Chronically elevated endothelin levels reduce pulmonary vascular reactivity to nitric oxide

Evaluating Riociguat in the Treatment of Pulmonary Arterial Hypertension: A Real-World Perspective

Pulmonary hypertension (PH) is a broad term describing the mean pulmonary artery pressure, as measured by right heart catheterization, exceeds 20mmHg. Pulmonary arterial hypertension (PAH) exists when PH is accompanied by a normal wedge pressure and elevated pulmonary vascular resistance. PAH is typified by dysmorphic and dysfunctional pulmonary arterial vasculature. Attempting to restore the functionality of the pulmonary artery is a hallmark of care to the PAH patient. Riociguat is a powerful stimulator of soluble guanylate cyclase and increases blood flow through the pulmonary arteries by dilating vascular smooth muscle cells. This review examines the pharmacology of riociguat, the fundamental clinical trials applying it to PAH patients, practical aspects when selecting its use, and future directions for its utilization.

[The place of riociguat in the treatment of patients with pulmonary arterial hypertension associated with systemic connective tissue diseases]

Pulmonary hypertension (PH) can develop in different systemic autoimmune rheumatic diseases (SARD), such as systemic scleroderma (SSD), systemic lupus erythematosus, rheumatoid arthritis, and mixed connective tissue disease In most cases, patients with SARD develop WHO group I PH (pulmonary arterial hypertension associated with systemic connective tissue diseases, PAH-SCTD). General prevalence of this pathology reaches 15 cases per million adults. Most cases of PAH-SCTD are induced by SSD. Survival of PAH-SCTD patients is generally lower than survival of patients with other forms of LAH. Treatment of any SARD, including in LAH, implies a complex approach using glucocorticoids, disease-modifying anti-rheumatic drugs (cyclophosphamide, methotrexate, azathioprine, and others), and genetically engineered biologics. Specific targeted therapy is indicated for most patients with PAH-SCTD. The representative of a new class (soluble guanylate cyclase (sGC) stimulators), riociguat, has been approved for the treatment of PAH. This drug has a unique double mechanism of action: (i) sGC sensibilization to endogenous nitric oxide (NO) by stabilizing the NO-sGC bond; and (ii) direct, NO-independent sGC stimulation. For patients with PAH-SCTD, riociguat is the major alternative to phosphodiesterase-5 inhibitors both as monotherapy and combination therapy.

Clinical Analysis of 122 Cases with Mycoplasma Pneumonia Complicated with Atelectasis: A Retrospective Study

INTRODUCTION

This study aims to explore the clinical characteristics, treatment, and prognosis of mycoplasma pneumonia complicated with atelectasis.

METHODS

A retrospective analysis was performed on 122 children with mycoplasma pneumonia complicated with atelectasis. These children were hospitalized in the Xiamen Campus of the Pediatric Hospital of Fudan University and the Children's Hospital of Xiamen between December 2015 and December 2018. A diagnosis was made for each case on the basis of the clinical symptoms and signs, Mycoplasma pneumoniae-specific IgM antibody, and imaging results.

RESULTS

Among the 122 cases with mycoplasma pneumonia complicated with atelectasis, all cases had retractable M. pneumoniae infection, 102 cases underwent fibrobronchoscopic lavage treatment, and all cases were treated with macrolide antibiotics after a definite diagnosis was made. Furthermore, 107 cases improved and were discharged. Follow-up was performed for 3-4 weeks for all patients, and all patients, including the five cases with retractable disease, recovered well.

CONCLUSION

The major clinical manifestations for M. pneumoniae pneumonia are fever and stimulatory dry cough. Macrolide antibiotics remain the treatment of choice.

Treatment of pediatric pulmonary arterial hypertension: A focus on the NO-sGC-cGMP pathway

OBJECTIVE

While pulmonary arterial hypertension (PAH) is rare in infants and children, it results in substantial morbidity and mortality. In recent years, prognosis has improved, coinciding with the introduction of new PAH-targeted therapies, although much of their use in children is off-label. Evidence to guide the treatment of children with PAH is less extensive than for adults. The goal of this review is to discuss the treatment recommendations for children with PAH, as well as the evidence supporting the use of prostanoids, endothelin receptor antagonists (ERAs), and phosphodiesterase type 5 inhibitors (PDE5i) in this setting.

