Putative mediator role of endothelin-1 in asthma and other lung diseases

Differences in the DNA Methylome of T cells in Adults With Asthma of Varying Severity

Background

DNA methylation plays a critical role in asthma development, but differences in DNA methylation among adults with varying asthma severity or asthma endotypes are less well-defined.

Objective

To examine how DNA methylomic patterns differ among adults with asthma based on asthma severity and airway inflammation.

Methods

Peripheral blood T cells from 35 adults with asthma in Beijing, China were serially collected over time (130 samples total) and analyzed for global DNA methylation using the Illumina MethylationEPIC Array. Differential methylation was compared among subjects with varying airway inflammation and severity, as measured by fraction of exhaled nitric oxide, forced expiratory volume in one second (FEV1), and Asthma Control Test (ACT) scores.

Results

Significant differences in DNA methylation were noted among subjects with different degrees of airway inflammation and asthma severity. These differences in DNA methylation were annotated to genes that were enriched in pathways related to asthma or T cell function and included gene ontology categories related to MHC class II assembly, T cell activation, interleukin (IL)-1, and IL-12. Genes related to P450 drug metabolism, glutathione metabolism, and developmental pathways were also differentially methylated in comparisons between subjects with high vs low FEV1 and ACT. Notable genes that were differentially methylated based on asthma severity included RUNX3, several members of the HLA family, AGT, PTPRC, PTPRJ, and several genes downstream of the JAK2 and TNF signaling pathway.

Conclusion

These findings demonstrate how adults with asthma of varying severity possess differences in peripheral blood T cell DNA methylation that contribute to the phenotype and severity of their overall disease.

A Par3/LIM Kinase/Cofilin Pathway Mediates Human Airway Smooth Muscle Relaxation by TAS2R14

TAS2Rs (bitter taste receptors) are GPCRs (G protein-coupled receptors) expressed on human airway smooth muscle (HASM) cells; when activated by receptor agonists they evoke marked airway relaxation. In both taste and HASM cells, TAS2Rs activate a canonical Gβγ-mediated stimulation of Ca2+ release from intracellular stores by activation of PLCβ (phospholipase Cβ). Alone, this [Ca2+]i signaling does not readily account for relaxation, particularly since bronchoconstrictive agonists acting at Gq-coupled receptors also increase [Ca2+]i. We established that TAS2R14 activation in HASM promotes relaxation through F-actin (filamentous actin) severing. This destabilization of actin was from agonist-promoted activation (dephosphorylation) of cofilin, which was pertussis toxin sensitive. Cofilin dephosphorylation was due to TAS2R-mediated deactivation of LIM domain kinase. The link between early receptor action and the distal cofilin dephosphorylation was found to be the polarity protein partitioning defective 3 (Par3), a known binding partner with PLCβ that inhibits LIM kinase. The physiologic relevance of this pathway was assessed using knock-downs of cofilin and Par3 in HASM cells and in human precision-cut lung slices. Relaxation by TAS2R14 agonists was ablated with knock-down of either protein as assessed by magnetic twisting cytometry in isolated cells or intact airways in the slices. Blocking [Ca2+]i release by TAS2R14 inhibited agonist-promoted cofilin dephosphorylation, confirming a role for [Ca2+]i in actin-modifying pathways. These results further elucidate the mechanistic basis of TAS2R-mediated HASM relaxation and point toward nodal points that may act as asthma or chronic obstructive pulmonary disease response modifiers or additional targets for novel bronchodilators.

Tobacco smoking aggravates airway inflammation by upregulating endothelin-2 and activating the c-Jun amino terminal kinase pathway in asthma

BACKGROUND

Asthma is closely associated with tobacco smoking (TS) and is more difficult to effectively treat after exposure to TS.

OBJECTIVE

To observe the effects of TS on the expression of endothelin-2 (ET-2) and airway inflammation in asthmatic rats and to explore the related mechanisms.

METHODS

We established an animal model of asthma with ovalbumin (OVA)/Al(OH)₃ and subjected different animal groups to TS and/or dexamethasone/bosentan. The differences in the inflammatory cell infiltration, the pathological changes to the bronchial wall and the bronchial smooth muscle thickness, and the expression of ET-2, c-Jun amino terminal kinase (JNK1/2), malondialdehyde (MDA), and glutathione peroxidase (GSH) in the lung tissue and of interleukin (IL)-7 in bronchoalveolar lavage fluid (BALF) were assessed.

RESULTS

Exposure to TS or OVA caused an obvious increase in the inflammatory cells in the BALF over what was observed in the control group. In asthma models, the expression of ET-1, JNK1/2, MDA, and GSH in the lung tissues, as well as that of IL-17 in the BALF, was increased. After treatment with dexamethasone/bosentan, the expression of IL-17, JNK1/2, MDA, and GSH decreased compared to the smoking group; airway inflammation and the staining intensity in the lung tissue were also reduced.

CONCLUSION

TS exposure can clearly exacerbate airway inflammation in asthmatic rats, while bosentan can alleviate airway inflammation through regulation of the ET-2/JNK1/2 signalling pathway.

