertension and pulmonary vascular disease is explained. The histopathologic process and the various diagnostic tools are described and are followed by the current and future therapy at our disposal.

Pulmonary hypertension associated with sickle cell disease: pathophysiology and rationale for treatment

Approximately one third of patients with sickle cell disease (SCD) have pulmonary hypertension (PH), which increases their risk of death. Endothelin (ET)-1 is elevated in SCD and appears to play a key role in many of the pathologic processes in this disease, including PH, suggesting that endothelin receptor antagonists such as bosentan may be effective in treating patients with SCD, particularly those with PH. Other possible treatments include sildenafil, epoprostenol, and oral arginine. Data from controlled clinical trials are needed to establish the most effective treatment of patients with PH associated with SCD.

[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.

Current treatment options in children with pulmonary arterial hypertension and experiences with oral bosentan

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by vasoconstriction and progressive remodelling of the pulmonary arterial wall leading to right ventricular failure and death. Idiopathic PAH (IPAH) and PAH associated with congenital heart defects account for the majority of paediatric patients with PAH. During the last few decades, several pharmacological approaches have been introduced, including calcium channel-blockers (CCBs), prostacyclin analogues, endothelin receptor antagonists and, most recently, phosphodiesterase inhibitors. This paper reviews the treatment options available to children with a special focus on the initial experience with bosentan. Although CCBs have been shown to increase survival in IPAH, the beneficial effect appears to be limited to a small number of patients, defined as 'responders' to the vasoreactivity testing. With the availability of prostacyclin (intravenous epoprostenol) and then prostacyclin analogues, the treatment options have increased markedly and particularly in patients who have not responded to conventional therapy. Although epoprostenol has been shown to be efficacious in PAH, the drug is not ideal owing to serious complications arising from the invasive mode of application, particularly in children. Phosphodiesterase-5 inhibitors have also shown beneficial effects. Targeting the endothelin (ET) system with the oral, dual ET(A)/ET(B) receptor antagonist, bosentan has been demonstrated to improve the cardiopulmonary haemodynamics, exercise capacity, quality-of-life and survival in adult patients with PAH. Specific ET(A) antagonists may also present the same beneficial profile. Recent experience with bosentan in paediatric patients with PAH indicates that the results obtained in adult patients may be extrapolated to children, thus offering a safe and effective therapy that is easy to administer.

Endothelin receptor antagonists

Endothelin receptor antagonists (ERAs) have been developed to block the effects of endothelin-1 (ET-1) in a variety of cardiovascular conditions. ET-1 is a powerful vasoconstrictor with mitogenic or co-mitogenic properties, which acts through the stimulation of 2 subtypes of receptors [endothelin receptor subtype A (ETA) and endothelin receptor subtype B (ETB) receptors]. Endogenous ET-1 is involved in a variety of conditions including systemic and pulmonary hypertension (PH), congestive heart failure (CHF), vascular remodeling (restenosis, atherosclerosis), renal failure, cancer, and cerebrovascular disease. The first dual ETA/ETB receptor blocker, bosentan, has already been approved by the Food and Drug Administration for the treatment of pulmonary arterial hypertension (PAH). Trials of endothelin receptor antagonists in heart failure have been completed with mixed results so far. Studies are ongoing on the effects of selective ETA antagonists or dual ETA/ETB antagonists in lung fibrosis, cancer, and subarachnoid hemorrhage. While non-peptidic ET-1 receptor antagonists suitable for oral intake with excellent bioavailability have become available, proven efficacy is limited to pulmonary hypertension, but it is possible that these agents might find a place in the treatment of several cardiovascular and non-cardiovascular diseases in the coming future.

The Effect of a Combination of Inhaled Nitric Oxide and an EndothelinA-Receptor Antagonist onHemodynamic Dysfunction in Experimental AcutePulmonary Thromboembolism

Although either inhaled nitric oxide (NO) or endothelinA receptor antagonist has been tried in the treatment of various forms of pulmonary hypertension, the effects of combination therapy have not been reported. We evaluated the effects of inhaled NO alone or a combination of inhaled NO and ZD2574 (an endothelinA receptor antagonist) in an experimental canine acute pulmonary thromboembolism model. Forty parts per million of inhaled NO alone, or a combination of inhaled NO and 10 mg/kg of ZD2574 was administered 1 hour after embolization with an autologous blood clot. We compared the hemodynamic and gas exchange parameters between the two treatment groups. Two treatment regimens decreased mean pulmonary arterial pressure and pulmonary vascular resistance and attenuated decrease in cardiac output. Moreover, systemic arterial hypotension or worsening of hypoxemia did not occur in either of the treatment groups. In the combined group, more favorable hemodynamic outcomes were maintained than in the inhaled NO alone group. And hemodynamic deterioration shown after NO withdrawal was attenuated in the combined group. These findings suggest that when inhaled NO is concomitantly administered with an ETA receptor antagonist, more favorable hemodynamic outcomes can be expected during and after NO inhalation in acute pulmonary thromboembolism.