DATA SOURCES

Nonsystematic PubMed literature search and authors' expertise.

STUDY SELECTION

Articles were selected concentrating on the nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) pathway in PAH. The methodology of an ongoing study evaluating the sGC stimulator riociguat in children with PAH is also described.

RESULTS

Despite recent medical advances, improved therapeutic strategies for pediatric PAH are needed. The efficacy and tolerability of riociguat in adults with PAH have been well trialed.

CONCLUSION

The pooling of data across trials, supplemented by registry data, will help to confirm the safety and tolerability of prostanoids, ERAs, and PDE5i in children. Ongoing studies will clarify the place of sGC stimulators in the treatment strategy for pediatric PAH.

Tanshinone IIA protects against chronic intermittent hypoxia-induced myocardial injury via activating the endothelin 1 pathway

Tanshinone IIA (Tan IIA) may exert significant protective effects against heart oxidative stress damage in obstructive sleep apnoea (OSA) syndrome. Chronic intermittent hypoxia (CIH)-triggered left ventricular dysfunction is used in a rat model to mimic CIH in OSA patients. 48 rats were randomly divided into three groups: normal control (NC) group, CIH group and CIH+Tan IIA group with 16 rats in each group. At the end of experiment (day 21), the blood pressure, Plasma ET-1 and NO content, hemodynamic indexes, heart histology, myocardial apoptosis as well as the expression of eNOS, ET-1, ET_A receptor and ET_B receptor were compared among different groups. Tan IIA was able to inhibit the increase of blood pressure induced by CIH. Meanwhile, rat cardiac function in Tan IIA group was evaluated by hemodynamic indexes, histopathological examination. Higher ventricular eNOS activity was induced by Tan IIA with a reduction in both ET-1 and ET_A receptor expression. However, Tan IIA largely inhibited the decrease of ET_B receptor expression. This study demonstrated that Tan IIA has the potential to benefit rat heart against CIH via endothelin system.

RESPITE: switching to riociguat in pulmonary arterial hypertension patients with inadequate response to phosphodiesterase-5 inhibitors

A proportion of pulmonary arterial hypertension (PAH) patients do not reach treatment goals with phosphodiesterase-5 inhibitors (PDE5i). RESPITE investigated the safety, feasibility and benefit of switching from PDE5i to riociguat in these patients.

RESPITE was a 24-week, open-label, multicentre, uncontrolled study. Patients in World Health Organization (WHO) functional class (FC) III, with 6-min walking distance (6MWD) 165–440 m, cardiac index <3.0 L·min⁻¹·m⁻² and pulmonary vascular resistance >400 dyn·s·cm⁻⁵ underwent a 1–3 day PDE5i treatment-free period before receiving riociguat adjusted up to 2.5 mg maximum t.i.d. Exploratory end-points included change in 6MWD, WHO FC, N-terminal prohormone of brain natriuretic peptide (NT-proBNP) and safety.

Of 61 patients enrolled, 51 (84%) completed RESPITE. 50 (82%) were receiving concomitant endothelin receptor antagonists. At week 24, mean±sd 6MWD had increased by 31±63 m, NT-proBNP decreased by 347±1235 pg·mL⁻¹ and WHO FC improved in 28 patients (54%). 32 patients (52%) experienced study drug-related adverse events and 10 (16%) experienced serious adverse events (2 (3%) study drug-related, none during the PDE5i treatment-free period). Six patients (10%) experienced clinical worsening, including death in two (not study drug-related).

In conclusion, selected patients with PAH may benefit from switching from PDE5i to riociguat, but this strategy needs to be further studied.

Switching to riociguat in PAH patients with inadequate response to PDE5i improved exercise capacity and NT-proBNPhttp://ow.ly/e6xL30dXCgy

Air Pollution-Induced Vascular Dysfunction: Potential Role of Endothelin-1 (ET-1) System