Regulation of Airway Smooth Muscle Contraction in Health and Disease

Airway smooth muscle (ASM) extends from the trachea throughout the bronchial tree to the terminal bronchioles. In utero, spontaneous phasic contraction of fetal ASM is critical for normal lung development by regulating intraluminal fluid movement, ASM differentiation, and release of key growth factors. In contrast, phasic contraction appears to be absent in the adult lung, and regulation of tonic contraction and airflow is under neuronal and humoral control. Accumulating evidence suggests that changes in ASM responsiveness contribute to the pathophysiology of lung diseases with lifelong health impacts.Functional assessments of fetal and adult ASM and airways have defined pharmacological responses and signaling pathways that drive airway contraction and relaxation. Studies using precision-cut lung slices, in which contraction of intrapulmonary airways and ASM calcium signaling can be assessed simultaneously in situ, have been particularly informative. These combined approaches have defined the relative importance of calcium entry into ASM and calcium release from intracellular stores as drivers of spontaneous phasic contraction in utero and excitation-contraction coupling.Increased contractility of ASM in asthma contributes to airway hyperresponsiveness. Studies using animal models and human ASM and airways have characterized inflammatory and other mechanisms underlying increased reactivity to contractile agonists and reduced bronchodilator efficacy of β₂-adrenoceptor agonists in severe diseases. Novel bronchodilators and the application of bronchial thermoplasty to ablate increased ASM within asthmatic airways have the potential to overcome limitations of current therapies. These approaches may directly limit excessive airway contraction to improve outcomes for difficult-to-control asthma and other chronic lung diseases.

Cardiopulmonary functions and adenotonsillectomy: surgical indications need revision

OBJECTIVE

To assess cardiac functions in adenotonsillar or tonsillar hypertrophy.

METHODS

A prospective, interventional, academic centre based study was conducted on 25 children with adenotonsillar or tonsillar hypertrophy. All patients underwent pulsed 2-dimensional Doppler echocardiography, pulse oximetry and 12-lead electrocardiography. These assessments were repeated three months later to determine the impact of adenotonsillectomy.

RESULTS

There were significant differences in mean arterial oxygen saturation, pulmonary flow acceleration time and mean pulmonary artery pressure post-operatively. Adenotonsillectomy led to significant improvements in pulmonary flow acceleration time and pulmonary flow velocity time index, while tonsillectomy resulted in right ventricular early and late diastolic velocity index improvement.

CONCLUSION

Upper airway obstruction in children affects cardiac functioning and this can subsequently lead to morbidity and delayed growth. Hence, revision of surgical indications is advocated in adenotonsillar hypertrophy to avoid irreversible damage to cardiopulmonary functions.

Pharmacokinetics and preliminary safety data of a single oral dose of bosentan, a dual endothelin receptor antagonist, in cats

The objective of this study was to evaluate the pharmacokinetic properties and adverse effect profile of single-dose oral bosentan, a dual endothelin receptor antagonist, in healthy cats. Pharmacokinetic parameters were determined following a single mean ± SD oral dose of 3.2 ± 0.6 mg/kg of bosentan in 6 adult cats. Blood was collected for quantification of bosentan via high-performance liquid chromatography with ultraviolet detection. Blood and urine were evaluated for CBC, plasma biochemical profile, and urinalysis, and repeat physical examinations were performed to evaluate for adverse effects. The mean terminal half-life of bosentan was 20.4 ± 17.2 h. The mean peak plasma concentration was 0.49 ± 0.24 g/mL, and the mean time to maximum plasma concentration was 6.8 ± 8.6 h. The area under the curve was 5.14 ± 3.81 h·μg/mL. Oral bosentan tablets were absorbed in cats, and no clinically important adverse events were noted. Further evaluation of repeat dosing, investigation into the in vivo efficacy of decreasing endothelin-1 concentrations in cats, as well as safety in conjunction with other medications is warranted.

Bronchial epithelium as a target for innovative treatments in asthma

Increasing evidence of a critical role played by the bronchial epithelium in airway homeostasis is opening new therapeutic avenues. Its unique situation at the interface with the environment suggests that the subtle regulation orchestrated by the epithelium between tolerance and specific immune response might be impaired in asthma. Airway mucus is acting as a physical and a biological fluid between the environment and the epithelium, synergistically moved by the cilia. In asthma, excessive mucus production is a hallmark of airway remodeling. Since many years we tried to therapeutically target mucus hypersecretion, but actually this option is still not achieved. The present review discusses the dynamic processes regulating airway mucus production. Airway inflammation is central in current asthma management. Understanding of how the airway epithelium influences the TH2 paradigm in response to deleterious agents is improving. The multiple receptors expressed by the airway epithelium are the transducers of the biological signals induced by various invasive agents to develop the most adapted response. Airway remodeling is observed in severe chronic airway diseases and may result from ongoing disturbance of signal transduction and epithelial renewal. Chronic airway diseases such as asthma will require assessment of these epithelial abnormalities to identify phenotypic characteristics associated with predicting a clinical benefit for epithelial-directed therapies.