Enhanced expression of transient receptor potential channels in idiopathic pulmonary arterial hypertension

Pulmonary vascular medial hypertrophy caused by excessive pulmonary artery smooth muscle cell (PASMC) proliferation is a major cause for the elevated pulmonary vascular resistance in patients with idiopathic pulmonary arterial hypertension (IPAH). Increased Ca(2+) influx is an important stimulus for PASMC proliferation. Transient receptor potential (TRP) channel genes encode Ca(2+) channels that are responsible for Ca(2+) entry during cell proliferation. Normal human PASMC expressed multiple canonical TRP (TRPC) isoforms; TRPC6 was highly expressed and TRPC3 was minimally expressed. The protein expression of TRPC6 in normal PASMC closely correlated with the expression of Ki67, suggesting that TRPC6 expression is involved in the transition of PASMC from quiescent phase to mitosis. In lung tissues and PASMC from IPAH patients, the mRNA and protein expression of TRPC3 and -6 were much higher than in those from normotensive or secondary pulmonary hypertension patients. Inhibition of TRPC6 expression with TRPC6 small interfering RNA markedly attenuated IPAH-PASMC proliferation. These results demonstrate that expression of TRPC channels correlates with the progression of the cell cycle in PASMC. TRPC channel overexpression may be partially responsible for the increased PASMC proliferation and pulmonary vascular medial hypertrophy in IPAH patients.

Pulmonary vascular remodeling: a target for therapeutic intervention in pulmonary hypertension

Pulmonary vascular remodelling is an important pathological feature of pulmonary hypertension, leading to increased pulmonary vascular resistance and reduced compliance. It involves thickening of all three layers of the blood vessel wall (due to hypertrophy and/or hyperplasia of the predominant cell type within each layer), as well as extracellular matrix deposition. Neomuscularisation of non-muscular arteries and formation of plexiform and neointimal lesions also occur. Stimuli responsible for remodelling involve transmural pressure, stretch, shear stress, hypoxia, various mediators [angiotensin II, endothelin (ET)-1, 5-hydroxytryptamine, growth factors, and inflammatory cytokines], increased serine elastase activity, and tenascin-C. In addition, there are reductions in the endothelium-derived antimitogenic substances, nitric oxide, and prostacyclin. Intracellular signalling mechanisms involved in pulmonary vascular remodelling include elevations in intracellular Ca2+ and activation of the phosphatidylinositol pathway, protein kinase C, and mitogen-activated protein kinase. In animal models of pulmonary hypertension, various drugs have been shown to attenuate pulmonary vascular remodelling. These include angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists, ET receptor antagonists, ET-converting enzyme inhibitors, nitric oxide, phosphodiesterase 5 inhibitors, prostacyclin, Ca2+ -channel antagonists, heparin, and serine elastase inhibitors. Inhibition of remodelling is generally accompanied by reductions in pulmonary artery pressure. The efficacy of some of the drugs varies, depending on the animal model of the disease. In view of the complexity of the remodelling process and the diverse aetiology of pulmonary hypertension in humans, it is to be anticipated that successful anti-remodelling therapy in the clinic will require a range of different drug options.

Pulmonary vasoregulation by endothelin in conscious dogs after left lung transplantation

We tested the hypothesis that regulation of the pulmonary circulation by endogenous endothelin (ET) during normoxia and hypoxia was altered in conscious dogs 1 mo after left lung autotransplantation (LLA). Sham-operated control and post-LLA dogs were chronically instrumented to measure the left pulmonary vascular pressure-flow (LP-Q) relationship. LP-Q plots were generated on separate days during normoxia and hypoxia (arterial PO(2) approximately 50 Torr) in the intact condition, after selective ET(A)-receptor inhibition (BQ-485), and after combined ET(A+B)-receptor inhibition (bosentan). Although LLA resulted in a chronic increase in pulmonary vascular resistance, the ET-receptor antagonists had no effect on the LP-Q relationship during normoxia in either group. The magnitude of hypoxic pulmonary vasoconstriction (HPV) was flow dependent in both groups, and the HPV response was potentiated post-LLA compared with control. ET(A)-receptor inhibition attenuated the HPV response to the same extent in both groups. ET(A+B)-receptor inhibition attenuated the HPV response to a greater extent than did ET(A)-receptor inhibition alone, and this effect was greater post-LLA compared with control. Plasma ET-1 concentration only increased during hypoxia in the LLA group. These results indicate that ET does not regulate the baseline LP-Q relationship in either group. Both ET(A)- and ET(B)-receptor activation mediate a component of HPV in conscious dogs, and the vasoconstrictor influence of ET(B)-receptor activation is enhanced post-LLA.