Exposure to air pollution negatively impacts cardiovascular health. Studies show that increased exposure to a number of airborne pollutants increases the risk for cardiovascular disease progression, myocardial events, and cardiovascular mortality. A hypothesized mechanism linking air pollution and cardiovascular disease is the development of systemic inflammation and endothelium dysfunction, the latter of which can result from an imbalance of vasoactive factors within the vasculature. Endothelin-1 (ET-1) is a potent peptide vasoconstrictor that plays a significant role in regulating vascular homeostasis. It has been reported that the production and function of ET-1 and its receptors are upregulated in a number of disease states associated with endothelium dysfunction including hypertension and atherosclerosis. This mini-review surveys epidemiological and experimental air pollution studies focused on ET-1 dysregulation as a plausible mechanism underlying the development of cardiovascular disease. Although alterations in ET-1 system components are observed in some studies, there remains a need for future research to clarify whether these specific changes are compensatory or causally related to vascular injury and dysfunction. Moreover, further research may test the efficacy of selective ET-1 pharmacological interventions (e.g., ETA receptor inhibitors) to determine whether these treatments could impede the deleterious impact of air pollution exposure on cardiovascular health.

Exercise Lowers Plasma Angiopoietin-Like 2 in Men with Post-Acute Coronary Syndrome

Pro-inflammatory angiopoietin-like 2 (angptl2) promotes endothelial dysfunction in mice and circulating angptl2 is higher in patients with cardiovascular diseases. We previously reported that a single bout of physical exercise was able to reduce angptl2 levels in coronary patients. We hypothesized that chronic exercise would reduce angptl2 in patients with post-acute coronary syndrome (ACS) and endothelial dysfunction. Post-ACS patients (n = 40, 10 women) were enrolled in a 3-month exercise-based prevention program. Plasma angptl2, hs-CRP, and endothelial function assessed by scintigraphic forearm blood flow, were measured before and at the end of the study. Exercise increased VO₂peak by 10% (p<0.05), but did not significantly affect endothelial function, in both men and women. In contrast, exercise reduced angptl2 levels only in men (-26±7%, p<0.05), but unexpectedly not in women (+30±16%), despite similar initial levels in both groups. Exercise reduced hs-CRP levels in men but not in women. In men, levels of angptl2, but not of hs-CRP, reached at the end of the training program were negatively correlated with VO₂peak (r = -0.462, p = 0.012) and with endothelial function (r = -0.419, p = 0.033) measured at baseline: better initial cardiopulmonary fitness and endothelial function correlated with lower angptl2 levels after exercise. Pre-exercise angptl2 levels were lower if left ventricular ejection time was long (p<0.05) and the drop in angptl2 induced by exercise was greater if the cardiac output was high (p<0.05). In conclusion, in post-ACS men, angptl2 levels are sensitive to chronic exercise training. Low circulating angptl2 reached after training may reflect good endothelial and cardiopulmonary functions.

Lung Capillary Stress Failure and Arteriolar Remodelling in Pulmonary Hypertension Associated with Left Heart Disease (Group 2 PH)

Left heart diseases (LHD) represent the most prevalent cause of pulmonary hypertension (PH), yet there are still no approved therapies that selectively target the pulmonary circulation in LHD. The increase in pulmonary capillary pressure due to LHD is a triggering event leading to physical and biological alterations of the pulmonary circulation. Acutely, mechanosensitive endothelial dysfunction and increased capillary permeability combined with reduced fluid resorption lead to the development of interstitial and alveolar oedema. From repeated cycles of such capillary stress failure originate more profound changes with pulmonary endothelial dysfunction causing increased basal and reactive pulmonary vascular tone. This contributes to pulmonary vascular remodelling with increased arterial wall thickness, but most prominently, to alveolar wall remodelling characterized by myofibroblasts proliferation with collagen and interstitial matrix deposition. Although protective against acute pulmonary oedema, alveolar wall thickening becomes maladaptive and is responsible for the development of a restrictive lung syndrome and impaired gas exchanges contributing to shortness of breath and PH. Increasing awareness of these processes is unraveling novel pathophysiologic processes that could represent selective therapeutic targets. Thus, the roles of caveolins, of the intermediate myofilament nestin and of endothelial calcium dyshomeostasis were recently evaluated in pre-clinical models. The pathophysiology of PH due to LHD (group II PH) is distinctive from other groups of PH. Therefore, therapies targeting PH due to LHD must be evaluated in that context.