Endothelin-1 concentrations in bronchoalveolar lavage fluid of cats with experimentally induced asthma

BACKGROUND

There is a need for biomarkers for diagnosis, therapeutic monitoring, and prognosis for asthma in cats. Endothelin-1 (ET-1) is implicated in the pathogenesis of inflammatory airway diseases in other species but not the cat.

OBJECTIVE

To conduct a prospective experimental study to show that experimentally asthmatic cats, but not control cats without airway inflammation, would have increased concentrations of ET in BALF.

ANIMALS

Eleven healthy, adult research cats.

METHODS

Prospective experimental study. Six healthy cats without airway inflammation were used as controls. Asthma was induced using Bermuda grass allergen (BGA) in 5 cats. Collection of BALF for total nucleated cell and differential counts was performed. The concentration of ET-1 in cell-free BALF samples was determined. Data were analyzed using a Mann-Whitney U-test with P < .05 considered significant.

RESULTS

The median [range] BALF total cell numbers, eosinophil numbers, and eosinophil percentages were significantly higher in the cats following experimental induction of asthma (1,870 cells/μL [1,450-3,440], 711 cells/μL [356-1,686] and 38% [20-49]) compared to baseline control parameters (462 cells/μL [239-780], 18 cells/μL [18-62] and 3.5% [0-8]) (P < .01). The median [range] BALF ET concentration was also significantly higher after induction of asthma (1.393 fmol/mL[0.977-2.247]) compared to healthy control cats (0.83250 fmol/mL [0.625-1.038]) (P = .012).

CONCLUSIONS AND CLINICAL IMPORTANCE

This study suggests that BAL ET-1 concentration can be used to differentiate normal cats from those with experimentally induced asthma. If the same holds true for cats with naturally developing asthma, BAL ET-1 may prove a useful diagnostic biomarker for asthma.

Release of NT-pro brain natriuretic peptide in children before and after adenotonsillectomy

OBJECTIVES

To measure serum B-type natriuretic peptide, especially N-terminal segment of its prohormone (NT-proBNP) and pulmonary arterial pressure levels and to determine whether NT-proBNP concentrations correlate with pulmonary arterial pressure levels in children before and after adenotonsillectomy.

METHODS

Twenty children with adenoid and tonsil hypertrophy and 20 healthy subjects were included in the study. Transthoracic echocardiography was performed in all patients to assess pulmonary artery systolic and diastolic pressure with cardiac dysfunction. The NT-proBNP was analyzed for correlation with pulmonary artery pressure.

RESULTS

Our results showed that prohormone serum concentrations and pulmonary arterial pressures were significantly higher in the study group than in the control group at the preoperative evaluation. A significant decrease was detected among patients after surgery (p<0.05). There was no significant difference between the study and control groups for prohormone serum concentration and pulmonary arterial pressure at the postoperative evaluation (p>0.05).

CONCLUSION

We found increased serum prohormone levels and height pulmonary artery pressures in the children with adenoid and tonsil hypertrophy when comparing with healthy subjects. Our study supported that increased serum prohormone levels and pulmonary artery pressures as a result of adenoid and tonsil hypertrophy are reversible. Pediatric cardiologs and otolaryngologs should keep in mind an increased pulmonary artery pressure during management of children with adenoid and tonsil hypertrophy. Furthermore, Doppler echocardiography may be useful in the monitoring of pulmonary arterial pressure and in the follow-up of surgical outcome of children with adenoid and tonsil hypertrophy.

Association of cystic fibrosis genetic modifiers with congenital bilateral absence of the vas deferens

OBJECTIVE

To investigate whether genetic modifiers of cystic fibrosis (CF) lung disease also predispose to congenital bilateral absence of the vas deferens (CBAVD) in association with cystic fibrosis transmembrane conductance regulator (CFTR) mutations. We tested the hypothesis that polymorphisms of transforming growth factor (TGF)-β1 (rs 1982073, rs 1800471) and endothelin receptor type A (EDNRA) (rs 5335, rs 1801708) are associated with the CBAVD phenotype.

DESIGN

Genotyping of subjects with clinical CBAVD.

SETTING

Outpatient and hospital-based clinical evaluation.

PATIENT(S)

DNA samples from 80 subjects with CBAVD and 51 healthy male controls from various regions of Europe. This is one of the largest genetic studies of this disease to date.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Genotype analysis.

RESULT(S)

For single nucleotide polymorphism (SNP) rs 5335, we found increased frequency of the CC genotype among subjects with CBAVD. The difference was significant among Turkish patients versus controls (45.2% vs. 19.4%), and between all cases versus controls (36% vs. 15.7%). No associations between CBAVD penetrance and polymorphisms rs 1982073, rs 1800471, or rs 1801708 were observed.

CONCLUSION(S)

Our findings indicate that endothelin receptor type A polymorphism rs 5335 may be associated with CBAVD penetrance. To our knowledge, this is the first study to investigate genetic modifiers relevant to CBAVD.