Perindopril, an angiotensin converting enzyme inhibitor, in pulmonary hypertensive rats: comparative effects on pulmonary vascular structure and function

1. Hypoxic pulmonary hypertension in rats (10% O2, 4 weeks) is characterized by changes in pulmonary vascular structure and function. The effects of the angiotensin converting enzyme inhibitor perindopril (oral gavage, once daily for the 4 weeks of hypoxia) on these changes were examined. 2. Perindopril (30 mg kg-1 d-1) caused an 18% reduction in pulmonary artery pressure in hypoxic rats. 3. Structural changes (remodelling) in hypoxic rats included increases in (i) critical closing pressure in isolated perfused lungs (remodelling of arteries <50 microm o.d.) and (ii) medial wall thickness of intralobar pulmonary arteries, assessed histologically (vessels 30 - 100 and 101 - 500 microm o.d.). Perindopril 10 and 30 mg kg-1 d-1 attenuated remodelling in vessels < or = 100 microm (lungs and histology), 30 mg kg-1 d-1 was effective in vessels 101 - 500 microm but neither dose prevented hypertrophy of main pulmonary artery. 3 mg kg-1 d-1 was without effect. 4. Perindopril (30 mg kg-1 d-1) prevented the exaggerated hypoxic pulmonary vasoconstrictor response seen in perfused lungs from hypoxic rats but did not prevent any of the functional changes (i.e. the increased contractions to 5-HT, U46619 (thromboxane-mimetic) and K+ and diminished contractions to angiotensins I and II) seen in isolated intralobar or main pulmonary arteries. Acetylcholine responses were unaltered in hypoxic rats. 5. We conclude that, in hypoxic rats, altered pulmonary vascular function is largely independent of remodelling. Hence any drug that affects only remodelling is unlikely to restore pulmonary vascular function to normal and, like perindopril, may have only a modest effect on pulmonary artery pressure.

Endothelin abnormalities in patients with pulmonary embolism

BACKGROUND

Endothelin (ET) is an endothelium-derived multifunctional peptide involved in the local regulation of the vascular tone.

STUDY OBJECTIVES

To assess changes of endogenous ET production/excretion in the acute phase (36 h from the event) of pulmonary embolism (PE).

PARTICIPANTS

Ten patients with acute PE, nine patients with acute lung injury (ALI), and 12 healthy volunteers (HVs).

MEASUREMENTS AND RESULTS

ET was detected by radioimmunoassay in venous and arterial blood as well as in 24-h urine specimens. For each subject, arterial/venous immunoreactive ET (ir-ET) ratio was evaluated as an index of its pulmonary extraction/synthesis. Creatinine clearance was employed in each case to obtain a corrected renal ir-ET clearance. Renal ir-ET clearance was comparable in all three groups. Arterial/venous ir-ET ratio was comparable in PE and in ALI patients (1.31 +/- 0.25 vs 1.24 +/- 0.20; p = 0.7), while it was significantly higher in PE patients than in HV subjects (0.85 +/- 0.07; p = 0.0001). Accordingly, 24-h urine ir-ET excretion was higher in PE (120.50 +/- 27.36 ng/24 h) and ALI patients (135.80 +/- 21.60 ng/24 h) than in HV subjects (68.33 +/- 9.31 ng/24 h; p = 0.0001).

CONCLUSIONS

Abnormalities of ET metabolism-mainly related to increased synthesis and/or defective pulmonary handling-occur in the acute phase of PE. The relevance of this finding with respect to the pathogenesis and/or management of pulmonary thromboembolism remains to be elucidated.

Identification of endothelin-1 in the pathophysiology of metastatic adenocarcinoma of the prostate

Prostate cancer is the second most common cause of death from cancer in U.S. men, and advanced, hormone-refractory disease is characterized by painful osteoblastic bone metastases. Endothelin-1, more commonly known as a potent vasoconstrictor, is a normal ejaculate protein that also stimulates osteoblasts. We show here that plasma immunoreactive endothelin concentrations are significantly elevated in men with metastatic prostate cancer and that every human prostate cancer cell line tested produces endothelin-1 messenger RNA and secretes immunoreactive endothelin. Exogenous endothelin-1 is a prostate cancer mitogen in vitro and increases alkaline phosphatase activity in new bone formation, indicating that ectopic endothelin-1 may be a mediator of the osteoblastic response of bone to metastatic prostate cancer.