Molecular imaging of the pulmonary circulation in health and disease

The pulmonary circulation, at the unique crossroads between the left and the right heart, is submitted to large physiologic hemodynamic variations and possesses numerous important metabolic functions mediated through its vast endothelial surface. There are many pathologic conditions that can directly or indirectly affect the pulmonary vasculature and modify its physiology and functions. Pulmonary hypertension, the end result of many of these affections, is unfortunately diagnosed too late in the disease process, meaning that there is a crying need for earlier diagnosis and surrogate markers of disease progression and regression. By targeting endothelial, medial and adventitial targets of the pulmonary vasculature, novel molecular imaging agents could provide early detection of physiologic and biologic perturbation in the pulmonary circulation. This review provides the rationale for the development of molecular imaging agents for the diagnosis and follow-up of disorders of the pulmonary circulation and discusses promising targets for SPECT and positron emission tomographic imaging.

Endothelin receptor antagonists -- their role in pulmonary medicine

INTRODUCTION

Understanding of the function of endothelin-1 in the pathophysiology of endothelial disease, in particular pulmonary arterial hypertension (PAH), has paved the way for the development of endothelin-receptor antagonists (ERAs) and explains the leading role they now play in the treatment armamentarium for this disease.

BACKGROUND

Three active ERA drugs (bosentan, sitaxentan, ambrisentan) are currently approved for the treatment of PAH in France. Several randomised clinical trials have demonstrated their efficacy and safety in PAH.

PERSPECTIVES AND CONCLUSION

Besides its vasoconstrictor effect, endothelin-1 (ET-1) plays a pivotal role in cell proliferation and apoptosis. ERAs are innovative drugs potentially useful in some pulmonary disorders such as idiopathic pulmonary fibrosis or systemic sclerosis, even though the preliminary results published remain insufficient or controversial.

CONCLUSION

ERAs play a major role in the management of pulmonary vascular disease. Other drugs, still under study, could prove useful in the treatment of infiltrating pneumonias.

Tobacco-associated pulmonary vascular dysfunction in smokers: role of the ET-1 pathway

Pulmonary vascular remodeling and dysfunction associated to tobacco smoking might pave the way for the subsequent development of pulmonary hypertension. Its prognosis is dreadful and its underlying mechanisms are so far largely unknown in humans. To assess the potential role of endothelin-1 and its receptors in smokers' pulmonary artery vasoactive properties. Endothelium-dependent vasodilation to ACh was assessed in pulmonary vascular rings from 34 smokers and compared with that of 10 nonsmokers. The effects of ET-A (BQ 123) or ET-B (BQ 788) blockers and that of an ET-B activator (sarafotoxin) were evaluated. Endothelin-1 was quantitated by ELISA. Expression of its receptors was quantitated by Western blotting. Smokers exhibited an impaired pulmonary endothelium-dependent vasodilation compared with nonsmokers (P < 0.01). In the former group, 8 of 34 subjects exhibited a marked endothelial dysfunction (ED(+)) whereas 26 (ED(-)) (P < 10(-4)) displayed a vasorelaxation to ACh that was comparable to that of nonsmokers. In ED(+) subjects, ET-A was overexpressed (P < 0.05) and inversely correlated (P < 10(-2)) with the response to ACh. Sarafotoxin significantly improved vasodilation in all subjects (P < 10(-2)). In conclusion, tobacco smoking is associated to an impaired pulmonary vasorelaxation at least partly mediated by an ET-1/ET-A-dependent dysfunction.

Cigarette smoke exposure up-regulates endothelin receptor B in human pulmonary artery endothelial cells: molecular and functional consequences

BACKGROUND AND PURPOSE

Pulmonary arteries from smokers and chronic obstructive pulmonary disease patients show abnormal endothelium-dependent vascular reactivity. We studied the effect of cigarette smoke extract (CSE) on endothelin receptor B (ET(B) ) expression in human pulmonary artery endothelial cells (HPAECs) and its role in endothelial dysfunction.

EXPERIMENTAL APPROACH

ET(B) receptor expression was measured by real time RT-PCR, Western blot and immunofluorescence. Cell contraction, intracellular Ca(2+) , F/G-actin, RhoA activity, myosin light chain phosphorylation, ET, NO, thromboxane (Tx)A(2) and reactive oxygen species (ROS) were measured by traction microscopy, fluorescence microscopy, phalloidin fluorescence, colorimetric assay, Western blot, elisa and DCFDA fluorescence respectively.