Transcriptional regulation of monocyte chemotactic protein-1 release by endothelin-1 in human airway smooth muscle cells involves NF-kappaB and AP-1

BACKGROUND AND PURPOSE

Endothelin-1 (ET-1) is implicated in airway inflammation in asthma, but the mechanisms of its effects are poorly understood. We studied the effect of ET-1 on expression of the chemokine, monocyte chemotactic protein-1 (MCP-1), in primary cultures of human airway smooth muscle cells.

EXPERIMENTAL APPROACH

MCP-1 release was measured by elisa. Pharmacological antagonists/inhibitors, reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting were used to study ET receptors and kinase cascades. Transcriptional regulation was studied by real-time RT-PCR, transient transfection studies and chromatin immunoprecipitation assay. Major findings were confirmed in cells from three donors and mechanistic studies in cells from one donor.

KEY RESULTS

ET-1 increased MCP-1 release through an ET(A) and ET(B) receptor-dependent mechanism. ET-1 increased MCP-1 mRNA levels but not mRNA stability suggesting it was acting transcriptionally. ET-1 increased the activity of an MCP-1 promoter-reporter construct. Serial deletions of the MCP-1 promoter mapped ET-1 effects to a region between -213 and -128 base pairs upstream of the translation start codon, containing consensus sequences for activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB). ET-1 promoted binding of AP-1 c-Jun subunit and NF-kappaB p65 subunit to the MCP-1 promoter. Blocking the inhibitor of kappaB kinase-2 with 2-[(aminocarbonyl)amino]-5-[4-fluorophenyl]-3-thiophenecarboxamide (TPCA-1) decreased ET-1-stimulated MCP-1 production. p38 and p44/p42 mitogen-activated protein kinases were involved in upstream signalling.

CONCLUSIONS AND IMPLICATIONS

ET-1 regulated MCP-1 transcriptionally, via NF-kappaB and AP-1. The upstream signalling involved ET(A), ET(B) receptors, p38 and p44/p42 mitogen-activated protein kinases. These may be targets for novel asthma therapies.

Endothelin-1 increases expression of cyclooxygenase-2 and production of interlukin-8 in hunan pulmonary epithelial cells

Inducible cyclooxygenase (COX-2) and inflammatory cytokines play important roles in inflammatory processes of chronic obstructive pulmonary disease (COPD). Endothelin-1 (ET-1) might be also involved in the pathophysilogical processes in COPD. In the present study, we determined whether ET-1 could regulate the expression of COX-2 and alter the production of interleukin-8 (IL-8) in human pulmonary epithelial cells (A549). Induced sputum samples were collected from 13 stable COPD patients and 14 healthy subjects. The COX-2 protein, ET-1, PGE(2) and IL-8 in these sputum samples were analyzed. A549 cells were incubated with ET-1 in the presence or absence of celecoxib, a selective COX-2 inhibitor. The expression of COX-2 protein in the cell and the amounts of PGE(2) and IL-8 in the medium were measured. The levels of COX-2 protein, ET-1, PGE(2) and IL-8 were significantly increased in induced sputum from COPD patients when compared to healthy subjects. ET-1 increased the expression of COX-2 protein, as well as the production of PGE(2) in A549 cells. Increased production of PGE(2) was inhibited by celecoxib. ET-1 also increased the production of IL-8. Interestingly, ET-1-induced production of IL-8 was also inhibited by celecoxib. These findings indicate that ET-1 plays important roles in regulating COX-2 expression and production of IL-8 in A549 cells. ET-1 mediated production of IL-8 is likely through a COX-2-dependent mechanism.

Polymorphisms in the endothelin-1 (EDN1) are associated with asthma in two populations

Endothelin-1 (EDN1) has been reported to be implicated in the pathophysiology of asthma. Literature results on the genetic association of EDN1 in asthma are inconsistent. Eleven single nucleotide polymorphisms in EDN1 were genotyped in 342 and 100 families from UK and Norway, respectively. Asthma, bronchial hyperreactivity (BHR) and atopic asthma phenotypes were analyzed for the family-based association. Five single nucleotide polymorphisms (SNPs) were associated with asthma (0.0017<or=P<or=0.0291), five with BHR (0.0026<or=P<or=0.0315) and three with atopic asthma (0.0016<or=P<or=0.041) in the UK population. Three SNPs were associated with asthma (0.0041<or=P<or=0.019), seven with BHR (0.0018<or=P<or=0.041) and two with atopic asthma (0.0123<or=P<or=0.0153) in the Norwegian population. A polymorphism (rs1800541) in the promoter region of EDN1 was replicated in the two populations. A nonsynonymous coding polymorphism (rs5370) resulting in a change of amino acid Asn to Lys at position 198 was also replicated. The results of haplotype-based association analyses strongly supported the ones of single SNP associations. This study demonstrates the significant evidence of association between polymorphisms in EDN1 and asthma.

beta2-Adrenoceptor agonist modulates endothelin-1 receptors in human isolated bronchi

Chronic exposure of human isolated bronchi to beta(2)-adrenergic agonists, especially fenoterol, potentiates smooth muscle contraction in response to endothelin-1 (ET-1), a peptide implicated in chronic inflammatory airway diseases. Our objective was to determine whether ET-1 receptors ETA and ETB are involved in fenoterol enhancement. Twenty-two human bronchi were sensitized to ET-1 by prolonged incubation with 0.1 microM fenoterol (15 h, 21 degrees C). Removing the epithelium after fenoterol incubation limited the maximal contraction (0.10+/-0.36 g without epithelium versus 1.18+/-0.22 with, n=8, P=0.04). After 15 h incubation, 14 and 8 paired rings were fixed, respectively, for immunolabeling of bronchial ETA and ETB receptors, and to determine the mRNA expression levels using real-time quantitative reverse transcription polymerase chain reaction. ETA and ETB receptor mRNA expressions were 1.27- +/- 0.14-fold (not significant) and 2.24- +/- 0.28-fold (P<0.01) higher, respectively, in fenoterol-treated bronchi than in paired controls. Fenoterol incubation significantly increased epithelial ETA and ETB receptor labeling intensity scores (P=0.001 and P=0.002, respectively, versus controls), and enhanced the diffuse localization of ETA receptors on the epithelial cells (P=0.002 versus controls), but did not change the ETB-receptor immunolabeling intensity on airway smooth muscle. We conclude that fenoterol-induced sensitization of human isolated bronchi involves epithelial ETA and ETB receptors, which suggests perturbation of the epithelial regulation of airway smooth muscle contraction in response to ET-1.

Evaluation of arterial endothelin-1 levels, before and during a sleep study, in patients with bronchial asthma and chronic obstructive pulmonary disease

BACKGROUND

Endothelin (ET)-1 has been implicated in the pathogenesis of asthma and chronic obstructive pulmonary disease (COPD). The ET-1 levels are elevated during exacerbations of asthma and COPD in bronchoalveolar lavage, serum, and sputum, falling with treatment of the exacerbations.

OBJECTIVE

The aim of this study was to examine the ET-1 blood levels in stable asthmatic patients and stable COPD patients during alertness and sleep.

MATERIALS AND METHODS

We examined 48 COPD and 20 asthmatic patients. All underwent forced spirometry, measurement of SaO2 and of arterial ET-1 levels and nocturnal polysomnography. ET-1 levels were also determined during nocturnal oxyhaemoglobin desaturation.

RESULTS

The daytime SaO2 level of our asthmatic patients was higher than that of our COPD patients (p < 0.001). Daytime SaO2 level of our non-desaturator COPD patients was higher than that measured in desaturator COPD patients. Nightime SaO2 level in our asthmatic patients was higher than that in our desaturator COPD patients (p < 0.001). Daytime ET-1 levels in desaturator COPD patients were higher than those observed in normal individuals, in non-desaturator COPD patients and in asthmatic patients. The COPD desaturator patients had higher levels of ET-1 during nighttime than during daytime (p < 0.001).

CONCLUSION

Asthmatic patients did not exhibit desaturation of haemoglobin during the night. ET-1 levels are significantly higher in desaturator COPD patients compared with non-desaturator COPD patients, both during the day and during the night. ET-1 levels in stable COPD patients are significantly higher than in patients with stable asthma. These findings are consistent with the hypothesis that ET-1 is implicated in the pathogenesis of COPD and asthma.

Endothelin-1 (ET-1) decreases human bronchial epithelial cell migration and proliferation: implications for airway remodeling in asthma

The respiratory epithelium is a protective barrier that also functions as an interactive metabolically active component of the lung. The healing and repair of the epithelium involves initial migration of epithelial cells, and subsequent proliferation. The purpose of our study was to assess the effect of inflammatory mediators, in particular endothelin-1 (ET-1), on bronchial epithelial cell proliferation and migration. Under the conditions studied, ET-1 slows proliferation of human bronchial epithelial cells, compared to control (p < 0.01). The presence of ET-1 results in slower migration of epithelial cells compared to control (p < 0.04). Based on these in vitro findings, ET-1 could potentially lead to inhibition of repair of the lung epithelium and enhanced remodeling.

T cell phenotype in allergic asthma and atopic dermatitis

BACKGROUND

T cells are key regulators of immunologic disease parameters. However, their contribution to the process of tissue remodeling is ill defined. In the present study, we investigated gene expression of allergy-characteristic, IL-4-rich T cell cDNAs to monitor expression of genes that might participate in the pathogenesis of allergic diseases.

METHODS

cDNAs of freshly isolated and restimulated CD4+ T cells from patients with allergic asthma (AA) or atopic dermatitis (AD) and healthy subjects were analyzed on Nylon membrane-based DNA arrays. Three patients were selected for an allergy-characteristic T cell phenotype with high IL-4 expression (AA) or IL-13 expression (AD).

RESULTS

Several gene families such as the TGF-beta family, chemokines and chemokine receptors were found to be upregulated. Matrix metalloproteinases and their inhibitors were also found to be expressed in an enhanced manner. Furthermore, factors regulating tissue turnover such as fibroblast growth factors and neurotrophic as well as vasoactive factors were found be expressed at a higher level in allergic patient compared to healthy donors.