KEY RESULTS

Cigarette smoke extract dose-dependently increased ET(B) receptor expression in HPAECs after 24h incubation. CSE-induced ET(B) expression was attenuated by bosentan, the ET(B) receptor antagonist BQ788, the Rho kinase antagonist Y27632 and the antioxidant N-acetylcysteine. A monoclonal antibody to ET-1 prevented CSE-induced ET(B) receptor overexpression. Twenty-four hour exposure to ET-1 dose-dependently increased ET(B) receptor expression, mimicking the effect of CSE. CSE-induced ET(B) receptor overexpression caused greater cell contraction; increased intracellular Ca(2+) ; increased F/G-actin and RhoA activity; increased myosin light chain phosphorylation; augmented TxA(2) and ROS production; and decreased NO after acute ET-1 (10nM). These effects were attenuated by bosentan, BQ788, Y27632 and N-acetylcysteine.

CONCLUSIONS AND IMPLICATION

Cigarette smoke extract induced ET(B) receptor overexpression by a feed forward mechanism mediated partly by ET release, promoting HPAEC dysfunction and attenuated by ET(B) receptor blockade, Rho kinase and ROS inhibition. These results provide support for the use of bosentan in CS-related endothelial dysfunction.

Congenital diaphragmatic hernia: endothelin-1, pulmonary hypertension, and disease severity

RATIONALE

Endothelin-1 (ET1) is dysregulated in pulmonary hypertension (PH). It may be important in the pathobiology of congenital diaphragmatic hernia (CDH).

OBJECTIVES

We hypothesized that ET1 levels in the first month would be higher in infants with CDH who subsequently expired or were discharged on oxygen (poor outcome). We further hypothesized that ET1 levels would be associated with concurrent severity of PH.

METHODS

We sampled plasma at 24 to 48 hours, and 1, 2, and 4 weeks of age in 40 prospectively enrolled newborns with CDH. We performed echocardiograms to estimate pulmonary artery pressure at less than 48 hours of age and weekly to 4 weeks. PH was classified in relationship to systemic blood pressure (SBP): less than 2/3 SBP, 2/3 SBP-systemic is related to pressure, or systemic-to-suprasystemic pressure.

MEASUREMENTS AND MAIN RESULTS

ET1 levels at 1 and 2 weeks were higher in infants with poor outcome compared with infants discharged on room air (median and interquartile range: 27.2 [22.6, 33.7] vs. 19.1 [16.1, 29.5] pg/ml, P = 0.03; and 24.9 [17.6, 39.5] vs. 17.4 [13.7, 21.8] pg/ml, P = 0.01 at 1 and 2 weeks, respectively). Severity of PH was significantly associated with increasing ET1 levels at 2 weeks (16.1 [13.7, 21.8], 21.0 [17.4, 31.1], and 23.6 [21.9, 39.5] pg/ml for increasing PH class, P = 0.03). Increasing severity of PH was also associated with poor outcome at that time (P = 0.001).

CONCLUSIONS

Infants with CDH and poor outcome have higher plasma ET1 levels and severity of PH than infants discharged on room air. Severity of PH is associated with ET1 levels.

Change in pharmacological effect of endothelin receptor antagonists in rats with pulmonary hypertension: role of ETB-receptor expression levels

BACKGROUND AND PURPOSE

The endothelin (ET) system is activated in pulmonary arterial hypertension (PAH). The therapeutic value of pharmacological blockade of ET receptors has been demonstrated in various animal models and led to the current approval and continued development of these drugs for the therapy of human PAH. However, we currently incompletely comprehend what local modifications of this system occur as a consequence of PAH, particularly in small resistance arteries, and how this could affect the pharmacological response to ET receptor antagonists with various selectivities for the receptor subtypes. Therefore, the purposes of this study were to evaluate potential modifications of the pharmacology of the ET system in rat pulmonary resistance arteries from monocrotaline (MCT)-induced pulmonary arterial hypertension.

EXPERIMENTAL APPROACH

ET-1 levels were quantified by ELISA. PreproET-1, ETA and ETB receptor mRNA expressions were quantified in pulmonary resistance arteries using Q-PCR, while protein expression was evaluated by Western blots. Reactivity to ET-1 of isolated pulmonary resistance arteries was measured in the presence of ETA (A-147627), ETB (A-192621) and dual ETA/B (bosentan) receptor antagonists.