CONCLUSION

The present study reveals and confirms genes relevant for allergy and highlights an approach to applying a DNA array technique for diagnostic discrimination of allergic diseases.

Modulation and roles of the endothelins in the pathophysiology of pulmonary embolism

Recent research on the endothelins (ETs) and their pathways in acute pulmonary embolism (APE) has led to significant advances in the understanding of this disease. ETs are potent vasoconstrictors and bronchoconstrictors found abundantly in the lung and can be released by stimuli such as endothelial injury, hypoxia, or thrombin, a key product in the coagulation cascade. Many studies using different approaches and methods of inducing pulmonary embolization, both in vitro and in vivo in various species, have mostly shown that ETs play an important role in the pathophysiology of APE. These results were obtained by comparing the hemodynamic data in the presence or absence of various ETs inhibitors, but also by assessing the modulation of the ET-related elements of this system by molecular, cell biology, and pharmacological methods. Based on the current understanding, a mechanism involving the ET pathway in the pathophysiology of APE is proposed for the reader's considerations. We postulate that ETs are primary mediators in APE based on the following: (i) their source from pulmonary endothelial cells where the primary injury takes place; (ii) their direct vasconstrictive, bronchoconstrictive, and promitogenic effects via distinct ET receptors; and (iii) their indirect effects associated with the secondary release of thromboxane and other mediators, which are released from inflammatory cells and platelets, which together can potentiate the overall hemodynamic response, most specifically the pulmonary vascular bed. Such combined effects of ETs on bronchomotor and vasomotor tone in the lung can adversely affect ventilation perfusion matching and lead to severe hypoxemia without causing significant changes in the chest X-ray of these patients. Thus, we may consider ET inhibitors as future current therapeutic agents in patients with PE.

In vitro sensitization of human bronchus by beta2-adrenergic agonists

Incubation of human distal bronchi from 48 patients for 15 h with 10(-7) M fenoterol induced sensitization characterized by an increase in maximal contraction to endothelin-1 (ET-1) and acetylcholine (ACh). Incubation of human bronchi with 10(-6), 3 x 10(-6), and 10(-5) M forskolin (an adenyl cyclase activator) reproduced sensitization to ET-1 and ACh. The sensitizing effect of fenoterol was inhibited by coincubation with gliotoxine (a nuclear factor-kappaB inhibitor), dexamethasone, indomethacin (a cyclooxygenase inhibitor), GR-32191 (a TP prostanoid receptor antagonist), MK-476 (a cysteinyl leukotriene type 1 receptor antagonist), SR-140333 + SR-48968 + SR-142801 (neurokinin types 1, 2, and 3 tachykinin receptor antagonists) with or without HOE-140 (a bradykinin B(2) receptor antagonist), SB-203580 (an inhibitor of the 38-kDa mitogen-activated protein kinase, p38(MAPK)), or calphostin C (a protein kinase C blocker). Our results suggest that chronic exposure to fenoterol induces proinflammatory effects mediated by nuclear factor-kappaB and pathways involving leukotrienes, prostanoids, bradykinin, tachykinins, protein kinase C, and p38(MAPK), leading to the regulation of smooth muscle contraction to ET-1 and ACh.

Doppler echocardiographic evaluation of pulmonary arterial pressure in children with allergic rhinitis

In children, persistent upper airway obstruction may lead to increased pulmonary arterial pressure (PAP). Allergic rhinitis (AR) is one of the frequent cause of persisting upper airway obstruction by nasal blockage in childhood. Regular use of nasal topical corticosteroids are effective in reducing nasal blockage and obstruction. However, whether symptomatic children with AR have increased PAP and curative effect of topical steroids are not known. The aims of this study were to clarify whether children having active symptoms of AR have increased PAP and to investigate the curative effect of reducing nasal obstruction by topical corticosteroids. Twenty-three children, aged between 5 and 16, diagnosed as AR, consisted of 17 seasonal AR (SAR) and seven perennial AR (PAR), were included in the study. Nineteen age and sex matched healthy children were received as controls. PAP was measured by using Doppler echocardiography in all subjects and symptom scores of AR were recorded in rhinitis group. After first evaluation, nasal steroid, budesonid, was given to rhinitis group for three months. Mean systolic PAP was 33.4+/-3.1 for children with AR mmHg and 23.6+/-4.3 mmHg for the control group. The difference was statistically significant (P<0.05). Mean systolic PAP of children with PAR was significantly higher than children with SAR (P<0.05). In rhinitis group, mean PAP decreased significantly after relief of upper airway obstruction by nasal corticosteroid therapy to normal level of 24.9+/-3.6 mmHg (P<0.05). Our results showed that children with AR may have significantly higher PAP than healthy subjects and decreased to normal levels after relieving nasal blockage by nasal corticosteroids. Nevertheless, Doppler echocardiography is a safe, non-invasive and practical tool for cardiac investigation of children with AR. Therefore, in symptomatic period, evaluation of PAP of children with AR by using Doppler echocardiography may be useful in the planning and following of their therapy.