KEY RESULTS

In rats with PAH, plasma ET-1 increased (p < 0.001) while pulmonary levels were reduced(p < 0.05). In PAH arteries, preproET-1 (p < 0.05) and ETB receptor (p < 0.001) gene expressions were reduced, as were ETB receptor protein levels (p < 0.05). ET-1 induced similar vasoconstrictions in both groups. In arteries from sham animals, neither bosentan nor the ETA or the ETB receptor antagonists modified the response. In arteries from PAH rats, however, bosentan and the ETA receptor antagonist potently reduced the maximal contraction, while bosentan also reduced sensitivity (p < 0.01).

CONCLUSIONS AND IMPLICATIONS

The effectiveness of both selective ETA and dual ETA/B receptor antagonists is markedly increased in PAH. Down-regulation of pulmonary resistance arteries ETB receptor may contribute to this finding.

Endothelin-3-dependent pulmonary vasoconstriction in monocrotaline-induced pulmonary arterial hypertension

Blockade of the endothelin (ET) system is beneficial in pulmonary arterial hypertension (PAH). The contribution of ET-3 and its interactions with ET receptors have never been evaluated in the monocrotaline (MCT)-induced model of PAH. Vasoreactivity of pulmonary arteries was investigated; ET-3 localization was determined by confocal imaging and gene expression of prepro-ET-3 quantified using RT-PCR. ET-3 plasma levels tended to increase in PAH. ET-3 localized in the media of pulmonary arteries, where gene expression of prepro-ET-3 was reduced in PAH. ET-3 induced similar pulmonary vasoconstrictions in sham and PAH rats. In sham rats, the ET(A) antagonist A-147627 (10nmol/l) significantly reduced the maximal response to ET-3 (E(max) 77+/-1 to 46+/-2%, mean+/-S.E.M., P<0.001), while the ET(B) antagonist A-192621 (1mumol/l) reduced the sensitivity (EC(50) 21+/-7 to 59+/-16nmol/l, P<0.05) without affecting E(max). The combination of both antagonists completely abolished ET-3-induced pulmonary vasoconstriction. In PAH, the ET(A) antagonist further reduced the maximal response to ET-3 and shifted the EC(50) (E(max) 23+/-2%, P<0.001, EC(50) 104+/-24nmol/l, P<0.05), while the ET(B) antagonist only shifted the EC(50) (123+/-36nmol/l, P<0.05) without affecting the E(max). In PAH, dual ET receptor inhibition did not further reduce constriction compared to selective ET(A) inhibition. ET-3 significantly contributes to pulmonary vasoconstriction by activating the ET(B) at low concentration, and the ET(A) at high concentration. The increased inhibitory effect of the ET(A) antagonist in PAH suggests that the contribution of ET(B) to ET-3-induced vasoconstriction is reduced. Although ET-3 is a potent pulmonary vasoconstrictor in PAH, its potential pathophysiologic contribution remains uncertain.

Contribution of xanthine oxidase-derived superoxide to chronic hypoxic pulmonary hypertension in neonatal rats

Xanthine oxidase (XO)-derived reactive oxygen species (ROS) formation contributes to experimental chronic hypoxic pulmonary hypertension in adults, but its role in neonatal pulmonary hypertension has received little attention. In rats chronically exposed to hypoxia (13% O(2)) for 14 days from birth, we examined the effects of ROS scavengers (U74389G 10 mg.kg(-1).day(-1) or Tempol 100 mg.kg(-1).day(-1) ip) or a XO inhibitor, Allopurinol (50 mg.kg(-1).day(-1) ip). Both ROS scavengers limited oxidative stress in the lung and attenuated hypoxia-induced vascular remodeling, confirming a critical role for ROS in this model. However, both interventions also significantly inhibited somatic growth and normal cellular proliferation in distal air spaces. Hypoxia-exposed pups had evidence of increased serum and lung XO activity, increased vascular XO-derived superoxide production, and vascular nitrotyrosine formation. These changes were all prevented by treatment with Allopurinol, which also attenuated hypoxia-induced vascular remodeling and partially reversed inhibited endothelium-dependent arterial relaxation, without affecting normal growth and proliferation. Collectively, our findings suggest that XO-derived superoxide induces endothelial dysfunction, thus impairing pulmonary arterial relaxation, and contributes to vascular remodeling in hypoxia-exposed neonatal rats. Due to the potential for adverse effects on normal growth, targeting XO may represent a superior "antioxidant" strategy to ROS scavengers for neonates with pulmonary hypertension.

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.