Increased endothelin-1 associated with bacterial infection in lung transplant recipients

BACKGROUND

Endothelin-1 (ET-1) has fibrogenic and inflammatory properties. Its pathogenic role in pulmonary fibrosis and certain inflammatory airway diseases is now well known. Its production is, in part, triggered by infectious processes. Episodes of infection are suspected to be involved in the development of bronchiolitis obliterans syndrome (BOS), which is the main feature of chronic lung rejection and the major factor limiting the long-term survival of transplanted patients. We postulated that ET-1 is upregulated during infectious complications arising from the graft and that this could partly explain the remodeling of airway structures observed in BOS. We, therefore, set up this study to assess ET-1 expression in relation to complications of the graft in human lung transplant recipients.

METHODS

ET-1 mRNA was quantified by reverse transcription-competitive polymerase chain reaction in cells from 119 samples of bronchoalveolar lavage (BAL) fluid from 17 lung transplant recipients. ET-1 and big ET-1 proteins were assessed in BAL cell culture supernatants by enzyme immunoassay. Transbronchial biopsies (n=21) were stained immunohistochemically for ET-1 receptors.

RESULTS

Episodes of bacterial infection strongly correlated with increased ET-1 mRNA and protein expression. ET-1 receptors were also upregulated during these episodes, especially on endothelial and smooth muscle cells. Five of the seven patients with the highest ET-1 levels subsequently developed BOS.

CONCLUSIONS

These results raise the possibility that ET-1, part of whose production is triggered by infectious postgraft complications, might play a role in the development of BOS through its potential effects on airway remodeling.

Functional Interactions Between Tumor and Peripheral Nerve in a Model of Cancer Pain in the Mouse

Cancer is usually accompanied by pain, which tends to increase in relation to metastatic infiltration and destruction. In the United States, 30% to 40% of newly diagnosed cancer patients and 67% to 90% of patients with advanced cancer report moderate to severe pain. Relief for approximately 90% of patients with cancer-related pain may be provided by the World Health Organization's "analgesic ladder," which involves progressing from non-opioid (e.g., acetaminophen, ibuprofen) to weak opioid (e.g., codeine), to strong opioid (e.g., morphine, fentanyl) intervention for pain relief. The severity of cancer pain is affected by diverse factors. In addition to the obvious factors of tumor size and degree of metastatic destruction, the type of tumor and its location are also important factors that contribute to pain severity. Severe cancer pain is especially associated with tumors involving bone destruction and nerve infiltration. Cancer pain seems to involve diverse mechanisms, including characteristics of both nociceptive and neuropathic pain. Unfortunately, even opioid analgesics often produce poor pain relief against neuropathic pain derived from peripheral nerve or root damage common to cancers involving bone metastases and nerve infiltration. In addition, these drugs may induce adverse side effects since they affect various physiological functions, including hormone secretion, neurotransmitter release, feeding, gastrointestinal motility, and respiratory activity. Currently, drug therapies utilizing antidepressants and anticonvulsants are being used to relieve neuropathic pain whereas cancer pain is treated largely with opiods in cancer patients.

Sputum and plasma endothelin-1 levels in exacerbations of chronic obstructive pulmonary disease

BACKGROUND

Endothelin (ET)-l is a bronchoconstrictor peptide produced in the airways. It has been implicated in the pathogenesis of asthma and virally mediated airway inflammation and may play a role in exacerbations of chronic obstructive pulmonary disease (COPD).

METHODS

Seventy one patients with COPD were followed prospectively and sampled for plasma and sputum ET-1 levels when stable and during an exacerbation. Sputum was also examined for cytokines, human rhinovirus, and Chlamydia pneumoniae.

RESULTS

Plasma ET-1 levels were available for 67 patients with stable COPD (mean (SD) 0.58 (0.31) pg/ml); 28 pairs of stable-exacerbation plasma samples had a mean stable ET-1 level of 0.54 (0.30) pg/ml rising to 0.67 (0.35) pg/ml at exacerbation (mean difference 0.13, 95% confidence interval (CI) 0.04 to 0.21, p = 0.004). Plasma ET-1 levels in the 67 patients with stable COPD were inversely correlated with baseline forced expiratory volume in one second (FEV(1); r = -0. 29, p = 0.022) and forced vital capacity (FVC; r = -0.38, p = 0.002). The change in plasma ET-1 levels during an exacerbation correlated with the change in oxygen saturation (SaO(2); r = -0.41, p = 0.036). In 14 stable-exacerbation pairs of sputum samples median stable ET-1 levels were 5.37 (0.97-21.95) pg/ml rising to 34.68 (13.77-51.95) pg/ml during an exacerbation (mean difference 25.14, 95% CI 3.77 to 46.51, p = 0.028). This increase in sputum ET-1 levels correlated with the increase in plasma ET-1 levels (r = 0.917, p = 0.001) and sputum interleukin (IL)-6 levels (r = 0.718, p = 0.013).

CONCLUSIONS

Sputum levels of ET-1 rise in COPD patients during an exacerbation and this is reflected by a smaller rise in plasma ET-1 levels. ET-1 may have a role in mediating airway inflammatory changes during exacerbations of COPD.

LU135252, an endothelin(A) receptor antagonist did not prevent pulmonary vascular remodelling or lung fibrosis in a rat model of myocardial infarction

The early intervention with endothelin(A) (ET(A)) receptor antagonists following coronary artery ligation has been shown to reduce the development of pulmonary hypertension, despite a lack of improvement in left ventricular function. The present study examined the contribution of pulmonary vascular remodelling and the progression of lung fibrosis in the development of pulmonary hypertension and the subsequent role of endothelin-1 in these processes in a rat model of myocardial infarction (MI). The administration of 60 mg kg(-1) per day of the specific ET(A) receptor antagonist LU135253 ((+)-(S)-2-(4, 6-dimethoxy-pyrimidin-2-yloxy)-3-methoxy-3,3-diphenyl-propionic acid) 24 h following coronary artery ligation, failed to improve left ventricular contractile indices, but reduced the extent of pulmonary hypertension, as reflected by the significant decrease in right ventricular systolic pressure. The medial wall thickness of small pulmonary arteries (50 - 200 microm) was significantly increased 4 weeks following MI, albeit LU135253 treatment did not ameliorate this pattern of vascular remodelling. The steady-state mRNA levels of collagen, fibronectin, transforming growth factor-beta(1), and -beta(3) were significantly increased in the lungs of MI rats. The treatment with LU135252 did not alter this pattern of gene expression. Thus, these data demonstrate pulmonary vascular remodelling and the increased expression of extracellular matrix proteins represent underlying mechanisms implicated in the development of pulmonary hypertension in the MI rat. Despite the amelioration of the pulmonary hypertensive state, ET(A) receptor blockade was insufficient to reverse pulmonary vascular remodelling, or the development of lung fibrosis in the MI rat.

Pulmonary fibrosis and chronic lung inflammation in ET-1 transgenic mice

The pulmonary endothelin (ET) system has been implicated in the pathogenesis of chronic lung diseases such as pulmonary hypertension, asthma, chronic obstructive lung disease, idiopathic pulmonary fibrosis, and bronchiolitis obliterans. However, the etiologic role of ET-1 in these diseases has not yet been established. We recently demonstrated that ET-1 transgenic mice, generated using the human prepro-ET-1 expression cassette including the cis-acting transcriptional regulatory elements, had predominant transgene expression in lung, brain, and kidney. We used these mice in the present study to analyze the pathophysiologic consequences of long-term pulmonary overexpression of ET-1. We found that ET-1 overexpression in the lungs did not result in significant pulmonary hypertension, but did result in development of a progressive pulmonary fibrosis and recruitment of inflammatory cells (predominantly CD4-positive cells). Our study provides evidence that a long-term activated pulmonary ET system, without any other stimuli, produces chronic lymphocytic inflammation and lung fibrosis. This suggests that overexpression of ET-1 may be a central event in the pathogenesis of lung diseases associated with fibrosis and chronic inflammation, such as pulmonary fibrosis and bronchiolitis.

Strategies to antagonise the cyclosporine A-induced proliferation of human pulmonary artery smooth muscle cells: anti-endothelin-1 antibodies, verapamil, and octreotide

The present study investigated the mechanisms mediating the actions of the immunosuppressive drug cyclosporine A (CsA) on human pulmonary artery smooth muscle cell (PASMC) proliferation. The new hydroxyethyl derivative of D-serine(8)-cyclosporine, SDZ IMM 125, was used for comparison. CsA-induced proliferation was determined by incorporation of [(3)H]thymidine ([(3)H]Thy). CsA in the concentration range between 0.1 nM and 0.1 microM induced a concentration-dependent increase in proliferation after 24, 48, and 72 hr of incubation. Higher CsA concentrations were cytotoxic. When proliferation experiments were performed in the presence of a monoclonal antibody against endothelin-1 (ET-1), CsA-induced proliferation was totally inhibited. No inhibition occurred in the presence of the same antibody when heat-inactivated or a non-specific monoclonal antibody. In parallel, CsA increased the production of ET-1, as determined by radioimmunoassay. Incubation of PASMCs with ET-1 at the concentration range at which the latter was released by CsA induced cell proliferation. The somatostatin derivative Sandostatin (SDT; octreotide), which is an inhibitor of the growth of smooth muscle cells as well as a potent inhibitor of ET-1 secretion, inhibited both the CsA-induced ET-1 release and the increase in [3H]Thy incorporation by PASMCs. A similar effect was observed for the calcium channel blocker verapamil (VP). SDZ IMM 125 induced weaker effects than CsA in terms of PASMC proliferation and ET-1 secretion. In conclusion, CsA increased the rate of proliferation of PASMCs, while SDZ IMM 125 induced a weaker effect. Anti-ET-1 antibody, VP, and SDT significantly inhibited CsA-induced PASMC proliferation.